The large systematic deviations in haptic parallelity matching are most likely due to the biasing influence of the hand-centered egocentric reference frame. Previous results showed that eliminating or reducing this bias resulted in smaller deviations, with significantly larger effects observed in female participants. The current study investigated the effect of reducing the egocentric bias in a pure haptic condition. Blind-folded male and female participants had to feel the orientation of a reference bar with their non-dominant hand and to parallel this orientation on a test bar with their dominant hand. In one condition, they were instructed to use their flat-stretched hand to feel and match the bars, while in the other condition (HPF), they were instructed to set the test bar while gripping the bar with the fingers and thumb. It was hypothesized that the latter would reduce the biasing influence of the hand-centered egocentric reference frame. Results showed that this was indeed the case. Deviations were significantly smaller for HPF; however, this effect was the same in both genders. The previously observed gender effect, showing a significantly larger improvement for women when reducing the influence of the egocentric reference frame, was not replicated. A spatial orientation task that might seem to be easily and veridically performed often results in large errors when the task has to be performed haptically without visual input. The task at hand involves two bars that need to be paralleled with regard to their orientation. In the so-called haptic parallelity task Kappers , particiWhile different egocentric reference frames have been suggested for haptic tasks, including a hand- and shoulder-centered , with a mean age of 24 years , took part in the experiment. Mean age of the male participants was 24 years , while the mean age of the female participants was 23.5 years . One participant showed left-handed dominance, the other participants were right-handed as assessed by a Dutch translation of the hand preference questionnaire of Annett Annett . ParticiThe setup was the same as used in the previous studies Van Mier , 2016. TTwo conditions of the haptic parallelity task were used in the current study. Participants were blindfolded and had to feel the orientation of the reference bar with their non-dominant hand, while they had to parallel this orientation with the dominant hand at the reference bar. Parallel setting was performed bimanually. During the duration of each trial, both bars were touched simultaneously. In both conditions, the orientation of the reference bar had to be explored using the flat-stretched non-dominant hand. Usually, participants perform the haptic parallelity task by feeling and matching the bars using their flat-stretched hands, with the middle finger aligned to the orientation of the bar. This was also the case in the current study. In the occasional instance participants did not stretch the hand, they were instructed by the experimentor to do so. Participants started the study with the condition in which the test bar was haptically paralleled to the reference bar using the flat-stretched hand (HPH)  and of the female participants 49.3 cm (SD 3.2). Therefore, the mean distance between the centres of the plates was 108 cm for men and almost 100 cm for women.For each trial, the experimenter positioned the reference bar in one of the four predetermined orientations, and the test bar was oriented at either 70° or 120°. The experimenter placed the non-dominant hand of the participant above the reference bar and the dominant hand above the test bar. The task of the participant was to rotate the test bar in such a way that it felt parallel with respect to the reference bar, using both hands simultaneously and without switching hands while exploring and orienting the bars. There was no time limit set to perform the task and participants were not given feedback about their performance. After participants had set the test bar and were satisfied with the result, the experimenter recorded the orientation of the bar by reading the orientation indicated by the arrow-shaped end of the bar.The smallest deviation between the orientation of the test bar and the reference bar was the dependent variable. When deviations were counterclockwise to the reference bar, they were noted as negative values, with clockwise deviations being noted as positive values. This was reversed for the left-handed participant, with counter-clockwise deviations being noted as positive values and clockwise deviations as negative values. To study the effect of setting the test bar with the fingers, a repeated measurement ANOVA was performed with the following independent factors: condition (2: HPH and HPF), orientation , and repetition  as within-subject factors. A second analysis was performed including additionally gender  as between-subject factor. There was no violation of sphericity of the independent variables. Because of the small sample size, normality was tested using the Shapiro–Wilk test. The results showed that the deviations in both conditions were normally distributed in both genders. In addition, the deviations of the orientations in both conditions were normally distributed in both genders with the exception of the deviations for the 0° and 90° orientations for males in the HPF condition. This was due to the deviation of one male participant who had much larger deviations for these orientations in the HPF condition than the other male participants.F = 1.94, p = 0.16], nor was there a significant interaction. Mean deviation for the first trial was 31.8°, for the second trial 33.7°, and for the third trial 34.5°. We, therefore, averaged over repetitions.Analysis showed that there was no significant main effect of repetition  and orientation . While a mean deviation of 38.4° was found in the condition, where the flat-stretched hand was used to set the test bar (HPH), a much smaller mean deviation of 28.3° was found in the condition, where the test bar was gripped with the fingers (HPF). Deviations for the different orientations were in line with earlier reported differences regarding cardinal and oblique orientations. The mean deviation for the cardinal orientation of 90° was smallest (24.6°) and largest for the oblique orientation of 135° (42.0°). The cardinal orientation of 0° resulted in a mean deviation of 30.6° with a mean deviation of 36.1° for the oblique orientation of 45°. Pairwise comparisons of the four orientations using a Bonferroni correction showed that the deviation of the 135° orientation was significantly different from the deviations of the other orientations . In addition, the deviation for the 90° orientation was significantly different from the 45° orientation (p = 0.002). Although this pattern regarding deviations for the different orientations was the same in both conditions  = 4.55, p = 0.006]. Differences in deviations between both conditions were most pronounced for the 0° orientation (difference of 16°) and least for the orientation of 135° (difference of 4.6°).To study the effect of condition and orientation for all 20 participants, regardless of gender, a repeated measurement ANOVA was performed with condition and orientation as independent variables and deviation as dependent variable. This analysis showed significant main effects of condition  as well as main effects of condition  and orientation . While female participants had a mean deviation of 41.6°, a mean deviation of 25.0° was found for male participants. The interaction of condition and gender showed a trend . As can be seen in Fig. Including gender as a between-subject factor in the abovementioned repeated measurement ANOVA showed a main effect of gender [Figure This study was conducted to investigate if reducing the influence of the hand-centered egocentric reference frame would decrease deviations in a pure haptic parallelity task. In this task, the orientation of a reference bar that was perceived with one hand had to be paralleled on a test bar that was manipulated with the other hand. To address this question, performance was assessed in a condition in which the test bar had to be matched using the flat-stretched hand and in a condition in which the test bar had to be rotated by gripping the bar with all fingers. It was hypothesized that in the latter condition, the bias of the hand-centered egocentric reference frame would be reduced, resulting in a decrease in deviations. The results support this hypothesis; deviations in the latter condition were significantly smaller than in the former.We replicated previously reported results regarding haptic parallelity, with large and systematic deviations (e.g., Fernández-Díaz and Travieso Comparing the deviations in both conditions revealed that the deviations in the HPF condition were significantly smaller than in the HPH condition. Rotating the reference bar while using the fingers instead of the flat-stretched hand reduced the deviations by more than 26%. This is most likely due to a decrease in the egocentric bias of the hand. While both hands are aligned when the test and reference bar are felt and rotated by the flat-stretched hand, this is not the case when the reference bar has to be rotated using the fingers. In that case, it is most likely that an arm-centered reference frame is used. The current result is in line with earlier findings regarding the reduction of the bias of the hand in haptic parallel setting. Van Mier  found a While cardinal orientations resulted in smaller deviations than oblique orientations in both conditions, a significant interaction of condition and orientation was found. The orientation of 0° had considerably smaller deviations in the HPF condition than in the HPH condition than the other orientations. It is possible that this was due to biomechanical aspects. In this orientation, it is easier to rotate the flat-stretched hand in a more clockwise direction than when the bar is gripped with the fingers.When two bars are horizontally far apart and each touched by one of the hands, the orientation of the hands will be different, as well as the position of the hands in relation to the body (Kappers and Viergever It was additionally hypothesized that if gripping the reference bar with the fingers would result in smaller deviations, this effect would be most pronounced in female participants. It was found that deviations in the HPF condition were almost 16° smaller than in the HPH condition for women, while they were just a bit more than 4° smaller for men. In addition, all women showed smaller deviations in the HPF condition, while some men showed increases. However, the interaction of gender and condition was not significant, but only showed a trend. This result might even have been skewed by one of the female participants who showed an improvement of more than 60° when performing the task with the fingers. Excluding this participant resulted in an average improvement of 10.8° for the 9 female participants. Because both genders showed a similar improvement in the HPF condition, our second hypothesis was not confirmed. These results do not replicate earlier findings by Van Mier , 2016 shDue to the fixed setup of the current study in which gripping and setting the test bar with all fingers was always performed after orienting the test bar with the flat-stretched hand, one could argue that the smaller deviations in the second condition are the result of a practice effect. However, if that would be the case, we would have expected a decrease in deviations as an effect of repetition. On the contrary, deviations did not decrease but actually increased over the three repetitions, although the effect was not significant. Hermens et al.  did not Taken together, the findings from the current study support the idea that the egocentric reference frame in the haptic parallelity task is mainly centered at the hand. Deviations from parallelity were much smaller when the bias of the hand was reduced and participants had to match the orientation by setting the bar using the fingers. This effect was found to be similar in female and male participants.


Analyzing the fluid behavior in complex porous media like gas diffusion layers (GDLs) in polymer electrolyte fuel cells (PEFCs) can be accurately done using the lattice Boltzmann method (LBM). This article shows the data obtained from a study in which diffusion parameters such as porosity, gas phase tortuosity and diffusibility are computed considering simulated porous media [1]. The data were computed when a water drop obstacle is placed inside the GDL domain and the size of the water-drop is varied. Additionally, figures showing the evolution of the flow velocity field are presented alongside graphics that presents the change in local and bulk porosity for each obstacle size. Finally, there is a detailed method explanation concerning the implementation of the lattice Boltzmann method and a general description of computational codes for the domain and obstacle generation as well as the boundary conditions simulation. Data and processes in this article can be exploited in new attempts to solve real case problems in complex mesoscale media. Fig. 1 Porosity, Tortuosity and Diffusibility data were collected after several runs of our code. There were seven iterations for each case to obtain an acceptable standard deviation for each group of data. Bulk Porosity is the average value of local porosities calculated by comparing the void spaces with the whole volume. Tortuosity was obtained by measuring the flow path length and the shortest path length of the medium. Finally, diffusibility is the ratio between the bulk porosity and the tortuosity. 22.1To obtain the computed data of the velocity of the fluid, the LBM was applied. This method works best on complex structures at mesoscale size. First it needs a digitally generated porous medium representing a GDL in which a water drop it is placed. Then it implements boundary condition on the surroundings of the medium and on the interface between fluid and fibers. The computing details are explaining bellow.2.2The first step in the code is the creation of the 3D matrix using zeros to represent voids. In this study a 100 × 100 × 100 zeros matrix was created. This matrix corresponds to a 200 × 200 × 200 μm space inside a GDL [A sample of the code used to generate the media and the water drop is shown in 2.3To obtain the fluid behavior inside the simulated media, the whole domain has been divided into lattice elements in which the lattice Boltzmann method (LBM) can be applied. All elements interact with the surrounding ones by means of linked velocities. In this 3D case, every element has 19 velocity vectors in different directions.The method provides a relation between equilibrium and particle distribution for each node. In flow analysis, the equilibrium distribution mainly depends on the local density, velocity and weighting factor for every direction. It also considers collisions in the system and the time it takes to reach a balance. On the other hand, the particle distribution focuses on the position of the node, its velocities and the time lapse to flow in all directions ,5.2.4The behavior of the fluid depends highly on the equilibrium distribution. In every lattice element, the density and velocity are updated after the collision while the weighting factor of each direction remains constant. This changes the particle velocities in the different directions which interact to the surrounding lattice elements. To maintain the accuracy to real world cases, boundary conditions need to be applied to the interactions between elements .The boundary conditions for the porous media are implemented on the volume limits and in every fluid-solid interface. In this case in which the fluid flows in a single dimension the boundary conditions are divided as presented in Samples of the boundary conditions codes used are resumed in 2.5The algorithm founds the velocity field for each node until the whole system reaches a steady state condition . The fir2.6There are three diffusion parameters shown in the previous data: Bulk Porosity, Gas Phase Tortuosity and Diffusibility . The por


PD) for the treatment of benign conditions and malignant periampullary tumors. In addition, various surgical techniques in terms of port placement, dissection, and reconstruction have evolved in different centers depending on the preferred method commonly used by the surgeon through accumulated experience. In our center, we used a stepwise approach and standardized our surgical technique to overcome this technically demanding procedure. A collaborative implementation of video review and analysis, practice training and simulation, operating room didactics, and strict adherence to our stepwise approach in Lap PD, might potentially improve the surgical skills of young hepatobiliary surgeons and possibly overcome the volume‐based learning curve of Lap PD.Because of today's advancements in surgical techniques and perioperative management skills, surgeons are beginning to explore the usefulness of the laparoscopic approach in managing periampullary tumors. However, as a result of its innate complexity and associated high surgery‐related complications, its applicability to the general surgical community remains controversial. To date, only retrospective data from high‐volume centers support the safety and feasibility of laparoscopic pancreaticoduodenectomy (Lap  In particular, for malignant periampullary tumor, the radicality of the resection itself warrants careful tissue handling to preserve the oncological benefit. As such, open pancreaticoduodenectomy remains the standard approach for a periampullary tumor.However, in the era of minimally invasive surgery, surgeons are beginning to explore the usefulness and safety of laparoscopic pancreaticoduodenectomy (Lap PD). Pioneered by Gagner and Pomp in 1994 in a patient with pancreatic divisum,Nevertheless, with today's advancements in surgical techniques and perioperative management skills, Lap PD is thought to be an appropriate approach for treating periampullary pathological conditions, particularly in high‐volume centers.Most importantly, standardization of various surgical techniques might be the key to overcome their innate complexity. Therefore, we describe our surgical technique and apply a stepwise approach as a benchmark to overcome the pitfalls of Lap PD.2Surgical indications for Lap PD may be similar to those for Open PD.Nevertheless, we standardized our Lap PD selection criteria for patients with periampullary tumor. Whether to carry out Lap PD or Open PD can be decided preoperatively or intraoperatively. In general, we select patients with benign and low‐grade malignant periampullary lesions, periampullary cancer not involving major vascular structure, and good performance status as good candidates for Lap PD. Intraoperatively, wise decision‐making for open conversion to laparotomy is paramount. For patient safety, failure to progress within 1 hour of dissection as a result of severe pancreatitis or adhesions, unexpected vascular invasion, unexpected adjacent organ involvement requiring combined organ resection, unusual vascular anatomy, and uncontrolled bleeding may warrant open conversion to laparotomy.3Standard dissection during PD is thought to be optimal when carrying out Lap PD.There are several important randomized controlled studies comparing extended and standard dissection in periampullary cancer. Most of the studies concluded that there was no survival benefit from carrying out extended lymphadenectomy compared to standard lymphadenectomy.Therefore, based on currently available evidence and surgical techniques of Lap PD, standard dissection is feasible when carrying out Lap PD. However, extended dissection including para‐aortic lymph nodes and perineural soft tissue around the SMA is allowed for margin‐negative resection in selected cases and by selected expertise.4Placement and number of trocars varied across centers. The number of trocars varied from five to seven.4.1Three laparoscopic graspers, two laparoscopic dissectors, and one laparoscopic needle holder with straight plastic handles were used for Lap PD. Ultrasonic  and bipolar energy devices are fundamental requirements for Lap PD. A bipolar energy device is especially useful in blunt dissection and for complete coagulation around major vascular structures.5Different surgical techniques in terms of port placement, dissection, and reconstruction have been reported in different high‐volume centers.Recently, we began to explore the feasibility of laparoscopic pancreaticoduodenectomy for treating periampullary tumor and began to standardize our surgical technique.In a stepwise approach, Lap PD consists of the “resection phase” and the “reconstruction phase.” Each is subdivided into a series of steps to guide the beginner's approach to Lap PD Table .According to tissue condition, the operation sequence may be changed, but the step‐by‐step approach in Table 5.15.1.1An incision is made into the gastrocolic ligament a few centimeters from the gastroepiploic arcade of the body of the stomach, using a LigaSure instrument . By doing this, the left‐hand grasper of the operator grasps the stomach while the assistant left‐hand grasper retracts the colonic side to create an effective tension for dissection Figure . The dis5.1.2The assistant lifts the stomach in a 12 o'clock position to properly expose the pyloric area. This will clearly expose the right gastroepiploic vessels, which can be effectively ligated using laparoscopic clips. Either individual control of the artery and the vein or simultaneous control of these vessels is acceptable. This will also facilitate dissection and separation of the antero‐superior part of the head of the pancreas and the inferior part of the first portion of the duodenum Figure . Bleedin5.1.3Next, the superior part of the first portion of the duodenum is dissected. The assistant right‐hand grasper retracts the liver while the assistant left‐hand grasper retracts the first portion of the duodenum to expose the hepatoduodenal ligament. The peritoneal lining of the hepatoduodenal ligament is incised just above the first portion of the duodenal wall and along the lesser curvature of the stomach antrum to expose the right gastric artery  is inserted and positioned from the greater curvature to the lesser curvature 1‐2 cm from the pylorus Figure . The tra5.1.5The left‐hand grasper of the assistant will pull down the mesenteric attachment of the inferior border of the pancreas to allow a clear view of the superior border of the pancreas. The peritoneal lining of the hepatoduodenal ligament is incised along the pancreatic neck. Once opened, the common hepatic artery is usually identified and can be followed caudally to expose the gastroduodenal artery. The portal vein can be identified and exposed by dissecting the triangular‐shaped tissue bordered by the common hepatic artery, gastroduodenal artery, and superior border of the neck of the pancreas Figure . This ca5.1.6The transected right gastroepiploic vein can be followed down to its origin to identify the location of the superior mesenteric vein (SMV). Once the SMV is identified, the left‐hand grasper of the assistant holds the right dorsal part of the mesentery just caudal to the origin of the right gastroepiploic vein on the SMV. By doing this, the SMV can be clearly exposed for further dissection. The peritoneal lining on the antero‐inferior aspect of the neck of the pancreas is dissected along the adventitia of the SMV, clearing all fatty tissues around it up to the inferior border of the pancreas Figure . Small t5.1.7Once the dissection reaches the inferior border of the pancreas, the inferior peritoneal covering is dissected toward the left and right sides of the SMV. Using blunt dissection with a bipolar energy device, a small window can be created between the anterior border of the SMV and the posterior neck of the pancreas. A large right‐angled dissector can now be inserted along this window up to the superior border of the neck of the pancreas Figure . Once th5.1.8During this time, the right‐hand grasper of the assistant holds the ligamentum teres to facilitate liver retraction. Dissection of the hepatoduodenal ligament (HDL) is started at the junction of the common hepatic artery and gastroduodenal artery, removing all the lymph nodes and connective tissues surrounding the common hepatic artery and superior margin of the pancreas Figure A. Dissec5.1.9Proper orientation of the head and body of the pancreas is one of the key points during this procedure. The avascular plane of the anterior aspect of the transverse mesocolon is followed to the head of the pancreas. During this time, the gastrocolic trunk can be visualized within the mesentery. The transected right gastroepiploic vein (RGEV) can be followed down to its origin in the gastrocolic trunk. The anterior inferior pancreaticoduodenal vein on the right lateral side of the RGEV can also be identified to its origin in the gastrocolic trunk Figure . With a 5.1.10A full Kocher's maneuver was carried out to mobilize the duodenum and head of the pancreas. The lateral peritoneal attachments of the duodenum were dissected, exposing the inferior vena and aorta. Dissection was continued to the lateral border of the aorta Figure . The assOnce full kocherization is achieved, separation of the duodenum and head of the pancreas from the colonic mesentery can start through dissection along the right lateral border of the SMV. Once the SMV is identified, the left‐hand grasper of the assistant holds the right dorsal part of the mesentery just caudal to the origin of the right gastroepiploic vein on the SMV and pulls it left to rotate the mesentery in a clockwise position. When this is done, the SMV can be clearly exposed for further dissection. Dissection will continue along the adventitia of the SMV, clearing all fatty tissues around it up to the inferior border of the uncinate process pancreas Figure . Small tIn cases where there were some enlarged lymph nodes around the para‐aortic area, the lymph nodes and some connective tissues anterior to the inferior vena cava and aortocaval (station 16a and 16b) area were sampled for frozen section biopsy Figure .5.1.11The right‐hand grasper of the assistant holds the transverse colon and retracts it cephalad to expose the ligament of Treitz. The proximal 10‐cm segment of the jejunum is identified. The length of the proximal jejunum can vary according to patient's condition. For example, obese patients have a longer proximal jejunum, which needs to be considered for future retrocolic fashioned pancreaticojejunostomy and hepaticojejunostomy in the reconstruction phase. The assistant left‐hand grasper holds the distal part of the jejunum while the surgeon holds the proximal part. The mesentery is dissected down to its mesenteric root. The jejunum is then transected using an Endo‐GIA Figure A. The me5.1.12Next, the tape around the neck of the pancreas is pulled up at a 12 o'clock position. An energy device is used to partially transect the pancreas up to its duct, after which the transection is continued using scissors Figure . This prOnce the pancreas is transected, dissection of the uncinate process is carried out. Complete exposure of the uncinate process can be accomplished by superior‐medial retraction of the transverse mesocolon. This retraction can also clearly define the border of the uncinate process of the pancreas. It is important to emphasize that there are multiple small vessels originating from the SMV, PV, and SMA between the connective tissues of these vessels and the uncinate process and the head of the pancreas. Dissection can be facilitated using an energy device and laparoscopic clips. With the magnified view of the laparoscope, small vessels can be easily recognized and safely clipped. However, dissection of the uncinate process is among one of the most difficult parts of the resection stage. In particular, the inferior pancreaticoduodenal artery (IPDA) from the SMA can be encountered on the posterior border of the SMV Figure A. This a5.1.13After the head of the pancreas is free, the proximal portion of the common hepatic duct is clipped with a bulldog clamp to avoid bile spillage after transection while the distal portion is clipped with a hemoclip or bulldog clamp. The common hepatic duct is transected just above the origin of the cystic duct using scissors Figure . The spe5.2This stage is believed to be one of the biggest obstacles to wide application of Lap PD in clinical practice. However, when surgeons know the basic surgical principles for pancreaticojejunostomy (PJ) and hepaticojejunostomy (HJ) and some technical tips, these procedures can be safely carried out. In the near future, robotic surgical systems will play a large role in this stage. However, as a result of its high cost, not every patient can undergo robotic surgery. Therefore, pancreatic surgeons must have good surgical skills to undertake these challenging surgical procedures to fulfill the goal of minimally invasive surgery.5.2.1This step is the most challenging. However, through didactics and simulation, this step can be safely conducted. Instruments must be handled carefully to avoid cutting and injury to the pancreatic remnant during the anastomosis. Usually, four stitches are applied for a <2‐mm pancreatic duct‐to‐mucosa PJ. For a duct >2 mm, six or more sutures can be used depending on the size of the duct. Achieving an exact angle of the needle is one of the most difficult steps during anastomosis. The following steps are our surgical strategy in managing the remnant pancreas during Lap PD.Interrupted suture, two‐layer, duct‐to‐mucosa PJ with a short stent is our standard approach for managing the remnant pancreas.A laparoscopic camera is placed through Port B, using Port a and Port A as working ports to allow a more ergonomic position.The jejunal limb is brought to the pancreatic stump in a retrocolic way. In specific cases, the jejunal limb can be pulled up through the retromesenteric window.The posterior layer is sutured first from the superior to the inferior border of the pancreas. After reaching the pancreatic duct, stay sutures are used in the pancreatic duct. A 6 o'clock suture is placed before completing the outer/posterior interrupted sutures. Usually, one to two stay sutures in the posterior aspect of the duct (6 o'clock position) are used to avoid suture confusion.The posterior layer interrupted sutures are continued.Next, the duct‐to‐mucosa anastomosis is continued. Stay sutures in the 3 and 9 o'clock positions are used at the jejunal opening. Additional sutures in the 12 o'clock position are used depending on the size of the pancreatic duct.Once the duct‐to‐mucosa anastomosis is achieved, the anterior layer is completed using interrupted sutures from superior to inferior border pancreas.Rotation with a blunt angle‐fashioned needle mounted on a laparoscopic needle holder is carried out allowing a curving  movement for appropriate PJ suturing. Figure 5.2.2Posterior continuous and anterior interrupted sutures are placed for hepaticojejunostomy Figure . Using d5.2.3The umbilical wound (Port‐A site) is extended by approximately 5 cm, which is enough to accommodate extraction of the specimen. A 50‐cm Roux‐en‐Y limb of the jejunum from the hepaticojejunostomy site is marked for the duodenojejunostomy. The duodenum and jejunum must be carefully oriented laparoscopically, tagged with sutures, and removed through the small umbilical wound for anastomosis. End‐to‐side or side‐to‐side duodenojejunostomy can be carried out manually. Figure 6As a preliminary form of image‐guided surgery, intraoperative ICG can help in deciding whether to carry out minimally invasive pancreatectomy. Kim et alIn Lap PD, initially reported by Rho et al,7Recently, a number of retrospective studies evaluating the efficacy of Lap PD have been carried out8Although open PD remains the standard treatment for benign and malignant periampullary tumors, it is cautiously thought that Lap PD can be a good alternative option for well‐selected patients with experienced laparoscopic pancreatic surgeons. The innate complexity of the procedure itself is the main pitfall of Lap PD. However, for Lap PD to become accepted as safe and feasible in general, standardization of the procedure is paramount. Our collaborative strategy of outside‐the‐operating room didactics and simulation and inside‐the‐operating room step‐by‐step mastery of the lap PD procedure may considerably overcome the volume‐based learning curve of lap PD.Conflicts of Interest: Authors declare no conflicts of interest for this article.


Motor deficits are the most common symptoms after stroke. There is some evidence that intensity and amount of exercises influence the degree of improvement of functions within the first 6 months after the injury.The purpose of this pilot study was to evaluate the feasibility and acceptance of semi-autonomous exercises with an upper extremity exoskeleton in addition to an inpatient rehabilitation program. In addition, changes of motor functions were examined.Ten stroke patients with a severe upper extremity paresis were included. They were offered to perform a semi-autonomous training with a gravity-supported, computer-enhanced device  six times per week for 4 weeks. Feasibility was evaluated by weekly structured interviews with patients and supervisors.Motor functions were assessed before and after the training period using the Wolf Motor Function Test (WMFT). The Wilcoxon Signed Rank Test was used for assessing pre-post differences. The Pearson correlation co-efficient was used for correlating the number of completed sessions with the change in motor function. Acceptance of the device and the level of satisfaction with the training were determined by a questionnaire based on visual analogue scales.Neither patients nor supervisors reported side effects. However, one patient had to be excluded from analysis because of transportation difficulties from the ward to the treatment facility. Therefore, analysis was based on nine patients. On average, 13.2 (55%) sessions were realized. WMFT results showed significant improvements of proximal arm functions. The number of sessions correlated with the degree of shoulder force improvement. Patients rated the exercises to be motivating, and enjoyable and would continue using the Armeo®Spring at home if they had the opportunity.Using an upper extremity exoskeleton for semi-autonomous training in an inpatient setting is feasible without side effects and is positively rated by the patients. It might further support the recovery of upper extremity function.ISRCTN42633681.The trial was retrospectively registered. Registration number  Stroke belongs to the most common causes of death and disability worldwide . The preIn our study, we were interested if technology-assisted exercises that are offered in addition to a conventional inpatient neurological rehabilitation program are accepted by the patients and if such an extra-training apart from the usual therapy schedule and without support by therapists is feasible. We included severely affected stroke patients without ability to use the upper extremity in activities of daily living. An exoskeleton that provides an adjustable arm support and allows gravity-supported and computer-enhanced arm exercises (ArmeoSpring) was chosen for the additional training . Severaln = 4) as well as after a hemorrhagic stroke (n = 6).Nine subacute patients (mean time since stroke = 9.6 weeks ± 3 weeks) and one chronic patient  were included. The group consisted of seven male and three female patients with a mean age of 59.2 ± 12.6 years. In four of the patients the right hemi-body was affected and six were left-side affected. Patients were included after an ischemic  and a spasticity ≥2 . The reason for choosing these thresholds for pain and spasticity was that higher degrees of pain or spasticity might interfere with training and assessments.The study was approved by the ethical committee of the University of Constance. Patients gave informed consent before entering the study.Feasibility was explored by structured interviews with patients and supervisors once per week. In addition, both groups were asked to report any unexpected events immediately. The interview focused on side effects during the training session and any adverse event in association with the training.In order to record the changes of arm and hand motor skills, the patients were tested at baseline and after the training period with the Wolf Motor Function Test (WMFT) . The WMFThe acceptance of the device and the level of satisfaction with the training were determined by seven questions Table . The ratThe number of realized training sessions (out of a maximum from 24 appointments) and the duration of each training session were recorded. Based on this, the percentage of utilization and the mean duration of the sessions were calculated.After termination of the treatment period and analysis of utilization patients were contacted by telephone in order to explore why the patients had not realized all offered sessions. We performed a semi-structured interview. First, we asked them to provide reasons for non-participation. Then, we specifically asked for motivational aspects, fatigue, factors as having visitors, staying at home on a weekend day, transient illnesses. The latter issue was also derived from the patient’s chart.We used the Armeo®Spring exoskeleton  which is a passive instrumented arm orthosis with a spring mechanism for adjustable arm weight support, combined with a training software program and a 3D workspace.The exoskeleton gives weight support to the patient’s paretic arm and hand. The amount of weight support, the training workspace as well as the complexity of the virtual tasks can be individually chosen and adjusted to the patient’s active movement capacity. Movement parameters include muscle strength, active range of motion, movement velocity, coordination, and the ability to lift the arm against gravity.In preparation of this study, Hocoma AG developed a self-training module within the Armeo®Control software which can be accessed via login passwort by the patient himself/herself, by a patient’s relative or by the training supervisor. Thus the patient is enabled to perform an individualized, semi-autonomous extra training without having to know the details of digital adjustment of the software and without the presence of skilled therapy staff. The choice and difficulty level of those individualized training tasks and games, however, can only be adjusted by skilled therapists.The semi-autonomous training was supervised by persons without therapeutical education who had been instructed how to adjust the exoskeleton to the affected arm and how to login in case the patient was unable to enter in his/her password. Once this setup was finished the patients had to exercise on their own. One patient was accompanied by his wife on a regular basis, all other patients were rarely accompanied by a family member (once per week).All participants received the conventional, intense neurorehabilitation program with a multidisciplinary approach offered at our institution. The treatments addressing the upper extremity included occupational therapy, upper extremity circuit training, exercises with the SAEBOflex , bimanual co-ordination exercises, functional electrical stimulation.Self-contained training with the Armeo®Spring device was possible on weekends and during early evenings. The room was open for 2 h per day. We recommended to perform exercises for 30 min per session. Thus, up to 3 patients could perform their training one after the other. It took 5 to 8 min to adjust the ArmeoSpring according to each patient’s individual needs. Therefore, a fourth patient would not have sufficient time for training within the given time window. The additional exercise opportunities were offered on 6 days per week for a period of 4 weeks. Thus, a maximum of 2 4 additional treatments was available,After baseline evaluation, an occupational therapist (who was member of the research group) defined the initial setup of software parameters individually. In the same session, an individualized, 30 min training was compelled for the patient, The following day was defined as the start of the training period.Further adjustments of the difficulty levels were done once a week according to the patient’s clinical development. In detail, the patient’s performance with the ArmeoSpring was assessed and more difficult programs were chosen if the patient showed a high performance level on the hitherto existing tasks. We carefully avoided excessive increases of task difficulty in order to prevent frustration .The statistical evaluation was carried out with IBM SPSS Statistics 24.p < 0,05.The “Wilcoxon Signed Rank Test”was used for assessment of pre-post differences. Correlations between the number of realized sessions and changes of motor performance were done with the Pearson correlation co-efficient. Statistical significance was set at On average, 13.2 appointments were used, corresponding to a percentage use of 55 ± 13.4%. The range of completed sessions was between 9 and 18, corresponding to a median of 61.9% with a range between 37.5 and 75%. The mean duration of each training session was 33 ± 8 min. The most frequent reason for omission of a session was being too fatigued by the regular training program (8 patients). Other reasons were: having visitors during the weekend (6 patients), spending one weekend day at home (5 patients), feeling not well due to a cold (3 patients), transient lack of motivation (2 patients), diarrhea (1 patient), low back pain (1 patient).The number of conventional therapy sessions aimed at improving upper extremity function was on average 6.7 per week, corresponding to 3.78 ± 1.1 h per week and 15.1 ± 4.5 h for the 4 week period. With additional semi-autonomous training the number increased to 9.6 sessions per week, corresponding to 5.39 ± 1.4 h per week and 21.6 ± 5.6 h for the 4 week period.The duration of inpatient rehabilitation ranged from 6 to 22 weeks with a mean of 12 ± 4.3 weeks. During this time, patients received a mean of 44.3 ± 16.4 h of therapies focusing on the upper extremity.A total of 15 different PC games was offered. In 14 games, patients trained horizontal abductions and adductions , in 8 games shoulder extension and flexion were exercised (eight patients), in four games grasping and releasing were trained (four patients), in three games elbow flexion and extension were exercised (four patients), in two games supination and pronation were trained (two patients) and in one game internal and external shoulder rotation was trained (one patient). The amount of anti-gravity mechanical support provided by the ArmeoSpring was adjusted by the supervisors on a weekly basis and changed from strong to less support.The correlation between the number of used appointments and pre-post differences was not significant for the 15 WMFT items; however, the co-efficient indicated a trend.r = 0.645; p = 0.061). No significant correlation was found for the seven WMFT items of shoulder and arm functions .  Fig. .Fig. 1ThResults show that patients rated the exercises to be motivating, enjoyable and easy to understand. The participants also stated that they were satisfied with their own performance of the exercises. They indicated that they likely would continue the training in their home environment if there was an Armeo®Spring device close to their home.The effect of the additional training at the Armeo®Spring was estimated by the patients in the middle section of the VAS scale. Furthermore, it was found that inserting and attaching the arm into the exoskeleton was classified as feasible but not simple.n = 4) and without neglect (n = 6). The allocation of patients to the group with or the group without neglect was based on detailed neuropsychological tests that detected neglect symptoms even without neglect being relevant in activities of daily living. If neglect had an impact on our method of data acquisition, neglect patients would have achieved higher numbers. The results between the two groups did not differ. We consider this as indirect evidence that there was no “mislocalization” when marking the position on the line. Moreover, during exercising with the ArmeoSpring, there was no indication of less attention for the left part of the screen.Patients suffering from neglect symptoms might have difficulties to correctly identify the middle of a line. Therefore, we re-analyzed the data by subdividing the group into patients with . She missed two of the appointments due to a cold and the other four appointments due to weekend days spent at home.This study demonstrates that semi-autonomous training with a exoskeleton is feasible for stroke patients with severe upper extremity paresis but it also indicates some limitations. To our knowledge, this is the first study to explore such a training within an inpatient rehabilitation period. Other groups have demonstrated that technology-assisted self-administered training is feasible at the patient’s home –24.During the treatment period, no adverse effects occurred. None of the patients aborted the study due to problems with the device or the exercises. Subjective ratings indicated an overall satisfaction with the additional treatment option. After the treatment period some motor functions were significantly improved. However, due to the lack of a control group, it is impossible to ascribe these improvements to the additional exercises.A major limitation of feasibility was the patient transportation from the ward to the treatment room and back. In order to keep additional involvement of staff as low as possible, we deliberately decided not to organize this transport by employees of the hospital. As a consequence, one of the patients had to be excluded from the study because he had been unable to attend the offered appointments due to transportation difficulties. This limitation is, of course, restricted to severely affected patients. Patients with minor to moderate motor deficits would not have had problems with reaching the treatment facilities. For future studies or the implementation of such an additional training as an adjunct to conventional in-patient rehabilitation the question of transportation needs to be solved.Fortunately, realisation of therapy was easy and without difficulty. The supervising persons were able to use the Armeo®Spring exoskeleton after a brief introduction of 3 h. They did not report problems with handling of device or patients. Thus, the staff requirements for such an additional training are limited.On average, the patients took advantage of only about half of the offered training appointments, with a considerable range of usage from a minimum of nine and a maximum of 18 used appointments. The reasons for not participating in all offered appointments varied. Fatigue induced by the regular inpatient exercise program was the most important issue. This suggests that for more severely affected patients the capacity for increasing the amount of therapies during an inpatient rehabilitation is limited. Our results suggest that 3 to 4 additional exercise sessions per week are well accepted but that 6 additional sessions per week are not feasible for all patients.After 4 weeks of additional training significant improvements of motor functions were found for shoulder force and for those items of the WMFT that evaluate proximal arm functions.. Since most patients were in the subacute phase after stroke and all participated in an inpatient rehabilitation program and due to the lack of a control group it is not possible to ascribe these improvements to the additional exercises. However, notably, motor improvements were most prominent for those functions that are typically trained with the Armeo®Spring. In addition, we found a correlation between the number of extra training sessions and the degree of shoulder force improvement. This may be interpreted as an indirect indication that additional exercises contributed to improvements of proximal arm functions. However, in order to assess the effects of additional training a randomized controlled trial is required. Several studies using the ArmeoSpring device have already demonstrated improvements in motor functions. Chan et al.  found anParticipants uttered a high acceptance of the training, ranking the exercises to be well understandable, motivating and enjoyable, with mean values between 8.67 and 7.04. The high value in stating the will to continue the training in an ambulatory setting emphasizes the motivation of the participants. Other research groups have published similar results indicating a higher level of acceptance for robotic therapies with gaming elements (e.g. ).The clamping of the arm into the exoskeleton was classified as feasible but not really simple. The patients judged their own performance in the exercises to be good. The answer with the lowest value and the highest standard deviation occurred when asking how strongly the training helped to improve their arm functions. Presumably, this reluctant answer is due to the fact that despite improvements of proximal arm functions it remained difficult to use the arm in activities of daily living because of a persistently impaired hand function.This study was designed as a pilot study. The significance is limited due to the small sample size, the lack of a control group and some heterogeneity of the group, since one of the patients was in the chronic phase after stroke.daily additional training is less accepted or may not be feasible.Semi-autonomous training with an upper extremity exoskeleton in addition to standard inpatient therapy was feasible and well-accepted by stroke patients with a severe upper extremity paresis. Preliminary data suggest that motor function improvement might be associated with the amount of additional exercises. The WMFT was sensitive enough to display the improvements. However, patients did not make use of all appointments that were offered, indicating that


The working–sleeping cycle strategy used for sensor nodes with limited power supply in wireless sensor networks can effectively save their energy, but also causes opportunistic node connections due to the intermittent communication mode, which can affect the reliability of data transmission. To address this problem, a data collection scheme based on opportunistic node connections is proposed to achieve efficient data collection in a network with a mobile sink. In this scheme, the mobile sink first broadcasts a tag message to start a data collection period, and all nodes that receive this message will use the probe message to forward their own source information to the mobile sink. On receiving these probe messages, the mobile sink then constructs an opportunistic connection random graph by analyzing the source information included in them, and calculates the optimal path from itself to each node in this random graph, therefore a spanning tree could be generated with the mobile sink play as the root node, finally, it broadcasts this spanning tree so that each node could obtain an optimal path from itself to the mobile sink to forward the sensing data. In addition, a routing protocol that adapts to different nodes operating statuses is proposed to improve the reliability of data transmission. Simulation results show that the proposed scheme works better concerning the packet delivery rate, energy consumption and network lifetime. As a popular way of information access, Wireless Sensor Networks (WSNs) have been widely used in smart industrial fields  to underThe use of mobile sinks in WSNs to replace the traditional static base stations for data collection is believed to be able to improve the network lifetime, and the feasibility of this scheme is demonstrated in details in Reference . UsuallyTo cope with this challenge, researchers have proposed the working–sleeping cycle strategy for sensor nodes, in which nodes can go to sleep to save energy while they are free of work. These studies usually focus on designing node-scheduling schemes to accomplish data transmission, in which the working–sleeping cycle strategy can be categorized into synchronous and asynchronous . TherefoIn fact, the reasons why opportunistic node connections exist in WSNs can be summarized as follows: (1) WSNs are often deployed in harsh environments where wireless signals are susceptible to interference, which may cause link instability , furtherThis work considers that all sensor nodes adopt an asynchronous working–sleeping cycle strategy to save energy and a mobile sink is used to collect data in the network, as shown in To deal with this problem, the random graph theory originated by the pioneering work of Erdős and Rényi  was adopIn this work, by taking the randomness of opportunistic node connections into account, we propose a novel random graph model named Opportunistic Connection Random Graph (OCRG) for WSNs. Inspired by the work of Fu et al. , who firAn opportunistic connection random graph is constructed to reflect the opportunistic node connections caused by an asynchronous working–sleeping cycle strategy;For each node, an energy efficient probe message forwarding mechanism is used to minimize the overall energy consumption in network when forwarding the source information to the mobile sink;A routing protocol which adapts to different nodes operating statuses is proposed to improve the reliability of data transmission when nodes are forwarding their sensing data along the calculated optimal path.In the scheme, first, the mobile sink can launch a data collection task anywhere in network at any time by broadcasting a tag message that declares its data collection period, and each node that receives this message will forward its source information  included in a probe message to the mobile sink. Here the energy efficient probe message forwarding mechanism is designed to minimize the overall energy consumption. On receiving these probe messages, the mobile sink first constructs an opportunistic connection random graph by analyzing the source information included in them, then calculates the optimal path from itself to each node in this random graph, and hence a spanning tree could be generated where the mobile sink play as the root node, and finally it broadcasts this spanning tree so that each node can obtain the optimal path from itself to the mobile sink, and according to which to forward the sensing data. In addition, a routing protocol which adapts to different nodes operating statuses is proposed to improve the reliability of data transmission when nodes forwarding their sensing data along the calculated optimal path. The experimental results show that this scheme can effectively improve the reliability of the data transmission while prolonging the network lifetime. The main contributions of this paper are summarized as follows:The rest of the paper is organized as follows: In traditional WSNs, all sensor nodes including the sink nodes are static, sensor nodes near the sink have more traffic loads for they have to participate in forwarding sensing data from all other nodes to the sink, therefore they easily exhaust their limited energy, and which will cause network partition. This problem is called the hot-spot problem  and it hTo address this problem, in recent years researchers have introduced the mobile sink concept to networks. By fully exploiting the mobility of the mobile sink, the nodes around the sink could change continually, therefore the energy consumption in routing is distributed more evenly in the network, and thereby it prolongs the network lifetime. According to the work of the previous researchers, the path design for mobile sinks can be classified into predefined paths , controlAll these approaches can equalize the energy consumption of nodes, but they are not flexible enough to prolong the network lifetime because they have not considered designing different node operating statuses. Therefore, the working–sleeping cycle strategy was introduced to WSNs, in which researchers considered that the proper scheduling of sensor nodes to sleep or work could effectively reduce their unnecessary energy consumption, thus prolonging the network lifetime.According to the node operating status, the researches can easily be divided into two main categories. In the first category, the studies aimed at synchronous working–sleeping cycle strategy, for example, in Reference , the autAll these schemes can reduce the nodes’ energy consumption, but the working–sleeping cycle strategy for sensor nodes will cause opportunistic node connections, which can further result in the link instability. Therefore, modelling this kind of WSNs is a challenging task, and thus random graph theory was introduced in WSNs.In Reference , the autIn this work, for any node who needs to send its source information that included in the probe message to the mobile sink, an energy efficient probe message forwarding mechanism is proposed. On receiving these probe messages and by analyzing the included source information, the mobile sink can determine the neighbor relationships of these nodes and calculate the link connectivity between any two adjacent nodes, and according to which, the mobile sink can construct an OCRG.This section gives an analysis of the network model and the energy model used in this work.r. In addition, all nodes adopt asynchronous working–sleeping cycle strategy for sensing and communication, and the working time α and the sleeping time γ for each node can be anisochronous. Therefore, sensor nodes can communicate with each other only when they are in their working statuses. Moreover, this network supports multiple mobile sinks to collect data and each mobile sink has a unique Sink ID (SID) to distinguish from each other, however, we only use single mobile sink to describe the design principle in this work for simplicity. The mobile sink can move randomly and collect data actively anywhere in network at any time, it will always be in the working status for having sufficient energy and has two adjustable radio range lR and sR, of which lR is the long radio range that is fixed in each data collection period but adjustable in different periods used to broadcast the tag message to launch a data collection task, and sR is the short radio range that is always equal to r used to transfer data. The symbols and parameters used in network are summarized in The network model used in this paper assumes that all sensor nodes are distributed in region Ω randomly and independently, and each node has a unique ID with radio range 1,t2] or .ampε be the energy consumed in the transmission amplifier, elecE be the basic energy consumed during transmitting and receiving per bit respectively, and dvi,vj) by a long radio range On receiving a tag message, by obtaining the duration for this data collection included in this message, a node can calculate its whole working time (according to its own working–sleeping scheduling) and its status transition  frequency during this data collection period, which will be used to construct the OCRG in further.For a node in current data collection scope, the method of Received Signal Strength Indication (RSSI) is used to estimate its distance to the mobile sink, the value of which is used to calculate its Expected Optimal Hops (EOH) (Definition 1) according to Lemma 1. The EOH of a node will be employed to select proper forwarders to minimize the overall energy consumption when forwarding the probe message to the mobile sink.In order to facilitate the sleeping node to participate in data collection when it wakes up, the mobile sink can choose to re-broadcast the tag message randomly, and in this case, the nodes that have received the same tag message will not deal with it again.Definition 1.Expected Optimal Hops (EOH). The Expected Optimal Hops denote the number of hops it takes to forward a probe message from any node to the mobile sink with the minimized energy consumption.It should be noted that EOH is different from the shortest path, according to the energy model, the energy consumption for a node to transfer data to the mobile sink is not linearly related to the length of the data transmission path.Lemma 1.i in a data collection scope, its EOH satisfies:For any node v is the distance between node vi and the mobile sink.where dProof of Lemma 1.B-bit data from node vksin along the path , where k is the hops on the path and satisfies 1 ≤ k ≤ N − 1. To unify the path representation, vksin is represented by i+kv in the next proof process, from which it means that it needs k hops to forward a probe message from iv to vksin. Then, the energy consumption function with respect to k for this forwarding can be calculated as follows:Assuming that there is viC(k), we can use the average value inequality to derive inequality of viC(k) which can be described as follows:To get the minimum value of iv, ivk+, k) satisfies the following inequality:Since the sum of the distances for any two adjacent nodes on the path  included in the probe messages to the mobile sink. The format of the probe message is given in The “Message Source” field is used to indicate the ID of the node sending this probe message. The “Source Information” field is used to store the whole working time, the status transition frequency, and the neighbors’ IDs of the message source. The “Sink ID” field indicates the SID of the mobile sink launching this data collection task, and which is also the forwarded destination for the probe messages. The “Forwarders ID” field is used to store the IDs of nodes that have forwarded this probe message in sequence. In the process of forwarding a probe message, each time the message is relayed by a node (forwarder), it should add its ID in the “Forwarders ID” field in the probe message. The “EOH” field is used to store the value of EOH for the message source.Since a probe message can be generated from any node that received a tag message and the opportunistic node connections in the network decrease the efficiency of probe message forwarding, it is necessary to design an energy efficient probe message forwarding mechanism to minimize the overall energy consumption when forwarding them to the mobile sink.mv receives a probe message, it will check the IDs stored in “Forwarders ID” field in this probe message to learn whether it has forwarded it or not.In the mechanism, only the nodes that have received this tag message can participate in the probe message forwarding. When an intermediate node mv has not forwarded this message, as shown in mv has forwarded this message, as shown in mv, nv from it and adds its ID in it. In the next, by calculating NF based on this field and obtaining the value of EOH in this message, mv can further calculate (EOH–NF) to find a neighbor whose EOH is closest to it from the explored neighbors as an optimal forwarder.Here if mv receives this probe message from pv, if only the neighbor pv is in working status, as shown in pv. However, if pv is also in sleeping status, as shown in mv stops forwarding it. Algorithm 1 gives the detailed energy efficient probe message forwarding mechanism.Considering the asynchronous working–sleeping cycle strategy for nodes, when Algorithm 1. Energy efficient probe message forwarding mechanism1. mv receives a probe message:When an intermediate node 2. if (mv has not forwarded the probe message)3. Add its ID in the “Forwarders ID” field included in the probe message;4. Calculate NF based on the “Forwarders ID” field;5. the EOH is obtained from the “EOH” fieldCalculate (EOH–NF);  // 6. if (mv has neighbors)  //p is not includedv7. Select the neighbor whose EOH is closest to (EOH–NF) as an optimal forwarder;8. Forward the probe message to it;9. end if10. else11. m has forwarded the probe message to vn, but then receives this message again from itsuppose that v//12. Explore the neighbors that have not forwarded this probe message;13. mv, nv from the “Forwarders ID” field;Delete the IDs of 14. mv adds its ID in the “Forwarders ID” field;Node 15. Calculate NF based on the “Forwarders ID” field;16. Calculate (EOH–NF);17. if (the explored neighbors exist)18. Select the neighbor whose EOH is closest to (EOH–NF) as an optimal forwarder;19. Forward the probe message to it;20. end if21. end if22. if (only the neighbor pv of mv is in working status)23. pv;Forward the probe message to 24. else  //m is in sleeping statusv25. Stop forwarding this probe message;26. end ifAfter receiving these probe messages, the mobile sink constructs an OCRG (Definition 2) by analyzing the included source information to reflect the opportunistic node connections in this data collection scope.Definition 2.e).Opportunistic Connection Random Graph (OCRG). The OCRG is constructed based on the intermittent communication caused by asynchronous working–sleeping cycle strategy of nodes, which can be analyzed from all the source information, to reflect the opportunistic node connections in the data collection scope, denoted as G and (13), Based on the analysis above, the mobile sink can first obtain the message source set V by gathering their IDs stored in the “Message Source” field included in the probe messages, and then obtain the edge set E by analyzing the neighbors’ IDs of each message source that stored in the “Source Information” field, by gathering all message sources’ whole working time and status transition frequencies stored in the “Source Information” field it can calculate the link connectivity between any two adjacent nodes in set V according to Equation (14), thus constructing an OCRG.By constructing OCRG, the mobile sink models the opportunistic node connections in the data collection scope, based on which, it could calculate the optimal data forwarding path in advance for each node to send their sensing data to improve the reliability of data transmission. Furthermore, the source node could obtain its data forwarding path in advance therefore reduce the delay in each hop, and due to the intermittent communication mode of the nodes, it could also improve the success rate of the data transmission.iv, jv and kv that adopt the asynchronous working–sleeping cycle strategy to save energy. Nodes iv and jv are adjacent neighbors while jv and kv are adjacent neighbors, and the link connectivity between them are iv is not adjacent to jv, their link connectivity Pivkv is 0.Once the OCRG is constructed, it needs to find the optimal path from any node to the mobile sink to realize the reliable sensing data forwarding. In this work, a spanning tree algorithm (Algorithm 2) is designed to calculate the optimal path with the max value of Path Connectivity (PC) (Definition 3) from the mobile sink to each node based on this OCRG. By employing this algorithm, the mobile sink can produce a spanning tree, based on which, each node can get its optimal path to the sink with the corresponding PC of it. Therefore, the mobile sink will broadcast this spanning tree to nodes under the long radio range Definition 3.Path Connectivity (PC). In the OCRG, the PC of a path is related to the link connectivity between any two adjacent nodes on this path, which is used to reflect the reliability of this path when delivering data. As for a path  set K: including the nodes whose optimal paths from the mobile sink to themselves are known, and (ii) set U: including the remaining nodes. In the beginning, set K includes only the mobile sink while set U includes the remaining nodes in the OCRG, and a node in set U will be transferred to set K if the mobile sink finds the optimal path to it.The algorithm includes two phases, of which the first phase is initialization. In this phase, the mobile sink calculates the PC of the paths from itself to all nodes in set U as follows:And the nodes on each path can be denoted as follows:In the second phase, the mobile sink selects a node For each path, once the PC of it is updated, the nodes on it should be updated as follows:Repeating the work in second phase until set U is empty, a spanning tree with the mobile sink as the root node can be generated.The algorithm improves the efficiency of finding the optimal path. If the mobile sink calculates and selects the optimal path of each node directly, for each node, it needs to explore all the possible paths between them to determine which one has the maximum PC, which is inefficient and brings high delay. Furthermore, when the network density increases or the data collection scope expands, the number of the paths from a node to the mobile sink increases greatly, which could further decrease its efficiency.Algorithm 2. The spanning tree algorithm1. Input: an OCRG;2. Output: a spanning tree with the mobile sink as the root node;3. Add 4. Add the remaining nodes in the OCRG into set U;5. for each node do //  initialization6. if (7. is the PC of the path fromto8. is used to store the nodes on the path fromto9. else10. 11. 12. end if13. end for14. set the PC of the path fromto15. while (set U is not empty)16. Select the node 17. Transfer 18. for each neighbor do    //is still in set U19. temp ←20. if  used in this table indicates the PC of the path from the mobile sink to node When the spanning tree is generated, the mobile sink should broadcast it to the nodes under its long radio range On receiving these probe messages, the mobile sink could re-construct an OCRG, then re-calculate the optimal path from itself to each node in this OCRG and update the spanning tree accordingly.In fact, for a node, its optimal path on the spanning tree is the most reliable path for it to forward its sensing data to the mobile sink. However, due to using the asynchronous working–sleeping cycle strategy for nodes, so during data transmission process along this path, any forwarder on the path may be in sleeping status which could lead to the failed link connection, it further causes the failure of data transmission. To solve this problem, a routing protocol that adapts to different nodes operating statuses is proposed to improve the reliability of data transmission and Algorithm 3 gives the detailed routing protocol. In this routing protocol, assuming that the sensing data from node --For each neighbor Algorithm 3. The routing protocol1. Assuming that the sensing data from node 2. When an intermediate node 3. if  than that in ExOR and RPRDC as As shown in The proposed scheme outperforms POFA when the number of nodes in network is less than 900, but as the network density increases continuously, POFA performs better. This can be explained by that in POFA, a node needs to select multiple forwarders to achieve its target reliability, and the improvement of network connectivity increases the possibility of achieving this target reliability rapidly, which further improves its PDR. The main reason that the proposed scheme is always performs better than ExOR and RPRDC can be explained by the different routing strategies they employed. In RPRDC, the routing is divided into random dispersion and reliability path exploration, of which the packet reception rate, residual energy, and link quality of the node are considered, but it lacks the global information between the node and the sink. Furthermore, ExOR adopts the metric ETX associated with the link connectivity in network, to reflect the expected transmission times required to forward a data from a node to the mobile sink, and it selects a node with a minimum value of ETX as the forwarder during the data forwarding. However, in the proposed scheme, the metric PC reflects the connectivity of a path directly and the routing protocol can guarantee the data always be forwarded along a path with a max value of PC, so it achieves a higher success rate of data delivering than that in ExOR and RPRDC.In the next scenario, we conduct a simulation to evaluate the performance of these four algorithms in PDR with a large enough data collection scope, in which the mobile sink keeps stationary in the center of network and the long radio range The PDR in POFA is always higher than that in the proposed scheme, ExOR and RPRDC, which can be explained by that, in POFA, this large data collection scope increases the number of possible paths for a source node to send its sensing data to the mobile sink, which improves the success rate of data delivering greatly. However, in the proposed scheme, ExOR and RPRDC, this large scope increases the number of hops the nodes that near the edge of the data collection scope takes to forward their sensing data, which decreases the success rate of data delivering greatly. In addition, the proposed scheme achieves a better performance in PDR than that in ExOR and RPRDC. Since the node adopts the intermittent communication mode, the delay of data delivering in each hop will affect the success rate of this forwarding, especially when the node is far away from the mobile sink. In ExOR, a node needs to run a protocol to explore the neighbors that received the data and from which to select forwarders, therefore it delays the data forwarding and then decreases the success rate of data delivering. During the reliable path exploration phase of RPRDC, a node needs to calculate the reliability of its neighbors to select the optimal forwarder, thus causing additional delay. Compared with ExOR and RPRDC, in the proposed scheme, the path for a source node to forward its sensing data is calculated in advance, so it has a shorter delay in each hop of data forwarding, which is the main reason that it can achieve almost five times and four times improvement in PDR over ExOR and RPRDC, respectively. In addition, our proposed routing protocol can change the current path adaptively when it is failed, thus blocks the decline of the PDR.In this section, two scenarios are designed to evaluate the performance of EC in network. In the first scenario, we evaluate the EC for a source node to forward its sensing data to the mobile sink successfully. In the second scenario, we evaluate the total EC in network varies by time.Lots of tests show that the EC increases as the network density expands and it increases more obviously in POFA than that in the proposed scheme, ExOR and RPRDC. The main reason is that the increased number of nodes increases the hops a source node takes in date delivering, as shown in The EC in the proposed scheme is slightly higher than that in ExOR, and they are much lower than that in POFA. The reason is that, in POFA, its data forwarding strategy increases its PDR by selecting multiple forwarders but at the expense of energy, as network density expands, the improved network connectivity increases the success rate of each hop of data forwarding, which further increases hops and the times of reliability calculation it takes, so that the EC in it is always high. In the proposed scheme, the neighbor of a node increases as the network density increases, when a node on the optimal path adjusts the path due to the next hop node is in sleeping status, it needs to select an optimal neighbor that can maximized the PC of the path from it to the sink, this process increases the times of calculation by using the PCs of all neighbors, which further increases the EC.The EC in the proposed scheme is slightly higher than that in ExOR, but they are much lower than that in POFA. In POFA, each node selects multiple forwarders to achieve the target reliability until one of them connected to the mobile sink, the number of forwarders increases greatly as In the proposed scheme, the total EC is mainly consist of the energy consumption caused by the probe message forwarding and the sensing data delivering. By employing the EOH metric, the proposed energy efficient probe message forwarding mechanism can decrease the energy consumption for forwarding the probe message. By analyzing these messages, the mobile sink could construct the spanning tree and broadcast it, so the source node could obtain its optimal path with the max PC to the sink before sending its sensing data. Therefore, during data delivering, a node can save the energy consumed by selecting the forwarders.In this section, the mobile sink can launch multiple data collection tasks anywhere in network randomly, and we conduct simulations to evaluate the performance of NL according to the number of death nodes, of which the NL is defined as the lifetime for 25 percent nodes that exhaust their energy in network.In Reference , the autIn POFA, the node dies faster than that in the proposed scheme, ExOR and RPRDC. The main reason is that it always seeks to improve the reliability of data transmission in each hop, but at the expense of energy consumption, which speeds up the death of nodes. In addition, the time of the death of 200 nodes (25 percent nodes in network) in the proposed scheme is longer than that in ExOR, POFA and RPRDC. The reason is that, despite the nodes on the optimal paths may take more data forwarding tasks, which can reduce their lifetime and furthermore decreases the network connectivity. However, by calculating the optimal path for nodes in advance to forward the data, and employing the flexible routing protocol that could change the data forwarding path adaptively in the low connectivity network, the proposed scheme consumes less energy of nodes, which is also the reason that as the number of the data collection tasks launched by the mobile sink increases, the time for the death of the same number of nodes in the proposed scheme is getting longer than that in ExOR, POFA and RPRDC.The proposed data collection scheme is also applicable to the scenario where multiple mobile sinks employed in network simultaneously, by considering the distance between the mobile sinks, a feasible scheme is proposed. To show how it works in detail, two mobile sinks are taken as an example, as shown in In In this scenario, the mobile sinks could use the proposed data collection scheme to perform their own data collection tasks directly.In In this case, the data collection scope of the two mobile sinks are overlapped. To clarify the data delivering destination for nodes within the overlapping area, when a node receives a tag message for the first time, it takes this SID of a mobile sink included in the message as its data forwarding destination until the data collection task is completed, and during this process, it neglects other mobile sinks’ data collection task even if it receives the tag messages they broadcast.This scheme increases the flexibility of data collection, and by using multiple mobile sinks, it can collect data from multiple network regions simultaneously, which is applicable in prospect applications.In this paper, we propose a novel data collection scheme based on opportunistic node connections in network with a mobile sink, which can be used in smart industrial fields. In the scheme, the mobile sink can launch a data collection task anywhere in network at any time by broadcasting a tag message, a node that receives this message can forward its probe message that includes its source information to the mobile sink by using the energy efficient probe message forwarding mechanism to minimize the overall energy consumption. On receiving these messages, the mobile sink first adopts the random graph theory to constructs an opportunistic connection random graph, then calculates the optimal path from itself to each node in this graph, hence a spanning tree is generated where the mobile sink is the root node, and it finally broadcasts this spanning tree to all nodes under its long radio range so that they can obtain the optimal paths from themselves to the mobile sink. Accordingly, a routing protocol which adapts to different nodes operating status is proposed to improve the reliability of data transmission. The simulation results show that the proposed scheme works better concerning the packet delivery ratio, energy consumption and network lifetime.The possible future work are, first, studying the synergy between mobile sinks, and exploring the impact of the comprehensive factors such as the number of mobile sinks and the their long radio ranges on data collection efficiency. Second, studying the energy efficient cross-layer protocol design , so that


MV was recorded with the iLOAD® app by two independent researchers to evaluate the inter-rater agreement.Sixteen young healthy individuals (four women and 12 men) were tested in two sessions separated by 48 h. The 10 repetition maximum (RM) load was determined in the first testing session in the half squat exercise. The second testing session consisted of 3 sets of 10 repetitions during the half squat exercise performed against the 10RM load. Both the r ≥ 0.987), as well as for the whole training session . Trivial-small differences and nearly perfect correlations were observed between the iLOAD® app and the linear encoder  for MV  and total work . Bland-Altman plots did not reveal heteroscedasticity of the errors between the iLOAD® app and the linear encoder for MV (r2 = 0.010) and total work (r2 < 0.001).Trivial differences and nearly perfect correlations were observed between raters for the MV values collected under individual sets (effect size [ES] ≤ 0.02, iLOAD® is a valid smartphone app which can provide real-time feedback of the MV and total work completed in a set of multiple repetitions in the half squat exercise. Resistance training (RT) is a fundamental part of training for competitive athletes  as well PowerLift® app has been validated for measuring mean velocity (MV) of individual repetitions during several RT exercises  . Smartphxercises . Howeverrotocols .iLOAD® app. The ®iLOAD app provides the MV (m s−1) and total work (J) of a training set in real-time using the smartphone’s timer and calculator. However, the iLOAD® app has not been scientifically validated. Thus, the main objective of this study was to validate the ®iLOAD app for RT monitoring during the half squat exercise. The half squat exercise was chosen because it is related to daily physical activities such as standing up from a sitting position and it has also been demonstrated to be effective for strength and muscle mass development, performance enhancement and injury prevention  to compare the magnitude of the MV and total work of a training session between the ®iLOAD app and a linear encoder (reference method). It was hypothesized that a high level of agreement would be obtained between raters (rater 1 vs. rater 2) and devices (®iLOAD app vs. linear encoder). Of note, it would be important to obtain a high level of agreement between raters to confirm that the outcomes collected with the ®iLOAD app do not depend on the rater. The confirmation of our hypotheses would place the ®iLOAD app as a cheap, portable and time-efficient tool for RT monitoring.To address this gap, our research group has recently developed the evention . SpecifiSixteen young healthy individuals, four women  and 12 men , volunteered to participate in this study. All participants were familiar with the half squat exercise and had at least one year of RT experience. Prior to testing and after detailed explanation of the procedures and risks of the study, participants gave their written consent to participate in the study. The study protocol adhered to the tenets of the Declaration of Helsinki and was approved by the Catholic University of Brasilia (54813016.0.0000.0029).®iLOAD app for monitoring MV and total work during a RT session  and a linear encoder  were used to calculate MV and total work of each training set. After familiarization with the ®iLOAD app, two independent researchers recorded MV over the training sets with the ®iLOAD app to evaluate the inter-rater agreement. The average value of both raters was considered to explore the concurrent validity of the ®iLOAD app with respect to the linear encoder. Both testing sessions were performed at the same time of the day for each participant.This study was designed to determine the validity of the  session . Partici®iLOAD app for the computations of MV and total work. This measurement was collected while the participants held the unloaded Smith machine barbell (17 kg). The 90° knee angle was determined with a manual goniometer . To ensure a consistent countermovement depth during all repetitions, an elastic cord was positioned to contact with the participants’ buttocks when they reached a 90° knee angle. In addition, an adhesive tape was located on the ground to instruct the participants to place their feet always in the same position. After these measurements, participants completed a warm-up consisting of 5 min of submaximal running on a treadmill at a self-selected pace, followed by 15 repetitions with the 17 kg bar of the Smith machine used in the present study . Thereafter, the 10RM load during the half squat exercise was evaluated following the protocol proposed by the American College of Sports Medicine  (All measurements were conducted at the same laboratory (“Laboratório de Estudos da Força” of “Universidade Católica de Brasília”). Anthropometric data was assessed at the beginning of the first session with a stadiometer  and an electronic scale . The vertical distance of the barbell for each participant between a knee angle of 90° and the standing position (hips and knees fully extended and feet flat on the floor) was determined with a measuring tape . This distance was introduced in the nterval) . The iniThe warm-up of the second testing session consisted of 5 min of submaximal running on a treadmill at a self-selected pace, 15 repetitions with the unloaded Smith machine barbell, and five repetitions with the previously determined 10RM load. Three minutes after completing the last warm-up set, participants were instructed to perform three sets of 10 repetitions during the half squat exercise against the 10RM load with 3 min of rest between sets. Participants were instructed to complete all sets as quickly as possible maintaining the same range of motion during all repetitions. All sets started with a ’go’ instruction from one of the raters, and were considered finished when the concentric phase of the last repetition was completed.®iLOAD app and the linear encoder:Mean velocity (MV) and total work of the three sets were calculated from the recordings of both the ® appiLOAD: The ®iLOAD app was installed in two smartphones  with an actualized operating system . Two independent raters were positioned in front of the participants and recorded the time needed to complete each set. The raters were familiarized with procedures during two preliminary sessions which consisted of the same protocols. The inputs of the ®iLOAD app for each set were the load (in kilograms), number of repetitions, vertical distance of the barbell, and time needed to complete the set (in seconds). The time needed to complete each set was determined by the chronometer of the smartphone. The smartphone’s chronometer was initiated after the ’go’ signal used to indicate the start of the set in the ®iLOAD app and it was stopped when the subject completed the last repetition of the set . Of note, because of the greater mechanochemical efficiency during the eccentric action  when compared to the concentric action  of a single complete repetition  was connected to a laptop  with custom made software . The cable of the linear encoder was fixed perpendicularly to the barbell and recorded displacement-time data at 1,000 Hz. An Excel® spreadsheet was used to calculate the MV and total work from the raw displacement-time data provided by the software as follows: - p > 0.05). The inter-rater agreement for the recordings of MV with the ®iLOAD app, as well as the concurrent validity of the ®iLOAD app respect to the linear encoder for measuring MV and total work were assessed by independent samples t-tests, Cohen’s d effect size , Pearson’s correlation coefficients (r) and Bland-Altman plots. Note that the total work was not compared between raters because its value does not depend on the time recorded by the raters . Heteroscedasticity of error was defined as a r2 > 0.10  as well as for the whole training session . Bland-Altman plots also revealed very low systematic bias (≤0.003 m s−1) and random errors (≤0.033 m s−1), while heteroscedasticity of the errors was observed for the sets 2 (r2 = 0.208) and 3 (r2 = 0.199), but not for the set 1 (r2 = 0.045) or the whole training session (r2 = 0.074)  .®iLOAD app with respect to the linear encoder. Although significant differences between the ®iLOAD app and the linear encoder were observed for MV during the sets 2 and 3 as well as for the whole training session (p < 0.05), the magnitude of the differences were trivial-small and the correlations were always nearly perfect between both devices for MV and total work   .®iLOAD app with respect to a linear encoder (reference method) for monitoring MV and total work during a RT session conducted with the half squat exercise. The experimental data collected in the present study supported our two hypotheses. Namely, the ®iLOAD app showed a very high inter-rater agreement for the recordings of MV, and also a very high validity for the measurements of MV and total work when compared to the data collected with the linear encoder. These results highlight that the ®iLOAD app could be a valuable tool for RT monitoring because it is cheap, easy to use, portable and time-efficient.This study was designed to determine the concurrent validity of the ®PowerLift . It should be noted that the main difference between both apps is that ®iLOAD provides the MV of a training set  and ®PowerLift reveals the MV of the concentric phase of individual repetitions. Therefore, these apps provide complementary information that could be valuable for prescribing and evaluating the effect of RT programs. Collectively, these results highlight that the outcomes of different smartphone apps specifically designed for monitoring movement velocity should not differ between different evaluators. This result could be expected because smartphone apps  are very easy to use. However, it would be important to determine in further studies the potential effect of testers’ experience with the use of smartphone apps on the accuracy of their outcomes.Our first hypothesis was confirmed since the inter-rater agreement for the measurement of MV was very high. The inter-rater agreement was comparable to the results reported by ®iLOAD app showed a very high level of agreement with respect to the MV collected with the linear encoder. Previous studies have also observed a high validity of ®PowerLift for measuring the MV of individual repetitions during a variety of RT exercises compared to a linear encoder (®PowerLift app), but also for monitoring the MV of a set of multiple repetitions (®iLOAD app). However, it should be noted that, in the present study, the MV values collected with the ®iLOAD app were slightly lower compared to the MV values provided by the linear encoder . These results suggest that the data collected with the ®iLOAD app should not be used interchangeably with the data provided by a linear encoder when the expected differences are small. Our results reinforce the potential applicability of the ®iLOAD app for monitoring RT based on movement velocity. However, it remains to be elucidated whether the MV of a set may guide coaches and athletes in the same manner as traditional velocity-based training which is based exclusively on the velocity of the concentric phase (The linear encoder is frequently considered as the gold-standard for monitoring movement velocity during RT exercises . Support encoder  or a hig encoder . Therefooder see . This reic phase .®iLOAD app and the linear encoder in all sets. These results suggest that the total work of a RT session can be accurately quantified with the ®iLOAD app. The only inputs needed by the ®iLOAD app to calculate total work are the vertical displacement of the barbell during a single repetition, the user body mass, the load lifted, and the number of repetitions performed. To our knowledge, ®iLOAD is the first smartphone app that has been designed to quantify total work during RT sessions. The recording of total work is important because it is considered as one of the most objective measures to quantify the total volume during RT, and it is also one of the most appropriate methods for equating training volume in different RT exercises (®iLOAD app allows practitioners to obtain real-time accurate measures of the total work performed during a RT session. This augmented feedback may help to improve both physical performance (Regarding total work, no significant differences and nearly perfect correlations were found between the xercises . Note thformance  and psycformance  in athle®iLOAD app is not without limitations. The main issue related to the ®iLOAD app is that the MV encompasses the whole training set and not only the MV of the concentric phase of individual repetitions. Note that velocity-based RT guidelines has been proposed considering only the MV of the concentric phase of individual repetitions (®iLOAD app could also provide valuable information to prescribe and monitor RT programs. Another important issue is that we only examined the validity of the ®iLOAD app for sets consisting of approximately 10 repetitions and, consequently, future studies should clarify whether the ®iLOAD app can also provide accurate data when performing a lower number of repetitions. Finally, for testing purposes, it would also be important to determine the reliability of ®iLOAD app for the measurement of MV during sets consisting of different number of repetitions in a variety of RT exercises.The use of the etitions . Therefo®iLOAD app showed a high validity for monitoring the MV and total work in a set of multiple repetitions during the half squat exercise. Therefore, the ®iLOAD app can be considered as a cheap, easy to use, portable and time-efficient tool for RT monitoring. Future studies should explore the validity of the ®iLOAD app for RT monitoring with other RT exercises.The main finding of the present study is that the 10.7717/peerj.7372/supp-1Supplemental Information 1Data used for statistical analysisClick here for additional data file.10.7717/peerj.7372/supp-2Supplemental Information 2Zip file with code.Click here for additional data file.