This study aims to enhance conventional vibration energy harvesting systems (VEHs) by repositioning the piezoelectric patch (PZT) in the middle of a fixed–fixed elastic steel sheet instead of the root, as is commonly the case. The system is subjected to an axial simple harmonic force at one end to induce transversal vibration and deformation. To further improve power conversion, a baffle is strategically installed at the point of maximum deflection, introducing a slapping force to augment electrical energy harvesting. Employing the theory of nonlinear beams, the equation of motion for this nonlinear elastic beam is derived, and the method of multiple scales (MOMS) is used to analyze the phenomenon of parametric excitation. This study demonstrates through experiments and theoretical analysis that the second mode yields better power generation benefits than the first mode. Additionally, the voltage generation benefits of the enhanced system with the added baffle (slapping force) surpass those of traditional VEH systems. Overall, the proposed model proves feasible and holds promising potential for efficient vibration energy harvesting applications in various industrial sectors. Advancements in technology and global population growth have catalyzed the growth of green energy, a pivotal aspect of the emerging industrial revolution. Within the realm of eco-friendly energy sources, vibration energy, despite its significance, often remains underexplored. Vibrations, prevalent in diverse settings from compact devices to substantial structures like buildings and vehicles, offer a potential yet untapped resource. A focal point of current research lies in vibrational energy harvesters (VEH) designed to efficiently harness this energy. The conventional approach involves utilizing a piezoelectric patch (PZT) on an elastic steel sheet to convert mechanical energy into electrical energy during sheet vibrations, known as single elastic-steel VEH systems (SES-VEHs). However, this configuration demands extended and pliable PZT patches, increasing costs while seeking enhanced efficiency. A novel alternative, double elastic-steel VEH systems (DES-VEHs), has been proposed by some researchers. This approach positions the PZT patch at the free end of a single elastic steel sheet, which is subsequently subjected to impact force from another sheet. The DES-VEH eliminates the need for elongated and delicate PZTs. Nonetheless, challenges persist in achieving optimal deformation and power generation simultaneously. The ongoing exploration of this domain exhibits the potential to revolutionize energy-harvesting methods, contributing to reduced environmental impact. This study aims to enhance the conventional vibration energy harvester (VEH) design by positioning a PZT on a fixed–fixed elastic steel sheet. Transverse vibration and deformation are induced by applying a simple harmonic force axially to one end of the fixed–fixed steel sheet. At the juncture of maximum deformation (possibly near the midpoint), a baffle is introduced to generate an impact force (slapping) on the PZT, thereby increasing energy conversion. Through the integration of the advantages of SES-VEH and DES-VEH, this approach achieves optimal power generation efficiency.VEHs do not require external power and possess superior power–electricity coupling, making them compatible with microelectro-mechanical system (MEMS) fabrication. Moreover, their broad applicability is attributable to the lack of additional devices such as coils and magnets. The traditional method for applying piezoelectric energy involves accumulating energy before supplying power to other electronic devices. However, Sodano and Inman  broke thShibata et al.  installeIn recent years, there has been a surge in research on energy harvesting systems that rely mainly on impact force. Notably, several new studies were published almost simultaneously, demonstrating the growing importance of this field. One example is the work of Fu et al. , who useMokhtari et al. ,16 proviZhu and Zu  attachedDerakhshani et al.  developeMei et al.  introducIn addition, when buckling beams are applied to objects undergoing severe vibrations, the system is typically placed on the ground, and energy is generated by utilizing the weight of passing vehicles or crowds. Ansari et al.  proposedDrawing from the discussed theoretical models, numerical analyses, and experimental applications, this study investigates the axial actuation amplitude and frequency of a nonlinear fixed–fixed Euler–Bernoulli beam. It analyzes the beam’s vibration stability and power generation efficiency across different modes and amplitudes, introducing an additional baffle to induce slapping force. A comparative assessment of power generation efficiency with and without the supplementary baffle aims to identify the optimal input frequency and baffle placement for efficient slapping energy. This design offers dual operational modes: vertical placement into the ground  is employed to analyze this phenomenon.Analyzing parametric excitation led to the determination of the system’s unstable range, revealing the benefits of energy harvesting. The unstable range was validated through numerical analysis and fixed-point plots. Furthermore, the accuracy of the fixed-point plots was confirmed through the application of the fourth-order Runge–Kutta (RK-4) numerical method to generate time–response and phase plots. The maximization of the benefits of electrical energy conversion was achieved by combining the nonlinear equation with the piezoelectric equation while varying external forces and frequencies.In the second segment of this study, a simple experiment was conducted using an elastic steel sheet to replicate the behavior of an elastic beam. Fixed boundary conditions for the beam’s ends were established using a C-shaped device. One end of the beam was held stationary, while the other end featured a horizontal sliding track and an actuator to induce vibration disturbances imitating buckling behavior. The experiment comprised two groups. Initially, the point of maximum deformation was identified using the elastic beam’s mode shape. Subsequently, a comparison was made between the power generation efficiency of piezoelectric patches placed at the root and at the location of maximum deformation. Subsequent to this, a piezoelectric patch was positioned at the point of maximum deformation, and a baffle was introduced to enhance the impact force. This facilitated the determination of the highest power generation efficiency and the validation of the accuracy of the theoretical model.The rapid growth of wearable technologies calls for innovative advancements in energy generation systems. This work responds to this demand by introducing a unique approach to vibration energy harvesting. This study addresses the limitations of existing methods by strategically positioning a piezoelectric patch at the peak deformation point of an elastic steel sheet. This deliberate placement optimizes energy conversion efficiency by harnessing the maximum mechanical stress during vibrations. Additionally, the integration of an augmenting baffle introduces a novel element that amplifies the voltage generation capabilities of the system. By exploring the distinct advantages of the second mode and investigating the impact of the baffle, this research unveils new dimensions in vibration energy harvesting effectiveness. This study additionally investigates the frequency response of parametric excitation, extending the resonant frequency range around the linear natural frequency. This expansion contributes to a broader usable bandwidth compared to conventional designs.This study employs a nonlinear Euler–Bernoulli beam as the theoretical model. The elastic beam is fixed at one end, while the other end contains a roller allowing horizontal sliding. To simulate the buckling phenomenon, an actuator is positioned at the slidable end of the beam. This study investigates the buckling behavior of the elastic beam by applying external forces and varying the frequency. To evaluate power generation efficiency, piezoelectric patches (PZTs) are strategically placed at two specific locations along the beam: the point of maximum deformation and the root. A comparative analysis is conducted to determine the effectiveness of these locations in generating power. For a more comprehensive understanding of the coordinate definition and the composition of the two-dimensional theoretical model, please refer to E is the Young’s modulus of the beam, A is the cross-sectional area of the beam, I is the moment of inertia of the beam, ’ represents the differential with respect to m/EA is extremely small. After dividing Equation (1) by EA, the longitudinal inertial force Based on the nonlinear beam theory of Neyfeh and Pai , the twoThe following boundary conditions are assumed:c1 and c2 can be obtained from the boundary conditions (Equation (3)) as The coefficients In order to make the research convenient for future analysis, the dimensionless form of Equation (4) can be obtained by firstly dividing equation (4) by From the research of Rajora et al. , it is kfC is the piezoelectric coupling coefficient, and pC is the capacitance of the piezoelectric patch. lP , then lP. Dividing Equation (9) by The force acting on the beam by the PZT is expressed as:Dividing Equation (10) by W can be expressed as:The MOMS divides time into two scales—fast and slow; let The end-point axial force is assumed to be a time-varying function, which can be expressed as The The The W0 is divided into the spatial and time domains, and defined as:The separation of variables method is used to find the mode shape of the system. The lateral deformation Substituting Equation (19) into Equation (16) gives:m = 1, 2, 3, …. The mode shapes of the elastic beam can then be obtained as follows:Using the boundary conditions, the characteristic equation of the elastic beam can be obtained as follows:By defining The The Z is the dimensionless amplitude of the axial disturbance.The System frequency is defined as Bm0 represents the amplitude of the mth mode, the subscript m represents the mth mode, and the subscript 0 represents the time scale under the severe change in T0 time. Substituting Equation (26) into the term composed of the order of m = 1), and considering the dimensionless frequency Among these, Similarly, the terms are analyzed in the order of If m = 2), and considering the dimensionless frequency For the case of the second mode (After solving Equation (32), the mq to the system yields the following equations for each time scale:In this section, the frequency response of the system under parametric excitation will be analyzed. The orthogonality of the mode shape is utilized to decouple the dynamic equations at each scale. Introducing a simple harmonic disturbance external force Equation of order Equation of order Equation of order mth mode In order to analyze the frequency response of the system, the frequency of the external force mB represents the amplitude of the mth mode, subscript m represents the mth mode, and subscript j represents different time scales. In the following, the first mode (m = 1) and The general solution of the time domain is expressed as follows:The expression After isolating the secular terms in Equations (34)–(36) and equating them to 0, the solvability condition for each mode can be derived. To construct the tuned frequency–response diagram  of the dimensionless amplitude Bm for this nonlinear system, the NEQNF subroutine within IMSL, along with the Levenberg–Marquardt algorithm, is employed.In this section, the correctness of the fixed-point plots and the initial voltage generation benefit of this model will be verified. The fourth-order Runge–Kutta (RK-4) method is used to obtain the time–response and phase plots. The piezoelectric equation and the elastic beam equation are solved simultaneously to obtain the theoretical voltage output, which is then used to verify the unstable region of the system.The concept of small perturbation Is introduced, letting The first mode , (31) and (33)) were obtained in After determining the instability region of the system, numerical methods are used to verify its correctness. Additionally, time–response plots and phase plots are created using the fourth-order Runge–Kutta method to verify the maximum amplitude point (indicated by a black circle) of fixed-point plots. Taking To achieve the best voltage generation efficiency, precise placement (repositioning) of the PZT at the maximum deformation (amplitude) location of the elastic beam is essential. The maximum amplitude can be determined by means of fixed-point plots. By combining the piezoelectric coupling nonlinear beam equation (Equation (40)) with the voltage function (Equation (10)) and setting the magnitude of the external force (actuator amplitude) to 0.6, The theoretical voltage output can be calculated using the fourth-order Runge–Kutta (RK-4) method. The results are presented as response graphs of voltage versus time, as depicted in Based on the observations from In this section, the findings of the theoretical model are presented. The installation of a piezoelectric patch at the point of maximum deformation, coupled with the addition of a baffle to introduce a slapping force, was investigated. The voltage generation efficiency of the baffle was compared at two key location: the maximum amplitude position of the elastic beam and the half-maximum amplitude position. For a clearer understanding, the detailed coordinate definitions and the components of the theoretical model are illustrated in The impact force of the elastic beam hitting the baffle is regarded as the slapping force on the PZT, and the slapping force is expressed as:Divide Equation (41) by Using the small perturbation method, and letting Substitute the first mode . These tools allowed us to determine the first two natural frequencies of the steel, which were found to be 16.2 Hz and 28.8 Hz, as illustrated in The optimal electric power output is achieved when the loading resistance matches the internal resistance of the system. To determine the internal resistance of this system, a 20 K ohm load was arbitrarily selected for the system, and an output voltage of 0.82865 volts was measured. By substituting this result into Equations (45) and (46), the theoretical internal resistance value was calculated to be 65.9 K ohms. In a subsequent step, the load resistance within the range of 36 K to 76 K ohms was experimentally tested, and the corresponding output voltage and power were measured, as presented in Based on the measured natural frequencies, the first mode was excited at 16.2 Hz in this experiment, while the second mode will be excited at 28.8 Hz. Measurements were initially conducted on the system without any additional slapping force. The voltage generation efficiency of the PZT was measured when installed at both the root and at the maximum amplitude position of the elastic steel. The voltage output of the system was recorded, and subsequently, the root mean square value was calculated from the collected data. Next, a baffle was introduced at the maximum amplitude position of the elastic steel, and the voltage generation efficiency was measured when the slapping force was applied at both the maximum amplitude position and at the half-maximum amplitude position of the steel. In this part of the experiment, the first mode was excited at 16.2 Hz and the second mode at 28.8 Hz. To calculate the output voltage of the system, a 66 K load resistance was connected in series. The voltage of the non-slapping force system was then measured, and the voltage generation efficiency of the elastic beam was measured when the PZT was installed at the maximum amplitude and at the root, respectively a–d. The From the experimental results, the voltage generation efficiency generated at the maximum amplitude position can be observed to be better in the condition with no slapping force. Subsequently, a baffle was installed in this system to analyze the effect of the slapping force. The voltage generation efficiency was measured of the baffle located at the maximum amplitude position of the elastic beam and at the half-maximum amplitude position, respectively a–d. The Next, the dimensional theoretical voltage diagrams of the non-slapping force were computed using the RK-4 method a–d. The As observed from Subsequently, the dimensional theoretical voltage diagram was calculated, considering the slapping force, using numerical methods a–d. The As shown in To further investigate the voltage generation efficiency in the unstable region depicted in From the results presented in −3 μW/mm3~3.73 × 10−2 μW/mm3. The present investigation achieved a maximum voltage and power output of 3.83 V and 0.222 mW with slapping force  further enhanced the voltage generation benefits, leading to even higher power conversion efficiency.The conventional vibration energy harvesting system utilized the vibration deformation of an elastic beam to generate electricity. In this research, a slapping force was introduced to enhance the voltage generation efficiency. The voltage generation output was evident, showcasing significant potential in the future industrial market for wireless sensors or microelectro-mechanical system structures.This study delved into the analysis of parametric excitation in a nonlinear elastic beam with fixed–fixed (roller) boundary conditions. The equation of motion was derived using Newton’s Second Law, Euler’s angle transformation, and the Taylor series, within the framework of nonlinear beam theory. Employing the method of multiple scales (MOMS), the phenomenon of parametric excitation was investigated. Verification of the presence of unstable regions was achieved through the generation of fixed-point plots, time–response plots, and phase plots. These plots affirm the accuracy of pinpointing unstable regions. Furthermore, this study integrated the piezoelectric equation with the nonlinear equation, enabling exploration of the nonlinear system’s unstable regions under a variety of frequencies and external forces. This exploration aimed to determine the maximum voltage efficiency achievable. In the final phase, a baffle was introduced into the system to impart a slapping force onto the Piezoelectric (PZT) element. Through this addition, we aimed to assess the potential enhancement of power conversion benefits. This comprehensive investigation yielded the following conclusions:This study presents a novel perspective on vibration energy harvesting, focusing on precise positioning and enhancement techniques. By highlighting the advantages of the second mode, revealing the benefits of the added baffle, and expanding the bandwidth of the resonant vibration region, this work contributes substantially to current knowledge in this area. The unique insights and inventive methodologies showcased here hold promising potential for advancing energy generation systems in various sectors.


Primary parapharyngeal space tumors are rare, and due to the complex anatomy of the parapharyngeal space, their diagnosis and treatment are challenging. Pleomorphic adenoma is the most common histologic type followed by paragangliomas and neurogenic tumors. They can present as a neck lump or an intraoral submucosal mass with the displacement of the ipsilateral tonsil or might be asymptomatic and discovered incidentally on imaging obtained for other reasons. Magnetic resonance imaging (MRI) with gadolinium is the imaging of choice. Surgery remains the treatment of choice and many approaches have been described. In this study, we present three patients with PPS pleomorphic adenoma (two primary and one recurrent), which were resected successfully with a transcervical-transparotid approach without mandibulotomy. Division of the following anatomical structures: the posterior belly of the digastric muscle, stylomandibular ligament, stylohyoid muscle and ligament, and styloglossus muscle is a very important tip for the surgeons because enables displacement of the mandible providing excellent exposure for complete tumor excision. The only postoperative complication was temporary facial nerve palsy in two patients who fully recovered within two months. The aim of this mini case series is to present our experience, together with some tips and benefits of the transcervical-transparotid approach for the resection of pleomorphic adenomas of the PPS. Primary tumors of the parapharyngeal space are not common, accounting for only 0.5% of all head and neck tumors . Most ofThe differential diagnosis of benign PPS tumors includes pleomorphic adenomas of the salivary glands, which are the most common, followed by paragangliomas and neurogenic tumors . PPS tumSurgical excision remains the best treatment for PPS tumors. Different surgical approaches have been described, including transcervical, transparotid, transoral, infratemporal, and transmandibular . Alone oIn this article, we present three cases of parapharyngeal space pleomorphic adenomas resected with a combined transcervical-transparotid approach without mandibulotomy, together with some tips for better visualization of the tumor with this approach.Case 1A 40-year-old male patient presented to our department two years ago with a left parapharyngeal space tumor that was found incidentally on a pituitary MRI, which he underwent because of pathological prolactin levels. He also complained of snoring and sleep apnea. MRI of the neck revealed a tumor of the left parapharyngeal space with benign characteristics and dimensions 3.9 Χ 3.9 Χ 2.7 cm, which caused narrowing of the oropharynx Figure During physical examination, there was no palpable neck mass but there was an evident bulging of the left lateral pharyngeal wall causing displacement of the left tonsil and left soft palate. The tumor was resected through a transcervical-transparotid approach and a biopsy showed a pleomorphic adenoma. The patient had a temporary facial nerve palsy (House-Brackmann II) postoperatively, which fully recovered (HB I) after one month, and he also mentioned improvement in snoring and sleep apnea in the next postoperative months. The patient was on regular follow-up postoperatively and the latest follow-up was six months ago  with an MRI that showed no signs of recurrence.Case 2A 30-year-old woman presented to our department a year ago with a left parapharyngeal space tumor, of dimensions 3.1 X 2.6 X 3.4 cm, which was found incidentally on a head and neck MRI that she underwent due to episodes of syncope. The possible diagnosis from the MRI was a neurogenic tumor , which fully recovered within two months. She was discharged from the hospital in three days.Case 3A 37-year-old woman with a repeatedly recurrent pleomorphic adenoma of the parapharyngeal space presented to our department 8 months ago. She had undergone three previous surgeries during the last 10 years in other hospitals. According to her medical record, she suffered from thrombophilia. Preoperatively, a complete investigation of the coagulation profile was performed with normal INR, PT, and aPTT values, and in addition, a consult with the hematologist was done. MRI showed a multinodular recurrent pleomorphic adenoma  was used. A skin incision was performed as shown in Figure Next, the main trunk of the facial nerve was recognized while exiting from the stylomastoid foramen Figure .The superficial lobe was mobilized, and its caudal portion (MSGS level II) was resected in order to expose the deep lobe of the gland. With caution, the caudal part of the deep lobe (MSGS level III) was also resected. The posterior belly of the digastric muscle, the stylomandibular ligament, the stylohyoid muscle and ligament, and the styloglossus muscle were recognized and divided. This step of the procedure is very important because it enables the displacement of the mandible upward with a retractor, providing a much better surgical field and access to the parapharyngeal space. The submandibular gland was also mobilized and retracted upward and part of the fat of the submandibular compartment was resected to improve access. It is not necessary to resect the submandibular gland. The facial vein was ligated. The common carotid artery with its bifurcation was recognized, and caution was shown not to damage the internal carotid artery by pressing it on the styloid process during the resection of the tumor near the skull base. The internal jugular vein was preserved. The hypoglossal, accessory, and glossopharyngeal nerves were recognized and protected. For confirmation, we used the neuromonitoring system and delivered electrical pulses to the nerves, especially the hypoglossal and accessory nerves, and we noticed the contraction of the muscles of the tongue and the shoulder.The dissection reached the skull base superiorly and the superior constrictor pharyngeal muscle medially. The position of the internal carotid artery and the glossopharyngeal nerve were continuously monitored during these last steps of the surgery. Then, the tumor was resected with blunt dissection with the capsule intact Figures , 8B.Copious irrigation of the wound is important if there is any tumor spillage. Finally, drain insertion and layered closure were performed. In the third case, because it was a reoperation, it was more difficult to recognize the facial nerve, which was not in its usual place, and there were multiple nodules that should be resected, which prolonged the time of the operation and increased the risk for complication.The parapharyngeal space is one of the most anatomically complex spaces of the neck. Tumors of varying histopathologies develop in this region, with most of them of benign nature. Due to the complex anatomical relationships and histological diversity, the diagnosis and treatment of PPS tumors present a challenge for physicians. It is helpful in determining the possible diagnosis to distinguish whether a lesion arises in the prestyloid or the poststyloid compartment. As a general rule, prestyloid lesions usually displace the internal carotid artery (ICA) posteriorly while poststyloid lesions displace the ICA anteromedially . Most prRegarding clinical presentation, benign PPS tumors usually present as a neck mass or an intraoral swelling causing asymmetry of the ipsilateral tonsil, soft palate, and lateral pharyngeal wall. They can cause symptoms like snoring, glomus sensation, dysphagia, and dysphonia related to mass effect and impaired vagal nerve function. It is not uncommon though for patients to present with a parapharyngeal tumor that was incidentally discovered on imaging obtained for other reasons. Symptoms like otalgia, facial pain, and trismus should raise suspicion of malignancy . In our Imaging studies are crucial for the diagnostic workup of these tumors and are used to predict the origin, side, and size of parapharyngeal tumors. Pre-operative assessment typically includes an MRI and/or CT scan. Angiography is required in cases of vascular lesions. MRI with gadolinium is the examination of choice because it can be typical for many lesions of the parapharyngeal space. Usually on MRI examination, salivary gland neoplasms are typically T2 hyperintense, and it is possible to recognize a fat plane between the parotid and the mass while schwannomas are typically T1 isointense or hypointense, with enhancement during the administration of gadolinium ,10. In oMost patients with parapharyngeal space masses are treated with surgery and the aim of surgery is to entirely remove the lesion with minimal postoperative complications. The selected surgical approach must be wide enough to guarantee the complete removal of the tumor and to prevent injury to the vessels and nerves of the upper neck . Many suThe transcervical approach is most appropriate for the resection of small tumors of the inferior part of the parapharyngeal space .The transcervical-transparotid approach is recommended for tumors adjacent to the facial nerve such as deep-lobe parotid tumors and minor salivary gland tumors. Through this approach, it is not only possible to identify and preserve the facial nerve but also the external and internal carotid arteries, the internal jugular vein, the cranial nerves IX, X, XI, XII, and the sympathetic nervous system chain. Although a superficial parotidectomy might be necessary to be performed to identify and carefully preserve the facial nerve, an effort is made to preserve the superficial lobe of the parotid gland in order to reduce the risk of developing Frey’s syndrome and for better cosmesis , 15,16. The transoral approach has also been described but most authors do not recommend routine use of this technique because the limited exposure has been related to a higher risk of tumor rupture, incomplete removal, facial nerve injury, fistula, and uncontrollable hemorrhage . HoweverTransoral robotic surgery (TORS) has been used in recent years to resect small benign lesions of the parapharyngeal space with promising results. Supporters of the approach claim that TORS provides a better three-dimensional view of the surgical area and safer tumor dissection but due to the limited availability of the expensive equipment and the potential for complication, there are very few centers worldwide that perform this approach ,20.In conclusion, an optimal surgical approach should be the safest and most effective method for providing complete tumor removal and preventing injury to the vessels and nerves of the parapharyngeal space. Intraoperative visibility of all vital anatomical structures is essential in performing a safe and radical dissection of the tumor. On the other hand, the surgical approach should also advocate providing minimal functional and cosmetic side effects.Parapharyngeal space tumors are rare, and their diagnosis and treatment are challenging due to the complex anatomy of the region. They may present with few clinical symptoms or can be entirely asymptomatic until reaching large dimensions. Asymptomatic tumors are usually diagnosed incidentally on radiological examinations of the head and neck for other reasons. The majority are benign tumors and arise from the salivary glands. Pleomorphic adenoma is the most common histologic type. Surgery is considered the treatment of choice after a complete investigation. Surgical strategy is determined by location, size, and pathology. In this mini case series, we demonstrate that the transervical-transparotid approach with a division of the following anatomical structures: stylomandibular ligament, posterior belly of the digastric muscle, stylohyoid muscle and ligament, and styloglossus muscle provides excellent exposure and enables complete excision of primary and recurrent parapharyngeal space pleomorphic adenomas with minimal morbidity. The use of intraoperative nerve monitoring is very important, and we recommend it through this approach for preventing facial nerve damage.


A nonlinear MEMS multimass sensor is numerically investigated, designed as a single input-single output (SISO) system consisting of an array of nonlinear microcantilevers clamped to a shuttle mass which, in turn, is constrained by a linear spring and a dashpot. The microcantilevers are made of a nanostructured material, a polymeric hosting matrix reinforced by aligned carbon nanotubes (CNT). The linear as well as the nonlinear detection capabilities of the device are explored by computing the shifts of the frequency response peaks caused by the mass deposition onto one or more microcantilever tips. The frequency response curves of the device are obtained by a pathfollowing algorithm applied to the reduced-order model of the system. The microcantilevers are described by a nonlinear Euler-Bernoulli inextensible beam theory, which is enriched by a meso-scale constitutive law of the nanocomposite. In particular, the microcantilever constitutive law depends on the CNT volume fraction suitably used for each cantilever to tune the frequency bandwidth of the whole device. Through an extensive numerical campaign, the mass sensor sensitivity estimated in the linear and nonlinear dynamic range shows that, for relatively large displacements, the accuracy of the added mass detectability can be improved due to the larger nonlinear frequency shifts at resonance (up to 12%). In the past decades MEMS have been subject to disruptive developments in several fields of engineering both in research and applications . The lower power consumption and higher sensitivity are distinct advantages with respect to comparable macro devices. A general introduction about MEMS devices can be found in  with an Accurate models still need to achieve better agreement between analytical/numerical predictions and experiment results, and explore the use of new materials and technical capabilities. Initial imperfections of the structure, together with electrostatic actuation and nonlinear damping effects, are discussed in ,9. Moreofound in ,16. Therfound in . A microfound in . This mifound in ,20. On tfound in ,22 wherefound in  while thfound in ,25. Difffound in ,27 to acfound in ,29.Numerous studies have been carried out to explore new mass detection strategies exploiting nonlinear effects. A parametrically excited clamped-clamped beam with cubic stiffness nonlinearity is explored as micromass sensor in . The priIn the present work, a single-input single-output (SISO) system is investigated making use of a path following algorithm optimized to tackle several degrees of freedom. The baseline idea of the SISO system can be found in  where a One of the key aspects of the proposed design is the use of CNT nanocomposite material  for the microcantilever detectors. Due to their excellent mechanical, thermal, electrical, and tribological properties, compared with their lightweight nature, CNT-based nanocomposites reached in the last decades a widespread use in various engineering applications , respectively A parametric analysis is initially performed in order to investigate the sensitivity of the eigenfrequencies with respect to the CNT content variation and beam length. In  r. While the natural frequency ratio monotically increases as the CNT volume fraction increases, by considering longer and longer lengths of CNT beam made of the same mixture, the natural frequency ratio tends to a plateaux. In particular, a nanocomposite beam with a 2.8% CNT volume fraction has the same value of the 1st natural frequency of a silicon beam of equal length.The influence of the beam length is also considered in  If one chooses to set the first frequency of a microbeam to a certain target frequency, the microbeam could be designed in terms of a suitable length and CNT volume fraction.  jth mode The Galerkin method is adopted to reduce the nonlinear integral-partial-differential equations of motion into a reduced-order model (ROM). By setting the unknown vector cast asIv¨+Lv=−nBy taking one trial function for each cantilever, a 5-dof overall ROM is obtained . This approach was shown to be acceptable in ,54 whereZenodo repository website: https://doi.org/10.5281/zenodo.6616482 (accessed on 8 May 2023). In particular, the search of periodic solutions is based on computing the fixed points of the Poincaré map whose Jacobian turns out to be the monodromy matrix, whose eigenvalues are the Floquet multipliers which dictate the stability of the periodic solutions [In order to obtain the periodic responses and the frequency response curves, we employed the adaptive pseudo-arclength pathfollowing procedure proposed in , developolutions ,56. The olutions .jth microcantilever; unless otherwise stated, we set for The dynamic behavior of the device is investigated by computing the frequency response curves for different device configurations, in particular, accounting for the case of additional masses In the following, we present and discuss some numerical results aimed at demonstrating the sensitivity of the SISO system to the presence of additional tip masses. Note that in all figures reporting the frequency response curves of the SISO system, thin curves are referred to systems without tip masses, thick curves to systems with tip masses.The frequency response curves reported in Similar qualitative results can be found in Such a mass sensitivity is further investigated for increasing values of additional masses. We assume to add the tip mass just to the first (from left) microbeam. Such figures not only reveal the expected trend of the resonance peak shift upon increasing the tip mass, but they also highlight a change in the length of the unstable branch of the response curve. In fact, around the first bending mode frequency, the shift in frequency occurs with a hardening nonlinear response which becomes more and more evident see ; on the In this work the operating principles of a nonlinear MEMS multi-mass sensor are investigated. The device consists of an array of microcantilevers, made of carbon nanotube nanocomposite material, possessing a functionalized surface at their tips that can absorb molecules of target materials. The microcantilever sensors are clamped onto a shuttle mass which, in turn, is subject to electrostatic excitation. The system is treated as a single input-single output (SISO) system. Each microcantilever is modeled as a nonlinear Euler-Bernoulli beam undergoing a moderately large resonance motions.The modal characteristics of the mechanical system are investigated carrying out a parametric study varying the CNT volume fraction in each microbeam. The frequency response and stability are investigated by path following the periodic solutions of the device near the lowest three bending modes of the microcantilevers.The main finding is that the dynamic mass sensitivity measured as frequency shifts induced by the target mass absorbed at the cantilevers tip is enhanced by the nonlinear resonances of the microcantilevers modes, especially for higher modes. In particular, around the first bending mode frequency, we gain a frequency shift of the 12% in frequency by adding a 10% tip-mass, while for the second mode, the frequency shift is of 9% with 5% additional mass.Although the experimental validation of the proposed model has not been considered, and future works will focus on this point, the accuracy of the nonlinear beam model for CNT-nanocomposites, adapted to the specific SISO system here theoretically designed, was widely validated in previous research contributions. In the present work, we showed how the fine tuning of the frequencies of the microcantilevers is positively effected by the carbon nanotube volume fraction in the nanocomposite material. Such innovative potentiality paves the way towards an effective design of multimass sensors since the microcantilevers may self-detect their motion exploiting the electrical conductivity of the CNT nanocomposites.


Over time, the first aid knowledge of the trained children gradually declined at the two- and six-month follow-up assessments, although it remained higher than their pre-training level. Conclusions: First aid training provided by their teachers improved the knowledge of 6–8-year-old primary school children in first aid and trauma management.Objectives: The primary objective of this pilot study was to examine the effectiveness of teaching first aid to 6–8-year-old children within their primary school setting. The study aimed to address two key research questions: (1) Can children of this age group acquire first aid and trauma management skills from their schoolteachers? (2) How long do children retain the acquired first aid knowledge? Methods: A pilot experimental study with an educational intervention was conducted in a single primary school in Greece. A total of 60 schoolchildren aged 6–8 years were randomly selected for participation, with 30 children assigned to the training group and 30 children assigned to the control group, which did not receive any intervention. To assess the children’s understanding of first aid, a specialized questionnaire was administered to all children one day before the training, as well as to the training group one day after the training, and at two and six months following the training. Results: Prior to the training, there were no significant differences in first aid knowledge between the children in the training group and those in the control group. However, one day after the training, the trained children demonstrated significantly higher scores ( The World Health Organization (WHO) recognizes the importance of educating individuals of all ages on essential health topics, including the ability to respond to emergencies . First aWhile previous studies have primarily focused on specialized first aid training for children above the age of ten , a few iCan children of this age group acquire first aid and trauma management skills from their schoolteachers?How long do children retain the acquired first aid knowledge?This pilot study aims to assess the effectiveness of schoolteachers in teaching first aid to 6–8-year-old children in a Greek primary school. The study aims to address the following research questions:By examining these research questions, we seek to shed light on the potential of schoolteachers as educators in fostering first aid knowledge among young children. The findings of this study may contribute to the development of comprehensive and age-appropriate first aid education programs, ultimately empowering children to become confident and competent first responders in times of emergency.An experimental study with educational intervention was conducted in a randomly selected primary school, involving children in the 6–8 years age group. Prior to their participation, written informed consent was obtained from the parents or guardians of the children. The participants were divided into two groups: the training group and the control group . All chiTo assess the children’s knowledge and understanding of first aid, a structured questionnaire was administered to the training group one day prior to the commencement of the course, one day after completing the course, as well as at two months and six months post-training. The questionnaire, which encompassed twelve questions, including demographic information and ten questions focused on first aid scenarios, consisted of eight multiple-choice questions and two questions involving sequencing . It is wt-tests to compare the control group and the intervention group, and paired t-tests were employed to compare the pre-training, post-training, and follow-up results within the training group (significance level: p < 0.05). Additionally, it is important to mention that the study has been registered as a clinical trial under the identifier NCT05563129 since 3 October 2022.Statistical analysis was performed using independent The University of Ioannina Ethics committee granted approval for this study (26 November 2021), ensuring that the research adheres to ethical guidelines and principles. Prior to the commencement of the study, comprehensive information was provided to the participating children, their parents, and the involved schoolteachers, both in written and oral formats. The researcher ensured that all parties involved were well-informed about the nature and purpose of the study. In particular, the parents of the children were informed about their rights, including the option to withdraw their child from the study at any time, without the need to provide a reason, and with complete anonymity. This approach aimed to prioritize the welfare and comfort of the children and their families, ensuring that their participation was voluntary and based on informed consent. To formalize their agreement for their child’s participation in the study, the parents were requested to provide written informed consent, indicating their understanding and willingness to involve their child in the research.By following these ethical procedures and obtaining informed consent, the study ensures transparency, respect for autonomy, and protection of the rights and well-being of all participants involved.The training program implemented in this study encompassed a comprehensive approach, incorporating both theoretical components in the form of e-presentations and practical elements through role-playing exercises. Each lesson had a duration of 45 min, and the training spanned across three consecutive days. The responsibility of delivering the course fell upon two experienced classroom teachers. The training curriculum covered various essential topics related to first aid. The initial lessons aimed to familiarize the children with the meaning and significance of first aid, emphasizing its role in providing immediate assistance during emergencies. The main rules of first aid were also taught, equipping the children with a foundational understanding of how to respond appropriately in different situations.One crucial aspect addressed in the training program was phoning an ambulance. The children were educated on the correct phone number to call for emergency medical services and were taught when it is necessary to contact an ambulance. Furthermore, they were guided on providing the vital information required to ensure prompt and efficient medical assistance. The training program also addressed specific injury scenarios commonly encountered by children. Topics such as head trauma, nose bleeding, choking, and bleeding were covered in detail, enabling the children to develop the necessary skills to respond effectively to such incidents.To ensure the teachers’ proficiency in delivering the training, they received a comprehensive 2-h first aid training themselves. This additional training equipped them with the knowledge and expertise needed to effectively engage with the children and facilitate their learning.Crucially, the training program was tailored to the age group of the participating children, considering the types and frequencies of accidents they are likely to encounter in their everyday lives . This apThe study encompassed a sample size of 60 children, accounting for approximately 35% of the total school population. These children belonged to the 6–8 years age group, with a distribution of 34 girls and 26 boys. On average, the participants had an age of 7.22 years. To assess the effectiveness of the training program, the knowledge of the children in the training group was evaluated at multiple time points. The evaluation process involved the administration of a study questionnaire, which served as a reliable tool for measuring the children’s understanding of first aid concepts. The first evaluation was conducted one day before the training course to establish a baseline of their existing knowledge. Subsequent evaluations were carried out one day after the completion of the course, as well as at two and six months after the training program concluded.During the six-month evaluation, one child was absent, resulting in the completion of the questionnaire by 29 children. This robust evaluation process allowed for the analysis of knowledge retention and the long-term impact of the training program. In contrast, the control group, comprising children who did not receive the training, underwent a single evaluation at the beginning of the study. This evaluation served as a benchmark for comparing the knowledge levels between the trained group and the control group, highlighting the impact of the training program on the children’s understanding of first aid concepts. p < 0.05) in their scores compared to the control group. Over the subsequent two and six months following the training, a gradual decline in knowledge was observed among the trained group. Despite this decline, their scores remained higher than both their pre-training scores and those of the control group, indicating a sustained advantage in first aid knowledge retention. Immediately after receiving the first aid training, the majority of children in the training group displayed a solid grasp of key concepts such as phoning an ambulance , as well as dealing with head injuries, nose bleeding, bleeding, and choking. These areas of knowledge were particularly well-retained by the children in the training group. However, after the six-month period, there was a notable decrease in their knowledge regarding the handling of nose bleeding and trauma, as well as the proper actions to prevent choking. The comparison between the trained and untrained children (control group) prior to the training revealed no significant difference in their initial levels of first aid knowledge. However, one day after the completion of the first aid course, the children in the training group demonstrated a significant improvement , as well as addressing head injuries, nosebleeds, bleeding from injuries, and choking. These findings align with previous research, which has also indicated that young schoolchildren are capable of providing first aid ,10.While the children’s performance on the first aid knowledge test declined at the two- and six-month follow-up assessments compared to their immediate post-training scores, their scores remained higher than their pre-training levels and those of the control group. This observation aligns with the findings reported by Banfai et al. ,11. AlthNotably, our study also emphasized the importance of addressing head injuries and trauma management in the primary school curriculum. Head injuries are a common occurrence reported within school settings , yet theIn an effort to optimize the effectiveness and cost efficiency of our intervention, we enlisted the children’s regular schoolteachers to conduct the first aid program. While many studies have employed specialized first aid instructors ,16, a feTeaching first aid to children is a crucial step in fostering their responsibility and safety as active members of society . EquippiChildren may have a basic awareness of certain parts of first aid prior to getting professional first aid instruction. They may be aware of how to summon assistance in an emergency or where to find an adult if someone is harmed. They may be knowledgeable of bandaging and using ice packs to treat small wounds. Their knowledge, however, may be insufficient and lack the depth and accuracy needed to provide good support. They may be unaware of CPR, choking control, and how to respond to diverse injuries ,8,9. ForThere are several reasons why teaching first aid to children is important . First aWhen teaching first aid to children, it is important to use age-appropriate methods and materials ,23. YounWe believe that the first aid program should be made mandatory in schools. Young children can learn first aid and their schoolteachers can teach first aid ,26. BecaWhile this study provides valuable insights into the effectiveness of the first aid training program for young children, it is important to acknowledge certain limitations that should be taken into consideration when interpreting the results. One limitation of the study is the relatively small sample size. Although the study included 60 children, representing approximately 35% of the total school population, a larger sample size would have provided a more robust and representative dataset. A larger sample would have allowed for a more comprehensive analysis and increased generalizability of the findings. Another limitation is the lack of ongoing assessment for the control group over the six-month period. Since all participants were from the same school, it is plausible that the control group may have acquired some knowledge incrementally during this time. Without reassessment, it is challenging to accurately compare the progress and knowledge retention between the trained and untrained children throughout the study period. Furthermore, the study did not undergo formal validation, which may limit its applicability to other populations. Validation studies are crucial in establishing the reliability and generalizability of research findings across different settings, age groups, and cultural contexts. Therefore, caution should be exercised when extrapolating the results of this study to other populations or educational settings. These limitations highlight the need for future research to address these shortcomings. Studies with larger sample sizes, longitudinal assessments of control groups, and validation in diverse populations would contribute to a more comprehensive understanding of the effectiveness and generalizability of first aid training programs for young children.First aid is an essential skill that empowers individuals to provide immediate assistance during emergencies. By instilling a culture of first aid from childhood, we can cultivate a society where people possess the aptitude and confidence to respond effectively in crisis situations ,25. StarThis pilot study aimed to assess the effectiveness of teaching first aid to 6–8-year-old children in primary school, delivered by their own schoolteachers. The findings of the study present promising outcomes, indicating that children within this age group have the capacity to grasp basic first aid principles, including knowing how to call an ambulance , as well as effectively addressing common scenarios such as head injuries, nosebleeds, bleeding from injuries, and choking, when instructed by their schoolteachers. While the children’s performance on the first aid knowledge test declined at the two- and six-month follow-up assessments compared to their immediate post-training scores, their scores remained superior to their pre-training levels and those of the control group. This observation suggests that the scenario-based training implemented in the study effectively developed the children’s first aid knowledge, and that they retained a significant portion of this knowledge even six months after the training.This study sheds light on the potential of incorporating scenario-based first aid and trauma management training in primary schools. By developing children’s first aid knowledge from an early age, we equip them with valuable life skills that can make a significant difference in emergency situations. Further research and advancements in this field will undoubtedly contribute to refining the curriculum and methodology for teaching young children about trauma management, ensuring their preparedness to respond effectively in real-life scenarios.


Constricted ear has a prevalence of 5.2 to 10% among ear abnormalities, and various surgical methods are suggested for treatment. We introduce a case of a constricted ear treated with a simple method using a novel concept cartilage graft and transposition flap, along with the well-known Mustardé suture, which is used for pediatric patients with mild to moderate constricted ears of Tanzer classification type IIA. A 10-year-old female patient visited the hospital complaining of an abnormality in the congenital right ear. Surgical approach was planned under the diagnosis of Tanzer classification type IIA constricted right ear. Posterior helix onlay graft and perichondrocutaneous transposition flap using excessive helical cartilage were performed along with the Mustardé suture. In the immediate postoperative period, ear contour was improved, and it was well-maintained without recurrence until 6 months' follow-up. In conclusion, the combination of Mustardé suture, and cartilage onlay graft and perichondrocutaneous transposition flap in the mild to moderate constricted ear would be a useful surgical option, producing aesthetically good results in a simple and effective method. Constricted ear, also known as lop ear or cup ear, is a congenital ear abnormality. The etiology is related to problems in the process of spreading the upper helix over the antihelix at 3 to 4 months of gestational age.Constricted ears are most often corrected by molding a conforming splint in neonatal period.Various methods of flap and cartilage refashioning are used for surgical treatment of constricted ears, but it is controversial as to which method has the most efficient and best results, and numerous modifications are made according to individual clinical conditions. In particular, for the surgical correction of mild to moderate constricted ears, good results are difficult to obtain with a solitary method; hence, there have been several reports of using a combination of various methods.A 10-year-old female patient visited the hospital complaining of a right ear abnormality, which was observed since birth. The patient had no history of other treatments, including molding for the affected ear. Due to the shape of the ear, it was inconvenient to fix the upper ear when wearing a mask, and the patient preferred morphological normalization.On physical examination, the right ear had a congenital morphological abnormality. At the time of the visit, the ear shape showed hooding of the upper lateral portion of the helical rim (Darwin's tubercle area), and flattening of the superior and inferior crura and body of the antihelix was observed . The siFirst, the incision line of the Z-shape was drawn with the tip at an angle of 40 degrees to cover the upper two-thirds of the posterior side of the right ear . SubperZ-shape (On the posterior surface of the antihelix showing flattening, the area to create a square antihelical crura was designed, and after designing the area for Mustardé suture, a horizontal mattress Mustardé suture was performed at four points and3.-shape .Postoperatively for 1 week, dressing was performed by applying molding using Vaseline gauze to the anterior and posterior directions of the ear. After surgery, wound healing was achieved without hematoma or infection. The shape of the ear was successfully maintained without any additional signs of recurrence or complications, except for a minimal scar appearance on the posterior surface of the ear observed 6 months after the surgery .Tanzer classification type IIA is defined as moderate compression of the helix and scapha, and distinguished from type IIB in that loss of vertical height is observed and with little need for supplemental skin.In mild to moderate constricted ears, it is difficult to maintain the shape of the antihelix crus with only the Mustardé suture, and to reinforce this, a method for securing the crus shape through reinforcement using concha cartilage or free-floating costal cartilage has been introduced.For excessive posterior side skin, the upper flap is positioned as the auriculocephalic sulcus after transposition by utilizing Z-shape transposition flaps for initial incision and skin closure. This technique corrects the curvature of the helix through tightening of the posterior skin after cartilage reposition. Furthermore, the space of the upper portion of the helix, which was secured through the transposition flap, was able to secure and reinforce the fixation of the cartilage end through the onlay graft on the posterior side in the temporal area.In conclusion, for a mild to moderate constricted ear case of Tanzer classification IIA, we performed a simple and effective method that combined the posterior helix onlay graft and perichondrocutaneous transposition flap using excessive helical cartilage along with the existing Mustardé suture. We concluded that this method was able to produce good results and can be used for various cases of constricted ear surgery.


Transhumeral amputees experience considerable difficulties with controlling a multifunctional prosthesis  due to the lack of available muscles to provide electromyographic (EMG) signals. The residual limb motion strategy has become a popular alternative for transhumeral prosthesis control. It provides an intuitive way to estimate the motion of the prosthesis based on the residual shoulder motion, especially for target reaching tasks. Conventionally, a predictive model, typically an artificial neural network (ANN), is directly trained and relied upon to map the shoulder–elbow kinematics using the data from able-bodied subjects without extracting any prior synergistic information. However, it is essential to explicitly identify effective synergies and make them transferable across amputee users for higher accuracy and robustness. To overcome this limitation of the conventional ANN learning approach, this study explicitly combines the kinematic synergies with a recurrent neural network (RNN) to propose a synergy-space neural network for estimating forearm motions  based on residual shoulder motions. We tested 36 training strategies for each of the 14 subjects, comparing the proposed synergy-space and conventional neural network learning approaches, and we statistically evaluated the results using Pearson’s correlation method and the analysis of variance (ANOVA) test. The offline cross-subject analysis indicates that the synergy-space neural network exhibits superior robustness to inter-individual variability, demonstrating the potential of this approach as a transferable and generalized control strategy for transhumeral prosthesis control. Amputation of the upper limb at any level can considerably affect an individual’s ability to perform the activities of daily living (ADLs). The proficiency for such activities decreases with higher amputation levels . The genIn the myoelectric control domain, which is the most widely used control approach for prosthetic arms , the numAlthough such measures allowed transhumeral amputees better control over their multifunctional prosthetic arms, the control was slow, sequential, and unnatural as physiologically appropriate muscles were unavailable. Such counter-intuitive control strategies and a lack of functionality are often the reasons for the high rejection rates of these devices ,9. FurthNumerous investigations have been conducted to explore alternative solutions, such as those based on myokinetic signals  using thConcerning the target reaching task or control of the prosthetic elbow joint motion in transhumeral amputees, the ideal case would involve the prosthetic device acting as a natural extension of the human body. A promising scheme to achieve this is automatically controlling the prosthetic elbow joint based on the natural relationships between the arm joints. Analyses of such joint coordination approaches have shown evidence that recurrent patterns exist in the joint kinematics for upper limb movements while performing reaching or grasping tasks. For example, between the elbow flexion and humeral inclination during reaching , betweenIn the present study, we have also focused on a synergistic method for intuitive control of the prosthetic elbow joint for transhumeral amputees. The majority of previous such motion-based approaches using residual limb motion rely on ANNs ,20 to idThis paper presents the concept of the synergy-space neural network, whereby we explicitly combine the kinematic synergies with the learning system to address the limitation of the direct estimation method, aiming for a more robust and transferable control strategy. Synergies have been observed to be repeatable and shared across similar tasks and subjects. Therefore, we extract the synergistic information from the movement data and incorporate only the most significant synergy components in the learning process, enabling more precise and efficient training of the ANN while taking advantage of the shared nature of these synergies enhancing the transferability of the model. The idea is to train the ANN to predict the corresponding activation signals (see Equation ), which C are replaced with the LSTM-predicted signals The implementation of the proposed synergy-space neural network as a transferable model for forearm motion estimation using residual shoulder kinematics during horizontal reaching movements.Personalized LSTM Models Evaluation: To validate the proposed methodology and its better learning capability through a detailed comparison between the performance of the synergy-space neural network and the direct estimation approach.Cross-Subject Evaluation: To demonstrate the strength of the synergy-space neural network as a transferable decoder, indicating its ability to handle inter-individual variabilities.midhuber , the reaThe remainder of this paper consists of the following sections. Humans can generate coordinated, efficient, and sophisticated movements by fully utilizing the dynamics of their complex musculoskeletal systems. The need to control and perpetually adjust a large number of DOFs is expected to be computationally formidable. To manipulate the inherently redundant musculoskeletal system for voluntary movement generation, the CNS must simultaneously activate and coordinate many muscles, each comprising thousands of motor units. Neuroscience researchers have proven that the concept of motor synergies exists within the CNS ,26,27, wThere are numerous interpretations of this concept; most commonly, the CNS uses a considerably small set of instructions to control a large group of muscles for movement generation. Owing to the co-activation of a set of muscles using fewer neural commands, i.e., motor synergies, the EMG activities of these muscles tend to be spatially and temporally correlated, which is referred to as muscle synergies. At the same time, this covariation of the muscle activation imparts a certain level of coordination among closely related joints, coupling the angular movements in various joints, referred to as kinematic synergies . Having In various investigations, a wide range of motor behaviors has been explained and are suggested to be produced by synergies. The comprehensive analysis in  by d’Avet in trial number l, and N is the number of extracted spatial synergy components. residuals term, where X represents the source signals, W defines the synergy components, and C is the corresponding activation signal matrix.Many studies have identified synergies  at the electromyographic, kinetic, and kinematic levels during the last few decades. The calculations for extracting various types of synergies have been formalized by authors in ,34,35,36 rewrite  in a sim rewrite  after igE in  method, which is one of the most widely used algorithms for solving ; its corE in  with resFourteen healthy right-handed subjects  volunteered for this investigation. The subjects were 20–28 years old, with no known upper limb neuromuscular disorders. All subjects had given informed consent prior to participation in this experiment.To record the motion data of a subject’s arm movements during reaching tasks, we used Perception neuron pro, an inertial measurement unit (IMU) sensor-based full-body motion capture system. Although the accuracy of this system is inferior to that of optical cameras, it is possible to capture motions without spatial constraints from anywhere within the communicable range of the device. The device uses individual sensors called neurons, each housing an IMU, attached to different body parts a. We useThe sensor system communicates with the axis neuron pro software that processes raw motion data to formulate a 3D skeletal model in real time. Motion information from the developed skeletal model, such as the position and angle of each joint, can be obtained at a sampling frequency of 120 Hz. In our experiments, the data under consideration were the three shoulder orientation angles along X, Y, and Z axes, i.e., internal–external rotation, flexion–extension, and abduction–adduction of the shoulder joint, and two forearm orientation angles, i.e., pronation–supination and flexion–extension of the elbow joint; hereafter, these are referred to as Bearing in mind that the purpose of a prosthetic device is to assist the user with their ADLs, we designed the workspace based on a routine activity by considering the user’s everyday environment instead of constrained movements in a laboratory or restricted environment. Reaching for objects placed on a table is a common scenario in daily life, which also targets arm movements in the horizontal plane only, specifically on the top surface of a table. A 40 cm × 40 cm target grid a with a Dataset 1: with multiple (15 times) repetitive reaching movements toward each target point.Dataset 2: with reaching movements toward random target points .Dataset 1 with multiple repetitive movements was first used to extract the kinematic synergies and later as the training data for the neural network. Afterward, dataset 2, with reaching movements toward random target points, was used to cross-validate the trained neural network.PCA has been used in numerous studies to investigate natural movements, such as catching  or reachX having size In this study, we performed a synergistic analysis using PCA as we are working with kinematic synergies. Dataset 1 was first segmented to acquire the data of interest, i.e., one individual reaching movement from the onset of the reaching motion until returning to the start/rest point as in . We thenataset X  was obtaWe retained the minimum of the most significant PCs that explain at least In the present work, we trained a neural network to predict the extracted activation signals based on shoulder kinematics. As both sets of data are time-series signals, it is necessary to use an ANN that suitably processes the time-series or sequential data. Different ANN architectures have been employed in various studies to determine inter-joint coordination during human arm movements. The authors in  used a rWe used python’s machine learning library, Keras, to implement the LSTM model. There are various parameters in the neural network, and the estimation accuracy may change depending on the settings of these parameters. Therefore, we first tested the learning efficiency and estimation accuracy of the LSTM model by varying the parameters, such as the batch input size, number of LSTM hidden layers, number of nodes in each layer, and number of training epochs. These parameters affect the learning and estimation efficiencies of the model. The batch size controls the number of samples shown to the network before the weight updates are applied. If the input batch size is large, the model can quickly process the entire training dataset; however, it can overlook certain features during training that might be crucial to learning.On the other hand, we can increase the complexity and expressiveness of the model by optimizing the number of LSTM hidden layers and the number of neurons in each layer. Even in the case of using only a single hidden layer, the LSTM model can learn the characteristics of the time-series data. The efficiency can be improved by stacking multiple layers. However, if the model is made more complex than necessary, the training may not be effective. Similarly, if we increase the number of nodes, the model requires more time for learning with no significant change in accuracy. The same is also true for the number of training epochs. Estimating the time-varying activation signals is classified as a regression problem, so we use the mean squared error (MSE) as the loss function and Adam as the optimization function, as has been widely used in similar studies.Lastly, to avoid the overfitting problem, a dropout rate of 10% is used in each layer, whereby 10% of the neurons are dropped randomly. Supervised learning is then carried out, where the neural network develops the regression model based on the input–output pairs. As for the training data, at a single time step, we can apply a total of six inputs to the model: the he model . The modIn the present work, we compared the performances of the synergy-space neural network approach, where the shoulder kinematics are mapped to synergistic activation signals, with the direct estimation approach, wherein the neural network is used to map the shoulder kinematics to the forearm kinematics. To thoroughly investigate this comparison, we devised a comprehensive strategy to train and test 36 different LSTM models for each subject and analyze the performances. The devised strategy was based on the following criteria.First, we devised a scenario based on our proposed learning methodology for the LSTM model. This defines the approach chosen for training the network, that is, either synergy-space or direct estimation. Three strategies were devised based on the number of synergistic components used and the learning approach.Synergy-Space estimation using 2 synergies components:W and their corresponding activation signals C from the reaching motion data considering five DOFs of the arm, i.e., W to estimate the required forearm motions.In this case, we first extract the synergies Synergy-space estimation using 1 synergy component:W and their corresponding activation signals C from the reaching motion data considering only two DOFs of the forearm, i.e., W are used to estimate the required forearm motions.In this case, we extracted the synergies Direct estimation:For direct estimation, no prior information or synergistic components are extracted from the reaching motion data recorded during arm movements. The LSTM model is directly trained to predict As noted previously, a single layer of LSTM can learn the necessary features of the time-series data. By stacking multiple layers of LSTMs, this ability can be enhanced. Thus, to verify the appropriate number of hidden layers for our task, we tested three scenarios with varying numbers of hidden LSTM layers in our model. For each learning methodology mentioned earlier, we constructed and trained three different models, namely M1, M2, and M3, having one, two, and three hidden LSTM layers, respectively.As previously mentioned, we can apply a total of six inputs to our model, represented by t, and N is the total number of data points.For the evaluation of the trained LSTM model, the estimated forearm orientation angles  test. The ANOVA compares three or more populations to ascertain whether the variability between group means is larger than the variability in the observations within the groups. A significance level or threshold is chosen, and a p-value is less than the threshold. In that case, the statistically significant ANOVA is followed up with the Tukey HSD (honest significant difference), a post hoc test pinpointing which learning methodology exhibits a statistically significant difference.To show the pertinence of each learning methodology, we perform the ANOVA test using the RMSE values obtained by comparing the estimated and actual forearm motions for the various LSTM models trained using the synergy-space and direct estimation approaches. We chose a significance level of 0.05, one of the standard choices. Suppose the calculated As discussed previously, one of the characteristics of the synergies is that they are shared among similar tasks to some extent. This suggests that a generalized or transferable control model can be developed based on the synergy-space neural network approach using the data recorded from healthy subjects. Therefore, cross-subject testing was performed to test this assumption for the robustness of the learning methodologies.For the case of the synergy-space method, we performed the cross-subject analysis using, for example, subject A’s input data fed to the LSTM models trained using the other subjects’ data and then employing subject A’s synergy matrix for the forearm motion prediction. However, for the case of the direct estimation method, the cross-subject analysis was performed using, for example, subject A’s input data fed to the LSTM models trained using the other subjects’ data for subject A’s forearm motion prediction.The evaluations were performed by calculating the RMSE values to compare the estimated motions with the actual measured values. For the cross-subject analysis, we used model M2 with six inputs  and model M2 with two inputs . The ANOVA was then performed to statistically verify the difference between the cross-subject results based on the synergy-space and direct estimation approaches.In this study, we trained and evaluated 36 different LSTM models for each of the 14 subjects. The training strategy was devised based on three different learning methodologies. We constructed 3 separate LSTM models and trained each model using 4 different combinations of the input signals , suggesting a significant difference in the performance of the two approaches.The statistically significant ANOVA was followed-up with the Tukey HSD (honest significant difference), a post hoc test pinpointing which learning methodology exhibits a statistically significant difference. The post hoc Tukey HSD test results are reported in Similar results were also obtained for the cross-subject evaluations using the LSTM model M2 with two inputs only, presented in We have proposed and evaluated the synergy-space neural network for transhumeral prosthesis control. By explicitly incorporating kinematic synergies into the model, our approach addresses the limitations of traditional ANNs and provides a more robust and superior transferability across different subjects. Our rigorous evaluation of the model has shown promising results, demonstrating its potential.We evaluated the performance of the proposed synergy-space approach for personalized LSTM models and compared it to the direct estimation method. The results of Pearson’s correlation method and the ANOVA analysis indicate that the proposed method performs comparably to the direct estimation method, with no significant difference in performance. However, the proposed approach still performs well, even with the reduction in dimensionality, suggesting its efficient and better learning capabilities for personalized LSTM models.In the various tested scenarios, we observed that using shoulder internal–external rotations (The synergy-space approach demonstrated its superiority during the cross-subject evaluation as a more robust and transferable learning methodology. It showed more minor variations in the estimation accuracy when using one subject’s motion data and extracted the synergy matrix for forearm motion estimation using the personalized LSTM models of the other thirteen subjects. However, one of the limitations of this study for the actual implementation on amputee users will be obtaining the subject-specific synergy matrix. This is because, as mentioned earlier, amputee users cannot provide the necessary motion information.Based on the properties of synergies being repeatable and shared across similar tasks and subjects, one practical solution can be to create a generalized synergy matrix based on the data of all the able-bodied participants and use it for amputee users’ forearm motion prediction. Another possibility would be to use motion data from the user’s healthy arm to generate a synergy matrix for the amputated arm. As the synergy matrix represents the inter-joint coordination, the LSTM model needs to learn a simplified relation between the shoulder kinematics and the activation signals. That means effectively extracting synergies can significantly affect performance.This first investigation of the proposed synergy-space neural network demonstrates its potential as a robust and transferable predictive model, which was successfully confirmed through the cross-subject evaluation results. This finding can contribute toward creating a synergistic and generalized control strategy for transhumeral prostheses and other rehabilitation applications.The primary aim of this study was to improve the control of transhumeral prostheses, focusing on their transferability across users. A highly accurate transferable predictive model is necessary for transhumeral amputees because individual calibration or personalized learning methods cannot be used effectively as they cannot provide the required data.In this research, we proposed the synergy-space neural networks, as a transferable model, to predict the joint angles of the forearm motion based on the residual shoulder motion. We presented the implementation and evaluation of the proposed method, discussing its learnability and robustness for transferability to amputee users. The study was conducted with able-bodied subjects, focusing on reaching movements of the arm in the horizontal plane only. We compared the synergy-space neural network approach with the direct estimation method, using the actual and estimated joint angular values for the performance evaluation. In the best-case scenario, average RMSEs of We investigated the transfer learning ability of the proposed model through cross-subject analysis. The results indicate that the synergy-space neural network exhibited superior learning capabilities compared to the traditional direct estimation method during cross-subject evaluations. This highlights the strength of our approach as a transferable decoder, demonstrating its ability to handle inter-individual variabilities and providing a more generalized model for transhumeral prosthesis control.In the future, we can send the output of predicted joint angles from the proposed model to a transhumeral prosthesis for real-time control. As a next step, this approach would be extended to incorporate reaching motions in three-dimensional space. The ultimate goal in the future is to develop a framework for the real-time estimation of forearm motions to further test and improve the proposed approach, such that it can be employed on actual transhumeral prostheses that allow users to control the device intuitively.