Neck pain is a common complaint in the general population. Despite the consistent ongoing pain and the resulting economic burden on affected individuals, there have only been a few studies investigating the treatment of acute neck pain. This study aims to evaluate the effectiveness, safety, and cost-effectiveness of the motion style acupuncture treatment (MSAT) and acupuncture treatment for acute neck pain.This 2-armed, parallel, multi-centered randomized controlled trial will be conducted at 4 community-based hospitals in Korea. A total of 128 subjects will be randomly assigned, at a 1:1 ratio, to the MSAT and the acupuncture treatment groups. Treatment will be administered 2 to 3 times a week for 2 weeks. The primary outcome will be the visual analog scale of neck pain on movement. The secondary outcomes will be the numeric rating scale of the neck, neck disability index, Northwick Park questionnaire, patient global impression of change, range of motion of the neck, 5-level EuroQol-5 dimension, 12-item Short-Form Health Survey, and EuroQol visual analogue scale. This protocol has been registered at the Clinicaltrials.gov (NCT04539184).To our knowledge, this study is the first well-designed multi-centered randomized controlled trial to evaluate the effectiveness, safety, and cost-effectiveness of MSAT on acute neck pain. The results of this study will be useful for clinicians in primary medical institutions that frequently treat acute neck pain patients and for policymakers working with national health insurance. Neck pain can develop into considerably severe pain, disability, and cause a financial burden. Years lived with disability from neck pain per 100,000 population was reportedly 352 from 1990 to 2017, and the neck pain was the fourth main cause of years lived with disability according to the 2016 Global Burden of Disease.Neck pain is one of the common musculoskeletal disorders in the general population. Although the prevalence of neck pain varies by studies conducted and the time period, the 1-year prevalence rate is reportedly 25.8% reported that the point prevalence of acute neck pain to be around 10%. There is currently no consensus for the definition of acute neck pain but is often defined as pain that does not last for more than 4 weeks.,8 There is no standardized guideline for the treatment of acute neck pain but in a study of patients that visited general practitioners for acute neck pain in the Netherlands, 42% of patients were prescribed non-steroidal anti-inflammatory drugs and muscle relaxation. In addition, other studies have reported on the effectiveness of laser therapy and cervical spine thrust manipulation on acute neck pain.Among the different types of neck pains, acute neck pain is considered a self-limiting disorder and adults can experience pain during typical activities . Acute neck pain is caused by loads applied internally to the tissues or external loads such as a fall and direct impact to the head or neck. However, little is known about the prevalence and treatment of acute neck pain, especially those not caused by whiplash. Vernon et al–14 However, the supporting evidence and data for the effectiveness and safety of MSAT are insufficient as only a few related studies have been conducted.The motion-style acupuncture technique (MSAT), which combines traditional acupuncture and movement therapy, is a treatment that induces passive and active movements of the patient with the needles inserted, after a traditional acupuncture treatment. All movements are made under the observation and guidance of a physician. MSAT has been increasingly used to relieve musculoskeletal pain in Korean clinical practice and recently has gained attraction in China as a method to enhance the effect of traditional acupuncture treatment. However, the study was only conducted for patients with a whiplash injury due to a traffic accident and the effectiveness of MSAT alone could not be examined since it was in a combination with the integrative Korean medicine treatment. Therefore, this 2-parallel, multi-centered randomized trial has been designed to evaluate the effectiveness, safety, and cost-effectiveness of MSAT and acupuncture treatment for acute neck pain that has not been caused by whiplash injury.Recently, the combination of MSAT and integrative Korean medicine treatment was reported to be effective for rapid pain reduction and range of motion (ROM) improvement in patients with pain in the cervical spine region due to acute whiplash injury.22.1This 2-armed, parallel, multi-centered randomized controlled trial (RCT) will be conducted at four community-based hospitals in Korea; Jaseng Hospital of Korean Medicine, Daejeon Jaseng Hospital of Korean Medicine, Bucheon Jaseng Hospital of Korean Medicine, and Haeundae Jaseng Hospital of Korean Medicine. A total of 128 patients, 64 for the MSAT and 64 for the acupuncture treatment groups, will be recruited from the 4 hospitals. Treatment will be performed 2 to 3 times a week for 2 weeks, followed by a follow-up for 8 weeks after randomization , at each of the institutions, before initiating the participant recruitment process . The protocol has been registered at the Clinicaltrials.gov (NCT04539184). Information regarding the healthcare institutions and investigators can be found on the clinical trial registration website.2.22.2.11)Neck pain onset or worsening within 1 month2)Visual Analog Scale (VAS) of neck pain on movement or at rest of 5 or higher3)Age between 19 and 70 years old4)Participants that provided informed consent2.2.21)Participants diagnosed with a serious disease that can cause pain 2)Progressive neurologic deficits or severe neurologic deficits3)Participants diagnosed with a soft tissue disease that can cause pain 4)Presence of chronic diseases 5)Participants on steroids, immunosuppressants, or psychotropic medication6)Participants who are inadequate or unsafe for acupuncture 7)Participants that took NSAIDs or underwent acupuncture treatment within the last 3 days8)Participants that had undergone cervical surgery within the last 3 months9)Participants that had a traffic accident within a month10)Pregnant women or women who planned to conceive11)Participants that had participated in another clinical trial within 1 month or planned to participle in other trials within 6 months of the enrollment12)Participants that could not provide informed consent13)Participants that found it difficult to participate in the trial according to the investigator's decisionThe patient may be dropped in clinical trials in the case of an unexpected risk or serious adverse events are occurred. The PI would make the final decision if to drop the patient.2.3All treatments, including the MSAT and acupuncture treatment, will be administered by Korean medicine doctors who have more than 3 years of clinical experience and received standardized training on both the Korean medicine treatment and MSAT. All treatments will be carried out for a total of 2 weeks.2.3.1The protocol for trapezius MSAT is as follows; the patient sits on a chair or the floor, straightens from low back up to the neck, pulls their chin slightly toward the body, and directs their gaze towards the front. In this position, the physician rotates the neck alternately from left to right with 3 disposable needles  inserted into the upper trapezius on both sides of the subject at a depth of about 5 to 10 mm. The neck movement range shall only be up to the ROM and the physician examines whether there is a difference from the normal ROM and presence of other abnormalities in the movement. When the side with the smaller left-to-right ROM is set as the affected side, the left-to-right turning motion is performed regarding the ROM on the affected side. At this time, with the midline of the body as the reference, the patient breathes in when moving closer to the midline and breathes out when moving away from the midline. The above movements are repeated 8 to 10 times and the physician examines whether the movement of the patient's head and neck area is normal. In case of a problem with the movement, the physician guides the patient by placing 1 hand on the posterior cervical region and the other hand on the face, thereby correcting the movement. After completing the repetitive movements, the maximum ROM is checked again and if it does not achieve normal ROM, the left-to-right turning motion is repeated. The procedure continues for a specified treatment time (within 15 minutes) and at the discretion of the physician, the treatment process could either be continued or undergo only the movement therapy or the acupuncture treatment without movement  after the treatment process.A total of 6 treatments will be performed 3 times a week for 2 weeks; however, depending on the patient's condition or circumstances, a total of 4 to 6 treatments for trapezius MSAT may be performed during 2 weeks.2.3.2The protocol for trapezius acupuncture is as follows; Acupuncture points are selected from primary meridians  and extraordinary meridians  on the bilateral upper and middle trapezius according to the physician's discretion. Acupuncture is performed with needles inserted into 6 to 12 selected points. Disposable needles  are used for the insertion, and depending on the characteristics of the acupuncture point, after the perpendicular or oblique insertion, a twirling method is performed for the patient to feel the acupuncture sensation.A total of 6 treatments will be performed 3 times a week for 2 weeks; however, depending on the patient's condition or circumstances, a total of 4 to 6 treatments may be performed when conducting the treatment twice a week. Duration for the needle insertion will be approximately 15 minutes.2.3.3rd week (visit 9), the primary endpoint in both MSAT and control groups. There are no treatment restrictions during the f/u period after the primary endpoint. However, during the study period, acetaminophen (maximum 4 g per day) will be allowed to all subjects and the use of the drug will be recorded in a self-report method.All treatments  for relieve neck pain are prohibited until the 32.42.4.1,17The primary outcome of this study will be the difference between the baseline (Week 1) and the primary endpoint, week 3 (visit 8) for the neck pain felt during movement. The VAS is an assessment tool on which the patient indicates the level of pain along a continuous line of 100 mm in length, with one end indicating no pain and the other indicating the worst pain possible.The VAS of neck pain felt on movement will be measured 7 times in total; at the screening, baseline, the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.22.4.2.1The VAS of neck pain felt at rest will be measured 6 times in total; at the baseline, the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.2.2,18 The patient selects the appropriate point, with no pain as 0 and the worst pain possible as 10. The level of pain felt by the patient on movement and at rest will be assessed.NRS is a numeric pain scale for an objective assessment of subjective pain felt by patients.NRS will be measured 6 times in total; at the baseline, the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.2.3,20NDI is an assessment tool for disabilities caused by neck pain while performing daily activities and consists of 10 items. Scores from 0 to 5 can be selected for each item, allowing for a total score of 50 points. The higher the score, the greater the disability in daily living.NDI will be measured 6 times in total; at the baseline, the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.2.4 In this study, the Korean version of the NPQ, translated and validated by Lee at al, will be used.The NPQ is a questionnaire that consists of 9-question items on daily life activities affected by the neck pain . Each question consists of 5 levels with 0 to 4 points, and a higher score indicates more severe consequent patient disabilities.NPQ will be measured 3 times in total; at the baseline, week 3 (visit 8), and week 8 (visit 9).2.4.2.5PGIC is a scale that assesses the patient's perception of improvement in 7 stages, and the subject responds to the improvement in functional limitations after treatment with a 7-point Likert scale. . This assessment scale was originally developed for psychological purposes but is currently used in other medical fields for assessing the improvement of pain.PGIC will be measured twice in total; at week 3 (visit 8) and week 8 (visit 9).2.4.2.6For the assessment of the expectancy for treatment of the patients, a 9-point Likert scale will be used.During the first visit at Week 1 (baseline), the subjects will select a score in response to a question “How much do you think the treatment you receive during the clinical trial period will relieve your symptoms?” .2.4.2.7Muscle weakness and loss of sensation will be examined and recorded. The active ROMs for the neck for flexion, extension, lateral flexion, and rotation will also be measured. In addition, the pain and discomfort status during each movement will be measured and recorded.Physical examination and measurement of ROM will be performed 6 times in total; at the baseline, the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.2.8EQ-5D indirectly estimates the quality weight of a specific health condition through a survey of the health condition through multiple aspects. It is the most widely used tool for assessing the quality of life. EQ-5D-5L is composed of 5 items  that investigates the current health status. The subjects respond to the questions using the 5-point Likert scale.  In this study, the Korean version EQ5D-5L will be used with its validity verified.EQ-5D-5L will be measured 3 times in total; at the baseline, week 3 (visit 8), and week 8 (visit 9).2.4.2.9The SF-12 is a survey questionnaire that assesses the health-related quality of life. The SF-12 consists of 12 questions in 8 domains that evaluates the physical and mental health. Domains related to physical health include physical functioning, role physical, body pain, and general health, and domains related to mental health include vitality, social functioning, role-emotional, and mental health. The higher the score, the better the quality of life. In this study, the validated Korean version of the SF-12 will be used.SF-12 will be measured 3 times in total; at the baseline, week 3 (visit 8), and week 8 (visit 9).2.4.2.10EQ-VAS is one of the tools that assess the quality of life. The patient can indicate their health condition along a continuous vertical line of 100 mm in length, with the bottom end indicating the worst health condition possible and the top end indicating the best health condition possible.EQ-VAS will be measured 3 times in total; at the baseline, week 3 (visit 8), and week 8 (visit 9).2.4.2.11 will be used and will be converted to costs for use in the economic evaluation.For the economic evaluation, medical costs, non-medical costs, and cost of loss of productivity will be measured. For evaluation of cost items, a separately developed structured questionnaire will be used. Medical costs include not only the formal medical expenses incurred when using medical services at medical institutions but also the informal medical expenses incurred such as purchasing health foods and medical devices. The expenses associated with the use of medical services, such as transport expenses, patient time expenses, and caregiving service expenses, will be categorized as non-medical expenses. The cost of loss of productivity refers to the cost of economic loss incurred by the inability to participate in labor due to the disease itself or premature death due to the disease. To calculate the loss of productivity costs, the Work Productivity and Activity Impairment Questionnaire (WPAI)Medical costs will be measured every visit and productivity loss costs will be measured 4 times in total; at the last visit of each week during the intervention period (visits 4 and 7), week 3 (visit 8), and week 8 (visit 9).2.4.2.12The type and dose of medication  taken during the study period will be checked through a questionnaire during each visit. For treatments other than the medication taken such as the injections, the number of the treatments will be recorded.2.5The timeline of the study is shown in Table 2.6t test as the primary analysis, the result showed that 106 subjects in total (53 per group) will be required. However, since the analysis of covariance is the primary analysis in this study, using the correlation coefficient of the mean difference between the baseline value and primary endpoint calculated through the pilot study, 0.24, the corrected number of samples was determined to be 100. Considering a dropout rate of 20% and recruitment from 4 institutions, a total of 128 subjects (64 subjects per group) were calculated as the number of samples required to conduct the clinical trial.To estimate the number of study subjects, the results of the unpublished pilot study was used. Based on the pilot study, the effect size of MSAT for patients with neck pain is 0.55. When estimating the number of samples while using the The calculation was performed based on the assumption level of significance at α=0.05 (2-sided test) and 80% of the power of the test with type 2 error (β) at 0.2. G∗Power 3.1.9.7 was used to estimate the sample size.2.7Subjects will be recruited using online advertising media and promotional posters, inside, and outside the study institutions.2.8In this study, a balanced block randomization method will be used. Each study institution will be set as strata, and 2, 4, or 6 will be used at random for the block size. Randomization will be performed by the statistical analysis manager using SAS Version 9.4  to create a random table with the same probability of each individual being selected. When a random table is assigned for each institution, it will be divided into a control group and an experimental group according to the randomization code, and 64 subjects will be assigned to each of the groups.The generated randomization results will be sealed in envelopes, delivered to each institution, and managed in a cabinet with a double lock. Randomization will be conducted only on subjects who have voluntarily provided written consent after a sufficient explanation of the clinical trial. The randomization envelope will be opened in front of the subject, the subject will be assigned to the randomized group, and the envelope will be stored separately in a cabinet with a double lock. Randomization results cannot be viewed in advance and cannot be changed after assignment2.9Due to the nature of the intervention in this study, it is impossible to blind the physicians and patients. However, in this study, the statistical analysis manager and the outcome assessor will be blinded to secure objectivity and reduce the bias as much as possible. Outcome assessment will be performed in a separate space before the treatment is performed by an assessor, who will not participate in the treatment and does not know the patient's group assignment, and has received standardized training for the data collection procedures.2.10In this study, an electronic Case Report Form (e-CRF), based on the internet-based clinical research management systems operated by the Korea Disease Control and Prevention Agency, will be used. Before commencing the study, standard operating procedures (SOP) will be developed, and training will be provided for investigators in each of the institutions about the detailed SOP and e-CRF writing guidelines. Double data entry verification will be conducted to ensure the accuracy of the data entered into the e-CRF and the investigators of each institution will be responsible for the accuracy of the entered data. Data entered in the e-CRF will be cleaned, locked, and concealed from all investigators, except for the investigator in charge of data management.2.11This study will be a randomized controlled study that analyzes the pain intensity scale, functional scale, quality of life, and costs data results of patients who meet the selection criteria.The primary analyses will be the intention-to-treat analysis, which evaluates those who have received treatment at least once, and the per-protocol analysis, which evaluates only those who have successfully completed the clinical study, excluding those who have been dropped out; the 2 analyses will be performed concurrently.For processing the missing values, multiple imputations using the Markov Chain Monte Carlo method will be used as the primary method, and 20 imputed datasets will be generated. In addition, the last observation carried forward method will be used for the sensitivity analysis.The sociodemographic characteristics and treatment expectancy of the subjects will be evaluated for each of the groups. Continuous variables will be represented as mean (standard deviation) or median (quartiles), and categorical variables will be represented as a frequency (%).The effectiveness endpoint of this clinical trial will be the difference in the amount of change between baseline and each time point by the group for the continuous outcomes . Analysis of Covariance will be performed using the baseline values of each variable as covariates and the group as a fixed factor.For the sensitivity analysis, datasets without the imputed values will be used to analyze the degree of change from the baseline. The mixed-effects repeated measures analysis will be performed for the primary and secondary outcomes at all time points. The time variable will be included as a categorical variable and the interaction terms of group and time will be included at each time point to evaluate the difference in the effectiveness of MSAT.t test.To compare the total amount of difference between 2 groups for each outcome within the treatment period (2 weeks) and the entire study period (8 weeks), the areas under the curve (AUC) within each period after randomization will be calculated. The difference in AUC between the 2 groups will be compared using the independent student Survival analysis for VAS of neck pain will be performed. At each time point, the patient ratio will be comparatively analyzed for each time point when the neck pain VAS falls below half of the baseline. A Kaplan–Meier survival analysis will be used to estimate the time until less than half of the neck pain recovery occurs after randomization, and the differences between groups will be compared using a log-rank test. Also, the Cox model will be used to estimate the hazard ratio.P < .05. In addition, the analysis will be performed after the end of the study  and interim analysis will not be allowed.All statistical analyses will be performed using the SAS version 9.4 statistical package  with the significance level set to In addition, this study aims to investigate the cost-effectiveness between MSAT and acupuncture treatment through an economic evaluation. The primary economic endpoint will be the incremental cost-effectiveness ratios of cost per Quality Adjusted Life Years (QALY) of the MSAT group against the acupuncture treatment group. The analysis period is the entire study period including the intervention period and follow-up period, and if estimation for the subsequent period is required, the costs and effectiveness after the follow-up period will be estimated by extrapolation through a regression model or a secondary analysis with decision modeling analysis.Medical costs will be calculated based on the number of treatments and the unit cost. For the unit cost, data on health insurance costs, institutional cost data, and patient answers will be used. The quality of life estimation for the QALY calculation, the quality of life derived by EQ-5D-5L will be used as the main endpoint, and EQ-VAS, and SF-6D will be used for the sensitivity analysis. The AUC method will be used for calculation. The units for the costs will be unified in Korean currency (won) as of 2020 and a 5% discount rate will be applied based on the guidelines for the economic evaluation of the Health Insurance Review and Assessment Service and represented in US dollars using the published exchange rate.Considering the characteristics of non-parametric data, 95% CI of the incremental cost-effectiveness ratios of cost per QALY will be estimated using the bootstrapping technique. In addition, the probability that of MSAT being cost-effective will be examined using the cost-effectiveness acceptability curves graph according to the degree of willingness to pay. All analyses will be made for costs through the healthcare system and social perspectives.2.12In this study, all adverse events occurring during the clinical trial will be examined and recorded. The adverse event refers to any undesirable and unintended signs , symptoms, or diseases that appear after the treatment in the clinical trial process, and is not necessary that the adverse event has a causal relationship with the treatment. Adverse events will be collected through patient complaints or observations, and the occurrence of adverse events between groups will be examined by occurrence frequency.The investigator will evaluate the causal relationship between the respective treatment method and the adverse events that occurred on a 6-point scale . In addition, the severity will be categorized into 3 levels using Spilker classification method.1.Mild did not impair the participant's normal activities of daily living (ADLs), caused minimal discomfort and required no additional treatment2.Moderate: significantly impaired the participant's normal ADLs and may have required treatment but they were resolved after treatment, and3.Severe: severely impaired the participant's normal ADLs, required intense treatment, and left sequelae)2.13Monitoring will be conducted to ensure the safety of the study's subjects and the integrity of the study data. Monitoring will be conducted through a total of 3 monitoring visits after the introductory meeting from the first subject screening time in the order of 2 regular monitoring visits, and 1 end-of-study monitoring visit at the end of the study. The monitoring will be conducted by the monitoring personnel in the host institution. Monitoring will be conducted by collating and comparing the case report forms and supporting documents, and examining the safety matters of the study's subjects.Monitoring is planned to be conducted a total of 3 monitoring visits, 2 regular monitoring visits from the time of initial patient enrollment, and one end monitoring visit at the time of completion of the trial.2.142.14.1Before initiating the study, the study protocol, CRF, informed consent form, and patient recruitment announcement will be submitted to the IRB at each site to obtain the appropriate approval for the study . All modifications to the protocol, CRF, informed consent form, and others will be subject to the approval of the IRB. All modifications will be updated on the trial registry. All clinical investigators participating in this study will be educated about the Helsinki Declaration and the Korean Good Clinical Practice Guidelines, the study protocol, and the SOP to protect the patients participating in this study.2.14.2Before the start of the clinical study, the investigator will provide sufficient information on the overall processes of clinical trial and treatment in a face-to-face meeting with the patient. The Investigator will obtain a signed informed consent from the patient and provide a copy of the consent form to the patient.2.14.3The results of this study will be shared with the participants, healthcare professionals, and the public by publishing or through trial registry. Only investigators who were directly or indirectly involved in the study will be listed as authors on study-related publications. The datasets used in the study are available from the corresponding author on reasonable request.2.15All personal information data of study subjects participating in this study will be managed under the strict supervision of the IRB and the personal information of the study subjects will be kept strictly confidential. All data collected from the subjects, that provided their consent to participate in this study, will be treated anonymously. In case of sharing this information with other institutions for research purposes, they may be provided in the form of arbitrary codes after excluding personal information.2.16In the case of direct harm in relation with this study, appropriate medical care may be obtained as determined by the investigator. Compensations for any damage would be proceeded according to the pre-designated insurance policy related to the study. All participants will be provided with an emergency contact number to reach study investigators so that they can receive the necessary support when they have any question or problem.3,14 Liu et al and Lin et al reported greater improvements in pain and ROM in the MSAT group compared to the control group with other types of treatments such as loxoprofen, physical therapy, and conventional acupuncture in RCT for acute low back pain patients. Shin et al reported greater effective improvement of pain and physical functionality in the MSAT treatment group compared to the diclofenac injection group in their study with patients with severe, acute low back pain. Luo et al reported superior outcomes in the MSAT group compared to the conventional acupuncture treatment group in a short-term treatment in their clinical study on cervical spondylosis. In an RCT with 100 WAD patients from traffic accidents conducted by Kim et al, the group that underwent a combination of trapezius MSAT and integrative Korean medicine treatment demonstrated a faster pain reduction and ROM improvements than the group with integrative Korean medicine treatment alone. However, qualitative evidence for the effectiveness and safety of MSAT is still insufficient.For spinal disease, the treatment that utilizes passive and active movements of the patient after needle insertion has gained recent widespread usage in China as well as in Korea.To our knowledge, this study is the first well-designed, multi-centered RCT that evaluates the effectiveness, safety, and cost-effectiveness of MSAT for acute neck pain. Due to the nature of the study design, the physician and patients cannot be blinded, but the outcome assessors and statistical analysts will be blinded to retain objectivity as much as possible.The results of this study will be useful for clinicians in primary medical institutions, that are frequently visited by patients with acute neck pain, and for policymakers working in healthcare insurance.Conceptualization: Doori Kim, Yoon Jae Lee, In-Hyuk Ha.Investigation: Yoon Jae Lee, Kyoung Sun Park, Suna Kim, Ji-Yeon Seo, Hyun Woo Cho.Methodology: Doori Kim, Yoon Jae Lee, Kyoung Sun Park.Supervision: In-Hyuk Ha.Writing – original draft: Doori Kim.Writing – review & editing: Yoon Jae Lee.


This article conceptualizes and mathematically models a dielectrophoretic microfluidic device with two sets of interdigitated transducer vertical electrodes for separation of a binary heterogeneous mixture of particles based on size; each set of electrodes is located on the sidewalls and independently controllable. To achieve separation in the proposed microfluidic device, the small microparticles are subjected to positive dielectrophoresis and the big microparticles do not experience dielectrophoresis. The mathematical model consists of equations describing the motion of each microparticle, fluid flow profile, and electric voltage and field profiles, and they are solved numerically. The equations of motion take into account the influence of phenomena, such as inertia, drag, dielectrophoresis, gravity, and buoyancy. The model is used for a parametric study to understand the influence of parameters on the performance of the microfluidic device. The parameters studied include applied electric voltages, electrode dimensions, volumetric flow rate, and number of electrodes. The separation efficiency of the big and small microparticles is found to be independent of and dependent on all parameters, respectively. On the other hand, the separation purity of the big and small microparticles is found to be dependent on and independent of all parameters, respectively. The mathematical model is useful in designing the proposed microfluidic device with the desired level of separation efficiency and separation purity. The magnitude and degree of non-uniformity of the electric field depends on the dimensions and shape of the microchannel and the electrodes as well as the electrode configuration. Researchers have proposed electrode configurations for purposes of separation of microparticles based on size [Devices employing flow passages with hydraulic diameters smaller than 1 mm are referred to as microfluidic devices ,3; the bic field ,5,6,7,8. on size ,5,6,7,8. on size ,5,6,7,8; on size ,10,11,12Re(fCM) can be easily altered by varying the operating signal. Thus, the operating frequency of the proposed device should be such that microparticles of a particular size will experience pDEP while microparticles of other size will experience negligible DEP. Re(fCM) with operating frequency for polystyrene  and silica microparticles  [Re(fCM) is dependent on the operating frequency. It can be noticed that for both types of microparticles, irrespective of their radii, the Re(fCM) is positive and negative at low and high operating frequencies, respectively. Furthermore, it can be noticed from crN) of a microparticle can be calculated using Equation (3).Among all the different parameters influencing DEP force, the polarity of 0.82 nS) . It can çetin et al.  modeled The microfluidic device conceptualized in this document can find application in the area of disease diagnosis, especially that requiring investigation of blood ,24. DiagThis work is the first to model the microfluidic device shown in The mathematical model of the microfluidic device conceptualized in the previous section of this document is detailed in this section. The mathematical model of the microfluidic device consists of equations of motion, equation of fluid flow, equations of electric voltage, and field. In microfluidic devices the flow is very small and one-dimensional, i.e., flow has velocity only in axial direction. Equation (4) represents the equations of the motion while Equation (5) is the equation of fluid flow . Equations (6) and (7) describe the electric voltage and electric field inside the microchannel, respectively.The equation of motion, Equation (4), accounts for forces such as that associated with gravity, drag, buoyancy, and DEP. The force associated with gravity and buoyancy are provided in Equations (8) and (9), respectively. The force associated with gravity and buoyancy have only one component and it is in the vertical direction. The force related to drag that is acting on the microparticle is shown in Equation (10) while that related to DEP is presented in Equation (11). The solution of equation of fluid flow, Equation (5), is required for determining drag which in turn is required for calculating the trajectory of the microparticles and is provided in Equation (12) .(8)Fg,x−5 s. A MATLAB program was developed for solving Equation (4). For solving Equation (4), there are two initial conditions as depicted in Equation (13) and Equation (14). The initial displacements of the microparticle are presented in Equation (13) while the initial velocities of the microparticle are shown in Equation (14). The microparticle can start from any location across from the cross-section of the microchannel and this represents the initial displacement of the microchannel. The initial velocities of the microparticle are same as that of the fluid at the initial location of the microparticle.Equation (4) is solved using Finite Difference Method (FDM). For this, the differential terms are replaced by difference terms. The second order differential terms are replaced by second order central difference term. The time step is maintained at 10The electric field required for solving Equation (4) is obtained by solving Equation (7). The electric field depends on the electric potential and thus it needs to be determined throughout the microchannel and for this Equation (6) needs to be solved. Equation (6) is solved using FDM as well after replacing second order differential terms by second order central difference schemes; the boundary conditions associated with Equation (6) include known voltages on the electrodes while the remaining boundaries are assumed to be insulated. It needs to be stressed here that solving Equation (6) for the entire microchannel will be computationally taxing and time consuming. To overcome this, Eqution (6) is solved only in a repeating unit of the microchannel and later information on electric voltage inside the repeating unit is mapped on the entire microchannel; similar apporach is taken with regards to the electric field and DEP force. The repeating unit is schematically shown in The performance of microfluidic devices employed for separation is quantified in terms of separation efficiency (SE), Equation (15), and separation purity (SP), Equation (16) . SE and SE and SP; this approach has been previously adopted by researchers [All studies are done by uniformly releasing several microparticles from the inlet of the microchannel and subsequently tracking their trajectories to determine earchers ,25,26. Oearchers ,28,29. Aearchers .pp1 = Vpp2). With the increase in electrode dimensions, the SE of 2.5 μm microparticles increases for all applied electric voltages. The residence time, of 2.5 μm microparticles, increases with the increase in electrode dimensions and this leads to a greater number of microparticles being captured on the electrodes thereby leading to the observed increase in SE, of 2.5 μm microparticles, for a specific applied electric voltage; residence time is the time spent by a microparticle inside the microchannel. For certain cases of equal applied electric voltages, all 2.5 μm microparticles released from the center of the inlet of the microchannel experience same pDEP from both sets of IDT electrodes due to which they remain uncaptured. This coupled with the fact that the number of 2.5 μm microparticle captured and subsequently released remain the same, the SP of the same remains independent of the electrode dimensions.The SP of both 2.5 μm and 5 μm microparticles are shown in pp; this is because the microparticles in the vertical plane through the center the microchannel experience equal pDEP from both sets of electrodes thereby preventing them from being attracted to the electrodes and subsequently captured on the same.The effect of volumetric flow rate on SP of 2.5 μm and 5 μm microparticles are shown in pp. At 20 Vpp, the microparticles in the vertical plane passing through the center of the microchannel experience same pDEP force from both sets of electrodes due to which they remain uncaptured and subsequently the associated SE lower than 100%. At equal applied electric voltages of 20 Vpp, the pDEP force is strong to capture all but those microparticles in the vertical plane through the center of the microchannel and thus, the SE is independent of the number of electrodes. On the other hand, the SE of 5 μm microparticles is independent of the number of electrodes; to achieve separation of the heterogeneous mixture, the 5 μm microparticles just need to remain suspended in the microchannel and this is unaffected by the number of electrodes thereby maintaining the SE of the constant at 100%.The influence of number of electrodes on the SE of 2.5 μm and 5 μm microparticles is provided in pp, the SP of 5 μm microparticle is constant irrespective of the number of electrodes. At equal electric voltages of 20 Vpp, none of the 2.5 μm microparticles in the vertical plane passing through the center of the microchannel are captured on the electrodes and subsequently they appear at the exit along with the 5 μm microparticles. As the number of 2.5 μm microparticles appearing at the exit of microchannel, along with 5 μm microparticle, is always same, the SP of 5 μm remains constant.For both equal and unequal applied electric voltages, there exists a vertical plane in the microchannel in which the DEP force is zero. This implies that the small microparticles in this vertical plane will not be attracted to the electrodes thereby influencing the SE of small microparticle and the SP of the big microparticle. This is the limitation of the microfluidic device; nevertheless, the device still exhibits good SE and SP as can be seen from the previous section.This document presents a dielectrophoretic microfluidic device with multiple finite sized vertical electrodes, arranged in interdigitated transducer configuration, for separation of microparticles based of size. The electrodes on one side of the wall are controlled independently from the electrodes on the other side of the wall. In this device, microparticles of a specific size are captured on the electrodes while bigger microparticles pass through the microchannel unaffected to realize separation. The influence of parameters (operating and geometric) on the performance metrics, separation efficiency and separation purity, are quantified in this document. Separation efficiency of the small microparticles increase with the increase in applied electric voltage, width of electrodes, and number of electrodes while it reduces with the increase in the volumetric flow rate; the variation in separation efficiency can be attributed to the residence of the microparticles in the device. The separation efficiency of the 5 μm microparticle is always 100% as separation does not depend on the dielectrophoretic force. The separation purity of the 2.5 μm microparticles is independent of the applied electric voltage, electrode dimensions and the number of electrodes; however, volumetric flow rate influences separation purity. Separation purity of 5 μm microparticles are influenced by applied electric voltages, width of electrodes, volumetric flow rate, and number of electrodes and it is observed to increase with the increase in these parameters; this improvement in separation purity of 5 μm microparticles is due to the increase in separation efficiency of 2.5 μm microparticles with the increase in the parameters.


Two spectral feature extraction strategies, namely, principal component analysis (PCA) and the optimal band combination algorithm, were introduced to choose spectral variables. Linear models and random forests (RF) were used for predictive models. The coefficient of determination (R2), root mean square error (RMSE), and the ratio of the performance to the interquartile distance (RPIQ) were used to evaluate the predictive performance of the model. The results indicated that the variables (2DI and 3DI) derived from the optimal band combination algorithm outperformed the PCA variables (1DV) regardless of whether linear or RF models were used. An inherent gap exists between 2DI and 3DI, and the performance of 2DI is significantly poorer than that of 3DI. The accuracy of the prediction model increases with the increasing number of spectral variable dimensions (in the following order: 1DV < 2DI < 3DI). This study proves that the 3DI is the first choice for the optimal band combination algorithm to derive sensitive parameters related to SOM in the coal mining area. Furthermore, the optimal band combination algorithm can be applied to hyperspectral or multispectral images and to convert the spectral response into image pixels, which may be helpful for a soil property spatial distribution map.Soil organic matter (SOM) is a crucial indicator for evaluating soil quality and an important component of soil carbon pools, which play a vital role in terrestrial ecosystems. Rapid, non-destructive and accurate monitoring of SOM content is of great significance for the environmental management and ecological restoration of mining areas. Visible-near-infrared (Vis-NIR) spectroscopy has proven its applicability in estimating SOM over the years. In this study, 168 soil samples were collected from the Zhundong coal field of Xinjiang Province, Northwest China. The SOM content (g kg The correlation graphs for the contour and slices were used to visualize the optimal band combinations and sensitive spectral response regions. We designed a computer program based on MATLAB version R2018b  to assist with the calculations and analyses. The optimal band combinations in Equations (1)−(5) and Equations (6)–(10) are denoted as the two-dimensional spectral index form (2DI) and three-dimensional spectral index form (3DI), respectively.Where The 168 samples were sorted in ascending order of SOM content. Then, we placed one of the three samples into the validation set and the other two samples into the calibration set. This procedure led to a calibration set and a validation set with 112 and 56 samples, respectively.Random forests (RF) are the product of ensemble learning and are currently popular in the fields of classification and regression . Specifitreesn), the number of variables per tree (trym), and the minimum number of terminal nodes (nodesize). The default value of treesn (500) has proven to be insufficient to produce stable results [treesn value of 1000. For nodesize, we use the default values in the package. For the optimization of trym value, it ranged from one to five and from one to 10, both were tested at the interval of one for the two-variable combinations (mentioned in the next The fitting of an RF model is controlled by the specification of three parameters: the number of trees ( results . Therefop < 0.05) exist between the calibration and validation sets and between the SOM content and Vis-NIR spectral data [R2), root mean square error (RMSE), and the ratio of the performance to the interquartile distance (RPIQ). Bellon-Maurel et al. [trym value was selected. The confidence intervals and prediction intervals [Analysis of variance (ANOVA) was used to verify whether significant differences  at the 0.05 significance level.The range of the entire SOM data set was 45.45 g kg6 g kg−1 . The kurThe average spectral reflectance of the different SOM classes is illustrated in S was greater than 90%. The eigenvector of PC1  presented three positive peaks within 400–609, 1329–1645 and 1860–2089 nm that can be attributed to the presence of Fe oxides, haematite, O-H, humic acid and smectite [The eigenvectors extracted by PCs were used to identify the obvious absorption characteristics of the SOM content . The cumsmectite . In the r) varied from 0.43 (PC4) to –0.37 (PC1) and from 0.31 (PC4) to –0.42 (PC3), respectively , followed by NDI , DI , SI  and PI . The optimal wavelength combinations differed in each 2DV form were extracted for subsequent linear and non-linear regression analyses with the SOM content  by using a three-dimensional slice map  performed the best in estimating the SOM, and the correlations (r) reached a maximum of 0.85 , followed by 2DI (R2c ranging from 0.33 to 0.48 and R2v ranging from 0.30 to 0.49) and 1DV (R2c ranging from 0.01 to 0.19 and R2v ranging from 0.01 to 0.18). The optimum model yields an RPIQ of 1.50 (< 2.70), indicating that the prediction effect of the model is not reliable. Therefore, the prediction accuracy of a single variable is insufficient, and it is difficult to effectively explain the spatial variation of the SOM in this region.The 15 potential variables extracted via PCA and the 2DI and 3DI algorithms are summarized in R2 and RMSE of the calibration and validation sets were then subjected to ANOVA; no statistically significant difference between calibration and verification was found (p > 0.05), indicating the stability of the established model ; 1DV+3DI yields good outcomes (RPIQ = 3.48); and the 1DV+2DI model had insufficient predictability (RPIQ = 2.48).Using the spectral parameter combination as the model input see  and RF aed model . Using tWe used the relative importance of the predictor variables derived from the RF model to interpret relationships between the SOM content and different input sources . To the In electromagnetic theory, SOM is represented as an organic compound containing functional groups with relatively discrete absorption characteristics in the Vis-NIR range . In the The goal of feature extraction is to minimize errors and exclude unreliable or noisy data to the greatest extent, which is essential to improve the interpretability of the model and/or reduce the complexity of the prediction model . Hong etR2 and small RMSE , the contribution rate of 2DI variables was much lower than that of 3DI variables  displays no shortage of imagination and information. Combined with the method of optimal three-band indices, this study provides useful insights into the assessment of soil nutrition concentrations in other regions.In this study, two spectral feature extraction strategies  were introduced to extract spectral variables. The results indicated that the model performance of the optimal band combination algorithm is better than that of PCA, regardless of whether linear or non-linear models are used. In the variables extracted by the optimal band combination algorithm, the performance of the 2DI is poorer than that of the 3DI. In summary, the accuracy of the prediction model increases with the increasing number of spectral parameter dimensions, which is consistent with our previous hypothesis. Therefore, the three-band index should be the preferred variable for spectral estimation of the SOM. Moreover, compared to the two-dimensional image map, the three-dimensional slice map of the correlation (


LC50SM) on the basis of which it was possible to determine the toxicity of thermal decomposition and combustion products in agreement with the standards in force in several countries of the EU and Russia. The analysis was carried out on the basis of the registration of emissions of chemical compounds during the thermal decomposition and combustion of polymer materials at three different temperatures. Moreover, the degradation kinetics of the polymeric belts by using the thermogravimetric (TGA) technique was evaluated. Test results have shown that products of thermal decomposition resulting from the neoprene (NE22), leder leder (LL2), thermoplastic connection (TC), and extra high top cower (XH) belts can be characterized as moderately toxic or toxic. Their toxicity significantly increases with the increasing temperature of thermal decomposition or combustion, especially above 450 °C. The results showed that the belts made of several layers of polyamide can be considered the least toxic in fire conditions. The TGA results showed that NBR/PA/PA/NBR belt made with two layers of polyamide and the acrylonitrile–butadiene rubber has the highest thermal stability in comparison to other belts.The article presents the potential impact of flat drive and transport belts on people’s safety during a fire. The analysis distinguished belts made of classically used fabric–rubber composite materials reinforced with cord and currently used multilayer polymer composites. Moreover, the products’ multilayers during the thermal decomposition and combustion can be a source of emissions for unpredictable and toxic substances with different concentrations and compositions. In the evaluation of the compared belts, a testing methodology was used to determine the toxicometric indicators (W Flat belts are used in machines and devices fulfilling both drive and transport function ,2,3. ClaNowadays, scientists are testing to not only improve the construction properties of machine parts, but also to limit the effects of fire on machines and devices ,19. SoloCzarnecka-Komorowska et al. developed a method of increasing the thermal resistance of polyoxymethylene (POM) , which i1.5)n, where R is a hydrogen atom or an organic group  [Polyhedral oligomeric silsesquioxanes (POSS) are nanostructures with the empirical formula of (RSiOe units) ,36,37. Te units) ,36,37. Pe units) .Numerous studies have been conducted to increase fire resistance and the effects of combustion and thermal decomposition of polymer composites ,40,41,42Nowadays, fiber-reinforced composites are commonly used materials for tension belts. Such material not only provides a high strength-to-weight ratio but also exhibits unique properties such as high strength, stiffness, attenuation property, flexural strength, and resistance to corrosion, wear, impact, and fire ,41,42. ALC50M) with the classification of materials according to the thermal decomposition and combustion products in terms of their toxicity.The aim of this paper is an assessment of the toxicity of thermal decomposition products of flat belt combustion from the polymer materials used. The results were to the thermogravimetry (TGA) and the toxicometric indicators , as shown in For toxicological testing, and to determine toxicometric indicators, four types of drive and transport belts were investigated. The belts made of different materials such as classic material named neoprene (abbreviation NE22) and polymer composite materials belts used nowadays such as leder leder (abbreviation LL2), thermoplastic connection (abbreviation TC), and extra high top cower (abbreviation XH) were compared. The NE22 belt was produced by a Brecoflex , and LL2Selected physical properties of multilayers polymer composites belts are listed in The classic belt marked as NE22 was made of a layer of woven polyester and covered with polychloroprene a. The voThe LL2 flat belt, which was shown in The TC belt was made of two polyurethane (TPU) layers, lower black (TPU) with a rough structure and upper green (conductive TPU) with a smooth structure c. The blThe XH belt was built of four polymers layers d. The upSEM microscopic images of the fracture surfaces of the tested belts are shown in −1 with a resolution of 4 cm−1 and an average number of scans of 16. Spectroscopic data were treated using the dedicated software Spectra Manager .To evaluate the toxicity of combustion and chemical decomposition of the belts, the Fourier-transform infrared spectroscopy (FT-IR) method was used. The measurements were carried out using a Jasco FT/IR 4700 apparatus . IR spectra were recorded in the spectral range of 4000–500 cmThe solid masses of the belts were measured by an electronic balance . The density was measured based on PN-EN ISO 1183-1:2005 standards . Ethyl aThe morphology of the fractured surfaces of belts samples was analyzed using a scanning electron microscope  with high-resolution imaging. The fractured surfaces of belts was investigated at 23 °C, in a vacuum, using the back-scattered electron (BSE) signal, with an accelerating voltage of 15 kV. Prior to the SEM analysis, the prepared samples were coated with a thin layer (20 nm) of carbon powder. A magnification of 1000× was used. The morphology of the belts was observed using an Opta-Tech camera  at 20× magnification.−1, and the cooling rate was set to 10 °C/min. The thermal properties of belts were evaluated by the initial decomposition temperature (iT) and the corresponding temperature at which the mass was reduced by 5% (T5%), 10% (T10%) and 50% (T50%), and temperature (maxT), corresponding to the maximum mass loss rate, which was the peak of the first derivative of the rate of thermal decomposition (DTG) curve. In addition, the fraction of the solid residue at 800 °C was obtained. Furthermore, in order to obtain kinetics parameters, TGA scans at 10, 20, and 30 °C/min were carried out, and the Kissinger method [The thermogravimetric analysis (TGA) of belts was carried out using a thermogravimeter: a Netzsch TG 209 F1 apparatus . The samples (about 10 ± 0.2 mg) were placed in a ceramic crucible and heated from room temperature to 800 °C at the rate of 10 °C/min in a nitrogen atmosphere. The flow gas rate was 40 mL Lr method .aE is the apparent activation energy (kJ mol−1), A is a pre-exponential factor (s−1), R is the gas constant (8.314 J mol−1 K−1), and maxT is the temperature of maximum rate of mass loss [Kissinger’s method  uses theass loss .The principle of the method is based on the quantitative, chemical determination of the products of thermal decomposition or combustion of materials determining the toxicity of the fire environment.Due to the lack of standards regarding the methodology for testing toxic products of thermal decomposition and the combustion of machine parts, a standard used in construction was used. About 4 ± 0.1 g of samples were prepared for testing, maintaining the uniform distribution of the represented layers. The tests were carried out in agreement with a Polish standard PN-B-02855:1988  regardinThe tests were carried out using an FT-IR analyzer , which continuously measured the mass concentrations of the tested components; the test stand is shown in 2), hydrogen cyanide (HCN), nitrogen dioxide (NO2), hydrogen chloride (HCl), and sulfur dioxide (SO2). Compounds not shown in the qualitative analysis were omitted in the quantitative test.The testing was carried out in two stages. In the first stage of testing, a qualitative analysis of the composition of products of thermal decomposition and combustion was carried out, superimposing the measured results on the standard spectra. The analysis of the tested material samples was carried out to determine carbon (C), hydrogen (H), nitrogen (N), sulfur (S), and chlorine (Cl) in order to exclude the possibility of carbon monoxide (CO), carbon dioxide , nitrogen dioxide (NO2), hydrogen chloride (HCl), and sulfur dioxide (SO2), the products of decomposition and combustion had to be passed through the absorbing scrubbers during the slide of the furnace on the sample (30 min) and its return to the starting point (5 min). The test was performed twice at each temperature. The test was repeated a third time if the difference in results between the samples exceeded 30%.In the second stage of testing, the samples were subjected to quantitative analysis of emitted compounds  during thermal decomposition and combustion. The tests were carried out at temperatures of 450 ± 5, 550 ± 5, and 750 ± 5 °C and at an air flow rate of 100 ± 10 dmDuring the tests, the concentrations of carbon monoxide, carbon dioxide, hydrogen chloride, hydrogen cyanide, nitrogen dioxide, and sulfur dioxide were determined.−−1).toxicometric indicator −toxicometric indicator −toxicometric indicator  of the mentioned products of thermal decomposition and combustion were determined. Specific emission (E) means the mass of toxic products produced during thermal decomposition and the combustion of a unit mass of a material under given test conditions. Next, by associating them with the properties of concentration limits  with was used to evaluate a qualitative identification of polymers. The obtained FT-IR spectra were interpreted with respect to the bands from the polymers in the analyzed belt. The results of FT-IR tests of the products of thermal decomposition and combustion were analyzed for NE22, LL2, TC, and XH samples. The spectra from the FT-IR analysis of combustion products of samples NE22, LL2, TC, and XH are shown in For the NE22 sample, the spectrum comes from the 300 s test, LL2 sample after 615 s, while for the XH after 645 s, and XH after 720 s of the test. Each IR spectrum was corrected for the presence of water and compared with a standard spectrum for the individual substances.2, NO2, NO, HCN, CO2, CO, HCl, HBr and HF gases was searched for on the spectra. Moreover, compared in detail the substances that were identified in the products of thermal decomposition of each belt, which illustrated in For the purpose of toxicity studies, the presence of SO−1 indicate the presence of SO2. A characteristic curve for the identification of NO2 are signals ranging from 1570 to 1650 cm−1 and for NO these are peaks between the wavenumber values of 1800 and 1940 cm−1. The presence of CO2 in the analyzed spectra was confirmed on the basis of the presence of the characteristic four peaks in the wavenumber range between 3560 and 3740 cm−1, while CO appears as two peaks between 2100 and 2200 cm−1. HCN is a substance whose presence is confirmed by two peaks in the range of 3200 to 3360 cm−1. HBr, HCl and HF appear as multiple peaks in the ranges 2400 to 2200 cm−1, 2650 to 3090 cm−1 and 3780 to 4200 cm−1, respectively. Their presence was not confirmed in any of the tested belt samples. −1, which indicate the presence of methane, however, it was not the subject of this analysis.The second stage of testing concerned the qualitative analysis of products of thermal decomposition and combustion of the belts NE22, LL2, XH, and TC, for 30 min at oven temperatures of 450, 550 and 750 °C, as presented in 2 during the combustion of all belts increased with increasing temperature. Carbon dioxide was found to be the largest product during the first step of degradation in nitrogen for all polymers, indicating the scission of the urethane bond [2 emissions in 450 °C for the LL2 belt were 400 mg/g, which is higher than the 100 mg/g of the TC belt, indicating that the natural leather of the LL2 belt significantly increased the toxicity during combustion, which was not observed for other belts. In the case of NE22 and HX belts, the emissions of substances at the same temperature were about 0 mg/g. During the toxicity test, the mass loss of products of decomposition and combustion of belts was also analyzed.Generally, in ane bond . The CO2Materials used for drive or transport belts can pose a threat to human health and life due to the emission of toxic products of thermal decomposition and combustion, such as carbon monoxide, hydrogen chloride, and hydrogen cyanide. They may affect safe evacuation conditions. The emission of toxic gases by burning materials in concentrations exceeding the lethal levels for humans can effectively prevent this evacuation, causing threats to health and life.The LC50MW) significantly decreases with the increase of the combustion temperature and thermal decomposition tested at 450 and 550 °C. On the other hand, at 750 °C, the value of the LC50MW results indicated that the belts made by polymer materials can affect the increase the toxicity emissions to the environment as the fire temperature increases.The LC50SM) were related to the classification criteria of toxicity of products of thermal decomposition and combustion in accordance with PN-B-02855, as presented in The obtained results of the toxicometric indicators  belts or toxic (LL2 belt) in the conditions of fire .LC50SMW) of the LL2 belt was 33.8 g/m3, which is lower than, e.g., NE22 and XH belts, indicating that the natural leather has a slightly reduced the WLC50SM compared with the polyamide/NBR material. In the case of both NE22 and XH belts, the WLC50SM was about 60 and 47 g/m3, respectively. This behavior is due to the chemical composition of the polymeric materials used to make the polyamide belts. It can be seen that the toxicometric indicator of the TC belt was 195 g/m2, which is higher than those of the other belts. Due to the TC belt being made by several polyurethane layers, it indicates the lowest toxicity during thermal decomposition and combustion.It can be observed that belts made of classic NE22 materials (polyester/chloroprene) and most of those used today, e.g., XH and TC belts, are classified in the same group of moderately toxic materials. The results showed that the most environmentally unfavorable material among the tested belts was the LL2 belt, which is made of multilayers of leather and is characterized by classification as toxic compound material. The value of toxicometric indicator , which may be a component of the assessment of the cause of fires in the area of machine operation. The values of LC50SMW for drive and transport belts, epoxy resins used for finishing industrial floors [The literature contains the values of toxicometric indicators  averages the individual toxicometric indicators determined for all tested products of thermal decomposition and the combustion of materials at three different temperatures. Meanwhile, the quantitative assessment of toxic fire hazard should consider the amounts of individual toxic gases released in a specific stage of a fire, with particular regard to the initial phase of its development, in which effective evacuation is possible. To assess the actual toxic hazard during a fire, attention should be paid to the toxicometric indicators (WLC50SM). The significance of the issue is increased by the percentage of mortality caused by smoke and the toxicity of fire products, which in the case of house fires is indicated at 60%–80% [The most dangerous are very toxic materials, which can be prohibited (when used inside a building) by legislators . However 60%–80% ,63,64,65 60%–80% ,67.T5 wt %, T10 wt %, and T50 wt %, respectively), as well as the temperature of maximum mass loss (maxT).TGA can serve as a useful indicator of polymer decomposition and flammability behavior ,19,40. TThermogravimetric analysis is one of the methods used for evaluation of the decomposition of polymers at the function of temperature ,68,69. FmaxT) at different heating rates  are shown in The values of maximum decomposition temperature  and thermoplastic polyurethane (TC sample). It also means that the XH belt made with NBR/PA fabric/PA film/NBR layers was characterized by the highest thermal stability, which means reducing the flammability of the belt made of such materials ,72.max) [For example, the polychloroprene of the synthetic rubber from which the NE22 belt was made is self-extinguishing compared to butadiene-based rubber (NBR). Compared to the polymer produced in the polyaddition process of a polyol with a diisocyanate, the decomposition of polyurethane begins at the temperature of 318.4 °C, i.e., 80% loss and up to 300 °C, up to 420 for all PU into monomers . In the max) .The actual thermal decomposition of the NE22 belt takes place in two steps. The largest weight loss step is about 23% and occurs in the first decomposition step at 313 °C, which is mainly due to the elimination of HCl and is seen as a large peak in the DTG curve. The second weight loss step of the degradation process is about 3% and occurs at 420 °C due to the combustion of carbon. For XH and TC belts, the maximum decomposition rate is almost the same (about 10 %/min). The maximum decomposition rate of the LL2 belt is about 4 %/min, which is much lower than that of other belts, and the char residue at 800 °C of a LL2 belt is 20 mass%.Additionally, it can be seen in max thermal decomposition rate due to the high energy of molecular cohesion. In the first stage of decomposition of a diene rubber, the catalytic dissociation of bonds is decomposed in the macromolecule skeleton, and in the second stage, the degradation and thermal breakdown of macromolecular fragments containing butadiene units occur, which is accompanied by the release of CO, CO2, and HCN destruction products [In the case of the XH belt, which is made of NBR/PA film/PA fabric/NBR, the belt is also characterized by lower values of the DTGproducts .maxT) of the belts shifts to a higher temperature, e.g., from 448.4 to 464.5 °C for the XH belt, which shortens the time needed for the sample to reach the same temperature, and the material cannot decompose completely, leading the peak maxT rate shift to a high value [It can be seen that that with the increasing of the heating rate, the peak mass loss rate  does not provide grounds for determining the actual fire hazard. The results showed that the most environmentally unfavorable material among the tested belts was the LL2 belt, which is made of multilayers of leather and polyamide 6 characterized by classification as toxic compound material.Flat drive and transport belts made of composites can become a serious toxic hazard during a fire. An improvement in the strength and durability of the belts seems to reduce this hazard; however, the results of testing showed no significant improvement in reducing the effects of a fire on the drive and transport belts. The emission of toxic products of thermal decomposition and combustion can cause a lethal hazard during a fire in places where transmission gears and conveyor belts are used. Material classification based on the toxicometric indicator (WA useful parameter for quantifying the threat of toxic products of combustion may be the critical mass of the material, which indicates how much of the material can be used in a given room, so that in the event of a fire, the concentration limits of products of thermal decomposition and combustion are not exceeded. However, published studies indicate that drive and transport belts require further work on their chemical composition to minimize their negative impact on human health and life during a fire. Based on the TGA analysis, it was found that the XH belt has higher thermal stability in the temperature range up to 300 °C, when compared to the other TC belts made with thermoplastic polyurethane.


This paper utilizes the advanced potential of pseudodynamic three-dimensional finite-element modeling to study the axial mechanical behavior of square and rectangular reinforced concrete columns, confined with fiber reinforced polymer (FRP) jackets and continuous composite ropes in seismic applications. The rigorous and versatile Riedel-Hiermaier-Thoma (RHT) material model for concrete is suitably calibrated/modified to reproduce the variable behavior of characteristic retrofitted columns with deficient internal steel reinforcement detailing, suffering nonuniform local concrete cracking and crushing or bulging and bar buckling. Similarly, the 3D FRP jacket or rope confinement models may account for damage distribution, local fracture initiation and different interfacial bonding conditions. The satisfactory accuracy of the reproduced experimental stress-strain envelope behavior enables the analytical investigation of several critical design parameters that are difficult to measure reliably during experiments. Additional parametric analyses are conducted to assess the effects of steel quality. The significant variation of the field of developed strains on the FRP jacket at the ultimate and of the developed strains and deformations on steel cages among different columns are thoroughly investigated. This advanced analytical insight may be directly utilized to address missing critical parameters and allow for more reliable FRP retrofit design of seismic resistant reinforced concrete (RC) columns. Further, it allows for arbitrary 3D seismic analysis of columns  or addresses predamages. Advanced fiber reinforced polymer (FRP) materials made of carbon, glass or aramid fibers, and structural fiber ropes, are widely used in several structural retrofit applications worldwide or as an internal reinforcement ,16,17,18All these experimental investigations have led to the proposal of a large amount of semi empirical models trying to predict with accuracy the ultimate stress and strain behavior of concrete columns when subjected to monotonic axial loading ,56,57,58Yu et al.  made a cThe extensive investigation of the recent experimental and analytical databases by Fanaradelli et al. ,71 suggeThe approach followed herein is the utilization of several characteristic existing experimental efforts of columns under axial concentric loading-unloading-reloading cycles of increasing compressive displacement cc) and the corresponding axial strain (εcc) and the ultimate axial stress (fcu) and strain (εcu) of confined concrete at the failure of the column. These characteristic values are depicted in cu = fcc. For columns with descending second branches, based on the loading control (and loading rate) followed during the tests, very low axial stress values may be recorded at failure. However, based on the existing design recommendations [cc . Therefore, the failure (ultimate) stress may be fcu = 0.85 × fcc if there is a gradual load drop  or higher than 0.85 × fcc and lower than fcc if there is an abrupt FRP fracture. Based on this approach the corresponding εcc and εcu are defined at the same points, see also [The final database by Fanaradelli and Rousakis  gathers ndations ,73, the see also ,53,58,63cu for all the columns of the corresponding database presents AAE higher than 50%. This paper suggests that the gathered characteristics and experimental results are not adequate in order to accurately predict the strain at failure. Therefore, 3-dimensional FE models of characteristic columns were developed and analyzed pseudodynamically, aiming at addressing unidentified design parameters through thorough assessment of the analytical results at regions that the corresponding experimental results were not available or impossible to measure . RC squroach in , Ilki etroach in  and Isleroach in . All theThe rigorous and versatile 3-dimensional pseudodynamic finite-element modeling was used for the first time to study the axial mechanical behavior of square and rectangular RC columns, confined with FRP jackets and continuous composite ropes for seismic resistant applications. Advanced material models for concrete, composites and steel are suitably calibrated to conduct numerous analyses. ANSYS Explicit Dynamics  was usedThe Riedel-Hiermaier-Thoma (RHT) model ,77,78 waThis failure surface can be used to represent the following aspects of the response of geological materials: pressure hardening, strain hardening, strain rate hardening in tension and compression, third invariant dependence for compressive and tensile meridians, strain softening (shear induced damage) and coupling of damage due to porous collapse. It enables the reproduction of monotonic, repeated or cyclic imposed displacements  highly inelastic behaviors, damage redistribution effects and highly local degrading behavior. The RHT model was suitably calibrated through extensive and comprehensive investigations to eliminate the effect of the rate of axial loading and to provide satisfactory hardening or softening or crashing behavior of concrete under triaxial loading and the effects of predamaged concrete core and damage redistribution. In these pseudodynamic analyses, plastic deformation is computed by reference to the Von Mises yield criterion. Therefore, the local yield condition isp0 is the yield strength and A the tangent modulus.The onset of yielding (plastic flow) is purely a function of the deviatoric stresses (distortion). A bilinear isotropic hardening model was used to define the yield stress (Y) as a linear function of plastic strain, εThe model for structural reinforced polymer composites was suitably calibrated taking into consideration the common properties of epoxy resins used for fiber sheet impregnation and bonding on concrete. Therefore, the analyses may reproduce local damage initiation of the jacket  and thus consider the effects of the corner radius of the section. Full bonding of the jacket on concrete was considered in all cases . As the fibers in the FRP jackets, considered in the present study, were all oriented in the hoop direction, the stiffness (both tensile and compressive) in the axial direction  was negligibly small. Therefore, the elastic lamina option was used to model an orthotropic elastic material. A local coordinate system was assigned to the FRP jacket, and the hoop direction and the axial direction were adopted as the first principal and second principal material orientations, respectively.The modulus of elasticity in the axial direction and the shear modulus were both assumed to have lower values than the ones provided by the manufactures for the net fiber sheet, because they take into account the impregnation with the epoxy resin. For example, for the carbon fibers for specimen series BS1C/BS2C of FE analysis includes the following steps: (1) the geometric characteristics of the members of the model were determined, (2) the properties of the materials were defined, (3) the connections and contacts among members were assigned and (4) the type of discretization of the model and the density of discretization was determined depending on the number of seeds in each surface and the suitable meshing technique . Seeds are constant nodes, placed along the perimeter of the cross sections. They control the precise location of the meshing nodes. Thus, special care was taken for the seed distribution, in order to take into account, the curvature of the edges and crucial detailing of the specimens. The main target of meshing is the compatibility of the nodes between the concrete core and the FRP jacket in order to avoid convergence problems during analysis, (5) the mode of imposed displacement over time was defined to simulate pseudodynamic application. Monotonic axial displacement was forced at the top of the column, directly on the concrete core and not on the FRP jacket and (6) the boundary conditions of the model were determined. “Fixed Support” was chosen at the base of the column. The monotonic mode can provide the envelope analytical load-displacement curve and thus avoid the extremely time-consuming cyclic mode, as the experimental response between identical columns subjected to monotonic or cyclic loading was fairly close to each other.Two body interactions were created. All the elements adopted the “Frictionless” type. This type simulated friction conditions between all the elements. For the second “Body Interaction”, only the elements that made up the longitudinal and transverse reinforcement were selected and for the integration of the reinforcement within the concrete core. When an element consists of several parts, it is necessary to determine the connections between the elements. Based on numerous investigations with five available contact options, the interaction surface between the FRP and the concrete that is in contact was considered fully “bonded” for all specimens. All the nodes of bodies included in bonded interactions were tied to faces of involved bodies.Explicit mesh was followed to form accurate 3D grid. Six-node elements  and present satisfactory convergence with the experimental results up to the ultimate conditions of the column series BS1C, as shown in The performance of the FE analytical models for the columns with steel stirrups spaced at 95 mm (BS2C series) was similar, as presented in The performance of the FE models against the experimental behavior of RC columns of the square concrete section of very low concrete strength and with a different corner radius with steel reinforcements of intermediate quality are presented in The comparisons for the RC columns of rectangular section with steel reinforcements of lower quality and sparse stirrups are presented in Based on the advanced and reliable FE analyses, several aspects of the behavior of the retrofitted RC columns may be further investigated. The RHT model for concrete may provide quantification of the local damage initiation, extent and development within the concrete core through the index named after the damage coefficient  at different levels of imposed displacements. The FE analyses suggest that the first local damage for BS1C1C initiated at the concrete located at the middle-side regions of the specimen at its middle-height, between the two steel stirrups and the FRP jacket a at 0.00Similarly, specimen BS1C3C shows first local damage in the concrete at the center of the specimen, between the two steel stirrups and the FRP jacket e at the These analyses suggest that in experiments the effects of slender bars could be more pronounced (for the FRP jacket to reach its capacity) as the bars are in reality self-anchored inside the column and not fixed on the bottom and top boundaries as in the FE models. However, no unstable behavior of the bars under compression was recorded in the FE analyses up to the ultimate axial strain. It seems that there might be an interaction between the local damage of the concrete and the FRP fracture that needs further experimental and numerical investigation.The analytical elaboration for the specimens BS2C1C and BS2C3C with stirrups at 95 mm spacing (BS2C series) shows that the concrete failed locally and the FRP also reached its local failure. For BS2C1C, for axial strain of 0.009375, the concrete local failure started at the corner region of the mid-height stirrup a–c. At tThe FE results for BS2C3C were similar with the initiation of local failure within the concrete but without simultaneous local FRP failure. However, at the ultimate condition, the damage spread further within the concrete and FRP strain at the ultimate condition was again higher than its capacity a–c.Specimen BS2C5C behaved differently than the other two specimens of this series. Specimen BS2C5C had 5 layers of CFRP and the concrete did not exhibit local damage. It is observed that in the last step of the loading, there was severe damage at the corners of the middle stirrup, but the concrete did not fail locally e,f. The The ratio of strain at the corner of the middle stirrup to strain of the corner in-between the two stirrups in the BS2C1C specimen was close to 3, while in the other two specimens the same ratio was about 2. This is a consequence of the first development of concrete cracks at the corner, at the level of the middle stirrup as is shown in the corresponding figures. The ratio of the maximum strain at the corner, at the level of the middle stirrup to the minimum strain of the mid-side at the same level for all these specimens, was close to 1. It seems there was more uniform strain distribution along this axis for the three specimens. It seems that there was a more pronounced interaction between the local damage of the concrete and the FRP fracture at the corners that needs further experimental and numerical investigation.The FE analyses for specimen LSR-R-1-3-10b, with a very low corner radius of 10 mm, suggest that the first local damage initiates at the concrete located at the four corners of the specimen at the level of the stirrup and it is extended to more than the half height of it. The first local damage was shown for an axial strain of 0.045 a. It is The FE analytical behavior of column LSR-R-1-3-20b was similar. The concrete local failure initiated at the 0.033 axial strain and it was located at the same concrete area d. The coSpecimen LSR-R-1-3-40b shows similar damage development inside the concrete core f–h. Thercu < 0.85 × fcc < fcc) and the ultimate stress fcu was less than 15% of the maximum bearing stress. So, there was a revision of the ultimate value to the 0.85 × fcc and of the corresponding value for εcu compared to the experimental stress-strain curves of the test results. The analytical results were evaluated for the ultimate axial strain equal to 0.005.The FE analysis shows that local damage initiated at the concrete located at the area around the longitudinal steel bars at the level of the stirrup a,b in spSpecimen R2.0H2CL4 exhibited similar behavior to the previous column. The concrete area located around the longitudinal steel bars at the level of the stirrup was crucial a,b. The cc). The maximum tensile strains on the FRP were similarly low around 0.004–0.0064.It seems that in both cases, due to the high side ratio , the effectiveness of the confinement provided by the steel stirrups and the FRP jacket was too low to enhance the deformability and strength of the plain concrete or to restrict the unstable behavior of slender steel bars. Therefore, there was a degrading post-peak stress-strain behavior and the bearing stress was more or less stabilized at very low levels for structural applications (lower than (0.80–0.85) × fBS2C3C .BS2C3C_360 .BS2C3C_450 .The presented FE analyses did not deal with the effect of the quality of steel reinforcement on the effectiveness of the external FRP confinement. Additional FE analyses were performed for conventional longitudinal bars of 14 mm diameter with nominal yield strengths: 360 MPa, 450 MPa and 560 MPa. All different analyses were terminated for the same ultimate tensile strain of the FRP at the corner, at the level between two stirrups, as assessed for specimen BS2C3C (0.009179). For specimen BS2C3C_360, the ultimate stress from the FE analysis was 46.5 MPa at a strain of 0.01125 and specimen BS2C3C_450 provided analytical stress of 48.71 MPa at a strain of 0.01195.The analytical elaboration for the specimens BS2C3C_360 and BS2C3C_450 show that the material that finally fails was again the concrete, as in specimen BS2C3C. For BS2C3C_360, the tensile FRP strain at the ultimate condition, at the corner region of the mid-height stirrup was 0.01308 and at the corner of this stirrup it was 0.01398 b. For spIt is also observed that the differences in the characteristic values for the strain of the FRP and longitudinal and transverse steel reinforcements among these specimens were marginal. Comparing the FE results of these three RC columns, it seems that the axial stress-strain capacity of the columns was marginally decreased due to the lower yield stress of the steel bars. The bars of lower yield stress marginally affected the axial deformability levels of the columns, exhibiting a decrease of axial strain ductility.Analyses were performed on cylindrical columns confined with Ropes of Polypropylene by Rousakis  Figure a. These VFR = 738 MPa and a tensile elongation at a failure of 4.6%. The first column had one layer with 5.83 mm spiral spacing , the second one had one layer with 13.18 mm spiral spacing  and the third had one layer with 20.06 mm spiral spacing . The columns of the v1 group had stopped early for safety reasons before the fracture of the confining means.The vinylon fiber ropes (VFRs) of the study consisted of three Z-twisted fiber strands . They had a low E-modulus of 15,900 MPa, a tensile strength of ft/fc was 0.1 (where ft is the tensile strength and fc is the compressive strength [The concrete was modeled using the RHT concrete model. The compressive strength for specimen VinL1v1R1 was 17.9 MPa and the tensile strength ratio fstrength ). The coThe analytical stress-strain curve for specimens of the VinL1v1 group subjected to axial compression is depicted in Finally, analyses were carried out on square RC columns confined with ropes of polypropylene by ,47 Figub,c. Thesy,long = 500 MPa and fy,stirrup = 220 MPa, respectively. The modulus elasticity of steel was Es = 200,000 MPa and the Poisson’s ratio ν = 0.3.For the simulation of PPFR, which is a Z-twisted two-strand rope, the ultimate stress was 405.3 MPa, the tensile modulus of elasticity was 2.0 GPa and 20.36% elongation at failure. The yield strength of the longitudinal steel and stirrups was fThree-dimensional finite-element modeling was used herein to study the axial mechanical behavior of square and rectangular RC columns, confined with FRP jackets and continuous composite ropes. The pseudodynamic approach was utilized for the first time to enable for the reproduction of monotonic, repeated or cyclic imposed displacements . It may capture demanding inelastic behaviors, damage redistribution effects and local degrading behavior. The analytical models of the small and real scale columns under investigation were developed based on suitably calibrated material models, realistic representation of all the internal steel detailing and the external FRP jacketing, suitably designed FE meshing and interactions among different materials and interfaces and proper body interactions (necessary for the pseudodynamic process). The analytical results of RC columns confined with composites compared well with the experimental stress-strain curves of several characteristic RC columns of the square or rectangular concrete section with varying concrete strength, corner radius, FRP jacket mechanical properties or non-bonded composite rope confinement. In particular, the FE analyses follow closely the experimental curves for specimen series BS1C/BS2C and LSR-R-1-3 with ascending curves and for specimen series R2.0H2CL with descending second branches. All the analyses were stopped at the experimental ultimate axial displacement while the corresponding ultimate axial stress in all cases exhibited an AAE of 13%. Therefore, the proposed validated pseudodynamic modeling approach enabled for the first time to investigate analytically several critical design parameters and conduct parametric analyses.The advanced FE models considered the effects of the slenderness of bars, deficient stirrups or local crushing of the concrete and therefore were used as a basis to investigate the effects of steel reinforcement quality on the stress-strain behavior of the columns. Several parametric analyses were investigating the influence of different yield stress of longitudinal steel and stirrups . It is observed that the bars of lower yield stress affected marginally the axial deformability levels of the columns, exhibiting a decrease of axial strain ductility.FRP jacket fracture is widely accepted as the failure criterion for most of the experimentally investigated cases and for the proposed design models. Further, the contribution of steel bars and stirrups may be variable. This study focused on the significant variation of the field of developed strains on the FRP jacket at the ultimate condition and on the developed strains and deformations on steel cages among different columns. Eventually, all steel bars under compression exhibited and maintained strains higher than the yield one with high variation along the axis. All stirrups under tension exceeded their yield strain or achieved strains very close to it. The measured deformations suggest nonuniform bulging of the retrofitted column both axially and transversely. The critical position to place strain gauges in order to measure the representative axial strain of the steel reinforcement under axial compression in experiments (close to the average one for the column), may be in the middle-height of the area of interest (far from end boundaries) and at the mid-distance between successive stirrups  and not at the area close to the stirrups. The investigated variable field of FRP strains suggest that there was, in some cases, local fracture of the jacket at the corner region  while the global behavior of the column did not reach the ultimate failure. This aspect was captured due to the suitable composite jacket modeling among others. The measured FRP tensile strains were higher at the corner region at the height of the stirrups for most of the specimens. For lower FRP confinement and for lower corner radius there was a high local damage development in the concrete and local bulging in both the concrete and FRP. It seems there was an interaction between the local damage of the concrete and the FRP fracture that needs further investigation. Finally, the advanced parametric FE analyses confirm previous investigations ,67,68 anAll these investigated critical parameters will significantly enrich the extensive experimental databases for such retrofitted columns gathered in ,71. The