Seung Nam Min

Accuracy and Reliability of The Spine-Pelvis Monitor to Record Three-Dimensional Characteristics of The Spine-Pelvic Motion

Objective: The aim of this study is to evaluate the accuracy and reliability of Spine-Pelvis Monitor(SPM) that was developed to measure 3-dimensional motion of spine and pelvis using tilt sensor and gyro sensor. Background: The main cause of low back pain is very much associated with the task using the low back and pelvis, but no measurement technique can quantify the both spine and pelvis. Method: For testing the SPM, 125 angles from three anatomical planes were measured three times in order to evaluate the accuracy and reliability. The accuracy of SPM in measuring dynamic motion was evaluated using digital motion analysis system. The motion pattern captured by two measuring methods was compared with each other. In result, the percentage error and Cronbach coefficient alpha were calculated to evaluate the accuracy and reliability. Results: The percentage error was 0.35% in flexion-extension on sagittal plane, 0.43% in lateral bending on coronal plane, and 0.40% in twisting on transverse plane. The Cronbach coefficient alpha was 1.00, 0.99 and 0.99 in sagittal, coronal and transvers plane, respectively. Conclusion: The SPM showed less than 1% error for static measurement, and showed reasonably similar pattern with the digital motion system. Application: The results of this study showed that the SPM can be the measuring method of spine pelvis motion that enhances the kinematic analysis of low back dynamics.

3D Hand Anthropometry of Korean Teenager’s and Comparison with Manual Method

The requirements of wearing products fitting comfort was continuously increasing and considerable attentions had been paid for a long time. The assessment of the physical dimensions of the human hand provided a metric description to establish human-machine compatibility. Higher accuracy in hand anthropometric measurements could be achieved with the aids of an image analysis system. Scanning of hand surfaces either 2D or 3D was an alternative method for manual measurements. Three-dimensional anthropometry may lead to significant improvement in fitting comfort of wearing products. The purpose of this study was to measure 3D hand anthropometry and compared it with manual methods. For that purpose, 10 hand measurements of the right hand (lengths, breadths, and circumference of hand and fingers) were taken from 1,700 middle and high school students by age ranged from 13 to 19 years old. The hand was measured by manual (using anthropometric sliding, spreading calipers and measuring tape) and using a high-resolution 3D hand scanner (NEXHAND H-100, Knitech, South Korea) with the scanning accuracy ± 0.5 mm. From the scanned data, the hand measurements were extracted using scanning software (Enhand, Knitech, South Korea). Mean and standard deviation for each hand measurements were calculated. T-test statistical test on the data revealed that there was no significant difference between the manual and 3D hand measurements (p > 0.05). Therefore, 3D anthropometry can be replaced with manual methods. The data gathered may be used for ergo-design applications of hand tools and devices. And also it can provide a great help to develop a hand anthropometry database for hand wearing products.

Evaluation of the Functional and Non-functional Seat Sponge Effect in Sitting Chairs

Objective: The purpose of this study was to evaluate comfort levels of functional and non-functional chairs using subjective comfort rating, interface pressure measurement, muscle activity measurement, and skin temperature measurement. Background: Chairs are used for a prolonged period of time for sitting in many places such as the office, at university, at school, in industry, and so on. Almost all people use chairs in their everyday life. The functional properties of the chair are associated with comfort. Method: The subjective evaluation contains questions regarding chair comfort which can be rated with five point scale. The body-seat interface pressure was measured using a pressure mat system. The symmetry of sitting was measured using electromyography. The change in body part (thigh and buttock) temperature before and after sitting on a chair was measured with an infrared camera. Results: Participants rated significantly (p Conclusion: Overall, interface pressure measurement, muscle activity measurement, thermal imaging and subjective comfort score results showed that the functional chair was more comfortable than the non-functional chair. Application: The adopted methodologies could be used to measure the seating comfort of train seats.

The Effects of Wearing Spandex Underwear on Muscle Activity and Heart Rate

Objective: The purpose of this study was to analyze the effects of wearing spandex underwear on the muscle activity and heart rate during flexion and extension of trunk and knee joint. Background: Back pain continues to be the leading overall cause of physical illness and lowering productivity in workplace. Recently, the utility of assistive garment or back belt have been discussed to lessen the back pain as well as to preserve the right posture. Method: Ten males and ten females participated in the experiment. Gender, wearing spandex underwear and postures were used for independent variables, and muscle activity, the level of asymmetry of muscle activity and variation of heart rate were used as dependent variables. Muscle activity and heart rate were measured during flexion and extension of trunk and knee joint. Results: When wearing spandex underwear, the muscle activity was relatively low compared to the condition not wearing the spandex underwear. The symmetry of muscle activity and the variation of heart rate were statistically significant at the 0.05 significance level. In particular, it was found that the symmetry of muscle activity increased while wearing spandex underwear. Conclusion: Spandex underwear has an effect that can reduce asymmetry of right and left muscles which are relevant to leg because spandex underwear equally supports right and left low-back muscles. Application: The spandex underwear used in this study can apply to the rehabilitation as an useful assistive device.

Quantitative Comparison of the E-book and Paper-book by using Eye-tracker

Objective: The aim of the study is to evaluate the difference of legibility between e-book and paper-book by using eye-tracker. Background: Despite of many researches on the e-book and paper-book, there are few researches on the difference between e-book and paper-book. In addition, the researches on the e-book were only dependent on the e-book reader. This study focused on the comparison of e-book and paper-book controlled with the same environments. Method: This study was conducted with 2×3 within-subject design. Independent variables include the types of book (e-book, paper-book) and font sizes (8pt, 10pt, 12pt). Dependent variables are four measures of fixation duration, saccade length, blink rate and subjective discomfort. Analysis of Variance (ANOVA) with repeated measured design was used to investigate the main and interaction effects of independent variables on each of the dependent variables. The multiple comparisons were performed by post hoc analysis and Bonferroni correction was applied. Results Fixation duration at e-book was longer than paper-book (p<0.01). Saccade length at e-book was shorter than paper-book (p<0.05). Blink rate at e-book was higher than paper-book (p<0.1). Subjective discomfort at e-book was higher than paper-book (p<0.1). Legibility at 8pt was better than 10pt, 12pt (p<0.01) in fixation duration, saccade length and subjective discomfort. Conclusion: It was found that the legibility at e-book are worse than paper-book from this study. These results indicated that the legibility of e-book was needed to be validated and improved to replace the paper-book. Application: This study suggests improving something related to fixation duration, saccade length, blink rate and subjective discomfort for betterment of e-book.

Development of an Algorithm for Stroke Prediction: A National Health Insurance Database Study in Korea

Background: Stroke is the second leading cause of death worldwide and remains an important health burden both for the individuals and for the national healthcare systems. Potentially modifiable risk factors for stroke include hypertension, cardiac disease, diabetes, and dysregulation of glucose metabolism, atrial fibrillation, and lifestyle factors. Objects: We aimed to derive a model equation for developing a stroke pre-diagnosis algorithm with the potentially modifiable risk factors. Methods: We used logistic regression for model derivation, together with data from the database of the Korea National Health Insurance Service (NHIS). We reviewed the NHIS records of 500,000 enrollees. For the regression analysis, data regarding 367 stroke patients were selected. The control group consisted of 500 patients followed up for 2 consecutive years and with no history of stroke. Results: We developed a logistic regression model based on information regarding several well-known modifiable risk factors. The developed model could correctly discriminate between normal subjects and stroke patients in 65% of cases. Conclusion: The model developed in the present study can be applied in the clinical setting to estimate the probability of stroke in a year and thus improve the stroke prevention strategies in high-risk patients. The approach used to develop the stroke prevention algorithm can be applied for developing similar models for the pre-diagnosis of other diseases.

Anthropometric Data for Biomechanical Hand Model

The aim of this study was to investigate the anthropometric data for the segment masses, center of mass (COMs) of the segments of inertia, and radii of gyration are required for the development of the biomechanical hand model. The segment masses were calculated on the basis of the segment volume using a density of 1.1 g/cm3. The segment volume was estimated from the measured length between the participants’ distal and proximal joints (segment length) and the diameters of their knuckles. The COMs for the proximal and middle segments and the distal segment were determined by approximating the phalanx by the frustum of a cone and a cylindrical homogeneous rigid body, respectively. The diameters of the knuckles were measured for each participant. We assume that they have a uniform density. The moments of inertia of the proximal and middle segments were determined by approximating the phalanx as the frustum of a conical homogenous rigid body. The diameters of the knuckles were measured for each participant. The moments of inertia of the distal segments were determined by approximating the phalanx as a cylindrical rigid body. The radii of gyration, Kx, Ky, and Kz, of the segment about the x axis, y axis, and z axis are defined as Pytel and Kiusalaas. This information will be provide useful data for development of biomechanical hand model.

Development of Stroke Diagnosis Algorithm Through Logistic Regression Analysis with National Health Insurance Database

This study purpose is to derive a model equation for developing a stroke pre-diagnosis algorithm with the potentially modifiable risk factors. In this study, logistic regression analysis technique was used for model derivation. It is one of the methods employed in the machine-learning field of statistics. Korea’s National Health Insurance Service (NHIS), one of the largest administrative health care databases around the world, has been used widely in academic studies. From the NHIS Corporation, 500,000 enrollees’ databases were collected. For the regression analysis, 367 stroke patients’ data were selected from the NHIS database. The control group consisted of 500 patients who were followed up for two consecutive years and who had no history of stroke. As a result, the separation accuracy with the modifiable risk factors was 64.7%. The results of this study are expected to be useful for the development of stroke pre-diagnosis algorithms.

Comparison of Cognitive Loads between Koreans and Foreigners in the Reading Process

Objective: This study aims to measure cognitive load levels by analyzing the EEG of Koreans and foreigners, when they read a Korean text with care selected by level from the grammar and vocabulary aspects, and compare the cognitive load levels through quantitative values. The study results can be utilized as basic data for more scientific approach, when Korean texts or books are developed, and an evaluation method is built, when the foreigners encounter them for learning or an assignment. Background: Based on 2014, the number of the foreign students studying in Korea was 84,801, and they increase annually. Most of them are from Asian region, and they come to Korea to enter a university or a graduate school in Korea. Because those foreign students aim to learn within Universities in Korea, they receive Korean education from their preparation for study in Korea. To enter a university in Korea, they must acquire grade 4 or higher level in the Test of Proficiency in Korean (TOPIK), or they need to complete a certain educational program at each university’s affiliated language institution. In such a program, the learners of the Korean language receive Korean education based on texts, except speaking domain, and the comprehension of texts can determine their academic achievements in studying after they enter their desired schools (Jeon, 2004). However, many foreigners, who finish a language course for the short-term, and need to start university study, cannot properly catch up with university classes requiring expertise with the vocabulary and grammar levels learned during the language course. Therefore, reading education, centered on a strategy to understand university textbooks regarded as top level reading texts to the foreigners, is necessary (Kim and Shin, 2015). This study carried out an experiment from a perspective that quantitative data on the readers of the main player of reading education and teaching materials need to be secured to back up the need for reading education for university study learners, and scientifically approach educational design. Namely, this study grasped the difficulty level of reading through the measurement of cognitive loads indicated in the reading activity of each text by dividing the difficulty of a teaching material (book) into eight levels, and the main player of reading into Koreans and foreigners. Method: To identify cognitive loads indicated upon reading Korean texts with care by Koreans and foreigners, this study recruited 16 participants (eight Koreans and eight foreigners). The foreigners were limited to the language course students studying the intermediate level Korean course at university-affiliated language institutions within Seoul Metropolitan Area. To identify cognitive load, as they read a text by level selected from the Korean books (difficulty: eight levels) published by King Sejong Institute (Sejonghakdang.org), the EEG sensor was attached to the frontal love (Fz) and occipital lobe (Oz). After the experiment, this study carried out a questionnaire survey to measure subjective evaluation, and identified the comprehension and difficulty on grammar and words. To find out the effects on schema that may affect text comprehension, this study controlled the Korean texts, and measured EEG and subjective satisfaction. Results: To identify brain’s cognitive load, beta band was extracted. As a result, interactions (Fz: p =0.48; Oz: p =0.00) were revealed according to Koreans and foreigners, and difficulty of the text. The cognitive loads of Koreans, the readers whose mother tongue is Korean, were lower in reading Korean texts than those of the foreigners, and the foreigners’ cognitive loads became higher gradually according to the difficulty of the texts. From the text four, which is intermediate level in difficulty, remarkable differences started to appear in comparison of the Koreans and foreigners in the beginner’s level text. In the subjective evaluation, interactions were revealed according to the Koreans and foreigners and text difficulty (p =0.00), and satisfaction was lower, as the difficulty of the text became higher. Conclusion: When there was background knowledge in reading, namely schema was formed, the comprehension and satisfaction of the texts were higher, although higher levels of vocabulary and grammar were included in the texts than those of the readers. In the case of a text in which the difficulty of grammar was felt high in the subjective evaluation, foreigners’ cognitive loads were also high, which shows the result of the loads’ going up higher in proportion to the increase of difficulty. This means that the grammar factor functions as a stress factor to the foreigners’ reading comprehension. Application: This study quantitatively evaluated the cognitive loads of Koreans and foreigners through EEG, based on readers and the text difficulty, when they read Korean texts. The results of this study can be used for making Korean teaching materials or Korean education content and topic selection for foreigners. If research scope is expanded to reading process using an eye-tracker, the reading education program and evaluation method for foreigners can be developed on the basis of quantitative values.

Analysis of Human Body Suitability for Mattresses by Using the Level of PsychoPhysiological Relaxation and Development of Regression Model

Objective: The purpose of this study is to find the level of physical relaxation of individual subject by monitoring psychophysiological biofeedback to different types of mattresses. And, the study also aims to find a protocol to make a selection of the best mattress based on the measured information. Background: In Korea, there are an increasing number of people using western style bed. However, they are often fastidious in choosing the right mattress for them. In fact, people use their past experience with their old mattress as well as the spontaneous experience they encounter in a show room to finally decide to buy a bed. Method: Total five mattresses were tested in this study. After measuring the elasticity of the mattresses, they were sorted into five different classes. Physiological and psychological variables including Electromyography (EMG), heart rates (HR), oxygen saturations (SaO2) were used. In addition, the peak body pressure concentration rate was used to find uncomfortably pressured body part. Finally, the personal factors and subjective satisfaction were also examined. A protocol was made to select the best mattress for individual subject. The selection rule for the protocol considered all the variables tested in this study. Results: The result revealing psychological comfort range of 0.68 to 0.95, dermal comfort range of 3.15 to 6.07, back muscle relaxation range of 0.25 to 1.64 and personal habit range of 2.0 to 3.4 was drawn in this study. Also a regression model was developed to predict biofeedback with the minimal use of biofeedback devices. Moreover results from the proposed protocol with the regression equation and subjective satisfaction were compared with each other for validation. Ten out of twenty subjects recorded the same level of relaxation, and eight subjects showed one-level difference while two subjects showed two-levels difference. Conclusion: The psychophysiological variables and suitability selection process used in this study seem to be used for selecting and assessing ergonomic products mechanically or emotionally. Application: This regression model can be applied to the mattress industry to estimate back muscle relaxation using dermal, psychophysiology and personal habit values.