• 신재생에너지
• /
• 제3권3호
• /
• pp.14-19
• /
• 2007

A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

• 대한의생명과학회지
• /
• 제26권3호
• /
• pp.186-191
• /
• 2020

This study was designed to investigate the median nerve cross-sectional area of the upper extremity which is the main cause of CTS in the 20s and 30s. The median nerve cross-sectional area (MNC-area) of each part of the upper limb was measured in healthy 20s and 30s females and males without neurological diseases or other diseases. This MNC-area was compared with the hand, wrist, finger, and other body indexes. The research group was divided into 20s female and male groups, and the 30s were also divided into female and male groups. In the comparison between the ages, the hand, and wrist configurations in the 30s were significantly higher than those of the 20s. The mean median nerve cross-sectional area was significantly larger in the male group than in the female group in both 20s and 30s, and it was larger in both men and women than in the 20s. Hand and wrist configurations were also positively correlated with the median nerve cross-sectional area in both 20s and 30s. The median values of hand ratio and wrist ratio were 2.26 and 0.65, respectively. This median value of hand ratio was inversely correlated with the median nerve cross-sectional area. The median nerve cross-area of the 20s was 6.88~7.38 ㎟ in the male group and 5.69~6.99 ㎟ in the female group, respectively. The median nerve cross-area of the 30s was 6.32~8.89 ㎟ in the male group and 6.15~7.17 ㎟ in the female group, respectively. The mean median nerve cross-sectional area was positively correlated with body mass index in both groups. Most of the variables were higher in their 30s than in their 20s.

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
• /
• pp.22-25
• /
• 2000

To improve the performance of high temperature superconducting current leads, variable cross-sectional area is considered. The cross-sectional area is varied as a function of current density to fix the safety factor along lead length. New integration method is devised to find optimum cross-sectional area distribution. New design of current lead has low heat leak into cryostat and less material than constant cross-sectional area leads. Conduction cooled lead is considered. The developed method is applied to Bi2223 current leads sheathed Ag-Au alloy.

• 대한치과교정학회지
• /
• 제25권6호
• /
• pp.655-664
• /
• 1995

Sixty male patients with polysomnographically documented OSA were included in this study. A pair of cephalograms were obtained in the upright and supine positions. In the supine position, the ANB angle, lower facial height and the cross-sectional area of soft palate increased and there was a decrease in the vertical airway length and oropharynx cross-sectional area. Positional changes did not affect the cross-sectional area of tongue, but the cross-sectional area of the oropharynx decreased in the supine position. The obese group had higher AI and RDI. Maxillary unit length, C3-H, the cross-sectional areas of tongue, soft palate and oropharynx were significantly greater in the group Obese than in non-obese group. No correlation was noted between the mandibular unit length and OSA severity, The group of small mandibular unit length showed shorter lower facial height and maxillary unit length, and smaller cross-sectional area of tongue than the long mandibular unit length group. Hyold bone positioned more inferiorly and cross-sectional area of nasopharynx decreased as the OSA severity increased.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.117-120
• /
• 2002

In this study the occlusion of dural-sac, the outer membrane of spinal cord in the lumbar region, was quantitatively analyzed using one motion segment finite element model. Occlusion was quantified by calculating cross sectional area change of dural-sac far different compressive impact duration(loading rate) due to bony fragment at the posterior wall of the cortical shell in vertebral body. Dural-sac was occluded most highly in the range of 8∼12 msec impact duration by the bony fragment intruding into the spinal canal. t=400 msec case 4% cross sectional area change was calculated, which is the same as the cross sectional area change under 6 kN of static compressive loading.

• 척추신경추나의학회지
• /
• 제8권2호
• /
• pp.39-46
• /
• 2013

Objectives : To identify the association between cross-sectional area of lumbar regional muscle and stability(ST), center of pressure(COP) assessed by tetrax. Methods : Patients(n=55) who had taken L-SPINE MRI and Tetrax(Sunlight, Israel) were analyzed retrospectively. To evaluate the cross-sectional area of lumbar regional muscle, L-SPINE MRI was used. Data of ST, COP were accumulated by using dynamic equilibrium analysis by Tetrax. Of the lumbar regional muscles, the Psoas muscles and the Paraspinalis muscles were examined. Using Pearson correlation, we analyzed COP, ST and the difference between the cross-sectional area of lumbar regional muscles. Results : The variance of cross-sectional area of both sides of Psoas muscle and COP had moderate positive correlation(r=0.621). Between variance of cross-sectional area of both sides of Paraspinalis and lumbar regional muscle and COP there was low positive correlation(r=0.287, r=0.329) ST also had low correlation with variance of cross-sectional area of both sides of Psoas muscle. Conclusion : The variance of cross-sectional area between both sides of Psoas muscle had moderate correlation with COP.

• 한국초전도ㆍ저온공학회논문지
• /
• 제19권3호
• /
• pp.44-48
• /
• 2017

Current lead is a device that connects the power supply and superconducting magnets. High temperature superconductor (HTS) has lower thermal conductivity and higher current density than normal metal. For these reasons, the heat load can be reduced by replacing the normal metal of the current lead with the HTS. Conventional HTS current lead has same cross-sectional area in the axial direction. However, this is over-designed at the cold-end (4.2 K) in terms of current. The heat load can be reduced by reducing this part because the heat load is proportional to the cross-sectional area. Therefore, in this paper, heat load was calculated from the heat diffusion equation of HTS current leads with uniform and non-uniform cross-sectional areas. The cross-sectional area of the warm-end (65K) is designed considering burnout time when cooling system failure occurs. In cold-end, Joule heat and heat load due to current conduction occurs at the same time, so the cross-sectional area where the sum of the two heat is minimum is obtained. As a result of simulation, current leads for KSTAR TF coils with uniform and non-uniform cross-sectional areas were designed, and it was confirmed that the non-uniform cross-sectional areas could further reduce the heat load.

• Journal of Acupuncture Research
• /
• 제30권4호
• /
• pp.45-53
• /
• 2013

Objectives : The purpose of this study was to evaluate the relationship between cross-sectional areas of the paraspinal and psoas muscles with low back pain. Methods : We assessed the cross-sectional area of the psoas and paraspinal muscles at the superior part of L4 level and vertebral body of L4 of 132 patients who were hospitalized with a chief complaint of low back pain at Jaseng Hospital of Korean Medicine from January 2013 to April 2013. After calculating the mean psoas area, we divided the patients into 2 groups by whether the psoas cross section was larger or smaller than the mean, and compared the admission period, verbal numeric rating scale(NRS) of low back pain(LBP), and improvement of verbal NRS of LBP. We also subcategorized the patients into acute and chronic groups according to the duration period, and compared the cross-sectional area of the psoas and paraspinal muscles. Results : Although analyses of the verbal NRS of LBP, and improvement of verbal NRS of LBP between groups with larger and smaller psoas cross section areas showed no significant difference, the admission period was significantly shorter in the group with larger psoas cross section areas. There was no significant difference in analyses of cross section areas in the acute and chronic groups. Of the possible prognostic variables, improvement of verbal NRS of LBP showed no correlation, while the admission period displayed a significant correlation. The cross-sectional area of the psoas and paraspinal muscles divided by the area of the vertebral body of L4 had a significant negative correlation with age. Conclusions : The cross-sectional area of the psoas and paraspinal muscles were correlated with the admission period in LBP patients, and the cross-sectional area of the surrounding muscles divided by the area of the L4 vertebral body was negatively correlated with age.

• 대한물리의학회지
• /
• 제15권1호
• /
• pp.55-63
• /
• 2020

PURPOSE: This study examined the effects of handgrip exercise, which was started two weeks after surgery for shoulder rotator cuff repair, on the extent of muscle activation around the shoulder and the cross-sectional area of the supraspinatus muscle. METHODS: Among patients diagnosed with rotator cuff rupture by an orthopedic surgeon and rotator cuff repair was performed using an arthroscope, 28 were selected as subjects. These subjects were allocated randomly to the experimental group and control group with 14 subjects in each group. An electromyogram was measured as a measure of the extent of muscle activation around the shoulder for a total of six times (%RVC). The cross-sectional area of the supraspinatus muscle was measured before and after the rotator cuff repair by magnetic resonance imaging. RESULTS: The extent of muscle activation in accordance with time in both the experimental group and control group displayed significant differences in various muscles including the anterior deltoid, pectoralis major, upper trapezius and infraspinatus muscle(p<.05). A significant difference in the variation of the cross-sectional area of the supraspinatus muscle was observed between the experimental group and the control group(p<.05). CONCLUSION: Handgrip exercise helps rehabilitate the shoulder joint at the acute stage after rotator cuff repair when assertive exercise therapy cannot be applied.

• 대한의용생체공학회:의공학회지
• /
• 제24권5호
• /
• pp.421-425
• /
• 2003

한 개 척추 운동 분절에 대한 유한요소 모델을 이용하여 수직 충격력이 가해질 경우 발생되는 척추 경막의 교합을 해석 하였다. 교합은 수직 충격력의 지속 시간 변화에 따른 골편의 이동으로 인한 척추 경막의 단면적 변화를 계산하여 계량화 하였다. 계산 결과 8∼12ms 의 충격 지속 시간에서 골편의 이동으로 인한 가장 큰 척추 경막의 단면적 변화가 나타났으며 $\Delta$t = 400 ms의 경우에서는 4%만의 척추 경막의 단면적 변화가 나타났다, 이와 같은 해석 결과는 6kN의 수직 정 하중이 가해질 경우에 발생되는 량이 유사한 값으로 이 정도의 충격 지속 시간은 준 정 하중 상태와 유사함을 보이고 있었다.