• 대한기계학회논문집B
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• 제26권3호
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• pp.465-473
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• 2002

Screw compressor type chiller is widely used in refrigeration for capacity over 30 RT. To enhance the chiller performance, an economizer which increases the cooling capacity and COP can be adopted. In this study the performance of an economizer is studied by using a simulation program. Simulation results are compared with experiment data to verify the validation of a simulation program. Maximum economizer injection pressure is estimated and the performance of an economizer for various evaporation and condensation temperatures is calculated. From the results, the performance enhancement of an economizer by using R22 and R407C is compared.

• 재활복지공학회논문지
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• 제11권4호
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• pp.323-330
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• 2017

무릎 슬리브는 재활뿐만 아니라 스포츠 활동 시 손상 예방의 목적으로도 사용되고 있다. 무릎 슬리브의 스포츠 손상 예방을 정의하기 위해서는 고유수용성감각으로부터 기인하는 균형을 평가하는 것이 중요한 요소이다. 본 연구의 목적은 골지 건 기관 자극 패드 무릎 슬리브의 효과를 분석하는 것이다. 5명의 건강한 성인 남성이 본 연구의 실험대상자로 참여하였다. 실험대상자들은 일반 무릎 슬리브와 자극 패드 슬리브를 착용한 상태에서 각각 BIODEX에서 설정된 타겟(Target) 각도를 재연하였고, 한 발 서기 동작을 수행하였다. 각도 재연성 평가의 결과를 보면, 5명의 실험대상자 중 4명의 실험대상자는 무릎 슬리브를 착용했을 때 보다 자극 패드 슬리브 착용 시 %Target angle이 증가하는 결과를 보였다. 한 발 서기 동작 수행 시 무릎 슬리브 착용 시 보다 자극 패드 슬리브 착용 시 유지 시간(duration time)이 증가했으며 x, y 방향에서 COP 길이가 모두 감소했다(COPx - 무릎 슬리브: $162.06{\pm}58.99mm$, 자극 패드 무릎 슬리브: $149.03{\pm}45.30mm$; COPy - 무릎 슬리브: $310.79{\pm}115.89mm$, 자극 패드 무릎 슬리브: $291.57{\pm}76.53mm$). 초기 전이구간, 정적 구간, 말기 전이구간이 차지하는 비율은 무릎 슬리브 착용 시와 자극 패드 무릎 슬리브 착용 시에 유의한 차이를 보였다 (all, p < 0.05). 본 연구의 결과로부터 골지 건 기관 자극 패드 무릎 슬리브 착용이 고유수용성 감각과 균형에 긍정적인 영향을 미치는 것을 확인할 수 있었다.

• Physical Therapy Rehabilitation Science
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• 제5권1호
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• pp.34-39
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• 2016

Objective: Hip abductors play a role in providing stability and movement to the lower limbs. The purpose of this study was to examine the effects of hip abductor fatigue on static balance and gait in the general population. Design: One group pre-test post-test design. Methods: Thirteen university students in their twenties volunteered for the study and had underwent a functional assessment. To induce fatigue, the subjects were instructed to raise their dominant lower extremity up against a load of 50% of 1 repetition maximum while producing hip abduction in a side-lying position. Subjects were instructed to maintain an abduction speed of 30 repetitions per minute to induce fatigue. Muscle fatigue was considered to be established when subjects were unable to perform hip abduction three consecutive times along with the metronome. A post-test of balance and gait was performed immediately in order to prevent fatigue recovery. The center of pressure (COP) distance area was measured using the Zebris FDM-S Multifunction Force measuring plate. Gait performance was analyzed using the GAITRite. Results: The COP distance was increased after fatigue was induced. There was a significant increase in the standard deviation of the medio-lateral and antero-posteror distance (p<0.05). Although there was no significant difference in gait parameters, there was a significant decrease in single support time after fatigue was induced (p<0.05). Conclusions: There was an increase in static balance instability and a significant decrease in single support time during gait due to hip abductor muscle fatigue.

• Physical Therapy Rehabilitation Science
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• 제8권3호
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• pp.158-161
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• 2019

Objective: Attentional focus is one of the critical factors that has consistently been demonstrated to enhance motor performance and motor skill. Focusing attention on the inside of the body while engaging in a particular exercise is called internal focus (IF) and focus on the external environment is called external focus (EF). The purpose of this study was to identify effects of IF and EF of attention on postural balance in healthy school-aged children. Design: Cross-sectional study. Methods: Twenty-four healthy school-aged children participated in this study. School-aged children was defined as children ages 8-12 years old. They performed the one-legged standing with EF (focusing on the marker at the level of participants' chest and 150 cm away), IF (focusing the supporting feet), and control (no instruction) respectively. The order of the focus condition was randomly selected. The center of pressure (COP) range, distance, and velocity was measured to compare the effects of applying different attentional focuses in the three conditions. Results: The results of our study show that differences in COP range, distance, and velocity among groups were not significant between the different attentional focuses, although all variables of EF were smaller than IF. It is postulated that the reason for this may be that school school-aged children between 8-12 years old go through a transitional phase from IF to EF in effective motor learning. Conclusions: These findings reveal that the type of attentional focus did not have any effect on postural balance in healthy school-aged children.

• 대한물리의학회지
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• 제15권2호
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• pp.101-108
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• 2020

PURPOSE: The purpose of this study was to investigate the effect of treadmill walking training using the metronome on the gait pattern. METHODS: A total of 33 healthy persons were studied consisting of 17 female and 16 male in the 20-30 age group. A gait analysis program was installed on a treadmill with a built - in gait analysis sensor and laptop. After 9 minutes of treadmill walking, gait analysis was performed for 1 minute. The mean values of the differences in the step length, angle of COP, separation line standard deviation and step force of the lower legs affecting walking symmetry were calculated for treadmill walking and treadmill walking using the metronome. The Shapiro-Wilk test was used to test the normality of the collected data and a paired t-test was performed to analyze the difference in walking before and after using the metronome. RESULTS: As a result of the analysis, the mean of difference between the measured values of the bilateral lower extremity for step length, angle of COP, separation line standard deviation and step force were statistically significant before and after treadmill walking using the metronome. CONCLUSION: Therefore, the treadmill walking training using the metronome is effective in decreasing the difference in the foot width, gait angle, gait distribution, and foot pressure. Because of this, the treadmill walking training using the metronome has a significant effect on walking symmetry among the elements for correct walking, which is a means for enabling efficient and continuous walking.

• PNF and Movement
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• 제18권2호
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• pp.183-194
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• 2020

Purpose: Functional ankle instability (FAI) causes tension in the joints, ligaments, and tendons, and the impact on visual and vestibular organs leads to imbalance. This study compared the effects of a traditional balance training program to virtual reality training to improve FAI. Methods: Twenty-four participants with FAI (CAIT score < 24) were assigned to a virtual reality training group (n = 13) and a traditional balance training group (n = 11). Both groups pursued their respective training program for four weeks. After a ten-minute warm-up, participants completed a 30-minute training session, three times per week. The traditional balance training group underwent static and dynamic training using a balance board and a stability trainer pad while the virtual reality group underwent balance training using a virtual reality program. Biorescue was used to measure changes in the speed and length of center of pressure (COP) for single-leg stance pre- and post-training. Results: The speed and length of COP improved significantly in both groups after training as compared to before (p < 0.05). However, there were no significant differences in these outcomes between the virtual reality training group and the traditional balance training group (p>0.05). Conclusion: The study findings confirm the effectiveness of both virtual reality training and traditional balance training in reducing ankle instability, with no difference in treatment effects.

• Physical Therapy Rehabilitation Science
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• 제7권4호
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• pp.179-185
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• 2018

Objective: The purpose of this study was to analyze and compare vertical ground reaction forces during sit to stand (STS) and gait between female elderly and young individuals using the Wii Balance Board (WBB). Design: Cross-sectional study. Methods: Fifty-one female elderly people (age: $75.18{\pm}4.60years$), and 13 young people (age: $29.85{\pm}3.69years$) performed the five times STS test and gait respectively on the WBB. We analyzed time (s), vertical peak (%), integral summation (Int_SUM, %), and counter variables (%) in STS and 1st peak (body weight, BW%), 2nd peak (BW%), peak minimum (BW%), time (second), center of pressure (COP) path length (mm), and Int_SUM (BW%) in gait. The independent t-test was used to assess for differences in STS, gait ability, and general characteristics between the female elderly group and young adults group. With the first and last trials excluded, the mean value was obtained from the middle three of the five trials. Results: During STS, Int_SUM and time of young adults were significantly less than of the female elderly subjects. There were no significant differences in peak and counter variables. In gait, all variables (1st peak, 2nd peak, min, time, COP_path, and Int_SUM) showed significant differences between groups (p<0.05). This study demonstrated that the validity of vertical ground reaction forces occurring during STS and gait was significant in female elderly and young adults. Conclusions: Based on the measurement of vertical ground reaction forces in STS and gait using the WBB, it is possible to clinically improve the quality of geriatric physical therapy. Further studies are necessary to examine concurrent validity of elderly patients who have undergone total hip or knee replacement.

• 대한물리의학회지
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• 제15권4호
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• pp.163-174
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• 2020

PURPOSE: This study examined the effects of Robot Tilt-table Training (RTT) on the lower extremity strength, balance, gait, and satisfaction with rehabilitation, in patients with subacute stroke (less than six months after stroke onset), and requiring intensive rehabilitation. METHODS: A total of 29 subacute stroke patients were divided into an RTT group (n = 14) and a Body Weight Support Treadmill Training (BWSTT) group (n = 15). The mean age of patients was 62 years. RTT and BWSTT were performed for four weeks, three times a week, for 30 minutes. Isometric strength of the lower extremities before and after intervention was compared by measuring the maximal voluntary isometric contraction of the lower extremity muscles. To compare the balance function, the center of pressure (COP) path-length and COP velocity were measured. Timed Up & Go test (TUG) and 10 Meter Walking Test (10 MWT) were evaluated to compare the gait function. A satisfaction with rehabilitation survey was conducted for subjective evaluation of the subject's satisfaction with the rehabilitation training imparted. RESULTS: In the intra-group comparison, both groups showed significant improvement in lower extremity strength, balance, gait, and satisfaction with rehabilitation, by comparing the parameters before and after the intervention (p < .05). Comparison of the amount of change between groups revealed significant improvement for all parameters in the RTT group, except for the 10 MWT (p < .05). CONCLUSION: Both groups are effective for all variables, but the RTT group showed enhanced efficacy for variables such as lower extremity strength, balance, gait, and satisfaction with rehabilitation, as compared to the BWSTT group.

• 한국전문물리치료학회지
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• 제27권1호
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• pp.78-86
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• 2020

Background: Flat-footed persons with collapsed medial longitudinal arch lose flexibility after skeletal maturity, resulting in several deformities and soft tissue injuries. Although arch support taping is usually applied in the clinic to support the collapsed arch, research on the use of different types of tape for more efficient arch support in flat-footed persons is lacking. Objects: The purpose of this study was to examine three conditions (barefoot, kinesio tape, and dynamic tape) and compare their effects on static and dynamic balance in persons with asymptomatic flexible flatfoot. Methods: Twenty-two subjects (9 females and 13 males) with asymptomatic flexible flatfoot participated in this study. The subjects performed the Y-balance test to measure the composite reach score. The subjects also performed a 30-second standing test to measure the center of pressure (COP) path length and a walking test to measure anteroposterior and lateral variability using the Zebris FDM system. One-way repeated-measures analysis of variance compared the three conditions applied to the subjects' feet for each balance variable. Results: The composite reach score significantly increased following the application of dynamic tape compared with barefoot and that of kinesio tape compared with barefoot. There was no significant difference in the COP path length during standing among the three conditions. Anteroposterior and lateral variability during walking significantly with dynamic tape application compared with barefoot. Conclusion: The results of this study suggest that, in persons with asymptomatic flexible flatfoot, application of kinesio tape and dynamic tape may be effective in increasing the composite reach score in Y-balance test, whereas application of dynamic tape may be effective in reducing anteroposterior and lateral variability during walking.

• 한국전문물리치료학회지
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• 제21권2호
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• pp.8-17
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• 2014

The purpose of this study was to examine the effects of hip joint mobilization (HJM) on walking ability, balance ability, and the joint range of motion in stroke patients to minimize the problems of the musculoskeletal system in patients with central nervous system diseases. All volunteers were randomly assigned to the HJM group ($n_1=14$) and the general neurodevelopment therapy (NDT) group ($n_2=16$). The HJM procedure involved applying Maitland mobilization techniques (distraction, lateral gliding, inferior gliding, and anterior gliding) by grade 3 to both hip joint. The mobilization process included mobilization and NDT for 15 min/day, 3 days a week for 4 weeks. The outcome measures were evaluated, including the hip joint passive range of motion (ROM) test and femur head anterior glide test (FHAG) using prone figure four test, dynamic and static balance abilities [timed up and go (TUG) test and center of pressure (COP) analysis], and walking ability [10-meter walking test (10MWT) and 6-min walking test (6MWT)]. Both the groups showed significant post-training differences in the hip joint ROM (FHAG and degree of hip extension) and 10MWT. The post-training improvements in the TUG test were significantly greater in patients of the HJM group than in the NDT group; however, there were no post-training improvements in COP in both groups. Patients in the HJM group showed post-training improvement in the 6MWT; however, statistically significant differences were not observed. Patients in the NDT group showed post-training improvements in the 6MWT. These results suggest that HJM improves hip joint ROM, dynamic balance ability, and walking speed in stroke patients. However, further studies are required to evaluate the long-term therapeutic efficacy of HJM in stroke patients.