• Clinics in Shoulder and Elbow
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• 제7권2호
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• pp.57-64
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• 2004

The purposes of this study were to evaluate the presence or absence of pain with the jerk test as a predictor of the success of nonoperative treatment for posteroinferior instability of the shoulder and to identify pathologic lesion responsible for the pain in the jerk test. Eighty-nine shoulders(81 patients), which had posteroinferior instability with positive posterior clunk in the jerk test, were nonoperatively treated. The patients were divided into two groups with respect to the presence of pain in the jerk test: painless jerk group(54 shoulders) and painful jerk group(35 shoulders). Response to the nonoperative treatment was evaluated after at least 6 months rehabilitation program. Patients who did not respond to the rehabilitation underwent arthroscopic examination to identify any pathologic lesion. The painful jerk group had higher failure rate with nonoperative treatment (p<0.001). In the painless jerk group, fifty shoulders (93%) responded to rehabilitation program after a mean of 4 months. Four shoulders(7%) were unresponsive to the rehabilitation. In the painful jerk group, five shoulders(16%) were successful with the rehabilitation while the other thirty shoulders(84%) failed. All 34 shoulders, which were unresponsive to the rehabilitation, had a variable degree of posteroinferior labral lesions. In conclusion, the jerk test is a hallmark for predicting the prognosis of nonoperative treatment in the posteroinferior instability. Shoulders with symptomatic posteroinferior instability and a painful jerk test have posteroinferior labral lesion.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.279-283
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• 2006

The GPS receiver developed by KARI for the satellite launch vehicle should operate under severe dynamic environments such as high acceleration and jerk. Several terrestrial tests including the outdoor centrifuge test are planed in order to verify performances of the GPS receiver before flight. This paper deals with preliminary test results of the GPS receiver using a GPS signal generator before the centrifuge test that is a performance test of the GPS receiver using live GPS satellite signals. Test methods of the GPS receiver for the satellite launch vehicle under high centripetal acceleration and jerk utilizing a GPS signal generator are described. The simulation results are also analyzed in this paper.

• 한국운동역학회지
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• 제16권2호
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• pp.1-8
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• 2006

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

• 한국철도학회논문집
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• 제6권4호
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• pp.286-293
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• 2003

The prototype of Korean high speed train (HSR350), composed of two power cars, two motorized cars and three trailer cars, has been designed, fabricated and tested. In this paper, the body vibration has been reviewed from the viewpoint of the vehicle's safety and the vibration limits for components and sub-assemblies mounted on the car-body using by the experimental method. And, the dynamic characteristics, such as jerk, natural mode and kinematic mode, have been reviewed. The KHST has been run to 300 km/h in the KTX line and the results of on-line test show that it has no problems in the vehicle's safety and the vibration limits. And the characteristics of body vibrations has been predicted at 350 km/h by fitting curve about the measured acceleration signals.

• 한국운동역학회지
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• 제24권4호
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• pp.349-357
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• 2014

The purpose of this study was to examine the differences in the performance of dancing motions depending on the level of skill by investigating pulmonary functions, ground reaction force, and jerk cost. The subjects of this study were 12 professional dancers (career: 16 yrs) and 12 amateur dancers (career: 9 yrs) who had similar physical conditions. We selected four motion phases which included the diagonal line motion, the deep flexion motion, the breath motion, and the turn motion with one leg after a small step walking motion, with Goodguri Jangdan. In the experiment, 6 infrared cameras were installed in order to analyze the value of the jerk costs and the force plate form. Finally, we measured the pulmonary functions of the subjects. For data analysis, independent t-tests according to each event, were carried out in the data processing. According to the results of FVC % Predicted, the professional dancers showed greater lung capacities than the amateur dancers, indicating that the level of dancing skill influences lung capacity. Based on the result of the balance test, the professional dancers used more vertical power than did the amateur dancers when performing maximal flexion motion. The professional dancers used a propulsive force of pushing their body forward by keeping the center of body higher while the amateur dancers used a braking power by keeping their bodies backward. When performing medial-lateral movements, the amateur dancers were less stable than the professional dancers. There were no differences in values of jerk costs between the amateur dancers and the professional dancers.

• 전력전자학회논문지
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• 제5권5호
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• pp.515-521
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• 2000

본 논문은 전동차용 추진장치인 IGBT VVVF 인버터의 현차시험에 관한 것이다. IGBT VVVF인버터는 1,650kVA급으로 개발되었다. 추진 인버터의 신뢰성과 성능을 확인하기 위하여 서울시 지하철 6호선에서 본선시험을 하였다. 시험 차량구성은 4M4T로 구성되었으며, 전장품은 4대의 VVVF인버터, 16대의 견인전동기 및 2대의 SIV로 구성하였다. 추진장치는 1C4M으로 구성하였다. 현차시험을 통하여 추진용 인버터의 우수한 가·감속 능력과 가가속도 특성 및 구배에서의 등판능력을 확인 할 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1685-1690
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• 2010

This paper describes the calculation and application of the speed profile for the train speed control when the train is operated by ATO(Automatic Train Operation). We propose a speed profile calculation method considering the speed limitation and the jerk limitation, in order to maintain the quality of the train automatic operation. In previous works, ATO calculates a desired speed profile along the time, and controls the train to follow the profile. In this case, it may be hard to follow the restrictive speed along the location or to stop the train with a low location error, because of the difference between the desired location at each time and the real location of the train due to the control error. In the proposed method in this paper, we calculate a desired speed profile along the time considering the speed and jerk limitation first, and derive a speed profile along the location using it. If the restrictive speed profile is changed or the train speed strayed from the speed profile, ATO system calculates new speed profile and applies it immediately. Because ATO system controls the train speed based on the train location, the accuracy of the train location control can be improved. A simulation system for the test of the automatic train operation using this method is designed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.576-580
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• 2000

This paper describes about the field test of IGBT VVVF inverter for the propulsion system. The 1650kV class IGBT VVVF inverter has been developed. Therefore the field test is performed in SMG 6 Line to confirm its the reliability and performance. The train consists of 4M4T and the electrical equipment for field test are as follows : VVVF inverter 4 sets 16 traction motors and 3 SIVs The propulsion system which have the excellent acceleration/deceleration and the jerk chracteristics as well as starting ability on slope are taken through the field test.

• 한국운동역학회지
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• 제25권1호
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• pp.1-10
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• 2015

Objective : The purpose of this study was to find some kinetic variable's relationships between personal records and low records in female high jump. Methods : Collected data of the subjects(N=8, ages: $25.5{\pm}1.85$, height: $173{\pm}5.83$, mass: $54.75{\pm}6.36$ personal record: $1.71{\pm}0.04$, low record: $1.62{\pm}0.03$) were used for the last three strides and take-off phase. Five video cameras set in 30frames/s were used for recording. After digitizing motion, the Direct Linear Transformation(DLT) technique was employed to obtain 3-D position coordinates. The kinematic and kinetic factors of distance, velocity, angle, impulse, jerk variables were calculated. A paired t-test was applied for the difference of variables between personal records and lower records and for correlation with performances and variables. The significance level was accepted at p<.05. Results : There was no relationship between pattern of stride and performance. However, rate of change of velocity was related with cental of mass height(CMH) at peak point(PP). Knee, hip, backward lean, foot plant, approach and take off angle showed no difference between best record and low record. Vertical impulse momentum also showed no difference between performances. Conclusion : According to a t-test result, there were significant differences in CMH at PP and jerk at touch down between best record and low record.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.40-44
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• 1998

In this paper, a kinematic and dynamic model for an excavator is presented. A graphic user interface program for kinematic-dynamic analysis for the excavator is developed. To predict the stiffness and damping properties of the joint between the vehicle and the track, a parameter study is executed. Using the predicted joint stiffness and damping, the jerk simulation for the excavator is reproduced. Simulation results are compared with the test results to confirm the validity of the simulation model.