• 대한산업공학회지
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• 제33권4호
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• pp.410-418
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• 2007

This article suggests the methods to investigate adverse movement across global stock markets arising from insolvency of subprime mortgage in U.S. Our application deals with asymptotic tail dependence of daily stock index returns (KOSPI, DJIA, Shanghai Composite) of three countries; Korea, U.S., and China, over specific period via extreme value theory and copula functions. Daily stock index returns among three countries show higher extremal dependence during the period exposed to systematic shock. We confirm that extreme value theory and copula functions have potential to well describe the extreme dependence between three countries' daily stock index returns.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.379-386
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• 2001

Fluid viscous dampers have been used as energy dissipators or STU's (Shock Transmission Unit) in earthquake resistant designs for bridges. Viscous dampers have many advantages compared to other friction type or visco-elastic type of dampers. They do neither increase internal pier forces due to their out of phase response, nor produce reaction forces at the low velocities associated with thermal movements. Therefore, they anable the super structure to restore itself perfectly after a severe movement dut to seismic excitations. This paper investigates the response of bridges designed with viscous dampers in regard to damping coefficients, properties of dampers, and arrangements of dampers. For this purpose, time-history dynamic analyses have been performed using a very simple model relevant to a typical bridge example. Based on the results, it presents some design duidelines on how to determine a proper damping ratio and on how to arrange dampers. In usual cases, damping coefficients corresponding to about 0.2-0.3 of damping ratios seem to be very effective in bridge designs.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.224-229
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• 2000

This paper describe a (mite element computer simulation of a absorption system using full scale car crash test. The full scale test selected for this study is a 80kmh frontal, side and 25% offset impact of a 1993 Ford Taurus vehicle into a absorption system. This absorption system has external rubber and internal steel pannel. This simulation has completed for decision of these components energy absorption performance. Dynamical performance of this system and movement are obtained from this simulation. and then We can appreciate the safety of passenger from measure the vehicle C.G's acceleration.

• 동력기계공학회지
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• 제13권3호
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• pp.59-64
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• 2009

This study presents a new approach to pressure control of a impression cylinder for roll coater which is a kind of face pressure control between blanket roll and impression roll. Roll-to-Roll method for printing is a very useful tool for mass production such as RFID elements, smart sensors and solar cell devices. In this study, a decupling control strategy of the roll coater which is a combination of a cylinder system, a dry system and two pressure regulators with two pneumatic cylinders was discussed. Also, the characteristics of component such as a pressure regulator having a pressure reducing function and the movement of a blanket roll and a impression cylinder were analyzed using the Matlab software. From this results, the techniques of a shock and a vibration reduction were suggested.

• 전기학회논문지P
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• 제59권4호
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• pp.440-443
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• 2010

This paper deals with the method of vibration measurement of a gun barrel structure using mechanical filter. When a bullet with high speed is moving within a gun barrel type structure with low bending vibration frequencies, it is difficult to measure the bending vibration signals of the structure. For example, noncontact type sensors such as displacement or velocity sensor are not appropriate for the measurement of vibrational signals because of the movement effect of the equipment frame through the moving structures or effect of the ground vibration. One of contact type sensors such as accelerometer is profitable for measurement of vibrational signals because of its wide measurement ranges. In the case of a gun barrel structure including high vibrational signals like shock waves, however, it is necessary to propose vibration measurement method filtering high frequencies. The purpose of the paper is to propose the proper vibrational measurement technique filtering high frequencies of a gun barrel type structure.

• 한국운동역학회지
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• 제20권1호
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• pp.91-99
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• 2010

The purpose of this study was to the kinetic variables effects from the use of arch support inserts on low-arched people. We selected 10 people for the research and separated them into 2 groups, 5 people for the normal arched group and 5 people for the low arched group. Each group wear shoes which have a 3 step convertible arch support (level 0, level 2, level 5) and we measured their foot pressure and 3D motion analysis data. As a result, we found that the mean pressure at the heel of the low arched group was decreased when using the arch supports. The arch support induced the correct grounding area for the foot and dispersion of foot pressure. 3D motion analysis found that as the height of the arch support was increased, the movement of the Y-axis(inversion-eversion) was increased to relieve the shock to the heel. The arch support insert limited the range of motion(ROM) of the Z-axis(abduction-adduction) of the low arched person's ankle joint and prevented ankle injury caused by the excessive eversion when walking. Low arched people are seen to be easily tired due to the ineffective shock absorption of the knees and abnormal walking motion. In order to improve the problems, a 3 step convertible arch support(level 5) insert would improve the low-arched people's walking ability. In other words, the low arched people should be expected to walk as well as normal arched people when they wear shoes with the arch support insert.

• 한국자동차공학회논문집
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• 제22권4호
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• pp.10-19
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• 2014

Despite the movement of safe traffic by the Korean government to reduce deaths in traffic accidents, the casualties increase year by year. In particular, more and more accidents and casualties are reported from car collisions from the back of the vehicles parked for managing traffic accidents on the road, cleaning main roads and medial strips, repairing roads. In order to response to these accidents, the government should take protective measures for road users. In the last decade, seventy-one cases have been reported to occur during highway repair and maintenance. As a result, eight persons were killed and seventy-six were injured, showing the high death rate of 11.3 percent. Therefore, it seems urgent to take some actions against it. The United States and European countries legislate that vehicles of road repair and maintenance should be mandatorily equipped with shock absorber at the back. Korea, however, does not have such legislative measures, which are needed at this time to protect workers on the road. This study compares the performance of the traditional shock absorber for road maintenance vehicles with that of the rear safety guard using air bag, manufactured in accordance with related laws in Korea. Based on the results of the 60km/h rear collision test, this paper proposes improvements in related laws and regulations in an attempt to reduce casualties.

• 한국운동역학회지
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• 제20권4호
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• pp.395-406
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• 2010

The purpose of this study was to analyze the changes in kinematic and kinetic parameters of lower extremity joint according to rehabilitation period. Fourteen collegiate male athletes(age: $22.1{\pm}1.35$ years, height: $182.46{\pm}9.45cm$, weight: $88.63{\pm}9.25kg$) and fourteen collegiate athletes on functional ankle instability(age: $21.5{\pm}1.35$ years, height: $184.45{\pm}9.42cm$, weight: $92.85{\pm}10.85kg$) with the right leg as dominant were chosen. The subjects performed drop landing. The date were collected by using VICON with 8 camera to analyze kinematic variables and force platform to analyze kinetic variables. There are two approaches of this study, one is to compare between groups, the other is to find changes of lower extremity joint after rehabilitation. In comparison to the control group, FAI group showed more increased PF & Inversion at IC and decreased full ROM when drop landing. Regarding the peak force and loading rate, it resulted in higher PVGRF and loading. FAI group used more increased knee and hip ROM because of decreased ankle ROM to absorb the shock. And it used sagittal movement to stabilize. In terms of rehabilitation period, FAI group showed that landing patterns were changed and it increased total ankle excursion and used all lower extremity joint close to normal ankle. Regarding the peak force and loading rate, FAI group decreased PVGRF and loading rate. and also showed shock absorption using increased ankle movement. And COP variable showed that proprioception training increased stability during 8 weeks. The results of this study suggest that 8 weeks rehabilitation period is worthwhile to be considered as a way to improve neuromuscular control and to prevent sports injuries.

• 한국운동역학회지
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• 제18권4호
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• pp.135-142
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• 2008

본 연구는 9명의 피험자가 2주간 하루 6시간동안 후족부 경사각을 이용한 신발인 S사(社) 신발을 착용하여 보행하였으며 신발을 처음 신었을 때와 2주간 하루 6시간 이상 착용한 후의 데이터를 통해 기존의 운동화와 S사(社) 신발간의 비교를 수행하였다. 1. 기립자세에서의 S사(社) 신발의 착용 시 근전도의 활동인 증가하고 압력분포 중심 움직임은 약 60% 정도 증가하였다. 2. 피험자의 보행 시 S사(社) 신발을 착용하였을 때 신발의 힐 부부분의 $20^{\circ}$ 경사각으로 인해 heel strike 시 발목이 약 $14^{\circ}$ 정도 발등 쪽으로 굽혀짐을 확인하였으며 무릎에서는 이를 보완하기 위해 $2^{\circ}$ 정도 굴곡 됨을 보였다. 3. 이로 인해 최대 지면반력이 보다 빠르게 나타났으나 크기는 변하지 않았다. 4. S사(社) 신발의 착용하고 보행 시 지지기에서 발목과 무릎의 부하는 21-61%의 감소하는 결과를 나타내었다. 결과적으로 S사(社) 신발 착용시 목과 무릎각의 굴곡 각을 증가시켜 보행 시 몸이 곧게 서도록 하였다. 또한 보행 시 부하를 감소시킬 수 있음을 나타냈으나 2주간의 신발 착용으로 인한 신체의 변화는 나타나지 않음을 보였다.

• 한국산업보건학회지
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• 제15권2호
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• pp.114-123
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• 2005

We analyzed the demographic and job features of 197 shipyard workers with work-related musculoskeletal disorders(WMSDs) compensated by the Industrial Accident Compensation Insurance Act, and the features of the disorders, the causes of operation and the induced behaviors. The three shipbuilding companies surveyed were located in Busan Metropolitan city and Gyungsangnam-do. The results were as follows. 1. The ages of WMSDs patients in shipyard were $43.6{\pm}8.6$ and the job tenure was $14.3{\pm}5.6$. The 40's of them was 40.1%, and the 30's was 29.4%. Patients less than 5 year-work duration were 85.3%, and ones more than 16 year-work duration 6.6%. In occupations, welders were 32.5%, pre-welders 17.3%, and setting engineers 6.6%. 2. The causes of WMSDs in shipyard were works(95.4%) and outer crash or accident shock (3.6%). Based on the standard of the NIOSH induced behaviors, the causes were awkward posture (62.9%), excessive movement(19.3%) and repetitive movement(13.7%). 3. The compensated WMSDs by body part was the highest, 36%, in the spines, 32.0% in both the upper limbs and the spines, and 14% in the upper limbs. The number of cases of WMSDs in body were 96 in the cervical, 79 in the lumbar and 72 in the shoulders. 4. As a result of chi-square test(${\chi}^2$) between diagnosis and operation in body, welding and spot welding had the most diagnoses in all parts of the body among other occupations. Chi-square test(${\chi}^2$) between diagnosis and induced behavior in body showed that awkward postures recorded the highest rate and repetitive movements was the second. 5. The most hazardous occupation was the welding(incidence rate=9.7) and the most hazardous behavior was the awkward posture.