Numerical investigation on pressure responsiveness properties of the skirt-cushion system of an air cushion vehicle

Xu, Shengjie,Tang, Yujia,Chen, Kejie,Zhang, Zongke,Ma, Tao,Tang, Wenyong The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.-

The pressure responsiveness property of a skirt-cushion system, which is closely related to the overall performance of Air Cushion Vehicles (ACVs), has always been the difficulty and challenging problem involving cushion aerodynamics and flexible skirt dynamics. Based on a widely used bag and finger skirt-cushion system, the pressure responsiveness properties are investigated numerically. The physical process and mechanism are analyzed and a numerical method for evaluating the pressure responsiveness property is proposed. A cushion-skirt information communication platform is also presented for interchanging the force and the skirt configuration between cushion aerodynamics and flexible skirt dynamics. The pressure responsiveness of a typical skirt-cushion system is calculated and the results demonstrate that the pressure responsiveness property helps alleviate the influence of the cushion height changing on the overall performance of ACVs. Finally, the influences of skirt geometrical and cushion aerodynamic parameters on the pressure responsiveness properties are discussed systematically, giving insight into the design of skirt-cushion systems.

Numerical investigation on pressure responsiveness properties of the skirt-cushion system of an air cushion vehicle

Xu, Shengjie,Tang, Yujia,Chen, Kejie,Zhang, Zongke,Ma, Tao,Tang, Wenyong The Society of Naval Architects of Korea 2020 International Journal of Naval Architecture and Oc Vol.12 No.1

The pressure responsiveness property of a skirt-cushion system, which is closely related to the overall performance of Air Cushion Vehicles (ACVs), has always been the difficulty and challenging problem involving cushion aerodynamics and flexible skirt dynamics. Based on a widely used bag and finger skirt-cushion system, the pressure responsiveness properties are investigated numerically. The physical process and mechanism are analyzed and a numerical method for evaluating the pressure responsiveness property is proposed. A cushion-skirt information communication platform is also presented for interchanging the force and the skirt configuration between cushion aerodynamics and flexible skirt dynamics. The pressure responsiveness of a typical skirt-cushion system is calculated and the results demonstrate that the pressure responsiveness property helps alleviate the influence of the cushion height changing on the overall performance of ACVs. Finally, the influences of skirt geometrical and cushion aerodynamic parameters on the pressure responsiveness properties are discussed systematically, giving insight into the design of skirt-cushion systems.

궁중 연향 왕실 방석(方席)에 관한 연구

석진영 대한건축학회 2022 대한건축학회논문집 Vol.38 No.7

During the Joseon Dynasty, a banquet with sitting cushions was mainly held in the yard of the royal quarters in front of the royal palace. If a leopard sitting cushion was used in the architectural space of a banquet, it indicated the highest rank in the royal seat during the Joseon Dynasty, which continued until the Gojong period. The long leaning cushion did not appear in the banquet seats during the Jeongjo period, but was used during the Sunjo period. The dragon-patterned sitting mat was used only for the king’s seat after the Sunjo period. This was to establish the king’s political authority, subdividing the hierarchy based on the mat’s pattern. Banquets held during the Sunjo period used the dragon-patterned sitting mat for the king, the floral sitting mat for Queen Sunwon, Crown Prince Hyomyeong, and the crown princess. For the sitting cushion, Manhwa and leopard sitting cushions were placed. Eventually, the crown prince and princess’s sitting cushions were replaced with leopard sitting cushions. The king’s throne had five levels of mats and Pyeoncha had five levels. The royal throne including the crown prince consisted of five stages, and the Socha bowing seat, and Pyeoncha had three levels. The seat for alcohol offerings had two stages; the arrangement of the sitting cushions indicated the rank of the seat for alcohol offering, the lowest was the crown prince’s seat. The number of stages and mats were the highest during the Jeongjo period. A pattern of this complex stage appeared in the Sunjo period and settled down after the Heonjong period. In the King’s hierarchy, there was the most, odd number of sitting cushions, and the status was classified by the number of mats used. During a banquet, the sitting cushion was placed according to the seat status. An arrangement by type, pattern, and color was used to distinguish the hierarchy of participants. The sitting cushion established the king’s political hierarchy and more specifically stratified the level of its royal participants. Sitting cushions were used on the royal family seats and for participants in the architectural space of a banquet. It was lastly planned in the banquet architectural space division, defining the differences in position according to the status and subdividing the royal hierarchy for some increased. 궁궐 연향에서 방석은 다양한 위차에 배설되었으며 유형과 문양, 색상 등이 구분되어 배설된 것은 참여자와 왕실을 구분하기 위한 것이다. 방석은 전하의 정치적 위계를 확립하고 왕실 참여자의 등급을 더욱 구체적으로 구분하기 위한 기능을 수행하였다. 방석은 연향의 건축공간에서 왕실과 참여자의 위차를 세분화하여 구분하였으며, 연향 왕실 공간 구획에서 마지막 위차를 규정하고 왕실 위계를 세분화하였다. 조선후기 왕권과 왕실의 정치적 질서·의례적 명분, 유교적 위계질서를 지키며 신분 체제를 견고히 하고자 상징적으로 방석을 이용하였다.

휠체어 시트쿠션의 접촉압력 특성 비교연구

강영식,양성환,조문선 대구대학교 특수교육재활과학연구소 2010 특수교육재활과학연구 Vol.49 No.1

Selecting the appropriate wheelchair seat cushion for relieving and preventing the risk of pressure ulcers is greatly important to the wheelchair users. Appropriate seat cushion should be made to distribute the contact pressure evenly and reduce the peak pressure and the high contact pressure area. This study offered comparative information on the contact pressure distribution of different wheelchair seat cushions. For this objective, contact pressure distribution of four cushion models were investigated first and the effect of the quantity of air in the cushion was studied also. At last, the influence of body mass index on the pressure distribution was investigated. Each of 17 healthy persons was seated on the four models of cushions analyzed(no cushion, low-profile air, high-profile air, gel-air), which was presented in randomized order. The pressure distribution and contact area of the user-cushion interface were obtained with a pressure measurement system. Investigation shows that the wheelchair seat cushions is effective to distribute the contact pressure evenly and reduce the peak pressure and high-pressure contact area. The gel-air cushion yielded lower readings for all pressure parameters analyzed than the other three cushion models(p>0.05 with high-profile air, p<0.05 with other cushion models). And also, the quantity of air in the cushion has a great effect on the characteristics of contact pressure distribution and the effectiveness of seat cushion was reduced to the obesity group users. 휠체어를 사용하는 사용자들은 장시간 고정된 자세로 앉아서 생활하는 경우가 많다. 따라서, 둔부에 집중되는 압력을 분산시켜줄 수 있는 적절한 시트쿠션의 사용은 욕창 예방을 위해서 매우 중요하다고 할 수 있다. 본 연구에서는 시트쿠션의 접촉 압력 특성을 비교, 분석함으로써, 시트쿠션을 평가, 분석하기 위한 기본 자료를 제공하고, 이를통해 시트쿠션의 선택 및 설계에 유용한 정보를 제공하고자 하였다. 이를 위해 3가지 모형의 시트쿠션(무쿠션, 낮은 셀 타입 공기쿠션, 높은 셀 타입 공기쿠션, 젤-공기쿠션)을 대상으로 접촉압력을 측정, 비교, 분석하였으며, 공기 주입형 쿠션의 공기주입량에 따른 특성 비교 및 체질량 지수에 의해 분류한 사용자 그룹간의 상호 비교, 분석을 실시하였다. 연구 결과 시트의 사용은 둔부에 걸리는 최고 압력을 낮추고, 압력을 분산하며, 높은 압력이 걸리는 면적을 줄여주는 효과가 있는 것으로 나타났으며, 젤-공기주입 형태의 쿠션과 높은 셀 타입의 공기주입 쿠션의 특성이 상대적으로 좋은 것으로 평가되었다. 또한, 공기주입 쿠션의 경우 적절한 사용압력을 유지해 주는 것이 시트의 접촉압력 특성 결정에 매우 큰 영향을 주는 것으로 평가되었으며, 비만한 그룹의 사용자는 타 그룹 사용자에 비해 시트쿠션의 사용효과가 다소 떨어지는 것으로 나타났다.

휠체어 사용자의 욕창 예방을 위한 맞춤형 융복합 하이브리드 오프로딩 방석의 소재에 관한 연구

양승완(Yang, Seung Wan),장완호(Jang, Wan Ho),김종배(Kim, Jong Bae) 한국전시산업융합연구원 2020 한국과학예술융합학회 Vol.38 No.5

욕창 예방 방석은 욕창을 예방하고 압력 감소를 위해 대표적으로 사용되는 방법이며, 스스로 적절한 자세 변경이 어려운 중증 장애인에게 필수적인 보조기기이다. 욕창 위험성이 있는 장애인은 여러 형태의 욕창 예방 방석을 사용하고 있지만, 65.2%가 여전히 욕창을 경험하는 것으로 보고되고 있다. 최근에는 오프로딩 기술을 여러 형태의 소재와 결합된 융복합 하이브리드 형태의 욕창 예방 방석이 보고되고 있다. 본 연구는 휠체어 사용자의 욕창 예방 방석 디자인을 근거로 다양한 소재를 적용한 맞춤형 융복합 하이브리드 오프로딩 방석의 시제품을 제작하고, 각 소재별 압력 및 만족도를 조사하였다. 각 대상자 별로 융복합하이브리드 미적용 방석, 3D메쉬, 메모리폼, 라텍스 적용 방석을 중재하였다. 선행 연구를 근거로 휠체어 사용자가 욕창이 주로 발생하는 부위인 IT, GT, Coccyx 부위에 소재에 따른 압력을 측정하였다. 압력을 비교한 결과, 비하이브리드 방석에 비해 융복합 하이브리드 방석의 압력 분산 효과가 우수한 것으로 조사되었으며, 융복합 하이브리드 방석 소재에 따른 압력 분산의 효과는 라텍스, 3D메쉬, 메모리폼 순으로 조사되었다. 소재에 따른 만족도는 3D메쉬, 라텍스, 메모리폼, 비하이브리드 방석 순으로 조사되었다. 융복합 하이브리드 방석 서비스 시 사용자에 따라 소재별 압력의 효과와 소재에 대한 만족도에 차이가 있는 점을 고려해서 적용해야 한다. 본 연구의 결과를 통해 앞으로 진행될 맞춤형 융복합 하이브리드 오프로딩 방석의 상용화에 긍정적인 영향을 줄 수 있을 거라고 기대한다. The pressure ulcer prevention cushion is a representative method used to prevent pressure ulcer and reduce pressure, and is an essential assistive device for people with severely disabilities changing their proper posture on their own. People with disabilities at risk of pressure ulcers use various types of cushions, but it is reported that 65.2% still experience pressure ulcers. Recently, a convergence hybrid type of pressure ulcer prevention cushion in which off-loading technology is combined with various types of materials has been reported. This study produced a prototype of a customized convergence hybrid off-loading cushion that applied various materials based on the design of preventive pressure ulcer cushions for wheelchair users, and investigated the pressure and satisfaction of each material. For each subject, including a non-hybrid cushion, 3D mesh, memory foam, and latex cushion were mediated. Based on previous studies, the pressure according to the material was measured on the IT, GT, and Coccyx areas, which are areas where pressure ulceres mainly occur in wheelchair users. As a result of comparing the pressure, it was investigated that the pressure dispersion effect of the convergence hybrid cushion was superior to that of the non-hybrid cushion, and the effect of pressure dispersion according to the convergence hybrid cushion material was investigated in the order of latex, 3D mesh, and memory foam. Satisfaction according to the material was surveyed in the order of 3D mesh, latex, memory foam, and non-hybrid cushion. In the case of convergence hybrid cushion service, it should be applied in consideration of differences in the effect of pressure for each material and satisfaction with materials depending on the user. It is expected that the results of this study will have a positive effect on the commercialization of customized convergence hybrid off-loading cushions in the future.

욕창방지용 휠체어 쿠션 신기술의 압력 비교 : 예비 연구

황보승우,김종배 대한보조공학기술학회 2015 대한보조공학기술학회지 Vol.7 No.1

Objective : The purpose of this study was to introduce new technologies of pressure ulcer preventive wheelchair cushion and identify whether the pressure differs from these new technologies. Methods : This study was conducted for total 6 days, from 18th to 23rd of June, 2015. The participants were one healthy man and a woman each. Three new types of pressure ulcer preventive wheelchair cushion were used for this study. Each of the wheelchair cushions was provided for 45 minutes and X3 Medical v6.0 was used for comparing the measured pressure. The peak pressure of the first frame (Pre Peak Pressure), the peak pressure of the last fram (Post Peak Pressure), and the average peak pressure of the first, middle, and last frames (Average Peak Pressure) were analysed by X3 Medical v6.0. Results : As a result, Pre, Post, and Average Peak Pressures of Java cushion were all lowest among three cushions. In Lock cushion, Post and Average Peak Pressures were highest. Galaxy cushion indicated highest Pre Peak Pressure. Conclusion : Since the peak pressure areas of the three cushions are different, it’s difficult to conclude which cushion was the most effective for preventing pressure ulcer. However, Java cushion had lower Peak Pressure than both Galaxy and Lock cushion when applied for 45 minutes. Considering the technologies of the three wheelchair cushions, further studies are required for comparing these cushions when applied for longer time with a clear standard. Moreover, the study must be conducted with current long-term wheelchair users instead of non-disabled subjects. 목적 : 본 연구의 목적은 욕창방지용 휠체어 쿠션의 신기술을 소개하고, 이 신기술에 따른 압력이 차이가 있는지를 알아보고자 함이다. 연구방법 : 본 연구는 2015년 6월 18일부터 23일까지 6일간 진행되었다. 일반 성인 남녀 2명을 대상으로 진행하였으며, 실험은 신기술의 욕창방지용 휠체어 쿠션 세 종류를 사용하였다. 각각의 쿠션은 45분간 적용되었으며, 측정된 압력 값을 비교하기 위해 X3 Medical v6.0을 사용하였다. 압력 측정의 맨 첫 번째 구간의 최대 압력 값, 맨 마지막 구간의 최대압력 값, 그리고 첫 번째, 중간, 마지막 구간을 합하여 3으로 나눈 평균 최대 압력 값을 각각 분석하였다. 결과 : 각 쿠션별로 측정된 압력 값을 분석한 결과, Java 쿠션이 최대 압력의 초기, 후기, 평균값 모두 가장 낮게 나타났다. Lock 쿠션은 최대 압력의 후기 값과 평균값이 가장 높았다. Galaxy 쿠션은 최대 압력의 초기 값이 가장 높았다. 결론 : 3가지 쿠션의 각 최대 압력 값이 부위에 따라 다르기 때문에 욕창 예방에 가장 효과적인 쿠션을 결론짓기에는 다소무리가 있으나, 45분 동안 적용한 기준으로 측정한 최대 압력의 값은 Java 쿠션이 Galaxy와 Lock 쿠션보다 낮게 나타났다. 그러나 욕창방지용 휠체어 쿠션 세 종류가 가지고 있는 기술의 특성을 고려하였을 때, 명확한 기준을 설정하여 보다 긴 시간동안의 압력 값을 비교하는 연구가 필요할 것으로 예상되며, 일반인이 아닌 실제 휠체어를 장기간 사용하는 대상자로 연구를 진행해볼 필요가 있다.

Cushion pressure control system for an intelligent air-cushion track vehicle

Altab Hossain,Ataur Rahman,A.K.M. Mohiuddin 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.4

This paper presents the control system of cushion pressure for the developed intelligent air-cushion track vehicle (IACTV) for operating on swamp terrain and wet fields. A novel auto-adjusting supporting system is designed for the vehicle’s intelligent air-cushion system. Focusing on minimizing the total power demand of the vehicle, an optimization model has been established, for examining the effects of vehicle parameters and load distribution on power consumption by controlling air-cushion pressure. Then optimum cushion pressure is determined based on the developed optimum pressure – sinkage relationship and the pressure in the cushion chamber is controlled by the Fuzzy controller by maintaining volume flow rate and continuously monitored by the pressure sensor attached with the cushion chamber. The ultrasonic displacement sensor is used to measure the sinkage of the vehicle. The output voltages of the ultrasonic displacement are used to operate the pull-in solenoid switch through the microcontroller which closes the circuit of the compressor motor. Distribution of vehicle load to the air-cushion system is controlled by Fuzzy Logic controller by maintaining the inside pressure of the cushion.

골판지를 이용한 완충 포장재의 물리적 특성에 관한 연구

최승진,신중민 한국포장학회 2006 한국포장학회지 Vol.12 No.1

Cushioning systems, which are cushion material and its designed configuration, are important to protect fragile items since they act as buffers between the impact force and the fragile product. As cushioning materials, several plastic foams are commonly used in industry. However, the utilization of the plastic material has been causing a solid waste problem and pollution. Thus, as an alternative cushion material to the plastic foams, a corrugated cushion, which is considered environmentally friendly and cheap material, was put into drop tests and its impact shock attenuation was investigated. Flat and free drop data were recorded and compared to the dynamic shock of EPS cushion. In addition, the mathematical model of the shock attenuation of the corrugated cushion was developed. The result showed that the corrugated cushion gave an excellent protection for items that were subjected to the limited number of drops. There was no significant difference of the shock absorbing ability between the EPS and corrugated cushions. Energy density model of cushioning material successfully explained the mechanical behavior and fatigue of the corrugated cushions.

컴퓨터 시뮬레이션에 의한 관성과 마찰 에너지를 이용하는 충격흡수시설의 개발

김동성,김기동,고만기,김광주 한국방재학회 2009 한국방재학회논문집 Vol.9 No.2

Crash cushions are protective devices that prevent errant vehicles from impacting on fixed objects. This function is accomplished by gradually decelerating a vehicle to a safe stop in a relatively short distance. Commonly used crash cushions generally employ one of two concepts to accomplish this function. The first concept involves the absorption of the kinetic energy of a moving vehicle by crushable or plastically deformable materials and the other one involves the transfer of the momentum of a moving vehicle to an expendable mass of material located in the vehicle's path. Crash cushions using the first concept are generally referred to as compression crash cushions and crash cushions using the other concept are generally referred to as inertial crash cushion. The objective of this research is the development of a compression-type crash cushion by employing the two concepts simultaneously. To minimize the number of full-scale crash tests for the development of the crash cushion, preliminary design guide considering inertial and frictional energy absorption was constructed and computer simulation was performed. LS-DYNA program, which is most widely used to analyze roadside safety features, was used for the computer simulation. The developed crash cushion satisfied the safety evaluation criteria for various impact conditions of CC2 performance level in the Korean design guide. 충격흡수시설은 주행차로를 벗어난 차량이 도로상의 고정된 구조물과의 직접적인 충돌을 방지하도록 하기 위한 보호시설이다. 이러한 기능은 충돌차량이 안전하게 점진적으로 멈추도록 속도를 감소시킴으로써 이루어진다. 기존의 일반적인 충격흡수시설에는 이러한 기능을 수행하기 위해서 다음의 두 가지 개념 중 하나가 적용된다. 첫 번째 개념은 파괴 또는 소성변형이 가능한 재료에 의해 충돌차량의 운동에너지를 흡수하는 것이고, 두 번째 개념은 충돌차량의 운동량을 차량의 이동경로에 놓인 소모성 재료의 질량체에 전달하는 것이다. 일반적으로 첫 번째 개념을 이용한 충격흡수시설은 압축(비관성) 충격흡수시설로 분류되고, 두 번째 개념을 이용한 충격흡수시설은 관성 충격흡수시설로 분류된다. 본 논문의 목적은 위에서 언급한 두 가지 개념을 동시에 적용한 압축형 충격흡수시설의 개발이다. 실물차량 충돌시험을 최소화 할 수 있도록 관성 에너지와 마찰 에너지 소산을 고려한 예비설계 가이드를 수립하고 충격흡수시설 개발을 위한 컴퓨터 시뮬레이션을 수행하였다. 시뮬레이션을 위하여 도로안전시설물 해석에 가장 많이 사용되는 LS-DYNA를 이용하였다. 개발된 충격흡수시설은 국내지침 CC2급의 다양한 충돌조건에 대한 성능평가 기준을 만족하였다.

휠체어 사용 장애인을 위한 맞춤형 욕창 예방 방석 디자인 연구

김정현(Kim, Jeong Hyun),김종배(Kim, Jong Bae) 한국전시산업융합연구원 2016 한국과학예술융합학회 Vol.24 No.-

본 연구의 배경 및 목적은 다음과 같다. 휠체어와 착석 시스템에 대한 정의를 보면 보행이 어려운 사람의 이동을 지원하고 적절한 자세의 앉기가 가능하도록 수정하거나 조절해주는 보조기구로 되어 있다. 그러나 최근 국내 휠체어 사용 장애인을 대상으로 연구한 결과 여전히 많은 수의 장애인이 욕창으로 인한 합병증이 발병하고 있으며, 휠체어 사용 시 가장 불편한 신체 부위로 엉덩이와 허리를 선택하였다. 이러한 결과는 욕창 예방 방석을 사용하고 있으나 여전히 발병률이 감소되지 않고 있으며, 앉기 자세에 대한 불편함이 일상생활을 방해하는 대표적인 요소임을 알 수 있었다. 따라서 본 연구에서는 휠체어를 사용하는 장애인을 위해 맞춤형 욕창 예방 방석의 디자인을 의학적 이론기반 융합 연구를 통해 제안하고 이를 제작하였다. 디자인에 대한 제안은 휠체어 사용 장애인의 특징과 욕창 발생에 대한 의학적 배경, 앉기 자세에 대한 해부학적인 요소를 근거로 디자인 하였다. 또한 욕창 예방방석과 휠체어 프레임의 인체 공학적 특징을 기반으로 한 이론적 근거를 바탕으로 욕창 예방 방석을 제작하였다. 욕창 예방 방석 디자인의 기본적 개념은 휠체어 사용 장애인의 엉덩이 좌면에 발생하는 압력을 감소시키고 적절하게 분배하며, 바른 앉기 자세가 가능하도록 골반과 체간을 지지해주는 것이다. 이러한 이론적 근거를 바탕으로 맞춤형 욕창 예방방석을 디자인하고 제작하였다. 비장애인을 대상으로 사용성 평가 실험 연구를 진행하였으며, 피실험자의 좌면을 스캔하여 방석을 제작하였다. 이렇게 제작된 맞춤형 방석과 현재 상용화되어 판매중인 조절형 욕창 예방 방석 2개 제품과 비교 테스트를 수행하였다. 실험을 수행한 결과, 궁둥뼈에 나타나는 최대압력지수 값이 3개 제품중 가장 낮게 나타났으며, 압력을 분포시키는 분산지수도 가장 낮게 측정되었다. 그러나 엉덩이 좌면 전체에 나타나는 평균 압력은 다른 제품보다 다소 높게 나타나 추후 연구에서 이런 문제점을 보완할 필요가 있었다. 향후 진행될 연구에서는 좌면의 전반적인 평균 압력 감소를 위한 디자인의 추가적인 설계가 요구되며, 이에 대한 테스트가 필요할 것으로 보인다. The background and objectives of this research are as follows. The definition of a wheelchair and the seating system are a type of adaptive device that supports mobility of those who have difficulty ambulating and modifies or adjusts appropriate sitting. However, according to the results of a recent study on wheelchair users in Korea, a number of people with disability have complications from pressure ulcers, and pointed out hips and waist as the most uncomfortable parts of the body when using a wheelchair. These results present that although ulcer preventive cushions are used, incidence has not been on a decline, and the discomfort of the sitting posture is the main factor that disrupts every day life. The purpose of this research was to test the design of customized cushions for people with disabilities that prevents pressure ulcers. The proposals for the design was made considering the features of a wheelchair user, medical backgrounds for the occurrence of pressure ulcers, and the anatomical designs of the sitting posture. In addition, the pressure ulcer preventive cushion was built on a rationale based on the ergonomic features of the pressure ulcer preventive cushion and the wheelchair frame. The basic concept of the design of the pressure ulcer preventive cushion is to reduce and appropriately distribute the pressure caused from the eating surface and support pelvis and trunk for correct sitting posture. Customized pressure ulcer preventive cushions were designed and produced based on this rationale. Preliminary experiments were conducted to people without disabilities, and the cushions were produced by scanning the seat-contacted area of the subjects. A comparison test was performed on 1) tailor-made cushions and 2) commercially-shaped cushions that customize or adjust to prevent pressure ulcers. As a result of this experiment, the peak pressure index of ischial tuberosity values appeared the lowest of the three products, and the dispersion index also measured the lowest. However, since the average pressure index of the seat-contacted area presented higher values than other product, it was necessary to compensate for these problems in the further researches. Additional adjustments to the design to reduce the overall average of pressure on the seating-contacted area and the necessary test will be done in future researches. Measuring not only pressure, but also shear force and blood flow that affects the occurrence of pressure ulcer to increase the reliability and validity of the value data to the results is needed to verify the effectiveness of the pressure ulcer preventive cushion.