비접촉 조건에서의 Naegleria fowleri에 의한 표적세포의 세포독성

강창근,Il-Hwa Hong,Jong-Hyun Kim 한국동물위생학회 2019 韓國家畜衛生學會誌 Vol.42 No.4

Naegleria fowleri, a pathogenic free-living amoeba, leads to a fatal infection known as primary amebic meningoencephalitis (PAM) in human and animals. PAM is an acute, fulminant, necrotizing, and hemor-rhagic disease that leads to death in approximately seven days. In this study, we investigate the cytotox-icity of target cells and the secreted molecules of N. fowleri under the non-contact condition. The target cell (U87MG cell) treated with N. fowleri lysates showed no morphological changes and no cytotoxicity. By contrast, the U87MG cells co-cultured with N. fowleri trophozoites under the non-contact condition induced morphological changes and reduction in number. When U87MG cells were co-cultured with N. fowleri trophozoites under the non-contact condition for 30 min, 2 hr, and 4 hr, the levels of cytotox-icity of target cells were 32.3, 35.5, and 37.8%, respectively. Particularly, when the ratio of amoeba to target cells is 10 to 1, the level of cytotoxicity of target cells was 49.7% at 30 min. To show the proteins secreted from N. fowleri under the non-contact condition, we carried out 2D electrophoresis and observed 6 major proteins. Finally, these results suggest that the molecules released from N. fowleri un-der the non-contact condition induce the cell death and this process is an important step in pathogenesis of N. fowleri.

계단 오르기 동안 지면 접촉 조건에 따른 뇌졸중 환자의 근활성도 비교

윤혜진,오덕원,김경환,기경일,Youn, Hye-Jin,Oh, Duck-Won,Kim, Kyung-Hwan,Ki, Kyong-Il 대한고유수용성신경근촉진법학회 2010 PNF and Movement Vol.8 No.2

Purpose : This study aimed to investigate the effect of differing ground contact conditions on the eletromyographic(EMG) activity in rectus femoris, biceps femoris, tibialis anterior, gastrocnemius medialis during step-up activity in patients with hemiparesis. Methods : 10 hemiparetic patients performed step-up activity on three different ground contact conditions: entire ground contact, 2/3 ground contact, 1/3 groud contact. Result : The EMG activities of gastrocnemius medialis significantly changed on 1/3 ground contact(p<.05). However, no significant changed rectus femoris, biceps femoris, tibialis anterior between three differing ground contact conditions (p>.05). Conclusion : This study provides that EMG activities of gastrocnemius medialis significantly changed on different ground contacts. Therefore, this method can be used to strengthen the gastrocnemius medialis.

Analysis of Load Characteristic and Contact Patch Characteristic of Support Insert Run-Flat Tire under Zero-Pressure Condition

Zang Liguo,Wang Xingyu,Wu Chongyou,Teng Fei,Shaoqing Yang 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.5

Support insert run-flat tire is a kind of safety tire based on common tire structure. It has the advantages of simple structure, easy disassembly and strong bearing capacity. However, when driving under zero-pressure condition, it can not meet the requirements of heavy load, high mobility and long-distance. Aiming at this problem, the finite element model is established. The load and contact patch characteristics of the model are simulated by ABAQUS. The radial stiffness curve and the contact pressure distribution under zero-pressure are obtained. The results show that the radial stiffness curve presents a certain nonlinearity in the sidewall loading stage. When the insert contacts the tire, it is approximately linear. The contact pressure distribution cloud diagram under zero-pressure condition shows that there is warpage. The tire test bench was set up and the relevant test scheme was formulated. The radial stiffness curve and the footprint of the support insert run-flat tire under zeropressure condition were obtained. The research results show that the simulation and test results are in good agreement. This research is of great significance to the performance analysis of whole support insert run-flat tire under zero- pressure condition.

Cohesive frictional-contact model for dynamic fracture simulations under compression

Baek, Hyunil,Park, Kyoungsoo Elsevier 2018 International journal of solids and structures Vol.144 No.-

<P><B>Abstract</B></P> <P>In this study, a cohesive frictional-contact model is developed by integrating the cohesive zone model and the frictional-contact model to predict fracture behaviors under compression. In the cohesive zone model, a potential-based model, named as the PPR model, is employed to define the traction-separation relation. A frictional force is approximated using a Coulomb frictional model, which accounts for a stick/slip condition. A normal contact force is estimated by employing a penalty method. In order to evaluate stable normal contact forces, penalty parameters are defined by introducing non-dimensional contact parameters. This leads to less sensitive error of contact pressure with respect to the change in material properties and time increments. Furthermore, an example of an earthquake rupture and masonry shear tests under compression are simulated using the proposed framework. The computational results demonstrate that the cohesive frictional-contact model reproduces slip-weakening behaviors along a fault plane and captures experimental shear stress-slip relations according to the change in compressive stress on the fracture surface.</P>

튜브진동 시 판스프링 지지부의 미끄럼변위와 마멸 분석

김형규(Hyung-Kyu Kim),이영호(Young-Ho Lee),송주선(Ju-Sun Song) 한국트라이볼로지학회 2003 한국트라이볼로지학회 학술대회 Vol.37 No.-

Tube oscillation behaviour is experimentally investigated for the study on the fuel rod fretting that is caused by the flow-induced vibration in nuclear reactor. The experiment was conducted in air at room temperature. The specimen of tube assembly was supported by plate springs which simulated the spacer grids and fuel rods of a fuel assembly. To investigate the influence of contact condition between the grids and rods, normal load of 10 and 5 N, gaps of 0.1 and 0.3 ㎜ were applied. The range of the oscillation at the center of the fuel rod specimen was varied as 0.2, 0.3 and 0.4 ㎜ to simulate the fuel rod vibration due to flow. Displacements near the contact were measured with four displacement sensors during the tube oscillation. As results, the shape of oscillation (phase) varied depending on the contact condition. The oscillation displacement increased considerably from the contact to gap condition. The displacement increased further as the gap size increased. It is regarded that the spring shape influences the tube oscillation behaviour. Simple calculation showed that the slip displacement was very small. Therefore, cumulative damage concept is necessary for the fuel rod wear. The mechanism of plowing is thought required to explain the severe wear in the case of gap existence.

슬러지 순화조건과 접촉부하가 혐기상태에서 인과 유기물의 거동에 미치는 영향

박동근 한국환경과학회 1994 한국환경과학회지 Vol.3 No.4

Batch experiments were performed to evaluate the effect of sludge acclimation and contact load on the behavior of phosphorus and organic substrates under anaerobic conditions. Four different sludges were acclimated in the sequencing batch reactors operated by intermittent aeration. All the experiments performed in a bench scale have shown the following results: 1. The unreleaseable phosphorus contents for four different sludges are the range of 16 ㎎ P/g SS to 24 ㎎ P/g SS, depending on the sludge acclimation conditions. 2. All the specific substrate uptake rates(SSUR) are expressed in the first order equation for releaseable phosphorus contents. The reaction rate coefficient, k, has the values of 4.0, 8.9, and 13.8 mg COD/㎎ P/hr, depending on the contact load and sludge species. 3. As reaction proceeds, the ratios of ΔP to - ΔCOD at high contact load are almost constant. in the range of 0.10 to 0.14, but at low contact load, they increase from 0.08 to 0.27.

튜브 프레팅마멸 연구를 위한 접촉부 미끄럼 거동의 실험적 분석

송주선(Ju-Sun Song),김형규(Hyung-Kyu Kim),이영호(Young-Ho Lee),김재훈(Jae-Hoon Kim) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-

To study the fretting wear problem of a nuclear fuel, the behaviour of slip displacement at the contact is investigated in this paper. The slip displacement was evaluated from the vibration amplitudes measured during a fretting wear experiment in real time basis. The experiment was conducted in air at room temperature and one span of a fuel assembly was simulated. The contact condition between the grids and rods varied as the normal force of 5 N and gap of 0.2 ㎜. The fuel rod was vibrated with the frequency of 30 ㎐ and the center oscillation of 0.7 ㎜. Simple geometrical equations were used for the axial and transverse slip displacement. The trace of rod movement was investigated, which was affected by the contact condition. The vibration characteristic was not altered during the experiment when a specific contact condition was applied. The severest wear on the rod occurred in the case of axial slip and gap existence. It implies that the mechanism of impact wear should be understood for studying the fuel fretting problem.

라이닝 재료에 따른 저널 베어링의 압력 분포 특성

신상훈(Sang-Hoon Shin),임채환(Chae Whan Rim),고대은(Dae-Eun Ko) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.9

저널 베어링인 선미관 후부 베어링의 후방부에 발생하는 발열 사고는 프로펠러 하중이 추진축을 처지게 하여 후방부에 과도한 국부압착압력이 작용하는 것이 주된 원인이다. 선미관 베어링의 라이닝 재료로 사용되는 화이트 메탈보다 영률이 훨씬 작은 재료를 사용한다면 축과의 접촉 면적을 크게 함으로써 발열 사고의 원인이 되는 국부압착압력의 저감이 가능할 것이다. 본 연구의 목적은 영률이 작은 재료로 만들어진 베어링 제품의 적용에 앞서, 축계 해석을 통해 새로운 제품 적용시의 압착압력 분포특성을 파악하고 허용 압력을 결정하는데 있다. 국부압착압력의 계산에 있어서는 접촉 너비를 따라 반 타원 형상의 압력 분포를 가정한 Hertzian 접촉 조건을 도입하였으며, 엔진 가동 상태의 프로펠러 하중, 열 효과 및 선체 변형을 고려하였다. 해석 결과를 통해 영률이 작은 제품은 기존 제품을 적용한 실적선에 비해 국부압착압력의 상당한 저감이 가능함을 확인하였고, 또한 하중 조건이 바뀌더라도 압력 분포의 변화가 작아 강건 설계가 가능한 장점이 있음을 알 수 있었다. 본 연구를 통해 제시되는 제품의 성능 사양을 제조사가 보장한다면 영률이 작은 제품의 적용이 가능하리라 판단된다. The main reason for the heat induced accidents occurring at the after stern tube journal bearing is the excessive local pressure caused by the deflection of the propulsion shaft due to the propeller loads. It is expected that the contact area could beenlarged and the local pressure reduced accordingly by using a lining material having alow Young"s modulus instead of the existing white metal. The purpose of this work is to investigate the characteristics of the pressure distribution and determine the allowable pressure value in the case where bearing products made of materials having a low Young"s modulus are used. In this study, the propeller loads, heat effect, and hull deflection are considered in the evaluation of the local pressure of the ship propulsion shaft. Also, the Hertzian contact condition was applied. From the analysis results in the case where a lining material with a low Young"s modulus was used, it was found that a robust design could be achieved and the local pressure could be reduced effectively independent of the load conditions. It will be possible to producenew products made of materials having a low Young"s modulus if the manufacturer confirms the performance specifications drawn by this study.

NEW TYRE-ROAD CONTACT MODEL FOR APPLICATIONS AT LOW SPEED

D. GARCIA-POZUELO,V. DIAZ,M. J. L. BOADA 한국자동차공학회 2014 International journal of automotive technology Vol.15 No.4

Most of the tyre models have been developed for high speed, combined forces, etc., however, in certain testsit is necessary to know tyre behaviour at very low speed in order to evaluate different systems. So, during vehicle inspectionand maintenance of the steering and brake system, by means of sideslip tester and roller brake tester respectively, the forcestransmitted by the tyres are measured; all of these inspections are carried out at low speeds. Furthermore, usually, automobilevehicles run at low speeds during an important part of their operating life (less than 60 km/h), mainly during urban traffic, andin steady state conditions. Therefore, it is particularly interesting to develop an accurate model of the contact patch tyrepavementfor low speeds without the complexity of models that cover a wide speed range but provide less precision at verylow speeds. The dynamometer plate has proved to be an appropriate test equipment to characterise the tyre-pavement contactat low speed and the steering geometry and wheel alignment. It has the feature of being able to carry out tests with the tyreinstalled in the vehicle as in completely real conditions. The main aim of this research is to set up a contact model betweentyre and pavement at very low speed based on the measurement of longitudinal and lateral forces. A test methodology thatallows carrying out the experimental tests in a systematic and controlled way with the dynamometer plate has also beendeveloped. From this model it will be possible to estimate the forces that tyres are capable of transmitting in differentsituations to act in the parameters which affect these forces and maximize them.

파이어링 상태의 일정 축 각속도에서 엔진베어링의 마모 해석

전상명(Sang Myung Chun) 한국트라이볼로지학회 2018 한국윤활학회지(윤활학회지) Vol.34 No.4

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a fourstrokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.