• 공학교육연구
• /
• 제2권1호
• /
• pp.51-58
• /
• 1999

본 연구는 가상 현실(virtual reality)을 활용하여 실제 고가의 실험장비를 구입하지 않고도 개인용 컴퓨터에서 인터넷상으로 가상적인 프레스를 이용한 압축실험을 할 수 있도록 하는 것이다. 가상압축실험의 구현은 인터넷을 통하여 세 개의 모듈 즉 입력, 계산, 결과로 나누어 계산되어진다. 입력모듈에서는 압축실험을 위하여 인터넷 사용자가 재료의 실험적인 특징을 입력하고 그 입력 값을 서버 컴퓨터로 보내주는 과정이며, 계산모듈은 서버 컴퓨터에 있는 시뮬레이션 해석프로그램을 이용하여 입력모듈의 입력 값을 받아들여 결과를 계산한 후 파일로 저장하는 과정이다. 결과모듈에서는 서버 컴퓨터에서 계산된 결과를 인터넷 사용자에게 도표와 그림 그리고 3차원 애니메이션을 보여주는 과정으로 되어있다. 이를 구현하기 위하여 인터넷의 언어인 HTML, CGI, VRML, JAVA를 사용하였으며, 유한요소법(FEM)을 이용한 해석프로그램은 포트란(Fortran) 언어로 제작되었다. 현재 인터넷상에서의 가상현실을 이용한 응용분야가 급속히 확대되므로 앞으로 공학적인 가상 실험에 관한 연구가 많이 이루어져 실제 실험을 대체할 것이다.

• Structural Engineering and Mechanics
• /
• 제73권5호
• /
• pp.487-500
• /
• 2020

Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.

• Natural Product Sciences
• /
• 제25권1호
• /
• pp.38-43
• /
• 2019

Microbial wound infection prolonged the hospitalization and increase the cost for wound management. Silver is commonly used as antimicrobial wound dressing. However, it causes several adverse side effects. Hence, this study was aimed to evaluate the antimicrobial efficiency of Swietenia macrophylla seed extract on clinical wound pathogens. Besides, the bioactive constituents of the seed extract were also determined. S. macrophylla seeds were extracted with methanol by maceration method. The seed extract inhibited 5 test bacteria and 1 yeast on disc diffusion assay. The antibacterial activity was broad spectrum, as the extract inhibited both Gram positive and Gram negative bacteria. On kill curve analysis, the antibacterial activity of the seed extract was concentration-dependent, the increase of extract concentration resulted in more reduction of bacterial growth. The extract also caused 99.9% growth reduction of Bacillus subtilis relative to control. A total of 21 compounds were detected in gas chromatography- mass spectrometry analysis. The predominant compounds present in the extract were oleic acid (18.56%) and linoleic acid (17.72%). In conclusion, the methanolic extract of S. macrophylla seeds exhibited significant antimicrobial activity on clinical wound pathogens. Further investigations should be conducted to purify other bioactive compounds from the seeds of S. macrophylla.

• Nuclear Engineering and Technology
• /
• 제56권7호
• /
• pp.2875-2880
• /
• 2024

The development of nuclear power plants is in three phases. The first phase is a consideration before the decision on the NPP construction program is approved, the second phase is the preparatory work for making contracts and preparing for the construction of NPP after the NPP construction policy is approved, and the third phase is contracting, licensing and building the first NPP. As a volcanically active country, Indonesia contains over 130 active volcanoes that are part of the Pacific Ring of Fire. The volcanic aspect is one of the safety factors considered while deciding the location of an NPP. Research on the potential of natural external risks to the determination of nuclear power plants in Indonesia, including the volcanic aspect, has been conducted based on the safety reference or safety guide of the IAEA and the Nuclear Energy Regulatory Body (BAPETEN) Regulation. Due to technological advancements, safety needs have evolved so the existing Indonesia National Standard (SNI) must be updated to comply with BAPETEN regulations. The substance in SNI 18-2034-1990 relating to volcanic features seems less relevant in actual conditions, given that more complete and exact criteria for determining a site guarantee the safety and health of residents and surrounding the environment site. The study intends to conduct a gap analysis of volcanic issues in SNI and volcanic regulations. The method used is identification requirements for volcanic aspects in SNI 18-2034-1990 about Determining Site of Nuclear Reactor Guidance with BAPETEN Chairman Regulation (BCR) number 4 of 2018 about Nuclear Installation Site Evaluation Safety Provisions and BCR number 5 of 2015 about Evaluation of Nuclear Installation Sites for Volcanic Aspects, and analysis uses a qualitative method of inductive techniques. The outcome of this research applies to suggesting a revision of SNI number 18-2034-1990, especially the volcanic aspect.

• 한국제4기학회지
• /
• 제13권1호
• /
• pp.25-33
• /
• 1999

지리산 천왕봉 아고산 지역 (해발 1,600∼l,700m)에 자라는 구상나무의 연륜생장과 기후와의 관계를 북사면(장군봉)과 남사면(중봉)을 대상으로 조사하였다. 각 지역에서 10여 본에서 생장편을 임목당 2개씩을 채취하였다. 채취된 코어는 크로스데이팅후 연륜폭을 측정하여 얻어진 연륜시리즈(연대기)를 표준화한 후, 기후인자(월강수량과 월평균기온)와 연륜생장과의 관계를 반응함수를 이용하여 분석하였다. 반응함수로 즉 월기후인자로 연륜연대기 총변동의 45.9∼53.8%를 설명할 수 있었다. 강수와 연륜생장과의 관계는 중봉과 장군지역 모두에서 3∼5월, 8월에 대해 정의 관계를 보이고 2월과 7월에 대해서는 부의 관계를 나타내 유사한 결과를 보였다. 기온에 대한 관계는 남사면에 위치한 구상나무가 북사면에 위치한 구상나무에 비해 2월과 8월에서 높은 부의 관계를 나타내었으며 4월 기온과는 두 지역 모두 유의한 정의 관계를 나타내었다. 두 사면지역의 구상나무 연륜생장과 기후와의 관계는 전체적으로는 큰 차이를 보여주지 않았다. 아한대 수종의 연륜생장이 강수보다는 기온에 민감하여 월기온과 대체로 정의 관계를 갖는 반면에 지리산 구상나무의 경우는 기온과 부의 관계를 갖는 경향이 크며 강수의 영향 특히 봄기간 동안의 수분수지가 중요한 것으로 생각된다. 구상나무 연륜과 기후와의 유의한 관계를 이용하여 향후 소빙기를 포함하는 장기간의 고기후를 복원할 수 있을 것이다.

• 한국운동역학회지
• /
• 제27권2호
• /
• pp.117-124
• /
• 2017

Objective: The purpose of this study was to examine the effect of changes in degrees of freedom of the fingers (i.e., the number of the fingers involved in tasks) on the task performance during force production and releasing task. Method: Eight right-handed young men (age: $29.63{\pm}3.02yr$, height: $1.73{\pm}0.04m$, weight: $70.25{\pm}9.05kg$) participated in this study. The subjects were required to press the transducers with three combinations of fingers, including the index-middle (IM), index-middle-ring (IMR), and index-middle-ring-little (IMRL). During the trials, they were instructed to maintain a steady-state level of both normal and tangential forces within the first 5 sec. After the first 5 sec, the subjects were instructed to release the fingers on the transducers as quickly as possible at a self-selected manner within the next 5 sec, resulting in zero force at the end. Customized MATLAB codes (MathWorks Inc., Natick, MA, USA) were written for data analysis. The following variables were quantified: 1) finger force sharing pattern, 2) root mean square error (RMSE) of force to the target force in three axes at the aiming phase, 3) the time duration of the release phase (release time), and 4) the accuracy and precision indexes of the virtual firing position. Results: The RMSE was decreased with the number of fingers increased in both normal and tangential forces at the steady-state phase. The precision index was smaller (more precise) in the IMR condition than in the IM condition, while no significant difference in the accuracy index was observed between the conditions. In addition, no significant difference in release time was found between the conditions. Conclusion: The study provides evidence that the increased number of fingers resulted in better error compensation at the aiming phase and performed a more constant shooting (i.e., smaller precision index). However, the increased number of fingers did not affect the release time, which may influence the consistency of terminal performance. Thus, the number of fingers led to positive results for the current task.

• 자원환경지질
• /
• 제46권6호
• /
• pp.495-508
• /
• 2013

물의 $^{18}O/^{16}O$와 $^2H/H$ 조성을 레이저를 이용하여 분석하는 기술은 기존의 IRMS를 이용한 분석방식에 비해 간편한 시료 전처리, 쉬운 장비 유지보수와 현장에서도 응용이 가능하다는 장점을 가지고 있다. 현재 사용되는 레이저 방식을 이용한 물의 안정동위원소 분석은 분석원리에 따라 OA-ICOS(Off-Axis Integrated Cavity Output Spectroscopy)를 이용한 방식과 WS-CRDS(Wavelength-Scanned Cavity Ring-Down Spectroscopy)를 이용한 방식으로 구분된다. WS-CRDS 방식은 기화된 물 시료를 질소 가스를 이용해 광학 공동(optical cavity)로 이동시킨 후 특정 파장에서의 동위원소체가 가지고 있는 흡수도와 레이저를 투과시켜 광학 공동을 투과하여 나오는 레이저 신호의 감쇠시간의 비측정을 통해 수 ppb에서 수십 ppt까지의 감도로 물의 안정동위원소 조성이 측정 가능하다. 이 연구에서는 WS-CRDS 방식의 분석원리와실제 물시료를 활용하여 기기의 안정성과 동위원소비 질량분석기(Isotope Ratio Mass Spectrometry; IRMS) 방법과의 교차분석을 포함한 기기 성능평가 결과를 소개하고 수리학 분야에서 다양한 주제에 대한 적용 가능성을 제시하였다.

• 대한인간공학회지
• /
• 제32권6호
• /
• pp.503-509
• /
• 2013

Objective: The purpose of this study is to analyze the individual finger force between dominant hand and non-dominant hand and to investigate an effect of the individual finger on the total grip strength depending on dominant hand and non-dominant hand. Background: Many studies on the ratio of the grip force between dominant hand and non-dominant hand has been researched. While a 10% rule which is a ratio of the grip force between dominant hand and non-dominant hand has been applied in most studies, studies on the rate of the individual finger force between dominant hand and non-dominant hand have been insufficiently researched. Method: The experiment was preceded with 17 subjects (male, mean 25.8 ages). The individual finger force and total grip strength were measured using pliers being able to change the grip span from 45 to 80mm. Results: The difference of total grip strength between dominant hand and non-dominant hand is following 10% rule. However, the difference of individual finger force between dominant hand and non-dominant hand are not same as the difference of total grip strength. Especially in the case of grip span with 50mm, the differences between total grip strength, index finger, middle finger, ring finger, and little finger were $9.87{\pm}14.80%$, $8.95{\pm}37.17%$, $13.71{\pm}28.27%$, $6.77{\pm}24.35%$, $39.29{\pm}42.46%$, respectively, with p=0.018 of statistical significance. Additionally, the results of regression analysis in 50 and 60mm of grip span showed that the difference in ring finger affected the most to the total grip strength; and the effects followed in order of index finger, middle finger, and little finger. Conclusion: Our study suggests that an effect of individual finger and grip span of pliers have to be considered when explaining the difference of the total grip strength between dominant hand and non-dominant hand. Application: This result is expected to be used for designing ergonomic hand tool.

• 한국ITS학회 논문지
• /
• 제8권5호
• /
• pp.57-70
• /
• 2009

교통여건의 변화로 좌 우회전, 중앙버스 및 자전거 전용신호에 대한 요구가 증대되고 있다. 그러나 현재 운영되고 있는 표준규격 교통신호제어기는 4색등화기를 기반으로 하고 있어, 3색등화기의 방향별 차종별 전용신호를 운영하는 데 제약이 있다. 따라서 본 연구는 기존 표준 교통신호제어기에서 좌 우회전 및 중앙버스의 전용신호를 제어할 수 있는 물리적 소프트웨어적인 방안을 제시하였다. 물리적으로 보행 적, 보행 녹, 적, 황, 화살표 및 녹색등화의 6개 출력단자로 설계된 4색등화기의 신호등구동장치(LSU)를 적, 황, 녹색의 3개 씩 2단 배열로 그룹화 하여, 3색등화기의 전용신호로 사용하는 방안을 제시하였다. 소프트웨어적으로 신호 맵 데이터의 코드값을 3색등화기의 적1 황1 녹1 적2 황2 녹색2의 LSU 출력에 맞게 설정하여, 링별(A/B링) LSU별로 전용신호를 스텝별로 구동하는 방안을 제안하였다. 전용신호 도입 시의 운영효과를 중앙버스전용차로가 운영되고, 좌회전이 허용되는 서울시 망우역교차로를 대상으로 분석한 결과 버스전용차로가 운영되고 있는 주도로(동-서)에서 지체가 크게 개선되어 교차로 전체의 지체시간이 70초/대 이상 개선되는 것으로 분석되었다.

• Geomechanics and Engineering
• /
• 제25권3호
• /
• pp.207-219
• /
• 2021

Several additives are used to enhance the geotechnical properties (e.g., shear wave velocity, shear modulus) of soils to provide sustainable, economical and eco-friendly solutions in geotechnical and geo-environmental engineering. In this study, piezoelectric ring actuators are used to measure the shear wave velocity of unreinforced, fiber, cemented, and fiber reinforced cemented Toyoura sand. One dimensional oedometer tests are performed on medium dense specimens of Toyoura sand-cement-fiber-silica flour mixtures with different percentages of silica flour (0-42%), fiber and cement (e.g., 0-3%) additives. The experimental results indicate that behavior of the mixtures is significantly affected by the concentration of silica flour, fiber and cement additives. Results show that with the addition of 1-3% of PVA fibers, the shear wave velocity increases by only 1-3%. However, the addition of 1-4% of cement increases the shear wave velocity by 8-35%. 10.5-21% increase of silica flour reduces the shear wave velocity by 2-5% but adding 28-42% silica flour significantly reduces the shear wave velocity by 12-31%. In addition, the combined effect of cement and fibers was also found and with only 2% cement and 1% fiber, the shear wave velocity increase was found to be approximately 24% and with only 3% cement and 3% fibers this increased to 35%. The results from this study for the normalized shear modulus and normalized mean effective stress agree well with previous findings on pure Toyoura sand, Toyoura silty sand, fiber reinforced, fiber reinforced cemented Toyoura sand. Any variations are likely due to the difference in stress history (i.e., isotropic versus anisotropic consolidation) and the measurement method. In addition, these small discrepancies could be attributed to several other factors. The potential factors include the difference in specimen sizes, test devices, methods of analysis for the measurement of arrival time, the use of an appropriate Ko to convert the vertical stresses into mean effective stress, and sample preparation techniques. Lastly, it was investigated that there is a robust inverse relationship between α factor and 𝞫₀ exponent. It was found that less compressible soils exhibit higher 𝜶 factors and lower 𝞫₀ exponents.