• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2007년도 정기 학술대회 논문집
• /
• pp.421-426
• /
• 2007

A parametric study to investigate the effects of composition variables on the glass transition and mechanical properties of CNT-based nanocomposites was performed using molecular dynamics simulations. In this study, matrix chain length and CNT length were chosen as the candidate characteristic parameters. In order to understand the effect of both parameters in detail, three sample sets having different chain lengths with the same CNT configuration and two sample sets having different CNT lengths with same chain length were prepared. Other parameters such as volume fraction and density were fixed to enable rigorous comparisons. Amorphous polyethylene is used as matrix polymer and (10,0) zigzag CNT is embedded into the matrix to reinforce polymer matrix. As a result, longer polymer chain length of matrix solely increased glass transition temperature but no reinforcing enhancement was observed. CNT length showed similar increase with little enhancement of elastic modulus. In addition to this, nanocomposites showed temperature-dependent elastic modulus jump passing thorough the glass transition region agrees well with experimental results.

• 해양환경안전학회지
• /
• 제27권1호
• /
• pp.67-73
• /
• 2021

본 연구는 충돌 사고 중에서 정박지에서 대기하고 있는 선박과 이 정박지를 통항하는 선박 간 충돌사고가 자주 발생함에 따라, 정박선 사이를 통항하는 선박의 충돌위험을 예측할 수 있는 모델을 개발하기 위한 기초 연구로 통항 선박의 안전 영역을 도출하는 것이 목적이다. 이를 위해 우리나라 최대 항만인 부산항 남외항 정박지를 대상 해역으로 선정하고 정박선이 가장 많이 대기한 기간 VTS(Vessel Traffic Service) 항적 자료를 추출하여 분석하였다. 정박선 사이를 통항하는 선박의 길이(L)를 기준으로 정박선과 어느 정도의 안전한 거리(D)를 두고 통과하는지를 알기 위하여 통항 선박의 방위별 D/L 비를 구하였다. D/L 비 분포의 평균 domain을 기준으로 기존 선박 domain 범위 안으로 정박선이 존재할 비율을 분석하여 VTS 관제사의 위험 정도를 반영한 domain을 도출하였다. 추후 연구로는 정박선 사이의 최소 안전거리인 Domain-watch와 정박지 통항 선박의 안전 domain을 활용한 정박지 통항 선박의 충돌위험도 평가 및 분석을 하고, 이를 통해 VTS가 정박지를 좀 더 효율적이고 안전하게 관리하기 위한 모델을 개발하고자 한다.

• 대한수학회지
• /
• 제40권6호
• /
• pp.951-962
• /
• 2003

In this paper we address focal points and treat manifolds (M, g) whose Lorentzian metric tensors g have a spacelike $C^{0}$-hypersurface $\Sigma$ [10]. We apply Jacobi fields for such manifolds, and check the local length maximizing properties of $C^1$-geodesics. The condition of maximality of timelike curves(geodesics) passing $C^{0}$-hypersurface is studied.ied.

• Restorative Dentistry and Endodontics
• /
• 제24권4호
• /
• pp.628-632
• /
• 1999

Currently electronic apex locators have been widely used to determine working length in endodontic treatment. According to Manufacture's recommendation, it is beneficial to find the working length before instrumenting the canal. However, in crown-down pressureless technique, working length of tooth is established following coronal instrumentation 3mm short of radiographic apex. In narrow canals, mechanically formed constriction might be established by coronal instrumentation in some distance from anatomical constriction. The purpose of this study was to evaluate the accuracy of Root-ZX in the canal with mechanical constriction following considerable coronal enlargement with ProFile .06 series. The 40 root canals in 30 extracted mandibular molars were accessed, and their actual length (AL) established by passing a size 10 file just through the minor apical foramen. The teeth were then embedded in an acrylic container with normal saline. The initial canal length(IL) was measured with Root-ZX by negotiating a size 10 file to the apical constriction. The canal was sequentially enlarged to size 40 with ProFile .06 file 3mm short of actual length. The enlarged final canal lengths (FL) were obtained with a size 15 file. The average values of IL, FL were calculated and compared using Repeated measures Analysis of Variance followed Turkey's Studentized Range test. The results were obtained as follows: 1. The initial canal length was 0.12mm shorter than actual canal length(P>0.05). 2. The differences between initial canal length and final canal length were not significant(P>0.05). 3. As a result of this study, regardless of mechanically formed constriction. Root-ZX differentiated between mechanical and anatomic constriction.

• Restorative Dentistry and Endodontics
• /
• 제24권4호
• /
• pp.623-627
• /
• 1999

During canal instrumentation of a curved canal, restoring force of endodontic instrument remove more dentin from the inner wall of the curvature. This effect tends to straighten the canal and thus may significantly shorten the working length. This study was to determine the mean reduction in working length after instrumentation according to the curvature. The curvature of mandibular mesial root was determined before instrumentation. 30 canals were divided into 3 groups each 10 on the basis of degree of curvature. Experimental groups as follows. In group 1, canals having curvature from 15 to 20 degrees: in group 2, canals having curvature from 20 to 30degrees; in group 3, canals having curvature above 30 degrees. Experimental teeth in all groups were accessed, and their actual working length determined by passing a size 15 K-file(IAF) just through the minor apical foramen. The canals were sequentially enlarged to size 35 with ProFile .06 series. The change of working length was calculated by measuring the tip of IAF beyond apical foramen by using stereomicroscope. The change of canal curvature following instrumentation were measured using the Schneider technique. The results were as follows. 1. The greatest changes of curvature and working length were observed in the group 3 canals(P<0.05), next were group 2 canals and group 1 canals(P>0.05). 2. Group 1 canals showed a mean reduction in 1.61 degrees and length of 0.12m respectively(P>0.05). 3. Group 2 canals showed a mean reduction in 3.42 degrees(P<0.05) and length of 0.25mm(P>0.05) respectively. 4. Group 3 canals showed a mean reduction in 7.23 degrees(<0.05) and length of 0.64mm respectively(P<0.05).

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.2251_2252
• /
• 2009

In this paper, an attempt has been made by incorporating variable wheel arrangement for a car-like robot. In this scheme, the car-like robot controls its body height and the length of forward and backward wheels while driving in omni-direction. Experimental results show that the proposed car-like robot with wheel arrangement variable structure presents effectiveness of several situations.(a. left and right turn, b. longitudinal and latitudinal parking, c. control of body height and the length of forward and backward wheels, d. passing over obstacles, e. adaptive cruise control.)

• The Journal of the Acoustical Society of Korea
• /
• 제15권1E호
• /
• pp.20-28
• /
• 1996

Speech sounds were practically applied to a cochlear filter which was simulated by an electrical transmission line. The amplitude of the basilar membrane displacement was calculated along the length of the cochlea in temporal response. And the envelope of the amplitude according to the length was arranged for each discrete time interval. The resulting time response of the speech sound was then displayed as a color image. Five vowels such as a, e, I, o, u were applied and their results were compared. The whole procedure of the visualization method of the speech sound using the cochlear filter is described in detail. The filter model response to voice is visualized by passing the voice through the cochlear filter model.

• 전자공학회논문지D
• /
• 제34D권3호
• /
• pp.123-130
• /
• 1997

We determine the dispersion profile of a dispersion decreasing fiber(DDF) for optimum pulse compression from a trade-off between high pulse compression and low pedestal power/short DDF length. We find that the optimum vlaue of the exponential dispersion decreasing factor .alpha. is 0.95 and that the corresponding optimum fiber length is 1.5 times of the initial soliton period. Passing through the dDF, ~10 times of pulse comparession ratio can be achieved without significant increase in pedestal power. To compress relatively broad pulses using a given DDF optimized at a specific pulse width, we also detemrine the optimum input pulse amplitude, as a function of input pulse width.

• 한국산업융합학회 논문집
• /
• 제7권2호
• /
• pp.161-166
• /
• 2004

The impact factor of bridges is analyzed based on experimental data to examine the characteristics of the dynamic responses of bridges. The experimental impact factors are compared with the impact factor of Korean Highway Design Specification and Japan T-load in terms of the span length. According to the superstructural types of bridges, the variation of the impact factor is analyzed. When vehicles are passing on a bridge, the dynamic effect acts on the bridge impact factor more than at the time of design because of the velocity of vehicles, the surface roughness reduction due to the deterioration of the bridge deck pavement, and the disconnection of the bridge entrance and the expansion joint. Because the actual value is greater than the expected value at the time of design, the dynamic response of the bridge accelerates the deterioration of the bridge due to the accumulation of fatigue, and the bridge's life-time is shortened and can have an influence on the serviceability and safety of the bridge.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제5권4호
• /
• pp.360-366
• /
• 2005

In the past, when there were few vehicles on the road, the T.O.D.(Time of Day) traffic signal worked very well. The T.O.D. signal operates on a preset signal cycling which cycles on the basis of the average number of average passenger cars in the memory device of an electric signal unit. Now days, with increasing many vehicles on restricted roads, the conventional traffic light creates startup-delay time and end-lag-time. The conventional traffic light loses the function of optimal cycle. And so, $30-45\%$ of conventional traffic cycle is not matched to the present traffic cycle. In this paper we proposes electro sensitive traffic light using fuzzy look up table method which will reduce the average vehicle waiting time and improve average vehicle speed. Computer simulation results prove that reducing the average vehicle waiting time which proposed considering passing vehicle length for optimal traffic cycle is better than fixed signal method which doesn't consider vehicle length.