• 한국정보과학회논문지:시스템및이론
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• 제35권8호
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• pp.385-393
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• 2008

사용자가 가능한 센서 가까이에서 이동하는 문제를 최단거리유지 문제(Best Coverage Problem)라 하며, 무선 연결의 안정성을 높이기 위해서 두 개의 센서로부터 최대한 가까이 위치하며 움직이는 이동경로를 차선거리유지 경로(Second Best Coverage Path)라고 한다. 이 논문에서는 센서들의 집합 U와 시작점 s, 끝점 t가 주어질 때, s에서 t까지 이르는 모든 경로 중에서, 가장 가까운 두 개의 센서까지 거리 중 큰 값이 최소가 되는 차선거리유지 경로를 찾는 O(n logn)-시간 알고리즘을 제시하며, 차선거리유지 경로를 따라 움직일 때가 최단거리유지 경로를 따라 움직일 때 보다, 네트워크에의 연결이 보다 안정적임을 보여주는 실험결과도 또한 제시한다.

• Journal of Korean Neurosurgical Society
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• 제55권5호
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• pp.261-266
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• 2014

Objective : With the increased use of interspinous spacers in the treatment of lumbar stenosis, knowledge of the geometry of the interspinous space is important. To prevent dislodgment of an interspinous spacer, the accurate depth and width of the interspinous space needs to be established to facilitate the best intraoperative selection of correct spacer size. Methods : To determine the depth and width of the interspinous space, two methods are available which utilize plain film and magnetic resonance imaging (MRI). Data analysis of the interspinous depth and width was undertaken in 100 patients. Results : The standard deviations were variable, since skin thickness (zone 1) was altered by sex and age. The difference in the zone 1 distance between adjacent interspinous processes varied according to gender (p<0.05), but was not influenced by age [p=0.32 by analysis of variance between groups (ANOVA)]. Zone 2, the supraspinous, and zone 3, the interspinous ligament depths, comprise the operative working area during insertion of an interspinous spacer. There were no differences with regard to gender or age (p>0.05). For zones 6 and 7, the interspinous distances at the narrowest and widest points, respectively, were found to decrease with the aging process, but the decrease was not statistically significant. There were no differences with regard to gender (p>0.05). Conclusion : This study provides additional information on the interspinous space. This statistical data are valuable for use in the design of interspinous spacers.

• 한국도로학회논문집
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• 제16권6호
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• pp.181-189
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• 2014

PURPOSES : Ambiguous decision on whether rural or urban area for road design can increase the construction cost and restrict the land use of surrounding area. However, administrative classification on rural and urban area is not directly related to road design because of this classification is not based on the engineering viewpoint, so method which can explain the road design context is required. METHODS : Method which enables to identify the area for road design is suggested based on the deceleration expected to be experienced by drivers who use the road section concerned. Deceleration rate corresponding to the area such as rural or urban suggested in Road Design Guideline is used as the criteria to identify the area by comparing this value with the estimated deceleration rate at the road section concerned. Speed profile method is utilized to derive the deceleration rate, and speed estimation way for reflecting both road geometry and intersection is suggested using stopping sight distance concept. RESULTS : The procedure of the method application is suggested, and the design example utilizing the method is provided. CONCLUSIONS : The method is expected to be used to identify the area for road design with engineering viewpoint, and design consistency among the roads with similar driving environment can be made.

• 한국공작기계학회논문집
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• 제15권6호
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• pp.88-96
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• 2006

The objective of this research works is to develop back panel dies of PDP TV with a large size. In order to design the geometry of the dies and an initial size of blank optimally, the finite element analysis has been carried out using AUTOFORM V4.2. The conner radius of the upper trimming area and the distance from the outer line of the blank holder to the outer line of the blank have been selected as design parameters to remove the wrinkling of the trimming area. The results of the analyses have been shown that a feasible product without wrinkles and skid lines can be obtained when the conner radius ranges from 6mm to 8mm and the distance lines in the range of 40-60mm. From the proposed design of the dies and an initial blank size, the final die set of the back panel has been successfully manufactured.

• 대한교통학회지
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• 제25권2호
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• pp.157-165
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• 2007

본 연구에서는 GPS(Global Positioning System), INS(Inertial Navigation System), DMI(Distance Measuring Unit) 등 각종 센서를 장착한 차량을 이용하여 차량의 위치정보와 자세정보를 취득하고, 취득된 차량의 주행정보를 이용하여 도로 종단선형을 분석할 수 있는 알고리즘을 개발하였다. 개발된 종단선형 분석 알고리즘은 도로의 종단경사, 종단곡선 시종점 및 도로 종단곡선 길이 등을 분석할 수 있고, 종단경사와 종단곡선을 모형화하였다. 또 개발한 알고리즘의 현장 적용성을 검증하기 위하여, 실제 도로에서 취득한 데이터를 이용하여 종단선형을 분석하였고, 이 결과를 도면과 비교하였다.

• 한국생산제조학회지
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• 제23권6호
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• pp.533-538
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• 2014

We fabricated grooved mushroom structures with anisotropic wettability on silicon substrates using basic MEMS processes. The geometry of these grooved mushroom structures could be changed by controlling the additional IPA solution during Si etching by TMAH solution. To understand anisotropic wettability, contact angles (CAs) of hexadecane droplets were measured in the orthogonal and parallel directions to grooved lines. The CA measurement results displayed anisotropic wetting on the grooved mushroom structures. However, specimens with $80{\mu}m$ distance between top layers displayed isotropic and superoleophobic wetting. This study demonstrates that the thickness of the top layer is more critical than the width or height of the ridge when determining the wettability of organic solvent. Despite the wide distance between top layers ($80{\mu}m$), the specimen with a thin top layer (100 nm) showed highly anisotropic wetting and low CA due to the pinning of droplets at the edge of the top layer.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.1022-1028
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• 2020

One of the possible options for spent-fuel management in Korea is pyroprocessing, which is a process for electrochemical recycling of spent nuclear fuel. Nuclear material accountancy is considered to be a safeguards measure of fundamental importance, for the purposes of which, the amount of nuclear material in the input and output materials should be measured as accurately as possible by means of chemical analysis and/or non-destructive assay. In the present study, a neutron measurement system based on the fast-neutron energy multiplication (FNEM) and passive neutron albedo reactivity (PNAR) techniques was designed for nuclear material accountancy of a spent-fuel assembly (i.e., the input accountancy of a pyroprocessing facility). Various parameters including inter-detector distance, source-to-detector distance, neutron-reflector material, the structure of a cadmium sleeve around the close detectors, and an air cavity in the moderator were investigated by MCNP6 Monte Carlo simulations in order to maximize its performance. Then, the detector responses with the optimized geometry were estimated for the fresh-fuel assemblies with different ²³⁵U enrichments and a spent-fuel assembly. It was found that the measurement technique investigated here has the potential to measure changes in neutron multiplication and, in turn, amount of fissile material.

• 대한수학회보
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• 제58권5호
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• pp.1279-1300
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• 2021

Let P be a finite point set in ℝ² with the set of distance n-chains defined as ∆_n(P) = {(|p₁ - p₂|, |p₂ - p₃|, …, |p_n - p_n+1|) : p_i ∈ P}. We show that for 2 ⩽ n = O_|P|(1) we have ${\mid}{\Delta}_n(P){\mid}{\gtrsim}{\frac{{\mid}P{\mid}^n}{{\log}^{\frac{13}{2}(n-1)}{\mid}P{\mid}}}$. Our argument uses the energy construction of Elekes and a general version of Rudnev's rich-line bound implicit in [28], which allows one to iterate efficiently on intersecting nested subsets of Guth-Katz lines. Let G is a simple connected graph on m = O(1) vertices with m ⩾ 2. Define the graph-distance set ∆_G(P) as ∆_G(P) = {(|p_i - p_j|)_{i,j}∈E(G) : p_i, p_j ∈ P}. Combining with results of Guth and Katz [17] and Rudnev [28] with the above, if G has a Hamiltonian path we have ${\mid}{\Delta}_G(P){\mid}{\gtrsim}{\frac{{\mid}P{\mid}^{m-1}}{\text{polylog}{\mid}P{\mid}}}$.

• 로봇학회논문지
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• 제14권1호
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• pp.65-73
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• 2019

In this paper, we propose an algorithm that estimates the location of lunar rover using IMU and vision system instead of the dead-reckoning method using IMU and encoder, which is difficult to estimate the exact distance due to the accumulated error and slip. First, in the lunar environment, magnetic fields are not uniform, unlike the Earth, so only acceleration and gyro sensor data were used for the localization. These data were applied to extended kalman filter to estimate Roll, Pitch, Yaw Euler angles of the exploration rover. Also, the lunar module has special color which can not be seen in the lunar environment. Therefore, the lunar module were correctly recognized by applying the HSV color filter to the stereo image taken by lunar rover. Then, the distance between the exploration rover and the lunar module was estimated through SIFT feature point matching algorithm and geometry. Finally, the estimated Euler angles and distances were used to estimate the current position of the rover from the lunar module. The performance of the proposed algorithm was been compared to the conventional algorithm to show the superiority of the proposed algorithm.

• 한국가시화정보학회지
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• 제19권2호
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• pp.26-31
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• 2021

The spanwise growth of turbulence structures in turbulent pipe flow was investigated using the direct numerical simulation data of Re_𝜏 = 544, 934 and 3008. Two-point correlations and pre-multiplied energy spectra of streamwise velocity fluctuations were examined along the spanwise direction. The arclength direction is defined as r𝛳, which is useful for an analogy with the spanwise direction for channels or boundary layers; here, r and 𝛳 are the radial distance from the core and the azimuthal angles, respectively. Both analyses showed that the arclength scales increased with increasing the wall-normal distance. It showed that the coherent structures were confined in the core region due to the crowding effect of a circular pipe geometry. The pipe flow simulation could describe a realistic geometrical flow along the azimuthal direction, unlike the simulations of turbulent channel or boundary layer flow using periodic boundary conditions along the spanwise direction. The present results provided the spanwise organization of energy-containing motions over a broad range of scales in turbulent pipe flow.