• Journal of the Korean Society for Precision Engineering
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• v.24 no.6
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• pp.86-95
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• 2007

This paper presents the optimal design of an exhaust system of a vacuum-compatible air bearing using a genetic algorithm. To use the air bearings in vacuum conditions, the differential exhaust method is adopted to minimize the air leakage, which prevents air from leaking into a vacuum chamber by recovering air through several successive seal stages in advance. Therefore, the design of the differential exhaust system is very important because several design parameters such as the number of seals, diameter and length of an exhaust tube, pumping speed and ultimate pressure of a vacuum pump, seal length and gap(bearing clearance) influence on the air leakage, that is, chamber's degree of vacuum. In this paper, we used a genetic algorithm to optimize the design parameters of the exhaust system of a vacuum-compatible air bearing under the several constraint conditions. The results indicate that chamber's degree of vacuum after optimization improved dramatically compared to the initial design, and that the distribution of the spatial design parameters, such as exhaust tube diameter and seal length, was well achieved, and that technical limit of the pumping speed was well determined.

• Journal of Biomedical Engineering Research
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• v.26 no.1
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• pp.17-22
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• 2005

Small animal PET using a dual layer phoswich detector has been developed to obtain high and uniform spatial resolution. In this study, a simple analytic model to optimize the lengths of a dual layer phoswich detector was derived and validated by Monte Carlo simulation. For a small animal PET scanner with a 10㎝ ring diameter, the optimal length of the phoswich detector consisting of various crystal materials, such as LSO and LuYAP, were calculated analytically and validated using GATE. The detector module consisted of 8×8 arrays of crystals, with each phoswich detector element having a 2㎜×2㎜ sensitive area. The total crystal length was fixed to 20㎜. The optimal lengths of the phoswich detector layers, as functions of the crystal materials and order, conveniently derived by the analytic equation, showed good agreement with those estimated by the time consuming simulation. The simple analytical model can be used for the fast and accurate design of an optimal phoswich detector for small animal PET to achieve high spatial resolution and uniformity.

• Journal of Advanced Navigation Technology
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• v.16 no.5
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• pp.801-809
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• 2012

Dispersion management (DM) is the typical technique compensating for the distorted signals due to interaction of group velocity dispersion (GVD) and optical nonlinear effects for transmitting wavelength division multiplexed (WDM) channel with the excellent performance. Optimal net residual dispersion (NRD) and effective launching power range of optical transmission links with random distribution and artificial distribution of single mode fiber (SMF) length and residual dispersion per span (RDPS) required to flexibly design of optical links in DM. It is confirmed that optimal net residual dispersion (NRD) are +10 ps/nm and -10 ps/nm controlled by precompensation and postcompensation, respectively, in both of the considered distribution patterns of SMF length and RDPS. And, in optimal NRD, system performance in optical links with the descending distribution of SMF length and the ascending distribution of RDPS among the artificial distribution patterns are more improved, consequently, effective launching power range is expanded by almost 2 dB than those in optical links with the uniform distribution.

• Journal of Korean Society of Transportation
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• v.25 no.2 s.95
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• pp.145-155
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• 2007

The objectives of this study aye to develop an on-line departure time-based travel time estimation method and to determine an optimal link length for the estimation. This study developed a link-based rolling horizon logic as the travel time estimation method. In order to determine an optimal link length, the information error of the travel time provision from the user's perspective was defined and employed as a selection criterion. It was found that, when the travel time aggregation size was set as five minutes, a link length of four kilometers gave the most accurate result.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.327-334
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• 2013

In this study, the optimal slit length of perforated wall with single chamber below the still water level (SWL) is studied through the two dimensional test. The relationship between the reflection coefficient and the shape of structures such as chamber width(B) and slit length(S) are investigated by applying the various wave conditions. The random waves were used for the test by using Bretschneider-Mitsuyasu frequency spectrum. Minimum reflection coefficient is obtained at $B/L_s{\approx}0.15$ condition, this result is different from the regular wave condition. Also the minimum reflection coefficients are measured at $S/H_s{\approx}2.5$. This means that the optimal slit length below the still water level is 2.5 times of the incident wave height.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1785-1796
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• 1998

This paper is concerned with the relationships between optimal number of wavelengths and tuning time in time division multiplexing(TDM) scheduling on wavelength division multiplexing(WDM) optical passive star networks. We assume that the traffic is nonuniform and each node has a tunable transmitter and a fixed receiver. Each node transmits spckets to all other nodes. Most of the earlier protocols on TDM based scheduling for WDM star networks [7, 8, etc.] use whold given wavelength chnnels. But in this paper, we investigate the optimal number of wavelengths that yidels minimum frame length when tuning time exists. It appears within the availble number of wavelengths that yields minimum frame length when tuning time exists. It appears within the available number of wavelengths. We analyze the relationships between optimal number of wavelengths and tuning time by experiments. We analyze the reationships between optimal number of wavelengths and tuning time by experiments. We also discuss on the possibility of reduction of frame length by increasing the number of nodes trans-mitters and receivers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.58-65
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• 2016

This study analyzed the structural weld strength for a door hinge for a field artillery ammunition support vehicle. In order to determine the optimal conditions, we measured the modal analysis and analyzed the leg length of a rear door hinge. From these methods, we acquired the vibration frequency of normal mode and the optimal welding leg length conditions. It was possible to obtain a structural stability for a rear door hinge of the field artillery ammunition support vehicle. In the future, this should be used as a reference source for the weld strength analysis of high vibration and high weight structures for another welding system design.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.113-120
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• 2013

This paper presents a mathematical model to determine the optimal length of static messages that can achieve more efficient use of a FlexRay network. In order to determine the optimal length of static message, the proposed model evaluates the given set of messages with respect to a network utilization index, which is defined in this work. The efficient use of a FlexRay network is achieved by reallocating any static message whose length is equal or greater than the resulting value to the dynamic segment. The effectiveness of the proposed method is investigated by applying to the SAE benchmark data.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1539-1542
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• 2002

In layout of LSI and PWB, block pack- ing problem is very important in order to reduce chip area. Sequence-pair is typical one of conventional pack- ing method and can search nearly-optimal solution by using Simulated Annealing(SA). SA takes huge computation time due to evaluating of various packing results. Therefore, Sequence-pair is not effective enough for fast layout evaluation including estimation of wire length and rotation of every blocks. This paper proposes an efficient block packing method to minimize wire length and chip area. Our method searches an optimal packing efficient- ly by using a cluster growth algorithm with changing the most valuable packing score on packing process.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.501-507
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• 2021

In this study, In order to prevent the safety accidents caused by the sliding, to develop the non-slip grating, the stability judgment based on the span length of the grating and the gap of the bearing bar is performed. The structural analysis of Grating was carried out in accordance with the provisions set out in Grating's load-bearing test conditions. As the span length increases, the deflection increases and the stress and span length tend to be proportional to each other. It was shown that the larger the span, the linear increase in stress and exponential increase in deformation of grating. The maximum stress of grating was approximately 58.2 MPa, indicating a very stable safety rate of about 4.3 compared to the yield strength of the grating material. Based on these results, it will be able to be utilized as the basic data for determining the optimal dimensions of non-slip grading by performing optimal designs in the future.