• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.10
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• pp.1493-1500
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• 2015

For efficient and economical train operation in low-density railway line, on-board oriented train control system, which reduces expensive wayside equipment, is being developed. In this paper, we discuss a tram signal priority strategy which enables efficient and safe train operation when the developing system is applied to train-tram railway environment. Based on the well-known transit signal priority strategies, we develop a tram signal priority algorithm and conduct simulations by using model-based systems engineering (MBSE) tool. Various considerations such as operation procedure, linkage to existing road traffic system, applicability with respect to crossroad types, and so on, are also dealt with.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.50-56
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• 2006

Residual gas fraction in a combustion process is very crucial to improve combustion and cyclic variations. Especially, the residual gas fraction is strongly affected by backflow of the residual gas during the valve overlap period in an idle operation. Therefore, it is one of the most interesting that valve timings can affect flow characteristics of gas exchange process, especially during idle operation. This analysis investigates residual gas fraction with respect to valve timing changes which is critical for combustion efficiency and engine performance. Flow characteristics of residual gas by changing intake and exhaust valve timing are calculated by CFD methodology during an idle operation in an SI engine. It is analyzed that retarded EVO and advanced IVO results in the increase of valve overlap period and consequently, residual gas fraction. Futhermore, changes in IVO have stronger effects on variation of residual gas fraction.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.4
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• pp.152-161
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• 2011

The operation of vending machine system presents a decision-making problem which consists of determining the product allocation to vending-machine storage compartments, replenishment intervals of vending machines, and vehicle routes, all of which have critical effects on system profit. Especially, it becomes more difficult to determine the operation variables optimally when demand for a product that is out-of-stock spills over to another product or is lost. In this paper, we propose a heuristic for solving the operation problem of the vending machine system and evaluate it by comparing with Yang's algorithm on various test problems with respect to system profit via a computer simulation. The results of computational experiments show a substantial profit increase of the proposed heuristic over Yang's algorithm. Sensitivity analysis indicates that some input variables impact the profit increase significantly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.963-970
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• 2005

The combustion instability of turbulent flames is the most important problem of the gas turbine combustor. Thus improved understanding of mechanisms of combustion instability is necessary for the design and operation of gas turbine combustors. In this study, the cause of the combustion instability in a rearward-step dump combustor was investigated with respect to the fuel flow modulation; choked fuel flow, unchoked fuel flow and fully premixed mixture flow. We observed various types of combustion instabilities with respect to the change of equivalence ratio, fuel flow conditions and fuel injection location. Particularly in the unchoked fuel flow condition, it was found that the oscillation time of combustion instability is strongly related to the convection time of the fuel and that the pressure fluctuation in a lab-scale combustor is highly related to the vortex and the equivalence ratio fluctuations due to fuel flow modulation and unmixedness of the fuel and air.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.38-44
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• 2003

In this study, endurance limit and fatigue behavior of load carrying fillet welded cruciform joints depending on commonly used welding methods such as SMAW, SAW, MIG and FCAW are investigated. In respect of endurance limit SMAW specimen showes highest result, and then MIG, SAW, FCAW in descending order. However, SMAW specimen showes lowest crack growth rate and it followed by MIG, FCAW, SAW. By these results, it is needed to use SMAW or MIG welding methods for welding structures with small welding capacity and SAW or FCAW methods for large welding structures with respect to economic benefits and operation efficiency of welding. It was also shown fatigue crack growth rate was more influenced by the strenght of welding materials than the endurance limit of welding materials.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.27-34
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• 2000

HTS wires processed by PIT method are now available for magnet applications. But, those wires can not be used over 40 K due to weak link. This leads to necessity of development of coated conductor which can retain high $J_c$ at high field in liquid nitrogen. In this paper, various technical issues and the R&D status for both PIT wires and coated conductor were discussed. The difference of coated conductor's processes were also investigated and summarized. Various requirements for a design of HTS magnets were discussed. Anisostropic $J_c$ property with respect to magnetic field was considered to determine the coil's critical current. Low n value is a critical parameter to degrade a field stability with respect to time for a persistent mode HTS magnet. The relation between the margin of operation current and n value was investigated. Prototype HTS magnets with PIT wires are being developed for various applications such as crystal growth, MRI, magnetic separator and etc. HTS magnets will come into wide use in various fields of industries if the HTS wires with a low performance cost is developed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4606-4611
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• 2011

In this paper, it is reviewed vulnerability of security in DS-MAC communication protocol of sensor network, and analyzed in the respect of security effectiveness, which is consumed at each stage of communication procedure in according to vulnerability of denial of service and modification attack. In this paper, we present about the respect of security effectiveness of transmission and reception in case of operation mode with or without authentication scheme between sensor node.

• Environmental Engineering Research
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• v.11 no.4
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• pp.201-207
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• 2006

A simple empirical model with good quantitative prediction of inter-particle and intra-particle distance in a cake layer with respect to ionic strength was developed. The model is an inverse length scale with functions of interaction energy and hydrodynamic factor and it explains that the inter-particle and intra-particle distance in a cake is directly related to the effective size of particles. Particle compressibility with respect to ionic strength was also predicted by the model. The model corroborated very well with experimental results of polystyrene microsphere latex particles microfiltation in a dead end operation. From the results of the model, specific cake resistance could be controlled by the same variables affecting the height of particle energy barrier described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.408-418
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• 1998

This paper presents the implementation of comparator which is self-testing with respect to the faults caused by any single physical defect likely to occur in NMOS and CMOS integrated circuit. The goal is to use it for the fault-tolerant system. First, a new fault model for PLA(Programmable Logic Array) is presented. This model reflects several physical defects in VLSI circuits. It focuses on the designs based on PLA because VLSI chips are far too complex to allow detailed analysis of all the possible physical defects that can occur and of the effects on the operation of the circuit. Second, this paper shows that these design, which has been implemented with 2 level AND-ORor NOR-NOR circuit, are optimal in term of size. And it also presents a formal proof that a comparator implemented using NOR-NOR PLA, based on these design, is sol f-testing with respect to most single faults in the presented fault model. Finally, it discusses the application of the self-testing comparator as a building block for the implementation of the fault-tolerant system.

• Honam Mathematical Journal
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• v.44 no.1
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• pp.78-97
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• 2022

In this study, new properties of various filters on a Sheffer stroke BL-algebra are studied. Then some new results in filters of Sheffer stroke BL-algebras are given. Also, stabilizers of nonempty subsets of Sheffer stroke BL-algebras are defined and some properties are examined. Moreover, it is shown that the stabilizer of a filter with respect to a/n (ultra) filter of a Sheffer stroke BL-algebra is its (ultra) filter. It is proved that the stabilizer of the subset {0} of a Sheffer stroke BL-algebra is {1}. Finally, it is stated that the stabilizer St(P, Q) of P with respect to Q is an ultra filter of a Sheffer stroke BL-algebra when P is any filter and Q is an ultra filter of this algebra.