• Journal of IKEEE
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• v.25 no.1
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• pp.101-108
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• 2021

This paper proposes a parallel control method of a modular DC/DC converter for electric vehicle (EV) chargers. The EV chargers have been increasing the power capacity using modular converters. There are output current imbalances between the modules, which are caused by the difference of the impedance, delay of the gate driver, and error of the sensors. The conventional strategies for the equal distribution of the output current cause the voltage drop or the high volume and cost of the converters. Therefore, the proposed parallel control strategy effectively balances the output current of modules using a current compensation method. The proposed strategy is verified by simulations. Additional experimental results will be added under various conditions.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1991.10a
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• pp.77-89
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• 1991

One of the important problems concerning the efficient operation of an automated manufacturing system is the flow control problem. Most research papers about scheduling and control of a FMS consider fabrication, machining and assembly independently. In this paper an effective flow control strategy for a FMS with an assembly subsystem which may be called FMAS (Flexible Machining and Assembly System) is designed using the operation-oriented and, combined Push and Pull control method. The flow control system to be described here could meet production demands with a minimum makespan while satisfying assigned due-dates and keeping a low volume of work-in-process at the same time. The control mechanism also considers machine failures and rush jobs.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.133-142
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• 2002

To improve the hydraulic control performance of ABS, it is necessary to establish an efficient control algorithm. And also it is necessary to ova]Hate a hydraulic modulator with solenoid valve quantitatively. In this paper, FEM and permeance method are used to analyze dynamic characteristics of outlet valve. In return, mathmatical modeling of a hydraulic modulator and operating pressure is presented, and the model parameters of an outlet valve are moving plunger, spring constant and orifice diameter. This study shows the way to improve the dynamic characteristic of an ABS outlet valve heavily depending on operating pressure. It is recommended that operating pressure should be justified at the first step toward the design to get the optimal design of an outlet valve.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.95-98
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• 2003

The physics of the plume-induced shock and separation particulary at a high plume to exit pressure ratio and supersonic speeds up to Mach 3.0 with aid without a passive control method, porous extension, were studied using computational techniques. Mass-averaged Navier-Stokes equations with the RNG k-$\varepsilon$ turbulence model were solved using a fully implicit finite volume scheme and a 4-stage Runge-Kutta method. The courol methodology for plume-afterbody interactions is to use a perforated wall attached at either the nozzle exit or the edge of the missile base. The Effect of porous wall length on plume interference is also investigated. The computational results show the main effect of the porous extension on plume-afterbody interactions is to in the plume from strongly underexpanding during a change in flight conditions. With control, a change in porous extension length has no significant effect on plume interference.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.5
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• pp.575-582
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• 1988

This paper presents an energy analysis on the VAV system of 10-story building in Seoul using DOE-2 program and Modified Bin Method. The use of VAV system is an excellent means of saving energy in new buildings and/or retrofit. The fan control techniques considered are cycling, discharge dampers, inlet vanes, and motor speed control. The monthly and annual energy consumption is calculated for fan control techniques, components, and chiller types. The results of annual fan electricity use are compared using DOE-2 and Modified Bin Method, and show fairly good agreement. In addition, factors affecting energy consumption are also described.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.233-239
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• 2007

The main objective of this study was to evaluate the effect of recycled PET fiber made from waste PET bottle on the control of plastic shrinkage cracking of cement based composites. PET is blown as a plastic material and used in a variety products such as a beverage bottle. However, waste PET bottles are thrown after the usage, raising huge problems in terms of the environment. Thus, the research on the method to recycle the PET bottles indicates important aspects in environment and economy. The method to recycle waste PET bottles as a reinforcing fiber for cement based composites is one of effective methods in terms of the recycle of waste PET bottles. In this research, the effect of recycled PET fiber geometry and length on the control of plastic shrinkage was examined through thin slab tests. A test program was carried out to understand the influence of fiber geometry, length and fiber volume fraction. Three type of recycled PET fibers including straight, twist crimped and embossed type. Three volume fraction and two fiber length were investigated for each of the three fiber geometry. Test results indicated that recycled PET fibers are effective in controlling plastic shrinkage cracking in cement based composites. In respect to effect of length of fiber, longer fiber was observed to have efficient cracking controlling with low volume fraction in same fiber geometry while shorter fiber controled plastic shrinkage cracking efficiently as addition rate increase. Also, embossed type fibers were more effective in controlling plastic shrinkage cracking than other geometry fiber at low volume fraction. But, for high volume fraction, straight type fibers were most effective in plastic shrinkage cracking controlling in cement based composites.

• Journal of the Korean Society of Tobacco Science
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• v.15 no.2
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• pp.145-151
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• 1993

Using a flue - cured tobacco variety, KF lH9, recently bred and released to farming, effect of growth regulators(fatty alcohol and C - MH) on the change of alkaloid contents and dynamics of MH uptake and distribution were investigated. An efficient sucker control method was also pursued. Treatment of fatty alcohol at button stage remarkably increased the rate of C - MH uptake. However, except in the plants treated with 2- fold volume of C - MH, residue of C -MH was kept under maximum residue level(80 ppd). C - MH residue in stalk was higher than in foliage in general. Compared to untreated control, leaf weight per unit area was increased by the treatment even in lower leaves where vigorous transfer of C - MH from treated tips was indicated and sucker control higher than 94.9% was achieved with all treatments except for sole half volume C - MH treatment at topping stage. Alkaloid content in foliage was reduced by dual treatment of fatty alcohol and C - MH but increased in stalk and root.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.3
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• pp.207-214
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• 1997

We collected airborne complex mixtures in a industrial area of Yeochun, and examined whether these complex mixtures could affect gap junctional intercellular communication (GJIC) in a cultured WBF-344 rat liver epithelial cells (LEC). Since the reduction of GJIC plays an important role in chemical carcinogenesis, measurement of changes of GJIC is a meaningful method to screen carcinogenicity of these mixtures. High and low volume samples were dissolved in dimethyl sulfoxide (DMSO) and tested. Blank filter extractions were also examined for exclud-ing possible toxicity of filter itself, and TPA (12-O-tetradecanoylphorbol-13-acetate) and DMSO were used as positive and negative control, respectively. When the cells were exposed to samples at concentration below that required to maintain rather than 85% cell viability based on the result of neutral red uptake assay, maximal inhibition of GJIC was observed at 1hr after treatment with both high and low volume samples by scrape-loading dye transfer assay. In fluorescence recovery after photobleaching assay, recovery rates via gap junctions were 33%/min in high volume sample and 62%/min in low volume sample. In together, airborne samples collected in Yeochun inhibited GJIC in a cultured WBF-344 rat LEC. These results suggest airborne samples tested in this experiment may attribute to cause a certain type and degree of cancers in in vivo when exposured for some periods.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.2
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• pp.243-253
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• 2022

Spent filters with a high radiation dose rate of 2 mSv·hr^-1 or more are not easily managed. So far, the Korean policy for spent filter disposal is to store them temporarily at nuclear power plants until the waste filters can be easily managed. Nuclear power plant decommissioning in Korea is starting with Kori unit 1. Volume reduction of waste generated during decommissioning can reduce the cost and optimize the space usage at disposal site. Therefore, efficient volume reduction is a very important factor during the decommissioning process. A conceptual method, based on the experiences of developing 200 and 800 ton compactors at Orion EnC, has been developed considering worker exposure with the followings a crusher (upgrade of compaction efficiency), an automatic dose measuring system with a NaI(Tl) detector, a shield box, an inner drum to prepare for easy handling of drums and packaging, a 30 ton compactor, and an automatic robot system. This system achieves a volume reduction ratio of up to 85.7%; hence, the system can reduce the disposal cost and waste volume. It can be applied to other types of wastes that are not easily managed due to high dose rates and remote control operation necessity.

• Advances in nano research
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• v.14 no.4
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• pp.303-312
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• 2023

In this study, the bifurcation analysis of functionally graded material is done using exponential volume fraction law. Shell theory of Love is used for vibration of shell. The Galerkin's method is applied for the formation of three equations in eigen value form. This eigen form gives the frequencies using the computer software MATLAB. The variations of natural frequencies (Hz) for Type-I and Type-II functionally graded cylindrical shells are plotted for exponential volume fraction law. The behavior of exponent of volume fraction law is seen for three different values. Moreover, the frequency variations of Type-I and -II clamped simply supported FG cylindrical shell with different positions of ring supports against the circumferential wave number are investigated. The procedure adopted here enables to study vibration for any boundary condition but for brevity, numerical results for a cylindrical shell with clamped simply supported edge condition are obtained and their analysis with regard various physical parameters is done.