• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.4
• /
• pp.88-95
• /
• 2013

A new droop control method which can be applied to 3-phase 4-wire uninterruptible power supply is proposed in this paper. The droop control method for parallel operation is very attractive one as UPS parallel operation can be carried out without any data communication devices provided among UPS systems connected, but it reportedly shows a PnP(plug-and-play) problem. A basic reason why a circulating current could flow among parallel-connected UPS systems is clearly investigated as well when droop-controlled-ups systems are operated in the manner of PnP. The proposed algorithm is deduced from the investigated result and is basically structured to keep a balanced frequency and balanced voltage profile against power variation. This paper shows that balanced parallel operation of droop control method can be obtained under unbalanced load as well as balanced load conditions when PnP operation is needed and load change occurs.

• Proceedings of the KIEE Conference
• /
• 2006.11a
• /
• pp.275-278
• /
• 2006

This paper describes a probabilistic annual congestion cost assessment of a grid at a composite power system derived from a model. This probabilistic congestion cost assessment simulation model includes capacity limitation and uncertainties of the generators and transmission lines. In this paper, the proposed probabilistic congestion cost assessment model is focused on an annualized simulation methodology for solving long-term grid expansion planning issues. It emphasizes the questions of "how should the uncertainties of system elements (generators, lines and transformers, etc.) be considered for annual congestion cost assessment from the macro economic view point"? This simulation methodology comes essentially from a probabilistic production cost simulation model of composite power systems. This type of model comes from a nodal equivalent load duration curve based on a new effective load model at load points. The characteristics and effectiveness of this new simulation model are illustrated by several case studies of a test system.

• Korean Journal of Rural Living Science
• /
• v.10 no.2
• /
• pp.85-100
• /
• 1999

This study was to get basic data for the establishment of proper labor counterplan so that we estimated farm work volume and work loads by crops. We examined the method of work practices such as a work posture, work time, measured work environment such as hot, cold, humidity and ultraviolet rays and calculated physical loads induced by them. Also we surveyed work environment, work posture, sleeping time and work time because they affect on farmer's health. Farmer's health survey was investigated by questionnaire and measured farmer's physical load. The types of farm work were classified into greenhouse farming, rice farming, dry field farming, stock farming and special crop farming. 11 crops were selected, for example, greenhouse melon, riceㆍred pepper, milky cow farming, pear, grapes, dropwort, sweet potato, potato, radish, and cabbage. We also chose subject districts haying the most yield of 11 crops. Our survey was conducted for the period when farmers think the hardest period in physical work load. The farm work models based on work standard were presented according with farmer's health.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.835-838
• /
• 2008

In this study, long-term compression displacement of damping materials used to reduce floor impact noise and compressive load that crack begins to happen in Ondol layers including the material were measured as basic research to make guide line for right choice of damping material considering structural stability of Ondol layer. From the result, it was found that compression displacement by elapsed time as well as early displacement of damping material when load is applied on Ondol layer are should be included in the guide line for the choice of damping materials. And no problem is expected to be in structural stability of Ondol layer in case choose a damping material that compression displacement at three months later from inflict load is within 10% than initial thickness.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.2
• /
• pp.20-26
• /
• 1997

A 6-component load cell (Fx=Fy=Fz=10Kg, Mx=My=Mz=1Kg-m)) is designed and manufactured. Basic mechanism of the operation is measuring strains coresponding to pure bending stresses, at certain portions of the device, due to forces and moments given. Wheastone bridge is used for the strain measurement and the amplified output signals from the bridge are decoupled to give the real forces and moments by using the influence coefficient matrix obtained through the calibration. Based on the result of the calibration test, the developed load cell is believed to be quite accurate and reliable. We also believe that the design experience provided us 'With essential information for future design of various types of conventional or object oriented force measuring device.

• Journal of Power System Engineering
• /
• v.18 no.5
• /
• pp.48-54
• /
• 2014

In this paper, three refrigeration systems bypassing hot-gas to compressor outlet, compressor and condenser outlet and evaporator inlet are theoretically compared to offer basic design data for performance depending on cooling load using a HYSYS program. The main results are summarized as follows : First, the COP of third system is the highest. Next, the COP of second system is higher than first one. And, the temperature of compressor inlet of third system is constant for all cooling load. Compared to first and second system, the compressor inlet temperature of the first system is higher than second one for all cooling loads. From the above results, third system, which is bypassing hot-gas to evaporator inlet, is more advantageous when considering the precise temperature control and excellent performance of oil and water cooler of industrial machine.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.1
• /
• pp.128-136
• /
• 2013

This study presents the development of Gateway Control Module using SAE J1939 protocol for the commercial vehicles. Presently, the load rate of CAN bus is increased by the single network composition and addition of new ECUs for development of intelligent vehicles. Because the embedded system of the integrated network control function has the errors of the CAN bus caused by the increase of ECU, it is needed for development of commercial vehicles. Also, this study presents the development of smart functions that can diagnosis CAN bus errors, fault diagnosis of ECU and basic function that arbitrates CAN bus between ECUs of commercial vehicle. GCM was designed for 4channel separation about Gateway function as solution of load rate decrease and smart functions. HILS(Hardware in the loop simulation)system that can achieve simulation about CAN Messages of all systems on vehicle was applied to evaluate performance and verification of all functions and performance. The load rate on CAN bus was decreased at using functions what was delivery, block and process of GCM. Through this, it was enabled to organize systematic architecture for gateway.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.39 no.1
• /
• pp.54-63
• /
• 1997

The purpose of this study is to analyse deformation properties by carrying out of flexure experimentations after fabricating polymer concrete sandwich panels which are composed of the polymer concrete in facing and expanded polystyren in cores, and to provide the basic data necessary to design, fabricate and operate the structure using these polymer concrete sandwich panels The analysed result of this study is summarized as follows. 1. The result of experiment on flexural deflection indicated that the thicker the thickness of both cores and facing of the polymer concrete sandwich panels, the smaller the deflection but the larger the ultimate shear force. In addition, it was also shown that the thicker the thickness of these cores and facing, the smaller the increasing rate of the deflection with the increase of load. 2. The breaking shape of polymer concrete sandwich panels by experiment on flexure was different according to the thickness of facing. When the facing was 5mm in thickness, it was the flexure while it was the flexure and shear failure when the facing was 5mm in thickness. As a result, it seems that the thickness of the facing has a great effect on failure. 3. There were induced not only the related formula between load, deflection and deformation according to the thickness of cores and facing on the basis of the flexure experiment, but also formula between load, horizontal displacement, Then, it seems that it will be possible to estimate the above elements by using these related formulas.

• Wind and Structures
• /
• v.21 no.5
• /
• pp.461-487
• /
• 2015

In recent years, the Graphics Processing Unit (GPU) has become a competitive computing technology in comparison with the standard Central Processing Unit (CPU) technology due to reduced unit cost, energy and computing time. This paper describes the derivation and implementation of GPU-based algorithms for the analysis of wind loading uncertainty on high-rise systems, in line with the research field of probability-based wind engineering. The study begins by presenting an application of the GPU technology to basic linear algebra problems to demonstrate advantages and limitations. Subsequently, Monte-Carlo integration and synthetic generation of wind turbulence are examined. Finally, the GPU architecture is used for the dynamic analysis of three high-rise structural systems under uncertain wind loads. In the first example the fragility analysis of a single degree-of-freedom structure is illustrated. Since fragility analysis employs sampling-based Monte Carlo simulation, it is feasible to distribute the evaluation of different random parameters among different GPU threads and to compute the results in parallel. In the second case the fragility analysis is carried out on a continuum structure, i.e., a tall building, in which double integration is required to evaluate the generalized turbulent wind load and the dynamic response in the frequency domain. The third example examines the computation of the generalized coupled wind load and response on a tall building in both along-wind and cross-wind directions. It is concluded that the GPU can perform computational tasks on average 10 times faster than the CPU.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.6
• /
• pp.89-94
• /
• 2010

A large portion of the energy cost of a building is cooling and heating to maintain a comfortable indoor environment. Air conditioning is now one of the important parts in the building design, as increase in energy consumption and pollutant emission in energy conversion process. In this study, elements that affects the energy consumption of model building are identified and the perfomance analysis of the alternative a Low Energy Cooling Systems considering characteristics of model building and energy saving performance is analyzed. In this study, elements that affect the energy consumption of office building are identified and energy saving performance of the alternative air conditioning system is analyzed. As a result, applied to earn and suggest basic data for energy saving measures. In this study, EnergyPlus simulation program was used to evaluate the energy load when alternative Low Energy Cooling Systems are applied to the model building. The reliability of simulation program is verified by comparing actual energy load from operation data of building management office and predicted energy load using simulation program. For Low Energy Cooling System application which considers the purpose and characteristics of the building, reasonable and energy-saving air conditioning method obtained by analyzing energy consumption elements for each expected air conditioning methods is used to deduct result of this study.