• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.419-424
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• 2002

The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial criticality In February, 1995. Many experiments should be safely performed to activate the utilization of the HANARO. A flow simulation facility is being developed for the endurance test of reactivity control units for extended life times and the verification of structural integrity of those experimental facilities prior to loading in the HANARO. This test facility is composed of three major parts; a half-core structure assembly, flow circulation system and support system. The flow circulation system is composed of a circulation pump, a core flow pipe, a core bypass flow pipe and instruments. The system is to be filled with de-mineralized water and the flow should be met the design flow to simulate similar flow characteristics in the core channel of the half-core test facility to the HANARO. This paper, therefore, describes an analytical analysis to study the flow behavior of the system. The computational flow analysis has been performed for the verification of system pressure variation through the three-dimensional analysis program with standard k-$\epsilon$ turbulence model and for the verification of the structural piping integrity through the finite element method. The results of the analysis are satisfied the design requirements and structural piping integrity of flow circulation system.

• Korean Institute of Interior Design Journal
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• no.15
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• pp.69-78
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• 1998

Purchasing should be considered as an exciting entertainment by itself in these days. Customers can be satisfied with making their own choices and dreaming of their better lives through the action of buying,. However the customers are not rushing into stores without any special reason except when the store has something attracts them. Generally speaking the customers will willingly spend their time and effort in shopping only when they are attracted by well-displyed goods and reasonably planned layout. Based upon these concepts interior design as a creative marketing tool plays a great role in enhancing customer's circulation and the productivity of a store. This study is to propose the layouts which are increasing the customer's circulation by contacting the customers with commodities as many as possible. This study is primarily revolved around the parts affecting customer's circulation among the factors of store's layouts. This study was consist of theoretical consideration about the store's layouts on the foundation of conference and existing works and several proposals. The results of this research are as below: 1) The entrance and exit of a retail store should be apart from each other to increase customers' circulation. It is regarded as ideal to locate the entrance on the right side of front to control moving line of customers. 2) A shop should be surrounded with the main aisles which is straightened inward from the main entrance. 3) Placing magnets which can be anything that attracts customers' attention at the corner of store can lead customers inward and increase customers' circulation.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.366-376
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• 2004

Use of artificial circulation system has become popular in Korean reservoirs to control algal blooms and subsequent color, taste and odor problems in drinking water. It was found that the most of aeration system in Korean reservoirs are under-designed compared to existing installations in US and Australia. This was especially true for larger reservoirs greater than $5{\times}10^7m^3$ in volume since it is common to install the system in the vicinity of intake areas only. Consequently, successful cases of artificial circulation systems operations are limited to few small reservoirs less than $1{\times}10^7m^3$. It is suggested that the design methods need to be developed considering physical characteristics and water quality kinetics inside of reservoirs. Also operation methods of artificial circulation systems need to be established considering the water quality dynamics, stratification and morphological characteristics of reservoirs. Finally, it is suggested to maintain comprehensive and long term monitoring programs to validate the application of artificial circulation system in reservoirs.

• The KSFM Journal of Fluid Machinery
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• v.7 no.1 s.22
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• pp.30-35
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• 2004

The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. Many experiments should be safely performed to activate the utilization of the HANARO. HANARO flow simulation facility is being developed for the endurance test of reactivity control units for extended life time and the verification of structural integrity of those experimental equipments prior to loading in the HANARO. This facility is composed of three major parts; a half-core structure assembly, a flow circulation system and a support system. The flow circulation system is composed of a circulation pump, a core flow piping, a core bypass flow piping and instruments. The system is to be filled with de-mineralized water and the flow should be met the design requirements to simulate a similar flow characteristics in the core channel of the half-core structure assembly to the HANARO. This paper, therefore, presents an analytical analysis to study the flow behavior of the system. Computational flow analysis has been performed for the verification of system pressure variation through the three-dimensional analysis program with the standard $k-{\epsilon}$ turbulence model and for the verification of the structural piping integrity through the finite element method. According to the analysis results, it could be said that the design requirements and the structural piping integrity of the flow circulation system are satisfied.

• Journal of Auto-vehicle Safety Association
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• v.10 no.1
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• pp.32-37
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• 2018

This paper proposes autonomous speed control strategy for an Electric Vehicle on urban road. SNU campus road is used to reperesent urban road situation. Motor efficiency of driving on campus circulation road can be improved by controlling velocity properly. Given information of campus road, especially slope of road, acceleration is selected from candidate, considering consumed power, human factor and driving time. To apply urban situation, preceding vehicle is also considered. With preceding vehicle, acceleration is defined according to clearance and relative velocity. Acceleration is bounded in normal range. Proposed acceleration control method is activated with proper velocity range for campus circulation road. With acceleration control, motor efficiency becomes better than driving with constant vehicle. To evaluate the performance of proposed acceleration controller, simulation study is conducted via MATLAB.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.445-452
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• 2004

Intermittent deep draw artificial circulation system is one of the most widely used destratification systems to control algal bloom in reservoirs in Korea. However, there have been neither theoretical background of design criteria nor operation guide line for efficient application of the system available for such systems. A design method was developed to calculate required compressor capacity and number of circulation units considering physical interactions between stratified water layers and plumes induced by the intermittent deep draw artificial circulation system. The program was tested with data observed in Yeoncho Lake. The results indicated that the developed method can applied in the fields successfully. Further validation processes would improve design and operation methods.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1272-1278
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• 2019

A lumped kinetic modeling platform is developed to investigate the coupled nuclear/thermo-fluid features of the closed natural circulation loop in a low power lead cooled fast reactor. This coolant material serves a reliable choice with noticeable thermo-physical safety characteristics in terms of natural convection. Boussienesq approximation is resorted to appropriately reduce the governing partial differential equations (PDEs) for the fluid flow into a set of ordinary differential equations (ODEs). As a main contributing step, the coolant circulation speed is accordingly correlated to the loop operational power and temperature levels. Further temporal analysis and control synthesis activities may thus be carried out within a more consistent state space framework. Nyquist stability criterion is thereafter employed to carry out a sensitivity analysis for the system stability at various power and heat sink temperature levels and results confirm a widely stable natural circulation loop.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1325-1333
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• 2017

The sensorless control of blushless DC motor(BLDCM) is based on the $120^{\circ}$ control in which the back electromotive force(Back EMF) for estimating the position of the rotor can be detected. However, the $120^{\circ}$ control has a disadvantage that the torque constant is small as compared with $180^{\circ}$ control which can not detect the back EMF. The $150^{\circ}$ control which complements these problems makes it possible to detect the back EMF and improve the torque constant by 12.5% compared to the $120^{\circ}$ control. Therefore, this paper compares the output characteristics of BLDCM through finite element method analysis (FEA) by the conventional and proposed control methods of BLDCM for water circulation system and proposes design for downsizing and weight reduction of BLDCM according to secured torque constant. The validity of the proposed control and design proposal is proved through simulation and experimental results by comparing the output characteristics of $120^{\circ}$ control and $150^{\circ}$ control.

• KIEAE Journal
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• v.15 no.4
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• pp.37-43
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• 2015

Purpose : The study applied control strategy to reduce through optimal control and operation of pump by applying control on variable speed to the circulation pump of HVAC system in the office building. The study has the purpose to review validity of control on variable speed as ESMs(Energy Saving Measures) and establish the control technology on variable speed pump. The study performed reduction analysis of building energy and economic evaluation of pump through energy effectiveness control strategy of HVAC system. Method: The study sought possible reduction through energy control strategy which can provide proper flow fitting to building load by applying control on variable speed pump. The study applied control strategy to reduce through pressure differential set-point control and operation of pump by applying control on variable speed to the circulation pump of HVAC system in the office building. Result : The results showed that about 16-35% of pump energy could be saved by using these optimal control strategies. In the result of analysis on 10 years life cycle cost of analysis on payback period of initial investment pump, variable speed pump control showed 5.1 years.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.768-776
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• 2007

A new type of the fluid circulation blood pressure simulator was proposed to enhance the blood pressure simulator used for the development and evaluation of automatic sphygmomanometers. Various pressure waveform of fluid flowing in the pipe was reproduced by operating the proportional control valve after applying a pressure on the fluid in pressurized oil tank. After that, appropriate fluid was supplied by operating the proportional control valve, which enabled to reproduce various pressure wave of the fluid flowing in the tube. To accomplish this work, the mathematical model was carefully reviewed in cooperating with the proposed simulator. After modeling the driving signal as input signal and the pressure in internal tube as output signal, the simulation on system parameters such as internal volume, cross-section of orifice and supply pressure, which are sensitive to dynamic characteristic of system, was accomplished. System parameters affecting the dynamic characteristic were analyzed in the frequency bandwidth and also reflected to the design of the plant. The performance evaluator of fluid dynamic characteristic using proportional control signal was fabricated on the basis of obtained simulation result. An experimental apparatus was set-up and measurements on the dynamic characteristic, nonlinearity, and rising and falling response was carried out to verify the characteristic of the fluid dynamic model. Controller was designed and thereafter, simulation was performed to control the output signal with respect to the reference input in the fluid dynamic model using the proposed proportional control valve. Hybrid controller combined with an proportional controller and feed-forward controller was fabricated after applying a disturbance observer to the control plant. Comparison of the simulations between the conventional proportional controller and the proposed hybrid simulator indicated that even though the former showed good control performance.