• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.251-257
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• 2017

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.1969-1975
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• 2012

The air brake system used in heavy vehicle is very important from the point of safety due to its weight. In general, air brake system generates relatively long response time and large loss of pressure. It is known that the response time can be decreased by optimal design of brake system, i.e., by increasing the system pressure, minimizing the air line, and material of components. In this study, We developed experimental rigs for the measurement of braking response of heavy duty trucks and compared with the simulated results obtained from the net work fluid flow system analysis code (FLOWMASTER). The effect of several parameters such as, system pressure, diameter of pipe, chamber temperature on the brake response performance have been examined.

• Fire Science and Engineering
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• v.13 no.3
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• pp.35-42
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• 1999

A occupant load density of contemporary office buildings were surveyed by a building w walk through procedure in Korea. The survey results of ten office buildings are range from 1 2 2 2 213.14 m !person 041.4 ft !person) to 22.69 m /person (244.34 ft !person) with 95% confidence l level and the mean occupant load density is 17.92 m2/person 092.87 ft2/야rson). The impacts of occupant load on evacuation flow time was analyzed by applying time-based egress m model, SIMULEX with various occupant load densities from previous studies. I In order to demonstrate the validation of egress modeling method, fire evacuation exercise a and computer simulation were used to simulate the actual evacuation plan for a high-rise office building. An analysis and comparison of the results of these approaches was made to i illustrate the influence of model limitations on the result of prediction The result of the study shows that the introduction of occupant load concept in building c code of Korea is essential to achieving resonable building life safety design in future.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.55-62
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• 2012

In this research, the algorithm for simulating specific grain size distribution(GSD) with large diameter granular material was developed using the distinct element analysis program $PFC^{3D}$(Particle Flow Code). This modeling approach can generate the initial distinct elements without clump logic or cluster logic and prevent distinct element from escaping through the confining walls during the process. Finally the proposed distinct element model is used to simulate large triaxial compression test of the rockfill material and we compared the simulation output with lab test results. Simulation results of Assembly showed very well agreement with the GSD of the test sample and numerical modeling of granular material would be possible for various stress conditions using this application through the calibration.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.729-732
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• 2010

The present study has been motivated by the development of a reliable numerical methodology for simulation of kerosene/LOx coaxial swirl injectors. To deal with thermodynamic non-ideality and anomalies of transport properties pronounced at supercritical pressures, a set of subroutine libraries has been constructed based on the cubic equations of state, and applied to an existing flamelet analysis code. For computational efficiency, two-dimensional axisymmetric RANS formulation with swirl was adopted and validated successfully against an isothermal coaxial swirling jet. For the actual problem with high pressure combustion, however, numerical results show that the RANS models yield excessive production of turbulence probably due to high density gradient magnitude in the vicinity of mixing layer of swirling film flow, and imply strongly further improvement of the turbulence models.

• KIEAE Journal
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• v.16 no.4
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• pp.71-77
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• 2016

Purpose : The energy saving in a residential building (apartment) sector is known as one of the effective solution of energy reduction. In South Korea, the government has recently reinforced regulations associated with the energy performance of buildings. However, there is a lack of research on the methods for the energy performance diagnosis that is used to analyze the wall thermal performance of the existing apartments. Because a reliable diagnosis is necessary to save the building energy, this study analyzed wall thermal performance of an existing apartment in Seoul. Method : This paper applied two methods for analysis of the thermal insulation performance; HFM(Heat Flow Meter) method and ASTR(Air-Surface Temperature Ratio) method. The HFM method is suggested by ISO9869-1 code to measure the thermal performance. The ASTR method is proposed by this study for the simplified In-situ measurement and it uses three temperature data (interior wall surface, interior and exterior air) and the overall heat transfer coefficient. This study conducted the experiment of an existing apartment in Seoul using these methods and analyzed the results. Furthermore, the energy simulation tool of the building was used to suggest retrofit of the building based on the results of measurements. Result : The error rate of HFM method and ASTR method was analyzed in about 17 to 20%. As the results of comparison between the initial design values of the wall and the measured values, the 26% degradation of insulation thermal performance was measured. Lastly, the energy simulation tool of the building shows 10.8% energy savings in accordance with the construction of suggested retrofit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.625-631
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• 2002

This paper presents a MSB-first digit-serial systolic array for computing modular multiplication of A(x)B(x) mod G(x) in finite fields $GF(2^m)$. From the MSB-first multiplication algorithm in $GF(2^m)$, we obtain a new data dependence graph and design an efficient digit-serial systolic multiplier. For circuit synthesis, we obtain VHDL code for multiplier, If input data come in continuously, the implemented multiplier can produce multiplication results at a rate of one every [m/L] clock cycles, where L is the selected digit size. The analysis results show that the proposed architecture leads to a reduction of computational delay time and it has much more simple structure than existing digit-serial systolic multiplier. Furthermore, since the propose architecture has the features of unidirectional data flow and regularity, it shows good extension characteristics with respect to m and L.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.70-78
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• 2009

Floodplain areas of major South Korean rivers were determined by analyzing topographical maps and hydraulic properties of floodplain soil were measured using disc tension infiltrometer. To assess the possibility of treating secondary effluents of municipal wastewater with floodplain soil, a computer code for the analysis of unsaturated flow in soil was employed along with searches conducted in the literature. Based on the data generated, an estimate of total floodplain filtration capacity in Korea was obtained. The results of our study reveal that Korean floodplains have surface soil that is adequate for treating water. Moreover, the distributions of floodplains are substantial over the entire reaches of the rivers, indicating that the conditions are favorable for floodplain filtration as additional treatment of secondary effluent. The capacity of floodplain filtration in Korea is circa 182,000,000 $m^3$/day and most of the rivers are estimated to have enough capacity of floodplain filtration to meet all the secondary effluent, indicating that this technology may be expected to make further improvements on river water quality. Furthermore, this method may also be applied to better the source-water quality for drinking water.

• Journal of the Korean Institute of Gas
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• v.24 no.1
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• pp.23-32
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• 2020

It is not easy to fully fuel high pressure(70 MPa) hydrogen in a hydrogen vehicle tank quickly. This is because the temperature inside the tank rises rapidly due to heat caused by the Joule-Thomson effect, etc. So fueling protocols such as SAE J2601 in the U.S. and JPEC-S 0003 in Japan appeared. However, there is a problem with these protocols that a number assumption are introduced and the content is too complex and limited in scope. This study was conducted to develop a new protocol based on complete real-time communication. In this study, the hydrogen fueling simulation program were used to examine how the pressure ramp rate affects the temperature and pressure rise in the tank and the fueling flow rate. The results confirmed that the first parameter to be considered in determining the pressure ramp rate is the temperature of the tank.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.627-633
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• 2019

This study aimed to predict the resistance and propulsion performance of a ship using computational fluid dynamics (CFD) and a database as well as establish an assessment method for the energy efficiency design index (EEDI) using the results. First, the total resistance of the studied ship is obtained using CFD. A flow analysis is conducted with the free surface and trim and sinkage using a commercial CFD code (STAR-CCM+). The effective power of the ship is assessed based on the CFD results. The quasi-propulsive efficiency is calculated from an empirical prediction equation using experimental data and similar material. Finally, a general calculation program for the EEDI is established based on the hydrodynamic results, ship information for principal particulars, conversion factor of $CO_2$ for fuels, and fuel consumption.