• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.53-62
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• 2011

During the construction of vertical cutoff walls, filtration of bentonite slurry into the adjacent soil formation fabricates a layer of bentonite filter cake on the wall surface. The bentonite filter cake possesses much lower hydraulic conductivity compared to that of backfill materials in the cutoff wall. Hydraulic conductivity of bentonite filter cakes formed with three different types of bentonites has been measured by performing the modified fluid loss test under various pressure levels. Three different mixture ratios, 4, 6, and 8%, were selected for fabricating bentonite filter cakes to represent common field conditions. Two analysis methods for interpreting the experimental data from the modified fluid loss tests were employed to estimate hydraulic conductivity of the bentonite cakes. The range of hydraulic conductivities of the three bentonite cakes is between $2.15{\times}10^{-11}\;m/s$ and $2.88{\times}10^{-10}\;m/s$ which is 1 to 2.7 orders of magnitude lower than that of the design cutoff wall backfill. The stress distribution and thickness of the bentonite cakes were also evaluated in this paper.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.173-178
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• 2015

In these days, the world has been increasing the development of various underwater vehicles such as ROVs (Remotely operated underwater vehicles) and AUVs (Autonomous underwater vehicles). And the importance of submarine's maneuverability is especially being emphasized. Therefore, accurate values of the derivatives in equations of motion are required to control motion of the submarines. The aims of the present study are to experimentally derive Hydrodynamic derivatives derived by the vertical planar motion mechanism (VPMM) model test, and to estimate vertical dynamic stability was estimated by using the linear hydrodynamic derivatives, the hydrodynamic derivatives of the submarine, which have a high propriety, were provided by using the fourier analysis of measured forces and moments. Furthermore it is confirmed that the experimental derivatives shows well agreement with the theoretical estimations, and the dynamic stability of the submarine was estimated as a good state, which implies that the value is greater than zero.

• Journal of the Korean GEO-environmental Society
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• v.4 no.3
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• pp.27-40
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• 2003

In the present study, a newly modified soil nailing technology named as the PSN(Pretension Soil Nailing) system is proposed. Effects of various factors related to the design of the pretension soil nailing system, such as the length of a sheathing pipe and the fixed cone, are examined throughout a series of the displacement-controlled field pull-out tests. 9 displacement-controlled field pull-out tests are performed in the present study and the pretension forces are also evaluated based on the measurements. In addition, both short-term and long-term characteristics of pull-out deformations of the newly proposed PSN system are analyzed and compared with those of the general soil nailing system by carrying out the stress-controlled field pull-out tests. A numerical approach is further made to determine a postulated failure surface as well as a minimum safety factors of the proposed PSN system using the shear strength reduction technique and the $FLAC^{2D}$ program. Global minimum safety factors and local safety factors at various excavation stages computed in case of the PSN system are analyzed throughout comparisons with the results expected in case of the general soil nailing system. An efficiency of the PSN system is also dealt with by analyzing the wall-facing deformations and the adjacent ground surface settlements.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.3
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• pp.49-61
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• 2019

Swine manure has been recognized as a organic sources for composting and many research was conducted to efficiently utilize and treat. This study was to evaluate a feasibility for producing swine manure compost under various treatment with mixture of swine manure and saw dust. Treatments were designed as follows; non aerated composting pile(REF), aerated composting pile of $100L/m^3$(EXP1), and aerated composting pile of $150L/m^3$(EXP2). The total days of fermentation were 28 days and each samples were collected at every 7 days from starting of composting. Temperature sensors were installed under 30~40cm from the surface of composting pile. Inner temperature in composting piles of EXP1 and EXP2 was rapidly increased to $67{\sim}75^{\circ}C$ within 1~2 days. The elevated temperatures found during the thermophilic phase are essential for rapid degradation of organic materials. While swine manure composted, moisture content, total nitrogen, EC of EXP1, EXP2 in sample at 28 days were lower than those of REF. But, pH and organic matter of EXP1, EXP2 in sample at 28 days were higher than those of REF. After finishing fermentation experiment, maturity was evaluated with germination test. Calculated germination index(GI) at REF, EXP1 and EXP2 were 23.49, 68.50 and 51.81, respectively. The values of germination index were higher at EXP1 and EXP2 which is aerated composting piles than REF which is non aerated composting pile. According to the results, composting process by aerated static pile compost had significant effect on the reduction of required period for composting. Supplying adequate amount of air to compost swine manure will greatly reduce composting period.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.39-39
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• 1998

본 연구는 500KW급 수평축 풍력발전기용으로 개발된 회전날개의 시제품 제작에 앞서 축소모델에 대한, 이론적으로 예측된 공력성능과 신축에 의한 공력성능을 비교 검토함으로서, 설계결과를 검증하고, 필요한 경우 설계를 보완하여 개발위험도를 최소화하기 위해 수행되었다. 시험모델의 크기는 실제의 5%로서 직경이 2.1m이며 날개의 시위길이는 0.2r/R에서 0.101m, 날개끝에서 0.043m 이고, 날개단면형 상온 FX-S-03-182이다. 블레이드의 재질은 Glass/Epoxy 복합재료로 제작되었으며, 실제 풍황을 모사하기 위해 자연풍 상태에서 실험하였다. 실험장치의 구성은 15m 높이의 타워에 회전날개와 전자브레이크 및 각종 센서를 장착하였고, 날개가 회전하기 시작하면 제동장치에 의해 부하를 주면서 토크, 회전수, 풍속 등을 각각의 센서로부터 자료획득장치를 통해 자료처리를 할 수 있도록 하였다. 실험하는 동안 풍속은 4m/s-13m/s 정도로서 시동 풍속인 4m/s와 정격풍속인 12m/s를 포함하여 회전날개의 전체적인 특성을 파악하기 용이하였고, 이론적인 예측성능과 측정된 성능을 비교 검토한 결과 비슷한 결과를 얻어 공력설계 및 해석 방법을 검증하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.18-21
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• 2008

Acoustic design parameters of a half-wave resonator are studied experimentally for acoustic stability in a model combustor. According to standard acoustic-test procedures, acoustic-pressure signals are measured. Quantitative acoustic properties of damping factor and sound absorption coefficient are evaluated and thereby, the acoustic damping capacity of the resonator is characterized. The diameter and the number of a half-wave resonator, its distribution are selected as design parameters for optimal tuning of the resonator. Acoustic damping capacity increases as the resonators with diameter increases. The optimum number of resonators or the optimum open-area ratio decreases as boundary absorption decreases.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.81-89
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• 2011

This paper introduces a recently developed thinning-out timber framed earth retaining wall system. Timber framed retaining walls are usually designed by using design code of gravity type retaining wall but internal stability of timber framed earth retaining walls is often neglected. In this study, it is recommended to use the design code for segmental retaining walls by National Concrete Masonry Association (NCMA, 1997) to check internal stability of timber framed earth retaining wall. Based on the several shear test results for 3 types of timber frames, a simple design chart including internal stability is suggested.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.1-10
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• 2010

Design and performance evaluation of $H_2O_2$ monopropellant thrusters to be used at reaction control of space launch vehicles were presented in this paper. Design thrust level was determined as 100, 250 Newton which is nominal thrust level for commercial space launch vehicles. Qualification thruster models including solenoid valves were developed after the reactor design were evaluated at engineering thruster models. Each thruster was evaluated by measurement of characteristic velocity, thrust, specific impulse, and pulse response times at sea level test condition.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.52-57
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• 2000

In this paper, we designed the 16 Kbps speech coder that has compatibility with CS-ACELP algorithm(G.729). The speech signal is sampled at rate of 16 KHz, divided into two narrowband signal by QMF filterbank, and decimated to rate of 8 KHz. The lower-band signal is encoded by CS-ACELP and the upper-band signal is encoded by Adaptive Transform Coding(ATC) algorithm. At the receiver, two band signals are synthesized by decoder of CS-ACELP and ATC, respectively. The reconstructed output is obtained by passing the QMF synthesis bank. The proposed wideband coder is evaluated with ITU-T G.722 coder through the Mean Opinion Score(MOS) test.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.129-132
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• 2008

Coupled shear wall system is the primary seismic load resisting system of buildings. The coupling beam of these buildings must exhibit excellent ductility and energy dissipation capacity. To achieve better ductility and energy dissipation, the steel coupling beam embedded in the reinforced concrete walls is proposed. Performance of the steel coupling beam is mainly effected by embedment length. ACI equation and BS equation were examined with 23 previous test results. The statistical study uses the values of mean value, standard deviation, correlation coefficient, normal distribution curve, and error analysis. Through the analytical program, the evaluation of the 2 equations was established.