• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.116-121
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• 2006

The pressurization system in a liquid rocket propulsion system provides a controlled gas pressure in the ullage space of the vehicle propellant tanks. It is advantage to employ a hot gas heat exchanger in the pressurization system to increase the specific volume of the pressurant and thereby reduce over-all system weight. Therefore a significant improvement in pressurization system performance can be achieved, particularly in a cryogenic system. For this study air and $CN_2$ are employed as external fluid and pressurant respectively Numerical analysis on the pressurant discharging characteristics have been compared with the experimental results performed at the PTF(Propellant-feeding Test Facility). It is shown that the discrepancy of analytic and experimental results is within about ${\pm}15%$. It is estimated that the temperature drop rate of cryogenic pressurant immersed liquid oxygen can be predicted using this analytic approach method.

• Korean journal of applied entomology
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• v.48 no.2
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• pp.245-251
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• 2009

Without pesticide applications, mass-trapping by sex pheromone was successful to control Spodoptera litura (Fabricius) in a large scale tomato glasshouse (10,000 $m^2$) at a low cost of 60 won/$m^2$. Pheromone traps were placed both inside and outside of the glasshouse. Inside the glasshouse traps were installed in a regular space, one trap per 500 $m^2$, to catch the moths that were present in the glasshouse, and traps were also set outside of the glasshouse, at intervals of ca. 20 m, to prevent the moths from invading the glasshouse. In the experiment, more than 400 S. litura were captured per trap.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.158-167
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• 1999

There are substantial difficulties in assessing the volume of soill/rock to be excavated and the cost thereof, which is attributable to the subjective and qualitative methods of rock mass classification prevailing at the moment. This paper intends to introduce more objective and quantitative rock mass classification method easily applicable to the excavation of granites in Muakjae, Seoul. As a result of such study it is proven that Schmidt hammer and point load strength tests are fairly reliable and easily applicable to estimate and quantify uniaxial compressive strength of granitic material in Seoul. In an efforts to confirm the granitic rock mass conditions in 12 meters underground, seismic refraction surveys were made on the top of vertical exposures from where underlying rock mass conditions could be directly inspected. Rock mass boundaries determined by seismic refraction methods were found to agree within a 1m variance with visible differences in rock mass conditions in the vertical exposure beneath the test site. Thus it can be concluded that detailed geotechnical mapping on cutting slopes is a most efficient, dependable and cost-effective technique in assessing likely excavation conditions of shallow granitic mass in Seoul.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.101-106
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• 2014

The penetration testing provides 1 dimensional profiles of properties applicable to limited investigation areas, although N-value has been linked to a wide range of geotechnical design parameters based on empirical correlations. The nondestructive test using elastic waves is able to produce 2 or 3 dimensional property maps by inversion process with high efficiency in time and cost. As both N-value and elastic wave velocities share common dominant factors that include void ratio, degree of saturation, and in-situ effective stress, the correlation between the two properties has been empirically proposed by previous studies to assess engineering properties. This study presents the experimentally measured elastic wave velocities of Jumunjin sands under at-rest lateral displacement condition with varying the initial void ratio and degree of saturation. Results show that the stress condition predominantly influences the wave velocities whereas void ratio and saturation determine the stress-velocity tendency. The correlation among the dominant factors is proposed by multiple regression analysis with the discussion of relative impacts on parameters.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.163-170
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• 2008

Switching characteristics in both linear and nonlinear loads are analysed for a 3-phase voltage disturbance generator applicable to the performance test of custom power devices. Since the line current of the linear load is continuous the natural commutation of the SCR thyristors comprising the generator is carried out with ease. However, in case of nonlinear load the natural commutation scheme is different from that of the linear load due to the discontinuous load current. Through the analysis it is found that a specific switching condition can provide the voltage sag, swell, outage, and voltage unbalance generation in nonlinear load too. The operation of the voltage disturbance generation is described and the usefulness of the generator is verified through simulation and experimental results. It is expected that the generator can be used in the performance test of the custom power devices with low implementation cost and easy control.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.794-801
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• 2003

As it is important to measure the degree of the deterioration and predict service life caused by chloride in concrete structure the methods of measuring chloride in the concrete is raised important problems. This study is to set a new standard for using of the colorimetric method through grasping the character of the colorimetric distinction method, and measuring the chloride content at the place discolored. Also, to predict chloride content around embeded bar and time reaching limit chloride concentration through measuring the chloride content of concrete surface by colorimetric distinction method and this study presents the new concept of concrete degradation and diagnosis of the durability by salt damage. According the results, it is possible to use colorimetric distinction method as simplified measurement to measure the fixed quantity of the chloride concentration. What is more, it would make calculation of concrete surface chloride had a wide fluctuation at the general environment extended. Also, it would be make estimating durability of reinforced concrete structures applied to the basic data.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.1-6
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• 2004

The requirements for harsh environment electronic controllers in automotive applications have been steadily becoming more and more stringent. Electronic substrate technologists have been responding to this challenge effectively in an effort to meet the performance, reliability and cost requirements. An effect of the plasma cleaning at the ECM(Engine Control Module) alumina substrate and the intermetallic compound layer between Sn-37wt%Pb solder and pad joints after reflow soldering has been studied. Organic residual carbon layer was removed by the substrate plasma cleaning. So the interfacial adhesive strength was enhanced. As a result of AFM measurement, conductor pad roughness were increased from 304 nm to 330 nm. $Cu_6/Sn_5$ formed during initial reflow process at the interface between TiWN/Cu pad and solder grew by the succeeding reflow process, so the grains became coarse. A cellular-shaped $Ag_3Sn$ was observed at the interface between Ag-Pd conductor pad and solder. The diameters of the $Ag_3Sn$ grains ranged from about 0.1∼0.6 $\mu\textrm{m}$. And a needle-shaped was also observed at the inside of the solder.

• Journal of Mushroom
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• v.13 no.4
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• pp.310-313
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• 2015

This study was carried out to re-use the post-harvest substrate of Pleurotus pulmonarius. In this study, we used two mixing ratio. First, a mixing ratio is developed by Gangwon Province Agriculturl Research and Extension Services[Poplar sawdust(10)+Cottonseed hull(50)+Cottonseed mal(20)+Beet pulp(20)]. Second, mixing ratio is developed by farmers[Poplar sawdust(60)+Cottonseed hull(10)+Cottonseed mal(10)+Beet pulp(20)]. First mixing ratio research results, Hosan was no difference in the yield by 30%, Yield of the Hwasan has increased by 20%. Second mixing ratio research results, Hosan was no difference in the yield by 20%. However, Hwasan has decreased.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.255-262
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• 2015

In the absence of a deterministic algorithm for economic load dispatch optimization problem (ELDOP), existing algorithms proposed as solutions are inevitably non-deterministic heuristic algorithms. This paper, therefore, proposes a balance-and-swap algorithm to solve an ELDOP. Firstly, it balances the initial value to ${\Sigma}P_i=P_d$ by subsequently reducing power generation for each adult-step and baby-step and selects the minimum cost-generating method. Subsequently, it selects afresh the minimum cost-generating method after an optimization of the previously selected value with adult-step baby-step swap and giant-step swap methods. Finally, we perform the $P_i{\pm}{\beta}$, (${\beta}=0.1,0.01,0.001,0.0001$) swap. When applied to the 3 most prevalently used economic load dispatch problem data, the proposed algorithm has obtained improved results for two and a result identical to the existing one for the rest. This algorithm thus could be applied to ELDOP for it has proven to consistently yield identical results and to be applicable to all types of data.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.127-134
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• 2012

Four river project in the South Korea contributes to solve flood damages and water shortages. Also, it has purpose for creating water ecosystem and improving the level of people' cultural leisure and quality of life through inducing water quality improvement and river restoration. It is necessary to monitor a variety of observing data in river areas among dozens to hundreds of kilometer for safe river administration. The 20th construction area of the four river project is located on Hapcheon areas, where wireless mesh network was installed to manage the basin. In the process of network construction, the characteristic of surrounding areas is considered about embodying secure service by investing the least expense. Besides, transmission environment analysis is performed such as LOS tests and reception level analysis, and transmission speed measurement to create safe service. Reception level in all places is confirmed among -55 dBm ~ -70 dBm, and data transmission speed proves more than 20 Mbps.