• 소성∙가공
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• 제19권2호
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• pp.95-100
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• 2010

Drawing and normalizing are efficient means for controlling strength, fatigue and machinability of free machining steel. Normally strength and machinability are conflicting properties which need to be optimized. In this study, the effects of normalizing temperature and reduction of area on strength, fatigue and machinability were investigated. Fine grains were generated at lower normalizing temperature and fatigue life was increased with decreasing grain size. Matrix was work hardened and elongated with increasing reduction of area. Inclusions also were elongated and cross-sectional area of inclusions along drawing axis was decreased. The effects of work hardening and grain size on fatigue life were significant, but only work hardening affected machinability. Shape and distribution of inclusions after drawing had little effect on fatigue life and machinability.

• Journal of electromagnetic engineering and science
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• 제17권3호
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• pp.153-158
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• 2017

This work reports on the effect of plasma area on the frequency characteristics of the monostatic radar cross section (RCS) of a square metallic plate. A dielectric barrier discharge (DBD) plasma actuator consisting of 10 rings is proposed. The actuator is fabricated in three different configurations such that only three inner rings, seven inner rings, and all rings can be biased. By applying an 18-kV bias at 1 kHz, the three types of DBD actuators generate plasma with a total area of 16.96, 36.74, and $53.69cm^2$, respectively, in a ring or circular form. The experimental results reveal that when the DBD actuator is placed in front of a $20mm{\times}20cm$ conducting plate, the monostatic RCS is reduced by as much as 18.5 dB in the range of 9.41-11.65 GHz. Furthermore, by generating the plasma and changing the area, the frequency of maximum reduction in the monostatic RCS of the plate can be controlled. The frequency is reduced by nearly 20% in the X band when all rings are biased. Finally, an electromagnetic model of the plasma is obtained by comparing the experimental and full-wave simulated results.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2001년도 추계 학술대회지
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• pp.72-90
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• 2001

Environment agriculture carried out from 1999 in Daeho reclaimed saline area, located in central east cost of Choongnam Korea, resulted in dramatic reduction of amount of nitrogen fertilizer and application times and amount of pesticides. The ecological status of Daeho reclaimed saline area was considered to still very sound from the results of ecological survey on flora and fauna. However, it was desirable to adapt precision agriculture for production of high eating quality of rice and preservation of Daeho ecosystem. Especially, precise application of nitrogen and phosphorus fertilizer was recommendable for prevention of water pollution in environment rice cultivation by duck or mud snail or crab. The bioefficacy of Scirpus maritimus and Echinochloa crus-galli in paddy field of environment rice cultivation by duck or mud snail or crab in Daeho reclaimed saline area was revealed very low. Therefor, it was concluded that the pre-measures of reduction of natural weed population were necessary for successful environment agriculture. The most desirable and ideal environmentally sound agriculture in Daeho reclaimed saline area was performance of crop rotation, introduction of legume crops and green manure crops, and also, simultaneous management of crop production and animal husbandry for smooth flow of energy cycle within the closed Daeho ecosystem.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.591-596
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. Two models are examined: a planar two-dimensional channel, and an axisymmetric tube. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and compared to existing experimental data. Computational results for an axisymmetric tube show that as cross-sectional area falls with a reduction in downstream pressure, flow rate increases and reaches a maximum when the speed index (mean velocity divided by wave speed) is near unity at the point of minimum cross-section area, indicative of wave speed flow limitation or "choking" (flow speed equals wave speed) in previous one-dimensional studies. For further reductions in downstream pressure, flow rate decreases. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is ${\le}$ 2 the area throat is located near the downstream end; as wall taper is increased to ${\ge}$ 3 the constriction moves to the upstream end of the tube. In the planar two-dimensional channel, area reduction and flow limitation are also observed when outlet pressure is decreased. In contrast to the axisymmetric case, however, the elastic wall in the two-dimensional channel forms a smooth concave surface with the area throat located near the mid-point of the elastic wall. Though flow rate reaches a maximum and then falls, the flow does not appear to be choked.

• 한국안전학회지
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• 제31권1호
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• pp.105-110
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• 2016

Mountainous disasters such as landslides and debris flow are difficult to forecast. Debris flow in particular often flows along the valley until it reaches the road or residential area, causing casualties and huge damages. In this study, the researchers selected Seoraksan National Park area located at Inje County (Inje-gun), Gangwon Province-where many mountainous disasters occur due to localized torrential downpours-for the damage reduction and cause analysis of the area experiencing frequent mountainous disasters every year. Then, the researchers conducted the field study and constructed geospatial information data by GIS method to analyze the characteristics of the disaster-occurring area. Also, to extract more precise geographic parameters, the researchers scanned debris flow triggering area through terrestrial LiDAR and constructed 3D geographical data. LiDAR geographical data was then compared with the existing numerical map to evaluate its precision and made the comparative analysis with the geographic data before and after the disaster occurrence. In the future, it will be utilized as basic data for risk analysis of mountainous disaster or disaster reduction measures through a fine-grid topographical map.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2680-2700
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• 2017

Finite field arithmetic over GF($2^m$) is used in a variety of applications such as cryptography, coding theory, computer algebra. It is mainly used in various cryptographic algorithms such as the Elliptic Curve Cryptography (ECC), Advanced Encryption Standard (AES), Twofish etc. The multiplication in a finite field is considered as highly complex and resource consuming operation in such applications. Many algorithms and architectures are proposed in the literature to obtain efficient multiplication operation in both hardware and software. In this paper, a modified serial multiplication algorithm with interleaved modular reduction is proposed, which allows for an efficient realization of a sequential polynomial basis multiplier. The proposed sequential multiplier supports multiplication of any two arbitrary finite field elements over GF($2^m$) for generic irreducible polynomials, therefore made versatile. Estimation of area and time complexities of the proposed sequential multiplier is performed and comparison with existing sequential multipliers is presented. The proposed sequential multiplier achieves 50% reduction in area-delay product over the best of existing sequential multipliers for m = 163, indicating an efficient design in terms of both area and delay. The Application Specific Integrated Circuit (ASIC) and the Field Programmable Gate Array (FPGA) implementation results indicate a significantly less power-delay and area-delay products of the proposed sequential multiplier over existing multipliers.

• Korean Journal of Hydrosciences
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• 제7권
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• pp.21-35
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• 1996

This Study is to develop the suitable hydrologic models for determination of the size and location of detention storage facilities to restrain stormwater runoff in urban areas. Hypothetical areas of two levels are considered to seize the hydrologic response characteristics. A one-square-kilometer ares is selected for the catchment level, and a 10-square-kilometer area consisting of 10 catchments is adapted at the watershed level as representative of urban drainage area. In this analysis, different rainfall freqyencies, land uses, drainage patte군, basin shates and detention storage policies are considered. Folw reduction effect of detention storage facilities is deduced from storage ratio and detention basin factor. A substantial saving in detention storage volumes is achieved 노두 the detention storage is planned at the watershed level rather than the catchment level. For the application of real watersheds, two watersheds in Seoul metropolitan area-Jamshil 2 and Seongnae 1-are selected on the basis of hydrologic response charactaristics. Through the regression analysis between dimensionless deterntion storage volume, dimensionless upstream area ratio and reduction rate of storage ratio, the regression equations to determine the size and location of detention storage faclities are presented.

• 기술사
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• 제15권2호
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• pp.24-31
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• 1982

This study concerns with the reduction of the COD and deceleration of dyeing wastewater from DAEGU city area by ozonation. The COD reduction by ozonation follows near linear relationships versus ozonation time, temperature and concentration. The color in dyeing wastewater and of dyes can he strikingly reduced as the water is quasi colorless after ozone treatment. COD reduction rate of wastewater was found not to be dependented on pH, however, high temperature gave better results, although economically not feasible. The ozonation of dyeing wastewater can give good results when dyes, scouring agent and sticking agents were pre-separated.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1999년도 정기총회 및 춘계 공동 학술발표회
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• pp.62-63
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• 1999

Reduction 2,4,6-Trinitrotoluene by zero valent iron was studied in a batch reactor under anoxic conditions. Results showed that the removal of TNT was a pseudo-first order and the rate was dependent on the available metal surface area. Final product, presumably triaminotoluene, accumulated in the solution as well as on the metal surface. However, little amounts of aminodinitrotoluenes were detected. Therefore, it is postulated that the reduction of nitro group occurs simultaneously in all three position.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1020-1023
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• 2004

Recently, Cooling tower are used the necessary element in a residential area and living space on the viewpoint of indoor temperature control. The purpose of this study is to assistance the comfortable environment and economical measures of noise transmission mechanism on tile cooling tower. The results show that noise evaluation interact the main factor of distance reduction and diffraction reduction. Noise criterion apply to the NC level and equivalent transmission loss about already the design of noise reduction.