• Nuclear Engineering and Technology
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• 제32권2호
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• pp.128-141
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• 2000

The critical heat flux (CHF）experiments have been carried out in a wide range of pressures for an internally heated vertical annulus. The experimental conditions covered ranges of pressures from 0.57 to 15.01 MPa, mass fluxes of 0 kg/$m^2$s and from 200 to 650 kg/$m^2$s, and inlet subcoolings from 85 to 413 kJ/kg. The characteristics of the present data and the effect of pressure on CHF are discussed. Most of the CHFs were identified to dryout of the liquid film in the annular or annular-mist flow. For the mass flux of 200 kg/$m^2$s, there were the indications that the CHF occurred at the transition from annular to annular-mist How in the pressure range of 3~10 MPa. For the mass fluxes of 550 and 650 kg/$m^2$s, the CHFs had a maximum value at a pressure of 2~3 MPa, and the pressure at the maximum CHF values had a trend moving toward the pressure at the peak value of pool boiling CHF as the mass flux decreased. The CHF data under a zero mass flux condition indicate that both the effects of pressure and inlet subcooling on the CHF were smaller, compared with those on the CHF with net water upward flow.

• 상하수도학회지
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• 제18권2호
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• pp.201-207
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• 2004

Dissolved air flotation (DAF) is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. Most of particle-bubble collision occurs in the DAF contact zone. This initial contact considered by the researchers to play a important role for DAF performance. It is hard to make up conceptual model through simple mass balance for estimating collision efficiency in the contact zone because coupled behavior of the solid-liquid-gas phase in DAF system is 90 complicate. In this study, 2-phase(gas-liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using an Eulerian-Eulerian approach based on the assumption that very small particle is applied in the DAF system. For the modeling of turbulent 2-phase flow in the reactor, the standard $k-{\varepsilon}$ mode I(liquid phase) and zero-equation(gas phase) were used in CFD code because it is widely accepted and the coefficients for the model are well established. Particle-bubble collision efficiency was calculated using predicted turbulent energy dissipation rate and gas volume fraction. As the result of this study, the authors concluded that bubble size and recycle ratio play important role for flow pattern change in the reactor. Predicted collision efficiency using CFD showed good agreement with measured removal efficiency in the contact zone. Also, simulation results indicated that collision efficiency at 15% recycle ratio is higher than that of 10% and showed increasing tendency of the collision efficiency according to the decrease of the bubble size.

• 조명전기설비학회논문지
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• 제21권6호
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• pp.55-64
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• 2007

본 논문은 부하직렬 고주파 공진 DC/DC 컨버터에 가변 가능한 공진커패시터를 병렬로 삽입한 LCC형 고주파 공진 DC/DC 컨버터의 특성과 설계 예를 나타내고 있으며, 또한 턴-오프시 스위칭 손실을 줄이기 위해 ZVS를 가지는 소프트 스위칭을 사용하였다. 제안 컨버터는 PFM(Pulse Frequency Modulation) 스위칭 패턴을 사용하여 동작되며, PFM 제어에 의해 제안 회로의 출력전압을 제어하였다. 병렬커패시터의 커패시턴스의 변화에 따라, DC/DC 컨버터의 분석은 일반적으로 무차원화 파라미터를 사용하여 나타내었고, 회로 동작 특성은 스위칭 주파수와 파라미터로 행하였다. 또한 본 논문은 특성평가에 의해 제안 DC/DC 컨버터의 동작 특성과 회로 설계 방법을 제시하였다. 더욱이 본 논문은 실험을 통해 이론 분석의 정당성을 입증하였다. 향후 제안한 DC/DC 컨버터는 반도체 및 FPD의 클린룸에 선형이동 시스템의 비접촉 전원장치에 적용 가능하다고 생각된다.

• 한국재료학회지
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• 제3권2호
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• pp.151-157
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• 1993

In situ on-axis rf magnetron sputtering 방법으로 $Y_1$B$a_2$C${u_4}\;{_2O_x}$의 비화학 양론적인 타게트를 사용하여 $T_c$, $_{zero}$/-88.2K, ${\Delta}{T_c}$, <1.5K의 고온초전도 박막을 제조하고, 활성이온식각법으로 이 박막을 patterning하여 그 특성을 조사하였다. 제조된 패턴은 깨끗한 경계면을 가지고 있음이 관찰되었으며, 패턴 폭이 5${\mu}$m에서 2${\mu}$m로 좁아짐에 따라 임계온도와 임계전류밀도의 특성저하가 나타났으나, 그 저하폭이 크지 않아 소자로서 응용하기에 충분한 특성을 가지고 있음을 확인하였다. 한편 RIE방법에 의하여 미크론 이하의 선폭 제조가능성을 확인하였다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.416-419
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• 2007

국내의경우, 초기 Cost모델 작성을 위한 비용관련 정보의 축적이 체계적으로 이루어지지 않고, 과거에 수행된 유사 프로젝트의 실적데이터에 대한 정보가 부족해 주 기능 대비 비용에 대한 효용성을 명확히 판단하기 어려워 신뢰할 수 있는 대상선정이 이루어지지 않고 있다. 따라서, 본 연구는 과거 수행된 유사 프로젝트의 비용 정보를 축적, 공유, 활용, 학습할 수 있고, VE활동의 대상선정을 위해 준비단계에서 수행되는 Cost모델의 체계적이고 효율적 분석이 가능한 웹기반 'Cost 모델 분석 시스템(Cost Model Analysis System: CMAS)'의 개념적 모형을 제시하고자 한다. 본 연구에서 제시한 Cost모델 분석 시스템의 개념적 모형을 활용하여 실질적인 시스템이 구축된다면 효과적인 VE 수행을 위한 합리적이고 신뢰성 있는 대상선정이 이루어질 것으로 판단된다.

• Journal of Animal Science and Technology
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• 제56권7호
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• pp.23.1-23.7
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• 2014

Background: Scanning of the genome for selection signatures between breeds may play important role in understanding the underlie causes for observable phenotypic variations. The discovery of high density single nucleotide polymorphisms (SNPs) provide a useful starting point to perform genome-wide scan in pig populations in order to identify loci/candidate genes underlie phenotypic variation in pig breeds and facilitate genetic improvement programs. However, prior to this study genomic region under selection in commercially selected Berkshire and Korean native pig breeds has never been detected using high density SNP markers. To this end, we have genotyped 45 animals using Porcine SNP60 chip to detect selection signatures in the genome of the two breeds by using the $F_{ST}$ approach. Results: In the comparison of Berkshire and KNP breeds using the FDIST approach, a total of 1108 outlier loci (3.48%) were significantly different from zero at 99% confidence level with 870 of the outlier SNPs displaying high level of genetic differentiation ($F_{ST}{\geq}0.490$). The identified candidate genes were involved in a wide array of biological processes and molecular functions. Results revealed that 19 candidate genes were enriched in phosphate metabolism (GO: 0006796; ADCK1, ACYP1, CAMK2D, CDK13, CDK13, ERN1, GALK2, INPP1; MAK, MAP2K5, MAP3K1, MAPK14, P14KB, PIK3C3, PRKC1, PTPRK, RNASEL, THBS1, BRAF, VRK1). We have identified a set of candidate genes under selection and have known to be involved in growth, size and pork quality (CART, AGL, CF7L2, MAP2K5, DLK1, GLI3, CA3 and MC3R), ear morphology and size (HMGA2 and SOX5) stress response (ATF2, MSRB3, TMTC3 and SCAF8) and immune response (HCST and RYR1). Conclusions: Some of the genes may be used to facilitate genetic improvement programs. Our results also provide insights for better understanding of the process and influence of breed development on the pattern of genetic variations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4002-4014
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• 2015

ITU-R M.1842-1, as a well-known specification dedicated to maritime mobile applications, has standardized wireless transmission protocols according to the particular characteristics of a maritime communications scenario. A time division multiple access (TDMA) frame structure, along with modulation schemes to achieve a high data rate, has been described clearly in ITU-R M.1842-1. However, several specification items are still under "to be decided" status, which brings ambiguity to research works. In addition, the current version of ITU-R M.1842-1 is focused mainly on maritime transmissions in open-sea areas, where the cyclic prefix (CP) is set to zero and only 16-QAM is used in the multi-carrier (MC) system. System performance might be dramatically degraded in coastline areas due to the inter-symbol interference (ISI) caused by selective fading. This is because there is a higher probability that the signal will be reflected by obstacles in coastline areas. In this paper, we introduce the transmission resource block (TRB) dedicated to ITU-R M.1842-1 for a ship ad-hoc network (SANET), where the pilot pattern of TRB is based on the terrestrial trunked radio (TETRA). After that, we evaluated SANET performance under the maritime channel model in a coastline area. In order to avoid noise amplification and to overcome the ISI caused by selective fading, several strategies are suggested and compared in the channel estimation and equalization procedures, where the link-level simulation results finally validate our proposals.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.194-194
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• 2016

Gansu, located in the northwestern region, is a typical agricultural province of arid, semiarid in China. The shortage of water resources is the biggest obstacle of Gansu Province's development, and the dry farming water-saving is the eternal theme of Gansu agricultural sustainable development. In recent years, intensify reform in Gansu, has walked out a successful way in the agricultural water-saving. Using the integrated river basin governance as opportunity, the total water-using quantity was regarded as rigidity to retrain, distributed to counties (districts), irrigated areas, towns, associations, groups step by step. Agricultural water price was substantially increased, with the surface water price from about $0.1RMB/m^3$ to more than $0.2 RMB/m^3$, and the ground water from zero to more than $0.1RMB/m^3$. Simultaneously, the difference water prices and over-quota water progression price markup were carried out. The transaction of water rights was encouraged to impel the peasant to establish the consciousness of saving-water. The regulatory documents were formulated to standardize the scope, condition, mode, program etc. of agriculture water-rights transaction, to guarantees the transaction of water rights is carries out in order. The pattern of farming was optimized and adjusted, reducing the high water-consumption crop, increasing economic crops with high benefit and low water-consumption, developing industrialized agricultures such as green house. The relative engineering and measuring facility were comprehensively improved, with the anti-seepage of canal system and the enforcement of dynamo-electric well, developing high-efficient water-saving irrigation and overall metering facilities. The water fine-grained management has realized, and obvious water-saving effect has obtained: water-using rate in the irrigation area by river water has brought up to 0.57 from 0.52, and by well water up to 0.84 from 0.76. Although the water price has increased, the proportion that the water rate expenditure accounted for the cost lasts decline, and the farmers' income has gone up. The peasants express, the used water is few, and it is few to till land, but the income is many, and life is better.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.49-60
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• 2022

Motivated by the high-resolution properties of high-order Weighted Essentially Non-Oscillatory (WENO) and flux limiter (FL) for steep-gradient problems and the robust convergence of Jacobian-free Newton-Krylov (JFNK) methods for nonlinear systems, the preconditioned JFNK fully implicit high-order WENO and FL schemes are proposed to solve the transient two-phase two-fluid models. Specially, the second-order fully-implicit BDF2 is used for the temporal operator and then the third-order WENO schemes and various flux limiters can be adopted to discrete the spatial operator. For the sake of the generalization of the finite-difference-based preconditioning acceleration methods and the excellent convergence to solve the complicated and various operational conditions, the random vector instead of the initial condition is skillfully chosen as the solving variables to obtain better sparsity pattern or more positions of non-zero elements in this paper. Finally, the WENO_JFNK and FL_JFNK codes are developed and then the two-phase steep-gradient problem, phase appearance/disappearance problem, U-tube problem and linear advection problem are tested to analyze the convergence, computational cost and efficiency in detailed. Numerical results show that WENO_JFNK and FL_JFNK can significantly reduce numerical diffusion and obtain better solutions than traditional methods. WENO_JFNK gives more stable and accurate solutions than FL_JFNK for the test problems and the proposed finite-difference-based preconditioning acceleration methods based on the random vector can significantly improve the convergence speed and efficiency.

• 한국정보통신학회논문지
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• 제25권12호
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• pp.1874-1881
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• 2021

폭설로 인한 도로 미끄러짐과 함께 영하의 기온으로 도로와 차량 통행용 다리, 터널 출입구 쪽에서 주로 발생하는 블랙아이스는 운전자의 시야에서는 아스팔트의 이미지가 투과되어 보이기에 잘 인식되지 않아서 자동차들이 미끄러지는 (슬립 현상) 상황을 발생시키기에 차량이 제동력을 잃어서, 대형 교통사고로 이어져 심각한 인명과 재산상 손실을 초래하고 있다. 본 논문에서는 기존에 연구되었던 블랙아이스 감지 방법들(인공위성 촬영, 초음파 수신으로 미끄러짐의 패턴을 확인, 도로 표면의 온도측정, 차량 주행 중 타이어의 마찰력 차이를 확인하기)의 단점들을 보완하고, 블랙아이스를 감지하는 센서의 크기를 줄여서 많은 이동체에 적용할 수 있도록 하고자 적외선 카메라를 이용하여 도로 상태를 확인하고, 이 정보를 딥러닝 학습을 통하여 블랙아이스를 판별하는 방법을 제안하고자 한다.