• 대한조선학회논문집
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• 제59권6호
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• pp.393-399
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• 2022

During the ship hull design process, resistance performance estimation is generally calculated by simulation using computational fluid dynamics. Since such hull resistance performance simulation requires a lot of time and computation resources, the time taken for simulation is reduced by CPU clusters having more than tens of cores in order to complete the hull design within the required deadline of the ship owner. In this paper, we propose a method for estimating resistance performance of ship hull by simulation using a graph neural network. This method converts the 3D geometric information of the hull mesh and the physical quantity of the surface into a mathematical graph, and is implemented as a deep learning model that predicts the future simulation state from the input state. The method proposed in the resistance performance experiment of simple hull showed an average error of about 3.5 % throughout the simulation.

• 대한조선학회논문집
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• 제60권2호
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• pp.110-119
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• 2023

The prediction of ship resistance performance is typically obtained by Computational Fluid Dynamics (CFD) simulations or model tests in towing tank. However, these methods are both costly and time-consuming, so hull-form designers use statistical methods for a quick feed-back during the early design stage. It is well known that results from statistical methods are often less accurate compared to those from CFD simulations or model tests. To overcome this problem, this study suggests a new approach using a Convolution Neural Network (CNN) with voxelized hull-form data. By converting the original Computer Aided Design (CAD) data into three dimensional voxels, the CNN is able to abstract the hull-form data, focusing only on important features. For the verification, suggested method in this study was compared to a parametric method that uses hull parameters such as length overall and block coefficient as inputs. The results showed that the use of voxelized data significantly improves resistance performance prediction accuracy, compared to the parametric approach.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권4호
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• pp.147-155
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• 2006

The drag reduction (DR) and heat transfer efficiency reduction (ER) of non-ionic surfactant were investigated as a function of fluid velocity, temperature, and surfactant concentration. An experimental apparatus consisting of two temperature controlled water storage tanks, pumps, test specimen pipe and the piping network, two flow meters, two pressure gauges, a heat exchanger, and data logging system was built. From the experimental results, it was concluded that existing alkyl ammonium surfactant (CTAC Cethyl Trimethyl Ammonium Chloride) had DR of $0.6{\sim}0.8$ at $1,000{\sim}2,000ppm$ concentration with fluid temperature ranging between $50{\sim}60^{\circ}C$. However, the DR was very low when the fluid temperature was $70{\sim}80^{\circ}C$. The new amine oxide and betaine surfactant(SAOB Stearyl Amine Oxide + Betaine) had lower DR at fluid temperatures ranging between $50{\sim}60^{\circ}C$ compared with CTAC. However, with fluid temperature ranging between $70{\sim}80^{\circ}C$ the DR was $0.6{\sim}0.8$ when the concentration level was $1,000{\sim}2,000ppm$.

• 설비공학논문집
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• 제19권2호
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• pp.133-141
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• 2007

The drag reduction (DR) and heat transfer efficiency reduction (HTER) of nonionic surfactant according to the fluid velocity, temperature and surfactant concentration were investigated experimentally. For this study, several kinds of new surfactant which contains amine-oxide and betaine were developed. And experimental apparatus equipped with two water storage tanks temperature controlled, pumps, testing pipe network, two flowmeters, two pressure gauges, heat exchanger, and data logging system was built. Results showed that existing alkyl ammonium surfactant (CTAC) had DR of $0.6{\sim}0.8$ for $1,000{\sim}2,000\;ppm$ in fluid temperature of $50{\sim}60^{\circ}C$ and had very low DR in fluid temperature over $70^{\circ}C$. And new amino oxide and betaine surfactant (SAOB) had lower DR in fluid temperature of $50{\sim}60^{\circ}C$ compared with CTAC but in fluid temperature of $70{\sim}80^{\circ}C$ DR was $0.6{\sim}0.8$ for 1$1,000{\sim}2,000\;ppm$.

• Geomechanics and Engineering
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• 제18권6호
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• pp.585-594
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• 2019

In-situ leaching could be one of the promising mining methods to extract the minerals from deep fractured rock mass. Constrained by the low permeability at depth, however, the performance does not meet the expectation. In fact, the rock mass permeability mainly depends on the pre-existing natural fractures and therefore play a crucial role in in-situ leaching performance. More importantly, fractures have various characteristics, such as aperture, persistence, and density, which have diverse contributions to the promising method. Hence, it is necessary to study the variation of fluid rate versus fracture parameters to enhance in-situ leaching performance. Firstly, the subsurface fractures from the depth of 1500m to 2500m were mapped using the discrete fracture network (DFN) in this paper, and then the numerical model was calibrated at a particular case. On this basis, the fluid flow through fractured rock mass with various fracture characteristics was analyzed. The simulation results showed that with the increase of Fisher' K value, which determine the fracture orientation, the flow rate firstly decreased and then increased. Subsequently, as another critical factor affecting the fluid flow in natural fractures, the fracture transmissivity has a direct relationship with the flow rate. Sensitive study shows that natural fracture characteristics play a critical role in in-situ leaching performance.

• 한국수자원학회논문집
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• 제52권2호
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• pp.149-161
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• 2019

본 연구에서는 3차원 이산 균열망 수치모형을 이용하여 균열망을 구성하는 균열요소의 길이분포가 유체 흐름 특성이 미치는 영향에 대해 수치적으로 분석하였다. 균열요소의 길이분포의 생성을 위해 절단멱분포법칙을 적용하였으며, 지수 ${\beta}_l$을 1.0에서부터 6.0까지 변화시키면서 유체 흐름 모의를 수행하였다. 모의결과 지수 ${\beta}_l$이 증가함에 따라 균열요소들의 길이분포는 점차적으로 작아지며, 이로 인해 균열망의 투수성에 영향을 미치는 균열요소들 간의 연결성은 취약해지는 것으로 나타났다. 각각의 지수 ${\beta}_l$에 대해 균열요소 각각에서 계산된 유량분포를 분석하였을 때 ${\beta}_l=1.0$에서의 평균유량이 ${\beta}_l=6.0$에 비해 약 447배 크게 산정되었으며, 균열망의 유출경계에서 계산된 유량의 경우 ${\beta}_l=1.0$일 때가 6.0에 비해 약 6,440배 크게 산정되었다.

• IMMUNE NETWORK
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• 제13권6호
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• pp.240-248
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• 2013

In this study, we compared the immune cell populations in rheumatoid arthritis (RA) synovial fluid, which shows lymphoid tissue-like structure, with those in tonsils, which are normal secondary lymphoid tissues. Firstly, we found that $CD4^-CD11b^+$ macrophages were the major population in RA synovial fluid and that B cells were the major population in tonsils. In addition, synovial fluid from patients with osteoarthritis, which is a degenerative joint disease, contained $CD4^+CD11b^+$monocytes as the major immune cell population. Secondly, we categorized three groups based on the proportion of macrophages found in RA synovial fluid: (1) the macrophage-high group, which contained more than 80% macrophages; (2) the macrophage-intermediate group, which contained between 40% and 80% macrophages; and (3) the macrophage-low group, which contained less than 40% macrophages. In the macrophage-low group, more lymphoid tissue inducer (LTi)-like cells were detected, and the expression of OX40L and TRANCE in these cells was higher than that in the other groups. In addition, in this group, the suppressive function of regulatory T cells was downregulated. Finally, CXCL13 expression was higher in RA synovial fluid than in tonsils, but CCL21 expression was comparable in synovial fluid from all groups and in tonsils. These data demonstrate that increased lymphocyte infiltration in RA synovial fluid is correlated with an increase in LTi-like cells and the elevation of the chemokine expression.

• 에너지공학
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• 제21권2호
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• pp.144-151
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• 2012

지역난방시스템이란 열에너지를 생산하고 만들어진 열에너지를 넓은 지역에 공급하는 시스템이다. 지역난방시스템은 국부난방보다 더 효율적이고 친환경적이라고 할 수 있다. 생산 된 열은 단열 배관 네트워크를 통해 사용자들에게 공급된다. 지역난방시스템의 효율적인 운전을 위해서는 여러 가지 운전 조건에서 배관망 네트워크의 유량, 압력 및 온도 분포를 예측하는 것이 중요하다. 본 연구에서는 지역난방용 지중매설 배관망 네트워크에서의 열-유체 동적거동을 수학적 모델을 사용하여 예측하였다. 수학적 모델은 물질, 운동량 및 에너지 수지식을 사용하였다. 모델링의 결과를 검증하기 위하여 강남지역 지역난방시스템에서 측정한 결과와 모델링의 결과를 비교하였다.

• 에너지공학
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• 제19권2호
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• pp.116-120
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• 2010

국내 집단에너지 사업의 대표적인 지역난방시스템은 전체 배관망이 약 3,000 km에 이르고 있다. 이러한 장거리 배관망을 통한 열수송에서는 마찰 저항으로 인해 많은 펌프동력이 필요하게 된다. 효율적인 장거리 열수송을 위한 연구로서 대표적인 방법 중 하나가 마찰저감제를 투입하는 것이다. 이러한 마찰저감제는 파이프내 표면의 마찰저항을 감소시킴으로써 유체의 유동을 향상시키게 되는 것이다. 본 연구에서는 친환경 계면활성제인 Amine Oxide $C_{18}$을 이용하여 $80{\sim}110^{\circ}C$의 온도범위에서 단기간 동안에 마찰저감 특성을 비교하고, 장기간 동안 퇴화현상을 비교 평가함으로써 향후 지역난방 시스템에서 적용 가능성을 평가하기 위하여 지역 난방시스템을 축소하여 실험장치를 제작하였다. 마찰저감제를 첨가하지 않은 파이프내의 차압과 마찰저감제를 첨가하였을때의 차압을 비교하여 마찰저감율을 측정하였다. 단기성능 실험결과 마찰저감제는 온도의 영향을 받아 유체의 온도가 높아질수록 마찰저감율이 낮게 나타났다. $80^{\circ}C$의 실험에서 최대 30%의 마찰저감율이 나타났으며, $100^{\circ}C$ 이상에서는 마찰저감율이 감소하여 약 15%의 마찰저감율을 보였다. 장기성능 실험결과 $80^{\circ}C$의 실험에서는 1000 ppm 0.8 m/s의 유속에서 마찰저감율의 지속시간이 155시간동안 유지되었으며 온도가 높아질수록 지속시간이 감소하였다.

• Genomics & Informatics
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• 제14권1호
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• pp.2-11
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• 2016

The advances in mass spectrometry-based proteomics technologies have enabled the generation of global proteome data from tissue or body fluid samples collected from a broad spectrum of human diseases. Comparative proteomic analysis of global proteome data identifies and prioritizes the proteins showing altered abundances, called differentially expressed proteins (DEPs), in disease samples, compared to control samples. Protein biomarker candidates that can serve as indicators of disease states are then selected as key molecules among these proteins. Recently, it has been addressed that cellular pathways can provide better indications of disease states than individual molecules and also network analysis of the DEPs enables effective identification of cellular pathways altered in disease conditions and key molecules representing the altered cellular pathways. Accordingly, a number of network-based approaches to identify disease-related pathways and representative molecules of such pathways have been developed. In this review, we summarize analytical platforms for network-based protein biomarker discovery and key components in the platforms.