• 대한조선학회논문집
• /
• 제45권2호
• /
• pp.124-131
• /
• 2008

This paper presents the analysis of resistance performance and bow waves for the resistance-minimized hull form of small fishing boat by using numerical simulations and model tests. The resistance-minimized hull form is developed from an original hull form which is selected from existing small fisher boats in our country. In order to estimate the resistance performance for the original and the developed hull form, several numerical simulations and model tests are carried out. Marker and Cell(MAC) method and Marker-Density method are adopted to simulate the free-surface bow waves around advancing hull surface. The results of numerical simulations are compared with the model tests in towing tank. The results show that the resistance performance of the resistance-minimized hull form is improved than that of the original hull form. The results of this study will be a good guide to the hull form development of small fishing boats in future.

• 공업화학
• /
• 제17권2호
• /
• pp.150-157
• /
• 2006

최근 들어 크롬대체 도금공정의 필요성이 대두되고 있는 가운데, 크롬도금과 색차가 적고 기계적 특성이 우수하며 환경 친화적인 주석 계 합금도금의 사용이 확대되고 있다. 따라서 본 연구에서는 Sn-Co 합금도금공정을 바탕으로 광택제, 착화제로서 glycine 사용에 대한 연구를 수행하고자 하였다. Sn-Co 합금도금과 glycine 첨가에 따른 물리적 특성 및 표면 광택측정을 위해 Hull-cell 분석 및 도금표면분석을 수행하였다. Hull-cell 분석결과 glycine의 첨가량이 증가함에 따라 광택특성은 우수한 것으로 관찰되었으며, 표면광택성이 가장 우수한 도금조건으로는 $50^{\circ}C$, pH = 8의 조건에서 전전류 공급량 1 A로 1 min간 도금한 경우 음극전류밀도 $1A/dm^2$인 영역을 추천할 수 있었다. 동일조건의 pilot 실험을 $10{\mu}m$ 두께로 Ni하지 도금 후 Sn-Co 합금도금액 기본조성인 0.03 M $SnCl_{2}{\cdot}2H_{2}O$, 0.05 M $CoSO_{4}{\cdot}7H_{2}O$, 0.7 M $K_{4}P_{2}O_{7}$의 혼합 용액에서 수행하 였다. $0.2{\sim}0.6 {\mu}m$의 도금두께를 갖는 Sn-Co 합금도금 표면의 기계적 특성과 도금표면의 성분분석 결과 glycine의 첨가량이 15 g/L일 때 우수한 밀착성, 내식성, 내마모성을 보였다. 따라서 Sn-Co 합금도금공정에 glycine을 첨가한 용액을 크롬도금공정의 최적 도금용액으로 추천할 수 있었다.

• 생물환경조절학회지
• /
• 제10권2호
• /
• pp.106-110
• /
• 2001

양액재배용 배지로 팽연화 왕겨를 사용할 경우 반촉성 및 억제 재배용으로 사용 가능한 횟수는 3회 사용시 $Ca^{++}$의 다량 용출로 인한 배지의 다져짐이 나타나며 원형여지크로마토그래피상의 부숙도 판정에서도 2작기 경과동안 거의 부숙되는 것으로 미루어 2회까지 사용이 안정적인 것으로 판단되였다. 2회 사용일수의 합산이 245일 이고 정상적인 급액은 이루어지지 않았으나 30일 정도의 재상용전 기간 동안에도 습윤상태를 유지한 것으로 미루어 장기재배 1작기에도 사용이 가능한 것으로 판단되나 펄라이트의 적정 사용기간에 비해 1/3 정도로 사용기간은 짧은 편이었다. 교체비용을 포함한 배지 재료비는 펄라이트 대비 65.3% 정도로 경제적이었다.

• 한국표면공학회지
• /
• 제43권2호
• /
• pp.64-72
• /
• 2010

CuSnZn electroplating was investigated as alternative to Ni plating. Evaluation of electrolyte and plating process was performed to control physical characteristics of the film, and to collect practical data for application. Hull-cell test was conducted for basic comparison of two commercialized products and developed product. Based on hull-cell test results, long term test of three electrolytes was performed. Various analysis on long term tested electrolyte and samples have been done. Reliable and practical data was collected using FE-SEM (FEI, Sirion), EDX (ThermoNoran SIX-200E), ICP Spectrometer (GBC Scientifi c, Integra XL), FIB (FEI, Nova600) for anlysis. Physical analysis and reliability test of the long term tested film were also carried out. Through this investigation plating time, plating speed, electrolyte composition, electrolyte metal consumption, hardness and corrosion resistance has been compared. This set of data is used to predict and control the chemical composition of the film and modify the physical characteristics of the CuSnZn alloy.

• Journal of Mechanical Science and Technology
• /
• 제15권4호
• /
• pp.465-472
• /
• 2001

A numerical study is carried out to clarify the characteristics of flow fields and breaking phenomena around a high speed catamaran hull advancing on calm water. Computations are carried out for Froude numbers between 0.2 and 1.0 and for ratios of the distance between hulls to the catamaran length varying between 0.2 and 0.5 for a mathematically defined Wigley hull. A Navier-Stokes solver which includes the nonlinearities of free surface conditions is employed. Computations are performed in a rectangular grid system based on the Marker & Cell method. For validation, present computation results are compared with existing experimental results. As an application, the results of the displacement catamaran are used for the breaking analysis.

• 한국표면공학회지
• /
• 제10권1호
• /
• pp.1-18
• /
• 1977

To support the domestic plating industry concerning localized products, survey was conducted in with chemicals and properties of plating solution. Collected samples from 55 factories throughout the country were investigated by spectigated by spectrograph, Hull cell test chemical analysis method to find major chemical components of the plating solution.

• 대한조선학회논문집
• /
• 제48권6호
• /
• pp.501-508
• /
• 2011

In order to control the tip vortex cavitation occurring around the tip of a rotating propeller blade, researches on the propeller cavitation and blade tip vortex flows have been increased. In this paper, the propeller tip vortex flow for a blunt and sharp tips was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. In numerical open water test, torques, thrusts, pressure distributions and vortex flows were compared for various rotating speeds. To consider a hull wake, the nominal wake was specified in inlet boundary condition. Pressure distributions and vortex flows with the hull wake were investigated for various propeller rotating angles. From the results, it was confirmed that the blunt tip propeller delayed the tip vortex flow.

• 공업화학
• /
• 제19권2호
• /
• pp.228-235
• /
• 2008

니켈 표면처리 공정에서 전류밀도에 따라 니켈의 전착두께가 증가되었으며, 증가폭은 $6{\sim}10A/dm^2$에서 저전류보다 높게 나타났다. 전류밀도를 측정하기 위해 Hull-cell 분석을 수행 하였다. 최적 공정온도는 $60^{\circ}C$, pH는 3.5~4.0이었고, 전해용액 중 니켈이온의 농도는 300 g/L 이상에서 농도에 따라 전착두께가 증가되었다. 전류밀도에 따라 용액 중 니켈이온 감소 속도가 증가되었는데, 이는 음극표면에서 니켈 전착 량에 따른 전착두께의 증가를 나타낸다. 그러나 전착속도가 빠를 경우 니켈 전착 층의 치밀성은 저하되며, 표면의 상태는 불규칙하게 변화된다. 니켈이온의 전착과정이 불규칙하게 일어나 조직의 pin hole 등을 야기해 표면특성을 저하시키는 것으로 확인되었다. 광택니켈 전착 후 25 h 내식을 유지한 결과, 낮은 전류밀도를 유지하는 것이 내식특성이 우수한 것으로 나타났다. 프로그램모사 결과, 전류밀도가 높아질수록 확산 층의 두께는 증가하며, 음극표면의 농도는 낮아진다. 농도분포는 낮은 전류밀도에서 고른 분포를 나타내었으며 이는 일정한 전착두께를 예측할 수 있다. 생산성 저하를 예방하기 위해 공정시간은 크게 변화시키지 않았으며, 전류밀도와 전착두께를 변화시키면서 공정변수를 조절하였다. 본 연구의 표면분석 결과 조직특성이나 내식성 등의 표면 물성이 낮은 전류밀도를 사용할 경우에 더욱 우수한 것으로 나타났다.

• Journal of Microbiology and Biotechnology
• /
• 제20권5호
• /
• pp.893-903
• /
• 2010

A cellulolytic and xylanolytic enzyme complex-producing alkalothermoanaerobacterium strain, Tepidimicrobium xylanilyticum BT14, is described. The cell was Grampositive, rod-shaped, and endospore-forming. Based on 16S rRNA gene analysis and various lines of biochemical and physiological properties, the strain BT14 is a new member of the genus Tepidimicrobium. The strain BT14 cells had the ability to bind to Avicel, xylan, and corn hull. The pH and temperature optima for growth were 9.0 and $60^{\circ}C$, respectively. The strain BT14 was able to use a variety of carbon sources. When the bacterium was grown on corn hulls under an anaerobic condition, a cellulolytic and xylanolytic enzyme complex was produced. Crude enzyme containing cellulase and xylanase of the strain BT14 was active in broad ranges of pH and temperature. The optimum conditions for cellulase and xylanase activities were pH 8.0 and 9.0 at $60^{\circ}C$, respectively. The crude enzyme had the ability to bind to Avicel and xylan. The analysis of native-PAGE and native-zymograms indicated the cellulosebinding protein showing both cellulase and xylanase activities, whereas SDS-PAGE zymograms showed 4 bands of cellulases and 5 bands of xylanases. Evidence of a cohesinlike amino acid sequence seemed to indicate that the protein complex shared a direct relationship with the cellulosome of Clostridium thermocellum. The crude enzyme from the strain BT14 showed effective degradation of plant biomass. When grown on corn hulls at pH 9.0 and $60^{\circ}C$ under anaerobic conditions, the strain BT14 produced ethanol and acetate as the main fermentation products.

• 청정기술
• /
• 제11권3호
• /
• pp.153-164
• /
• 2005

This study found a reliable evaluation for four kinds of pb-Free plating solutions and it's layers, through pure Sn, SnAg, SnBi and SnCu. These four kind of solutions are widely used to pb-Free plating. Hull-cell, Harring-blum, coverage, throwing power, current efficiency, stability, life-time, composition, hardness, roughness, abrasion, scratch, solderability, corrosion, contact angle, morphology, SIR(Surface insulation resistance) and Whisker test were experimented. Also, Using ICP, XRF, FE-SEM, EDS, temperature/humidity chamber, solderability tester, hardness tester, roughness tester, abrasion tester, salt spray tester, contact angle tester, SIR tester, and microscope. In this paper could be shown the systematic and various analysis for reliability about four kinds of pb-Free plating solutions, processes and it's deposit surface.