• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1993년도 학술대회지
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• pp.155-163
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• 1993

An American ginseng(Panax quillquefolium L) industry has emerged in British Columbia, Canada over the past ten years. Interest has grown very rapidly and with this development, attention is now moving away from field production issues and emphasis is being directed to enhancements in ginseng storage, drying and processing. There is a dearth of knowledge on these aspects even though they are crucial to international competitiveness. Enhancement dicatates the application of a systems approach to optimizing the harvest and post - harvest production system(crop digging, pre - washing cold storage. washing, drying and post - drying storage). Research in British Columbia to date has focussed on drying and storage issues and has resulted in the design of an enhanced commercial drying system. The role of dryer management, loading rates, airflow rates and pre - drying cold storage on American ginseng root drying rates and root quality were examined. From the dryer management experiments, there are distinct advantages to size sorting root to yield optimum drying rates. If unsorted root is used, efficiency is increased if the trays are systematically rotated. Loading rate experiments illustrate that increasing rates above those currently used in commercial dryers are possible without any sacrifice in quality. This has significant implications for commercial drying. Pre - drying cold storage is a most significant tool for managing drying operations. Over a period of six weeks, no discernable decrease in quality was found as a consequence of cold storage. Further, the moisture loss and the associated root surface changes(loss of surface soil in storage for example) provide new challenges for root quality management. Continued research and technological innovation will be crucial in addressing the demanding challenges of the future.

• 소성∙가공
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• 제17권2호
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• pp.124-129
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• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 한국방재안전학회논문집
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• 제10권1호
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• pp.19-27
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• 2017

최근 도심지에서 상하수도 등의 지중매설관 노후 및 접합 불량에 따른 누수에 의해 일어나거나, 터널굴착 및 지하구조물 시공 시 부실시공 또는 관리 부실로 인한 지하수의 유입으로 지중공동이 발생하고 이로 인하여 지반침하가 빈번하게 발생하고 있다. 이에 본 연구에서는 포화-불포화 다공성 매질에 대한 지하수 변동을 예측할 수 있는 수치모델(SEEFLOW3D)을 개발하였으며 개착식 및 비개착식 굴착 시나리오를 구성하여 지반굴착에 따른 영향을 모사하였다. 또한, 개발모델의 검증을 위해 범용수치해석 프로그램(Visual MODFLOW)과 비교 분석을 수행하였다. 그 결과 평균 오차는 -3.95~5.72%이며 정규화 된 RMSE는 0.56~4.62%로 나타났다. 향후 본 연구의 개발모델은 지반굴착 공사 시 지하수 유출량을 예측하고 이에 따른 차수벽의 최적 설계 등을 위한 해석툴로 활용 가능할 것으로 기대된다.

• 디지털콘텐츠학회 논문지
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• 제11권4호
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• pp.463-471
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• 2010

하수 처리장은 화학적, 물리적, 생물학적 처리가 복합적으로 연계된 공정으로 구성 되는데, 각각의 단위공정과 전체시스템의 처리 성능 및 운영 상태의 정도를 파악 하려면 처리공정의 수학적 모델을 빠르게 연산 할 수 있는 컴퓨터 시뮬레이터를 이용하면 편리하다. 주어진 물리적 환경에서 처리공정의 오염물질, 화학물질, 생물학적 매체의 질량 수지를 계산하는 컴퓨터 시뮬레이터는 데이터의 입출력 과정과 수학모델의 연산과정을 효율적으로 수행하는 응용 소프트웨어로써 처리조 내부에서 일어나는 반응의 상태를 정량적으로 추산하는 도구이다. 이러한 시뮬레이션 소프트웨어는 처리시설의 성능 및 효율을 예측하여 운용자에게 최적 관리를 위한 의사결정의 타당성을 제공하게 되는데, 시뮬레이션 소프트웨어를 처리시설에 적합하도록 시나리오를 설정하고 데이터 수집 시스템에 연결하면 실시간으로 처리시설의 분석이 가능한 자동화 운영 시스템의 역할을 수행한다. 본 논문에서는 통합전산망에서 수집되는 데이터를 시뮬레이션 소프트웨어에서 운용, 실제 운영 상태와 시뮬레이션 결과를 실시간 비교, 분석하여 최적의 운전인자를 도출할 수 있는 시나리오 운영 소프트웨어 "WEC-Sim"의 설계 및 구현에 대하여 논한다.

• 한국기계가공학회지
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• 제16권6호
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• pp.69-74
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• 2017

In the current machining industry, machining precision is necessary and machining is being carried out. In this ultra-precision machining industry, the fixation of the workpiece is very important and the degree of machining depends on the degree of fixation of the workpiece. In ultra-precision machining, various methods, such as using a vise chuck or the like and using bolt nut coupling, are used for fixing a workpiece to an existing machine tool. In particular, when the precision gripping force of the jig is insufficient during machining of the ultra-precision mold parts, the machining material shakes due to the vibration or friction, and the machining precision is lowered. In the ultra-precision machining of power transmission parts, such as gears, the accuracy of the product is then determined. In addition, the amount of heat generated during machining has a significant effect on the machining accuracy. This is because the vibration value changes according to the grasp force of the jig that fixes the workpiece, and the change in the calorific value due to the change in the main shaft rotation speed of the ultra-precision machining. The increase in the spindle rotation speed during machining decreased the heat generation during machining, and the machining accuracy was also good, and it was confirmed that the machining heat changed according to the fixed state of the workpiece and the machining accuracy also changed. In this study, we try to optimize the driving part of the power vise by using structural analysis, rather than the power vise, using the basic mechanical-type power unit.

• 대한기계학회논문집B
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• 제41권8호
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• pp.497-503
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• 2017

산소호흡기의 실질적인 개발 제작 및 안정성 파악을 위해서는 산소유동의 이론적인 연구가 필요하다. 이에 본 연구에서는 상용 해석 툴인 COMSOL 멀티피직스를 이용하여 산소호흡기의 사용시간 연장을 위한 고압용 감압기 설계를 진행하였다. 기존 감압기의 오리피스 내 핀 형태의 실린더 삽입 방법을 제안했으며, 새로 제시한 오리피스에 대해 3 mm, 6 mm 그리고 9 mm의 길이에서 유동 특성 분석 및 최적 길이를 도출하였다. 기존 감압기에서 토출되는 질량유량 0.028 kg/s 을 기준으로, 최대 감압기 입구 압력인 300 bar 경우 약 33%, 감압기 입구 압력조건인 50 bar, 75 bar 그리고 100 bar에서는 평균 32.71% 내외로 기존 질량조건을 만족하였다. 가공 용이성을 고려할 때 기존의 감압기와 길이가 동일하여 별도의 가공이 필요 없는 3 mm가 가장 적합하다고 판단된다.

• Structural Engineering and Mechanics
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• 제19권4호
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• pp.381-399
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• 2005

Base isolation technologies have been proven to be very efficient in protecting structures from seismic hazards during experimental and theoretical studies. In recent years, there have been more and more engineering applications using base isolators to upgrade the seismic resistibility of structures. Optimum design of the base isolator can lessen the undesirable seismic hazard with the most efficiency. Hence, tracing the nonlinear behavior of the base isolator with good accuracy is important in the engineering profession. In order to predict the nonlinear behavior of base isolated structures precisely, hundreds even thousands of degrees-of-freedom and iterative algorithm are required for nonlinear time history analysis. In view of this, a simple and feasible exact formulation without any iteration has been proposed in this study to calculate the seismic responses of structures with base isolators. Comparison between the experimental results from shaking table tests conducted at National Center for Research on Earthquake Engineering in Taiwan and the analytical results show that the proposed method can accurately simulate the seismic behavior of base isolated structures with elastomeric bearings. Furthermore, it is also shown that the proposed method can predict the nonlinear behavior of the VCFPS isolated structure with accuracy as compared to that from the nonlinear finite element program. Therefore, the proposed concept can be used as a simple and practical tool for engineering professions for designing the elastomeric bearing as well as sliding bearing.

• 한국축산식품학회지
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• 제44권1호
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• pp.146-164
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• 2024

Owing to the residual toxicity and adverse health effects of chemical preservatives, there is an increasing demand for using natural preservatives in food. Although many natural extracts have been evaluated, research on their antibacterial effects remains insufficient. Therefore, this study aimed to explore the possibility of developing Psidium guajava, Ecklonia cava, and Paeonia japonica (Makino) Miyabe & Takeda extracts as natural food preservatives. Further, the effect of mixing these extracts on microbial growth and quality was evaluated during the refrigeration of sausages. Optimal mixing ratios were determined based on the minimum inhibitory and bactericidal concentrations of each mixed extract against the Listeria monocytogenes, Salmonella spp. and Escherichia coli. D-optimal mixing design optimization tool was further used to obtain an optimum mixing ratio of Formulation 1 (F1). The antibacterial activity of F1 increased with increasing concentration, with similar activities at 0.5% and 1%. The sausages with synthetic or natural preservatives showed significantly lower lipid oxidation than those of the control and grapefruit extract-treated sausages after 4 wk of refrigeration. Total plate counts were observed only in the control and treatment groups stored for 3 wk, and no significant effect of ascorbic acid was observed. Compared to the other samples, sausages with added natural extracts showed the highest overall acceptability scores initially and after 4 wk. Therefore, similar amounts of grapefruit seed and natural extracts had the same effect on microbiological analysis and lipid rancidity during sausage storage. Hence, this mixture can serve as a potential natural preservative in meat products.

• Advances in Energy Research
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• 제1권2호
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• pp.147-163
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• 2013

The world faces several issues of energy crisis and environmental deterioration due to over-dependence on single source of which is fossil fuel. Though, fuel is needed as ingredients for industrial development and growth of any country, however the fossil fuel which is a major source of energy for this purpose has always been terrifying thus the need for alternative and renewable energy sources. The search for alternative energy sources resulted into the acceptance of a biofuel as a reliable alternative energy source. This work presents the study of optimization of process of transesterification of vegetable oil to biodiesel using NaOH as catalyst. A $2^4$ factorial design method was employed to investigate the influence of ratio of oil to methanol, temperature, NaOH concentration, and transesterification time on the yield of biodiesel from vegetable oil. Low and high levels of the key factors considered were 4:1 and 6:1 mole ratio, 30 and $60^{\circ}C$ temperatures, 0.5 and 1.0 wt% catalyst concentration, and 30 and 60 min reaction time. Results obtained revealed that oil to methanol molar ratio of 6:1, tranesetrification temperature of $60^{\circ}C$, catalyst concentration of 1.0wt % and reaction time of 30 min are the best operating conditions for the optimum yield of biofuel from vegetable oil, with optimum yield of 95.8%. Results obtained on the characterizzation of the produced biodiesel indicate that the specific gravity, cloud point, flash point, sulphur content, viscosity, diesel index, centane number, acid value, free glycerine, total glycerine and total recovery are 0.8899, 4, 13, 0.0087%, 4.83, 25, 54.6. 0.228mgKOH/g, 0.018, 0.23% and 96% respectively. Results also indicate that the qualities of the biodiesel tested for are in conformity with the set standard. A model equation was developed based on the results obtained using a statistical tool. Analysis of variance (ANOVA) of data shows that mole ratio of ground nut oil to methanol and transesterification time have the most pronounced effect on the biodiesel yield with contributions of 55.06% and 9.22% respectively. It can be inferred from the results various conducted that vegetable oil locally produced from groundnut oil can be utilized as a feedstock for biodiesel production.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2003년도 제27회 추계학술대회
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• pp.44-44
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• 2003

As a basic measurement tool in the areas of animal models of human disease, gene expression and therapy, and drug discovery and development, small animal PET imaging is being used increasingly. An ideal small animal PET should have high sensitivity and high and uniform resolution across the field of view to achieve high image quality. However, the combination of long narrow pixellated crystal array and small ring diameter of small animal PET leads to the degradation of spatial resolution for the source located at off center. This degradation of resolution can be improved by determining the depth of interaction (DOI) in the crystal and by taking into account the information in sorting the coincident events. Among a number of 001 identification schemes, dual layer phsowich detector has been widely investigated by many research groups due to its practicability and effectiveness on extracting DOI information. However, the effects of each crystal length composing dual layer phoswich detector on DOI measurements and image qualities were not fully characterized. In order to minimize the DOI effect, the length of each layer of phoswich detector should be optimized. The aim of this study was to perform simulations using a simulation tool, GATE to design the optimum lengths of crystals composing a dual layer phoswich detector. The simulated small PET system employed LSO front layer LuYAP back layer phoswich detector modules and the module consisted of 8${\times}$8 arrays of dual layer crystals with 2 mm ${\times}$ 2 mm sensitive area coupled to a Hamamatsu R7600 00 M64 PSPMT. Sensitivities and variation of radial resolutions were simulated by varying the length of LSO front layer from 0 to 10 mm while the total length (LSO + LuYAP) was fixed to 20 mm for 10 cm diameter ring scanner. The radial resolution uniformity was markedly improved by using DOI information. There existed the optimal lengths of crystal layers to minimize the variation of radial resolutions. In 10 cm ring scanner configuration, the radial resolution was kept below 3.4 mm over 8 cm FOV while the sensitivity was higher than 7.4% for LSO 5 mm : LuYAP 15 mm phoswich detector. In this study, the optimal length of dual layer phoswich detector was derived to achieve high and uniform radial resolution.