• Journal of Biosystems Engineering
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• 제26권5호
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• pp.469-474
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• 2001

Milling the rice with low moisture requires more energy, produces more cracked rice, and results in reducing taste of cooked rice. Accordingly, it is necessary to add moisture to the rice with low moisture to obtain optimum moisture level for milling and taste of rice. This study was performed to evaluate the influence of initial moisture content and absorption rate on rice crack, milling energy and whiteness of milled rice and to obtain the information for design of rewetting system mounted on stirring device in grain bin. The tests were conducted for the four levels of initial moisture content in the range of 11.4 to 14.5%(w.b.) and six levels of absorption rate in the range of 0.04 to 1.0%, w.b./hr. In the case of lower moisture content below 12%(w.b.), crack ratios of brown rice were remarkably high regardless of initial moisture contents. Therefore, it was found that rough rice below 12%(w.b.) in initial moisture content could not rewetted by spraying water without crack generation of low level. Absorption rate must be below 0.3%, w.b./hr to maintain crack ratio increase of less than 1% regardless of initial moisture contents. In the case of allowable crack ratio increase of 2% and 5%, it was found that the maximum absorprion rate was respectively 0.6%, w.b./hr and 1.0%, w.b./hr in the initial moisture content of above 13.5%(w.b.). Rewetting the rough rice in moisture content of 11.4 to 14.5%(w.b.) to 14.3 to 16.9%(w.b.) decreased milling energy consumption by 15.9 to 22.3%. The effect of energy saving was higher in the samples of higher initial moisture content. Whiteness of milled rice was decreased by 0.5 to 1.5.

• Journal of Biosystems Engineering
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• 제27권2호
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• pp.89-96
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• 2002

The trend of consumption of vegetable soybeans is increasing because they are recognized as the clean vegetable. The works requiring the most intensive labor are threshing and seperation ones, and they form about 80% of total labour for vegetable soybeans production. It is necessary to develop the vegetable soybeans-thresher for the sake of cost down of vegetable soybeans production. The purpose of this study is to acquire the basic informations to design of the vegetable soybeans-thresher. We make the experimental system which control the speed of threshing cylinder and the teeth gap and investigate the detachment forces. The result are as follows ; The ratio of un-threshed soybeans-pod to stem after threshing work is decreasing as the threshing cylinder speed increases: 0.0% and 2.8% at 55m/s and 18m/s of threshing cylinder speed respectively. Also the ratio of un-threshed soybeans-pod to stem is shown as 2.0% below in the condition of 64~160mm of teeth gap and over 28m/s of threshing cylinder speed. The damaged pod ratio of detached soybeans after threshing work is decreasing as the threshing cylinder speed increases: 4.8% and 1.3% at 55m/s and 18m/s of threshing cylinder speed respectively. The minimum damaged pod ratio of detached soybeans are shown as 1.0%, 1.5% and 1.9% at 18m/s, 28m/s and 37m/s of threshing cylinder speed respectively. The average detachment forces of pods are shown as 1.5kg$_{f}$ for 3 grains, 1.2kg$_{f}$ for 2 grains and 0.8kg$_{f}$ for 1 grain respectively. The maximum detachment force of pod is shown as 2.7kg$_{f}$ for 3 grains. grains.

• Journal of Biosystems Engineering
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• 제10권2호
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• pp.55-62
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• 1985

박(朴)(1982, 1983, 1984 및 1985)이 개발(開發)한 배합사료공장(配合飼料工場)의 투자비용(投資費用) 및 운전비용(運轉費用)의 수학적모형(數學的模型)을 이용(利用)하여, 배합사료공장(配合飼料工場)의 적정(適正) 시스템의 설계(設計)를 예(例)를 들어 소개하였다. 적정(適正)시스템의 설계(設計)를 위(爲)하여 비선형(非線型) 프로그램의 "Single Objective Programming Problem(단일목적함수(單一目的函數))"와 "'Multiple Objective Decision Making Method(다목적함수(多目的函數))"의 2가지 방법(方法)을 적용(適用)하였다. Single Objective Programming Problem에서는 "Generalized Reduced Gradient(GRG) Method"를 이용(利用)하였고, Multiple Objective Decision Making Method(MODM)에서는 "Interactive Nonlinear Goal Program(INGP)"를 이용(利用)하였으며 그 결과(結果)는 다음의 몇가지로 요약(要約)할 수 있다. 1. 박(朴)이 개발(閒發)한 수학적(數學的) 모형(模型)들은 2 가지 방법(方法) 모두 사료공장(飼料工場)의 최적화(最適化) 설계(設計)에 효과적으로 이용(利用)할 수가 있었다. 2. MODM방법(方法)에 의(依)하여 얻어진 최적(最適)시스템은 Single Objective Program Problem에서 구(求)한 결과(結果)보다 균형(均衡)이 있는 시스템이었으며 장래(將來)의 사료원료(飼料原料), 사료구매시장(飼料購買市場), 기타 다른 조건(條件)들의 변화)에 대(對)해서 보다 탄력(彈力)이 있는 시스템으로 나타났다. 3. 엄밀한 의미(意味)에서 절대적(絶對的)인 최적사료공장(最適飼料工場)이란 있을 수 없으며, 주위의 조건(條件), 원료가격(原料價格), 사료가격(飼料價格), 공장주(工場主)의 취향 및 설계조건등(設計條件等)에 따라 최적(最適) 시스템은 각각(各各) 다르게 나타난다.

• 대한조선학회논문집
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• 제53권2호
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• pp.85-91
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• 2016

The most important factor in the structural design of ships and offshore structures operating in arctic region is ice load, which results from ice-structure interaction during the ice collision process. The mechanical properties of ice related to strength and failure, however, show very complicated aspect varying with temperature, volume fraction of brine, grain size, strain rate and etc. So it is nearly impossible to establish a perfect material model of ice satisfying all the mechanical characteristics completely. Therefore, in general, ice collision analysis was carried out by relatively simple material models considering only specific aspects of mechanical characteristics of ice and it would be the most significant cause of inevitable errors in the analysis. Especially, it is well-known that the most distinctive mechanical property of ice is high dependency on strain rate. Ice shows brittle attribute in higher strain rate while it becomes ductile in lower strain rate range. In this study, the simulation method of ice collision to ship hull using the nonlinear dynamic FE analysis was dealt with. To consider the strain rate effects of ice during ice-structural interaction, strain rate dependent constitutive model in which yield stress and hardening behaviors vary with strain rate was adopted. To reduce the huge amount of computing time, the modeling range of ice and ship structure were restricted to the confined region of interest. Under the various scenario of ice-ship hull collision, the structural behavior of hull panels and failure modes of ice were examined by nonlinear FE analysis technique.

• 항공우주시스템공학회지
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• 제15권3호
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• pp.87-92
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• 2021

본 연구에서는 plunger 타입 유량조절장치를 적용한 가스발생기의 지상연소시험에서 발생한 현상에 대하여 해석적 접근을 수행하였고, 추후 가스발생기 설계에 요구되는 설계인자를 파악하였다. 토출관 내 연소 생성물이 부착되지 않은 경우의 압력상승은 콘 형태의 침식연소를 가정한 해석 결과와 경향이 유사하였으며, 다른 시험 결과에서의 압력상승은 침식연소와 함께 토출관 내 연소 생성물 부착에 따른 토출 특성 변화를 가정하여 해석한 결과와 유사한 경향을 보였다. 또한, 동일한 토출 특성 변화 상수에 대해 압력지수의 영향을 비교한 결과, 지상연소시험에서 수행한 그레인 형상과 토출면적에 대해 압력지수 0.45 이상의 경우에 연소 생성물 부착이 연소실 압력에 미치는 영향이 매우 큰 것으로 파악되었다.

• Geomechanics and Engineering
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• 제17권1호
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• pp.81-95
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• 2019

Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextiles may encounter severe stresses which can be higher than they will experience in-service. This paper aims to investigate the installation damage of geotextiles, in order to obtain a good approach to the estimation of the material's strength reduction factor. A series of full-scale tests were conducted to simulate the installation process. The study includes four deliberately poorly-graded backfill materials, two kinds of subgrades with different CBR values, three nonwoven needle-punched geotextiles of classes 1, 2 and 3 (according to AASHTO M288-08) and two different relative densities for the backfill materials. Also, to determine how well or how poorly the geotextiles tolerated the imposed construction stresses, grab tensile tests and visual inspections were carried out on geotextile specimens (before and after installation). Visual inspections of the geotextiles revealed sedimentation of fine-grained particles in all specimens and local stretching of geotextiles by larger soil particles which exerted some damage. A regression model is proposed to reliably predict the installation damage reduction factor. The results, obtained by grab tensile tests and via the proposed models, indicated that the strength reduction factor due to installation damage was reduced as the median grain size and relative density of the backfill decreases, stress transferred to the geotextiles' level decreases and as the as-received grab tensile strength of geotextile and the subgrades' CBR value increase.

• 한국재난정보학회 논문집
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• 제15권2호
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• pp.206-213
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• 2019

연구목적: 본 연구에서는 친환경 소재인 알톱밥과 EPDM칩을 사용하여 친환경 포장재의 개발을 목적으로 한다. 연구방법: 친환경 재료로 환경적으로 문제가 없고, EPDM칩을 사용함으로써 보행감을 높이며, 알톱밥에 소금물 혼합 우드스테인과 우레탄바인더를 혼합하여 내구성을 향상시킨다. 연구결과: 배합설계 시험을 통하여 최적 배합비를 산출하였고, 배합비를 바탕으로 세립의 알톱밥과 EPDM칩을 사용하여 보도의 표층재, 단입도의 알톱밥만을 사용하여 투수성과 반탄력을 갖춘 보도의 기층재 및 자전거도로의 표층재로 구성하였고 시험시공을 통해 적용공법을 제시하였다. 결론: 본 연구를 통해 기존의 탄성포장재와 달리 휨강도를 제시하고 우수한 투수계수를 나타냄으로 보도포장재로서 경제적인 시공이 바로 가능할 것으로 판단된다.

• Journal of Animal Science and Technology
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• 제63권5호
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• pp.1018-1033
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• 2021

In this study, we aimed to assess the effect of flaking on the nutrient digestibility of corn grain in ruminants. In this regard, in vitro rumen fermentation, in situ rumen degradability, and in vivo metabolic experiments were performed. The automated gas production technique was used for the in vitro fermentation experiments. Six types of corn flakes with various degrees of gelatinization (32%, 41%, 48%, 66%, 86%, and 89%) were ground and incubated in rumen fluid to measure rumen fermentation characteristics and digestion rate. The in situ degradability of ground corn, whole corn, and corn flakes with 62% and 66% gelatinization was measured by incubation in the rumen of two cannulated Holstein cows. In vivo metabolic experiments were performed using 12 crossbred goats (29.8 ± 4.37 kg) using a 3 × 3 Latin square design. The dietary treatments consisted of ground corn and flaked corn with 48% or 62% gelatinization. In vitro experiments showed that as the degree of gelatinization increased, the digestion rate increased linearly, while the discrete lag time decreased linearly (p < 0.05). The effective rumen dry matter degradability, determined by in situ fermentation, was 37%p lower in corn flakes than ground corn, assuming a passage rate of 6%/h (p < 0.01), and there was no difference between the two flakes. In the in vivo experiment, there was no difference in dry matter intake, average daily gain, feed efficiency, and nitrogen utilization among the treatment groups (p > 0.05); however, the crude fat digestibility was lower for corn flakes than for ground corn (p < 0.05). To summarize, the rate of fermentation of corn flakes increased as the degree of gelatinization increased. However, non-ground corn flakes had lower rumen digestibility and did not improve in vivo apparent nutrient digestibility, compared with ground corn. In contrast to the assumption that flaked corn provides more energy to ruminant animals than ground corn, we conclude that the digestibility and energy value of corn flakes are lower than those of ground corn if mastication does not sufficiently reduce the particle size of corn flakes.

• The Journal of Advanced Prosthodontics
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• 제14권2호
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• pp.96-107
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• 2022

PURPOSE. Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this in vitro study. MATERIALS AND METHODS. Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HT^White (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 "Dentistry - Ceramic materials", were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A₁ and Group B₁) were merely the sintered specimens. The specimens of the second subgroups (Group A₂ and Group B₂) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A₁/A₂, and B₁/B₂) was evaluated by the t-test. In all tests, P values smaller than 5% were considered statistically significant. RESULTS. A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant. CONCLUSION. The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.

• 한국추진공학회지
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• 제24권4호
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• pp.1-11
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• 2020

본 연구에서는 추진제 연소면적을 조절하여 이중추력 프로파일을 구현하는 단일연소관 이중추력 로켓모터의 내탄도성능 분석 방법을 제시한다. 천이 구간에서의 연소속도 보정계수 및 비추력의 점진적 변화를 고려하며 성능 예측에 필요한 변수를 획득할 수 있는 분석법을 제시하고, 해당 분석법을 적용한 결과와 천이 구간 내 변화를 고려하지 않는, 기존 연구의 분석법을 적용한 결과를 비교함으로써 새로 제시하는 분석법에서 개선된 부분을 확인한다. 추진제 초기 온도 또는 배치 조건이 다른 네 가지의 시험 조건에 대하여 제시하는 분석법을 이용해 내탄도 변수를 획득하고, 이를 이용하여 각 시험 조건별로 성능 예측을 수행한다. 해당 예측 결과는 실제 연소시험 결과와 잘 일치하며, 따라서 본 연구의 분석법을 기반으로 설계 형상이 동일한 이중추력 모터의 성능 예측이 가능함을 확인할 수 있다.