• 한국분말재료학회지
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• 제16권1호
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• pp.56-62
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• 2009

The degree of WC decomposition and hardness of thermally sprayed WC-Co coatings are important factors determining the wear resistance of the coatings. In order to minimize the degree of decomposition and to increase hardness, the effects of processing parameters of high velocity oxyfuel(HVOF) spraying on various characteristics of nanostructured WC-12Co coating have been evaluated by an experimental design method. The HVOF sprayed WC-12Co coatings consisted of various carbide phases including WC, $W_2C$ and $W_3Co_3C$, with a much reduced carbon content. The degree of WC decomposition and decarburization was affected by changing barrel length and spray distance. The hardness of WC-Co coatings was strongly related to droplet temperature at substrate, and increased with increasing fuel addition and/or decreasing spray distance. The effective control of processing parameters was discussed in detail for manufacturing a high performance WC-Co coating.

• Journal of Biosystems Engineering
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• 제19권1호
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• pp.42-49
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• 1994

Texturization of plant protein means the physical or chemical recomposition method of plant protein damaged during the extracting process of soybean oil. As a stable protein supplement, substituted for meat, needs of texturized products have been increased. Twin screw extruder is a very effective tool for texturization process as a physical method. This research, using defatted soy flour as raw material and twin screw extruder manufactured in domestic, showed that plant protein was texturized successfully on the operating conditions of barrel temperature of $120{\sim}140^{\circ}C$, material feed rate of 30~36kg/hr and water content of 20~25%. It also showed that the shape of die affected the texturization continuity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.853-858
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• 2001

Generally, mixed materials of LDPE, EVA and foaming agent are manufactured by crosslinking foaming or chemical foaming process. Above materials were used in a microcellular foaming injection molding process. Influence of each factor such as injection type, temperature of barrel, rate of mixed materials and contents of foaming agent was estimated by DOE(Design of Experiments). As a result of experiments, injection type and rate of LDPE, EVA have an influence on foaming rate. This data can be used in field of application of LDPE and EVA.

• Mycobiology
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• 제33권4호
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• pp.240-242
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• 2005

A soft rot of fruits caused by Mucor racemosus occurred on cherry tomato collected in Agricultural Products Wholesale Market in Jinju, Korea. The disease infection usually occurred wounded areas after cracking of fruits. At first, the lesions started with water soaked and rapidly softened and diseased lesion gradually expanded. Colonies were white to brownish to gray in color. Sporangia were $32{\sim}54\;{\mu}m$ in size and globose in shape. Sporangiophores were $8{\sim}14\;{\mu}m$ in width. Sporangiospores were $5{\sim}12\;{\times}\;4{\sim}8\;{\mu}m$ in size, ellipsoidal to subglobose in shape. Columella was $27{\sim}42\;{\mu}m$ in size, obovoid, ellipsoidal, cylindrical-ellipsoidal, slightly pyriform in shape. Chlamydospores were numerous in sporangiophores and barrel-shaped when young, subglobose in old cultures. Optimum growth temperature was about $25^{\circ}C$. The fungus was identified as M. racemosus Fres.. This is the first report of soft rot on cherry tomato caused by M. racemosus in Korea.

• Food Science and Biotechnology
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• 제14권6호
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• pp.758-765
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• 2005

Instant powders that only require mixing with water prior to consumption can be produced by extrusion for use in products such as instant beverages. Both extrusion processing conditions and particle size of powder are important to end-product characteristics. In this study, a twin-screw extruder was used under various processing conditions (feed moisture, barrel temperature, and screw speed) to produce extrudates from soft wheat flour, which were ground to powders with particle size ranges of less than 93, 93-145, and $145-249\;{\mu}m$. Effects of adding soy lecithin to wheat flour before extrusion were also investigated. Water absorption, solubility, suspension viscosity, and dispersibility of wheat powders were related to specific. mechanical energy measured during extrusion. Powder particle size was important to instant properties, especially ease of dispersal in water and stability to sedimentation. Addition of lecithin significantly improved dispersibility of powders.

• 한국식품조리과학회지
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• 제27권6호
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• pp.745-754
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• 2011

To improve the textural properties of gluten free rice flour based products, the physicochemical and pasting properties of extruded non-waxy rice flours using extruder were investigated. The high yielding Tongil type rice variety, Hanarum was used. Hanarum rice flour was prepared by dry milling from soaked and dried rice grain. The operation conditions of twin screw extruder were 250 rpm of screw speed, $160^{\circ}C$ of barrel temperature, and 24, 27, and 30% of moisture content. Hanarum extruded rice flour (HERF) were lower in crude lipid and ash contents, but higher in crude protein than Hanarum rice flour (HRF). The color values of HERF showed significantly different (p<0.05) with different moisture contents. Water binding capacities, apparent amylose contents, and damaged starch of HERF were higher than those of HRF. Moisture contents affected water binding capacities of HERF. Solubility increased with increasing heating temperature and solubilities of HERF differed significantly (p<0.05). X-ray crystallinity was changed after extrusion cooking and that of HERF showed sharp peaks at $2{\theta}=18-20^{\circ}$. The pasting viscosities of HERF kept lower values (~ 10 RVU) constantly.

• Coupled systems mechanics
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• 제11권2호
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• pp.151-166
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• 2022

Peltier cells have low efficiency, but they are becoming attractive alternatives for affordable and environmentally clean cooling. In this line, the current article develops closed-form and semianalytical solutions to improve the temperature distribution of Bi₂Te₃ thermoelements. From the distribution, the main objective of the current work-the optimal electric intensity to maximize cooling-is inferred. The general one-dimensional differential coupled equation is integrated for linear and quadratic geometry of thermoelements, under temperature constant properties. For a general shape, a piece-wise solution based on heat flux continuity among virtual layers gives accurate analytical solutions. For variable properties, another piece-wise solution is developed but solved iteratively. Taking advantage of the formulae, the optimal intensity is directly derived with a minimal computational cost; its value will be of utility for more advanced designs. Finally, a parametric study including straight, two linear, barrel, hourglass and vase geometries is presented, drawing conclusions on how the shape of the thermoelement affects the coupled phenomena. A specially developed coupled and non-linear finite element research code is run taking into account all the materials of the cell and using symmetries and repetitions. These accurate results are used to validate the analytical ones.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.941-951
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• 2016

The aim of this work is to simulate the thermohydraulic consequences of a main steam line break and to compare the obtained results with Rossendorf Coolant Mixing Model (ROCOM) 1.1 experimental results. The objective is to utilize data from steady-state mixing experiments and computational fluid dynamics (CFD) calculations to determine the flow distribution and the effect of thermal mixing phenomena in the primary loops for the improvement of normal operation conditions and structural integrity assessment of pressurized water reactors. The numerical model of ROCOM was developed using the FLUENT code. The positions of the inlet and outlet boundary conditions and the distribution of detailed velocity/turbulence parameters were determined by preliminary calculations. The temperature fields of transient calculation were averaged in time and compared with time-averaged experimental data. The perforated barrel under the core inlet homogenizes the flow, and therefore, a uniform temperature distribution is formed in the pressure vessel bottom. The calculated and measured values of lowest temperature were equal. The inlet temperature is an essential parameter for safety assessment. The calculation predicts precisely the experimental results at the core inlet central region. CFD results showed a good agreement (both qualitatively and quantitatively) with experimental results.

• 한국식품영양과학회지
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• 제34권2호
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• pp.247-254
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• 2005

본 실험은 홍삼, 백삼, 압출성형 공정변수인 수분함량을 25%와 30%로 달리하여 제조한 압출성형수삼의 화학적 성분을 비교하였다. 조회분, 조지방, 총당의 경우 홍삼, 백삼, 압출성형수삼 간의 차이가 거의 나타나지 않았고, 환원당의 경우 백삼시료에서 다른 처리구보다 낮은 함량을 나타내었다. 아미노산은 수삼을 파쇄하여 7$0^{\circ}C$에서 건조한 수삼(A처리구)에서 낮은 함량을 나타내었고, 수분함량 25%, 배럴 11$0^{\circ}C$, 스크루 회전속도 200 rpm에서 압출성형한 수삼(B처리구)보다 수분함량 30%, 배럴 11$0^{\circ}C$, 스크루 회전속도 200 rpm에서 압출성형한 수삼(C처리구)이 높은 함량을 나타내었다. 조사포닌의 경우에는 A처리구가 4.02%, B와 C처리구가 4.77%, 4.12%이고, 수삼 표피를 제거하지 않은 피부백삼(D처리구)은 3.56%, 수삼 표피를 제거한 피부백삼(E처리구)의 경우는 3.25%, 홍삼(F처리구)은 4.02%로 조사되었다. 총 진세노사이드는 조사포닌의 경우와 유사한 결과를 나타내었다. 즉 A처리구가 6.031 mg/g, B와 C처리구가 8.108 mg/g, 6.876 mg/g으로 조사되었고, D처리구는 7.978 mg/g, E처리구의 경우는 5.591 mg/g, F처리구는 9.834 mg/g로 측정되었다. F처리구에서 홍삼특유 사포닌이라고 알려진 $R_{g3}$가 측정되었다. 말톨의 경우에는 홍삼과 압출성형수삼 처리구에서만 관찰되었다. 산성다당체는 압출성형에 의해 2∼3% 증가하였다. 결론적으로 압출성 형수삼은 홍삼의 성분과 유사한 결과를 나타내었으며, 압출성형공정변수의 변화를 통해 홍삼에 포함된 홍삼특유 사포닌인 $R_{g3}$도 전환될 수 있을 것으로 판단되었다.

• 산업식품공학
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• 제15권2호
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• pp.155-161
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• 2011

본 실험은 압출성형을 통한 저DE덱스트린 제조공정을 확립하기 위해서 수분함량 25, 35% 배럴온도 100, $120^{\circ}C$, 스크루 회전속도 150, 250 rpm에서 압출성형한 전분을 알 파아밀라아제로 당화시켰을 때 당화특성을 연구하였다. 수 분용해지수는 원료전분 수분함량이 25%로 감소할 경우 증 가되었으며, 수분흡착지수도 수분의 감소와 함께 전체적으 로 증가하였다. 환원당함량의 경우 수분함량이 낮고 배럴온 도 높을수록 증가되었다. 120 분간 당화 후 DE 63.8로 높 게 나타났다. 비기계적 에너지 투입량(SME)의 증가와 함께 수분용해도는 증가하는 경향이었다. 또한 수분함량의 감소 와 함께 비기계적 에너지 투입량과 수분용해도는 증가하였 다. 페이스트점도는 원료전분의 수분이 낮고, 스크루 회전 속도가 증가할수록 전분사슬의 절단에 따라 저온최고점도 가 감소하는 경향을 보였다. 초기반응속도는 수분함량이 25%로 낮고 배럴온도 $120^{\circ}C$, 스크루 회전수 250 rpm에서 $2.26{\times}10^{-3}mmol/mL{\cdot}min$로 가장 높았다. 시중 호화전분 $1.83{\times}10^{-3}mmol/mL{\cdot}min$에 비해서도 높은 결과를 보였다. 당화속도상수는 히구치모델을 응용하였으며, 수분함량이 낮 고 배럴온도가 $120^{\circ}C$일 때 전체적으로 높게 나타났다. 본 실험에서 초기반응속도, 당화속도상수, 당화수율 등을 고려 할 때, 최적조건은 수분함량 25%, 배럴온도 $120^{\circ}C$, 스크루 회전속도 250 rpm이었다.