• 소성∙가공
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• 제23권3호
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• pp.145-150
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• 2014

Precision control of the slab is crucial for product quality and production economy in hot strip mills. The current study presents a new model for predicting width spread of a slab with a rectangular cross section during roughing. The model is developed on the basis of the extremum principle for a rigid plastic material and a three dimensional admissible velocity field. This model incorporates the effect of process variables such as the shape factor and the ratio of width to thickness. We compare the results of this model to 3-D finite element (FE) process simulations and also to results from a previous study.

• Journal of the Korean Wood Science and Technology
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• 제15권4호
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• pp.64-68
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• 1987

To develope the utilities of the chestnut bur, which is wasted after harvesting chestnut in farmhouses, the feasibilities of adhesion(urea resin) extenders of the powder for plywood were examined. These experiments were implemented on experimental scale at Forestry Research Institute(Seoul) and on a plywood mill scale at Eugon Industrial Co LTD(Inchon) for more reliable data. In this paper, it was proved that the chestnut bur powder caused to rise the glue viscosity but the chaff powder to down reversely. The most effective mixing ratio were wheat flour 5kg, chaff powder: 5kg and chestnut bur powder. 5kg per 100kg of urea resin. At this condition, the viscosity were most appropriate (1,320 2,230 cps) for glue spreading operations, and the dry shear strengthes were most adequate(10.7-13.2kg/$cm^2$), wood failure ratio 82-88%). The chestnut bur powder, can be utilized for plywood adhesion extenders without any change of present process lines in plywwod mills.

• 한국해양공학회지
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• 제11권3호
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• pp.56-68
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• 1997

This work was intended to study the effect of a partial pressure ratio and a total pressure of reactive gases on the properties of TiC$_{x}$N$_{1-x}$ . coated layer. In this regard, various TiC$_{x}$N$_{1-x}$ coatings were synthesized with C2112 and N2 Mixture gas of different compositions by Arc Ion Plating process which has been highlighted for an industrial purpose. It was revealed from colors and X-ray diffraction patterns that the concentration of carbon of a TiC$_{x}$N$_{1-x}$ coating increases with a partial pressure ratio (PC$_{2}$H$_{2}$/PN$_{2}$) as well as a total pressure Of $C_{2}$H$_{2}$ and N$_{2}$ mixture gas. Accordingly, the hardness of TiC$_{x}$N$_{1-x}$ coated layer increased but the adhesion to the substrate of SKH 51 was degraded. On the other hand, the deposition rate was independent of a partial pressure ratio and a total pressure of mixture gas. It was found that a uniform gas distribution is critical for an industrial application since the composition of a coating depends strongly on the location of a substrate inside of the furnace. As a result of milling tests with different TiC$_{x}$N$_{1-x}$ coated end mills, the one which has a low carbon concentration was better than others studied in this work.d in this work.

• 한국콘텐츠학회논문지
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• 제15권7호
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• pp.428-435
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• 2015

우리 기업의 타인자본조달에 관한 통계지표를 살펴보면 대기업은 은행의 기업대출과 회사채 등의 직접금융을 함께 사용하여 자본을 조달하고 있는 반면, 중소기업은 은행대출에 계속 의지하고 있음을 확인할 수 있다. 이러한 현실을 감안하여 본 연구에서는 기업의 타인자본조달을 실증분석하는데 있어 표본선택편의가 존재하고 이를 감안한 연구모형을 사용해야 한다고 주장한다. 이러한 주장을 뒷받침하기 위해 1990년부터 2013년까지의 상장기업 자료를 통해 부채구조를 설명하는 실증분석을 수행한 결과 선행연구에서와 마찬가지로 기업의 회사채사용에 있어 기업규모, 1대주주 지분율, 유형자산 구성비, 수익성, 배당성향 등이 영향을 미치고 있음을 확인할 수 있었으며, 패널표본선택모형에 투입된 Inverse Mills Ratio 변수가 유의하게 나타나 패널표본선택모형을 사용하는 것이 타당함을 확인하였다. 이러한 결과는 기업의 타인자본조달에 있어 표본선택편의가 존재하며 이에 관한 연구에서 이를 반드시 감안해야 함을 의미한다.

• 대한기계학회논문집A
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• 제29권9호
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• pp.1270-1275
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• 2005

Rolling process to fabricate a strip with even thickness is significant to enhance the quality of the strip. The thickness of a strip can be effectively controlled by pair-cross mills. However, pair-cross mill generates thrust in the axial direction of roller and causes skewness, deflection, twist and even accidental roll chock failure. Therefore, accurate estimation of the thrust of the pair-cross mill during rolling process is necessary to monitor the failure of roll and the quality of products. An empirical equation given by Mitsubishi Heavy Industry (MHI) is hitherto employed, where the thrust is expressed in terms of rolling force, reduction ratio and crossed angle. However it turns out that the MHI empirical equation provides somehow inaccurate and unsuitable thrust in practical rolling processes. Moreover, we learn that three parameters involved in MHI equation are coupled each other. In this paper, axiomatic design principle is employed to select appropriate parameters involved in approximate equation in order to make parameters uncoupled. A quadratic equation using response surface method with new parameters is suggested. The accuracy of the approximate model is examined by comparing with real experimental data.

• 펄프종이기술
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• 제47권2호
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• pp.34-41
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• 2015

Recovered paper has been widely used as a main raw material of papermaking in Korea. Recycling of recovered paper helps to reduce production cost and preserve an environment. To recycle recovered paper efficiently, de-inking is a key process in recycling mills. De-inking process would be affected by various influencing factors such as the type of de-inking agent, mixed ratio of recovered paper, season, and process conditions. In this study, fatty acid and nonionic surfactant were used as the de-inking agent in froth-flotation process of mixed recovered paper. De-inking properties of mixed recovered paper were investigated according to the addition level of each chemical. Nonionic surfactant had a small effect on de-inking efficiency of mixed recovered paper due to decreased reject. As the additional level of fatty acid increases, fragmented ink particles increased and then optical properties of recycled paper decreased because fragmented ink particles adsorbed onto the fiber surface.

• Asian-Australasian Journal of Animal Sciences
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• 제11권5호
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• pp.597-607
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• 1998

Processing is generally employed to alter the physical and chemical properties of feeds used in pig diets, using hammer/roller mills, pellet mills and extruders/expanders. The reported optimum particle sizes of corn are approximately $500{\mu}m$, $500-700{\mu}m$, $400-600{\mu}m$, for nursery, growing-finishing, and breeder pigs respectively. Optimum particle size of grains are affected by diet complexity. There was a trend towards reducing particle size in order to increase ADG in pigs fed a simple diet, though such was not the case for pigs fed a complex diet. Uniformity of particle size also affects the nutritional values of swine feeds. Uniform particle sizes would consistently give greater nutrient digestibilities. In terms of pellet quality, it is reported that a higher incidence of fmes in pelleted feeds has a direct correlation with poorer feed conversion ratio in pigs. Particle and pellet sizes are also very important for pelleting in terms of grinding, digestibility, stomach ulceration and pellet durability. A particle size of $600{\mu}m$, or slightly less, seemed optimal for com in fmishing pigs, and the 5/32 in. diameter pellets supported the best efficiencies of gain during nursery and finishing phases. Extruder and/or expander processes would allow the feed industry an increased flexibility to utilize a wider spectrum of feed ingredients, and improve pellet quality of finished feeds. It would appear that extruded or expanded diets containing highly digestible ingredients have little effect on the growth performance of pigs, and the feeding values of the feeds over pelleted diets were not improved as pigs grew. The extruder or expander is much more effective than a pelletizer in salmonella control. Gastric ulcerations and/or keratinizations were consistently reported in pigs fed mash and processed diets containing finely ground grains, whereas carcass quality was not affected by diet processing methods such as pelleting, extruding or expanding. In corn- or sorghum-based diets, the electrical energy consumption is 4-5 times higher in the expanding than in the pelleting process. But the expander's processing cost was half of that shown by an extruder. Finally, the decision of which feed processing technology to adopt would depend on the processing cost, and any potential improvement in growth performance and digestibilities of nutrients should offset the increased operating and capital costs related to the extruder/expander technology over mash or pelleting processes in pigs.

• 펄프종이기술
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• 제39권4호
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• pp.61-67
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• 2007

Paper sludges collected from three different paper mills were physico-chemically analyzed in order to use them as raw materials for making bed soils and seedling pots. The sludge from a fine paper mill contained lots of inorganic pigment particles used for coating, as those from a newsprint mill and a tissue mill had not. It was clearly through XRD analysis confirmed that all sludges included calcium carbonate. The paper sludge from the tissue mill contained the greatest amount of particles, which would contribute to water absorption and nutrient storage. The sludge from the fine paper mill had the highest density due to many inorganic elements. While the ash content and the total nitrogen content were the highest in the sludge from the fine paper mill, the C/N ratio was the lowest in the fine paper mill sludge. All sludges seemed to have insufficient contents of potassium. The sludges from the newsprint mill and the tissue mill showed more silicon contents than that from the fine paper mill. It was concluded that the sludge from the fine paper mill would be able to be the most efficient raw materials for making bed soils and seedling pots and the other two sludges would be more efficient for intensive culture for crops such as rice and grain with additional supplement of nitrogen and other nutrients.

• Steel and Composite Structures
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• 제46권1호
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• pp.75-92
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• 2023

The novel composite cold-formed steel (CFS)/engineered cementitious composites (ECC) beams have been recently presented. The new composite section exhibited superior structural performance as a flexural member, benefiting from the lightweight thin-walled CFS sections with improved buckling and torsional properties due to the restraints provided by thinlayered ECC. This paper investigated the shear performance of the new composite CFS/ECC section. Twenty-eight simply supported beams, with a shear span-to-depth ratio of 1.0, were assembled back-to-back and tested under a 3-point loading scheme. Bare CFS, composite CFS/ECC utilising ECC with Polyethylene fibres (PE-ECC), composite CFS/MOR, and CFS/HSC utilising high-strength mortar (MOR) and high-strength concrete (HSC) as replacements for PE-ECC were compared. Different failure modes were observed in tests: shear buckling modes in bare CFS sections, contact shear buckling modes in composite CFS/MOR and CFS/HSC sections, and shear yielding or block shear rupture in composite CFS/ECC sections. As a result, composite CFS/ECC sections showed up to 96.0% improvement in shear capacities over bare CFS, 28.0% improvement over composite CFS/MOR and 13.0% over composite CFS/HSC sections, although MOR and HSC were with higher compressive strength than PE-ECC. Finally, shear strength prediction formulae are proposed for the new composite sections after considering the contributions from the CFS and ECC components.

• 한국결정성장학회지
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• 제18권6호
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• pp.264-270
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• 2008

산업현장에서 발생되는 다양한 종류의 폐기물을 이용하여 에코골재를 제조하였다. 에코골재는 폐기물을 분쇄하고 조립성형 후, 로타리 킬른에서 $1125^{\circ}C$/15 min의 조건으로 소성하여 제조되었다. 본 연구진에 의해 제조된 에코골재 K73(Coal bottom ash 70 wt%: Dredged soil 30 wt%)과 K631(Clay 60 wt%: Stone sludge 30 wt%: Spent bleaching clay 10 wt%)을 이용하여 경량 콘크리트 흡음재를 제조하였으며, 비교를 위해 독일에서 수입된 DL(독일산 'L'사 인공경량골재)을 이용한 흡음재 역시 같은 조건으로 제조하였다. 골재의 종류, 물-시멘트비(W/C=20, 25, 30%) 그리고 설계 공극률(20, 25, 30%)의 변화에 따른 흡음특성변화를 관찰하였다. 실험결과, 경량 콘크리트 흡음재의 실제 공극률은 설계 공극률보다 $5{\sim}10%$ 정도 높게 나타났다. 임피던스관을 이용한 흡음재의 흡음계수 측정 결과, K631골재를 이용한 경량 콘크리트 흡음재(W/C=20%, V=25%)가 1000, 3150 Hz에서 각각 0.88의 흡음계수를 나타내었다.