• 한국수소및신에너지학회논문집
• /
• 제30권1호
• /
• pp.1-7
• /
• 2019

The preparation and catalytic activities of various transition metal carbide crystallites (VC, MoC, WC) were examined in this study. In particular, the effect of different kinds of transition metal crystallites were scrutinized on the ammonia decomposition reaction. The experimental results showed that BET surface areas ranged from $8.3m^2/g$ to $36.3m^2/g$ and oxygen uptake values varied from $9.1{\mu}mol/g$ to $25.4{\mu}mol/g$. Amongst prepared transition metal carbide crystallites, tungsten compounds (WC) were observed to be most active for ammonia decomposition reaction. The main reason for these results were considered to be related to the extent of electronegativity between these materials. Most of transition metal carbide crystallites were exceeded by Pt/C crystallite. However, the steady state reactivities for some of transition metal carbide crystallites (WC) were comparable to or even higher than that determined for the Pt/C crystallite.

• Journal of Animal Science and Technology
• /
• 제65권1호
• /
• pp.197-208
• /
• 2023

The objective of this study was to investigate the effects of a traditional dry period (60 d) versus a no dry period (0 d) on the milk production, physiological response, and metabolic status of dairy cows exposed to heat stress during the transition period. Holstein dairy cows (n = 15) with similar expected calving dates were randomly assigned to two different dry period lengths: (1) no dry period (n = 7) and (2) a traditional dry period of 60 days (n = 8). All cows were studied from 8 weeks before expected calving to 10 weeks after calving and experienced heat stress during the transition period. The results showed that cows with no dry period decreased their milk yield in subsequent lactation, but compensated for the loss of milk yield accounted for by additional milk yield before calving. The energy balance at postpartum was improved in cows with no dry period compared to cows with a traditional dry period. There were no significant differences in the physiological response and blood metabolites at postpartum between the dry period lengths of dairy cows exposed to heat stress during the transition period. Taken together, our results showed that omitting the dry period improved the milk production and metabolic status of dairy cows exposed to heat stress during the transition period.

• Asian-Australasian Journal of Animal Sciences
• /
• 제24권4호
• /
• pp.479-484
• /
• 2011

The study was conducted on 20 Holstein X Sahiwal cross bred dairy cows, with an average milk production of $2,752{\pm}113.79$ liters in $284{\pm}5.75$ days during a single lactation, that were divided in to two groups of 10 animals. We investigated the oxidative stress and antioxidant status during the transition period in dairy cows. In this study, plasma level of MDA was considered as an indicator of lipid peroxidation and SOD, catalase, GSH and GSHPx as antioxidants. The lipid peroxidation was significantly (p<0.001) higher in cows during early lactation as compared to the cows in advanced pregnancy. A significant positive correlation (r = +0.831, p<0.01) was determined between MDA and catalase in early lactating cows. In early lactating cows, blood glutathione was significantly lower than in advanced pregnant cows. However, early lactating cows showed non-significant negative correlation for all antioxidant enzymes with lipid peroxidation. In conclusion, dairy cows seemed to have more oxidative stress and low antioxidant defense during early lactation or just after parturition than advanced pregnant cows, and this appears to be the reason for their increased susceptibility to production diseases (e.g. mastitis, metritis, retention of fetal membranes etc.) and other health problems.

• 기술혁신연구
• /
• 제15권2호
• /
• pp.61-81
• /
• 2007

A typical small firm in consumer goods sectors of developing countries is an OEM supplier to big MNCs. Lacking design and marketing capability, a small firm relies on the MNCs for survival but their long term growth is not guaranteed as the MNCs are always looking for, and ready to relocate to, cheaper production sites. In this light, we can say that there is something like "OEM trap" from which most firms from LDCs find difficult to move out (Lee 2005). In this situation, one way for long term growth and catch-up is to make a transition to the OBM (own brand manufacturer). But, the transition is not easy or even risky. This paper analyzes the cases of three companies in Korea to find out common features in their successful transition to OBM. They are Aurora World (a flush toy maker), Hankook Chinaware (a chinaware maker), and Hanacobi (a plastic-made food container maker with the Lock-and-Lock brand). These firms can be commonly characterized by 1) arranging access to external knowledge base and steady increase of in-house R&D efforts and capabilities leading to acquisition of formal IPRs and their management, and 2) establishment of global production networks with factories in lower-income countries as well as their own independent global marketing network.

• 자원ㆍ환경경제연구
• /
• 제29권4호
• /
• pp.443-468
• /
• 2020

전기차 관련 기술 발달과 보급 확대로 화물, 이륜차 등 일반승용 부문을 넘어 육상수송 전반에 걸친 연료전환 효과가 발생하고 있다. 본 연구는 대도시에서 긴 주행거리를 운행하는 사업용 승용차(택시)의 연료전환에 따라 발생하는 대기환경편익을 택시의 운행특성과 충전전력의 발전원별 비중을 동시에 반영하여 추정하였다. 분석 결과 LPG를 연료로 하는 택시의 연료 전환 효과는 제8차 전력수급기본계획을 기초로 한 발전원별 비중을 고려했을 때 약 21.5원/km로 분석되었으며, 택시 한 대가 출고되어 폐차될 때까지의 전체 운행거리를 기준으로 할 때 약 860만 원 수준으로 추정되었다. 이러한 연구 결과는 최근 국내외에서 활발히 추진되고 있는 재생에너지발전 및 전기자동차 보급 확대 정책의 필요성 및 당위성을 보여준다.

• 대한산업공학회지
• /
• 제11권2호
• /
• pp.1-9
• /
• 1985

In this study, two stage transfer line with limited repair capability is modeled to formulate optimal dynamic repair priority policy. The method of Markov Chains is used to analyze the analytical model of this line. An efficient algorithm is developed, utilizing the block tridiagonal structure of the transition probability matrix, to obtain the steady state probabilities and system performance measures, such as the steady state production rate of the line and the average in-process inventory in the interstage buffer.

• 한국응용곤충학회지
• /
• 제4권
• /
• pp.1-6
• /
• 1965

In Korea the most important plant industry is the rice-growing but she has not yet attained self-sufficiency with regard to rice which is the basic food of Korean. In the past, various measures of increasing rice production have been tried with some success but the increasing rate of did not show the sufficient result. Judging from experiences, disease control may be the most important factor which has influence on increasing of rice production in Korea. During the past 60 years three periods divided by the transition of rice diseases were noted, and especially the recent transition attracted much attention . That is, sheath blight and stripe which were minor diseases in the past have promptly spread all over the country and caused heavy losses to rice plant, and also local outbreak of bacterial leaf blight and dwarf were noticed. Various environmental factors are related to such transition of rice disease. Above all, cultivated varieties susceptible to these diseases, increase of application of nitrogenous fertilizer, earlier transplanting and density of transplanting are considered to be lucre closely related to the development of these diseases and successive development of blast. On the other hand. application of forage fungicides such as organic mercury compounds specific to blast contributed to reduce prevalent area if blast in spite of wide spread of susceptible varieties and increase of application of nitrogenous fertilizer. These facts were confirmed by Korean investigators At the present which various diseases to control coexist in the same region, no one variety resistant to all of these diseases is provided and cultural practices for the control of these diseases often do not produce sufficient yield of rice. it is emphasized that a role of pesticides is very great.

• 한국기계가공학회지
• /
• 제19권6호
• /
• pp.29-35
• /
• 2020

Transition Nozzles are used in industrial air-cooled heat exchangers and widely used in industrial sites as an important component in the heat energy transfer between a heat source and an actuating fluid. There is a worldwide demand for transition nozzles with various materials and shapes, depending on the use environment. This paper aims to improve the transition nozzle forging process suitable for the production of many varieties using Steps 1 to 6 of the TRIZ Methodology for Problem Solving. By utilizing the TRIZ Methodology, this study derives a method to design a variable mold, which is more efficient and can reduce costs compared with having to use several molds. To verify the suitability of the methods derived using the TRIZ technique, a forging analysis is performed on a transition nozzle using DEFORMⓇ, a commercial program for plasticity analysis, and the nozzle material is evaluated for damage as a result of deformation of the transition nozzle thickness. The derived methods can be applied to transition nozzle formation equipment to improve the efficiency of the formation process.

• 천문학논총
• /
• 제13권1호
• /
• pp.129-134
• /
• 1998

Observations of the J=1-0 transition line of HCN were made at the center of Comet C/1995 O1 (Hale-Bopp) from November, 1996 to April, 1997 with the 14-m radio telescope at the TRAO (Taeduk Radio Astronomical Observatory). From the obtained data, an HCN production rate at each observed date was derived. The rapid variation of the HCN production rate near the perihelion was detected, and it is thought to be caused by jet(s) from the nucleus. The correlation between the visual magnitude and the HCN production rate is found to be $Q_{HCN}=27.03-0.11(m_v-5log{\Delta})$.

• 한국유기농업학회:학술대회논문집
• /
• 한국유기농업학회 2001년도 심포지엄
• /
• pp.192-206
• /
• 2001

A major challenge in the transition from conventional to organic production in a grain intensive region such as the Com Belt legion of the U.S.A. is how to profitably select and manage a crop relation. The opportunity cast of forgoing grain production for forage and green manure crops is significant. Many organic researchers and writers emphasize the need to bring an animal enterprise into the farming system for diversification and enhanced labor utilization. Livestock also add value to grain and forage crops to offset decreased grain production and can recapture nutrients used in crop production that can be recycled through manure. In grain intensive regions, organic farmers should consider swine production as a natural fit for the farming system. Swine are very efficient and adaptable animals that can add value to both grain and forage crops. While somewhat lacking, there is a reasonable body of literature on organic and sustainable swine production. However, there is relatively little specific information available to organic farmers to assist in the initial decision to enter organic swine production and to evaluate marketing alternatives. The primary focus of this paper is to give some background on organic animal production(emphasis on swine) in the Central United States and outline production and marketing decisions and considerations, relative to market trends, demographics and standards(U.S.). At the farm level, decisions must be made regarding resources, such as land, labor, financial and social capital, all relative to opportunities, all in the context of the standards and market forces beyond the farm. At the personal level the farmer must also make decisions about convictions regarding organic or environmentally friendly agriculture, willingness to change, impacts on lifestyle and family, and the transition to organic methods within the planning horizon of the farmer and the family business.