• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2775-2780
• /
• 2007

The ballistic range has long been employed in a variety of engineering fields such as high-speed impact engineering, projectile aerodynamics and aeroballistics, since it can create very high-pressure states in a short time. Since the operation of the ballistic range includes many complicated processes, each should be studied in detail for the best operation of the device. One of the main processes which have a major influence in its operation is the compression of the driver gas. Most of the studies available in this field hardly discuss this process in detail and thus lack a proper understanding of its effect. In the present study, a computational analysis has been made to investigate the compression process in the pump tube of a ballistic range. The results obtained are validated with some experimental data. It is seen that the pump tube parameters and the piston mass significantly affect the compression process and the time to build up the required diaphragm rupture pressure.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 추계학술대회
• /
• pp.406-411
• /
• 2003

It is clearly demonstrated that deeper cups could be formed by single and double stretch-drawings from smaller circular blanks due to such wall-thinning action than in the usual deep-drawing of larger blanks. From this fact, it is emphasized that the deep-drawability of a sheet metal Is not evaluated simply by the conventional L.D.R (limiting drawing ratio), but the depth of the drawn cup should also be taken into account. Many experimental data about various metals and thicknesses given in this paper offer a valuable information in this process for more general use which recommends to replace the conventional deep-drawing process by the stretch-drawing process both for single and double operations. In the single stretch-drawing, it is also confirmed that a deeper cup can be produced by raising the blank-holding force at later stage of operation.

• 에너지공학
• /
• 제24권2호
• /
• pp.55-58
• /
• 2015

The mesoporous metal organic framework structure Fe-BTC was successfully synthesized by hydrothermal process with noticeable yield. The synthesis operation was conducted at intermediate temperature and for shortened operation time as compared to conventional procedures. This process approach with reduced operating temperature and shortened operation time may open an opportunity window towards process economy with reduction in energy consumption. A simple mathematical approach of diffraction indexing using X-ray diffraction patterns of synthesized powder was employed to confirm its crystalline nature and to investigate its high temperature stability. The crystallite size was calculated by using Debye-Scherrer equation.

• 한국연소학회지
• /
• 제16권4호
• /
• pp.23-30
• /
• 2011

In the iron and steel manufacturing, sintering process precedes blast furnace to prepare feed materials by agglomerating powdered iron ore to form larger particles. There are several techniques which have devised to improve sintering production and productivity including flue gas recirculation(FGR) and additive gas enriched operation. The application of those techniques incurs variations of process configurations as well as inlet and outlet gas conditions such as temperature, composition, and flow rate which exert direct influence on reactions in the bed or the operation of the entire plant. In this study, an approach of sintering bed modeling using flowsheet process simulator was devised in consideration of FGR and the change of incoming and outgoing gas conditions. Results of modeling for both normal and FGR sintering process were compared in terms of outgoing gas temperature, concentration, and moisture distribution pattern as well as incoming gas conditions. It is expected to expand the model for various process configurations with FGR, which may provide the usefulness for design and operation of sintering plant with FGR.

• 대한안전경영과학회지
• /
• 제17권2호
• /
• pp.183-190
• /
• 2015

For the sustainable development, companies are making a lot of efforts such as activities of sales increase and cost reduction. Among these, efforts to use limited resources efficiently and effectively is still being made steadily. And many methods for management innovation are being introduced and used. However there were partial or temporary effects only. So there are not enough to achieve operations performance to cover the entire system. Therefore, in order to maximize performance or to improve sustainability across the companies, it is necessary to rebuild the existing system with process perspective not with existing functional perspective. This study was performed to achieve the objective that is operation performance improvement of certification body. So literature review was researched and analyed about the process innovation and the process approach. And basic model which is compatible with ISO/IEC 17021 requirement for the certification body was established in this study. Based on this model, one of the certification body was selected and operation system for this organization was established, documented and implemented through the process approach method. In the result, operations performance of certification body on the side of efficiency and effectiveness is analyzed and the effect of reconstruction of system on operations performance was figured out

• 한국콘텐츠학회논문지
• /
• 제3권4호
• /
• pp.63-68
• /
• 2003

본 논문은 통신 네트워크 운용관련 민감도 측정에 관한 연구를 위해 네트워크 운용 적정비용 산출 및 효율화 방안을 제안하였다. 통신 네트워크 운용효율화를 위해 네트워크 운용 효율성 측정을 위한 모형을 개발하였다. 전반적/포괄적 관점에서 산출된 네트워크 운용의 적정비용에 대해 품질수준 개선을 위한 요소, 고객만족도 관련 요소 등과의 연계성을 중심으로 재평가하고 개선하는 것이 본 논문의 가장 핵심적인 연구이다. 이러한 과정은 네트워크 운용의 가장 큰 부분을 차지하는 것이 품질관련 활동이고 품질관련 활동은 결국 고객만족도로 나타나게 되는 것이기 때문에, 각 요소별 개별적인 변화가 상호간에 미치는 영향을 중심으로 상관관계를 정립하여 민감도 측정을 바탕으로 네트워크운용비용을 산출하는 것이 진정한 의미의 적정수준 분석이라 할 수 있다. 따라서, 본 논문에서는 네트워크 운용에 대한 체계적인 모형의 구축 및 효율성 측정을 위한 다양한 시나리오에 따른 민감도 측정을 위한 시스템을 개발하였다.

• 환경위생공학
• /
• 제23권4호
• /
• pp.73-82
• /
• 2008

In this study, a dry single-phase anaerobic digestion process (Dranco system) was investigated to evaluate the optimum operational conditions. Several factors such as injection rate of organic waste, biogas production, $CH_4$ content in the biogas, pH of the sludge, $NH_3$-N and VFA concentration were investigated based on the operation of the digestion process for 2 months (short term) and 8 months (long-term). The operation results showed that a small quantity of food waste should be injected every week and that a 10% increase of the microorganism injection rate should be needed. However, normal operation was conducted after 11 weeks based on the designed quantity. The $CH_4$ content in the biogas was high at the beginning and the end of the food injection. However, it was low during week days. When the biogas production was high, the $CH_4$ concentration was low. The biogas production increased with an increase of the injection rate. $100m^3$/ton of biogas was produced from normal operation of the digestion process based on the designed quantity. The pH values of the digestion tank based on short-term operation ranged from 8 to 8.5. However, the pH values ranged from 7.45 to 8.15 after 4 weeks of long-term operation. The $NH_3$-N concentration of short-term operation ranged from 4,500 to 5,500 ppm and it gradually decreased to 2,000ppm after normal operation was commenced. For long-term operation, it was 5,000ppm initially and 3,800ppm after normal operation was commenced. The VFA concentration of sludge was less than 900ppm and 2,500ppm for short and long-term operations, respectively, after normal operation. Overall, the differences between sludge pH, $NH_3$-N and VFA concentrations may be due to the different types of microorganisms and the digestion ability of the microorganisms which exist in the accumulation of non digested organics. Moreover, it may be also caused by the type of food waste. Further investigation is needed to confirm these relationships.

• 상하수도학회지
• /
• 제18권2호
• /
• pp.191-200
• /
• 2004

DAF process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when the freshwater blooms occut or raw water turbidity become high. Pre-sedimentation iS prepared in case when raw water turbidity is very high by rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while it is difficult to remove in sedimentation. One of the main concerns in adoption of DAF (Dissolved Air-Flotation) process is a high raw water turbidity problem. That is, DAF is not adequate for raw water, which is more turbid than 100NTU. In order to avoid this problem, pre-sedimentation basins are prepared in DAF plant to decrease the turbidity of DAF influent. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, DAF process coupled with sedimentation is suggested that pre-sedimentation with optimum coagulation prior to DAF would be appropriate.

• 대한산업공학회지
• /
• 제21권3호
• /
• pp.329-343
• /
• 1995

Traditionally, machining process sequence was influenced and constrained by the design information obtained from CAD data base, i.e., class of operations, geometric shape, tooling, geometric tolerance, etc. However, even though all the constraints from design information are considered, there may exist more than one way to feasibly machine parts. This research is focused on the integrated problem of operations sequencing and machine tools selection in the presence of the product mix and their production volumes. With the transitional costs among machining operations, the operation sequencing problem can be formulated as a well-known Traveling Salesman Problem (TSP). The transitional cost between two operations is expressed as the sum of total machining time of the parts on a machine for the first operation and transportation time of the parts from the first machine to a machine for the second operation. Therefore, the operation sequencing problem formulated as TSP cannot be solved without transitional costs for all operation pairs. When solved separately or serially, their mutual optima cannot be guaranteed. Machining operations sequencing and machine tool selection problems are two core problems in process planning for discretely machined parts. In this paper, the interrelated two problems are integrated and analyzed, zero-one integer programming model for the integrated problem is formulated, and the solution methods are developed using a Tabu Search technique.

• 소성∙가공
• /
• 제6권5호
• /
• pp.446-455
• /
• 1997

A Combined extrusion operation consists of forward and backward extrusion forming and it is possible to make the process be simple by employing it. But the metal flow pattern induced by the operation is hard to analyze accurately because the flows are non-steady, which have at least two directions dependent upon each other. So engineers in the industrial factories had conducted the two extrusion operations separately. A new process was designed by the industrial expert for forming of an alu-minum preform using the combined extrusion operation. In this study, experiments and finite element analysis was carried out to determine the process parameters. Through the preliminary experiment, it was shown that warm forming condition was more desirable than cold or hot ones. And optimal shape of initial billet could be also determined. From the compatibility test, bonde-lube was chosen as the optimal lubricant and 20$0^{\circ}C$ as the material temperature by the inspection of micro-structure. The operation was simulated by the rigid-plastic finite element method to examine the metal flow. Disap-pearing of dead metal zone was observed as the punch fell down and desirable shape was obtained from the one operation. As a result of this study, 7 operations could be reduced and 225% of material saved.