• 소성∙가공
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• 제22권4호
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• pp.204-215
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• 2013

As a pressure vessel, a small seamless aluminum liner with inner volume of about 6.75L is made from an initial billet material of AA6061-O. To produce the aluminum liner, warm forging including backward extrusion and head nosing was numerically simulated using a billet initially pre-heated to about $480^{\circ}C$. Compression tests on the billet material were performed at various temperatures and strain rates, and the measured mechanical properties were used in the numerical simulations. For the backward extrusion and the head nosing, the tool geometries were designed based on the desired configuration of the aluminum liner. Furthermore, the structural integrity of the tooling was evaluated to ensure adequate tool life. The seamless aluminum liner has an endurance limit of about 1.47MPa ($15Kg_f/cm^2$), estimated based on the required inner pressure. The results confirm that the small seamless aluminum liner of AA6061-O can be successfully made by using the two stage warm forging procedures without any bursting failures.

• 소성∙가공
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• 제20권8호
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• pp.562-567
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• 2011

This paper deals with effects of certain important factors in a tube drawing operation, such as the use of a mandrel, die radius and tangential angle at die outlet, on the deformation behavior of a small-diameter seamless tube. Both experimental and finite element simulation studies are carried out to assess the effects of the above parameters. Experiments and finite element predictions are compared. The use of a mandrel simplifies the design of tube drawing, but also induces some difficulties from increased process complexity. The effects of die outlet tangential angle and radius are discussed in detail.

• 소성∙가공
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• 제20권8호
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• pp.611-618
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• 2011

Flow forming is an incremental forming process in which rollers are used to form cylindrical parts with repeated turning of both roller and starting material. Both sheet and tube can be used as the starting material. The process is highly useful for producing hollow shaped parts from a tube, with the benefit of the average strain in the final shape being significantly lower than that from a sheet material. In the present study, the flow forming process was studied and optimized for producing a hollow shaped part from seamless steel tube by both experiment and numerical analysis. Upon considering the difficulty of forming seamless steel sheet, the thickness reduction was distributed over several tool paths. In the end, an optimum process condition was attained, and the experiment verified the simulation results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.318-321
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• 2006

In this strudy, the free-bulge test and FE analysis have been used to define the fracture criteria based on the cockroft and Latham's criterion in warm hydroforming of Al 6061 tube. Full annealing and T6 treatment for heat treatment of Al 6061 tube ware used in this study. As-extruded, full annealed and T6-treated Al 6061 seamless tubes were prepared. To evaluate the hydroformability, uni-axial tensile test and bulge test were performed between room temperature and $200^{\circ}C$. And measured flow stress was used to simulate the warm hydroforming. A commercial FEM code, DEFORM-$2D^{TM}$, was used to calculate the damage value. A forming limit based ductile fracture criteria has been proposed by the results of experimental and FE analysis. The calculated values for fracture criteria will be efficient to predict the forming limit in hydroforming for real complex shaped part.

• 인터넷정보학회논문지
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• 제7권6호
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• pp.51-62
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• 2006

기존의 다른 어떤 종류의 게임보다도 큰 부하와 거대한 하나의 가상월드가 MMORPG(Massively Multiplayer Online Role-Playing Game)의 중요한 특징이다. 이러한 Seamless 환경에서는, 독립된 게임 서버들이 관리하는 하위의 공간들을 모아 하나의 거대한 가상 월드로 구축한다. 게임 개발자들의 노력에도 불구하고 게이머들은 여전히 클라이언트와 서버, 필드 서버들 간의 상호작용에서 비롯된 과다한 메시지 트래픽에 대해 불만을 가지고 있다. 본 논문에서는 메시지 트래픽을 줄이기 위해 MigAgent를 이용한 새로운 게임 서버 구조를 제안한다. 일반적으로 PC(Player Character)가 다른 필드 서버로 이동할 때 발생하는 메시지 트래픽이 최고조에 이른다. MigAgent는 이런 PC들을 처리하고 예기치 못한 상황에 대처하기 위한 에이전트 역할을 수행한다. 관심영역과 인접 셀의 크기 비율에 따라 그 효과를 분석함으로써 이 시스템의 효과를 분석한다.

• Corrosion Science and Technology
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• 제16권6호
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• pp.305-316
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• 2017

Austenitic stainless steels have been widely used for various systems of nuclear power plants. Among these stainless steels, small pipes with diameter less than 14 inch have been produced in the form of seamless pipe. Annealing and cooling process during the manufacturing process can affect corrosion properties of seamless stainless steels. Therefore, 12 inch-diameter of as-received 304L stainless steel pipe was annealed and aged in this study. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. U-bend method in an autoclave was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ or 40% NaOH solution at $340^{\circ}C$. As-received specimen showed relatively high degree of sensitization and intergranular corrosion rate. Carbon segregation was also observed near grain boundaries. Annealing treatment could give the dissolution of segregated carbon into the matrix. Aging treatment could induce segregation of carbon and finally form carbides. Microstructural analysis confirmed that high intergranular corrosion rate of the as-received seamless pipe was due to micro-galvanic corrosion between carbon segregation and grains.

• 한국정보과학회논문지:정보통신
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• 제29권2호
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• pp.147-155
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• 2002

인터넷을 통해 사용자 정보가 여러 망을 거치는 동안 연동지점에서의 처리 지연은 고속 전송에 큰 부담이 되며 종단간의 심리스 연결이 가능하다면 좋은 해결책이 될 것이다. 이 논문에서는 ATM-LAN에 유력한 MPOA 망과 백본 기술로 적용이 검토되고 있는 MPLS 망을 심리스 연결하기 위한 방안을 제시한다. 두 망의 특징을 비교하고, 연동에 필요한 요구사항을 제시하며, 적용 가능한 세가지 연동 방안을 기술한다. 제시된 연동방안은 LER에서 ATM VC와 LSP를 심리스 연결함으로써 IP 룩업에 소요되는 처리 지연을 최소화하고 종단간 전송 지연을 줄인다. 각 연동 방안들의 세부 동작 절차와 특징을 기술하고, 잭슨망 이론을 이용하여 제시된 연동 방안들의 종단간 전송지연을 분석하고 그 결과를 비교한다.

• 한국의상디자인학회지
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• 제21권4호
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• pp.69-79
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• 2019

This study aims to seek knitting methods that can enhance the neck design of seamless knitwear and to find out how to improve the designs by comparing and analyzing the characteristics of the knitting methods used for v-neck pullovers. The investigator analyzed the characteristics of the knitting methods and assessed the wearing sensation by using six different pieces of clothing for the experiment. The results were analyzed based on a variance analysis (ANOVA). Among the items showing significant results, the Duncan-test was used for more intensive research. As a result, while using the basic pattern of knitting methods, Experiment Clothes A ended up binding on the back neckline, and not making the hem of back. Also, the neck was the widest. In the case of the special neck, Experimental Clothes B (1:1), which had the least number of the knitting course in relation to the knitting ratio, the bottom part of the back body had the most wrinkles. According to the result of wearing sensation, the front part, the side part, and the back part showed similar results (p<0.000) in all items. Specifically, the appearance of the Experiment Clothes A (normal) in both the front and rear aspects were evaluated as the best. In the case of the special neck, the Experimental Clothes F was ranked the highest, whereas the Experimental Clothes B (1:1) was ranked the lowest. Based on the results of the study, it seems possible to provide concrete and technical data for the planning of unique and productive designs. With regard to seamless knitwear neck designs, a comparative analysis of the knitting method of v-neck pullovers will be of practical use in the development and manufacturing of the product.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.304-310
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• 2001

Flow pulsation often causes vibration and noise in piping systems and therefore has been a troublesome concern for fluid system engineers. According to frequency increase in this paper under the influence wave form of velocity in springly flow and viscosity are drop coefficient of viscosity become increase so that impedance and resistance. The transient variations of flow rate are measured by a modified impedance tube method which is realized by virtue of the present analytical technique. At pipe line in order to eliminate vibration, confirm happened intermittently impedance characteristics. We make a test and frequency analysis and have to minimize obstructive component at hydraulic circuit.

• Journal of Communications and Networks
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• 제7권2호
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• pp.207-221
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• 2005

The proliferation of wireless local area networks (WLANs) offering high data rate in hot spot area have spurred the demand for possible WLANs and third-generation (3G) cellular network integration solutions as the initiative step towards 4G systems. This paper provides a novel architecture for seamless location-aware integration of WLANs into 3G cellular networks and also an analysis for the efficient handover techniques. We introduce location as a key context in secure roaming mechanism for context-aware interworking in 4G systems. The fast secure roaming with location-aware authentication is implemented at an entity called location-aware service (LAS) broker that utilizes the concepts of direction of user and pre-warming zone. The location-ware interworking architecture supports seamless roaming services among heterogeneous wireless networks including WLANs, wireless metropolitan area networks (WMANs), and 3G cellular networks. This paper also includes a description of procedures needed to implement efficient mobility and location management. We show how the LAS broker with pre-warming and context transfer can obtain significant lower latency in the vertical handover.