• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1992.03a
• /
• pp.103-114
• /
• 1992

Cogging is generally the initial and primary step in the manufacture of practically all large open-die forgings, and consists of forging and ingot by reducing the cross-section and simultaneously enlarging the body. A three-dimensional thermo-viscoplastic finite element model is used to study the distribution of internal stresses and strains of workpiece and temperature of workpiece and die during cogging process. Simulations are carried out on an circular ingot, using v-die and flat die, to study the effects of die configuration, die width, penetration depth, temperature gradient, die overlapping and pass design.

• Transactions of Materials Processing
• /
• v.11 no.3
• /
• pp.223-230
• /
• 2002

Matched die forming technology has been used widely as a sheet metal forming method for a long time. This conventional method, however, needs a high cost and long delivery time to prepare a set of matched dies or, in many cases, several sets of dies. For more than ten years, some alternative methods using single die or non-matched dies have been developed and applied practically in various fields of industry. Elasto-forming, fluid forming, hydro-forming, and blow forming are some examples of these new methods. Recently, a dieless sheet forming technology using a reconfigurable matrix of punch elements has been developed, and started to be used in some industries such as aircraft and railroads. A new concept of dieless forming technology has also been proposed to overcome the drawback of the conventional dieless forming technology.

• Macromolecular Research
• /
• v.9 no.1
• /
• pp.1-19
• /
• 2001

Poly(p-phenylene pyromellitimide) and poly(4,4'-biphenylene pyromellitimide) are representatives of fully rod-like polyimides. Their structure and properties in thin films are reviewed. The polymers exhibit some excellent properties such as high molecular packing coefficient, high mechanical modulus, and low thermal expansion coefficient, and low interfacial stress, so that they are very attractive to both industry and academia. However, these polymers are very brittle and thus practically useless. Some chemical modifications to improve such drawback with a little sacrifice of the high modulus are described: i) incorporation of short side groups into the polymer backbone and ii) insertion of proper linkages into the polymer backbone.

• Journal of Sericultural and Entomological Science
• /
• v.43 no.1
• /
• pp.29-32
• /
• 2001

At present, more than 300 races of the Silkworm are conserved and used as valuable genetic resources. But because of the uneffectiveness of manual data management, faster and systematic data base construction is needed. So, development of silkworm genetic resources management program has been begun and the result can be practically used. When developing the program, Visual basic was used for data input system construction, and MS Access for database. IIS(Internet Information System) and ASP(Active Server Page) was also used for searching data and information with Internet Web Server and Web Browser which is comfortable for constructing database and providing information. Data input item consists of 46 practical characteristics such as race name, moltinism, larval period and pupation percentage etc.. And these characteristics are classified with qualitative and quantitative character. Photographs of silkworm, cocoon and other related items were scanned and the image data was recorded on the database.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.605-610
• /
• 1991

In inverter system for driving induction motor, the output harmonics are hamrful in induction motor drive because it leads to ripple torque and induction interference. For electrical drives using PWM(Pulsewidth Modulation) inverters and ac motors, the methods for efficiency optimal control have been developed. In this paper, two different PWM methods for inverter and voltage control technique are described. In order to reduce or minimize losses, various forms of PWM strategy such as, PM (Positive Modulation) and NM (Negative Modulation) are discussed. The results show the feasibility of obtaining practically sinusoidal output waveforms which are highly desirable in most inverter application.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.9
• /
• pp.62-68
• /
• 2011

Power system needs to sustain high reliability due to its complexity and security. The reliability prediction method is usually based on independent failure. However, in practice, the Common Cause Failures(CCF) and Cascading failure occur to the facilities in power system as well as independent failures in many cases. The CCF and Cascading failure turn out the system collapse seriously in a wide range. Therefore to improve the reliability of the power system practically, it is required that the analysis is conducted by using the CCF and Cascading failure. This paper describes the CCF and Cascading failure modeling combined with independent failure. The incorporated model of independent failure, CCF and cascading failure is proposed and analyzed, and it is applied to the distribution power system in order to examine this method.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.14 no.1
• /
• pp.17-27
• /
• 2010

In this paper, we apply homotopy perturbation method (HPM) for solving ninth and tenth-order boundary value problems. The suggested algorithm is quite efficient and is practically well suited for use in these problems. The proposed iterative scheme finds the solution without any discretization, linearization or restrictive assumptions. Several examples are given to verify the reliability and efficiency of the method. The fact that the proposed homotopy perturbation method solves nonlinear problems without using Adomian's polynomials can be considered as a clear advantage of this technique over the decomposition method.

• 한국HCI학회:학술대회논문집
• /
• 2009.02a
• /
• pp.163-167
• /
• 2009

3D human body scan technique is known to be practically useful in industrial field as the technique becomes more precise and cheaper. Landmark extraction is essential for full utilization of the scan data. In this paper, we suggest an algorithm for automatic landmark extraction. For this purpose, we perform markerless matching to the target data using PCA analysis and quasi-Newton optimization. Landmarks are extracted from the topology of resulting body.

• Korean Management Science Review
• /
• v.15 no.2
• /
• pp.201-210
• /
• 1998

Truck dispatching is one of the most commonly occurring problems of transprot management. We developed an interactive decision support system named IDSSTD, for the truck dispatching problem where two conflicting objectives are treated and travel speed varies depending on the passing areas and time of day. The IDSSTD aids the decision-making process by allowing the user to interact directly with the database, to direct data to a decision model, and to portray results in a convenient form. The IDSSTD is consisted of two major interactive phases. The pre-scheduling interactive phase is to reduce the complexity of a given problem before applying the BC-saving heuristic algorithm and the post-scheduling interactive phase is to improve practically the algorithmic solution. The IDSSTD has the capabilities of its own manipulation(analysis and recommendation) and diverse graphic features in order to facilitate a user's interaction.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.32 no.4
• /
• pp.37-50
• /
• 2007

Dramatic development of information technology requires new type of sales strategy to enterprise S/W dealers. That is, one should thoroughly consider diversified types of enterprise S/W and more elaborated consumer needs to establish successful sales strategy. However, various factors that should be considered in establishing enterprise S/W sales strategy are different according to types of enterprise S/W and hard to be managed systematically which led to the current situation where they have not been discussed enough. Therefore, this study introduced the relationship between the factors that affect selection of enterprise S/W using the concept of cognitive map on various enterprise S/W sales cases. Through this process, this study grouped the cognitive maps of similar cases to introduce their characteristics and made this result to be practically useful to enterprise S/W sales strategy.