• Journal of Korea Foundry Society
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• v.40 no.2
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• pp.34-42
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• 2020

The effects of the initial balancing pressure, filling pressure and maximum build-up pressure on the casting characteristics of the thick-wall thickness casting during the counter-pressure casting process were investigated. Water model experiment and a computer simulation were carried out to evaluate the characteristics during the filling and solidification stages in counter-pressure casting (CPC); as a reference, the low-pressure casting (LPC) process was used. The average dendrite cell size decreased with an increase in the solidification rate and maximum build-up pressure. A turbulent flow occurred during the filling stage of the LPC process, resulting in the formation of inner gas, while a lamellar flow pattern dominated during the CPC process and was more evident with an increase in the initial balancing pressure, improving the mechanical properties of the castings.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.81-86
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• 2017

The high-pressure resin transfer molding (HP-RTM) process has a very effective for the mass production of carbon fiber reinforced plastic (CFRP) for light weight in the automotive industry. In developing robust equipment, new process and fast cure matrix systems reduces significantly the cycle time less than 5 minutes in recent years. This paper describes the cavity pressure, temperature and molding characteristics of the HP-RTM process. The HP-RTM mold was equipped with two cavity pressure sensors and three temperature sensors. The cavity pressure characteristics of the HP-RTM injection, pressurization, and curing processes were studied. This experiment was conducted with selected process parameters such as mold cap size, maximum press force, and injection volume. Consequently, this monitoring method provides correlations between the selected process parameters and final forming characteristics in this work.

• Composites Research
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• v.27 no.6
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• pp.254-259
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• 2014

In this study, a device and pressure press process that is able to substitute autoclave process is developed. This process complements disadvantages of autoclave process which are long process-time and high production cost. The developed device provides air pressure as well as the vacuum which are greatest feature of autoclave process. The device is sealed using hydraulic pressure to keep the air pressure inside the mold. The transfer of the heat is designed to be direct. The heating and pressure charging time are decreased by reducing the interior space. Tooling cost is reduced dramatically compared to autoclave process. Spring-back phenomenon is measured and compared. The temperatures of several parts of the mold during molding are measured. The fiber volume fraction of the parts molded by autoclave process and by the developed process are compared.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.460-467
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• 1998

The investigation deals with the manufacturing process design and deformation analysis for seamless pressure vessels Axisymmetric multistage deep drawing is a complex and important sheet metal forming process in the industry. In this study the process design for large size cylindrical shells with various thickness is performed and a general guideline for forming process design of pressure vessels will be suggested. Thus in this paper for the verification of the forming process design the forming analysis of pressure vessels will be carried out by PAM-STAMP which is on the basis of finite element analysis. In this case the formability of pressure vessels is evaluated using the results of computer simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.607-612
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• 1992

For hydroforming process, determination of back-up fluid pressure in chamber is one of the most essential tasks. In this paper, we present a back-up pressure estimation system which estimates the back-up pressure of hydroforming process utilizing a multi-layered neural network. The neural network learns the nonlinear relation ship between the back-up pressure and the geometric state variables of hydroforming process. The proposed method does not necessitate sophisticated analysis on hydroforming process but some geometric intuition. The experimental results show that the neural network well approximates the nonlinear relationship between the back-up pressure and the geometric state variables of hydroforming process, thus giving the good estimation of back-up pressure vs punch stroke curve.

• The Research Journal of the Costume Culture
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• v.21 no.1
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• pp.117-128
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• 2013

Studies show that time pressure affects the purchase decision-making process of consumers. However, in the case of apparel shopping, few studies have looked into the influence of time pressure on the purchase decision-making process. This study aims to determine how perceived time pressure in apparel shopping, time pressure situations, and product type and the interactions between these variables influence the clothing purchase process. An empirical study was conducted among males and females in their 20s and 30s. Perceived time pressure in apparel shopping was measured using four items. Time pressure situations and product types were given in the form of scenarios. A $2{\times}2{\times}2$ experimental design was used, and perceived time pressure in apparel shopping, time pressure situations, and product type were used to create eight different situations. The dependent variables included decision-making speed, anticipated regret, and anticipated purchase satisfaction. Data from 512 subjects were collected through an online data collection. Results showed that the high perceived time pressure group and the shopping situation with time pressure involved a significantly high level of decision-making time, anticipated regret, and anticipated purchase satisfaction. Marketers must understand the real-time pressure situations of consumers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.491-495
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• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• Korean Journal of Medicinal Crop Science
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• v.22 no.2
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• pp.134-139
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• 2014

This study was to investigate the improvement of immune activities of the extracts from Codonopsis lanceolata by stepwise steaming process and high pressure process. The phenol contents was $8.742{\mu}g/mg$ which was higher than that from conventional extraction using 70% ethyl alcohol at $80^{\circ}C$ for 24 hours. All of extracts at a concentration of $1.0mg/m{\ell}$ showed relatively low cytotoxicity on human normal kidney cell (HEK293) in range of 16 19%. The immune B and T cell growth was improved by extracts using the steamed and high pressure precess of C. lanceolata up to $180{\times}10^4cells/m{\ell}$ and $96{\times}10^4cells/m{\ell}$, respectively. The extract prepared also greatly increased the secretion of both IL-6 and TNF-${\alpha}$ from the stepwise steamed and high pressure process. This results can conclude that stepwise steamed and high pressure process effectively released active biomaterials which could important role in enhancing immune activity in the body.

• Korean Journal of Medicinal Crop Science
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• v.19 no.2
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• pp.103-110
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• 2011

This study was performed to enhance anticancer activities of Lithospermum erythrorhizon by eluting high amount of shikonin through ultra high pressure process. Extraction yield was increased up to 5~10% by ultra high pressure process, compare to the normal extraction processes such as water solvent extraction, 70% ethyl alcohol solvent extraction. The cytotoxicity of the extracts ($1.0{\mu}g/m{\ell}$) from ultra high pressure process was showed the lowest cytotoxicity 13.4% for human lung cell (HEL299). The anticancer activities showed 80~85% by adding $1.0{\mu}g/m{\ell}$ of the extracts from ultra high pressure process in several cancer cell lines such as AGS, Hep3B, MCF-7 and HeLa cells. Among them, MCF-7 cell of the endocrine system was highest inhibited than other cells. The anticancer activities of the extracts from ultra high pressure extraction process showed 10~15%, which was higher than the extracts from normal extraction processes. From HPLC analysis of the extracts, the contents of shikonin in the extracts from ultra high pressure process was 11.42% (w/w), which was 20% higher than others. This results indicate that ultra high pressure process could increase the extraction yield of shikonin and other contents, which resulted in higher anticancer activities.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.350-355
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• 1990

A pressure tracking of hydroforming process is considered in this paper. To account for nonlinearities and uncertainty of the process. A fuzzy SOC based iterative learning control algorithm is proposed. A series of experimentals were performed for the pressure tracking control of the process. The experimental results show that regardless of inherent nonlinearties and uncertainties associated with hydraulic system. A good pressure tracking control performance is obtained using the proposed fuzzy learning control algorithm.