• Design & Manufacturing
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• v.17 no.4
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• pp.72-78
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• 2023

Injection molding is a process widely used in various industries because of its high production speed and ease of mass production during the plastic manufacturing process, and the product is molded by injecting molten plastic into the mold at high speed and pressure. Since process conditions such as resin and mold temperature mutually affect the process and the quality of the molded product, it is difficult to accurately predict quality through mathematical or statistical methods. Recently, studies to predict the quality of injection molded products by applying artificial neural networks, which are known to be very useful for analyzing nonlinear types of problems, are actively underway. In this study, structural optimization of neural networks was conducted by applying multi-task learning techniques according to the characteristics of the input and output parameters of the artificial neural network. A structure reflecting the characteristics of each process step was applied to the input parameters, and a structure reflecting the quality characteristics of the injection molded part was applied to the output parameters using multi-tasking learning. Building an artificial neural network to predict the three qualities (mass, diameter, height) of injection-molded product under six process conditions (melt temperature, mold temperature, injection speed, packing pressure, pacing time, cooling time) and comparing its performance with the existing neural network, we observed enhancements in prediction accuracy for mass, diameter, and height by approximately 69.38%, 24.87%, and 39.87%, respectively.

• Journal of Embryo Transfer
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• v.29 no.3
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• pp.241-248
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• 2014

This study was carried out to evaluate the effects of embryonic stage, cryoprotectant, and freezing-thawing method on the rates of survival and development of the cryopreserved mouse early embryo and finally to establish the cryopreservation method of surplus embryos obtained during assisted reproductive technology (ART). Two to eight cell embryos were obtained from oviducts of mated $F_1$ hybrid female mice superovulated by PMSG and hCG. Two-step EG, DMSO and 4-step EG, DMSO were used as cryoprotectant and dehydration and rehydration method of embryos, and slow-cooling or rapid-cooling method was used as frozen program. The survival rates of embryos were measured after thawing and rehydration, and the developmental rates of embryos were compared and observed during culturing embryos for 24, 48, 72, 96 hrs. As for the survival and development rates of embryos according to embryonic stage, the survival rate of 2 cell stage in EG and DMSO was significantly higher than 4~8 cell (65.4% versus 61.2%, 81.1% versus 72.5%) (p<0.01, p<0.01), but the development rates of 4~8 cell embryos in EG and DMSO were significantly higher than 2 cell embryos for whole culture period (p<0.01) and the development rates of 4~8 cell embryos in EG were significantly higher than 2 cell embryos in DMSO (p<0.01). As for the survival and development rates of embryos according to cryoprotectant, the survival rate of 2 cell embryo in DMSO was significantly higher than that in EG(77.0% versus 64.4%) (p<0.01), whereas the development rate of embryos was not differ till 24 hrs. The development rate from morular to hatching blastocyst, however, was sinificantly higher in EG than in DMSO during 48 hr (p<0.01). The survival rate of 4~8 cell embryo was 62.5% in EG and 73.3% in DMSO. The development rates of embryo in EG were significantly higher for whole culture periods (p<0.01, 0.05). In respect to the effect of freezing and thawing program on the survival and development rates of embryos, method of slow cooling and rapid thawing was more effective than that of rapid cooling and rapid thawing. The survival rate of embryo in 2 cell stage was higher than in 4~8 cell stage, and EG appears more effective cryoprotectant than DMSO because EG showed better development rates of embryos in 2 and 4~8 cell stage. Moreover, slow cooling and rapid thawing method was considered as the best cryopreservation program.

• Design & Manufacturing
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• v.2 no.5
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• pp.30-33
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• 2008

Injection Molding is the most effective process for mass production of plastic parts. The injection molding process is composed with several steps such as Filling, Packing, Holding, Cooling, Ejecting. Among them, filling and packing process should be considered carefully to improve accuracy of dimension, surface quality of plastic parts. Usually the quality above-mentioned is managed with weight of part after molding on the field. In this paper, a series of experiment for molding automotive front bumper was conducted with cavitity temperature sensor to optimize switch-over time(V-P switching), hot runner vale gate sequence time during filling and packing step for the purpose of uniform quality, weight at every molding. As a result, it was found that it is effective method to use temperature sensor in injection molding for quality control of plastic molding.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.215-220
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• 2002

Recently, linear motor has been developed for linear motion of machine tools. Linear motor is useful to design the linear motion, high speed and high accuracy, because of the simple system not required the additional mechanical part such as coupling and ballscrew. This paper tested performance of linear motor relevant to motioning and positioning table such as F.R.F., step response and positional accuracy Linear motion system using linear motor requires the effective cooling system because it cause to decrease the positional error and to protect the motor coil. Therefore the positional error measurement was made to evaluate the effect of the temperature variation.

• Tribology and Lubricants
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• v.23 no.3
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• pp.109-116
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• 2007

A scroll compressor is on the increase in the use for the cooling and ambition machinery because of the advantages about high efficiency, low vibration and low noise. The design of thrust bearing for scroll compressor has depended on the experience. The lubrication considering the squeeze flow was applied for high side shell and low side shell of scroll thrust bearing. This work was based on governing fluid lubrication equation at the general coordinate. It shows the behavior for an orbiting scroll with direct numerical analysis using FDM. This study obtained the theoretical design value by finding load capacity and tilting angle of an orbiting scroll for thrust bearing in a scroll compressor. Especially this work performed the analysis about the design parameter. The program was written using Visual C++ to enhance user to change the design parameter easily. In particular the result value and the pressure profile were displayed as windows in every step for user to understand without difficulty.

• Journal of Sericultural and Entomological Science
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• v.42 no.1
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• pp.1-5
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• 2000

To investigate the possibility of crypreservation of mulberry seeds in liquid nitrogen(LN$_2$), characteristics of the seeds were examined after picking mulberry syncarps and drying-heat treatment. Storage in LN$_2$has the potential of providing indifinite preservation of valuable seed germplasm. Determining the tolerance of seeds among given cultivars to LN$_2$cooling and subsequent rewarming is the first step to establishing the feasibility of LN$_2$storage. Seeds of 4 mulberry varities were treated to LN$_2$(-196$\^{C}$) for 24 hours after drying heat treatment. Seed moisture content of Daeryukppong was the highest. As moisture content of mulberry seed was below 1%, storage in LN$_2$was safe. And drying heat treatment for 60 minutes was suitable to prevent decreased germination rate and germination vigor of seeds. The seeds of Cheongilppong were unsuibable to cryopreserve in LN$_2$for longterm storage.

• 한국가스학회:학술대회논문집
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• 2007.04a
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• pp.27-32
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• 2007

Dimethyl Ether (DME, $CH_3OCH_3$) is the simplest ether and is considered as one of the leading candidates in the quest for a substitute fur petroleum-based fuels. In this work, we analyzed the one-step synthesis of DME in a shell and tube type fixed bed reactor and carried out a simulation with a one-dimensional, steady state model of a heterogeneous catalyst bed, while taking into consideration the heat and mass transfer between the catalyst pellets and reactants gas and the effectiveness factor of the catalysts, together with the reactor cooling through the reactor tube wall. The reactor simulation was carried out under steady state condition and we compared the simulation results with the experimental data obtained from operations of a pilot-scale reactor and found good agreement between them.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.232-257
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• 2003

It has been shown that transparent microemulsion gels of flexibly adjustable viscosity containing less than 10％ w/w surfactants can be obtained just by cooling down through a new 1-step preparation procedure (via 4 different in-situ colloidal systems) using PIT-technology with a range of emulsifiers, co-emulsifiers and lipids. They can be used for a wide scope of applications. Specific examples have been given with antiperspirant formulas that proof the stability of these thickened microemulsions even with high content of electrolytes and low pH. We propose that the structure of these microemulsion gels can be described by cross-linking of nano-fine oil droplets via an ABA-triblock copolymer. A new generation of transparent antiperspirant roll-ons with significantly improved skin tolerance can now be formulated as an attractive alternative to alcohol-based products.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.354-354
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• 2008

Recently, due to the tremendous growth of media technology, demands of the aspheric glass lens which is a high-performance and miniaturized is gradually increasing. Generally, the aspheric glass lens is manufactured by GMP(Grass Molding Press) method using WC(tungsten carbide) mold core. In this study, the thermal deformation which occurs in the cooling step of GMP was considered, and it was compensated the form of mold core. The lens which was molded by compensated mold core was satisfied that can be applied to the actual specifications.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.97-103
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• 2001

The study on the high-speed machine tool is very important for the improvement of productivity since it can shortens cutting and non-cutting time. Especially, high speed of feed drive system is the major research field. In the industries of the advanced countries, the feed drive systems at the speed of 60 m/min have been already developed based on the high lead ball screws. In this study, a high speed feed drive system at the speed of 60 m/ min has been developed, and its movements characteris-tics are investigated. As the movement characteristics, positioning accuracy, angular accuracy, straightness and micro step-response are measured. Thermal characteristics of the system is also discussed. For measuring the movement characteris-tics, a laser interferometer, a memory-based Hi-coder and a cooling device are used. The experimental results confirm that the movement characteristics and the thermal behavior of the system are satisfactory in the aspect of accuracy and stability.