• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.330-335
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• 2003

This paper reports the optimum structure of the vacuum packaged Porous poly-silicon Nano-Structured (PNS) emitter. The PNS layer was obtained by electrochemical etching process into polycrystalline silicon layer in a process controlled to anodizing condition. Current-voltage studies were carried out to optimize process condition of electron emission properties as a function of anodizing condition and top electrode thickness. Also, we measured in advance the electron emission properties as a function of substrate temperature because the vacuum packaged process was performed under the condition of high temperature ambient (430$^{\circ}C$). Auger Electron Spectrometer (AES) studies shows that Au as a top-electrode was diffused to PNS layer during temperature experiments. Thus, we optimized the thickness of top-electrode in order to make the vacuum package PNS emitter. As a result, the vacuum Packaged PNS emitter was successfully emitted by optimizing process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.71-74
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• 2001

Using the Taguchi method, optimum process condition of lead frame blanking has been determined in the point of view of shape of blanked profile. As the main process parameters, clearance, strip holding pressure and bridge width are selected. According to the orthogonal array table, three levels of experiment have been carried out for each factors. The optimal blanking condition is analyzed with the SN ratio. It has been verified that the optimal process condition can be determined with a combination of basic blanking experiment and experiment design method. Both the effect of each factors and gain can be judged in the quantitative manners from the analysis of SN ratio.

• Transactions of Materials Processing
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• v.11 no.2
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• pp.132-137
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• 2002

Using the Taguchi method, optimum process condition of lead frame blanking has been determined in the point of view of shape of blanked profile. As the main process parameters, clearance, strip holding pressure and bridge width are selected. According to the orthogonal array table, three levels of experiment have been carried out for each factor. The optimal blanking condition is analyzed with the SN ratio. It has been verified that the optimal Process condition can be determined with a combination of basic blanking experiment and experiment design method. Both the effect of each factor and gain can be judged in the quantitative manner from the analysis of SN ratio.

• Journal of Korean Society for Quality Management
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• v.32 no.3
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• pp.109-125
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• 2004

This paper deals with an optimal process control problem in production of hull structural steel plate with high defective rate. The main quality characteristic(dependent variable) is the internal quality(defect) of plates and is dependent on process parameters(independent variables). The dependent variable(quality characteristics) has three categorical ordinal data and there are 35 independent variables(29 continuous variables and 6 categorical variables). In this paper, we determine the main factors and to develop the mathematical model between internal quality predicted probabilities and the main factors. Secondly, we find out the optimal process condition of main factors through analysis of variance(ANOVA) using simulation. We consider three models to obtain the main factors and the optimal process condition: linear, quadratic, error models.

• Transactions of Materials Processing
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• v.11 no.6
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• pp.513-518
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• 2002

The equivalent boundary conditions have been applied to the front door panel forming process, in order to demonstrate its reliability and validity. The elongation in the bead forming process is applied to the binder wrap process as the equivalent displacement boundary condition and the restraining force in the drawing process is applied to stamping process as the equivalent force boundary condition. The result calculated with the equivalent boundary conditions shows closer coincidence with the experimental result than simulation with different boundary conditions. The numerical result fully demonstrates that drawbead forming simulation for calculation of equivalent boundary conditions is necessary and effective.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.60-63
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• 2003

Semi-solid forming is the process of stirring alloy during solidification, making the mixture of liquid and solid, solidifying it, reheating it to the solid-liquid coexistent temperature, and then injecting this semi solid slurry into dies. In the semi-solid die casting process, it is very important to find out the correlation of injection condition, microstructure and mechanical properties. Especially, an improper injection condition is the main cause of liquid segregation and non-homogeneous mechanical properties due to the difference of solid fraction according to the position of the products. To ensure the database requisite to the semi-solid die casting product, it is essential to acquire the mechanical properties considering liquid segregation to the injection condition. In this study, the effect of injection condition on liquid segregation, formability, microstructure and mechanical properties in a thin product was investigated.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.59-66
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• 2000

To investigate the optimum brazing condition, variation of bonded structure and mechanical properties of novel brazed pure Al with bonding condition (brazing temperature, time and Si/flux ratio) was studied. A basic study of the bonding mechanism was also examined. The optimum brazing condition was obtained at $590^{\circ}$ for 2 minutes and the bonded structure showed that it is composed of almost entirely eutectic Al-Si with near eutectic composition. At higher brazing temperature $630^{\circ}$, hypoeutectic Al-Si structure was observed in the bonded area and resulted in erosion of base metal. The thickness of eutectic layer formed in optimum brazing temperature increased linearly with the square root of time, showing a general diffusion controlled process. The ultimate tensile strength of bonded joint brazed at an optimum brazing condition was about 60% of base metal and its fracture surface showed a brittle mode.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.111-116
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• 2006

Tribologcal property of the ceramics used in severe condition was investigated and both $Al_2O_3$ ball and Al/SiC composite made by thermal spray process[TSP] were used as a specimen in this study. Four kinds of material couple in ball and disk specimens were tested in the dry condition by using ball-on-disk type tribo-tester. Friction coefficient, surface roughness, wear rate, and photograph of the worn surface were investigated. Generally, High SiC contents[$40{\sim}50%$] specimens showed very low friction coefficient below 0.05 and little wear rate in dry condition. And also, low SiC contents[0%] specimens showed a moderate wear rate and high coefficient of friction at the same condition.

• Journal of Welding and Joining
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• v.20 no.2
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• pp.102-108
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• 2002

Resistance spot welding of aluminum alloys is based upon Joule heating of the components by passing a large current in a short duration. Since aluminum alloys have the potential to replace steels fur automobile body assemblies, it is important to study the process robustness of aluminum spot welding process. In order to evaluate the effects of process parameters on the weld quality, major process variables and abnormal process conditions were selected and analyzed. A newly developed two-stage, sliding-level experiment was adopted fur effective parameter design and analysis. Suitable ranges of welding current and button diameters were obtained through the experiment. The effects of the factors and their levels on the variation of acceptable welding current were considered in terms of main effects. From the results, it is concluded that any abnormal process condition decreases the suitable current range in the weld lobe curve. Pareto analysis of variance was also introduced to estimate the significant factors on the signal-to-noise (S/N) ratio. Among the six factors studied, fit-up condition is found to be the most significant factor influencing the SM ratio. Using a Pareto diagram, the optimal condition is determined and the SM ratio is significantly improved using the optimal condition.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.4
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• pp.113-134
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• 1994

A radial basis hybrid neural network (RHNN) is presented for an on-line detection of machine condition change. Two-phase modeling by RHNN is designed for describing a machine condition process and for predicting future signal. A moving block procedure is also designed for detecting a process change. A fast on-line learning algorithm, the recursive least square estimation, is introduced. Experimental results showed the RHNN could be utilized efficiently for on-line machine condition monitoring.