• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.193-198
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• 2011

Recently sapphire crystals are used in LED applications. The Czochralski (CZ) growth process is one of the most important techniques for growing high quality sapphire single crystal. A successful growth of perfect single crystals requires the control of heat and mass transport phenomena in the CZ growth furnace. In this study, the growth processes of the sapphire crystal in an inductively heated CZ furnace have been analyzed numerically using finite element method. The results shown that the high temperature positions moved from the crucible surface to inside the melt and the crystal-melt interface changed to the flat shape when the rpm was increased. Also the crystal-melt interface shape has been influenced by the shoulder shape of the grown crystal during the initial stage.

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.83-89
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• 2001

Most technologies of reduction process used in the heat treatment of existent metal products are related to metals applied to bolts and parts of automobiles, and nonmetal such as copper. Heating conditions and reduction gases produced in above processes depend on types of products to be treated thermally but heating systems employ electricity commonly and the reduction gases are separated into additional production equipment and a gas dryer and inefficiently provided into the system. Electrical heating system has the advantage of convenient temperature-control but is not economical because of disadvantages of high electricity-running cost and extra installation cost of a transformer. Accordingly, development of the system which has economical heating mode in which provision of reduction gas and heating conditions are unified is necessary for improvement of economy and efficiency in current reduction processes. This study aimed to develop a new advanced heat treatment furnace using catalytic combustion. thereby minimizing the cost during heating, supplying heat and reductive gas at the same time and controlling operating condition freely by changing electrical heating system to heating system by the gas combustion and regeneration of wasted heat.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.318-321
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• 2003

Steel slag is produced during steel making process. Compared with the blast furnace slag, converter slag has the expansibility due to the reaction with water and free CaO. Therefore it is specified in Standard Specification for Concrete in Korea that steel slag aggregate must not be used in concrete. In this study, atomized steel slag aggregate is conducted from converter slag by the atomizing method. Atomized steel slag and conventional converter slag are same in its composite by nature in the converter but compounds of the composite become different because of different method of slag treatment. Especially atomized steel slag aggregate overcomes expansibility that is the weak point for usage. It is researched whether it has the possibility, suitability for fine aggregate in concrete. Slump and air content are measured in fresh concrete, compressive and bending strength in hardened concrete. These is compared with control concrete with washed sand.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.38.1-38
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• 2002

In steel works, Locomotives and torpedo ladle cars are used to convey the smelted iron that comes out Blast Furnace to the mill making mill. In this process, Identification of the vehicles position is very important because the area is broad and efficient operation affects a productivity and investment. At present condition, there are many ways to use to identify the vehicles number and position. This paper will present the new ways using GPS/DR based method. For this, we practiced the site test to gather the real data. First, we collect the velocity data at the wheel of the vehicles with the direction data via process computer. Second, after installing the gyroscope we gathered the data wit...

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.5-14
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• 2003

Principles of a novel pulse growing method are described. The method realized in the crystal growing on a seed from melts under raw melt feeding provided a more reliable control of the crystallization process when producing large alkali halide crystals. The slow natural convection of the melt in the crucible at a constant melt level is intensified by rotating the crucible, while the crystal rotation favors a more symmetrical distribution of thermal stresses over the crystal cross-section. Optimum rotation parameters for the crucible and crystal have been determined. The spatial position oi the solid/liquid phase interface relatively to the melt surface, heaters and the crucible elements are considered. Basing on that consideration, a novel criterion is stated, that is, the immersion extent of the crystallization front (CF) convex toward the melt. When the crystal grows at a <> CF immersion, the raised CF may tear off from the melt partially or completely due to its weight. This results in avoid formation in the crystal. Experimental data on the radial crystal growth speed are discussed. This speed defines the formation of a gas phase layer at the crystal surface. The layer thickness il a function of time a temperature at specific values of pressure in the furnace and the free melt surface dimensions in the gap between the crystal and crucible wall. Analytical expressions have been derived for the impurity component mass transfer at the steady-state growth stage describing two independent processes, the impurity mass transfer along the <> path and its transit along the <> one. The heater (and thus the melt) temperature variation is inherent in any control system. It has been shown that when random temperature changes occur causing its lowering at a rate exceeding $0.5^{\circ}C/min$, a kind of the CF decoration by foreign impurities or by gas bubbles takes place. Short-term temperature changes at one heater or both result in local (i.e., at the front) redistribution of the preset axial growth speed.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.136-144
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• 2002

Melting method has long been considered difficult to realize because of problems such as the low foamability of molten metal, the varying size of cellular structures and solidification shrinkage. The parameters to solve the problem in electric furnace were stirring temperature, stirring velocity, heating velocity and foaming temperature It is important to consider the effects of induction heating, because it brings about the inner flow by the temperature gradient. Aspect ratio also depends on the induction heating. Mechanical properties are dependent on cell sizes and aspect rations. Therefore, this paper presents the effects of these parameters on the cell sizes. For the sake of this, combined stirring process was used to fabricate aluminum foam materials by the above mentioned parameters. Image analysis was performed to calculate the cell sizes, distributions, and aspect ratioes at the cross section of feared aluminum in the direction of height.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.273-283
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• 2000

In this paper we suggest an optimal design method of Fuzzy-Neural Networks(FNN) model for complex and nonlinear systems. The FNNs use the simplified inference as fuzzy inference method and Error Back Propagation Algorithm as learning rule. And we use a HCM(Hard C-Means) Clustering Algorithm to find initial parameters of the membership function. The parameters such as parameters of membership functions learning rates and momentum weighted value is proposed to achieve a sound balance between approximation and generalization abilities of the model. According to selection and adjustment of a weighting factor of an aggregate objective function which depends on the number of data and a certain degree of nonlinearity (distribution of I/O data we show that it is available and effective to design and optimal FNN model structure with a mutual balance and dependency between approximation and generalization abilities. This methodology sheds light on the role and impact of different parameters of the model on its performance (especially the mapping and predicting capabilities of the rule based computing). To evaluate the performance of the proposed model we use the time series data for gas furnace the data of sewage treatment process and traffic route choice process.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.199-205
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• 1998

Cullet Quality Control in auto glass bottle factory is the most important in recent days because of the increasing cost of materials in glass bottle. Since the composition of plate glass cullet is similar, the cullet quality using plate cullet in glass bottle factory is easily controlled. In addition to this, the price of plate glass cullet is so low that the cost reduction can be achieved. If the ratio of plate glass cullet and gush is over 25%, the liquidity of glass water become worse, which is caused by different compositions and viscosity of the components. As a results, Furnace bottom temperature becomes low and glass water becomes inhomogeneous. Thus production efficiency of glass bottle becomes low because of increasing devitrification in Dead Corner part in glass melting furnace. Three experimental methods – (1) increasing melting temperature, (2) using Booster, (3) using bubbler – were performed to increase the furnace bottom temperature and glass water homogeneity. The amounts of plate glass cullet was able to increase up to 90%, 70% and 60% without any devitrification using booster, bubbler and the method of glass melting temperature increase from $1480^{\circ}C$ to $1560^{\circ}C$ respectively. It is not possible to increase the glass melting temperature without the reduction of furnace operation time and the increase of fuel cost. The booster process has disadvantage of much electric energy consumption. Since the bubbler process uses physical convection of melting glass based on compression air, the homogeneity of molten glass is not so good as that of booster process but it can reduce the cost of glass bottle.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.68-74
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• 2005

The electrical arc furnace (EAF) classified as a special waste contains many flux components producing melts during a sintering process, so it decreases the sintering temperature and improves the mechanical properties of specimens. Increasing dust content in a clay-dust system brick, however, may cause the fraction defective higher due to the excessive liquid produced. To control the liquid behavior produced during sintering process for the clay-dust system specimens, the $Al_2O_3$ was added and the physical properties were analyzed. The microstructure for the clay-dust system body sintered with $Al_2O_3$ became homogeneous and the overall size of pores decreased. Adding $Al_2O_3$ to clay-dust system body increased the mechanical properties and the temperature of maximum strength increased as much as $50^{\circ}C$, and the apparent density increased and the absorption decreased. The mullite ($3Al_2O_3{\cdot}2SiO_2$) was produced during sintering process by reaction of $Al_2O_3$ and $SiO_2$ which could participate to liquid-producing-process and the viscosity of melts increased which was proved by measuring a critical viscosity temperature (Tcv) therefore, the refractoriness of specimens were improved to lower the fraction defective.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.6 no.3
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• pp.210-216
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• 2006

In the rule based modeling, data partitioning plays crucial role be cause partitioned sub data set implies particular information of the given data set or system. In this paper, we present an empirical study result of the data pattern estimation to find underlying data patterns of the given data. Presented method performs crisp type clustering with given n number of data samples by means of the sequential agglomerative hierarchical nested model (SAHN). In each sequence, the average value of the sum of all inter-distance between centroid and data point. In the sequel, compute the derivation of the weighted average distance to observe a pattern distribution. For the final step, after overall clustering process is completed, weighted average distance value is applied to estimate range of the number of clusters in given dataset. The proposed estimation method and its result are considered with the use of FCM demo data set in MATLAB fuzzy logic toolbox and Box and Jenkins's gas furnace data.