• Korean Architects
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• s.523
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• pp.13-13
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• 2012

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1999.04a
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• pp.426-426
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• 1999

;There are many sources of uncertainty in a typical production and inventory system. There is uncertainty as to how many items customers will demand during the next day, week, month, or year. There is uncertainty about delivery times of the product. Uncertainty exacts a toll from management in a variety of ways. A spurt in a demand or a delay in production may lead to stockouts, with the potential for lost revenue and customer dissatisfaction. Firms typically hold inventory to provide protection against uncertainty. A cushion of inventory on hand allows management to face unexpected demands or delays in delivery with a reduced chance of incurring a stockout. The proposed strategies are used for the design of a probabilistic inventory system. In the traditional approach to the design of an inventory system, the goal is to find the best setting of various inventory control policy parameters such as the re-order level, review period, order quantity, etc. which would minimize the total inventory cost. The goals of the analysis need to be defined, so that robustness becomes an important design criterion. Moreover, one has to conceptualize and identify appropriate noise variables. There are two main goals for the inventory policy design. One is to minimize the average inventory cost and the stockouts. The other is to the variability for the average inventory cost and the stockouts The total average inventory cost is the sum of three components: the ordering cost, the holding cost, and the shortage costs. The shortage costs include the cost of the lost sales, cost of loss of goodwill, cost of customer dissatisfaction, etc. The noise factors for this design problem are identified to be: the mean demand rate and the mean lead time. Both the demand and the lead time are assumed to be normal random variables. Thus robustness for this inventory system is interpreted as insensitivity of the average inventory cost and the stockout to uncontrollable fluctuations in the mean demand rate and mean lead time. To make this inventory system for robustness, the concept of utility theory will be used. Utility theory is an analytical method for making a decision concerning an action to take, given a set of multiple criteria upon which the decision is to be based. Utility theory is appropriate for design having different scale such as demand rate and lead time since utility theory represents different scale across decision making attributes with zero to one ranks, higher preference modeled with a higher rank. Using utility theory, three design strategies, such as distance strategy, response strategy, and priority-based strategy. for the robust inventory system will be developed.loped.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.2
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• pp.246-253
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• 2007

All of the machines in a production line can be classified into bottleneck and non-bottleneck machines. A bottleneck is a resource whose capacity limits the throughput of the whole production facility. This paper addresses a batch sizing problem at the bottleneck machine. Traditionally, most batch sizing decisions have been made based on the EOQ (economic order quantity) model where setup and inventory costs are considered while throughput rate is assumed to be given. However, since batch size affects the capacity of the bottleneck machine, the throughput rate may not be constant. As the batch size increases, the frequency of the setup decreases. The saved setup time can be transferred to processing time, which results in higher throughput. But, the larger batch size may also result in longer lead time and larger WIP inventory level. This paper presents an alternative method to determine batch size at the bottleneck machine in a manufacturing line. A linear search algorithm is introduced to find optimal throughput rate and batch size at the same time. Numerical examples are provided to see how the proposed method works and to investigate the effects of some parameters.

• Journal of Welding and Joining
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• v.21 no.7
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• pp.59-64
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• 2003

Microstructure and shear strength of Sn-Zn lead-free solders and Au/Ni/Cu UBM joint under thermal aging conditions was investigated. The samples were aged isothermally at 10$0^{\circ}C$ and 15$0^{\circ}C$ for 300, 600, and 900 hours. The IMCs(Intermetallic Compound) at the interface between solder and UBM were examined by FESEM and TEM. The results showed that the shear strength was decreased with aging time and temperature. The solder ball with high activated RA flux had about 8.2% higher shear strength than that of RMA flux. Poor wetting and many voids were observed in the fractured solder joint with of RMA flux. The decreased shear strengths were caused by IMC growth and Zn grain coarsening. Zn reacted with Au and then was transformed to the $\beta$ -AuZn compound. Although AuZn grew first, $r-Ni_5Zn_{21}$ compounds were formed with aging time. The layers indicated by $Ni_5Zn_{21}(1)$, (2), and (3) were formed with the thickness of ∼0.7 ${\mu}{\textrm}{m}$, ∼4 ${\mu}{\textrm}{m}$, and ∼2 ${\mu}{\textrm}{m}$, respectively.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.10a
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• pp.99-102
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• 2000

In the supply chain network design, how to select the best location, capacity configuration of the suppliers and to assign manufacturers orders are a challenging issue. Especially when multi-tiers'suppliers are existed, the performance of supply chain is influenced by 2$\^$nd/ and 3$\^$rd/ suppliers. Supplier selection is multi-criteria problem which includes both qualitative and quantitative factors in supply chains. In order to select the best supplier it is necessary to make a trade off between these two factors such as cost, product quality, capacity, production lead time, deliver lead time and transportation lead tine of supplier constraints existed in multi-tiers supplier purchasing chain. In these circumstances, purchasing agents should decide two problems: which is the best supplier in each tier and how much should be purchased from each selected supplier. This research is intended to develop an integration of an analytical hierarchy process (AHP) and mathematical modeling proposed to consider two factors which may be conflicted in choosing the best supplier in each tier and placing the optimum order quantities to the supplier among multi-tiers suppliers.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.1-8
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• 1992

The morphology of lead titanate powders prepared by sol-gel and coprecipitation techniques was investigated as a function of firing temperature and soaking time. PbTiO3 precursor powders were derived from a mixed solution of lead nitrate and titanium tetrachloride at 40℃ to 43℃ and pH of 9.0 to 9.7, and fired at temperatures 350-1000℃ for 1-10h in air. An increase of particle size and agglomeration with increasing calcination temperature and duration could be observed. By annealing sol-gel derived powder at 700℃, the tially-formed acicular(and/or prismatic) primary particles transformed to polyhedral shape with soaking time, and further soaking caused coarsening the polyhedral particles with rounded edges. However, the morphology of the coprecipitated powders was not varied during crystallization.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.6
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• pp.698-704
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• 1999

There are several types of defects of SMDs mounted on PCB, that is, missing components, misalignment, wrong parts and poor solder joints. This research study mainly focuses on measuring of deviation of SMD leads using the partial image of component, not using the full image. This processing based on the partial image has the advantage of the reduction in calculation time compared to the full image. Since position of lead is calculated with respect of the reduction in calculation time compared to the full image. Since position of lead is calculated with respect to pad, the accuracy of the system is not dependent on percise positioning stage. The grabbed image of gray scale is converted into binary format using a cutomatic threshold. After small fragments in the image is removed by a series of morphology operations such as opening and closing, the centroids of PCB pads and SMD leads is obtained together with labeling of blobs. Translational shift and rotationial angle of SMD are succedingly estimated using above information and chip data. The expression that can calculate the maximum deviation of leads with respect to PCB pads has been derived, and inferior mounting of SMD is judged by a given criterion. Some experiments have been executed to verify this measuring scheme.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1219-1224
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• 2005

We prepared lead ion-selective PVC membranes that were based on N,N'-bis-thiophene-2-ylmethylene-ethane-1,2-diamine as a membrane carrier. The membrane electrode has a linear dynamic range between 1.0 ${\times}$ $10^{-5}$ and 1.0 ${\times}$ $10^{-1}$ M with a Nernstian slope of 29.79 mV per decade, and its detection limit was 2.04 ${\times}$ $10^{-6}$ M at room temperature. The potentiometric response is independent of the pH of the solution in the pH range of 5-7. The proposed electrode revealed good selectivity and response for $Pb^{2+}$ over a wide variety of other metal ions in pH 5.0 buffer solutions, and there was good reproducibility of the base line on the subsequent measurements. The membrane electrode has a relatively fast response time, satisfactory reproducibility and a relatively long life time.

• Industrial Engineering and Management Systems
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• v.3 no.1
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• pp.52-58
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• 2004

This report examines the issue of designing an efficient production system by increasing several types of flexibility. Increasing manufacturing flexibility is a key strategy for efficiently improving market responsiveness in the face of uncertain market demand for final products. The manufacturing system comprises multiple plants, of which individual plants have multiple manufacturing lines that are designed to produce limited types of products in accordance with their size and materials. Imbalance in the workload occurs among plants as well as among manufacturing lines because of fluctuations in market demand for final products. Thereby, idleness of some manufacturing lines and longer lead times in some manufacturing lines occur as a result of the high workload. We clarify how these types of flexibility affect manufacturing performance by improving only one type of flexibility or by improving multiple types of flexibility simultaneously. The average lead time and the imbalance in workload are adopted as measures of manufacturing performance. Three types of manufacturing flexibility are interrelated: machine flexibility, routing flexibility, and process flexibility. Machine flexibility refers to the various types of operations that a machine can perform without requiring the prohibitive effort of switching from one order to another. Routing flexibility is the capability of processing a given set of part types using more than one line (alternative line) in the plant. Process flexibility results from being able to build different types of final products at the same plant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.803-806
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• 2011

1 mol% $Li_2O$ excess $0.9(Na_{0.52}K_{0.48})NbO_3-0.1LiTaO_3$ lead-free piezoelectric multilayer ceramic actuators were investigated to determine their aging properties. To reduce the thermal aging behavior, we applied a rectified unipolar electric field of 5 kV/mm to the specimen to accelerate the electric aging behavior. By employing a rectified unipolar electric field for the piezoelectric actuators, we could remove undesirable heating from the relaxation current in the motion of the ferroelectric domain. To accelerate the aging test, the applied electric fields had a frequency of 900 Hz. To have enough time for charging and discharging, we employed an accurate time constant to design the equivalent circuit model for the aging tester. To extract exact aging behavior, we measured the pseudo-piezoelectric coefficient before and after the aging process. We also measured the electro-mechanical coupling coefficient, the frequency-dependent dielectric permittivity, and the impedance to compare with fresh and aged specimen.