• Journal of Korean Society for Quality Management
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• v.45 no.2
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• pp.293-306
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• 2017

Purpose: In this study, an optimal design level of influencing factors on semiconductor polishing process was determined to minimize flexion of both sides on wafers. Methods: First, significant interactions are determined by the stepwise regression method. ANOVA analysis on SN ratio and mean of dependent variable are performed to draw mean adjustment factors. In addition, the optimal levels of mean adjustment factors are decided by comparing means of each level of mean adjustment factors. Results: As a result of ANOVA, a mean adjustment factor was determined as a width of formed flexion on the plate. The mean of the difference has the nearest to 0 in the case when the width of formed flexion has level 2 (4mm). Conclusion: Optimal design levels of semiconductor polishing process are determined as follows; (i) load applied to the wafer carrier has a level 1 (3psi), (ii) load applied to the wafer has a level 1(3psi), (iii) the amount of slurry supplied during polishing has a level 3 (300 co/min), (iv) the width of formed flexion on the plate has level 2 (4mm).

• Journal of Hydrogen and New Energy
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• v.29 no.1
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• pp.19-24
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• 2018

Fuel cells are used to generate electricity with a reformer. In particular, methanol has various advantages among the fuels for reformer. Methanol steam reformer devices can efficiently supply hydrogen to PEM fuel cell. This study investigated the optimal operation conditions of a methanol steam reforming process. For this purpose, aspen HYSYS was used for the optimization of reforming process. The optimal operating condition could be designed by setting independent variables such as temperature, pressure and steam to carbon ratio (SCR). The optimal temperature and steam to carbon ratio were $250-270^{\circ}C$ and 1.3-1.5, respectively. It is advantageous to operate at a pressure of 15-20 barg, considering the performance of the hydrogen purifier. In addition, a heat exchange network was designed to supply heat constantly to reformer through the latent heat of steam.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.99-104
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• 2002

This study deals with the optimal design of a DC reactor type high-Tc superconducting fault current limiter(SFCL). The condition in which the cost function is minimized under given constraints is one of the things to be first considered in developing SFCLS. This condition is a group of the values corresponding to the variables the cost function depends on. In this paper, the length of tape was taken as a dependent variable, the inductance of DC reactor and the turns ratio of magnetic core reactors as independent variables. For the SFCL available at the level of 6.6kV-200A, we examined 4 cases; at the fault times of 80msec, 50msec, 30msec and 10msec. Since thyristors would be utilized instead of diodes, we chose the result at 10msec as the basic data. Considering safety factor 30%, our optimal design was decided to be the inductance 570mH, the critical current over 620A, the turns ratio 0.89 and the fault time within 20msec.

• Mycobiology
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• v.31 no.4
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• pp.214-220
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• 2003

The fruiting body of Paecilomyces fumosoroseus was collected at Mt. Mani, Ganghwa Island, Korea in September, 2001. This study was carried out to obtain the basic informations for the mycelial growth and fruiting body production of P. fumosoroseus in artificial media. The optimal conditions for the mycelial growth were obtained at $25^{\circ}C$ and in the range of pH $6{\sim}9$, respectively. P. fumosoroseus showed the favorable growth on Hamada medium. The carbon and nitrogen source favorable for mycelial growth were dextrin and histidine, respectively. Optimum C/N ratio suitable for optimal growth of P. fumosoroseus was observed on the culture media adjusted to the ratio of 40:1. The mycelial growth of P. fumosoroseus was optimal on corn meal agar supplemented with 30% of silkworm pupae. The most favorable fruiting body formation of P. fumosoroseus was obtained in the medium containing unpolished rice supplemented with 20%(w/w) silk worm pupae at $25^{\circ}C$ under 100 lux.

• Industrial Engineering and Management Systems
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• v.13 no.2
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• pp.231-249
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• 2014

This paper discusses a green supply chain with a manufacturer and a collection trader, and it proposes an optimal production planning for remanufacturing of parts in used products with quality classification errors made by the collection trader. When a manufacturer accepts an order for parts from a retailer and procures used products from a collection trader, the collection trader might have some quality classification errors due to the lack of equipment or expert knowledge regarding quality classification. After procurement of used products, the manufacturer inspects if there are any classification errors. If errors are detected, the manufacturer reclassifies the misclassified (overestimated) used products at a cost. Accordingly, the manufacturer decides to remanufacture from the higher-quality used products based on a remanufacturing ratio or produce parts from new materials. This paper develops a mathematical model to find how quality classification errors affect the optimal decisions for a lower limit of procurement quality of used products and a remanufacturing ratio under the lower limit and the expected profit of the manufacturer. Numerical analysis investigates how quality of used products, the reclassification cost and the remanufacturing cost of used products affect the optimal production planning and the expected profit of a manufacturer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1185-1191
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• 2008

This paper presents an approach to define an optimal piezoactuator length to actively control structural vibration. The optimal ratio of the piezoactuator length against the beam length when a pair of piezoceramic actuator and accelerometer is used to suppress unwanted vibration with direct velocity feedback(DVFB) control strategy is not clearly defined so far. It is well known that DVFB control can be very useful when a pair of sensor and actuator is collocated on structures with a high gain and excellent stability. It is considered that three different collocated Pairs of piezoelectric actuators (20, 50 and 100 mm long) and accelerometers installed on three identical clamped-clamped beams($30{\times}20{\times}1mm$). The response of each sensor-actuator pair requires strictly positive real(SPR) property to apply a high feedback gain. However the length of the piezoactuator affects the SPR property of the sensor-actuator response. Intensive simulation and experiment show the effect of the actuator length variation is strongly related with the frequency range of the SPR property. Thus an optimal length ratio was suggested to obtain relevant performance with a good stability under the DVFB strategy.

• Steel and Composite Structures
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• v.29 no.6
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• pp.749-758
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• 2018

This article derived a hybrid coupling technique using the higher-order displacement polynomial and three soft computing techniques (teaching learning-based optimization, particle swarm optimization, and artificial bee colony) to predict the optimal stacking sequence of the layered structure and the corresponding frequency values. The higher-order displacement kinematics is adopted for the mathematical model derivation considering the necessary stress and stain continuity and the elimination of shear correction factor. A nine noded isoparametric Lagrangian element (eighty-one degrees of freedom at each node) is engaged for the discretisation and the desired model equation derived via the classical Hamilton's principle. Subsequently, three soft computing techniques are employed to predict the maximum natural frequency values corresponding to their optimum layer sequences via a suitable home-made computer code. The finite element convergence rate including the optimal solution stability is established through the iterative solutions. Further, the predicted optimal stacking sequence including the accuracy of the frequency values are verified with adequate comparison studies. Lastly, the derived hybrid models are explored further to by solving different numerical examples for the combined structural parameters (length to width ratio, length to thickness ratio and orthotropicity on frequency and layer-sequence) and the implicit behavior discuss in details.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.503-518
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• 2023

In tall constructions, the outriggers are regarded as a structural part capable of effectively resisting lateral loads. This study analyses the efficacy of hybrid outrigger system in high rise RCC building for various structural parameters identified. For variations in α, which is defined as the ratio of the relative flexural stiffness of the core to the axial rigidity of the column, static and dynamic analyses of hybrid outrigger system having a virtual and a conventional outrigger at two distinct levels were conducted in the present study. An investigation on the optimal outrigger position was performed by taking the results from absolute maximum inter storey drift ratio (ISD_max), roof acceleration (acc_roof), roof displacement (disp_roof), and base bending moment under both wind and seismic loads on analytical models having 40, 60 and 80 storeys. An ideal performance index parameter was introduced and was utilized to obtain the optimal position of the hybrid outrigger system considering the combined response of ISD_max, acc_roof, disp_roof and, criteria required for the structure under wind and seismic loads. According to the behavioural study, increasing the column area and outrigger arm length will maximise the performance of the hybrid outrigger system. The analysis results are summarized in a flowchart which provides the optimal positions obtained for each dependent parameter and based on ideal performance index which can be used to make initial suggestions for installing a hybrid outrigger system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.582-587
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• 2007

In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

• Journal of Mechanical Science and Technology
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• v.14 no.7
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• pp.764-772
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• 2000

In this paper, an engine-CVT integrated control algorithm is suggested by considering the inertia torque and the CVT ratio change response lag in acceleration. In order to compensate for drive torque time delay due to CVT response lag, two algorithms are presented: (1) an optimal engine torque compensation algorithm, and (2) an optimal engine speed compensation algorithm. Simulation results show that the optimal engine speed compensation algorithm gives better engine operation around the optimal operation point compared to the optimal torque compensation while showing nearly the same acceleration response. The performance of the proposed engine-CVT integrated control algorithms are compared with those of conventional CVT control, and It is found that optimal engine operation can be achieved by using integrated control during acceleration, and improved fuel economy can be expected while also satisfying the driver's demands.