• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.11 no.4
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• pp.6-18
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• 1982

The performance of two typical types of solar hot water heating system was tested in Seoul. Types of systems studied are single-tank internal external heat exchanger system and single-tank internal heat exchanger system. Comparing to experimental results, a transient system simulation program was made to analyze the performance of the selected system. The climate data, Standard Weather Year for Seoul, required for the simulation was provided. Computer simulations were used to estimate the effect of significant parameters upon system performance. The followings are obtained. 1. In the domestic solar water Heating system, the value $20-40kg/m^2\;h$ for flow rate through the collector is much better than the recommended value $72kg/m^2\;h$ in the solar heating system. 2. The effectiveness of collector heat exchanger and storage tank size are found to have only a small effect upon system performance. 3. The hot water draw pattern has a significant effect on system performance. A higher system efficiency achieved when draw-off occurred around noon than when it occurred around early morning. Using the above results, the reference solar hot water system which provides $300\ell$ of hot water per day, was selected as a guide for designer. And simplified graphical method was developed based on the modified f-chart method to determine required collector area. When the system design parameters of the proposed system differs from the reference system, required collector area can be calculated from area adjustment factors.

• Smart Structures and Systems
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• v.32 no.6
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• pp.371-382
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• 2023

Box girder bridges are now widely used in bridge construction, and it is necessary to perform load rating regularly to evaluate the load capacity of box girder bridges. Load testing is a common measure for load rating. However, the bridge must be loaded by many trucks under different loading conditions, which is time-consuming and laborious. To solve this problem, this paper proposes a load rating method for box girder bridges based on rapid moving loads testing. The method includes three steps. First, the quasi-influence factors of the bridge are obtained by crossing the bridge with rapidly moving loads, and the structural modal parameters are simultaneously obtained from the dynamic data to supplement. Second, an objective function is constructed, consisting of the quasi-influence factors at several measurement points and structural modal parameters. The finite element model for load rating is then updated based on the Rosenbrock method. Third, on this basis, a load rating method is proposed using the updated model. The load rating method proposed in this paper can considerably reduce the time duration of traditional static load testing and effectively utilize the dynamic and static properties of box girder bridges to obtain an accurate finite element model. The load capacity obtained based on the updated model can avoid the inconsistency of the evaluation results for the different structural members using the adjustment factors specified in codes.

• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.87-91
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• 2024

SiO₂, renowned for its excellent insulating properties, has been used in the semiconductor industry as a valuable dielectric material. High-quality SiO₂ films find applications in gate spacers and interlayer insulation gap-fill oxides, among other uses. One of the prevalent methods for depositing these SiO₂ films is plasma enhanced chemical vapor deposition (PECVD) favored for its relatively low processing costs and ability to operate at low temperatures. However, compared to the increasingly utilized atomic layer deposition (ALD) method, PECVD exhibits inferior film characteristics such as uniformity. This study aims to produce SiO₂ films with uniformity as close as possible to those achieved by ALD through the adjustment of PECVD process parameters. we conducted a total of nine PECVD processes, varying the process time and gas flow rates, which were identified as the most influential factors on the PECVD process. Furthermore, ellipsometry analysis was employed to examine the uniformity variations of each process. The experimental results enabled us to elucidate the relationship between uniformity and deposition rate, as well as the impact of gas flow rate and deposition time on the process outcomes. Additionally, thickness measurements obtained through ellipsometer facilitate the identification of optimal process parameters for PECVD.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1473-1476
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• 1997

This paper presents a scheme for continuous-time fuzzy modelling of nonlinear systems, based on the adjustment technique and the genetic algorithm technque. The fuzzy model is characterized by fuzzy "If-then" rules whcih represent locally linear input-output relations whose consequence part is defined as subsystem of a nonlinear system. To compute the final output and deal with the initialization and unmeasurable signal problems in on-line estimatio of the fuzzy model, a discrete-time model is obtaned. Then the parameters of both the premis and consequence of the fuzzy model are adjusted on-line by a genetic algorithm. A simulation work is carried out to demonstrate the effectiveness of the proposed method.ed method.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.433-436
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• 2007

We analyzed the sloped ground safety factor, which is not presented in the design specification, using a computational analysis program L-Pile Plus 13.8. To achieve this we chose a required parameter set and a level ground safety factor presented in the design specification, and then determined its values comparing with the change of the safety factor according to the parameter. Using these parameters, we estimated the sloped ground safety factor for the slope of 35 degrees considering the improvement value of the slope presented in the design specification. As a result of this analysis, we obtained the smaller safety factor by about 0.7 times than the case of the level ground and verified that a number of concrete poles fail to assure 1 degree of the safety factor. We, therefore, concluded that an adjustment of the embedment depth is required in the case of the sloped ground.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1086-1090
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• 2001

In this paper, a method deciding the permissible gains of the P and PT controllers for a retarded process under stable condition is proposed. For analysis, the controlled process is assumed to be first-order system with time delay. At first, the adjustable parameter sets causing stability limit are obtained based on the frequency domain condition which makes the roots of the characteristic equation locate on the imaginary axis. And the cut-in frequency ${\omega}_p$ to bring the parameter set to P control from PI control is derived is derived in terms of L and $T_m$ then ${\omega}_p$ is used to compute the maximum gain with stable condition. The results indicate that the permissible controller gains can be described by a unique if parameters L and $T_m$ are know.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.4
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• pp.285-294
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• 2007

In this paper, we investigate a novel online estimation algorithm for dynamic Bayesian network(DBN) parameters, given as conditional probabilities. We sequentially update the parameter adjustment rule based on observation data. We apply our algorithm to two well known representations of DBNs: to a first-order Markov Chain(MC) model and to a Hidden Markov Model(HMM). A sliding window allows efficient adaptive computation in real time. We also examine the stochastic convergence and stability of the learning algorithm.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.3-32
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• 2016

High power impulse magnetron sputtering (HiPIMS) technique has been developed for more than 15 years. It is characterized by its ultra-high peak current and peak power density to obtain unique thin film properties, such as high hardness, good adhesion and tribological performance. However, its low deposition rate makes it hard to be applied in industries. In this work, the development of HiPIMS system and integration of radio frequency (RF) or mid-frequency (MF) power supplies were introduced. Effects of duty cycle and repetition frequency on the microstructure, mechanical property, optical and electrical properties of some binary, ternary and quarternary nitride coatings and oxide thin films were discussed. It can be observed that the deposition rate was effectively increased by the superimposed HiPIMS with RF or MF power. High hardness, good adhesion and sufficient wear resistance can be obtained through a proper adjustment of processing parameters of HiPIMS power system.

• Communications for Statistical Applications and Methods
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• v.27 no.1
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• pp.65-77
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• 2020

Geometric charts are effective in monitoring the fraction nonconforming in high-quality processes. The in-control fraction nonconforming is unknown in most actual processes; therefore, it should be estimated using the Phase I sample. However, if the Phase I sample size is small the practitioner may not achieve the desired in-control performance because estimation errors can occur when the parameters are estimated. Therefore, in this paper, we adjust the control limits of geometric charts with the bootstrap algorithm to improve the in-control performance of charts with smaller sample sizes. The simulation results show that the adjustment with the bootstrap algorithm improves the in-control performance of geometric charts by controlling the probability that the in-control average run length has a value greater than the desired one. The out-of-control performance of geometric charts with adjusted limits is also discussed.

• International Journal of Safety
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• v.1 no.1
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• pp.1-6
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• 2002

It is important to control the high accurate position and force to prevent unexpected accidents by a robot manipulator. Direct-drive robots are suitable to the position and force control with high accuracy, but it is difficult to design a controller because of the system's nonlinearity and link-interactions. This paper is concerned with the study of the stabilization force control of direct-drive robots. The proposed algorithm is consists of the feedback controllers and the neural networks. After the completion of learning, the outputs of feedback controllers are nearly equal to zero, and the neural networks play an important role in the control system. Therefore, the optimum adjustment of control parameters is unnecessary. In other words, the proposed algorithm does not need any knowledge of the controlled system in advance. The effectiveness of the proposed algorithm is demonstrated by the experiment on the force control of a parallelogram link-type robot.