• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.145-151
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• 1996

The effectiveness of physiological or chemical acid - alkali solution was investigated as the method to control pH value of nutrient solution in hydroponics dynamically. Lettuces were cultivated using NH$_4$H$_2$PO$_4$ as physiological acid and NaNO$_3$ as physiological alkali or H$_2$SO$_4$ as chemical acid in dynamic control system. The pH of nutrient solution was controlled satisfactorily in the range of pH 5.5-6.5, regardless of treatments. Chemical acid changed pH of solution faster than chemical acid when supplied to the nutrient solution. Any of them did not show any harmful symptom. It is recommended that chemical acid is preferred during the growing stage and physiological acid like as NH$_4$H$_2$PO$_4$ is preferred from several days before harvest stage.

• 보존과학연구
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• s.34
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• pp.84-99
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• 2013

There are more than 2,900 different species of termites in the world, and just there are 23 species in Japan. They caused more severe infestation compared with Korea. When a structure has become infested with termites, it is important that appropriate action must be taken: the chemical pest control (fumigation, soil termiticide treatment, bait system etc.) or the non-chemical pest control (low oxygen treatment, carbon dioxide treatment, high/low temperature treatment etc.). Especially, there were attempts to make practical protocol of various alternatives since the fumigant(methyl bromide) had been phased out in 2005 in Japan, and practically non-chemical methods would be effective alternatives for some cases, where the scale of infestation is small and limited and when long treatment is possible. But most of all, it is important that the process of pest control is made according to each species of termites with consideration for different characteristics of termites.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.448-457
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• 1996

Chemical application is one of the most important field operation in rice production . Rolling of a boom due to local unevenness and softness in fields causes a local under/over-application of spray. This study was conducted to develop a control system for balancing a boom. A boom mounting mechanism was modfied and a control algorithm was developed in the study. The results for testing the performance of the control system showed that the system could balance the boom in flat and inclined fields. This research can contribute to improve spraying uniformity in applying agricultural chemicals with a boom sprayers.

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.743-746
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• 1998

The Belousov-Zhabotinskii (BZ) reaction, which is composed of a bromate-organic acid-metal catalyst and an acidic solution is a commonly employed chemical oscillating reaction system. Cyclohexanedione (CHD) has been used as an initial organic substrate in oscillation systems. We studied each system of 1,4-CHD/BrO3-/Ce4/H+ and 1,3-CHD/BrO3-/Ce4+/H+ oscillating reactions, and studied the control of oscillating characters in a CHD/BrO3-/Ce4+/H+ batch system using a mixed substrate of 1,4-CHD and 1,3-CHD under a fixed total CHD concentration. In the mixed reactions, 1,4-CHD was used as a main substrate and small amounts of 1,3-CHD were used in order to vary the oscillatory behaviours by changing the mixing amount ratio of two substrates.

• Fire Science and Engineering
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• v.29 no.5
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• pp.73-78
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• 2015

Since the hydrofluoric acid spill accident in Gumi in 2012, the current situation has continued to suffer from makeshift responses or feeble national system maintenance in preparing real countermeasures against chemical accidents, regardless of their repeated occurrence and seriousness. Industrial chemical accidents have an enormous ripple effect on the whole country and society. The purpose of this study is to propose ways of establishing directions for the national disaster management system against repeated occurrence of chemical accidents. To achieve this goal, the present study proposed improvement measures of response system for industrial chemical accident through the analysis of the current response system and structural causes of disaster control failure for chemical accidents.

• Journal of the Semiconductor & Display Technology
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• v.4 no.3 s.12
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• pp.29-33
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• 2005

As the integrated devices become more and more sophistcated, the diameter of wafers increased up to 300 mm and strict level of cleaning is necessary to remove the particulates on the surface of wafer. Therefore we need a new type of wet-station which can reduce DI water and chemical in the cleaning process. Moreover, it is important to control the temperature and the concentration of chemical in the wet-station. In the conventional chemical supply system, it is difficult not only to fit the mixing rate of chemicals in cleaning process, but also to fit the quantity and temperature. Thus, we propose a new chemicals supply system, which overcomes above problems by the analysis of fluid and thermal transfer on chemical supply system.

• Journal of the Korean Institute of Gas
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• v.9 no.2 s.27
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• pp.28-33
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• 2005

Because chemical industrial facilities deal with large amount of hazardous materials, the damage affect to off-site as well as on-site when an accident occurs. So it is necessary to develop a Risk Representation System for effective control and response to major accidents. In this study a Risk Representation System(S/W) was developed to help analyzing actual risk and to set an alternative that can reduce the analyzed risk by drawing the level of individual plant's risk on a digital map network.

• International Journal of Control, Automation, and Systems
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• v.4 no.6
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• pp.763-768
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• 2006

The two-for-one(TFO) twister is precision machinery that twists fibers rapidly under constant tension. Since the quality of the twisted yarn is directly deteriorated by faults of the twister, such as the distortion of the spinning axis, bearing abrasion, and tension irregularity, it is important to detect faults of the TFO twister at an early stage. In this research, a new algorithm is proposed to detect faults of the TFO twister and their causes, by measuring the vibrations of the TFO twister and obtaining frequency components with a FFT algorithm. The TFO twister with faults showed increased vibrations and each fault generated vibrations at different frequencies. By analyzing changes of characteristics of vibrations, we can determine faulty twisters. The proposed fault detection algorithm can be implemented cheaply with a signal processor chip. It can be used to find when to repair a faulty TFO twister without much loss of yam on-line.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.5
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• pp.450-457
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• 2004

In this research, the automatic synthesis of knowledge models is proposed. which are the basis of the methods using qualitative models adapted widely in fault diagnosis and hazard evaluation of chemical processes. To provide an easy and fast way to construct accurate causal model of the target process, the Role-Behavior modeling method is developed to represent the knowledge of modularized process units. In this modeling method, Fault-Behavior model and Structure-Role model present the relationship of the internal behaviors and faults in the process units and the relationship between process units respectively. Through the multiple modeling techniques, the knowledge is separated into what is independent of process and dependent on process to provide the extensibility and portability in model building, and possibility in the automatic synthesis. By taking advantage of the Role-Behavior Model, an algorithm is proposed to synthesize the plant-wide causal model, Fault-Causality Graph (FCG) from specific Fault-Behavior models of the each unit process, which are derived from generic Fault-Behavior models and Structure-Role model. To validate the proposed modeling method and algorithm, a system for building FCG model is developed on G2, an expert system development tool. Case study such as CSTR with recycle using the developed system showed that the proposed method and algorithm were remarkably effective in synthesizing the causal knowledge models for diagnosis of chemical processes.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.5
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• pp.609-615
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• 2021

Chemical accidents can happen anywhere in the world. To prevent chemical accidents, Korea introduced the Chemicals Control Act. However, Small and medium-sized businesses do not meet these regulations. Accordingly, the Ministry of Environment is providing a chemical safety management support project for Small and medium-sized businesses. However, there are many small and medium-sized businesses, and businesses that need support need priority. In this study, the risk of the plants was classified into hig h, medium, and low risk based on four methods. As a result, out of 90 plants subject to the study, high risk was 30% and medium risk was 70%. The industries with the high risk were chemical products manufacturing and paint manufacturing. The plating and printing industries showed relatively medium risk. This risk classification has the advantage that it can obtain intuitive and quick results. These studies can be used as basic data for chemical safety management of local governments and Ministry of Environment.