• Journal of Korean Society for Quality Management
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• v.32 no.1
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• pp.75-91
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• 2004

The Internet has produced a great variety of VOC data. However, they are hardly helpful for CRM because they are not integrated with VOC data of the related businesses yet. This paper has set up a system for the said VOC data to actually become helpful for CRM The system has two aspects. From the aspect of products, the customers' needs for products will be analyzed to produce what they actually want. From the aspect of customers, on the other hand, decent relationships with them shall be maintained constantly by thoroughly analyzing all the related data. The analyses on both of these aspects have the advantage of maximizing customer satisfaction by active CRM that makes us recognize what customers prefer, or complain of in advance and then provide them with tailor-made service.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.11a
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• pp.3-8
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• 2004

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.54-60
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• 2011

This paper is a basic study on volatile organic compounds(VOC) recovery system in a crude oil carrier. VOC is easily evaporated in cargo tankers during loading and transportation of crude oil, causes serious environmental contamination and a huge economic loss. An ejector system is designed to mix VOC gas into crude oil flow to reduce VOC concentration. Detail two-phase flow inside the ejector is simulated using a commercial CFD code. To verify the numerical prediction, a scale-down experiment is conducted. Instead of crude oil and VOC, water and air are used as the working fluids. Flow characteristics and main parameters are obtained by two-phase flow visualization and PIV measurements. Air volume flow rate induced by the ejector is compared with respect to the volume flow rate of water using experimental and numerical results. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

• Analytical Science and Technology
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• v.19 no.6
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• pp.553-558
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• 2006

In this study, an attempt was made to measure uncertainties involved in the VOC analysis for the VOC working standards prepared by a dilution technique using Tedlar bags. For this purpose, VOC standard gases of benzene, toluene, xylene, and styrene were prepared at four different concentrations (4, 8, 20, and 40 ppb). These standard samples were then loaded on to the GC system equipped with air server/thermal desorption (AS/TD) system. Each of these four standard concentrations was analyzed individually to derive their respective calibration results. These calibration data sets were then compared across four different compounds. According to this comparison, differences in calibration patterns were moderately insignificant within the selected concentration range of 4~40 ppb. It was also observed that the loss of styrene standard was fairly high compared to other VOCs investigated simultaneously. The results of our study suggest that the analytical uncertainty associated with the preparation of VOC starndard gas using a dilution technique can be assessed in a fairly reasonable manner for samples with a narrow concentration range.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.755-761
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• 2015

Photocatalytic VOCs removal test in gas phase is generally performed by placing the light source on the outside due to maintaining a constant temperature inside the test chamber. The distance between light source and photocatalysts is importantin the VOC degradation test since the intensity of light is rapidly decreased as the distance farther. Especially, for the choice of light source as UVLED, this issue is more critical because UVLED light source emits lots of heat and it is hard to measure the exact concentration of VOCs due to changed temperature in the test chamber. In this study, we modified VOC removal test chamber base on the protocol of air cleaner test and evaluated the efficiency of photocatalystunder UVLED irradiation. Photocatalystsof two different samples (commercial $TiO_2$ and the synthesized vanadium doped $TiO_2$) weretested for the p-xylene degradation in the closed chamber system and compared with each other in order to exclude any experimental uncertainties. During the VOC removal test, VOC concentrations were monitored and corrected at regular time intervals because the temperature in the chamber increases ${\sim}20^{\circ}C$ due tothe heat of UVLED. The results showed that theconversion ratio of p-xylene has 40~43% difference before and after the temperature correction. Based on those results, we conclude that the VOC concentration correction must be required for the VOC removal test in a closed chamber system under UVLED light source and obtained the corrected efficiencies of various photocatlysts.

• Explosives and Blasting
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• v.33 no.3
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• pp.21-28
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• 2015

The objective of this study is to develop a method for monitoring continuously the combustion propagation behavior of commercial thermite reaction mixtures using conventional continuous VOD (velocity of detonation) system. In order to monitor the combustion front propagation with elapsed time during thermite reaction, the VOD system employs two types of commercial VOD probes and one self-made probe: VOD PROBEROD-OS, VOD PROBEROD-HS and VOD PROBEROD-ES, respectively. Among the probes, the only self made VOD PROBEROD-ES successfully demonstrates the velocity of combustion propagation (VOC) with elapsed time. It was found that VOC of the thermite reaction mixture inside a steel tube has been reached around 200m/s within 100mm distance from the ignition and dramatically increased up to about twice the speed of sound in the range between 100mm and 300mm distance. Finally the VOC reached up to around 800m/s. This results imply that it is necessary to use over 300mm long cartridge of thermite reaction mixture in order to achieve normal VOC of the mixture.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.472-474
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• 2006

• Bulletin of Korea Environmental Preservation Association
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• v.26 no.7_8
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• pp.51-54
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• 2004

산업화가 진행되면서 우리나라에서도 90년대 초반부터 악취문제가 점차 사회적인 관심거리로 등장하게 되었다. 1995년 대기환경보전법상에 휘발성유기화합물질 규제 규정을 신설하였으며 1996년에 여천지역을 환경오염으로 인한 특별대책지역으로 지정하였다.<중략>

• Journal of Information Technology Services
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• v.19 no.6
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• pp.1-13
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• 2020

Recently, 80% of big data consists of unstructured text data. In particular, various types of documents are stored in the form of large-scale unstructured documents through social network services (SNS), blogs, news, etc., and the importance of unstructured data is highlighted. As the possibility of using unstructured data increases, various analysis techniques such as text mining have recently appeared. Therefore, in this study, topic modeling technique was applied to the Korea Highway Corporation's voice of customer (VOC) data that includes customer opinions and complaints. Currently, VOC data is divided into the business areas of Korea Expressway Corporation. However, the classified categories are often not accurate, and the ambiguous ones are classified as "other". Therefore, in order to use VOC data for efficient service improvement and the like, a more systematic and efficient classification method of VOC data is required. To this end, this study proposed two approaches, including method using only the latent dirichlet allocation (LDA), the most representative topic modeling technique, and a new method combining the LDA and the word embedding technique, Word2vec. As a result, it was confirmed that the categories of VOC data are relatively well classified when using the new method. Through these results, it is judged that it will be possible to derive the implications of the Korea Expressway Corporation and utilize it for service improvement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2439-2447
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• 1994

In this paper, We analyze Colpitts type voltage contrqlled oscillator(VCO) used in personal handheld phone using a nonlinear analysis with third-order model. The resul shows the non-exponentially decaying shifting bias superimposed on the oscillator output which is different with the exponentially decaying shifting bias from the linear analysis. The stable oscillation criterion during a frequency change in a design of VOC can be also determined using proposed non-linear analysis. The theory is confirmed using PSPICE simulation and the experimental result of GaAs VCO matched very well with the theory.