• 한국환경과학회지
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• 제13권1호
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• pp.55-59
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• 2004

The effect of ozone on the formation and the removal of disinfection byproducts(DBPs) of chlorination process was studied to elucidate the performance of water treatment process. The samples of raw water, prechlorination process, and preozonation process were analyzed quantitatively according to the Standard Methods for the Examination of drinking water. As a result, most of total trihalomethanes(THMs) which were formed in prechlorine treatment process was not removed in the preozonation process. Most of haloacetic acids(HAAs), haloacetonitriles(HANs), and chloral hydrate(CH) was removed in sedimentation and biological activated carbon(BAC) filtration processes. However, DBPs were increased more or less by postchlorine step. In particular, the formation of THMs and HAAs depends on ozone more than chlorine, but, the formation of HANs and CH depends on chlorine more than ozone. The seasonal variation of DBPs concentration for the year needs to be investigated to study the temperature effect because DBPs strongly depend on temperature among various efficient factors.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.25-33
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• 2022

본 연구에서는 흑액 증발공정에 소비되는 스팀의 절감량을 예측하기 위해 증발기 수에 따른 다중 효용 증발공정 모델을 개발하였다. 개발한 공정 모델은 흑액의 예열 및 증발 과정으로 구성되어 있고, 스팀 사용량을 예측하기 위해 가상의 재비기가 추가되었다. 시뮬레이션 결과, 2중 효용 증발기에서 스팀 사용량은 48.9% 감소하였고, 증발기 수가 증가함에 따라 스팀 사용량이 감소하여 8중 효용 증발기에서 최대 76.5% 감소함을 확인하였다. 시뮬레이션 결과를 증발기 수에 따른 포화증기의 잠열 회수량, 스팀 사용량, 각 증발기의 포화증기 생산량으로 분석하여 최적의 증발기 수 도출을 위한 방안을 제시하였다.

• Structural Engineering and Mechanics
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• 제76권2호
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• pp.175-191
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• 2020

In this study, the effect of Nano silica (SiO2) on the buckling strength of the glass fiber reinforced laminates containing the machining process causes holes were investigated. The tests have been applied on two status milled and non-milled. To promote the mechanical behavior of the fiber-reinforced glass epoxy-based composites, Nano sio2 was added to the matrix to improve and gradation. Nano sio2 is chosen because of flexibility and high mechanical features; the effect of Nanoparticles on surface serenity has been studied. Thus the effect of Nanoparticles on crack growth and machining process and delamination caused by machining has been studied. We can also imply that many machining factors are essential: feed rate, thrust force, and spindle speed. Also, feed rate and spindle speed were studied in constant values, that the thrust forces were studied as the main factor caused residual stress. Moreover, entrance forces were measured by local calibrated load cells on machining devices. The results showed that the buckling load of milled laminates had been increased by about 50% with adding 2 wt% of silica in comparison with the neat damaged laminates while adding more contents caused adverse effects. Also, with a comparison of two milling tools, the cylindrical radius-end tool had less destructive effects on specimens.

• 소성∙가공
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• 제15권8호
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• pp.544-549
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• 2006

In this work, we have employed the strain gradient plasticity theory to investigate the effect of material size on the deformation behavior in metal forming process. Flow stress is expressed in terms of strain, strain gradient (spatial derivative of strain) and intrinsic material length. The least square method coupled with strain gradient plasticity was used to calculate the components of strain gradient at each element of material. For demonstrating the size effect, the proposed approach has been applied to plane compression process and micro rolling process. Results show when the characteristic length of the material comes to the intrinsic material length, the effect of strain gradient is noteworthy. For the microcompression, the additional work hardening at higher strain gradient regions results in uniform distribution of strain. In the case of micro-rolling, the strain gradient is remarkable at the exit section where the actual reduction of the rolling finishes and subsequently strong work hardening take places at the section. This results in a considerable increase in rolling force. Rolling force with the strain gradient plasticity considered in analysis increases by 20% compared to that with conventional plasticity theory.

• 한국정보시스템학회지:정보시스템연구
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• 제17권4호
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• pp.181-206
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• 2008

This study aims to investigate the impacts of managerial and technical IT knowledges on firm's financial performance. Specifically, the study examines the following three effects between IT personnel knowledges and financial performance: (1) direct effect, (2) mediating effect of business process performance, and (3) moderating effect of firm size, between them. An empirical study resulted in the followings. First, both managerial and technical IT knowledges do not have direct influences on financial performance. Second, unlike technical IT knowledge, managerial IT knowledge indirectly affects financial performance through business process performance, confirming the mediating role of business process performance. Third, while technical IT knowledge produce no direct and indirect effect on financial performance regardless of firm size, managerial IT knowledge exerts significant impacts on financial performance although such effects represent some different patterns according to firm size. That is, in the smaller group, the association between managerial IT knowledge and financial performance is partially mediated by business process performance and in the larger group, that relationship fully mediated.

• 대한환경공학회지
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• 제30권8호
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• pp.823-830
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• 2008

Rhodamine B(RhB) 탈색에 대한 광전기촉매 공정의 적용가능성을 분말 TiO$_2$를 충전한 슬러리 광전기촉매 반응기에서 연구하였다. 광전기촉매 공정의 반응기 시스템은 분말 TiO$_2$, Pt 전극 및 3개의 8 W UV-C 등으로 구성되어 있다. 전류, 전해질, 공기 유량 및 전극 재질과 같은 운전 인자의 영향을 고찰하였다. 광전기촉매 공정의 최적 광촉매 량과 전류는 각각 0.4 g/L과 0.02A이었다. 광촉매 공정과 전기분해 단독 공정에 의해 분해되는 RhB의 합보다 광전기촉매 공정에 의해 더 빨리 분해되었는데, 광촉매 공정과 전기분해 공정의 결합에 의한 시너지 효과를 나타내는 것으로 사료되었다. 광전기촉매 공정은 공기 유량에 의해 영향을 받는 것으로 나타났고 최적 공기 유량은 2 L/min이었다. RhB 탈색에 대한 전극 재질과 NaCl 효과는 본 실험범위에서는 크지 않은 것으로 나타났다.

• 한국기계가공학회지
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• 제13권2호
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• pp.81-88
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• 2014

Synthetic products such as casting tape and splints are rapidly replacing conventional plaster casts to treat orthopedic patients. Most synthetic products are produced through a polymerization process with related chemical agents. In this study, the effect of the process parameters on the residual NCO content within a prepolymer for casting tape and the hardening temperature for casting tape were experimentally evaluated. In order to verify the effects of the process parameters, an experimental method was adopted. From an S/N ratio analysis, optimal parameter combinations were determined to produce a pre-polymer with a suitable residual NCO content and alower hardening temperature. Prediction models for the NCO content and the hardening temperature were developed and confirmed.

• 한국소음진동공학회논문집
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• 제13권7호
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• pp.532-538
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• 2003

This paper studies on the noise reduction for a small automobile DC Motor (a window motor) using the 6 sigma process. The application of 6 sigma process suggested reliable and valuable statistical data for the quality of the DC motor at the production line. In the measurement step in 6 sigma process. the FMEA(failure mode effect analysis) were used for the detection of noise sources. The application of 6 sigma Process gave not only the improving method for the quality of the DC motor but also the confidence of improvement Itself since it was done on the basis of the test results for a number of DC motors at the production line. Consequently the 6 sigma process was proved very effective for the noise reduction at the production line.

• 한국환경보건학회지
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• 제34권6호
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• pp.439-445
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• 2008

The feasibility study for the application of the removal and mineralization of Rhodamine B (RhB) was performed in a batch electrochemical reactor. The electro/UV process was consisted of DSA (dimensionally stable anode) electrode and UV-C or ozone lamp. The experimental results showed that RhB removal by the ozone lamp was higher than that of the UV-C lamp. Optimum current of the electro/UV process was 1 A. The electrochemical, UV and electro/UV process could completely degrade RhB, while a prolonged treatment was necessary to reach a high level RhB mineralization. It was observed that RhB removal in electro/UV process is similar to the sum of the UV and electrolytic decolorization. However, it was found that the COD of RhB could be degraded more efficiently by the electro/UV process (90.2 %) than the sum of the two individual oxidation processes [UV (19.7%) and electrolytic process (50.8%)]. A synergetic effect was demonstrated between the UV and electrolysis.

• 소성∙가공
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• 제9권6호
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• pp.615-623
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• 2000

The industrial application of hydroforming has a great potential in saying cost and achieving dimensional accuracy in automotive industry presently. The aim of the following article is to investigate the effect of process parameters on hydroformed part. Firstly, we have to investigate the change of mechanical properties for sheet and pipe material according to various radius/thickness ratio(r/t). The change of mechanical properties affects the yield stress more than the total elongation. Increase of yield stress for pipe has a bad influence on formability of hydroforming. Among the roll-forming process, the sizing process didn't change mechanical properties. The process parameters such as the initial pressure, mandrel shape and friction have seriously influenced on formability of hydroforming. Therefore we need to check formability of given material through the FE analysis in the beginning stage of process design and the predicted hydroforming process parameters ate generally a good starting point for the prototype tryout stage. The results of pretending, hydroforming analysis using FE model are good agreement with experimental results.