• 상하수도학회지
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• 제11권1호
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• pp.64-73
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• 1997

Most of the municipal wastewater treatment plants operated in Korea are designed for high concentrations municipal sewage. However, activated sludge process employed by municipal wastewater treatment plant is operated at low organic loading. The objective of this study was to determine optimum operating condition of activated sludge process for treatment of low concentration municipal sewage. Three bench scale activated sludge reactors were operated to investigate the effect of HRT and SRT on the COD and TSS removal efficiency. The average concentration of TSS, SCOD, SBOD and TKN in influent were 118mg/l, 61mg/l, 21mg/l, and 12mg/l, respectively. The activated sludge reactors operated with various HRT and SRT showed about 89-93% TSS removal efficiency. HRT and SRT does not affect the TSS removal efficiency of actvatied sludge process significantly. However, HRT affected the SCOD removal efficiency slightly. As the HRT decreases from 13hours to 3hours, the SCOD removal efficiency decreases from 67% to 56%. The average effluent TCOD concentration of the reactor operated with 3hours of HRT was approximatly 40-45mg/l. Kinetic coefficient yield (Yt) and decay coefficients(Kd) were 0.594-0.954 mgMLVSS/mgCOD and $0.0197-0.0317day^{-1}$, respectively. Low concentration municipal sewage can be treated with 3 hours of HRT without effluent quality deterioration and SRT does not affect the substrate removal efficiency at this operation condition.

• 한국환경보건학회지
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• 제28권1호
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• pp.93-97
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• 2002

The aim of this study was to evaluate on the removal effect of total nitrogen and phosphorus with municipal wastewater in ultrasonic nutrient removal (UNR) process using ultrasonic sludge carbon source. The removal efficiency for total nitrogen was 44.2% at biological nutrient removal (BNR) process, 50.8% at UNR process. The removal efficiency for total phosphorus was 45.6% at BNR process, 46.2% at UNR process. The removal of nitrogen was effectively influenced by ultrasonic sludge carbon source.

• 상하수도학회지
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• 제24권1호
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• pp.109-117
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• 2010

In the present study, the degradation characteristics of Lindane by Advanced Oxidation Processes(UV/$H_2O_2$, Photo-Fenton process) were studied. The degradation efficiency of Lindane in aqueous solution was investigated at various initial pH values, Fenton's reagent concentrations and initial concentrations of Lindane. GC-ECD was used to analyze lindane. Lindane has not been degraded without application of AOPs over two hours. But, approximately 5% of lindane was degraded with UV or $H_2O_2$ alone. Lindane with UV/$H_2O_2$ process showed approximately 7% higher removal efficiency than $H_2O_2$ process. In the UV/$H_2O_2$ process, the pH values did not affect the removal efficiency. The optimal mole ratio of $H_2O_2/Fe^{2+}$ for lindane degradation is about 1.0 in Photo-Fenton process. Also, the experimental results showed that lindane removal efficiency increased with the decrease of initial concentration of lindane. Under the same conditions, the order lindane of removal efficiency is as following : Photo-Fenton process > UV/$H_2O_2$ process > $H_2O_2$ process. In addition, intermediate products were identified by GC-MS techniques. Than PCCH(Pentachlorocyclohexene) was identified as a reaction intermediate of the Photo-Fenton process.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.622-627
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• 2009

Business process engineering (BPE) is a top-down management approach for increasing efficiency and productivity through radical and fundamental changes to the business processes of the organization. BPE requires firms to initially develop a model of the existing business processes of the firm to distinguish functional tasks from processes used for coordinating inputs, activities and outputs. The model is used for understanding the business processes in the organization and to simulate the effect of changes to the processes. The model can also be used to justify business processes, which involves assessing whether the business process provides value to the customer in its current configuration. Justification requires a careful examination of the key business processes used by the firm to identify systemic shortcomings in the process and to create a new business process to produce greater efficiency. BPE also considers automating as many business processes as possible to increase operational efficiency and the integration of business process tasks. The construction industry has been slow to adopt BPE because of its project approach in which a major firm contracts with various functional service providers and regards each project as unique. The industry focuses on functional task efficiency rather than business process efficiency. There is no formal methodology or criteria for determining whether a business process is effective for a construction firm in its current configuration. The use of performance measures such as costs, task duration times or other metrics can be useful in evaluating the effectiveness of an existing business process and for modeling the possible outcome of a fundamental and radical change to the process.

• Current Photovoltaic Research
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• 제6권1호
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• pp.27-30
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• 2018

The dependency of the electrical characteristics of silicon solar-cells on the depth of damaged layer induced by wire-sawing process was investigated. To compare cell efficiency with residual sawing damage, silicon solar-cells were fabricated by using as-sawn wafers having different depth of saw damage without any damaged etching process. The damaged layer induced by wire-sawing process in silicon bulk intensely influenced the value of fill factor on solar cells, degrading fill factor to 57.20%. In addition, the photovoltaic characteristics of solar cells applying texturing process shows that although the initial depth of saw-damage induced by wire-sawing process was different, the value of short-circuit current, fill-factor, and power-conversion-efficiency have an almost same, showing ~17.4% of cell efficiency. It indicated that the degradation of solar-cell efficiency induced by wire-sawing process could be prevented by eliminating all damaged layer through sufficient pyramid-surface texturing process.

• 산업공학
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• 제16권spc호
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• pp.76-81
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• 2003

BPMS (Business Process Management Systems) is aninformation system that systematically supports designing, administrating, and improving the business processes. It can execute the business processes by assigning tasks to human or computer agents according to the predefined definitions of the processes. In this research we developed a task assignment algorithm that can maximize overall process efficiency under the limitation of agents' capacity. Since BPMS manipulates the formal and predictable business processes, we can analyze the processes using queuing theory to achieve overall process efficiency. We first transform the business processes into queuing network model in which the agents are considered as servers. After that, workloads of agents are calculated as server utilization and we can determine the task assignment policy by balancing the workloads. This will make the workloads of all agents be minimized, and the overall process efficiency is achieved in this way. Another application of the results can be capacity planning of agents in advance and business process optimization in reengineering context. We performed the simulation analysis to validate the results and also show the effectiveness of the algorithm by comparing with well known dispatching policies.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.240-244
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• 1998

The analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composites using coal tar pitch as a matrix precursor at each cyle. Three factors were defined in analyzing the densification process: impregnation efficiency, retention efficiency, and overall densification efficiency. The relationships developed were applied to the experimental results for three densification cycles of C/C composites with pitches as an impregnant to evaluate the factors which may depend on the impregnant and on the route of carbonization. The impregnation efficiency increased with the repeated process cycles whereas the retention efficiency decreased irrespective of the impregnant and carbonization route. Carbonization route P+A+G, in which pressure carbonizationl (P) and graphitization (G) were done before after atmospheric pressure carboniztion (A) respectively, using impregnant of high carbon yields was the most effective method in densifying C/C composites.

• Journal of Electrochemical Science and Technology
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• 제10권1호
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• pp.14-21
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• 2019

Supported liquid membrane process usually is used for recovering or enrichment of valuable metals in the industrial wastewater. But, even if the metals in the wastewater was separated with high chemical selectivity, it cannot be enough concentrated since separation performance of supported liquid membrane (SLM) process is limited by concentration gradient between feed solution and stripping solution. If metal concentration in the stripping solution to be enough low, transport of metal through membrane can be accomplishment constantly. Therefore, Electrodialysis (ED) has been placed after SLM process and the stripping solution of SLM was used as the feed solution for the ED process. Transport of ions in the solutions is successfully performed by ED process. Thus, the metal concentration in the stripping solution does not rise as to stop ion transport. Besides, valuable metals easily are concentrated by ED process for re-use. In this study, effects of operation parameters like initial Cd(II) concentration, HCl concentration in the feed solution of SLM and applied voltage are investigated on separation efficiency, flux and permeability of the both processes. As the feed solution concentration increased, all performance values has increased. When initial concentration of 100 mg/L is used, separation performances (SP) are 55% and 70%, for SLM and consecutive process, respectively. The best HCl concentration in the feed solution of SLM has determined as 2 M, in this conditions SP are 64% and 72%, for SLM and consecutive process, respectively. With increased of applied voltage on ED process, SP of the consecutive process has been raised from 72% to 83%. According to the obtained experimental data, consecutive process has better separation performance than SLM. When the separation performances of both processes were compared for the same operating conditions, it was determined higher the separation efficiency, permeability and flux values of the consecutive process, 8%, 9% and %10.6, respectively. Consequently, the use of the consecutive process increases the performance efficiency of both processes. The consecutive process studied has quite a good chemical separation efficiency, and enrichment capability. Moreover, this process requires few water and energy.

• 한국환경과학회지
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• 제8권6호
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• pp.725-730
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• 1999

The advanced oxidation process (AOP) using ozone combined with hydrogen peroxide and ultraviolet treatment were evaluated for biodegradable dissolved organic carbon (EDOC) formation and dissolved organic carbon (DOC) removal. Oxidation treatment were conducted alone or combination with ozone, hydrogen peroxide and ultraviolet processes. Ozone dosage of ozone process was varied from $0.5mg/l{\ell}\cdot}min$ to $5mg/{\ell}{\cdot}min$. Ozone/hydrogen peroxide process was done using $20mg/{\ell}{\cdot}min$ of hydrogen peroxide concentration. Ozone/ultraviolet process was irradiated with $12mW/cm^2$ of density and 254nm. Ozone dosage was varied from $0.5mg/{\ell}{\cdot}min$ to $5mg/{\ell}{\cdot}min$ at the ozone/hydrogen peroxide and ozone/ultraviolet processes too. Contact time of all the process was 20 minutes. Oxidation treatment were performed on microfiltration effluent samples. BDOC formation was reached to an optimum at ozone dosage of $1.5mg/{\ell}{\cdot}min$ in the ozone/hydrogen peroxide process and $1mg/{\ell}{\cdot}min$ in ozone/ultraviolet process, after which BDOC formation was decreased at higher ozone dosages. But BDOC formation was increased with ozone dosages increasing in ozone process. The efficiency of DOC removal was higher AOPs than ozone process. Ozone/ultraviolet proces was the highest for DOC removal efficiency in each process. THMFP. removal efficiency by ozone/ultraviolet process was higher than that by each of ozone process and ozone/hydrogen peroxide process.

• 한국정보시스템학회:학술대회논문집
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• 한국정보시스템학회 2003년도 추계학술대회
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• pp.55-63
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• 2003

Workflow Management System (WFMS) is a software system to support an efficient execution, control and management of complex business processes. Since traditional commercial systems mainly focus on automating processes, they don't have methods for enhancing the task performer's efficiency. In this paper, we propose a new method of executing business processes more efficiently in that a whole process is scheduled considering the degree of the participants' workload. The method allows managing the largest constraints among constituent resources of the process. We utilize DBR scheduling techniques to develop the method. We first consider the differences between workflow process models and DBR application models, and then develop the modified drum, buffer and rope. This leads us to develop WF-DBR (WorkFlow-DBR) that can control the proper size of the task performers' work list and arrival rate of process instances. Use of WF-DBR improves the efficiency of the whole process as well as the participants' working condition. We then carry out a set of simulation experiments and compare the effectiveness of our approach with that of scheduling techniques used in existing systems.