• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.613-616
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• 2005

In general, the hollow jet valve, the fixed cone valve had been used for the urgency released or maintenance of the flow rate. Nowadays, the butterfly valve, the gate valve are applied in economic performance and operation maintenance more than the hollow jet valve, the fixed cone valve. However, in the case of butterfly valve, it should be required the strict application standard to the cavitation coefficient because the structural axis and disk were situated in pipe channel and the occurring the shock problem by Karman Vortex. And, the judgment data for choice were slight lowdown in water supply and drainage facilities standard or Japanese penstock technology standard, various standard of KOWACO etc. Therefore. there were investigated the valve inside phenomenon (cavitation, disk chattering, vibration) by velocity of flow and the stability examination of body by high velocity of flow through flow scale model test using the numerical analysis and PIV to establish the applicable extensibility of the butterfly valve for the urgency released valve.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.119-131
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• 2017

This study evaluated the feasibility of recovering and recycling nitrogen (N) and phosphorus (P) from livestock excreta as struvite ($MgNH_4PO_4{\cdot}6H_2O$) in South Korea. Our experimental results showed that struvite precipitation was a very effective way to recover N and P from livestock excreta. Moreover, our study demonstrated that struvite precipitates from livestock excreta (SPL) contain higher concentrations of N, P, and magnesium (Mg) as compared to compost and liquid manure from livestock excreta. In addition, although SPL contain high concentrations of copper (Cu) and zinc (Zn), they meet the fertilizer criteria for concentrations of heavy metals. In South Korea, SPL cannot currently be used as a fertilizer due to legal constraints. Legal permission for SPL use would offer greater choice in livestock excreta management. In conclusion, recovery and recycling of N and P from livestock excreta as struvite can be an effective tool for managing nutrients in livestock excreta.

• School Mathematics
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• v.15 no.3
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• pp.533-550
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• 2013

Teachers' mathematical knowledge for teaching (MKT) strongly influence student achievement (Hill, Rowan, & Ball, 2005). However, there is generally no record that shows the levels of teachers' MKT in schools and districts. Because of the limited resources, schools and districts need some criteria to decide how to distribute their resources to help teachers improve MKT. This study explores what factors in teachers' backgrounds are related to their levels of MKT. This article examines the relationships between the MKT of 336 elementary teachers and their demographic, educational, and teaching backgrounds. To measure MKT, I used a series of multiple-choice problems. The number of years teaching mathematics is not critical to these measures. Implications are discussed with regard to policy for mathematics teacher education.

• Journal of Astronomy and Space Sciences
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• v.35 no.1
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• pp.39-46
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• 2018

In this study, the performance of ranging techniques for the Korea Pathfinder Lunar Orbiter (KPLO) space communication system is investigated. KPLO is the first lunar mission of Korea, and pseudo-noise (PN) ranging will be used to support the mission along with sequential ranging. We compared the performance of both ranging techniques using the criteria of accuracy, acquisition probability, and measurement time. First, we investigated the end-to-end accuracy error of a ranging technique incorporating all sources of errors such as from ground stations and the spacecraft communication system. This study demonstrates that increasing the clock frequency of the ranging system is not required when the dominant factor of accuracy error is independent of the thermal noise of the ranging technique being used in the system. Based on the understanding of ranging accuracy, the measurement time of PN and sequential ranging are further investigated and compared, while both techniques satisfied the accuracy and acquisition requirements. We demonstrated that PN ranging performed better than sequential ranging in the signal-to-noise ratio (SNR) regime where KPLO will be operating, and we found that the T2B (weighted-voting balanced Tausworthe, voting v = 2) code is the best choice among the PN codes available for the KPLO mission.

• Journal of the Korea Society of Computer and Information
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• v.22 no.1
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• pp.143-151
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• 2017

In this paper, we suggest a method utilizing OSHW(Open Source HardWare) in order to raise up students who are competent in IT convergence and integration as a basic research to improve the university software education. Software education cannot be too much emphasized in the age of big change of Fourth Industrial Revolution. It hardly seems to have changes in the software education area of university where has to train competent technicians to be deployed into the industrial field, although software education is planned even in elementary, middle, and high school. In this situation, we expect that utilizing OSHW in software education can result in gaining a meaningful effect. However, we don't have various and systemic approach which use it as a education system component, unlike the response and necessity OSHW market. Therefore in this paper we suggest models which constitute software education environment based on OSHW and exemplify how to use it in each model. In addition, we compare and analyze each model in order to give a criteria to choice one of them according to the condition.

• Safety and Health at Work
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• v.8 no.1
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• pp.1-10
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• 2017

Considerable effort has been made to address the issue of occupational health and environmental exposure to mercury. This review reports on the current literature of mercury exposure and health impacts on dental personnel. Citations were searched using four comprehensive electronic databases for articles published between 2002 and 2015. All original articles that evaluated an association between the use of dental amalgam and occupational mercury exposure in dental personnel were included. Fifteen publications from nine different countries met the selection criteria. The design and quality of the studies showed significant variation, particularly in the choice of biomarkers as an indicator of mercury exposure. In several countries, dental personnel had higher mercury levels in biological fluids and tissues than in control groups; some work practices increased mercury exposure but the exposure levels remained below recommended guidelines. Dental personnel reported more health conditions, often involving the central nervous system, than the control groups. Clinical symptoms reported by dental professionals may be associated with low-level, long-term exposure to occupational mercury, but may also be due to the effects of aging, occupational overuse, and stress. It is important that dental personnel, researchers, and educators continue to encourage and monitor good work practices by dental professionals.

• Journal of the Korean Society of Fashion and Beauty
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• v.3 no.2 s.2
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• pp.39-46
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• 2005

Art-Make-up has resulted in occupying one of the central areas of this culture. Art Make-up is currently undergoing various changes. The viewpoint of modern make-up is the infiniteness of emotion such as the subjectively individualized expressions and aesthetic values breaking with conventional thought. The most significant change is the idea of the 'grotesque'. The purpose of this research is to re-clarify the development of the diversity, professionalism and artistic feature through the study of Art make-up based on the 'grotesque' style. This also strives to focus attention at observing the deep and mysterious workings of the human inner world. In order to explain the features of 'grotesque' Art make-up, six images below are presented. Firstly, Inharmonious images. Secondly, disgusting inhuman images. Thirdly, mechanical images. Fourthly, distorted and exaggerated images. Fifthly, diabolic and horrific images. And, lastly, playful images. These six images thoroughly demonstrate the 'grotesque' features. The fact at we can see the 'grotesque' features in Art make-up explains the enormous growth of Art make-up and the unlimited range of expression in this field. It also implies that the choice of material and theme is not restricted to universal artistic criteria. In closing, it is necessary that Art make-up is thought of not as actual art but more as a tool for its subjects. As a result, this research will provide valuable information for studies in the future.

• The Korean Journal of Financial Management
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• v.2 no.1
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• pp.21-34
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• 1986

The purpose of this study is to analyse the risk and uncertainty involved in the capital budgeting which is executed in long periods and requires massive capital expenditure. Under risk and uncertainty conditions, the estimates in the capital budgeting are random variables rather than known constants. Two approaches have emerged in performing economic analysis that explicitly incorporate risk and uncertainty conditions in the analysis. One approach is to develop a descriptive model which describes the economic performance of an individual investment alternative. But no recomendation would be forthcoming from the model. Rather, the decision-maker would be furnished descriptive information concerning each alternative; the final choice among the alternatives would required a separate action. The second approach is to develop a normative model which includes an objective function to be maximized or minimized. The output from the model prescribes the course of action to be taken. Owing to the fact that the normative approach considers the fitness of criteria for decision-making its reasonableness looks better. But it is almost imposible that we correctly and easily derive the individuals' utility function. So within we recognize the limits of the descriptive methods, it is more practicle to analyse the investment alternatives by sensitivity analysis.

• KIEE International Transactions on Power Engineering
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• v.5A no.1
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• pp.46-55
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• 2005

This paper proposes a new method for choice of the best transmission system expansion plan on the side of highest satisfaction level of decision maker using fuzzy integer programming. The proposed method considers the permissibility and ambiguity of the investment budget (economics) for constructing the new transmission lines and the delivery marginal rate (reliability criteria) of the system by modeling the transmission expansion problem as a fuzzy integer programming one. It solves the optimal strategy (reasonable as well as flexible) using a fuzzy set theory-based on branch and bound method that utilizes a network flow approach and the maximum flow-minimum cut set theorem. Under no or only a very small database for the evaluation of reliability indices, the proposed technique provides the decision maker with a valuable and practical tool to solve the transmission expansion problem considering problem uncertainties. Test results on the 63-bus test system show that the proposed method is practical and efficiently applicable to transmission expansion planning.

• The Korean Journal of Cytopathology
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• v.4 no.1
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• pp.9-15
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• 1993

The aim of the present study is to demonstrate the usefulness of intraoperative fine needle aspiration (FNA) of pancreatic lesions in 30 patients. A conclusive diagnosis was done in 27 patients and the diagnoses of three patients were deferred. No complications followed the procedure. Based on histologic findings of the resected specimens in 20 cases and of cell blocks in 10 cases, the final diagnoses were adenocarcinoma in 19 cases, chronic pancreatitis in nine cases and tuberculosis in two cases. The sensitivity, specificity and diagnostic accuracy were 95%, 100% and 96% resepectively and there were no false positives. The smear of aspirate was stained with toluidine blue and examined by light microscope. The presence of there-dimensional clusters of disoriented cells and the increased nuclear/cytoplasmic ratio with large prominent nucleoli were the most helpful criteria for a diagnosis of malignancy in the pancreas. The intraoperative FNA of pancreatic lesions was considered as a simple, safe, and highly specific and sensitive tool in differentiating benign from malignant lesions. The intraoperative FNA can be recommended as the first tool of choice of intraoperative diagnostic procedure in lesions of the pancreas.