• 한국수소및신에너지학회논문집
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• 제20권6호
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• pp.526-533
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• 2009

In this paper, cycle performance analysis of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system with internal heat exchanger is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree and gas cooling pressure and evaporating temperature in the propane (R290) low temperature cycle and the carbon dioxide (R744) high temperature cycle. The main results were summarized as follows : The COP of cascade refrigeration system of $CO_2-C_3H_8$ (R744-R290) increases with the increasing subcooling degree, but decreases with the increasing superheating degree. The COP of cascade refrigeration system increases with the increasing evaporating temperature, but decreases with the increasing gas cooling pressure. Therefore, superheating and subcooling degree, compressor efficiency, evaporating temperature and gas cooling pressure of $CO_2-C_3H_8$ (R744-R290) cascade refrigeration system have an effect on the COP of this system.

• 동력기계공학회지
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• 제10권1호
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• pp.12-18
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• 2006

A three-degree of freedom model of intake system was contrived and investigated in various ways for the purpose of the amelioration of the volumetric efficiency in a low and transient engine speed for a multi cylinder diesel engine. The basic concept beyond this model started from the theory that each degree of freedom model has volumetric efficiency peak as many as its number of the degree of freedom. The volumetric efficiency affects significantly to the engine performance; torque characteristics, fuel economy and emission level. For commercial vehicles and stationary engines, the engine is designed so as to produce their best performance near the normal engine speeds, thus the low engine speed area has a tendency of poor volumetric efficiency. The aim of this study was highlighted on the amelioration of volumetric efficiency of low engine speed area in a multi cylinder diesel engine matched with an additional Helmholtz resonator. By the use of VIS(variable induction system) volumetric efficiency at low engine speed range was significantly improved. The availability of control by combination of VIS and CIS(conventional induction system) will be proposed as a variable induction system that would be an appropriate model for amelioration of the volumetric efficiency at low engine speed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3117-3132
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• 2012

The tree topology in multicast systems has high transmission efficiency, low latency, but poor resilience to node failures. In our work, some nodes are selected as backbone nodes to construct a tree-like core overlay. Backbone nodes are reliable enough and have strong upload capacity as well, which is helpful to overcome the shortcomings of tree topology. The core overlay is organized into a spanning tree while the whole overlay is of mesh-like topology. This paper focuses on improving the performance of the application-layer multicast overlay by optimizing the core overlay which is periodically adjusted with the proposed optimization algorithm. Our approach is to construct the overlay tree based on the out-degree weighted reliability where the reliability of a node is weighted by its upload bandwidth (out-degree). There is no illegal solution during the evolution which ensures the evolution efficiency. Simulation results show that the proposed approach greatly enhances the reliability of the tree-like core overlay systems and achieves shorter delay simultaneously. Its reliability performance is better than the reliability-first algorithm and its delay is very close to that of the degree-first algorithm. The complexity of the proposed algorithm is acceptable for application. Therefore the proposed approach is efficient for the topology optimization of a real multicast overlay.

• 대한설비공학회지:설비저널
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• 제17권4호
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• pp.408-417
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• 1988

This study optimized the condenser dimension of heat pump system with the heat sources which are solar irradiation and ambient air. At first, the author selected the principal design factors influencing the performance of heat pump system. And the author considered the variation of condenser dimension according to the variation of the selected design factors, that is, ambient air temperature, condenser temperature, degree of superheating, degree of sub-cooling and irradiation. As a result this study, among refrigerants R12, R22 and R500, refrigerant R22 has more heating output than R12 and R500, and the coefficient of performance on this heat pump system is not greatly influenced by the degree of superheating and degree of sub cooling. The ambient air temperature is below $5^{\circ}C$ at balance point and the optimal tube length of condenser dimension is about 3.8 m. Also the author gained the optimal design diagram for the optimization of condenser dimension according to various design factors.

• 한국컴퓨터정보학회논문지
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• 제24권1호
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• pp.93-100
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• 2019

One of critical issues in dealing with 360-degree realistic contents is the performance degradation in searching and recognition process since they support up to 4K UHD quality and have all image angles including the front, back, left, right, top, and bottom parts of a screen. To solve this problem, in this paper, we propose an efficient search and comparison method for 360-degree realistic contents. The proposed method first corrects the distortion at the less distorted regions such as front, left and right parts of the image excluding severely distorted regions such as upper and lower parts, and then it extracts feature points at the corrected region and selects the representative images through sequence classification. When the query image is inputted, the search results are provided through feature points comparison. The experimental results of the proposed method shows that it can solve the problem of performance deterioration when 360-degree realistic contents are recognized comparing with traditional 2D contents.

• 종양간호연구
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• 제3권1호
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• pp.24-44
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• 2003

The purposes of this study was to identify and propose the expected role of the oncology nurse specialist by embodying role theory to oncology nurse specialist. The subjects of this study were 149 persons in 14 hospitals, who were classified to 4 groups, oncology nurse specialists(ONS) group, head nurses and charge nurses(HN & CN) group in hemato-oncology ward, registered nurses(RN) group in hemato-oncology ward, and hematologists & oncologists(H&O) group. The questionnaire which was consisted of 89 items for role of oncology nurse specialist, was made by researcher with a field study and literature review about role of oncology nurse specialist and verified by matrix delphi technique about content validity and construct validity. The data were collected from October 22, 2002 to November 5, 2002. All 4 groups proposed that ONS should perform an expert practitioner role first of all. But ONS group, RN group and H&O group proposed orderly expert practitioner, educator, researcher, consultant, and administrator & change agent, but HN & CN group did expert practitioner, educator, consultant, researcher, administrator & change agent. Expert practitioner had the most highest necessary degree in all groups and most highest performance degree in ONS group. That was consistent with results that all groups proposed role of expert practitioner at first. 4 items out of 20 items showed the meaningful differences between groups. For role of educator, oncology nurse specialist group proposed necessary degrees over 4.0 point out of 5.0 in all items. 4 items out of 18 items showed the meaningful differences between groups. For role of researcher, 3 nurses groups proposed a high necessary degree, but performance of ONS group was most lowest among 5 roles. 6 items out of 14 items showed the meaningful differences between groups. The role of consultant had high necessary degree in some items related to hematopoietic stem cell transplantation. 2 items out of 17 items showed the meaningful differences between groups. In nursing behaviors of administrator & change agent, those items about enacting principle, cost development and participation of professional academy had a high necessary degree. 4 items out of 18 items showed the meaningful differences between groups. Oncology nurse specialists group performed 5 roles orderly, expert practitioner, consultant, educator, administrator & change agent, researcher. This result was different from expected role of themselves as well as the other groups. There was a different necessary degree between role and embodied nursing behaviors of role. ONS group and RN group proposed orderly educator, researcher, administrator & change agent, expert practitioner, consultant, but the other groups did educator, expert practitioner, researcher, consultant, administrator & change agent. The expected standards of oncology nurse specialist in this study were usually master's degree, total career of 5-7 years, oncology career of 3-5 years and certification. But for the post, qualification and qualification institution, various opinions were suggested. In the conclusion, there was a different necessary degree between role and embodied nursing behaviors of role. All groups proposed expert practitioner at first in abstract role, but educator at first in embodied nursing behaviors of role. So we have to consider this difference carefully in the future research. ONS acted the role of expert practitioner first of all, but we should develope and expand the roles of researcher, and administrator & change agent. We should enact roles by role behaviors induced from mutual agreements in necessary degree and performance degree, and bargain the role behaviors that showed the meaningful differences between groups But, we should consider carefully which group's opinion we have to select. I suggested 36 items out of 89 items, in which ONS proposed necessary degree over 4.0 out of 5.0 and half of them performed as the nursing behaviors of oncology nurse specialist that did not induce role stress. For the future, We should role bargain the role with other groups based on these items.

• 산업경영시스템학회지
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• 제20권42호
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• pp.151-159
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• 1997

This Study intends to analyse the degree which Psychological Anxiety affects to Physical Performance using Multivariate Statistical Analysis. For this, we accumulated two type's datum : (1)Data about Psychological anxiety by Spielberger's STAI- Ⅰ·Ⅱ, (2)Data about Physical Performance by AEFH's FITKIT.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1472-1474
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• 2001

In this paper, a method was presented to estimate the contamination degree of outdoor insulator by the measurement of surface leakage current. Contamination is one of the most important factor to determine the performance of insulator. Thus, it is very important to exam the contamination degree on the outdoor insulator. There are many limits, such as reliability of data, interval of measurement and similarity of environmental conditions, in conventional method. So, the estimation technique for contamination has been needed to monitor the accurate pollution degree of insulator in situ. In this investigation, phase difference was measured to compare the variance of phase difference with the contamination degree and relative humidity. From the result, we could confirm the capability of the estimation method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.177-180
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• 2000

The objective of this study is to analyze the degree of surface-glossing of cement mortar with the grading of aggregate and contents of limestone powder. According to the experimental results, degree of surface-glossing of cement mortar using river sand is higher than that of crushed sand. As F.M of aggregates is less than 2.78, degree surface-flossing of cement mortar has better performance, Also, as the contents of limestone power increase, degree of surface-flossing is shown to be improved, And it shows that degree of surface-glossing decrease with elapse of age.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3630-3656
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• 2018

Degree distribution can provide basic information for structural characteristics and internal relationship in social network. It is a critical procedure for social network topology analysis. In this paper, based on the mean-field theory, we study a special type of social network with exponential distribution of time intervals. First of all, in order to improve the accuracy of analysis, we propose a spreading coefficient algorithm based on intimate relationship, which determines the number of the joined members through the intimacy among members. Then, simulation show that the degree distribution of follows the power-law distribution and has small-world characteristics. Finally, we compare the performance of our algorithm with the existing algorithms, and find that our algorithm improves the accuracy of degree distribution as well as reducing the time complexity significantly, which can complete 29.04% higher precision and 40.94% lower implementation time.