• Tuberculosis and Respiratory Diseases
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• v.48 no.4
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• pp.478-486
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• 2000

Background : In acute lung injury, alveolar macrophages play a pivotal role in the inflammatory process during the initiation phase and in the reconstruction and fibrosis process during the later phase. Recently, it has been proven that alveolar macrophages are constituted by morphologically, biochemically and immunologically heterogenous cell subpopulations. The possibility of alterations to these characteristics of the alveolar macrophage population during lung disease has been raised. To investigate such a possibility a hyperoxic rat lung model was made to check the distributional and morphological changes of rat alveolar macrophage subpopulation in acute hyperoxic lung injury. Method : Alveolar macrophage were lavaged from normal and hyperoxic lung injury rats and separated by discontinuous gradients of percoll. After cell counts of each density fraction were accessed, the morphomeric analysis of alveolar macrophages was performed on cytocentrifuged preparations by transmission electron micrograph. Result : 1. The total alveolar macrophage cell count significantly increased up to 24 hours after hyperoxic challenge (normal control group $171.6{\pm}24.1{\times}10^5$, 12 hour group $194.8{\pm}17.9{\times}10^5$, 24 hour group $207.6{\pm}27.1{\times}10^5$, p<0.05). oHoHH However the 48 hour group ($200.0{\pm}77.8{\times}10^5$) did not show a significant difference. 2. Alveolar septal thickness significantly increased up to 24 hours after hyperoxic challenge(normal control group $0.7{\pm}0.2{\mu}m$, 12 hour group $1.5{\pm}0.4{\mu}m$, 24 hour group $2.3{\pm}0.4{\mu}m$, p<0.05). However the 48 hour group did not show further change ($2.5{\pm}0.4{\mu}m$). Number of interstitial macrophage markedly increased at 24 hour group. 3. Hypodense fraction(fraction 1 and fraction 2) of alveolar macrophage showed a significant increase following hyperoxic challenge ($\beta=0.379$.$\beta=0.694$. p<0.05) ; however, fraction 3 was rather decreased following the hyperoxic challenge($\beta=0.815$. p<0.05), and fraction 4 showed an irregular pattern. 4. Electron microscopic observation of alveolar macrophage from each fraction revealed considerable morphologic heterogeneity. Cells of the most dense subfraction(fraction 4) were small, round, and typically highly ruffled with small membrane pseudopods. Cells of the least dense fraction (fraction 1) were large and showed irregular eccentric nucleus and high number of heterogenous inclusions. Conclusion : In conclusion, these results suggest that specific hypodense alveolar macrophage subpopulation may play a an important role in an acute hyperoxic lung injury model But further study, including biochemical and immunological function of these subpopulations, is needed.

• Journal of the Ergonomics Society of Korea
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• v.35 no.4
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• pp.263-275
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• 2016

Objective: This paper introduces the regulatory oversight approaches and issues to consider in the course of safety culture oversight model development in the nuclear field. Common understanding on regulatory oversight and present practices of international communities are briefly reviewed. The nuclear safety culture oversight model of Korea is explained focusing on the development of safety culture definition and components, and their basic meanings. Oversight components are identified to represent the multiple human and organizational elements which can affect and reinforce elements of defense in depth system for nuclear safety. Result of validation study on safety culture components is briefly introduced too. Finally, the results of the application of the model are presented to show its effectiveness and feasibility. Background: The oversight of nuclear licensee's safety culture has been an important regulatory issue in the international community of nuclear safety regulation. Concurrent with the significant events that started to occur in the early 2000s and that had implications about safety culture of the operating organizations, it has been natural for regulators to pay attention to appropriate methods and even philosophy for intervening the licensee's safety culture. Although safety culture has been emphasized for last 30 years as a prerequisite to ensure high level of nuclear safety, it has not been of regulatory scope and has a unique dilemma between external oversight and the voluntary nature of culture. Safety culture oversight is a new regulatory challenge that needs to be approached taking into consideration of the uncontrollable aspects of cultural changes and the impacts on licensee's safety culture. Although researchers and industrial practitioners still struggle with measuring, evaluating, managing and changing safety culture, it was recognized that efforts to observe and influence licensees' safety culture should not be delayed. Method: Safety culture components which regulatory oversight will have to focus on are developed by benchmarking the concept of physical barriers and introducing the defense in depth philosophy into organizational system. Therefore, this paper begins with review of international regulatory oversight approaches and issues associated with the regulatory oversight of safety culture, followed by the development of oversight model. The validity of the model was verified by statistical analysis with the survey result obtained from survey administration to NPP employees in Korea. The developed safety culture oversight model and components were used in the "safety culture inspection" activities of the Korean regulatory body. Results: The developed safety culture model was confirmed to be valid in terms of content, construct and criterion validity. And the actual applicability in the nuclear operating organization was verified after series of pilot "safety culture inspection" activities. Conclusion: The application of the nuclear safety culture oversight model to operating organization of NPPs showed promising results for regulatory tools required for the organizations to improve their safety culture. Application: The developed oversight model and components might be used in the inspection activities and regulatory oversight of NPP operating organization's safety culture.

• Journal of the Korea Institute of Building Construction
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• v.17 no.6
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• pp.559-566
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• 2017

The bidding method of public works is decided based on the experience of the officials in charge and the convenience of the work, but the validity of decision making process for the bidding method has not been verified. Another challenge in the bidding method selection is its objective validation is not easy because the decision making is based on experience, when a new type of project is ordered or a new bidding method is applied In this study, therefore, a decision making model to facilitate the selection of a public construction project delivery method was developed and examined with its applicability. This model was developed using the Analytic Hierarchy Process and was verified through 32 persons who were actually in charge of the works. As a result of applying this model, 5 of the 32 persons showed consistency in using the model. and they expressed positive opinions about the model. The model can provide a guide while recognizing the fact that they cannot depend entirely on the model. Therefore, the model proposed in this study is expected to reduce the work-related burden of the persons who are involved in the related work and help the objective performance of their tasks when a new bidding method or project appears in the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11B
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• pp.979-986
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• 2006

DSTM is one of the 1Pv6/IPv4 transition mechanisms using IPv4-in-IPv6 tunneling for communication between IPv6 node with dual stack and Ipv4-only node. In DSTM, the DSTM server using the DHCPv6 is vulnerable to DoS attacks which can exhaust the IPv4 address pool. In this paper, an authentication model using a HRAA (Human Recognition Address Allocation) scheme was proposed to protect DHCP server against DoS attacks. The proposed authentication model in DSTM that uses an image file for verification is effective because only human can respond to the challenge for authenticated address allocation. The proposed model can be used anytime and anywhere in a DSTM domain, and is secure against DoS attacks.

• Journal of Korean Academy of Nursing
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• v.25 no.4
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• pp.790-806
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• 1995

The present study examined the causal relationships among nurses' job environment /job characteristics(work overload, lack of autonomy, professional role conflict, interpersonal relationships), maturity, job stress, job satisfaction and turnover intention by constructing and testing a theoretial framework. Based on Katz and Kahn's (1978) theory of organizational open system and Kahn, Wolfe, Quinn, and Snoek's (1964) theory of stress, nurses' turnover intention, job satisfaction and job stress were conceived of as outcomes of the interplay between personal characteristics and work environment. Personal aspects associated with outcome variables included professional knowlege and skill, and maturity(challenge, commitment, control, responsibility). The work environment factors involved work overload, lack of autonomy, professional role conflict, and interpersonal relationships (social support). Three university hospitals located in Seoul were selected to participate. The total sample of 443 registered nurses represents a response rate of 96 percent. Linear structural relationships (LISREL) technique was used to test the fit of the proposed conceptual model to the data and to examine the causal relationships among variables. The result showed that both the proposed model and the modified model fit the data excellently, revealing considerable explanatinal power for job stress and job satisfaction. The explanatory power of turnover intention was relatively lower than those of stress and satisfaction. In predicting nurses' stress, satisfaction and turnover intention, the findings of this study clearly demonstrated that professional role conflict might be the most important variable of the all the environmental variables and personal characteristics. The results were dis-cussed, including directions for the future research and practical implications drawn from the research were suggested.

• The Journal of Information Systems
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• v.16 no.1
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• pp.201-230
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• 2007

Recently, the growth of e-Learning systems and its related information technology has presented a unique challenge for both schools and industry. It would make an extremely phenomenal paradigm shift in the educational method and practice. Methods of assessing the quality of e-teaming services and contents are critical issue in both practice and research. Moreover, many researchers are interested in what qualify factors more affect to the Performance of e-Learning service. Nevertheless, service quality is a construct that is difficult to define and measure. e-Learning services are composed of many factors, and they are more complicated than the traditional education services because they we performed on the distance basis and the many platforms of IT infrastructure. The purposes of our research are to classify the e-Learning service dimension and identify their factors, to develop the measurement of the factors, and finally to test empirically their relationship between the service factors and e-Learning service performance. For the development of the service factors we considered SERVQUAL model and SERVPERF model which were developed in the service marketing area. The SERVQUAL model was more fitted to the e-Learning services than the latter. From that we derived several factors that fit to our research domain, ie, tangibles, access, reliability, credibility, security, responsiveness, assurance, empathy. We combined three factors of them(reliability, credibility, security) into a factor, system stability for the semantic simplicity, and divided responsiveness factor into system operator responsiveness and teacher responsiveness as the entity based dimension classification. In the e-Learning services research, Most researcher are mentioned the quality factors of contents, so we added to two contents quality factors, ie, contents production method and richness of contents itself. We examined the relationship between the service quality factors and e-Learning performance(student satisfaction and service reuse intention). As result three quality factors(contents production method, teacher responsiveness, empathy) significantly affected student satisfaction. To the other performance variable, ie, service reuse intention, the teacher related quality factors(such as teacher responsiveness, assurance, empathy) affected only. In conclusion, even in the on-line distance teaming, the teacher's role md earnestness is as important as ever.

• Journal of the Korean Geographical Society
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• v.43 no.2
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• pp.220-234
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• 2008

In many security monitoring contexts, the performance or efficiency of surveillance sensors/networks based on a single sensor type may be limited by environmental conditions, like illumination change. It is well known that different modes of sensors can be complementary, compensating for failures or limitations of individual sensor types. From a location analysis and modeling perspective, a challenge is how to locate different modes of sensors to support security monitoring. A coverage-based optimization model is proposed as a way to simultaneously site k different sensor types. This model considers common coverage among different sensor types as well as overlapping coverage for individual sensor types. The developed model is used to site sensors in an urban area. Computational results show that common and overlapping coverage can be modeled simultaneously, and a rich set of solutions exists reflecting the tradeoff between common and overlapping coverage.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.35-40
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• 2015

Centrifugal pumps consume considerable amounts of energy in various industrial applications. Therefore, improving the efficiency of pumps machine is a crucial challenge in industrial world. This paper presents numerical investigation of flow characteristics in volutes of centrifugal pumps in order to compare the energy consumption. A wide range of volumetric flow rate has been investigated for each case. The standard k-${\varepsilon}$ is adopted as the turbulence model. The impeller rotation is simulated employing the Multi Reference Frames(MRF) method. First, two different conventional design methods, i.e., the constant angular momentum(CAM) and the constant mean velocity (CMV) are studied and compared to a baseline volute model. The CAM volute profile is a logarithmic spiral. The CMV volute profile shape is an Archimedes spiral curve. The modified volute models show lower head value than baseline volute model, but in case of efficiency graph, CAM curve has higher values than others. Finally for this part, CAM curve is selected to be used in the simulation of different cross-section shape. Two different types of cross-section are generated. One is a simple rectangular shape, and the other one is fan shape. In terms of different cross-section shape, simple rectangular geometry generated higher head and efficiency. Overall, simulation results showed that the volute designed using constant angular momentum(CAM) method has higher characteristic performances than one by CMV volute.

• Journal of Korea Water Resources Association
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• v.41 no.11
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• pp.1153-1162
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• 2008

The use of radar rainfall for hydrological appraisal has been a challenge due to the limitations in raw data generation followed by the complex analysis needed to come up with precise data interpretation. In this study, RAIDOM (RAdar Image DigitalizatiOn Method) has been developed to convert synthetic radar CAPPI(Constant Altitude Plan Position Indicator) image data from Korea Meteorological Administration into digital format in order to come up with a more practical and useful radar image data. RAIDOM was used to examine a severe local rainstorm that occurred in July 2006 as well as two other separate events that caused heavy floods on both upper and mid parts of the HanRiver basin. A distributed model was developed based on the available radar rainfall data. The Flood Hydrograph simulation has been found consistent with actual values. The results show the potentials of RAIDOM and the distributed model as tools for flood prediction. Furthermore, these findings are expected to extend the usefulness of radar rainfall data in hydrological appraisal.

• Journal of Digital Convergence
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• v.16 no.3
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• pp.513-525
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• 2018

The purpose of this study is to explore the experience of participants in the adventurous leisure activities and to examine the structural relations of the cognitive experience, the emotional experience and adherence intention. Robust quantitative measures were developed from rich qualitative data. The five dimensions selected from two preliminary tests were being away, technical enhancement, fascination with nature, challenge, and interpersonal trust. The cognitive dimensions have a significant effect on the emotional arousal - pleasure dimension. Our study also shows a positive causal relationship between emotional experience and adherence intention. Implications of this study include 1) a developed questionnaire for measuring the cognitive experience dimension of adventure leisure and establishing a foundation for future research, and 2) an identified psychological model among cognitive, emotion, and intention. We offer opportunities to better understand the psychological factors that motivate participation in adventure leisure.