• Progress in Medical Physics
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• v.16 no.4
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• pp.183-191
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• 2005

The utilization of PET has been increased so fast since the usefulness of the PET has been proved in various clinical and research fields. Among the many applications, the PET Is especially useful in oncology and most of the clinical PET scans are peformed for the oncologic examination Including the different diagnosis of malignant and benign tumors and assessment of the treatment effects and recurrent tumors. As the PET-CT scanners are widely available, there is Increasing interest in the application of the PET Images to the radiation treatment planning. Although the CT images are conventionally used for the target volume determination in the radiation treatment planning, there are fundamental limitation In use of only the anatomical information. Therefore, the volume determination of the functionally active tumor region using the PET would be important for the treatment planning. However, the accurate determination of the tumor boundary is not simple in PET due to the relatively low spatial resolution of the currently available PET scanners. In this study, computer simulations were peformed to study the relationship between the lesion size, PET resolution, lesion to background ratio and the threshold of Image Intensity to determine the true tumor volume.

• Journal of Distribution Science
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• v.17 no.8
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• pp.107-118
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• 2019

Purpose - The present study examines the effect of service employees' experienced customer incivility through their emotional exhaustion. We identified service employees' emotion regulation ability as a boundary condition (i.e., moderating variable) that decreased the positive relationship between service employees' experienced customer incivility and their emotional exhaustion. Furthermore, we also investigated the negative relationship between service employees' experienced customer incivility and their service performance via emotional exhaustion. Research design, data, and methodology - Drawing on AET (affective event theory) and COR (conservation of resources) theory, we developed three research hypotheses (i.e., mediation, moderation, and moderated mediation). Online panel survey data from 552 frontline employees at several service organizations (e.g., department stores, retail stores, hotels, restaurants, airlines, banking, insurance company, and etc) in South Korea were examined. To assess two types of validity (i.e., convergent and discriminant validity) and reliability of measurement model, we employed the CFA (confirmatory factor analysis) using M-plus 8.2 software. Internal consistency also was tested by Cronbach' α. In addition, we employed the SPSS PROCESS MACRO 2.16, which was recommended by Hayes (2013, 2015), to estimate mediation, moderation, and moderated mediation effects. Results - As predicted, the negative relationship between service employees' experienced customer incivility and their service performance was mediated by emotional exhaustion. Furthermore, service employees' emotion regulation ability also played a significant moderating role of the relationship between service employees' experienced customer incivility and emotional exhaustion, such that this relationship was less pronounced when service employees had a high level of their emotion regulation ability than when thir emotion regulation ability was low. Service employees' emotion regulation ability further moderated this mediation effect of service employees' experienced customer incivility on service performance through emotional exhaustion. These findings have theoretical implications for employees' experienced customer incivility and emotion regulation ability research and provide managerial implications for practitioners. Conclusions - This study empirically elaborated the previous model of service employees' experienced customer incivility and personal resource (e.g., emotion regulation ability) literature by presenting the findings that service employees' experienced customer incivility influences their service performance via emotional exhaustion and that emotion regulation ability effectively reduces this negative effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.221-221
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• 2014

The present work proposes an improved numerical simulator for design and modification of large area capacitively coupled plasma (CCP) processing chamber. CCP, as notoriously well-known, demands the tremendously huge computational cost for carrying out transient analyses in realistic multi-dimensional models, because electron dissociations take place in a much smaller time scale (${\Delta}t{\approx}10-8{\sim}10-10$) than time scale of those happened between neutrals (${\Delta}t{\approx}10-1{\sim}10-3$), due to the rf drive frequencies of external electric field. And also, for spatial discretization of electron flux (Je), exponential scheme such as Scharfetter-Gummel method needs to be used in order to alleviate the numerical stiffness and resolve exponential change of spatial distribution of electron temperature (Te) and electron number density (Ne) in the vicinity of electrodes. Due to such computational intractability, it is prohibited to simulate CCP deposition in a three-dimension within acceptable calculation runtimes (<24 h). Under the situation where process conditions require thickness non-uniformity below 5%, however, detailed flow features of reactive gases induced from three-dimensional geometric effects such as gas distribution through the perforated plates (showerhead) should be considered. Without considering plasma chemistry, we therefore simulated flow, temperature and species fields in three-dimensional geometry first, and then, based on that data, boundary conditions of two-dimensional plasma discharge model are set. In the particular case of SiH4-NH3-N2-He CCP discharge to produce deposition of SiNxHy thin film, a cylindrical showerhead electrode reactor was studied by numerical modeling of mass, momentum and energy transports for charged particles in an axi-symmetric geometry. By solving transport equations of electron and radicals simultaneously, we observed that the way how source gases are consumed in the non-isothermal flow field and such consequences on active species production were outlined as playing the leading parts in the processes. As an example of application of the model for the prediction of the deposited thickness uniformity in a 300 mm wafer plasma processing chamber, the results were compared with the experimentally measured deposition profiles along the radius of the wafer varying inter-electrode gap. The simulation results were in good agreement with experimental data.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.813-818
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• 1998

Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5338-5343
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• 2013

In a haptic system, a virtual wall is modeled as a virtual spring. The larger the stiffness of the virtual spring is, the more improved the reality of the virtual wall is, but the more unstable the haptic system becomes. This paper shows how to increase the stiffness of the virtual spring while the stability of the haptic system is guaranteed and shows the effects of a mass (Md) and a damper (Bd) of a haptic device on the stability when first-order hold method is applied and a virtual wall is modeled as a virtual spring (Kw). The simulation results show the boundary of the virtual spring is proportional to the square root of the mass (Md) and the damper (Bd) while maintaining the stability. The relation among the virtual spring (Kw), the mass (Md) and the damper (Bd) of the haptic device, and sampling time (T) is inferred as $K_w{\leq}{1.611M_d}^{0.50}{B_d}^{0.50}T^{-1.51}$, by using the simulation results. The maximum available stiffness of the virtual spring in first-order hold method is larger than in zero-order hold method. So the reality of the virtual wall can be improved.

• Korean Journal of Cognitive Science
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• v.21 no.4
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• pp.481-503
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• 2010

In the present study, we examined global and local characteristics of eye movements while 17 Korean third-graders read a Korean story and an expository text. In story reading, children fixated for about 213ms at an eojeol(word cluster), made a forward saccade of about 3.6 characters to the next eojeol, and regressed backward at 30.8% on average. In expository text reading, children fixated for about 214ms at an eojeol, made a forward saccade of about 3.3 characters to the next eojeol, and regressed backward at 31% on average. In addition, the effects of eojeol length, word frequency and landing position were examined. The gaze duration in the long ejoels was longer than in the short eojeols. In a further analysis where the repeatedly used eojeols were excluded, the eojeol length effect appeared in the low-frequency words, but seemed to disappear in the high-frequency words. In terms of landing position, the eyes seemed to land near the center of an eojeol more frequently than on the boundaries. When the eyes landed at the boundary of an eojeol, the eyes tended to fixate the eojeol again.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.351-367
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• 2011

Few previous researches have been studied in terms of franchisees' perceptions of franchisors' entrepreneurial activities within the boundary of restaurant franchising industry settings. The sampling frame for this study included 605 restaurant franchisees in the business-format franchising system in Korea and data were collected from 1 October 2009 to 28 February 2010. This study, from franchisees' views, investigated the relationship among franchisors' entrepreneurship, external environment, organizational structure(mechanistic-organic) and managerial performance, with structural equation modeling(SEM). The research findings were, firstly, external environment positively affected entrepreneurship which positively affected market orientation and managerial performance, and secondly, market orientation made franchisors select organic structure and heighten managerial performance. Also, external environment led franchisors to adopt organic structure and aggravated their managerial performance. The implications of these findings were as follows. Firstly, the more franchiors had initiatives, innovatedness and risk-taking attitudes, the higher they had managerial performances and market orientation. Secondly, franchisors should keep and heighten market share with keeping in mind with customer orientation, competition orientation, harmony between departments, long-term orientation and profitability. Thirdly, continuous and cautious environmental scanning was necessary because external restaurant environment made organizational structure being changed and managerial performance being aggravated.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.262-266
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• 2007

Polycrystalline $Mn_xFe_{3-x}O_4$ thin films were synthesized on Si(100) substrates using sol-gel method and the effects of Mn substitution on the structural, magnetic, and magnetotransport properties were analyzed. X-ray diffraction revealed that cubic structure is maintained up to x = 1.78 with increasing lattice constant for increasing x. Such increase of the lattice constant is attributable to the substitution of $Mn^{2+}$ (with larger ionic radius) ions into tetrahedral $Fe^{3+}$(with smaller ionic radius) sites. VSM measurements revealed that $M_s$ does not vary significantly with x, qualitatively explainable by comparing spin magnetic moments of Mn and Fe ions. On the other hand, $H_c$ was found to decrease with increasing x, attributable to the decrease of magnetic anisotropy due to the decrease of $Fe^{2+}$ density through $Mn^{2+}$ substitution. Magnetoresistance (MR) of the $Mn_xFe_{3-x}O_4$ films was found to decrease with increasing x. Analysis of the MR data in comparison with the VSM results gives an indication of the tunneling of spin-polarized carriers through the grain boundaries of the polycrystalline samples at low external field and spin-flip of the carriers at high external field.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.4
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• pp.43-61
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• 2017

The wetlands are facing environmental changes such as desiccation that occurs with the passage of time and reduced ecosystem services from wetlands in the city. In order to maintain the ecosystem services provided by wetlands in urban areas, a system thinking about the trade-off phenomenon of ecosystem services occurring as the wetlands undergo environmental changes is needed. Therefore, the purpose of this study is to develop strategies for wetland design using system thinking approach to enhance the resilience of ecosystem services degraded by the desiccation of wetlands and other disturbances. The objectives of this study include the system boundary and variables. Second, analyzing the dynamics of wetland design strategy. Third, it analyzes the trade-off phenomenon of ecosystem services in terms of the hydrology, hydric soil, and plants strategies to mitigate these effects. Fourth, wetland basic design to improve the resilience of ecosystem services. A wetland in Abuk-Mountain Neighborhood Park, Miryang-si, Gyeongsangnam-do, has been selected as a case study. Causal loop diagrams(CLDs) are used to analyze feedback in the wetland regime. In summary, hydrology, hydric soil, and plants is suggested as system boundaries to design plan. Design strategies for the wetland focused on robustness, redundancy, rapidity, and resourcefulness as a result of CLD analysis are first proposed in order to effectively maintain the wetland regime over the long term. Secondly, in a section related to hydrology, the CLD results show the trade-offs between provisioning-cultural services and regulating services. In order to control these services, a "water cycling system" has been implemented due to its strength in terms of robustness. The CLDs for hydric soil showed the trade-offs between regulating services and supporting services. An "installation of storm drainage for maintaining water levels" was selected due to the strength offered in terms of redundancy and rapidity. The CLDs for plants showed the trade-offs between provisioning - cultural services and regulating services. In order to control the strategic points, the "planting of indigenous vegetation" was suggested given the strength in terms of redundancy. In this study, a wetland design method is proposed that can improve the resilience of wetland ecosystem services by analyzing the dynamics overtime. The results of this research can theoretically be applied to help restore ecosystem services in wetlands using ecological landscape design. In addition, this study will contribute to reducing maintenance costs by improving wetland resilience.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.4
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• pp.259-268
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• 2005

There has been a growing interest in the elimination of anoxic layer in the Youngsan River Estuarybecause the anoxic water mass caused mainly by the inflow of fresh water from the sea wall might cause the mass reduction of benthos during summer. An ocean outfall system to discharge treated wastewater into sea water may be used as one of the effective and economical ways to eliminate the anoxic layer. The suitable ocean outfall design is generally proposed for the prediction of the buoyant jet behavior in the near field. The parameters including CTD and current data are taken into account f3r more reliable buoyant jet behavior calculation. One of the numerical models, CORMIX 1, approved by EPA is used herein for the prediction of the trajectorial variation of the cross-sectional salinity and DO concentration distribution on the calculated buoyant jet boundary according to the tidal periods. On the basis of the results, it is suggested that the single port outfall is a useful system to eliminate the anoxic layer. Proper strategies are also proposed for achieving desirable ambient conditions.