• Tribology and Lubricants
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• v.31 no.5
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• pp.221-228
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• 2015

It is possible to prevent a piston from contacting the cylinder by changing the shape of the piston or by applying micro-textures, such as micro-grooves or micro-holes, over the piston surface. Usually, the minimum radial clearance reaches its minimum value at the beginning of the suction stroke because the pressure around the piston is low and almost axisymmetric such that the net pressure force on the piston is not sufficiently high to support the piston from touching the cylinder. In this study, we apply a series of saw-tooth-shaped grooves on the piston surface, and numerically investigate the effects of groove depth, groove angle, and the number of grooves with radial clearance variations using a finite difference method. We conduct a dynamic analysis of the piston for various changes in groove geometries to obtain the minimum radial clearance variation for the entire compression cycle. The minimum radial clearance increases while friction loss decreases when we apply the series of saw-tooth-shaped grooves on the piston. In addition, we analyze the impact of the change in the groove shape variable due to changes in radial clearance. Leakage variations are relevant to radial clearance, but have almost no effect on the groove parameters.

• Nuclear Engineering and Technology
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• v.45 no.5
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• pp.573-580
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• 2013

The combined effects of reactivity coefficients, along with other core nuclear characteristics, determine reactor core behavior in normal operation and accident conditions. The Power Coefficient of Reactivity (PCR) is an aggregate indicator representing the change in reactor core reactivity per unit change in reactor power. It is an integral quantity which captures the contributions of the fuel temperature, coolant void, and coolant temperature reactivity feedbacks. All nuclear reactor designs provide a balance between their inherent nuclear characteristics and the engineered reactivity control features, to ensure that changes in reactivity under all operating conditions are maintained within a safe range. The $CANDU^{(R)}$ reactor design takes advantage of its inherent nuclear characteristics, namely a small magnitude of reactivity coefficients, minimal excess reactivity, and very long prompt neutron lifetime, to mitigate the demand on the engineered systems for controlling reactivity and responding to accidents. In particular, CANDU reactors have always taken advantage of the small value of the PCR associated with their design characteristics, such that the overall design and safety characteristics of the reactor are not sensitive to the value of the PCR. For other reactor design concepts a PCR which is both large and negative is an important aspect in the design of their engineered systems for controlling reactivity. It will be demonstrated that during Loss of Regulation Control (LORC) and Large Break Loss of Coolant Accident (LBLOCA) events, the impact of variations in power coefficient, including a hypothesized larger than estimated PCR, has no safety-significance for CANDU reactor design. Since the CANDU 6 PCR is small, variations in the range of values for PCR on the performance or safety of the reactor are not significant.

• Nuclear Engineering and Technology
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• v.47 no.1
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• pp.74-84
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• 2015

If a transient occurs in a nuclear power plant (NPP), operators will try to protect the NPP by estimating the kind of abnormality and mitigating it based on recommended procedures. Similarly, operators take actions based on severe accident management guidelines when there is the possibility of a severe accident occurrence in an NPP. In any such situation, information about the occurrence time of severe accident-related events can be very important to operators to set up severe accident management strategies. Therefore, support systems that can quickly provide this kind of information will be very useful when operators try to manage severe accidents. In this research, the occurrence times of several events that could happen during a severe accident were predicted using support vector machines with short time variations of plant status variables inputs. For the preliminary step, the break location and size of a loss of coolant accident (LOCA) were identified. Training and testing data sets were obtained using the MAAP5 code. The results show that the proposed algorithm can correctly classify the break location of the LOCA and can estimate the break size of the LOCA very accurately. In addition, the occurrence times of severe accident major events were predicted under various severe accident paths, with reasonable error. With these results, it is expected that it will be possible to apply the proposed algorithm to real NPPs because the algorithm uses only the early phase data after the reactor SCRAM, which can be obtained accurately for accident simulations.

• Journal of Ecology and Environment
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• v.47 no.3
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• pp.85-102
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• 2023

Background: Ecophysiological characteristics of Rosa rugosa were analyzed under different environmental factors from May to October 2022. Photosynthesis, chlorophyll fluorescence, chlorophyll content, leaf water content (LWC), osmolality, carbohydrate content, and total ion content were measured to compare the physiological characteristics of R. rugosa at two study sites (i.e., in large pots and in the Goraebul coastal sand dune area). Results: When R. rugosa was exposed to high temperatures, photosynthetic parameters including net photosynthetic rate (P_N) and stomatal conductance (g_s) in both experiment areas declined. In addition, severe photoinhibition occurs when R. rugosa is continuously exposed to high photosynthetically active radiation (PAR), and because of this, relatively low Y(II) (i.e., the quantum yield of photochemical energy conversion in photosystem II [PSII]) and high Y(NO) (i.e., the quantum yield of non-regulated, non-photochemical energy loss in PSII) in the R. rugosa of the pot were observed. As the high Y(NPQ) (i.e., the quantum yield of regulated non-photochemical energy loss in PSII) of R. rugosa in the coastal sand dune, they dissipated the excessed photon energy through the non-photochemical quenching (NPQ) mechanism when they were exposed to relatively low PAR and low temperature. Rosa rugosa in the coastal sand dune has higher chlorophyll a and carotenoid content. The high chlorophyll a + b and low chlorophyll a/b ratios seemed to optimize light absorption in response to low PAR. High carotenoid content played an important role in NPQ. As a part of the osmotic regulation in response to low LWCs, R. rugosa exposed to high temperatures and continuously high PAR used soluble carbohydrates and ions to maintain high osmolality. Conclusions: We found that F_v/F_m was lower in the potted plants than in the coastal sand dune plants, indicating the vulnerability of R. rugosa to high temperatures and PAR levels. We expect that the suitable habitat range for R. rugosa will shrink and move to north under climate change conditions.

• Korea Journal of Hospital Management
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• v.2 no.1
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• pp.1-21
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• 1997

In order to analyze the shifts in the volume and profits of Computed Tomography(CT) and Magnetic Resonance Imaging(MRI) utilization for a year before and after the implementation of insurance coverage for CT, this study has been undertaken examining CT and MRI cost data from 'Y' University Hospital situated in Seoul, Korea. Following are the results of this study: 1. The medical insurance payment for CT, implemented on January 1, 1996, increased CT utilization from January 1996 to April 1996 due to low insurance premiums: however, from May 1996 the number of CT cases significantly decreased as a result of strengthened medical cost reviews and the new 'Detailed standards for approval of CT' announced near the end of April 1996 by the insurer. 2. Since the implementation of insurance coverage for CT, CT fee reduction rates for reimbursements by the insurer to the hospital were 50% and 40% for January and February, respectively, and 31% and 15% for March and April. A significant point in the lowering of the reduction rate was reached in May at 11%; furthermore, since June the reduction rate fell below the average reduction rate for reimbursements for all procedures. If the 'Detailed standards for approval of CT' had been announced before the implementation of insurance coverage for CT, CT utilization would not have been so high due to the need to meet those 'standards'. In addition, loss of hospital profits resulting from the reduction for reimbursements would not have occurred. 3. The shifts in MRI utilization showed that there was no particular change with the beginning of insurance coverage for CT, and the introduction of the 'Detailed standards for approval of CT' made MRI utilization increase because MRI is free of restrictions imposed by the insurer. 4. The relationship between CT utilization and MRI utilization showed that they were supplementary to each other before insurance coverage for CT, but that CT was substituted for MRI because of strengthened medical cost reviews after t~e beginning of insurance coverage for CT. 5. The shifts in volume by patient characteristics showed that the number of inappropriate case patients, according to the insurer's "Standards for approval", decreased more than the number of appropriate case patients after the introduction of insurance coverage for CT. Therefore, the health insurance fee schemes for CT have influenced patient care. 6. The shifts in profits from CT utilization showed a net profit decrease of 31.6%. In order to match the pre-coverage profit level, 5,471 more cases would need to be seen and productivity would need to be increased by 32.7%. This profit decrease resulted from a decrease of CT utilization and low reimbursements. With insurance coverage, net profits from CT were 24.4%, and a margin of safety ratio was 39.6%. Because of the net profits and margin of safety ratio, CT utilization fees for insured appropriate cases could not be considered inappropriate. 7. The shifts in profits from MRI utilization before and after the introduction of CT coverage showed that in order to match pre-CT coverage profit levels, 2,011 more cases would need to be seen and productivity would need to be increased by 9.2%. The reasons for needing to increase the number of cases and productivity result from cost burdens created by adding new MRI units. But with CT coverage already begun, MRI utilization increased. Combined with a minor increase in the MRI fee schedule, MRI utilization showed a net profit increase of 18.5%. Net profits of 62.8% and a 'margin of safety ratio' of 43.1% for MRI utilization showed that the hospital relied on this non-covered procedure for profits. 8. The shifts in profits from CT and MRI utilization showed the net profits from CT decreased by 2.33billion Won while the net profits from MRI increased by 815.7million Won. Overall, these two together showed a net profit decrease of 1.51billion Won. The shifts in utilization showed a functional substitutionary relationship, but the shifts in profits did not show a substitutionary relationship. From these results, We can conclude that if insurance is to be expanded to include previously uncovered procedures using expensive medical equipment, detailed standards should be prepared in advance. The decrease in profits from the shifts in coverage and changes in fees is a difficult burden that should be shared, not carried by the hospital alone. Also, a new or improved fee schedule system should include revised standards between items listed and the appropriateness of the fee schedule should constantly be ensured. This study focused on one university hospital in Seoul and is therefore limited in general applicability. But it is valuable for considering current issues and problems, such as the influence of CT coverage on hospital management. Future studies will hopefully expand the scope of the issues considered here.

• Journal of Environmental Policy
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• v.11 no.4
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• pp.3-37
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• 2012

In perspective of biodiversity conservation and protected areas (PAs), the aims of the study are to review the mid-long term national plans, which deal with national territory and environment in Korea, and to find out the way to improve this issue. Key issues were drawn by referring "Biodiversity 2011-2020 Strategic Targets" and "Protected Area Decision" in CBD CoP-10 and 7 National comprehensive or basic Plans were reviewed. Quoting Biodiversity 2011-2020 Strategic Target 5, "By 2020, the rate of loss of all natural habitats, including forests, is at least halved and where feasible brought close to zero, and degradation and fragmentation is significantly reduced", most of national plans included various methods such as "No Net Loss of Green", "No Net Loss of Wetlands", and so on. Regarding the target 11, "By 2020, at least 17% of terrestrial and inland water, and 10% of coastal and marine areas, ecologically representative and well connected systems of PAs and other effective area-based conservation measures, and integrated into the wider landscape and seascapes", 15% by 2015 was set up as a target of total PAs in Korea and 13% by 2015 or 2020 was set up as a target of coastal and marine PAs. CBD CoP-10 Decision X/31 (Protected Areas) invites parties to develop a national long-term action plan for the implementation of PoWPA and describes 10 issues that need greater attention. National action plan for the implementation of PoWPA doesn't be mentioned at any national plans even PoWPA. Regarding the 10 issues, most of issues were well reflected within various national plans, however there is still a need to improve the details and corelation between plans. Particularly, in terms of management effectiveness evaluation (MEE), there was no national plan to directly deal with MEE even though CBD invites parties to work towards assessing 60% of the total PAs by 2015. Based on the review results, below 4 items were suggested; (1)"The Comprehensive Plan of the National Territory" needs more attention on the Biodiversity Conservation and PAs, (2)Consider to establish "National PA System Plan" embedded into "the Comprehensive Plan of National Environment", (3)Establish a "National Action Plan for the implementation of PoWPA", (4)Improve the National Plans through linking with Biodiversity 2011-2020 Strategic Targets and relevant PA key issues.

• Korean journal of applied entomology
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• v.52 no.1
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• pp.23-27
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• 2013

Investigations were conducted to prevent entrance of Bemisia tabaci (Gennadius) with very fine mesh nets. B. tabaci vectors tomato yellow leaf curl virus in tomatoes. B. tabaci could be completely prevented to penetrate into an 83 mesh net, though few of them passed the 60 mesh net. An independent 60 mesh net cage was built within one of the three interconnected common plastic greenhouse ($21.0{\times}18.3m$) in order to find its usefulness as a crop protection tool from insect pests. TYLCV infected tomato plants were not detected, though a few eggs of B. tabaci and mines of Liriomyza trifolii (Burgess) were detected locally at the entrance of the sliding door. There were practically no significant differences between treatments of nets and the conventional plant height, leaf length and width, number of floret clusters, sugar brix, and product yield. In viewpoints of commercialization, it could be considered highly prospectful to apply to the nets to glasshouses or other greenhouses in which the growing period of crops is long, if the nets were used in the openings of sides, ceilings, and entrances of the greenhouse. However, it might be necessary to take preventive measures for occurrences of insect pests living in soil, temporarily or permanently, as well as high humidity diseases.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.240-252
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• 2015

In the original licensing application for the prototype fast-breeder reactor, MONJU, the event progression during an unprotected loss of flow (ULOF), which is one of the technically inconceivable events postulated beyond design basis, was evaluated. Through this evaluation, it was confirmed that radiological consequences could be suitably limited even if mechanical energy was released. Following the Fukushima-Daiichi accident, a new nuclear safety regulation has become effective in Japan. The conformity of MONJU to this new regulation should hence be investigated. The objectives of the present study are to conduct a preliminary evaluation of ULOF for MONJU, reflecting the knowledge obtained after the original licensing application through CABRI experiments and EAGLE projects, and to gain the prospect of in-vessel retention for the conformity of MONJU to the new regulation. The preliminary evaluation in the present study showed that no significant mechanical energy release would take place, and that thermal failure of the reactor vessel could be avoided by the stable cooling of disrupted-core materials. This result suggests that the prospect of in-vessel retention against ULOF, which lies within the bounds of the original licensing evaluation and conforms to the new nuclear safety regulation, will be gained.

• Korean small business review
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• v.41 no.4
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• pp.65-86
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• 2019

This study empirically analyzed how the elements of entrepreneurship and the fear of entrepreneurial failure influence entrepreneurial intention with each other in a situation that encourages startups. In particular, the moderating effect of fear of entrepreneurial failure was verified by dividing the fear of entrepreneurial failure into three sub-variables: fear of financial loss, fear of psychological loss, and fear of career loss. As a result, it was found that proactiveness and risk-taking had a positive effect on entrepreneurial intention, but innovativeness did not. Fear of entrepreneurial failure(all of sub-variables) was found to have no significantly moderating effect on the relationship between entrepreneurship and entrepreneurial intention. Therefore it seemed to have a negative effect as a independent variable. However, considering the regression coefficient(β) is positive or negative depending on the interaction terms of the sub-variables of fear of entrepreneurial failure and the entrepreneurship, it could be inferred that the moderating effect could be positive or negative. Based on this research results, a sophisticated entrepreneurship education program to inspire entrepreneurship and lower the fear of failure is needed in order to promote startups. And at the same time, a social safety net construction plan to reduce the fear of entrepreneurial failure needs to be prepared.

• Journal of Technologic Dentistry
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• v.35 no.2
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• pp.145-155
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• 2013

Purpose: The recent proliferation of the aging population, oral health care is closely related to the mental health of the elderly is very important being recognized. Provide basic data for improving the quality of life for the elderly, to determine whether the oral health of the elderly whether oral self-perception of health and any related wish. Methods: Surveys to May 20 from April 15, 2011, subjects were elderly and living in Daejeon and Chungnam 277 people were examined. All the statistics using SPSS 18.0 for the determination of statistical significance, and the significance level was 0.05. Results: 1. Recognized, the most common oral health, self-aware bad the state (46.2%) there was no significant difference in the general characteristics according to self-Oral health status, remaining natural dimensions or the intra-oral prosthetic, there was no significant difference. More teeth, residual phase, in accordance with intra-oral prosthetic mandibular Not all dentures, partial dentures, full dentures net self-perception of oral health status better recognized. 2. According to the type of partial dentures, oral health status self-phase, mixed mandibular removable, fixed, fixed, removable partial dentures in order to recognize that good oral health, self-aware state, showed between them, there was no significant difference. 3. Of variable dimension that has nothing to do with the remaining natural maxillary and mandibular prosthetic maxillary prosthetic mandibular partial dentures, age income, a positive correlation was negatively correlated. The case of the mandible, the mandibular prosthetic mandibular partial denture, maxillary prosthetic, the amount of income were correlated. 4. Intra-oral Prosthetics correlation variables in the maxillary, mandibular prosthesis, the positive correlation between income, age was negatively correlated, if the income of the mandible. Maxillary partial denture has nothing to do with the variable portion of the mandibular denture, age was a negative correlation was found. Conclusion: Satisfaction and how now it is important simply to live as long, but you need to pay attention to the quality of life, sometimes with an aging population and the increase of soybean To buy the loss of teeth causes the typical health problems of the elderly. Elderly people of any relevant oral health and the oral cavity by the state to determine whether to provide the basic data for oral health education was more residual value, intra-oral prosthetics there is no more self-aware, the oral health status is good to recognize that appeared. Strengthen the oral health education to improve the quality of life of the elderly, and is thought to be necessary to increase the number of residual.