• Tribology and Lubricants
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• v.35 no.1
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• pp.44-51
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• 2019

The paper presents the rotordynamic performance measurements and model predictions of a fuel cell electric vehicle (FCEV) air compressor supported on gas foil bearings (GFBs). The rotor has an impeller on one end and a thrust runner on the other end. The front (impeller side) and rear (thrust side) gas foil journal bearings (GFJBs) are located between the impeller and thrust runner to support the radial loads, and a pair of gas foil thrust bearings are located on both sides of the thrust runner to support the axial loads. The test GFJBs have a partial arc shim foil installed between the top foil and bump strip layers to enhance hydrodynamic pressure generation. During the rotordynamic performance tests, two sets of orthogonally installed eddy-current displacement sensors measure the rotor radial motions at the rotor impeller and thrust ends. A series of speed-up and coast-down tests to 100k rpm demonstrates the dominant synchronous (1X) rotor responses to imbalance masses without noticeable subsynchronous motions, which indicates a rotordynamically stable rotor-GFB system. Finite element analysis of the rotor determines the rotor free-free (bending) natural modes and frequencies well beyond the maximum rotating frequency. The predicted damped natural frequencies and damping ratios of the rotor-GFB system reveal rotordynamic stability over the speeds of interest. The imbalance response predictions show that the predicted critical speeds and rotor amplitudes strongly agree with the test measurements, thus validating the developed rotordynamic model.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.491-505
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• 2018

As an alternative to deep geological disposal technology, which is considered as a reference concept, the domestic applicability of deep borehole disposal technology for high level radioactive waste, including spent fuel, has been preliminarily evaluated. Usually, the environment of deep borehole disposal, at a depth of 3 to 5 km, has more stable geological and geo-hydrological conditions. For this purpose, the characteristics of rock distribution in the domestic area were analyzed and drilling and investigation technologies for deep boreholes with large diameter were evaluated. Based on the results of these analyses, design criteria and requirements for the deep borehole disposal system were reviewed, and preliminary reference concept for a deep borehole disposal system, including disposal container and sealing system meeting the criteria and requirements, was developed. Subsequently, various performance assessments, including thermal stability analysis of the system and simulation of the disposal process, were performed in a 3D graphic disposal environment. With these analysis results, the preliminary evaluation of the domestic applicability of the deep borehole disposal system was performed from various points of view. In summary, due to disposal depth and simplicity, the deep borehole disposal system should bring many safety and economic benefits. However, to reduce uncertainty and to obtain the assent of the regulatory authority, an in-situ demonstration of this technology should be carried out. The current results can be used as input to establish a national high-level radioactive waste management policy. In addition, they may be provided as basic information necessary for stakeholders interested in deep borehole disposal technology.

• Korean Journal of Clinical Pharmacy
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• v.29 no.3
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• pp.166-172
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• 2019

Background: Hypercalcemia is an important metabolic emergency condition in cancer patients. Bisphosphonate is the treatment of choice for hypercalcemia, whereas calcitonin and hydration with furosemide are recommended for acute supportive therapy. However, data regarding real-world treatment patterns and outcomes of pharmacological treatments are limited. Therefore, we aimed to investigate the treatment patterns and clinical outcomes of hypercalcemia treatment in solid tumor patients. Methods: Electronic medical records of 123 adults with solid cancers and albumin-corrected calcium levels >10.5 mg/dL or ionized calcium levels >1.35 mmol/L were reviewed. We retrospectively analyzed the pharmacological treatment and recovery rate according to the severity of hypercalcemia. Results: A total of 177 cases were identified, of which 49 were not treated and 30 were treated with hydration only. In moderate-to-severe cases, 86.5% received pharmacological treatment. Thirty-four cases (19.2%) were treated with bisphosphonate alone and 58 cases (32.8%) were treated with bisphosphonate and calcitonin. In mild hypercalcemia cases, the recovery rate was higher for those receiving hydration only or pharmacological treatment (79.7%) than for those receiving no treatment (61.4%, p = 0.041). Most moderate-to-severe cases were treated with medication and of those treated, 56.3% recovered. The recovery rate was lower in those treated with bisphosphonate alone (38.2%) than in those who underwent calcitonin combination treatment (73.7%, p = 0.001). Conclusions: Bisphosphonate combined with calcitonin was found to be more effective than bisphosphonate alone for the treatment of moderate-to-severe hypercalcemia. Considering the current shortage of calcitonin, further efforts are required to ensure its stable supply.

• Convergence Security Journal
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• v.17 no.5
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• pp.63-69
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• 2017

In the early 1990s, IETF(Internet Engineering TaskForce) had started the discussion on new address protocol that can modify and supplement various drawbacks of existing IPv4 address protocol with the introduction of CIDR(Classless Inter-Domain Routing) which is a temporary solution for IPv4 address depletion, NAT, private IP address. While various standards related to new address protocol has been proposed, the SIPP(Simple Internet Protocol Plus) was adopted among them because it is regarded as the most promising solution. And this protocol has been developed into current IPv6. The new concepts are introduced with modifying a lot of deficiencies in the exisitng IPv4 such as real-time data processing, performance on QoS, security and the efficiency of routing. Since many security threats in IPv6 environment still exist, the necessity of stable data communication environment has been brought up continuously. This paper deveopled one-way communication algorithm in IPv6 based on the high possibility of protecting the system from uncertain and potential risk factors if the data is transmitted in one way. After the analysis of existing IPv6 and ICMPv6, this paper suggests one-way communication algorithm as a solution for existing IPv6 and ICMPv6 environment.

• Management & Information Systems Review
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• v.38 no.1
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• pp.181-199
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• 2019

The purpose of this study is to examine whether or not the volatility of the 1997~1998 Asian crisis still affects the monthly stock returns of Korea, Japan, Singapore, Hong Kong and China from 1980 to 2018. This study investigated whether the volatility has already fallen to pre-crisis levels. To illustrate the possible structural changes in the unconditioned variance due to the Asian financial crisis, we use the MRS-GARCH model, which is a regime switching model. The main results of this study were as follows: First, the stock return of each country was weak in the high volatility regime except Japan resulted by the Asian financial crisis from 1997 to 1998 until March 2018, and the Asian stock market has not yet calmed down except for the global financial crisis period of 2007 and 2008. Second, the conditional volatility has been significantly and persistently decreased and eliminated after the Asian financial crisis. Thus, we could be judged that the Asian stock market was not fully recovered(stable) due to the Asian crisis including the capital liberalization high inflation, worsening current account deficit, overseas low interest rates and expansion of credit growth in 1997 and 1998, but the Asian stock market was largely settled down, except for the 2007 and 2008 in Global financial crises. Considering the similarity between the Asian stock markets and the similar correlation of the regime switching, it may be worthwhile to analyze the MRS-GARCH model.

• Korean Journal of Environment and Ecology
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• v.33 no.1
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• pp.116-123
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• 2019

This study focused on defining concepts such as biology push (biology-based biomimicry) and technology pull (technology problem-based biomimicry) in the multidisciplinary field of ecological imitation and analyzing the status of related research and technology at the domestic and international levels. From an ecological point of view, biomimicry is defined as ecological mimicry in which ideas obtained through classification and investigation of principles of biology and ecology are applied to the concepts of engineering and technology. We also defined the biology push as the ecological imitation based on biological characteristics starting from an ecological viewpoint and technology pull as the ecological imitation based on technical problems starting from technical needs. Although biomimicry studies often focus on the technology development by finding stable and eco-friendly source materials from biological and ecological characteristics, we wanted to emphasize the unlimited potential of research of biomimicry that can begin with an idea based on biological and ecological characteristics. This study presents the need to develop the research and technology further based on the biological and ecological viewpoints that can contribute to future sustainable development.

• International Journal of Computer Science & Network Security
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• v.21 no.5
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• pp.73-83
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• 2021

The information space, the main components of which are information resources, means of information interaction, and information infrastructure, is a sphere of modern social life in which information communications play a leading role. The objective process is the gradual but stable entry of the national information space into the European and world information sphere, in the context of which there is a legitimate question of its protection as one of the components of the national security of Ukraine. However, the implementation of this issue in practice immediately faces the need to respect the rights and fundamental freedoms guaranteed by international regulations and the Constitution of Ukraine, especially in the field of cybersecurity. The peculiarity of the modern economy is related to its informational nature, which affects the sharp increase in cyber incidents in the field of information security, which is widespread and threatening and affects a wide range of private, corporate, and public interests. The problem of forming an effective information security system is exacerbated by the spread of cybercrime as a leading threat to information security both in Ukraine and around the world. The purpose of this study is to analyze the state of cybersecurity and on this basis to identify new areas of the fight against cybercrime in Ukraine. Methods: the study is based on an extensive regulatory framework, which primarily consists of regulatory acts of Ukraine. The main methods were inductions and deductions, generalizations, statistical, comparative, and system-structural analysis, grouping, descriptive statistics, interstate comparisons, and graphical methods. Results. It is noted that a very important component of Ukraine's national security is the concept of "information terrorism", which includes cyberterrorism and media terrorism that will require its introduction into the law. An assessment of the state of cybersecurity in Ukraine is given. Based on the trend analysis, further growth of cybercrimes was predicted, and ABC analysis showed the existence of problems in the field of security of payment systems. Insufficient accounting of cybercrime and the absence in the current legislation of all relevant components of cybersecurity does not allow the definition of a holistic system of counteraction. Therefore, the proposed new legal norms in the field of information security take into account modern research in the field of promising areas of information technology development and the latest algorithms for creating media content.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.744-758
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• 2021

This study is aimed at identifying the possibility and effectiveness of teaching methods education for professors through the development of online teaching content and providing important implications for future online teaching content development and utilization strategies by looking at the differences in the experience and needs of professors who have taken online teaching content. A university surveyed 83 professors who took the seven teaching contents developed between 2015 and 2018, and took them from 2017 to 2019. As a result of the study, professors often took online teaching content for self-development purposes, were satisfied with the overall content, and cited the low psychological burden and resistance of education through personal learning, and the possibility of repeated learning online. The differences between importance and execution in content composition, the areas of statistically significant difference were easy-to-understand delivery, appropriate and sufficient examples, interest and motivation, facilitating interaction between learners, appropriate difficulty, reflection of current trends, appropriate presentation order and ethical composition. The importance level recognized by professors in the area was higher than execution level. In conclusion, opinions for improving online teaching content were appropriate and sufficient examples in the area of content composition, interest and motivation, and reflection of the latest trends. In the area of ease of use, there was stable playback, relay function, and location-independent.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.1
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• pp.49-61
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• 2021

The repeated shipboard measurements that have been conducted by the National Institute of Fisheries Science (NIFS) for more than a half century, provide the valuable long-term hydrographic data with high spatial-temporal resolution. However, this unprecedent dataset has been rarely used for oceanic climate sciences because of its reliability issue. In this study, temporal variability of salinity error in the NIFS data was quantified by means of extremely small variability of salinity in the deep layer of the south-western East Sea, in order to contribute to studies on long-term variability of the East Sea. The NIFS salinity errors estimated on the isothermal surfaces of 1℃ have a remarkable temporal variation, such as ~0.160 g/kg in the year of 1961~1980, ~0.060 g/kg in 1981~1994,~0.020 g/kg in 1995~2002, and ~0.010 g/kg in 2003~2014 on average, which basically represent bias error. In the recent years, even though the quality of salinity has been improved, there still remain relatively large bias errors in salinity data presumably due to failure of salinity sensor managements, especially in 2011, 2013, and 2014. On the contrary, the salinity in the year of 2012 was very accurate and stable, whose error was estimated as about 0.001 g/kg comparable to the salinity sensor accuracy. Thus, as long as developing proper data quality control procedures and sensor management systems, I expect that the NIFS shipboard hydrographic data could have good enough quality to support various studies on ocean response to climate variabilities. Additionally, a few points to improve the current NIFS shipboard measurements were suggested in the discussion section.

• Journal of Digital Convergence
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• v.19 no.2
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• pp.61-69
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• 2021

The military pension deficit is increasing due to an increase in the average life expectancy and pension option rate, and a significant reason for this is estimated to be a continued increase in the number of military pension recipients. In terms of the soundness of military pension finances, this paper uses the Markov chain model to validate the stability of the military group, suggesting the direction of future military pension system in terms of the ratio of pension receipts to employees, and verifying the feasibility of the method applied through verification. Through this paper, we have confirmed that the initial 45,270 military personnel converge to 43,141 after a certain period of time and reach a stable state, which is expected to help us to estimate the long term size of military pension recipients to confirm the direction of national financial support. Military man who are eligible for pensions for more than 20 years have a relatively low rate of turnover or retirement compared to ordinary private groups, making it easier to define their status and simplify state transition probabilities. Therefore, it is expected that the sustainability of the military pension will be confirmed from a long term perspective by viewing the military group as a system and applying it to the Markov chain model by checking the probability of transfer of status such as promotion, maintaining the current grade, and retirement during the period.