• ETRI Journal
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• v.41 no.5
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• pp.574-584
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• 2019

A new Mirai variant found recently was equipped with a dynamic update ability, which increases the level of difficulty for DDoS mitigation. Continuous development of 5G technology and an increasing number of Internet of Things (IoT) devices connected to the network pose serious threats to cyber security. Therefore, researchers have tried to develop better DDoS mitigation systems. However, the majority of the existing models provide centralized solutions either by deploying the system with additional servers at the host site, on the cloud, or at third party locations, which may cause latency. Since Internet service providers (ISP) are links between the internet and users, deploying the defense system within the ISP domain is the panacea for delivering an efficient solution. To cope with the dynamic nature of the new DDoS attacks, we utilized an unsupervised artificial neural network to develop a hierarchical two-layered self-organizing map equipped with a twofold feature selection for DDoS mitigation within the ISP domain.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.75-83
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• 1998

This study was done to recognize the importance of errors in measurements of cephalometric radiograph and to find the anatomical structures those need special care to select as a reference points through the detection of the systematic errors and estimation of random errors. For this purose, 100 cephalometric radiographs were prepared by usual manner and 61 reference points, and 130 measurement variables were established. Measurement errors were detected and estimated by the comparison of the 25 randomly-selected samples for repeated measurements with the main sample. The following results were obtained : 1. In comparison of the repeated measurements, there were statistical significant differences in 24 variables which were 18.4% of 130 total variables. 2. The frequency of the difference in identification of the reference points between the repeated measurements was very high in the root apex of upper incisor(as), the most posterior wall of maxilla(tu), soft tissue nasion(n'), soft tissue frontal eminence(ft), and ad3 in airway. 3. After correction of reference points marking until the level of below 5% significance, the range of random errors were from 0.67 to 1.71 degree or mm. 4. The variable shown the largest random error was the interincisal angle(ILs-ILi). 5. Measurement errors were mainly caused by the lack of precision in anatomic definitions and obscure radiographic image. From the above results, the author could find the high possibility of errors in cephalometric measurements and from this point, we should include error analysis in all the studies concerning measurments. In is essential to have a concept of error analysis not only for the investigator but also for a reader of other articles.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.260-266
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• 2009

Non-revenue water reduction(NRW) technologies are implemented to evaluate and manage leakages scientifically in water distribution systems under local governments. A development of quantitative leakage indicator by measuring minimum night flow, pressure control policy by installation of PRV(pressure reducing valve) and the establishment of leakage prevention schemes by residual life modeling of deteriorated water pipes are reviewed and studied. Estimation models of allowable leakage are developed by measuring and analyzing minimum night flow at residential and commercial area in Nonsan city, which is suggested from UK water industry and can improve an existing leakage indicator for the evaluation of non-revenue water. Also, pressure control method is applied and analyzed to Uti distribution area in Sacheon city in the operation aspect. As results, $466\;m^3/day$ of leakage can be reduced and it is expected that 113million won of annual cost can be saved. In the part of corrosion velocity and residual life assessment, non-linear prediction models of residual thickness are proposed by assessment of corrosion velocity based on exposure years, soil and water quality etc., since the deteriorated water pipe play a major role to increase leakage. It is expected that collection data and analyzing results can be applied effectively and positively to reduce non-revenue water by accumulating surveying data and verifying the results in the business field of water distribution systems under local governments.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.117-127
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• 2006

Recently International Water Association(IWA) has proposed new performance indicators for water supply services and their successful applications are being reported continually. According to the various reports, the percentage indicators were suggested not to be used for performance comparison, especially where the targeted areas have great difference in consumption per service connection. But unfortunately in Korea the revenue water ratio, one of the percentage indicators is still being used to set up the goal of water-related administration and to compare the performances between systems. Therefore this study aimed to prove the inapplicability of the percentage indicators with nation-wide data and to suggest better performance indicators for more efficient water loss management. According to the result of the comparison of various performance indicators with conventional one, it is roved that percentage indicators ca not evaluate the performance efficiently where the local situations are significantly different. It is suggested that the better performance indicators such as real losses per service connection or ILI should be used to benchmark the performances of water suppliers on water loss management so thai the problems of water losses could be identified easily and recovered effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.495-505
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• 2010

In this paper, the effect of Near-Far Problem (NFP) among distributed nodes in OFDMA-based Wireless Mesh Networks (WMNs) is analyzed by investigating statistical characteristics of Time Difference of Arrival (TDoA) and Desired-to-Undesired power Ratio (DUR). In order to overcome the effects of Inter-Symbol Interference (ISI), Inter-Carrier Interference (ICI), and Inter Link Interference (ILI), caused by TDoA in WMNs, we derive effective SINR for each subcarrier, and then, propose the optimal starting point of FFT window which can minimize BER for each subcarrier. In addition, we propose a subcarrier-based Zero Forcing - 2 Dimensional Ordered Successive Interference Cancellation (ZF-2DOSIC) technique for signal detection in WMNs with TDoA. It is verified by simulation that the effective SINR and uncoded BER performances of the proposed signal detection technique for OFDMA-based WMNs are significantly improved, compared with those of conventional technique.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.3.1-3.12
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• 2022

Background: Influenza illness causes several disruptions to the workforce. The absenteeism that often ensues has economic implications for employers. This study aimed to estimate the cost-benefit of influenza vaccination in a healthcare setting from the employer's perspective. Methods: A cross-sectional questionnaire survey was conducted in a private hospital in 2018-2019 comparing voluntary vaccinated with non-vaccinated employees with influenza vaccine. The analyses were made based on self-reporting on absenteeism and presenteeism from Influenza-like illnesses (ILIs). The costs incurred, both direct and indirect costs, were included in the study. A cost-benefit analysis was performed by measuring the cost of the vaccination program. The costs of absenteeism and reduced productivity were calculated using 3 hypothesised levels of effectiveness in the following percentage of productivity of 30%, 50%, and 70%. The costs were also calculated based on four scenarios: with and without operating income and with and without replacement. The benefits of the influenza vaccination from the employer's perspective were analysed. The benefit to cost ratio was determined. Results: A total of four hundred and twenty-one respondents participated. The influenza vaccination rate was 63.0%. The rate of ILI of 38.1% was significantly lower among vaccinated. The ILI-related absenteeism reported was also significantly lower amongst vaccinated employees at 30% compared to 70% non-vaccinated. Employers could save up to USD 18.95 per vaccinated employee when only labour cost was included or 54.0% of cost savings. The cost-saving rose to USD 155.56 when the operating income per employee was also included. The benefit to cost ratio confirmed that the net cost-benefit gained from the vaccination was more than the net cost of vaccination. Conclusions: Influenza vaccination for working adults was cost-saving and cost-beneficial when translated into financial investments for the employer. A workplace vaccination demonstrates a significant cost-benefit strategy to be applied in any institutional setting.

• Archives of Pharmacal Research
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• v.20 no.5
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• pp.396-403
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• 1997

In order to direct the form of the immune response in an antigen-specific manner, we constructed a fusion protein (OVA/IL12) that contained the T cell-dependent antigen, ovalbumin (OVA), covalently linked to murine interleukin-12 (IL-12). The OVA/IL12 protein was produced in a baculovirus expression system and was purified by anti-OVA immunoaffinity chromatography. The purified OVA/ILI2 protein displayed potent IL-12 bioactivity in an IL-12 proliferation assay. BALB/c mice immunized with the OVA/IL12 protein produced increased quantities of anti-OVA IgG2a antibody compared with mice immunized with recombinant OVA alone. Lymph node cells from the immunized mice with the OVA/IL12 protein produced large amounts of IFN-,Y when restimulated in vitro with OVA, while those from mice immunized with the OVA protein produced little or no IFN-.gamma.. In contrast, immunization with a mixture of OVA and free recombinant IL-12 also induced IFN-.gamma. production, which was not OVA-specific. These studies indicate that the OVA/IL12 fusion protein can induce OVA-specific, Th1-dominated immune responses, and that the covalent linkage of OVA and IL-12 confines the effect of IL-12 to OVA-specific cells.

• Journal of Magnetics
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• v.15 no.4
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• pp.199-203
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• 2010

This paper discusses the effectiveness of high magnetization saturation in ILI (In-Line Inspection) using an MFL (Magnetic Flux Leakage) tool, and introduces a practical method for improving the magnetization level together with the piggability. Thin steel plates, replacing the conventional wire brushes were used as conductors to transfer the magnetic flux to the pipe wall. The newly designed MFL tool was compared with the conventional version by means of FEM (Finite Element Method) analysis and full-scale experiments. In the results, the newly developed magnetization system obtained a stronger MFL signal amplitude, specially 2.7 times stronger, than that obtained by the conventional magnetization system for the same defect dimensions.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.530-537
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• 2008

Austenitic stainless steels(SUS 304, SUS 316), which are used for safety control valve of LNG carrier, are occasionally exposed in the cryogenic environment. In this regards, it is required to evaluate the mechanical characteristics under the low temperature environment. In this study, a series of uniaxial tensile test was carried out varying temperature for austenitic stainless steel. The phenomena of the strain-induced plasticity have been observed on the all temperature ranges. The critical value for threshold of 2nd hardening due to the phase transformation induced plasticity as well as the increase of hardening have been reported. The summarized experimental results would be used for the validation of numerical techniques applicable for the nonlinear hardening behavior of austenitic stainless steel under the cryogenic temperature environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.423-423
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• 2021

국내에서는 '물손실(누수)을 얼마나 잘 관리하고 있는지' 평가하는 물손실관리 수행능 지표를 '유수율(누수율)' 로 판단하고 있다. 하지만, 유수율은 실제 관리자의 의지와 무관한 인자에 영향을 받을 수 있으며, 지역의 여건상 유수율이 높게 나올 수밖에 없는 지역이 있는가 하면 반대로 지역의 여건 상 유수율이 낮게 나올 수밖에 없는 지역이 있다. 따라서 유수율만을 이용하여 물손실관리 수행능력을 평가하는 지표로는 미흡함이 있는 것으로 판단될 뿐만 아니라 IWA에서는 전통적인 백분율을 이용한 지표(손실율, 유수율, 무수율 등)의 문제를 언급하면서 수자원의 효율적인 사용 혹은 상수도사업의 경제성을 나타내는 목적 외에는 사용하지 말아야 한다고 권고하였다. 현재까지의 연구를 보면, 국내 실정에 맞는 다양한 물손실관리 수행능 지표들이 언급되면서 이에 대한 적합성 및 적용성에 대한 많은 연구들이 진행되어 왔다. 기존의 연구들은 지자체 단위로 물손실관리 수행능 지표에 대한 연구를 진행하였다면, 본 연구에서는 소블럭 단위로 수도통계자료를 분석하여 물손실관리를 위한 어떠한 지표를 이용하는 것이 타당한 방법인지 제시하고자 하였다. 비교분석을 하기 위한 지표인 소블럭별 유수율, 실손실율(누수율), 1인당 실손실량, 급수전당 실손실량, 누수평가지표(ILI)를 산정하고, 그 결과에 따라 소블럭별 순위를 결정하였다. 유수율과 급수인구를 고려한 1인당 실손실량과의 비교분석에서 높은 R² (결정계수)값과 소블럭별 순위변동 폭이 적은 것으로 나타났으나, 유수율과 급수전수를 고려한 급수전당 실손실량 및 배수관의 연장과 급수전수, 평균압력을 고려한 누수평가지표와의 비교분석에서는 낮은 R²값과 소블럭별 순위 변동폭이 큰 것으로 나타났다. 앞서 언급한 것처럼, 유수율만을 이용하여 물손실관리 수행능을 설명하기에는 부족할 것으로 판단되며, 유수율 외에도 다양한 지표들을 종합적으로 고려했을 때 가장 바람직한 물손실관리 수행능 평가가 될 것으로 사료된다.