• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.612-622
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• 2007

As compared with wired network environment, mobile VOD service in wireless network environment is difficult to guarantee the quality of VOD service due to the limitation of the system resources. Moreover, the wireless network has small bandwidth resources and short access range so that has limitations for providing the service to a large number of mobile clients. The limited battery capacity of a mobile device becomes an obstacle to mobile clients for enjoying VOD service for a long time. Therefore, these drawbacks should be considered in developing mobile VOD applications. This paper proposes a new technique for improving QoS of mobile VOD service by jointly use of broadcasting technique, which can provide VOD service to a large number of mobile clients simultaneously, and bursty communication technique, which can reduce the power consumption of a mobile device. With having these two techniques, streaming data are divided into segments, each of which is grouped into a particular packet and then transmitted at a time in the busty communication manner. In the performance evaluation, the power consumption on WNIC of a mobile device can be reduced by over 80%, and the initial service delay can be reduced in proportion to the number of channels compared with the existing staggered broadcasting technique.

• Plant Journal
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• v.17 no.1
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• pp.38-49
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• 2021

In order to increase power plant efficiency, the steam temperature was increased to 610 ℃ which deteriorates the durability of the boiler tube and as the use of low-calorie coal increases the post combustion and delayed combustion phenomenon, the overheating of the final reheater and the tube rupture are becoming frequent. In order to prevent overheating of the final reheater, desuperheater water injection was increased, leading to a decrease in boiler efficiency. In this study install a baffle plate at the back of some overheated tube groups, thereby reduce the temperature of the tube by reducing the amount of combustion gas, and the reduced combustion gas moves to an adjacent place to increase the temperature of other tubes. As a result of the study, the temperature deviation between tubes decreased 1.5. And the heat-reducing injection amount was reduced to 6,929 kg/h and the maximum tube temperature was reduced to 623.4℃ which is 6.6℃ more below than the control standard of 630℃.

• Journal of the Korean Society for information Management
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• v.39 no.2
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• pp.1-33
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• 2022

Voice shopping is gaining attention following the trend of non-contact E-commerce by enabling people to shop via voice command. Therefore, in this study, voice shopping service heuristics using a display-mounted voice interface were developed in preparation for the future where voice shopping becomes a part of daily life in the world. First, as a theoretical approach, a literature survey of 50 papers on the design principles of 'visual interface,' 'voice interface,' and 'shopping service' was conducted to produce a total of 29 draft design principles. Second, as an empirical approach, a focus group interview was conducted on consumer decision-making processes in shopping experiences and information-seeking behavior within the context of shopping to draft the heuristics. This was to supplement the user experience, a weak part of the literature research. Finally, a Delphi survey asked 20 experts in UX, service planning, artificial intelligence development, and shopping to evaluate the heuristics draft developed through the above two stages. After three rounds of Delphi surveys, the final heuristics were proposed.

• Journal of Korea Foundry Society
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• v.41 no.6
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• pp.543-549
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• 2021

Aluminum cast iron has excellent oxidation resistance and good resistance to sulfide and corrosion. Compared to Ti and Ni alloys, it is expected to be a substitute material for structural materials and stainless steels because it is relatively inexpensive to use Fe, which is a non-strategic element. This results in a weight reduction effect of about 30% as compared to the use of stainless steel. With regard to aluminum as an alloying material, it is an element that has been widely used for the alloying of cast iron in recent years. Practical use has been delayed owing to the resulting lack of ductility at room temperature and the sharp decrease in the strength above 600℃ of this alloy, however. The cause of the weak room temperature ductility is known to be environmental embrittlement by hydrogen, and the addition of various alloying elements has been attempted in order to mitigate these shortcomings. Although alloying elements such as vanadium, chromium, and manganese are mainly used to increase the hardness and wear resistance of gray cast iron, the price of finished products containing these elements and the problems associated with alloys with this material impose many limitations.

• Journal of Industrial Convergence
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• v.20 no.10
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• pp.17-24
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• 2022

Lora, a non-band network technology of the long-distance wireless standard LPWAN standard, uses ABP and OTTA methods and AES-128-based encryption algorithm (shared key) for internal terminal authentication and integrity verification. Lora's recent firmware tampering vulnerability and shared-key encryption algorithm structure make it difficult to defend against MITM attacks. In this study, the consensus algorithm(PBFT) is applied to the Lora network to enhance safety. It performs authentication and PBFT block chain creation by searching for node groups using the GPS module. As a result of the performance analysis, we established a new Lora trust network and proved that the latency of the consensus algorithm was improved. This study is a 4th industry convergence study and is intended to help improve the security technology of Lora devices in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.821-830
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• 2023

Various studies has tried to unveil causes of cost overrun and schedule delay in the road construction project. However, these causes need standardization due to difference by guidelines, relevant research, and facilities. Therefore, this study identifies and elaborate standard road construction cost and schedule variation factors that can be used in the planning and execution of the project. variation factors have been derived and grouped through literature review and modified and supplemented through expert interview. In addition, the connection with the relevant guidance factors is confirmed and the usability is reviewed by applying actual road construction cases. The factors suggested in this study comprehensively include factors of related guidelines and previous research, more clearly distinguish, support decision making.

• Journal of radiological science and technology
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• v.36 no.4
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• pp.313-318
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• 2013

Positron emission tomography/computed tomography (PET/CT) imaging with fluorodeoxyglucose (FDG) have been used as a powerful fusion modality in nuclear medicine not only for detecting cancer but also for staging and therapy monitoring. Nevertheless, there are various causes of FDG uptake in normal and/or benign tissues. The purpose of present study was to investigate whether additional delayed imaging can improve the diagnosis to differentiate the rates of FDG uptake at axillary lymph nodes (ALN) between malignant and benign in breast cancer patients. 180 PET/CT images were obtained for 27 patients with ALN uptake. The patients who had radiotherapy and chemotherapy were excluded from the study. $^{18}F$-FDG PET/CT scan at 50 min (early phase) and 90 min (delayed phase) after $^{18}F$-FDG injection were included in this retrospective study. The staging of cancers was confirmed by final clinical according to radiologic follow-up and pathologic findings. The standardized uptake value (SUV) of ALN was measured at the Syngo Acquisition Workplace by Siemens. The 27 patients included 18 malignant and 9 ALN benign groups and the 18 malignant groups were classified into the 3 groups according to number of metastatic ALN in each patient. ALNs were categorized less than or equal 3 as N1, between 4 to 9 as N2 and more than 10 as N3 group. Results are expressed as the mean${\pm}$standard deviation (S.D.) and statistically analyzed by SPSS. As a result, Retention index (RI-SUV max) in metastasis was significantly higher than that in non-metastasis about 5 fold increased. On the other hand, RI-SUV max in N group tended to decrease gradually from N1 to N3. However, we could not prove significance statistically in malignant group with ANOVA. As a consequence, RI-SUV max was good indicator for differentiating ALN positive group from node negative group in breast cancer patients. These results show that dual-time-point scan appears to be useful in distinguishing malignant from benign.

• Korean Journal of Food Science and Technology
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• v.41 no.6
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• pp.706-711
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• 2009

Hepatoprotective effects of corn gluten hydrolysates (CGH) were investigated in rats orally treated with ethanol (30%(v/v), 3 g/kg body weight/day) for 4 weeks. Six-week old Sprague-Dawley male rats were divided into four dietary groups: normal diet (N), alcohol diet (E), E+CGH 1% diet (CGH-1%), and E+CGH 3% diet (CGH-3%). Body weights and liver indices were not significantly different among the four groups. However, food intakes were lower in the CGH groups than in the normal group (p<0.05). The administration of CGH significantly reduced serum alkaline phosphatase activity by 30% compared to the alcohol diet group. Among the antioxidative enzymes assessed, catalase activity was significantly decreased by 79% in the CGH diet groups compared to the alcohol diet group. In comparison to the alcohol-treated group, aldehyde dehydrogenase activity was increased by 20%, while microsomal ethanol oxidizing system activity was decreased by 20% in the CGH-treated groups. Furthermore, the area under the curve of the blood acetaldehyde concentration versus time profile after the administration of ethanol was significantly lower for the CGH rats than for the ethanol or asparaginic acid treated groups. Thus, CGH seems to offer beneficial effects by protecting against ethanol-induced hepatotoxicity by improving the acetaldehyde-related metabolizing system.

• Journal of Korean Society of Transportation
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• v.32 no.4
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• pp.327-335
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• 2014

The Korean government, as of last year, is attempting to introduce a competitive system in the rail-market. However there are some pertinent issues which need to be addressed in order to select the best possible organization for optimum railway traffic control. As there are no standard guidelines in selecting an agency, objective evaluation factors need to be properly applied to ensure the best possible decision is made. Through literature review and various interviews with experts, appropriate criteria were selected to evaluate the suitability of each potential operator. As generally mentioned, both safety and efficiency play vital roles in the selection process but in addition, there are other factors such as security and fairness, which also need to be considered. The individual weight of these factors were calculated by the AHP, in which three groups of experts were interviewed to acquire their expertise. According to the results, as a potential operator, the score of a railway operating company and the management cooperation of railway is 2.75 and 3.85, respectively. In the future, in preparation towards becoming a competitive rail-market, this research is expected to assist in choosing the best party to control the rail traffic system.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.203-207
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• 2009

Copper is known as a replacement for aluminum wire which is used for semiconductor. Because specific resistance of Cu ($1.67{\mu}{\Omega}$-cm) is lower than that of Al ($2.66{\mu}{\Omega}$-cm), Cu reduce RC delay time. Although melting point of Cu($1085^{\circ}C$) is higher than melting point of Al, Cu have characteristic to easily react with Silicon(Si) in low temperature, and it isn't good at adhesive strength with Si. For above these reason, research of diffusion barrier to prevent reaction between Cu and Si and to raise adhesive strength is steadily advanced. Our study group have researched on W-C-N (tungsten-carbon-nitrogen) Diffusion barrier for preventing diffusion of Cu through semiconductor. By recent studies, It's reported that W-C-N diffusion barrier can even precent Cu and Si diffusing effectively at high temperature. In this treatise, we vaporized different proportion of N into diffusion barrier to research Cu's Electromigration based on the results and studied surface hardness in the heat process using nano scale indentation system. We gain that diffusion barrier containing nitrogen is more stable for Cu's electromigration and has stronger surface hardness in heat treatment process.