• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권4호
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• pp.1351-1372
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• 2022

A self-organizing multiple unmanned aerial vehicles (multi-UAVs) deployment based on virtual forces has a difficulty in ensuring the quality-of-experience (QoE) of users because of the difference between the assumed center for users in a hotspot and an actual center for users in the hotspot. This discrepancy is aggravated in a non-uniform and mobile user distribution. To address this problem, we propose a new density based virtual force (D-VF) multi-UAVs deployment algorithm which employs a mean opinion score (MOS) as a metric of QoE. Because MOS is based on signal-to-noise ratio (SNR), a sum of users' MOS is a good metric not only to secure a wide service area but to enhance the link quality between multi-UAVs and users. The proposed algorithm improves users' QoE by combining virtual forces with a random search force for the exploration of finding multi-UAVs' positions which maximize the sum of users' MOS. In simulation results, the proposed deployment algorithm shows the convergence of the multi-UAVs into the position of maximizing MOS. Therefore, the proposed algorithm outperforms the conventional virtual force-based deployment scheme in terms of QoE for non-uniform user distribution scenarios.

• 한국해양공학회지
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• 제17권2호
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• pp.34-39
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally condrcted by using S-N curves, as specified in the codeds and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02 ). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.184-191
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• 2016

In recent years, there are a number of studies that have been carried out to explore the alternative for Mineral Oil (MO) as dielectric insulating fluid in transformers due to the increasing tight regulation on safety and environment. Vegetable oils have been identified as suitable candidate since it is biodegradable, non-toxic and high flash/fire points which ensure more in-service safety. Among the types of vegetable oils considered for transformers application are Palm Oil (PO) and Coconut Oil (CO). This paper presents an experimental study on the lightning breakdown voltages of PO and CO under non-uniform electric field based on needle-sphere electrodes configuration at 3 small gap distances. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The main focus of this study is to examine the lightning breakdown performance of RBDPO and CO under different test conditions and assess its suitability as dielectric insulating fluid in transformers. The effect of voltage polarities (positive and negative) and testing methods (rising-voltage, up-and-down and multiple-voltage) were investigated. The data obtained from all tests were analysed by Weibull distribution in order to determine the withstand voltages for each type of oils. It was found that the breakdown voltages of RBDPO and CO are comparable with MO under positive lightning impulse. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO and CO. There is no significant effect of testing methods and voltage polarities on lightning breakdown voltages of RBDPO and CO. Based on the statistical analysis, it is found that the breakdown voltages of RBDPO and CO at 1% probability are slightly lower than MO.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.69-74
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally conducted by using S-N curves, as specified in the codes and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.127-132
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• 2002

Recent deepwater offshore structures in Gulf of Mexico utilize butt welded tubular joints. Application of welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical because the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimating the fatigue behavior of these tubular members in the design stage is generally conducted by using S-N curves specified in the codes and standards. Applying the stress concentration factor of the welded structure to S-N approach often results in very conservative assessment because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fracture mechanics and fitness for service (FFS) technology have been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves to be used and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. An attempt was made to develop set of S-N curves based on fracture mechanics approach by considering non-uniform stress distribution and a threshold stress intensity factor. Series of S-N curves generated from this approach were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02"). Similar comparison with API X′ was made for tubular joint.. These initial crack depths are larger than the limits of inspection by current Non-destructive examination (NDE) means, such as Automatic Ultrasonic Inspection (AUT). Thus a safe approach can be taken by specifying acceptance criteria that are close to limits of sizing capability of the selected NDE method. The comparison illustrates conservatism built into the S-N design curve.

• 대한수의학회지
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• 제42권1호
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• pp.81-88
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• 2002

The purpose of this study was to conduct diagnosis of bovine paratuberculosis in Kangwon area. Blood samples were collected from 2,261 dairy cows of 162 herds, and the ELISA and immunoblotting using recombinant 34KDa protein of M. paratuberculosis were conducted. The feces collected from dairy cows were cultured on HEY medium with mycobactin-J and PCR was conducted with washing solution of medium 4 weeks after culture. The ELISA had sensitivity of 83.3% and specificity of 96.7%. And the immunoblotting had sensitivity of 83.3% and specificity of 100%. Of the 2,261 dairy cows, 371 cows(16.4%) were positive in ELISA and 75 cows(3.3%) were positive in immunoblotting. And of the 162 herds, 109 herds(67.3%) had an apparent paratuberculosis prevalence by ELISA and 40 herds(24.7%) by immunoblotting. The geographic distribution of herds with paratuberculosis was not uniform. Of the 241 feces samples including 110 feces from ELISA positive cow, 9 feces were positive in culture and PCR. PCR was able to detect the growth of M. paratuberculosis as early as 4 weeks of culture.

• Wind and Structures
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• 제38권1호
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• pp.43-58
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• 2024

To ensure the flutter stability of three-tower suspension bridges under skew wind, by using the computational procedure of 3D refined flutter analysis of long-span bridges under skew wind, in which structural nonlinearity, the static wind action(also known as the aerostatic effect) and the full-mode coupling effect etc., are fully considered, the flutter stability of a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River in completion and during the deck erection is numerically investigated under the constant uniform skew wind, and the influences of skew wind and aerostatic effects on the flutter stability of the bridge under the service and construction conditions are assessed. The results show that the flutter critical wind speeds of three-tower suspension bridge under service and construction conditions fluctuate with the increase of wind yaw angle instead of a monotonous cosine rule as the decomposition method proposed, and reach the minimum mostly in the case of skew wind. Both the skew wind and aerostatic effects significantly reduce the flutter stability of three-tower suspension bridge under the service and construction conditions, and the combined skew wind and aerostatic effects further deteriorate the flutter stability. Both the skew wind and aerostatic effects do not change the evolution of flutter stability of the bridge during the deck erection, and compared to the service condition, they lead to a greater decrease of flutter critical wind speed of the bridge during deck erection, and the influence of the combined skew wind and aerostatic effects is more prominent. Therefore, the skew wind and aerostatic effects must be considered accurately in the flutter analysis of three-tower suspension bridges.

• 유통과학연구
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• 제13권11호
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• pp.79-92
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• 2015

Purpose - The aim of this study is to develop an empirical model of the effects of traditional market service quality factors on customer value, relationship quality, and behavior. The specific objectives of the study are as follows: 1) to classify study objects into cultural tourism markets and non-cultural tourism markets as well as to verify the differences in service quality among the two markets and, 2) to present practical service marketing methods that fit with the characteristics of the traditional markets by amending the five quality evaluation items of SERVQUAL (a multiple-item scale for measuring service quality)to suit the characteristics of the traditional markets and establish the relationship among customer value, relationship quality, and behavior intention. Research design, data, and methodology - The study methods of empirical investigation are as follows. First, this study selected for a study object the Suwon Paldalmun Gate Market to represent the cultural tourism market, and general traditional markets to represent the non-cultural tourism market. This study also conducted personal interviews in order to increase the response rate and collected a total of 418 responses between March 18, 2014 and April 05, 2014. The total of 418 responses used for this study excluded 14 responses that had either misleading information or missing values. Results - This study verified the perceived differences of service quality based on traditional market specialization through an independent sample t-test. It appeared that the perceived service quality of the cultural tourism market was generally higher than that of the non-cultural tourism market. This study executed a path analysis in order to examine the effects of service quality factors on customer value, relationship quality, and behavior intention. This study also comprehensively analyzed the specialized market and non-specialized market separately. Although there were some differences among the results, the overall results were uniform. It appeared that convenience, reliability, and empathy, among the service quality factors, exerted meaningful effects on customer value. On the other hand, convenience, reliability, responsiveness, and empathy, excluding the tangibles, exerted meaningful effects on the relationship quality. In addition, it appeared that all service quality factors exerted meaningful effects on the customer value, relationship quality, and behavior intention. Therefore, the study verified that all of the hypotheses formulated in the study were generally adopted. Conclusions - The implication of this study may be classified into academic and practical implication as follows. With respect to the academic implication, it seems that this study is among the early studies to verify the differences between the cultural tourism market and the non-cultural tourism market. The practical implication of this study is that the perceived service quality, such as convenience, reliability, responsiveness, and tangibles, excluding empathy, was higher in the cultural tourism market than in the non-cultural tourism market. This means that customer satisfaction is enhanced by governmental aid such as hardware, software, and information and communications technology.

• 한국정보과학회논문지:소프트웨어및응용
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• 제33권10호
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• pp.823-835
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• 2006

멀티미디어 서비스가 전체 인터넷의 많은 부분을 차지하고 있으며, 계속해서 관심이 증가되고 있다. 네트워크가 다양해지고 구성 단말들의 종류도 다양해짐에 따라, 획일적인 컨텐츠로 멀티미디어 서비스를 하는 것이 불가능해졌다. 각 단말별 요구도 다양해지고, 네트워크의 대역폭도 다양해짐에 따라서 적응적인 서비스가 요구된다. 비디오 트랜스코딩은 멀티미디어 데이타를 적응성 있게 서비스할 수 있는 좋은 방법이다. 본 논문은 멀티미디어 데이타를 스트리밍 하기 위해 부호기, 트랜스코더, 복호기로 구성된 시스템을 제안한다. 부호기는 예측 주기를 이용하여 트랜스코딩할 경우의 계산 복잡도 및 PSNR을 향상시켰고, 복호기는 일반적인 미디어 재생기와 거의 유사하다. 트랜스코더에서는 부호기의 예측주기와 프레임율을 조절하는 삭제주기를 통해서 효율적인 계산 과정을 선택한다. 실험 결과, 기존의 트랜스코더와 부호기, 복호기를 이용한 시스템에 비해서 본 논문에서 제안한 시스템이 계산복잡도와 PSNR에서 높게 나타났다.

• 교육녹색환경연구
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• 제7권1호
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• pp.1-14
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• 2008

Gyeonggi Province is trying to increase the number of public libraries from 100 as of December, 2006 to 150 in 2010. However most of existing public libraries preferred mid-to-large scale libraries, so they were restricted to be located in around a zone of life. For this reason most local residents have been excluded from right to use libraries and have difficulties to get library services for the knowledge and information society of the 21st century. The alternative to the small library is a school library. Both schools and public libraries are located in around a zone of life because residents can get an access to them easily. First, considering that small-scale public libraries of communities usually service about 10,000-20,000 people, I estimate that an open-style school library services 24class, 840people (24class*35people) of elementary school by 2003 Korean Library Standard (edited by Korean Library Association). Second, it requires systematic protection policies so that the open-style school of library can function as a local public library and a part of library cooperation system in accordance with local plans. All the open-style school libraries don't intend to open and we had better consider the suitable service areas. Third, it's desired for the management efficiency that the open-style school libraries being established afterward are divided into a branch-scale, a hall-scale and so on, not being uniform management model. And it also needs that one of them in the area enlarges the scale, and then supports other school libraries. According to these results of the research, as cooperation between the public library policy of a local government and school library policy, it needs a systematic support.