• Wind and Structures
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• 제30권5호
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• pp.499-509
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• 2020

The aeroelastic stability of a long-span suspension footbridge with a bluff deck (prototype section) was examined through static and dynamic wind tunnel tests using a 1:10 scale sectional model of the main girder, and the corresponding aerodynamic countermeasures were proposed in order to improve the stability. First, dynamic tests of the prototype sectional model in vertical and torsional motions were carried out at three attack angles (α = 3°, 0°, -3°). The results show that the galloping instability of the sectional model occurs at α = 3° and 0°, an observation that has never been made before. Then, the various aerodynamic countermeasures were examined through the dynamic model tests. It was found that the openings set on the vertical web of the prototype section (web-opening section) mitigate the galloping completely for all three attack angles. Finally, static tests of both the prototype and web-opening sectional models were performed to obtain the aerodynamic coefficients, which were further used to investigate the galloping mechanism by applying the Den Hartog criterion. The total damping of the prototype and web-opening models were obtained with consideration of the structural and aerodynamic damping. The total damping of the prototype model was negative for α = 0° to 7°, with the minimum value being -1.07%, suggesting the occurrence of galloping, while that of the web-opening model was positive for all investigated attack angles of α = -12° to 12°.

• 한국환경과학회지
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• 제25권4호
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• pp.525-534
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• 2016

The biological wastewater treatment plant, which uses microbial community to remove organic matter and nutrients in wastewater, is known as its nonlinear behavior and uncertainty to operate. Therefore, operation of the biological wastewater treatment process much depends on observation and knowledge of operators. The manual inspection of human operators is essential to manage the process properly, however, it is impossible to detect a fault promptly so that the process can be exposed to improper condition not securing safe effluent quality. Among various process faults, equipment malfunction is critical to maintain normal operational state. To detect equipment faults automatically, the dynamic time warping was tested using on-line oxidation-reduction potential (ORP) and dissolved oxygen (DO) profiles in a sequencing batch reactor (SBR), which is a type of wastewater treatment process. After one cycle profiles of ORP and DO were measured and stored, they were warped to the template profiles which were prepared already and the distance result, accumulated distance (D) values were calculated. If the D values were increased significantly, some kinds of faults could be detected and an alarm could be sent to the operator. By this way, it seems to be possible to make an early detecting of process faults.

• 한국환경복원기술학회지
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• 제9권4호
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• pp.1-12
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• 2006

The usages of urban riverine areas for the Gapchoen and Yudungcheon in Daejoen City were evaluated by analyzing riverbed characteristics and water quality and by surveying the status of the floodplain usage including questionnaires of people visiting the rivers. Both rivers appear to be stable with insignificant bed changes as the riverbeds are dominated by gravels. Water qualities of both rivers have been improved significantly over the past decade although there are quite large seasonal fluctuations, which is common in most rivers in Korea. The results of floodplain usage analyses show that Gapcheon is dominated with static uses (>70%) such as promenades and resting facilities, while Yudungcheon by dynamic uses (>44%) such as sports facilities. Overall, both rivers require better plans for riverine area usage management considering a balance between the dynamic uses and the static uses such as natural observation places for education and habitats for birds and fish in the rivers. The questionnaire survey results indicate that overall the present status of both rivers are satisfactory and that water quality improvement is one of the key factors to enhance the value of the riverine areas. Future river restoration should be conducted by taking into account the characteristics of urban rivers in harmony with surrounding natural sceneries.

• 대한전자공학회논문지SD
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• 제37권12호
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• pp.50-59
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• 2000

본 논문에서는 고집적 SRAM의 다양한 고장을 검출하기 위하여 동적 전원 공급 전류를 관찰하는 방법을 이용하였다. 다양한 고장을 가정하여 고장이 없는 경우와 고장이 발생한 경우 transition write시의 Iddt 펄스의 크기가 크게 다른 것을 이용하여 쓰기 동작만으로 구성된 메모리 테스트 알고리듬을 개발하였다. 새로운 알고리듬은 기존의 March B 알고리듬에 비해서 7/17의 짧은 길이를 가지고도 더 많은 잠재적인 고장을 검출할 수 있다.

• 한국조경학회지
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• 제26권4호
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• pp.1-13
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• 1999

Previous research for visual assessment of streetscape employed static simulation methods to represent future landscape. However, streetscape is experienced sequentially, and thus dynamic simulations can be more effective. This study tried to adopt computer animation in the evaluation of streetscape, and examined its effects and possibilities. Three development scenarios for the redevelopment districts of Sokong-Ro and Banpo-Ro in Seoul were designed, and simulations were produced by three methods-photo-retouching, computer still image, and animation. A preference questionnaire was asked to 69 university students, and the effects of simulation methods on visual preference were examined. In addition, the frames of the animation were reclassed to identify the visibility of physical elements. The relationships between the visibility and visual preference were analyzed. The results showed that visual preference can be explained by three factors-Amenity, Tidiness, and Variousness-that account for 62.4% of the total variance, and the Amenity showed the highest proportion: 36.0%. Among the three simulation methods, animation showed the largest difference in preference for the most important factor(Amenity), and yielded the highest correlation between visibility of physical elements and Amenity. This result demonstrated that dynamic simulations can provide more accurate observation of visual changes, especially because the simulated landscape is experienced sequentially. The results also revealed that the sequential change in the visibility of physical elements can be examined easily and precisely by animation. This benefit of animation enables analysts to identify the points where the landscape varies the most, and thus visual preference should be evaluated.

• Journal of Acupuncture Research
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• 제22권2호
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• pp.211-217
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• 2005

Objectives : Terminal stage cancer patient from primary hepatocellular carcinoma metastasized into lungs was administered with cultivated wild ginseng herbal acupuncture for 5 months and observed progression. Methods : Cultivated wild ginseng herbal acupuncture was administered 5 times a week at about 150cc dosage per week. Dynamic CT was taken and interpreted at a university hospital. Results : Above patient was diagnosed with hepatocellular carcinoma and received one procedure of lobectomy and three procedures of TACE, but because of metastasis, chance of improvement was very obscure. Intensive treatment of cultivated wild ginseng herbal acupuncture five times a week for five months in association with moxibustion was done on the patient. Near elimination of the cancer cells metastasized into lungs were confirmed in terms of radiological impression through dynamic CT. Conclusion: From the results obtained in this study, cultivated wild ginseng herbal acupuncture can be an effective measure against terminal stage cancer. But this is a single case study and lack of extensive follow-up must be compensated by further researches.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2003년도 Proceeding
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• pp.141-148
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• 2003

Customer retention is a common concern for many industries and a critical issue for the survival in today's greatly compressed marketplace. Current customer retention models only focus on detection of potential defectors based on the likelihood of defection by using demographic and customer profile information. In this paper, we propose a dynamic procedure for defection detection and prevention using past and current customer behavior by utilizing SOM and Markov chain. The basic idea originates from the observation that a customer has a tendency to change his behavior (i.e. trim-out his usage volumes) before his eventual withdrawal. This gradual pulling out process offers the company the opportunity to detect the defection signals. With this approach, we have two significant benefits compared with existing defection detection studies. First, our procedure can predict when the potential defectors could withdraw and this feature helps to give marketing managers ample lead-time for preparing defection prevention plans. The second benefit is that our approach can provide a procedure for not only defection detection but also defection prevention, which could suggest the desirable behavior state for the next period so as to lower the likelihood of defection. We applied our dynamic procedure for defection detection and prevention to the online gaming industry. Our suggested procedure could predict potential defectors without deterioration of prediction accuracy compared to that of the MLP neural network and DT.

• 소성∙가공
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• 제11권6호
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• pp.529-537
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• 2002

A series of load-relaxation tests and tensile tests were conducted to study the high temperature deformation mechanism of fine duplex gamma TiAl alloy at temperatures ranging from 800 to 105$0^{\circ}C$. Results of load relaxation test showed that deformation behavior at a small imposed strain ($\varepsilon$≒0.05) was dominated by dislocation glide and dislocation climb. To investigate the deformation behavior at a large amount of strain, the processing map was constructed using a dynamic materials model. Two domains were characterized in the processing map obtained at a strain level of 0.6. One domain was found at the region of 98$0^{\circ}C$ and $10^{-3}/sec$ with a peak efficiency of 48%, which was identified as a domain of dynamic recrystallization from the microstructural observation. The order was observed at the region of 125$0^{\circ}C$ and $10^{-4}/sec$ with a peak efficiency of 64%. The strain rate sensitivity measured indicates that the material was deformed by the superplasticity in the region.

• 천문학회지
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• 제55권6호
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• pp.215-220
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• 2022

To seek an atmospheric heating mechanism operating on the Sun we investigated a heating source generated by a downflow, both of which may arise in a magnetic loop dynamically formed on the Sun via flux emergence. Since an observation shows that the illumination of evolving magnetic loops under the dynamic formation occurs sporadically and intermittently, we performed a magnetohydrodynamic simulation of flux emergence to obtain a high-cadence simulated data, where temperature enhancement was identified at the footpoint of an evolving magnetic loop. Unlike a rigid magnetic loop with a confined flow in it, the evolving loop in a low plasma β atmosphere is subjected to local compression by the magnetic field surrounding the loop, which drives a strong supersonic downflow generating an effective footpoint heating source in it. This may introduce an energy conversion system to the magnetized atmosphere of the Sun, in which the free magnetic energy causing the compression via Lorentz force is converted to the flow energy, and eventually reduced to the thermal energy. Dynamic and thermodynamic states involved in the system are explained.

• The Korean Journal of Physiology and Pharmacology
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• 제22권6호
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• pp.705-712
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• 2018

The tube formation assay is a widely used in vitro experiment model to evaluate angiogenic properties by measuring the formation of tubular structures from vascular endothelial cells (ECs). In vitro experimental results are crucial when considered the advisability of moving forward to in vivo studies. Thus, the additional attentions to the in vitro assay is necessary to improve the quality of the pre-clinical data, leading to better decision-making for successful drug discovery. In this study, we improved the tube formation assay system in three aspects. First, we used human endothelial colony forming cells (ECFCs), which are endothelial precursors that have a robust proliferative capacity and more defined angiogenic characteristics compared to mature ECs. Second, we utilized a real-time cell recorder to track the progression of tube formation for 48 hours. Third, to minimize analysis error due to the limited observation area, we used image-stitching software to increase the microscope field of view to a $2{\times}2$ stitched area from the $4{\times}$ object lens. Our advanced tube formation assay system successfully demonstrated the time-dependent dynamic progression of tube formation in the presence and absence of VEGF and FGF-2. Vatalanib, VEGF inhibitor, was tested by our assay system. Of note, $IC_{50}$ values of vatalanib was different at each observation time point. Collectively, these results indicate that our advanced tube formation assay system replicates the dynamic progression of tube formation in response to angiogenic modulators. Therefore, this new system provides a sensitive and versatile assay model for evaluating pro- or anti-angiogenic drugs.