• 대한수학회보
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• 제51권3호
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• pp.681-689
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• 2014

In this paper, we investigate the influence of boundary dissipations on decay property of the solutions for a semilinear wave equation with damping and memory condition on the boundary using the multiplier technique.

• 대한수학회논문집
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• 제38권3호
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• pp.943-966
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• 2023

In this paper, we study the initial-boundary value problem for viscoelastic wave equations of Kirchhoff type with Balakrishnan-Taylor damping terms in the presence of the infinite memory and external time-varying delay. For a certain class of relaxation functions and certain initial data, we prove that the decay rate of the solution energy is similar to that of relaxation function which is not necessarily of exponential or polynomial type. Also, we show another stability with g satisfying some general growth at infinity.

• Journal of the Korean Wood Science and Technology
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• 제24권1호
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• pp.81-86
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• 1996

This study was performed to evaluate the reduction in bending properties of radiata pine sapwood associated with incipient brown-rot decay. Decayed bending specimens by Tyromyces palustris and Gloeophyllum trabeum for varoious periods were tested destructively. Brown-rot decay by T. palustris and G. trabeum caused serious reduction in bending properties at very early stages of decay, with about 30 percent decrease in bending strength observed for only 1~2 percent weight loss. In general, the reduction in bending properties caused by T. palustris was somewhat greater than that by G. trabeum. Work to maximum load was reduced most severely and rapidly from the onset of decay, while modulus of elasticity showed a much more moderate rate of reduction. Modulus of rupture was affected by decay to a greater extent than was modulus of elasticity. Since a relatively strong correlation between weight loss and bending strength was observed, the residual strength of decayed wood can be predicted by weight loss due to decay. The results of this study indicate that very early stages of brown-rot decay reduce the bending strength significantly. Thus, it is recommended that all load-bearing members in wooden structures, especially those that are periodically wetted, should be inspected regularly to prevent a sudden failure even though there are no definite signs of decay.

• 대한수학회논문집
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• 제35권1호
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• pp.321-338
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• 2020

In this paper, we investigate the viscoelastic plate equation with a constant delay term and logarithmic nonlinearities. Under some conditions, we will prove the global existence. Furthermore, we use weighted spaces to establish a general decay rate of solution.

• 호남수학학술지
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• 제44권2호
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• pp.281-295
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• 2022

This paper deals with the long - time behavior of global bounded solutions for a non-autonomous dispersive-dissipative equation with time-dependent nonlinear damping terms under the null Dirichlet boundary condition. By a new Lyapunov functional and Łojasiewicz-Simon inequality, we show that any global bounded solution converges to a steady state and get the rate of convergence as well, which depends on the decay of the non-autonomous term g(x, t), when damping coefficients are integral positive and positive-negative, respectively.

• 한국환경복원기술학회지
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• 제17권2호
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• pp.73-83
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• 2014

This study was conducted to evaluate defects in Zelkova serrata trees using an ultrasonic tomograph (PICUS) and suggest a management plan to maintain it as a natural and cultural resource. In previous study, health information of 16 protected trees were obtained by surveying the following categories; tree appearance, crown, bark, root exposure, water and nutrition, deterioration, pest, vitality, ground status, and pollutant. The average score of health was 16.5 in 16 trees, which means that general monitor is needed for management. In this study, the evaluation result of tree's inside defects using an ultrasonic tomograph showed that 43.8% of decay rate has been found in 16 trees. In fact, some trees look to be good even though they actually have a defects causing broken by natural disaster such as strong wind. Therefore, it is urgent to put some support to the trees and come up with a protective plan. The results of this study would be useful as basic data in developing a guideline for the efficient conservation and management of big and old trees.

• 농업과학연구
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• 제39권1호
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• pp.1-8
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• 2012

Rapid loss of grape berry quality after harvest occurs due to poor postharvest management. Understanding physiological properties between cultivars is required to develop practical technologies to control fast quality deterioration of tables grapes. Physiological characteristics of whole cluster, rachis and berries were examined to find their effects on postharvest behaviour of table grapes. 'Tamnara' showed high respiration rate and browning of rachis compared to 'Campbell Early'. Weight loss of rachis of 'Cheongsoo' was highest of three cultivars. Berry decay in 'Cheongsoo' begins at the connection portion between peduncle and berry, and berry decay of 'Cheongsoo' was the most severe among three cultivars. Precooling at $0^{\circ}C$ showed better results than cooling at $10^{\circ}C$ regardless of cultivars but cooling effect decreased when simulated marketing period increased up to 10 days. Plastic film wrapping was effective on reducing decay in general but not at higher marketing temperature. For successful commercialization of newly developed grapes, the inhibition technology of rachis browning in 'Tamnara' is required and decay control in 'Cheongsoo' through establishment of cold chain system is recommended.

• 한국치위생학회지
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• 제4권2호
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• pp.165-177
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• 2004

The purpose of this study was to analyze the influence of child's general property, mother's social and economic property, mother's knowledge and behavior in oral hygiene upon the appearance and treatment of child's primary tooth decay. For the purpose, oral examination was applied to one hundred three(103) small children who were at the age between four(4) and seven(7) and went to two(2) places of day care centers located in Seoul, and questionnaire was done to their mothers. The results of the study are as follows. 1. The number of children's dt is 1.55, the number of their ft is 1.42, dft index for primary tooth is 2,98, ft rate is 45.61%, and the higher child's age is, the higher their value is. 2. Mother's age, educational background, and occupation does not show significant difference with dft index for primary tooth. The higher mother's monthly average income is, the higher child's ft rate is. 3. dft index for primary tooth does not show significant difference according 10 mother's knowledge in oral hygiene. And, the child of mother using dental floss does show higher it rate in comparison with the one of mother who does not use dental floss, 4. Experience using dental clinic to treatment tooth decay does show significant difference with dft index for primary tooth. And experience using dental clinic for the purpose of oral examination and preventive treatment does show significant difference with ft rate. 5. From the result of multiple regression with dependent variable of dft index for primary tooth, there is no variable having significant influence. From the result of multiple regression with dependent variable of ft rate, explanatory variable is 43%, child's age, mother's occupation, mother's monthly average income, and experience using dental clinic to prevent tooth decay are significant explanatory elements. Through the above results, we can know that mother should practice positive behavior in oral hygiene for child to improve oral health. Under the reason, oral health education should be applied toward mothers as soon as possible, and governmental support should be followed so that mothers can participate in the education.

• 한국농공학회지
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• 제41권4호
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• pp.37-46
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• 1999

Field experimnet of constructed wetland for rural wastewater treatment was performed from July 1998 to April 1999 including winter to examine the seasonal effect on the wetland performance. The system worked without freezing even under $-10^{\circ}C$ of air temperature as long as watewater was flowing. BOD removal rates varied in similar pattern as the air temperature, and winter performance was relatively lower than that in the growing season. However, removing performance during winter was still significant, and BOD removal rates were almost the the same as in the growing season. SS removal rate was relativelyless affected by temmperature, but lower decay rate during the winter can result in accumulation of the SS in the system, which releases constituents in the next spring and can affect whole system performance. The winter removal rates of nutrients like T-N and T-P were decreased about half compared to the growing season and low temperature. To maintain stabilized wetland performanced including winter time, supplying minimum heating for plants could be an alternative in field application. Experimental data was compared with NADB(North Americal Wetlands for Water Quality treatment database), and general performance of the system was within the reasonable range. The pollutant loading and effluent concentration of the experimented system were in high margin. Base on the experiment and databases, the required effluent water quality could be achieved if loading rate adjusted as ilulstrated in the database.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.83-83
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• 2002

목적： 현재 임상적으로 사용되고 있는 확산경사자장의 세기 이상( > 1200)의 강한 확산 경사자장이 가해진 경우 뇌구조물들의 확산계수값을 조사하고 고자장(Bo = 3T)에서 이러한 강한 확산 경사자장을 이용하는 경우 1.5T에서 시행하는 경우와의 차이점을 비교 연구해보고자 하였다. 대상 및 방법： 정상 성인 3명을 대상으로 b-value를 0부터 3500까지 변화시키며 확산강조영상을 최대경사자장 40 mT/m, slew rate 150 T/m/s의 경사자장계가 장착된 3T MR scanner (General Electric, USA)에서 획득하였다. 사용한 펄스열은 Stejskal-Tanner type의 확산강조 경사자장이 포함된 single-shot SE EPI를 사용하였으며 영상획득시 사용한 파라미터는 다음과 같다. TR/TE= 10000/95.1, Thickness/space=512mm, FOV=24$\times$21cm, Matrix=128$\times$128, NEX=1 뇌구조물들에 관심 영역을 설정하고 b-value에 따른 신호감소를 측정하였다. 측정된 데이터를 hi-exponential decay 모델을 이용하여 분석하였다.