• East Asian mathematical journal
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• 제32권5호
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• pp.659-675
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• 2016

In this paper, we study the generalized Kirchhoff type equation in the presence of past and finite history $$\large u_{tt}-M(x,t,{\tau},\;{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^t}\;h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\\hspace{25}-{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_{-{\infty}}}^t}\;k(t-{\tau}){\Delta}u(x,t)d{\tau}+{\mid}u{\mid}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the expoential decay rate of the Kirchhoff type energy.

• 소음진동
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• 제9권6호
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• pp.1187-1192
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• 1999

The purpose of this study is to determine the most appropriate experimental method of the measurement of "damping loss factors" (DLF) for the statistical energy analysis(SEA) calculation. The successful prediction of vibration levels from the structure is critically dependent on the accurate estimation of DLF's not only in conventional vibration analysis but especially in SEA. Unforunately, calculation of accurate DLF is not an easy matter. So experimental methods are made use of for the DLF values. Three kinds of experimental methods for estimating DLF, i.e. decay rate method, half-power bandwidth method and power balance method, are presented and tests are carried out for the plate and the cylindrical shell examples. Pro and con of each methods is reviewed. Finally, calculated DLF values are used for vibration level estimation using commercial SEA software and compared with measured vibration data.tion data.

• 대한의용생체공학회:의공학회지
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• 제6권2호
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• pp.63-68
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• 1985

Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70$\pm$1.32mmHg/min)compared to CF dialyzers(4.32$\pm$0.55mmHg/min)(p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHe/min)on the reused dialyzers(2 out of 40 CP and S out 26 C-DAK) were attributed to the Possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD is a more sensitive test than UFR test to evaluate the integrity of the fibers.

• 한국환경보건학회지
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• 제26권4호
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• pp.115-121
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• 2000

To evaluate the cytotoxicity of cadmium compounds, this study was conducted to measure the in vitro magnetometry, LDH release and cellular apoptosis using alveolar macrophages of hamsters. A series of magnetometric measurements in cadmium-added groups showed a significant dose-dependent decay of the relaxation curves. The LDH release rates showed a dose-dependently increasing tendency as the dose gradually increased. The positive rates of apoptosis were significantly higher in cadmium-added groups than the control groups. Conclusively, the cytotoxicity increased in a dose dependent way as the concentration of cadmium added increased, which reflected in the decay of relaxation curve in magnetometry, and increased LDH release rate and positive rate of apoptosis.

• Journal of Photoscience
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• 제6권3호
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• pp.129-133
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• 1999

Microperoxidase 8 (MP8) has been prepared by sequential hydrolysis of cytochrome C by pepsin and trypsin. This five-coordinated heme-octapetide fragment provides a uniques structure to evaluate the electronic coupling efficiency to the iron through axial position and porphyrin edge. At alkali pH, Ru(bpy)2(im)22+ is completely quenched in AcMP8Ru complex . Transient kinetics measurement showed the decay rate to be ~1 $\times$1012S-1. Ruthenium bipyridine complex with a carboxyl group substituted bipyridine has been prepared adn reacted with MR 8 to yield N-terminus bound RuMP8 complex. The luminescence decay rate has been measured as 1 $\times$109S-1. By using semiclassical electron transfer theory, we found the electron transfer efficiency through axial positioin of iron prophyrin is as good through prophyrin edge.

• Bulletin of the Korean Chemical Society
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• 제12권1호
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• pp.47-51
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• 1991

Spin-lattice relaxation of methyl protons in 2,6-dichlorotoluene and N-methyl phthalimide, each dissolved in CDCl$_3$, has been studied at 34$^{\circ}$C and the contribution from spin-rotation interaction to the relaxation process has been separated from that due to dipole-dipole interactions among methyl protons. The results show that the spin-rotational contributions to the initial rate of relaxation in 2,6-dichlorotoluene and N-methyl phthalimide amount to 18 and 31%, respectively, of the total relaxation rate at 34$^{\circ}$C. The method of separating the spin-rotational contribution from that of dipolar interactions adopted in this paper is based on the well known fact that in an A$_3$ spin system such as methyl protons in liquid phase dipolar relaxation mechanism gives non-exponential decay of the z-component of total magnetization of protons while the random field fluctuation such as spin-rotational mechanism causes exponential decay.

• 지구물리
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• 제9권3호
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• pp.171-179
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• 2006

Predictive equations of ground motions are one of the most important factors in the seismic hazard analysis. Unfortunately, studies on predictive equations of ground motions in Korea had been hampered due to the lack of seismic data. To overcome the lack of data, seismologists adopted the stochastic method based on the seismological model. Korean predictive equations developed by the stochastic method show large differences in their predictions. It was turned out through the analysis of the existing studies that the main sources of the differences are the uncertainties in the (Brune) stress drop and spectral decay rate . Therefore, it is necessary to focus the future research on the reduction of the uncertainties in the two parameters.

• 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.

• 한국치위생학회지
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• 제10권2호
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• pp.361-374
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• 2010

Objectives : The purpose of this study was to provide some basic data for effective prevention and oral health education for oral health. For that purpose, a self-administered questionnaire was distributed to the boys of three high schools in Gyeonggi Province. Methods : The questionnaire consisted of items about the practice of oral health control and knowledge of decay according to grade, number of snacking, preferred taste, and toothbrushing. Total 487 questionnaires were put to analysis using the SPSS WIN 13.0 program. Results : 1. The biggest number of the boys brushed their teeth twice a day. The 10th graders brushed teeth three times a day, and the 11th and 12th graders tended to brush teeth twice a day(${\chi}^2$=18.21, p<.05). 2. As for the way of toothbrushing, 39.0% of the boys said they brushed teeth the way they felt like, being followed by those who said they brushed teeth turning the toothbrush up and down and brushing both the teeth and gums(32.6%). As for the number of snacking, those who had snacks three times a day or more brushed teeth turning the toothbrush up and down and brushing both the teeth and gums. Those who hardly had snacks more tended to brush teeth the way they felt like than those who had snacks(${\chi}^2$=21.28, p<.05). And as for preferred tastes, those who preferred a sweet and salty taste more tended to brush teeth the way they felt like than others. And those who preferred a hot taste brushed teeth turning the toothbrush up and down and brushing both the teeth and gums(${\chi}^2$=26.85, p<.01). 3. The respondents' percentage of correct answers for 'Decay is caused by bacteria' was 81.5%. Those who preferred a hot taste recorded the highest percentage of correct answers(${\chi}^2$=21.95, p<.00). 4. Their percentage of correct answers for 'Decay is accompanied by pain from the beginning' was 78.2%. The 12th graders had the highest rate of correct answers, and the 11th graders had the highest rate of wrong answers(${\chi}^2$=11.56, p<.00). 5. Their percentage of correct answers for 'Fluorine is helpful to the prevention of decay' was 75.4%. Those who hardly had snacks recorded the highest rate of correct answers(${\chi}^2$=10.05, p<.02). 6. Their percentage of correct answers for 'There is a way to supply fluorine into the waterworks' was 29.2%, which means the percentage of wrong answers was much higher. The percentage of wrong answers was the highest in the 11th grade(${\chi}^2$=7.06, p<.03). 7. The respondents' mean scores of knowledge of decay were 13.15 of total 18. While the 12th graders showed the highest level of knowledge of decay, the 11th graders were lower in the level of knowledge of decay than the other graders. And there were significant differences(F=5.41, p<.01) according to grade with no such differences according to the number of snacking and preferred taste. Conclusions : Oral health education should be applied to the boys all through their life to have a great effect, and it is important that they should always put the oral health education into practice to be a successful education.

• The Korean Journal of Ecology
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• 제27권2호
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• pp.115-120
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• 2004

Coarse woody debris (CWD, $\ge$ 5 cm in maximum diameter) is an important functional component, especially to nutrient cycling in forest ecosystems. To compare mass and nutrient dynamics of CWD in natural oak forests, a two-year study was conducted at Quercus serrata and Q. variabilis stands in Yangpyeong, Kyonggi Province. Total CWD (snag, stump, log and large branch) and annual decomposition mass (Mg/ha) were 1.9 and 0.4 for the Q. serrata stand and 7.5 and 0.5 for the Q. variabilis stand, respectively. Snags covered 72% of total CWD mass for the Q. variabilis stand and 42% for the Q. serrata stand. Most of CWD was classified into decay class 1 for both stands. CWD N and P concentrations for the Q. variabilis stand significantly increased along decay class and sampling time, except for P concentration in 2002. There were no differences in CWD N concentration for the Q. serrata stand along decay class and sampling time. However, CWD P concentration decreased along sampling time. CWD N and P contents (kg/ha) ranged from 3.5∼4.7 and 0.8∼1.3 for the Q. serrata stand to 22.8∼23.6 and 3.7∼4.7 for the Q. variabilis stand. Nitrogen and P inputs (kg/ha/yr) into mineral soil through the CWD decomposition were 0.7 and 0.3 for the Q. serrata stand and 1.6 and 0.3 for the Q. variabilis stand, respectively. The number of CWD and decay rate were main factors influencing the difference in CWD mass and nutrient dynamics between both stands.