• Applied Biological Chemistry
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• 제32권4호
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• pp.332-337
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• 1989

재수화한 동결건조 즉석미반의 리올로지 성질을 통상법으로 취반한 미반과 비교하면서 조사하였다. 온도$(60{\sim}90^{\circ}C)$를 달리한 복원시간에 따른 미립 경도의 역수(연화도)는 복원온도에 상관없이 1차 반응 속도식에 따라 감소하였고, 경도반응의 속도 상수 값은 온도에 따라 증가하였으며, 이의 활성화 에너지는 6.1 kcal/g-mol이었다. 여러 온도 $(60{\sim}90^{\circ}C)$에서 복원시킨 즉석미반의 압축응력 완화 곡선은 통상법으로 취반한 미반과 마찬가지로 일반화된 Maxwell의 6요소 역학모형으로 설명되었고, 즉석미반은 취반미보다 완화되기 쉬우나 복원온도가 높을수록 탄력성이 높아지는 특성을 나타내었다.

• Wind and Structures
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• 제21권2호
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• pp.119-158
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• 2015

The characteristics of the coherence functions of X axial, Y axial, and RZ axial (i.e., body axis) wind forces on the Shanghai World Trade Centre - a 492 m super-tall building with section varying along height are studied via a synchronous multi-pressure measurement of the rigid model in wind tunnel simulating of the turbulent, and the corresponding mathematical expressions are proposed there from. The investigations show that the mathematical expressions of coherence functions in across-wind and torsional-wind directions can be constructed by superimposition of a modified exponential decay function and a peak function caused by turbulent flow and vortex shedding respectively, while that in along-wind direction need only be constructed by the former, similar to that of wind speed. Moreover, an inductive analysis method is proposed to summarize the fitted parameters of the wind force coherence functions of every two measurement levels of altitudes. The comparisons of the first three order generalized force spectra show that the proposed mathematical expressions accord with the experimental results well. Later, the influences of coherence functions on wind-induced dynamic responses are analyzed in detail based on the proposed mathematical expressions and the frequency-domain method of random vibration theory.

• 천문학회지
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• 제50권6호
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• pp.167-178
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• 2017

We present a study of the inexplicit connection between radio jet activity and ${\gamma}$-ray emission of BL Lacertae (BL Lac; 2200+420). We analyze the long-term millimeter activity of BL Lac via interferometric observations with the Korean VLBI Network (KVN) obtained at 22, 43, 86, and 129 GHz simultaneously over three years (from January 2013 to March 2016); during this time, two ${\gamma}$-ray outbursts (in November 2013 and March 2015) can be seen in ${\gamma}$-ray light curves obtained from Fermi observations. The KVN radio core is optically thick at least up to 86 GHz; there is indication that it might be optically thin at higher frequencies. To first order, the radio light curves decay exponentially over the time span covered by our observations, with decay timescales of $411{\pm}85$ days, $352{\pm}79$ days, $310{\pm}57$ days, and $283{\pm}55$ days at 22, 43, 86, and 129 GHz, respectively. Assuming synchrotron cooling, a cooling time of around one year is consistent with magnetic field strengths $B{\sim}2{\mu}T$ and electron Lorentz factors ${\gamma}$ ~ 10 000. Taking into account that our formal measurement errors include intrinsic variability and thus over-estimate the statistical uncertainties, we find that the decay timescale ${\tau}$ scales with frequency ${\nu}$ like ${\tau}{\propto}{\nu}^{-0.2}$. This relation is much shallower than the one expected from opacity effects (core shift), but in agreement with the (sub-)mm radio core being a standing recollimation shock. We do not find convincing radio flux counterparts to the ${\gamma}$-ray outbursts. The spectral evolution is consistent with the 'generalized shock model' of Valtaoja et al. (1992). A temporary increase in the core opacity and the emergence of a knot around the time of the second ${\gamma}$-ray event indicate that this ${\gamma}$-ray outburst might be an 'orphan' flare powered by the 'ring of fire' mechanism.

• 대한토목학회논문집
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• 제32권6B호
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• pp.399-406
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• 2012

본 연구의 목적은 폐기물매립지에서의 온실가스 발생량 예측모델 및 모델에 적용된 변수들의 산정방법을 개발하는 것이다. 본 연구에서는 온실가스 발생예측 모델 중 1차 반응모델의 변수인 메탄잠재발생량과 메탄발생속도상수를 평가하기 위하여 수정 Gompertz 식과 Logistic 식을 미분한 2개의 식을 적용하였다. 변수들은 실제 폐기물매립지에서의 매립가스 발생량에 대한 실측값과 예측값과의 통계학적 비교를 통해 산정하였다. 매립가스 발생량에 대한 실측값과 수정 Gompertz 식 및 Logistic 식을 미분하여 나타낸 2개의 식을 이용한 매립가스 발생량 예측값에 대한 회귀분석결과 결정계수는 각각 0.92와 0.94로 나타나, 폐기물매립지에서의 매립가스 발생량에 대한 측정값이 있을 경우 회귀분석을 통해 변수를 산정할 수 있는 것으로 나타났다. 또한 실측값이 없는 폐기물매립지에서의 온실가스 발생량을 예측할 수 있도록 하기 위하여 수정 Gompertz 식과 Logistic 식을 미분한 2개의 식을 기초로 하여 예측모델을 개발하였으며, 이 모델들의 정확성을 평가하기 위하여 Qcs(실측값):Q(예측값)의 비에 대한 빈도분포를 평가한 결과 LandGEM 모델보다 높은 정확성을 나타내었다. 따라서 본 연구에서 개발한 모델들은 폐기물매립지에서의 온실가스 발생량 예측에 적합한 것으로 사료된다.

• 한국치위생학회지
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• 제2권1호
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• pp.43-61
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• 2002

The purpose of this study was focus on development of educational objectives by using oral health education in the elementary school from now on. Based on the results of analysis compared with a model of educational objectives and contents by reflecting the programs for analysis were the oral health education programs of the Ministry of health and social Affairs in Korea, and the programs of two states in u.s. in order to construct goals and contents of oral health education in school. The results in this study can be arranged as follows: First, an analysis on the educational objectives of dental health education program resulted that, from a viewpoint of Bloom's taxonomy of educational objectives, in case of domestic, most learning objectives expressed in the handbook of Ministry of Health and social Welfare were given too much emphasis to the cognitive domain of 37 an items in all. Affective domain were appeared the lack of balance of the development domain. Second, the result of analysis for the programs of two states of America, the cognitive domain were the most abundant of 48 an items in all, and were not significantly different to those of Korea in the form of objectives domain or statement. However a big different was shown that they organized the same objectives domain as a pattern of repeating and deepening at every grade. Third, in this study, 10 educational objectives of dental health education were established, based on the result of analyzing those existing educational programs as central figure. Those are oral cavity, brushing, nutrition of teeth, fluoride, flossing, teeth injury, dental decay, periodontal disease, malocclusion, routine dental visits. And general objectives and specific objectives of each learning area were stated and arranged grade by grade.

• Environmental Engineering Research
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• 제22권4호
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• pp.339-346
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• 2017

The objective of this study is the evaluation of the performance of a large-scale respirometer (LSR) of 17.7 L in the determination of the methane generation rate constant (k) values. To achieve this objective, a comparison between anaerobic (GB21) and LSR tests was conducted. The data were modeled using a linear function, and the resulting correlation coefficient ($R^2$) of the linear regression is 0.91. This result shows that despite the aerobic conditions, the biodegradability values that were obtained from the LSR test produced results that are similar to those from the GB21 test. In this respect, the LSR test can be an indicator of the anaerobic biodegradability for landfill waste. In addition, the results show the high repeatability of the tests with an average coefficient of variance (CV) that is lower than 10%; furthermore, the CV for the LSR is lower than that of the GB21, which indicates that the LSR-test method could provide a better representation of waste samples. Therefore, the LSR method allows for both the prediction of the long-term biodegradation potential in a shorter length of time and the reduction of the sampling errors that are caused by the heterogeneity of waste samples. The k values are $0.156y^{-1}$ and $0.127y^{-1}$ for the cumulative biogas production (GB21) and the cumulative oxygen uptake for the LSR, respectively.

• 대한환경공학회지
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• 제38권3호
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• pp.128-134
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• 2016

S 매립장 매립가스 발전시설을 대상으로 발전량에 미치는 주요 요소와 그 영향도를 분석하였다. 50 MWh 24시간의 정상가동 일수는 2007년부터 2014년까지의 총 운전기간 일수대비 70.9%이었으며, 실제 생산한 전력은 이론적인 최대 발전 가능량 3,428,400 MW의 79.3%이었다. 발전효율에 영향을 미치는 주요 요소는 정기점검 등이 44.0%, 황화수소로 인한 감축운전이 37.4% 그리고 공기예열기 세정 18.6% 순이었다. 그러나 황화수소 감축운전 기간이 2년인 점을 감안하면 고농도 황화수소 발생이 매립가스 발전에 가장 큰 영향을 미치고 있었다. 장기적인 발전 가능량 분석결과 매립종료 해인 2018년 35.9 MWh 이었으며 이후 지속적으로 감소하여 2028년 16.6 MWh, 2038년에는 8.4 MWh 이하가 될 것으로 예측되었다.

• 한국수산과학회지
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• 제25권6호
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• pp.457-473
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• 1992

양향성 대륙붕에서 1차 파동방정식은 양 해안경계에서의 바람응력과, 대륙붕폭에 걸친 바람응력의 회전효과를 갖는다. 황해에서 바람응력 회전효과는 대륙붕파를 발생시키는 힘으로서 무시될 수 있다. 켈빈파는 대륙붕파보다 약화될 때까지의 거리가 매우 크기 때문에 황해 북쪽만(별)을 거의 약화되지 않고 통과할 수 있다. 파동특성을 따라 적분하는 수치방법은 반대방향으로 전파되는 파동을 수용하기 위해 조절되었다. 보다 실제와 가까운 해안선을 사용한 결과, 모델재생이 해류에서는 개선되었으나 해수면에서는 거의 개선되지 않았다. 이것은 해수면을 주로 결정하는 켈빈파가 해저지형의 변화에 영향을 극히 적게 받음을 의미한다 보다 개선된 해수면 재생을 위해서는 동지나 해에서 황해로 전파되는 켈빈파의 에너지를 알 필요가 있다. 해안을 따른 순풍류와 골을 따른 역풍류의 기본구조는 계절풍에 의해 발생하는 황해의 계절순환을 뒷받침한다.

• Smart Structures and Systems
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• 제25권6호
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• Steel and Composite Structures
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• 제51권1호
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.