• Advances in nano research
• /
• 제9권4호
• /
• pp.277-294
• /
• 2020

In current paper, nonlocal (NLT), nonlocal strain gradient (NSGT) and Gurtin-Murdoch surface/interface (GMSIT) theories with classical theory (CT) are utilized to investigate vibration and stability analysis of Double Walled Piezoelectric Nanosensor (DWPENS) based on cylindrical nanoshell. DWPENS simultaneously subjected to direct electrostatic voltage DC and harmonic excitations, structural damping, two piezoelectric layers and also nonlinear van der Waals force. For this purpose, Hamilton's principle, Galerkin technique, complex averaging and with arc-length continuation methods are used to analyze nonlinear behavior of DWPENS. For this work, three nonclassical theories compared with classical theory CT to investigate Dimensionless Natural Frequency (DNF), pull-in voltage, nonlinear frequency response and stability analysis of the DWPENS considering the nonlocal, material length scale, surface/interface (S/I) effects, electrostatic and harmonic excitation.

• 대기
• /
• 제26권4호
• /
• pp.665-672
• /
• 2016

In this study, we examine future changes in the Hadley cell (HC) strength using CMIP5 climate change simulations. The current study is an extension of a previous study by Seo et al. that used all 30 available models. Here, we select 18-23 well-performing models based on their significant internal sensitivity of the interannual HC strength variation to the latitudinal temperature gradient variation. The model projections along with simple scaling analysis show that the inter-model variability in the HC strength change is a result of the inter-model spread in the meridional temperature gradient across the subtropics for both DJF and JJA, not by the tropopause height or gross static stability change. The HC strength is expected to weaken significantly during DJF, while little change is expected in the JJA HC strength. Compared to the calculations with all model members, selected model statistics increase the linear correlation between the changes in HC strength and meridional temperature gradient by 13~23%, confirming the robust sensitivity of the HC strength to the meridional temperature gradient. Two scaling equations for the selected models predict changes in HC strength better than all-member predictions. In particular, the prediction improvement in DJF is as high as 30%. The simple scaling relations successfully predict both the ensemble-mean changes and model-to-model variations in the HC strength for both seasons.

• 지구물리와물리탐사
• /
• 제25권1호
• /
• pp.38-43
• /
• 2022

화산의 화도나 불발탄과 같이 축 대칭을 갖지만 단면의 반지름이 변하는 경우 대칭축에 수직인 얇은 원판들의 반응을 더하여 모델링하는 것이 효율적이다. 이런 모양의 이상체에 대한 자력 및 자력 변화율 텐서 모델링을 위해서는 얇은 원판에 대한 해석해가 필수적이다. 따라서 이 논문에서는 원판형 이상체에 대한 벡터 자력과 자력 변화율 텐서 반응식을 유도하였다. 벡터 자력은 중력 변화율 텐서를 자력으로 변환하는 포아송 관계식을 이용하여 원판형 이상체의 기존 중력 변화율 텐서로부터 유도하였다. 자력 변화율 텐서는 직교 좌표계의 미분 관계식을 원통 좌표계로 미분 관계식으로 변환한 후 벡터 자력을 미분하여 유도하였다. 벡터 자력과 자력 변화율 텐서는 원판형 이상체의 축 대칭성을 이용한 립쉬츠-한켈(Lipschitz-Hankel) 적분을 기반으로 구하였다.

• Steel and Composite Structures
• /
• 제18권1호
• /
• pp.1-28
• /
• 2015

In this paper, the dynamic response of functionally gradient steel (FGS) composite cylindrical panels in steady-state thermal environments subjected to impulsive loads is investigated for the first time. FGSs composed of graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Thermo-mechanical material properties of FGS composites are predicted according to the microhardness profile of FGS composites and approximated with appropriate functions. Based on the three-dimensional theory of thermo-elasticity, the governing equations of motionare derived in spatial and time domains. These equations are solved using the hybrid Fourier series expansion-Galerkin finite element method-Newmark approach for simply supported boundary conditions. The present solution is then applied to the thermo-elastic dynamic analysis of cylindrical panels with three different arrangements of material compositions of FGSs including ${\alpha}{\beta}{\gamma}M{\gamma}$, ${\alpha}{\beta}{\gamma}{\beta}{\alpha}$ and ${\gamma}{\beta}{\alpha}{\beta}{\gamma}$ composites. Benchmark results on the displacement and stress time-histories of FGS cylindrical panels in thermal environments under various pulse loads are presented and discussed in detail. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of FGS structures under time-dependent mechanical loadings.

• 한국작물학회지
• /
• 제65권4호
• /
• pp.339-345
• /
• 2020

Recently, abnormal weather conditions, such as extreme high temperatures and droughts, have increased in frequency due to climate change, there has accordingly been growing concern regarding the detrimental effects on field crop, including soybean. Therefore, this study was conducted to examine the effects of increased temperatures on soybean growth and yield using a temperature gradient chamber (TGC). Two major types of soybean cultivar, a medium- seed cultivar such as Daepung-2 and a large-seed cultivar such as Daechan, were used and four temperature treatments, aT+1℃ (ambient temperature+1℃), aT+2℃ (ambient temperature+2℃), aT+3℃ (ambient temperature+3℃) and aT+4℃ (ambient temperature+4℃) were established to examine the growth response and seed yield of each cultivar. Seed yield showed a higher correlation with seed weight (r=0.713***) and an increase in temperature affected seed yield by reducing the single seed weight. In particular, the seed growth rate of the large-seed cultivar (Daechan) increased at high temperature, resulting in a reduction in the number of days for full maturity. Our results accordingly indicate that large-seed cultivar, such as Daechan, is potentially vulnerable to high temperature stress. The results of this study can be used as basic data in the development of cultivation technology to reduce the damage caused by elevated temperatures. Also, further research is required to evaluate the response of each process contributing to seed yield production under high temperatures.

• 한국정보통신학회논문지
• /
• 제10권1호
• /
• pp.88-95
• /
• 2006

PID 제어기는 구조가 간단하고 적용이 용이하다는 장점으로 인하여 널리 사용되고 있는 제어방식이다. 이러한 선형 PID 제어기는 시스템의 파라메터가 변화가 있거나 부하 특성이 비 선형적으로 변화할 때에 적절한 이득과 성능을 얻기 어려워 고성능 제어 특성을 기대하기 어렵다. 본 연구에서는 세포성 면역 반응과 경사감소학습에 기초하여 비선형 PID 제어기를 설계하고, 설계된 제어기의이득과 비선형 함수의 파라메터들을 실시간 적응적으로 학습할 수 있는 학습 알고리즘을 개발하고, 이를 제어시스템에 적용하였다. 제안된 비선형 PID 제어기는 비선형 직류 모터 시스템의 파라메터들이 변화하거나 주파수가 다른 추종 명령에 대하여, 적응적으로 이득을 변화 시키며 추종함을 보였다.

• 말소리와 음성과학
• /
• 제5권1호
• /
• pp.91-98
• /
• 2013

This paper investigated Korean prosody as it relates to graded internal structure in an identification function. Within Korean prosody, variants regarded as dialectal variations can appear as different prosodic scales, which contain the range of within-category variations. The current experiment was intended to show how the prosodic scale corresponding to the range of within-category differences relates to f0 contours for speakers of two Korean dialects, North Kyungsang and South Cholla. In an identification task, participants responded by selecting an item from two answer choices. The probability of choosing the correct response from the two choices was computed by a logistic regression analysis using intercepts and slopes. That is, the correct response between two choices was used to show a linear line with an s-shape presentation. In this paper, to investigate the graded internal structure of labeling, 25%, 50%, and 75% of predicted probability were assessed. Listeners from North Kyungsang showed progressive variations, whereas listeners from South Cholla revealed random patterns in the internal structure of the identification function. In this paper, the results were plotted using scatterplot graphs, applying the range of within-category variation and predicted probability obtained from the logistic regression analyses. The scatterplot graphs showed the different degree of the responses for f0 scales (i.e., variations within categories). The results demonstrate that the gradient structures of native pitch accent users become more progressive in response to f0 scales.

• Journal of Electrical Engineering and Technology
• /
• 제11권1호
• /
• pp.234-240
• /
• 2016

We propose a novel framework for markerless camera-based games. By using a visual camera, our method may yield robust human body segmentation with high performance comparable to the segmentation using depth cameras. The edges of human bodies are detected by subtracting gradient backgrounds, and human body regions are segmented by the operations based on mathematical morphology. Collisions between detected regions and virtual objects are determined by finding the colliding time using intra-frame positions of virtual objects. Experimental results show that the proposed method may produce robust segmentation of human bodies, thereby and the collision responses are more accurate than previous methods. Therefore, the proposed framework can be widely used in camera-based games requiring high performance.

• Structural Engineering and Mechanics
• /
• 제44권2호
• /
• pp.139-161
• /
• 2012

In this paper, the static behavior of bi-directional functionally graded (FG) non-uniform thickness circular plate resting on quadratically gradient elastic foundations (Winkler-Pasternak type) subjected to axisymmetric transverse and in-plane shear loads is carried out by using state-space and differential quadrature methods. The governing state equations are derived based on 3D theory of elasticity, and assuming the material properties of the plate except the Poisson's ratio varies continuously throughout the thickness and radius directions in accordance with the exponential and power law distributions. The stresses and displacements distribution are obtained by solving state equations. The effects of foundation stiffnesses, material heterogeneity indices, geometric parameters and loads ratio on the deformation and stress distributions of the FG circular plate are investigated in numerical examples. The results are reported for the first time and the new results can be used as a benchmark solution for future researches.

• Steel and Composite Structures
• /
• 제28권3호
• /
• pp.381-388
• /
• 2018

In this paper, forced vibration of micro cylindrical shell reinforced by functionally graded carbon nanotubes (FG-CNTs) is presented. The structure is subjected to transverse harmonic load and modeled by beam model. The size effects are considered based on strain gradient theory containing three small scale parameters. The mixture rule is used for obtaining the effective material properties of the structure. Based on sinusoidal shear deformation theory of beam, energy method and Hamilton's principle, the motion equations are derived. Applying differential quadrature method (DQM) and Newmark method, the frequency curves of the structure are plotted. The effect of different parameters including, CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency curves of the structure is studied. Numerical results indicate that the dynamic deflection of the FGX-CNT-reinforced cylindrical is lower with respect to other type of CNT distribution.