• Advances in nano research
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• 제14권2호
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• pp.141-154
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• 2023

Effects of viscoelastic foundation on vibration of curved-beam structure with clamped and simply-supported boundary conditions is investigated in this study. In doing so, a micro-scale laminate composite beam with two piezoelectric face layer with a carbon nanotube reinforces composite core is considered. The whole beam structure is laid on a viscoelastic substrate which normally occurred in actual conditions. Due to small scale of the structure non-classical elasticity theory provided more accurate results. Therefore, nonlocal strain gradient theory is employed here to capture both nano-scale effects on carbon nanotubes and microscale effects because of overall scale of the structure. Equivalent homogenous properties of the composite core is obtained using Halpin-Tsai equation. The equations of motion is derived considering energy terms of the beam and variational principle in minimizing total energy. The boundary condition is assumed to be clamped at one end and simply supported at the other end. Due to nonlinear terms in the equations of motion, semi-analytical method of general differential quadrature method is engaged to solve the equations. In addition, due to complexity in developing and solving equations of motion of arches, an artificial neural network is design and implemented to capture effects of different parameters on the inplane vibration of sandwich arches. At the end, effects of several parameters including nonlocal and gradient parameters, geometrical aspect ratios and substrate constants of the structure on the natural frequency and amplitude is derived. It is observed that increasing nonlocal and gradient parameters have contradictory effects of the amplitude and frequency of vibration of the laminate beam.

• Advances in nano research
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• 제14권4호
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• pp.375-389
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• 2023

In this study, free vibration analysis of functionally graded (FG) porous truncated conical shell panels reinforced by graphene platelets (GPLs) has been investigated for the first time. Additionally, the effect of three different types of porosity distribution and five different types of GPLs patterns on dynamic response of the shell are also studied. Halpin-Tsai micromechanical model and Voigt's rule are used to determine Young modulus, shear modulus and Poisson's ratio with mass densities of the shell, respectively. The main novelties of present study are: applying 3D elasticity theory and the finite element method in conjunction with Rayleigh-Ritz method to give more accurate results unlike other simplified shell theories, and also presenting a general 3D solution in cylindrical coordinate system that can be used for analyses of different structures such as circular, annular and annular sector plates, cylindrical shells and panels, and conical shells and panels. A convergence study is performed to justify the correctness of the obtained solution and numerical results. The impact of porosity and GPLs patterns, the volume of voids, the weight fraction of graphene nanofillers, semi vertex and span angles of the cone, and various boundary conditions on natural frequencies of the functionally graded panel have been comprehensively studied and discussed. The results show that the most important parameter on dynamic response of FG porous truncated conical panel is the weight fraction of nanofiller and adding 1% weight fraction of nanofiller could increase 57% approximately the amounts of natural frequencies of the shell. Moreover, the porosity distribution has great effect on the value of natural frequency of structure rather than the porosity coefficient.

• The Plant Pathology Journal
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• 제18권4호
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• pp.204-209
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• 2002

Andhra Pradesh is one of the major groundnut growing states in India. A total of 182 groundnut samples collected at harvesting from farmers fields in five districts, namely; Anantapur, Chittoor, Cuddapah, Kurnool, and Mahaboobnagar, during 1999 and 2000 rainy seasons were evaluated for the presence of mycotoxins (both aflatoxins and zearalenone) and toxigenic fungi. In samples collected from each district, average seed infection by Aspergillus flavus and Fusarium spp. was 11.9-18.3% and 5.6-12.8% in 1999, and 9.5-14.1% and 9.4-11.9% in 2000, respectively. Among the samples collected, 20.3% and 16.5% were contaminated with aflatoxin in 1999 and 2000, respectively, and in 11.4% and 8.7% of the seed samples collected in two seasons, the aflatoxin content was >30 $\mu\textrm{g}$/kg. An alarming aflatoxin content of 851.9$\mu\textrm{g}$/kg was found in samples collected from Anantapur district during the rainy season in 1999. Zearalenone was not detected in any of the samples collected in 1999, while 2 out of 103 samples collected in 2000 were contaminated with 35.1 and 129.4$\mu\textrm{g}$/kg. Under in vitro cultural conditions, 35.8% of the 173 A. flavus isolates collected from the groundnut samples produced aflatoxins at concentrations of 94.3-1598.6 ng/$\textrm{m}{\ell}$ and 3% of the 266 Fusarium spp. isolates produced 98.1-847.3 $\mu\textrm{g}$/g of zearalenone. The results emphasize the need for a more systematic and regular monitoring of pre-harvest aflatoxin contamination.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.154-154
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• 2022

The frequency of natural disasters, including floods and drought events, driven by climate change has increased in recent times. Investigating the climate regimes and the roles of climate variables are indispensable to forestall future climate change-related disasters. This study compares the variability of two popular and widely used climate indices i.e., the United Nations Environment Programme (UNEP) aridity index and the Modified De-Martonne (MDM) index to assess the trend of climate change in the Chungcheong provinces of South Korea. The trend of annual and monthly climate indices was conducted using a non-parametric Mann-Kendall test and Kolmogorov-Smirnov normality test with daily climate data of 48 years (1978-2020) from 10 synoptic stations. The findings indicate that UNEP and MDM indices had a wet climate regime for the annual trend, with the UNEP index indicating a relatively humid trend of 60% humid, 20% semi-arid, and 10% sub-humid for the 48-years study period. However, the MDM index showed a high frequency of a severe wet climatic condition followed by the semi-arid condition. The months of July and August had the highest occurring frequency of the wet climatic condition (90%) for both UNEP and MDM indices. Comparing the two provinces, Chungnam showed a relatively wetter climatic condition using the UNEP index, while the MDM index indicated no significant regional difference in climate regime between the two provinces. The Kolmogorov-Smirnov normality test showed that all the 10 stations are normally distributed for monthly climate conditions at a 5% significant level in the two provinces except five stations for UNEP index and four stations for MDM index in the month of January.

• 한국의류학회지
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• 제34권2호
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• pp.291-302
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• 2010

This study details the actual wearing conditions and favored design of ready-made pants for obese women, particularly for those in their twenties and thirties. The actual problems that customers feel and the preferred design of pants were suggested based on the survey and from the standpoint of consumers. The findings of the survey are as follows. The actual wearing conditions in the survey, 80.5% like wearing pants. The main reason to prefer pants is that pants are more convenient for social or professional work activities. The main reason to avoid wearing pants is that the pants (in general) do not mask an obese body shape. The most favored was Denim/Elastic and the second most favored was Cotton/Elastic from the survey. On average, elastic materials are preferred over non-elastic materials. The reason was the comfort in wearing and convenience in social or professional activities that could mask obesity. In terms of the style, the most favored was blue jeans and the second favored was semi-formal. A straight-silhouette is the most favored as it was able to help mask obesity. The most favored position for the waistline is 4 cm lower than the natural waistline. The most favored pant length is where the pants slightly touch the floor when they stand with shoes on. For obese women the pants development that covers the weak points of the body shape giving, which is comfortable and active are desired.

• Steel and Composite Structures
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• 제37권6호
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• pp.711-731
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• 2020

This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, 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 core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

• 한국환경생태학회지
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• 제28권2호
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• pp.123-127
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• 2014

여우는 멸종위기 1급으로 현재 국립공원관리공단에서 복원사업을 추진 중에 있다. 본 연구는 여우의 기본적인 행동패턴을 파악하기 위하여 종복원기술원 중부복원센터에서 관리중인 개체들을 대상으로 2012년 5월부터 2013년 4월까지 수행하였다. 연구결과 여우의 활동 개시 시각은 평균 $16:59{\pm}01:20t$, 활동 종료 시각은 평균 $05:50{\pm}03:02t$으로 나타났으며, 수컷이 암컷보다 활동 개시 시각과 종료 시각이 빠른 것으로 나타났다. 계절별 활동 시간은 여름이 14시간 5분으로 가장 길었으며, 겨울이 10시간 11분으로 가장 짧았다. 여우의 활동은 주로 야간에 이루어졌으며, 활동 개시 시각은 일몰 시각에 영향을 받는 것으로 나타났다. 그러나 활동 종료 시각은 일출 시각과 유의적인 관계가 확인되지 않았다. 일일 채식활동 횟수는 최소 1회에서 최대 8회로, 수컷($2.40{\pm}1.66$)이 암컷($1.87{\pm}1.24$)보다 많았으며, 11월이 3.52회로 가장 높고 1월이 1.28회로 가장 낮았다. 일일 음수활동 횟수는 평균 $2.03{\pm}1.296$회로, 암컷과 수컷간의 차이는 나타나지 않았으며, 채식활동 빈도가 증가할수록 음수활동 빈도도 증가하는 것으로 나타났다. 본 연구는 비록 사육 상태의 개체로 이루어 졌지만, 사육 개체의 일일 사양관리, 방사 개체의 모니터링과 행동특성에 따른 서식지 관리에 활용될 수 있을 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.571-576
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• 1994

In recent years, ultrasonic has been widely applied in measurement and industrial fields and its application range has been expanded as a result of continuous research and development. Wire Bonding Machine, an instrument fabricating semi-conductor, makes use of ultrasonic bonding method. In order to improve the currently used wire bonding machine using ultrasonic energy, technical accumulation is needed steadily through development of exciting device of ultrasonic composed of piezoelectic vibrator and horn. This study investigates the design conditions affecting the dynamic characteristics through the theoretical and experimental analysis of piezoelectric vibrator and horn, The study conducts separately the system identification of piezoelectric vibrator in time domain and the modal analysis of horn in frequency domain. In theoretical model, the integrated modeling is conducted via a combination of dynamic identification of piezoelectric vibrator and theoretical analysis of horn. Hence comparison is made for theoretical and experimental results of the dynamic characteristics of the ultrasonic transducer composed of piezoelectric vibrator and horn. Form the results of this study we develop the design technique of ultrasonic transducer using dynamic characteristic analysis and propose the possibility of ultrasonic welding considering the optimal condition of the natural frequency and vibration mode of horn.

• Structural Engineering and Mechanics
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• 제50권1호
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• pp.53-71
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• 2014

A semi-analytical method is developed to consider free vibrations of a functionally graded elastic plate resting on Winkler elastic foundation and in contact with a quiescent fluid. Material properties are assumed to be graded distribution along the thickness direction according to a power-law in terms of the volume fractions of the constituents. The fluid is considered to be incompressible and inviscid. In the analysis, the effect of an in-plane force in the plate due to the weight of the fluid is taken into account. By satisfying the compatibility conditions along the interface of fluid and plate, the fluid-structure interaction is taken into account and natural frequencies and mode shapes of the coupled system are acquired by employing energy methods. The results obtained from the present approach are verified by those from a finite element analysis. Besides, the effects of volume fractions of functionally graded materials, Winkler foundation stiffness and in-plane forces on the dynamic of plate are elucidated.

• 제어로봇시스템학회논문지
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• 제22권11호
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• pp.904-911
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• 2016

This paper presents a novel driving system by the humanoid robot to drive a vehicle in disaster response situations. To enhance robot's capability for substituting human activities in responding to natural and man-made disaster, the one of prerequisite skills for the rescue robot is the mounted mobility to maneuver a vehicle safely in disaster site. Therefore, our driving system for the humanoid is developed in order to steer a vehicle through unknown obstacles even under poor communication conditions such as time-delay and black-out. Especially, the proposed system includes a tele-manipulation interface and stable navigation strategies. First, we propose a new type of path estimation method to overcome limited communication. Second, we establish navigation strategies when the operator cannot recognize obstacles based on Dynamic Window Approach. The effectiveness of the proposed developments is verified through simulation and experiments, which demonstrate suitable system for driving a vehicle in disaster response.