• Asian-Australasian Journal of Animal Sciences
• /
• v.13 no.5
• /
• pp.636-640
• /
• 2000

Cup-plant (Silphium perfoliatum L.) has potential to produce high biomass and highly digestible forage in the wetlands where other productive forages do not grow or produce well. However, high moisture content at harvest is a considerable disadvantage of cup-plant for the production of high quality silage. This study was conducted to determine the effect of moisture content on the characteristics of cup-plant silage. Harvested cup-plant was ensiled in farm scale plastic bag silos and laboratory silos. In the plastic bag silos, first growth (FG) and regrowth (RG) cup-plant was harvested, wilted and ensiled. Dry matter content of FG and RG was 280 g/kg and 320 g/kg after 48 hr of wilting. The silage made with FG had pH 5.3 and 5.63 g/kg DM of acetate as a major volatile fatty acid. The composition of lactate, butyrate and acetate production was 1.0: 0.9: 2.3. The pH of silage made with RG was 4.5 and lactate was a major fermentation end product (16.8 g/kg DM). In the laboratory silos, wilted and unwilted first growth cup-plant material was ensiled to compare the early fermentation end products at days 2, 4, 11, and 40. Wilting increased dry matter content by 42% in the harvested material. Wilted silage showed about one unit lower pH until day 11. The contents of ammonia nitrogen and acetate were higher in un wilted silage, while that of lactate was higher in wilted silage (p<0.05). Butyrate and propionate were not detected in the wilted silage until day 40. We conclude from the results that moisture control is essential for the production of high quality cup-plant silage and high pH of cup-plant silage is due to low concentrations of fermentation end products.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.307-307
• /
• 2014

정보화 시대로 접어들면서 동일한 공간에 더 많은 정보를 저장할 수 있고, 보다 빠른 동작이 가능한 비휘발성 메모리 소자에 대한 요구가 증가하고 있다. 하지만, 최근 비휘발성 메모리 소자 관련 연구보고에 따르면, 메모리 소자의 소형화 및 직접화 측면에서, 전하 저장을 기반으로 하는 기존의 Floating-Gate(FG) Flash 메모리는 20 nm 이하 공정에서 한계가 예측 되고 있다. 따라서, 이러한 FG Flash 메모리의 한계를 해결하기 위해, 기존에 FET 기반의 FG Flash 구조와 같은 3 terminal이 아닌, Diode와 같은 2 terminal로 동작이 가능한 ReRAM, PRAM, STT-MRAM, PoRAM 등 저항변화를 기반으로 하는 다양한 종류의 차세대 메모리 소자가 연구되고 있다. 그 중, 저항 변화 메모리(ReRAM)는 CMOS 공정 호환성, 3D 직접도, 낮은 소비전력과 빠른 동작 속도 등의 우수한 동작 특성을 가져 차세대 비휘발성 메모리로 주목을 받고 있다. 또한, 상하부 전극의 2 terminal 만으로 소자 구동이 가능하기 때문에 Passive Crossbar-Array(CBA)로 적용하여 플래시 메모리를 대체할 수 있는 유력한 차세대 메모리 소자이다. 하지만, 이를 현실화하기 위해서는 Passive CBA 구조에서 발생할 수 있는 Read Disturb 현상, 즉 Word-Line과 Bit-Line을 통해 선택된 소자를 제외하고 주변의 다른 소자를 통해 흐르는 Sneak Leakage Current(SLC)를 차단하여 소자의 메모리 State를 정확히 sensing하기 위한 연구가 선행 되어야 한다. 따라서, 현재 이러한 이슈를 해결하기 위해서, 많은 연구 그룹에서 Diodes, Threshold Switches와 같은 ReRAM에 Selector 소자를 추가하는 방법, 또는 Self-Rectifying 특성 및 CRS 특성을 보이는 ReRAM 구조를 제안 하여 SLC를 차단하고자 하는 연구가 시도 되고 있지만, 아직까지 기초연구 단계로서 아이디어에 대한 가능성 정도만 보고되고 있는 현실 이다. 이에 본 논문은 Passive CBA구조에서 발생하는 SLC를 해결하기 위한 새로운 아이디어로써, 본 연구 그룹에서 선행 연구로 확보된 안정적인 저항변화 물질인 SiN를 정류 특성을 가지는 n-Si/Ti 기반의 Schottky Diode와 결합함으로써 기존의 CBA 메모리의 Read 동작에서 발생하는 SLC를 차단 할 수 있는 1SD-1R 구조의 메모리 구조를 제작 하였으며, 본 연구 결과 기존에 문제가 되었던 SLC를 차단 할 수 있었다.

• Journal of Information Processing Systems
• /
• v.12 no.3
• /
• pp.392-409
• /
• 2016

The aim of this paper is to examine the effectiveness of combining three popular tools used in pattern recognition, which are the Active Appearance Model (AAM), the two-dimensional discrete cosine transform (2D-DCT), and Kernel Fisher Analysis (KFA), for face recognition across age variations. For this purpose, we first used AAM to generate an AAM-based face representation; then, we applied 2D-DCT to get the descriptor of the image; and finally, we used a multiclass KFA for dimension reduction. Classification was made through a K-nearest neighbor classifier, based on Euclidean distance. Our experimental results on face images, which were obtained from the publicly available FG-NET face database, showed that the proposed descriptor worked satisfactorily for both face identification and verification across age progression.

• BMB Reports
• /
• v.33 no.3
• /
• pp.228-233
• /
• 2000

The steady-state investigation of the mechanism of Dhydroxyisovalerate dehydrogenase was performed in order to understand this type of kinetic patterns. The initial velocity was measured with various amounts of both substrates, NADPH and 2-ketoisovalerate. Double reciprocal plots gave patterns that conversed on or near the abscissa. Binding studies indicated that NADPH bound first to the enzyme. The product $NADP^+$ was found to be a competitive inhibitor with respect to NADPH at a constant concentration of 2-ketoisovalerate. However, it showed noncompetitive inhibition against 2-ketoisovalerate at a fixed amount of NADPH. Another product, D-hydroxyisovalerate, was a non-competitive inhibitor versus NADPH and 2-ketoisovalerate at constant levels of 2-ketoisovalerate and NADPH, respectively. These results were comparable with an ordered bi-bi mechanism, in which NADPH bound first to the enzyme, followed by the binding of 2- ketoisovalerate. $NADP^+$ is the last product to be released. The ordered reaction manner of D-hydroxyisovalerate dehydrogenase from 2-ketoisovalerate to D-hydroxyisovalerate allows the accurate regulation of valine metabolism and it may lead to the regulation of total biosynthesis of enniatins in the Fusarium species.

• Steel and Composite Structures
• /
• v.42 no.1
• /
• pp.23-32
• /
• 2022

In this paper, a nonlinear numerical method to solve the large deflection problem is introduced. And the non-dimensional load-deflection behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates is parametrically investigated. The large deflection problem is formulated according to the von Kármán nonlinear theory and the (1,1,0)^* hierarchical model, and it is approximated by 2-D natural element method (NEM). The shear locking phenomenon is suppressed by the selectively reduced integration method. The nonlinear matrix equations are solved by combining the incremental loading scheme and the Newton-Raphson iteration method. The proposed method is validated from the benchmark experiments, where the propose method shows an excellent agreement with the reference methods. The nonlinear behavior of FG-CNTRC plates is evaluated in terms of the non-dimensional load-deflection curve, and it is parametrically investigated with respect to the existence/non-existence and gradient pattern of CNTs, the width-to-thickness and aspect ratios of plates and the type of boundary conditions. The non-dimensional central deflection is significantly reduced when CNTs and added, and it decreases with the volume fraction of CNTs. But, it shows a uniform increase in proportion to the width-to-thickness and aspect ratios. Both the gradient pattern of CNTs and the type of boundary conditions do also show the remarkable effects.

• Computers and Concrete
• /
• v.33 no.3
• /
• pp.275-284
• /
• 2024

This work presents a comprehensive investigation of buckling behavior of bidirectional functionally graded imperfect beams exposed to several thermal loading with general boundary conditions. The nonlinear governing equations are derived based on 2D shear deformation theory together with Von Karman strain-displacement relation. The beams are composed of two different materials. Its properties are porosity-dependent and are continuously distributed over the length and thickness of the beams following a defined law. The resulting equations are solved analytically in order to determine the thermal buckling characteristics of BDFG porous beams. The precision of the current solution and its accuracy have been proven by comparison with works previously published. Numerical examples are presented to explore the effects of the thermal loading, the elastic foundation parameters, the porosity distribution, the grading indexes and others factors on the nonlinear thermal buckling of bidirectional FG beam rested on elastic foundation.

• Advances in nano research
• /
• v.10 no.4
• /
• pp.313-325
• /
• 2021

This paper is concerned with the buckling behavior of 2D and quasi-3D problem of functionally graded nanobeam founded on high order shear deformation beams theory and made by two different types of porous distribution materials in Nano- and micro-scales. The used Quasi-3D formulation takes into account the transverse shear effect and uses only three variables. Both formulations do not include the correction factor that is required in the first shear deformation theory proposed by Timoshenko. Governing equations are derived using the principle of virtual work. Analytical resolutions for buckling of FG nanobeam are introduced under tow different boundary conditions, and the results obtained are compared to those proposed in literatures.

• Advances in nano research
• /
• v.12 no.2
• /
• pp.117-137
• /
• 2022

Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

• Steel and Composite Structures
• /
• v.52 no.5
• /
• pp.501-513
• /
• 2024

Two-directional functionally graded materials (2D-FGMs) show extraordinary physical properties which makes them ideal candidates for designing smart micro-switches. Pull-in instability is one of the most critical challenges in the design of electrostatically-actuated microswitches. The present research aims to bridge the gap in the static pull-in instability analysis of microswitches composed of 2D-FGM. Euler-Bernoulli beam theory with geometrical nonlinearity effect (i.e. von-Karman nonlinearity) in conjunction with the modified couple stress theory (MCST) are employed for mathematical formulation. The micro-switch is subjected to electrostatic actuation with fringing field effect and Casimir force. Hamilton's principle is utilized to derive the governing equations of the system and corresponding boundary conditions. Due to the extreme nonlinear coupling of the governing equations and boundary conditions as well as the existence of terms with variable coefficients, it was difficult to solve the obtained equations analytically. Therefore, differential quadrature method (DQM) is hired to discretize the obtained nonlinear coupled equations and non-classical boundary conditions. The result is a system of nonlinear coupled algebraic equations, which are solved via Newton-Raphson method. A parametric study is then implemented for clamped-clamped and cantilever switches to explore the static pull-in response of the system. The influences of the FG indexes in two directions, length scale parameter, and initial gap are discussed in detail.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.5
• /
• pp.1349-1355
• /
• 2014

A three-dimensional (3D) $Co_3O_4$/mildly oxidized multiwalled carbon nanotubes (moCNTs)/reduced mildly oxidized graphene oxide (rmGO) ternary composite was prepared via a simple and green hydrolysishydrothermal approach by mixing $Co(Ac)_2{\cdot}4H_2O$ with moCNTs and mGO suspension in mixed ethanol/$H_2O$. As characterized by scanning electron microscopy and transmission electron microscopy, $Co_3O_4$ nanoparticles with size of 20-100 nm and moCNTs are effectively anchored in mGO. Cyclic voltammetry and galvanostatic charge-discharge measurements were adopted to investigate the electrochemical properties of $Co_3O_4$/moCNTs/rmGO ternary composite in 6 M KOH solution. In a potential window of 0-0.6 V vs. Hg/HgO, the composite delivers an initial specific capacitance of 492 $Fg^{-1}$ at 0.5 $Ag^{-1}$ and the capacitance remains 592 $Fg^{-1}$ after 2000 cycles, while the pure $Co_3O_4$ shows obviously capacitance fading, indicating that rmGO and moCNTs greatly enhance the electrochemical performance of $Co_3O_4$.