• Journal of Forest and Environmental Science
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• 제38권2호
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• pp.122-127
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• 2022

Agroforestry in terms of intercropping cow pea as summer forage with Grewia tenax was undertaken under sub -irrigation system in two consecutive seasons of 2017 and 2018 in saline soil of Khartoum State of Sudan. The aims were to find out suitable agro forestry system for saline soils as well as to investigate effect of tree spacing on field summer forage crop under semi -irrigation system. Therefore G. tenax trees that spaced at 4×4 m were used as main factor versus cow pea crop that incorporated at 25×50 cm intervals by using completely randomized block design with 3 replications. Trees and crop parameters were determined in terms of plant growth and yield. In addition to land equivalent ratio and soil chemical and physical properties at different layers were determined. The results revealed that, soil parameters in terms of CaCo₃, SAR, ESP, pH paste and EC ds/m were increased with increasing soil depths. Meanwhile tree growth did not show any significant differences in the first season in 2017. Whereas in the second season in 2018 tree growth namely; tree height, tree collar and canopy diameters were higher under intercropping than in sole trees. Cow pea plant height recorded significant differences under sole crop in the first season in 2017. Unlike the forage fresh yield that was significant under the inter cropped plots. Tree fruit yield was higher under sole trees and land equivalent ratio was more advantageous under GS2 (1.5 m) which amounted to 4. Therefore it is possible to introduce this agroforestry system under saline soils to provide summer forage of highly nutritive value to feed animals and to increase farmers' income as far as to halt desertification and to sequester carbon.

• Tribology and Lubricants
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• 제10권1호
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• pp.62-68
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• 1994

The analysis of statically indeterminate bearing-shaft system was investigated. The moment loads and misalignment angles which were induced in the ball bearings were determined, and the influence of span length of this system on the moment loads and fatigue lives was identified. The sliding and spinning speeds between balls and raceways which affected the performance of ball bearing evaluated. The equation to estimate the cage speed of ball bearing under moment loads was proposed. This equation had been verified by the test results of measuring of cage speed, which was useful to the prediction of ball bearing under moment loads.

• Structural Engineering and Mechanics
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• 제32권3호
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• pp.399-406
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• 2009

A three-dimensional panel system, which was offered as a new method for construction in Jordan using relatively high strength modular panels for walls and ceilings, is investigated in this paper. The panel consists of two steel meshes on both sides of an expanded polystyrene core and connected together with a truss wire to provide a 3D system. The top face of the ceiling panel was pored with regular concrete mix, while the bottom face and both faces of the wall panels were cast by shotcreting (dry process). To investigate the structural performance of this system, an extensive experimental testing program for ceiling and wall panels subjected to static and dynamic loadings was conducted. The load-deflection curves were obtained for beam and shear wall elements and wall elements under transverse and axial loads, respectively. Static and dynamic analyses were conducted, and the performance of the proposed structural system was evaluated and compared with a typical three dimensional reinforced concrete frame system for buildings of the same floor areas and number of floors. Compressive strength capacity of a ceiling panel is determined for gravity loads, while flexural capacity is determined under the effect of wind and seismic loading. It was found that, the strength and serviceability requirements could be easily satisfied for buildings constructed using the three-dimensional panel system. The 3D panel system is superior to that of conventional frame system in its dynamic performance, due to its high stiffness to mass ratio.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.135-140
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• 1998

The concept of dissipativity and passivity are of interest to us from a theoretical as well as a practical point of view. It is well known that the Riccati equation is derived from the dissipation inequality which expresses the fact that the system is dissipative; the energy stored inside the system doesn't exceed the amount of supply which flows into the system. The pencil model is regarded as a representation based on behavioral approach introduced by J.C. Willems. It has first order in the internal variable and zeroth order in the external variable. In general, any matrix pencil is transformed into a canonical form which is consist of several kind of sub-pencils, One of them has row full rank for $^\forall S\;\in\;\mathds{C}\;\bigcup{\infty}$, we call it under-determined mode of the model. In our opinion, most important properties of dynamical system lay in the mode. According to the properties of canonical form for pencil, it is shown that the storage function which characterizes the dissipativity of the system can be written as a LMI for the under-determined mode, if the system doesn't include impulse mode.

• Smart Structures and Systems
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• 제34권2호
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• pp.97-116
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• 2024

The standard l₁-norm regularization is recently introduced for impact force identification, but generally underestimates the peak force. Compared to l₁-norm regularization, l_p-norm (0 ≤ p < 1) regularization, with a nonconvex penalty function, has some promising properties such as enforcing sparsity. In the framework of sparse regularization, if the desired solution is sparse in the time domain or other domains, the under-determined problem with fewer measurements than candidate excitations may obtain the unique solution, i.e., the sparsest solution. Considering the joint sparse structure of impact force in temporal and spatial domains, we propose a general l_p-norm (0 ≤ p < 1) regularization methodology for simultaneous identification of the impact location and force time-history from highly incomplete measurements. Firstly, a nonconvex optimization model based on l_p-norm penalty is developed for regularizing the highly under-determined problem of impact force identification. Secondly, an iteratively reweighed l₁-norm algorithm is introduced to solve such an under-determined and unconditioned regularization model through transforming it into a series of l₁-norm regularization problems. Finally, numerical simulation and experimental validation including single-source and two-source cases of impact force identification are conducted on plate structures to evaluate the performance of l_p-norm (0 ≤ p < 1) regularization. Both numerical and experimental results demonstrate that the proposed l_p-norm regularization method, merely using a single accelerometer, can locate the actual impacts from nine fixed candidate sources and simultaneously reconstruct the impact force time-history; compared to the state-of-the-art l₁-norm regularization, l_p-norm (0 ≤ p < 1) regularization procures sufficiently sparse and more accurate estimates; although the peak relative error of the identified impact force using l_p-norm regularization has a decreasing tendency as p is approaching 0, the results of l_p-norm regularization with 0 ≤ p ≤ 1/2 have no significant differences.

• Structural Engineering and Mechanics
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• 제37권4호
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• pp.401-413
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• 2011

The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.42-45
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• 2001

The characteristics of smart skin for wireless LAN system under compression load are investigated. The smart skin structure is composed of 3 layers of face material and 2 layers of core material. Theoretical formula for determining buckling load is derived by Rayleigh-Ritz method and compared with experimental result. The maximum length of specimen that buckling does not occur is determined by only face material. In the experiment, if load supporting capability and the antenna property such as radiation pattern and reflection coefficient were examined.

• Coupled systems mechanics
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• 제7권6호
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• pp.707-729
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• 2018

The semi-active optimal vibration control of nonlinear torsion-bar suspension vehicle systems under random road excitations is an important research subject, and the boundedness of MR dampers and the uncertainty of vehicle systems are necessary to consider. In this paper, the differential equations of motion of the coupling torsion-bar suspension vehicle system with MR damper under random road excitation are derived and then transformed into strongly nonlinear stochastic coupling vibration equations. The dynamical programming equation is derived based on the stochastic dynamical programming principle firstly for the nonlinear stochastic system. The semi-active bounded parametric optimal control law is determined by the programming equation and MR damper dynamics. Then for the uncertain nonlinear stochastic system, the minimax dynamical programming equation is derived based on the minimax stochastic dynamical programming principle. The worst-case disturbances and corresponding semi-active bounded parametric optimal control are obtained from the programming equation under the bounded disturbance constraints and MR damper dynamics. The control strategy for the nonlinear stochastic vibration of the uncertain torsion-bar suspension vehicle system is developed. The good effectiveness of the proposed control is illustrated with numerical results. The control performances for the vehicle system with different bounds of MR damper under different vehicle speeds and random road excitations are discussed.

• Earthquakes and Structures
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• 제19권6호
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• pp.445-457
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• 2020

An ultra-high voltage (UHV) transmission system has the advantages of low circuitry loss, high bulk capacity and long-distance transmission capabilities over conventional transmission systems, but it is easier for this system to cross fault rupture zones and become damaged during earthquakes. This paper experimentally and numerically investigates the seismic responses and collapse failure of a UHV transmission tower-line system crossing a fault. A 1:25 reduced-scale model is constructed and tested by using shaking tables to evaluate the influence of the forward-directivity and fling-step effects on the responses of suspension-type towers. Furthermore, the collapse failure tests of the system under specific cross-fault scenarios are carried out. The corresponding finite element (FE) model is established in ABAQUS software and verified based on the Tian-Ma-Qu material model. The results reveal that the seismic responses of the transmission system under the cross-fault scenario are larger than those under the near-fault scenario, and the permanent ground displacements in the fling-step ground motions tend to magnify the seismic responses of the fault-crossing transmission system. The critical collapse peak ground acceleration (PGA), failure mode and weak position determined by the model experiment and numerical simulation are in relatively good agreement. The sequential failure of the members in Segments 4 and 5 leads to the collapse of the entire model, whereas other segments basically remain in the intact state.

• 대한산업공학회지
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• 제14권2호
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• pp.99-114
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• 1988

The objective of this study is mainly related to design aspects of Multi-aisle S/R machine system (MASS) which can substantially reduce high initial investment cost of Automated Storage/Retrieval System. Firstly, the average travel time of the S/R machine is determined under single and dual commands, from which the average performance of S/R machine is evaluated. Secondly, a design model is developed and the system parameters, such as length and height of the system, and the number of S/R machines, traversers and aisles are determined which provide minimum initial investment and operating costs. Also, through experiments, sensitivity analysis is made for the throughput and storage volume.