127 research outputs found
Analysis of Homeland Security Regulations, Small Steps Forward, Giant Leaps to Go
Full text linkThis paper reviews the use of cost-benefit analysis in evaluating homeland security regulations. Until the recent use of "break-even analysis" by the Department of Homeland Security, analysis of regulations to reduce the risk of a terrorist attacks have been severely lacking. The costs were likely to be understated particularly because the costs of restrictions on immigration and of the curbing of civil liberties are omitted. Benefits were often left uncalculated leaving it impossible to meaningfully evaluate the policies being promulgated. The use of break-even analysis has improved the ability to evaluate homeland security policy. However, DHS needs to provide this information in a more consistent format in order to allow comparison of regulatory initiatives. DHS also needs to provide its own assessment of what the break-even analysis tells us about the likelihood that the benefits of their regulations outweigh their costs.
Mathematical Modeling of a Moving Planar Payload Pendulum on Flexible Portal Framework
Full text linkMathematical modeling of a moving planar payload pendulum on elastic portal framework is presented in this paper. The equations of motion of such a system are obtained by modeling the portal frame using finite element in conjunction with moving finite element method and moving planar payload pendulum by using Lagrange’s equations. The generated equations indicate the presence of nonlinear coupling between dynamics of portal framework and the payload pendulum. The combinational direct numerical integration technique, namely Newmarkand fourth-order Runge-Kutta method, is then proposed to solve the coupled equations of motion. Several numerical simulations are performed and the results are verified with several benchmarks. The results indicate that the amplitude and frequency of the payload pendulum swing angle are greatly affected by flexibility of structure and the cable in term of carriage speed
DYNAMICS AND CONTROL OF FLEXIBLE GANTRY CRANE SYSTEM
Full text linkGantry crane system, a non-slewing-luffing crane system is most widely used in many work places. However, the heavier lifting capacities and the greater size of gantry crane, the vibrational motion become more significant during crane operations and it must be considered. The equations of motion of the system can be obtained by modeling the crane framework using finite element in conjuction with moving finite element method and gantry crane by using Lagrange’s equations. The combinational direct integration technique, namely Newmark- and fourth-order Runge-Kutta method is proposed to solve the coupled equations of motion.
Numerical simulation results show that the combination of flexibility of crane framework and hoist cable produces greater amplitudes and lower swing angles frequency compared to the gantry crane system with flexible hoist cable or crane framework only with respect to the rigid model. Furthermore, all the flexible models of gantry crane system have lower frequencies in the time histories of swing angles of payload with respect to the rigid model for all the parametric studies. The trends of maximum displacements of crane framework and hoist cable increase with the increase of payload mass and initial swing angle of payload. The increases are slightly linear for payload mass and nonlinear for initial swing angle of payload. Under the increase of structural damping, hoist cable stiffness, cross-sectional dimensions of crane framework and hoist cable length, the trends decrease for all the maximum displacements.
Control simulations clearly demonstrate that Zero-Vibration-Derivative-Derivative (ZVDD), Fuzzy Logic Controller (FLC) and Proportional-Integral-Derivative (PID) controllers have rough fluctuations in controlling flexible gantry crane with respect to their performances in controlling the rigid model of gantry crane. Compared to FLC and PID, ZVDD has larger steady state error
SLOW DRIFT MOTIONS IDENTIFICATION OF FLOATING STRUCTURES USING TIME-VARYING INPUT -OUTPUT MODELS
No full textThis study presents the identification of slow drift motions of floating structures from
model test data. To compute the slow drift motions, nonlinear and nonstationary system
identification which exploits the concept of a state-space based time domain input-ouput
models is proposed, comprising the time-varying nonlinear autoregressive with
exogenous input (TVNARX) and Volterra models. Three steps of improvements had
been made to increase the modeling capacity of input-output models. The first step is
presenting the backward estimator and combined forward-backward estimator instead of
the only forward estimator in the original input-output models; the second step is
reformulating the input-output models into a state-space model so that the Kalman
Smoother (KS) adaptive filter can be used to estimate the model coefficients; the third
step is optimization of KS parameters using evolutionary computing algorithms such as
Particle Swarm Optimization (PSO), Genetic Algorithm (GA) and Artificial Bee Colony
(ABC) to form the PSO-KS, GA-KS and ABC-KS as estimation methods
Optimizing the Gains of PD controller Using Artificial Bee Colony for Controlling the Rigid Gantry Crane System
Full text linkControl position and reduction of swinging of the payload of a rigid gantry crane system is a challenging work because of under-actuated system. This paper addresses challenges by proposing the artificial bee colony (ABC) algorithm to optimize the gains of the PD controller to form what the so-called the artificial bee colony (ABC)-PD controller. The effectiveness of the proposed control algorithm is tested under constant step functions and compared with Ziegler-Nichols (ZN)-PD controller. The results show that the proposed controller produces slower rise time and peak time, but faster settling time than the ZN-PD controller as well as no overshoot under the predefined trajectories. Â
Reflexión sobre la naturaleza de la Consulta Previa, a partir de la obra de Edwar Vargas Araujo.
Full text linkThe author essayically discusses the futility of the figure of the Previous Consultation, as expressed in the Ecuadorian and Bolivian Magna Cartas, as long as it does not produce a legal obligation on the State. It is argued that the previous consultation does nothing more than generate a "calligraphic" reference, that is, not a real political force, which puts the environment and the Amerindian eco-culture at risk by the mining and hydrocarbon companies in protected territories.El autor diserta ensayísticamente acerca de futilidad de la figura de la Consulta Previa, tal como se expresa en las Cartas Magnas ecuatoriana y boliviana, mientras ella no produzca obligación jurídica sobre el Estado. Se argumenta, junto a Edwar Vargas Araujo, que la consulta Previa no hace más que generar una referencia “caligráfica”, esto es, no de fuerza política real, lo que pone en riesgo el ambiente y la eco-cultura amerindia por parte de las empresas mineras e hidro-carburíferas en territorios protegidos
Application of empirical mode decomposition method for characterization of random vibration signals
Full text linkCharacterization of finite measured signals is a great of importance in dynamical modeling and system identification. This paper addresses an approach for characterization of measured random vibration signals where the approach rests on a method called empirical mode decomposition (EMD). The applicability of proposed approach is tested in one numerical and experimental data from a structural system, namely spar platform. The results are three main signal components, comprising: noise embedded in the measured signal as the first component, first intrinsic mode function (IMF) called as the wave frequency response (WFR) as the second component and second IMF called as the low frequency response (LFR) as the third component while the residue is the trend. Band-pass filter (BPF) method is taken as benchmark for the results obtained from EMD method
Mathematical Modeling of a Moving Planar Payload Pendulum on Flexible Portal Framework
Full text linkMathematical modeling of a moving planar payload pendulum on elastic portal framework is presented in this paper. The equations of motion of such a system are obtained by modeling the portal frame using finite element in conjunction with moving finite element method and moving planar payload pendulum by using Lagrange's equations. The generated equations indicate the presence of nonlinear coupling between dynamics of portal framework and the payload pendulum. The combinational direct numerical integration technique, namely Newmarkand fourth-order Runge-Kutta method, is then proposed to solve the coupled equations of motion. Several numerical simulations are performed and the results are verified with several benchmarks. The results indicate that the amplitude and frequency of the payload pendulum swing angle are greatly affected by flexibility of structure and the cable in term of carriage speed
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