Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Some of the complex logistical problems faced by companies combine the needs for strategic and tactical decisionsconcerning the interrelated issues of clustering, scheduling, and routing. Various strategies can be used to solve theseproblems. We present a problem of this type, involving a company whose fundamental objective is thecommercialization of its product in the domestic market. The paper focuses on a model of and method for a solution tothe problem of scheduling visits to customers, taking into account the relationship with other phases of productmarketing. The model is nonlinear, involves binary and continuous variables, and solved heuristically. Computationalexperiments show that the proposed solution performed very well for both real-life and theoretical instances.

Watermarking is identified as a major technology to achieve copyright protection and multimedia security. Therefore,recent studies in literature include some evident approaches for embedding data into a multimedia element. Becauseof its useful frequency component separation, the Discrete Wavelet Transform (DWT) is commonly used inwatermarking schemes. In a DWT-based scheme, the DWT coefficients are modified with the data that represents thewatermark. In this paper, we present a hybrid non-blind scheme based on DWT and Singular Value Decomposition(SVD). After decomposing the cover image into four sub bands (LL, HL, LH and HH), we apply the SVD to LL bandand modify diagonal singular value coefficients with the watermark itself by using a scaling factor. Finally, LL bandcoefficients are reconstructed with modified singular values and inverse DWT is applied to obtain watermarked image.Experimental results show that the proposed algorithm is considerably robust and reliable. In comparison to theprevious literature, peak signal-to-noise ratio (PSNR) values of watermarked images are increased by approximately20%. In terms of PSNR values before and after attacks and of normalized similarity ratio (NSR); although watermarkis embedded into LL sub band; our proposed method gives much more satisfactory results on filtering, scaling,Gaussian, JPEG compression, rotation and cropping than that of previous literature.

Synchronization of multiple chaotic oscillators in Hamiltonian form is numerically studied and is achieved by appealingto complex systems theory [1-5]. The topology that we consider is the irregular coupled network. Two cases areconsidered: i) chaotic synchronization without master oscillator (where the final collective behaviour is a new chaoticstate) and ii) chaotic synchronization with master oscillator (where the final collective behaviour is imposed by thedynamics of the master oscillator to multiple slave oscillators). The Hysteretic and Rössler chaotic oscillators inHamiltonian form will be used as examples.

Sensors are regarded as significant components of electronic devices. In most applications of wireless sensornetworks (WSNs), important and critical information must be delivered to the sink in a multi-hop and energy-efficientmanner. Inasmuch as the energy of sensor nodes is limited, prolonging network lifetime in WSNs is considered to bea critical issue. In order to extend the network lifetime, researchers should consider energy consumption in routingprotocols of WSNs. In this paper, a new energy-efficient routing protocol (EERP) has been proposed for WSNs usingA-star algorithm. The proposed routing scheme improves the network lifetime by forwarding data packets via theoptimal shortest path. The optimal path can be discovered with regard to the maximum residual energy of the nexthop sensor node, high link quality, buffer occupancy and minimum hop counts. Simulation results indicate that theproposed scheme improves network lifetime in comparison with A-star and fuzzy logic(A&F) protocol.

This work presents a practical method for estimating the full kinematic state of a vehicle, along with sensor errorparameters, through the integration of inertial and GPS measurements. This kind of system for determining attitudeand position of vehicles and craft (either manned or unmanned) is essential for real time, guidance and navigationtasks, as well as for mobile robot applications.The architecture of the system is based in an Extended Kalman filtering approach in direct configuration. In this case,the filter is explicitly derived from the kinematic model, as well as from the models of sensors error. The architecturehas been designed in a manner that it permits to be easily modified, in order to be applied to vehicles with diversedynamical behaviors.The estimated variables and parameters are: i) Attitude and bias-compensated rotational speed of the vehicle, ii)Position, velocity and bias-compensated acceleration of the vehicle and iii) bias of gyroscopes and accelerometers.Experimental results with real data show that the proposed method is enough robust for its use along with low-costsensors.

In this paper, a control algorithm for improving vehicle handling has been proposed by applying correction angle to the steered wheel, based on the optimal and adaptive theory using Simulink MATLAB software. A 4DOF model with nonlinear tire and SBW subsystem is presented using hardware in the loop method. Since some space variables cannot be measured, an estimator is used to extract the measurable variables from the simulated model and convert them to the required variables of the controller. These variables are transmitted to the controller and then it adopts itself with new conditions and applies the best modification on the steering. The results reveal that the proposed controller can significantly improve vehicle handling during severe maneuvers.

ABSTRACTIn this paper the response of a microgrid to the interfaced harmonic distorted load is analyzed. A new controlalgorithm to mitigate harmonic distortion is considered for distributed generators (DGs) and the effect of this controlscheme is shown in the currents of DGs and other loads.The proposed control algorithm is compared with the conventional control strategy for harmonic distorted loads that issinusoidal source current strategy based on the instantaneous reactive power (IRP) theory. PSCAD simulation resultsfor IRP theory control show high total harmonic distortion (THD) and 3rd harmonic percent. In comparison innervoltage and current controllers of the proposed control scheme with their disturbance rejection capability, mitigateTHD and 3rd harmonic percent. For this control system MATLAB simulation results are shown.By demonstrating the traditional sinusoidal source current control strategy based on IRP theory, it is concluded thatignoring the distortion power (D) in compensating process and also sub-harmonics of Pαβ crossing from the controllerinterior high pass filter cause the presence of some harmonic components and high THD.

Today the increased world population and therefore the growth demand has forced the researchers to investigatebetter water canal networks distributing much more water while at least keeping its quality. Canal design formulas areexplicitly obtained for different cross-sections considering minimum area but optimal design of canal sectionsconsidering seepage and evaporation losses are still an open area to study. In this study, two different algorithms areapplied to this problem and results are compared with the one in literature. Genetic algorithm and sequential quadraticprogramming technique are used in optimization. Triangular, rectangular and trapezoidal cross-sections areoptimized. It is seen that both algorithms are giving more accurate results than in literature.

The aim of this paper is to solve the problem of placing safety stock over a Logistic Network (LN) that is representedby a Generic Bill of Materials (GBOM). Thus the LN encompasses supplying, assembling, and delivering stages. Wedescribe, in detail, the recursive algorithm based on Dynamic Programming (DP) to solve the placing safety stockproblem under guaranteed-service time models. We also develop a java-based application (JbA) that both models theLN and runs the recursive DP algorithm. We solved a real case of a company that manufactures fixed brake andclutch pedal modules of cars’ brake system. After running JbA, the levels of inventory decreased by zero in 55 out of65 stages.

In this work a technique to heighten the breakdown voltage and the transition frequency (fT) in standard MOStechnology is presented. By using an optimized extended drift region at the drain, a CMOS FET can achieve higherbreakdown voltage. To enhance the operation frequency, the standard analog/digital pads were modified to decreasecoupling effects with the substrate. These two enhancements make the proposed MOSFET structure suitable for midpowerRF applications. Experimental measurements on a High Voltage MOSFET (HVMOS FET) show a breakdownvoltage of 20 V, IP3 of +30.2 dBm and an improvement of 31.9% and 34.7% of the extrinsic fT and fmax, respectively.