The increasing number of wireless broadband access users in local and wide area networks is the principal expression of the need for flexible and omnipresent wireless connectivity. In order to satisfy users' requi...
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The increasing number of wireless broadband access users in local and wide area networks is the principal expression of the need for flexible and omnipresent wireless connectivity. In order to satisfy users' requirements in the presence of the wireless medium, sophisticated multiple access, multiple elemental antenna and adaptation techniques are required. The use of multiple elemental antenna arrays at the base station allows intracell channel reuse by multiple spatially separable users through space division multiple access (SDMA). In this paper, the author investigates the implement of three elemental antenna arrays and proposes an adaptive algorithm to allocate channels to four users based on the number of users and elements of antenna, while appropriately adjusting to n users and m elemental antenna arrays. The unified consideration of such adaptive algorithm techniques yields significant through the benefits.
The authors present an adaptive force/position control strategy for flexible joint robot manipulators subject to holonomic constraints. Convergence and stability results are guaranteed regardless of the joint flexibil...
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The authors present an adaptive force/position control strategy for flexible joint robot manipulators subject to holonomic constraints. Convergence and stability results are guaranteed regardless of the joint flexibility value, in the non-adaptive as well as in the adaptive case. The joint flexibility matrix can be incorporated into the parameter vector of the adaptive controller. When the system physical parameters are unknown, an additional assumption is needed, i.e., the constraints are assumed to be linear.< >
Weight divided adaptive control method for a microwave FeedForward Power Amplifier (FFPA) is presented. In this adaptive controller, an output signal of a power amplifier is used as reference signal. Additionally, ref...
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Weight divided adaptive control method for a microwave FeedForward Power Amplifier (FFPA) is presented. In this adaptive controller, an output signal of a power amplifier is used as reference signal. Additionally, reference signal is divided by the weight of adaptive filter, so that characteristics of the power amplifier, such as temperature dependence, do not have influence on the convergence performances. The proposed adaptive algorithm and the convergence condition are derived analytically and we clarify that the proposed weight divided adaptive algorithm is more stable than the conventional Normalized Least Mean Square (NLMS) algorithm. Then, the convergence condition considering phase calibration error is discussed. The effectiveness of the proposed algorithm are also verified by the nonlinear simulations of the FFPA having AM-AM and AM-PM nonlinearity of GaAsFET.
It has been considered impossible to demodulate a fast frequency-hopping (FFH) spread-spectrum signal coherently in a frequency selective fading channel as a result of difficulties with making the receiver local oscil...
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It has been considered impossible to demodulate a fast frequency-hopping (FFH) spread-spectrum signal coherently in a frequency selective fading channel as a result of difficulties with making the receiver local oscillator track the phase of a received signal that lacks phase continuity. This paper proposes a coherent demodulator for both FFH-PSK (phase-shift keying) and FFH-FSK (frequency-shift keying) signal employing a method in which the received signal is noncoherently down-converted and phase-adjusted by an adaptive algorithm. Computer-simulations show that performance is better than in the case of noncoherent demodulators and that the interference-rejection effect of the adaptive algorithm produces strong protection against interferences from other CDMA users.
Self-adaptive mechanisms are gaining momentum in industrial processes. It is understandable that as the complexity increases, the human work must be augmented. Considering this, the authors have developed one such sol...
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Self-adaptive mechanisms are gaining momentum in industrial processes. It is understandable that as the complexity increases, the human work must be augmented. Considering this, the authors have developed one such solution for the punch-forming process, using additive manufacturing, i.e., a 3D-printed punch, to draw into shape 6061-T6 aluminum sheets. This paper aims to highlight the topological study used to optimize the punch form shape, the methodology of the 3D printing process, and the material used. For the adaptive algorithm, a complex Python-to-C++ bridge was created. It was necessary as the script has computer vision (used for calculating stroke and speed), punch force, and hydraulic pressure measurement capabilities. The algorithm uses the input data to control its subsequent actions. Two approaches are used in this experimental paper, a pre-programmed direction and an adaptive one, for comparison purposes. The results, namely the drawing radius and flange angle, were statistically analyzed using the ANOVA methodology for significance. The results indicate significant improvements when using the adaptive algorithm.
The computational cost of mid-frequency response could be considerably high for finite element systems because each response evaluation needs the numerical solving of a system of complex equations. The mode superposit...
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The computational cost of mid-frequency response could be considerably high for finite element systems because each response evaluation needs the numerical solving of a system of complex equations. The mode superposition method requires to calculate various modes within a range that is several times of the given excitation frequency interval, yet the accuracy of result is still unknown. In this paper, a new and innovative method for calculating the mid-frequency response of a proportional damping system is proposed. First, the middle modes and frequencies to be calculated are adaptively determined. Then, the unknown lower-order mode and higher-order mode contribution is approximated by the partial sum of a convergent power series. By using an iterative algorithm and considering only the left or right end of the excitation frequency interval, the number of terms in the sum is adaptively determined. A remarkable conclusion is established here that the resulting expression of frequency response is perfectly valid for the entire excitation frequency interval. The frequency response analysis can thus be performed by using this expression, and by changing the excitation frequency only. Finally, two numerical examples are presented to illustrate the accuracy and effectiveness of the proposed new method. The result shows that the proposed method can significantly reduce CPU (central processing unit) computational time with respect to the direct method for mid-frequency response analysis.
In this paper, based on an adaptive algorithm, an adaptive peak power reduction scheme (APPR) is proposed that can reduce the peak power and suppress radiated power outside the bandwidth. In the proposed method, no su...
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In this paper, based on an adaptive algorithm, an adaptive peak power reduction scheme (APPR) is proposed that can reduce the peak power and suppress radiated power outside the bandwidth. In the proposed method, no sudden nonlinear processing such as clipping is used, but the gain calculated by the adaptive algorithm is multiplied by the modulation signal. Hence, reduction of the peak power of the modulation signal and decreased radiation outside the bandwidth can be realized simultaneously. Further, since the proposed method can reduce the peak without dependence on the spectral shape of the modulation signal, the method can be applied to various wireless communications systems that have modulation signals with a large peak power. In order to evaluate the effectiveness of the proposed scheme, numerical simulations are performed with OFDM signals having a large peak power as the modulation signals in order to demonstrate the excellent peak reduction effects. (C) 2006 Wiley Periodicals, Inc.
A simple algorithm is presented which does not require inversion of the covariance matrix of received signals. Besides computational simplicity, it has the advantage of reducing the sensitivity to beam pointing error.
A simple algorithm is presented which does not require inversion of the covariance matrix of received signals. Besides computational simplicity, it has the advantage of reducing the sensitivity to beam pointing error.
This paper solves the binary single-constrained Knapsack Problem (KP) and undertakes a sensitivity analysis of its optimum solution. Given a knapsack of capacity c, and a set of n items, with each item j, j = 1, . . ....
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This paper solves the binary single-constrained Knapsack Problem (KP) and undertakes a sensitivity analysis of its optimum solution. Given a knapsack of capacity c, and a set of n items, with each item j, j = 1, . . . ,n, characterised by a weight w(j) and a profit p(j), the binary single-constrained KP picks a subset of these items with maximal total profit while obeying the constraint that the maximum total weight of the chosen items does not exceed c. This paper proposes an adaptive branch and bound tree search algorithm that exactly solves the problem, and provides the limits of the sensitivity intervals, which guarantee the stability of the optimal solution when the profit of any arbitrary item is perturbed. Next, the paper adapts the exact algorithm for the perturbation of the weight coefficient of an arbitrary item. The computational results demonstrate the effectiveness of the adaptive algorithm. [Received: 16 March 2007;Revised: 08 August 2007;Accepted: 16 November 2007]
There are some cases where feedforward control can be utilized effectively, e.g., the active noise control and the vibration control of a building. When there exists an indeterministic factor or a fluctuation, the ada...
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There are some cases where feedforward control can be utilized effectively, e.g., the active noise control and the vibration control of a building. When there exists an indeterministic factor or a fluctuation, the adaptive filter must be introduced. The algorithm that adjusts the coefficient of the adaptive filter has mostly been based on the filtered-x algorithm. A problem in this approach, however, is that the stability is not guaranteed and the stepwidth of least-mean square (LMS) algorithm must carefully be determined. From such a viewpoint, this paper proposes the adaptive algorithm both in the time and the frequency domains, where an arbitrary stepwidth can be used, and the robust stability is guaranteed even if an additive noise is mixed. As the first step, the infinite impulse response (IIR) adaptive filter is considered, aiming at implementation of the controller in the time domain, and the properties of the adaptive algorithm are analyzed. Then, the adaptive algorithm in the frequency domain is proposed where the controller is implemented using the frequency-sampling filter and the stability is guaranteed. In contrast to the case of the design in the time domain, the implementation in the frequency domain has the advantage that the realization is ensured independently of the order or the structure. Finally, the usefulness of the proposed adaptive algorithm is demonstrated by numerical example and experiment in the active noise canceler.
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