Programmable Logic Controller (PLC) has been widely used in the industrial control. Inherently, the PLC-based system is a class of Hybrid Dynamical System (HDS) in which continuous state of the plant is controlled by the discrete logic-based controller. This paper firstly presents the formal algebraic model of the PLC-based control systems which enable the designer to formulate the various kinds of optimization problem. Secondly, the optimization problem of the 'sensor parameters,' such as the location of the limit switch in the material handling system, the threshold temperature of the thermostat in the temperature control system, is addressed. Finally, we formulate this problem as Mixed Logical Dynamical Systems (MLDS) form which enables us to optimize the sensor parameters by applying the Mixed Integer Programming.

We propose a novel approach for designing a low power datapath in wireless communication systems. Especially, we focus on the digital FIR filter. Our proposed approach can reduce the power consumption and the circuit area of the digital FIR filter by optimizing the bitwidth of the each filter coefficient with keeping the filter calculation accuracy. At first, we formulate the constraints about keeping accuracy of the filter calculations. We define the problem to find the optimized bitwidth of each filter coefficient. Our defined problem can be solved by using the commercial optimization tool. We evaluate the effects of consuming power reduction by comparing the digital FIR filters designed in the same bitwidth of all coefficients. We confirm that our approach is effective for a low power digital FIR filter.

We propose a method of controlling the view divergence of data freshness when copies of sites in a replicated database are updated asynchronously. The view divergence of the replicated data freshness is the difference in the recentness of the updates reflected in the data acquired by clients. Our method accesses multiple sites and provides a client with data that reflects all the updates received by the sites. First, we define the probabilistic recentness of updates reflected in acquired data as read data freshness (RDF). The degree of RDF of data acquired by clients is the range of view divergence. Second, we propose a way to select sites in a replicated database by using the probability distribution of the update delays so that the data acquired by a client satisfies its required RDF. This way calculates the minimum number of sites in order to reduce the overhead of read transactions. Our method continues to adaptively and reliably provide data that meets the client's requirements in an environment where the delay of update propagation varies and applications' requirements change depending on the situation. Finally, we evaluate by simulation the view divergence we can control using our method. The simulation showed that our method can control the view divergence to about 1/4 that of a normal read transaction for 100 replicas. In addition, the increase in the overhead of a read transaction imposed by our method is not as much as the increase in the total number of replicas.

Spatial correlation among antenna elements both at transmitter and receiver sides in MIMO communications is known to have a crucial impact on system performances. Another factor that can severely degrade receiver performances is the timing offset relative to the channel delay profile. In this paper we derive a novel receiver for turbo MIMO equalization in space-time-trellis-coded (STTrC) system to jointly address the problems described above. The equalizer is based on low complexity MMSE filtering. A joint detection technique of the several transmit antennas is used to reduce the receiver's sensitivity to the spatial correlation at the transmitter and receiver sides. Furthermore, only the significant portion of the channel impulse response (CIR) is taken into account while detecting signals. The remaining portion of CIR is regarded as the unknown interference which is effectively suppressed by estimating its covariance matrix. By doing this the receiver's complexity can be reduced since only a portion of the CIR has to be estimated and used for signal detection. Furthermore, by suppressing the interference from the other paths outside the equalizers coverage the receiver's sensitivity to the timing offset can be reduced. The proposed receiver's performance is evaluated using field measurement data obtained through multidimensional channel sounding. It is verified through computer simulations that the performance sensitivity of the joint detection-based receiver to the spatial correlation is significantly lower than with the receiver that detects only one antenna at a time. Furthermore, the performance sensitivity to the timing offset of the proposed receiver is shown to be significantly lower than that of the receiver that ignores the existence of the remaining multipath CIR components.

This letter considers frame synchronization in non-synchronized sampling discrete multi-tone (DMT) based asymmetric digital subscriber line (ADSL)/very high speed DSL (VDSL) systems in the presence of timing error. We propose a frame synchronization method which is based on the observation that the normalized correlation between two sequences separated by the FFT length is Cauchy random variable. The proposed approach uses less number of correlators, reducing computational complexity as well as demodulation delay than a previous approach. Therefore, ADSL/VDSL modems can be more power efficient and computationally less complex via the proposed frame synchronization method. Simulation results demonstrate the effectiveness of the proposed approach, comparing with the previous approach.

The performance of en-route web caching mainly depends on where the caches are located and how the cache contents are managed. In this paper, we address the problem of proxy placement in en-route web caching for tree networks, i.e., computing the optimal locations for placing k web proxies in a network such that some specified objectives are achieved. Based on our proposed model, we formulate this problem as an optimization problem and compute the optimal locations using a computationally efficient dynamic programming-based algorithm. We also extend our solution for tree networks to solve the same problem for autonomous systems. Finally, we implement our algorithms and evaluate our model on several performance metrics through extensive simulation experiments. We also compare the performance of our model with the best available heuristic KMPC model, as well as the random proxy placement model. The implementation results show that our model outperforms all the other models with respect to all performance metrics considered. The average improvements of our model over the KMPC model and the random proxy placement model are about 31.9 percent and 58.6 percent in terms of all the performance metrics considered.

This paper presents a wavelength lock system using a Z-cut quartz etalon supported at the middle point. The Z-cut quartz etalon possesses the cavity length modulation and the low temperature coefficient. We propose a Z-cut quartz etalon supported at the middle point in order to improve the modulation index and response time. The mechanism of the center supported Z-cut quartz etalon is described. We also show that the etalon possesses a high modulation index, a high Q factor, and a rapid response time in experimental results. A self-tuning dither oscillator realized by using quartz etalon is also described.

Parallel execution of the carry propagate adder (CPA) and leading non-zero (LNZ) detector that processes the CPA result is a common way to reduce the latencies of floating-point instructions. However, the conventional methods usually cause one-bit errors. We developed an exact LNZ detection circuit operating in parallel with the CPA. The circuit is implemented in the floating-point unit of our newly developed embedded processor core. Circuit simulation results show that the LNZ circuit has a similar speed to the CPA, and it contributes to make a small low-power FPU for an embedded processor core.

This paper presents two new intelligent methods to linearize the Multi-Carrier Power Amplifiers (MCPA). One of the them is based on the Neuro-Fuzzy controller while the other uses two small neural networks as a polar predistorter. Neuro-Fuzzy controllers are not model based, and hence, have ability to control the nonlinear systems with undetermined parameters. Both methods are adaptive, low complex, and can be implemented in base-band part of the communication systems. The performance of the linearizers is obtained via simulation. The simulation is performed for three different scenarios; namely, a multi-carrier amplifier for GSM with four channels, a CDMA amplifier and a multi-carrier amplifier with two tones. The simulation results show that Neuro-Fuzzy Controller (NFC) and Neural Network Polar Predistorter (NNPP) have higher efficiencies so that reduce IMD3 by more than 42 and 32 dB, respectively. The practical implementation aspects of these methods are also discussed in this paper.

Fair scheduling algorithms have been proposed to tackle the problem of bursty and location-dependent errors in wireless packet networks. Most of those algorithms ensure the fairness property and guarantee the QoS of all sessions in a large-scale cellular network such as GSM or GPRS. In this paper, we propose the Weighted-Sacrificing Fair Queueing (WSFQ) scheduling algorithm for small-area and device-limited wireless networks. WSFQ slows down the growth of queue length in limited-buffer devices, still maintains the properties of fairness, and guarantees the throughputs of the system. Moreover, WSFQ can easily adapt itself to various kinds of traffic load. We also implement a packet-based scheduling algorithm, the Packetized Weighted Sacrificing Fair Queueing (PWSFQ), to approach the WSFQ. WSFQ and PWSFQ are evaluated by comparing with other algorithms by mathematical analysis and simulations.

Materialized views, which are derived from base relations and stored in the database, offer opportunities for significant performance gain in query evaluation by providing quick access to the pre-computed data. A materialized view can be utilized in evaluating a query if it has pre-computed result of some part of the query plan. Although many approaches to utilizing materialized views in evaluating a query have been proposed, there exist several restrictions in selecting such views. This paper proposes new ways of utilizing materialized views in answering an aggregate query. Views including relations that are not referred to in the given query are utilized. Attributes missing from a view can be recovered under certain conditions. We identify the conditions where a view may be used in evaluating a query and present the algorithm to search for the most efficient query among the equivalent ones. We also report on a simulation based on the TPC-H and GRID databases. Simulation results show that our approach provides impressive performance improvements to the data warehousing environment where aggregate views are often pre-computed and materialized.

This study proposes a novel adaptive fuzzy control methodology to remove disadvantages of traditional fuzzy approximation based control. Meanwhile, the highly uncertain robot manipulator is taken as an application with either guaranteed robust tracking performances or asymptotic stability in a global sense. First, the design concept, namely, feedforward fuzzy approximation based control, is introduced for a simple uncertain system. Here the desired commands are utilized as the inputs of the Takagi-Sugeno (T-S) fuzzy system to closely compensate the unknown feedforward term required during steady state. Different to traditional works, the assumption on bounded fuzzy approximation error is not needed, while this scheme allows easier implementation architecture. Next, the concept is extended to controlling manipulators and achieves global robust tracking performances. Note that a linear matrix inequality (LMI) technique is applied and provides an easier gain design. Finally, numerical simulations are carried out on a two-link robot to illustrate the expected performances.

In this letter, a novel design of a branch-line coupler with considerable reduction in its size and suppressed harmonic passband is proposed. By embedding a defected ground structure (DGS) unit cell under a microstrip line, compact branch-line couplers are easily achieved. The electrical length is scaled appropriately according to the slow-wave effect. In this case, the experimental coupling (S21 or S31) is comparable to that of conventional branch-line couplers. Also, experimental results indicate that DGS section is quite effective for the suppression of higher order harmonics.

Path following circuits (PFC's) are circuits for solving nonlinear problems on the circuit simulator SPICE. In the method of PFC's, formulas of numerical methods are described by circuits, which are solved by SPICE. Using PFC's, numerical analysis without programming is possible, and various techniques implemented in SPICE will make the numerical analysis very efficient. In this paper, we apply the PFC's of the homotopy method to various nonlinear problems (excluding circuit analysis) where the homotopy method is proven to be globally convergent; namely, we apply the method to fixed-point problems, linear programming problems, and nonlinear programming problems. This approach may give a new possibility to the fields of applied mathematics and operations research. Moreover, this approach makes SPICE applicable to a broader class of scientific problems.

This paper addresses the estimation of time delay between two spatially separated noisy signals by system identification modeling with the input and output corrupted by additive white Gaussian noise. The proposed method is based on a modified adaptive Butler-Cantoni equalizer that decouples noise variance estimation from channel estimation. The bias in time delay estimates that is induced by input noise is reduced by an IIR whitening filter whose coefficients are found by the Burg algorithm. For step time-variant delays, a dual mode operation scheme is adopted in which we define a normal operating (tracking) mode and an interrupt operating (optimization) mode. In the tracking mode, only a few coefficients of the impulse response vector are monitored through L1-normed finite forward differences tracking, while in the optimization mode, the time delay optimized. Simulation results confirm the superiority of the proposed approach at low signal-to-noise ratios.

A siphon-trap(ST) of a Petri net N = (P,T,E,α,β) is defined as a set S of places such that, for any transition t, there is an edge from t to a place of S if and only if there is an edge from a place of S to t. A P-invariant is a |P|-dimensional vector Y with YtA = for the place-transition incidence matrix A of N. The Fourier-Motzkin method is well-known for computing all such invariants. This method, however, has a critical deficiency such that, even if a given Perti net N has any invariant, it is likely that no invariants are output because of memory overflow in storing intermediary vectors as candidates for invariants. In this paper, we propose an algorithm STFM_N for computing minimal-support nonnegative integer invariants: it tries to decrease the number of such candidate vectors in order to overcome this deficiency, by restricting computation of invariants to siphon-traps. It is shown, through experimental results, that STFM_N has high possibility of finding, if any, more minimal-support nonnegative integer invariants than any existing algorithm.

This letter presents a timing synchronization method of high-rate wireless personal area network (WPAN) systems encountered with a multipath fading channel. Two-stage timing synchronization using constant amplitude zero auto-correlation (CAZAC) training symbols and correlation techniques is adopted. At the same time, a simple way of setting a reliable threshold used to estimate WPAN timing is provided.

The role of electric field in metal-induced lateral crystallization (MILC) of amorphous Si (a-Si) under limited Ni-supply condition has been investigated. The nominal lateral-growth rate was increased from 3.6 µm/h (no-electric field) to 23 µm/h at the positive electrode side and reduced to 2.8 µm/h at the negative electrode side in presence of the electric field of 20 V/cm. However, spontaneously nucleated needle-like Si crystals were observed in the enhanced positive electrode side, which have been found to be independent of the MILC. Further investigation under the condition where Ni in the supply region was removed on the way of crystallization revealed that the electric field enhanced crystallization greatly reduced. These results indicate that the electric field does not enhance the MILC growth but enhances the diffusion of Ni in a-Si which takes place prior to the MILC growth.

Under the assumption that clock can be inputted to each register at an arbitrary timing, the minimum feasible clock period can be determined if delays between registers are given. This minimum feasible clock period might be reduced if delays between some registers are increased by delay insertion. In this paper, we propose a delay insertion algorithm to reduce the minimum clock period. First, the proposed algorithm determines a clock schedule ignoring some constraints. Second, the algorithm inserts delays to recover ignored constraints according to the delay-slack and delay-demand of the obtained clock schedule. We show that the proposed algorithm achieves the minimum clock period by delay insertion if the delay of each element in the circuit is unique. Experiments show that the amount of inserting delay and computational time are smaller than the conventional algorithm.

Several regular topologies have been proposed to be used as the logical topology for WDM networks. These topologies are usually evaluated and compared based on the metrics related to network performance. It can be simply shown that this is generally not sufficient since better network performance can be achieved by increasing more network facilities. However, doing this eventually increases the network cost. Thus, the comparison of topologies must be performed by using an evaluation function that includes both the network performance metric and the network cost. In this paper, we propose a model to find the optimum regular logical topology for wavelength routed WDM networks. ShuffleNet, de Bruijn graph, hypercube, Manhattan Street Network, and GEMNet are the five well-known and commonly used regular topologies compared in this paper. By solving the two subproblems on node placement optimization, and routing and wavelength assignment, we obtain the evaluation function used in the topology comparison. Numerical results show that GEMNet is the optimum logical topology for the wavelength routed WDM networks, where it can take one of the three forms of ShuffleNet, de Bruijn graph, and its own configurations.