This paper proposes a simple control method to improve the ignition behavior of cold cathode fluorescent lamp (CCFL) in digital-dimming control. Due to restriking manipulation in digital-dimming mode, the lamp life of CCFL is reduced substantially. To extend the lamp life, we realize a digital-dimming controller with soft-starting technique (DDC-SST) to reduce the high ignition voltage and to eliminate the ignition current spike. The half-bridge resonant inverter is employed in the presented backlight system. Complete analysis and design considerations are discussed in detail in this paper. Simulation and experimental results are close to the theoretical prediction. The overall efficiency of the system achieved at the rated power is over 91%. The ignition voltage is reduced about 30% without any lamp current spike occurred under digital-dimming operation.

With the need and adoption of link aggregation where multiple links exist between two adjacent nodes in order to increase transmission capacity between them, there arise the problems of service guarantee and fair sharing of multiple servers. Although a lot of significant work has been done for single-server scheduling disciplines in the past years, not much work is available for multi-server scheduling disciplines. In this paper, we present and investigate two round robin based multi-server scheduling disciplines, which are Multi-Server Uniform Round Robin (MS-URR) and Multi-Server Deficit Round Robin (MS-DRR). In particular, we analyze their service guarantees and fairness bounds. In addition, we discuss the misordering problem with MS-DRR and present a bound for its misordering probability.

An adaptive interpolated FIR (IFIR) echo canceller was recently proposed for xDSL applications. This canceller consists of an FIR filter, an IFIR filter, and a tap-weight overlapping and nulling scheme. The FIR filter is used to cancel the short and rapidly changing head echo while the IFIR filter is used to cancel the long and slowly decaying tail echo. This echo canceller, which inherits the stable characteristics of the conventional FIR filter, requires low computational complexity. It is well known that the interpolation filter for an IFIR filter has great influence on the interpolated result. In this paper, a least-squares method is proposed to obtain optimal interpolation filters such that the performance of the IFIR echo canceller can be further improved. Simulations with a wide variety of loop topologies show that the optimal IFIR echo canceller can effectively cancel the echo up to 73.0 dB (for an SHDSL system). About 57% complexity reduction can be achieved compared to a conventional FIR filter.

The effects of air-intake format of forced-air-cooled equipment on the efficiency of air conditioning systems are studied. A modern data center features a large number of information-processing devices to provide telecommunication services. These devices generate considerable heat, and the equipment that houses these devices often employs "forced air cooling" in which a cooling effect is achieved by sucking in large amounts of room air. An air conditioning system used for a machine room filled with such equipment therefore requires high fan driving power resulting in significantly low air conditioning efficiency. In this study, we first performed mockup-based experiments to obtain a quantitative understanding of how different air-intake formats for equipment affect the temperature at various room locations such as equipment intake. We then created a model for predicting the temperature at various locations, and on the basis of this model, we analyzed the factors affecting intake temperature and examined how intake temperature affects air conditioning efficiency. It was found that placing air inlets in the lower 1/3 portion of forced-air-cooled equipment could prevent the equipment from reabsorbing the hot air that it blows out and therefore improve air conditioning efficiency.

This study investigates the effect of the method of time division in frequency domain ICA on estimation accuracy of ICA. We show that source signals expressed in the frequency domain lose non-Gaussianity and independence because of the long and overlapping window function, respectively, in time division. Consequently, the estimation accuracy of ICA decreases.

This paper proposes an independent control for parallel-connected multiple uninterruptible power supply (UPS) systems based upon a very simple control scheme. Here, the amplitude and phase angle of the output voltage are the controllable variables. With the only measurement of the output current, the active and reactive components are calculated to define the control variables. The entire system including the equations for the circuit, control and voltage limiters is well represented by a small-signal model, in which the computation of its eigenvalues constitutes the stability proof of the system. The root locus diagram gives an overall panorama of the system performance as a function of a certain gain and it aims to aid the further understanding and the design of the control. The experimental verification is carried out using a mere proportional-integral control scheme, which is a special case of the general control equation used in the theoretical analysis. For some situations, experiments show a flow of lateral current between UPS's, which causes an unbalanced current distribution. By increasing the proportional gain of the control equation for the output voltage amplitude, the lateral current can be substantially suppressed with a consequent improvement of the load sharing. Experimental results under various conditions show excellent results in terms of synchronization, load sharing and stability for three distinct output rating UPS's connected in parallel.

Discrete-time queueing models have been studied for many years because of their direct applicability in the performance evaluation of digital communication system and networks, where buffers are used to temporarily store information packets which cannot be transmitted instantaneously. In this paper, we investigate the behavior of a discrete-time multiserver buffer system with infinite buffer size. Packets arrive in the system according to a two-state correlated arrival process. The service times of the packets are assumed to be independent and identically distributed according to a geometric distribution. We present an analytical technique, based on the use of generating functions, for the analysis of the system. Explicit expressions are obtained for the mean values, the variances and the tail distributions of the system contents and the packet delay. The influence of the various model parameters on the behavior of the system is shown by means of some numerical examples.

New Recommendation and Future Standards highlight the Power Factor Correction (PFC) converter as a basic requirement for switching power supplies. Most high-frequency power factor correctors use resistor emulation to achieve a near-unity power factor and a small line current distortion. This technique requires forcing the input current with an average-current-mode control to follow the input voltage. Stability of this system was discussed previously by using some linear models. However, in this paper, two nonlinear phenomena have been encountered in the PFC circuit, period doubling bifurcation and chaos. Detection of these new instability phenomena in the stable regions predicted by the prior linear PFC models makes us more susceptible towards them, and reveals the need to consider a nonlinear models. A nonlinear model performing the practical operation of a boost PFC converter has been developed. Then, a simplified and accurate nonlinear model has been proposed and verified experimentally. As a result from this model, instability maps have been introduced to determine the boundary between stable and unstable operating ranges. Then, the period doubling bifurcation has been studied through a new proposed technique based on the capacitor storage energy. It is cleared that, As the load lessens, a required extra storage power is needed to achieve the significant increase in the output voltage. Then, if the PFC system can provide this extra energy, the operation can reach stability with new zero-storage energy else the system will have double-line zero energy that is period doubling bifurcation.

We consider a rate control algorithm for elastic services to allocate bandwidth in a network subject to throughput and fairness constraints. Our algorithm achieves a max-min fair bandwidth allocation among contending elastic connections, and has desirable properties in that it can operate in a decentralized and asynchronous manner accounting in part for heterogeneity in round trip delays. The algorithm is simple and scalable in that, 1) the network links make local measurements of capacity and calculate local 'explicit rates' which are fed back to sources without requiring knowledge of the number of on-going connections, while 2) sources adjust their transmission rates so as not to exceed the received explicit rate indication. The algorithm is designed to track a "dynamic" network environment. We discuss its stability, convergence, and feasibility issues related to fair allocation and rate-based flow control. We also consider the role of sessions with priorities to differentiate among users with elastic services. Through rigorous analysis and simulations, we have shown that it has indeed desirable characteristics for networks with elastic services as well as other service types, which are expected to be common in future network environment.

This paper presents a novel self-excited ZVS half-bridge converter. This converter including a self-oscillating control circuit is very simply constructed. The converter achieves excellent efficiency, low voltage stress across the switches and low EMI noise by using zero-voltage-switching technique. This converter stores not only magnetic energy in the primary winding of the transformer but also electrostatic energy on the resonant capacitor during the on-periods, so that the converter realizes the miniaturization of the transformer, the reduced conduction losses and the low current stress in the switch. This paper analyzes the behavior of static characteristics by using an extending state-space-averaging method and presents design equations. Based on the analysis, two prototype converters are designed for a 120 W output and a 350 W output. Experimental results are given for two converters and they confirm the validity of the theory. The proposed converters have displayed excellent performance.

The design, manufacture, and test results are presented for a 90polarization-rotating Van Atta array reflector with suppressed scattered field for the 1.27-GHz band. The reflector consists of 48 element antennas, half for horizontal polarization and half for vertical polarization. It receives a horizontally or vertically polarized wave and retransmits a vertically or horizontally polarized wave, respectively. The measured cross-polarized radar cross section of the reflector was 15.8 dBm2 on average, which agreed well with a theoretical prediction. Although the suppression of the scattered field was limited to about -20 dB relative to the retransmitted field, we could suppress more the scattered field by accurate positioning and careful characteristics adjustment of element antennas. Theoretical calculations showed that total phase errors of the element antennas including positioning errors and impedance characteristics errors have to be within 7.5to suppress the scattered field by less than -30 dB.

In this letter, a generalized extension of the linear Z4 space time (ST) code of [1] is conducted to obtain a linear Zw structure that can be flexibly used for various numbers of transmitter antennas, number of states, and modulation types. Additionally, the corresponding recursive systematic (RS) code structure is presented. The optimal code of the quadrature phase shift keying (QPSK) and 8 phase shift keying (PSK) modulation with 2 transmit antenna case is obtained from a code search and analyzed in comparison to the codes of [5]. Additionally, the structure for the 8, 32, and other number of states that were not provided in are [1] presented in this paper.

With the growing design complexity of contemporary embedded systems, real-time operating systems (RTOSs) have become one of important components of such complex embedded systems. This paper presents an RTOS-centric hardware/software cosimulator which we have developed for embedded system design. One of the most remarkable features in our cosimulator is that it has a complete simulation model of an RTOS which is widely used in industry, so that application tasks including RTOS service calls are natively executed on a host computer. Our cosimulator also features cosimulation with functional simulation models of hardware written in C/C++ and cosimulation with HDL simulators. A case study with a JPEG decoder application demonstrates the effectiveness of our cosimulator.

The polarized absorption measurement was employed to investigate the orientational order of the 4-n-4-pentyl-cyanobiphenyl (5CB) film of sub-nanometer thick. It was confirmed that this optical technique is simple but effective to observe the second orientational order parameter, S2, of the organic ultra thin film at the interface region.

Newly designed cyclometalated iridium phosphors bearing 2,3-diphenylquinoxalines were characterized to provide highly efficient and vivid-red emitting materials for electrophosphorescent organic light-emitting devices. Excellent quantum efficiencies for photoluminescence (PL) within a range 50-79% were observed in dichloromethane solutions at room temperature. A greatly improved PL decay lifetime of 1.1 µsec was also observed in CBP coevaporated film. Luminescence peak wavelengths of the phosphors lay within a preferable range 653-675 nm in evaporated films. The most vivid-red electroluminescence with 1931 CIE chromaticity coordinates of (x=0.70, y=0.28) was successfully attained.

The problem of signal restoration in the presence of observation space noise has been tackled extensively. However, restoration of degraded signals in the presence of signal space noise leads to considerable complexity because it becomes difficult to distinguish between the original signal and the noise. In this paper, a partial projection filter has been devised for the restoration of signals degraded by both the signal space and the observation space noises. A closed form of the proposed filter has been derived and its performance has been verified experimentally.

This paper presents a novel ZVS bidirectional 1 kW class DC-DC converter used for a photovoltaic (PV) system. The proposed circuit is based on a boost&buckboost converter, which consists of a boost converter and a buckboost converter. Bidirectional soft switching is realized by using of coupled inductors and auxiliary switches in the circuit. From the analysis of the circuit operation, ZVS conditions of the switches are derived. In the experiment, the maximum efficiency of the proposed converter during forward power flow was 97.1% on output power of 320 W.

This paper presents a novel current driving method for the synchronous rectifier (SR) in a Flyback topology. Compared to the previous proposed Current Driven Synchronous Rectifier (CDSR), the proposed CDSR features simple structure, low power loss and good performance. The proposed SR driving method is implemented in a 64 W Flyback converter with universal input, and efficiency as high as 92.5% is achieved at low input (90 V ac) and full load condition.

A look-up table (LUT) cascade is a new type of a programmable logic device (PLD) that provides an alternative way to realize multiple-output functions. An LUT ring is an emulator for an LUT cascade. Compared with an LUT cascade, the LUT ring is more flexible. In this paper we discuss the realization of multiple-output functions with the LUT ring. Unlike an FPGA realization of a logic function, accurate prediction of the delay time is easy in an LUT ring realization. A prototype of an LUT ring has been custom-designed with 0.35 µm CMOS technology. Simulation results show that the LUT ring is 80 to 241 times faster than software programs on an SH-1, and 36 to 93 times faster than software programs on a PentiumIII when the frequencies for the LUT ring and the MPUs are the same, but is slightly slower than commercial FPGAs.

This paper treats the least-squares linear filtering and smoothing problems of discrete-time signals from uncertain observations when the random interruptions in the observation process are modelled by a sequence of independent Bernoulli random variables. Using an innovation approach we obtain the filtering algorithm and a general expression for the smoother which leads to fixed-point, fixed-interval and fixed-lag smoothing recursive algorithms. The proposed algorithms do not require the knowledge of the state-space model generating the signal, but only the covariance information of the signal and the observation noise, as well as the probability that the signal exists in the observed values.