Power-Controlled Reverse Channel Training in a Multiuser TDD-MIMO Spatial Multiplexing System With CSIR

This paper considers the design of a power-controlled reverse channel training (RCT) scheme for spatial multiplexing (SM)-based data transmission along the dominant modes of the channel in a time-division duplex (TDD) multiple-input and multiple-output (MIMO) system, when channel knowledge is available at the receiver. A channel-dependent power-controlled RCT scheme is proposed, using which the transmitter estimates the beamforming (BF) vectors required for the forward-link SM data transmission. Tight approximate expressions for 1) the mean square error (MSE) in the estimate of the BF vectors, and 2) a capacity lower bound (CLB) for an SM system, are derived and used to optimize the parameters of the training sequence. Moreover, an extension of the channel-dependent training scheme and the data rate analysis to a multiuser scenario with M user terminals is presented. For the single-mode BF system, a closed-form expression for an upper bound on the average sum data rate is derived, which is shown to scale as ((L-c - L-B,L- tau)/L-c) log logM asymptotically in M, where L-c and L-B,L- tau are the channel coherence time and training duration, respectively. The significant performance gain offered by the proposed training sequence over the conventional constant-power orthogonal RCT sequence is demonstrated using Monte Carlo simulations.

GROUND COOLING SYSTEM FOR IMPROVING THE EFFICIENCY OF LOW TEMPERATURE POWER GENERATION

This paper presents an analysis of an organic Rankine cycle (ORC) with dry cooling system aided by an earth-coupled passive cooling system. Several organic fluids were considered as working fluids in the ORC in the temperature range of 125-200 degrees C. An earth-air-heat-exchanger (EMU) is studied for a location in the United States (Las Vegas) and another in India (New Delhi), to pre cool the ambient air before entering an air-cooled condenser (ACC). It was observed that the efficiency of the system improved by 1-3% for the system located in Las Vegas and fluctuations associated with temperature variations of the ambient air were also reduced when the EAHE system was used. A ground-coupled heat pump (GCHP) is also studied for these locations where cooling water is pre cooled in an underground buried pipe before entering a condenser heat exchanger in a closed loop. The area of the buried pipe and the condenser size are calculated per kW of power generation for various working fluids.

An adaptive sliding mode control law for the power maximization of the wind turbine system

POWERENG 2011

The predicting power of models for eutrophication

Restoration of water-bodies from eutrophication has proved to be extremely difficult. Mathematical models have been used extensively to provide guidance for management decisions. The aim of this paper is to elucidate important problems of using models for predicting environmental changes. First, the necessity for a proper uncertainty assessment of the model, upon calibration, has not been widely recognized. Predictions must not be a single time trajectory; they should be a band, expressing system uncertainty and natural variability. Availability of this information may alter the decision to be taken. Second, even with well-calibrated models, there is no guarantee they will give correct projections in situations where the model is used to predict the effects of measures designed to bring the system into an entirely different ”operating point”, as is typically the case in eutrophication abatement. The concept of educated speculation is introduced to partially overcome this difficulty. Lake Veluwe is used as a case to illustrate the point. Third, as questions become more detailed, such as ”what about expected algal composition”, there is a greater probability of running into fundamental problems that are associated with predicting the behaviour of complex non-linear systems. Some of these systems show extreme initial condition sensitivity and even, perhaps, chaotic behaviour, and are therefore fundamentally unpredictable.

The oculomotor system: (1) Vertical-horizontal interaction and signal recognition, (2) Time delays and power spectra

In the first section of this thesis, two-dimensional properties of the human eye movement control system were studied. The vertical - horizontal interaction was investigated by using a two-dimensional target motion consisting of a sinusoid in one of the directions vertical or horizontal, and low-pass filtered Gaussian random motion of variable bandwidth (and hence information content) in the orthogonal direction. It was found that the random motion reduced the efficiency of the sinusoidal tracking. However, the sinusoidal tracking was only slightly dependent on the bandwidth of the random motion. Thus the system should be thought of as consisting of two independent channels with a small amount of mutual cross-talk.

These target motions were then rotated to discover whether or not the system is capable of recognizing the two-component nature of the target motion. That is, the sinusoid was presented along an oblique line (neither vertical nor horizontal) with the random motion orthogonal to it. The system did not simply track the vertical and horizontal components of motion, but rotated its frame of reference so that its two tracking channels coincided with the directions of the two target motion components. This recognition occurred even when the two orthogonal motions were both random, but with different bandwidths.

In the second section, time delays, prediction and power spectra were examined. Time delays were calculated in response to various periodic signals, various bandwidths of narrow-band Gaussian random motions and sinusoids. It was demonstrated that prediction occurred only when the target motion was periodic, and only if the harmonic content was such that the signal was sufficiently narrow-band. It appears as if general periodic motions are split into predictive and non-predictive components.

For unpredictable motions, the relationship between the time delay and the average speed of the retinal image was linear. Based on this I proposed a model explaining the time delays for both random and periodic motions. My experiments did not prove that the system is sampled data, or that it is continuous. However, the model can be interpreted as representative of a sample data system whose sample interval is a function of the target motion.

It was shown that increasing the bandwidth of the low-pass filtered Gaussian random motion resulted in an increase of the eye movement bandwidth. Some properties of the eyeball-muscle dynamics and the extraocular muscle "active state tension" were derived.

20-W average power, high repetition rate, nanosecond pulse with diffraction limit from an all-fiber MOPA system

In this article, we report an all-fiber master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse with diffraction-limit. The system was constructed using a (2 + 1) X 1 multimode combiner. The Q-Switched, LD pumped Nd:YVO4 solid-state laser wets used (is master oscillator. The 976-nm fiber-coupled module is used as pump source. A 10-m long China-made Yb3+-doped D-shape double-clad large-mode-area fiber was used as amplifier fiber. The MOPA produced as much as 20-W average power with nanosecond pulse and near diffraction limited. The pulse duration is maintained at about 15 its during 50-175 kHz. The system employs a simple and compact architecture and is therefore suitable for the use in practical applications such as scientific and military airborne LIDAR and imaging. Based oil this system. the amplification performances of. the all fiber amplifier is investigated. (C) 2008 Wiley Periodicals, Inc.

A power optimised narrowband power-line communication system

Narrowband Power-line Communication (NPLC) technology uses a narrow bandwidth to transmit information. Its major applications include control, smart home systems and security. This paper proposes a power optimised NPLC system to minimise its systemic power consumption without compromising its communication ability. By using the proposed Smart Energy Conservation Layer which reads the signal strength from the PLC channel, a power optimised system is achieved to provide the essential transmitting power to secure the communications. Compared to commercial systems, the potential power saving could be up to 99% in a household environment, as demonstrated by the experimental results. © 2013 IEEE.

IMPROVED PEAK POWER METHOD FOR MEASURING FREQUENCY RESPONSES OF PHOTODETECTORS IN A SELF-HETERODYNE SYSTEM

An improved peak power method for measuring frequency responses of photodetectors in a self-heterodyne system consisting of a distributed Bragg reflector laser is proposed. The time-resolved spectrum technique is used to measure the peak power of the beat signal and the intrinsic linewidth of heat signal for calibration. The experimental results show that the impact of the thermal-induced frequency drift, which is the main reason for producing an error in measurement by conventional peak power method and spectrum power method, can be removed.

High-power electroabsorption modulator for radio over fibre system

An electroabsorption modulator using an intra-step quantum well (IQW) active region is fabricated for a radio over fibre system. The strain-compensated InGaAsP/InGaAsP IQW shows good material quality and improved modulation properties, high extinction ratio efficiency (10 dB V-1) and low capacitance (< 0.42 pF), with which high frequency (> 15 GHz) can be obtained. High-speed measurement under high-power excitation shows no power saturation up to an excitation power of 21 dBm. To our knowledge, the input optical power is the highest reported for a multi-quantum well EAM without a heat sink.