Diversity analysis for frequency-selective MIMO-OFDM systems with general spatial and temporal correlation model

In this paper, the effect of a general spatial and temporal fading correlation structure on the performance of coded multiple-input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems is studied. The analysis handles an arbitrary joint transmit-receive spatial correlation model, including the non-Kronecker model. An upper bound on the maximum achievable diversity order for frequency-selective MIMO-OFDM systems with general temporal and spatial correlation is derived. Furthermore, a space-time-frequency code design that can achieve the upper bound for any arbitrarily correlated channel scenario is provided. The general framework of the analysis includes space-frequency (SF)-coded systems as a special case. For the SF-coded MIMO-OFDM system, it is shown that any SF code designed to achieve full diversity in the independent fading channel can achieve full diversity in an arbitrary spatially correlated channel. The derived analytical results are consistent with those in the existing literature for special correlation structures. Extensive simulation results are provided to confirm the theoretical analysis.     

Fuzzy Geographic Information Systems for Phytoremediation Plant Selection

Geographic information systems (GIS) technology was combined with fuzzy logic to construct a phytoremediation plant selection tool. Phytoremediation involves the use of vegetation for treatment of contaminated soils, sediments, and water. In this paper, the focus is on one particular phytoremediation mechanism plant-assisted bioremediation of polycyclic aromatic hydrocarbon (PAH) soil contamination. Many plants show potential for PAH remediation, but factors such as growth requirements, climate, and soil conditions need to be considered. Given the spatial nature of the data involved, GIS was chosen as the basis for the plant selection tool. Eight candidate plants were selected because of their PAH phytoremediation potential, and their growth requirements were represented using fuzzy membership functions to account for parameters’ uncertainty. Vermont and South Carolina were selected as case studies, and calculations were performed to determine the suitability ratings for each of the candidate plants in these areas based on the plants’ growth requirements with respect to climate and soil attributes.     

Design∕Control Optimization of Cross‐Ply Laminates Under Buckling and Vibration

The optimal layer thicknesses and optimal feedback control function are determined for a symmetric, cross‐ply laminate. The objectives of the optimization are to maximize the biaxial buckling load (design objective) and to minimize the dynamic response to external disturbances (control objective) subject to a constraint on the expenditure of control energy. The design∕control problem is formulated as a multiobjective optimization problem by employing a performance index that combines the design and control objectives in a weighted sum. Numerical results are given for a laminate made of an advanced composite material. Comparisons of controlled and uncontrolled laminates as well as optimally designed and nonoptimal laminates indicate the benefits of treating the design and control problems in unified formulation. The implications of solving these two problems are discussed. The values of optimal design and control variables are given for a number of problem parameters.     

Maximum Principle for Optimal Boundary Control of Vibrating Structures with Applications to Beams

A maximum principle is derived for open-loop boundary control of one dimensional structures undergoing transverse vibrations. The optimal control law is obtained using a maximum principle and the applicability of the results to the boundary control of vibrating beams is demonstrated. The method of solution involves the transformation of the original problem into one with homogeneous boundary conditions for a general set of boundary forces and torques. An adjoint variable is introduced and used in the formulation of a Hamiltonian function which in turn leads to the derivation of the maximum principle. The effectiveness of the proposed control mechanism is illustrated numerically and it is shown that the implementation of the optimal boundary control using one force actuator can lead to substantial decrease in the dynamic response of a vibrating beam.     

Interfacial tensions of oil,water, chemical dispersant systems

Oil-water interfacial tension measurements are reported for systems of crude oils, distilled and salt water, and chemical dispersants, using the spinning drop technique. By varying the amount of dispersant and the volumetric ratio of water to oil it is possible to deduce an effective oil-water partition coefficient for the interfacial tension reducing species and to suggest a relationship between the extent of interfacial tension reduction and dispersant concentration. The implications of the results in assessing the mechanism and effectiveness of the chemical dispersion process are discussed.     

Thermodynamics of HCl in water—ethylene carbonate mixtures

The emf of the cell: Pt; H₂ (1 atm.)/HCl (m), Ethylene carbonate (x), H₂O (100?x)/AgCl, Ag is measured at 5° interval in the temperature range 25 to 45°C. The standard potential of the silver—silver chloride electrode, E^o_m, is determined in each solvent mixture covering the range 0–78% EC. The temperature coefficient is calculated using the method of least squares. The mean activity coefficient of HCl, γ_±, is determined for molalities between 0.01 and 0.05 m in each case. The primary, secondary and total medium effects are calculated. From the variation of the mean activity coefficient with temperature, the relative partial molal heat content $\text{L}$₂ of HCl is computed. $\text{L}$₂ passes through a minimum at 30% for 0.05 m HCl at all temperatures. The effect of temperature on $\text{L}$₂ permits the evaluation of the corresponding relative partial molal specific heat $\text{J}$₂.     

Measurements of cavity ringdown spectroscopy of acetone in the ultraviolet and near-infrared spectral regions: potential for development of a breath analyzer

We report a study on the cavity ringdown spectroscopy of acetone in both the ultraviolet (UV) and the near-infrared (NIR) spectral regions to explore the potential for development of a breath analyzer for disease diagnostics. The ringdown spectrum of acetone in the UV (282.4-285.0 nm) region is recorded and the spectrum is in good agreement with those obtained by other spectral techniques reported in the literature. The absorption cross-section of the C-H stretching overtone of acetone in the NIR (1632.7-1672.2 nm) is reported for the first time and the maximum absorption cross-section located at 1666.7 nm is 1.2 x 10(-21) cm(2). A novel, compact, atmospheric cavity with a cavity length of 10 cm has been constructed and implemented to investigate the technical feasibility of the potential instrument size, optical configuration, and detection sensitivity. The detection limit of such a mini cavity employing ringdown mirrors of reflectivity of 99.85% at 266 nm, where acetone has the strongest absorption, is approximately 1.5 ppmv based on the standard 3 criteria. No real breath gas samples are used in the present study. Discussions on the detection sensitivity and background spectral interferences for the instrument development are presented. This study demonstrates the potential of developing a portable, sensitive breath analyzer for medical applications using the cavity ringdown spectral technique.     

Dynamic optimization of framed structures

An analytical procedure for the determination of the least weight structure which satisfies a specific frequency requirement plus upper and lower bounds on the design variables is presented. The design algorithm is an iterative solution of the Kuhn-Tucker optimality criterion. The procedure is to modify an existing design to first obtain the correct structural frequency and then, while the frequency is held constant, to minimize the weight. This is accomplished using gradient equations derived in matrix notation for direct application to the finite element method of analysis.

The most important features of the algorithm are: (a) a small number of design iterations are needed to reach optimal or near-optimal design, (b) structural elements with a wide variety of size stiffness may be used.

The procedure has been completely automated in a computer program. Results of two numerical examples show that the method is convergent and that optimized configurations can be determined in as few as 10 redesign cycles.     

Studies on β-alkoxypropionitriles as solvents for extractive distillation

Five solvents of the β-alkoxypropionitrile series have been studied by gas-chromatography in order to examine their potential usefulness as solvents for extractive distillation. Four isomers of C₄-olefin and a diene were used as solutes for the determination of activity coefficients at infinite dilution at 30°C. Relative volatilities were calculated for these solvents and compared with those for other commercial solvents used currently. Relative volatilities of seven C₄-hydrocarbons in two solvents were also studied and compared with the existing literature data for β-methoxypropionitrile containing 5% antisolvent. The present g.c. studies show that besides the well-studied β-methoxypropionitrile, the second member of the series, β-ethoxypropionitrile, also has the potential for use as a selective solvent.     

Preparation of New Fibers on the Basis of Codeine Imprinted Polymer

A monolithic copolymer of methacrylic acid-ethylene glycol dimathacrylate as a fiber with 2 cm length and 0.3 mm diameter, containing codeine (CO) template was prepared through thermal radical co-polymerization procedure. This fiber is a robust recognition material capable of mimicking natural systems, combined with solid-phase micro-extraction (SPME) and gas chromatography/mass spectrometry for the extraction of trace CO from various street-drug samples. Effective experimental parameters such as Methacrylic Acid (MAA), Ethylene glycol dimethacrylate (EDMA), and CO proportions, nature, and dimension of mold, copolymerization time and temperature were optimized. Experimental studies such as scanning electron microscopy (SEM) reveal that highly homogenate fiber was achieved that can preciously be used for the above mentioned goals.