Simple polynomial detectors for CDMA downlink transmissions on frequency-selective channels

In code-division multiple-access (CDMA) transmissions, computing the multiuser minimum mean-squared error (MMSE) detector coefficients requires the inversion of the covariance matrix associated to the received vector signal, an operation usually difficult to implement when the spreading factor and the number of users are large. It is therefore interesting to approximate the inverse by a matrix polynomial. In this correspondence, means for computing the polynomial coefficients are proposed in the context of CDMA downlink transmissions on frequency-selective channels, the users having possibly different powers. Derivations are made in the asymptotic regime where the spreading factor and the number of users grow toward infinity at the same rate. Results pertaining to the mathematics of large random matrices, and in particular to free probability theory, are used. Spreading matrices are modeled as isometric random matrices (spreading vectors orthonormality is a natural assumption in downlink) and also as random matrices with independent and identically distributed (i.i.d.) elements.     

On the asymptotic distribution of the correlation receiver output for time-hopped UWB signals

In ultra-wideband (UWB) communications based on time-hopping (TH) impulse radio, one of the most frequently studied receivers is the correlation receiver. The multiuser interference (MUI) at the output of this receiver is sometimes modeled as a Gaussian random variable. In order to justify this assumption, the conditions of validity of the Central Limit Theorem (CLT) have to be studied in an asymptotic regime where the number of interferers and the processing gain grow toward infinity at the same rate, with the channel degree being kept constant. An asymptotic study is made in this paper based on the so-called Lindeberg's condition for the CLT for martingales. Nonsynchronized users sending their signals over independent multipath channels are considered. These users may also have different powers. It is shown that when the frame length grows and the repetition factor is kept constant, then the MUI does not converge in distribution toward a Gaussian random variable. On the other hand, this convergence can be established if the repetition factor grows at the rate of the frame length. In this last situation, closed-form expressions for the signal-to-interference-plus-noise ratio (SINR) are given for TH pulse amplitude modulation (PAM) and pulse position modulation (PPM) UWB transmissions.     

Immersed stress method for fluid–structure interaction using anisotropic mesh adaptation

This paper presents advancements toward a monolithic solution procedure and anisotropic mesh adaptation for the numerical solution of fluid–structure interaction with complex geometry. First, a new stabilized three‐field stress, velocity, and pressure finite element formulation is presented for modeling the interaction between the fluid (laminar or turbulent) and the rigid body. The presence of the structure will be taken into account by means of an extra stress in the Navier–Stokes equations. The system is solved using a finite element variational multiscale method. We combine this method with anisotropic mesh adaptation to ensure an accurate capturing of the discontinuities at the fluid–solid interface. We assess the behavior and accuracy of the proposed formulation in the simulation of 2D and 3D time‐dependent numerical examples such as the flow past a circular cylinder and turbulent flows behind an immersed helicopter in a forward flight. Copyright © 2013 John Wiley & Sons, Ltd.     

Confidence limits for Neyman type A-distributed events

The Neyman type A distribution, a generalised, 'contagious' Poisson distribution, finds application in a number of disciplines such as biology, physics and economy. In radiation biology, it best describes the distribution of chromosomal aberrations in cells that were exposed to neutrons, alpha radiations or heavy ions. Intriguingly, no method has been developed for the calculation of confidence limits (CLs) of Neyman type A-distributed events. Here, an algorithm to calculate the 95% CL of Neyman type A-distributed events is presented. Although it has been developed in response to the requirements of radiation biology, it can find application in other fields of research. The algorithm has been implemented in a PC-based computer program that can be downloaded, free of charge, from www.pu.kielce.pl/ibiol/neta.     

Use of adjunctive treatment with interferon-gamma in an immunocompromised patient who had refractory multidrug-resistant tuberculosis of the brain

We describe a patient with acute lymphocytic leukemia and multidrug-resistant tuberculosis of the brain and spinal cord. Despite treatment with six antituberculous drugs and a steroid medication for 11 months, there was no appreciable clinical or radiological improvement in the patient's condition. Within 5 months of initiating adjunctive therapy with IFN-gamma and granulocyte colony stimulating factors, substantial neurological and radiological improvement was noted. Therapy with IFN-gamma was continued for 12 months, resulting in complete resolution of the lesions in the brain and spinal cord.     

Determinants of ultrafine particles,black carbon,nitrogen dioxide,and carbon monoxide concentrations inside vehicles in the Paris area: PUF-TAXI study

This study presents real-time concentrations of traffic-related air pollutants during 499 trips conducted by 50 Parisian taxi drivers from PUF-TAXI project. Ultrafine particles (UFP), black carbon (BC), and nitrogen dioxide (NO₂)/carbon monoxide (CO) were measured inside vehicles by Diffusion Size Classifier Miniature^®, microAeth^®, and Gas-Pro^®, respectively, for nine hours. Vehicle/trip data characteristics were collected by questionnaires and on ambient conditions by monitoring stations. The associations between pollutant levels and their potential determinants were analyzed using generalized estimating equation model. Determinants of in-vehicle pollutants levels were identified: (1) ambient factors (meteorology and ambient pollution)—affecting BC, NO_2, and CO; (2) vehicle characteristics—affecting all pollutants; and (3) trip-related driving habits—affecting UFP, BC, and CO. We highlight that commuters can, therefore, avoid high in-vehicle air pollutant concentrations mainly by (1) closing windows and activating air-conditioning under air recirculation mode in congested traffic; (2) smooth driving; and (3) maintaining cabin air filters.     

Identification and transport investigation of microbial volatile organic compounds in full-scale stud cavities

An experimental project was conducted to investigate mold products, namely spores and volatile organic compounds (VOCs) in the cavity of full-scale stud wall assemblies. Twenty specimens were constructed and tested to inquire the capacity of wall cavities to restrain mold products, emanating from studs with 10% of their surface covered with mold, from penetrating into the indoor space. The tests were designed primarily to study the movement of spores. The project was subsequently extended to investigate the identification of microbial volatile organic compounds (MVOCs) and their transport through the building envelope. This paper presents the experimental design, testing procedure and a summary of the analysis conducted to identify mold related VOCs and their transport from the cavity to the indoor space, and the evaluation of the influence of experimental factors on this transport. Six experimental factors were investigated: air leakage path; mold presence; wall construction configurations (insulation, vapor barrier and sheathing material) and ambient conditions (dry and wet conditions). The chemical analysis of VOCs (volatile organic compounds) was performed using gas chromatography/mass spectrometry (GC/MS). Results are analyzed using multiple regression analysis to identify the mold related VOCs, and to determine the transport through the building envelope. Five VOCs are confirmed to be related to the mold presence in the cavity and the transport of these MVOCs is supported by the data. However, no significant effect of the construction factors on MVOC transport is detected.     

Investigation of solar potential of housing units in different neighborhood designs

The paper presents a methodology for investigating the influence of three major parameters in the design of two-storey housing units in different neighborhood layouts, on solar energy utilization potential. The parameters are geometric shapes of individual units, density of units and site layouts. Rectangular and L shape with different values of the angle enclosed between the wings of this shape are studied. The density parameter is represented by detached and multiplexed units. The effect of parallel rows of units is also studied. Site layouts include a straight road and south and north facing semi-circular roads. The EnergyPlus simulation package is used to simulate 26 configurations consisting of combinations of the parameter values. Effects are evaluated as the change from reference configurations of the response parameters - incident and transmitted irradiation of facades and integrated PV electricity generation. The results indicate that the total electricity generation is governed by active roof surface area which is affected by both shape and orientation. Up to 50% increase in electricity generation can be achieved in some housing units of certain configurations, compared to the reference. Variation of surface orientation, particularly in curved layouts enables the spread of peak electricity generation over up to 6 h.