Rain Scatter Interference in mm-Wave Broadband Fixed Wireless Access Networks Caused by a 2-D Dynamic Rain Environment

The classical Mie scattering theory together with the bistatic radar equation has been applied in this paper to quantify interference levels in broadband fixed wireless access (BFWA) for two different network topologies: mesh and cellular. The complete scattering analysis takes into account the realistic variations of rainfall along the propagation paths and inside the common volume. The interfering element is a rain cell model that follows closely the experimental characteristic dimension, decay and movement obtained in recent research by the authors. The signal-to-interference power ratios (S/I) for two different frequencies, 28 and 42 GHz, and several scattering angles have been calculated. They show that, when two beams cross each other, rain-induced interference must be taken into account for an efficient planning of radio communication systems operating at these millimeter-wave frequencies as well as for an adequate design and implementation of fade mitigation techniques.     

Avoiding crevice corrosion by laser surface treatment

The present work shows that laser surface alloying of the creviced area on Al 7175-T7351 with chromium can avoid crevice corrosion. Corrosion takes places outside the crevice in conditions where the ratio of anodic area to cathodic area is favourable to minimize corrosion. As laser surface processing is adequate for treating small areas there is an enormous potential in this technology.     

Carbon fibre cloth as an electrode material: electrical conductivity and mass transfer

The paper deals with carbon fibre cloth electrodes, employed in the fabrication of composite materials. The electrical conductivity of single bundles, groups of bundles and cloth is studied. Ohm's law applies to the electrical conduction in the direction of the fibre length, but bundle conductivity decreases with the number of fibres in the bundle. Electrochemical mass transfer between a flowing electrolyte and a cloth arranged as a flow-through or a flow-by porous electrode indicates the existence of double porosity in the material. Due to double porosity, only the external surface of the cloth works as an electrode. This finding shows that the material is not suitable for such an application.     

Simultaneous analysis of downlink beacon dynamics and skybrightness temperature. Part I. Remote sensing of a slant path

This paper investigates the remote sensing of height and displacement velocity of turbulent clouds, composed mainly of liquid water, using a combination of simultaneous radiometric and geostationary satellite beacon measurements. Because a radiometer integrates the sky brightness temperature distribution observed within the solid angle subtended by the antenna beamwidth, the paper shows how this process can be modeled as a low-pass filter using the small angle approximation and the frozen-in hypothesis. The 3-dB cutoff frequency of that filter is used in conjunction with the Fresnel frequency of the amplitude scintillations power spectrum to derive the cross-path wind speed and the height of the turbulent layer/cloud. In order to quantify the 3-dB cutoff frequency of the filter-radiometer, a dual aperture radiometer was constructed and was used in conjunction with a ground station receiver monitoring the 39.5-GHz beacon transmissions of ITALSAT F1 and measuring amplitude scintillations. The experimental results derived on cloud heights are then compared with the vertical profiles obtained by a 94-GHz radar, indicating agreement except in those cases where the thickness of the cloud structure becomes important. This aspect is then discussed in the paper and a radiometric definition is given for the cloud height. Finally, the important aspect of instrumentation is described including the effect of the radiation pattern of a radiometer antenna upon the cross correlation and cross spectrum between two coaxial measured antenna temperatures     

Propagation of flicker in electric power networks due to windenergy conversions systems

Wind energy conversion systems (WECS) produce fluctuating output power, which may cause voltage fluctuations and flicker. Flicker assessment in networks may be difficult since its evaluation requires long computing time and special procedures to calculate the flicker severity index, Pst. In this paper, a frequency domain method to study flicker propagation is presented. This method is based on propagation of frequency components from WECS output currents throughout the grid. In this way, a fast flicker analysis in a network of any size can be performed. Also, an algorithm for flicker measurement in the frequency domain, which allows Pst calculation, is proposed. Several study cases have been performed, and results have been compared with time domain simulations, showing good agreement between them     

Breast abscess with lethal septicemia due to Pseudomonas aeruginosa in a patient with AIDS

OBJECTIVE: The incidence of Pseudomonas aeruginosa in HIV-infected patients has increased over the last years. We describe a case of pseudomonal breast abscess complicated with fatal septicemia in an AIDS patient. CASE REPORT: A 21-year-old woman was admitted for fever, chills, nausea, vomiting and pain in the breast. She had a swelling in the right breast of 3 days duration. HIV infection had been confirmed 6 years earlier. CD4 count was 2/mm3. Surgical drainage produced a blue-green purulent discharge which grew Pseudomonas aeruginosa on culture. Despite cloxacilin, then ceftazidime and amikacin, initial improvement was followed 2 weeks later by nodular pulmonary infiltration with cavitation. P. aeruginosa was recovered from sputum and blood cultures, but stepwise resistance developed and the patient died 3 months after admission. DISCUSSION: Breast abscesses are infrequent in nonlactating women. P. aeruginosa is rarely involved, even in HIV patients. Due to the risk of resistance, prompt administration of appropriate antibiotics is required.     

Characterization of hydroxyl-terminated polybutadiene

Commercial samples of hydroxyl terminated polybutadienes (HTPB) were analysed by ¹H and ¹³C NMR spectroscopy, in regard to hydroxylated end groups. The results were discussed and compared with those reported so far.     

Effect of HTPB structure on prepolymer characteristics and on mechanical properties of polybutadiene-based polyurethanes

Oligobutadiene-based prepolymers and polyurethanes (PU) were prepared from hydroxyl terminated polybutadiene (HTPB), three diisocyanates (aromatic, alicyclic and aliphatic) and two chain extenders (containing hydroxyl or amino groups). The free NCO content in the prepolymers varied systematically and the characteristic of these products were interpreted in terms of NCO group reactivity, propagation reactions and HTPB functionality. The mechanical properties of the polyurethane elastomers derived from the prepolymers were discussed in terms of hard and soft segment structures.     

Signage Versus Environmental Affordances: Is the Explicit Information Strong Enough to Guide Human Behavior During a Wayfinding Task?

This study aims to explore how people behave when they have to find a location within a complex building and are confronted with situations where directional signage (i.e., explicit information) is in opposition to environmental affordances that naturally direct users towards a specific path, creating a situation with conflicting information (e.g., a brighter corridor vs. a darker corridor but with a directional sign indicating to follow the darker one). A virtual reality–based methodology was used and a between‐subject design was considered. Thus, participants were given the tasks of finding three publicly accessible central points in a virtual hotel and confronted with a two forced‐choice task of local scenes in which environmental variables (i.e., corridor width and brightness) and signage varied systematically, in two experimental conditions (i.e., neutral and signage). For the signage condition, signs were inserted to explicitly point in the opposite direction than that implicitly suggested by the environmental affordances, creating situations with conflicting information. Results indicate that environmental variables were able to direct people indoors acting as environmental affordances. Users preferred to follow the wider and brighter paths. However, when directional signage pointed in the opposite direction of the paths preferred by the participants, most of them complied with signage.