Electronic neutron personal dosimetry with superheated drop detectors

The prototype of an electronic personal neutron dosemeter based on superheated drop detectors is presented. This battery operated device comprises a neutron sensor, bubble-counting electronics and a temperature controller ensuring an optimal dose equivalent response. The neutron sensor is a 12 ml detector vial containing an emulsion of about 50,000 halocarbon-12 droplets of 100 microns diameter. The temperature controller is a low-power, solid-state device stabilising the emulsion at 31.5 degrees C by means of an etched foil heater. The microprocessor controlled counting electronics relies on a double piezo-electric transducer configuration to record bubble formation acoustically via a comparative pulse-shape analysis of ambient noise and detector signals. The performance of the dosemeter was analysed in terms of the requirements presently developed for neutron personal dosemeters. The detection threshold is about 1 microSv, while the personal dose equivalent response to neutrons in the thermal to 62 MeV range falls within a factor 1.6 of 13 bubbles per microSv.     

Pervasive Personal Computing in an Internet Suspend/Resume System

The Internet suspend/resume model of mobile computing cuts the tight binding between PC state and PC hardware. By layering a virtual machine on distributed storage, ISR lets the VM encapsulate execution and user customization state; distributed storage then transports that state across space and time. This article explores the implications of ISR for an infrastructure-based approach to mobile computing. It reports on experiences with three versions of ISR and describes work in progress toward the OpenISR version     

TARA: Topology-Aware Resource Adaptation to Alleviate Congestion in Sensor Networks

Network congestion can be alleviated either by reducing demand (traffic control) or by increasing capacity (resource control). Unlike in traditional wired or other wireless counterparts, sensor network deployments provide elastic resource availability for satisfying the fidelity level required by applications. In many cases, using traffic control can violate fidelity requirements. Hence, we propose the use of resource control: increasing capacity by enabling more nodes to become active during periods of congestion. However, a naive approach to increase resources without a careful consideration of the type of congestion, traffic pattern, and network topology make the situation worse. In this paper, we present TARA, a topology-aware resource adaptation strategy to alleviate congestion. The core of TARA is our capacity analysis model, which can be used to estimate capacity of various topologies. Detailed performance results show that TARA can achieve data delivery rate and energy consumption that is close to an ideal offline resource control algorithm.     

Above ground standing biomass and carbon storage in village bamboos in North East India

Bamboo forms an important component in the traditional landscape of North East India. For biomass estimation of village bamboos of Barak Valley, North East India, allometric relationships were developed by harvest method describing leaf, branch and culm biomass with DBH as an independent variable using a log linear model. The culm density of the stand was 8950 culms ha⁻¹ during 2005 of which 67% of growing stock was represented by Bambusa cacharensis, 17.88% by Bambusa vulgaris and 15.12% by Bambusa balcooa. Above ground stand biomass was 121.51 t ha⁻¹ of which 86% was contributed by culm component followed by branch (10%) and leaf (4%). With respect to species, B. cacharensis made up to 46% of total stand biomass followed by B. vulgaris (28%) and B. balcooa (26%). Carbon storage in the above ground biomass was 61.05 t ha⁻¹. Allocation of C was more in culm components (53.05 t ha⁻¹) than in branch (5.81 t ha⁻¹) and leaf (2.19 t ha⁻¹). Carbon storage in the litter floor mass was 2.40 t ha⁻¹, of which leaf litter made up the highest amount (1.37 t ha⁻¹) followed by sheath (0.86 t ha⁻¹) and branch (0.17 t ha⁻¹). Carbon stock in the soil up to 30 cm depth was 57.3 t ha⁻¹. Gross C stock in the plantation was estimated to be 120.75 t ha⁻¹. Carbon storage estimated in the bamboo stand of present study offers insights into the opportunity of village bamboos in the rural landscape for carbon storage through carbon sequestration. Management and utilization of village bamboos as a potential source of carbon sink by smallholder farmers are discussed in the context of their livelihood security and the Millennium Development Goals of the United Nations.     

An electronically tunable microstrip bandpass filter using thin-film Barium-Strontium-Titanate (BST) varactors

A tunable third-order combline bandpass filter using thin-film barium-strontium-titanate varactors and fabricated on a sapphire substrate is reported. Application of 0-200-V bias varied the center frequency of the filter from 2.44 to 2.88 GHz (16% tuning) while achieving a 1-dB bandwidth of 400 MHz. The insertion loss varied from 5.1 dB at zero bias to 3.3 dB at full bias, while the return loss exceeded 13 dB over the range. The third-order intercept of the filter was found to be 41 dBm.     

Evaluation of Thermocyclic Oxidation Behavior of HVOF-Sprayed NiCrFeSiB Coatings on Boiler Tube Steels

High velocity oxy-fuel (HVOF) spray process has grown into a well-accepted industrial technology for obtaining coatings resistant to significant surface degradation processes. In the present study, HVOF process was used to deposit Ni-based hardfacing NiCrFeSiB alloy powder on kinds of boiler tube steels designated as SA210 grade-A1, SA213-T11, and SA213-T22. The microstructures and several properties of the as-sprayed coatings have been investigated. Thermocyclic oxidation studies were performed in static air at 900 °C. NiCrFeSiB-coated steels showed slow oxidation kinetics and considerably lower weight gains than that of uncoated steels. The superior performance of NiCrFeSiB coatings can be attributed to continuous and protective thin oxide scale of amorphous SiO₂ and Cr₂O₃ formed on the surface of the oxidized coatings. The combined technique of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray analysis, and electron probe microanalysis are used to characterize reaction products of the oxidized surfaces.     

New Indices: An Application of Measuring the Aging Process of Some Asian Countries with Special Reference to Bangladesh

Commonly used aging measures such as the proportion of older people, the proportion of people aged less than 15 years, and the aging index (aged-child ratio) are based on a simple head count ratio (HCR). The HCR is a crude measure as it fails to give any idea about the tail distribution of the population age. Here an attempt has been made to develop new aging indices (age gap, age distribution sensitive and generalized) taking into account both tails of the population age distribution i.e., distribution of the population aged under fifteen and over sixty. These new indices have been applied to the Bangladesh population based on data collected from secondary sources: the international data base, US Census Bureau and Bangladesh Bureau of Statistics (BBS), for the years 1961, 1981 and 2001 and for some selected Asian countries for 1960, 1980 and 2000 using data from the international UN data base. Conventional aging indices have also been calculated and compared with new ones. Cross-country analysis has also been performed to study the sensitivity of aging indices. Analysis shows an increasing in the speed of aging and new indices indicate the process is faster than conventional ones. For example, relative increases in the speed of aging in 2001 compared to 1981 for conventional and new aging indices (aged-young age gap and aged-young distribution sensitive) are 28.97, 39.19 and 42.04% respectively. The findings also indicate that population aging at the peak is not clear but at the base it is evident. Again the aging process with respect to sex and urban-rural dwelling is also different. From cross-country analysis it is found that the new indices are more sensitive than conventional ones.     

Unsteady two-dimensional and axisymmetric MHD boundary-layer flows

Summary Nonsimilar solution of the unsteady laminar incompressible magneto-hydrodynamic boundary layer flow and heat transfer for an electrically conducting fluid over two-dimensional and axisymmetric bodies in the presence of an applied magnetic field has been obtained. The effects of surface mass transfer, Joule heating and viscous dissipation are included in the analysis. Numerical computation have been carried out for the flow over a circular cylinder and a sphere using an implicit finite difference scheme in combination with a quasi-linearization technique. It is observed that magnetic field and suction cause the location of vanishing skin friction to move downstream while, the effect of injection is just the opposite. The effect of magnetic field on the skin friction is more pronounced as compared to its effect on the heat transfer. On the other hand, the heat transfer is strongly affected by the viscous dissipation and the effect is more for larte times. However, heat transfer responds comparatively less to the fluctuations of the free stream than the skin friction.