Estimation of the thermohydraulic efficiency of swirlers at small Reynolds numbers

To estimate the thermohydraulic efficiency of different types of swirlers of heat exchange in pipes, we have generalized the experimental data, which has made it possible to determine the optimal range of Reynolds numbers and the optimal geometric sizes of swirlers. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 23–30, January–February, 2009.     

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain.     

Performance evaluation of a submerged membrane bioreactor for the treatment of brackish oil and natural gas field produced water

Produced water, which is co-produced during oil and gas manufacturing, represents one of the largest sources of oily wastewaters. Therefore, treatment of this produced water may improve the economic viability and lead to a new source of water for beneficial use. In this study a submerged hollow fiber membrane bioreactor (MBR) has been studied experimentally for the treatment of brackish oil and natural gas field produced water. This type of wastewater is also characterized with relatively moderate to high amount of salt, oil and total petroleum hydrocarbons (TPH). However, the bacteria which are growing in conventional activated sludge and MBR cannot survive at these strict conditions, therefore acclimation of the bacteria is of vital importance. The performance of the biological system, membrane permeability, the rate and extent of TPH biodegradability have been investigated under different sludge age and F/M ratios. The results obtained by gas chromatography analyses showed that the MBR system could be very effective in the removal of TPH from produced water and a significant improvement in the effluent quality was achieved.     

A cross-layer approach for partition detection at overlay layer for structured P2P in MANETs

Due to limited radio range and mobility of nodes in mobile ad hoc networks (MANETs), the network partitioning and merging could occur frequently. When structured peer-to-peer (P2P) overlays are running over MANETs, then network partition in the physical network can also cause network partition at the overlay layer. Existing approaches for structured P2P overlay over MANETs do not detect network partition at the overlay layer. This paper proposes a cross-layer approach to detect network partition at the overlay layer for structured P2P overlay over MANETs. Simulation results show that the proposed approach is highly effective and efficient in terms of routing overhead, success ratio and false-negative ratio.     

An incremental neural network for tissue segmentation in ultrasound images

This paper presents an incremental neural network (INeN) for the segmentation of tissues in ultrasound images. The performances of the INeN and the Kohonen network are investigated for ultrasound image segmentation. The elements of the feature vectors are individually formed by using discrete Fourier transform (DFT) and discrete cosine transform (DCT). The training set formed from blocks of 4x4 pixels (regions of interest, ROIs) on five different tissues designated by an expert is used for the training of the Kohonen network. The training set of the INeN is formed from randomly selected ROIs of 4x4 pixels in the image. Performances of both 2D-DFT and 2D-DCT are comparatively examined for the segmentation of ultrasound images.     

Evidence of PAH production under lean combustion conditions

While it is common knowledge that PAH formation can be expected at rich combustion conditions, this paper presents experimental and computational evidence that PAH formation can also be expected under lean, or cool, combustion conditions. Experimental evidence for diesel engine operation at lean conditions, as well as the literature references related to waste tire and coal combustion, are cited as supportive evidence of conclusions drawn here. A computational model based on reaction mechanisms for three surrogate fuels: C₂H₂, C₇H₁₆ and C₁₄H₂₈, was validated against the available diesel engine data, and projected to both lean and rich combustion conditions. The finding was that for the adiabatic case, minimum production of PAHs occurs at equivalence of unity and increases as equivalence becomes either lean or rich; the latter observation being consistent with the common knowledge.     

Electronic properties of GaxIn1−xP from pseudopotential calculations

Based on a pseudopotential scheme within the virtual crystal approximation, we present a theoretical investigation of the electronic properties of Ga_xIn_1−xP. The effect of alloy disorder on energy band-gaps has been examined and found to be not negligible. The composition dependence of energy band-gaps and electron effective mass is shown to be non-linear. In agreement with experiment, a direct-to-indirect band-gap crossover is found to occur close to x = 0.7. Besides, the electron valence and conduction charge densities for Ga_0.50In_0.50P derived from pseudopotential band-structure calculations are reported and trends in bonding and ionicity are discussed.     

Reserves Accumulated in Non-Photosynthetic Organs during the Previous Growing Season Drive Plant Defenses and Growth in Aspen in the Subsequent Growing Season

Plants store non-structural carbohydrates (NSC), nitrogen (N), as well as other macro and micronutrients, in their stems and roots; the role of these stored reserves in plant growth and defense under herbivory pressure is poorly understood, particularly in trees. Trembling aspen (Populus tremuloides) seedlings with different NSC and N reserves accumulated during the previous growing season were generated in the greenhouse. Based on NSC and N contents, seedlings were assigned to one of three reserve statuses: Low N–Low NSC, High N–Medium NSC, or High N–High NSC. In the subsequent growing season, half of the seedlings in each reserve status was subjected to defoliation by forest tent caterpillar (Malacosoma disstria) while the other half was left untreated. Following defoliation, the effect of reserves was measured on foliar chemistry (N, NSC) and caterpillar performance (larval development). Due to their importance in herbivore feeding, we also quantified concentrations of phenolic glycoside compounds in foliage. Seedlings in Low N-Low NSC reserve status contained higher amounts of induced phenolic glycosides, grew little, and supported fewer caterpillars. In contrast, aspen seedlings in High N-Medium or High NSC reserve statuses contained lower amounts of induced phenolic glycosides, grew faster, and some of the caterpillars which fed on these seedlings developed up to their fourth instar. Furthermore, multiple regression analysis indicated that foliar phenolic glycoside concentration was related to reserve chemistry (NSC, N). Overall, these results demonstrate that reserves accumulated during the previous growing season can influence tree defense and growth in the subsequent growing season. Additionally, our study concluded that the NSC/N ratio of reserves in the previous growing season represents a better measure of resources available for use in defense and growth than the foliar NSC/N ratios.     

Decay and termite resistance of plywood treated with various fire retardants

This study evaluated the ability of white and brown rot fungi and termites to decompose fire retardant-treated (FRT) or untreated-plywood by measuring mass loss. Plywood was manufactured using Ekaba (Tetraberlinia bifoliolata Harms.) veneers which were previously treated with either boric acid, borax, mono-ammonium phosphate (MAP), or di-ammonium phosphate (DAP). Plywood specimens were then subjected to fungal decay resistance tests performed according to Japanese Industrial Standard (JIS) A-9201 method using a brown-rot fungus, Fomitopsis palustris (Berkeley et Curtis) Murrill and a white-rot fungus, Trametes versicolor (L. ex Fr.) Quel. The specimens were also assayed against the subterranean termite, Coptotermes formosanus Shiraki to determine termite resistance. Boron and phosphorus chemicals used in the study increased the resistance of plywood panels against both fungal and termite attack. Plywood panels treated with boric acid and borax resulted in less mass losses when compared to MAP and DAP-treated specimens in decay and termite resistance tests.