Speed enhancement of a class of digital phase locked loops (DPLLs) by dynamic gain control technique

A dynamic gain modification algorithm of a class of digital phase locked loops (DPLLs) has been proposed. It has been shown analytically that the modified DPLL based on the proposed algorithm can be designed to have a faster transient response besides having steady-state response and frequency acquisition range same as that of a conventional DPLL. Numerical simulation results have been given to support the analytical predictions.     

Offshore hydrocarbon production and potential of Thailand

Four commercial gas/condensate fields have been delineated in the Gulf of Thailand with total gas reserves of at least 7 trillion ft³. Efforts are being made to bring up from 500–700 MMCFD of gas ashore by 1983/84. The completion of the first phase of the pipeline system will enable production from Union Oil Co. of Thailand's Erawan gas field from mid-September 1981, at a flow rate of from 200 to 250 MMCFD. Also, 6000–7500 b/d of condensate will be recovered as a by-product. Small amounts of crude oil were also encountered in some wells. The remnants suggest a wide variation of organic sources from continental woody material as a primary source to minor components from marine algae. Hydrocarbon accumulations in deep Tertiary sedimentary basins in the Gulf are well developed at depths ranging from 1009 to 2691 m where mature source beds are closely associated with reservoir deltaic sands within growth-fault structures. Other prospective productive anomalies in the Gulf appear to have a large potential.Deep water drilling beyond 200 m water depth in the Andaman Sea revealed that the Tertiary source beds are mainly immature. Tertiary sediments in the Andaman Sea, therefore, have a low potential for hydrocarbon accumulations.The pre-Tertiary sedimentary basins that lie undisturbed within the “Cold Basin” region beneath the offshore areas of the Andaman Sea and the Gulf of Thailand have more favorable conditions for hydrocarbon potential. Study of source beds and reconstruction of the paleogeography of pre-Tertiary rocks, especially the carbonate facies along the coastal plains of Thailand, will provide important information on pre-Tertiary hydrocarbon potential.     

Synthesis and characterization of dual particle (MWCT+B4C) reinforced sintered hybrid aluminum matrix composites

ABSTRACT

Metal matrix nanocomposites (MMNCs) consist of a metal matrix reinforced with nanoparticles, featuring physical and mechanical properties very different from those of the matrix. Especially carbon nanotubes (CNTs) can improve the matrix material in terms of wear resistance, damping properties, and mechanical strength. The present investigation deals with the synthesis and characterization of aluminum matrix reinforced with micro-B₄C particles, and multiwall carbon nanotubes (MWCNTs) which have been prepared by powder metallurgy route. Powder mixture containing fixed weight (%) of B₄C and different wt% of MWCNT as reinforcement constituents that are uniaxial cold pressed and later green compacts are sintered in continues electric furnace. Microstructure and Mechanical properties such as microhardness and density are examined. Microstructure of samples has been investigated using scanning electron microscope (SEM). X-ray diffraction(XRD), energy dispersive x-ray (EDAX), atomic force microscope (AFM), and transmission electron microscope (TEM). TEM microstructure of the nanocomposite shows the homogeneous dispersion of MWCNT in the aluminum matrix. The results indicated that the increase in wt % of MWCNT improves the bonding and mechanical properties.     

Mechanisms of virus control during iron electrocoagulation--microfiltration of surface water

Results from a laboratory-scale study evaluating virus control by a hybrid iron electrocoagulation - microfiltration process revealed only 1.0-1.5 log MS2 bacteriophage reduction even at relatively high iron dosages (∼13 mg/L as Fe) for natural surface water containing moderate natural organic matter (NOM) concentrations (4.5 mg/L dissolved organic carbon, DOC). In contrast, much greater reductions were measured (6.5-log at pH 6.4 and 4-log at pH 7.5) at similar iron dosages for synthetic water that was devoid of NOM. Quantitative agreement with Faraday’s law with 2-electron transfer and speciation with phenanthroline demonstrated electrochemical generation of soluble ferrous iron. Near quantitative extraction of viruses by dissolving flocs formed in synthetic water provided direct evidence of their removal by sorption and enmeshment onto iron hydroxide flocs. In contrast, only approximately 1% of the viruses were associated with the flocs formed in natural water consistent with the measured poor removals. 1-2 logs of virus inactivation were also observed in the electrochemical cell for synthetic water (no NOM) but not for surface water (4.5 mg/L DOC). Sweep flocculation was the dominant destabilization mechanism since the ζ potential did not reach zero even when 6-log virus reductions were achieved. Charge neutralization only played a secondary role since ζ potential → 0 with increasing iron electrocoagulant dosage. Importantly, virus removal from synthetic water decreased when Suwanee River Humic Acid was added. Therefore, NOM present in natural waters appears to reduce the effectiveness of iron electrocoagulation pretreatment to microfiltration for virus control by complexing ferrous ions. This inhibits (i) Fe²⁺ oxidation, precipitation, and virus destabilization and (ii) virus inactivation through reactive oxygen species intermediates or by direct interactions with Fe²⁺ ions.     

STUDY OF A LABORATORY-SCALE FROTH FLOTATION PROCESS USING ARTIFICIAL NEURAL NETWORKS

A three-layer feed-forward artificial neural network (ANN) model, trained using the error back propagation algorithm, has been established to simulate the froth flotation process for the beneficiation of coal fines. The network model validates the experimentally observed qualitative and quantitative trends. The optimal model parameters in terms of network weights have been estimated and can be used to compute the parameters of the coal flotation process over wide-ranging experimental conditions.     

Experimental Analysis on Three Body Abrasive Wear Behaviour of Stir Cast Al LM 25/TiC Metal Matrix Composite

In this paper, the abrasive wear behavior of Al LM 25/10 wt% TiC metal matrix composite has been studied experimentally. The composite specimens were fabricated using stir casting technique. Microstructural evaluation revealed uniform distribution of reinforcement particles throughout the matrix. Abrasive wear experiments were designed for different values of load, speed and time through response surface methodology and were performed using three body abrasion tester. Surface plots for wear rate against all combinations of parameters revealed that wear rate increased with increasing load and time, but decreased with increasing speed. The generated regression equation established proper relation between parameters and wear rate, confirming the accuracy of the developed model. The results of optimization of process parameters revealed that a minimum wear rate of 0.00104 mm³/Nm was obtained at 27 N, 139 rpm and 3 min. Scanning electron microscope analysis results substantiated that wear rate was comparatively more at higher loads.     

Measurement of thermophysical properties and analysis of heat transfer during freezing of slab-shaped food commoditiesMesure des propriétés thermophysiques et analyse du transfert de chaleur au cours de la congélation d'aliments en forme de plaques

Experiments have been designed to measure water content, packing density and transient temperatures during cooling and freezing of fresh green peas packed in rectangular containers. Specific heat capacity in unfrozen and frozen states and latent heats of fusion are calculated from the measured water content. Experimental temperature records are used to calculate bulk thermal diffusivity, both in the frozen and unfrozen states, on the basis of transient heat transfer analysis. In the frozen state, the measured thermal diffusivity was found to vary almost linearly with temperature. A calculation scheme has been presented and applied to compute temperature variations during immersion and air-freezing of peas, using the measured thermal properties. The proposed scheme yielded the calculated freezing time lying within ±8% of its measured values. The calculated temperatures, with both first and second (Von Neumann) type of boundary conditions, were in good agreement with the measurements of present and earlier investigations.     

The Puzzle of Hereditary Spastic Paraplegia: From Epidemiology to Treatment

Inherited neurodegenerative pathology characterized by lower muscle tone and increasing spasticity in the lower limbs is termed hereditary spastic paraplegia (HSP). HSP is associated with changes in about 80 genes and their products involved in various biochemical pathways, such as lipid droplet formation, endoplasmic reticulum shaping, axon transport, endosome trafficking, and mitochondrial function. With the inheritance patterns of autosomal dominant, autosomal recessive, X-linked recessive, and mitochondrial inheritance, HSP is prevalent around the globe at a rate of 1–5 cases in every 100,000 individuals. Recent technology and medical interventions somewhat aid in recognizing and managing the malaise. However, HSP still lacks an appropriate and adequate therapeutic approach. Current therapies are based on the clinical manifestations observed in the patients, for example, smoothing the relaxant spastic muscle and physiotherapies. The limited clinical trial studies contribute to the absence of specific pharmaceuticals for HSPs. Our current work briefly explains the causative genes, epidemiology, underlying mechanism, and the management approach undertaken to date. We have also mentioned the latest approved drugs to summarise the available knowledge on therapeutic strategies for HSP.     

Effects of erythromycin on the rabbit pleura: its potential role as a pleural sclerosant

Tetracycline (TCN) has been considered the agent of choice for pleurodesis in patients with symptomatic malignant pleural effusions and recurrent pneumothoraces. However, the intravenous form of TCN used for pleurodesis is no longer available. Erythromycin, like TCN, often produces irritation when administered intravenously. In view of these irritant properties, we tested the effect of erythromycin as a pleural sclerosant in rabbits as compared with TCN. Normal saline was used as a control. Adult rabbits weighing 2.5 to 3.0 kg underwent sterile placement of a silastic pleural tube in the right pleural space. Erythromycin (n = 17) or TCN (n = 6), each in doses of 35 mg/kg in 2 ml saline, was administered via the tube. Control animals (n = 6) received 2 ml saline. The chest tubes were left in place for removal of pleural fluid and to maintain lung expansion. Animals were killed 8 d after receiving the various treatments, and their pleural surfaces were examined grossly and histologically. Numerous adhesions were present between the visceral and parietal pleurae in all animals receiving erythromycin and TCN, but not in those receiving saline. On light microscopy, pleurae treated with erythromycin or TCN were histologically identical, showing inflammation, edema, and fibroblast proliferation in the submesothelial tissues. The saline-treated animals had a normal pleura. Because erythromycin produced pleural inflammation and adhesions within 8 d of treatment, we propose that it may have a potential role as a pleural sclerosant.