Modified register-exchange Viterbi decoder for low-power wireless communications

In this paper, a new implementation of the Viterbi decoder (VD), based on a modified register-exchange (RE) method, is proposed. Conceptually, the RE method is simpler and faster than the trace-back (TB) method. However, the disadvantage of the RE method is that every bit in the memory must be read and rewritten for each bit of information decoded. The proposed implementation adopts the "pointer" concept: a pointer is assigned to each register. Instead of copying the contents of one register to another, the pointer which points to the first register is altered to point to the second register. Power-dissipation, performance, memory size, and the speed of the survivor sequence management are analyzed for both the TB method, and the proposed RE method. The analysis indicates an average power reduction of 23% for the new VD, compared to the power dissipation of the VD described in the literature for the third generation of wireless applications. The bit-error rate is 10/sup -5/ with a signal-to-noise ratio of approximately 6.3 dB for a continuous, uncontrolled encoded sequence. Moreover, the memory requirements of the new implementation are reduced by half. All the read and write operations in the survivor sequence management are executed at the data rate frequency which increases the maximum frequency.     

Some synthetic detergents from petroleum products

Deodorized and dewaxed Egyptian petroleum fraction, boiling range 200–270 C, was subjected to liquid phase oxidation at various temperatures in the presence of Co acetate as catalyst. The synthesized naphthenic acids were then converted to naphthenic acid amides and naphthenic alcohols. These products were ethoxylated to different mole ratios of ethylene oxide. The ethoxylates with an average 5 mol ethylene oxide/mol prepared hydrophobes were sulphated and phosphated to anionics. The surface active properties of all the nonionic and anionic surfactants were evaluated.     

Persistence of some phenylamide pesticides in the aquatic environment—II. Adsorption on clay minerals

Adsorption of IPC, CIPC, Linuron, Neburon and Vitavax on bentonite clays (H-, Fe- and Ca-forms) was investigated. Adsorption was found to conform with Freundlich's equation and to depend on the nature of saturating cation as well as the chemical structure of phenylamides. Considerable amounts of bentonite are needed to bring about effective removal of these pesticides from polluted water. The role of suspended clay minerals in the decontamination of surface waters will be rather limited.     

Persistence of some phenylamide pesticides in the aquatic environment—III. Biological degradation

Mixed population of microorganisms of river water and sewage did not metabolize IPC, CIPC, Linuron, Monuron, Stam and Vitavax during the tested period lasting for 4 months. Bacillus cereus, when added to the aqueous solutions of these pesticides, was capable to degrade IPC, Linuron, Stam and Vitavax whereas CIPC and Monuron were chemically stable. The investigated phenylamides have no inhibitory effects on bacteria and are not expected to affect the process of self-purification of surface waters. Susceptibility of phenylamides to biodegradation in aquatic environment and their health hazards were discussed.     

Stack-and-Draw Applied to the Engineering of Multi-Material Fibers with Non-Cylindrical Profiles

Here, it is demonstrated that the stack-and-draw approach can be expanded to unusual materials association and profile geometries to generate fiber assemblies with unprecedented functionalities. This approach relies on the stacking of flat oxide glass slides into a preform, which is then thermally elongated into tens-of-meters-long ribbon fibers with preserved cross-section ratio. Fabrication methodology is introduced. In order to illustrate the versatility of the method, a panel of fibers with diverse geometries and functions is exposed, including glass-only exposed-core fibers for chemical sensing and, upon the insertion of metal electrodes, H-shaped multi-cavity structures and compact, glass-metal fiber optical detectors applied to a gas analysis by means of fiber-tip plasma spectroscopy. It is believed this new approach will offer an attractive, straightforward solution for designing innovative, complex multimaterial fiber platforms with enhanced functionalities.     

Uptake and the effects of cyanazine on Scenedesmus obliquus and Anabaena flos-aquae

Microalgal species vary in their sensitivity to the triazine herbicides, including cyanazine. The current investigation was carried out to examine the uptake and the effects of cyanazine on Chl (a) content, growth rate, EC₅₀, and protein and amino acid contents of two different algal species; namely Scenedesmus obliquus (green alga) and Anabaena flos-aquae (blue green alga). With regard to the differential sensitivity, the present findings revealed that S.obliquus is more sensitive to the inhibitory effects of cyanazine compared to A.flos-aquae (EC₅₀ = 26 vs. 113 µg/L, respectively). Additionally, the lowest applied concentrations of the tested herbicide increased the Chl (a) content of both algal cultures as well as its rate of uptake.     

Role of adsorbents in the removal of soluble aromatic hydrocarbons from drinking waters

Soluble aromatic hydrocarbons impart undesirable effects on the taste and odour of drinking waters. Adsorption of benzene, toluene. O-oxylene, ethylbenzene and cyclo-hexane on clays and powdered activated carbon was found to confirm with Freundlich's model. Adsorption parameters reflect the effects of solubility, chemical structure, competitive interactions and available surface area on the adsorption process. Clay minerals showed low adsorption capacity for the studied compounds whereas use of powdered carbon presents a feasible method for the removal of soluble aromatic hydrocarbons.     

Removal of phenylamide pesticides from drinking waters—I. Effect of chemical coagulation and oxidants

Chemical coagulation with aluminium or ferric sulphates is not an effective mean for the removal of phenylamide pesticides from drinking water. The effects of chlorine, u.v.-catalyzed chlorination and chlorine dioxide on phenylamides were investigated. Several aniline derivatives and intermediate products having the amide linkage intact were detected in the treated solutions. The presence of such degradation products may exert the same undesirable effects on water quality as the parent compounds. Chlorine dioxide tends to be the oxidant of choice for the removal of phenylamides from polluted waters.     

Adsorption of Sevin and Baygon on granular activated carbon

Adsorption of Sevin and Baygon on granular activated carbon was investigated. Adsorption parameters of Freundlich and Langmuir isotherms are useful indications of the adsorption capacity of carbon and the anticipated sharpness of breakthrough front. Adsorption of tested carbamates depends on their chemical structure and branching of the side chains. Contact time tends to be the most important factor controlling the efficiency of the adsorption process and a linear relationship was obtained between the logarithm of contact time and volume of effluent passing the column before breakthrough of Sevin.     

Memoryless Viterbi decoder

The problem of survival memory management of a Viterbi decoder (VD) was solved by introducing a novel pointer implementation for the register exchange method, where a pointer is assigned to each row of memory in the survivor memory unit (SMU). The content of the pointer which points to one row of memory is altered to point to another row of memory, instead of copying the contents of the first row to the second. In this paper, the one-pointer VD is proposed; if the initial state of the convolutional encoder is known, the entire SMU is reduced to only one row. Because the decoded data bits are generated in the required order, even this row of memory is dispensable. Thus, the one-pointer architecture, referred to as memoryless VD (MLVD), reduces the power consumption of a traditional traceback VD by approximately 50%, but has some performance degradation. A prototype of the MLVD with a one third convolutional code rate and a constraint length of nine is mapped into a Xilinx 2V6000 chip, operating at 25 MHz with a decoding throughput of more than 3 Mbps and a latency of two data bits.