Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation.     

Biofilm adaptation to sulfate reduction in anaerobic immobilized biomass reactors sujected to different COD/sulfate ratios.

Various aspects of biofilm adaptation to sulfate reduction in horizontal-flow anaerobic immobilized biomass (HAIB) reactors subjected to increasing sulfate concentrations and different COD/sulfate ratios are presented and discussed. Four bench-scale HAIB reactors filled with vegetal carbon (R1 and R2) and polyurethane foam matrices (R3 and R4) were utilized. Influent sulfate concentrations ranging from 500 to 3000 mg/L were applied at COD/sulfate ratios ranging from 5.0 to 1.7. Reactors R1 and R4 were operated with higher sulfate loads than those applied to R2 and R3. For the same COD/sulfate ratio, the highest sulfate reduction efficiency (approximately 80%) was displayed by the vegetal carbon reactor (R2) subjected to low sulfate loads. According to the results of our molecular biology analyses, the different support materials provided different biomass colonization conditions. The lowest diversity of sulfate-reducing bacteria was found in the HAIB filled with polyurethane foam matrices operating with high sulfate loads.     

A Customized Radiation Sensor for Ionization Collection

The measurement of absorbed doses is fundamental to radiation biology and oncology. A customized parallel plate radiation sensor was designed and fabricated as a precursor to investigating novel materials, such as carbon nanotubes, as a substitute for conventional metallic conducting plates or active volume medium. This sensor contains two thick and large-area electrodes that provide the sensor with a good signal-to-noise ratio. The 6 MV and 15 MV photon beams produced by a Varian Clinac 21 EX medical linear accelerator were used in the experiments. The linear accelerator was calibrated such that 1 monitor unit (MU) produces 1 cGy of dose in water with depth of 5 cm for a calibration geometry of source-to-axis distance equal to 100 cm and 10times10 cm² field size at the point of measurement. Ionization measurements were performed by varying the bias voltages, electrode separations, exposures, and angles of the incident beam to characterize the sensor. Signal saturation characteristics of the sensor with different electrode separations and exposures were investigated. This sensor displayed excellent linear response to exposure up to 600 MU. An analytical modeling using the pencil beam model and simulations based on device configuration were given to explain the results. In oblique incident beam experiments, the prototype sensor showed an accurate response compared to simulation results for a small field size of 1times1 cm². The sensor was tested to be suitable in the study of ionization collection efficiencies for different materials     

Upgrading of a reliable water supply system at the Kola nuclear power plant for service life extension

Measures taken to develop and put into operation three new exterior channels for emergency process water with two additional 60VTs pumping units, which remain operational even during an earthquake and were installed in the second block pumping station, are described. In addition, the three existing 12NDS horizontal pumping units were used as a basis to develop a third channel for the emergency process water. Above-ground water ducts with thermal insulation and heating systems to prevent freezing during the anticipation state, which is the constant state of the emergency system, were laid. As a result of upgrading with the development of three channels, the emergency process water feeding reached an adequately safe level of reliability. __________ Translated from Atomnaya énergiya, Vol. 100, No. 3, pp. 173–177, March, 2006.     

Optical DQPSK Receiver With Enhanced Dispersion Tolerance

We propose and analyze a novel differential quadrature phase-shift-keying (DQPSK) receiver architecture based on optical frequency discriminator filtering and direct detection. Our simulations show that such a receiver provides significantly enhanced tolerance to chromatic dispersion compared with the conventional delay-interferometer-based receiver. Preliminary measurement results demonstrate the novel DQPSK demodulator concept at 20 Gb/s.     

Synthesis of reagents for inhibiting the growth of sulfate-reducing bacteria in petroleum production

Quaternary ammonium salts were synthesized on the basis of hexamethylenetetramine and piperylene hydrochloride. Conditions for the synthesis of mono-, di-, tri-, and tetraalkenylhexamethylenetetrammonium chlorides in aqueous solutions were optimized. The main physicochemical characteristics of the synthesized compounds were determined and the structures were established. The suppression of the growth of sulfate-reducing bacteria was studied.     

Secure vehicular communication systems: implementation, performance, and research challenges

Vehicular communication systems are on the verge of practical deployment. Nonetheless, their security and privacy protection is one of the problems that have been addressed only recently. In order to show the feasibility of secure VC, certain implementations are required. In [1] we discuss the design of a VC security system that has emerged as a result of the European SeVe- Com project. In this second article we discuss various issues related to the implementation and deployment aspects of secure VC systems. Moreover, we provide an outlook on open security research issues that will arise as VC systems develop from today?s simple prototypes to fullfledged systems.     

The Hacking Tradition

This issue's works in progress department features a novel technology that embeds a six-degrees-of-freedom force-torque sensor into a physical artifact to transform existing 3D passive artifacts into contact-sensitive interface devices. The department also presents an approach for rewriting binary to better correlate application usage with contextual information.     

Production of silver‐doped analcime by isomorphous substitution technique

BACKGROUND: Metal‐exchanged zeolites have been reported to have significant limitations on cayalytic activity, such as counterbalancing the negative framework charges and limitation of active space. Alternative methods of incorporating silver ions into the framework of zeolites are therefore necessary. This paper reports on a technique for producing silver doped analcime by isomorphous substitution of silver ion into the framework of analcime. The amount of aluminium in the gel composition was reduced by a factor of 5%, 10% and 20% and an equivalent amount of silver was added to the gel and treated in a conventional manner for zeolite crystallisation. Some of the aluminium in the reaction gel was replaced with the silver. The silver‐doped analcime samples where characterised by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐rays (EDX), Fourier transform infrared (FTIR) spectroscopy and inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) analysis. RESULTS: The amount of silver ions loaded for each reduction of aluminium as determined by EDX were found to be (w/w) 0.29%, 1.41% and 2.10%, respectively. XRD pattern SEM images of the silver‐doped analcime showed the presence of zeolite P in addition to analcime. CONCLUSION: Silver‐doped analcime was successfully produced with different silver loadings and may exhibit higher anti‐microbial activities than silver‐exchanged counterparts. Copyright © 2008 Society of Chemical Industry     

Effect of mineral matter on coal self-heating rate

Adiabatic self-heating tests have been conducted on subbituminous coal cores from the same seam profile, which cover a mineral matter content range of 11.2-71.1%. In all cases the heat release rate does not conform to an Arrhenius kinetic model, but can best be described by a third order polynomial. Assessment of the theoretical heat sink effect of the mineral matter in each of the tests reveals that the coal is less reactive than predicted using a simple energy conservation equation. There is an additional effect of the mineral matter in these cases that cannot be explained by heat sink alone. The disseminated mineral matter in the coal is therefore inhibiting the oxidation reaction due to physicochemical effects.