Synthesis of carbon-nitride films using a fast-switched dual-source low energy ion beam deposition system

Thin C_xN_y films were deposited in UHV using alternating low energy ion beams of C⁺ and N⁺ or N₂⁺ in the energy range of 5 to 100 eV. The ion beam deposition system is equipped with two Freeman ion sources, mass analysis and fast automated beam switching, allowing perpendicular bombardment of the target with a single ion beam at a time. The composition and density of the films were studied by ARS (in situ), XPS and RBS. The dependence of the film properties and growth mechanisms on ion energy, beam switching rate, and C-to-N arrival ratio have been investigated. The influence of the deposition parameters on the film stoichiometry is discussed. Exposure of the film to atmosphere leads to oxygen incorporation, resulting in a lowered surface concentration of nitrogen. The XPS N 1s and C Is binding energies vary in a relatively broad range indicating that several bond states may be present. The influence of the substrate material on film growth has also been studied. On Si{100}, film growth commences with the formation of an interfacial silicon nitride. No film growth was observed on gold, however deposition was possible on tantalum and molybdenum.     

Removal of Aniline and Nitro-Substituted Aniline from Wastewater by Particulate Nanoporous MCM-48

The particulate nanoporous material MCM-48 (Mobil Crystalline Material No. 48) was synthesized and characterized in order to use it as an adsorbent for the removal of adsorbate, such as aniline and nitro-substituted anilines, including 2-nitroaniline, 3-nitroaniline, and 4-nitroaniline from wastewater. The characterizations of MCM-48 were investigated by applying XRD, SEM, EDAX, BET surface area, and FTIR. The adsorption kinetics was investigated too. The batch adsorption studies demonstrated that the MCM-48 had a significant ability to the adsorption of aniline and nitro-substituted aniline from wastewater. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. The four molecules adsorbed according to type I Langmuir adsorption with a maximum uptake were calculated to be approximately 94 mg g^?1. The findings showed that the kinetics of the reaction is very rapid and followed a pseudo-second-order model. It is clearly indicated that the Langmuir model is more suitable for chemical organic compounds adsorption on mesoporous material than the Freundlich model.     

Constellation-switching precoding for blind detection of co-channel signals: application to 8-ary signaling

Blind detection of co-channel signals in wireless scenarios may be achieved with the help of data precoding techniques. In this letter we propose a new data precoding / blind detection approach that is based on a unique modification to the signal constellation of each of the co-channel signals. Detection is based on exploiting the embedded constellation property. The new approach can be seen as a generalization to some earlier precoding techniques that were based on phase modifications. Demonstration of the proposed method involves application to 8-ary amplitude-phase modulations, with performance shown to be reasonably close to an MMSE receiver. Performance results for a semi-blind receiver for 4-ary signaling are also given to demonstrate further possible applications of the new scheme.     

Block phase-precoding for blind multiuser detection of BPSK/DS-CDMA signals

A new approach for blind multiuser detection of binary phase-shift keying/direct-sequence code-division multiple-access signals is proposed, based on precoding the phase of the transmitted data uniquely for each user, over a block of data. This would enable separation and detection of a desired user's signal in an unknown multipath channel without channel estimation. The method does not involve any sacrifice in data rate or system bandwidth. The proposed method exhibits good performance, compared with some existing methods.     

Modified constant modulus algorithm for blind DS/CDMA detection

A new blind adaptive multiuser detector for synchronous DS/CDMA systems based on a modified constant modulus algorithm is proposed. This detector is shown to outperform the minimum output energy detector in a downlink channel occupied by a large number of users. This blind detector is a good candidate for downlink receivers     

Reducing heat gain from sheet metal-clad walls by utilizing industrially wasted materials (experimental study)

Buildings' walls are covered to reduce environmental impact and esthetics, and cladding materials vary based on public preference and financial capacity. Metal sheets with glossy surfaces are commonly used, but researchers propose using aluminum sheets and filling gaps with commercial waste materials, like, fabric roll sticks or circular plastic hollow parts. A test room with internal dimensions of 1 × 1 × 2 m used in Baghdad (latitude 33.2° N) was used to study thermal behavior, with a window-type air conditioner providing standard thermal conditions. The air gap attached to the top of the test wall was either left open or closed during the day. Results showed that double-layer bamboo packing preserved 52.1% with a closed-air gap and 49.5% with an open-air gap, but no discernible difference was observed between the two situations.     

Block modulus precoding for blind multiuser detection of DS-CDMA signals

We propose a blind multiuser detector based on a new data precoding technique for direct-sequence code-division multiple-access signals. The modulus of all users' data is block encoded, using a sequence that is unique for each user. This precoding method, together with the analytical constant modulus algorithm for detection, enables a closed-form, one-shot detection of the desired user's signal in a multipath channel using one or more antennas. The detection process does not involve or require a channel estimation step. The proposed detector is shown to be extremely near-far resistant, and can operate properly in the presence of severe carrier frequency offset.