Closed‐Form Expressions for Selection Combining System Statistics over Correlated Generalized‐K Fading Channels in the Presence of Interference

This paper considers the effects of simultaneous correlated multipath fading and shadowing on the performances of a signal‐to‐interference ratio (SIR)‐based dual‐branch selection combining (SC) diversity receiver. This analysis includes the presence of cochannel interference. A generalized fading/shadowing channel model in an interference‐limited correlated fading environment is modeled by generalized‐K distribution. Closed‐form expressions are obtained for probability density function and cumulative distribution function of the SC output SIR, as well as for the outage probability. Based on this, the influence of various fading and shadowing parameter values and the correlation level on the outage probability is examined.     

The hydrothermal synthesis of super-paramagnetic barium hexaferrite particles

Superparamagnetic Ba-hexaferrite nanoparticles were prepared using modified hydrothermal synthesis. The precursor and hydroxide [OH⁻] concentrations were optimized and the synthesis temperature and time were drastically reduced. The size and the morphology of synthesized nanoparticles was confirmed by transmission electron microscopy (TEM) images. The crystal structure of the nanoparticles was characterized by X-ray diffraction data. Powders synthesized at 160 °C exhibit a bimodal particle size distribution while those synthesized at T_S = 150 °C show a monomodal particle size distribution. Zero-field-cooling (ZFC) and field-cooling (FC) magnetization measurements were performed using a superconducting quantum interference device magnetometer from 2 to 300 K to investigate the magnetic properties of nanoparticles. The FC/ZFC magnetization measurements showed a typical superparamagnetic behavior. The synthesized superparamagnetic particles exhibit a disc-like shape, in average 11 nm wide and 3 nm thick with a room temperature magnetization of approximately 10 Am²/kg at 5 T.     

Properties of microlenses produced on a layer of tot'hema and eosin sensitized gelatin

Gelatin sensitized with tot'hema and eosin (compounds used in medical therapy) appears to be an excellent material for microlens fabrication. Lenses are produced by irradiation with a 532 nm laser beam. Aspheric concave lenses are formed rapidly with low power radiation. The lens profile is analyzed, as well as imaging properties. Physics of lens formation is also proposed. All material constituents are nonpoisonous, resulting in an environmentally safe, low toxicity material.     

Low-temperature synthesis of magnetically recoverable,superparamagnetic, photocatalytic,nanocomposite particles

A new, simple, low-temperature method for the synthesis of superparamagnetic, photocatalytic, nanocomposite particles for applications in the decomposition of pollutants in water is presented. The method is based on the coating of clusters of superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles with a photocatalytic anatase layer using the hydrolysis of aqueous TiOSO₄. The clusters of an appropriate size between 100 and 200 nm form by the simultaneous agglomeration of the aminopropyl-triethoxy-silane-grafted maghemite nanoparticles with a size of approximately 15 nm in a suspension of diluted TiOSO₄. During a sudden increase of pH with the addition of NaOH the titania is heterogeneously nucleated at the cluster surfaces. If the hydrolysis was conducted at an elevated temperature of 90 °C, the titania layer was nanocrystalline anatase. The composition of the nanocomposite particles, i.e., the thickness of the anatase layer, can be controlled simply by changing the starting TiOSO₄/Fe₂O₃ ratio for low titania contents, and by multiple coatings to get high titania contents. The photocatalytic activity of the nanocomposites was evaluated in the photocatalytic decomposition of formic acid. The activity seems to increase with an increase in the thickness and the crystallinity of the anatase coating, whereas it decreased after the calcination of the as-synthesized nanocomposite. The coating of the maghemite nanoparticles with a thin layer of insulating silica also slightly improves the photocatalytic activity.     

Investigation on electrical and microstructural properties of Thick Film Lead-Free resistor series under various firing conditions

The paper presents investigation of four lead free thick film resistor pastes, developed at ITME, denoted R-100, R-1k, R-10k and R-100k with sheet resistivities of 0.1, 1, 10 and 100 kΩ/□, respectively. The resistors were based on RuO₂ as the conductive phase. The aim of the work was to evaluate the influence of firing conditions of the resistive pastes on a sintering process. The pastes were screen printed onto alumina substrate with prefired AgPd lead-free terminations. They were fired at several temperatures from 750 to 950 °C for 10 min at peak temperature, as well as fired at the highest temperature for 6 h, in order to bring the sintering process into the equilibrium. The properties of the resistors, i.e , sheet resistivity and temperature coefficient of resistance (TCR), microstructure changes, glass crystallization upon firing, etc., were examined. Dried and fired resistor samples were evaluated by X-Ray diffraction analysis and by the scanning electron microscopy. The RuO₂ conductive phase maintained the same crystal structure regardless of the firing conditions. No devitrification was observed in lead-free resistors glasses. The lattice constants of RuO₂ were uniform after firing at temperatures over 800 °C. The resistors matched the desired resistivity and the TCR was the least temperature dependent at the firing temperatures around 850 °C.     

Rectifier-Inverter Frequency Changers with Suppressed DC Link Components

Rectifier-inverter types of static frequency changers (SFC's) typically employ bulky dc link reactive components to establish the required dc bus voltage. The negative effects of these components on overall system performance and evolution have been the subject of many past research publications. It is demonstrated that these unwanted components can be eliminated through the use of suitable SFC power circuit topologies. Two such topologies (i.e.,SFC Structures 1 and 2) are investigated here. These converter structures employ state-of-the-art power semiconductor components and optimized rectifier-inverter switching schemes. Finally, theoretical and experimental results show that proposed converter structures offer significant performance improvements at the cost of only moderate power and logic circuit complexity.     

Electro-hydraulic load sensing with a speed-controlled hydraulic supply system on forming-machines

High-power transmission capacity at low-energy losses, low noise emissions, high reliability, and ease of maintenance, as well as convenient cost-effectiveness, are required for industrial applications regarding variable electro-hydraulic supply systems. Only up-to-date principles regarding volumetrically controlled hydraulic energy using variable supply systems and appropriate control strategy have proven satisfactory for these requirements. The aim of the present work was to study the applicability of a low-priced drive concept using a speed-controlled induction motor in combination with a constant-displacement pump applied in a load-sensing control strategy. The suggested approach of the drive concept has been experimentally verified on a prototype of the drive. A hydraulic press-brake used for the machining of casting products in the automotive industry was taken into consideration.     

An example of a hybrid system: coherent optical system with Costasloop in receiver-system for transmission in baseband

The possibility of hybrid system construction is considered in this paper. The coherent optical system is the constituent part of this system. The first part of the system is constructed in passband (optical cable is transmission medium), and the second part of the system is constructed in baseband. The heterodyne optical receiver is used as optical receiver. Estimation is not done just after demodulation, but it is done at the end of the section in baseband. Taking into account shot noise of photodetectors, laser phase noise (transmitter laser and local laser) and noise which is generated during transmission by means of the section in baseband, we determine the performances of the proposed system     

Evaluation of Phase-Commutated Converters for Slip-Power Control in Induction Drives

Three different phase-commutation thyristor bridges are applied to slip-power control of an induction motor. The performance of the drive is experimentally evaluated for each thyristor bridge with respect to input power factor, efficiency, total. input current, size of the dc-link inductor, and regulation. The best results are obtained with the eight-thyristor bridge while the conventional six-thyristor converter offers the worst overall performance.