A 22.5 MHz current-mode KHN-biquad using differential voltage current conveyor and grounded passive elements

In this paper, a current-mode (CM) Kerwin–Huelsman–Newcomb (KHN) biquad is proposed. The circuit employs three differential-voltage current conveyors (DVCCs) as active elements together with two capacitors and four resistors as passive elements, which all are grounded. The circuit simultaneously provides the three basic filter functions, namely bandpass (BP), highpass (HP) and lowpass (LP) functions. The notch and allpass (AP) functions can be obtained by connecting appropriate output currents directly without using additional active elements. The output signals are obtained at high output impedance ports, which is important for easy cascading in CM operation. SPICE simulation results are given to verify the theoretical analyses.     

Performances of DPSK and FSK CDMA systems with complex signature sequences

This paper investigates the performance of direct‐sequence code‐division multiple‐access (CDMA) communication systems in Gaussian noise channels using binary and M‐ary noncoherent signaling schemes with complex signature sequences. Differential‐phase‐shift‐keyed (DPSK) signaling with differentially coherent demodulation and frequency‐shift‐keyed (FSK) signaling with noncoherent demodulation are considered. Upper and lower bounds are presented for the probability of bit error (p.b.e.) of binary DPSK and binary FSK systems when the number of users is small. Simulation and Gaussian approximation are used to obtained the p.b.e. when the number of users is large. Two types of complex sequences (FZC and 4‐phase sequences) and one type of binary sequences (Gold sequences) are used for evaluating numerical results. Results show that complex sequences outperform binary sequence when the number of users is small. However, as the number of users gets large, all sequences have similar performances. These suggest that complex sequences should be used when the number of users is small, but binary sequences should be used when the number of users is large, as binary sequences are easier to generate. This revised version was published online in June 2006 with corrections to the Cover Date.     

Control of thermoelectric properties in ZrO2/CoSb3 nano‐dispersed composites

Nano‐dispersed ZrO₂/CoSb₃ composites of various composition were prepared by uniaxial hot pressing of nano‐sized powders of thermoelectric CoSb₃ intermixed with ceramic nano‐powders. The phase purity, the microstructure, and the temperature dependent transport parameters of the composites were investigated. Non‐dispersed samples from nano‐sized CoSb₃ powders show higher electrical conductivity compared to melt‐grown material which is attributed to the presence of a small excess of metallic Sb, but they exhibit lower thermal conductivity due to the fine‐grained structure. Addition of 5 at.‐% ZrO₂ enhances the ratio of electrical to thermal conductivity, whereas hardly affects the Seebeck coefficient. In this manner the nano‐dispersion method provides an effective approach to improving the material´s thermoelectric performance.     

Biogenic amine content and biogenic amine quality indices of sardines (Sardina pilchardus) stored in modified atmosphere packaging and vacuum packaging

A comparative study of the effects of packaging on the formation of biogenic amines during storage of sardines (Sardina pilchardus) at 4 °C in air, modified atmosphere pack (MAP) and vacuum pack (VP) was carried out. Sardines were organoleptically acceptable for up to 3 days in air, 12 days in MAP and 9 days in VP. The biogenic amine content generally increased in all treatments with increasing storage time. The concentrations of putrescine and/cadaverine in fish stored in air reached maximum levels of 12.2 mg/100g at 12 days and 10.0 mg/l00 g at 15 days. Significant differences were found (P < 0.05) in the levels of cadaverine and putrescine among the three treatments. Spermidine and spermine levels increased slightly and did not change much throughout the storage period for all experimental conditions. The amine contents of sardine were highest in sardine stored in air, followed by VP and MAP. Quality indices related to the contents of the major biogenic amines were calculated and they correlated well with organoleptic qualities.     

A New and Exact Analysis of DS-CDMA Cellular Radio System Based on the Physical Interpretation of Nakagami Wideband Channel

In this paper we present the performance of two uplink/downlink DS-CDMA receivers in a Nakagami wideband channel. Two detection methods were considered; namely, coherent and differential detection RAKE receivers based on maximal ratio combining technique. We consider a new physical interpretation of the Nakagami channel and the instantaneous power of the multiple access interferers. In comparison with the previous researches in the literature, which are based on Gaussian approximation, this approach results in a more accurate solution for the problem. We analyzed and derived closed form formulae for probability of bit error for DS-CDMA cellular radio system in the Nakagami wideband channel. We presented a set of numerical results for coherent downlink receivers.     

Biomolecules in Metal and Semiconductor Nanoparticle Growth

Exerting control over the size, morphology, and complexity of metal and semiconductor nanoparticles and nanostructures is a requisite for exploring novel phenomena, and the potential applications of these nanomaterials. Bottom-up colloidal chemistry syntheses can benefit from using biomolecules as active elements to influence the formation of inorganic nanoparticles. In this review, we will discuss how three main biomolecule types, (namely DNA; amino acids, peptides, and proteins; and enzymes), can affect the growth of metal and semiconductor nanoparticles. We will present and discuss the templating and non-templating roles of those biomolecules, featuring key aspects and prospects of biomolecule-assisted metal and semiconductor nanoparticle growth.     

Evaluation of different restoration techniques on fracture resistance of teeth with palatinal cusp fracture

We evaluated reattached tooth fragments in terms of fracture resistance in endodontically treated maxillary premolars with one remaining wall. In total, 60 double-rooted, mature, human maxillary premolars with double canals were used. Ten intact teeth were served as a control group without any application. After endodontic treatment, the palatal wall of the teeth was cut parallel to the horizontal axis on the cementoenamel junction using a diamond disc. The teeth were randomly divided into five groups (n = 10) and were restored as follows. Group 1: restored with composite resin; Group 2: palatal wall bonded to the teeth using adhesive resin, then restored with composite resin; Group 3: teeth restored as in Group 2, plus a post space prepared below 2 mm from the palatinal cusp horizontally, then fibre post bonded using adhesive resin cement; Group 4: cavity enlarged to a depth of 2 mm in the cusp of the palatal wall, then restoration performed as in Group 2; and Group 5: fibre post placed in the root canal and then restoration performed as in Group 1. Failure load testing was performed with a universal testing machine. Kruskal–Wallis and Conover’s multiple comparison tests were used to analyse the data. In the restoration groups the highest median load at failure was observed in Group 4, in which cusp capping was used; the lowest was found in Group 3, in which a horizontal fibre post was applied with the reattached tooth fragments.     

A novel full-wave rectifier/sinusoidal frequency doubler topology based on CFOAs

In this paper, a high-efficiency class-F power amplifier (PA) is designed using integration between a low voltage p-HEMT transistor and a miniaturized microstrip suppressing cell. It results in nth harmonic suppression and high power added efficiency (PAE) under low radio frequency (RF) input powers. The simulation is performed based on harmonic balance analysis. The proposed power amplifier is fabricated, and measurements results validated the simulations. The proposed power amplifier operates at 1.8 GHz with 100 MHz bandwidth and an average PAE of 71.1%, with very low drain voltage of 2 V. At fundamental frequency of 1.8 GHz, the maximum measured PAE is 73.5% at about 12 dBm RF input power. The maximum output power and gain are 23.4 and 17.5 dBm in RF input power ranges of 0–12 dBm, respectively. The fabricated class-F PA with such characteristics can be used for power amplifications in wireless transmitters such as 4G (4th generation)-LTE (long term evolution) communication systems.     

Non‐preemptive Queueing Model of Spectrum Handoff Scheme Based on Prioritized Data Traffic in Cognitive Wireless Networks

In this study, a non‐preemptive M/G/1 queueing model of a spectrum handoff scheme for cognitive wireless networks is proposed. Because spectrum handoff gives secondary users an opportunity to carry on their transmissions, it is crucially important to determine the actions of primary users. In our queueing model, prioritized data traffic is utilized to meet the requirements of the secondary users. These users’ packets are categorized into three different priority classes: urgent, real‐time, and non‐real time. Urgent data packets have the highest priority, while non‐real time data packets have the lowest priority. Riverbed (OPNET) Modeler simulation software was used to simulate both reactive and proactive decision spectrum handoff schemes. The simulation results were consistent with the analytical results obtained under different load and traffic conditions. This study also revealed that the cumulative number of handoffs can be drastically decreased by exploiting priority classes and utilizing a decent spectrum handoff strategy, such as a reactive or proactive decision‐based strategy.