Physical Layer Design Alternatives for High Speed Outdoor Packet Radio Local and Medium Area Networks

In the last few years, the development of wireless local area networks (WLANs) has become a major goal in the field of computer and wireless communications. The Network Technologies Research group at the Communications Research Center in Canada has been working on a project to develop a high speed outdoor WLAN. In contrast to many existing WLANs, the new WLAN supports multimedia traffic such as voice, data and video; and will be used mainly in an outdoor environment with a cell coverage range of approximately 20 km. In this paper the physical layer design alternatives for the outdoor WLAN with a speed of 10 to 20 Mbps are described. Simulation results for some of the techniques considered to be used for the WLAN system are presented. The study is concluded by proposing two possible systems that one may consider for the implementation of a high speed outdoor WLAN. Although this study was primarily focused on WLAN applications, the results presented in this paper are applicable to several high speed wireless networks.     

Effects of ohmic thawing on histological and textural properties of beef cuts

The changes in the histology and the texture of beef cuts during ohmic thawing were compared with those during conventional thawing method. The beef cut samples were thawed from −18 to 10 °C by applying different voltage gradients (10, 20 and 30 V/cm) during ohmic treatment whereas conventional thawing was applied at constant temperature (25 °C, 95% RH) in the controlled incubator. There were significant differences between the effects of thawing methods in terms of hardness, chewiness, gumminess of beef cut samples (p < 0.05). The sample treated ohmically at 30 V/cm voltage gradient was significantly different from the other thawed samples in terms of springiness, cohesiveness and resilience (p < 0.05). The change in the textural properties was explained by investigating the histological changes of beef cuts for both thawing method. Ohmic thawing provided the thawed meat sample having lower textural and histological changes rather than conventionally thawed ones.     

Microstructure and bond strength of diffusion-bonded nickel aluminide–titanium joints

Diffusion bonding of Ni₇₅Al₂₅ alloy to commercially pure titanium was carried out at 900 °C for different times under 2 MPa in vacuum. The microstructure of transition joints was revealed by scanning electron microscopy (SEM). Good bonding was observed on all the samples. Chemical compositions of the interface of the bonded samples were identified by energy dispersive spectroscopy. EDS results indicated the formation of the different compositions at the interface of the bonded samples. X-ray diffraction studies showed the presence of TiNi, Ti₂Ni, Ni₃Al, Ni4.22Al0.9 and Ti phases on the fractured surfaces of bonded samples. It was observed that the shear strengths of joints increased with increasing of bonding time. The maximum shear strength was found as 205 MPa for the bonded couple treated for 2 h.     

Rapid Transmutation of High-Level Nuclear Wastes in a Catalyzed Fusion-Driven System

The aim of this study is to investigate the high-level waste (HLW) transmutation potential of fusion-driven transmuter (FDT) based on catalyzed D–D fusion plasma for various fuel fractions. The Minor actinide (MA) (²³⁷Np, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm) and long-lived fission product (LLFP) (⁹⁹Tc, ¹²⁹I and ¹³⁵Cs) nuclides discharged from high burn-up pressured water reactor-mixed oxide spent fuel are considered as the HLW. The volume fractions of the MA and LLFP are raised from 10 to 20% stepped by 2% and 10 to 80% stepped by 5%, respectively. The transmutation analyses have been performed for an operation period (OP) of up to 6 years by 75% plant factor (η) under a first-wall neutron load (P) of 5 MW/m² by using two different computer codes, the XSDRNPM/SCALE4.4a neutron transport code and the MCNP4B Monte Carlo code. The numerical results bring out that the considered FDT has a high neutronic performance for an effective and rapid transmutation of MA and LLFP as well as the energy generation along the OP.     

Effect of Magnesium and Osteoblast Cell Presence on Hydroxyapatite Formation on (Ti,Mg)N Thin Film Coatings

TiN and (Ti,Mg)N thin film coatings were deposited on Ti substrates by an arc-physical vapor deposition technique. The effect of cell presence on hydroxyapatite (HA) formation was investigated using surfaces with four different Mg contents (0, 8.1, 11.31, and 28.49 at.%). Accelerated corrosion above 10 at.% Mg had a negative effect on the performance in terms of both cell proliferation and mineralization. In the absence of cells, Mg-free TiN coatings and low-Mg (8.1 at.%)-doped (Ti,Mg)N surfaces led to an early HA deposition (after 7 days and 14 days, respectively) in cell culture medium (DMEM), but the crystallinity was low. More crystalline HA structures were obtained in the presence of the cells. HA deposits with an ideal Ca/P ratio were obtained at least a week earlier, at day 14, in TiN and low-Mg (8.1 at.%)-doped (Ti,Mg)N compared with that of high-Mg-containing surfaces (>10 at.%). A thicker mineralized matrix was formed on low-Mg (8.1 at.%)-doped (Ti,Mg)N relative to that of the TiN sample. Low-Mg doping (<10 at.%) into TiN coatings resulted in better cell proliferation and thicker mineralized matrix formation, so it could be a promising alternative for hard tissue applications.     

Algae as a promising resource for biofuel industry: facts and challenges

Energy is the main driving force of society today that should be handled as a whole starting from production to consumption. With the rapid increase in the energy necessity, alternative methods and sources are becoming a crucial topic that should be scientifically highlighted with all their pros and cons. Especially the problems related to the fossil sources of energy triggered the search on the renewable alternatives like algae. In order to reach the desired amounts of energy with the satisfactory quality and quantity, understanding the algae as a living thing with the biological mechanism and existing production technologies are the key points to have a projection for commercialization. In this regard, technical facts and challenges on algal biofuel production should be evaluated. Keeping in mind the specifications and possible advantages related to their taxonomy, algae can serve as a promising source to reduce fossil fuel consumption. With the progress in the modern technology, reaching an effective production process will be possible, and this will help the algal biofuels to prove their maturity as a sustainable source for future. Within this context, the aim of this review is to point out the crucial technical challenges about algal fuels comprising both the macroalgae and microalgae as a reliable source of renewable energy. Copyright © 2016 John Wiley & Sons, Ltd.     

Amperometric Simultaneous Measurement of Copper and Cobalt Ions with Polythiophene Incorporating Pendant Terpyridine Groups

Terpyridine containing thiophene monomer was synthesized. Electrochemical behavior of the monomer was studied by cyclic voltammetry. This monomer was polymerized via electrochemical methods and the resultant polymer was characterized. The stepwise fabrication process of the polymeric film electrode and its electrochemical sensing performance towards simultaneously Co and Cu ions were evaluated. The sensing parameters of the polymer electrode were investigated in detail, and the determination conditions were optimized. Under the optimal conditions, sensor response peak is linear to the Co ion concentration in the range of 1.0-50.0 µM and the Cu ion concentration in the range of 1.0–20.0 µM. Detection limit of terpyridine-based polythiophene film electrode for Co and Cu is respectively 100 nM and 0.05 nM.     

Hydrogen generation from sodium borohydride with Ni and Co based catalysts supported on Co3O4

Hydrogen is an alternative and clean energy carrier, but there are still some production related problems. In this aspect, it is crucial to efficiently generate hydrogen from hydrogen rich materials such as sodium borohydride. In this study, Co₃O₄ supported Ni and Co catalysts are synthesized via microwave irradiation technique for hydrogen generation from sodium borohydride. In this context, firstly, Co₃O₄ support material is synthesized by chemical method. Then, Ni and Co catalysts are decorated onto Co₃O₄ support material by microwave irradiation-polyol method. Prepared catalysts and support material are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-mass spectrometer (ICP/MS). A new system is designed by our group in order to determine the activity of the prepared catalysts for hydrogen generation. The effects of different initial NaOH concentrations on hydrogen generation rate are investigated. It is observed that the rate of hydrogen generation increased with an increase in initial NaOH concentration. Co-Co₃O₄ catalyst at 10% NaOH initial concentration shows the highest hydrogen generation rate as 2823 ml/g_cat.min. In summary, Co-based catalysts are exhibited more activity than Ni-based catalysts in terms of hydrogen generation.     

Measuring water utility performance using nonparametric linear programming

In this study, a cutting-edge methodology for measuring the performance of water utilities based on two-stage Data Envelopment Analysis (DEA) was applied to individual districts of a California-based water utility. A bootstrap technique involving the construction of confidence intervals was implemented to overcome the deterministic nature of conventional DEA, and a number of exogenous variables were incorporated into the model to help identify the factors affecting technical efficiency. Results indicated high overall performance achieved by the utility on average (92%). The number of connections and precipitation were found to be statistically significant exogenous variables, and both were determined to have a negative impact on efficiencies. The findings of this study are expected to be useful for guiding subsequent managerial improvement initiatives.