The effect of post-treatments on the powder morphology of titanium dioxide (TiO2) powders synthesized for cold spray

In this study, a novel synthesis method of TiO₂ powders that can be cold sprayed is presented. The synthesis technique is a simple hydrolysis method of titanyl sulfate (TiOSO₄) in distilled water with a small addition of inorganic salt. At a relatively low hydrolysis temperature, pure anatase TiO₂ can be obtained and post-synthesis treatments (annealing or hydrothermal treatment) do not alter this phase structure. The powder is agglomerated with fine nano primary particles, with different post-synthesis treatments leading to different TiO₂ nanostructures. Annealing causes a significant growth of primary particles with the existence of internal pores within a particle. On the other hand, hydrothermal treatment produces a unique oriented agglomeration structure where the primary particles are agglomerated in one single crystal axes. It is believed that the synergistic effect of inorganic ion adsorption and post-treatments results in the observed nanostructures. After cold spraying, it is revealed that these TiO₂ powders could be deposited via supersonic solid phase deposition (cold spray).     

Supercritical CO2 extraction of pigment components with pharmaceutical importance from Chlorella vulgaris

BACKGROUND: Chlorella vulgaris is a green microalgae that contains various pigment components of carotenoids and chlorophylls. Supercritical CO₂ is widely used for extraction of pharmaceutical compounds because it is non‐oxic and easily separated from extracted material by simply depressurizing. In this work, pharmaceutical compounds from Chlorella vulgaris have been extracted using supercritical CO₂ with or without entrainer at various extraction conditions. RESULTS: Based on high performance liquid chromatography (HPLC) analysis, the extracts contained pigment components, such as lutein, β‐carotene, chlorophyll a and b. Higher extraction pressure and temperature promoted higher lutein extraction by supercritical CO₂. The optimum pressure and temperature for extraction were obtained as 50 MPa and 80 °C. Ethanol as an entrainer was more effective than acetone for the extraction of pigment components. Pigment components in the extract obtained by supercritical CO₂ with and without entrainer were compared with the extract obtained by a conventional extraction method. CONCLUSION: Supercritical CO₂ has been successfully applied for the extraction of pigment components from Chlorella vulgaris. Supercritical CO₂ enabled high selectivity for lutein extraction; however, the lutein yield was lower than that obtained by extraction using supercritical CO₂ with ethanol and soxhlet. Copyright © 2008 Society of Chemical Industry     

Efficient routing for IP subnet VLAN over Ethernet

Existing IP routing algorithms have been developed mainly for non‐VLAN networks. For these routing algorithms to work, an end station must be attached to its associated network. The introduction of VLAN has, however, allowed the physical location of the end station to be changed from time to time. Therefore, some extra mechanism is required to support routing in VLAN environment. Existing approaches have some drawbacks in terms of inefficiency in traffic forwarding and switch software complexity. In this paper, a simple and efficient method for routing over IP subnet VLAN in Ethernet is proposed. This method has been implemented in hardware and found to work correctly. Various measurements and analyses have been performed to verify the efficiency of this protocol. Copyright © 2002 John Wiley & Sons, Ltd.     

Editorial: Special Issue on High Performace Distributed Computing

The Journal of Supercomputing -     

Calibration of a Photodiode Array Spectrometer Against the Copper Point

This paper describes a method to calibrate photodiode array spectrometers in the spectral radiance mode using a fixed-point blackbody as a reference source. Fixed-point blackbodies are characterized by their excellent emissivity, uniformity, and stability, which make them superior to both conventional standard lamps and variable temperature blackbodies. The temperature of these fixed points is accurately determined being traceable to either the International Temperature Scale (ITS-90) or thermodynamically through radiometric standards. The potential advantage of the fixed-point traceability chain is that it can be universally reproduced without recourse to any hierarchical calibrations or standards. The paper presents the calibration system and discusses the limitations of such an approach. The method used obtained an uncertainty of around 1.4 % ( \(k = 2\) ) associated with radiance responsivity across the spectral region from 550 nm to 1050 nm, which is comparable to what is readily achieved with a lamp-tile or lamp-illuminated spherical source.     

Stray light correction for diode-array-based spectrometers using a monochromator

Photodiode-array-based spectrometers are increasingly being used in a wide variety of applications. However, the signal measured by this type of instrument often is not what is anticipated by the user and is often subject to contamination from stray light. This paper describes an efficient and low-cost stray light correction approach based on a relatively simple system using a monochromator-based source. The paper further discusses the limitations of using a monochromator instead of a laser, as used by previous researchers, and its impact on the quality of the stray light correction. The reliability and robustness of the stray light correction matrix generated have been studied and are also reported.     

Resonance condition of a microfiber knot resonator immersed in liquids

Effects of immersing a microfiber knot resonator (MKR) in liquid solutions that have refractive indices close to that of silica are experimentally demonstrated and theoretically analyzed. Significant improvement in resonance extinction ratio within 2 to 10 dB was observed. To achieve a better understanding, a qualitative analysis of the coupling ratio and round-trip attenuation of the MKR is performed by using a curve-fitting method. It was observed that the coupling coefficient at the knot region increased when immersed in liquids. However, depending on the initial state of the coupling and the quantity of the increment in the coupling coefficient when immersed in a liquid, it is possible that the MKR may experience a deficit in the coupling parameter due to the sinusoidal relationship with the coupling coefficient.     

Temperature and nonlinearity corrections for a photodiode array spectrometer used in the field

Temperature and nonlinearity effects are two important factors that limit the use of photodiode array spectrometers. Usually the spectrometer is calibrated at a known temperature against a reference source of a particular spectral radiance, and then it is used at different temperatures to measure sources of different spectral radiances. These factors are expected to be problematic for nontemperature-stabilized instruments used for in-the-field experiments, where the radiant power of the site changes continuously with the sun tilt. This paper describes the effect of ambient temperature on a nontemperature-stabilized linear photodiode array spectrometer over the temperature range from 5?°C to 40?°C. The nonlinearity effects on both signal amplification and different levels of radiant power have also been studied and are presented in this paper.     

Effects of rf power on the structural properties of carbon nitride thin films prepared by plasma enhanced chemical vapour deposition

Carbon nitride (CN_x) thin films were deposited by radio frequency plasma enhanced chemical vapour deposition (rf PECVD) technique from a gas mixture of methane (CH₄), hydrogen (H₂) and nitrogen (N₂). The effects of rf power on the structural properties of CN_x thin films were discussed in this paper. It was found that rf power had significant effects on the growth rate, structural and morphological properties of the deposited films. The point of transition of the growth rate trend marked the equilibrium condition for primary and secondary reactions in growth kinetics of the film with respect to rf power. The films grown at this optimum rf power were most ordered in structure with high surface roughness and had the lowest N incorporation. This work showed that H etching effects and ion bombardment effects increase with increase in rf power and strongly influenced the structure of the CN_x films.     

IBLEACH: intra-balanced LEACH protocol for wireless sensor networks

Wireless sensor networks (WSNs) are composed of many low cost, low power devices with sensing, local processing and wireless communication capabilities. Recent advances in wireless networks have led to many new protocols specifically designed for WSNs where energy awareness is an essential consideration. Most of the attention, however, has been given to the routing protocols since they might differ depending on the application and network architecture. Minimizing energy dissipation and maximizing network lifetime are important issues in the design of routing protocols for WSNs. In this paper, the low-energy adaptive clustering hierarchy (LEACH) routing protocol is considered and improved. We propose a clustering routing protocol named intra-balanced LEACH (IBLEACH), which extends LEACH protocol by balancing the energy consumption in the network. The simulation results show that IBLEACH outperforms LEACH and the existing improvements of LEACH in terms of network lifetime and energy consumption minimization.