The impact of data aggregation on the performance of wireless sensor networks

With the increasing need for different energy saving mechanisms in Wireless Sensor Networks (WSNs), data aggregation techniques for reducing the number of data transmissions by eliminating redundant information have been studied as a significant research problem. These studies have shown that data aggregation in WSNs may produce various trade‐offs among some network related performance metrics such as energy, latency, accuracy, fault‐tolerance and security. In this paper, we investigate the impact of data aggregation on these networking metrics by surveying the existing data aggregation protocols in WSNs. Our aim is twofold: First, providing a comprehensive summary and comparison of the existing data aggregation techniques with respect to different networking metrics. Second, pointing out both the possible future research issues and the need for collaboration between data management and networking research communities working on data aggregation in WSNs. Copyright © 2006 John Wiley & Sons, Ltd.     

Some properties of thin medium density fiberboard panels treated with sunflower waste oil vapor

The objective of this study was to investigate the effect of hot waste oil vapor on some of the physical and bending properties of commercially manufactured thin medium density fiberboard (tMDF) panels. The samples were treated with waste oil vapor at a temperature of 220 °C for 10 and 20 min time durations. Based on the findings in this work, the water absorption and thickness swelling of the samples were improved by the treated panels with hot vapor oil and heat. It appears that the samples had some discoloration as a result of treatment processes. It was also observed that modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples were adversely influenced. However, it seems that the thermal conductivity of the samples enhanced by such treatments. Panel products treated with these processes could have some promising potential in various applications including outdoor use.     

Pore Formation During Solidification of Aluminum: Reconciliation of Experimental Observations,Modeling Assumptions,and Classical Nucleation Theory

An in-depth discussion of pore formation is presented in this paper by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory for homogeneous and heterogeneous nucleation, with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and the corresponding probability of vacancies clustering to form that size have been calculated using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with the reinterpretations of in situ observations as well as the assumptions made in the literature to model pore formation.     

On the Intrinsic Fracture Pressure of Liquid and Solid Aluminum Around Its Melting Temperature

To determine the intrinsic fracture pressure of aluminum, data from studies that have used molecular dynamic simulations, the van der Waals method as well as experimental observations have been gathered and analyzed. Results indicate that aluminum has an intrinsic fracture pressure of ??4 GPa at its melting temperature in both liquid and solid states. Moreover, the Fisher equation can be used to estimate the intrinsic fracture pressure of liquid aluminum.     

Determination of Some Endocrine-Disrupting Metals and Organochlorinated Pesticide Residues in Baby Food and Infant Formula in Turkish Markets

There is a paucity of data in respect of the nutritional quality of complementary foods for infants and young children aged between 6 and 12 months. In this study, we developed and validated an analytical method for determination of the endocrine-disrupting organochlorine pesticides (OCPs) and elements (As, Cd, and Pb) in infant formula and baby foods. Therefore, it found out the contamination level of the both OCPs and some trace metals (As, Cd, and Pb) in widely consumed infant formula and baby food in Turkey. Metal concentrations in baby foods and infant formula were determined by inductively coupled plasma mass spectrometry. Samples were digested with nitric acid and hydrogen peroxide in a microwave oven. Determination of 24 organochlorine pesticide residues in baby foods and infant formula was completed by using gas chromatography double mass spectrometry. QuEChERS extraction method was carried out in the sample preparation part. The analytical performance of the entire procedure, such as linearity, the detection of limit, limit of quantification, specificity/selectivity, recovery (%), and precision, were assessed. The recoveries ranged from 93% (As) to 100% (Pb) for elements 78–98% for organochlorine pesticide residues (OCPs) at 100 ng mL^?1. According to the results, lead, cadmium, and pesticides were not detected in any of the samples, while arsenic was detected in 16 samples.     

Taguchi optimization approach for the polypropylene fiber reinforced concrete strengthening with polymer after high temperature

In this study, the strengthening with polymer the polypropylene fiber reinforced concrete exposed to high temperature was examined. Taguchi L₉ (3³) orthogonal array was used for the design of experiments. Three different parameters were used in the study; polypropylene fiber percentage (0 %, 1 % and 2 %), high temperature degree (300 °C, 600 °C and 900 °C) and curing period (3, 7 and 28 days). Cube samples of 100x100x100 mm sizes were produced for the compressive strength and ultrasonic pulse velocity tests. The samples were removed from the water and dried at 105?±?5 °C, and then they were exposed to temperatures of 300 °C, 600 °C and 900 °C. Then, the polymerization of monomer and the vinyl acetate monomer impregnation on the samples were carried out. The compressive strength and ultrasonic pulse velocity tests were made. Taguchi analysis showed that the largest compressive strength and ultrasonic pulse velocity were obtained at a rate of 0 % from the samples with polypropylene fiber exposed to 600 °C and kept for 28 days as cure period. It was determined as the result of Anova analysis that high temperature had made biggest effect on the compressive strength and ultrasonic pulse velocity of the concrete reinforced with polymer.     

Cost assessment and evaluation of various hydrogen delivery scenarios

In this paper, performance and cost assessment studies, including the stages of hydrogen storage, transmission and distribution of three different hydrogen delivery pathways are undertaken comparatively. The produced hydrogen is stored under different temperatures and pressures and then transported to the nearby cities for distribution. In addition, three different methods for the transportation of the produced hydrogen to the distribution centers are studied, which are as transportation for hydrogen by the pressurized tanks, cryogenic liquid hydrogen tanker and the gas pipelines. Moreover, the transmission options from the distribution center to the target consumer are also examined for three different conditions. As a result, the hydrogen production capacity, the levelized cost of energy distribution (in $/kg), the infrastructure costs (truck, tanker number, gas line costs, etc.) for the selected transmission scenario are calculated. Furthermore, the environmental impact (greenhouse gas (GHG) emissions) and some application parameters of the proposed system (e.g., number of hydrogen fuel stations and the distance between the stations, length of the distribution lines, etc.) are also determined. The highest levelized cost of delivery is obtained as 8.02 $/kg H₂ for the first scenario whereas the lowest cost is obtained as 2.73 $/kg H₂ for the third scenario.     

A new catalyst of AlCu@ZnO for hydrogen evolution reaction

Thin films of undoped ZnO, Al-doped ZnO, Cu-doped ZnO, and AlCu@ZnO deposited on indium tin oxide were performed by the sol-gel spin coating method. The prepared ZnO thin films were investigated for their structural and electrical properties after annealing at 500 °C for 1 h. ZnO thin films were characterized by electrochemical impedance spectroscopy, linear sweep voltammetry, scanning electron microscopy, Fourier transform infrared spectroscopy and Mott Schottky. According to the results obtained from the Nyquist diagrams of the ZnO thin films, the resistance value was found to decrease with binary doping and the resistance value was found to be lowest in AlCu@ZnO doped thin film containing 0.01 M Al and 0.1 M Cu. As ZnO thin films go to cathodic potentials, it is seen that the cathodic current value of ZnO with undoped is the lowest. It has been found that only Al and Cu doping showed less cathodic current than double doping.     

Analysis and performance assessment of a combined geothermal power-based hydrogen production and liquefaction system

In this paper, the thermodynamic study of a combined geothermal power-based hydrogen generation and liquefaction system is investigated for performance assessment. Because hydrogen is the energy of future, the purpose of this study is to produce hydrogen in a clear way. The results of study can be helpful for decision makers in terms of the integrated system efficiency. The presented integrated hydrogen production and liquefaction system consists of a combined geothermal power system, a PEM electrolyzer, and a hydrogen liquefaction and storage system. The exergy destruction rates, exergy destruction ratios and exergetic performance values of presented integrated system and its subsystems are determined by using the balance equations for mass, energy, entropy, energy and exergy and evaluated their performances by means of energetic and exergetic efficiencies. In this regard, the impact of some design parameters and operating conditions on the hydrogen production and liquefaction and its exergy destruction rates and exergetic performances are investigated parametrically. According to these parametric analysis results, the most influential parameter affecting system exergy efficiency is found to be geothermal source temperature in such a way that as geothermal fluid temperature increases from 130 °C to 200 °C which results in an increase of exergy efficiency from 38% to 64%. Results also show that, PEM electrolyzer temperature is more effective than reference temperature. As PEM electrolyzer temperature increases from 60 °C to 85 °C, the hydrogen production efficiency increases from nearly 39% to 44%.     

Color stability of frozen whole tilapia exposed to pre‐mortem treatment with carbon monoxide

BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre‐mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO‐treated whole, gutted tilapia, frozen for 2 and 4 months at ? 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration. RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO‐treated and untreated tilapia. However, even after 4 months of frozen storage, a*‐value of CO‐treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO‐euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO‐treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle. CONCLUSION: Color stability of tilapia fillets was significantly improved by pre‐mortem CO treatment. The color of CO‐treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre‐mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry