On the scalability of ad hoc networks

We investigate the inherent scalability problem of ad hoc networks originated from the nature of multihop networks. First, the expected packet traffic at the center of a network is analyzed. The result shows that the expected packet traffic at the center of a network is linearly related with the network size, that is, the expected packet traffic at the center of a network is O(k), where k is the radius of a network. From the result, the upper bound of the diameter of a network D=2k, that guarantees the network is scalable, is obtained. The upper bound is given by C/r-1, where C is the channel capacity available to each node and r is the packet arrival rate at each node.     

Identification and Characterization of a Welwitindolinone Alkaloid Biosynthetic Gene Cluster in the Stigonematalean Cyanobacterium Hapalosiphon welwitschii

The identification of a 36 kb welwitindolinone (wel) biosynthetic gene cluster in Hapalosiphon welwitschii UTEX B1830 is reported. Characterization of the enzymes responsible for assembling the early biosynthetic intermediates geranyl pyrophosphate and 3‐((Z)‐2′‐isocyanoethenyl)indole as well as a dedicated N‐methyltransferase in the maturation of N‐methylwelwitindolinone C isothiocyanate solidified the link between the wel pathway and welwitindolinone biosynthesis. Comparative analysis of the ambiguine and welwitindolinone biosynthetic pathways in two different organisms provided insights into the origins of diverse structures within hapalindole‐type molecules.     

Characterization and application of electrospun alumina nanofibers

Alumina nanofibers were prepared by a technique that combined the sol–gel and electrospinning methods. The solution to be electrospun was prepared by mixing aluminum isopropoxide (AIP) in ethanol, which was then refluxed in the presence of an acid catalyst and polyvinylpyrolidone (PVP) in ethanol. The characterization results showed that alumina nanofibers with diameters in the range of 102 to 378 nm were successfully prepared. On the basis of the results of the XRD and FT-IR, the alumina nanofibers calcined at 1,100°C were identified as comprising the α-alumina phase, and a series of phase transitions such as boehmite → γ-alumina → α-alumina were observed from 500°C to 1,200°C. The pore size of the obtained γ-alumina nanofibers is approximately 8 nm, and it means that they are mesoporous materials. The kinetic study demonstrated that MO adsorption on alumina nanofibers can be seen that the pseudo-second-order kinetic model fits better than the pseudo-first-order kinetic model.     

Effect of electron beam irradiation on the electrical and optical properties of ITO/Ag/ITO and IZO/Ag/IZO films

We have investigated the effect of electron beam irradiation as well as insertion of a Ag layer on the electrical and optical properties of the ITO or IZO films. The results show that electron beam irradiation as well as inserting a very thin Ag layer can significantly reduce sheet resistance of the ITO/Ag/ITO and IZO/Ag/IZO films. The electron beam irradiation also increases light transmittance and optical band gap of the ITO/Ag/ITO multilayer films; meanwhile, it has not influence on the transmittance of the IZO/Ag/IZO films. These results can be explained by that In and Zn cation in IZO film have strong tendency to preserve their coordination with oxygen.     

Kinetics of aluminum dross dissolution in sec-butyl alcohol for aluminum sec-butoxide

Al sec-butoxide (ASB) has been used as a precursor for activated aluminas but its cost is higher than any other type of precursor. This study was carried out on the dissolution kinetics for synthesis of the ASB from Al dross waste. The reaction was performed under the molar ratio of Al dross and sec-butyl alcohol (SBA) of 3 mol SBA/mol Al with a catalyst of 10^?3 mol HgI₂/mol Al and three different dissolution temperatures of 80, 90 and 100 °C. The Al reactant was used with Al dross of 3–5 mm size range. As a result of the experiment, the dissolution reaction gave a 65% yield after 24 h. The dissolution mechanism was determined by the shrinking core model assumed by the shape of spherical particles. Especially, the kinetic data were well fitted by a chemical reaction in the model. By the Arrhenius equation, the apparent activation energy was determined to be 40.9 kJ mol^?1 at the given reaction temperatures.     

Flexible photodiodes constructed with CdTe nanoparticle thin films and single ZnO nanowires on plastics

We construct a flexible pn heterostructured photodiode using a CdTe nanoparticle thin film and a single ZnO nanowire (NW) on a plastic substrate. The photocurrent characteristics of the flexible photodiode are examined under illumination with 325 nm wavelength light and the photocurrent efficiencies at bias voltages of ± 2.5 V are estimated to be 8.0 and 2.1 μA W(-1) under forward and reverse bias conditions, respectively. The photocurrent generation of the pn heterostructured photodiode is dominantly associated with the transport of the photogenerated charge carriers in the single ZnO NW. Furthermore, the operations of our flexible photodiode are investigated in the upwardly and downwardly bent states, as well as in the flat state.     

Minimalist counting in sensor networks (Noise helps)

We propose a novel algorithm for counting N indistinguishable objects, called targets, by a collection of sensors. We adopt a minimalist scenario where sensors are unaware of the (non-empty) intersections of sensing regions, and so simple addition of all sensor counts inflates estimates of the total number of targets. The multiple counting in intersections must be accounted for, but with nothing more than the sensor counts, this is clearly impossible. However, noise is typically present in the target counting of many, if not most, applications. We make the key observation that if there is a (target-dependent) noise source affecting all sensors simultaneously, then it couples those with non-empty intersections. Exploitation of this coupling allows us to extract multiple-counting statistics from stochastic correlation patterns, and hence to compute accurate estimates of N via the classical inclusion–exclusion formula. Cumulants are the correlation measures of choice. Our analysis brings out and resolves certain technicalities that arise in our statistical counting algorithm. Examples are worked out to show the potential of the new algorithm. The paper concludes with a discussion of alternative models and open problems.     

Routing Protocol for Heterogeneous Hierarchical Wireless Multimedia Sensor Networks

Recently, wireless multimedia sensor networks (WMSNs) have emerged as one of the most important technologies, driven by the development of powerful multimedia device such as CMOS. WMSNs require several factors such as resource constraints, specific QoS, high bandwidth and so on. In this paper, we propose a hierarchical heterogeneous network model based routing protocol for WMSNs. In our proposal, proposed network model is classified into monitoring class, delivery class and aggregation class. Also we define two kinds of the routing path in order to ensure bandwidth and QoS. In simulation results, we illustrate the performance of our proposal.     

Electrochemical sensing using quantum-sized gold nanoparticles

This paper describes the electrocatalytic activity of quantum-sized thiolate protected Au(25) nanoparticles and their use in electrochemical sensing. The Au(25) film modified electrode exhibited excellent mediated electrocatalytic activity that was utilized for amperometric sensing of biologically relevant analytes, namely, ascorbic acid and uric acid. The electron transfer dynamics in the Au(25) film was examined as a function of Au(25) concentration, which manifested the dual role of Au(25) as an electronic conductor as well as a redox mediator. The electron transfer study has further revealed the correlation between the electronic conductivity of the Au(25) film and the sensing sensitivity.     

In situ,quantitative characterization of gelation and fusion mechanism in poly(vinyl chloride) plastisols by small angle light scattering (SALS)

The present paper explores an effective means of characterizing structural changes of poly(vinyl chloride) (PVC) particles during gelation and fusion of PVC plastisols with small angle light scattering (SALS). The SALS method was shown to provide an in situ observation of swelling of PVC particles as well as quantitative information of average size of swollen particles while they are in progress of gelation and fusion. In addition, the SALS method enabled one to evaluate the relative solvent power of plasticizers from the manner of increase in the correlation distances.