Mechanical behaviour of agro-residue reinforced poly(3-hydroxybutyrate-co-3-hydroxyvalerate), (PHBV) green composites: A comparison with traditional polypropylene composites

Novel green composites were successfully fabricated by incorporating agro-residues as corn straw (CS), soy stalk (SS) and wheat straw (WS) into the bacterial polyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, by melt mixing technique. Effects of these biomass fibers on mechanical, thermal, and dynamic mechanical properties of PHBV were investigated. A comparative study of biomass fiber-reinforced polypropylene composite systems was performed. The tensile and storage modulus of PHBV was improved by maximum 256% and 308% with the reinforcement of 30 wt.% agricultural byproducts to it. For equal amounts of (30%) biomass fibers, tensile and flexural modulii of PHBV composites showed much higher values than corresponding PP composites. Alkali treatment of wheat straw fibers enhanced strain @ break and impact strength of PHBV composites by ∼35%, hardly increasing strength and modulus compared to their untreated counterparts. DMA studies indicated better interfacial interaction of PHBV with the biomass fibers than PP. Scanning electron microscopy (SEM), used to study the morphology of composites, also revealed similar outcomes.     

A new route toward semiconductor nanospintronics: highly Mn-doped GaAs nanowires realized by ion-implantation under dynamic annealing conditions

We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.     

Effect of temperature on X-ray, IR and magnetic properties of nickel ferrite prepared by oxalate co-precipitation method

Polycrystalline Nickel ferrite was synthesized by oxalate co-precipitation method at different sintering temperatures (700, 800, 900, 1000 and 1100°C) and characterized by X-ray diffraction and far IR absorption techniques. The lattice parameter (a), A-site and B-site radii (r _A , r _B ) were computed. XRD shows the formation of single phase cubic spinel structure. The crystallite sizes are calculated by Scherrer formula. The crystallite size is found to be increasing with sintering temperature. Porosity and Bond lengths on A-site and B-site were calculated and found to be minimum for the sample sintered at 800°C. The Far IR absorption bands are observed around 600 cm^?1 and 400 cm^?1 on the tetrahedral and octahedral sites respectively. Magnetization parameters such as saturation magnetization (Ms), magnetic moment (n_B) were calculated and the results are discussed with the help of existing theories. Saturation magnetization was found to be 47.85 emu/gm for the sample sintered at 1100 °C. Physical densities are obtained by Archimedes principle and are found to be 97.36% of their corresponding X-ray densities.     

Improved prediction model for time-dependent deformations of concrete: Part 7—Short form of BP-KX model,statistics and extrapolation of short-time data

For structures that do not have a high sensitivity to creep or for preliminary design of any structures, practising engineers demand a short formula for predicting the material creep properties. Such a formula is given in the present addendum to a previous six-part paper. It is based on optimal fitting of the previously published log-double power law to the formulae of the BP-KX model. A simple formula giving directly the compliance function rate is also presented. Finally, a simple method of improving the predictions on the basis of short-time measurements is described, and tables giving the statistics of the deviations of the prediction formulas of the simplified model and its short form from the data in the literature are presented.     

A methodology for the design of SFS/SCD circuits for a class of unordered codes

We present two design methods that produce concurrently testable and cascadable combinational blocks for a given logic function. In the first method, the designed block is strongly fault-secure and code-disjoint. Any unordered coding scheme can be used for the input and output. The second method produces designs that are strongly fault-secure and strongly code-disjoint. Here the encoding requires some simple density properties that are seen to be satisfied by the commonly used coding schemes. This makes the method applicable to a larger class of coding schemes than the existing methods. We also show that our designs have lower hardware overhead.     

Partitioning circuits for improved testability

Exhaustive self-testing of combinational circuitry within the framework of the level-sensitive scan design (LSSD) discipline requires that every output node depend on a small number of input nodes. We present here efficient algorithms that take an arbitrary block of combinational logic and add to it the smallest number of bits of new LSSD registers necessary to: (1) partition the logic so that no output depends on more thank inputs, and (2) maintain timing within the block (so that all input-to-output paths encounter the same number of bits of register). Our partitioning algorithms conform to two different design constraints. We also show that the unconstrained partitioning problem is NP-complete.A portion of the research of the first and third authors was done while visiting Bell Communications Research. Sandeep Bhatt was also supported in part by NSF Grant DCR 84-05478 and ONR Grant N00014-82-K-0184, and Arnold Rosenberg by NSF Grants MCS-81-01213 and DMC-85-04308. A preliminary version of this paper was presented at the Fourth MIT VLSI Conference on Advanced Research in VLSI.     

Assurance of dynamic adaptation in distributed systems

Long running applications often need to adapt due to changing requirements or changing environment. Typically, such an adaptation is performed by dynamically adding or removing components. In these type of adaptations, components are often added to or removed from multiple processes in the system. As a result, during adaptation, the system may consist of both changed and unchanged processes, causing old and new components to overlap. This overlapping of components during adaptation may induce cross-component communication, which may lead to behavior during adaptation that is unpredictable and/or undesirable.In this paper, we discuss an approach to model and verify overlap adaptation. We use the transitional-invariant lattice and the transitional-faultspan lattice to verify the correctness of adaptation in the absence and the presence of faults, respectively. We also discuss a framework to support implementation of overlap adaptation.     

Continuous verification using multimodal biometrics

Conventional verification systems, such as those controlling access to a secure room, do not usually require the user to reauthenticate himself for continued access to the protected resource. This may not be sufficient for high-security environments in which the protected resource needs to be continuously monitored for unauthorized use. In such cases, continuous verification is needed. In this paper, we present the theory, architecture, implementation, and performance of a multimodal biometrics verification system that continuously verifies the presence of a logged-in user. Two modalities are currently used - face and fingerprint - but our theory can be readily extended to include more modalities. We show that continuous verification imposes additional requirements on multimodal fusion when compared to conventional verification systems. We also argue that the usual performance metrics of false accept and false reject rates are insufficient yardsticks for continuous verification and propose new metrics against which we benchmark our system     

Analysis and modeling of highway truck traffic volume variations during severe winter weather conditions in Canada

Railway Engineering Science - This paper investigates the impact of cold and snow on daily and hourly truck traffic volume on a primary highway in Alberta, Canada. This research is based on a...