Even-weighted codes for error detection

For a binary symmetric channel, a code V with only evenweighted words performs better than a corresponding code V? with both odd- and even-weighted words, from the point of the probability of undetected errors. We derive an estimate of the improvement in the performance.     

One-Step Atmospheric Pressure Synthesis of the Ground State of Fe Based LaFeAsO<Subscript>1−<Emphasis Type="Italic">δ</Emphasis></Subscript>

We report an easy and versatile one-step synthesis route for a newly discovered Fe based LaFeAsO_1−δ compound with 0.0≤δ≤0.15. Instead of widely used high-pressure-high-temperature (HPHT) synthesis, we applied the normal atmosphere solid-state reaction route. The stoichiometric mixtures of Fe, La₂O_3, La, and As in ratio LaFeAsO_1−δ with 0.0≤δ≤0.15 are sealed in an evacuated quartz tube and further heated at 500, 850, and 1,100 °C in Ar for 12, 12, and 33 hours, respectively, in a single step. The resulting compounds are single phase LaFeAsO crystallized in tetragonal P4/nmm structure. These samples showed the ground state spin density wave (SDW) like metallic behavior below around 150 K. In conclusion, the ground state (non-superconducting) of newly discovered Fe based superconductor is synthesized via an easy one-step solid-state reaction route.     

Design and analysis of a novel mechanical loading machine for dynamic in vivo axial loading

This paper describes the construction of a loading machine for performing in vivo, dynamic mechanical loading of the rodent forearm. The loading machine utilizes a unique type of electromagnetic actuator with no mechanically resistive components (servotube), allowing highly accurate loads to be created. A regression analysis of the force created by the actuator with respect to the input voltage demonstrates high linear correlation (R(2) = 1). When the linear correlation is used to create dynamic loading waveforms in the frequency (0.5-10 Hz) and load (1-50 N) range used for in vivo loading, less than 1% normalized root mean square error (NRMSE) is computed. Larger NRMSE is found at increased frequencies, with 5%-8% occurring at 40 Hz, and reasons are discussed. Amplifiers (strain gauge, linear voltage displacement transducer (LVDT), and load cell) are constructed, calibrated, and integrated, to allow well-resolved dynamic measurements to be recorded at each program cycle. Each of the amplifiers uses an active filter with cutoff frequency at the maximum in vivo loading frequencies (50 Hz) so that electronic noise generated by the servo drive and actuator are reduced. The LVDT and load cell amplifiers allow evaluation of stress-strain relationships to determine if in vivo bone damage is occurring. The strain gauge amplifier allows dynamic force to strain calibrations to occur for animals of different sex, age, and strain. Unique features are integrated into the loading system, including a weightless mode, which allows the limbs of anesthetized animals to be quickly positioned and removed. Although the device is constructed for in vivo axial bone loading, it can be used within constraints, as a general measurement instrument in a laboratory setting.     

Improved lithium cyclability and storage in a multi-sized pore ("differential spacers") mesoporous SnO2

A wide pore distribution mesoporous morphology stabilizes SnO(2) structure during lithium insertion and removal and in the process remarkably enhances the lithium storage and cyclability.     

Intelligent Query-Based Data Aggregation Model and Optimized Query Ordering for Efficient Wireless Sensor Network

Data aggregation algorithms play a primary role in WSN, as it collects and aggregates the data in an energy efficient manner so that the life expectancy of the network is extended. This paper intends to develop a query-based aggregation model for WSN using the advanced optimization algorithm called group search optimization (GSO). The proposed model is constructed in such a way that the querying order (QO) can be ranked based on latency and throughput. Accordingly, the main objective of the proposed GSO-based QO is to minimize the latency and maximize the throughput of WSN. The proposed data aggregation model facilitates the network administrator to understand the best queries so that the performance of the base station can be improved. After framing the model, it compares the performance of GSO-based QO with the traditional PSO-based QO, FF-based QO, GA-based QO, ABC-based QO and GSO-based QO in terms of idle time and throughput. Thus the data aggregation performance of proposed GSO-based QO is superior to the traditional algorithms by attaining high throughput and low latency.     

Creep and Oxidation Behavior of GTAW Welded ET45 Micro Alloy Tube

Metallurgical and Materials Transactions A - Ethylene pyrolysis furnace tubes are subjected to a variety of failure mechanisms such as creep, oxidation, carburization, and thermal shock. Therefore,...     

Chemical composition,oral toxicity and antimicrobial activity of Iranian propolis

Propolis is a resinous natural hive product derived from plant exudates collected by honeybees. Due to biological and pharmacological activities, it has been extensively used in folk medicine. The present study was designed to investigate the chemical composition, subchronic toxicity, antimicrobial activity of Iranian propolis ethanolic extract, which has not been studied previously. One hundred and nine compounds were identified by gas chromatography–mass spectrometry analysis. Forty-five days subchronic toxicity of oral propolis extract was investigated in male rats. During the study no significant behavioral and clinical toxicity has been seen in animals however, hematologic, blood biochemistry and histopathologic data studies exhibited some significant differences between the groups. The ethanolic extract of propolis inhibited the growth of all examined microorganisms including bacteria and fungi with the highest antimicrobial activity against Gram-positive bacteria such as Staphylococcus aureus and Staphylococcus epidermidis.     

Mathematical Model and Experimental Validation of Free Surface Size Segregation for Polydisperse Granular Materials

 A mathematical model of free surface size segregation of granular matter is proposed. The material is assumed to be dry, cohesionless and to consist of several populations with distinct diameter ranges. It is not necessary that one population is predominant. The extent of segregation depends mainly on the relative amount of small and large particles and on the diameter ratios but not on their absolute values. The model predicts how the fractions of these populations change from the position where the material is fed onto a heap to its bottom. It is based on ideas of L. Prigozhin} to treat binary mixtures. Introducing a new scheme to interpolate the local deposition rates from situations with one predominant population it becomes possible to handle mixtures with three and more diameters. The model may be applied to storage systems of any kind, such as bunkers, hoppers, silos or mixing beds, provided the source is sufficiently weak and concentrated. Numerical simulations are discussed for conical and ramp-like geometries and for ternary mixtures. In order to validate the model a few experiments were conducted. As measured by the natural variability of the problem and the simplicity of the model, which is sufficiently easy to be used in an industrial controller, good agreement between theory and experiment is found. Received: 2 August 2001     

Plasma Nitriding of Low Alloy Sintered Steels

Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably.It was observed that monophase compound layer, γ‘, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.     

Sensitive Functions and Approximate Problems

Properties of functions that are good measures of the CRCW PRAM complexity of computing them are investigated. While theblock sensitivityis known to be a good measure of the CREW PRAM complexity, no such measure is known for CRCW PRAMs. It is shown that the complexity of computing a function is related to itseverywhere sensitivity, introduced by Vishkin and Wigderson. Specifically, the time required to compute a functionf: Dⁿ→Rof everywhere sensitivityes(f) withPprocessors and unbounded memory isΩ(log[log es(f)/(log(|D|+4P/es(f)))]). This improves results of Azar and of Vishkin and Wigderson. This lower bound is used to derive new lower bounds for someapproximate problems. These problems can often be solved faster than their exact counterparts and for many applications, it is sufficient to solve the approximate problem. It is shown thatapproximate selection,approximate counting,approximate compaction, andpadded sortingall require timeΩ(log log n) with a linear number of processors, if the level of accuracy desired is moderately high. For these levels of accuracy, no lower bounds were known for these problems on the PRAM model. The lower bounds for some of the problems are tight.