Using an induction prover for verifying arithmetic circuits

We show that existing theorem proving technology can be used effectively for mechanically verifying a family of arithmetic circuits. A theorem prover implementing: (i) a decision procedure for quantifier-free Presburger arithmetic with uninterpreted function symbols; (ii) conditional rewriting; and (iii) heuristics for carefully selecting induction schemes from terminating recursive function definitions; and (iv) well integrated with backtracking, can automatically verify number-theoretic properties of parameterized and generic adders, multipliers and division circuits. This is illustrated using our theorem prover Rewrite Rule Laboratory (RRL). To our knowledge, this is the first such demonstration of the capabilities of a theorem prover mechanizing induction. The above features of RRL are briefly discussed using illustrations from the verification of adder, multiplier and division circuits. Extensions to the prover likely to make it even more effective for hardware verification are discussed. Furthermore, it is believed that these results are scalable, and the proposed approach is likely to be effective for other arithmetic circuits as well.     

The Effects of Process Characteristics on the Value of B2B E-Procurement

Even as more organizations are moving towards implementing Web-based B2B procurement solutions, they are unsure of the real benefits of the Web. In other words, what is the value of B2B e-procurement to an organization and how to measure this value? What factors affect this value? In this paper, we discuss an evaluation framework to determine the value of B2B e-procurement and the effect of process characteristics on the value. We use an empirical study to highlight the different value created by different procurement types. We then develop a more comprehensive economic model to capture the additional effects of demand volume and process complexity. The integration of theoretical and empirical approaches provides a strong foundation to develop and evaluate useful adoption strategies for B2B e-procurement.     

Heat transfer enhancement of concentrated solar absorber using hollow cylindrical fins filled with phase change material

A concentrated solar absorber with finned phase change materials was experimentally studied using a Scheffler type parabolic dish concentrator. The absorber's inner surface was fixed with hollow cylindrical containers filled with phase change material (PCM) for heat transfer augmentation. The absorber's selected PCM was acetanilide (Melting point of 116 °C)—the cylindrical capsules protruding into the fluid side to create turbulence and mixing and acting as fins. The absorber surface temperature was observed to be about 130–150 °C during the outdoor tests while passing fluid through the absorber. The fluid flow rate varied from 60 to 100 kg/h during the outdoor experiments. The peak energy and exergy efficiency of parabolic dish collector (PDC) at the fluid flow rate of 80 kg/h with PCM integrated solar absorber was found to be about 67.88% and 6.96%, respectively. The integration of cylindrical PCM containers resulted in more heat transfer augmentation in the solar absorbers. The optimized solar absorber could be suitable for various applications like steam generation, biomass gasification, space heating, and hydrogen generation.     

Ion-Exchange Behavior of New and Novel Zirconium(IV)-Based Composite Cation-Exchangers

The synthesized polyaniline-Zr(IV) selenoiodate and polyaniline-Zr(IV) selenomolybdate composite ion exchangers were characterized by Fourier transform infrared spectroscopy, UV spectra, X-ray diffraction, scanning electron microscope, thermogravimetric analysis, and conductivity studies. The ion-exchange capacities, effect of eluent concentration, elution time, elution behavior, and pH on ion-exchange capacity were also studied to exploit the ion-exchange capability of the composites. The study revealed that polyaniline-Zr(IV) selenoiodate and polyaniline-Zr(IV) selenomolybdate ion exchangers are having excellent ion-exchange capacity values for K⁺ ion 1.36 and 1.44?meq?g^?1, respectively. The organic polymeric part of the composites provides mechanical and chemical stability, whereas the inorganic part supports the ion-exchange behavior and thermal stability. The increase in electrical conductivity is due to the inorganic and organic parts. A mechanism for the formation of the polyaniline-Zr(IV) selenoiodate and polyaniline-Zr(IV) selenomolybdate composite ion exchangers is discussed, which may also be applied for the preparation of other composite ion exchangers. Sorption behavior of metal ions on the composites was studied in different solvent systems. On the basis of distribution coefficient values (K_d), it has been found that the cation-exchange materials are highly selective for Pb(II)-ions. Such modified composite materials can be applied as an electrochemically switchable ion exchanger for water treatment, especially water softening.     

Heating value of biodiesel: An empirical and theoretical exploration

The heating value of a fuel affects both the brake thermal efficiency and combustion characteristics of an engine. Its value for fuel blend cannot be calculated based on the blend ratio even though the heating values of blend fuels are known. Therefore, a relationship was formulated from the experimental data to predict the heating values of fuel blends. This study was carried out to compute the theoretical heating values of raw as well as purified pungamia oil with different blend ratio by means of SPSS software (ver. 16). The Durbin–Watson (multiple regressions) tests were carried out in the present study to validate the experimental results. The values of density, flash point, viscosity, and percentage of blends were considered an independent variable, and the heating value was considered a dependent variable for the analysis of heating values of different pungamia oil blends with diesel. The theoretically calculated heating values and relationship between the independent variables were around ± 1%. Also, these values were compared with that of the experimental results of other researchers and the variation was only about 2%. Thus, the validations of developed relation with experimental results show good compliance.     

Optimal ordering decisions under two returns policies

To avoid stockouts and maintain product availability, retailers typically carry excess units and subsequently incur higher cost. In case of style/fashion goods, demand forecasting is extremely difficult due to short selling cycles. The purpose of this study was to minimise the cost of excess stocking without compromising product availability. To achieve these conflicting objectives, our study includes two ordering instances and two returns policies. The time between orders subsequently helps resolve demand uncertainty. Existing studies consider only one type of returns policy, that is, returns on the entire purchase quantity; whereas our study considers two types of returns policies: returns on the first order size and returns on the entire purchase quantity. This study also includes models for the retailer and the supply chain system. Analytical and numerical insights into our study enable the retailer to select his appropriate returns policies to maximise his as well as system’s expected profits. We also show that perfect coordination of partners will help them improve their profits considerably.     

An index to characterize gas-solid and solid-solid mixing from average volume fraction fields

A mixing index based on solid volume fraction fields is developed for gas-solid flows. Conventional mixing indices are based on particle realizations of granular mixing and are applicable to experimental data or discrete element method simulations. However, these indices cannot be used as-is for multifluid models, and an index for characterizing mixing in gas-solid flows from continuous fields is needed. The performance of the new mixing index is tested in two applications. The first is a 3D simulation of the mixing of biomass and sand in a fluidized bed reactor, and the second is a 2D simulation of binary particle segregation in a fluidized bed. The simulations are performed using OpenFOAM®. The mixing index is used to quantify gas-solid mixing using solid volume fractions and solid-solid mixing using solid fractions. The formulation of conventional mixing indices is extended to be used with solid volume fractions fields, and methods for performance improvement are presented.