Symbolic analysis approach to settling time minimization in sc networks

The paper presents a method of settling time minimization in switched capacitor (SC) circuits. This problem has been discussed in recent papers because of high-frequency applications of SC networks. In comparison with the methods elaborated up to now and limited to biquads, the method presented in this paper can be used for an SC circuit containing an arbitrary number of operational amplifiers coupled together in each switching state and modelled as ideal transconductances. the fifth-order ladder bilinear SC filter is considered for illustration of the method and SPICE simulations.     

Room temperature characterization of Hg1-xCdxTe P-on-n heterostructure photodiodes

Measurements of 77K R_oA and 300K reverse bias dynamic impedance (R_dA) products at one volt reverse bias has been carried out to assess the degree of correlation of this figure of merit. Planar P-on-n heterostructures were grown on near lattice-matched CdZnTe substrates with Hg_1-xCd_xTe (0.20< x <0.30) by molecular beam epitaxy. These devices were passivated with CdTe and doped with indium and arsenic as n- and p-type dopants, respectively. Current-voltage characteristic of these devices exhibit thermally generated dark currents at small and modest reverse bias. We have observed that R_oA values of these long wavelength infrared P-on-n heterostructure photodiodes at 77K correlate with room temperature R_dA values. Diode arrays with high room temperature R_dA values at one volt reverse bias also have high R_oA values at 77K. Similarly, low R_dA values at room temperature indicate poor performance at 77K where deviation from diffusion current occurs at reverse bias of 0.2 to 1 volt at room temperature. The results presented here, for a small samples of devices, demonstrate that room temperature measurements of current-voltage characteristics to evaluate Hg_1-xCd_xTe (0.22< x <0.28) diode performance and array uniformity at lower temperatures can be used. This provides an acceptable criteria for further study at lower temperatures.     

Catalyst instabilities during the liquid phase partial oxidation of methane

A promising catalytic system for the low temperature oxidation of methane to a methanol derivative has been investigated under both batch and semi-continuous operation in two different reactor types. The system comprises of a bimetallic palladium and copper(II) chloride catalyst contained in a trifluoroacetic acid (TFA) and an aqueous phase. Methane, oxygen and a co-reductant carbon monoxide constitute the gas phase. Typical operating conditions were a temperature of 85 °C and a pressure of 83 bar.

The yields of the methyl trifluoroacetate product observed in this present work were less than those obtained in other batch autoclave works, which employed only 4 ml of liquid phase, compared with 50 ml in this study. Furthermore, an encouraging initial product formation rate of ca. 40 mol/m³ h, quickly decreased after the first hour, and came to an apparent end after only 2 h. This observation had not been reported previously.

Work performed in a semi-continuous porous tube reactor (300 ml of re-circulating liquid phase) also showed the same reaction characteristics as in the batch reactor. Thus, the deteriorating product formation rate cannot be attributed to gaseous reactant depletion (batch operation). The results suggest problems associated with catalyst instabilities, e.g. with the previously elucidated Wacker chemistry.     

Surface geometry of slide bearings after percussive burnishing

A review of literature about the effect of oil pockets on improvement of sliding elements tribological performance as well as about the changes of surface topography during “zero-wear” process is shown. The paper presents also the results of experimental investigations done in the Department of Manufacturing Processes and Production Organisation of Rzeszow University of Technology, connected with the creation of oil pockets on sliding surfaces. In order to simulate a deterministic surface a program for the visualisation of pits was written. The procedures for assessment of the oil pocket size of specific shape and oil pockets coverage are presented. The tendencies of changes of surface topography and oil pockets dimensions during “zero-wear” process are also described.     

Necessary and sufficient conditions for the universality of programming formalisms

Summary Over many familiar datatypes the notion of computable coincides with the notion of flowchartable. It is also known that flowcharts are not a universal programming formalism over arbitrary datatypes, in the sense that there are datatypes over which not all computable functions are flowchartable. In this paper we consider various extensions and restrictions of the basic formalism of flowcharts, and then for every such formalism, we characterize the datatypes over which the computable functions are exactly the functions programmable in this formalism. We say that a function is computable over a datatype if it is effective relative to the primitive operations and relations of the datatype.     

Exosomal Cargo May Hold the Key to Improving Reproductive Outcomes in Dairy Cows

The reproductive status of dairy cows remains a challenge for dairy farmers worldwide, with impaired fertility linked to a significant reduction in herd profitability, due in part to impaired immunity, increased metabolic pressure, and longer postpartum anestrous interval (PPAI). Exosomes are nanovesicles released from a variety of cell types and end up in circulation, and carry proteins, bioactive peptides, lipids, and nucleic acids specific to the place of origin. As such, their role in health and disease has been investigated in humans and animals. This review discusses research into exosomes in the context of reproduction in dairy herds and introduces recent advances in mass-spectrometry (MS) based proteomics that have a potential to advance quantitative profiling of exosomal protein cargo in a search for early biomarkers of cattle fertility.     

Improved Accuracy of High-Order WENO Finite Volume Methods on Cartesian Grids

We propose a simple modification of standard weighted essentially non-oscillatory (WENO) finite volume methods for Cartesian grids, which retains the full spatial order of accuracy of the one-dimensional discretization when applied to nonlinear multidimensional systems of conservation laws. We derive formulas, which allow us to compute high-order accurate point values of the conserved quantities at grid cell interfaces. Using those point values, we can compute a high-order flux at the center of a grid cell interface. Finally, we use those point values to compute high-order accurate averaged fluxes at cell interfaces as needed by a finite volume method. The method is described in detail for the two-dimensional Euler equations of gas dynamics. An extension to the three-dimensional case as well as to other nonlinear systems of conservation laws in divergence form is straightforward. Furthermore, similar ideas can be used to improve the accuracy of WENO type methods for hyperbolic systems which are not in divergence form. Several test computations confirm the high-order accuracy for smooth nonlinear problems.     

Algorithms for spatial collocation pattern mining in a limited memory environment: a summary of results

Rapid growth of spatial datasets requires methods to find (semi-)automatically spatial knowledge from these sets. Spatial collocation patterns represent subsets of spatial features whose instances are frequently located together in a spatial neighborhood. In recent years, efficient methods for collocation discovery have been developed, however, none of them assume limited size of the operational memory or limited access to memory with short access times. Such restrictions are especially important in the context of the large size of the data structures required for efficient identification of collocation instances. In this work we present and compare three algorithms for collocation pattern mining in a limited memory environment. The first algorithm is based on the well-known joinless method introduced by Shekhar and Yoo. The second and third algorithms are inspired by a tree structure (iCPI-tree) presented by Wang et al. In our experimental evaluation, we have compared the efficiency of the algorithms, both on synthetic and real world datasets.     

Long-term cyclability of nanostructured LiFePO4

Amorphous LiFePO₄ was obtained by lithiation of FePO₄ synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH₄)₂(SO₄)₂·6H₂O and NH₄H₂PO₄, using hydrogen peroxide as oxidizing agent. Nano-crystalline LiFePO₄ was obtained by heating amorphous nano-sized LiFePO₄ for different periods of time. The materials were characterized by TG, DTA, X-ray powder diffraction, scanning electron microscopy (SEM) and BET. All materials showed very good electrochemical performance in terms of energy and power density. Upon cycling, a capacity fading affected the materials, thus reducing the electrochemical performance. Nevertheless, the fading decreased upon cycling and after the 200th cycle the cell was able to cycle for more than 500 cycles without further fading.     

Damage localization for beams based on the wavelet correlation operator

The continuous wavelet transform (CWT) is one of the crucial damage identification tools in the vibration-based damage assessment. Because of the vanishing moment property, the CWT method is capable of featuring damage singularity in the higher scales, and separating the global trends and noise progressively. In the classical investigations about this issue, the localization property of the CWT is usually deemed as the most critical point. The abundant information provided by the scale-domain information and the corresponding effectiveness are, however, neglected to some extent. Ultimately, this neglect restricts the sufficient application of the CWT method in damage localization, especially in noisy conditions. In order to address this problem, the wavelet correlation operator is introduced into the CWT damage detection method as a post-processing. By means of the correlations among different scales, the proposed operator suppresses noise, cancels global trends, and intensifies the damage features for various mode shapes. The proposed method is demonstrated numerically with emphasis on characterizing damage in noisy environments, where the wavelet scale Teager-Kaiser energy operator is taken as the benchmark method for comparison. Experimental validations are conducted based on the benchmark data from composite beam specimens measured by a scanning laser vibrometer. Numerical and experimental validations/comparisons present that the introduction of wavelet correlation operator is effective for damage localization in noisy conditions.