Bayesian Unit Root Test in Nonnormal AR(1) Model

In this paper, we approximate the distribution of disturbances by the Edgeworth series distribution and propose a Bayesian analysis in a nonnormal AR(1) model. We derive the posterior distribution of the autocorrelation and the posterior odds ratio for unit roots hypothesis in the AR(1) model when the first four cumulants of the Edgeworth series distribution are finite and the higher order cumulants are negligible. We also apply the posterior analysis to eight real exchange rates and investigate whether these exchange rates behave like a random walk or not.     

Segregation of B, P, and C in the Ni-Based Superalloy, Inconel 718

Small additions of B, P, and C can result in dramatic changes in the mechanical performance and welding behavior of Inconel 718. Although additions of B and P improve the mechanical properties, they have a detrimental effect on weldability. Adding C mitigates the negative effect on welding while retaining the improvements in mechanical performance. In this study, precise observations of the segregation of B, P, and C to the grain boundaries are made using site-specific atom probe tomography and NanoSIMS. Changes in the segregation behavior provide a quantitative explanation for the welding response, where hot cracking is attributed to the formation of a eutectic film. Calculations of the relative positions of the B, P, and C revealed that these atoms were less likely to cluster together in the presence of C, providing insight into the likely mechanisms behind the segregation behavior in this complex, multicomponent alloy.     

ISI-free pulses with reduced sensitivity to timing errors

We consider the linear combination of two ISI free pulses, the raised cosine (RC) and the recently proposed better than raised cosine (BTRC). We determine their optimum combination using the distribution of timing error. The obtained pulses perform better than RC and BTRC for fixed as well as randomly distributed timing errors.     

An efficient merging scheme for prescribed skew clock routing

In ultra-deep submicron very large-scale integration (VLSI) designs, clock network layout plays an increasingly important role on determining circuit quality indicated by timing, power consumption, cost, power-supply noise, and tolerance to process variations. In this brief, a new merging scheme is proposed for prescribed nonzero skew routings which are useful in reducing clock cycle time, suppressing power-supply noise, and improving tolerance to process variations. This technique is simple and easy to implement for practical applications. Experimental results on benchmark circuits with both buffered and unbuffered routings exhibit large improvement on wirelength and buffer cost compared with other existing works.     

Ultrasensitive 2D Bi2O2Se Phototransistors on Silicon Substrates

2D materials are considered as intriguing building blocks for next‐generation optoelectronic devices. However, their photoresponse performance still needs to be improved for practical applications. Here, ultrasensitive 2D phototransistors are reported employing chemical vapor deposition (CVD)‐grown 2D Bi₂O₂Se transferred onto silicon substrates with a noncorrosive transfer method. The as‐transferred Bi₂O₂Se preserves high quality in contrast to the serious quality degradation in hydrofluoric‐acid‐assisted transfer. The phototransistors show a responsivity of 3.5 × 10⁴ A W^?1, a photoconductive gain of more than 10⁴, and a time response in the order of sub‐millisecond. With back gating of the silicon substrate, the dark current can be reduced to several pA. This yields an ultrahigh sensitivity with a specific detectivity of 9.0 × 10¹³ Jones, which is one of the highest values among 2D material photodetectors and two orders of magnitude higher than that of other CVD‐grown 2D materials. The high performance of the phototransistor shown here together with the developed unique transfer technique are promising for the development of novel 2D‐material‐based optoelectronic applications as well as integrating with state‐of‐the‐art silicon photonic and electronic technologies.     

Thermodynamics and kinetics of methane hydrate formation and dissociation in presence of calcium carbonate

Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca²⁺, CO₃^2?, HCO₃^?, CO₂, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10?wt%.     

Limitations of the current microbial identification system for identification of clinical yeast isolates

The ability of the rapid, computerized Microbial Identification System (MIS; Microbial ID, Inc.) to identify a variety of clinical isolates of yeast species was compared to the abilities of a combination of tests including the Yeast Biochemical Card (bioMerieux Vitek), determination of microscopic morphology on cornmeal agar with Tween 80, and when necessary, conventional biochemical tests and/or the API 20C Aux system (bioMerieux Vitek) to identify the same yeast isolates. The MIS chromatographically analyzes cellular fatty acids and compares the results with the fatty acid profiles in its database. Yeast isolates were subcultured onto Sabouraud dextrose agar and were incubated at 28 degrees C for 24 h. The resulting colonies were saponified, methylated, extracted, and chromatographically analyzed (by version 3.8 of the MIS YSTCLN database) according to the manufacturer's instructions. Of 477 isolates of 23 species tested, 448 (94%) were given species names by the MIS and 29 (6%) were unidentified (specified as "no match" by the MIS). Of the 448 isolates given names by the MIS, only 335 (75%) of the identifications were correct to the species level. While the MIS correctly identified only 102 (82%) of 124 isolates of Candida glabrata, the predictive value of an MIS identification of unknown isolates as C. glabrata was 100% (102 of 102) because no isolates of other species were misidentified as C. glabrata. In contrast, while the MIS correctly identified 100% (15 of 15) of the isolates of Saccharomyces cerevisiae, the predictive value of an MIS identification of unknown isolates as S. cerevisiae was only 47% (15 of 32), because 17 isolates of C. glabrata were misidentified as S. cerevisiae. The low predictive values for accuracy associated with MIS identifications for most of the remaining yeast species indicate that the procedure and/or database for the system need to be improved.     

Tata钢厂改进铸机对铸坯质量的改善

2002年,Tata钢厂改进了它的一台六流铸机,改进内容包括在结晶器中加入电磁搅拌器(EMS)和在中间包和结晶器之间使用浸入式水口(SEN)以能提供一种封闭式浇注工艺.改进的目标是提高铸坯的现行质量并且开发其生产多种高附加值钢材品种的能力,以丰富产品种类.改进的铸机投入生产后,要生产出合乎质量要求的铸坯就必须对铸机的一些操作参数进行优化.本文讨论了Tata钢厂依据不同的优化方法使用改进的铸机所取得的一些经验.     

On multiscale approaches to three-dimensional modelling of morphogenesis.

In this paper we present the foundation of a unified, object-oriented, three-dimensional biomodelling environment, which allows us to integrate multiple submodels at scales from subcellular to those of tissues and organs. Our current implementation combines a modified discrete model from statistical mechanics, the Cellular Potts Model, with a continuum reaction-diffusion model and a state automaton with well-defined conditions for cell differentiation transitions to model genetic regulation. This environment allows us to rapidly and compactly create computational models of a class of complex-developmental phenomena. To illustrate model development, we simulate a simplified version of the formation of the skeletal pattern in a growing embryonic vertebrate limb.