A fourth-order single-bit switched-capacitor /spl Sigma/-/spl Delta/ modulator for distributed sensor applications

In this paper, we present a switched-capacitor sigma-delta (/spl Sigma/-/spl Delta/) modulator for high resolution applications. In particular, this /spl Sigma/-/spl Delta/ modulator is well suited for distributed sensor networks. The circuit, implemented in a double-poly, double-metal 0.6 /spl mu/m CMOS technology, is based on a fourth-order single-loop architecture with a sampling frequency of 256 kHz. The chip consumes 50 mW from a single 5-V supply and achieves a signal-to-noise ratio of 104.9 dB over a bandwidth of 400 Hz, corresponding to a resolution of 17.1 bits.     

Cycling reliability of RF-MEMS switches with Gold–Platinum multilayers as contact material

Microsystem Technologies - Contact resistance is the main parameter used for assessing the high cycling reliability of RF microelectromechanical (RF-MEMS) switches. In this paper the use of a...     

Effects of PEMFC operating parameters on the performance of an integrated ethanol processor

In this paper the performance of a complete fuel cell system processing ethanol fuel has been analyzed as a function of the main fuel cell operating parameters. The fuel processor is based on the steam reforming process, followed by high- and low-temperature shift reactors, and carbon monoxide preferential oxidation reactor, which are coupled to a polymeric fuel cell (PEMFC). The goal was to analyze and improve the fuel cell system performance by simulation techniques. PEMFC operation has been analyzed using an available parametric model, which was implemented within HYSYS environment software. Pinch Analysis concepts were used to investigate the process energy integration and determine the maximum efficiency minimizing ethanol consumption. The system performance was analyzed for the SR-12 Modular PEM Generator, the Ballard Mark V fuel cell and the BCS 500 W stack. The net system efficiency is dependent on the required power demand. Efficiency values higher than 50% at low loads and less than 30% at high power demands are computed. In addition, the effect of fuel cell temperature, pressure and hydrogen utilization was analyzed. The trade-off between the reformer yield and the fuel cell performance defines the optimal operation pressure. The cell temperature determines operating zones where the water, involved in the reforming reactions, can be produced or demanded.     

Arsenic species in an arsenic hyperaccumulating fern, Pityrogramma calomelanos: a potential phytoremediator of arsenic-contaminated soils

The fern Pityrogramma calomelanos is a hyperaccumulator of arsenic that grows readily on arsenic-contaminated soils in the Ron Phibun district of southern Thailand. P. calomelanos accumulates arsenic mostly in the fronds (up to 8350 microg As g(-1) dry mass) while the rhizoids contain the lowest concentrations of arsenic (88-310 microg As g(-1) dry mass). The arsenic species in aqueous extracts of the fern and soil were determined by high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICPMS) which served as an arsenic specific detector. Only a small part of the arsenic (6.1-12%) in soil was extracted into water, and most of this arsenic (> 97%) was present as arsenate. The arsenic in the fern rhizoids was approximately 60% water-extractable, 95% of which was present as arsenate. In contrast, arsenic in the fern fronds was readily extracted into water (86-93%) and was present mainly as arsenite (60-72%) with the remainder being arsenate. Methylarsonate and dimethylarsinate were detected as trace constituents in only two fern samples. Preliminary estimates of phytoremediation potential suggest that P. calomelanos might remove approximately 2% of the soil arsenic load per year. With due consideration to the type of arsenic compounds present in the fern, and their water-solubility, the option of disposing high arsenic ferns at sea is raised for discussion.     

Using Physical and Logical Constraints for Invoice Understanding

This work presents a methodology for invoice understanding. The invoices of our domain can be grouped into classes according to their logo. The understanding phase is based on two knowledge levels: a specific knowledge for each class, called a document model; and knowledge on the whole domain of interest, called a domain model. The invoices of a known class are understood by its document model, while the invoices of an unknown class are understood by using the domain model. The main contribution of this work is related to the use of the physical and logical constraints of the domain of interest for document understanding, without using an OCR system. Our approach has been tested by some experiments that are intended to identify some regions within invoices of unknown classes. In most cases, the results have shown the reliability of the approach.     

Reliability of RF MEMS switches due to charging effects and their circuital modelling

The reliability of RF MEMS switches is typically reduced by charging effects occurring in the dielectrics. The aim of this paper is to discuss these effects, and to propose analytical and equivalent circuit models which account for most of the physical contributions present in the structure.     

Serum autoantibodies in chronic hepatitis C: comparison with autoimmune hepatitis and impact on the disease profile

Antibodies to nuclei (ANA), smooth muscle (SMA), and liver/kidney microsomes type 1 (anti-LKM1) may occur in chronic hepatitis C. Distinct subspecificities, including ANA with the homogeneous pattern (ANA-H) and SMA with antiactin specificity (SMA-AA), are found in autoimmune hepatitis (AIH). This study was performed to characterize the hepatitis C virus (HCV)-associated autoantibodies and to evaluate their influence on the profile of the disease. Two hundred ninety consecutive patients with chronic hepatitis C and 35 control cases with AIH were screened for autoantibodies by indirect immunofluorescence (IFL) at 1:40 serum dilution. The ANA pattern was defined by IFL on HEp-2 cells and the SMA-AA identified by the presence of at least two of the following elements: 1) SMA(T) or SMA(G) pattern by IFL on kidney sections; 2) XR1 precipitating system by counterimmunoelectrophoresis; or 3) typical pattern by IFL on liver sections from phalloidin-intoxicated rats. ANA, SMA, and anti-LKM1 occurred in 9%, 20%, and 6% of chronic hepatitis C cases, respectively. The overall prevalence of autoantibodies was 30% (87 of 290). Compared with AIH, HCV-associated ANA and SMA exhibited ANA-H and SMA-AA at a lower prevalence (38% vs. 71%, P = .04 and 8% vs. 87%, P < .000001, respectively) and had a lower median titer (1:80 vs. 1:320, P < .001 and 1:40 vs. 1:320, P < .000001, respectively). The concomitant positivity for ANA-H and SMA-AA was detected in none of the HCV cases, but in 46% of AIH sera (P < .000001). Two parameters were independently associated with the autoantibodies in chronic hepatitis C: high alanine transaminase (ALT) serum levels (F = 14.04) and female gender (F = 5.03). At the univariate analysis, patients with autoantibodies had a more severe portal-periportal necroinflammation (median Scheuer's score: 2.05 vs. 1.64, P = .003). The presence of autoantibodies did not influence the response to interferon (IFN). In chronic hepatitis C, serum autoantibodies are common, but their subspecificities are distinct from those occurring in AIH. Whereas the absence of ANA-H and/or SMA-AA does not exclude AIH, the characterization of ANA and SMA may help to discriminate between the two conditions. As compared with the seronegative counterpart, autoantibody-positive chronic hepatitis C is more common in females and exhibits a more severe biochemical and histological activity. The response to IFN therapy, however, is similar.