Aromatization of n-butane over new LD-HBS catalysts. Effect of the gallium oxide support

It is shown that even pure quartz, other silicas or aluminas can enhance the aromatization activity of a ZSM-5 zeolite. Incorporation of gallium oxide onto these supports increases further the production of aromatics. The use of supported gallium oxide co-catalyst obtained by co-evaporation of a colloidal silica and a Ga salt has led to extremely high aromatization performance for the hybrid catalyst.     

Finite element simulation of package stress in transfer molded MEMS pressure sensors

The goal of this paper is to investigate the effect of residual packaging stress resulting from transfer molding of a micro electro mechanical system pressure sensor. A model of a silicon diaphragm micro electro mechanical system pressure sensor geometry was used to simulate the stresses developed during the molding process. The analyses were carried out with an assumption that the epoxy molding compound was a temperature dependent elastic material. Finite element analysis was used to calculate the residual packaging stress. The stress values were used to obtain the electrical output signal and sensitivity of the packaged sensor. In this way, a direct link was established between package stress and device performance.The calculated output signal and sensitivity were compared with experimental data to verify the simulated stress and hence determine the effect of the packaging process on the pressure sensor. Four different service temperatures were considered to examine the temperature effects on the output signal and the sensitivity for the packaged sensor.     

Analysis of a low-pass filter employing a 4-pin capacitor

Capacitors with two or three leads tend to make poor low-pass filters at high frequencies (e.g., >100 MHz) due to the mutual inductance between the input and output sides of the filter. This work proposes a four-lead low-pass filter capacitor design that minimizes the magnetic flux coupling between the input and output. Measurements of a prototype capacitor confirm that it performs significantly better than a typical two-lead capacitor at high frequencies.     

The effect of size of sub-sample on mineral analysis values of apple fruits

Apple fruits were divided into opposite sectors of different sizes, and the mineral analyses of the sectors were compared with whole fruit values. Opposite sectors as small 8-12% of whole fruit weight were found to be as representative as larger sectors. There was no evidence of either a constant or a proportional bias arising as a result of sub-sampling. Sub-sampling variation was greater for Ca than for N, P, K and Mg.     

Performance degradation of LC-tank VCOs by impact of digital switching noise in lightly doped substrates

In mixed analog-digital designs, digital switching noise is an important limitation for the performance of analog and RF circuits. This paper reports a physical model describing the impact of digital switching noise on LC-tank voltage-controlled oscillators (VCOs) in lightly doped substrates. The model takes into account the propagation from the source of substrate noise to the different components in the VCO and the resulting modulation of the oscillator frequency. The model is validated with measurements on a 3.5-GHz LC-tank VCO designed in 0.18-/spl mu/m CMOS. It reveals that for this VCO, impact occurs mainly via the nonideal metal ground lines for lower frequencies and low tuning voltage and via the integrated inductors for higher frequencies and high tuning voltage. To make the design immune to substrate noise, the parasitic resistance of the on-chip ground interconnect has to be kept as low as possible and inductors have to be shielded. Hence, the developed model allows investigating the dominant mechanisms behind the impact of substrate noise on a VCO, which is crucial information for achieving a substrate noise immune design.     

Ultra-wide-band transmitter for low-power wireless body area networks: design and evaluation

The successful realization of a wireless body area network (WBAN) requires innovative solutions to meet the energy consumption budget of the autonomous sensor nodes. The radio interface is a major challenge, since its power consumption must be reduced below 100 /spl mu/W (energy scavenging limit). The emerging ultra-wide-band (UWB) technology shows strong advantages in reaching this target. First, most of the complexity of an UWB system is in the receiver, which is a perfect scenario in the WBAN context. Second, the very little hardware complexity of a UWB transmitter offers the potential for low-cost and highly integrated solutions. Finally, in a pulse-based UWB scheme, the transmitter can be duty-cycled at the pulse rate, thereby reducing the baseline power consumption. We present a low-power UWB transmitter that can be fully integrated in standard CMOS technology. Measured performances of a fully integrated pulse generator are provided, showing the potential of UWB for low power and low cost implementations. Finally, using a WBAN channel model, we present a comparison between our UWB solution and state-of-the-art low-power narrow-band implementations. This paper shows that UWB performs better in the short range due to a reduced baseline power consumption.     

Current situation on regulations for mycotoxins. Overview of tolerances and status of standard methods of sampling and analysis

A worldwide enquiry was undertaken in 1986-1987 to obtain up-to-date information about mycotoxin legislation in as many countries of the world as possible. Together with some additional data collected in 1981, information is now available about planned, proposed, existing or absence of legislation in 66 countries. Details about tolerances, legal bases, responsible authorities, prescribed methods of sampling and analysis and disposition of commodities containing inadmissible amounts of mycotoxins, are given. The information concerns aflatoxins in foodstuffs, aflatoxin M1 in dairy products, aflatoxins in animal feedstuffs, and other mycotoxins in food- and feedstuffs. In comparison with the situation in 1981, limits and regulations for mycotoxins have been expanded in 1987 with more countries having legislation (proposed or passed) on the subject, more products, and more mycotoxins covered by this legislation. The differences between tolerances in the various countries are sometimes quite large, which makes harmonization of mycotoxin regulations highly desirable.     

Estimation of genetic parameters for production and reproduction in Finnish Ayrshire cattle

Records of AI-sired cows born between 1978 and 1982 were used to form two composite production and reproduction data sets. First (second) consisted of 35,568 (26,443) first lactations of daughters of 270 (237) sires. Traits were FCM, heifer, and first parity nonreturn rates, days between calving and first insemination, and days open, with means 5075 (5280) kg, .62 (.62), .44 (.49), 81 (81) d and 110 (111) d. (Co)variance components were estimated by REML with an expectation maximization algorithm. Sire model included age, month, herd-year effects, and relationships among sires. Records on animals with observations missing on some traits were included. Estimates of heritabilities, averaged over data sets, were nonreturn rates for heifers and for cows, .02; FCM, .32; days to first insemination, .19; and days open, .10. Genetic correlations between first parity fertility and yield were unfavorable; the highest, .43, was between FCM and days open. Heifer nonreturn rate had a .09 correlation with production and a .26 correlation with cow nonreturn rate. Phenotypic correlations were in the same direction as genetic correlations but were smaller in magnitude. Results suggest that selection only for production would cause deterioration in level of fertility. When economical, AI sires should be evaluated for daughter fertility. A multi-trait model including milk production, days open and relationships among bulls is recommended for genetic evaluation.     

The role of ion characteristics in determining the structural and electrical quality of InN grown by metalorganic molecular beam epitaxy

The effects of growth temperature and nitrogen plasma biasing on the electrical and structural properties of InN grown using electron cyclotron resonance metalorganic molecular beam epitaxy (ECR MOMBE) have been investigated. These results are compared to those found from InN grown using a higher energy radio frequency (rf) plasma source (rf MOMBE). By varying the bias of the nitrogen plasma or the growth temperature, it is possible to achieve smooth surface morphologies. However, biasing can also be used to increase the mobility by a factor of two while the growth temperature has only a small effect. By contrast, use of an rf plasma improves mobility by nearly a factor of ten. None of the growth conditions investigated were found to significantly alter the electron concentration, which was measured to be 1−5 × 10²⁰ cm⁻³.     

Nonparametric regression analysis achieved with topographic mapsdeveloped in combination with projection pursuit learning: anapplication to density estimation and adaptive filtering of grey-scaleimages

A novel approach to nonparametric regression analysis using topographic maps is proposed. The maps are trained with the extended maximum entropy learning rule (eMER) in combination with projection pursuit regression (PPR) learning. Rather than a single map, several maps are developed along optimally chosen projection directions in the input space. In this way, the regression performance improves in the case of sparsely sampled input spaces. We explore two applications of the eMER/PPR combination: (1) probability density estimation from pilot estimates and (2) adaptive filtering of grey-scale images. The first case is used as a testbed for comparing different, both classic and neural network-based, regression techniques. The results show that our eMER/PPR combination yields a superior regression performance for small data sets. In the second case, the regression model is trained on a noisy subimage. The model obtained after training reduces the noise content of the full image by more than 20 dB