Corrosion behavior of Al–Si–Cu–(Sn, Zn) brazing filler metals

The corrosion behavior of Al–Si–Cu–(Sn, Zn) filler metals in a 3.5% NaCl aqueous solution were studied using electrochemical tests. The results showed that the addition of Sn or Zn to the Al–Si–Cu filler metal raised its corrosion current density sharply and caused its corrosion potential to become more active. Sn or Zn elements exert harmful effects on such low-melting-point brazing filler metals in that the corrosion resistance is degenerated, and damage is accelerated with an increase in the Sn or Zn content. Scanning electron microscopy (SEM) micrographs of the corroded surfaces of these Al–Si–Cu–(Sn, Zn) filler metals indicate that the Al-rich phase (i.e., Al–Si, Al–Si–Cu, and Al–Si–Cu–Sn eutectic phases) dissolves preferentially, while the Si particles and CuAl₂(θ) intermetallic compounds remain intact.     

Continuous Production of Glucose from Dextrin by Glucoamylase Immobilized on Porous Silica

Glucoamylase was covalently attached to porous silica particles and investigated for its applicability as an industrial catalyst in the production of glucose from starch hydrolysates. Reactivity at various reaction conditions, as well as enzyme loading, reaction kinetics, diffusional effects, and thermal stability, were determined in laboratory scale experiments. Pilot scale tests on continuous production of glucose were performed in a 1 cubic foot packed column reactor that could produce approximately 1,000 lbs/d glucose at 40°C. The maximum glucose concentration (based on dissolved solids) varied from 87 to 93% depending on the dextrose equivalent (D.E.) and degree of retrogradation of the feed dextrin. In 80 days of continuous operation no appreciable enzyme deactivation was observed. Initial sterilization of the reactor and continuous heat sterilization of the feed stream (120°C, 3–4 min) virtually ensured operation of the immobilized enzyme reactor at low levels of contamination, typical bacteria counts of the product effluent being 30–50/ml. Occasional interruption of the system resulted in much higher levels of microorganisms but did not affect the overall enzyme reactivity.     

Characterization of ZnO nanowires grown on Si (100) with and without Au catalyst

ZnO nanowires were grown on Si (100) substrates with and without Au catalyst by chemical vapor deposition employing the vapor-liquid-solid (VLS) and vapor-solid (VS) mechanisms, respectively. The diameters of the resulting nanowires were in the range 80-150 nm with typical length about 10 μm. The near-band-edge (NBE) emission of ZnO nanowires grown with and without catalyst was observed at 382 nm and 386 nm, respectively. The intensity of the NBE emission of ZnO nanowires grown without the catalyst was higher than that of the green luminescence. By sharp contrast, the intensity of the NBE emission of ZnO nanowires grown with catalyst was lower than that of green luminescence. The X-ray diffraction (XRD) spectrum of the ZnO nanowires grown without catalyst exhibited a peak intensity of c-plane 5 times higher than that of m-plane and 10 times higher than that of a-plane. However, the XRD spectrum of the ZnO nanowires grown with catalyst exhibited a peak intensity of the c-plane about 1.5 times higher than that of the m-plane and 4 times higher than that of a-plane intensity. Thus, the ZnO nanowires grown without catalyst have a preferential orientation along the c-axis direction. Our results show that the catalyst strongly effects optical and structural properties of the ZnO nanowires.     

Absorption of lodine into Starch Granules in Aqueous Suspension

The rate of iodine absorption by granular starch suspended in KI solution is examined. The rate controlling step is found to be the intraparticle diffusion of iodine. The process agrees well with a core-shrinking model. The apparent diffusivity of iodine in granular starch is determined to be (6.8 ± 0.5) × 10⁻⁸ cm²/sec at 25°C.     

A Lie group approach to a neural system for three-dimensionalinterpretation of visual motion

A novel approach is presented to neural network computation of three-dimensional rigid motion from noisy two-dimensional image flow. It is shown that the process of 3-D interpretation of image flow can be viewed as a linear signal transform. The elementary signals of this linear transform are the 2-D vector fields of the six infinitesimal generators of the 3-D Euclidean group. This transform can be performed by a neural network. Results are also reported of neural network simulations for the 3-D interpretation of image flow and a comparison of the performance of this approach with that using conventional methods. Computer simulation results verify the Lie-group-based neural network approach to three-dimensional motion perception.     

Null shift and beam squint in circularly polarized offset-reflector antenna

A formula for the null shift of the difference mode pattern of an offset-reflector antenna is derived. It is shown that this null shift and the beam squint of the sum mode pattern have different values. Such a phenomenon must be considered in the design of a two-channel tracking system.     

The effect of electrode arrangement on spectral distance measuresfor discrimination of EMG signals

The proper electrode placement in applying cepstral coefficients for electromyogram (EMG) signature discrimination was investigated. The authors measured EMG signals of different motions with two electrode arrangements simultaneously. Electrode pairs were located separately on dominant muscles (S-type arrangement) and closely in the region between muscles (C-type arrangement). The application of the cepstral method to signals derived from a C-type arrangement did not achieve the same discrimination as with a S-type arrangement. The authors used a simplified model to elucidate the poor performance in C-type signals. The bandwidth of signals obtained from S-type placement is wider than that from C-type. Narrower bandwidth decreases the importance of the more discriminative parts for both autoregressive (AR) and cepstral methods. The cepstral method is more sensitive to such variation, so the degradation in performance is more serious for the cepstral method. Second, the amplitude of C-type signal is lower than the S-type; therefore, the C-type signal is more sensitive to the disturbance of noise, especially in the high-frequency band. As high-frequency noise increases, the spectral difference between different EMG signals is gradually dominated by the low-frequency part, which is more informative. Thus, the performances of both methods are improved with increasing high-frequency noise. The improving rate of the AR method is faster than the cepstral method; therefore, its discriminative efficiency may exceed the cepstral method with C-type arrangement     

Retinoic acid syndrome: a case report

The objective of this study was to investigate the impact of allergy to hymenoptera venom on the occupational activities of patients undergoing immunologic treatment for insect sting anaphylaxis. The design was a cross-sectional study conducted in a sample of 500 out of 1,500 patients undergoing venom immunotherapy for insect sting reaction in 13 allergy clinics in Israel. A self-administered questionnaire was used to collect data about demographic characteristics of patients, severity of the allergic reaction and adverse effects on occupational activities. Of the 204 respondents who were part of the labour force, 48.5% reported adverse effects on routine occupational activities. The factors with a significant influence on the probability of adverse occupational effects were: (1) patient's type of work (blue collar vs. white collar: OR = 3.22, p < 0.001: army vs. white collar: OR = 5.28, p = 0.001); (2) severity of the allergic reaction (severe reaction vs. mild/moderate reaction: OR = 2.34, p = 0.007). Our findings suggest that severe insect sting allergy has an adverse impact on patients' occupational activities. This factor requires special attention by the medical community. Social workers and occupational physicians should collaborate in the assessment and management of these patients.     

Design of a self-routing frequency division multiple access(SR-FDMA) network using an optical ring filter with or without gain as arouter

Self-routing frequency division multiple access (SR-FDMA) network with ASK coherent detection and dual ring topology is proposed. The router, which employs the optical ring filter, is used as a means for selecting the desired channel carrier and at the same time as a bypass of the other channel carriers. The channel capacity and the carrier-to-noise ratio are investigated with the consideration of cross talk and power budget penalty. We find that there exists an optimum coupling coefficient of the transceiver coupler and a trade-off in selecting channel number and data rate. The results show that the router with gain can suppress the cross talk, compensate the power budget penalty, and largely increase the channel number. Therefore, with this router, a self-routing, high-density FDMA network is feasible