An Experimental and Theoretical Study of the Flow of Xerographic Developer Powders from Small Hoppers

An experimental and theoretical study is presented which characterizes the flow of xerographic developer powders out of small hoppers. A small hopper in this reference is defined as one having a maximum height of 12 in. Two walls of the hopper converge at the gate and the remaining two walls are parallel to each other. The flow is studied as a function of the gate opening, hopper angle, particle size, the total height of the particulate material in the hopper, and the angle of repose. Experimental results are presented for particle diameters between 100 ? and 600 ?. A theory is presented to predict flow rates. The predicted functional dependence agrees very well with the observations. The predicted flow rates are about 3.75 times higher than the observed ones. It is suggested that this is due to a resistive force originating in particle interactions. Inclusion of this correction factor in the theory results in very good agreement between theoretical predictions and experimental observations.     

A new method for nuclear ADCs using the vernier approximation technique

The paper describes a new method of analog-to-digital conversion. The method named the vernier approximation technique utilizes two scales made of chains of resistors sliding over each other, one being called the main scale and the other the vernier scale. The vernier scale is moved by applying the input analog voltage as a voltage shift at both ends. This voltage shift is digitized using the comparators connected between the corresponding points on main and vernier scales. All the quantization steps are derived from a single quantization step using the process of sliding and vernier scaling resulting in high differential linearity. The scheme uses a balancing technique to balance the points on the main scale with the corresponding points on the vernier scale. The scheme works with the speed of a “sequential parallel approximation technique” giving a higher speed of operation than either the Wilkinson technique or the successive approximation technique used for nuclear ADCs. The technique gives high accuracy even with use of ordinary components such as 1% resistors.     

Alternate Testing of RF Transceivers Using Optimized Test Stimulus for Accurate Prediction of System Specifications

In the recent past, with the emergence of System-on-Chip (SoC), focus has shifted towards testing system specifications rather than device or module specifications. While the problem of test accessibility for test stimulus application and response capture for such high-speed systems remains a challenge to the test engineers, new test strategies are needed which can address the problem in a practical manner. In this paper, the problem of testing the transmitter and the receiver subsystems of a RF transceiver for system level specification is addressed. Instead of using different conventional test stimuli for testing each of the system level specifications of RF subsystems, a specially crafted test stimulus is used for testing all the specifications from the response of the subsystem-under-test. A new simulation approach has also been developed to perform fast behavioral simulations in frequency domain for the system-under-test. In the test method, frequency domain test response spectra are captured and non-linear regression models are constructed to map the spectral measurements onto the specifications of interest. In the presented simulation results, the test stimuli have been validated using netlist level simulation of the subsystem-under-test and specifications have been predicted within an error of ±3% of the actual value.Soumendu Bhattacharya was born in Calcutta, India, in 1978. He received his Bachelors degree from Indian Institute of Technology, Kharagpur, India, in 2000. In 2002, he received the M.S.E.E. degree in electrical engineering from Georgia Institute of Technology, Atlanta, USA. He is currently working toward his Ph.D. degree. In the summer of 2001, he worked as a summer intern in National Semiconductor, Santa Clara, CA, USA. His research interests are in the area of test generation for mixed-signal and RF circuits and systems and design-for-test.Achintya Halder received the B.S. degree in electronics and electrical communication engineering from the Indian Institute of Technology, Kharagpur, in 1998. He worked as an IC design engineer with Texas Instruments until 2000. Currently, he is a Ph.D. student and a research assistant with the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta. His research area is analog/RF and mixed signal testing.Ganesh P. Srinivasan received the B.E. degree in Electronics and Communication Engineering from the National Institute of Technology and Science, University of Madras, Chennai (Madras), India, in 2002. He received the M.S. degree in Electrical and Computer engineering from the Georgia Institute of Technology, Atlanta, GA, in 2004 and is currently pursuing his Ph.D. degree in Electrical and Computer Engineering at the Georgia Institute of Technology, Atlanta, GA. His research interests include low cost testing approaches for analog/RF and mixed-signal circuits, and improving performance of low cost testers for enabling high quality tests.Abhijit Chatterjee received the Bachelor of Technology degree in electrical engineering from the Indian Institute of Technology, Kanpur, India, in 1981, the M.S. degree in electrical engineering and computer science from University of Illinois at Chicago in 1983 and the Ph.D. degree in electrical and computer engineering from the University of Illinois at Urbana-Champaign in 1990. Until December 1992, he was a Research Staff Member at the General Electric Research and Development Center in Schenectady, NY. His work has been cited by the Wall Street Journal and presented on a Japanese network TV program called High Tech Shower International. He is a collaborating partner in NASAs New Millennium Project. Dr. Abhijit Chatterjee is also the author of one U.S. patent and has over one hundred publications in referenced journals and conferences.     

Mercury chalcogenides under pressure

The mercury chalcogenides, HgTe and Hg_1?x Cd _x Te, have received considerable attention in recent years because of their use in infrared photon detectors. This article is concerned with some recent experiments on the Γ₆-Γ₈ band crossover in these systems induced by pressure. It is shown that although the inverted band model is valid for HgTe, the conclusions of the earlier workers on the pressure induced Γ₆-Γ₈ crossover are erroneous. Experimental results show that it is difficult to observe the band crossover due to an intervening structural phase transition from cubic zinc blend to the cinnabar structure. However pressure experiments on the semiconductor alloy system Hg_0·9Cd_0·1 Te clearly indicate this crossover. New results on the zinc blend-cinnabar phase transformation are also presented. The striking behaviour of thermoelectric power in the high pressure cinnabar phase is correlated with the available experimental data on the structurally similar elemental semiconductors like selenium and tellurium.     

Selective ion-exchange in MAPO-36 and its application in toluene disproportionation

MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg²⁺ in the framework of AlPO-36 and ion-exchanged with Fe³⁺, Zn²⁺, La³⁺ and Ce³⁺ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36. The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)₂⁺ to MO⁺. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h.     

Comparison of the Effects of an Ionic Liquid and Other Salts on the Properties of Electrospun Fibers, 2 – Poly(vinyl alcohol)

Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039–0.259 mol · kg^?1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector.

     

Effect of PP-g-MAH compatibilizer content in polypropylene/nylon-6 blends

A method commonly used to induce compatibility between polyamides and polyolefins is by chemical modification of the polyolefins. This concept has been employed to produce compatibilized blend of nylon 6 (N6) and polypropylene copolymer (PPCP) by adding maleic anhydride grafted polypropylene (PP-g-MAH) as a third component. The blends of N6, PPCP and PP-g-MAH were prepared using a twin screw extruder. TEM of the blends revealed better dispersion and reduction in the size of the dispersed phase. In case of N6 rich blends, about 25% increase in tensile strength was observed with just three phb of PP-g-MAH. The maximum impact strength and flexural modulus were observed at around 30% PPCP. The incorporation of PP-g-MAH increased the flexural modulus of N6/PPCP blends significantly.     

Synthesis and characterization of MgAl2O4–ZrO2 composites

Different types of dense 5–97% ZrO₂–MgAl₂O₄ composites have been prepared using a MgAl₂O₄ spinel obtained by calcining a stoichiometric mixture of aluminium tri-hydroxide and caustic MgO at 1300 °C for 1 h, and a commercial yttria partially stabilized zirconia (YPSZ) powder as starting raw materials by sintering at various temperatures ranging from 1500 to 1650 °C for 2 h. The characteristics of the MgAl₂O₄ spinel, the YPSZ powder and the various sintered products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area, particle size analysis, Archimedes principle, and Vickers indentation method. Characterization results revealed that the YPSZ addition increases the sintering ability, fracture toughness and hardness of MgAl₂O₄ spinel, whereas, the MgAl₂O₄ spinel hampered the sintering ability of YPSZ when sintered at elevated temperatures. A 20-wt.% YPSZ was found to be sufficient to increase the hardness and fracture toughness of MgAl₂O₄ spinel from 406 to 1314 Hv and 2.5 to 3.45 MPa m^1/2, respectively, when sintered at 1600 °C for 2 h.