Mechanics of the low-flow limit in slot-die coating with no vacuum

Slot-die coating is a premetered, film-deposition process compatible with a wide range of materials. Of topical interest to precision electronics applications is the deposition of high-cost nanomaterial dispersions over moderately sized (>10 cm² ) areas with submicron wet film thickness. In this work, a two-dimensional (2D) model has been developed to understand the limits of the process and to predict the thinnest possible film achievable. Coined the low-flow limit, this parametric operating boundary presents the minimum uniform, defect-free film achievable at a given set of liquid properties and die/substrate geometry. We investigate the low-flow limit with a model that allows menisci to locate anywhere on the die lands, faces, and substrates with prescribed contact angles, thereby minimizing the assumptions on the bead configuration. The model is validated via comparison of its low-flow limit predictions to published experimental data. Analysis yields insights into the mechanics of coating bead breakdown at the low-flow limit.     

Purification and characterization of a papaya (Carica papaya L.) pectin methylesterase isolated from a commercial papain preparation

We purified a Carica papaya pectin methylesterase (CpL-PME; EC 3.1.1.11) from a commercial papain preparation. This CpL-PME was separated from the abundant cysteine endopeptidases activities using sequential hydrophobic interaction and cation-exchange chromatographies and then purified by affinity chromatography using Sepharose-immobilized kiwi PME inhibitor protein to obtain a single electrophoretically homogeneous protein. The enzyme was purified 92-fold with 38% yield, providing a specific activity of 1200 U/mg. The molecular weight was determined to be 35,135 by MALDI-TOF-MS in linear mode. MALDI-TOF-MS peptide mass fingerprinting following trypsin digestion indicated CpL-PME represents a novel Carica PME isoform. The CpL-PME required salt for activity, and it showed a broad activity range (pH 6–9) and moderate thermostability (optimum ca. 70 °C). A calcium-insensitive methylated lime pectin treated with CpL-PME to reduce degree of methylesterification by 6% converted the substrate to high calcium sensitivity, indicating a processive mode of action. These properties support further research to apply CpL-PME to tailor pectin nanostructure.     

On Chip Signal Generators for Low Overhead ADC BIST

Testing of ADCs deeply embedded in SOCs is a significant challenge due to access limitations. ADC Built-in self-test (BIST) is considered a promising alternative to traditional test. This paper investigates implementation issues in adapting the stimulus error identification and removal (SEIR) algorithm, originally developed for production test, into a practical ADC BIST solution. Signal generators with very low transistor count and area consumption are presented. Extremely simple methods for generating small constant voltage level shifts are introduced and evaluated. Simulation results show that the generated signals, together with the level shifts, are able to test a 16-bit ADC to 16 bit accuracy levels. These results demonstrate that accurate BIST of deeply embedded analog and mixed-signal (AMS) blocks may be practically implemented on chip with very low overhead.     

Contrasting energy efficiency in various ceramic sintering processes

Regarding the recent energy costs and environmental concerns, energy efficient and sustainable manufacturing processes have become important topics. In this paper, a number of novel sintering methods were reviewed to illustrate their potential to reduce energy consumption during ceramic processing. Three approaches: adding sintering aid, increasing heating rate, and applying electric field on the reduction of the energy consumption were considered, and the underlying mechanism in each approach was explored. Next, the laser sintering that is utilized in additive manufacturing approaches and the new Cold Sintering Process (CSP) were introduced as potential techniques for the further improvement of energy efficiency. Since the need of furnaces was eliminated in these latter techniques, their heat dissipation during sintering would significantly decline. For example, it was demonstrated that the energy consumption for BaTiO₃ powder can decrease from 2800 kJ/g for conventional techniques to 30 kJ/g for CSP. A simple parameter, “Normalized Excess Energy”, was used as a first order approximation to compare the energy merit in the different sintering techniques.     

The Role of Li2CO3 and PbO in the Low-Temperature Sintering of Sr, K, Nb (SKN)-Doped PZT

It is demonstrated that the use of ∼0.9 mol% Li₂CO₃ (LC) as a sintering aid for Sr, K, Nb modified Pb(Zr_{1− x} ,Ti _x )O₃ (PZT) ceramics is effective only in the presence of excess PbO (∼2 mol%). It is shown that LC and PbO react to form the compound, Li₂PbO₃ (LPO) which has a melting temperature of ∼836°C. Using dilatometry, we were able to correlate shrinkage during heating of a green ceramic to the melting of the LPO. Consequently, complete densification and sizeable grain growth are achieved by solution-precipitation of the ceramic through the liquid phase. Importantly, sintering is not particularly effective with such small additions of either LC or PbO alone. In confirmation of this model, the LPO compound was presynthesized and used as the only sintering aid in the same PZT composition. The densification behavior of this mixture compared well with the case of separate additions.     

Weakly Coupled Relaxor Behavior of BaTiO3–BiScO3 Ceramics

The structural and dielectric properties of (1− x )BaTiO₃– x BiScO₃ ( x =0–0.5) ceramics were investigated to acquire a better understanding of the binary system, including determination of the symmetry of the phases, the associated dielectric properties, and the differences in the roles of Bi₂O₃ and BiScO₃ substitutions in a BaTiO₃ solid solution. The solubility limit for BiScO₃ into the BaTiO₃ perovskite structure was determined to be about x =0.4. A systematic structural change from the ferroelectric tetragonal phase to a pseudo-cubic one was observed at about x =0.05–0.075 at room temperature. Dielectric measurements revealed a gradual change from proper ferroelectric behavior in pure BaTiO₃ to highly diffusive and dispersive relaxor-like characteristics from 10 to 40 mol% BiScO₃. Several of the compositions showed high relative permittivities with low-temperature coefficients of capacitance over a wide range of temperature. Quantification of the relaxation behavior was obtained through the Vogel–Fulcher model, which yielded an activation energy of 0.2–0.3 eV. The attempt characteristic frequency was 10¹³ Hz and the freezing temperature, T _f, ranged from −177° to −93°C as a function of composition. The high coercive fields, low remanent polarization, and high activation energies suggest that in the BiScO₃–BaTiO₃ solid solutions, the polarization in nanopolar regions is weakly coupled from region to region, limiting the ability to obtain long-range dipole ordering in these relaxors under field-cooled conditions.     

Effect of Acceptor (Mg) Concentration on the Resistance Degradation Behavior in Acceptor (Mg)-Doped BaTiO3 Bulk Ceramics: I. Impedance Analysis

Degradation behavior of the electrical resistance of acceptor (Mg)-doped BaTiO₃ ceramics was contrasted against different acceptor concentrations. Coarse-grained specimens with uniform grain sizes and different acceptor concentrations were prepared by sintering both in air and a reducing atmosphere. The specimens sintered under both atmospheres showed similar trends in the degradation behavior with a critical dependence on the acceptor concentration. The time to degradation decreased systematically with the increase of acceptor concentration. An impedance spectroscopy study was conducted on these samples at various temperatures. An equivalent circuit analysis of these data was considered, from which bulk and grain-boundary conductivity was determined for each composition as a function of grain size. Attempts were made also to determine the ionic conductivity for the different samples as a function of temperature and doping concentration.     

3GPP LTE的预编码和空间多路复用MIMO技术

当多路径信道在一个或多个MIMO接收机上无法提供足够的SINR时,3GPP LTE中的预编码技术可以极大地提高系统性能.测试结果表明,各种测量均可在多路径和信道失真条件下,对预编码系统的操作和性能进行非常有用的深入分析.