Study of the preparation of ruthenia based catalytic materials by heating their precursors

Thermal behaviour of hydrous ruthenia (RuO₂·nH₂O) and ruthenia containing 10% titania ((RuO₂)_0.9–(TiO₂)_0.1nH₂O) was characterised on heating in air by emanation thermal analysis (ETA), thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA). The anhydrous ruthenia and ruthenia containing 10% titania samples were prepared by heating their hydrous precursors at 500°C in air. The temperature intervals of the samples dehydration and crystallisation were determined. XRD, TEM and surface area measurements were also used for the characterisation of the samples. The ETA results, evaluated by a mathematical model, brought about new information about surface area and microstructure development of the intermediate products of the oxides under in situ conditions of the heating in air. A good agreement between ETA and the results of other methods was obtained. The NO_x reduction by CO was used to test the catalytic properties of these samples.     

Experimental optimization of the probe for eddy-currentdisplacement transducer

The experimental optimization of the coil for an eddy-current displacement transducer probe is presented in the paper. The coil geometry is optimized for the special design of the transducer as a meter of the real part of the probe's impedance. Measurement of the transducer's transfer function has been performed with several samples of ring-shaped coils, as well as with the flat, pancake-shaped coil and with the single-layered cylindrical coil. For the sake of comparison, measurement with the ferrite-cored coil has been included too. The measurement results clearly indicate that the optimal coil geometry is a ring with a uniform and very small cross section of the winding     

Influence of heat treatment on phase transformation of clay-iron oxide composite

Magnetic clay composite prepared by the method of precipitation of iron oxide onto the clay surface was subjected to a heat treatment. The presence of iron oxide phase in composite before the heating was determined by the Mössbauer spectroscopy method as γ-Fe₂O₃. Structural changes of maghemite in clay composite after heating at selected temperatures in N₂ and Ar/H₂ atmosphere were studied using Mössbauer spectroscopy, X-ray diffraction, TG/DSC and SEM methods. It was shown the full transformation of γ-Fe₂O₃ to α-Fe₂O₃ in the inert atmosphere at temperature 650 °C and only a partial transformation to Fe₃O₄ in the reductive atmosphere at 300 °C.     

基于MTT比色和响应面法优化侧孢短芽孢杆菌最大活菌数培养条件

目的：探索获得侧孢短芽孢杆菌（Brevibacillus laterosporus）最大活菌数的最佳培养基成分及培养条件。方法：在建立MTT比色法与平板计数法的相关回归方程基础上,对获得最大活菌数的侧孢短芽孢杆菌最适培养基成分（碳源、氮源、无机盐）和培养条件（初始pH、温度、接种量、磷酸二氢钾）进行优化。结果：MTT比色法与平板计数法对活菌数测定结果表现出显著的线性关联（R²>0.999）;麦芽糖、氯化钙、初始pH、磷酸二氢钾为显著影响因子,最佳发酵条件为麦芽糖8.75 g/L,氯化钙0.17 g/L,初始pH 7.07、磷酸二氢钾3.73 g/L,此条件下活菌数为8.12×10⁸ CFU/mL,与理论活菌数（8.25×10⁸ CFU/mL）无显著差异。结论：基于MTT比色和响应面法优化侧孢短芽孢杆菌最大活菌数培养条件,优化后的活菌数较优化前提高了3.02倍。     

Fully balanced CMOS current-mode circuits

A fully balanced current-mode circuit topology has been developed for analog signal processing applications. The basic building block, a 5-V fully balanced current mirror/amplifier, has been fabricated using a standard 2-μm n-well CMOS process. With a peak signal to bias current ratio i/I=0.5, the open-loop total harmonic distortion was-70 dB. With the addition of sampling switches, the current mirror/amplifier forms a fully balanced switched-current integrator that exhibits first-order cancellation of clock-feedthrough/charge-injection effects. Fully balanced SI ladder filters have been implemented using a 2-μm p-well CMOS process. For a sampling frequency of 128 kHz, the five-pole Chebyshev low-pass ladder filters met design specifications of 0.1-dB passband ripple and 5-kHz bandwidth. The dynamic range was 81.5 dB, and the total power dissipation was 14 mW with V_dd 5 V     

改性土体材料圆柱体试件轴心抗压试验研究

为改善传统土坯砌体民居的土体材料的基本力学性能,通过在土体材料中分别掺入不同掺量的麦秸秆、生石灰或粗砂,形成改性土体材料,制作了直径100 mm×高110 mm圆柱体试件,通过试件抗压强度试验的试验现象和结果的分析,研究不同掺和量对试件基本力学性能的影响,分别提出掺和麦秸秆、生石灰或粗砂试件的最佳掺和比例范围.试验结果表明,当麦秸秆掺和量达到一定范围时,极限荷载和抗变形能力提高明显,当生石灰或粗砂掺和量达到一定范围时,极限荷载提高显著但抗变形能力下降.     

Low-power CMOS continuous-time filters

A design technique for low-power continuous-time filters using digital CMOS technology is presented. The basic building block is a fully-balanced integrator with its unity-gain frequency determined by a small-signal transconductance and MOSFET gate capacitance. Integrator excess phase shift is reduced using balanced signal paths, and open-loop gain is increased using low-voltage cascode amplifiers. Two-pole bandpass and five-pole lowpass ladder filters have been implemented in a 1.2 μm n-well CMOS process. The lowpass prototypes provided 300 kHz-1000 kHz bias-current-tunable -3 dB bandwidth, 67 dB dynamic range with 1% total harmonic distortion (THD), and 30 μW/pole (300 kHz bandwidth) power dissipation with a 1.5 V supply; the bandpass prototypes had a tunable center frequency of 300 kHz-1000 kHz, Q of 8.5, and power dissipation of 75 μW/pole (525 kHz center frequency) from a 1.5 V supply. The active filter area was 0.1 mm²/pole for both designs     

A dimensional analysis‐based model for the prediction of nitrogen concentrations in Laborec River,Slovakia

During the past decades, several models that predict the concentration profiles after a discharge of pollutants in a river have been developed. A model that predicts nitrogen concentrations in a river has been developed and is presented in this paper. The developed model that determines nitrogen concentrations in a water stream is based on a dimensional analysis. Fundamentals of the modelling of the pollutant predictions in a water stream consist of a derivation of function dependency from expressed non‐dimension arguments. Non‐dimension arguments are stated from variables, which influence the occurrence of pollutants. The model for the prediction of nitrogen concentrations in water streams has been developed for the Laborec River (eastern Slovakia). The differences between the nitrogen concentrations predicted from developed models and measured concentrations in the river are also discussed here.     

Analog logic techniques steer around the noise

CMOS folded source-coupled logic (FSCL) and current-steering logic (CSL), developed to complement conventional CMOS static logic in high-precision mixed-signal applications, are examined. The key feature of FSCL and CSL is the reduction in power-supply noise-current spikes by two orders of magnitude or more compared to conventional CMOS logic. Hence, FSCL and CSL are attractive for the high-speed logic sections of CMOS mixed-mode integrated circuits, while conventional logic is appropriate for the low-speed digital subsections     

Efficient and Reusable Pb(II) Metal–Organic Framework for Knoevenagel Condensation

A microporous lead–organic framework {[Pb₄(µ₈-MTB)₂(H₂O)₄]·5DMF·H₂O}_n (MTB?=?methanetetrabenzoate, DMF?=?N,N′-dimethylformamide) was synthesized and studied as a catalyst in Knoevenagel condensation reactions. The framework is built from tetranuclear [Pb₄(µ₃-COO)(µ₂-COO)₆(COO)(H₂O)₄] clusters and exhibits a 3D structure, with repeated 1D jar-like cavities with sizes about 14.98?×?7.88 and 14.98?×?13.17 Å² and BET specific surface area of 980 m² g^?1. To obtain open framework with unsaturated Pb(II) sites needed for catalysis, the thermal activation of the solvent exchanged sample was performed (DMF was exchanged by EtOH). The activated compound was tested in Knoevenagel condensation of bulky aldehydes and active methylene compounds at different temperatures. Excellent catalytic conversion and selectivity in condensation of small-sized aldehydes with malononitrile was observed, which indicates that the opened Pb(II) sites play a significant role in the heterogeneous catalytic process. Leaching test confirmed the stability of the catalyst in catalytic reactions. Moreover, the compound displayed good recyclability after several reuses without significant decrease in the original catalytic activity.

Graphical Abstract

Novel Pb(II) metal–organic framework was tested in Knoevenagel condensation. The catalyst showed excellent catalytic conversion, selectivity and recyclability. Aldehydes with lower kinetic diameter demonstrated high conversions and yields. Catalyst is less efficient for condensation of larger aromatic aldehydes.

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