Repositioning Error Compensation in Discontinuous Ground-Based SAR Monitoring

The discontinuous mode of ground-based synthetic aperture radar (GB-SAR) is suitable for monitoring creep landslides. However, the instrument needs to be installed and disassembled repeatedly, which could inevitably cause repositioning error, and severely affect the accuracy of deformation measurements. This paper performs a detailed theoretical analysis of the repositioning error based on the Taylor expansion of a ternary function, and it can be built as a linear multi-parameter model. Simulations are made to validate the effectiveness of this model compared with two common first-order and second-order models. Then a compensation method based on the permanent scatterer (PS) technique is proposed. Two experiments of discontinuous monitoring are discussed. The first one is an equivalent discontinuous experiment, which utilizes two corner reflectors to evaluate the compensation accuracy. The other one is a discontinuous experiment taken on a steep mountain. Compared with the common methods, the proposed method can better compensate for the error phase and benefit high-precision deformation monitoring.

Discontinuous Dissolution Reaction in a Fe-13.5 at. % Zn Alloy

The dissolution process of a lamellar structure with α and Γ phases formed during a discontinuous precipitation reaction is investigated here with a Fe-13.5 at. % Zn alloy by means of optical microscopy and scanning and transmission electron microscopy. The α phase is a solute-depleted solid solution and the Γ phase is the intermetallic compound Fe3Zn10. The examination reveals that the dissolution occurs in a discontinuous mode by a receding of the former reaction front of the discontinuous precipitation towards the position of the original grain boundary. A new solid solution in the post-dissolution area is especially inhomogeneous and reflects the former locations of the Γ lamellae (“ghost images”) and the receding reaction front (“ghost lines”). A simulation procedure is applied to determine the Zn concentration profiles left in the post-dissolution region. Their shapes are mostly affected by the Zn content at the positions where the Γ lamellae have just been dissolved, which was also confirmed by the quantitative microchemical analysis.

On the Sizing of the DC-Link Capacitor to Increase the Power Transfer in a Series-Series Inductive Resonant Wireless Charging Station

Wireless inductive-coupled power transfer is a very appealing technique for the battery recharge of autonomous devices like surveillance drones. The charger design mainly focuses on lightness and fast-charging to improve the drone mission times and reduce the no-flight gaps. The charger secondary circuit mounted on the drone generally consists of a full-bridge rectifier and a second-order filter. The filter cut-off frequency is usually chosen to make the rectifier output voltage constant and so that the battery is charged with continuous quantities. Previous works showed that an increase in power transfer is achieved, if compared to the traditional case, when the second-order filter resonant frequency is close to the double of the wireless charger excitation and the filter works in resonance. This work demonstrates that the condition of resonance is necessary but not sufficient to achieve the power increment. The bridge rectifier diodes must work in discontinuous-mode to improve the power transfer. The paper also investigates the dependence of the power transfer increase on the wireless excitation frequency. It is found the minimum frequency value below which the power transfer gain is not possible. This frequency transition point is calculated, and it is shown that the gain in power transfer is obtained for any battery when its equivalent circuit parameters are known. LTSpice simulations demonstrate that the transferred power can be incremented of around 30%, if compared to the case in which the rectifier works in continuous mode. This achievement is obtained by following the design recommendations proposed at the end of the paper, which trade off the gain in power transfer and the amplitude of the oscillating components of the wireless charger output.

Low frequency operation and micro-controller implementation for multilevel quasi Z source inverter in photovoltaic application

A microcontroller based pulse width modulation implementation for multilevel quasi Z source inverter is proposed in this paper. The component design of quasi z source inverter (qZSI) is first considered with continuous and discontinuous mode of operations. The low switching frequency operation of multilevel quasi Z source inverter is proposed in this paper. The detailed modelling for qZSI is then established for effective implementation of PIC microcontroller (PIC 16F877A) for generating the switching signals. A prototype of five level quasi z-source inverter have been developed and the control signal to the gate drivers have been applied by properly adjusting the shoot through and non shoot through switching states. The hardware result shows the effective implementation of the proposed scheme.

Fast Motion Speed Alters the Sit-to-Walk Spatial and Temporal Pattern in Healthy Young Men

Sit-to-Walk (STW) is a critical task for daily independence, yet its two inherent destabilizing events (seat-off, walking initiation) may diminish postural stability under fast motion speed (FS). This study aimed at the FS effect on the STW spatial and temporal patterns, with a specific interest in the relative STW temporal pattern. The STW kinetics and kinematics were recorded (n=18 men, 20.7±2.0 years) at preferred and FS. Statistics included One-Way repeated measures ANOVA (SPSS 25.0, p≤0.05). The FS spatial pattern reveals a discontinuous mode of the forward ground reaction force, indicating a balance rather than a propulsive strategy during the Rising phase. The FS relative temporal pattern reveals the prolongation of the Leaning phase (most possibly due to the feet repositioning), the shortening of the Rising and the Walking phases, and a relative delay in the spatial variables (p≤0.05). Overall, the results do not allow the STW consideration at FS as a “magnified” with respect to force, or a “shrinked-in” with respect to time, copy of the preferred motion speed. As more generic and versatile than the absolute one, the relative temporal pattern may be used as a reference for a variety of populations.

LLC Resonant Tank based Converter for EV Charging Application

The aim of the article is to maximize the battery life using LLC resonant tank. LLC tank designing methodology and also the practical designing examination is introduced in LLC multi converter. Designed dc- dc converter increases the battery life by eliminating low and high frequency current ripples. In addition, bridgeless cuk converter is used for power factor improvement. To achieve the better power factor and to reduce the conduction losses the cuk converter is aimed to function in discontinuous mode of conduction (DCM). DC output voltage ranging 42-24 V for 650 W is obtained from the modelling for battery charging application.

β-Galactosidase from Lactobacillus helveticus DSM 20075: Biochemical Characterization and Recombinant Expression for Applications in Dairy Industry

β-Galactosidase encoding genes lacLM from Lactobacillus helveticus DSM 20075 were cloned and successfully overexpressed in Escherichia coli and Lactobacillus plantarum using different expression systems. The highest recombinant β-galactosidase activity of ∼26 kU per L of medium was obtained when using an expression system based on the T7 RNA polymerase promoter in E. coli, which is more than 1000-fold or 28-fold higher than the production of native β-galactosidase from L. helveticus DSM 20075 when grown on glucose or lactose, respectively. The overexpression in L. plantarum using lactobacillal food-grade gene expression system resulted in ∼2.3 kU per L of medium, which is approximately 10-fold lower compared to the expression in E. coli. The recombinant β-galactosidase from L. helveticus overexpressed in E. coli was purified to apparent homogeneity and subsequently characterized. The Km and vmax values for lactose and o-nitrophenyl-β-d-galactopyranoside (oNPG) were 15.7 ± 1.3 mM, 11.1 ± 0.2 µmol D-glucose released per min per mg protein, and 1.4 ± 0.3 mM, 476 ± 66 µmol o-nitrophenol released per min per mg protein, respectively. The enzyme was inhibited by high concentrations of oNPG with Ki,s = 3.6 ± 0.8 mM. The optimum pH for hydrolysis of both substrates, lactose and oNPG, is pH 6.5 and optimum temperatures for these reactions are 60 and 55 °C, respectively. The formation of galacto-oligosaccharides (GOS) in discontinuous mode using both crude recombinant enzyme from L. plantarum and purified recombinant enzyme from E. coli revealed high transgalactosylation activity of β-galactosidases from L. helveticus; hence, this enzyme is an interesting candidate for applications in lactose conversion and GOS formation processes.