Multi-defect detection based on ultrasonic Lamb wave sign phase coherence factor imaging method

The ultrasonic Lamb wave total focusing method (TFM) only uses the amplitude of the defective scattered signal for virtual focused imaging, while ignoring the phase information of the scattered signal and the dispersion characteristics of the Lamb wave, resulting in low imaging resolution and easily produced artefacts in imaging. To solve this problem, an ultrasonic Lamb wave imaging method based on phase coherence is proposed in this paper and the sign coherence factor (SCF) in the full matrix scattering signal is extracted. Moreover, the method uses the SCF to weight the amplitude of the full matrix scattering signal, suppresses the side lobes of the defect echo signal and the Lamb wave dispersion effect, improves the ultrasonic Lamb wave imaging resolution and weakens the artefacts. Finally, single- and multiplehole defects in aluminium plates are detected for experimental validation using an ultrasonic phased array. The array performance indicator and signal-to-noise ratio are used as indicators for quantitative assessment of imaging performance. The results show that compared with the TFM imaging, the SCF imaging can effectively suppress the noise and scattered signal side lobes, improve the array performance indicator (API) by 69.1% and improve the signal-to-noise ratio (SNR) by 73.9%. In addition, the SCF imaging can effectively weaken the interference of scattered signals between multiple through-hole defects, resulting in fewer artefacts in imaging.

Probe Standoff Optimization Method for Phased Array Ultrasonic TFM Imaging of Curved Parts

The reliability of the ultrasonic phased array total focusing method (TFM) imaging of parts with curved geometries depends on many factors, one being the probe standoff. Strong artifacts and resolution loss are introduced by some surface profile and standoff combinations, making it impossible to identify defects. This paper, therefore, introduces a probe standoff optimization method (PSOM) to mitigate such effects. Based on a point spread function analysis, the PSOM algorithm finds the standoff with the lowest main lobe width and side lobe level values. Validation experiments were conducted and the TFM imaging performance compared with the PSOM predictions. The experiments consisted of the inspection of concave and convex parts with amplitudes of 0, 5 and 15 λAl, at 12 standoffs varying from 20 to 130 mm. Three internal side-drilled holes at different depths were used as targets. To investigate how the optimal probe standoff improves the TFM, two metrics were used: the signal-to-artifact ratio (SAR) and the array performance indicator (API). The PSF characteristics predicted by the PSOM agreed with the quality of TFM images. A considerable TFM improvement was demonstrated at the optimal standoff calculated by the PSOM. The API of a convex specimen’s TFM was minimized, and the SAR gained up to 13 dB, while the image of a concave specimen gained up to 33 dB in SAR.

Developing methods for taking into account the radiation coming from Earth in simulations of incoming electric power on the Russian Segment of the International Space Station in experiment Albedo

The paper describes the implementation of space experiment Albedo, which provided a framework for developing methods of taking into account the radiation emitted by the system «atmosphere–underlying terrain» in simulations of the operation of the power supply system of the Russian Segment of the International Space Station. As a result of the implementation of the space experiment a procedure was developed for determining and using characteristics of radiation coming from Earth in the simulation of a space station power supply system, including procedures and special software for determining solar array performance and simulating power input coming from solar arrays taking into account Earth albedo, as well as recommendations are given for the control modes of power supply systems of orbital spacecraft. As a result of testing computational schemes for evaluating the solar array performance and simulating electric power output that takes into account the Earth albedo, substantiated values were obtained for the proposed reference parameter for evaluating the performance of solar arrays of the Service Module of the International Space Station. Key words: Russian Segment of the International Space Station, solar arrays, electric power input, solar array performance estimate, radiation coming from Earth, albedo.

Development of Compute-in-Memory Memristive Crossbar Architecture with Composite Memory Cells

In this chapter, we discuss the compute-in-memory memristive architectures and develop a 2M1M crossbar array which can be applied for both memory and logic applications. In the first section of this chapter, we briefly discuss compute-in-memory memristive architectural concepts and specifically investigate the current state off the art composite memristor-based switch cells. Also, we define their applications e.g. digital/analog logic, memory, etc. along with their drawbacks and implementation limitations. These composite cells can be designed to be adapted into different design needs can enhance the performance of the memristor crossbar array while preserving their advantages in terms of area and/or energy efficiency. In the second section of the chapter, we discuss a 2M1M memristor switch and its functionality which can be applied into memory crossbars and enables both memory and logic functions. In the next section of the chapter, we define logic implementation by using 2M1M cells and describe variety of in-memory digital logic 2M1M gates. In the next section of the chapter, 2M1M crossbar array performance to be utilized as memory platform is described and we conceived pure memristive 2M1M crossbar array maintains high density, energy efficiency and low read and write time in comparison with other state of art memory architectures. This chapter concluded that utilizing a composite memory cell based on non-volatile memristor devices allow a more efficient combination of processing and storage architectures (compute-in-memory) to overcome the memory wall problem and enhance the computational efficiency for beyond Von-Neumann computing platforms.

Custom Memory Design for Logic-in-Memory: Drawbacks and Improvements over Conventional Memories

The speed of modern digital systems is severely limited by memory latency (the “Memory Wall” problem). Data exchange between Logic and Memory is also responsible for a large part of the system energy consumption. Logic-in-Memory (LiM) represents an attractive solution to this problem. By performing part of the computations directly inside the memory the system speed can be improved while reducing its energy consumption. LiM solutions that offer the major boost in performance are based on the modification of the memory cell. However, what is the cost of such modifications? How do these impact the memory array performance? In this work, this question is addressed by analysing a LiM memory array implementing an algorithm for the maximum/minimum value computation. The memory array is designed at physical level using the FreePDK 45nm CMOS process, with three memory cell variants, and its performance is compared to SRAM and CAM memories. Results highlight that read and write operations performance is worsened but in-memory operations result to be very efficient: a 55.26% reduction in the energy-delay product is measured for the AND operation with respect to the SRAM read one. Therefore, the LiM approach represents a very promising solution for low-density and high-performance memories.

Enhanced Cas12a multi-gene regulation using a CRISPR array separator

The type V-A Cas12a protein can process its CRISPR array, a feature useful for multiplexed gene editing and regulation. However, CRISPR arrays often exhibit unpredictable performance due to interference between multiple guide RNA (gRNAs). Here, we report that Cas12a array performance is hypersensitive to the GC content of gRNA spacers, as high-GC spacers can impair activity of the downstream gRNA. We analyze naturally occurring CRISPR arrays and observe that natural repeats always contain an AT-rich fragment that separates gRNAs, which we term a CRISPR separator. Inspired by this observation, we design short, AT-rich synthetic separators (synSeparators) that successfully remove the disruptive effects between gRNAs. We further demonstrate enhanced simultaneous activation of seven endogenous genes in human cells using an array containing the synSeparator. These results elucidate a previously underexplored feature of natural CRISPR arrays and demonstrate how nature-inspired engineering solutions can improve multi-gene control in mammalian cells.

Multipoint Detection Technique with the Best Clock Signal Closed-Loop Feedback to Prolong FPGA Performance

The degradation effect of a field-programmable gate array becomes a significant issue due to the high density of logic circuits inside the field-programmable gate array. The degradation effect occurs because of the rapid technology scaling process of the field-programmable gate array while sustaining its performance. One parameter that causes the degradation effect is the delay occurrence caused by the hot carrier injection and negative bias temperature instability. As such, this research proposed a multipoint detection technique that detects the delay occurrence caused by the hot carrier injection and negative bias temperature instability degradation effects. The multipoint detection technique also assisted in signaling the aging effect on the field-programmable gate array caused by the delay occurrence. The multipoint detection technique was also integrated with a method to optimize the performance of the field-programmable gate array via an automatic clock correction scheme, which could provide the best clock signal for prolonging the field-programmable gate array performance that degraded due to the degradation effect. The delay degradation effect ranged from 0° to 360° phase shifts that happened in the field-programmable gate array as an input feeder into the multipoint detection technique. With the ability to provide closed-loop feedback, the proposed multipoint detection technique offered the best clock signal to prolong the field-programmable gate array performance. The results obtained using the multipoint detection technique could detect the remaining lifetime of the field-programmable gate array and propose the best possible signal to prolong the field-programmable gate array’s performance. The validation showed that the multipoint detection technique could prolong the performance of the degraded field-programmable gate array by 13.89%. With the improvement shown using the multipoint detection technique, it was shown that compensating for the degradation effect of the field-programmable gate array with the best clock signal prolonged the performances.

Transfer Modeling for 1T1R Crossbar Arrays with Line Resistances

Progress of neuromorphic computing and next-generation information storage technologies hinges on the development of emerging nonvolatile memory (eNVM) devices, which are typically organized employing the crossbar array architecture. To facilitate quantitative performance analysis of eNVM crossbar array architecture, this paper proposes a way to study the one-transistor-one-resistor (1T1R, R: eNVM devices) crossbar arrays based on matrix algebra method. The comparative analysis of 1T1R crossbar array modeling based on matrix algebra method and compact-model SPICE simulations verifies the accuracy of the proposed method, which can be directly used for static quantitative analysis and evaluation of 1T1R crossbar array performance. With the proposed method, the optimization of array operation schemes and current backflow issue are discussed. Our analysis indicates that the proposed method is capable of flexibly adjusting array parameters and consider the influence of line resistance on array operation, and can provide guidance for improving the sensing margin of the array through multi-parameter co-simulation. The proposed matrix algebra-based 1T1R crossbar array modeling method can bridge the gap between the accuracy and flexibility of the available methods.

Investigating the Effect of Changing Ratios and Flowrates on Photovoltaic Thermal and Evacuated Tube Collector Array Performance for Different Building Types

Photovoltaic thermal and/or evacuated tube collectors on building roofs can be effectively used to reduce fossil fuel use for heating and reliance on the electrical grid. To evaluate the potential of this reduction, a set of models were created for rooftop photovoltaic thermal and evacuated tube collector energy production, both thermal and electricity, and tested using a series of potential layouts. Five collector area ratios, two layout options, and three working fluid flowrates were investigated using five reference buildings as case studies. From these case studies it was determined that in Toronto’s climate, the exclusive use of photovoltaic thermal collectors produces the most total energy, while using only evacuated tube collectors maximally offsets greenhouse gasses. The results suggest that district heating would be highly effective to reduce the carbon footprint of city cores like the Toronto 2030 District.