Search results

The digital down converter (DDC) is a principal component in modern communication systems. The DDC process traditionally entails quadrature down conversion, bandwidth reducing filters and commensurate sample rate reduction. To avoid group delay, distortion linear phase FIR filters are used in the DDC. The filter performance specifications related to deep stopband attenuation, small in-band ripple and narrow transition bandwidth lead to filters with a large number of coefficients. To reduce the computational workload of the filtering process, filtering is often performed as a two-stage process, the first stage being a down sampling Hoegenauer (or cascade-integrated comb) filter and a reduced sample rate FIR filter. An alternative option is an M-Path polyphase partition of a band cantered FIR filter. Even though IIR filters offer reduced workload to implement a specific filtering task, the authors avoid using them because of their poor group delay characteristics. This paper aims to propose the design of M-path, approximately linear phase IIR filters as an alternative option to the M-path FIR filter.

Two filter designs are presented in the paper. The first approach uses linear phase IIR low pass structure to reduce the filter’s coefficient. Whereas the second approach uses multipath polyphase structure to design approximately linear phase IIR filter in DDC.

The authors have compared the performance and workload of the proposed polyphase structured IIR filters with state-of-the-art filter design used in DDC. The proposed design is seen to satisfy tight design specification with a significant reduction in arithmetic operations and required power consumption.

The proposed design is an alternate solution to the M-path polyphase FIR filter offering very less number of coefficients in the filter design. Proposed DDC using polyphase structured IIR filter satisfies the requirement of linear phase with the least number of computation cost in comparison with other DDC structure.

This study aims to ensure reliable analysis of dynamic responses in asphalt pavement structures. It investigates noise reduction and data mining techniques for pavement dynamic response signals.

The paper conducts time-frequency analysis on signals of pavement dynamic response initially. It also uses two common noise reduction methods, namely, low-pass filtering and wavelet decomposition reconstruction, to evaluate their effectiveness in reducing noise in these signals. Furthermore, as these signals are generated in response to vehicle loading, they contain a substantial amount of data and are prone to environmental interference, potentially resulting in outliers. Hence, it becomes crucial to extract dynamic strain response features (e.g. peaks and peak intervals) in real-time and efficiently.

The study introduces an improved density-based spatial clustering of applications with Noise (DBSCAN) algorithm for identifying outliers in denoised data. The results demonstrate that low-pass filtering is highly effective in reducing noise in pavement dynamic response signals within specified frequency ranges. The improved DBSCAN algorithm effectively identifies outliers in these signals through testing. Furthermore, the peak detection process, using the enhanced findpeaks function, consistently achieves excellent performance in identifying peak values, even when complex multi-axle heavy-duty truck strain signals are present.

The authors identified a suitable frequency domain range for low-pass filtering in asphalt road dynamic response signals, revealing minimal amplitude loss and effective strain information reflection between road layers. Furthermore, the authors introduced the DBSCAN-based anomaly data detection method and enhancements to the Matlab findpeaks function, enabling the detection of anomalies in road sensor data and automated peak identification.

Numerous types of shunt active power filters have been proposed in many papers. The classification of these filters depends on various points of view. However, every type of a shunt active filter, which compensates non‐active component of load current, irrespective of the method used to detect this component and control strategies of the filter, should keep supply source current equal to active current of a load‐and‐filter circuit. This goal can be achieved in many ways, using various structures of active filters. But different realizations of filters cause differences in their properties. This paper, which is meant to serve as a review and synthesis of earlier work, shows some possibilities of forming of single‐phase shunt active filter behaviour. The following active filter properties are discussed: operation with an immediate reaction in the supplying source branch to a load current change, and with the reaction only once in each supplying source cycle; regulation by the filter of the non‐active current component of fundamental frequency; active filtering and simultaneous feeding of DC load with stabilizing DC voltage; operation with stabilization of supplying source current amplitude; reducing filter switching frequency; and reducing current distortions in the supplying source branch. All the waveforms presented were produced using a computer simulation method.

Aluminium alloys can be used as lightweight and high-strength materials in combination with the technology of laser beam welding, an efficient joining method, in the manufacturing of automotive parts. The purposes of this paper are to conduct laser welding experiments with Al2024 in the lap joint configuration, model the laser welding process parameters of Al2024 alloys and use propounded models to optimize the process parameters.

Laser welding of Al2024 alloy has been conducted in the lap joint configuration. Then, the influences of explanatory variables (laser peak power, scanning speed and frequency) on outcome variables (weld width [WW], throat length [TL] and breaking load [BL]) have been investigated with Poisson regression analysis of the data set derived from experimentation. Thereafter, a multi-objective genetic algorithm (MOGA) has been used using MATLAB to find the optimum solutions. The effects of various input process parameters on the responses have also been analysed using response surface plots.

The promulgated statistical models, derived with Poisson regression analysis, are evinced to be well-fit ones using the analysis of deviance approach. Pareto fronts have been used to demonstrate the optimization results, and the maximized load-bearing capacity is computed to be 1,263 N, whereas the compromised WW and TL are 714 µm and 760 µm, respectively.

This work of conducting laser welding of lap joint of Al2024 alloy incorporating the Taguchi method and optimizing the input process parameters with the promulgated statistical models proffers a neoteric perspective that can be useful to the manufacturing industry.

ADVANCES in engine technology are evaluated herein, and, for the purposes of improving future noise evaluation of commercial jet aircraft, adjustments to current evaluation techniques are suggested.

The primary aim of this paper is to present a novel design approach for a ring voltage-controlled oscillator (VCO) suitable for L-band applications, whose oscillation frequency is less sensitive to power supply variations. In a few decades, with the advancement of modern wireless communication equipment, there has been an increasing demand for low-power and robust communication systems for longer battery life. A sudden drop in power significantly affects the performance of the VCO. Supply insensitive circuit design is the backbone of uninterrupted VCO performance. Because of their important roles in a variety of applications, VCOs and phase locked loops (PLLs) have been the subject of significant research for decades. For a few decades, the VCO has been one of the major components used to provide a local frequency signal to the PLL.

First, this paper chose to present recent developments on implemented techniques of ring VCO design for various applications. A complementary metal oxide semiconductor (CMOS)-based supply compensation technique is presented, which aims to reduce the change in oscillation frequency with the supply. The proposed circuit is designed and simulated on Cadence Virtuoso in 0.18 µm CMOS process under 1.8 V power supply. Active differential configuration with a cross-coupled NMOS structure is designed, which eliminates losses and negates supply noise. The proposed VCO is designed for excellent performance in many areas, including the L-band microwave frequency range, supply sensitivity, occupied area, power consumption and phase noise.

This work provides the complete design aspect of a novel ring VCO design for the L-band frequency range, low phase noise, low occupied area and low power applications. The maximum value of the supply sensitivity for the proposed ring VCO is 1.31, which is achieved by changing the VDD by ±0.5%. A tuning frequency range of 1.47–1.81 GHz is achieved, which falls within the L-band frequency range. This frequency range is achieved by varying the control voltage from 0.0 to 0.8 V, which shows that the proposed ring VCO is also suitable for low voltage regions. The total power consumed by the proposed ring VCO is 14.70 mW, a remarkably low value using this large transistor count. The achievable value of phase noise is −88.76 dBc/Hz @ 1 MHz offset frequency, which is a relatively small value. The performance of the proposed ring VCO is also evaluated by the figure of merit, achieving −163.13 dBc/Hz, which assures the specificity of the proposed design. The process and temperature variation simulations also validate the proposed design. The proposed oscillator occupied an extremely small area of only 0.00019 mm² compared to contemporary designs.

The proposed CMOS-based supply compensation method is a unique design with the size and other parameters of the components used. All the data and results obtained show its originality in comparison with other designs. The obtained results are preserved to the fullest extent.

Resettlement programmes provide support for young offenders during their custodial sentence and for approximately nine months after release. This article describes how the costs and benefits of providing an effective service of this kind were estimated based on the ‘RESET’ programme, published evidence on the costs of crime and the likely reduction in offending due to an intensive support programme. The cost of crime has been estimated at £46,459 per year (after allowing for a reduction due to the time spent in custody), plus prison custody at an average of £30,475 and emergency accommodation at an average of £1,106, making a total of £78,040 for each offender. Using a fairly modest assumption that good support in resettlement could lead to approximately a 35% reduction in frequency and a 10% reduction in seriousness of offending, a saving of £20,407 per offender per year could be achieved. These savings would more than offset the average cost of a good quality resettlement service of £8,074. The scheme would break even if the frequency of offending were reduced by only 20%.

The purpose of this study is to discuss the effect of hybrid cascode compensation with quality factor (Q-factor) control module for the three-stage amplifiers driving ultra-large load capacitors. Compared to the present frequency compensation solutions, it extends the amplifier bandwidth by establishing an extra AC feedback pathway besides the primary pathway through the Miller capacitor, increasing the loop gain at the gain–bandwidth product (GBW) frequency by pushing to the higher frequencies the nondominant poles.

A Q-factor control block is used to improve the damping factor of the compensation loop with no power or area overhead, thereby reducing the frequency peaking and the undesired oscillation in the time response for small load capacitors. The Q-factor control module is realized by a tiny-size on-chip capacitor, and provides an extra feedback loop to feed the damping current back to the input stage. A left-half-plane (LHP) zero is also introduced to further improve the stability.

A prototype of the proposed amplifier is simulated in 180-nm CMOS with a quiescent current of 24-µA from 1.80-V voltage supply. It achieves a 3.98-MHz gain–bandwidth product for 500-pF load capacitor, while the overall compensation capacitor is limited to 0.5-pF and the DC gain is extended beyond 100-dB.

The proposed amplifier is absolutely stable for the load capacitors ranging between 80-pF and 100-nF.

This study aims to assess Brazilian adult consumers’ behavior, aged 18–70, when purchasing ready-to-eat food during the first months of the Coronavirus disease 2019 (COVID-19) pandemic.

Participants answered an online questionnaire about behaviors related to the purchase of ready-to-eat food from food services: changes in usage frequency during the pandemic, reasons for altering purchase habits, types of food and beverages bought before and during the pandemic and the frequency of on-site (consumption in food services) and off-site (delivery, take-away and drive-through) service utilization at lunch and dinner.

Out of 970 individuals who participated in the study, during the pandemic, 38% of participants reduced their food service usage, whereas 18% stopped using it. The main reasons given by participants who reduced and stopped food service usage were cooking at home (52% and 59%, respectively) and feeling afraid of contracting COVID-19 (26% and 22%, respectively). The reduction was more frequent among divorced/widowed/single individuals (p = 0.001) and in total social distancing, that is, all day long (p = 0.03). A significant reduction in on-site consumption frequency occurred for lunch and dinner (p < 0.001), whereas an increase in the off-site consumption frequency service for lunch (p = 0.016) and a reduction for dinner (p = 0.01) occurred compared to pre-COVID-19. However, 48% of participants used these services at least once a week in both periods. Most consumed foods and drinks before and during the pandemic were pasta/pizza (74% and 64%, respectively), snack/burgers (66% and 59%, respectively), soft drinks (41% and 37%, respectively) and alcoholic beverages (37% and 25%, respectively).

Knowledge about food choices away from home during the pandemic is scarce. High consumption of food away from home has been associated with a greater risk of developing chronic non-communicable diseases, such as obesity, diabetes and others. Eating behavior is influenced by the cultural, social, economic and personal characteristics of each individual. Understanding the main changes related to the consumption of ready-to-eat food and what the affected consumers profile in a time of unprecedented crisis, it is important to provide scientific knowledge that allows one to anticipate the implications for the future of individuals’ health and food systems and, consequently, to develop public policy or awareness and promotion actions of public health that encourage adopting healthier and balanced eating habits.