Theoretical Design Considerations Research Articles

Theory and design consideration of a THz superradiant waveguide FEL

We present theoretical analysis and design considerations of a THz superradiant FEL. We derive analytical expressions for the spectral parameter of THz radiation, emitted superradiantly in a rectangular waveguide using a Longitudinal Section Magnetic mode expansion. The results compare well with numerical simulations using UCLA GPTFEL code. GPT simulations of the accelerator e-beam transport show that the chirp provided by a hybrid photocathode RF gun, can produce tight bunching at the undulator site below σ = 100fs. This enables intense superradiant emission up to 3THz, limited by the beam bunching factor. Phase-space analysis of the beam transport indicates that keeping the beam bunching parameter small enough for higher THz frequency operation is limited by the energy spread of the beam in the gun.

Surface acoustic wave spectroscopy for non‐destructive coating and bulk characterization at temperatures up to 600°C enabled by piezoelectric aluminum nitride coated sensor

Surface acoustic wave spectroscopy has been established as non‐destructive and fast method for characterization of mechanical properties of surfaces and bulk materials in both research and industry. The present work shows that by application of a novel and robust aluminum nitride (AlN) coated piezoelectric contact sensor the advantages of the method can be extended from room temperature to at least 600°C. An overview of sensor concepts and applications of the method is discussed first, followed by theoretical and practical considerations for design and coating of a novel temperature stable contact sensor. After fabrication of such a sensor using magnetron sputtering, it was tested in a modified surface acoustic wave spectroscopy setup with an incorporated heating table concerning signal amplitude and frequency range. The AlN coated sensor was found to perform well up to 600°C, with temperature limited by the specification of the heating table. At room temperature, performance was acceptable when compared with a conventional contact sensor using a PVDF piezoelectric foil. Application of the high temperature capabilities of the setup was demonstrated by measuring temperature stability of hydrogen‐free amorphous carbon coatings (a‐C and ta‐C) depending on their sp3 carbon ratio. In another example, high precision temperature dependent measurement of Young's modulus for ultrasonic fatigue test specimen was taken, achieving an accuracy better than 1%. Use of the developed sensor opens up new possibilities in material science for in situ study of temperature depending mechanical properties for coatings and surfaces.

DAMPAK GAMIFIKASI DALAM PEMBELAJARAN BAHASA INGGRIS

Gamification, the incorporation of game elements into non-game contexts, has emerged as a promising strategy to enhance motivation and engagement in English language learning. This type of research is library research. The research results show that, the synthesis of theoretical insights, empirical findings, and instructional considerations highlights the importance of Gamification in English Language Learning. The significance of incorporating gaming aspects into language education is highlighted by the convergence of theoretical foundations, empirical data, and instructional design considerations

Design Considerations of Capacitive Power Transfer Systems

Capacitive power transfer (CPT) is a near-field wireless power transfer (WPT) technology that has attracted attention in different charging applications. By utilizing electric fields, CPT gives charging systems advantages in terms of cost, weight, flexibility, and mobility. This paper surveys a number of empirical published works in a period between 2015 and 2023. Additionally, it discusses theoretical and practical design considerations of a CPT system to understand and improve the technology and its applications. The paper studies the one- and two-port measuring approaches using vector network analyzers to determine the coupling parameters and compares the measurements to the simulated values using COMSOL Multiphysics ©. The two-port approach gives more accurate results than the one-port approach. The paper designs and tests a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {13.56 \text {M} \text {Hz} }$ </tex-math></inline-formula> CPT system using the two-port measurement results. The system transfers <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {100 \text {W}}$ </tex-math></inline-formula> at 87.4% efficiency and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {30 mm }$ </tex-math></inline-formula> separation distance. Lastly, the paper discusses the design limitations and challenges of the CPT systems, aiming to emphasize the design obstacles that can drive the advancement of the CPT systems for wireless charging applications.

A Single-Source Single-Stage Switched-Boost Multilevel Inverter: Operation, Topological Extensions, and Experimental Validation

In this article, we present a family of multilevel converters with the single-stage dynamic voltage-boosting feature, reduced number of circuit components, modular structure, bidirectional operation, continuous input current, and acceptable overall efficiency. The proposed structure is based on a three-level single-stage boost integrated inverter with an embedded quasi-H-bridge (QHB) cell. It is comprised of five unidirectional power switches and a floating capacitor. By differential connection of two or three QHB cells and with the aim of a single inductor/input dc source, several derived topologies for both the single and three-phase applications with different multilevel output voltage performances have been achieved. The aforementioned advantages make this converter a suitable candidate for renewable energy applications. Theoretical analysis, design consideration, comparative study, and several experimental results for a 3-kW laboratory-built system are presented to validate the effectiveness and feasibility of this proposal.

A Cascaded Half-Bridge Three-Level Inverter With an Inductive DC-Link for Flexible Voltage Boosting

Voltage boosting three-level inverters may present a monotonically increasing or decreasing voltage gain when enlarging the pulsewidth modulation (PWM) ratio. To produce a flexible voltage gain, this article proposes a novel three-phase three-level PWM inverter by cascading a traditional two-level three-leg (B6) inverter with half-bridges. The proposed inverter is supplied by an inductive dc-link consisting of a dc source in series with an inductor that is charged by shooting through the half-bridges in the B6 structure. The voltages across the cascaded half-bridges are subsequently boosted, and the output voltage is stepped up due to the cascaded connection. A moderate voltage gain is achieved with proper selections of two modulation variables while maximizing the PWM ratio. In particular, when the two modulation variables are equal, a constant voltage boosting gain of two is maintained irrespective of the PWM ratio. Additionally, low voltages are induced on the components, which facilitates the use of low-voltage devices. The operating principle of the proposed inverter with a modified third-harmonic-injection PWM scheme is presented, followed with theoretical analysis, comparison, and design considerations. Experimental tests on a 1.5-kVA inverter prototype verify its feasibility.

A Sharing-Branch Modular Multilevel DC Transformer With Wide Voltage Range Regulation for DC Distribution Grids

As the key equipment in dc distribution grids, dc transformer (DCT) suffers from low power density caused by a large number of submodules (SMs). Hence, this article proposes a novel DCT for the interconnection of medium-voltage dc (MVdc) and low-voltage dc (LVdc) distribution grids, which adopts a series-connected half-bridge SM branch (SSB) on MV-side to achieve low voltage stress of devices and reduce the number of SMs. Quasi square wave modulation strategy and phase-shifted control are employed to realize bidirectional power transmission control and zero-voltage switching (ZVS) for all switches. Furthermore, in order to ensure low current stress and ZVS within wide voltage range, a certain number of SMs are constantly inserted or bypassed to achieve voltage matching. Besides, smooth transition control strategy is employed to avoid current spikes caused by abruptly bypassing or inserting SMs. Based on the theoretical analysis, design consideration and control strategy are elaborated. Finally, a 500&#x00A0;kW&#x002F;6&#x2013;12&#x00A0;kV&#x002F;750&#x00A0;V simulation model and a 2&#x00A0;kW prototype are built to verify the proposed DCT.

Learning Affordances: Theoretical Considerations for Design of Immersive Virtual Reality in Training and Education

Technological advances have led to a rapid increase in the implementation of virtual reality (VR) across multiple sectors of society. Further, we are seeing more researchers explore how the technology can be used to promote learning and training in a variety of domains. But there is a problematic gap between development of VR for training and education and learning theory to ensure its efficacy. We address this need by providing a theoretical lens through which to evaluate existing research in VR. We consider technology developments that have made VR more sophisticated and draw from research in the learning and cognitive sciences to evaluate their utility as learning affordances. With this, we examine existing research as a way to illustrate the practical value of theoretical evaluation. We conclude with a discussion how this theoretical framing can point the way for both better designed studies to accelerate learning and training as well as for more innovative adaptations for accelerating learning in immersive virtual reality.

An Adaptive Synchronous Rectifier Control Scheme for High Power Density High Efficiency Interleaved Boost Converter With Passive Soft-Switching Cell

This study proposes an adaptive synchronous rectifier (SR) control scheme for high power density and high-efficiency interleaved boost converter (IBC) with passive soft-switching cell (PSC) (IBC-PSC). The PSC designed for the IBCs is one of the good solutions to minimize switching losses. However, the PSC needs a large boost inductance; otherwise, the conduction loss dramatically increases as the load decrease due to large circulating currents. Finally, there is a tradeoff between power density and efficiency. The proposed control scheme provides adaptive gating signals for the SR switches. It deactivates the SR switches at zero SR current and makes the main switches turn on with zero-voltage-switching (ZVS) regardless of the input voltage and load conditions, which results in reducing the conduction and switching losses despite significantly smaller boost inductance compared to the traditional IBC-PSCs. As a result, IBC-PSC with high power density and high efficiency can be realized. Theoretical analysis, implementation, and design considerations for the proposed control scheme were discussed and verified experimentally.

Soft Switching Interleaved High Step-Up Converter With Multifunction Coupled Inductors

This article presents an efficient interleaved soft switching dc-dc converter for high step-up applications. In the proposed converter, two multifunction coupled inductors are employed to increase the voltage gain, accomplish soft switching operation for all semiconductors in a wide range of load variations, and smooth the input current. Besides, the leakage inductance energy is recovered to enhance the voltage gain and efficiency while assisting soft switching condition for the switches and diodes. In addition, no auxiliary switch or extra magnetic element is employed in the proposed converter while the voltage stress of switches and diodes is rather low. These have led to simple structure, high density, low cost, and improved efficiency. Theoretical analysis and design considerations for the proposed converter are presented. Moreover, the experimental results of a 48 to 500 V laboratory prototype approve the effectiveness of the proposed topology.

CMOS fully integrated terahertz thermal detector using metamaterial absorber and proportional-to-absolute temperature sensor

Terahertz (THz) detectors have drawn much attention and have been widely applied in imaging, spectroscopy, and sensing fields. An uncooled monolithic resonant THz thermal detector implemented in a standard 55-nm CMOS process is presented. The integration of a frequency selective metamaterial (MM) absorber coupled with an optimized proportional-to-absolute temperature (PTAT) sensor leads to an approach toward uncooled, compact, low-cost, easy-integration, and mass-production THz detectors. The theoretical analysis, design considerations, and characteristic measurements are demonstrated in detail. The proposed thermal detector is designed to resonate at 2.58 THz for the accessible THz source and the natural atmospheric window. The MM absorber achieves near-perfect absorptivity of 98.6%, and the optimized PTAT sensor obtains a high-temperature sensitivity of 10.11 mV / ° C. The calculated responsivity is 49.81 V / W at 2.58 THz with a calculated noise-equivalent power (NEP) of 0.78 μW / Hz0.5 at a modulation frequency of 3 Hz. Relatively better experimental results are obtained at 2.58 THz with a maximum responsivity of 48.3 V / W and a minimum NEP of 1.06 μW / Hz0.5.

Theoretical Model and Design Considerations of U-Shaped Fiber Optic Sensors: A Review

A wide range of geometrical deformations of fiber optic sensors (FOSs) have been explored to improve their performance. In particular, fiber optics bent into a U-shape present various advantages over other approaches and considerably improved performance in terms of sensitivity. The improvement in sensitivity can be understood as a result of the enhanced penetration depth of the evanescent field and higher evanescent power in the cladding or surrounding medium. Consequently, a larger portion of the propagating light experiences changes due to variations in the local refractive index (RI). In view of their significant benefits, U-shaped FOSs deserve a thorough investigation. This review outlines the theoretical model and design considerations along with the fabrication process of U-shaped FOSs. In addition, this paper aims to provide researchers with guidelines on the factors to consider in designing and optimizing U-shaped FOSs.

Fully Soft-Switching Nonisolated Quasi-Z$-Source DC–DC Converter With High-Voltage Gain

This article proposes a quasi-Z-source converter, which creates the soft-switching conditions for all semiconductor devices without using any auxiliary circuit and/or any auxiliary switch. All the mentioned features are achieved by using only one resonant path. In addition, only one power switch has been applied in the proposed converter, which leads more simplicity of the converter operation and circuit control in comparison with other similar structures. Using the advantages of the Z-source converter in addition with applying only one resonant path creates a high-voltage gain for the proposed topology. Since the soft-switching condition is achieved for all semiconductor devices, the power losses are very low and the efficiency is very high. The theoretical analysis and design considerations are presented. A laboratory prototype converter is implemented. The experimental results are considered, which confirm the performance of the proposed converter.

Toward a High-Throughput Wireless Smart Arena for Behavioral Experiments on Small Animals

This work presents a high-throughput and scalable wirelessly-powered smart arena for behavioral experiments made of multiple EnerCage Homecage (HC) systems, operating in parallel in a way that they can fit in standard racks that are commonly used in animal facilities. The proposed system, which is referred to as the multi-EnerCage-HC (mEHC), increases the volume of data that can be collected from more animal subjects, while lowering the cost and duration of experiments as well as stress-induced bias by minimizing the involvement of human operators. Thus improving the quality, reproducibility, and statistical power of experiment outcomes, while saving precious lab space. The system is equipped with an auto-tuning mechanism to compensate for the resonance frequency shifts caused by the dynamic nature of the mutual inductance between adjacent homecages. A functional prototype of the mEHC system has been implemented with 7 units and analyzed for theoretical design considerations that would minimize the effects of interference and resonance frequency bifurcation. Experiment results demonstrate robust wireless power and data transmissions capabilities of this system within the noisy lab environment.

Maxwell Fisheye Lens Based Retrodirective Array

A Maxwell fisheye lens using parallel plate index grading is presented in this study to develop a passive retrodirective antenna array. As a proof-of-concept a design frequency of 10 GHz was selected for fabrication and experiment. The design principals of the lens are discussed, which enables 85% energy flow at the drain probe (also referred to as image point) of the lens. It is shown that the image in the Maxwell fisheye lens has a point symmetry with a reverse phase, which makes it possible to realize passive retrodirective action using the lens. This arrangement is significantly more practical than previous passive retrodirective topologies due to the un-constrained number of connections to radiating elements that it can support without the need for multi-layer technology. In the realization described here, a cross-polarized microstrip patch antenna array is connected to the source and drain probes of the lens structure in order to form the retrodirective array. The strategy for selecting the optimal transmission line lengths required to connect the antennas to the lens for maximum re-radiation power is described and implemented. Experimental results for a prototype high efficiency passive retrodirective array based on the theoretical design considerations presented in this paper are reported.

A Novel Dual-Input ZVS DC/DC Converter for Low-Power Energy Harvesting Applications

In this paper, a novel dual-input dc/dc topology is proposed for low-power energy harvesting applications. The converter is able to interface with two different power sources simultaneously. In the proposed topology, two boost converters are integrated with a shared diode and a filter capacitor, while the gate signals of two power MOSFETs are complimentary with certain dead-bands. The proposed topology may operate either in discontinuous-conduction mode or in hybrid conduction mode. In each operation mode, zero-voltage switching is achieved for both MOSFETs, while zero-current switching is achieved for the power diode, without any additional auxiliary circuit. Theoretical analysis, circuit modeling, and design considerations are also addressed in detail in this paper. Finally, a 10.1-W, 200-kHz prototype is designed and tested to validate the proof of concept. Experimental results are in accordance with the theoretical analysis.

A 1.2-V 2.41-GHz Three-Stage CMOS OTA With Efficient Frequency Compensation Technique

A performance-boosting frequency-compensation technique, called feed-forward Gm-stage and regular Miller plus indirect compensation (FGRMIC), is presented in this paper. The proposed structure consists of three parts that ensure the stability and significantly improve the performance, such as gain–bandwidth product (GBW), slew rate, and sensitivity. The first part is a feed-forward transconductance stage, and the second part is a Miller capacitor in series with one resistor. The third part is an indirect compensation capacitor combined with a resistor. Detailed theoretical analysis and design considerations are provided to demonstrate the stability of the compensation scheme. Measurement results show that the implemented amplifier, driving a 2-pF load capacitance, achieves a GBW of 2.41 GHz with a phase margin of 82.6° while consuming 12.6 mW with a 1.2-V supply voltage in a TSMC 65-nm CMOS technology. Large-signal step response indicates that the implemented three-stage FGRMIC amplifier settles with 1% settling error within 1.41 ns.

New Bridgeless Buck PFC Converter with Improved Input Current and Power Factor

The bridgeless buck power factor correction (PFC) converters feature the merits of low output voltage and high efficiency while their inherent dead angles in the input current will deteriorate the input current harmonics and power factor (PF). Aiming to reduce the dead angles, a new bridgeless buck PFC converter is proposed in this paper. Through integrating the main buck circuit and the auxiliary flyback circuit with one magnetic core, the dead angles in the input current of the proposed bridgeless buck PFC converter is eliminated so that the PF and input current harmonics are improved. The proposed bridgeless buck PFC converter is designed to operate in discontinuous conduction mode (DCM) with the merits of simple controller and nature current shaping ability. A new logic control circuit is provided. The detailed theoretical derivations and design consideration are presented. The experimental comparison among the proposed bridgeless buck PFC converter, the conventional buck PFC converter, and the conventional bridgeless buck PFC converter is displayed to validate the effectiveness of the new converter.

A Family of Zero-Voltage-Switching Magnetic Coupling Nonisolated Bidirectional DC–DC Converters

This paper proposes a family of magnetic coupling nonisolated bidirectional dc-dc converters, which can achieve soft-switching operation in both power flow directions with a simple auxiliary circuit. Compared with conventional zero-voltage-transition converters, the additional resonant inductor is eliminated and magnetic core number is reduced. Therefore, both high efficiency and low cost are achieved. First, a general zero-voltage-switching (ZVS) magnetic coupling structure is proposed for a bidirectional buck/boost converter, based on which 13 different ZVS topologies with different connections of auxiliary circuit are derived. It is very beneficial in practical industrial applications because engineers can choose an optimal one according to converter performance characteristics, and the topology derivation methodology can be easily extended to other bidirectional dc-dc converters. Second, based on the general structure, operation principle and performance characteristics of all proposed topologies are simultaneously obtained, which can facilitate topology comparison and selection processes. Finally, in order to verify the effectiveness of theoretical analysis, design considerations and experiment results of a 500-W prototype circuit are demonstrated.

A Discontinuous Conduction Mode Single-Stage Step-Up Rectifier for Low-Voltage Energy Harvesting Applications

In this paper, a novel ac/dc converter is proposed for low-voltage and low-power ac rectification applications. The proposed converter manages the energy harvested from microscale electromagnetic generators (MEGs). It integrates the conventional boost and buck–boost topologies with a shared inductor, a bidirectional switch, and two split filtering capacitors. The boost and the buck–boost topologies function in the positive and negative half input cycles, respectively. The inductor is energized by being shorted with the input source through the mosfet channel without using the diodes. This enables active rectification of low-amplitude (below 0.7 V) ac voltages. Theoretical analysis, design considerations, and control method are detailed. A 40-mW circuit prototype, which converts a 0.4-V peak, 100-Hz ac voltage source to 3.3-V dc, is designed and tested to verify the proof of concept.