High Efficiency Design Research Articles

Broadband Sequential Load Modulated Balanced Amplifier With Extended Design Space Using Second Harmonic Manipulation

This article presents the design methodology of a broadband radio frequency (RF)-input sequential load modulated balanced amplifier (SLMBA) with extended high-efficiency design space, by introducing the second-harmonic load manipulation over an enlarged range for the control amplifier (CA). The extension of CA load design space not only can provide the time-domain-varying drain current waveform inside the entire design continuum but also allows maintaining high efficiency at output power back-off (OBO) over an extended operation bandwidth. To validate the theory, a broadband SLMBA operating at 2.05–3.65 GHz was designed and fabricated using packaged gallium nitride (GaN) transistors. The implemented power amplifier (PA) attains a measured 45.2–46.8-dBm peak output power. Drain efficiency (DE) of 61.2%–79.7% at saturation and 50.5%–66.2% at 8-dB OBO is achieved throughout the designed bandwidth. When tested with a 100-MHz long-term evolution (LTE) signal with a peak-to-average-power ratio (PAPR) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8$</tex-math> </inline-formula> dB, the proposed SLMBA achieves 50.7%–63.5% average DE over 2.05–3.55 GHz and better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 45.1 dBc adjacent channel power ratio (ACPR) after digital predistortion (DPD).

M-StruGAN: An Automatic 2D-Plan Generation System under Mixed Structural Constraints for Homestays

Existing methods for generating 2D plans based on intelligent systems usually require human-defined rules, and their operations are complex. GANs can solve these problems through independent research and learning. However, they only have generative design research based on a single constraint condition, and whether they can generate a qualified design scheme under many constraints is still unclear. Therefore, this paper develops the M-StruGAN generative model based on the structural design framework of a GAN. Its application research is extended to the 2D-plan layout generation of homestay based on the constraints of hybrid structures, and the feasibility of the method is comprehensively verified through three aspects: image synthesis quality assessment, scheme rationality assessment, and scheme design quality assessment. Experimental results show that the quality of the drawings generated by M-StruGAN is qualified, designers have a high degree of acceptance of the design results of M-StruGAN, and M-StruGAN completed the learning of the critical points of the 2D layout. Finally, through the human–computer interaction application of M-StruGAN, it can be found that compared with traditional design methods, M-StruGAN based on pix2pixHD has high-definition image quality, higher design efficiency, lower design cost, and more stable design quality.

Optimized Resonant Network Design for High Energy Transfer Efficiency of the WPT System

This paper proposes an active resonant network based on variable resonant capacitances to improve the operating performance of the LCC-S compensated topology in the wireless power transfer (WPT) system for electric vehicles under coil-misaligned conditions. By adjusting the series and parallel compensation capacitances on the transmitting side, the output voltage can be kept constant and the energy transfer efficiency can be improved under different coil offsets. The switch-controlled capacitors (SCCs) are used to change the compensation capacitances continuously. To find the proper compensation capacitances to achieve the excellent performance of the system, the optimization algorithm is applied, and the corresponding digital control strategy is described to regulate the equivalent capacitances of SCCs. Experimental results with a 2.7 kW power scale show that the output voltage is constant, and the operating efficiency is always over 90% in the WPT system with an active resonant network under different misalignment conditions. In addition, the system is delivering an equal amount of energy for all misalignments within the range of 80 mm, which improves the expected value of transferred energy by about 29%.

Thermal Analysis and Junction Temperature Estimation under Different Ambient Temperatures Considering Convection Thermal Coupling between Power Devices

The convection thermal coupling between adjacent power devices in power converters is dependent on the ambient temperature. When the ambient temperature changes, the convection thermal coupling also changes. This results in an inaccurate thermal model that causes errors in the prediction of the thermal distribution and junction temperature based on a fixed ambient temperature for power devices in converters application. To solve this variable-ambient-temperature-related issue, a thermal coupling experiment for semiconductor power devices (the MOSFET and diode) was performed to discuss the influence of the thermal coupling effect between adjacent devices and the FEM (Finite Element Method) thermal models for the power devices considering the convection thermal coupling are established. Through these simulations, the junction temperatures of devices under different ambient temperatures were obtained, and the relationships between the junction temperature and ambient temperatures were established. Moreover, the junction temperatures of power devices under different ambient temperatures were calculated and temperature distributions are analyzed in this paper. This method shows a strong significance and has potential applications for high-efficiency and high-power density converter designs.

A highly active Pd clusters hosted by magnesium hydroxide nanosheets promoting hydrogen storage

Liquid organic hydrogen carriers (LOHCs) represent promising candidates for large-scale hydrogen storage, yet the design of high-efficiency and low-cost catalysts on the dehydrogenation of LOHCs remains challenging. Herein, we develop a two-dimensional (2D) magnesium hydroxide nanosheet that hosts Pd clusters (Pd/Mg(OH)2) for the dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NEC), an important reaction for H2 transportation. The catalyst boosts the activity up to a 12H-NEC conversion of 100 % and the hydrogen release of 5.72 wt% with a low metal loading of 0.5 wt%, while the hydrogen release on Pd/MgO is only 2.34 wt% with the conversion rate of 71 % under the same conditions. Coupling various characterization technologies (HAADF-STEM, EXAFS, EPR and In-situ DRIFTS) with DFT calculations, it was found that the work function of magnesium hydroxide nanosheets for the dehydrogenation reaction due to the strong metal-support interaction, which makes Pd species have better dispersion, forms Pdn+-OH stable Pd cluster and reduces the dehydrogenation barrier as well, thus enhancing the dehydrogenation performance and improving the hydrogen production greatly. This work provides a new promising way to design advanced dehydrogenation catalyst with high activity for the hydrogen storage.

Fixed-Frequency PWM Control and Stability of Series-Stacked Buffer for 2ω-Power Decoupling

Active second-harmonic ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> ) filters have become an integral technology for single-phase power converters in high-power density designs. The series-stacked buffer (SSB) has emerged as an attractive topology among the existing solutions due to its low power, high efficiency, and compact design. However, one of the challenges in adopting SSB lies in its control, where hysteresis current control has been adopted conventionally. This results in a wide variation in the switching frequency, making the digital control implementation and filter design complex. On the other hand, fixed-frequency pulsewidth modulation (PWM) control necessitates developing a model for the systematic controller design to ensure stability and desired filtering performance. The assumption of SSB modeled as a second-harmonic current source, independent of the dc bus circuit components, fails to capture the dc bus loading effect on the SSB. In this work, a dynamic model of SSB is developed where the main dc bus and its passive elements are considered. The derived model enables a systematic approach for the controller design while ensuring the desired <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> filtering. The stability limits and parameter sensitivities of the model are studied analytically and in simulations. The analytical model is validated, and the proposed controller performance and stability limit are verified experimentally on a hardware prototype. A video demonstrating the transition from stable to unstable operation is provided.

A Wideband High-Efficiency Transmit-Reflect-Array Antenna for Bidirectional Radiations With Distinct Circular Polarizations Based on a Metasurface

In this communication, we present the modeling, design, and experiments of a wideband high-efficiency transmit-reflect-array (TRA) antenna with independent manipulations for transmitted and reflected beams with distinct circular polarizations working in the millimeter-waveband. A polarization-dependent full-space metasurface is designed to transmit the left-handed circularly-polarized (LCP) wave for a transmitarray (TA) operation, and at the same time to reflect the right-handed circularly-polarized (RCP) wave for a reflectarray (RA) operation. The TRA is then optimized with a rectangular shape for a high aperture efficiency (AE) based on a system-level analysis combining the characteristics of a Fermi feed antenna. The experimentally measured results are in good agreement with the simulated ones, achieving a peak gain of 22 dBi (21.5 dBi), a 1 dB gain bandwidth of 18.2% (24.6%), and a 3 dB axial ratio (AR) bandwidth of 38.6% (38.5%) for TA (RA) operation. A total AE as high as 61.2% is realized by comprehensively considering TA and RA operations. The design strategy and the well-performed TRA may find promising applications in wireless and satellite communication systems with bidirectional communication scenarios.

Electronic metal − support interaction directed electron-deficient nanoparticulate Ru on Ti3C2 MXene-derived TiO2 nanoflowers for robust benzene semi-hydrogenation

Regulating the geometric and electronic configurations of interfacial active sites is an attractive approach to design high-efficiency catalysts. Here, guiding by the electronic metal–support interaction (EMSI), we constructed the chemical state-tunable nanoparticulate Ru on three-dimensional (3D) porous TiO2 nanoflowers derived from 2D Ti3C2 MXene nanosheets (Ru/TMTFs-x). Benefitting by the unique geometric architecture and EMSI-directed electron-deficient configuration of Ru, the catalysts are efficient in benzene semi-hydrogenation, achieving a high turnover frequency (TOF, 7.2 s−1) and an excellent initial cyclohexene selectivity (78%) on the most electron-deficient Ru/TMTFs-773 catalyst. Despite that the TOFs are nearly identical along with the enhancement in electron-deficient degree of Ru on Ru/TMTFs-x by tuning the Ti4+: Ti3+ molar ratios, which was originated from the resemblances in Ru size and acidity, a positive correlation between cyclohexene selectivity and electron-deficient degree of Ru was recognized. By virtue of kinetics analyses and density functional theory (DFT) calculations, the promotion in net generation rate of cyclohexene and the weakening in cyclohexene adsorption on Ru/TMTFs-x when lowering the electron density of Ru are responsible for the selectivity enhancement. A linearity between selectivity and the percentage of Ti4+ sites was identified, further corroborating the EMSI-mediated selectivity enhancement on Ru/TMTFs-x.

The dataset of the manuscript "GPU-HADVPPM V1.0: high-efficient parallel GPU design of the Piecewise Parabolic Method (PPM) for horizontal advection in air quality model (CAMx V6.10)"

The dataset of the manuscript "GPU-HADVPPM V1.0: high-efficient parallel GPU design of the Piecewise Parabolic Method (PPM) for horizontal advection in air quality model (CAMx V6.10)"

Towards the development of energy sharing methodology between different buildings for high efficient neighborhood design

Devising methods to recover waste heat and to share it within a neighborhood can lower the energy footprint of this neighborhood and reduce its dependence on the utility grids. This paper presents a novel methodology for capturing waste energy from individual buildings and sharing the recovered energy with an entire neighborhood. A survey of the current state of research on energy sharing is presented. A mixed-use neighborhood consisting of retail, residential, and greenhouse buildings is modeled to develop a holistic design of energy sharing strategy. Neighborhood-level waste heat recovery and distribution network is modeled in the EnergyPlus-DesignBuilder co-simulation platform. The energy sharing methodology is applied to different neighborhood configurations and neighborhood densities. The results show that with the application of energy sharing methodology integrated with energy efficient design and on-site solar energy, a net reduction of 74% energy in the mixed-use neighborhood is achieved compared to a design complying with the minimum requirement of the applicable energy codes. Similarly, a net 90.46% reduction in greenhouse gas (GHG) emissions is realized by energy sharing and on-site carbon capturing using neighborhood greenhouse.

Electronic Modulation and Mechanistic Study of Ru-Decorated Porous Cu-Rich Cuprous Oxide for Robust Alkaline Hydrogen Oxidation and Evolution Reactions.

Rational design of high-efficiency and viable electrocatalysts is essential in overcoming the bottleneck of sluggish alkaline hydrogen oxidation/evolution reaction (HOR/HER) kinetics. In this study, a metal-organic framework-derived strategy for constructing a Pt-free catalyst with Ru clusters anchored on porous Cu-Cu2 O@C is proposed. The designed Ru/Cu-Cu2 O@C exhibits superior HOR performance, with a mass activity of 2.7 mA at 50 mV, which is about 24 times higher than that of state-of-the-art Pt/C (0.11 mA ). Significantly, Ru/Cu-Cu2 O@C also displays impressive HER performance by generating 26 mV at 10 mA cm-2 , which exceeds the majority of documented Ru-based electrocatalysts. Systematic characterization and density functional theory (DFT) calculations reveal that efficient electron transfer between Ru and Cu species results in an attenuated hydrogen binding energy (HBE) of Ru and an enhanced hydroxy binding energy (OHBE) of Cu2 O, together with an optimized H2 O adsorption energy with Cu2 O as the H2 O*-capturing site, which jointly facilitates HOR and HER kinetics.

Enhanced adsorption of 3,4-methylenedioxymethamphetamine by magnetic graphene oxide-polydopamine nanohybrid modified zeolitic imidazolate framework-67 and its micro-mechanism: Experiments and calculations

Exploring the structure-dependent adsorption mechanism of contaminants in wastewater is beneficial to high-efficiency adsorbents design and environmental remediation. In this study, emerging porous material of zeolitic imidazolate framework-67 (ZIF-67) has been modified by the magnetic graphene oxide-polydopamine nanohybrid (mGOP) to obtain three-dimensional ZIF-67/mGOP through an in-situ growth strategy, which was applied to adsorb 3,4-methylenedioxymethamphetamine (MDMA, “ecstasy”) in wastewater. A combination of characterizations, experiments (pH, humic acid and ion strength effect) and quantum chemical calculations revealed the microscopic adsorption mechanism involves each single component, of which the hydrogen bond (O/N…HO) and π–π electron donor acceptor (π–π EDA) interactions of mGOP endowed favourable adsorption of ZIF-67/mGOP, and mechanisms of the pore filling and Co-O chelation of ZIF-67 played synergistic effect. Such nanocomposite as a ZIFs-based adsorbent exhibited ultra-high porosity (total pore volume = 0.4033 cm3/g) and specific surface area (995.22 m2/g), revealed the heterogeneity and multilayer adsorption properties, and obtained a theoretical maximum adsorption capacity of 159.845 μg/g which higher than that of mZIF-67 alone. Overall, this work provided an effective strategy for rationally modulate ZIFs-based composites and exploration of adsorption mechanism.

Organopolysulfides as high-performance cathode materials for rechargeable aluminum-ion batteries

The development of aluminum-ion batteries (AIBs) is significantly confined by the limited high-performance cathode materials. Herein, organopolysulfides are investigated as active cathode materials to fabricate AIBs. A liquid-phase phenyl tetrasulfide (PTS) can deliver a capacity above 600 mAh g−1 after activation, with the maintenance of 253 mAh g−1 after 100 cycles. Owing to the different S locations, PTS shows several voltage plateaus and an average voltage of ∼0.7 V vs. Al3+/Al with no decay upon cycling. More importantly, the liquid PTS can serve as a high-Coulombic-efficiency cathode (∼99.88% ± 0.57% after stabilization), enlighting the design of high-efficiency and low-resistance conversion-type cathode materials for AIBs. By experimental characterizations accompanied by theoretical calculations, it is found that PTS undergoes stepwise reaction procedures during discharge with final products of Al2S3 and AlCl2-coordinated phenyl sulfide, and partially reforms with elemental S and other organopolysulfides during charge. This study demonstrates new opportunities for the design of high-efficiency conversion-type cathode materials for advanced AIBs.

Thermoeconomic appraisal of a novel power and hydrogen cogeneration plant with integration of biomass and geothermal energies

The present research aims at development and design of a new high-efficiency power/hydrogen co-production framework running by biomass/geothermal renewable resources. In this regard, to attain global energy transition goals based on green hydrogen utilization of renewable resources instead of conventional fossil fuel-based routes for hydrogen production is followed. The proposed system structure consists mainly of a gas turbine coupled to a geothermal assisted Rankine unit which extracts the gas turbine wasted heat to run a water electrlyzer for H2 production. To illustrate a comprehensive performance evaluation, technical (thermodynamic), environmental and economic aspects are considered and assessed. Eight performance indices are evaluated including: power and hydrogen productions, thermal and exergetic efficiencies, environmental damage and emission index, LCOP and overall system cost. In addition, a bi-objective optimization is implemented with respect to efficiency and product cost. Results show that, the cogeneration framework under optimum condition, operates with exergetic efficiency of 42.37% and levelizedproductcostof68.52$/MWh, whose emitted CO2 is 0.7443kg/kWh. Also, compared to basic design point conditions, it is found out that optimization leads to performance enhancements by 7.5%, 9.0% and 7.7% for the three mentioned indicators, respectively.

Design and fabrication process flow for high-efficiency and flexible InGaN solar cells

We present the design of high-efficiency and flexible InGaN solar cells based on nano-pyramid absorbers, which allows for high indium incorporation and reduced polarization effects while maintaining high crystalline quality. The process uses nanoscale selective area growth and van der Waals epitaxy on two-dimensional (2D) hexagonal boron nitride on sapphire substrates. The 2D layer enables mechanical release of solar cells via self-lift-off and its transfer to a flexible substrate. Through coupled optical and electrical simulations, we compare different designs of the p- and n-regions and propose two device architectures that combine mechanical flexibility and high power conversion efficiency (up to 16.4%). This approach can provide a solution for the fabrication of high-efficiency, low-cost and flexible InGaN-based solar cells.

High-efficiency and compact two-dimensional exit pupil expansion design for diffractive waveguide based on polarization volume grating.

We propose a two-dimensional exit pupil expansion (2D-EPE) design of a diffractive waveguide (DW) based on polarization volume grating (PVG). The designed waveguide structure and pupil expansion principle are introduced in this paper. The light propagation behavior and available field of view (FoV) of the proposed waveguide are investigated by simulations. In addition, the waveguide sample based on the proposed design is prepared, and an imaging system based on a monochromatic MicroLED projector is built for AR imaging experiments. The experimental results show that the prepared waveguide system can achieve a clear AR display with a diagonal FoV of 30° and obtain an exit pupil magnification of nearly 20 times compared to the entrance pupil size. The optical imaging efficiency was measured to be 3.85%, and the backward light leakage rate was as low as 8.7%. This work further enhances the feasibility and practicality of the PVG-waveguide technology and provides a promising candidate for AR-DW applications.

Completely reconfigured Fe1-xS/C ultra-thin nanocomposite lamellar structure for highly efficient oxygen evolution

The surface reconfiguration of electrocatalysts during oxygen evolution reaction (OER) is much more important to reveal the actual catalytic active species, thus realizing the optimization of electrocatalyst activity. Herein, we demonstrate a simple strategy to achieve the complete electrochemical reconfiguration of Fe1-xS nanocrystals/ultra-thin carbon (Fe1-xS NCs/@ UT-C) nano-lamellar structure during the OER process. The uniform dispersion of Fe1-xS nanocrystals on the ultra-thin carbon layer favors the rapid complete reconfiguration. Such rapid reconfiguration creates new actual catalytic active species of amorphous iron-based oxide transformed from Fe1-xS, which is coupled with an ultra-thin carbon layer to facilitate the charge transfer of OER. More detailed, partly graphitization of the ultra-thin carbon layer not only affords to overcome the ohmic losses but also enhances the overall electrical conductivity and OER activity of the material. The Fe1-xS NCs/@UT-C as pre-catalyst shows high OER activity with a low overpotential of only 303 mV at 100 mA cm−2 and a Tafel slope of 55 mV/dec. In addition, the reconfigured catalyst has good stability for 168 h in alkaline conditions. This work is beneficial to understand the reconfiguration of electrocatalysts and design high-efficiency nonprecious metal-based electrocatalysts.

Design Efficiency of the Asymmetric Minimum Projection Uniform Designs

Highly efficient designs and uniform designs are widely applied in many fields because of their good properties. The purpose of this paper is to study the issue of design efficiency for asymmetric minimum projection uniform designs. Based on the centered L2 discrepancy, the uniformity of the designs with mixed levels is defined, which is used to measure the projection uniformity of the designs. The analytical relationship between the uniformity pattern and the design efficiency is established for mixed-level orthogonal arrays with a strength of two. Moreover, a tight lower bound of the uniformity pattern is presented. The research is relevant in the field of experimental design by providing a theoretical basis for constructing the minimum number of projection uniform designs with a high design efficiency under a certain condition. These conclusions are verified by some numerical examples, which illustrate the theoretical results obtained in this paper.

Design of a feasible high-efficiency 63NiO/ZnO integrated betavoltaic battery

The conventional betavoltaic battery design fails to eliminate the inherent influence of the radioactive source self-absorption effect, leading to a bottleneck in the efficiency and power of betavoltaic batteries. In this paper, a feasible high-efficiency 63NiO/ZnO integrated betavoltaic battery is designed and compared with the conventional betavoltaic battery. Simulation results show that the proposed betavoltaic battery has better output performance and breaks the upper limit of efficiency and power. The work presented here provides valuable insights for radioisotope battery designs, and the physical modeling procedure discussed can serve as a good reference for further applications in simulating heterojunctions of type-II semiconductors.

An Advanced Load-Line Analysis Software for use in the Design and Simulation of Microwave Low-Distortion, High-Efficiency and High-Power GaN HEMT Amplifiers

An Advanced Load-Line Analysis Software for use in the Design and Simulation of Microwave Low-Distortion, High-Efficiency and High-Power GaN HEMT Amplifiers