Load Modulation Research Articles

Experimental and numerical study of thermal and electrical potential of BIPV/T collector in the form of air-cooled photovoltaic roof tile

Among renewable energy sources, Building-Integrated Photovoltaic/Thermal (BIPV/T) systems are gaining increasing interest. To improve their economic competitiveness, technologies that increase their efficiency are searched for. The paper is devoted to evaluating the impact of various air-cooling configurations on the thermal and electrical performance of a photovoltaic roof tile. A numerical model of the own experimental system was developed in the ANSYS Fluent software for a wide range of input variables. The original approach based on the SST k-ω turbulence model, Discrete Ordinates radiation model, and the use of Solar Load module were proposed. Such a numerical model allows representation of semi-transparent layers and variable solar irradiance, which is a unique realization of real system modelling. Numerous analyses conducted indicate a higher heat recovery potential for an airflow duct with a height of 25 mm for all configurations analysed. The highest value of recovered heat flux was approximately 330 W/m2 under conditions of a volumetric air flow rate of 7.5 m3/h and solar irradiance equal to 900 W/m2. Good agreement of the results of the multivariant CFD simulations with new experimental ones was confirmed. Insight into the flow phenomena behind the achieved thermal results supplemented the knowledge. The highest electrical efficiency obtained experimentally was 5.76 % for a channel with a height of 50 mm, volumetric flow rate equal to 7.5 m3/h and solar irradiance equal to 600 W/m2. The presented methodology and the results obtained can be useful in research devoted to optimising BIPV/T air-based cooling systems, which will then be tested in-situ. Moreover, new experimental data collection can be used for the verification of numerical models.

Revealing low temperature-mechanical coupling failure mechanisms in CFRP laminates with in-situ observations

The number of layers and ply orientations determined the service performance of carbon fiber-reinforced polymer (CFRP) materials. Under low-temperature service conditions, the unclear weakening mechanism of mechanical properties of CFRP aggravates the failure risks of aerospace structures. In present work, the unclear correlation between layers with alternating orientations and the tensile-failure mechanisms of CFRP, the low temperature-mechanical coupling micromechanical behavior, and the failure mechanism of CFRP was experimentally revealed by using a horizontal testing instrument integrated with a low-temperature loading module and real-time optical imaging function. Based on various temperatures in a range from −40 °C to room temperature (RT) and two strain rates, the gradually decreasing trends of tensile strength, Young's modulus, and elongation after fracture with decreasing temperature are obtained. Three failure modes including fiber brittle fracture, fiber pull-out, and interface debonding are proposed to reveal the low temperature-mechanical coupling failure mechanism. Low-temperature asynchronous shrinkage of carbon fiber and epoxy resin promoted the transition from fiber brittle fracture to delamination at the interface. The proposed instrument could establish the approximatively actual service conditions involving low temperature and mechanical load.

Experimental and numerical comparisons among various skewed blades of low speed axial fan rotors

Literature indicates that there is lack of study related to the effects of axially skewed blades on the aerodynamic performance of axial flow fans. In this study rotors of various blade skews, namely, axial, circumferential and axial-circumferential types, are studied and their aerodynamic performances are compared to those of the baseline radial rotors of two types, namely, constant chord and varying chord. The skew in a blade can be considered as combination of sweep and dihedral. The skew change from the circumferential to axial type causes reversal of dihedral induced radial blade force and hence a reversal of meridional streamline curvature which in turn reverses the modulation of the end-wall loads. The inherent forward sweep in the forward skewed blades also modulates hub and tip loads. Thus, in a forward axial skew blade the forward sweep and positive dihedral combine favorably to unload the tip and to upload the hub. In the forward circumferentially skewed blades, forward sweep and the negative dihedral have mutually countering effects on end-wall load modulation. The highlight of this study is that it has demonstrated experimentally the unloading of the tip in the forward axially skewed blades which resulted in reduced losses and better performance including increased stall margin. Reduced tip loading was also verified from the casing pressure sensor measurements which showed weakening of tip vortex. The relative influence of sweep and dihedral on performance was additionally demonstrated in the axially-circumferentially skewed rotor of the constant chord type, with improvements attributable to higher sweep.

Non-Linear Simulation by Harmonic Balance Techniques of Load Modulated Power Amplifier Driven by Random Modulated Signals

The simulation of the steady state and the non-linear stability of a load modulated power amplifier (LMPA) driven by a random modulated generator, fully performed in the frequency domain by harmonic balance (HB) techniques, is presented. The non-linear microwave circuit and the driving pseudo-random modulated (PRM) generator are integrally defined in the frequency domain. The simulation is implemented and performed using commercially available circuit simulation software. The demodulation of the output signal of the LMPA is implemented with optimally matched filters as software-defined demodulation. The simulated dynamic results of a Quasi-MMIC GaN Doherty power amplifier (DPA) are shown and compared to the measured results with a 16-QAM driving signal at 10 MS/s. The time-domain measurement allows the validation of the new simulation technique through the comparison of both the measured and the simulated error vector magnitude (EVM), the left and right adjacent channel power ratios (ACPRs) versus the average output power. This new simulation is then called pseudo-random modulated harmonic balance (PRM-HB) simulation. The full PRM-HB simulation of an LMPA driven by a random modulated signal, performed in the frequency domain at the design circuit level, results in an advanced simulation tool in the frame of the design of RF circuits and subsystems for telecommunication applications.

Design of an efficiency enhanced wideband Doherty power amplifier based on synthesising of a modified harmonic‐control load modulation network

AbstractA design of a broadband Doherty power amplifier (DPA) using a novel harmonic control network (HCN) is presented. The DPA structure focused on manipulating harmonic components using this new HCN to enhance the bandwidth of operation and power efficiency. The proposed HCN combines a third harmonic suppression network (THSN) with the second harmonic impedance inverter circuit (SHIIC). In the design, the second harmonic component of the main transistor and the peaking transistor are short‐circuited by their associated SHIIC. Additionally, the carefully designed SHIIC and THSN circuit placed between the main and peaking transistors realise open circuit conditions at the third harmonic for both transistors at the saturation state and back‐off regions. Side by side with the aid of the properly designed post‐matching tuned network (PMTN), these harmonic loading conditions make both amplifiers to operate in continuous Class‐F modes with enhanced‐added efficiencies over wideband conditions. As a result, a succession of highly efficient DPA modes can be formed over a continuous frequency range in the full Doherty region, resulting in a reduced‐size enhanced power efficiency wideband DPA. For verification, a wideband DPA operating from 1.1 to 1.8 GHz was designed and implemented using the proposed topology. The measured drain efficiency of the implemented DPA at 6‐dB back‐off is 52.5%–67.5%, while the saturated power across the specified bandwidth is 43–43.7 dBm. The fabricated DPA exhibits an average efficiency of 48.7%–59.4%, when supplied by a 40‐MHz long‐term evolution (LTE) signal with a 7.5‐dB peak‐to‐average power ratio (PAPR). Performing digital pre‐distortion (DPD) improves the adjacent channel power ratio (ACLR) from −25.8 dBc to −47.6 dBc.

A 28 GHz transformer-based Doherty power amplifier for FR2 5G applications in 40 nm CMOS

ABSTRACT In this paper, a 28 GHz transformer-based Doherty power amplifier (DPA) is designed in Huali Microelectronics (HLMC) 40 nm CMOS process. The impedance inverter is converted into transformer form to calculate and design the power combiner based on the transformer voltage combination. A switchable cap array is added to the auxiliary output to increase the robustness of the active load modulation. The DPA achieves 17.1 dBm saturated power with 33.67% peak power added efficiency ( PA E max ) and 19.93% PA E PBO 6 dB at 6 dB power back-off.

The effect of reward expectation on working memory of emotional faces under different levels of cognitive load: an ERP study.

Using event-related potentials (ERPs), this study examined the impact of reward expectations on working memory of emotional faces under different levels of cognitive load in a task combining the N-back paradigm and the reward expectation paradigm. The experiment involved presenting high- or low-reward cues followed by an N-back task for emotional faces with different loads. The accuracy results showed that under a high task load, both reward and emotion effects were significantly observed. However, these effects disappeared under a low task load. Analysis of the ERP data revealed that the early P2 and VPP components exhibited greater responses to fearful faces than to neutral faces. In the later stages, the P3 and LPP components showed greater reactions to high rewards than to low rewards. Additionally, the P2 component was found to be modulated by task load in relation to rewards, the EPN component demonstrated task load modulation with respect to emotions, and the N170 component showed an interaction effect between rewards and emotions. These findings imply that load regulates the reward effect and the emotional superiority effect in the process of working memory for emotional faces. In the cognitive processing of working memory, motivation and emotion jointly influence processing. Emotional factors have a greater impact in the early stage of processing, while motivation factors have a greater impact in the late stage of processing.

Probiotic-Induced Modulation of Microbiota Composition and Antibiotic Resistance Genes Load, an In Vitro Assessment.

The imbalance of the gut microbiota (GM) is known as dysbiosis and is associated with disorders such as obesity. The increasing prevalence of microorganisms harboring antibiotic resistance genes (ARG) in the GM has been reported as a potential risk for spreading multi-drug-resistant pathogens. The objective of this work was the evaluation, in a fecal culture model, of different probiotics for their ability to modulate GM composition and ARG levels on two population groups, extremely obese (OB) and normal-weight (NW) subjects. Clear differences in the basal microbiota composition were observed between NW and OB donors. The microbial profile assessed by metataxonomics revealed the broader impact of probiotics on the OB microbiota composition. Also, supplementation with probiotics promoted significant reductions in the absolute levels of tetM and tetO genes. Regarding the blaTEM gene, a minor but significant decrease in both donor groups was detected after probiotic addition. A negative association between the abundance of Bifidobacteriaceae and the tetM gene was observed. Our results show the ability of some of the tested strains to modulate GM. Moreover, the results suggest the potential application of probiotics for reducing the levels of ARG, which constitutes an interesting target for the future development of probiotics.

Inverted sequential load-modulated balanced amplifier for extending dynamic power range over wide bandwidth

This paper propose an inverted sequential load-modulated balanced amplifier (ISLMBA) for extending the dynamic power range of a power amplifier (PA) over a wide bandwidth. The proposed ISLMBA consists of a control amplifier (CA) and a balanced PA (BPA) pair. A composited impedance inverter is inserted between each BPA transistor and the output coupler. The composited impedance inverter is composed by the intrinsic elements and output matching network (OMN) of the BPA transistor. In this way, the intrinsic elements can be fully absorbed into the impedance inverter over a wide bandwidth. Meanwhile, the load modulation trajectories of the BPA transistors can be optimized over a wide bandwidth by tuning the characteristic impedance of the impedance inverter. The theoretical current, voltage and load-modulation profiles of the ISLMBA are comprehensively analyzed. It is illustrated that the proposed ISLMBA could maintain high efficiency at deep output back-off power level over a wide bandwidth. Moreover, this work designs and fabricates an ISLMBA operating over 1.3–2.55 GHz to verify the proposed PA architecture. The fabricated ISLMBA exhibits a saturation drain efficiency (DE) of 54.5%–73.8% and a saturation output power of 42.9–45.9 dBm. At the same time, the fabricated ISLMBA achieves a 10 dB back-off DE of 42.1%–63.9% over the frequency band of interest. When the fabricated ISLMBA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 10.2 dB at 2.0 GHz, the measured adjacent channel leakage ratios (after predistortion) are −47.7 and −48.8 dBc at the lower and upper bands, respectively.

Simplified Emulation of Active Load Modulation for a Millimeter-Wave GaN MMIC Doherty Power Amplifier Design

Based on large-signal simulations, this article proposes a simplified method to emulate the active load modulation between the carrier and peaking transistors in a Doherty power amplifier (DPA) design. In contrast to the conventional load–pull method, the proposed method contributes to emulating the active load modulation between the load-modulated transistors with considering their nonlinear interaction. It offers the advantages of predicting the real-world performance of the load-modulated transistors and providing the optimum load-modulation trajectories to be synthesized in a DPA design. To verify the proposed method, a two-way millimeter-wave (mmWave) gallium nitride (GaN) microwave monolithic integrated circuit (MMIC) DPA is designed from 25.5 to 27 GHz. The measured results show that the realized MMIC DPA achieves power-added efficiency (PAE) higher than 30% at saturation, 27% at 6-dB back-off, and 21.5% at 8-dB back-off, with a saturated output power higher than 31.4 dBm across the band. When tested using a 400-MHz modulated signal with digital predistortion (DPD), the MMIC DPA shows adjacent channel power ratio (ACPR) levels 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> 40 dBc over the band.

Research on the Role of Artificial Intelligence in the Core of Intelligent Translation Systems

With the development of the world economy and the expansion of foreign trade, the status of English as a global language in English teaching is increasingly elevated, and language translation is an indispensable link. In the new intelligent translation and reading system based on language models, its translation part includes at least one dictionary used for translation. The system includes: reading and writing database, loading module, editing module, label module, trigger module, annotation module, and word addition module. Among them, the read-write database is used to store literature; The loading module is used to load article materials as reading documents. It adopts natural language processing technology to save system translation and reading time and improve system efficiency. In order to test the advantages of the system used in this article, 200 vocabulary words were input into the system and compared with the traditional system for translation accuracy. The translation accuracy of the system in this article was 94.64%, while the translation accuracy of the traditional system was 83.34%. The system in this article helps to improve translation efficiency and enhance reading experience.

Sequential Load-Modulated Balanced Amplifier With Asymmetrical Output Coupling for a Load Modulation Continuum

Sequential Load-Modulated Balanced Amplifier With Asymmetrical Output Coupling for a Load Modulation Continuum

Design and Application of Virtual Simulation Teaching System under Artificial Intelligence Orientation

Abstract This paper builds a virtual simulation teaching system based on the Unity simulation platform, which contains a network connection module, resource loading module, and so on. Using the combination of natural interaction and virtual simulation teaching system, the design of Kinect depth information and SVM classifier for gesture recognition classification is integrated with the virtual simulation teaching scene to realize cross-platform collaborative interaction. The virtual simulation teaching process involves a large number of gesture interaction processes, using mf-score multi-feature selection of features that play a vital role in the classification of the data set, eliminating the raw noise of the customized gesture data and improving the contrast of the gesture image. The results of the practical application of the virtual simulation teaching system show that the discipline to which the virtual simulation course belongs (0.008) and the time of identification (0.047) have a significant effect on its application activity. The multisensory, immersive, and interactive nature of virtual simulation teaching (P &lt; 0.001) all have a highly significant positive effect on learners’ foreign language useability. The foreign language assessment score at the end of the virtual simulation course is (92.74±3.32), which is significantly different from the traditional teaching method (P&lt;0.01). The teaching system in this paper meets the requirements of most learners in terms of interactive interface, function, and content.

A circuit solving method for output matching network parameters of Doherty power amplifiers

In this paper, all possible numerical solutions are provided when the matching conditions for Doherty power amplifier (DPA) back-off and saturation states are met. Firstly, this article presents an impedance expression of the DPA. Then all circuit parameter solutions can be solved for the load modulation of DPA using this expression. In the process of solving circuit parameters, the impedance matching of the DPA at the saturation level is established through the analysis of the S-parameter matrix. Then by limiting the impedance solution range of DPA at the output power back-off (OBO) level, the circuit parameter solutions that satisfy the specified conditions are meticulously screened. The output matching network of the DPA is designed according to the obtained circuit parameter solutions for broadband operation. To validate the proposed design method, a broadband DPA operating from 1.2 to 2.4 GHz is designed and measured based on the proposed method. Under the continuous wave excitation, the measured drain efficiency at 6 dB OBO level and saturation (SAT) level are 44%–56% and 51%-65.4% from 1.2 to 2.2 GHz, respectively. The peak output power is 45.1–46.3 dBm.

Development Review of Highly Efficient Sequential Power Amplifier with Extended Back-Off Range for Broadband Application

Similar to a Doherty power amplifier (DPA), a sequential power amplifier (SPA) is mainly composed of a main amplifier, an auxiliary amplifier and a combiner. However, SPA breaks the bandwidth limitation of the impedance inverter in the DPA, and also simplifies the design procedure. Since the main amplifier has no load modulation, it is easy for the SPA to realize broadband operation and improve the output back-off (OBO) power range. Therefore, SPA has great advantages and potential in expanding bandwidth, improving drain efficiency and expanding the back-off range of a power amplifier simultaneously. This paper describes the evolution and classification of the SPA. First, the basic theory of the SPA is reviewed. Then, some two-way SPAs using coupler and circulator as a power combiner are discussed. Thirdly, the latest popular sequential load modulated balanced amplifier is overviewed.

Development Review of Broadband and Multi-Band Outphasing Power Amplifiers for High-Efficiency Amplification

Outphasing power amplifiers (OPAs) can be used in wireless information and power transfer systems due to their excellent conversion efficiency. With the rapid advancement of technology, there is a strong demand for OPAs to achieve wideband and multi-band operations to enhance frequency coverage. This paper provides a comprehensive review of the research progress on the development of broadband and multi-band board-level OPAs. Firstly, the paper introduces the fundamental components of an OPA. Then, the paper delves into a detailed analysis of the load modulation of OPAs. Subsequently, previous works on the circuit topology and design methods for broadband and multi-band OPAs are discussed and compared. The paper highlights various design strategies and their respective advantages and disadvantages. Finally, the paper explores some potential design methods for broadband and multi-band OPAs, discussing emerging technologies and highlighting potential research directions.

Technological features of OOG transportation by sea transport

The article discusses the features of the transportation of oversized cargo by sea on container ships. The main governing documents and rules for the confirmation and placement of oversized cargo are indicated. The problems are reflected in the guidance documentation, since at the moment it is impossible to take into account all the features of a specific oversized cargo when creating a loading plan and cargo fastening tools on a flat rack. The scheme of placement of oversized cargo on a container ship is given. Options for attaching oversized cargo to a flat rack are considered in detail. The loads are divided into categories, for each of which the methods of fastening are given in accordance with the peculiarities of the geometric shapes of the load and the weight distribution. The conclusion indicates the need to create a software module for standardizing the rules for loading oversized cargo, which will systematize all the characteristics of oversized cargo, calculate the best options for placing cargo on a ship, taking into account the safety requirements and optimality of the cargo plan, reduce accidents during loading / unloading and transportation. It was also noted that the standardization of the loading module for oversized cargo will allow integrating information about the transportation of oversized cargo into the overall system for determining the efficiency and quality of container shipping.

Standing Reactive Postural Responses of Lower Limbs With and Without Self-Balance Assistance in Individuals With Spinal Cord Injury Receiving Epidural Stimulation.

Spinal cord epidural stimulation can promote the recovery of motor function in individuals with severe spinal cord injury (SCI) by enabling the spinal circuitry to interpret sensory information and generate related neuromuscular responses. This approach enables the spinal cord to generate lower limb extension patterns during weight bearing, allowing individuals with SCI to achieve upright standing. We have shown that the human spinal cord can generate some standing postural responses during self-initiated body weight shifting. In this study, we investigated the ability of individuals with motor complete SCI receiving epidural stimulation to generate standing reactive postural responses after external perturbations were applied at the trunk. A cable-driven robotic device was used to provide constant assistance for pelvic control and to deliver precise trunk perturbations while participants used their hands to grasp onto handlebars for self-balance support (hands-on) as well as when participants were without support (free-hands). Five individuals with motor complete SCI receiving lumbosacral spinal cord epidural stimulation parameters specific for standing (Stand-scES) participated in this study. Trunk perturbations (average magnitude: 17 ± 3% body weight) were delivered randomly in the four cardinal directions. Participants attempted to control each perturbation such that upright standing was maintained and no additional external assistance was needed. Lower limb postural responses were generally more frequent, larger in magnitude, and appropriately modulated during the free-hands condition. This was associated with trunk displacement and lower limb loading modulation that were larger in the free-hands condition. Further, we observed discernible lower limb muscle synergies that were similar between the two perturbed standing conditions. These findings suggest that the human spinal circuitry involved in postural control retains the ability to generate meaningful lower limb postural responses after SCI when its excitability is properly modulated. Moreover, lower limb postural responses appear enhanced by a standing environment without upper limb stabilization that promotes afferent inputs associated with a larger modulation of ground reaction forces and trunk kinematics. These findings should be considered when developing future experimental frameworks aimed at studying upright postural control and activity-based recovery training protocols aimed at promoting neural plasticity and sensory-motor recovery.

Koopman model predictive control based load modulation for primary frequency regulation

AbstractConventional power systems function under the assumption that loads are uncontrollable, and that the generation control is the primary means of preserving system voltage, frequency, and stability. Thanks to recent advancements of power electronics technology and communication schemes, demand‐side resources are now capable of providing fast frequency regulation. Controllable loads can provide upward/downward reserve during frequency excursions. In this paper, the authors consider collective contribution of large clusters of controllable loads which modulate their aggregate demand power to regulate the primary frequency. Koopman model predictive control is designed to handle local frequency variations caused by various disturbances at each load bus, considering uncertain load models. The efficacy of the proposed method has been validated using the New‐England power system considering two scenarios, namely, load variation, and generation outage.

Design of a Dual-Band Load-Modulated Sequential Amplifier with Extended Back-off

This letter presents a dual-band load-modulated sequential amplifier (LMSA). The proposed amplifier changed the attenuator terminated at the isolation port of the four-port combiner of the traditional sequential power amplifier (SPA) architecture into a reactance modulation network (RMN) for load modulation. The impedance can be maintained pure resistance by designing RMN, thus realizing high efficiency and a good portion of the output power in the multiple bands. Compared to the dual-band Doherty power amplifier with a complex dual-band load modulation network (LMN), the proposed LMSA has advantages as maintaining high output power back-off (OBO) efficiency, wide bandwidth and simple construction. A 10-watt dual-band LMSA is simulated and measured in 1.7-1.9 GHz and 2.4-2.6 GHz with saturated efficiencies 61.2-69.9% and 54.4-70.8%, respectively. The corresponding 9 dB OBO efficiency is 46.5-57.1% and 46.4-54.4%, respectively.