Balancing Capability Research Articles

A High Power Factor LED Driver with Intrinsic Current Balancing Capability

The research proposed a novel LED driver with the functions of power-factor correction (PFC) and current balancing. A flyback converter and a Class-D series resonant converter were integrated by sharing an active switch to form a single-stage circuit topology. The flyback converter played the role of a PFC circuit. The component parameters were designed to make the flyback converter to operate at discontinuous-conduction mode (DCM). In this way, the input line current can be sinusoidal, resulting in near unity power factor and low total harmonic distortion in current (THDi). The resonant converter was connected in series with a differential-mode transformer with a turns ratio of 1 to drive four LED strings. The current of the four LED strings will be automatically and evenly balanced by using the 1:1 transformer. This article analyzed the different modes of operation in detail, derived the mathematical equations and designed the parameters of the circuit components. Finally, a 72-W prototype LED driver was implemented and tested. A satisfactory performance has verified the feasibility of the proposed LED driver.

Turning the energy channel of side-chain TADF polymers by monomer optimization for high-efficiency solution-processed white OLEDs

Suppressing non-radiative channel in luminescent polymer is the key factor for high device efficiency of organic light-emitting diodes (OLEDs). In this paper, we synthesized three side-chain TADF polymers, PTRZ-TRZ, PTRZ-TPA and PTRZ-Cz, to deeply investigate the relationship between energy transfer and molecular structure. The photophysical measurements show that the copolymerized monomer has significant effect on the exciton deexcitation process of TADF fragment. The rigid carbazole unit can efficiently separate the TADF units to inhibit the aggregation-caused quenching (ACQ) of polymer, while electron-donating triphenylamine unit will induce the severe charge transfer state to form low energy exciplex, which lead to severe energy leakage of the excited TADF. Moreover, according to the single-charge devices test, the ideal separation unit also can improve the capability of charge injection and carrier balance. As a result, the solution-processed OLEDs host with PTRZ-Cz achieved the external quantum efficiency (EQEmax) of 14.2%, which was much higher than that of PTRZ-TPA and PTRZ-TRZ. By doping red phosphorescent emitter Ir(MDQ)2(acac), the hybrid white OLED devices (T-P WOLEDs) based on PTRZ-Cz achieved the maximum current efficiency (CEmax), power efficiency (PEmax) and EQEmax of 46.8 cd/A, 32.6 lm/W and 20.7%, respectively, with a high CRI of 80.6. The outcomes obtained in this study can provide useful insights into the structure−property relationship for further development of efficient TADF polymer hosts for solution-processable OLEDs.

Reliability Analysis of Multi-Level PFC Converter-Based Charger for Light EV Charging Application

Electric vehicle (EV) charging architectures with two stages consist of rectification and a DC–DC conversion stage. Multi-level rectifiers are emerging as better alternatives in the rectification stage of EV charging applications. As they possess minimum voltage stress on switches, better harmonic profile at the grid side, lower dv/dt stress, and higher voltage capability. In this article, a five-level rectifier in conjunction with a phase shift full bridge converter is implemented for EV charging applications. The rectifier has the inherent capacitor voltage balancing capability and maintains unity power factor at the source side under varieties of operating conditions. The reliability of power electronic converters can be estimated by accessing the reliability of each component in converters. To establish the suitability of the implemented system for real-time EV charging applications, comprehensive performance analysis has been carried out including reliability assessment, the impact of parametric variations on reliability, calculation of losses and efficiency. The battery charger is mathematically modeled and validated experimentally in laboratory. The comparative analysis of the rectifier with state-of-the-art literature has been also carried out.

Performance Evaluation of Multi-Typed Precipitation Products for Agricultural Research in the Amur River Basin over the Sino–Russian Border Region

Precipitation data are crucial for research on agricultural production, vegetation growth, and other topics related to environmental resources and ecology. With an increasing number of multi-typed gridded precipitation products (PPs), it is important to validate the applicability of PPs and improve their subsequent monitoring capabilities to ensure accurate precipitation-based research. This study evaluates the performance of four mainstream PPs—European Centre for Medium-Range Weather Forecasts Reanalysis V5 (ERA5), ERA5-Land, Multi-Source Weighted-Ensemble Precipitation (MSWEP), and integrated multi-satellite retrievals for the Global Precipitation Mission (GPM)—in capturing the characteristics of precipitation intensity and derived agricultural drought in the crop-enrichment area over the Sino–Russian border region. The results show that, overall, GPM has the most balanced capability among the different experimental scenarios, with well-identified seasonal precipitation intensities. ERA5-Land had strong abilities in depicting annual distribution from spatial/stationary outcomes and obtained advantages in daily multi-parameter consistency verification. When evaluating monthly data in different agroclimatic areas, MSWEP and GPM had outstanding performances in the regions of Russia and China, respectively. For evaluating precipitation intensities and agricultural drought based on daily and monthly precipitation, MSWEP and GPM demonstrated finer performances based on combined agricultural thematic areas (ATAs). However, seasonal effects and affiliated material features were found to be the main factors in exhibiting identification capabilities under different scenarios. Despite good handling of intensity recognition in the eastern Chinese area, ERA5′s capabilities need to be improved by extending sources for calibrating gauged data and information on dry–wet conditions. Overall, this study provides insight into the characterization of PP performances and supports optimal product selection for different applications.

A multi-level rectifier with voltage balancing capability for EV charging

ABSTRACT In two-stage electric vehicle (EV) battery chargers, ac-dc conversion stage contributes significantly in determining the power quality. At this stage, multilevel rectifiers (MLRs) featuring switches with lower voltage rating and better input voltage waveform quality can be adopted. However, balancing capacitor voltage in MLR is an important challenge. In this paper, a single-phase five-level power factor correction (PFC) rectifier with self-balancing capacitor is implemented for EV battery charging. The complimentary switching scheme adopted for rectifier reduces number of gate driver circuits and ensures capacitor voltage balancing. The rectifier shows added benefit of reduced voltage stress across switches and not requiring an external filter at the dc side as the load is parallelly connected with one of the capacitors. The operating principle, control strategy, modulation technique and design features of the implemented five-level rectifier is discussed in detail. The implemented control scheme enhances rectifier performance by establishing precise output voltage regulation during load fluctuations while maintaining unity power factor at input side. The five-level rectifier is validated experimentally and compared with other existing multilevel and non-multilevel rectifier topologies. The peak efficiency of 93.8% is achieved at 2 kW of output power.

Series/Parallel Li-ion Battery Modules Active Equalisation Considering Load and No-Load Operation

Series and series/parallel connection of Li-ion modules is required to build Li-ion energy storage systems (ESS) up to the desired voltage level and energy capacity. Embedding several modules and the required electrical connections into a complete ESS is an endeavour engineering problem that raises the need for equalisation techniques. This paper proposes an equalisation method for Li-ion energy modules using a voltage-sharing technique under load and no-load conditions. The proposed system uses module-level dc/dc power converters for power exchange and equalisation. The proposed method is validated by simulations and experimentally, including the integration with the hierarchical control system typically used in ESS. The experimental validation is implemented using 2-connected series modules and 2-parallel strings, even though it can be easily extended to an arbitrary number of modules. The proposed no-load equalisation method allows a limited balancing capability even with the energy modules and the dc/dc converter disconnected from the subsequent power conversion stages, typically an inverter.

남녀 대학 축구 선수의 균형 능력과 족저압 단순 비교

In this study, we will compare and analyze the balance ability and plantar pressure of male and female college soccer players, and try to provide basic data for exercise programs that are useful for improving the competitiveness of soccer players and preventing injury, as well as the difference in balance ability. All data were tested independently using the SPSS 26.0 program, and all statistical significance levels were set to .05 to investigate the difference in balance and plantar pressure capabilities between groups. BR As a result of this study, the following conclusions were obtained. First, in balance ability, group B was higher on the left side, and group A was statistically significantly higher on the right side. Second, no significant difference appeared between the Front and Back groups in balance ability. Third, the plantar pressure was high in Group A for the forefoot and Group B for the hindfoot, but no significant difference was observed in the middle foot.

Design of a Large Field of View and Low-Distortion Off-Axis Optical System Based on a Free-Form Surface

Free-form surfaces have good aberration correction capability and balance capability for nonrotationally symmetric imaging systems. In this study, we analyzed the quantitative relationship between X–Y polynomial combination and aberration for the efficient design of X–Y free-form optical systems. The purpose of this study was to provide an exhaustive design method for off-axis triple inverse optical systems with X–Y free-form surfaces. Finally, we designed a free-form off-axis optical system with a large field of view (FOV) and low distortion based on the off-axis triple inverse optical system without an intermediate image plane. The primary mirror (PM) of the system adopted an X–Y polynomial free-form surface to correct the aberration of different FOVs of the system and improve the image width and quality. The optical system had a focal length of 1000 mm, an F-value of 9.5, an FOV angle of 23° × 1°, a maximum distortion grid in the FOV less than or equal to −0.05%, and a full-field average wave aberration better than 0.055 λ (λ/18.2, λ = 632.8 nm). The analysis of the design results showed that the system had high-quality imaging and a compact structure. This design method can provide a technical reference for the study of such free-form off-axis systems.

Online Digital Implementation of Wide Voltage Range RMS-Current-Optimized Control With Voltage Balancing Capability for DAB Converter

The dual active bridge (DAB) converter is widely used in renewable energy power generation systems with wide input voltage characteristics. An inappropriate duty cycle will lead to a larger inductor RMS current and low efficiency. In this paper, an efficiency-oriented optimized triple-phase-shift (OTPS) scheme is proposed for the dual active bridge (DAB) converter that can reduce the inductor root-mean-square (RMS) current for a wide input voltage and realize zero voltage switching (ZVS). The ZVS condition contains the direction and amplitude of the inductor current to make the ZVS area more accurate. In addition, the OTPS scheme also has the capability of voltage balancing without additional voltage equalizers under unbalanced load. The influence of deadtime on voltage balance is analyzed and a voltage balancing scheme with compensation of the duty cycle is proposed. To reduce resource occupation and operation time, an on-line implementation scheme of variable parameter control (VPC) based on field programable gate array (FPGA) is proposed. Without a look-up table, the sum of the operation time of the control module and modulation module is only 0.66 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s, and the required memory bits are only 459k. Both operation time and memory bits are reduced by more than 90% compared to existing literature. Finally, the whole proposed process is verified by the experimental results.

AC-Voltage Controller for Grid-Forming Converters

This article presents a voltage controller designed to operate grid-forming (GFM) converters under different grid impedance scenarios demonstrating good performance in conjunction with external power-synchronization loops (PSLs), e.g., droop control. GFM converters are required to have fast, accurate and stable voltage–frequency response, self-synchronization, power balance, grid supporting and fault ride-through (FRT) capabilities; either they are connected to the grid or to other generators. State-of-the-art voltage controllers are mainly focused on achieving either good voltage tracking and disturbance rejection or wide stability range and robustness. This proposal fulfils both tendencies as, first, it shows fast dynamic response, accurate voltage tracking, and total cancellation of output current disturbances at both positive-and negative-sequences of fundamental frequency because the controller presents zero-output impedance. Second, the controller shows a good sensitivity function and a wide stability range, which permit its operation in grid-connected and stand-alone mode. Finally, the proposed controller exhibits a good performance combined with a PSL under a wide range of grid impedance scenarios, showing seamless transition between grid-connected and stand-alone mode and vice versa, demonstrating also FRT capabilities preserving GFM operation under symmetrical and asymmetrical grid-fault events.

Creating a call center test bench for load balancing Asterisk servers in a cluster

The article deals with the issues of increasing throughput in call centers. The current solution is to cluster call servers and evaluate their characteristics to ensure efficient operation and the necessary fault tolerance. It is shown that one of the main aspects of the quality functioning of the call center is load balancing of servers in the cluster.&#x0D; The features of the call-center modeling process are considered. The organization scheme of the call center of the company and the network model of the call center have been created. Virtualization technology was used to create a network model of a call center. The VMWare ESXI 6.7 hypervisor and the vCenter client were used as a network configuration platform.&#x0D; An analysis of load balancing was carried out using different algorithms and strategies.&#x0D; Asterisk PBX was configured and a server cluster was created. A test bench was developed and configured using the Zabbix open source product to explore a cluster of call servers. A bandwidth characteristic for the Asterisk _1 server and a network map were obtained, which actually represents a simulated structure of the call center network.&#x0D; The process of load testing on three Asterisk servers and the implementation of Zabbix load balancing capabilities are shown. A custom SIPp session script has been created for accepting calls and load testing. The number of calls that the call center is able to handle is calculated. It has been determined that a single Asterisk server with its current settings can handle a maximum of 915 concurrent calls. The process of load balancing on a cluster of SIP servers has been launched. A cluster of Asterisk servers has been found to be capable of handling 2550 simultaneous calls.

ECH[formula omitted]OA: An Enhanced Chimp-Harris Hawks Optimization Algorithm for copyright protection in Color Images using watermarking techniques

This paper proposes a hybrid Enhanced Chimp-Harris Hawks Optimization Algorithm (ECH3OA) that combines both enhanced Chimp Optimization algorithm (ChOA) and Harris Hawks optimization algorithm (HHO). HHO is a robust algorithm in solving optimization issues. However, it suffers from a balancing problem between exploitation and exploration. On the other hand, ChOA algorithm is another powerful algorithm with the capability of balancing between exploitation and exploration. However, ChOA suffers from low convergence and falling in the local minimum. The novelty of ECH3OA as a proposed optimization algorithm is concentrated in three contributions. The first is an enhanced ChOA that uses Levy Flight to improve its exploration phase. The second contribution of the algorithm is proposing an updated formula to calculate escaping energy of the prey as a selector between exploitation and exploration. Finally, the four cases of exploitation using HHO are used in the proposed algorithm. The effectiveness of the proposed algorithm is proved by comparing its performance with other eleven state-of-the-art algorithms on 23 standard benchmark function, 30 benchmark function of different modalities from CEC2017, 10 complex functions from CEC2019, and six standard real world engineering problems. Friedman average rank and Wilcoxon rank-sum (p-value) tests are applied as non-parametric statistical tests. Among the different benchmark suits, ECH3OA is ranked first among the other algorithms. We also applied ECH3OA for copyright protection in Color Images using Crypto-Watermarking Techniques. The results show better durability and transparency level of the watermark as compared to recent studies.

Evolutionary approach to construct robust codes for DNA-based data storage.

DNA is a practical storage medium with high density, durability, and capacity to accommodate exponentially growing data volumes. A DNA sequence structure is a biocomputing problem that requires satisfying bioconstraints to design robust sequences. Existing evolutionary approaches to DNA sequences result in errors during the encoding process that reduces the lower bounds of DNA coding sets used for molecular hybridization. Additionally, the disordered DNA strand forms a secondary structure, which is susceptible to errors during decoding. This paper proposes a computational evolutionary approach based on a synergistic moth-flame optimizer by Levy flight and opposition-based learning mutation strategies to optimize these problems by constructing reverse-complement constraints. The MFOS aims to attain optimal global solutions with robust convergence and balanced search capabilities to improve DNA code lower bounds and coding rates for DNA storage. The ability of the MFOS to construct DNA coding sets is demonstrated through various experiments that use 19 state-of-the-art functions. Compared with the existing studies, the proposed approach with three different bioconstraints substantially improves the lower bounds of the DNA codes by 12-28% and significantly reduces errors.

What is the Value of a Balanced Total Knee Arthroplasty? Getting It Right the First Time

BackgroundInstability is a leading cause of early failure following total knee arthroplasty (TKA). Enabling technologies can improve accuracy, but their clinical value remains undetermined. The purpose of this study was to determine the value of achieving a balanced knee joint at the time of TKA. MethodsA Markov model was developed to determine the value from reduced revisions and improved outcomes associated with TKA joint balance. Patients were modeled for the first 5 years following TKA. The threshold to determine cost-effectiveness was set at an incremental cost effectiveness ratio of $50,000/quality-adjusted life year (QALY). A sensitivity analysis was performed to evaluate the influence of QALY improvement (ΔQALY) and Revision Rate Reduction on additional value generated compared to a conventional TKA cohort. The impact of each variable was evaluated by iterating over a range of ΔQALY (0 to 0.046) and Revision Rate Reduction (0% to 30%) and calculating the value generated while satisfying the incremental cost effectiveness ratio threshold. Finally, the impact of surgeon volume on these outcomes was analyzed. ResultsThe total value of a balanced knee for the first 5 years was $8,750, $6,575, and $4,417 per case, for low, medium, and high-volume surgeons, respectively. Change in QALY accounted for greater than 90% of the value gain with a reduction in revisions making up the rest in all scenarios. The economic contribution of revision reduction was relatively constant regardless of surgeon volume ($500/case). ConclusionAchieving a balanced knee had the greatest impact on ΔQALY over early revision rate. These results can help assign value to enabling technologies with joint balancing capabilities.

DDCM: a decentralized density clustering and its results gathering approach

The use of distributed clustering is an important method of solving large-scale data mining problems. There are still some problems associated with distributed clustering, such as a performance bottleneck on the master node and network congestion caused by global broadcasting. This paper proposes a decentralized clustering method based on density clustering and the content-addressable network technique. It can form a cluster with excellent scalability and load balancing capabilities based on several surrounding nodes. In addition, a method is presented for optimizing the way clustering results are gathered in different application scenarios. Based on our extensive experiments, the proposed approach performs three times better than benchmark algorithms in terms of efficiency and has a stable expanding ratio of about 0.6 for large-scale data sets.

Domain Knowledge-Based Human Capital Strategy in Manufacturing AI

As the Industry 4.0 paradigm accelerates, the importance of artificial intelligence (AI) in manufacturing industry is increasing. Manufacturing AI requires balanced capabilities between industry-specific domain knowledge and AI capability. Nevertheless, many manufacturing AI startups are mainly focusing on human capital based on AI or data science capability. This article focused on the importance of human capital based on domain knowledge for the success of manufacturing AI. In this article, the relationship between domain knowledge and corporate performance was analyzed for 127 global manufacturing AI startups. Furthermore, the moderating effects of educational level and cofounder size for domain knowledge were analyzed. In addition, an expanded analysis was conducted on effect between domain knowledge, educational level, cofounder size, and corporate performance by business model. This article has new implications for and provides practical contributions to the human capital strategy for manufacturing AI corporates.

Partially Isolated Multiport Converter With Automatic Current Balancing Interleaved PWM Converter and Improved Transformer Utilization for EV Batteries

Multiport converters (MPCs) that can regulate multiple input/output ports have been proposed to reduce the converter count in electric vehicle battery systems consisting of multiple batteries (12-V, 48-V, and high-voltage batteries). Conventional MPCs consist of an interleaved PWM converter and DAB converter, and an active current balancing control is indispensable for the interleaved converter. Furthermore, the transformer utilization unavoidably decreases because switches are driven with a nominal duty cycle of 0.75 for 48-/12-V batteries. This article proposes a novel MPC with an automatic current balancing capability and improved transformer utilization. A flying capacitor (FC) is added to the interleaved PWM converter to automatically balance inductor currents. The added FC also allows operations with a nominal duty cycle of 0.5 for 48-/12-V batteries, improving the transformer utilization. The experimental verification tests using a 1-kW prototype demonstrated the automatic current balancing capability, improved transformer utilization, and flexible power exchange among three batteries.

New balance capability index as a screening tool for mild cognitive impairment

BackgroundMild cognitive impairment (MCI) is not just a prodrome to dementia, but a very important intervention point to prevent dementia caused by Alzheimer's disease (AD). It has long been known that people with AD have a higher frequency of falls with some gait instability. Recent evidence suggests that vestibular impairment is disproportionately prevalent among individuals with MCI and dementia due to AD. Therefore, we hypothesized that the measurement of balance capability is helpful to identify individuals with MCI.MethodsFirst, we developed a useful method to evaluate balance capability as well as vestibular function using Nintendo Wii balance board as a stabilometer and foam rubber on it. Then, 49 healthy volunteers aged from 56 to 75 with no clinically apparent cognitive impairment were recruited and the association between their balance capability and cognitive function was examined. Cognitive functions were assessed by MoCA, MMSE, CDR, and TMT-A and -B tests.ResultsThe new balance capability indicator, termed visual dependency index of postural stability (VPS), was highly associated with cognitive impairment assessed by MoCA, and the area under the receiver operating characteristic (ROC) curve was more than 0.8, demonstrating high sensitivity and specificity (app. 80% and 60%, respectively).ConclusionsEarly evidence suggests that VPS measured using Nintendo Wii balance board as a stabilometer helps identify individuals with MCI at an early and preclinical stage with high sensitivity, establishing a useful method to screen MCI.

Active power balance capability of security and stability control system (SSCS) against outage of UHVDC

The aim of the security and stability control system (SSCS) is to maintain active power balance and frequency stability. For large SSCS, it is difficult to find the state space and the transition rates of the paths. The flat design yields more complex topology. Considering the random outages, the ultra-high-voltage dc (UHVDC) has more capacity levels and states. The existing evaluation cannot quantify the power balance capability of the SSCS. This paper newly quantifies active power balance capability of the multi-level SSCS with partial or complete outage of the UHVDC. An incidence matrix is proposed to describe the topology of the SSCS. A recursive solution to calculate the transition rates is proposed. The equivalent downward transition rate is newly defined. The increasable generation and the transition rates of the UHVDC at any initial state are newly included. The numerical analysis shows that the incidence matrix and recursive algorithm reduces the calculation effort for the practical SSCS with multi-level, redundancy component, and flat design. The active power balance capability of the SSCS is decided by the increasable power, the reduced generation and the downward transition rate.

Amorphous Mixed-Vanadium-Tungsten Oxide Films as Optically Passive Ion Storage Materials for Solid-State Near-Infrared Electrochromic Devices.

Near infrared (NIR) electrochromic (EC) devices that selectively modulate the NIR light without affecting the daylight represent a promising window technology for saving energy consumption of buildings. Current research efforts have been focused on developing NIR-EC materials, while little attention has been directed to the optically passive ion storage materials that are crucial for balancing charges in a full NIR-EC device. Herein, we report that amorphous phase mixed-vanadium-tungsten oxide films exhibit minimum optical change with high ion storage capacity, which enables the usage of the mixed-metal oxides as optically passive counter electrode materials for NIR-EC devices. The mixed-vanadium-tungsten oxide films are synthesized by a room-temperature solution-based photodeposition method that allows us to precisely engineer the metal compositions and thicknesses of the mixed-metal oxide films, thus optimizing their optical inertness and ion storage capability. A solid-state NIR-EC device assembled with the mixed-vanadium-tungsten oxide film as an ion storage layer and the amorphous tungsten oxide hydrate as the NIR-EC layer shows fast response speed with cycling stability up to 10,000 cycles, proving the outstanding charge balancing capability of mixed-metal oxide. Our work provides an efficient strategy for developing optically passive ion storage films with high ion storage capability for high-performance EC devices.