Parallel Connection Research Articles

Crowd Flow Prediction: An Integrated Approach Using Dynamic Spatial–Temporal Adaptive Modeling for Pattern Flow Relationships

ABSTRACTPredicting crowd flows in smart cities poses a significant challenge for the intelligent transportation system (ITS). Traffic management and behavioral analysis are crucial and have garnered considerable attention from researchers. However, accurately and timely predicting crowd flow is difficult due to various complex factors, including dependencies on recent crowd flow and neighboring regions. Existing studies often focus on spatial–temporal dependencies but neglect to model the relationship between crowd flow in distant areas. In our study, we observe that the daily flow of each region remains relatively consistent, and certain regions, despite being far apart, exhibit similar flow patterns, indicating a strong correlation between them. In this paper, we proposed a novel Multiscale Adaptive Graph‐Gated Network (MSAGGN) model. The main components of MSAGGN can be divided into three major parts: (1) To capture the parallel periodic learning architecture through a layer‐wise gated mechanism, a layer‐wise functional approach is employed to modify gated mechanism, establishing parallel skip periodic connections to effectively manage temporal and external factor information at each time interval; (2) a graph convolutional‐based adaptive mechanism that effectively captures crowd flow traffic data by considering dynamic spatial–temporal correlations; and (3) we proposed a novel intelligent channel encoder (ICE). The task of this block is to capture citywide spatial–temporal correlation along external factors to preserve correlation for distant regions with external elements. To integrate spatio‐temporal flexibility, we introduce the adaptive transformation module. We assessed our model's performance by comparing it with previous state‐of‐the‐art models and conducting experiments using two real‐world datasets for evaluation.

Measurement and Identification of Flame Describing Function (FDF) Based on Parallel Subsystem Model

Because of the need for low pollutant emissions, industrial gas turbines typically use partially premixed gases for combustion. However, the nonlinear dynamic characteristics of partially premixed flames have not been studied sufficiently. Therefore, this study focuses on the dynamics of a partially premixed flame generated by a swirler with fuel holes on its surface and designs a flame describing function (FDF) identification method based on the parallel subsystem model. This method can separate the flame dynamic characteristics into a parallel connection of the nonlinear and linear models. The nonlinear model is related to the disturbance frequency and velocity perturbation amplitude, whereas the linear model depends only on the disturbance frequency. This method is verified using a simulation. Finally, experimental research on partially premixed flames is conducted. Based on the experimental data, the identification method successfully separates the FDF into a nonlinear model with saturation characteristics and a linear model with Gaussian distribution characteristics. The flame model obtained by the identification method is the foundation for the analysis of combustion thermoacoustic stability and active/passive control strategy.

A Microgrid Stability Improvement Method by Applying Virtual Adaptive Resistor Paralleling with a Grid-Connected Inverter

An increase in renewable energy generation in the microgrid can cause voltage oscillation problems. To address this issue, an equivalent circuit of the microgrid was established, including a synchronous generator, grid-connected inverter, and constant power load. Then, the impact of different renewable energy generation ratios, different direct current (DC) voltage loops, and phase-locked loop control bandwidths of the grid-connected inverter on microgrid stability were analyzed. The results indicate that an increase in the renewable energy generation ratio leads to a decrease in the stability margin of the microgrid. A microgrid stability improvement method involving the parallel connection of a virtual resistor with the grid-connected inverter was proposed. The resistance value of the virtual resistor was obtained through an adaptive algorithm. This method ensures the stable operation of the microgrid under different renewable energy generation ratios.

Identification of heart rate dynamics during treadmill and cycle ergometer exercise: the role of model zeros and dead time.

The response of heart rate to changes in exercise intensity is comprised of several dynamic modes with differing magnitudes and temporal characteristics. Investigations of empirical identification of dynamic models of heart rate showed that second-order models gave substantially and significantly better model fidelity compared to the first order case. In the present work, we aimed to reanalyse data from previous studies to more closely consider the effect of including a zero and a pure delay in the model. This is a retrospective analysis of 22 treadmill (TM) and 54 cycle ergometer (CE) data sets from a total of 38 healthy participants. A linear, time-invariant plant model structure with up to two poles, a zero and a dead time is considered. Empirical estimation of the free parameters was performed using least-squares optimisation. The primary outcome measure is model fit, which is a normalised root-mean-square model error. A model comprising parallel connection of two first-order transfer functions, one with a dead time and one without, was found to give the highest fit (56.7 % for TM, 54.3 % for CE), whereby the non-delayed component appeared to merely capture initial transients in the data and the part with dead time likely represented the true dynamic response of heart rate to the excitation. In comparison, a simple first-order model without dead time gave substantially lower fit than the parallel model (50.2 % for TM, 47.9 % for CE). This preliminary analysis points to a linear first-order system with dead time as being an appropriate model for heart rate response to exercise using treadmill and cycle ergometer modalities. In order to avoid biased estimates, it is vitally important that, prior to parameter estimation and validation, careful attention is paid to data preprocessing in order to eliminate transients and trends.

Photocatalyst immobilisation on cylindrical surface: Scale-up potential of continuous photocatalytic reactor

The use of continuous photocatalytic reactor is important for sustainable water treatment technology. Photocatalyst immobilisation on supports (of varying shapes and sizes) having the desired degree of uniformity and smoothness is challenging, and is evolving. The major concerns are the geometry of the surface (which restricts the scalability of such systems) and the appropriate adhesion of the photocatalyst. Flat surface has an inherent limitation of low photocatalyst area per floor space, and poor light distribution, whereas cylindrical surfaces can overcome all these limitations. In this work, we have developed and assessed the photocatalyst coating methodology over cylindrical (quartz) surface and have prepared a modular (continuous) photocatalytic reactor. We have immobilised titanium-dioxide on the outer surface of a cylindrical quartz tube using a rotating (coating) mechanism, using the viscous sol prepared from the sol-gel method followed by heat treatment, and not with any binder to the as-synthesized powder. Various characterization techniques, including ultraviolet-diffuse reflectance spectroscopy, energy-dispersive spectroscopy, x-ray diffraction, field-emission scanning electron microscopy, optical surface profilometry, and ultraviolet–visible spectroscopy, are used to evaluate the impact of process conditions – number of layers, rotational speed, and sol viscosity, on the coating uniformity, smoothness, and layer thickness. The performance of the custom-made (modular-type) reactor is evaluated for degradation of the model molecule (pollutant). The reactor performance and capacity can be easily scaled up by parallel connections or introducing multiple coated tubes (to increase the photocatalyst area). The outcome of the work will be of immense value in scaling up the continuous large scale photocatalytic operation and treatment process.

Simulation Study on Factors Affecting the Output Voltage of Extended-Range Electric Vehicle Power Batteries

The power battery configuration of an extended-range electric vehicle directly affects the overall performance of the vehicle. Optimization of the output voltage of the power battery can improve the overall power and economy of the vehicle to ensure its safe operation. Factors affecting the output voltage of power batteries under different operating conditions, such as nominal voltage and the number of series and parallel connections of the battery cells, have been studied. This study uses AVL Cruise to establish an overall model of an extended-range electric vehicle to simulate the output voltage characteristics under the different operating conditions of the NEDC (New European Driving Cycle), WLTC (World Light Vehicle Test Cycle) and CLTC (China Light Duty Vehicle Test Cycle). The influence of the output voltage of the power battery under different operating conditions is studied to ensure that the power battery can output energy with high efficiency. The operating conditions have an impact on the output voltage with an idle voltage fluctuation of the operating conditions. The nominal voltage variation and the number of series and parallel connections of the battery cells affect the frequency and time of breakdown.

Tip effect of NiCo-LDH with low crystallinity for enhanced energy storage performance of yarn-shaped supercapacitors

Layered double hydroxides (LDHs) are considered promising materials for supercapacitor applications. However, the development of yarn-shaped supercapacitors (YSCs) with high electrochemical performance utilizing LDHs remains challenging. In this study, the NiCo-LDHs with various morphologies (nano-needles, nano-sheets, needle-sheet composites, and nano-flowers) were grown on carbon nanotubes (CNTs)-functionalized cotton yarn via a co-precipitation technique for YSC applications. Among these, the yarn incorporating nano-needle NiCo-LDHs exhibited reduced crystallinity yet demonstrated a superior areal capacitance compared to other morphologies, following a diffusion-controlled process. Finite element simulations were subsequently conducted to investigate this phenomenon, revealing that the lower-crystallinity nano-needle NiCo-LDHs accumulated a greater charge at their tips, thereby enhancing redox reactions and achieving higher energy storage capacitance. Subsequently, the yarns with nano-needle NiCo-LDHs were assembled into flexible quasi-solid-state symmetric YSCs, achieving a peak areal capacitance of 124.27 mF cm−2 and an exceptionally high energy density of 39.4 μWh cm−2 at a current density of 0.2 mA cm−2. Furthermore, our YSCs can be scaled up through serial or parallel connections and integrated into fabrics, making them suitable for wearable energy storage applications. This work provides an efficient method for fabricating high-performance YSCs and demonstrates significant potential for wearable energy storage devices.

Experiments on the performance of low temperature air source heat pump based on parallel connection of evaporators

An air source heat pump experimental bench with evaporators connected in parallel at low ambient temperatures is established to investigate the key parameters and operating performance after this retrofit. Experimental tests are conducted on the novel heat pump unit to study the optimal refrigerant charge, heat production capacity and COP at different ambient temperatures, to observe the frost condition in the operation of the unit, and to optimise the control logic. Results show that the optimum refrigerant charge amount after retrofit is 26 kg. Further experiments show that under the condition of −12 °C, heat production capacity of the retrofitted unit is increased by 5.39%, the COP is increased by 4.13%, and the evaporating temperature is increased by 1.50 °C; under the condition of 2 °C, the heat production capacity of the retrofitted unit is increased by 5.72%, the heating COP is increased by 2.51%, and the evaporating temperature is increased by 2.93 °C. At the same operating time, the modified unit has less frost on the evaporator surface. The optimum suction superheat after the modification is 1 °C, and it is at this point that the unit has the highest heating COP, which is 7% higher than at 0 °C suction superheat. The heat production and COP are less affected by the supplement gas superheat. Through the modification of the parallel evaporator, the overall heating performance and frost prevention ability of the unit are greatly improved.

Linear-acoustic effects of asymmetrical undercutting of toneholes of woodwind instruments.

The influence of the presence and magnitude of asymmetrical undercutting of the toneholes of woodwind instruments on the change in their effective radius and the corresponding shift of the eigenfrequencies of the air duct is considered. Within the framework of the electro-acoustic analogy, a tonehole with an asymmetrical undercutting along the axis of the main bore is presented as a cascade connection of two holes with different radii (undercutting and not undercutting parts of the hole), and with a sideway undercutting-in the form of a parallel connection. Formulas for numerical calculations are given that make it possible to determine the effective radius of such holes for the open state in the low-frequency approximation. Based on the obtained dependencies, using the transmission-matrix method, the eigenfrequencies of an air duct with one hole were calculated and compared with the results of computer modeling in the COMSOL Multiphysics 5.6 program. It is shown that increasing the degree and angle of undercutting leads to an increase in the effective radius, a displacement of the "center of gravity" of the sound hole along the main bore axis, and has effect on the shift of resonant frequency.

High-frequency Resonance Suppression of Railway Traction Power Supply System Based on the Combination of Single-tuned and C-type Filters

Background: Railroad transportation in the actual operation process, there are also many dangerous accidents caused by resonance, which greatly affect the safety of railroad transportation. A comprehensive examination of the operational dynamics within the power branch of a traction substation is imperative for sustaining system equilibrium. Discrepancies between these facets pose a potential threat to the safety of railway transport. Thus, a meticulous analysis of highfrequency resonance characteristics and the formulation of effective suppression techniques become paramount. Objective: Harmonics from grid-side locomotive traction braking are scrutinized under different operational scenarios and different train runs. The aim is to develop an effective harmonic management strategy to normalize the THD and thus maintain the traction power supply system to become more stable. Methods: This study investigates the high-frequency harmonic resonance characteristics using a control variable approach. Harmonics and negative sequences generated during locomotive traction braking under different operating conditions are investigated by means of extensive analysis. These challenges require the implementation of a harmonic management method. This method uses a combination of two monotonic filters and a C filter in parallel. This method applies to different operating conditions and can dynamically adapt harmonics to changes in the number of trains, which is related to the actual dynamics of the traction power system closely. Results: A comparative evaluation of seven operating conditions shows that the filter in this patent exceeds the efficiency of existing methods. The filter reduces the fluctuations during spectral changes, and the voltage distortion rate decreases from the previous 2.33% to 0.55%, making it more adaptable and promising effective harmonic management in high voltage and high current situations. Conclusion: Through multiple simulation tests, a synergistic configuration involving the C-type filter and two single-tuned parallel connections under regenerative braking conditions emerges. This refined, patented filter design not only mitigates the impact of negative sequence during the filtration process but also substantially diminishes high harmonics and THD.

Binary Biomass-Based Electrolyte Films for High-Performance All-Solid-State Supercapacitor.

Solid-state electrolytes have received widespread attention for solving the problem of the leakage of liquid electrolytes and effectively improving the overall performance of supercapacitors. However, the electrochemical performance and environmental friendliness of solid-state electrolytes still need to be further improved. Here, a binary biomass-based solid electrolyte film (LSE) was successfully synthesized through the incorporation of lignin nanoparticles (LNPs) with sodium alginate (SA). The impact of the mass ratio of SA to LNPs on the microstructure, porosity, electrolyte absorption capacity, ionic conductivity, and electrochemical properties of the LSE was thoroughly investigated. The results indicated that as the proportion of SA increased from 5% to 15% of LNPs, the pore structure of the LSE became increasingly uniform and abundant. Consequently, enhancements were observed in porosity, liquid absorption capacity, ionic conductivity, and overall electrochemical performance. Notably, at an SA amount of 15% of LNPs, the ionic conductivity of the resultant LSE-15 was recorded at 14.10 mS cm-1, with the porosity and liquid absorption capacity reaching 58.4% and 308%, respectively. LSE-15 was employed as a solid electrolyte, while LNP-based carbon aerogel (LCA) served as the two electrodes in the construction of a symmetric all-solid-state supercapacitor (SSC). The SSC device demonstrated exceptional electrochemical storage capacity, achieving a specific capacitance of 197 F g-1 at 0.5 A g-1, along with a maximum energy and power density of 27.33 W h kg-1 and 4998 W kg-1, respectively. Furthermore, the SSC device exhibited highly stable electrochemical performance under extreme conditions, including compression, bending, and both series and parallel connections. Therefore, the development and application of binary biomass-based solid electrolyte films in supercapacitors represent a promising strategy for harnessing high-value biomass resources in the field of energy storage.

영어권 한국어 학습자의 보조사 ‘도’ 사용 발달 연구A Study of English-Speaking Korean Learners’ Acquisition of the Particle to “also”

ABSTRACT English-speaking learners of Korean frequently have difficulty acquiring the Korean particle “to,” which is translatable as also. This study conducts two analyses: an error analysis of English-speaking learners’ use of “to” and a comparison of the use of “to” by advanced learners and native speakers. First, our error analysis of the learner corpus finds that beginners frequently make errors in positioning “to” and in combining “to” with other particles; intermediate learners also have difficulty with positioning “to” correctly, as well as with using “to” to make parallel connections. Advanced learners still struggle with parallel connections, but their overall error rate is significantly less. Second, the study’s contrastive interlanguage analysis investigates whether advanced learners can use diverse polysemous meanings of the particle “to” and whether they can use complex grammatical patterns, including “to,” as proficiently as native speakers. Compared to native speakers, advanced learners use two meanings less frequently: an “extreme presentation” meaning, where “to” can be translated as even; and an “emphasis” meaning, which lacks a single-word English translation. Our analysis also found that advanced learners use two grammatical patterns less frequently than native speakers: complex combinations of particles including “to,” and adding the meaning of “to” to a predicate.

An optical fiber high sensitivity temperature sensor with MZI and FPI parallel connection

Accurate detection of temperature is of great significance in the field of medical research. The focal point of this article centers around an optical fiber sensor that integrates Fabry Perot interferometer (FPI) filled with polydimethylsiloxane (PDMS) and Mach Zehnder interferometer (MZI), leveraging the principle of the vernier effect. By introducing the vernier effect principle, the sensitivity is 31.09 nm/°C in the detection range of 36 ∼ 40°C, and the maximum temperature measurement error is about 0.55 %. In addition, good linear response and longtime stability make it suitable for application in various scenarios where accurate temperature measurement is required.

Low Vibration Control Scheme for Permanent Magnet Motor Based on Resonance Controllers

For an electric locomotive traction motor, it is necessary to maintain relatively low vibration and noise due to the higher design standards. By using effective motor control strategies and implementing current harmonic suppression schemes, motor efficiency and vibration and noise suppression can be effectively improved. This study investigates the current harmonic suppression strategy for permanent magnet synchronous motors by (1) constructing a mathematical model of the permanent magnet motor to explore the sources of low-order harmonics currents such as fifth and seventh harmonics, as well as high-order harmonics at switch frequencies and their multiples, and analyzing the electromagnetic force characteristics generated by the current, and (2) establishing a vector control system for the permanent magnet motor. To suppress the fifth and seventh harmonic components in the current, a resonance controller is constructed, which utilizes the parallel connection of a resonator and PI controller to achieve low-order harmonic suppression. The factors affecting the effectiveness of the resonance controller’s suppression are also analyzed. The experiments are conducted, and the current harmonic suppression scheme constructed in this study can effectively reduce the harmonics in the current, thereby reducing motor vibration and noise.

Simulation and Experimental Research on a New Symmetrical Hydraulic Piezoelectric Energy Harvester

This study introduces a new symmetrical hydraulic piezoelectric energy harvester. By integrating theoretical analysis, simulation, and empirical testing, the research delves into the energy‐harvesting potential of monolithic single‐side output, monolithic two‐side parallel‐connected output, stacked one‐side parallel‐connected output, and stacked two‐side parallel‐connected output under varying parameter configurations. Additionally, it elucidates the energy dissipation occurring during the energy‐harvesting process of stacked piezoelectric disks. It has been observed that the primary determinant of voltage is the amplitude of pulsation, not the static pressure. Concurrently, the study also addresses the consistency of power generation between multiple channels. A study is made on whether there is a proportional relationship between single‐channel power generation and multi‐channel power generation. The root mean square (RMS) voltage of each connection sharply rises with resistance from 2 to 100 KΩ. It is found that the performance of parallel connection of monolithic piezoelectric disk is better than that of other connection methods. At 3 MPa and 100 Hz, the optimal resistance is 16 KΩ, yielding a maximum average power of 1155.63 μW and an optimal power density of 1.774 μW (bar mm3)−1. Consequently, the research offers a novel approach to addressing the issue of sustainable energy supply for low‐power electronic devices and sensors.

An Improved Instance Segmentation Method for Complex Elements of Farm UAV Aerial Survey Images.

Farm aerial survey layers can assist in unmanned farm operations, such as planning paths and early warnings. To address the inefficiencies and high costs associated with traditional layer construction, this study proposes a high-precision instance segmentation algorithm based on SparseInst. Considering the structural characteristics of farm elements, this study introduces a multi-scale attention module (MSA) that leverages the properties of atrous convolution to expand the sensory field. It enhances spatial and channel feature weights, effectively improving segmentation accuracy for large-scale and complex targets in the farm through three parallel dense connections. A bottom-up aggregation path is added to the feature pyramid fusion network, enhancing the model's ability to perceive complex targets such as mechanized trails in farms. Coordinate attention blocks (CAs) are incorporated into the neck to capture richer contextual semantic information, enhancing farm aerial imagery scene recognition accuracy. To assess the proposed method, we compare it against existing mainstream object segmentation models, including the Mask R-CNN, Cascade-Mask, SOLOv2, and Condinst algorithms. The experimental results show that the improved model proposed in this study can be adapted to segment various complex targets in farms. The accuracy of the improved SparseInst model greatly exceeds that of Mask R-CNN and Cascade-Mask and is 10.8 and 12.8 percentage points better than the average accuracy of SOLOv2 and Condinst, respectively, with the smallest number of model parameters. The results show that the model can be used for real-time segmentation of targets under complex farm conditions.

Utilizing Connection of Multiple Peltier Cells to Enhance the Coefficient of Performance

Peltier cells are commonly used in low-power cooling applications, such as automotive refrigerators and electronics temperature regulation systems. These applications are typically low-energy in nature. There is currently a growing emphasis on energy conservation and waste heat utilization in the energy industry. This paper explores the possibility of improving the heating or cooling coefficient of performance (COP) of Peltier cells through intelligent serial and parallel connections. The purpose of this work is to raise the question of whether it would be possible to reconsider the concept of harnessing the “energy” potential of Peltier cells. The utilized model is in line with the current state of the art, and the case study is based on parameters measured on a commercially available Peltier cell. The resulting COP, when considering current materials, remains inferior to the COP of compressor-based heat pumps. For low-power devices, it can represent a technically and economically comparable solution.

Flexible quantum data bus for quantum networks

We consider multipath generation of Bell states in quantum networks, where a preprepared multipartite entangled two-dimensional cluster state serves as a resource to perform different tasks on demand. We show how to achieve parallel connections between multiple, freely chosen groups of parties by performing appropriate local measurements along a diagonal, staircase-shaped path on a two-dimensional cluster state. Remarkably, our measurement scheme preserves the entanglement structure of the cluster state such that the remaining state is again a two-dimensional cluster state. We demonstrate strategies for generating crossing, turning, and merging of multiple measurement lines along the two-dimensional cluster state. The results apply to local area as well as to long-distance networks. Published by the American Physical Society 2024

Development of a Novel Retinal Surgery Robot Based on Spatial Variable Remote Center-of-Motion Mechanism

Abstract This article reports the design, modeling, and experiments of a novel retinal surgery robot based on spatial variable remote center-of-motion (RCM) mechanism. The general design criteria for parallel mechanisms are proposed, and the planar five-bar mechanisms are evaluated and selected. The planar-spatial evolution process, including the parallel connection of the planar mechanism and the equivalent substitution of joints, is adopted to develop a spatial variable RCM mechanism and then the robot. The mobility and singularity of the robot are analyzed, and the forward/inverse kinematics and workspace are modeled. Dimension optimization is conducted based on a comprehensive performance indicator that characterizes the motion range of linear actuators and the global dexterity performance index of robot. The prototyped robot is fabricated and assembled, and the kinematic calibration is performed. The position error of end-effector is within 34 μm, and both the position error and deviation of the RCM point are within 23 μm. The robot is demonstrated to reach the desired position and execute the RCM motion with high precision simultaneously.

Network topology planning method for interconnecting large-scale renewable generators considering dynamic stability limitations

It is well-known that the connection of renewable generators (RGs) can result in stability issues. However, existing network topology planning methods primarily focus on economic factors and static safety constraints, often neglecting dynamic stability considerations. The aim of this study is to avoid the risk of oscillations at the planning stage, rather than addressing them through damping control after their occurrence. First, an index is proposed for numerically evaluating the impact of different network topologies on the stability of connecting RGs, concluding that parallel connection is the most stable among various topologies. Then, in scenarios involving multiple collection regions of RGs, a method is proposed to select the connection locations of RGs. This indicates that the distribution of wind generators should consider the transmission line length of collection nodes, rather than connecting all wind generators to one of them. Finally, the network topology planning steps from a dynamic stability perspective are summarized. It is meaningful to improve the stability of a power system connected by large-scale RGs without the need for additional damping control. Two case studies are conducted to validate the accuracy of the analyzed results, but in the future, more applicable examinations will be conducted.