Switching Points Research Articles

A predictive algorithm for maximum power point tracking in solar photovoltaic systems through load management

In solar photovoltaic (PV) systems, maximum power point tracking (MPPT) is achieved when the impedance of the system load matches that of the PV array. The conventional approach to MPPT is to manage the output power of the PV array to adjust its impedance. This requires power electronics such as an inverter or charge controller, which induces cost and power loss. A PV system can also vary the system load by switching on and off parts of the load to match the impedances and find the maximum power point. It offers an inexpensive and efficient solution to MPPT as it does not require any conventional MPPT device. However, the demonstrated load-matching PV system is subject to power loss due to many unsuccessful switches. The algorithm in that system deployed a trial-and-error approach since the optimum switch points are typically unknown. This paper presents a predictive algorithm that can dynamically estimate the optimum switch points throughout the day using the powers measured from unsuccessful switches. It allows the system to track the maximum power point with minimum switches. The improved load-matching PV system has applications in PV-powered electrolytic hydrogen production.

Investigating the Inflation–Output Nexus for the Euro Area: Old Questions and New Results

The relationship between inflation and real GDP growth is one of the most widely researched topics in macroeconomics. At the same time, it is certainly not an exaggeration to claim that this nexus also stands at the heart of monetary policy, given the fact that low inflation in combination with high and sustained output growth should be the central objective of any sound economic policy. The latter notion becomes even more obvious when taking account of the fact that many central banks all over the world have selected target levels for inflation and communicated them to the public. Against this background, it is of utmost importance for central banks to understand more about the nature and formation of the relationship between inflation and real GDP. This study attempts to shed more light on the specific shape of this relationship for the euro area and, more specifically, on the issue of possible regime shifts therein. The analysis provides strong evidence for non-linear effects in the euro area. As a by-product, and seemingly the novel contribution, of this paper, the methods used allow for the quantification of a switching point across the different regimes. It is found that this breakpoint closely matches the ECB’s previous definitions of price stability and its new inflation target of 2%. While these results look encouraging, further research in this area seems to be warranted.

Multi-Constrained Geometric Guidance Law with a Data-Driven Method

A data-driven geometric guidance method is proposed for the multi-constrained guidance problem of variable-velocity unmanned aerial vehicles (UAVs). Firstly, a two-phase flight trajectory based on a log-aesthetic space curve (LASC) is designed. The impact angle is satisfied by a specified straight-line segment. The impact time is controlled by adjusting the phase switching point. Secondly, a deep neural network is trained offline to establish the mapping relationship between the initial conditions and desired trajectory parameters. Based on this mapping network, the desired flight trajectory can be generated rapidly and precisely. Finally, the pure pursuit and line-of-sight (PLOS) algorithm is employed to generate guidance commands. The numerical simulation results validate the effectiveness and superiority of the proposed method in terms of impact time and angle control under time-varying velocity.

Looking into the Market Behaviors through the Lens of Correlations and Eigenvalues: An Investigation on the Chinese and US Markets Using RMT.

This research systematically analyzes the behaviors of correlations among stock prices and the eigenvalues for correlation matrices by utilizing random matrix theory (RMT) for Chinese and US stock markets. Results suggest that most eigenvalues of both markets fall within the predicted distribution intervals by RMT, whereas some larger eigenvalues fall beyond the noises and carry market information. The largest eigenvalue represents the market and is a good indicator for averaged correlations. Further, the average largest eigenvalue shows similar movement with the index for both markets. The analysis demonstrates the fraction of eigenvalues falling beyond the predicted interval, pinpointing major market switching points. It has identified that the average of eigenvector components corresponds to the largest eigenvalue switch with the market itself. The investigation on the second largest eigenvalue and its eigenvector suggests that the Chinese market is dominated by four industries whereas the US market contains three leading industries. The study later investigates how it changes before and after a market crash, revealing that the two markets behave differently, and a major market structure change is observed in the Chinese market but not in the US market. The results shed new light on mining hidden information from stock market data.

Hybrid Heat Pump Performance Evaluation in Different Operation Modes for Single-Family House

Hybrid heat pump (HHP) represents a heating system (HS) that simultaneously utilises two or more energy sources. The key novelty is the integration of an optimised control strategy, effectively maximising the efficiency of both the heat pump and gas boiler segments. In this study, a HHP system that consists of an air-source heat pump (ASHP) and a condensing-type gas boiler (GB) for a two-story single-family house was calculated and validated. The results from three different calculation methods were obtained: the heat pump manufacturer’s calculator, the simulator programme, and the calculations based on real measured data. Two operation modes were tested: economic mode, where the cheapest energy resource becomes the priority, and ecological mode, where the system operates using the energy resource with lowest CO2 emissions. When comparing consumed energy, there was a 15.36% variance between the manufacturer’s program and the actual measured data, while for produced energy, the difference amounted to 25.81%. It was found that the balance point temperature is −7 °C, where the heat pump unit of the HHP system can cover necessary heat losses until that point, while the gas boiler operates at lower temperatures. Changes in electricity price can significantly influence the point of the system switch, but the possibility to cover heat loads of the heat pump unit always has to be taken into account.

Active Neutral Point Clamped Three-level Synchronous Space Vector Width Modulation Research

Active neutral point clamped (ANPC) topology is widely studied because it makes loss equalization possible. To reduce the switching frequency of high power traction systems, the multi-mode modulation strategy is used in many modulation methods. To reduce the fluctuation problem when switching between different carrier ratios in multi-mode synchronous space vector pulse width (SSVPWM) modulation algorithm, this paper studies the stator flux under different modes and proposes a multi-mode SSVPWM switching strategy based on the pulse insertion method. In this strategy, the stator flux deviation of two modes before and after the switching point is calculated online and the switch sequence is inserted at the switching time to compensate, and the smooth transition between different modes is realized with experimental verification of validity.

Extension of switch point algorithm to boundary-value problems

Extension of switch point algorithm to boundary-value problems

Evaluation of ship emission intensity and the inaccuracy of exhaust emission estimation model

Atmospheric pollution from maritime traffic is rising sharply and has brought great challenges to maritime management. The purpose of the study aims to establish a reliable approach to estimate the number of pollutants emitted by ships. The temporal, spatial and voluminal emission intensity of CO2, NOX, CO, NMVOC, PM2.5 and SO2 are investigated using the Ship Traffic Emission Assessment Model. Then, the inaccuracy of the Ship Traffic Emission Assessment Model is evaluated by calculating the emission fluctuations at switch points between different operation modes. The results revealed that ship speed could significantly affect the temporal, spatial and voluminal emission intensities of ships. Compared to temporal and voluminal emission, the intensity of spatial emission increases dramatically when the speed is close to 0. In addition, it was also shown that the Ship Traffic Emission Assessment Model induces an inaccuracy whenever the ship changes the operation mode. The research results provide guidance to plan the operation and management strategies to reduce pollutants from ships.

An improved sufficient condition of almost sure exponential stability for semi-Markov jump systems with asynchronous control

The purpose of this paper is to study almost sure exponential stability (ASES) of a class of semi-Markov jump systems with/without asynchronous controller. Based on the stationary distribution and ergodicity of semi-Markov switching process, sufficient stability conditions of semi-Markov jump systems are established firstly, which significantly improved some known results. Then, the sufficient conditions of ASES for semi-Markov jump systems with asynchronous controller is investigated. To be pointed out that the stochastic Lyapunov function constructed in this paper is new, which couples the switching points of semi-Markov process and a newly defined segment bounded function. Finally, two examples are given to show the superiority of our conclusions.

A Dynamic Model of Human Limb Selection

Two experiments and a dynamic model forhuman limb selection are reported. In Experiment 1, left-handed and right-handed participants (N = 36) repeatedly used one hand for grasping a small cube. After a clear switch in the cube’s location, perseverative limb selection was revealed in both handedness groups. In Experiment 2, the cubes were presented in a clockwise and counter-clockwise sequence to right-handed participants (N = 15). A spatial shift in the switch point between right-hand use and left-hand use was observed. The model simulates the experiments by implementing the nonlinear multiple-timescale dynamics of the action-selection process underlying limb selection. It integrates two mechanisms that were earlier proposed to underlie this selection aspect of manual activity: limb dominance and attentional information. Finally, the model is used to simulate an influential earlier experiment, by establishing a conceptual link between cross-lateral inhibition asymmetry and the direction and strength of handedness.

Combined vacuum-assisted geotextile and geomembrane tubes for sludge dewatering: a theoretical switching point

Treating the high water-content sludge with vacuum-assisted prefabricated horizontal drains (PHDs) placed inside, geotextile tubes have the advantage of multiple drainage paths, and geomembrane tubes have the superiority of high vacuum maintenance. Therefore, converting the geotextile tube into a geomembrane tube during slurry dewatering is an effective measure for greater dewatering efficiency and better dehydration effect. In this study, a profound plane-strain consolidation model considering two-dimensional seepage is developed for explaining the dewatering mechanism of sludge in the geo-tubes. Analytical solutions are given and validated by the experiment. The impact of major variables on tube efficiency is further discussed to reference the practice design. Parametric analyses reveal the critical time corresponding to the optimal efficiency of the geotextile tube, after which its consolidation efficiency decreases significantly. However, the consolidation efficiency of a geomembrane tube increases throughout the duration. Consequently, a switching point corresponding to the iso-efficiency state of the geotextile tube and geomembrane tube can be determined for the tube conversion.

F-Type Single Phase Five Level Inverter

In modern industrial and power electronics applications, high-voltage and high-current integrated modular power transistors (IGBTs) are increasingly being utilized. The F-type inverter, which is a modified version of the T-type inverter, has emerged as a promising option. This configuration separates the common point of the bidirectional power switch, reducing voltage stress and resulting in lower inverter costs and losses. The F-type inverter has a simplified design and lower conduction losses, making it a viable choice for medium-voltage applications compared to the clamp diode NPC inverter configuration. Detailed analysis of losses and efficiency has been conducted, and a simulation and experimental prototype have been built to validate the theoretical basis. In addition, the voltage rating of the power switches in the T-type three-level inverter is a limiting factor, as it is only 50% of the input DC voltage for each inverter phase leg.

Clinical Outcomes and Patient Experience of Biosimilar to Biosimilar Infliximab Switching in Patients with Inflammatory Bowel Disease: A Prospective, Single-Centre, Phase IV Interventional Study with a Nested Qualitative Study

Background and Aims. Regulatory pathways compare biosimilars with originator molecules only and not with other biosimilars. With the development of multiple infliximab biosimilars, patients may be asked to transition between them. Data is emerging but there is still a gap in the evidence on switching between infliximab biosimilars. Our aim was to conduct a full evaluation of switching a cohort of IBD patients from one biosimilar (CT-P13) to another (SB2) in a real-world setting including clinical and patient experience and molecular and drug immunogenicity aspects of the process. Methods. Prospective, phase IV interventional study of patients on CT-P13 switched to SB2. Demographics, disease history, validated disease activity scores, PROMs, and laboratory measurements were collected. Semistructured qualitative interviews were also conducted. Results. 133 out of 158 patients agreed to participate. Mean disease duration was 9.2 years. There was no difference in mean haemoglobin, platelet count, albumin, and C-reactive protein before and after switching. Mean faecal calprotectin at baseline and at week 30/32 was 306 μg/g versus 210 μg/g. Mean pMCS and mHBI at baseline were 1.54 and 3.14 versus 1.18 and 2.91 at week 30/32, respectively. Thirty-five subjects discontinued. There were 16 serious adverse events. Thematic analysis identified six major themes that reflected the patient experience—trust, clinical status at the point of switching, past experience, general disposition, information provision, and concerns/anxiety. Conclusions. Switching from CT-P13 to SB2 is safe and effective. Certain factors must be considered in supporting patient decision-making. These results support the development of clear, streamlined, and well-monitored biosimilar switching programmes.

Throttling Loss Energy-Regeneration System Based on Pressure Difference Pump Control for Electric Forklifts

At present, the hydraulic systems of electric forklifts and traditional internal combustion forklifts are mostly valve-controlled speed-regulation systems, which have large throttling losses and potential energy waste. To further improve the energy-saving ability of electric forklifts, the forklift’s common working conditions are analyzed in this paper. A throttling loss energy-regeneration system based on pressure difference pump control is designed, and the system’s working principle is described. Aiming to deal with the problem that the pump−valve compound speed regulation with constant pressure difference could not realize high controllability and energy saving at the same time, a control strategy for variable pressure difference pump−valve compound speed regulation based on pressure balance control is proposed. The handle signal is positively related to the target speed of the oil cylinder. In the low-speed stage, the closed-loop control of the actual output torque of the motor/generator keeps the pressure difference across the proportional throttle valve unchanged, and the speed adjustment is realized by changing the opening of the proportional throttle valve. In the high-speed stage, the valve opening area is kept unchanged and the target pressure difference is changed to achieve the target speed. Finally, the feasibility of the control strategy is verified through an AMESim simulation, and the minimum pressure difference switching point is determined through experiments. The experiments show that the system’s energy-saving efficiency can reach 21.5% under a 1 t load. With the increase in the load, the system’s energy-saving efficiency can be further improved.

Geothermal-solar energy system integrated with hydrogen production and utilization modules for power supply-demand balancing

The power generation of geothermal energy is severely restricted by its low grade and limited flexibility. We propose integrating geothermal and solar energy and introducing hydrogen energy modules to achieve a flexible and highly efficient renewable power supply for communities. The comprehensive thermodynamic models of the proposed combined system are established, and the daily performance of the system is simulated and analyzed based on a power supply-demand matching strategy. From the results, the switching points of hydrogen generation/consumption mode occur at 6 h and 18 h. During the day time, the system's overall energy efficiency varies between 13.28% and 14.36%, representing a significant improvement compared to the previous geothermal-solar combined system only with 5.67% energy efficiency. Then, the effects of geothermal water temperature and solar radiation intensity on the system's daily performance are analyzed, showing the daily net hydrogen production amount increases from −28.71 kg to 306.24 kg with the improved geothermal grade. Finally, the fluctuant electricity profiles of two typical communities are taken into the simulation for case analysis. The good demand-supply matching results for both cases showcase the dynamic capture ability of the models and validate the applicability of the proposed system.

Lexical tonal effects in code-switching: A comparative study of Cantonese, Mandarin, and Vietnamese switching with English

Aims and objectives: Previous research has revealed much about the syntactic and social variables conditioning code-switching (i.e., the alternation between two or more languages in a discourse or utterance); however, little is known about the phonological effects. Our work explores this area by asking two main questions: (1) Does lexical tone affect code-switching between a tonal language and a non-tonal language? and (2) Is this effect (or lack thereof) observable cross-linguistically? Methodology: We examine natural code-switching production between Cantonese and English, Mandarin and English, and Vietnamese and English. We use a semi-automatic natural-language processing method to process and extract relevant variables, including tonal categories at switch points. Data and analysis: Data include transcribed natural speech from three bilingual corpora: the HLVC corpus (Cantonese/English, 25 speakers), the SEAME corpus (Mandarin/English, 20 speakers), and the CanVEC corpus (Vietnamese/English, 45 speakers). We use logistic mixed-effects models to examine tonal effects, taking into account other factors such as frequency and grammatical category. Findings/conclusion: We found a robust tonal effect in Cantonese/English, a less robust effect in Mandarin/English, and no effect in Vietnamese/English. This indicates there is a tonal effect in code-switching between a tonal and a non-tonal language, but this effect is language-dependent. We also found a specific T3 ‘step-up’ pattern at Cantonese-English switch points and offered some possible phonological explanations. Originality: This is the first study that systematically investigates tonal effects in code-switching across different language pairs, using comparable data and methods. Our finding of a Cantonese-English T3 ‘step-up’ pattern is also a novel discovery that hitherto has not been documented. Significance/implications: Theoretically, our findings support Clyne’s ‘facilitation theory’ in code-switching at a prosodic level. Empirically, we nevertheless emphasised the complexity of different prosodic features and social variables in play, thereby rejecting the idea of ‘predicting’ code-switching solely based on linguistic factors.

Testing the somatic marker hypothesis in decisions-from-experience with non-stationary outcome probabilities.

The Somatic Marker Hypothesis (SMH) posits that in experience-based choice, people develop physiological reactions that mark options as either positive or negative. These somatic markers aid decision making because they differentiate between "good" and "bad" options during pre-choice deliberation. We examined this proposed role for somatic states in two decision-from-experience tasks (each N = 36) in which participants selected repeatedly with full feedback (i.e., for obtained and forgone outcomes) between two unlabeled options that returned wins or losses, with half receiving an additional summary of past outcomes. The probabilities of good and bad outcomes changed at an unannounced point. Participants completed a 100-trial game with a switch in the optimal option after trial 40 (Study 1) or a 200-trial game with switch points after trial 40 and trial 120 (Study 2). Skin conductance (SC) was measured continuously as an index of emotional intensity, from which we extracted measures of anticipatory SC (pre-choice) and outcome SC (post-choice). Participants reliably selected the optimal option prior to any switches. They also altered their choices appropriately when the payoffs changed, though optimal play following payoff switches was reduced. Losses resulted in a greater outcome SC than wins, but only in Study 1, as did the finding that the outcome SC was greater when the forgone outcome was positive. Anticipatory SC did not reliably predict optimal play in either study. These results provide little support for the SMH. Our studies point to the importance of using diverse tasks and measures and very large sample sizes when testing the role of somatic states in decision making.

A novel mesh discretization strategy for numerical solution of optimal control problems in aerospace engineering

An effective approach is proposed for optimal control problems in aerospace engineering. First, several interval lengths are treated as optimization variables directly to localize the switching points accurately. Second, the variable intervals are usually refined into more subintervals homogeneously to obtain the trajectories with high accuracy. To reduce the number of optimization variables and improve the efficiency, the control and the state vectors are parameterized using different meshes in this paper such that the control can be approximated asynchronously by fewer parameters where the trajectories change slowly. Then, the variables are departed as independent variables and dependent variables, the gradient formulae, based on the partial derivatives of dependent parameters with respect to independent parameters, are computed to solve nonlinear programming problems. Finally, the proposed approach is applied to the classic moon lander and hang glider problems. For the moon lander problem, the proposed approach is compared with CVP, Fast-CVP and GPM methods, respectively. For the hang glider problem, the proposed approach is compared with trapezoidal discretization and stopping criteria methods, respectively. The numerical results validate the effectiveness of the proposed approach.

Tolerance of repeated toxic injuries of murine livers is associated with steatosis and inflammation

The human liver has a remarkable capacity to regenerate and thus compensate over decades for fibrosis caused by toxic chemicals, drugs, alcohol, or malnutrition. To date, no protective mechanisms have been identified that help the liver tolerate these repeated injuries. In this study, we revealed dysregulation of lipid metabolism and mild inflammation as protective mechanisms by studying longitudinal multi-omic measurements of liver fibrosis induced by repeated CCl4 injections in mice (n = 45). Based on comprehensive proteomics, transcriptomics, blood- and tissue-level profiling, we uncovered three phases of early disease development—initiation, progression, and tolerance. Using novel multi-omic network analysis, we identified multi-level mechanisms that are significantly dysregulated in the injury-tolerant response. Public data analysis shows that these profiles are altered in human liver diseases, including fibrosis and early cirrhosis stages. Our findings mark the beginning of the tolerance phase as the critical switching point in liver response to repetitive toxic doses. After fostering extracellular matrix accumulation as an acute response, we observe a deposition of tiny lipid droplets in hepatocytes only in the Tolerant phase. Our comprehensive study shows that lipid metabolism and mild inflammation may serve as biomarkers and are putative functional requirements to resist further disease progression.

Quadratically Constrained Linear Programming-based energy-efficient driving for High-speed Trains with neutral zone and time window

Among the numerous challenges that are faced during the daily operation of high-speed rail, the management of the neutral zones in the catenary during unexpected disturbances remains underinvestigated. This study proposes a computerised method for managing the operations of a high-speed train with regenerative braking for passing neutral zones under disturbance to minimise energy consumption. For the first time, different mechanism-based Automatic Passing Neutral Zone systems, including the Magnetic Induction System and Automatic Train Protection, are analysed and modelled as location-based and time-based constraints, respectively. Motion constraints caused by disturbances are described by time windows. Forced coasting and air brake-allowed passing neutral zone rules are considered in these models. The original nonlinear model with location-based constraints is transcribed as a quadratically constrained linear model and then solved. The optimality consistency and its establishment condition between the original and transcribed models are analysed based on the Karush–Kuhn–Tucker conditions. A high-quality solution is obtained when the establishment condition holds. The model with time-based constraints is novelly transformed into an optimal switching point problem. A series of sub-problems are iteratively and efficiently solved. Comprehensive experiments are conducted based on practical data from a high-speed rail system in China. The proposed method is significantly beneficial when compared to Mixed-integer Linear Programming and Artificial Driving Algorithms. Moreover, the impacts of different mechanism-based automatic passing neutral zone systems, operation rules, and a combination of time window settings are extensively analysed.