Full Operation Research Articles

Exploring incomplete decoupling modeling with window and cross-window mechanism for skeleton-based action recognition

Skeleton-based action recognition relies on capturing connections between joints to extract action-specific features. Current approaches utilizing temporal convolution for inter-frame joint relationships only capture connections within the same joint across different frames. It neglects potential connections between joints in different frames. However, modeling all joints across frames will encode a plethora of redundant features that impede the recognition of action. In this study, a novel and effective skeleton window attention mechanism (SWAM) is proposed that consists of window attention module (WAM) and spatial–temporal attention regularization (STAR). WAM directly capture short-range features within isolated windows. It consolidates all joints from adjacent frames into the window and performs full attention operations on them. STAR enhances the model’s focus on structural action features, counteracting the vanilla attention mechanism’s oversight. Furthermore, this study introduces the cross-window mechanism (CWM) that consists of three components: cross-window fusion (CWF), cross-window shift (CWS), and cross-window aggregation (CWA). These components collectively break the limitations imposed by window boundaries, enabling efficient interactions between windows and facilitating the capture of long-range dependencies. Integrating SWAM and CWM, we introduce the skeleton window attention network (SWA-Net), which embodies a novel approach of incomplete decoupling modeling. It can extract action features from different joints in different frames without capturing excessive redundant features. Compared with the state-of-the-art methods, it achieves better results on NTU-RGB+D, NTU-RGB+D 120 and Kinetics-Skeleton 400 datasets.

An improved design for a zero-tillage experimental plot drill

Adoption of conservation farming practices such as zero tillage when planting field research plots is essential to the replication of on-farm practices. The problem is that most drill options fail to meet expectations as they are not built to the scale required, compromise the need for uniformity of plant emergence within plot areas, lack portability, or have been designed and equipped in a manner that is not relevant to farm-scale seeder technologies and practices. Agronomists and Technicians at Agriculture and Agri-Food Canada engaged with engineering expertise to design and build two prototype drills that are now in full operation.

System Design, Optimization and 2nd Law Analysis of a 100 MWe Double Reheat s-CO2 Power Plant at Full Load and Part Loads

Super-critical Carbon dioxide (s-CO2) power plants are considered to be efficient and environmentally friendly compared to the traditional Rankine cycle-based steam power plants and Brayton cycle-based gas turbine power plants. In this work, the system design of a coal-fired 100 MWe double reheat s-CO2 power plant is presented. The system is also optimized for efficiency with turbine inlet pressures and the recompression ratio as the variables. The components needed, mass flow rates of various streams and their pressures at various locations in the system have been established. The plant has been studied based on 1st and 2nd laws at full load and at part loads of 80%, 60% and 40%. Operating parameters such as mass flow rate, pressure and temperature have considerably changed in comparison to full load operation. It was also observed that the 1st law efficiency is 53.96%, 53.93%, 52.63% and 50% while the 2nd law efficiency is 51.88%, 51.86%, 50.61% and 48.1% at 100%, 80%, 60% and 40% loads, respectively. The power plant demonstrated good performance even at part loads, especially at 80% load, while the performance deteriorated at lower loads. At full load, the highest amount of exergy destruction is found in the main heater (36.6%) and re-heaters (23.2% and 19.6%) followed by the high-temperature recuperator (5.7%) and cooler (4.1%). Similar trends were observed for the part load operation. It has been found that the recompression ratio should be kept high (>0.5) at lower loads in order to match the performance at higher loads. Combustion and heat exchange due to finite temperature differences are the main causes of exergy destruction, followed by pressure drop.

Hydrogen Transport and Evolution in Ni-MH Batteries by Neutron Imaging.

Efficiency losses due to side reactions are one of the main challenges in battery development. Despite providing valuable insights, the results of standard analysis on the individual components cannot be simply extrapolated to the full operating system. Therefore, non-destructive, and high resolution approaches that allow the investigation of the full system are desired. Herein, we combined neutron radiography and tomography with electrical monitoring of the state of charge of commercial Ni-mischmetal hydride batteries, to track the exchange and transport of hydrogen under operating conditions. This non-destructive approach allowed both the quantification of the hydrogen distribution in the electrodes in 4D, and the distinction between the electrochemically exchanged hydrogen and the hydrogen gas pressure generated by side reactions, as a function of the applied potential and current. One of the most counter-intuitive observation is that the generation of hydrogen gas during discharge depends on the charging state of the battery. The results presented provide critical new insights in the mechanisms governing the electrochemical processes during Nimischmetal hydride battery operation, and also pave the way for the extrapolation of this approach to the investigation of state-of-the-art Li-ions batteries.

Rating and sizing analysis of the solar chimney power plant considering uncertainty in solar radiation and under different load conditions

ABSTRACT The main focus of this research is on modeling and analyzing an industrial-scale solar chimney power plant (SCPP) under actual or realistic conditions. While most of earlier studies considered the steady state kind of solar radiation, this study is based on the assumption of the diffuse and erratic nature of solar energy in calculating the sizing rating of SCPP. Moreover, the use of uncertainties in solar radiations is time-consuming and difficult, and hence a theoretical approach is used to get the required results. Statistics and probability theory concerning solar radiation and weather data of Mumbai, India region are used for said analysis. The best generator rating and daily energy output are determined by taking into consideration variables like chimney height, collector radius, and storage thickness below the absorber plate of SCPP. Based on the aforementioned characteristics, one may construct SCPP sizing curves to yield 136, 435, and 945 kWh energy generation in 24 h period. It is essential to consider the full load and part load operations of the generator in order to prevent the unused kinetic energy linked to low velocity and increased velocity. While the majority of the past research by various researchers was carried out under full-load conditions, this study also addresses half-load situations. The current effort will help manufacturers and the scientific community develop sizing and rating taking into account different sun radiation statistics.

Primjena višekriterijske analize u odabiru čokacije LNG terminala

Positioning of large energy facilities is, as a rule, accompanied by a strong rejection of local and regional communities, without which it is not possible to determine the location and construction conditions for the facility in spatial plans. However, a synergy of three components may enable a successful project realization. Firstly, the application of verified and objective scientific methods for the selection of the most appropriate LNG terminal location. Secondly, the consideration of the best world practices in project documentation preparation for such terminal construction. And lastly, the continuous involvement of the local community into the entire process. The paper presents an approach aimed at solving the problem of choice by applying the methodology of choosing the “best compromise location” based on system characteristics, available data, set criteria, and limitations. The key “dimension” of such a problem is “space”, i.e. the spatial aspects of location selection. The paper provides an overview of the activities, procedures, and methods used to define the optimal location of the receiving LNG terminal in the Republic of Croatia as part of the analysis and research carried out by EKONERG and in the function of creating the Spatial Plan of Primorje-Gorski Kotar County. Accordingly, the main objective of this paper was to highlight the specifics of LNG terminal site selection as well as the possibility of objectively defining the optimal location using the multi-criteria decision-making method that simultaneously takes into account all influential factors and criteria in defining it. The paper uses the methodology of multi-attribute decision process and multicriteria analysis of the selection of the optimal location of the LNG terminal on the territory of Primorje-Gorski Kotar County. It systematically and scientifically analyses, consistently formulates, and proposes elimination and comparative criteria necessary to determine the optimal location of the LNG terminal for the purpose of drafting regional level spatial planning documents. The presented methodology was carried out using the process of multicriteria ranking of variants. The method of weighted sum values was used. Weighting factors are determined partly in an exact way (where possible) and partly based on the application of Delphi group decision-making methods. The methodology was tested on a concrete example of variant analysis for the location of LNG terminals in the Republic of Croatia. By implementing the presented methodology, the location of the northern part of the island of Krk was determined as optimal for the location of the LNG terminal. The aforementioned was implemented in the Spatial Plan of Primorje-Gorski Kotar County, and the first phase of the receiving LNG terminal was built and put into full operation.

Research on and Assessment of the Reliability of Railway Transport Systems with Induction Motors

Increasing the efficiency and reliability of modern railway transport is accompanied by an increase in monitoring and diagnostic systems for the current state of electric drives. Modern railway transport contains a large number of induction motors to ensure the operation of the drives of various mechanisms. In the article, based on the operational statistics of engine failures and the proposed scheme for diagnosing them, studies were carried out and a model was developed for assessing the reliability of a transport system equipped with an on-board diagnostic system for the current state. When building the models, the Markov method was used, including the construction of graphs for the five most relevant states of the induction electric motor during operation. The results obtained are relevant for evaluating the effectiveness of using the built-in diagnostic system and scheduling routine maintenance, which will affect the efficiency of railway transport. Based on the process of the diagnosis of railway transport systems with induction motors, five operating states of the object studied were interpreted: the state of full operation, state “S0”; the state of incomplete serviceability, state “S1”; critical serviceability, state “S2”; the state of the pre-damage condition, state “S3”; the state of unserviceability (defect), state “S4”. Subsequently, a five-state model of the operation process of railway transport systems with induction motors was developed. This model is also described by equations of state: Kolmogorov–Chapman equations. The reliability quantities determined form the basis for simulation reliability studies. The effect of the simulation study is the reliability quantities determined in the form of reliability functions and probabilities of the occurrences of the operating states of railway transport systems with induction motors; an important part of the reliability study of the system examined is to estimate the times of the occurrences in the object studied of the operating states in the future.

Fuel Consumption Investigation for Quran Disposal Incinerator System

In this study, the fuel consumption characteristic of a Quran incineration system was conducted. The experiment examines the relation between fuel usage and Quran loads as well as how the usage of blower affects the fuel utilization. The result proved that the blower unit shortens the combustion time and uses less fuel. Nevertheless, the electrical source to power the blower will increase the operating costs, especially during full loading operation. Therefore, this study will provide insight in determining the balance between the combustion duration over the operational costing of such a system.

A three-phase reactor assessment for the deployment of Liquid Organic Hydrogen Carriers (LOHCs): dybenzyltoluene and indoles mixture systems as case studies

As a result of the large increase in the production of renewable energies, energy storage and energy carrier systems are required to meet the most ambitious objectives. In this area, hydrogen stands out as one of the most powerful tools. However, its low volumetric energy density and its challenging storage conditions lead to the search for new forms of storage. Liquid organic hydrogen carriers (LOHCs) are positioned as a promising option to store hydrogen using a catalytic reversible reaction at moderate temperature. Notwithstanding, although reactor technology is the core section of the LOHC process, it has not been assessed yet. Therefore, in this work, a three-phase reactor analysis is performed including mass, heat, and momentum phenomena along with kinetics. In particular, the two most important reactors for three-phase reactions are evaluated, trickle bed and slurry. And two of the most attractive LOHCs systems, dybenzyltoluene and a mixture composed of 1,2-dimethylindole and 7-ethylindole, are considered. The influence of the operating and design variables was studied. The results show that, for hydrogenation slurry reactors, a first region may be formed where gas–liquid is the main resistance (60%–95%). It eventually ends up with a second one where kinetics becomes the controlling step. At this point, a better catalyst use is expected for the first region. Alternatively, trickle bed hydrogenation reactors are largely controlled by mass transfer over almost the whole reactor length. If the dehydrogenation process is assessed, kinetics resistance is predominant. Surrogate models are developed to optimize the reactor performance and to include the full reactor operation in futures process design analysis allowing for an effective deployment of LOHCs systems.

A NEW SEAWATER LOW-HEAD TURBINE FOR THE OBREC

The OBREC (Overtopping Breakwater for wave Energy Conversion) is based on the overtopping phenomenon [1] where incoming waves run over an overtopping ramp and fall into a reservoir located above the sea level inside a conventional rubble mound breakwater, or into a vertical caisson breakwater. The wave energy is transformed into potential energy, with some contribution of kinetic energy. Then, the flow is driven through a turbine addressing the final transformation into electrical energy. The OBREC prototype is located in the middle of the San Vincenzo breakwater, in Naples harbour (Italy). The key target of the whole pilot project was to demonstrate the high capacity factor of the system (expressed as the ratio of the electrical energy produced to the electrical energy that could have been produced at continuous full power operation), even in a low-energy wave climate. At the study site, in fact, the yearly average wave power was found to be 1.8 kW/m over the last 42 years [2]. However, during last 5 years, a maximum wave height of over 5 m has been registered, confirming the high reliability under severe wave conditions.
 Due to the short monitoring period and to the undersize of the previous power take-off (PTO) systems, no definitive power matrix is available for OBREC [3]. The energy conversion efficiency of OBREC has been deeply investigated over the last years through both physical and numerical model tests. Within the ongoing full-scale monitoring activities in real environments, a new set of power take-off was installed. A propeller-type pico-turbine equipment was in 2021, and its final setting was completed in 2022. Performance and reliability of the entire structure were closely monitored under different “stress tests”, i.e. start & stop cycle in marine environment with a high variable combination of flow rate/hydraulic head.
 This paper presents the design stage for the new equipment and preliminary results from these tests numerical and field tests.
 
 
 Contestabile, P., Crispino, G., Di Lauro, E., Ferrante, V., Gisonni, C., & Vicinanza, D. (2020). Overtopping breakwater for wave Energy Conversion: Review of state of art, recent advancements and what lies ahead. Renewable Energy, 147, 705-718.
 Contestabile, P., Russo, S., Azzellino, A., Cascetta, F., Vicinanza, D. (2022). "Combination of local sea winds/land breezes and nearshore wave energy resource: Case study at MaRELab (Naples, Italy)", Energy Conversion and Management, ISSN 0196-8904, 257, 115356, https://doi.org/10.1016/j.enconman.2022.115356 
 Mariani, A., Crispino, G., Contestabile, P., Cascetta, F., Gisonni, C., Vicinanza, D., & Unich, A. (2021). Optimization of Low Head Axial-Flow Turbines for an Overtopping BReakwater for Energy Conversion: A Case Study. Energies, 14(15), 4618.

Design of permanent magnet synchronous motor control system for electric vehicle air conditioning compressor

The permanent magnet synchronous motor (PMSM) is extensively utilized in electric vehicle air conditioning compressor control systems due to its numerous advantages, including high efficiency, lightweight design, compact size, excellent reliability, and low maintenance costs. In order to achieve PMSM without position sensor full speed range operation, this paper designs an optimized control strategy for full speed range operation. At low and zero speed, the I/F control mode is employed to achieve quick motor startup with minimized repetition rate, avoiding the overcurrent problem that is easy to occur by traditional V/F control, and the control is switched to the Phase-locked Loop (PLL) adaptive sliding mode observer (SMO) for position estimation at medium and high speed, avoiding the problems of high-frequency jitter and low position accuracy of traditional SMO. The feasibility of this strategy is confirmed by the simulation results of Simulink.

Emulation of Integrated Starter/Generator Using Power Electronic Devices

Integrated starter/generator (ISG) is an important facility in transportation power systems. Using power electronics based motor emulator (ME) to test the motor controller is an emerging technique to optimize the design process of the motor drive system. In this paper, an ME is designed to test the control system of ISG in the full operation process. Facing the challenge of dual-mode emulation, a voltage-in-voltage-out interface is proposed to handle the causality problem caused by operation mode change during the starting/generating process. The LCL interface with predictive voltage closed-loop control is proposed to ensure emulation accuracy. A prototype of ME has been developed. The experiment has been done to validate the performance of the emulator, showing that the proposed method can be used to test the ISG controller in full operational mode with accuracy and fast dynamics.

Seismic Protection of Structures Using Vibration Controlling Devices: A Review

Abstract: Past earthquake record depicts there is a significant increase in human loss, structural as well as economic losses. The current seismic design philosophy for building and infrastructures should be changed from lifesaving to business continuity for modern and resilient societies. Structure should be designed to be quickly restored to full operation with minimal disruption and low cost following a large earthquake. Analysis of this earthquakes show that a large number of existing structure need to be upgrade for their seismic action with new seismic design. This paper attempts the review of different aspects related to seismic design with various vibration controlling devices. Designing philosophy and case studies are discussed in this literature. Summarizing, it gives the total idea of the different literature review and recent research works summary.

Effects of diesel-biodiesel fuel blends doped with zinc oxide nanoparticles on performance and combustion attributes of a diesel engine

To improve the fuel properties and enhance the overall characteristics of a diesel engine, the current work assesses the performance and combustion attributes of a diesel engine fueled by different blends of diesel, second generation biodiesel, and zinc oxide (ZnO) nanoparticles. The biodiesel was prepared using the transesterification of waste cooking vegetable oil. Zinc oxide nanoparticles were dispersed in diesel and biodiesel fuel blends at one dosage level of 50 ppm using ultrasonication process to prevent their agglomeration in the base liquid. The experiments were performed at different engine speeds (1700, 2000, 2300, 2600, 2900) RPM and full load operating conditions. The experimental results revealed that the addition of ZnO compensated for the poor combustion characteristic of biodiesel and hence promoted diesel engine performance and combustion attributes. The engine torque improved by 6.74, 4.9 and 3.69% while the BSFC reduced by 5.6, 6.44 and 2.5% for B0ZnO, B20ZnO and B40ZnO fuel blends compared to B0, B20 and B40 respectively at 2300 RPM. In addition, the engine heat release rate, ignition delay period and in-cylinder pressure were promoted. ZnO nanoparticles additives could be an effective approach for improving the combustion and performance characteristics in diesel engine applications.

Life Testing and Redox Cycling of Ni- and Ru-Doped Strontium Iron Titanate Exsolution Fuel Electrodes in Electrolyte-Supported Solid Oxide Cells

Recently perovskite materials have gained much attention as potential candidates for solid oxide cell (SOC) fuel electrodes due to their advantages of redox stability, coking resistance and sulfur resistance over their cermet counterparts. Enhanced electrochemical performance has also been observed for some of these perovskite materials resulting from exsolution, where nano-sized metal particles are formed on the material surface under reducing conditions. However, the degradation mechanism of these perovskite fuel electrodes has yet to be fully understood and the relationship between their long-term stability and operating envrionments (fuel-cell/electrolysis, fuel compositions, redox cycles, operating pressure, etc.) has not been fully investigated.Here, life tests were conducted in open-circuit and reversible operation at 850oC on electrolyte-supported symmetric and full cells with Ni and Ru-doped strontium iron titanate (Sr0.95Ti0.3Fe0.63Ni0.07O3 and Sr0.95Ti0.03Fe0.63Ru0.07O3) as fuel electrodes (SrTi0.3Fe0.6Co0.1O3 used as the air electrode in the full cells). For both materials, higher degradation rate was observed when operated with 97% H2 + 3% H2O compared with 50% H2 + 50% H2O as fuel; an increase in ohmic resistance and gas adsorption/desorption resistance contributed to most of the degradation observed. STFN also showed higher degradation rates than STFRu in both fuel compositions. Exsolution from both compositions was confirmed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with both fuel compositions and in situ X-ray Diffraction (XRD) showed the simultaneous perovskite to Ruddlesden-Popper (RP) phase transformation. The faster perovskite-RP phase transformation is believed to be responsible for the higher degradation rates observed for cells using fuel electrode materials with less stable perovskite structure (STFN over STFRu) and tested in more reducing fuel compositions (97% H2 over 50% H2). Moreover, redox cycles were introduced for STFN and STFRu during life tests and partial performance recovery was observed; in situ XRD and SEM microstructural analysis suggests that the recovery resulted from a transformation from RP back to perovskite for both materials. Finally full cell reversible operation durability tests (6 hrs each in fuel cell and electrolysis modes at 0.8 A/cm2) conducted at 850oC with 50% H2 + 50% H2O as fuel at 1 atm showed reasonably good stability over 1000 h. Initial reversible life testing at 3 atm operating pressure showed higher degradation rates, and the possible reasons for this will be discussed.

Transient Solid Oxide Cell Reactor Model Used in rSOC Mode-Switching Analysis and Power Split Control of an SOFC-Battery Hybrid

Defossilization of the global energy system requires a transition towards intermittent renewable energy sources and approaches that enable efficient conversion of primary energy sources into electrical energy. Due to their high efficiency in converting chemical into electrical energy and vice versa, solid oxide cell (SOC) systems provide solutions for both of these aspects. Within this contribution, two researched cases utilizing SOC's are presented, based on simulation studies and experiments.Characteristically, SOC reactors produce hydrogen from steam in solid oxide electrolysis (SOE) mode, or electricity from reformates in solid oxide fuel cell (SOFC) mode. An application of both modes as reversible solid oxide cell (rSOC) is to balance a renewable power supply with storage and power production, leading to high utilization of the same equipment. An application in SOFC mode is the maritime transportation powertrain. In both cases, transient operation is needed whenever mode transitions occur. In particular, switching between rSOC modes implies transitioning exothermal SOFC, endothermal, thermoneutral and exothermal SOE operation. Similarly, supplying the power demand of a maritime drivetrain in SOFC mode leads to various exothermic levels, as pertinent to part or full load operation. Operating strategies are needed to suppress potentially damaging thermal stresses during these transitions in the electrochemical SOC reactors. In order to identify such operating strategies, experiments have been carried out and a transient model has been developed for the analysis of rSOC mode-switching and SOFC drivetrain power supply, which are presented in this study. The 1D+1D SOC dynamic multi-reactor model includes the individual SOC reactors, piping and insulation, and is implemented in the in-house developed transient energy process system simulation framework TEMPEST [1,2]. The model couples the transient balances of mass and energy with electrochemistry, internal reforming kinetics, heat transfer, and flow distribution. As a result, temperature and voltage characteristics at cell, stack, and module levels are obtained to analyze for e.g. unwanted thermal stress. In the EU project SWITCH [3], experiments were performed at DLR with a Large Stack Module (LSM) from SolydEra (formerly SOLIDpower) to validate the model in transient 75 kW electrolysis mode, 25 kW fuel cell mode and mode-switching operation between electrolysis and polygeneration mode. The so called polygeneration mode refers to simultaneous generation of hydrogen and electricity at partial fuel utilization with natural gas, biogas or e-methane. Simulative studies of mode-switching procedures from SOE to SOFC-mode polygeneration show that drawing fuel cell current soon after reaching open circuit voltage and sufficiently in advance of the methane ramp completion leads to a reduced temperature decrease at the inlet of the cell without reaching oxygen to carbon ratios low enough to favor carbon deposition. In the EU project NAUTILUS [4], the mismatch between the transient response possibilities of SOFC systems and the power demand of a ship is addressed by connecting Li-ion batteries to the powertrain. Batteries respond to highly transient ship load demand changes, while the SOFC’s provide base part load to full load, according to a power split control strategy. A battery model developed and parametrized by the Chair for Electrochemical Energy Conversion and Storage Systems of RWTH Aachen University [5] was added to TEMPEST and validated using DLR experiments with a 40 kWh Li-ion battery. Simulation results of the SOFC-battery hybrid in Figure 1 show that a rule-based power split control strategy [6] ensures that the power demand of the ship is met at all times while the battery state of charge (SoC) remains within specified range, and the SOFC power is drawn at one of three fixed power levels for reduced thermal stress. An experimental campaign to test this and other control strategies with a 32 kW LSM from SolydEra and the 40 kWh battery is in progress at DLR. Acknowledgements Project SWITCH has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 875148. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Project NAUTILUS has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 861647.

Investigation of Structural Strength and Fatigue Life of Rotor System of a Vertical Axial-Flow Pump under Full Operating Conditions

Axial-flow pumps consider both the conventional pump mode and the pump as turbine (PAT) mode operation and put forward higher requirements for long-term operation stability and structural strength; therefore, it is of great engineering significance to evaluate the structural strength and fatigue life of the rotor under full operating conditions. In this study, based on computational fluid dynamics and the one-way fluid-structure interaction algorithm, the structural strength and fatigue life of the rotor system of a large vertical axial-flow pump under full operating conditions were evaluated and studied. The results show that blade deformation and equivalent stress are generally higher in the PAT mode than in the pump mode. The maximum deformation in both modes occurs at the tip of the blade, while the area of stress concentration is at the root of the blade. Both the deformation and the equivalent stress increase with increasing flow rate. The minimum safety factor occurs at the blade root in both modes, and the safety factor in the PAT mode is relatively smaller than that in pump mode. Therefore, when designing and manufacturing axial flow pumps for turbine duties, priority should be given to material strength at the blade root during PAT mode operation to ensure safe and stable operation. The aim of this study is to provide technical references and theoretical foundations for evaluating the service cycle of axial-flow pumps and the influence on pump life under different operation modes.

Large-signal time-domain equivalent circuit model for PEM fuel cell stacks

Hydrogen fuel cells have become one of the most viable power sources for electric aircraft. Models representing the electrical behavior of the fuel cell stack over the full dynamic operation region are essential for the development of power electronic energy systems powered by fuel cell stacks. This work presents an electrical equivalent circuit model for PEM fuel cell stacks representing the static and dynamic electrical behavior of the fuel cell stack under pulsed loads up to frequencies of 10 kHz. Dynamic phenomena on time scales slower than the considered timescale of power-electronic switching, such as reactant flow, membrane hydration, and temperature effects, are considered stationary. The parameterization method proposed is developed on measured data from a 110 W PEM fuel cell stack and validated with a set of measured data from a 2 kW stack. The time-domain simulated behavior of the parameterized model shows an accurate representation of the measured behavior: the parameterized model reproduces both the static polarization behavior and the behavior under high-frequency pulsed loading with errors of less than 1% with respect to the nominal stack voltage. The model is suitable for dynamic simulation of power electronic systems directly connected to fuel cell stacks and can be parameterized without special electrochemical impedance spectroscopy measurements.

Adapting empirical solar radiation pressure model for BDS-3 medium Earth orbit satellites

For the precise orbit determination (POD) of global navigation satellite systems (GNSS) constellation, it is very difficult to precisely model the solar radiation pressure (SRP) force acting on GNSS satellites. For GPS satellites, the ECOM model developed by the Center for Orbit Determination in Europe has been utilized by most of International GNSS Service (IGS) analysis centers. However, it should be adapted and optimized to the characteristics of satellites of each GNSS system or even individual satellites. It was extended to the ECOM2 model for GLONASS satellites and then for Galileo satellites by employing a box–wing model. Since November 2020, the third generation of the BeiDou satellite system (BDS-3) has been in its full operation and there are about 200 globally distributed IGS ground stations tracking BDS-3 signals, which creates a great potential to evaluate and optimize its SRP modeling. From the POD processing carried out in this study, we found significant fluctuations of up to 20 cm in overlapping orbit differences for satellites over eclipses in the radial direction and of about 20 and 50 cm in the cross and along directions for ECOM2 and ECOM models. Then, based on numerical analyses we demonstrate that the fourth- and sixth-order sine terms in the Sun direction can significantly reduce the overlapping orbit differences of ECOM. Therefore, an adapted SRP model by adding the fourth- and sixth-order sine periodical terms in the Sun direction to the ECOM model is presented. The adapted model is then validated for BDS-3 POD and orbit prediction. Results show that fluctuations in the amplitude of overlapping estimated orbits using ECOM models are reduced from 20 to < 10 cm in the radial-track component and satellite laser ranging residuals are reduced to half by the adapted SRP model. For the predicted BDS-3 satellite orbits, the RMS values over deep eclipses can be improved from about 7, 14 and 26 cm to about 3, 5 and 12 cm, in the radial, cross and along directions, respectively, compared to the ECOM model.

Electro-optical hybrid full-adder based on surface plasmon polaritons

Optical computing has advantages such as high speed and anti-electromagnetic interference, and the adder is the key component that composes optical computing units. This paper proposes an electro-optic hybrid full-adder based on surface plasmon polaritons, which combines the advantages of flexible circuit control, storability, high speed and electromagnetic interference immunity in optical computing. By using surface plasmon polariton technology, the limitation of optical diffraction is overcome, and the size of the full-adder is limited to 26.7 µm2, which improves the integration of more logical computing units on a single chip. By utilizing the MOS structure, the addition operation function of optical logic is controlled, thus reducing the junction capacitance area and improving the operation speed. The feasibility of the design scheme was verified through FDTD simulation experiments, and the correctness of the logic was achieved when the transmission rate exceeded 200 Gbit. This research provides a theoretical and practical reference for the electro-optical hybrid full addition operation of surface plasmon polaritons.