Separate Circuits Research Articles

Аналіз застосування технологій ПЛІС в складі IoT

The subject of study in this article and work is the modern technologies of programmable logic devices (PLD) classified as FPGA, and the peculiarities of its application in Internet-of-Things domain at different architectural layers of the implementation, as well as the elements of decision making during choosing of appropriate solutions based on FPGA in the context of implementation of IoT tasks with the requirements of intensive computations. The goal is to analyze the possibilities and peculiarities of the application of technology of programmable logic devices as part of the modern architecture of the Internet of Things with the improvement of decision making process during the choosing of appropriate technical solutions for the use of FPGA with taking into account the types of tasks. Tasks: to analyze the current state of demands regarding the use of FPGA technology in IoT projects; to analyze the challenges and limitations for the application of FPGA technology at different layers during the prototyping of IoT infrastructure; to propose ways of the use of FPGA technology in the IoT infrastructure with the use of high-speed computations; to analyze the advantages and disadvantages of the proposed approaches of integration of FPGA technology; to provide recommendations and determine the further direction of the research of the use of FPGA technology as a part of the IoT infrastructure considering of AI/ML tasks; to provide a practical example of the use of FPGA technology during the creation of a high-performance IoT system. According to the tasks, the following results were obtained. The analysis of the current state of the use of FPGA technology in IoT projects is performed, that showed the significant potential of these technologies for the implementation of high-speed computations in Internet of Things systems. A classification of the ways of applying FPGA in the tasks of real-time data processing and implementation of neural networks is proposed. The set of limitations of the possibility of FPGA technology applying at different layers of IoT infrastructure is defined. It includes high equipment costs, the need for specific design skills, limitations in energy consumption, and the complexity of the integration with existing systems. The practical example of the use of the IoT system with the implementation of high-intensive computations is provided. Conclusions. The main contribution and scientific novelty of the obtained results is that the conducted analysis allows to make a decision about the possibility of applying programmable logic in the construction of IoT projects and home automation systems. Based on the proposed classification of types of IoT tasks, there is a possibility of making a decision on the application of FPGA technology as a separate integrated circuit in the system or using a complete instance of FPGA as a Service in the cloud environment.

The role of miscible PAG lubricants in ammonia refrigeration systems reduction and compactness

Today’s society is going through an expanding use of natural refrigerants, earlier present only in big industrial facilities. This has made necessary the charge reduction and compactness improvement of the equipment, to fit the safety measures and standards requirements. The refrigerant charge and the complexity of an ammonia refrigeration system are mainly because of flooded evaporators use and the need for an efficient oil separation system, since conventional lubricants and ammonia are immiscible. The use of ammonia miscible lubricants can address the oil separation problem. A Poly-Alkylene-Glycol (PAG) can be designed and formulated to be miscible with ammonia, and the plant operated like a conventional halocarbon refrigerant one. The circulating lubricant will be recovered through the compressor suction port of the compressor. This will help in the operation of Direct Expansion (DX) evaporators, reducing to a testimonial size the oil separation circuit. This article is a translation of the article by Muñoz-Alonso M, Dixon L, Seeton CJ, Karnaz J. The role of miscible PAG lubricants in ammonia refrigeration systems reduction and compactness. In: Proceedings of the 9th IIR Conference on the Ammonia and CO2 Refrigeration Technologies. Ohrid: IIF/IIR, 2021. DOI: 10.18462/iir.nh3-co2.2021.0018 Published with the permission of the copyright holder.

Assessment of Hysteresis Models for LiFePO4

The selection of the cathode material is an important task in the design phase of batteries for mobile applications. One material of increasing interest is LiFePO4 (LFP) due to its improved energy density, good thermal stability and durability. In contrast to other commonly used cathode materials, LFP features a clear phase separation between the lithium rich and the lithium poor phase, leading to a pronounced voltage plateau over wide ranges of state of charge (SOC). The level of this plateau also changes for charge and discharge operation, even at very low C-rates. This voltage hysteresis in combination with the wide plateau gives some ambiguity to the correlation between voltage and SOC, which is a challenge for battery management systems. Thus its correct description is crucial if a cell model is meant to serve as virtual twin supporting control function development and calibration. Beyond that, a highly dynamic battery development process requires models that run significantly faster than real-time and parametrization processes which allow for accurate validation and easy adaptation to modified electrodes. A simulation approach complying with these requirements is the electrochemical pseudo-two dimensional (P2D) model, though adaptions to the core model are needed to appropriately capture hysteresis-affected voltage plateau characteristics for phase-separating materials such as LFP.The goal of this study is to extend an existing P2D framework with two approaches capable of describing hysteresis effects and analyzing these extensions regarding result plausibility, computational cost and effort of parametrization. The first model of interest is based on the one-state hysteresis model proposed by Plett. This approach allows for fast simulation and accurate reproduction of the charge and discharge voltages at low C-rates but lacks deeper physical consideration of the phase-separating origin of the hysteresis and thus might lose accuracy to predict system responses on dynamic pulses. In this approach, the voltage hysteresis is not a simulation result, it is due to the input of two separate open circuit voltages for charge and discharge. The second model of interest applies variable solid diffusion (VSSD) featuring a reduced Fickian diffusion coefficient in the plateau region. Lower diffusion at a given C-rate leads to steeper concentration gradients between lithium rich and lithium poor phase. With this approach, effective phase boundaries within the representative particles can be obtained. In the limiting case, when the Fickian diffusion coefficient becomes zero or even negative at some lithium concentration, phase separation persists also when no current is applied. In this setting, the voltage hysteresis at low C-rates is an emergent phenomenon, it is not an input. The physical basis of the approach also allows to consider mechanical stresses and their impact on the voltage gap between charge and discharge. Concentration gradients cause a mismatch of volume demands and thus lead to local stresses, which in turn alter the chemical potential.Results emphasizing advantages and disadvantages of the two hysteresis models are presented. Charge and discharge simulations are performed for several C-rates and the voltage hysteresis is extrapolated to infinitely small currents. Furthermore, the effect of resting phases with zero current as in Galvanostatic Intermittent Titration Technique measurements is discussed. As hysteresis models are often tested only on charge/discharge cycles with constant currents over large SOC regions, the responses of the simulation models are also assessed in pulse tests and dynamic profiles giving a realistic picture of automotive applications. Here special focus is put on energetical aspects of the one-state model and on intra-particle concentration profiles for the VSSD model.

Chronic morphine treatment induces sex- and synapse-specific cellular tolerance on thalamo-cortical mu opioid receptor signaling.

How cellular adaptations give rise to opioid analgesic tolerance to opioids like morphine is not well understood. For one, pain is a complex phenomenon comprising both sensory and affective components, largely mediated through separate circuits. Glutamatergic projections from the medial thalamus (MThal) to the anterior cingulate cortex (ACC) are implicated in processing of affective pain, a relatively understudied component of the pain experience. The goal of this study was to determine the effects of chronic morphine exposure on mu-opioid receptor (MOR) signaling on MThal-ACC synaptic transmission within the excitatory and feedforward inhibitory pathways. Using whole cell patch-clamp electrophysiology and optogenetics to selectively target these projections, we measured morphine-mediated inhibition of optically evoked postsynaptic currents in ACC layer V pyramidal neurons in drug-naïve and chronically morphine-treated mice. We found that morphine perfusion inhibited the excitatory and feedforward inhibitory pathways similarly in females but caused greater inhibition of the inhibitory pathway in males. Chronic morphine treatment robustly attenuated morphine presynaptic inhibition within the inhibitory pathway in males, but not females, and mildly attenuated presynaptic inhibition within the excitatory pathway in both sexes. These effects were not observed in MOR phosphorylation-deficient mice. This study indicates that chronic morphine treatment induces cellular tolerance to morphine within a thalamo-cortical circuit relevant to pain and opioid analgesia. Furthermore, it suggests this tolerance may be driven by MOR phosphorylation. Overall, these findings improve our understanding of how chronic opioid exposure alters cellular signaling in ways that may contribute to opioid analgesic tolerance.NEW & NOTEWORTHY Opioid signaling within the anterior cingulate cortex (ACC) is important for opioid modulation of affective pain. Glutamatergic medial thalamus (MThal) neurons synapse in the ACC and opioids, acting through mu opioid receptors (MORs), acutely inhibit synaptic transmission from MThal synapses. However, the effect of chronic opioid exposure on MThal-ACC synaptic transmission is not known. Here, we demonstrate that chronic morphine treatment induces cellular tolerance at these synapses in a sex-specific and phosphorylation-dependent manner.

A novel configuration for providing continuous renal replacement therapy via the ECMO circuit in VV ECMO without alarm adjustment.

It is common for patients on venovenous extracorporeal membrane oxygenation (VV ECMO) to require continuous renal replacement therapy (CRRT). This can be done using separate vascular access for the CRRT circuit, by placing the CRRT hemofilter within the ECMO circuit, or through a separate CRRT circuit connected to the ECMO circuit. When a CRRT circuit is connected to the ECMO circuit, the inflow and outflow CRRT limbs can both be placed pre-ECMO pump or the CRRT circuit can span the ECMO pump, with the CRRT inflow post-ECMO pump and the outflow pre-ECMO pump. Both configurations require the CRRT alarms to be inactivated due to high positive pressure experienced post-pump and low negative pressure pre-pump. We describe a novel technique that does not require separate venous access and still allows the CRRT alarms to be activated. The CRRT inflow line is connected to the post-oxygenator de-airing port. The CRRT outflow line is connected to the pre-pump side of the ECMO circuit. Pigtails allow for these connections and act as resistors negating the large range of pressures generated by the ECMO centrifugal pump. We implemented this configuration in 11 patients with 100% success rate allowing for alarms to be maintained in all patients. The median number of interruptions per 100 CRRT days was 11.7. The median CRRT filter lifespan was 2.2days, and the average blood flow was maintained at 311mL/min. This configuration allows for efficient use of CRRT in ECMO patients while maintaining the safety alarms on the CRRT machine.

Effects of selected cathode materials on a magnetically enhanced vacuum arc thruster

We discuss the effects of the ion distribution of a magnetically-enhanced Vacuum Arc Thruster using different cathode materials (Fe, Al, Cu) and magnetic field strengths. We develop a formalism, which is based on physical and geometric ideas, that describes the data for the inclusion of a magnetic field better than previous models (R2 > 0.89 for worst case). Our tests were performed on a Vacuum Arc Thruster with 270 A discharge current and an average pulse length of 3.5 ms. The magnetic field generator, driven by a separate capacitive discharge circuit, produced field strengths ranging from 0 to 250 mT along the thruster's centerline. We obtained the thrust correction factor and theoretical thrust from our measurements. It was found that application of magnetic fields increased ion density and axial momentum along the plasma plume's centerline. At higher magnetic field strengths (∼250 mT) the thrust factor decreased across all materials. For our electrodes, the inclusion of a protruding magnetic nozzle was seen to cancel the benefits arising from beam collimation due to the magnetic field. The iron electrode performed best, which may be due to its ferromagnetic nature.

An Improved Bi-Switch Flyback Converter with Loss Analysis for Active Cell Balancing of the Lithium-Ion Battery String

This paper focuses on the active cell balancing of lithium-ion battery packs. An improved single-input, multioutput, bi-switch flyback converter was proposed to achieve effective balancing. The proposed topology simplifies the control logic by utilising a single MOSFET switch for energy transfer and two complementary pulses to control the cell-selecting switches. The proposed topology can decrease the number of switching devices as well as the size and cost of the system. The bi-switch flyback converter eliminates the need for a separate buffer circuit to minimise leakage and electromagnetic inductance. Losses and energy efficiency were analysed at each end of the proposed topology. The appropriate MATLAB simulations investigated the balancing characteristics of various state of charge (SOC) imbalances. A comparison is made between the balancing speed and energy transfer efficiency of the proposed topology and a conventional topology that employs a multi-input and multi-output flyback converter in a static mode. The results of the MATLAB simulation were validated by the OPAL-RT (OP5700) real-time simulator. The balancing data of the proposed topology were compared using MATLAB simulation and real-time simulation. This work may reduce the time required to assemble and commission the hardware for the proposed topology’s real-time implementation.

Even‐Order Harmonic Distortion Observations During Multiple Geomagnetic Disturbances: Investigation From New Zealand

AbstractLarge geomagnetic storms are a space weather hazard to power transmission networks due to the effects of Geomagnetically Induced Currents (GICs). GIC can negatively impact power transmission systems through the generation of even‐order current and voltage harmonics due to half‐cycle transformer saturation. This study investigates a decade of even‐order voltage total harmonic distortion (hereon referred to as Even‐Order Total Harmonic Distortion (ETHD)) observations provided by Transpower New Zealand Ltd., the national system operator. We make use of ETHD measurements at 139 locations throughout New Zealand, monitored at 377 separate circuit breakers, focusing on 10 large geomagnetic disturbances during the period 2013–2023. Analysis identified 5 key substations, which appeared to act as sources of ETHD. The majority of these substations include single phase transformer banks, and evidence of significant GIC magnitudes. The ETHD from the source substations was found to propagate into the surrounding network, with the percentage distortion typically decaying away over distances of 150–200 km locally, that is, at a rate of −0.0043 %km−1. During the study period some significant changes occurred in the power network, that is, removal of the Halfway Bush (HWB) single phase bank transformer T4 in November 2017, and decommissioning of the New Plymouth substation in December 2019. Decommissioning of these two assets resulted in less ETHD occurring in the surrounding regions during subsequent geomagnetic storms. However, ETHD still increased at HWB with increasing levels of GIC, indicating that three phase transformer units were still susceptible to saturation, albeit with about 1/3 of the ETHD percentage exhibited by single phase transformers.

A novel approach to retrograde autologous priming for infant, pediatric and adult populations undergoing congenital heart surgery.

Retrograde Autologous Priming (RAP) of cardiopulmonary bypass (CPB) circuits is an effective way to reduce prime volume, commonly through the transfer of prime into separate reservoirs or circuit manipulation. We describe a simple and safe technique for RAP without the need for any circuit modifications or manipulations. For this technique, a separate roller pump for ultrafiltration (UF) is used. After adequate heparinization and arterial cannulation, the UF pump is initiated slowly, removing prime through the effluent of the UF, replacing with the patient's blood from the aortic cannula. Once the arterial line and UF circuit are autologous primed, the arterial head displaces reservoir crystalloid toward the UF circuit at a flow rate equal to the UF pump, displacing the crystalloid prime with blood from the UF circuit, autologous priming the boot and oxygenator with blood, crystalloid again being removed by the effluent. After venous cannulation, the venous line prime is replaced with autologous blood, the crystalloid removed by the effluent of the UF circuit via the arterial head. During RAP, if the patient becomes hypovolemic, either autologous volume is transfused back to the patient, or CPB is initiated, without the need for circuitry modifications. The patient population in this sample consisted of 63 patients ranging between 6.1kg and 115.6kg. The smaller the patient, the less blood volume available for RAP and therefore the less prime volume able to be removed. Overall percent removal increases as our patients size increases compared to total circuit volume. This RAP technique is a safe and effective way to achieve a standardized asanguinous prime for many regardless of patient or circuit size in the absence of contraindications such as low starting hematocrit, emergency surgery or physiologic instability. Most importantly, this potentially reduces the amount of hemodilution patients see from CPB initiation and therefore the lowest nadir hematocrit and consequently the amount of required homologous blood products needed during surgery.

Modelling, analysis and validation of a dynamic dense medium separation circuit model for detecting medium losses

Dense medium separation circuits use a dense medium to separate low density waste material from high density valuable minerals. Since the dense medium is an expensive consumable, it is recovered after separation of the valuable minerals from waste. A dynamic nonlinear model of a dense medium separation circuit of an iron ore plant in South Africa is developed to track the flow of medium in the circuit. An extended Kalman filter is designed for estimating observable but unmeasured states. The model is validated using online plant data. This paper serves as a precursor for further work to detect and mitigate expensive medium losses in the circuit.

Cutting and Shield Gases Pressure Effects on Plasma Cutting Quality

In this paper, the effects of the shield gas on cut quality in plasma arc cutting were quantified experimentally. Measurements were performed on plasma arc cutting kerfs (PACs) cut through a 4 mm (1/8 in.) S355 steel plates with a Gys Neocut105 cutter equipped with a Toparc AT-125 torch. This system uses compressed air as both cutting and shield gas. Separate circuits for shielding air and cutting air were used. This way, the influences of the shield air and the cutting air could be studied independently. A full 3-factor, 3-level Taguchi design was followed. The studied factors are the cutting air pressure, the shield air pressure, and the arc current. The measured responses are the removed steel surface and the right and left bevel angles. As expected, the current proved to have the greatest influence on the kerf surface. The cutting air pressure significantly influenced the kerfs’ shapes while the shield air flow rate proved less important yet sensitive. Some negative bevel angles at high plasma, high cutting, and high shield air pressures have also been observed.

Design and analysis of 4-bit absolute-value comparator in 65nm technology using hybrid TG/CMOS

Comparators are an important part of the calculator architecture, and rapid advances in semiconductor and electronics technology have placed higher demands on their performance. Optimization of digital systems involves several levels in order to make improvements in their power consumption, delay, and other parameters. This paper designs a low-power, high speed, and area efficient 4-bit absolute-value comparator, which utilizes a static Complementary Metal-Oxide-Semiconductor (CMOS) and Transmission Gate (TG) hybrid structure. The design optimizes the system at the level of separate circuit blocks, logic gates and transistors. The logic functions are realized by means of transcoding and magnitude Comparison, and the input signals are all driven by two-stage inverters. MUX and XOR with excellent performance of TG structure are implemented using simulation and analysis. In this paper, the transistor sizes and supply voltages of each logic gate are calculated and optimized using MATLAB by applying logic effort theory. The design uses a 65nm technology, and transient simulation of the overall system in Cadence successfully realizes its logic functions with 0.83ns delay and 49.6uw power consumption, proving the effectiveness of the design. This study based on theoretical calculations and simulations is a good reference for the design and theoretical study of very large-scale integrated circuits (VLSI).

Separate gut-brain circuits for fat and sugar reinforcement combine to promote overeating

Food is a powerful natural reinforcer that guides feeding decisions. The vagus nerve conveys internal sensory information from the gut to the brain about nutritional value; however, the cellular and molecular basis of macronutrient-specific reward circuits is poorly understood. Here, we monitor invivo calcium dynamics to provide direct evidence of independent vagal sensing pathways for the detection of dietary fats and sugars. Using activity-dependent genetic capture of vagal neurons activated in response to gut infusions of nutrients, we demonstrate the existence of separate gut-brain circuits for fat and sugar sensing that are necessary and sufficient for nutrient-specific reinforcement. Even when controlling for calories, combined activation of fat and sugar circuits increases nigrostriatal dopamine release and overeating compared with fat or sugar alone. This work provides new insights into the complex sensory circuitry that mediates motivated behavior and suggests that a subconscious internal drive to consume obesogenic diets (e.g., those high in both fat and sugar) may impede conscious dieting efforts.

Laser-Guided, Self-Confined Graphitization for High-Conductivity Embedded Electronics.

Facile fabrication of highly conductive and self-encapsulated graphene electronics is in urgent demand for carbon-based integrated circuits, field effect transistors, optoelectronic devices, and flexible sensors. The current fabrication of these electronic devices is mainly based on layer-by-layer techniques (separate circuit preparation and encapsulation procedures), which show multistep fabrication procedures, complicated renovation/repair procedures, and poor electrical property due to graphene oxidation and exfoliation. Here, we propose a laser-guided interfacial writing (LaserIW) technique based on self-confined, nickel-catalyzed graphitization to directly fabricate highly conductive, embedded graphene electronics inside multilayer structures. The doped nickel is used to induce chain carbonization, which firstly enhances the photothermal effect to increase the confined temperature for initial carbonization, and the generated carbon further increases the light-absorption capacity to fabricate high-quality graphene. Meanwhile, the nickel atoms contribute to the accelerated connection of carbon atoms. This interfacial carbonization inherently avoids the exfoliation and oxidation of the as-formed graphene, resulting in an 8-fold improvement in electrical conductivity (~20,000 S/m at 7,958 W/cm2 and 2 mm/s for 20% nickel content). The LaserIW technique shows excellent stability and reproducibility, with ±2.5% variations in the same batch and ±2% variations in different batches. Component-level wireless light sensors and flexible strain sensors exhibit excellent sensitivity (665 kHz/(W/cm2) for passive wireless light sensors) and self-encapsulation (<1% variations in terms of waterproof, antifriction, and antithermal shock). Additionally, the LaserIW technique allows for one-step renovation of in-service electronics and nondestructive repair of damaged circuits without the need to disassemble encapsulation layers. This technique reverses the layer-by-layer processing mode and provides a powerful manufacturing tool for the fabrication, modification, and repair of multilayer, multifunctional embedded electronics, especially demonstrating the immense potential for in-space manufacturing.

Nucleus accumbens and dorsal medial striatal dopamine and neural activity are essential for action sequence performance.

Separable striatal circuits have unique functions in Pavlovian and instrumental behaviors but how these roles relate to performance of sequences of actions with and without associated cues are less clear. Here, we tested whether dopamine transmission and neural activity more generally in three striatal subdomains are necessary for performance of an action chain leading to reward delivery. Male and female Long-Evans rats were trained to press a series of three spatially distinct levers to receive reward. We assessed the contribution of neural activity or dopamine transmission within each striatal subdomain when progression through the action sequence was explicitly cued and in the absence of cues. Behavior in both task variations was substantially impacted following microinfusion of the dopamine antagonist, flupenthixol, into nucleus accumbens core (NAc) or dorsomedial striatum (DMS), with impairments in sequence timing and numbers of rewards earned after NAc flupenthixol. In contrast, after pharmacological inactivation to suppress overall activity, there was minimal impact on total rewards earned. Instead, inactivation of both NAc and DMS impaired sequence timing and led to sequence errors in the uncued, but not cued task. There was no impact of dopamine antagonism or reversible inactivation of dorsolateral striatum on either cued or uncued action sequence completion. These results highlight an essential contribution of NAc and DMS dopamine systems in motivational and performance aspects of chains of actions, whether cued or internally generated, as well as the impact of intact NAc and DMS function for correct sequence performance.

An in vitro comparison of intra-operative isohemagglutinin and human leukocyte antigen removal techniques in pediatric heart transplantation

Background: Highly sensitized pediatric patients awaiting heart transplantation experience longer wait times and thus higher waitlist mortality. Similarly, children less than 2 years of age have increased waitlist times and mortality when compared to their older peers. To improve the likelihood of successful transplantation in these patients, various strategies have been utilized, including peri-operative plasmapheresis. However, limited data exists comparing plasmapheresis techniques for antibody reduction. This study’s aim was to compare the in vitro magnitude of isohemagglutinin titers (IT) and human leukocyte antigen (HLA) antibody removal and the time required between membrane-based plasmapheresis (MP) and centrifuge-based plasmapheresis (CP) incorporated into the extracorporeal (EC) circuit. Methods: Two MP (Prismaflex) and two CP (Spectra Optia, Terumo BCT) circuits were incorporated into four separate EC circuits primed with high titer, highly sensitized type O donor whole blood. Assays were performed to determine baseline IT and anti-HLA antibodies and then at 30-minute increments until completion of the run (two plasma volume exchanges) at two hours. Results: There was a decrease in anti-A and anti-B IgM and IgG titers with both MP and CP. Mean anti-A and anti-B titer reduction was by 4.625 titers (93.7% change) and 4.375 titers (93.8% change) using MP and CP, respectively. At 2 h of apheresis, CP reduced 62.5% of all ITs to ≤ 1:4, while MP reduced 50% of ITs to ≤ 1:4. Additionally, reduction of anti-HLA class II antibody to mean fluorescence intensity (MFI) &lt;3000 was achieved with both MP and CP. At 2 h of apheresis, CP reduced MFI by 2–3.5 fold and MP reduced MFI by 1.7–2.5 fold. Both demonstrated similar hemolytic and thrombotic profiles. Conclusions: In this in vitro plasmapheresis model of IT and anti-HLA antibody reduction, both MP and CP incorporated into the EC circuit can be used quickly and effectively to reduce circulating antibodies. While CP may have some greater efficiency, further study is necessary to verify this in vivo.

Semi-Empirical Models for Stack and Balance of Plant in Closed-Cathode Fuel Cell Systems for Aviation

In recent years, there has been a growing interest in utilizing hydrogen as an energy carrier across various transportation sectors, including aerospace applications. This interest stems from its unique capability to yield energy without generating direct carbon dioxide emissions. The conversion process is particularly efficient when performed in a fuel cell system. In aerospace applications, two crucial factors come into play: power-to-weight ratio and the simplicity of the powerplant. In fact, the transient behavior and control of the fuel cell are complicated by the continuously changing values of load and altitude during the flight. To meet these criteria, air-cooled open-cathode Proton Exchange Membrane (PEM) fuel cells should be the preferred choice. However, they have limitations regarding the amount of thermal power they can dissipate. Moreover, the performances of fuel cell systems are significantly worsened at high altitude operating conditions because of the lower air density. Consequently, they find suitability primarily in applications such as Unmanned Aerial Vehicles (UAVs) and Urban Air Mobility (UAM). In the case of ultralight and light aviation, liquid-cooled solutions with a separate circuit for compressed air supply are adopted. The goal of this investigation is to identify the correct simulation approach to predict the behavior of such systems under dynamic conditions, typical of their application in aerial vehicles. To this aim, a detailed review of the scientific literature has been performed, with specific reference to semi-empirical and control-oriented models of the whole fuel cell systems including not only the stack but also the complete balance of plant.

Testing of Regulating and Non-Regulating Hydraulic Pumps

Abstract This article deals with the testing of regulating and non-regulating hydraulic pumps in laboratory conditions. The laboratory test was carried out on the hydraulic device consisting of two separate hydraulic circuits (for testing the non-regulating hydraulic pump and regulating hydraulic pump). A throttle valve or proportional throttle valve is used for loading. During the laboratory tests, the flow efficiency of the non-regulating hydraulic pump at rotation speed n = 1,500 rpm (nominal speed) was η pp = 98.91% (0 MPa) and η pp = 94.97% (20 MPa), and for the regulating hydraulic pump, the values were η pp = 97.57% (0 MPa) and η pp = 94.54% (20 MPa). The determined values of flow efficiency of hydraulic pumps determine the correct operation of the experimental hydraulic laboratory equipment.

LONG-LIFE PULSED VACUUM-ARC PLASMA SOURCE

The design of a pulsed vacuum-arc plasma source with an ignition system based on dielectric surface breakdown is presented and the principle of its operation is described. In the engineered plasma source, a four-section anode is used along with an equal number of arc ignition sections. Additionally, separate power supply circuits are employed for both the main pulsed arc discharge and the arc ignition circuit. Independent operation of each section of this device is carried out, essentially constituting a combination of four pulsed plasma sources in one, the coordinated functioning of which is ensured by the control system. Practical tests of the pulsed plasma source have revealed its advantages as followed: a fourfold increase in the ignition system life-time; achieving uniform depletion of the cathode working surface; and, under specific conditions, enhancing the productivity of the plasma source.

System-Based Protection Method for High-Voltage Pulse Generator Switching Units in Biomass Electroporation

Background High-voltage pulsed electric field (PEF) technology has emerged as a promising technique for enhancing cell membrane permeabilization for biotechnological and medical applications. Given the parametric instability and low resistivity of biomass when used as an electrical load, it is imperative for the switching unit to meet specific requirements in terms of load capacity and protection against overloads and short circuits. Methods We introduce a novel system for safeguarding against overload and short-circuit currents by optimizing existing hardware-software resources. Our approach hinges on using the energy storage capacitor (ESC) both for energy storage and as a current sensor. By monitoring voltage drop during discharge, we estimate current parameters. Rapid discharge signals a short circuit. The microcontroller calculates ESC discharge limits based on preset parameters within a defined timeframe. If this limit is surpassed, the system promptly halts current pulses and discontinues supply to the load, ensuring reliable protection for the switching unit. Results By employing a system-based protection approach, we are able to reduce the complexity of circuit design, thereby enabling a unified control strategy that remains consistent regardless of the number and type of transistors used. This approach eliminates the need for separate circuit solutions to address this issue. Conclusions By utilizing a system method to protect the switching elements from short-circuit currents, we established a unified system structure for the circuit protection that is independent of current surges at the pulse fronts, as well as the specific number and type of transistors and switching modules employed. This method not only enhances the efficiency and reliability of the technology but also simplifies the design process and ensures a unified approach to protection, regardless of the system's configuration.