Transient Overload Research Articles

Secondary correction of infertility and oncophobia by means of psychological intervention (clinical case description)

The analysis of psychological correction for post-traumatic stress disorder and progressive chronic psychological stress was carried out. Strategy of the first consultation was based on the principle of A.A. Ukhtomsky, the theory of functional systems by P.K. Anokhin, A. Maslows pyramid of needs, taking into account the hierarchy of emotional stress and cognitive function in the structure of PS, social immobilization and the characteristics of the energy supply of the central nervous system. An algorithm for psychological counseling was developed: 1. Provocation to ensure an intense emotional reaction of suppressed aggression to a stimulus (NLP) under the control of the psychological and physiological state (NLP calibration, lie verification and profiling). 2. Inhibition of the activity of the limbic system and zeroing of emotional stress with the use of pattern interrupt (short-term confusion), followed by breathing control under conditions of transient hypoxia and overload of the representative systems. 3. Conducting resource-relaxation trance (Ericksonian hypnosis). 4. Post-hypnotic suggestion, cognitive analysis and embedding of new patterns of behavior and response to stress. 5. Teaching the method of zeroing emotional stress and reaction to external stimuli. Within 3 weeks after a single consultation, emotional stress disappeared, relations in the professional sphere normalized (transferred to a more prestigious job with a slight increase in salary), friendly relations with a neighbor-friend were restored, and mutual understanding was reached with parents. At the same time, against the background of regression of uterine hypertonicity, the painful formation in the pelvic cavity, perceived as an oncological pathology, disappeared, and the woman got pregnant.

Deuterium retention in solid and liquid tin after low-temperature plasma exposure

Recently, plasma-facing components based on liquid metals were proposed for a prospective nuclear fusion reactor in order to circumvent challenges that occur for solid metal components, such as erosion lifetime, neutron embrittlement or transient overloading. One candidate material is liquid tin. We present a systematic study of the behavior of solid and liquid tin exposed to a low-temperature deuterium plasma at temperatures between 300 and 515 K, focusing on deuterium retention and thermal release as well as on tin erosion and re-deposition. We find strong variations of deuterium depth profiles, deuterium release spectra, and tin erosion rates, which are correlated to dramatic changes in the surface morphology. In particular, we find evidence for massive gas bubble formation in tin, which can lead to the evolution of a thick, sponge-like layer for tin exposed to deuterium plasma just below the melting point, and to the rapid formation of a macroscopic gas pocket below liquid tin. We present evidence for strongly temperature-dependent chemical erosion of tin by deuterium plasma in the solid state. In the liquid state, a high tin erosion rate occurs, which is apparently induced by ejection of tin microdroplets. Furthermore, we observed strong plasma-assisted, low-temperature wetting of tin on tungsten near the melting point of tin. We tentatively propose the hypothesis that all of the observed effects may be influenced by tin-deuterium chemistry, e.g. the formation and de-composition of stannane molecules.

Abstract 265: Systemic Inflammation and Cardiac Macrophage Infiltration Accompany Stretch-induced Myocardial Injury in Swine Subjected to Transient Pressure Overload

Objective: Transient pressure overload (TPO) elicits stretch-induced myocyte injury in the absence of ischemia or infarction, but the extent to which this is associated with inflammation is unclear. The present study was designed to assess immune activation after TPO in swine and compare the inflammatory cytokine profile to that observed after myocardial infarction (MI). Methods: Swine received a brief infusion of phenylephrine (18 mg/hr iv; 30-60 min) to induce TPO and were studied for 1 hr (n=5), 3 hr (n=6), or 24 hr (n=6) before analysis of myocardial macrophage gene expression (CD68) via qPCR. Serial blood sampling was performed to assess neutrophil and monocyte counts as well as circulating cardiac troponin I (cTnI), IL-6, TNF-α, and CRP. Cytokine levels were compared to those from a separate group (n=5) subjected to a 60 min LAD occlusion to produce MI. Results: TPO increased circulating cTnI (from 20±5 ng/L to 340±58 ng/L at 3 hr and 1520±616 ng/L at 24 hr; p<0.01) without evidence of infarction. Compared with controls (n=6), swine subjected to TPO exhibited increased CD68 gene expression at 1, 3, and 24 hr ( A ). This was accompanied by a rise in peripheral blood neutrophils and monocytes ( B ) as well as an elevation in circulating IL-6, TNF-α, and CRP that was comparable to that observed after MI ( C ). Conclusion: Myocyte injury following TPO elicits mobilization of neutrophils and monocytes and a rise in circulating inflammatory cytokines comparable to that observed after MI. This is accompanied by an increase in cardiac macrophages and may be an important mechanism by which repetitive episodes of TPO lead to interstitial fibrosis and diastolic dysfunction without anatomic hypertrophy.

Designing real‐time systems using imprecise discrete‐event system specifications

SummaryReal‐time (RT) systems include hardware and software components interacting in a tight fashion. Although formal methods for RT systems development have advanced, they are sometimes difficult to apply in practical applications, and scalability is compromised as the complexity of the system scales up. Instead, using modeling and simulation (M&S) methods and tools has showed to be useful for verification of practical aspects of RT systems (and having the advantage to be able to including models of the physical environment they interact with). Although several efforts exist in M&S of RT systems, none of them has considered problems of transient overloading in the RT systems specifications. Here, we introduce a new theoretical framework called I‐DEVS (imprecise discrete event systems specification) with the goal of guaranteeing responses to inputs within specified time constraints under such transient overloading conditions. The solution presented here has the advantages of a formal specification and the practicality of an M&S‐based approach. We also discuss how to define hierarchical models running in RT, and we present a set of tools that can be applied to develop RT‐embedded applications, and RT simulations.

Weakly-hard Real-time Guarantees for Earliest Deadline First Scheduling of Independent Tasks

The current trend in modeling and analyzing real-time systems is toward tighter yet safe timing constraints. Many practical real-time systems can de facto sustain a bounded number of deadline-misses, i.e., they have Weakly-Hard Real-Time (WHRT) constraints rather than hard real-time constraints. Therefore, we strive to provide tight Deadline Miss Models (DMMs) in complement to tight response time bounds for such systems. In this work, we bound the distribution of deadline-misses for task sets running on uniprocessors using the Earliest Deadline First (EDF) scheduling policy. We assume tasks miss their deadlines due to transient overload resulting from sporadic jobs, e.g., interrupt service routines. We use Typical Worst-Case Analysis (TWCA) to tackle the problem in this context. Also, we address the sources of pessimism in computing DMMs, and we discuss the limitations of the proposed analysis. This work is motivated by and validated on a realistic case study inspired by industrial practice (satellite on-board software) and on a set of synthetic test cases. The synthetic experiment is dedicated to extensively study the impact of EDF on DMMs by presenting a comparison between DMMs computed under EDF and Rate Monotonic (RM). The results show the usefulness of this approach for temporarily overloaded systems when EDF scheduling is considered. They also show that EDF is especially useful for WHRT tasks.

Effect of Prime Mover's Characteristics on the Survivability of a Synchronous Generator-Based Distributed Energy Resource During Transient Overload Conditions

Recently, prime-mover stalling phenomenon was observed in a synchronous generator-based distributed energy resource (DER) for large step load changes during experimental testing at the Consortium for Electric Reliability Technology Solutions Microgrid. It is found to highly impact the generator's survivability during transient overload conditions. The stalling occurs in synchronous generator-based DER because of a sustained imbalance between electrical load demand and mechanical power available from the prime mover, thus depleting the generator's stored kinetic energy. In particular, mechanical power capability of the prime mover and stored kinetic energy in the rotating mass are the causal factors. This article evaluates two different types of prime movers—reciprocating engine and combustion gas turbine—for the DER survivability. The characteristics of these two commonly used prime movers are investigated during transient overload conditions by simulation case studies using PSCAD/EMTDC software.

Fault-tolerant Real-time Fair Scheduling on Multiprocessor Systems with Cold-standby

The ability to maintain functional and temporal correctness in the presence of faults is a key requirement in many safety-critical embedded systems. This work proposes an efficient fault recovery mechanism for real-time multiprocessor systems scheduled using a low overhead, semi-partitioned optimal proportional fair scheduling technique. We assume a system that can handle a single permanent processor fault at any time, using cold back-ups (with pre-specified activation / recovery time subsequent to the detection of a fault). As a result of the fault, the system may suffer transient overloads during such recovery periods, potentially leading to unacceptable fairness deviations and consequent rejections / early terminations of critical jobs. The proposed fault-tolerant scheduler, called Fault Tolerant Fair Scheduler (FT-FS), attempts to minimize such job terminations / rejections during recovery, by judiciously redistributing slacks accumulated by a subset of jobs, delivering more sustainable performance in the process. Experimental results reveal that the proposed FT-FS algorithm performs appreciably even under high system loads. Practical applicability of our proposed scheme has been illustrated using a case study on aircraft flight control system.

Modeling method for electrothermal cosimulation of high‐power IGBT

AbstractTo accurately simulate the electrical characteristics of high‐power insulated gate bipolar transistor (IGBT) applied under transient overload extreme conditions, this article presents an electrothermal modeling method based on PSpice and Simulink. In this method, the structural parameters of the IGBT module are accurately extracted through a scanning electron microscope, and the corresponding seven‐layer RC thermal network model is established in Simulink. Besides, a new lumped‐charge physical model is constructed in PSpice, which can accurately describe the electrical behaviors of IGBT at different temperatures by circuit simulation. Then, cosimulation under a multirate simulation strategy is realized through a Matlab script file, which controls both the PSpice circuit simulation and the Simulink thermal simulation. Finally, the method is verified through a short‐circuit experiment on an ABB 3.3 kV/1500 A high‐power IGBT module. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Transient Overload Characteristics of PM-Assisted Synchronous Reluctance Machines, Including Sensorless Control Feasibility

Synchronous reluctance (SyR) machines are a high-efficiency alternative to induction motors for variable-speed applications. To mitigate the well known downside of their lower power factor, permanent-magnet-assisted topologies, in which either rare-earth or ferrite magnets are inserted into the rotor in suitable quantities, are often adopted. The design and optimization procedures for PM-assisted topologies have been thoroughly discussed in the related literature. This paper compares SyR machines assisted with NdFeB and ferrite magnets, focusing on torque overload capability and feasibility of saliency-based position estimation algorithms. Three prototypes were realized and tested. They all have the stator of a commercial induction motor and the same custom-designed SyR rotor laminations. Among the three prototypes, one is a pure SyR motor, and the other two have NdFeB and ferrite magnets, respectively; both are designed to give the same torque at rated current. Results from simulations and experiments are presented comparing the transient overload capability of the three machines, in terms of torque capability and de-magnetization limit. A dynamic thermal model of the machines was developed within this scope. Moreover, the feasibility of saliency-based sensorless methods was investigated and is presented here for the three machines, both at high- and low-current loads. The results of the paper suggest that the ferrite-assisted solution is the best candidate for replacing induction motors in variable-speed applications, for its optimal tradeoff between performance and cost.

Dual admittance catheter-derived biventricular pressure-volume analysis in swine: comparison with contrast-enhanced computed tomography during transient pressure overload

Dual admittance catheter-derived biventricular pressure-volume analysis in swine: comparison with contrast-enhanced computed tomography during transient pressure overload

Survivability of Prime-Mover Powered Inverter-Based Distributed Energy Resources During Microgrid Islanding

Inverter-based distributed energy resources (DERs) can supply high-quality ac power in a microgrid due to their fast dynamic response. To achieve high reliability in an islanded microgrid, they are normally operated as voltage-controlled sources. However, the net load supplied by voltage-controlled inverter-based DERs can exceed their rated capacity, particularly during their transition from the grid-connected operation mode. Therefore, a comprehensive analysis of the DER survivability for overload conditions is crucial. Several experimental tests were conducted at the Consortium for Electric Reliability Technology Solutions Microgrid Testbed on the prime-mover powered inverter-based DER for learning about its survivability during overload conditions. In this paper, a thorough investigation of the inverter-based DER's survivability is carried out based on the prime-mover stalling phenomenon. Analytical expressions are derived for key design parameters of load-shedding algorithms, such as time-to-threshold frequency, maximum time delay , and maximum survivability time . The theoretical estimates are validated with the results obtained from the experimental testing. Furthermore, the minimum load-shedding estimate is determined for any prime-mover powered inverter-based DER to survive a transient overload condition.

Survivability of Synchronous Generator-Based Distributed Energy Resources for Transient Overload Conditions in a Microgrid

A synchronous generator-based distributed energy resource (DER) is commonly employed in microgrids due to its low cost and simple controls. However, there are many challenges to the DER operation when it is sized for supplying the critical loads alone in a microgrid. In particular, the DER would experience an overload condition during the microgrid transition from grid-connection to islanded operation, when the noncritical loads are also supplied momentarily. Therefore, it is very important to have a clear understanding on the survivability of a synchronous generator-based DER for transient overload conditions. Recently, experimental tests on survivability of the DER were carried out in the Consortium for Electric Reliability Technology Solutions Microgrid Testbed at American Electric Power. In this paper, an in-depth analysis of the synchronous generator-based DER operation during transient overload conditions is presented. The key relationships governing the system dynamic behavior of synchronous generator-based DER are analyzed to design the load shedding scheme for its survivability. Several case studies are illustrated to demonstrate the validity of the proposed load shedding method.

Integration of optimal operational dispatch and controller determined dynamics for microgrid survivability

The reliability and resilience of the electrical power grids are essential to industry, economy and society. Microgrids that are able to island from the bulk electrical grid are one technology that may vastly improve electrical power service to customer loads. To achieve these improvements, an islanded microgrid should be able to operate through the loss of one of its generators without shedding electrical load. The loss of one generator will typically result in significant additional loads, including transient overloads, being placed on the remaining generators. There is also the possibility of additional generator tripping during these processes (i.e. cascading failures), which would likely result in the collapse of the microgrid. The novelty of our work consists in incorporating dynamic models of generator controllers into a microgrid optimal dispatch formulation with the ultimate goal to avoid operational failures and ensure the “survivability” of all-inverter microgrids to generator loss and transient overloads. The integration of generator and controller dynamics into the optimal dispatch formulation significantly increases the computational complexity. As we develop algorithms to restore speed of the optimization, our method can be readily implemented into a new operational strategy capable of an unprecedented level of reliability against generator contingencies. In addition, we quantitatively illustrate the effect of the survivability constraints on the microgrid operating costs and how the related trade-off between capital and operating costs should be taken into account at the design stage. The methods developed here also apply to the dispatch of off-grid microgrids.

SiC MOSFET Device Parameter Spread and Ruggedness of Parallel Multichip Structures

This paper presents a preliminary study of the impact of device electro-thermal parameter spread and temperature variation on the robustness of SiC MOSFET parallel multi-chip power switch architectures. Reference is made to 1200 V – 80 mΩ rated commercial devices. Some major parameters are identified and selected, presenting experimental evidence of their impact during transient overload events. An advanced physics-based simulation model is then employed to extend the analysis to a more comprehensive set of parameters and operational conditions.

Winding Thermal Model for Short-Time Transient: Experimental Validation in Operative Conditions

This paper presents the validation of a first-order winding thermal model in machine operative conditions. The proposed model can be used in motor control strategies for the winding temperature prediction during transient overload, or vice versa , for the prediction of the maximum time duration of the overload maintaining the winding temperature within the limit imposed by the class of insulation. The thermal model has been validated using two different electrical machines. The first one is a 10-kW automotive starter-generator prototype for mini-hybrid powertrain equipped with distributed bar windings, while the second one is a 2.2 kW total enclosed fan cooled industrial induction motor equipped with conventional stranded wire windings. Depending on the application for both machines, a short-duty transient operation in overload conditions could be required. In particular, the automotive starter-generator must accomplish engine cranking and torque assistance during the vehicle acceleration and braking, while the industrial induction machine could operate in intermittent service in overload conditions when used in machine tool applications. As a consequence, an accurate stator winding temperature prediction is mandatory to fully exploit the machine performance. For both motors, the thermal model parameters have been evaluated by fast experimental approach, and, subsequently, the model has been validated during operative overload conditions.

Two Design Procedures for PM Synchronous Machines for Electric Powertrains

This paper presents a design environment for permanent-magnet synchronous motors (PMSMs). Two design examples for electric vehicle (EV) traction are presented: one interior PM machine of the PM-assisted synchronous reluctance type and one concentrated-winding surface-mounted PM motor. The parametric design software used in this paper includes design equations, finite element analysis (FEA), and multiobjective optimization algorithms for the design of PMSMs. This paper presents two possible design methodologies, for the two mentioned test cases. EV application was chosen for its many challenging aspects, involving flux weakening for extended speed range, discontinuous duty cycles, high transient overload requirements, high efficiency over a large area of operation, and so forth. The design examples are compared with selected benchmark designs in terms of operating range in the torque versus speed domain and efficiency maps, all FEA evaluated. Besides magnetics, thermal and structural aspects are included in the study.

Integration of virtual and on-line machining process control and monitoring

This paper presents a virtually assisted on-line milling process control and monitoring system. A part machining process is simulated to predict the cutting forces, torque, power, chip load and other process states. The simulated machining states are accessed by a real time monitoring system which detects the tool failure and adaptively adjusts the feed by predicting the forces from the feed and spindle drive motor current supplied by CNC. The integration of virtual simulation with real time measurements avoids false tool failure detection and transient overloads of the tools during adaptive control. The system has been implemented on a CNC machining centre for use in production.

A three level LTE downlink scheduling framework for RT VBR traffic

In recent literature, it has been observed that obtaining low overhead LTE downlink scheduling mechanisms that ensure a descent QoS is a challenging task especially in the presence of transient overloads. This paper proposes a novel three level LTE downlink scheduling framework (called TLS). The three major objectives of the proposed framework includes low overall traffic flow selection and mapping overheads at each Transmission Time Interval (TTI), maintaining acceptable QoS levels for various real-time (RT) variable bit rate (VBR) flows even during transient overloads through graceful degradation, and maximizing spectral efficiency by effectively exploiting multi-user diversity. Both the outermost and the second level of TLS employs a novel adjustable frame-based approach to provide efficient service even in the face of ever changing wireless channel conditions, system workloads, traffic bit rates etc. A low-overhead O(1) look-up based scheme is used in the innermost layer of the framework to physically allocate bandwidth resources to the traffic flows at each TTI. Simulation results clearly reveal that TLS outperforms the existing schedulers with respect to QoS, goodput and spectral efficiency.

Transient sacroiliac joint-related pain is a common problem following lumbar decompressive surgery without instrumentation

ObjectivePatients with lumbar stenosis profit substantially from decompressive surgery. The change of body position and walking behaviour after successful surgery might lead to changed force effects on the entire spine and on the sacroiliac joint (SIJ). We analyzed the incidence of postoperative SIJ-related pain. MethodsThe authors analyzed the records of 100 consecutive patients from three institutions, who underwent decompressive surgery without instrumentation. The diagnosis of SIJ-related pain was confirmed by periarticular infiltration. The radiological changes of the sacroiliac joint were assessed in plain radiographs in both groups: patients with SIJ pain (group 1) and patients without SIJ pain (group 2) after surgery. Results22 patients required medical attention due to SIJ-related pain after surgery. While the walking distance increased substantially in both groups without difference (p=0.150), the analysis of overall satisfaction favoured group 2 (p=0.047). Female patients suffered more from SIJ pain after surgery (p=0.036). Age, severity of radiological changes or number of operated segments appeared not to trigger SIJ-related pain. ConclusionThe adaptation of a changed body posture and gait could lead to transient overload of the SIJ and surrounding myofascial structures. The patients should be informed about this possible condition to avoid uncertainty, discontent, unnecessary diagnostics and to induce a quick, specific treatment. Non-diagnosed sacroiliac joint-related pain could be a possible, but reversible reason for the diagnosis of a “failed-back-surgery”.

Adaptive resource synchronization in hierarchical real-time systems

In this paper we outline the Adaptive Resource Allocation Protocol (ARAP) as an improved resource synchronization algorithm for hierarchically scheduled real-time systems. ARAP exploits knowledge about task utilization, using a proportional-integral-derivative (PID) controller, to estimate required resource bandwidth and improve scheduling decisions. Our analysis and experiments with RTSIM show that ARAP provides better temporal isolation and resource utilization during periods of transient overload compared to state-of-the-art resource synchronization algorithms. Implemented as part of VxWorks , the results are confirmed using an avionic system, for which ARAP substantially reduced the number of hard real-time deadline misses.