Single Loop Research Articles

Asymmetric Two-Step Thermosiphon for Containment Cooling of Small Modular Reactors

A thermosiphon is a heat transfer device that utilizes the phase change of a liquid and has a single closed-loop shape in a gravity-dominant field. This can be expressed as a single-step thermosiphon because boiling and condensation occur once per cycle. In contrast, the multistep thermosiphon, introduced for the first time in the field of thermal engineering in this study, is a new heat transfer mechanism in which boiling and condensation occur several times per cycle in a single loop with multiple channels. The new mechanism has a superior heat transfer rate compared to the existing single-step thermosiphon, and the operating pressure of the loop can be lowered. However, as the heat transfer rate increases, the circulation flow in the channel tends to pulsate. This thermohydraulic characteristic was confirmed through theoretical and computational analyses of a two-step thermosiphon. In this study, an improved concept of an asymmetric two-step thermosiphon was developed that can be applied to heat exchanger design by eliminating pulsating flow while maintaining the advantages of a two-step thermosiphon. The newly proposed heat transfer mechanism, termed the multistep thermosiphon, can be effectively used in the design of heat exchangers in industrial fields. In particular, if the asymmetric two-step thermosiphon is applied to the design of small nuclear reactor containments currently being developed in several countries, there are several advantages associated with the reduction of the containment volume and design pressure.

Dead-time compensation and single-loop control strategy for ground power unit

Instead of the auxiliary power system, the ground power unit supplies to airplanes during stopovers in airports, which is an important means of reducing carbon emissions of airport. However, under the restraint of switching frequency and high dynamic response speed, a single control loop is usually implemented in 400 Hz voltage-source inverter, the sampling and control of the inductor current in the LC filter are avoided, result in the design of the control system being more difficult, and the direction of the dead-time compensation can not be obtained due to the lack of the current polarity. In view of the above problem, this paper firstly analyzes the influence on the output voltage of inverter due to the dead-time, including the errors of fundamental amplitude and phase, and the low-order harmonic distortion. Then, according to the state equation of the inductor current, a current observation model without zero drift is proposed to obtain the polarity of the inductor current. On this basis, feedforward compensation is carried out for the voltage error generated by the dead-time. Combined with the amplitude-frequency characteristic curve, the parameter optimization design method of the single closed-loop proportional-resonant controller is presented. Finally, a simulation model and an experimental platform are established to verify the feasibility and effectiveness of the current observation model, dead-time compensation method and controller parameter optimization design method proposed in this paper.

Evolutionary mechanisms in the plastic deformation of γ'-Ni3(Al, Ti)-strengthened additively manufactured nickel-based 939 superalloys at intermediate temperatures

Tensile interruption experiments with different strains were conducted on additively fabricated nickel-based Inconel 939 superalloys at 700 ℃ to investigate the evolution of multiple deformation mechanisms. The microstructures of different strain groups captured by transmission electron microscopy (TEM) were analyzed, and it was concluded that a total of four various deformation mechanisms were identified, of which the first to be activated was the Orowan loop bypassing γ', and a tendency of transition from double to single loop was observed. Anti-phase boundary (APB) shearing was subsequently initiated, with a needed critical resolved shear stress level of approximately 195.82 MPa. Stacking faults (SFs) and deformation twinnings (DTs) were observed at higher stress, accompanied by the dissociation of dislocations. In addition, the magnitude of the stacking fault energy of AM 939 superalloys at intermediate temperature was calculated and estimated by matching the experimental phenomena with the critical shear stress.

Overcoming the relative bandwidth limitations of single VCO frequency synthesizers by implementing a novel PLL architecture

Abstract Frequency-modulated continuous-wave radar systems profit from increasing the absolute bandwidths of the generated frequency chirps to improve range resolution. As the relative bandwidth of SiGe-voltage-controlled oscillators (VCOs) is limited to about 80%, increasing the center frequency fundamentally or via frequency multiplication is the most direct way to increase that absolute bandwidth. However, as some applications require penetration depth, which dramatically decreases with frequency, other solutions are necessary. Therefore, state-of-the-art concepts rely on the down-conversion of generated frequency chirps via two separately stabilized frequency sources. This article implements a novel architecture, offering relative bandwidths of >100% within a single phase-locked loop (PLL). Therefore, two VCOs at different center frequencies are fed into a down-conversion mixer, whose output is directly stabilized via that PLL with one loop filter generating both tuning voltages. Those circuit blocks can be summarized as one equivalent VCO, offering a higher relative bandwidth and a significantly more linear tuning curve. Thereby, a solution to limited relative bandwidths with high VCO gain variation of single VCO synthesizers is offered while substantially reducing the hardware and implementation effort compared to the state-of-the-art.

Critical characteristics of spin − 1/2 four-leg nanotube: Monte Carlo Simulation

In this study, we aim to investigate theoretically the critical characteristics of spin −1/2 four-leg nanotube for the nanotechnology applications. The Ising model simulated by Monte Carlo simulation is adopted with the first exchange coupling J , the second exchange coupling between the second nearest neighbor atomic spins J ′ and the transverse exchange coupling J z , and the external magnetic field h as parameters. Herein, we examine the local properties of spin −1/2 four-leg nanotube by analyzing the magnetization, susceptibility and hysteresis loop behavior as function of J ′ , J Z and h . The obtained results show that the isotropic ‐ 1 / 2 four-leg nanotube Ising model presents critical behavior at ferromagnetic to paramagnetic phase transition where the Curie temperature T C increases according to vertical and second nearest neighbor exchange coupling. Furthermore, under external magnetic field, the magnetization keeps the second order transition and the magnetic susceptibility declines with the increase of applied external magnetic field value. In addition to that, we have found single ferromagnetic hysteresis loops, for which the shape increases by increasing the second nearest neighbor exchange coupling when T = J . Finally, the critical temperature shows perfect mirror symmetry relative to the vertical and increases with the second nearest neighbor exchange coupling.

A proton birdcage coil integrated with interchangeable single loops for multi-nuclear MRI/MRS.

Energy metabolism is fundamental for life. It encompasses the utilization of carbohydrates, lipids, and proteins for internal processes, while aberrant energy metabolism is implicated in many diseases. In the present study, using three-dimensional (3D) printing from polycarbonate via fused deposition modeling, we propose a multi-nuclear radiofrequency (RF) coil design with integrated 1H birdcage and interchangeable X-nuclei (2H, 13C, 23Na, and 31P) single-loop coils for magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS). The single-loop coil for each nucleus attaches to an arc bracket that slides unrestrictedly along the birdcage coil inner surface, enabling convenient switching among various nuclei and animal handling. Compared to a commercial 1H birdcage coil, the proposed 1H birdcage coil exhibited superior signal-excitation homogeneity and imaging signal-to-noise ratio (SNR). For X-nuclei study, prominent peaks in spectroscopy for phantom solutions showed excellent SNR, and the static and dynamic peaks of in vivo spectroscopy validated the efficacy of the coil design in structural imaging and energy metabolism detection simultaneously.

Investigating coronal loop morphology and dynamics from two vantage points

Coronal loops are the fundamental building blocks of the solar corona. Therefore, comprehending their properties is essential in unraveling the dynamics of the upper solar atmosphere. In this study, we conduct a comparative analysis of the morphology and dynamics of a coronal loop observed from two different spacecraft: the High Resolution Imager (HRIEUV) of the Extreme Ultraviolet Imager on board the Solar Orbiter, and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. These spacecraft were separated by 43° during this observation. The main findings of this study are that (1) the observed loop exhibits similar widths in both the HRIEUV and AIA data, suggesting that the cross-sectional shape of the loop is circular; (2) the loop maintains a uniform width along its entire length, supporting the notion that coronal loops do not exhibit expansion; and (3) notably, the loop undergoes unconventional dynamics, including thread separation and abrupt downward movement. Intriguingly, these dynamic features also appear similar in data from both spacecraft. Although based on observation of a single loop, these results raise questions about the validity of the coronal-veil hypothesis and underscore the intricate and diverse nature of the complexity within coronal loops.

Commonality and difference in the eigenfunctions of various types of acoustic trapped modes

We investigate and compare various types of acoustic trapped modes (TMs) in resonator–waveguide systems. The goal is to understand the commonality and difference between the mechanisms of common (symmetry protected, invisibility protected and symmetry–periodicity protected) and accidental TMs, occurring continuously and discretely in the resonator length–frequency two-parameter space. The latter type cannot yet be explained via an operator decomposition. Here, all TMs are explained in the same way by analysing why and how the propagating-wave loops in the eigenfunctions can satisfy the eigenmode condition (loop magnitude and phase constraints for closure) and the wave-trapping condition (loop zero-radiation condition) simultaneously. Firstly, the unified analysis reveals the commonality that one or multiple coupled propagating-wave loops satisfy TM conditions, and the difference. In common TMs, the loop zero radiation is independent of the single loop phase constraint that selects the TM frequency as a continuous function of resonator length. On the other hand, loop zero radiation in accidental TMs depends on the loop phase constraints and there are two phase constraints. Only at the crossing points of the two phase constraints can zero-radiation loops be ensured. Secondly, in contrast to previous studies, it suggests that modal degeneracy, avoided crossing and resonance-width bifurcation are not the mechanisms of accidental TMs.

Comparative analysis of different loop types for urine culture collection: Implications for quantitative bacterial growth and culture results

We hypothesized that the loop material and size could affect the results of the culture when compared to the calibrated pipette. A total of 484 urine samples were included in the study, and each sample was plated by using different loop types and the calibrated pipette. The bacterial counts per milliliter were calculated and compared, with a focus on the important cutoff values of 10³ and 10⁴ CFU/ml for further identification. When considering the 10³ CFU/ml as cutoff value, 1 µl and 10 µl plastic loops gave the highest sensitivity (86.8 %), whereas the 10 µl metal loop had the lowest sensitivity (64.2 %). For the 10⁴ CFU/ml cutoff value, 1 µl plastic loop inoculation demonstrated the highest sensitivity (75.9 %), while the 10 µl metal loop provided the lowest sensitivity (26.5 %). These results suggest that the single use plastic loops are functional, sensitive, useful especially for critical sample.

Single-loop tunable PT-symmetric optoelectronic oscillator based on a phase modulator.

In this paper, a single-loop tunable parity-time (PT) symmetric optoelectronic oscillator (OEO) based on a dual-mode optical phase modulator (PM) and a microwave photonic filter (MPF) has been proposed, analyzed, and designed. By adjusting the polarization angle θ between the input linearly polarized light and the z axis of the PM, the two-mode splitting ratio of the PM can be controlled, which results in a PT-symmetric structure based on a single physical loop. By adjusting the pump light wavelength, the center frequency of the stimulated Brillouin scattering (SBS)-based MPF can be tuned, which enables a fine tunable output frequency. The results reveal that, by adjusting the pump light wavelength with a step size of 0.0001nm, a frequency tuning accuracy of 12.5MHz can be obtained. Simultaneously, the OEO output frequency can be tuned from 0.9 to 22GHz, while the side-mode suppress ratio (SMSR) is 53dB, and the phase noise is -133.8d B c/H z at a frequency offset of 10kHz.

Parallel connected natural circulation loops using different working fluids: experimental results

Natural Circulation Loops (NCLs) are closed-loop systems that transport heat from a source to a heat sink without a pump, relying on free convection of the working fluid. Previous research has focused on the stability and influence of different operative parameters on NCLs. This experimental study investigates the thermo-hydraulic performance of three parallel-connected NCLs with small inner diameters using three different working fluids: deionized water, glycol aqueous solution (50+50% wt), and FC-43 dielectric fluid. This study examines the steady-state behaviour of the NCLs at various heat sink temperatures and heat powers. The results indicate that the common one-dimensional model for a single loop’s steady-state can be applied to this configuration and for all the tested fluids, and a proposed figure of merit can describe the working fluids and predict their steady-state behaviour.

Electrochemical impedance response of a thick and porous calcium carbonate layer deposited by thermal growth on a carbon steel electrode

Thermal calcareous scaling has been studied on a simulated heat-exchange carbon steel cylinder set-up in a CaCO3 -rich CO2-saturated solution (SIcalcite=2) using in situ electrochemical methods and ex situ surface characterization. Open circuit potentiometry (OCP) and electrochemical impedance spectroscopy (EIS) indicate dramatic increases to the impedance of the electrode over the first two days. The response quickly changes from a single capacitive loop in the early hours to an impedance characterized by a 45° slope at low frequency in Nyquist format, suggesting fast precipitation kinetics towards a protective state. At the end of 14-day tests, SEM and µ-Raman spectroscopy detected a distinctly layered aragonite-calcite scale. The bi-layered precipitate film is proposed to limit the diffusion of cathodic reactants across the porous, permeable scale, resulting in the 45° slope linear tail characteristic of the so-called transmission line response. EIS responses are experimentally re-evaluated away from open circuit, prior to proposing a bespoke equivalent circuit based on De Levie’s porous electrode model to link the electrochemical data to surface observations.

Computational and analytical study on the stability and utility aspects of single-phase natural circulation loop in parabolic trough collector

The use of passive heat transport devices in solar thermal energy devices is critical to make the systems more reliable and sustainable. Hence, linking single phase natural circulation loop to parabolic trough collector is the apt solution. In this regard, a 3-D computational model is built and validated for steady state and transient results. To acquire realistic results, solar irradiance pattern over the receiver is explored from SolTrace® and applied to the loop. The upper threshold of the horizontal heater horizontal cooler loop is found and validated using linear stability analysis. Since the loop is unstable at lower loads, instability restraining techniques viz. loop inclination (θ = 4°) and orifice insertion (β = 0.7) are employed. Although loop inclination gave desired results, the orifice couldn't improve the behavior due to loop geometry. The type of heat flux pattern does affect the initial transients of the loop, but it does not affect the steady state results in any manner. The loop was also tested with Therminol VP 1 and compared the stability aspects with water. In the end, intending NCL application in PTC, transient analysis was undertaken considering whole day solar flux distribution, which gave convincing results.

Cooling hybrid/electric vehicle battery module: exploring the thermal potential of single evaporator Loop heat Pipe

ABSTRACTA novel Loop Heat Pipe (LHP) is developed as passive cooling system for Battery Thermal Management System (BTMS). LHPs are more efficient than traditional heat pipes at transferring heat at larger distances, which is essential for keeping the batteries in a safe and efficient temperature range. The Single Evaporator Loop Heat Pipe (SE-LHP) BTMS is tested on a battery module comprising of twelve 18,650 lithium-ion battery cells. The tests are conducted at various charge and discharge rates (1C, 1.5C, and 2C) and ambient temperatures ranging from 30°C to 45°C. The SE-LHP BTMS significantly reduces the maximum cell temperature compared to a module without BTMS. At an ambient temperature of 35°C, the SE-LHP BTMS attains temperature drops of 15%, 16.4%, and 16.29% during battery charge rates of 1C, 1.5C, and 2C, respectively. The SE-LHP BTMS also increases the discharge capacity of the battery module. For the 1.5C discharge rate, the discharge capacity increases from 41% State of Charge (SOC) to 0% SOC with the SE-LHP BTMS, compared to 39% SOC without BTMS. For the 2C discharge rate, the discharge capacity increases from 59% SOC to 0% SOC with the SE-LHP BTMS, compared to 56% SOC without BTMS. The SE-LHP BTMS also helps to keep even temperature spreading among the battery cells. When the module is exposed to ambient temperatures ranging from 30°C to 45°C, the SE-LHP BTMS keeps a temperature difference of less than 2.43°C and 3.38°C among the battery cells for all charge and discharge rates, respectively.

Application of two classes of inverse problems for optimization and management of the natural hydrocarbon field development process

The article considers two classes of inverse problems in the modeling of hydrocarbon field development: optimization and adaptation of the development history. They jointly form the basis for field development management in a closed loop, based on a constantly updated 3D geological and technological model. The problems of model adaptation (identification) arise due to the point-by-point measurements and the inaccuracy of determining the initial data on porosity and permeability of the host rocks and other parameters of the deposit when building the 3D model. Such problems are regarded as the inverse ones, because the consequence – field measurements – is used to determine their cause. The problems under consideration are related to the identification of both porosity and permeability of the reservoir and other key parameters that determine the dynamics of development. Geologically consistent formulation ensures that the adapted model retains the original geological principles of the distribution of reservoir properties. The second class of problems under consideration is the problems of optimization (regulation) of development. One of the sought-after formulations is related to the optimal redistribution of a given target level of production from the field to all production wells in time. In this case, the technological limitations of surface equipment are taken into account. The maximized criterion reflects the economic effect of the asset development. In this article, without going into details of mathematical realization, the authors consider practical examples of solving these problems using full-scale 3D multiphase filtration models of the real fields. The algorithms based on the current methods of optimal control theory are used, which were developed and implemented by the researchers of Oil and Gas Research Institute of the Russian Academy of Sciences in the SimMatch software package and confirmed their effectiveness on numerous synthetic and real examples. Application and further development of these methods within the framework of a single loop, taking into account continuous information from the entire set of sensors, will significantly increase the efficiency of intelligent wells and field control systems.

Multi-variable anti-disturbance controller with state-dependent switching law for adaptive cycle engine

Compared with the conventional turbofan engine, the adaptive cycle engine (ACE) has more extensive flight envelope and the more types and number of adjustable components. While the performance of each mission profile is improved adaptively, the controller design of profile switching process will face strong flight condition disturbance and internal uncertainty. The traditional control system's single loop controller and discrete switching method of control parameters are to some extent difficult to meet the adaptive and robustness requirements of ACE. Thus, this paper proposed a multi-variable decoupling anti-disturbance controller for ACE based on the results of flight envelope partitioning with similar distances, embedded a state-dependent switching law. By analyzing the impact of inlet disturbances, internal actuator actuation, and random degradation of component performance on different switching laws, the adjust time and overshoot of the controller with state-dependent switching law proposed in this paper are reduced by an average of about 11.91 % and about 9.98 %, and the average thrust linearity and robustness has increased by about 0.096 % and 20.02 %. Finally, the reliability and feasibility of the control system were verified based on a hydraulic driven semi-physical experimental platform, providing reference for more complex and dynamic engine operation control in the future.

Simplified Methods for Generative Design That Combine Evaluation Techniques for Automated Conceptual Building Design

Smart design and construction have emerged as pivotal forces in the construction industry. Numerous studies have been conducted in the realm of design optimization, using artificial intelligence data-driven approaches and optimization theories. This increase in research has sparked interest in generative design, a process that automatically generates algorithm-based design alternatives, thereby reducing human effort and time by a significant margin. The objective of this study was to explore the potential of generative design to boost productivity within architectural practices and reduce redundant and unnecessary tasks for an aging construction workforce. Specifically, it illustrates the process of selecting superior alternatives by generating various three-dimensional layouts, using a generative design methodology. This occurs during the creation of a building layout concept with subsequent partial evaluations. The methodology of this study was mainly divided into four stages: objective setting, design algorithm development, the establishment of evaluation methodology, and the comparison of the results’ values. The findings of this study confirmed that the design algorithm and evaluation methodology form a single loop, generating a multitude of design alternatives that satisfy the algorithm designer’s evaluation criteria.

Non-cascaded finite time control of PMSLM based on super-twisting observer

A novel control strategy based on finite time control and super-twisting observer is proposed to improve the control performance and robustness for permanent magnet synchronous linear motor (PMSLM) drive system. First of all, the velocity-current single loop control which called non-cascade structure control is proposed by the finite time control, then the response velocity of the PMSLM drive system can be improved. Secondly, to improve the disturbance rejection performance, a super-twisting observer is designed to feedforward the load. Furthermore, the strictly convergence of the proposed control strategy is implemented. Finally, comparative simulations and experiments are designed on PI control, sliding mode control, and the proposed control method. Results demonstrate that the proposed method has better robustness and control performance.

Revelation after three decades of ablation therapy: two loops instead of a single re-entry loop drive atrial tachycardia

Revelation after three decades of ablation therapy: two loops instead of a single re-entry loop drive atrial tachycardia There is an urgent need to better understand and localise the sources of cardiac arrhythmia in order to improve its treatment. SmartHeart proposes a radical new approach—applying network theory to study cardiac arrhythmia mechanisms. Network theory has myriad applications throughout biology, physics and social sciences. However, it has never been applied to the heart. In this proposal, we will apply network theory to clinical data of cardiac arrhythmia, backed up by computer simulations, to automatically detect the source of the arrhythmia for complex atrial tachycardia, atrial fibrillation and ventricular tachycardia. As we will identify possible ablation targets, the goal of this project is to improve the treatment for the patient.

Innovative mechanisms for designing the system of public administration of the industry

Subject. This article discusses the development of wind energy in Russia. Objectives. The article aims to identify a set of key management objects and develop a process model for the functioning of the State management system of the electric power industry. Methods. For the study, we used a systems analysis. Results. Based on the analysis of the regulatory legal acts governing the development of the electric power industry in Russia, the article designs a single control loop for the industry. It finds that the problems of the existing system of governance lie in the fragmentation and disparity of its elements with each other. For the received projects of the federal system of public administration in the energy sector, the article offers complete lists of elements that eliminate the identified problems. Conclusions. The results of the study can be taken into account when developing projects for the use of renewable energy sources in Russia.