Temperature Feedback Research Articles

Research on Thermal Insulation Measures of Power Equipment Condition Monitoring Device in Cold Regions

Outdoor winter temperatures in other northern regions such as Heilongjiang Province are relatively low. As an important equipment of ensuring the safety of transmission lines, the stability of the condition monitoring devices is facing great challenges. In order to ensure that the condition monitoring device can operate reliably in winter, so as to avoid the influence of low temperature in winter on the reliability of the condition monitoring device, in this paper a device is designed that uses solar heat for heat preservation for power equipment condition monitoring device. The device uses an all-glass vacuum solar collector tube to convert solar energy into heat, and realizes instant feedback and control of temperature through a bimetallic temperature sensor. After testing, in winter, the internal temperature of the heat insulation box can be increased by about 30°C compared with the outside, which can effectively improve the winter operating environment of the device.

Bioresorbable Microdroplet Lasers as Injectable Systems for Transient Thermal Sensing and Modulation.

Minimally invasive methods for temperature sensing and thermal modulation in living tissues have extensive applications in biological research and clinical care. As alternatives to bioelectronic devices for this purpose, functional nanomaterials that self-assemble into optically active microstructures offer important features in remote sensing, injectability, and compact size. This paper introduces a transient, or bioresorbable, system based on injectable slurries of well-defined microparticles that serve as photopumped lasers with temperature-sensitive emission wavelengths (>4-300 nm °C-1). The resulting platforms can act as tissue-embedded thermal sensors and, simultaneously, as distributed vehicles for thermal modulation. Each particle consists of a spherical resonator formed by self-organized cholesteric liquid crystal molecules doped with fluorophores as gain media, encapsulated in thin shells of soft hydrogels that offer adjustable rates of bioresorption through chemical modification. Detailed studies highlight fundamental aspects of these systems including particle sensitivity, lasing threshold, and size. Additional experiments explore functionality as photothermal agents with active temperature feedback (ΔT = 1 °C) and potential routes in remote evaluation of thermal transport properties. Cytotoxicity evaluations support their biocompatibility, and ex vivo demonstrations in Casper fish illustrate their ability to measure temperature within biological tissues with resolution of 0.01 °C. This collective set of results demonstrates a range of multifunctional capabilities in thermal sensing and modulation.

Optimal control of temperature feedback control ratchets

<sec>Biomolecular motors are macromolecules of enzyme proteins that convert chemical energy into mechanical energy. Experimental studies have shown that the directed movement of the biomolecular motor fully participates in the material transport process in the cell. Theoretically, the directed movement of biomolecular motors can be studied by the ratchet model. However, in most of feedback control ratchet models, none of the influences of external factors on experimental manipulation is considered, especially the inevitable random error, systematic error and human error in the experiment. Therefore, in order to further study the influences of error factors on feedback control ratchets, Cao's research group (Feito M, Cao F J <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://doi.org/10.1140/epjb/e2007-00255-7"> 2007 <i>Eur. Phys. J. B</i> <b>59</b> 63</ext-link>) pioneered the idea of error probability and discussed the transport behavior of feedback ratchets in the presence of error probability.</sec><sec>Based on Cao's error ratchet model, in this paper the temperature factor in introduced to further control the feedback ratchets, and the directed transport characteristics of the coupled Brownian particles in the temperature feedback ratchets are studied. The effects of temperature factor, phase difference and temperature frequency on the directed transport of coupled Brownian particles are discussed in detail. It is found that the temperature factor does not always reduce the directed transport of Brownian particles. There is a minimum value which means that the temperature factor can enhance the directed transport of the feedback ratchets within a certain change interval. In addition, in a small temperature amplitude range, the directed transport of the coupled particles exhibits a multi-peak structure with the change of temperature frequency. It is means that the appropriate temperature change frequency can enhance the directed transport of the feedback ratchets multiple times. The conclusions obtained in this paper can not only inspire experimental selection of appropriate temperature feedback information to optimize the directed transport of the Brownian ratchets, but also provide theoretical references for analyzing and processing the experimental data, especially error analysis.</sec>

EFFECT OF FISSION SOURCE SPECTRUM ON MONTE CARLO CALCULATION OF EX-CORE QUANTITIES

The Consortium for Advanced Simulation of Light Water Reactors (CASL) Virtual Environment for Reactor Applications (VERA) offers unique capabilities to combine highfidelity in-core radiation transport with temperature feedback using MPACT and CTF with a follow-on fixed source transport calculation using the Shift Monte Carlo code to calculate ex-core quantities of interest. In these coupled calculations, MPACT provides a fission source to Shift for the follow-on radiation transport calculation. In past VERA releases, MPACT passed a spatially dependent source without the energy distribution to Shift. Shift then assumed a235U Watt spectrum to sample the neutron source energies. There were concerns that, in cases with burned or mixed oxide (MOX) fuel near the periphery of the core, the assumption of a235U Watt spectrum for the source neutron energies would not be accurate for studying ex-core quantities of interest, such as pressure vessel fluence or detector response. Therefore, two additional options were implemented in VERA for Shift to sample neutron source energies: (1) a nuclide-dependent Watt spectra for235U,238U,239Pu, and241Pu, and (2) to use the standard 51-energy group MPACT spectrum. Results show that the 51-group MPACT spectrum is not suitable for ex-core calculations because the groups have been fine-tuned for in-core calculations. Differences in relative detector response due to235U and nuclide-dependent Watt spectra sampling schemes were negligible; however, the use of nuclide-dependent Watt spectra for vessel fluence calculations was found to be important for fuel cycles with burned and fresh fuel.

ON-THE-FLY INTERPOLATION OF CONTINUOUS TEMPERATURE-DEPENDENT THERMAL NEUTRON SCATTERING DATA IN RMC CODE

Thermal neutron scattering data have an important influence on the high-fidelity neutronics calculation of thermal reactors. Due to the limited storage capabilities of computers, a discrete ACE representation of the secondary neutron energy and angular distribution has been used for Monte Carlo calculation since the early 1980s. The use of this discrete representation does not produce noticeable effects in the integral calculations such as keff eigenvalues, but can produce noticeable deficiencies for differential calculations. A new continuous representation of the thermal neutron scattering data was created in 2006, but was not widely known. Recently, the continuous representation of the thermal neutron scattering ACE data based on ENDF/B-Ⅷ.0 library was officially released and was available for all users. The new representation shows great difference compared with the discrete one. In order to utilize the more physical and rigorous representation data for high fidelity neutronic-thermohydraulic coupling calculation, the on-the-fly treatment capability was proposed and implemented in RMC code. The two-dimensional linear-linear interpolation method was used to calculate the inelastic scattering cross sections and the secondary neutron energies and angles. The on-the-fly treatment capability was tested by a pressurized water reactor assembly. Results show that the on-the-fly treatment capability has high accuracy, and can be used to consider the temperature feedback in the neutronic-thermohydraulic coupling calculations. However, the efficiency of the on-the-fly treatment still need to be improved in the near future.

Experimental study of ISHTAR thermostatic irradiation device for the MARIA research reactor

Materials and core components for the next generation power reactors technologies require testing that can be performed in existing research reactors. Such experiments employ devices dedicated to reflect the relevant thermal and neutron parameters simulating conditions present in, for example, but not limited to, HTGR reactors. A novel thermostatic irradiation device named ISHTAR (Irradiation System for High-Temperature Reactors) has been designed and constructed in the MARIA research reactor. Its mission is to enable irradiation of samples in controlled, homogeneous temperature field reaching 1000°C and inert gas atmosphere. The high temperature is achieved by a combination of electric and gamma heating, together with carefully designed thermal insulation. Additionally, samples holder made of graphite with high thermal conductivity enables the temperature homogenization in all directions. Device will be placed inside the Beryllium matrix of MARIA core and cooled with forced circulation of water from the reactor pool loop. This paper presents the outcome of experiments conducted with the rig prototype in external hydraulic mock-up of the MARIA reactor irradiation channel. The results have proved that the desired conditions for irradiation of the samples were achieved and their comparison against computational data has shown the adequacy of the design process. Finally, the loss of flow scenario was tested in protected and unprotected conditions (meaning with and without the safety system based on temperature feedback), proving the operational safety of the ISHTAR design. Experimental results will be used in the future to validate the numerical models (two and three dimensional) of the irradiation rig, providing an improved understanding of free convection and radiation phenomena modeling.

Exploring the Solution of Bionic Prosthesis Lacking Perceptual Feedback System: Using Invasive and Non-invasive Techniques

The bionic prosthesis is a more advanced research direction in the prosthesis, but there are still many shortcomings. One of them is the lack of an effective perceptual feedback system, which included the feedback of position, force, texture, roughness, temperature, and other environmental information, as well as the information perception ability of the prosthesis itself[1]. This defect limits the normal operation of the prosthesis and endanger the safety of users. By analyzing the sensory feedback mechanism of the human body, it is found in this paper, the main reason for the lack of an effective perceptual feedback system of the bionic prosthesis is that there is no structure connected with the internal nerves of the human body in the mechanical prosthesis. Therefore, the perceptual signals collected by artificial sensors cannot be transmitted to the cerebral cortex by invasive method, or lack specific in vitro devices to stimulate patients to produce specific perceptual feedback by non-invasive methods. At present, through the use of invasive and non-invasive technology, we have mastered the form of electrical stimulation, vibration stimulation, and other forms of perceptual feedback. Due to the larger amount of feedback information, shorter training time than other methods, non-invasive electrical stimulation feedback has become a promising research area in this field.

THE TCA BENCHMARK FOR VALIDATION OF TEMPERATURE FEEDBACK CALCULATIONS

The TCA benchmark was investigated as a possible candidate for validation of temperature feedback calculations. This benchmark has low-enriched uranium fuel, light water moderation and reflection, and a temperature range of 20–60 °C. The use of three different nuclear data libraries was considered, viz. ENDF/B-VIII.0, JEFF-3.3, and JENDL-4.0. Since the results were not as good as hoped for, additional studies were performed to identify the cause(s) of discrepancies. The benchmark values depend on a choice of delayed neutron data, so it was investigated whether this could be the cause of discrepancies. Also, an assessment was made based on critical configurations only, i.e. avoiding the use of delayed neutron data, whether the calculations exhibit a bias in relation to the benchmark in the results for the effect of temperature. Indications were found that such a bias exists. It is concluded that the choice of delayed neutron data has a significant effect on the benchmark values themselves. The use of three major nuclear data libraries leads to a range of benchmark values for each configuration, rather than one value. Also, one has to take into account the possibility of a bias in the calculation of temperature effects. It is not clear at this point what the cause of the bias is.

Optimization of thermal buckling control for composite laminates with PFRC actuators using trigonometric shear deformation theory

This work aims to explore optimal design and control of thermal buckling for composite laminates with piezoelectric fiber reinforced composite (PFRC) actuators. Four-variable trigonometric shear deformation theory without introduction of a shear correction factor is used in the structural modeling. The high accuracy of the present approach is examined by analyzing the critical buckling temperature and natural frequency compared with references results. A temperature feedback control approach is proposed in designing the controller. Taking fiber angle as the optimization design variable, layerwise optimization approach (LOA) is applied to maximize critical buckling temperature of piezolaminated plate and a set of stacking sequences are obtained. The resulting analysis demonstrates that the proposed control approach can clearly increase the critical buckling temperature of piezo-laminated plates. The optimization process developed is useful in devising stacking sequences for the piezo-laminated structures in thermal environments.

A Miniaturized Adaptive Dual-Comb Based on Piezoelectric Transducer and Multi-stage Temperature Feedback

A Miniaturized Adaptive Dual-Comb Based on Piezoelectric Transducer and Multi-stage Temperature Feedback

Automatic focusing of Cassegrain telescope based on environmental temperature feedback

Automatic focusing of Cassegrain telescope based on environmental temperature feedback

Thermal Feedback System From Robot Hand for Telepresence

In this study, we propose a thermal feedback system using a flexible thermal display glove (master part) and a robot hand (slave part) for telepresence. A piezoelectric sensor in the glove detects the posture of the user, which is required to operate the robot hand, while the robot hand monitors the temperature change of a grasped object and transfers the temperature feedback through thermoelectric devices mounted on the glove. Specifically, we utilize a controller to manage the thermal feedback system. Further, a series of experiments are conducted to evaluate the performance of the thermal feedback control system under heating and cooling conditions, and the responses at various desired temperatures are examined. The maximum temperature error and standard deviation under the steady-state conditions of the control system are studied. The power consumption during the response time and holding time is calculated and analyzed. Furthermore, the operation of the integrated thermal feedback system is demonstrated, and the performance of the controlled system is evaluated.

Diversity of East China Summer Rainfall Change in Post-El Niño Summers

East China has experienced positive precipitation anomalies in post-El Niño summers, mainly in the Yangtze-Huaihe River Valley. This kind of monsoonal rainfall change induced by El Niño, however, is not always the same due to El Niño diversity and mean state change. Here, we use cluster analysis on the post-El Niño (PE) East China summer precipitation anomalies to identify the diversity of this El Niño-induced monsoon change. The result shows that PE East China summer rainfall anomalies mainly display three different modes for all selected 20 El Niño events from 1957 to 2016. Cluster 1 shows the middle and lower reaches of the Yangtze River demonstrate strong wet anomalies, while South and North China are dominated by dry anomalies, similar to a sandwich mode. Cluster 2 is distinguished by dry anomalies over South China and wet anomalies over North China, exhibiting a dipole mode. Compared with Cluster 1, the change caused by Cluster 3 is different, showing negative anomalies over the Yangtze-Huaihe River Valley. The three clusters are correlated with successive events of El Niño, a quick transfer to a strong La Niña and a quick transfer to a weak La Niña respectively. The associated anomalous anticyclone (AAC) focuses on (120°E, 20°N) in Cluster 1, which expands southward for Cluster 2 and moves eastward for Cluster 3. The feedback of AAC-sea surface temperature (SST) mainly works for supporting the AAC in Cluster 1, but it is weak for Cluster 2; the strong easterly anomalies related to La Niña contribute to the AAC location change for Cluster 2. Both AAC-SST feedback and easterly anomalies support the AAC of Cluster 3. The CMIP5 output can capture these diverse responses in circulation except that their simulated AAC for Cluster 1 is significant to the east of the observed.

Investigation on Short-Circuit Characterization and Optimization of 3.3-kV SiC MOSFETs

The short-circuit (SC) ruggedness of 3.3-kV silicon carbide (SiC) MOSFETs is of great importance for traction applications. In this article, the SC characterization and failure mechanism of 3.3-kV planar-gate SiC MOSFETs are systematically studied by experiments and simulations. The measured SC withstanding time (SCWT) of 3.3-kV SiC MOSFETs is about 17 μs, and the SC energy density is 15.5 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Research demonstrates that the current clamping phenomenon is attributed to the high density of interface traps (Dit) in the gate oxide of 3.3-kV SiC MOSFETs. Furthermore, the positive temperature feedback mechanism and the triggering of parasitic n-p-n transistor are proved to cause the SC failure. At last, three optimized cell structures are proposed for improving the SC capability of 3.3-kV SiC MOSFETs, where the optimal SCWT is enhanced by 23% without degrading the forward conduction capability.

Flapping actuation using temperature feedback control of coated shape memory alloy actuators

Shape memory alloys (SMAs) have been considered as actuators for micro application due to its high strength to weight ratio. Although it is mostly considered for linear or rotary actuation, in this study a technique using a temperature feedback control system has been proposed to produce oscillation at steady state suitable for flapping wing actuation in micro air vehicles (MAVs). A proportional-integral-derivative (PID) controller was used in the temperature feedback system to tune the frequency of oscillation of the shape memory alloy actuator. This system is compact as the oscillation can be produced without using components to translate from linear to rotary motion. Another challenge to be addressed is the slow cooling rate of the SMA actuator that occurs through natural convection resulting in slower flapping actuation. Thus, a viable approach to improve the actuation response is by coating the SMA to reduce hysteresis. An experimental study was conducted to evaluate the effects of heat convection on the SMA actuator's control performance by using SMA wire coated with silicone rubber. Its actuation was compared to the uncoated SMA wire to establish the effects of heat convection on SMA actuation behaviour. The response of the temperature feedback system of the SMA actuator for the flapping actuation under wind loading was evaluated using wind tunnel testing. The experimental results show that coated SMA wire resulted in increased actuation frequency. However, this effect became negligible as the airflow provided sufficient cooling and resulted in higher flapping frequency at Reynolds number greater than 7.5 × 103. Wind tunnel testing demonstrated that shape memory alloy actuators using a PID based temperature feedback control system may be used to produce flapping actuation at low Reynolds numbers.

Accurate position control of shape memory alloy actuation using displacement feedback and self-sensing system

Numerous shape memory alloy (SMA) linear actuator designs have been proposed for accurate position control using different techniques such as displacement feedback, temperature feedback, force feedback and resistance feedback. Each of these techniques has its advantage, as well as constraint and limitation. Self-sensing SMA actuation is considered to be cost-effective as it eliminates the use of external sensor in the system. However, its performance relative to other methods has not been widely discussed. In this study, two techniques were proposed for accurate position control of displacement in the range of 2 mm. The performance of the system using position feedback and self-sensing SMA actuation was evaluated through an experimental test bench developed in this research. The results show that the position feedback system has faster time response and higher accuracy, however, it is costly due to the laser displacement used in the system. The self-sensing SMA actuation produced slower time response and the accuracy was less than 90%. It was found that by providing tension to SMA actuator, the actuation temperature of the SMA actuator increased and the accuracy of the self-sensing system can be improved.

SiCTeC: An inexpensive, easily assembled Peltier device for rapid temperature shifting during single-cell imaging.

Single-cell imaging, combined with recent advances in image analysis and microfluidic technologies, have enabled fundamental discoveries of cellular responses to chemical perturbations that are often obscured by traditional liquid-culture experiments. Temperature is an environmental variable well known to impact growth and to elicit specific stress responses at extreme values; it is often used as a genetic tool to interrogate essential genes. However, the dynamic effects of temperature shifts have remained mostly unstudied at the single-cell level, due largely to engineering challenges related to sample stability, heatsink considerations, and temperature measurement and feedback. Additionally, the few commercially available temperature-control platforms are costly. Here, we report an inexpensive (<$110) and modular Single-Cell Temperature Controller (SiCTeC) device for microbial imaging—based on straightforward modifications of the typical slide-sample-coverslip approach to microbial imaging—that controls temperature using a ring-shaped Peltier module and microcontroller feedback. Through stable and precise (±0.15°C) temperature control, SiCTeC achieves reproducible and fast (1–2 min) temperature transitions with programmable waveforms between room temperature and 45°C with an air objective. At the device’s maximum temperature of 89°C, SiCTeC revealed that Escherichia coli cells progressively shrink and lose cellular contents. During oscillations between 30°C and 37°C, cells rapidly adapted their response to temperature upshifts. Furthermore, SiCTeC enabled the discovery of rapid morphological changes and enhanced sensitivity to substrate stiffness during upshifts to nonpermissive temperatures in temperature-sensitive mutants of cell-wall synthesis enzymes. Overall, the simplicity and affordability of SiCTeC empowers future studies of the temperature dependence of single-cell physiology.

Development of the NuScale Power Module in the INL Modelica Ecosystem

This paper provides a comprehensive overview of the development of a NuScale power module in the Modelica process model ecosystem at Idaho National Laboratory (INL) as part of the U.S. Department of Energy’s Office of Nuclear Energy Integrated Energy Systems (IES) program. Model development has led to the creation of a dynamic NuScale module in the Modelica language that operates under natural circulation and is consistent with design parameters set forth in the design certification documentation for the Nuclear Regulatory Commission (NRC). Controllers have been developed that are consistent with controllers mentioned by NuScale design certification documents. While characteristic time constants may differ due to controller gains, the actual control actions of the system are consistent with NuScale prescribed actions. In addition to natural circulation and controllers, the NuScale power module includes hot channel calculations, reactivity control, and a pressurizer. Hot channel calculations include bulk fluid temperature, outer clad temperature, fuel centerline temperature, and departure from nuclear boiling ratios. Reactivity control incorporates moderator and fuel temperature feedback mechanisms, boron concentration, and control bank positions. A pressurizer with sprays and heaters was developed to maintain primary system pressure within bounds. Further, the model has been developed to allow the user to input beginning-, middle-, or end-of-cycle reactivity conditions. Three simulations were run that demonstrate the capability of the model controllers to meet target parameters while preserving system values within reasonable bounds. The first simulation is an initialization study at 160 MW(thermal)/50 MW(electric) that compares the model steady-state values with the design certification values. This simulation demonstrates the capability of the model to operate in natural circulation mode and closely matches operating values set forth in the NRC design certification documents. The second simulation is a power uprate from 160 MW(thermal)/50 MW(electric) to 200 MW(thermal)/60 MW(electric), and the final simulation is of a typical summer day where the turbine demand oscillates throughout the day. These illustrate the capabilities of the system to operate under natural circulation while maintaining system parameters within controller bounds and to match turbine output with turbine demand. This work adds a systems-level model of the NuScale power module with associated control systems, reactivity coefficients, control banks, coolant through fuel temperature profiles, and associated mass flow rates throughout the system that have been added to the Modelica ecosystem. This model will be the basis of work that is utilized in the Joint Use Modular Plant program at INL, which proposes to utilize a single power module to support research, development, and demonstration activities, with a specific aim to demonstrate various IES configurations. As part of the ecosystem, the NuScale module can be quickly integrated with existing Modelica modules (e.g., thermal energy storage, reverse osmosis, high-temperature steam electrolysis, gas turbines) to model energy grids in different geographical locations.

A Fast Leakage-Aware Green’s-Function-Based Thermal Simulator for 3-D Chips

In this article, we propose a fast thermal modeling tool, 3DSim , using a Green’s-function-based approach. Green’s-function-based approaches have been shown to be faster than the traditional finite-difference-based techniques. Our proposed tool can model steady-state and transient thermal profiles for both 2-D and 3-D chips, which may contain multiple active layers and fluid-carrying microchannels for heat removal. The unique advantage of our tool is that it models leakage power analytically using a piecewise-linear leakage model, thereby eliminating the need to iterate multiple times through the leakage–temperature feedback loop. We use several algebraic techniques and transforms to compute the thermal profile analytically and thereby speedup the process of calculation. To the best of our knowledge, transform-based approaches have not been used before to model the temperature in 3-D chips with microchannels. Our approach provides a $150\times $ speedup over state-of-the-art thermal simulators, with an error limited to 5%.

Reactor performance and safety characteristics of two-phase composite moderator concepts for modular high temperature gas cooled reactors

Graphite moderators have an extensive historical performance record, but also feature inherent challenges for modular High Temperature Gas-Cooled Reactors (mHTGRs). Challenges with graphite include non-uniform expansion and contraction under irradiation and build-up of potential energy during the bombardment of high energy neutrons that results in a large energy release under annealing. These challenges have led to the investigation and development of alternative moderators to be utilized in mHTGRs, including beryllium- and hydride-based concepts with compositions selected for favorable moderating power and the potential for improved in-service lifetime as compared to graphite. The proposed moderators are fabricated as two-phase composites with magnesium oxide, MgO, as the radiation-stable host matrix and beryllium metal, Be, beryllium oxide, BeO, or zirconium hydride, ZrHx=1 (to account for hydrogen loss from the hydride phase during processing), as the entrained moderating phase. Here, we evaluate the reactor performance and safety characteristics of these moderator concepts relative to a graphite reference using a Ft. Saint Vrain-style fuel block. We assessed the cycle length, discharge burnup, natural resource utilization, neutron flux spectra, moderating power, moderating ratio, critical size, moderator and fuel temperature feedback, fuel cycle cost, spent nuclear fuel and high level waste radioactivity per unit energy generated, and environmental impact per unit energy generated. The results demonstrate that the advanced moderators have the potential for comparable or enhanced cycle performance to that of the graphite reference case with significantly improved performance for an optimized moderator-to-fuel ratio design. These advanced moderators are also assessed from a reactor safety standpoint for Design Basis Accidents (DBAs) including Pressurized Loss of Forced Cooling and Depressurized Loss of Forced Cooling accidents for a 350 megawatt thermal prismatic-type mHTGR. The full core thermohydraulic analysis of DBAs show that the high volumetric heat capacity of the beryllium-based moderator grants them a greater margin to fuel failure in these analyses than a conventional graphite moderated system, but the lower thermal conductivity of the beryllium-based moderators leads to longer times at elevated temperatures.