Thermal Performance in Multi-Pass Solar Systems With Well-Mixed Storage

1987 ◽  
Vol 109 (2) ◽  
pp. 94-100
Author(s):  
J. M. Gordon ◽  
Y. Zarmi
Keyword(s):  
System Performance ◽  
Closed Loop ◽  
Open Loop ◽  
Thermal Coupling ◽  
Storage Tanks ◽  
Actual System ◽  
Solar Systems ◽  
Penalty Factor ◽  
First Time ◽  
Partial Depletion

An approximate analysis of multi-pass, closed-loop solar systems with well-mixed storage tanks is presented. The thermal coupling of the storage tank both to the collector-storage loop (“charging” cycle) and the load-storage loop (“discharging” cycle) is shown to reduce system performance by a penalty factor, called the partial depletion factor, when compared to one-pass, open-loop systems in which the storage fluid is completely consumed by the load by the end of each 24-hour day (total depletion). This penalty factor is typically around 20 percent for systems with a daytime-only load and 30 percent for systems with a nighttime-only load. Our analysis provides, for the first time, the explanation for the findings of various experiments and numerical simulations. We establish the approximate validity of a “quasi-steady state” approach, wherein actual system performance is approximated by a calculation based on the repetition of one representative day. The approach is general in that it is applicable to all solar collector types.

The Simulation Analysis of Temperature Effects on System Performance of Silicon Micro-Gyroscope

2014 ◽  
Vol 529 ◽  
pp. 375-378
Author(s):  
Yun Peng Deng ◽  
Bo Yang ◽  
Xing Jun Wang ◽  
Bo Dai
Keyword(s):  
System Performance ◽  
Closed Loop ◽  
Simulation Analysis ◽  
Simulation Models ◽  
Temperature Characteristic ◽  
Open Loop ◽  
Scale Factor ◽  
Drive System ◽  
Zero Bias ◽  
Relative Change

The effects of temperature variation on the system performance is discussed in this paper. The temperature characteristic of the natural frequency and quality factor is analyzed theoretically firstly. Then the simulation models of the open-loop drive system, the closed-loop drive system, the closed-loop sense system and the quadrature correction system are constructed to simulate the temperature characteristic of the scale factor and zero bias. The simulation results demonstrate the relative change of the scale factor in the closed-loop drive system, that is 1.35%, almost decreases by 67 times relative to the open-loop drive system and the variation of the zero bias in the closed-loop drive system, that is 0.2789°/s, almost decreases by 364 times relative to the open-loop drive system. At the same time, the relative change of the scale factor in the closed-loop sense system, that is 0.000029%, almost decreases by 46551 times relative to the closed-loop drive system. The variation of the zero bias in the closed-loop sense system, that is 1.2×10-11°/s, almost decreases by 2.3×1010 times relative to the closed-loop drive system, which shows the proposed method is feasible and correct.

scholarly journals Temperature Compensation of the MEMS-Based Electrochemical Seismic Sensors

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 387
Author(s):  
Chao Xu ◽  
Junbo Wang ◽  
Deyong Chen ◽  
Jian Chen ◽  
Wenjie Qi ◽  
...  
Keyword(s):  
Temperature Effects ◽  
Temperature Compensation ◽  
Closed Loop ◽  
Low Frequency ◽  
Open Loop ◽  
Micro Electro Mechanical Systems ◽  
Temperature Changes ◽  
Seismic Sensors ◽  
First Time ◽  
Frequency Curves

Electrochemical seismic sensors that employ liquid as their inertial masses have the advantages of high performances in the low-frequency domain and a large working inclination. However, the surrounding temperature changes have serious impacts on the sensitivities of the sensors, which makes them unable to work as expected. This paper studied the temperature characteristics of electrochemical seismic sensors based on MEMS (micro–electro–mechanical systems), and analyzed the influences of the temperature effects on the open-loop and closed-loop amplitude-frequency curves. Most importantly, the temperature compensation circuits based on thermistors were developed, which effectively adjusted pole frequencies and sensitivity coefficients, and finally realized the real-time temperature compensation for both open-loop and closed-loop measurements for the first time. The results showed that in the temperature range of −10 °C ~ +40 °C, and with the 3 dB bandwidth range of 0.01 Hz ~ 40 Hz, the change of the maximum sensitivity was reduced from about 25 dB before temperature compensation to less than 2 dB after temperature compensation.

Multi-Scale Modeling of the Heart for Closed-Loop Evaluation of Pacemaker Software

2013 ◽  
Author(s):  
Zhihao Jiang ◽  
Rahul Mangharam
Keyword(s):  
Closed Loop ◽  
Timed Automata ◽  
Heart Rhythm ◽  
Open Loop ◽  
Actual System ◽  
Cardiac Pacemakers ◽  
Multi Scale ◽  
Counter Example ◽  
Electrical Pacing ◽  
Abstraction Levels

Implantable cardiac pacemakers restore normal heart rhythm by delivering external electrical pacing to the heart. The pacemaker software is life-critical as the timing of the pulses determine its ability to control the heart rate. Recalls due to software issues have been on the rise with the increasing complexity of pacing algorithms. Open-loop testing remains the primary approach to evaluate the safety of pacemaker software. While this tests how the pacemaker responds to stimulus, it cannot reveal pacemaker malfunctions which drive the heart into an unsafe state over multiple cycles. The safety and efficacy of pacemaker software should be considered in closed-loop with the physical environment of the heart. Formal Methods-based Model Checking has been an effective method for mathematically verifying all possible executions of the closed-loop system against safety properties. In this work, we used Timed automata to develop a series of heart models at different abstraction levels, which capture the timing behavior of the heart. By maintaining the Timed Simulation relation between each abstraction level, properties satisfied by the abstract model also hold in the actual system. With a Counter-Example-Guided Abstraction and Refinement (CEGAR) framework we can verify pacemaker efficiently without sacrificing accuracy.

On closed-loop equilibrium strategies for mean-field stochastic linear quadratic problems

2020 ◽  
Vol 26 ◽  
pp. 41
Author(s):  
Tianxiao Wang
Keyword(s):  
Optimal Control ◽  
Closed Loop ◽  
Optimal Control Problems ◽  
Mean Field ◽  
Open Loop ◽  
Time Inconsistency ◽  
Control Problems ◽  
Linear Quadratic ◽  
Linear Quadratic Optimal Control ◽  
Equilibrium Strategies

This article is concerned with linear quadratic optimal control problems of mean-field stochastic differential equations (MF-SDE) with deterministic coefficients. To treat the time inconsistency of the optimal control problems, linear closed-loop equilibrium strategies are introduced and characterized by variational approach. Our developed methodology drops the delicate convergence procedures in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. When the MF-SDE reduces to SDE, our Riccati system coincides with the analogue in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. However, these two systems are in general different from each other due to the conditional mean-field terms in the MF-SDE. Eventually, the comparisons with pre-committed optimal strategies, open-loop equilibrium strategies are given in details.

Comparison of Dc-Dc SEPIC, CUK and Flyback Converters Based LED Drivers

2020 ◽  
pp. 99-107
Author(s):  
Erdal Sehirli
Keyword(s):  
Integrated Circuit ◽  
Closed Loop ◽  
Input Voltage ◽  
Open Loop ◽  
Current Sensor ◽  
Switching Frequency ◽  
Led Driver ◽  
Advantages And Disadvantages ◽  
Led Drivers ◽  
Conduction Mode

This paper presents the comparison of LED driver topologies that include SEPIC, CUK and FLYBACK DC-DC converters. Both topologies are designed for 8W power and operated in discontinuous conduction mode (DCM) with 88 kHz switching frequency. Furthermore, inductors of SEPIC and CUK converters are wounded as coupled. Applications are realized by using SG3524 integrated circuit for open loop and PIC16F877 microcontroller for closed loop. Besides, ACS712 current sensor used to limit maximum LED current for closed loop applications. Finally, SEPIC, CUK and FLYBACK DC-DC LED drivers are compared with respect to LED current, LED voltage, input voltage and current. Also, advantages and disadvantages of all topologies are concluded.

Non-Plasmonic SERS with Silicon: Is It Really Safe? New Insights into Opto-Thermics of Core/Shell Microbeads

2018 ◽  
Author(s):  
Nicolò Bontempi ◽  
Irene Vassalini ◽  
Stefano Danesi ◽  
Matteo Ferroni ◽  
Paolo Colombi ◽  
...  
Keyword(s):  
Critical Role ◽  
Raman Laser ◽  
Core Shell ◽  
Thermal Coupling ◽  
Melting Points ◽  
Experimental Proof ◽  
Weakly Coupled ◽  
Light Management ◽  
Laser Sources ◽  
First Time

<p>Here we investigate for the first time the opto-thermal behavior of SiO<sub>2</sub>/Si core/shell microbeads (Si-rex) irradiated with three common Raman laser sources (lambda=532, 633, 785 nm) under real working conditions. We obtained an experimental proof of the critical role played by bead size and aggregation in heat and light management, demonstrating that in the case of strong opto-thermal coupling the temperature can exceed that of the melting points of both core and shell components. In addition, we also show that weakly coupled beads can be utilized as stable substrates for plasmon-free SERS experiments.</p>

scholarly journals Parallel Point Clouds: Hybrid Point Cloud Generation and 3D Model Enhancement via Virtual–Real Integration

2021 ◽  
Vol 13 (15) ◽  
pp. 2868
Author(s):  
Yonglin Tian ◽  
Xiao Wang ◽  
Yu Shen ◽  
Zhongzheng Guo ◽  
Zilei Wang ◽  
...  
Keyword(s):  
Point Cloud ◽  
Closed Loop ◽  
Real Data ◽  
Point Clouds ◽  
Autonomous Driving ◽  
Training Model ◽  
Labor Cost ◽  
Open Loop ◽  
Training Dataset ◽  
Data Annotation

Three-dimensional information perception from point clouds is of vital importance for improving the ability of machines to understand the world, especially for autonomous driving and unmanned aerial vehicles. Data annotation for point clouds is one of the most challenging and costly tasks. In this paper, we propose a closed-loop and virtual–real interactive point cloud generation and model-upgrading framework called Parallel Point Clouds (PPCs). To our best knowledge, this is the first time that the training model has been changed from an open-loop to a closed-loop mechanism. The feedback from the evaluation results is used to update the training dataset, benefiting from the flexibility of artificial scenes. Under the framework, a point-based LiDAR simulation model is proposed, which greatly simplifies the scanning operation. Besides, a group-based placing method is put forward to integrate hybrid point clouds, via locating candidate positions for virtual objects in real scenes. Taking advantage of the CAD models and mobile LiDAR devices, two hybrid point cloud datasets, i.e., ShapeKITTI and MobilePointClouds, are built for 3D detection tasks. With almost zero labor cost on data annotation for newly added objects, the models (PointPillars) trained with ShapeKITTI and MobilePointClouds achieved 78.6% and 60.0% of the average precision of the model trained with real data on 3D detection, respectively.

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