The application of entransy theory in heat transfer optimization of heat exchanger networks and multi-stage latent heat storage systems

Under the pressure of energy deficiency and the greenhouse effect, thermal energy recovery and recycling is of significant importance for the sustainable development of society. Various theories and technologies have been employed to enhance the performance of thermal energy systems. Entransy is a physical quantity to characterize the potential energy of heat transfer. Entransy theories including entransy dissipation extremum and entransy-dissipation-based thermal resistance have been widely used in heat transfer enhancement and heat exchangers optimization. The foundation of entransy theory is based on a hypothesis that heat transfer can be described as the transport of thermomass. In this thesis, the entransy theory was elaborated systematically, and the conservation equations of thermomass transport and heat transfer momentum were derived. After that, the new concepts of exothermic potential and endothermic potential were proposed to describe the heat exchange potential as a supplement to entransy theory. A pinch-analysis-based method was adopted to optimize the design of heat exchanger networks (HEN) in a chemical production process. In this approach, the pinch was identified using entransy dissipation minimization. Then, heat exchangers and heating/cooling utilities were organized around the pinch. It is shown that the retrofitted HEN reached a better heat recovery, meanwhile the energy consumption of auxiliary utilities was reduced. Later on, entransy dissipation minimization was applied to the optimization of a multi-stage PCM thermal energy storage system for heat exchange with heat transfer fluid (HTF). The system is constituted with several heat exchanger units in series, and the PCM in each unit has different phase transition temperature. Entransy dissipation minimization and entropy generation minimization were employed respectively to optimize the stage number (n), the number of transfer units (NTU), and PCM phase transition temperatures. In heat storage process, the results showed that, under the condition of fixed inlet/outlet HTF temperatures, entransy dissipation minimization leads to higher average storage temperature, and therefore better heat recovery performance. Similarly, in cool/cold storage process, entransy dissipation minimization also showed a superiority over entropy generation minimization. It can be concluded that entransy theory is applicable in the heat transfer optimization of HEN and multi-stage PCM thermal energy storage system. However, experimental validations need to be done in the further research to make the designs available in practice

Existence of Nontrivial Solutions for a Critical Perturbed Quasilinear Elliptic System

We consider a perturbed quasilinear elliptic system involving the p-Laplacian with critical growth terms in RN. Under proper conditions, we establish the existence of nontrivial solutions by using the variational methods

pH and temperature dual-sensitive molecular imprint polymers for BSA based on Cu2+ coordination

A novel kind of pH and temperature dual-sensitive Molecular imprint polymers (MIPs) combined with Cu2+ coordination (SiO2@CS/NIPAM-Cu2+-MIP) has been synthesized using glycidyl methacrylate-iminodiacetic acid (GMA-IDA) as a metalchelating ligand, with bovine serum albumin (BSA) as template protein, combined with pNIPAM and chiston (CS) as temperature and pH sensitive monomers, respectively. The coordination effect of GMA-IDA-Cu2+ has been shown to be beneficial to improve the adsorption capacity and adsorption specificity of BSA. The influence of pH not only changed the charge force between the polymer and protein in the imprinting system, but also deformed the imprinting cavity through the protonation of NH3+ on CS. Further, the thermo-sensitivity of the imprinted polymer was also found to be satisfactory. Withthe joint efforts of coordination, electrostatic action and good matching of imprinted sites, higher adsorption capacity (173.48 mg∙g-1) and imprinting factor (2.72) have been obtained at pH 4.6 and 35ºC. Although it took about 4 h to reach saturation adsorption, the cyclability of the SiO2@CS/NIPAM-Cu2+-MIP was found to be acceptable and the adsorptioncapacity was maintained at original 81.16% after six cycles. It is for the first time that GMA-IDA-Cu2+ has been used to prepare the pH and temperature dual-sensitive imprinted polymer for BSA

Numerical simulation of circulating tumor cell separation in a dielectrophoresis based Y-Y shaped microfluidic device

Efficient and effective separation of circulating tumor cells from biological samples to promote early diagnosis of cancer is important but challenging, especially for non-small cell lung cancer (NSCLC). In this article, a Y-Y shaped microfluidic device was designed to isolate NSCLC cells with a dielectrophoresis approach. Numerical simulations were conducted that the trajectories of cells were traced by solving the electric potential distribution and the flow field in a microchannel. The effects of inlet flow rate ratio of blood sample and buffer on separation performance were studied and optimized by the numerical investigation. Under optimal operating conditions, the separation efficiency can reach around 99%, which is achieved with 100 kHz AC, electrodes potential ranging from 1.6 V to 2.2 V, and flow rate ratio from 1.9 to 2.5. This study presents a potentially efficient, facile and low-cost route for circulating tumor cell separation

Physics-informed neural network simulation of conjugate heat transfer in manifold microchannel heat sinks for high-power IGBT cooling

This study explores the application of Physics-Informed Neural Networks (PINNs) in modeling fluid flow and heat transfer dynamics within intricate geometric configurations, focusing on manifold microchannel (MMC) heat sinks designed for efficient high-power IGBT cooling. A deep neural network architecture comprising two sub-PINNs, one for flow dynamics and another for thermal behavior, is developed, each initialized with a sine activation function to capture high-order derivatives and address the vanishing gradient problem. Comparisons between PINN and CFD simulations reveal close agreement, with both methods showing an increase in pressure drop and a decrease in temperatures as inlet velocity increases. Discrepancies arise in scenarios with rapid flow pattern or gradient changes, highlighting PINNs' sensitivity to geometric complexity and numerical stability. Overall, this study underscores PINNs' potential as a promising tool for advancing thermal management strategies across various engineering applications

A Flexible Sensor and MIMU-Based Multisensor Wearable System for Human Motion Analysis

Motivation: Magnetic–inertial measurement units (MIMUs) and flexible sensors are widely used in the wearable measurement system for human motion monitoring, clinical gait detection, and robotics motion control. However, MIMUs demonstrate measurement error due to magnetic disturbance in the indoor environment, and flexible sensors usually have low performance on linearity and accuracy. Objective: This article is intended to eliminate the low-accuracy problem caused by magnetic disturbances and improve the measurement accuracy of MIMU–flexible-sensor-based wearable systems. Approach: 1) a three-stage real-time adaptive anti-disturbance data fusion (RT-ADF) algorithm is proposed, which contains an anti-disturbance filter based on a double Mahony filter along with a state observer, a signal holder for sensors’ data transmit synchronously, and a data fusion based on an adaptive Kalman filter; 2) the proposed algorithm is used and validated its performance on a designed MIMU–flexible sensor wearable system; and 3) ten groups of knee motions (flexion/extension), ten groups of hip motions (adduction/abduction), and ten groups of elbow motions (flexion/extension) have been done by seven subjects in the experiments. Main Results: The designed multisensor wearable system based on the presented data fusion algorithm demonstrates a high-accuracy performance under the magnetic disturbance environment, and the maximum root mean square error (RMSE) of the measured continuous 3-D motion angle of the knee, hip, and elbow cross all the experiments was 1.23°, 1.15°, and 3.67° for each axis.<br/

Continuous photon energy modulation in IMRT of pancreatic cancer

Purpose: To develop a novel IMRT optimization method based on the principle of photon energy synthesis that simultaneously optimizes fluence map and beamlet energy. The method was validated on pancreatic cancers to demonstrate the benefits of the additional degree of freedom of photon energy in IMRT.Methods: Previous work has demonstrated that the effect of a photon beam of known energy can be achieved by the combination of two existing energy photons in the proper ratio. It further implied that any energy photon can be synthesized. Based on this, we propose the concept of continuous beamlet energy modulation in IMRT, or IMRT-BEM. The IMRT-BEM was modeled as the simultaneous optimization of two fluence maps, one for the low energy beam and one for the high energy beam, and it was implemented in an in-house inverse planning system. The IMRT-BEM was applied on 10 pancreatic cancer cases, where the IMRT-BEM plan was compared with single-energy IMRT plans of 6 MV (IMRT-6MV) and 15 MV photons (IMRT-15MV).Results: The IMRT-BEM plan provides a noticeable reduction to the volume irradiated at the high dose level (PTV105%) for PTV, at least 24.7% (6.4 ± 6.8 vs. 31.1 ± 18.7 (p = 0.005) and 43.8 ± 19.8 (p = 0.005) for IMRT-BEM, IMRT-6MV, and IMRT-15MV respectively). For target dose coverage, there were statistically significant improvements between the IMRT-BEM plans and the other two plans in terms of CI and HI. Compared to the IMRT-6MV plan, there were significant reductions in the Dmean of the spinal cord, liver, bowel, duodenum, and stomach. The irradiation volumes of the medium dose (V20Gy, and V40Gy) for the duodenum and bowel were reduced significantly. There were no significant differences between the IMRT-BEM and IMRT-15MV plans except for the Dmean of the spinal cord and the duodenum, the V20Gy, and V40Gy for the duodenum, and the V20Gy of the stomach.Conclusion: IMRT-BEM has certain dosimetric advantages for PTV and improves OAR sparing in pancreatic cancer, and can be effectively used in radiation treatment planning, providing another degree of freedom for planners to improve treatment plan quality

Survey on Dim Small Target Detection in Clutter Background: Wavelet, Inter-Frame and Filter Based Algorithms

AbstractDim small target is an active and important research area in image processing and pattern recognition. Various algorithms have been proposed to detect and track dim small target. This paper reviews some algorithms for dim small target detection, including the wavelet based algorithms, inter-frame difference based algorithms and filter based algorithms. Also, the further development of the technologies has been briefly analyzed

A Flexible Sensor and MIMU-Based Multisensor Wearable System for Human Motion Analysis

Motivation: Magnetic–inertial measurement units (MIMUs) and flexible sensors are widely used in the wearable measurement system for human motion monitoring, clinical gait detection, and robotics motion control. However, MIMUs demonstrate measurement error due to magnetic disturbance in the indoor environment, and flexible sensors usually have low performance on linearity and accuracy. Objective: This article is intended to eliminate the low-accuracy problem caused by magnetic disturbances and improve the measurement accuracy of MIMU–flexible-sensor-based wearable systems. Approach: 1) a three-stage real-time adaptive anti-disturbance data fusion (RT-ADF) algorithm is proposed, which contains an anti-disturbance filter based on a double Mahony filter along with a state observer, a signal holder for sensors’ data transmit synchronously, and a data fusion based on an adaptive Kalman filter; 2) the proposed algorithm is used and validated its performance on a designed MIMU–flexible sensor wearable system; and 3) ten groups of knee motions (flexion/extension), ten groups of hip motions (adduction/abduction), and ten groups of elbow motions (flexion/extension) have been done by seven subjects in the experiments. Main Results: The designed multisensor wearable system based on the presented data fusion algorithm demonstrates a high-accuracy performance under the magnetic disturbance environment, and the maximum root mean square error (RMSE) of the measured continuous 3-D motion angle of the knee, hip, and elbow cross all the experiments was 1.23°, 1.15°, and 3.67° for each axis.<br/

Defining the role of oxygen tension in human neural progenitor fate.

Hypoxia augments human embryonic stem cell (hESC) self-renewal via hypoxia-inducible factor 2α-activated OCT4 transcription. Hypoxia also increases the efficiency of reprogramming differentiated cells to a pluripotent-like state. Combined, these findings suggest that low O2 tension would impair the purposeful differentiation of pluripotent stem cells. Here, we show that low O2 tension and hypoxia-inducible factor (HIF) activity instead promote appropriate hESC differentiation. Through gain- and loss-of-function studies, we implicate O2 tension as a modifier of a key cell fate decision, namely whether neural progenitors differentiate toward neurons or glia. Furthermore, our data show that even transient changes in O2 concentration can affect cell fate through HIF by regulating the activity of MYC, a regulator of LIN28/let-7 that is critical for fate decisions in the neural lineage. We also identify key small molecules that can take advantage of this pathway to quickly and efficiently promote the development of mature cell types