Cold storage condensation heat recovery system with a novel composite phase change material

© 2016 Elsevier Ltd. Using condensation heat from cold storage refrigeration systems to provide heat for domestic hot water preparation and industrial hot water supply promotes energy conservation. However, few studies have investigated cold storage condensation heat recovery using phase change materials (PCMs). In this study, a cold storage condensation heat recovery system that uses PCMs has been designed and analysed. According to the principle of energy cascade recycling, different operation modes could be effectively switched to recycle condensation heat. Furthermore, a novel and suitable phase change composite material is developed for cold storage condensation heat recovery, which has a relatively large latent heat, high thermal conductivity, and an appropriate phase change temperature (i.e. 80 °C). With carnauba wax (CW) as the PCM and expanded graphite (EG) as the additive, a composite was developed with an optimal mass ratio of CW:EG = 10:1. The thermal and physical properties and the interior structure of the composite were then investigated using a scanning electron microscope (SEM), thermal constants analyser (Hot Disk), differential scanning calorimeter (DSC), and Fourier transform infrared spectrometer (FT-IR). Furthermore, experiments on the melting and solidification processes and accelerated thermal cycling were also conducted. It was found that at the optimal mass ratio of 10:1, the temperatures of the CW/EG composite in the melting and solidification processes were 81.98 °C and 80.43 °C, respectively, while the corresponding latent heats were 150.9 J/g and 142.6 J/g, respectively. During both processes, CW could retain its original worm-like structure after being completely adsorbed by EG. Compared to only CW, the melting and solidification time of the CW/EG composite were reduced by 81.7% and 55.3%, respectively, while its thermal conductivity was 16.4 times higher. After 1000 runs of accelerated thermal cycling, the endothermic/exothermic phase change temperatures of CW and the CW/EG composite increased by only 0.42%/0.42% and 0.23%/0.27%, respectively, while their endothermic/exothermic latent heats decreased by 4.96%/4.78% and 2.05%/3.44%, respectively. These results indicate that both CW and the CW/EG composite have excellent thermal reliability, while the CW/EG composite exhibits a slightly better performance. Finally, the experiments show that the CW/EG composite has desirable thermal and physical properties such as high thermal conductivity and reliability; Hence, it has good potenti al as a material for facilitating condensation heat recovery from cold storage refrigeration systems

Background Subtraction Based on Perception-Contained Piecewise Memorizing Framework

A key issue for full-time video surveillance is to search or establish a reference image of background which corresponds to current video frame. However, background that was ever in presence long time ago is enclosed or discarded due to background forgetting assumption. How to rapidly pick up or even rebuild long-term background needs to be discussed. This paper aims to present a framework for background maintenance in order to solve the problem. A piecewise memorizing framework is proposed for matching, updating and even rebuilding long-term background. Based on the metaphors of psychological selective attention theory, the framework is composed of a prior piecewise perception processor for intensity stationary test. Besides, a hierarchical memorizing mechanism constitutes the other part of the framework for overcoming the exponential forgetting of long period background appearances. Applied to Gaussian mixture model (GMM), this framework is capable of maintaining short-term background states, identifying long period background appearances, and rapidly adjusting to new background states according to different expressions derived from the prior perception of scene intensity changes. Its effectiveness can be demonstrated by experimental results for solving various typical problems

Achieving Scalable Capacity in Wireless Mesh Networks

Wireless mesh networks play a critical role in enabling key networking scenarios in beyond-5G (B5G) and 6G networks, including integrated access and backhaul (IAB), multi-hop sidelinks, and V2X. However, it still poses a challenge to deliver scalable per-node throughput via mesh networking, which significantly limits the potential of large-scale deployment of wireless mesh networks. Existing research has achieved $O(1)$ per-node throughput in a dense network, but how to achieve scalability remains an unresolved issue for an extended wireless network where the network size increases with a constant node density. This issue prevents a wireless mesh network from large-scale deployment. To this end, this paper aims to develop a theoretical approach to achieving scalable per-node throughput in wireless mesh networks. First, the key factors that limit the per-node throughput of wireless mesh networks are analyzed, through which two major ones are identified, i.e., link sharing and interference. Next, a multi-tier hierarchical architecture is proposed to overcome the link-sharing issue. The inter-tier interference under this architecture is then mitigated by utilizing orthogonal frequency allocation between adjacent tiers, while the intra-tier interference is reduced by considering two specific transmission schemes, one is MIMO spatial multiplexing with time-division, the other is MIMO beamforming. Theoretical analysis shows that the multi-tier mesh networking architecture can achieve a per-node throughput of $\Theta(1)$ in both schemes, as long as certain conditions on network parameters including bandwidth, antenna numbers, and node numbers of each tier are satisfied. A case study on a realistic deployment of 10,000 nodes is then carried out, which demonstrates that a scalable throughput of $\Theta(1)$ is achievable with a reasonable assumption on bandwidth and antenna numbers.Comment: ~12pages, 4 figures, submitted to IEEE TIT, part of this work has been published in IEEE MASS 202

Dynamic simulation of smoke diffusion and gas pollution

Gas pollution is a common phenomenon in natural life. Aiming at the low efficiency of simulating smoke diffusion based on physical model and the poor effect of drawing gas pollution based on empirical model, a hybrid model method is proposed to draw the dynamic gas pollution caused by smoke diffusion. Firstly, the semi Lagrangian method is used to model the smoke, and the k-d tree is introduced to improve the computational efficiency; secondly, to solve the problem of insufficient details in smoke simulation, the fluctuating wind field based on linear filter method is introduced into the external force term to optimize the trajectory of smoke particles; the bidirectional shot function combined with the real smoke texture is selected for rendering to avoid the problem of obvious particle sense and significantly improve the smoke diffusion details; then, the optimized Gaussian plume model is introduced to establish the relationship between the physical model and the empirical model, and the pollution attenuation formula and the optimized Perlin noise are used to improve the lack of details of global gas pollution and increase the realism of gas pollution changes; by improving the time axis algorithm, the problem of fixed gas pollution color is solved, and the dynamic gradual gas pollution is obtained. Finally, several groups of analysis and comparison experiments are designed. The results show that this method can draw a realistic dynamic gas pollution scene in real-time

GPU Accelerated High Intensity Ultrasound Acoustical Power Computation

International audienceThe simulation of the hepatocellular carcinoma therapy effects is often used for the intervention planning. As the physical-based model of the simulation is very time-consuming, the speed of this method becomes an obstacle during the clinical application simulation. In order to accelerate the simulation, a GPU-based (Graphic Processing Unit) acceleration method of the pressure field estimation is proposed in this paper. The results demonstrate that the proposed acceleration method can solve the time-consuming problem

Nicotine Induces Hypoxia-Inducible Factor-1AExpression in Human Lung Cancer Cells via Nicotinic Acetylcholine Receptor ^Mediated Signaling Pathways

Purpose: Nicotine, the major component in cigarette smoke, can promote tumor growth and angiogenesis in various cancers, including lung cancer. Hypoxia-inducible factor-1α (HIF-1α) is overexpressed in human lung cancers, particularly in non - small cell lung cancers (NSCLC), and is closely associated with an advanced tumor grade, increased angiogenesis, and resistance to chemotherapy and radiotherapy. The purpose of this study was to investigate the effects of nicotine on the expression of HIF-1aand its downstream target gene, vascular endothelial growth factor (VEGF), in human lung cancer cells. Experimental Design: Human NSCLC cell lines A549 and H157 were treated with nicotine and examined for expression of HIF-1α and VEGF using Western blot or ELISA. Loss of HIF-1α function using specific small interfering RNA was used to determine whether HIF-1α is directly involved in nicotine-induced tumor angiogenic activities, including VEGF expression, cancer cell migration, and invasion. Results: Nicotine increased HIF-1α and VEGF expression in NSCLC cells. Pharmacologically blocking nicotinic acetylcholine receptor - mediated signaling cascades, including the Ca2+/ calmodulin, c-Src, protein kinase C, phosphatidylinositol 3-kinase, mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2, and the mammalian target of rapamycin pathways, significantly attenuated nicotine-induced up-regulation of HIF-1α protein. Functionally, nicotine potently stimulated in vitro tumor angiogenesis by promoting tumor cell migration and invasion. These proangiogenic and invasive effects were partially abrogated by treatment with small interfering RNA specific for HIF-1α. Conclusion: These findings identify novel mechanisms by which nicotine promotes tumor angiogenesis and metastasis and provide further evidences that HIF-1α is a potential anticancer target in nicotine-associated lung cancer. © 2007 American Association for Cancer Research

Bisphosphonates Suppress Insulin-Like Growth Factor 1-Induced Angiogenesis Via the HIF-1α/VEGF Signaling Pathways in Human Breast Cancer Cells

Adjunctive chemotherapy with bisphosphonates has been reported to delay bone metastasis and improve overall survival in breast cancer. Aside from its antiresorptive effect, bisphosphonates exhibit antitumor activities, in vitro and in vivo, via several mechanisms, including antiangiogenesis. In this study, we investigated the potential molecular mechanisms underlying the antiangiogenic effect of non-nitrogen-containing and nitrogen-containing bisphosphonates, clodronate and pamidronate, respectively, in insulin-like growth factor (IGF)-1 responsive human breast cancer cells. We tested whether bisphosphonates had any effects on hypoxia-inducible factor (HIF)-1α/vascular endothelial growth factor (VEGF) axis that plays a pivotal role in tumor angiogenesis, and our results showed that both pamidronate and clodronate significantly suppressed IGF-1-induced HIF-1α protein accumulation and VEGF expression in MCF-7 cells. Mechanistically, we found that either pamidronate or clodronate did not affect mRNA expression of HIF-1α, but they apparently promoted the degradation of IGF-1-induced HIF-1α protein. Meanwhile, we found that the presence of pamidronate and clodronate led to a dose-dependent decease in the newly-synthesized HIF-1α protein induced by IGF-1 in breast cancer cells after proteasomal inhibition, thus, indirectly reflecting the inhibition of protein synthesis. In addition, our results indicated that the inhibitory effects of bisphosphonates on the HIF-1α/VEGF axis are associated with the inhibition of the phosphoinositide 3-kinase/AKT/ mammalian target of rapamycin signaling pathways. Consistently, we demonstrated that pamidronate and clodronate functionally abrogated both in vitro and in vivo tumor angiogenesis induced by IGF-1-stimulated MCF-7 cells. These findings have highlighted an important mechanism of the pharmacological action of bisphosphonates in the inhibition of tumor angiogenesis in breast cancer cells. © 2009 UICC