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Extracting thermal energy from medium-deep ground layer for building heating is a promising means for pushing forward cleaner heating initiative. There is no available analytical model that can provide fast, accurate and effective simulation of both fluid and soil temperature field of deep borehole heat exchanger (DBHE) under complex geothermal gradient and subsurface stratifications. In this study, a stratified segmented finite line source method (SS-FLS) is proposed as an main contribution and novelty. The proposed model is validated by comparing with finite element method, model degradation example, and actual engineering project data of DBHE. The accuracy and robustness of the SS-FLS is fully checked. Then the effects of stratification on soil temperature field and fluid temperature field are investigated. It is found that the shape of temperature contour and temperature distribution have direct link with stratification as well as heat extraction rate on the heat pump side. Moreover, two critical model parameters are discussed in details which poses an important guide for both model application and system analysis. [Display omitted] • Stratified segmented finite line source (SS-FLS) method is proposed. • SS-FLS model is accurate, fast and easy-implemented for DBHE applications. • Impacts radius of DBHE is enlarging from shallow to deeper layers. • The fluid in the coaxial tube of DBHE is cooled down at the same pace. [ABSTRACT FROM AUTHOR]

Insulators are the most common equipment in power systems, and the failure of insulators would be the direct threat to the stability and safety of the system. With the advantages of being non-contact and non-destructive, infrared imaging technology is efficient for monitoring and evaluating the thermal condition of insulators. Detecting the position of the insulator string in an infrared image is a crucial step for automatic diagnosis, thus an efficient and robust representation of insulator string is necessary. This paper proposes a novel method for insulator strings detection, and presents an appearance representation for insulator strings in infrared image based on Binary Robust Invariant Scalable Keypoints (BRISK) and Vector of Locally Aggregated Descriptors (VLAD). We name this feature generation method Binary Feature Pooling. A classification model based on Support Vector Machine (SVM) is integrated into multi-scale sliding window framework for locating insulator string in infrared image. Then redundant regions are merged by non-maximum suppression and shape prior knowledge constraints. The classification accuracy of the proposed method is 89.1026% on our standard infrared insulator dataset, and insulator strings under various conditions can be successfully detected. The results show that this method can detect multiple insulator strings in infrared images with low resolution and complex background. [ABSTRACT FROM PUBLISHER]

[Display omitted] • A numerical model is proposed for seasonal thermal energy storage (STES) couple with solar collector. • The model is featured as relatively high computational speed and accuracy. • An analysis on technical planning and operational design for the STES is offered. • The key parameters for system design and control are investigated with instructive results. Seasonal thermal energy storage (STES) systems are a key component in expanding the share of renewables in energy programs because they provide schedulability and flexibility. However, such a large-scale system requires careful planning to avoid high investment costs. Therefore, numerical models are becoming increasingly important as an alternative. This paper develops a numerical model of STES coupled with solar collector. The model was verified based on the experimental data of the Huangdicheng Project in China. The results show that the relative error in the charging mode and discharging mode is only 1.57 % and 0.46 %, respectively. Then, the effects of different charging and discharging mode on the heat storage efficiency of the tank and the efficiency of solar collector systems in STES were studied. The study found that in the initial charging stage, the water temperature rise curve caused by different flow rates is very different. In the design of the collector-storage area ratio, the relatively economical collector-storage ratio of this model is around 3768 L/m2. The selection of different proportions of discharging energy in the discharge stage has a great impact on the heat storage efficiency of the system in the next year. Moreover, the influence of different depth-diameter ratios of the tank on the system heat storage efficiency is discussed in detail, which has important guiding significance for model application and system analysis. This paper provides some references for the scale design and operation optimization of cylindrical STES. [ABSTRACT FROM AUTHOR]

The geothermal heat pump system based on deep borehole heat exchanger (DBHE) is one of the important systems to realize cleaner heating. It is key to ensure that DBHE can make full use of the dynamic characteristics of deep heat extraction and recovery (HER) in a long period of time to maintain the stability of geothermal field as well as sustainable development of DBHE and geothermal energy. This study mainly has made contributions in the following four aspects: (1) Through numerical analysis with a "stratified segmented finite line source method" (S2-FLS) and its model analytical expression, the impacts of heating duration and heating load distribution on the long-term operation performance of DBHE is revealed, which provides a theoretical basis for the optimal operation of DBHE. (2) The numerical analysis explained how complex geological conditions affect the dynamic heat extraction and heat recovery of DBHE in intermittent operation mode, which provides a theoretical basis for DBHE drilling site selection. (3) The model robustness is fully checked and an initial investigation on DBHE array with HER is presented, which may lead to massive application of deep geothermal systems. • A robust, efficient and easy implemented model is proposed for deep borehole heat exchanger. • The long-term heat extraction/recovery ability of deep borehole heat exchanger is verified. • Analysis on geological conditions can provide guides for drilling site selection. • The deep borehole array with heat extraction and recover is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: The present work prepared a series of soy protein isolate/agar blend films containing 33% glycerol as plasticizer by solution casting and thermo-molding methods. The microstructure and mechanical properties of the blend films were evaluated in relation to the agar/protein ratio as well as the processing methods. Experimental results revealed that hydrogen bonding interactions existed between soy protein and agar. The casting films possessed more homogeneous interfaces compared with the molding films, leading to the superior mechanical properties than those molding films. Owing to the rigid three-dimensional network formed by the agar, the tensile strength of casting blend films was enhanced. With the increase of agar in the casting blend films, the crosslinking density increased and was responsible for the variations in tensile strength. [Copyright &y& Elsevier]

• A new analytical model is proposed for deep geothermal systems. • New observations in non-uniform insulated system in cooling mode. • Turning points are identified when non-uniformity of insulation is investigated. • Multi-factor based evaluation is performed based on orthogonal test design. Deep borehole heat exchanger (DBHE) based ground source heat pump (GSHP) is a promising system for geothermal energy application in medium-deep layer. In this study, DBHE with non-uniform pipe insulation is proposed and numerically investigated. An effective analytical model is built based on segmented finite line-source method and a newly derived water heat transfer model. The year-round field test data are used for model verification. In-depth analyses are given to a comparison between the uniform and non-uniform insulation cases in both heating and cooling modes, and sensitivity analysis on non-uniformity of insulation. A orthogonal test is conducted for energy performance evaluation and optimization. It is found that DBHE with non-uniform insulation can outperform the one with full insulation in cooling mode, which offers new insights. In addition, an optimum insulation length can be identified through the non-uniformity analysis on insulation. It shows that the order of influence factor is heating season duration ratio, flow rate of working fluid, material thermal resistance non-uniformity of the center pipe, pipe sizing ratio, borehole depth, and insulation length non-uniformity of the center pipe. By choosing the proper system design parameters, the system energy saving could be up to 21.8%. [ABSTRACT FROM AUTHOR]

• A new analytical model is proposed for deep borehole heat exchanger. • The model takes full consideration of seepage, stratification, and geothermal gradient. • The model is featured as high computational speed, robust, and flexibility. • An analysis on heat extraction and recover of single and multiple DBHE is offered. Deep geothermal energy can be used as space heating as an important sustainable, clean and efficient method through deep borehole heat exchanger (DBHE). However, the heat transfer of DBHE is much more complex than conventional shallow borehole and there is no available analytical modeling tool. This study fully considered the complex geological conditions of seepage, stratification, and geothermal gradient in the modeling. A S3-FLS with full name of "stratified-seepage-segmented finite line source method" is proposed and then verified through multi-facets comparison with numerical models and real project data. In addition, the unsteady heat transfer of water flow inside coaxial tube is established and incorporated with the S3-FLS model. The new model is featured as high computational speed, robustness, and flexibility. Those features are supported by the model analysis in this study, via investigating the impact of borehole segmentation, comparison between unsteady and steady water heat transfer and impact of complex geological conditions on system simulation. In addition, it is shown that the model can be easily used for dynamic heat extraction and recovery analysis, as well as DBHE array analysis, through some initial illustrations. [ABSTRACT FROM AUTHOR]

Abstract The concentrations, variations and distribution of molybdenum (Mo) in catchment outlet sediments from China were studied in this contribution based on the results of recently-finished, continental-scale, China Geochemical Baselines (CGB) project. The data from CGB were combined with other published data-sets with the purpose of understanding the spatial distribution of Mo in China and, in addition, relating the observed geochemical features to natural and/or anthropogenic processes. This geochemical mapping with a density of ca. 3000 km2 per site involves catchment sediments in two horizons at each site: a top sample (TOS) at a depth of 0–25 cm and a bottom sample (BOS) at a depth greater than 100 cm. In total, 3382 TOS and 3380 BOS samples were collected. The analytical results show that the concentrations of Mo in the catchment outlet sediments of China range from 0.07 to 57.86 μg/g for the TOS and 0.09–32.43 μg/g for the BOS. The median and mean values of the TOS data are 0.73 and 1.01 μg/g respectively, and those of the BOS data are 0.71 and 0.94 μg/g. The variations of both the TOS and BOS are high at this continental scale. The Mo concentrations vary greatly from one geological and/or geographic unit to another. For instance, from the Cathaysia Block with the TOS and BOS median values of 1.22 and 1.46 μg/g to the North China craton with those of approximately 0.61 and 0.58 μg/g. Various processes govern the spatial distribution of Mo in the catchment sediments of China but regional-scale natural sources (e.g. lithologies) predominate. Sedimentary sandstones and carbonate rocks, alluvium in plain terrain and aeolian materials (e.g. loess) account for the extensive low concentrations (<0.5 μg/g) at such regions as the Songpan-Ganzi orogen and Songliao Basin; whereas shales, basalts and granitoids like granodiorite, plagiogranite and granite porphyry are taken to be responsible for the high concentrations (>1.2 μg/g) in the Yangtze and Cathaysia blocks. Simultaneously, some local mineralized areas can be also identified at this scale because the sampled sites just happened to fall on sediments derived from mineralized rocks or anthropogenic addition by mining activities. Furthermore, the TOS share the similar patterns with the BOS indicating relatively stable inheritance and no apparent extensive secondary enrichment or depletion in the catchment sediments of China. The CGB demonstrates that a series of baseline levels of Mo are needed at different regions and scales and ultra-low density mapping can still deliver robust geochemical patterns. Highlights • Concentrations and distribution of Mo in catchment sediments of China were studied. • The spatial distribution patterns of Mo are dominated by lithologies. • Local mineralized regions can be identified due to proper sampled sites. • Ultra-low density geochemistry can still deliver robust geochemical patterns. • A series of baselines at different scales would be required for various purposes. [ABSTRACT FROM AUTHOR]

This article reports on the fabrication of modified high-density polyethylene (HDPE) foams with complex cellular structure (CCS) using supercritical CO 2 as a physical blowing agent by a cooling and two-step depressurization method. HDPE was modified by dicumyl peroxide (DCP) and carbon nanotubes (CNTs) to improve its viscoelasticity and foaming behavior. The gel content test demonstrated that the cross-linking structure formed in the modified HDPE samples. Compared with that of neat HDPE, the viscoelasticity of modified HDPE was improved largely, which was characterized by rotational rheometer and torque rheometer. The introduction of DCP and CNTs had a slightly effect on the thermal behaviors of HDPE. The foaming properties of various HDPE samples showed that the cross-linking structure caused by DCP improved the foamability of HDPE and CNTs acted as a nucleating agent for cell nucleation. The degree of the first-step depressurization was critical to control the CCS evolution in HDPE foam. [ABSTRACT FROM AUTHOR]

• A three-zone model is proposed for non-uniform heat distribution inside tank storage. • A modified finite cylindrical source model is proposed for ground temperature simulation. • The proposed model is flexible in implementation and efficient in computation. • The new model is compared with numerical validated benchmarks. Buildings consume large amount of energy for cooling in summer and heating in winter. A renewable energy-based district heating using seasonal thermal storage can better serve for a lower carbon space heating for buildings. The research objective is to propose a first semi-analytical model of large-scale water tank storage as an efficient and flexible tool for further development of TES. A new idea of "three-zone method" is proposed for detailed heat and mass flow inside water storage with least increase in computational burden and better capture of internal non-uniform thermal distribution. All three modes of charging, discharging and standby are modeled separately with high flexibility. A modified finite cylindrical source model for TES was proposed, for the first time, for transient heat transfer in the ground, which is inspired by analytical model of ground source heat pump. A complete comparison was made between the new semi-analytical model and validated reference data, which shows a good match in temperature profile in different locations. This study will pave a way for a further systematical study on seasonal thermal storage. [ABSTRACT FROM AUTHOR]

The solvent-coordinated metal cations as templates affecting the architectures of anionic heterothiometallic Mo(W)/S/Ag polymeric clusters was investigated. Four W/S/Ag polymeric clusters {[Tb(DMSO) 8 ][W 3 S 12 Ag 3 ]} n ( 1 , DMSO = dimethyl sulfoxide), {[Tb(DMF) 8 ][W 3 S 12 Ag 3 ]} n ( 2 , DMF = N,N′-dimethylformamide), {[Tb(NMP) 8 ][W 4 S 16 Ag 5 ]} n ( 3 , NMP = N-methyl-2-pyrrolidone) and {[Mg(NMP) 6 ][W 2 S 8 Ag 2 ]·2NMP} n ( 4 ) with distinct 1-D anionic structures were obtained by the reactions of (NH 4 ) 2 WS 4 , AgI and M(NO 3 ) x (M = Tb, x = 3; M = Mg, x = 2) in corresponding solvents (DMSO, DMF or NMP). 1 – 4 were determined by elemental analysis, IR, UV–Vis, thermogravimetric analysis, X-ray powder and single crystal diffractions. Directed by different solvent-coordinated trivalent terbium metal cations, 1 shows a 1-D anionic helical chain architecture; 2 exhibits a 1-D anionic zigzag chain with hexanuclear [W 3 S 12 Ag 3 ] 3 − repeated units; 3 possesses another kind of 1-D anionic zigzag chain with the unique nonanuclear planar square-like [W 4 S 16 Ag 5 ] 3 − repeated units. While induced by NMP-coordinated bivalent magnesium metal cation, 4 exhibits a 1-D anionic linear chain structure. [ABSTRACT FROM AUTHOR]

A novel flame retardant TGIC-DOPO, which was constructed by phosphaphenanthrene and triazine-trione groups, was synthesized via a controllable ring-opening addition reaction between 1,3,5-triglycidyl isocyanurate (TGIC) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The flame-retardant effect of TGIC-DOPO on an epoxy resin, diglycidyl ether of bisphenol-A (DGEBA), cured with 4,4'-diamino-diphenyl sulfone was investigated. The results of the limited oxygen index (LOI), UL94 vertical burning test, and cone calorimeter test indicated that the TGIC-DOPO imparted flame-retardant properties to DGEBA thermosets. When the mass fraction of TGIC-DOPO reached 12wt.%, the DGEBA thermoset acquired a LOI value of 33.3%, UL94 V-0 rating, and the lower peak of heat release rate (pk-HRR) at 481 kW/m². Specifically, the DGEBA thermoset with 6wt.% TGIC-DOPO had an LOI value of 33.3%, whereas the DGEBA thermoset with 10wt.% TGIC-DOPO had the highest LOI value of 35.2% among the specimens. Meanwhile, the time to ignition, pk-HRR, average of effective heat of combustion (av-EHC), and total heat release of the DGEBA thermoset were all negatively correlated with the mass fraction of TGIC-DOPO. Moreover, the average CO2 and CO yields exhibited a downtrend with increasing mass fraction of TGIC-DOPO from 6wt.%. The reduction of av-EHC with increase of TGIC-DOPO content in thermosets confirmed the free radical quenching effect of TGIC-DOPO in gaseous phase during combustion. The macromorphology, micromorphology and element content of the residues from the cone calorimeter test revealed the bi-phase flame-retardant effect of TGIC-DOPO. Furthermore, the pyrolysis route of TGIC-DOPO were investigated via Py-GC/MS, which disclosed that the decomposed TGIC-DOPO with double flame-retardant groups released various fragments with quenching effect on free radical chain reaction of combustion. The fragments enhanced the flame-retardant performance of DGEBA thermosets both in gaseous and condensed phases. The flame-retardant performance of TGIC-DOPO was resulted by the quenching effect of TGIC-DOPO and the synergistic effect of phosphaphenanthrene and triazine-trione groups. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA)/polybutylene succinate (PBS) and the PLA/PBS/montmorillonite (MMT) composites were prepared by melt extrusion. The morphology structure, mechanical, thermal, and dynamic rheological properties of the composites were characterized, as well as foaming extrusion behavior of the composites was also studied. The results showed that MMT particles were intercalated into the PLA/PBS matrix forming an ‘intercalation’ structure. The toughness of PLA could be improved by blending with PBS. The comprehensive evaluation of mechanical properties of PLA/PBS was further improved by adding MMT. MMT could play the role of heterogeneous nucleation to improve the crystallization effect of PLA/PBS composite. The melt strength of PLA could be significantly increased by the synergies of MMT and PBS. Meanwhile, MMT could act as a compatibilizer to enhance the interfacial interaction between PLA and PBS. The synergies of PBS and MMT effectively reduced the density of PLA blend foam products, and increased their cell density, uniformity of cell size, and shape distribution. [ABSTRACT FROM PUBLISHER]

Deep convolutional neural networks (DCNNs) with alternating convolutional, pooling and decimation layers are widely used in computer vision, yet current works tend to focus on deeper networks with many layers and neurons, resulting in a high computational complexity. However, the recognition task is still challenging for insufficient and uncomprehensive object appearance and training sample types such as infrared insulators. In view of this, more attention is focused on the application of a pretrained network for image feature representation, but the rules on how to select the feature representation layer are scarce. In this paper, we proposed a new concept, the layer entropy and relative layer entropy, which can be referred to as an image representation method based on relative layer entropy (IRM_RLE). It was designed to excavate the most suitable convolution layer for image recognition. First, the image was fed into an ImageNet pretrained DCNN model, and deep convolutional activations were extracted. Then, the appropriate feature layer was selected by calculating the layer entropy and relative layer entropy of each convolution layer. Finally, the number of the feature map was selected according to the importance degree and the feature maps of the convolution layer, which were vectorized and pooled by VLAD (vector of locally aggregated descriptors) coding and quantifying for final image representation. The experimental results show that the proposed approach performs competitively against previous methods across all datasets. Furthermore, for the indoor scenes and actions datasets, the proposed approach outperforms the state-of-the-art methods. [ABSTRACT FROM AUTHOR]