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Background: Nicotiana belongs to the Solanaceae family that includes important crops such as tomato, potato, eggplant, and pepper. Nicotiana species are of worldwide economic importance and are important model plants for scientific research. Here we present the comparative analysis of the transcriptomes of six wild diploid Nicotiana species. Wild relatives provide an excellent study system for the analysis of the genetic basis for various traits, especially disease resistance. Results: Whole transcriptome sequencing (RNA-seq) was performed for leaves of six diploid Nicotiana species, i.e. Nicotiana glauca, Nicotiana noctiflora, Nicotiana cordifolia, Nicotiana knightiana, Nicotiana setchellii and Nicotiana tomentosiformis. For each species, 9.0-22.3 Gb high-quality clean data were generated, and 67,073-182,046 transcripts were assembled with lengths greater than 100 bp. Over 90 % of the ORFs in each species had significant similarity with proteins in the NCBI non-redundant protein sequence (NR) database. A total of 2491 homologs were identified and used to construct a phylogenetic tree from the respective transcriptomes in Nicotiana. Bioinformatic analysis identified resistance gene analogs, major transcription factor families, and alkaloid transporter genes linked to plant defense. Conclusions: This is the first report on the leaf transcriptomes of six wild Nicotiana species by Illumina paired-end sequencing and de novo assembly without a reference genome. These sequence resources hopefully will provide an opportunity for identifying genes involved in plant defense and several important quality traits in wild Nicotiana and will accelerate functional genomic studies and genetic improvement efforts of Nicotiana or other important Solanaceae crops in the future. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by thermal foaming of active cross-linkable units terminated polyester ammonium salts (PEAS) precursor powders. The active cross-linking strategy was realized by breaking C C bonds in maleic anhydride under heating treatment. Results showed that the formation of cross-linked structure before complete imidization effectively resisted matrix shrinkage and endowed PIFs with outstanding mechanical properties. The room temperature compressive strength and modulus of PIFs with four repeating units reached as high as 2.34 and 56.1 MPa, respectively. Moreover, the PIFs exhibited excellent thermal properties with onset decomposition temperatures ranging from 490 to 550 °C and the glass transition temperatures exceeding 290 °C. The PIFs displayed better thermal insulation, and the values of thermal conductivity fell within a range of 0.056–0.090 W m−1 K−1, which demonstrates potential application as high temperature resistant structural materials in aerospace and energy sectors. [Display omitted] • Rigid PIFs were fabricated by thermal foaming of active cross-linkable units terminated PEAS precursor powders. • Cross-linking structure was formed before complete imidization which endowed PIFs with outstanding mechanical properties. • Relationship between chain structure and properties of rigid PIFs were investigated. [ABSTRACT FROM AUTHOR]

Background: Tobacco (Nicotiana tabacum L.) is an important model system, which has been widely used in plant physiological studies and it is particularly useful as a bioreactor. Despite its importance, only limited molecular marker resources are available for genome analysis, genetic mapping and breeding. Restriction-site associated DNA sequencing (RAD-seq) is a powerful new method for targeted sequencing across the genomes of many individuals. This approach has broad potential for genetic analysis through linkage mapping. Results: We constructed a RAD library using genomic DNA from a BC1 backcross population. Sequencing of 196 individuals was performed on an Illumina HiSeq 2500. Two linkage maps were constructed, one with a reference genome and another, termed as de novo identification of single nucleotide polymorphism (SNP) by RAD-seq, without a reference genome. Overall, 4138 and 2162 SNP markers with a total length of 1944.74 and 2000.9 cM were mapped to 24 linkage groups in the genetic maps based on reference genome and without reference, respectively. Conclusions: Using two different SNP discovery methods based on next generation RAD sequencing technology, we have respectively mapped 2162 and 4318 SNPs in our backcross population. This study gives an excellent example for high density linkage map construction, irrespective of genome sequence availability, and provides saturated information for downstream genetic investigations such as quantitative trait locus analyses or genomic selection (e.g. bioreactor suitable cultivars). [ABSTRACT FROM AUTHOR]

To optimize the structural parameters of the enhanced cyclone with shunt device (ECSD), the effects of the cylinder-to-cone ratio and the vortex finder-to-cylinder ratio on the performance of the ECSD were studied. The Reynolds stress model and discrete phase model were used to capture the three-dimensional strong rotational turbulence in the ECSD and predict the motion of particles, respectively. The simulation results show that the optimal cylinder-to-cone ratio ranges from 0.5 to 2.8, and both the total and reduced separation efficiencies of the ECSD can reach more than 80% when the vortex finder length keeps 100 mm or the vortex finder-to-cylinder ratio remains 0.67. The maximums of total and reduced separation efficiencies are 88.4% and 86.9%, respectively, with the cylinder-to-cone ratio of 1.63 and vortex finder-to-cylinder ratio of 0.67, which is different from the optimal cylinder-to-cone ratio for a Stairmand cyclone. [Display omitted] • Optimal cylinder-to-cone ratio for the performance of ECSD is 1.63. • The overall energy consumption decreases with increasing cylinder-to-cone ratio in general. • The position of cylinder-cone interface is an important factor affecting the short-circuit flow. • When cylinder-to-cone ratio is too large, the longer vortex finder can make flow field of ECSD more stable. [ABSTRACT FROM AUTHOR]

Because of insufficient research on single well groundwater heat pump systems, a physical simulation experiment table has been set up to study the flow and heat transfer law in these systems. Experimental research on building load variations has been carried out. The results show that in the same experimental conditions the absorption quantities of standing column well (SCW) are only 50. 3% and 45. 9% of pumping and recharging well ( PRW) and pumping and recharging well filled with gravel (PRWFG) respectively. In addition, the radial thermal influence scope of SCW is less than 186. 5 mm. However, the heat absorption quantities of SCW, PRW and PRWFG reduce to 51. 0%, 31. 6% and 19. 5% individually, when the flow rate of outlet water drop from 0. 54 m³/h to 0. 315 m³/h. Thereby the load capacity of SCW is the least one in these three systems. However, the variation of the flow rate of outlet water can impact on SCW more significantly. It is more obvious that increasing the flow rate of the outlet water can improve the load capacity and the thermal influence scope of the thermal source wells. Thus, the load capacity of thermal source wells can be increased. [ABSTRACT FROM AUTHOR]

As the global energy crises and environmental problems become more and more serious, ground source heat pump (GSHP) systems are perhaps the most widely used green HVAC system, with an estimated 1.1 million ground source heat pumps installed worldwide. These systems have become an important energy-saving and environment protection technology for use in residential and commercial buildings in China. These applications included two types of systems: closed-loop (ground-coupled) and open-loop. As one kind of semi-closed-loop systems, single well groundwater heat pump (SWGWHP) systems have become increasingly popular for use because of their economic advantages from lower installation cost, lower operating cost, and improved overall performance in regions with suitable geological conditions. In general, SWGWHP systems included three different variations, i.e. standing column well (SCW) system, pumping & recharging well (PRW) system, and pumping & recharging well filled with gravel (PRWFG) system. Compared with SCW system, the well pipe in PRW system and PRWFG system are divided into three parts by clapboards, i.e. production zone, seals zone and injection zone. In recent decades, considerable research efforts have been spent on SWGWHP systems, especially on SCW system. However, little attention has been focused on the PRW system and PRWFG system. For GSHP systems, sand tank experiment is one of the important methods of laboratory investigation for discussing the performance of geothermal heat exchanger, due to many parameters can be set and adjusted more easily and economically than that in in-situ experiments. In order to provide a framework for discussing the influence on distances between pumping and injection screens (DPI) in SWGWHP systems, a sand tank experiment system was designed and set up in Harbin Institute of Technology, China. In this study, we tested the temperature of outlet and inlet water, the aquifer temperature, and flow rate of outlet water. From the reasonable results obtained in these tests, the absorption and rejection quantities of SWGWHP systems were calculated. The results pointed out that with increasing the DPI, the outlet water temperature and heat transfer quantities of these three kinds of thermal wells can be improved significantly. When the conditions permit, the DPI should be increased greatly. Additionally, when the DPI increases the same value, the improvements of outlet water temperature are as follows: the SCW system is the best, followed by PRWFG system, and PRW system. It can be concluded that increasing the DPI is more beneficial to the thermal well with serious thermal breakthrough. Moreover, when the DPI is short, increasing the DPI can improve the temperature difference between outlet and inlet water and heat absorption quantities of PRW system significantly. When the DPI increases to a certain value, this improvement of thermal breakthrough is not significant. However, the PRWFG and SCW systems are different, i.e. increasing the DPI that benefits are always obvious. With the distance between the measuring point and thermal well increasing, the influence of thermal well on the measuring point is weaker. With the DPI increasing, the influence of the cold inlet water on the radial extent of the aquifer is weaker. The thermal influence scope of SCW system is the smallest one among the three types of thermal wells. Although there are some differences between the laboratory model tests and complexity of the practical geological conditions, the rules obtained from the experiments for the guidance of practical project still have great significance. [ABSTRACT FROM AUTHOR]

In recent years, there are many subway lines under construction in cold regions of China. In severe cold regions, due to the harsh winter weather, cold protection has become a key task for subway operations. In this study, field experiments on the influence of cold protection technologies on the thermal environment and train-induced unsteady airflow (TIUA) of a typical island station in Harbin were conducted. The results show that the temperature, wind speed, and air volume of the entrance and the piston duct all change periodically under the driving interval. For the cold protection technologies at the entrance and exit, the cold-proof effect of the door curtain is stronger than that of the hot air curtain and the outer door. The air inflow and outflow volumes through the entrance without the inner and outer curtains are 1.4–2.2 and 2.1–2.3 times higher than those with inner and outer curtains, respectively. For the cold protection technologies at piston duct, the cold-proof effect of electric roller blinds is stronger than that of wind pavilion cover. Compared with the use of the two cold protection technologies, the average temperature of the piston duct when the electric roller shutter is fully opened is 1.8–2.0 °C lower than it, and the air inflow and outflow through the piston duct are also 1.3 and 1.4 times higher than it respectively. • The effect of cold protection technologies at entrance and piston duct was analyzed. • Periodical changes in temperature, wind speed and TIUA affect by driving interval. • The door curtain at entrance effectively prevent the intrusion of cold air. • Cold-proof effect of electric roller blinds was stronger than wind pavilion cover. [ABSTRACT FROM AUTHOR]

In recent years, numerous subway lines have been under construction with the rapid development of subways in the cold regions of China. Harbin, a typical city in severe cold regions, has harsh winter weather, and the lowest outdoor temperature can reach −37.7 °C. Therefore, the thermal environment of the station and the thermal comfort of passengers are facing huge challenges. Owing to the complexity of the subway environment, few field test studies, especially long-term tests, have been conducted. In this study, long-term field test on the thermal environment, questionnaire survey and thermal comfort analysis of two typical subway stations were conducted. A revised comfort temperature was proposed based on the constant changes in passenger metabolism. The field test results showed that the temperature and moisture content of the station were affected by the type of platform door, interval driving, operating time, and piston effect. The results of the questionnaire survey showed that the temperature, humidity, and thermal comfort of the two subway stations were satisfactory for most passengers. Passengers experienced a noticeable draft only in the aisle. After calculation, the lower limits of the comfortable temperature for the aisle, hall, and platform of the Harbin Metro were determined to be 10.6, 11.2, and 13.8 °C, respectively. The data obtained in this study provide a valuable reference for the construction and operation of subways in severe cold regions. • Long-term field test of subway stations in severe cold region was conducted. • Low limits of the comfortable temperature were proposed. • Thermal environment made more than 70% of passengers feel comfortable. • Passengers were always in a state of hot deficit from outdoor to platform. [ABSTRACT FROM AUTHOR]

• A comprehensive failure consequence evaluation model of DHNs is proposed. • The topological loss index evaluates the vulnerability of DHNs from the perspective of topology. • The functional and economic loss indexes measure the loss of heating quality and property economy after failures, respectively. The control system of some existing district heating networks (DHNs) is not sufficient to handle urgent failure scenarios, which cannot make timely and effective responses within a short period after failures. The failure of this uncontrollable DHN will cause more severe consequences. To search critical areas for protection, this study proposed a failure consequence evaluation model. Then, the calculation model of each evaluation index was established based on graph theory, information entropy and safety economics considering topology, function, casualty and economy losses. Spearman correlation coefficient was applied to analyze the correlation of various evaluation indexes and we studied the applicability of each index. Finally, we simulated a single-heat-source DHN case for failure consequences. According to the simulation results, the critical isolation areas are effectively-identified, and the results indicate the applicability of the evaluation model. Moreover, the factors affecting the failure consequences were explored through sensitivity analysis. Among the three sensitive factors of maintenance time, unit price of electricity, water and heat, compensation coefficient, the maintenance time has the most significant influence on failure consequences. When the maintenance time reduces by 20%, the property economic loss in each isolation area reduces by 8.5–29.28%. [ABSTRACT FROM AUTHOR]

PURPOSE: To explore the mechanism of failure of ProTaper NiTi handfiles during root canal preparation. METHODS: A total of 2061 discarded ProTaper handfiles were collected after clinical use. The files were studied under stero-microscope to determine the type of defect. The fractured files were photographed digitally and the pictures were analyzed by software Image-Pro Plus to measure the distance from the break point to the tip. The data were statistically analyzed by using SPSS 11.0 software package. RESULTS: Plastic deformation was observed in 166 files (8.2%), and the types of defects included unwinding, winding flutes, and plastic bending. Instrument separation occurred in 581 files (28.2%), and the fracture rate was the highest in the F2 file group (41.7%). The Sx file group had the highest facture level, and the mean distance from the breakpoint to the file tip was (4.4±1.1) mm. CONCLUSIONS: For shaping files, especially at the apical level, the main cause of menial failure is overload of torque, whereas for finishing files, especially at the higher level, is cycle fatigue. Understanding the defect types of ProTaper handfiles is useful for avoiding file breakage during root canal therapy. [ABSTRACT FROM AUTHOR]

A new algorithm was presented to deal with the multi-target tracking problem. Firstly the target number in an interest region was modeled as a stochastic process; secondly the state vector was augmented with target number; and finally the state estimation was carried using the multi-model particle filter (MMPF) , and the numerical simulation was proposed to identify the efficiency of this method in multi- sensor/multi-target tracking application. The simulation results show that the improved method can be applied to track the maneuvering targets effectively by using the non-linear dynamic model. [ABSTRACT FROM AUTHOR]

The experiments were carried out to test the effect of air temperature and humidity on a novel PCM based reversed-cycle defrosting for air source heat pump( ASHP), and the results showed that PCM based reversed-cycle defrosting method could keep the suction pressure of compressor higher than 0. 35 MPa, which was father higher than the system's low suction protection pressure. The system's defrosting time and energy consumption increased with the relative humidity when air temperature was kept constant. Furthermore, the system's defrosting time and energy consumption increased first and then decreased with the decrease of air temperature, and the most defrosting time and energy were consumed when the outdoor air temperature was -3 °C. It could be concluded that the air temperature and humidity affected the defrosting process greatly and the system's reliability was improved greatly because shutting down of ASHP unit due to low suction pressure protection during defrosting could be effectively avoided by the PCM based heat exchanger, and - 3 °C working condition could be selected as the most adverse design condition for the PCM based heat exchanger when the relative humidity was constant because the most defrosting time-and energy were needed. [ABSTRACT FROM AUTHOR]

To discuss the operating characteristics of a new kind of energy-storage air source heat pump when supplying hot water, the unit's performance in different conditions was studied by experiments. The results show that the unit can operate efficiently and stably, and the unit's mean REE reduces with the increase of hot water supply flux. There also exists a break of hot water supply because the high flow rate of circulation water causes intensive disturbance in the heat storage tank, and the time of break is prolonged with the decrease of outdoor temperature. Moreover, the heat supple ability and mean REE of the unit reduces with the decrease of outdoor temperature. [ABSTRACT FROM AUTHOR]

To study the energy utilization of heat pump station for the recovery of waste heat of circulating water in the steam condenser of a coal-fired power plant, the primary energy ratio of the heat pump stations driven by different energy sources for the reclamation of waste heat was analyzed through energy flow diagram. The results show that the electric heat pump energy-supply system consumes 45.79% electricity although the total efficiency of electric heat pump energy-supply system is only 2% lower than that of heat pump energy - supply system driven by steam turbine, as well as approximately equals to that of system driven by gas turbine. Moreover, the situation maybe occurs that the electricity generated by power plant is not enough to its heal pump station with the decrease of the electric generation efficiency and COP of heat pump. By contrast, the primary energy ratio of the heat pump stations driven by steam turbine and gas turbine reaches 1.57 and 1.60, 14.77% and 17.00% higher than that of electric heat pump station, respectively, because of introducing the primary energy exteriorly. Therefore, the heat pump stations driven by steam turbine and gas turbine are better than the electric heat pump station in energy utilization. [ABSTRACT FROM AUTHOR]

To research the principle of air-source heat pump water unit with energy storage and the application feasibility in this field, the prototype of the hot water unit is developed. Performance of the unit in every mode is studied by experiments. Test results show that the unit can efficiently work in multiple modes, such as heat storage mode, heat and cooling storage mode, hot water supply mode, hot water and chilled water supply mode. Especially, the unit works with higher average energy efficiency ratio in heat and cooling storage mode as well as hot water and chilled water supply mode. In energy storage process, water temperature distribution in hot/chilled water tanks is comparatively uniform, which is favorable for improving the capacity of thermal storage. At the mean time, increasing accumulator volume and debasing location of compressor startup can improve the energy-saving potential and enhance reliability of the unit. [ABSTRACT FROM AUTHOR]

Using phase change material of phase-change temperature 6 °C, a triple-sleeve energy storage exchanger was proposed, in which the exchanger, air source and solar heat pump were integrated. Cool storage characteristics of the triple-sleeve energy storage exchangers with direct evaporative was simulated by a mathematical model. Comparing with the traditional ice storage, the average evaporation temperature of high-temperature phase change cold storage was 10 °C higher than that of the ice storage. The COP values of high-temperature phase change cold storage were increased by nearly 25 percent than that of the ice-storage. The power saving rate of the phase change cold storage achieved 36% at the same cooling capacity. [ABSTRACT FROM AUTHOR]

To study the effect of aquifer's hydro geological conditions on standing column well (SCW), the operating characteristics of SCW under different hydro geological parameters were analyzed through large numbers of calculation eases. The results show that the aquifer with larger horizontal permeability coefficient enhances the ratio of original groundwater exchange and lightens the change of pumping temperature. The aquifer stagnant thermal conductivity has little effect on pumping temperature if SCW is in the aquifer with good permeability, however, if with poor permeability, the pumping temperature would be rapidly increased with the increase of the aquifer stagnant thermal conductivity. The permeability coefficient is a key parameter to influence the change extent of pumping temperature obviously. [ABSTRACT FROM AUTHOR]

Using the mathematical model validated by a field test, the perennial operation of pumping & recharging well (PRW) was simulated to explore the feasibility and potential of seasonal thermal energy storage (STES) of PRW. Meanwhile, a quantitative analysis model of STES was established based on the pumping and reinjeetion temperature. Results show that for the existence of thermal breakthrough, the operation of previous seasons has much effect on the temperature of pumping water in the later operation seasons. This behavior verifies that the PRW apparently has the phenomenon of STES. If the accumulated loads of space heating and cooling are kept in balance, the pumping temperature and the thermal energy storage ratio will basically remain unchanged. For a PRW in Beijing with summer-winter operation mode, the STES approximately provides 73% of low-temperature heat source and 24% of heat sink. However, if the accumulated loads are in unbalance, the pumping temperature will increase or reduce much annually and even the PRW may not work. [ABSTRACT FROM AUTHOR]

• Effect of vapor injection on defrosting performance is studied. • An optimal opening of injection electronic expansion valve exists. • Defrosting time can be shortened by 20.61% by vapor injection. • 17.98% reduction in power consumption is obtained at the optimal opening. • Defrosting efficiency is increased by 6.22% at the optimal opening. During the defrosting process in cold regions, the air source heat pump with vapor injection encounters some problems, e.g. long defrosting time and low defrosting efficiency. To solve these problems, a new defrosting strategy through injecting medium-pressure vapor refrigerant into compressor during defrosting process was proposed based on its special structure. Five groups of experiments having different openings of injection electronic expansion valve were designed and conducted to investigate the effect of this defrosting strategy. Results indicate that an optimal opening of injection electronic expansion valve exists during defrosting process with vapor injection. For the experimental air source heat pump, it is 50%. At the opening of less than 50%, the experimental unit can run safely and defrosting performance improves gradually with the opening increase. When the opening increases to greater than 50%, the defrosting process is unsteady. At the optimal opening of injection electronic expansion valve, the defrosting time and power consumption are respectively decreased by 20.61% and 17.98%, while the defrosting efficiency is improved by 6.22%. [ABSTRACT FROM AUTHOR]

Lightweight and excellent mechanical properties rigid polyurethane foams (RPUFs) play an irreplaceable role in aerospace, construction and transportation fields. Microstructure is an important factor in controlling properties of RPUFs. In this study, RPUFs with different cell structures were fabricated by adjusting foaming agent. The relationship between cell structure parameters (cell size, wall thickness, closed cell rate and cell anisotropy) and density was determined based on SEM analysis. The compressive, bending, impact, heat insulation and sound insulation properties were tested. The results showed that cell structure was related to mechanical properties, which was reflected in the linear relationship between log (density) and log (mechanical properties). RPUF 0.4 with a density of 148 kg/m3 possessed excellent compressive strength, flexural strength, flexural modulus and impact strength of 2.89 MPa, 2.60 MPa, 35.41 MPa and 1.06 kJ/m2. Thermal and sound insulation properties were depended on cell size and closed cell rate, the thermal conductivity of RPUFs ranged from 0.0398 to 0.0515 W/(m·K), and the sound transmission loss of RPUF 1.4 exceeded 25 dB in 500–5000 Hz. The comprehensive properties were regulated by adjusting cell structure, which provides a theoretical basis for the design of RPUFs with specific properties. [Display omitted] • The rigid polyurethane foams (RPUFs) with different cell sizes were fabricated through adjusting H 2 O content. • The mechanical, thermal and sound insulation properties of RPUFs were studied based on the cell structure and density. • The relationship between density and mechanical properties was constructed to predict the properties of RPUFs. • The RPUFs exhibited excellent comprehensive properties, which were expected to serve as building materials. [ABSTRACT FROM AUTHOR]

• ECSF has a maximum total separation efficiency of 95 % and 77 % for PM10 and PM2.5. • Auxiliary airflow can remove the particles deposited in discharge pipe with its velocity no exceeding 5 m/s. • The diameter of underflow pipe should not be smaller than that of cone outlet. • In addition to the inner and outer vortices, there is also a reversed vortex in the ECSF. A novel cyclone design called enhanced cyclone with split flow (ECSF) incorporates bypass flow and underflow to eliminate or suppress localized secondary flow observed in conventional cyclones. The present study aims to investigate the mechanism of ECSF in suppressing localized secondary flow and explore methods for regulating the bottom flow rate. The turbulent characteristics within the ECSF are obtained using Reynolds stress model, while the trajectory of particles is predicted using discrete phase model to derive the separation performance. The accuracy of the simulation model has been validated through experimental verification. The results demonstrated that the full separation efficiency of ECSF for PM10 and PM2.5 remained above 90 % and 70 %, respectively. Moreover, it exhibited an increasing trend with the rise in the full split ratio, eventually stabilizing at approximately 95 % and 77 %, correspondingly, when the full split ratio reached 20 %. The bypass flow and underflow effectively eliminated or suppressed the upper ash ring and processing vortex core (PVC) phenomenon, respectively. However, the exacerbation of the short-circuit flow phenomenon hindered further improvement in separation efficiency beyond a full diversion ratio of 20 %. When the full split ratio is relatively small, particles may accumulate in the discharge pipe, which can be resolved by introducing auxiliary airflow; however, it is crucial to ensure that the flow rate of auxiliary flow does not exceed 14.29 % of that of feed flow to avoid compromising the separation efficiency. Furthermore, the split flow induces an additional reversed vortex within the ECSF, which extends from the overflow pipe to conical section. Its structural characteristics are influenced by both back pressure of discharge outlet and diameter of underflow pipe. To ensure optimal performance of the ECSF, it is recommended that the underflow pipe diameter should not be smaller than that of the outlet in conical section. [ABSTRACT FROM AUTHOR]

Polyimide foam (PIF) has been extensively used as structural and thermal insulation materials. Five semi-rigid PIFs with different diamine structures were fabricated by unrestricted foaming process with polyester ammonium salt (PEAS) precursor powders. All PIFs exhibited a nearly homogeneous spherical closed pore structure with an average pore size of 123–335 μm and a high closed-cell rate (87.4–95.5%). Results indicated that the molecular structure, melt viscosity and foaming temperature were important factors that affected the foaming process and pore structure. The values of 10% compression strength of PIFs at both 25 and 200 °C were in the range of 0.16–0.35 and 0.09–0.16 MPa, respectively, with PIF BTDA-MDA and PIF BTDA-DMBZ exhibiting the best mechanical performance. All PIFs exhibited outstanding thermal stability, with glass transition temperatures of 312–378 °C and 5% weight loss temperatures of 504.5–564.5 °C in nitrogen and 501.8–562.0 °C in air, respectively. The prepared PIFs exhibited extremely low thermal conductivity and thermal diffusivity, which can be used as thermal insulation materials. Based on above findings, the prepared semi-rigid PIFs demonstrate a great potential for being utilized as thermal insulation and structural support materials in high-tech fields such as aerospace, marine transportation, and microelectronics. [Display omitted] • Lightweight semi-rigid PIFs were prepared using PEAS precursor foaming method. • The foaming behavior was affected by molecular structure and foaming temperature. • The melt viscosity of PEAS determined the cell structure of PIFs. • All PIFs exhibited superior mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

• The valve network model simplifies the reliability analysis of DHNs. • The hierarchy structure of DHNs is proposed considering topology and reliability. • The evaluation models imply relationship between reliability segment elements. • The reliability design rules are proposed to divide reliability segments in DHNs. As a kind of critical infrastructure, district heating networks (DHNs) ensure people's life and productivity in cold area. Optimizing the reliability of DHNs has been an urgent topic for many scholars. In this study, we defined reliability segments to build a valve network, and established branched and looped pipeline models. We varied the number, heat load, and length of the reliability segments to study their influence on reliability. Then, we proposed reliability design rules for single-heat-source branched and single-looped DHNs. For branched DHNs, the failure effect of an upstream reliability segment is more serious than that of a downstream segment. The core of these rules is to ensure the reliability segment closer to the heat source contains more heat load and few fault components. For single-looped DHNs, the failure effect scope of each reliability segment is only itself. The core of these rules is to ensure the reliability segment that cannot easily fail contains more heat load. Both sets of design rules are to improve the DHN reliability by reducing the fault probability of reliability segments with severe failure effect. Finally, a case study of reliability segment design on a single-looped DHN proved the effectiveness of the proposed design rules. [ABSTRACT FROM AUTHOR]

The feasibility of the enhanced cyclone with split flow (ECSF) for applications in high temperature conditions and complex spaces was validated through numerical simulation, investigating the influence of operating temperature and tilt angle on ECSF performance and flow field. The Reynolds stress model and discrete phase model were employed to calculate the intricate rotating turbulence and trajectories of particle motion within the ECSF, respectively. The findings demonstrate that the separation capacity of ECSF diminishes with the increment of operating temperature. Moreover, the tilt angle has negligible influence on both performance and flow field characteristics of ECSF regardless of high or low feed flow rates or operating temperatures. This means that ECSF can be flexibly installed. This research provides valuable insights for promoting wider applications of ECSF. [Display omitted] • Separation efficiency and energy consumption of ECSF decrease with increasing operating temperature. • Suppression of local secondary flow by split flow is enhanced with increasing operating temperature. • Increase of operating temperature changes the triple-vortex structure of ECSF into a double-vortex structure. • ECSF can be installed flexibly as tilt angle has almost no effect on its performance and flow field. [ABSTRACT FROM AUTHOR]

A new multi-row helically coiled tube (MHCT) heat exchanger was applied in surface water-source heat pump system in recent years. To investigate the heat transfer and pressure drop characteristics of the MHCT heat exchanger, an experiment system was built to realize the heat extraction in winter and heat rejection in summer with low velocities of surface water. Four experiment modes were conducted by varying the parameters of surface water and medium. The results show that the increase of the inlet temperature or velocity of medium and the temperature of surface water can improve inside convection intensity, among which the effect of medium velocity is the most distinct. Besides, the mixed heat convection was carried out on surface water side, and the intensity was also affected by the variation of the medium parameters. As the temperature of surface water or medium and the medium velocity do a change with a constant surface water velocity, the effect of natural convection is critical to outside convective intensity. Through comparisons, it is acceptable to take arithmetic average coil diameter into the SHCT correlations of inside Nusselt number and friction factor for the engineering design of the MHCT. The correlations of purely forced convection on the MHCT underestimate the experimental outside Nusselt numbers and cannot consider the effects of medium side. • The thermal interaction between the surface water and the medium was considered. • The variation of medium parameters influence the outside convection intensity. • A comparison with the previous works on Nusselt number was carried out. • The correlations of purely forced convection underestimate outside Nusselt number. [ABSTRACT FROM AUTHOR]

Controlling the turbulence intensity helps to reduce the energy consumption of the hydrocyclone. In de-foulant hydrocyclone (DFH), reducing the energy consumption can improve the overflow kinetic energy to suck and flush away the foulants at underflow. In this study, a conical surface (CS) is inserted near the locus of zero vertical velocity (LZVV) to control the turbulence intensity of DFH. We investigated the effects of different sizes and positions of CS and the inlet velocity on the separation performance. The results showed that, owing to the presence of CS, the energy consumption of the DFH was decreased by approximately 40% whereas the separation efficiency increased by approximately 5%. Moreover, the separation efficiency first decreased and then increased with the increase in inlet velocity, which was different from that of the DFH without CS. Furthermore, we also found that radial particle migration mainly occurred at the cone bottom of the DFH. Unlabelled Image • A hydrocyclone with an inner conical surface (CS) is proposed. • Approximately 40% of the hydrocyclone energy consumption decreased by CS. • The CS improved the hydrocyclone separation efficiency. • The CS weakened the turbulence and increased the split ratio. [ABSTRACT FROM AUTHOR]

Strata thermal conductivity (λ e) influences efficiency of medium-depth ground heat exchangers. However, a systematic approach to the acquisition of λ e is still lacking. Hence, stratigraphic heat conduction was analyzed using geophysical test in Shenyang, combined with composite modeling. Cenozoic strata (0–730m) exhibited an average λ e of 1.32 W·m−1·K−1 due to higher porosity and mud content; Archaean (730–2500m) strata displayed a higher λ e of 2.80 W·m−1·K−1, due to dense quartz sandstone with lower porosity and mud content. The CBHE in Shenyang can achieve excellent heat extraction relying on good thermal conduction. Spearman correlation revealed strong negative correlations between λ e and acoustic time difference, permeability, and porosity, while positive correlations were observed with depth, resistivity, wave speed, and rock skeleton. Higher rock skeleton thermal conductivity intensified the decrement effect of mud content on λ e , while higher mud content diminished the enhancement effect of rock skeleton thermal conductivity. As porosity increased, the decline in λ e slowed, particularly pronounced at higher saturation levels. λ e exhibited a gradual decrease with temperature, with a more notable change rate observed at lower porosity levels. Principles for enhancing thermal conduction were elucidated through a three-phase analysis. These findings provide foundation for the study and design of medium-depth boreholes. [Display omitted] • Conducted geological tests at a depth of 2500m in Shenyang, southern Songliao basin. • Created a combined thermal conductivity model considering temperature correction. • Analyzed the correlation and influence mechanism of geological factors. • Dense and hard rock formations (low porosity and mud content) favor thermal conduction. [ABSTRACT FROM AUTHOR]

Urban infrastructure, particularly district heating networks (DHNs), faces a significant threat from natural disasters such as earthquakes, which can result in extensive damage and disruptions. This study focuses on DHNs' vulnerability assessment to seismic hazards, considering both their physical integrity and operational resilience. Our proposed two-staged vulnerability analysis framework provides a comprehensive evaluation of the seismic impact on DHNs, identifying critical factors that contribute to the seismic resilience of these networks. The first phase of the framework generates customized failure scenarios for seismic zones using two methods: the Two-Tier Random Sampling Method (TTRS) and the Integrated Failure Probability Method (IPRS). IPRS directly calculates the integrated failure probability for heating pipes in known seismic zones, thereby reducing the need for extensive random sampling required by TTRS. The second stage of the analysis assesses DHNs' vulnerability using an advanced stochastic repair time model. This model incorporates factors such as repair-crew productivity, lifeline interactions, and resource constraints, enabling an assessment of economic losses resulting from earthquake-induced heating failures. It also examines topological and functional losses, providing a holistic understanding of DHNs' vulnerability. Validation of the proposed framework using a real-case DHN in China, located near a seismic zone, underscores its efficacy. Seismic magnitude is a key factor affecting DHNs' vulnerability, especially when it's <6.0, while the seismic epicenter's impact is relatively modest. In addition to understanding DHNs' vulnerability, our findings offer insights into enhancing seismic resilience. Protecting mainlines between heat sources can reduce topological vulnerability by up to 98.21%, functional vulnerability by up to 70.63%, and economic loss by up to 82.74%. • Two-stage framework evaluates seismic vulnerability of district heating networks. • Integrated failure probability formula for heating pipes facing known seismic area. • Stochastic repair time model factoring infrastructural interdependencies for realism. • Provides decision recommendations for securing heat-supply against seismic risks. [ABSTRACT FROM AUTHOR]