Stability of K-struvite in High Temperature and Acid-base Environment

K-struvite was prepared by precipitation method,and the stability of K-struvite in high temperature and acid-base environment were investigated by X-ray diffraction(XRD),thermogravimetric analysis(TG/DSC),and infrared spectroscopy(FT-IR).The results show that K-struvite decomposes from 50 to 110℃,and the mass loss begins at 50℃before being completely destroyed at 110℃,then further heating at temperature above 500℃leading to complete loss of the binding water in K-struvite.Moreover,K-struvite is more stable in alkaline environments than acidic environment.

Study of main factors influencing unsteady-state temperature drop in oil tank storage under dynamic thermal environment coupling

With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperature drop in storage tanks under actual dynamically changing environments, this paper considers the influence of dynamic thermal environment and internal crude oil physical properties on the fluctuating changes in crude oil temperature. A theoretical model of the unsteady-state temperature drop heat transfer process is developed from a three-dimensional perspective. According to the temperature drop variation law of crude oil storage tank under the coupling effect of various heat transfer modes such as external forced convection, thermal radiation, and internal natural convection, the external dynamic thermal environment influence zone, the internal crude oil physical property influence zone, and the intermediate transition zone of the tank are proposed. And the multiple non-linear regression method is used to quantitatively characterize the influence of external ambient temperature, solar radiation, wind speed, internal crude oil density, viscosity, and specific heat capacity on the temperature drop of crude oil in each influencing zone. The results of this paper not only quantitatively explain the main influencing factors of the oil temperature drop in the top, wall, and bottom regions of the tank, but also provide a theoretical reference for oil security reserves under a dynamic thermal environment.

A CombustionModel for Explosive Charge Affected by a Bottom Gap in the Launch Environment

Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differentdefects. This paper formulates an efficient computational model of the combustion of an explosive charge affectedby a bottom gap in the launch environment in the context of the material point method. The current temperatureis computed accurately from the heat balance equation, and different physical states of the explosive charges areconsidered through various equations of state. Microcracks in the explosive charges are described with respectto the viscoelastic statistical crackmechanics (Visco–SCRAM) model. Themethod for calculating the temperatureat the bottomof the explosive charge with respect to the bottomgap is described. Based on this combustionmodel,the temperature history of a Composition B (COMB) explosive charge in the presence of a bottom gap is obtainedduring the launch process of a 155-mm artillery. The simulation results show that the bottom gap thickness shouldbe no greater than 0.039 cm to ensure the safety of the COM B explosive charge in the launch environment. Thisconclusion is consistent with previous results and verifies the correctness of the proposed model. Ultimately, thispaper derives amathematical expression for themaximumtemperature of the COMB explosive chargewith respectto the bottomgap thickness (over the range of 0.00–0.039 cm), and establishes a quantitative evaluationmethod forthe launch safety of explosive charges.The research results provide some guidance for the assessment and detectionof explosive charge safety in complex launch environments.

Spatial Optimization Strategies for High Temperature Heat Exposure Based on Thermally Vulnerable Populations and Case Studies

The objective of this study is to investigate the factors that contribute to brittleness and to identify strategies for mitigating these factors in populations with varying degrees of thermal vulnerability,based on the potential impact of extreme heat exposure on human survival and habitability.The physiological condition of lower adaptability to high temperature environments and the assessment of individuals who may have higher tolerance time in high temperature environments based on spatial perspectives suggest the need for targeted spatial optimization strategies for commuters and disadvantaged populations.This is demonstrated through a case study.These optimization measures encompass a variety of aspects,including the integration of transportation systems,the expansion of grey space corridors,the improvement of green space layout,and the implantation of green infrastructure.The study aims to reduce the exposure time of thermally vulnerable individuals to high temperature environments through spatial optimization strategies,to enhance the resilience of urban green spaces to heat stress,and to reduce the probability of heat-wave occurrence.

Effect of Ultra-low Temperature on Carbonation Performance of SFRRC and Prediction Model

Through the rapid carbonation test of SFRRC with different fiber volume fractions at ultralow temperature,the influence of ultra-low temperature damage on the carbonation resistance of SFRRC was analyzed,which provides a theoretical basis for the application of SFRRC in ultra-low temperature engineering.The experimental results show that ultra-low temperatures can significantly weaken the carbonization resistance of SFRRC.When the temperature reaches 160℃,the carbonization depth increases by 67.66%compared with the normal state.The proper amount of steel fiber has an evident influence on the carbonation resistance of the material.However,when the addition amount exceeds the optimum content,the carbonation resistance of the material decreases.The grey prediction model established by constructing the original sequence can reasonably predict the carbonation resistance of SFRRC after ultra-low temperatures.

Prediction of thermal environment via revision of PMV index with body temperature

PMV(Predicted Mean Vote) is a widely used index for evaluating the thermal environment.However,few studies have been conducted to take physiological values directly as evaluating indices.This paper assumes a linear relation between body temperature and both sweating rate and heat produced by shivering,and introduces the linear relation into the human heat balance equation to revise the classic PMV.And the assumption of linear relation is subsequently proved.The revised PMV possesses the same characteristic of dependent heat load as that of the classic one,and moreover it is convenient to be calculated.

Silicon carbide resonant tuning fork for microsensing applications in high-temperature and high G-shock environments

We present the fabrication and testing of a silicon carbide （SiC） balanced mass doublended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform hightemperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64 000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/μe and strain resolution of 0. 045 μe in a 10 kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to micro-electro-mechanical systems （MEMS） designers creating sensors for a variety of different applications.

Population dynamics of excited atoms in non-Markovian environments at zero and finite temperature

The population dynamics of a two-atom system, which is in two independent Lorentzian reservoirs or in two independent Ohmic reservoirs respectively, where the reservoirs are at zero temperature or finite temperature, is studied by using the time-convolutionless master-equation method. The influences of the characteristics and temperature of a non-Markovian environment on the population of the excited atoms are analyzed. We find that the population trapping of the excited atoms is related to the characteristics and the temperature of the non-Markovian environment. The results show that, at zero temperature, the two atoms can be effectively trapped in the excited state both in the Lorentzian reservoirs and in the Ohmic reservoirs. At finite temperature, the population of the excited atoms will quickly decay to a nonzero value.

Skin Temperature and Body Surface Section in Non-Uniform and Asymmetric Outdoor Thermal Environment

In indoor environments and shady outdoor environments, there is little influence of short-wavelength solar radiation, so a strikingly non-uniform and asymmetric environment is not formed. In outdoor sunny environment, however, shaded areas occur even for the same site of the body, and a remarkable difference in skin temperature is considered to occur under the influence of the short-wavelength solar radiation. The purpose of this study is to clarify the influence of the non-uniform and asymmetric thermal radiation of short-wavelength solar radiation in outdoor environment on the division of the body surface section and the calculation of the mean skin temperature. The skin temperature of the front of the coronal surface, which was facing the sun and where the body received direct short-wavelength solar radiation, and the skin temperature of the rear of the coronal surface, which was in the shadow and did not receive direct short-wavelength solar radiation were respectively measured. The feet, upper arm, forearm, hand and lower leg, which are susceptible to short-wavelength solar radiation in a standing posture, had a noticeable difference in skin temperature between sites in the sun and in shade. The mean skin temperature of sites facing the sun was significantly higher than the mean skin temperature of those in the shade.

Surface Thermal Environment and Water Temperature Regulation of Rapidly Developing Small and Medium-Sized Cities

[Objective] This study aimed to investigate the temperature regulation effect of surface thermal environment and waters on the temperature, as well as the influencing factors, in Binzhou City, Shandong Province, so as to provide scientific basis for layout planning of urban waters. [Method] Based on the Landsat image of 2009 and 2014, the surface temperature was retrieved using mono-window algorithm and the distribution characteristics of surface temperature of different land types were analyzed. By arranging temperature points on the temperature line and water characteristic statistics, the temperature regulation effect of waters, as well as the influencing factors was analyzed. [Result](1) The order of surface temperature of different land types in summer was building land > cultivated land > woodland > water body, while in winter, the order was cultivated land > woodland > building land > water body. In terms of summer-winter average thermal level, the order was building land > cultivated land > woodland > water body.(2) The temperature regulation effect of waters showed a strong nonlinear relationship with the distance.(3) Large-area water bodies had better cooling effect. Under the condition of same area, the temperature regulated area of multiple small-area water bodies was larger than that of single large-area water body.(4) The increase in the proportion of non-building land around the water body increased the range of water cooling.(5) When the area of water bodies was small, the smaller the ratio of perimeter to area was, the larger the influence range of water cooling was. [Conclusion] The temperature regulation effect of waters in Binzhou City showed a strong nonlinear relationship with the distance, and was affected by the size of the water body, the complexity of the boundary and the composition of the surrounding land.

Discord and entanglement in non-Markovian environments at finite temperatures

The dynamic evolutions of the discord and entanglement of two atoms immersed in two independent Lorentzian reservoirs at zero and finite temperatures have been investigated by using the time-convolutionless master-equation method.Our results show that,nonzero temperature can induce the entanglement sudden death and accelerate the decays of discord and entanglement.The discord and the entanglement have different robustness for different initial states and their robustness may change under certain conditions.When both the non-Markovian effect and detuning are present simultaneously,due to the memory and feedback effect of non-Markovian reservoirs,the discord and entanglement can be effectively protected even at nonzero temperature by increasing the non-Markovian effect and the detuning.

Effects of Low Temperature and Ultra-low Temperature on Pollen Viability of Tomato(Lycopersicon esculentum Mill.)

The pollen of two tomato varieties, Ryau961721 and Ryau9327D, was adopted in our research. The two tomato varieties were bred by College of Land- scape and Horticulture, Yunnan Agricultural University. The collected pollen was stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circumstances. Then it was inoculated to the medium and cultured at 28 ℃ in thermostat incubator. The pollen viability was determined by electron microscope. The results showed that compared to that of pollen stored in control （25 ℃） circumstance, the viability of pollen stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circum- stances for 1 -3 d did not change significantly. In addition, pollen viability trended to decrease with the increase of freeze-thaw cycle and storage time. The pollen lost basically the viability by the 7th d in the storage.

Innovation for forming aluminum alloy thin shells at ultra-low temperature by the dual enhancement effect

Integral thin shells made of high strength aluminum alloys are urgently needed in new generation transportation equipment. There are challenges to overcoming the co-existing problems of wrinkling and splitting by the cold forming and hot forming processes. An innovative technology of ultra-low temperature forming has been invented for aluminum alloy thin shells by the new phenomenon of ‘dual enhancement effect’. That means plasticity and hardening are enhanced simultaneously at ultra-low temperatures. In this perspective, the dual enhancement effect is described, and the development, current state and prospects of this new forming method are introduced. This innovative method can provide a new approach for integral aluminum alloy components with large size, ultra-thin thickness, and high strength. An integral tank dome of rocket with 2 m in diameter was formed by using a blank sheet with the same thickness as the final component, breaking through the limit value of thickness-diameter ratio.

Anisotropic Rock Poroelasticity Evolution in Ultra-low Permeability Sandstones under Pore Pressure,Confining Pressure,and Temperature:Experiments with Biot's Coefficient

This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient under different conditions were carried out.Results showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between materials.Biot's coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as well.Generally,Biot's coefficient remains stable with increased temperature.Lithology,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's coefficient.For strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's coefficient.For skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's coefficient.The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.

Ultra-low temperature anodic bonding of silicon and glass based on nano-gap dielectric barrier discharge

The article improves the process of dielectric barrier discharge(DBD)activated anode bonding.The treated surface was characterized by the hydrophilic surface test.The results showed that the hydrophilic angle was significantly reduced under nano-gap conditions and the optimal discharge voltage was 2 kV.Then,the anodic bonding and dielectric barrier discharge activated bonding were performed in comparison experiments,and the bonding strength was characterized by tensile failure test.The results showed that the bonding strength was higher under the nano-gap dielectric barrier discharge.This process completed 110°C ultra-low temperature anodic bonding and the bonding strength reached 2 MPa.Finally,the mechanism of promoting bonding after activation is also discussed.

Spatiotemporal Evolution Characteristics of Urban Land Surface Temperature Based on Local Climate Zones in Xi’an Metropolitan,China

Local climate zones(LCZs)are an effective nexus linking internal urban structures to the local climate and have been widely used to study urban thermal environment.However,few studies considered how much the temperature changed due to LCZs transformation and their synergy.This paper quantified the change of urban land surface temperature(LST)in LCZs transformation process by combining the land use transfer matrix with zonal statistics method during 2000–2019 in the Xi’an metropolitan.The results show that,firstly,both LCZs and LST had significant spatiotemporal variations and synchrony.The period when the most LCZs were converted was also the LST rose the fastest,and the spatial growth of the LST coincided with the spatial expansion of the built type LCZs.Secondly,the LST difference between land cover type LCZs and built type LCZs gradually widened.And LST rose more in both built type LCZs transferred in and out.Finally,the Xi’an-Xianyang profile showed that the maximum temperature difference between the peaks and valleys of the LST increased by 4.39℃,indicating that localized high temperature phenomena and fluctuations in the urban thermal environment became more pronounced from 2000 to 2019.

Novel Cascade Refrigeration Cycle for Cold Supply Chain of COVID-19 Vaccines at Ultra-Low Temperature -80°C Using Ethane (R170) Based Hydrocarbon Pair

Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80°C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.

基于Visual Environment的铝合金增材制造温度场数值模拟

为了探究工艺参数对增材制造温度场的影响,利用Visual Environment软件建立4043铝合金增材制造有限元模型,考察增材制造沉积方向、层间间隔时间和基板预热温度对温度场的影响,并通过试验验证模拟结果。结果表明,随间隔时间和增材制造层数增加,第1层中点峰值温度与谷值温度逐渐降低,反向沉积增材制造可获得更好的成形质量,合理范围内的基板预热可使成形件温度分布更均匀,可为增材成形参数优化提供参考。

Experimental study on thermal environment in large-space building with low sidewall air supply

The thermal environmental characteristics are experim-entally studied in terms of different air supply volumes and outdoor meteorological parameters in a large-space building which is air conditioned with a low sidewall air supply.The experimental results show that the indoor vertical temperature distributions under different condition are similar.The maximum vertical temperature difference（MVTD）is up to about 20 ℃,and it linearly changes with the sol-air temperature.The indoor vertical temperature gradients（VTGs）in the upper,central and lower zones are different.The influence of the sol-air temperature on the VTGs in the upper and the lower zones is greater than that in the central zone.The characteristics of the VTGs in the three zones affected by the air supply volume are the same as those affected by the sol-air temperature.Besides,because of the small air velocity,the predicted mean vote（PMV）on comfort in the occupied zone is slightly high and the air temperature difference between the head and the ankle is usually more than 3 ℃.

Ester-based anti-freezing electrolyte achieving ultra-low temperature cycling for sodium-ion batteries

With the continuous advancement of industrialization,sodium-ion batteries(SIBs)need to operate in various challenging circumstances,particularly in extremely cold conditions.However,at ultra-low tem-peratures,the reduced ionic conductivity and sluggish Na+migration of commonly carbonate-based elec-trolytes will inevitably lead to a sharp decrease in the capacity of SIBs.Herein,we design a carboxylate ester-based electrolyte with excellent ultra-low temperature performance by straightforward cosolvent strategy.Due to the low viscosity,melting point,and sufficient ionic conductivity of the designed elec-trolyte,the resulting Na||Na_(3)V_(2)(PO_(4))_(2)O_(2)F can achieve the capacity retention of 96%(100 cycles at 0.1 C)at-40℃ and can also operate stably even at-50℃.Besides,galvanostatic intermittent titration tech-nique(GITT),ex-situ X-ray photoelectron spectroscopy(XPS),and high-resolution transmission electron microscopy(TEM)tests are employed to analyze and confirm that the carboxylate ester-based electrolyte promotes robust and uniform cathode/electrolyte interface layer formation and accelerates ion diffusion kinetics,which collectively facilitates the better low-temperature performance.In addition,the assembled hard carbon||NVPOF full cells further prove the practicability of the carboxylate ester-based electrolyte at low-temperature,which delivers high discharge capacity of 108.4 and 73.0 mAh g^(-1) at-25 and-40℃.This work affords a new avenue for designing advanced low-temperature electrolytes for SIBs.