A Concise Model and Analysis for Heat-Induced Withdrawal Reflex Caused by Millimeter Wave Radiation

In this study, we consider the heat-induced withdrawal reflex caused by exposure to an electromagnetic beam. We propose a concise dose-response relation for predicting the occurrence of withdrawal reflex from a given spatial temperature profile. Our model is distilled from sub-step components in the ADT CHEETEH-E model developed at the Institute for Defense Analyses. Our model has only two parameters: the activation temperature of nociceptors and the critical threshold on the activated volume. When the spatial temperature profile is measurable, the two parameters can be determined from test data. We connect this dose-response relation to a temperature evolution model for electromagnetic heating. The resulting composite model governs the process from the electromagnetic beam deposited on the skin to the binary outcome of subject’s reflex response. We carry out non-dimensionalization in the time evolution model. The temperature solution of the non-dimensional system is the product of the applied power density and a parameter-free function. The effects of physical parameters are contained in non-dimensional time and depth. Scaling the physical temperature distribution into a parameter-free function greatly simplifies the analytical solution, and helps to pinpoint the effects of beam spot area and applied power density. With this formulation, we study the theoretical behaviors of the system, including the time of reflex, effect of heat conduction, biological latency in observed reflex, energy consumption by the time of reflex, and the strategy of selecting test conditions in experiments for the purpose of inferring model parameters from test data.

Effect of bipolar-plates design on corrosion,mass and heat transfer in proton-exchange membrane fuel cells and water electrolyzers:A review

Attaining a decarbonized and sustainable energy system,which is the core solution to global energy issues,is accessible through the development of hydrogen energy.Proton-exchange membrane water electrolyzers(PEMWEs)are promising devices for hydrogen production,given their high efficiency,rapid responsiveness,and compactness.Bipolar plates account for a relatively high percentage of the total cost and weight compared with other components of PEMWEs.Thus,optimization of their design may accelerate the promotion of PEMWEs.This paper reviews the advances in materials and flow-field design for bipolar plates.First,the working conditions of proton-exchange membrane fuel cells(PEMFCs)and PEMWEs are compared,including reaction direction,operating temperature,pressure,input/output,and potential.Then,the current research status of bipolar-plate substrates and surface coatings is summarized,and some typical channel-rib flow fields and porous flow fields are presented.Furthermore,the effects of materials on mass and heat transfer and the possibility of reducing corrosion by improving the flow field structure are explored.Finally,this review discusses the potential directions of the development of bipolar-plate design,including material fabrication,flow-field geometry optimization using threedimensional printing,and surface-coating composition optimization based on computational materials science.

Developing Operational Model for Heat Pumps as Space Heating and Domestic Hot Water Provider

In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is on the increase. The operation and working principle of heat pumps must be well understood in the investigations of their impacts on the grid and the grid assets, especially distribution transformers which could be overloaded due to higher peak load demand. This work develops an operational model of heat pumps as combined space heating and domestic hot water provider implemented in MATLAB. The developed operational model of heat pumps is adaptable and repeatable for different input parameters. The developed model is used to generate daily average demand profiles of heat pumps for a typical winter weekday and a typical summer weekday. The generated demand profiles of heat pumps by the developed model compared well with the demand profiles of heat pumps generated from actual field projects which are usually expensive and time-tasking.

The Effect of Water Flow Velocity on Heat Collection Performance of Active Heat Storage and Release System for Solar Greenhouses

In order to explore the influence of water velocity on the heat collection performance of the active heat storage and release system for solar greenhouses,six different flow rates were selected for treatment in this experiment.The comprehensive heat transfer coefficient of the active heat storage and release system at the heat collection stage was calculated by measuring the indoor solar radiation intensity,indoor air temperature and measured water tank temperature.The prediction model of water temperature in the heat collection stage was established,and the initial value of water temperature and the comprehensive heat transfer coefficient were input through MATLAB software.The simulated value of water temperature was compared with the measured value and the results showed that the best heat transfer effect could be achieved when the water flow speed was 1.0 m3h-1.The average relative error between the simulated water tank temperature and the measured value is 2.70-6.91%.The results indicate that the model is established correctly,and the variation trend of water temperature can be predicted according to the model in the heat collection stage.

Evaluating Water Withdrawals for Regional Water Management Under a Data-driven Framework

With an increase in population and economic development,water withdrawals are close to or even exceed the amount of water available in many regions of the world.Modelling water withdrawals could help water planners improve the efficiency of water use,water resources allocation,and management in order to alleviate water crises.However,minimal information has been obtained on how water withdrawals have changed over space and time,especially on a regional or local scale.This research proposes a data-driven framework to help estimate county-level distribution of water withdrawals.Using this framework,spatial statistical methods are used to estimate water withdrawals for agricultural,industrial,and domestic purposes in the Huaihe River watershed in China for the period 1978–2018.Total water withdrawals were found to have more than doubled,from 292.55×10^(8)m^(3) in 1978 to 642.93×10^(8)m^(3) in 2009,and decreased to 602.63×10^(8)m^(3) in 2018.Agricultural water increased from 208.17×10^(8)m^(3) in 1978 to 435.80×10^(8)m^(3) in 2009 and decreased to 360.84×10^(8)m^(3) in 2018.Industrial and domestic water usage constantly increased throughout the 1978–2018 period.In 1978,industrial and domestic demands were 20.35×10^(8)m^(3) and 60.04×10^(8)m^(3),respectively,and up until 2018,the figures were 105.58×10^(8)m^(3) and 136.20×10^(8)m^(3).From a spatial distribution perspective,Moran’s I statistical results show that the total water withdrawal has significant spatial autocorrelation during 1978–2018.The overall trend was a gradual increase in 1978–2010 with withdrawal beginning to decline in 2010–2018.The results of Getis-Ord G_(i)^(*)statistical calculations showed spatially contiguous clusters of total water withdrawal in the Huaihe River watershed during1978–2010,and the spatial agglomeration weakened from 2010 to 2018.This study provides a data-driven framework for assessing water withdrawals to enable a deeper understanding of competing water use among economic sectors as well as water withdrawal modelled with proper data resource and method.

Spatial Patterns of Irrigation Water Withdrawals in China and Implications for Water Saving

By considering numerical features, spatial variation, and spatial association, the spatial patterns of China's irrigation water withdrawals in 2001 and 2010 were explored at the regional, provincial, and prefectural scales. In addition, an overlay analysis was used to develop specific water-saving guidance for areas under different levels of water stress and with different degrees of irrigation water withdrawals. It was found that at the regional scale, irrigation water withdrawals were highest in the Middle-Lower Yangtze River region in both years, while at the provincial scale, the largest irrigation water withdrawals occurred in Xinjiang. During 2001–2010, the total of irrigation water withdrawals decreased; however, in the Northeast region, especially in Heilongjiang Province, it experienced a dramatic increase. The spatial variation was largest at the prefectural scale, with an apparent effect. The spatial association was globally negative at the provincial scale, and Xinjiang was the only significant high-low outlier. In contrast, the association displayed a significant positive relationship at the prefectural scale, and several clusters and outliers were detected. Finally, it was found that the water stress in the northern part of China worsened and water-saving irrigation techniques urgently need to be applied in the Northeast region, the Huang-Huai-Hai Plain region, and Gansu-Xinjiang region. This study verified that a multi-scale and aspect analysis of the spatial patterns of irrigation water withdrawals were essential and provided water-saving advice for different areas.

Development and Experimental Study of Air Source Heat Pump Water Heater

The principle and development prospect of air source heat pump water heat were introduced,as well as the designation of condenser (storage water tank),experimental study on installations was also carried out.The results showed that air source heat pump water heater was superior to conventional system.Under the operation of cooling and heating,heat pump comprehensive utilization equipment could improve heating performance,reduce energy consumption,and recycle condensing heat to provide hot water.

Variable chlorophyll fluorescence in response to water plus heat stress treatments in three coniferous tree seedlings

Effects of water and heat stress treatments on chlorophyll fluorescence of Chinese fir (Cunninghamia lanceolata), Masson pine (Pinus massoniana) and western redcedar (Thuja plicata D. Don)_seedlings were monitored during a three-cycle stress period. It was shown that ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of these three species responded differently to water stress treatments. The Fv/Fm ratio of western redcedar decreased dramatically after water stress, while that of Chinese fir had only a slight reduction and that of Masson pine had no significant change. The experiment also showed that the Fv/Fm ratio of all three species differed significantly under heat stress treatments. Concerning three different water plus heat stress cycles, it was found that the Fv/Fm ratios of Chinese fir and Masson pine measured at the end of each water plus heat stress cycle were not significantly different. However, the Fv/Fm ratio of western redcedar was diminished significantly in response to an increase of stress time. Keywords Chinese fir - Chlorophyll fluorescence - Heat stress - Masson pine - Water stress - Western redcedar CLC number Q945.17 - S791.248 Document code A Biography: Yu Fang-yuan (1965-), male, Ph. Doctor. Associate professor in College of Forest Resources and Environment, Nanjing, Forestry University, Nanjing 210037, P. R. China.Responsible editor: Zhu Hong

Experimental study on characteristics of transcritical heat pump water heater using refrigerant HFC125

To evaluate the performance of heat pumps using refrigerant HFC125,an experimental rig of a DC-inverter heat pump water heater is designed and set up,and the research on the transcritical heat pump water heater is carried out experimentally.It is found that there is a top value of the coefficient of performance（COP）when the system runs at 95 Hz of frequency.The relationships between the COP and compressor frequency,condensation pressure,evaporation pressure,condensation water temperature rise,and discharge temperature are discussed and analyzed at 95 Hz.And the COP of the HFC125 transcritical cycle is also compared with that of a R410 subcritical heat pump under the same conditions.The results indicate that there exists an optimum frequency for a better COP,and the system COP shows an increasing tendency with the decrease in condensation pressure and compressor ratio while the evaporation pressure remains invariant,and the COP decreases rapidly when cooling water temperature rises over 47.5 ℃.Compared with the R410A sub-critical cycle,the COP of HFC125 transcritical cycle significantly increases by 12% on average.

Research on Solar Water Heating System and Architectural Integration Design—A Case Study of Anqing Children Welfare Home

Taking the planning and major architectural design projects of Anqing Children Welfare Home for example,through the research on categories and each component of solar water heating system,the paper discussed strategies and methods to realize solar energy and architectural integration design in the climate condition and location environment of Anhui Province.

Experimental Study of Thermoelectric Heat Pump Water Heater with Exhaust Heat Recovery from Kitchens

A new kind of thermoelectric heat pump water heater for kitchens exhaust heat recovery was presented,and its performances were investigated under different operating voltages.The experiment results show that the coefficient of performance decreases and the temperature difference between the hot and cold sides becomes larger with the increase of the operating voltage,but the heating time becomes short.The higher the temperature of water,the greater the temperature difference between the hot and cold sides,leading to a smaller coefficient of performance.Under an exhaust temperature of 36 ℃,the coefficient of performance decreases from 1.66 to 1.22 when the temperature of water increases from 28 ℃ to 46 ℃ with operating voltage 16 V.Performance tests illustrate that,compared with the conventional electrical water heaters,the new kind of thermoelectric heat pump water heater is more coefficient.

Rapid and Continuous Production of LiFePO4/C Nanoparticles in Super Heated Water

A rapid and continuous method for production of LiFePO4/C nanoparticles in super heated water is described, wherein soluble starch was used as carbon precursor. The effects of pH, flow rate, temperature, and pressure on the formation of LiFePO4/C particles were investigated. Results showed that the pH value was the key factot on the formation of phase pure LiFePO4, which only formed at pH = 7; the LiFePO4/C-occurred as particles with about 70-200 nm size and LiFePO4 was covered by a thin carbon layer; higher flow rate, higher pressure, and lower temperature led to smaller particles of LiFePO4/C.

Operation Performance of Central Solar Heating System with Seasonal Storage Water Tank in Harbin

This paper presented a preliminary research on the central solar heating system with seasonal storage(CSHSSS)used in cold climate in China.A mathematical model of the solar energy seasonal storage water tank used in the central solar heating system was firstly developed based on energy conservation.This was followed by the simulation of the CSHSSS used in a two-floor villa in Harbin,and analysis of the impacts on storage water temperature of tank volume,solar collector area,tank burial depth,insulation thickness around the tank,etc.The results show there is a relatively economical tank volume to optimize the system efficiency,which decreases with increasing tank volume at the constant collector area,and increases with increasing collector area at the constant tank volume.Furthermore,the insulation thickness has obvious effect on avoiding heat loss,while the tank burial depth doesn't.In addition,the relationship between the solar collector efficiency and storage water temperature is also obtained,it decreases quickly with increasing storing water temperature,and then increases slowly after starting space heating system.These may be helpful for relevant design and optimization in cold climates in China and all over the world.

Variation of fluxes of water vapor, sensible heat and carbon dioxide above winter wheat and maize canopies

Surface energy fluxes were measured using Bowen-Ratio Energy Balance technique (BREB) and eddy correlation system at Luancheng of Hebei Province, on the North China Plain from 1999 to 2001. Average diurnal variation of surface energy fluxes and CO2 flux for maize showed the inverse “U” type. The average peak fluxes did not appear at noon, but after noon. The average peak CO2 flux was about 1.65 mg m-2 s-1. Crop water use efficiency (WUE) increased quickly in the morning, stabilized after 10:00 and decreased quickly after 15:00 with no evident peak value. The ratio of latent heat flux (λE) to net solar radiation (Rn) was always higher than 70% during winter wheat and maize seasons. The seasonal average ratio of sensible heat flux (H) divided byR n stayed at about 15% above the field surface; the seasonal average ratio of conductive heat flux (G) divided by Rn varied between 5% and 13%, and the averageG/R> n from the wheat canopy was evidently higher than that from the maize canopy. The evaporative fraction (EF) is correlated to the Bowen ratio in a reverse function.EF for winter wheat increased quickly during that revival stage, after the stage, it gradually stabilized to 1.0, and fluctuated around 1.0. EF for maize also fluctuated around 1.0 before the later grain filling stage, and decreased after that stage.

Transient Heat Transfer Study of Direct Contact Condensation of Steam in Spray Cooling Water

We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 1045 mm. We applied a new analysis method for the steam state equation to analyze the molar quantity change in steam over the course of the experiment and determined the transient steam variation. We also investigated the influence of flow rates and temperatures ofcooling water on the efficiency ofsteam condensation. Our experimental results show that appropriate increasing of the cooling water flow rate can significantly accelerate the steam condensation. We achieved a rapid increase in the total volumetric heat transfer coefficient by increasing the flow rate of cooling water, which indicated a higher thermal convection between the steam and the cooling water with higher flow rates. We found that the temperature ofcooling water did not play an important role on steam condensation. This method was confirmed to be effective for rapid recovering ofsteam.

Water and heat transport in hilly red soil of southern China:I. Experiment and analysis

Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture and heat depends on soil physical properties and the climate conditions. Red soil is heavy clay and high content of free iron and aluminum oxide. The climate conditions are characterized by the clear four seasons and the serious seasonal drought. The great annual and diurnal air temperature differences result in significant fluctuation in soil temperature in top layer. The closed and evaporating columns experiments with red soil were conducted to simulate the coupled transfer of soil water and heat under the overlaying and opening fields’ conditions, and to analyze the effects of soil temperature gradient on the water transfer and the effects of initial soil water contents on the transfer of soil water and heat. The closed and evaporating columns were designed similarly with about 18 °C temperatures differences between the top and bottom boundary, except of the upper end closed or exposed to the air, respectively. Results showed that in the closed column, water moved towards the cold end driven by temperature gradient, while the transported water decreased with the increasing initial soil water content until the initial soil water content reached to field capacity equivalent, when almost no changes for the soil moisture profile. In the evaporating column, the net transport of soil water was simultaneously driven by evaporation and temperature gradients, and the drier soil was more influenced by temperature gradient than by evapo- ration. In drier soil, it took a longer time for the temperature to reach equilibrium, because of more net amount of transported water.

Coupled Transfer of Water and Heat in Red Soil: Experiment and Numerical Modelling

Coupled transfer of soil water and heat in closed columns of homogeneous red soil was studied under laboratory conditions. A coupled model was constructed using soil physical theory, empirical equations and experimental data to predict the coupled transfer. The results show that transport of soil water was affected by temperature gradient, and the largest net water transport was found in the soil column with initial water content of 0.148 m3 m-3. At the same time, temperature changes with the transport of soil water was in a nonlinear shape as heat parameters were function of water content, and the changes of temperature were positively correlated with the net amount of water transported. Numerical modelling results show that the predicted values of temperature distribution were close to the observed values, while the predicted values of water content exhibited limited deviation at both ends of the soil column due to the slight temperature changes at both ends. It was indicated that the model proposed here was applicable.

Effects of biodegradable mulch on soil water and heat conditions,yield and quality of processing tomatoes by drip irrigation

To combat the problem of residual film pollution and ensure the sustainable development of agriculture in oasis areas,a field experiment was carried out in 2019 at the Wuyi Farm Corps Irrigation Center Test Station in Urumqi,Northwest China.Four types of biodegradable mulches,traditional plastic mulchs and a control group(bare land;referred to as CK)were compared,including a total of six different treatments.Effects of mulching on soil water and heat conditions as well as the yield and quality of processing tomatoes under drip irrigation were examined.In addition,a comparative analysis of economic benefits of biodegradable mulches was performed.Principal component analysis and gray correlation analysis were used to evaluate suitable mulching varieties for planting processing tomatoes under drip irrigation.Our results show that,compared with CK,biodegradable mulches and traditional plastic mulch have a similar effect on retaining soil moisture at the seedling stage but significantly increase soil moisture by 0.5%-1.5%and 1.5%-3.0%in the middle and late growth periods(P<0.050),respectively.The difference in the thermal insulation effect between biodegradable mulch and plastic mulch gradually reduces as the crop grows.Compared with plastic mulch,the average soil temperature at 5-20 cm depth under biodegradable mulches is significantly lowered by 2.04°C-3.52°C and 0.52°C-0.88°C(P<0.050)at the seedling stage and the full growth period,respectively,and the water use efficiency,average fruit yield,and production-investment ratio under biodegradable mulches were reduced by 0.89%-6.63%,3.39%-8.69%,and 0.51%-6.33%(P<0.050),respectively.The comprehensive evaluation analysis suggests that the black oxidized biological double-degradation ecological mulch made from eco-benign plastic is the optimal film type under the study condition.Therefore,from the perspective of sustainable development,biodegradable mulch is a competitive alternative to plastic mulch for large-scale tomato production under drip irrigation in the oasis.

Response of spikelet water status to high temperature and its relationship with heat tolerance in rice

In rice, high-temperature stress(HT) during flowering results in decreased grain yield via a reduction in spikelet fertility;however, the effect of plant water status on spikelet fertility under HT remains unknown. To investigate the relationship between spikelet water status and spikelet fertility under HT, two experiments were performed under temperature-controlled conditions using four genotypes with varying tolerance to HT. Rice plants were exposed to HT for seven consecutive days during the flowering stage under three soil water treatments(soil water potential 0, -20, and -40 kPa), as well as under hydroponic conditions in a separate experiment. HT significantly decreased spikelet fertility, pollen fertility, and anther dehiscence under each of the three water treatments. HT significantly increased the spikelet transpiration rate, and this change was accompanied by a significant decrease in the internal temperature of the spikelets. HT decreased pollen grain diameter in heat-sensitive genotypes. HT had varying effects on the water potential of panicles and anthers but increased anther soluble-sugar concentration. Different aquaporin genes showed different expression profiles under HT, and the expression levels of PIPs for plasma membrane intrinsic proteins and TIPs for tonoplast intrinsic proteins increased in anthers but decreased in glumes.Correlation analyses showed that anther dehiscence and pollen(spikelet) fertility were tightly associated with anther water status, and the expression levels of almost all anther aquaporin genes were significantly correlated with anther dehiscence under HT. In summary, an increased spikelet transpiration rate and decreased internal spikelet temperature were associated with alleviation of the effects of HT in rice genotypes with varying degrees of heat tolerance, and the response of spikelet water status to HT, involving increased total expression of aquaporins and soluble sugar content, thereby improved pollen fertility,anther dehiscence, and spikelet fertility, especially in heat-resistant genotypes. The heat-resistant genotypes N22 and SY63 may adopt different approaches to reduce heat damage.

Different discretization method used in coupled water and heat transport mode for soil under freezing conditions

A coupled water and heat transport mode is established based on the Richards equation to study water flow and heat transport in soil during freezing process. Both the finite difference and finite element method are used in the discretization, respectively. Two different computer programs are written and used to simulate an indoor unidirectional frozen test. The freezing depth, freezing rate and temperature variation are compared among lab tests, finite difference calculation simulation and finite element calculation simulation. Result shows that： the finite difference method has a better performance in freezing depth simulation while the finite element method has a better performance in numerical stability in one-dimensional freezing simulation.