The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formabilit...The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formability of Al-Cu-Li alloy is vital.A thorough comparison of the effects of cryo-deformation and ambient temperature large pre-deformation(LPD)on the creep ageing response in the 2195 alloy sheet at 160℃with different stresses has been made.The evolution of dislocations and precipitates during creep ageing of LPD alloys are revealed by X-ray diffraction and transmission electron microscopy.High-quality 2195 alloy sheet largely pre-deformed by 80%without edge-cracking is obtained by cryo-rolling at liquid nitrogen temperature,while severe edge-cracking occurs during room temperature rolling.The creep formability and strength of the 2195 alloy are both enhanced by introducing pre-existing dislocations with a density over 1.4×10^(15)m^(−2).At 160℃and 150 MPa,creep strain and creep-aged strength generally increases by 4−6 times and 30−50 MPa in the LPD sample,respectively,compared to conventional T3 alloy counterpart.The elongation of creep-aged LPD sample is low but remains relevant for application.The high-density dislocations,though existing in the form of dislocation tangles,promote the formation of refined T1 precipitates with a uniform dispersion.展开更多
Based on the initial field temperature data of ECMWF 850 hPa from Jan- uary 2012 to December 2015, linear interpolation method of ECMWF was employed to calculate the 850 hPa temperature values at 8:00 and 20:00 of 7...Based on the initial field temperature data of ECMWF 850 hPa from Jan- uary 2012 to December 2015, linear interpolation method of ECMWF was employed to calculate the 850 hPa temperature values at 8:00 and 20:00 of 7 stations (Jiamusi, Tangyuan, Huachuan, Huanan, Fujin, Tongjiang, Fuyuan). Combined with the observed daily minimum and maximum air temperatures at the same time of the 7 stations, the correlations of the 850 hPa temperature values at 8:00 and 20:00 with the daily maximum or minimum air temperature of the ground meteorological obser- vation stations were established, and the ground observation data in accordance with the relevant analysis and correlation test principle of the prediction equation for factor were primarily selected. Regression method was used to establish forecast e- quation dividing into counties, month by month. The results showed that the 850 hPa temperature values at 8:00 and 20:00 were significantly correlated with the daily maximum or minimum air temperature, and the established temperature fore- cast equation was of certain guiding significance for the forecast of daily minimum and maximum temperature, which could help to improve the forecast accuracy.展开更多
On April 14, 2010, an earthquake reaching 7.1 Richter scale struck Jiegu Town of Yushu. More than 2 698 people were confirmed dead, and 12 135 were injured, of which 1 434 were severely injured. Rescue operation was c...On April 14, 2010, an earthquake reaching 7.1 Richter scale struck Jiegu Town of Yushu. More than 2 698 people were confirmed dead, and 12 135 were injured, of which 1 434 were severely injured. Rescue operation was carried out soon after the disaster; however, the rescue teams face great challenges of altitude hypoxia, freezing temperature and very bad weather. Thus, 1 434 severe injuries were rapidly transported airlifted to hospitals in Xining and neighboring provinces for effective treatment. The extremity trauma (49.9 % ) was the most common patteru of injuries. Asphyxia (40.8 % ) was by far the most important reason for death. A high incidence of acute altitude illness in the lowland rescuers was a special medical problem during the highest earthquake in Yushu. We have learned more lessons from Yushu Earthquake.展开更多
The long-term trend of diurnal temperature range(DTR)over Nigeria was examined using daily station-based datasets for the period 1971–2013.The results show that the regionally averaged DTR has decreased significantly...The long-term trend of diurnal temperature range(DTR)over Nigeria was examined using daily station-based datasets for the period 1971–2013.The results show that the regionally averaged DTR has decreased significantly(-0.34°C per decade)over the Nigerian Sahel(north of 10°N),but there has been a slight increasing trend(0.01°C per decade)over the Nigerian Guinea Coast.The annual decreasing trend of DTR in the Nigerian Sahel is mainly attributable to the significant increasing trend in daily minimum temperature(Tmin,0.51°C per decade),which far outstrips the rate of increase in the daily maximum(Tmax,0.17°C per decade).In contrast,the comparable trends in Tmin(0.19°C per decade)and Tmax(0.20°C per decade)may explain the non-significant trend of the DTR averaged over the Guinea Coast region.It is observed that the DTR has decreased more in boreal summer(June–July–August)than in boreal winter(December–January–February)for the regions.Furthermore,it is found that the significant DTR declining trend over the Nigerian Sahel is closely associated with an increasing trend of annual and summer precipitation in the region,but the increasing DTR trend in the Nigerian Guinea Coast region can be attributed to the decreasing trend of cloud cover over the region.展开更多
Polychaete Neanthes japonica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this study, the relations of body weight, salinity and temperature to...Polychaete Neanthes japonica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this study, the relations of body weight, salinity and temperature to oxygen consumption and ammonia excretion of N. japonica were determined. Three different groups in body weight (large: 2.34±0.36 g, middle: 1.50±0.21 g and small: 0.62±0.12 g) were set for all experiments. Results show that the body weight is negatively related to the rates of oxygen consumption and ammonia excretion; and the relationship is significant. The oxygen consumption and ammonia excretion at 24℃ decreased at salinity from 5 to 30 and increased above 30, indicating that both lower and higher salinity are adverse and certain degree of salinity stress is necessary for enhancing the energy demand. At salinity 30, rising temperature from 18℃ to 30℃, the oxygen consumption increased before 27℃ and then decreased. However, the relation of ammonia excretion and temperature seems more complex. Two-way ANOVA shows that salinity, temperature and body weight all have a significant effect on the oxygen consumption and ammonia excretion of the worm. Moreover, interaction between salinity/temperature and body weight is also significant. O:N (oxygen/nitrogen) ratio varies greatly in this case from 5.97 to 463.22, indicating that N. japonica can regulate the type of metabolic substrate against environment changes.展开更多
Carbon-carbon composite (C/C) materials are prone to severe oxidation and volatilization problems. To address these issues, mullite (3Al2O3.2SiO2)/silicon carbide (SIC) coatings were deposited on C/C composite s...Carbon-carbon composite (C/C) materials are prone to severe oxidation and volatilization problems. To address these issues, mullite (3Al2O3.2SiO2)/silicon carbide (SIC) coatings were deposited on C/C composite substrates characterized into high and low densities. The coatings were applied by a two-step approach: pack cementation and silica sol based slurry coating processes. The relationship between the microstructure of 3Al2O3·2SiO2/SiC coatings and C/C substrates during isothermal oxidation cycle at 1 500 ℃ was investigated using X-ray diffractometer (XRD) and scanning electron microscope (SEM) mounted with energy dispersive spectrometer (EDS). The results indicate that the density of the substrates has a marked effect on the coatings. Dense, thick and well-bonded coatings are obtained in the high density substrate. After 106 h of isothermal oxidation, the high density substrate with 3Al2O3-2SiO2/SiC coating offers effective protection as compared to low density substrate suffering recession.展开更多
Some crude oils with high water cut have the capability to flow below the oil gel point, while the oil particles adhere to the pipe wall in the form of paste, also called "wall sticking". Wall sticking is a ...Some crude oils with high water cut have the capability to flow below the oil gel point, while the oil particles adhere to the pipe wall in the form of paste, also called "wall sticking". Wall sticking is a serious problem during the pipeline transportation, leading to partial or total blockage of the pipeline and energy wastage. In this paper, a series of laboratory flow loop experiments were conducted to observe the wall sticking characteristics of crude oil with high water cut, high viscosity and high gel point at low transportation temperatures. The effects of shear stress and water cut on the wall sticking rate and occurrence temperature were investigated. Experimental results indicated that the wall sticking rate and occurrence temperature were lower under stronger shear stress and higher water cut conditions. A criterion of wall sticking occurrence temperature(WSOT) and a regression model of wall sticking rate were then established. Finally, the software was developed to calculate the pressure drop along the pipelines of crude oils with high water-cut. It was able to predict the wall sticking thickness of gelled oil and then calculate the pressure drop along the pipelines. A typical case study indicated that the prediction results obtained from the software were in agreement with actual measured values.展开更多
High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than...High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...展开更多
This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China&...This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China's Mainland from 1960 to 2008. During these 48 years four high frequency centers of cold surge events were located in Xinjiang, central North China, northeast China, and southeast China. A main frequency peak of cold surge events occurs in autumn for the four regions and another peak is detected in spring over northeast China and southeast China. The regional pattern of cold surge frequencies is in accordance with the perturbation kinetic energy distribution in October December, January, and February April. The long-term decreasing trend ( 0.2 times/decade) of cold surge frequencies in northeast China and decadal variations in China are related to the variations of the temperature difference between southern and northern China in the winter monsoon season; these variations are due to the significant rising of winter temperatures in high latitudes.展开更多
Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The ...Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.展开更多
Sodium-ion batteries (NIBs) show great prospect on the energy storage applications benefiting from thei low cost and the abundant Na resources despite the expected lower energy density compared wit lithium-ion batte...Sodium-ion batteries (NIBs) show great prospect on the energy storage applications benefiting from thei low cost and the abundant Na resources despite the expected lower energy density compared wit lithium-ion batteries (LIBs). To further enhance the competitive advantage, especially in energy densit3 developing the high-capacity carbon anode materials can be one of the effective approaches to realiz this goal. Herein, we report a novel carbon anode made from charcoal with a high capacity of ~400 Ah g i, wherein about 85% (〉330 mAh g^-1) of its total capacity is derived from the long plateau regio below ~0.1 V. which differs fiom those of typical hard carbon materials (~300 mAh g^-l) in NIBs but i similar to the graphite anode in LIBs. When coupled with air-stable Nao.gCuo.22Feo.3oMno.4802 oxid cathode, a high-energy density of ~240 Wh kg^-1 is achieved with good rate capability and cyclin stability. The discovery of this promising carbon anode is expected to further improve the energy densit of NIBs towards large-scale electrical energy storage.展开更多
Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy (Ea, 55-70 kJ/mol). Here we report a simple...Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy (Ea, 55-70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 ℃ by introducing air to promote the catalysis. With the assistance of air, 〉99% conversion and 〉99% selectivity were achieved over Pd(111)/Al2O3 with an overall turnover frequency (TOF) of 621 h-1, -80 times greater than that of the state-of-art Pd catalyst at 30 ℃. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent Ea (8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.展开更多
Photoperiod and temperature are two pivotal regulatory factors of plant flowering. The floral transition of plants depends on accurate measurement of changes in photoperiod and temperature. The flowering time of rice ...Photoperiod and temperature are two pivotal regulatory factors of plant flowering. The floral transition of plants depends on accurate measurement of changes in photoperiod and temperature. The flowering time of rice (Oryza sativa) as a facultative short-day (SD) plant is delayed under long-day (LD) and/or low temperature conditions. To elucidate the regulatory functions of photoperiod and temperature on flowering time in rice, we systematically analyzed the expression and regulation of several key genes (Hd3a, RFT1, Ehdl, Ghd7, RID1/Ehd2/OsIdl, Se5) involved in the photoperiodic flowering regulatory pathway under different temperature and photoperiod treatments using a photoperiod-insensitive mutant and wild type plants. Our re- sults indicate that the Ehdl-Hd3a/RFT1 pathway is common to and conserved in both the photoperiodic and temperature flow- ering regulatory pathways. Expression of Ehdl, Hd3a and RFT1 is dramatically reduced at low temperature (23~C), suggesting that suppression of Ehdl, Hd3a and RFT1 transcription is an essential cause of delayed flowering under low temperature con- dition. Under LD condition, Ghd7 mRNA levels are promoted at low temperature (23~C) compared with normal temperature condition (28℃), suggesting low temperature and LD treatment have a synergistic role in the expression of Ghd7. Therefore, upregulation of Ghd7 might be a crucial cause of delayed flowering under low temperature condition. We also analyzed Hdl regulatory relationships in the photoperiodic flowering pathway, and found that Hdl can negatively regulate Ehdl transcription under LD condition. In addition, Hdl can also positively regulate Ghd7 transcription under LD condition, suggesting that the heading-date of rice under LD condition is also regulated by the Hdl-Ghd7-Ehdl-RFT1 pathway.展开更多
We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. ...We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, dif- fering with the other four C^1, G2, C13 and 6"33 constants. The Poisson's ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B]C44 investigations revealed that VzAIC is brittle and the brittleness decreases with pressure. Also, we found that V2A1C is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grtineisen pa- rameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.展开更多
By optimizing the diffusion temperature and time,four groups of samples with different sheet resistances are achieved.The front screen printing pattern and firing temperature are fine-tuned according to the needs.The ...By optimizing the diffusion temperature and time,four groups of samples with different sheet resistances are achieved.The front screen printing pattern and firing temperature are fine-tuned according to the needs.The performance of the low-and-plateau-temperature doping recipe(as recipe A)is better than that of the low-and-multiple-temperature doping recipe(as recipe B).And the 19.24%efficiency of volume production of monocrystalline solar cells with 238.95 mm2 and 80?/sq sheet resistance is obtained in the traditional process line.0.48%more efficiency is achieved than 60?/sq due to the reduction of the phosphorus surface doping and shallow junction by the low-and-plateau-temperature diffusion recipe.The module test shows that by using two drive-in zones,not only do we have a higher efficiency,but also have a stabler and lower power loss in encapsulation manufacture.It is showed that power of a large improvement will be gotten by statistical analysis and PC1D simulation.展开更多
基金Projects(52274404,52305441,U22A20190)supported by the National Natural Science Foundation of ChinaProjects(2022JJ20065,2023JJ40739)supported by the Natural Science Foundation of Hunan Province,China+2 种基金Project(2022RC1001)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2023ZZTS0972)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2021YFB3400903)supported by the National Key R&D Program of China。
文摘The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formability of Al-Cu-Li alloy is vital.A thorough comparison of the effects of cryo-deformation and ambient temperature large pre-deformation(LPD)on the creep ageing response in the 2195 alloy sheet at 160℃with different stresses has been made.The evolution of dislocations and precipitates during creep ageing of LPD alloys are revealed by X-ray diffraction and transmission electron microscopy.High-quality 2195 alloy sheet largely pre-deformed by 80%without edge-cracking is obtained by cryo-rolling at liquid nitrogen temperature,while severe edge-cracking occurs during room temperature rolling.The creep formability and strength of the 2195 alloy are both enhanced by introducing pre-existing dislocations with a density over 1.4×10^(15)m^(−2).At 160℃and 150 MPa,creep strain and creep-aged strength generally increases by 4−6 times and 30−50 MPa in the LPD sample,respectively,compared to conventional T3 alloy counterpart.The elongation of creep-aged LPD sample is low but remains relevant for application.The high-density dislocations,though existing in the form of dislocation tangles,promote the formation of refined T1 precipitates with a uniform dispersion.
文摘Based on the initial field temperature data of ECMWF 850 hPa from Jan- uary 2012 to December 2015, linear interpolation method of ECMWF was employed to calculate the 850 hPa temperature values at 8:00 and 20:00 of 7 stations (Jiamusi, Tangyuan, Huachuan, Huanan, Fujin, Tongjiang, Fuyuan). Combined with the observed daily minimum and maximum air temperatures at the same time of the 7 stations, the correlations of the 850 hPa temperature values at 8:00 and 20:00 with the daily maximum or minimum air temperature of the ground meteorological obser- vation stations were established, and the ground observation data in accordance with the relevant analysis and correlation test principle of the prediction equation for factor were primarily selected. Regression method was used to establish forecast e- quation dividing into counties, month by month. The results showed that the 850 hPa temperature values at 8:00 and 20:00 were significantly correlated with the daily maximum or minimum air temperature, and the established temperature fore- cast equation was of certain guiding significance for the forecast of daily minimum and maximum temperature, which could help to improve the forecast accuracy.
基金"973" National Key Basic Research and Development Program (No.2012CB518202)Project of Qinghai Development of Science and Technology (No.2011-N-150)
文摘On April 14, 2010, an earthquake reaching 7.1 Richter scale struck Jiegu Town of Yushu. More than 2 698 people were confirmed dead, and 12 135 were injured, of which 1 434 were severely injured. Rescue operation was carried out soon after the disaster; however, the rescue teams face great challenges of altitude hypoxia, freezing temperature and very bad weather. Thus, 1 434 severe injuries were rapidly transported airlifted to hospitals in Xining and neighboring provinces for effective treatment. The extremity trauma (49.9 % ) was the most common patteru of injuries. Asphyxia (40.8 % ) was by far the most important reason for death. A high incidence of acute altitude illness in the lowland rescuers was a special medical problem during the highest earthquake in Yushu. We have learned more lessons from Yushu Earthquake.
基金jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)[grant number XDA19030403]the National Natural Science Foundation of China [grant number 41575095]+2 种基金the CAS ‘Belt and Road Initiatives’ Program on International Cooperation [grant number 134111KYSB20160010]Victor Nnamdi DIKE acknowledges support from the CAS–TWAS(The World Academy of Sciences)President FellowshipHyacinth NNAMCHI is supported by the International Federation for Science(W/4849)
文摘The long-term trend of diurnal temperature range(DTR)over Nigeria was examined using daily station-based datasets for the period 1971–2013.The results show that the regionally averaged DTR has decreased significantly(-0.34°C per decade)over the Nigerian Sahel(north of 10°N),but there has been a slight increasing trend(0.01°C per decade)over the Nigerian Guinea Coast.The annual decreasing trend of DTR in the Nigerian Sahel is mainly attributable to the significant increasing trend in daily minimum temperature(Tmin,0.51°C per decade),which far outstrips the rate of increase in the daily maximum(Tmax,0.17°C per decade).In contrast,the comparable trends in Tmin(0.19°C per decade)and Tmax(0.20°C per decade)may explain the non-significant trend of the DTR averaged over the Guinea Coast region.It is observed that the DTR has decreased more in boreal summer(June–July–August)than in boreal winter(December–January–February)for the regions.Furthermore,it is found that the significant DTR declining trend over the Nigerian Sahel is closely associated with an increasing trend of annual and summer precipitation in the region,but the increasing DTR trend in the Nigerian Guinea Coast region can be attributed to the decreasing trend of cloud cover over the region.
基金Supported by the National Natural Science Foundation of China (No. 30490233)the Three-Gorge Project and the Estuarine Environment (No. SX2004-018) from the Three Gorges Project Construction Committee
文摘Polychaete Neanthes japonica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this study, the relations of body weight, salinity and temperature to oxygen consumption and ammonia excretion of N. japonica were determined. Three different groups in body weight (large: 2.34±0.36 g, middle: 1.50±0.21 g and small: 0.62±0.12 g) were set for all experiments. Results show that the body weight is negatively related to the rates of oxygen consumption and ammonia excretion; and the relationship is significant. The oxygen consumption and ammonia excretion at 24℃ decreased at salinity from 5 to 30 and increased above 30, indicating that both lower and higher salinity are adverse and certain degree of salinity stress is necessary for enhancing the energy demand. At salinity 30, rising temperature from 18℃ to 30℃, the oxygen consumption increased before 27℃ and then decreased. However, the relation of ammonia excretion and temperature seems more complex. Two-way ANOVA shows that salinity, temperature and body weight all have a significant effect on the oxygen consumption and ammonia excretion of the worm. Moreover, interaction between salinity/temperature and body weight is also significant. O:N (oxygen/nitrogen) ratio varies greatly in this case from 5.97 to 463.22, indicating that N. japonica can regulate the type of metabolic substrate against environment changes.
基金Project(2011CB605805) supported by the National Basic Research Program of ChinaProject(51021063) supported by the Creative Research Group of National Natural Science Foundation of China
文摘Carbon-carbon composite (C/C) materials are prone to severe oxidation and volatilization problems. To address these issues, mullite (3Al2O3.2SiO2)/silicon carbide (SIC) coatings were deposited on C/C composite substrates characterized into high and low densities. The coatings were applied by a two-step approach: pack cementation and silica sol based slurry coating processes. The relationship between the microstructure of 3Al2O3·2SiO2/SiC coatings and C/C substrates during isothermal oxidation cycle at 1 500 ℃ was investigated using X-ray diffractometer (XRD) and scanning electron microscope (SEM) mounted with energy dispersive spectrometer (EDS). The results indicate that the density of the substrates has a marked effect on the coatings. Dense, thick and well-bonded coatings are obtained in the high density substrate. After 106 h of isothermal oxidation, the high density substrate with 3Al2O3-2SiO2/SiC coating offers effective protection as compared to low density substrate suffering recession.
基金the support from the projects of the National Natural Science Foundation of China(No.51374224)for this research
文摘Some crude oils with high water cut have the capability to flow below the oil gel point, while the oil particles adhere to the pipe wall in the form of paste, also called "wall sticking". Wall sticking is a serious problem during the pipeline transportation, leading to partial or total blockage of the pipeline and energy wastage. In this paper, a series of laboratory flow loop experiments were conducted to observe the wall sticking characteristics of crude oil with high water cut, high viscosity and high gel point at low transportation temperatures. The effects of shear stress and water cut on the wall sticking rate and occurrence temperature were investigated. Experimental results indicated that the wall sticking rate and occurrence temperature were lower under stronger shear stress and higher water cut conditions. A criterion of wall sticking occurrence temperature(WSOT) and a regression model of wall sticking rate were then established. Finally, the software was developed to calculate the pressure drop along the pipelines of crude oils with high water-cut. It was able to predict the wall sticking thickness of gelled oil and then calculate the pressure drop along the pipelines. A typical case study indicated that the prediction results obtained from the software were in agreement with actual measured values.
基金Supported by Science and Technology Committee of Tianjin (No.06YFGPGX08400)Ministry of Science and Technology of China (No.2009GJF20022)Innovation Fund of Tianjin University
文摘High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...
基金supported jointly by the National Natural Science Foundation of China (40975039)the National Basic Research Program of China (2006CB400504/ 2009CB421401 and GYHY20070605)
文摘This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China's Mainland from 1960 to 2008. During these 48 years four high frequency centers of cold surge events were located in Xinjiang, central North China, northeast China, and southeast China. A main frequency peak of cold surge events occurs in autumn for the four regions and another peak is detected in spring over northeast China and southeast China. The regional pattern of cold surge frequencies is in accordance with the perturbation kinetic energy distribution in October December, January, and February April. The long-term decreasing trend ( 0.2 times/decade) of cold surge frequencies in northeast China and decadal variations in China are related to the variations of the temperature difference between southern and northern China in the winter monsoon season; these variations are due to the significant rising of winter temperatures in high latitudes.
基金Projects(51878245,U1965105)supported by the National Natural Science Foundation of ChinaProject(2019GSF110006)supported by the Key Research and Development Program of Shandong Province,China+2 种基金Project(2020Z035)supported by the Ningbo 2025 Science and Technology Major Project,ChinaProject(KJ2017B01)supported by the Scientific Research Project of Department of Education of Anhui Province,ChinaProject(2019CEM001)supported by the State Key Laboratory of High Performance Civil Engineering Materials,China。
文摘Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.
基金supported by the National Key Technologies R&D Program(2016YFB0901500)National Natural Science Foundation of China(51725206,51421002,51232005,and 51372131)
文摘Sodium-ion batteries (NIBs) show great prospect on the energy storage applications benefiting from thei low cost and the abundant Na resources despite the expected lower energy density compared wit lithium-ion batteries (LIBs). To further enhance the competitive advantage, especially in energy densit3 developing the high-capacity carbon anode materials can be one of the effective approaches to realiz this goal. Herein, we report a novel carbon anode made from charcoal with a high capacity of ~400 Ah g i, wherein about 85% (〉330 mAh g^-1) of its total capacity is derived from the long plateau regio below ~0.1 V. which differs fiom those of typical hard carbon materials (~300 mAh g^-l) in NIBs but i similar to the graphite anode in LIBs. When coupled with air-stable Nao.gCuo.22Feo.3oMno.4802 oxid cathode, a high-energy density of ~240 Wh kg^-1 is achieved with good rate capability and cyclin stability. The discovery of this promising carbon anode is expected to further improve the energy densit of NIBs towards large-scale electrical energy storage.
基金supported by the Ministry of Science and Technology of China(2017YFA0207302,2015CB93230)the National Natural Science Foundation of China(21420102001,21333008)
文摘Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy (Ea, 55-70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 ℃ by introducing air to promote the catalysis. With the assistance of air, 〉99% conversion and 〉99% selectivity were achieved over Pd(111)/Al2O3 with an overall turnover frequency (TOF) of 621 h-1, -80 times greater than that of the state-of-art Pd catalyst at 30 ℃. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent Ea (8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.
基金supported by the National Natural Science Foundation of China (Grant Nos. 31171515 and 30871328)Tianjin Natural Science Foundation of China (Grant No. 11JCZDJC17900)+1 种基金the Program of Tian-jin Municipal Education Commission (Grant No. 20090609)Knowledge Innovation Program of Tianjin Normal University (Grant No. 52X09039)
文摘Photoperiod and temperature are two pivotal regulatory factors of plant flowering. The floral transition of plants depends on accurate measurement of changes in photoperiod and temperature. The flowering time of rice (Oryza sativa) as a facultative short-day (SD) plant is delayed under long-day (LD) and/or low temperature conditions. To elucidate the regulatory functions of photoperiod and temperature on flowering time in rice, we systematically analyzed the expression and regulation of several key genes (Hd3a, RFT1, Ehdl, Ghd7, RID1/Ehd2/OsIdl, Se5) involved in the photoperiodic flowering regulatory pathway under different temperature and photoperiod treatments using a photoperiod-insensitive mutant and wild type plants. Our re- sults indicate that the Ehdl-Hd3a/RFT1 pathway is common to and conserved in both the photoperiodic and temperature flow- ering regulatory pathways. Expression of Ehdl, Hd3a and RFT1 is dramatically reduced at low temperature (23~C), suggesting that suppression of Ehdl, Hd3a and RFT1 transcription is an essential cause of delayed flowering under low temperature con- dition. Under LD condition, Ghd7 mRNA levels are promoted at low temperature (23~C) compared with normal temperature condition (28℃), suggesting low temperature and LD treatment have a synergistic role in the expression of Ghd7. Therefore, upregulation of Ghd7 might be a crucial cause of delayed flowering under low temperature condition. We also analyzed Hdl regulatory relationships in the photoperiodic flowering pathway, and found that Hdl can negatively regulate Ehdl transcription under LD condition. In addition, Hdl can also positively regulate Ghd7 transcription under LD condition, suggesting that the heading-date of rice under LD condition is also regulated by the Hdl-Ghd7-Ehdl-RFT1 pathway.
基金supported by the National Natural Science Foundation of China (Grant Nos.10974139,10964002,11104247 and 11176020)the Provincial Natural Science Foundation of Guizhou (Grant Nos.[2009]2066 and TZJF-2008-42)+2 种基金the Provincial Natural Science Foundation of Hainan (Grant No.110001)the Provincial Natural Science Foundation of Chong Qing(Grant No.CSTCcstc2011jja90002)the Provincial Natural Science Foundation of Zhejiang (Grant No.Y201121807)
文摘We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, dif- fering with the other four C^1, G2, C13 and 6"33 constants. The Poisson's ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B]C44 investigations revealed that VzAIC is brittle and the brittleness decreases with pressure. Also, we found that V2A1C is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grtineisen pa- rameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.
基金supported by the National High Technology Research and("863"program)(Grant Nos.2012AA0503032011AA050504)+1 种基金Independent Innovation Project of Shandong Province(Grant Nos.2010ZHZX1A07022011ZHZX1A0701)
文摘By optimizing the diffusion temperature and time,four groups of samples with different sheet resistances are achieved.The front screen printing pattern and firing temperature are fine-tuned according to the needs.The performance of the low-and-plateau-temperature doping recipe(as recipe A)is better than that of the low-and-multiple-temperature doping recipe(as recipe B).And the 19.24%efficiency of volume production of monocrystalline solar cells with 238.95 mm2 and 80?/sq sheet resistance is obtained in the traditional process line.0.48%more efficiency is achieved than 60?/sq due to the reduction of the phosphorus surface doping and shallow junction by the low-and-plateau-temperature diffusion recipe.The module test shows that by using two drive-in zones,not only do we have a higher efficiency,but also have a stabler and lower power loss in encapsulation manufacture.It is showed that power of a large improvement will be gotten by statistical analysis and PC1D simulation.