The received signal of the polarization sensitive array is proved to have trilinear model characteristics. The blind parallel factor(PARAFAC) signal detection algorithm for the polarization sensitive array is propos...The received signal of the polarization sensitive array is proved to have trilinear model characteristics. The blind parallel factor(PARAFAC) signal detection algorithm for the polarization sensitive array is proposed. The trilinear alternating least square (TALS) algorithm is used to abtain the source matrix, and then the matrix is judged. Simulation results show that the bit error rate (BER) of the detection algorithm is close to that of the non-blind decorrelating method and the algorithm works well under the array error condition. BER difference between the non-blind method and this algorithm is less than 2 dB under a high SNR. The algorithm is blind and robust. The channel fading, the direction of arrive(DOA) imformation and the polarization information are needless in the algorithm.展开更多
Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical application...Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical applications of this type of battery still suffer from low specific capability, poor cycle sta- bility, instable electrolytes, and unstable polymer binders. Herein, we report a facile method of synthesizing binder free and flexible cathodes with C0304 nanowire arrays vertically grown onto carbon textiles. When employed as a cathode for Na-O2 batteries, this cathode exhibits superior performance, including a reduction of charge overpotential, high specific capacity (4687 mAh/g), and cycle stability up to 62 cycles. These enhanced performance can be attributed to the synergistic effect of the porosity and catalytic activity of the C0304 nanowire catalyst.展开更多
lntracellular redox homeostasis plays a critical role in determining tumor cells' sensitivity to drug-induced apoptosis. Here we investigated the role of thioredoxin-1 (TRX1), a key component of redox regulation, i...lntracellular redox homeostasis plays a critical role in determining tumor cells' sensitivity to drug-induced apoptosis. Here we investigated the role of thioredoxin-1 (TRX1), a key component of redox regulation, in arsenic trioxide (AS2O3)-induced apoptosis. Over-expression of wild-type TRX1 in HepG2 cells led to the inhibition of As2O3-induced cytochrome c (cyto c) release, caspase activation and apoptosis, and down-regulation of TRX1 expression by RNAi sensitized HepG2 cells to As2O3-induced apoptosis. Interestingly, mutation of the active site of TRX1 from Cys^32/35 to Ser^32/35 converted this molecule from an apoptotic protector to an apoptotic promoter. In an effort to understand the mechanisms of this conversion, we used isolated mitochondria from mouse liver and found that recombinant wild-type TRX1 could protect mitochondria from the apoptotic changes. In contrast, the mutant form of TRX1 alone elicited mitochondria-related apoptotic changes, including the mitochondrial permeability transition pore (mPTP) opening, loss of mitochondrial membrane potential, and cyto c release from mitochondria. These apoptotic effects were inhibited by cyclosporine A (CsA), indicating that mutant TRX1 targeted to mPTP. Alteration of TRX1 from its reduced form to oxidized form in vivo by 2,4-dinitrochlorobenzene (DNCB), a specific inhibitor ofTRX reductase, also sensitized HepG2 cells to As203-induced apoptosis. These data suggest that TRX1 plays a central role in regulating apoptosis by blocking cyto c release, and inactivation of TRX1 by either mutation or oxidization of the active site cysteines may sensitize tumor cells to As2O3-induced apoptosis.展开更多
The effects of a novel three-step aging process (T76+T6) on the electrochemical corrosion behavior of 7150 extruded aluminum alloy were evaluated and compared with those of the conventional retrogression and re-agi...The effects of a novel three-step aging process (T76+T6) on the electrochemical corrosion behavior of 7150 extruded aluminum alloy were evaluated and compared with those of the conventional retrogression and re-aging process (T77). The open circuit potential (OCP), cyclic polarization and electrochemical impedance spectra (EIS) of the A1 alloys were measured after treatment in three solutions (3.5% NaCl (mass fraction); 10 mmol/L NaCl + 0.1 mol/L Na2SO4; 4 mol/L NaCl + 0.5 mol/L KNO3 + 0.1 mol/L HNO3). The parameters including the corrosion potential, pitting potential, pit transition potential and steepness, and potential differences were extensively discussed to evaluate the corrosion behavior of the Al alloys. The electrochemical and scanning electron microscopy (SEM) data show that compared with the 7150-T77 Al alloy, the T76 + T6 aged 7150 A1 alloy exhibits better resistance to pitting corrosion, inter-granular corrosion (IGC) and exfoliation corrosion, which is attributed to further coarsening and inter-spacing of the grain boundary particles (GBPs) as revealed by transmission electron microscopy. Furthermore, the hardness tests indicate that an attractive combination of strength and corrosion resistance was obtained for the 7150 Al alloy with T76 + T6 treatment.展开更多
The phase relationships in the Zn-Al-Ti system at 450 and 600℃ were experimentally determined using equilibrated alloys method.The specimens were investigated by means of scanning electron microscopy coupled with ene...The phase relationships in the Zn-Al-Ti system at 450 and 600℃ were experimentally determined using equilibrated alloys method.The specimens were investigated by means of scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffractometry.Eleven and eight three-phase regions are confirmed in the 450 and 600℃ isothermal sections,respectively.The Ti2Al5 which only exists at high temperature(990-1199.4℃)in Ti-Al binary system is confirmed in two isothermal sections due to the dissolution of zinc.The T phase is confirmed as a ternary compound rather than an extension phase of TiZn3 at 450℃.The T2 phase is a new ternary phase stable at 450 and 600℃ in Zn-Al-Ti ternary system.展开更多
The title compound of karounidiol (C30H48O2), a main active triterpene component of snakegourd seed, was isolated from unsaponifiable matter of the seed oil of Trichosanthes kirilowii Maxim., and characterized by X-ra...The title compound of karounidiol (C30H48O2), a main active triterpene component of snakegourd seed, was isolated from unsaponifiable matter of the seed oil of Trichosanthes kirilowii Maxim., and characterized by X-ray diffraction analysis. It crystallizes in orthorhombic system, space group P212121 with C30H48O2CH3OHH2O (C31H54O4), a = 7.515(1), b = 14.407(1), c = 27.799(2) , V = 3009.8(5) 3, Z = 4, Dx = 1.087 g/cm3, Mr = 490.77, F(000) = 1088 and = 0.086 mm-1. The final R = 0.0840 and wR = 0.2289 for 2752 observed reflections (|F|2 ≥ 2|F|2). The molecular crystal structure of karounidiol shows relative stereochemistry of (3,13,14, 20)-3,29-dihydroxy-13-methyl-26-norolean-7,9(11)-diene. The molecule is composed of five six- membered rings with ring junctures of A/B trans, C/D trans and D/E cis.展开更多
Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS a...Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS and AFM. The experimental results show that the implantation of boron atom can reduce the internal stress and improve the adhesion strength of the films. The critical load of scratch test rises to 27.45 N, compared to 1.75 N of c-BN film on the unimplanted HSS. The AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. Then the composition of the boron implanted layer was analyzed by the XPS. And the influence of the boron implanted layer on the internal stress and adhesion strength of c-BN films were investigated.展开更多
Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octyl...Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octylthiophene2,5-diyl) -(p-N, N-dimethylamino ) benzylidenequinomethane-2, 5-diyl)] (POTDMABQ), were synthesized.The band gaps of the two polymers are calculated as 1. 75 eV for PBTDMABQ and 1. 69 eV for POTDMABQ,respectively. The homogenous films of the two polymers were prepared and their third-ordernonlinear optical properties were studied by the backward degenerate four-wave mixing at 532 nm. Byusing the relative measurement technique, the third-order nonlinear optical susceptibilities ofPBTDMABQ and POTDMABQ are calculated as 5. 62 X 10^(-9) and 1. 22 X 10^(-8) ESU, respectively. It isfound that substituted alky groups have strong effects on the band gap and nonlinear opticalproperties of the two polymers. The relatively big third-order nonlinear optical susceptibilitiesand small band gap of POTDMABQ resulted mainly from the longer alkyl with strong electron-donatingability can enhance the delocation degree of conjugated π electronics.展开更多
This paper deals with the development and evolution of modern Yellow River delta and the erosion or deposition rates of its different sections. In June, 1996, Yellow Rivers terminal course was artificially turned east...This paper deals with the development and evolution of modern Yellow River delta and the erosion or deposition rates of its different sections. In June, 1996, Yellow Rivers terminal course was artificially turned eastwards to empty into the sea and then the 11th lobe of the modern Yellow River delta began to form. This course change may mark the beginning of the 3rd subdelta formation. As a result of that, the Yellow River delta advances towards east by north with the 1st, 2nd and 3rd subdeltas arranged in succession. Coast zone in the deltaic area is divided into 7 different sections according to their different erosion or deposition rates: the relatively stable section from Dakou River to Shunjiang Stream, the weakly retreating section from Shunjiang Stream to the Tiaohe River mouth, the strongly retreating section from the Tiaohe River mouth to the station 106, the artificially stable section due to stone dam protection from the station 106 to Gudong Oilfield, the strong deposition section from Gudong Oilfield to Dawenliu Haipu, the weakly deposition section from Dawenliu Haipu to the Zimai Stream mouth, and the stable section from the Zimai Stream mouth to the Jiaolai River mouth. It is predicted that the erosion and deposition situations of the sections will nearly remain the same in 10 years, but the retreating and silting-up rates will tend to become slower gradually. Human activities have an evident influence on the changes of the coastline.展开更多
The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results s...The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures: the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC.展开更多
The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution(BF_3-CH_3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron tri...The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution(BF_3-CH_3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron trifluoride methanol complex and sodium methoxide to produce enriched ^(10)B methylborate was proposed based on a detailed mechanism study, and was verified by acid-base titration method and conductivity method. It was found that this reaction is first order reaction and the rate constant is 0.022 min^(-1) at 338 K(65 ℃), the activity energy is 65 k J/mol. In addition, it was found that the conductivity method is more feasible to measure the kinetic curve than acid-base titration method.展开更多
In this paper we report on recent development in the areas of optical vortices generated by micro-optical elements and applications of optical vortices, including optical manipulation, radial polarization and secure f...In this paper we report on recent development in the areas of optical vortices generated by micro-optical elements and applications of optical vortices, including optical manipulation, radial polarization and secure free space optical communication展开更多
The bis(tributyltin) ester of succinic acid was synthesized by the reaction of disodium salt of succinic acid with tributyltin chloride in a molar ratio of 1:2. The crystal structure was determined by X-ray single-cry...The bis(tributyltin) ester of succinic acid was synthesized by the reaction of disodium salt of succinic acid with tributyltin chloride in a molar ratio of 1:2. The crystal structure was determined by X-ray single-crystal diffraction. It belongs to orthorhombic with space group Pccn, a = 20.949(3), b = 17.470(3), c = 20.345(3) Angstrom, V = 7446(2) Angstrom(3), Z = 8, D-c = 1.242 g/cm(3), mu = 1.365 mm(-1), F(000) = 2864, R = 0.0544 and wR = 0.1417. The tin atom is of five-coordination in a trigonal bipyramidal structure by bridging two carboxylate groups in different directions and the resulting structure which contains straight twist large ring channels along the axes of a, b and c is a three-dimensional framework polymer containing two different tin atoms.展开更多
High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system suc...High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.展开更多
The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen ...The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen photosensitization,the reactive singlet oxygen species are generated through the energy transfers from photosensitizer(PS)to ground triplet oxygen molecule.In this work,we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation.Then we utilized the molecular orbital(MO)overlaps to approximate it,where the MOs were computed from isolated single molecules.As demonstrated with quantitative results,this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O_(2),providing us a simple but effective way to predict the coupling of triplet fusion reactions.展开更多
The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading...The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading equipment corresponding to the CT machine. Through the CT scanning, the clear CT images which include from the microcracks compressed stage to growth stage, bifurcation stage, development stage, crack fracture stage,the rock sample failure until to unloading stage in the different stress states were obtained. The CT values, CT images and the other data have been analyzed. Based on the results of the CT testing of meso damage evolution law of rock,the stress threshold value of meso damage of rock is given, and the stress strain complete process curve of rock is divided into some sections. The initial rock damage propagation law is given in this paper.展开更多
Changping Plain, located in the northwest of Beijing, has become an important groundwater recharge area for the Beijing Plain and an important source for the urban water supply. In this study, groundwater samples were...Changping Plain, located in the northwest of Beijing, has become an important groundwater recharge area for the Beijing Plain and an important source for the urban water supply. In this study, groundwater samples were collected during the dry and wet seasons in 2015 from 24 monitoring wells distributed in Changping Plain. A Piper-Tri-linear diagram, a Schoeller diagram, a Gibbs diagram, and the isotope technique were used to investigate the temporal and spatial variations in the concentrations of groundwater hydrochemicals and the sources of groundwater recharge. The results indicated: 1) seasonal variations in the concentrations of HCO3^–, Ca^2+, and Na^+ were significant; the spatial variations of these ions were more dramatic in the dry season than in the wet season due to the dilution effect of precipitation; 2) Most groundwater samples had a HCO3-Ca-Mg based hydrochemical type and a few had a HCO3-Na-K based hydrochemical type; the hydrochemical type tended to evolve from HCO3-Ca-Mg based to HCO3-Na-K based in some monitoring wells that showed distinct seasonal variation; 3) the groundwater in the study area originated mainly from atmospheric precipitation, and it is affected by evaporation and concentration processes.展开更多
One-dimensional ZnMn2O4 nanowires have been prepared and investigated as anode materials in Li rechargeable batteries. The highly crystalline ZnMn2O4 nanowires about 15 nm in width and 500 nm in length showed a high s...One-dimensional ZnMn2O4 nanowires have been prepared and investigated as anode materials in Li rechargeable batteries. The highly crystalline ZnMn2O4 nanowires about 15 nm in width and 500 nm in length showed a high specific capacity of about 650 mAh.g-1 at a current rate of 100 mA.g-1 after 40 cycles. They also exhibited high power capability at elevated current rates, i.e., 450 and 350 mAh.g 1 at current rates of 500 and 1000 mA.g 1, respectively. Formation of Mn3O4 and ZnO phases was identified by ex situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies after the initial discharge-charge cycle, which indicates that the ZnMn2O4 phase was converted to a nanocomposite of Mn3O4 and ZnO phases immediately after the electrochemical conversion reaction.展开更多
Herein, we report a versatile strategy to fabri- cate three-dimensional melamine sponge (MS)-Au/ceria nanowire (NW) networks to realize in situ continuous reduction of p-nitrophenol in a consecutive flow system. T...Herein, we report a versatile strategy to fabri- cate three-dimensional melamine sponge (MS)-Au/ceria nanowire (NW) networks to realize in situ continuous reduction of p-nitrophenol in a consecutive flow system. This system has proven to be high activity and stability. The ceria NW networks with large surface area can stabi- lize tiny Au nanoparticles dispersed on the ceria NWs, which are loaded on the framework of MS by dip-coating, and enhance the synergistic effect between ceria NWs networks and Au nanoparticles, leading to extremely high activity and good stability for catalytic application. The low-cost raw materials and catalyst with high activity and stability may make this three-dimensional MS-Au/ceria NWs composite material promising for continuous cat- alytic reaction application in industry or other fields.展开更多
文摘The received signal of the polarization sensitive array is proved to have trilinear model characteristics. The blind parallel factor(PARAFAC) signal detection algorithm for the polarization sensitive array is proposed. The trilinear alternating least square (TALS) algorithm is used to abtain the source matrix, and then the matrix is judged. Simulation results show that the bit error rate (BER) of the detection algorithm is close to that of the non-blind decorrelating method and the algorithm works well under the array error condition. BER difference between the non-blind method and this algorithm is less than 2 dB under a high SNR. The algorithm is blind and robust. The channel fading, the direction of arrive(DOA) imformation and the polarization information are needless in the algorithm.
基金supported by the 100 Talents Programme of the Chinese Academy of Sciencesthe National Basic Research Program of China(973 Program,2014CB932300,2012CB215500)the National Natural Science Foundation of China(21422108,51472232,51301160)~~
文摘Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical applications of this type of battery still suffer from low specific capability, poor cycle sta- bility, instable electrolytes, and unstable polymer binders. Herein, we report a facile method of synthesizing binder free and flexible cathodes with C0304 nanowire arrays vertically grown onto carbon textiles. When employed as a cathode for Na-O2 batteries, this cathode exhibits superior performance, including a reduction of charge overpotential, high specific capacity (4687 mAh/g), and cycle stability up to 62 cycles. These enhanced performance can be attributed to the synergistic effect of the porosity and catalytic activity of the C0304 nanowire catalyst.
文摘lntracellular redox homeostasis plays a critical role in determining tumor cells' sensitivity to drug-induced apoptosis. Here we investigated the role of thioredoxin-1 (TRX1), a key component of redox regulation, in arsenic trioxide (AS2O3)-induced apoptosis. Over-expression of wild-type TRX1 in HepG2 cells led to the inhibition of As2O3-induced cytochrome c (cyto c) release, caspase activation and apoptosis, and down-regulation of TRX1 expression by RNAi sensitized HepG2 cells to As2O3-induced apoptosis. Interestingly, mutation of the active site of TRX1 from Cys^32/35 to Ser^32/35 converted this molecule from an apoptotic protector to an apoptotic promoter. In an effort to understand the mechanisms of this conversion, we used isolated mitochondria from mouse liver and found that recombinant wild-type TRX1 could protect mitochondria from the apoptotic changes. In contrast, the mutant form of TRX1 alone elicited mitochondria-related apoptotic changes, including the mitochondrial permeability transition pore (mPTP) opening, loss of mitochondrial membrane potential, and cyto c release from mitochondria. These apoptotic effects were inhibited by cyclosporine A (CsA), indicating that mutant TRX1 targeted to mPTP. Alteration of TRX1 from its reduced form to oxidized form in vivo by 2,4-dinitrochlorobenzene (DNCB), a specific inhibitor ofTRX reductase, also sensitized HepG2 cells to As203-induced apoptosis. These data suggest that TRX1 plays a central role in regulating apoptosis by blocking cyto c release, and inactivation of TRX1 by either mutation or oxidization of the active site cysteines may sensitize tumor cells to As2O3-induced apoptosis.
基金Projects(51134007,51201186)supported by the National Natural Science Foundation of ChinaProject(51327902)supported by the Major Research Equipment Development,China+1 种基金Projects(2012CB619502,2010CB731701)supported by the National Basic Research Program of ChinaProject(12JJ6040)supported by the Natural Science Foundation of Hunan Province,China
文摘The effects of a novel three-step aging process (T76+T6) on the electrochemical corrosion behavior of 7150 extruded aluminum alloy were evaluated and compared with those of the conventional retrogression and re-aging process (T77). The open circuit potential (OCP), cyclic polarization and electrochemical impedance spectra (EIS) of the A1 alloys were measured after treatment in three solutions (3.5% NaCl (mass fraction); 10 mmol/L NaCl + 0.1 mol/L Na2SO4; 4 mol/L NaCl + 0.5 mol/L KNO3 + 0.1 mol/L HNO3). The parameters including the corrosion potential, pitting potential, pit transition potential and steepness, and potential differences were extensively discussed to evaluate the corrosion behavior of the Al alloys. The electrochemical and scanning electron microscopy (SEM) data show that compared with the 7150-T77 Al alloy, the T76 + T6 aged 7150 A1 alloy exhibits better resistance to pitting corrosion, inter-granular corrosion (IGC) and exfoliation corrosion, which is attributed to further coarsening and inter-spacing of the grain boundary particles (GBPs) as revealed by transmission electron microscopy. Furthermore, the hardness tests indicate that an attractive combination of strength and corrosion resistance was obtained for the 7150 Al alloy with T76 + T6 treatment.
基金Project(51971189)supported by the National Natural Science Foundation of ChinaProject(2019JJ60011)supported by Zhuzhou Joint Fund of Hunan Natural Science Foundation,ChinaProject(KFBM20180001)supported by Jiangsu Key Laboratory of Materials Surface Science and Technology(Changzhou University),China。
文摘The phase relationships in the Zn-Al-Ti system at 450 and 600℃ were experimentally determined using equilibrated alloys method.The specimens were investigated by means of scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffractometry.Eleven and eight three-phase regions are confirmed in the 450 and 600℃ isothermal sections,respectively.The Ti2Al5 which only exists at high temperature(990-1199.4℃)in Ti-Al binary system is confirmed in two isothermal sections due to the dissolution of zinc.The T phase is confirmed as a ternary compound rather than an extension phase of TiZn3 at 450℃.The T2 phase is a new ternary phase stable at 450 and 600℃ in Zn-Al-Ti ternary system.
基金the State Science and Technology Commission (No. 96-903-02-02)
文摘The title compound of karounidiol (C30H48O2), a main active triterpene component of snakegourd seed, was isolated from unsaponifiable matter of the seed oil of Trichosanthes kirilowii Maxim., and characterized by X-ray diffraction analysis. It crystallizes in orthorhombic system, space group P212121 with C30H48O2CH3OHH2O (C31H54O4), a = 7.515(1), b = 14.407(1), c = 27.799(2) , V = 3009.8(5) 3, Z = 4, Dx = 1.087 g/cm3, Mr = 490.77, F(000) = 1088 and = 0.086 mm-1. The final R = 0.0840 and wR = 0.2289 for 2752 observed reflections (|F|2 ≥ 2|F|2). The molecular crystal structure of karounidiol shows relative stereochemistry of (3,13,14, 20)-3,29-dihydroxy-13-methyl-26-norolean-7,9(11)-diene. The molecule is composed of five six- membered rings with ring junctures of A/B trans, C/D trans and D/E cis.
基金National Natural Science Foundation ofChina(No.59971065)
文摘Cubic boron nitride(c-BN) films were deposited on W6Mo5Cr4V2 high speed steel(HSS) substrate implanted with boron ion by RF-magnetron sputtering. The films were analyzed by the bending beam method, scratch test, XPS and AFM. The experimental results show that the implantation of boron atom can reduce the internal stress and improve the adhesion strength of the films. The critical load of scratch test rises to 27.45 N, compared to 1.75 N of c-BN film on the unimplanted HSS. The AFM shows that the surface of the c-BN film on the implanted HSS is low in roughness and small in grain size. Then the composition of the boron implanted layer was analyzed by the XPS. And the influence of the boron implanted layer on the internal stress and adhesion strength of c-BN films were investigated.
基金National Natural Science Foundation of China (60277002)
文摘Two novel poly[(3-alkylthiophene-2,5-diyl)-(benzylidenequinomethane-2,5-diyl)s] derivatives, poly[ (3-butylthiophene-2,5-diyl)-( p-N,N-dimethylamino) benzylidenequinomethane-2,5-diyl) ] ( PBTDMABQ) and poly [( 3-octylthiophene2,5-diyl) -(p-N, N-dimethylamino ) benzylidenequinomethane-2, 5-diyl)] (POTDMABQ), were synthesized.The band gaps of the two polymers are calculated as 1. 75 eV for PBTDMABQ and 1. 69 eV for POTDMABQ,respectively. The homogenous films of the two polymers were prepared and their third-ordernonlinear optical properties were studied by the backward degenerate four-wave mixing at 532 nm. Byusing the relative measurement technique, the third-order nonlinear optical susceptibilities ofPBTDMABQ and POTDMABQ are calculated as 5. 62 X 10^(-9) and 1. 22 X 10^(-8) ESU, respectively. It isfound that substituted alky groups have strong effects on the band gap and nonlinear opticalproperties of the two polymers. The relatively big third-order nonlinear optical susceptibilitiesand small band gap of POTDMABQ resulted mainly from the longer alkyl with strong electron-donatingability can enhance the delocation degree of conjugated π electronics.
基金The study is supported by the China National Natural Science Foundation (project No. 49476282)by the Shandong Province Natural Science Foundation (project No. 98E04075).
文摘This paper deals with the development and evolution of modern Yellow River delta and the erosion or deposition rates of its different sections. In June, 1996, Yellow Rivers terminal course was artificially turned eastwards to empty into the sea and then the 11th lobe of the modern Yellow River delta began to form. This course change may mark the beginning of the 3rd subdelta formation. As a result of that, the Yellow River delta advances towards east by north with the 1st, 2nd and 3rd subdeltas arranged in succession. Coast zone in the deltaic area is divided into 7 different sections according to their different erosion or deposition rates: the relatively stable section from Dakou River to Shunjiang Stream, the weakly retreating section from Shunjiang Stream to the Tiaohe River mouth, the strongly retreating section from the Tiaohe River mouth to the station 106, the artificially stable section due to stone dam protection from the station 106 to Gudong Oilfield, the strong deposition section from Gudong Oilfield to Dawenliu Haipu, the weakly deposition section from Dawenliu Haipu to the Zimai Stream mouth, and the stable section from the Zimai Stream mouth to the Jiaolai River mouth. It is predicted that the erosion and deposition situations of the sections will nearly remain the same in 10 years, but the retreating and silting-up rates will tend to become slower gradually. Human activities have an evident influence on the changes of the coastline.
基金supported by the National Basic Research Program of China(973 Program,Grant No.2012CB417404)
文摘The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures: the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC.
基金Supported by the Independent Innovation Fund of Tianjin University(No.1307)
文摘The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution(BF_3-CH_3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron trifluoride methanol complex and sodium methoxide to produce enriched ^(10)B methylborate was proposed based on a detailed mechanism study, and was verified by acid-base titration method and conductivity method. It was found that this reaction is first order reaction and the rate constant is 0.022 min^(-1) at 338 K(65 ℃), the activity energy is 65 k J/mol. In addition, it was found that the conductivity method is more feasible to measure the kinetic curve than acid-base titration method.
文摘In this paper we report on recent development in the areas of optical vortices generated by micro-optical elements and applications of optical vortices, including optical manipulation, radial polarization and secure free space optical communication
基金the National Natural Science Foundation of China (No. 20271025)the Natural Science Foundation of Shandong province (No. Z2001B02)the State Key Laboratory of Crystal Materials,Shandong University
文摘The bis(tributyltin) ester of succinic acid was synthesized by the reaction of disodium salt of succinic acid with tributyltin chloride in a molar ratio of 1:2. The crystal structure was determined by X-ray single-crystal diffraction. It belongs to orthorhombic with space group Pccn, a = 20.949(3), b = 17.470(3), c = 20.345(3) Angstrom, V = 7446(2) Angstrom(3), Z = 8, D-c = 1.242 g/cm(3), mu = 1.365 mm(-1), F(000) = 2864, R = 0.0544 and wR = 0.1417. The tin atom is of five-coordination in a trigonal bipyramidal structure by bridging two carboxylate groups in different directions and the resulting structure which contains straight twist large ring channels along the axes of a, b and c is a three-dimensional framework polymer containing two different tin atoms.
基金National Science and Technology Major Project(No.2016ZX04003001)
文摘High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.
基金the supports from the Chinese Academy of Sciences(CAS)Institute of Chemistry,CAS+3 种基金the supports from the National Natural Science Foundation of China(No.21933011)the Beijing Municipal Science&Technology Commission(No.Z191100007219009)the K.C.Wong Education Foundationthe support from the National Natural Science Foundation of China(No.21773073)。
文摘The reaction of triplet fusion,also named triplet-triplet annihilation,has attracted a lot of research interests because of its wide applications in photocatalytic,solar cells,and bioimaging.As for the singlet oxygen photosensitization,the reactive singlet oxygen species are generated through the energy transfers from photosensitizer(PS)to ground triplet oxygen molecule.In this work,we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation.Then we utilized the molecular orbital(MO)overlaps to approximate it,where the MOs were computed from isolated single molecules.As demonstrated with quantitative results,this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O_(2),providing us a simple but effective way to predict the coupling of triplet fusion reactions.
基金FundofStateKeyLaboratoryofFrozenSoilEngineeringofChina !(No 980 2 No 2 0 0 3 )
文摘The real in time computerized tomography (CT) testing of the meso damage propagation law of the whole sandstone failure process under triaxial compression has been completed using the newest specified triaxial loading equipment corresponding to the CT machine. Through the CT scanning, the clear CT images which include from the microcracks compressed stage to growth stage, bifurcation stage, development stage, crack fracture stage,the rock sample failure until to unloading stage in the different stress states were obtained. The CT values, CT images and the other data have been analyzed. Based on the results of the CT testing of meso damage evolution law of rock,the stress threshold value of meso damage of rock is given, and the stress strain complete process curve of rock is divided into some sections. The initial rock damage propagation law is given in this paper.
基金National Natural Science Foundation of China(41572240)
文摘Changping Plain, located in the northwest of Beijing, has become an important groundwater recharge area for the Beijing Plain and an important source for the urban water supply. In this study, groundwater samples were collected during the dry and wet seasons in 2015 from 24 monitoring wells distributed in Changping Plain. A Piper-Tri-linear diagram, a Schoeller diagram, a Gibbs diagram, and the isotope technique were used to investigate the temporal and spatial variations in the concentrations of groundwater hydrochemicals and the sources of groundwater recharge. The results indicated: 1) seasonal variations in the concentrations of HCO3^–, Ca^2+, and Na^+ were significant; the spatial variations of these ions were more dramatic in the dry season than in the wet season due to the dilution effect of precipitation; 2) Most groundwater samples had a HCO3-Ca-Mg based hydrochemical type and a few had a HCO3-Na-K based hydrochemical type; the hydrochemical type tended to evolve from HCO3-Ca-Mg based to HCO3-Na-K based in some monitoring wells that showed distinct seasonal variation; 3) the groundwater in the study area originated mainly from atmospheric precipitation, and it is affected by evaporation and concentration processes.
文摘One-dimensional ZnMn2O4 nanowires have been prepared and investigated as anode materials in Li rechargeable batteries. The highly crystalline ZnMn2O4 nanowires about 15 nm in width and 500 nm in length showed a high specific capacity of about 650 mAh.g-1 at a current rate of 100 mA.g-1 after 40 cycles. They also exhibited high power capability at elevated current rates, i.e., 450 and 350 mAh.g 1 at current rates of 500 and 1000 mA.g 1, respectively. Formation of Mn3O4 and ZnO phases was identified by ex situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies after the initial discharge-charge cycle, which indicates that the ZnMn2O4 phase was converted to a nanocomposite of Mn3O4 and ZnO phases immediately after the electrochemical conversion reaction.
基金the funding support from the National Natural Science Foundation of China(2143100621521001)+8 种基金the National Basic Research Program of China(2014CB9318002013CB931800)the Users with ExcellenceGrant of Hefei Science Center of Chinese Academy of Sciences(2015HSC-UE007)the Chinese Academy of Sciences(KJZDEW-M01-1)the National Natural Science Foundation of China(5147115721401183)Youth Innovation Promotion Association of Chinese Academy of Sciences(2014298)Anhui Provincial Natural Science Foundation(1508085QB28)the Fundamental Research Funds for the Central Universities(WK2060190026)
文摘Herein, we report a versatile strategy to fabri- cate three-dimensional melamine sponge (MS)-Au/ceria nanowire (NW) networks to realize in situ continuous reduction of p-nitrophenol in a consecutive flow system. This system has proven to be high activity and stability. The ceria NW networks with large surface area can stabi- lize tiny Au nanoparticles dispersed on the ceria NWs, which are loaded on the framework of MS by dip-coating, and enhance the synergistic effect between ceria NWs networks and Au nanoparticles, leading to extremely high activity and good stability for catalytic application. The low-cost raw materials and catalyst with high activity and stability may make this three-dimensional MS-Au/ceria NWs composite material promising for continuous cat- alytic reaction application in industry or other fields.