Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numer...Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.展开更多
Esophageal cancer is the 7th leading cause of cancer deaths worldwide.While squamous cell carcinoma is the most prevalent histology internationally,adenocarcinoma of the distal esophagus accounts for nearly 50% of cas...Esophageal cancer is the 7th leading cause of cancer deaths worldwide.While squamous cell carcinoma is the most prevalent histology internationally,adenocarcinoma of the distal esophagus accounts for nearly 50% of cases in developed countries due to the differences in the etiologic factors such as gastroesophageal reflux disease(GERD) and obesity that predominate.While surgery is the mainstay of treatment of this disease,the utilization of chemoradiation,eitherused postoperatively or neoadjuvantly,has become a standard practice in the United States.What is the optimal management approach is still an area of contention,however,and may be different in different regions around the world.This article reviews some of these controversies,including the role for surgery in patients treated with definitive chemoradiation.At the end,we will also outline recommendations regarding radiotherapy procedures and techniques.展开更多
An efficient screening assay was developed and validated for simultaneous assessment of compound-mediated inhibition of six major human cytochrome P450 （CYP） enzymes. This method employed a cocktail of six probe sub...An efficient screening assay was developed and validated for simultaneous assessment of compound-mediated inhibition of six major human cytochrome P450 （CYP） enzymes. This method employed a cocktail of six probe substrates （i.e., phenacetin, amodiaquine, diclofenac, S-mephenytoin, dextromethorphan and midazolam for CYPIA2, 2C8, 2C9, 2C19, 2D6 and 3A4, respectively） as well as individual prototypical inhibitors of the six CYP enzymes in human liver microsomes under optimized incubation conditions. The corresponding marker metabolites （i.e., acetaminophen, N-desethylamodiaquine, 4-OH-diclofenac, 4-OH-S- mephenytoin, dextrorphan and 1-OH-midazolam） in the incubates were quantified using LC-MS/MS methods either by an internal standard （IS） calibration curve or a simpfified analyte-to-IS peak area ratio approach. The results showed that the IC5o values determined by the cocktail approach were in good agreement with those obtained by the individual substrate approach as well as those reported in the literature. Besides, no remarkable difference was observed between the two quantification approaches. In conclusion, this new cocktail assay can be used for reliable screening of compound-mediated CYP inhibition.展开更多
The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineraliza...The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineralization of photocrosslinkable HA polymers through sol-gel synthesis.In this way,it has been possible to overcome some limitations due to classical approaches based on the physical blending of inorganic fillers into polymer matrix.To this aim,methacrylated and maleated HA,synthesized with similar degree of substitution(DS)were compared in terms of mechanical and physico-chemical properties.The success of in situ biomineralization was highlighted by reflect Fourier transform infrared spectroscopy and thermogravimetric analysis.Furthermore,mechanical characterization demonstrated the reinforcing effect of inorganic fillers evidencing a strong correlation with DS.The swelling behavior resulted to be correlated with filler concentration.Finally,the cytotoxicity tests revealed the absence of toxic components and an increase of cell proliferation over culture time was observed,highlighting these bio-nanocomposite hyaluronan derivatives as biocompatible hydrogel with tunable properties.展开更多
This paper describes recent device developments with relaxor ferroelectric Pb(Zn_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PZN–PT)single crystals carried out at Microfine Materials Technologies Pte.Ltd,Singapore.Promising[011]-p...This paper describes recent device developments with relaxor ferroelectric Pb(Zn_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PZN–PT)single crystals carried out at Microfine Materials Technologies Pte.Ltd,Singapore.Promising[011]-poled transverse cuts of PZN–PT single crystals and the results on the effect of electric field and axial compressive stress on the rhombohedral-to-orthorhombic(R–O)phase transformation behavior of such cuts are presented and discussed.The single crystal devices described include a compact lowfrequency broadband power-efficient underwater tonpilz projector,high sensitivity shear accelerometers and acoustic vector sensors(AVS).The unique characteristics offered by these PZN–PT single crystal devices are highlighted,which serve as examples of newgeneration piezoelectric devices and systems for a wide range of demanding applications.展开更多
In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize ph...In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina pro- moted crystallization of fused silica during sintering at 1180-1220 ℃ and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 ~C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 ℃. In addition, deflection resis- tance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry （SEMJEDS） analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite.展开更多
This paper investigated high-damping Cu-Al-Be-B cast alloys using metallographic analysis, X-ray diffraction (XRD) and electrical resistance measurements for transformation temperatures. The results showed that beryll...This paper investigated high-damping Cu-Al-Be-B cast alloys using metallographic analysis, X-ray diffraction (XRD) and electrical resistance measurements for transformation temperatures. The results showed that beryllium can stabilize β phase, resulting in a thermo-elastic martensite microstructure leading to high-damping capacity in cast Cu-Al-Be-B alloys. Trace additions of boron to Cu-Al-Be alloys can significantly refine the grains, providing high strength and ductility to the alloys. A factorial design of experiment method was used to optimize the composition and properties of cast Cu-Al-Be-B alloys. The optimal microstructure for thermo-elastic martensite can be obtained by adjusting the amounts of aluminum and beryllium to eutectoid or pseudo-eutectoid compositions. An optimized cast Cu-Al-Be-B alloy was developed to provide excellent mechanical properties, tensile strength σ_b=767MPa, elongation δ=7.62%, and damping capacity S. D. C=18.70%.展开更多
Experiments of ionospheric tomography at low latitudes along 120°E meridian and some findings from analyses of such experimental data are presented. An improved reconstruction algorithm of computerized ionospheri...Experiments of ionospheric tomography at low latitudes along 120°E meridian and some findings from analyses of such experimental data are presented. An improved reconstruction algorithm of computerized ionospheric tomography is proposed. In this algorithm, both differential Doppler phase and differential Doppler frequency data are jointly used and the integral phase constants are determined in the reconstruction process. Our findings indicate that the reconstructed ionospheric equatorial anomaly crests usually show a tilt in rough alignment with the local geomagnetic field, coinciding with the feature predicted by the fountain mechanism. The crest locations are found to move daily in response to changes in equatorial electrodynamics. When the crest moves from one day to the next day, the tilting angle changes so as to be still aligned with the local magnetic field. It is statistically found that an equator-ward motion of the crests is accompanied with a latitudinal broadening of the crest region. The reconstructed images also indicate that the crest location determined by the maximum electron density often does not coincide with that determined by the vertical total electron content. Besides, a deep depletion of ionospheric electron density appeared just 20 minutes after sudden commencement of a moderate magnetic storm at geomagnetic latitudes around 10°N where equatorial anomaly crests usually sit. The depleted hole extends over both the bottom and top F-region, with a steep wall on its equatorial side. The present study demonstrates that ionospheric tomographic technology is very useful and effective to the investigation of the equatorial and low-latitude ionospheric structures and dynamics.展开更多
Radiation-induced segregation(RIS) is a typical non-equilibrium process that can dramatically alter the behavior of defect sinks and material properties under irradiation. However, RIS mechanisms have been rarely stud...Radiation-induced segregation(RIS) is a typical non-equilibrium process that can dramatically alter the behavior of defect sinks and material properties under irradiation. However, RIS mechanisms have been rarely studied around small He bubbles owing to the technical challenges involved in direct measurements of local chemistry. Here, using state-of-the-art atom probe tomography, we report the RIS behavior near He bubbles in the Fe Ni Co Cr high-entropy alloy that indicates Co segregates most strongly, followed by weaker Ni segregation, whereas Fe and Cr are depleted almost to the same degree. Exceptionally, the magnitude of Co segregation around He bubbles is higher than previously measured values at voids and dislocation loops. Electron energy-loss spectroscopy was used to measure the He density and pressure inside individual bubbles. We demonstrate that He bubbles are over-pressurized at the irradiation temperature that could result in the vacancy bias and the subsequent vacancy-dominated RIS mechanism.First-principles calculations further reveal that there are repulsive interactions between He and Co atoms that may reduce the frequency of Co-vacancy exchange. As a result, He atoms likely retard Co diffusion via the vacancy mechanism and enhance the heterogeneity of RIS in Co-containing multicomponent alloys. These insights could provide the basis for understanding He effects in nuclear materials and open an avenue for tailoring the local chemical order of medium-and high-entropy alloys.展开更多
Open clusters(OCs)are infrequent survivors of embedded clusters gestated in molecular clouds.Up to now,little is known about the initial conditions for the formation of OCs.Here,we studied this issue using high-precis...Open clusters(OCs)are infrequent survivors of embedded clusters gestated in molecular clouds.Up to now,little is known about the initial conditions for the formation of OCs.Here,we studied this issue using high-precision astrometric parameters provided by Gaia data release 3.The statistics show that the peculiar motion velocities of OCs vary slightly from infancy to old age,providing a remarkable opportunity to use OCs to trace their progenitors.Adopting a dynamical method,we derived the masses of the progenitor clumps where OCs were born,which have statistical characteristics comparable to previously known results for clumps observed in the Galaxy.Moreover,the masses of the progenitor clumps of OCs indicate they should be capable of gestating massive O-type stars.In fact,after inspecting the observed OCs and O-type stars,we found that there are many O-type stars in OCs.The destructive stellar feedback from O-type stars may disintegrate the vast majority of embedded clusters,and only those sufficiently dense ones can survive as OCs.展开更多
A new search for two-neutrino double-beta(2νββ)decay of^(136)Xe to the 0+1 excited state of 136Ba is performed with the full EXO-200 dataset.A deep learning-based convolutional neural network is used to discriminat...A new search for two-neutrino double-beta(2νββ)decay of^(136)Xe to the 0+1 excited state of 136Ba is performed with the full EXO-200 dataset.A deep learning-based convolutional neural network is used to discriminate signal from background events.Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two.With the addition of the Phase II dataset taken with an upgraded detector,the median 90%confidence level half-life sensitivity of 2νββdecay to the 0+1 state of 136Ba is 2.9×10^(24)yr using a total^(136)Xe exposure of 234.1 kg yr.No statistically significant evidence for 2νββdecay to the 0^(+)_(1)state is observed,leading to a lower limit of T2ν1/2(0^(+)→0^(+)_(1))>1.4×10^(24)yr at 90%confidence level,improved by 70%relative to the current world's best constraint.展开更多
1 Results 2-pyrazolines and carbaozole derivatives are well known fluorescent compounds with high quantum yields[1],and have been investigated in many other respects[2,3].In this paper,carbazole radical was introduced...1 Results 2-pyrazolines and carbaozole derivatives are well known fluorescent compounds with high quantum yields[1],and have been investigated in many other respects[2,3].In this paper,carbazole radical was introduced to pyrazoline ring on C-5,and a novel derivative,named 1-phenyl-3-biphenyl-5-(N-ethyl carbazole-3-yl)-2-pyrazoline (PBEP) (5) was synthesized: The product PBEP was characterized by IR,1H NMR,and elementary analysis.Yield: 47.2%.M.P 104-106 ℃.1H NMR (CDCl3) δ/10-6: 1.5(3H,—CH3).2.4(2H,—...展开更多
This paper studies a class of variational problems which involving both bulk and surfaceenergies. The bulk energy is of Dirichlet type though it can be in very general forms allowingunknowns to be scalar or vectors.Th...This paper studies a class of variational problems which involving both bulk and surfaceenergies. The bulk energy is of Dirichlet type though it can be in very general forms allowingunknowns to be scalar or vectors.The surface energy is an arbitrary elliptic parametric integralwhich is defined on a free interface. One also allows other constraints such as volumes of partitioning sets. One establishes the existence and regularity theory, in particular, the regularityof the free interface of such problems.展开更多
Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggre...Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggregate＂ was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.展开更多
The accuracy between ordinary kriging and regression kriging was compared based on the combined consideration of sample size,spatial structure,and auxiliary variables(terrain indices and electromagnetic induction surv...The accuracy between ordinary kriging and regression kriging was compared based on the combined consideration of sample size,spatial structure,and auxiliary variables(terrain indices and electromagnetic induction surveys) for a variety of soil properties in two contrasting landscapes(agricultural vs.forested).When spatial structure could not be well captured by point-based observations(e.g.,when the ratio of sample spacing over correlation range was > 0.5),or when a strong relationship existed between target soil properties and auxiliary variables(e.g.,their R2 was > 0.6),regression kriging(RK) was more accurate for interpolating soil properties in both landscapes studied.Otherwise,ordinary kriging(OK) was better.Soil depth and wetness condition did not appear to affect the selection of kriging for soil moisture interpolation,because they did not significantly change the ratio of sample spacing over correlation range and the relationship with the auxiliary variables.Because of a smaller ratio of elevation change over total study area(E/A = 1.2) and multiple parent materials in the agricultural land,OK was generally more accurate in that landscape.In contrast,a larger E/A ratio of 6.8 and a single parent material led to RK being preferable in the steep-sloped forested catchment.The results from this study can be useful for selecting kriging for various soil properties and landscapes.展开更多
基金The work reported here is funded by Australian Coal Industry’s Research Program(ACARP)grant no.C26063.
文摘Estimation of horizontal stress magnitudes from borehole breakouts has been an attractive topic in the petroleum and mining industries,although there are critical research gaps that remain unfilled.In this paper,numerical simulation is conducted on Gosford sandstone to investigate the borehole breakout and its associated borehole size effect,including temperature influence.The discrete element method(DEM)model shows that the borehole breakout angular span is constant after the initial formation,whereas its depth propagates along the minimum horizontal stress direction.This indicates that the breakout angular span is a reliable parameter for horizontal stress estimation.The borehole size effect simulations illustrated the importance of borehole size on breakout geometries in which smaller borehole size leads to higher breakout initiation stress as well as the stress re-distribution from borehole wall outwards through micro-cracking.This implies that the stress may be averaged over a distance around the borehole and breakout initiation occurs at the borehole wall rather than some distance into the rock.In addition,the numerical simulation incorporated the thermal effect which is widely encountered in deep geothermal wells.Based on the results,the higher temperature led to lower breakout initiation stress with same borehole size,and more proportion of shear cracks was generated under higher temperature.This indicates that the temperature might contribute to the micro-fracturing mode and hence influences the horizontal stress estimation results from borehole breakout geometries.Numerical simulation showed that breakout shape and dimensions changed considerably under high stress and high temperature conditions,suggesting that the temperature may need to be considered for breakout stress analysis in deep locations.
文摘Esophageal cancer is the 7th leading cause of cancer deaths worldwide.While squamous cell carcinoma is the most prevalent histology internationally,adenocarcinoma of the distal esophagus accounts for nearly 50% of cases in developed countries due to the differences in the etiologic factors such as gastroesophageal reflux disease(GERD) and obesity that predominate.While surgery is the mainstay of treatment of this disease,the utilization of chemoradiation,eitherused postoperatively or neoadjuvantly,has become a standard practice in the United States.What is the optimal management approach is still an area of contention,however,and may be different in different regions around the world.This article reviews some of these controversies,including the role for surgery in patients treated with definitive chemoradiation.At the end,we will also outline recommendations regarding radiotherapy procedures and techniques.
文摘An efficient screening assay was developed and validated for simultaneous assessment of compound-mediated inhibition of six major human cytochrome P450 （CYP） enzymes. This method employed a cocktail of six probe substrates （i.e., phenacetin, amodiaquine, diclofenac, S-mephenytoin, dextromethorphan and midazolam for CYPIA2, 2C8, 2C9, 2C19, 2D6 and 3A4, respectively） as well as individual prototypical inhibitors of the six CYP enzymes in human liver microsomes under optimized incubation conditions. The corresponding marker metabolites （i.e., acetaminophen, N-desethylamodiaquine, 4-OH-diclofenac, 4-OH-S- mephenytoin, dextrorphan and 1-OH-midazolam） in the incubates were quantified using LC-MS/MS methods either by an internal standard （IS） calibration curve or a simpfified analyte-to-IS peak area ratio approach. The results showed that the IC5o values determined by the cocktail approach were in good agreement with those obtained by the individual substrate approach as well as those reported in the literature. Besides, no remarkable difference was observed between the two quantification approaches. In conclusion, this new cocktail assay can be used for reliable screening of compound-mediated CYP inhibition.
基金the H2020-MSCA-RISE-2016,SECOND.R.I.,Grant Agreement No 734391Progetto Premiale di AREA SCIENCE PARK“OPEN LAB-A System of Open Research Facilities”for the support。
文摘The main driving idea of the present study was the comparison between two different chemical modifications of hyaluronic acid(HA)followed by the development of nanocomposite hydrogels directly in situ by biomineralization of photocrosslinkable HA polymers through sol-gel synthesis.In this way,it has been possible to overcome some limitations due to classical approaches based on the physical blending of inorganic fillers into polymer matrix.To this aim,methacrylated and maleated HA,synthesized with similar degree of substitution(DS)were compared in terms of mechanical and physico-chemical properties.The success of in situ biomineralization was highlighted by reflect Fourier transform infrared spectroscopy and thermogravimetric analysis.Furthermore,mechanical characterization demonstrated the reinforcing effect of inorganic fillers evidencing a strong correlation with DS.The swelling behavior resulted to be correlated with filler concentration.Finally,the cytotoxicity tests revealed the absence of toxic components and an increase of cell proliferation over culture time was observed,highlighting these bio-nanocomposite hyaluronan derivatives as biocompatible hydrogel with tunable properties.
文摘This paper describes recent device developments with relaxor ferroelectric Pb(Zn_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PZN–PT)single crystals carried out at Microfine Materials Technologies Pte.Ltd,Singapore.Promising[011]-poled transverse cuts of PZN–PT single crystals and the results on the effect of electric field and axial compressive stress on the rhombohedral-to-orthorhombic(R–O)phase transformation behavior of such cuts are presented and discussed.The single crystal devices described include a compact lowfrequency broadband power-efficient underwater tonpilz projector,high sensitivity shear accelerometers and acoustic vector sensors(AVS).The unique characteristics offered by these PZN–PT single crystal devices are highlighted,which serve as examples of newgeneration piezoelectric devices and systems for a wide range of demanding applications.
文摘In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina pro- moted crystallization of fused silica during sintering at 1180-1220 ℃ and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 ~C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 ℃. In addition, deflection resis- tance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry （SEMJEDS） analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite.
文摘This paper investigated high-damping Cu-Al-Be-B cast alloys using metallographic analysis, X-ray diffraction (XRD) and electrical resistance measurements for transformation temperatures. The results showed that beryllium can stabilize β phase, resulting in a thermo-elastic martensite microstructure leading to high-damping capacity in cast Cu-Al-Be-B alloys. Trace additions of boron to Cu-Al-Be alloys can significantly refine the grains, providing high strength and ductility to the alloys. A factorial design of experiment method was used to optimize the composition and properties of cast Cu-Al-Be-B alloys. The optimal microstructure for thermo-elastic martensite can be obtained by adjusting the amounts of aluminum and beryllium to eutectoid or pseudo-eutectoid compositions. An optimized cast Cu-Al-Be-B alloy was developed to provide excellent mechanical properties, tensile strength σ_b=767MPa, elongation δ=7.62%, and damping capacity S. D. C=18.70%.
文摘Experiments of ionospheric tomography at low latitudes along 120°E meridian and some findings from analyses of such experimental data are presented. An improved reconstruction algorithm of computerized ionospheric tomography is proposed. In this algorithm, both differential Doppler phase and differential Doppler frequency data are jointly used and the integral phase constants are determined in the reconstruction process. Our findings indicate that the reconstructed ionospheric equatorial anomaly crests usually show a tilt in rough alignment with the local geomagnetic field, coinciding with the feature predicted by the fountain mechanism. The crest locations are found to move daily in response to changes in equatorial electrodynamics. When the crest moves from one day to the next day, the tilting angle changes so as to be still aligned with the local magnetic field. It is statistically found that an equator-ward motion of the crests is accompanied with a latitudinal broadening of the crest region. The reconstructed images also indicate that the crest location determined by the maximum electron density often does not coincide with that determined by the vertical total electron content. Besides, a deep depletion of ionospheric electron density appeared just 20 minutes after sudden commencement of a moderate magnetic storm at geomagnetic latitudes around 10°N where equatorial anomaly crests usually sit. The depleted hole extends over both the bottom and top F-region, with a steep wall on its equatorial side. The present study demonstrates that ionospheric tomographic technology is very useful and effective to the investigation of the equatorial and low-latitude ionospheric structures and dynamics.
基金the funding support from the Hong Kong Research Grant Council (Grant Nos. City U11214820 and City U11205018)the funding support from the National Natural Science Foundation of China (NSFC) under project 11922215+2 种基金the funding support from the Natural Science Foundation of Guangdong Province in China (Grant No. 2019A1515011836)the support from National Natural Science Foundation of China (Grant No. 11974156)Guangdong International Science Collaboration Project (Grant No. 2019A050510001)。
文摘Radiation-induced segregation(RIS) is a typical non-equilibrium process that can dramatically alter the behavior of defect sinks and material properties under irradiation. However, RIS mechanisms have been rarely studied around small He bubbles owing to the technical challenges involved in direct measurements of local chemistry. Here, using state-of-the-art atom probe tomography, we report the RIS behavior near He bubbles in the Fe Ni Co Cr high-entropy alloy that indicates Co segregates most strongly, followed by weaker Ni segregation, whereas Fe and Cr are depleted almost to the same degree. Exceptionally, the magnitude of Co segregation around He bubbles is higher than previously measured values at voids and dislocation loops. Electron energy-loss spectroscopy was used to measure the He density and pressure inside individual bubbles. We demonstrate that He bubbles are over-pressurized at the irradiation temperature that could result in the vacancy bias and the subsequent vacancy-dominated RIS mechanism.First-principles calculations further reveal that there are repulsive interactions between He and Co atoms that may reduce the frequency of Co-vacancy exchange. As a result, He atoms likely retard Co diffusion via the vacancy mechanism and enhance the heterogeneity of RIS in Co-containing multicomponent alloys. These insights could provide the basis for understanding He effects in nuclear materials and open an avenue for tailoring the local chemical order of medium-and high-entropy alloys.
基金funded by the National Natural Science Foundation of China(NSFC)Grant No.11933011the Key Laboratory for Radio Astronomy+2 种基金support from the Natural Science Foundation of Jiangsu Province(grant number BK20210999)the Entrepreneurship and Innovation Program of Jiangsu ProvinceNSFC grant No.12203104。
文摘Open clusters(OCs)are infrequent survivors of embedded clusters gestated in molecular clouds.Up to now,little is known about the initial conditions for the formation of OCs.Here,we studied this issue using high-precision astrometric parameters provided by Gaia data release 3.The statistics show that the peculiar motion velocities of OCs vary slightly from infancy to old age,providing a remarkable opportunity to use OCs to trace their progenitors.Adopting a dynamical method,we derived the masses of the progenitor clumps where OCs were born,which have statistical characteristics comparable to previously known results for clumps observed in the Galaxy.Moreover,the masses of the progenitor clumps of OCs indicate they should be capable of gestating massive O-type stars.In fact,after inspecting the observed OCs and O-type stars,we found that there are many O-type stars in OCs.The destructive stellar feedback from O-type stars may disintegrate the vast majority of embedded clusters,and only those sufficiently dense ones can survive as OCs.
文摘A new search for two-neutrino double-beta(2νββ)decay of^(136)Xe to the 0+1 excited state of 136Ba is performed with the full EXO-200 dataset.A deep learning-based convolutional neural network is used to discriminate signal from background events.Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two.With the addition of the Phase II dataset taken with an upgraded detector,the median 90%confidence level half-life sensitivity of 2νββdecay to the 0+1 state of 136Ba is 2.9×10^(24)yr using a total^(136)Xe exposure of 234.1 kg yr.No statistically significant evidence for 2νββdecay to the 0^(+)_(1)state is observed,leading to a lower limit of T2ν1/2(0^(+)→0^(+)_(1))>1.4×10^(24)yr at 90%confidence level,improved by 70%relative to the current world's best constraint.
文摘1 Results 2-pyrazolines and carbaozole derivatives are well known fluorescent compounds with high quantum yields[1],and have been investigated in many other respects[2,3].In this paper,carbazole radical was introduced to pyrazoline ring on C-5,and a novel derivative,named 1-phenyl-3-biphenyl-5-(N-ethyl carbazole-3-yl)-2-pyrazoline (PBEP) (5) was synthesized: The product PBEP was characterized by IR,1H NMR,and elementary analysis.Yield: 47.2%.M.P 104-106 ℃.1H NMR (CDCl3) δ/10-6: 1.5(3H,—CH3).2.4(2H,—...
文摘This paper studies a class of variational problems which involving both bulk and surfaceenergies. The bulk energy is of Dirichlet type though it can be in very general forms allowingunknowns to be scalar or vectors.The surface energy is an arbitrary elliptic parametric integralwhich is defined on a free interface. One also allows other constraints such as volumes of partitioning sets. One establishes the existence and regularity theory, in particular, the regularityof the free interface of such problems.
基金NSC under Grant No.98-2221-E-027-057-MY2the Center for Research on Earthquake Engineering(NCREE)
文摘Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggregate＂ was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.
基金Supported by the United States Department of Agriculture National Research Initiative Grant(No.2002-35102-12547)
文摘The accuracy between ordinary kriging and regression kriging was compared based on the combined consideration of sample size,spatial structure,and auxiliary variables(terrain indices and electromagnetic induction surveys) for a variety of soil properties in two contrasting landscapes(agricultural vs.forested).When spatial structure could not be well captured by point-based observations(e.g.,when the ratio of sample spacing over correlation range was > 0.5),or when a strong relationship existed between target soil properties and auxiliary variables(e.g.,their R2 was > 0.6),regression kriging(RK) was more accurate for interpolating soil properties in both landscapes studied.Otherwise,ordinary kriging(OK) was better.Soil depth and wetness condition did not appear to affect the selection of kriging for soil moisture interpolation,because they did not significantly change the ratio of sample spacing over correlation range and the relationship with the auxiliary variables.Because of a smaller ratio of elevation change over total study area(E/A = 1.2) and multiple parent materials in the agricultural land,OK was generally more accurate in that landscape.In contrast,a larger E/A ratio of 6.8 and a single parent material led to RK being preferable in the steep-sloped forested catchment.The results from this study can be useful for selecting kriging for various soil properties and landscapes.
