Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability...Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.展开更多
In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that ea...In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that each strand of the cable inside the joint is able to come to the outermost by transposition. This paper presents analysis, calculation and figures for the strand transposition. According to the twist procedures of the superconducting cable, the author computed the actual pitch of each stage cable, consecutively computed the projection of each stage cable on the axis of the cable (z axis) and the corresponding twist angle as the z coordinate changes, which is then drawn by AutoCAD. From the results shown in the figures, the minimal cable length, which enables each strand to transpose almost equally to the outermost of the cable in such a length, call be determined as the optimal joint length.展开更多
The effect of cooling rate after 40% hot deformation on structure and mechanical properties of low alloy wear resistance cast iron was investigated by metallographic, scanning electron microscopes and detection of pro...The effect of cooling rate after 40% hot deformation on structure and mechanical properties of low alloy wear resistance cast iron was investigated by metallographic, scanning electron microscopes and detection of properties. The results show that for the cast steel after deformed, the amount of granular carbides of precipitation during the cooling decreased with the increase of the cooling rate, but the hardness was obviously enhanced, as a result, better mechanical properties will be obtained by force air cooling(cooling rate is about 7 ℃·s-1). And the reason of the change for structure and mechanical properties of the cast steel were analyzed.展开更多
The Influence of RE on wear resistance of wear resistant cast iron containing low alloy was studied by means of slide wear and impact wear test. Moreover, its microstructure and characteristics of wearing surface was ...The Influence of RE on wear resistance of wear resistant cast iron containing low alloy was studied by means of slide wear and impact wear test. Moreover, its microstructure and characteristics of wearing surface was analyzed. The experimental results show that RE can improve the wear resistance of wear resistant cast iron containing low alloy, especially for impact wear resistance. The optimum wear resistance of wear resistant cast iron containing low alloy modified by RE of 0.046% can be obtained by normalization at 950 ℃ for 3 h. Moreover, the coordinated effect of rare earths and heat treatment was also revealed in this paper.展开更多
In order to study the micro genetic mechanism and main geological controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai sea in China, the clay mineral composition, irreducible wate...In order to study the micro genetic mechanism and main geological controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai sea in China, the clay mineral composition, irreducible water saturation, salinity and conductive minerals of low resistivity reservoir were studied by using the data of core, cast thin section and analysis, and compared with normal resistivity reservoir. At the same time, the control effect of sedimentary environment on low resistivity reservoir was discussed. The results show that the additional conductivity of high bound water content and high montmorillonite content in the reservoir together leads to the significant reduction of reservoir resistivity, which is the main microscopic cause of the formation of low resistance, and is mainly controlled by the sedimentary background such as paleoclimate and sedimentary cycle. During the deposition period of NgIII formation, the paleoclimate was dry and cold, and it was at the end of the water advance of the medium-term sedimentary cycle. The hydrodynamic force of the river channel was weak, the carrying capacity of the riverbed was weak, and the river channel swayed frequently, resulting in fine lithologic particle size, high shale content and complex pore structure of the reservoir, resulting in significant reduction of reservoir resistance. The research conclusion would have strong guiding significance for the development of low resistivity reservoirs in this area.展开更多
Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for re...Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.展开更多
large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion proces...large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope(SEM). Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread(LDIT) is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.展开更多
Two types of low carbon MgO - C refractories with 6% graphite were prepared using microporous magnesiarich spinel (5 - 3 and 3 - 1 mm ) and fused magnesia (5 - 3 and 3 - 1 mm ) as coarse aggregates, respectively, ...Two types of low carbon MgO - C refractories with 6% graphite were prepared using microporous magnesiarich spinel (5 - 3 and 3 - 1 mm ) and fused magnesia (5 - 3 and 3 - 1 mm ) as coarse aggregates, respectively, fused magnesia ( ≤1 mm) as fine aggregate, magnesia powder (≤ 0. 088 mm ) , flake graphite powder ( ≤0. 088 mm), metal Al powder ( 〈0. 074 mm) as matrix, and phenol resin as binder. After curing at 220 ℃ and coke-embedded firing at 1 500 ℃ , the apparent porosity, cold crushing strength, cold modulus of rupture, permanent linear change on heating, thermal shock resistance and slag resistance of the specimens were studied comparatively. The results indicate that: ( 1 ) after curing at 220 ℃ and coke-embedded firing at 1 500 ℃, the specimen with microporous magnesia-rich spinel replacing fused magnesia has lower bulk density and higher apparent porosity than the common low car- bon MgO - C specimen. After curing at 220 ℃, the specimen with microporous aggregate has lower strength than common low carbon MgO - C specimen, but after coke-embedded firing at 1 500℃, it has higher strength and lower permanent linear change on heating; (2) low carbon MgO - C specimen using microporous magnesia-rich spinel to replace fused magnesia aggregate has better thermal shock resistance but worse slag resistance.展开更多
To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock condu...To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock conductivity during displacement were analyzed by displacement resistivity experiments simulating the process of reservoir formation and production, together with the data from thin sections, mercury injection and nuclear magnetic resonance experiments. In combination with geological understandings, the genetic mechanisms of LRPs were revealed, then the saturation interpretation model was selected, the variation laws and distribution range of the model parameters were defined, and finally an updated comprehensive saturation interpretation technique for the LRPs has been proposed. In the study area, the LRPs have resistivity values of less than 1 Ω·m, similar to or even slightly lower than that of the water layers. Geological research reveals that the LRPs were developed in low-energy depositional environment and their reservoir spaces are controlled by micro-scale pore throats, with an average radius of less than 0.7 μm, so they are typical microporous LRPs. Different from LRPs of sandstone and mudstone, they have less tortuous conductive paths than conventional reservoirs, and thus lower resistivity value under the same saturation. Archie’s formula is applicable to the saturation interpretation of LRPs with a cementation index value of 1.77-1.93 and a saturation index value of 1.82-2.03 that are 0.2-0.4 lower than conventional reservoirs respectively. By using interpretation parameters determined by classification statistics of petrophysical groups(PGs), oil saturations of the LRPs were calculated at bout 30%-50%,15% higher than the results by conventional methods, and basically consistent with the data of Dean Stark, RST, oil testing and production. The 15 wells of oil testing and production proved that the coincidence rate of saturation interpretation is over 90%and the feasibility of this method has been further verified.展开更多
The influence of heating temperature on mechanical properties of low chromium wear resistant cast iron containing rare earth elements was studied by means of metallographic examination, scanning electron microscopic e...The influence of heating temperature on mechanical properties of low chromium wear resistant cast iron containing rare earth elements was studied by means of metallographic examination, scanning electron microscopic examination and mechanical property test. The experimental results show that heating temperature has great effect on impact toughness (α_k), bending fatigue (σ_(bb)) and relative toughness (σ_(bb)×f), but little effect on hardness (HRC). When the specimen was held at 960 ℃ for 3 h, it has better comprehensive mechanical properties, and the reason and regularity of the change for mechanical properties of the cast iron were reviewed.展开更多
[Objective] This study was conducted to compare the genetic diversity and growth performance of two Litopenaeus vannamei populations at low temperature. [Method] One population(selected population, SP) was produced ...[Objective] This study was conducted to compare the genetic diversity and growth performance of two Litopenaeus vannamei populations at low temperature. [Method] One population(selected population, SP) was produced through inbreeding and 3 years of selection from seven popula- tions of L. vannamei introduced from the United States and Singapore. The other population (hybridized population, HP) was the F1 generation of the crosses between Population SP and some excellent populations introduced from South Korea and Singapore. The growth performance of the two populations at low temperature was compared, and the genetic diversity and genetic differentiation between the two populations were assessed using 13 microsatellite loci. [Result] The shrimps of population HP had better growth performance than those of population SP. The average body weight (BW) for population HP, which was (13.18±3.65) g/ind., was significantly higher than that of population SP, which was (12.20±3.14) g/ind. The coefficient of variation in body weight for population SP was 25.74%, and that for population HP was 27.69%. The other growth indices of popula- tion HP were all higher than those of population SP. One-way analysis of variance (ANOVA) indicated that there were highly significant differences in both BW and width of third abdominal segment (WTAS) between HP and SP(P〈0.001). The specific growth rate (SGR) and absolute growth rate (AGR) for population HP were (5.09±0.61) %/d and (0.26±0.60) g/d, respectively, while the SGR and AGR for population SP were (4.94±0.57) %/d and (0.24±0.63) g/d., both significantly lower than those of population HP (P〈0.001). Genetic diversity analysis revealed that the number of alleles (Na) of population HP (Na=7.9) was slightly higher than that of population SP (Na=7.6). The average polymorphic information content (PIC) of HP and SP populations was similar 0.63 and 0.62, both indicating high level of genetic diversity. The average observed heterozygosity (HQ) of HP and SP was 0.492 and 0.483, and the expected heterozygosity(He) was 0.675 and 0.663, respectively. Both Ho and He of population HP were higher than those of population SP, suggesting that HP had higher genetic diversity than population SP. Moreover, the mean of FsT values at the 13 microsatellite loci between HP and SP was 0.155 6, suggesting there was a significant genetic differentiation between the two populations. [Conclusion] Our results provide a theoretical basis for the breeding of new L. vannamei strains that are resistant to low temperature.展开更多
The formation and growth of thermal fatigue crack and the function of RE and heat treatment in wear resistance of cast iron containing low alloy were investigated,and it was analyzed in view of the activation energy f...The formation and growth of thermal fatigue crack and the function of RE and heat treatment in wear resistance of cast iron containing low alloy were investigated,and it was analyzed in view of the activation energy for the crack′s propagation. The results show that the thermal fatigue cracks are mainly generated at eutectic carbides,and the cracks are grown by themselves spreading and joining each other. RE can improve the eutectic carbide′s morphology,inhibit the generation and propagation of thermal fatigue cracks,therefore,promote the activation energy for the crack′s propagation,and especially,which is more noticeable in case of the RE modification in combination with heat treatment.展开更多
The main focus of study is to characterize lower and upper cretaceous carbonate deposits with Low Resistivity Pay, in Persian Gulf. Four oil reservoirs in the Cretaceous including the Zubair, Buwaib, Shuaiba and Khati...The main focus of study is to characterize lower and upper cretaceous carbonate deposits with Low Resistivity Pay, in Persian Gulf. Four oil reservoirs in the Cretaceous including the Zubair, Buwaib, Shuaiba and Khatiyah Formations of Southern fields have been analyzed. Here is a look at that to determine main factors on decreasing resistivity in pay zone. In some intervals resistivity responses reach less than 6 to 1 ohm·m. Significant hydrocarbon accumulations are “hidden” in low resistivity Pay zone, (LRPZ). LRPZ reservoirs have been found in some formations in Persian Gulf. Causes of LRPZ reservoirs on the basis of experimental analysis include clay-coated grains, carbonate with interstitial dispersed clay. On the other side Smectite and Kaolinite of main clays types have high CEC and greater impact on lowering resistivity. Micritization and Pyritization of digenetic process have noticeable impact on LRPZ. It is mentioned that Lønøy method applied to address pore throat sizes which contain Inter crystalline porosity, Chalky Limestone, Mudstone micro porosity. Pore systems are classified at class 2 and 3 Lucia and pore size varies from 0.5 to 4 micron. NMR Core and Log results show different pore size distribution. NMR core and MRIL results explain that decreasing of resistivity in pay zone is related to texture and grain size variation not being existence of moved water. Irreducible water estimate for this reservoir was between 30% and 50%. T2 cut off estimates, for defining irreducible water saturation, 115 ms.展开更多
The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffract...The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffraction(XRD), scanning electron microscopy(SEM), electron probe micro-analysis(EPMA), N2 adsorption, and X-ray photoelectron spectroscopy(XPS). The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.展开更多
The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to variou...The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to various surfaces at low temperatures(from-18℃ to-80℃).Moreover,this supramolecular adhesive has good adhesion ability in the presence of water.展开更多
Qi, blood and the meridians are fundamental concepts in Chinese medicine(CM), which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to d...Qi, blood and the meridians are fundamental concepts in Chinese medicine(CM), which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.展开更多
Current off saturation in the Moxizhuang (莫西庄) Off Field in central Junggar (准噶尔) basin was evaluated by logging interpretation and measured on core samples, and the paleo-oil saturation in both the pay zone...Current off saturation in the Moxizhuang (莫西庄) Off Field in central Junggar (准噶尔) basin was evaluated by logging interpretation and measured on core samples, and the paleo-oil saturation in both the pay zones and water zones was investigated by grain-containing-oil inclusion (GOI) analysis. The pay zones in this field have low off saturation and display low resistivity and small contrast between pay zones and water zones, and are classified as low-porosity, low oil saturation, and low resistivity reservoirs. Both the current low oil-saturation pay zones and the water zones above 4 365 m have high GOI values (up to 38%), suggesting high paieo-oil saturation. The significant difference between current oil saturation from both logging interpretation and core sample measurement and paleo-oil saturation indicated by GOI analysis suggests that this low off-saturation field evolved from a high off-saturation pool. Lateral re-migration and spill of formally trapped oil owing to changes in structural configuration since Neogene was the most plausible mechanism for off loss in the Moxizhuang Oil Field. The combined effects of differential accumulation in the charge phase and the differential re-migration and spill of accumulated oil in Neogene are responsible for the complicated correlation between residual oil saturation and porosity/permeability of the reservoir sandstones and the distribution of low oil-saturation pay zones and paieo-oil zones (current water zones).展开更多
Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and ...Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.展开更多
From the magnetotelluric detection in the epicentral region and the adjacent areas of the 1605 M7.5 Qiongzhou earthquake, we have discovered there is a low resistive body in the deep crust of the epicentral region. Th...From the magnetotelluric detection in the epicentral region and the adjacent areas of the 1605 M7.5 Qiongzhou earthquake, we have discovered there is a low resistive body in the deep crust of the epicentral region. The low resistive body extends straightly from the depth of about 13 km to the upper mantle, which is supposed as an uprising mantle pole. We therefore consider it is just the existing mantle pole and its upwelling thermal material that result in the faulting and stick-slipping activities of the upper crust, which is an important factor for the M7.5 Qiongzhou great earthquake occurrence. The postseismic faulting activity is characterized by creep, which shows that the risk is greatly decreased for the occurrence of a great earthquake with similar intensity in the future.展开更多
Ultrathin film-based transparent conductive oxides(TCOs)with a broad work function(WF)tunability are highly demanded for e cient energy conversion devices.However,reducing the film thickness below 50 nm is limited due...Ultrathin film-based transparent conductive oxides(TCOs)with a broad work function(WF)tunability are highly demanded for e cient energy conversion devices.However,reducing the film thickness below 50 nm is limited due to rapidly increasing resistance;furthermore,introducing dopants into TCOs such as indium tin oxide(ITO)to reduce the resistance decreases the transparency due to a trade-o between the two quantities.Herein,we demonstrate dopant-tunable ultrathin(≤50 nm)TCOs fabricated via electric field-driven metal implantation(m-TCOs;m=Ni,Ag,and Cu)without com-promising their innate electrical and optical properties.The m-TCOs exhibit a broad WF variation(0.97 eV),high transmittance in the UV to visible range(89–93%at 365 nm),and low sheet resistance(30–60Ωcm-2).Experimental and theoretical analyses show that interstitial metal atoms mainly a ect the change in the WF without substantial losses in optical transparency.The m-ITOs are employed as anode or cathode electrodes for organic light-emitting diodes(LEDs),inorganic UV LEDs,and organic photovoltaics for their universal use,leading to outstanding performances,even without hole injection layer for OLED through the WF-tailored Ni-ITO.These results verify the proposed m-TCOs enable e ective carrier transport and light extraction beyond the limits of traditional TCOs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62205231 and 22002102)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX223271)Jiangsu Key Laboratory for Environment Functional Materials。
文摘Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.
文摘In an integrated structure low resistance CICC joint, current is conducted by outer cable strands coming into touch with the conductive Cu sole. So it is an important condition for satisfying joint performance that each strand of the cable inside the joint is able to come to the outermost by transposition. This paper presents analysis, calculation and figures for the strand transposition. According to the twist procedures of the superconducting cable, the author computed the actual pitch of each stage cable, consecutively computed the projection of each stage cable on the axis of the cable (z axis) and the corresponding twist angle as the z coordinate changes, which is then drawn by AutoCAD. From the results shown in the figures, the minimal cable length, which enables each strand to transpose almost equally to the outermost of the cable in such a length, call be determined as the optimal joint length.
文摘The effect of cooling rate after 40% hot deformation on structure and mechanical properties of low alloy wear resistance cast iron was investigated by metallographic, scanning electron microscopes and detection of properties. The results show that for the cast steel after deformed, the amount of granular carbides of precipitation during the cooling decreased with the increase of the cooling rate, but the hardness was obviously enhanced, as a result, better mechanical properties will be obtained by force air cooling(cooling rate is about 7 ℃·s-1). And the reason of the change for structure and mechanical properties of the cast steel were analyzed.
文摘The Influence of RE on wear resistance of wear resistant cast iron containing low alloy was studied by means of slide wear and impact wear test. Moreover, its microstructure and characteristics of wearing surface was analyzed. The experimental results show that RE can improve the wear resistance of wear resistant cast iron containing low alloy, especially for impact wear resistance. The optimum wear resistance of wear resistant cast iron containing low alloy modified by RE of 0.046% can be obtained by normalization at 950 ℃ for 3 h. Moreover, the coordinated effect of rare earths and heat treatment was also revealed in this paper.
文摘In order to study the micro genetic mechanism and main geological controlling factors of low resistivity reservoir in NgIII formation of X oilfield in Bohai sea in China, the clay mineral composition, irreducible water saturation, salinity and conductive minerals of low resistivity reservoir were studied by using the data of core, cast thin section and analysis, and compared with normal resistivity reservoir. At the same time, the control effect of sedimentary environment on low resistivity reservoir was discussed. The results show that the additional conductivity of high bound water content and high montmorillonite content in the reservoir together leads to the significant reduction of reservoir resistivity, which is the main microscopic cause of the formation of low resistance, and is mainly controlled by the sedimentary background such as paleoclimate and sedimentary cycle. During the deposition period of NgIII formation, the paleoclimate was dry and cold, and it was at the end of the water advance of the medium-term sedimentary cycle. The hydrodynamic force of the river channel was weak, the carrying capacity of the riverbed was weak, and the river channel swayed frequently, resulting in fine lithologic particle size, high shale content and complex pore structure of the reservoir, resulting in significant reduction of reservoir resistance. The research conclusion would have strong guiding significance for the development of low resistivity reservoirs in this area.
基金supported by the National Natural Science Foundation of China(Nos.12141502 and 12005017).
文摘Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.
基金Supported by National Natural Science Foundation of China(Grant No.51372216)Jiangsu Science and Technology Plan Project of China(Grant No.BE2015113)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.BKJB460016)
文摘large diameter internal thread of high-strength steel(LDITHSS) manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope(SEM). Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread(LDIT) is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.
文摘Two types of low carbon MgO - C refractories with 6% graphite were prepared using microporous magnesiarich spinel (5 - 3 and 3 - 1 mm ) and fused magnesia (5 - 3 and 3 - 1 mm ) as coarse aggregates, respectively, fused magnesia ( ≤1 mm) as fine aggregate, magnesia powder (≤ 0. 088 mm ) , flake graphite powder ( ≤0. 088 mm), metal Al powder ( 〈0. 074 mm) as matrix, and phenol resin as binder. After curing at 220 ℃ and coke-embedded firing at 1 500 ℃ , the apparent porosity, cold crushing strength, cold modulus of rupture, permanent linear change on heating, thermal shock resistance and slag resistance of the specimens were studied comparatively. The results indicate that: ( 1 ) after curing at 220 ℃ and coke-embedded firing at 1 500 ℃, the specimen with microporous magnesia-rich spinel replacing fused magnesia has lower bulk density and higher apparent porosity than the common low car- bon MgO - C specimen. After curing at 220 ℃, the specimen with microporous aggregate has lower strength than common low carbon MgO - C specimen, but after coke-embedded firing at 1 500℃, it has higher strength and lower permanent linear change on heating; (2) low carbon MgO - C specimen using microporous magnesia-rich spinel to replace fused magnesia aggregate has better thermal shock resistance but worse slag resistance.
基金Supported by the CNPC Scientific Research and Technology Development Project (2019D-4410)。
文摘To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock conductivity during displacement were analyzed by displacement resistivity experiments simulating the process of reservoir formation and production, together with the data from thin sections, mercury injection and nuclear magnetic resonance experiments. In combination with geological understandings, the genetic mechanisms of LRPs were revealed, then the saturation interpretation model was selected, the variation laws and distribution range of the model parameters were defined, and finally an updated comprehensive saturation interpretation technique for the LRPs has been proposed. In the study area, the LRPs have resistivity values of less than 1 Ω·m, similar to or even slightly lower than that of the water layers. Geological research reveals that the LRPs were developed in low-energy depositional environment and their reservoir spaces are controlled by micro-scale pore throats, with an average radius of less than 0.7 μm, so they are typical microporous LRPs. Different from LRPs of sandstone and mudstone, they have less tortuous conductive paths than conventional reservoirs, and thus lower resistivity value under the same saturation. Archie’s formula is applicable to the saturation interpretation of LRPs with a cementation index value of 1.77-1.93 and a saturation index value of 1.82-2.03 that are 0.2-0.4 lower than conventional reservoirs respectively. By using interpretation parameters determined by classification statistics of petrophysical groups(PGs), oil saturations of the LRPs were calculated at bout 30%-50%,15% higher than the results by conventional methods, and basically consistent with the data of Dean Stark, RST, oil testing and production. The 15 wells of oil testing and production proved that the coincidence rate of saturation interpretation is over 90%and the feasibility of this method has been further verified.
文摘The influence of heating temperature on mechanical properties of low chromium wear resistant cast iron containing rare earth elements was studied by means of metallographic examination, scanning electron microscopic examination and mechanical property test. The experimental results show that heating temperature has great effect on impact toughness (α_k), bending fatigue (σ_(bb)) and relative toughness (σ_(bb)×f), but little effect on hardness (HRC). When the specimen was held at 960 ℃ for 3 h, it has better comprehensive mechanical properties, and the reason and regularity of the change for mechanical properties of the cast iron were reviewed.
基金Supported by Central Public-interest Scientific Institution Basal Research Fund,Yellow Sea Fisheries Research Institute,CAFS(20603022017001)National Natural Science Foundation of China(41676148)Taishan Scholar Program for Seed Industry and China Agriculture Research System(CARS-48)
文摘[Objective] This study was conducted to compare the genetic diversity and growth performance of two Litopenaeus vannamei populations at low temperature. [Method] One population(selected population, SP) was produced through inbreeding and 3 years of selection from seven popula- tions of L. vannamei introduced from the United States and Singapore. The other population (hybridized population, HP) was the F1 generation of the crosses between Population SP and some excellent populations introduced from South Korea and Singapore. The growth performance of the two populations at low temperature was compared, and the genetic diversity and genetic differentiation between the two populations were assessed using 13 microsatellite loci. [Result] The shrimps of population HP had better growth performance than those of population SP. The average body weight (BW) for population HP, which was (13.18±3.65) g/ind., was significantly higher than that of population SP, which was (12.20±3.14) g/ind. The coefficient of variation in body weight for population SP was 25.74%, and that for population HP was 27.69%. The other growth indices of popula- tion HP were all higher than those of population SP. One-way analysis of variance (ANOVA) indicated that there were highly significant differences in both BW and width of third abdominal segment (WTAS) between HP and SP(P〈0.001). The specific growth rate (SGR) and absolute growth rate (AGR) for population HP were (5.09±0.61) %/d and (0.26±0.60) g/d, respectively, while the SGR and AGR for population SP were (4.94±0.57) %/d and (0.24±0.63) g/d., both significantly lower than those of population HP (P〈0.001). Genetic diversity analysis revealed that the number of alleles (Na) of population HP (Na=7.9) was slightly higher than that of population SP (Na=7.6). The average polymorphic information content (PIC) of HP and SP populations was similar 0.63 and 0.62, both indicating high level of genetic diversity. The average observed heterozygosity (HQ) of HP and SP was 0.492 and 0.483, and the expected heterozygosity(He) was 0.675 and 0.663, respectively. Both Ho and He of population HP were higher than those of population SP, suggesting that HP had higher genetic diversity than population SP. Moreover, the mean of FsT values at the 13 microsatellite loci between HP and SP was 0.155 6, suggesting there was a significant genetic differentiation between the two populations. [Conclusion] Our results provide a theoretical basis for the breeding of new L. vannamei strains that are resistant to low temperature.
文摘The formation and growth of thermal fatigue crack and the function of RE and heat treatment in wear resistance of cast iron containing low alloy were investigated,and it was analyzed in view of the activation energy for the crack′s propagation. The results show that the thermal fatigue cracks are mainly generated at eutectic carbides,and the cracks are grown by themselves spreading and joining each other. RE can improve the eutectic carbide′s morphology,inhibit the generation and propagation of thermal fatigue cracks,therefore,promote the activation energy for the crack′s propagation,and especially,which is more noticeable in case of the RE modification in combination with heat treatment.
文摘The main focus of study is to characterize lower and upper cretaceous carbonate deposits with Low Resistivity Pay, in Persian Gulf. Four oil reservoirs in the Cretaceous including the Zubair, Buwaib, Shuaiba and Khatiyah Formations of Southern fields have been analyzed. Here is a look at that to determine main factors on decreasing resistivity in pay zone. In some intervals resistivity responses reach less than 6 to 1 ohm·m. Significant hydrocarbon accumulations are “hidden” in low resistivity Pay zone, (LRPZ). LRPZ reservoirs have been found in some formations in Persian Gulf. Causes of LRPZ reservoirs on the basis of experimental analysis include clay-coated grains, carbonate with interstitial dispersed clay. On the other side Smectite and Kaolinite of main clays types have high CEC and greater impact on lowering resistivity. Micritization and Pyritization of digenetic process have noticeable impact on LRPZ. It is mentioned that Lønøy method applied to address pore throat sizes which contain Inter crystalline porosity, Chalky Limestone, Mudstone micro porosity. Pore systems are classified at class 2 and 3 Lucia and pore size varies from 0.5 to 4 micron. NMR Core and Log results show different pore size distribution. NMR core and MRIL results explain that decreasing of resistivity in pay zone is related to texture and grain size variation not being existence of moved water. Irreducible water estimate for this reservoir was between 30% and 50%. T2 cut off estimates, for defining irreducible water saturation, 115 ms.
基金the funding support from the National Natural Science Foundation of China(No.51571027)
文摘The corrosion behavior of corrosion resistant steel(CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel(CS) using corrosion loss, polarization curves, X-ray diffraction(XRD), scanning electron microscopy(SEM), electron probe micro-analysis(EPMA), N2 adsorption, and X-ray photoelectron spectroscopy(XPS). The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.
基金the Outstanding Youth Scientist Foundation of Hunan Province(No.2021JJ10010)the Huxiang Young Talent Program from Hunan Province(No.2018RS3036)+1 种基金the Fundamental Research Funds for the Central Universities from Hunan Universitysupported by the Hunan Provincial Innovation Foundation for Postgraduate(No.CX20200446)。
文摘The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to various surfaces at low temperatures(from-18℃ to-80℃).Moreover,this supramolecular adhesive has good adhesion ability in the presence of water.
基金Supported by the National Basic Research Program of China(973 Program,No.2015CB554502)ENN Group Research Project(No.20160013)
文摘Qi, blood and the meridians are fundamental concepts in Chinese medicine(CM), which are components of the human body and maintain physiological function. Pathological changes of qi, blood and meridians may lead to discomfort and disease. Treatment with acupuncture or herbal medicine aims to regulate qi and blood so as to recover normal function of the meridians. This paper explores the nature of qi as well as compares and correlates them with the structures of the human body. We propose a conceptualization of qi as being similar to the interstitial fluid, and the meridians as being similar to interstitial space of low hydraulic resistance in the body. Hence, qi running in the meridians can be understood as interstitial fluid flowing via interstitial space of low hydraulic resistance.
基金the National Natural Science Foundation of China (No. 40772089)973 Projects (No. 2005CB422105)Program for Changjiang Scholars and Innovative Research Team in the University (IRT0658).
文摘Current off saturation in the Moxizhuang (莫西庄) Off Field in central Junggar (准噶尔) basin was evaluated by logging interpretation and measured on core samples, and the paleo-oil saturation in both the pay zones and water zones was investigated by grain-containing-oil inclusion (GOI) analysis. The pay zones in this field have low off saturation and display low resistivity and small contrast between pay zones and water zones, and are classified as low-porosity, low oil saturation, and low resistivity reservoirs. Both the current low oil-saturation pay zones and the water zones above 4 365 m have high GOI values (up to 38%), suggesting high paieo-oil saturation. The significant difference between current oil saturation from both logging interpretation and core sample measurement and paleo-oil saturation indicated by GOI analysis suggests that this low off-saturation field evolved from a high off-saturation pool. Lateral re-migration and spill of formally trapped oil owing to changes in structural configuration since Neogene was the most plausible mechanism for off loss in the Moxizhuang Oil Field. The combined effects of differential accumulation in the charge phase and the differential re-migration and spill of accumulated oil in Neogene are responsible for the complicated correlation between residual oil saturation and porosity/permeability of the reservoir sandstones and the distribution of low oil-saturation pay zones and paieo-oil zones (current water zones).
文摘Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.
基金Joint Seismological Science Foundation of China (104123).
文摘From the magnetotelluric detection in the epicentral region and the adjacent areas of the 1605 M7.5 Qiongzhou earthquake, we have discovered there is a low resistive body in the deep crust of the epicentral region. The low resistive body extends straightly from the depth of about 13 km to the upper mantle, which is supposed as an uprising mantle pole. We therefore consider it is just the existing mantle pole and its upwelling thermal material that result in the faulting and stick-slipping activities of the upper crust, which is an important factor for the M7.5 Qiongzhou great earthquake occurrence. The postseismic faulting activity is characterized by creep, which shows that the risk is greatly decreased for the occurrence of a great earthquake with similar intensity in the future.
基金supported by a National Research Foundation of Korea(NRF)grant funded by the Korean government under Grant No.2016R1A3B1908249。
文摘Ultrathin film-based transparent conductive oxides(TCOs)with a broad work function(WF)tunability are highly demanded for e cient energy conversion devices.However,reducing the film thickness below 50 nm is limited due to rapidly increasing resistance;furthermore,introducing dopants into TCOs such as indium tin oxide(ITO)to reduce the resistance decreases the transparency due to a trade-o between the two quantities.Herein,we demonstrate dopant-tunable ultrathin(≤50 nm)TCOs fabricated via electric field-driven metal implantation(m-TCOs;m=Ni,Ag,and Cu)without com-promising their innate electrical and optical properties.The m-TCOs exhibit a broad WF variation(0.97 eV),high transmittance in the UV to visible range(89–93%at 365 nm),and low sheet resistance(30–60Ωcm-2).Experimental and theoretical analyses show that interstitial metal atoms mainly a ect the change in the WF without substantial losses in optical transparency.The m-ITOs are employed as anode or cathode electrodes for organic light-emitting diodes(LEDs),inorganic UV LEDs,and organic photovoltaics for their universal use,leading to outstanding performances,even without hole injection layer for OLED through the WF-tailored Ni-ITO.These results verify the proposed m-TCOs enable e ective carrier transport and light extraction beyond the limits of traditional TCOs.