The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipita...The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel. The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fee lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).展开更多
In steels 16Mn and X60 with low S content (0. 003～0. 005%), rare earth metals (REM) still show ef- fects on purifying the molten steel and controlling the sulphide morphology. The optimum ratio of RE/S is about 2. 0,...In steels 16Mn and X60 with low S content (0. 003～0. 005%), rare earth metals (REM) still show ef- fects on purifying the molten steel and controlling the sulphide morphology. The optimum ratio of RE/S is about 2. 0, which causes lower content of oxygen and inclusions and higher impact toughness. The amount of REM in solid solution in the steel was determined by means of inductive coupling plasma (ICP) spectroscopy. The dissolved REM in low S steel could decrease the propor- tion of pearlite and increase the strength of the steel.展开更多
Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amp...Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.展开更多
This paper presents the design of an ultra low-voltage (ULV) pseudo operational transconductance amplifier (P-OTA) that is able to operate with a single supply voltage as low as 0.4 V. The proposed circuit is based on...This paper presents the design of an ultra low-voltage (ULV) pseudo operational transconductance amplifier (P-OTA) that is able to operate with a single supply voltage as low as 0.4 V. The proposed circuit is based on the bulk-driven technique and use of cross-coupled self-cascode pairs that boosts the differential DC gain. The stability condition of this structure for the DC gain is considered by definition of two coefficients to cancel out a controllable percentage of the denominator. This expression for stability condition yield optimized value for the DC gain. Also, as the principle of operation of the proposed technique relies on matching conditions, Monte Carlo analyzes are considered to study of the behavior of the proposed circuit against mismatches. The designed P-OTA have a DC gain of 64 dB, 212 KHz unity gain bandwidth, 57phase margin that is loaded by 10 pF differential capacitive loads, while consume only 16 μW. Eventually, from the proposed P-OTA, a low-power Sample and Hold (S/H) circuit with sampling frequency of 10 KS/s has been designed and simulated. The correct functionality for this configuration is verified from –30℃ to 70℃. The simulated data presented is obtained using the HSPICE Environment and is valid for the 90 nm triple-well CMOS process.展开更多
Geothermal resources are a promising approach to clean renewable energy;90%of them are deep reservoirs of hot dry rock that require hydraulic fracturing to create a network of connections among wells to enable efficie...Geothermal resources are a promising approach to clean renewable energy;90%of them are deep reservoirs of hot dry rock that require hydraulic fracturing to create a network of connections among wells to enable efficient heat exchange,known as an Enhanced Geothermal System(EGS).The Pohang EGS project in south Korea led to a devasting Mw5.5 earthquake,triggered by the reservoir's EGS stimulation,the largest earthquake known to have been induced by EGS development.Detailed investigations have been conducted to understand the cause of the Pohang earthquake;the conclusion has been that overpressurized injected fluids migrated into an unknown fault triggering this large earthquake.Detailed velocity images for the source zone of the 2017 Pohang earthquake,which could be helpful for further understanding its inducing mechanism,are unavailable.However,we have assembled detailed aftershock data recorded by 41 local stations installed within about three months after the Mw5.5 Pohang earthquake,and have then applied the V_(p)/V_(s)model's consistency-constrained double-difference seismic tomography method to determine the high-resolution three-dimensional Vp(compressional wave velocity),Vs(shear wave velocity),and V_(p)/V_(s)models of the source region that we report here,as well as earthquake locations within the source region.The velocity images reveal that the deep source area of the 2017 Pohang earthquake is dominated by low Vp,high Vs,and low V_(p)/V_(s)anomalies,a pattern that can be caused by overpressurized vapors due to high temperatures at these depths.Based on aftershock locations and velocity features,our studies support the conclusion that the 2017Pohang earthquake was triggered by injected EGS fluids that migrated into a blind fault.展开更多
Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room tempera...Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth.展开更多
The low cycle fatigue （LCF） behavior of P92 martensitic steel was investigated under different controlled strain amplitudes at room and high temperatures （873 K）. The cyclic stress responses at all temperatures an...The low cycle fatigue （LCF） behavior of P92 martensitic steel was investigated under different controlled strain amplitudes at room and high temperatures （873 K）. The cyclic stress responses at all temperatures and strain amplitudes exhibited obviously rapid softening behavior at the early stage of fatigue life, and there was no saturated stage at high temperature. The fracture surfaces of the fatigue samples were observed by scanning electron microsco py （SEM） and optical microscopy. It was shown that crack initiation and propagation occurred transgranularly at both testing temperatures. A typical character was the high density crack branches or secondary cracks along fatigue striations at high temperature, which initiated from the oxidized inclusions and grain boundaries. Further investiga- tion by transmission electron microscopy （TEM） showed that the softening behavior was attributed to the micro- structure evolution during fatigue life, such as annihilation of dislocations and migration of martensite laths as well as carbide coarsening, especially for samples tested at high temperature.展开更多
试验用CrNi3Si2MoV钢（／％：0．21C，1．75Si，0．29Mn，0．0060P，0．0007S，1．03Cr，2．86Ni，0．31Mo，0．08V）由50kg真空感应炉冶炼，并锻成中15mm的钢棒。通过Gleeble-3800热模拟试验机、扫描、透射电镜（SEM、TEM）和X-射线衍...试验用CrNi3Si2MoV钢（／％：0．21C，1．75Si，0．29Mn，0．0060P，0．0007S，1．03Cr，2．86Ni，0．31Mo，0．08V）由50kg真空感应炉冶炼，并锻成中15mm的钢棒。通过Gleeble-3800热模拟试验机、扫描、透射电镜（SEM、TEM）和X-射线衍射仪（XRD）等研究了1200oC奥氏体化的CrNi3Si2MoV钢在750℃10％～70％热变形＋淬火至330℃和550℃1min的淬火分配（Q＆P，Qnenching and Partitioning）处理后，热变形量对Q＆P处理试验钢组织和硬度的影响。试验结果表明，热变形＋Q＆P处理后CrNi3Si2MoV钢的组织为板条奥氏体＋5．7％～17．2％薄膜状残留奥氏体；变形量为30％时残留奥氏体量最大（17．2％），50％变形时HV值最大为448，当变形量达70％时该钢发生明显的再结晶，组织细化，钢的硬度降低。展开更多
通过焊接热模拟研究了不同焊接线能量下建筑用Cr-Mo、Cr-Mo-P低合金钢的显微组织、物相组成和韧-脆转变温度,分析了P的晶界偏聚行为对焊接接头脆性的影响。结果表明,随着焊接线能量的增加,Cr-Mo和Cr-Mo-P低合金钢的韧-脆转变温度都增大...通过焊接热模拟研究了不同焊接线能量下建筑用Cr-Mo、Cr-Mo-P低合金钢的显微组织、物相组成和韧-脆转变温度,分析了P的晶界偏聚行为对焊接接头脆性的影响。结果表明,随着焊接线能量的增加,Cr-Mo和Cr-Mo-P低合金钢的韧-脆转变温度都增大;在相同焊接线能量下,Cr-Mo-P低合金钢的韧-脆转变温度都要高于Cr-Mo钢;随着焊接线能量的增加,建筑用Cr-Mo和Cr-Mo-P低合金钢组织由板条贝氏体为主转变为以粒状贝氏体为主,且细条状M/A岛状组织的尺寸呈现逐渐增加的趋势;P的晶界浓度先增加而后降低,在焊接线能量为60 k J/cm时取得最大值;焊接后热处理降低了建筑用Cr-Mo和Cr-Mo-P钢热模拟试样的韧-脆转变温度,这主要与热模拟试样热处理后贝氏体束尺寸基本不变,而M/A组元尺寸减小有关。展开更多
基金The DFG(Deutsche Forschungsgemeinschaf)is gratefully acknowledged for the financial support(DFG-BI 418/9-1).
文摘The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel. The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fee lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).
文摘In steels 16Mn and X60 with low S content (0. 003～0. 005%), rare earth metals (REM) still show ef- fects on purifying the molten steel and controlling the sulphide morphology. The optimum ratio of RE/S is about 2. 0, which causes lower content of oxygen and inclusions and higher impact toughness. The amount of REM in solid solution in the steel was determined by means of inductive coupling plasma (ICP) spectroscopy. The dissolved REM in low S steel could decrease the propor- tion of pearlite and increase the strength of the steel.
基金Foundation of Verification Researches for Army Control Technology (513310101).
文摘Applicability of regional P/S amplitude ratios for the discrimination of low-magnitude seismic events was tested and proved using earthquakes and explosions in Central Asia. Results obtained show that regional P/S amplitude ratios which may discriminate medium or large magnitude events well, are also applicable to low magnitude events Their performances for low magnitude events are almost as good as that for medium or large events. Statistical comparisons based on 25 P/S discriminate from the four seismic stations WMQ, BLK, MUL and MAK showed that the average misclassification rate for low-magnitude seismic events averagely was only 2 percent higher than that for medium and large magnitude seismic events.
文摘This paper presents the design of an ultra low-voltage (ULV) pseudo operational transconductance amplifier (P-OTA) that is able to operate with a single supply voltage as low as 0.4 V. The proposed circuit is based on the bulk-driven technique and use of cross-coupled self-cascode pairs that boosts the differential DC gain. The stability condition of this structure for the DC gain is considered by definition of two coefficients to cancel out a controllable percentage of the denominator. This expression for stability condition yield optimized value for the DC gain. Also, as the principle of operation of the proposed technique relies on matching conditions, Monte Carlo analyzes are considered to study of the behavior of the proposed circuit against mismatches. The designed P-OTA have a DC gain of 64 dB, 212 KHz unity gain bandwidth, 57phase margin that is loaded by 10 pF differential capacitive loads, while consume only 16 μW. Eventually, from the proposed P-OTA, a low-power Sample and Hold (S/H) circuit with sampling frequency of 10 KS/s has been designed and simulated. The correct functionality for this configuration is verified from –30℃ to 70℃. The simulated data presented is obtained using the HSPICE Environment and is valid for the 90 nm triple-well CMOS process.
基金supported by the National Natural Science Foundation of China(42304056)the Natural Science Foundation of Hebei Province(D2023305007)+1 种基金supported by the Basic Research Project(GP2020-017,GP2020027)of the Korea Institute of Geoscience and Mineral Resources(KIGAM)funded by the Ministry of Science and ICT of Korea。
文摘Geothermal resources are a promising approach to clean renewable energy;90%of them are deep reservoirs of hot dry rock that require hydraulic fracturing to create a network of connections among wells to enable efficient heat exchange,known as an Enhanced Geothermal System(EGS).The Pohang EGS project in south Korea led to a devasting Mw5.5 earthquake,triggered by the reservoir's EGS stimulation,the largest earthquake known to have been induced by EGS development.Detailed investigations have been conducted to understand the cause of the Pohang earthquake;the conclusion has been that overpressurized injected fluids migrated into an unknown fault triggering this large earthquake.Detailed velocity images for the source zone of the 2017 Pohang earthquake,which could be helpful for further understanding its inducing mechanism,are unavailable.However,we have assembled detailed aftershock data recorded by 41 local stations installed within about three months after the Mw5.5 Pohang earthquake,and have then applied the V_(p)/V_(s)model's consistency-constrained double-difference seismic tomography method to determine the high-resolution three-dimensional Vp(compressional wave velocity),Vs(shear wave velocity),and V_(p)/V_(s)models of the source region that we report here,as well as earthquake locations within the source region.The velocity images reveal that the deep source area of the 2017 Pohang earthquake is dominated by low Vp,high Vs,and low V_(p)/V_(s)anomalies,a pattern that can be caused by overpressurized vapors due to high temperatures at these depths.Based on aftershock locations and velocity features,our studies support the conclusion that the 2017Pohang earthquake was triggered by injected EGS fluids that migrated into a blind fault.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11434006, and 51871112)the National Basic Research Program of China (Grant No. 2015CB921502)+1 种基金the 111 Project (Grant No. B13029)Shandong Provincial Natural Science Foundation (Grant No. ZR2018MA035)
文摘Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth.
基金Sponsored by Key Project of Shanghai Science and Technology Commission of China(10521100500)
文摘The low cycle fatigue （LCF） behavior of P92 martensitic steel was investigated under different controlled strain amplitudes at room and high temperatures （873 K）. The cyclic stress responses at all temperatures and strain amplitudes exhibited obviously rapid softening behavior at the early stage of fatigue life, and there was no saturated stage at high temperature. The fracture surfaces of the fatigue samples were observed by scanning electron microsco py （SEM） and optical microscopy. It was shown that crack initiation and propagation occurred transgranularly at both testing temperatures. A typical character was the high density crack branches or secondary cracks along fatigue striations at high temperature, which initiated from the oxidized inclusions and grain boundaries. Further investiga- tion by transmission electron microscopy （TEM） showed that the softening behavior was attributed to the micro- structure evolution during fatigue life, such as annihilation of dislocations and migration of martensite laths as well as carbide coarsening, especially for samples tested at high temperature.
文摘试验用CrNi3Si2MoV钢（／％：0．21C，1．75Si，0．29Mn，0．0060P，0．0007S，1．03Cr，2．86Ni，0．31Mo，0．08V）由50kg真空感应炉冶炼，并锻成中15mm的钢棒。通过Gleeble-3800热模拟试验机、扫描、透射电镜（SEM、TEM）和X-射线衍射仪（XRD）等研究了1200oC奥氏体化的CrNi3Si2MoV钢在750℃10％～70％热变形＋淬火至330℃和550℃1min的淬火分配（Q＆P，Qnenching and Partitioning）处理后，热变形量对Q＆P处理试验钢组织和硬度的影响。试验结果表明，热变形＋Q＆P处理后CrNi3Si2MoV钢的组织为板条奥氏体＋5．7％～17．2％薄膜状残留奥氏体；变形量为30％时残留奥氏体量最大（17．2％），50％变形时HV值最大为448，当变形量达70％时该钢发生明显的再结晶，组织细化，钢的硬度降低。
文摘通过焊接热模拟研究了不同焊接线能量下建筑用Cr-Mo、Cr-Mo-P低合金钢的显微组织、物相组成和韧-脆转变温度,分析了P的晶界偏聚行为对焊接接头脆性的影响。结果表明,随着焊接线能量的增加,Cr-Mo和Cr-Mo-P低合金钢的韧-脆转变温度都增大;在相同焊接线能量下,Cr-Mo-P低合金钢的韧-脆转变温度都要高于Cr-Mo钢;随着焊接线能量的增加,建筑用Cr-Mo和Cr-Mo-P低合金钢组织由板条贝氏体为主转变为以粒状贝氏体为主,且细条状M/A岛状组织的尺寸呈现逐渐增加的趋势;P的晶界浓度先增加而后降低,在焊接线能量为60 k J/cm时取得最大值;焊接后热处理降低了建筑用Cr-Mo和Cr-Mo-P钢热模拟试样的韧-脆转变温度,这主要与热模拟试样热处理后贝氏体束尺寸基本不变,而M/A组元尺寸减小有关。
