A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of...A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.展开更多
We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the thre...We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.展开更多
Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quali...Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 0.48 W. The maximum CW operation output power at room temperature is 1.48 W. The lateral divergence angle θ‖ and vertical divergence angle θ⊥ are as low as 15.3° and 13.8° without side-lobes at a current of 6 A.展开更多
Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the ...Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.展开更多
We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drai...We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drain electrodes and the pentacene active layer. The threshold voltage decreased remarkably from ca. -20 V to a few volts （below -7.6 V） while the mobility in- creased 1.5-3 times after the insertion of the interlayer of only ca. 2 nm, which could be attributed to the reduction of the car- tier injection barrier. The results suggest a simple and effective way to achieve low-threshold-voltage pentacene-based organic thin film transistors with high mobility on silicon dioxide dielectric.展开更多
To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fa...To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fabricated. The threshold current was reduced to 8 mA. An output power of 76 mW was achieved at 100 mA current at room temperature, with a slope efficiency of 0.83 W/A and a horizon divergent angle of 6.3°. The maximum single mode output power of the device reached as high as 450 mW.展开更多
A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity ...A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.展开更多
Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black sp...Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.展开更多
We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the soft...We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the softening parameter, we show that though the very low-energy structure （VLES） and high low-energy structure （HLES） are both due to the interaction between the ionic CP and the electron, the two structures have different physical mechanisms： the VLES can be attributed to the electron-ion Coulomb interaction at a rather small distance and the HLES is more likely to be ascribed to the electron-ion Coulomb interaction at a large distance.展开更多
Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor netwo...Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.展开更多
This paper studies the transient pressure of percolation during one production and one shutting in one dimension porous media with threshold pressure gradient, the differential equations are derived and solved with nu...This paper studies the transient pressure of percolation during one production and one shutting in one dimension porous media with threshold pressure gradient, the differential equations are derived and solved with numerical computation. Basing on numerical solution, it is analyzed that: 1. the relation between the steady pressure at well bore (or at endpoint) and threshold pressure gradient, shut-in time, and the corresponding formulae are derived; 2, the regulation of transient pressure peak. The result is very useful and will help experiments and applications in the development of low permeability reservoirs with threshold pressure gradient.展开更多
Silicon-on-insulator (SOI) CMOS technology is a very attractive option for implementing digital integrated circuits for low power applications. This paper presents migration of standby subthreshold leakage control tec...Silicon-on-insulator (SOI) CMOS technology is a very attractive option for implementing digital integrated circuits for low power applications. This paper presents migration of standby subthreshold leakage control technique from a bulk CMOS to SOI CMOS technology. An improved SOI CMOS technology based circuit technique for effective reduction of standby subthreshold leakage power dissipation is proposed in this paper. The proposed technique is validated through design and simulation of a one-bit full adder circuit at a temperature of 27℃, supply voltage, VDD of 0.90 V in 120 nm SOI CMOS technology. Existing standby subthreshold leakage control techniques in CMOS bulk technology are compared with the proposed technique in SOI CMOS technology. Both the proposed and existing techniques are also implemented in SOI CMOS technology and compared. Reduction in standby subthreshold leakage power dissipation by reduction factors of 54x and 45x foraone-bit full adder circuit was achieved using our proposed SOI CMOS technology based circuit technique in comparison with existing techniques such as MTCMOS technique and SCCMOS technique respectively in CMOS bulk technology. Dynamic power dissipation was also reduced significantly by using this proposed SOI CMOS technology based circuit technique. Standby subthreshold leakage power dissipation and dynamic power dissipation were also reduced significantly using the proposed circuit technique in comparison with other existing techniques, when all circuit techniques were implemented in SOI CMOS technology. All simulations were performed using Microwindver 3.1 EDA tool.展开更多
BACKGROUND Low back pain(LBP)is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-rep...BACKGROUND Low back pain(LBP)is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBP.No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain,despite this being a suggested risk factor for LBP.AIM To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBP.METHODS This is a an observational before and after study of 26 participants(13 men,13 women)between 20-35 years old.Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5.Pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back(Borg CR10=7/10).Wilcoxon signed-rank test was used for analyze values from the before and after test conditions.Mann-Whitney U test was used to investigate potential gender difference.RESULTS Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%.For all pain pressure threshold locations tested,there was a significant difference for the study population with moderate-large decreased(r=-0.56)pressure pain threshold after exposure to prolonged flexed sitting posture(P<0.01).Comparisons between gender did not show any significant difference.CONCLUSION The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBP and significantly reduced lumbar interspinous pressure pain thresholds.No gender-based differences were observed.展开更多
A low energy uneven cluster protocol design method is proposed. Aiming at the random choosing for cluster head of traditional Leach protocol, and the defect of the single hop from all the cluster heads to the sink nod...A low energy uneven cluster protocol design method is proposed. Aiming at the random choosing for cluster head of traditional Leach protocol, and the defect of the single hop from all the cluster heads to the sink node, an improved method for Leave protocol is advanced. Firstly, the election model of cluster head is improved, and the node residual energy is considered in the process of threshold and the cluster head election to improve the whole network life circle. In the multi-hop route, choosing the maximum energy and the nearest node as the next hop and a route transferring data among many clusters is formed. The experiment shows the method having great improvement compared with Leach protocol and prolonging the network life cycle.展开更多
Dust accumulation on photovoltaic (PV) panels degrades PV panels’ performance;leading to decreased power output and consequently high cost per generated kilowatt. Research addressing the severity of dust accumulation...Dust accumulation on photovoltaic (PV) panels degrades PV panels’ performance;leading to decreased power output and consequently high cost per generated kilowatt. Research addressing the severity of dust accumulation on PV panels has been ongoing since the 1940s, but proposed solutions have tended to increase the cost of PV systems either from oversizing or from cleaning the system. The objective of this work, therefore, is to design and implement a low-cost affordable automated PV panel dust cleaning system for use in rural communities of Sub-Saharan Africa (SSA);where financial resources are limited and significantly strained in meeting livelihood activities. Complete design and implementation details of a prototype system are provided for easy replication and capitalization on PV systems for sustainable energy needs. The system detects dust based on the innovative use of light-dependent resistors. Testing and observation of the system in operational mode reveal satisfactory performance;measured parameters quantify a power output increase of 33.76% as a result of cleaning dust off the PV panel used in the study.展开更多
To meet the increasing demands for higher performance and low-power consumption in present and future Systems-on-Chips (SoCs) require a large amount of on-die/embedded memory. In Deep-Sub-Micron (DSM) technology, it i...To meet the increasing demands for higher performance and low-power consumption in present and future Systems-on-Chips (SoCs) require a large amount of on-die/embedded memory. In Deep-Sub-Micron (DSM) technology, it is coming as challenges, e.g., leakage power, performance, data retentation, and stability issues. In this work, we have proposed a novel low-stress SRAM cell, called as IP3 SRAM bit-cell, as an integrated cell. It has a separate write sub-cell and read sub-cell, where the write sub-cell has dual role of data write and data hold. The data read sub-cell is proposed as a pMOS gated ground scheme to further reduce the read power by lowering the gate and subthreshold leakage currents. The drowsy voltage is applied to the cell when the memory is in the standby mode. Further, it utilizes the full-supply body biasing scheme while the memory is in the standby mode, to further reduce the subthreshold leakage current to reduce the overall standby power. To the best of our knowledge, this low-stress memory cell has been proposed for the first time. The proposed IP3 SRAM Cell has a significant write and read power reduction as compared to the conventional 6 T and PP SRAM cells and overall improved read stability and write ability performances. The proposed design is being simulated at VDD = 0.8 V and 0.7 V and an analysis is presented here for 0.8 V to adhere previously reported works. The other design parameters are taken from the CMOS technology available on 45 nm with tOX = 2.4 nm, Vthn = 0.224 V, and Vthp = 0.24 V at T = 27?C.展开更多
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2008AA03Z402)the National Natural Science Foundation of China (Grant No. 61076044)the Natural Science Foundation of Beijing,China(Grant Nos. 4092007 and 4102003)
文摘A multi-hole vertical-cavity surface-emitting laser （VCSEL） operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-refleetor of an oxidation- confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10% are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CB632801 and 2013CB632803the National Natural Science Foundation of China under Grant Nos 61435014,61306058 and 61274094the Beijing Natural Science Foundation under Grant No 4144086
文摘We report on the room-temperature cascade laser （QCL） at λ -4.7μm. cw operation of a surface grating Both grating design and material distributed feedback （DFB） quantum optimization are used to decrease the threshold current density and to increase the output power. For a high-reflectivity-coated 13-μm-wide and 4- mm-long laser, high wall-plug efficiency of 6% is obtained at 20℃ from a single facet producing over I W of ew output power. The threshold current density of DFB QCL is as low as 1.13kA/cm^2 at 10℃ and 1.34kA/cm2 at 30℃ in cw mode. Stable single-mode emission with a side-mode suppression ratio of about 30 dB is observed in tile working temperature range of 20-50℃.
文摘Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in ridge-waveguide QW laser fabrication. This method was applied in 980 nm VCSELs fabrication to form a high-quality native oxide current blocking layer, which simplifies the device process. A significant reduction of threshold current and a distinguished device performance are achieved. The 500 μm diameter device has a current threshold as low as 0.48 W. The maximum CW operation output power at room temperature is 1.48 W. The lateral divergence angle θ‖ and vertical divergence angle θ⊥ are as low as 15.3° and 13.8° without side-lobes at a current of 6 A.
基金supported by the National Natural Science Foundation of China(62305244,52372003,62374112,62105078)Shandong Province Natural ScienceFoundation(ZR2021QE060,ZR2021QF009)+2 种基金Natural Science Foundation of Heilongjiang Province of China(ZD2023E004)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2022QNRC001)Youth science and technology innovation team of Shandong Province institution of higher learning(2022KJ258).
文摘Visible light microlasers are essential building blocks for integrated photonics.However,achieving low-threshold(μw),continuous-wave(CW)visible light lasing at room temperature(RT)has been a challenge because of the formidable requirement of population inversion at short wavelengths.Rare-earth(RE)-activated microcavities,featuring highquality factor(Q)and small mode volume of whispering gallery modes,offer a great opportunity for achieving infrared-to-visible upconversion(UC)lasing.Here,we report that batch-produced nano-glass composite(GC)microspheres incorporating RE-doped fluoride nanocrystals show efficient UC emissions.These multi-phase composite microspheres exhibit a high Q value(≥10^(5)),comparable to that of conventional multi-component glass microspheres.The UC lasing with pure red,green,and blue(RGB)emissions are demonstrated based on a highly efficient tapered fiber-microsphere system.More importantly,the GC microspheres manifest reduced(by 45%)lasing threshold and enhanced(more than four times)slope effciency.These characteristics,together with excellent long-term stability,suggest a promising solution to achieving highly robust,stand-alone,low-threshold,and versatile UC microlasers.
基金financially supported by the National Basic Research Program of China (973 Program) (Grant No. 2007CB936302)the National Natural Science Foundation of China (Grant No. 20833002)
文摘We herein report the effective performance enhancement of the pentacene-based organic thin film transistors with silicon di- oxide dielectric by inserting a thin metal phthalocyanines interlayer between Au source/drain electrodes and the pentacene active layer. The threshold voltage decreased remarkably from ca. -20 V to a few volts （below -7.6 V） while the mobility in- creased 1.5-3 times after the insertion of the interlayer of only ca. 2 nm, which could be attributed to the reduction of the car- tier injection barrier. The results suggest a simple and effective way to achieve low-threshold-voltage pentacene-based organic thin film transistors with high mobility on silicon dioxide dielectric.
基金supported by the National Military Electronic Component Program of China(No.1107XG0700)
文摘To achieve low threshold current as well as high single mode output power, a graded index separate confinement heterostructure （GRIN-SCH） A1GaInAs/A1GaAs quantum well laser with an optimized ridge wave- guide was fabricated. The threshold current was reduced to 8 mA. An output power of 76 mW was achieved at 100 mA current at room temperature, with a slope efficiency of 0.83 W/A and a horizon divergent angle of 6.3°. The maximum single mode output power of the device reached as high as 450 mW.
基金supported by the National Natural Science Foundation of China(No.62175181)。
文摘A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.
基金supported by the Lakehead University Graduate Fellowship, Nature Science and Engineer Research Council Scholarship of Canada (NSERC) PGS A,the National Natural Science Foundation of China (Grant No. 30872000)K. C. Wong Education Foundation of Hong Kong (2008) and the funding initiative of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences to the author and NSERC research grant to Qing-Lai Dang
文摘Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10925420,11074026,11174330,and 11274050)the National Basic Research Program of China (Grant Nos.2011CB808102 and 2013CB922201)
文摘We investigate the low-energy structure （LES） in the above-threshold ionization spectrum at a mid-infrared laser wavelength with a semiclassical model. Using a softened Coulomb potential （CP） and changing the softening parameter, we show that though the very low-energy structure （VLES） and high low-energy structure （HLES） are both due to the interaction between the ionic CP and the electron, the two structures have different physical mechanisms： the VLES can be attributed to the electron-ion Coulomb interaction at a rather small distance and the HLES is more likely to be ascribed to the electron-ion Coulomb interaction at a large distance.
基金The National High Technology Research and Development Program of China (863 Program) (No. 2007AA01Z2A7)Program for Special Talents in Six Fields of Jiangsu Province
文摘Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.
文摘This paper studies the transient pressure of percolation during one production and one shutting in one dimension porous media with threshold pressure gradient, the differential equations are derived and solved with numerical computation. Basing on numerical solution, it is analyzed that: 1. the relation between the steady pressure at well bore (or at endpoint) and threshold pressure gradient, shut-in time, and the corresponding formulae are derived; 2, the regulation of transient pressure peak. The result is very useful and will help experiments and applications in the development of low permeability reservoirs with threshold pressure gradient.
文摘Silicon-on-insulator (SOI) CMOS technology is a very attractive option for implementing digital integrated circuits for low power applications. This paper presents migration of standby subthreshold leakage control technique from a bulk CMOS to SOI CMOS technology. An improved SOI CMOS technology based circuit technique for effective reduction of standby subthreshold leakage power dissipation is proposed in this paper. The proposed technique is validated through design and simulation of a one-bit full adder circuit at a temperature of 27℃, supply voltage, VDD of 0.90 V in 120 nm SOI CMOS technology. Existing standby subthreshold leakage control techniques in CMOS bulk technology are compared with the proposed technique in SOI CMOS technology. Both the proposed and existing techniques are also implemented in SOI CMOS technology and compared. Reduction in standby subthreshold leakage power dissipation by reduction factors of 54x and 45x foraone-bit full adder circuit was achieved using our proposed SOI CMOS technology based circuit technique in comparison with existing techniques such as MTCMOS technique and SCCMOS technique respectively in CMOS bulk technology. Dynamic power dissipation was also reduced significantly by using this proposed SOI CMOS technology based circuit technique. Standby subthreshold leakage power dissipation and dynamic power dissipation were also reduced significantly using the proposed circuit technique in comparison with other existing techniques, when all circuit techniques were implemented in SOI CMOS technology. All simulations were performed using Microwindver 3.1 EDA tool.
文摘BACKGROUND Low back pain(LBP)is a common condition with large burden worldwide.Exposure to prolonged sitting with a flexed lumbar posture has been suggested in the literature to be a potential risk factor for self-reported LBP.No study has previously investigated whether exposure to prolonged flexed sitting posture provokes discomfort/pain and decreased interspinous pressure pain thresholds for healthy young men and women without back pain,despite this being a suggested risk factor for LBP.AIM To investigate whether sitting in a prolonged flexed lumbar posture provokes discomfort and lowers interspinous pressure pain thresholds in the lumbar spine for healthy young men and women without previous LBP.METHODS This is a an observational before and after study of 26 participants(13 men,13 women)between 20-35 years old.Algometry was used to examine the pain threshold for pressure applied between spinous processes of the lumbar spine L1-L5.Pressure algometer measures were performed in prone before and after participants were instructed to sit in a fully flexed posture for a maximum of 15 min or until discomfort was experienced in the low back(Borg CR10=7/10).Wilcoxon signed-rank test was used for analyze values from the before and after test conditions.Mann-Whitney U test was used to investigate potential gender difference.RESULTS Fully flexed lumbar spine sitting posture up to 15 min provoked temporary discomfort but the proportion of participants experiencing discomfort 7/10 in the low back was 62%.For all pain pressure threshold locations tested,there was a significant difference for the study population with moderate-large decreased(r=-0.56)pressure pain threshold after exposure to prolonged flexed sitting posture(P<0.01).Comparisons between gender did not show any significant difference.CONCLUSION The result showed that exposure to fully flexed lumbar sitting posture for up to 15 min produced temporary discomfort in the low back in young healthy adults with no previous history of LBP and significantly reduced lumbar interspinous pressure pain thresholds.No gender-based differences were observed.
文摘A low energy uneven cluster protocol design method is proposed. Aiming at the random choosing for cluster head of traditional Leach protocol, and the defect of the single hop from all the cluster heads to the sink node, an improved method for Leave protocol is advanced. Firstly, the election model of cluster head is improved, and the node residual energy is considered in the process of threshold and the cluster head election to improve the whole network life circle. In the multi-hop route, choosing the maximum energy and the nearest node as the next hop and a route transferring data among many clusters is formed. The experiment shows the method having great improvement compared with Leach protocol and prolonging the network life cycle.
文摘Dust accumulation on photovoltaic (PV) panels degrades PV panels’ performance;leading to decreased power output and consequently high cost per generated kilowatt. Research addressing the severity of dust accumulation on PV panels has been ongoing since the 1940s, but proposed solutions have tended to increase the cost of PV systems either from oversizing or from cleaning the system. The objective of this work, therefore, is to design and implement a low-cost affordable automated PV panel dust cleaning system for use in rural communities of Sub-Saharan Africa (SSA);where financial resources are limited and significantly strained in meeting livelihood activities. Complete design and implementation details of a prototype system are provided for easy replication and capitalization on PV systems for sustainable energy needs. The system detects dust based on the innovative use of light-dependent resistors. Testing and observation of the system in operational mode reveal satisfactory performance;measured parameters quantify a power output increase of 33.76% as a result of cleaning dust off the PV panel used in the study.
文摘To meet the increasing demands for higher performance and low-power consumption in present and future Systems-on-Chips (SoCs) require a large amount of on-die/embedded memory. In Deep-Sub-Micron (DSM) technology, it is coming as challenges, e.g., leakage power, performance, data retentation, and stability issues. In this work, we have proposed a novel low-stress SRAM cell, called as IP3 SRAM bit-cell, as an integrated cell. It has a separate write sub-cell and read sub-cell, where the write sub-cell has dual role of data write and data hold. The data read sub-cell is proposed as a pMOS gated ground scheme to further reduce the read power by lowering the gate and subthreshold leakage currents. The drowsy voltage is applied to the cell when the memory is in the standby mode. Further, it utilizes the full-supply body biasing scheme while the memory is in the standby mode, to further reduce the subthreshold leakage current to reduce the overall standby power. To the best of our knowledge, this low-stress memory cell has been proposed for the first time. The proposed IP3 SRAM Cell has a significant write and read power reduction as compared to the conventional 6 T and PP SRAM cells and overall improved read stability and write ability performances. The proposed design is being simulated at VDD = 0.8 V and 0.7 V and an analysis is presented here for 0.8 V to adhere previously reported works. The other design parameters are taken from the CMOS technology available on 45 nm with tOX = 2.4 nm, Vthn = 0.224 V, and Vthp = 0.24 V at T = 27?C.
