Ultrasound is used in various chemical reaction processes, and these reactions are influenced by ultrasonic frequency. A threshold power is required for the ultrasonic degradation reaction and oxidation reaction cause...Ultrasound is used in various chemical reaction processes, and these reactions are influenced by ultrasonic frequency. A threshold power is required for the ultrasonic degradation reaction and oxidation reaction caused by hydroxyl radicals, and the cavitation threshold power is also influenced by frequency generally. In this study, the effects of frequency on the threshold power of methylene blue degradation and KI oxidation were investigated in the range between 22.8 kHz and 1640 kHz. The threshold power of KI oxidation reaction increased with increasing frequency. This phenomenon well agrees with previous study, and it is revealed that the generation of I-3?ion is caused by oxidation reaction of Iˉ ions with hydroxyl radicals. On the other hand, the threshold power of methylene blue degradation reaction was not affected by frequency. The ultrasonic degradation of methylene blue is considered to be caused by hydroxyl radicals, and there is a linear relationship between degradation rate constant and sonochemical efficiency value. However, it is guessed that the degradation of methylene blue is occurred inside cavitation bubble by pyrolysis at high frequency regions.展开更多
The calculation time in the Monte Carlo simulations consistently represents an essential issue. It is often very long, and its decrease constitutes a challenge for the simulator. Generally, an MC simulation is qualifi...The calculation time in the Monte Carlo simulations consistently represents an essential issue. It is often very long, and its decrease constitutes a challenge for the simulator. Generally, an MC simulation is qualified as quality or not according to two main criteria: the calculation time and the accuracy of the results. However, in most cases, the optimization of one criterion affects negatively the other. Therefore, a compromise between both of them is always required in this kind of simulation. The present work aims at studying the impact of the production threshold(or cut) of the GEANT4 toolkit on the calculation of the power deposition in the MEGAPIE spallation target.The production threshold of secondaries is a GEANT4 intrinsic parameter. It indicates the limit of energy we can reach in the production of secondary particles. This study has allowed us to make the following conclusions. First,the influence of the cut on the calculation of the deposited power depends on the volume size, its arrangement and the importance of the electromagnetic processes occurring within. Second, the accuracy of the calculations can be acceptable only below a given value of the cut energy.Third, this accuracy remains almost unchangeable from a certain value of the cut. The study has also made it possible to explore the prevalence of certain interactions in the zone of spallation in the MEGAPIE target.展开更多
In order to understand the mechanism of the confinement bifurcation and H-mode power threshold in magnetically confined plasma,a new dynamical model of the L-H transition based on edge instability phase transition（E...In order to understand the mechanism of the confinement bifurcation and H-mode power threshold in magnetically confined plasma,a new dynamical model of the L-H transition based on edge instability phase transition（EIPT） has been developed.With the typical plasma parameters of the EAST tokamak,the self-consistent turbulence growth rate is analyzed using the simplest case of pressure-driven ballooning-type instability,which indicates that the L-H transition can be caused by the stabilization of the edge instability through EIPT.The weak E？×？B flow shear in L-mode is able to increase the ion inertia of the electrostatic motion by increasing the radial wave number of the tilted turbulence structures,which play an important role for accelerating the trigger process of EIPT rather than directly to suppress the turbulent transport.With the acceleration mechanism of E？×？B flow shear,fast L-H and H-L transitions are demonstrated under the control of the input heating power.Due to the simplified scrape-offlayer boundary condition applied,the ratio between the heating powers at the H-L and L-H transition respectively differs from the ratio by Nusselt number.The results of the modeling reveal a scaling of the power threshold of the L-H transition,P_（L-H）？∝？n^（0.76） B^（0.8） for deuterium plasma.It is found finite Larmor radius induces an isotope effect of the H-mode power threshold.展开更多
The rate equations,which is suitable to erbium-doped fiber lasers pumped at 980 nm and 1 480nm wavelengths respectively,are investigated,and analytical expressions of the threshold pump powers under two pump wavelengt...The rate equations,which is suitable to erbium-doped fiber lasers pumped at 980 nm and 1 480nm wavelengths respectively,are investigated,and analytical expressions of the threshold pump powers under two pump wavelengths are derived.As a result,some important parameters can be quantitatively specified.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
Based on the particle-in-cell technology and the secondary electron emission theory, a three-dimensional simulation method for multipactor is presented in this paper. By combining the finite difference time domain met...Based on the particle-in-cell technology and the secondary electron emission theory, a three-dimensional simulation method for multipactor is presented in this paper. By combining the finite difference time domain method and the panicle tracing method, such an algorithm is self-consistent and accurate since the interaction between electromagnetic fields and particles is properly modeled. In the time domain aspect, the generation of multipactor can be easily visualized, which makes it possible to gain a deeper insight into the physical mechanism of this effect. In addition to the classic secondary electron emission model, the measured practical secondary electron yield is used, which increases the accuracy of the algorithm. In order to validate the method, the impedance transformer and ridge waveguide filter are studied. By analyzing the evolution of the secondaries obtained by our method, multipactor thresholds of these components are estimated, which show good agreement with the experimental results. Furthermore, the most sensitive positions where multipactor occurs are determined from the phase focusing phenomenon, which is very meaningful for multipactor analysis and design.展开更多
A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the int...A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the internal quantum efficiency increased. For uncoated broad-area lasers, the threshold current density was as low as 144 A/cm2 （72 A/cm^2 per quantum well）, and the slope efficiency was 0.2 W/A. The internal loss was 11 cm^-1 and the internal quantum efficiency was 27.1%. The maximum output power of 357 mW under continuous-wave operation at room temperature was achieved. The electrical and optical properties of the laser diode were improved.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
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
It is demonstrated that inherent coating adhesion and damage threshold are correlated for Ta2O5 and HfO2 coatings widely used in optoelectronic devices. By utilizing a newly proposed 1-h boiling water test combined wi...It is demonstrated that inherent coating adhesion and damage threshold are correlated for Ta2O5 and HfO2 coatings widely used in optoelectronic devices. By utilizing a newly proposed 1-h boiling water test combined with the optical aging under high-power laser irradiation, we show that an optical coating that survives the 1-h boiling water test withstands the damage threshold, ensuring the field service life even in harsh environments. Besides the standard evaluation methods, which may have limitations for applications required in harsh environments, the 1-h boiling water test can serve as an alternative method of reliability assessment for optical coatings. A heuristics herein can be used as a gating item for qualification of optical coatings for various applications.展开更多
Low power supply operation with leakage power reduction is the prime concern in modern nano-scale CMOS memory devices. In the present scenario, low leakage memory architecture becomes more challenging, as it has 30% o...Low power supply operation with leakage power reduction is the prime concern in modern nano-scale CMOS memory devices. In the present scenario, low leakage memory architecture becomes more challenging, as it has 30% of the total chip power consumption. Since, the SRAM cell is low in density and most of memory processing data remain stable during the data holding operation, the stored memory data are more affected by the leakage phenomena in the circuit while the device parameters are scaled down. In this survey, origins of leakage currents in a short-channel device and various leakage control techniques for ultra-low power SRAM design are discussed. A classification of these approaches made based on their key design and functions, such as biasing technique, power gating and multi-threshold techniques. Based on our survey, we summarize the merits and demerits and challenges of these techniques. This comprehensive study will be helpful to extend the further research for future implementations.展开更多
CMOS devices play a major role in most of the digital design, since CMOS devices have larger density and consume less power. The integrated circuit performance mostly depends on the basic devices and its scaling metho...CMOS devices play a major role in most of the digital design, since CMOS devices have larger density and consume less power. The integrated circuit performance mostly depends on the basic devices and its scaling methods, but in conventional CMOS devices in ultra deep submicron technology, leakage power becomes the major portion apart of dynamic power. The demerits of the conventional CMOS is less speed and, more leakage, for any digital design PDP is the figure of merit which can be used to determine energy consumed per switching event, hence we designed a NOVEL NMOS and PMOS which has superior performance than conventional PMOS and NMOS, the design and performance checked at 90 nm, 180 nm and 45 nm technology and calculate the performance values.展开更多
文摘Ultrasound is used in various chemical reaction processes, and these reactions are influenced by ultrasonic frequency. A threshold power is required for the ultrasonic degradation reaction and oxidation reaction caused by hydroxyl radicals, and the cavitation threshold power is also influenced by frequency generally. In this study, the effects of frequency on the threshold power of methylene blue degradation and KI oxidation were investigated in the range between 22.8 kHz and 1640 kHz. The threshold power of KI oxidation reaction increased with increasing frequency. This phenomenon well agrees with previous study, and it is revealed that the generation of I-3?ion is caused by oxidation reaction of Iˉ ions with hydroxyl radicals. On the other hand, the threshold power of methylene blue degradation reaction was not affected by frequency. The ultrasonic degradation of methylene blue is considered to be caused by hydroxyl radicals, and there is a linear relationship between degradation rate constant and sonochemical efficiency value. However, it is guessed that the degradation of methylene blue is occurred inside cavitation bubble by pyrolysis at high frequency regions.
文摘The calculation time in the Monte Carlo simulations consistently represents an essential issue. It is often very long, and its decrease constitutes a challenge for the simulator. Generally, an MC simulation is qualified as quality or not according to two main criteria: the calculation time and the accuracy of the results. However, in most cases, the optimization of one criterion affects negatively the other. Therefore, a compromise between both of them is always required in this kind of simulation. The present work aims at studying the impact of the production threshold(or cut) of the GEANT4 toolkit on the calculation of the power deposition in the MEGAPIE spallation target.The production threshold of secondaries is a GEANT4 intrinsic parameter. It indicates the limit of energy we can reach in the production of secondary particles. This study has allowed us to make the following conclusions. First,the influence of the cut on the calculation of the deposited power depends on the volume size, its arrangement and the importance of the electromagnetic processes occurring within. Second, the accuracy of the calculations can be acceptable only below a given value of the cut energy.Third, this accuracy remains almost unchangeable from a certain value of the cut. The study has also made it possible to explore the prevalence of certain interactions in the zone of spallation in the MEGAPIE target.
基金supported by National Natural Science Foundation of China under Contract Nos.11575235 and 11422546China Postdoctoral Science Foundation under Contract No.2016M602043+2 种基金the National Magnetic Confinement Fusion Science Program of China under Contract No.2015GB101002Key Research Program of Frontier Sciences,CAS,Grant No.QYZDB-SSW-SLH001K C Wong Education Foundation
文摘In order to understand the mechanism of the confinement bifurcation and H-mode power threshold in magnetically confined plasma,a new dynamical model of the L-H transition based on edge instability phase transition（EIPT） has been developed.With the typical plasma parameters of the EAST tokamak,the self-consistent turbulence growth rate is analyzed using the simplest case of pressure-driven ballooning-type instability,which indicates that the L-H transition can be caused by the stabilization of the edge instability through EIPT.The weak E？×？B flow shear in L-mode is able to increase the ion inertia of the electrostatic motion by increasing the radial wave number of the tilted turbulence structures,which play an important role for accelerating the trigger process of EIPT rather than directly to suppress the turbulent transport.With the acceleration mechanism of E？×？B flow shear,fast L-H and H-L transitions are demonstrated under the control of the input heating power.Due to the simplified scrape-offlayer boundary condition applied,the ratio between the heating powers at the H-L and L-H transition respectively differs from the ratio by Nusselt number.The results of the modeling reveal a scaling of the power threshold of the L-H transition,P_（L-H）？∝？n^（0.76） B^（0.8） for deuterium plasma.It is found finite Larmor radius induces an isotope effect of the H-mode power threshold.
文摘The rate equations,which is suitable to erbium-doped fiber lasers pumped at 980 nm and 1 480nm wavelengths respectively,are investigated,and analytical expressions of the threshold pump powers under two pump wavelengths are derived.As a result,some important parameters can be quantitatively specified.
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℃.
基金Project supported by the National Key Laboratory Foundation,China(Grant No.9140C530103110C5301)
文摘Based on the particle-in-cell technology and the secondary electron emission theory, a three-dimensional simulation method for multipactor is presented in this paper. By combining the finite difference time domain method and the panicle tracing method, such an algorithm is self-consistent and accurate since the interaction between electromagnetic fields and particles is properly modeled. In the time domain aspect, the generation of multipactor can be easily visualized, which makes it possible to gain a deeper insight into the physical mechanism of this effect. In addition to the classic secondary electron emission model, the measured practical secondary electron yield is used, which increases the accuracy of the algorithm. In order to validate the method, the impedance transformer and ridge waveguide filter are studied. By analyzing the evolution of the secondaries obtained by our method, multipactor thresholds of these components are estimated, which show good agreement with the experimental results. Furthermore, the most sensitive positions where multipactor occurs are determined from the phase focusing phenomenon, which is very meaningful for multipactor analysis and design.
基金supported by the Beijing Natural Science Foundation, China (Grant No. 4112058)
文摘A high power GaSb-based laser diode with lasing wavelength at 2 μm was fabricated and optimized. With the optimized epitaxial laser structure, the internal loss and the threshold current density decreased and the internal quantum efficiency increased. For uncoated broad-area lasers, the threshold current density was as low as 144 A/cm2 （72 A/cm^2 per quantum well）, and the slope efficiency was 0.2 W/A. The internal loss was 11 cm^-1 and the internal quantum efficiency was 27.1%. The maximum output power of 357 mW under continuous-wave operation at room temperature was achieved. The electrical and optical properties of the laser diode were improved.
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.
文摘It is demonstrated that inherent coating adhesion and damage threshold are correlated for Ta2O5 and HfO2 coatings widely used in optoelectronic devices. By utilizing a newly proposed 1-h boiling water test combined with the optical aging under high-power laser irradiation, we show that an optical coating that survives the 1-h boiling water test withstands the damage threshold, ensuring the field service life even in harsh environments. Besides the standard evaluation methods, which may have limitations for applications required in harsh environments, the 1-h boiling water test can serve as an alternative method of reliability assessment for optical coatings. A heuristics herein can be used as a gating item for qualification of optical coatings for various applications.
文摘Low power supply operation with leakage power reduction is the prime concern in modern nano-scale CMOS memory devices. In the present scenario, low leakage memory architecture becomes more challenging, as it has 30% of the total chip power consumption. Since, the SRAM cell is low in density and most of memory processing data remain stable during the data holding operation, the stored memory data are more affected by the leakage phenomena in the circuit while the device parameters are scaled down. In this survey, origins of leakage currents in a short-channel device and various leakage control techniques for ultra-low power SRAM design are discussed. A classification of these approaches made based on their key design and functions, such as biasing technique, power gating and multi-threshold techniques. Based on our survey, we summarize the merits and demerits and challenges of these techniques. This comprehensive study will be helpful to extend the further research for future implementations.
文摘CMOS devices play a major role in most of the digital design, since CMOS devices have larger density and consume less power. The integrated circuit performance mostly depends on the basic devices and its scaling methods, but in conventional CMOS devices in ultra deep submicron technology, leakage power becomes the major portion apart of dynamic power. The demerits of the conventional CMOS is less speed and, more leakage, for any digital design PDP is the figure of merit which can be used to determine energy consumed per switching event, hence we designed a NOVEL NMOS and PMOS which has superior performance than conventional PMOS and NMOS, the design and performance checked at 90 nm, 180 nm and 45 nm technology and calculate the performance values.
