The time-interleaved analog-to-digital conversion(TIADC)technique is an effective method for increasing the sampling rate in a waveform digitization system.In this study,a 20-Gsps TIADC system was designed.A wide-band...The time-interleaved analog-to-digital conversion(TIADC)technique is an effective method for increasing the sampling rate in a waveform digitization system.In this study,a 20-Gsps TIADC system was designed.A wide-bandwidth performance was achieved by optimizing the analog circuits,and a sufficient effective number of bits(ENOB)performance guaranteed using the perfect reconstruction algorithm for mismatch error correction.The proposed system was verified by tests,and the results indicated that a-3 dB bandwidth of 6 GHz and the ENOB performance of 8.7 bits at 1 GHz and 7.6 bits at6 GHz were successfully achieved.展开更多
An all-optical analog-to-digital converter (ADC) based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integra...An all-optical analog-to-digital converter (ADC) based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift (SSFS) module within a wavelength range of 1550 nm-1580 nm. A dispersion coefficient as high as -19800 ps/(km.nm) with +0.5 ps/(km.nm) variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate (MSSR) is 50.45 GSa/s with full width at half maximum (FWHM) variation less than 2.52 ps, along with the 2-bit effective- number-of-bit and Gray code output.展开更多
Proposed is an interference type of optical analog-to-digital conversion(ADC). The refractive index of Fabry-Perot cavity changes with different voltages. The Fabry-Perot resonator converts electronic intensity into l...Proposed is an interference type of optical analog-to-digital conversion(ADC). The refractive index of Fabry-Perot cavity changes with different voltages. The Fabry-Perot resonator converts electronic intensity into light wavelength through selecting lights of different wavelengthes. The parameters of the scheme are acquired with the transmission matrix of optical element and the time of steady-state light field. The maximum sampling speedes of 4-bit, 6-bit, 7-bit, 8-bit and 9-bit(ADC) are 1.695×1010 count/s, 4.33×109 count/s, 2.38×109 count/s, 1.24×109 count/s and 5.9×108 count/s, respectively.展开更多
The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-...The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-band is realized by combining with the local oscillator and the power control circuit to complete functions such as amplification, filtering and gain. In order to achieve the performance optimization and a high level of integration of the Ku-band monolithic microwave integrated circuits(MMIC) operating chip, the 3 D vertical interconnection micro-assembly technology is used. By stacking solder balls on the printed circuit board(PCB), the technology decreases the volume of the original transceiver to a miniaturized module. The module has a good electromagnetic compatibility through special structure designs. This module has the characteristics of miniaturization, low power consumption and high density, which is suitable for popularization in practical application.展开更多
Objective:Glioblastoma(GBM)is the most prevalent and aggressive adult primary cancer in the central nervous system.Therapeutic approaches for GBM treatment are under intense investigation,including the use of emerging...Objective:Glioblastoma(GBM)is the most prevalent and aggressive adult primary cancer in the central nervous system.Therapeutic approaches for GBM treatment are under intense investigation,including the use of emerging immunotherapies.Here,we propose an alternative approach to treat GBM through reprogramming proliferative GBM cells into non-proliferative neurons.Methods:Retroviruses were used to target highly proliferative human GBM cells through overexpression of neural transcription factors.Immunostaining,electrophysiological recording,and bulk RNA-seq were performed to investigate the mechanisms underlying the neuronal conversion of human GBM cells.An in vivo intracranial xenograft mouse model was used to examine the neuronal conversion of human GBM cells.Results:We report efficient neuronal conversion from human GBM cells by overexpressing single neural transcription factor Neurogenic differentiation 1(Neuro D1),Neurogenin-2(Neurog2),or Achaete-scute homolog 1(Ascl1).Subtype characterization showed that the majority of Neurog2-and Neuro D1-converted neurons were glutamatergic,while Ascl1 favored GABAergic neuron generation.The GBM cell-converted neurons not only showed pan-neuronal markers but also exhibited neuron-specific electrophysiological activities.Transcriptome analyses revealed that neuronal genes were activated in glioma cells after overexpression of neural transcription factors,and different signaling pathways were activated by different neural transcription factors.Importantly,the neuronal conversion of GBM cells was accompanied by significant inhibition of GBM cell proliferation in both in vitro and in vivo models.Conclusions:These results suggest that GBM cells can be reprogrammed into different subtypes of neurons,leading to a potential alternative approach to treat brain tumors using in vivo cell conversion technology.展开更多
A new method creating depth information for 2D/3D conversion was proposed. The distance between objects is determined by the distances between objects and light source position which is estimated by the analysis of th...A new method creating depth information for 2D/3D conversion was proposed. The distance between objects is determined by the distances between objects and light source position which is estimated by the analysis of the image. The estimated lighting value is used to normalize the image. A threshold value is determined by some weighted operation between the original image and the normalized image. By applying the threshold value to the original image, background area is removed. Depth information of interested area is calculated from the lighting changes. The final 3D images converted with the proposed method are used to verify its effectiveness.展开更多
Nonlayered two-dimensional(2D)materials have attracted increasing attention,due to novel physical properties,unique surface structure,and high compatibility with microfabrication technique.However,owing to the inheren...Nonlayered two-dimensional(2D)materials have attracted increasing attention,due to novel physical properties,unique surface structure,and high compatibility with microfabrication technique.However,owing to the inherent strong covalent bonds,the direct synthesis of 2D planar structure from nonlayered materials,especially for the realization of large-size ultrathin 2D nonlayered materials,is still a huge challenge.Here,a general atomic substitution conversion strategy is proposed to synthesize large-size,ultrathin nonlayered 2D materials.Taking nonlayered CdS as a typical example,large-size ultrathin nonlayered CdS single-crystalline flakes are successfully achieved via a facile low-temperature chemical sulfurization method,where pre-grown layered CdI2 flakes are employed as the precursor via a simple hot plate assisted vertical vapor deposition method.The size and thickness of CdS flakes can be controlled by the CdI2 precursor.The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS,which has been evidenced by experiments and theoretical calculations.The atomic substitution conversion strategy demonstrates that the existing 2D layered materials can serve as the precursor for difficult-to-synthesize nonlayered 2D materials,providing a bridge between layered and nonlayered materials,meanwhile realizing the fabrication of large-size ultrathin nonlayered 2D materials.展开更多
A digital background calibration technique that corrects the capacitor mismatches error is proposed for successive approximation register analog-to-digital converter (SAR ADC). The technique is implemented in SAR ADC ...A digital background calibration technique that corrects the capacitor mismatches error is proposed for successive approximation register analog-to-digital converter (SAR ADC). The technique is implemented in SAR ADC which is based on tri-level switching. The termination capacitor in the Digital-to-Analog Converter (DAC) is regarded as a reference capacitor and the digital weights of all other unit capacitors are corrected with respect to the reference capacitor. To make a comparison between the size of the unit capacitor and that of the reference capacitor, each input sample is quantized twice. The unit capacitor being calibrated is swapped with the reference capacitor during the second conversion. The difference between the two conversion results is used to correct the digital weight of the unit capacitor under calibration. The calibration technique with two reference capacitors is presented to reduce the number of parameters to be estimated. Behavior simulation is performed to verify the proposed calibration technique by using a 12-bit SAR ADC with 3% random capacitor mismatch. The simulation results show that the Signal-to-Noise and Distortion Ratio (SNDR) is improved from 57.2 dB to 72.2 dB and the Spurious Free Dynamic Range (SFDR) is improved from 60.0 dB to 85.4 dB.展开更多
A method for precise conversion between virtual world and real world is put forward in this paper. The method aims to precisely establish the connection between the virtual coordinates and the real coordinates with Op...A method for precise conversion between virtual world and real world is put forward in this paper. The method aims to precisely establish the connection between the virtual coordinates and the real coordinates with OpenGL. In the virtual world, two virtual cameras are set to capture the left and right perspective planar images, and coordinates of the planar images can be calculated by the perspective projection model. With coordinates of planar images, coordinates of the stereo- scopic image synthesized in the real world can be calculated by the binocular observation model. Therefore, the corresponding connection between the two systems is established. Experimental re- suits match data from this method well. Therefore, this method can precisely realize the conversion and the interactivity, laying a solid foundation for further study.展开更多
The speed and cost of A/D conversion are conflict to each other. As micro-controller speed is increasing and its internal function is improving, full utilization of its internal resource can dramatically increase ...The speed and cost of A/D conversion are conflict to each other. As micro-controller speed is increasing and its internal function is improving, full utilization of its internal resource can dramatically increase A/D conversion speed and without compromising conversion quality. MSP430F11x1 series micro-controller is exploited to increase A/D conversion speed.展开更多
This article proposes a general framework for the conversion of U-238 and Th-232 utilizing fusion-produced neutrons. This recognizes that emerging fusion technologies may not produce sufficient net energy output to ju...This article proposes a general framework for the conversion of U-238 and Th-232 utilizing fusion-produced neutrons. This recognizes that emerging fusion technologies may not produce sufficient net energy output to justify stand-alone applications, yet may be commercially viable for breeder transmutation or hybrid fusion-fission reactor concepts proposed herein to dispose of nuclear wastes and long life high radioactive fission products remaining in shutdown nuclear power plants. Results show that this could be achievable within a decade, given an appropriate fusion source. However, if 20% beryllium of nuclei density is added to the convertor blanket, the efficiency of the conversion process can be significantly increased. Also, the neutron energy spectrum resulting from dense D-D plasma core fusion is much softer than D-T fusion neutron source, hence the probability of (n, p) (n, α) backward decay reaction paths will be smaller and the conversion efficiency will be elevated.展开更多
It is of practical significance for the decision-making on country food security and farmland protection to analyze the conversion margins for the major uses of agricultural land and their variations. Based on the pan...It is of practical significance for the decision-making on country food security and farmland protection to analyze the conversion margins for the major uses of agricultural land and their variations. Based on the panel data of wheat, corn, vegetable, fruit, and forests productions from 520 investigated farmer households of 13 investigated villages in Shandong Province from 2003 to 2009, and using Cobb-Douglas production function, the revenue conversion margins can be obtained separately, between different grain-crops (wheat, corn) and different non-grain crops (vegetable, fruit, forests), and the conversion relationship between growing grain( wheat, corn) and going out for non-farm work. The results show that from 2003 to 2009, growing wheat and corn are more economically and reasonably for farmers, compared with growing vegetable, but growing wheat and corn are becoming less economically and less reasonably day by day, compared with planting forests. Moreover, the conversion margin between wheat and fruit shows obvious scissors difference. Just from 2007, farmers' growing fruit became economically and reasonably, but until 2009, compared with going out to work after abandoning farm8land, growing wheat had no economic rationality. From 2003 to 2009, farmers' growing corn is more profitable than growing fruit and going out for non-farm work after abandoning farmland. The subsidies for wheat and corn have increased farmers' comparative income from food production remarkably, but the subsidies cannot change the general tendency that farmers transform food (wheat, corn) production into non-food (especially forests) production. The revenue difference between growing wheat, corn and vegetable and growing fruit and forests is being pulled ceaselessly bigger, and the tendency that farmers transform wheat, corn and vegetable growing lands into fruit and forests growing lands has become increasingly apparent.展开更多
MoS_(2) is a highly promising material for application in lithium-ion battery anodes due to its high theoretical capacity and low cost.However,problems with a fast capacity decay over cycling,especially at the first c...MoS_(2) is a highly promising material for application in lithium-ion battery anodes due to its high theoretical capacity and low cost.However,problems with a fast capacity decay over cycling,especially at the first cycles,and poor rate performance have deterred its practical implementation.Herein,electrodes comprised solely of few-layers 2D MoS_(2) nanosheets have been manufactured by scalable liquid-phase exfoliation and spray deposition methods.The long-standing controversy questioning the reversibility of conversion processes of MoS_(2)-based electrodes was addressed.Raman studies revealed that,in 2D MoS_(2) electrodes,conversion processes are indeed reversible,where nanostructure played a key role.Cycling of the electrodes at high current rates revealed an intriguing phenomenon consisting of a continuously increasing capacity after ca.100-200 cycles.This phenomenon was comprehensively addressed by a variety of electrochemical and microscopy methods that revealed underlying physical activation mechanisms that involved a range of profound electrode structural changes.Activation mechanisms delivered a capacitive electrode of a superior rate performance and cycling stability,as compared to the corresponding pristine electrodes,and to MoS_(2) electrodes previously reported.Herein,we have devised a methodology to overcome the problem of cycling stability of 2D MoS_(2) electrodes.Moreover,activation of electrodes constitutes a methodology that could be applied to enhance the energy storage performance of electrodes based on other 2D nanomaterials,or combinations thereof,strategically combining chemistries to engineer electrodes of superior energy storage properties.展开更多
The synthesis of high value-added chemical products using CO_(2)and CH_(4)is a promising CO_(2)conversion technology that can reduce greenhouse gas emissions while also alleviating the energy crisis.However,problems s...The synthesis of high value-added chemical products using CO_(2)and CH_(4)is a promising CO_(2)conversion technology that can reduce greenhouse gas emissions while also alleviating the energy crisis.However,problems such as high energy consumption and strict reaction conditions in reforming process hinder the further development of the technology.In this work,carbon-nitrogen based composites were prepared for the first time according to the design principle from morphology to heterojunction,which is innovatively applied in the process of photocatalytic CH4reforming.Firstly,C_(3)N_(4)materials with different dimensions(D) are prepared and applied to a CO_(2)-CH_(4)photocatalytic system.Additionally,the 2D/2D TiO_(2)/g-C_(3)N_(4)heterostructure is constructed with the ultrasonic impregnation method to further improve charge generation,transfer,and separation efficiency.It is worth noting that the yield of CO reaches173.80 μmol g^(-1),and the catalytic performance is improved by 1546% compared to bulk C_(3)N_(4).Moreover,the physical and chemical properties of 2D/2D TiO_(2)/g-C_(3)N_(4)materials are studied using a variety of cha racterization methods.Furthermore,the work fu nction and adsorption energy of different C3N4/TiO_(2)models for CO_(2)adsorption are calculated by density functional theory(DFT).Then,a possible catalytic mechanism for photocatalytic CO_(2)and CH_(4) conversion is proposed based on DFT calculations and experimental results.This work provides a new technical route for the rapid conversion of CO_(2)and CH_(4) at room temperature,as well as a new research concept for achieving carbon neutrality.展开更多
基金supported in part by the National Natural Science Foundation of China(No.11675173)the Youth Innovation Promotion Association CASthe CAS Center for Excellence in Particle Physics(CCEPP)。
文摘The time-interleaved analog-to-digital conversion(TIADC)technique is an effective method for increasing the sampling rate in a waveform digitization system.In this study,a 20-Gsps TIADC system was designed.A wide-bandwidth performance was achieved by optimizing the analog circuits,and a sufficient effective number of bits(ENOB)performance guaranteed using the perfect reconstruction algorithm for mismatch error correction.The proposed system was verified by tests,and the results indicated that a-3 dB bandwidth of 6 GHz and the ENOB performance of 8.7 bits at 1 GHz and 7.6 bits at6 GHz were successfully achieved.
基金supported by the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-030A1)China Postdoctoral Science Foundation(Grant No.2015M580978)
文摘An all-optical analog-to-digital converter (ADC) based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift (SSFS) module within a wavelength range of 1550 nm-1580 nm. A dispersion coefficient as high as -19800 ps/(km.nm) with +0.5 ps/(km.nm) variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate (MSSR) is 50.45 GSa/s with full width at half maximum (FWHM) variation less than 2.52 ps, along with the 2-bit effective- number-of-bit and Gray code output.
基金Natural Science Foundation from Colleges and Universities of Jiangsu Provine(06KJD510034)
文摘Proposed is an interference type of optical analog-to-digital conversion(ADC). The refractive index of Fabry-Perot cavity changes with different voltages. The Fabry-Perot resonator converts electronic intensity into light wavelength through selecting lights of different wavelengthes. The parameters of the scheme are acquired with the transmission matrix of optical element and the time of steady-state light field. The maximum sampling speedes of 4-bit, 6-bit, 7-bit, 8-bit and 9-bit(ADC) are 1.695×1010 count/s, 4.33×109 count/s, 2.38×109 count/s, 1.24×109 count/s and 5.9×108 count/s, respectively.
文摘The idea of Ku-band transceiver frequency conversion module design based on 3D micropackaging technology is proposed. By using the double frequency conversion technology,the dual transceiver circuit from Ku-band to L-band is realized by combining with the local oscillator and the power control circuit to complete functions such as amplification, filtering and gain. In order to achieve the performance optimization and a high level of integration of the Ku-band monolithic microwave integrated circuits(MMIC) operating chip, the 3 D vertical interconnection micro-assembly technology is used. By stacking solder balls on the printed circuit board(PCB), the technology decreases the volume of the original transceiver to a miniaturized module. The module has a good electromagnetic compatibility through special structure designs. This module has the characteristics of miniaturization, low power consumption and high density, which is suitable for popularization in practical application.
基金supported by the Charles H.“Skip”Smith Endowment Fund and the Verne M.Willaman Endowment Fund from the Pennsylvania State University to G.C。
文摘Objective:Glioblastoma(GBM)is the most prevalent and aggressive adult primary cancer in the central nervous system.Therapeutic approaches for GBM treatment are under intense investigation,including the use of emerging immunotherapies.Here,we propose an alternative approach to treat GBM through reprogramming proliferative GBM cells into non-proliferative neurons.Methods:Retroviruses were used to target highly proliferative human GBM cells through overexpression of neural transcription factors.Immunostaining,electrophysiological recording,and bulk RNA-seq were performed to investigate the mechanisms underlying the neuronal conversion of human GBM cells.An in vivo intracranial xenograft mouse model was used to examine the neuronal conversion of human GBM cells.Results:We report efficient neuronal conversion from human GBM cells by overexpressing single neural transcription factor Neurogenic differentiation 1(Neuro D1),Neurogenin-2(Neurog2),or Achaete-scute homolog 1(Ascl1).Subtype characterization showed that the majority of Neurog2-and Neuro D1-converted neurons were glutamatergic,while Ascl1 favored GABAergic neuron generation.The GBM cell-converted neurons not only showed pan-neuronal markers but also exhibited neuron-specific electrophysiological activities.Transcriptome analyses revealed that neuronal genes were activated in glioma cells after overexpression of neural transcription factors,and different signaling pathways were activated by different neural transcription factors.Importantly,the neuronal conversion of GBM cells was accompanied by significant inhibition of GBM cell proliferation in both in vitro and in vivo models.Conclusions:These results suggest that GBM cells can be reprogrammed into different subtypes of neurons,leading to a potential alternative approach to treat brain tumors using in vivo cell conversion technology.
文摘A new method creating depth information for 2D/3D conversion was proposed. The distance between objects is determined by the distances between objects and light source position which is estimated by the analysis of the image. The estimated lighting value is used to normalize the image. A threshold value is determined by some weighted operation between the original image and the normalized image. By applying the threshold value to the original image, background area is removed. Depth information of interested area is calculated from the lighting changes. The final 3D images converted with the proposed method are used to verify its effectiveness.
基金This work was supported by National Natural Science Foundation of China(21825103,11774044,52072059)the Hubei Provincial Natural Science Foundation of China(2019CFA002)+1 种基金the Fundamental Research Funds for the Central Universities(2019kfyXMBZ018 and 2020kfyXJJS050)We also thank the technical support from Analytical and Testing Center in Huazhong University of Science and Technology.
文摘Nonlayered two-dimensional(2D)materials have attracted increasing attention,due to novel physical properties,unique surface structure,and high compatibility with microfabrication technique.However,owing to the inherent strong covalent bonds,the direct synthesis of 2D planar structure from nonlayered materials,especially for the realization of large-size ultrathin 2D nonlayered materials,is still a huge challenge.Here,a general atomic substitution conversion strategy is proposed to synthesize large-size,ultrathin nonlayered 2D materials.Taking nonlayered CdS as a typical example,large-size ultrathin nonlayered CdS single-crystalline flakes are successfully achieved via a facile low-temperature chemical sulfurization method,where pre-grown layered CdI2 flakes are employed as the precursor via a simple hot plate assisted vertical vapor deposition method.The size and thickness of CdS flakes can be controlled by the CdI2 precursor.The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS,which has been evidenced by experiments and theoretical calculations.The atomic substitution conversion strategy demonstrates that the existing 2D layered materials can serve as the precursor for difficult-to-synthesize nonlayered 2D materials,providing a bridge between layered and nonlayered materials,meanwhile realizing the fabrication of large-size ultrathin nonlayered 2D materials.
文摘A digital background calibration technique that corrects the capacitor mismatches error is proposed for successive approximation register analog-to-digital converter (SAR ADC). The technique is implemented in SAR ADC which is based on tri-level switching. The termination capacitor in the Digital-to-Analog Converter (DAC) is regarded as a reference capacitor and the digital weights of all other unit capacitors are corrected with respect to the reference capacitor. To make a comparison between the size of the unit capacitor and that of the reference capacitor, each input sample is quantized twice. The unit capacitor being calibrated is swapped with the reference capacitor during the second conversion. The difference between the two conversion results is used to correct the digital weight of the unit capacitor under calibration. The calibration technique with two reference capacitors is presented to reduce the number of parameters to be estimated. Behavior simulation is performed to verify the proposed calibration technique by using a 12-bit SAR ADC with 3% random capacitor mismatch. The simulation results show that the Signal-to-Noise and Distortion Ratio (SNDR) is improved from 57.2 dB to 72.2 dB and the Spurious Free Dynamic Range (SFDR) is improved from 60.0 dB to 85.4 dB.
基金Supported by the National Natural Science Foundation of China ( 60674052)
文摘A method for precise conversion between virtual world and real world is put forward in this paper. The method aims to precisely establish the connection between the virtual coordinates and the real coordinates with OpenGL. In the virtual world, two virtual cameras are set to capture the left and right perspective planar images, and coordinates of the planar images can be calculated by the perspective projection model. With coordinates of planar images, coordinates of the stereo- scopic image synthesized in the real world can be calculated by the binocular observation model. Therefore, the corresponding connection between the two systems is established. Experimental re- suits match data from this method well. Therefore, this method can precisely realize the conversion and the interactivity, laying a solid foundation for further study.
文摘The speed and cost of A/D conversion are conflict to each other. As micro-controller speed is increasing and its internal function is improving, full utilization of its internal resource can dramatically increase A/D conversion speed and without compromising conversion quality. MSP430F11x1 series micro-controller is exploited to increase A/D conversion speed.
文摘This article proposes a general framework for the conversion of U-238 and Th-232 utilizing fusion-produced neutrons. This recognizes that emerging fusion technologies may not produce sufficient net energy output to justify stand-alone applications, yet may be commercially viable for breeder transmutation or hybrid fusion-fission reactor concepts proposed herein to dispose of nuclear wastes and long life high radioactive fission products remaining in shutdown nuclear power plants. Results show that this could be achievable within a decade, given an appropriate fusion source. However, if 20% beryllium of nuclei density is added to the convertor blanket, the efficiency of the conversion process can be significantly increased. Also, the neutron energy spectrum resulting from dense D-D plasma core fusion is much softer than D-T fusion neutron source, hence the probability of (n, p) (n, α) backward decay reaction paths will be smaller and the conversion efficiency will be elevated.
基金The Important Project of Knowledge Innovation Engineering of Chinese Academy of Sciences:the Pilot Project of Farmland-conservation and Modern Sustainable High Efficiency Agriculturethe Second Subject:the Regulation Mechanism for Requisition-compensation Balance of Cultivated Land and the Pilot Study on Productive Farmland Conservation in Yucheng,Shandong Provincethe Seventh Special Topic:the Strategic Research on Farmland-conservation and Agriculture Sustainable Development in Shandong Province
文摘It is of practical significance for the decision-making on country food security and farmland protection to analyze the conversion margins for the major uses of agricultural land and their variations. Based on the panel data of wheat, corn, vegetable, fruit, and forests productions from 520 investigated farmer households of 13 investigated villages in Shandong Province from 2003 to 2009, and using Cobb-Douglas production function, the revenue conversion margins can be obtained separately, between different grain-crops (wheat, corn) and different non-grain crops (vegetable, fruit, forests), and the conversion relationship between growing grain( wheat, corn) and going out for non-farm work. The results show that from 2003 to 2009, growing wheat and corn are more economically and reasonably for farmers, compared with growing vegetable, but growing wheat and corn are becoming less economically and less reasonably day by day, compared with planting forests. Moreover, the conversion margin between wheat and fruit shows obvious scissors difference. Just from 2007, farmers' growing fruit became economically and reasonably, but until 2009, compared with going out to work after abandoning farm8land, growing wheat had no economic rationality. From 2003 to 2009, farmers' growing corn is more profitable than growing fruit and going out for non-farm work after abandoning farmland. The subsidies for wheat and corn have increased farmers' comparative income from food production remarkably, but the subsidies cannot change the general tendency that farmers transform food (wheat, corn) production into non-food (especially forests) production. The revenue difference between growing wheat, corn and vegetable and growing fruit and forests is being pulled ceaselessly bigger, and the tendency that farmers transform wheat, corn and vegetable growing lands into fruit and forests growing lands has become increasingly apparent.
基金financial support from the China Scholarship Council(CSC grant.201808330389)。
文摘MoS_(2) is a highly promising material for application in lithium-ion battery anodes due to its high theoretical capacity and low cost.However,problems with a fast capacity decay over cycling,especially at the first cycles,and poor rate performance have deterred its practical implementation.Herein,electrodes comprised solely of few-layers 2D MoS_(2) nanosheets have been manufactured by scalable liquid-phase exfoliation and spray deposition methods.The long-standing controversy questioning the reversibility of conversion processes of MoS_(2)-based electrodes was addressed.Raman studies revealed that,in 2D MoS_(2) electrodes,conversion processes are indeed reversible,where nanostructure played a key role.Cycling of the electrodes at high current rates revealed an intriguing phenomenon consisting of a continuously increasing capacity after ca.100-200 cycles.This phenomenon was comprehensively addressed by a variety of electrochemical and microscopy methods that revealed underlying physical activation mechanisms that involved a range of profound electrode structural changes.Activation mechanisms delivered a capacitive electrode of a superior rate performance and cycling stability,as compared to the corresponding pristine electrodes,and to MoS_(2) electrodes previously reported.Herein,we have devised a methodology to overcome the problem of cycling stability of 2D MoS_(2) electrodes.Moreover,activation of electrodes constitutes a methodology that could be applied to enhance the energy storage performance of electrodes based on other 2D nanomaterials,or combinations thereof,strategically combining chemistries to engineer electrodes of superior energy storage properties.
基金The financial support from the National Natural Science Foundation of China (22178089)the Hunan Provincial Innovation Foundation for Postgraduate (CX20220392)。
文摘The synthesis of high value-added chemical products using CO_(2)and CH_(4)is a promising CO_(2)conversion technology that can reduce greenhouse gas emissions while also alleviating the energy crisis.However,problems such as high energy consumption and strict reaction conditions in reforming process hinder the further development of the technology.In this work,carbon-nitrogen based composites were prepared for the first time according to the design principle from morphology to heterojunction,which is innovatively applied in the process of photocatalytic CH4reforming.Firstly,C_(3)N_(4)materials with different dimensions(D) are prepared and applied to a CO_(2)-CH_(4)photocatalytic system.Additionally,the 2D/2D TiO_(2)/g-C_(3)N_(4)heterostructure is constructed with the ultrasonic impregnation method to further improve charge generation,transfer,and separation efficiency.It is worth noting that the yield of CO reaches173.80 μmol g^(-1),and the catalytic performance is improved by 1546% compared to bulk C_(3)N_(4).Moreover,the physical and chemical properties of 2D/2D TiO_(2)/g-C_(3)N_(4)materials are studied using a variety of cha racterization methods.Furthermore,the work fu nction and adsorption energy of different C3N4/TiO_(2)models for CO_(2)adsorption are calculated by density functional theory(DFT).Then,a possible catalytic mechanism for photocatalytic CO_(2)and CH_(4) conversion is proposed based on DFT calculations and experimental results.This work provides a new technical route for the rapid conversion of CO_(2)and CH_(4) at room temperature,as well as a new research concept for achieving carbon neutrality.