The Solar Upper Transition Region Imager(SUTRI)onboard the Space Advanced Technology demonstration satellite(SATech-01),which was launched to a Sun-synchronous orbit at a height of~500 km in 2022 July,aims to test the...The Solar Upper Transition Region Imager(SUTRI)onboard the Space Advanced Technology demonstration satellite(SATech-01),which was launched to a Sun-synchronous orbit at a height of~500 km in 2022 July,aims to test the on-orbit performance of our newly developed Sc/Si multi-layer reflecting mirror and the 2k×2k EUV CMOS imaging camera and to take full-disk solar images at the Ne VII 46.5 nm spectral line with a filter width of~3 nm.SUTRI employs a Ritchey-Chrétien optical system with an aperture of 18 cm.The on-orbit observations show that SUTRI images have a field of view of~416×416 and a moderate spatial resolution of~8″without an image stabilization system.The normal cadence of SUTRI images is 30 s and the solar observation time is about16 hr each day because the earth eclipse time accounts for about 1/3 of SATech-01's orbit period.Approximately15 GB data is acquired each day and made available online after processing.SUTRI images are valuable as the Ne VII 46.5 nm line is formed at a temperature regime of~0.5 MK in the solar atmosphere,which has rarely been sampled by existing solar imagers.SUTRI observations will establish connections between structures in the lower solar atmosphere and corona,and advance our understanding of various types of solar activity such as flares,filament eruptions,coronal jets and coronal mass ejections.展开更多
Geological hazard is an adverse geological condition that can cause loss of life and property.Accurate prediction and analysis of geological hazards is an important and challenging task.In the past decade,there has be...Geological hazard is an adverse geological condition that can cause loss of life and property.Accurate prediction and analysis of geological hazards is an important and challenging task.In the past decade,there has been a great expansion of geohazard detection data and advancement in data-driven simulation techniques.In particular,great efforts have been made in applying deep learning to predict geohazards.To understand the recent progress in this field,this paper provides an overview of the commonly used data sources and deep neural networks in the prediction of a variety of geological hazards.展开更多
Trusted Execution Environment(TEE)is an important part of the security architecture of modern mobile devices,but its secure interaction process brings extra computing burden to mobile devices.This paper takes open por...Trusted Execution Environment(TEE)is an important part of the security architecture of modern mobile devices,but its secure interaction process brings extra computing burden to mobile devices.This paper takes open portable trusted execution environment(OP-TEE)as the research object and deploys it to Raspberry Pi 3B,designs and implements a benchmark for OP-TEE,and analyzes its program characteristics.Furthermore,the application execution time,energy consumption and energy-delay product(EDP)are taken as the optimization objectives,and the central processing unit(CPU)frequency scheduling strategy of mobile devices is dynamically adjusted according to the characteristics of different applications through the combined model.The experimental result shows that compared with the default strategy,the scheduling method proposed in this paper saves 21.18%on average with the Line Regression-Decision Tree scheduling model with the shortest delay as the optimization objective.The Decision Tree-Support Vector Regression(SVR)scheduling model,which takes the lowest energy consumption as the optimization goal,saves 22%energy on average.The Decision Tree-K-Nearest Neighbor(KNN)scheduling model with the lowest EDP as the optimization objective optimizes about 33.9%on average.展开更多
Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with ...Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with uniform northwest-southeast shear senses and magmatism probably resulted from a decratonization event during the retreat of the paleo-Pacific Plate. Here we used two-dimensional finite element thermomechanical numerical models to investigate critical parameters controlling the formation of MCCs under far-field extensional stress. We observed three end-member deformation modes: the MCC mode, the symmetric-dome mode, and the pure-shear mode. The MCC mode requires a Moho temperature of ≥700 ℃ and an extensional strain rate of ≥5 × 10^(-16)s^(-1), implying that the lithosphere had already thinned when the MCC was formed in the Mesozoic. Considering that the widespread MCCs have the same northwest-southeast extension direction in the NCC, we suggest that the MCCs are surface expressions of both large-scale extension and craton destruction and that rollback of the paleo-Pacific slab might be the common driving force.展开更多
Low pH is a major limiting factor for the production of black pepper (Piper nigrum L.) in Hainan province. Black pepper gardens often exhibit a decrease in soil pH (to 5.5 - 5.0) on orchards with a multi-year producti...Low pH is a major limiting factor for the production of black pepper (Piper nigrum L.) in Hainan province. Black pepper gardens often exhibit a decrease in soil pH (to 5.5 - 5.0) on orchards with a multi-year production history. An exploratory hydroponic experiment was conducted to examine the effects of increasingly acid nutrient solution pH (7.0, 5.5, 4.0, and 3.5) on seedling growth, tissue nutrient concentrations and root morphological traits. The results indicated that low pH may directly inhibit root development and function, limit K, Ca and Mg absorption and reduce seedling growth. At pH 5.5, black pepper attained maximum growth, while the minimum growth occurred at pH 3.5. It can be concluded that low pH reduces plant growth and is associated with low root nutrient concentrations of Ca and Mg, which may explain the decline of the yield in the seven pepper gardens of the Institute.展开更多
As the web-server based business is rapidly developed and popularized, how to evaluate and improve the reliability of web-servers has been extremely important. Although a large num- ber of software reliability growth ...As the web-server based business is rapidly developed and popularized, how to evaluate and improve the reliability of web-servers has been extremely important. Although a large num- ber of software reliability growth models (SRGMs), including those combined with multiple change-points (CPs), have been available, these conventional SRGMs cannot be directly applied to web soft- ware reliability analysis because of the complex web operational profile. To characterize the web operational profile precisely, it should be realized that the workload of a web server is normally non-homogeneous and often observed with the pattern of random impulsive shocks. A web software reliability model with random im- pulsive shocks and its statistical analysis method are developed. In the proposed model, the web server workload is characterized by a geometric Brownian motion process. Based on a real data set from IIS server logs of ICRMS website (www.icrms.cn), the proposed model is demonstrated to be powerful for estimating impulsive shocks and web software reliability.展开更多
Objective:To study the relationship between expressions of α-,β-catenins and cyclin D1 and the occurrence, infiltration and metastasis of breast cancer. Methods: High sensitive S-P immunohistochemical method was use...Objective:To study the relationship between expressions of α-,β-catenins and cyclin D1 and the occurrence, infiltration and metastasis of breast cancer. Methods: High sensitive S-P immunohistochemical method was used to detect the protein expressions of α-,β-catenins and cyclin D1 in the 60 cases of breast cancer tissues. Results: Abnormal immu-noreactivities of α-and β-catenins were observed in 37 (61.7%) and 42 (70%) cases of breast cancer tissues, respectively. There were 28 cases (46.7%) who showed cyclin D1 overexpression. The abnormal expression rates of α-and β-catenins in infiltrating lobular carcinoma (ILC) were significantly higher than those in infiltrating ductal carcinoma (IDC) (P<0.05), but they had no relations to the extent of differentiation and lymphatic metastasis of breast cancer (P>0.05). The overexpression rate of cyclin D1 was correlated with tumor stage and lymphatic metastasis of breast cancer (P<0.05), but not with histological type and the extent of differentiation (P>0.05). Cyclin D1 overexpression was observed in 57.1% (24/42) of these cases that showed abnormal staining of β-catenin, but only observed in 22.2% (4/18) of these cases with normal membranous staining of β-catenin. There was a significantly positive correlation between the abnormal expression of β-catenin and overexpression of cyclin D1 (rs=0.321, P<0.05). Conclusion: The abnormal expression of β-catenin may play an important role in the genesis of breast cancer by triggering cyclin D1 overexpression in breast cancer. The abnormal expressions of α-and β-catenins are not a key factor in malignant cell metastasis in breast cancer, but may also involve in the progress.展开更多
In order to minimize the harmonic distortion rate of the current at the common coupling point,this paper proposes a coordinated allocation strategy of harmonic compensation capacity considering the performance of acti...In order to minimize the harmonic distortion rate of the current at the common coupling point,this paper proposes a coordinated allocation strategy of harmonic compensation capacity considering the performance of active power filters(APF).On the premise of proportional distribution of harmonic compensation capacity,the harmonic compensation rate of each APF is considered,and the harmonic current value of each APF to be compensated is obtained.At the same time,the communication topology is introduced.Each APF takes into account the compensation ability of other APFs.Finally,three APFs with different capacity and performance are configured at the harmonic source to suppress the same harmonic source,and the harmonic distortion rate is reduced to 1.73%.The simulation results show that the strategy can effectively improve the compensation capability of the multiple APF cascaded system to the power grid without increasing the installed capacity.展开更多
In China, little information is known about the nutrient requirements of jackfruits and the traditional nutrient management usually depends on the experience. Therefore, in this study, an attempt was made to standardi...In China, little information is known about the nutrient requirements of jackfruits and the traditional nutrient management usually depends on the experience. Therefore, in this study, an attempt was made to standardize the leaf sampling technique and the suitable range of leaf nutrient concentrations for jackfruit (Artocarpus heterophyllus Lam.) nutrient status diagnosis. The sampling result was affected by canopy height, leaf age and time of sampling. Therefore, the three factors were studied. The results illustrated that the stability in level of nutrient concentrations was in 3 - 6 month-old leaves from the central part of the canopy. The most stable period was from April to May for leaf sampling. It was recommended that the stable intracanopy and stable period of nutrient concentrations could be used as the standards of leaf sampling technique. Based on the leaf sampling technique, the standard of leaf nutrient concentrations was summarized, and could be used as the standard of nutrient suitability evaluation.展开更多
Vibration isolation system(VIS)is usually applied to improve the pointing capability and resolution of a space optical payload.A novel vibration isolator is introduced.The equivalent stiffness model of the isolator is...Vibration isolation system(VIS)is usually applied to improve the pointing capability and resolution of a space optical payload.A novel vibration isolator is introduced.The equivalent stiffness model of the isolator is derived by analyzing its static characteristics.A VIS based on the bipod configuration is developed.Its dynamic model is derived and verified using the finite element method and experiments.Because this isolator contains viscoelastic material’which makes the frequency responsive analysis more difficult’an efficiency analysis approach based on the complex stiffness of viscoelastic material is proposed to calculate the transmissibility of the isolator.Finally’a prototype of the vibration isolator is manufactured and experimental studies are carried out.The experimental results show that the analytical results are in good correspondence with the experimental data and the isolator can effectively attenuate the vibrations for the optical payloads.Keywords:isolator;viscoelastic material;space optical展开更多
Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identif...Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identified the evolution characteristics of energy and metal demand driven by industrial revolutions,and analyzed the trends of energy and metal demand driven by the fourth industrial revolution which is happening currently.Results indicated that fossil fuels were the major energy sources which boosted up the past three industrial revolutions,whereas their consumption increased at a slowing pace as the economy was growing continually;after the third industrial revolution,the consumption of fossil fuels decoupled gradually with the economic growth.As the industrial structure transformed as the industrial revolutions went on,more and more metals were used in the industries,and the consumption of different metals showed different trends.In recent years,a new technological revolution has surged mainly driven by the overall application of new information technologies.The technological advance in information,new energies,new materials,etc.,will speed up the industrial transformation and exert a deep effect on the demand of energy and metals.It can be inferred that the ratio of clean,non-polluting,renewable energy will rise while the ratio of fossil fuels will drop in the energy demand,and the demand of rare metals will perhaps enter a fast-growing period,while the demand of traditional bulk metals will fluctuate at mid-high levels.Following the new industrial revolution,China should adopt an energy transition strategy of developing low-carbon and free-carbon technologies simultaneously,reinforce the domestic and international metal supply system with the aim of enhancing global governance capability,strengthen the deep development of rich rare metals and broaden the overseas supply channels of scare rare metals.展开更多
The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed us...The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and TEM and the mechanical response of this array microstructure was characterized for flexural strength and fracture behavior. The result shows that the growth of the larger aspect ratio grains initiate mainly from the seeds through the heterogeneous nucleation mechanism during the process of phase transformation, and the intergranular phase BaAl2Si20s services as good refractory materials. In contrast to conventional processing, a stable bimodal microstructure and complicated component with a lower cost can be achieved using the abovementioned process theoretically and practically.展开更多
With the widespread application of power electronic equipment in the power grid,the harmonic problem of the power grid becomes more pronounced,reducing the efficiency of power production,transmission,and utilization,a...With the widespread application of power electronic equipment in the power grid,the harmonic problem of the power grid becomes more pronounced,reducing the efficiency of power production,transmission,and utilization,and interfering with the normal operation of the power grid.Based on the requirements of harmonic suppression and power system protection,a shunt active power filter(SAPF)is proposed as an effective harmonic suppression method.However,there are problems with impulse current and impulse voltage in the starting process of SAPF.Impulse current and impulse voltage cause the power grid and switchgear to bear greater current stress and voltage stress,which seriously affect the security and reliability of the power grid and may damage the switchgear.To effectively solve the problem of impulse current and impulse voltage,the starting process of SAPF is divided into the uncontrolled rectification stage and the transition stage.The mathematical model of the DC side of APF is established.The causes of impulse current and impulse voltage in the uncontrolled rectifier and transition phases are analyzed.By introducing voltage square,a new starting impulse suppression strategy of active power filter based on the slow rising curve is proposed,fundamentally solving the problems of impulse current and impulse voltage.Simulation results verify the effectiveness and feasibility of this method.展开更多
Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time pro...Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time provides solid restrictions and standards for testing tectonic carbon processes against global measurements.Despite this,modeling the causal relationship between tectonic events and atmospheric CO_(2)levels remains a challenge.We examine the current state of the global tectonic CO_(2)research and suggest a conceptual workflow for numerical experiments that integrates plate tectonics and deep carbon dynamics.Future tectonic carbon cycle modeling should include at least four modules:(1)simulation of carbon-carrying processes,such as carbon ingassing and outgassing at the scale of minerals;(2)calculation of CO_(2)fluxes in tectonic settings like subduction,mantle plume,and plate rifting;(3)reconstruction of carbon cycling within the plates-scale tectonic scenario,particularly involving the processes of supercontinent convergence and dispersion;and(4)comparison with atmospheric CO_(2)history data and iterations,aiming to find the coincidental link between different tectonic carbon fluxes and climate changes.According to our analysis,the recent advancements in each of the four modules have paved the path for a more general assembly.We envision that the large variety of carbon transportation parameters across more than ten orders of magnitude in both time and space is the primary technical hurdle in simulating tectonic carbon dynamics.We propose a boundary-condition-connected approach for simulating the global carbon cycle to realize carbon exchange between the solid earth and surface spheres.展开更多
A series of chemotherapeutic drugs that induce DNA damage,such as cisplatin(DDP),are standard clinical treatments for ovarian cancer,testicular cancer,and other diseases that lack effective targeted drug therapy.Drug ...A series of chemotherapeutic drugs that induce DNA damage,such as cisplatin(DDP),are standard clinical treatments for ovarian cancer,testicular cancer,and other diseases that lack effective targeted drug therapy.Drug resistance is one of the main factors limiting their application.Sensitizers can overcome the drug resistance of tumor cells,thereby enhancing the antitumor activity of chemotherapeutic drugs.In this study,we aimed to identify marketable drugs that could be potential chemotherapy sensitizers and explore the underlying mechanisms.We found that the alcohol withdrawal drug disulfiram(DSF)could significantly enhance the antitumor activity of DDP.JC-1 staining,propidium iodide(PI)staining,and western blotting confirmed that the combination of DSF and DDP could enhance the apoptosis of tumor cells.Subsequent RNA sequencing combined with Gene Set Enrichment Analysis(GSEA)pathway enrichment analysis and cell biology studies such as immunofluorescence suggested an underlying mechanism:DSF makes cells more vulnerable to DNA damage by inhibiting the Fanconi anemia(FA)repair pathway,exerting a sensitizing effect to DNA damaging agents including platinum chemotherapy drugs.Thus,our study illustrated the potential mechanism of action of DSF in enhancing the antitumor effect of DDP.This might provide an effective and safe solution for combating DDP resistance in clinical treatment.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)under Grants 11825301,12003016,12073077the National Key R&D Program of China No.2021YFA0718600+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences with the Grant No.XDA15018400the Youth Innovation Promotion Association of CAS(2023061)。
文摘The Solar Upper Transition Region Imager(SUTRI)onboard the Space Advanced Technology demonstration satellite(SATech-01),which was launched to a Sun-synchronous orbit at a height of~500 km in 2022 July,aims to test the on-orbit performance of our newly developed Sc/Si multi-layer reflecting mirror and the 2k×2k EUV CMOS imaging camera and to take full-disk solar images at the Ne VII 46.5 nm spectral line with a filter width of~3 nm.SUTRI employs a Ritchey-Chrétien optical system with an aperture of 18 cm.The on-orbit observations show that SUTRI images have a field of view of~416×416 and a moderate spatial resolution of~8″without an image stabilization system.The normal cadence of SUTRI images is 30 s and the solar observation time is about16 hr each day because the earth eclipse time accounts for about 1/3 of SATech-01's orbit period.Approximately15 GB data is acquired each day and made available online after processing.SUTRI images are valuable as the Ne VII 46.5 nm line is formed at a temperature regime of~0.5 MK in the solar atmosphere,which has rarely been sampled by existing solar imagers.SUTRI observations will establish connections between structures in the lower solar atmosphere and corona,and advance our understanding of various types of solar activity such as flares,filament eruptions,coronal jets and coronal mass ejections.
文摘Geological hazard is an adverse geological condition that can cause loss of life and property.Accurate prediction and analysis of geological hazards is an important and challenging task.In the past decade,there has been a great expansion of geohazard detection data and advancement in data-driven simulation techniques.In particular,great efforts have been made in applying deep learning to predict geohazards.To understand the recent progress in this field,this paper provides an overview of the commonly used data sources and deep neural networks in the prediction of a variety of geological hazards.
基金funded by National Key Research and Development Program of China under Grant No.2019YFC1520904 from January 2020 to April 2023funded by Shaanxi Innovation Program under Grant 2023-CX-TD-04 January 2023 to December 2025.
文摘Trusted Execution Environment(TEE)is an important part of the security architecture of modern mobile devices,but its secure interaction process brings extra computing burden to mobile devices.This paper takes open portable trusted execution environment(OP-TEE)as the research object and deploys it to Raspberry Pi 3B,designs and implements a benchmark for OP-TEE,and analyzes its program characteristics.Furthermore,the application execution time,energy consumption and energy-delay product(EDP)are taken as the optimization objectives,and the central processing unit(CPU)frequency scheduling strategy of mobile devices is dynamically adjusted according to the characteristics of different applications through the combined model.The experimental result shows that compared with the default strategy,the scheduling method proposed in this paper saves 21.18%on average with the Line Regression-Decision Tree scheduling model with the shortest delay as the optimization objective.The Decision Tree-Support Vector Regression(SVR)scheduling model,which takes the lowest energy consumption as the optimization goal,saves 22%energy on average.The Decision Tree-K-Nearest Neighbor(KNN)scheduling model with the lowest EDP as the optimization objective optimizes about 33.9%on average.
基金supported by the National Natural Science Foundation of China(Grant No.41774112)。
文摘Widespread magmatism, metamorphic core complexes(MCCs), and significant lithospheric thinning occurred during the Mesozoic in the North China Craton(NCC). It has been suggested that the coeval exhumation of MCCs with uniform northwest-southeast shear senses and magmatism probably resulted from a decratonization event during the retreat of the paleo-Pacific Plate. Here we used two-dimensional finite element thermomechanical numerical models to investigate critical parameters controlling the formation of MCCs under far-field extensional stress. We observed three end-member deformation modes: the MCC mode, the symmetric-dome mode, and the pure-shear mode. The MCC mode requires a Moho temperature of ≥700 ℃ and an extensional strain rate of ≥5 × 10^(-16)s^(-1), implying that the lithosphere had already thinned when the MCC was formed in the Mesozoic. Considering that the widespread MCCs have the same northwest-southeast extension direction in the NCC, we suggest that the MCCs are surface expressions of both large-scale extension and craton destruction and that rollback of the paleo-Pacific slab might be the common driving force.
文摘Low pH is a major limiting factor for the production of black pepper (Piper nigrum L.) in Hainan province. Black pepper gardens often exhibit a decrease in soil pH (to 5.5 - 5.0) on orchards with a multi-year production history. An exploratory hydroponic experiment was conducted to examine the effects of increasingly acid nutrient solution pH (7.0, 5.5, 4.0, and 3.5) on seedling growth, tissue nutrient concentrations and root morphological traits. The results indicated that low pH may directly inhibit root development and function, limit K, Ca and Mg absorption and reduce seedling growth. At pH 5.5, black pepper attained maximum growth, while the minimum growth occurred at pH 3.5. It can be concluded that low pH reduces plant growth and is associated with low root nutrient concentrations of Ca and Mg, which may explain the decline of the yield in the seven pepper gardens of the Institute.
基金supported by the International Technology Cooperation Project of Guizhou Province(QianKeHeWaiGZi[2012]7052)the National Scientific Research Project for Statistics(2012LZ054)
文摘As the web-server based business is rapidly developed and popularized, how to evaluate and improve the reliability of web-servers has been extremely important. Although a large num- ber of software reliability growth models (SRGMs), including those combined with multiple change-points (CPs), have been available, these conventional SRGMs cannot be directly applied to web soft- ware reliability analysis because of the complex web operational profile. To characterize the web operational profile precisely, it should be realized that the workload of a web server is normally non-homogeneous and often observed with the pattern of random impulsive shocks. A web software reliability model with random im- pulsive shocks and its statistical analysis method are developed. In the proposed model, the web server workload is characterized by a geometric Brownian motion process. Based on a real data set from IIS server logs of ICRMS website (www.icrms.cn), the proposed model is demonstrated to be powerful for estimating impulsive shocks and web software reliability.
文摘Objective:To study the relationship between expressions of α-,β-catenins and cyclin D1 and the occurrence, infiltration and metastasis of breast cancer. Methods: High sensitive S-P immunohistochemical method was used to detect the protein expressions of α-,β-catenins and cyclin D1 in the 60 cases of breast cancer tissues. Results: Abnormal immu-noreactivities of α-and β-catenins were observed in 37 (61.7%) and 42 (70%) cases of breast cancer tissues, respectively. There were 28 cases (46.7%) who showed cyclin D1 overexpression. The abnormal expression rates of α-and β-catenins in infiltrating lobular carcinoma (ILC) were significantly higher than those in infiltrating ductal carcinoma (IDC) (P<0.05), but they had no relations to the extent of differentiation and lymphatic metastasis of breast cancer (P>0.05). The overexpression rate of cyclin D1 was correlated with tumor stage and lymphatic metastasis of breast cancer (P<0.05), but not with histological type and the extent of differentiation (P>0.05). Cyclin D1 overexpression was observed in 57.1% (24/42) of these cases that showed abnormal staining of β-catenin, but only observed in 22.2% (4/18) of these cases with normal membranous staining of β-catenin. There was a significantly positive correlation between the abnormal expression of β-catenin and overexpression of cyclin D1 (rs=0.321, P<0.05). Conclusion: The abnormal expression of β-catenin may play an important role in the genesis of breast cancer by triggering cyclin D1 overexpression in breast cancer. The abnormal expressions of α-and β-catenins are not a key factor in malignant cell metastasis in breast cancer, but may also involve in the progress.
基金This work was supported in part by the National Natural Science Foundation of China(Grant No.61863023).
文摘In order to minimize the harmonic distortion rate of the current at the common coupling point,this paper proposes a coordinated allocation strategy of harmonic compensation capacity considering the performance of active power filters(APF).On the premise of proportional distribution of harmonic compensation capacity,the harmonic compensation rate of each APF is considered,and the harmonic current value of each APF to be compensated is obtained.At the same time,the communication topology is introduced.Each APF takes into account the compensation ability of other APFs.Finally,three APFs with different capacity and performance are configured at the harmonic source to suppress the same harmonic source,and the harmonic distortion rate is reduced to 1.73%.The simulation results show that the strategy can effectively improve the compensation capability of the multiple APF cascaded system to the power grid without increasing the installed capacity.
文摘In China, little information is known about the nutrient requirements of jackfruits and the traditional nutrient management usually depends on the experience. Therefore, in this study, an attempt was made to standardize the leaf sampling technique and the suitable range of leaf nutrient concentrations for jackfruit (Artocarpus heterophyllus Lam.) nutrient status diagnosis. The sampling result was affected by canopy height, leaf age and time of sampling. Therefore, the three factors were studied. The results illustrated that the stability in level of nutrient concentrations was in 3 - 6 month-old leaves from the central part of the canopy. The most stable period was from April to May for leaf sampling. It was recommended that the stable intracanopy and stable period of nutrient concentrations could be used as the standards of leaf sampling technique. Based on the leaf sampling technique, the standard of leaf nutrient concentrations was summarized, and could be used as the standard of nutrient suitability evaluation.
文摘Vibration isolation system(VIS)is usually applied to improve the pointing capability and resolution of a space optical payload.A novel vibration isolator is introduced.The equivalent stiffness model of the isolator is derived by analyzing its static characteristics.A VIS based on the bipod configuration is developed.Its dynamic model is derived and verified using the finite element method and experiments.Because this isolator contains viscoelastic material’which makes the frequency responsive analysis more difficult’an efficiency analysis approach based on the complex stiffness of viscoelastic material is proposed to calculate the transmissibility of the isolator.Finally’a prototype of the vibration isolator is manufactured and experimental studies are carried out.The experimental results show that the analytical results are in good correspondence with the experimental data and the isolator can effectively attenuate the vibrations for the optical payloads.Keywords:isolator;viscoelastic material;space optical
文摘Industrial revolutions have a profound impact on energy and metal demand.Based on technological improvement,industrial transformation,and changes of energy and metal consumption in the United States,this paper identified the evolution characteristics of energy and metal demand driven by industrial revolutions,and analyzed the trends of energy and metal demand driven by the fourth industrial revolution which is happening currently.Results indicated that fossil fuels were the major energy sources which boosted up the past three industrial revolutions,whereas their consumption increased at a slowing pace as the economy was growing continually;after the third industrial revolution,the consumption of fossil fuels decoupled gradually with the economic growth.As the industrial structure transformed as the industrial revolutions went on,more and more metals were used in the industries,and the consumption of different metals showed different trends.In recent years,a new technological revolution has surged mainly driven by the overall application of new information technologies.The technological advance in information,new energies,new materials,etc.,will speed up the industrial transformation and exert a deep effect on the demand of energy and metals.It can be inferred that the ratio of clean,non-polluting,renewable energy will rise while the ratio of fossil fuels will drop in the energy demand,and the demand of rare metals will perhaps enter a fast-growing period,while the demand of traditional bulk metals will fluctuate at mid-high levels.Following the new industrial revolution,China should adopt an energy transition strategy of developing low-carbon and free-carbon technologies simultaneously,reinforce the domestic and international metal supply system with the aim of enhancing global governance capability,strengthen the deep development of rich rare metals and broaden the overseas supply channels of scare rare metals.
基金This work was financially supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the Minis-try of Education of China (05-04) and the projects to tackle the Key Problem in Science and Technology of Shaanxi Province, China(No.2004K07-G13).
文摘The silicon nitride based ceramics obtained by the addition of β-Si3N4 seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed using XRD, SEM, and TEM and the mechanical response of this array microstructure was characterized for flexural strength and fracture behavior. The result shows that the growth of the larger aspect ratio grains initiate mainly from the seeds through the heterogeneous nucleation mechanism during the process of phase transformation, and the intergranular phase BaAl2Si20s services as good refractory materials. In contrast to conventional processing, a stable bimodal microstructure and complicated component with a lower cost can be achieved using the abovementioned process theoretically and practically.
基金supported by the National Natural Science Foundation of China under Grant 61863023.
文摘With the widespread application of power electronic equipment in the power grid,the harmonic problem of the power grid becomes more pronounced,reducing the efficiency of power production,transmission,and utilization,and interfering with the normal operation of the power grid.Based on the requirements of harmonic suppression and power system protection,a shunt active power filter(SAPF)is proposed as an effective harmonic suppression method.However,there are problems with impulse current and impulse voltage in the starting process of SAPF.Impulse current and impulse voltage cause the power grid and switchgear to bear greater current stress and voltage stress,which seriously affect the security and reliability of the power grid and may damage the switchgear.To effectively solve the problem of impulse current and impulse voltage,the starting process of SAPF is divided into the uncontrolled rectification stage and the transition stage.The mathematical model of the DC side of APF is established.The causes of impulse current and impulse voltage in the uncontrolled rectifier and transition phases are analyzed.By introducing voltage square,a new starting impulse suppression strategy of active power filter based on the slow rising curve is proposed,fundamentally solving the problems of impulse current and impulse voltage.Simulation results verify the effectiveness and feasibility of this method.
基金supported by the National Natural Science Foundation of China(Grant Nos.41888101 and 41625016)XPLORER PRIZE。
文摘Plate tectonics plays a critical role in modulating atmospheric CO_(2)concentration on the geological timescale(≥106year).A growing consensus on tectonic and Earth’s CO_(2)history in the Cenozoic and deeper time provides solid restrictions and standards for testing tectonic carbon processes against global measurements.Despite this,modeling the causal relationship between tectonic events and atmospheric CO_(2)levels remains a challenge.We examine the current state of the global tectonic CO_(2)research and suggest a conceptual workflow for numerical experiments that integrates plate tectonics and deep carbon dynamics.Future tectonic carbon cycle modeling should include at least four modules:(1)simulation of carbon-carrying processes,such as carbon ingassing and outgassing at the scale of minerals;(2)calculation of CO_(2)fluxes in tectonic settings like subduction,mantle plume,and plate rifting;(3)reconstruction of carbon cycling within the plates-scale tectonic scenario,particularly involving the processes of supercontinent convergence and dispersion;and(4)comparison with atmospheric CO_(2)history data and iterations,aiming to find the coincidental link between different tectonic carbon fluxes and climate changes.According to our analysis,the recent advancements in each of the four modules have paved the path for a more general assembly.We envision that the large variety of carbon transportation parameters across more than ten orders of magnitude in both time and space is the primary technical hurdle in simulating tectonic carbon dynamics.We propose a boundary-condition-connected approach for simulating the global carbon cycle to realize carbon exchange between the solid earth and surface spheres.
基金supported by the National Natural Science Foundation of China (41888101 and 41625016)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (311021003)the National Key Research and Development Program of China (2022YFF0802800)。
基金supported by the National Natural Science Foundation of China(No.82104192)the Zhejiang Provincial Natural Science Foundation(No.LR22H310002)+1 种基金the Scientific Research Fund of Zhejiang University(No.XY2021044)the Zhejiang University K.P.Chao’s High Technology Development Foundation.
文摘A series of chemotherapeutic drugs that induce DNA damage,such as cisplatin(DDP),are standard clinical treatments for ovarian cancer,testicular cancer,and other diseases that lack effective targeted drug therapy.Drug resistance is one of the main factors limiting their application.Sensitizers can overcome the drug resistance of tumor cells,thereby enhancing the antitumor activity of chemotherapeutic drugs.In this study,we aimed to identify marketable drugs that could be potential chemotherapy sensitizers and explore the underlying mechanisms.We found that the alcohol withdrawal drug disulfiram(DSF)could significantly enhance the antitumor activity of DDP.JC-1 staining,propidium iodide(PI)staining,and western blotting confirmed that the combination of DSF and DDP could enhance the apoptosis of tumor cells.Subsequent RNA sequencing combined with Gene Set Enrichment Analysis(GSEA)pathway enrichment analysis and cell biology studies such as immunofluorescence suggested an underlying mechanism:DSF makes cells more vulnerable to DNA damage by inhibiting the Fanconi anemia(FA)repair pathway,exerting a sensitizing effect to DNA damaging agents including platinum chemotherapy drugs.Thus,our study illustrated the potential mechanism of action of DSF in enhancing the antitumor effect of DDP.This might provide an effective and safe solution for combating DDP resistance in clinical treatment.