In this study the copper and lead adsorption efficiency onto banana peels powder was investigated. The agroindustrial waste recovery represents one of the Circular Economy pillars. In the view of the synthesis of an e...In this study the copper and lead adsorption efficiency onto banana peels powder was investigated. The agroindustrial waste recovery represents one of the Circular Economy pillars. In the view of the synthesis of an environmentally friendly adsorbent material, the powder was used without any preliminary chemical or thermal activation, but only after simple washing, drying and grinding. The bio-adsorbent was characterized by the FTIR technique and tested in batch mode on synthetic aqueous solutions containing Pb and Cu in the range 10–90 mg·L^(-1). A selection of two(Langmuir, Freundlich) and three(Sips, Redlich–Peterson, Koble–Corrigan) parameter isotherm models was chosen to fit adsorption equilibrium data by non-linear regression procedure. The best fit isotherm model was selected relying on the error function with the lowest average percentage error(APE) value, among those characterized by the highest R^2 values. As expected, the three-parameter models are found to better represent both metals bio-adsorption, with APE and R^2 values always lower and higher, respectively, than the corresponding values obtained for the two-parameter models.展开更多
Metal magnetic memory（MMM） testing has been widely used to detect welded joints. However, load levels, environmental magnetic field, and measurement noises make the MMM data dispersive and bring difficulty to quanti...Metal magnetic memory（MMM） testing has been widely used to detect welded joints. However, load levels, environmental magnetic field, and measurement noises make the MMM data dispersive and bring difficulty to quantitative evaluation. In order to promote the development of quantitative MMM reliability assessment, a new MMM model is presented for welded joints. Steel Q235 welded specimens are tested along the longitudinal and horizontal lines by TSC-2M-8 instrument in the tensile fatigue experiments. The X-ray testing is carried out synchronously to verify the MMM results. It is found that MMM testing can detect the hidden crack earlier than X-ray testing. Moreover, the MMM gradient vector sum K_（vs） is sensitive to the damage degree, especially at early and hidden damage stages. Considering the dispersion of MMM data, the K_（vs） statistical law is investigated, which shows that K_（vs） obeys Gaussian distribution. So K_（vs） is the suitable MMM parameter to establish reliability model of welded joints. At last, the original quantitative MMM reliability model is first presented based on the improved stress strength interference theory. It is shown that the reliability degree R gradually decreases with the decreasing of the residual life ratio T, and the maximal error between prediction reliability degree R_1 and verification reliability degree R_2 is 9.15%. This presented method provides a novel tool of reliability testing and evaluating in practical engineering for welded joints.展开更多
In order to solve some key problems associated with the rapid manufacturingof metallic functional part, a new technique using vacuum solid-state pressure diffusion weldingprocess to join the metallic slice sheets is p...In order to solve some key problems associated with the rapid manufacturingof metallic functional part, a new technique using vacuum solid-state pressure diffusion weldingprocess to join the metallic slice sheets is put forward. The following results can be drawn fromthe experiments: only 1 percent shrinkage happened in the stack direction and it came from theregular system error. The atoms diffuse between joint interfaces clearly and new grains formedmeanwhile. The average shear strength of welding zone is more than 100 MPa and micro hardness ofwelding zone is almost the same as that of matrix. It is shown from above results that the vacuumsolid-state pressure diffusion welding process is an available technique to join metal slice sheetsfor the rapid manufacturing of metallic functional parts.展开更多
Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface ...Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron（SE） and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.展开更多
In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Associ...In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Association rules were used to analyze correlation and check consistency between indices. This study shows that the judgment obtained by weak association rules or non-association rules is more accurate and more credible than that obtained by strong association rules. When the testing grades of two indices in the weak association rules are inconsistent, the testing grades of indices are more likely to be erroneous, and the mistakes are often caused by human factors. Clustering data mining technology was used to analyze the reliability of a diagnosis, or to perform health diagnosis directly. Analysis showed that the clustering results are related to the indices selected, and that if the indices selected are more significant, the characteristics of clustering results are also more significant, and the analysis or diagnosis is more credible. The indices and diagnosis analysis function produced by this study provide a necessary theoretical foundation and new ideas for the development of hydraulic metal structure health diagnosis technology.展开更多
To determine the solutions of the well-known problem of a finite width strip with single edge crack,some results on elasto-plastic fracture analysis for metallic foams are reported.Meanwhile,in order to discuss and pu...To determine the solutions of the well-known problem of a finite width strip with single edge crack,some results on elasto-plastic fracture analysis for metallic foams are reported.Meanwhile,in order to discuss and put an insight into the nonlinear fracture analysis,the Dugdale model for plastic deformation of this configuration for metallic foams is recommended and solved.Combining the asymptotic solution with the Dugdale model and elastic solution,the stress field in the plastic zone and the size of the plastic zone are expressed as analytical forms.Based on Williams expansion method,the estimate of the scale factor is also completed and analyzed.In view of these analytical solutions,the results show the scale factor is a useful parameter for the fracture theory of metallic foams.展开更多
A rheological model is proposed that incorporates the serrated flow nature of metallic glasses. It involves the process of the nucleation, propagation and the arrest of a shear bands in the samples subjected to compre...A rheological model is proposed that incorporates the serrated flow nature of metallic glasses. It involves the process of the nucleation, propagation and the arrest of a shear bands in the samples subjected to compressive deformation at room temperature. Numerical resolution of the constitutive equations resulting from the model is compared with the stress-strain curve obtained from in-situ nano-compression test in SEM of Zrbased metallic glass. Parametric identification method was applied and enabled us to release the physical parameters of the model. The obtained results showed that the model is adequately valid to describe the experimental data and the almost adjustable model parameters are physically meaningful and comparable to literature.展开更多
Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are di...Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are displayed during stable plastic flows at strain rates of 2×10-4 s-1 and 5×10-5 s-1,respectively,which means that serration behavior depends on the strain rate.However,the remarkable agreement between measured slip-avalanche magnitudes and the scaling behavior,i.e.a universal complementary cumulative distribution function（CCDF）predicted by mean-field theory（MFT）model,indicates that the plasticity of the present Fe-based BMGs can be tuned by imposed strain rates：Smax^6）ε-λ.This tuned plasticity is elucidated with expended free-volume model.Moreover,the scaling behavior of serrated flows for other strain rates can be predicted as well.展开更多
CNMC combines social responsibility with corporate vision as it expands in Africa TODAY non-ferrous metals(metals other than iron and alloys that do not contain an appreciable amount of iron) are an indispensable par...CNMC combines social responsibility with corporate vision as it expands in Africa TODAY non-ferrous metals(metals other than iron and alloys that do not contain an appreciable amount of iron) are an indispensable part of every aspect of our lives. From daily necessities like telephones and electric cookers,to sophisticated equipment like satellites and radar,non-ferrous展开更多
This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental...This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental results will be presented here which have been obtained using a physical model(mini-LIMMCAST)operating with the low melting point alloy GaInSn.According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle(SEN)has been studied up to Hartmann numbers of about 400.The Ultrasound-Doppler-Velocimetry(UDV)was applied for measurements of the flow pattern in the mould.Local conductivity anemometers were used to measure the turbulent quantities of the flow.The effect of the magnetic field on the flow structure turned out to be manifold and rather complex.The magnetic field causes a deflection of the jet,at which the respective exit angle from the nozzle ports becomes more flat.Thus,both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced.A significant return flow occurs in the adjacent regions of the jet.Specific vortices are formed with axes being aligned with the magnetic field direction.Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic(MHD)flows.The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume.Variations of the wall conductivity showed a striking impact on the resulting flow structures.展开更多
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new e...Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400℃.The parameters of the facility and the dimensions of the test sections will be given,and the possibilities for flow investigations in tundish,submerged entry nozzle and mould will be discussed.In addition,the smaller set-up Mini-LIMMCAST will be presented,which works with the room-temperature liquid alloy GaInSn.The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution.New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400℃.First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena:fully contacfless electromagnetic tomography of the flow in the mould,flow monitoring by a multitude of ultrasonic sensors,and analysis of the flow in the mould under the influence of an electromagnetic brake: intensification of the flow turbulence contrary to the expected flow damping,injection of argon bubbles through the stopper rod:occurrence of pressure oscillations.展开更多
Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention has to be paid on its geometry.In this paper the main prin...Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention has to be paid on its geometry.In this paper the main principles of a novel SEN type will be described.Water modeling and Computational Fluid Dynamics(CFD)are applied to characterize the flow pattern under different conditions.Furthermore,the interaction with electromagnetic stirring(M-EMS)is analyzed by means of a liquid melt model.Finally,actual steel plant performance data and observations are discussed.展开更多
The human body model（HBM） stress of a no-connect metal cover is tested to obtain the characteristics of abnormal electrostatic discharge,including current waveforms and peak current under varied stress voltage and d...The human body model（HBM） stress of a no-connect metal cover is tested to obtain the characteristics of abnormal electrostatic discharge,including current waveforms and peak current under varied stress voltage and device failure voltage.A new discharge model called the ＂sparkover-induced model＂ is proposed based on the results.Then,failure mechanism analysis and model simulation are performed to prove that the transient peak current caused by a sparkover of low arc impedance will result in the devices＇ premature damage when the potential difference between the no-connect metal cover and the chip exceeds the threshold voltage of sparkover.展开更多
Based on the transmission line theory of the buried metallic structures, the concerned harmful effects to the buried oil and natural gas pipelines caused by the power line short-circuit fault are further discussed. A ...Based on the transmission line theory of the buried metallic structures, the concerned harmful effects to the buried oil and natural gas pipelines caused by the power line short-circuit fault are further discussed. A closed-form expression of the induced voltage caused by the short-circuit fault of the ultra-high voltage power （UHVAC） transmission line is given. The transmission line model of the buried pipeline is set up and a set of formulas for calculating induced voltage on the pipeline and the parameters of the buried pipeline in actual environment condition are given. At last, the characteristic of the harm^hl effects on the buried pipeline from the power line short-circuit fault are discussed.展开更多
基金the Dept. of Chemical Engineering Materials Environment of Sapienza University of Rome
文摘In this study the copper and lead adsorption efficiency onto banana peels powder was investigated. The agroindustrial waste recovery represents one of the Circular Economy pillars. In the view of the synthesis of an environmentally friendly adsorbent material, the powder was used without any preliminary chemical or thermal activation, but only after simple washing, drying and grinding. The bio-adsorbent was characterized by the FTIR technique and tested in batch mode on synthetic aqueous solutions containing Pb and Cu in the range 10–90 mg·L^(-1). A selection of two(Langmuir, Freundlich) and three(Sips, Redlich–Peterson, Koble–Corrigan) parameter isotherm models was chosen to fit adsorption equilibrium data by non-linear regression procedure. The best fit isotherm model was selected relying on the error function with the lowest average percentage error(APE) value, among those characterized by the highest R^2 values. As expected, the three-parameter models are found to better represent both metals bio-adsorption, with APE and R^2 values always lower and higher, respectively, than the corresponding values obtained for the two-parameter models.
基金Supported by National Natural Science Foundation of China(Grant Nos.11272084,11472076)PetroChina Innovation Foundation(Grant No.2015D-5006-0602)Postdoctoral Science Research Developmental Foundation of Chinese Heilongjiang Province(Grant No.LBH-Q13035)
文摘Metal magnetic memory（MMM） testing has been widely used to detect welded joints. However, load levels, environmental magnetic field, and measurement noises make the MMM data dispersive and bring difficulty to quantitative evaluation. In order to promote the development of quantitative MMM reliability assessment, a new MMM model is presented for welded joints. Steel Q235 welded specimens are tested along the longitudinal and horizontal lines by TSC-2M-8 instrument in the tensile fatigue experiments. The X-ray testing is carried out synchronously to verify the MMM results. It is found that MMM testing can detect the hidden crack earlier than X-ray testing. Moreover, the MMM gradient vector sum K_（vs） is sensitive to the damage degree, especially at early and hidden damage stages. Considering the dispersion of MMM data, the K_（vs） statistical law is investigated, which shows that K_（vs） obeys Gaussian distribution. So K_（vs） is the suitable MMM parameter to establish reliability model of welded joints. At last, the original quantitative MMM reliability model is first presented based on the improved stress strength interference theory. It is shown that the reliability degree R gradually decreases with the decreasing of the residual life ratio T, and the maximal error between prediction reliability degree R_1 and verification reliability degree R_2 is 9.15%. This presented method provides a novel tool of reliability testing and evaluating in practical engineering for welded joints.
基金This project is supported by National Natural Science Foundation of China(No.59875088) Municipality Science Foundation of Chongqing (No.2000-6062).
文摘In order to solve some key problems associated with the rapid manufacturingof metallic functional part, a new technique using vacuum solid-state pressure diffusion weldingprocess to join the metallic slice sheets is put forward. The following results can be drawn fromthe experiments: only 1 percent shrinkage happened in the stack direction and it came from theregular system error. The atoms diffuse between joint interfaces clearly and new grains formedmeanwhile. The average shear strength of welding zone is more than 100 MPa and micro hardness ofwelding zone is almost the same as that of matrix. It is shown from above results that the vacuumsolid-state pressure diffusion welding process is an available technique to join metal slice sheetsfor the rapid manufacturing of metallic functional parts.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1537211 and 11675278)the China Postdoctoral Science Foundation(Grant No.2016M602944XB)
文摘Calculations of secondary electron yield（SEY） by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron（SE） and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.50539010)the Special Fund for Public Welfare Industry of the Ministry of Water Resources of China(Grant No.200801019)
文摘In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Association rules were used to analyze correlation and check consistency between indices. This study shows that the judgment obtained by weak association rules or non-association rules is more accurate and more credible than that obtained by strong association rules. When the testing grades of two indices in the weak association rules are inconsistent, the testing grades of indices are more likely to be erroneous, and the mistakes are often caused by human factors. Clustering data mining technology was used to analyze the reliability of a diagnosis, or to perform health diagnosis directly. Analysis showed that the clustering results are related to the indices selected, and that if the indices selected are more significant, the characteristics of clustering results are also more significant, and the analysis or diagnosis is more credible. The indices and diagnosis analysis function produced by this study provide a necessary theoretical foundation and new ideas for the development of hydraulic metal structure health diagnosis technology.
基金Supported by the National Natural Science Foundation of China(10972035)
文摘To determine the solutions of the well-known problem of a finite width strip with single edge crack,some results on elasto-plastic fracture analysis for metallic foams are reported.Meanwhile,in order to discuss and put an insight into the nonlinear fracture analysis,the Dugdale model for plastic deformation of this configuration for metallic foams is recommended and solved.Combining the asymptotic solution with the Dugdale model and elastic solution,the stress field in the plastic zone and the size of the plastic zone are expressed as analytical forms.Based on Williams expansion method,the estimate of the scale factor is also completed and analyzed.In view of these analytical solutions,the results show the scale factor is a useful parameter for the fracture theory of metallic foams.
文摘A rheological model is proposed that incorporates the serrated flow nature of metallic glasses. It involves the process of the nucleation, propagation and the arrest of a shear bands in the samples subjected to compressive deformation at room temperature. Numerical resolution of the constitutive equations resulting from the model is compared with the stress-strain curve obtained from in-situ nano-compression test in SEM of Zrbased metallic glass. Parametric identification method was applied and enabled us to release the physical parameters of the model. The obtained results showed that the model is adequately valid to describe the experimental data and the almost adjustable model parameters are physically meaningful and comparable to literature.
基金the financial support of National Natural Science Foundation of China(No.51371122)the financial support of National Natural Science Foundation of China(No.51501220)+1 种基金the Youth Natural Science Foundation of Shanxi Province,China(No.2015021005)the Natural Science Foundation of Jiangsu Province(BK20150170)
文摘Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are displayed during stable plastic flows at strain rates of 2×10-4 s-1 and 5×10-5 s-1,respectively,which means that serration behavior depends on the strain rate.However,the remarkable agreement between measured slip-avalanche magnitudes and the scaling behavior,i.e.a universal complementary cumulative distribution function（CCDF）predicted by mean-field theory（MFT）model,indicates that the plasticity of the present Fe-based BMGs can be tuned by imposed strain rates：Smax^6）ε-λ.This tuned plasticity is elucidated with expended free-volume model.Moreover,the scaling behavior of serrated flows for other strain rates can be predicted as well.
文摘CNMC combines social responsibility with corporate vision as it expands in Africa TODAY non-ferrous metals(metals other than iron and alloys that do not contain an appreciable amount of iron) are an indispensable part of every aspect of our lives. From daily necessities like telephones and electric cookers,to sophisticated equipment like satellites and radar,non-ferrous
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) as Part of the Collaborative Research Centre SFB609 "Electromagnetic Flow Control in Metallurgy,Crystal Growth and Electrochemistry"
文摘This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental results will be presented here which have been obtained using a physical model(mini-LIMMCAST)operating with the low melting point alloy GaInSn.According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle(SEN)has been studied up to Hartmann numbers of about 400.The Ultrasound-Doppler-Velocimetry(UDV)was applied for measurements of the flow pattern in the mould.Local conductivity anemometers were used to measure the turbulent quantities of the flow.The effect of the magnetic field on the flow structure turned out to be manifold and rather complex.The magnetic field causes a deflection of the jet,at which the respective exit angle from the nozzle ports becomes more flat.Thus,both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced.A significant return flow occurs in the adjacent regions of the jet.Specific vortices are formed with axes being aligned with the magnetic field direction.Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic(MHD)flows.The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume.Variations of the wall conductivity showed a striking impact on the resulting flow structures.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) in frame of the SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400℃.The parameters of the facility and the dimensions of the test sections will be given,and the possibilities for flow investigations in tundish,submerged entry nozzle and mould will be discussed.In addition,the smaller set-up Mini-LIMMCAST will be presented,which works with the room-temperature liquid alloy GaInSn.The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution.New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400℃.First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena:fully contacfless electromagnetic tomography of the flow in the mould,flow monitoring by a multitude of ultrasonic sensors,and analysis of the flow in the mould under the influence of an electromagnetic brake: intensification of the flow turbulence contrary to the expected flow damping,injection of argon bubbles through the stopper rod:occurrence of pressure oscillations.
文摘Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention has to be paid on its geometry.In this paper the main principles of a novel SEN type will be described.Water modeling and Computational Fluid Dynamics(CFD)are applied to characterize the flow pattern under different conditions.Furthermore,the interaction with electromagnetic stirring(M-EMS)is analyzed by means of a liquid melt model.Finally,actual steel plant performance data and observations are discussed.
基金supported by the National Natural Science Foundation of China(No.60927006)
文摘The human body model（HBM） stress of a no-connect metal cover is tested to obtain the characteristics of abnormal electrostatic discharge,including current waveforms and peak current under varied stress voltage and device failure voltage.A new discharge model called the ＂sparkover-induced model＂ is proposed based on the results.Then,failure mechanism analysis and model simulation are performed to prove that the transient peak current caused by a sparkover of low arc impedance will result in the devices＇ premature damage when the potential difference between the no-connect metal cover and the chip exceeds the threshold voltage of sparkover.
基金supported by the National Natural Science Foundation of China(60671055,61171051)the Doctorate Foundation of the Ministry of Education of China(200700130046)
文摘Based on the transmission line theory of the buried metallic structures, the concerned harmful effects to the buried oil and natural gas pipelines caused by the power line short-circuit fault are further discussed. A closed-form expression of the induced voltage caused by the short-circuit fault of the ultra-high voltage power （UHVAC） transmission line is given. The transmission line model of the buried pipeline is set up and a set of formulas for calculating induced voltage on the pipeline and the parameters of the buried pipeline in actual environment condition are given. At last, the characteristic of the harm^hl effects on the buried pipeline from the power line short-circuit fault are discussed.
