Non-Synchronous Deformation Effect of Particle in Sheet Metal Forming Process

A new concept referred to the non-synchronous deformation effect of particle in sheet metal forming is proposed. The results of finite element analysis show that the flow resistance of sheet metal can be effectively reduced and thus the forming property can be greatly improved if the moving and deformation state of the neighboring elements with equal perpendicular distance to the entrance contour of die is non-synchronous. Experiment tests are presented and the results agree well with FEA simulation. In addition, the mechanism of the non-synchronous effect is analyzed in detail.

Incorporating empirical knowledge into data-driven variable selection for quantitative analysis of coal ash content by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy(LIBS)has become a widely used atomic spectroscopic technique for rapid coal analysis.However,the vast amount of spectral information in LIBS contains signal uncertainty,which can affect its quantification performance.In this work,we propose a hybrid variable selection method to improve the performance of LIBS quantification.Important variables are first identified using Pearson's correlation coefficient,mutual information,least absolute shrinkage and selection operator(LASSO)and random forest,and then filtered and combined with empirical variables related to fingerprint elements of coal ash content.Subsequently,these variables are fed into a partial least squares regression(PLSR).Additionally,in some models,certain variables unrelated to ash content are removed manually to study the impact of variable deselection on model performance.The proposed hybrid strategy was tested on three LIBS datasets for quantitative analysis of coal ash content and compared with the corresponding data-driven baseline method.It is significantly better than the variable selection only method based on empirical knowledge and in most cases outperforms the baseline method.The results showed that on all three datasets the hybrid strategy for variable selection combining empirical knowledge and data-driven algorithms achieved the lowest root mean square error of prediction(RMSEP)values of 1.605,3.478 and 1.647,respectively,which were significantly lower than those obtained from multiple linear regression using only 12 empirical variables,which are 1.959,3.718 and 2.181,respectively.The LASSO-PLSR model with empirical support and 20 selected variables exhibited a significantly improved performance after variable deselection,with RMSEP values dropping from 1.635,3.962 and 1.647 to 1.483,3.086 and 1.567,respectively.Such results demonstrate that using empirical knowledge as a support for datadriven variable selection can be a viable approach to improve the accuracy and reliability of LIBS quantification.

Patterning single-layer materials by electrical breakdown using atomic force microscopy

The development of nanoelectronics and nanotechnologies has been boosted significantly by the emergence of 2D materials because of their atomic thickness and peculiar properties,and developing a universal,precise patterning technology for single-layer 2D materials is critical for assembling nanodevices.Demonstrated here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores,nanostrips,and other nanostructures on demand.This can be achieved by voltage scanning or applying a constant voltage while moving the tip.By measuring the electrical current,the formation process on single-layer materials was shown quantitatively.The present results provide evidence of successful pattern fabrication on single-layer MoS2,boron nitride,and graphene,although further confirmation is still needed.The proposed method holds promise as a general nanomachining technology for the future.

Research on batch multielement rapid quantitative analysis based on the standard curve-assisted calibration-free laserinduced breakdown spectroscopy method

This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.

Laser-induced breakdown spectroscopy as a method for millimeter-scale inspection of surface flatness

A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.

Estimating the yield stress of soft materials via laser-induced breakdown spectroscopy

Taking three typical soft samples prepared respectively by loose packings of 77-,95-,and 109-μm copper grains as examples,we perform an experiment to investigate the energy-dependent laser-induced breakdown spectroscopy(LIBS)of soft materials.We discovered a reversal phenomenon in the trend of energy dependence of plasma emission intensity:increasing initially and then decreasing separated by a well-defined critical energy.The trend reversal is attributed to the laser-induced recoil pressure at the critical energy just matching the sample's yield strength.As a result,a one-to-one correspondence can be well established between the samples'yield stress and the critical energy that is easily obtainable from LIBS measurements.This allows us to propose an innovative method for estimating the yield stress of soft materials via LIBS with attractive advantages including in-situ remote detection,real-time data collection,and minimal destructive to sample.

Effects of improved amino acid balance diet on lysine mammary utilization, whole body protein turnover and muscle protein breakdown on lactating sows

Background The study objective was to test the hypothesis that low crude protein(CP)diet with crystalline amino acids(CAA)supplementation improves Lys utilization efficiency for milk production and reduces protein turnover and muscle protein breakdown.Eighteen lactating multiparous Yorkshire sows were allotted to 1 of 2 isocaloric diets(10.80 MJ/kg net energy):control(CON;19.24%CP)and reduced CP with“optimal”AA profile(OPT;14.00%CP).Sow body weight and backfat were recorded on d 1 and 21 of lactation and piglets were weighed on d 1,14,18,and 21 of lactation.Between d 14 and 18,a subset of 9 sows(CON=4,OPT=5)was infused with a mixed solution of 3-[methyl-2H3]histidine(bolus injection)and[13C]bicarbonate(priming dose)first,then a constant 2-h[13C]bicarbonate infusion followed by a 6-h primed constant[1-13C]lysine infusion.Serial blood and milk sampling were performed to determine plasma and milk Lys enrichment,Lys oxidation rate,whole body protein turnover,and muscle protein breakdown.Results Over the 21-d lactation period,compared to CON,sows fed OPT had greater litter growth rate(P<0.05).Compared to CON,sows fed OPT had greater efficiency of Lys(P<0.05),Lys mammary flux(P<0.01)and whole-body protein turnover efficiency(P<0.05).Compared to CON,sows fed OPT tended to have lower whole body protein breakdown rate(P=0.069).Muscle protein breakdown rate did not differ between OPT and CON(P=0.197).Conclusion Feeding an improved AA balance diet increased efficiency of Lys and reduced whole-body protein turnover and protein breakdown.These results imply that the lower maternal N retention observed in lactating sows fed improved AA balance diets in previous studies may be a result of greater partitioning of AA towards milk rather than greater body protein breakdown.

Estimating the grain size of microgranular material using laser-induced breakdown spectroscopy combined with machine learning algorithms

Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piecewise univariate model must be constructed to estimate grain size due to the complex dependence of the plasma formation environment on grain size.In the present work,we tentatively construct a unified calibration model suitable for LIBS-based estimation of those grain sizes.Specifically,two unified multivariate calibration models are constructed based on back-propagation neural network(BPNN)algorithms using feature selection strategies with and without considering prior information.By detailed analysis of the performances of the two multivariate models,it was found that a unified calibration model can be successfully constructed based on BPNN algorithms for estimating the grain size in the range of tens to hundreds of micrometers.It was also found that the model constructed with a priorguided feature selection strategy had better prediction performance.This study has practical significance in developing the technology for material analysis using LIBS,especially when the LIBS signal exhibits a complex dependence on the material parameter to be estimated.

Phase field model for electric-thermal coupled discharge breakdown of polyimide nanocomposites under high frequency electrical stress

In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of Polyimide(PI) composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of Joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.

Characteristics of laser-induced breakdown spectroscopy of liquid slag

Rapid online analysis of liquid slag is essential for optimizing the quality and energy efficiency of steel production. To investigate the key factors that affect the online measurement of refined slag using laser-induced breakdown spectroscopy(LIBS), this study examined the effects of slag composition and temperature on the intensity and stability of the LIBS spectra. The experimental temperature was controlled at three levels: 1350℃, 1400℃, and 1450℃. The results showed that slag composition and temperature significantly affected the intensity and stability of the LIBS spectra. Increasing the Fe content and temperature in the slag reduces its viscosity, resulting in an enhanced intensity and stability of the LIBS spectra. Additionally, 42 refined slag samples were quantitatively analyzed for Fe, Si, Ca, Mg, Al, and Mn at 1350℃, 1400℃, and 1450℃.The normalized full spectrum combined with partial least squares(PLS) quantification modeling was used, using the Ca Ⅱ 317.91 nm spectral line as an internal standard. The results show that using the internal standard normalization method can significantly reduce the influence of spectral fluctuations. Meanwhile, a temperature of 1450℃ has been found to yield superior results compared to both 1350℃ and 1400℃, and it is advantageous to conduct a quantitative analysis of the slag when it is in a “water-like” state with low viscosity.

Integrated Experimental and Simulation Investigation of Breakdown Voltage Characteristics Across Electrode Configurations in SF_(6) Circuit Breakers

This study investigates the breakdown voltage characteristics in sulfur hexafluoride(SF6)circuit breakers,employing a novel approach that integrates both experimental investigations and finite element simulations.Utilizing a sphere-sphere electrode configuration,we meticulously measured the relationship between breakdown voltage and electrode gap distances ranging from 1 cm to 4.5 cm.Subsequent simulations,conducted using COMSOL Multiphysics,mirrored the experimental setup to validate the model’s accuracy through a comparison of the breakdown voltage-electrode gap distance curves.The simulation results not only aligned closely with the experimental data but also allowed the extraction of detailed electric field strength,electric potential contours,and electric current flow curves at the breakdown voltage for gap distances extending from 1 to 4.5 cm.Extending the analysis,the study explored the electric field and potential distribution at a constant voltage of 72.5 kV for gap distances between 1 to 10 cm,identifying the maximum electric field strength.A comprehensive comparison of five different electrode configurations(sphere-sphere,sphere-rod,sphere-plane,rod-plane,rod-rod)at 72.5 kV and a gap distance of 1.84 cm underscored the significant influence of electrode geometry on the breakdown process.Moreover,the research contrasts the breakdown voltage in SF6 with that in air,emphasizing SF6’s superior insulating properties.This investigation not only elucidates the intricate dynamics of electrical breakdown in SF6 circuit breakers but also contributes valuable insights into the optimal electrode configurations and the potential for alternative insulating gases,steering future advancements in high-voltage circuit breaker technology.

交通流Breakdown现象与交通扰动演化模型

建立了用以间接证明交通流自发breakdown现象的交通扰动演化模型.基于跟车思想制定了"继承"和"改变"两种车辆行驶规则;基于交通波动理论刻画了车辆经历扰动的减速波和加速波,并结合到达车流的车头时距分布,建立了扰动演化模型.模型考虑了"迟滞"现象和"二次扰动"现象,采用蒙特卡罗方法进行数值模拟,对比了五种形式的breakdown概率,分析了模型中重要参数对计算结果的影响及原因.

On-State Breakdown Model for High Voltage RESURF LDMOS

An analytical breakdown model under on state condition for high voltage RESURF LDMOS is proposed.The model considers the drift velocity saturation of carriers and influence of parasitic bipolar transistor.As a result,electric field profile of n drift in LDMOS at on state is obtained.Based on this model,the electric SOA of LDMOS can be determined.The analytical results partially fit to our numerical (by MEDICI) and experiment results.This model is an aid to understand the device physics during on state accurately and it also directs high voltage LDMOS design.

Breakdown Voltage and Charge to Breakdown Investigation of Gate Oxide of 0.18μm Dual Gate CMOS Process with Different Measurement Methods

Breakdown voltage （Vbd） and charge to breakdown （Qbd） are two parameters often used to evaluate gate oxide reliability. In this paper,we investigate the effects of measurement methods on Vbd and Qbd of the gate oxide of a 0.18μm dual gate CMOS process. Voltage ramps （V-ramp） and current ramps （J-ramp） are used to evaluate gate oxide reliability. The thin and thick gate oxides are all evaluated in the accumulation condition. Our experimental results show that the measurement methods affect Vbd only slightly but affect Qbd seriously,as do the measurement conditions.This affects the I-t curves obtained with the J-ramp and V-ramp methods. From the I-t curve,it can be seen that Qbd obtained using a J-ramp is much bigger than that with a V-ramp. At the same time, the Weibull slopes of Qbd are definitely smaller than those of Vbd. This means that Vbd is more reliable than Qbd, Thus we should be careful to use Qbd to evaluate the reliability of 0.18μm or beyond CMOS process gate oxide.

Improved Breakdown Voltage of Partially Depleted SOI nMOSFETs with Half-Back-Channel Implantation

FB （floating-body） and BC （body-contact） partially depleted SOI nMOSFETs with HBC（half-back-channel） implantation are fabricated. Test results show that such devices have good performance in delaying the occurrence of the “kink” phenomenon and improving the breakdown voltage as compared to conventional PDSOI nMOS- FETs,while not decreasing the threshold voltage of the back gate obviously. Numerical simulation shows that a reduced electrical field in the drain contributes to the improvement of the breakdown voltage and a delay of the “kink” effect. A detailed analysis is given for the cause of such improvement of breakdown voltage and the delay of the “kink” effect.

Off-State Breakdown Characteristics of Body-Tied Partial-Depleted SOI nMOS Devices

Partial-depleted SOI(silicon on insulator) nMOS devices are fabricated with and without silicide technology,respectively.Off-state breakdown characteristics of these devices are presented with and without body contact,respectively.By means of two-dimension(2D) device simulation and measuring junction breakdown of the drain and the body,the difference and limitation of the breakdown characteristics of devices with two technologies are analyzed and explained in details.Based on this,a method is proposed to improve off-state breakdown characteristics of PDSOI nMOS devices.

A High Breakdown Voltage Thin SOI Device with a Vertically Linearly Graded Concentration Drift Region

As the thickness of an SOI layer varies,a minimum breakdown voltage is reached when the thickness is about 2μm. The vertical electric field of the SOI LDMOS with a drift region which is vertically linearly graded is constant. The vertically linearly graded concentration drift can be achieved by impurity implanting followed by thermal diffusion. In this way,the vertical breakdown voltage of SOI LDMOS with 2μm thickness SOI layer can be improved by 43%. The on-state resistance is lowered by 24 % because of the higher impurity concentration of the SOI surface.

Unified Breakdown Model of SOI RESURF Device with Uniform/Step/Linear Doping Profile

A unified breakdown model of SOI RESURF device with uniform,step,or linear drift region doping profile is firstly proposed.By the model,the electric field distribution and breakdown voltage are researched in detail for the step numbers from 0 to infinity.The critic electric field as the function of the geometry parameters and doping profile is derived.For the thick film device,linear doping profile can be replaced by a single or two steps doping profile in the drift region due to a considerable uniformly lateral electric field,almost ideal breakdown voltage,and simplified design and fabrication.The availability of the proposed model is verified by the good accordance among the analytical results,numerical simulations,and reported experiments.

Realizing High Breakdown Voltage SJ-LDMOS on Bulk Silicon Using a Partial n-Buried Layer

A new design concept is proposed to eliminate the substrate-assisted depletion effect that significantly degrades the breakdown voltage （BV） of conventional super junction-LDMOS. The key feature of the new concept is that a partial buried layer is implemented which compensates for the charge interaction between the p-substrate and SJ region,realizing high breakdown voltage and low on-resistance. Numerical simulation results indicate that the proposed device features high breakdown voltage,low on-resistance,and reduced sensitivity to doping imbalance in the pillars. In addition, the proposed device is compatible with smart power technology.

Analytical Model of Surface Field Distribution and Breakdown Voltage for RESURF LDMOS Transistor

An analytical model of the surface field distribution and breakdown voltage of the reduced surface field lateral double diffusion MOS transistor is proposed.Based on the 2-D Poisson's equation solution,the derived model gives the closed form solutions of the surface potential and electrical field distributions as a function of the structure parameters and drain bias.A criterion for obtaining the optimal trade-off between the breakdown voltage and on-resistance is also presented to serve to quantify the maximum breakdown voltage and optimal relations of all design parameters.Analytical results are shown in good agreement with the numerical analysis obtained by the semiconductor device simulator MEDICI and previous reported experimental data.