To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the ...To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the effectiveness of flexibility management strategies under different climate conditions and extreme weather events.Using both typical and extreme weather data from cities in five major climate zones of China,this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies in the context of different climates.The results show that the peak load flexibility and overall energy performance of the three short-term strategies were affected by the surrounding climate conditions.The peak load reduction rate of the pre-cooling and zone temperature reset strategies declined linearly as outdoor temperature increased.Under extreme climate conditions,the daily peak-load time was found to be over two hours earlier than under typical conditions,and the intensive solar radiation found in the extreme conditions can weaken the correlation between peak load reduction and outdoor temperature,risking the ability of a building’s HVAC system to maintain a comfortable indoor environment.展开更多
The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures ...The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures and winter(October-March)daily minimum temperatures on blood pressure and lipid profiles across government staff,com-pany employees,and researchers.We examined 209,477 physical examination records from a physical examination center in the First Affiliated Hospital of USTC from 2017 to 2021.Employing a segmented regression model within the frame-work of generalized linear regression(GLM),we examined the causal impact of extreme temperatures on health outcomes.Additionally,sensitivity analyses were conducted via distributed lag nonlinear models(DLNMs),with a focus on ob-serving the long-term effects over a period of 21 days.Our findings indicate that government staff face increased health risks during extremely low temperatures,regardless of the season.Compared with participants experiencing median tem-peratures,government staff exposed to extremely low temperatures(below the 10th percentile,below 24℃)in the sum-mer presented maximum increases of 2.32 mmHg(95%CI:1.542-3.098)in diastolic blood pressure and 6.481 mmHg(95%CI:5.368-7.594)in systolic blood pressure.In winter,government staff exposed to temperatures below the 10th per-centile(below 1℃)demonstrated maximum increases of 0.278 mmol/L(95%CI:0.210-0.346)in total cholesterol,0.153 mmol/L(95%CI:0.032-0.274)in triglycerides,and 0.077 mmol/L(95%CI:0.192-0.134)in low-density lipoprotein.Conversely,warm winters benefit company employees,whereas researchers exhibit lower sensitivity to temperature changes in winter.The maximum temperatures in summer and minimum temperatures in winter had greater impacts on in-dividuals.Small temperature fluctuations impact health more than large changes do.Notably,both the maximum and min-imum temperatures were better predictors of health outcomes than the daily average temperature was.Blood pressure con-sistently displayed significant associations with temperature across all three groups,with extremely low temperatures in-creasing the risk and extremely high temperatures reducing it.However,the relationship between temperature and blood lipids is complex.展开更多
Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties w...Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties will be affected by extreme conditions.Understanding the behaviour of solder joints under extreme conditions is vital to determine the durability and reliability of solder joint.This review paper aims to comprehensively explore the underlying failure mechanism affecting solder joint reliability under extreme conditions.This study covers an in-depth analysis of effect extreme temperature,mechanical stress,and radiation conditions towards solder joint.Impact of each condition to the microstructure including solder matrix and intermetallic compound layer,and mechanical properties such as fatigue,shear strength,creep,and hardness was thoroughly discussed.The failure mechanisms were illustrated in graphical diagrams to ensure clarity and understanding.Furthermore,the paper highlighted mitigation strategies that enhancing solder joint reliability under challenging operating conditions.The findings offer valuable guidance for researchers,engineers,and practitioners involved in electronics,engineering,and related fields,fostering advancements in solder joint reliability and performance.展开更多
In this study, the influence of opening parameters on the ultimate strength of perforated plates subjected to extreme cyclic loading in the presence of material kinematic hardening and isotro pic hardening was analyze...In this study, the influence of opening parameters on the ultimate strength of perforated plates subjected to extreme cyclic loading in the presence of material kinematic hardening and isotro pic hardening was analyzed. It is found that the ultimate strength of the perforated plates decreases rapidly and stabilizes in the first four cycles. Plates with oblong openings have a greater ultimate strength compared to plates with rectangular openings, while the relative strengthening ratio decreases over the duration of the cycle. The location of the openings is also an important parameter that affects the strength of the structure, as the plates with openings close to the edges in the longitudinal direction have higher strengths, while in the transverse direction the strengths are higher when the openings are close to the center. Among the three opening-strengthening methods compared, the Carling stiffener method maintains a better strengthening effect under cyclic loads for many periods.展开更多
This paper investigates methods of value-at-risk (VaR) estimation using extreme value theory (EVT). It compares two different estimation methods, 'two-step subsample bootstrap' based on moment estimation and m...This paper investigates methods of value-at-risk (VaR) estimation using extreme value theory (EVT). It compares two different estimation methods, 'two-step subsample bootstrap' based on moment estimation and maximum likelihood estimation (MLE), according to their theoretical bases and computation procedures. Then, the estimation results are analyzed together with those of normal method and empirical method. The empirical research of foreign exchange data shows that the EVT methods have good characters in estimating VaR under extreme conditions and 'two-step subsample bootstrap' method is preferable to MLE.展开更多
This paper analyzed the extreme climatic characteristics of maize in Heilongjiang Province during different growth periods using the climate data and maize yield data from 1961 to 2020,and applied the principal compon...This paper analyzed the extreme climatic characteristics of maize in Heilongjiang Province during different growth periods using the climate data and maize yield data from 1961 to 2020,and applied the principal component analysis to analyze the extent of different extreme climatic events affecting maize yield.The results showed that the extreme cold events showed a decreasing trend,and the extreme warm events showed an increasing trend,and the trend of extreme precipitation change was not obvious.Maize yield was negatively correlated with TN10p(cold nights),TX10p(warm days)and T8(days below the lower temperature limit),and positively correlated with TN90p(warm nights).T34(days above the upper temperature limit)and TX90p(warm days)during the tasseling-milking period were negatively correlated with the maize yield,and this part was concentrated in the southern part of Heilongjiang Province.The maize yield was positively correlated with the extreme precipitation during the seedling period and negatively correlated with the extreme precipitation during the filling-maturity period of maize,but the correlations were not significant.The effects of extreme weather events on maize yield were higher during the seedling and the filling-maturity periods than those during the jointing-tasseling and the tasseling-milking periods.The effects of extreme precipitation on the maize yield were less than those of the extreme temperature during different growth periods in all regions,but the effects of the extreme precipitation on maize yield were significantly higher in the Songnen Plain than those in other regions.There were regional differences in the impact of climate extremes on maize during different growth periods.The area with the greater impact of climate extremes during the seedling period was the Songnen Plain,the areas with the greater impact of climate extremes during the jointing-tasseling period were the northern part of the Sanjiang Plain,and the areas with the greater impact of climate extremes during the filling-maturity period were the Lesser Khingan Mountains and the semi-mountainous areas of Mudanjiang.展开更多
Rock burst is a kind of geological disaster in rock excavation of high stress areas.To evaluate intensity of rock burst,the maximum shear stress,uniaxial compressive strength,uniaxial tensile strength and rock elastic...Rock burst is a kind of geological disaster in rock excavation of high stress areas.To evaluate intensity of rock burst,the maximum shear stress,uniaxial compressive strength,uniaxial tensile strength and rock elastic energy index were selected as input factors,and burst pit depth as output factor.The rock burst prediction model was proposed according to the genetic algorithms and extreme learning machine.The effect of structural surface was taken into consideration.Based on the engineering examples of tunnels,the observed and collected data were divided into the training set,validation set and prediction set.The training set and validation set were used to train and optimize the model.Parameter optimization results are presented.The hidden layer node was450,and the fitness of the predictions was 0.0197 under the optimal combination of the input weight and offset vector.Then,the optimized model is tested with the prediction set.Results show that the proposed model is effective.The maximum relative error is4.71%,and the average relative error is 3.20%,which proves that the model has practical value in the relative engineering.展开更多
A method for fast 1-fold cross validation is proposed for the regularized extreme learning machine （RELM）. The computational time of fast l-fold cross validation increases as the fold number decreases, which is oppo...A method for fast 1-fold cross validation is proposed for the regularized extreme learning machine （RELM）. The computational time of fast l-fold cross validation increases as the fold number decreases, which is opposite to that of naive 1-fold cross validation. As opposed to naive l-fold cross validation, fast l-fold cross validation takes the advantage in terms of computational time, especially for the large fold number such as l 〉 20. To corroborate the efficacy and feasibility of fast l-fold cross validation, experiments on five benchmark regression data sets are evaluated.展开更多
Factors for determining the spindle size are the shaft diameter, positions of bearing and motor, and entire length of the spindle. Then, it is important to find the assembling of the optimal design variables, which sa...Factors for determining the spindle size are the shaft diameter, positions of bearing and motor, and entire length of the spindle. Then, it is important to find the assembling of the optimal design variables, which satisfy the stiffimss and rotational speed required to the spindle. A general full factorial design method was used to verify some factors that affect the natural frequency of a spindle. It is verified that the shorter shaft length and bearing span length represent the higher natural frequency, and there are some effects according to the change in the levels of factors. The detailed spindle dimension is determined by applying an EVD method, which can define the optimal bearing position through considering the limiting condition. Based on the estimated regression model, the optimal spindle size and bearing distance that can improve the primary natural frequency are obtained, and the influence of design factors on the natural frequency is also analyzed.展开更多
Wetting condition of micro/nanostructured surface has received tremendous attention due to the potential applications in commercial,industrial,and military areas.Surfaces with extreme wetting properties,e.g.,superhydr...Wetting condition of micro/nanostructured surface has received tremendous attention due to the potential applications in commercial,industrial,and military areas.Surfaces with extreme wetting properties,e.g.,superhydrophobic or superhydrophilic,are extensively employed due to their superior anti-icing,drag reduction,enhanced boiling heat transfer,self-cleaning,and anti-bacterial properties depending on solid-liquid interfacial interactions.Laser-based techniques have gained popularity in recent years to create micro/nano-structured surface owing to their high flexibility,system precision,and ease for automation.These techniques create laser induced periodic surface structures(LIPSS)or hierarchical structures on substrate material.However,micro/nanostructures alone cannot attain the desired wettability.Subsequent modification of surface chemistry is essentially needed to achieve target extreme wettability.This review paper aims to provide a comprehensive review for both laser texturing techniques and the following chemistry modification methods.Recent research progress and fundamental mechanisms of surface structure generation via different types of lasers and various chemistry modification methods are discussed.The complex combination between the laser texturing and surface chemistry modification methods to decide the final wetting condition is presented.More importantly,surface functionalities of these surfaces with extreme wetting properties are discussed.Lastly,prospects for future research are proposed and discussed.展开更多
Projectiles made of reactive structure materials(RSM)can damage the target with not only kinetic but also chemical energy,but the enhanced damage potential of RSM may become compromised if extreme loading condition di...Projectiles made of reactive structure materials(RSM)can damage the target with not only kinetic but also chemical energy,but the enhanced damage potential of RSM may become compromised if extreme loading condition disintegrates the projectile before the target is reached.In this work,a ductile coating of Ni was introduced to a tungsten-zirconium(W-Zr)alloy,a typical brittle RSM,to preserve the damage potential of the projectile.Detonation driving tests were carried out with X-ray photography and gunpowder deflagration driving tests were carried out with high-speed photography for the coated and uncoated RSM samples,respectively.The craters on the witness target were analyzed by scanning electron microscopy and X-ray diffraction.The Ni coating was found to effectively preserve the damage potential of the W-Zr alloy under extreme loading conditions,whereas the uncoated sample fractured and ignited before impacting the target in both detonation and deflagration driving.The crack propagation between the reactively brittle core and the ductile coating was analyzed based on the crack arrest theory to mechanistically demonstrate how the coating improves the structural integrity and preserves the damage potential of the projectile.Specifically,the Ni coating envelops theW-Zr core until the coated sphere penetrates the target,and the coating is then eroded and worn to release the reactive core for the projectile to damage the target more intensively.展开更多
The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the ...The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate.展开更多
The effects of introducing M.sedula derivatives having different Cu^2+-resistance on bioleaching capacity of a defined consortium(consisting of A.brierleyi DSM1651 and M.hakonensis HO1-1)were studied in column reactor...The effects of introducing M.sedula derivatives having different Cu^2+-resistance on bioleaching capacity of a defined consortium(consisting of A.brierleyi DSM1651 and M.hakonensis HO1-1)were studied in column reactors at 70℃.Introducing M.sedula copA mutant,a copper sensitive derivative,only had negligible effects on bioleaching.While introducing M.sedula ARS50-2,a Cu^2+resistant strain,substantially consolidated bioleaching process,with 27.77%more copper recovered after 58 d of bioleaching.Addition of M.sedula ARS50-2 likely enhanced the sulfur oxidation capacity of consortium after the 24th day under the Cu^2+stress.The majority of extreme thermoacidophiles were attached on minerals surface as indicated by quantitative PCR(qPCR)data.Successions of microbial community of extremely thermoacidophilic consortia that attached on surface of minerals were different from those in leachate.M.hakonensis HO1-1 was the dominant species attached on minerals surface in each column reactor throughout bioleaching process.The sessile M.sedula ARS50-2 remained as a major species till the 34th day.A.brierleyi DSM1651 was the most abundant planktonic species in leachate of each column reactor.These results highlight that higher Cu^2+-resistance is a beneficial trait for extreme thermoacidophiles to process copper minerals.展开更多
Extreme learning machine(ELM)has been proved to be an effective pattern classification and regression learning mechanism by researchers.However,its good performance is based on a large number of hidden layer nodes.Wit...Extreme learning machine(ELM)has been proved to be an effective pattern classification and regression learning mechanism by researchers.However,its good performance is based on a large number of hidden layer nodes.With the increase of the nodes in the hidden layers,the computation cost is greatly increased.In this paper,we propose a novel algorithm,named constrained voting extreme learning machine(CV-ELM).Compared with the traditional ELM,the CV-ELM determines the input weight and bias based on the differences of between-class samples.At the same time,to improve the accuracy of the proposed method,the voting selection is introduced.The proposed method is evaluated on public benchmark datasets.The experimental results show that the proposed algorithm is superior to the original ELM algorithm.Further,we apply the CV-ELM to the classification of superheat degree(SD)state in the aluminum electrolysis industry,and the recognition accuracy rate reaches87.4%,and the experimental results demonstrate that the proposed method is more robust than the existing state-of-the-art identification methods.展开更多
Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock ma...Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.展开更多
Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and tr...Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and transmission electron microscope,with the size of 20−60 nm,the number of more than 30 in each cell at average,which indicated that F.thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain.Intriguingly,the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis,suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals.Moreover,under the different energy source culture conditions of FeSO4 and CuFeS2,the size and the morphology of the nanocrystals are different.It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential(ORP)leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size,which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F.thermophilum by iron and ORP gradient culture.展开更多
As a new neural network model,extreme learning machine(ELM)has a good learning rate and generalization ability.However,ELM with a single hidden layer structure often fails to achieve good results when faced with large...As a new neural network model,extreme learning machine(ELM)has a good learning rate and generalization ability.However,ELM with a single hidden layer structure often fails to achieve good results when faced with large-scale multi-featured problems.To resolve this problem,we propose a multi-layer framework for the ELM learning algorithm to improve the model’s generalization ability.Moreover,noises or abnormal points often exist in practical applications,and they result in the inability to obtain clean training data.The generalization ability of the original ELM decreases under such circumstances.To address this issue,we add model bias and variance to the loss function so that the model gains the ability to minimize model bias and model variance,thus reducing the influence of noise signals.A new robust multi-layer algorithm called ML-RELM is proposed to enhance outlier robustness in complex datasets.Simulation results show that the method has high generalization ability and strong robustness to noise.展开更多
The main aim of this research is to get a better knowledge and understanding of the micro-scale oscillatory networks behavior in the solid propellants reactionary zones. Fundamental understanding of the micro-and nano...The main aim of this research is to get a better knowledge and understanding of the micro-scale oscillatory networks behavior in the solid propellants reactionary zones. Fundamental understanding of the micro-and nano-scale combustion mechanisms is essential to the development and further improvement of the next-generation technologies for extreme control of the solid propellant thrust. Both experiments and theory confirm that the micro-and nano-scale oscillatory networks excitation in the solid propellants reactionary zones is a rather universal phenomenon. In accordance with our concept,the micro-and nano-scale structures form both the fractal and self-organized wave patterns in the solid propellants reactionary zones. Control by the shape, the sizes and spacial orientation of the wave patterns allows manipulate by the energy exchange and release in the reactionary zones. A novel strategy for enhanced extreme thrust control in solid propulsion systems are based on manipulation by selforganization of the micro-and nano-scale oscillatory networks and self-organized patterns formation in the reactionary zones with use of the system of acoustic waves and electro-magnetic fields, generated by special kind of ring-shaped electric discharges along with resonance laser radiation. Application of special kind of the ring-shaped electric discharges demands the minimum expenses of energy and opens prospects for almost inertia-free control by combustion processes. Nano-sized additives will enhance self-organizing and self-synchronization of the micro-and nano-scale oscillatory networks on the nanometer scale. Suggested novel strategy opens the door for completely new ways for enhanced extreme thrust control of the solid propulsion systems.展开更多
基金National Key R&D Program of China of the 13th Five-Year Plan(No.2018YFD1100704)。
文摘To meet the challenge of mismatches between power supply and demand,modern buildings must schedule flexible energy loads in order to improve the efficiency of power grids.Furthermore,it is essential to understand the effectiveness of flexibility management strategies under different climate conditions and extreme weather events.Using both typical and extreme weather data from cities in five major climate zones of China,this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies in the context of different climates.The results show that the peak load flexibility and overall energy performance of the three short-term strategies were affected by the surrounding climate conditions.The peak load reduction rate of the pre-cooling and zone temperature reset strategies declined linearly as outdoor temperature increased.Under extreme climate conditions,the daily peak-load time was found to be over two hours earlier than under typical conditions,and the intensive solar radiation found in the extreme conditions can weaken the correlation between peak load reduction and outdoor temperature,risking the ability of a building’s HVAC system to maintain a comfortable indoor environment.
基金supported by the National Natural Science Foundation of China(72072169)the Fundamental Re-search Funds for the Central Universities(YD2040002015).
文摘The impact of extreme temperatures on the health of individuals in different organizations remains uncertain.We employed stratified analyses to examine the impacts of summer(April-September)daily maximum temperatures and winter(October-March)daily minimum temperatures on blood pressure and lipid profiles across government staff,com-pany employees,and researchers.We examined 209,477 physical examination records from a physical examination center in the First Affiliated Hospital of USTC from 2017 to 2021.Employing a segmented regression model within the frame-work of generalized linear regression(GLM),we examined the causal impact of extreme temperatures on health outcomes.Additionally,sensitivity analyses were conducted via distributed lag nonlinear models(DLNMs),with a focus on ob-serving the long-term effects over a period of 21 days.Our findings indicate that government staff face increased health risks during extremely low temperatures,regardless of the season.Compared with participants experiencing median tem-peratures,government staff exposed to extremely low temperatures(below the 10th percentile,below 24℃)in the sum-mer presented maximum increases of 2.32 mmHg(95%CI:1.542-3.098)in diastolic blood pressure and 6.481 mmHg(95%CI:5.368-7.594)in systolic blood pressure.In winter,government staff exposed to temperatures below the 10th per-centile(below 1℃)demonstrated maximum increases of 0.278 mmol/L(95%CI:0.210-0.346)in total cholesterol,0.153 mmol/L(95%CI:0.032-0.274)in triglycerides,and 0.077 mmol/L(95%CI:0.192-0.134)in low-density lipoprotein.Conversely,warm winters benefit company employees,whereas researchers exhibit lower sensitivity to temperature changes in winter.The maximum temperatures in summer and minimum temperatures in winter had greater impacts on in-dividuals.Small temperature fluctuations impact health more than large changes do.Notably,both the maximum and min-imum temperatures were better predictors of health outcomes than the daily average temperature was.Blood pressure con-sistently displayed significant associations with temperature across all three groups,with extremely low temperatures in-creasing the risk and extremely high temperatures reducing it.However,the relationship between temperature and blood lipids is complex.
基金fully supported by a Tabung Amanah Pusat Pengurusan Penyelidikan&Inovasi(PPPI)(Grant No.PS060-UPNM/2023/GPPP/SG/1)Universiti Pertahanan Nasional Malaysia(UPNM)for funding this study。
文摘Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties will be affected by extreme conditions.Understanding the behaviour of solder joints under extreme conditions is vital to determine the durability and reliability of solder joint.This review paper aims to comprehensively explore the underlying failure mechanism affecting solder joint reliability under extreme conditions.This study covers an in-depth analysis of effect extreme temperature,mechanical stress,and radiation conditions towards solder joint.Impact of each condition to the microstructure including solder matrix and intermetallic compound layer,and mechanical properties such as fatigue,shear strength,creep,and hardness was thoroughly discussed.The failure mechanisms were illustrated in graphical diagrams to ensure clarity and understanding.Furthermore,the paper highlighted mitigation strategies that enhancing solder joint reliability under challenging operating conditions.The findings offer valuable guidance for researchers,engineers,and practitioners involved in electronics,engineering,and related fields,fostering advancements in solder joint reliability and performance.
文摘In this study, the influence of opening parameters on the ultimate strength of perforated plates subjected to extreme cyclic loading in the presence of material kinematic hardening and isotro pic hardening was analyzed. It is found that the ultimate strength of the perforated plates decreases rapidly and stabilizes in the first four cycles. Plates with oblong openings have a greater ultimate strength compared to plates with rectangular openings, while the relative strengthening ratio decreases over the duration of the cycle. The location of the openings is also an important parameter that affects the strength of the structure, as the plates with openings close to the edges in the longitudinal direction have higher strengths, while in the transverse direction the strengths are higher when the openings are close to the center. Among the three opening-strengthening methods compared, the Carling stiffener method maintains a better strengthening effect under cyclic loads for many periods.
基金the National Natural Science Foundation of China (No. 79970041).
文摘This paper investigates methods of value-at-risk (VaR) estimation using extreme value theory (EVT). It compares two different estimation methods, 'two-step subsample bootstrap' based on moment estimation and maximum likelihood estimation (MLE), according to their theoretical bases and computation procedures. Then, the estimation results are analyzed together with those of normal method and empirical method. The empirical research of foreign exchange data shows that the EVT methods have good characters in estimating VaR under extreme conditions and 'two-step subsample bootstrap' method is preferable to MLE.
基金Supported by the"Thirteenth Five-Year"Key Research and Development Project Sub-project"Integration and Demonstration of Spring Maize Solar and Hot Water Resources Utilization Technology in Humid Areas of Heilongjiang Province"(2018YFD0300103-1)。
文摘This paper analyzed the extreme climatic characteristics of maize in Heilongjiang Province during different growth periods using the climate data and maize yield data from 1961 to 2020,and applied the principal component analysis to analyze the extent of different extreme climatic events affecting maize yield.The results showed that the extreme cold events showed a decreasing trend,and the extreme warm events showed an increasing trend,and the trend of extreme precipitation change was not obvious.Maize yield was negatively correlated with TN10p(cold nights),TX10p(warm days)and T8(days below the lower temperature limit),and positively correlated with TN90p(warm nights).T34(days above the upper temperature limit)and TX90p(warm days)during the tasseling-milking period were negatively correlated with the maize yield,and this part was concentrated in the southern part of Heilongjiang Province.The maize yield was positively correlated with the extreme precipitation during the seedling period and negatively correlated with the extreme precipitation during the filling-maturity period of maize,but the correlations were not significant.The effects of extreme weather events on maize yield were higher during the seedling and the filling-maturity periods than those during the jointing-tasseling and the tasseling-milking periods.The effects of extreme precipitation on the maize yield were less than those of the extreme temperature during different growth periods in all regions,but the effects of the extreme precipitation on maize yield were significantly higher in the Songnen Plain than those in other regions.There were regional differences in the impact of climate extremes on maize during different growth periods.The area with the greater impact of climate extremes during the seedling period was the Songnen Plain,the areas with the greater impact of climate extremes during the jointing-tasseling period were the northern part of the Sanjiang Plain,and the areas with the greater impact of climate extremes during the filling-maturity period were the Lesser Khingan Mountains and the semi-mountainous areas of Mudanjiang.
基金Project(2013CB036004)supported by the National Basic Research Program of ChinaProject(51378510)supported by the National Natural Science Foundation of China
文摘Rock burst is a kind of geological disaster in rock excavation of high stress areas.To evaluate intensity of rock burst,the maximum shear stress,uniaxial compressive strength,uniaxial tensile strength and rock elastic energy index were selected as input factors,and burst pit depth as output factor.The rock burst prediction model was proposed according to the genetic algorithms and extreme learning machine.The effect of structural surface was taken into consideration.Based on the engineering examples of tunnels,the observed and collected data were divided into the training set,validation set and prediction set.The training set and validation set were used to train and optimize the model.Parameter optimization results are presented.The hidden layer node was450,and the fitness of the predictions was 0.0197 under the optimal combination of the input weight and offset vector.Then,the optimized model is tested with the prediction set.Results show that the proposed model is effective.The maximum relative error is4.71%,and the average relative error is 3.20%,which proves that the model has practical value in the relative engineering.
基金supported by the National Natural Science Foundation of China(51006052)the NUST Outstanding Scholar Supporting Program
文摘A method for fast 1-fold cross validation is proposed for the regularized extreme learning machine （RELM）. The computational time of fast l-fold cross validation increases as the fold number decreases, which is opposite to that of naive 1-fold cross validation. As opposed to naive l-fold cross validation, fast l-fold cross validation takes the advantage in terms of computational time, especially for the large fold number such as l 〉 20. To corroborate the efficacy and feasibility of fast l-fold cross validation, experiments on five benchmark regression data sets are evaluated.
基金Project(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE) of Korea
文摘Factors for determining the spindle size are the shaft diameter, positions of bearing and motor, and entire length of the spindle. Then, it is important to find the assembling of the optimal design variables, which satisfy the stiffimss and rotational speed required to the spindle. A general full factorial design method was used to verify some factors that affect the natural frequency of a spindle. It is verified that the shorter shaft length and bearing span length represent the higher natural frequency, and there are some effects according to the change in the levels of factors. The detailed spindle dimension is determined by applying an EVD method, which can define the optimal bearing position through considering the limiting condition. Based on the estimated regression model, the optimal spindle size and bearing distance that can improve the primary natural frequency are obtained, and the influence of design factors on the natural frequency is also analyzed.
基金Project(52105175)supported by the National Natural Science Foundation of ChinaProject(BK20210235)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(JSSCBS20210121)supported by the Jiangsu Provincial Innovative and Entrepreneurial Doctor Program,China。
文摘Wetting condition of micro/nanostructured surface has received tremendous attention due to the potential applications in commercial,industrial,and military areas.Surfaces with extreme wetting properties,e.g.,superhydrophobic or superhydrophilic,are extensively employed due to their superior anti-icing,drag reduction,enhanced boiling heat transfer,self-cleaning,and anti-bacterial properties depending on solid-liquid interfacial interactions.Laser-based techniques have gained popularity in recent years to create micro/nano-structured surface owing to their high flexibility,system precision,and ease for automation.These techniques create laser induced periodic surface structures(LIPSS)or hierarchical structures on substrate material.However,micro/nanostructures alone cannot attain the desired wettability.Subsequent modification of surface chemistry is essentially needed to achieve target extreme wettability.This review paper aims to provide a comprehensive review for both laser texturing techniques and the following chemistry modification methods.Recent research progress and fundamental mechanisms of surface structure generation via different types of lasers and various chemistry modification methods are discussed.The complex combination between the laser texturing and surface chemistry modification methods to decide the final wetting condition is presented.More importantly,surface functionalities of these surfaces with extreme wetting properties are discussed.Lastly,prospects for future research are proposed and discussed.
基金National Natural Science Foundation of China.Grant ID:11872123.
文摘Projectiles made of reactive structure materials(RSM)can damage the target with not only kinetic but also chemical energy,but the enhanced damage potential of RSM may become compromised if extreme loading condition disintegrates the projectile before the target is reached.In this work,a ductile coating of Ni was introduced to a tungsten-zirconium(W-Zr)alloy,a typical brittle RSM,to preserve the damage potential of the projectile.Detonation driving tests were carried out with X-ray photography and gunpowder deflagration driving tests were carried out with high-speed photography for the coated and uncoated RSM samples,respectively.The craters on the witness target were analyzed by scanning electron microscopy and X-ray diffraction.The Ni coating was found to effectively preserve the damage potential of the W-Zr alloy under extreme loading conditions,whereas the uncoated sample fractured and ignited before impacting the target in both detonation and deflagration driving.The crack propagation between the reactively brittle core and the ductile coating was analyzed based on the crack arrest theory to mechanistically demonstrate how the coating improves the structural integrity and preserves the damage potential of the projectile.Specifically,the Ni coating envelops theW-Zr core until the coated sphere penetrates the target,and the coating is then eroded and worn to release the reactive core for the projectile to damage the target more intensively.
基金Project(51178100)supported by the National Natural Science Foundation of ChinaProject(1105007001)supported by the Foundation of the Priority Academic Development Program of Higher Education Institute of Jiangsu Province,ChinaProject(3205001205)supported by the Teaching and Research Foundation for Excellent Young Teachers of Southeast University,China
文摘The extreme temperature differences in fiat steel box girder of a cable-stayed bridge were studied.Firstly,by using the long-term measurement data collected by the structural health monitoring system installed on the Runyang Cable-stayed Bridge,the daily variations as well as seasonal ones of measured temperature differences in the box girder cross-section area were summarized.The probability distribution models of temperature differences were further established and the extreme temperature differences were estimated with a return period of 100 years.Finally,the temperature difference models in cross-section area were proposed for bridge thermal design.The results show that horizontal temperature differences in top plate and vertical temperature differences between top plate and bottom plate are considerable.All the positive and negative temperature differences can be described by the weighted sum of two Weibull distributions.The maximum positive and negative horizontal temperature differences in top plate are 10.30 ℃ and -13.80 ℃,respectively.And the maximum positive and negative vertical temperature differences between top plate and bottom plate are 17.30 ℃ and-3.70 ℃,respectively.For bridge thermal design,there are two vertical temperature difference models between top plate and bottom plate,and six horizontal temperature difference models in top plate.
基金Project(207154)supported by the Postdoctoral Research Funding of Central South University,ChinaProjects(31470230,51320105006,51604308)supported by the National Natural Science Foundation of China+2 种基金Project(2017RS3003)supported by the Youth Talent Foundation of Hunan Province,ChinaProject(2018JJ2486)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2018WK2012)supported by the Key Research and Development Projects in Hunan Province,China。
文摘The effects of introducing M.sedula derivatives having different Cu^2+-resistance on bioleaching capacity of a defined consortium(consisting of A.brierleyi DSM1651 and M.hakonensis HO1-1)were studied in column reactors at 70℃.Introducing M.sedula copA mutant,a copper sensitive derivative,only had negligible effects on bioleaching.While introducing M.sedula ARS50-2,a Cu^2+resistant strain,substantially consolidated bioleaching process,with 27.77%more copper recovered after 58 d of bioleaching.Addition of M.sedula ARS50-2 likely enhanced the sulfur oxidation capacity of consortium after the 24th day under the Cu^2+stress.The majority of extreme thermoacidophiles were attached on minerals surface as indicated by quantitative PCR(qPCR)data.Successions of microbial community of extremely thermoacidophilic consortia that attached on surface of minerals were different from those in leachate.M.hakonensis HO1-1 was the dominant species attached on minerals surface in each column reactor throughout bioleaching process.The sessile M.sedula ARS50-2 remained as a major species till the 34th day.A.brierleyi DSM1651 was the most abundant planktonic species in leachate of each column reactor.These results highlight that higher Cu^2+-resistance is a beneficial trait for extreme thermoacidophiles to process copper minerals.
基金supported by the National Natural Science Foundation of China(6177340561751312)the Major Scientific and Technological Innovation Projects of Shandong Province(2019JZZY020123)。
文摘Extreme learning machine(ELM)has been proved to be an effective pattern classification and regression learning mechanism by researchers.However,its good performance is based on a large number of hidden layer nodes.With the increase of the nodes in the hidden layers,the computation cost is greatly increased.In this paper,we propose a novel algorithm,named constrained voting extreme learning machine(CV-ELM).Compared with the traditional ELM,the CV-ELM determines the input weight and bias based on the differences of between-class samples.At the same time,to improve the accuracy of the proposed method,the voting selection is introduced.The proposed method is evaluated on public benchmark datasets.The experimental results show that the proposed algorithm is superior to the original ELM algorithm.Further,we apply the CV-ELM to the classification of superheat degree(SD)state in the aluminum electrolysis industry,and the recognition accuracy rate reaches87.4%,and the experimental results demonstrate that the proposed method is more robust than the existing state-of-the-art identification methods.
基金Project(2010CB732101) supported by the National Basic Research Program of ChinaProjects(51079145,51379201) supported by the National Natural Science Foundation of China
文摘Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.
基金Project(2018JJ1041)supported by the Natural Science Foundation of Hunan,ChinaProjects(51774332,51934009,U1932129)supported by the National Natural Science Foundation of China。
文摘Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and transmission electron microscope,with the size of 20−60 nm,the number of more than 30 in each cell at average,which indicated that F.thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain.Intriguingly,the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis,suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals.Moreover,under the different energy source culture conditions of FeSO4 and CuFeS2,the size and the morphology of the nanocrystals are different.It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential(ORP)leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size,which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F.thermophilum by iron and ORP gradient culture.
基金Project(21878081)supported by the National Natural Science Foundation of ChinaProject(222201917006)supported by the Fundamental Research Funds for the Central Universities,China。
文摘As a new neural network model,extreme learning machine(ELM)has a good learning rate and generalization ability.However,ELM with a single hidden layer structure often fails to achieve good results when faced with large-scale multi-featured problems.To resolve this problem,we propose a multi-layer framework for the ELM learning algorithm to improve the model’s generalization ability.Moreover,noises or abnormal points often exist in practical applications,and they result in the inability to obtain clean training data.The generalization ability of the original ELM decreases under such circumstances.To address this issue,we add model bias and variance to the loss function so that the model gains the ability to minimize model bias and model variance,thus reducing the influence of noise signals.A new robust multi-layer algorithm called ML-RELM is proposed to enhance outlier robustness in complex datasets.Simulation results show that the method has high generalization ability and strong robustness to noise.
基金supported by the Western-Caucasus Research Center
文摘The main aim of this research is to get a better knowledge and understanding of the micro-scale oscillatory networks behavior in the solid propellants reactionary zones. Fundamental understanding of the micro-and nano-scale combustion mechanisms is essential to the development and further improvement of the next-generation technologies for extreme control of the solid propellant thrust. Both experiments and theory confirm that the micro-and nano-scale oscillatory networks excitation in the solid propellants reactionary zones is a rather universal phenomenon. In accordance with our concept,the micro-and nano-scale structures form both the fractal and self-organized wave patterns in the solid propellants reactionary zones. Control by the shape, the sizes and spacial orientation of the wave patterns allows manipulate by the energy exchange and release in the reactionary zones. A novel strategy for enhanced extreme thrust control in solid propulsion systems are based on manipulation by selforganization of the micro-and nano-scale oscillatory networks and self-organized patterns formation in the reactionary zones with use of the system of acoustic waves and electro-magnetic fields, generated by special kind of ring-shaped electric discharges along with resonance laser radiation. Application of special kind of the ring-shaped electric discharges demands the minimum expenses of energy and opens prospects for almost inertia-free control by combustion processes. Nano-sized additives will enhance self-organizing and self-synchronization of the micro-and nano-scale oscillatory networks on the nanometer scale. Suggested novel strategy opens the door for completely new ways for enhanced extreme thrust control of the solid propulsion systems.
