Real time remaining useful life(RUL) prediction based on condition monitoring is an essential part in condition based maintenance(CBM). In the current methods about the real time RUL prediction of the nonlinear degrad...Real time remaining useful life(RUL) prediction based on condition monitoring is an essential part in condition based maintenance(CBM). In the current methods about the real time RUL prediction of the nonlinear degradation process, the measurement error is not considered and forecasting uncertainty is large. Therefore, an approximate analytical RUL distribution in a closed-form of a nonlinear Wiener based degradation process with measurement errors was proposed. The maximum likelihood estimation approach was used to estimate the unknown fixed parameters in the proposed model. When the newly observed data are available, the random parameter is updated by the Bayesian method to make the estimation adapt to the item's individual characteristic and reduce the uncertainty of the estimation. The simulation results show that considering measurement errors in the degradation process can significantly improve the accuracy of real time RUL prediction.展开更多
To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance asses...To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.展开更多
An accelerated laboratory method（saturated ammonium nitrate solution immersion method） was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic mod...An accelerated laboratory method（saturated ammonium nitrate solution immersion method） was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic modulus, quality, p H value, the Ca/Si, and mineral phase, it could be found that the first cement decalcification degradation process was the decalcification of calcium hydroxide, and then CSH gel, AFm, etc. The secondary ettringite deposition happened and the decalcification degradation depth was proportional to the square root of time. Moreover, the corresponding strength of cement would be gradually reduced, cement rock volume shrinkage occurred, p H values decreased, the surface elastic modulus decreased down to a certain level, and slightly changed and the Ca/Si was 3.1 from the beginning and lasted down to 1.3.展开更多
The microbial degradation of aromatic organic pollutants is incomplete due to their metabolic characteristics,which can easily produce certain highly toxic intermediates.Therefore,this article designs a dual template ...The microbial degradation of aromatic organic pollutants is incomplete due to their metabolic characteristics,which can easily produce certain highly toxic intermediates.Therefore,this article designs a dual template molec-ularly imprinted sensor(DTMIP/Fe-Mn@C)for iron manganese metal nanomaterials,prepared Fe-Mn@C com-posite materials by a one pot method were coated on the surface of glassy carbon electrodes and covered with molecularly imprinted membranes through electropolymerization and elution methods,achieving real-time de-tection of specific intermediate products 2-methylbutyric acid(2-MBA)and 3-methylbutyric acid(3-MBA)de-graded by azo dyes.In order to determine the detection sensitivity and intensity range of the sensor,optimization experiments were conducted on various parameters that affect the detection performance,such as the type of func-tional monomer and its composition ratio with the template molecule,detection time window,environmental pH value,etc.Finally,o-Phenylenediamine was determined as the functional monomer,with a molar ratio of 1:1:6 to the template molecules 2-MBA and 3-MBA.Electrochemical testing was conducted in a neutral environment with an incubation time of 5 min and pH=7.The results indicate that the sensor has a relatively wide detection range,high sensitivity,obvious recognition features,and excellent stability for 2-MBA and 3-MBA.This new dual template molecularly imprinted sensor can quickly and accurately determine the safety of highly toxic interme-diates in the degradation process of aromatic organic pollutants,providing a theoretical basis and application potential for trace detection and real-time monitoring.展开更多
In the environment of space radiation, the high-energy charged particles or high-energy photons acting on a spacecraft can cause either temporary device degradation or permanent failure. The traditional probability mo...In the environment of space radiation, the high-energy charged particles or high-energy photons acting on a spacecraft can cause either temporary device degradation or permanent failure. The traditional probability model is difficult to obtain reliable estimation of unit radiation resistance performance with small samples. Considering that different products will change differently after high-energy particle radiation, we construct a model based on the gamma degradation process. This model can efficiently describe the law of unit radiation resistance variation with the total radiation dose levels under the effect of the total dose and displacement damage. Finally, the proposed model is used to assess the anti-radiation performance of the N-channel power MOSFET device STRH60N20FSY3 produced by STM to obtain average unit radiation resistance, survival probability, survival function, etc.展开更多
Whitlockite(WH,Ca_(18)Mg_(2)(HPO_(4))_(2)(PO_(4))_(12))is an important inorganic phase in human bones and has positive significance for participating in the bone reconstruction process.In this paper,we report differen...Whitlockite(WH,Ca_(18)Mg_(2)(HPO_(4))_(2)(PO_(4))_(12))is an important inorganic phase in human bones and has positive significance for participating in the bone reconstruction process.In this paper,we report different doping strategies to prepare WH and WH-Ln(Eu/Tb)nanocrystals,and have successfully synthesized WH-Ln(Eu/Tb)nanoparticles(NPs)with bright red or green fluorescence based on ions exchange doping by two-step hydrothermal reaction.WH-5%Ln(Eu/Tb)NPs with the best fluorescence properties were successfully applied to live cell imaging,and WH-5%Eu NPs were implanted into the bone defect site in rabbit femoral condyles to visually observe its degradation process.The related results would help us understand WH nanocrystals and further expand their potential applications in tissue engineering and related fields.展开更多
The degradation process modeling is one of research hotspots of prognostic and health management(PHM),which can be used to estimate system reliability and remaining useful life(RUL).In order to study system degradatio...The degradation process modeling is one of research hotspots of prognostic and health management(PHM),which can be used to estimate system reliability and remaining useful life(RUL).In order to study system degradation process,cumulative damage model is used for degradation modeling.Assuming that damage increment is Gamma distribution,shock counting subjects to a homogeneous Poisson process(HPP)when degradation process is linear,and shock counting is a non-homogeneous Poisson process(NHPP)when degradation process is nonlinear.A two-stage degradation system is considered in this paper,for which the degradation process is linear in the first stage and the degradation process is nonlinear in the second stage.A nonlinear modeling method for considered system is put forward,and reliability model and remaining useful life model are established.A case study is given to validate the veracities of established models.展开更多
Nicosulfuron(NSR),a sulfonylurea herbicide,readily infiltrates water bodies,potentially compromising aquatic ecosystems and human health.In this study,bacteria consortium YM2 was isolated and cultivated from pesticide...Nicosulfuron(NSR),a sulfonylurea herbicide,readily infiltrates water bodies,potentially compromising aquatic ecosystems and human health.In this study,bacteria consortium YM2 was isolated and cultivated from pesticide plant active sludge for NSR wastewater bioremediation.Response surface methodology analysis demonstrated that under optimal cultivation conditions(9.41 g L^(-1)maltodextrin,21.37 g L^(-1)yeast extract,and 12.45 g L^(-1)NaCl),the YM2 bacteria consortium achieved 97.49%NSR degradation within 4 d.Optimal degradation parameters were established at 30℃,pH 6.0,1%inoculum,and 20 mg L^(-1)initial NSR concentration.The degradation system demonstrated resistance to heavy metal ions including Cd^(2+),Pb^(2+),Ni^(2+),and Zn^(2+),with degradation primarily occurring through bacterial extracellular enzymes(92.17%).During the degradation process,reactive oxygen species,oxidative stress,cell membrane permeability,cell surface hydrophobicity,and apoptosis rate exhibited initial increases followed by decreases.Additionally,bioflm formation-related genes luxS,waaE,spo0A,and wza showed temporal and concentration-dependent expression patterns.NSR concentrations in wastewater and soil were reduced to 1.92 and 2.72 mg L^(-1),respectively.In a simulated wastewater treatment unit with a 12-h hydraulic retention time,YM2 achieved 84.55%NSR degradation after 10 d.These fndings provide a theoretical foundation for microbial remediation of NSR contamination.展开更多
Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operat...Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operation. In this work, CO_2 induced degradation of aqueous diethanolamine(DEA) solution was conducted in a 1.25 L jacketed glass reactor that functioned as an absorber and stripper at atmospheric conditions. Pure CO_2 was bubbled through the reactor until the solution became saturated. In this study, the concentrations of DEA used were in the range of concentrations between 2 mol·L^(-1) and 4 mol·L^(-1). In the degradation experiment, six generic cycles were conducted for each run. Each cycle was configured with the absorption and desorption of carbon dioxide at 55 ℃ and 100 ℃, respectively. Samples were collected after a predetermined experimental time and analyzed by ion chromatography(IC) to identify unknown ionic degradation products(DGPs). In the IC analysis, three different columns were used for anion, cation and ion exclusion systems, which are Metrosep A Supp 5150/4.0, Metrosep C Supp 4 150/4.0 and Metrosep Organic Acids, respectively. The major identified DGPs of D01 DEA2 M, D02 DEA3 M, and D03 DEA4 M are nitrite, acetate and ammonium. Phosphate product was found in the degraded amine samples which might be due to the contamination of water or chromatographic system.展开更多
The second law of thermodynamics implies that any animate and inanimate systems degrade and inevitably stops functioning.It is irreversible over time that can be labeled as‘‘the degradation arrow of time".From ...The second law of thermodynamics implies that any animate and inanimate systems degrade and inevitably stops functioning.It is irreversible over time that can be labeled as‘‘the degradation arrow of time".From perspective of products’reliability design,it is essential to build appropriate models of describing the degradation arrow of time.The current modeling approaches mainly include the model-driven(having assumed forms based on cognitive experience of mankind)and data-driven(using data learning techniques without form hypothesis)approaches.In this paper,we just investigate and review the model-driven degradation approaches,hoping to provide suggestions of the model construction or selection for scholars or engineers.First,for the single mechanism,degradation law models and stochastic process models are classified as separately depicting the tendency and fluctuation of degradation.For the degradation law model,we propose the concept of meta-models as original types for various personal models.For the stochastic process model,two main types including the non-monotonic and monotonical types are presented.Then,four multi-mechanism degradation types are discussed,that are competitive degradation,multi-stage degradation,coexistence of degradation and impact,and coexistence of degradation and failure.Besides,for the multi-performance degradation,independent and coupling models are introduced.The forms,connotations,applicability and insufficiency of these models are described with a series of examples from the literature and our own experiences.The final explicit suggestions about the potential future work are provided for the development of new degradation models.展开更多
The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated t...The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope （SEM） and scanning probe microscopy （SPM）. It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical appli- cations.展开更多
To predict the remaining useful life(RUL) for a class of nonlinear multi-degradation systems, a method is presented. In the real industrial processes, systems are usually composed by several parts or components, and t...To predict the remaining useful life(RUL) for a class of nonlinear multi-degradation systems, a method is presented. In the real industrial processes, systems are usually composed by several parts or components, and these parts or components are working in the same environment, thus the degradations of these parts or components will be influenced by common factors. To describe such a phenomenon in degradations, a multi-degradation model with public noise is proposed. To identify the degradation states and the unknown parameters, an iterative estimation method is proposed by using the Kalman filter and the expectation maximization(EM) algorithm. Next, with known thresholds,the RUL of each degradation can be predicted by using the first hitting time(FHT). In addition, the RUL of the whole system can be obtained by a Copula function. Finally, a practical case is used to demonstrate the method proposed.展开更多
Duloxetine(DUL), an antidepressant drug, has been detected in surface water and wastewater effluents, however, there is little information on the formation of its transformation products(TPs). In this work, hydrolysis...Duloxetine(DUL), an antidepressant drug, has been detected in surface water and wastewater effluents, however, there is little information on the formation of its transformation products(TPs). In this work, hydrolysis, photodegradation(UV irradiation) and chlorination experiments were performed on spiked distillated water, under controlled experimental conditions to simulate abiotic processes that can occur in the environment and wastewater treatment plants(WWTPs). Eleven TPs, nine from reaction with UV light and two from chlorine contact, were formed and detected by ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, and nine of them had their chemical structures elucidated upon analyses of their fragmentation patterns in MS/MS spectra. The formation and degradation of the TPs were observed. The parent compound was completely degraded after30 min in photodegradation and after 24 hr in chlorination. Almost all TPs were completely degraded in the experiments. The ecotoxicity and mutagenicity of the TPs were predicted based on several in silico models and it was found that a few of these products presented more ecotoxicity than DUL itself and six TPs showed positive mutagenicity. Finally, wastewater samples were analyzed and DUL and one TP, possibly formed by chlorination process, were detected in the effluent, which showed that WWTP not only did not remove DUL, but also formed a TP.展开更多
Polyimide （PI） film is an important type of insulating material used in inverter-fed motors. Partial discharge （PD） under a sequence of high-frequency square impulses is one of the key factors that lead to prematu...Polyimide （PI） film is an important type of insulating material used in inverter-fed motors. Partial discharge （PD） under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage （BCSIV） is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage （PDIV）. The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy （FTIR） and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy （SEM）. The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond （C-O-C） and imide ring （C-N-C） on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant e to increase and dielectric loss tan ~ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI oolvmer bulk.展开更多
While alpine meadow degradation presents a significant ecological challenge,research on the complex patterns of soil property changes induced by degradation has been somewhat limited.In this study,we investigated the ...While alpine meadow degradation presents a significant ecological challenge,research on the complex patterns of soil property changes induced by degradation has been somewhat limited.In this study,we investigated the Maqu alpine meadow,meticulously categorizing it into different grassland types exhibiting varying degrees of degradation based on factors such as vegetation coverage and community,soil characteristics,and landscape features.These classifications included typical grassland,degraded grassland,desertified grassland,and sandy land.In August 2018,we established three quadrats at each sample point and collected soil samples at five depths(surface(0-2 cm),2-5 cm,5-10 cm,10-20 cm,and 20-40 cm)to analyze soil particle size distribution(PSD)and nutrients content.The results revealed a discernible trend:alpine meadow degradation led to selective loss of nutrient-rich soil fine particles,resulting in significant alterations in soil PSD and nutrients,particularly pronounced in grasslands with low degrees of degradation.Moreover,within a specific range of degradation degree,the clay content in the shallow soil of alpine meadow increased with the degradation degree,but it declined when the degradation degree exceeded a certain threshold.Degradation also disrupted the intricate relationship between soil nutrients,with notable variations in their coupling.This difference was also reflected in the influence of soil physical and chemical properties on soil nutrients,with the explanatory power of each environmental indicator on soil nutrients decreasing significantly with increasing degradation.This study systematically analyzed the variation in soil physical and chemical properties throughout the degradation process,revealing the mechanism of soil nutrient imbalance and decline caused by the degradation process.It provides crucial theoretical foundations and reference points for the preservation and rejuvenation of alpine meadows,enriching the methodology for assessing the impact of grassland degradation.展开更多
The current work deals with ZnO-Ag nanocomposites（in the wide range of x in the Zn1-x O-Ag x chemical composition） synthesized using microwave assisted solution combustion method.The structural, morphological and op...The current work deals with ZnO-Ag nanocomposites（in the wide range of x in the Zn1-x O-Ag x chemical composition） synthesized using microwave assisted solution combustion method.The structural, morphological and optical properties of the samples were characterized by XRD（X-ray diffraction）, FTIR（Fourier transform infrared spectrometry）, SEM（scanning electron microscopy technique）, EDX（energy dispersive X-ray spectrum）, ICP（inductively coupled plasma technique）, TEM（transmission electron microscopy）, BET（Brunauer–Emmett–Teller method）, UV–Vis（ultraviolet–visible spectrophotometer） and photoluminescence spectrophotometer. The photocatalytic activity of the ZnO-Ag was investigated by photo-degradation of Acid Blue 113（AB 113） under UV illumination in a semi-batch reactor. This experiment showed that ZnO-Ag has much more excellent photocatalytic properties than ZnO synthesized by the same method. The enhanced photocatalytic activity was due to the decrease in recombination of photogenerated electron-holes. The results showed the improvement of ZnO photocatalytic activity and there is an optimum amount of Ag（3.5 mol%） that needs to be doped with ZnO.The effect of operating parameters such as p H, catalyst dose and dye concentration were investigated. The reaction byproducts were identified by LC/MS（liquid chromatography/mass spectrometry） analysis and a pathway was proposed as well. Kinetic studies indicated that the decolorization process follows the first order kinetics. Also, the degradation percentage of AB113 was determined using a total organic carbon（TOC） analyzer. Additionally, cost analysis of the process, the mechanism and the role of Ag were discussed.展开更多
TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed ...TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed to characterize the TiNT electrodes. The linear voltammetry results under irradiation showed that the TiNT electrode annealed at 450℃ presented the highest photoelectrochemical activity. By combining photocatalytic with electrochemical process, a significantly synergetic effect on ammonia degradation was observed with Na2SO4 as supporting electrolyte at pH 10.7. Furthermore, the photoelectrocatalytic efficiency on the ammonia degradation was greatly enhanced in presence of chloride ions without the limitation ofpH. The degradation rate was improved by 14.8 times reaching 4.98 × 10^-2 min^-1 at pH 10.7 and a faster degradation rate of 6.34 × 10^-2 min^-1 was obtained at pH 3.01. The in situ photoelectrocatalytic generated active chlorine was proposed to be responsible for the improved efficiency. On the other hand, an enhanced degradation of ammonia using TiNT electrode fabricated in fluorinated organic solution was also confirmed compared to TiNT electrode anodized in fluorinated water solution and TiO2 film electrode fabricated by sol-gel method. Finally, the effect of chloride concentration was also discussed.展开更多
A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the su...A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the surface in the Bohai Sea in August, 2001 with field observations, shows that the model simulates the dataset reasonably well. The Laizhou Bay, Bohai Bay, and Liaodong Bay were contaminated heavily near shore. Based on the optimal discharge flux method, the Environmental Capacity (EC) and allocated capacities of COD in the Bohai Sea are calculated. For seawater of Grades I to IV of the Chinese National Standard, the ECs of COD in the Bohai Sea were 77×104 t/a, 116×104 t/a, 154×104 t/a and 193×104 t/a, respectively. The Huanghe (Yellow) River pollutant discharge accounted for the largest percentage of COD at 14.3%, followed by that of from the Liugu River (11.5%), and other nine local rivers below 10%. The COD level in 2005 was worse than that of Grade II seawater and was beyond the environmental capacity. In average, 35% COD reduction is called to meet the standard of Grade I seawater.展开更多
In this paper,a novel remaining useful life prediction approach considering fault effects is proposed.The Wiener process is used to construct the degradation process of single performance characteristic with the fault...In this paper,a novel remaining useful life prediction approach considering fault effects is proposed.The Wiener process is used to construct the degradation process of single performance characteristic with the fault effects.The first passage time based remaining useful life distribution is calculated by assuming fault occurrence moment is a random variable and follows a certain distribution.Expectation maximization algorithm is employed to estimate model parameters,where the fault occurrence moment is considered as a missing data.Finally,a Copula function is used to describe the dependence between the multiple performance characteristics and derive joint remaining useful life(RUL)distribution of product with the fault effects.The effectiveness of the proposed approach is verified by the experiments of turbofan engines.展开更多
基金Projects(51475462,61374138,61370031)supported by the National Natural Science Foundation of China
文摘Real time remaining useful life(RUL) prediction based on condition monitoring is an essential part in condition based maintenance(CBM). In the current methods about the real time RUL prediction of the nonlinear degradation process, the measurement error is not considered and forecasting uncertainty is large. Therefore, an approximate analytical RUL distribution in a closed-form of a nonlinear Wiener based degradation process with measurement errors was proposed. The maximum likelihood estimation approach was used to estimate the unknown fixed parameters in the proposed model. When the newly observed data are available, the random parameter is updated by the Bayesian method to make the estimation adapt to the item's individual characteristic and reduce the uncertainty of the estimation. The simulation results show that considering measurement errors in the degradation process can significantly improve the accuracy of real time RUL prediction.
基金Project(2006.318.223.02-01) supported by the Ministry of Transportation and Communications through the Scientific and Technological Funds of ChinaProject(2007AA11Z104) supported by the High Technology Research and Development of ChinaProject(20090072110045) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.
基金Funded by the Natural Science Foundation of Ministry of Housing and Urban-Rural Development of the People's Republic of China(No.2009-K4-27)
文摘An accelerated laboratory method（saturated ammonium nitrate solution immersion method） was used to analyze the degradation of cement decalcification process. By studying the changes of intensity, volume, elastic modulus, quality, p H value, the Ca/Si, and mineral phase, it could be found that the first cement decalcification degradation process was the decalcification of calcium hydroxide, and then CSH gel, AFm, etc. The secondary ettringite deposition happened and the decalcification degradation depth was proportional to the square root of time. Moreover, the corresponding strength of cement would be gradually reduced, cement rock volume shrinkage occurred, p H values decreased, the surface elastic modulus decreased down to a certain level, and slightly changed and the Ca/Si was 3.1 from the beginning and lasted down to 1.3.
基金supported by the Bingtuan Industrial Technology Research Institute,Bingtuan New materials Research Institute innovation platform project,Research initiation project of Shihezi University(No.RCZK202330)the Science and Technology Program-Regional Innovation Guidance Program(No.2023ZD080)Tianchi Talent Project(No.CZ002735).
文摘The microbial degradation of aromatic organic pollutants is incomplete due to their metabolic characteristics,which can easily produce certain highly toxic intermediates.Therefore,this article designs a dual template molec-ularly imprinted sensor(DTMIP/Fe-Mn@C)for iron manganese metal nanomaterials,prepared Fe-Mn@C com-posite materials by a one pot method were coated on the surface of glassy carbon electrodes and covered with molecularly imprinted membranes through electropolymerization and elution methods,achieving real-time de-tection of specific intermediate products 2-methylbutyric acid(2-MBA)and 3-methylbutyric acid(3-MBA)de-graded by azo dyes.In order to determine the detection sensitivity and intensity range of the sensor,optimization experiments were conducted on various parameters that affect the detection performance,such as the type of func-tional monomer and its composition ratio with the template molecule,detection time window,environmental pH value,etc.Finally,o-Phenylenediamine was determined as the functional monomer,with a molar ratio of 1:1:6 to the template molecules 2-MBA and 3-MBA.Electrochemical testing was conducted in a neutral environment with an incubation time of 5 min and pH=7.The results indicate that the sensor has a relatively wide detection range,high sensitivity,obvious recognition features,and excellent stability for 2-MBA and 3-MBA.This new dual template molecularly imprinted sensor can quickly and accurately determine the safety of highly toxic interme-diates in the degradation process of aromatic organic pollutants,providing a theoretical basis and application potential for trace detection and real-time monitoring.
基金supported by the National Natural Science Foundation of China(Grant Nos.71371067&70901024)Hunan Provincial Natural Science Foundation of China
文摘In the environment of space radiation, the high-energy charged particles or high-energy photons acting on a spacecraft can cause either temporary device degradation or permanent failure. The traditional probability model is difficult to obtain reliable estimation of unit radiation resistance performance with small samples. Considering that different products will change differently after high-energy particle radiation, we construct a model based on the gamma degradation process. This model can efficiently describe the law of unit radiation resistance variation with the total radiation dose levels under the effect of the total dose and displacement damage. Finally, the proposed model is used to assess the anti-radiation performance of the N-channel power MOSFET device STRH60N20FSY3 produced by STM to obtain average unit radiation resistance, survival probability, survival function, etc.
基金supported by the National Natural Science Foundation of China(Nos.22078265,21908179,and 21838009)the Shaanxi Provincial Science Foundation(Nos.2017SF-201 and 2018JQ2052).
文摘Whitlockite(WH,Ca_(18)Mg_(2)(HPO_(4))_(2)(PO_(4))_(12))is an important inorganic phase in human bones and has positive significance for participating in the bone reconstruction process.In this paper,we report different doping strategies to prepare WH and WH-Ln(Eu/Tb)nanocrystals,and have successfully synthesized WH-Ln(Eu/Tb)nanoparticles(NPs)with bright red or green fluorescence based on ions exchange doping by two-step hydrothermal reaction.WH-5%Ln(Eu/Tb)NPs with the best fluorescence properties were successfully applied to live cell imaging,and WH-5%Eu NPs were implanted into the bone defect site in rabbit femoral condyles to visually observe its degradation process.The related results would help us understand WH nanocrystals and further expand their potential applications in tissue engineering and related fields.
基金National Outstanding Youth Science Fund Project,China(No.71401173)
文摘The degradation process modeling is one of research hotspots of prognostic and health management(PHM),which can be used to estimate system reliability and remaining useful life(RUL).In order to study system degradation process,cumulative damage model is used for degradation modeling.Assuming that damage increment is Gamma distribution,shock counting subjects to a homogeneous Poisson process(HPP)when degradation process is linear,and shock counting is a non-homogeneous Poisson process(NHPP)when degradation process is nonlinear.A two-stage degradation system is considered in this paper,for which the degradation process is linear in the first stage and the degradation process is nonlinear in the second stage.A nonlinear modeling method for considered system is put forward,and reliability model and remaining useful life model are established.A case study is given to validate the veracities of established models.
基金financially supported by the Jilin Province Development and Reform Commission(Innovation Capacity Building)Project,China(20231036-3)the Key R&D Project of the Science and Technology Development Plan of Jilin,China(20230203014SF)。
文摘Nicosulfuron(NSR),a sulfonylurea herbicide,readily infiltrates water bodies,potentially compromising aquatic ecosystems and human health.In this study,bacteria consortium YM2 was isolated and cultivated from pesticide plant active sludge for NSR wastewater bioremediation.Response surface methodology analysis demonstrated that under optimal cultivation conditions(9.41 g L^(-1)maltodextrin,21.37 g L^(-1)yeast extract,and 12.45 g L^(-1)NaCl),the YM2 bacteria consortium achieved 97.49%NSR degradation within 4 d.Optimal degradation parameters were established at 30℃,pH 6.0,1%inoculum,and 20 mg L^(-1)initial NSR concentration.The degradation system demonstrated resistance to heavy metal ions including Cd^(2+),Pb^(2+),Ni^(2+),and Zn^(2+),with degradation primarily occurring through bacterial extracellular enzymes(92.17%).During the degradation process,reactive oxygen species,oxidative stress,cell membrane permeability,cell surface hydrophobicity,and apoptosis rate exhibited initial increases followed by decreases.Additionally,bioflm formation-related genes luxS,waaE,spo0A,and wza showed temporal and concentration-dependent expression patterns.NSR concentrations in wastewater and soil were reduced to 1.92 and 2.72 mg L^(-1),respectively.In a simulated wastewater treatment unit with a 12-h hydraulic retention time,YM2 achieved 84.55%NSR degradation after 10 d.These fndings provide a theoretical foundation for microbial remediation of NSR contamination.
基金the Ministry of Science,Technology and Innovation,Malaysia(MOSTI),for funding the project:RG003/09AET as well as the University of Malaya for allowing full access to several key laboratories to perform experimental work
文摘Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operation. In this work, CO_2 induced degradation of aqueous diethanolamine(DEA) solution was conducted in a 1.25 L jacketed glass reactor that functioned as an absorber and stripper at atmospheric conditions. Pure CO_2 was bubbled through the reactor until the solution became saturated. In this study, the concentrations of DEA used were in the range of concentrations between 2 mol·L^(-1) and 4 mol·L^(-1). In the degradation experiment, six generic cycles were conducted for each run. Each cycle was configured with the absorption and desorption of carbon dioxide at 55 ℃ and 100 ℃, respectively. Samples were collected after a predetermined experimental time and analyzed by ion chromatography(IC) to identify unknown ionic degradation products(DGPs). In the IC analysis, three different columns were used for anion, cation and ion exclusion systems, which are Metrosep A Supp 5150/4.0, Metrosep C Supp 4 150/4.0 and Metrosep Organic Acids, respectively. The major identified DGPs of D01 DEA2 M, D02 DEA3 M, and D03 DEA4 M are nitrite, acetate and ammonium. Phosphate product was found in the degraded amine samples which might be due to the contamination of water or chromatographic system.
基金co-supported by the National Natural Science Foundation of China(Nos.51675025,and 61573043)。
文摘The second law of thermodynamics implies that any animate and inanimate systems degrade and inevitably stops functioning.It is irreversible over time that can be labeled as‘‘the degradation arrow of time".From perspective of products’reliability design,it is essential to build appropriate models of describing the degradation arrow of time.The current modeling approaches mainly include the model-driven(having assumed forms based on cognitive experience of mankind)and data-driven(using data learning techniques without form hypothesis)approaches.In this paper,we just investigate and review the model-driven degradation approaches,hoping to provide suggestions of the model construction or selection for scholars or engineers.First,for the single mechanism,degradation law models and stochastic process models are classified as separately depicting the tendency and fluctuation of degradation.For the degradation law model,we propose the concept of meta-models as original types for various personal models.For the stochastic process model,two main types including the non-monotonic and monotonical types are presented.Then,four multi-mechanism degradation types are discussed,that are competitive degradation,multi-stage degradation,coexistence of degradation and impact,and coexistence of degradation and failure.Besides,for the multi-performance degradation,independent and coupling models are introduced.The forms,connotations,applicability and insufficiency of these models are described with a series of examples from the literature and our own experiences.The final explicit suggestions about the potential future work are provided for the development of new degradation models.
基金Supported by Major State Basic Research Program of China ("973"Program,No. 2011CB610500)
文摘The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope （SEM） and scanning probe microscopy （SPM）. It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical appli- cations.
基金supported by the National Natural Science Foundation of China(6129032461473164+1 种基金61490701)the Research Fund for the Taishan Scholar Project of Shandong Province of China(LZB2015-162)
文摘To predict the remaining useful life(RUL) for a class of nonlinear multi-degradation systems, a method is presented. In the real industrial processes, systems are usually composed by several parts or components, and these parts or components are working in the same environment, thus the degradations of these parts or components will be influenced by common factors. To describe such a phenomenon in degradations, a multi-degradation model with public noise is proposed. To identify the degradation states and the unknown parameters, an iterative estimation method is proposed by using the Kalman filter and the expectation maximization(EM) algorithm. Next, with known thresholds,the RUL of each degradation can be predicted by using the first hitting time(FHT). In addition, the RUL of the whole system can be obtained by a Copula function. Finally, a practical case is used to demonstrate the method proposed.
基金supported by Brazilian Federal Agency Coordenacao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)for PhD grants(No.99999.000845/2014-00)Fundacao para a Ciência e a Tecnologia(FCT)Portugal(Projects UID/MULTI/00612/2013,PEst-OE/QUI/UI0612/2013 and LISBOA-01-0145-FEDER-022125)
文摘Duloxetine(DUL), an antidepressant drug, has been detected in surface water and wastewater effluents, however, there is little information on the formation of its transformation products(TPs). In this work, hydrolysis, photodegradation(UV irradiation) and chlorination experiments were performed on spiked distillated water, under controlled experimental conditions to simulate abiotic processes that can occur in the environment and wastewater treatment plants(WWTPs). Eleven TPs, nine from reaction with UV light and two from chlorine contact, were formed and detected by ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, and nine of them had their chemical structures elucidated upon analyses of their fragmentation patterns in MS/MS spectra. The formation and degradation of the TPs were observed. The parent compound was completely degraded after30 min in photodegradation and after 24 hr in chlorination. Almost all TPs were completely degraded in the experiments. The ecotoxicity and mutagenicity of the TPs were predicted based on several in silico models and it was found that a few of these products presented more ecotoxicity than DUL itself and six TPs showed positive mutagenicity. Finally, wastewater samples were analyzed and DUL and one TP, possibly formed by chlorination process, were detected in the effluent, which showed that WWTP not only did not remove DUL, but also formed a TP.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.U1234202,U1134205,51177136,and 51107104)
文摘Polyimide （PI） film is an important type of insulating material used in inverter-fed motors. Partial discharge （PD） under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage （BCSIV） is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage （PDIV）. The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy （FTIR） and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy （SEM）. The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond （C-O-C） and imide ring （C-N-C） on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant e to increase and dielectric loss tan ~ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI oolvmer bulk.
基金research was supported by the National Key Research and Development Program of China(2020YFA0608403)the National Natural Science Foundation of China(42171083)the Natural Science Foundation of Gansu Province(23JRRA601).
文摘While alpine meadow degradation presents a significant ecological challenge,research on the complex patterns of soil property changes induced by degradation has been somewhat limited.In this study,we investigated the Maqu alpine meadow,meticulously categorizing it into different grassland types exhibiting varying degrees of degradation based on factors such as vegetation coverage and community,soil characteristics,and landscape features.These classifications included typical grassland,degraded grassland,desertified grassland,and sandy land.In August 2018,we established three quadrats at each sample point and collected soil samples at five depths(surface(0-2 cm),2-5 cm,5-10 cm,10-20 cm,and 20-40 cm)to analyze soil particle size distribution(PSD)and nutrients content.The results revealed a discernible trend:alpine meadow degradation led to selective loss of nutrient-rich soil fine particles,resulting in significant alterations in soil PSD and nutrients,particularly pronounced in grasslands with low degrees of degradation.Moreover,within a specific range of degradation degree,the clay content in the shallow soil of alpine meadow increased with the degradation degree,but it declined when the degradation degree exceeded a certain threshold.Degradation also disrupted the intricate relationship between soil nutrients,with notable variations in their coupling.This difference was also reflected in the influence of soil physical and chemical properties on soil nutrients,with the explanatory power of each environmental indicator on soil nutrients decreasing significantly with increasing degradation.This study systematically analyzed the variation in soil physical and chemical properties throughout the degradation process,revealing the mechanism of soil nutrient imbalance and decline caused by the degradation process.It provides crucial theoretical foundations and reference points for the preservation and rejuvenation of alpine meadows,enriching the methodology for assessing the impact of grassland degradation.
文摘The current work deals with ZnO-Ag nanocomposites（in the wide range of x in the Zn1-x O-Ag x chemical composition） synthesized using microwave assisted solution combustion method.The structural, morphological and optical properties of the samples were characterized by XRD（X-ray diffraction）, FTIR（Fourier transform infrared spectrometry）, SEM（scanning electron microscopy technique）, EDX（energy dispersive X-ray spectrum）, ICP（inductively coupled plasma technique）, TEM（transmission electron microscopy）, BET（Brunauer–Emmett–Teller method）, UV–Vis（ultraviolet–visible spectrophotometer） and photoluminescence spectrophotometer. The photocatalytic activity of the ZnO-Ag was investigated by photo-degradation of Acid Blue 113（AB 113） under UV illumination in a semi-batch reactor. This experiment showed that ZnO-Ag has much more excellent photocatalytic properties than ZnO synthesized by the same method. The enhanced photocatalytic activity was due to the decrease in recombination of photogenerated electron-holes. The results showed the improvement of ZnO photocatalytic activity and there is an optimum amount of Ag（3.5 mol%） that needs to be doped with ZnO.The effect of operating parameters such as p H, catalyst dose and dye concentration were investigated. The reaction byproducts were identified by LC/MS（liquid chromatography/mass spectrometry） analysis and a pathway was proposed as well. Kinetic studies indicated that the decolorization process follows the first order kinetics. Also, the degradation percentage of AB113 was determined using a total organic carbon（TOC） analyzer. Additionally, cost analysis of the process, the mechanism and the role of Ag were discussed.
基金supported by the National Natural Science Foundation of China (Nos. 21277134, 21107103)the State Key Laboratory of Environmental, Criteria and Risk Assessment Chinese Research Academy of Environmental Sciences
文摘TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed to characterize the TiNT electrodes. The linear voltammetry results under irradiation showed that the TiNT electrode annealed at 450℃ presented the highest photoelectrochemical activity. By combining photocatalytic with electrochemical process, a significantly synergetic effect on ammonia degradation was observed with Na2SO4 as supporting electrolyte at pH 10.7. Furthermore, the photoelectrocatalytic efficiency on the ammonia degradation was greatly enhanced in presence of chloride ions without the limitation ofpH. The degradation rate was improved by 14.8 times reaching 4.98 × 10^-2 min^-1 at pH 10.7 and a faster degradation rate of 6.34 × 10^-2 min^-1 was obtained at pH 3.01. The in situ photoelectrocatalytic generated active chlorine was proposed to be responsible for the improved efficiency. On the other hand, an enhanced degradation of ammonia using TiNT electrode fabricated in fluorinated organic solution was also confirmed compared to TiNT electrode anodized in fluorinated water solution and TiO2 film electrode fabricated by sol-gel method. Finally, the effect of chloride concentration was also discussed.
基金Supported by 908 Program of the State Ocean Administration of China (Nos.908-02-02-02,908-02-02-03)the State Ocean Administration Foundation of China (No.200805065)
文摘A three-dimensional advection-diffusion model coupled with the degradation process is established for describing the transport of chemical oxygen demand (COD). Comparison of the simulated distribution of COD at the surface in the Bohai Sea in August, 2001 with field observations, shows that the model simulates the dataset reasonably well. The Laizhou Bay, Bohai Bay, and Liaodong Bay were contaminated heavily near shore. Based on the optimal discharge flux method, the Environmental Capacity (EC) and allocated capacities of COD in the Bohai Sea are calculated. For seawater of Grades I to IV of the Chinese National Standard, the ECs of COD in the Bohai Sea were 77×104 t/a, 116×104 t/a, 154×104 t/a and 193×104 t/a, respectively. The Huanghe (Yellow) River pollutant discharge accounted for the largest percentage of COD at 14.3%, followed by that of from the Liugu River (11.5%), and other nine local rivers below 10%. The COD level in 2005 was worse than that of Grade II seawater and was beyond the environmental capacity. In average, 35% COD reduction is called to meet the standard of Grade I seawater.
基金supported by General Program of National Natural Science Foundation of China(61773080)China Central Universities Foundation(2019CDYGZD001)+1 种基金Scientific Reserve Talent Programs of Chongqing University(cqu2018CDHB1B04)Graduate Research and Innovation Foundation of Chongqing(CYB20065)。
文摘In this paper,a novel remaining useful life prediction approach considering fault effects is proposed.The Wiener process is used to construct the degradation process of single performance characteristic with the fault effects.The first passage time based remaining useful life distribution is calculated by assuming fault occurrence moment is a random variable and follows a certain distribution.Expectation maximization algorithm is employed to estimate model parameters,where the fault occurrence moment is considered as a missing data.Finally,a Copula function is used to describe the dependence between the multiple performance characteristics and derive joint remaining useful life(RUL)distribution of product with the fault effects.The effectiveness of the proposed approach is verified by the experiments of turbofan engines.
