A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and instead of...A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and instead of pneumatic valve the displacement is controlled by electronic control valve. In order to know the control mechanism well and get a good control effect, a mathematical model for the variable displacement mechanism is developed according to the geometrical and kinematical information of the compressor. Using the model, the effect of relevant parameters on variable displace control is estimated. It is helpful to make the optimum decision in the flow control of AAC. As the novel displacement control device, the structure and control rule of electronic control valve is introduced. It can get better effect than the conventional pneumatic valves. And by using this new electronic control device, the optimum systemic control of AAC is available.展开更多
A novel thermal-assisted ultra-violet(UV) photocatalysis digestion method for the determination of total phosphorus(TP) in water samples was introduced in this work. The photocatalytic experiments for TP digestion wer...A novel thermal-assisted ultra-violet(UV) photocatalysis digestion method for the determination of total phosphorus(TP) in water samples was introduced in this work. The photocatalytic experiments for TP digestion were conducted using a 365 nm wavelength UV light and Ti O2 particles as the photocatalyst. Sodium tripolyphosphate and sodium glycerophosphate were used as the typical components of TP and the digested samples were then determined by spectrophotometry after phosphomolybdenum blue reaction. The effects of operational parameters such as reaction time and temperature were studied for the digestion of TP and the kinetic analysis of two typical components was performed in this paper. The pseudo-first-order rate constants k of two phosphorus compounds at different temperatures were obtained and the Arrhenius equation was employed to explain the effect of temperature on rate constant k. Compared with the conventional thermal digestion method for TP detection, it was found that the temperature was decreased from 120 °C to 60 °C with same conversion rate and time in this thermal-assisted UV digestion method, which enabled the digestion process work at normal pressure. Compared with the individual ultra-violet(UV) photocatalysis process, the digestion time was also decreased from several hours to half an hour using the thermal-assisted UV digestion method. This method will not lead to secondary pollution since no oxidant was needed in the thermal-assisted UV photocatalysis digestion process, which made it more compatible with electrochemical detection of TP.展开更多
The oxidation of carbon nanotubes, C60 and graphite was studied by thermogravimetric (TG) analysis and differential thermal analysis (DTA) technique, and the oxidation kinetic models of three carbon materials studied ...The oxidation of carbon nanotubes, C60 and graphite was studied by thermogravimetric (TG) analysis and differential thermal analysis (DTA) technique, and the oxidation kinetic models of three carbon materials studied were analyzed by mechanism-function method. The results indicate that three carbon species adopt different oxidation mechanisms due to their different structures. The oxidation of carbon nanotubes with cylindrical structure follows contracting volume reaction mechanism [R3 mechanism, 1- (1- α)^1/3 = kt], indicating that the oxidation of carbon nanotubes takes place from the ends to the center. For graphite with planar sandwich structure, the oxidation starts at the edges initially and gradually moves toward the center, which corresponds to contracting area phase boundary reaction mechanism [R2 mechanism, 1 - (1 - α)^1/2 = kt]. The oxidation of C60 with spherical structure, however, is complex and apparently cannot be illustrated with a single kinetic model. The values of apparent activation energy obtained by the mechanism-function method are (145 ± 5) kJ·mol^-1 for carbon nanotubes and (193 ± 7) kJ·mol^-1 for graphite, respectively, while the value of apparent activation energy for C60 determined using Kissinger method is 91 kJ·mol^-1。展开更多
This work deals with the kinetics of co-condensation polymerization of AB2 and AB monomers, giving expressions of the two-dimensional molecular weight distribution function and the number/weight average molecular weig...This work deals with the kinetics of co-condensation polymerization of AB2 and AB monomers, giving expressions of the two-dimensional molecular weight distribution function and the number/weight average molecular weights of the resulting copolymers. The two-dimensional molecular weight distribution depends on two indices, n and l, which are the respective numbers of AB2 and AB units in a copolymer species. The evolution of the two-dimensional weight and z distributions during the co-condensation polymerization has been evaluated systematically. Finally, the two-dimensional distribution was transformed into a one-dimensional molecular weight distribution with only one variable (the molecular weight of the products instead of the degree of polymerization). The calculated results show that the highly branched copolymer has a very broad molecular weight distribution when the co-condensation polymerization approaches completion.展开更多
Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperforma...Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.展开更多
A pulsed discharge plasma（PDP） reactor with net anode and net cathode was established for investigating the pyrene degradation in soil under different pulse peak voltage,air flow rate,pyrene content in soil,initial ...A pulsed discharge plasma（PDP） reactor with net anode and net cathode was established for investigating the pyrene degradation in soil under different pulse peak voltage,air flow rate,pyrene content in soil,initial p H value and initial water content of the soil.Pyrene oxidation within the 60 min discharge time was fitting according to the pseudo-first order equation and the corresponding reaction kinetics constants（k values） were calculated.The obtained results show that pyrene oxidation under all the different reaction conditions obeyed the pseudo-first order equation well.Higher pulsed peak voltage and appropriate air flow rate were in favor of the increase of reaction rate of pyrene oxidation.A higher k value could be achieved in the lower initial pyrene content（the value was 100 mg kg^-1）.The k value of pyrene oxidation in the case of p H=4 was 11.2 times higher than the value obtained under the condition of p H=9,while the initial water content of the soil also has a large effect on the oxidation rate of pyrene due to the effect of PDP.展开更多
In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of...In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of methane and propane(700–1000 K,10–20 bar)were studied experimentally and using kinetic modeling tools at stoichiometric fuel-tooxygen ratios.All the experiments were conducted through insentropic compression.The reliable experimental data were obtained by using the adiabatic core hypothesis,which can be used to generate and validate the detailed chemical kinetics model.The IDTs of methane and propane were recorded by a rapid compression machine(RCM)and compared to the predicted values obtained by the NUIGMech 3.0 mechanism.To test the applicability of NUIGMech 3.0 under different reaction conditions,the influence of temperature in the range of 700–1000 K(and the influence of pressure in the range of 10–20 bar)on the IDT was studied.The results showed that NUIGMech 3.0 could reasonably reproduce the experimentally determined IDT under the wide range of conditions studied.The constant volume chemical kinetics model was used to reveal the effect of temperature on the elementary reaction,and the negative temperature coefficient(NTC)behavior of propane was also observed at 20 bar.The experimental data can serve as a reference for the correction and application of kinetic data,as well as provide a theoretical basis for the safe conversion of low-carbon hydrocarbon chemicals.展开更多
The large accumulation of coal gangue,a common industrial solid waste,causes severe environmental problems,and green development strategies are required to transform this waste into high-value-added products.In this s...The large accumulation of coal gangue,a common industrial solid waste,causes severe environmental problems,and green development strategies are required to transform this waste into high-value-added products.In this study,low-cost ceramsites adsorbents were prepared from waste gangue,silt coal,and peanut shells and applied to remove the organic dye methylene blue from wastewater.We investigated the microstructure of ceramsites and the effects of the sintering atmosphere,sintering temperature,and solution pH on their adsorption performance.The ceramsites sintered at 800℃under a nitrogen atmosphere exhibited the largest three-dimensional-interconnected hierarchical porous structure among the prepared ceramsites;further,it exhibited the highest methylene blue adsorption performance,with an adsorption capacity of 0.954 mg·g^(−1),adsorption efficiency of over 95%,and adsorption equilibrium time of 1 h at a solution pH of 9.The removal efficiency remained greater than 75%after five adsorption cycles.The adsorption kinetics data were analyzed using various models,including the pseudosecond-order kinetic model and Langmuir equation,and the adsorption was attributed to electrostatic interactions between the dyes and ceramsites,n-interactions,and hydrogen bonds.The prepared coal gangue ceramsites exhibited excellent adsorption capacities,removal rates,and cyclic stabilities,demonstrating their promising application prospects for the comprehensive utilization of solid waste and for wastewater treatment.展开更多
This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on asses...This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on assessing the coupled chemical effects of NH_(3) and CO_(2) on C2H4 combustion chemistry.The chemical effects could be evaluated by comparing fictitious inert NH_(3) or CO_(2) with normal active NH_(3) or CO_(2).The results revealed that the addition of NH_(3) decreased the mole fractions and production rates of key soot precursors,such as acetylene,propynyl,and benzene.When CO_(2) was used as the dilution gas,the coupled chemical effects of NH_(3) and CO_(2) were affected by the chemical effects of CO_(2) to varying degrees.With the oxidizer-side CO_(2) addition,the coupled chemical effects of NH_(3) and CO_(2) reduced the mole fractions of H,O,OH radicals,acetylene,propynyl,and benzene,while the effects differed from the fuel-side CO_(2) addition.The coupled chemical effects of NH_(3) and CO_(2) also promoted the formation of aldehyde contaminants,such as acetaldehyde,to some extent,particularly with CO_(2) addition on the oxidizer side.展开更多
The synthesis of carbide coatings on graphite substrates using molten salt synthesis(MSS),has garnered significant interest due to its cost-effective nature.This study investigates the reaction process and growth kine...The synthesis of carbide coatings on graphite substrates using molten salt synthesis(MSS),has garnered significant interest due to its cost-effective nature.This study investigates the reaction process and growth kinetics involved in MSS,shedding light on key aspects of the process.The involvement of Ti powder through liquid-phase mass transfer is revealed,where the diffusion distance and quantity of Ti powder play a crucial role in determining the reaction rate by influencing the C content gradient on both sides of the carbide.Furthermore,the growth kinetics of the carbide coating are predominantly governed by the diffusion behavior of C within the carbide layer,rather than the chemical reaction rate.To analyze the kinetics,the thickness of the carbide layer is measured with respect to heat treatment time and temperature,unveiling a parabolic relationship within the temperature range of 700-1300℃.The estimated activation energy for the reaction is determined to be 179283 J·mol^(-1).These findings offer valuable insights into the synthesis of carbide coatings via MSS,facilitating their optimization and enhancing our understanding of their growth mechanisms and properties for various applications.展开更多
In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are e...In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are established using MATLAB Simscape to analyze their kinetics and dynamics in the lifting and holding stages.The simulation findings are compared to the analytical calculation results in the steady state,and both methods show good agreement.In the early lifting stage,Model 1 produces greater force and discharges goods in the container faster than Model 2.Meanwhile,Model 2 reaches a higher force and ejects goods from the container cleaner than its counterpart at the end lifting stage.The established simulation models can consider the effects of dynamic loads due to inertial moments and forces generated during the system operation.It is crucial in studying,designing,and optimizing the structure of hydraulic-mechanical systems.展开更多
A novel process was developed for the decomposition of vanadium slag using KOH sub-molten salt under ambient pressure, and the effects of reaction temperature, alkali-to-ore mass ratios, particle size, and stirring sp...A novel process was developed for the decomposition of vanadium slag using KOH sub-molten salt under ambient pressure, and the effects of reaction temperature, alkali-to-ore mass ratios, particle size, and stirring speed on vanadium and chromium extraction were studied. The results suggest that the reaction temperature and KOH-to-ore mass ratio are more influential factors for the extraction of vanadium and chromium. Under the optimal reaction conditions （temperature 180 °C, initial KOH-to-ore mass ratio 4：1, stirring speed 700 r/min, gas flow 1 L/min, and reaction time 300 min）, vanadium and chromium extraction rates can reach up to 95% and 90%, respectively. Kinetics analysis results show that the decomposing process of vanadium slag in KOH sub-molten salt can be well interpreted by the shrinking core model under internal diffusion control. The apparent activation energies for vanadium and chromium are 40.54 and 50.27 kJ/mol, respectively.展开更多
At 0.12 mmol/L γ-glutamyl p-nitroaniline(GGPNA),an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase(GGT) reaction process and the integration with the classical initial rate met...At 0.12 mmol/L γ-glutamyl p-nitroaniline(GGPNA),an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase(GGT) reaction process and the integration with the classical initial rate method to measure serum GGT.For the improved integrated method,an integrated rate equation,which used the predictor variable of reaction time and considered inhibitions by both GGPNA and products,was nonlinearly fit to GGT reaction processes.For the integration strategy,classical initial rates were estimated when GGPNA consumption percentages were below 50%;otherwise,maximal reaction rates of GGT were estimated by the improved integrated method and converted into initial rates according to the differential rate equation at 0.11 mmol/L GGPNA.The inte-gration strategy was validated using optimized GGT kinetic parameters and 10-s intervals to record reaction curves within 8.0 min.By the integration strategy,there was a linear response from 0.9 to 32.0 U/L GGT,coefficients of variation were below 3.5%for GGT from 8.0 to 32.0 U/L(n=5) ,and GGT activities in clinical sera responded linearly to their classical initial rates at 2.00 mmol/L GGPNA with an expected slope.Therefore,the integration strategy was successful in measuring GGT at 0.12 mmol/L GGPNA.展开更多
The addition of effective additives can effectively improve the pyrolysis performance of oil sludge(OS)and have a great potential to reduce pyrolysis costs.In the present study,co-pyrolysis performance of OS with diff...The addition of effective additives can effectively improve the pyrolysis performance of oil sludge(OS)and have a great potential to reduce pyrolysis costs.In the present study,co-pyrolysis performance of OS with different proportions of additives at a heating rate of 10°C/min was conducted in a thermal analyzer.Walnut shell,Fe_(2)O_(3),K_(2)CO_(3),PVC and the pyrolysis char produced from OS at the final pyrolysis temperature of 700℃were selected as the additives.TG results showed that the OS pyrolysis with and without additives can be divided into five reaction stages,which include volatilization of free water,the escape of light components,the cleavage of heavy components,carbon decomposition and inorganic minerals decomposition.The addition of additives decreased the maximum weight loss rate when the blending ratio was 5 wt%during OS pyrolysis.Kinetic analysis revealed that the overall activation energy of pyrolysis reaction was lower during pyrolysis of OS with the addition of walnut shells and pyrolysis char.The activation energy of three main reaction stages all decreased during co-pyrolysis of OS with K_(2)CO_(3)and PVC.展开更多
Chemical looping gasification(CLG)characteristics and kinetic analysis of Chlorella(CHL),simulated Chlorella(V-CHL)and medium-chain triglycerides(MCT)were investigated using a thermogravimetric analyzer coupled with a...Chemical looping gasification(CLG)characteristics and kinetic analysis of Chlorella(CHL),simulated Chlorella(V-CHL)and medium-chain triglycerides(MCT)were investigated using a thermogravimetric analyzer coupled with an online mass spectrometer.The apparent activation energy was obtained via Kissinger-Akahira-Sunose(KAS)method.In the result of the weightless behavior,the addition of oxygen carrier inhibited the decomposition of V-CHL at lower temperatures but promoted its decomposition at high temperatures.The values of chemical looping process characteristic parameters showed that a 10 wt%oxygen carrier would maximize the release of volatile products in the CLG of MCT,with 5.12×10^(-6)%⋅min^(-1)⋅℃^(-3).Oxygen carriers also affected gaseous products.The LHV of gaseous products of CHL reached the largest when the oxygen carrier was 10 wt%,which was 8.13 MJ/m^(3).And the gaseous product of MCT had the largest LHV with 30 wt%oxygen carrier,which was 8.83 MJ/m^(3).According to the kinetic analysis,the minimum value of apparent activation energy of MCT chemical looping gasification was 89.54 kJ⋅mol^(-1) with the oxygen carrier of 30 wt%,which was 50%less than that of MCT pyrolysis.And the minimum value for V-CHL was obtained when the mass fraction of Fe2O3 was 50 wt%.This paper could provide a reference for the choice of algae,the design of reactors,and the targeted regulation of the gaseous product for the algae CLG process.展开更多
A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The ...A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The flow is stopped when the reagent zone comes in the flow cell, where absorbance-time data are collected at 580nm wavelength. The linear range of the determination is 0.1 -10μg/ml CN-. The sampling rate is 60h-1 and the relative standard deviation is 1.6% (n=16) at 5.0 μg/ml CN-1 level. With satisfactory results, the proposed method was applied to the determination of free cyanide in wastewater without sample pretreatment.展开更多
Human Activity Recognition(HAR)has always been a difficult task to tackle.It is mainly used in security surveillance,human-computer interaction,and health care as an assistive or diagnostic technology in combination w...Human Activity Recognition(HAR)has always been a difficult task to tackle.It is mainly used in security surveillance,human-computer interaction,and health care as an assistive or diagnostic technology in combination with other technologies such as the Internet of Things(IoT).Human Activity Recognition data can be recorded with the help of sensors,images,or smartphones.Recognizing daily routine-based human activities such as walking,standing,sitting,etc.,could be a difficult statistical task to classify into categories and hence 2-dimensional Convolutional Neural Network(2D CNN)MODEL,Long Short Term Memory(LSTM)Model,Bidirectional long short-term memory(Bi-LSTM)are used for the classification.It has been demonstrated that recognizing the daily routine-based on human activities can be extremely accurate,with almost all activities accurately getting recognized over 90%of the time.Furthermore,because all the examples are generated from only 20 s of data,these actions can be recognised fast.Apart from classification,the work extended to verify and investigate the need for wearable sensing devices in individually walking patients with Cerebral Palsy(CP)for the evaluation of chosen Spatio-temporal features based on 3D foot trajectory.Case-control research was conducted with 35 persons with CP ranging in weight from 25 to 65 kg.Optical Motion Capture(OMC)equipment was used as the referral method to assess the functionality and quality of the foot-worn device.The average accuracy±precision for stride length,cadence,and step length was 3.5±4.3,4.1±3.8,and 0.6±2.7 cm respectively.For cadence,stride length,swing,and step length,people with CP had considerably high inter-stride variables.Foot-worn sensing devices made it easier to examine Gait Spatio-temporal data even without a laboratory set up with high accuracy and precision about gait abnormalities in people who have CP during linear walking.展开更多
In this study two genistein derivatives(G1 and G2)are reported as inhibitors of acetylcholinesterase(AChE)and butyrylcholinesterase(BuChE),and differences in the inhibition of AChE are described.Although they differ i...In this study two genistein derivatives(G1 and G2)are reported as inhibitors of acetylcholinesterase(AChE)and butyrylcholinesterase(BuChE),and differences in the inhibition of AChE are described.Although they differ in structure by a single methyl group,the inhibitory effect of G1(IC50¼264 nmol/L)on AChE was 80 times stronger than that of G2(IC50¼21,210 nmol/L).Enzyme-kinetic analysis,molecular docking and molecular dynamics(MD)simulations were conducted to better understand the molecular basis for this difference.The results obtained by kinetic analysis demonstrated that G1 can interact with both the catalytic active site and peripheral anionic site of AChE.The predicted binding free energies of two complexes calculated by the molecular mechanics/generalized born surface area(MM/GBSA)method were consistent with the experimental data.The analysis of the individual energy terms suggested that a difference between the net electrostatic contributions(ΔEele+ΔGGB)was responsible for the binding affinities of these two inhibitors.Additionally,analysis of the molecular mechanics and MM/GBSA free energy decomposition revealed that the difference between G1 and G2 originated from interactions with Tyr124,Glu292,Val294 and Phe338 of AChE.In conclusion,the results reveal significant differences at the molecular level in the mechanism of inhibition of AChE by these structurally related compounds.展开更多
Biodegradation has become a popular alternative remediation technology for its economic and ecological advantages. An aerobic bacterium （strain ZW） capable of degrading α-pinene was isolated from a biofilter by a s...Biodegradation has become a popular alternative remediation technology for its economic and ecological advantages. An aerobic bacterium （strain ZW） capable of degrading α-pinene was isolated from a biofilter by a selective enrichment. Based on the 16S rRNA gene analysis and physiochemical properties, this strain was identified as Pseudomonas veronii. Under the optimized condition achieved by the response surface methodology （RSM）, as well as pH 6.82, temperature 26.3℃ and NaC1 concentration 1.36%, almost 100% α-pinene could be removed within 45 hr. Enzymatic biodegradation by the crude intracellular enzyme could be described well by the Michaelis-Menten model in which the maximum degradation rate Vraax and the half-saturation constant Km were calculated to be 0.431 mmol/（L.min） and 0.169 mmol/L, respectively. Activity assay of catechol suggested that the strain ZW possessed a catechol- 1,2-dioxygenase and could decompose benzene-ring through ortho ring cleavage. Based on the identified intermediates by GC/MS, a new metabolic pathway was proposed, in which the final metabolites were some simpler organic and inorganic compounds. The present work demonstrated that the strain ZW would have a great application prospect for the remediation of α-pinene-contaminated environment.展开更多
Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energ...Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.展开更多
文摘A novel variable displacement compressor (VDC) for automotive air conditioner (AAC) is introduced, which inherits the advantages of common wobble plate type VDC. It has fewer parts and makes less noise, and instead of pneumatic valve the displacement is controlled by electronic control valve. In order to know the control mechanism well and get a good control effect, a mathematical model for the variable displacement mechanism is developed according to the geometrical and kinematical information of the compressor. Using the model, the effect of relevant parameters on variable displace control is estimated. It is helpful to make the optimum decision in the flow control of AAC. As the novel displacement control device, the structure and control rule of electronic control valve is introduced. It can get better effect than the conventional pneumatic valves. And by using this new electronic control device, the optimum systemic control of AAC is available.
基金Supported by the National Natural Science Foundation(61372053)the National High Technology Research and Development Program(2012AA040506)
文摘A novel thermal-assisted ultra-violet(UV) photocatalysis digestion method for the determination of total phosphorus(TP) in water samples was introduced in this work. The photocatalytic experiments for TP digestion were conducted using a 365 nm wavelength UV light and Ti O2 particles as the photocatalyst. Sodium tripolyphosphate and sodium glycerophosphate were used as the typical components of TP and the digested samples were then determined by spectrophotometry after phosphomolybdenum blue reaction. The effects of operational parameters such as reaction time and temperature were studied for the digestion of TP and the kinetic analysis of two typical components was performed in this paper. The pseudo-first-order rate constants k of two phosphorus compounds at different temperatures were obtained and the Arrhenius equation was employed to explain the effect of temperature on rate constant k. Compared with the conventional thermal digestion method for TP detection, it was found that the temperature was decreased from 120 °C to 60 °C with same conversion rate and time in this thermal-assisted UV digestion method, which enabled the digestion process work at normal pressure. Compared with the individual ultra-violet(UV) photocatalysis process, the digestion time was also decreased from several hours to half an hour using the thermal-assisted UV digestion method. This method will not lead to secondary pollution since no oxidant was needed in the thermal-assisted UV photocatalysis digestion process, which made it more compatible with electrochemical detection of TP.
基金Supported by the Natural Science Foundation of Zhejiang Province (No. 500105).
文摘The oxidation of carbon nanotubes, C60 and graphite was studied by thermogravimetric (TG) analysis and differential thermal analysis (DTA) technique, and the oxidation kinetic models of three carbon materials studied were analyzed by mechanism-function method. The results indicate that three carbon species adopt different oxidation mechanisms due to their different structures. The oxidation of carbon nanotubes with cylindrical structure follows contracting volume reaction mechanism [R3 mechanism, 1- (1- α)^1/3 = kt], indicating that the oxidation of carbon nanotubes takes place from the ends to the center. For graphite with planar sandwich structure, the oxidation starts at the edges initially and gradually moves toward the center, which corresponds to contracting area phase boundary reaction mechanism [R2 mechanism, 1 - (1 - α)^1/2 = kt]. The oxidation of C60 with spherical structure, however, is complex and apparently cannot be illustrated with a single kinetic model. The values of apparent activation energy obtained by the mechanism-function method are (145 ± 5) kJ·mol^-1 for carbon nanotubes and (193 ± 7) kJ·mol^-1 for graphite, respectively, while the value of apparent activation energy for C60 determined using Kissinger method is 91 kJ·mol^-1。
基金The Project Supported by the National Natural Science Foundation of China (No. 50233030)
文摘This work deals with the kinetics of co-condensation polymerization of AB2 and AB monomers, giving expressions of the two-dimensional molecular weight distribution function and the number/weight average molecular weights of the resulting copolymers. The two-dimensional molecular weight distribution depends on two indices, n and l, which are the respective numbers of AB2 and AB units in a copolymer species. The evolution of the two-dimensional weight and z distributions during the co-condensation polymerization has been evaluated systematically. Finally, the two-dimensional distribution was transformed into a one-dimensional molecular weight distribution with only one variable (the molecular weight of the products instead of the degree of polymerization). The calculated results show that the highly branched copolymer has a very broad molecular weight distribution when the co-condensation polymerization approaches completion.
基金supported by Beijing Natural Science Foundation(JQ20004)National Key Research and Development Program(2016YFA0202500)Scientific and Technological Key Project of Shanxi Province(20191102003).
文摘Oxygen reduction reaction(ORR)constitutes the core process of many energy storage and conversion devices including metal–air batteries and fuel cells.However,the kinetics of ORR is very sluggish and thus highperformance ORR electrocatalysts are highly regarded.Despite recent progress on minimizing the ORR halfwave potential as the current evaluation indicator,in-depth quantitative kinetic analysis on overall ORR electrocatalytic performance remains insufficiently emphasized.In this paper,a quantitative kinetic analysis method is proposed to afford decoupled kinetic information from linear sweep voltammetry profiles on the basis of the Koutecky–Levich equation.Independent parameters regarding exchange current density,electron transfer number,and electrochemical active surface area can be respectively determined following the proposed method.This quantitative kinetic analysis method is expected to promote understanding of the electrocatalytic effect and point out further optimization direction for ORR electrocatalysis.
基金Supported by National Natural Science Foundation of China(No.21207052)
文摘A pulsed discharge plasma（PDP） reactor with net anode and net cathode was established for investigating the pyrene degradation in soil under different pulse peak voltage,air flow rate,pyrene content in soil,initial p H value and initial water content of the soil.Pyrene oxidation within the 60 min discharge time was fitting according to the pseudo-first order equation and the corresponding reaction kinetics constants（k values） were calculated.The obtained results show that pyrene oxidation under all the different reaction conditions obeyed the pseudo-first order equation well.Higher pulsed peak voltage and appropriate air flow rate were in favor of the increase of reaction rate of pyrene oxidation.A higher k value could be achieved in the lower initial pyrene content（the value was 100 mg kg^-1）.The k value of pyrene oxidation in the case of p H=4 was 11.2 times higher than the value obtained under the condition of p H=9,while the initial water content of the soil also has a large effect on the oxidation rate of pyrene due to the effect of PDP.
基金supported by the National Natural Science Foundation of China [Grant No. 22278452]the SINOPEC Research Institute of Safety Engineering for financially supporting this project。
文摘In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of methane and propane(700–1000 K,10–20 bar)were studied experimentally and using kinetic modeling tools at stoichiometric fuel-tooxygen ratios.All the experiments were conducted through insentropic compression.The reliable experimental data were obtained by using the adiabatic core hypothesis,which can be used to generate and validate the detailed chemical kinetics model.The IDTs of methane and propane were recorded by a rapid compression machine(RCM)and compared to the predicted values obtained by the NUIGMech 3.0 mechanism.To test the applicability of NUIGMech 3.0 under different reaction conditions,the influence of temperature in the range of 700–1000 K(and the influence of pressure in the range of 10–20 bar)on the IDT was studied.The results showed that NUIGMech 3.0 could reasonably reproduce the experimentally determined IDT under the wide range of conditions studied.The constant volume chemical kinetics model was used to reveal the effect of temperature on the elementary reaction,and the negative temperature coefficient(NTC)behavior of propane was also observed at 20 bar.The experimental data can serve as a reference for the correction and application of kinetic data,as well as provide a theoretical basis for the safe conversion of low-carbon hydrocarbon chemicals.
基金supported by the Natural Science Foundation of China under Grant(No.52172099)the Provincial Joint Fund of Shaanxi(2021JLM-28).
文摘The large accumulation of coal gangue,a common industrial solid waste,causes severe environmental problems,and green development strategies are required to transform this waste into high-value-added products.In this study,low-cost ceramsites adsorbents were prepared from waste gangue,silt coal,and peanut shells and applied to remove the organic dye methylene blue from wastewater.We investigated the microstructure of ceramsites and the effects of the sintering atmosphere,sintering temperature,and solution pH on their adsorption performance.The ceramsites sintered at 800℃under a nitrogen atmosphere exhibited the largest three-dimensional-interconnected hierarchical porous structure among the prepared ceramsites;further,it exhibited the highest methylene blue adsorption performance,with an adsorption capacity of 0.954 mg·g^(−1),adsorption efficiency of over 95%,and adsorption equilibrium time of 1 h at a solution pH of 9.The removal efficiency remained greater than 75%after five adsorption cycles.The adsorption kinetics data were analyzed using various models,including the pseudosecond-order kinetic model and Langmuir equation,and the adsorption was attributed to electrostatic interactions between the dyes and ceramsites,n-interactions,and hydrogen bonds.The prepared coal gangue ceramsites exhibited excellent adsorption capacities,removal rates,and cyclic stabilities,demonstrating their promising application prospects for the comprehensive utilization of solid waste and for wastewater treatment.
基金National Natural Science Foundation of China(52076110,52106160)Jiangsu Provincial Natural Science Foundation of China(BK20200490,BK20220955)Fundamental Research Funds for the Central Universities(30923010208 and 30920031103).
文摘This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on assessing the coupled chemical effects of NH_(3) and CO_(2) on C2H4 combustion chemistry.The chemical effects could be evaluated by comparing fictitious inert NH_(3) or CO_(2) with normal active NH_(3) or CO_(2).The results revealed that the addition of NH_(3) decreased the mole fractions and production rates of key soot precursors,such as acetylene,propynyl,and benzene.When CO_(2) was used as the dilution gas,the coupled chemical effects of NH_(3) and CO_(2) were affected by the chemical effects of CO_(2) to varying degrees.With the oxidizer-side CO_(2) addition,the coupled chemical effects of NH_(3) and CO_(2) reduced the mole fractions of H,O,OH radicals,acetylene,propynyl,and benzene,while the effects differed from the fuel-side CO_(2) addition.The coupled chemical effects of NH_(3) and CO_(2) also promoted the formation of aldehyde contaminants,such as acetaldehyde,to some extent,particularly with CO_(2) addition on the oxidizer side.
基金This work was financially supported by the National Natural Science Foundation of China(No.52171144)the Fundamental Research Special Zone Program of Shanghai Jiao Tong University(No.21TQ1400215).
文摘The synthesis of carbide coatings on graphite substrates using molten salt synthesis(MSS),has garnered significant interest due to its cost-effective nature.This study investigates the reaction process and growth kinetics involved in MSS,shedding light on key aspects of the process.The involvement of Ti powder through liquid-phase mass transfer is revealed,where the diffusion distance and quantity of Ti powder play a crucial role in determining the reaction rate by influencing the C content gradient on both sides of the carbide.Furthermore,the growth kinetics of the carbide coating are predominantly governed by the diffusion behavior of C within the carbide layer,rather than the chemical reaction rate.To analyze the kinetics,the thickness of the carbide layer is measured with respect to heat treatment time and temperature,unveiling a parabolic relationship within the temperature range of 700-1300℃.The estimated activation energy for the reaction is determined to be 179283 J·mol^(-1).These findings offer valuable insights into the synthesis of carbide coatings via MSS,facilitating their optimization and enhancing our understanding of their growth mechanisms and properties for various applications.
基金Ho Chi Minh City University of Technology(HCMUT)Vietnam National University Ho Chi Minh City(VNU-HCM)for supporting this study。
文摘In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are established using MATLAB Simscape to analyze their kinetics and dynamics in the lifting and holding stages.The simulation findings are compared to the analytical calculation results in the steady state,and both methods show good agreement.In the early lifting stage,Model 1 produces greater force and discharges goods in the container faster than Model 2.Meanwhile,Model 2 reaches a higher force and ejects goods from the container cleaner than its counterpart at the end lifting stage.The established simulation models can consider the effects of dynamic loads due to inertial moments and forces generated during the system operation.It is crucial in studying,designing,and optimizing the structure of hydraulic-mechanical systems.
基金Project(2013CB632605)supported by the National Basic Research Development Program of ChinaProjects(51274178,51274179)supported by the National Natural Science Foundation of China
文摘A novel process was developed for the decomposition of vanadium slag using KOH sub-molten salt under ambient pressure, and the effects of reaction temperature, alkali-to-ore mass ratios, particle size, and stirring speed on vanadium and chromium extraction were studied. The results suggest that the reaction temperature and KOH-to-ore mass ratio are more influential factors for the extraction of vanadium and chromium. Under the optimal reaction conditions （temperature 180 °C, initial KOH-to-ore mass ratio 4：1, stirring speed 700 r/min, gas flow 1 L/min, and reaction time 300 min）, vanadium and chromium extraction rates can reach up to 95% and 90%, respectively. Kinetics analysis results show that the decomposing process of vanadium slag in KOH sub-molten salt can be well interpreted by the shrinking core model under internal diffusion control. The apparent activation energies for vanadium and chromium are 40.54 and 50.27 kJ/mol, respectively.
基金Project supported by the National Natural Science Foundation of China (No.30200266)the Program for New Century Excellent Talents in University of Ministry of Education of China(No.NCET-09-928)
文摘At 0.12 mmol/L γ-glutamyl p-nitroaniline(GGPNA),an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase(GGT) reaction process and the integration with the classical initial rate method to measure serum GGT.For the improved integrated method,an integrated rate equation,which used the predictor variable of reaction time and considered inhibitions by both GGPNA and products,was nonlinearly fit to GGT reaction processes.For the integration strategy,classical initial rates were estimated when GGPNA consumption percentages were below 50%;otherwise,maximal reaction rates of GGT were estimated by the improved integrated method and converted into initial rates according to the differential rate equation at 0.11 mmol/L GGPNA.The inte-gration strategy was validated using optimized GGT kinetic parameters and 10-s intervals to record reaction curves within 8.0 min.By the integration strategy,there was a linear response from 0.9 to 32.0 U/L GGT,coefficients of variation were below 3.5%for GGT from 8.0 to 32.0 U/L(n=5) ,and GGT activities in clinical sera responded linearly to their classical initial rates at 2.00 mmol/L GGPNA with an expected slope.Therefore,the integration strategy was successful in measuring GGT at 0.12 mmol/L GGPNA.
基金supported by Natural Science Foundation of Shandong Province(ZR2020QE199)State Key Laboratory of Pollution Control and Resource Utilization research(No.PCRRF19023)Key Research and Development Program of Liaoning Province(No.2020JH2/10300099)。
文摘The addition of effective additives can effectively improve the pyrolysis performance of oil sludge(OS)and have a great potential to reduce pyrolysis costs.In the present study,co-pyrolysis performance of OS with different proportions of additives at a heating rate of 10°C/min was conducted in a thermal analyzer.Walnut shell,Fe_(2)O_(3),K_(2)CO_(3),PVC and the pyrolysis char produced from OS at the final pyrolysis temperature of 700℃were selected as the additives.TG results showed that the OS pyrolysis with and without additives can be divided into five reaction stages,which include volatilization of free water,the escape of light components,the cleavage of heavy components,carbon decomposition and inorganic minerals decomposition.The addition of additives decreased the maximum weight loss rate when the blending ratio was 5 wt%during OS pyrolysis.Kinetic analysis revealed that the overall activation energy of pyrolysis reaction was lower during pyrolysis of OS with the addition of walnut shells and pyrolysis char.The activation energy of three main reaction stages all decreased during co-pyrolysis of OS with K_(2)CO_(3)and PVC.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(Grant Nos:22038011,51976168)the K.C.Wong Education Foundation,and the Natural Science Basic Research Program of Shaanxi(Program No.2021JLM-17).
文摘Chemical looping gasification(CLG)characteristics and kinetic analysis of Chlorella(CHL),simulated Chlorella(V-CHL)and medium-chain triglycerides(MCT)were investigated using a thermogravimetric analyzer coupled with an online mass spectrometer.The apparent activation energy was obtained via Kissinger-Akahira-Sunose(KAS)method.In the result of the weightless behavior,the addition of oxygen carrier inhibited the decomposition of V-CHL at lower temperatures but promoted its decomposition at high temperatures.The values of chemical looping process characteristic parameters showed that a 10 wt%oxygen carrier would maximize the release of volatile products in the CLG of MCT,with 5.12×10^(-6)%⋅min^(-1)⋅℃^(-3).Oxygen carriers also affected gaseous products.The LHV of gaseous products of CHL reached the largest when the oxygen carrier was 10 wt%,which was 8.13 MJ/m^(3).And the gaseous product of MCT had the largest LHV with 30 wt%oxygen carrier,which was 8.83 MJ/m^(3).According to the kinetic analysis,the minimum value of apparent activation energy of MCT chemical looping gasification was 89.54 kJ⋅mol^(-1) with the oxygen carrier of 30 wt%,which was 50%less than that of MCT pyrolysis.And the minimum value for V-CHL was obtained when the mass fraction of Fe2O3 was 50 wt%.This paper could provide a reference for the choice of algae,the design of reactors,and the targeted regulation of the gaseous product for the algae CLG process.
基金This study was supported by the National Natural Science Foundation of China
文摘A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The flow is stopped when the reagent zone comes in the flow cell, where absorbance-time data are collected at 580nm wavelength. The linear range of the determination is 0.1 -10μg/ml CN-. The sampling rate is 60h-1 and the relative standard deviation is 1.6% (n=16) at 5.0 μg/ml CN-1 level. With satisfactory results, the proposed method was applied to the determination of free cyanide in wastewater without sample pretreatment.
文摘Human Activity Recognition(HAR)has always been a difficult task to tackle.It is mainly used in security surveillance,human-computer interaction,and health care as an assistive or diagnostic technology in combination with other technologies such as the Internet of Things(IoT).Human Activity Recognition data can be recorded with the help of sensors,images,or smartphones.Recognizing daily routine-based human activities such as walking,standing,sitting,etc.,could be a difficult statistical task to classify into categories and hence 2-dimensional Convolutional Neural Network(2D CNN)MODEL,Long Short Term Memory(LSTM)Model,Bidirectional long short-term memory(Bi-LSTM)are used for the classification.It has been demonstrated that recognizing the daily routine-based on human activities can be extremely accurate,with almost all activities accurately getting recognized over 90%of the time.Furthermore,because all the examples are generated from only 20 s of data,these actions can be recognised fast.Apart from classification,the work extended to verify and investigate the need for wearable sensing devices in individually walking patients with Cerebral Palsy(CP)for the evaluation of chosen Spatio-temporal features based on 3D foot trajectory.Case-control research was conducted with 35 persons with CP ranging in weight from 25 to 65 kg.Optical Motion Capture(OMC)equipment was used as the referral method to assess the functionality and quality of the foot-worn device.The average accuracy±precision for stride length,cadence,and step length was 3.5±4.3,4.1±3.8,and 0.6±2.7 cm respectively.For cadence,stride length,swing,and step length,people with CP had considerably high inter-stride variables.Foot-worn sensing devices made it easier to examine Gait Spatio-temporal data even without a laboratory set up with high accuracy and precision about gait abnormalities in people who have CP during linear walking.
基金This work was funded in part of the Research Special Fund for Public Welfare Industry of Health(No.200802041)the National Great Science and Technology Projects(2012ZX09301002,2014ZX09507003-002)+1 种基金the International Collaboration Project(2011DFR31240)Institue of Chinese Materia Medica,China Academy of Chinese Medical Sciences&Peking Union Medical College graduate student innovation fund(2013-1007-18).
文摘In this study two genistein derivatives(G1 and G2)are reported as inhibitors of acetylcholinesterase(AChE)and butyrylcholinesterase(BuChE),and differences in the inhibition of AChE are described.Although they differ in structure by a single methyl group,the inhibitory effect of G1(IC50¼264 nmol/L)on AChE was 80 times stronger than that of G2(IC50¼21,210 nmol/L).Enzyme-kinetic analysis,molecular docking and molecular dynamics(MD)simulations were conducted to better understand the molecular basis for this difference.The results obtained by kinetic analysis demonstrated that G1 can interact with both the catalytic active site and peripheral anionic site of AChE.The predicted binding free energies of two complexes calculated by the molecular mechanics/generalized born surface area(MM/GBSA)method were consistent with the experimental data.The analysis of the individual energy terms suggested that a difference between the net electrostatic contributions(ΔEele+ΔGGB)was responsible for the binding affinities of these two inhibitors.Additionally,analysis of the molecular mechanics and MM/GBSA free energy decomposition revealed that the difference between G1 and G2 originated from interactions with Tyr124,Glu292,Val294 and Phe338 of AChE.In conclusion,the results reveal significant differences at the molecular level in the mechanism of inhibition of AChE by these structurally related compounds.
基金supported by the National Natural Science Foundation of China (No. 51178431)the International S&T Cooperation Program of China (No.2011DFA92660)+1 种基金the Key Project of Science and Technology Department of Zhejiang Province (No. 2011C13023)Zhejiang Provincial Funds for Distinguished Young Scientists (No. R5090230)
文摘Biodegradation has become a popular alternative remediation technology for its economic and ecological advantages. An aerobic bacterium （strain ZW） capable of degrading α-pinene was isolated from a biofilter by a selective enrichment. Based on the 16S rRNA gene analysis and physiochemical properties, this strain was identified as Pseudomonas veronii. Under the optimized condition achieved by the response surface methodology （RSM）, as well as pH 6.82, temperature 26.3℃ and NaC1 concentration 1.36%, almost 100% α-pinene could be removed within 45 hr. Enzymatic biodegradation by the crude intracellular enzyme could be described well by the Michaelis-Menten model in which the maximum degradation rate Vraax and the half-saturation constant Km were calculated to be 0.431 mmol/（L.min） and 0.169 mmol/L, respectively. Activity assay of catechol suggested that the strain ZW possessed a catechol- 1,2-dioxygenase and could decompose benzene-ring through ortho ring cleavage. Based on the identified intermediates by GC/MS, a new metabolic pathway was proposed, in which the final metabolites were some simpler organic and inorganic compounds. The present work demonstrated that the strain ZW would have a great application prospect for the remediation of α-pinene-contaminated environment.
基金Project supported by the National Basic Research Program(973 Program,2012CBA01205)。
文摘Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.
