The microscopic structures of the endosperm of indica rice varieties with different quality before and after gelatinization were observed using scanning electron microscope. The results showed that the degree of gelat...The microscopic structures of the endosperm of indica rice varieties with different quality before and after gelatinization were observed using scanning electron microscope. The results showed that the degree of gelatinization varied in different parts of the grain and in different varieties under the same experimental conditions. The gelatinization of dorsal side was the most complete. Its cells were decomposed totally into puff-like or flocculent materials. The ventral side gelatinized less thoroughly, appearing agglomerate and some cell frames were still visible. The middle part gelatinized most incompletely and the cells were still integrated. Evident differences in gelatinization were observed among different varieties, the dorsal, ventral and middle parts of high quality varieties gelatinized more thoroughly than those of the corresponding parts of low quality varieties respectively. An obvious concavity often appeared in the middle of the cross-section of the low quality grains while the cross-section of high quality grains was normally flat. The same phenomenon was noted when comparing the early maturing indica rice and the late maturing indica rice. Varietal difference of gelatinization in dorsal sides was not as distinct as in middle parts and ventral sides. The difference among dorsal side, middle part and ventral side in gelatinization was greater in low quality grains than that of high quality grains. In addition, a lot of ruptured cells were observed in the cross-section of high quality rice, while few of them could be found in the low quality rice. Apparently, the number of ruptured cells is positively correlated with rice quality. Quality of rice grain also has positive correlation with the rate of water absorption and extension. High rates of water absorption and extension lead to better gelatinization of rice grain, and hence indicate good quality.展开更多
Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent he...Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent heterogeneity and complex internal structure of coal,a well-established method for predicting permeability based on microscopic fracture structures remains elusive.This paper presents a novel integrated approach that leverages the intrinsic relationship between microscopic fracture structure and permeability to construct a predictive model for coal permeability.The proposed framework encompasses data generation through the integration of three-dimensional(3D)digital core analysis and numerical simulations,followed by data-driven modeling via machine learning(ML)techniques.Key data-driven strategies,including feature selection and hyperparameter tuning,are employed to improve model performance.We propose and evaluate twelve data-driven models,including multilayer perceptron(MLP),random forest(RF),and hybrid methods.The results demonstrate that the ML model based on the RF algorithm achieves the highest accuracy and best generalization capability in predicting permeability.This method enables rapid estimation of coal permeability by inputting two-dimensional(2D)computed tomography images or parameters of the microscopic fracture structure,thereby providing an accurate and efficient means of permeability prediction.展开更多
In order to study the deterioration characteristics of the microscopic structure of sandstones in freeze-thaw cycles, tests of180 freeze-thaw cycles were performed on sandstone specimens. The nuclear magnetic resonan...In order to study the deterioration characteristics of the microscopic structure of sandstones in freeze-thaw cycles, tests of180 freeze-thaw cycles were performed on sandstone specimens. The nuclear magnetic resonance （NMR） technique was applied tothe measurement of sandstone specimens and analysis of the magnetic resonance imaging. Then, the fractal theory was employed tocompute the fractal dimension values of pore development of rocks after different freeze-thaw cycles. The results show that the massand porosity of rocks grow with the increase of freeze-thaw cycles. According to the NMR T2 distribution of sandstones, the poresizes of rock specimens increase after 180 freeze-thaw cycles, especially that of the medium-sized and small-sized pores. The spatialdistribution of sandstone pores after freeze-thaw cycles has fractal features within certain range, and the fractal dimension ofsandstones tends to increase gradually.展开更多
[Objective] The paper was to explore the microscopic structure of rabbit hair. [Method] Single rabbit hair with typical features was selected to observe its mi- croscopic structure from tip to root, and its fiber diam...[Objective] The paper was to explore the microscopic structure of rabbit hair. [Method] Single rabbit hair with typical features was selected to observe its mi- croscopic structure from tip to root, and its fiber diameter was also measured. [Result] The rabbit hair tip was constituted by scale layer and cortical layer, without medullary layer; the middle part was generally constituted by scale layer, cortical layer and medullary layer; the root had no medullary layer, and the scale layer was wheatear-shaped. This was the property of rabbit hair, which could be used for comparative studies with other animal fiber and species identification. Rabbit hair had developed medullary layer, and fiber diameter was positively related to column number of medullary cavity. The hair generally was single column, and coarse hair was multi-column. Single rabbit hair was the finest in the tip, coarse in the middle and tapering in the root. The diameter difference of various parts was large, and the ex- ternal growth characteristics was spindle-shaped. [Conclusion] Using biological micro- scope method to identify different animal fur and product species is more objective and simple.展开更多
[Objective] This study aimed to compare the effects of Chinese quality-improving fragrunce-increasing tobacco flue-curing technology, Chinese three- stage tobaeeo flue-curing technology and Zimbabwean tobaceo flue-eur...[Objective] This study aimed to compare the effects of Chinese quality-improving fragrunce-increasing tobacco flue-curing technology, Chinese three- stage tobaeeo flue-curing technology and Zimbabwean tobaceo flue-euring technology on microscopie structure of flue-cured tobacco leaves to provide theoretical basis for tobacco flue-curing. [ Method ] Middle leaves of tobacco cultivar K326 were collected in Pengshui County of Chongqing City for flue-curing experiment using three flue-curing technologies. Leaf samples were collected regularly in the flue-curing process, to investigate the microscopic structure of flue-cured tobaceo leaves. [ Result] During three flue-curing processes, leaves, palisade tissues and sponge tissues shrank gradually. Three flue-euring processes exhibited significant differ- ences in the peak of tissue shrinkage ： microscopic structure of flue-cured tobacco leaves in Chinese three-stage tobacco flue-curing process shrank earliest, follower by Chinese quality-improving fragrance-increasing tobacco flue-curing process; flue-eured tobacco leaves in Zimbabwean tobacco flue-curing process presented the latest shrinkage. At 84 h post-curing, leaf thickness in three flue-curing processes showed a descend order of Chinese three-stage tobacco flue-curing process 〉 Chinese quality-improving fragrance-increasing tobacco flue-curing process 〉 Zimbabwean tobacco flue-curing process. Upper and lower epidermal cells in Zimb- abwean tobacco flue-curing process ruptured earlier than other two flue-curing processes; eventually, the majority of cells ruptured and mixed with palisade tissues and sponge tissues. In Chinese quality-improving fragranee-increasing tobacco flue-curing process, only a small number of epidermal cells in dried leaves ruptured. Among three flue-curing technologies, Zimbabwean tobacco flue-curing technology exhibited the greatest damage to epidermal cells, followed by Chinese three-stage tobaceo flue-curing technology; Chinese quality-improving fragrance-increasing tobacco flue-curing technology had the minimum damage to epidermal cells. Mese- phyll cross-section exhibited significant morphological changes in stomata. To be specific, at 0 - 12 h post-curing, stomata of tobacco leaves closed with slightly prominent stamatal apparatuses on upper and lower epidermis; at 24 -72 h post-curing, stomata of tobaceo leaves changed gradually from opening to closure with significantly prominent stomatal apparatuses on upper and lower epidermis; at 84 h post-curing, stomata of tobacco leaves closed, and the majority of stomatal appa- ratuses were significantly prominent. In Chinese quality-improving fragrance-increasing tobacco flue-curing process, only a small number of epidermal ceils ruptured at 84 h pest-flue-curing; palisade tissues and sponge tissues shrank almost simultaneously. Significant gaps were observed between palisade tissues and between pal- isade tissues and sponge tissues. Chinese quality-improving fragrance-increasing tobacco flue-curing technology exhibited lower disorder level compared with other two flue-curing technologies. [ Conclusion] Chinese quality-improving fragrance-increasing tobacco flue-curlng technology was conducive to maintaining the micro- scopic structure integrity of flue-cured tobacco leaves and obtaining high-quality flue-cured tobacco leaves.展开更多
Understanding the impact of mining disturbances and creep deformation on the macroscopic deformation and the microscopic pore and fracture structures(MPFS)of coal is paramount for ensuring the secure extraction of coa...Understanding the impact of mining disturbances and creep deformation on the macroscopic deformation and the microscopic pore and fracture structures(MPFS)of coal is paramount for ensuring the secure extraction of coal resources.This study conducts cyclic loading-unloading and creep experiments on coal using a low-field nuclear magnetic resonance(NMR)experimental apparatus which is equipped with mechanical loading units,enabling real-time monitoring the T2spectrum.The experiments indicated that cyclic loading-unloading stress paths initiate internal damage within coal samples.Under identical creep stress conditions,coal samples with more initial damages had more substantial instantaneous deformation and creep deformation during the creep process.After undergoing nearly 35 h of staged creep,the total strains for coal samples CC01,CC02,and CC03 reach 2.160%,2.261%,and 2.282%,respectively.In the creep stage,the peak area ratio of seepage pores and microfractures(SPM)gradually diminishes.A higher degree of initial damage leads to a more pronounced compaction trend in the SPM of coal samples.Considering the porosity evolution of SPM during the creep process,this study proposes a novel fractional derivative model for the porosity evolution of SPM.The efficacy of the proposed model in predicting porosity evolution of SPM is substantiated through experimental validation.Furthermore,an analysis of the impact mechanisms on key parameters in the model was carried out.展开更多
Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we syst...Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we systematically study the microscopic pore structures of shales by using Argon-ion polishing Scanning Electron Microscope(SEM),high-pressure mercury injection and low-temperature nitrogen adsorption and desorption experiments.The study results show that:the Longmaxi Shale in this area are dominated by nano-scale pores which can be classified into organic pores,inorganic pores(intergranular pores,intragranular pores,inter-crystalline pores and dissolution pores),microfractures(intragranular structure fractures,interlayer sliding fractures,diagenetic shrinkage joints and abnormal-pressure fractures from organic evolution),among which organic pores and clay mineral pores are predominant and organic pores are the most common;a TOC value shows an obvious positive correlation with the content of organic pores,which account for up to 50%in the lower-quality shales with a TOC of over 2%where they are most developed;microscopic pore structures are very complex and open,with pores being mainly in cylinder shape with two ends open,or in parallel tabular shape with four sides open and 2–30 nm in diameter,being mostly medium pores.On this basis,factors affecting the micropore structures of shales in this area are studied.It is concluded that organic matter abundance and thermal maturity are the major factors controlling the microscopic pore structures of shales,while the effects of clay mineral content are relatively insignificant.展开更多
We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and micr...We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and microscopic pore structure properties of composites was studied by combining macroscopic and microscopic testing methods.The experimental results show that the addition of EMR can improve the working performance of the slurry and enhance the strength in the later stage,the 28 d compressive strength value of the slurry doped with EMR can reach 49.5 MPa.The Mn element and NH4_(+)^(-)N in EMR react with MgO in the raw material to produce Struvite and Mn(OH)_(2)and Mn_(3)(PO_(4))·6H_(2)O gel,the hydration products coexist with each other and lap each other to form a dense microfine structure and effectively refine the pores.The hydration process consists of five stages,mainly concentrated in the first 10 h or less to exothermic mainly,infrared spectral absorption band is mainly composed of O-H bond,H-O-H bond,PO_(4)bond and metal oxygen bond 3 parts,EMR makes the wave number of the absorption band from the ground wave number to the high wave number.EMR doping T_(2)spectral relaxation time will lag behind,the pore size distribution changes.The total porosity and bound fluid saturation decrease with increasing,the free fluid saturation shows the opposite trend,the permeability decreases and then increases.展开更多
Transforming a scattering medium into a lens for imaging very simple binary objects is possible;however,it remains challenging to image complex grayscale objects,let alone measure 3D continuous distribution objects.He...Transforming a scattering medium into a lens for imaging very simple binary objects is possible;however,it remains challenging to image complex grayscale objects,let alone measure 3D continuous distribution objects.Here,we propose and demonstrate the use of a ground glass diffuser as a scattering lens for imaging complex grayscale fringes,and we employ it to achieve microscopic structured light 3D imaging(MSL3DI).The ubiquitous property of the speckle patterns permits the exploitation of the scattering medium as an ultra-thin scattering lens with a variable focal length and a flexible working distance for microscale object measurement.The method provides a light,flexible,and cost-effective imaging device as an alternative to microscope objectives or telecentric lenses in conventional MSL3DI systems.We experimentally demonstrate that employing a scattering lens allows us to achieve relatively good phase information and robust 3D imaging from depth measurements,yielding measurement accuracy only marginally lower than that of a telecentric lens,typically within approximately 10μm.Furthermore,the scattering lens demonstrates robust performance even when the imaging distance exceeds the typical working distance of a telecentric lens.The proposed method facilitates the application of scattering imaging techniques,providing a more flexible solution for MSL3DI.展开更多
To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,...To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,Scanning Electron Microscopy(SEM),and Nuclear Magnetic Resonance(NMR)experiments were conducted.The mechanical property degradation laws and evolution characteristics of the microscopic pore structure of moraine soil under Freeze-Thaw(F-T)conditions were revealed.After F-T cycles,the stress-strain curves of moraine soil showed a strain-softening trend.In the early stage of F-T cycles(0–5 cycles),the shear strength and elastic modulus exhibited damage rate of approximately 10.33%±0.8%and 16.60%±1.2%,respectively.In the later stage(10–20 cycles),the strength parameters fluctuated slightly and tended to stabilize.The number of F-T cycles was negatively exponentially correlated with cohesion,while showing only slight fluctuation in the internal friction angle,thereby extending the Mohr-Coulomb strength criterion for moraine soil under F-T cycles.The NMR experiments quantitatively characterized the evolution of the internal pore structure of moraine soil under F-T cycles.As the number of F-T cycles increased,fine and micro pores gradually expanded and merged due to the frost-heaving effect during the water-ice phase transition,forming larger pores.The proportion of large and medium pores increased to 59.55%±2.1%(N=20),while that of fine and micro pores decreased to 40.45%±2.1%(N=20).The evolution of pore structure characteristics was essentially completed in the later stage of F-T cycles(10–20 cycles).This study provides a theoretical foundation and technical support for major engineering construction and disaster prevention in the Qinghai-Xizang Plateau.展开更多
Coal and gas outburst is a frequent dynamic disaster during underground coal mining activities.After about 150 years of exploration,the mechanisms of outbursts remain unclear to date.Studies on outburst mechanisms wor...Coal and gas outburst is a frequent dynamic disaster during underground coal mining activities.After about 150 years of exploration,the mechanisms of outbursts remain unclear to date.Studies on outburst mechanisms worldwide focused on the physicochemical and mechanical properties of outburst-prone coal,laboratory-scale outburst experiments and numerical modeling,mine-site investigations,and doctrines of outburst mechanisms.Outburst mechanisms are divided into two categories:single-factor and multi-factor mechanisms.The multi-factor mechanism is widely accepted,but all statistical phenomena during a single outburst cannot be explained using present knowledge.Additional topics about outburst mechanisms are proposed by summarizing the phenomena that need precise explanation.The most appealing research is the microscopic process of the interaction between coal and gas.Modern physical-chemical methods can help characterize the natural properties of outburst-prone coal.Outburst experiments can compensate for the deficiency of first-hand observation at the scene.Restoring the original outburst scene by constructing a geomechanical model or numerical model and reproducing the entire outburst process based on mining environment conditions,including stratigraphic distribution,gas occurrence,and geological structure,are important.Future studies can explore outburst mechanisms at the microscale.展开更多
In order to effectively utilize the high reactivity coke, the gasification characteristics of high and low reactivity cokes were investigated at 1100 ℃. Low reactivity coke A and high reactivity coke B were chosen an...In order to effectively utilize the high reactivity coke, the gasification characteristics of high and low reactivity cokes were investigated at 1100 ℃. Low reactivity coke A and high reactivity coke B were chosen and charged into the reaction tube in two methods. The results indicated that the mass loss ratio of high reactivity coke in mixed cokes was more significant than that of single high reactivity coke in the middle stage of reaction. Nevertheless, the mass loss ratio of low reactivity coke in mixed cokes was less than that of single low reactivity coke. It was mainly attributed to gas diffusion and internal reaction of coke. When high and low reactivity cokes were mixed, the practical average mass loss ratio was nearly the same as the weighted average. The microscopic structures of coke indicated that with the increase of reaction time, the external and internal layers of low reactivity coke reacted more uniformly with CO2, whereas the reaction degree of external layer of high reactivity coke was obviously higher.展开更多
Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature ...Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration.展开更多
Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution la...Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution law of pores and fractures in the Cretaceous tight reservoir in the Liuhe Basin,and reveals its controlling effect on tight oil and gas accumulation.The results show that intercrystalline pores,intergranular pores and dissolution pores are scattered and only developed in shallow tight reservoirs,while microfractures are developed in both shallow and deep layers,which are the main type of reservoir space in the study area.The results of mercury intrusion porosimetry and nitrogen gas adsorption show that with the increase of depth,the proportion of macropores(microcracks)increases,while the proportion of micropores decreases.There are two stages of microfractures developed in the study area,corresponding to the initial fault depression stage from late Jurassic to early late Cretaceous and compressional uplift at the end of late Cretaceous.According to the principle of“inversion and back-stripping method”,combined with the data of optical microscopy and inclusions,the time of each key diagenesis and its contribution to porosity are revealed,and the porosity evolution history of reservoirs in different diagenetic stages is quantitatively restored.The porosity reduction rate of compaction can reach more than 80%,which is the main reason for reservoir densification.The relationship between pore evolution history and oil and gas accumulation history reveals that during the oil and gas filling period of the Xiahuapidianzi Formation(90-85 Ma),the reservoir porosity is only 1.15%,but the development of microfractures in the first stage of the reservoir is conducive to oil and gas accumulation.展开更多
Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxi...Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance(NMR) detection was conducted.Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging(NMRI) techniques. The results revealed that seepage pores and microfractures(SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores(AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damagestate adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics(size and degree of difficulty) of coal.展开更多
A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based ...A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride （FC） and polymer ferric sulfate （PFS） pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.展开更多
The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of ...The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of La were measured, and the mechanisms and the effects of La on sulfide inclusions, microstracture and properties of steel were determined. Strip-like sulfides disappear in heavy rail steel with La/（O＋S）〉3.50, which is shown that the metallurgical function of modifying sulfide inclusions has been achieved by La. La can fine the grain size of the austenite in heavy rail steel. Under the experimental condition, the plasticity and the impacting toughness of heavy rail steel with 0.005wt% La can evidently be improved.展开更多
In experimental conditions simulating reducing atmosphere in Blast Furnace, the samples of Al 2O 3 C brick were heated at high temperature. Their microscopic structures were observed by Scanning Electric Telescope ...In experimental conditions simulating reducing atmosphere in Blast Furnace, the samples of Al 2O 3 C brick were heated at high temperature. Their microscopic structures were observed by Scanning Electric Telescope and rupture and compressive strength measured before and after heating observed the changes. According to these measurements, the reasons causing the changes were analyzed.展开更多
Using the laser granularity survey technology , logy, X-ray powder diffraction, scanning electron microscopy （SEM） and infrared spectrum anal）sis methods, we studied the microscopic structure and chemical bonds cha...Using the laser granularity survey technology , logy, X-ray powder diffraction, scanning electron microscopy （SEM） and infrared spectrum anal）sis methods, we studied the microscopic structure and chemical bonds changes of β-C2 S monomineral under the high energy ball grinding function. The result indicates that, continuously under the mechanical power, β-C2 S crystal size would decrease, the micro strain and the effective Beff parameter would increase, and the amorphous phases would be presented. Furthermore, the mechanical power would cause Si-O bond broken and reorganized, the specific surface area would increase, the energy of micro-powder agglomeration vibration would be enhanced and the crystal would be disordered. Finally, β- C2 S was caused to have the mechanochemical change and the activity enhancement.展开更多
Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the redu...Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the reduced glass transition temperatures and the excess volume,we found that the Cu-Zr glasses have the largest GFA at Cu65Zr35 composition.To get more detailed information of local structure,we calculated the pair correlation functions,partial pair correlation functions,the excess entropy,chemical order parameter,coordination number,and Voronoi index of Cu-Zr liquids.We found that there exists an obvious and close relationship among the GFA,the excess entropy calculated using the total pair correlation functions,chemical order parameters,and some Cu centered cluster with Voronoi index <0,2,8,1> and Zr centered cluster with Voronoi index <0,3,6,4>,which all have nonlinear dependences on Cu/Zr concentration and have extreme values at liquid Cu65Zr35 composition.展开更多
文摘The microscopic structures of the endosperm of indica rice varieties with different quality before and after gelatinization were observed using scanning electron microscope. The results showed that the degree of gelatinization varied in different parts of the grain and in different varieties under the same experimental conditions. The gelatinization of dorsal side was the most complete. Its cells were decomposed totally into puff-like or flocculent materials. The ventral side gelatinized less thoroughly, appearing agglomerate and some cell frames were still visible. The middle part gelatinized most incompletely and the cells were still integrated. Evident differences in gelatinization were observed among different varieties, the dorsal, ventral and middle parts of high quality varieties gelatinized more thoroughly than those of the corresponding parts of low quality varieties respectively. An obvious concavity often appeared in the middle of the cross-section of the low quality grains while the cross-section of high quality grains was normally flat. The same phenomenon was noted when comparing the early maturing indica rice and the late maturing indica rice. Varietal difference of gelatinization in dorsal sides was not as distinct as in middle parts and ventral sides. The difference among dorsal side, middle part and ventral side in gelatinization was greater in low quality grains than that of high quality grains. In addition, a lot of ruptured cells were observed in the cross-section of high quality rice, while few of them could be found in the low quality rice. Apparently, the number of ruptured cells is positively correlated with rice quality. Quality of rice grain also has positive correlation with the rate of water absorption and extension. High rates of water absorption and extension lead to better gelatinization of rice grain, and hence indicate good quality.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY23E040001)Fundamental Research Funding Project of Zhejiang Province,China(Project Category A,Grant No.2022YW06)National Key R&D Program of China(Grant No.2023YFF0614902).
文摘Accurate prediction of coal reservoir permeability is crucial for engineering applications,including coal mining,coalbed methane(CBM)extraction,and carbon storage in deep unmineable coal seams.Owing to the inherent heterogeneity and complex internal structure of coal,a well-established method for predicting permeability based on microscopic fracture structures remains elusive.This paper presents a novel integrated approach that leverages the intrinsic relationship between microscopic fracture structure and permeability to construct a predictive model for coal permeability.The proposed framework encompasses data generation through the integration of three-dimensional(3D)digital core analysis and numerical simulations,followed by data-driven modeling via machine learning(ML)techniques.Key data-driven strategies,including feature selection and hyperparameter tuning,are employed to improve model performance.We propose and evaluate twelve data-driven models,including multilayer perceptron(MLP),random forest(RF),and hybrid methods.The results demonstrate that the ML model based on the RF algorithm achieves the highest accuracy and best generalization capability in predicting permeability.This method enables rapid estimation of coal permeability by inputting two-dimensional(2D)computed tomography images or parameters of the microscopic fracture structure,thereby providing an accurate and efficient means of permeability prediction.
基金Projects(41502327,51474252)supported by the National Natural Science Foundation of ChinaProject(2013YQ17046310)supported by the National Key Scientific Instrument and Equipment Development Project of China+1 种基金Project(20130162120012)supported by the Special Research Fund for the Doctoral Program of Higher Education of ChinaProject(2015CX005)supported by Innovation Driven Plan of Central South University,China
文摘In order to study the deterioration characteristics of the microscopic structure of sandstones in freeze-thaw cycles, tests of180 freeze-thaw cycles were performed on sandstone specimens. The nuclear magnetic resonance （NMR） technique was applied tothe measurement of sandstone specimens and analysis of the magnetic resonance imaging. Then, the fractal theory was employed tocompute the fractal dimension values of pore development of rocks after different freeze-thaw cycles. The results show that the massand porosity of rocks grow with the increase of freeze-thaw cycles. According to the NMR T2 distribution of sandstones, the poresizes of rock specimens increase after 180 freeze-thaw cycles, especially that of the medium-sized and small-sized pores. The spatialdistribution of sandstone pores after freeze-thaw cycles has fractal features within certain range, and the fractal dimension ofsandstones tends to increase gradually.
基金Supported by Special Fund for Basic Research in National Non-profit Scientific Research Institute(Chinese Academy of Agricultural Sciences,Lanzhou Animal Husbandry and Veterinary Research Institute)(1610322012010)~~
文摘[Objective] The paper was to explore the microscopic structure of rabbit hair. [Method] Single rabbit hair with typical features was selected to observe its mi- croscopic structure from tip to root, and its fiber diameter was also measured. [Result] The rabbit hair tip was constituted by scale layer and cortical layer, without medullary layer; the middle part was generally constituted by scale layer, cortical layer and medullary layer; the root had no medullary layer, and the scale layer was wheatear-shaped. This was the property of rabbit hair, which could be used for comparative studies with other animal fiber and species identification. Rabbit hair had developed medullary layer, and fiber diameter was positively related to column number of medullary cavity. The hair generally was single column, and coarse hair was multi-column. Single rabbit hair was the finest in the tip, coarse in the middle and tapering in the root. The diameter difference of various parts was large, and the ex- ternal growth characteristics was spindle-shaped. [Conclusion] Using biological micro- scope method to identify different animal fur and product species is more objective and simple.
基金Supported by General Program of Science and Technology Project of China National Tobacco Corporation[ZYB(2012)No.122]Science and Technology Project of Chongqing Branch of China National Tobacco Corporation(NY20110601070010)
文摘[Objective] This study aimed to compare the effects of Chinese quality-improving fragrunce-increasing tobacco flue-curing technology, Chinese three- stage tobaeeo flue-curing technology and Zimbabwean tobaceo flue-euring technology on microscopie structure of flue-cured tobacco leaves to provide theoretical basis for tobacco flue-curing. [ Method ] Middle leaves of tobacco cultivar K326 were collected in Pengshui County of Chongqing City for flue-curing experiment using three flue-curing technologies. Leaf samples were collected regularly in the flue-curing process, to investigate the microscopic structure of flue-cured tobaceo leaves. [ Result] During three flue-curing processes, leaves, palisade tissues and sponge tissues shrank gradually. Three flue-euring processes exhibited significant differ- ences in the peak of tissue shrinkage ： microscopic structure of flue-cured tobacco leaves in Chinese three-stage tobacco flue-curing process shrank earliest, follower by Chinese quality-improving fragrance-increasing tobacco flue-curing process; flue-eured tobacco leaves in Zimbabwean tobacco flue-curing process presented the latest shrinkage. At 84 h post-curing, leaf thickness in three flue-curing processes showed a descend order of Chinese three-stage tobacco flue-curing process 〉 Chinese quality-improving fragrance-increasing tobacco flue-curing process 〉 Zimbabwean tobacco flue-curing process. Upper and lower epidermal cells in Zimb- abwean tobacco flue-curing process ruptured earlier than other two flue-curing processes; eventually, the majority of cells ruptured and mixed with palisade tissues and sponge tissues. In Chinese quality-improving fragranee-increasing tobacco flue-curing process, only a small number of epidermal cells in dried leaves ruptured. Among three flue-curing technologies, Zimbabwean tobacco flue-curing technology exhibited the greatest damage to epidermal cells, followed by Chinese three-stage tobaceo flue-curing technology; Chinese quality-improving fragrance-increasing tobacco flue-curing technology had the minimum damage to epidermal cells. Mese- phyll cross-section exhibited significant morphological changes in stomata. To be specific, at 0 - 12 h post-curing, stomata of tobacco leaves closed with slightly prominent stamatal apparatuses on upper and lower epidermis; at 24 -72 h post-curing, stomata of tobaceo leaves changed gradually from opening to closure with significantly prominent stomatal apparatuses on upper and lower epidermis; at 84 h post-curing, stomata of tobacco leaves closed, and the majority of stomatal appa- ratuses were significantly prominent. In Chinese quality-improving fragrance-increasing tobacco flue-curing process, only a small number of epidermal ceils ruptured at 84 h pest-flue-curing; palisade tissues and sponge tissues shrank almost simultaneously. Significant gaps were observed between palisade tissues and between pal- isade tissues and sponge tissues. Chinese quality-improving fragrance-increasing tobacco flue-curing technology exhibited lower disorder level compared with other two flue-curing technologies. [ Conclusion] Chinese quality-improving fragrance-increasing tobacco flue-curlng technology was conducive to maintaining the micro- scopic structure integrity of flue-cured tobacco leaves and obtaining high-quality flue-cured tobacco leaves.
基金the National Science Fund for Distinguished Young Scholars(No.52225403)the Natural Science Foundation of Shanxi Province(No.202303021212073)the National Natural Science Foundation of China(No.52104210)。
文摘Understanding the impact of mining disturbances and creep deformation on the macroscopic deformation and the microscopic pore and fracture structures(MPFS)of coal is paramount for ensuring the secure extraction of coal resources.This study conducts cyclic loading-unloading and creep experiments on coal using a low-field nuclear magnetic resonance(NMR)experimental apparatus which is equipped with mechanical loading units,enabling real-time monitoring the T2spectrum.The experiments indicated that cyclic loading-unloading stress paths initiate internal damage within coal samples.Under identical creep stress conditions,coal samples with more initial damages had more substantial instantaneous deformation and creep deformation during the creep process.After undergoing nearly 35 h of staged creep,the total strains for coal samples CC01,CC02,and CC03 reach 2.160%,2.261%,and 2.282%,respectively.In the creep stage,the peak area ratio of seepage pores and microfractures(SPM)gradually diminishes.A higher degree of initial damage leads to a more pronounced compaction trend in the SPM of coal samples.Considering the porosity evolution of SPM during the creep process,this study proposes a novel fractional derivative model for the porosity evolution of SPM.The efficacy of the proposed model in predicting porosity evolution of SPM is substantiated through experimental validation.Furthermore,an analysis of the impact mechanisms on key parameters in the model was carried out.
文摘Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we systematically study the microscopic pore structures of shales by using Argon-ion polishing Scanning Electron Microscope(SEM),high-pressure mercury injection and low-temperature nitrogen adsorption and desorption experiments.The study results show that:the Longmaxi Shale in this area are dominated by nano-scale pores which can be classified into organic pores,inorganic pores(intergranular pores,intragranular pores,inter-crystalline pores and dissolution pores),microfractures(intragranular structure fractures,interlayer sliding fractures,diagenetic shrinkage joints and abnormal-pressure fractures from organic evolution),among which organic pores and clay mineral pores are predominant and organic pores are the most common;a TOC value shows an obvious positive correlation with the content of organic pores,which account for up to 50%in the lower-quality shales with a TOC of over 2%where they are most developed;microscopic pore structures are very complex and open,with pores being mainly in cylinder shape with two ends open,or in parallel tabular shape with four sides open and 2–30 nm in diameter,being mostly medium pores.On this basis,factors affecting the micropore structures of shales in this area are studied.It is concluded that organic matter abundance and thermal maturity are the major factors controlling the microscopic pore structures of shales,while the effects of clay mineral content are relatively insignificant.
基金Funden by the National Natural Science Foundation of China(Nos.51868044 and 52178216)the Basic Research Program of Qinghai Province(No.2022-ZJ-921)+2 种基金“the Innovation Star”Project for Excellent Postgraduates in Gansu Province(No.2022-CXZX-450)the Hongliu First-class Discipline Construction Program of Lanzhou University of TechnologyScience and Technology Project of Gansu Provincial Department of Transportation(No.2022-23)。
文摘We considered adding different amounts(1%,2%,3%,and 4%)of EMR to prepare manganese residue polymer magnesium phosphate cement composite(EMR-PMPC).The influence mechanism of EMR doping on the early macroscopic and microscopic pore structure properties of composites was studied by combining macroscopic and microscopic testing methods.The experimental results show that the addition of EMR can improve the working performance of the slurry and enhance the strength in the later stage,the 28 d compressive strength value of the slurry doped with EMR can reach 49.5 MPa.The Mn element and NH4_(+)^(-)N in EMR react with MgO in the raw material to produce Struvite and Mn(OH)_(2)and Mn_(3)(PO_(4))·6H_(2)O gel,the hydration products coexist with each other and lap each other to form a dense microfine structure and effectively refine the pores.The hydration process consists of five stages,mainly concentrated in the first 10 h or less to exothermic mainly,infrared spectral absorption band is mainly composed of O-H bond,H-O-H bond,PO_(4)bond and metal oxygen bond 3 parts,EMR makes the wave number of the absorption band from the ground wave number to the high wave number.EMR doping T_(2)spectral relaxation time will lag behind,the pore size distribution changes.The total porosity and bound fluid saturation decrease with increasing,the free fluid saturation shows the opposite trend,the permeability decreases and then increases.
基金supported by the National Natural Science Foundation of China(Grant Nos.62275188 and 62505216)the Central Guidance on Local Science and Technology Development Fund(Grant No.YDZJSX2024D019)+1 种基金the International Scientific and Technological Cooperative Project in Shanxi Province(Grant No.202104041101009)the Natural Science Foundation of Shanxi Province of China through Research Project(Grant No.20210302123195).
文摘Transforming a scattering medium into a lens for imaging very simple binary objects is possible;however,it remains challenging to image complex grayscale objects,let alone measure 3D continuous distribution objects.Here,we propose and demonstrate the use of a ground glass diffuser as a scattering lens for imaging complex grayscale fringes,and we employ it to achieve microscopic structured light 3D imaging(MSL3DI).The ubiquitous property of the speckle patterns permits the exploitation of the scattering medium as an ultra-thin scattering lens with a variable focal length and a flexible working distance for microscale object measurement.The method provides a light,flexible,and cost-effective imaging device as an alternative to microscope objectives or telecentric lenses in conventional MSL3DI systems.We experimentally demonstrate that employing a scattering lens allows us to achieve relatively good phase information and robust 3D imaging from depth measurements,yielding measurement accuracy only marginally lower than that of a telecentric lens,typically within approximately 10μm.Furthermore,the scattering lens demonstrates robust performance even when the imaging distance exceeds the typical working distance of a telecentric lens.The proposed method facilitates the application of scattering imaging techniques,providing a more flexible solution for MSL3DI.
基金support from the National Natural Science Foundation of China(Grant Nos.42107193,42077245)supported by the Sichuan Science and Technology Program(2025YFNH0008,2025YFNH0004)+1 种基金the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(SKLGP2023Z006)the Everest Scientific Research Program 2.0:Research on mechanism and control of glacial lake outburst chain catastrophe in Qinghai-Xizang Plateau based on man-earth coordination perspective.
文摘To investigate the strength degradation characteristics and microscopic damage mechanisms of moraine soil under hydro-thermo-mechanical coupling conditions,a series of X-ray Diffraction(XRD),standard triaxial testing,Scanning Electron Microscopy(SEM),and Nuclear Magnetic Resonance(NMR)experiments were conducted.The mechanical property degradation laws and evolution characteristics of the microscopic pore structure of moraine soil under Freeze-Thaw(F-T)conditions were revealed.After F-T cycles,the stress-strain curves of moraine soil showed a strain-softening trend.In the early stage of F-T cycles(0–5 cycles),the shear strength and elastic modulus exhibited damage rate of approximately 10.33%±0.8%and 16.60%±1.2%,respectively.In the later stage(10–20 cycles),the strength parameters fluctuated slightly and tended to stabilize.The number of F-T cycles was negatively exponentially correlated with cohesion,while showing only slight fluctuation in the internal friction angle,thereby extending the Mohr-Coulomb strength criterion for moraine soil under F-T cycles.The NMR experiments quantitatively characterized the evolution of the internal pore structure of moraine soil under F-T cycles.As the number of F-T cycles increased,fine and micro pores gradually expanded and merged due to the frost-heaving effect during the water-ice phase transition,forming larger pores.The proportion of large and medium pores increased to 59.55%±2.1%(N=20),while that of fine and micro pores decreased to 40.45%±2.1%(N=20).The evolution of pore structure characteristics was essentially completed in the later stage of F-T cycles(10–20 cycles).This study provides a theoretical foundation and technical support for major engineering construction and disaster prevention in the Qinghai-Xizang Plateau.
基金financially supported by the State Key Research Development Program of China(No.2016YFC0600708)the Fundamental Research Funds for the Central Universities(No.2009kz03)+1 种基金the Scientific and Technological Innovation Leading Talents of“Ten thousand plan”of the Organization Department of the Central Committee of the CPC(No.W02020049)the International Clean Energy Talent Program of State Scholarship Fund of China Scholarship Council(No.201902720011)。
文摘Coal and gas outburst is a frequent dynamic disaster during underground coal mining activities.After about 150 years of exploration,the mechanisms of outbursts remain unclear to date.Studies on outburst mechanisms worldwide focused on the physicochemical and mechanical properties of outburst-prone coal,laboratory-scale outburst experiments and numerical modeling,mine-site investigations,and doctrines of outburst mechanisms.Outburst mechanisms are divided into two categories:single-factor and multi-factor mechanisms.The multi-factor mechanism is widely accepted,but all statistical phenomena during a single outburst cannot be explained using present knowledge.Additional topics about outburst mechanisms are proposed by summarizing the phenomena that need precise explanation.The most appealing research is the microscopic process of the interaction between coal and gas.Modern physical-chemical methods can help characterize the natural properties of outburst-prone coal.Outburst experiments can compensate for the deficiency of first-hand observation at the scene.Restoring the original outburst scene by constructing a geomechanical model or numerical model and reproducing the entire outburst process based on mining environment conditions,including stratigraphic distribution,gas occurrence,and geological structure,are important.Future studies can explore outburst mechanisms at the microscale.
基金Item Sponsored by National Basic Research Program of China(2012CB720401)National Key Technology Research and Development Program in 12th Five-year Plan of China(2011BAC01B02)
文摘In order to effectively utilize the high reactivity coke, the gasification characteristics of high and low reactivity cokes were investigated at 1100 ℃. Low reactivity coke A and high reactivity coke B were chosen and charged into the reaction tube in two methods. The results indicated that the mass loss ratio of high reactivity coke in mixed cokes was more significant than that of single high reactivity coke in the middle stage of reaction. Nevertheless, the mass loss ratio of low reactivity coke in mixed cokes was less than that of single low reactivity coke. It was mainly attributed to gas diffusion and internal reaction of coke. When high and low reactivity cokes were mixed, the practical average mass loss ratio was nearly the same as the weighted average. The microscopic structures of coke indicated that with the increase of reaction time, the external and internal layers of low reactivity coke reacted more uniformly with CO2, whereas the reaction degree of external layer of high reactivity coke was obviously higher.
基金Supported by the Science and Technology Planning Project of Sichuan Province,China(2020YJ0135)National Natural Science Foundation of China(51874250)。
文摘Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration.
基金founded by the National Natural Science Foundation of China(41922015)。
文摘Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution law of pores and fractures in the Cretaceous tight reservoir in the Liuhe Basin,and reveals its controlling effect on tight oil and gas accumulation.The results show that intercrystalline pores,intergranular pores and dissolution pores are scattered and only developed in shallow tight reservoirs,while microfractures are developed in both shallow and deep layers,which are the main type of reservoir space in the study area.The results of mercury intrusion porosimetry and nitrogen gas adsorption show that with the increase of depth,the proportion of macropores(microcracks)increases,while the proportion of micropores decreases.There are two stages of microfractures developed in the study area,corresponding to the initial fault depression stage from late Jurassic to early late Cretaceous and compressional uplift at the end of late Cretaceous.According to the principle of“inversion and back-stripping method”,combined with the data of optical microscopy and inclusions,the time of each key diagenesis and its contribution to porosity are revealed,and the porosity evolution history of reservoirs in different diagenetic stages is quantitatively restored.The porosity reduction rate of compaction can reach more than 80%,which is the main reason for reservoir densification.The relationship between pore evolution history and oil and gas accumulation history reveals that during the oil and gas filling period of the Xiahuapidianzi Formation(90-85 Ma),the reservoir porosity is only 1.15%,but the development of microfractures in the first stage of the reservoir is conducive to oil and gas accumulation.
基金supported by the National Natural Science Foundation of China(Nos.52121003,51827901 and 52204110)China Postdoctoral Science Foundation(No.2022M722346)+1 种基金the 111 Project(No.B14006)the Yueqi Outstanding Scholar Program of CUMTB(No.2017A03).
文摘Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance(NMR) detection was conducted.Full-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging(NMRI) techniques. The results revealed that seepage pores and microfractures(SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores(AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damagestate adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics(size and degree of difficulty) of coal.
基金supported by the National Natural Science Foundation of China (No.50978014)the Fundamental Research Funds for the Central Universities (No.2011JBM077)
文摘A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride （FC） and polymer ferric sulfate （PFS） pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.
基金supported by the National Natural Science Foundation of China(No.50374029)and(No.50204005).
文摘The mechanisms of La in heavy rail steel were studied by means of experimental measurements, microstructure observation and theoretical analysis in the present work. For heavy rail steel, the state and the content of La were measured, and the mechanisms and the effects of La on sulfide inclusions, microstracture and properties of steel were determined. Strip-like sulfides disappear in heavy rail steel with La/（O＋S）〉3.50, which is shown that the metallurgical function of modifying sulfide inclusions has been achieved by La. La can fine the grain size of the austenite in heavy rail steel. Under the experimental condition, the plasticity and the impacting toughness of heavy rail steel with 0.005wt% La can evidently be improved.
文摘In experimental conditions simulating reducing atmosphere in Blast Furnace, the samples of Al 2O 3 C brick were heated at high temperature. Their microscopic structures were observed by Scanning Electric Telescope and rupture and compressive strength measured before and after heating observed the changes. According to these measurements, the reasons causing the changes were analyzed.
文摘Using the laser granularity survey technology , logy, X-ray powder diffraction, scanning electron microscopy （SEM） and infrared spectrum anal）sis methods, we studied the microscopic structure and chemical bonds changes of β-C2 S monomineral under the high energy ball grinding function. The result indicates that, continuously under the mechanical power, β-C2 S crystal size would decrease, the micro strain and the effective Beff parameter would increase, and the amorphous phases would be presented. Furthermore, the mechanical power would cause Si-O bond broken and reorganized, the specific surface area would increase, the energy of micro-powder agglomeration vibration would be enhanced and the crystal would be disordered. Finally, β- C2 S was caused to have the mechanochemical change and the activity enhancement.
基金Funded by the National Natural Science Foundation of China (Grant Nos. 11074253,10874182 and 50803066)the Foundation of the Education Committee of Anhui Province,China (Grant Nos. KJ2010A031 and KJ2010A012)
文摘Molecular dynamics(MD) simulations were performed to investigate the glass forming ability(GFA) and microscopic structural properties of liquid Cu-Zr alloys.Based on the analysis of composition dependences of the reduced glass transition temperatures and the excess volume,we found that the Cu-Zr glasses have the largest GFA at Cu65Zr35 composition.To get more detailed information of local structure,we calculated the pair correlation functions,partial pair correlation functions,the excess entropy,chemical order parameter,coordination number,and Voronoi index of Cu-Zr liquids.We found that there exists an obvious and close relationship among the GFA,the excess entropy calculated using the total pair correlation functions,chemical order parameters,and some Cu centered cluster with Voronoi index <0,2,8,1> and Zr centered cluster with Voronoi index <0,3,6,4>,which all have nonlinear dependences on Cu/Zr concentration and have extreme values at liquid Cu65Zr35 composition.
