最新刊期
卷 47 ， 期 Z1 ， 2015
- 摘要：Abstract:In open channels, free overfall is a situation where the flow separates from the rigid bed to form a free nappe due to a sudden drop in the channel bed, the relationship of the end-depth to the critical depth is constant, it could be used as a simple flow measuring device. EDR is dependent of roughness and slope. This paper study the effect of roughness and slope on EDR, associating with practical condition. The experiment results show that EDR decreased with the increase of slope degree; EDR increased with the increase of roughness and experimental data are closely correlated with the correlation .The discharge formula established according to the experimental result in this paper and the experimental result abroad，and the mean error of discharge calculating results is less than 1.35%关键词：rectangular open canal,discharge measurement,free overfall,experiment
- 2152
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:At river confluence, water transportation is convenient, so it is easy to build cities and towns. However, flow structure in junction zone is relatively complex, there are a series of questions such as bank erosion and sediment deposition. So it is necessary to regulate confluence flow. The characteristics of separation zone at 90° river confluence were studied in the study by numerical simulation, and a kind of regulation method of optimizing dike lines to reduce or eliminate separation zone was proposed. The dike line meets the elliptic equation, the ellipse semi-major axis is length of the separation zone, the ellipse semi-minor axis is width of the separation zone. The results indicated that the optimized dike line is the best regulation method when the momentum ratio is 0.40.关键词：river confluence;separation zone;momentum ratio;numerical simulation;regulation method
- 1963
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Channel confluence is universal, in which obvious interaction of water flows and complicated stage-discharge relation exists. The effects of discharge ratio between main channel and branch channel on the flow characteristics including the water-level fluctuation along the river, stage-discharge relation and incipient velocity at confluence zone were studied based on the physical model tests. The results indicated that the strength of water-level fluctuation at confluence zone was closely related to discharge ratio between main channel and branch channel and river pattern, and incipient velocity variation along the river at confluence zone was obviously different from the one in single channel.关键词：channel confluence;stage-discharge relation;characteristics of water-level fluctuation;sediment incipient velocity
- 1749
- |
- 4
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract: By model test, the ventilation volume was studied through hydraulic parameters. The results showed that the ventilation volume was influenced by two aspects: On the one hand it was the ability of water to accommodate air itself, which was decided by the water depth mainly. On the other hand it was the ability of water to absorb air from the bottom of the cavity, which was decided by velocity at the flip bucket and cavity length. The analysis showed that when the water depth was shallow, the ability of water to accommodate air itself played a leading role in the development of aeration. when the water depth was deep, the ability of water to absorb air from the bottom of the cavity played a leading role in the development of aeration. Based on the test result, an empirical formula of ventilation volume about flip bucket was proposed considering the two reasons above.关键词：Aeration;flip bucket;ventilation volume;cavity length
- 1960
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:A united computational model of hydraulic，mechanical and electrical parts in the hydropower system was built，and the two-order predictor-corrector method was used to assure both of the computational precision and speed. The object-oriented programming language VC++ was used to write the program of the each part，and enclosed into an icon，sequentially，the universal icon library for the hydropower system was established. The effect of operation characteristic of the unit was analyzed under the fluctuation of the power network，it is shown that the power angle，d-axial voltage and q-axial voltage of the generator are clearly affected by the fluctuation of the power network voltage，and the power，the rotating speed of the generator and the water level in surge chamber are observably influenced by the fluctuation of the power network frequency，the fluctuation of the power network phrase angle can lead to the fluctuation of the operation parameters，but it can come back the previous balance condition. While the power network fluctuates, the hydraulic and electrical operation parameters will affect each other by the adjustment of the governor and the excitation system，and the fluctuation frequency of the electrical parameters of the generator is equal to the natural frequency of the water hammer.关键词：hydropower;power network;predictor-corrector method;object-oriented
- 1518
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:When there were numerous deep and weak planes in the gravity dam foundation, the calculation model was always simplified into multi-slip planes model. There were two main issues if the safety factor still was calculated as the Gravity Dam Design Code（DL5108－1999）and (SL319-2005): (1) the distribution of horizontal and vertical loads was vary; (2) the formula was too complex to calculate iteratively. So the calculation formulas of simplified partial factor and single safety factor were derived by using the equal safety coefficient method. It was proved by practical engineering: (1) be more practicable by applying the deduced formulas to calculate the safety coefficient of multi-slip planes model;(2) the safety factor calculated by the stress distribution method was smaller than by the gravity distribution method;(3) the safety factor calculated by directly simplifying the multi-slip planes model into double slip planes model was larger than by multi-slip planes model.关键词：gravity dam;multi-slid planes;stability against sliding;calculation formula
- 1560
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract: Hardfill dam is a new type of dam whose structural feature is between that of gravity dam and earth-rock dam. It has a relatively low overall stress level and unclear stress concentration, but the adaptability of Hardfill to foundation is still to be discovered, so it is very necessary to carry on researches on the structural failure mode and stability of Hardfill to different foundations. The paper adopts geologic mechanics failure model test and FEM calculation, and has made researches and analysis on the failure mode and stability of Hardfill Dam on homogeneous foundation and foundation with complex structural plane under the action of external load. The result shows, the Hardfill dam heel first cracks on homogeneous foundation and the crack goes upwards to the dam toe till overall instability occurs, with an obvious overload safety coefficient; on foundation with complex structural plane, plastic failure first appears mainly at weak structural surface, which leads to an overall sliding failure, and the stability safety is relatively weaker than that on homogeneous foundation. Keywords: Hardfill Dam; homogeneous foundation; complex foundation; failure mode; geologic mechanics model test; FEM (Finite Element Method) calculation关键词：Hardfill Dam;homogeneous foundation;complex foundation;failure mode;geologic mechanics model test;FEM (Finite Element Method) calculation
- 2
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Immediately after the Lushan M 7.0 earthquake occurred on April 20, 2013 in Sichuan province, a field survey was conducted within the earthquake-stricken area to investigate the damages to dams and reservoirs caused by the earthquake. Based on the survey results, a preliminary damage evaluation of 9 selected reservoirs in Baoxing and Tianquan counties was also performed. Field survey indicated that typical damages to these dams included deformation and failure of subsidiary structures, dam seepage, and indirect damage caused by geological disasters such as landslides and collapse, whereas the main structures of most dams remained intact or largely intact. To further analyze potential risks to dams caused by the earthquake, the risk analysis method by Bureau (2003) was improved and employed to calculate the total seismic risks of 19 dams in the quake-hit areas. Improvement to Bureau (2003)’s method include modifications to dam height risk factor and downstream hazard factor based on dam construction, local economy, and population. Result indicated that the overall risk level of the dams in the earthquake-stricken area ranked moderate, which was consistent with the field investigation results. The total seismic risk analysis presented in the paper can be useful for further damage assessment and post-quake reinforcement of dams.关键词：Lushan Earthquake;field investigation of reservoir damage;earthquake damage assessment;risk rating
- 1714
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The permeability coefficient of clay had been not calculated using the easily measured parameters. For this problem，according to the analysis of invalid pore effects on soil seepage characteristics, the invalid void ratio were defined first. Caculation formulas of the efficient void ratio were derivated by the liquid limit. Then, the empirical formulas of clay permeability coefficient were obtained by modifying the common empirical formulas of sand permeability coefficient .Finally, based on the empirical formula of clay permeability coefficient, the seepage of an engineering project was calculated. By analyzing the difference between considered and unconsidered the invalid void ratio, comparing the calculated value of permeability coefficient with the measured value of laboratory test, the reasonable of the empirical formulas of clay permeability coefficient had been verified.关键词：Clay;invalid void ratio;Consistency index;empirical formula of permeability coefficient
- 1287
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Temperature is one of the important factors affecting the mechanical properties of rocks. To investigate the influences of temperature on fracture characteristics and strength of marble, the uniaxial and triaxial compression tests on marble samples with natural state and heated with 200℃ or 800℃ have been carried out. The results show that thermal treatments have great influences on the failure forms and strength of marble samples. Under the condition of uniaxial compression，the natural specimen failed in tension-shear mode, on the contrast, the specimens heated by high temperature tend to fail in tension. In triaxial compression tests, the natural specimens failed in shear mode. The samples heated with 200℃ failed in modes of shear and the tension-shear. The specimens heated with 800℃ failed in mode of shear, tension-shear and bulging deformation. After heated with 200℃, the specimens have a slight increase in cohesion, and little variations in internal friction angle. But After heated with 800℃, the specimens have a considerable reduction in cohesion, and a slight increase in internal friction angle. Rock failure modes become complex and strengths disperse widely because of heating. It is more reasonable for Mogi-Coulomb failure criterion to analysis strengths of the marble specimens under natural or heated condition.
- 1684
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The strength and failure forms under high water pressure are important for deep buried and high water pressure tunnel and under groud mining. The conventional uniaxial experiment and the compression tests under different water pressure were carried out by using MTS and YSL-200 test system. The effect of the water pressure on compression strength and failure model of saturated sandstone was analysed, and the acting of pore water pressure and confining pressure on rock strength was discussed. The results showed that the saturated sandstone was “X-type” shear failure under water pressure, and water pressure accelerated the failure of rock obviously while the rock was in crack propagation area; the pressure water could seep into rock interior through propagated cracks so that the moisture content of rocks was increased and the pore water pressure of rock interior was affected; when water pressure was low, the confining pressure was greater than the pore water pressure, the rock strength was enhanced by water pressure; but when water pressure was relatively high, the pore water pressure had risen to offset the increased confining pressure, and the rock strength under water pressure was similar to uniaxial compressive strength.关键词：water pressure;strength;failure model;pore water pressure;confining pressure;sandstone
- 2099
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract: Mixed with a certain proportion of solid aggregate, not only the costs of high-water-concretion can be reduced, but the physical and mechanical properties of the high-water-concretion can be improve. Based on the basic property of the high-water-concretion, the new modified high-water-concretion after doping was studied. By using soil mechanics’ triaxial testing methods, the specimens which were separately incorporated in the aggregate size were 5~10mm, 10~20mm, 20~40mm, 40~60mm, non-doped , the mixed and the river sand’ s aggregate were performed of consolidated undraining shear test. The results showed that different doping particle have a significant impact on the strength and mechanical parameters of the specimen：The smaller the particle size, the higher the strength and the mechanical parameters; the strength and mechanical parameters of mixing specimen and river sand specimen is much better than a single particle doping specimen. These experiments prove that the use of gravel aggregate doped material to the material for high-water-concretion has a strong feasibility.关键词：High-water-concretion;doping;aggregate;mechanical parameters;strength
- 1501
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Creep property of surrounding rock is one of major factors which influence the long-term stability of tunnels. For the analytical solution of the stress and displacement in rocks around deep buried tunnel, the solution formulas only used for tunnel in the shape of circular, oval and rectangle have already been solved. But for the tunnel with arch crown, there is no analytical solution yet. Based on the process of solution for elastic displacement of rocks around the tunnel with any shape, complex variable theory is used to derive the elastic analytical solution for rocks around deep buried tunnel with arch crown by simplifying calculation model. Then, the analytical solution for viscoelastic displacement is gotten by applying the elastic and viscoelastic correspondence principle, the Laplace transforms and inverse transforms. Combined with one soft rock tunnel project, three analysis types have done and compared including analytical solution, elastic finite elements method and rheological process in FLAC3D. The results indicates that, the rule of the boundary displacement of three kinds of calculation methods are basically similar, the initial elastic deformation are basically identical, and the viscous deformation rule is similar to numerical simulation and field data, that validate the practicality and reliability of the formula of displacement.关键词：Tunnel;Surrounding rock;Tunnel with arch crown;Complex function;Mapping function;analytical solution;viscoelasticity;Rheology
- 1558
- |
- 4
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the effect of depth-width ratio of tunnel on the tunnel stability, experiment in combination with numerical studies were adopted. For the case of a tunnel containing a crack was also considered. Stresses around the tunnel were calculated by using concrete damaged plasticity model in ABAQUS code，and for the tunnel with crack the stress intensity factors were calculated with J integral method，and for depth-width ratio 0.9 case, XFEM(extended finite element method) in ABAQUS code was adopted to simulate the crack development path, and the results are in good agreement with the experimental results. The results showed that, tunnel stability varies with depth-width ratio K varying, for non-crack tunnel model, the compressive strength comes to the largest with K=1.5 and comes to the lowest with K=1.0; for tunnel model with one crack, the compressive strength comes to the largest with K=1.7 and comes to the lowest with K=0.7.关键词：depth-width ratio;tunnel;numerical simulation;stress intensity factor;tunnel stability
- 1817
- |
- 6
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The durability experiments of shotcrete with and without steel fiber under bending stress in accelerated carbonation corrosive environments were carried out to investigate the carbonation regularity of tunnel lining. Meanwhile, the concrete carbonization predictive model was modified for considered bending stress, steel fiber addition and construction mode. The results showed that the carbonation depth was obeyed Fick first law and diffusion coefficient was raised with the bending stress level increased. The carbonation depth of shotcrete was much less than that of ordinary concrete. Simultaneously, the carbonation resistance of steel fiber reinforced shotcrete (SFRS) was much better than that of shotcrete. For analyzing the mechanical properties and microstructure of shotcrete after carbonation, the cubic compressive strength, splitting tensile strength and flexural strength were increased with carbonation depth raised. The channels for carbon dioxide taking into shotcrete were provided by the original micro pores and creaks. Moreover, the favorable conditions for calcite crystal nucleation and growing were also supplied by ettringite and portlandite which consists in defeats. With the carbonation reaction development, the carbonation products were continuously consumed and blocked the micro-pores.关键词：bending stress;shotcrete;steel fiber;carbonation;microstructure
- 2243
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:This work presents a study on pressure-induced amorphization (PIA) in β-LiAlGeO4 using synchrotron radiation X-ray diffraction and Raman laser spectroscopy respectively under high pressure up to 29.7and20.3 gigapascals (GPa). It is the first time that amorphous structure under compression was observed in LiAlGeO4 by the results revealed that at300K β-LiAlGeO4 underwent progressive amorphization at pressures above 11.9GPa and became completely amorphous above 14.5 GPa. Simultaneously, The Raman data shows the transformation in the 15 GPa. After the release of pressure the system was recovered as an amorphous state and did not retain the so-called structural memory. Then give a bulk modulus and the Grüneisen parameters I of LiAlGeO4.关键词：LiAlGeO4;Pressure-induced amorphization;Synchrotron radiation;Raman spectroscopy
- 2173
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:A classification method of software attack technique for automated modeling—POPDDA was proposed, since it’s difficult for existing software attack classification methods to satisfy the demand of the automated modeling. In this paper, firstly, by analyzing the necessary attribute information of software attack technique needed in the process of automated modeling, the classification was done. Besides, it evaluated the classification availability of POPDDA by Amoroso standard. Secondly, a corresponding attack knowledge base was built based on POPDDA and used it to create automated attack modeling. Finally, the modeling effectiveness was analyzed based on experimental. The experimental results showed that the POPDDA can match Amoroso standard and satisfied the requirements for the automated modeling, and also can solve inefficiencies and inaccuracy in manual modeling and avoided remodeling.关键词：taxonomy;attribute;attack technique;auto-modeling
- 1928
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:A method for breaking the generalized RSA public key scheme was proposed using Lagrange’s reduction algorithm based on the two-dimension lattice and the lower bound of Euler's totient function. Moreover, the corresponding attack algorithm was also given and it was proved that the RSA modulus N could be factorized in polynomial time. Compared with the original continued fraction attack, this method removed the steps of computing and repeatedly verifying the convergent of continued fraction, obtained the prime factor p directly, so it simplified the whole solving procedures and improved the factoring efficiency. The results show that this method has lower time complexity, works faster in the experiment, and can be efficiently used to attack the generalized RSA public key scheme.关键词：generalized RSA;public key scheme;continued fraction;two-dimension lattice;Lagrange’s reduction
- 1785
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:According to the gradient structural similarity (GSSIM) of adjacent image blocks, a fast CU partitioning algorithm of HEVC intra coding is proposed. In the intra prediction, whether the current coding unit will be partitioned further that will be determined by mean GSSIM of current CU to achieve the purpose of trimming quadtree, reducing computational complexity. The results show that in the case of slight increase of code rate and basically unchanged video quality, the average time of HEVC intra coding is reduced 36.67% to 48.50% by the proposed algorithm.关键词：gradient;SSIM;Canny;HEVC;fast split
- 2
- |
- 1
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Two anti-light interference algorithms were proposed to solve the problem of image quality reduction due to the light interference in multi-projector display system. 1. The point to point algorithm: The corresponding mapping relation between camera and projector is built firstly, then the luminance and saturation of output images would be promoted according to the mapping relation and experimental data; 2. The image enhancement anti-light interference algorithm: To offset the effect of light interference indirectly, the image quality on display wall is enhanced by using a combination of various image enhancement algorithms. The theoretical derivation of the two algorithms were provided and experimental verification was implemented in a dome display system which was composed of 24 projectors. Finally, the experimental results demonstrated the validity of the proposed algorithms.关键词：light interference;multi-projector tiled display;image quality enhancement;subpixel alignment;unsharp masking
- 1485
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Because of the complex structure of the rock images, using the general image processing methods to segment the ore-bearing rock particle images may cause uneven, owe segmentation and over segmentation phenomenon. In order to improve the accuracy of rock image segmentation, a kind of ore image segmentation algorithm is proposed based on graph theory. In this algorithm, the first step is to reduce images by multi-scale analysis, then, the ore image is segmented by using Normalized Cut. Various categories of ore-bearing rocks are segmented by NCut and the segmentation images are compared with the segmentation results of traditional image processing methods such as threshold、watershed and clustering analysis, FCM and other processing methods in the experiment. The result of the experiment shows that for some specific rocks, the new algorithm is better than the traditional ones.关键词：rock particle image, graph theory, Normalized Cut, image segmentation
- 2246
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:The existence of particle cluster contaminants on the components of IR optical system not only changes the stray light radiation characteristics of the system, but also degrades the system signal to noise ratio. In this paper, the model for the distribution of particle cluster contaminants has been given. A Cassegrain telescope has been taken as a typical example and using the ASAP optical ray tracing software, the change of the system stray radiation and the contrast ratio between point objects and background has also been simulated before and after the primary mirror was contaminated. So as the effects of different cluster contaminants position on system radiation has been discussed. The results indicate that the existence of the cluster not only alter the system’s stray radiation properties, but also decreased the target-to-background contrast obviously. Further study shows that the position of contaminants cluster aggregation also effects more or less on the system stray light radiation and the contaminate of the mirror boundary has more effect than the centre. Therefore, in practical applications, the factional area coverage of particles on optical components should be strictly controlled and the mirror should be cleaned reasonably in time.
- 1653
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to accurately estimate the parameters of laser micro-Doppler signal, an innovative time-frequency analysis method-nonlinear matching pursuit (NMP) was employed in this research. As there were great limitations in the strong background noise and weak modulation conditions, an approach designated as weighted average frequency algorithm (WAFA-NMP) was proposed to further improve the NMP. Weighted average frequencies and amplitudes were computed to determine the corresponding point on the time–frequency space. In addition, a sub-sampling method for the weak modulation problem was proposed based on WAFA-NMP. Simulation results showed that the proposed algorithm can achieve better performance compared with the Wigner-Ville (WV) distribution and smoothed pseudo Wigner-Ville (SPWV) distribution, the valuation accuracy was 96% on average, and the noise immunity can be low to -10dB.关键词：micro-Doppler signal;nonlinear matching pursuit;feature extraction;time-frequency analysis
- 1519
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Currently most of the compressed sensing to date has focused on static finite-dimension signals. The real-time homotopy algorithm based on the L1-homotopy recovery algorithm was proposed in this paper when dividing signal into disjoint blocks and processing each block independently is either infeasible or inefficient for time-varying streaming signals. The method iteratively processed measurements over a sliding overlapping window and chosed the L1-homotopy recovery algorithm that could avoid solving a new L1 program from scratch at the next iteration to solve a weighted L1-norm problem for estimating sparse coefficients. The algorithm had also been fully proved that it could be used to process electrocardiosignals in the field of medicine. Our experiment results on very long real-time electrocardiosignals demonstrated the good performance of the algorithm in real-time system, with the relative error of the reconstructed signal controlled within 10-2, which effectively lessened great storage burden the ambulatory electrocardiograph (ECG) had brought about.关键词：Compressed sensing;Blocking artifact;L1-homotopy recovery algorithm;ECG
- 1937
- |
- 6
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In order to know the microstructure evolution regularity of ZG12Cr9Mo1Co1NiVNbNB ferritic heat resistant steel used in the high temperature urgently, the influence of microstructure of this steel caused by aging high temperature has been studied using transmission electron microscope and energy spectrometer in this paper. The results showed that the microstructure contained martensite lath, high dislocation density and precipitates after aging at 700℃ for 100h. And the precipitates were Fe(Cr, Mo)23C6, VC, and Laves phase（Fe2Mo）. The larger Fe(Cr, Mo)23C6 carbides mainly distributed in the martensite and the original austenite grain boundary. VC mainly distributed in the matrix. In addition, the number density of them was increased. The size of the Fe(Cr, Mo)23C6 carbides was also increased during aging. And the thermal stability of VC was better than Fe(Cr, Mo)23C6 carbides.关键词：ZG12Cr9Mo1Co1NiVNbNBferritic heat resistant steel;microstructure;precipitates;aging
- 1631
- |
- 2
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:Six mixtures were designed on fly ash based geopolymeric recycled concrete (GRC), which using recycled coarse aggregates (RA) to substitute nature coarse aggregates (NA) with different ratios of 0%，50% and 100%．According to the present code on ordinary concrete(GB/T 50082-50082)and taking into account the characteristics of the geopolymer concrete, multiple comparative analysis were conducted by measuring the compressive strength, weight and dynamic elastic modulus of specimens at different cycles. Furthermore, the microstructure of the specimens attacked by sulphates was also investigated. The performances of sulphates attack resistance and the damage mechanism and of GRC and recycled aggregates concrete (RAC) in the same erosion condition are analyzed and discussed. Results turned out that the maximum weight variation of both RAC and GRC were small in the whole process, that is, 1.8% for RAC and 0.7% for GRC. The compressive strength of RAC varies in similar way, and the RAC50 performs the best corrosion resistance judged by corrosion resistance coefficient. The compressive strength of GRCs decreased with more recycled aggregates. The corrosion resistance coefficient shows that erosion process accelerated the strength development of GRC. Dynamic elastic modulus reflect the strength change mechanism of both RAC and GRC. Furthermore, microscopic and chemical analysis shows that the pore structure of RAC takes the most important role in in sulfate attack resistance while, GRC depends on the intrinsic defects of recycled aggregates.关键词：geopolymer, recycled concrete, sulfate erosion, dynamic elastic modulus, corrosion resistance coefficient
- 1556
- |
- 6
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:In welan gum fermentation process by Sphingomonas sp. ATCC 31555, the level of dissolved oxygen drops with the viscosity of broth increasing, leading to the reduced yield of welan gum. To improve the oxygen concentration in the fermentation system and increase welan gum yield, addition of oxygen carrier was studied and multiple adding methods were used. Glycerin had no significance on welan gum yield, while dodecane, n-hexane, H2O2 could increase the yield of welan gum to a certain degree, and H2O2 was the best oxygen carrier. Optimizing adding concentration and time of H2O2 with one-factor experimental design were 15 mmol/L at the 8 h in fermentation, and Glucose utilization had high larger increase at the same time. In addition, 1.91% of welan gum was obtained when adding 5 mmol/L H2O2 at the 4, 8, 12 h keeping the total amount (15 mmol/L) of adding H2O2 constant, increased 30.02% comparing with the blank group. Moreover, a small amount of complete cells could be observed in the experimental group at 72 h fermentation, when extended the fermentation period to the 84 h, 1.99% of welan gum was obtained, increased 4.21% comparing with the group of 72 h in fermentation. 5 L fermentation to expand training, welan yield reached 2.09%, higher than shake flask experiment results.
- 2
- |
- 0
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract:For improving the calculation precision of piezoelectric materials containing crack, the virtual crack closure technology were introduced into the background grid of element-free Galerkin method. Based on the theory of enriched element-free method, electromechanical virtual crack closure technique was put forward. The new approach well simulated the singularity at the crack tip, simplified the solving process, improved the calculation accuracy. The influence of the different number of gauss points and different length of crack on the calculation precision of the intensity factor was discussed. Compared with the analytical solution and numerical results of electromechanical-coupling virtual crack closure technique based on finite element method. Numerical example results illustrated that this method is feasible.关键词：enriched element-free Galerkin method;electromechanical-coupling virtual crack closure technique;piezoelectric materia
- 1546
- |
- 6
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract: According to the theory of swing movable teeth meshing , this paper analyzed a calculation method of heat flow that swing movable teeth transmission produced during the drive process and established the finite element calculation model of the central internal gear’s body temperature by using the theory of Tribology and Blok. Through the example cases, the steady temperature field distribution of central internal gear and the sensitivity of body temperature on speed, load and lubricating-oil temperature were analyzed. The results indicated that the maximum body temperature was near the inflection point of internal gear profile curve. In addition, the body temperature rose as the rotational speed, load and oil temperature increase, but the distribution of the temperature field remained the same. This research provided a theoretical basis for the calculation of the thermal deformation and the profile modification of the internal gear, and it had significant guidance to improve the transmission performance of swing movable teeth transmission.关键词：swing movable teeth transmission;frictional heat flux;steady-state body temperature;Sensitive nature
- 1647
- |
- 4
- |
- 0
发布时间：2023-11-14 - 摘要：Abstract: According to the transmission structure and principle of two-tooth difference swing-rod movable teeth transmission, the theoretical and actual profile equation of central wheel was derived according to the engagement theory of two-tooth difference swing-rod movable teeth transmission and the tooth profile is simulated using MATLAB software.The effects of parameters,such as the transmission ratio,radius of movable tooth, length of swing-rod and the cam profile,on the tooth profile of the centeral wheel is analyzed. Formulas for calculating curvature and curvature radius of the central wheel are deduced and its variation curve was plotted respectively. The solid model of centeral wheel is established in Pro/E software and the curvature distribution characteristics is simulated using the Pro/E software.The research result can be used as the references for geometrical design of this type of geometric design and accuracy analysis.关键词：two-tooth difference;swing-rod movable teeth transmission;tooth profile analysis;simulation
- 1676
- |
- 0
- |
- 0
发布时间：2023-11-14
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0