双头单螺杆泵定子衬套力学行为分析

为研究双头单螺杆泵定子衬套的受力状态及内轮廓线的变形规律,分析了内压、压差、材料非线性、橡胶泊松比等多种因素对定子衬套应力、应变及内轮廓线变形规律的影响,并拟合出双头单螺杆泵定子衬套在均匀内压作用下内轮廓线位移的方程式及非均匀内压下内轮廓线最大位移公式。分析结果表明:均匀压力下,衬套应力、应变呈周期性变化,内轮廓线位移呈正弦规律变化,位移与内压成线性关系;压差作用下,衬套应力、应变最大值向压差作用处转移,内轮廓线变形规律发生改变,位移及其变形幅度均增大;衬套橡胶泊松比微小的变化即会对衬套变形产生非常大的影响。因此,实际生产中应注意注胶工艺及泊松比的变化。研究结果为定子、转子过盈量的选取及线型的优化设计提供了理论基础,对提高双头单螺杆泵工作效率和使用寿命具有重要工程实际意义。

Study on Plant Landscape Design of Urban Comprehensive Park

The urban comprehensive park is the main body of the urban environment construction, and the plant landscape is the most important landscape element of the comprehensive park. It is helpful for the landscape design of the comprehensive park to improve the environmental quality and the sustainable development of the city. Taking the ＂Nanjiang Park＂ in Xiaoshan District of Hangzhou as the research object, the landscape design of plants was explored and analyzed. The results showed that there were significant differences in the application forms of plant land- scapes in different functional zones in comprehensive parks. The specific forms of the garden elements had different needs of plant landscape construction. According to the results of case studies, it found that comprehensive parks could improve the functions, create the aesthetic sense, enhance the atmosphere and enhance the taste through plant landscape design. In addition, corresponding suggestions were put forward according to the current situation with the aim to provide references for the future plant landscape design related with garden greens.

EFFICIENT NUMERICAL METHOD FOR DYNAMIC ANALYSIS OF FLEXIBLE ROD HIT BY RIGID BALL

Impact dynamics of flexible solids is important in engineering practice. Obtaining its dynamic response is a challenging task and usually achieved by numerical methods. The objectives of the study are twofold. Firstly, the discrete singular convolution （DSC） is used for the first time to analyze the impact dynamics. Secondly, the efficiency of various numerical methods for dynamic analysis is explored via an example of a flexible rod hit by a rigid ball. Three numerical methods, including the conventional finite element （FE） method, the DSC algorithm, and the spectral finite element （SFE） method, and one proposed modeling strategy, the improved spectral finite element （ISFE） method, are involved. Numerical results are compared with the known analytical solutions to show their efficiency. It is demonstrated that the proposed ISFE modeling strategy with a proper length of con- ventional FE yields the most accurate contact stress among the four investigated models. It is also found that the DSC algorithm is an alternative method for collision problems.

Comprehensive investigation of stress intensity factors in rotating disks containing three-dimensional semi-elliptical cracks

Initiation and propagation of cracks in rotating disks may cause catastrophic failures. Therefore, determination of fracture parameters under different working con- ditions is an essential issue. In this paper, a comprehensive study of stress intensity factors （SIFs） in rotating disks containing three-dimensional （3D） semi-elliptical cracks subjected to different working conditions is carried out. The effects of mechanical prop- erties, rotational velocity, and orientation of cracks on SIFs in rotating disks under cen- trifugal loading are investigated. Also, the effects of using composite patches to reduce SIFs in rotating disks are studied. The effects of patching design variables such as mechanical properties, thickness, and ply angle are investigated separately. The modeling and analytical procedure are verified in comparison with previously reported results in the literature.

Studying solutions for the fatigue of the FAST cable-net structure caused by the process of changing shape

The Five-hundred-meter Aperture Spherical Radio Telescope （FAST） is supported by a cable-net structure, whose change in shape leads to a stress range of approximately 500 MPa. This stress range is more than twice the standard recom- mended value. The cable-net structure is thus the most critical and fragile part of the FAST reflector system. In this study, we first search for a more appropriate deforma- tion strategy that reduces the stress amplitude generated by the process of changing shape. Second, we roughly estimate the tracking trajectory of the telescope during its service life, and conduct an extensive numerical investigation to assess the require- ments for fatigue resistance. Finally, we develop a new type of steel cable system that satisfies the cable requirements for construction of FAST.

Large deflection of annular throttle-slices in shock absorbers

method was used to derive the stiffness curve equation of a single throttle-slice in shock absorbers. The analytical formula of large deflection for superposed throttle-slices was deduced directly and generalized. The undetermined coefficients of analytical for- mula were obtained through the finite element method （FEM） and curve fitting. Numerical results show that the analytical formula has satisfactory accuracy.

Finite Element Analysis of Thiopave Modified Asphalt Pavement

With the aim of studying the anti-rutting performance of Thiopave modified asphalt mixture applied to the upper layer of pavement, the strain-hardening creep model in ABAQUS finite element software was used to analyze the rutting under the condition of introducing temperature field. Compared with the calculation results of the rutting of ordinary asphalt pavement, it is found that Thiopave can improve the temperature sensitivity of asphalt mixture. With the increase of temperature, the rutting change of Thiopave modified asphalt pavement is smaller than that of ordinary asphalt. Thiopave also has a certain degree of improvement in the fatigue resistance of asphalt pavements, which can be applied to sections with high traffic volume in high temperature areas.

NONCONFORMING STABILIZED FINITE ELEM ENTMETHODS BASED ON RIESZ-REPRESENTING OPERATORS

Follow ing the fram ew ork of the finite elem ent m ethods based on Riesz-representing operators developed by Duan Huoyuan in 1997,through discreteRieszrepresenting-operators on som e virtual(non-) conform ing finite-dim ensionalsubspaces,a stabilization form ulation is pre- sented for the Stokes problem by em ploying nonconform ing elem ents.This form ulation is uni- form ly coercive and notsubject to the Babus ka-Brezzicondition,and the resulted linear algebraic system is positive definitew ith the spectralcondition num berO(h- 2 ). Quasi-optim alerrorbounds are obtained,which is consistentwith the interpola- tion properties ofthe finite elem entsused.

Performance of Dielectric Barrier Discharge Reactors on Elemental Mercury Oxidation in the Coal-Fired Flue Gas

The oxidation of elemental mercury （Hg~） by dielectric barrier discharge reactors was studied at room temperature, where concentric cylinder discharge reactor （CCDR） and surface discharge plasma reactor （SDPR） were employed. The parameters （e.g. Hg^0 oxidation efficiency, energy constant, energy yield, energy consumption, and O3 concentration） were discussed. From comparison of the two reactors, higher Hg^0 oxidation efficiency and energy constant in the SDPR system were obtained by using lower specific energy density. At the same applied voltage, energy yield in the SDPR system was larger than that in the CCDR system, and energy consumption in the SDPR system was much less. Additionally, more 03 was generated in the SDPR system. The experimental results showed that 98% of Hg^0 oxidation efficiency, 0.6 J·L^-1 of energy constant, 13.7 μg·J^-1 of energy yield, 15.1 eV·molecule^-1 of energy consumption, and 12.7 μg·J^-1 of O3 concentration were achieved in the SDPR system. The study reveals an alternative and economical technology for Hg^0 oxidation in the coal-fired flue gas.

Stress and Thermal Analysis of the In-Vessel Resonant Magnetic Perturbation Coils on the J-TEXT Tokamak

A set of four in-vessel saddle coils was designed to generate a helical field on the J- TEXT tokamak to study the influences of the external perturbation field on plasma. The coils are fed with alternating current up to 10 kA at frequency up to 10 kHz. Due to the special structure, complex thermal environment and limited space in the vacuum chamber, Jt is very important to make sure that the coils will not be damaged when undergoing the huge electromagnetic forces in the strong toroidal field, and that their temperatures don＇t rise too much and destroy the in- sulation. A 3D finite element model is developed in this paper using the ANSYS code, stresses are analyzed to find the worst condition, and a mounting method is then established. The results of the stress and modal analyses show that the mounting method meets the strength requirements. Finally, a thermal analysis is performed to study the cooling process and the temperature distribution of the coils.

Quantitative Inversion of REEs in Ion-Adsorbed Rare Earth Ores from the Liutang Area(South China),Based on Measured Hyperspectral Data

Rare earth minerals are important strategic resources to economic development all over the world.In this study,multiple linear regression and back propagation(BP) neural network methods are used to invert the contents of ion adsorbed rare earth elements(REEs) and exploring the feasibility of quantitative inversion of REEs through measured hyperspectral data in Liutang rare earth mines,South China.The result shows that the spectral curve of the rare earth ore samples has obvious absorption characteristics around 390,930,1 400,1 900 and 2 200 nm,and continuum removal and the 1st derivative treatment can highlight the absorption characteristics.The modeling accuracies of BP neural network are higher than that of multiple linear regression model.The BP neural network model of the 1st derivative data in 400–1 000 nm bands has the best inversion result of the total content of REEs,R2 reaches 0.98,the ratio of the performance to deviation(RPD) is larger than 3.0.The quantitative inversion model of each REE(except for Ce) has high precision,R2 is greater than 0.90 and RPD is greater than 3.0.The results indicate that quantitative inversion of REEs using measured spectra not only has great potential and feasibility in the exploration of rare earth minerals,but also provides a rapid test method for the content of ion-adsorbed rare earth elements.

Visual perception on the architectural elements of the built heritage of a historic temple town： A case study of Kumbakonam, India

This paper aims to investigate the changes in the virtual perception on the built heritage at the traditional core setttement of Kumbakonam Town at Tamitnadu and to analyze their implica- tions. Specifically, the major objectives of the study are （1） to identify the architectural elements that manifest the built heritage of Kumbakonam Town and （2） to assess the contMbutions of these elements to the changes in the visuat perception of the town. To achieve these objectives, this study adopts an empirical model that analyzes the architectural elements of the buildings in the study area. Direct observations and documentations of 373 buildings are collected to analyze those etements that contribute to the changes in the visual perception on the built heritage of Kumbakonam Town. An ordinary regression model is used to examine the characteristics of the built heritage across the chariot processional route of the town. Several architectural elements, including pitasters, horizontal cornices, arched windows, and ornamental parapets, improve the image of the town. These empirical findings support the policy framework that enhances the visual perception of Kumbakonam Town.

Testing the systematic status of Homalictus and Rostrohalictus with weakened cross-vein groups within Halictini(Hymenoptera:Halictidae)using low-coverage whole-genome sequencing

The halictid genus Lasioglossum,as one of the most species-rich bee groups with persistently contentious subgeneric boundaries,is one of the most challenging bee groups from a systematic standpoint.An enduring question is the relationship of La-sioglossum and Homalictus,whether all halictine bees with weakened distal wing ve-nation comprise one or multiple genera.Here,we analyzed the phylogenetic relation-ships among the subgroups within Lasioglossum s.l.based on thousands of single-copy orthologs and ultraconserved elements,which were extracted from 23 newly sequenced low-coverage whole genomes alongside a published genome(22 ingroups plus 2 out-groups).Both marker sets provided consistent results across maximum likelihood and coalescent-based species tree approaches.The phylogenetic and topology test results show that the Lasioglossum and Hemihalictus series are reciprocally monophyletic and Homa-lictus and Rostrohalictus are valid subgenera of Lasioglossum.Consequently,we lower Homalictus to subgenus status within Lasioglossum again,and we also raise Rostrohalic-tus to subgenus status from its prior synonymy with subgenus Hemihalictus.Lasioglossum przewalskyi is also transferred to the subgenus Hemihalictus.Ultimately,we redefine La-sioglossum to include all halictine bees with weakened distal wing venation.