上旋转桥式起重机的两种典型回转机构

简要介绍了旋转桥式起重机,提出了上旋转桥式起重机的两种典型回转机构,即环轨式回转机构和回转支承式回转机构,并对这两种机构进行了详细介绍和对比。

上旋转电磁挂梁起重机回转机构电动机计算

上旋转电磁挂梁起重机的回转机构可采用滚动轴承式回转支承,文中简要介绍了采用此回转机构的起重机小车及吊具,提出了回转机构电动机的计算方法,并探讨了这种方法在实际应用中发现的问题及解决措施。

基于轻量化设计特性的核工业建筑用上旋转起重机结构设计

建筑料场中有大量原材料需要调运和制造成半成品,特别是对于核工业模块化工业建筑,由于其模块化部件均为在钢厂预制成形,具有体积大、重量较重的特点,因此在制作和建筑施工中需要增加工业起重装备进行吊装运输作业。本文介绍一种具有上旋转功能的工业起重机,由于该起重机可以实现物料360°自由旋转,因而具有使用灵活的特点。同时该起重机采用轻量化设计结构,具有显著的节能特性。

浅析桥式旋转起重机的几种常见形式

论述了带旋转的桥式起重机的常见结构、连接形式。分析了这几种形式的工作原理、结构特点、使用范围等,最后得出结论:旋转起重机可以极大的提高效率,上旋转起重机体积大、造价高,但实用性强。下旋转起重机结构小,成本低,但具有不能承受偏载的缺点。刚性连接使用于定位精确、效率更高的场合,但重量增加较大、成本高,挠性连接定位不准、晃动较大,但成本低、重量小。

Dynamic Characteristics Analysis of the Offshore Wind Turbine Blades

The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine the effectiveness of offshore wind turbines.With different rotating speeds and blade length,the rotating blades generate various centrifugal stiffening effects.To directly analyze the centrifugal stiffening effect of blades,the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade,including the centrifugal stiffening effect and the axial force calculation formula.The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates.The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed,and then the fundamental frequency correction formula was built based on the rotating speed and the blade length.The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results.The error of calculation results between them is less than 0.5%.

Relationship between critical seismic acceleration coefficient and static factor of safety of 3D slopes

Many analytical methods have been adopted to estimate the slope stability by providing various stability numbers,e.g.static safety of factor(static FoS)or the critical seismic acceleration coefficient,while little attention has been given to the relationship between the slope stability numbers and the critical seismic acceleration coefficient.This study aims to investigate the relationship between the static FoS and the critical seismic acceleration coefficient of soil slopes in the framework of the upper-bound limit analysis.Based on the 3D rotational failure mechanism,the critical seismic acceleration coefficient using the pseudo-static method and the static FoS using the strength reduction technique are first determined.Then,the relationship between the static FoS and the critical seismic acceleration coefficient is presented under considering the slope angleβ,the frictional angleφ,and the dimensionless coefficients B/H and c/γH.Finally,a fitting formula between the static FoS and the critical seismic acceleration coefficient is proposed and validated by analytical and numerical results.

Effects Analysis of Mg^2＋, dNTPs and Taq DNA Polymerase on SSR-PCR System of Pear

Effects of Mg^2＋, NTPs and Taq DNA polymerase in pear SSR-PCR system were analyzed by quadratic regressive orthogonal rotational combinational design. Results showed： absolute IOD （Integrated OD of each band） value of target band reduced with concentration rising of Mg^2＋ and Taq DNA polymerase, but heightened with concentration rising of dNTPs. The decay rate of absolute IOD value increased progressively with rising Mg^2＋ concentration, decreased gradually with rising Taq DNA polymerase concentration; the rising speed would be slower than the dNTPs increase. Absolute IOD value would reduce with concentration rising of dNTPs at a low level of Mg^2＋ concentration. Conversely it would rise with the increase of dNTPs while high Mg^2＋ concentration. Absolute IOD value would generally rise with concentration rising of Taq DNA polymerase while low Mg^2＋ concentration. On the contrary it would reduce with concentration rising of Taq DNA polymerase while high Mg^2＋ concentration.

Optimization based accurate scheduling for generation and reserve of power system

With the improvement of electricity markets,the gradual aggravation of energy shortage and the environment pollution,it is urgent to formulate a new model to precisely satisfy the system demand for energy and reserve.Currently,power system opti-mization dispatching is always formulated as a discrete-time scheduling model.In this paper,we first demonstrate through an example that the upper and lower bounds of spinning reserve offered by a unit,given in the discrete-time model framework as constraints,is unreachable.This causes the problem that the reserve delivery obtained by the discrete-time scheduling model cannot be carried out precisely.From the detailed analysis of the ramp rate constraints,it is proved that the reachable upper and lower bounds of spinning reserve in every period can be expressed as functions of two variables,i.e.,generation level of unit at the start and end of this period.Thus,a new method is provided to calculate the upper and lower bounds of spinning reserve which are reachable in average.Furthermore,a new model based on this proposed method for joint scheduling of generation and reserve is presented,which considers the ability to realize the scheduled energy and reserve delivery.It converts the opti-mization based accurate scheduling for generation and reserve of power system from a continuous-time optimal control prob-lem to a nonlinear programming problem.Therefore,the proposed model can avoid the difficulties in solving a continu-ous-time optimal control problem.Based on the sequential quadratic programming method,numerical experiments for sched-uling electric power production systems are performed to evaluate the model and the results show that the new model is highly effective.

An experimental study on the effects of relative rotation direction on the wake interferences among tandem wind turbines

An experimental study was conducted to investigate the effects of relative rotation direction on the wake interferences among two tandemwind turbines models.While the oncoming flow conditions were kept in constant during the experiments,turbine power outputs,wind loads acting on the turbines,and wake characteristics behind the turbines were compared quantitatively with turbine models in either co-rotating or counter-rotating configuration.The measurement results reveal that the turbines in counter-rotating would harvest more wind energy from the same oncoming wind,compared with the co-rotating case.While the recovery of the streamwise velocity deficits in the wake flows was found to be almost identical with the turbines operated in either co-rotating or counter-rotating,the significant azimuthal velocity generated in the wake flow behind the upstream turbine is believed to be the reason why the counter-rotating turbines would have a better power production performance.Since the azimuthal flow velocity in the wake flow was found to decrease monotonically with the increasing downstream distance,the benefits of the counter-rotating configuration were found to decrease gradually as the spacing between the tandem turbines increases.While the counter-rotating downstream turbine was found to produce up to 20%more power compared with that of co-rotating configuration with the turbine spacing being about 0.7D,the advantage was found to become almost negligible when the turbine spacing becomes greater than 6.5D.It suggests that the counter-rotating configuration design would be more beneficial to turbines in onshore wind farms due to the smaller turbine spacing(i.e.,~3 rotor diameters for onshore wind farms vs.~7 rotor diameters for offshore wind farms in the prevailing wind direction),especially for those turbines sited over complex terrains with the turbine spacing only about 1–2 rotor diameters.

Effects of Probe Support on the Flow Field of a Low-Speed Axial Compressor

This paper presents an investigation on the effect of probe support on the flow field of an axial compressor.The experiment is carried out in a large-scale low-speed research compressor.A cylindrical probe support intruding to 50% blade span was installed at 50% chord upstream from the rotor leading edge.The region from 5° to 32° off the probe support in the direction of rotation at the rotor outlet was measured with a 5-hole probe and a high-response total pressure probe.The experiment is performed at both near-design and near-stall points.The measuring results of 5-hole probe and high-response total pressure probe indicate that the probe blockage effect is different at different blade spans.The wake of the probe support weakens the leakage vortex intensity at the tip region,leading to greater total pressure rise.At near-design condition,the presence of probe support has a negative effect on the region from 75% to 92% span,while improves the flow field below 75% span.At near stall condition,the probe support has a negative effect on the region from 70% to 90% span,and almost has no influence on the flow field below 70% span.

Grade classification of neuroepithelial tumors using high-resolution magic-angle spinning proton nuclear magnetic resonance spectroscopy and pattern recognition

Clinical data have shown that survival rates vary considerably among brain tumor patients,according to the type and grade of the tumor.Metabolite profiles of intact tumor tissues measured with high-resolution magic-angle spinning proton nuclear magnetic resonance spectroscopy (HRMAS 1H NMRS) can provide important information on tumor biology and metabolism.These metabolic fingerprints can then be used for tumor classification and grading,with great potential value for tumor diagnosis.We studied the metabolic characteristics of 30 neuroepithelial tumor biopsies,including two astrocytomas (grade I),12 astrocytomas (grade II),eight anaplastic astrocytomas (grade III),three glioblastomas (grade IV) and five medulloblastomas (grade IV) from 30 patients using HRMAS 1H NMRS.The results were correlated with pathological features using multivariate data analysis,including principal component analysis (PCA).There were significant differences in the levels of N-acetyl-aspartate (NAA),creatine,myo-inositol,glycine and lactate between tumors of different grades (P<0.05).There were also significant differences in the ratios of NAA/creatine,lactate/creatine,myo-inositol/creatine,glycine/creatine,scyllo-inositol/creatine and alanine/creatine (P<0.05).A soft independent modeling of class analogy model produced a predictive accuracy of 87% for high-grade (grade III-IV) brain tumors with a sensitivity of 87% and a specificity of 93%.HRMAS 1H NMR spectroscopy in conjunction with pattern recognition thus provides a potentially useful tool for the rapid and accurate classification of human brain tumor grades.

EQUIVARIANT COHOMOLOGY AND REPRESENTATIONS OF THE SYMMETRIC GROUP

In a recent paper the author constructed a continuous map from the configuration space of n distinct ordered points in 3-space to the flag manifold of the unitary group U(n), which is compatible with the action of the symmetric group. This map is also compatible with appropriate actions of the rotation group SO(3). In this paper the author studies the induced homomorphism in SO(3)-equivariant cohomology and shows that this contains much interesting information involving representations of the symmetric group.