Methods for estimating rotational components of seismic ground motion and their numerical comparisons

Rotational components play an important role in natural earthquake research,engineering seismic investigation,building monitoring,seismic exploration and other fields.Traditional researches mainly focus on three translational components,but less on rotational ones.As the precision of rotational sensing techniques has increased,many scholars have paid more attention to the seismic rotational motions.Because the rotational observations are not very popular before and now,approximately converting the translational components into rotational components is utilized in rotation analysis.Based on numerical six-component seismic data with the finite difference method,we compare three different conversion methods,the travelling-wave,frequency-domain and the difference method,to analyze their characteristics and feasibilities when they are applied to estimate rotational components with translational observations.

Seismic response of large-span spatial structures under multi-support and multidimensional excitations including rotational components

To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.

Time-frequency response spectrum of rotational ground motion and its application

The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS） of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.

Intensity Evolution of Zonal Shear Line over the Tibetan Plateau in Summer:A Perspective of Divergent and Rotational Kinetic Energies

Based on the ERA5 reanalysis datasets during 1980-2019,a total of eleven zonal shear lines(ZSLs)that caused heavy precipitation and lasted more than 60 hours over the Tibetan Plateau in summer are selected for composite analysis.By decomposing the kinetic energy(K)near the ZSL into divergent and rotational kinetic energies(K_(D)and K_(R))and the kinetic energy of interaction between the divergent wind and the rotational wind(K_(R)D),the influence of the rotational and divergent winds on the evolution of the ZSL intensity is investigated from the perspective of K_(D)and K_(R).The main results are as follows.The ZSL is a comprehensive reflection of rotation and convergence.The intensity evolution of ZSL is essentially synchronized with those of K,K_(R),and K_(RD)but lags behind K_(D)by about three hours.The enhancement of K is mainly contributed by K_(R),which is governed by the conversion from K_(D)to K_(R).Furthermore,the increase in the conversion from K_(D)to K_(R)is controlled by the geostrophic effect term Af,which is determined by the joint enhancement of the zonal rotational and meridional divergent wind components(u_(R)and v_(D)).Therefore,the joint enhancement of u_(R)and v_(D)controls the increase of the ZSL intensity,leading to increased precipitation.

THE INTERDECADAL VARIATION OF THE SOUTH ASIAN HIGH AND ITS ASSOCIATION WITH THE SEA SURFACE TEMPERATURE OF TROPICAL AND SUBTROPICAL REGIONS

This study aims to explore the interdecadal variation of South Asian High(SAH) and its relationship with SST(sea surface temperature) of the tropical and subtropical regions by using the NCEP/NCAR monthly reanalysis data from 1948 to 2012, based on the NCAR CAM 3.0 general circulation model. The results show that: 1) the intensity of SAH represents a remarkable interdecadal variation characteristic, the intensity of SAH experienced from weak to strong at the late 1970 s, and after the late 1970 s, its strength is enhanced and the area is expanded in the east-west direction.The expansion degree is greater westward than eastward, while it is opposite in summer. 2) Corresponding to the interdecadal variation of SAH intensity, after the late 1970 s, the divergent component of wind field has two ascending and three descending areas. Of the two ascending areas, one is located in the East Pacific, the other location varies with the season from the Indian Ocean in winter to the South China Sea and West Pacific in summer. Three descending areas are located in the north-central Africa, the East Asia and the Middle Pacific region respectively. 3) Corresponding to the interdecadal variation of SAH intensity, the rotational component of wind field at the lower level is an anomalous cyclone over the South China Sea and West Pacific in summer, while in winter, it is an anomalous cyclone over the Indian Ocean, and an anomalous anticyclone over the equatorial Middle Pacific. 4) Numerical simulations show that the interdecadal variation of SAH is closely related to the SST of the tropical and subtropical regions. The SST of Indian Ocean plays an important role in winter, while in summer, the SST of the South China Sea and West Pacific plays an important role, and the SST of the East Pacific also plays a certain role.

Scaling of motion and governing equations for baroclinic large-scale motions in equatorial ocean

An obvious characteristic of the baroclinic large-scale motions in the equatorial ocean is that the meridional scale H of motion is far smaller than the zonal scale L. The scaling of motion carefully with this striking characteristic in this paper results in two conclusions, i. e., the Coriolis terms associated with the horizontal component of the rotation vector cannot be neglected in the governing equations; and the use of the absence of heating is not suitable to the equatorial region. In this paper the equatorial β-plane nondimensional governing equations with the small parametersδ_0 andδ_1 have been Obtained.

A review of cooling technologies for high temperature rotating components in gas turbine

Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.

The design and dynamic performance of a moment actuator

It is increasingly recognized that machines and other vibrational sources can impart structure-borne sound power into supporting and connected structures through rotational components of excitation as well as translational components. It is well known that the rotational components are difficult to cstimate since moments are not easy to generate and measure. In this paper a prototype moment actuator is discussed. It consists of two parallel rods of giant magnctostrictive matcrial. The performance of the actuator has been investigated by means of a transfer function involving magnitude and phase. A quantity, 'purity of moment excitation', has been proposed to estimate the ability of the actuator to impart moments.

Water Vapor Transport around the Tibetan Plateau and Its Effect on Summer Rainfall over the Yangtze River Valley

The water vapor transport around the Tibetan Plateau（TP） and its effect on the rainfall in the Yangtze River valley（YRV） in summer are investigated by decomposing the moisture transport into rotational and divergent components.Based on the ERA-Interim and PREC/L（Precipitation Reconstruction over Land） data from 1985 to 2014,the vertically integrated features of the two components are examined.The results show that the divergent part dominates the western TP while the rotational part dominates the rest of the TP,implying that moisture may be mostly locally gathered in the western TP but could be advected to/from elsewhere over the rest of the TP.The divergent and rotational moisture fluxes exhibit great temporal variability along the southern periphery of the TP,showing sensitivity of water vapor to the steep topography there.Correlation analysis reveals that it is over the southeastern corner of the TP and to its south that a significant correlation between rotational zonal moisture transport and summer rainfall in the YRV appears,suggesting that the southeastern corner of the TP may serve as a moisture transport bridge between the South Asian（Indian） monsoon and the East Asian monsoon.Further composite analysis indicates that anomalous eastward（westward） zonal water vapor transport from the South Asian monsoon via the southeastern corner of the TP favors more（less） precipitation in the YRV in summer.