Three bias errors in the measurement of structural intensity

There are many possible bias errors in the measurement of structural intensity and some of them have been theoretically examined. Attempting to analyse all the bias errors at the same time results in a very complicated analysis and makes it difficult to draw clear conclusions.The bias errors are usually analysed individually. In this paper a theoretical study of three bias errors in the measurement of structural intensity is presented by using the twor-accelerometer array technique. It is assumed that the physical and material properties of the test structure are known. The analysis will be restricted to one-dimensional beams, but it can be extended to two-dimensional plates.

On Sea Surface Roughness Parameterization and Its Effect on Tropical Cyclone Structure and Intensity

A new parameterization scheme of sea surface momentum roughness length for all wind regimes, including high winds, under tropical cyclone （TC） conditions is constructed based on measurements from Global Positioning System （GPS） dropsonde. It reproduces the observed regime transition, namely, an increase of the drag coefficient with an increase in wind speed up to 40 m s-1 , followed by a decrease with a further increase in wind speed. The effect of this parameterization on the structure and intensity of TCs is evaluated using a newly developed numerical model, TCM4. The results show that the final intensity is increased by 10.5% （8.9%） in the maximum surface wind speed and by 8.1 hPa （5.9 hPa） in the minimum sea surface pressure drop with （without） dissipative heating. This intensity increase is found to be due mainly to the reduced frictional dissipation in the surface layer and little to do with either the surface enthalpy flux or latent heat release in the eyewall convection. The effect of the new parameterization on the storm structure is found to be insignificant and occurs only in the inner core region with the increase in tangential winds in the eyewall and the increase in temperature anomalies in the eye. This is because the difference in drag coefficient appears only in a small area under the eyewall. Implications of the results are briefly discussed.

IMPACT OF SEA SPRAY ON TROPICAL CYCLONE STRUCTURE AND INTENSITY CHANGE

In this paper,the effects of sea spray on tropical cyclone(TC)structure and intensity variation are evaluated through numerical simulations using an advanced sea-spray parameterization from the National Oceanic and Atmospheric Administration/Earth System Research Laboratory(NOAA/ESRL),which is incorporated in the idealized Advanced Research version of the Weather Research and Forecast (WRF-ARW)model.The effect of sea spray on TC boundary-layer structure is also analyzed.The results show that there is a significant increase in TC intensity when its boundary-layer wind includes the radial and tangential winds,their structure change,and the total surface wind speed change.Diagnosis of the vorticity budget shows that an increase of convergence in TC boundary layer enhances TC vorticity due to the dynamic effect of sea spay.The main kinematic effect of the friction velocity reduction by sea spray produces an increment of large-scale convergence in the TC boundary layer,while the radial and tangential winds significantly increase with an increment of the horizontal gradient maximum of the radial wind, resulting in a final increase in the simulated TC intensity.The surface enthalpy flux enlarges TC intensity and reduces storm structure change to some degree,which results in a secondary thermodynamic impact on TC intensification.Implications of the new interpretation of sea-spray effects on TC intensification are also discussed.

Structural deformation of nitro group of nitromethane molecule in liquid phase in an intense femtosecond laser field

The structural deformation of NO2 group induced by an intense femtosecond laser field of liquid nitromethane（NM）molecule is detected by time-and frequency-resolved coherent anti-Stokes Raman spectroscopy（CARS） technique with the intense pump laser. Here, we present the mechanism of molecular alignment and deformation. The CARS spectra and its FFT spectra of liquid NM show that the NO2 torsional mode couples with the CN symmetric stretching mode and that the NO2 group undergoes ultrafast structural deformation with a relaxation time of 195 fs. The frequency of the NO2 torsional mode in liquid NM（50.8±0.3 cm^-1） at room temperature is found. Our results prove the structural deformation of two groups in liquid NM molecule occur simultaneously in the intense laser field.

NUMERICAL SIMULATION ON RE-INTENSIFICATION OF TROPICAL REMNANT RE-ENTERING THE SEA:A CASE STUDY

When Typhoon Toraji(2001)reached the Bohai Gulf during 1-2 August 2001,a heavy rainfall event occurred over Shandong province in China along the gulf.The Advanced Research version of the Weather Research and Forecast(WRF-ARW)model was used to explore possible effects of environmental factors,including effects of moisture transportation,upper-level trough interaction with potential vorticity anomalies,tropical cyclone(TC)remnant circulation,and TC boundary-layer process on the re-intensification of Typhoon Toraji,which re-entered the Bohai Gulf after having made a landfall.The National Centers for Environmental Prediction(NCEP)global final(FNL)analysis provided both the initial and lateral boundary conditions for the WRF-ARW model.The model was initialized at 1200 UTC on 31 July and integrated until 1200 UTC on 3 August 2001,during which Toraji remnant experienced the extratropical transition and re-intensification.Five numerical experiments were performed in this study,including one control and four sensitivity experiments.In the control experiment,the simulated typhoon had a track and intensity change similar to those observed.The results from three sensitivity experiments showed that the moisture transfer by a southwesterly lower-level jet,a low vortex to the northeast of China,and the presence of Typhoon Toraji all played important roles in simulated heavy rainfall over Shandong and remnant re-intensification over the sea,which are consistent with the observation.One of the tests illustrated that the local boundary layer forcing played a secondary role in the TC intensity change over the sea.

Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics:Theoretical and numerical analysis and application

The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.

Obtaining More Information about Precipitation Biases over East Asia from Hourly-Scale Evaluation of Model Simulation

The hourly summer precipitation simulations over East Asia by the Chinese Academy of Meteorological Science Climate System Model(CAMS-CSM)high-resolution Atmospheric Model Intercomparison Project(AMIP)runs(T255,~50 km)were evaluated based on the merged hourly precipitation product released by the China Meteorological Administration(CMA).The results show that the simulation biases are closely related to the topography,with the precipitation amount and frequency overestimated(underestimated),and duration of precipitation events being longer(shorter),over the western high-altitude(eastern plain)regions of China.Six regions with large discrepancies were further analyzed.In terms of the frequency-intensity structure,the overestimation of precipitation frequency is mainly due to the excessive simulated weak precipitation over the four regions with positive biases:the southern edge of the Tibetan Plateau(STP),the northeastern edge of the Tibetan Plateau(NETP),the eastern periphery of the Tibetan Plateau(EPTP),and the mountainous area of North China(NCM);while the underestimation of frequency is mainly due to the insufficient precipitation with moderate intensity over the two regions with negative biases:lower reaches of the Yangtze River(LYR)and the South China coast(SCC).Based on the duration-diurnal structure analysis,two kinds of precipitation events with different natures can be distinguished.The long-duration night to early morning precipitation events have a significant contribution to the precipitation amount biases for all the six key regions,and this kind of precipitation mainly affects the precipitation diurnal variation over the mountainous areas or steep terrain.Although the short-duration afternoon precipitation events only have a greater contribution to the precipitation amount biases over the SCC region,this kind of precipitation affects the diurnal variation over the NCM region and the two key regions with negative biases.Such a detailed hourly-scale evaluation is helpful for enriching the understanding of simulation biases and to further improve model performance.

A NEW STRUCTURE OF SMALL INTENSELY FLUORESCENT CELLS IN SUPERIOR MESENTERIC GANGLION OF HUMAN FETUS

Superior mesenteric ganglia of six fetuses (35-40 weeks old) were investigated by histochemical fluorescent method. In addition to solitary SIF cells and clusters of SIF cells reported previously, a new structure of SIF cells was found and named ''SIF-cell nodule''. The SIF-cell nodule was composed of a large number of SIF cells and was encapsulated by dense connective tissue. Some blood vessels and nerve fibers entered the nodule. Based on the morphology, we speculated that SIF-cell nodule might be an endocrine gland.