Radiosonde observations of vertical wave number spectra for gravity waves in the lower atmosphere over Central China

International audienceVertical wave number spectra of inertial gravity waves in the troposphere and lower stratosphere over six stations at latitudes from 20° N to 40° N were statistically studied by using the data from Radiosonde observation on a twice daily basis at 08:00 and 20:00 LT. Statistically, the spectral characteristics seem to be independent of the local observation time, and show considerable conformity between the spectral of zonal and meridional kinetic energy densities. Compared with the spectra of the kinetic energy density, the spectra of the potential energy density are steeper. in addition the characteristic wave numbers of the spectra also show considerable consistency among the observations at different stations. As for the spectral slopes, they are systematically smaller (in magnitude) than the canon value of ?3, and exhibit slight height, seasonal and latitudinal variability. In addition to these universal characteristics, the spectral structures also exhibit departures and variations, and most of the departures and variations are related to the strong tropospheric jets. Generally, in the case of strong shear due to the tropospheric jet, there usually occur larger characteristic wave numbers and smaller spectral slopes. These departures seem to be persistent and climatological rather than transitory, indicating the significant impacts of the sheared background winds on the spectral structures of gravity waves

A restricted memory quasi-Newton bundle method for nonsmooth optimization on Riemannian manifolds

In this paper, a restricted memory quasi-Newton bundle method for minimizing a locally Lipschitz function over a Riemannian manifold is proposed, which extends the classical one in Euclidean spaces to the manifold setting. The curvature information of the objective function is approximated by applying the Riemannian version of the quasi-Newton updating formulas. The subgradient aggregation technique is used to avoid solving the time-consuming quadratic programming subproblem when calculating the candidate descent direction. Moreover, a new Riemannian line search procedure is proposed to generate the stepsizes, and the process is finitely terminated under a new version of the Riemannian semismooth assumption. Global convergence of the proposed method is established: if the serious iteration steps are finite, then the last serious iterate is stationary; otherwise, every accumulation point of the serious iteration sequence is stationary. Finally, some preliminary numerical results show that the proposed method is efficient

Improved Performance of d₃₁-Mode Needle-actuating Transducer with PMN-PT Piezocrystal

Prototypes of a PZT-based ultrasound needle-actuating device have shown the ability to reduce needle penetration force and enhance needle visibility with color Doppler imaging during needle insertion for tissue biopsy and regional anesthesia. However, the demand for smaller, lighter devices and the need for high performance transducers have motivated investigation of a different configuration of needle-actuation transducer, utilizing the d 31-mode of PZT4 piezoceramic, and exploration of further improvement in its performance using relaxor-type piezocrystal. This paper outlines the development of the d 31-mode needle actuation transducer design from simulation to fabrication and demonstration. Full characterization was performed on transducers for performance comparison. The performance of the proposed smaller, lighter d 31-mode transducer is comparable with that of previous $d-{33}$-mode transducers. Furthermore, it has been found to be much more efficient when using PMN-PT piezocrystal rather than piezoceramic. </p

A Quasi-27-Day Oscillation Activity From the Troposphere to the Mesosphere And Lower Thermosphere at Low Latitudes

Using meteor radar, radiosonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and lower thermosphere through a quasi-27-day intraseasonal oscillation (ISO). It is interesting that the quasi-27-day ISO is observed in the troposphere, stratopause and mesopause regions, exhibiting a three-layer structure. In the MLT, the amplitude in the zonal wind increases from about 4 ms−1 at 90 km to 15 ms−1 at 100 km, which is diferent from previous observations that ISOs occurs generally in winter with an amplitude peak at about 80–90 km, and then are rapidly weakened with increasing height. Outgoing longwave radiation (OLR) and specifc humidity demonstrate that there is a quasi-27-day periodicity in convective activity in the tropics, which causes the ISO of the zonal wind and gravity wave (GW) activity in the troposphere. The upward propagating GWs are further modulated by the oscillation in the troposphere and upper stratosphere. As the GWs propagate to the MLT, the quasi-27-day oscillation in the wind feld is induced with a clear phase opposite to that in the lower atmosphere through instability and dissipation of these modulated GWs. Wavelet analysis shows that the quasi-27-day variability in the MLT appears as a case event rather than a persistent phenomenon, and has not a clear corresponding relation with the solar rotation efect within 1 year of observations

Quality Risk Evaluation of the Food Supply Chain Using a Fuzzy Comprehensive Evaluation Model and Failure Mode, Effects, and Criticality Analysis

Evaluating the quality risk level in the food supply chain can reduce quality information asymmetry and food quality incidents and promote nationally integrated regulations for food quality. In order to evaluate it, a quality risk evaluation indicator system for the food supply chain is constructed based on an extensive literature review in this paper. Furthermore, a mathematical model based on the fuzzy comprehensive evaluation model (FCEM) and failure mode, effects, and criticality analysis (FMECA) for evaluating the quality risk level in the food supply chain is developed. A computational experiment aimed at verifying the effectiveness and feasibility of this proposed model is conducted on the basis of a questionnaire survey. The results suggest that this model can be used as a general guideline to assess the quality risk level in the food supply chain and achieve the most important objective of providing a reference for the public and private sectors when making decisions on food quality management