A Study on the Explicit Expression of Critical Stress and Euler Stress and its Application

Both the tangent modulus theory and the double modulus theory are classical theories which can be applied to the elastic-plastic stability analysis of columns. In the traditional tangent modulus theory, numerous iterations are required to calculate the critical buckling stress and this makes the method very time-consuming. In this paper, an explicit formula for establishing a direct correlation between the critical stress and the Euler stress has been proposed to reduce trial calculations. This formula can be applied to spherical shells by simplifying their stiffened plates to the form of beams on elastic foundations. The explicit expressions of both modulus theories can be used to calculate the ultimate strength of a spherical shell under pressure. The results from the proposed expression are compared with experimental results and other numerical results

Identification of induced polarization of submarine hydrocarbons in marine controllable source electromagnetic exploration

The identification of hydrocarbons buried on the seafloor is highly dependent on geophysical exploration capabilities. Seismic exploration has been an important tool in providing information on submarine stratigraphy before offshore drilling, but it is a challenge to identify the nature and saturation of the fluid in the structure by seismic exploration. Of all the physical properties, electrical parameters are the most sensitive to the fluids in the reservoir and would be able to be combined with seismic data to improve the identification of hydrocarbons at depth. However, the marine controlled-source electromagnetic method usually only considers the effect of electromagnetic induction and ignores the induced polarization (IP) effects. The IP effects can occur in the stratum where the reservoir is located due to a variety of factors, so considering the IP effects will make the modeling more reasonable and thus give more accurate results when interpreting and processing the data. We have used the integral equation method for modeling, adopted the scattering and superposition methods to calculate the dyadic Green’s function required in the study, replaced the real resistivity with a complex resistivity that takes into account the IP effects, investigated the response patterns of different ion polarization models, and analyzed the influence patterns of various model parameters. These investigations will provide important contributions to the study of submarine hydrocarbon detection. The field data also show the amplitude, and phase response results of polarizability show that it gradually increases from the offset

モモノゴマダラノメイガの産卵行動における寄主植物香気の機能

この博士論文は内容の要約のみの公開（または一部非公開）になっています筑波大学 (University of Tsukuba)201

On the design of low phase noise and flat spectrum optical parametric frequency comb

Optical frequency combs (OFCs) have become increasingly pervasive in recent years, with their advantageous frequency coherence properties enabling significant developments in numerous fields, such as optical communications, spectroscopy, and microwave signal processing. Recent interest in OFC development emphasizes minimizing and mitigating phase noise of individual comb lines for high-quality signal generation, processing, and detection. Cavity-less electro-optic combs and parametric combs are attractive sources for these applications in that they permit flat spectra, tunable tone spacing, and robustness to temperature variations. Although previous research has demonstrated broadband parametric OFC generation, the scaling of the phase noise has not been systematically investigated. Here, we demonstrate a 25 GHz-spacing cavity-less parametric OFC generator and investigate the interaction between electronic and optical noise sources that affect its phase noise and linewidth. In addition, we study the optimal design of a nonlinear amplified loop mirror based pulse shaper with a focus on the impact of pump power on the signal-to-pedestal power ratio, which ultimately influences the spectral flatness and the optical signal-to-noise ratio (OSNR) after the parametric expansion. Notably, we design the OFC using all polarization-maintaining (PM) components, demonstrating the performance of PM highly nonlinear fibers in parametric comb generation. This results in a PM cavity-less comb with <9 dB power variation over 110 nm, >0 dBm power per tone, <10 kHz linewidth, and >23 dB OSNR. These characteristics make it highly desirable for application in communication and signal processing

The development and validation of an artificial intelligence-based screening method for atrial septal defect in children's chest x-rays

PurposeFor precise diagnosis and effective management of atrial septal defects, it is of utmost significance to conduct elementary screenings on children. The primary aim of this study is to develop and authenticate an objective methodology for detecting atrial septal defects by employing deep learning (DL) on chest x-ray (CXR) examinations.MethodsThis retrospective study encompassed echocardiographs and corresponding Chest x-rays that were consistently gathered at Qingdao Women's and Children's Hospital from 2018 to 2022. Based on a collaborative diagnosis report by two cardiologists with over 10 years of experience in echocardiography, these radiographs were classified as positive or negative for atrial septal defect, and then divided into training and validation datasets. An artificial intelligence model was formulated by utilizing the training dataset and fine-tuned using the validation dataset. To evaluate the efficacy of the model, an assessment of the area under the curve, sensitivity, specificity, accuracy, positive predictive value, and negative predictive value was conducted employing the validation dataset.ResultsThis research encompassed a total of 420 images from individuals. The screening accuracy and recall rate of the model surpass 90%.ConclusionsOne of profound neural network models predicated on chest x-ray radiographs (a traditional, extensively employed, and economically viable examination) proves highly advantageous in the assessment for atrial septal defect

IC 225: a dwarf elliptical galaxy with a peculiar blue core

We present the discovery of a peculiar blue core in the elliptical galaxy IC 225 by using images and spectrum from the Sloan Digital Sky Survey (SDSS). The outer parts of the surface brightness profiles of u-, g-, r-, i- and z-band SDSS images for IC 225 are well fitted with an exponential function. The fitting results show that IC 225 follows the same relations between the magnitude, scale length and central surface brightness for dwarf elliptical galaxies. Its absolute blue magnitude (M_B) is -17.14 mag, all of which suggest that IC 225 is a typical dwarf elliptical galaxy. The g-r color profile indicates a very blue core with a radius of 2 arcseconds, which is also clearly seen in the RGB image made of g-, r- and i-band SDSS images. The SDSS optical spectrum exhibits strong and very narrow nebular emission lines. The metal abundances derived by the standard methods, which are 12+log(O/H) = 8.98, log(N/O) = -0.77 and 12+log(S+/H+) = 6.76, turn out to be significantly higher than that predicted by the well-known luminosity-metallicity relation. After carefully inspecting the central region of IC 225, we find that there are two distinct nuclei, separated by 1.4 arcseconds, the off-nucleated one is even bluer than the nucleus of IC 225. The asymmetric line profiles of higher-order Balmer lines indicate that the emission lines are bluer shifted relative to the absorption lines, suggesting that the line emission arises from the off-center core, whose nature is a metal-rich Hii region. To the best of our knowledge, it is the first high-metallicity Hii region detected in a dwarf elliptical galaxy.Comment: 7 figures, accepted for publication in A

Preparation and Characterization of Polyurethane/Nanocopper Composites and Their Application in Intrauterine Devices

A novel intrauterine devices material, polyurethane/nano-copper (PU/NC) nanocomposite, was prepared. The structure, morphology, copper ion (Cu2+) release rate, and water absorption of PU/NC nanocomposites were investigated. The results indicated that the nanocoppers were uniformly dispersed in the matrix. The release rates of Cu2+ of PU/NC nanocomposites remained stable during the experimentation time. These results indicated that the PU/NC nanocomposites have a great potential to replace current commercial intrauterine devices materials