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  • Author: Shuai Yang x
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Abstract

Aiming at the problem of the sudden increase of the working resistance of the support in the transition section of the mixed workface, this paper adopts the physical simulation to study the fracture and movement characteristics of the overburden strata in the backfilling section and the caving section after analysis of the system layout of mixed workface. Then, the definition of the transition section of the mixed workface is given. Next, a numerical model of the transition section length is established based on the geological conditions of the Ji15-31010 mixed workface of Pingdingshan No.12 Coal Mine. In the numerical simulation, it is used to study the influence of the advancing length of the mixed workface and the length of the backfilling section on the transition section length. The results show that with the increase of the advancing length of the mixed workface and the decrease of the backfilling section length, the transition section length increases continuously and eventually stabilizes. The range of variation is 6.2~13.5 m, corresponding to 4~9 hydraulic supports with a width of 1.5 m. Based on the above conclusions and the price of transitional hydraulic supports, the 4 transitional hydraulic supports used in the transition section of the Ji15-31010 mixed workface is determined. Filed measurement shows that as the mixed workface is advanced from 10 m to 40 m, the transition section length increases from 2 supports to 4 supports, and decreases to 2 supports again when advanced to 60 m. This indicates that the main roof of the mixed workface between 40 and 60 m experiences the initial caving. The maximum length of the transition section is 6.0 m, corresponding to 4 hydraulic supports.

Abstract

To address the problems of the suspended buffer spring’s safety and service life, we introduce the basic operating principles and structure parameters of the suspended buffer; followed by establishing a new numerical model of the buffer spring vibration using Femap software. The vibration characteristics of the spring form the basis for spring safety check and service life prediction. Therefore, the principles influencing the gangue particle size and feeding rate on the vibration characteristics of the buffer spring were analyzed. The results have indicated that the vibration frequency, axial pressure peak and the maximum and minimum axial pressure within the periodic vibration had power relations with gangue particle size D, while they had linear relations with the gangue feeding rate v except for the vibration frequency that had nothing to do with the feeding rate. According to the ultimate axial pressure of the spring, the relations between the shear pressure and tensile strength as well as the vibration characteristics, the spring’s safety check formula and service life formula were obtained. Based on the backfilling parameters of the working face in Dongping Coal Mine, the crushed gangue particle size and spring service life were determined. Based on the engineering practice in Dongping Coal Mine, the spring service life was obtained. And the fatigue fracture of the spring was also analyzed.

Abstract

The ground state energy, some low-lying excited state energies and oscillator strengths for a hydrogen atom confined in both a Debye screening potential and finite impenetrable spherical box have been calculated. These have been calculated using a linear variational method based on B-spline basis functions. The results have been compared with those of other authors. The evaluated energies and oscillator strengths with respect to different plasma screening parameters with a certain confinement radii are discussed.

The active compounds in the roots of Scutellaria baicalensis Georgi, a traditional Chinese medicinal plant, are mainly fl avonoids which have anti-inflammatory, antitumour, and anti- HIV activity, respectively. The increasing annual average temperature has rendered the S. baicalensis plants grown in some ancient producing regions no longer suitable for their medicinal usage. Hydrogen peroxide plays an important role in root responses to abnormal temperature in S. baicalensis. Baicalin and baicalein and antioxidative enzymes were anticipated to detoxify H2O2 in S. baicalensis. Here, we show that abnormal temperatures (10 and 40 °C) decreased the content of flavonoids as compared with the normal temperature (30 °C), and the transcripts of UDP-glucuronate:baicalein 7-O-glucuronosyltransferase and β-glucuronidase involved in the interconversion between baicalin and baicalein were affected by the 40-°C treatment. High temperature also increased the activities of catalase and peroxidase. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that the transcript levels of peroxidase 2, peroxidase 3, monodehydroascorbate reductase 2, and dehydroascorbate reductase were significantly increased under high-temperature conditions. The respective genes would be candidates for improvement of the adaptation of S. baicalensis plants to abnormal temperatures and for regulation of the contents of the active compounds.

Abstract

In this paper, we propose a statistical classification method based on discriminant analysis using the first and second moments of positions of each nucleotide of the genome sequences as features, and compare its performances with other classification methods as well as natural vector for comparative genomic analysis. We examine the normality of the proposed features. The statistical classification models used including linear discriminant analysis, quadratic discriminant analysis, diagonal linear discriminant analysis, k-nearest-neighbor classifier, logistic regression, support vector machines, and classification trees. All these classifiers are tested on a viral genome dataset and a protein dataset for predicting viral Baltimore labels, viral family labels, and protein family labels.

Organic thin-film field-effect transistors (OTFTs) are emerging as attractive candidates for low-price, large-area, and flexible circuit applications. A variety of organic compounds have been utilized as active semiconductor materials for OTFTs, among which phthalocyanine compounds have attracted considerable attention owing to their remarkable chemical and thermal stability as well as good field-effect performance. Here, we review recent results on the phthalocyanine-based OTFTs. The correlation between the crystal packing structure and the charge transport property is discussed, and we conclude with a description of the future prospects for phthalocyanine-based OTFTs.

Abstract

A simple ultra-wideband magneto-electric dipole antenna utilizing a differential-fed structure is designed. The antenna mainly comprises three parts, including a novel circular horned reflector, two vertical semicircular shorted patches as a magnetic dipole, and a horizontal U-shaped semicircular electric dipole. A differential feeding structure working as a perfect balun excites the designed antenna. The results of simulation have a good match with the ones of measurement. Results indicate that the designed antenna achieves a wide frequency bandwidth of 107 % which is 3.19~10.61 GHz, when VSWR is below 2. Via introducing the circular horned reflector, the designed antenna attains a steady and high gain of 12±1.5dBi. Moreover, settled broadside direction main beam, high front-to-back ratio, low cross polarization, and the symmetrical and relatively stable radiation patterns in the E-and H-plane are gotten in the impedance bandwidth range. In the practical applications, the proposed antenna that is dc grounded and has a simple structure satisfies the requirement of many outdoor antennas.

Abstract

In this paper, a novel triple-band dipole antenna is presented. The proposed antenna has a very simple structure and is easily designed. The idea of the antenna is based on the traditional wideband bow-tie dipole antenna. Via etching slots on the bow-tie patch, three bent dipoles with different lengths which correspond to different operating frequencies are formed. Hence, the triple-band antenna is generated. Each operating frequency band realizes wideband and can be adjusted almost independently. And the antenna is fed by a 50 Ω microstrip line and a wideband microtrip-to-coplanar-stripline (CPS) transition as a balun. The good performances of the proposed antenna are achieved by a mass of simulations and measurements. The measured results have a good agreement with the simulated ones. The results show that the proposed antenna obtains three bandwidths at 2.38~2.65 GHz (10.7 %), 3.17~4.08 GHz (25.1 %), and 4.75~6.00 GHz (23.2 %) with the reflection coefficient less than −10 dB. In addition, the stable gain and quasi-omnidirectional radiation patterns are obtained in the operating frequency bands. Therefore, the proposed antenna is suitable for WLAN/WiMAX/LTE applications.

Abstract

(C25H27AgN4O5S)n, monoclinic, P21/c (no. 14), a =8.4459(2) Å, b = 23.8845(5) Å, c = 13.0653(3) Å, β =105.096(2)°, V = 2544.66(10) Å3, Z = 4, R gt(F) = 0.0315, wR ref(F 2) = 0.0689, T = 293(2) K.

Abstract

In this study, band gaps of SH-waves (horizontally polarized shear waves) propagating in a thermal-sensitive viscoelastic matrix are investigated. Metallic films acting as heat sources are periodically embedded into the matrix, which establishes a periodically inhomogeneous thermal field. The homogenous matrix is therefore transformed into functionally gradient phononic crystals (PCs). A three-parameter solid model is employed to describe the viscoelasticity of the present matrix. By virtue of a transfer matrix method incorporated within a laminated model, the dispersion equation of SH-waves is finally obtained, from which the band gaps are determined. The transmission spectra of a finite-periodic PC are also solved to validate the band gaps. In numerical examples, the influences of incident angles of SH-waves and viscoelasticity of matrix on band gaps are discussed first. Then the research focuses on the means to tune the band gaps by manipulating the inputted powers of heat sources. Numerical examples demonstrate that such a strategy is effective and convenient in tuning the positions and widths of band gaps. A viscous parameter, i.e., the ratio of initial-state to final-state storage moduli, significantly affects the band locations and bandwidths, while the locations of low-order band gaps hardly move with the incident angle of SH-waves. Band gaps of several orders are expected to locate in lower-frequency domain, and the total bandwidth becomes larger as the inputted heat flux increases. This paper lays theoretical foundation to manufacture viscoelastic functionally graded PCs which can be used in frequency-selective devices.