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  • 1
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    Efficient Procedures of Sensitivity Analysis for Structural Vibration Systems with Repeated Frequencies (2013)
    Hindawi
    Details
    Publication Date: 2013-02-21
    Description: Derivatives of eigenvectors with respect to structural parameters play an important role in structural design, identification, and optimization. Particularly, calculation of eigenvector sensitivity is considered when the eigenvalues are repeated. A relaxation factor embedded in the combined approximations (CA) method makes it effective to the structural response at various modified designs. The proposed method is feasible after overcoming the defection of irreversibility of the characteristic matrix. Numerical examples show that it is easy to implement the computational procedure, and the method presented in this paper is efficient for the general linear vibration damped systems with repeated frequencies.
    Print ISSN: 1110-757X
    Electronic ISSN: 1687-0042
    Topics: Mathematics
    Published by Hindawi
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  • 2
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    Guidance Law Design for a Class of Dual-Spin Mortars (2015)
    Hindawi
    Details
    Publication Date: 2015-10-29
    Description: To minimize the cost and maximize the ease of use, a class of dual-spin mortars is designed which only rely on GPS receiver and geomagnetic measurements. However, there are some problems to be solved when the range is small, such as low correction authority and trajectory bending. Guidance law design for this mortar is detailed. Different guidance laws were designed for the ascending and descending segments, respectively. By taking variable parameter guidance law in the vertical plane and using compensation in the lateral plane, the problems mentioned above were resolved. Roll angle resolving algorithms with geomagnetic measurements were demonstrated and the experiment results proved to be effective. In order to verify the effectiveness, Seven-Degrees-of-Freedom (7-DOF) rigid ballistic model were established and hardware in the loop simulation was introduced. After the transform function of the actuator was obtained, the control model of the shell was improved. The results of the Monte Carlo simulation demonstrate that the guidance law is suitable and the mortar can be effectively controlled.
    Print ISSN: 1687-5966
    Electronic ISSN: 1687-5974
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Hindawi
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  • 3
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    Study on the Stress Relaxation Behavior of Large Diameter B-GFRP Bars Using FBG Sensing Technology (2013)
    Hindawi
    Details
    Publication Date: 2013-10-10
    Description: Corrosion of steel tendons in certain aggressive environments could lead to durability problems of civil engineering. More recently, fiber-reinforced polymer (FRP) rods have been introduced in the market as tendons for prestressed concrete structures because of their lower modulus behavior. However, previous studies on the FRP mechanical time dependent behavior regarding the stress relaxation of large diameter GFRP have not been well understood. This paper investigates the influence of stress levels on the relaxation behavior of a GFRP bar griped with a seamless pipe under sustained deformations ranging from 30% to 60% of its ultimate strain. In order to study the behavior of stress relaxation, two basalt-glass fiber hybrid composite (B-GFRP) bars were developed and instrumented with fiber Bragg grating (FBG) strain sensors. It can be found that the test results reveal that the seamless pipe grip method can undertake 70% of ultimate tensile load of the B-GFRP bar, which can satisfy the requirement of stress relaxation of B-GFRP bar subjected to prestress. The model proposed for evaluating stress relaxation ratio can reflect the influences of the nature of B-GFRP bar and the property of grip method.
    Print ISSN: 1550-1329
    Electronic ISSN: 1550-1477
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 4
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    An Optimal Electric Dipole Antenna Model and Its Field Propagation (2016)
    Hindawi
    Details
    Publication Date: 2016-05-10
    Description: An optimal electric dipole antennas model is presented and analyzed, based on the hemispherical grounding equivalent model and the superposition principle. The paper also presents a full-wave electromagnetic simulation for the electromagnetic field propagation in layered conducting medium, which is excited by the horizontal electric dipole antennas. Optimum frequency for field transmission in different depth is carried out and verified by the experimental results in comparison with previously reported simulation over a digital wireless Through-The-Earth communication system. The experimental results demonstrate that the dipole antenna grounding impedance and the output power can be efficiently reduced by using the optimal electric dipole antenna model and operating at the optimum frequency in a vertical transmission depth up to 300 m beneath the surface of the earth.
    Print ISSN: 1687-5869
    Electronic ISSN: 1687-5877
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 5
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    Efficient Procedures of Sensitivity Analysis for Structural Vibration Systems with Repeated Frequencies (2013)
    Hindawi
    Details
    Publication Date: 2013-01-31
    Description: Derivatives of eigenvectors with respect to structural parameters play an important role in structural design, identification, and optimization. Particularly, calculation of eigenvector sensitivity is considered when the eigenvalues are repeated. A relaxation factor embedded in the combined approximations (CA) method makes it effective to the structural response at various modified designs. The proposed method is feasible after overcoming the defection of irreversibility of the characteristic matrix. Numerical examples show that it is easy to implement the computational procedure, and the method presented in this paper is efficient for the general linear vibration damped systems with repeated frequencies.
    Print ISSN: 1110-757X
    Electronic ISSN: 1687-0042
    Topics: Mathematics
    Published by Hindawi
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  • 6
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    FBG-Based Creep Analysis of GFRP Materials Embedded in Concrete (2013)
    Hindawi
    Details
    Publication Date: 2013-12-27
    Description: This paper presents a typical study regarding the creep interaction behavior between prestressed glass fiber reinforced polymer (GFRP) bar and concrete when this GFRP bar is subjected to a constant external pullout force. A number of optical fiber Bragg grating (FBG) sensors were mounted on GFRP bar surface by using an innovative installation method to measure strain distributions. Test results indicate that the complicated interaction at GFRP bar-concrete interface can be evaluated using a transitional factor. Variation trends of this transitional factor indicate three typical zones characterized by different strain/stress variation trends of the GFRP bar when prestress values are sustained at specific levels. These three typical zones include stress release zone, stress transition zone, and continuous tension zone. Test results also suggest that the instant stress loss at the interaction interface between concrete and GFRP bar was quite limited (less than 5%) in present test. Contributed proportion of each GFRP bar section was obtained to represent the creep behavior of the GFRP bar embedded in concrete. This investigation improved the understanding of the short-term interaction behavior between prestressed GFRP bar and concrete.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 7
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    Faulty Line Selection Based on Modified CEEMDAN Optimal Denoising Smooth Model and Duffing Oscillator for Un-Effectively Grounded System (2020)
    Hindawi
    Details
    Publication Date: 2020-04-06
    Description: As the un-effectively grounded system fails, the zero-sequence current contains strong noise and nonstationary features. This paper proposes a novel faulty line selection method based on modified complete ensemble empirical mode decomposition with adaptive noise (MCEEMDAN) and Duffing oscillator. Here, based on multiscale permutation entropy, fuzzy c-means clustering, and general regression neural network for abnormal signal detection, the MCEEMDAN is proposed. The endpoint mirror method is used to suppress the endpoint effect problem in the decomposition stage. The proposed algorithm is able to decompose the original signal into a series of intrinsic mode functions, which can complete the first filtering. The research shows that it can efficiently suppress the mode confusing phenomenon of empirical mode decomposition (EMD) and is also more complete and orthogonal than ensemble empirical mode decomposition (EEMD) and complementary ensemble empirical mode decomposition (CEEMD). The optimal denoising smooth model is established for choosing optimal intrinsic mode functions to complete the second filtering. It can ensure that the reconstructed filtered signal has better smoothness and similarity. The optimal denoising smooth model of MCEEMDAN can not only keep useful details of the original signal but also reduce the noise and smooth signal. The bifurcation characteristic of the chaotic oscillator is applied in weak signal detection. The zero-sequence current’s denoising result is extracted as the input signal of the Duffing system. The faulty line could be selected by observing the phase diagram of the system. The research results verify the usability and effectiveness of the proposed method.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 8
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    Effects of Irreducible Fluid Saturation and Gas Entry Pressure on Gas Production from Hydrate-Bearing Clayey Silt Sediments by Depressurization (2020)
    Hindawi
    Details
    Publication Date: 2020-07-22
    Description: Gas hydrates in the Shenhu area are mainly hosted in clayey silt sediments, which have the relatively high irreducible fluid saturation and gas entry pressure. And then, they will have an impact on gas production from hydrate-bearing clayey silt sediments, which was evaluated by the numerical simulations of SH2 site in Shenhu area in this paper. The results showed that, with the increase in irreducible water saturation and irreducible gas saturation, the amount of water production and gas production was obviously reduced. When the irreducible water saturation increased from 0.10 to 0.50, the cumulative CH4 production volume decreased from 1668799 m3 to 1536262 m3, and the cumulative water production volume dropped from 620304 m3 to 564797 m3, respectively. When the irreducible gas saturation increased from 0.01 to 0.05, the cumulative CH4 production volume dropped from 1812522 m3 to 1622121 m3, and the cumulative water production volume dropped from 672088 m3 to 600617 m3, respectively. In addition, the capillary pressure increased obviously with the increase in gas entry pressure, but the effect on gas production was small and the effect on water production could be negligible. In conclusion, irreducible water and gas saturation had an important effect on the gas production from gas hydrate, whereas the effects of gas entry pressure could be ignored.
    Print ISSN: 1468-8115
    Electronic ISSN: 1468-8123
    Topics: Geosciences
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  • 9
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    Experimental and Theoretical Studies on Flexural Performance of Stainless Steel Reinforced Concrete Beams (2020)
    Hindawi
    Details
    Publication Date: 2020-06-27
    Description: In this paper, the flexural characteristics of stainless steel (SS) reinforced concrete beams are studied and analyzed. We mainly focus on their crack mode, failure mode, load-deflection curve, and bearing capacity. Six beams with test parameters, including the diameter of reinforcement, the type of the reinforcement, and the stirrup spacing, were tested in 4-point bending. The test results indicate that the failure mode of SS reinforced concrete beam can be divided into three stages: elastic stage, cracking stage, and failure stage. The midspan section deformation of SS reinforced concrete beam conforms to the assumption of plane section. Under the same reinforcement condition, the normal section and the oblique section bearing capacities of the SS reinforced concrete beams are significantly higher than those of the ordinary reinforced concrete beams. In addition, the prediction of cracking moment and bearing capacity calculated by ACI 318-14 and GB 50010-2010 was also evaluated. The calculation results of the two codes were safe and conservative, and GB 50010-2010 provided more accurate prediction of cracking moments. Furthermore, to verify the reliability of the test results, finite element models were established and the analytical results corroborated well with the test results.
    Print ISSN: 1687-8086
    Electronic ISSN: 1687-8094
    Topics: Architecture, Civil Engineering, Surveying
    Published by Hindawi
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  • 10
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    Deep RetinaNet for Dynamic Left Ventricle Detection in Multiview Echocardiography Classification (2020)
    Hindawi
    Details
    Publication Date: 2020-08-01
    Description: Background. Currently, echocardiography has become an essential technology for the diagnosis of cardiovascular diseases. Accurate classification of apical two-chamber (A2C), apical three-chamber (A3C), and apical four-chamber (A4C) views and the precise detection of the left ventricle can significantly reduce the workload of clinicians and improve the reproducibility of left ventricle segmentation. In addition, left ventricle detection is significant for the three-dimensional reconstruction of the heart chambers. Method. RetinaNet is a one-stage object detection algorithm that can achieve high accuracy and efficiency at the same time. RetinaNet is mainly composed of the residual network (ResNet), the feature pyramid network (FPN), and two fully convolutional networks (FCNs); one FCN is for the classification task, and the other is for the border regression task. Results. In this paper, we use the classification subnetwork to classify A2C, A3C, and A4C images and use the regression subnetworks to detect the left ventricle simultaneously. We display not only the position of the left ventricle on the test image but also the view category on the image, which will facilitate the diagnosis. We used the mean intersection-over-union (mIOU) as an index to measure the performance of left ventricle detection and the accuracy as an index to measure the effect of the classification of the three different views. Our study shows that both classification and detection effects are noteworthy. The classification accuracy rates of A2C, A3C, and A4C are 1.000, 0.935, and 0.989, respectively. The mIOU values of A2C, A3C, and A4C are 0.858, 0.794, and 0.838, respectively.
    Print ISSN: 1058-9244
    Electronic ISSN: 1875-919X
    Topics: Computer Science , Media Resources and Communication Sciences, Journalism
    Published by Hindawi
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