Response Surface Method based on Radial Basis Functions for Modeling Large-Scale Structures in Model Updating

The Response Surface (RS) Method based on Radial Basis Functions (RBFs) is Proposed to Model the Input-Output System of Large-Scale Structures for Model Updating in This Article. as a Methodology Study, the Complicated Implicit Relationships between the Design Parameters and Response Characteristics of Cable-Stayed Bridges Are Employed in the Construction of an RS. the Key Issues for Application of the Proposed Method Are Discussed, Such as Selecting the Optimal Shape Parameters of RBFs, Generating Samples by using Design of Experiments, and Evaluating the RS Model. the RS Methods based on RBFs of Gaussian, Inverse Quadratic, Multiquadric, and Inverse Multiquadric Are Investigated. Meanwhile, the Commonly Used RS Method based on Polynomial Function is Also Performed for Comparison. the Approximation Accuracy of the RS Methods is Evaluated by Multiple Correlation Coefficients and Root Mean Squared Errors. the Antinoise Ability of the Proposed RS Methods is Also Discussed. Results Demonstrate that RS Methods based on RBFs Have High Approximation Accuracy and Exhibit Better Performance Than the RS Method based on Polynomial Function. the Proposed Method is Illustrated by Model Updating on a Cable-Stayed Bridge Model. Simulation Study Shows that the Updated Results Have High Accuracy, and the Model Updating based on Experimental Data Can Achieve Reasonable Physical Explanations. It is Demonstrated that the Proposed Approach is Valid for Model Updating of Large and Complicated Structures Such as Long-Span Cable-Stayed Bridges. © 2012 Computer-Aided Civil and Infrastructure Engineering

Twin-field quantum key distribution without optical frequency dissemination

Twin-field (TF) quantum key distribution (QKD) has rapidly risen as the most viable solution to long-distance secure fibre communication thanks to its fundamentally repeater-like rate-loss scaling. However, its implementation complexity, if not successfully addressed, could impede or even prevent its advance into real-world. To satisfy its requirement for twin-field coherence, all present setups adopted essentially a gigantic, resource-inefficient interferometer structure that lacks scalability that mature QKD systems provide with simplex quantum links. Here we introduce a novel technique that can stabilise an open channel without using a closed interferometer and has general applicability to phase-sensitive quantum communications. Using locally generated frequency combs to establish mutual coherence, we develop a simple and versatile TF-QKD setup that does not need service fibre and can operate over links of 100 km asymmetry. We confirm the setup's repeater-like behaviour and obtain a finite-size rate of 0.32 bit/s at a distance of 615.6 km.Comment: 14 pages, 7 figure

Casing Pipe Damage Detection with Optical Fiber Sensors: A Case Study in Oil Well Constructions

Casing pipes in oil well constructions may suddenly buckle inward as their inside and outside hydrostatic pressure difference increases. For the safety of construction workers and the steady development of oil industries, it is critically important to measure the stress state of a casing pipe. This study develops a rugged, real-time monitoring, and warning system that combines the distributed Brillouin Scattering Time Domain Reflectometry (BOTDR) and the discrete fiber Bragg grating (FBG) measurement. The BOTDR optical fiber sensors were embedded with no optical fiber splice joints in a fiber-reinforced polymer (FRP) rebar and the FBG sensors were wrapped in epoxy resins and glass clothes, both installed during the segmental construction of casing pipes. In situ tests indicate that the proposed sensing system and installation technique can survive the downhole driving process of casing pipes, withstand a harsh service environment, and remain intact with the casing pipes for compatible strain measurements. The relative error of the measured strains between the distributed and discrete sensors is less than 12%. The FBG sensors successfully measured the maximum horizontal principal stress with a relative error of 6.7% in comparison with a cross multipole array acoustic instrument

Dynamic responses analysis of submerged floating tunnel under impact load

Submerged floating tunnel (SFT) may be subjected to sudden impact loads such as submarine and shipwreck. Besides the local damage caused by impact, the overall transient dynamic response may also affect its driving safety. Based on the dynamic impact finite element software, the full-length model and the locally truncated accurate model with solid element of the SFT are established respectively. By applying different spring stiffness constraints on the boundary of the truncated model, its first three modes are consistent with the full-length model, thus their dynamic characteristics are basically the same. The truncated model is further used to simulate the impact of a massive object on the SFT under different impact velocities, impact mass, impact angles and impact positions. The velocity and mass of the impact object have positive influences on the peak contact force, the displacement amplitude of the tube and the length of the damaged area. When the impact angle is perpendicular to the SFT tube, the contact force, displacement amplitude and the damaged area are the largest. The change of the impact position has little effect on the contact force and the damage area, but it will affect the distribution of displacement amplitude

Intracranial Capillary Hemangioma in the Posterior Fossa of an Adult Male

Intracranial capillary hemangioma (ICH) is a rare entity, with approximately 24 reported cases in the literature. There are only three reported cases of ICH in an adult male. In this case report, we describe the fourth documented case of ICH in an adult male and, to the best of our knowledge, the first ever documented case of ICH in the posterior fossa of an adult male. We also discuss its imaging appearance and differential diagnosis

Sparse Frequency Waveform Design for Radar-Embedded Communication

According to the Tag application with function of covert communication, a method for sparse frequency waveform design based on radar-embedded communication is proposed. Firstly, sparse frequency waveforms are designed based on power spectral density fitting and quasi-Newton method. Secondly, the eigenvalue decomposition of the sparse frequency waveform sequence is used to get the dominant space. Finally the communication waveforms are designed through the projection of orthogonal pseudorandom vectors in the vertical subspace. Compared with the linear frequency modulation waveform, the sparse frequency waveform can further improve the bandwidth occupation of communication signals, thus achieving higher communication rate. A certain correlation exists between the reciprocally orthogonal communication signals samples and the sparse frequency waveform, which guarantees the low SER (signal error rate) and LPI (low probability of intercept). The simulation results verify the effectiveness of this method