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This paper first investigates the influence of the dispersion-decreasing optical fiber structure on the self-similar pulses interaction and compression. The dynamic of the evolution of a pair of self-similar pulses in a dispersion-decreasing optical fiber with normal group-velocity dispersion (ND-DDF) under different gain coefficient g 0 of DDF is analyzed, and the chirp evolution is also studied to analyze the propagation characteristic of self-similar pulses. The numerical simulations show that the change of gain coefficient g 0 of DDF can impact directly on the linear chirp of the self-similar pulses. We find out that the smaller g 0 can generate better high-quality femto-second pulses than the higher g 0 after pulses compression. Finally, we got a pair of ultra-short pulses with a FWHM of 124 fs at g 0 = 0.015 m −1 , indicating efficient and high-quality pulse compression.

Illuminance uniformity and illuminating efficiency are always the key problems of Light Emitting Diode (LED) lighting system design. This study focuses on designing a suitable aspherical surface to create a rectangular and uniform illumination by studying the influence of optical aspheric parameters for a 3D microscopic measurement system. The 3D microscopic measurement system is constructed based on Scheimpflug condition. Then the optical design of LED source to obtain a rectangular-shaped illumination pattern on the DMD chip is simulated and optimized by optical tracing simulation software (TracePro). Our research focuses on the design of the second surface, where the key point of the design is to find appropriate conic constant K2 and the paraxial radius of curvature R2 of the lens, while the first surface of lens is considered as a plane. The conic constant K2 is researched by using the normal equation for conic aspheric and is discussed respectively when the conicoid is parabolic, elliptic and hyperboloidal. The result indicates that paraboloid can get a better uniform rectangular illumination within region than ellipsoid and hyperboloid. The illumination uniformity of the predetermined illumination area on the DMD chip reaches 86.83%.

The transfer of prestress force from prestressing strands to the surrounding concrete is dependent on the bond between the two materials. Understanding the actual bond stress distribution along the transfer length results in optimized design of the transfer zone of prestressed concrete members. Equations of estimating the transfer length in ACI 318 code and AASHTO LRFD bridge design specifications simply take into account the effect of the strand diameter only. The objective of this study is to provide a generalized procedure for determining the bond stress–slip relationship accurately by incorporating the effects of additional parameters, such as concrete compressive strength at prestress release, center-to-center strand spacing, and concrete bottom cover. First, the bond stress distribution along the transfer length of a prestressed concrete member is formulated based on longitudinal slip–strain compatibility, force equilibrium and invariable bond stress–slip relationship along the transfer length. Second, a generalized Inverse Problem-Solving approach is introduced to determine best parameter coefficients through minimizing the discrepancy between the calculated and measured results. Two types of measurements (i.e., transfer length and end slip) reported in the literature are utilized to demonstrate the proposed approach. Predicted transfer length and end slip values using the calibrated bond stress–slip relationship show better agreement with the test data compared to those predicted by ACI 318 code and AASHTO LRFD bridge design specifications. Third, a computational procedure is developed and an example is presented to assist engineers using the developed formulae for determining the bond stress distribution along the transfer length of prestressed concrete members.

In this paper, finite-element analysis (FEA) of the prestressed concrete-steel composite (PCSC) girder is performed to investigate strain and stress distributions in the girder sections and determine the influence of stud distribution on stresses in the concrete bottom flange. Approaches of FEA are discussed for the material and element models of steel, concrete, and strands, and element models of the bond between the concrete and strand and the shear studs, loading and boundary conditions, and convergence issues. A PCSC girder specimen is fabricated and instrumented in the structural laboratory to validate the proposed fabrication and design procedures. FEA and service design using the age-adjusted elasticity modulus method (AEMM) are both validated using the strain profiles at different sections and values of concrete surface strains and camber/deflection. Test results indicate that the cracking moment, ultimate moment, and ultimate shear of the PCSC girder can be well predicted using the AEMM a...

A new prestressed concrete-steel composite (PCSC) girder system is developed to provide a viable alternative for steel and prestressed concrete I-girders in bridges. The PCSC girder is composed of a lightweight W-shaped steel section with shear studs on its top and bottom flanges to achieve composite action with the pretensioned concrete bottom flange and the cast-in-place concrete deck. The PCSC girder is lightweight, economical, durable, and easy to fabricate. The proposed fabrication procedure is similar to those of prestressed concrete girders and does not need specialized equipment, materials, and forms. A service design procedure is proposed using the age-adjusted elasticity modulus method to evaluate the time-dependent stresses and strains in the PCSC girder caused by creep and shrinkage effects of concrete and relaxation of strands. The strength design method is proposed for the design of PCSC girders at prestress release. A design procedure is proposed to assist engineers to accomplish economic design and production of PCSC girders, and design examples are presented to illustrate the design procedure.

Strength design method for pretensioned flexural concrete members at prestress release was developed in 2001 as a rational alternative to the working stress design method. Load and resistance factors for the developed strength design method were selected to match those used in similar applications (e.g., tied columns) without reliability-based calibration. The purpose of this paper is to present the calibration of resistance factors for the strength design of pretensioned flexural concrete members at release to achieve a target reliability index of 3.5. Resistance models were developed to capture material, fabrication, and professional uncertainty. Statistical parameters of load and resistance were obtained from the literature. Formulae for strength design at release were developed for rectangular and flanged sections in cases when top reinforcement is needed and when top reinforcement is not necessarily needed. Reliability analysis was conducted for several rectangular and inverted-T sections and resistance factors of 0.75 and 0.70 were recommended in light of the results for 5 ksi (34.5 MPa) and 8 ksi (55.2 MPa) concrete strengths, respectively. Moreover, a simplified design procedure was proposed to assist designers and producers in applying the strength design method at prestress release. Three design examples were also presented and compared against those designed using the working stress method.

Nine simply supported circular steel concrete-filled tubes (CFTs), two circular steel posttensioned concrete-filled tubes (PTCFTs), and one circular steel fiber–reinforced concrete-filled tube (FRCFT) have been tested in an instrumented drop-weight impact facility. The weight and the height of the drop-weight were varied to cause failure in some test specimens. The failure modes and local damages in those specimens have been investigated extensively. Failure in the steel tubes was commonly tensile facture or rupture along the circumference. Concrete core in the impact area commonly crushed under compression and cracked under tension. The use of prestressing strands and steel fibers significantly restrained the concrete tension cracks in the PTCFT and FRCFT specimens, respectively. The experimental results are analyzed in the context of principles of energy and momentum conservation.

The properties of the self-similar parabolic pulses interaction in a dispersion-decreasing optical fiber with normal group-velocity dispersion are firstly investigated in our paper. We find that two parabolic pulses separated by a time-delay create oscillation with a sinusoidal fit at the beginning of their overlap, and then further evolve into a train of asymptotic dark solitons. Additionally, outside the overlap regime, the evolution is equal to a single pulse’ propagating behavior. The chirp after interaction in the parabolic pulses still allows for efficient and high-quality pulse compression.

With the development of multimedia computer technology , interactive projection is becoming an interactive display system and entertainment in people's daily life.Interactive projector based on actual needs, design gesture based feature extraction algorithm Hu moments, identified by SVM classification shot type, and ultimately through experiments verify the effectiveness and practicality of the system.

In this paper, we experiment the capabilities of continuous density Hidden Markov Model (CHMM) to model the offline diagram sketch signals such as the electrical circuit diagram and the flowchart diagram . We attempt to imitate the online signals by extracting the offline diagram data as the time-varying coordinate sequence based on the Gradient Sharpening and Freeman code, considering that is generated by a two-level stochastic process. The underlying process governs the stroke production from a neuron-motor control point of view: go straight line, change direction line, produce a curve. A second stochastic process delivers the continuous density observed signal, which is the sequence of offline extracted points. A stroke segmentation technique based on CHMM architecture and geometric features is proposed. On a dataset of 180 hand-drawn sketches, the proposed method allows to classify correctly more than 90% of the points with respect to the connector and symbol classes.