Straight Region Research Articles

Parametric analysis of innovative corrugated profile of soil‐steel composite bridge

AbstractComposite soil‐steel corrugated structures are well recognized and widely used for construction of culverts and pedestrian or animal crossings. Moreover, for the past decade corrugated soil‐steel structures because of their large span are also recognized and chosen for bridges and tunnels engineering. Record holder composite corrugated structure of 32.40 m span encourages new research in the development of innovations. This paper investigates innovative the deepest corrugation cross‐section strengthened with circular hollow section steel pipes influence on plate utilization of large span soil‐steel composite bridge. The numerical 2D model of 17.5 m span structure was developed for investigation. Parametric analysis indicated that introduction of circular pipes will reduce corrugated profile steel thickness because of reduction of buckling length of straight region of corrugation. Moreover, 3D numerical analysis of buckling shapes allowed to conclude that local buckling of the deepest corrugation of 500 × 237 mm could be controlled strengthening the plates with circular steel pipes.

Surface Plasmon Resonance Sensor Based on Waveguides Inscribed in No-Core Fiber

We present a surface plasmon resonance (SPR) refractive index sensor based on femtosecond laser inscribed waveguides in a no-core fiber sandwiched between two sections of single mode fibers. The waveguides inscribed have a trapezoidal structure which consists of three sections: two slant waveguides to direct light out and back into the core of single mode fiber and a straight waveguide close to and in parallel with the surface of no-core fiber. A thin layer of Cr+Ag is coated on the surface of NCF to cover the straight waveguide region. The device is compact and has good mechanical robustness. The experimental results obtained show that the device has a refractive index sensitivity of ~3234 nm/RIU in the refractive index range of 1.34-1.37, and is expected to have practical applications in the fields of bio-medicine and environmental monitoring.

The Influence of Processing Conditions on the Quality of Bent Solid Wood from European Oak

Bending of solid wood from European oak is one of the most demanding technological processes due to its specific structural and physical properties and variability. We investigated the influence of wood moisture content (MC) and stiffness, determined by NDT, as well as previous drying methods on the bending ability of the wood. The best quality was obtained with bending specimens bent at a moisture content of at least 16% and quarter- or semi-quartersawn. The number of rejected specimens increased slightly when HF bending was used. Single-stage predrying of oak to a final MC of 8% resulted in a high rejection rate (>70%) regardless of drying technique. The acceptance rate was higher for less stiff specimens where the ratio of ultrasonic velocity in the straight (vS) and bent region (vB) was less than 0.5 (vB/vS).

Numerical evaluation on fatigue crack growth and life predictions of an FPSO mooring system

This study aims to systematically study the fatigue crack propagation characteristics of the mooring system for a floating production storage and offloading vessel (FPSO) through the fracture mechanics-based approach. The remaining fatigue life of the mooring lines is predicted by a self-integrated program through the simulation of the crack growth behavior. Additionally, parametric studies are performed to investigate the influence of initial crack status (location/size/shape) on mooring crack propagation characteristics. Results illustrate that the remaining fatigue life at the uppermost position of mooring lines at the wave-ward side is similar, which is approximately 178 years longer than that of mooring lines at the wave-back side. Fatigue issues are the severest in the crown region, where the critical fatigue life is about 49% of that in the bend region and 19.9% of that in the straight region. With the increase of the initial crack size and aspect ratio, the remaining fatigue life experiences a remarkable decrease with amplitudes up to 47.8% and 30.1% respectively. The integrated evaluation program is a promising tool for the damage tolerance design of mooring system due to the excellent capability in predicting the remaining fatigue life and charactering the crack growth behavior.

Computational assessment of effects of throat diameter on combustion and turbulence characteristics in a pre-chamber engine

Towards fundamental investigation of key physical aspects of pre-chamber combustion, the current work utilizes computational fluid dynamics to comprehend the effect of the throat diameter in an engine operated with methane. Previous studies showed that this parameter is dominant in pressure build-up and flow pattern inside the pre-chamber, suggesting that a detailed characterization is necessary. This pre-chamber type is composed of an upper conical part that lodges the spark plug and fuel injector, followed by a straight and tubular region called throat, which tip accommodates the nozzles responsible for the charge exchange between pre and main chambers. Two types of pre-chamber having distinct throat diameters are investigated, while utilizing consistent experimental data for validation of the model. The combustion process is modeled with the G-Equation model; the laminar flame speed was tabulated from a methane oxidation mechanism reduced from the GRI 3.0; the turbulent flame speed was computed using Peters' relation. The simulations were run for a full cycle, starting at exhaust valve opening. A homogeneous charge of methane is considered at the intake port, maintaining a global λ = 1.8, while 3% of total energy fuel is added through the pre-chamber. The results show that the throat changes the flow field inside the pre-chamber, impacts the air-fuel ratio, stratification, turbulence, jet dynamics, and ultimately the pre and main chambers combustion processes and heat fluxes. The combustion regime according to the Borghi-Peters diagram were found to lay in the thin reaction zone and in the flamelet regime.

Design of an ultrasharp silicon multimode waveguide bend assisted by multiregional subwavelength grating structures

Sharp multimode waveguide bends are beneficial to improve the integration density of the on-chip mode-division multiplexing (MDM) systems, which can be used to increase the optical information transmission capacity. A method of designing a multimode bending structure based on subwavelength gratings is proposed in this paper, through the mode conversion and matching between the straight and bending waveguide. The proposed bending structure is composed of a 90-deg arc-bend with a radius of 5 μm combined with the shallow-etched grating structures on the top, and two-mode converters on the input and output straight waveguide realized also with the help of nonuniform grating-like structures, achieving a total effective bending radius of 8.25 μm and high transmission efficiencies of the first three TE modes (TE0 − TE2) in a wide wavelength range of 1500 to 1600 nm. At the center wavelength of 1550 nm, the calculated excess losses of the three modes TE0, TE1, and TE2 are 0.21, 0.19, and 0.59 dB, respectively, and the crosstalks for all modes are less than −26.58 dB. More importantly, we add a non-uniform grating converter in the straight waveguide region which pre-deviates the mode fields inside the straight waveguide to help further reduce the size of the bending part to only 5 μm, which will be helpful for large scale integration when a great number of bends are cascaded.

A lattice Boltzmann model for the Navier-Stokes equation

The lattice Boltzmann model is a vital numerical calculation tool, which has become a useful solution to fluid problems because of the limitations of the Navier-Stokes equation and other macroscopic models in solving such problems. Here, the effectiveness of this model in the nearly incompressible Navier-Stokes equation is investigated as follows. First, the principle and excellent characteristics of the lattice Boltzmann model in numerical calculations are described and analyzed. Second, the approximate incompressible Navier-Stokes equations of the BGK (Bhatnagar-Gross-Krook) model in lattice Boltzmann method are analyzed. Finally, the two-dimensional five discrete velocity (D2N5) model in BGK model is taken as an example, and the vector rebound boundary scheme and the single point second-order boundary scheme based on the Dirichlet boundary condition are derived. Numerical results based on the Poiseuille flow and Taylar-Green vortex show that the BGK-based vector rebound boundary scheme has second-order accuracy only when the proportional distance is 0.5, and in other cases it cannot reach the accuracy. For the single-point second-order boundary scheme, the second-order accuracy can be achieved both in the Poiseuille flow based on the straight boundary region and in the Taylar-Green vortex based on the curved boundary. Through Maxwell iteration, the vector BGK model based on discretization is stable. When the boundary position is in the middle of two lattice points, the vector rebound boundary scheme has second order accuracy, and the single point second order boundary scheme has better performance in second order accuracy. This provides an idea for dealing with boundary conditions in incompressible Navier-Stokes equations.

The Deformation Behavior and Bending Emissions of ZnO Microwire Affected by Deformation-Induced Defects and Thermal Tunneling Effect.

The realization of electrically pumped emitters at micro and nanoscale, especially with flexibility or special shapes is still a goal for prospective fundamental research and application. Herein, zinc oxide (ZnO) microwires were produced to investigate the luminescent properties affected by stress. To exploit the initial stress, room temperature in situ elastic bending stress was applied on the microwires by squeezing between the two approaching electrodes. A novel unrecoverable deformation phenomenon was observed by applying a large enough voltage, resulting in the formation of additional defects at bent regions. The electrical characteristics of the microwire changed with the applied bending deformation due to the introduction of defects by stress. When the injection current exceeded certain values, bright emission was observed at bent regions, ZnO microwires showed illumination at the bent region priority to straight region. The bent emission can be attributed to the effect of thermal tunneling electroluminescence appeared primarily at bent regions. The physical mechanism of the observed thermoluminescence phenomena was analyzed using theoretical simulations. The realization of electrically induced deformation and the related bending emissions in single microwires shows the possibility to fabricate special-shaped light sources and offer a method to develop photoelectronic devices.

Surface‐Bound Domain Penetration and Large Wall Current

AbstractBy controlling the domain nucleation in ferroelectric mesa‐like cells formed at the surfaces of X‐cut LiNbO3 single‐crystal films that are integrated with Si substrates, growth of a surface‐bound needle‐like domain is observed in a quarter‐ellipsoidal shape. This domain, which extends in the major polar direction, contracts into several equilibrium segments with unequal lengths after removal of the in‐plane applied electric fields. The curved wall region located near the domain tip that connects the two top nanoelectrodes exhibits 12‐fold magnification of the on‐current when compared with the straight wall region near the tail. The field‐dependent flexible domain length and the high electrical conduction in the tip region promote crossbar integration of high‐density multilevel information‐storing memory devices and selectors with sufficient readout currents, thus enabling data‐intensive applications to be performed using domain wall microelectronics.

Study on water transport in hydrophilic gas diffusion layers for improving the flooding performance of polymer electrolyte fuel cells

For hydrogen-based polymer electrolyte fuel cells (PEFCs), water transport control in gas diffusion layers (GDLs) by wettability distribution is useful to suppress the flooding problem. In this study, the water transport of a novel GDL with hydrophilic-hydrophobic patterns was investigated. First, we clarified that the water motion in the hydrophilic GDL with microstructures could be reproduced by the enlarged scale model. The scale model experiment also showed that the same water behavior in hydrophilic GDL can be obtained from Capillary numbers (Ca) in a range of Ca ~ 10−5 to 10−3. As the computational load is inversely proportional to Ca, the computational load could be reduced by 1/100th by using Ca ~ 10−3, which is 100 times higher than PEFC operation (Ca ~ 10−5). Finally, the simulation with Ca ~ 10−3 was performed, and we showed that the GDL with straight region of contact angle 50° minimized the water accumulation.

Compact Racetrack Resonator on LiNbO3

A small all-pass racetrack resonator with a large free spectral range (FSR) is proposed and designed with a 600-nm-thick LiNbO3-on-insulator (LNOI) optical waveguide. It is shown that intermode crosstalk happens in LiNbO3 waveguide bends because more than one modes are generated from the anisotropy of LiNbO3. A sharp LNOI waveguide arc-bend is realized theoretically by choosing the geometrical parameters optimally to achieve constructive interference between the excited modes. This is very useful to realize compact resonators on LNOI. In particular, a novel racetrack resonator with a straight coupling region as well as Euler-bends is proposed. Here the narrow straight waveguides are introduced in the coupling region so that sufficient coupling between the access waveguide and the resonator is achieved within a short length. Euler-bends are introduced to avoid mode-mismatching at the junction between the straight-bent sections. For the designed LNOI racetrack resonator with an equivalent bending radius of 18 μm, the free-spectral range (FSR) is as large as 5.8 nm, and the Q-factor is 6.5 ×105 when assuming that the LNOI waveguide has a propagation loss of 1 dB/cm.

A Novel Ultralow R ON,sp Triple RESURF LDMOS With Sandwich n-p-n Layer

This article proposes a novel ultralow specific ON-resistance (RON,sp) triple reduced surface field (RESURF) lateral double-diffused MOSFET (LDMOS) with sandwich np-n layer. Compared with the conventional triple RESURF LDMOS with n-type top layer (NTTR LDMOS), the new structure is characterized by an additional N-buried layer below the P-buried layer. Due to the introduction of N-buried layer, the concentration of N-top layer will decrease to ensure charge balance, thus making the surface electric field distribution better and the higher additional doping introduced by N-top and N-buried layers can be achieved. The dose and implantation energy of n-p-n layers were simulated and optimized. Furthermore, in order to eliminate the premature avalanche breakdown occurring in the source-centered termination region, substrate termination technology (STT) is applied to avoid the high electric field peaks generated in the curved source region with small curvature radius. But the use of STT makes it easy to breakdown in the transitional region compared with the straight region. Therefore, the transitional region is studied and the crucial parameter AL in the layout of transitional region is also optimized. The fabricated device experimentally demonstrated improved performance with low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> of 78.3 mΩ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and high breakdown voltage (BV) of 795 V, and the experimental R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> is 26.8% lower than that of the conventional triple RESURF LDMOS (CTR LDMOS) and 10% lower than that of the NTTR LDMOS based on L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> = 67 μm, which can break the silicon limit of CTR and NTTR LDMOS and meet the demand of 700-V high-voltage integrated circuit applications.

Numerical simulation and creep-life prediction of X20 steam piping

Creep behaviour of X20 (12Cr-1MoVNi) steam piping subjected to a typical operating pressure of 18 MPa and temperature of 550 °C have been investigated using finite element analysis code, Abaqus and fe-safe/Turbolife software. User subroutine script for the modified hyperbolic sine creep model used was developed in Fortran and implemented in Abaqus. The maximum creep stress and strain were developed on the intrados of the elbows in the piping network. The maximum creep stress and minimum creep rate were obtained after an hour of operation and the stress was observed to relax with increase in operational time while the creep strain increases with time. Under the specified operating conditions, the steam pipe is expected to survive a useful creep life of 15.3 and 16.9 years with corresponding maximum creep damage of 7.479×10-6 and 7.479×10-6 for machine-finished and fine machine-finished steam pipe surfaces respectively. Lastly, strong correlation exists between the numerically simulated and analytically computed creep strain rate at the straight region of the piping.

Ultra-Compact Broadband 2 × 2 3 dB Power Splitter Using a Subwavelength-Grating-Assisted Asymmetric Directional Coupler

An ultra-compact broadband 2 × 2 3 dB power splitter is proposed and demonstrated by utilizing a subwavelength- grating (SWG)-assisted asymmetric directional coupler. In the present design, a subwavelength grating is inserted into the straight coupling region of an asymmetric directional coupler, so that the refractive index and the dispersion properties of this structure are engineered for achieving an ultra-broad bandwidth and an ultra-compact footprint. For the present power splitter with a straight coupling region as short as 5.25 μm, the bandwidth is as large as 300 nm (1400~1700 nm) for achieving an imbalance of <; 0.4 dB and an excess loss of <; 0.33 dB for the fundamental transverse electrical (TE) mode. The fabricated splitter works well with an imbalance less than 0.5 dB and with an excess loss less than 1 dB in a broad wavelength-band from 1450 to 1650 nm.

A Novel Method for Reducing Springback of Hot Stretch Bending Parts

Due to the impact of temperature on springback in hot stretch bending(HSB) process, this paper proposed a modified hot stretch bending(MHSB) process in which a reheating process was added before post stretching. The reheating process was realized by controlling the current distribution in the straight region and the bent region of titanium extrusion. Prior to HSB tests, uniaxial tensile tests were carried out to determine the deformation behavior of extrusion under the temperature condition similar to the HSB processes investigated. The results of the tensile tests provided supporting evidence for that the temperature of post stretching strongly affected the forming accuracy of hot stretch bending parts. Particularly, much more joule heat generated in the bent region than in the straight region successfully reheated it to initial forming temperature by increasing current before post stretching. Accordingly, the springback was significantly reduced via the novel method compared to conventional hot stretch bending(CHSB) process. This method is proved to be an efficient and lower cost solution for reducing springback in HSB.

Lane Detection of Curving Road for Structural Highway With Straight-Curve Model on Vision

Curve is the traffic accident-prone area in the traffic system of the structural road. How to effectively detect the lane-line and timely give the traffic information ahead for drivers is a difficult point for the assisted safe driving. The traditional lane detection technology is not very applicable in the curved road conditions. Thus, a curve detection algorithm which is based on straight-curve model is proposed in this paper and this method has good applicability for most curve road conditions. First, the method divides the road image into the region of interest and the road background region by analyzing the basic characteristics of the road image. The region of interest is further divided into the straight region and the curve region. At the same time, the straight-curve mathematical model is established. The mathematical equation of the straight model is obtained by using the improved Hough transform. The polynomial curve model is established according to the continuity of the road lane-line and the tangent relationship between the straight model and the curve model. Then, the parameters of the curve model equation are solved by the curve fitting method. Finally, the detection and identification of the straight and the curve are realized respectively and the road lane-line is reconstructed. Experiments show that this method can accurately identify the curve lane-line, provide effective traffic information, make early warning, and it also has certain universality.

Multi-step forming punch (MFP) for improving stretch-flangeability of advanced high-strength steel

Dissimilar materials, such as aluminum alloys, magnesium alloys, and advanced high-strength steel, are being increasingly used in vehicle structures while the flangeability of lightweight materials is of great challenges to the traditional process. In the presented study, the multi-step flanging in one press stroke accomplished by a novel punch with a notch was designed. The concept of incremental forming was implemented to improve the punch shape of stretch flanging and enhance the stretch-flangeability of advanced high-strength steel. Analytical solutions and numerical simulations were carried out to investigate the deformation mechanism and thickness distribution. Compared with the single-step forming punch (SFP), flanging process was divided into three steps in one press stroke by multi-step forming punch (MFP), which combined multi-stage characteristic of incremental sheet forming with high efficiency of traditional stamping. The results showed that the maximum tensile strain with MFP dropped from 0.406 to 0.28 at the edge of the deformed blank comparing with the single-step flanging by transferring large strain around the stretch corner edge to straight flanging region, which was in agreement with the theoretical analysis. In addition, excessive thinning was suppressed with MFP which decreased from 25.63 to 18.13% by sacrificing punch stroke that increased from 23 to 53 mm. Both the theoretical analysis and simulation results illustrated the validity of MFP for advanced high-strength steel.

Automatic Registration of Images With Inconsistent Content Through Line-Support Region Segmentation and Geometrical Outlier Removal.

The implementation of automatic image registration is still difficult in various applications. In this paper, an automatic image registration approach through line-support region segmentation and geometrical outlier removal is proposed. This new approach is designed to address the problems associated with the registration of images with affine deformations and inconsistent content, such as remote sensing images with different spectral content or noise interference, or map images with inconsistent annotations. To begin with, line-support regions, namely a straight region whose points share roughly the same image gradient angle, are extracted to address the issues of inconsistent content existing in images. To alleviate the incompleteness of line segments, an iterative strategy with multi-resolution is employed to preserve global structures that are masked at full resolution by image details or noise. Then, geometrical outlier removal is developed to provide reliable feature point matching, which is based on affine-invariant geometrical classifications for corresponding matches initialized by scale invariant feature transform. The candidate outliers are selected by comparing the disparity of accumulated classifications among all matches, instead of conventional methods which only rely on local geometrical relations. Various image sets have been considered in this paper for the evaluation of the proposed approach, including aerial images with simulated affine deformations, remote sensing optical and synthetic aperture radar images taken at different situations (multispectral, multisensor, and multitemporal), and map images with inconsistent annotations. Experimental results demonstrate the superior performance of the proposed method over the existing approaches for the whole data set.

Identification of Basic Fibroblast Growth Factor as the Dominant Protector of Laminar Shear Medium from the Modified Shear Device in Tumor Necrosis Factor-α Induced Endothelial Dysfunction.

Background and Aims: Endothelial dysfunction is a hallmark of cardiovascular diseases. The straight region of an artery is protected from atherosclerosis via its laminar blood flow and high shear stress. This study investigated the cytoprotective effects of a new laminar shear medium (LSM) derived from a modified cone-and-plate shear device and identified basic fibroblast growth factor (bFGF) secreted by human aortic endothelial cells (HAECs) as the dominant protective factor in the LSM.Methods: Based on a modified cone-and-plate shear device system, HAECs were exposed to laminar shear (15 dynes/cm2) and static control for 24 h to produce a new supernatant LSM and static medium (SM). Evaluation of the protective effects of LSM and SM on endothelial dysfunction induced by tumor necrosis factor (TNF)-α (10 ng/mL), which leads to production of reactive oxygen species (ROS), inflammatory monocyte adhesion, and tissue factor activity. ROS induction-, inflammation-, and thrombosis-related genes and protein expression were evaluated by quantitative-PCR and western blotting. To identify the cytokines that played a key role in the cytoprotective action of the LSM, we used cytokine antibody arrays, selected an abundant marker cytokine, bFGF, and validated the different cytoprotective effects of recombinant bFGF (rbFGF) and neutralization by monoclonal antibody (rbFGF+Ab) co-treatment. Aortic and lung tissues from different groups of C57BL/6J mice were examined by immunohistochemistry. SB203580 (specific inhibitor of p38) and BIX02189 (specific inhibitor of MEK5) were used to identify bFGF as the main cytoprotective factor acting via p38/MAPK and MEK5-KLF2 pathways.Results: Compared with traditional LSM, the new LSM not only significantly decreased TNF-α-induced intracellular adhesion molecule 1 and plasminogen activator inhibitor type 1 gene expression, but also significantly increased heme oxygenase 1 gene expression. The new LSM and bFGF attenuated TNF-α-induced ROS induction, inflammation, and tissue factor activity and inhibited the inflammatory- and thrombosis-related gene/protein overexpression both in vitro and in vivo. Mechanistically, the cytoprotective action of bFGF was mediated via the p38/MAPK and MEK5-KLF2 pathways.Conclusion: bFGF was identified as the critical factor mediating the cytoprotective effects of LSM derived from the modified laminar shear system.

地震分布规律研究(4)—中国大地震分布的第四、五条直线区域

本文分析处理了我国新疆中部和西北边陲大地震经纬度分布数据，得到了两条几乎平行的直线，且与我们前文建立的三条直线大致平行。表明中国大地震主要分布在五条近似平行的直线区域，这就是本文建立的中国大地震分布五平行线区域理论。 This paper analyzes and deals with the latitude and longitude distribution data of great earthquake in the central Xinjiang and northwestern border area in our country, obtains two almost parallel straight lines, and is roughly parallel with the three straight lines that we established earlier. It shows that the large earthquakes in China are mainly distributed in five straight lines region in approximate parallelism. This is the theory of great earthquake regional distribution with five parallel lines in China.