Length Of Straight Section Research Articles

The Optimal Design of an Arch Girder of Variable Curvature and Stiffness by Means of Control Theory

The problem of optimal design of the statically indeterminate arch girder which constitutes the primary structural system of the arch bridge is presented. The task is to determine the optimal shape of the axis of the arch girder, as well as the optimal distribution of the cross section height, ensuring the minimum arch volume as well as fulfillment of the standard requirements. This optimisation task, with numerous control functions and constraints, is formulated as a control theory problem with maintaining the formal structure of the minimum principle and then transformed to the multipoint boundary value problem and solved by means of numerical methods. The numerical results are obtained with optimal control methods, using the Dircol software. Since the changes in the shape and cross-section of the arch affect the distribution of the dead and moving loads transferred on the girder from the bridge deck, the optimisation procedure is combined with the finite element method analysis, which together with the complexity of the multidecision arch optimisation problem accounts for the novelty of the proposed approach. The numerical analysis reveals that the optimal girder shape is the frame-arched structure, with considerable lengths of straight sections and only short arch elements, in the areas of the application of concentrated forces and moments. The presented method can be successfully extended to optimisation of structures with different static schemes and load categories taken into account.

Failure of Copper Oxide Line Under High Current Density

Cu2O shows p-type semiconductor characteristics, have been investigated intensively for applications to opto-electronic devices and thin-film transistors (TFTs). Cu2O film is built by sputtering or pulsed laser deposition technique. Thermal oxidation of Cu can also create Cu2O layer, the resistivity (depending on the degree of oxidation) of the layer is controlled by temperature of heat treatment. Recently, studies on high integration such as fabrication of Cu2O nanowires were performed, but high current density due to scaling down of electronic devices induces electromigration (EM) damages. EM is a phenomenon that atom’s transport in the line by electron wind. In general, EM is one of key reasons for the failure of metal lines in electronic devices. Recently, EM failure of p-type semiconductor made of poly-crystalline silicon nanowires was studied. In this study, we conducted acceleration tests of micro-sized line of copper oxide which had p-type semiconductor characteristics to reveal electric characteristics under high current density. Straight-shaped copper oxide line samples were created on silicon substrates. Briefly, oxidation (SiO2) layer was grown on silicon substrate by thermal treatment (1173K, overnight). Cu layer with ca. 650 nm thickness was deposited on the SiO2 layer by sputtering. Cu line was fabricated through photolithography and wet-etching process. Width and length of straight test section of the line were ca. 20 um and 460 um, respectively. The Cu line was oxidized by thermal treatment (473K, 5 min). The resistivity of the copper oxide film prepared under the same conditions was 10-5 order [Ωm]. In energy dispersive X-ray spectroscopy (EDX), the O/Cu ratio of the thermal treated Cu layer was higher than that of before thermal treated. Also, the resistance of obtained copper oxide line decreased according to increasing of ambient temperature (303 to 373 K). It was considerable that the obtained copper oxide line was semiconductor materials with main component of Cu2O. Acceleration electric failure test was performed to the obtained electric lines. The sample was heated to 373K by using ceramic plate heater. Constant current (1.0 MA/cm2) applied to the obtained line by using constant current power supply and galvanometer. As shown in Fig (a), sample 1 with relatively high electric resistance was broken near the center of the test section at relatively short time (several tens minute). It seems that Joule heating was the key factor of failure, and the sample line broke at the center part with high temperature. By contrast, sample 2 with relatively low electric resistance broke near the anode side in test section at relative long time (several hundreds minute), as shown in Fig (b). In the laser microscope observations, the cross-sectional area of sample 2 was increased at the cathode side and decreased at the anode side. There is a possibility that the atomic transport due to EM was affected the failure at sample 2. In general, EM failure of metal line was observed at cathode side, since atomic transport occurred from cathode to anode with electron transport. It was reported that the semiconductor line made of poly-crystalline silicon nanowires was broken at the anode side. The failure at anode side was guessed that regrowth of grain was occurred due to Joule heating, they called this phenomenon thermally-assisted electromigration. It was suggested that similar EM failure occurred in sample 2. Acceleration electric failure tests of dumbbell-shaped copper oxide lines were performed, and failure at the anode side was observed. There is a possibility that the failure is related to thermally-assisted electromigration. It is expected that more detailed mechanism of this phenomenon can be demonstrated by the failure tests using various oxidized samples. Figure 1

Shaping Cutter Original Profile for Fine-module Ratchet Teeth Cutting

The methods for determining geometric characteristics of a theoretical original profile of the cutter for cutting ratchet teeth with a module of 0.3–1.0 mm are considered in the article. Design models describing the shaping process of cutting edges of cutter teeth are developed. Systems of expressions for determining coordinates of the points of front and back edges of cutter teeth; the workpiece angles of rotation during the cutting process; the minimum cutter radius are received. The basic data when using the proposed technique are: radii of circumferences passing through cavities of cutter teeth and external cut teeth; the gradient angle and length of straight section of the front edge of a cut tooth; angles of rotation of the cutter and the workpiece at the moment of shaping.

The posting-buckling analysis and evaluations of limit drilling length for coiled tubing in the sidetrack horizontal well

Compared with the conventional tubing with threaded connection, the coiled tubing (CT) has the advantages of no screwing on and off and it has been widely used in drilling, work over and fracturing operations. But the difficulties of exerting bottom weight-on-bit and horizontal extended lengths are the key problems that restrict the CT drilling technology. In this work, based on energy method, the critical loads of sinusoidal and helical buckling are presented for the CT under bottom weight-on-bit in the curved borehole. According to the geometrical shape of sinusoidal or helical buckling in the curved borehole, introducing the sliding displacement boundary conditions of CT in the Lagrangian multiplier method, the gravitational potential energy and friction resistance dissipated energy are considered in the energy method, the contact force, friction resistance between CT and wellbore are then proposed with factors of well trajectory curvature and well deviation. Consider a sidetrack horizontal well with straight section length of 200 m and bending section length of 174 m, the buckling behavior and friction resistances are conducted for 238'' CT with different horizontal section lengths. The limit extended lengths are finally obtained for CT under different weight-on-bit and friction coefficients in the sidetrack horizontal well. This finding is important for CT applying in drilling, work over and fracturing operations.

3.5-μm radius race-track microlasers operating at room temperature with 1.3-μm quantum dot active region

We present detailed studies of optically pumped InAs/InGaAs quantum dot based racetrack microlasers with 3.5-μm bend radius operating at room temperature. Q factor over 8000 and room temperature threshold power in the mW-range were achieved in the racetrack microlasers with straight section length ranging from 0 to 4 μm. A systematic investigation of the influence of the racetrack straight section length on spatial distribution of optical modes is presented. The microcavity eigenmodes and electromagnetic field distribution calculated by means of three-dimensional numerical simulation demonstrate a good agreement with the experimental results obtained by micro-photoluminescence and scanning near-field optical microscopy. The racetracks demonstrate zigzagging behavior of the modes inside the cavity and the energy switching between the radial maxima in second-order modes. Higher-order modes are found to be suppressed in micro-photoluminescence spectra.

Experimental and numerical investigations on hydrodynamic and aerodynamic characteristics of the tunnel of planing trimaran

The planing trimaran possesses distinctive hybrid hydrodynamic and aerodynamic performance due to the presence of tunnel. The research described in this paper was carried out based on the observation of wave characteristics of a planing trimaran model in towing tests, in which the resistance drops as soon as the wave surface separates from tunnel roof. In order to gain a deeper insight into the relationship between wave flow and forces in tunnel region, a comprehensive series of viscous CFD simulations considering free-surface and 2-DOF motion of the hull (heave and pitch) have been performed for the tested model at the volume based Froude numbers ranging from 3.16 to 5.87. The calculated results were validated by comparison with experimental data and showed good agreement. Numerical results of wave contours, longitudinal wave cuts and lifting force distributions at the calculated speeds were presented for the analysis of ventilation process in tunnel region and the corresponding variation of tunnel forces. It is found that, for the speeds higher than Froude number of 4.52, the aerodynamic forces provide major tunnel lift and mainly act on the straight section of the tunnel. And, therefore, numerical simulations of two modified models have also been performed for the analysis of influence of straight section length on the hydrodynamic and aerodynamic performance of planing trimaran.

Study on Improved Road Geometry Conditions of Chicane Considering the Relationship between Road Geometry and Carbon Emissions Reduction

PURPOSES: Recently, many local governments have applied chicanes for traffic calming to ensure environment-friendly comfortable and safe roads. However, the geometry of a chicane is designed for speed reduction using a curved portion. This study aims to improve the road geometry conditions of chicanes for reducing carbon emissions and maintaining appropriate driving speeds by considering the relationship between road geometry and carbon emissions. METHODS: This study was conducted as follows. First, carbon emissions corresponding to changing acceleration of vehicles were studied. Second, vehicle acceleration caused by the relationship between the curve radius and the straight length was studied. Accordingly, desirable conditions of curve radius and length of the straight section for reducing carbon emissions were proposed. RESULTS: The existing literature on chicanes present the minimum value of stagger length and path angle in the primary variable condition. This study suggests the maximum values of the curve radius and length of straight section in the primary variable condition. Therefore, if a vehicle's speed at a chicane is 30 km/h, this study suggests a curve radius of up to 24 m. In addition, if the vehicle's speed is 24 km/h, this study suggests a length of straight section of up to 6.6 m. These are the geometric conditions for considering the control of acceleration to the vehicle's maximum speed. CONCLUSIONS: This paper proposes an application of geometric conditions to reduce carbon emissions and maintain appropriate speeds of vehicles through a combination of curve radius and length of straight section.

Design and Simulation of Supersonic Swirling Separator

Supersonic swirling separator has been developed for natural gas dehydration in recent years. Compared to Twister-I supersonic swirling separator, Twister-II type overcomes the disadvantage of uncontrolled shock and the steady swirling flow field contributes to high efficiency of gas-liquid separation. The design method is discussed. For the Laval nozzle, the contraction section is designed by double cubic curve method, while the method for expansion section is tapered tube method the same as the divergent tube, throat is smooth circular arc; the length of straight swirling pipe section for separation is 3-8 times of the diameter. The paper simulates the applicability of the supersonic swirling separator by Fluent. Studies have shown that the lower environmental temperature, the lower the outlet temperature, the easier water to cool, and the higher the separation efficiency. If the volume flow rate rises, the inlet velocity and the mass flow rate can be effectively improved. We can control the shock location by adjusting the pressure at the outlet of divergent pipe. The shock appears at the inlet in the working condition designed. When the outlet pressure is lower, the shock occurs in divergent tube; on the opposite, it moves forward. Beyond a certain degree, shock occurs at the Laval nozzle, the device fails to work.

Simulation of Taper Roll Deviation Rectification Ability in Continuous Annealing Furnace

Running deviation of cold strip affects smooth operation in continuous annealing furnace, and the taper roll technology has positive significance for the prevention of strip deviation. In this paper, a finite element model of cold strip in continuous annealing furnace is established, and it can be used to analysis deviation rectification ability of single taper roll with different conical height and straight section length, double taper roll with different total conical height, straight section length and taper ratio. The calculation results show that the conical height is the most important factor for deviation rectification, and the deviation rectification ability of double taper roll is better than single taper roll. The results provide reference for taper roll optimization design in continuous annealing furnace.

Parametric Effects on Internal Aerodynamics of Lobed Mixer-Ejector With Curved Mixing Duct

The internal flow characteristics inside lobed mixer-ejector with curved mixing duct and the parametric effects on the lobed mixer-ejector performance are investigated numerically and validated by experimental test. The curved mixing duct affects the development of the streamwise vortices induced by the lobed mixer. When the mixing process undergoes the transition from the straight section to the bent section, the flow inside the curved mixing duct is dominated by the impinging and centrifugal effects. In general, the pumping ratio is decreased approximately 20%–30% once the bent section is mounted on the straight duct. The mixer-ejector performance could by improved by increasing the straight section length, due to more fully momentum utilization of primary jet and weaker influence of bent section on the back pressure near nozzle exit. The mixer-ejector pumping capacity is also augmented with the increase of mixing duct area ratio until the area ratio is reached to 3.5. And the fully-utilization of primary jet momentum inside mixing duct with big area ratio needs long mixing distance. The pumping ratio is decreased as the increase of bent angle of curved mixing duct in approximately linear relationship. When the bent angle exceeds 45 deg, the thermal mixing efficiency is decreased rapidly as the increase of bent angle.

Relaxation of Spatially Advancing Coherent Structures in a Turbulent Curved Channel Flow

A direct numerical simulation is made for the incompressible turbulent flow in the 180 deg curved channel with a long straight portion connected to its exit port. An examination is made for how the organized coherent vortex grows and decays in the curved channel: the radius ratio of 0.92, the aspect ratio of 7.2, and the succeeding straight section length of 75 times the channel half width. The 1552 × 91 × 128 ( = 18,427,136) grids are allocated to the computational domain. The frictional-velocity-based Reynolds number is kept at 150 to resolve the long domain including curved and straight regions. In contrast to that the coherent vortex grows along the concave wall, the vortex remains strong in the convex-wall side after the curvature accompanying a tail of the small-scale turbulence near the convex wall. The dissimilarity between the onset and disappearing of the coherent vortex essentially comes from the mean pressure gradient, which aids or averts the near-wall fluid oppositely between the curvature inlet and the exit. The mean flow is decelerated near the inlet of the convex wall to destabilize the flow and to trigger the onset of the coherent vortex. Contrary, the mean flow is accelerated near the exit of the convex wall to weaken the coherent vortex, and is decelerated near the exit of the concave wall to enhance the turbulence. Therefore, the turbulence enhancement and attenuation occurs oppositely between the inlet and exit of the curvature, and the coherent vortex draws a wake in the convex-side rather than the concave-side where it starts.

J046022 CFRP製環状ばねの基本特性評価(〔J046-02〕高分子基複合材料の加工と評価(2))

Mechanical performance and failure analysis of unidirectional carbon fiber reinforced epoxy resin composite (CFRP) loop springs were investigated in this study. The straight line sections and attachment flat surfaces were introduced to these loop springs in practical applications. Two types of CFRP loop springs with the different straight line section length were fabricated and tested under static and cyclic loadings. The experimental results showed that the straight line segment length had a huge effect on the spring constant and the ultimate load. Good agreement was obtained between the experimental and theoretical spring constant, based on the cantilever model. CFRP loop springs had the fatigue lives beyond two million cycles, as the springs were subjected to a maximum cyclic load of approximately 60% of the ultimate load. The initial failure, which occurred at the inner layer of the circular arc section, caused the final fatigue fracture.

Numerical Simulation of Stable Turbulence Generated by the Pipe Flow of Self-Regulating Air Driving Power Supply for Airflow Piezoelectric Generator

In the pan or platform carrier supply system, the intake pipe structure of the generator is very important for stability and efficiency of the airflow vibration-driving work in the small-hole aerodynamic piezoelectricity generator. Hyperbolic curved nozzle produces higher jet velocity than straight-wall nozzle. Using CFD method, contrast and analyse the annular identical-cross-section straight pipe and annular hyperbolically curved pipe, the calculation results prove the superiority of the hyperbolically curved pipe. For the geometry characteristic of the annular hyperbolic curved pipe structure, influence on the velocity distribution through varying parameters of the structure size was found out. The results show that development of the velocity distribution is directly affected by the length of straight pipe section of the pipe; better velocity distribution is obtained when length of straight pipe increases properly. On the other hand, a smaller ratio of aperture ring gap has a significant contribution to the out airflow velocity distribution.

Potential for a new measurement of muon g-2 factor

The muon g-2 factor can be measured on an ordinary storage ring with a noncontinuous and nonuniform field. When the total length of straight sections of the ring is appropriate, the spin rotation frequency becomes almost independent of the particle momentum. In this case, a high-precision measurement of an average magnetic field can be carried out with polarized proton beams. A muon beam energy can be arbitrary. Possibilities to avoid a betatron resonance are analyzed and corrections to the g-2 frequency are considered. The proposed experiment can provide a high precision and an independent experimental result with different systematics.

Potential for a new muon [formula omitted] experiment

A new high-precision experiment to measure the muon g−2 factor is proposed. The developed experiment can be performed on an ordinary storage ring with a noncontinuous and nonuniform field. When the total length of straight sections of the ring is appropriate, the spin rotation frequency becomes almost independent of the particle momentum. In this case, a high-precision measurement of an average magnetic field can be carried out with polarized proton beams. A muon beam energy can be arbitrary. Possibilities to avoid a betatron resonance are analyzed and corrections to the g−2 frequency are considered.

Viscoelastic electrospun jets: Initial stresses and elongational rheometry

A novel method of characterization of viscoelastic longitudinal stresses in electrospun jets of semi-dilute and concentrated polymer solutions and melts is introduced. The measured longitudinal stresses at the beginning of the thin jet region in the jets of a 6wt% aqueous solution of polyethylene oxide (Mw=400kDa) were of the order of 100kPa, which is two orders of magnitude larger than in any other free viscoelastic jets issued from nozzles and orifices. This is attributed to elongation-driven stretching of polymeric liquids in the transition zone, between the preceding modified Taylor cone zone and the beginning of the thin jet region, where the stretching rates are of the order of 100–1000s−1. The Rouse relaxation times found were in the range of 3–8ms, and the moduli of elasticity were of the order of 100Pa. A novel explanation of the reasons for the formation of the straight sections in the electrospun jets is proposed. The straight sections are stabilized by the high initial longitudinal stresses in the jet generated due to strong electrically driven stretching in the transition zone. The further electrically driven stretching in the jet (after the transition zone) is relatively weak, and viscoelastic Rouse relaxation prevails. The relaxation distance of the longitudinal stresses along the jet increases with the applied voltage (which generates higher initial stresses in the transition zone) and thus the length of straight section of the jet should increase as the applied voltage increases.The results also point at an opportunity to develop an elongational rheometer for concentrated polymeric systems with stretching rates of the order of 100–1000s−1. The proposed rheometer employs excitation of electrically driven jets by single lateral pulses, and observation of the pulse propagation and widening along the jet. This reveals the level of the longitudinal stresses along the jet and allows evaluation of the viscoelastic Rouse relaxation time, modulus of elasticity and the elongational viscosity in the jet.

Experimental Study of a Combined-Cycle Engine Combustor in Ejector-Jet Mode

*† ‡ § § A combustor model of a rocket-ramjet combined-cycle engine was tested in an ejector-jet mode under a sea-level, still condition. The model had two rockets in the duct. Propellants were gaseous hydrogen and oxygen. Design factors of the combustor were cross sections at the entrance and the exit, length of the combustor, fuel injection position and rocket operating conditions. In the tests, the designed operation of the ejector-jet was successfully attained. That is, breathed air was choked at the throat section. Supersonic rocket exhaust and air were decelerated in the divergent duct with an increase of the wall pressure. Fuel was injected in the downstream straight section and combustion gas choked at the exit. Mean Mach number was unity, and mean combustion efficiency was 0.8 according to pitot pressure measurement and gas sampling. Thrust augmentation was confirmed with the measurements. Operating conditions predicted in the design process reasonably agreed with those in the experiment. Other design factors were also investigated. Suction performance was increased with increase of a mixture ratio of the rockets. Acceleration of the breathed air was affected by length of the upstream straight section. The combustion status was not affected by length of downstream straight section or position of fuel injection. Fuel increase caused an increase of the pressure until a stoicheometric condition.

Alterations of channel parameters in response to river regulation works since 1840 on the Lower Tisza River (Hungary)

In the last few years an increase in the frequency and magnitude of floods was detected on the Tisza River, endangering large areas of Hungary. The causes of these record floods were complex, including both natural and human induced factors. This paper focuses on river management works and their effect on planimetric and cross-sectional parameters, with special attention to the flood conductivity changes to the river channel. During 19th century river regulation works, half of the total length of the Tisza River was altered by cut-offs, while in the 20th century mostly revetments and groynes were constructed. Subsequently, horizontal and vertical channel parameters have changed considerably due to semi-natural bed processes. In order to reveal changes, hydrological map series (1842, 1890, 1929, 1957, 1976 and 1999) and cross-sectional surveys from the same dates were analysed. Prior to the intensive human interventions (before 1890s) the river's course was highly sinuous with some very sharp bends. Due to cut-offs both the length and sinuosity of the Tisza River decreased by 35%, while the lengths of straight sections and the river's slope doubled. As a consequence the river incised by up to 3.8 m until the 1929 survey, resulting better flood conductivity, which improved flood safety. In the 1920s river management favoured bank stabilisation in order to stop the lateral migration of the channel. Despite these measures, meander development has continued, however, in a distorted manner. This is reflected by the opposing processes of lengthening centre-line on the one hand and gradually decreasing radius of curvature on the other. These processes can be explained by the continuous development of natural point-bars on the convex bank, and the lack of lateral retreat on the concave stabilised bank. The width of the river decreased by 17–45%, while its mean and maximum depth increased by 5–48%. The area of cross-sections influenced by revetments decreased by 6–19%, resulting in a 6–15% decline in flood conductivity. The non-stabilised sections were influenced by upstream revetments. Therefore, their parameters show similar changes, but with a smaller rate. At present, the flood conductivity of the channel is worse than it was in its natural state. In all, it was found that the ongoing process of cross-sectional distortion is a significant factor in increasing flood stage and hazard, and high floods can be expected more frequently in the future partly due to this factor.

Low-threshold phase conjugate mirrors based on position-insensitive tapered waveguides

The potential for substantial threshold reduction in stimulated Brillouin scatter phase conjugate mirrors (PCMs) was systematically studied using tapered hollow glass waveguides filled with carbon disulfide. Using a low-threshold PCM of 100 cm straight section length and 10 μm inner diameter, the threshold was reduced by a factor of 1000 compared to the bulk liquid threshold. Use of a tapered input alleviated alignment sensitivity normally encountered with small-input-diameter fibers, and allowed for the fabrication of wide-field-of-view PCMs (and Brillouin amplifiers) of a type useful in many applications. Performance of the low-threshold PCM was found to meet theoretical expectations.

Three-dimensional equilibria in DRAKONS with inhomogeneous magnetic configuration

Equilibrium equations are derived for a plasma in an arbitrary inhomogeneous magnetic configuration and are solved for DRAKONS case. The second-order equilibrium beta limit for DRAKONS with triangular CRELs is discussed for longitudinally inhomogeneous magnetic field. Numerical calculations of the beta limit are made for a parabolic pressure profile and a given magnetic field distribution. It is shown that the beta limit with a longitudinally inhomogeneous magnetic field can be much higher than that with a homogeneous magnetic field, and affected to second-order largely by the ratio of the straight section length to the CREL length.