Abstract: In this paper a flexible hollow core waveguide for the terahertz spectral range is demonstrated Its cladding is composed of a circular arrangement of dielectric tubes surrounded by a heat-shrink jacket that allows the fiber to be flexible Characterization of straight samples shows that the hollow core allows the absorption caused by the polymethylmethacrylate tubes of the cladding to be reduced by 31 times at 0375 THz and 272 times at 0828 THz with respect to the bulk material, achieving losses of 03 and 016 dB/cm respectively Bending loss is also experimentally measured and compared to numerical results For large bending radii bending loss scales as Rb−2, whereas for small bending radii additional resonances between core and cladding appear The transmission window bandwidth is also shown to shrink as the bending radius is reduced An analytical model is proposed to predict and quantify both of these bending effects

Abstract: The design and development of a plastic optical fiber (POF) macrobend temperature sensor is presented. The sensor has a linear response versus temperature at a fixed bend radius, with a sensitivity of . The sensor system used a dummy fiber-optic sensor for reference purposes having a resolution below 0.3 °C. A comprehensive experimental analysis was carried out to provide insight into the effect of different surrounding media on practical macro-bend POF sensor implementation. Experimental results are successfully compared with bend loss calculations.

Abstract: A simple, low-cost, and high-sensitivity optical fiber displacement sensor is presented and fabricated by concatenating two core-offset joints (COJs) with a separation length of 13 mm using a commercial fusion splicer. The two COJs construct an in-line Mach-Zehnder interferometer (MZI). When the MZI is bent to have a bending radius of ~ 17 mm, the interference pattern of the MZI depends strongly on the bending radius. According to this character, we scheme the bent MZI as a displacement sensor in two ways providing two different bending types of the bent MZI. The displacement sensitivities obtained are up to 0.835 and 0.227 nm/μm in the large displacement variation ranges of 350 and 1000 μm, respectively.

Abstract: In view of its feasibility for fabrication and application, a bend-resistant large-mode-area photonic crystal fiber with a triangular core is proposed. In our design, the fiber proposes a solution to the issue of bend distortion. The mode field area of the fundamental mode at the wavelength of 1.064 μm achieves 930 μm2 at the straight state and 815 μm2 at a bending radius of 30 cm, respectively. The decrement of the mode field area at the bend state is only 12.473% compared to the straight state. Furthermore, when the fiber is bent with a bending radius of 30 cm, numerical results demonstrate that the fiber conforms to single-mode operation conditions and the bending orientation angle can be extended to ±55°. A large mode area at bent state and low sensitivity of bending orientation make the fiber of great potential in high-power fiber lasers.

Abstract: Crosstalk characteristic of heterogeneous MCF with homogeneous Aeff is investigated. It is experimentally confirmed that radius around which the crosstalk peaks (Rpk) of smaller than 50 mm is realizable by Δneff of larger than 0.0010.

Abstract: A buried pipe extends over long distances and passes through soils with different properties. In the event of an earthquake, the same pipe experiences a variable ground motion along its length. At bends, geometrically a more complicated problem exists where seismic waves propagating in a certain direction affect pipe before and after bend differently. Studying these different effects is the subject of this paper. Two variants for modeling of pipe, a beam model and a beam-shell hybrid model are examined. The surrounding soil is modeled with the conventional springs in both models. A suitable boundary condition is introduced at the ends of the system to simulate the far field. Effects of angle of incidence in the horizontal and vertical planes, angle of pipe bend, soil type, diameter to thickness ratio, and burial depth ratio on pipe strains at bend are examined thoroughly. It is concluded that extensional strains are highest at bends and these strains increase with the angle of incidence with the vertical axis. The pipe strains attain their peaks when pipe bend is around $$135^{\circ }$$ and exceed the elastic limit in certain cases especially in stiffer soils, but remain below the rupture limit. Then equations for predicting the seismic response of the buried pipe at bend are developed using the analytical data calculated above and regression analysis. It is shown that these semi-analytical equations predict the response with very good accuracy saving much time and effort.

Abstract: To predict and control wall thickness distribution of thin-walled rectangular 3A21 aluminum alloy tube, the experiments of rotary draw bending process under multi-dies constraints are conducted. It is found that the thickness changing rates in middle bent zone are large, and the maximum values are obtained nearby the tube ridges. The effects of core die, pressure die, mandrel die, and bend die on thickness changing rate are significant. And the thinning rate increases with increase of core number, bend velocity, clearance between tube–pressure die interface and mandrel extension, but it decreases with increase of bend radius and boost velocity of pressure die. The thickening rate increases with increase of core number, boost velocity of pressure die and clearance between tube–wiper die interface, but it decreases with increase of bend radius and bend velocity.

Abstract: The computational fluid dynamics modeling of solid particles hydrodynamic based on the Lagrangian framework for diluted solid-gas flow through 90° gas pipeline bend is carried out to discover the effect of particles size distribution on particles flow pattern and their erosive effect on the bend. Particles size distribution has been obtained experimentally by measuring the sizes of solid particles that are flowing through the gas pipelines of Aghajari gas booster station. Also the erosion rate at the outer wall of the bend is predicted. The pipeline bend under study has a pipe diameter of 56 inches and ratios of the bend radius of the curvature to the pipeline diameter of 1.5. For the validation of computational model, firstly, the computational modeling is performed for a published experimental solid-gas flow data. The computational results include radial gas velocity and radial particle velocity profiles on planes which are at different angles through the bend. The comparison between the predicted numerical results and similar experimental data proves that the predictions of the computational model are acceptable. Finally, the particles' size distributions on each plane through the bend and the erosion rate on the outer wall of the bend have been obtained. The maximum rate of erosion is found to be 3.2 nm/s, occurring between 40 and 65° of the bend.

Abstract: The invention discloses a bend driving early warning method based on vehicular access synergy. Firstly, visibility information at the position of an inlet of a bend is detected, and load information, speed information, license plate number information and model information of vehicles passing through the position which is 100m away from the inlet of the bend are detected. According to the vehicle model information, the vehicle load information, bend radius information and bend transverse slope angle information, a bend passing vehicle speed upper limit value corresponding to each vehicle is obtained, a corrected bend passing vehicle speed optimum speed limit value of each vehicle is finally obtained by the combination between the bend passing vehicle speed upper limit value of each before correction and the visibility information, and the bend passing vehicle speed optimum speed limit value and a corresponding license plate number are jointly sent to a variable speed limiting notice board to be displayed. The bend driving early warning method based on the vehicular access synergy has the advantages of being high in operating rate and reliability, providing the reliable information for a bend driving speed limit sign, effectively assisting a driver in avoiding possible side-turning accidents, ensuring driving safety, being universally applicable to the bend driving environment, overcoming the defect of the high cost of a vehicle-mounted early warning mode in traditional methods, and being high in implementation performance.

Abstract: The behaviours of smooth 90-degree pipe bends under cyclic loading have received substantial attention in recent years where shakedown and ratchetting domains have been determined. However, such data are considerably lacking for mitred pipe bends. In the current research, the lower bound shakedown limit loads of 90-degree mitred pipe bends are determined via a simplified direct non-cyclic numerical technique recently developed by Abdalla et al. (2007) The analysed mitred pipe bends are subjected to the combined effect of steady internal pressures and cyclic in-plane or out-of-plane bending moments. Both in-plane closing and opening bending moment cases are considered. The shakedown boundaries of three mitred pipe bend geometries with one, two, and three welded joints are determined and compared with the shakedown boundary of a smooth 90-degree pipe bend. All analysed bends have diameter to thickness ratio of 25 and bend radius of 1.5 times the pipe mean diameter. The results indicate that the shakedown boundaries of mitred bends have reduced domains compared with the smooth pipe bend of similar geometrical parameters. Shakedown domains of mitred bends increase in size as the number of welded joints increase until it approaches the shakedown boundary of the smooth pipe bend simulating a mitred bend with infinite number of welded joints. The percentage of the area under shakedown domain for the mitred pipe bends to that of the smooth pipe bend ranges from 20% for the single mitred pipe bend to 75% for the 3-weld mitred bend. Results also revealed that reducing the number of mitred welded joints, dominates reversed plasticity response at the expense of ratchetting response. Out-of-plane bending generally showed larger shakedown domain than the in-plane bending shakedown domain. Additionally, the shakedown domains for in-plane closing and opening moments are quite similar.

Abstract: An acoustic-attenuating wall panel for a nacelle of a turbine engine may include a radiused portion. The radiused portion may include an airflow surface having a concave configuration and which may be exposed to an airflow passing through the nacelle. The radiused portion may include an acoustic attenuating section.

Abstract: A semicircular fiber (SCF) was fabricated by flame-heated treatment for displacement sensing application. By launching a laser beam into the SCF, interference was created at the output port of the structure due to fiber-bending-induced birefringence. Experiments indicate that the resonant wavelength was shifted to shorter wavelengths with increasing transverse displacement. Displacement sensitivity increases with the decrease of the bending radius of the SCF. A high sensitivity of 1100 nm/mm was obtained for the SCF with a bending radius of 0.57 mm.

Abstract: In this paper, the modal analysis of a novel design of a hybrid long-range plasmonic waveguide is introduced and analyzed using the full-vectorial finite difference method. The suggested design has high index material as a cap to reduce the propagation loss and optimum bending radius as well. The analyzed parameters are the real effective index and propagation loss. In addition, the bending analysis of the reported design is introduced. The coupling is performed between three different waveguides: straight dielectric waveguide, straight hybrid long-range plasmon waveguide, and uniformly bent hybrid one.

Abstract: Bent tubular parts have attracted extensive applications in various industries due to high strength and light weight. However, tube bending (TB) is a strong knowledge-based tri-nonlinear physical process with multi-tool constrains, and minor inappropriate tooling design may induce several failures such as wrinkling, over thinning (even fracture), section distortion, and springback. In response to the urgent requirements of the tubular products with mass quantities and diverse specifications, we proposed an integrated methodology for robust and loop tooling design for TB by combining several technologies such as knowledge-based engineering, parametric CAD modeling, and parametric finite element modeling. Via the spreadsheet formatted rules extracted from different sources of knowledge, several sequences are automatically conducted to preliminarily avoid the wrinkling and section distortion, including the selection of tooling sets (bend die, clamp die, pressure die, wiper die, or mandrel die with flexible balls), the determination of die dimensions, 3D modeling of both external and internal tools, die assemble, and the selection of material type for each die. Then, by importing the feature parameters of tools into 3D-finite elements models, the bendability of tube under previously designed multi-tool constraints is quantitatively evaluated in terms of multi-defect, and the springback can be calculated to redesign the bending die by radius reduction. The design variables are only tube diameter, wall thickness, bending radius, bending angle, and material types. The tool design system is then implemented, and the reliability and efficiency of the system are experimentally verified in the aviation industries regarding several practical bending cases with different specifications and tubular materials.

Abstract: Ultra-thin chips of less than 20μm become flexible, allowing integration of silicon IC technology with highly flexible electronics. This combination allows for highly intelligent products of unprecedented thinness, flexibility and cost. Examples include sensor systems integrated into food packaging or healthcare and sport monitoring tags as wearable patches or even directly in clothing textile. During use the ultra-thin chips in these products can be bent to a very high curvature, which puts a large strain on the chips. In this paper the strength of ultra-thin chips at very high curvatures is evaluated, using a modified four-point bending method. Stand-alone ultra-thin chips are evaluated which achieve a minimum bending radius below 1mm, as well as assemblies containing integrated ultra-thin chips. The effect of chip thickness, bending direction and backside finish on strength and minimum bending radius is investigated using the developed method. The difference between blank ultra-thin silicon dies and daisy chain ultra-thin chips with bond pads and bumps is highlighted. Finally the high curvature behaviour is investigated of ultra-thin chips that were integrated on low-cost polyester foil substrates using several different low-temperature integration techniques. The excellent suitability of these ultra-thin chips on low-cost foil assemblies for highly flexible large area devices is shown.

Abstract: A simple mechanism useful to tailor the field profile in single mode optical fibers is proposed. It involves the local and permanent bend of the fiber with bending radius of few hundred micrometers. The permanent bend is obtained by local thermal treatment using the electric arc discharge method. The resultant sub-mm bend leads to a significant power coupling from the fundamental core mode to guided cladding modes. The order and number of the excited cladding modes depend on the geometrical features of the bent region, like angle and curvature rate. Also, since the light propagated by guided cladding modes interacts with the surrounding medium by evanescent wave, the field distribution can be additionally tailored by changing the refractive index of the medium surrounding the straight fiber region after the permanent bend. Here, the effects of permanent bend on the guided mode in single mode fiber is first theoretically introduced and then widely experimentally investigated. Finally, preliminary results of light re-coupling from excited cladding modes to the core mode using long period fiber gratings are reported opening new avenues for light manipulation within optical fibers.

Abstract: 10 kV class 4H-SiC bipolar diodes have been fabricated. Two different edge terminations (Mesa/JTE or MESA/JTE with JTE rings) with two different junction bend radius have been designed and tested. Measurement results show that the inclusion of JTE rings improve the edge termination efficiency. The measurements indicate also a better reverse performance of diodes with larger bend radius.

Abstract: The brittleness of the MgB2 wires prevents performing a cable architecture with very small bending radius, similar to NbTi Rutherford cables. Consequently, it is important to reduce the thickness of the superconducting materials in order to increase its bending strain limit. In this context, thin Ni sheathed MgB2 hollow wires, having wall thickness of the order of 20 μm and length of the order of 100 m, have been produced by the Reactive Mg-Liquid Infiltration process (Mg-RLI). The latest hollow monofilament made by Mg-RLI shows very high transport properties, having an engineering critical current density at 4.2 K, 3 T of 730 A/mm2. In this wire the small thickness of the MgB2 corona allows a twisting with pass of the order of a few cm and fulfils the thermal stability criterion for MgB2. We have demonstrated that cables made by such braided or twisted wires may be conveniently reinforced, by embedding the wires in a molten Mg bath, so that the Ni sheath is almost completely dissolved and the wires are clad by an eutectic Mg10%at Ni alloy. This alloyed matrix is structurally well connected to the MgB2 material, with minimal thermal and electrical resistance at the interface. A cable prototype based on this metallic composite has been prepared with 21 mono-core MgB2 wires, twisted around a central hole, which may be useful for cooling purposes. This cable design may be applied as current leads or in short bus-bars, for high current supply.

Abstract: Determining appropriate process parameters is key to obtain qualified TA18 (Ti–3Al–2.5V, ASTM Gr. 9) titanium alloy tubes with medium strength by numerically controlled (NC) bending at low cost. This paper focuses on the variations in wall thickness and cross-section under various operating parameters and mandrel parameters for the NC bending of TA18 tubes. We put forward a method for quickly determining the range of the axial mandrel feed. The method is based on the principle of an equivalent mandrel supporting radius for a given bending radius but employing some mandrels with varying diameters and the principle of an equivalent mandrel supporting angle for various bending radii but employing the same diameter mandrel. The finite element analysis and the experimental verification results show that the bending speed should be less than 0.5 rad/s and the pressure die velocity should be approximately equal to or slightly higher than the bending speed, and that the method for determining the range of the axial mandrel feed is feasible. Considering the effects of an equivalent mandrel supporting radius and equivalent mandrel supporting angle, the mandrel diameter and axial feed should be chosen in a compatible range.

Abstract: High flexibility has been one of advantages for one-dimensional semiconductor nanowires (NWs) in wide application of nanoscale integrated circuits. We investigate the bending effects on lasing action of CdSe NWs. Threshold increases and differential efficiency decreases gradually when we decrease the bending radius step by step. Red shift and mode reduction in the output spectra are also observed. The bending loss of laser oscillation is considerably larger than that of photoluminescence (PL), and both show the exponential relationship with the bending radius. Diameter and mode dependent bending losses are investigated. Furthermore, the polarizations of output can be modulated linearly by bending the NWs into different angles continuously.

Abstract: A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10 −3 to 10 −4 dB / turn or lower over 1300 to 1700 nm, and 2 × 10 −4 dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78 × 10 −4 dB / turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10 −4 dB / turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).

Abstract: The invention relates to an HF coaxial cable that comprises a cable inner conductor and a cable outer conductor, as well as an angular plug connection at at least one of its two cable ends. A method is also described for producing same. The invention is characterised in that said HF coaxial cable is designed as a conventional corrugated sheath cable comprising a cable outer conductor, in the form of a metal corrugated tube, to which a line impedance Z k and a minimum bending radius r k,min are allocated; in that at the at least one cable end, said cable inner conductor is joined to an inner conductor of a straight plug connector and the cable outer conductor is joined to an outer conductor of the straight plug connector; in that said corrugated sheath cable has, directly or indirectly following the straight plug connector, a bend that has a bending radius r α , where 0.2 r k,min ≦r α ≦0.9 r k,min , which alters the line impedance Z k by a maximum of 1 ohm; and in that the bend with the bending radius r α is produced by cold forming said corrugated sheath cable with the introduction of bending forces and tensile forces directed along said corrugated sheath cable.

Abstract: The invention provides a center-free arc bending radius measuring ruler and a bend pipe bending radius measuring method. The measuring ruler is respectively connected with a left supporting leg and a right supporting leg symmetrically at both ends of a cross beam; an extension rule is connected at the center of the cross beam; and the extension rule moves up and down along the vertical direction of the cross beam. The measuring method comprises the following steps of: firstly equally dividing the inner arc or outer arc of a bend pipe bending part into a plurality of parts; then respectively measuring the arc heights of partial arc segments by taking each equal diversion point as a beginning point in two directions of the inner arc or outer arc by adopting the center-free arc bending radius measuring ruler; then obtaining the radius of each partial arc segment through calculation; and finally calculating the average value of the radius of each partial arc segment so as to calculate a bend pipe bending radius. The tool has the characteristics of being simple to manufacture, simple to measure, easy to grasp and the like; the position of the circle center of a workpiece is not required to be found out; manual measurement can be carried out; the measuring ruler is convenient to observe and monitor; and the bend pipe bending radius can be measured under any condition of the workpiece.

Abstract: The invention discloses a phase-regulated cable for spaceflights and a method for preparing the same. The phase-regulated cable for spaceflights is characterized by comprising an inner conductor, an insulation layer, outer conductors and sheaths which are all coaxially and are sequentially arranged from inside to outside. The method for preparing the phase-regulated cable for spaceflights comprises the following steps of forming the inner conductor by drawing or twisting a single or multiple silver-plated copper wires; forming the insulation layer by using a lapping production line to manufacture a polytetrafluoroethylene micro-porous thin film and then pressing the thin film; forming an outer conductor I by using the lapping production line to lap a silver-plated copper flat belt and then rolling the flat belt with round rollers; forming an outer conductor II by lapping an aluminum foil and a polyimide composite belt; forming an outer conductor II by braiding copper-plated round copper wires; and forming a sheath I and a sheath II by using the lapping production line to lap a polyimide duplex polytetrafluoroethylene thin film and a polytetrafluoroethylene sealing tape; and thus obtaining a finished product of a phase-regulated cable. The phase-regulated cable for spaceflights small in laying bending radius, phase-regulated, low in loss and low in standing wave, and has strong resistance to high and low temperatures and radiation, improved anti-interference performance and good flame resistance.

Abstract: We consider the design methods and operation principles of a fast-response optical sensor for precise measurement of small temperature variations, which is based on ring resonators of micron size made from waveguides with one or two slots filled by a liquid crystal. The sensor sensitivity and measurement region can be changed by modifying the parameters of the waveguide or resonator, such as width of the waveguide strips or slots, slot separation, resonator bend radius, coefficient of coupling between the ring and input/output waveguides, etc. We analyzed the dependence of the transverse field distribution and effective indices of the orthogonally polarized modes in the slot and double-slot waveguides on the waveguide and resonator parameters, and we have considered the optimization of the temperature sensor structure based on such waveguides.