Double Configuration Research Articles

The failure mechanisms of fasteners under multi-axial loading

Fasteners in assemblies are often subjected to multi-axial loading; however, the role of load angle and the assembly design/geometry on the failure of fasteners are not well understood. Existing experimental data often convolutes multiple sources of uncertainty. Thus, numerical modeling is needed to make accurate conclusions about the failure mechanisms of fasteners. This paper investigates the mechanics that controls the loading angle effects on the mechanical response of fasteners by using a simple finite element bolt model without threads. The material model of this model is calibrated against tensile testing data, which minimizes the contribution of the fixture to the bolt's response. The calibrated material model is then used to investigate the loading fixture effects (including the fixture gap, compliance, and double shear loading configuration) on the mechanical response of the fasteners. After identifying the fixture parameters that the fastener's response is most sensitive to, a model of a simplified fixture is validated against experimental results. This investigation reveals that the loading angle effects and most of the loading fixture effects on fasteners' mechanical response are attributed to the change of stress concentrations at the contact tips. The primary contributions of this paper are novel insights into the failure mechanisms of fasteners, and that a reduced model of a fastener can be used to predict its constitutive behavior accurately.

Single and double bed stacked wire mesh cartridges for the catalytic treatment of diesel exhausts

Stacked stainless steel wire mesh monoliths were developed as supports for Pt/Co,Ce catalysts for diesel exhaust treatment. After the calcination of the metal structures at 900 °C, a Co,Ce layer was deposited over the meshes by means of an equimolar suspension of Co3O4 and CeO2 nanoparticles, followed by the incorporation of 1 wt.% Pt. Also, a double bed catalyst configuration was studied: a Pt,CeO2 pre-filter diesel catalyst oxidation (DOC) was developed to efficiently oxidize NO to NO2 which helps in regenerating the accumulated soot within the Co,Ce catalyzed diesel particulate filter (DPF). The catalytic monoliths, both as single and double bed configurations, were evaluated for the simultaneous combustion of volatile organic compounds (ethyl acetate, n-hexane or toluene) and soot. Co,Ce and Pt/Co,Ce structures presented similar catalytic activities, with a maximum soot combustion rate at 420 °C, whereas this value decreased to 400 °C for the double bed catalyst. Catalytic experiments with or without gaseous O2 or NO in the feed were carried out to ascertain the role of the catalytic components. The structured and powder catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), energy dispersive X-ray spectroscopy (EDX) and Laser Raman spectroscopy. The catalyst coating adherence was confirmed by ultrasound tests and the pressure drop of the catalytic structures was measured.

Leading-Edge Vortex Interactions at a Generic Multiple Swept-Wing Aircraft Configuration

Experimental investigations on a generic low-aspect-ratio aircraft configuration with triple and double delta wing planforms were performed at subsonic speed. Flowfield measurements by means of stereoscopic particle image velocimetry and force and moment measurements are used to investigate the system of interacting leading-edge vortices and its effect on the stability characteristics. The analysis comprises the discussion of the overall flowfield and of the vortex system including breakdown locations, vortex core data, and vortex trajectories. Topology considerations in selected crossflow sections highlight the flow patterns of the vortex system. The stability characteristics are discussed by means of the associated aerodynamic moment derivatives. Both the triple and double delta wing configurations feature a flowfield dominated by inboard and midboard vortices. The inboard vortex develops at a nonslender or slender wing section for the triple or double delta wing configurations, respectively, which entails different vortex characteristics and vortex–vortex interaction characteristics. The breakdown behavior associated with the different vortex types influences the stability of the midboard vortex in different ways. Both configurations exhibit pronounced instabilities in the medium to high angle-of-attack regimes, whereas the onset and magnitude of the instability are attenuated for the triple delta wing configuration.

Fractal-like overturning maps for stacked rocking blocks with numerical and experimental validation

A novel, compact mathematical formulation is presented to describe the dynamic rocking response of single and double block systems subjected to gravity and/or ground excitation. The derivation of the closed-form solutions of impacts and motion is based on the conservation of angular momentum and the Euler-Lagrange equation, respectively, and combines all the different cases of possible block relative rotating and impact modes (16 in total) into a single set of equations without the need of transient expressions. The derived equations that describe the impact modes are the equivalent to the expression derived by Housner and depend on the angular velocity of the blocks before impact. The analytical model is integrated numerically via an ad hoc algorithm and its reliability & accuracy are verified after various self-consistency tests and comparisons with the literature. In addition, several shaking table experiments were conducted in EQUALS laboratory in Bristol, set-up constructed to test free and forced rocking motion of single and double block configurations. The error margins of the measurements are determined, and the extracted data are in good agreement with the numerical results for most examined cases. The ideal Housner restitution coefficient of single block impact to a rigid base is adjusted to match experimental conditions, and it is found to be correlated with the block aspect ratio. The forced rocking of a two-block system is shown to exhibit numerous different response patterns depending on the excitation conditions. The integrated model is finally applied to produce normalised overturning maps for double block systems, subjected to single-pulse sine inputs, which uncover the existence of a fractal-type behaviour. This previously unsuspected trait of multi-block systems is reminiscent of the chaotic behaviour exhibited by a classical double pendulum and suggests that the risk of overturning can only be evaluated on a probabilistic sense.

Allocating nodes to hubs for minimizing the hubs processing resources: A case study

This paper addresses the problem of allocating the terminal nodes to the hub nodes in a telecommunication network. Since the flow processing induces some undesirable delay, the objective is to minimize the total flow processed by the hubs. This study focuses on a real life network of the tunisian operator Tunisie Telecom whose operations managers are concerned by the quality of service. We provide three compact formulations that give optimal solutions for networks of large size. In particular, the last two are obtained by applying the Reformulation-Linearization Technique to a nonlinear formulation of the problem. The latter formulation derived within this approach is the most computationally effective, as pointed out by the computational experiments conducted on the real life network of Tunisie Telecom with 110 nodes and 5 hubs. Finally, we discuss and compare between the single allocation and double allocation configurations.

Comparison of flow field and combustion in single and double side ported rotary engine

Intake and exhaust ports have great importance on performance of the rotary engines, since flow structure of the combustion chamber is depended on position and geometry of these ports. Similar to reciprocating engines that have different in-flow patterns according to valve characteristics of the engine, the flow patterns inside the combustion chamber change according to port position, quantity and channel geometry of rotary engines. In this study, air flow inside a double-side-ported rotary engine including 4 inlet and 2 exhaust ports with ports was numerically investigated by using computational fluid dynamic techniques. Numerical flow field results were compared with experimental data presented in the literature. Change of volumetric efficiency according to engine speed and flow field data were obtained for different port combinations. The results reveal that swirl and tumble motions are together formed in one side-ported engine simulations. When double-sided-ports are used, tumble motion is prevented by opposing air flow. Results show that double side intake port configuration has highest volumetric efficiency up to 8000 rpm. Single side intake port configuration has high volumetric efficiency up to 3000 rpm and it deteriorates rapidly after 3000 rpm because of high flow frictional losses. For all configurations, it is observed that rotating flows are prevailed by rotor motion at end of compression period and almost similar flow patterns are formed when rotor reaches at top dead center. After obtaining flow field results, combustion of single and double port intake configurations were compared with each other.

Imaging Michelson interferometer for a low-density gas jet characterization.

A new optical probing method with increased interferometric sensitivity for a low-density gas jet characterization is presented. The proposed technique employs a Michelson interferometer with a self-imaging object arm, which enables the relay imaging of the object on itself, and in this way, the phase sensitivity of the device is increased by a double propagation of the object laser beam through the gas jet. The wavelength of 405 nm was chosen to further increase the sensitivity by increasing the probe wavenumber. A low-density argon gas jet with various backing pressures was characterized by our method and by a commonly used Mach-Zehnder interferometer setup showing the expected twofold increase in the signal to noise ratio in the double pass configuration.

Design of an Ultra-Wideband High-Efficiency Rectifier for Wireless Power Transmission and Harvesting Applications

The wireless power transmission and harvesting techniques is becoming more and more important in industrial applications. A wide operating bandwidth is always expected for these two techniques. However, the existing rectifying structures usually can operate only over a narrow bandwidth. To achieve the wideband and efficient rectifying, the variation of optimum input impedance for the rectifier over the operating band should be as small as possible. For this issue, the voltage doubler configuration is analyzed and proved theoretically to exhibit slowly changing optimum input impedance. Based on this unique property, the simplified real frequency is utilized as the universal design approach together with the theoretical calculation. For demonstration, two rectifiers have been designed, fabricated, and measured for different input power levels. The proposed rectifiers showed the good characteristics in both efficiency and bandwidth. The rectifier applied in the high-power scenario kept conversion efficiency higher than 50% from 0.6 to 3 GHz, which corresponds to a relative bandwidth of 133%. The other rectifier designed for the low-power scenario maintained conversion efficiency higher than 40% within a wide bandwidth of 73.1%. The simulated and measured results agree well with each other, which validates the proposed structure and design methodology.

A matrix isolation ESR investigation of Mg+-N2.

The adducts formed between 25Mg+ with 14N2 and 25Mg+ with 15N2 have been trapped in a solid neon matrix and studied with electron spin resonance (ESR) spectroscopy. These radical species were formed through the interaction of laser ablated magnesium and nitrogen gas. The Mg+-N2 radical species was found to have a ground electronic state of 2Σ+ in a linear configuration with discrete coupling to the proximate nitrogen resolved in the spectra. Fitting the ESR spectra allowed magnetic parameters to be determined as follows: g⊥ = 2.0012(5), g∥ = 2.0015(8), A⊥(1-14N) = 32(3) MHz, A∥(1-14N) = 34(5) MHz, A⊥(1-15N) = 45(4) MHz, A∥(1-15N) = 47(6) MHz, A⊥(25Mg) = -581(5) MHz, and A∥(25Mg) = -582(5) MHz, and estimates derived for A⊥(2-14N) = 1(2) MHz, A∥(2-14N) = 2(5) MHz, A⊥(2-15N) = 2(2) MHz, and A∥(2-15N) = 4(6) MHz. Ab initio calculations using the coupled-cluster single double triple methodology showed that the linear form was 59.7 kcal mol-1 more stable than the T-shaped form. The potential energy curve around the equilibrium geometry was explored using the complete active space self-consistent field approach, and Hartree-Fock singles and double configuration interaction and multireference singles and double configuration interaction calculations of the hyperfine coupling constants were undertaken, and reasonable agreement with the experiment was observed.

Numerical Simulations of Projectile Nose Angle Effect in Ballistic Perforation of Double-Layered Steel Plates

The purpose of this paper is to study the ballistic perforation resistance of double-layered steel plates subjected to impact by conical projectiles with different nose angles. Based on nonlinear finite element theory, different rigid projectiles vertically penetrating into double-layered Weldox 460E steel plates are simulated with LS-DYNA code. The configurations in the penetration process and failure modes of steel plates are given. The results of monolithic and layered targets are studied and compared for projectiles with different nose angles. It is revealed that compared to the monolithic plate, the double layer configuration is able to improve the ballistic limit for the target under impact by blunt-nose projectiles, and for sharp-nose projectiles the double layer configuration obviously weakens the ballistic resistance.

Television as transitional medium

The development of television is never complete. It is a medium in permanent change, even if some aspects of television outlasted several decades. Television in the second decade of the 21st century looks different than in the 1950s of the 20th century. The screens are bigger, the picture is colourful, and the reception possibilities are more diverse, even mobile. Since the invention of television in the 1920s, the medium has undergone major changes, both in terms of technology and content. Television can therefore be seen on the one hand as a transitional medium - quasi a medium in permanent transition, because it repeatedly takes up and unites various technical developments. On the other hand, television can also be described as a transmedial medium because it incorporates aesthetic and narrative forms from other media into its programmes and at the same time has developed programme forms that radiate onto other, newer media (e.g. forms of television series form an important content on the Internet as web series or as an offer on streaming platforms such as Amazon Prime Video. Movistar+, Viaplay or Netflix). This double configuration of television as a transitional and transmedial medium makes up its fluid character. In the following, an initial attempt will be made to approach television in order to work out what actually constitutes this medium. Afterwards, the technical and institutional development of television is dealt with, before the development of programme forms is described. Finally, current developments resulting from the digitalization of television are presented.

Copper Iodide Interlayer for Improved Charge Extraction and Stability of Inverted Perovskite Solar Cells.

Nickel oxide (NiO) is one of the most promising and high-performing Hole Transporting Layer (HTL) in inverted perovskite solar cells due to ideal band alignment with perovskite absorber, wide band gap, and high mobility of charges. At the same time, however, NiO does not provide good contact and trap-free junction for hole collection. In this paper, we examine this problem by developing a double hole transport configuration with a copper iodide (CuI) interlayer for efficient surface passivation. Transient photo-current (TPC) measurements showed that Perovskite/HTL interface with CuI interlayer has an improved hole injection; CuI passivation reduces the concentration of traps and the parasitic charge accumulation that limits the flow of charges. Moreover, we found that CuI protect the HTL/perovskite interface from degradation and consequently improve the stability of the cell. The presence of CuI interlayer induces an improvement of open-circuit voltage VOC (from 1.02 V to 1.07 V), an increase of the shunt resistance RSH (100%), a reduction of the series resistance RS (−30%), and finally a +10% improvement of the solar cell efficiency.

Rection as a Synthesis of Reciprocal and Tensegrity Structure

There are several statements mentioning the possibilities of combining reciprocal and tensegrity structure. One of those is called reciprocal-tension (rection). This research was aimed to propose rection as a new structural system that also differs from both reciprocal and tensegrity. It defined rection structure and its characteristic, basic configuration and structural behaviour. Three simulations were conducted to test the hypothesis using dynamic relaxation method. The result showed that rection structure had the characteristics of (1) bar under bending stress, that do not touch each other, that hangs to each other reciprocally, and (2) self-equilibrated and pre-stressed system for enough rigidity. The research also concluded that the basic configurations of rection structure consist of upward fan reciprocal and positive double curvature configuration. Structural analysis also had been done on a 1:1 scale experiment and dynamic relaxation simulation.

Process development and coaxial sensing in fiber laser welding of 5754 Al-alloy

The use of Al-alloys is increasing in the automotive industry due to the pressing necessity to reduce weight and fuel consumption. Several parts concerning the car body are assembled through welding, where a high-quality seam is a key requirement. For this purpose, laser welding stands as an appealing option. On the other hand, laser welding of Al-alloys is a complex process due to the high reflectivity, reactivity, and crack susceptibility of these materials. In many cases, such issues limit the applicability of the autogeneous welding, which is an advantageous feature of laser welding. High-brilliance fiber lasers have been an enabling technology for improving the weldability of Al-alloys. However, laser welding of Al-alloys, especially in a lap-joint configuration, requires robust processing conditions able to maintain seam quality for each weld in high volumes even with part tolerances and tooling variability. Accordingly, this work discusses the process development and monitoring in laser welding of 5754 Al-alloy. In particular, the process was carried out in a double lap-joint configuration with 1 mm sheets, commonly used in automotive applications. A 3 kW fiber laser with in-source integrated monitoring capability was employed as the light source. The process feasibility zone was investigated as a function of laser power and welding speed, while the effect of focal position was investigated for the weld robustness. Weld seam types and defects were identified, as well as the monitoring signals associated light back-reflected from the process.

Optical system design of four-channel dual-band infrared panoramic imaging

In order to reduce the volume of a panoramic optical system, a four-channel infrared dual-band panoramic imager was designed using spatial multicamera image mosaicking. Each optical system of the imaging channel was designed in a double imaging configuration with an F-number of 2, working bands of MWIR 3 to 5 μm and LWIR 8 to 12 μm, and a full field of view (FOV) of 122 deg. By adopting refractive-diffractive hybrid optical elements and introducing aspheric designs, the system was made to achieve temperature compensation from −40 ° C to 60°C by means of optical passive athermalization. Results indicate that the system attained almost 100% cold stop efficiency. At the Nyquist frequency of 18 lp/mm, the modulation-transfer-function (MTF) of the MWIR system was higher than 0.70 at the edges of the FOV, whereas the MTF of LWIR system was greater than 0.35 for the same condition, both approaching the diffraction limit.

Critical investigation of glove–gown interface barrier performance in simulated surgical settings

The barrier properties of personal protective equipment are vital to healthcare personnel to protect themselves from possible infectious body fluids. Intraoperative exposure of healthcare personnel to body fluids can be substantial in both inpatient and outpatient settings. The glove–gown interface is known as one of the weakest points of the whole personal protective equipment system. However, there is a lack of scientific research designed to investigate the problem. This paper reports the results of experiments using a new testing methodology developed to quantify fluid leakage through the glove–gown interface while simulating surgical settings in terms of operating room personnel activities, exposure types, exposure durations, and physical stresses applied on the interface. This study represents one of the first efforts investigating the amount of fluid leakage through the glove–gown interface for a number of surgical gown and glove models while considering glove material differences and single vs. double gloving. The test results showed that there is a significant difference in fluid leakage amounts between three gown models and four glove models studied. The results also demonstrated that double gloving significantly reduced the fluid leakage compared to single glove use. The mean fluid leakage was lower in the double synthetic glove configurations (M = 2.76g) compared with all other configurations (3GLV, M = 8.3g; 4GLV, M = 9.49g; 5GLV, M = 3.08g; 6GLV, M = 20.03g; double latex, M = 5.22g). Findings highlighted a significant interaction between glove and gown designs, which suggests that gown and gloves should be designed together as a system to minimize or eliminate the fluid leakage.

40 dB gain all fiber bismuth-doped amplifier operating in the O-band

In this Letter, we investigate and compare the gain and noise figure characteristics of bismuth (Bi)-doped fiber amplifiers configured in both single and double signal pass implementations. A maximum gain of 25dB and a noise figure of 4dB is measured at 1360nm in the single pass configuration for -23 dBm input signal power, whereas in the double pass configuration the gain of the amplifier is improved significantly by 14dB allowing us to achieve a gain of 39dB with a noise figure of 5dB. To the best of our knowledge, this is the highest gain reported to date using Bi-doped fiber as a gain medium. Furthermore, we also study the gain and noise figure dependency on pump power, signal power, and pump wavelength for the double pass amplifier configuration. We observed similar gain and noise figure performance in the double pass configuration to that of the single pass configuration but with the benefit of less pump power and a shorter length of the Bi-doped fiber.

Resonance surface, microwave power absorption, and plasma density distribution in an electron cyclotron resonance ion source

Resonance surfaces for a 2.45 GHz electron cyclotron resonance ion source are investigated. In addition to the typical flat-B and minimum-B profiles, we have investigated on two new magnetic field structures, namely the torus zone and the double zone configurations. The impacts of such surfaces on the microwave power absorption are discussed. Furthermore, the uniformity of the ion emissive surfaces in connection with the resonance surfaces is examined. Different configurations for absorbing microwave power and simultaneously for producing uniform ion density distribution near the extraction wall of the source are discussed.

Experimental investigation of aero-optics induced by supersonic film based on near-field background-oriented schlieren.

The effective acquisition of a distorted wavefront is the foundation of studying how to suppress and correct aero-optical effects. The background-oriented schlieren (BOS) technique, as a commonly quantitative measurement method of flow field, has great application potential in aero-optical effect measurement. With consideration of the thickness change of the refractive index field, introduction of near-field correction and construction of the double telecentric configuration, wavefront measurement accuracy was improved. A standard plano-convex lens was utilized to quantitatively evaluate the improved results, and the effectiveness of the improvement was verified. Determination methods of spatial resolution, sensitivity, and dynamic measurement range of wavefront measurement based on BOS were studied. The influences of cross-correlation interrogation window size and step length on the wavefront reconstruction accuracy were investigated. The step length should be less than the size of the interrogation window to make the reconstructed results have a satisfactory accuracy. Wavefront results of supersonic film at different positions and cases were obtained. The fitting results show that there is a good linear relationship between the root mean square of the optical path difference (OPDrms) and ρ1/ρ∞ at different locations. Under different experimental cases, the aero-optical distortion tends to become stronger first and then weaker along the flow direction, and the aero-optical distortion around Position 3 is relatively strong. The large aperture approximation can be used to predict Strehl ratio values effectively in a considerable range by OPDrms.

Characteristics of phase delay in capacitive pick‐off circuits for MEMS resonators

In this Letter, the authors theoretically and experimentally investigate the characteristics of phase delay in capacitive pick-off circuits for micro-electromechanical systems (MEMS) resonators for the first time in history. An analytical model considering the phase delay for capacitive pick-off circuits is built up in theory. Only when they use their proposed novel modified double side-band demodulation configuration for resonators to extract motional amplitude and phase, the phase delay of pick-off circuits can be eliminated and extracted meanwhile in real time. Experiments show that the changing feature of phase delay primarily depends on temperature rather than drive frequency. Experimental results agree well with the theoretical model and reveal the relatively high correlation between the phase delay and temperature. This work provides a new indicator of temperature for resonators, using this phase delay of the pick-off interface, to make temperature compensation.