Tip Configuration Research Articles

Application of Ultrasonic Piezoelectric Technology for Rhinoplasty.

Application of Ultrasonic Piezoelectric Technology for Rhinoplasty.

Efficient coupling between single mode fibers and glass chip waveguides via graded refractive index fiber tips.

Coupling characteristics between a single mode fiber (SMF) and a waveguide embedded in a glass chip via a graded index fiber (GIF) tip are investigated at a wavelength of 976 nm. The GIF tips comprise a coreless fiber section and a GIF section. A depressed cladding waveguide in a ZBLAN glass chip with a core diameter of 35 μm is coupled with GIF tips that have a range of coreless fiber and GIF lengths. An experimental coupling efficiency as high as 88% is obtained while a numerical simulation predicts 92.9% for the same GIF tip configuration. Since it is measured in the presence of Fresnel reflection, it can be further improved by anti-reflection coating. Additionally, it is demonstrated that a gap can be introduced between the chip waveguide and the GIF tip while maintaining the high coupling efficiency, thus allowing a thin planar optical component to be inserted. The results presented here will enable miniaturization and simplification of photonic chips with integrated waveguides by replacing bulk coupling lenses with integrated optical fibers.

Experimental and numerical study of novel tip configurations in a turbine cascade

Two novel tip modelling methods are proposed in this paper. One novel tip is established by the mathematical method and the other is generated by the B-spline surface. And the genetic algorithm, the orthogonal design and the Kriging model are applied to optimize two kinds of novel tips numerically. The optimal mathematical tip and the optimal B-spline tip are acquired, respectively. The aerodynamic tests were investigated at the wind tunnel test section, including the flat tip, the squealer tip, the optimal mathematical tip and the optimal B-spline tip. The static pressure distributions on the casing and the blade surface were measured by the pressure taps. Meanwhile, the secondary flow and the loss were obtained by the five-hole probe at the exit section. A comparison of the simulation analysis results with the experimental results shows good agreement. Compared with the flat tip, the measured loss on the squealer tip, the optimal mathematical tip and the optimal B-spline tip is decreased by 7.2%, 10.5% and 12.6%, respectively.

Conducting and characterizing femto flow electrospray ionization.

Femto flow electrospray ionization (ESI) with flow rates ranging from 240 fL min-1 to the low pico level (<10 pL min-1) was conducted and measured using a submicron emitter tip and relay ESI configuration. Signature analyte ion current intensities and profiles were observed. The obtained flow rate and ionization current enabled size calculation for initial charged nanodroplets.

Omnidirectional / Unidirectional Antireflection-Switchable Structures Inspired by Dragonfly Wings

Randomly arranged irregular inclined conical structure-covered dragonfly wings, distinguished from periodic conical structure-covered cicada wings, are with high optical transparency for wide viewing angles. Bioinspired by the antireflective structures, we develop a colloidal lithography approach for engineering randomly arranged irregular conical structures with shape memory polymer-based tips. The structures establish a gradual refractive index transition to suppresses optical reflection in the visible spectrum. By manipulating the configuration of structure tips through applying common solvent stimulations or contact pressures under ambient conditions, the resulting unidirectional antireflection and omnidirectional antireflection performances are able to be instantaneously and reversibly switched. The dependences of structure shape, structure inclination, structure arrangement, and structure composition on the switchable antireflection capability are also systematically investigated in this study.

Strategies for extended lifetime of implantable intraperitoneal insulin catheters

Implantable insulin infusion systems using the intra-peritoneal route have dramatically changed the management of diabetes paving the way toward the realization of the potential “holy grail” of a fully implantable artificial pancreas. However, the wear duration of delivery catheters is compromised by the foreign body-mediated immune response. Both occlusion material present at the distal catheter tip end and fibrotic encapsulation surrounding the catheters influence the controlled and precise delivery of insulin, which eventually leads to the need for surgical intervention. The novel part of the current work is the investigation of the roles of implant physical properties (catheter size and tip configuration), as well as local inflammation control (through utilization of an anti-inflammatory agent) on the host fibrotic response using a previously developed animal model. The cellular and molecular response, the medication delivery efficacy as well as the ability to flush the catheters were examined and further compared among the different mitigation strategies. Reduction in catheter size as well as tuning the tip configuration from a cone shape to a round shape showed delayed host recognition and delayed propagation of the fibrotic response. However, the round shaped tips had an increased occurrence of lumen occlusion as a result of flow change. It became apparent that changing the physical properties of the catheters was not a long-term solution to catheter obstructions caused by the foreign body reaction. In comparison, control of the local inflammatory response through the use of an anti-inflammatory agent demonstrated a promising strategy for maintenance of catheter functionality without any type of obstructions. These finding will have a large impact toward the development of long-term use catheters for continuous intraperitoneal insulin infusion.

Rapid Sars-Cov-2 Virus Detection Using Modular Transistor-Based Biosensor Platform with Disposable Test Strips

There is tremendous interest in development of systems for fast and high throughput testing technology for transmissive diseases and emergency medicine, especially after the outbreak of SARS-CoV-2 virus (COVID-19). To date (Apr 23rd, 2021), the number of infected populations worldwide has reached above 145 millions with more than 3 millions fatalities from the pandemic. Electrochemical sensing could potentially meet the demand of rapid yet low-cost detection and diagnosis for decentralized and widespread use. Recent advances in electrochemical sensing for COVID-19 include analog signal detection using graphene based field effect transistors (FET) [1], electrochemical impedance-based detection [2], as well as sensing of the N-gene of SARS-CoV-2 using antisense oligonucleotides [3]. In this work, we present a modular and low-cost platform Si-MOSFET based biosensor system utilizing disposable cartilages for sensing of SARS-CoV-2 spiked peptide and inactivated virus.Figure 1 shows the overall schematics of the sensing system, which consists of a Si enhancement mode MOSFET (Texas Instruments SN74S124N) based circuit board and biofunctionalized test strips. The sensing test strips, Figure 2, are connected between the VGG and the gate electrode. A voltage-controlled oscillator (VCO), shown in Fig 3, converted the output drain waveform into a digital reading. The starting materials for the sensing cartridges are multi-electrode graphite-based sensor strips with a single electrode plated with Au for sensing. Figure 4 shows the surface morphology of the electroplated surface. The Au-plated surface was then functionalized, subsequently, with thioglycolic acid (TGA), N, N’-dicyclohexylcarbodi-imide and N-hydroxysuccinimide, to form chemical bonding between Au surface and the desired antibody. Diluted antibody was then incubated on the Au electrode surface to finalize the biofunctionalization.Figure 5 shows a schematic of the synchronous drain (VDD) and gate (VGG) waveform, as well as the resultant dynamic drain current (ID/Isen) and voltage (VD/Vsen) caused by the electric field induced deformation of the antigen/antibody complex [4]. Figure 6 shows the dynamic drain waveform of the NMOS transistor at different tested spike peptide concentrations. Figure 7 shows the voltage extracted at 750μs of the drain waveform, which is designated as the analog signal reported in this work. Two types of antibodies, SARS-CoV-Spike ECD monoclonal antibody and polyclonal spike antibody, were tested in this study. The built-in digital readout allows direct readout of the relative virus concentration. Both antibodies show sensitivity in range of 10-15 to 10-5 g/mL with digital signal sensitivity of 53/dec for monoclonal antibody and 56/dec for polyclonal antibody. Figure 8 shows the digital outputs for human inactivated virus (ATCC VR-1986HK) under test. The sensor strips with electrodes presented in Figure 2 can reach detection limits down to 100 PFU/mL with digital sensitivity of 150/dec for monoclonal antibody and 454/dec for polyclonal antibody. By slightly modifying the sensor tip configuration, the sensitivity for inactivated virus detection can be lowered to 5 PFU/mL. For the same range of peptide/virus concentration tested, a larger change in drain voltage/digital reading represents a high sensitivity to doped solution due to the different epitopes these antibodies interact with. The fast response time and low detection of limit exemplified by this technique provides an opportunity for inexpensive semiconductor-based sensor systems in such applications. This approach is versatile and can be functionalized with different antibodies for different viruses and the cartridges printed with multiple functional areas to test for multiple variants.[1] G. Seo et al., ACS Nano, vol. 14, p. 5135 (2020)[2] M. Z. Rashed et al., Biosens. Bioelectron., vol. 171, p. 112709 (2021)[3] M. Alafeef, et al, ACS Nano, vol. 14, pp. 17028–17045 (2020)[4] S. Shan et al., IEEE Trans. Biomed. Circuits Syst. vol 14, 1362 (2020) Figure 1

Effect of tip clearance on cavitating flow of a hydraulic axial turbine applied in turbopump

The requirements of Liquid Propellant Rocket Engine (LPRE) are high for thrust, specific impulse, and flow rate; thus, its components also have strict requirements. For the turbopumps (TPs), this means high flow rate, high rotational speed, and high pressure ratio, which makes their operations susceptible to the cavitation phenomenon, as observed in two previous works. In the first, cavitation regions were observed in the first stage of the Space Shuttle Main Engine (SSME) Liquid Oxygen (LOX) booster turbine, for 3.0, 5.5, and 8.0% tip clearances (relative to rotor blade height), using monophase flow (Lindquist Whitacker et al., 2017). In the second, the simulations were performed with multiphase flow, producing results more physically coherent for the 3.0% gap configuration (Whitacker et al., 2018). The characteristics of both types of simulations in space propulsion applications still require better understanding. Therefore, to compare monophase and multiphase results at various operating points and turbine configurations, steady-state turbulent 3-D Computational Fluid Dynamics (CFD) simulations were performed, based on Reynolds-Averaged Navier-Stokes (RANS) formulation. The same three tip configurations for the turbine first stage were simulated, and the calculations were validated using experimental results from the National Aeronautics and Space Administration (NASA) (Boynton and Rohlik, 1976). This made it possible to verify the effect of the tip clearance on the machine performance and internal flowfield. When the gap increased, the pressure loading decreased in a large region of the blade tip, the interaction was greater between the Tip Clearance Vortex (TCV) and a vortex generated around the shroud cavitation region (Cavitation Vortex - CV), and this interaction moved towards the middle of the blade-to-blade passage. Thus, the losses increased and the efficiency decreased. Various comparative aspects between the simulations using both mono and multiphase numerical schemes are also discussed.

Communication—An Optical Fiber Biosensor Based on a Lab-on-a-Tip Approach for User-Friendly Carbosulfan Detection in Vegetable Samples

The use of a disposable pipette tip was studied to create a lab-on-a-tip approach. The configuration of a pipette tip, fiber optics, and paper-based biosensor show the compatibility of creating a novel one-shot optical biosensor for carbosulfan as carbamate pesticide. Under optimal experimental parameters, the lab-on-a-tip could detect carbosulfan in the linear range value of 10–22000 μg l−1 with a detection limit value of 10 μg l−1. The results show good agreement with the HPLC method.

Aerodynamic topology optimization on tip configurations of turbine blades

Aerodynamic topology optimization on tip configurations of turbine blades

Wake effects on heat transfer from a turbine blade tip with different configurations and its corresponding shroud

The wakes that occur periodically owing to blade rotation, affect the HTCDs (heat transfer coefficient distributions) on the turbine blade tip and shroud. We investigated the wake effects on the HTCDs from the turbine blade tip with different configurations and the corresponding shroud. The NSM (naphthalene sublimation method) was used for measuring the local heat/mass transfer distributions (LHMTDs). Five different tip shapes were compared. The flow characteristics near turbine blade tip and shroud varied with respect to different tip shape. Especially, swirling flow and tip leakage flow patterns varied, which affected the HTD on the tip & shroud. In addition, the local heat transfer distributions (HTCDs) on the tip and the shroud varied with different tip configurations. However, when the wake effects were induced, the HTCDs on the tip & shroud became relatively uniform. Furthermore, the magnitudes of HTCDs on the tip & shroud were relatively similar in region of 0.3 < x/Cx < 0.8. owing to the wake effect. Therefore, the vertical rib case can be the best-adopted for the turbine blade tip by considering the reduced total PLC (pressure loss coefficients) and HTCDs.

Effect of shelf squealer tip configuration on aerothermal performance of gas turbine blade

The tip leakage flow between rotating turbine blades and the stationary turbine casing causes aerodynamic losses and high thermal loads. Numerous novel tip geometries have been proposed for reducing both of these effects, one of them is a shelf squealer tip. The objective of this study is to investigate the aerothermal performance of three squealer blade tip configurations: conventional, vertical shelf and inclined shelf. Heat transfer was measured to analyze heat transfer features on the blade tip using transient IR thermography method. Also, computational fluid dynamics simulation and particle image velocimetry were conducted to visualize the flow characteristics around the blade tip. The experiment was conducted under conditions of a Reynolds number of 140,000 which was based on the inlet velocity in a wind tunnel. Thermal loads with vertical and inclined shelf squealer tip configurations are lower than with the conventional squealer tip. Due to the recessed pressure side rim of the vertical shelf squealer tip, the tip leakage flow was less reattached comparing to conventional squealer tips. This resulted in reduced thermal load on the tip surface and a larger tip leakage vortex around the blade suction side, which increased aerodynamic losses. Especially in the inclined shelf squealer tip, a separation bubble was generated on its inclined pressure side rim, which reduced the tip leakage flow due to the vena contracta effect. Consequentially, the reduced tip leakage flow decreased both heat loads and aerodynamic losses for the inclined shelf squealer tip. Therefore, the inclined shelf squealer tip demonstrated a good performance with respect to both aerodynamic loss and heat transfer.

Experimental investigation of tip anhedral effects on the aerodynamics of a model helicopter rotor in hover

This study experimentally investigates the effects of tip anhedral on the rotor aerodynamic performance and the tip vortex characteristics in hovering flight. A five-bladed scaled helicopter rotor with blades that have either rectangular (baseline) or anhedral tip geometries was used as the experimental model. Thrust and torque measurements were performed at the tip Mach numbers (Mtip) of 0.3 and 0.4 at five different pitch angles. In addition, flow field measurements via phase-locked particle image velocimetry technique were conducted at Mtip = 0.4 for a selected pitch angle. Thrust and torque measurements reveal that the anhedral tip configuration reaches a maximum Figure of Merit (FOM) value of 0.67 yielding approximately 5% FOM improvement when compared to the rectangular blade at Mtip = 0.3. It is observed that the tip anhedral changes the tip vortex trajectory by increasing the radial contraction of the wake and decreasing the average axial convection speed in the range of the wake age considered in this study. The meandering amplitude of the tip vortex increases abruptly after the passage of the proceeding blade in both cases yet a greater increase is observed in the anhedral tip configuration. Moreover, the axial convection of the previously shed tip vortices in the downstream direction is significantly slowed down during the course of the blade passage such that they reside close to the rotor disc in the anhedral case. The resultant proximity of the tip vortices to the blade with anhedral tip configuration promotes the induced flow in the radially inwards direction, which probably attenuates the strength of the newly forming tip vortex. Accordingly, the maximum tangential velocity and circulation of the tip vortex are reduced by 20% and 13%, respectively, when compared to the rectangular blade case. The reduced tip-vortex circulation is consistent with the increased FOM value. A good agreement was found with the Vatistas vortex model using n=3 for the rectangular blade and n=2.2 for the blade with tip anhedral.

Effect of the Honeycomb Tip With Injection on the Aerodynamic Performance in a 1.5-Stage Turbine

Abstract Three kinds of rotor tip configurations have been investigated numerically in the LISA 1.5-stage turbine, including the flat tip, the honeycomb tip, and the honeycomb tip with injection. The effect of the cavity depth and the injection mass flowrate on the turbine performance is studied in detail, evaluated by the isentropic total-to-total efficiency and the tip leakage mass flowrate. The Reynolds-averaged Navier–Stokes (RANS) method and the k–ω turbulence model are adopted in all the present computations. The numerical results show that the first-stage efficiency is increased by up to 0.66% and the tip leakage mass flowrate is reduced by about 1.87% of the main flow. The pressure field and the flow feature inside the gap are explored. The flow structures and the total pressure loss contours in the rotor passage are presented. Finally, the total pressure loss is newly defined by considering the injection effect. It is indicated that the injection mass flowrate should be carefully determined for excellent overall performance.

Current-carrying friction behavior of graphene with intervention of interfacial current

Graphene has shown the great potential applications in the field of solid lubricants due to its outstanding mechanical properties and chemical inertness. The introduction of interfacial current at the graphene-lubricated surface is expected to tune the lubrication performance of graphene. Here in this work, an atomistic configuration of single-crystal silicon tip sliding against graphene supported by an elastic substrate is constructed to investigate the current-carrying friction behavior of graphene by using molecular dynamics simulations. The effects of applied voltages, normal loads and substrate stiffnesses on the current-carrying friction behavior of graphene are systematically explored. The simulation results show that when the bias voltage is applied to the graphene-based system, the friction force undertaken by the tip is one order of magnitude larger than when applying no bias voltage. The friction increases with the magnitude of bias voltage increasing, but the increasing rate varies in different directions of bias voltage. A similar friction-voltage relationship of graphene under different normal loads and substrate stiffnesses indicates its relatively stable current-carrying friction behavior and the robust current-carrying effect. The increased friction force of graphene after the introduction of interfacial current can be attributed to the expansion of current-carrying region, causing Coulomb interactions instead of van der Waals interactions to dominate the adhesions at the friction interface. Based on the Prandtl-Tomlinson model, the current-carrying friction mechanism of graphene is systematically discussed. It is found that such a friction mechanism is different from the pucker effect of graphene, but follows the energy barrier theory. This work promotes the graphene to be used as the typical solid lubricant under the complex operation conditions with the voltage-induced current going through friction interfaces.

Retraction Note to: Artificial neural networks for prediction Charpy impact energy of Al6061/SiCp-laminated nanocomposites

In this work, Charpy impact energy of Al6061-SiCp nanocomposites produced by mechanical alloying has been modeled by artificial neural networks in both crack divider and crack arrester configurations. Al6061 powders were mixed by 2, 3, and 5 vol % of SiC nanoparticles and ball-milled for 45 min. Afterward, the produced powders were hot-pressed in aluminum cans and then were extruded to produce a dense bulk. Charpy impact specimens were prepared from the produced samples in layered form with different adhesives and thickness of the layers. To build the model, training, validating, and testing was performed using 171 pair input-target data. The used data in the multilayer feed-forward neural networks models were arranged in a format of six input parameters including the thickness of layers, the number of layers, the adhesive type, the crack tip configuration, the content of SiC nanoparticles, and the test trial number. The output parameter was Charpy impact energy of the nanocomposites. The training, validating, and testing results in the neural network models have shown a strong potential for predicting Charpy impact energy of Al6061/SiCp nanocomposites in the considered range of input-target values.

Assessment of small-scale deformation characteristics and stress-strain behavior of NiTi based shape memory alloy using nanoindentation

The study is focused to understand the micro-mechanisms that govern the deformation behavior of a Ni-rich NiTi alloy at the sub-micron scale. This alloy undergoes reversible stress induced martensitic transformation leading to pseudoelasticity. Correspondingly, significant strain recoverability is noted. In this investigation, nanoindentation is utilized as the primary experimental tool. Various parameters including the indenter tip configuration, size and applied load levels are varied systematically. It is observed that compared to the most commonly used sharp Berkovich indenter tip, blunt spherical tip imposes reduced amount of strain and strain-gradient within the indentation volume. This opens up the window for systematically varying the sequential deformation modes in NiTi. Further in-depth analysis revealed that optimum combination of indenter tip configuration, size and applied load level is prerequisite to appreciate the pseudoelastic mechanism in NiTi. Most importantly, a tailored and simplified protocol is formulated for converting nanoindentation load-displacement response to corresponding indentation-stress-strain behavior for pseudoelastic alloy. These indentation-stress-strain curves featuring the signature deformation characteristics of NiTi alloy are realized without utilizing any specialized experimental modes. In a nutshell, this study highlights the importance of choosing adequate nanoindentation parameters for assessing the functional characteristics of pseudoelastic NiTi system at sub-micron scale. Accordingly, overall localized deformation behavior of this unique alloy is investigated.

Retraction Note to: Modeling ductile to brittle transition temperature of functionally graded steels by fuzzy logic

In this article, a model based on fuzzy logic (FL) for predicting ductile to brittle transition temperature of functionally graded steels in both crack divider and crack arrester configurations has been presented. Functionally graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced by electroslag remelting. For purpose of building the model, training and testing using experimental results from 140 specimens produced from two basic composites were conducted. The used data as inputs in FL models are arranged in a format of six input parameters that cover the FGS type, the crack tip configuration, the thickness of graded ferritic region, the thickness of graded austenitic region, the distance of the notch from bainite or martensite intermediate layer, and temperature. According to these input parameters, in the FL, the ductile to brittle transition temperature of each FGS specimen was predicted. It has been found that FL model will be valid within the ranges of variables. The training and testing results in the FL model have shown a strong potential for predicting the ductile to brittle transition temperature of each FGS specimen.

Assessment of Small-Scale Deformation Characteristics and Stress-Strain Behavior of NiTi Based Shape Memory Alloy Using Nanoindentation

The study is focused on appreciating the micro-mechanisms that govern the deformation behavior of a Ni-rich NiTi alloy at the sub-micron scale. This alloy undergoes reversible stress-induced-martensitic-transformation leading to pseudoelasticity. Correspondingly, significant strain recoverability is noted. In this investigation, nanoindentation is utilized as the primary experimental tool. Various parameters including the indenter tip configuration, size and applied load levels are varied systematically. It is observed that compared to the most commonly used sharp Berkovich indenter tip, blunt spherical tip imposes reduced amount of strain and strain-gradient within the indentation volume. This opens up the window for systematically varying the sequential deformation modes in NiTi. Further in-depth analysis revealed that optimum combination of indenter tip configuration, size and applied load level is prerequisite to appreciate the pseudoelastic mechanism in NiTi. Most importantly, a tailored and simplified protocol is formulated for converting nanoindentation load-displacement response to corresponding indentation-stress-strain behavior for pseudoelastic alloy. These indentation-stress-strain curves featuring the signature deformation characteristics of NiTi alloy are realized without utilizing any specialized experimental modes. In a nutshell, this study highlights the importance of choosing adequate nanoindentation parameters for assessing the functional characteristics of pseudoelastic NiTi system at sub-micron scale. Accordingly, overall localized deformation behavior of this unique alloy is appreciated.

An experimental study on the effects of winglets on the tip vortex interaction in the near wake of a model wind turbine

AbstractAn experimental study of the near wake up to four rotor diameters behind a model wind turbine rotor with two different wing tip configurations is performed. A straight‐cut wing tip and a downstream‐facing winglet shape are compared on the same two‐bladed rotor operated at its design tip speed ratio. Phase‐averaged measurements of the velocity vector are synchronized with the rotor position, visualizing the downstream location of tip vortex interaction for the two blade tip configurations. The mean streamwise velocity is found not to be strongly affected by the presence of winglet tip extensions, suggesting an insignificant effect of winglets on the time‐averaged inflow conditions of a possible downstream wind turbine. An analysis of the phase‐averaged vorticity, however, reveals a significantly earlier tip vortex interaction and breakup for the wingletted rotor. In contradistinction, the tip vortices formed behind the reference configuration are assessed to be more stable and start merging into larger turbulent structures significantly further downstream. These results indicate that an optimized winglet design can not only contribute to a higher energy extraction in a rotor's tip region but also can positively affect the wake's mean kinetic energy recovery by stimulating a faster tip vortex interaction.