bluuebunny/crossref_metadata_2025 huggingface dataset:
The Hololens Revolution
Authors: Noor Ahmed K.
Published: March 2018

This article discusses about an emerging kind of computing platform called mixed reality that is expected to change the way interaction with data takes place. Mixed reality in combination with technologies that enable interaction with holograms, called holographic computing, is poised to be the next big disruptive technology. The recording of the light field necessary to make a hologram requires a laser, a beam splitter, and a photographic medium that enables the light scattered from an object to be recorded and later reconstructed. One of the biggest breakthroughs is expected to come with the coupling of holographic computing and two other emerging artificial intelligence and information technologies: next-generation cognitive cybernetics capable of deep learning and even anticipatory capabilities, and the Internet of Things comprised of widespread connected embedded sensors. The possibilities for holographic computing are truly exciting, and the endless applications go as far as the human mind can imagine. Holographic computing is one of the major engineering tools for the 21st century
Can 3-D Printing Go Green?
Authors: Siegel R.P.
Published: March 2018

This article explores various advantages and disadvantages of 3D printing. As 3D printers have become smaller, less expensive, and easier to use, they have become increasingly popular. Additive manufacturing could make manufacturing more sustainable because it creates far less waste than traditional subtractive methods and because making products locally would shorten supply chains, reducing fuel use and carbon pollution from shipping. The researchers believe that 3D printing could ‘accelerate consumerism of nonbiodegradable throwaway plastic objects.’ Students have found that 3D printers use six common resin types: acrylates, thiols, alkenes, vinyl ethers, epoxides, and oxetanes. Acrylates, which the Ember printer uses, are the most common because they work well in a 3D printer and are considered safest for creating solid objects from liquids.
Some Details of Jet Engine Thrust
Authors: Langston Lee S.
Published: March 2018

This article throws light on details of jet engine thrust. The momentum flux of the engine exiting flow is greater than that which entered, brought about by the addition of the energy input from combusted fuel, and giving rise to engine thrust. Thrust arises from pressure and frictional forces on these surfaces, e.g., blades, vanes, endwalls, ducts, etc. This interior force view of thrust is easy to visualize but quite another thing to actually measure. In doing research on secondary flow in gas turbine passages, researchers have measured both steady-state momentum changes and surface forces, in the much simpler case of a turbine blade cascade. The thrust values for each component in the Rolls-Royce single spool engine have been shown in this paper. It has been noted that from the compressor, gas path flow enters the engine case diffuser, where a pressure gain produces another component of forward thrust of 2,186 lbt. Newton’s second law of motion allows us to examine engine component behavior that exhibits both forward and rearward propelling forces, which results in the net thrust our airline passengers have purchased.
Filling the Talent Gap
Authors: O’Heir Jeff
Published: March 2018

This article focuses on the need of engineers with the skills to build the Internet of Things (IoT) in the mechanical engineering industry. Many companies, especially those that cannot afford to train young employees, expect universities to do a better job in teaching mechanical engineering students practical IoT skills. Training efforts by corporations and organizations can help teach young mechanical engineers how to incorporate IoT technologies on the job. ASME hosts a series of global engineering competitions called the IShow, challenging young engineers to design a marketable product that will have a social impact. The University of Wisconsin–Madison IoT Lab is ‘a tech sandbox’ that is expected to bring together engineering and non-engineering students. Experts believe that one of the best ways to train young engineers is to have students from different majors collaborate on hands-on projects that include IoT components. A handful of university engineering departments have developed initiatives in which they are set up in partnership with government or industry, which are turning to universities to understand IoT and figure out how to take advantage of the technologies and related business and marketing strategies.
Calculation of Collection Efficiency on NREL Phase VI Blade
Authors: Zhu Xiaocheng , Hu Liangquan , Chen Jinge , Shen Xin , Du Zhaohui
Published: March 2018

Icing on wind turbines is a major problem in cold regions. To study blade icing, water droplet collection efficiency is calculated on the National Renewable Energy Laboratory (NREL) phase VI blade. First, water droplet conservation equations are embedded into ANSYS Fluent, and the results calculated by the Eulerian method are validated. For the two-dimensional (2D) airfoil, the peak collection efficiency error is 3.7%; for the three-dimensional (3D) blade, the peak collection efficiency error is 2.8%. Second, collection efficiency on the NREL phase VI blade is investigated. The results indicate that water droplets mainly impact on the blade leading edge, and the collection efficiency increases along the radial direction. Finally, the 3D rotating effect on collection efficiency is studied. The results demonstrate that, at a wind speed of 7 m/s, the 3D rotating effect has almost no influence on collection efficiency; however, the effect must be considered in water droplet collection at a wind speed of 10 m/s.
Multicoordination Control Strategy Performance in Hybrid Power Systems
Authors: Pezzini Paolo , Bryden Kenneth M. , Tucker David
Published: March 2018

This paper evaluates a state-space methodology of a multi-input multi-output (MIMO) control strategy using a 2 × 2 tightly coupled scenario applied to a physical gas turbine fuel cell hybrid power system. A centralized MIMO controller was preferred compared to a decentralized control approach because previous simulation studies showed that the coupling effect identified during the simultaneous control of the turbine speed and cathode airflow was better minimized. The MIMO controller was developed using a state-space dynamic model of the system that was derived using first-order transfer functions empirically obtained through experimental tests. The controller performance was evaluated in terms of disturbance rejection through perturbations in the gas turbine operation, and setpoint tracking maneuver through turbine speed and cathode airflow steps. The experimental results illustrate that a multicoordination control strategy was able to mitigate the coupling of each actuator to each output during the simultaneous control of the system, and improved the overall system performance during transient conditions. On the other hand, the controller showed different performance during validation in simulation environment compared to validation in the physical facility, which will require a better dynamic modeling of the system for the implementation of future multivariable control strategies.
Fabrication of Micro Diamond-Like Carbon-Nozzles by Plasma Oxidation Printing
Authors: Aizawa Tatsuhiko , Tamagaki Hiroshi , Wasa Kenji
Published: March 2018

The plasma oxidation printing (POP) was proposed as a digital manufacturing to shape the diamond-like carbon (DLC) thick film into a micronozzle on the tool steel substrate. Its head shape was first designed by computer-aided design (CAD) and printed onto DLC film by the maskless lithography. The unprinted DLC was removed in depth by the anisotropic etching. Fine circular nozzle with the inner diameter of 10 μm and the height of 10 μm was fabricated during the duration time of 3.6 ks. Different from the micromilling or the micro-electric discharging, the micronozzle geometry is directly fabricated from its CAD data. The micronozzle with the cross-star outlet was constructed without the change of processing procedure and without use of tooling.
A Numerical Investigation of the Effect of Inlet Preswirl Ratio on Rotordynamic Characteristics of Labyrinth Seal
Authors: Tsukuda Tomohiko , Hirano Toshio , Watson Cori , Morgan Neal R. , Weaver Brian K. , Wood Houston G.
Published: March 2018

Full three-dimensional (3D) computational fluid dynamics (CFD) simulations are carried out using ANSYS cfx to obtain the detailed flow field and to estimate the rotordynamic coefficients of a labyrinth seal for various inlet swirl ratios. Flow fields in the labyrinth seal with the eccentricity of the rotor are observed in detail and the detailed mechanisms that increase the destabilizing forces at high inlet swirl ratios are discussed based on the fluid governing equations associated with the flow fields. By evaluating the contributions from each term of the governing equation to cross-coupled force, it is found that circumferential velocity and circumferential distribution of axial mass flow rate play key roles in generating cross-coupled forces. In the case that circumferential velocity is high and decreases along the axial direction, all contributions from each term are positive cross-coupled force. On the other hand, in the case that circumferential velocity is low and increases along the axial direction, one contribution is positive but the other is negative. Therefore, cross-coupled force can be negative in the local chamber depending on the balance even if circumferential velocity is positive. CFD predictions of cross-coupled stiffness coefficients and direct damping coefficients show better agreement with experimental results than a bulk flow model does by considering the force on the rotor in the inlet region. Cross-coupled stiffness coefficients derived from the force on the rotor in the seal section agree well with those of the bulk flow model.
Robust Adaptive Control of the Nonlinearly Parameterized Human Shank Dynamics for Electrical Stimulation Applications
Authors: Yang Ruzhou , de Queiroz Marcio
Published: March 2018

In this paper, we introduce two robust adaptive controllers for the human shank motion tracking problem that is inherent in neuromuscular electrical stimulation (NMES) systems. The control laws adaptively compensate for the unknown parameters that appear nonlinearly in the musculoskeletal dynamics while providing robustness to additive disturbance torques. The adaptive schemes exploit the Lipschitzian and/or the concave/convex parameterizations of the model functions. The resulting control laws are continuous and guarantee practical tracking for the shank angular position. The performance of the two robust adaptive controllers is demonstrated via simulations.
Numerical Analysis of Transient Elastohydrodynamic Lubrication During Startup and Shutdown Processes
Authors: Lu Xiqun , Dong Qingbing , Zhou Kun , Zhao Bin , Zhao Bo
Published: March 2018

In this study, a numerical model is developed for the analysis of elastohydrodynamic lubrication (EHL) at transient conditions during startup and shutdown processes. The time-dependent solutions are derived from an iterative algorithm with surface roughness involved, and the initial value is specified as the solution of the dry contact for the startup or steady-state solution of the lubrication contact at the starting velocity for the shutdown. The technique of discrete convolution and fast Fourier transform (DC-FFT) is employed to improve the computational efficiency. Solutions for smooth surfaces are compared with those obtained numerically and experimentally, and good consistency can be found. Profiles of pressure and film thickness and contours of subsurface stresses are analyzed to reveal the effects of acceleration/deceleration on the lubrication evolution. An isotropic roughness is then taken into account for the analysis. It is concluded that the coupling effects of the lubricant cavitation and oriented roughness would result in complex profiles of pressure and film thickness due to their disturbances to the lubrication film. A machined rough surface is presented to demonstrate the generality of the model. The analysis may potentially provide guidance to estimate the behavior of mechanical elements.
Experimental and Theoretical Analysis of the Goswami Cycle Operating at Low Temperature Heat Sources
Authors: Demirkaya Gokmen , Padilla Ricardo Vasquez , Fontalvo Armando , Bula Antonio , Goswami D. Yogi
Published: March 2018

The Goswami cycle is a cycle that combines an ammonia–water vapor absorption cycle and a Rankine cycle for cooling and mechanical power purposes by using thermal heat sources such as solar energy or geothermal steam. In this paper, a theoretical investigation was conducted to determine the performance outputs of the cycle, namely, net mechanical power, cooling, effective first law efficiency and exergy efficiency, for a boiler and an absorber temperature of 85 °C and 35 °C, respectively, and different boiler pressures and ammonia-water concentrations. In addition, an experimental investigation was carried out to verify the predicted trends of theoretical analysis and evaluate the performance of a modified scroll expander. The theoretical analysis showed that maximum effective first law and exergy efficiencies were 7.2% and 45%, respectively. The experimental tests showed that the scroll expander reached a 30–40% of efficiency when boiler temperature was 85 °C and rectifier temperature was 55 °C. Finally, it was obtained that superheated inlet conditions improved the efficiency of the modified expander.
Characterizing the Effect of Cutting Condition, Tool Path, and Heat Treatment on Cutting Forces of Selective Laser Melting Spherical Component in Five-Axis Milling
Authors: Mahyar Khorasani Amir , Gibson Ian , Goldberg Moshe , Littlefair Guy
Published: March 2018

Additive manufacturing (AM), partly due to its compatibility with computer-aided design (CAD) and fabrication of intricate shapes, is an emerging production process. Postprocessing, such as machining, is particularly necessary for metal AM due to the lack of surface quality for as-built parts being a problem when using as a production process. In this paper, a predictive model for cutting forces has been developed by using artificial neural networks (ANNs). The effect of tool path and cutting condition, including cutting speed, feed rate, machining allowance, and scallop height, on the generated force during machining of spherical components such as prosthetic acetabular shell was investigated. Also, different annealing processes like stress relieving, mill annealing and β annealing have been carried out on the samples to better understand the effect of brittleness, strength, and hardness on machining. The results of this study showed that ANN can accurately apply to model cutting force when using ball nose cutters. Scallop height has the highest impact on cutting forces followed by spindle speed, finishing allowance, heat treatment/annealing temperature, tool path, and feed rate. The results illustrate that using linear tool path and increasing annealing temperature can result in lower cutting force. Higher cutting force was observed with greater scallop height and feed rate while for higher finishing allowance, cutting forces decreased. For spindle speed, the trend of cutting force was increasing up to a critical point and then decreasing due to thermal softening.
Selective-Compliance-Based Lagrange Model and Multilevel Noncollocated Feedback Control of a Humanoid Robot
Authors: Spyrakos-Papastavridis Emmanouil , Dai Jian S. , Childs Peter R. N. , Tsagarakis Nikos G.
Published: March 2018

This paper presents unified control schemes for compliant humanoid robots that are aimed at ensuring successful execution of both balancing tasks and walking trajectories for this class of bipeds, given the complexity of under-actuation. A set of controllers corresponding to the single-support (SS) and double-support (DS) walking phases has been designed based on the flexible sagittal joint dynamics of the system, accounting for both the motor and link states. The first controller uses partial state feedback (proportional–derivative–derivative (PDD)), whereas the second considers the full state of the robot (proportional–proportional–derivative–derivative (PPDD)), while both are mathematically proven to stabilize the closed-loop systems for regulation and trajectory tracking tasks. It is demonstrated mathematically that the PDD controller possesses better stability properties than the PPDD scheme for regulation tasks, even though the latter has the advantage of allowing for its associated gain-set to be generated by means of standard techniques, such as linear quadratic regulator (LQR) control. A switching condition relating the center-of-pressure (CoP) to the energy functions corresponding to the DS and SS models has also been established. The theoretical results are corroborated by means of balancing and walking experiments using the COmpliant huMANoid (COMAN), while a practical comparison between the designed controller and a classical PD controller for compliant robots has also been performed. Overall, and a key conclusion of this paper, the PPDD scheme has produced a significantly improved trajectory tracking performance, with 9%, 15%, and 20% lower joint space error for the hip, knee, and ankle, respectively.
Study of Response Difference Amplification and Bionic Coupled Circuit in Small Acoustic Array for Spatial Localization
Authors: Zhu Xinlei , Yang Ming , Zhang Yaqiong , Ta Na , Rao Zhushi
Published: March 2018

Precisions of localization are a function of the size of an array. A kind of parasitoid fly, Ormia ochracea, performs an extraordinary directional hearing ability despite its tiny-scaled auditory organ. In this paper, vibration modes and transfer functions of the Ormia ochracea's ear model were calculated, and the phase difference amplification in responses are analyzed to investigate the directional hearing mechanism. A novel three-element bionic model is proposed for spatial sound source localization for small distance-wavelength ratios. The amplification of the phase difference of this model is verified. In order to realize the bionic localization model, based on electric-mechanic analogy method, a system that consists of a triangular acoustic array and a bionic coupling circuit is designed and tested. Frequency responses of the circuit output, as a means of transfer function of the system, are taken into estimation of the source directions. The result has shown that this circuit design has better performance in estimating the direction of sound sources compared to the uncoupled array with same size.
On Instability Pockets and Influence of Damping in Parametrically Excited Systems
Authors: Sharma Ashu , Sinha S. C.
Published: March 2018

In most parametrically excited systems, stability boundaries cross each other at several points to form closed unstable subregions commonly known as “instability pockets.” The first aspect of this study explores some general characteristics of these instability pockets and their structural modifications in the parametric space as damping is induced in the system. Second, the possible destabilization of undamped systems due to addition of damping in parametrically excited systems has been investigated. The study is restricted to single degree-of-freedom systems that can be modeled by Hill and quasi-periodic (QP) Hill equations. Three typical cases of Hill equation, e.g., Mathieu, Meissner, and three-frequency Hill equations, are analyzed. State transition matrices of these equations are computed symbolically/analytically over a wide range of system parameters and instability pockets are observed in the stability diagrams of Meissner, three-frequency Hill, and QP Hill equations. Locations of the intersections of stability boundaries (commonly known as coexistence points) are determined using the property that two linearly independent solutions coexist at these intersections. For Meissner equation, with a square wave coefficient, analytical expressions are constructed to compute the number and locations of the instability pockets. In the second part of the study, the symbolic/analytic forms of state transition matrices are used to compute the minimum values of damping coefficients required for instability pockets to vanish from the parametric space. The phenomenon of destabilization due to damping, previously observed in systems with two degrees-of-freedom or higher, is also demonstrated in systems with one degree-of-freedom.
Steady-State Tilting-Pad Bearing Performance Under Reduced Oil Supply Flow Rates
Authors: Nichols Bradley R. , Fittro Roger L. , Goyne Christopher P.
Published: March 2018

Reduced oil supply flow rates in fluid film bearings can cause cavitation, or lack of a fully developed hydrodynamic film layer, at the leading edge of the bearing pads. Reduced oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses and is commonly referred to as starvation. This study looks at the effects of oil supply flow rate on steady-state bearing performance and provides increased experimental data for comparison to computational predictions. Tests are conducted on a five-pad tilting-pad bearing positioned in a vintage, flooded housing with oil supply nozzles. Pad temperatures, sump temperature, journal operating position, and motor input power are measured at various operating speeds ranging from 2000 to 12,000 rpm and various oil supply flow rates. Predicted results are obtained from bearing modeling software based on thermoelastohydrodynamic (TEHD) lubrication theory. A starved flow model was previously developed as an improvement over the original flooded flow model to more accurately capture bearing behavior under reduced flow conditions. Experimental results are compared to both flow models. The starved bearing model predicts significantly higher journal operating positions than the flooded model and shows good correlation with the experimental data. Predicted pressure profiles from the starved bearing model show cavitation of the upper unloaded pads that increase in severity with increasing speed and decreasing oil supply flow rate. The progressive unloading of these top pads explains the rise in shaft centerline position and helps further validate the starvation model.
Cavitation Bubble Dynamics Induced by Hydrodynamic Pressure Oil Film in Ultrasonic Vibration Honing
Authors: Guo Ce , Zhu XiJing , Liu Jia , Zhang Dan
Published: March 2018

During ultrasonic vibration honing (UVH), a thin hydrodynamic oil film formed can seriously affect the cavitation effect in the grinding fluid, but the mechanism is still unclear now. Based on the hydrodynamics theory, a revised cavitation bubble model with oil film pressure is developed, and it has been calculated by the four-order Runge–Kutta method. The calculation results show that the oil film pressure under UVH is a positive–negative alternant pulse pressure, and it can induce the secondary expansion of the bubble, leading to double microjets during the process of the bubble collapsing. The effects of ultrasonic amplitude, ultrasonic frequency, oil film height, and reciprocation speed of the honing stone on the bubble dynamics are discussed. With the increase of ultrasonic amplitude, the amplitude of the bubble expansion is increased, and the oscillation interval is extended. As increasing normalized oil film height, the variation of the bubble first expansion is slight, while the amplitude of the bubble secondary expansion is reduced and the oscillation interval is also shortened. The main effect of ultrasonic frequency and reciprocation speed of the honing stone on the bubble dynamics is connected with the secondary bubble expansion. The bubble secondary expansion is decreased with the increasing reciprocation speed of the honing stone, ultrasonic frequency, and oil film height. The results of the simulations are consistent with the surface roughness measurements well, which provides a theoretical prediction method of cavitation bubbles control.
Mathematical Modeling and Virtual Reality Simulation of Surgical Tool Interactions With Soft Tissue: A Review and Prospective
Authors: Malukhin Kostyantyn , Ehmann Kornel
Published: March 2018

This is an informed assessment of the state of the art and an extensive inventory of modeling approaches and methods for soft tissue/medical cutting tool interaction and of the associated medical processes and phenomena. Modeling and simulation through numerical, theoretical, computational, experimental, and other methods was discussed in comprehensive review sections each of which is concluded with a plausible prospective discussion biased toward the development of so-called virtual reality (VR) simulator environments. The finalized prospective section reflects on the future demands in the area of soft tissue cutting modeling and simulation mostly from a conceptual angle with emphasis on VR development requirements including real-time VR simulator response, cost-effective “close-to-reality” VR implementations, and other demands. The review sections that serve as the basis for the suggested prospective needs are categorized based on: (1) Major VR simulator applications including virtual surgery education, training, operation planning, intraoperative simulation, image-guided surgery, etc. and VR simulator types, e.g., generic, patient-specific and surgery-specific and (2) Available numerical, theoretical, and computational methods in terms of robustness, time effectiveness, computational cost, error control, and accuracy of modeling of certain types of virtual surgical interventions and their experimental validation, geared toward ethically driven artificial “phantom” tissue-based approaches. Digital data processing methods used in modeling of various feedback modalities in VR environments are also discussed.
Experimental Quantification of Fan Rotor Effects on Inlet Swirl Using Swirl Distortion Descriptors
Authors: Frohnapfel Dustin J. , Todd Lowe K. , O'Brien Walter F.
Published: March 2018

The prominence of highly integrated engine/airframe architectures in modern commercial aircraft design concepts has led to significant research efforts investigating the use of conventional turbofan engines in unconventional installations where severe inlet distortions can arise. In order to determine fan rotor capabilities for reducing or eliminating a complex inlet swirl distortion, an experimental investigation using a StreamVaneTM swirl distortion generator was conducted in a turbofan engine research platform. Three-dimensional (3D) flow data collected at two discrete planes surrounding the fan rotor indicated that the intensity of the swirl distortion was decreased by the fan rotor; however, substantial swirl distortion effects remained in the fan exit flow. Flow angle magnitudes and swirl intensity (SI) decreased by approximately 30–40% across the fan rotor, while the presence of large-scale features within the distortion profile was nearly eliminated. Secondary flow streamlines indicated that small-scale features of the distortion were less affected by the rotating component and remained coherent at the fan rotor outlet plane. These results led to the conclusion that swirl distortion survived interactions with the fan rotor, leading to off-design conditions cascading through downstream engine components.
General Correlation of Building Energy Use Via Hybrid Genetic Programming/Genetic Algorithm
Authors: Bourisli Raed I. , Altarakma Mohammed A. , AlAnzi Adnan A.
Published: March 2018

A hybrid algorithm that combines genetic programming (GP) and genetic algorithms (GAs) that deduce a closed-form correlation of building energy use is presented. Throughout the evolution, the terms, functions, and form of the correlation are evolved via the genetic program. Whenever the fitness of the best correlation stagnates for a specific number of GP generations, the GA optimizes the real-valued coefficients of each correlation in the population. When the GA, in turn, stagnates, correlations with optimized coefficients and powers are passed back to the GP for further search. The hybrid algorithm is applied to the problem of predicting energy use of a U-shape building. More than 800 buildings with various foot-print areas, relative compactness (RC), window-to-wall ratio (WWR), and projection factor (PF) values were simulated using the VisualDOETM energy simulation engine. The algorithm tries to minimize the difference between simulated and predicted values by maximizing the R2 value. The algorithm was able to arrive at a closed-form correlation that combines the four building parameters, accurate to within 4%. The methodology can be easily used to model any type of data behavior in any engineering or nonengineering application.
Lattice Boltzmann Simulation of Mixed Convection Heat Transfer in a Lid-Driven Square Cavity Filled With Nanofluid: A Revisit
Authors: Ekici Özgür
Published: March 2018

Mixed convection heat transfer of Al2O3 nanofluid in a lid-driven square cavity with differentially heated vertical walls is studied numerically with lattice Boltzmann method (LBM). In order to understand the reasons for the conflicting results on heat transfer enhancement in cavity problems, formulation of nondimensional properties and modeling thermophysical properties, in accordance with the relative effects of natural and forced convection flows, are examined. In addition to gain more insight into the physics, one of the goals of the study is to identify the reasons of existing contradictory findings; therefore, a single-phase formulation is adopted as has been the case in the majority of related literature to date. To isolate the effects of thermophysical properties on the results and to maintain the same natural and forced convection effects, all nondimensional parameters are defined using the corresponding thermophysical properties of the fluid under examination. Two different effective thermal conductivity and viscosity models are tested for a range of Reynolds and Rayleigh numbers to investigate their effects on the nanofluid behavior. Depending on the effective viscosity model, an increase or decrease is obtained in the average Nusselt number. It is also illustrated that the relative magnitudes of effective thermal conductivity values for different models do not translate into the heat transfer enhancement due to convective effects. Moreover, it is shown that thermal behavior of nanofluid approaches to the one of base fluid's as the buoyancy driven flow gets stronger, which is independent of the employed effective property models.
An Experimental Study on Bipolar Tissue Hemostasis and Its Dynamic Impedance
Authors: Li Xiaoran , Chen Roland , Li Wei
Published: March 2018

Bipolar tissue hemostasis is a medical procedure where high frequency alternating current is applied to biological tissue for wound closing and blood vessel sealing through heating. The process is often performed with a set of laparoscopic forceps in a minimal invasive surgery to achieve less bleeding and shorter recovery time. However, problems such as tissue sticking, thermal damage, and seal failure often occur and need to be solved before the process can be reliably used in more surgical procedures. In this study, experiments were conducted to examine process parameters and the dynamic behavior of bipolar heating process through electrical impedance measurements. The effects of electrode compression level, heating power, and time are analyzed. Heating energy and bio-impedance are evaluated for quality prediction. Tissue sticking levels were correlated to the size of denatured tissue zone. It is found that tissue denaturation starts from the center of the heated region. Dynamic impedance reveals the stages of tissue hemostasis process. However, it is strongly affected by the compression level and heating power. Existing criteria for quality prediction and control using the heating energy and minimal impedance are not reliable. The size of denatured tissue zone can be predicted with the heating energy; however, the prediction is strongly dependent on the compression level. To avoid sticking, a low power and low compression level should be used for the same denatured tissue zone size.
A Novel Synthesis Method for Nonperiodic Function Generation of an RCCC Mechanism
Authors: Liu Wenrui , Sun Jianwei , Zhang Bangcheng , Chu Jinkui
Published: March 2018

In this paper, the nonperiodic function synthesis of an RCCC mechanism is presented using a wavelet feature parameter (WFP) method. The output function and the sliding displacement of the RCCC mechanism are described by the wavelet approximate and wavelet details. Based on the relationship of wavelet details of the sliding displacement and its scaling, a normalization method for wavelet details of the sliding displacement is presented. The influence of proportional scaling of the linkage lengths is eliminated. An adaptive database is established. The problem of nonperiodic design requirements of RCCC mechanism function synthesis is solved. To demonstrate the feasibility of this method, two numerical examples are proposed. Based on the nonperiodic design requirements, the RCCC mechanisms are designed and simulated using matlab and catia software. The results show that the method proposed is effective for nonperiodic function generation of the RCCC mechanism with multiple positions.
Novel Defect Location Method for Pressure Vessel by Using L (0, 2) Mode Guided Wave
Authors: Zhai Shuangmiao , Zhou Shaoping , Chen Shaojie , Yang Bin , Li Yong
Published: March 2018

Pressure vessel plays an increasingly important role in process industries, in which its performance degradation, such as crack and corrosion, may lead to serious accidents and significant economic losses. Guided wave-based method is a cost-effective means for pressure vessel rapid interrogation. In this paper, the method based on direct-wave and fuzzy C-means clustering algorithm (FCM) is proposed to locate defect for pressure vessel. Finite element (FE) simulation is applied to analyze the propagation characteristics of guided waves. The experiment using the method based on direct-wave and FCM has been conducted on the barrel and head with different sensor arrays, respectively. The variation rule of the direct-wave difference with different distance coefficients has been studied. By combining FCM with the direct-wave difference, the defects on barrel and head can be detected accurately. The defect inspection experiment for pressure vessel using ellipse imaging algorithm is conducted as well. The experimental results show that the method based on direct-wave and FCM can locate the defects on barrel and head of the pressure vessel effectively and accurately.
Design and Validation of a Recirculating, High-Reynolds Number Water Tunnel
Authors: Elbing Brian R. , Daniel Libin , Farsiani Yasaman , Petrin Christopher E.
Published: March 2018

Commercial water tunnels typically generate a momentum thickness based Reynolds number (Reθ) ∼1000, which is slightly above the laminar to turbulent transition. The current work compiles the literature on the design of high-Reynolds number facilities and uses it to design a high-Reynolds number recirculating water tunnel that spans the range between commercial water tunnels and the largest in the world. The final design has a 1.1 m long test-section with a 152 mm square cross section that can reach speed of 10 m/s, which corresponds to Reθ=15,000. Flow conditioning via a tandem configuration of honeycombs and settling-chambers combined with an 8.5:1 area contraction resulted in an average test-section inlet turbulence level <0.3% and negligible mean shear in the test-section core. The developing boundary layer on the test-section walls conform to a canonical zero-pressure-gradient (ZPG) flat-plate turbulent boundary layer (TBL) with the outer variable scaled profile matching a 1/7th power-law fit, inner variable scaled velocity profiles matching the log-law and a shape factor of 1.3.
A Representation Theory-Based Model for the Rapid Pressure Strain Correlation of Turbulence
Authors: Panda J. P. , Warrior H. V.
Published: March 2018

In the presence of mean strain or rotation, the anisotropy of turbulence increases due to the rapid pressure strain term. In this paper, we consider the modeling of the rapid pressure strain correlation of turbulence. The anisotropy of turbulence in the presence of mean strain is studied and a new model is formulated by calibrating the model constants at the rapid distortion limit. This model is tested for a range of plane strain and elliptic flows and compared to direct numerical simulation (DNS) results. The present model shows agreement with DNS and improvements over the earlier models like those by Launder et al. (1975, “Progress in the Development of a Reynolds-Stress Turbulence Closure,” J. Fluid Mech., 68(3), pp. 537–566.) and Speziale et al. (1991, “Modelling the Pressure–Strain Correlation of Turbulence: An Invariant Dynamical Systems Approach,” J. Fluid Mech., 227(1), pp. 245–272.) that have been reported to give satisfactory performance for hyperbolic flows but not satisfactory for elliptic flows.
Effect of Large Amplitude Waves and Film Inertia on Mass Separation at a Sharp Corner
Authors: Sadeghizadeh Zahra , Drallmeier James A.
Published: March 2018

The separation of a shear-driven thin liquid film from a sharp corner is studied in this paper. Partial or complete mass separation at a sharp corner is affected by two different mechanisms: liquid film inertia, which affects liquid mass separation through force imbalance at the sharp corner, and large amplitude waves (LAW) at the interface, which contributes to liquid instability at the corner. Experimental results for liquid Ref number that varies from 100 to 300 and mean film thickness from 130 to 290 μm show that both film inertia and LAW effects correlate to mass separation results. The results suggest that while both inertia of the film substrate and LAW effects enhance the mass separation, the correlations between LAW characteristics and mass separation results provide better insight into the onset of separation and the impact of the gas phase velocity on separation for the conditions studied.
Characterization of a Superheated Water Jet Released Into Water Using Proper Orthogonal Decomposition Method
Authors: Sinha Avick , Chauhan Rajesh O. , Balasubramanian Sridhar
Published: March 2018

The external characteristics of a superheated water jet released into water at ambient conditions are dominated by the vapor bubble formation, which results in an unsteady flow dynamics. This hinders the use of classical methods to assess the mean flow and the turbulence characteristics. Here, the proper orthogonal decomposition (POD) technique was employed on the velocity measurements obtained using particle image velocimetry (PIV) to quantify the external characteristics of a superheated water jet released into water. This was done at three different inlet pressure ratios. From the energy modes obtained using the POD technique, it was observed that the first mode well represents the mean flow, while subsequent higher modes show the fluctuating nature. The phase-averaged properties were calculated by considering only the first mode. Unlike a canonical jet, the maximum value of the mean centerline velocity for a superheated jet occurs far downstream from the nozzle, at x/D ≈ 15, due to the thermal nonequilibrium in the jet attributed to the formation of vapor bubbles. The turbulent kinetic energy (TKE), size of the coherent structures (CS), and swirling strength showed a nonmonotonic decrease in the downstream direction, indicating that the vapor formation has significant influence on the jet dynamics. The novel aspect of this work is the use of POD technique for phase averaging, using which dynamics of a superheated jet have been quantified. The distribution of vapor bubbles in the flow field was also measured using the Shadowgraphy technique to substantiate the above observations.
End Fitting Effect on Stress Evaluation of Tensile Armor Tendons in Unbonded Flexible Pipes Under Axial Tension
Authors: Dong Leilei , Zhang Qi , Huang Yi , Liu Gang , Li Zhiyuan
Published: March 2018

This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is verified with a finite element (FE) simulation. Comparisons between the model predictions and the FE results in terms of the change in helical angle and transverse bending stress show good correlations. The verified model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear, and friction could significantly increase the stress at the end fitting compared with the frictionless case.
Dynamic States Recognition of Friction Noise in the Wear Process Based on Moving Cut Data-Approximate Entropy
Authors: Ding Cong , Zhu Hua , Sun Guodong , Jiang Yu , Wei Chunling
Published: March 2018

Wear experiments are performed to explore dynamic states changes of friction noise signals. A new characteristic parameter, moving cut data-approximate entropy (MC-ApEn), is adopted to quantitatively recognize dynamic states. Additionally, determinism (DET), one key parameter of recurrence quantification analysis, is applied to verify the reliability of recognition results of MC-ApEn. Results illustrate that MC-ApEn of friction noise has distinct changes in different wear processes, and it can accurately detect abrupt change points of dynamic states for friction noise. Furthermore, DET of friction noise rapidly declines first, then fluctuates around a small value, and finally increases sharply, which just corresponds to the evolution process of MC-ApEn. So, the reliability of wear state recognition on the basis of MC-ApEn can be confirmed. It makes it possible to accurately and reliably recognize wear states of friction pairs based on MC-ApEn.
Bearing Life Evaluation of Wheel Hub Ball Bearing Based on Finite Element Analysis
Authors: Raju D. V. , Dixit Pravin , Rathore Nitin , Lakshmikant Pala , Bubai Rudra , Verma Rahul
Published: March 2018

Automobile deep groove ball bearings experience severe contact stresses during vehicle maneuvering near the contact with inner and outer races. The accurate prediction of the contact stresses and life estimation of ball bearings has always been challenging, following the complex nature of the contact involved and the resulting rolling contact fatigue (RCF). The present paper performs the finite element (FE) analysis by using a general FE code, abaqus to accurately predict the contact stresses, bearing loads and bearing life in form of ISO 281 (1990) life of an automobile wheel hub ball bearings. Lundberg and Palmgren method is employed for the determination of the bearing life. RomaxDESIGNER, a bearing design software, is also applied to consider the effects of various bearing life adjustment factors, which are used to determine the DIN ISO 281 life. Large amount of bearing failure field data is used to validate the predictions from the study, achieving a very good correlation. Theoretical contact stress calculations based on the Hertz contact theory are also presented for each load case. Finally, an attempt has been made to develop a relation between the contact stress and the bearing life for the hub assembly ball bearings.
The Effect of Kinematic Conditions on Film Thickness in Compliant Lubricated Contact
Authors: Nečas David , Jaroš Tomáš , Dočkal Kryštof , Šperka Petr , Vrbka Martin , Křupka Ivan , Hartl Martin
Published: March 2018

The present paper deals with an investigation of film formation in compliant lubricated contact. Despite these contacts can be found in many applications of daily life including both biological and technical fields, so far little is known about the lubrication mechanisms inside the contacts. The main attention is paid to the effect of kinematic conditions on central film thickness. For this purpose, fluorescent microscopy method was employed. Experiments were realized in ball-on-disk configuration, while the ball was made from rubber and the disk was from optical glass. The contact was lubricated by glycerol and polyglycol to examine the effect of fluid viscosity. The measurements were conducted under pure rolling and rolling/sliding conditions. The entrainment speed varied from 10 to 400 mm/s and constant load of 0.2 N was applied. Experimental results were compared with two theoretical predictions derived for isoviscous-elastohydrodynamic lubrication (I-EHL) regime. It was found that the thickness of lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumptions. Against expectations, evident influence of slide-to-roll ratio (SRR) on film formation was observed. In the last part of the paper, some limitations of this study are discussed and several recommendations for further methodology improvement are suggested.
Effective Placement of a Cantilever Resonator on Flexible Primary Structure for Vibration Control Applications—Part 2: Model Updating and Experimental Validation
Authors: Lundstrom Troy , Jalili Nader
Published: March 2018

In this Part 2 of a two-part series, the experimental verification and comparison of this work are presented. In this paper, the effect of beam-type resonator position on flexible dynamics is determined experimentally. The system is excited using band-limited white noise via electrodynamic shaker, and the data are collected with several transducers and a high-speed camera for each actuator beam mounting location; the first four mode shapes and natural frequencies are determined, and a finite element model (FEM) is developed and updated using these data. An additional set of data is collected using a linear sine chirp forcing function and the updated/experimental frequency response functions (FRFs) and time responses for the base and actuator beam tips are found to correlate. Plots of experimentally determined percent modal strain energy versus attachment position for the first four modes is presented, and a final study is also performed showing the fractional root-mean-square (RMS) strain energy in the actuator with respect to the total system. A final set of data is collected in which the actuator beam is moved up the base beam, the piezoelectric patch of the actuator beam is energized with white noise, and the tip response of the base beam is measured; an RMS base beam velocity versus mount position plot was developed. From this work, it is determined that the most practical/optimal position for the secondary beam to serve as both a sensor and actuator to control base beam tip response over a wide frequency band is in the nondimensionalized range: 0.4≤e<0.6.