bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Stresses in a Rotating Disk of Variable Thickness
Authors: Lee Ti-Chiang 
Published: April 2021

Abstract
This paper presents an analytic solution of the stresses in a rotating disk of variable thickness. By introducing two parameters, the profile of the disk is assumed to vary exponentially with any power of the radial distance from the center of the disk. In some respects this solution may be considered as a generalization of Malkin’s solution, but it differs essentially from the latter in the method of solution. Here, the stresses are solved through a stress function instead of being solved directly. The required stress function is expressed in terms of confluent hypergeometric functions. Numerical examples are also shown for illustration.
Forced Lateral Vibration of Beam Carrying a Concentrated Mass
Authors: Hoppmann W. H. 
Published: April 2021

Abstract
In this paper a study is made of the problem of the lateral vibration of a simply supported beam with a concentrated mass attached at its mid-point. A force assumed to act at the mass in a direction normal to the length of the beam is represented by a sinusoidally time-varying function. The homogeneous form of the Bernoulli-Euler beam equation is solved considering the problem as one with time-dependent boundary conditions. To represent an important case of forced vibrations the solution is transformed to give the deflection and bending strain caused by a pulse type of load. Curves are plotted whereby the contributions to deflection and strain from the higher modes of vibration may be examined as functions of the ratio of attached mass to mass of beam. Results of computations for a specific beam and set of masses are presented, as well as experimental results for the same beam with similar pulse-type loads applied. Oscillograms show rather trenchantly the slow transition of the mass-beam system toward a one-degree-of-freedom system as the concentrated mass is increased.
Correlation of Creep Properties by a Diffusion Analogy
Authors: Green Leon 
Published: April 2021

Abstract
The necessity of atom movements for both creep and self-diffusion suggests a method of correlating the constant-stress creep properties of pure metals. The concept of steady-state creep is discarded, and two empirical approximations for the strain-time behavior of pure polycrystalline metals lead to a creep equation defining an activation energy as the only undetermined constant. For cases where the orientation of individual crystals is important, a second constant is required. Application of this equation to published creep data effects a correlation which indicates that the apparent activation energies observed for creep and self-diffusion show a similar temperature dependence. The effect of stress upon the activation energy for several metals is described approximately, but the need for further experiments encompassing lower values of stress is revealed. The qualitative effects of impurities, grain size, cold-working, and surface conditions upon creep as predicted by a diffusion analogy are found to be in agreement with experimental results, but it is noted that the analogy does not hold if creep deformation is obtained as a result of slip.
Minimum Weight of Tapered Round Thin-Walled Columns
Authors: Feigen Morris 
Published: April 2021

Abstract
It is shown that the optimum wall thickness of a cylindrical round tube column is a function of load only and is independent of diameter. The optimum wall thickness of a tapered round thin-walled column is found to be constant along its length. The optimum shape of a tapered round thin-walled column is derived, being that column whose bending stress in the buckled state is constant along its length. The weight ratio of the optimum tapered column to an equal-strength optimum cylindrical column is found to be 0.8924. It is shown that a double truncated cone whose diameter ratio is in the range 0.35 ⩽ D1/D2 ⩽ 0.50 closely approaches the optimum column. If it is specified that no portion of the double truncated cone shall yield, then the weight advantage of the cone over the cylindrical column is rapidly lost as the stress in the cylindrical column approaches the yield stress. In the inelastic range the weight advantage of the tapered column will be less than in the elastic range.
The Characteristics of Fuel Motion Which Affect Airplane Dynamics
Authors: Graham E. W. , Rodriguez A. M. 
Published: April 2021

Abstract
Problems in aircraft dynamics such as stability and response of the rigid airplane may be affected by fuel motion in the tanks. Such problems also might arise in connection with missiles. In this paper the response of the fuel to simple harmonic motions of a rectangular tank in translation, pitching, and yawing is studied. Using the force and moment expressions, simple mechanical systems equivalent to the fuel are constructed. These systems respond to motions of the tank walls in the same fashion as the fuel, producing identical forces and moments. The use of such mechanical analogies should simplify in many cases the analysis of the complete dynamic system.
The Elastic Sphere Under Concentrated Loads
Authors: Sternberg E. , Rosenthal F. 
Published: April 2021

Abstract
This paper contains an exact solution for the stress distribution in an elastic sphere under two equal and opposite concentrated loads, applied at the end points of a diameter. The solution is based on the Boussinesq stress-function approach to axisymmetric problems and is represented as a sum of two solutions: A singular solution in closed form, and a series solution corresponding to surface tractions which are finite and continuous throughout the surface of the sphere. It is shown that the singularity at the points of application of the loads is not identical with that arising at a concentrated load acting normal to a plane boundary. The existence of pseudosolutions to the problem under consideration, as well as to concentrated-force problems in general, is illustrated, and the validity of the present solution is confirmed through a limit process applied to the case of tractions uniformly distributed over a portion of the boundary. The numerical results for the normal stress on the plane of symmetry perpendicular to the load axis, are compared with the corresponding stress values obtained in a recent three-dimensional photoelastic investigation of the same problem by Frocht and Guernsey (1).
Large Deflection Theory for Orthotropic Rectangular Plates Subjected to Edge Compression
Authors: Yusuff Syed 
Published: April 2021

Abstract
A theory is presented of the large deflections of orthotropic (orthogonally anisotropic) rectangular plates when the plate is initially slightly curved and its boundaries are subjected to the conditions prevailing in edgewise compression tests. Results are given of computations carried out for four different combinations of load and lamination in Fiberglas panels. These theoretical results duplicate the substantial variations in the load-strain and load-deflection diagrams obtained earlier in experiments at the Polytechnic Institute of Brooklyn.
Combined Tension-Torsion Tests for Aluminum Alloy 2S-O
Authors: Phillips Aris 
Published: April 2021

Abstract
In this paper ten combined tension-torsion tests with thin-walled circular tubes of aluminum alloy 2S-O are described. All specimens were loaded with variable stress ratios. It has been found that the theory of plastic flow represents the experimental results with much greater accuracy than does the theory of plastic deformations.
Gravitational Stresses on Deep Tunnels
Authors: Yu Yi-Yuan 
Published: April 2021

Abstract
Gravitational stresses around a horizontal tunnel opening are determined by means of Muschelišvili’s complex variable method for solving two-dimensional elasticity problems. The tunnel is located at a large but finite depth underneath the horizontal ground surface. It has the shape of a general ovaloid, including the rounded-cornered square, the ellipse, and the circle as its special cases. The surrounding material is assumed to be elastic, isotropic, and homogeneous. Two problems are solved. In one problem an unlined tunnel is considered, which has a boundary free from external stresses. In the other the tunnel has a rigid lining, and a perfect bond is assumed to exist between the lining and the surrounding material so that the displacements at the boundary are zero.
Influence of Bistable Plunge Stiffness on Nonlinear Airfoil Flutter
Authors: Corrêa Renan F. , Marques Flávio D. 
Published: April 2021

Abstract
Aeroelastic systems have nonlinearities that provide a wide variety of complex dynamic behaviors. Nonlinear effects can be avoided in practical applications, as in instability suppression or desired, for instance, in the energy harvesting design. In the technical literature, there are surveys on nonlinear aeroelastic systems and the different manners they manifest. More recently, the bistable spring effect has been studied as an acceptable nonlinear behavior applied to mechanical vibration problems. The application of the bistable spring effect to aeroelastic problems is still not explored thoroughly. This paper contributes to analyzing the nonlinear dynamics of a typical airfoil section mounted on bistable spring support at plunging motion. The equations of motion are based on the typical aeroelastic section model with three degrees-of-freedom. Moreover, a hardening nonlinearity in pitch is also considered. A preliminary analysis of the bistable spring geometry's influence in its restoring force and the elastic potential energy is performed. The response of the system is investigated for a set of geometrical configurations. It is possible to identify post-flutter motion regions, the so-called intrawell and interwell. Results reveal that the transition between intrawell to interwell regions occurs smoothly, depending on the initial conditions. The bistable effect on the aeroelastic system can be advantageous in energy extraction problems due to the jump in oscillation amplitudes. Furthermore, the hardening effect in pitching motion reduces the limit cycle oscillation (LCO) amplitudes and also delays the occurrence of the snap-through.
Feasibility Verification of Blood Viscosity Estimation by Two-Dimensional Ultrasonic-Measurement-Integrated Blood Flow Analysis
Authors: Kadowaki Hiroko , Kishimoto Takuya , Tokunaga Takeshi , Mori Koji , Saito Takashi 
Published: April 2021

Abstract
Although blood viscosity has attracted much attention for its effect on hemodynamic parameters related to atherosclerosis, quantitative method for evaluating blood viscosity in vivo is not currently established. The purpose of this study was to verify the feasibility of blood viscosity estimation by a two-dimensional ultrasonic-measurement-integrated (2D-UMI) analysis system that computes an intravascular blood flow field by feeding back an ultrasonic measurement data to a numerical simulation. A method to estimate blood viscosity was proposed by reproducing the flow field of an analysis object in the feedback domain of ultrasonic Doppler velocity in a 2D-UMI blood flow analysis system, and evaluating the variation of the Doppler velocity caused by the analysis viscosity in the nonfeedback domain at the downstream side. In a numerical experiment, a viscosity estimation was performed for numerical solutions of sinusoidal oscillating flows analyzed as a blood flow model in a human common carotid artery at four different types of blood viscosities. The estimation viscosities were made to correspond to those of all analysis objects by giving proper conditions on the feedback gain and feedback domain to optimize the accuracy of the 2D-UMI blood flow analysis. In conclusion, the feasibility of blood viscosity estimation by 2D-UMI analysis was established. Simultaneous measurement of the in vivo blood viscosity and flow field can be easily performed in many clinical cases by its widespread use at clinical sites, thereby clarifying the relationship between hemodynamics and vascular pathology for various blood flow fields.
Data Assimilation of Steam Flow Through a Control Valve Using Ensemble Kalman Filter
Authors: Fang Peixun , He Chuangxin , Wang Peng , Xu Sihua , Liu Yingzheng 
Published: April 2021

Abstract
The present work concentrates on the simulation enhancement of steam flow through a control valve using the data assimilation (DA) approach based on ensemble Kalman filter (EnKF). The k-ω shear stress transport (SST) model is used as the predictive model in which the model constants are optimized by DA. The selected measurement data at different operating conditions are used as observation, while the rest data are involved for validation. Before DA, four flow patterns which arise on their respective operating conditions are identified and analyzed to illustrate the basic characteristics of flow in the control valve. Then DA is performed based on the sample computation by perturbing the model constants and the EnKF process to determine the optimal model constants. These optimized constants are subsequently used for the precomputation of the valve flow with significant improvement on the flow rate prediction. The velocity and turbulent kinetic energy fields with default and DA-optimized model constants are also compared. The results show that the DA enhanced model constants can significantly reduce the predicted volume flow rate error at all opening ratios presently concerned. With the optimized model constants, the velocity and turbulent kinetic energy distributions are greatly modified in the valve seat between main valve and control valve.
TOTAL FOCUSING METHOD BASED ULTRASONIC PHASED ARRAY IMAGING IN THICK STRUCTURES
Authors: Sumana  , Kumar Anish 
Published: April 2021

Abstract
Ultrasonic non-destructive testing traditionally uses a conventional monolithic transducer. An approach similar to this comprising of independent single transmissions but with reception performed by all the elements in phased array ultrasonics is known as Full Matrix Capture (FMC). The acquired data is processed by Total Focusing Method (TFM). Conventional FMC-TFM has limitations in the inspection at large depth in attenuating materials due to single element transmission. To improve the beam forming process, coherent recombination of the plane wave with specific angles is utilized in transmission and the same aperture is used for the reception in Plane Wave Imaging (PWI). A new methodology called Angle Beam Virtual Source FMC-TFM (ABVSFMC-TFM) is proposed to inspect thick attenuating materials such as nickel base alloys. The ABVSFMC method leads to improved Signal to Noise Ratio (SNR) as compared to the conventional FMC due to increased energy with directivity during transmission using a group of elements and improved divergence as compared to the PWI due to a small virtual source near the sample surface. In the present paper, FMC-TFM, PWI-TFM and ABVSFMC-TFM methods are compared for inspection of thick nickel base superalloy (Alloy 617) with slots at various depths in the range of 25-200 mm. Optimization of the incidence angle has been performed by beam computation in CIVA software. Results obtained by CIVA simulations are discussed and also compared for the three methods.
Intercept Factor for a Beam-Down Parabolic Trough Collector
Authors: Uzair Muhammad , Rehman Naveed ur 
Published: April 2021

Abstract
This paper presents a method for evaluating the intercept factor (γ) of a beam-down parabolic trough collector (BDPTC), accounting for collector design, solar cone, and shading on the aperture due to secondary reflectors. A numerical ray-tracing technique was developed and used for the purpose. Validation was performed by comparing the results with rays traced in a two-dimensional drafting program. The effects of changing the rim-angle and angular misalignment associated with the primary and secondary concentrators for various designs are presented and discussed in detail. The optimum values of the design parameters for low, medium, and high concentration ratio BDPTCs are reported. An online tool for quickly estimating γ is also launched in this paper.
Free and Forced Wave Vibration Analysis of a Timoshenko Beam/Frame Carrying a Two Degrees-of-Freedom Spring-Mass System
Authors: Mei C. 
Published: April 2021

Abstract
In this paper, free and forced vibrations of a transversely vibrating Timoshenko beam/frame carrying a discrete two-degrees-of-freedom spring-mass system are analyzed using the wave vibration approach, in which vibrations are described as waves that propagate along uniform structural elements and are reflected and transmitted at structural discontinuities. From the wave vibration standpoint, external excitations applied to a structure have the effect of injecting vibration waves to the structure. In the combined beam/frame and two-degrees-of-freedom spring-mass system, the vibrating discrete spring-mass system injects waves into the distributed beam/frame through the spring forces at the two spring attached points. Assembling the propagation, reflection, transmission, and external force injected wave relations in the beam/frame provides an analytical solution to vibrations of the combined system. In this study, the effects of rotary inertia and shear deformation on bending vibrations are taken into account, which is important when the combined structure involves a short beam element or when higher frequency modes are of interest. Numerical examples are given, with comparisons to available results based on classical vibration theories. The wave vibration approach is seen to provide a systematic and concise solution to both free and forced vibration problems in hybrid distributed and discrete systems.
Diverse and competing interests around tobacco: qualitative analysis of two decades of parliamentary questions in India
Authors: Varma Amiti , Chilgod Latha , Bhojani Upendra 
Published: April 2021

IntroductionIndia continues to enhance tobacco control regulations protecting the public health while housing a widespread tobacco industry. This implies complexities in regulating tobacco. As part of a broader inquiry on the political economy of tobacco, we aimed to understand the concerns of Indian parliamentarians around tobacco.MethodsWe sourced transcripts of tobacco-related questions asked by parliamentarians between the years 1999 and 2019 from the electronic archives of both the houses of Indian parliament. We analysed the frequency of questions during different regimens, segregated by the states and the political parties that parliamentarians belonged to, as well as by the government ministries to which these questions were posed. We also conducted thematic content analysis of these questions, identifying specific themes defining parliamentarians’ concerns.Results729 unique parliamentarians asked 1315 questions about tobacco, conveying varied concerns related to health, commerce, labour and agriculture sectors. Over time, the focus of the questions shifted from majorly trade to majorly health-related concerns. We show how the tobacco regulations in India are multi-institutional and are a result of negotiations of several legitimate and competing, interests. We found important state-level differences in the number and nature of these questions.ConclusionParliamentary questions constitute a useful resource in studying tobacco politics. Tobacco regulations are a product of complex negotiation of varied and competing concerns. We identify core arguments in favour and against tobacco control that would help tobacco control advocates and agencies to better prepare and engage with diverse political voices around tobacco.
Women’s childbirth experiences in the Swedish Post-term Induction Study (SWEPIS): a multicentre, randomised, controlled trial
Authors: Nilvér Helena , Wessberg Anna , Dencker Anna , Hagberg Henrik , Wennerholm Ulla-Britt , Fadl Helena , Wesström Jan , Sengpiel Verena , Lundgren Ingela , Bergh Christina , Wikström Anna-Karin , Saltvedt Sissel , Elden Helen 
Published: April 2021

ObjectiveTo compare childbirth experiences in women randomly assigned to either induction of labour at 41 weeks or to expectant management until 42 weeks, in the Swedish Post-term Induction Study.DesignA register-based, multicentre, randomised, controlled, superiority trial.SettingWomen were recruited at 14 hospitals in Sweden, 2016–2018.ParticipantsWomen with an uncomplicated singleton pregnancy were recruited at 41 gestational weeks.InterventionsThe women were randomly assigned to induction of labour at 41 weeks (induction group, n=1381) or expectant management until 42 weeks (expectant management group, n=1379).Outcome measuresAs main outcome, women’s childbirth experiences were measured using the Childbirth Experience Questionnaire version 2 (CEQ2), in 656 women, 3 months after the birth at three hospitals. As exploratory outcome, overall childbirth experience was measured in 1457 women using a Visual Analogue Scale (VAS 1–10) within 3 days after delivery at the remaining eleven hospitals.ResultsThe total response rate was 77% (2113/2760). There were no significant differences in childbirth experience measured with CEQ2 between the groups (induction group, n=354; expectant management group, n=302) in the subscales:own capacity(2.8 vs 2.7, p=0.09),perceived safety(3.3 vs 3.2, p=0.06) andprofessional support(3.6 vs 3.5, p=0.38) or in the total CEQ2 score (3.3 vs 3.2, p=0.07), respectively. Women in the induction group scored higher in the subscaleparticipation(3.6 vs 3.4, p=0.02), although with a small effect size (0.19). No significant difference was observed in overall childbirth experience according to VAS (8.0 (n=735) vs 8.1 (n=735), p=0.22).ConclusionsThere were no differences in childbirth experience, according to CEQ2 or overall childbirth experience assessed with VAS, between women randomly assigned to induction of labour at 41 weeks or expectant management until 42 weeks. Overall, women rated their childbirth experiences high.Trial registration numberISRCTN26113652.