The low-noise optimisation method for gearbox in consideration of operating conditions

This paper presents a comprehensive procedure to calculate the steady dynamic response and the noise radiation generated from a stepping-down gearbox. In this process, the dynamic model of the cylindrical gear transmission system is built with the consideration of the time-varying mesh stiffness, gear errors and bearing supporting, while the data of dynamic bearing force is obtained through solving the model. Furthermore, taking the data of bearing force as the excitation, the gearbox vibrations and noise radiation are calculated by numerical simulation, and then the time history of node dynamic response, noise spectrum and resonance frequency range of the gearbox are obtained. Finally, the gearbox panel acoustic contribution at the resonance frequency range is calculated. Based on the conclusions from the gearbox panel acoustic contribution analyses and the mode shapes, two gearbox stiffness improving plans have been studied. By contrastive analysis of gearbox noise radiation, the effectiveness of the improving plans is confirmed. This study has provided useful theoretical guideline to the gearbox design

Exploring motivations, constraints, and perceptions toward sport consumers\u27 smartphone usage.

Today’s technology trend in the United States is influenced by the growing population of 182.6 million smartphone users (Statista Inc., 2015). The technology trend has also affected the sport consumption behaviors in terms of how they obtain information, share similar interests, and purchase goods in support of their fandom. The range of efforts varies depending on sport consumers’ level of fandom and their technological comfort level towards using a smartphone. Thus, understanding the relationship between sport and technology provides benefits for sport managers to discover innovative ways to further engage current fans and attract new consumers using smartphones. Considering the benefits associated with smartphone technology, the primary purpose of this study was to examine motivations, constraints, and technological perceptions toward smartphones as it relates to sport consumers’ fan identification. Specifically, the study examined (a) primary communication channels (b) factors that influence users (c) factors that prevent users from consuming sport (d) smartphonespecific technological perceptions, and (d) the differences in sport consumers’ motivations, constraints, and technological perceptions to follow sport based on sex, age, and fan identification, and (e) factors that predict actual usage, all based on sport consumers’ smartphone usage. Using a cross-sectional survey design, data were collected from the tech-savvy Amazon MTurk users (N = 372) living in the United States. The results of this study revealed three unique factors of motivations (i.e. intrinsic, social, diversion), three factors of constraints (i.e. personal, security, technology), and two factors of technological perceptions (i.e. hedonic, utilitarian) for smartphone usage in sport context. Among these factors, intrinsic motivations, personal constraints, hedonic perceptions and utilitarian perceptions were found to significantly predict actual usage. Further analysis also revealed that sport consumers’ behaviors significantly differed based on the level of fan identification (i.e. high or low). The sport consumers also identified that they connected to the official sites the most followed by sport-related apps, and social media sites. In sports they followed, NFL was ranked the highest, followed by MLB, and NCAA Football, and within these sports, they followed their favorite team the most, leagues the second, and players the third. The result of current study provided a holistic view towards understanding sport consumption behaviors by considering motivations, constraints, and technological perceptions associated with smartphone usage. The information captured in this study is particularly useful when designing a mobile marketing campaign to better engage current fans and attract new fans. In addition, sport managers will be able to further encourage sport consumers’ motivating factors, while reducing the constraining factors by considering technological perceptions of the smartphones. Furthermore, the current study’s proposed scale could be used to assess motivations, constraints, and technological perceptions associated with actual usage to reflect upon specific characteristics of the fan identification

State switching in Bi-doped La[sub 0.67]Ca[sub 0.33]MnO[sub 3] and the effects of current

Electronic transport and magnetic properties of La0.477Bi0.193Ca0.33MnO3 have been experimentally studied. Different resistive behaviors are observed in the cooling and warming processes. The system first stays at a high resistive state, and switches to a state of lower resistivity when it is cooled below a critical temperature. However, keeping the sample at a temperature below ;60 K, a relaxation to the high resistive state takes place. This process is current dependent, and the application of a large current slows down the relaxation greatly. There is a strong competition between the two resistive states, which causes a switch of the system between states. © 2002 American Institute of Physics.published_or_final_versio

Identification of nonlinearity in conductivity equation via Dirichlet-to-Neumann map

We prove that the linear term and quadratic nonlinear term entering a nonlinear elliptic equation of divergence type can be uniquely identified by the Dirichlet to Neuman map. The unique identifiability is proved using the complex geometrical optics solutions and singular solutions

Properties of Central Caustics in Planetary Microlensing

To maximize the number of planet detections, current microlensing follow-up observations are focusing on high-magnification events which have a higher chance of being perturbed by central caustics. In this paper, we investigate the properties of central caustics and the perturbations induced by them. We derive analytic expressions of the location, size, and shape of the central caustic as a function of the star-planet separation, $s$, and the planet/star mass ratio, $q$, under the planetary perturbative approximation and compare the results with those based on numerical computations. While it has been known that the size of the planetary caustic is \propto \sqrt{q}, we find from this work that the dependence of the size of the central caustic on $q$ is linear, i.e., \propto q, implying that the central caustic shrinks much more rapidly with the decrease of $q$ compared to the planetary caustic. The central-caustic size depends also on the star-planet separation. If the size of the caustic is defined as the separation between the two cusps on the star-planet axis (horizontal width), we find that the dependence of the central-caustic size on the separation is \propto (s+1/s). While the size of the central caustic depends both on $s$ and q, its shape defined as the vertical/horizontal width ratio, R_c, is solely dependent on the planetary separation and we derive an analytic relation between R_c and s. Due to the smaller size of the central caustic combined with much more rapid decrease of its size with the decrease of q, the effect of finite source size on the perturbation induced by the central caustic is much more severe than the effect on the perturbation induced by the planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte

Use of gamma spectroscopy for neutronic analysis of LMFBR Blankets

"November, 1971."Also issued as an Sc. D. thesis by the first author and supervised by the second and third author, MIT Dept. of Nuclear Engineering, 1972Includes bibliographical references (pages 158-162)It was the purpose of the present investigation to extend and apply Ge(Li) gamma-ray spectroscopy to the study of fast reactor blankets. The focal point for this research was the Blanket Test Facility at the MITR and Blanket No. 2, a realistic mockup of the blanket reflector region of a large liquid metal cooled fast breeder reactor. It was found that Ge(Li) detectors can be simultaneously used as both high energy neutron spectrometers and continuous gamma-ray spectrometers. The broadened internal conversion spectral line at 691.4 KeV has been analyzed for the former purpose, and the Compton recoil continuum has been analyzed and unfolded for the latter. This development makes the Ge(Li) spectrometer an extremely valuable shield analysis tool. The moisture content of the sodium chromate used in the blanket mockup has been confirmed to be less than 0.1 w/o by prompt activation analysis. Prompt capture and inelastic gamma, and decay gamma spectra emitted by the blanket were also analyzed to perform a neutron balance with mixed results. The inability to resolve U-238 prompt capture gammas made it necessary to use the low energy Np-239 decay gammas, with the attendant uncertainties due to large self-shielding corrections. Lack of data on the variation of prompt gamma yield with neutron energy for all blanket constituents also contributed to the uncertainties, which together made it impossible to develop this method to the point where reliable practical application can be recommended.U.S. Atomic Energy Commission contract AT(11-1)-306

Two-dimensional structures of ferroelectric domain inversion in LiNbO3 by direct electron beam lithography

We report on the fabrication of domain-reversed structures in LiNbO3 by means of direct electron beam lithography at room temperature without any static bias. The LiNbO3 crystals were chemically etched after the exposure of electron beam and then, the patterns of domain inversion were characterized by atomic force microscopy (AFM). In our experiment, an interesting phenomenon occurred when the electron beam wrote a one-dimensional (1-D) grating on the negative c-face: a two-dimensional (2-D) dotted array was observed on the positive c- face, which is significant for its potential to produce 2-D and three-dimensional photonic crystals. Furthermore, we also obtained 2-D ferroelectric domain inversion in the whole LiNbO3 crystal by writing the 2-D square pattern on the negative c-face. Such a structure may be utilized to fabricate 2-D nonlinear photonic crystal. AFM demonstrates that a 2-D domain-reversed structure has been achieved not only on the negative c-face of the crystal, but also across the whole thickness of the crystal.Comment: 17 pages, 4 figure

Effects of raster angle and material components on mechanical properties of polyether-ether-ketone/calcium silicate scaffolds

Polyetheretherketone (PEEK) was widely used in the fabrication of bone substitutes for its excellent chemical resistance, thermal stability and mechanical properties that were similar to those of natural bone tissue. However, the biological inertness restricted the osseointegration with surrounding bone tissue. In this study, calcium silicate (CS) was introduced to improve the bioactivity of PEEK. The PEEK/CS composites scaffolds with CS contents in gradient were fabricated with different raster angles via fused filament fabrication (FFF). With the CS content ranging from 0 to 40% wt, the crystallinity degree (from 16% to 30%) and surface roughness (from 0.13 ± 0.04 to 0.48 ± 0.062 µm) of PEEK/CS scaffolds was enhanced. Mechanical testing showed that the compressive modulus of the PEEK/CS scaffolds could be tuned in the range of 23.3–541.5 MPa. Under the same printing raster angle, the compressive strength reached the maximum with CS content of 20% wt. The deformation process and failure modes could be adjusted by changing the raster angle. Furthermore, the mapping relationships among the modulus, strength, raster angle and CS content were derived, providing guidance for the selection of printing parameters and the control of mechanical properties

Genetic diversity of Iris lactea var. chinensis germplasm detected by inter-simple sequence repeat (ISSR)

The genetic diversity of 24 Iris lactea var. chinensis were analysed by using 100 ISSR primers of which only 11 primers generated distinct amplified products. Among the 24 materials, a total of 214 bands were detected, of which 170 bands were polymorphic. The percentage of polymorphic bands (PPB) was 79%. The ISSR-based genetic similarity (GS) values among 24 accessions ranged from 0.400 to 0.929. Abundant genetic diversity among I. lactea var. chinensis accessions was revealed by ISSR markers.Based on the UPGMA cluster analysis and principal components analysis (PCA), the 24 materials investigated were divided into four groups, most of genetic variation was within a group. Genetic distance was found to be related to geographic distance among I. lactea var. chinensis