Nonlinearity and Fractal Properties of Climate Change during the Past 500 Years in Northwestern China

By using detrended fluctuation analysis (DFA), the present paper analyzed the nonlinearity and fractal properties of tree-ring records from two types of trees in northwestern China, and then we disclosed climate change characteristics during the past 500 years in this area. The results indicate that climate change in northwestern China displayed a long-range correlation (LRC), which can exist over time span of 100 years or longer. This conclusion provides a theoretical basis for long-term climate predictions. Combining the DFA results obtained from daily temperatures records at the Xi’an meteorological observation station, which is near the southern peak of the Huashan Mountains, self-similarities widely existed in climate change on monthly, seasonal, annual, and decadal timescales during the past 500 years in northwestern China, and this change was a typical nonlinear process

Generation of ring-shaped optical vortices in dissipative media by inhomogeneous effective diffusion

By means of systematic simulations we demonstrate generation of a variety of ring-shaped optical vortices (OVs) from a two-dimensional input with embedded vorticity, in a dissipative medium modeled by the cubic-quintic complex Ginzburg-Landau equation with an inhomogeneous effective diffusion (spatial-filtering) term, which is anisotropic in the transverse plane and periodically modulated in the longitudinal direction. We show the generation of stable square- and gear-shaped OVs, as well as tilted oval-shaped vortex rings, and string-shaped bound states built of a central fundamental soliton and two vortex satellites, or of three fundamental solitons. Their shape can be adjusted by tuning the strength and modulation period of the inhomogeneous diffusion. Stability domains of the generated OVs are identified by varying the vorticity of the input and parameters of the inhomogeneous diffusion. The results suggest a method to generate new types of ring-shaped OVs with applications to the work with structured light.Comment: 24 pages, 5 figures; Nonlinear Dynamics, in pres

Research on Mud Flow Rate Measurement Method Based on Continuous Doppler Ultrasonic Wave

In deep-water drilling processes, the flow rate of drilling mud inside an annular pipe is significant judgment data for early kick detection. On the basis of the continuous-wave Doppler ultrasound, this paper proposes a new detection method of nonoriented continuous-wave Doppler ultrasound. The method solves the problem of the ultrasound having great attenuation in mud and not receiving effective signals by using a continuous ultrasound. Moreover, this method analyzes the nonoriented characteristics of ultrasound reflection on principle and proposes the detection of ultrasound Doppler frequency shift by detecting Lamb wave, which releases the detection of oil-based mud flow rate in a nonintrusive annular pipe. The feasibility of the method is verified through theoretical analysis and numerous experiments on a gas kick simulation platform. The measurement result has reached a flow accuracy approximating to the intrusive flow meter

The viral aetiology of cervical cancer: Psychosocial issues

This work stems from the discovery that certain sexually transmitted types of human papillomavirus (HPV) are the main causal agents in cervical carcinogenesis. The thesis sets out to explore the psychosocial issues that arise from linking a sexually transmitted infection with cervical cancer. Four studies were carried out. Study 1 was a survey of women attending a well-woman clinic (n=1032) and assessed awareness and knowledge about HPV. Study 2 used a population representative sample of men and women (n=1937) to assess beliefs about the risk factors for cervical cancer. Study 3 used in-depth interviews to explore the beliefs and experiences of 74 women who had taken part in HPV testing. Study 4 was a continuation of Study 3, in which 30 women were interviewed following participation in their second HPV test, a year after the first. Awareness of HPV and its link with cervical cancer was found to be low. Although there was higher awareness of sexual activity as a risk factor for cervical cancer, this was far from universal. Women testing positive for HPV who understood that it was sexually transmitted frequently reported negative emotional and social responses, different from those that have been found among women with abnormal smear test results. Leventhal's Common Sense Model of self-regulation in health and illness provided a useful framework within which to conceptualise the relationship between women's cognitive representations of HPV and their responses to the infection. It seemed that women were also engaged in the self-regulation of their relationships and were motivated to develop representations of HPV that did not impugn their current partners. Diagnosis with persistent HPV infection was associated with higher levels of anxiety about health and with the desire for immediate further investigation by colposcopy, rather than continued surveillance. The introduction of HPV testing and vaccination should be accompanied by widespread public education. If information provision is not handled in a sensitive way, it could cause confusion and stigmatise cervical cancer. More research is needed to develop ways to communicate information about HPV effectively

A Review of Linear Regression and some Basic Proofs for Lasso

The goal of this paper is to do some basic proofs for lasso and have a deep understanding of linear regression. In this paper, firstly I give a review of methods in linear regression, and most concerns with the method of lasso. Lasso for ¡®least absolute shrinkage and selection operator¡¯ is a regularized version of method adds a constraint which uses norm less or equal to a given value t. By doing so, some predictor coefficients would be shrank and some others might be set to 0. We can attain good interpretation and prediction accuracy by using lasso method. Secondly, I provide some basic proofs for lasso, which would be very helpful in understanding lasso. Additionally, some geometric graphs are also given and one example is illustrated

Analysis and optimization of the engine valve train

Facing the challenge of characteristics improvement, like power output, fuel economy and emissions reduction, the high level of dependability of the valve train is required in order to strengthen the capability of the overall engine system. Furthermore, in response to the existing defects derived from original design of valve train, some major components, especially the cam and valve spring need to be optimized accurately based on the optimizing theory as well as their performances after the simulation. This paper presents the kinematic and dynamic modeling process of a valve train from a gasoline engine using AVL-Tycon platform and analyses the simulation results in comparison with the qualification terms of this practical engine. In addition, an optimization method of the valve train is proposed in accordance with original simulation results

Dynamic Characteristic and Parameter Analysis of a Modular Building with Suspended Floors

Over the past few years, modular buildings have become an important form of environmentally friendly architecture. Prefabricated construction methods have gained a lot of attention because they produce less construction waste and require less labor and water. However, the seismic performance of modular buildings needs to be improved. This paper proposes a prefabricated steel module with a suspended floor, which is based on a multi-tuned mass damped floor system. This paper also derives the form of a motion equation which is unified with the construction process of modular buildings, which can describe the change law of the mass, stiffness, and damping matrix of the structure in the processes of connecting the main structure with the suspended floor slab and of joining different floors. Since the performances of tuned mass damping devices are closely related to the dynamic characteristics of the structure, this paper uses ABAQUS for numerical analysis and mathematical induction (MI) to propose and verify a simplified method for calculating the lateral stiffness of the entire story from a single module’s lateral stiffness. Based on the principle of reducing the stiffness difference in the structure along different directions, a standard scheme of the horizontal extension of the module building is also specified. The results show that the simplified calculation method is reasonable and that the lateral stiffness of the structure increases linearly with the number of modules. Finally, the recommended values for the tuned frequency ratio and tuned damping ratio are given by investigating the dynamic response of the structure under Gaussian white noise excitation. The results show that the recommended tuning frequency ratio and damping ratio ranges in modular buildings are close to those for FIS buildings

Reduction of Residual Quenching Stresses in 2A14 Aluminum Alloy Tapered Cylinder Forgings via a Novel Cold Bulging Process

This study combined finite element method (FEM) simulations and physical experiments to develop a novel cold bulging process, with the aim of studying and mitigating the quenching residual stresses in 2A14 tapered cylinder forgings. The samples underwent cold bulging at different ratios (0–4.0%) to evaluate the residual stress reduction performance (via the hole-drilling strain-gauge method) and the improvements in their mechanical properties. The FEM simulation and experimental results revealed that our proposed cold bulging process reduced the quenching residual stresses by up to 85–87%. The density and uniformity of the precipitated phases increased along with the extent of cold bulging, as confirmed by transmission electron microscope (TEM) observations. Furthermore, compared to the unprocessed samples, the tensile and yield strengths, and elongation of the samples with 3% cold bulging were significantly enhanced (65 MPa, 55 MPa, and 1.7%, respectively)

Influence of thermomechanical processing on coarse particles, grain structure, and mechanical properties of Al–Cu alloy rings

Rings made of 2219 Al alloy are typically manufactured by multi-directional forging (MDF) and ring rolling at 460 °C, followed by heat treatment. However, this process often results in coarse elongated grains and a large number of coarse Al2Cu particles, resulting in rings with poor mechanical properties. As a strategy to refine the microstructure and improve the mechanical properties, a novel thermomechanical process was tested for ring manufacturing, with MDF at 510 °C and ring rolling at 240 °C. The results showed that use of MDF at higher temperatures resulted in increased spherical shapes and decreased numbers of coarse Al2Cu particles due to more complete dissolution. Decreasing the rolling temperature from 460 °C to 240 °C resulted in finer grain structure due to the increased nucleation ratio of static recrystallization during subsequent solution heat treatment. Samples prepared using this novel process exhibited fine equiaxed grains with sufficient dissolving of coarse Al2Cu particles, thus this method significantly improved the mechanical properties of the prepared material and decreased the anisotropy in three orthogonal directions