Ten-year longitudinal investigation of astigmatism: The Yamagata Study (Funagata)

Despite numerous investigations into ocular or corneal astigmatism, the dynamic nature of astigmatism remains poorly understood. To reveal potential associations between age and astigmatism, 264 Japanese participants who underwent systemic and ophthalmological examinations in Funagata Town (Yamagata Prefecture, Japan) were evaluated over a 10-year period. Astigmatism was evaluated with regard to the cylinder power, cylinder axis, and vector analyses. Whereas the refractive cylinders showed age-related increases in patients in their 40s to 60s, the corneal cylinders did not change over 10 years. Nevertheless, cylindrical axis of the cornea demonstrated a continuous shift toward against-the-rule (ATR) astigmatism. Vector analyses revealed that the astigmatic shift toward ATR progressed continually after patients reached their 40s, although the shift did not accelerate with age. These novel insights may pave the way for the development of potential strategies for vision correction, including refractive surgeries, and vision-quality maintenance in the elderly.

Research on sealing characteristics of annular power cylinder based on twin-rotor piston engine

The sealing characteristics of an annular power cylinder based on the Twin-rotor piston engine are studied, which provides a theoretical foundation for the sealing design of a new high-power density piston engine. In this paper, the basis thermodynamic realization process of an annular power cylinder is presented. The Runge Kutta equation is used to establish the coupled leakage model of adjacent working chambers under annular piston seal. And the sealing performance of the annular power cylinder is analyzed in detail. Moreover, the influence of rotor speed and compression ratio on the sealing characteristics and leakage is studied. Finally, some tests are carried out to verify the sealing principle and simulation results, which verifies the theoretical basis of simulation analysis. Results show that there are double pressure peaks in the leakage chamber between two working chambers, which is beneficial to reduce the leakage rate. Besides, increasing the speed and decreasing the compression ratio can help to reduce gas leakage. Furthermore, the effects of speed variation on the leakage are only significant when rotating at low speed. Changing the compression ratio has a greater effect on the slope of the leakage curve at a low compression ratio, and the lower the compression ratio, the better the sealing effect.

Monoharmonic method for calculating the frequency characteristics of the dynamic stiffness of nonlinear dynamic objects

The paper comprises results of algorithm design for monoharmonic method for calculating the frequency characteristics of the dynamic stiffness of nonlinear dynamic objects with a specified computational error and for a minimum time. The proposed alternative method relates to auto-integration methods and is based on numerical integration of the nonlinear differential equation system for a mathematical model of a dynamic object with monoharmonic input actions at fixed frequencies, and analysis of responses to these actions by Fourier method. The integration process at each fixed frequency continues until the average values of Fourier coefficients of the investigated harmonic of dynamic stiffness of a nonlinear dynamic object on the input monoharmonic force or moment action for a passed number of periods of the input signal become sensibly constant. The efficiency of the developed method and algorithm is studied using the example of calculation of frequency characteristics of the dynamic stiffness of a hydraulic power cylinder with closed hydraulic lines. The obtained frequency characteristics of the dynamic stiffness can be used to evaluate the damping properties of nonlinear dynamic objects. Key words: frequency characteristics of dynamic stiffness; calculation method; nonlinear dynamic objects.

MESIN ROLL PELAT BAHAN PEWTER

The design of the machine roll plate made from pewter to be developed is a machine that is simple, easy to be usde and does not endanger the user and use 1 phase ac motors. The system uses two cylinder rolls at the top and bottom with a thickness regulator by using a screw system. The material used is steel st. 40 for the roll materials and to get the smooth rolling process, then roll grinding cylinder. For the power cylinder roll will be analyzed by the software that is to know the voltage that occurs in the cylinder roll when rolling the pewter plate by assumed load of 1000 kg. The result of this research is the engine may roll the plate pewter with a size of 260 mm x 70 mm x 3 mm to a size of 430 mm x 77 mm x 1 mm, which takes 6 minutes of 1 plate pewter, plate surface pewter solid and smooth, and the size of the plate length increases ± 98% and ± 7% width, thus saving time, effort and cost in the casting process.