Nonlinear vibrations of tapered circular plates elastically restrained against rotation at the edges

Large amplitude free vibration characteristics of tapered circular plates elastically restrained against rotation is studied in this paper using the finite element method. Linear frequency parameter and ratios of nonlinear to linear periods are obtained for various values of rotational spring parameter and taper parameter and are presented in the form of tables.     

Behaviour of materials subjected to an impact force and new evaluation method for impact strength

The size dependence of the amplitude of a stress pulse produced in a rod subjected to an impact force is theoretically considered. Impact fatigue experiments were performed to see the size dependence of the strength of structural materials. According to these results, impact fatigue life of a short specimen was shorter than that of a long one. Based on these considerations, it is shown that the superposition of stress waves with reversed phase is effective to improve the impact fatigue life. In addition, a new method is proposed to evaluate the impact strength of materials with stress unit. By this method, influences of strain rate on the impact tensile strength I_m,t and impact bending strength I_m,b are investigated for carbon steel, aluminium alloy and PMMA using their dynamic stress strain relations which are measured directly on each specimen.     

Elastic–plastic analysis of an elbow with a through-wall axial crack at crown under in-plane bending

Piping elbows under bending moment are vulnerable to cracking at crown. The structural integrity assessment requires knowledge of the J-integral. The J-integral values for axially through-wall cracked thick elbows under in-plane bending moment are not available in open literature. This paper presents the J-integral results for 90°, long radius elbows subjected to in-plane opening bending moment based on a large number of finite element analyses covering a wide range of standard geometries. The non-linear elastic–plastic finite element analyses were performed using WARP3D software. Both geometric and material non-linearity were considered in the study. The geometry considered were for R_m/t = 5, 6, 7.5, 9, 12, 15, 20 and 25 with crack angles of 9°, 18°, 27° and 36° and strain hardening exponent, ‘n’ varied for 2, 3, 5, 7 and 10.     

Volume charge near the boundary of a dielectric irradiated with an electron beam

A. M. Gor'kii Kharkov State University. Translated Atomnaya Énergiya, Vol. 70, No. 4, pp. 256-257, April, 1991.     

A one dimensional model for the prediction of stratification in horizontal pipes subjected to fluid temperature transient at inlet: Part II. Thermal model

Various thermal interactions that are of interest during stratification in horizontal pipes are analyzed in this paper. The interactions studied are those that occur between a slow and a fast moving stream or between the fluid and the pipe wall. A lumped capacity approach in the radial direction is used to model the fluid-wall and fluid-fluid interactions. However the internal resistance of the stationary layer is approximately accounted for in the model. The application of the model to sodium flowing in a 15.2 cm ID stainless steel pipe shows that fluid-fluid interaction can reduce the magnitude of maximum stratification by about 18% as compared to the case in which interaction is not considered or is of little consequence (e.g. for water). This implies that stratification predictions based on the hydrodynamical model alone tend to be conservative. It is also shown that the magnitude of the stratification based on the pipe wall temperature can be higher than that predicted from the hydrodynamic model.     

The accelerator mass spectrometry facility at the University of Washington: Current status and an application to the 14C profile of a tree ring

The University of Washington accelerator mass spectrometry system, based upon a Model FN tandem accelerator, is described. Preliminary data on ¹⁴C in thin sequential sections of a single Sitka spruce annual ring (1963) are presented; the ¹⁴C profile reflects the dramatic nuclear-weapons-induced changes in atmospheric ¹⁴C observed for 1963.     

Particulars of radiolysis and mass transfer in two-phase water coolant of a nuclear power facility with steam generation at an interphase surface

A model of an interphase transfer of stable products of the radiolysis of water in boiling coolant is developed taking account of the intensity of their delivery to the interphase boundary in the liquid phase and removal into the vapor phase with vapor generation on the interphase surface. A computational study is made of the radiolysis of the coolant and interphase transfer of the products of the radiolysis of water in the core and on the pulling section of BWR of the Oskarshamn-2 nuclear power plant in Sweden. A comparison of the computational data with the results of the technical measurements of the coolant composition of the BWR at the Oskarshamn-2 nuclear power plant showed that the accumulation of stable products of the radiolysis of water in the vapor-gas phase of the coolant is determined by the kinetics of radiolysis in the liquid phase, the concentration of the oxygen-containing components in the liquid phase is due to the present of hydrogen peroxide in it.     

Experimental determination of the absorbed dose to water in a scanned proton beam using a water calorimeter and an ionization chamber

The absorbed dose to water is the reference physical quantity for the energy absorbed in tissue when exposed to beams of ionizing radiation in radiotherapy. The SI unit of absorbed dose to water is the gray (Gy = 1 J/kg). Ionization chambers are used as the dosimeters of choice in the clinical environment because they show a high reproducibility and are easy to use. However, ionization chambers have to be calibrated in order to convert the measured electrical charge into absorbed dose to water. In addition, protocols require these conversion factors to be SI traceable to a primary standard of absorbed dose to water. We present experimental results where the ionization chamber used for the dosimetry for the scanned proton beam facility at PSI is compared with the direct determination of absorbed dose to water from the METAS primary standard water calorimeter. The agreement of 3.2% of the dose values measured by the two techniques are within their respective statistical uncertainties.     

BISOL相邻两电荷态相同质量重离子束相位能量调节的物理设计

放射性核束物理是国际核物理研究的前沿,滴线区新物理、铁以上重元素的天体合成过程、超重稳定岛核素合成等关键科学问题的突破将对整个自然科学产生重大影响,这些研究都需要高强度的极端丰中子核束。将中国先进研究堆及强流氘离子加速器打靶产生的放射性核束传输至物理终端,采用两电荷态束流同时加速可以有效提高束流强度;通过分析离子束分离注入同步加速原理,采用静电高压调节离子束相位差,速率调节器同步离子束能量,分别计算得到不同种类核束引出电压参数和速率同步参数;同时分析计算了电压调节与离子束相位差变化关系,得到电压调节参数。计算结果表明,当调节电压幅值取±8 k V时,可满足不同种类离子相位调节需求。     

Enhancement of proton collimation and acceleration by an ultra-intense laser interacting with a cone target followed by a beam collimator

A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating, accelerating and guiding protons, using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism. In addition, the problems involved are studied by using two-dimensional particle-in-cell simulations. The results show that the proton beam can be collimated, accelerated and guided effectively through this type of target. Theoretically, a formula is derived for the combined electric field of accelerating protons. Compared with a proton beam without a beam collimator, the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10% respectively. Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field, and that the beam collimator plays a role in focusing energy. In addition, the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I. The more prominent point is that the proton number of type II is 2.2 times higher than that of type I. This kind of target has important applications in many fields, such as fast ion ignition in inertial fusion, high energy physics and proton therapy.