Hierarchical tapered bar elements undergoing axial deformation

A method is described to model the dynamics of tapered axial bars of various cross sections based on the well-known Craig/Bampton component mode synthesis technique. This element is formed in terms of the static constraint modes and interface restrained normal modes. This is in contrast with the finite elements as implemented in NASTRAN where the interface restrained normal modes are neglected. These normal modes are in terms of Bessel functions. Restoration of a few of these modes leads to higher accuracy with fewer generalized coordinates. The proposed models are hierarchical so that all lower order element matrices are embedded in higher order element matrices. The advantages of this formulation compared to standard NASTRAN truss element formulation are demonstrated through simple numerical examples

Transient loads analysis for space flight applications

A significant part of the flight readiness verification process involves transient analysis of the coupled Shuttle-payload system to determine the low frequency transient loads. This paper describes a methodology for transient loads analysis and its implementation for the Spacelab Life Sciences Mission. The analysis is carried out using two major software tools - NASTRAN and an external FORTRAN code called EZTRAN. This approach is adopted to overcome some of the limitations of NASTRAN's standard transient analysis capabilities. The method uses Data Recovery Matrices (DRM) to improve computational efficiency. The mode acceleration method is fully implemented in the DRM formulation to recover accurate displacements, stresses, and forces. The advantages of the method are demonstrated through a numerical example

A noniterative improvement of Guyan reduction

In determining the natural modes and frequencies of a linear elastic structure, Guyan reduction is often used to reduce the size of the mass and stiffness matrices and the solution of the reduced system is obtained first. The reduced system modes are then expanded to the size of the original system by using a static transformation linking the retained degrees of freedom to the omitted degrees of freedom. In the present paper, the transformation matrix of Guyan reduction is modified to include additional terms from a series accounting for the inertial effects. However, the inertial terms are dependent on the unknown frequencies. A practical approximation is employed to compute the inertial terms without any iteration. This new transformation is implemented in NASTRAN using a DMAP sequence alter. Numerical examples using a cantilever beam illustrate the necessary condition for allowing a large number of additional terms in the proposed series correction of Guyan reduction. A practical example of a large model of the Plasma Motor Generator module to be flown on a Delta launch vehicle is also presented

Anomalous thermal expansion of Sb2_2Te3_3 topological insulator

We have investigated the temperature dependence of the linear thermal expansion along the hexagonal c axis ($\Delta L$), in-plane resistivity ($\rho$), and specific heat ($C_p$) of the topological insulator Sb$_2$Te$_3$ single crystal. $\Delta L$ exhibits a clear anomaly in the temperature region 204-236 K. The coefficient of linear thermal expansion $\alpha$ decreases rapidly above 204 K, passes through a deep minimum at around 225 K and then increases abruptly in the region 225-236 K. $\alpha$ is negative in the interval 221-228 K. The temperature dependence of both $\alpha$ and $C_p$ can be described well by the Debye model from 2 to 290 K, excluding the region around the anomaly in $\alpha$

Identification and phylogenetic analysis of filamentous Cyanobacteria using random amplified polymorphic DNA (RAPD) fingerprinting

RAPD techniques were used for the detection of genetic heterogeneticity among the axenic culture of fresh water cyanobacterial isolates. The electrophoretic patterns for 12 cyanobacterial strainsbelonging to 2 genera (8 Oscillatoria strains and 4 Lyngbya strains) were used for molecular analysis using the RAPD technique. A total of 12 cyanobacterial isolates were selected and mass cultured inBG11 medium. Genomic DNA was extracted from fresh water cyanobacterial isolates and was amplified using primers D7, M13, OPC11, OPC12, OPC13, OPC14 and OPC15 and distinct PCR fingerprint were generated. Unique banding patterns were observed from all tested cyanobacterial species and their molecular weights of each band were used to calculate their genetic distance among them. Random amplification of polymorphic DNA (RAPD) was carried out for the phylogenetic characterization of these strains. RAPD fingerprinting results clearly showed the genetic variation among the cyanobacterial isolates

Multi-Objective Optimization in Friction Welding Process Parameters on EN353 Alloy Steel using Taguchi based GRA

Joining of similar materials by varying the input factors on a continuous drive friction welding process is done in this study. The intention is to find the optimal solution in friction welding input process parameters. Among several types of welding processes, friction welding forms good metal joints. The process factors considered for this material joining practice are Upset Time (UT), Heating Time (HT), Heating Pressure (HP), Upset Pressure (UP), chemical composition and measurements of the materials. Frictional joints provide better mechanical properties, hence it is attracted by researchers. Here, EN353 is used as the specimen, for its extensive usage in the automobile and manufacturing sectors. Axial shortening, hardness testing and the temperature during welding are evaluated, compared and optimized using Taguchi Design of Experiments (DoE) scheme using L27 orthogonal array and Grey Relational Analysis (GRA)

Analysis of welding distortion using finite element method

Welding distortion is experienced during the fabrication of many structures and the control of the distortion within limits is one of the important requi-rements for a practising engineer. The analysis of weld-ing distortion is needed for taking precautionary measu-res during fabrication. In earlier times, empirical cum analytical type of analysis was popularly employed but with the advent of powerful computers, numerical techn-iques are becoming popular for the analysis of welding distortion in various structures. In this paper, the analysis of welding distortion during circumferential welding of a thin pipe using finite element method is discussed. The analysis is of transient thermal elastic plastic in nature as the accumulated plastic strains caused by the localised heat input are responsible for the distortion in the component. The thermal and elastic plastic analyses are carried out using four noded bilinear degenerated shell element which assumes that the thermal and stress gradients in the local thickness direction are negligible. For carrying out the finite element analyses, computer programs are written in C language and are run in a PC with 80486 configuration and 25 MHz clock speed. Due to the limitations in the memory size, the analyses are carried out using out of core technique which involves many memory operations during the formulation and solu-tion stages. The details of the models, the solution techniques and the thermal, displacement and stress results are presented in this paper

The Myanmar Peace Center : Its Origins, Activities, and Aspirations

The Myanmar Peace Center (MPC) is one of the newest organizations with a focus on peace in Asia. It was initially formed in October 2012 with a core group of 13 members. Since then it has gone on to become a much larger and also much more institutionalized organization. The nature of its work differs from that of most other peace research centers in that it is the organization appointed by the Myanmar President and government to bring an end to ethnic and sectarian conflict in the country. The MPC, unlike other organizations, is actively involved in negotiating peace with the countrys major ethnic insurgent groups, many of which have been fighting the government for almost six decades now. This article traces the origins of the MPC and its mandate within the Myanmar governments ongoing attempts to sign a nation-wide ceasefire deal to bring closure to the long history of ethnic conflict that has plagued the country. It also identifies the organizational structure of the MPC and the key personnel involved in the ongoing negotiation efforts. The MPC faces a number of obstacles to its ongoing work and these are examined as well, together with a projection of how the institution will evolve as the country heads towards the next parliamentary elections in 2015