A methodology for assessing gamebird use of short rotation coppice

Gamebirds provide a considerable incentive to plant and manage new woodlands. The supplementary income thus generated can improve their overall value. Other studies suggest that Short Rotation Coppice (SRC) crops may provide an attractive habitat for some gamebird species and could increase the value of the crop. To investigate this, the use by pheasants and partridge of different types of SRC at one site was assessed.

A method using sand quadrats to record gamebird footprints and hence relative use was developed. Pheasant footprints were recorded more frequently in the quadrats alongside the willow coppice, whereas partridge footprints occurred more frequently alongside the poplar coppice. Footprint analysis offers a reliable method of investigating how gamebirds use different types of SRC within small areas. The results are considered in terms of the placement of short rotation coppice plantations in the landscape to improve their ecological design.     

Robot Pose Estimation in Unknown Environments by Matching 2D Range Scans

A mobile robot exploring an unknown environment has no absolute frame of reference for its position, other than features it detects through its sensors. Using distinguishable landmarks is one possible approach, but it requires solving the object recognition problem. In particular, when the robot uses two-dimensional laser range scans for localization, it is difficult to accurately detect and localize landmarks in the environment (such as corners and occlusions) from the range scans.In this paper, we develop two new iterative algorithms to register a range scan to a previous scan so as to compute relative robot positions in an unknown environment, that avoid the above problems. The first algorithm is based on matching data points with tangent directions in two scans and minimizing a distance function in order to solve the displacement between the scans. The second algorithm establishes correspondences between points in the two scans and then solves the point-to-point least-squares problem to compute the relative pose of the two scans. Our methods work in curved environments and can handle partial occlusions by rejecting outliers.     

In－BiCaVIG的晶体生长与性能

本文报导了用助熔剂法成功地生长大尺寸掺铟ＢｉＣａＶＩＧ晶体的方法以及实验结果，介绍了该单晶在近红外区的磁光器件中的重要应用。     

孔径法测量铜带残余应力的试验研究

介绍了用于薄板残余应力测量的新方法——孔径法,该方法是通过测量冲孔直径的变化来间接求出各方向的残余应力;文中详细阐述了残余应力的标定方法;由于可针对不同材料建立了被测材料的平均应力(σ_l)与被测板材宽度(B)、厚度(H)以及冲孔后直径变化率(△D_i/D)之间的数学模型,因而使薄板残余应力测量变得简便而经济;此外还对该方法的分辨率与测量精度进行了实验、计算与分析。     

Rene′95粉末合金喷丸强化研究

研究了Ｒｅｎｅ′９５热等静压粉末高温合金喷丸后的残余应力场、组织结构、致密度及其与疲劳性能的关系。结果指出，喷丸强化能够有效地提高合金高周和低周疲劳强度。     

Residual Stress Evolution in Repair Welds

Abstract: The aim of this paper is to study the influence of the repair procedure on the evolution of residual stress distribution in butt welds. C-Mn steel coupon plates of 11 mm thickness were prepared, subjected to stress relief heat treatment and welded with two beads, using the gas metal arc welding process. After the deposition of two weld beads, two successive repair welds were made on the middle length of the second bead. Longitudinal and transverse residual stresses were measured in the vicinity of the weld, after deposition of the two weld beads and after each repair weld. Residual stress evaluation was conducted using an X-ray diffraction method. The repair welds caused a decrease in magnitude of the initial longitudinal residual welding stresses, and an increase of the transverse residual stress magnitude, in tension at points within the repair length, and in compression at points outside the repair length.     

Dynamic analysis and drilling degrees of freedom

Finite element methods for dynamic analysis employing elements with drilling degrees of freedom are presented. The formulation is based on a variational principle in which displacements and rotations are interpolated independently. The issue of zero masses corresponding to rotational degrees of freedom is addressed and techniques for defining consistent and lumped rotational mass matrices are presented.     

An efficient assumed strain element model with six DOF per node for geometrically non-linear shells

The present paper describes an assumed strain finite element model with six degrees of freedom per node designed for geometrically non-linear shell analysis. An important feature of the present paper is the discussion on the spurious kinematic modes and the assumed strain field in the geometrically non-linear setting. The kinematics of deformation is described by using vector components in contrast to the conventional formulation which requires the use of trigonometric functions of rotational angles. Accordingly, converged solutions can be obtained for load or displacement increments that are much larger than possible with the conventional formulation with rotational angles. In addition, a detailed study of the spurious kinematic modes and the choice of assumed strain field reveals that the same assumed strain field can be used for both geometrically linear and non-linear cases to alleviate element locking while maintaining kinematic stability. It is strongly recommended that the element models, described in the present paper, be used instead of the conventional shell element models that employ rotational angles.     

Creep of aromatic polyamide fibres

Creep of Kevlar 29, Kevlar 49 and PRD 49-III fibres was investigated. The fibres exhibited transient creep and the strain-time relationship was represented by a logarithmic time law. The creep strain recovered with time when the load was removed. Upon reloading to the same creep stress the strain-time relationship was again logarithmic but the creep rate was reduced. Modulus measurements were made during the creep test and these showed that the modulus increased with time. This result indicated a crystallite rotation mechanism which could account for the experimentally observed creep strain. Creep in PRD 49-III fibres exhibited a small temperature dependence over the temperature range 20°C to 150°C. The apparent creep activation energy was consistent with the range of values reported for hydrogen bonding. This suggests one possible creep mechanism in which the combined action of stress and thermal activation causes rearrangement of intercrystalline bonds in the crystallite boundaries resulting in boundary creep. Boundary creep allows crystallite rotation which produces the macroscopic creep strain. Boundary creep is discussed in terms of the fibre morphology and a model of delayed elasticity.     

Residual stress measurements in bevel gear after different production phases

This article discusses residual stress measurements by means of electrochemical removal of material layers with residual stresses and simultaneous measurement of strain on the opposite specimen side with strain gages. Exact measurements are impossible particularly because of the small bevel gear module. With the method presented, the average residual stresses in the tooth root plane and underlying layers are measured. Residual stress distribution after each consecutive production phase is plotted and analyzed. Residual stress measurements enable the engineer to adequately assess each individual production phase and by that improve the quality of the complete production process.