Rubber-modified epoxy resins: 1. Equilibrium physical properties

Dilatometry, thermal mechanical analysis, differential scanning calorimetry, electron microscopy and mechanical measurements are reported on a series of rubber-modified epoxy resins. The data obtained is discussed in terms of the interplay of molecular mobility, network and domain structure of the resins. Three transitions were identified; two being assigned respectively to the onset of motion of the acrylonitrile/butadiene units and epoxy units. The higher temperature transition is more difficult to assign, but appears to be associated with specific interactions involving the interface between the epoxy and acrylonitrile/butadiene interfaces or the crosslinked regions of the epoxy resin.     

Picosecond pulse generation and its simulation in a nonlinear optical mirror mode-locked laser

A nonlinear mirror composed of a lithium triborate crystal and a dichroic output coupler is used to passively mode lock an Nd:YVO4 laser that is pumped by a diode laser array. A mode-locked output power of 3.2 W, a repetition rate of 178 MHz, a pulse width of 8.4 ps, and a beam quality parameter (M2) of 1.27 are obtained at 1064 nm for a pump power of 10.0 W. The numerical simulation for the steady-state pulse width agrees well with the bandwidth-limited value. A double-pass average gain g(ave) is defined by considering the constancy of the output energy. In the simulation g(ave) is kept as a free parameter, and its value required for the bandwidth-limited pulse is found to be 0.047, whereas its calculated value, based on our definition, is 0.057.     

Noncanonical vortex transformation and propagation in a two-dimensional optical system

We produced an axial and canonical optical vortex by using a computer-generated hologram and then converted it to a noncanonical vortex by passing it through a cylindrical lens. We conducted an experimental study of the shape and trajectory of the noncanonical vortex as it propagates in free space and obtained an analytical expression explaining our experimental results. The computed trajectory and shape of the noncanonical vortex agree quite well with our experimental results.     

Foot landmarking for footwear customization

As consumers are becoming increasingly selective of what they wear on their feet, manufacturers are experiencing problems developing and fitting the right footwear. Literature suggests that shoes with a shape similar to feet may be comfortable because they attempt to maintain the feet in a neutral posture. The objective of this paper is to develop a metric to quantify mismatches between feet and lasts and also to be able to generate the two-dimensional outline of the foot using the minimum number of landmarks. Fifty Hong Kong Chinese were participants in the experiment. In addition to subject weight, height, foot length and foot width, the left foot outlines were drawn and 18 landmarks were marked on each of the two-dimensional foot outlines. A step-wise procedure was used to reduce the chosen 18 landmarks to eight, such that the mean absolute negative error (an indicator of 'tightness') between the foot outline and the modelled curve was 1.3 mm. These eight landmarks seem to show an improvement over those proposed by other researchers, thus showing the importance of choosing the right landmarks for modelling the foot. The positive and negative absolute errors were on average 1.8 mm and 1.3 mm respectively. Moreover, the mean errors for the toe region and for the rest of the foot were 1.7 mm and 1.6 mm respectively. The results indicate that the foot outline, an important component for footwear functionality and fitting, may be modelled using eight critical landmarks.     

Optical tomographic microscope for quantitative imaging of phase objects

We describe a tomographic microscope, for imaging phase objects, that makes use of the transport-of-intensity equation to estimate the phase of the transmitted light through the object. The wave-front data from optical fibers are reconstructed with an algorithm that incorporates correction for the ray bending. The reconstructed refractive-index cross sections of the fibers are found to be in agreement with the available values specified in the catalogs.     

Exploring the effects of chemical composition in hot rolled steel product using Mahalanobis distance scale under Mahalanobis–Taguchi system

Classification of hot rolled steel product from the point of view of reaching the target mechanical property, based on chemical composition of the steel, is a common objective practiced in the industrial rolling mill. After examining the ability of measurement scale of Mahalanobis–Taguchi system in classifying the steel plate as “OK” or “Diverted”, study on the changing nature of Mahalanobis distance, obtained from previous work, with the corresponding increments in the chemical composition over their respective working ranges, is carried out in order to explain the behaviour of Mahalanobis distances from the knowledge of materials science. As the nature of Mahalanobis distance illustrated by the study does not contradict the subject knowledge, the robustness of the measurement scale used in Mahalanobis–Taguchi system is therefore established.