LaRC TPI 1500 series polymers

The crystallization behavior and the melt flow properties of two batches of 1500 series LaRC-TPI polymers from Mitsui Toatsu Chemicals (MTC) were investigated. The characterization methods include Differential Scanning Calorimetry, the x ray diffractography and the melt rheology. The as-received materials possess initial crystalline melting peak temperatures of 295 and 305 C, respectively. These materials are less readily recrystallizable at elevated temperatures when compared to other semicrystalline thermoplastics. For the samples annealed at temperatures below 330 C, a semicrystalline polymer can be obtained. On the other hand, a purely amorphous structure is realized in the samples annealed at temperatures above 330 C. Isothermal crystallization kinetics were studied by means of the simple Avrami equation. The viscoelastic properties at elevated temperatures below and above glass transition temperature of the polymers were measured. Information with regard to the molecule sizes and distributions in these polymers were also extracted from melt rheology

Artificial Neural Network for Spectrum unfolding Bonner Sphere Data

The use of Bonner Sphere Spectrometer (BSS) is a well-established method of measuring the energy distribution of neutron emission sources. The purpose of this research is to apply the Generalized Regression Neural Network (GRNN), a kind of Artificial Neural Network (ANN), to predict the neutron spectrum using the count rate data from a BSS. The BSS system was simulated with the MCNP5 Monte-Carlo code to calculate the response to neutrons of different energies for each combination of thermal neutron detector and polyethylene sphere. One hundred and sixty-three different types of neutron spectra were then investigated. GRNN Training and testing was carried out in the MATLAB environment. In the GRNN testing, eight-one predicted spectra were obtained as outputs of the GRNN. Comparison with standard spectra shows that 97.5% of the prediction errors were controlled below 1%, indicating ANN could be used as an alternative with high accuracy in neutron spectrum unfolding methodologies. Advantages and further improvements of this technique are also discussed

LOWER EXTREMITY JOINT KINETICS DURING LANDING OF A DROP JUMP FROM DIFFERENT HEIGHTS AND LANDING SURFACES

This study aimed to investigate the biomechanical effect of the lower extremity joints from a vertical fall of 30 cm and 60 cm to a soft mat and a stiff floor respectively. Result shows, from either height, the joint forces and peak joint moments decrease significantly, while the joint angles changes to a greater degree when landing on a soft mat and it needs more time from initial contact till the action stops. 'Each joint moment is effect of external moment and internal muscle moment together. The correct landing technique is that moments of all joints reduce simultaneously, Le. the contraction and passive extension of muscles should be controlled in sequence and magnitude. The highest muscle moment on contact landing is observed at hip joint on 'both landing conditions and the muscles of the knee and ankle joints guided by the hip muscles assist each other