Properties of polycarbonate/acrylonitrile-butadiene-styrene blends

To help make a good polymer blend by melt blending, the properties of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) systems with various compositions have been investigated. As ABS is blended into PC to form a binary system, Brabender torque is reduced, a phenomenon that results in Improved processability of PC. With increasing ABS content, the mechanical properties of the blends such as tensile strength, modulus, hardness, and shrinkage decrease. However, with the variation of composition, Izod impact strength shows a maximum, while elongation at break exhibits a minimum. These phenomena are discussed with dynamic viscoelasticities and scanning electron microscopic morphological results. The value of ΔT_g(T_gβPC ? T_gβABS) is at its smallest when the ratio of PC to ABS is 90:10, However, the value rises with an increase in ABS because the butadiene content of the ABS hinders compatibility in the binary system. At the 90:10 composition, the damping height is optimal. In addition, the dispersed phase of the ABS is most ideal, absorbing the impact force and showing high impact strength. Composition ratios other than 90:10 present high damping as well as undesirable phase separation because of poor adhesion between two phases. As a result, the mechanical properties are reduced.     

Study on poly(2,6-dimethyl-1,4-phenylene oxide)/SBS triblock copolymer blends

The relationship between the miscibility and the physical properties of polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PS), high-impact polystyrene (IPS) and poly(styrene-block-butadiene-block-styrene) (SBS), which are blended in different compositions by a twin-screw extruder is discussed. The three types of SBS that were used are SBS1, SBS2 and SBS3 having different styrene/butadiene ratios. Dynamic mechanical analysis and differential scanning calorimetry were used to study the miscibility. The morphology was examined by SEM. The miscibility of the blends decreases with decreasing PS content. The notch sensitivity is improved by blending. Finally, the micelle model was used to explain the testing phenomena.     

Theoretical study of turbulent plane jet interacting with small amplitude wave

Abstract

The radiation stress due to the presence of waves is considered in the equation of motion for the velocity distribution and boundary thickness after the interaction of turbulent plane jet with small amplitude waves. On the basis of the characteristics of turbulent plane jet and small amplitude waves, the velocity distribution about the average of wave period may be assumed to be a Gaussian distribution. Behavior of the fluctuation due to wave motion is also investigated. And from experimental results, the coefficient of velocity distribution c ₁ is found to be 0.105.     

Experimental study of the particle paths in solitary water waves

We provide experiments that had been conducted to investigate the particle trajectory beneath a solitary water wave. Experimental results show that the surface drift is larger than the bottom drift. Meanwhile, the ratio of the net horizontal displacement to the total height of the trajectory at the free surface and subsurface will decrease with the initial vertical position and increase with the relative wave height.     

POSITION CONTROL EMPLOYING FUZZY-SLIDING MODE AND GENETIC ALGORITHMS WITH A MODIFIED EVOLUTIONARY DIRECTION OPERATOR

This study presents a novel controller by employing fuzzy-sliding mode control and genetic algorithms equipped with a modified evolutionary direction operator for optimal position control with an induction motor. Applying the sliding mode control technique provides the proposed controller with many advantages, such as a small overshoot, tiny steady-state error, rapid response, and adaptability to equipment parameters variation and external disturbance. The genetic algorithm optimizes the parameters of fuzzy membership functions defined according to expert experience, and its supplementary modified evolutionary direction operator determines improved search directions. The proposed approach is applied to a position servo system. Computational results indicate that the proposed controller exhibits excellent performance with all the advantages mentioned above. Moreover, the proposed controller is immune to the chattering problem that typically affects general controllers.     

Miscibility study of polycarbonate and SBS triblock copolymer blends

Polymer blends of Polycarbonate (PC) and Styrene-Butadiene-Styrene triblock (SBS) have been investigated. SBS copolymers have four different styrenic contents, three of which are linear SBS. PC and PS blends are partially miscible as revealed by dynamic mechanical analysis with two clear Tgs near 100–150°C. On the contrary, PC/SBS blends have only one Tg with a left shoulder. Based on the PS domain model of pure SBS, we suggest a micelle model based on the structure when the micelle and absorb PC in the PC/SBS blends. The micelle plays an important role in improving the miscibility. The proposed micelle model has been empolyed to interpret the testing results, such as toughness, impact strength, dynamic mechanical property and SEM morphologies. This proposed micelle model seems a worth-while method to explain the properties of partialtly miscible blends of PC and SBS.     

Fluid flow and connectivity in fractured rock

A numerical simulation using the boundary integral element method is used to solve fluid flow through a network of discrete fractures. The fracture network is composed of three orthogonal fracture sets, with fracture length, density, and location characterized by appropriate probability distributions. Emphasis is placed on understanding how fracture connectivity influences fluid flow within a network of fractures. Based on the percolation process, a three-dimensional discrete fracture model has been developed to investigate the effect of the percolation factor and the percolation frequency on connectivity and flowrate. The numerical model results indicate that there exists a sharp threshold flowrate for the case of constant mean fracture length and varying fracture volume density as well as for the case of constant fracture volume density and varying mean fracture length. The values of percolation threshold and critical percolation frequency are predicted to be approximately 1.1 and 0.35, respectively, for circular fractures. The results also indicate that an increase in the percolation factor increases the degree of interconnection and, thus, increases the flowrate of a fracture network.     

Extended Boussinesq Equations for Water-Wave Propagation in Porous Media

This paper presents a new Boussinesq-type model equations for describing nonlinear surface wave motions in porous media. The mathematical model based on perturbation approach reported by Hsiao et al. is derived. The drag force and turbulence effect suggested by Sollitt and Cross are incorporated for observing the flow behaviors within porous media. Additionally, the approach of Chen for eliminating the depth-dependent terms in the momentum equations is also adopted. The model capability on an applicable water depth range is satisfactorily validated against the linear wave theory. The nonlinear properties of model equations are numerically confirmed by the weakly nonlinear theory of Liu and Wen. Numerical experiments of regular waves propagating in porous media over an impermeable submerged breakwater are performed and the nonlinear behaviors of wave energy transfer between different harmonics are also examined.     

Numerical Simulations of Nonlinear Short Waves Using a Multilayer Model

The multilayer model developed by Lynett and Liu is used for simulating the evolution of deep-water waves in a constant depth. The computational model is tested with experimental data for nonlinear monochromatic and biharmonic waves with kh values as high as 8.3. The experiments were conducted in a super wave tank with dimensions of 300?m×5?m×5.2?m located at Tainan Hydraulics Laboratory of National Cheng-Kung University. The nonlinearity of the waves tested, ka, range from 0.0627 to 0.1577. The overall comparisons between the multilayer model and the experiments are quite good, indicating that the multilayer model is adequate for both linear and nonlinear deep-water waves.     

Recognition of quadratic surface of revolution using a robotic vision system

Reverse engineering using 3D scanners has been gaining increasing popularity. One challenging task that remains is to recognize the geometric feature from the cloud data scanned. In this study, a robotic vision system is used to recognize quadratic surfaces of revolution on an object.The top-view image of an object is used to detect the surface boundary by loop analysis technique. The boundary of a single surface is extracted according to the 2D loop of that surface. The robot then projects laser lines through the principal axes of the loop to get the sectional curves. The surface is recognized by a curve-fitting method based on the characteristics of these curves.This study provides a simple and faster method to detect the manufacture features on an object that contains quadratic surfaces. The data structure can be output in IGES format for re-design or rapid manufacture of the object.