1,722,253 research outputs found
Miscibilities and rheological properties of poly(butylene succinate)-poly(butylene terephthalate) blends
No full textAn aliphatic/aromatic polyester blend has been dealt with in this study. As an aliphatic polyester, poly(butylene succinate) (PBS) was used, which is thought to possess biodegradability, but it is relatively expensive. It has been blended with poly(butylene terephthalate) (PBT) in order to obtain a biodegradable blend with better mechanical properties and lower cost. The miscibilities of PBS-PBT blends were examined not only from the changes of T-g but also from log G'-log G " plots. Dynamic mechanical thermal analyzer (DMTA) was an appropriate, sensitive method to obtain the glass transitions properly. Thermal stabilities of PBS and PET were also verified at the temperature of 240 degrees C. A transesterification reaction between two polyesters at 240 degrees C was hardly detectable so that it did not affect the miscibilities and properties of the blends. (C) 1999 John Wiley & Sons, Inc
Miscibility and biodegradability of poly(butylene succinate)/poly(butylene terephthalate) blends
No full textAs one of the biodegradable polymers, the blend of poly(butylene succinate) and poly(butylene terephthalate) is dealt with in this study. In our previous work, it was demonstrated that PBS and PET are immiscible not only from the changes of T-g but also from logG'-log G " plots. It is expected that the biodegradability of the blends could be improved by enhancing the miscibility. We tried to induce the transesterification reaction between two polyesters with various time intervals to enhance the miscibility of the blends. The extent of transesterification reaction was examined by H-1-NMR. We utilized a dynamic mechanical thermal analyzer and a rotational rheometer to investigate the changes in miscibility. We also verified the biodegradability of PBS/PBT blends after the transesterification reaction by the composting method
Miscibility and rheological properties of poly(butylene succinate/poly(butylene terephthalate) blends
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A RIGID PLASTIC FINITE-ELEMENT FORMULATION CONSIDERING THE EFFECT OF GEOMETRIC CHANGE AND ITS APPLICATION TO HYDROSTATIC BULGING
No full textExperimental Study of Grid Frequency Regulation Ancillary Service of a Variable Speed Heat Pump
No full textThis paper describes an analysis of a variable speed heat pump (VSHP), which responds to direct load control (DLC) signals to provide grid frequency regulation (GFR) ancillary service, while ensuring the comfort of building occupants. A data-driven dynamic model of the VSHP is developed through real-time experimental studies with a time horizon ranging from seconds to hours. The model is simple, yet still sufficiently comprehensive to analyze the operational characteristics of the VSHP. The DLC scheme is then experimentally applied to the VSHP to evaluate its demand response (DR) capability. Two control methods are considered for a practical implementation of the DLC-enabled VSHP and a further improvement of the DR capability, respectively. Additionally, a small-signal analysis is carried out using the aggregated dynamic response of a number of DLC-enabled VSHPs to analyze their contribution to GFR in an isolated power grid. For experimental case studies, a laboratory-scale microgrid is then implemented with generator and load emulators. We show that the DLC-enabled VSHP can effectively reduce grid frequency deviations and required reserve capacities of generators.112012sciescopu
EXPERIMENTAL-STUDY OF PARTICLE DEPOSITION ONTO A CIRCULAR-CYLINDER IN HIGH-TEMPERATURE PARTICLE-LADEN FLOWS
No full textDeposition (transport) of particles onto a cold circular cylindrical surface in high-temperature particle-laden cross flows was investigated experimentally. Local particle deposition efficiencies for two Reynolds numbers (Re = 36, 54) and three wall/gas temperature ratio parameters (T(w)/T(infinity) = 0.731, 0.853, 0.987) were obtained by using scanning electron microscopy (SEM) techniques. Solid TiO2 particles, generated by a fluidized-bed particle generator, ranged in diameter from 0.065 to 20-mu-m. Mainstream particle number density and velocity fields were measured by laser-Doppler anemometry (LDA). Calibration for particle concentration was accomplished with the particle size and number density data obtained from inertial impaction and filtration methods. Thermophoresis and inertial impaction are the important deposition mechanisms for these experimental conditions. The effects of particle size, target temperature ratio parameter, and flow Reynolds number on the particle deposition rates at each local angular position were estimated. The experimental particle deposition rates for small particles are compared to the theoretical thermophoresis correlation
Modeling and Analysis of a Variable Speed Heat Pump for Frequency Regulation Through Direct Load Control
No full textThis paper presents a dynamic model of a variable speed heat pump (VSHP) in a commercial building that responds to direct load control (DLC) signals, updated every 4 s, for the improvement of grid frequency regulation (GFR). The model is simplified for real-time simulation studies with the time horizon ranging from seconds to hours, but still sufficiently comprehensive to analyze the operational characteristics such as the heat rate and coefficient of performance. A variable speed drive-controlled induction motor model is also established for the adjustment of the VSHP input power. A dynamic model of an experimental room is then developed to estimate the effect of the DLC application to the VSHP on its indoor air temperature for two different cooling systems. Furthermore, small signal analysis is performed to evaluate both the transient response of the DLC-enabled VSHP and its contribution to GFR. Finally, with an isolated microgrid implemented with MATLAB/SIMULINK, simulation studies demonstrate that the VSHP can be effectively exploited as the DLC-enabled load while still ensuring building occupant comfort and long-term device performance.113126sciescopu
A RIGID PLASTIC FINITE-ELEMENT FORMULATION FOR THE ANALYSIS OF GENERAL DEFORMATION OF PLANAR ANISOTROPIC SHEET METALS AND ITS APPLICATIONS
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