The objective of the present work is to get insights into the mechanistic origin of the reinforcement effects of nanoclay on a segmented polybutadiene polyurethane-urea system. To this end, a convergent analysis of the hard domain morphology and conformational state of soft segment in the nanocomposites was carried out by using a combination of complementary characterization techniques, namely, Fourier transform infrared spectroscopy, small angle neutron scattering, transmission electron microscopy, modulated differential scanning calorimetry and dynamic mechanical analysis. Analysis of small angle neutron scattering data by a combination of Percus–Yevick hard sphere and Zernike-Ornstein model coupled with direct visualization of the dispersed hard domain morphology from transmission electron microscopy provided insight on clay induced changes in the hard domain morphology. A monotonic decrease in the domain size as well as the average interdomain distance was observed with increasing nanoclay content in the polymer matrix. Analysis of the carbonyl stretching region from FTIR showed increased degree of hydrogen bonding for the urethane carbonyl groups of the nanocomposites compared to the neat matrix. A combination of calorimetric and dynamic mechanical analysis revealed the existence of a constrained amorphous region; quantified to be ≈ 16% at the highest clay content experimented. The manifestation of these morphological and conformational changes on the nano-, micro- and macro scale reinforcements in the nanocomposites was investigated by mechanical properties at these length scales using nanoindentation, DMA and tensile testing, respectively. 相似文献
Energy management in buildings is indispensable which would control the energy use as well as the cost involved while maintaining comfort conditions and requirements in indoor environments. Energy management is intensely coupled with energy efficiency and increasing of which would provide a cost-effective pathway for reducing greenhouse gas emissions. In recent years, the magnitude of energy consumption in buildings seems to crest from the normal demand and that has to be carefully addressed through implementing energy conservative and energy management techniques. In the class of having several energy efficient schemes, thermal energy storage (TES) technologies for buildings are increasingly attractive among architects and engineers. In the scenario of growing energy demand worldwide, the possibility of improving the energy efficiency of TES systems can be achieved from break-through research efforts. The prime intention of this paper is to review the potential research studies pertaining to a variety of latent heat energy storage (LHES) and cool thermal energy storage (CTES) systems solely dedicated for building heating, cooling and air conditioning (A/C) applications. Technical revelations regarding the integration and performance evaluation of heat storage materials in building fabric elements as well as using separate heat storage facility to satisfy the space thermal load demand have been gleaned from numerous research contributions and presented. Emphasis is also given on advanced heat storage materials produced using micro and nanoparticles to realize their improved heat transfer characteristics which would eventually enhance the overall performance of these TES systems. Furthermore, the sustainable aspects of these TES systems to gain the Leadership in Energy and Environmental Design (LEED) credentials for low carbon/high performance buildings are signified. 相似文献
Long Term Evolution-Advanced (LTE-A) offers several new technologies to improve the performance of the user. However, poor received signal and interference from adjacent cells in the cell-edge area can reduce the efficiency of using individual technology. Therefore, the cell-edge users have lower throughput compared to the other users in the cell and LTE-A standard. An efficient downlink radio resource management scheme is proposed in this paper by combining the coordinated multipoint transmission and reception technique along with carrier aggregation technique to achieve higher throughput for the cell-edge user and better overall performance. The proposed method jointly transmits multiple component carriers to the cell-edge user from different cells to increase the bandwidth, strengthen the received signal, and reduce the interference while it satisfies several constraints. Modified largest weighted delay first packet scheduling algorithm is deployed for resource allocation, which takes into account the delay parameters, the probability of packet loss, and data rates of the user. The obtained system-level simulation results show that the proposed method significantly enhances the throughput performances, spectral efficiency, and fairness index, compared with the existing conventional methods.
Analog Integrated Circuits and Signal Processing - This paper proposes a dynamic voltage frequency scaling technique (DVFS) for a CMOS differential bootstrapped ring-voltage controlled oscillator... 相似文献
Floorplanning is crucial in VLSI chip design as it determines the time-to-market and the quality of the product. In this work, Variable-Order Ant System (VOAS) is developed and combined with a floorplan model namely Corner List (CL) to optimize the area and wirelength. CL is used to represent the floorplan layout. Although CL has proven to have the same search space and time complexity as Corner Sequence (CS), comparatively, CL has more corners to be selected. This compensates the sequence weakness, where modules can be placed freely onto the corners, which are not bounded by the floorplan contour. Two groups of ants, namely VOAS and reconnaissance ants, which will collaborate with each other to determine the local information, are introduced. Through this cooperation, VOAS ant can ascertain its local information greedily, based on the local search space information carried out by reconnaissance ants. Subsequently, VOAS ant proposes a new variable-order property to prioritize the global and local explorations. The variable-order property enables the ants in VOAS to weigh a better choice of modules for the floorplanning, based on the local and global information. The update rules of VOAS are modified in order to handle two-dimensional problem, such as VLSI floorplanning. VOAS shows improved results in terms of purely area optimization as well as composite function of area and wirelength, as compared to other state-of-the-art and recent floorplanning/placement algorithms based on Microelectronics Centre of North Carolina (MCNC) and Gigascale Systems Research Center (GSRC) benchmarks. 相似文献
This paper presents a comprehensive review of ambient RF energy harvester circuitry working on integrated circuits. The review covers 3 main blocks in an RF energy harvesting system implemented on chip. The blocks are the rectifier, impedance matching circuit and power management unit. The review of each block includes its operational principle, reported state-of-the-art circuit enhancement techniques, and design trade-offs. We compare the circuits in each block with respect to the techniques adopted to improve the performances for RF energy harvesting. To identify the benefits and limitations associated with the architecture we discuss the advantages and disadvantages of the circuit topologies in each block of an ambient RF energy harvester. 相似文献
Regenerative medicine via its application in soft tissue reconstruction through novel methods in adipose tissue engineering (ATE) has gained remarkable attention and investment despite simultaneous reports on clinical incidence of graft resorption and impaired vascularization. The underlying malaise here once identified may play a critical role in optimizing implant function. Our work attempts to determine the fate of donor cells and the implant in recipient micro environment using adipose-derived mesenchymal stem cells (ASCs) on a type I collagen sponge, an established scaffold for ATE. Cell components within the construct were identified 21 days post implantation to delineate cell survival, proliferation & terminal roles in vivo. ASC’s are multipotent, while collagen type I is a natural extra cellular matrix component. Commercially available bovine type I collagen was characterized for its physiochemical properties and cyto-compatibility. Nile red staining of induced ASCs identified red globular structures in cell cytoplasm indicating oil droplet accumulation. Similarly, in vivo implantation of the cell seeded collagen construct in rat model for 21 days in the dorsal muscle, showed genesis of chicken wire network of fat-like cells, which was demonstrated histologically using a variety of staining techniques. Furthermore, fluorescent in situ hybridization (FISH) technique established the efficiency of transplantation wherein the male donor cells with labeled Y chromosome was identified 21 days post implantation from female rat model. Retrieved samples at 21 days indicated adipogenesis in situ, with donor cells highlighted via FISH. The study provides an insight to stem cells in ATE from genesis to functionalization. 相似文献