Novel Low-Complexity Partial Transmit Sequences Scheme for PAPR Reduction in OFDM Systems Using Adaptive Differential Evolution Algorithm

A low-complexity partial transmit sequence (PTS) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is presented. However, the conventional PTS scheme requires an exhaustive searching over all combinations of allowed phase factors. Consequently, the computational complexity increases exponentially with the number of the subblocks. This paper presents a novel approach to the PAPR problem to reduce computational complexity based on the relationship between phase weighing factors and transmitted bit vectors. In this paper, we aim to obtain the desirable PAPR reduction with the low computational complexity. Since the process of searching the optimal phase factors can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a stochastic optimization technique called modified differential evolution, to search the optimal combination of phase factors with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction.     

Improving MANET performance by a hop‐aware and energy‐based buffer management scheme

A hop‐aware and energy‐based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real‐time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real‐time and non‐real‐time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end‐to‐end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop‐aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end‐to‐end delays for real‐time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.     

Numerical accuracy of multipole expansion for 2D MLFMA

A numerical study of the multipole expansion for the multilevel fast multipole algorithm (MLFMA) is presented. In the numerical implementation of MLFMA, the error comes from three sources: the truncation of the addition theorem; the approximation of the integration; the aggregation and disaggregation process. These errors are due to the factorization of the Green's function which is the mathematical core of the algorithm. Among the three error sources, we focus on the truncation error and a new approach of selecting truncation numbers for the addition theorem is proposed. Using this approach, the error prediction and control can be improved for the small buffer sizes and high accuracy requirements.     

应用于生产土工布的针刺技术

本文阐述了针刺土工布的性能要求及工艺过程，对影响产品质量的因素进行了讨论和说明；针对土工布的生产，推荐和介绍了迪罗ＤＩ－ＬＯＯＭ系列针刺机及其特殊性能指标以及防粘针刺土工布的生产线，并提供了设备的有关数据。     

K-band MMIC active band-pass filters

Two K-band active band-pass filters using 0.15-/spl mu/m GaAs pHEMT technology, with one fixed-frequency and the other tunable, are designed, fabricated, and tested. The fixed-frequency filter has its central frequency at 22.6 GHz, with 900-MHz bandwidth (4%). The tunable filter can be tuned from 19.5 to 21.5 GHz with the same bandwidth. Both circuits have a common size of 1 mm /spl times/ 1 mm. To our knowledge, the tunable filter is the highest frequency tunable active filter ever reported.     

Accurate model of arbitrary wire antennas in free space, above orinside ground

An accurate model of wire antennas in free space, above or inside lossy ground is presented in which the current is assumed to flow on the surface of the wire and the testing is also performed on the surface. To replace the traditional delta-gap source, a more accurate source model is developed by using the Huygens' principle. From this principle and reciprocity theorem, a variational formulation of the input admittance is derived. When the triangle function is chosen as both basis and weighting functions, all the elements of impedance matrix and source vector are formulated in closed forms, which can be rapidly computed. Several numerical results are given. Comparing with measured data, both the current distribution and input impedance by this model are more accurate than those of delta-gap model     

Minimum time control of conductive heating systems formicroelectronics processing

A minimum time control scheme is designed to improve repeatability by minimizing the loading effects induced by the common processing condition of placement of a semiconductor wafer at ambient temperature on a large thermal-mass bake plate at processing temperature. The minimum time control strategy provides an optimal solution for minimizing the worst case deviation from a nominal temperature set-point during the load disturbance condition. This results in a predictive controller that performs a predetermined heating sequence prior to the arrival of the wafer as part of the resulting feedforward/feedback strategy to eliminate the load disturbance. The controller is easy to design and implement and makes it more suitable for online implementation such as automatic online tuning of a feedforward controller. Experimental results depict an order-of-magnitude improvement in the settling time and the integral-square temperature error between the optimal predictive controller and a feedback controller for a typical load disturbance     

嵌入式系统中USB总线的应用

详细阐述了一种用于嵌入式系统中的USB总线接口电路,该电路是基于USB专用芯片CH375实现的,并给出了系统硬件实现和应用程序。实验结果表明,该电路具有成本低、可靠性高等特点,可方便地集成到各种嵌入式系统中。     

Biomimetic Lamellar Chitosan Scaffold for Soft Gingival Tissue Regeneration

Mucogingival surgery has become a common procedure for soft gingival tissue reparation in dental clinical practice, which mainly relies on autograft or commercial collagen membranes (CM). However, the autograft faces grand challenges in source availability and long-term post-surgery pain management, and the CM is restricted by its poor mechanical properties in an aqueous environment. Here, it is reported that a bio-inspired lamellar chitosan scaffold (LCS) with long range ordered porous structure, manufactured through a bidirectional freezing method, can serve as a promising gingival tissue engineering material. The LCS not only exhibits excellent mechanical properties in the hydrated state but also accelerates vessel formation and soft tissue regeneration in vivo. Most interestingly, the LCS is found to be capable of inducing macrophage differentiation to M2 macrophages, which is thought to play an important role in tissue regeneration. These advantages combined with its easy and low-cost preparation process make the LCS a promising candidate for dental clinical applications.     

Physical parameters extraction from current–voltage characteristic for diodes using multiple nonlinear regression analysis

In this work, the two-step iteration combined with the nonlinear multiple regression technique to extract physical parameters for diodes, using a simple physical-based current–voltage (I–V) model is demonstrated. This statistical method can be applied for sampling for a wide variety of diodes including light-emitting diodes (LEDs) and Schottky diodes. Our results show the technique is an accurate and systematic approach for extracting diode parameters. The calculated recombination currents indicate the recombination efficiency for LEDs and the quality for Schottky diodes.