RESUMO
In this paper, a novel wideband power amplifier (PA) operating in the 2-6 GHz frequency range is presented. The proposed PA design utilizes a combination technique consisting of a distributed equalization technique, multiplexing the power supply network and matching network technique, an LR dissipative structure, and an RC stability network technique to achieve significant bandwidth while maintaining superior gain flatness, high efficiency, high gain, and compact size. For verification, a three-stage PA using the combination technique is designed and implemented in a 0.25 µm GaN high-electron-mobility transistor (HEMT) process. The fabricated prototype demonstrates a saturated output power of 4 W, a power gain of 21 dB, a gain flatness of ±0.6 dB, a power-added efficiency of 39-46%, and a fractional bandwidth of 100% under the operating conditions of drain voltage 28 V (continuous wave) and gate voltage -2.6 V. Moreover, the chip occupies a compact size of only 2.51 mm × 1.97 mm.
RESUMO
The last decade of phylogenetics has seen the development of many methods that leverage constraints plus dynamic programming. The goal of this algorithmic technique is to produce a phylogeny that is optimal with respect to some objective function and that lies within a constrained version of tree space. The popular species tree estimation method ASTRAL, for example, returns a tree that (1) maximizes the quartet score computed with respect to the input gene trees and that (2) draws its branches (bipartitions) from the input constraint set. This technique has yet to be used for parsimony problems where the input are binary characters, sometimes with missing values. Here, we introduce the clade-constrained character parsimony problem and present an algorithm that solves this problem for the Dollo criterion score in [Formula: see text] time, where n is the number of leaves, k is the number of characters, and [Formula: see text] is the set of clades used as constraints. Dollo parsimony, which requires traits/mutations to be gained at most once but allows them to be lost any number of times, is widely used for tumor phylogenetics as well as species phylogenetics, for example analyses of low-homoplasy retroelement insertions across the vertebrate tree of life. This motivated us to implement our algorithm in a software package, called Dollo-CDP, and evaluate its utility for analyzing retroelement insertion presence / absence patterns for bats, birds, toothed whales as well as simulated data. Our results show that Dollo-CDP can improve upon heuristic search from a single starting tree, often recovering a better scoring tree. Moreover, Dollo-CDP scales to data sets with much larger numbers of taxa than branch-and-bound while still having an optimality guarantee, albeit a more restricted one. Lastly, we show that our algorithm for Dollo parsimony can easily be adapted to Camin-Sokal parsimony but not Fitch parsimony.
RESUMO
A novel type of high-χ block copolymer, polystyrene-block-polycarbonate (PS-b-PC), which contains an active -NH- group on the polymer backbone between the PS block and the PC block, has been successfully synthesized. Vertical micro-phase separation can be successfully achieved on Si substrates with neutral-layer-free materials with a pitch of 16.8 nm. Water contact angle experiments indicate that PS and PC have approximate surface energy values on Si substrates. A hydrogen bond mechanism has been proposed for the formation of a periodic and lamella-forming phase separation structure, with the domains oriented perpendicular to the substrate. A combination of both theory and experimental verification proves that the hydrogen bonding plays a dominant role as a real driving force to promote vertical micro-phase separation in the absence of a neutral layer. Subsequently, the study of a novel block copolymer on four different types of substrate without any neutral layer further confirms that the newly synthesized material enables greater flexibility and potential applications for the fabrication of various nanostructures and functional electronic devices in a simple, cost-effective and efficient way, which is of considerable importance to contemporary and emerging technology applications.
