This paper presents an experimental investigation of the following questions: how does the average-case complexity of random 3-SAT, understood as a function of the order (number of variables) for fixed density (ratio of number of clauses to order) instances, depend on the density? Is there a phase transition in which the complexity shifts from polynomial to exponential in the order? Is the transition dependent or independent of the solver? Our experiment design uses three complete SAT solvers embodying different algorithms: GRASP, CPLEX, and CUDD. We observe new phase transitions for all three solvers, where the median running time shifts from polynomial in the order to exponential. The location of the phase transition appears to be solver-dependent. GRASP shifts from polynomial to exponential complexity near the density of 3.8, CPLEX shifts near density 3, while CUDD exhibits this transition between densities of 0.1 and 0.5. This experimental result underscores the dependence between the solver and the complexity phase transition, and challenges the widely held belief that random 3-SAT exhibits a phase transition in computational complexity very close to the crossover point. 相似文献
Simultaneous switching noise (SSN) compromises the integrity of the power distribution structure on multilayer printed circuit boards (PCB). Several methods have been used to investigate SSN. These methods ranged from simple lumped circuit models to full-wave (dynamic) three-dimensional Maxwell equations simulators. In this work, we present an efficient and simple finite-difference frequency-domain (FDFD) based algorithm that can simulate, with high accuracy, the capacity of a PCB board to introduce SSN. The FDFD code developed here also allows for simulation of real-world decoupling capacitors that are typically used to mitigate SSN effects at sub 1 GHz frequencies. Furthermore, the algorithm is capable of including lumped circuit elements having user-specified complex impedance. Numerical results are presented for several test boards and packages, with and without decoupling capacitors. Validation of the FDFD code is demonstrated through comparison with other algorithms and laboratory measurements. 相似文献
Ta‐doped cubic phase Li7La3Zr2O12 (LLZ) lithium garnet received considerable attention in recent times as prospective electrolyte for all‐solid‐state lithium battery. Although the conductivity has been improved by stabilizing the cubic phase with the Ta5+ doping for Zr4+ in LLZ, the density of the pellet was found to be relatively poor with large amount of pores. In addition to the high Li+ conductivity, density is also an essential parameter for the successful application of LLZ as solid electrolyte membrane in all‐solid‐state lithium battery. Systematic investigations carried out through this work indicated that the optimal Li concentration of 6.4 (i.e., Li6.4La3Zr1.4Ta0.6O12) is required to obtain phase pure, relatively dense and high Li+ conductive cubic phase in Li7?xLa3Zr2?xTaxO12 solid solutions. Effort has been also made in this work to enhance the density and Li+ conductivity of Li6.4La3Zr1.4Ta0.6O12 further through the Li4SiO4 addition. A maximized room‐temperature (33°C) total (bulk + grain boundary) Li+ conductivity of 3.7 × 10?4 S/cm and maximized relative density of 94% was observed for Li6.4La3Zr1.4Ta0.6O12 added with 1 wt% of Li4SiO4. 相似文献
This study presents a comprehensive analysis of the entropy of condensed phases, its temperature, pressure, and composition dependence on a macroscopic correlative platform. Two principal contributions to total nonconfiguration entropy (ST) are outlined. They are: (i) the pure thermal (Sth) contribution arising from the isochoric temperature dependence of Gibbs energy (GT) and (ii) the elastic contribution (Sel) representing the dilatational volume effects. It is then argued that entropy variation among a group of alloy phases can be exclusively related to molar volume, only when both thermal pressure (pth) and thermal entropy terms assume common values for all members. This argument is extended to establish a linear relationship between transformation entropy (ΔStr) and transformation-induced volumetric strain (ΔVtr/V). The temperature and pressure dependencies of entropy have been discussed in terms of the complementing roles of Sth and Sel and simple approximations to these effects are suggested. A macroscopic power law relation for systematizing the standard entropy variation using a composite scaling parameter (MV2/3/Tm) has been proposed, and its validity is demonstrated for both solid and liquid metals. This power law correlation has been exploited to deduce the following outcome: (i) a simple approximation for the initial slope (dp/dTm) of p–Tm melting curve, (ii) self-consistent correlation of entropy with specific heat and Debye temperature, (iii) estimation of entropy of metastable phases, and (iv) correlating dilute solution entropy with volume effects of alloying.
The three GxxxG repeating motifs from the C-terminal region of β-amyloid (Aβ) peptide play a significant role in regulating the aggregation kinetics of the peptide. Mutation of these glycine residues to leucine greatly accelerates the fibrillation process but generates a varied toxicity profile. Using an array of biophysical techniques, we demonstrated the uniqueness of the composite glycine residues in these structural repeats. We used solvent relaxation NMR spectroscopy to investigate the role played by the surrounding water molecules in determining the corresponding aggregation pathway. Notably, the conformational changes induced by Gly33 and Gly37 mutations result in significantly decreased toxicity in a neuronal cell line. Our results indicate that G33xxxG37 is the primary motif responsible for Aβ neurotoxicity, hence providing a direct structure–function correlation. Targeting this motif, therefore, can be a promising strategy to prevent neuronal cell death associated with Alzheimer's and other related diseases, such as type II diabetes and Parkinson's. 相似文献
Seventy-two pearl millet genotypes were water stressed at panicle development and grain filling stages. Neither grain yields, yield components, protein percent nor total protein per unit area were affected by water deficit during panicle development but protein content per grain was increased. When plants were water stressed during grain filling, grain yield, grains per unit area and 1000 grain weight were reduced, but grain protein percentage increased. Total protein per unit area was reduced primarily due to lower grain yield. The protein content per grain was unaffected by stress, suggesting that the apparent increase in protein percentage is due to reduced carbohydrate accumulation under stress. 相似文献
The first step in the process of vegetable oil refining is degumming, in which phospholipids and mucilaginous gums are removed
that otherwise result in a low-grade oil. A membrane process is remarkably simple yet potentially offers many advantages in
degumming. Studies were conducted on surfactant-aided membrane degumming with soybean and rapeseed oils in a magnetically
stirred flat membrane batch cell with different types of microfiltration membranes. The reduction of phospholipids in soybean
oil was in the range of 85.8–92.8% during the membrane process. The phosphorus content of membrane permeates of soybean oil
was in the range of 20–58 mg/kg. Crude rapeseed oil contained higher amount of nonhydratable phospholipids and hence resulted
in lower reduction in phospholipids, in the range of 66.4–83.2%. Addition of hydratable phospholipids could improve the efficiency
of degumming in the membrane process without using any electrolyte, resulting in improvement of quality as well as quantity
of the phospholipids. 相似文献