USB热门应用③USB装置摆脱电源线束缚

不论我们购买任何移动办公室的配备,都要携带一堆累赘的电源线.而对于某些可借助通用串行总线(USB)连结端口连至台式机或笔记本电脑的消费性电子装置,以后可能不再需要专门的电源线了,因为通过USB线撷取电源的电子装置已日渐风行.     

The lattice of semigroup varieties

Semigroups are considered here in terms of the identities which they may satisfy with the emphasis on the identities and on classes of semigroups defined by identities, rather than on the semigroups themselves. These classes, called varieties, form a lattice under inclusion and it is illuminating to interpret properties of semigroup identities and varieties in terms of this lattice, its cardinality, its atoms, its infinite chains, and so on. This paper is an expansion of addresses to the Southeastern Section of the Mathematical Association of America at East Carolina University, March 1968 and to the Symposium on Semigroups and Rings at the University of Puerto Rico, Mayaguez, March 1970. The preparation of the paper was supported in part by NSF Grants GP 6597 and GP 20638.     

Location Science Research: A Review

This document presents a broad review of facility location and location science research. The goal of this report is not to provide an exhaustive list of location science topics (an undertaking far beyond the scope of a single journal article), but rather to provide the reader with a more general review of the location science research landscape. This document starts with a short introduction to some of the more germane aspects of all location science research.     

Proton magnetic resonance studies of compounds with bridgehead nitrogen. 38—solvent effects in the 1H NMR spectra of nitrogen heterocyclic systems containing a 1,3-arrangement of heteroatoms

Solvent effects on the ¹H NMR parameters of perhydro-oxazolo[3,4?a]pyridine, perhydropyrido[1,2?c]?[1,3]oxazine and perhydrothiazolo[3,4?a]pyridine derivatives are described. Particularly marked are changes in the proton-proton geminal coupling constants of the NCH₂O and NCH₂S methylene protons with solvent and these are attributed to reaction field and solvation effects rather than to changes in the position of conformational equilibria.     

Compounds with bridgehead nitrogen. 40—Stereochemistry of perhydronaphthaleno[3,4-e]pyrido[1,2c]-[1,3]oxazines

Seven of the possible diastereoisomeric perhydronaphthaleno[3,4-e]pyrido[1,2-c][1,3]oxazines have been synthesized and the configurations and preferred conformations of these assigned on the basis of IR and ¹H NMR spectroscopy and the application of conformational principles.