Estimation and Optimization of the Principal H-Maser Parameters

The scale along the coordinate axes in the equations of motion hitherto used for an H-maser (in relative units) is shown to depend on Q as the quality factor for an H-maser. This hinders both analysis of the operation of the H-maser and optimization of its parameters. The modified equations of motion proposed here do not have that shortcoming. We determine the atomic flux into the bulb that gives the H-maser the best metrological characteristics.     

Allocentric Versus Egocentric Spatial Memory After Unilateral Temporal Lobectomy in Humans.

Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in the gaseous H2S barrier properties of damaged silicate coated nylon 6 films

The damage imposed on SiO _x deposited nylon 6 films as a result of abrasion with a cotton cloth and Gelboflex testing was examined by evaluating the rate at which copper plates, which were enveloped by the damaged films, were corroded by H₂S. Abrasion with a cotton cloth caused some micro-cracking of the SiO _x layer and the permeation rate of H₂S approached that of the uncoated nylon 6 film. Damage to the SiO _x layer by twisting and crushing progressed gradually with the number of Gelboflex test cycles and correspondingly the corrosion rate of the copper plates increased. Comparison of the corrosion rates of the copper plates kept in the pouches made of various commercial films with those obtained for the damaged SiO _x deposited nylon 6 films showed a clear relationship between the H₂ permeation rate of the films and the corrosion rate of the copper plates by H₂S.     

Three takes on telecom's troubles

Spectrum asked three IEEE members from the telecommunications sector to comment on the industry's current woes and prospects. Roch Guerin discusses bandwidth as a commodity and how to deal with it. The impact of technological change on telecommunications is enormous and calls for a shift in business models. Technology is making bandwidth a commodity and it should not matter who supplies it. Competition is vital and commodity providers must be decoupled from value providers. Frank Ferrante points out that the Year 2000 crisis resulted in manufacturers being deluged with orders for new upgraded systems. Vast sums were spent to meet the demand in time. However, when Y2K was over, production stayed high and inventories continued to build, while demand effectively stopped overnight. Dazzling new innovations are needed to compel the masses to spend and manufacturers must apply their resources to deliver quickly and efficiently. Jules A. Bellisio discusses the role of engineers in bringing new ideas to the market place. Many engineers have put together ventures for the sole purpose of attracting capital. The underlying technology and business propositions were there solely to lure the unsuspecting. By allowing engineers to use technology simply to cover for a scam, then the profession is also to blame for the current problems.     

Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 2: Charakterisierung der Gefügeausbildung mittels hochauflösender Durchstrahlungselektronenmikroskopie und Feinbereichsbeugung

Chemical Composition and Microstructure of Polymer‐Derived Glasses and Ceramics in the Si–C–O System. Part 2: Characterization of microstructure formation by means of high‐resolution transmission electron microscopy and selected area diffraction Liquid or solid silicone resins represent the economically most interesting class of organic precursors for the pyrolytic production of glass and ceramics materials on silicon basis. As dense, dimensionally stable components can be cost‐effectively achieved by admixing reactive filler powders, chemical composition and microstructure development of the polymer‐derived residues must be exactly known during thermal decomposition. Thus, in the present work, glasses and ceramics produced by pyrolysis of the model precursor polymethylsiloxane at temperatures from 525 to 1550 °C are investigated. In part 1, by means of analytical electron microscopy, the bonding state of silicon was determined on a nanometre scale and the phase separation of the metastable Si–C–O matrix into SiO₂, C and SiC was proved. The in‐situ crystallization could be considerably accelerated by adding fine‐grained powder of inert fillers, such as Al₂O₃ or SiC, which permits effective process control. In part 2, the microstructure is characterized by high‐resolution transmission electron microscopy and selected area diffraction. Turbostratic carbon and cubic β‐SiC precipitate as crystallization products. Theses phases are embedded in an amorphous matrix. Inert fillers reduce the crystallization temperature by several hundred °C. In this case, the polymer‐derived Si–C–O material acts as a binding agent between the powder particles. Reaction layer formation does not occur. On the investigated pyrolysis conditions, no crystallization of SiO₂ was observed.     

The rank and kernel of extended 1-perfect /spl Zopf//sub 4/-linear and additive non-/spl Zopf//sub 4/-linear codes

A binary extended 1-perfect code of length n + 1 = 2/sup t/ is additive if it is a subgroup of /spl Zopf//sub 2//sup /spl alpha// /spl times/ /spl Zopf//sub 4//sup /spl beta//. The punctured code by deleting a /spl Zopf//sub 2/ coordinate (if there is one) gives a perfect additive code. 1-perfect additive codes were completely characterized and by using that characterization we compute the possible parameters /spl alpha/, /spl beta/, rank, and dimension of the kernel for extended 1-perfect additive codes. A very special case is that of extended 1-perfect /spl Zopf//sub 4/-linear codes.     

可替代石磨水洗的经纱染色和匹染

1　引言石磨水洗牛仔布的成本是非常高的 ,但由于客户喜欢陈旧、磨损的外观 ,所以这种高成本又是十分必要的。那么 ,如何将这么高的成本降下来呢 ?通常的做法是把工厂转移到劳动力低廉的发展中国家。如果有着悠久历史的纺织品公司因为劳动力成本较高而不再具有竞争力 ,他们将不得不寻找另外一种可替代石磨水洗而同样能获得满意外观的方法。这是一种似乎对于我们具有实际意义的想法 ,它似乎具有逻辑性又很合理 ,但是这可能吗 ?当然 ,这种方法必须工艺简单 ,保证附加成本较低 ;必须可连续生产 ,以保证产量较高 ;必须可在常规设备上采用现有工…     

Parameterisation of slant-Haar transforms

A parameterisation of the slant-Haar transform is presented, which includes an existing version of the slant-Haar transform. An efficient algorithm for the slant-Haar transform is developed and its computational complexity is estimated. The parametric slant-Haar transforms are compared to the Karhunen-Loeve transform. The parametric slant-Haar is shown to perform better than the commonly used slant-Haar and slant-Hadamard transforms for the first-order Markov model and also performs better than the discrete cosine transform for images approximated by the generalised image correlation model