Optimal Solutions for the Temporal Precedence Problem

Abstract. In this paper we refer to the Temporal Precedence Problem on Pure Pointer Machines . This problem asks for the design of a data structure, maintaining a set of stored elements and supporting the following two operations: insert and precedes . The operation insert (a) introduces a new element a in the structure, while the operation precedes (a,b) returns true iff element a was inserted before element b temporally. In [11] a solution was provided to the problem with worst-case time complexity O (log log n ) per operation and O(n log log n) space, where n is the number of elements inserted. It was also demonstrated that the precedes operation has a lower bound of Ω (log log n ) for the Pure Pointer Machine model of computation. In this paper we present two simple solutions with linear space and worst-case constant insertion time. In addition, we describe two algorithms that can handle the precedes (a,b) operation in O (log log d ) time, where d is the temporal distance between the elements a and b .     

从数据结构角度设计导游系统

从数据结构角度为旅游胜地设计导游系统。向游人提供景点的信息查询服务,根据指定的景点提供相关的景点信息。任意给定起点和终点,查询两点之间的最短路径。     

Delamination Analysis for Laminated Composites. II: Numerical Verification

A validation of the delamination analysis models developed in a companion paper is provided through comparisons of predictions with finite‐element and elasticity solutions. The models are applied to the analysis of composite compression specimens reinforced with end tabs. An elasticity solution for the gage section of the specimens is developed. A comparison of the characteristic roots shows that the predictions of the models include the material and geometric parameters that control the behavior, and the roots corresponding to the basic stretching and bending modes are accurately predicted. The stress distribution at the interface between tabs and specimen is in good agreement with a finite‐element simulation. The interlaminar shear and peel stresses show an exponential increase with a maximum intensity at the free edges of the tabs. The behavior of previously tested specimens is explained; and practical guidelines for specimen design are provided to avoid unwanted extraneous modes of failure. The influence of the deformation modes associated with each model is investigated. An assessment of the accuracy and level of complexity is presented.     

Towards an optimum language data model

Maximizing the satisfaction of a value in an engineering design is usually limited by tradeoffs in which other values become unacceptably sacrificed. In a few cases, however, the maximization is limited by a boundary between what is mathematically possible and what is not. Round wheels, vertical pillars, and binary memory elements are examples of optimum engineering structures which result from such mathematical limits. It is proposed that optimum characteristics of a language data model result similarly by minimizing the variety of primitive data objects, the complexity of those objects, and the number of objects needed to represent data states. Reducing these measures is needed to combine both rich data structure and powerful operations in one language. The minimizations lead to a narrow range of designs for language semantics in which the potential advantages of specialization is small compared with the advantages of commonality. Universal language for support of technical literacy appears to be an appropriate scope of generality in language design.     

FODA — the formal specification of ODA document structures and its use as a basis for conformance testing

The Office Document Architecture (ODA) is an International Standard which is developed by TC 97/sc 18 of the International Organization for Standardization (ISO) in close collaboration with CCITT's Study Group VIII and with ECMA. This paper describes the current state of a formal specification of the ODA document structures by mathematical means and its use for conformance specification and conformance testing.     

On the cost of searching signature trees

A precise analysis of the retrieval of signature trees is presented. A signature tree is a data structure constructed over a signature file to speed up searching all those signatures, which match a given query signature. The methods used include a detailed study of probabilistic analysis in conjunction with suitable contour integration of complex variabled functions.     

Electrooptic studies on polymer‐dispersed liquid‐crystal composite films. III. Poly(methyl methacrylate‐co‐butyl acrylate)/E7 and poly(methyl methacrylate‐co‐butyl acrylate)/E8 composites

Composite films composed of poly(methyl methacrylate‐co‐butyl acrylate) (PMMABA) and nematic‐type liquid crystals E7 and E8 (commercial products from E. Merck, Darmstadt, Germany) were prepared through solvent casting in chloroform. The morphology and electrooptic responses were studied. Scanning electron microscopy observations showed that the liquid‐crystal phase (E7 or E8), as larger, elongated, interconnected cavities, was continuously embedded in a spongelike PMMABA matrix. At a specific level of the liquid‐crystal (E7 or E8) loading (30/70 wt %), the effects of the voltage, temperature, and frequency of an applied alternating‐current electric field on the transmittance of the composite films were measured with a He–Ne laser (wavelength = 632.8 nm). The results were interpreted in terms of the aggregation structure, interfacial interaction, and solubility of the liquid crystal in the matrix polymer. The results indicated that, under these experimental conditions, the output could be controlled to a desired level by the selection of suitable liquid crystals to prepare polymer‐dispersed liquid‐crystal, electrooptic, active composite films with a response time of the order of only milliseconds or less. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Application of ultrasonic waves in activation of microcrystalline cellulose

In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3‐diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymer transcrystallinity induced by carbon nanotubes

In this work, we provide the evidence of polymer transcrystallinity in the presence of carbon nanotubes (CNTs). The interfacial morphology of carbon nanotube fiber-polypropylene matrix is investigated by means of polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The supramolecular microstructures of polypropylene transcrystals induced by the nanotube fiber are observed in the range of isothermal crystallization temperatures from 118 °C to 132 °C. The dynamic process of transcrystallization is analyzed by using the theory of heterogeneous nucleation. Microstructure analysis shows that the nanotubes can nucleate the growth of both α- and γ-transcrystal, and α-transcrystals dominate the overall interfacial morphology. Close to the nanotube fiber surface, a cross-hatched lamellar microstructure composed of mother lamellae and daughter lamellae is observed.