Formal specification and refinement of a safe train control function

Motivated by the design and development challenges of the BART case study, an approach for developing and analyzing a formal model for reactive systems is presented. The approach makes use of a domain specific language for specifying control algorithms able to satisfy competing properties such as safety and optimality. The domain language, called SPC, offers several key abstractions such as the state, the profile, and the constraint to facilitate problem specification. Using a high-level program transformation system such as HATS being developed at the University of Nebraska at Omaha, specifications in this modelling language can be transformed to ML code. The resulting executable specification can be further refined by applying generic transformations to the abstractions provided by the domain language. Problem dependent transformations utilizing the domain specific knowledge and properties may also be applied. The result is a significantly more efficient implementation which can be used for simulation and gaining deeper insight into design decisions and various control policies. The correctness of transformations can be established using a rewrite-rule based induction theorem prover Rewrite Rule Laboratory developed at the University of New Mexico.

facilitating formal specification acquisition by using recursive functions on context-free languages

Although formal specification techniques are very useful in software development, the acquisition of formal specifications is a difficult task. This paper presents the formal specification language LFC, which is designed to facilitate the acquisition and validation of formal specifications. LFC uses context-free languages for syntactic aspect and relies on a new kind of recursive functions, i.e. recursive functions on context-free languages, for semantic aspect of specifications. Construction and validation of LFC specifications are machine-aided. The basic ideas behind LFC, the main aspects of LFC, and the use of LFC and illustrative examples are described.

Formalization and specification for controlling process modularity in mobile computing

新的计算模式，普适计算和全局计算，正在作为高度分布式和移动计算的计算模式展现出来。这篇论文探讨了在抽象层面上支持这些新型计算模式的适合的形式化基础，关注在进程移动单位上的控制, 以便在分布式与移动计算环境下更好地协调进程的移动性。 论文的第一部分概述了针对分布式、移动计算的现有进程演算模型中的进程移动单元，并且设计了一种在此方面更优、更具弹性的进程框架。为了表示这种进程框架，我们提出了一种新的、针对移动和分布式系统的进程演算,这种进程演算的优点是动态、弹性的控制进程的移动单元；具体的思路就是扩展π- calculus以及其支持分布式和移动性的变体。我们把这种新的演算叫做Modular π-calculus。我们通过这种演算的提出来说明进程框架提供了一种针对移动进程更为合适的协调机制以及编程模型，例如移动的代理和动态组件载入的支持。之后，我们通过讨论互模拟的几种提法来具体说明能够反映演算设计的进程描述的关键，之后我们讨论了它们的具体性质。 本文的第二部分提出了一个对进程模型的行为和性质进行推理的规约框架。首先，提出了一个对Modularπ-calculus中进程的系统性质进行规约的模态逻辑。为了更好的理解该逻辑，文中对由这个逻辑推出的进程等价的特征进行了研究，并且证明了该逻辑的区分能力介于互模拟和结构一致之间。接下来关于这个规约框架的自动化，本文针对该逻辑和Modular π-calculus的有限控制子集，提出了模型检测算法，并且给出了算法正确性的证明。同时文中贯穿了一些实际且直观的例子，以展现本文提出的一组框架即演算、逻辑和模型算法的有效性。

Ultrasonic Tomography and Its Applications in oilfield

UTT (Ultrasonic Tomography Tool) is widely used in the oil industry and can be used to inspect corrosion, casing wall damage, casing breakoff, and casing distortion in the well borehole with the maximum environment temperature being 125 °C, and the pressure being 60 MPa. UTT consists of tool head, upper centralization, electronic section, lower centralization, transmitters, and receivers. Its outer diameter is 4.6 cm and length is 320 cm. The measured casing diameter ranges from 60 mm to 254 mm. The tomography resolution is 512×512. The borehole measurement accuracy is 2 mm. It can supply 3D pipe tomography, including horizontal and vertical profile. This paper introduces its specification, measurement principle, and applications in oilfield.damage, casing breakoff, and casing distortion in the well borehole with the maximum environment temperature being 125 °C, and the pressure being 60 MPa. UTT consists of tool head, upper centralization, electronic section, lower centralization, transmitters, and receivers. Its outer diameter is 4.6 cm and length is 320 cm. The measured casing diameter ranges from 60 mm to 254 mm. The tomography resolution is 512×512. The borehole measurement accuracy is 2 mm. It can supply 3D pipe tomography, including horizontal and vertical profile. This paper introduces its specification, measurement principle, and applications in oilfield.

Mesofracture mechanics: a necessary link

Classical fracture mechanics is based on the premise that small scale features could be averaged to give a larger scale property such that the assumption of material homogeneity would hold. Involvement of the material microstructure, however, necessitates different characteristic lengths for describing different geometric features. Macroscopic parameters could not be freely exchanged with those at the microscopic scale level. Such a practice could cause misinterpretation of test data. Ambiguities arising from the lack of a more precise range of limitations for the definitions of physical parameters are discussed in connection with material length scales. Physical events overlooked between the macroscopic and microscopic scale could be the link that is needed to bridge the gap. The classical models for the creation of free surface for a liquid and solid are oversimplified. They consider only the translational motion of individual atoms. Movements of groups or clusters of molecules deserve attention. Multiscale cracking behavior also requires the distinction of material damage involving at least two different scales in a single simulation. In this connection, special attention should be given to the use of asymptotic solution in contrast to the full field solution when applying fracture criteria. The former may leave out detail features that would have otherwise been included by the latter. Illustrations are provided for predicting the crack initiation sites of piezoceramics. No definite conclusions can be drawn from the atomistic simulation models such as those used in molecular dynamics until the non-equilibrium boundary conditions can be better understood. The specification of strain rates and temperatures should be synchronized as the specimen size is reduced to microns. Many of the results obtained at the atomic scale should be first identified with those at the mesoscale before they are assumed to be connected with macroscopic observations. Hopefully, "mesofracture mechanics" could serve as the link to bring macrofracture mechanics closer to microfracture mechanics.

A field model interpretation of crack initiation and growth behavior in ferroelectric ceramics: change of poling direction and boundary condition

Strain energy density expressions are obtained from a field model that can qualitatively exhibit how the electrical and mechanical disturbances would affect the crack growth behavior in ferroelectric ceramics. Simplification is achieved by considering only three material constants to account for elastic, piezoelectric and dielectric effects. Cross interaction of electric field (or displacement) with mechanical stress (or strain) is identified with the piezoelectric effect; it occurs only when the pole is aligned normal to the crack. Switching of the pole axis by 90degrees and 180degrees is examined for possible connection with domain switching. Opposing crack growth behavior can be obtained when the specification of mechanical stress sigma(infinity) and electric field E-infinity or (sigma(infinity), E-infinity) is replaced by strain e and electric displacement D-infinity or (epsilon(infinity), D-infinity). Mixed conditions (sigma(infinity),D-infinity) and (epsilon(infinity),E-infinity) are also considered. In general, crack growth is found to be larger when compared to that without the application of electric disturbances. This includes both the electric field and displacement. For the eight possible boundary conditions, crack growth retardation is identified only with (E-y(infinity),sigma(y)(infinity)) for negative E-y(infinity) and (D-y(infinity), epsilon(y)(infinity)) for positive D-y(infinity) while the mechanical conditions sigma(y)(infinity) or epsilon(y)infinity are not changed. Suitable combinations of the elastic, piezoelectric and dielectric material constants could also be made to suppress crack growth. (C) 2002 Published by Elsevier Science Ltd.

Damage analysis of tetragonal perovskite structure ceramics implicated by asymptotic field solutions and boundary conditions

Cracking of ceramics with tetragonal perovskite grain structure is known to appear at different sites and scale level. The multiscale character of damage depends on the combined effects of electromechanical coupling, prevailing physical parameters and boundary conditions. These detail features are exhibited by application of the energy density criterion with judicious use of the mode I asymptotic and full field solution in the range of r/a = 10(-4) to 10(-2) where r and a are, respectively, the distance to the crack tip and half crack length. Very close to the stationary crack tip, bifurcation is predicted resembling the dislocation emission behavior invoked in the molecular dynamics model. At the macroscopic scale, crack growth is predicted to occur straight ahead with two yield zones to the sides. A multiscale feature of crack tip damage is provided for the first time. Numerical values of the relative distances and bifurcation angles are reported for the PZT-4 ceramic subjected to different electric field to applied stress ratio and boundary conditions that consist of the specification of electric field/mechanical stress, electric displacement/mechanical strain, and mixed conditions. To be emphasized is that the multiscale character of damage in piezoceramics does not appear in general. It occurs only for specific combinations of the external and internal field parameters, elastic/piezoelectric/dielectric constants and specified boundary conditions. (C) 2002 Published by Elsevier Science Ltd.

Adiabatic shear localization: occurrence, theories, and applications

Evolutionary Conservation of Dazl Genomic Organization and its Continuous and Dynamic Distribution Throughout Germline Development in Gynogenetic Gibel Carp

To investigate germline development and germ cell specification, we identified a Dazl homolog (CagDazl) from gynogenetic gibel carp (Carassius auratus gibelio). Its cDNA sequence and BAC clone sequence analyses revealed the genomic organization conservation and conserved synteny of the Dazl family members and their neighborhood genes among vertebrates, especially in fish. Moreover, a polyclonal antibody specific to CagDazl was produced and used to examine its expression and distribution throughout germline development at protein level. Firstly, ovary-specific expression pattern of CagDazl was confirmed in adult tissues by RT-PCR and Western blot. In addition, in situ hybridization and immunofluorescence localization demonstrated its specific expression in germ cells, and both its transcript and protein were localized to germ plasm. Then, co-localization of CagDazl and mitochondrial cloud was found, confirming that CagDazl transcript and its protein are germ plasm component and move via METRO pathway during oogenesis. Furthermore, the CagDazl is abundant and continuous throughout germline development and germ cell specification including primordial germ cell (PGC) formation, oogonium differentiation, oocyte development, and embryogenesis, and the dynamic distribution occurs at different development stages. The data suggest that maternal CagDazl might play an important role in gibel carp PGC formation. Therefore, CagDazl is a useful and specific marker for tracing germ plasm and germ cell development in the gynogenetic gibel carp. In addition, in comparison with previous studies in sexual reproduction species, the continuous and dynamic distribution of CagDazl protein in the germ plasm throughout the life cycle seems to have significant implication in sex evolution of vertebrates. J. Exp. Zool. (Mol. Deu. Euol.) 312B:855-871, 2009. (C) 2009 Wiley-Liss, Inc.

A zebrafish forebrain-specific zinc finger gene can induce ectopic dlx2 and dlx6 expression

Identifcation of the earliest forebrain-specific markers should facilitate the elucidation of molecular events underlying vertebrate forebrain determination and specification. Here we report the sequence and characterization of fez (forebrain embryonic zinc finger), a gene that is specifically expressed in the embryonic forebrain of zebrafish. Fez encodes a putative nuclear zinc finger protein that is highly conserved in Drosophila, zebrafish, Xenopus, mouse, and human. In zebrafish, the expression of fez becomes detectable at the anterior edge of the presumptive neuroectoderm by 70% epiboly. During the segmentation period, its expression is completely restricted to the rostral region of the prospective forebrain. At approximately 24 h postfertilization, fez expression is mostly confined to the telencephalon and the anterior-ventral region of the diencephalon. Although fez expression is present in one-eyed pinhead (oep) and cyclops (cyc) zebrfish mutants, the pattern is altered. Forced expression of fez induces ectopic expression of dlx2 and dlx6, two genes involved in brain development. Knockdown of fez function using a morpholino-based antisense oligo inhibited dlx2 expression in the ventral forebrain. Our studies indicate that fez is one of the earliest markers specific for the anterior neuroectoderm and it may play a role in forebrain development by regulating Dlx gene expression. (C) 2001 Academic Press.