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51.
The fact that Z is a specification language only, with no associated program development method, is a widely recognised problem.
As an answer to that, we present ZRC, a refinement calculus based on Morgan's work that incorporates the Z notation and follows
its style and conventions. This work builds upon existing refinement techniques for Z, but distinguishes itself mainly in
that ZRC is completely formalised. In this paper, we explain how programs can be derived from Z specifications using ZRC.
We present ZRC-L, the language of our calculus, and its conversion laws, which are concerned with the transformation of Z
schemas into programs of this language. Moreover, we present the weakest precondition semantics of ZRC-L, which is the basis
for the derivation of the laws of ZRC. More than a refinement calculus, ZRC is a theory of refinement for Z.
Received July 1997 / Accepted in revised form October 1998 相似文献
52.
Bartasyte A Chaix-Pluchery O Kreisel J Santiso J Margueron S Boudard M Jiménez C Abrutis A Weiss F 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(12):2623-2631
A systematic study of domain structure and residual stress evolution with film thickness and of phase transition in c/a epitaxial PbTiO(3)/LaAlO(3) films using X-ray diffraction and Raman spectroscopy is reported. Both techniques revealed that the films are under tensile residual stress in the film plane and that a-domains are more stressed than c-domains. The two components of the large A(1)(TO) Ramanmodes are associated with a- and c-domains and their intensity ratio correlates to the volume fraction of a-domains. The evolution of the Raman signature with temperature revealed that the spectrum of a-domains disappears around 480 degrees C, whereas c-domains present an anomaly in their spectrum at 500 degrees C but maintain a well-defined Raman signature up to 600 degrees C. 相似文献
53.
Previs MJ VanBuren P Begin KJ Vigoreaux JO LeWinter MM Matthews DE 《Analytical chemistry》2008,80(15):5864-5872
The identification and quantification of specific phosphorylation sites within a protein by mass spectrometry has proved challenging when measured from peptides after protein digestion because each peptide has a unique ionization efficiency that alters with modification, such as phosphorylation, and because phosphorylation can alter cleavage by trypsin, shifting peptide distribution. In addition, some phosphorylated peptides generated by tryptic digest are small and hydrophilic and, thus, are not retained well on commonly used C18 columns. We have developed a novel C-terminal peptide (2)H-labeling derivatization strategy and a mass balance approach to quantify phosphorylation. We illustrate the application of our method using electrospray ionization liquid chromatography-mass spectrometry by quantifying phosphorylation of troponin I with protein kinase A and protein kinase C. The method also improves the retention and elution of hydrophilic peptides. The method defines phosphorylation without having to measure the phosphorylated peptides directly or being affected by variable miscleavage. Measurement of phosphorylation is shown to be linear (relative standard error <5%) with a detection limit of <10%. 相似文献
54.
Cult3D是一个实现基于普通电脑的交互式人体结构三维显示的有效平台。在对内耳结构三维数据处理的基础上,使用Cult3D Designer编辑器,采用组织事件、动作与对象的关联的编程手段实现了对内耳三维对象的复杂交互动作控制,完成基于普通电脑的交互式虚拟内耳显微解剖浏览系统。 相似文献
55.
John Derrick Eerke Boiten Jim Woodcock Joakim von Wright 《Electronic Notes in Theoretical Computer Science》2002,70(3):1-2
This volume contains the Proceedings of the REFINE 2002 workshop. The Workshop was held in Copenhagen, Denmark on July 20 and 21, 2002, as a satellite event to FLoC'02 as an FME-affiliated workshop.Refinement is one of the cornerstones of a formal approach to software engineering. Refinement is the process of developing a more detailed design or implementation from an abstract specification through a sequence of mathematically-based steps that maintain correctness with respect to the original specification.The aim of this BCS FACS refinement workshop was to bring together people who are interested in the development of more concrete designs or executable programs from abstract specifications using formal notations, tool support for formal software development, and practical experience with formal refinement methodologies.The purpose of the workshop was to provide a forum for discussion of common ground and key differences. Topics of interest included:
- • Simulation techniques
- • Foundations and semantics
- • Case studies (specification and verification)
- • Compositional and modular reasoning
- • Object-orientation
- • Time
- • Specification notations
- • Programming models
- • Verification and tool support
- •
- John Derrick<
- jd1@ukc.ac.uk
, University of Kent, UK.
- •
- Eerke Boiten<
- eab2@ukc.ac.uk
, University of Kent, UK.
- •
- Jim Woodcock<
- jcpw@ukc.ac.uk
, University of Kent, UK.
- •
- Joakim von Wright<
- jockum.wright@abo.fi
, Åbo Akademi University, Finland
56.
This paper considers the problem of electing an eventual leader in an asynchronous shared memory system. While this problem
has received a lot of attention in message-passing systems, very few solutions have been proposed for shared memory systems.
As an eventual leader cannot be elected in a pure asynchronous system prone to process crashes, the paper first proposes to
enrich the asynchronous system model with an additional assumption. That assumption (denoted AWB) is particularly weak. It is made up of two complementary parts. More precisely, it requires that, after some time, (1) there
is a process whose write accesses to some shared variables be timely, and (2) the timers of (t−f) other processes be asymptotically well-behaved (t denotes the maximal number of processes that may crash, and f the actual number of process crashes in a run). The asymptotically well-behaved timer notion is a new notion that generalizes and weakens the traditional notion of timers whose durations are required to
monotonically increase when the values they are set to increase (a timer works incorrectly when it expires at arbitrary times,
i.e., independently of the value it has been set to).
The paper then focuses on the design of t-resilient AWB-based eventual leader protocols. “t-resilient” means that each protocol can cope with up to t process crashes (taking t=n−1 provides wait-free protocols, i.e., protocols that can cope with any number of process failures). Two protocols are presented.
The first enjoys the following noteworthy properties: after some time only the elected leader has to write the shared memory,
and all but one shared variables have a bounded domain, be the execution finite or infinite. This protocol is consequently
optimal with respect to the number of processes that have to write the shared memory. The second protocol guarantees that
all the shared variables have a bounded domain. This is obtained at the following additional price: t+1 processes are required to forever write the shared memory. A theorem is proved which states that this price has to be paid
by any protocol that elects an eventual leader in a bounded shared memory model. This second protocol is consequently optimal
with respect to the number of processes that have to write in such a constrained memory model. In a very interesting way,
these protocols show an inherent tradeoff relating the number of processes that have to write the shared memory and the bounded/unbounded
attribute of that memory. 相似文献
57.
Armando Jiménez Zavala 《电力部件与系统》2014,42(13):1474-1483
Abstract—Time series models provide a powerful tool to extract nonstationary features from measured data. In this article, a statistical framework based upon a dynamic harmonic regression model for examining modal behavior is provided. In this model, temporal patterns in measured data are modeled within a stochastic state space setting. Estimates of the states or time-varying parameters are then obtained using an optimal estimation method based on the Kalman filter. Techniques to estimate future values of the unobserved signal are also analyzed. The widely applicable technique is illustrated on both simulated and measured data. Factors that affect the performance of the method are discussed, including the effects of non-linear trends, data quality, and sampling design. Connections with other modal identification methods are also investigated. 相似文献
58.
59.
We consider the structured singular value problem with real parametric uncertainty only. Using techniques from algebraic geometry, we propose two algorithms that in principle can yield the precise value of the structured singular value at a fixed frequency. Their ability to do so depends upon their ability to find all common roots to a system of polynomial equations. The first algorithm is applicable to problems with two real parameters each of multiplicity two. The second algorithm is applicable to problems with n distinct real parameters. These algorithms have proved useful in applications to aerospace control law analysis. 相似文献
60.
Jim Williams 《电子产品世界》2006,(21):154-155
J-FET的自偏压特性可被用来设计一个从低至300mV的电压获取电源的DC/DC转换器.太阳能电池、热电堆和单级燃料电池等均具有低于600mV的输出电压,它们是这种转换器的常用电源. 相似文献