A note on the complexity of program evaluation

A simple problem concerning evaluation of programs is shown to be nonelementary recursive. The problem is the following: Given an input-free programP (i.e. all variables are initially 0) without nested loops using only instructions of the formx ← 1, x ← x + y, \(x \leftarrow x\dot - y\) ,do x... end, doesP output 0? This problem has time complexity \(2^{2^{ {\mathinner{\mkern2mu\raise1pt\hbox{.}\mkern2mu \raise4pt\hbox{.}\mkern2mu\raise7pt\hbox{.}\mkern1mu}} ^2 } } \) }cn-levels for some constantc. Other results are presented which show how the complexity of the 0-evaluation problem changes when the nonlooping instructions are varied. For example, it is shown that 0-evaluation is PSPACE-complete even for the case when the nonlooping instructions are onlyx ← x + 1,if x = 0then y ←y \(y \leftarrow y\dot - 1\) .     

Elastic wave emission from damage processes

The theory of elastic wave emission (i.e., acoustic emission; AE) from damage processes such as slip and microcracking is discussed. Analogous developments in the literature on earth-quake seismology and dynamic dislocation theory are noted and utilized. A general representation of the displacement field of an AE event is given in terms of the double-couple response to a distribution of moment density tensor in the source region. Results are specialized to a point source model and to a general far-field analysis of outgoing elastic waves, and conditions for validity of such representations and their low-frequency specializations are noted. Emitted wave fields are compared for tensile opening and slip events, and procedures which might enable the approximate determination of the size or area increase of tensile microcracks are discussed.     

On restricted one-counter machines

Let be the class of real-time nondeterministic one-counter machines whose counters make at mostone reversal. Let ₁ (respectively, ₂) be the subclass consisting of machines whose only nondeterministic move is in the choice of when to reverse the counter (respectively, when to start using the counter). ₁ and ₂ are among the simplest known classes of machines for which the universe problem has been shown undecidable. (The universe problem for a class of machines is the problem of deciding if an arbitrary machine in the class accepts all its inputs.) Here, we show that the classes of languages accepted by machines in ₁ and ₂ are incomparable. Moreover, the union of the language classes is properly contained in the class defined by . We also, briefly, look at the closure properties of these machines.This research was supported in part by NSF Grant MCS78-01736.     

Re-engineering the Engineering Change Management process for a drawing-less environment

Currently, 3D models and 2D drawings are the main basic elements that together form and carry the product definition throughout the product lifecycle. With the advent of the Digital Product Definition trend, industries have been interested in adopting a Model-based Definition (MBD) approach that enables the integration of drawing annotations directly onto a 3D model, thereby minimizing the need to generate engineering drawings. This drawing-less environment requires a way to adequately carry the product definition throughout a product's lifecycle while supporting all of the downstream users’ specific needs. The objective of this article is to present a solution to carry the Engineering Change Management (ECM) process in a drawing-less environment. Therefore, based on ECM process requirements from two Canadian aerospace companies, we propose an MBD dataset which consists of an MBD model and a distribution file. The proposed MBD dataset is evaluated and the MBD-driven ECM process is outlined.     

Impairment in long-term retention but not short-term performance on a water maze reversal task following hippocampal or mediodorsal striatal n-methyl-d-aspartate receptor blockade.

Male Long-Evans rats were injected with 32 ng/μl of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediodorsal striatum had similar latencies to locate the platform on the reversal day. Rats infused with CPP into the dorsal hippocampus or mediodorsal striatum failed to search preferentially in the novel location during a 24-hr, drug-free retention test, whereas all other groups searched preferentially in this location. Therefore, blocking dorsal hippocampal or mediodorsal striatal NMDA receptors selectively blocked long-term spatial retention without producing short-term performance deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

以编程方式填充Excel 2003工作表

引言 Micmsoft Visual Studio 2005 Tools for the Microsoft Office System（Visual Studio 2005 Tools for Office）为要编写Microsoft Office Word 2003和Microsoft Office Excel 2003后台代码的开发提供了许多工具．以满足各种业务场景的需要。比如．您可能想犏写业务逻辑．以符理用Excel工作表中预算数据，或者希望使用通过Web服务获得的销售数据填充Word文档中的表格。如果已经在使用Microsoft Visual Studio．NET，就可以使用Visual Studio 2005 Tools for Office来满足这些场景以及许多其他的场景的需要。     

Web sites of the Fortune 500 companies: Facing customers through home pages

The growing popularity of the information superhighway has opened up exciting opportunities for companies looking to, not only maintain their current customer base, but also to reach new customers. One of the most popular methods to enter into cybermarketing has been to establish a home page or Web site on the Internet. Almost two-thirds of Fortune 500 companies currently maintain home pages on the Web. An analysis of the content of corporate home pages provides useful insights. Over four-fifths of the companies display products and services (93.2%) and company overview (86.1%) information. Roughly three-fourths of the companies present interactive feedback (79.3%) and what's new (71.1%). Less than one-third (26.2%) of Fortune 500 companies provide for online business. An analysis of the data also provides valuable insight into the future trends of home page usage by large business organizations.     

An innovative software architecture to improve information flow from CAM to CNC

Over the years, machine tool evolution has allowed faster equipment, using new configurations, to manufacture parts that were almost impossible to machine in the past. Despite this tremendous evolution in machine and control technologies, the metalworking industry is still using the old ISO 6983 G-Codes programming interface to control the motion of these machines. This programming interface is not the most flexible or most appropriate for use by new open-architecture machine controllers and object-oriented high-level machining interfaces such as ISO 14649 (STEP-NC). This work proposes an innovative language, the ‘Base Numerical Control Language (BNCL),’ which is based on a low-level simple instruction set-like approach. The architecture is designed around two concepts: the BNCL virtual machine, which acts as a virtual microprocessor, and the BNCL virtual hardware, which is an abstraction of the machine tool. The language is characterised by its simplicity and flexibility, two qualities that are critical in a market in which the capabilities and performance of machines are constantly improving. The proposed architectural concepts are validated through various computer simulation and physical tests, including performance throughput, trajectory driving, and CNC controller extension capabilities.     

Piecewise H infinity: controller design of discrete time fuzzy systems.

This paper presents a new H infinity controller design method for the discrete time fuzzy systems based on the piecewise Lyapunov functions. The basic idea of the proposed approach is to construct the controller for the fuzzy systems in such a way that a discrete time piecewise Lyapunov function can be used to establish the global stability with H infinity-disturbance attenuation performance of the resulting close loop fuzzy control systems. It is shown that the control laws can be obtained by solving a set of linear matrix inequalities (LMIs) that is numerically tractable with commercially available software. Numerical example is given to demonstrate the advantage of the proposed method.