物件導向軟體之架構(Object-Oriented Software Construction)探討

Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

An overview of AspectJ

An application program interface (API) provides a set of functions for application developers who build Web applications on Microsoft Corporation's .NET™ platform.

Application program interface for network software platform

The term model-driven engineering (MDE) is typically used to describe software development approaches in which abstract models of software systems are created and systematically transformed to concrete implementations. In this paper we give an overview of current research in MDE and discuss some of the major challenges that must be tackled in order to realize the MDE vision of software development. We argue that full realizations of the MDE vision may not be possible in the near to medium-term primarily because of the wicked problems involved. On the other hand, attempting to realize the vision will provide insights that can be used to significantly reduce the gap between evolving software complexity and the technologies used to manage complexity.

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Model-driven Development of Complex Software: A Research Roadmap

From the Publisher:
Designing application and middleware software to run in concurrent and networked environments is a significant challenge to software developers The patterns catalogued in this second volume of Pattern-Oriented Software Architectures (POSA) form the basis of a pattern language that addresses issues associated with concurrency and networking
The book presents 17 interrelated patterns ranging from idioms through architectural designs They cover core elements of building concurrent and network systems: service access and configuration, event handling, synchronization,
and concurrency All patterns present extensive examples and known uses in multiple programming languages, including C++, C, and Java
The book can be used to tackle specific software development problems or read from cover to cover to provide a fundamental understanding of the best practices for constructing concurrent and networked applications and middleware
About the Authors
This book has been written by the award winning team responsible for the first POSA volume "A System of Patterns", joined in this volume by Douglas C Schmidt from University of California, Irvine (UCI), USA
Visit our Web Page

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Pattern-Oriented Software Architecture, Patterns for Concurrent and Networked Objects

A series of laboratory experiments has been conducted in order to elucidate the sediment-induced mixing processes accompanying riverine outflows; specifically, the discharge of a warm, fresh, particle-laden fluid over a relatively dense, cool brine. In a parameter regime analogous to recently acquired field measurements, hypopycnal (surface) plumes were subject to a convective instability driven by some combination of heat diffusing out of the warm, fresh, sediment-laden plume and particle settling within it. Convection was robust in the presence or absence of intense turbulence, at sediment concentrations as low as 1 kg m−3, and took the form of millimetre-scale, sediment-laden fingers descending from the base of the surface plume. A consequence of the convective instability of the original hypopycnal plume is the generation of a hyperpycnal (bottom-riding) flow. The experiments presented here indicate that natural river outflows may thus generate hyperpycnal plumes when sediment concentrations are 40 times less than those required to render the outflow heavy relative to the oceanic ambient. The resulting hyperpycnal plumes may play an important role in transporting substantial quantities of sediment to the continental slope and beyond.

Hyperpycnal plume formation from riverine outflows with small sediment concentrations

[1] As part of the STRATAFORM program, a bottom-boundary layer (BBL) tripod was deployed at 120 m depth in the northern thalweg of the Eel Canyon during winter 2000. Increases of the near-bottom suspended-sediment concentrations (SSC) recorded at the canyon head were not directly related to the Eel River discharge, but were clearly linked to the occurrence of storms. BBL measurements revealed that during intensifications of the wave orbital velocity, sediment transport at the head of the canyon occurred as sediment gravity flows directed down-canyon. Observational evidence for near-bed sediment gravity-flow transport included an increase toward the bed of the down-canyon component of wave-averaged velocity and high estimated SSC. At higher sampling frequencies (1 Hz), the current components during these events fluctuated at the same periodicity as the pressure, reflecting a clear influence of the surface-wave activity on the generation and maintenance of the sediment gravity flows. The origin of such flows is not related to the formation of fluid muds on the shelf or to intense wave-current sediment resuspension around the canyon head region. Rather, liquefaction of sediment deposited at the head of the canyon (induced by wave-load excess pore water pressures during storms) combined with elevated slopes around the canyon head appear to be the mechanisms initiating sediment transport. The resulting fluidized-sediment layer can easily be eroded, entrained into the water column, and transported down-canyon as a sediment gravity flow. Results from this study reveal that storm-induced sediment gravity flows occur periodically in the Eel Canyon head, and suggest that this kind of sediment transport process can occur in other submarine canyons more frequently than previously expected.

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Storm‐induced sediment gravity flows at the head of the Eel submarine canyon, northern California margin

We have performed a series of laboratory experiments that clarify the nature of the transition between fluid‐mud and grain‐flow behavior. The surface velocity structure and the speed of the nose of debris flows in channels with semicircular cross sections were measured with several cameras and visual tracers, while the mass flow rate was recorded using a load cell at the exit chamber. Other rheological tests were used to calculate independently the yield strength and matrix viscosity of the debris‐flow mixture. Shear rates were varied by nearly an order of magnitude for each mixture by changing the channel radius and slope. Shear rates were significantly higher than expected (6–55 s−1), given the modest slopes examined (10.7°–15.2°). The large values were primarily a result of the concentration of shear into narrow bands between a central nondeforming plug and the sidewall. As a result, the shear rate of interest was calculated by using the width of the shear band and the plug velocity, as oppose...

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Experimental Study of the Grain‐Flow, Fluid‐Mud Transition in Debris Flows

Submarine Mass Movements on Continental Margins

Mixing processes in gravity current fronts have only recently been quantified due to their complex, unsteady nature. The similarity of the mixing processes in these pioneer works, however, has not been explored adequately. Experiments that explore a wide range of fronts have been performed. These experiments have used techniques that exhaustively sample the temporal (using a high-speed conductivity probe) and spatial (using planar laser-induced fluorescence) density field more thoroughly than any previous work. Both types of experiments have confirmed earlier research suggesting that low Reynolds number fronts mix differently and less than higher Reynolds number flows. Similarity appeared to be achieved for Req>1000, where Req is a Reynolds number based upon the cube root of the buoyancy flux into the front and the height of current. It appears that certain secondary mixing processes, seen by other researchers studying stratified mixed layers, are responsible for the earlier changes seen with Reynolds num...

Jeffrey D. Parsons

Papers

Hyperpycnal plume formation from riverine outflows with small sediment concentrations

Storm‐induced sediment gravity flows at the head of the Eel submarine canyon, northern California margin

Experimental Study of the Grain‐Flow, Fluid‐Mud Transition in Debris Flows

Submarine Mass Movements on Continental Margins

Similarity of gravity current fronts