Aspect Orientation Research Articles

Refactoring middleware with aspects

Middleware platforms, such as Web services, J2EE, CORBA, and DCOM, have become increasingly popular during the last decade. They have been very successful in solving distributed computing problems for a large family of application domains. The architecture of middleware systems have gone through many significant cycles of evolution, both in terms of the completeness of functionality and the range of adoptions for different types of platforms. However, at the same time, it is getting increasingly difficult to achieve and to maintain a high level of adaptability and configurability because the structure of the middleware architecture is becoming overly complicated and rigid. We attribute that problem to the limitations of traditional software decomposition methods. Aspect-oriented programming, on the contrary, has introduced new design perspectives that permit the superimpositions of different abstraction models on top of one another. This is a very powerful technique for separating and simplifying design concerns. In our effort of applying principles of aspect orientation to the middleware architecture, we first pragmatically analyze the use of aspects in the middleware architecture. We then show that aspects are the correct remedy for the above outlined middleware problems by quantifying crosscutting concerns in the legacy implementations of several prominent middleware systems. Our aspect analysis results strongly indicate that modularity of middleware architecture is greatly hindered by the wide existence of tangled logic. To go one step further, we factor out a number of crosscutting concerns identified in the mining process, reimplement them as aspects, and superimpose them back into the refactored architecture. This allows us to use a set of software engineering metrics to quantify the refactorization in terms of changes in the structural complexity, modularity, and performance of the resulting system. This aspect-oriented refactoring proves that aspect orientation is capable of composing orthogonal design requirements. The final "woven" system is able to correctly provide both the fundamental functionality and the "aspectized" functionality with negligible overhead and an overall leaner architecture. Furthermore, the "aspectized" feature can be configured in and out during compile-time, which greatly enhances the configurability of the architecture.

Continuum theory for ionic field charging of spheroidal aerosols in nonuniform electric field

Classical theory for the ionic field charging previously developed for a spherical particle in a uniform electric field is extended for prolate and oblate spheroidal particles in uniform and nonuniform electric fields. Spheroidal particles are either dielectrics or perfect conductors. The nonuniform electric field is modeled as a two-dimensional linear field commonly developed in wire-cylinder and wire-plate electrodes systems. Assuming that the particle orientation remains unchanged during the charging process the saturation charge and the time evolution of the particle charge are determined as functions of the aspect ratio and orientation of the particle. Although the saturation charge depends strongly on the particle shape and orientation, the results for spherical particles apply to within an order of magnitude to spheroidal particles in most cases. For a collection of spheroidal particles with a uniform orientation distribution the ensemble averages for the saturation charge and the time evolution of the particle charge are also determined. A simple formula is proposed as an approximate expression for the ensemble average for the saturation charge. It is found that the ensemble average for the time evolution of the relative saturation for a spheroidal particle with a moderate aspect ratio can be approximated using the well-known formula for a spherical particle in a uniform electric field.

ASOPE and the Fabled Promise of Process Knowledge Capture and Reuse

This paper addresses the question of how process knowledge should be structured. The use of aspect orientation as an abstraction for capturing and using process knowledge is reported. A description of the method, ASOPE (aspect oriented process engineering), is given, and the context of its development from ideas generated by research on software engineering is described. ASOPE introduces two new abstractions — generic process patterns and process aspects. An illustrative example of the use of these ideas is given. Finally, the limitations of the work are described and a number of avenues for further development are proposed.

ステレオ観察による楕円体粒子の軸比と方位の決定

ステレオ観察による楕円体粒子の軸比と方位の決定

The motion of a rigid body in viscous fluid bounded by a plane wall

The boundary-integral method is used to calculate the hydrodynamic force and torque on an arbitrary body of revolution whose axis of symmetry is oriented at an arbitrary angle relative to a planar wall in the zero-Reynolds-number limit. The singular solution of the Stokes equations in the presence of a planar wall is used to formulate the integral equations, which are then reduced to a system of linear algebraic equations by satisfying the no-slip boundary conditions on the body surface using the boundary collocation method or weighted residual technique.Numerical tests for the special case of a sphere moving parallel or perpendicular to a planar wall show that the present theory is accurate to at least three significant figures when compared with the exact solutions for gap widths as small as only one-tenth of the particle radius. Higher accuracy can be achieved and solutions can be obtained for smaller gap widths at the expense of more computation time and larger storage requirements.The hydrodynamic force and torque on a spheroid with varying aspect ratio and orientation angle relative to the planar wall are obtained. The theory is also applied to study the motion of a toroidal particle or biconcave shaped disc adjacent to a planar wall. The coincidence of the drag and torque of a biconcave-shaped body and a torus having an aspect ratio b/a = 2 with the same surface area shows that in this case the hole of a torus has little influence on the flow field. On the other hand, for an aspect ratio b/a = 10, the effect of the hole is significant. It is also shown that when the body is not very close to the wall, an oblate spheroid can be used as a good approximation of a biconcave-shaped disc.

Anisotropic sintering shrinkage in injection-moulded composite ceramics

Abstract The sintering shrinkage of injection-moulded silicon nitride bars reinforced with 0–30 vol.% silicon carbide platelets or whiskers was measured in three orthogonal directions. The extent of shrinkage anisotropy is discussed in relation to inclusion aspect ratio, volume fraction and orientation.

Visual Simulation Requirements for Aircraft Aspect Recognition at Real World Distances

A research program is underway whose goal is to provide engineering guidelines on target image sufficiency for training tactics and maneuvering skills in ground based flight simulators. A preliminary experiment was carried out in the Naval Training Equipment Center's Visual Technology Research Simulator (VTRS), using computer-generated aircraft images displayed on a dome via a variable-resolution target projector. The experiment examined aspect recognition sensitivity, or the distance at which subjects could determine the orientation of another aircraft. For our initial effort, the aspect (orientation) recognition task was simplified in the following ways: a) on each trial one of only 16 stationary target orientations of a TA4J aircraft was presented, b) targets had the same length/width ratio; c) subjects made binary up/down judgments; d) a staircase method provided thresholds for aspect recognition range. Four different target luminances, and three background luminances were combined with four different levels of projector resolution in a partial parametric study to assess the relative effects of contrast, resolution and brightness. All main effects were found to be significant. Over the ranges studied, contrast accounted for the most variance and brightness the least. In the best condition studied, aspect recognition was performed successfully at >4 miles (a 5.5 arc minute target), whereas the most degraded condition showed thresholds at 1.5 miles (a 14 arc minute target). These are comparable to distances known to be required in outdoor training ranges and in combat. An additional finding is that reliable subject differences were substantial (>20% of the total accounted for variance). The four subjects who were tested in this study had normal or better vision by static and dynamic tests of contrast sensitivity. Individual differences in these subjects' contrast sensitivity scores were predictive of their visual performance on this target aspect recognition task. These data are discussed from the standpoint of the utility of this paradigm for providing guidelines for training equipment design.

Spectroscopy of the extreme ultraviolet dayglow at 6.5Å resolution: Atomic and ionic emissions between 530 and 1240Å

EUV spectra (530‐1500Å) of the day airglow in up, down and horizontal aspect orientations have been obtained with 6.5Å resolution and a limiting sensitivity of 5R from a rocket experiment. Below 834Å the spectrum is rich in previously unobserved OII transitions connecting with 4So, ²Do, and ²Po states. Recent broad‐band photometric observations of geocoronal HeI 584Å emission can be understood in terms of the newly observed OII emissions. The OI 989Å and OI 1304Å emissions exhibit similar dependence on altitude and viewing geometry with the OI 989Å brightness 1/15 that of OI 1304. Emission at 1026Å is identified as geocoronal HI Lyman‐β rather than OI multiplet emission and observed intensities agree well with model estimates. An unexpectedly high NI 1200/NI 1134Å brightness ratio is evidence of a significant contribution from photodissociative excitation of N2 to the NI 1200Å source function.