5,416 research outputs found
Comprehension of object-oriented software cohesion: The empirical quagmire
Chidamber and Kemerer (1991) proposed an object-oriented (OO) metric suite which included the Lack of Cohesion Of Methods (LCOM) metric. Despite considerable effort both theoretically and empirically since then, the software engineering community is still no nearer finding a generally accepted definition or measure of OO cohesion. Yet, achieving highly cohesive software is a cornerstone of software comprehension and hence, maintainability. In this paper, we suggest a number of suppositions as to why a definition has eluded (and we feel will continue to elude) us. We support these suppositions with empirical evidence from three large C++ systems and a cohesion metric based on the parameters of the class methods; we also draw from other related work. Two major conclusions emerge from the study. Firstly, any sensible cohesion metric does at least provide insight into the features of the systems being analysed. Secondly however, and less reassuringly, the deeper the investigative search for a definitive measure of cohesion, the more problematic its understanding becomes; this casts serious doubt on the use of cohesion as a meaningful feature of object-orientation and its viability as a tool for software comprehension
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Object-oriented cohesion as a surrogate of software comprehension: An empirical study
The concept of software cohesion in both the procedural and object-oriented paradigm is well known and documented. What is not so well known or documented is the perception of what empirically constitutes a cohesive 'unit' by software engineers. In this paper, we describe an empirical investigation using object-oriented (OO) classes as a basis. Twenty-four subjects (drawn from IT experienced and IT inexperienced groups) were asked to rate ten classes sampled from two industrial systems in terms of their overall cohesiveness; a class environment was used to carry out the study. Four key results were observed. Firstly, class size (when expressed in terms of number of methods) did not tend to influence the perception of cohesion by any subjects. Secondly, well-commented classes were rated most highly amongst both IT experienced and inexperienced subjects. Thirdly, the empirical study suggests that cohesion comprises a combination of various class factors including low coupling, small numbers of attributes and well-commented methods, rather than any single, individual class feature per se. Finally, the research supports the view that cohesion is a subjective concept reflecting a cognitive combination of class features; as such it is a surrogate for class comprehension
An Analytical Study for Subsonic Oblique Wing Transport Concept
The oblique wing concept has been investigated for subsonic transport application for a cruise Mach number of 0.95. Three different mission applications were considered and the concept analyzed against the selected mission requirements. Configuration studies determined the best area of applicability to be a commercial passenger transport mission. The critical parameter for the oblique wing concept was found to be aspect ratio which was limited to a value of 6.0 due to aeroelastic divergence. Comparison of the concept final configuration was made with fixed winged configurations designed to cruise at Mach 0.85 and 0.95. The crossover Mach number for the oblique wing concept was found to be Mach 0.91 for takeoff gross weight and direct operating cost. Benefits include reduced takeoff distance, installed thrust and mission block fuel and improved community noise characteristics. The variable geometry feature enables the final configuration to increase range by 10% at Mach 0.712 and to increase endurance by as much as 44%
Scaling of the Random-Field Ising Model at Zero Temperature
The exact determination of ground states of small systems is used in a
scaling study of the random-field Ising model. While three variants of the
model are found to be in the same universality class in 3 dimensions, the
Gaussian and bimodal models behave distinctly in 4 dimensions with the latter
apparently having a discontinuous jump in the magnetization. A finite-size
scaling analysis is presented for this transition.Comment: 14 pages Latex, 4 figure
The role of law and ethics in developing business management as a profession
Currently, business management is far from being recognised as a profession. This paper suggests that a professional spirit should be developed which could function as a filter of commercial reasoning. Broadly, management will not be organised within the framework of a well-established profession unless formal knowledge, licensing, professional autonomy and professional codes of conduct are developed sufficiently. In developing business management as a profession, law may play a key role. Where the idea is that business management should be more professsionalised, managers must show that they are willing to adopt ethical values, while arriving at business decisions. The paper argues that ethics cannot survive without legal regulation, which, in turn, will not be supported by law unless lawyers can find alternative solutions to the large mechanisms of the official society, secured by the monopolised coercion of the nation state. From a micro perspective of law and business ethics, communities can be developed with their own conventions, rules and standards that are generated and sanctioned within the boundaries of the communities themselves
Lattice Boltzmann simulations of lamellar and droplet phases
Lattice Boltzmann simulations are used to investigate spinodal decomposition
in a two-dimensional binary fluid with equilibrium lamellar and droplet phases.
We emphasise the importance of hydrodynamic flow to the phase separation
kinetics. For mixtures slightly asymmetric in composition the fluid phase
separates into bulk and lamellar phases with the lamellae forming distinctive
spiral structures to minimise their elastic energy.Comment: 19 pages, 5 figure
Sea Surface Salinity: The Next Remote Sensing Challenge
A brief history of salinity remote sensing is presented. The role of sea surface salinity (SSS) in the far north Atlantic and the influence of salinity variations on upper ocean dynamics in the tropics are described. An assessment of the present state of the technology of the SSS satellite remote sensing is given
Glassy behaviour in an exactly solved spin system with a ferromagnetic transition
We show that applying simple dynamical rules to Baxter's eight-vertex model
leads to a system which resembles a glass-forming liquid. There are analogies
with liquid, supercooled liquid, glassy and crystalline states. The disordered
phases exhibit strong dynamical heterogeneity at low temperatures, which may be
described in terms of an emergent mobility field. Their dynamics are
well-described by a simple model with trivial thermodynamics, but an emergent
kinetic constraint. We show that the (second order) thermodynamic transition to
the ordered phase may be interpreted in terms of confinement of the excitations
in the mobility field. We also describe the aging of disordered states towards
the ordered phase, in terms of simple rate equations.Comment: 11 page
Mass-radius relationships for exoplanets
For planets other than Earth, interpretation of the composition and structure
depends largely on comparing the mass and radius with the composition expected
given their distance from the parent star. The composition implies a
mass-radius relation which relies heavily on equations of state calculated from
electronic structure theory and measured experimentally on Earth. We lay out a
method for deriving and testing equations of state, and deduce mass-radius and
mass-pressure relations for key materials whose equation of state is reasonably
well established, and for differentiated Fe/rock. We find that variations in
the equation of state, such as may arise when extrapolating from low pressure
data, can have significant effects on predicted mass- radius relations, and on
planetary pressure profiles. The relations are compared with the observed
masses and radii of planets and exoplanets. Kepler-10b is apparently 'Earth-
like,' likely with a proportionately larger core than Earth's, nominally 2/3 of
the mass of the planet. CoRoT-7b is consistent with a rocky mantle over an
Fe-based core which is likely to be proportionately smaller than Earth's. GJ
1214b lies between the mass-radius curves for H2O and CH4, suggesting an 'icy'
composition with a relatively large core or a relatively large proportion of
H2O. CoRoT-2b is less dense than the hydrogen relation, which could be
explained by an anomalously high degree of heating or by higher than assumed
atmospheric opacity. HAT-P-2b is slightly denser than the mass-radius relation
for hydrogen, suggesting the presence of a significant amount of matter of
higher atomic number. CoRoT-3b lies close to the hydrogen relation. The
pressure at the center of Kepler-10b is 1.5+1.2-1.0 TPa. The central pressure
in CoRoT-7b is probably close to 0.8TPa, though may be up to 2TPa.Comment: Added more recent exoplanets. Tidied text and references. Added extra
"rock" compositions. Responded to referee comment
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