Greedy Strategy Works for k-Center Clustering with Outliers and Coreset Construction

We study the problem of k-center clustering with outliers in arbitrary metrics and Euclidean space. Though a number of methods have been developed in the past decades, it is still quite challenging to design quality guaranteed algorithm with low complexity for this problem. Our idea is inspired by the greedy method, Gonzalez\u27s algorithm, for solving the problem of ordinary k-center clustering. Based on some novel observations, we show that this greedy strategy actually can handle k-center clustering with outliers efficiently, in terms of clustering quality and time complexity. We further show that the greedy approach yields small coreset for the problem in doubling metrics, so as to reduce the time complexity significantly. Our algorithms are easy to implement in practice. We test our method on both synthetic and real datasets. The experimental results suggest that our algorithms can achieve near optimal solutions and yield lower running times comparing with existing methods

Recognising object-oriented software design quality : a practitioner-based questionnaire survey

Design quality is vital if software is to be maintainable. What practices do developers actually use to achieve design quality in their day-to-day work and which of these do they find most useful? To discover the extent to which practitioners concern themselves with object-oriented design quality and the approaches used when determining quality in practice, a questionnaire survey of 102 software practitioners, approximately half from the UK and the remainder from elsewhere around the world was used. Individual and peer experience are major contributors to design quality. Classic design guidelines, well-known lower level practices, tools and metrics all can also contribute positively to design quality. There is a potential relationship between testing practices and design quality. Inexperience, time pressures, novel problems, novel technology, and imprecise or changing requirements may have a negative impact on quality. Respondents with most experience are more confident in their design decisions, place more value on reviews by team leads and are more likely to rate design quality as very important. For practitioners, these results identify the techniques and tools that other practitioners find effective. For researchers, the results highlight a need for more work investigating the role of experience in the design process and the contribution experience makes to quality. There is also the potential for more in-depth studies of how practitioners are actually using design guidance, including Clean Code. Lastly, the potential relationship between testing practices and design quality merits further investigation

Sub-Stream Fairness and Numerical Correctness in MIMO Interference Channels

Signal-to-interference plus noise ratio (SINR) and rate fairness in a system are substantial quality-of-service (QoS) metrics. The acclaimed SINR maximization (max-SINR) algorithm does not achieve fairness between user's streams, i.e., sub-stream fairness is not achieved. To this end, we propose a distributed power control algorithm to render sub-stream fairness in the system. Sub-stream fairness is a less restrictive design metric than stream fairness (i.e., fairness between all streams) thus sum-rate degradation is milder. Algorithmic parameters can significantly differentiate the results of numerical algorithms. A complete picture for comparison of algorithms can only be depicted by varying these parameters. For example, a predetermined iteration number or a negligible increment in the sum-rate can be the stopping criteria of an algorithm. While the distributed interference alignment (DIA) can reasonably achieve sub-stream fairness for the later, the imbalance between sub-streams increases as the preset iteration number decreases. Thus comparison of max-SINR and DIA with a low preset iteration number can only depict a part of the picture. We analyze such important parameters and their effects on SINR and rate metrics to exhibit numerical correctness in executing the benchmarks. Finally, we propose group filtering schemes that jointly design the streams of a user in contrast to max-SINR scheme that designs each stream of a user separately.Comment: To be presented at IEEE ISWTA'1

Object-Oriented Software Design Metrics

The adoption of the Object-Oriented paradigm is expected to help produce better and cheaper software. The main concepts of this paradigm, namely, inheritance, encapsulation, information hiding or polymorphism, are the keys to foster reuse and achieve easier maintainability. However, the use of constructs that support those concepts can be more or less intensive, mainly depending on the designer ability. Advances in quality and productivity need to be correlated with the use of those constructs. Therefore, we need to evaluate them quantitatively to guide OO design. The availability of these metrics should allow comparison of different systems or different implementations of the same system, thus helping to derive some design heuristics that could/should be included in design tools. Those heuristics would at least be a valuable help to new staff members. "Blind" choice (or creation) is dangerous, so a set of common requirements for metrics and corresponding rationale was introduced, which includes the need for formal definition, language independence, dimensionlessness, ease of calculation and early obtainability. A suitable metrics set named MOOD was then proposed. We believe that these metrics can help in setting OO design standards at the organization level, helping OO practitioners to guide their development process and, hopefully, leaving them in a cheerful MOOD..

A new routing metric for wireless mesh networks

In Wireless Mesh Networks the main goal is to achieve the best possible quality and efficiency of data transmission between source and destination nodes. To achieve such transmission, a routing algorithm should select better paths by taking the quality of wireless links into account. Simple path selection based on minimal hop count often leads to poor performance due to the fact that paths with low hop count often have higher packet loss rates. Better paths can be obtained by characterizing the actual quality of wireless link. A number of link quality aware routing metrics such as Expected Transmission Count (ETX), Expected Transmission Time (ETT), Weighted Cumulative Expected Transmission Time (WCETT), Metric of Interference and Channel Switching (MIC), Interference Aware Metric (iAWARE) etc have been explored. This study highlights some shortcomings of these routing metrics and proposes the design of a novel metric called ETX- 3 hop, which addresses the discussed weaknesses and works more efficiently under various link quality conditions. ETX-3hop consists of a more accurate method to measure the link quality and a path metric that better captures the quality of a path. The performance of the ETX-3hop metric is compared against the original ETX with different path metrics. In extensive simulations, ETX-3hop metric outperforms the original ETX metric in terms of network throughput

Optimal excitation controllers, and location and sizing of energy storage for all-electric ship power system

The Navy\u27s future all-electric ship power system is based on the integrated power system (IPS) architecture consisting of power generation, propulsion systems, hydrodynamics, and DC zonal electric distribution system (DC-ZEDS). To improve the power quality, optimal excitation systems, and optimal location and sizing of energy storage modules (ESMs) are studied. In this dissertation, clonal selection algorithm (CSA) based controller design is firstly introduced. CSA based controller design shows better exploitation ability with relatively long search time when compared to a particle swarm optimization (PSO) based design. Furthermore, \u27optimal\u27 small population PSO (SPPSO) based excitation controller is introduced. Parameter sensitivity analysis shows that the parameters of SPPSO for regeneration can be fined tuned to achieve fast optimal controller design, and thus exploiting SPPSO features for problem of particles get trapped in local minima and long search time. Furthermore, artificial immune system based concepts are used to develop adaptive and coordinated excitation controllers for generators on ship IPS. The computational approaches for excitation controller designs have been implemented on digital signal processors interfaced to an actual laboratory synchronous machine, and to multimachine electric ship power systems simulated on a real-time digital simulator. Finally, an approach to evaluate ESM location and sizing is proposed using three metrics: quality of service, survivability and cost. Multiple objective particle swarm optimization (MOPSO) is used to optimize these metrics and provide Pareto fronts for optimal ESM location and sizing --Abstract, page iv

Critical Opportunity Areas for Building Performance

Green buildings are a proposed holistic solution to reduce energy consumption while simultaneously improving an array of factors affecting the indoor quality of life for building occupants. However, green building performance varies and may not achieve intended design goals. Research has concluded that no single factor determines the actual energy performance of buildings. To deliver energy-efficient buildings an integrated design that considers climate, technology, operation and maintenance and occupant behavior should be implemented. This work aimed to employ a holistic lens to relate human-building interaction and building performance characteristics. Specifically, systems theory and complex-problem solving techniques were employed to capture the dynamic interactions between the social and technical parts and processes of building systems and identify gaps causing the underperformance of buildings. Synergies not captured in the current design process but impact the ability of a building system to achieve its design goals were outlined. Performance metrics that a single system inadvertently affects along social, physical and economic dimensions were identified as well as high-impact opportunity areas for the creation of high-performance buildings. Addressing these synergies in the building equipment and full building design will enable stakeholder-centered systems integration, improving the efficiency and efficacy of buildings

An investigation into establishing a generalised approach for defining similarity metrics between 3D shapes for case-based reasoning (CBR)

This thesis investigates the feasibility of establishing a generalised approach for defining similarity metrics between 3D shapes for the casting design problem in Case-Based Reasoning (CBR). This research investigates a new approach for improving the quality of casting design advice achieved from a CBR system using casting design knowledge associated with past cases. The new approach uses enhanced similarity metrics to those used in previous research in this area to achieve improvements in the advice given. The new similarity metrics proposed here are based on the decomposition of casting shape cases into a set of components. The research into metrics defines and uses the Component Type Similarity Metric (CTM) and Maximum Common Subgraph (MCS) metric between graph representations of the case shapes and are focused on the definition of partial similarity between the components of the same type that take into account the geometrical features and proportions of each single shape component. Additionally, the investigation extends the scope of the research to 3D shapes by defining and evaluating a new metric for the overall similarity between 3D shapes. Additionally, this research investigates a methodology for the integration of the CBR cycle and automation of the feature extraction from target and source case shapes. The ShapeCBR system has been developed to demonstrate the feasibility of integrating the CBR approach for retrieving and reusing casting design advice. The ShapeCBR system automates the decomposition process, the classification process and the shape matching process and is used to evaluate the new similarity metrics proposed in this research and the extension of the approach to 3D shapes. Evaluation of the new similarity metrics show that the efficiency of the system is enhanced using the new similarity metrics and that the new approach provides useful casting design information for 3D casting shapes. Additionally, ShapeCBR shows that it is possible to automate the decomposition and classification of components that allow a case shape to be represented in graph form and thus provide the basis for automating the overall CBR cycle. The thesis concludes with new research questions that emerge from this research and an agenda for further work to be pursued in further research in the area

Development of SecureMet: A Tool for Aligning Security Metrics and Organizations Security Objectives

The purpose of this project is to develop a tool henceforth called SecureMet to help an organization to determine the security metrics aligned with its security objectives based on the organization’s capabilities. The majority of organizations face a common problem in determining their security metrics aligned with their security objectives. SecureMet will be able to assist the organization in choosing the suitable security metrics and helping it to enhance its capabilities to achieve its security objectives. The tool is developed based on the Quality Function Development (QFD) approach, while existing frameworks such as the SSE-CMM and COBIT are used as guides in the determination and choice of the security capabilities and security objectives. The methodology employed for this project is based on the Rapid Application Develoment (RAD) model and is divided into four parts, namely, the requirement analysis phase, the design phase, the development phase and the verification phase