Sort vs. hash revisited

Efficient algorithms for processing large volumes of data are very important both for relational and new object-oriented database systems. Many query-processing operations can be implemented using sort- or hash-based algorithms, e.g. intersections, joins, and duplicate elimination. In the early relational database systems, only sort-based algorithms were employed. In the last decade, hash-based algorithms have gained acceptance and popularity, and are often considered generally superior to sort-based algorithms such as merge-join. In this article, we compare the concepts behind sort- and hash-based query-processing algorithms and conclude that (1) many dualities exist between the two types of algorithms, (2) their costs differ mostly by percentages rather than by factors, (3) several special cases exist that favor one or the other choice, and (4) there is a strong reason why both hash- and sort-based algorithms should be available in a query-processing system. Our conclusions are supported by experiments performed using the Volcano query execution engine     

Volcano-an extensible and parallel query evaluation system

To investigate the interactions of extensibility and parallelism in database query processing, we have developed a new dataflow query execution system called Volcano. The Volcano effort provides a rich environment for research and education in database systems design, heuristics for query optimization, parallel query execution, and resource allocation. Volcano uses a standard interface between algebra operators, allowing easy addition of new operators and operator implementations. Operations on individual items, e.g., predicates, are imported into the query processing operators using support functions. The semantics of support functions is not prescribed; any data type including complex objects and any operation can be realized. Thus, Volcano is extensible with new operators, algorithms, data types, and type-specific methods. Volcano includes two novel meta-operators. The choose-plan meta-operator supports dynamic query evaluation plans that allow delaying selected optimization decisions until run-time, e.g., for embedded queries with free variables. The exchange meta-operator supports intra-operator parallelism on partitioned datasets and both vertical and horizontal inter-operator parallelism, translating between demand-driven dataflow within processes and data-driven dataflow between processes. All operators, with the exception of the exchange operator, have been designed and implemented in a single-process environment, and parallelized using the exchange operator. Even operators not yet designed can be parallelized using this new operator if they use and provide the interator interface. Thus, the issues of data manipulation and parallelism have become orthogonal, making Volcano the first implemented query execution engine that effectively combines extensibility and parallelism     

Stochastic servomechanism design via optimal filter theory

The feedback realization of the continuous optimal filter is applied to familar problems of the design of servomechanisms with stochastic inputs and disturbances. This approach leads immediately to optimal feedback configurations and, interestingly, to integral plus derivative control for the wind torque disturbed antenna servo problem. As in optimal filter theory, time-varying gains are generated for the finite time or "lock on" problem. Since digital computer programs are already available for computing these gains the design of complex intercoupled servos is feasible. The application to "minimum bandwidth" servo design is indicated.     

HERMES - a versatile personal robotic assistant

We have developed a humanoid robot, HERMES, to study several key technologies that are important for personal robots, such as robot design, sensors and perception, locomotion, localization and navigation, manipulation, human-robot communication and interaction, adaptability and learning, system architecture and integration, and dependability. The robot's skill-based system architecture was derived from a qualitative model of human information processing and insights gained from psychological literature dealing with skill acquisition, human performance and motor learning. HERMES' system architecture, several of its skills and the design principles are introduced, and some experiments carried out with the real robot are presented, including a long-term test where HERMES served in a museum, far away from its home laboratory, for more than six months up to 12 hours per day. During this period the robot and its skills were regularly demonstrated to the public by nonexpert presenters. Also, HERMES interacted with the visitors, chatted with them in English, French and German, answered questions and performed services as requested by them.     

Das Lipidmuster in Traubenkernen,Traubenkämmen und Traubenschalen nach einer heißen aeroben Rotte

Lipid Patterns in Grape Seed, Grape Combs and Grape Skin after Hot Aerobic Rotting In the course of microbial conversion processes of grape seed cake a certain population succession can be observed which is characteristic for the course of the highly exothermic process of the biological husks humification. The energy demand is mainly covered by the lipoid depot compounds whose alteration in content and pattern is investigated in the course of thermic rotting. The fatty acid esters disappear, whereas microbial processes cause an increased occurrence of free fatty acids at the end of the process, whereby palmitic, stearic, oleic and linoleic acid are predominant, in the grape seed product linoleic acid preponderates above all. Even after finishing the heat producing process a residual content of triglycerides in the substrate can be detected, whereas in the grape seed oil lipids of higher carbon number than in comb and skin material are present.     

Winds of change – Predicting water-based recreationists' support and opposition for offshore wind energy development in the Great Lakes

This study examined the factors influencing water-based recreationists' perceptions of support and opposition towards off-shore wind energy development (OWD) on Lake Erie. Much of the proposed or future Lake Erie OWD infrastructure may either be within or adjacent to public lands, waters, and protected areas, raising concerns about the potential environmental and social impacts upon recreation stakeholders. The limited body of OWD research within the United States has suggested there are numerous factors that may influence overall perceptions of support and opposition such as political orientation and beliefs in climate change. Moreover, recent research has proposed that the perceived recreation impact of OWD may be the most important predictor of support and opposition. This study confirmed this premise and found the perceived recreation impact of OWD to be the strongest predictor of support. Results of a multiple linear regression suggested that political orientation (β?=?0.135), beliefs in the anthropogenic causation of climate change (β?=?0.207), beliefs in the occurrence of climate change (β?=?0.213), and the perceived recreation impact of OWD among water-based recreationists (β?=?0.439) were significant predictors of support for OWD on Lake Erie (R²?=?0.46). Study findings corroborated previous research which suggested that regional climate change beliefs and political attitudes may influence support for OWD. From a policy and management standpoint, study results highlight the importance of assessing and communicating recreation experience and use impacts when planning, developing, and managing OWD and related decisions in the United States.     

Encapsulation of parallelism and architecture-independence inextensible database query execution

Emerging database application domains demand not only high functionality, but also high performance. To satisfy these two requirements, the Volcano query execution engine combines the efficient use of parallelism on a wide variety of computer architectures with an extensible set of query processing operators that can be nested into arbitrarily complex query evaluation plans. Volcano's novel exchange operator permits designing, developing, debugging, and tuning data manipulation operators in single-process environments but executing them in various forms of parallelism. The exchange operator shields the data manipulation operators from all parallelism issues. The design and implementation of the generalized exchange operator are examined. The authors justify their decision to support hierarchical architectures and argue that the exchange operator offers a significant advantage for development and maintenance of database query processing software. They discuss the integration of bit vector filtering into the exchange operator paradigm with only minor modifications     

Transactional support for adaptive indexing

Adaptive indexing initializes and optimizes indexes incrementally, as a side effect of query processing. The goal is to achieve the benefits of indexes while hiding or minimizing the costs of index creation. However, index-optimizing side effects seem to turn read-only queries into update transactions that might, for example, create lock contention. This paper studies concurrency control and recovery in the context of adaptive indexing. We show that the design and implementation of adaptive indexing rigorously separates index structures from index contents; this relaxes constraints and requirements during adaptive indexing compared to those of traditional index updates. Our design adapts to the fact that an adaptive index is refined continuously and exploits any concurrency opportunities in a dynamic way. A detailed experimental analysis demonstrates that (a) adaptive indexing maintains its adaptive properties even when running concurrent queries, (b) adaptive indexing can exploit the opportunity for parallelism due to concurrent queries, (c) the number of concurrency conflicts and any concurrency administration overheads follow an adaptive behavior, decreasing as the workload evolves and adapting to the workload needs.     

Energy and carbon footprints of ethanol production using banana and cooking banana discard: A case study from Costa Rica and Ecuador

Banana and cooking banana (Musa spp.) production systems accumulate a considerable quantity of discard due to high quality demands of markets. Ripe fruits have high sugar contents, which can be easily processed to ethanol. The present study aimed to quantitatively assess the production potential of ethanol from Musa spp. discard and to analyze the energy and carbon (C) footprints of this production system using a life cycle approach. The study compared three case studies differing in management practices, which were (I) a coffee producer’s cooperative in Costa Rica using Musa spp. as shade trees, (II) organic banana producers from Ecuador, and (III) conventional banana producers from Ecuador. It was found that banana and cooking banana discard accumulated at a rate of 1.4-3.4 t ha⁻¹, of which around 118-266 l ethanol could be produced on a yearly basis. The case study from Costa Rica yielded a net-energy balance (NEB) of 19.3 MJ l⁻¹ and avoided carbon emissions of 0.48 kg l⁻¹. It was closely followed by the organic banana producers from Ecuador with a NEB of 17.1 MJ l⁻¹ and avoided carbon emissions of 0.44 kg l⁻¹. NEB and avoided carbon emissions for the conventional banana farms in Ecuador were much lower (7.2 MJ l⁻¹ and 0.34 kg l⁻¹).Despite providing economic benefits to farmers through a biomass source that would have been otherwise lost, the study gave clear evidence that the ecological footprint of this ethanol production system is significantly influenced by the resource use during the production life cycle.     

On the derivative of the trace of a matrix quadratic form

In the optimisation of linear systems with a random plant gain, the problem of computing the derivative of the trace of a matrix quadratic form is encountered. A derivation of this derivative is presented.