346 research outputs found
Ordering kinetics in two-dimensional hexagonal pattern of cylinder-forming PS-b-PMMA block copolymer thin films: Dependence on the segregation strength
No full textIdentifying task-based sessions in search engine query logs
No full textThe research challenge addressed in this paper is to devise effective techniques for identifying task-based sessions, i.e. sets of possibly non contiguous queries issued by the user of a Web Search Engine for carrying out a given task. In order to evaluate and compare different approaches, we built, by means of a manual labeling process, a ground-truth where the queries of a given query log have been grouped in tasks. Our analysis of this ground-truth shows that users tend to perform more than one task at the same time, since about 75% of the submitted queries involve a multi-tasking activity. We formally define the Task-based Session Discovery Problem (TSDP) as the problem of best approximating the manually annotated tasks, and we propose several variants of well known clustering algorithms, as well as a novel efficient heuristic algorithm, specifically tuned for solving the TSDP. These algorithms also exploit the collaborative knowledge collected by Wiktionary and Wikipedia for detecting query pairs that are not similar from a lexical content point of view, but actually semantically related. The proposed algorithms have been evaluated on the above groundtruth, and are shown to perform better than state-of-the-art approaches, because they effectively take into account the multi-tasking behavior of users. Copyright 2011 ACM
Convenience in Funding Upgrading Works
No full textWith reference to upgrading actions on existing building stock, Construction Procurement Guidance, No.7 Whole Life Costs (Office of Government Commerce) states: ‘All procurement must be made solely on the basis of value for money in terms of the optimum combination of global costs and quality to meet the user’s requirements’. Cash-flow analyses allow showing the economic value of investments for alternative technological upgrading works extended all along their service lives. Optimisation of choices is not only a matter of cash-flow analyses—choices should not be made only according to the lowest costs but also considering several aspects that can be brought back to the concept of ‘technical-sustainable value’, which mainly derives from competent functional and environmental assessments of the reference analysis system. The mentioned interrelation should theoretically be adequately considered but this is seldom the case in the common building practice. Cost estimate for an engineered system has to entail much more detailed analyses on costs, energy, sustainability and technologies. Possible technological solutions would be convenient in terms of technological/technical utility, but less convenient in monetary terms for the funding subject. Under the economic point of view, cash outflow means less economic convenience in funding a given technology. All that stated above, nowadays effective data-display global cost-quality indicators are rarely available in literature. The present manuscript introduces to the reader fundamentals of an economic tool proposal designed by the author with the use of synthetically displaying interrelations between cash-flow scenarios and quality-sustainability in upgrading processes on existing buildings. Fundamentals have been tested on a reference case study. Then, fundamentals have been contextualized to the Italian Legislative framework: in Italy, in multi-owner existing residential buildings, expenditure allocation is carried out based on thousandths. The thousandth type to be considered is due to the configuration of the case under review and to balance-sheet expenditure to be allocated to owners. Property thousandths allocated to housing units have been used to allocate expenses for technological/energy upgrading works. The author has tried to find out the amount of a possible bank investment that a user might start at building Time ‘0’ to theoretically clear possible economic losses, trying to highlight technical utility of the technological solution that would be disadvantaged in economic terms. ‘Neutral’ mathematical finance formulas have been used to calculate the theoretical capital to be invested by an owner based on the reference cash-flow scenario. Conclusion will be drawn at the end of the manuscript
Modeling and Predicting the Task-by-task Behavior of Search Engine Users
No full textWeb search engines answer user needs on a query-by-query fashion, namely they retrieve the set of the most relevant results to each issued query, independently. However, users often submit queries to perform multiple, related tasks. In this paper, we first discuss a methodology to discover from query logs the latent tasks performed by users. Furthermore, we introduce the Task Relation Graph (TRG) as a representation of users' search behaviors on a task-by-task perspective. The task-by-task behavior is captured by weighting the edges of TRG with a relatedness score computed between pairs of tasks, as mined from the query log. We validate our approach on a concrete application, namely a task recommender system, which suggests related tasks to users on the basis of the task predictions derived from the TRG. Finally, we show that the task recommendations generated by our solution are beyond the reach of existing query suggestion schemes, and that our method recommends tasks that user will likely perform in the near future
Recupero edilizio e nuova costruzione. Non solo risparmio energetico. Importanza della valutazione della fattibilità applicativa a monte della modellazione energetica
No full textThe expressions ‘low environmental impact’ and ‘energy efficiency’ mean much more than ‘compliance to regulation and technical specifications’ (89/106/ EEC, article 4).
Nowadays, solutions implemented in actions on buildings at least have to comply with regulatory values or parameters with reference to a specific time outlook. This is due to policies and guidelines issued at several levels, starting from the European one to get to the local one, promoting: for new buildings, reviews of design processes so as to create sustainable buildings providing for high-quality housing, for existing buildings, reviews on as-built assets so as to limit energy consumption.
Designers selecting potentially applicable ‘sustainable’ technologies should not only assess their profiles in terms of energy and performance which, of course, are essential.
Together with the abovementioned issues, in addition to convenience, critical points and viability constraints should be reasonably taken into account during the selection process.
For this purpose, some ideas are introduced in form of a journalistic discourse, which, according to the author, can be useful to those designers who have to select from different ranges of viable technological solutions, both based on traditional building practices and on new or emerging practices
Detecting Task-Based Query Sessions Using Collaborative Knowledge
No full textOur research challenge is to provide a mechanism for splitting into user task-based sessions a long-term log of queries submitted to a Web Search Engine (WSE). The hypothesis is that some query sessions entail the concept of user task. We present an approach that relies on a centroid-based and a density-based clustering algorithm, which consider queries inter-arrival times and use a novel distance function that takes care of query lexical content and exploits the collaborative knowledge collected by Wiktionary and Wikipedia
Discovering tasks from search engine query logs
No full textAlthough Web search engines still answer user queries with lists of ten blue links to webpages, people are increasingly issuing queries to accomplish their daily tasks (e.g., finding a recipe, booking a flight, reading online news, etc.). In this work, we propose a two-step methodology for discovering tasks that users try to perform through search engines. First, we identify user tasks from individual user sessions stored in search engine query logs. In our vision, a user task is a set of possibly noncontiguous queries (within a user search session), which refer to the same need. Second, we discover collective tasks by aggregating similar user tasks, possibly performed by distinct users. To discover user tasks, we propose query similarity functions based on unsupervised and supervised learning approaches. We present a set of query clustering methods that exploit these functions in order to detect user tasks. All the proposed solutions were evaluated on a manually-built ground truth, and two of them performed better than state-of-the-art approaches. To detect collective tasks, we propose four methods that cluster previously discovered user tasks, which in turn are represented by the bag-of-words extracted from their composing queries. These solutions were also evaluated on another manually-built ground truth
Quality versus efficiency in document scoring with learning-to-rank models
No full textLearning-to-Rank (LtR) techniques leverage machine learning algorithms and large amounts of training data to induce high-quality ranking functions. Given a set of documents and a user query, these functions are able to precisely predict a score for each of the documents, in turn exploited to effectively rank them. Although the scoring efficiency of LtR models is critical in several applications – e.g., it directly impacts on response time and throughput of Web query processing – it has received relatively little attention so far. The goal of this work is to experimentally investigate the scoring efficiency of LtR models along with their ranking quality. Specifically, we show that machine-learned ranking models exhibit a quality versus efficiency trade-off. For example, each family of LtR algorithms has tuning parameters that can influence both effectiveness and efficiency, where higher ranking quality is generally obtained with more complex and expensive models. Moreover, LtR algorithms that learn complex models, such as those based on forests of regression trees, are generally more expensive and more effective than other algorithms that induce simpler models like linear combination of features. We extensively analyze the quality versus efficiency trade-off of a wide spectrum of state-of-the-art LtR, and we propose a sound methodology to devise the most effective ranker given a time budget. To guarantee reproducibility, we used publicly available datasets and we contribute an open source C++ framework providing optimized, multi-threaded implementations of the most effective tree-based learners: Gradient Boosted Regression Trees (GBRT), Lambda-Mart (Λ-MART), and the first public-domain implementation of Oblivious Lambda-Mart (Ωλ-MART), an algorithm that induces forests of oblivious regression trees. We investigate how the different training parameters impact on the quality versus efficiency trade-off, and provide a thorough comparison of several algorithms in the quality-cost space. The experiments conducted show that there is not an overall best algorithm, but the optimal choice depends on the time budget
Mitogenomes from Two Uncommon Haplogroups Mark Late Glacial/Postglacial Expansions from the Near East and Neolithic Dispersals within Europe
No full textThe current human mitochondrial (mtDNA) phylogeny does not equally represent all human populations but is biased in favour of representatives originally from north and central Europe. This especially affects the phylogeny of some uncommon West Eurasian haplogroups, including I and W, whose southern European and Near Eastern components are very poorly represented, suggesting that extensive hidden phylogenetic substructure remains to be uncovered. This study expanded and re-analysed the available datasets of I and W complete mtDNA genomes, reaching a comprehensive 419 mitogenomes, and searched for precise correlations between the ages and geographical distributions of their numerous newly identified subclades with events of human dispersal which contributed to the genetic formation of modern Europeans. Our results showed that haplogroups I (within N1a1b) and W originated in the Near East during the Last Glacial Maximum or pre-warming period (the period of gradual warming between the end of the LGM, ~19 ky ago, and the beginning of the first main warming phase, ~15 ky ago) and, like the much more common haplogroups J and T, may have been involved in Late Glacial expansions starting from the Near East. Thus our data contribute to a better definition of the Late and postglacial re-peopling of Europe, providing further evidence for the scenario that major population expansions started after the Last Glacial Maximum but before Neolithic times, but also evidencing traces of diffusion events in several I and W subclades dating to the European Neolithic and restricted to Europe
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