Vehicular Ad hoc Networks (VANETs) are emerging as a promising approach to improving traffic safety and providing a wide range of wireless applications for drivers and passengers. To perform reliable and trusted vehicular communications, one prerequisite is to ensure a peer vehicle’s credibility by means of digital certificates validation from messages that are sent out by other vehicles. However, in vehicular communication systems, certificates validation is more time consuming than in traditional networks, due to the fact that each vehicle receives a large number of messages in a short period of time. Another issue that needs to be addressed is the unsuccessful delivery of information between vehicles and other entities on the road as a result of their high mobility rate. For these reasons, we need new solutions to accelerate the process of certificates validation. In this thesis, we propose a certificate revocation status validation scheme using the concept of clustering; based on data mining practices, which can meet the aforementioned requirements. We employ the technique of k -means clustering to boost the efficiency of certificates validation, thereby enhancing the security of a vehicular ad hoc network. Additionally, a comprehensive analysis of the security of the proposed scheme is presented. The analytical results demonstrate that this scheme can effectively improve the validation of certificates and thus secure the vehicular communication in vehicular networks.

Subject searching—seeking information with a subject or topic in mind—is often involved in carrying out undergraduate assignments such as term papers and research reports. It is also an important component of information literacy—the abilities and experiences of effectively finding and evaluating, and appropriately using, needed information—which universities hope to cultivate in undergraduates by the time they complete their degree programs. By exploring the subject searching of a small group of upper-level, academically successful undergraduates over a school year I sought to acquire a deeper understanding of the contexts and characteristics of their subject searching, and of the extent to which it was similar in quality to that of search and domain experts. Primary data sources for this study comprised subject searching diaries maintained by participants, and three online subject searches they demonstrated at the beginning, middle, and end of the study during which they talked aloud while I observed, followed by focused interviews. To explore the quality of study participants’ subject searching I looked for indications of advanced thinking in thoughts they spoke aloud during demonstration sessions relating to using strategy, evaluating, and creating personal understanding, which represent three of the most challenging and complex aspects of information literacy. Applying a layered interpretive process, I identified themes within several hundred instances of participants’ advanced thinking relating to these three information literacy elements, with evaluative themes occurring most often. I also noted three factors influencing the extent of similarity between the quality of participants’ advanced thinking and that of search and domain experts which reflected matters that tended to be i) pragmatic or principled, , ii) technical or conceptual, and iii) externally or internally focused. Filtered through these factors, participants’ instances of advanced thinking brought to mind three levels of subject searching abilities: the competent student, the search expert, and the domain expert. Although relatively few in number, I identified at least some advanced thinking evincing domain expert qualities in voiced thoughts of all but one participant, suggesting the gap between higher order thinking abilities of upper-level undergraduates and information literate individuals is not always dauntingly large.

Event-related potentials were recorded as subjects were presented with pairs of words, one word at a time, to examine the electrocortical manifestations of association formation and the effect of intra-list semantic similarity. Two types of lists were presented: Same – all pairs belonged to the same semantic category; Different – all pairs belonged to a different semantic category. Subjects were told to memorize the pairs for a following paired associate recall test. Recall was better for the Different than Same lists. Subsequent recall was predicted by the amplitudes of a potential lasting throughout the epoch and the P555 to each word of a pair (likely reflecting state- and item-related encoding activity, respectively), as well as a late positive wave that occurred after the offset of the second word, which is thought to reflect association formation. A larger N425 was elicited by pairs in the Different than Same lists, likely reflecting semantic integration.

法拍屋市場已成為台灣重要的購屋管道之一，然而房地產為異質商品，其價格受到品質差異的影響很大。其中法拍屋底價的訂定方式和一般房屋不同：拍賣底價由公定房屋估價人員根據區域資料使用特徵價格理論方法先訂出初估價格，再與債權人、債務人三方協商討論而訂定。故本論文加入「定價偏誤」因子，以特徵價格模型探究民國八十九年至九十一年間影響台北縣市法拍屋拍定價格的各項因素及影響程度，並得出如下之結論: 1.影響台北縣市法拍屋拍定價格的顯著因子及影響幅度為:定價折價程度(影響幅度0.9798%)、總建物面積(影響幅度0.4709%)、土地持分價格(影響幅度0.4838%)、拍次(隱含價格-17.0308萬元)、競標人數(隱含價格7.611萬元)、房屋現況(非空屋)(隱含價格-18.950萬元)、房屋現況(出租)(隱含價格40.501萬元)、車位(隱含價格80.772萬元)、點交(隱含價格8.8073萬元)、建材(隱含價格69.748萬元)、建物型態(一樓) (隱含價格648.856萬元)、建物型態(大樓) (隱含價格674.94萬元)、建物型態(公寓) (隱含價格464.385萬元)、建物型態(透天) (隱含價格516.971萬元)、房價指數(隱含價格-8.888萬元)、區位變數(台北市) (隱含價格80.429萬元)。 2.分別比較台北縣市法拍屋資料，可以發現持分土地價格(+)、競標人數(+)、車位有無(+)、是否點交(+)對台北市法拍屋拍定價格影響較大;而總建物面積(+)、拍次(-)、建材(+)、建物型態、房價指數(-)對台北縣拍交價格影響則較大。 / Real estate properties are real assets that can produce goods and service in the economy. Among them, the foreclosure market has become an imperative means to acquiring a house. The auction market in Taiwan is composed of non-performing assets. They’ll have a discount up to 20% in every action. Is this a really good target to invest? In fact, houses are heterogeneity assets; they can only be estimated correctly by controlling of variables such as location variables and the physical condition of the property. Moreover, the listing price of foreclosure is quite different from that of an ordinary house. It is first calculated by appraisers, and the final listing price is obtained by the negotiation of the court, creditor and debtor. Thus, there could be mispricing of list price, and this mispricing is expected to have an impact on the selling price. This study applies Hedonic model and uses data from year 2000 to 2002 of Taipei City and Taipei County to examine the effect of these physical and foreclosure elements on the selling price of foreclosure and thus reach the following conclusions: 1.All the foreclosure and physical condition variables are remarkable in our sample, as well as the location variable. They are degree of underpricing, total building area, holding land price, the bid times, numbers of bidders, current status of this building, parking space, situation of handing over item by item, building material, object type, housing price index and location. 2.It shows that holding land price(+),numbers of bidders(+),parking space(+),situation of handing over item by item(+) have greater influence on the foreclosure selling price in Taipei city while total area(+),number of auctions(-), material used(+),object type, and housing price index(-) weight more on the selling price in Taipei county.

To explore progressively larger biomolecular systems, methods to model explicit solvent cheaply are required. In this work, the use of Graphics Processing Units, found in commodity video cards, for solving the constraints, calculating the non-bonded forces and generating the pair list in the case of the fully constrained three site SPC water model is investigated. It was shown that the GPU implementation of the SPC constraint-solving algorithm SETTLE was overall 26% faster than a conventional implementation running on a Central Processing Unit (CPU) core. The non-bonded forces were calculated up to 17 times faster than using a CPU core. Using these two approaches, an overall speed up of around 4 times was found. The most successful implementation of the pair-list generation ran at 38% the speed of a conventional grid-based implementation on a CPU core. In each investigation the accuracy was shown to be sufficient using a variety of numerical and distributional tests. Thus, the use of GPUs as parallel processors for MD calculations is highly promising. Lastly, a method of calculating a constraint force analytically is presented.

The influence of steel metallurgy on rock bolt SCC was studied using a series of commercial carbon and low-alloyed steels. The chemical composition, their mechanical properties and the microstructures of these steels varied considerably in order to gather information for the discussion of the metallurgical influences under Hydrogen Embrittlement (HE) and Stress Corrosion Cracking (SCC) conditions. In order to understand the metallurgical influences on Rock Bolt SCC, an evaluation was carried out to fifteen commercial steels. The experiments reproduced the Stress Corrosion Cracking condition at which commercial rock bolts had failed in Australians mines. Due to the selected materials, stress and electrolyte condition it is expected that Hydrogen Embrittlement (HE) will affect the steel failure. The approach was to use the Linearly Increasing Stress Test (LIST) and exposing the sample to a dilute pH 2.1-sulphate solution, in accordance with prior studies. Stress Corrosion Cracking was evaluated by analysing the decrease in tensile strength, loss of ductility and fractography observed using Scanning Electron Microscopy (SEM). The initial series of test to the fifteen steels were performed at the free corrosion potential (f.c.p.) vs. Ag/AgCl. From this initial test only five steels (AISI 1008, AISI 4140, AISI 4145H, pipeline X-65 and X-70) did not show Stress Corrosion Cracking features. These five steel were tested in accordance with the Linearly Increased Stress Test (LIST) in the dilute pH 2.1 sulphate solution at different electronegative applied potential to minimum value of -1500mV. The experimental procedure tried to reproduce the Stress Corrosion Cracking condition to identify the most aggressive condition the steel is able to support before failing due to Stress Corrosion Cracking to then compare the theory of SCC and HE in low carbon and low alloy steel with the obtained experimental results. The investigation compared the well-known theory of SCC and HE in low carbon and low alloy steel with the obtained experimental results. Surprisingly, the experimental result did not always agree with the theory.

[Truncated abstract] Parallel computing is recognised today as an important tool in the solution of a wide variety of computationally intensive problems, problems which were previously considered intractable. While it offers the promise of vastly increased performance, parallel computing introduces additional complexities which are not encountered with sequential processing. One of these is the scheduling problem, in which the individual tasks comprising a parallel program are scheduled onto the processors comprising the parallel architecture. The objective is to minimise execution time while still preserving the precedence relations between the tasks. Scheduling is of vital importance since a poor task schedule can undo any potential gains from the parallelism present in the application. Inappropriate scheduling can result in the hardware being used inefficiently, or worse, the program could run slower in parallel than on a single processor. The scheduling problem is one of the more difficult problems facing the parallel programmer. In fact, it is NP-complete in the general case. As a result, a large number of heuristic methods with sub-optimal performance but polynomial, rather than exponential, time complexity have been proposed. In order to simplify their algorithms, researchers have restricted the problem: by making assumptions concerning the parallel architecture or imposing limitations on the task graph representing the parallel program. The evolution of the task scheduling problem has involved the gradual relaxation of these restrictions. A major change occurred when the assumption of zero inter-processor communication costs was removed. This was driven by the increasing popularity of distributed-memory message-passing multiprocessors.

University, Diss., 2003--Kiel.

Media channels play an important role in the flow, construction, and curation of knowledge in software development. Understanding how developers use media channels is key to improving developer practices and supporting channel evolution. In this thesis, I investigate the way developers use media channels to curate knowledge within the R software development community. By applying a case study methodology consisting of mining archival data and survey methods, I investigate the R community on Stack Overflow and the R-help mailing list, using a qualitative approach. The findings reveal that Stack Overflow and mailing lists foster knowledge co-construction differently---crowd-sourced and participatory respectively. Furthermore, developers use actively both channels to optimize knowledge exchange and curation. My thesis contributes to the understanding of knowledge curation by developer communities, and describes a model for a systematic comparison of two or more media channels, within a community of practice. This model allows knowledge categorization and can be used in future studies to explore knowledge flow within multiple media channels. Moreover, based on my observations in conjunction with the survey data analysis, I extracted a set of recommendations to assist practitioners in the use of multiple Question and Answer (Q&A) channels. / Graduate

Väntelistor till barnpsykiatrisk vård är vanligt förekommande och tiden på väntelista har visats vara påfrestande för familjerna som väntar. Denna studie har undersökt hur föräldrar upplever tiden på väntelista till Barn- och ungdomspsykiatrin (BUP), samt vilka behov av stöd de upplever sig ha under tiden de väntar. Sju föräldrar vars barn väntade på utredning inom BUP intervjuades. Data bearbetades genom tematisk analys. Resultatet visar att föräldrarna upplevde brist på kontroll och hopplöshet, delvis på grund av att de befann sig i ovisshet under väntetiden. Vidare visar resultatet att stödinsatser som innefattar information, konsultation, avlastning och behandling efterfrågades. Resultatet diskuteras med hjälp av teorin om Locus of Control (LOC) och begreppet ovisshetsdiskrepans. Vidare forskning behövs för att öka förståelsen för hur information gällande väntetiden påverkar upplevelsen av väntetiden. Därtill behövs forskning som undersöker om och hur upplevelsen av väntetiden påverkar kommande utredning eller behandling. / Waiting lists in child and adolescent psychiatry are common and waiting for mental health services has been shown to be challenging for the families involved. This study aimed to explore how parents of children on a waiting list for an assessment experienced the wait. The study also explored what kind of support the parents felt that they needed during this period. Interviews were conducted with seven parents of children on waiting lists and data was analyzed using thematic analysis. Results showed that the parents experienced a lack of control and hopelessness during the wait, partly because of the uncertainty that characterized the waiting time. Results concerning parental support showed that information, consultation, social support and treatment were requested. Results were discussed using the theoretical framework Locus of Control (LOC) and uncertainty discrepancy. Future studies exploring how information about the waiting time affects the waiting list experience are needed. In addition, future studies that explore if and how the waiting list experience affects the coming assessment or treatment are needed.