1,723,354 research outputs found
Zuo yi ge hao dui yuan.
No full text陳正, 命夫著.獨幕劇.本電子書乃根據《香港版權條例(第528章)》而複製, 並只可在大學圖書館系統內的獨立電子書系統上使用.Chen Zheng, Mingfu zhu.Ben dian zi shu nai gen ju "Xianggang ban quan tiao li (Di 528 zhang)" er fu zhi, bing zhi ke zai da xue tu shu guan xi tong nei de du li dian zi shu xi tong shang shi yong.Du mu ju
Recording Process Documentation in the Presence of Failures
No full textScientific and business communities present unprecedented requirements on provenance, where the provenance of some data item is the process that led to that data item. Previous work has conceived a computer-based representation of past executions for determining provenance, termed process documentation, and has developed a protocol, PReP, to record process documentation in service oriented architectures. However, PReP assumes a failure free environment. Failures lead to process documentation unable to be recorded, losing the evidence that a process occurred. This is not acceptable in the applications relying on process documentation and would cause disastrous consequences. This paper describes our solution, F-PReP, a protocol for recording process documentation in the presence of failures. A complete formalization of the protocol using Abstract State Machines is also presented
Recording accurate process documentation in the presence of failures
No full textScientific and business communities present unprecedented requirements on provenance, where the provenance of some data item is the process that led to that data item. Previous work has conceived a computer-based representation of past executions for determining provenance, termed process documentation, and has developed a protocol, PReP, to record process documentation in service oriented architectures. However, PReP assumes a failure free environment. The presence of failures may lead to inaccurate process documentation, which does not reflect reality and hence cannot be trustful and utilized. This paper outlines our solution, F-PReP, a protocol for recording accurate process documentation in the presence of failures
Premixed flame ignition: Theoretical development
No full textPremixed flame ignition is a fundamental issue in combustion. A basic understanding of this phenomenon is crucial for fire safety control and for the development of advanced combustion engines. Significant efforts have been devoted to understanding the mechanisms of ignition and determining critical ignition conditions, such as critical flame radius, minimum ignition energy, and minimum ignition power, which have remained challenging research topics for centuries. This review provides an in-depth investigation of the forced-ignition of laminar premixed flames in a quiescent flammable mixture, with emphasis on theoretical developments, particularly those based on activation energy analysis. First, the fundamental concepts are overviewed, including spark ignition, characteristic time scales, and critical ignition conditions. Then, the chronological development of premixed flame ignition theories is discussed, including homogeneous explosion, thermal ignition theory, flame ball theory, quasi-steady ignition theory, and, more importantly, transient ignition theory. Premixed flame ignition consists of three stages: flame kernel formation, flame kernel expansion, and transition to a selfsustaining flame. These stages are profoundly affected by the coupling of positive stretch with preferential diffusion, characterized by the Lewis number. Specifically, positive stretch makes the expanding ignition kernel weaker at larger Lewis numbers, consequently increasing the critical ignition radius and MIE. The premixed flame ignition process is dominated by flame propagation dynamics. Both quasi-steady and transient ignition theories demonstrate that the critical flame radius for premixed ignition differs from either flame thickness (by thermal ignition theory) or flame ball radius (by flame ball theory). Particularly, the transient ignition theory appropriately acknowledges the "memory effect" of external heating, offering the most accurate description of the evolution of the ignition kernel and the most sensible evaluation of minimum ignition energy. In addition, the effects of transport and chain-branching reactions of radicals, finite droplet vaporization, and repetitive heating pulses on premixed flame ignition are discussed. Finally, a summary of major advances is provided, along with comments on the applications of premixed flame ignition theory in ignition enhancement. Suggested directions for future research are presented
Studio in vitro e ex vivo dell'attività antiossidante di Casimiroa spp, Croton lechleri, Ribes nigrum e Boswellia serrata nella prevenzione dell'aterosclerosi
Get PDFIn vitro and ex vivo antioxidant activity of Casimiroa spp, Croton lechleri, Ribes nigrum, and Boswellia serrata in atherosclerosis prevention
Oxidative and glycoxidative stress are postulated to be the primary events in the pathogenesis of type 2 diabetes mellitus and its vascular implications. Further, LDL oxidation in the vessel wall plays a key role in atherogenesis, also related to damage from oxygen species (ROS). Moreover, the risk for development of atherosclerosis is by approximately three-fold increased in patients with diabetes. The medicinal plants are widely used in folk medicine for the treatment of cardiovascular diseases and diabetes mellitus. The genus Casimiroa (Rutaceae) includes few species which have their habitat in Central America and Mexico; among these, the most common are Casimiroa edulis Llave et lex. and Casimiroa pubescens Ramirez. The decoction of leaves and seeds are traditionally used for treating hypertension. The sap of Croton lechleri (Euphorbiaceae), a South American tree, is used topically in the treatment of wound healing and orally, in a dilute form, mainly for gastric ulcers and intestinal diseases. The gum resin of Boswellia serrata (Burseraceae), which grows in dry mountainous regions of India, Northern Africa and Middle East, has been traditionally used to treat various chronic inflammatory diseases. Ribes nigrum (Grossulariaceae), a species native to central and northern Europe and northern Asia, is a traditional medicine for the treatment of inflammatory disorders such as rheumatic diseases.
The aim of this research was to investigate the antioxidant activity of these medicinal plants by means of several experimental methods in vitro and ex vivo to outline their role in the prevention and/or treatment of cardiovascular diseases related to oxidative stress.
The antioxidant activity was evaluated by DPPH method, and ORAC (Oxygen Radical Absorbance Capacity) assay. Also, the total phenolic content (TPC) was determined by the use of Folin-Ciocalteu reagent, and the total flavonoid content (TFC) by complexation with chloride aluminium. The activity of the plant extracts on LDL oxidation was studied by monitoring the formation of conjugated dienes, and the quantification of thiobarbituric acid reactive substances (TBARS). Finally, their inhibitory effect on advanced glycation end products (AGEs) formation were evaluated by means of BSA-glucose/ribose fluorescence assay.
In DPPH assay, Croton lechleri sap and blackcurrant (Ribes nigrum) bud extract showed higher scavenging activity in comparison with Casimiroa extracts, whereas in the ORAC assay the Casimiroa leaf extracts showed a high ORAC value and Croton lechleri an activity even higher. In TPC test, Croton lechleri showed the highest value (713.76 ± 32.23 mg GAE/g). In the LDL oxidation assay, the plant extracts exhibited considerable protective effects by prolonging the oxidation lag phase; for example, at the concentration of 0.8 µg/ml Croton lechleri increased the lagtime by 58.6%, and in the antiglycation study all extracts inhibited the AGEs formation significantly in the BSA-glucose model. The results from this research suggest that the medicinal plants Croton lechleri, Casimiroa spp. and Ribes nigrum, even if in different manner, may have implications in the prevention of atherosclerotic vascular diseases, whereas Boswellia serrata showed a minor role
Recording process documentation in the presence of failures in service oriented architectures
No full textScientific and engineering communities (e.g., chemistry, bioinformatics and engineering manufacturing) have presented unprecedented requirements for knowing the provenance of their data products, i.e., where they originated from, how they were produced and what has happened to them since creation. Without such important knowledge, scientists and engineers cannot reproduce, analyse or validate experiments and processes.Previous work has conceived a computer-based representation of a past process for determining provenance, termed process documentation. However, current provenance systems do not adequately address the problem of reliably recording process documentation in large scale environments like Service Oriented Architectures. For example, a service may not be available and network connection may be broken. In this context, reliably recording process documentation becomes challenging, given that the documentation produced in a process can be spread over multiple provenance repositories across the world.The presence of failures (specifically, the crash of provenance repositories and communication failures) may prevent process documentation from being recorded, losing the evidence that a process occurred. This would have disastrous consequences and hence is not acceptable in the domains that rely on process documentation to determine the provenance of their data products. In this thesis, we systematically analyse all situations that may occur during capturing process documentation in the event of assumed failures. We then present a novel coordinator-based protocol that is formally proved to record complete process documentation.In addition, we use graphs to intuitively represent the topology of process documentation recorded in multiple interlinked provenance repositories, which helps us to investigate the entire retrievability of distributed process documentation. Finally, we evaluate a system architecture that employs the protocol and supports practical issues such as communication, storage and performance. The results show that the system can record complete and retrievable process documentation while maintaining acceptable performance
Theoretical analysis on the forced ignition of a quiescent mixture by heat and radical sources
No full textForced ignition of premixed flame plays a crucial role in fundamental combustion research. In this work, a theoretical investigation is conducted interpreting the flame kernel development subject to heat and radical ignition sources. Adopting simplified two-step reaction mechanism, the present theoretical model incorporates both chain-branching and recombination reaction paths and reveals their synergistic effect during the forced ignition process. The transient evolution of flame kernel driven by heat and radical addition can be obtained by solving an implicit ordinary differential equation, which is rigorously derived from first principles based on large activation energy asymptotics. The findings reveal that an increase in fuel Lewis number adversely affects the fuel supply rate at the flame front, while a decrease in the radical Lewis number inhibits radical accumulation, both of which exhibit negative impacts on ignition process. For ignition source with uniform rate profile, there exist a critical heating power, below which the flame kernel cannot reach the critical radius despite extended ignition duration. Exceeding this threshold, the minimum ignition energy varies non-monotonically with increasing heating power. Particularly, comparing with the purely thermal ignition source, the heat and radical ignition sources can effectively reduce the thermal load on ignition device, which can be attributed to the synergistic effects of heat and radicals in the ignition process. A comparative analysis on various rate profiles of ignition source, including uniform, trigonometric and Gaussian, indicates that the Gaussian profile has superior efficiency in facilitating flame kernel expansion and transition to self-sustained spherical flame. Specifically, ignition source with Gaussian profile shows the lowest minimum ignition energy, which is primarily due to its capability for concentrated and optimally timed energy deposition, especially for large fuel Lewis numbers. The present analysis provides insightful understandings of forced ignition for premixed flame and offers practical perspectives for real-world applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Implementation and Evaluation of a Protocol for Recording Process Documentation in the Presence of Failures
No full textThe provenance of a particular data item is the process that led to that piece of data. Previous work has enabled the creation of detailed representation of past executions for determining provenance, termed process documentation. However, current solutions to recording process documentation assume a failure free environment. Failures result in process documentation not being recorded, thereby causing the loss of evidence that a process occurred. We have designed F-PReP, a protocol to guarantee the recording of process documentation in the presence of failures. This paper discusses its implementation and evaluates its performance. The result reveals that it introduces acceptable overhead
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