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排序方式: 共有1268条查询结果,搜索用时 234 毫秒
21.
22.
H. Ludwig 《Desalination》1981,36(2):153-178
To make RO an economical process, plant and operating costs have been reduced by developing compact modules, led by polyamide hollow fibre modules which recover energy from the reject when desalinating highly saline brackish water and seawater. Such plants only start to pay their way at product rates of around 400m3 /d +. Energy costs for desalination systems with lower capacities can also be reduced considerably by operating the RO plants at conversion rates of more than 30%. To what extent the required higher conversion rates can be obtained for a particular application depends on concentration of scales-forming content matter (calcium sulphate, strontium sulphate, barium sulphate and calcium carbonate), salt content of the raw water, concentration of fouling substances such as iron, manganese, anorganic and organic matter, risk of biological growth due to algae, shells and bacteria. The scope and type of conditioning and pre-treatment are based on these factors. 相似文献
23.
24.
Gerhard Bayer Martin Hofmann Ludwig J. Gauckler 《Journal of the American Ceramic Society》1991,74(9):2205-2208
New oxide compounds with α-PbO2 structure have been synthesized by solid-state reactions. These are derived from ZrTiO4 and HfTiO4 by a different kind of ionic substitution. The thermal expansion behavior of these phases was investigated by means of a dilatometer and an X-ray heating diffractometer. These measurements revealed rather low expansion for some of the Zr(Me3+ /Me5+ )O4 , solid solutions. This behavior is attributed to their high expansion anisotropy, which leads to extended formation of microcracks. 相似文献
25.
26.
The current Web Services Agreement specification draft proposes a simple request-response protocol for agreement creation
only addressing bilateral offer exchanges. This paper proposes a framework augmenting this WS-Agreement to enable negotiations
according to a variety of bilateral and multilateral negotiation protocols. The framework design is based on a thorough analysis
of taxonomies for negotiations from the literature in order to allow for capturing a variety of different negotiation models
within a single, WS-Agreement compatible, framework. In order to provide for the intended flexibility, the proposed protocol
takes a two-stage approach: a meta-protocol is conducted among interested parties to agree on a common negotiation protocol
first before the real negotiation is carried out in the second step due to the protocol established in the first step. 相似文献
27.
Swarm Intelligence Approaches for Grid Load Balancing 总被引:1,自引:0,他引:1
With the rapid growth of data and computational needs, distributed systems and computational Grids are gaining more and more
attention. The huge amount of computations a Grid can fulfill in a specific amount of time cannot be performed by the best
supercomputers. However, Grid performance can still be improved by making sure all the resources available in the Grid are
utilized optimally using a good load balancing algorithm. This research proposes two new distributed swarm intelligence inspired
load balancing algorithms. One algorithm is based on ant colony optimization and the other algorithm is based on particle
swarm optimization. A simulation of the proposed approaches using a Grid simulation toolkit (GridSim) is conducted. The performance
of the algorithms are evaluated using performance criteria such as makespan and load balancing level. A comparison of our
proposed approaches with a classical approach called State Broadcast Algorithm and two random approaches is provided. Experimental
results show the proposed algorithms perform very well in a Grid environment. Especially the application of particle swarm
optimization, can yield better performance results in many scenarios than the ant colony approach. 相似文献
28.
One of congress’ goals for 2007 was for 80% of all tax and informational returns to be filed electronically. However, to date
that lofty goal has fallen well short. This research proposes a model of e-filing adoption. To test the model a survey is
administered to 260 participants. The instrument assesses citizen perceptions of trust, risk and optimism bias. Structural
equation modeling is used to evaluate the relationships between these three concepts and intention to use. The results indicate
that trust of the Internet, trust of the e-filer, perceived risk and optimism bias all have an impact on intention to use
e-filing. Implications for practice and research are discussed. 相似文献
29.
Marco Tiloca Christian Gehrmann Ludwig Seitz 《International Journal of Information Security》2017,16(2):173-193
DTLS is a transport layer security protocol designed to provide secure communication over unreliable datagram protocols. Before starting to communicate, a DTLS client and server perform a specific handshake in order to establish a secure session and agree on a common security context. However, the DTLS handshake is affected by two relevant issues. First, the DTLS server is vulnerable to a specific Denial of Service (DoS) attack aimed at forcing the establishment of several half-open sessions. This may exhaust memory and network resources on the server, so making it less responsive or even unavailable to legitimate clients. Second, although it is one of the most efficient key provisioning approaches adopted in DTLS, the pre-shared key provisioning mode does not scale well with the number of clients, it may result in scalability issues on the server side, and it complicates key re-provisioning in dynamic scenarios. This paper presents a single and efficient security architecture which addresses both issues, by substantially limiting the impact of DoS, and reducing the number of keys stored on the server side to one unit only. Our approach does not break the existing standard and does not require any additional message exchange between DTLS client and server. Our experimental results show that our approach requires a shorter amount of time to complete a handshake execution and consistently reduces the time a DTLS server is exposed to a DoS instance. We also show that it considerably improves a DTLS server in terms of service availability and robustness against DoS attack. 相似文献
30.
Service discovery is a critical task in distributed computing architectures for finding a particular service instance. Semantic
annotations of services help to enrich the service discovery process. Semantic registries are an important component for the
discovery of services and they allow for semantic interoperability through ontology-based query formulation and dynamic mapping
of terminologies between system domains. This paper evaluates two semantic registries—OWLJessKB implementation and instanceStore—to
determine the suitability of these with regards to the query response time and the overall scalability for use in mathematical
services. Mathematical ontologies from the MONET project are used to undertake comparison. The results demonstrate that the
performance of registries may be compared across two axes: (1) time to initialize (i.e. time to load an initial ontology into
memory); (2) time to query (i.e. time to reason with an ontology loaded into memory). 相似文献