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1.
Wireless Personal Communications - Distributed denial of service (DDoS) attacks disrupt the availability of cloud services. The detection of these attacks is a major challenge in the cloud... 相似文献
2.
The enzyme which forms glucocerebroside, ceramide: UDP-glucose glucosyltransferase, is inactivated in vitro by a cationic
analog of cerebroside, 2-decanoylamino-3-morpholinopropiophenone. A study of the inhibitor using intraperitoneal injection
into young mice showed that the level of the enzyme activity in liver was appreciably lowered between 3 and 6 hr after injection.
The activity increased subsequently, overshooting the normal level within 24 hr by about 20%, then returning to normal within
the next 24 hr. Additional effects observed in liver were an increase in lipid content (primarily in the triglyceride fraction
and ceramides) and a decrease in the glucocerebroside level. Body temperature dropped rapidly. Markedly similar effects were
produced by injecting chlorpromazine, which was tried in order to reduce the hyperirritability and inhibitory effects on monoamine
oxidase previously demonstrated by the glucosyltransferase inhibitor. Chlorpromazine did indeed block the hyperirritability
and resulted in enhancement of the keto amine's effects on the enzyme and lipids. It is possible that the two drugs in combination
would be helpful in ameliorating the symptoms due to the cerebroside accumulation that occurs in Gaucher disease. Diazepam
also produced a reduced level of glucosyltransferase. A color reaction for chlorpromazine, possibly suitable for quantitative
determination in tissues, was accidentally discovered. 相似文献
3.
Sangram Ganguly Arindam Samanta Mitchell A. Schull Nikolay V. Shabanov Cristina Milesi Ramakrishna R. Nemani Yuri Knyazikhin Ranga B. Myneni 《Remote sensing of environment》2008,112(12):4318-4332
The evaluation of a new global monthly leaf area index (LAI) data set for the period July 1981 to December 2006 derived from AVHRR Normalized Difference Vegetation Index (NDVI) data is described. The physically based algorithm is detailed in the first of the two part series. Here, the implementation, production and evaluation of the data set are described. The data set is evaluated both by direct comparisons to ground data and indirectly through inter-comparisons with similar data sets. This indirect validation showed satisfactory agreement with existing LAI products, importantly MODIS, at a range of spatial scales, and significant correlations with key climate variables in areas where temperature and precipitation limit plant growth. The data set successfully reproduced well-documented spatio-temporal trends and inter-annual variations in vegetation activity in the northern latitudes and semi-arid tropics. Comparison with plot scale field measurements over homogeneous vegetation patches indicated a 7% underestimation when all major vegetation types are taken into account. The error in mean values obtained from distributions of AVHRR LAI and high-resolution field LAI maps for different biomes is within 0.5 LAI for six out of the ten selected sites. These validation exercises though limited by the amount of field data, and thus less than comprehensive, indicated satisfactory agreement between the LAI product and field measurements. Overall, the inter-comparison with short-term LAI data sets, evaluation of long term trends with known variations in climate variables, and validation with field measurements together build confidence in the utility of this new 26 year LAI record for long term vegetation monitoring and modeling studies. 相似文献
4.
A two-legged robot will have to generate its near-optimal gaits after ensuring maximum dynamic balance margin and minimum power consumption, while moving on the rough terrains containing some staircases and sloping surfaces. Moreover, the changes of joint torques should lie below a pre-specified small value to ensure its smooth walking. The balance of the robot and its power consumption are also dependent on hip trajectory and position of the masses on various limbs. Both neural network- and fuzzy logic-based gait planners have been developed for the same, the training of which are provided using a genetic algorithm off-line. Once optimized, the planners are found to generate optimal gaits of the two-legged robot successfully for the test cases. 相似文献
5.
6.
Naren Narasimhan Elena Teica Rajesh Radhakrishnan Sriram Govindarajan Ranga Vemuri 《Formal Methods in System Design》2001,19(3):237-273
This paper presents a formal specification and a proof of correctness for the widely-used Force-Directed List Scheduling (FDLS) algorithm for resource-constrained scheduling of data flow graphs in high-level synthesis systems. The proof effort is conducted using a higher-order logic theorem prover. During the proof effort many interesting properties of the FDLS algorithm are discovered. These properties are formally stated and proved in a higher-order logic theorem proving environment. These properties constitute a detailed set of formal assertions and invariants that should hold at various steps in the FDLS algorithm. They are then inserted as programming assertions in the implementation of the FDLS algorithm in a production-strength high-level synthesis system. When turned on, the programming assertions (1) certify whether a specific run of the FDLS algorithm produced correct schedules and, (2) in the event of failure, help discover and isolate programming errors in the FDLS implementation.We present a detailed example and several experiments to demonstrate the effectiveness of these assertions in discovering and isolating errors. Based on this experience, we discuss the role of the formal theorem proving exercise in developing a useful set of assertions for embedding in the scheduler code and argue that in the absence of such a formal proof checking effort, discovering such a useful set of assertions would have been an arduous if not impossible task. 相似文献
7.
Large amount of literature is presently available on the topic of scour around uniform piers and its control. However, relatively fewer studies have been carried out so far on the topic of flow field and scour around compound piers. The state of art on the topic of flow structure and scour around circular compound piers is presented herein. The available literature reveals that variations in foundation and pier geometry significantly affect the maximum depth of scour and its temporal variation. In case of compound piers the scour depth is highly sensitive to the change in elevation of the top surface of the foundation well. As compared to uniform piers, a reduction is observed in maximum depth of scour around compound pier when the top surface of the well is kept below the general level of river bed. These observations however are yet to be quantified. Results from an experimental study on flow field around the compound piers are also presented. 相似文献
8.
9.
Douglas A Stow Allen Hope David Verbyla Fred Huemmrich Charles Racine Kenneth Tape Kenji Yoshikawa Brian Noyle David Douglas Gensuo Jia Donald Walker Aaron Petersen Ranga Myneni 《Remote sensing of environment》2004,89(3):281-308
The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. 相似文献
10.
In the present study, we report the synthesis of photoactive bismuth oxycarbonate (BOC, Bi2O2CO3) grafted NiFe layered double hydroxide (LDH) supported on g-C3N4 (15 wt% of g-C3N4) by coprecipitation method. The band gap of this photoactive material is determined to be 1.7 eV. The Bi2O2CO3 agglomerates are anchored on NiFe-LDH plates and g-C3N4 nanosheets intercalated between the LDH plates. This architecture helps in expediting electron transfer for hydrogen and oxygen evolution reactions. The pristine NiFe-LDH photoanode acquires bifunctional character because of Bi2O2CO3 agglomerates and g-C3N4 embedded in the architecture of BOC/NiFe-LDH@g-C3N4. This is found to be an efficient photoanode for oxygen evolution and photocathode for hydrogen evolution reactions. The water splitting process occurs along the heterojunction formed between g-C3N4 nanosheets and Bi2O2CO3 grafted NiFe-LDH. Further, an additional interfacial charge transfer aided by Bi2O2CO3 results in S-scheme mechanism, which enhances the rate of photoelectrochemical hydrogen and oxygen evolution reactions. 相似文献