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991.
AD7656与LPC2210的并行采集接口设计 总被引:1,自引:0,他引:1
引言在电力系统三相信号处理应用中,常需要同时对A、B、C三相电压和电流信号进行数据采集和处理。如三相功率、电能测量及谐波分析等。美国ADI公司的AD7656是16位6通道同时采样的模/数转换器,内部含有6个16位A/D转换器,具有转换精度高、速度快、功耗低、输入模拟信号幅度大、信噪比高等特点。Philips公司出品的LPC2210,是一款工业级的ARM控制器,处理速度快,性能稳定,与AD7656共同组成的6通道数据采集系统能在很大程度上提高系统的信号采集和处理能力。1AD7656的特点及工作原理1.1AD7656的特点图1为AD7656的内部功能框图。其主要特性为:◆6个16位独立的ADC通道。◆输入模拟信号的范围为±(10~15V)。◆最大转换速率为250ksps。◆低功耗,5V供电时在250ksps下功耗为140mW。◆片上2.5V参考电压和参考缓冲器。◆8/16位并行接口模式和串行接口模式。1.2工作原理AD7656是6通道16位逐次逼近型ADC,有2种接口模式:串行接口模式和高速的并行接口模式,并行接口模式又分为8位和16位传送方式。在数据转换时,3个转换信号CONVSTA/B/C,用来控制每对或每4... 相似文献
992.
Chih-Lyang Hwang Li-Jui Chang 《Fuzzy Systems, IEEE Transactions on》2008,16(5):1271-1284
993.
Yu-Chuan Chang Shyi-Ming Chen Churn-Jung Liau 《Fuzzy Systems, IEEE Transactions on》2008,16(5):1285-1301
994.
Soumyadeb Mitra Marianne Winslett Windsor W. Hsu Kevin Chen-Chuan Chang 《The VLDB Journal The International Journal on Very Large Data Bases》2008,17(2):225-242
Intense regulatory focus on secure retention of electronic records has led to a need to ensure that records are trustworthy,
i.e., able to provide irrefutable proof and accurate details of past events. In this paper, we analyze the requirements for
a trustworthy index to support keyword-based search queries. We argue that trustworthy index entries must be durable—the index
must be updated when new documents arrive, and not periodically deleted and rebuilt. To this end, we propose a scheme for
efficiently updating an inverted index, based on judicious merging of the posting lists of terms. Through extensive simulations
and experiments with two real world data sets and workloads, we demonstrate that the scheme achieves online update speed while
maintaining good query performance. We also present and evaluate jump indexes, a novel trustworthy and efficient index for join operations on posting lists for multi-keyword queries. Jump indexes support
insert, lookup and range queries in time logarithmic in the number of indexed documents. 相似文献
995.
Yu‐Ting Lin Po‐Hung Lin Sheue‐Ling Hwang Shie‐Chang Jeng 《Journal of the Society for Information Display》2008,16(10):1051-1062
Abstract— This study is intended to explore the legibility and visual fatigue of different age users under various surface treatments and reflectance of electronic paper. Through the method of character‐search task, the results indicated that compared with single types of treatment [anti‐reflection (AR) 0.8%, anti‐glare, 43% haze), the compound treatment of anti‐reflection and anti‐glare (ARC) exhibited the same legibility, and it showed superior properties to effectively reduce visual fatigue. Hence, it is suggested that electronic‐paper manufacturers should choose the compound surface treatment for better visual performance. On the other hand, the findings also validated that enhancing the reflectance of electronic paper to the same level as regular paper (about 80%) is worthy to be practically implemented. Based on the results of this study, electronic‐paper manufacturers can take useful information to fulfill ergonomic requirements on product design. 相似文献
996.
Yu‐Ting Lin Po‐Hung Lin Sheue‐Ling Hwang Shie‐Chang Jeng Yan‐Rung Lin 《Journal of the Society for Information Display》2008,16(1):91-99
Abstract— The intent of this study is to investigate some critical factors that affect legibility and visual fatigue while reading on an electronic‐paper display in terms of ergonomics. Anti‐reflection surface treatment, ambient illumination, and bending curvature are taken into account to evaluate their effects by using the method of letter‐search task. The results showed that the surface treatment with high degrees of anti‐reflection significantly improved the legibility and reduces visual fatigue. Thus, electronic‐paper manufacturers may choose a much better surface treatment in order to meet ergonomic demand. In addition, the findings in the present study also indicate that subjects reported less visual fatigue on a bending surface of a visual display unit, in comparison with a plane surface. It is proven that these ergonomic evaluations for electronic paper provide manufactures with useful information to design suitable products for users. 相似文献
997.
998.
Prasan Kumar Sahoo Chih-Yung Chang Sheng-Wen Chang 《Journal of Network and Computer Applications》2008,31(4):535-558
Bluetooth technology is specially designed for the wireless personal area networks to replace cable. Several challenges exist in Bluetooth scatternet formation and routing, since nodes can arrive and depart at arbitrary times. In this paper, novel route maintenance algorithms are proposed for the Bluetooth ad hoc networks, where nodes can enter or exit from the piconets time to time. Our protocols guarantee the connectivity among nodes and reconstruct the routes dynamically by considering location information of the nodes. Besides, it is proposed how to reduce the number of hops and to form the shortest route between the source and the destination due to addition of new nodes to a piconet. Performance analysis of our protocols show that they outperform in terms of end to end transmission delay, bandwidth consumption and average hop counts as compared to similar Bluetooth routing protocols that we have considered. 相似文献
999.
Privacy is becoming increasingly important due to the advent of e-commerce. E-commerce applications frequently require customers to divulge many personal details about themselves that must be protected carefully in accordance with privacy principles and regulations. Here, the authors define a privacy ontology to support the provision of privacy and help derive the level of privacy associated with e-commerce transactions and applications. The privacy ontology provides a framework against which e-commerce sites can benchmark their privacy policies and implementations. 相似文献
1000.
A feature relies on three dimensions (space, theme, and time) for its representation. Even though spatiotemporal models have
been proposed, they have principally focused on the spatial changes of a feature. In this paper, a feature-based temporal
model is proposed to represent the changes of both space and theme independently. The proposed model modifies the ISO’s temporal
schema and adds new explicit temporal relationship structure that stores temporal topological relationship with the ISO’s
temporal primitives of a feature in order to keep track feature history. The explicit temporal relationship can enhance query
performance on feature history by removing topological comparison during query process. Further, a prototype system has been
developed to test a proposed feature-based temporal model by querying land parcel history in Athens, Georgia. The result of
temporal query on individual feature history shows the efficiency of the explicit temporal relationship structure.
相似文献
E. Lynn UseryEmail: |