Electrical conductivity in iodine-doped ethyl cellulose

The electrical conductivity of solution-grown ethyl cellulose (EC) films, 5–30 μm thick, has been studied in the sandwich configuration (metal–EC–metal) as a function of iodine concentration from 0.5 to 5.0 wt% ratio. The studies were conducted in the temperature range 333–383 K, while the field was varied over the range (3.0–5.5) × 10⁴V/cm. Aluminium was used as the lower electrode, while the upper electrode was of Al, Ag, Cu, Au or Sn. Certain transient effects such as a large burst of current immediately after the application of field were observed. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories of electrical conduction. The results show that the electrical conduction follows Ohm's law at lower fields, while at higher fields, space-charge limited current (SCLC) was observed. It was also found that Richardson–Schottky emission was responsible, to some extent, for the transport of charge carriers in the polymer. The conductivity of the films increased on doping with iodine. The dopant molecules are considered to act as additional trapping centes and provide links between the polymer molecules in the amorphous region, thus resulting in the formation of charge transfer complexes.     

XML: a door to automated Web applications

In Japanese culture, your meishi conveys your place in the company, even in society, as well as your name, phone number, and e-mail address. That is to say, in Japan, business cards matter. They convey complex metadata about the people who carry them. Like people, Web pages come in an abundance of shapes and sizes (and sounds). What makes them machine interpretable-and therefore a new medium for communicating information globally-is Hypertext Markup Language. HTML allows the structural markup of Web documents, distinguishing the elements of a page with tags and declaring the physical relationships among the various document elements. This organizes the display of information and allows humans to read and use it. To give machines this capability, however, requires semantic markup, identifying what each particular element means on its own (for example, “this is a home street address” or “this is an e-mail address”). Semantic markup would change what is now simply displayed content to machine readable, structured content. The Extensible Markup Language (XML) specification, first released as two working drafts in 1997 by the World Wide Web Consortium, makes it dramatically easier to develop and deploy domain- and mission-specific Web pages. We describe the evolution of the Web's data representation from display formats to structural markup to semantic markup     

Dimensionality Reduction for Fast Similarity Search in Large Time Series Databases

The problem of similarity search in large time series databases has attracted much attention recently. It is a non-trivial problem because of the inherent high dimensionality of the data. The most promising solutions involve first performing dimensionality reduction on the data, and then indexing the reduced data with a spatial access method. Three major dimensionality reduction techniques have been proposed: Singular Value Decomposition (SVD), the Discrete Fourier transform (DFT), and more recently the Discrete Wavelet Transform (DWT). In this work we introduce a new dimensionality reduction technique which we call Piecewise Aggregate Approximation (PAA). We theoretically and empirically compare it to the other techniques and demonstrate its superiority. In addition to being competitive with or faster than the other methods, our approach has numerous other advantages. It is simple to understand and to implement, it allows more flexible distance measures, including weighted Euclidean queries, and the index can be built in linear time. Received 16 May 2000 / Revised 18 December 2000 / Accepted in revised form 2 January 2001     

I want my FTP: bits on demand

A look under the hood of the IETF's file transfer protocol, including a summary of the commands in the FTP standard. Today, FTP is used primarily for maintaining archives of public files, and is losing ground to HTTP even there. FTP simply doesn't maintain as much metadata: not creation date, not original location, not application data type. Its addressing structure is an opaque pathname at a host. Consider that in the context of mirroring or relocating information: FTP mirrors are an ad hoc, user driven abstraction; HTTP can send automatable redirection messages. Per-site metadata is also provided manually as OOindex files, compared to automatable Web spiders     

2021年混合云科技将如何发展?

很少有企业能预料到2020年出现的巨大变化.2020年出现的新冠肺炎疫情打乱了整个世界的节奏,迫使企业迅速调整其技术基础设施,让员工能远程开展工作的同时做好更长远的规划,以应对前所未有的不确定性.对很多企业而言,重新改造IT基础设施是其生存下去的关键.     

FPGA Implementation of Cross Virtual Concatenation Transmitter/ Receiver for Data Transmission over Next Generation SDH Systems

Cross Virtual Concatenation is the new technique proposed for bandwidth efficient transmission of data over SDH networks. SDH networks came into existence for reliable voice transmission. As the demand of data traffic grew in wide area networks, new technologies were developed and standardized for data transmission over SDH networks. The technologies used namely, GFP (generic framing procedure), VCAT (virtual concatenation) and LCAS (link capacity adjustment scheme) enable network operator to provide integrated voice and data services over their legacy SDH infrastructure. Data packets are encapsulated using framing protocols GFP. VCAT is a process of distributing the GFP framed data payload in number of virtual channels of same capacity forming a Virtually Concatenated Group (VCG). LCAS is used for dynamic bandwidth allocation. LCAS enhances the VCAT scheme with hitless in service addition and removal of VC’s to/from the VCG.VCAT combines homogeneous virtual channels together which in some cases limits the performance of VCAT. This paper describes the implementation of new concatenation technology named cross virtual concatenation (CVC), which combines heterogeneous VC’s together to utilize the SDH bandwidth more efficiently. CVC implementation requires only end node equipments to be upgraded as VCG members travel through the link similar to the conventional VCAT. This paper proposes FPGA implementation of transmitter and receiver circuits for 100 Mbps Ethernet data transmission over next Generation SDH systems using CVC, where two types of VC’s namely VC-3 and VC-12 are used for data transmission. Total Transmission delay is calculated as 125 μs. There is no complexity added at the receiver side due to this delay. The receiver is designed for 32 ms differential delay compensation which can be increased up to maximum 256 ms by increasing the buffer size at the receiver.