Results 1 - 10 of 87856
Results 1 - 10 of 87856. Search took: 0.081 seconds
|Sort by: date | relevance|
[en] We report on the experimental observation of the Fermi–Pasta–Ulam (FPU) recurrence in an experimental bi-modal nonlinear transmission line. The FPU recurrence is observed in the two transmission modes known as the low frequency mode and the high frequency mode. In each case, a spectrum analysis is performed in order to study the waves along the line. (paper)
[en] The protection of underground cables against transient over voltages resulting from lightning and other causes is important in cable-line. So, The SVL(Sheath Voltage Limiter) is installed in not only transmission power cable system but also plant cable system. This paper investigates the failure of SVL and presents improved configuration method of SVL in the underground cable system. EMTP(Electromagnetic Transient Program) is used in order to study the over voltages and modeling of components of the system such as overhead lines, underground cables, SVLs and towers
[en] This paper shows the design of a second-order multi-bit ΔΣ modulator with hybrid structure for ADSL applications. A modified two phase non-overlapping clock generator is designed to let PH2 borrow 12% of the time from PH1, which relaxes the speed of OTAs, comparators and the DEM block. The clock feed through problem of the passive adder is solved by revising the timing of the comparators and the adder. The chip is designed and fabricated in UMC 0.18 μm CMOS technology. Measurement results show that with an oversampling ratio of 32 and a clock rate of 80 MHz, the modulator can achieve 79 dB dynamic range, 71.3 dB SNDR, 11 mW power consumption from a 1.8 V power supply. The FOM is 1.47 pJ/step.
[en] In this paper, a general method of data transmission system design on PXI platform is proposed. It can be used in readout system design for physical experiments. It aims at providing reusable and general interfaces for customized design of PXI while maintaining the transmission performance. It has three main features: (1) universal logic hardware interface, (2) ethernet based socket software interface, and (3) specific and simple data transmission protocol. Data transmission on PXI bus can be realized with the said two universal interfaces coordinated by this specific protocol. Test shows that this method is feasible and stable. This method can be easily reused in readout system designs for different experiments. (authors)
[en] At the end of the 19th century Nikola Tesla started his work in the field of wireless energy transmission. More than 100 years after Tesla, the progress in modern semiconductor technology offer developers the possibility to realize highly efficient systems and have led to a revival of wireless energy transmission. The application ranges from the transmission of a few milliwatts in biomedical applications, over a few watts for the charging of mobile phones, to hundreds of kilowatts in the automotive sector. Depending on the used method, the possible transmission distances vary between a few centimeters up to thousands of kilometers. The physical basis of these technologies is the transmission of energy by electromagnetic waves. State-of-the-art systems use wavelengths ranging from radio waves to microwaves, to ultraviolet light. Current research focuses on optimizing transmission efficiency, increasing the possible transmission distance between transmitter and receiver, and improving spatial freedom of movement. This lecture gives an overview of the different approaches of wireless energy transmission and their physical background, the established industrial standards and the current state of research. In addition, the advantages and disadvantages of the individual methods are illustrated by selected commercial and scientific applications. (rössner)
[de]Die Idee der drahtlosen Energieübertragung wurde Ende des 19. Jahrhunderts von Nikola Tesla begründet. Die Fortschritte der modernen Halbleitertechnologie bieten Entwicklern die Möglichkeit zu Realisierung hocheffizienter Systeme und haben heute, mehr als 100 Jahre nach Tesla, zu einer Wiederbelebung der drahtlosen Energieübertragung geführt. Die Anwendungsgebiete reichen von der Übertragung einiger Milliwatt in biomedizinischen Applikationen, über wenige Watt für das Laden von Mobiltelefonen, bis hin zu hunderten von Kilowatt im Automobilbereich. Die möglichen Übertragungsdistanzen variieren je nach verwendeter Methode zwischen einigen Zentimetern bis hin zu tausenden von Kilometern. Die physikalische Grundlage dieser Technologien bildet die Energieübertragung durch elektromagnetische Wellen. Moderne Systeme verwenden je nach Applikation Wellenlängen vom Radiowellen-, über den Mikrowellen-, bis hin in den Bereich des ultravioletten Lichts. Die Schwerpunkte der aktuellen Forschung liegen in der Optimierung der Übertragungseffizienz, der Vergrößerung der möglichen Übertragungsdistanz zwischen Sender und Empfänger und der Verbesserung der räumlichen Bewegungsfreiheit. Dieser Vortrag gibt einen Überblick über die verschiedenen Ansätze zur drahtlosen Energieübertragung und deren physikalische Hintergründe, die etablierten Industriestandards und den aktuellen Stand der Forschung. Zusätzlich werden die Vor- und Nachteile der einzelnen Methoden anhand von ausgewählten kommerziellen und wissenschaftlichen Applikationen verdeutlicht. (author)
[en] Highlights: • An attack aimed at the parameter estimation algorithm is proposed. • This attack can be achieved by Eve's slightly change of the channel transmittance. • This attack can cause communication to be interrupted. • By using post-selection method, the effect of this attack can be nearly eliminated. - Abstract: In a fiber-based continuous-variable quantum key distribution (CVQKD) system, to perform the channel estimation, the channel transmittance is usually assumed to be a constant. Subsequently, when the channel parameters are intentionally manipulated, the employed parameter estimation method will lead to deviations of channel parameters and ultimately impacting the evaluation of the secret key rate. In this paper, we propose a denial-of-service attack strategy based on Eve's manipulation of the channel parameters. In particular, we analyze in detail the impact of this attack when the channel transmittance is attacked and obeys two-point distribution and uniform distribution. The result shows that in both cases, Eve's slight manipulation on the quantum channel will lead to large underestimation of the secure transmission distance by using the previous parameter estimation, which will lead to intentional terminations of the communication. To prevent this attack, a simple data post-selection should be added before parameter estimation.
[en] The approach used by Hydro-Quebec for the environmental assessment of siting power transmission line and towers in northern Quebec is described. Since the first approach was implemented in 1985, an overall revision has been undertaken to take advantage of the lessons learned from recent projects, to develop an approach applicable to various types of projects and environments, and to favor integration of information and consultation with the concerned public. The approach by successive reduction of territory has been retained for determining the optimum siting of facilities. The numerous modifications to the environmental assessment approach have led to the formation of a new approach having the following steps: technical evaluation of the project to determine the characteristics susceptible to be sources of environmental impact; characterizing the environment in which the project is to be located; determining the technical, economic, and environmental performance of the project and identifying a preferred solution; communicating the project evaluation to the public; choosing the final form of the project based on the comments received and establishing the environmental balance; and monitoring the project and its environmental impact after construction. The characteristics of the northern environment having an influence on this evaluation include the presence of environmentally sensitive terrain, reservoirs, work camps, aboriginal lands, and permafrost. 6 figs
[en] This paper deals with problems of speech transmission quality measurement in modern telecommunication networks. It focuses on problems caused by specific types of distortions and errors caused present in transmissions using TCP/IP networks
[en] There is magnetic force acting on the wall of a square coaxial transmission line when TEM wave propagates in it. The self-inductance can be determined based on a conformal transformation for the field region, which demonstrates that the inductance only depends on the side length ratio of the two walls instead of the length of the walls. The magnetic force on each side of the walls is then calculated by employing the principle of virtual work. It is proved that the magnetic force has the same magnitude and opposite direction to the electric force. And then the electromagnetic force on the wall is zero. The general meaning of this conclusion for all kinds of coaxial transmission line is proposed. - Highlights: • The self-inductance of square coaxial transmission line is determined. • The inductance only depends on the side length ratio of the two walls. • The magnetic force on each side of the walls is calculated. • The electromagnetic force on wall is zero. • The conclusion has general meaning for all kinds of coaxial transmission line
[en] Optimization of transmission tower structures is traditionally based on either optimization of members sizes with fixed topographical shape or based on structural analysis modelling strategies without taking cognizance of fabrication and constructability issue facing the contractors . This paper look into an integrated optimum design approach strategies whereby size, shape and topology are combined together with the fabrication issues in the construction of the transmission tower. The topographical algorithm is based on changing the inclination degree of the legs of the tower at first with optimum individual members sizing and later rationalized member sizes are performed through member groupings for the ease fabrication and construction of the transmission tower. The optimum weight using topographical algorithm obtained for the transmission tower is 10,924 kg for singular members and 18,430 kg for element grouping at 10° inclination angle.