Underwater Inductive Power Transfer with Wireless Charging Applications

Underwater wireless power transfer (UWPT) has become an area of great interest due to the advancement of autonomous underwater vehicles (AUVs) and electic boats. This paper seeks to investigate the variation of the coupling coefficient and power transfer in air versus in seawater. The design is based on a class E converter as it can achieve soft-switching inherently. I made the transmitter and receiver coils then measured self-inductance and parasitic resistance in air and in water. I noted that self-inductance increases when they are placed in water but the mutual inductance is lower. I then calculated the component values for the class E converter based on inductor values (140 μH and 105 μH) and simulated the circuit on LTspice. The power at the output was 74W which is lower than the required value. However, I noted that reducing the coils inductance values while maintaining the value of the other passive components increased the efficiency and power at the output upto four times (311W). The final value chosen for making the inductors was 115 μH and 75 μH as these values gave the maximum power at the output while achieving ZVS. I then designed the transmitter and receiver circuits on Altium and printed the PCBs. All the components were then soldered onto the board and the tests done

Spectrum Abundance and the Choice Between Private and Public Control

Prominent commentators have recently proposed that the government allocate significant portions of the radio spectrum as a wireless commons. The problem for commons proposals is that truly open access leads to interference, which renders a commons unattractive. Those advocating a commons assert, however, that a network comprising devices that operate at low power and repeat each other's messages can eliminate the interference problem. They contend that this possibility renders spectrum commons more efficient than privately owned spectrum, and in fact that private owners would not create these abundant networks (as I call them) in the first place. In this Article I argue that these assertions are not well-founded, and that efficiency considerations favor private ownership of the spectrum. Those advocating a commons do not propose a network in which anyone can transmit as she pleases. The abundant networks they envision involve significant control over the devices that will be allowed to transmit. On the question whether private entities will create these abundant networks, commons advocates emphasize the transaction costs of aggregating spectrum, but those costs can be avoided via allotment of spectrum in large swaths. The comparative question of the efficiency of private versus public control, meanwhile, entails an evaluation of the implications of the profit motive (enhanced ability and desire to devise the best networks, but also the desire to attain monopoly power) versus properties of government action (the avoidance of private monopoly, but also a cumbersome process than can be subject to rent-seeking). The deciding factor, in my view, is that these networks might not develop as planned, and so the flexibility entailed by private ownership, as well as the shifting of the risk of failure from taxpayers to shareholders, makes private ownership the better option. The unattractiveness of a commons in this context casts serious doubt on the desirability of commons more generally. Commons proponents have championed abundant networks because those networks avoid interference problems. If private ownership is a more efficient means of creating abundant networks, then the same would almost certainly be true for networks that run the risk of interference. Most uses of spectrum are subject to interference, so the failure of the commons advocates' arguments undermines the appeal of a commons for most potential uses of spectrum. (Updated December 2003.)

Telecommunication Network Security

YesOur global age is practically defined by the ubiquity of the Internet; the worldwide interconnection of cyber networks that facilitates accessibility to virtually all ICT and other elements of critical infrastructural facilities, with a click of a button. This is regardless of the user’s location and state of equilibrium; whether static or mobile. However, such interconnectivity is not without security consequences. A telecommunication system is indeed a communication system with the distinguishing key word, the Greek tele-, which means "at a distance," to imply that the source and sink of the system are at some distance apart. Its purpose is to transfer information from some source to a distant user; the key concepts being information, transmission and distance. These would require a means, each, to send, convey and receive the information with safety and some degree of fidelity that is acceptable to both the source and the sink. Chapter K begins with an effort to conceptualise the telecommunication network security environment, using relevant ITU-T2* recommendations and terminologies for secure telecommunications. The chapter is primarily concerned with the security aspect of computer-mediated telecommunications. Telecommunications should not be seen as an isolated phenomenon; it is a critical resource for the functioning of cross-industrial businesses in connection with IT. Hence, just as information, data or a computer/local computer-based network must have appropriate level of security, so also a telecommunication network must have equivalent security measures; these may often be the same as or similar to those for other ICT resources, e.g., password management. In view of the forgoing, the chapter provides a brief coverage of the subject matter by first assessing the context of security and the threat-scape. This is followed by an assessment of telecommunication network security requirements; identification of threats to the systems, the conceivable counter or mitigating measures and their implementation techniques. These bring into focus various cryptographic/crypt analytical concepts, vis a vis social engineering/socio-crypt analytical techniques and password management. The chapter noted that the human factor is the most critical factor in the security system for at least three possible reasons; it is the weakest link, the only factor that exercises initiatives, as well as the factor that transcends all the other elements of the entire system. This underscores the significance of social 2*International Telecommunications Union - Telecommunication Standardisation Sector 12 engineering in every facet of security arrangement. It is also noted that password security could be enhanced, if a balance is struck between having enough rules to maintain good security and not having too many rules that would compel users to take evasive actions which would, in turn, compromise security. The chapter is of the view that network security is inversely proportional to its complexity. In addition to the traditional authentication techniques, the chapter gives a reasonable attention to locationbased authentication. The chapter concludes that security solutions have a technological component, but security is fundamentally a people problem. This is because a security system is only as strong as its weakest link, while the weakest link of any security system is the human infrastructure. A projection for the future of telecommunication network security postulates that, network security would continue to get worse unless there is a change in the prevailing practice of externality or vicarious liability in the computer/security industry; where consumers of security products, as opposed to producers, bear the cost of security ineffectiveness. It is suggested that all transmission devices be made GPS-compliant, with inherent capabilities for location-based mutual authentication. This could enhance the future of telecommunication security.Petroleum Technology Development Fun

Multiple-access interference rejecting receivers in DS-CDMA communication system

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN037068 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Proceedings of the Mobile Satellite Conference

A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them

NASA compendium of satellite communications programs

A comprehensive review is given of worldwide satellite communication programs that range in time from the inception of satellite communications to mid-1974. Particular emphasis is placed on program results, including experiments conducted, communications system operational performance, and technology employed. The background for understanding these results is established through brief summaries of the program organization, system configuration, and satellite and ground terminal characteristics. Major consideration is given to the communications system aspects of each program, but general spacecraft technology and other experiments conducted as part of the same program are mentioned summarily