Optimum coding techniques for MST radars

The optimum coding technique for MST (mesosphere stratosphere troposphere) radars is that which gives the lowest possible sidelobes in practice and can be implemented without too much computing power. Coding techniques are described in Farley (1985). A technique mentioned briefly there but not fully developed and not in general use is discussed here. This is decoding by means of a filter which is not matched to the transmitted waveform, in order to reduce sidelobes below the level obtained with a matched filter. This is the first part of the technique discussed here; the second part consists of measuring the transmitted waveform and using it as the basis for the decoding filter, thus reducing errors due to imperfections in the transmitter. There are two limitations to this technique. The first is a small loss in signal to noise ratio (SNR), which usually is not significant. The second problem is related to incomplete information received at the lowest ranges. An appendix shows a technique for handling this problem. Finally, it is shown that the use of complementary codes on transmission and nonmatched decoding gives the lowest possible sidelobe level and the minimum loss in SNR due to mismatch

Decoding: Codes and hardware implementation

The MST radars vary considerably from one installation to the next in the type of hardware, operating schedule and associated personnel. Most such systems do not have the computing power to decode in software when the decoding must be performed for each received pulse, as is required for certain sets of phase codes. These sets provide the best signal to sidelobe ratio when operating at the minimum band length allowed by the bandwidth of the transmitter. The development of the hardware phase decoder, and the applicability of each to decoding MST radar signals are discussed. A new design for a decoder which is very inexpensive to build, easy to add to an existing system and is capable of decoding on each received pulse using codes with a band length as short as one microsecond is presented

How Addictive Drugs Disrupt Presynaptic Dopamine Neurotransmission

The fundamental principle that unites addictive drugs appears to be that each enhances synaptic dopamine by means that dissociate it from normal behavioral control, so that they act to reinforce their own acquisition. This occurs via the modulation of synaptic mechanisms that can be involved in learning, including enhanced excitation or disinhibition of dopamine neuron activity, blockade of dopamine reuptake, and altering the state of the presynaptic terminal to enhance evoked over basal transmission. Amphetamines offer an exception to such modulation in that they combine multiple effects to produce nonexocytic stimulation-independent release of neurotransmitter via reverse transport independent from normal presynaptic function. Questions about the molecular actions of addictive drugs, prominently including the actions of alcohol and solvents, remain unresolved, but their ability to co-opt normal presynaptic functions helps to explain why treatment for addiction has been challenging

African literature to-day

Being interested in African literature one seems to swim from the very beginning in a terminological maelstrom. What is African literature? Is it literature written by any African author in any language? That would mean approaching the question from a purely racial basis. It would imply the art of demonstrating that any piece of such literature could infallibly be recognised as African, a thing which, as far as I know has never been done. Or is African literature strictly bound to traditional African culture

Re-alignment of German car producers in times of profound changes

This research analyzes and assesses emerging macro-environmental trends in the automotive industry and their evolutionary effect on the competitive advantage of major premium car manufacturers in Germany. To answer this question, the historical key drivers for the success of the German car makers are explored. Furthermore, the probable core competencies and the resulting competitive advantage of the future are examined in order to propose new business strategies for OEMs. Also, the impact of COVID-19 on the companies within the scope of this thesis represents a research object. In order to anser these questions appropriately, in-depth interviews are conducted with five top-level managers from German OEMs and are subjected to a content-analysis. In addition to that, academic literature and business reports are supplemented to critically reflect both sources of knowledge and to get a holistic view on the topic. Also, in order to clarify current industry and market trends, Porter’s five forces and the PESTEL analysis were applied. Building upon the outcome of these frameworks, a TOWS anlysis and Confrontation matrix are conducted to be able to propose new strategies for the underlying companies. OEMs should strive for a stronger customer focus and a faster subsequent adaptability for changing customer needs which they make possible through a even higher innovative power than they had in the past. This enables OEMs to stay ahead of the stiff competition from Asia and China and help them to win the race of sustainability. To create these core competencies, OEMs are urged to engage cross-industry collaborations to avoid the threat of new entrants, increasing the innovative power and ensure sustained competitive advantage. The strong political, social, legal and environmental pressure to decrease CO2 emissions needs to be adressed quickly through the production of electric cars, further optimization of internal combustion engines and the use of lightweight materials.Esta investigação analisa e avalia as tendências macro-ambientais emergentes na indústria automóvel e o seu efeito evolutivo sobre a vantagem competitiva dos principais fabricantes de automóveis premium na Alemanha. Para responder a esta pergunta, são explorados os factores históricos fundamentais para o sucesso dos fabricantes alemães de automóveis. Além disso, são examinadas as prováveis competências nucleares e a vantagem competitiva resultante do futuro, a fim de propor novas estratégias de negócio para OEMs. Além disso, o impacto da COVID-19 sobre as empresas no âmbito desta tese representa um objecto de investigação. A fim de responder adequadamente a estas questões, são realizadas entrevistas aprofundadas com cinco gestores de topo de OEMs alemães e são submetidos a uma análise de conteúdo. Além disso, a literatura académica e os relatórios empresariais são complementados para reflectir criticamente ambas as fontes de conhecimento e para obter uma visão holística sobre o tema. Também, a fim de clarificar as tendências actuais da indústria e do mercado, foram aplicadas as cinco forças de Porter e a análise PESTEL. Com base no resultado destes quadros, é realizada uma matriz de análise e de confrontação TOWS para se poder propor novas estratégias para as empresas subjacentes. Os OEM devem esforçar-se por uma maior concentração no cliente e uma adaptabilidade subsequente mais rápida para a mudança das necessidades do cliente, que tornam possível através de um poder inovador ainda maior do que no passado. Isto permite aos OEM manterem-se à frente da dura concorrência da Ásia e da China e ajudá-los a vencer a corrida da sustentabilidade. Para criar estas competências centrais, os OEM são instados a envolverem-se em colaborações intersectoriais para evitar a ameaça de novos participantes, aumentando o poder inovador e assegurando uma vantagem competitiva sustentada. A forte pressão política, social, legal e ambiental para diminuir as emissões de CO2 precisa de ser rapidamente abordada através da produção de carros eléctricos, de uma maior optimização dos motores de combustão interna e da utilização de materiais leves

Meteor science from regular incoherent scatter radar ionospheric observations at Arecibo

International audienceWe report the observation and analysis of ionization flashes associated with the decay of meteoroids (so-called head echos) detected by the Arecibo 430 MHz radar during regular ionospheric observations in the spring and autumn equinoxes. These two periods allow pointing well-above and nearly-into the ecliptic plane at dawn when the event rate maximizes. The observation of many thousands of events allows a statistical interpretation of the results, which show that there is a strong tendency for the observed meteoroids to come from the apex as has been previously reported (Chau and Woodman, 2003). The velocity distributions agree with Janches et al. (2003) when they are directly comparable, but the azimuth scan used in these observations allows a new perspective. We have constructed a simple statistical model which takes meteor velocities as input and gives radar line of sight velocities as output. The intent is to explain the fastest part of the velocity distribution. Since the speeds interpreted from the measurements are distributed fairly narrowly about nearly 60 km/s?1, double the speed of the earth in its orbit, the obvious interpretation is that many of the meteoroids seen by the Arecibo radar are moving in orbits about the sun with similar parameters as the earth, but in the retrograde direction. However, some aspects of the measured velocity distributions suggest that this is not a complete description even for the fast part of the distribution, and it certainly says nothing about the slow part first described in Janches et al. (2003). Furthermore, we cannot conclude anything about the entire dust population since there are probably selection effects that restrict the observations to a subset of the population

Meteoroid velocity distribution derived from head echo data collected at Arecibo during regular world day observations

We report the observation and analysis of ionization flashes associated with the decay of meteoroids (so-called head echos) detected by the Arecibo 430 MHz radar during regular ionospheric observations in the spring and autumn equinoxes. These two periods allow pointing well-above and nearly-into the ecliptic plane at dawn when the event rate maximizes. The observation of many thousands of events allows a statistical interpretation of the results, which show that there is a strong tendency for the observed meteoroids to come from the apex as has been previously reported (Chau and Woodman, 2004). The velocity distributions agree with Janches et al. (2003a) when they are directly comparable, but the azimuth scan used in these observations allows a new perspective. We have constructed a simple statistical model which takes meteor velocities as input and gives radar line of sight velocities as output. The intent is to explain the fastest part of the velocity distribution. Since the speeds interpreted from the measurements are distributed fairly narrowly about nearly 60 km s^-1, double the speed of the earth in its orbit, is consistent with the interpretation that many of the meteoroids seen by the Arecibo radar are moving in orbits about the sun with similar parameters as the earth, but in the retrograde direction. However, it is the directional information obtained from the beam-swinging radar experiment and the speed that together provide the evidence for this interpretation. Some aspects of the measured velocity distributions suggest that this is not a complete description even for the fast part of the distribution, and it certainly says nothing about the slow part first described in Janches et al. (2003a). Furthermore, we cannot conclude anything about the entire dust population since there are probably selection effects that restrict the observations to a subset of the population