Quadrature generation techniques for frequency multiplication based oscillators

Frequency multiplication (FM) can be used to design low power frequency synthesizers. This is achieved by running the VCO at a much reduced frequency, while employing a power efficient frequency multiplier, and also thereby eliminating the first few dividers. Quadrature signals can be generated by frequency- multiplying low frequency I/Q signals, however this also multiplies the quadrature error of these signals. Another way is generating additional edges from the low-frequency oscillator (LFO) and develop a quadrature FM. This makes the I-Q precision heavily dependent on process mismatches in the ring oscillator. In this paper we examine the use of fewer edges from LFO and a single stage polyphase filter to generate approximate quadrature signals, which is then followed by an injection-locked quadrature VCO to generate high- precision I/Q signals. Simulation comparisons with the existing approach shows that the proposed method offers very good phase accuracy of 0.5deg with only a modest increase in power dissipation for 2.4 GHz IEEE 802.15.4 standard using UMC 0.13 mum RFCMOS technology.

Response time measurement in flow induced signal generation on semiconductors

Measurable electrical signal is generated when a gas flows over a variety of solids, including doped semiconductors, even at the modest speed of a few meters per second. The underlying mechanism is an interesting interplay of Bernoulli's principle and the Seebeck effect. The electrical signal depends on the square of Mach number (M) and is proportional to the Seebeck coefficient (S) of the solids. Here we present experimental estimate of the response time of the signal rise and fall process, i.e. how fast the semiconductor materials respond to a steady flow as soon as it is set on or off. A theoretical model is also presented to understand the process and the dependence of the response time on the nature and physical dimensions of the semiconductor material used and they are compared with the experimental observations. (c) 2007 Elsevier B.V. All rights reserved.

Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models

We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.

Internet- ja postikysely osallistavan suunnittelun menetelmänä Puijon metsäsuunnitteluprosessissa

Osallistavan suunnittelun määrä Suomessa on viime vuosina kasvanut huomattavasti. Asukaskyselyt ovat yksi tapa osallistaa asukkaita, ja ne sopivat erityisesti suuren yleisön osallistamiseen. Internetissä toteutetut asukaskyselyt nopeuttaisivat ja helpottaisivat asukaskyselyiden tekemistä mm. siksi, että tieto voidaan tallentaa suoraan sähköiseen muotoon. Internetin käyttö asukaskyselyiden tekemisessä on kuitenkin uusi menetelmä, josta on vasta vähän tutkimustietoa. Ongelmallista Internet-kyselyissä on se, että kasvaneista käyttäjämääristä huolimatta kaikilla ei edelleenkään ole mahdollisuutta käyttää Internetiä. Lisäksi Internet-kyselyn otos on yleensä valikoitunut ja otoskoon määritteleminen on hankalaa. Tutkielma toteutettiin osana Kuopion kaupungin Puijon alueen vuorovaikutteista suunnitteluprosessia. Tutkielman tavoitteena oli vertailla Internet-kyselyä postikyselyyn, jotta saataisiin selville, onko Internet-kysely kelvollinen osallistamismenetelmä. Lisäksi tavoitteena oli profiloida vastaajia mielipiteiden ja taustamuuttujien perusteella. Tutkielman aineistona oli Kuopiossa tammikuussa 2009 toteutetun, Puijon aluetta koskevan asukaskyselyn tulokset. Aineiston analysointiin käytettiin faktorianalyysia, klusterianalyysia, erotteluanalyysia ja korrespondenssianalyysia. Katoa tutkittiin ?2-testillä ja laskemalla ristitulosuhteet. Sekä Internet- että postikyselyn vastaajista muodostuivat Tyytymättömien, Tyytyväisten ja Luonnonsuojelijoiden vastaajaryhmät, joilla olivat melko samanlaiset mielipiteet ja taustamuuttujat molemmissa aineistoissa. Tyytymättömät olivat tyytymättömiä Puijon alueen nykytilaan eivätkä arvostaneet Puijoa. Myös Luonnonsuojelijat olivat tyytymättömiä Puijon alueen ja metsien nykyiseen hoitoon, mutta eivät kannattaneet metsänhoitoa. Tyytyväisten mielestä Puijon alueella kaikki on nyt kunnossa. Lisäksi postikyselyn aineistosta muodostui Kehittäjät-ryhmä ja Internet-kyselyn vastaajista Virkistäytyjät-ryhmä. Internet-kyselyssä 46–60-vuotiaat ja korkeakoulutetut olivat yliedustettuina, mutta kummallakaan kyselyllä ei saatu edustavaa otosta kuopiolaisista. Katoa oli paljon. Edes keskustelua herättänyt aihe ei riittänyt aktivoimaan kuopiolaisia vastaamaan kyselyyn ja tutkielmassa käytettyjen tutkimusmenetelmien kannalta kyselylomake oli puutteellinen. Tämän tutkielman tuloksista saatiin lopulta lähinnä suuntaviivoja Puijon suunnitelmaehdotuksille. Kunnissa tarvitaan uusia työkaluja osallistamiseen, ja tähän tarpeeseen Internet-kysely olisi kustannustehokas vastaus. Sen vuoksi Internet-kyselyä kannattaa edelleen tutkia ja kehittää. Internet-kyselyllä olisi mahdollista saada edustavampi otos, jos vastaajat valittaisiin satunnaisotannalla ja he saisivat salasanan kyselyyn. Myös kaikille avoimella kyselyllä voitaisiin kartoittaa mielipiteitä, kunhan tuloksia tulkittaisiin kriittisesti.

Chain of excitation spot generation by aperture engineering

An optical technique is proposed for obtaining multiple excitation spots. Phase-matched counter propagating extended depth-of-focus fields were superimposed along the optical axis for generating multiple localized excitation spots. Moreover, the filtering effect due to the optical mask increases the lateral resolution. Proposed technique introduces the concept of simultaneous multiplane excitation and improves three-dimensional resolution. (C) 2010 American Institute of Physics.

Generation of Cationic Two-Coordinate Group-13 Ligand Systems by Spontaneous Halide Ejection: Remarkably Nucleophile-Resistant (Dimethylamino)borylene Complexes

Spontaneous ejection of chloride from a three-coordinate boron Lewis acid can be effected by employing very electron rich metal substituents and leads to the formation of a sterically unprotected terminal (dimethylamino)borylene complex that has a short metal-boron bond and remarkable resistance to attack by nucleophilic and protic reagents.

How Scientists Retrieve Publications: An Empirical Study of How the Internet Is Overtaking Paper Media

The current mainstream scientific-publication process has so far been only marginally affected by the possibilities offered by the Internet, despite some pioneering attempts with free electronic-only journals and electronic preprint archives. Additional electronic versions of traditional paper journals for which one needs a subscription are not a solution. A clear trend, for young researchers in particular, is to go around subscription barriers (both for paper and electronic material) and rely almost exclusively on what they can find free on the Internet, which often includes working versions posted on the home pages of the authors. A survey of how scientists retrieve publications was conducted in February 2000, aimed at measuring to what extent the opportunities offered by the Internet are already changing the scientific information exchange and how researchers feel about this. This paper presents the results based on 236 replies to an extensive Web-based questionnaire, which was announced to around 3,000 researchers in the domains of construction information technology and construction management. The questions dealt with how researchers find, access, and read different sources; how many and what publications they read; how often and to which conferences they travel; how much they publish, and criteria for where they eventually decide to publish. Some of the questions confronted traditional and electronic publishing, with one final section dedicated to opinions about electronic publishing. According to the survey, researchers already download half of the material that they read digitally from the Web. The most popular method for retrieving an interesting publication is downloading it for free from the author's or publisher's Web site. Researchers are not particularly willing to pay for electronic scientific publications. There is much support for a scenario of electronic journals available freely in their entirety on the Web, where the costs could be covered by, for instance, professional societies or the publishing university.

How do Researchers Find and Retrieve Scientific Publications – A Case study of the Impact of the Internet on the Construction IT and Construction Management Research Communities

The World Wide Web provides the opportunity for a radically changed and much more efficient communication process for scientific results. A survey in the closely related domains of construction information technology and construction management was conducted in February 2000, aimed at measuring to what extent these opportunities are already changing the scientific information exchange and how researchers feel about the changes. The paper presents the results based on 236 replies to an extensive Web based questionnaire. 65% of the respondents stated their primary research interest as IT in A/E/C and 20% as construction management and economics. The questions dealt with how researchers find, access and read different sources; how much and what publications they read; how often and to which conferences they travel; how much they publish, and what are the criteria for where they eventually decide to publish. Some of the questions confronted traditional and electronic publishing with one final section dedicated to opinions about electronic publishing. According to the survey researchers already download half of the material that they read digitally from the Web. The most popular method for retrieving an interesting publication is downloading it for free from the author’s or publisher’s website. Researchers are not particularly willing to pay for electronic scientific publications. There is much support for a scenario of electronic journals available totally freely on the Web, where the costs could be covered by for instance professional societies or the publishing university. The shift that the Web is causing seems to be towards the "just in time" reading of literature. Also, frequent users of the Web rely less on scientific publications and tend to read fewer articles. If available with little effort, papers published in traditional journals are preferred; if not, the papers should be on the Web. In these circumstances, the role of paper-based journals published by established publishers is shifting from the core "information exchange" to the building of authors' prestige. The respondents feel they should build up their reputations by publishing in journals and relevant conferences, but then make their work freely available on the Web.

Generation of parabolic trajectories for current error space phasor similar to an SVPWM controller for control of switching frequency variation in current hysteresis PWM controlled IM drives

Switching frequency variation over a fundamental period is a major problem associated with hysteresis controller based VSI fed IM drives. This paper describes a novel concept of generating parabolic trajectories for current error space phasor for controlling the switching frequency variation in the hysteresis controller based two-level inverter fed IM drives. A generalized algorithm is developed to determine unique set of parabolic trajectories for different speeds of operation for any given IM load. Proposed hysteresis controller provides the switching frequency spectrum of inverter output voltage, similar to that of the constant switching frequency VC-SVPWM based IM drive. The scheme is extensively simulated and experimentally verified on a 3.7 kW IM drive for steady state and transient performance.

The Value of Being on the Net- the effects of Web sites of companies on consumer decision making

The unique characteristics of marketspace in combination with the fast growing number of consumers interested in e-commerce have created new research areas of interest to both marketing and consumer behaviour researchers. Consumer behaviour researchers interested in the decision making processes of consumers have two new sets of questions to answer. The first set of questions is related to how useful theories developed for a marketplace are in a marketspace context. Cyber auctions, Internet communities and the possibilities for consumers to establish dialogues not only with companies but also with other consumers make marketspace unique. The effects of these distinctive characteristics on the behaviour of consumers have not been systematically analysed and therefore constitute the second set of questions which have to be studied. Most companies feel that they have to be online even though the effects of being on the Net are not unambiguously positive. The relevance of the relationship marketing paradigm in a marketspace context have to be studied. The relationship enhancement effects of websites from the customers’ point of view are therefore emphasized in this research paper. Representatives of the Net-generation were analysed and the results show that companies should develop marketspace strategies while Net presence has a value-added effect on consumers. The results indicate that the decision making processes of the consumers are also changing as a result of the progress of marketspace