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921.
This study explored strengths and limitations of table formatting choices by engaging twenty-eight participants in information searches in online tables, presented on a small-screen interface (Palm IIIc). Table length across conditions was held constant at three screens long (24 rows total) but varied from one to three screens wide (approximately 35, 70, and 105 characters per line). Target information was positioned in either the upper left, lower left, upper right, or lower right quadrants. Data collected were time on task, error rate, and level of participants' confidence in their answers. Experimenters found that increased horizontal scrolling imposed the heaviest burden on information search. This study supports restricting table widths to one screen on handheld computers. If necessary, however, tables can go to two screens wide without critical detriment to usability. While ruled line formatting is slightly better than interface character in providing visual support for the burden of horizontal scrolling, neither formatting option adequately compensates for the added burden. 相似文献
922.
This study investigated the relationship between self-appraisals of performance, symptom severity and post-event rumination in social phobia, and evaluated the effect of treatment on these variables. A socially phobic group and a nonanxious control group performed an impromptu speech and were told that their performance would be evaluated. Participants appraised their performance immediately after the speech and 1 week later, and the frequency of post-event rumination during the week following the speech was assessed. The socially phobic group maintained the negative appraisals of their speech over the week, whereas the nonclinical group showed increased positivity about their performance The socially phobic group also engaged in more negative rumination than controls. Treatment improved perceptions of performance and reduced negative rumination. These results are discussed in the light of cognitive models of social phobia. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
923.
Microrheology as a tool for high-throughput screening 总被引:2,自引:0,他引:2
Microrheology can be used for high-throughput screening of the rheological properties of sample libraries of complex fluids. Two passive techniques are particularly suitable: video microscopy and diffusing-wave spectroscopy. The techniques complement each other very well and can be applied to samples that offer different experimental challenges. We offer a thorough analysis of the strengths and limitations of microrheology with the emphasis on high-throughput applications. To illustrate the potential of microrheology, results are presented for two representative cases: the rheological screening of aqueous solutions of a block copolypeptide library and the rheological phase diagram of a water/surfactant/salt system. 相似文献
924.
Weight-loss kinetics were studied for 10 industrial extruded samples of poly(vinyl chloride) (PVC) plasticized by 20–30% by weight of didecylphtalate at 85, 95, 105, 110, and 120deg;C. For the most unstable samples, which contained a light coplasticizer, the weight-loss rate obeyed Fick's law. In the other cases, it was constant in the early period of exposure. The apparent Arrhenius parameters (i.e., preexponential factor and activation energy) were intercorrelated and varied strongly from one sample to another. This was explained by the existence of two distinct kinetic regimes corresponding, respectively, to diffusion or evaporation, the whole process being controlled by the slowest step, and a transition between both regimes occurring in the temperature range of exposure. In the proposed model, small changes of the preexponential factor of diffusion from one sample to another are sufficient to take into account the observed behavior. 相似文献
925.
The term quality assurance (or QA) has a variety of interpretations. The most common one is that it ensures that developers, testers, or independent auditors have performed some form of scrutiny on a system to validate that it will work as required. Software quality assurance is similar but applies to the code or noncode artifacts. 相似文献
926.
The oscillator is arguably the most essential part of any communication system: it defines a channel frequency, or timing and synchronisation in a digital system. The phase noise of any oscillator has a fundamental lower limit. It limits the achievable efficiency of spectrum use and degrades the error rate in practical applications. Any low-noise oscillator can be described as a positive-feedback Q -multiplier circuit. Such a model shows that phase noise is minimised if the square of the effective circuit Q and the signal-to-noise ratio in the oscillator are maximised. This simple fact is true for all oscillators and it provides the basis for more efficient and lower noise designs 相似文献
927.
928.
The crystal structure of CaMgGeO4 is described. CaMgGeO4, Mr = 200.9, orthorhombic, Pnam, A = 11.285(5) Å, B = 5.016(2) Å, C = 6.435(2) Å, V = 364.36 Å3, Dx = 3.664 Mg/m3.λ(MoKa = 0.71069 Å, F(000) = 384, room temperature, final R = 0.045 for 1752 observed reflections. The structure is isomorphous with CaMgSiO4 (monticellite). 相似文献
929.
Streit D.C. Hafizi M.E. Umemoto D.K. Velebir J.R. Tran L.T. Oki A.K. Kim M.E. Wang S.K. Kim C.W. Sadwick L.P. Hwu R.J. 《Electron Device Letters, IEEE》1991,12(5):194-196
The authors have fabricated n-p-n GaAs/AlGaAs heterojunction bipolar transistors (HBTs) with base doping graded exponentially from 5×1019 cm-3 at the emitter edge to 5×1018 cm-3 at the collector edge. The built-in field due to the exponentially graded doping profile significantly reduces base transit time, despite bandgap narrowing associated with high base doping. Compared to devices with the same base thickness and uniform base doping of 1×1019 cm-3 , the cutoff frequency is increased from 22 to 31 GHz and maximum frequency of oscillation is increased from 40 to 58 GHz. Exponentially graded base doping also results ill consistently higher common-emitter current gain than uniform base doping, even though the Gummel number is twice as high and the base resistance is reduced by 40% 相似文献
930.
G Hendrickson R K Anderson P D Clayton J Cimino G M Hripcsak S B Johnson M McCormack S Sengupta S Shea R Sideli 《M.D. computing : computers in medical practice》1992,9(1):35-42
Over the past seven years, Columbia-Presbyterian Medical Center has been planning and implementing an integrated academic information management system. Accomplishments to date include establishing an institutional information architecture, installing a campus-wide network of workstations, recruiting the staff needed to develop and implement the system, and developing various applications. This paper presents the rationale and steps involved in these accomplishments, as well as data on use of the system so far. 相似文献