2,354 research outputs found

    An unexpected application of minimization theory to module decompositions

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    The aim of this work is to show how we can decompose a module (if decomposable) into an indecomposable module with the help of the minimization process.Comment: 15-02-200

    Understanding the Soft Budget Constraint

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    We propose a clarification of the notion of a soft budget constraint, a concept widely used in the analysis of socialist, transitional, and market economies. Our interpretation is broad enough to embrace most existing approaches to soft budget constraint phenomena and provides a classification of their causes and consequences. In light of this interpretation, we then review the theoretical literature on the subject and compare it with those on other dynamic commitment problems in economics.

    Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

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    Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years

    A Software-Defined Radio Receiver in 65nm CMOS Robust to Out-of-Band Interference

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    Two techniques are presented in this paper for a software-defined radio (SDR) receiver robust to out-of-band interference. Voltage gain is realized at IF simultaneously with low-pass filtering to mitigate blockers and out-of-band intermodulation distortion. A 2-stage polyphase harmonic rejection (HR) mixer concept robust to gain error achieves 2nd-6th HR of more than 60dB for 40 samples without trimming or calibration. A prototype 0.4-0.9G zero-IF receiver in 65nm CMOS has 34dB gain, 4dB NF, +3.5dBm IIP3 and +47dBm IIP2 while drawing 50mA from 1.2V

    The Effect of Shoe Forefoot Stiffness On The Windlass Mechanism In Running

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    Research evaluating the effects of running footwear on gait has deduced foot motion from upper and sole movement of footwear. The aim of the present study was to evaluate a technique that allows for direct assessment of the medial longitudinal arch (MLA) in running. A secondary purpose was to evaluate the effect of increased bending stiffness of footwear on the MLA during running. Using a unique marker set, a multi-segment foot model was created to analyze dorsiflexion of the first metatarsal, navicular displacement, rearfoot motion, and tibial rotation. Virtual markers were created based on the movement of these foot segments. Two different pairs of running shoes (flexible, stiff) were evaluated. 13 participants ran barefoot, and in both shoe conditions. The mean difference between actual and virtual markers created was 0.69 mm. Independent t-tests determined first metatarsal dorsiflexion was restricted in the stiff condition compared to the flexible (p \u3c 0.05) with an effect size of 0.36. The study provides a useful method of assessing foot motion while wearing footwear, and indicates that stiffer shoes restrict foot motion

    Distances of Stars by mean of the Phase-lag Method

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    Variable OH/IR stars are Asymptotic Giant Branch (AGB) stars with an optically thick circumstellar envelope that emit strong OH 1612 MHz emission. They are commonly observed throughout the Galaxy but also in the LMC and SMC. Hence, the precise inference of the distances of these stars will ultimately result in better constraints on their mass range in different metallicity environments. Through a multi-year long-term monitoring program at the Nancay Radio telescope (NRT) and a complementary high-sensitivity mapping campaign at the eMERLIN and JVLA to measure precisely the angular diameter of the envelopes, we have been re-exploring distance determination through the phase-lag method for a sample of stars, in order to refine the poorly-constrained distances of some and infer the currently unknown distances of others. We present here an update of this project.Comment: 4 pages, 1 figure, 2 tables, to appear in the Proceedings of the IAU Symposium No. 336: Astrophysical Masers: Unlocking the Mysteries of the Univers

    A 2.2GHz Sub-Sampling PLL with 0.16psrms Jitter and -125dBc/Hz In-band Phase Noise at 700μW Loop-Components Power

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    A divider-less PLL exploits a phase detector that directly samples the VCO with a reference clock. No VCO sampling buffer is used while dummy samplers keep the VCO spur <;-56dBc. A modified inverter with low short-circuit current acts as a power efficient reference clock buffer. The 2.2 GHz PLL in 0.18 μm CMOS achieves -125dBc/Hz in-band phase noise with only 700 μW loop-components power

    Spur-reduction techniques for PLLs using sub-sampling phase detection

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    A low-spur sub-sampling PLL exploits an amplitude-controlled charge pump which is immune to current source mismatch. A DLL/PLL dual-loop architecture and buffering reduces the disturbance of the sampler to the VCO. The 2.2GHz PLL in 0.18-μm CMOS achieves -121dBc/Hz in-band phase noise at 200kHz and consumes 3.8mW. The worst-case reference spur measured on 20 samples is -80dBc.\u
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