850 research outputs found

    A Generalized Jarque-Bera Test of Conditional Normality

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    We consider testing normality in a general class of models that admits nonlinear conditional mean and conditional variance functions. We derive the asymptotic distribution of the skewness and kurtosis coefficients of the model’s standardized residuals and propose an asymptotic x2 test of normality. This test simplifies to the Jarque-Bera test only when: (i) the conditional mean function contains an intercept term but does not depend on past errors, and (ii) the errors are conditionally homoskedastic. Beyond this context, it is shown that the Jarque-Bera test has size distortion but the proposed test does not.conditional heteroskedsaticity, conditional normality, Jarque-Bera test

    Search for serendipitous TNO occultation in X-rays

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    To study the population properties of small, remote objects beyond Neptune's orbit in the outer solar system, of kilometer size or smaller, serendipitous occultation search is so far the only way. For hectometer-sized Trans-Neptunian Objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wave lengths are needed. Here we report the effort of TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June 2007 to October 2011. No definite TNO occultation events were found in the 334 ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 m to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA

    A 60-Gb/s PAM4 Wireline Receiver With 2-Tap Direct Decision Feedback Equalization Employing Track-and-Regenerate Slicers in 28-nm CMOS

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    This article describes a 4-level pulse amplitude modulation (PAM4) receiver incorporating continuous time linear equalizers (CTLEs) and a 2-tap direct decision feedback equalizer (DFE) for applications in wireline communication. A CMOS track-and-regenerate slicer is proposed and employed in the PAM4 receiver. The proposed slicer is designed for the purposes of improving the clock-to-Q delay as well as the output signal swing. A direct DFE in a PAM4 receiver is made possible with the proposed slicer by having rail-to-rail digital feedback signals available with reduced delay, and accordingly relaxing the settling time constraint of the summer. With the 2-tap direct DFE enabled by the proposed slicer, loop-unrolling and inductor-based bandwidth enhancement techniques, which can be area/power intensive, are not necessary at high data rates. The PAM4 receiver fabricated in 28-nm CMOS technology achieves bit-error-rate (BER) better than 1E-12, and energy efficiency of 1.1 pJ/b at 60 Gb/s, measured over a channel with 8.2-dB loss at Nyquist

    Controlled Heterogeneous Nucleation and Growth of Germanium Quantum Dots on Nanopatterned Silicon Dioxide and Silicon Nitride Substrates

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    Controlled heterogeneous nucleation and growth of Ge quantum dots (QDs) are demonstrated on SiO_2/Si_3N_4 substrates by means of a novel fabrication process of thermally oxidizing nanopatterned SiGe layers. The otherwise random self-assembly process for QDs is shown to be strongly influenced by the nanopatterning in determining both the location and size of the QDs. Ostwald ripening processes are observed under further annealing at the oxidation temperature. Both nanopattern oxidation and Ostwald ripening offer additional mechanisms for lithography for controlling the size and placement of the QDs

    Alternative Ingredient Recommendation: A Co-occurrence and Ingredient Category Importance Based Approach

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    As many people will refer to a recipe when cooking, there are several recipe-sharing websites that include lots of recipes and make recipes easier to access than before. However, there is often the case that we could not get all the ingredients listed on the recipe. Prior research on alternative ingredient substitution has built a recommendation system considering the suitability of a recommended ingredient with the remained ingredients. In this paper, in addition to suitability, we also take the diversity of the ingredient categories and the novelty of new combination of ingredients into account. Besides, we combine suitability with novelty as an index, to see whether our method could help find out a new combination of ingredients that is possibly to be a new dish. Our evaluation results show that our proposed method attains a comparable or even better performance on each perspective

    Promoting Customers’ Augmented Reality Immersion in Restaurants

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    With the rapid growth of augmented reality (AR) applications, AR is set to influence companies and organizations in every industry. This study focuses on identifying how AR technology enhances memorable experiences through the lens of customer immersion. An AR 3D food ordering platform that included an AR food ordering app for customers and a restaurant management system for restaurants was implemented as part of the study, and the concept of AR immersion was further introduced. The investigation involved an empirical examination of the effects of perceived playfulness and personal innovativeness on three dimensions of AR immersion: engagement, engrossment, and total immersion. The results of an analysis of data collected from 343 restaurant customers who experienced using the AR food ordering app indicated that engagement and engrossment had direct effects on customer satisfaction, but total immersion did not. Perceived playfulness directly affected engagement, engrossment, and total immersion and indirectly affected customer satisfaction through its direct effects on engagement and engrossment. Similarly, personal innovativeness influenced customer satisfaction indirectly through its direct effects on engagement. In terms of the effects of AR immersion, engrossment should be the target, engagement is insufficient, and total immersion is unnecessary. A practical implication of our findings is that it is possible to increase customer satisfaction directly by increasing the levels of engagement and engrossment with an AR food ordering app
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