41,733 research outputs found
Retrodictive states and two-photon quantum imaging
We use retrodictive quantum theory to analyse two-photon quantum imaging
systems. The formalism is particularly suitable for calculating conditional
probability distributions.Comment: 5 pages, 3 figure
Statistical uncertainty in quantum optical photodetection measurements
We present a complete statistical analysis of quantum optical measurement
schemes based on photodetection. Statistical distributions of quantum
observables determined from a finite number of experimental runs are
characterized with the help of the generating function, which we derive using
the exact statistical description of raw experimental outcomes. We use the
developed formalism to point out that the statistical uncertainty results in
substantial limitations of the determined information on the quantum state:
though a family of observables characterizing the quantum state can be safely
evaluated from experimental data, its further use to obtain the expectation
value of some operators generates exploding statistical errors. These issues
are discussed using the example of phase-insensitive measurements of a single
light mode. We study reconstruction of the photon number distribution from
photon counting and random phase homodyne detection. We show that utilization
of the reconstructed distribution to evaluate a simple well-behaved observable,
namely the parity operator, encounters difficulties due to accumulation of
statistical errors. As the parity operator yields the Wigner function at the
phase space origin, this example also demonstrates that transformation between
various experimentally determined representations of the quantum state is a
quite delicate matter.Comment: 18 pages REVTeX, 7 figures included using epsf. Few minor corrections
made, clarified conclusion
Tak Kenal Maka Tak Sayang
Pepatah tak kenal maka tak sayang adalah istilah yang sangat sering sekali digunakan pada percakapan sehari-hari, untuk menyatakan apabila kita tidak mengenal seseorang, maka kita tidak memiliki perhatian kepada orang tersebut. Arti sebenarnya dari pepatah terebut adalah jika kita tidak mengerti atau memahami sesuatu hal/benda maka kita tidak akan tahu arti sebenarnya dan tidak dapat menghargai hal/benda tersebut. Hal tersebut juga berlaku dalam sistem sebuah Perusahan. Banyak pelaku bisnis keluarga yang menganggap bahwa sistem informasi akuntansi (SIA) dan struktur pengendalian Internal (SPI) serta investasi terkait SIA dan SPI sebagai sesuatu yang tidak penting dalam bisnis, karena toh tanpa SIA dan SPI pun Perusahaan masih bisa berjalan. Hal tersebut memang benar, ibarat sebuah mobil, SIA dan SPI bukanlah bensin, tetapi SIA dan SPI dapat dianalogikan sebagai kemudi dan rem pada sebuah mobil. Tanpa kemudi dan rem, mobil masih bisa berjalan, tetapi jalannya tentu saja tidak dapat diarahkan dan dikendalikan dengan benar. Yang mengarahkan dan mengendalikan dengan benar adalah kemudi dan rem. Demikian juga dalam Perusahaan. Tanpa SIA dan SPI, Perusahaan tentu saja bisa berjalan, tetapi tidak akan dapat diarahkan dan dikendalikan sesuai dengan keinginan pelaku bisnis
Identifying Retweetable Tweets with a Personalized Global Classifier
In this paper we present a method to identify tweets that a user may find
interesting enough to retweet. The method is based on a global, but
personalized classifier, which is trained on data from several users,
represented in terms of user-specific features. Thus, the method is trained on
a sufficient volume of data, while also being able to make personalized
decisions, i.e., the same post received by two different users may lead to
different classification decisions. Experimenting with a collection of approx.\
130K tweets received by 122 journalists, we train a logistic regression
classifier, using a wide variety of features: the content of each tweet, its
novelty, its text similarity to tweets previously posted or retweeted by the
recipient or sender of the tweet, the network influence of the author and
sender, and their past interactions. Our system obtains F1 approx. 0.9 using
only 10 features and 5K training instances.Comment: This is a long paper version of the extended abstract titled "A
Personalized Global Filter To Predict Retweets", of the same authors, which
was published in the 25th ACM UMAP conference in Bratislava, Slovakia, in
July 201
Decorrelation Times of Photospheric Fields and Flows
We use autocorrelation to investigate evolution in flow fields inferred by
applying Fourier Local Correlation Tracking (FLCT) to a sequence of
high-resolution (0.3 \arcsec), high-cadence ( min) line-of-sight
magnetograms of NOAA active region (AR) 10930 recorded by the Narrowband Filter
Imager (NFI) of the Solar Optical Telescope (SOT) aboard the {\em Hinode}
satellite over 12--13 December 2006. To baseline the timescales of flow
evolution, we also autocorrelated the magnetograms, at several spatial
binnings, to characterize the lifetimes of active region magnetic structures
versus spatial scale. Autocorrelation of flow maps can be used to optimize
tracking parameters, to understand tracking algorithms' susceptibility to
noise, and to estimate flow lifetimes. Tracking parameters varied include: time
interval between magnetogram pairs tracked, spatial binning applied
to the magnetograms, and windowing parameter used in FLCT. Flow
structures vary over a range of spatial and temporal scales (including
unresolved scales), so tracked flows represent a local average of the flow over
a particular range of space and time. We define flow lifetime to be the flow
decorrelation time, . For , tracking results represent
the average velocity over one or more flow lifetimes. We analyze lifetimes of
flow components, divergences, and curls as functions of magnetic field strength
and spatial scale. We find a significant trend of increasing lifetimes of flow
components, divergences, and curls with field strength, consistent with Lorentz
forces partially governing flows in the active photosphere, as well as strong
trends of increasing flow lifetime and decreasing magnitudes with increases in
both spatial scale and .Comment: 48 pages, 20 figures, submitted to the Astrophysical Journal;
full-resolution images in manuscript (8MB) at
http://solarmuri.ssl.berkeley.edu/~welsch/public/manuscripts/flow_lifetimes_v2.pd
Implementation of Design for Manufacture and Assembly principles in the construction project: A case study
Design for manufacture and assembly (DfMA) has been increasingly advocated by the global construction industry since it provides methodological procedures for evaluating and improving design for both manufacture and assembly. Many studies have investigated the DfMA principles suitable for different types of construction projects and advocated a wide implementation of DfMA in construction. However, it would be difficult to persuade stakeholders to implement DfMA principles in their projects without a clear specification of implementation procedures. This study aims to offer an intelligible description and analysis of implementation procedures of DfMA in a real construction project. It does so by undertaking a case study on a prefabricated bamboo building, in which a DfMA-focused design was required by the client. The study reveals how the knowledge of designer, engineer, and contractor has been integrated to implement DfMA principles in the design of building components and sub-components. This study also identifies the best practice of ensuring engineering performance and meanwhile attaining aesthetics in the application of DfMA principles
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