Geometry-Oblivious FMM for Compressing Dense SPD Matrices

We present GOFMM (geometry-oblivious FMM), a novel method that creates a hierarchical low-rank approximation, "compression," of an arbitrary dense symmetric positive definite (SPD) matrix. For many applications, GOFMM enables an approximate matrix-vector multiplication in $N \log N$ or even $N$ time, where $N$ is the matrix size. Compression requires $N \log N$ storage and work. In general, our scheme belongs to the family of hierarchical matrix approximation methods. In particular, it generalizes the fast multipole method (FMM) to a purely algebraic setting by only requiring the ability to sample matrix entries. Neither geometric information (i.e., point coordinates) nor knowledge of how the matrix entries have been generated is required, thus the term "geometry-oblivious." Also, we introduce a shared-memory parallel scheme for hierarchical matrix computations that reduces synchronization barriers. We present results on the Intel Knights Landing and Haswell architectures, and on the NVIDIA Pascal architecture for a variety of matrices.Comment: 13 pages, accepted by SC'1

Superconductivity and Stoichiometry in the BSCCO-family Materials

We report on magnetization, c-axis and ab-plane resistivity, critical current, electronic band structure and superconducting gap properties. Bulk measurements and photoemission data were taken on similar samples.Comment: 4 pages, latex, to be published in Journal of Superconductivity. two figures available from Jian Ma at [email protected]

The M Dwarf Problem in the Galaxy

We present evidence that there is an M dwarf problem similar to the previously identified G dwarf and K dwarf problems: the number of low-metallicity M dwarfs is not sufficient to match simple closed-box models of local Galactic chemical evolution. We estimated the metallicity of 4141 M dwarf stars with spectra from the Sloan Digital Sky Survey (SDSS) using a molecular band strength versus metallicity calibration developed using high resolution spectra of nearby M dwarfs. Using a sample of M dwarfs with measured magnitudes, parallaxes, and metallicities, we derived a relation that describes the absolute magnitude variation as a function of metallicity. When we examined the metallicity distribution of SDSS stars, after correcting for the different volumes sampled by the magnitude-limited survey, we found that there is an M dwarf problem, with the number of M dwarfs at [Fe/H] ~ -0.5 less than 1% the number at [Fe/H] = 0, where a simple model of Galactic chemical evolution predicts a more gradual drop in star numbers with decreasing metallicity.Comment: To be published in Monthly Notices of the RAS by the Royal Astronomical Society and Blackwell Publishing. 7 pages, 3 figure

War in the North? A Critical Study of News Coverage of the Lord's Resistance Army 2004-2008

In the northern region of Uganda a conflict between Ugandan governmental forces and the Lord's Resistance Army, a regional rebel movement, has been ongoing for more than 20 years. Though this conflict has resulted in the abduction of thousands of children, the mutilation and murder of thousands more and the displacement of millions, is has been largely ignored in the international media. This study employed mixed methods to evaluate the volume, frequency, tone and type of coverage the conflict has received in The New York Times, The Guardian (London), The Mail & Guardian (Johannesburg, SA) and the Monitor (Kampala, Uganda) from January 2004 - December 2008 to gain some sense in how the media is covering this conflict. To attain a deeper understanding of why the discourse surrounding this conflict is being shaped in the way it is through the media, the Theory of Media Gatekeeping was utilized to posit possible explanations for the differences in coverage between the four media outlets under study. The analysis demonstrated a general lack of coverage in the international periodicals in respect to the conflict, however, the Guardian and Mail & Guardian though low in volume provided generally more nuanced and in-depth analysis of the conflict than The New York Times. The study highlighted the general lack of coverage in the international press but also further demonstrated the ways in which the US media differs from the European press, a point that previous studies have identified. Results of the study revealed that the conflict is framed differently in the various periodicals and certain aspects are focused on more heavily in some periodicals than others. For instance, in the Mail & Guardian the Juba Peace Talks received more attention while in The New York Times episodes of violence were more prevalent. In line with other popular geopolitical studies, the results of this study further demonstrate the need for critical analysis of the press and other media because of their ability to shape public perception and knowledge of places and events

Interstellar reddening towards six small areas in Puppis-Vela

We investigate the distribution of the interstellar dust towards six small volumes of the sky in the region of the Gum nebula. New high-quality four-colour uvby and H\beta\ Str\"omgren photometry obtained for 352 stars in six selected areas of Kapteyn, complemented with data obtained in a previous investigation for two of these areas, were used to estimate the colour excess and distance to these objects. The obtained colour excess versus distance diagrams, complemented with other information, when available, were analysed in order to infer the properties of the interstellar medium permeating the observed volumes. On the basis of the overall standard deviation in the photometric measurements, we estimate that colour excesses and distances are determined with an accuracy of 0.010 mag and better than 30%, respectively, for a sample of 520 stars. A comparison with 37 stars in common with the new Hipparcos catalogue attests to the high quality of the photometric distance determination. The obtained colour excess versus distance diagrams testify to the low density volume towards the observed lines-of-sight. Very few stars out to distances of 1 kpc from the Sun have colour excesses larger than E(b-y) = 0.1 mag. In spite of the low density character of the interstellar medium towards the Puppis-Vela direction, the obtained reddening as a function of the distance indicates that two or more interstellar structures are crossed towards the observed lines-of-sight. One of these structures may be associated with the very low density wall of the Local Cavity, which has a distance of 100-150 pc from the Sun. Another structure might be related to the Gum nebula, and if so, its front face would be located at about 350 pc from the Sun.Comment: Accepted by Astronomy and Astrophysic

PHYSICIANS\u27 RESISTANCE TOWARDS INFORMATION SYSTEMS IN HEALTHCARE: THE CASE OF WORKAROUNDS

With the cost of healthcare delivery rising all over the world the way hospitals use their resources stands in the centre of attention in many countries. In order to make best use of doctors and nurses and costly medical appliances etc. the use of information systems plays a vital role. Although all physicians are usually obliged to use the systems anecdotal evidence shows that use-patterns are not always as expected. Some physicians do not like the system and find ways to avoid working with it. They establish so called workarounds . This research investigates into the root causes of workarounds used by hospital physicians. Based on information systems theories a framework is developed to structure the findings from eight interviews in three hospitals in Germany. The interview partners were assured complete anonymity and thus the interviews were very open. We identified six distinctive types of workarounds and discuss their causes. The setup of this research is of exploratory nature using a grounded theory approach. Our findings underline the existence of workarounds in medical environment and provide guidance how to cope with them

EXPORT: optical photometry and polarimetry of Vega-type and pre-main sequence stars

This paper presents optical UBVRI broadband photo-polarimetry of the EXPORT sample obtained at the 2.5m Nordic Optical Telescope. The database consists of multi-epoch photo-polarimetry of 68 pre-main-sequence and main-sequence stars. An investigation of the polarization variability indicates that 22 objects are variable at the 3sigma level in our data. All these objects are pre-main sequence stars, consisting of both T Tauri and Herbig Ae/Be objects while the main sequence, Vega type and post-T Tauri type objects are not variable. The polarization properties of the variable sources are mostly indicative of the UXOR-type behaviour; the objects show highest polarization when the brightness is at minimum. We add seven new objects to the class of UXOR variables (BH Cep, VX Cas, DK Tau, HK Ori, LkHa 234, KK Oph and RY Ori). The main reason for their discovery is the fact that our data-set is the largest in its kind, indicating that many more young UXOR-type pre-main sequence stars remain to be discovered. The set of Vega-like systems has been investigated for the presence of intrinsic polarization. As they lack variability, this was done using indirect methods, and apart from the known case of BD +31.643, the following stars were found to be strong candidates to exhibit polarization due to the presence of circumstellar disks: 51 Oph, BD +31.643C, HD 58647 and HD 233517.Comment: A&A accepte

Analisis Produktivitas Lahan Menggunakan Metode Highest and Best Use pada Lahan Kosong di Kawasan Grand Sungkono Lagoon Kota Surabaya

Pertumbuhan ekonomi dan permintaan properti khususnya di kota metropolitan seperti Kota Surabaya akan selalu meningkat dari tahun ke tahun. Untuk menyiasati kondisi tersebut, maka lahan yang akan dimanfaatkan harus dianalisis rencana peruntukannya secara tepat agar dapat memberikan nilai lahan yang tertinggi. Seperti halnya lahan kosong seluas 3.966 m2 yang terletak di Kawasan Grand Sungkono Lagoon Kota Surabaya yang dimiliki oleh PT PP Properti Tbk. Lahan tersebut semula direncanakan untuk apartemen (tower orlin), namun karena penjualan yang belum mencapai target akibat pandemi COVID-19, lahan kosong tersebut belum dapat dimulai pembangunannya dan perlu dilakukan perubahan serta modifikasi dari masterplan sebelumnya untuk alternatif properti yang akan dibangun pada lahan kosong tersebut. Penelitian ini bertujuan untuk menganalisis berbagai macam properti yang dapat menjadi alternatif pemanfaatan lahan dan menentukan properti yang dapat memberikan nilai lahan tertinggi dan terbaik untuk lahan kosong yang menjadi obyek penelitian ini. Alternatif pemanfaatan lahan didapatkan dengan analisis pasar dan pengamatan perkembangan properti di sekitar lahan kosong. Analisis produktivitas lahan pada penelitian ini akan menggunakan metode highest and best use untuk lahan kosong dengan beberapa variabel yaitu analisis aspek legal yang meliputi zoning dan building code, analisis aspek fisik yang meliputi lokasi lahan, ukuran & bentuk lahan, aksesbilitas lahan, dan preliminary design, aspek finansial yang meliputi perencanaan biaya investasi, perencanaan pendapatan, perencanaan pengeluaran, dan analisis arus kas, serta aspek produktivitas maksimum. Dari hasil penelitian ini didapatkan tiga alternatif properti untuk pengembangan lahan, yaitu perkantoran, hotel, dan apartemen. Dari ketiga alternatif tersebut, pengembangan lahan sebagai perkantoran merupakan alternatif bangunan dengan penggunaan tertinggi dan terbaik. Alternatif properti komersial perkantoran memiliki nilai lahan sebesar Rp 64.773.925,82/m2 dengan persentase kenaikan nilai lahan adalah sebesar 246% dari nilai lahan awal

Structure in the 3D Galaxy Distribution: I. Methods and Example Results

Three methods for detecting and characterizing structure in point data, such as that generated by redshift surveys, are described: classification using self-organizing maps, segmentation using Bayesian blocks, and density estimation using adaptive kernels. The first two methods are new, and allow detection and characterization of structures of arbitrary shape and at a wide range of spatial scales. These methods should elucidate not only clusters, but also the more distributed, wide-ranging filaments and sheets, and further allow the possibility of detecting and characterizing an even broader class of shapes. The methods are demonstrated and compared in application to three data sets: a carefully selected volume-limited sample from the Sloan Digital Sky Survey redshift data, a similarly selected sample from the Millennium Simulation, and a set of points independently drawn from a uniform probability distribution -- a so-called Poisson distribution. We demonstrate a few of the many ways in which these methods elucidate large scale structure in the distribution of galaxies in the nearby Universe.Comment: Re-posted after referee corrections along with partially re-written introduction. 80 pages, 31 figures, ApJ in Press. For full sized figures please download from: http://astrophysics.arc.nasa.gov/~mway/lss1.pd

Neural Nets with a Newton Conjugate Gradient Method on Multiple GPUs

Training deep neural networks consumes increasing computational resource shares in many compute centers. Often, a brute force approach to obtain hyperparameter values is employed. Our goal is (1) to enhance this by enabling second-order optimization methods with fewer hyperparameters for large-scale neural networks and (2) to perform a survey of the performance optimizers for specific tasks to suggest users the best one for their problem. We introduce a novel second-order optimization method that requires the effect of the Hessian on a vector only and avoids the huge cost of explicitly setting up the Hessian for large-scale networks. We compare the proposed second-order method with two state-of-the-art optimizers on five representative neural network problems, including regression and very deep networks from computer vision or variational autoencoders. For the largest setup, we efficiently parallelized the optimizers with Horovod and applied it to a 8 GPU NVIDIA P100 (DGX-1) machine.Comment: Accepted to PPAM conferenc