Semileptonic form factor ratio B_s->D_s/B->D and its application to BR(B^0_s->\mu^+\mu^-)

We present a (2+1)-flavor lattice QCD calculation of the form factor ratio between the semileptonic decays $\bar{B}^0_s \to D^+_sl^-\bar{\nu}$ and $\bar{B}^0 \to D^+l^-\bar{\nu}$. This ratio is an important theoretical input to the hadronic determination of the $B$ meson fragmentation fraction ratio $f_s/f_d$ which enters in the measurement of $\mathrm{BR}(B^0_s\to \mu^+\mu^-)$. Small lattice spacings and high statistics enable us to simulate the decays with a dynamic final $D$ meson of small momentum and reliably extract the hadronic matrix elements at nonzero recoil. We report our preliminary result for the form factor ratio at the corresponding momentum transfer of the two decays $f_0^{(s)}(M^2_\pi)/f_0^{(d)}(M^2_K)$.Comment: 7 pages, 6 figures. Talk presented at The XXIX International Symposium on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake Tahoe, California; Minor errors corrected, references and graphs update

A Multi-task Learning Approach for Improving Product Title Compression with User Search Log Data

It is a challenging and practical research problem to obtain effective compression of lengthy product titles for E-commerce. This is particularly important as more and more users browse mobile E-commerce apps and more merchants make the original product titles redundant and lengthy for Search Engine Optimization. Traditional text summarization approaches often require a large amount of preprocessing costs and do not capture the important issue of conversion rate in E-commerce. This paper proposes a novel multi-task learning approach for improving product title compression with user search log data. In particular, a pointer network-based sequence-to-sequence approach is utilized for title compression with an attentive mechanism as an extractive method and an attentive encoder-decoder approach is utilized for generating user search queries. The encoding parameters (i.e., semantic embedding of original titles) are shared among the two tasks and the attention distributions are jointly optimized. An extensive set of experiments with both human annotated data and online deployment demonstrate the advantage of the proposed research for both compression qualities and online business values.Comment: 8 Pages, accepted at AAAI 201

Semileptonic B to D decays at nonzero recoil with 2+1 flavors of improved staggered quarks. An update

The Fermilab Lattice and MILC collaborations are completing a comprehensive program of heavy-light physics on MILC (2+1)-flavor asqtad ensembles with lattice spacings as small as 0.045 fm and light-to-strange-quark mass ratios as low as 1/20. We use the Fermilab interpretation of the clover action for heavy valence quarks and the asqtad action for the light valence quarks. The central goal of the program is to provide ever more exacting tests of the unitarity of the CKM matrix. We present preliminary results for one part of the program, namely the analysis of the semileptonic decay B -> D l nu at nonzero recoil.Comment: 7 pp, 7 figs, Lattice 201

基于Kriging模型的地面气温空间插值研究

This paper aims to describe spatial interpolation methods to estimate surface air temperatures (SATs). The SAT at a particular location where SAT observations are not available is estimated through a Kriging interpolation between SAT measurements from 192 meteorological sites at which daily SAT observations have been obtained. A temporal de-trending method based on a Fourier series is used to model and remove the annual trend in original data in order to ensure the stationarity of de-trended data from which kriging parameters are determined. Furthermore, a spatial or surface de-trending in terms of geographic coordinates including altitude, latitude and longitude of each location is adopted in a Kriging model. Besides a Kriging model, an inverse distance weighting (IDW) interpolation method is tested as a comparison. The accuracies of both spatial interpolation approaches are assessed by calculating and comparing their mean absolute error (MAE) and root mean square error (RMSE) when taking each meteorological site as the target location in a cross-validation procedure. The results show that the Kriging model performs better than the IDW method at 174 sites. In addition, the temporal and spatial de-trending methods make the main contribution to the accurate capture of spatial correlations of SATs in the study area in a Kriging process

SmartSpaceT̳M̳ : opportunities for a new real estate product

Thesis (S.M.)--Massachusetts Institute of Technology, Program in Real Estate Development in Conjunction with the Center for Real Estate, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.In title on title page, double-underscored "TM" appears as superscript. Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 58-60).SmartSpaceTM, or "S2" for short, is a super-efficient, super-cool, super-small studio apartment with many built-in features designed to be built in very high density, prime, city locations. This thesis has two main objectives: 1) explore the design of SmartSpaceTM and recommend changes so that it will better fit the needs of its users; and 2) identify target markets and locations for S2 development. To achieve the first objective, I stayed in an S2 prototype unit for five days and five nights to get the full SmartSpaceTM experience. During my stay, I surveyed 14 graduate students and young professionals to collect their feedback regarding the design of the unit. My S2 experience was generally positive, but the unit felt more like a hotel than an apartment. To live there for a year or more, I recommended among other things, a larger, more functional kitchen, a redesigned bathroom/shower, and a bigger closet. Survey participants had similar and additional detailed feedback. The suggestions were reported to the developer and architect working on S2 so the improvements can be made. To achieve the second objective: 1) historical trends and precedents of small living space were studied; 2) housing representatives at major universities were interviewed about graduate student housing preferences; 3) patterns were identified in the S2 survey results to make conclusions as to what groups of people will most likely be interested in living in S2; and 4) a methodology was created utilizing demographic and rental data to find the most appropriate locations for S2 development.(cont.) Finally, the site where the first S2 building will be built was examined and assessed using the same criteria as those used in the site-selection methodology. The identified users are: graduate students, workers on temporary assignments (interns, traveling nurses, consultants, etc.), and recent movers. The locations found to be best for S2 development are: Financial District, Gramercy, Greenwich Village, and Midtown in Manhattan; Pacific Heights and Western Addition in San Francisco. The development site in Berkeley was found to be a fair location.by Si Yuan Qiu.S.M

Managerial Attributes and Executive Compensation

We study the role of firm- and manager-specific heterogeneities in executive compensation. We decompose the variation in executive compensation and find that time invariant firm and especially manager fixed effects explain a majority of the variation in executive pay. We then show that in many settings, it is important to include fixed effects to mitigate potential omitted variable bias. Furthermore, we find that compensation fixed effects are significantly correlated with management styles (i.e., manager fixed effects in corporate policies). Finally, the method used in the paper has a number of potential applications in financial economics.