Managing Risk of Bidding in Display Advertising

In this paper, we deal with the uncertainty of bidding for display advertising. Similar to the financial market trading, real-time bidding (RTB) based display advertising employs an auction mechanism to automate the impression level media buying; and running a campaign is no different than an investment of acquiring new customers in return for obtaining additional converted sales. Thus, how to optimally bid on an ad impression to drive the profit and return-on-investment becomes essential. However, the large randomness of the user behaviors and the cost uncertainty caused by the auction competition may result in a significant risk from the campaign performance estimation. In this paper, we explicitly model the uncertainty of user click-through rate estimation and auction competition to capture the risk. We borrow an idea from finance and derive the value at risk for each ad display opportunity. Our formulation results in two risk-aware bidding strategies that penalize risky ad impressions and focus more on the ones with higher expected return and lower risk. The empirical study on real-world data demonstrates the effectiveness of our proposed risk-aware bidding strategies: yielding profit gains of 15.4% in offline experiments and up to 17.5% in an online A/B test on a commercial RTB platform over the widely applied bidding strategies

Correlation of conductivity and angle integrated valence band photoemission characteristics in single crystal iron perovskites for 300 K < T < 800 K: Comparison of surface and bulk sensitive methods

A single crystal monolith of La0.9Sr0.1FeO3 and thin pulsed laser deposited film of La0.8Sr0.2Fe0.8Ni0.2O3 were subject to angle integrated valence band photoemission spectroscopy in ultra high vacuum and conductivity experiments in ambient air at temperatures from 300 K to 800 K. Except for several sputtering and annealing cycles, the specimen were not prepared in-situ.. Peculiar changes in the temperature dependent, bulk representative conductivity profile as a result of reversible phase transitions, and irreversible chemical changes are semi-quantitatively reflected by the intensity variation in the more surface representative valence band spectra near the Fermi energy. X-ray photoelectron diffraction images reflect the symmetry as expected from bulk iron perovskites. The correlation of spectral details in the valence band photoemission spectra (VB PES) and details of the conductivity during temperature variation suggest that valuable information on electronic structure and transport properties of complex materials may be obtained without in-situ preparation

Elastic constants of borocarbides. New approach to acoustic Measurement technique

A new version of the phase method of determining the sound velocity is proposed and implemented. It utilizes the ``Nonius'' measurement technique and can give acceptable accuracy (~1%) in samples of submillimeter size. Measurements of the sound velocity are made in single-crystal samples of the borocarbides RNi2B2C (R = Y,Lu,Ho). The elastic constants and the Debye temperature are calculated.Comment: 5 figures, 2 table

Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, $\tau_{\rm{AFM}}$ = ($\frac{1}{2} \frac{1}{2} \frac{1}{2}$), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below $T_{\rm{N}}~\approx 0.4$ K and corresponds to a magnetic correlation length of $\xi_{\rm{n}} \approx$ 80 $\rm{\AA}$, and a broad component that persists up to $T^*\approx$ 0.7 K and corresponds to antiferromagnetic correlations extending over $\xi_{\rm{b}} \approx$ 20 $\rm{\AA}$. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.Comment: 5 pages, 3 figure

Analysis of the roll properties of a tubular-type torsion beam suspension

Abstract: Tubular-type torsion beam rear-suspension systems are widely used in small passenger cars owing to their compactness, light weight, and cost efficiency. It is already known that the roll behaviour of a torsion beam suspension system can be approximated to that of a semitrailing arm suspension system. By this kinematic assumption, analytical equations to obtain the roll centre height, roll steer, and roll camber have already been developed in terms of geometry points. Therefore, this paper proposes an analytical method to calculate the torsional stiffness of a tubular beam from its cross-section area based on the assumption that a tubular beam is a series connection of finite lengths with a constant cross-section. In addition, a potential energy method is proposed to calculate the roll stiffness of a tubular torsion beam suspension system based on considering the bushing stiffness and torsional stiffness of the tubular beam without the use of any commercial computer-aided engineering (CAE) software. The torsional stiffness and roll stiffness predicted using the proposed method showed errors of about 4 per cent and 3.3 per cent respectively, when compared with results from commercial CAE software

Thermal expansion and magnetostriction of pure and doped RAgSb2 (R = Y, Sm, La) single crystals

Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb2 (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effect on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb2 and LaAgSb2. The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits (beta) were evaluated for YAgSb2 and LaAgSb2

Structural, electronic, magnetic, and thermal properties of single-crystalline UNi0.5Sb2

We studied the properties of the antiferromagnetic (AFM) UNi0.5Sb2 (TN \approx 161 K) compound in Sb-flux grown single crystals by means of measurements of neutron diffraction, magnetic susceptibility ({\chi}), specific heat (Cp), thermopower (S), thermal conductivity ({\kappa}), linear thermal expansion ({\Delta}L/L), and electrical resistivity ({\rho}) under hydrostatic pressures (P) up to 22 kbar. The neutron diffraction measurements revealed that the compound crystallizes in the tetragonal P42/nmc structure, and the value of the U-moments yielded by the histograms at 25 K is \approx 1.85 \pm 0.12 {\mu}B/U-ion. In addition to the features in the bulk properties observed at TN, two other hysteretic features centered near 40 and 85 K were observed in the measurements of {\chi}, S, {\rho}, and {\Delta}L/L. Hydrostatic pressure was found to raise TN at the rate of \approx 0.76 K/kbar, while suppressing the two low temperature features. These features are discussed in the context of Fermi surface and hybridization effects.Comment: 17 pages, 8 figure

Thermal expansion, heat capacity and magnetostriction of RAl3_3 (R = Tm, Yb, Lu) single crystals

We present thermal expansion and longitudinal magnetostriction data for cubic RAl3 (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl3 is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl3 show crystal electric field contributions and have strong magnetic field dependencies. de Haas-van Alphen-like oscillations were observed in the magnetostriction data of YbAl3 and LuAl3, several new extreme orbits were measured and their effective masses were estimated. Zero and 140 kOe specific heat data taken on both LuAl3 and TmAl3 for T < 200 K allow for the determination of a CEF splitting scheme for TmAl3