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With the modern software and online platforms to collect massive amount of data, there is an increasing demand of applying causal inference methods at large scale when randomized experimentation is not viable. Weighting methods that directly incorporate covariate balancing have recently gained popularity for estimating causal effects in observational studies. These methods reduce the manual efforts required by researchers to iterate between propensity score modeling and balance checking until a satisfied covariate balance result. However, conventional solvers for determining weights lack the scalability to apply such methods on large scale datasets in companies like Snap Inc. To address the limitations and improve computational efficiency, in this paper we present scalable algorithms, DistEB and DistMS, for two balancing approaches: entropy balancing and MicroSynth. The solvers have linear time complexity and can be conveniently implemented in distributed computing frameworks such as Spark, Hive, etc. We study the properties of balancing approaches at different scales up to 1 million treated units and 487 covariates. We find that with larger sample size, both bias and variance in the causal effect estimation are significantly reduced. The results emphasize the importance of applying balancing approaches on large scale datasets. We combine the balancing approach with a synthetic control framework and deploy an end-to-end system for causal impact estimation at Snap Inc., Comment: Submitted to KDD 2023

Cerium hexaboride (CeB6) as a heavy fermion compound displays a number of interesting low-temperature physical properties such as dense Kondo behavior and a complex magnetic phase diagram due to the interaction between itinerant and local electrons. Recently, the electron emission property of CeB6 has received much attention because it has potential applications in replacing the commercial LaB6 cathode and serving as new-generation thermal cathodes. In addition, by comparison with other metal cathodes, it also possesses some advantages, such as a low work function, low volatility, high brightness, thermal stability and high mechanical strength. However, so far the thermionic emission properties of CeB6 single crystal surfaces except for the (100) surfaces have been rarely reported. Whether the different crystal surfaces of CeB6 contribute to the various interesting emission properties is main research purpose of the present work. In this paper, the (110), (111), (210) and (310) crystal surfaces of single crystal CeB6 are determined by the X-ray Laue diffraction method, and their thermionic emission current densities are measured at different temperatures and applied voltages. As a result, the maximum emission current densities of the (110), (111), (210) and (310) crystal surfaces at 1873 K are 38.4, 11.54, 50.4 and 20.8 A/cm2, respectively. When their cathode temperatures are all 1773 K, their maximum emission current densities are 15.2, 5.43, 28.0 and 11.44 A/cm2. In addition, when the cathode temperature decreases to 1673 K, their maximum emission current densities are 4.24, 0.9, 6.2 and 2.43 A/cm2. It means that the thermionic emissions are strongly anisotropic for the different crystal surfaces. In general, the maximum emission current density of (100) crystal surface of LaB6 single crystal is about 10 A/cm2 at 1700 K. By comparing the emission current density of CeB6 single crystal at 1773 K with that of LaB6 at 1700 K, it is found that the emission properties of (210) crystal surface are maybe close to those of LaB6. The work function values of the (110), (111), (210) crystal surfaces calculated by the Richardson-Dushman formula are 2.64, 2.71 and 2.40 eV, respectively. Among these, the (210) crystal surface possesses the smallest value of the work function, which is hopeful for being used as an electron source of scanning electron microscopy. Zero-field magnetoresistivity measurments confirm the transition temperatures of TQ=3.3 K and TN=2.4 K. Field-angle dependent magnetoresistivity measurments show that the electrical resistivity varies between 69 μupΩ·cm and 73 μupΩ·cm when the crystal rotates from the[001] to the[011] direction. This indicates that the electrical resistivity in a magnetic field is also anisotropic.

We present neutron scattering data on $\mathrm{Ce}{({\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})}_{2}{\mathrm{Ge}}_{2}$ that show that magnetic ordering in the vicinity of a quantum critical point is restricted to short length scales even though all moments that are present have lined up with their neighbors. We argue that order is not limited by crystallographic defects but rather that quantum fluctuations disorder the system and dilute the magnetic moments to such an extent that a percolation network forms. The latter naturally explains how $E∕T$ scaling is possible in a system whose apparent dimensionality is above the upper critical dimension.

以CeB 6 和PrB 6 粉末为原料, 采用放电等离子烧结结合悬浮区域熔炼法成功制备了晶体质量良好的多元稀土六硼化物Ce 1- x Pr x B 6 ( x =0.1、0.2、0.4)单晶体, 并系统研究了该系列单晶体(100)晶面热电子发射性能。结果表明: Ce 0.8 Pr 0.2 B 6 单晶(100)晶面具有最好的热发射性能, 在1873 K, 最大电流发射密度达到66.07 A/cm 2 , 比CeB 6 单晶的电流发射密度提高约20%。此外, Ce 0.9 Pr 0.1 B 6 、Ce 0.6 Pr 0.4 B 6 单晶(100)晶面的热发射电流密度分别为65.81 A/cm 2 和65.31 A/cm 2 。Ce 0.8 Pr 0.2 B 6 单晶(100)晶面的逸出功最低, 为2.61 eV, 其它单晶(100)晶面的逸出功在2.64~2.753 eV范围内。因此, Ce 1- x Pr x B 6 多元稀土六硼化物单晶具有良好的发射性能和低的逸出功, 作为热阴极材料有很好的应用前景。

A sample of YBa 2 Cu 3 O 7 was constructed by stacking a number of small single crystals. Magnetization measurements were made in magnetic fields up to 38 T, both parallel to the c -axis and to the basal plane. At 1.4, 4.2 and 20.4 K, a large irreversible magnetization was observed. The significance of these results for the superconducting properties is discussed.

Construction des diagrammes temperature-composition, presentant la region du processus d'aimantation du premier ordre et des diagrammes de phases des spins

Mesures d'aimantation a 4,2 K dans des champs atteignant 35T, sur une serie d'alliages FeAl 1-x Cu x avec x≤0,35. Discussion de l'aimantation en termes d'amas satures disperses dans une matrice itinerante

Des mesures d'aimantation jusqu'a 35 T a 4,2 K sur Ce 1−x Gd x Al 3 montrent l'existence d'un couplage antiferromagnetique fort dans ce systeme. Pour GdAl 3 , on observe une transition de spin flop vers 6T. Estimation de l'anisotropie et des champs d'echange de GdAl 3

Magnetic isotherms in fields up to 35T have been measured at 4.2 and 77K on magnetically-aligned powders of (Pr,R) 2 Fe 14 B compounds with R = Gd, Nd, Er and Sm. Anisotropy constants up to sixth order have been derived. The influence of the various rare-earth substitutions upon the first-order magnetization process in Pr 2 Fe 14 B has been studied.