Field-aware Calibration: A Simple and Empirically Strong Method for Reliable Probabilistic Predictions

It is often observed that the probabilistic predictions given by a machine learning model can disagree with averaged actual outcomes on specific subsets of data, which is also known as the issue of miscalibration. It is responsible for the unreliability of practical machine learning systems. For example, in online advertising, an ad can receive a click-through rate prediction of 0.1 over some population of users where its actual click rate is 0.15. In such cases, the probabilistic predictions have to be fixed before the system can be deployed. In this paper, we first introduce a new evaluation metric named field-level calibration error that measures the bias in predictions over the sensitive input field that the decision-maker concerns. We show that existing post-hoc calibration methods have limited improvements in the new field-level metric and other non-calibration metrics such as the AUC score. To this end, we propose Neural Calibration, a simple yet powerful post-hoc calibration method that learns to calibrate by making full use of the field-aware information over the validation set. We present extensive experiments on five large-scale datasets. The results showed that Neural Calibration significantly improves against uncalibrated predictions in common metrics such as the negative log-likelihood, Brier score and AUC, as well as the proposed field-level calibration error.Comment: WWW 202

Background Subtraction for Night Videos

Motion analysis is important in video surveillance systems and background subtraction is useful for moving object detection in such systems. However, most of the existing background subtraction methods do not work well for surveillance systems in the evening because objects are usually dark and reflected light is usually strong. To resolve these issues, we propose a framework that utilizes a Weber contrast descriptor, a texture feature extractor, and a light detection unit, to extract the features of foreground objects. We propose a local pattern enhancement method. For the light detection unit, our method utilizes the finding that lighted areas in the evening usually have a low saturation in hue-saturation-value and hue-saturation-lightness color spaces. Finally, we update the background model and the foreground objects in the framework. This approach is able to improve foreground object detection in night videos, which do not need a large data set for pre-training

Observation of prolonged coherence time of the collective spin wave of atomic ensemble in a paraffin coated Rb vapor cell

We report a prolonged coherence time of the collective spin wave of a thermal 87Rb atomic ensemble in a paraffin coated cell. The spin wave is prepared through a stimulated Raman Process. The long coherence time time is achieved by prolonging the lifetime of the spins with paraffin coating and minimize dephasing with optimal experimental configuration. The observation of the long time delayed-stimulated Stokes signal in the writing process suggests the prolonged lifetime of the prepared spins; a direct measurement of the decay of anti-Stokes signal in the reading process shows the coherence time is up to 300 us after minimizing dephasing. This is one hundred times longer than the reported coherence time in the similar experiments in thermal atomic ensembles based on the Duan-Lukin-Cirac-Zoller (DLCZ) and its improved protocols. This prolonged coherence time sets the upper limit of the memory time in quantum repeaters based on such protocols, which is crucial for the realization of long-distance quantum communication. The previous reported fluorescence background in the writing process due to collision in a sample cell with buffer gas is also reduced in a cell without buffer gas.Comment: 4 pages, 4 figure

Spontaneously induced general relativity with holographic interior and general exterior

We study the spontaneously induced general relativity (GR) from the scalar-tensor gravity. We demonstrate by numerical methods that a novel inner core can be connected to the Schwarzschild exterior with cosmological constants and any sectional curvature. Deriving an analytic core metric for a general exterior, we show that all the nontrivial features of the core, including the locally holographic entropy packing, are universal for the general exterior in static spacetimes. We also investigate whether the f(R) gravity can accommodate the nontrivial core.Comment: 16 pages, 5 figures; v3: clarification improved, revised version accepted by PL

No relationship between the distribution of mast cells and the survival of stage IIIB colon cancer patients

<p>Abstract</p> <p>Background</p> <p>Mast cells promote the progression of experimental tumors and might be a valuable therapeutic target. However, the relevant clinical evidence is still controversial. This study analyzed the relationship between the distribution of mast cells and the survival of patients with colon cancer to study whether mast cells contribute to tumor progression.</p> <p>Materials and methods</p> <p>Ninety-three cases of pathologically confirmed primary cancer tissues matched with adjacent normal mucosa, metastases of regional-draining lymph nodes and regional-draining lymph nodes without metastases were collected from stage IIIB colon carcinoma patients between January 1997 and July 2004 at the Cancer Center of Sun Yat-Sen University. Tryptase-positive mast cells were counted. The relationships of the distribution of mast cells with clinicopathologic parameters and 5-year survival were analyzed.</p> <p>Results</p> <p>Although the mast cell count in the mucosa adjacent to the primary colon cancer was significantly higher than that in the stroma of the primary colon cancer, no difference in mast cell counts was observed between the stroma in lymph node metastasis and the lymph tissue adjacent to the metastasis. Additionally, the mast cell count in the regional-draining lymph node without the invasion of cancer cells was significantly higher than that in the stroma of lymph node metastasis and adjacent lymph tissue. However, none of those mast cell counts was related to 5-year survival.</p> <p>Conclusion</p> <p>Although mast cell count varied with location, none of the mast cell counts was related to 5-year survival, suggesting that mast cells do not contribute to the progression of stage IIIB colon cancer.</p

Thrust and torque production of a squid-inspired swimmer with a bent nozzle for thrust vectoring

A three-dimensional pulsed-jet propulsion model consisting of a flexible body and a steerable bent nozzle in tethered mode is presented and studied numerically. By prescribing the body deformation and nozzle angle, we examine the flow evolution and propulsive/turning performance via thrust vectoring. Our results show that the vortex ring is no longer axis-symmetric when the jet is ejected at an angle with the incoming flow. A torque peak is observed during jetting, which is mainly sourced from the suction force (negative pressure) at the lower part of the internal nozzle surface when the flow is directed downward through an acute angle. After this crest, the torque is dominated by the positive pressure at the upper part of the internal nozzle surface, especially at a relatively low jet-based Reynolds number (О(102)). The torque production increases with a larger nozzle bent angle as expected. Meanwhile, the thrust production remains almost unchanged, showing little trade-off between thrust and torque production which demonstrates the advantage of thrust vectoring via a bent nozzle. By decoupling the thrust at the internal and outer surfaces considering special characteristics of force generation by pulsed-jet propulsion, we find that variations in Reynolds number mostly affect the viscous friction at the outer surfaces. The influence of the maximum stroke ratio is also studied. Results show that both the time-averaged thrust and the torque decrease at a larger stroke ratio. [Abstract copyright: Creative Commons Attribution license.

Jet propulsion of a squid-inspired swimmer in the presence of background flow

Inspired by recent studies of a squid-like swimmer, we propose a three-dimensional jet propulsion system composed of an empty chamber enclosed within a deformable body with an opening. By prescribing the body deformation and jet velocity profile, we numerically investigate the jet flow field and propulsion performance under the influence of background flow during a single deflation procedure. Three jet velocity profiles, i.e., constant, cosine and half cosine, are considered. We find that the maximum circulation of the vortex ring is reduced at a higher background flow velocity. This is because stronger interaction between the jet flow and background flow makes it harder to feed the leading vortex ring. Regarding thrust production, our analysis based on conservation of momentum indicates that with the constant profile the peak thrust is dominated by the time derivative of the fluid momentum inside the body, while momentum flux related thrust accounts for the quasi-steady thrust. For the cosine profile, its peak is mainly sourced from momentum flux associated with the unsteady vortex ring formation. No prominent thrust peak exists with the half cosine profile whose thrust continuously increases during the jetting. For all the three jet velocity profiles, added-mass related thrust attributed to body deformation enhances the overall thrust generation non-negligibly. Under the present tethered mode, the background flow has negligible influence on the thrust attributed to momentum flux and momentum change of the fluid inside the body. However, it indeed affects the over pressure-related thrust but its effect is relatively small. The overall thrust declines due to the significantly increased drag force at large incoming flow speed despite the rise of added-mass related thrust. Unsteady thrust involving vortex ring formation becomes more important in the overall thrust generation with an increased background flow velocity, reflected by larger ratios of the unsteady impulse to jet thrust impulse

Accumulation Pattern of Flavonoids in Cabernet Sauvignon Grapes Grown in a Low-Latitude and High-Altitude Region

Particular climate conditions in a low-latitude and high-altitude region endow grape berries with distinctivequality characteristics. So far, few reports have been concerned with the formation of berry flavour in such aregion. This study aimed to investigate the accumulation pattern of flavonoids in Vitis vinifera L. cv. CabernetSauvignon grape berries growing at different altitudes of the highland in southwest China in two consecutivevintages. In addition to the 3-O-monoglucosides and 3-O-acyl monoglucosides of the five main anthocyanidins(delphinidin, cyanidin, peonidin, petunidin and malvidin), some uncommon anthocyanins, such as threediglucosides of anthocyanidins and pelargonidin-3-O-glucoside, were detected in the grape berries. Higheraltitude cultivation greatly promoted the production of anthocyanins and flavonols, particularly cyanidintypeanthocyanins and quercetin-type flavonols from the F3’H branch of the flavonoid biosynthetic pathway.Flavan-3-ols from both branches were comparatively less influenced by vineyard altitude. Vintage in thishigh-altitude region also had a dramatic influence on the accumulation of flavonoids. Most of the anthocyaninand flavonol components were affected more by vineyard altitude than by vintage, whereas the accumulationof flavan-3-ols differed mainly between vintages. The present data will not only improve the understandingof flavonoid accumulation in grapes from a high-altitude region with different climates, but also providepractical guidance for the production of high-quality grapes and wine