Debiasing Sequential Recommenders through Distributionally Robust Optimization over System Exposure

Sequential recommendation (SR) models are typically trained on user-item interactions which are affected by the system exposure bias, leading to the user preference learned from the biased SR model not being fully consistent with the true user preference. Exposure bias refers to the fact that user interactions are dependent upon the partial items exposed to the user. Existing debiasing methods do not make full use of the system exposure data and suffer from sub-optimal recommendation performance and high variance. In this paper, we propose to debias sequential recommenders through Distributionally Robust Optimization (DRO) over system exposure data. The key idea is to utilize DRO to optimize the worst-case error over an uncertainty set to safeguard the model against distributional discrepancy caused by the exposure bias. The main challenge to apply DRO for exposure debiasing in SR lies in how to construct the uncertainty set and avoid the overestimation of user preference on biased samples. Moreover, how to evaluate the debiasing effect on biased test set is also an open question. To this end, we first introduce an exposure simulator trained upon the system exposure data to calculate the exposure distribution, which is then regarded as the nominal distribution to construct the uncertainty set of DRO. Then, we introduce a penalty to items with high exposure probability to avoid the overestimation of user preference for biased samples. Finally, we design a debiased self-normalized inverse propensity score (SNIPS) evaluator for evaluating the debiasing effect on the biased offline test set. We conduct extensive experiments on two real-world datasets to verify the effectiveness of the proposed methods. Experimental results demonstrate the superior exposure debiasing performance of proposed methods. Codes and data are available at \url{https://github.com/nancheng58/DebiasedSR_DRO}.Comment: Accept by WSDM 202

A Map-Reduce-enabledSOLAPcubeforlarge-scaleremotelysensed data aggregation

Spatial On-LineAnalyticalProcessing(SOLAP)isapowerfuldecisionsupportsystemstoolforexploring the multidimensionalperspectiveofspatialdata.Inrecentyears,remotelysenseddatahavebeen integratedintoSOLAPcubes,andthisimprovementhasadvantagesinspatio-temporalanalysisfor environmentmonitoring.However,theperformanceofaggregationsinSOLAPstillfacesaconsiderable challenge fromthelarge-scaledatasetgeneratedbyEarthobservation.Fromtheperspectiveofdata parallelism, atile-basedSOLAPcubemodel,theso-calledTileCube,ispresentedinthispaper.Thenovel model implementsRoll-Up/Drill-AcrossoperationsintheSOLAPenvironmentbasedonMap-Reduce,a popular data-intensivecomputingparadigm,andimprovesthethroughputandscalabilityofraster aggregation. Therefore,thelongtime-series,wide-rangeandmulti-viewanalysisofremotelysensed data canbeprocessedinashorttime.TheTileCubeprototypewasbuiltonHadoop/Hbase,anddrought monitoring isusedasanexampletoillustratetheaggregationsinthemodel.Theperformancetesting indicated themodelcanbescaledalongwithboththedatagrowthandnodegrowth.Itisapplicableand natural tointegratetheSOLAPcubewithMap-Reduce.Factorsthatinfluence theperformancearealso discussed, andthebalanceofthemwillbeconsideredinfutureworkstomakefulluseofdatalocalityfor model optimisation

Bi-direction Direct RGB-D Visual Odometry

Direct visual odometry (DVO) is an important vision task which aims to obtain the camera motion via minimizing the photometric error across the different correlated images. However, the previous research on DVO rarely considered the motion bias and only calculated using single direction, therefore potentially ignoring useful information compared with leveraging diverse directions. We assume that jointly considering forward and backward calculation can improve the accuracy of pose estimation. To verify our assumption and solid this contribution, in this paper, we test various combination of direct dense methods, including different error metrics, e.g., (intensity, gradient magnitude), alignment strategies (Forward-Compositional, Inverse-Compositional), and calculation directions (forward, backward, and bi-direction). We further study the issue of motion bias in RGB-D visual odometry and propose four strategy options to improve pose estimation accuracy, e.g., joint bi-direction estimation; two stage bi-direction estimation; transform average with weights; and transform fusion with covariance. We demonstrate the effectiveness and efficiency of our proposed algorithms across a range of popular datasets, e.g., TUM RGB-D and ICL-NUIM, in which we achieve an impressive performance through comparing with state of the art methods and provide benefits for existing RGB-D visual odometry and visual SLAM systems

Efficacy of pegaspargase in extra nodal natural killer/T-cell lymphoma nasal type: A case report from China

Extranodal natural killer (NK)/T-cell lymphoma, nasal type, is a rare and highly aggressive disease with a grim prognosis. There is no known satisfactory treatment. The author herein to report one case of L-asparaginase extranodal NK/T-cell lymphoma primary treated with L-asparaginase methotrexate and dexamethasone

Cervical metastasis of esophagogastric junction cancer

As cervical metastases in esophagogastric junction cancer are extremely rare, the authors herein report a case. A 63-year-old woman presented with dysphagia since 6 months. Diagnostic endoscopy showed that the tumor was located at the esophagogastric junction and histopathological diagnosis of adenocarcinoma was offered. A subtotal gastrectomy was performed. Histopathological diagnosis was moderately differentiated adenocarcinoma, invading upto the serosa with metastases to perigastric nodes. The patient received chemotherapy of cisplatin and fluorouracil for one cycle and oral capecitabine for two cycles. Two years later, the patient presented with vaginal bleeding and magnetic resonance imaging of pelvis revealed a tumor of the cervix. Histopathological impression of the tumor was metastatic cervical adenocarcinoma and immunohistochemistry showed the tumor was cytokeratin, villin, and CDX2 were positive and cytokeratin 20, CA125, and CA199 were negative. The immunohistochemical profile was the same as that of primary

Isolated renal metastasis from squamous cell lung cancer

Abstract Renal metastasis from non-small cell lung cancer is rather uncommon. The mechanism underlying the occurrence of metastasis in this site is still not well understood. We report a case of a 53-year-old Chinese woman who had moderately differentiated squamous cell carcinoma of the lung. After a ten months post-surgery interval of disease free survival, computed tomography (CT) scan found that left renal parenchymal was occupied by a mass, confirmed by kidney biopsy to be a metastasis from squamous cell lung carcinoma. Based on this case, we are warned to be cautious in diagnosis and treatment when renal lesion are detected.</p

Petrogenesis and tectonic implications of early Devonian mafic dike-granite association in the northern West Junggar, NW China

Mafic dike-granite associations are common in extensional tectonic settings and important and pivotal in reconstructing crust-mantle geodynamic processes. We report results of zircon U-Pb and hornblende Ar-40-Ar-39 ages and major-element and trace-element data for mafic dike-granite association from the northern West Junggar, in order to constrain their ages, petrogenesis, and geodynamic process. The mafic dike-granite association was emplaced in the early Devonian. The Xiemisitai monzogranites have high SiO2 contents and low MgO, Cr, and Ni concentrations, suggesting that they were mainly derived from crustal sources and were probably generated by partial melt of the juvenile mid-lower crust. The mafic dikes have low Mg-# and Cr and Ni abundances, suggesting that they have experienced significant fractional crystallization. The Xiemisitai mafic dikes contain hornblende and biotite and display negative Nb-Ta-Ti anomalies, enrichment of LREEs and LILEs, and depletion of HREEs and HFSEs, consistent with an origin from a lithospheric mantle metasomatized by subducted slab-derived fluids. In addition, the Xiemisitai mafic dikes are plotted within melting trends with little to no garnet (Cpx: Grt=6:1) in their source. The La/Yb versus Tb/Yb plot also indicates the presence of less than 1% residual garnet in the source region for the Xiemisitai mafic dikes. Therefore, it can be inferred that the Xiemisitai mafic dikes were generated at a correspondingly shallow depth, mostly within the spinel stability field. The Xiemisitai mafic dikes were most probably generated by the partial melting of the metasomatized lithospheric mantle at relatively shallow depths (&lt;80km). The Xiemisitai mafic dike-granite association could have been triggered by asthenospheric upwelling as a result of the rollback of the subducted Irtysh-Zaysan oceanic lithosphere

Proteomic analysis of differential expression of cellular proteins in response to avian H9N2 virus infection of A549 cells

In this study, differentially expressed proteins in A549 cells (human lung adenocarcinoma epithelial cell line) infected with H9N2 avian influenza virus (AIV) were investigated by two-dimensional electrophoresis (2-DE). Sixteen different spots between the groups (ratio>2, p<0.05) were identified with mass spectrometry identification. Proteins located in the downstream of the NF-κB and IFN transcription factor pathways were identified, e.g. ISG15. Actin and keratin were also identified, which suggesting that the cytoskeleton may plays an important role in the AIV infection of mammalian cells. These findings could provide insights into the interaction between host and influenza viruses and might provide valuable information for clarifying the pathogenesis of viral infections as well