Optimal No-regret Learning in Repeated First-price Auctions

We study online learning in repeated first-price auctions with censored feedback, where a bidder, only observing the winning bid at the end of each auction, learns to adaptively bid in order to maximize her cumulative payoff. To achieve this goal, the bidder faces a challenging dilemma: if she wins the bid--the only way to achieve positive payoffs--then she is not able to observe the highest bid of the other bidders, which we assume is iid drawn from an unknown distribution. This dilemma, despite being reminiscent of the exploration-exploitation trade-off in contextual bandits, cannot directly be addressed by the existing UCB or Thompson sampling algorithms in that literature, mainly because contrary to the standard bandits setting, when a positive reward is obtained here, nothing about the environment can be learned. In this paper, by exploiting the structural properties of first-price auctions, we develop the first learning algorithm that achieves $O(\sqrt{T}\log^2 T)$ regret bound when the bidder's private values are stochastically generated. We do so by providing an algorithm on a general class of problems, which we call monotone group contextual bandits, where the same regret bound is established under stochastically generated contexts. Further, by a novel lower bound argument, we characterize an $\Omega(T^{2/3})$ lower bound for the case where the contexts are adversarially generated, thus highlighting the impact of the contexts generation mechanism on the fundamental learning limit. Despite this, we further exploit the structure of first-price auctions and develop a learning algorithm that operates sample-efficiently (and computationally efficiently) in the presence of adversarially generated private values. We establish an $O(\sqrt{T}\log^3 T)$ regret bound for this algorithm, hence providing a complete characterization of optimal learning guarantees for this problem

The influence of Product Photo display on Purchase intention in Cross-border E-commerce

Nowadays, cross-border e-commerce (CBEC) has become an important channel for promoting international trade. There are many factors that influence consumer participation in CBEC, including the display of product images in the product search list. Excellent and appropriate product photo display can not only attract more consumers, but also stimulate consumers\u27 willingness to buy. However, few studies have focused on the specific elements that should be included in a product photo in a CBEC setting. Based on cue utilization theory and ELM model, this study constructs a research model of consumer purchase intention under the background of CBEC from the perspective of task-relevant cues and affection-relevant cues. In addition, we explore the choice pattern of customers during online shopping by using the decision tree model, and then investigate the influence of specific elements in product photo on sales volume by using hierarchical regression. The data will be obtained from a well-known CBEC platform in China, using clothing products as key words to gather the three factors that consumers will normally first encounter in the search results: the price of goods, number of orders, and a photo of the merchandise. Results will have important theoretical and practical implications for CBEC researchers and practitioners

Technology for Improving Life of Thermal Recovery Well Casing

In steam injection process, casing is heated by steam, the change of casing temperature produces thermal stresses in the casing, the casing deforms when stresses exceed the yield point of its material. Casing failure is becoming increasingly prominent in thermal recovery wells, which severely restricts the development effect of such reservoirs, improving casing life of thermal recovery well has become a urgent problem to be solved. Through on-site survey and analysis, reasons for casing damage were determined as follows: strength change by high temperature, sand flow over of oil formation, poor cementing, unfavorable heat insulation and bad material for casing. In order to improve casing life, the supporting measures are introduced, the measures include pre-stress cementing technology, using casing head, thermal stress compensator, high-performance insulation tubing, high temperature cement slurry system, FRT110H special casing, and early sand control completion technology. Field application of these measures has gotten better effect in Shengli oilfield in recent years, the damage rate of thermal recovery well has decreased obviously, and this can provide reference for the efficient development of similar reservoirs at home and abroad.Key words: Casing failure; Thermal recovery wells; Special casing; Cementing; Sand control completio

Platelet-expressed immune checkpoint regulator GITRL in breast cancer

Breast cancer is the leading cause of cancer-related death in women. Most subtypes of breast cancer are immunologically silent, which makes the immunotherapy of patients with advanced breast cancer particularly challenging and new targets are urgently needed. Platelets play an important role in tumor progression as they promote proliferation, chemotherapy resistance, stemness, invasion, and immune evasion of malignant cells. As a new target of immune checkpoint therapy, GITRL has attracted more and more attention. Little is known about the role of pGITRL in breast cancer. We assumed that pGITRL may serve as a biomarker and a potential immunotherapeutic target in breast cancer. Here, we conducted a comparative analysis of pGITRL in breast cancer patients. pGITRL expression was upregulated in breast cancer patients as compared to healthy donors and especially increased in cases of intermediate tumor stages, low proliferation index, and absence of metastasis. GITR expression on NK cells increased in breast cancer patients as compared to healthy donors. Moreover, GITRL expression was enhanced during platelet activation in breast cancer patients. The capacity of GITRL upregulation upon platelet activation associated with the basal GITRL expression on resting platelets in both breast cancer and healthy donor cohorts. GITRL expression was enhanced during megakaryopoiesis and particularly upregulated in the presence of soluble factors derived from breast cancer cells. All the findings may suggest enhanced pGITRL levels and increased capacity of pGITRL regulation upon platelet activation in breast cancer as part of a tumor-educated platelet phenotype. Based on our data, pGITRL may serve as a readily available biomarker and a potential immunotherapeutic target in breast cancer