12 research outputs found
《嘯亭雜録》三條考辨
清代昭槤的著名筆記《嘯亭雜録》,存在著不少記載失實或錯誤的地方。本文對其中“本朝文人多壽”、“老年科目”、“青年科目”這三條進行考察辨析,理清事實,更正錯誤,藉以梳理相關歷史人物的生卒年問題,同時增進對《嘯亭雜録》乃至其他同類著作的認識
Constrained Bayesian Optimization with Adaptive Active Learning of Unknown Constraints
Optimizing objectives under constraints, where both the objectives and
constraints are black box functions, is a common scenario in real-world
applications such as scientific experimental design, design of medical
therapies, and industrial process optimization. One popular approach to
handling these complex scenarios is Bayesian Optimization (BO). In terms of
theoretical behavior, BO is relatively well understood in the unconstrained
setting, where its principles have been well explored and validated. However,
when it comes to constrained Bayesian optimization (CBO), the existing
framework often relies on heuristics or approximations without the same level
of theoretical guarantees.
In this paper, we delve into the theoretical and practical aspects of
constrained Bayesian optimization, where the objective and constraints can be
independently evaluated and are subject to noise. By recognizing that both the
objective and constraints can help identify high-confidence regions of interest
(ROI), we propose an efficient CBO framework that intersects the ROIs
identified from each aspect to determine the general ROI. The ROI, coupled with
a novel acquisition function that adaptively balances the optimization of the
objective and the identification of feasible regions, enables us to derive
rigorous theoretical justifications for its performance. We showcase the
efficiency and robustness of our proposed CBO framework through empirical
evidence and discuss the fundamental challenge of deriving practical regret
bounds for CBO algorithms
Simulation Study of Energy Absorption of X- and -Rays in Plastic Scintillating Fiber Arrays
Crevice Corrosion Behavior of 201 Stainless Steel in NaCl Solutions with Different pH Values by In Situ Monitoring
Crevice corrosion (CC) behavior of 201 stainless steel (SS) in 1 M NaCl + x M HCl/y M NaOH solutions with various pH was investigated using SECM and optical microscopic observations. Results show that the CC was initiated by the decrease in pH value within the crevice. The pH value near the crevice mouth falls rapidly to 1.38 in the first 2 h in the strongly acidic solution, while the pH value was observed to rise firstly and then decrease in the neutral and alkaline solutions. It indicates there is no incubation phase in the CC evolution of 201-SS in a pH = 2.00 solution, while an incubation phase was observed in pH = 7.00 and 11.00 solutions. Additionally, there appeared to be a radial pH variation within the gap over time. The pH value is the lowest at the gap mouth, which is in line with the in situ optical observation result that the severely corroded region is at the mouth of the gap. The decrease in pH value inside results in the negative shift of open circuit potential (OCP) and the initiation of CC of 201-SS. The increased anodic dissolution rate in the acidic solution accelerates the breakdown of passive film inside, reducing the initiation time and stimulating the spread of CC