FinRL-Meta: Market Environments and Benchmarks for Data-Driven Financial Reinforcement Learning

Finance is a particularly difficult playground for deep reinforcement learning. However, establishing high-quality market environments and benchmarks for financial reinforcement learning is challenging due to three major factors, namely, low signal-to-noise ratio of financial data, survivorship bias of historical data, and model overfitting in the backtesting stage. In this paper, we present an openly accessible FinRL-Meta library that has been actively maintained by the AI4Finance community. First, following a DataOps paradigm, we will provide hundreds of market environments through an automatic pipeline that collects dynamic datasets from real-world markets and processes them into gym-style market environments. Second, we reproduce popular papers as stepping stones for users to design new trading strategies. We also deploy the library on cloud platforms so that users can visualize their own results and assess the relative performance via community-wise competitions. Third, FinRL-Meta provides tens of Jupyter/Python demos organized into a curriculum and a documentation website to serve the rapidly growing community. FinRL-Meta is available at: https://github.com/AI4Finance-Foundation/FinRL-MetaComment: NeurIPS 2022 Datasets and Benchmarks. 36th Conference on Neural Information Processing Systems Datasets and Benchmarks Trac

Dynamic Datasets and Market Environments for Financial Reinforcement Learning

The financial market is a particularly challenging playground for deep reinforcement learning due to its unique feature of dynamic datasets. Building high-quality market environments for training financial reinforcement learning (FinRL) agents is difficult due to major factors such as the low signal-to-noise ratio of financial data, survivorship bias of historical data, and model overfitting. In this paper, we present FinRL-Meta, a data-centric and openly accessible library that processes dynamic datasets from real-world markets into gym-style market environments and has been actively maintained by the AI4Finance community. First, following a DataOps paradigm, we provide hundreds of market environments through an automatic data curation pipeline. Second, we provide homegrown examples and reproduce popular research papers as stepping stones for users to design new trading strategies. We also deploy the library on cloud platforms so that users can visualize their own results and assess the relative performance via community-wise competitions. Third, we provide dozens of Jupyter/Python demos organized into a curriculum and a documentation website to serve the rapidly growing community. The open-source codes for the data curation pipeline are available at https://github.com/AI4Finance-Foundation/FinRL-MetaComment: 49 pages, 15 figures. arXiv admin note: substantial text overlap with arXiv:2211.0310

Relationship between Surface Hardness and Peak Interfacial Frictional Coefficient in a Laboratory Scale Setting

This study aims to clarify the relationship between surface hardness and the peak interfacial frictional coefficient under different particle sizes. The relationship between particle size and the peak interfacial frictional coefficient with different surface hardness values has not been addressed in previous literature. A pile-soil interfacial shear test was conducted using a multifunctional interfacial shear instrument was developed in the laboratory. The influences of surface hardness and particle size on the shear characteristics of pile-soil interfaces and the peak interface friction coefficient were studied. The test results revealed that the interfacial shear stress-shear displacement curves showed typical softening behavior when the surface of the model pile was smooth. The difference in curve characteristics for different particle sizes gradually cleared as the surface hardness decreased. The initial shear stiffness of the interface increased with increasing surface hardness and decreased with increasing particle size. The peak interfacial friction coefficient decreased with increasing surface hardness for different particle sizes. Furthermore, the peak interface friction coefficient increased with increasing particle size when the surface was hard. However, when the surface was soft, the peak interfacial friction coefficient decreased with increasing particle size. The linear relationship between the peak interfacial friction coefficient and particle size for different surface hardness values was established

Load-Settlement Behaviour Analysis Based on the Characteristics of the Vertical Loads under a Pile Group

The nonlinear load-settlement behaviours of vertically loaded pile groups containing various numbers of piles (up to a few hundred piles in a group) are analysed using the method proposed by Lee and Xiao. This back-analysis method assumes the “local shear displacement” of a thin layer of disturbed soil along the pile–soil interface and the soil outside the interface is assumed to be linear elastic. Parametric studies are conducted to examine the load-displacement behaviours of the rigidly capped pile groups. Factors such as the number of piles in a group, pile slenderness (L/D), and pile spacing (S/D) are examined to study the effects on the performance of pile groups up to the failure state. Some phenomenological features of large pile groups under nonlinear conditions, which are difficult to obtain through an elastic analysis, are revealed in the present analysis

Relationship between Surface Hardness and Peak Interfacial Frictional Coefficient in a Laboratory Scale Setting

This study aims to clarify the relationship between surface hardness and the peak interfacial frictional coefficient under different particle sizes. The relationship between particle size and the peak interfacial frictional coefficient with different surface hardness values has not been addressed in previous literature. A pile-soil interfacial shear test was conducted using a multifunctional interfacial shear instrument was developed in the laboratory. The influences of surface hardness and particle size on the shear characteristics of pile-soil interfaces and the peak interface friction coefficient were studied. The test results revealed that the interfacial shear stress-shear displacement curves showed typical softening behavior when the surface of the model pile was smooth. The difference in curve characteristics for different particle sizes gradually cleared as the surface hardness decreased. The initial shear stiffness of the interface increased with increasing surface hardness and decreased with increasing particle size. The peak interfacial friction coefficient decreased with increasing surface hardness for different particle sizes. Furthermore, the peak interface friction coefficient increased with increasing particle size when the surface was hard. However, when the surface was soft, the peak interfacial friction coefficient decreased with increasing particle size. The linear relationship between the peak interfacial friction coefficient and particle size for different surface hardness values was established

The Effects and Vertical Bearing Capacity of Two Jacked Model Piles in Sand

The effects and vertical bearing capacity of two jacked piles in sand are still not well understood, and the mechanism of the adjacent pile’s uplift caused by the jacking pile in a double pile system is especially unclear, but these facets are important to the stability of the jacked pile. In this paper, a series of tests is performed on jacked model piles in sand, where in the influences of the pile length and the driving pile’s speed on the effects and vertical bearing capacity of two jacked piles were studied. The results revealed that the effects and vertical bearing capacity of the two jacked piles were mainly in relation to pile length and influenced by the driving speed. The horizontal displacement of the top of the first jacking pile during the installation of the post-jacking pile was caused by the difference in the stress state of the first jacking pile between the side of the pile’s face and its back side, in which the uplift displacement of the first jacking pile was also involved. The radial stress of the pile increased nonlinearly with the depth under different pile lengths and gradually converged to the passive earth pressure. The ultimate capacity of the double pile is approximately twice that of a single pile, and the ratio of the ultimate capacity of a single pile to the final jacking pressure was approximately 1.04

Site Measurement Study on Mechanical Properties of SMW Piles of Building Structures in Sandy Soil Areas

SMW (soil mixing wall) piles have been widely used in soft soil areas such as Jiangsu, Shanghai, Tianjin and so on, and they have many advantages, such as retaining the structures of foundation pits. In order to promote the application of SMW piles in sandy soil areas such as Henan province, SMW piles were used in a deep foundation pit project of a high-rise building in Zhengzhou. Three SMW piles in the middle area of the foundation pit were selected for site measurement to determine the mechanical properties of SMW piles in sandy soil areas. Several typical test sections were determined along the height of the pile. The vibrating string type of the reinforcement dynamometers were set on the H-shaped steel of each test section, and the stress distribution of the H-shaped steel along the depth of the pit was obtained via testing. The axial force, bending moment and shearing force of the H-shaped steel were further calculated, and the affecting factors and development laws of the internal force distribution of the H-shaped steel were analyzed in detail. The research shows that, at the stage of foundation pit excavation, the overall stress of H-shaped steel increases gradually. The axial force of H-shaped steel in an SMW pile is mainly affected by such factors as the weight of the H-shaped steel, the weight of the crown beam and the first support system, the weight of the breast beam and the second support system, and the frictional resistance of the cemented soil. The bending moment and shearing force of H-shaped steel are mainly affected by such factors as the lateral soil pressure and the concentrated forces of the two support systems. When the foundation pit was excavated to the base, the development of and changes in the law of internal force with regard to the H-shaped steel was analyzed. When the overall internal force of the H-shaped steel is at its maximum, the maximum absolute values in terms of the axial force, bending moment and shearing force are −481 KN, 371 KN·m and 123 KN. In the process of foundation pit excavation and backfilling, the point of contraflexure of the H-shaped steel moves down gradually, and the fixed end of corresponding SMW pile also moves down and stabilizes below the base. These results may provide a reference for the design and construction of SMW piles of building structures in sandy soil areas

All-Inorganic Perovskite Solar Cells

The research field on perovskite solar cells (PSCs) is seeing frequent record breaking in the power conversion efficiency (PCE). However, organic–inorganic hybrid halide perovskites and organic additives in common hole-transport materials (HTMs) exhibit poor stability against moisture and heat. Here we report the successful fabrication of all-inorganic PSCs without any labile or expensive organic components. The entire fabrication process can be operated in ambient environment without humidity control (e.g., a glovebox). Even without encapsulation, the all-inorganic PSCs present no performance degradation in humid air (90–95% relative humidity, 25 °C) for over 3 months (2640 h) and can endure extreme temperatures (100 and −22 °C). Moreover, by elimination of expensive HTMs and noble-metal electrodes, the cost was significantly reduced. The highest PCE of the first-generation all-inorganic PSCs reached 6.7%. This study opens the door for next-generation PSCs with long-term stability under harsh conditions, making practical application of PSCs a real possibility