Type inference in SQL

Type inference is an important concept in programming languages. In this Thesis, we study this problem and propose a framework for type inference in SQL, the database programming language for relational databases such as Oracle and Sybase. We consider a context-free grammar G SQL which covers the core features of the standard SQL. We add semantic rules to G SQL , following Knuth's method of "attribute grammars", to capture the set of schemas for which a query q ✹ L ( G SQL ) is well-defined. We show that G SQL is unambiguous and that our attribute grammar is non-circular. The set of schemas of a query is usually infinite. To finitely represent this set, we introduce schema tableaux, a variation of a well-known tool from database theory. By defining another attribute grammar for G SQL , we show that the set of schemas of a query q ✹ L ( G SQL ) can be finitely represented as a tableau which can be effectively computed given q as input. We discuss applications of our type inference methodology, and as a case study, we apply it on the suite of TPC Benchmark(TM) H queries, which has industry-wide relevance and a high degree of complexity. The experiments indicate the methodology in useful in practice, particularly in the context of database schema comprehension

Energy-efficient domain wall motion governed by the interplay of helicity-dependent optical effect and spin-orbit torque

Spin-orbit torque provides a powerful means of manipulating domain walls along magnetic wires. However, the current density required for domain wall motion is still too high to realize low power devices. Here we experimentally demonstrate helicity-dependent domain wall motion by combining synchronized femtosecond laser pulses and short current pulses in Co/Ni/Co ultra-thin film wires with perpendicular magnetization. Domain wall can remain pinned under one laser circular helicity while depinned by the opposite circular helicity. Thanks to the all-optical helicity-dependent effect, the threshold current density due to spin-orbit torque can be reduced by more than 50%. Based on this joint effect combining spin-orbit torque and helicity-dependent laser pulses, an optoelectronic logic-in-memory device has been experimentally demonstrated. This work enables a new class of low power spintronic-photonic devices beyond the conventional approach of all-optical switching or all-current switching for data storage.Comment: 21 pages, 5 figure

High-Performance Fine Defect Detection in Artificial Leather Using Dual Feature Pool Object Detection

In this study, the structural problems of the YOLOv5 model were analyzed emphatically. Based on the characteristics of fine defects in artificial leather, four innovative structures, namely DFP, IFF, AMP, and EOS, were designed. These advancements led to the proposal of a high-performance artificial leather fine defect detection model named YOLOD. YOLOD demonstrated outstanding performance on the artificial leather defect dataset, achieving an impressive increase of 11.7% - 13.5% in AP_50 compared to YOLOv5, along with a significant reduction of 5.2% - 7.2% in the error detection rate. Moreover, YOLOD also exhibited remarkable performance on the general MS-COCO dataset, with an increase of 0.4% - 2.6% in AP compared to YOLOv5, and a rise of 2.5% - 4.1% in AP_S compared to YOLOv5. These results demonstrate the superiority of YOLOD in both artificial leather defect detection and general object detection tasks, making it a highly efficient and effective model for real-world applications

Domain-wall motion induced by spin transfer torque delivered by helicity-dependent femtosecond laser

In magnetic wires with perpendicular anisotropy, moving domain with only current or only circularly polarized light requires a high power. Here, we propose to reduce it by using both short current pulses and femtosecond laser pulses simultaneously. The wires were made out of perpendicularly magnetized film of Pt/Co/Ni/Co/Pt. The displacement of the domain wall is found to be dependent on the laser helicity. Based on a quantitative analysis of the current-induced domain wall motion, the spin orbit torque contribution can be neglected when compared to the spin transfer torque contribution. The effective field of the spin transfer torque is extracted from the pulsed field domain wall measurements. Finally, our result can be described using the Fatuzzo-Labrune model and considering the effective field due to the polarized laser beam, the effective field due to spin transfer torque, and the Gaussian temperature distribution of the laser spot.Comment: 14 pages, 4 figure

YOLOCS: Object Detection based on Dense Channel Compression for Feature Spatial Solidification

In this study, we examine the associations between channel features and convolutional kernels during the processes of feature purification and gradient backpropagation, with a focus on the forward and backward propagation within the network. Consequently, we propose a method called Dense Channel Compression for Feature Spatial Solidification. Drawing upon the central concept of this method, we introduce two innovative modules for backbone and head networks: the Dense Channel Compression for Feature Spatial Solidification Structure (DCFS) and the Asymmetric Multi-Level Compression Decoupled Head (ADH). When integrated into the YOLOv5 model, these two modules demonstrate exceptional performance, resulting in a modified model referred to as YOLOCS. Evaluated on the MSCOCO dataset, the large, medium, and small YOLOCS models yield AP of 50.1%, 47.6%, and 42.5%, respectively. Maintaining inference speeds remarkably similar to those of the YOLOv5 model, the large, medium, and small YOLOCS models surpass the YOLOv5 model's AP by 1.1%, 2.3%, and 5.2%, respectively

Spin structure relation to phase contrast imaging of isolated magnetic Bloch and Neel skyrmions

Magnetic skyrmions are promising candidates for future storage devices with a large data density. A great variety of materials have been found that host skyrmions up to the room-temperature regime. Lorentz microscopy, usually performed in a transmission electron microscope (TEM), is one of the most important tools for characterizing skyrmion samples in real space. Using numerical calculations, this work relates the phase contrast in a TEM to the actual magnetization profile of an isolated Neel or Bloch skyrmion, the two most common skyrmion types. Within the framework of the used skyrmion model, the results are independent of skyrmion size and wall width and scale with sample thickness for purely magnetic specimens. Simple rules are provided to extract the actual skyrmion configuration of pure Bloch or Neel skyrmions without the need of simulations. Furthermore, first differential phase contrast (DPC) measurements on Neel skyrmions that meet experimental expectations are presented and showcase the described principles. The work is relevant for material sciences where it enables the engineering of skyrmion profiles via convenient characterization.Comment: 6 pages, 3 figure