1-form symmetries of 4d N=2 class S theories

We determine the 1-form symmetry group for any 4d4d\mathcal{N}=2𝒩=2 class S theory constructed by compactifying a 6d6d\mathcal{N}=(2,0)𝒩=(2,0) SCFT on a Riemann surface with arbitrary regular untwisted and twisted punctures. The 6d6d theory has a group of mutually non-local dimension-2 surface operators, modulo screening. Compactifying these surface operators leads to a group of mutually non-local line operators in 4d4d, modulo screening and flavor charges. Complete specification of a 4d4d theory arising from such a compactification requires a choice of a maximal subgroup of mutually local line operators, and the 1-form symmetry group of the chosen 4d4d theory is identified as the Pontryagin dual of this maximal subgroup. We also comment on how to generalize our results to compactifications involving irregular punctures. Finally, to complement the analysis from 6d, we derive the 1-form symmetry from a Type IIB realization of class S theories.

Magnetic Sans of Nanoparticles and Complex Systems

This chapter provides an overview on the magnetic SANS of nanoparticles and complex systems, which include ferrofluids, magnetic steels, and spin glasses and amorphous magnets. The underlying assumptions of the conventional particle-matrix-based model of magnetic SANS, which assumes uniformly magnetized domains, characteristic e.g., for superparamagnets, are discussed and we provide a complete specification of the micromagnetic boundary-value problem. First attempts to provide analytical expressions for the vortex-state-related magnetic SANS of thin circular discs are considered.

Dynamic Safety Certification for Collaborative Embedded Systems at Runtime

Traditionally, integration and quality assurance of embedded systems are done entirely at development time. Moreover, since such systems often perform safety-critical tasks and work in human environments, safety analyses are performed and safety argumentations devised to convince certification authorities of their safety and to certify the systems if necessary. Collaborative embedded systems, however, are designed to integrate and collaborate with other systems dynamically at runtime. A complete prediction and analysis of all relevant properties during the design phase is usually not possible, as many influencing factors are not yet known. This makes the application of traditional safety analysis and certification techniques impractical, as they usually require a complete specification of the system and its context in advance. In the following chapter, we introduce new techniques to meet this challenge and outline a safety certification concept specifically tailored to collaborative embedded systems.

Reproducible Tract Profiles (RTP): from diffusion MRI acquisition to publication

Reproducible Tract Profiles (RTP) comprises a set of methods to manage and analyze diffusion weighted imaging (DWI) data for reproducible tractography. The tools take MRI data from the scanner and process them through a series of analysis implemented as Docker containers that are integrated into a modern neuroinformatics platform (Flywheel). The platform guarantees that the entire pipeline can be re-executed, using the same data and computational parameters. In this paper, we describe (1) a cloud based neuroinformatics platform, (2) a tool to programmatically access and control the platform from a client, and (3) the DWI analysis tools that are used to identify the positions of 22 tracts and their diffusion profiles. The combination of these three components defines a system that transforms raw data into reproducible tract profiles for publication.Graphical abstractReproducible Tract Profiles (RTP) comprises a set of methods to manage and analyze diffusion weighted imaging (DWI) data for reproducible tractography. The RTP methods comprise two main parts. Server side software tools for storing data and metadata and managing containerized computations.Client side software tools that enable the researcher to read data and metadata and manage server-side computations.The server-side computational tools are embedded in containers that are linked to a JSON file with a complete specification of the computational parameters. The data and computational infrastructure on the server is fully reproducible.

Dismantling the AUT64 Automotive Cipher

AUT64 is a 64-bit automotive block cipher with a 120-bit secret key used in a number of security sensitive applications such as vehicle immobilization and remote keyless entry systems. In this paper, we present for the first time full details of AUT64 including a complete specification and analysis of the block cipher, the associated authentication protocol, and its implementation in a widely-used vehicle immobiliser system that we have reverse engineered. Secondly, we reveal a number of cryptographic weaknesses in the block cipher design. Finally, we study the concrete use of AUT64 in a real immobiliser system, and pinpoint severe weaknesses in the key diversification scheme employed by the vehicle manufacturer. We present two key-recovery attacks based on the cryptographic weaknesses that, combined with the implementation flaws, break both the 8 and 24 round configurations of AUT64. Our attack on eight rounds requires only 512 plaintext-ciphertext pairs and, in the worst case, just 237.3 offline encryptions. In most cases, the attack can be executed within milliseconds on a standard laptop. Our attack on 24 rounds requires 2 plaintext-ciphertext pairs and 248.3 encryptions to recover the 120-bit secret key in the worst case. We have strong indications that a large part of the key is kept constant across vehicles, which would enable an attack using a single communication with the transponder and negligible offline computation.

Discovering Specifications for Unknown Procedures - Work in Progress

We study automated verification of pointer safety for heap-manipulating imperative programs with unknown procedure calls or code pointers. Given the specification of a procedure whose body contains calls to an unknown procedure, we try to infer the possible specifications for the unknown procedure from its calling contexts. We employ a forward shape analysis with separation logic and an abductive inference mechanism to synthesize both pre- and postconditions for the unknown procedure. The inferred specification is a partial specification of the unknown procedure. Therefore it is subject to a later verification when the code or the complete specification for the unknown procedure are available. Our inferred specifications can also be used for program understanding.

The Application of Geometric Constraint Programming to the Design of Stephenson III Dwell Linkages

Stephenson III linkages provide a means to create an approximate dwell mechanism without the use of cams. The dwell cycle is created by first choosing or designing a four-bar linkage that contains a coupler path with a near circular segment. An external dyad is attached to the coupler point such that the center of the floating link of the dyad coincides with the center of the circular portion of the coupler curve. This connection produces a dwell in the external dyad as the four-bar linkage traverses the circular portion of the coupler curve. This paper demonstrates how the necessary conditions for a dwell linkage can be obtained with the use of Geometric Constraint Programming (GCP). The construction process is initiated by using GCP techniques to develop a four-bar linkage with a minimum of four path points that lie on a prescribed arc. This part of the problem also uses GCP to apply additional constraints to the four-bar linkage. These include the application of appropriate link dimensions to achieve a Grashof linkage with a crank input, and the specification of the required crank rotation angle during the dwell cycle of the mechanism. Once the four-bar is defined, an external dyad is attached to the coupler link of the four-bar to produce the specified dwell characteristics. The dwell dyad may include for its output either a rotational link whose range of angular travel is defined, or a sliding link whose range of linear motion is defined. GCP techniques are used to enforce a specified range of motion for the output dyad through the use of an instant center construction to define the limits of travel of the four-bar coupler curve relative to the dwell ground pivot. If the dwell dyad is designed for angular displacements, the construction is completed by using GCP to define the desired angular displacement of the dwell link, resulting in the specification of the link length and ground pivot location. If the dwell dyad is a linear (slider) output, the final part of the GCP construction is used to define the desired length of linear travel, which results in the complete specification of the slider path and angle. The GCP techniques are presented with the development of an example, with sample results presented for a dwell mechanism with a rotational dwell cycle, and also for a dwell mechanism with a linear (slider) dwell output. The example demonstrates the ability of GCP methods to use standard solid-modeling software to obtain Stephenson III linkages with dwells that deviate from the dwell position by less than 0.1% of total motion.

3D Printing Job Editor for Workflow Visualization Design and Implementation

This paper presents design and development of a viewing and editing tool, namely 3DPJ Editor, for Workflow visualization of 3D Print Job files. 3D Print Job (3DPJ) is an XML based format for 3D Printing job purposed to enable automation and integration of multiple vendor systems in a 3D Printing manufacture environment. The paper also shows preliminary 3DPJ format for further development of 3D Printing manufacture community with multiple vendors. The 3DPJ Format tries to separate content information and meta-data of 3D Print Jobs, in order to integrate different processes into one standard 3D Printing Workflow. The complete specification of 3DPJ should be further complex and comprehensive, and it should be gradually adopted by major 3D Printer vendors.