Divergence-Preserving Branching Bisimilarity

This note considers the notion of divergence-preserving branching bisimilarity. It briefly surveys results pertaining to the notion that have been obtained in the past one-and-a-half decade, discusses its role in the study of expressiveness of process calculi, and concludes with some suggestions for future work.Comment: In Proceedings EXPRESS/SOS 2020, arXiv:2008.1241

Normal Sequences with Non-Maximal Automatic Complexity

This paper examines Automatic Complexity, a complexity notion introduced by Shallit and Wang in 2001 [Jeffrey O. Shallit and Ming-wei Wang, 2001]. We demonstrate that there exists a normal sequence T such that I(T) = 0 and S(T) ? 1/2, where I(T) and S(T) are the lower and upper automatic complexity rates of T respectively. We furthermore show that there exists a Champernowne sequence C, i.e. a sequence formed by concatenating all strings of length one followed by concatenating all strings of length two and so on, such that S(C) ? 2/3

The K-Centre Problem for Necklaces

In graph theory, the objective of the k-centre problem is to find a set of $k$ vertices for which the largest distance of any vertex to its closest vertex in the $k$-set is minimised. In this paper, we introduce the $k$-centre problem for sets of necklaces, i.e. the equivalence classes of words under the cyclic shift. This can be seen as the k-centre problem on the complete weighted graph where every necklace is represented by a vertex, and each edge has a weight given by the overlap distance between any pair of necklaces. Similar to the graph case, the goal is to choose $k$ necklaces such that the distance from any word in the language and its nearest centre is minimised. However, in a case of k-centre problem for languages the size of associated graph maybe exponential in relation to the description of the language, i.e., the length of the words l and the size of the alphabet q. We derive several approximation algorithms for the $k$-centre problem on necklaces, with logarithmic approximation factor in the context of l and k, and within a constant factor for a more restricted case

An Evaluation of the Product Security Maturity Model Through Case Studies at 15 Software Producing Organizations

Cybersecurity is becoming increasingly important from a software business perspective. The software that is produced and sold generally becomes part of a complex landscape of customer applications and enlarges the risk that customer organizations take. Increasingly, software producing organizations are realizing that they are on the front lines of the cybersecurity battles. Maintaining security in a software product and software production process directly influences the livelihood of a software business. There are many models for evaluating security of software products. The product security maturity model is commonly used in the industry but has not received academic recognition. In this paper we report on the evaluation of the product security maturity model on usefulness, applicability, and effectiveness. The evaluation has been performed through 15 case studies. We find that the model, though rudimentary, serves medium to large organizations well and that the model is not so applicable within smaller organizations

Scattered one-counter languges have rank less than ω2\omega^2

A linear ordering is called context-free if it is the lexicographic ordering of some context-free language and is called scattered if it has no dense subordering. Each scattered ordering has an associated ordinal, called its rank. It is known that scattered context-free (regular, resp.) orderings have rank less than $\omega^\omega$ ($\omega$, resp). In this paper we confirm the conjecture that one-counter languages have rank less than $\omega^2$

Crystal Structure Prediction via Oblivious Local Search

We study Crystal Structure Prediction, one of the major problems in computational chemistry. This is essentially a continuous optimization problem, where many different, simple and sophisticated, methods have been proposed and applied. The simple searching techniques are easy to understand, usually easy to implement, but they can be slow in practice. On the other hand, the more sophisticated approaches perform well in general, however almost all of them have a large number of parameters that require fine tuning and, in the majority of the cases, chemical expertise is needed in order to properly set them up. In addition, due to the chemical expertise involved in the parameter-tuning, these approaches can be {\em biased} towards previously-known crystal structures. Our contribution is twofold. Firstly, we formalize the Crystal Structure Prediction problem, alongside several other intermediate problems, from a theoretical computer science perspective. Secondly, we propose an oblivious algorithm for Crystal Structure Prediction that is based on local search. Oblivious means that our algorithm requires minimal knowledge about the composition we are trying to compute a crystal structure for. In addition, our algorithm can be used as an intermediate step by {\em any} method. Our experiments show that our algorithms outperform the standard basin hopping, a well studied algorithm for the problem

Vision-based Safe Autonomous UAV Docking with Panoramic Sensors

The remarkable growth of unmanned aerial vehicles (UAVs) has also sparked concerns about safety measures during their missions. To advance towards safer autonomous aerial robots, this work presents a vision-based solution to ensuring safe autonomous UAV landings with minimal infrastructure. During docking maneuvers, UAVs pose a hazard to people in the vicinity. In this paper, we propose the use of a single omnidirectional panoramic camera pointing upwards from a landing pad to detect and estimate the position of people around the landing area. The images are processed in real-time in an embedded computer, which communicates with the onboard computer of approaching UAVs to transition between landing, hovering or emergency landing states. While landing, the ground camera also aids in finding an optimal position, which can be required in case of low-battery or when hovering is no longer possible. We use a YOLOv7-based object detection model and a XGBooxt model for localizing nearby people, and the open-source ROS and PX4 frameworks for communication, interfacing, and control of the UAV. We present both simulation and real-world indoor experimental results to show the efficiency of our methods

oritatami systemによる無限バイナリカウンタの実装

　本論文では数理モデル「oritatami system」上における無限バイナリカウンタの実装について記述する。無限バイナリカウンタとは、カウントアップ中に桁上りが起きた際にカウンタ自らビット幅を拡張しカウントアップを継続することができるカウンタのことを指す。　DNAからたんぱく質が合成される際の中間媒体であるRNAは合成と同時に自分自身に折り畳まれることで様々な情報処理を行っていること近年わかってきている。DNAやRNAはヌクレオチドが鎖のように連なった構造をしている。RNAが自分自身に折り畳まれるのは、そのヌクレオチド間で水素結合をしているからであり、RNAのヌクレオチド鎖はDNAのものに基づき合成されるため、互いに対応関係にある。RNAの折り畳まれ方は、そのヌクレオチドがどのような配列になっているかに大きく左右される。Geary、Rothemund、AndersenはDNAに基づき合成されたRNAが自己組織的にタイル状に折り畳まるようなヌクレオチド配列の設計に成功した。DNAを用いることでもタイル状の構造を作ることが可能なのは既に明らかになっていたことであるが、その場合温度の上げ下げが必要になってくる。一方でRNAが折り畳まる過程に温度の昇降は必要ない。これは今後生体内への応用を考えた際に、RNAの折り畳みがDNAのものより優位な点としてあげられる。このようにRNAが合成と同時に折り畳まるという現象は工学的な応用を見込むことができ、この現象を抽象化した数理モデルとして「oritatami system」が提案された。Gearyらはoritatami systemの上で有限バイナリカウンタを実装している。本研究では彼らのカウンタにオーバーフロー時の桁上がり処理を追加し、無限の数え上げを実現する電気通信大学201