Graph 4-braid groups and Massey products

We first show that the braid group over a graph topologically containing no $\Theta$-shape subgraph has a presentation related only by commutators. Then using discrete Morse theory and triple Massey products, we prove that a graph topologically contains none of four prescribed graphs if and only if its 4-braid groups is a right-angled Artin group.Comment: 23 pages, 4 figure

Determination of Cutting Date and Interval on Native Grass Management of Agricultural Waterways in South Korea

Agricultural waterways provide a buffer zone between crop fields and adjacent rivers or streams. Waterways are important resource for agriculture water management, water quality and biodiversity conservation. The total linear distance of waterway in Korea is about 180,000 km, and about 40% are concrete and about 60% are grassed waterways. At present, the percentage of concrete waterways is increasing because of their water management efficiency. Some argue that continued expansion of concrete waterways is not sustainable because it leads to potential-degradation of the earth\u27s environment. This concern has led to renewed efforts to use grassed waterways as an alternative to concrete. In addition, grassed waterways enhance the environment-friendly image of agriculture that Korea farmers want to promote. The objective of this experiment was to determine the effect of cutting date and interval of native grasses for water management efficiency of agricultural waterway

Towards Generating Secure Keys for Braid Cryptography

Braid cryptosystem was proposed in CRYPTO 2000 as an alternate public-key cryptosystem. The security of this system is based upon the conjugacy problem in braid groups. Since then, there have been several attempts to break the braid cryptosystem by solving the conjugacy problem in braid groups. In this paper, we first survey all the major attacks on the braid cryptosystem and conclude that the attacks were successful because the current ways of random key generation almost always result in weaker instances of the conjugacy problem. We then propose several alternate ways of generating hard instances of the conjugacy problem for use braid cryptography

New Signature Scheme Using Conjugacy Problem

We propose a new digital signature scheme based on a non-commutative group where the conjugacy search problem is hard and the conjugacy decision problem is feasible. We implement our signature scheme in the braid groups and prove that an existential forgery of the implementation under no message attack gives a solution to a variation of conjugacy search problem. Then we discuss performance of our scheme under suggested parameters

Biodegradable, flexible silicon nanomembrane-based NO x gas sensor system with record-high performance for transient environmental monitors and medical implants

Abstract: A novel transient electronics technology that is capable of completely dissolving or decomposing in certain conditions after a period of operation offers unprecedented opportunities for medical implants, environmental sensors, and other applications. Here, we describe a biodegradable, flexible silicon-based electronic system that detects NO species with a record-breaking sensitivity of 136 Rs (5 ppm, NO2) and 100-fold selectivity for NO species over other substances with a fast response (~30 s) and recovery (~60 s). The exceptional features primarily depend on not only materials, dimensions, and design layouts but also temperatures and electrical operations. Large-scale sensor arrays in a mechanically pliable configuration exhibit negligible deterioration in performance under various modes of applied loads, consistent with mechanics modeling. In vitro evaluations demonstrate the capability and stability of integrated NOx devices in severe wet environments for biomedical applications