When Less Is More: Consequence-Finding in a Weak Theory of Arithmetic

This paper presents a theory of non-linear integer/real arithmetic and algorithms for reasoning about this theory. The theory can be conceived as an extension of linear integer/real arithmetic with a weakly-axiomatized multiplication symbol, which retains many of the desirable algorithmic properties of linear arithmetic. In particular, we show that the conjunctive fragment of the theory can be effectively manipulated (analogously to the usual operations on convex polyhedra, the conjunctive fragment of linear arithmetic). As a result, we can solve the following consequence-finding problem: given a ground formula F, find the strongest conjunctive formula that is entailed by F. As an application of consequence-finding, we give a loop invariant generation algorithm that is monotone with respect to the theory and (in a sense) complete. Experiments show that the invariants generated from the consequences are effective for proving safety properties of programs that require non-linear reasoning

Alkyl substituted cucurbit[6]uril assisted competitive fluorescence recognition of lysine and methionine in aqueous solution

The use of competitive ratiometric fluorescence indicator displacement chemosensors derived from two alkyl substituted cucurbit[6]uril-based host-guest complexes is reported. In particular, the differing binding abilities of two cucurbit[6]uril derivatives towards the target analytes led to a useful ratiometric detection signal output for the discrimination of lysine and methionine versus the other tested α-amino acids in aqueous solution

Spaceborne miniaturized UHF dual band helix antenna with a small frequency ratio

This study proposes a novel miniaturized circularly polarized (CP) ultrahigh frequency (UHF) quadrifilar helix antenna for spaceborne applications. The dual-band operation is realized using four inverted-U shaped helical strips (IUSHSs) that are rotated and alternately arranged on the four faces of a hollow polyimide cuboid in a sequential rotation manner, which effectively reduces the size of the antenna. Furthermore, the four IUSHSs are connected by a cross-shape strip at the top of the antenna to control the dual resonant frequencies, resulting in a small dual-band frequency ratio. The proposed antenna is both lightweight and robust when compared with the conventional miniaturized CP antennas operating at similar bands with similar performance. In particular, its compact radiator provides effective miniaturized spaceborne solution without the need of high-dielectric coefficient materials. A device for spaceborne application that operates at 402/505 MHz is designed, fabricated, measured, and in-orbit tested with a weight of 651 g and an effective size of 0.161 7 0.161 7 0.228 λ3402MHz (λ402MHz is the wavelength at 402 MHz). The measured gain and axial ratio of the proposed antenna are better than 5.32 dBi and 2.18 dB, respectively, within 2 and 12 MHz bandwidth for the two bands. The test results proved that the methods used to design the proposed antenna are effective

CFD analysis of the regenerator performance of cryocooler under different accelerations

High temperature superconducting (HTS) technology is a promising enabling technology to allow the offshore wind turbines (WT) scaling up to 10 MW and beyond by radical reduction of the head mass. In order to provide adequate magnetic field, the HTS coils are supposed to work at a low temperature of 20-40 K, thus a cryogenic cooling system is required. Comparing with cooling by means of cryogenic liquids, the cryogen-free method which adopts conduction cooling with regenerative cryocoolers leads to certain advantages such as smaller size, simple structure and elimination of safety issues related with cryogens. These advantages are particularly valuable in superconducting WT operating in offshore condition, and thus the cryogen-free cooling system attracts more and more attention in demonstrating HTS WT projects. The cold head of the cryocooler linking to the superconducting filed coil rotates together with the rotor. The resulting centripetal acceleration and oriental variation may introduce streaming inside the regenerator and lead to performance degradation. However, up to now the influence of acceleration on the oscillating flow and heat transfer inside the regenerator has not yet been investigated. As a response to the demands of performance stable cryocooler system, in this paper we will study the impact of the gravity and centripetal acceleration on the regenerator performance. Two dimensional numerical model of the regenerator will be established by Ansys Fluent. The temperature and pressure distribution of the regenerator will be illustrated and the dependence of operating frequency, acceleration and regenerative material will also be discussed

Market Stakeholder Analysis of the Practical Implementation of Carbonation Curing on Steel Slag for Urban Sustainable Governance

Carbonation curing on steel slag is one of the most promising technologies for the iron and steel industry to manage its solid waste and carbon emissions. However, the technology is still in its demonstration stage. This paper investigates the market stakeholders of carbonation curing on steel slag for construction materials for its effective application by taking China as a case study. A holistic analysis of the competition, market size, and stakeholders of carbonation curing on steel slag was carried out through a literature review, a survey, a questionnaire, and interviews. The results showed that carbonation curing on steel slag had the advantages of high quality, high efficiency, low cost, and carbon reduction compared with other technologies. Shandong province was the most suitable province for the large-scale primary application of the technology. Stakeholder involvement to establish information platforms, enhance economic incentives, and promote adequate R&D activities would promote carbonation curing of steel slag into practice. This paper provides a reference for the commercialization of carbonation curing on similar calcium- and magnesium-based solid waste materials