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Compared to H2-assisted activation mode, the direct dissociation of CO2 into carbonyl (*CO) with a simplified reaction route is advantageous for CO2-related synthetic processes and catalyst upgrading, while the stable C = O double bond makes it very challenging. Herein, we construct a subnano MoO3 layer on the surface of Mo2N, which provides a dynamically changing surface of MoO3↔MoOx (x < 3) for catalyzing CO2 hydrogenation. Rich oxygen vacancies on the subnano MoOx surface with a high electron donating capacity served as a scissor to directly shear the C = O double bond of CO2 to form CO at a high rate. The O atoms leached in CO2 dissociation are removed timely by H2 to regenerate active oxygen vacancies. Owing to the greatly enhanced dissociative activation of CO2, this MoOx/Mo2N catalyst without any supported active metals shows excellent performance for catalyzing CO2 hydrogenation to CO. The construction of highly disordered defective surface on heterostructures paves a new pathway for molecule activation. The direct dissociation of CO2 into carbonyl (*CO) via a simplified reaction pathway benefits CO2-related synthesis and catalyst improvement, though the stability of the C = O double bond poses a significant challenge. Here, the authors design a subnano MoO3 layer on the surface of Mo2N, offering a dynamically adaptive surface for catalyzing CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

In this study, a novel cambered snow removal device is designed to achieve automatic snow removal in large curved areas, such as the south roof of a Chinese solar greenhouse. The theory of structural parameters and shear force is ambiguous. People are not based on the greenhouse structure parameters for the selection of snow removal devices. Therefore, the quantitative relationship between the structure of the greenhouse span and the number of scissor arm-length knots is analysed, and the relationship between the material strength and application distance is determined. This study's objectives are (1) to establish a theoretical model of scissor arm motion and (2) to analyse the force distribution of the scissor arm using multi-body dynamics. The results show that the scissor arm of a round-arch greenhouse has fewer sections but a larger arm length, whereas the scissor arm of a traditional solar greenhouse has more sections but a smaller arm length. Based on the shear force of the scissor structure, the optimised wall thickness reduces the force of the node by 17%. [ABSTRACT FROM AUTHOR]

Shears, being everyday objects, have received significantly less attention by archaeometallurgists than other edged tools or weapons. Yet, shear blades were forged with the same techniques as blades of, e.g. knives and swords. The most common shear type in ancient times was the bow shears, where the bow had to be flexible so it could be repeatedly bent without cracking or breaking. The shear-maker, therefore, faced the challenge of combining hard steel (the blades) with soft/flexible steel (the bow). In fact, bow shears are one of the first tools to be invented, where metal acts as a spring. Thus, ancient bow shears can be used for investigating the history and development of spring steel technology, which is currently unclear. Here, we present the metallurgical characterization of two 11th–12th c. single-bow shears from Sigtuna, Sweden. Both the blades and the bows of the two shears were found to be of decent quality and much better than in older shears from the Roman period. Although the steel qualities are not quite up to modern standards, this does not in itself prove that the Sigtuna blacksmiths lacked the technological knowledge to make ideal spring steel. Shears are relatively cheap everyday objects intended to be used until they break, at which point they are discarded. Therefore, it might not have been worth the Medieval blacksmiths' time and effort to perfect the material properties of steel used in shears. The shears' blades are on par with Medieval-period knife blades, and future studies on ancient shear-making should preferably involve comparisons of shears and knives from the same origins. [ABSTRACT FROM AUTHOR]

The role of mutation, which is an error process in gene evolution, in systems of cyclically competing species has been studied from various perspectives, and it is regarded as one of the key factors for promoting coexistence of all species. In addition to naturally occurring mutations, many experiments in genetic engineering have involved targeted mutation techniques such as recombination between DNA and somatic cell sequences and have studied genetic modifications through loss or augmentation of cell functions. In this paper, we investigate nonlinear dynamics with targeted mutation in cyclically competing species. In different ways to classic approaches of mutation in cyclic games, we assume that mutation may occur in targeted individuals who have been removed from intraspecific competition. By investigating each scenario depending on the number of objects for targeted mutation analytically and numerically, we found that targeted mutation can lead to persistent coexistence of all species. In addition, under the specific condition of targeted mutation, we found that targeted mutation can lead to emergences of bistable states for species survival. Through the linear stability analysis of rate equations, we found that those phenomena are accompanied by Hopf bifurcation which is supercritical. Our findings may provide more global perspectives on understanding underlying mechanisms to control biodiversity in ecological/biological sciences, and evidences with mathematical foundations to resolve social dilemmas such as a turnover of group members by resigning with intragroup conflicts in social sciences. [ABSTRACT FROM AUTHOR]

It is known that geometry of cutting tool affects the cutting forces in machining operations. In addition, the value of cutting forces changes during machining operations and creates a chaotic time series (signal). In this paper, we analyze the variations of the complex structure of cutting force signal in rough end milling operation using fractal theory. In fact, we analyze the variations of cutting force signal due to variations of tool geometry (square end mill versus serrated end mill). In case of each type of end mill, we did the machining operation in wet and dry conditions. Based on the results, the fractal structure of cutting force signal changes based on the type of milling tool. We also did the complexity analysis using approximate entropy to check the variations of the complexity of cutting force signal, where the similar behavior of variations between different conditions was obtained. The method of analysis that was used in this research can be applied to other machining operations to study the influence of different machining parameters on variations of fractal structure of cutting force. [ABSTRACT FROM AUTHOR]

The rock–paper–scissors (RPS) game is known as one of the simplest cyclic dominance models. This game is key to understanding biodiversity. Three species, rock ( R ), paper ( P ) and scissors ( S ), can coexist in nature. In the present paper, we first present a metapopulation model for RPS game with mutation. Only mutation from R to S is allowed. The total population consists of spatially separated patches, and the mutation occurs in particular patches. We present reaction–diffusion equations which have two terms: reaction and migration terms. The former represents the RPS game with mutation, while the latter corresponds to random walk. The basic equations are solved analytically and numerically. It is found that the mutation induces one of three phases: the stable coexistence of three species, the stable phase of two species, and a single-species phase. The phase transitions among three phases occur by varying the mutation rate. We find the conditions for coexistence are largely changed depending on metapopulation models. We also find that the mutation induces different paradoxes in different patches. [ABSTRACT FROM AUTHOR]

Human performance modeling is a core topic in ergonomics. In addition to deriving models, it is important to verify the kinds of tasks that can be modeled. Drury's law is promising for path tracking tasks such as navigating a path with pens or driving a car. We conducted an experiment based on the observation that paper-cutting tasks using scissors resemble such tasks. The results showed that cutting arc-like paths (1/4 of a circle) showed an excellent fit with Drury's law (R2 > 0.98), whereas cutting linear paths showed a worse fit (R2 > 0.87). Since linear paths yielded better fits when path amplitudes were divided (R2 > 0.99 for all amplitudes), we discuss the characteristics of paper-cutting operations using scissors. [ABSTRACT FROM AUTHOR]

We examined the possibility of inflicting serious injuries with sharp objects in an experimental setting by throwing four sharp objects from different distances and with different throwing techniques. Using an overarm-handle (OA/H), overarm-blade (OA/B), underarm-handle (UA/H), underarm-blade (UA/B) and thrust (T/H) throwing technique, 10 adults (sex ratio 1:1) threw a chef's knife, a skinning knife, a paring knife and office scissors from 4 m and 2 m distance at synthetic abdomen models made of 10%gelatin covered with synthetic skin. The amount of hits and penetrations of the target and their penetration depth were noted, as was the rotation of the blade tip towards the target along its flight trajectory. The chef's knife injury/hit ratio was 0.167/4 mand 0.160/2 m; the skinning knife recorded an injury/hit ratio of 0.087/4 m and 0.153/2 m; the paring knife of 0.087/4 m and 0.113/2 m; and the scissors 0.087/4 m and 0.067/2 m. Mean penetration depths were as follows: the chef's knife: 4 m, 4.42 cm, 2 m, 3.41 cm; the skinning knife: 4 m, 4.19 cm, 2 m, 4.11 cm; the paring knife: 4 m, 1.62 cm, 2 m, 1.55 cm; and the scissors: 4 m, 2.08 cm, 2 m, 0.95 cm. Handle-throw penetration-depths were: 4 m: 3.77 cm and 2 m: 2.86 cm; blade-throw depths were: 4 m: 3.14 cm and 2 m: 2.69 cm. Overarm-throw penetration-depths were: 4 m: 3.62 cm and 2 m: 3.25 cm; and underarm-throw penetration-depths were 4 m: 3.30 cm and 2 m: 2.30 cm. No thrust-throws with the paring knife and scissors could pierce the target. The tips pointed toward the target at angles of 60°-120°, earlier in handle-throws than blade-throws, especially with the paring knife and the scissors. When thrown, especially with a handle-held technique, heavier objects pierced more often and more deeply. Thrust-throws at short distances are unlikely to pierce a human. [ABSTRACT FROM AUTHOR]