3D Printing Adjustable Stiffness External Fixator for Mechanically Stimulated Healing of Tibial Fractures

External fixation is a long-standing but well-established method, which has been widely used for the treatment of fractures. To obtain the maximum benefit from the mechanical stimulus, the stiffness of the external fixator should be adjusted properly throughout the treatment phase. Nevertheless, the lack of a valid dynamic adjustable fixation device impedes this possibility. Based on the stiffness adjustment tolerance of the healing callus, this paper proposes an active-dynamic stiffness adjustable external fixator design method to meet stiffness requirements at different stages of the tibial fracture healing process. A novel external fixator with an adjustable stiffness configuration was designed, and the finite element method was used to simulate the stress distribution between fixator and fracture gap. The stiffness adjustment tolerance was determined based on previous studies. According to this tolerance, the optimal block structure dismantling sequence was sought and the corresponding stiffness was calculated through topology optimization for the entire external fixator model. The appropriate amount of variable stiffness at the fracture gap was applied by dismantling the configuration of the block structure external fixator during the healing process. A novel patient-specific adjustable stiffness external fixator for mechanically stimulated tibial fracture reduction and therapy was proposed. This enables surgeons to tailor the construction of the external fixator frame to the clinical needs of each patient. The presented dismantling approach of the block structure to produce conformable stiffness provides a new clinical treatment strategy for tibial fractures.

Symmetric RAFT-agent for synthesizing multiblock copolymers with different activated monomers

With a bifunctional symmetric RAFT agent well-defined polymer structures can be achieved. This paper shows the possibility to synthesize block copolymer systems consisting out of different activated monomers. With the novel bifunctional symmetric RAFT agent water-born polymer systems with a block structure (B-b-A-b-B) can be polymerized. The symmetric RAFT agent is designed to polymerize both more activated monomers (A) and less activated monomers (B). Due to the ability of a controlled radical polymerization of different activated monomers the dispersity of the resulting polymers is broader compared to common RAFT polymerizations. In regard to industrial applications like emulsifiers, stabilizers or viscosity modifiers the broader molecular weight distribution has no impact. Overall, this paper shows the possibility towards new functional polymers with unique properties.

Seasonal patterns of growth, alginate content and block structure of the alien invader Sargassum muticum (Fucales, Ochrophyta) from the Atlantic coast of Morocco

In the present study, alginate yield and composition were investigated during the seasonal life cycle of the alien brown alga Sargassum muticum harvested from the Atlantic coast of Morocco. Alginate yield ranged from 11.14% in winter to 25.62% in spring/early summer, coinciding with maximum vegetative growth. Monthly monitoring of the alginate block structure showed that the highest mannuronate (M)/guluronate (G) ratio was recorded during the maximum development of S. muticum, before sexual maturity and during resumption of vegetative growth, giving maximum flexibility to the alga. The unusually high molar monad fractions (FG) and dyad fractions (FGG) of guluronic acid in late summer/early autumn appeared to be related to stiffness of senescent thalli. Rheological characterisation showed that the alginate of S. muticum exhibited pseudoplastic behaviour, with the highest apparent viscosities measured in late summer/early autumn when the G blocks dominated the alginate structure. This study suggests that S. muticum could be exploited as an alginophyte for commercial applications. The best harvest time is May-June, which corresponds to the highest alginate yield, maximum thallus growth, and largely completed sexual reproduction, ensuring sustainable exploitation of the species.

BCEAD: A Blockchain-Empowered Ensemble Anomaly Detection for Wireless Sensor Network via Isolation Forest

The distributed deployment of wireless sensor networks (WSNs) makes the network more convenient, but it also causes more hidden security hazards that are difficult to be solved. For example, the unprotected deployment of sensors makes distributed anomaly detection systems for WSNs more vulnerable to internal attacks, and the limited computing resources of WSNs hinder the construction of a trusted environment. In recent years, the widely observed blockchain technology has shown the potential to strengthen the security of the Internet of Things. Therefore, we propose a blockchain-based ensemble anomaly detection (BCEAD), which stores the model of a typical anomaly detection algorithm (isolated forest) in the blockchain for distributed anomaly detection in WSNs. By constructing a suitable block structure and consensus mechanism, the global model for detection can iteratively update to enhance detection performance. Moreover, the blockchain guarantees the trust environment of the network, making the detection algorithm resistant to internal attacks. Finally, compared with similar schemes, in terms of performance, cost, etc., the results prove that BCEAD performs better.

Modeling of the stress-strain state at the Shtokman gas condensate field accounting its block structure

The stress-strain state of the Shtokman gas condensate field has been studied using mathematical modeling and accounting its block structure. It is assumed that the rock mass’s structure has a vertical block structure, which is under the influence of gravity and tectonic force fields. It has been revealed that the stress-strain state of the rocks depends essentially on relationships of initial operating efforts and in-situ gas pressure, which magnitude varies with its production; direction of the maximum forces and dip of angles of fault zones; and elastic characteristics of the main rock mass and fault zones. It has been established that the change in the dip of angle of fault zones and reducing the rocks’ stiffness increases tensile stress in the roof of a horizontal seam and near the sea bottom. A forecast assessment has been performed of the vertical displacement of a rock block contoured with faults relatively to the main rock mass.

A Lightweight Two-Layer Blockchain Mechanism for Reliable Crossing-Domain Communication in Smart Cities

The smart city is an emerging notion that is leveraging the Internet of Things (IoT) technique to achieve more comfortable, smart and controllable cities. The communications crossing domains between smart cities is indispensable to enhance collaborations. However, crossing-domain communications are more vulnerable since there are in different domains. Moreover, there are huge different devices with different computation capabilities, from sensors to the cloud servers. In this paper, we propose a lightweight two-layer blockchain mechanism for reliable crossing-domain communication in smart cities. Our mechanism provides a reliable communication mechanism for data sharing and communication between smart cities. We defined a two-layer blockchain structure for the communications inner and between smart cities to achieve reliable communications. We present a new block structure for the lightweight IoT devices. Moreover, we present a reputation-based multi-weight consensus protocol in order to achieve efficient communication while resistant to the nodes collusion attack for the proposed blockchain system. We also conduct a secure analysis to demonstrate the security of the proposed scheme. Finally, performance evaluation shows that our scheme is efficient and practical.

Рудно-метасоматическая зональность молибден-порфировой системы Аксу (Северо-Восток Азии)

The article presents the data from a comprehensive study of the Aksu Mo-porphyry system metasomatites (Korkodon-Nayakhan magmatic activation zone). The halo of metasomatic changes around the porphyry system, associated with the tectonic-block structure of the territory, is shown to be asymmetric. The core of the system is brought to the surface and located in a halo of kalifeldspar- muscovite metasomatites; the northwestern block is elevated and characterized by high-temperature epidote-biotite and epidote-pyroxene propylites, while in the southeastern block there is a consistent transition from kalifeldspar-sericite metasomatites to fragments of argillisite ones. The established zoning is confirmed by geochemical associations and mineralization types from the northwest to the southeast: in the northwest, Au-Bi (As, Cu) at the Solnechnoye ore occurrence; in the center, Mo (Cu, Au) at the Aksu deposit; in the southeast, Ag-Pb-Zn (Cu, Bi, As, Au) at the Vysokoye ore occurrence.

Investigation of the influence of the geodynamic position of coal-bearing dumps on their endogenous fire hazard

The paper investigates the hypothesis according to which one of the factors influencing the spontaneous combustion of coal-bearing dumps is its geodynamic position, i.e. its location in the geodynamically dangerous zone (GDZ) at the boundary of the Earth crust blocks. This hypothesis is put forward on the basis of scientific ideas about the block structure of the Earth crust and the available statistical data on the location of burning dumps and is studied using computer modeling. A dump located in the area of Eastern Donbass was chosen as the object of research. The simulation results show that the penetration of air into the dump body from the mine through the GDZ, which crosses the mining zone, is possible at an excess pressure of 1000 Pa created by the main ventilation fans. The fire source appearance in the dump body causes an increase in the temperature of the dump mass and becomes a kind of trigger that "turns on" the aerodynamic connection between the dump and the environment, carried out through the GDZ. It is concluded that the establishment of an aerodynamic connection between the mine workings and the dump through the GDZ can be an important factor contributing to the endogenous fire hazard of coal-bearing dumps. The simulation results can be used in the development of projects for monitoring coal-bearing dumps and measures to combat their spontaneous combustion.

A Blockchain-Based Implementation of IoT-Based Product Tracking

Blockchain is the technology behind several digital currencies. A blockchain is a chain of blocks that keeps records of information in a decentralized and distributed network, with digital signatures stored in each block. Because of the distributed nature of blockchain and other unique properties, transactions are more secure and tamper proof. The paper's methodology gives a detailed study of blockchain's fit in the supply chain industry. Data is stored on many chains using a multi-chain architecture in the framework. Additional to the data management model and block structure model, the model contains the data model and container structure model.