Progress of ultra-high-field superconducting magnets in China

High magnetic fields play a critical role in the development of modern science and technology, breeding many significant scientific discoveries and boosting the generation of new technologies. In the last few years, China has untaken a great deal of work on the application of Ultra-High-Field (UHF) superconducting magnet technology, such as for the Synergetic Extreme Condition User Facility (SECUF) in Beijing, the UHF nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI), nuclear fusion energy, particle accelerator, and so on. This paper reports the research status of UHF superconducting magnets in China from different perspectives, including design options, technical features, experimental progress, opportunities and challenges.

Covert Information Mapped Spatial and Directional Modulation toward Secure Wireless Transmission

Recently, the concept of spatial and direction modulation (SDM) has been developed to reap the advantages of both spatial modulation (SM) and directional modulation (DM). On the one hand, DM ensures the transmission security at the expected direction. On the other hand, the structure of SM-aided distributed receivers can enhance the security even if the eavesdropper is located in the same direction as the legitimate receiver. However, the above advantages are achieved based on the assumption that the eavesdropper is not equipped with distributed receivers. On the other hand, the information security can no longer be guaranteed when the eavesdropper is also equipped with distributed receivers. To alleviate this problem, we considered a joint design of SDM and covert information mapping (CIM) in order to conceive of a more robust structure of CIM-SDM. Furthermore, both the detection performances at the eavesdropper and the legitimate user were quantified through theoretical derivation. In general, both the analysis and simulation results supported that the proposed CIM-SDM structure provides more robust secure performance compared to the original SDM, even if the extreme condition of distributed receivers at the eavesdropper is considered, at the cost of moderate performance loss at the legitimate user.

Effects of Second-Order Hydrodynamics on the Dynamic Responses and Fatigue Damage of a 15 MW Floating Offshore Wind Turbine

In order to investigate the effects of second-order hydrodynamic loads on a 15 MW floating offshore wind turbine (FOWT), this study employs a tool that integrates AQWA and OpenFAST to conduct fully coupled simulations of the FOWT subjected to wind and wave loadings. The load cases covering normal and extreme conditions are defined based on the met-ocean data observed at a specific site. The results indicate that the second-order wave excitations activate the surge mode of the platform. As a result, the surge motion is increased for each of the examined load case. In addition, the pitch, heave, and yaw motions are underestimated when neglecting the second-order hydrodynamics under the extreme condition. First-order wave excitation is the major contributor to the tower-base bending moments. The fatigue damage of the tower-base under the extreme condition is underestimated by 57.1% if the effect of second-order hydrodynamics is ignored. In addition, the accumulative fatigue damage over 25 years at the tower-base is overestimated by 16.92%. Therefore, it is suggested to consider the effects of second-order wave excitations of the floating platform for the design of the tower to reduce the cost of the FOWT.

Evaluasi Postur Kerja Operator Pemasangan Fire Brick Berbasis Metode Rapid Upper Limb Assessment dan Work Ergonomic Risk Assessment Di PT ABA

A service provider is known as a job that profoundly depends on human work. Musculoskeletal disorder is considered a risk in such work. PT. ABA is a contractor service company that provide some services. The fire brick installation is a part of the refractory project, which is carried out continuously at the customer's request. Early results using the Nordic Body Map questionnaire found severe risk, which may lead to wellbeing difficulty. This study aims to evaluate musculoskeletal disorder risk due to inappropriate posture in fire brick installation activities. Rapid Upper Limb Assessment and Work Ergonomic Risk Assessment are ergonomic risk approaches used in this study. This research found two final scores using RULA and WERA calculation. RULA final score is 44, classified as a medium score. The evaluation results of the RULA method obtained a final score of 7 with an extreme condition. An urgent improvement is a necessity in order to improve posture and work positioning of fire brick installation.

Ant colonies in Denver areas: Did they affected by extreme condition?

The basic debates in science since a few years ago related issues of environmental and climate changes. Global warming huge effects in the biodiversity around the world. The classical example, an extreme condition in summer season under the pressure of climate change has a big impact on environmental especially the presence of ant colonies in Denver Colorado, USA. We know well, ant as famous social insect, strongest organism in daily work and ability adaptable in all of the environmental changes. The purpose of the research is to study the presence of ant colonies species and the impact of the environmental in Denver areas. The research was conducted in summer season (June – July 2021) in sidewalks of student’s dorm at Denver Colorado USA. The observation focused to ant species that survived around the environment. The parameter of observations: ant colonies species and their anticipated adapted in the extreme condition. The first data observation showed the dominant ant colonies identified as Tetramorium sp. (Hymenoptera: Formicidae). In the simple case effect of the extreme condition increasing soil temperature and humidity affected movement to another place, protecting them from sunlight exposure. There is the “natural real fact” why the diversity of organisms decreasing when they are under the pressure of their habitat changes. The conclusion of field observation was showed: the pavement ant (Tetramorium sp.) as the dominant ant in Denver areas. The ant colonies activities are strongest affected by the temperature of soil, humidity, and food availability. There is a need for effort in the management of the environment in the summer condition, such as: preparing to plant more plant production nectar and seeds around a nest of ant colonies.

On-site measurement and numerical investigation of thermal environment with different air distribution systems in ice arenas

It is important to strictly maintain the indoor thermal environment in ice arenas which have very different features to other commercial buildings. Separated air distribution system is widely used to create a dry and cold environment near the ice and a comfortable environment in the view stand. The warm and humid air from the view stand may lead to uneven temperature and humidity distribution in the rink, leading to extra energy consumption, even fog and frost on the ice. Unreasonable air supply in the ice rink zone will also make the spectators feel too cold and uncomfortable. Jet ventilation system is the most extensively used system in the ice rink zone. An innovative ground displacement ventilation system is proposed in the National Aquatics Centre, which will serve as the venue for the curling competition in the 2022 Beijing Winter Olympics. On-site measurement in the arena is carried out and computational fluid dynamics (CFD) simulation method is adopted in the present research. Measured thermal environment above the ice with different ventilation systems are compared and analysed. Result shows that the displacement ventilation system features a more obvious vertical stratification than jet ventilation system in this kind of large space buildings, and thus is more energy-efficient. A CFD model of the ice cube is setup and verified by measured data. The thermal environment in the ice rink with displacement ventilation under extreme condition is studied using the simulation method. The temperature and humidity in the ice field increases by 10.1 °C, 4.5 g/kg without air supply in the view stand, proving that the spectators in the view stand have a great impact on the thermal environment in the ice field.

Self-Lubricating Materials for Extreme Condition Applications

Lubrication for extreme conditions, such as high temperature, cryogenic temperature, vacuum pressure, high load, high speed, and corrosive environments, is a continuing challenge among tribologists and space engineers due to the inadequate friction and wear properties of liquid lubricants. As a result, tremendous research effort has been put forward to study lubrication mechanisms for various machine elements under challenging conditions over the past two decades. Self-lubricating materials have been most widely used for adequate lubrication in extreme conditions in recent years. This review paper presents state-of-the-art of materials for lubrication in extreme condition applications in aerospace, automotive, and power generation areas. More specifically, solid lubricants dispersed in various matrices for lubrication application were analyzed in-depth under challenging conditions. This study also reports the self-lubricating materials and their lubrication mechanisms. Finally, various applications and challenges of self-lubricating materials were explored.

Adaptable Invisibility Management Using Kirigami-Inspired Transformable Metamaterials

Many real-world applications, including adaptive radar scanning and smart stealth, require reconfigurable multifunctional devices to simultaneously manipulate multiple degrees of freedom of electromagnetic (EM) waves in an on-demand manner. Recently, kirigami technique, affording versatile and unconventional structural transformation, has been introduced to endow metamaterials with the capability of controlling EM waves in a reconfigurable manner. Here, we report for a kirigami-inspired sparse meta-architecture, with structural density of 1.5% in terms of the occupation space, for adaptive invisibility based on independent operations of frequency, bandwidth, and amplitude. Based on the general principle of dipolar management via structural reconstruction of kirigami-inspired meta-architectures, we demonstrate reconfigurable invisibility management with abundant EM functions and a wide tuning range using three enantiomers (A, B, and C) of different geometries characterized by the folding angle β. Our strategy circumvents issues of limited abilities, narrow tuning range, extreme condition, and high cost raised by available reconfigurable metamaterials, providing a new avenue toward multifunctional smart devices.