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High-energy density materials represent a significant class of advanced materials and have been the focus of energetic materials community. The main challenge in this field is to design and synthesize energetic compounds with a highest possible density and a maximum possible chemical stability. Here we show an energetic compound, [2,2′-bi(1,3,4-oxadiazole)]-5,5′-dinitramide, is synthesized through a two-step reaction from commercially available reagents. It exhibits a surprisingly high density (1.99 g cm −3 at 298 K), poor solubility in water and most organic solvents, decent thermal stability, a positive heat of formation and excellent detonation properties. The solid-state structural features of the synthesized compound are also investigated via X-ray diffraction and several theoretical techniques. The energetic and sensitivity properties of the explosive compound are similar to those of 2, 4, 6, 8, 10, 12-(hexanitrohexaaza)cyclododecane (CL-20), and the developed compound shows a great promise for potential applications as a high-energy density material. High energy density materials are of interest, but density is the limiting factor for many organic compounds. Here the authors show the formation of a high density energetic compound from a two-step reaction between commercially available compounds that exhibit good heat thermal stability and detonation properties.

Over the past century, the search for lead-free, environmentally friendly initiating substances has been a highly challenging task in the field of energetic materials. Here, an organic primary explosive featuring a fused-ring structure, 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide, was designed and synthesized through a facile two-step reaction from commercially available reagents. This organic initiating substance meets nearly all of the stringent criteria of environmentally friendly primary explosives for commercial applications: it is free of toxic metals and perchlorate, has a high density, high priming ability, unusual sensitivities towards non-explosive stimuli, excellent environmental resistance, decent thermal stability, high detonation performance, satisfactory flowability and pressure durability, and is low-cost and easy to scale-up. These combined properties and performance measures surpass the current and widely used organic primary explosive, DDNP. The fused-ring organic primary explosive reported herein may find real-world application as an initiating explosive device in the near future. The search for environmentally friendly, lead-free primary explosives continues to be important for both military and civil applications. Here the authors synthesize an organic fused-ring initiating substance that possesses many of the attributes necessary for commercial application.

Water inrush originating from hidden faults in the coal seam floor is challenging to prevent due to their concealed nature. This paper develops a coupled stress–seepage–damage model for simulating rock fracture, implemented using the finite element method. The model is validated against compression-seepage tests on rock samples, capturing realistic dynamics of shear and tensile damage as well as permeability. The model is applied to the 27305 working face of a coal mine in Shandong Province, China, revealing the evolution of water inrush caused by a hidden fault. The results indicate that as the working face progresses, both the floor damage and the internal damage within the hidden fault escalate gradually. When mining reaches 80 m, the hidden fault has been activated internally, and the depth of floor damage reaches 13 m, which still has a certain distance from the hidden fault. At 100 m, the depth of the floor damage has stabilized, while the stress concentration at the hidden fault's tip increases, and it begins to expand if conditions for tensile damage are met. By the time mining reaches 110 m, the hidden fault has expanded 9.2 m in length and connected with the floor damage zone, forming a water inrush channel that links the aquifer to the working face, presenting a significant water inrush risk. This work provides an intuitive approach to understanding the evolution of water inrush from a hidden fault, aiding in the prevention of water inrush disasters in practical engineering applications. Highlights A coupled stress-seepage-damage model was proposed to simulate the dynamics of hidden faults during the mining process. The model has been validated with several small-scale laboratory compression-seepage tests to demonstrate its capabilities. By applying the proposed coupling model to a real-world coal mining operation, we demonstrate the process of hidden faults fracture propagation in the floor strata during the working face excavation, which might lead to a water inrush disaster. The most critical scenario occurs when concealed faults are positioned beneath the working face, resulting in a significant increase in the compressive stress borne by these hidden faults. This increase continues until a damaged state is reached, thereby triggering the propagation of fractures. Microseismic monitoring technology proves to be an effective measure to prevent water inrush caused by hidden faults, and in our application, microseismic event distributions near the working face are consistent with our numerical analysis results.

For decades, neuromodulation technology has demonstrated tremendous potential in the treatment of neuropsychiatric disorders. However, challenges such as being less intrusive, more concentrated, using less energy, and better public acceptance, must be considered. Several novel and optimized methods are thus urgently desiderated to overcome these barriers. In specific, temporally interfering (TI) electrical stimulation was pioneered in 2017, which used a low-frequency envelope waveform, generated by the superposition of two high-frequency sinusoidal currents of slightly different frequency, to stimulate specific targets inside the brain. TI electrical stimulation holds the advantages of both spatial targeting and non-invasive character. The ability to activate deep pathogenic targets without surgery is intriguing, and it is expected to be employed to treat some neurological or psychiatric disorders. Recently, efforts have been undertaken to investigate the stimulation qualities and translation application of TI electrical stimulation via computational modeling and animal experiments. This review detailed the most recent scientific developments in the field of TI electrical stimulation, with the goal of serving as a reference for future research.

We have investigated the activation characteristics of mining faults and the effect of grouting reinforcement under thick loose layer and thin bedrock of the working face and evaluate their impact on the safety of mining at similar working faces. Implementing the geological conditions of the 331 working face of the Yangcun Coal Mine (China) of the Yankuang Energy Group Corporation, we have analyzed mechanically the process of fault activation at first. Subsequently, we have obtained the mechanical criterion of fault slip and the expression of relative strength of the nearby rock mass. Using numerical software we have simulated and analyzed the damage characteristics of different bedrock thicknesses on overlying rocks and faults in the fluid–solid coupling mode. In addition, we have studied the controlling effect of grouting reinforcement on fault activation, which has been verified in the field. The main results of our study show that: 1. The mechanical properties of the rock mass near the fault interface have changed and they are related to the cohesive force of the interface; 2. The water inrush mode of the working face changes under different bedrock thickness, and the thinner the bedrock, the less easily the fault is destroyed 3. The slip of the high-level fault is reduced after the grouting of the fault, the propagation of the fracture zone at the fault is suppressed, the seepage of the aquifer water is prevented, and the safe recovery is realized. The results of our study provide a scientific basis for the secure mining across the fault of the 331 working face of Yangcun Coal Mine. Based on the results of our study the working face can be mined safely from now on and in the future.

Water inrush disaster is a huge challenge to geotechnical and mining engineering, and easy to induce group death and injury accident. Similar simulation test is the basic method to reproduce the process of water inrush and research mechanism of water inrush disaster. Fluid–solid coupling materials are the key to success of similar simulation test. However, at present there are no mature materials to be widely accepted by scholars. The paper based on similar traditional simulation materials, with previous mass experiments, new fluid–solid coupling materials of impermeable layer, water-bearing layer and fault zone, was developed by adding various additives. With rock mechanics experiments, fluid–solid coupling material properties of strength, water-absorbing quality, permeability and expansibility were tested and obtained. Finally, the feasibility and applicability of fluid–solid coupling materials were verified. The research results can provide reliable fluid–solid coupling materials to similar simulation test on water inrush and also important to reveal water inrush mechanism.

Confined water inrush caused by fault activation is the main form of water disaster in deep mining. With theoretical analysis and similar simulation tests, the mechanism and evolution law of delayed water inrush caused by fault activation are revealed. At the theoretical level, the expansion and extension of the internal microstructure in the fault zone under the action of the mining stress field and seepage field are the essential causes of fault activation. Overlying strata movement and surrounding rock creep failure are the basic reasons for delayed water inrush caused by fault activation, and delayed time caused by surrounding rock creep failure is much longer than that of overlying strata movement. A similar simulation test was carried out with self-development solid–liquid coupling with similar simulation materials; the results show that delayed water inrush caused by fault activation with mining includes three stages. Micro-activation stage: Water inrush weakness point is formed because of the expansion and extension of the micro-fissure and structure at the bottom of the fault zone. Macro-activation stage: With the change in the stress of the waterproof coal pillar and surrounding rock, the micro-fissures and structures in the stress relief area and tension area of the fault zone expand and extend sharply; meanwhile, water intrudes into the interlayer stratification of the floor in the stress relief area, forming a strong laminar flow phenomenon, and cracks in the floor form and expand; finally, water-conducting channels in the fault zone and floor are formed. Water inrush stage: The waterproof coal pillar and water-resisting layer fail and are destroyed, and the first confined water inrush point is located at the junction of the waterproof coal pillar and gob floor.

Since the 1980s, several studies have reported a decline in all-White neighborhoods and a rising number of racially mixed neighborhoods, including what have been called multiethnic “global” neighborhoods. Previous research has shown that these changes between 1980 and 2010 partly reflected the rapidly rising shares of Hispanics and Asians in urban areas. However, they also showed that there had been a substantial change in the pattern of settlement, resulting in many transitions to greater diversity than could have been expected from this demographic shift. We update their analysis to 2020, comparing transitions in the 1980–2000 period to those in 2000–2020, to test whether the earlier observed trends have continued, intensified, or weakened. We also quantify the impact of residential changes on the numbers of persons in each racial/ethnic group who live in each type of neighborhood.

Since the 1980s, several studies have documented rising racial/ethnic diversity in neighborhoods in U.S. metropolitan areas, and others have reported a parallel decline in predominantly white neighborhoods and a rising number of multiethnic “global” neighborhoods. The authors examine three questions about these trends. First, do these trends represent a change in the pattern of segregation that has historically divided urban areas, or are they mainly a reflection of the overall changes in the urban population associated with the rapid growth in the number of Hispanic and Asian residents? Second, in what kinds of neighborhoods, classified by their racial/ethnic composition, is diversity rising? Third, how are trends in diversity associated with the various types of racial/ethnic transitions that have been reported in the literature on neighborhood change? The authors find that a large share of increases in diversity can be attributed to changes in overall metropolitan racial composition. As anticipated, however, diversity did typically increase in neighborhoods that developed a more inclusive composition, while those that lost their white presence became less diverse. On average, diversity was increasing in all types of neighborhoods irrespective of their initial racial composition, and similar changes were occurring in metropolitan areas with very different racial/ethnic composition.

The flow and heat transfer characteristics of magnetic nanofluids in a circular channel under the action of magnetic fields were studied through numerical simulation based on the finite element method. The results show that there are obvious secondary vortices on the cross-section, and a swirling flow is formed in the duct under the coupling effects of the magnetic field, velocity distribution, and thermal variations which destroys the boundary layer, accelerates the mixing of fluids, and enhances heat transfer. In the studied range, the maximum heat transfer coefficient can be increased by 102.65 %, and the maximum comprehensive heat transfer factor J is 1.69 compared to the ferrofluid not affected by the external magnetic field. In addition, the effect of enhancing heat transfer gradually decreases with the increase of θ, until heat transfer is slightly inhibited when the magnetic field is parallel to the flow direction.