Guanidinium l-glutamate

In the title compound, CH6N3 +·C5H8NO4 −, there are two independent cations and two independent anions in the asymmetric unit. In the crystal structure, cations and anions are linked by inter­molecular N—H⋯O hydrogen bonds into a three-dimensional network

Research progress and enlightenment on the application of social media in tourism abroad

With the wide application of information technology in tourism, new technologies and applications have a profound impact on the development of tourism, and promote the transformation of tourism research paradigm. Based on social media and closely combined with the reality of tourism, based on the review, the studies on social media and travel abroad related definition, the types of social media from social media, social media impact on tourism subject and object, social media applications in tourism in four aspects has carried on the summary and review. It is found that the foreign research on social media and tourism is in a rapid development stage. The profound impact of social media on tourism has gradually been recognized by scholars, but the breadth and depth of research still need to be strengthened. Finally, relevant research enlightenment is proposed from the perspective of basic theory and practical application

Laboratory study of acoustic velocity in different types of rocks at seismic frequency band

In order to understand the characteristics of acoustic wave propagation in rocks within seismic frequency band (<100 Hz), the velocities of longitudinal and transverse waves of four different types of rocks were tested using low-frequency stress-strain method by means of the physical testing system of rock at low frequency and the experimental data of acoustic velocities of four different types of rocks at this frequency band were obtained. The experimental results showed that the acoustic velocities of four different types of rocks increased with the increase of temperature and pressure within the temperature and pressure ranges set by the experiment. The acoustic velocity of fine sandstone at 50% water saturation was smaller than that of dry sample. The acoustic velocities of four different types of rocks were different and the velocities of longitudinal waves of gritstone, fine sandstone, argillaceous siltstone and mudstone increased in turn under similar conditions and were smaller than those at ultrasonic frequency. Few of existing studies focus on the acoustic velocity at seismic frequency band, thus, further understanding of the acoustic characteristics at this seismic frequency band still requires more experimental data

Experimental Study on Anisotropic Strength and Deformation Behavior of a Coal Measure Shale under Room Dried and Water Saturated Conditions

This paper presents an experimental investigation of anisotropic strength and deformation behavior of coal measure shale. The effect of two factors (i.e., anisotropy and water content) on shale strength and deformation behavior was studied. A series of uniaxial and triaxial compression tests were conducted on both room dried and water saturated samples for different lamination angles. The test results indicate that (1) the compressive strength, cohesion, internal friction angle, tangent Young’s modulus, and axial strain corresponding to the peak and residual strengths of room dried specimens exhibit anisotropic behavior that strongly depends on the orientation angle ; (2) in comparison to the room dried samples, the compressive strength and Young’s modulus as well as the anisotropy are all reduced for water saturated specimens; and (3) the failure mechanism of the samples can be summarized into two categories: sliding along lamination and shearing of rock material, with the type occurring in a particular situation depending strongly on the lamination orientation angles with respect to the major principal stress. According to the findings, it is strongly recommended that the effect of anisotropy and water content on the strength and deformation behavior of the rock must be considered in ground control designs

Percutaneous Nephrolithotomy under Local Infiltration Anesthesia in Kneeling Prone Position for a Patient with Spinal Deformity

Urolithiasis, a common condition in patients with spinal deformity, poses a challenge to surgical procedures and anesthetic management. A 51-year-old Chinese male presented with bilateral complex renal calculi. He was also affected by severe kyphosis deformity and spinal stiffness due to ankylosing spondylitis. Dr. Li performed the percutaneous nephrolithotomy under local infiltration anesthesia with the patient in a kneeling prone position, achieving satisfactory stone clearance with no severe complications. We found this protocol safe and effective to manage kidney stones in patients with spinal deformity. Local infiltration anesthesia may benefit patients for whom epidural anesthesia and intubation anesthesia are difficult

A novel backfill material for roof supports in the cut-through entries of longwall mining

U svrhu povećanja sigurnost u rudnicima, istraživači su razvili brzo skrutnjavajući cement koji sadrži veliku količinu vode (HWFSC). HWFSC se u biti sastoji od dvije komponente i može se miješati s velikim količinama vode. Kako bi se odredila njegova mehanička čvrstoća izvršen je niz ispitivanja jednoosne tlačne čvrstoće na HWFSC uzorcima s različitim omjerima vode i krute tvari. Rezultati su pokazali da je vršna čvrstoća znatno opadala s povećanjem W/S omjera, dok je zaostala čvrstoća pritom postupno rasla. Izvedivost ispune prokopa HWFSC-om tada se provjerila analizom slučaja. LaModel programom se procijenilo popuštanje bočnog stupa i deformacija prokopa. Rezultati također pokazuju da se primjena HWFSC za ispunu prokopa pokazala uspješnom u rješavanju složenih problema upravljanja s tla. Daljnja je analiza također pokazala da je HWFSC optimalni materijal za popunjavanje i zbog ekonomične cijene i sigurnosti krovišta.To enhance underground mining safety, researchers developed high-water and fast-setting cement (HWFSC). HWFSC essentially consists of two components and can be mixed with large quantities of water. To determine its mechanical strength, a series of uniaxial compressive strength tests were conducted on HWFSC specimens with different water-to-solid ratios. Results indicate that peak strength declined significantly with the increase in W/S ratio, whereas residual strength increased gradually with this enhancement. The feasibility of backfilling cut-through entries with HWFSC is then evaluated through a case study. The LaModel program was used to assess the yielding of the fender pillar and the deformation of the cut-through entry. Results also show that the use of HWFSC to backfill the cut-through entry addressed complicated ground control problems effectively. Further analysis also suggested that HWFSC was the optimal backfill material in terms of both economic cost and roof support safety

Mass and Heat Balance of a Lake Ice Cover in the Central Asian Arid Climate Zone

To improve the understanding of the seasonal evolution of the mass and heat budget of ice-covered lakes in the cold and arid climate zone, in-situ observations were collected during two winters (2016–2017 and 2017–2018) in Lake Wuliangsuhai, Inner Mongolia, China. The mean snow thickness was 5.2 and 1.6 cm in these winters, due to low winter precipitation. The mean ice thickness was 50.9 and 36.1 cm, and the ice growth rate was 3.6 and 2.1 mm day−1 at the lower boundary of ice. Analyses of mass and heat balance data from two winters revealed that the surface heat budget was governed by solar radiation and terrestrial radiation. The net heat flux loss of the ice was 9–22 W m−2, affected by the snow and ice thickness. Compared to boreal lakes, Lake Wuliangsuhai received more solar radiation and heat flux from the water. The ice temperature had a strong diurnal variation, which was produced by the diurnal cycles of solar radiation, and air and water temperatures. These results expand our knowledge of the evolution of mass and heat balance in temperate lakes of mid-latitude arid areas

Preparation of Iron-nickel Alloy Nanostructures via Two Cationic Pyridinium Derivatives as Soft Templates

In this paper, crystalline iron-nickel alloy nanostructures were successfully prepared from two cationic pyridinium derivatives as soft templates in solution. The crystal structure and micrograph of FeNi alloy nanostructures were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and the content was confirmed by energy-dispersive spectrometry. The results indicated that the as-prepared nanostructures showed slightly different diameter ranges with the change of cationic pyridinium derivatives on the surface. The experimental data indicated that the adsorption of cationic pyridinium compounds on the surface of particles reduces the surface charge, leading to an isotropic distribution of the residual surface charges. The magnetic behaviours of as-prepared FeNi alloy nanostructures exhibited disparate behaviours, which could be attributed to their grain sizes and distinctive structures. The present work may give some insight into the synthesis and character of new alloy nanomaterials with special nanostructures using new soft templates

Safety-assured, real-time neural active fault management for resilient microgrids integration

Federated-learning-based active fault management (AFM) is devised to achieve real-time safety assurance for microgrids and the main grid during faults. AFM was originally formulated as a distributed optimization problem. Here, federated learning is used to train each microgrid’s network with training data achieved from distributed optimization. The main contribution of this work is to replace the optimization-based AFM control algorithm with a learning-based AFM control algorithm. The replacement transfers computation from online to offline. With this replacement, the control algorithm can meet real-time requirements for a system with dozens of microgrids. By contrast, distributed-optimization-based fault management can output reference values fast enough for a system with several microgrids. More microgrids, however, lead to more computation time with optimization-based method. Distributed-optimization-based fault management would fail real-time requirements for a system with dozens of microgrids. Controller hardware-in-the-loop real-time simulations demonstrate that learning-based AFM can output reference values within 10 ms irrespective of the number of microgrids