scholarly journals Numerical and in-situ investigation on the ground behavior of the end roof in fully mechanized caving face

2021 ◽  
Vol 303 ◽  
pp. 01028
Author(s):  
Chuanwei Zang ◽  
Miao Chen ◽  
Yang Chen ◽  
Xuean Zhuang ◽  
Chenming Zhai ◽  
...  
Keyword(s):  
Coal Mining ◽  
Concentration Factor ◽  
High Efficiency ◽  
Vertical Displacement ◽  
High Yield ◽  
Support Pressure ◽  
Roof Structure ◽  
In Situ Investigation ◽  
And Migration ◽  
Seam Mining

Fully mechanized top coal caving is a major high-yield and high-efficiency coal mining method for thick seam mining. At present, it is affected by the further popularization and application of fully mechanized caving mining because the recovery rate is limited. The research on the technology of fully mechanized top coal caving and transitional coal mining is crucial. This paper aims at the top coal recovery with the top coal of the fully mechanized caving face and the transitional frame at both ends of the working face. With the top roof structure model of the fully mechanized caving face, the numerical simulation and field measurement is used to compare the end coal caving. With caving coal or not, the destruction and migration rules of the top coal in the fully mechanized caving face are obtained. The study found that at the end of the transport trough, the maximum concentration factor of the support pressure in the coal is 2.35, and the maximum vertical displacement is 9.2cm. And at the end of the return air trough, the support pressure concentration factor is 3.53, and the maximum vertical displacement of the roof is 102cm. The above research reveals the law of the occurrence of the pressure and the movement of the top coal when caving the coal at the end, while ensuring the safe production and efficient mining of the coal mine.

Research on the Overlying Strata in Full-Mechanized Coal Mining of Datong Jurassic Coal Multi-Layer Goaf

2012 ◽  
Vol 616-618 ◽  
pp. 402-405 ◽  
Author(s):  
Hong Chun Xia ◽  
Guo Sheng Gao ◽  
Bin Yu
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Pillar ◽  
Mining Area ◽  
Mechanics Model ◽  
Roof Structure ◽  
Geological Conditions ◽  
Seam Mining ◽  
The Impact ◽  
Overlying Strata

According to the specific geological conditions in themulti-layer worked-out areas of Yongding coal seam, by the methods of integration of theoretic analysis, numerical value calculation and so on, we studied movement law of Overlaying Strata and influence of coal pillar in Coal seam mining, obtained the basic law of the overlying strata movement in multiplayer, provides a theoretical basis for the safe and efficient exploitation of the success of multiplayer. Many mining area in China is mining of closed distance coal seam group, By the impact of coal seam in the overlying, face and the tunnel roof structure will be different injury in sub-coal seam mining, Roof structure has changed greatly, even damage and easily take the roof leakage, When the the goaf communication with the overlying coal seams, caused by the induced secondary disasters such as face air leakage, Therefore, exploitation of the law of motion of the overlying strata in the multiplayer is a pressing problem. Exploitation multiplayer seam few theoretical and technical foundation at home and abroad, affecting the validity of the mining, rationality. although a lot of research on theory and technology of coal mining over the years[1~5], But it was not able to an overall comprehensive analysis of upper goaf adjacent goaf and overlying the coal pillar and present mining face, create a dynamic structural mechanics model, which is likely to cause the occurrence of disasters.

scholarly journals Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yingfeng Yang ◽  
Hanze Ying ◽  
Zhixia Li ◽  
Jiang Wang ◽  
Yingying Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Molecular Structures ◽  
High Yield ◽  
Kinetic Control ◽  
High Concentration ◽  
Weak Association ◽  
Quantitative Synthesis ◽  
Thermodynamic Stabilization ◽  
Discrete Structures ◽  
Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

scholarly journals A Brief Review on Solvent-Free Synthesis of Zeolites

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 788
Author(s):  
Jinlin Mei ◽  
Aijun Duan ◽  
Xilong Wang
Keyword(s):  
High Efficiency ◽  
Raw Materials ◽  
Solvent Free ◽  
High Yield ◽  
Control Synthesis ◽  
Mechanical Mixing ◽  
Synthesis Mechanism ◽  
Wastewater Pollution ◽  
Low Efficiency ◽  
Solvent Free Synthesis

The traditional hydrothermal method to prepare zeolite will inevitably use a large amount of water as a solvent, which will lead to higher autogenous pressure, low efficiency, and wastewater pollution. The solvent-free method can be used to synthesize various types of zeolites by mechanical mixing, grinding, and heating of solid raw materials, which exhibits the apparent advantages of high yield, low pollution, and high efficiency. This review mainly introduces the development process of solvent-free synthesis, preparation of hierarchical zeolite, morphology control, synthesis mechanism and applications of solvent-free methods. It can be believed that solvent-free methods will become a research focus and have enormous industrial application potential.

scholarly journals Iodine reduction for reproducible and high-performance perovskite solar cells and modules

2021 ◽  
Vol 7 (10) ◽  
pp. eabe8130
Author(s):  
Shangshang Chen ◽  
Xun Xiao ◽  
Hangyu Gu ◽  
Jinsong Huang
Keyword(s):  
Solar Cells ◽  
High Performance ◽  
High Efficiency ◽  
Electronic Materials ◽  
Substantial Reduction ◽  
Perovskite Solar Cells ◽  
High Yield ◽  
Operation Conditions ◽  
Record Value ◽  
Precursor Powders

Perovskite-based electronic materials and devices such as perovskite solar cells (PSCs) have notoriously bad reproducibility, which greatly impedes both fundamental understanding of their intrinsic properties and real-world applications. Here, we report that organic iodide perovskite precursors can be oxidized to I2 even for carefully sealed precursor powders or solutions, which markedly deteriorates the performance and reproducibility of PSCs. Adding benzylhydrazine hydrochloride (BHC) as a reductant into degraded precursor solutions can effectively reduce the detrimental I2 back to I−, accompanied by a substantial reduction of I3−-induced charge traps in the films. BHC residuals in perovskite films further stabilize the PSCs under operation conditions. BHC improves the stabilized efficiency of the blade-coated p-i-n structure PSCs to a record value of 23.2% (22.62 ± 0.40% certified by National Renewable Energy Laboratory), and the high-efficiency devices have a very high yield. A stabilized aperture efficiency of 18.2% is also achieved on a 35.8-cm2 mini-module.

Design of a Retrovirus-Derived Vector for Expression and Transduction of Exogenous Genes in Mammalian Cells

1983 ◽  
Vol 3 (6) ◽  
pp. 1123-1132
Author(s):  
Archibald S. Perkins ◽  
Paul T. Kirschmeier ◽  
Sebastiano Gattoni-Celli ◽  
I. Bernard Weinstein
Keyword(s):  
Mammalian Cells ◽  
High Efficiency ◽  
Leukemia Virus ◽  
Restriction Enzymes ◽  
Virus Genome ◽  
Opposite Polarity ◽  
High Yield ◽  
Animal Cells ◽  
Murine Sarcoma Virus ◽  
Sarcoma Virus

We have developed a transfection vector for animal cells that contains long terminal repeat (LTR) sequences to promote expression. Plasmid p101/101, a derivative of plasmid pBR322 containing the complete Moloney murine sarcoma virus genome, was cut with restriction enzymes and religated so that both the 5′ and 3′ LTRs were retained and all but about 700 base pairs of the intervening viral sequences were removed. To test this vector, the Escherichia coli gene gpt was cloned into a unique Pst I site, between the two LTRs, with guanine and cytosine tailing, a method that can be generalized for insertion of any DNA segment into this vector. When DNA from recombinant plasmids in which the gpt gene was inserted in the same transcriptional polarity as the LTR sequences was transfected onto murine or rat fibroblast cultures, we obtained a high yield of Gpt + colonies. However, plasmid constructs with the gpt gene in the opposite polarity were virtually devoid of activity. With gpt in the proper orientation, restriction enzyme cuts within the LTRs or between the 5′ LTR and the gpt gene reduced transfection by more than 98%, whereas a cut between the gpt gene and the 3′ LTR gave an 80% reduction in activity. Thus, both 5′ and 3′ LTR sequences are essential for optimal gpt expression, although the 5′ LTR appears to play a more important role. When the LTR- gpt plasmid was transfected onto murine leukemia virus-infected mouse fibroblasts, we obtained evidence that RNA copies became pseudotyped into viral particles which could transfer the Gpt + phenotype into rodent cells with extremely high efficiency. This vector should prove useful for high-efficiency transduction of a variety of genes in mammalian cells.

High yield and greener C–H difluoromethylation reactions using copper iodide nanoparticles/boron nitride nanosheets as a versatile and recyclable heterogeneous catalyst

2021 ◽  
Author(s):  
Udayakumar Veerabagu ◽  
Gowsika Jaikumar ◽  
Fushen Lu ◽  
Franck Quero
Keyword(s):  
Boron Nitride ◽  
Heterogeneous Catalyst ◽  
High Efficiency ◽  
High Yield ◽  
Copper Iodide ◽  
Boron Nitride Nanosheets ◽  
Greener Synthesis ◽  
High Yields ◽  
Recyclable Heterogeneous Catalyst

The 3 wt% CuI/BNNS catalyst exhibited high efficiency for C–H difluoromethylation reactions and enabled greener synthesis at high yields using cyrene as a solvent. Furthermore, the catalyst could be easily recovered and recycled for at least five cycles.

scholarly journals Preparation of crotalus venom radiolabeled with technetium-99m as a tool for biodistribution study

2005 ◽  
Vol 48 (spe2) ◽  
pp. 9-12 ◽  
Author(s):  
Priscilla Brunelli Pujatti ◽  
Carlos Jorge Rodrigues Simal ◽  
Raquel Gouvêa dos Santos
Keyword(s):  
Biological Activity ◽  
High Efficiency ◽  
High Yield ◽  
Clinical Use ◽  
Crude Venom ◽  
Technetium 99M ◽  
Biodistribution Studies ◽  
Nuclear Medicine Procedures ◽  
Distribution Studies ◽  
Exogenous Source

Technetium-99m (99mTc) has been the radionuclide of choice for nuclear medicine procedures and experimental research. Because of its optimal nuclear properties, 99mTc is suitable for high efficiency detection with the advantage of reduced radiological waste. Crotalus venom (CV) has been shown to reduce tumors in clinical studies and tissue distribution studies are very important for clinical use. The goal of this work was to obtain CV labeled with 99mTc which preserves its biological activity. After labeling, biological activity was assessed by hemolytic activity evaluation. Labeled and crude venom caused indirect hemolysis provided that the incubation medium contained an exogenous source of lecithin. High yield radiolabeled-CV was obtained and biological activity was preserved. The results suggest that 99mTc-CV can be a useful tool for biodistribution studies.

scholarly journals Overexpression of Thermophilic α-amylase in Bacillus Licheniformis using a High Efficiency Chromosomal Integration and Amplification Strategy

2021 ◽  
Author(s):  
Peili Shen ◽  
Dandan Niu ◽  
Xuelian Liu ◽  
Kangming Tian ◽  
Permaul Kugenthiren ◽  
...  
Keyword(s):  
Bacillus Licheniformis ◽  
High Efficiency ◽  
High Yield ◽  
Chromosomal Integration ◽  
Bacillus Sp ◽  
Strain Development ◽  
Microbial Cell Factories ◽  
Cell Factories ◽  
New Strategy ◽  
Amplification Strategy

Abstract Highly efficient preparation of industrially important enzymes depends on development of the genetically stable and high-yield microbial cell factories, which is often a challengeable laboratory hard work. In aims to simplify strain development with high efficiency for enzyme overproduction, a new strategy based on chromosomal integration and amplification in Bacillus sp . was developed. A pair of plasmids, an integrated expression plasmid pUB'-Ex1 and a thermosensitive replicable plasmid pUB-MazF, were constructed. pUB'-Ex1 conditionally self-replicated in Bacillus sp . when the RepF in pUB-MazF expressed. pUB-MazF thermosensitively self-replicated in Bacillus sp . , which was easily cured from the host by inducing MazF expression with IPTG. Bacillus licheniformis BL-UBM that integrated with pUB-MazF was then transformed with pUB'-amyS derived from pUB'-Ex1 by in-frame cloning of amyS encoding a thermophilic α-amylase from Geobacillus stearothermophilus ATCC 31195. The transformant of B. licheniformis BL-UBM with pUB'-amyS was cultivated at 42 o C with the existence of 1 mmol/l IPTG and 500 μg/ml kanamycin and the recombinants with high α-amylase activities were selected. All tested recombinants were extremely high genetic stability. One of which, recombinant BLiS-002, carried five copies of amyS and produced the highest yield of α-amylase. It could yield 50,753 U/ml of α-amylase in a 50-l bioreactor. The strategy developed in this study is of application potential for convenient and quick strain development for industrially important enzyme overexpression.

scholarly journals A Mechanical Model of the Overlying Rock Masses in Undersea Coal Mining and a Stress-Seepage Coupling Numerical Simulation

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jie Fang ◽  
Lei Tian ◽  
Yanyan Cai ◽  
Zhiguo Cao ◽  
Jinhao Wen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Coal Mining ◽  
Water Inrush ◽  
Mining Area ◽  
Analysis Model ◽  
Fractured Zones ◽  
Working Face ◽  
Seam Mining ◽  
Overlying Strata

The water inrush of a working face is the main hidden danger to the safe mining of underwater coal seams. It is known that the development of water-flowing fractured zones in overlying strata is the basic path which causes water inrushes in working faces. In the engineering background of the underwater mining in the Longkou Mining Area, the analysis model and judgment method of crack propagation were created on the basis of the Mohr–Coulomb criterion. Fish language was used to couple the extension model into the FLAC3d software, in order to simulate the mining process of the underwater coal seam, as well as to analyze the initiation evolutionary characteristics and seepage laws of the fractured zones in the overlying strata during the advancing processes of the working face. The results showed that, during the coal seam mining process, the mining fractured zones which had been caused by the compression-shear and tension-shear were mainly concentrated in the overlying strata of the working face. Also, the open-off cut and mining working face were the key sections of the water inrush in the rock mass. The condition of the water disaster was the formation of a water inrush channel. The possible water inrush channels in underwater coal mining are mainly composed of water-flowing fractured zones which are formed during the excavation processes. The numerical simulation results were validated through the practical engineering of field observations on the height of water-flowing fractured zone, which displayed a favorable adaptability.

scholarly journals Study on the Influence of Mud Properties on the Stability of Excavated Face of Slurry Shield and the Quality of Filter Cake Formation

2020 ◽  
Vol 8 (4) ◽  
pp. 291
Author(s):  
Hu Wang ◽  
Jian Chen ◽  
Hongjun Liu ◽  
Lei Guo ◽  
Yao Lu ◽  
...  
Keyword(s):  
Filter Cake ◽  
Volume Ratio ◽  
Vertical Displacement ◽  
Support Pressure ◽  
Longitudinal Displacement ◽  
Growth Trend ◽  
Cake Formation ◽  
Geological Conditions ◽  
The Stability

In the construction of subsea tunnels, the stability and control of the excavation surface are the main concerns of the engineering community. In this paper, the Xiamen Metro Line 2 is used as the study case. The filter cake formation of mud shields is experimentally studied, and the excavation surface is numerically simulated. It is found that the formation of filter cake does not require a large pressure difference, and can be formed under 0.06 MPa. With the increase of pressure, the quality of filter cake is further improved, and a small amount of seawater (volume ratio less than 3%) also has a significant effect on the viscosity of mud. Under different cross-section geological conditions, with the decrease of the support pressure of the excavation face, the vertical displacement and vertical (Y-direction) displacement of the excavation face dome gradually increase, the maximum longitudinal displacement is 9.7 mm, the maximum longitudinal displacement can reach 23.9 mm, and the growth trend is nonlinear. According to different stratum conditions, during the excavation of the tunnel, the plastic area of the excavation face is different.

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