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Records with Subject: Other
Showing records 1 to 25 of 126. [First] Page: 1 2 3 4 5 Last
Air-Core-Liquid-Ring (ACLR) Atomization: Influences of Gas Pressure and Atomizer Scale Up on Atomization Efficiency
Marc O. Wittner, Heike P. Karbstein, Volker Gaukel
July 17, 2019 (v1)
Subject: Other
Keywords: ACLR, efficiency, high viscous feeds, pneumatic atomization, scale up
Air-core-liquid-ring (ACLR) atomizers present a specific type of internal mixing pneumatic atomizers, which can be used for efficient atomization of high viscous liquids. Generally, atomization efficiency is considered as a correlation between energy input and resulting droplet size. In pneumatic atomization, air-to-liquid ratio by mass (ALR) is commonly used as reference parameter of energy input. However, the pressure energy of the atomization gas is not considered in the calculation of ALR. In internal mixing ACLR atomizers, it can be assumed that this energy contributes to liquid disintegration by expansion of the gas core after exiting the atomizer. This leads to the hypothesis that droplet sizes decrease with increasing gas pressure at constant ALR. Therefore, the use of volumetric energy density (EV) as a reference parameter of energy input was investigated at different gas pressures between 0.4 and 0.8 MPa. Furthermore, scale up-related influences on the atomization efficiency... [more]
Measurement and Correlation of the Solubility of β-Cyclodextrin in Different Solutions at Different Temperatures and Thermodynamic Study of the Dissolution Process
Shanshan Jin, Xuewei Cui, Yingping Qi, Yongfeng Shen, Hua Li
July 11, 2019 (v1)
Subject: Other
Keywords: Apelblat equation, simplified Apelblat equation, solubility, β-Cyclodextrin, λh equation
A new improved formulation was studied to improve the rehydration properties of freeze-dried dumplings. To provide basic data for industrial applications, the solubility capabilities of β-Cyclodextrin in sucrose, NaCl, and a mixed solution were measured at temperatures ranging from 303.15 to 353.15 K using a laser monitoring method. The experimental values indicated that the solubility of β-Cyclodextrin in solvents increased with increasing temperature. The simplified Apelblat model, Apelblat model, and λh model were employed to analyze the experimental results using correlation tests. The relative average deviation (RAD) values between the experimental and calculated values were less than 0.095, 0.075, and 0.103 for the simplified Apelblat equation, Apelblat equation, and λh equation, respectively. Apparent thermodynamic analysis of β-Cyclodextrin dissolution was also performed at the mean temperature using the model parameters of Apelblat equation. Furthermore, thermodynamic properti... [more]
Availability Assessment of IMA System Based on Model-Based Safety Analysis Using AltaRica 3.0
Haiyong Dong, Qingfan Gu, Guoqing Wang, Zhengjun Zhai, Yanhong Lu, Miao Wang
June 18, 2019 (v1)
Subject: Other
Keywords: AltaRica 3.0, availability assessment, integrated modular avionics, model-based safety analysis
The integrated modular avionics (IMA) system is widely used in all classes of aircraft as a result of its high functional integration and resource utilization in developing advanced avionics systems. However, a series of challenges related to safety assessment exist in the background of the logical architecture for multi-message interactions of the IMA system. Traditional safety assessment methods are mainly based on engineering experience, and are difficult to reuse, incomplete, and even error-prone. Here we propose a method to assess the availability of the IMA system based on the thinking of model-based safety analysis. To aid the proposed method, we implement a tool to generate a AltaRica 3.0 file used to assess the IMA system model. The simulation results show that the proposed method makes the availability assessment fast, efficient, and effective. Moreover, we apply this method to the modification analysis of the IMA system under the condition of satisfying the safety requiremen... [more]
Degradation of Aqueous Polycyclic Musk Tonalide by Ultraviolet-Activated Free Chlorine
Lili Wang, Xiaowei Liu
June 10, 2019 (v1)
Subject: Other
Keywords: degradation mechanism, polycyclic musks, UV/chlorine advanced oxidation process, water treatment
Chlorine-incorporating ultraviolet (UV) provides a multiple barrier for drinking water disinfection. Meanwhile, post-UV employment can promote the degradation of micropollutants by radical production from chlorine residual photolysis. This work studied the degradation of one such chemical, tonalide (AHTN), by low-pressure UV-activated free chlorine (FC) under typical UV disinfection dosage of HCO 3 − > Cu 2 + > PO 4 3 − > Fe 2 + . Reaction product analysis showed ignorable formation of chlorinated intermediates and disinfection byproducts.
Dynamics of Water Quality: Impact Assessment Process for Water Resource Management
Ejaz-ul-Hassan Bhatti, Mudasser Muneer Khan, Syyed Adnan Raheel Shah, Syed Safdar Raza, Muhammad Shoaib, Muhammad Adnan
June 10, 2019 (v1)
Subject: Other
Keywords: sodium absorption, water management, water quality, wilcox diagram
Surface water is an important source of water supply for irrigation purpose and in urban areas, sewage water is being disposed of in nearby canals without treatment. A study was conducted to investigate the dynamics of water quality of irrigation canal as a result of this practice. The study ascertained the impact of different salinity parameters, indices and approaches to examine the hazardous effects on quality of canal water. The study analyses the samples collected for various parameters like pH, TDS, EC, Na, Cl, Ca, Mg, K, CO₃, HCO₃ etc. It helped to decide the restriction on use of water based on FAO-UN guidelines. Investigations were focused on assessment of contaminants affecting the quality of water and having hazardous effects on different stages of irrigation water usage. Wilcox diagram and Doneen’s approach-based analysis helped to identify the class and quality of water. This study shall help to analyze the quality of water and provide support to the decision makers for be... [more]
Purification of Flavonoids from Mulberry Leaves via High-Speed Counter-Current Chromatography
Pian Zhang, Kang-Ling Zhu, Jun Zhang, Yan Li, Heng Zhang, Yan Wang
June 10, 2019 (v1)
Subject: Other
Keywords: flavonoids, high-performance liquid chromatography, high-speed counter-current chromatography, mulberry leaf, separation
In order to obtain high-purity flavonoid products, the extracts from mulberry leaves were separated and purified via high-speed counter-current chromatography (HSCCC). Moreover, the product was detected via high-performance liquid chromatography (HPLC). The characteristic absorption wavelength of the rutin standard for HSCCC detection and HPLC analysis at 257 nm was tested by ultraviolet scanning analysis. The effect of solvent systems and mobile phase flow rate on the separation efficiency were then researched. Finally, the solvent system of V(ethyl acetate):V(n-butanol):V(water) = 4:1:5 was selected as the operating system for HSCCC. This work theoretically analyzed the impact of the molecular structure and polarity of flavonoids on the choice of solvent systems. The results showed that the mobile phase flow rate had a great influence on the separation efficiency. Furthermore, the separation efficiency increased as the mobile phase flow rate decreased. When the mobile phase flow rate... [more]
Phytochemical Content of Melissa officinalis L. Herbal Preparations Appropriate for Consumption
Vassiliki T. Papoti, Nikolaos Totomis, Aikaterini Atmatzidou, Kyriaki Zinoviadou, Anna Androulaki, Dimitris Petridis, Christos Ritzoulis
June 10, 2019 (v1)
Subject: Other
Keywords: antioxidants, decoctions, infusions, Melissa officinalis L., minerals, phenols
Melissa Officinalis L. (MOL) domestic preparations appropriate for consumption were studied by monitoring content in Na, K, Ca, Li, phenolic bioactives (total phenols, hydroxycinnamic acid derivatives and flavonols), and antioxidant activity (1,1-diphenyl-2-picrylhydrazyl radical inhibition (DPPH) and ferric reducing ability (FRAP)). The effects of practice applied, material to solvent ratio, time of preparation, and solvent were studied. MOL decoctions and infusions, commonly prepared at home, were better or of equal nutritional value to preparations upon ultrasounds or maceration concerning the studied parameters. Aqueous MOL preparations were richer in total phenols (704⁻1949 mg per 250 mL) and the examined macroelements (1.1⁻2.9, 30.5⁻288.4 and 50.1⁻176.1 mg Na, K and Ca per 250 mL, respectively) and showed better antioxidant activity compared to ethanol counterparts. The 25% w/v hydroethanolic MOL preparations, suitable for consumption, presented a significant content in phenolic... [more]
Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process
Zhonghui Li, Yue Niu, Enyuan Wang, Lanbo Liu, Honghao Wang, Mingfu Wang, Muhammad Ali
May 16, 2019 (v1)
Subject: Other
Keywords: charge separation, damage evolution, electrical potential, gas adsorption, gas-bearing coal
Coal mass is deformed and fractured under stress to generate electrical potential (EP) signals. The mechanical properties of coal change with the adsorption of gas. To investigate the EP response characteristics of gas-bearing coal during deformation and fracture, a test system to monitor multi-parameters of gas-bearing coal under load was designed. The results showed that abundant EP signals were generated during the loading process and the EP response corresponded well with the stress change and crack expansion, and validated this with the results from acoustic emission (AE) and high-speed photography. The higher stress level and the greater the sudden stress change led to the greater EP abnormal response. With the increase of gas pressure, the confining action and erosion effect are promoted, causing the damage evolution impacted and failure characteristics changes. As a result, the EP response is similar while the characteristics were promoted. The EP response was generated due to... [more]
Experimental Study on Mixed Mode Fracture Behavior of Sandstone under Water⁻Rock Interactions
Wen Hua, Jianxiong Li, Shiming Dong, Xin Pan
May 16, 2019 (v1)
Subject: Other
Keywords: degradation mechanism, fracture criteria, mixed mode fracture resistance, T-stress, water–rock interaction
Water⁻rock interactions can significantly deteriorate the physical and mechanical properties of rocks, and it has been identified as one of the significant factors influencing the stability and safety of structures in rock⁻soil engineering. In this study, the fracture mechanical properties of sandstone under periodic water⁻rock interactions and long-term immersion have been studied with central cracked Brazilian disk specimens. The degradation mechanism of water⁻rock interactions was also studied using a scanning electron microscope (SEM). Finally, the generalized maximum tangential stress and generalized maximum tangential strain criteria were adopted to evaluate the experimental results. The results show that periodic water⁻rock interactions can remarkably affect the fracture resistance of sandstone. With the increase in the number of cycles, the pure mode I, pure mode II, and mixed mode fracture toughness decreases greatly, however, the values of KIf/KIC and KIIf/KIC decrease slight... [more]
The Effects of Backfill Mining on Strata Movement Rule and Water Inrush: A Case Study
Jian Hao, Yongkui Shi, Jiahui Lin, Xin Wang, Hongchun Xia
May 16, 2019 (v1)
Subject: Other
Keywords: backfill mining, floor failure depth, ground pressure, strata movement, water inrush prevention
Backfill mining is widely used to control strata movement and improve the stress environment in China’s coal mines. In the present study, the effects of backfill mining on strata movement and water inrush were studied based on a case study conducted in Caozhuang Coal Mine. The in-situ investigation measured abutment pressure distribution (APD), roof floor displacement (RFD), and vertical stress in the backfill area. Results are as follows: (i) The range and peak of APD, RFD, and vertical stress in the backfill area are smaller than in traditional longwall mining with the caving method. (ii) Backfill mining could change the movement form and amplitude of overburden and improve the ground pressure environment. (iii) Floor failure depth (FFD) is much smaller in backfill mining. Backfill mining can be an effective method for floor water inrush prevention.
Experimental Study on the Shear-Flow Coupled Behavior of Tension Fractures Under Constant Normal Stiffness Boundary Conditions
Changsheng Wang, Yujing Jiang, Hengjie Luan, Jiankang Liu, Satoshi Sugimoto
May 16, 2019 (v1)
Subject: Other
Keywords: constant normal stiffness conditions, hydraulic aperture, rock fracture, shear-flow coupled test, transmissivity
This study experimentally investigated the effects of fracture surface roughness, normal stiffness, and initial normal stress on the shear-flow behavior of rough-walled rock fractures. A series of shear-flow tests were performed on two rough fractures, under various constant normal stiffness (CNS) boundary conditions. The results showed that the CNS boundary conditions have a significant influence on the mechanical and hydraulic behaviors of fractures, during shearing. The peak shear stress shows an increasing trend with the increases in the initial normal stress and fracture roughness. The residual shear stress increases with increasing the surface roughness, normal stiffness, and initial normal stress. The dilation of fracture is restrained more significantly under high normal stiffness and initial normal stress conditions. The hydraulic tests show that the evolutions of transmissivity and hydraulic aperture exhibit a three-stage behavior, during the shear process—a slight decrease s... [more]
Simulating the Filtration Effects of Cement-Grout in Fractured Porous Media with the 3D Unified Pipe-Network Method
Zizheng Sun, Xiao Yan, Weiqi Han, Guowei Ma, Yiming Zhang
April 15, 2019 (v1)
Subject: Other
Keywords: filtration effects, fractured porous medium, grout penetration, two-phase flow, unified pipe-network method
In grouting process, filtration is the retention and adsorption of cement-grout particles in a porous/fractured medium. Filtration partly/even completely blocks the transportation channels in the medium, greatly decreasing its permeability. Taking into account filtration effects is essential for accurately estimating the grout penetration region. In this paper, the 3D unified pipe-network method (UPM) is adopted for simulating 3D grout penetration process in a fractured porous medium, considering filtration effects. The grout is assumed to exhibit two-phase flow, and the filtration effects depend on not only the concentration and rheology of the grout but also the porosity and permeability of the fractured porous medium. By comparing the model with the experimental results, we firstly verify the proposed numerical model. Then sensitivity analysis is conducted, showing the influences of grout injection pressures, the water⁻cement ratios of grout (W/C) and the grout injection rates on fi... [more]
Acknowledgement to Reviewers of Processes in 2018
Processes Editorial Office
April 15, 2019 (v1)
Subject: Other
Rigorous peer-review is the corner-stone of high-quality academic publishing [...]
Ambient Pressure-Dried Graphene⁻Composite Carbon Aerogel for Capacitive Deionization
Chen Zhang, Xiaodong Wang, Hongqiang Wang, Xueling Wu, Jun Shen
April 15, 2019 (v1)
Subject: Other
Keywords: capacitive deionization, desalination, electrosorption, graphene–composite carbon aerogel (GCCA)
Capacitive deionization (CDI) technology possessing excellent desalination performance and energy efficiency is currently being widely studied in seawater desalination. In this work, the graphene⁻composite carbon aerogels (GCCAs) easily prepared by an ambient pressure drying method served as electrodes to remove salt ions in aqueous solution by CDI. The microstructure of the obtained GCCAs was found to depend on the component content in the precursor solution, and could be controlled through varying the mass ratio of resorcinol and formaldehyde to graphene oxide (RF/GO). The surface characteristics and microstructure of GCCAs were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In addition, the electrochemical tests and CDI experiments of GCCA electrodes were conducted in NaCl solution. Thanks to the reasonable pore structure and highly conductive network, GCCA-150 achieved the best salt adsorption capacity of 26.9 mg/... [more]
Numerical Investigation of Hydraulic Fracture Propagation Based on Cohesive Zone Model in Naturally Fractured Formations
Jianxiong Li, Shiming Dong, Wen Hua, Xiaolong Li, Xin Pan
April 15, 2019 (v1)
Subject: Other
Keywords: hydraulic fractures, multitude parameters, naturally fracture, PPCZ, propagation pattern, stress interference
Complex propagation patterns of hydraulic fractures often play important roles in naturally fractured formations due to complex mechanisms. Therefore, understanding propagation patterns and the geometry of fractures is essential for hydraulic fracturing design. In this work, a seepage⁻stress⁻damage coupled model based on the finite pore pressure cohesive zone (PPCZ) method was developed to investigate hydraulic fracture propagation behavior in a naturally fractured reservoir. Compared with the traditional finite element method, the coupled model with global insertion cohesive elements realizes arbitrary propagation of fluid-driven fractures. Numerical simulations of multiple-cluster hydraulic fracturing were carried out to investigate the sensitivities of a multitude of parameters. The results reveal that stress interference from multiple-clusters is responsible for serious suppression and diversion of the fracture network. A lower stress difference benefits the fracture network and he... [more]
Chemical Recycling of Used Printed Circuit Board Scraps: Recovery and Utilization of Organic Products
Se-Ra Shin, Van Dung Mai, Dai-Soo Lee
April 15, 2019 (v1)
Subject: Other
Keywords: chemical recycling, glycolysis, recycled polyol, rigid polyurethane foam, used printed circuit board
The disposal of end-of-life printed circuit boards (PCBs) comprising cross-linked brominated epoxy resins, glass fiber, and metals has attracted considerable attention from the environmental aspect. In this study, valuable resources, especially organic material, were recovered by the effective chemical recycling of PCBs. Pulverized PCB was depolymerized by glycolysis using polyethylene glycol (PEG 200) with a molecular weight of 200 g/mol under basic conditions. The cross-linked epoxy resins were effectively decomposed into a low-molecular species by glycolysis with PEG 200, followed by the effective separation of the metals and glass fibers from organic materials. The organic material was modified into recycled polyol with an appropriate viscosity and a hydroxyl value for rigid polyurethane foams (RPUFs) by the Mannich reaction and the addition polymerization of propylene oxide. RPUFs prepared using the recycled polyol exhibited superior thermal and mechanical properties as well as th... [more]
Special Issue on Feature Papers for Celebrating the Fifth Anniversary of the Founding of Processes
Michael A. Henson
April 9, 2019 (v1)
Subject: Other
The Special Issue “Feature Papers for Celebrating the Fifth Anniversary of the Founding of Processes„ represents a landmark for this open access journal covering chemical, biological, materials, pharmaceutical, and environmental systems as well as general computational methods for process and systems engineering. [...]
Formation Mechanism of Trailing Oil in Product Oil Pipeline
Enbin Liu, Wensheng Li, Hongjun Cai, Shanbi Peng
April 9, 2019 (v1)
Subject: Other
Keywords: Computational Fluid Dynamics, contamination, dead-leg, pipeline, trailing oil, transportation
Trailing oil is the tail section of contamination in oil pipelines. It is generated in batch transportation, for which one fluid, such as diesel oil follows another fluid, such as gasoline, and it has an effect on the quality of oil. This paper describes our analysis of the formation mechanism of trailing oil in pipelines and our study of the influence of dead-legs on the formation of trailing oil. We found that the oil replacement rate in a dead-leg is exponentially related to the flow speed, and the length of the dead-leg is exponentially related to the replacement time of the oil. To reduce the amount of mixed oil, the main flow speed should be kept at about 1.6 m/s, and the length of the dead-leg should be less than five times the diameter of the main pipe. In our work, the Reynolds time-averaged method is used to simulate turbulence. To obtain contamination-related experimental data, computational fluid dynamics (CFD) software is used to simulate different flow rates and bypass le... [more]
Investigation of Deep Mine Shaft Stability in Alternating Hard and Soft Rock Strata Using Three-Dimensional Numerical Modeling
Xiaoming Sun, Gan Li, Chengwei Zhao, Yangyang Liu, Chengyu Miao
April 9, 2019 (v1)
Subject: Other
Keywords: alternate strata, mine shaft, relief excavation, shaft lining, surrounding rock
The problem of shaft instability has always been a major difficulty in deep mining practices. The shaft fracture has a high probability of being located near the aquifers and the soft⁻hard rock contact zone. This paper describes the deformation and stress characteristics of surrounding rock and the shaft lining under the interactive geological conditions under soft and hard rock strata in Anju coal mine, Shandong Province, China. Using the Method of Geological Strength Index (GSI ) and considering the rock-softening characteristics of water, the parameters of rock mass are calibrated. By means of the 3DEC-trigon method, the variation characteristics of surrounding rock and the shaft lining are simulated. After shaft excavation, under the condition of no support, shear failure and tensile failure occur in shallow surrounding rock shafts, and a pressure relief zone is formed. Shear failure is the main destruction mode in deep surrounding rock. Because of the different strengths of the su... [more]
Recent Advance on Draw Solutes Development in Forward Osmosis
Qingwu Long, Yongmei Jia, Jinping Li, Jiawei Yang, Fangmei Liu, Jian Zheng, Biao Yu
April 8, 2019 (v1)
Subject: Other
Keywords: draw solutes, Energy, forward osmosis, membrane separation, regeneration
In recent years, membrane technologies have been developed to address water shortage and energy crisis. Forward osmosis (FO), as an emerging membrane-based water treatment technology, employs an extremely concentrated draw solution (DS) to draw water pass through the semi-permeable membrane from a feed solution. DS as a critical material in FO process plays a key role in determining separation performance and energy cost. Most of existing DSs after FO still require a regeneration step making its return to initial state. Therefore, selecting suitable DS with low reverse solute, high flux, and easy regeneration is critical for improving FO energy efficiency. Numerous novel DSs with improved performance and lower regeneration cost have been developed. However, none reviews reported the categories of DS based on the energy used for recovery up to now, leading to the lack of enough awareness of energy consumption in DS regeneration. This review will give a comprehensive overview on the exis... [more]
The Seepage Control of the Tunnel Excavated in High-Pressure Water Condition Using Multiple Times Grouting Method
Bin Gong, Yujing Jiang, Keisuke Okatsu, Xuezhen Wu, Jin Teduka, Koichi Aoki
April 8, 2019 (v1)
Subject: Other
Keywords: FLAC3D, high groundwater table, leakage control, multiple grouting, tunnel, ultramicro cement
Groundwater can cause many hazardous problems when a tunnel is excavating. Seepage force acting on the support structure and the tunnel surface cannot be negligible. Under high groundwater table condition, the seepage situation becomes more complex and it is more difficult to control the leakage of groundwater to flow into a tunnel. In the paper, a multiple times grouting method is proposed, and the mechanical deformation behavior of surrounding rock is analyzed using the FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) software according to the high groundwater table condition of the Hokusatsu tunnel. The results present that multiple times grouting can control leakage and the rock deformation well, compared with one-time grouting condition in rock breaking and high water pressure area. The seepage force decrease around the tunnel and the displacement is controlled effectively. The pore pressure reduces inside the grouting zone using a new kind of grouting material, which... [more]
Temporal Mixing Behavior of Conservative Solute Transport through 2D Self-Affine Fractures
Zhi Dou, Brent Sleep, Pulin Mondal, Qiaona Guo, Jingou Wang, Zhifang Zhou
April 8, 2019 (v1)
Subject: Other
Keywords: conservative solute, fractal, fracture, Mixing, roughness
In this work, the influence of the Hurst exponent and Peclet number (Pe) on the temporal mixing behavior of a conservative solute in the self-affine fractures with variable-aperture fracture and constant-aperture distributions were investigated. The mixing was quantified by the scalar dissipation rate (SDR) in fractures. The investigation shows that the variable-aperture distribution leads to local fluctuation of the temporal evolution of the SDR, whereas the temporal evolution of the SDR in the constant-aperture fractures is smoothly decreasing as a power-law function of time. The Peclet number plays a dominant role in the temporal evolution of mixing in both variable-aperture and constant-aperture fractures. In the constant-aperture fracture, the influence of Hurst exponent on the temporal evolution of the SDR becomes negligible when the Peclet number is relatively small. The longitudinal SDR can be related to the global SDR in the constant-aperture fracture when the Peclet number is... [more]
Shear-Flow Coupled Behavior of Artificial Joints with Sawtooth Asperities
Cheng Zhao, Rui Zhang, Qingzhao Zhang, Zhenming Shi, Songbo Yu
April 8, 2019 (v1)
Subject: Other
Keywords: artificial joint rock, hydraulic aperture, roughness, seepage pressure, shear-flow coupled test
The coupling between hydraulic and mechanical processes in rock joints has significantly influenced the properties and applications of rock mass in many engineering fields. In this study, a series of regular shear tests and shear-flow coupled tests were conducted on artificial joints with sawtooth asperities. Shear deformation, strength, and seepage properties were comprehensively analyzed to reveal the influence of joint roughness, normal stress, and seepage pressure on shear-flow coupled behavior. The results indicate that the shear failure mode, which can be divided into sliding and cutting, is dominated by joint roughness and affected by the other two factors under certain conditions. The seepage process makes a negative impact on shear strength as a result of the mutual reinforcing of offsetting and softening effects. The evolution of hydraulic aperture during the shear-flow coupled tests embodies a consistent pattern of four stages: shear contraction, shear dilation, re-contracti... [more]
Analysis of Overlying Strata Movement and Disaster-Causing Effects of Coal Mining Face under the Action of Hard Thick Magmatic Rock
Quanlin Wu, Quansen Wu, Yanchao Xue, Peng Kong, Bin Gong
April 8, 2019 (v1)
Subject: Other
Keywords: bed separation, disaster-causing mechanism, fracture, hard and thick magmatic rocks, orthogonal ratio test, similar simulation
When the hard and thick key strata are located above the working face, the bed separation structure is easy to be formed after mining because of the high strength and integrity of the hard and thick key strata and the initial breaking step is large. After the hard, thick strata are broken, the overburden will be largely collapsed and unstable in a large area and the dynamic disaster is easily induced. In this study, considering the fundamental deformation and failure effect of coal seam, the development law of the bed separation and the fractures under hard and thick magmatic rocks and the mechanism of breaking induced disaster of hard and thick magmatic rocks are studied by similar simulation tests. The results of the study are as follows: (1) The similar material ratio of coal seam is obtained by low-strength orthogonal ratio test of similar materials of coal seam, that is, cement:sand:water:activated carbon:coal = 6:6:7:1.1:79.9. (2) The magmatic rocks play a role in shielding the d... [more]
Novel Frequency Swapping Technique for Conducted Electromagnetic Interference Suppression in Power Converter Applications
Ming-Tse Kuo, Ming-Chang Tsou
March 26, 2019 (v1)
Subject: Other
Keywords: conduction electromagnetic interference (EMI), frequency jittering, frequency swapping, quasi-resonant flyback (QRF)
Quasi-resonant flyback (QRF) converters have been widely applied as the main circuit topology in power converters because of their low cost and high efficiency. Conventional QRF converters tend to generate higher average conducted electromagnetic interference (EMI) in the low-frequency domain due to the switching noise generated by power switches, resulting in the fact they can exceed the EMI standards of the European Standard 55022 Class-B emission requirements. The presented paper develops a novel frequency swapping control method that spreads spectral energy to reduce the amplitude of sub-harmonics, thereby lowering average conducted EMI in the low-frequency domain. The proposed method is implemented in a control chip, which requires no extra circuit components and adds zero cost. The proposed control method is verified using a 24 W QRF converter. Experimental results reveals that conducted EMI has been reduced by approximately 13.24 dBμV at 498 kHz compared with a control method wi... [more]
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