Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized test...Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized testers have been developed.This paper summarized some of the impact testers reported in open literatures and the emphasis was placed on the equipment structures,functions,technical parameters,advantages and disadvantage,etc.Some key issues about the development of the testers such as kinematic energy input mode,fixture design,combined load testing,sensor and data acquisition were discussed.Finally,the problems and prospects in the research and development of impact testers for spot welds were pointed out.展开更多
A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is compos...A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is composed of a gear pump, a reversing valve, a relief valve and other components. By using the steady penetration method, the permeability and non-Darcy flow β factor of broken coal samples under five different porosity levels were measured, the grain diameters of the coal samples were selected as 2.5-5 mm, 5-10 mm, 10-15 mm, 15-20 mm, 20-25 mm and 2.5-25 ram, respectively. After measuring the permeability under each porosity, the overfall pressure of the relief valve continuously increased until the coal sample was broken down. In this way, the flow type of liquid inside the broken coal samples changed from seepage to pipe flow. The correlation between breakdown pressure gradient （BPG） and porosity was analyzed, and the BPG was compared with the pressure gradient when seepage instability occurred. The results show that, ①the non-Darcy flow β factor was negative before broken coal samples with six kinds of diameters were broken down; ②the BPG of coal samples with a grain size of 2.5-25 mm was lower than that of the others; ③ the BPG of coal samples with a single diameter under the same porosity increased as the grain size increased; ④ the BPG could be fitted by an exponential function with porosity, and the exponent decreased as the grain size increased for coal samples with a single diameter; ⑤ the BPG was slightly less than the seepage instability pressure gradient. The change in liquid flow type from seepage to pipe flow could be regarded as the performance of the seepage instability.展开更多
AIM:To evaluate the effectiveness of our proposed bowel preparation method for colon capsule endoscopy.METHODS:A pilot,multicenter,randomized controlled trial compared our proposed "reduced volume method"(gr...AIM:To evaluate the effectiveness of our proposed bowel preparation method for colon capsule endoscopy.METHODS:A pilot,multicenter,randomized controlled trial compared our proposed "reduced volume method"(group A) with the "conventional volume method"(group B) preparation regimens.Group A did not drink polyethylene glycol electrolyte lavage solution(PEGELS) the day before the capsule procedure,while group B drank 2 L.During the procedure day,groups A and B drank 2 L and 1 L of PEG-ELS,respectively,and swallowed the colon capsule(PillCam COLON capsule).Two hours later the first booster of 100 g magnesium citrate mixed with 900 mL water was administered to both groups,and the second booster was administered six hours post capsule ingestion as long as the capsule had not been excreted by that time.Capsule videos were reviewed for grading of cleansing level,RESULTS:Sixty-four subjects were enrolled,with results from 60 analyzed.Groups A and B included 31 and 29 subjects,respectively.Twenty-nine(94%) subjects in group A and 25(86%) subjects in group B had adequate bowel preparation(ns).Twenty-two(71%) of the 31 subjects in group A excreted the capsule within its battery life compared to 16(55%) of the 29 subjects in group B(ns).Of the remaining 22 subjects whose capsules were not excreted within the battery life,all of the capsules reached the left side colon before they stopped functioning.A single adverse event was reported in one subject who had mild symptoms of nausea and vomiting one hour after starting to drink PEG-ELS,due to ingesting the PEG-ELS faster than recommended.CONCLUSION:Our proposed reduced volume bowel preparation method for colon capsule without PEG-ELS during the days before the procedure was as effective as the conventional volume method.展开更多
Low voltage ride through (LVRT) capability has become more and more an issue for newly integrated wind turbines. The LVRT programs described in this paper developed field tests for newly installed wind turbines on win...Low voltage ride through (LVRT) capability has become more and more an issue for newly integrated wind turbines. The LVRT programs described in this paper developed field tests for newly installed wind turbines on wind farms in Northeast China. It is therefore different from other papers that only validate LVRT control strategies through running computer software simulations. To examine a single wind turbine's LVRT capability, the wind turbine's terminal voltage dip was realized by using a grid voltage dip emulator, which was located on the 690 V side of the generator transformer. In this paper, by artificially making various grid faults, the dynamic behavior of DFIG and PMSG wind turbines are analyzed and compared, control strategies such as active/passive crowbar and chopper protection schemes are verified, and new active/reactive power compensation methods are investigated and compared.展开更多
Nano-metric magnesium silicate and zinc silicate with particle size of about 50-70nm were prepared in water by the method of chemical deposition. The antiwear and friction reducing abilities of the nano-silicates, as ...Nano-metric magnesium silicate and zinc silicate with particle size of about 50-70nm were prepared in water by the method of chemical deposition. The antiwear and friction reducing abilities of the nano-silicates, as well as their composites with oleic acid tri-ethanolamine （OATEA）, were evaluated on a four-ball friction tester. The topographies and tribochemical features of the worn surfaces were analyzed by scanning electron microscope （SEM） and X-ray photoelectron spectroscope （XPS）. Results show that nano-silicates alone provide poor antiwear and friction reducing abilities in water, but exhibits excellent synergism with OATEA in reducing friction and wear. The synergism in reducing friction and wear between nano- silicates and OATEA does exist almost regardless of particte sizes and species, and may be attributed, on one hand, to the formation of an adsorption film of OATEA, and, on the other hand, to the formation oftribochemical species of silicon dioxide and iron oxides on the friction surfaces. Tribo-reactions and tribo-adsorptions of nano-silicates and OATEA would produce hereby an effective composite boundary lubrication film, which could efficiently enhance the anti-wear and friction-reducing abilities of water.展开更多
The compound dry cleaning principle is briefly described.A beneficiation test on South African coal was conducted using a model compound dry cleaning apparatus.Excellent results were obtained and the optimum operating...The compound dry cleaning principle is briefly described.A beneficiation test on South African coal was conducted using a model compound dry cleaning apparatus.Excellent results were obtained and the optimum operating parameters were determined.They are：an amplitude of 3.0 mm,a motor frequency of 47.5 Hz,an air volume of 50%,a transverse angle of 7°,and a longitudinal angle of-2°.These conditions yield a clean coal containing 11%ash and a coal production of 75%.The organic efficiency,η,is 95.86%.These results show that the South African coal can be separated effectively by compound dry cleaning,which will popularize the compound dry cleaning method.展开更多
The performance of adjustable head fall mixer is studied in a pilot experiment. Experimental results indicate that the dispersal efficiency increases with the space between grids and mixing pipe, which could be up to ...The performance of adjustable head fall mixer is studied in a pilot experiment. Experimental results indicate that the dispersal efficiency increases with the space between grids and mixing pipe, which could be up to 96%. When the flow rate increases more than 31%, the dispersal efficiency decreases a little but still above 96%. It is demonstrated that special coagulant injection head makes significant Contribution to improving the mixer efficiency. The almost same turbidity of sedimentation effluent could be achieved with less coagulant, thus 30% chemical can be saved. Dissolved oxygen increases 2.5 mg/L in the mixing unit, which will benefit the following processes.展开更多
Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry slid...Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.展开更多
文摘Impact testing is a primary method to evaluate the impact property of resistance spot welding,which is an important quality index in automotive industry.For testing impact properties of spot welds,many customized testers have been developed.This paper summarized some of the impact testers reported in open literatures and the emphasis was placed on the equipment structures,functions,technical parameters,advantages and disadvantage,etc.Some key issues about the development of the testers such as kinematic energy input mode,fixture design,combined load testing,sensor and data acquisition were discussed.Finally,the problems and prospects in the research and development of impact testers for spot welds were pointed out.
基金Supported by the National Natural Science Foundation of China （50974107） the University Graduate Research and Innovation Project in Jiangsu Province （CXZZI2_0924）+1 种基金 the Applied Basic Research Project of Yancheng Institute of Technology （XKR2010010） the State Key Laboratory Open Foundation of Deep Geomechanics and Underground Engineering of China University of Mining and Technology （SKLGDUEK1014）
文摘A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is composed of a gear pump, a reversing valve, a relief valve and other components. By using the steady penetration method, the permeability and non-Darcy flow β factor of broken coal samples under five different porosity levels were measured, the grain diameters of the coal samples were selected as 2.5-5 mm, 5-10 mm, 10-15 mm, 15-20 mm, 20-25 mm and 2.5-25 ram, respectively. After measuring the permeability under each porosity, the overfall pressure of the relief valve continuously increased until the coal sample was broken down. In this way, the flow type of liquid inside the broken coal samples changed from seepage to pipe flow. The correlation between breakdown pressure gradient （BPG） and porosity was analyzed, and the BPG was compared with the pressure gradient when seepage instability occurred. The results show that, ①the non-Darcy flow β factor was negative before broken coal samples with six kinds of diameters were broken down; ②the BPG of coal samples with a grain size of 2.5-25 mm was lower than that of the others; ③ the BPG of coal samples with a single diameter under the same porosity increased as the grain size increased; ④ the BPG could be fitted by an exponential function with porosity, and the exponent decreased as the grain size increased for coal samples with a single diameter; ⑤ the BPG was slightly less than the seepage instability pressure gradient. The change in liquid flow type from seepage to pipe flow could be regarded as the performance of the seepage instability.
基金Supported by Foundation for Promotion of Cancer Research by Ministry of Health,Labor and Welfare in Japan
文摘AIM:To evaluate the effectiveness of our proposed bowel preparation method for colon capsule endoscopy.METHODS:A pilot,multicenter,randomized controlled trial compared our proposed "reduced volume method"(group A) with the "conventional volume method"(group B) preparation regimens.Group A did not drink polyethylene glycol electrolyte lavage solution(PEGELS) the day before the capsule procedure,while group B drank 2 L.During the procedure day,groups A and B drank 2 L and 1 L of PEG-ELS,respectively,and swallowed the colon capsule(PillCam COLON capsule).Two hours later the first booster of 100 g magnesium citrate mixed with 900 mL water was administered to both groups,and the second booster was administered six hours post capsule ingestion as long as the capsule had not been excreted by that time.Capsule videos were reviewed for grading of cleansing level,RESULTS:Sixty-four subjects were enrolled,with results from 60 analyzed.Groups A and B included 31 and 29 subjects,respectively.Twenty-nine(94%) subjects in group A and 25(86%) subjects in group B had adequate bowel preparation(ns).Twenty-two(71%) of the 31 subjects in group A excreted the capsule within its battery life compared to 16(55%) of the 29 subjects in group B(ns).Of the remaining 22 subjects whose capsules were not excreted within the battery life,all of the capsules reached the left side colon before they stopped functioning.A single adverse event was reported in one subject who had mild symptoms of nausea and vomiting one hour after starting to drink PEG-ELS,due to ingesting the PEG-ELS faster than recommended.CONCLUSION:Our proposed reduced volume bowel preparation method for colon capsule without PEG-ELS during the days before the procedure was as effective as the conventional volume method.
文摘Low voltage ride through (LVRT) capability has become more and more an issue for newly integrated wind turbines. The LVRT programs described in this paper developed field tests for newly installed wind turbines on wind farms in Northeast China. It is therefore different from other papers that only validate LVRT control strategies through running computer software simulations. To examine a single wind turbine's LVRT capability, the wind turbine's terminal voltage dip was realized by using a grid voltage dip emulator, which was located on the 690 V side of the generator transformer. In this paper, by artificially making various grid faults, the dynamic behavior of DFIG and PMSG wind turbines are analyzed and compared, control strategies such as active/passive crowbar and chopper protection schemes are verified, and new active/reactive power compensation methods are investigated and compared.
基金supported by the National Natural Science Foundation of China (No. 50275147)the Program for New Century Excellent Talents in Chinese University (No. NCET-04-1002)
文摘Nano-metric magnesium silicate and zinc silicate with particle size of about 50-70nm were prepared in water by the method of chemical deposition. The antiwear and friction reducing abilities of the nano-silicates, as well as their composites with oleic acid tri-ethanolamine （OATEA）, were evaluated on a four-ball friction tester. The topographies and tribochemical features of the worn surfaces were analyzed by scanning electron microscope （SEM） and X-ray photoelectron spectroscope （XPS）. Results show that nano-silicates alone provide poor antiwear and friction reducing abilities in water, but exhibits excellent synergism with OATEA in reducing friction and wear. The synergism in reducing friction and wear between nano- silicates and OATEA does exist almost regardless of particte sizes and species, and may be attributed, on one hand, to the formation of an adsorption film of OATEA, and, on the other hand, to the formation oftribochemical species of silicon dioxide and iron oxides on the friction surfaces. Tribo-reactions and tribo-adsorptions of nano-silicates and OATEA would produce hereby an effective composite boundary lubrication film, which could efficiently enhance the anti-wear and friction-reducing abilities of water.
基金financially supported by the National Natural Science Foundation of China(Nos.90510002 and 50921002)the Fundamental Research Funds for the Central Universities (China University of Mining and Technology)(No.2010ZDP01A06).
文摘The compound dry cleaning principle is briefly described.A beneficiation test on South African coal was conducted using a model compound dry cleaning apparatus.Excellent results were obtained and the optimum operating parameters were determined.They are：an amplitude of 3.0 mm,a motor frequency of 47.5 Hz,an air volume of 50%,a transverse angle of 7°,and a longitudinal angle of-2°.These conditions yield a clean coal containing 11%ash and a coal production of 75%.The organic efficiency,η,is 95.86%.These results show that the South African coal can be separated effectively by compound dry cleaning,which will popularize the compound dry cleaning method.
文摘The performance of adjustable head fall mixer is studied in a pilot experiment. Experimental results indicate that the dispersal efficiency increases with the space between grids and mixing pipe, which could be up to 96%. When the flow rate increases more than 31%, the dispersal efficiency decreases a little but still above 96%. It is demonstrated that special coagulant injection head makes significant Contribution to improving the mixer efficiency. The almost same turbidity of sedimentation effluent could be achieved with less coagulant, thus 30% chemical can be saved. Dissolved oxygen increases 2.5 mg/L in the mixing unit, which will benefit the following processes.
基金Project(2013GK3021)supported by the Science and Technology Plan of Hunan Province,ChinaProject supported by Young Teacher Growth Plan of Hunan University,China
文摘Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.
