Ship hull form of the underwater area strongly influences the resistance of the ship. The major factor in ship resistance is skin friction resistance. Bulbous bows, polymer paint, water repellent paint （highly water-...Ship hull form of the underwater area strongly influences the resistance of the ship. The major factor in ship resistance is skin friction resistance. Bulbous bows, polymer paint, water repellent paint （highly water-repellent wall）, air injection, and specific roughness have been used by researchers as an attempt to obtain the resistance reduction and operation efficiency of ships. Micro-bubble injection is a promising technique for lowering frictional resistance. The injected air bubbles are supposed to somehow modify the energy inside the turbulent boundary layer and thereby lower the skin friction. The purpose of this study was to identify the effect of injected micro bubbles on a navy fast patrol boat （FPB） 57 m type model with the following main dimensions： L=2 450 ram, B=400 mm, and T=190 mm. The influence of the location of micro bubble injection and bubble velocity was also investigated. The ship model was pulled by an electric motor whose speed could be varied and adjusted. The ship model resistance was precisely measured by a load cell transducer. Comparison of ship resistance with and without micro-bubble injection was shown on a graph as a function of the drag coefficient and Froude number. It was shown that micro bubble injection behind the mid-ship is the best location to achieve the most effective drag reduction, and the drag reduction caused by the micro-bubbles can reach 6%-9%.展开更多
Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwellin...Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices;and forces for the reef model were measured by load cell.The results of flume experiments agree well with the numerical data.In addition,the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes,showing a more complicated flow structure than that of a stand-alone reef.Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef.The role of the reef in water flow is to reduce flow velocity and generate turbulence.展开更多
Multihull ships are widely used for sea transportation, and those with four hulls are known as quadramarans. Hull position configurations of a quadramaran include the diamond, tetra, and slice. In general, multihull v...Multihull ships are widely used for sea transportation, and those with four hulls are known as quadramarans. Hull position configurations of a quadramaran include the diamond, tetra, and slice. In general, multihull vessels traveling at high speeds have better hydrodynamic efficiency than monohull ships. This study aims to identify possible effects of various quadramaran hull position configurations on ship resistance for hull dimensions of 2 m length, 0.21 m breadth, and 0.045 m thickness. We conducted a towing test in which we varied the hull spacing and speed at Fr values between 0.08 and 0.62 and measured the total resistance using a load cell transducer. The experimental results reveal that the lowest total resistance was achieved with a diamond quadramaran configuration at Fr = 0.1-0.6 and an effective interference factor of up to 0.35 with S/L = 3/10 and R/L = 1/2 at Fr = 0.62.展开更多
Conventional manometry presents significant challenges,especially in assessment of pharyngeal swallowing,because of the asymmetry and deglutitive movements of oropharyngeal structures.It only provides information abou...Conventional manometry presents significant challenges,especially in assessment of pharyngeal swallowing,because of the asymmetry and deglutitive movements of oropharyngeal structures.It only provides information about intraluminal pressure and thus it is difficult to study functional details of esophageal motility disorders.New technology of solid high resolution impedance manometry(HRIM),with 32 pressure sensors and 6 impedance sensors,is likely to provide better assessment of pharyngeal swallowing as well as more information about esophageal motility disorders.However,the clinical usefulness of application of HRIM in patients with oropharyngeal dysphagia or esophageal dysphagia is not known.We experienced a case of Huntington's disease presenting with both oropharyngeal and esophageal dysphagia,in which HRIM revealed the mechanism of oropharyngeal dysphagia and provided comprehensive information about esophageal dysphagia.展开更多
Experimentally, the electron drag effect on carbon nanotube surface in flowing liquids was investigated. It was found that electric current could be generated in metallic carbon nanotubes immersed in the liquids. Carb...Experimentally, the electron drag effect on carbon nanotube surface in flowing liquids was investigated. It was found that electric current could be generated in metallic carbon nanotubes immersed in the liquids. Carbon nanotubes were synthesized on Si substrate by hot filament chemical vapor deposition. The experimental results showed that the flow-induced current on the surface of carbon nanotube films was closely depended on the flow rate, concentration, properties and temperature of liquids. The flow-induced current was increased with the increasing of flow rate, concentration and temperature of liquids. The obtained results were discussed in detail.展开更多
A new method of switched reluctance wind power generation position sensorless based on DFNN by FEA was proposed, Through current and magnetic linkage to get the angle of SRG rotor position, the nonlinear mapping of cu...A new method of switched reluctance wind power generation position sensorless based on DFNN by FEA was proposed, Through current and magnetic linkage to get the angle of SRG rotor position, the nonlinear mapping of cur- rent-magnetic linkage-angle was built, By training these sample data from FEA, the angle of SRG rotor position was replaced by the output of DFNN to achieve SRG position sensorless. Simulation results show that the error between actual rotor position and estimate rotor position is small; SRG can commutate with great accuracy; and the output voltage of SRG wind power system under variable wind speed is essentially constant.展开更多
The current mine safety monitoring system used can only get the air volume change of roadway placed air velocity transducers, as this change is caused by this roadway, or for other roadway, and fault source has one po...The current mine safety monitoring system used can only get the air volume change of roadway placed air velocity transducers, as this change is caused by this roadway, or for other roadway, and fault source has one point or more, which be- longs to the problem of fault source diagnosis for ventilation system. Ventilation system fault can be attributed to the variation of air resistance of branch in the entire network. If the changes of air resistance for each branch in ventilation system are ana- lyzed, then it is impossible to place air velocity transducers in every branch. Therefore, the problem of the minimum quantities and location for placing air velocity transducers should be mainly studied. The relationship of air resistance and air volume variation of matrix method has been proposed, which can reflect the variation relationship between the air volume of the branch and air resistance of the relevant branches. Fault roadway range library of ventilation network built to determine fault roadway range will cause air velocity to exceed the limit. Minimum and full coverage of distribution method has been proposed, and the concept of branch coverage degree and impact roadway range library has also been brought forword to get the macro-distribution of air velocity transducers.展开更多
Graphene sponge(GS) with microscale size, high mechanical elasticity and electrical conductivity has attracted great interest as a sensing material for piezoresistive pressure sensor. However, GS offering a lower limi...Graphene sponge(GS) with microscale size, high mechanical elasticity and electrical conductivity has attracted great interest as a sensing material for piezoresistive pressure sensor. However, GS offering a lower limit of pressure detection with high gauge factor, which is closely dependent on the mechanical and electrical properties and determined by the fabrication process, is still demanded. Here, γ-ray irradiation reduced GS is reported to possess a gauge factor of 1.03 kPa^–1 with pressure detection limit of 10 Pa and high stress retention of 76% after 800 cycles of compressing/relaxation at strain of 50%. Compared with the carbon nanotube(CNT) reinforced GS, the improved lower limit of pressure detection and gauge factor of the GS prepared by γ-ray irradiation is due to the low compression stress(0.9 kPa at stain of 50%). These excellent physical properties of the GS are ascribed to the mild,residual free, and controllable reduction process offered by γ-ray irradiation.展开更多
基金Supported by the Directorate for Research and Community Service,University of Indonesia(RUUI Research Laboratory 2010),Jakarta,Indonesia
文摘Ship hull form of the underwater area strongly influences the resistance of the ship. The major factor in ship resistance is skin friction resistance. Bulbous bows, polymer paint, water repellent paint （highly water-repellent wall）, air injection, and specific roughness have been used by researchers as an attempt to obtain the resistance reduction and operation efficiency of ships. Micro-bubble injection is a promising technique for lowering frictional resistance. The injected air bubbles are supposed to somehow modify the energy inside the turbulent boundary layer and thereby lower the skin friction. The purpose of this study was to identify the effect of injected micro bubbles on a navy fast patrol boat （FPB） 57 m type model with the following main dimensions： L=2 450 ram, B=400 mm, and T=190 mm. The influence of the location of micro bubble injection and bubble velocity was also investigated. The ship model was pulled by an electric motor whose speed could be varied and adjusted. The ship model resistance was precisely measured by a load cell transducer. Comparison of ship resistance with and without micro-bubble injection was shown on a graph as a function of the drag coefficient and Froude number. It was shown that micro bubble injection behind the mid-ship is the best location to achieve the most effective drag reduction, and the drag reduction caused by the micro-bubbles can reach 6%-9%.
基金Supported by the National Natural Science Foundation of China(Nos.31072246,31272703)
文摘Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef.Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices;and forces for the reef model were measured by load cell.The results of flume experiments agree well with the numerical data.In addition,the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes,showing a more complicated flow structure than that of a stand-alone reef.Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef.The role of the reef in water flow is to reduce flow velocity and generate turbulence.
基金sponsored by the Directorate of Research and Community Services,University of Indonesia(Hibah PUPT-Tambahan UI 2015)
文摘Multihull ships are widely used for sea transportation, and those with four hulls are known as quadramarans. Hull position configurations of a quadramaran include the diamond, tetra, and slice. In general, multihull vessels traveling at high speeds have better hydrodynamic efficiency than monohull ships. This study aims to identify possible effects of various quadramaran hull position configurations on ship resistance for hull dimensions of 2 m length, 0.21 m breadth, and 0.045 m thickness. We conducted a towing test in which we varied the hull spacing and speed at Fr values between 0.08 and 0.62 and measured the total resistance using a load cell transducer. The experimental results reveal that the lowest total resistance was achieved with a diamond quadramaran configuration at Fr = 0.1-0.6 and an effective interference factor of up to 0.35 with S/L = 3/10 and R/L = 1/2 at Fr = 0.62.
文摘Conventional manometry presents significant challenges,especially in assessment of pharyngeal swallowing,because of the asymmetry and deglutitive movements of oropharyngeal structures.It only provides information about intraluminal pressure and thus it is difficult to study functional details of esophageal motility disorders.New technology of solid high resolution impedance manometry(HRIM),with 32 pressure sensors and 6 impedance sensors,is likely to provide better assessment of pharyngeal swallowing as well as more information about esophageal motility disorders.However,the clinical usefulness of application of HRIM in patients with oropharyngeal dysphagia or esophageal dysphagia is not known.We experienced a case of Huntington's disease presenting with both oropharyngeal and esophageal dysphagia,in which HRIM revealed the mechanism of oropharyngeal dysphagia and provided comprehensive information about esophageal dysphagia.
文摘Experimentally, the electron drag effect on carbon nanotube surface in flowing liquids was investigated. It was found that electric current could be generated in metallic carbon nanotubes immersed in the liquids. Carbon nanotubes were synthesized on Si substrate by hot filament chemical vapor deposition. The experimental results showed that the flow-induced current on the surface of carbon nanotube films was closely depended on the flow rate, concentration, properties and temperature of liquids. The flow-induced current was increased with the increasing of flow rate, concentration and temperature of liquids. The obtained results were discussed in detail.
基金Supported by the National Natural Science Foundation of China （50977080） the Science ＆ Technology Department Project of Hunan Province （2010F J3116） the Education Department Project of Hunan Province （ 10A 114）
文摘A new method of switched reluctance wind power generation position sensorless based on DFNN by FEA was proposed, Through current and magnetic linkage to get the angle of SRG rotor position, the nonlinear mapping of cur- rent-magnetic linkage-angle was built, By training these sample data from FEA, the angle of SRG rotor position was replaced by the output of DFNN to achieve SRG position sensorless. Simulation results show that the error between actual rotor position and estimate rotor position is small; SRG can commutate with great accuracy; and the output voltage of SRG wind power system under variable wind speed is essentially constant.
文摘The current mine safety monitoring system used can only get the air volume change of roadway placed air velocity transducers, as this change is caused by this roadway, or for other roadway, and fault source has one point or more, which be- longs to the problem of fault source diagnosis for ventilation system. Ventilation system fault can be attributed to the variation of air resistance of branch in the entire network. If the changes of air resistance for each branch in ventilation system are ana- lyzed, then it is impossible to place air velocity transducers in every branch. Therefore, the problem of the minimum quantities and location for placing air velocity transducers should be mainly studied. The relationship of air resistance and air volume variation of matrix method has been proposed, which can reflect the variation relationship between the air volume of the branch and air resistance of the relevant branches. Fault roadway range library of ventilation network built to determine fault roadway range will cause air velocity to exceed the limit. Minimum and full coverage of distribution method has been proposed, and the concept of branch coverage degree and impact roadway range library has also been brought forword to get the macro-distribution of air velocity transducers.
基金the National Natural Science Foundation of China(21503064)Anhui Provincial Natural Science Foundation for support(1508085QE103)+3 种基金the Ministry of Science and Technology of China(2015CB351903)the 100 Talents Program of the Chinese Academy of Sciences,USTC Startupthe Fundamental Research Funds for the Central Universities(WK2060140003)iChEM
文摘Graphene sponge(GS) with microscale size, high mechanical elasticity and electrical conductivity has attracted great interest as a sensing material for piezoresistive pressure sensor. However, GS offering a lower limit of pressure detection with high gauge factor, which is closely dependent on the mechanical and electrical properties and determined by the fabrication process, is still demanded. Here, γ-ray irradiation reduced GS is reported to possess a gauge factor of 1.03 kPa^–1 with pressure detection limit of 10 Pa and high stress retention of 76% after 800 cycles of compressing/relaxation at strain of 50%. Compared with the carbon nanotube(CNT) reinforced GS, the improved lower limit of pressure detection and gauge factor of the GS prepared by γ-ray irradiation is due to the low compression stress(0.9 kPa at stain of 50%). These excellent physical properties of the GS are ascribed to the mild,residual free, and controllable reduction process offered by γ-ray irradiation.
