An investigation made on the rotor blade tip vortex through use of a Three Dimensional Laser Doppler Velocimetry(3D LDV) is described. The experiment is conducted with a 2 m in diameter model helicopter rotor. By a ...An investigation made on the rotor blade tip vortex through use of a Three Dimensional Laser Doppler Velocimetry(3D LDV) is described. The experiment is conducted with a 2 m in diameter model helicopter rotor. By a series of measurements near blade tip, the velocity field near blade tip is documented, and through which, the tip vortex rollup and development are presented. The radial distribution of instantaneous velocities at various levels above and under the rotor disc is also measured in this investigation. Using this distribution, the influence of the tip vortex from the preceding blade on the follow up blade is discussed.展开更多
A novel, simple, rapid, economic and hypersensitive method of measuring Cr3＋ is described in this paper. Cr3＋ could be oxidated to H2CrO6, which is extracted by n-C5H11OH, so a trace amount of chromium is measured d...A novel, simple, rapid, economic and hypersensitive method of measuring Cr3＋ is described in this paper. Cr3＋ could be oxidated to H2CrO6, which is extracted by n-C5H11OH, so a trace amount of chromium is measured directly by spectrometers, Sandra sensitivity is S=6.40×10^-3 ug.cm-2.展开更多
The objective of this work is to assess the radiation hazards associated gamma rays from building materials. Natural gamma rays activities of natural radionuclide represented mainly by three natural radioactive series...The objective of this work is to assess the radiation hazards associated gamma rays from building materials. Natural gamma rays activities of natural radionuclide represented mainly by three natural radioactive series ^238U, ^235U and ^232Th, and the primordial ^40K in the samples of building materials which consist of bricks, ceramics, marble and gypsum from different areas of eastern Algeria are measured using gamma ray spectrometry. The values of the activities of these radionuclides do not clearly reflect the radiation hazard associated with these materials. Therefore, the radium equivalent （Raeq） concentration is defined taking into account the effectiveness of these isotopes in creating the radiation hazard. Radium equivalent activities, external and internal hazard indices （Hex and Hin） are calculated from the activities of ^226Ra, ^232Th and ^40K for suitability of the materials.展开更多
This paper presents an innovative and low-cost approach for nondestructive fruit quality analysis. The specialized optical fiber sensor developed and presented in this paper used a monochromatic wavelength, rather tha...This paper presents an innovative and low-cost approach for nondestructive fruit quality analysis. The specialized optical fiber sensor developed and presented in this paper used a monochromatic wavelength, rather than a broad spectrum, to measure the intact carambola （star fruit） intrinsic quality, namely pH and firmness. The main objective of this research was to investigate the two optical fiber sensors used in this work, namely, the optical fiber red system （OF-RS） that operated with the peak sensitivity at 635 nm and the optical fiber near the infrared spectroscopy system （OF-NIRS） that operated with the peak sensitivity at 880nm. Both systems showed good accuracy in the pH and firmness measurement of the intact carambola with the correlation coefficient R over 0.75, and the measurement results were comparable with those of the commercial spectrometer. The best measurement results were obtained using OF-RS （pH： R = 0.876; the root mean square error （RMSE） = 0.211 pH; firmness： R = 0.872; RMSE = 0.909 kgf）.展开更多
The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. ...The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG; and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.展开更多
文摘An investigation made on the rotor blade tip vortex through use of a Three Dimensional Laser Doppler Velocimetry(3D LDV) is described. The experiment is conducted with a 2 m in diameter model helicopter rotor. By a series of measurements near blade tip, the velocity field near blade tip is documented, and through which, the tip vortex rollup and development are presented. The radial distribution of instantaneous velocities at various levels above and under the rotor disc is also measured in this investigation. Using this distribution, the influence of the tip vortex from the preceding blade on the follow up blade is discussed.
文摘A novel, simple, rapid, economic and hypersensitive method of measuring Cr3＋ is described in this paper. Cr3＋ could be oxidated to H2CrO6, which is extracted by n-C5H11OH, so a trace amount of chromium is measured directly by spectrometers, Sandra sensitivity is S=6.40×10^-3 ug.cm-2.
文摘The objective of this work is to assess the radiation hazards associated gamma rays from building materials. Natural gamma rays activities of natural radionuclide represented mainly by three natural radioactive series ^238U, ^235U and ^232Th, and the primordial ^40K in the samples of building materials which consist of bricks, ceramics, marble and gypsum from different areas of eastern Algeria are measured using gamma ray spectrometry. The values of the activities of these radionuclides do not clearly reflect the radiation hazard associated with these materials. Therefore, the radium equivalent （Raeq） concentration is defined taking into account the effectiveness of these isotopes in creating the radiation hazard. Radium equivalent activities, external and internal hazard indices （Hex and Hin） are calculated from the activities of ^226Ra, ^232Th and ^40K for suitability of the materials.
文摘为研究适用于高温环境下微珠结构激光合作目标的反射性能,根据微珠结构激光合作目标的回归反射理论,设计和建立了用于测量微珠结构激光合作目标反射性能的实验系统。该系统使用激光波长为532 nm,激光发散角为1.2 mrad,最大输出功率为300 m W的半导体抽运全固态激光器作为激光发射装置,使用海洋公司的USB2000+型光纤光谱仪作为回波信号的接收装置。通过改变激光器的输出功率、测量距离等实验条件,对微珠结构激光合作目标和碳纤维板基底的反射性能进行了实验测量,并对所测量的实验结果进行了数据分析,为深入研究微珠结构的激光合作目标提供了测量方法和数据参考。
文摘This paper presents an innovative and low-cost approach for nondestructive fruit quality analysis. The specialized optical fiber sensor developed and presented in this paper used a monochromatic wavelength, rather than a broad spectrum, to measure the intact carambola （star fruit） intrinsic quality, namely pH and firmness. The main objective of this research was to investigate the two optical fiber sensors used in this work, namely, the optical fiber red system （OF-RS） that operated with the peak sensitivity at 635 nm and the optical fiber near the infrared spectroscopy system （OF-NIRS） that operated with the peak sensitivity at 880nm. Both systems showed good accuracy in the pH and firmness measurement of the intact carambola with the correlation coefficient R over 0.75, and the measurement results were comparable with those of the commercial spectrometer. The best measurement results were obtained using OF-RS （pH： R = 0.876; the root mean square error （RMSE） = 0.211 pH; firmness： R = 0.872; RMSE = 0.909 kgf）.
文摘The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating （FBG） sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG; and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution.
