Sharif Digital Repository

Operation of two different optical fiber sensor designs for distance measurements with a good sensitivity, resolution, and wide dynamic range is reported. Design is based on the intensity modulation due to reflectance measurement from a target surface. Two reported designs are fabricated with a triple-fiber assembly, in which one uses a double-transmitter, while another one uses a double-receiver fiber design. Reflection signals from different targets are tested with these sensors and results for the mirror and A4 paper surfaces are described. The response curve for both experiments starts from a near zero level, shows a maximum at a certain distance and gradually drops to the background... 

Design and operation of an opto-mechanical system employing a double-cell is reported here for the color liquid reflection studies. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected from the sample to a photodetector. By scanning the double-fiber assembly in one-direction reflection properties of different color liquids are investigated. Reflection signals depend on the cell surface structure and the cell filled material. Two sets of flat/cylindrical cells made of almost similar glass materials are used for this... 

Design and operation of an opto-mechanical system for surface profiling are reported in this study. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected off the surface to a photodetector. By scanning the double-fiber assembly in one-direction, reflection properties of different curved surfaces are investigated. Reflection signals for the cylindrical surfaces made with different curvatures and materials are reported. In order to see the effect of the surface material, for a fixed radius cylinder, the surface is... 

Design and operation of three different optical designs based on the light intensity modulation for investigation of the humidity effects on the air index of refraction are described. The measurement variable is the transmitted power, which depends on the refractive index of the medium in the path of a fiber-to-fiber optical design. Three different probes (probe #1, #2, and #3) are tested in which probe #1 and probe #2 can also check the presence of water or any other transparent liquid in the gap between the two axial fibers. Performances of the new systems are tested as a refractive index monitoring mean and experimental results are given. The variations of the modulated powers as... 

Intensity profiles for the single and fiber-to-fiber designs are described.Profiles for different arrangements using the red light LED and LED laser are compared. The near field output distribution bandwidths are compared and there is a close relation between the bandwidth and the source light, fiber size, and the fiber gap separation  

Progress of carbon nanotube (CNT) research and development in terms of published papers and patents is reported. Developments concerning CNT structures, synthesis, and major parameters, in terms of the published documents are surveyed. Publication growth of CNTs and related fields are analyzed for the period of 2000-2010. From the explored search term, "carbon nanotubes", the total number of papers containing the CNT concept is 52,224, and for patents is 5,746, with a patent/paper ratio of 0.11. For CNT research in the given period, an annual increase of 8.09% for paper and 8.68% for patents are resulted. Published papers for CNT, CVD and CCVD synthesis parameters for the period of 2000-2010... 

Fiber core size determination from power transmission modulation for different fibers is reported.Three different fibers are tested and power variations of lateral displacement of the second fiber are obtained (lamp, red LED). From the averaged bandwidths of the response curves the core diameter of each fiber is determined. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1225-1229, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25967 Copyright  

The resistance and capacitance values of the water samples are measured by using two different cell probes (length 10 cm and 5 cm) and a measuring module. Measured conductivities for the different water samples are compared where the lowest conductivity is obtained for the distilled water (3.28 μS/cm) and the highest value is for the boiled water 325.91 μS/cm. Using the measured series resistance values, and by knowing the frequency (1 kHz), the imaginary part of permittivity value is also determined. The imaginary part of the permittivity for the distilled water with the long cell probe is about 0.524 × 10 -7 F/m (for the short probe is 0.523 × 10-7 F/m) while for the boiled water sample is... 

In this study surface profiling is performed by using a scanning system and an opto-pair fiber design. In this method one fiber transmits the laser light to the target and the second one transmits back the light reflected off the target to a photodetector. The monitoring of the reflected light signal from a surface is accomplished by converting the photon light into an electric signal and measuring by a digital multimeter. By scanning an object mounted on a XYZ-translational stage the reflection signal profiles are obtained for plane and curved surfaces. Output reflection signal variations in the X-, Y-, and Z-directions are measured for different plane and cylindrical surfaces and compared.... 

This study presents an up to date progress of the national and international laser research and developments. The number of scientific publications and accepted patents are considered as a figure of merit and based on these numbers the growth pace for the period of 1990-2003 is investigated. The share of top nations in scientific publications and in particular laser publications in term of their Gross Domestic Product (GDP) is presented. Four countries including the USA, Japan, Germany and China have a laser publication contribution of 58.9% while the rest of the world including (189) countries contribute 41.1%. However, for the case of accepted patents, which are the more important factor,... 

The goal of this paper is to describe essential criteria for image analysis of planar laser-induced fluorescence (PLIF) signals. A new image file conversion method is introduced and some typical illustrative examples showing the potential applications of the method in PLIF experiments are presented. Analysis of row, column, and total pixel counts, and the dark noise related to an image are discussed. Image segmentation, averaging and background correction can be easily done by the reported method. In our analysis it is straightforward to inspect the pixel counts and check for saturation of the camera sensors. It is also feasible to obtain a particular row or column for interpretation and it... 

In many industries there is a need for a flexible system, which is capable of picking up some objects of various shapes, weights, and colors with arbitrarily position and orientation. Such system requires recognition and guiding sub-systems. The recognition system includes target function for the recognition sub-system and relation between object characteristics and recognition target. The laser sensor system can be used for such object recognition. Wire-based telemetry and control systems can cause many problems in shop floors and factories, and so there has been a strong growth of interest in wireless guidance like vehicles equipped with laser guiding and navigation systems. This article... 

Design and operation of an opto-mechanical sensor for mass measurements is reported. This device uses a pair of optical fibers and a reflecting coated lens. The light intensity modulation is based on the relative motion of the lens due to a given mass with respect to the optical fibers. The modulated intensity because of the weighing mass has been measured by using a digital voltmeter. A full-range sensitivity of about 11.5 mV/g for a dynamic range of 80 g is obtained. A mass resolution of better than 0.25 g has been measured with this device. The measured output response is checked against the expected theoretical one and a general agreement observed. A comparison with similar experimental... 

Design and operation of an optical fiber device for temperature sensing and thermal expansion measurement are reported. The modulated intensity has been measured by using a pair of 450 μm core fiber, one acting as the source and the other one as receiving fiber. In this design, the light intensity modulation is based on the relative motion of the optical fibers and a reflective coated lens. By using displacement calibration data for this sensor, the linear thermal expansion of the aluminum rod is determined. This sensor shows an average sensitivity of about 11.3 mV/°C for temperature detection and 7 μm/°C for thermal expansion detection. Device resolution for a linear expansion measurement... 

In this article, a full temporal and spatial description of discharge for pure nitrogen gas in a nearly uniform electric field is reported. Results of simulation given provide a full understanding of the discharge at different stages of the ionization process. Effects of the primary energetic electrons and the secondary electrons are clearly shown at each stage of the ionization growth being followed in the discharge gap. Presented are the local electric field distribution and temporal behavior of the streamers at each point of the discharge medium along with the secondary processes affecting ionization growth  

An optical guiding system is modeled and the signal processing and its operation are studied. Our model is based on the principle that two moving objects are considered, in which one is the moving robot, and the other one is the sought object. The reported system is capable of detecting and measuring the relative motion of the target, and, in response generating electrical signal capable of directing and guiding the vehicle on the shop floor. In this way, the respected robot or vehicle using such a device can maintain its aim on the related target scene at all times. The proposed system offers a higher degree of accuracy and reliability since it considers the state-of-art electronic and... 

The present study describes the result of an improved numerical method applied to our two-electrode spark gap discharge. The time evolution of the ionization current is obtained and mechanisms describing ionization growth in discharge are presented. The effect of E/N has been investigated by changing either the applied gap voltage or by varying the nitrogen gas pressure. Some fluctuations in the exponential ionization growth are noticed which are related to the secondary ionization by the cathode photoelectric emission. Simulated snapshots were obtained that clearly show the image of electron avalanches traversing the discharge gap. My results are compared with other computational methods...