عبدالله اسلامی مجد

Due to the limitations of conventional biological identification methods, spectroscopic methods, including laser induced breakdown spectroscopy, have been used to characterize the genus, species and strains of different bacteria in the static phase of growth. Due to the increading importance of biological problems, the characterization, detection and classification of bacterial specimens has been considered by researchers in the military, industrial and medical fields. In this paper, in order to monitor the changes in the elemental structure of bacteria in the growth process, the constituent elements of the two phases of exponential and static growth of Escherichia coli were studied and compared based on this spectroscopic method. In this experiment, Nd: YAG laser with 100 mJ pulse energy, spectrometer and CCD detector were used. The industrial strain of gram-negative Escherichia coli BL21 bacteria was selected. Bacteria were selected at three different times (2.5, 4 and 6 hours after inoculation) during the growth process in broth, at optical density of 0.4 and 0.8 (exponential growth phase) and optical density of 1.2 (Static growth phase), respectively, and after dry freezing, under pressure has been pressed into tablets. Considering the chemical structure of Escherichia coli, the elements of phosphorus, carbon, calcium, sodium, magnesium, potassium, oxygen, nitrogen and hydrogen were considered in the sample. The results showed that Escherichia coli bacteria in the growth process have different patterns of recognizable elemental composition in its structure in the growth process. It is predicted that due to the change in the composition of structural elements of bacteria in growth phases, the use of this spectroscopic method to identify bacteria will be dependent on the growth phase. The results of this study showed that this method can play an effective role in the development of polyphasic methods to indentify bacteria, determine the composition of the culture medium as well as optimizing and evaluating the production conditions in this industrial strain.

In this paper, a quasi-optical millimeter wave imaging antenna at central frequency of 94 GHz in W-band is designed. The designed imaging system requires resolution less than 30 mm at distance of 5 meters to recognize metal objects. This passive system consists of a combination of a dielectric lens (primary optics) to focus the radiation and a pyramidal horn (secondary optics) with open metal walls to properly direct and couple the focal radiation to the detector. The general parameters of this system are calculated using the geometrical optics method. Then the combination of Gaussian beam method and ABCD ray transfer matrix is used to analyze the lens antenna to find the location and size of the feeding horn. The powerful optical design software ZEMAX was used to design the lens and to verify the design results based on ray tracing. The designed dielectric lens is made of High Density Polyethylene (HDPE) with a diameter of 650 mm. Then, an optimized pyramidal horn with gain of 18.9 dB at center frequency of 94 GHz is designed. The simulation of the horn and investigation of its results performed using the FEKO and CST commercial softwares. The simulation results of the pyramid horn antenna indicate that its combination with dielectric lens is appropriate and the hybrid method (geometrical optics, Gaussian beam and ABCD matrix) to design the quasi-optical system, including the lens and the horn antenna for imaging with considered requirements, is accurate, simple and efficient.

In this paper, a Gaussian corrugated profile horn is designed, simulated and compared with a Gaussian profile horn with flat wall, at central frequency of 94 GHz. The proposed horn antenna consists of a corrugated section(mode converter and phase section) and a Gaussian profile section. The Gaussian profile Horn Antenna provides a smooth transition from waveguide to aperture, which improves matching between antenna and free space. This ensures better matching, better radiation pattern, more bandwidth and increases overall system efficiency. The corrugated horn also has low edge diffraction, improved pattern symmetry, and reduced transverse polarization, because these corrugations create same boundary conditions for electric and magnetic fields. The  symmetry pattern on the E and H orthogonal planes, the broad bandwidth as well as low sidelobes of this designed corrugated Gaussian profile horn, make it a good representative for use as a feed in millimeter wave imaging system in W band.

Laser guidance, is one of the most common methods in guided weapons. Due to the high precision of this method and its spot-shaped collision ability, it is widely used in modern warfare. The main part of these weapons is laser seeker, which can guide the  weapons to hit the target, based on the beams reflected from it. As a defensive action toward these weapons, and in order to deceive and distract the weapons route from its main paths and orientation toward the false target, a second reflective laser can be used. In this article, in order to achieve the specifications of the deceptive laser, first, the behavior of laser-guided weapons detector is simulated, then the detector testing system is designed and implemented. Based on simulations and tests, information on the dimensions, power, and time of laser beam decoding was obtained as follows. Changing the laser beam's dimensions of deception relative to the main beam has no effect on the detector's performance. To deceive the laser-guided weapon detector, only the laser beam power should increase the deception to the original laser beam.The more the laser beam decrypts in the early stages of the attack, the more likely it is to deception the operation. In the case where the power of the main beam and the deception beam is equal, the total deviation of the detector depends on the average deviation of each of the beams. If the laser beam's ratio of deception to the original laser beam is tripled, the detector will be more affected by the deception laser. 1- Changing the dimension of the deception spot rather than that of main spot has no effect on the performance of the detector.2-In order to deceive the laser- guided missile detector, the power of deception spot should only increase with the power of the main spot.3-If sending the deception spot takes place in the early stages of the attack, the deception operation is more likely to succeed. 4-In case the power of the main spot and deception are equal, the total deviation of the detector depends on the average deviation of each of the spots relative to the detector center. 5- If the power of deception spot is more than three times as much as that of the main spot, the detector is further affected by the deception spot.

Liquid drop suspension in another fluid occurs in many natural processes. Applying electric field has shown a promising outlook for the control of motion, deformation, breakup and guidance of the drops. In this study, the dynamic response of a liquid drop suspended in another fluid across two conducting electrodes held at different electrical potentials has been simulated. In this regard, the effects of electric potential, electrical conductivity and relative permittivity have been studied. According to results, an increase in electric potential and conductivity leads to increasing trend in drop deformation whereas this trend converts into an ascending-descending pattern due to increase in electrical permittivity. An insight into the flow patterns inside and outside the drop shows that the positioning of a liquid drop in an external electric field in addition to drop polarization results in an electric field induced within the drop which causes the creation of vortices inside the drop. Magnitude of electrical conductivity and permittivity factors compared to each other apparently affect the accumulation area of electrical charges on the drop surface which in turn determines the circulating direction of vortices within the drop. Increasing electric field intensity due to an increase in electrical potential or change in magnitude of other physical properties would fortify the electric charge on the drop surface escalating drop deformation towards drop breakup. In this condition, the electrical polarization in addition to drop prolation causes jet exit from which a continuous line of droplets is emerged until the total dissipation of the drop.

In this paper, a powerful contrast enhancement algorithm based on the histogram equalization, called triple dynamic clipped histogram equalization (TDCHE) is introduced. The proposed method consists of four main processes including partitioning, clipping, mapping and equalization. At first, the input image histogram is partitioned into three portions with a same number of pixels. Next, the histogram clipping process is performed by comparing the clipped threshold level with the average intensities occurred on each sub-histogram. Then, each sub-histogram is mapped to a new dynamic range using simple calculations and finally, equalization process of each histogram is independently accomplished. The proposed TDCHE technique is presented to achieve multiple objectives of maximum average information content (entropy), enhancement ratio control and maintaining the reasonable brightness. In addition, this method leads to a natural enhancement in the output image by providing sharp images, while preserving maximum details far from unnatural phenomena such as intensity saturation and noise enhancement. Evaluation of the proposed TDCHE method performance in terms of information content as well as visual quality shows perceived superiority of the proposed algorithm in comparison to the previously presented methods based on histogram equalization.

In this paper the effect of baffle and opto-mechanical vanes to control and reduce stray lights in a satellite remote sensing camera is investigated. For this purpose, the optical system is modeled in ZEMAX software and then conical and cylindrical housing models were designed with TracePro software. In next step, an opto-mechanical baffle with length of 100 mm and 13 internal vanes is designed. The baffle is designed so that in addition to satisfying the requirements of the system, its dimensions and number of vanes were minimum and FOV is preserved. Using of suitable housing, baffle and vanes eliminated stray lights at great angles and undesirable field of view was received to 9 degrees in conical model and 14 degrees in cylindrical model. Also, simulation results show that residual stray lights attenuated up to 10-5 times of entrance power.

In this paper, stray lights in optical system of remote sensing satellite camera is simulated. For this purpose, stray lights, sources of production and their destructive effects on the image quality is studied. Moreover, mechanisms to deal with these unwanted lights are presented. Then, the effect of optical housing and surface coatings on the performance of stray light in satellite camera, has been studied by the results of the simulation. Finally an optimal design includes a set of different techniques for improving the performance of the considered camera was selected. Simulation results show that by this method, at large angles, stray lights can be completely eliminated whereas at angles near the FOV, stray lights intensities can be very much reduced namely up to 100000 times of their original intensity without almost no serious disturbance in the camera’s field of view.

In this paper, the impacts of air, argon, helium and neon ambient gases under different gas pressures on radiations, emphasizing in the signal to radiation background and the expansion of laser induced plasma from laser metal interaction have been experimentally studied using spectroscopy, probe beam absorption, and scattering methods. The results show that the plasma radiations and its expansion behavior depend strongly on the ambient gas presure. The highest intensity of the copper spectral lines occurred in argon, neon, air, and helium, respectively. For all gases, by increasing the gas pressure from 5 to 100 mbar the plasma spectral radiation increases and then it saturates at the higher gas pressure. The continuum radiation also increases with the pressure and has the highest value for Ar, air, Ne and He gases, respectively. Plasma in He, Ne, air and Ar has the best singnal to backgrourd (S/B) ratio, respectively, and decreases with the pressure. The probe beam absorption and scattering results have also been compared with the Sedov-Taylor strong shock wave model. The maximum speed of the plasma plume expansion, occurred near the target surface under 750 mbar gas pressure, and was determined for helium to be about 25200 m/s, and through neon, air and argon gases, amounted to about 15625, 13900 and 11860 m/s, respectively, as they reduced significantly when they were far from the target surface and reached 2550, 1000, 700 and 690 m/s at 6 mm from the target for helium, neon, air and argon, respectively.

In this paper we describe a designed and implemented tester system for laser warning system.This warning system detects coded laser beams and decodes those that is used in laser guidance systems. This tester is able to generate laser coded pulses and decode received pulses and compare them. Experiments have shown that by this tester, we can check the ability of the laser warning systems in laser code detection and regenerate those codes. This system has a suitable accuracy for fault detection in laser warning systems

Electrospray is a branch of the scientific area of electrohydrodynamics which is based on electrical charging of liquids. The electrospray governing equations are a combination of hydrodynamic and electrostatic equations to which the addition of liquid breakup process escalates their complexity. This research work aims at developing a numerical solver to simulate the electrospray process in an emitter-disc configuration using Heptane as a working liquid under various electrical potentials. The simulation results in comparison with CFD and experimental data show good agreements both quantitatively and qualitatively. The results clearly have captured the formation of liquid flow profiles at the emitter exit demonstrating various electrospray modes. These modes initiate a microdripping mode at the lowest voltage, i.e. 3.5kV, prompting consecutively to spindle and pulsating cone-jet modes and ending in a stable cone-jet mode at the highest charging voltage, i.e. 6.5kV. In addition, it is also observed that the liquid cone and the vortex shaped within it would shrink as an increase in the electric potential is imposed. Although the increase in electric potential results in rise of the maximum magnitudes of electric field and velocity, the electric charge accumulation at all electric potential values occurs on the outer surface of the liquid flow implying its electrical conductivity.

An emulsion is a mixture of two immiscible liquids in which one liquid is dispersed in the form of small drops in the other liquid. The liquid in the form of droplets is called discrete phase whereas the other liquid is termed as a continuous phase. One of the common methods for emulsification is based on using microfluidic devices. Currently, the study of flow in microfluidic devices is highly regarded due to having many applications in various fields including droplet generation in relation with the standard and quality of human life. In this study, the process of droplet generation in microfluidic flow-focusing devices with orthogonal and intersecting flows has been simulated. The effects of viscosity and flow rate of discreted and continuous phases on droplet generation process have been investigated. According to simulation results, with increasing the flow rate of discreted phase (Qd) at a fixed continuous phase leads to the increment of droplet size whereas an increas in the flow rate of continuous phase (Qc) at a fixed discreted phase results in smaller droplet size. Moreover, for a constant Qc/Qd ratio, regardless of whether discrete or continuous phase flow rate is fixed, the equal droplet size is achieved. The higher viscosity of the discrete phase provides a larger droplet size whereas an increase in the viscosity of continuous phase leads to a smaller droplet size. The simulation results in comparison with experimental results show a good agreement confirming the accuracy of the method.

Milk and dairy products in many parts of the world constitute a major part of the human diet. This nutrient is composed of various elements such as calcium, potassium, chlorine, phosphorus, magnesium, zinc, etc. In animal nutrition, some heavy and dangerous metals like lead, arsenic and cadmium are transmitted through animal feed to the milk. The purpose of this study is introducing Laser Induced Breakdown Spectroscopy (LIBS) method for identifying and determining the element concentrations in pasteurized and raw cow milk. This research was done on six types of milk from different milk factories, and raw milk from a dairy industry in 2013. Each of these milks was analyzed 7 times by using LIBSCAN100 system and Plasus Specline software. In this research, the mean concentration of five major elements (calcium, phosphor, potassium, magnesium, and sodium), four partial elements (zinc, copper, and Iron), and three heavy metals (lead, cadmium, and arsenic) was determined. The variations of mean concentration of different elements in the pasteurized samples are as follows: Ca: [1000-11000µg/g], K: [0-13000 µg/g], Mg: [100-3000 µg/g], P: [0-1800 µg/g], Na: [200-3000 µg/g], Zn: [300-28100 µg/g], Cu: [100-10600 µg/g], Se: [1-113 µg/g], Fe: [100-8900 µg/g], Cd: [0.110-0.690 µg/g], Pb: [0.1-0.84 µg/g], As: [0-0.860 µg/g]. In this research, a new high speed non-destructive analytical method with no need to initial preparation is introduced. The results of analyze showed that the concentrations of nutrient elements are close to RDI factor, and the concentrations of toxic elements are under the PTWI threshold.

Background and Cereals are the most important components of a healthy diet. Rice is one of the most common consumed grains in the world and a staple food of people in everyday meals. This study aimed at introducing a novel analytical approach in investigation of harmful metals and necessary elements in some types of Iranian rice by using Laser Induced Breakdown Spectroscopy (LIBS) method. Six types of consumed rice produced in different parts of the country have been collected from the market in 2013. All types of rice have been analyzed for seven times using LIBSCAN100 system and then spectra recorded have been analyzed by Plasus Specieline software. In this study، necessary elements and harmful metals have been analyzed in all samples. The average concentrations of zinc، phosphorus، iron، potassium، calcium، fluorine، chromium (III)، and magnesium were 93. 660mg/kg، 87. 666mg/kg، 348mg/kg، 379. 166mg/kg، 343. 66 mg/kg، 22mg/kg، 24. 848mg/kg 1071. 833mg/kg، respectively. This average content for harmful metals were 6. 095mg/kg for lead، 0. 773mg/kg for mercury، 0. 963mg/kg for nickel، 2. 391mg/kg for chromium (VI)، and 0. 940mg/kg for arsenic. No samples were found with cadmium. The results indicate that، the concentration of magnesium was higher in necessary elements and that Isfahan Lenjan rice contained higher content of necessary elements. Chromium (VI) was the most common harmful metal among all samples. Furthermore، the local Tarom rice was found to be the safest in all samples. Laser Induced Breakdown Spectroscopy technique could be used as a fast، nondestructive، multi elemental analyzer that does not need initial preparation.