مجله علوم و فناوری های پدافند نوین
سال سوم شماره 1 (پیاپی 7، بهار 1391)

Scintillators are materials which exhibit scintillation)luminescence property(when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate. POPOP, 1,4-bis- (5-phenyl-oxazolyl-2)-benzene, is one of the organic scintillators that have applications in detecting the nuclear rays and charged particles. Herein, the synthesis of POPOP have been reconsidered and some synthetic methods have been investigated and a new and efficient method for the preparation of POPOP is presented. An intermediate was synthesized by the reaction of 2-aminoacetophenone with terphethaloyl dichloride. The oxazole rings in the final product (POPOP) were then formed by the reaction of this intermediate with concentrated sulfuric acid.

Presence of inhomogeneous environment and interfering targets in practical radar systems, cause a reduction at CA-CFAR performance in either detection probability of target or false alarm ratio of system. Hence EX-CFAR detector implies a soft thresholding, in which the excision parameter (β) plays a key role to determine a criterion for eliminating unordinary values at window of noise power estimation. Consequently in this paper the excision parameter have been surveyed and analyzed for different values of false alarm probabilities and the optimum ones are extracted. Since the considered radar of this paper was medium range poor resolution radar system, probability density function of K has been assumed in clutter modeling.Accordingly the shape and scale parameters are estimated for the assumed method. Consequently the performance of EX-CFAR implying the estimated values is evaluated and compared with CA-CFAR in circumstances of facing with 2, 3 or 4 interfering targets using MATLAB simulations. In these simulations, mono pulse detection was deliberated.

The use of trackers and seeker systems has an important role in the electronic warfare. A simple and inexpensive method is based on the use of reticle devices in the trackers. But the most limitation factor for using the reticle systems is resulting from their sensitivity to false targets such as flares. There are various methods to separate the real target from flares such as dual-band detection method and blind source separation (BSS) method. In this paper, we present new algorithms of separating the real target and flares based on the BSS method. For this reason, we utilize fm reticle, and by using a beam splitter in the modified system, the main signals are extracted from the mixed signals (including the target and flare signals). The time-domain and frequency-domain algorithms are designed and compared in this approach.

Audio Segmentation has got a widespread application in underwater signal processing specially observation of passing objects using their acoustic signals and also in audio annotation of a recorded meeting, which also used by intelligence services that is one of instances of passive defense.Audio Segmentation is the process of partitioning an audio stream into regions each of which corresponds to only one audio source or one speaker.There are various methods for speaker segmentation the most common methods of which are based on BIC criteria. These methods needs heavy statistical computations and are very time consuming.The main goal of this paper is to propose a new audio segmentation method based on pith frequency with acceptable accuracy along with a higher computation speed than BIC-based methods. This algorithm is about 2.4 times faster than the BIC-based segmentation an about %1 higher than that of the BIC-based method in accuracy.

Free space optic communications has received extensive interest over the past decade, and many potential applications for this technology have been suggested. Among various digital modulation formats for wireless optical links like OOK, PPM, DPIM and MDPIM, DPIM has got advantages in terms of transmission capacity, bandwidth requirement, power requirement and receiver design. DPIM displays a higher transmission capacity by eliminating all the unused time slots from within each symbol in PPM; and decreased bandwidth requirement and afford the possibility to introduce some redundancy into the code for security. Design of PPM receiver has more complexity compared to OOK and DPIM since both slot and symbol synchronizations are required at the receiver. In this study, DPIM Modem is implemented on FPGA and its Functionality is compared with PPM Modem.

Shigella dysentery producing shigatoxin (subunits A, B) is one of the most important human pathogenic intestinal bacteria. Entering to epithelial cells, the toxin inhibits protein synthesis leading to cell death. In spite of great investigation on vaccine production against S. dysentery studying to achieve significant stxA recombinant protein still remains important. The objective of this study was designing mutant stxA gene and expressing protein production as vaccine candidate against stx for further immunization studies. Three stxA mutant gene including (E167Q-A231D-G234E) were designed and the synthetic gene in pET28a plasmid was obtained and confirmed by PCR. Thereafter the plasmid was transformed into the host cell E. coli BL21 after which gene expression was optimized and protein purity assay was then performed. Preliminary studies led to mutant stop gene design after which it was confirmed by synthetic plasmid and PCR. The expression of this gene in E. coli BL21 host cell was then optimized and resulted in forming large amount of protein inclusion bodies. Purification of inclusion bodies and protein solubilization was performed with a combinatorial method. Regarding the mechanism of shigatoxin effect and simultaneous use of two different mutations in this gene, less toxicity is expected in comparison with previous mutants as vaccine candidate, posing a better vaccine candidate.

In parallel with advances in robots hardware, the motion planning science has become increasingly indispensable and complicated, and enables robots to enhance their capabilities in applications where the presence of humans is impractical or hazardous. The covering and minesweeping operations of outdoor areas are examples of such applications. This paper deals with the problem of covering and minesweeping of unknown environments by multiple mobile robots which have cooperative interactions. For searching the space, the new method of multi sensor-based random trees (MSRT) is developed, and for planning the robots’ paths toward the scattered items and their collection, a mathematical model similar to the multiple traveling salesman problem is proposed, which together with the k-means clustering, the A* search, and the visibility graph techniques plans the route of each robot. Comparisons with the counterpart mathematic model solved to optimality showed that the proposed method produces suboptimal solutions in much shorter computational times.

The immobilization of antibodies is one of the most important steps for the construction of biological diagnostic systems. Cellulose and PVDF are commonly used as supports for antibody immobilization despite their low efficiency. This study investigates the activation process of these supports in order to improve their immobilization capability. So as to apply a more operative immobilization of antibody, cellulose and PVDF were initially treated by cyanogen bromide and methanol respectively. In cellulose support which was treated by cyanogen bromide, the –OH groups constructed a cyclic imidocarbamate which is disposed to react with the amine groups of the antibody. In PVDF which was activated by methanol, hydrophilic property and surface adsorption were increased. After the activation procedure, anti-human antibody was immobilized on both supports and the immobilization quality was evaluated. The results showed that the applied changes on the supports had promising effects on the antibody capturing capacity. It was also shown that antibodies were more immobilized on the cellulose supports in comparison to PVDF. The activation processes can alter the physiochemical features of the support such as capillarity, flexibility, surface charges and delicacy, which may intensively influence the quality of immobilization.

Geophysical methods are used as locating tools and reconnaissance methods. Gravity method is used to locate underground structures and cavities using density contrast. In this paper, methods of airborne gravimetry and airborne gravity, gradiometry, corrections and their modern instruments have been presented. In order to evaluate the accuracy and efficiency of these methods, a developed program have been used. Artificial data of an underground structure have been provided by forward modeling for earth surface at different altitudes and then noise were added to data. Finally the results of the simulation and the accuracy of the presented instruments for different altitudes have been compared. In conclusion effective solutions to mitigate the probable detection of buried structures and the improvement of camouflage processes against airborne reconnaissance are provided.