Sharif Digital Repository

A new approach to evaluation of the data hiding capacity of digital video is presented in this paper. The paper reconsiders the conventional capacity estimation algorithms, in which the video signal is taken as a sequence of still images, that result in an exaggerated upper bound of hiding capacity or a much higher value than the actual embedding capacity. The proposed method for the capacity estimation is based on the human visual model in temporal domain, which leads to a more realistic, tighter bound for video capacity. In this method, according to temporal characteristic of every frame, a visibility based coefficient is extracted that is used to determine the hiding capacity. The maximum... 

A method based on direct immersion solid-phase microextraction (DI-SPME) coupled with high performance liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection (HPLC-PIF-FD) was developed to extract three pyrethroid insecticides, i.e. cyfluthrin, cypermethrin, and flumethrin from water samples. A sol-gel based coating fiber using 3-(trimethoxysilyl propyl) amine as precursor was prepared and used for the extraction of the pyrethroids from groundwater samples. A post-column photochemical reactor was designed and constructed for the derivatization of these environmentally important pollutants to increase their fluorescence... 

A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the... 

Nowadays users of the Web are encouraged to generate content on the Web by themselves. Weblogs are the most popular tools to do this. In fact Weblogs are one kind of social networks and they are one of the most important components in Web 2.0. Blogs are often situated within a Blog community of similar interest. These communities can be a useful way for readers to access space slice of millions of Weblogs. In this paper we introduce a new algorithm to infer communities based on their link structure. This algorithm uses self organizing maps to identify communities among Weblogs. The link pattern of each Weblog is the input for SOM. © 2007 IADIS  

Solar pond is a type of solar collector that stores solar energy in the form of heat. The solar pond can be used as a low-temperature heat source for electricity generation. In this paper, to find the most suitable power cycle for power generation from the solar pond, the performance of the Organic Rankine Cycle (ORC), Trilateral Flash Cycle (TFC) and their modified forms with an open feed liquid heater and an internal heat exchanger for different working fluids was investigated. Water was considered as the heat transfer fluid which transfers the stored heat from the solar pond to the working fluid of the cycle. The results indicate that in all cases, the energy and exergy efficiency of the... 

A novel amino-functionalized polymer was synthesized using 3-(trimethoxysilyl) propyl amine (TMSPA) as precursor and hydroxy-terminated polydimethylsiloxane (OH-PDMS) by sol-gel technology and coated on fused-silica fiber. The synthesis was designed in a way to impart polar moiety into the coating network. The scanning electron microscopy (SEM) images of this new coating showed the homogeneity and the porous surface structure of the film. The efficiency of new coating was investigated for headspace solid-phase microextraction (SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Effect of different... 

Reflection appears as a layer that partly covers the original image. This phenomenon may cause failure in extracting information from images of reflecting objects. This work presents an automated technique for determining of reflection area as well as its severity to define reliability of extracted information. This is done by analyzing histogram and objects found in the image. We present a strong detector based on combining the results of these two procedures. We presented new reflection detection algorithm and a new method to find a good threshold value for converting any image into a binary image. The average reflection detection accuracy of the proposed algorithm is more than 95% for... 

A head-space solid-phase microextraction (HS-SPME) method coupled to GC-MS was developed to extract fentanyl from human plasma. The protein binding was reduced by acidification and, eventually, the sample was deproteinized with trichloroacetic acid. The parameters influencing adsorption (extraction time, temperature, pH and salt addition) and desorption (desorption time and temperature) of the analyte on the fibre were investigated and validated for method development. The developed method proved to be rapid, simple, easy and inexpensive and offers high sensitivity and reproducibility. Linear range was obtained from 0.1 ng/ml to 2 μg/ml. The limit of detection was 0.03 ng/ml while an... 

A new method for digital video watermarking is presented in this paper. For data embedding we use 3-D ridgelet domain introduced by Helbert. The redundancy of this transform is substantial, so extraction of the hidden data is impossible in this domain. To overcome this problem, we introduce a modified ridgelet transform with little redundancy, and embed watermark in this domain. Experimental results show that this scheme is robust against collusion attack, frame cropping, frame swapping, frame dropping, noise attack and the MJPEG (Motion JPEG) compression