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دسترسی آزاد مقاله
1 - Optical and structural characterization of CdSe:Eu films at different volumes of europium concentration.
Diemiruaye Jeroh Azubike Ekpunobi Donald OkoliCadmium selenide films were prepared at different volumes of dopant (Europium) concentration by electrostatic-spray-pyrolysis technique. Optical results reveal low absorption and reflection with a corresponding high transmission in the visible region. Strong blue-shift چکیده کاملCadmium selenide films were prepared at different volumes of dopant (Europium) concentration by electrostatic-spray-pyrolysis technique. Optical results reveal low absorption and reflection with a corresponding high transmission in the visible region. Strong blue-shift is observed for the band gap energy in all cases of growth, indicating quantum confinement effect. Scanning electron studies reveal relatively smooth surface with small-sized grains on the surface. XRD confirms the crystalline nature of the films having hexagonal (wurtzite) structure with reduction in crystallinity of the film at increased volume of dopant concentration. EDX analysis confirmed the growth of CdSe:Eu film. پرونده مقاله -
دسترسی آزاد مقاله
2 - Synthesis, characterization and Microwave Absorption Properties of Novel Hard-soft Ferrite and Polyaniline-loaded Nanocomposite
Tolou Pourashraf Mohammad Yousefi Saeid Shokri َAbbas Ahmadi Parviz Aberoomand AzarNanocomposites of hard-soft ferrites (SrFe12O19) (1-x)/(Ni0.4Mn0.2Zn0.4Fe2O4) x with x = 0.2, 0.4, 0.6,and 0.8 are synthesized by the auto-combustion sol-gel method. In-situ polymerization is used to create polyaniline and hard-soft ferrite nanocomposites. X-ray powder چکیده کاملNanocomposites of hard-soft ferrites (SrFe12O19) (1-x)/(Ni0.4Mn0.2Zn0.4Fe2O4) x with x = 0.2, 0.4, 0.6,and 0.8 are synthesized by the auto-combustion sol-gel method. In-situ polymerization is used to create polyaniline and hard-soft ferrite nanocomposites. X-ray powder diffractometers (XRD), field emission scanning electron microscopes (FESEM), Fourier transform infrared spectra (FTIR),vibrating sample magnetometers (VSM), and vector network analyzers (VNA) have all been used to evaluate the structure, morphology, magnetic properties, and microwave absorption ofnanocomposites. FT-IR spectra are used to confirm and validate the existence of both tetrahedral and octahedral complexes, as well as the interactions between polymer chains and hard and soft nanoparticles, which show that ferrite nanocomposites are coated with polymers. In hard-soft and polymeric nanocomposites, XRD analysis reveals the presence of pure hard and soft phase characteristics as well as PANI characteristics. SEM images show that the particles agglomerate in hard-soft composites as the soft phase rises as a result of being magnetic, and images for polymericcomposites show cohesive PANI particles that surround the hard-soft ferrite particle's surface.These findings demonstrate that PANI and hard-soft ferrites can be properly connected. VSM analysis revealed that by adding polymers, the magnetic properties of hard-soft composites dropped significantly due to the nonmagnetic effects of PANI. The VNA test shows that PANI/(SrFe12O19)0.4/(Ni0.4Mn0.2Zn0.4Fe2O4)0.6 exhibits optimized reflection loss from -1.84 to -16.53 in the X-Band (8-12.5 GHz frequency range) when compared to (SrFe12O19)0.4/ (Ni0.4Mn0.2Zn0.4Fe2O4) 0.6 with a matching thickness of 3 mm. پرونده مقاله -
دسترسی آزاد مقاله
3 - بررسی جذب CO در نانوساختارهای کبالت با استفاده از تئوری تابعی چگالی (DFT): فازهای کریستالی مکعبی و هگزاگونال
فاطمه دولتی علی نخعی پور وحیدرضا داروگر زهره دولتی وجیهه افخمیدر این مقاله، انرژی جذب و ساختار مونوکسید کربن (CO) در فازهای کریستالی مکعبی(fcc) و هگزاگونال (hcp) در نانو ذرات کبالت با استفاده از محاسبات تابعی چگال (DFT) مورد ارزیابی قرار گرفته است. روند کلی فعالیت سنتز فیشر تروپش (FTS) بر روی کاتالیزورهای کبالت با مقایسه انرژی جذب چکیده کاملدر این مقاله، انرژی جذب و ساختار مونوکسید کربن (CO) در فازهای کریستالی مکعبی(fcc) و هگزاگونال (hcp) در نانو ذرات کبالت با استفاده از محاسبات تابعی چگال (DFT) مورد ارزیابی قرار گرفته است. روند کلی فعالیت سنتز فیشر تروپش (FTS) بر روی کاتالیزورهای کبالت با مقایسه انرژی جذب مورد بررسی قرار گرفت. با توجه به محاسبات، کاتالیزورهای کبالت در فازhcp، بازده و کارایی بهتری را نسبت به فاز فلزی fcc نشان می دهد. انرژی جذب CO در سطوح مختلف کبالت و همچنین انرژی فعال سازی جذب CO در تک لایه (1ML) در موقعیت عمودی (top) نسبت به اتم کبالت درفازهای کریستالی مکعبی و شش ضلعی نانوساختارهای کبالت محاسبه شد. نتایج نشان داد که بیشترین مقدار انرژی جذب در فازهای کریستالی fcc نسبت به hcp است. در نتیجه انرژی پایین جذب CO در موقعیت top کبالت در hcp می تواند فعالیت بالاتر این کاتالیست را نسبت به فازهای دیگر آن در واکنش FTS توضیح دهد. پرونده مقاله -
دسترسی آزاد مقاله
4 - A Way to Reduce Effects of Packet Loss in Video Streaming Using Multiple Description Coding
Mahboobe Shabanyan Ehsan AkhtarkavanMultiple description (MD) coding has appeared to be an attractive technique to decrease impact of network failures and increase the robustness of multimedia communications. Very common model of this technique is multiple-description lattice vector quantization, which is چکیده کاملMultiple description (MD) coding has appeared to be an attractive technique to decrease impact of network failures and increase the robustness of multimedia communications. Very common model of this technique is multiple-description lattice vector quantization, which is the best choice for robust data transmission over the unreliable network channels. However, MD coinciding lattice vector quantizer (MDCLVQ) is not considered discrete network conditions, so in this scheme, all videos are received or are not received. In this paper, this scheme is implemented in real network environment. So, raw video will be send in various packet, packets send independently and packets lose independently. The possibility of lossing all packets together is close to zero. Our object for increasing of resistance transfer in error- prone communication channels are used. This technique has been tested for standard videos "Akiyo", "Carphone", "Miss-America" and "Foreman". This results show that the quality of the reconstructed videos from the average PSNR values of the central decoder and the side decoders has been reached to grate degree, so increases error resilience over error-prone communication channels. پرونده مقاله -
دسترسی آزاد مقاله
5 - A Method to Reduce Effects of Packet Loss in Video Streaming Using Multiple Description Coding
Mahboobe Shabaniyan Ehsan AkhtarkavanMultiple description (MD) coding has evolved as a promising technique for promoting error resiliency of multimedia system in real-time application programs over error-prone communicational channels. Although multiple description lattice vector quantization (MDCLVQ) is a چکیده کاملMultiple description (MD) coding has evolved as a promising technique for promoting error resiliency of multimedia system in real-time application programs over error-prone communicational channels. Although multiple description lattice vector quantization (MDCLVQ) is an efficient method for transmitting reliable data in the context of potential error channels, this method doesn’t consider discreteness of network so that losing all descriptions is highly possible. It means all videos may be removed. In this study, we have implemented scheme of MDCLVQ in real-time environment of network, in a method that, raw video (i.e. video with no standard encoding (like MPEG)) is transmitted through independent packets inside of network. This technique leads in low or close to zero loss of all packets. Our purpose is to increase error resiliency and reliable data transmission in error-prone channels. The technique has been tested on some videos sources of Akiyo, Carphone, Foreman and Miss-America. The experimental results indicate that quality of reconstructed videos are substantially improved in terms of central and side PSNR. پرونده مقاله -
دسترسی آزاد مقاله
6 - X-ray peak broadening analysis in LaMnO3+δ nano-particles with rhombohedral crystal structure
Ahmad GholizadehIn this work, structural and magnetic properties of LaMnO3+δ compound prepared by citrate precursor method and annealed in presence of oxygen are investigated. The structural characterization of LaMnO3+δ by X-ray powder diffraction and using X’pert pac چکیده کاملIn this work, structural and magnetic properties of LaMnO3+δ compound prepared by citrate precursor method and annealed in presence of oxygen are investigated. The structural characterization of LaMnO3+δ by X-ray powder diffraction and using X’pert package and Fullprof program is evidence for a rhombohedral structure (R-3c space group) confirmed by FTIR measurement. The magnetic measurements show a super-paramagnetic behavior of LaMnO3+δ due to low values of coercive field and romance magnetization and also high value of saturation magnetization. In addition, a comparative study of the crystallite size of the compounds obtained from powder XRD is reported. The Williamson-Hall analysis, size-strain plot and Halder-Wagner methods were used to study the individual contributions of crystallite sizes and lattice micro-strain on isotropic line broadening of all the reflection peaks of the LaMnO3+δ compound. The results show the Halder-Wagner method is more accurate, with all data points touching the fitting line better than the other methods. The crystallite sizes estimated from XRD (30.86 nm) and particle size estimated from TEM method (36 nm) and also the magnetic core size (33.6 nm) estimated from magnetic measurement agree well, while a little difference reflects a spherical shape of the nanoparticles. پرونده مقاله -
دسترسی آزاد مقاله
7 - Variable band-gap Sr-hexagonal ferrites on carboxylated graphene oxide composite as an efficient photocatalytic semiconductor
Masomeh Taghipour Mohammad Yousefi Reza Fazaeli Masoud Darvish GanjiIn this study, Sr Gdx Fe(12 –x) O19 nanostructures (x= 0, 0.2(3% Gd), 0.4 (6%Gd),0.6(9%Gd), 0.8 (12%Gd)) were synthesized by self-combustion sol-gel method and then calcined at the temperature of for 3 h. This compound was then composited with functionalized graph چکیده کاملIn this study, Sr Gdx Fe(12 –x) O19 nanostructures (x= 0, 0.2(3% Gd), 0.4 (6%Gd),0.6(9%Gd), 0.8 (12%Gd)) were synthesized by self-combustion sol-gel method and then calcined at the temperature of for 3 h. This compound was then composited with functionalized graphene oxide (GO) for the photocatalytic degradation of Enrofeloxacin. FESEM, EDS, XRD, and FTIR analysis were employed to investigate the particle size, elemental composition, morphological structure, functional groups determination and structural composition of the samples. VSM, BET-BJH, TGA-DTA, DRS and zeta potential analysis were also used to assess the magnetic properties, surface area, thermal stability, band-gap determination and suspension stability of the specimens, respectively. For evaluation of performance, photocatalytic degradation of Enrofeloxacin (an antibiotic that is widely used for domestic animals) is performed. The results showed that the 3% and 6% Gd-doped composites had the highest efficiencies in the photocatalytic reaction.This research reports the successful synthesis of SrGdxFe12-xO19/GO-COOH composites and its characterization by various techniques. The results indicated that SrGdxFe12-xO19/GO-COOH composite can be employed as an applicable candidate for the photodegradation of ENR antibiotic drug from pharmaceutical industry effluent as well as the water resources. Analysis of the results by statistical software based on the response surface method showed that the prolongation of the radiation time and catalyst mass, as well as pH reduction, can enhance the efficiency of ENR photodegradation. By increasing the pollutant concentration, however, the degradation efficiency declined. پرونده مقاله
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