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حرية الوصول المقاله
1 - Impact of silica seeding and discharge voltage on plasma parameters at atmospheric pressure
Lekha Mishra Vijay Jha Bijoyendra NarayanThe interaction of cold plasma with heterogeneous catalysts has led to some peculiar behavior, especially with silica (SiO2) seeding in presence of 2% alumina (Al2O3). In this paper, we have measured plasma parameters in low temperature arc plasma. I - V characteristics أکثرThe interaction of cold plasma with heterogeneous catalysts has led to some peculiar behavior, especially with silica (SiO2) seeding in presence of 2% alumina (Al2O3). In this paper, we have measured plasma parameters in low temperature arc plasma. I - V characteristics of Langmuir probes are plotted using the data obtained from the experimental set up for single probe method in arc plasma at atmospheric pressure. It is revealed that the used seed modifies the electron temperature of the plasma appreciably while the temperature of the gas in the surrounding remains almost unchanged. The single probe characteristics have been utilized to measure the electron temperature, floating potential, Debye length and electron density. It is found that electron temperature decreases whereas electron density increases appreciably after seeding the arc plasma. The decrease in electron temperature and increase in electron density to 99.9% are observed after seeding the arc plasma with silica mixture as compared to those before seeding. Variations in plasma parameters such as electron temperature, electron density, plasma frequency and Debye length with discharge voltage are also plotted for the silica seeded arc plasma. تفاصيل المقالة -
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2 - Variational calculation with general density functional to solve the electronic Schrödinger equation directly for ground state: a recipe for self-consistent field solution
Sandor KristyanAbstractUsing orbital-free framework, a simple numerical optimization of the density functional for ground state electronic energy is described for any type of functional approximation, demonstrated via the example of linear combinations of homogeneous functionals of th أکثرAbstractUsing orbital-free framework, a simple numerical optimization of the density functional for ground state electronic energy is described for any type of functional approximation, demonstrated via the example of linear combinations of homogeneous functionals of the density. The numerical recipe is given and analyzed for solution: Originating from the linear dependence of nuclear-electron attraction functional on one-electron density (Vne[ρ0(r1)] = -ΣA = 1,…,MZA∫ρ0(r1)rA1-1dr1), and a quadratic LCAO approximation for ρ0, the optimization can be done with iterative use of lin-solver. This quadratic approximation, as simplest educated choice for ρ0, is compared and analyzed algebraically to the HF-SCF one in the Appendices. We call the attention that the introduction of a self-consistent field optimization of non-linear density functional is a new element in this part of the related, general theory. تفاصيل المقالة -
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3 - Effect of negative oxygen ions on the characteristics of plasma in a cylindrical DC discharge
Davoud Dorranian Mahsa AlizadehAbstractLangmuir probe measurements are performed in cylindrical dc glow discharge plasma. Plasma was generated in an evacuated glass tube, with circular plane disk electrodes. Measurements were carried out at different points along the axis of tube for different workin أکثرAbstractLangmuir probe measurements are performed in cylindrical dc glow discharge plasma. Plasma was generated in an evacuated glass tube, with circular plane disk electrodes. Measurements were carried out at different points along the axis of tube for different working pressures of pure argon and mixture of argon–oxygen gasses to obtain the plasma density and temperature as well as plasma and floating potentials. Variation of discharge potential as a function of discharge pressure for both plasmas is observed. It is shown that electron temperature, plasma potential, and floating potential in constant current mode and constant pressure are increased from cathode to anode on the axial points of the discharge tube, while electron density is decreased. To sustain the discharge process after adding oxygen to plasma, higher voltage is required since electrons are more energetic at lower density. تفاصيل المقالة -
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4 - Effect of negative ions on the characteristics of plasma in a cylindrical discharge
Farnaz Araghi Davoud DorranianAbstractThe effect of negative ions on the density, temperature, and potential of plasma in a direct current discharge regime has been studied experimentally. Nitrogen as an electronegative gas was used to produce negative ions in the plasma. Langmuir probe was employed أکثرAbstractThe effect of negative ions on the density, temperature, and potential of plasma in a direct current discharge regime has been studied experimentally. Nitrogen as an electronegative gas was used to produce negative ions in the plasma. Langmuir probe was employed to measure plasma parameters. Discharge was performed in an evacuated glass tube, with circular disk electrodes at different pressures. To obtain the spatial variation of plasma characters, measurements were done at different points on the axis of discharge tube. Argon and nitrogen gases were used as the working gas, and plasma current was kept constant at 5 mA during the experiments. Discharge voltage decreased sharply with increasing pressure for both argon and nitrogen plasmas; however, to sustain the discharge at constant current in nitrogen plasma, higher voltage was required in comparison with argon plasma. The plasma electron density was decreased from cathode to anode during the discharge process, while electron temperature was increased. Results confirm that nitrogen plasma contains negative ions, and discharge process is influenced by them noticeably. تفاصيل المقالة -
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5 - One-dimensional simulation of hydrogen production kinetic models by water vapor plasmolysis in a DBD plate reactor
Mostafa El-Shafie Shinji Kambara Yukio HayakawaAbstractThe results of one-dimensional time-dependent simulation modeling of hydrogen production from water vapor dissociation using non-thermal discharge plasma in a plate-type reactor were developed. Three different water vapor dissociation reaction mechanisms pathway أکثرAbstractThe results of one-dimensional time-dependent simulation modeling of hydrogen production from water vapor dissociation using non-thermal discharge plasma in a plate-type reactor were developed. Three different water vapor dissociation reaction mechanisms pathway models were simulated at a water vapor temperature of 573 K and same boundary conditions. The electron collision cross sections of electron water vapor were utilized based on the reaction mechanisms. The electron attachment and detachment processes were described in detail; additionally, the surface charge accumulation, recombination of charged species, positive and negative ions production and losses are considered. The electron density, electric field, electric potential, electron temperature and the hydrogen mass fraction are presented across the plasma discharge gap and over time. The first model was described as direct water vapor decomposition into their constituent’s elements hydrogen and oxygen molecules. It was revealed that the formed hydrogen molecules increased across the plasma discharge gap over time. In model II, the simulation reaction mechanisms pathway included products of H2O+, OH+, and O+ ions. It was found a significant change in the electric potential and electric field across the discharge gap due to the charged species inside the plasma gap. In model III, it was introduced H− radicals which controlled H atoms production by the electron detachment reaction. The most interesting results of these simulation models were the growing of hydrogen molecules across the plasma gap over time. Further, it was observed that the produced hydrogen mass fraction from model III was higher than model II and model I. تفاصيل المقالة -
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6 - بررسی و مقایسه عوامل موثر بر تغییرات اعداد هانسفیلد در اسکنرهای سی تی
آمنه عبداللهی قمی پرویز زبده سعید کریمخانی زندیهدف: با توجه به اهمیت همسانی اعداد CT در برنامههای تشخیصی و درمانهای رادیوتراپی سرطان، در این پژوهش عوامل موثر در میزان تغییرات اعداد هانسفیلد در اسکنرهای مختلف CT بررسی شده است تا جهت ارائه راهکارهای بهتر عملکردی در زمینه کالیبراسیون CT به منظور بهبود کیفیت سیستمهای أکثرهدف: با توجه به اهمیت همسانی اعداد CT در برنامههای تشخیصی و درمانهای رادیوتراپی سرطان، در این پژوهش عوامل موثر در میزان تغییرات اعداد هانسفیلد در اسکنرهای مختلف CT بررسی شده است تا جهت ارائه راهکارهای بهتر عملکردی در زمینه کالیبراسیون CT به منظور بهبود کیفیت سیستمهای کاربردی تشخیصی و درمانی و تاکید بر دقت و کنترل خطاهای حاصل از محاسبه دزهای برنامهریزهای درمان مفید واقع گردد.مواد و روشها: دادههای این پژوهش شامل اطلاعات کالیبراسیون دستگاههای سی تی در 10 مرکز مختلف کشور مستخرج از لیستهای آزمونهای کنترل کیفیت منتخب و مورد تأیید سازمان انرژی اتمی کشور بوده که صحّت عدد سی تی در آزمونهای اجرا شده مورد بررسی و تحلیل قرار گرفت.نتایج: ایجاد خطا و تغییر اعداد سی تی موجب تغییر در منحنی چگالی الکترونی عدد سی تی شده و نهایتاً در طراحی درمان و دز دریافتی بیمار اثر میگذارد.نتیجهگیری: میتوان با ارزیابی عوامل موثر بر خطای حاصل از روش سیستم طراحی درمان در تبدیل اعداد سی تی به دانسیته الکترونی بافتهای نرم، میزان خطا را به حداقل رساند. تفاصيل المقالة -
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7 - Adsorption of ozone molecules on AlP-codoped stanene nanosheet: A density functional theory study
Amirali AbbasiDensity functional theory calculations were carried out to investigate the structural and electronic properties of the adsorption of O3 molecules on AlP-codoped monolayers to fully exploit the gas sensing capability of these two-dimensional materials. Various adsorption أکثرDensity functional theory calculations were carried out to investigate the structural and electronic properties of the adsorption of O3 molecules on AlP-codoped monolayers to fully exploit the gas sensing capability of these two-dimensional materials. Various adsorption sites of O3 molecule on the considered nanosheets were examined in detail. The side oxygen atoms of the O3 molecule strongly bind to the tin atoms, and provide double contacting point between the nanosheet and O3 molecule. O3 adsorption on the Al-site of AlP-codoped structure is more favorable in energy than that on the pristine one. AlP-codoped stanene exhibits better semiconductor characteristics because of the band gap opening in the system. The total electron density plots show the charge distribution along the interacting side oxygen and tin atoms, which indicate the formation of chemical bonds between them. This formation of chemical bond was also evidenced by the projected density of states analysis. The large overlaps between the PDOS spectra of the oxygen and tin atoms exhibit the formation of chemical bonds between these atoms. The charge density difference calculations represent charge accumulation on the adsorbed O3 molecule. Our results thus suggest a theoretical basis for AlP-codoped stanene monolayer as efficient candidate for application in gas sensor devices. تفاصيل المقالة -
حرية الوصول المقاله
8 - Adsorption of ozone molecules on AlP-codoped stanene nanosheet: A density functional theory study
Amirali AbbasiDensity functional theory calculations were carried out to investigate the structural and electronicproperties of the adsorption of O3 molecules on AlP-codoped monolayers to fully exploit the gas sensingcapability of these two-dimensional materials. Various adsorption s أکثرDensity functional theory calculations were carried out to investigate the structural and electronicproperties of the adsorption of O3 molecules on AlP-codoped monolayers to fully exploit the gas sensingcapability of these two-dimensional materials. Various adsorption sites of O3 molecule on the considerednanosheets were examined in detail. The side oxygen atoms of the O3 molecule strongly bind to the tinatoms, and provide double contacting point between the nanosheet and O3 molecule. O3 adsorptionon the Al-site of AlP-codoped structure is more favorable in energy than that on the pristine one. AlPcodopedstanene exhibits better semiconductor characteristics because of the band gap opening in thesystem. The total electron density plots show the charge distribution along the interacting side oxygenand tin atoms, which indicate the formation of chemical bonds between them. This formation of chemicalbond was also evidenced by the projected density of states diagrams. The large overlaps between thePDOS spectra of the oxygen and tin atoms show the formation of chemical bonds between these atoms.The charge density difference calculations represent charge accumulation on the adsorbed O3 molecule.Our results suggest a theoretical basis for AlP-codoped stanene monolayer as efficient candidate forapplication in gas sensor devices. تفاصيل المقالة
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