In this study,the effect of micron-sized titanium and aluminum addition on the microstructural,mechanical and work-hardening behavior of pure Mg is investigated.Pure Mg reinforced with 10%Ti and 10%Ti-1%Al particulate...In this study,the effect of micron-sized titanium and aluminum addition on the microstructural,mechanical and work-hardening behavior of pure Mg is investigated.Pure Mg reinforced with 10%Ti and 10%Ti-1%Al particulates were synthesized through semi-powder metallurgy route followed by hot extrusion.Semi-powder metallurgy appears to be promising approach for the synthesis of Mg based composite,as it is free of ball milling.Tensile results indicate that the direct addition of micron-sized 10wt.%titanium particulates to pure Mg,caused an improvement in elastic modulus,0.2%yield strength,ultimate tensile strength,and failure strain(+72%;+41%;+29%;and+79%respectively).The addition of micron-sized 10wt.%titanium particles along with 1.0wt.%Al particles to pure Mg,resulted in an enhancement in elastic modulus,0.2%yield strength,ultimate tensile strength,and failure strain(+74%;+56%;+45%;and+241%respectively).Besides tensile test,Vickers hardness and work-hardening behavior of prepared composites were also examined.Impressive failure strain of Mg-10Ti-1Al composite can be attributed to the better compatibility of Ti particulates with Mg due to presence of alloying element Al.展开更多
A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy(OES).The s...A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy(OES).The samples of AISI 304 are nitrided for different treatment times under optimum conditions.The treated samples were analyzed by X-ray diffraction(XRD) to explore the changes induced in the crystallographic structure.The XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice.A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time(h).The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.展开更多
A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features o...A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes,impedance measurements have been performed and compared with equivalent circuit models.The measured impedance data is found to be in good agreement with simulated data.展开更多
The carburizing of titanium (Ti) is accomplished by utilizing energetic ion pulses of a 1.5 kJ Mather type dense plasma focus (DPF) device operated in methane discharge. X-ray diffraction (XRD) analysis confirms...The carburizing of titanium (Ti) is accomplished by utilizing energetic ion pulses of a 1.5 kJ Mather type dense plasma focus (DPF) device operated in methane discharge. X-ray diffraction (XRD) analysis confirms the deposition of polycrystalline titanium carbide (TIC). The samples carburized at lower axial and angular positions show an improved texture for a typical (200)TIC plane. The Williamson-Hall method is employed to estimate average crystallite size and microstrains in the carburized Ti surface. Crystallite size is found to vary from - 50 to 100 nm, depending on the deposition parameters. Microstrains vary with the sample position and hence ion flux, and are converted from tensile to compressive by increasing the flux. The carburizing of Ti is confirmed by two major doublets extending from 300 to 390 cm^-1 and from 560 to 620 cm^-1 corresponding to acoustic and optical active modes in Raman spectra, respectively. Analyses by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS) have provided qualitative and quantitative profiles of the carburized surface. The Vickers microhardness of Ti is significantly improved after carburizing.展开更多
Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples w...Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction (XRD) to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase (TN) owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth (μm). The results showed clear evidence of surface changes with substantial increase in surface hardness.展开更多
We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a st...We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing(FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission.展开更多
We study the behavior of cooperative multiplayer quantum games [Q.Chen,Y.Wang,J.T.Liu,and K.L.Wang,Phys.Lett.A 327 (2004) 98; A.P.Flitncy and L.C.L.Hollcnberg,Quantum Inf.Comput.7 (2007) 111] in thepresence of decoher...We study the behavior of cooperative multiplayer quantum games [Q.Chen,Y.Wang,J.T.Liu,and K.L.Wang,Phys.Lett.A 327 (2004) 98; A.P.Flitncy and L.C.L.Hollcnberg,Quantum Inf.Comput.7 (2007) 111] in thepresence of decoherence using different quantum channels such as amplitude damping,depolarizing and phase damping.It is seen that the outcomes of the games for the two damping channels with maximum values of decoherence reduce tosame value.However,in comparison to phase damping channel,the payoffs of cooperators are strongly damped underthe influence amplitude damping channel for the lower values of decoherence parameter.In the case of depolarizingchannel,the game is a no-payoff game irrespective of the degree of entanglement in the initial state for the larger valuesof decoherence parameter.The decoherence gets the cooperators worse off.展开更多
我们使量子化由使用一个纯起始的状态的最一般的形式调查纯、混合的 evolutionarily 稳定的策略(S 字) 的存在的鹰鸽子比赛。一个例子被认为拉比较在之间古典并且比赛的量版本。我们最一般的起始的量状态的选择使我们能使比赛对称或不...我们使量子化由使用一个纯起始的状态的最一般的形式调查纯、混合的 evolutionarily 稳定的策略(S 字) 的存在的鹰鸽子比赛。一个例子被认为拉比较在之间古典并且比赛的量版本。我们最一般的起始的量状态的选择使我们能使比赛对称或不对称。我们显示出那因为在那里存在的比赛参数的一个特别集合仅仅在比赛的古典版本混合了 S 字,量子化允许甚至纯策略是为除了混合 S 字的对称的比赛的 S 字。在另一方面,仅仅纯的策略 S 字能为鹰鸽子比赛的不对称的量版本存在。[从作者抽象]展开更多
Study on X-ray emission from a low energy (1.8 kJ) plasma focus devicepowered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175kA by using a lead-inserted copper-tapered anode ...Study on X-ray emission from a low energy (1.8 kJ) plasma focus devicepowered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175kA by using a lead-inserted copper-tapered anode is reported. The X-ray yield in different energywindows is measured as a function of hydrogen filling pressure. The maximum yield in 4π-geometry isfound to be (27.3+-1.1) J and corresponding wall plug efficiency for X-ray generation is 1.52+-0.06%. X-ray emission, presumably due to bombarding activity of electrons in current sheath at theanode tip was dominant, which is confirmed by the pinhole images. The feasibility of the device asan intense X-ray source for radiography is demonstrated.展开更多
We study the influence of the Unruh effect on quantum Stackelberg duopoly.It is shown that the acceleration of a noninertial frame strongly affects the payoffs of the firms.The validation of the subgame perfect Nash e...We study the influence of the Unruh effect on quantum Stackelberg duopoly.It is shown that the acceleration of a noninertial frame strongly affects the payoffs of the firms.The validation of the subgame perfect Nash equilibrium is limited to a particular range of acceleration of the noninertial frame.The benefit of the initial state entanglement in the quantum form of the duopoly in the inertial frame is adversely affected by the acceleration.The duopoly can become a follower advantage only in a small region of the acceleration.展开更多
The decoherence effect on multipartite entanglement in non-inertial frames is investigated.The GHZ state is considered to be shared between partners with one partner in the inertial frame whereas the other two are in ...The decoherence effect on multipartite entanglement in non-inertial frames is investigated.The GHZ state is considered to be shared between partners with one partner in the inertial frame whereas the other two are in accelerated frames.One-tangle and π-tangles are used to quantify the entanglement of the multipartite system influenced by phase damping and phase flip channels.It is seen that for the phase damping channel,entanglement sudden death (ESD) occurs for p > 0.5 in the infinite acceleration limit.On the other hand,in the case of the phase flip channel,ESD behavior occurs at p =0.5.It is also seen that entanglement sudden birth (ESB) occurs in the case of phase flip channel just after ESD,i.e.p > 0.5.Furthermore,it is seen that the effect of the environment on multipartite entanglement is much stronger than that of the acceleration of non-inertial frames.展开更多
Geometric quantum discord of fermionic systems in the relativistic regime,that is,beyond the single-mode approximation,is investigated.It is shown that geometric quantum discord for the fermionic systems in non-inerti...Geometric quantum discord of fermionic systems in the relativistic regime,that is,beyond the single-mode approximation,is investigated.It is shown that geometric quantum discord for the fermionic systems in non-inertial frames converges at an infinite acceleration limit,which means that the fermionic systems become independent of the choice of Unruh modes(qR)beyond single-mode approximation.The discord may vanish or be retained depending upon the level of mixedness of the fermionic system.The dynamics of geometric discord are investigated under amplitude damping,depolarizing,phase damping and flipping channels.The vanishing behavior of discord is seen for a higher level of decoherence in the infinite acceleration limit.The depolarizing channel dominantly affects the fermionic geometric discord as compared to the amplitude and phase damping channels.This implies that the depolarizing channel has most destructive influence on the discord of the fermionic systems.However,the flipping channels have a symmetrical effect on the discord.Moreover,the discord heavily depends on the mixedness parameter of the quantum state of the fermionic systems in accelerated frames beyond single-mode approximation.展开更多
Boris numerical scheme due to its long-time stability,accuracy and conservative properties has been widely applied in many studies of magnetized plasmas.Such algorithms conserve the phase space volume and hence provid...Boris numerical scheme due to its long-time stability,accuracy and conservative properties has been widely applied in many studies of magnetized plasmas.Such algorithms conserve the phase space volume and hence provide accurate charge particle orbits.However,this algorithm does not conserve the energy in some special electromagnetic configurations,particularly for long simulation times.Here,we empirically analyze the energy behavior of Boris algorithm by applying it to a 2D autonomous Hamiltonian.The energy behavior of the Boris method is found to be strongly related to the integrability of our Hamiltonian system.We find that if the invariant tori is preserved under Boris discretization,the energy error can be bounded for an exponentially long time,otherwise the said error will show a linear growth.On the contrary,for a non-integrable Hamiltonian system,a random walk pattern has been observed in the energy error.展开更多
Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scann...Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used for the structural and morphological analysis of the nitrided layers. Vickers' microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar (1 bar = 105 Pa). A considerable increase in surface microhardness (approximately by a factor of 2) is observed for longer duration (10 h) and 2-mbar pressure. Longer duration (10 h) and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.展开更多
Langmuir probe measurements of radio frequency (RF) magnetic pole enhanced inductively coupled (MaPE-ICP) argon plasma were accomplished to obtain the electron number densities and electron temperatures. The measu...Langmuir probe measurements of radio frequency (RF) magnetic pole enhanced inductively coupled (MaPE-ICP) argon plasma were accomplished to obtain the electron number densities and electron temperatures. The measurements were carried out with a fixed RF frequency of 13.56 MHz in a pressure range of 7.5 mTorr to 75 mTorr at an applied RF power of 10 W and 100 W. These results are compared with a global (volume average) model. The results show good agreement between theoretical and experimental measurements. The electron number density shows an increasing trend with both RF power and pressure while the electron temperature shows decreasing trend as the pressure increases. The difference in the plasma potentiM and floating potential as a function of electron temperature measured from the electrical probe and that obtained theoretically shows a linear relation with a small difference in the coefficient of proportionality. The intensity of the emission line at 750.4 nm due to 2pl → 1s2 (Paschen's notation) transition closely follows the variation of ne with RF power and filling gas pressure. Measured electron energy probability function (EEPF) shows that electron occupation changes mostly in the high-energy tail, which highlights close similarity of 750.4 nm argon line to he.展开更多
基金The present work was supported by the National Natural Science Funds of China(No.50725413)the Ministry of Science and Technology of China(MOST)(No.2010DFR50010 and 2011FU125Z07)Chongqing Science and Technology Commission(CSTC2013JCYJC60001).
文摘In this study,the effect of micron-sized titanium and aluminum addition on the microstructural,mechanical and work-hardening behavior of pure Mg is investigated.Pure Mg reinforced with 10%Ti and 10%Ti-1%Al particulates were synthesized through semi-powder metallurgy route followed by hot extrusion.Semi-powder metallurgy appears to be promising approach for the synthesis of Mg based composite,as it is free of ball milling.Tensile results indicate that the direct addition of micron-sized 10wt.%titanium particulates to pure Mg,caused an improvement in elastic modulus,0.2%yield strength,ultimate tensile strength,and failure strain(+72%;+41%;+29%;and+79%respectively).The addition of micron-sized 10wt.%titanium particles along with 1.0wt.%Al particles to pure Mg,resulted in an enhancement in elastic modulus,0.2%yield strength,ultimate tensile strength,and failure strain(+74%;+56%;+45%;and+241%respectively).Besides tensile test,Vickers hardness and work-hardening behavior of prepared composites were also examined.Impressive failure strain of Mg-10Ti-1Al composite can be attributed to the better compatibility of Ti particulates with Mg due to presence of alloying element Al.
基金supported by QAU URF,Pakistan Science Foundation(PSF)Project No.PSF/RES/Phys(152),HEC Project 20-2002(R&D)and HEC Project for Plasma Physics Laboratory Gomal University
文摘A glow discharge plasma nitriding reactor in the presence of an active screen cage is optimized in terms of current density,filling pressure and hydrogen concentrations using optical emission spectroscopy(OES).The samples of AISI 304 are nitrided for different treatment times under optimum conditions.The treated samples were analyzed by X-ray diffraction(XRD) to explore the changes induced in the crystallographic structure.The XRD pattern confirmed the formation of iron and chromium nitrides arising from incorporation of nitrogen as an interstitial solid solution in the iron lattice.A Vickers microhardness tester was used to evaluate the surface hardness as a function of treatment time(h).The results showed clear evidence of improved surface hardness and a substantial amount of decrease in the treatment time compared with the previous work.
基金partially supported by the Higher Education Commission Project No. 1852
文摘A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes,impedance measurements have been performed and compared with equivalent circuit models.The measured impedance data is found to be in good agreement with simulated data.
基金Project partially supported by the HEC research project at QAU Islamabadthe NESCOM for providing financial support for his M. Phil studies
文摘The carburizing of titanium (Ti) is accomplished by utilizing energetic ion pulses of a 1.5 kJ Mather type dense plasma focus (DPF) device operated in methane discharge. X-ray diffraction (XRD) analysis confirms the deposition of polycrystalline titanium carbide (TIC). The samples carburized at lower axial and angular positions show an improved texture for a typical (200)TIC plane. The Williamson-Hall method is employed to estimate average crystallite size and microstrains in the carburized Ti surface. Crystallite size is found to vary from - 50 to 100 nm, depending on the deposition parameters. Microstrains vary with the sample position and hence ion flux, and are converted from tensile to compressive by increasing the flux. The carburizing of Ti is confirmed by two major doublets extending from 300 to 390 cm^-1 and from 560 to 620 cm^-1 corresponding to acoustic and optical active modes in Raman spectra, respectively. Analyses by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS) have provided qualitative and quantitative profiles of the carburized surface. The Vickers microhardness of Ti is significantly improved after carburizing.
基金supported partially by the Higher Education Commission Research Project for Plasma Physics of Pakistan
文摘Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction (XRD) to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase (TN) owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth (μm). The results showed clear evidence of surface changes with substantial increase in surface hardness.
文摘We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing(FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission.
基金partial financial support under the National Scholarship Program for Pakistan
文摘We study the behavior of cooperative multiplayer quantum games [Q.Chen,Y.Wang,J.T.Liu,and K.L.Wang,Phys.Lett.A 327 (2004) 98; A.P.Flitncy and L.C.L.Hollcnberg,Quantum Inf.Comput.7 (2007) 111] in thepresence of decoherence using different quantum channels such as amplitude damping,depolarizing and phase damping.It is seen that the outcomes of the games for the two damping channels with maximum values of decoherence reduce tosame value.However,in comparison to phase damping channel,the payoffs of cooperators are strongly damped underthe influence amplitude damping channel for the lower values of decoherence parameter.In the case of depolarizingchannel,the game is a no-payoff game irrespective of the degree of entanglement in the initial state for the larger valuesof decoherence parameter.The decoherence gets the cooperators worse off.
文摘我们使量子化由使用一个纯起始的状态的最一般的形式调查纯、混合的 evolutionarily 稳定的策略(S 字) 的存在的鹰鸽子比赛。一个例子被认为拉比较在之间古典并且比赛的量版本。我们最一般的起始的量状态的选择使我们能使比赛对称或不对称。我们显示出那因为在那里存在的比赛参数的一个特别集合仅仅在比赛的古典版本混合了 S 字,量子化允许甚至纯策略是为除了混合 S 字的对称的比赛的 S 字。在另一方面,仅仅纯的策略 S 字能为鹰鸽子比赛的不对称的量版本存在。[从作者抽象]
基金This work was partially supported by Quaid-i-Azam University Research Grant, Ministry of Science & Technology Grant, Pakistan Science Foundation Project No. PSF/R&D/C-QU/Phys (199), Higher Education Commission Project for Plasma Physics, Pakistan Atomic
文摘Study on X-ray emission from a low energy (1.8 kJ) plasma focus devicepowered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175kA by using a lead-inserted copper-tapered anode is reported. The X-ray yield in different energywindows is measured as a function of hydrogen filling pressure. The maximum yield in 4π-geometry isfound to be (27.3+-1.1) J and corresponding wall plug efficiency for X-ray generation is 1.52+-0.06%. X-ray emission, presumably due to bombarding activity of electrons in current sheath at theanode tip was dominant, which is confirmed by the pinhole images. The feasibility of the device asan intense X-ray source for radiography is demonstrated.
基金Salman Khan is thankful to the World Federation of Scientists for partially supporting this work under the National Scholarship Program for Pakistan.
文摘We study the influence of the Unruh effect on quantum Stackelberg duopoly.It is shown that the acceleration of a noninertial frame strongly affects the payoffs of the firms.The validation of the subgame perfect Nash equilibrium is limited to a particular range of acceleration of the noninertial frame.The benefit of the initial state entanglement in the quantum form of the duopoly in the inertial frame is adversely affected by the acceleration.The duopoly can become a follower advantage only in a small region of the acceleration.
文摘The decoherence effect on multipartite entanglement in non-inertial frames is investigated.The GHZ state is considered to be shared between partners with one partner in the inertial frame whereas the other two are in accelerated frames.One-tangle and π-tangles are used to quantify the entanglement of the multipartite system influenced by phase damping and phase flip channels.It is seen that for the phase damping channel,entanglement sudden death (ESD) occurs for p > 0.5 in the infinite acceleration limit.On the other hand,in the case of the phase flip channel,ESD behavior occurs at p =0.5.It is also seen that entanglement sudden birth (ESB) occurs in the case of phase flip channel just after ESD,i.e.p > 0.5.Furthermore,it is seen that the effect of the environment on multipartite entanglement is much stronger than that of the acceleration of non-inertial frames.
文摘Geometric quantum discord of fermionic systems in the relativistic regime,that is,beyond the single-mode approximation,is investigated.It is shown that geometric quantum discord for the fermionic systems in non-inertial frames converges at an infinite acceleration limit,which means that the fermionic systems become independent of the choice of Unruh modes(qR)beyond single-mode approximation.The discord may vanish or be retained depending upon the level of mixedness of the fermionic system.The dynamics of geometric discord are investigated under amplitude damping,depolarizing,phase damping and flipping channels.The vanishing behavior of discord is seen for a higher level of decoherence in the infinite acceleration limit.The depolarizing channel dominantly affects the fermionic geometric discord as compared to the amplitude and phase damping channels.This implies that the depolarizing channel has most destructive influence on the discord of the fermionic systems.However,the flipping channels have a symmetrical effect on the discord.Moreover,the discord heavily depends on the mixedness parameter of the quantum state of the fermionic systems in accelerated frames beyond single-mode approximation.
基金Abdullah Zafar acknowledges the Chinese Scholarship Council(CSC)to support him as the 2015 CSC awardee(CSC No.2015GXZQ56).
文摘Boris numerical scheme due to its long-time stability,accuracy and conservative properties has been widely applied in many studies of magnetized plasmas.Such algorithms conserve the phase space volume and hence provide accurate charge particle orbits.However,this algorithm does not conserve the energy in some special electromagnetic configurations,particularly for long simulation times.Here,we empirically analyze the energy behavior of Boris algorithm by applying it to a 2D autonomous Hamiltonian.The energy behavior of the Boris method is found to be strongly related to the integrability of our Hamiltonian system.We find that if the invariant tori is preserved under Boris discretization,the energy error can be bounded for an exponentially long time,otherwise the said error will show a linear growth.On the contrary,for a non-integrable Hamiltonian system,a random walk pattern has been observed in the energy error.
基金supported by the Higher Education Commission (HEC) of Pakistan under a research project
文摘Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used for the structural and morphological analysis of the nitrided layers. Vickers' microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar (1 bar = 105 Pa). A considerable increase in surface microhardness (approximately by a factor of 2) is observed for longer duration (10 h) and 2-mbar pressure. Longer duration (10 h) and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.
基金supported partially by QAU URF, Pakistan Science Foundation (PSF) project No. PSF/RES/Phys (152)
文摘Langmuir probe measurements of radio frequency (RF) magnetic pole enhanced inductively coupled (MaPE-ICP) argon plasma were accomplished to obtain the electron number densities and electron temperatures. The measurements were carried out with a fixed RF frequency of 13.56 MHz in a pressure range of 7.5 mTorr to 75 mTorr at an applied RF power of 10 W and 100 W. These results are compared with a global (volume average) model. The results show good agreement between theoretical and experimental measurements. The electron number density shows an increasing trend with both RF power and pressure while the electron temperature shows decreasing trend as the pressure increases. The difference in the plasma potentiM and floating potential as a function of electron temperature measured from the electrical probe and that obtained theoretically shows a linear relation with a small difference in the coefficient of proportionality. The intensity of the emission line at 750.4 nm due to 2pl → 1s2 (Paschen's notation) transition closely follows the variation of ne with RF power and filling gas pressure. Measured electron energy probability function (EEPF) shows that electron occupation changes mostly in the high-energy tail, which highlights close similarity of 750.4 nm argon line to he.