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Intrinsic correlation between the generalized phase equilibrium condition and mechanical behaviors in hydrate-bearing sediments
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作者 Jiazuo Zhou Changfu Wei +2 位作者 Rongtao Yan Yuan Zhou Yi Dong 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第7期2822-2832,共11页
The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing ... The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs.In heating closed systems,the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate,reflecting the porous media effect in phase equilibrium.A generalized phase equilibrium equation was established for hydrate-bearing sediments,which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane.In contrast to bulk hydrate,hydrate-bearing sediment always contains a certain amount of unhydrated water,which keeps phase equilibrium with the hydrate within the hydrate stability field.With changes in temperature and pressure,a portion of pore hydrate and unhydrated water may transform into each other,affecting the shear strength of hydrate-bearing sediment.A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment.The model is validated by experimental data with various hydrate saturation,temperature and pressure conditions.The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress.The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation.The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves. 展开更多
关键词 Hydrate-bearing sediment generalized phase equilibrium Unhydrated water Partial dissociation Mechanical behavior
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THERMODYNAMIC EXPLANATION OF LEADING PHASE IN PEARLITE TRANSFORMATION
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作者 Liu, X.J. 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 1997年第2期145-150,共6页
In this paper a concept of 'leading probability' is presented. The difference in the leading probability between ferrite and cementite depends mainly upon the difference between their driving forces at the beg... In this paper a concept of 'leading probability' is presented. The difference in the leading probability between ferrite and cementite depends mainly upon the difference between their driving forces at the beginning of precipitation. The results of theromdynamic calculations showed that the leading probability of cementite increased with the increase of carbon concentration of austenite, and the decrease in transformation temperature was favourable to cementite's being the leading nucleus during pearlite transformation. 展开更多
关键词 leading phase pearlite transformation decomposition of austenite
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Observations and modelling of the travel time delay and leading negative phase of the 16 September 2015 Illapel,Chile tsunami
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作者 Peitao Wang Zhiyuan Ren +4 位作者 Lining Sun Jingming Hou Zongchen Wang Ye Yuan Fujiang Yu 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2021年第11期11-30,共20页
The systematic discrepancies in both tsunami arrival time and leading negative phase(LNP)were identified for the recent transoceanic tsunami on 16 September 2015 in Illapel,Chile by examining the wave characteristics ... The systematic discrepancies in both tsunami arrival time and leading negative phase(LNP)were identified for the recent transoceanic tsunami on 16 September 2015 in Illapel,Chile by examining the wave characteristics from the tsunami records at 21 Deep-ocean Assessment and Reporting of Tsunami(DART)sites and 29 coastal tide gauge stations.The results revealed systematic travel time delay of as much as 22 min(approximately 1.7%of the total travel time)relative to the simulated long waves from the 2015 Chilean tsunami.The delay discrepancy was found to increase with travel time.It was difficult to identify the LNP from the near-shore observation system due to the strong background noise,but the initial negative phase feature became more obvious as the tsunami propagated away from the source area in the deep ocean.We determined that the LNP for the Chilean tsunami had an average duration of 33 min,which was close to the dominant period of the tsunami source.Most of the amplitude ratios to the first elevation phase were approximately 40%,with the largest equivalent to the first positive phase amplitude.We performed numerical analyses by applying the corrected long wave model,which accounted for the effects of seawater density stratification due to compressibility,self-attraction and loading(SAL)of the earth,and wave dispersion compared with observed tsunami waveforms.We attempted to accurately calculate the arrival time and LNP,and to understand how much of a role the physical mechanism played in the discrepancies for the moderate transoceanic tsunami event.The mainly focus of the study is to quantitatively evaluate the contribution of each secondary physical effect to the systematic discrepancies using the corrected shallow water model.Taking all of these effects into consideration,our results demonstrated good agreement between the observed and simulated waveforms.We can conclude that the corrected shallow water model can reduce the tsunami propagation speed and reproduce the LNP,which is observed for tsunamis that have propagated over long distances frequently.The travel time delay between the observed and corrected simulated waveforms is reduced to<8 min and the amplitude discrepancy between them was also markedly diminished.The incorporated effects amounted to approximately 78%of the travel time delay correction,with seawater density stratification,SAL,and Boussinesq dispersion contributing approximately 39%,21%,and 18%,respectively.The simulated results showed that the elastic loading and Boussinesq dispersion not only affected travel time but also changed the simulated waveforms for this event.In contrast,the seawater stratification only reduced the tsunami speed,whereas the earth’s elasticity loading was responsible for LNP due to the depression of the seafloor surrounding additional tsunami loading at far-field stations.This study revealed that the traditional shallow water model has inherent defects in estimating tsunami arrival,and the leading negative phase of a tsunami is a typical recognizable feature of a moderately strong transoceanic tsunami.These results also support previous theory and can help to explain the observed discrepancies. 展开更多
关键词 2015 Chilean tsunami travel time delay leading negative phase numerical modeling corrected long wave earth’s elasticity loading seawater density stratification Boussinesq dispersion
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Amplitude spectrum compensation and phase spectrum correction of seismic data based on the generalized S transform 被引量:6
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作者 周怀来 王峻 +3 位作者 王明春 沈铭成 张听锟 梁平 《Applied Geophysics》 SCIE CSCD 2014年第4期468-478,510,511,共13页
We propose a method for the compensation and phase correction of the amplitude spectrum based on the generalized S transform. The compensation of the amplitude spectrum within a reliable frequency range of the seismic... We propose a method for the compensation and phase correction of the amplitude spectrum based on the generalized S transform. The compensation of the amplitude spectrum within a reliable frequency range of the seismic record is performed in the S domain to restore the amplitude spectrum of reflection. We use spectral simulation methods to fit the time-dependent amplitude spectrum and compensate for the amplitude attenuation owing to absorption. We use phase scanning to select the time-, space-, and frequencydependent phases correction based on the parsimony criterion and eliminate the residual phase effect of the wavelet in the S domain. The method does not directly calculate the Q value; thus, it can be applied to the case of variable Q. The comparison of the theory model and field data verify that the proposed method can recover the amplitude spectrum of the strata reflectivity, while eliminating the effect of the residual phase of the wavelet. Thus, the wavelet approaches the zero-phase wavelet and, the seismic resolution is improved. 展开更多
关键词 generalized S transform amplitude spectra phase spectra seismic resolution phase correction
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Determining the Main Gas-generation Phase of Marine Organic Matters in Different Occurrence States using the Kinetic Method 被引量:2
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作者 WANG Yunpeng ZHAO Changyi +6 位作者 WANG Zhaoyun WANG Hongjun ZOU Yanrong LIU Jinzhong ZHAO Wenzhi LIU Dehan LU Jialan 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2008年第1期197-205,共9页
This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas genera... This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas generation yields and rates in geological history computed by the acquired kinetic parameters of typical marine organic matters (reservoir oil, residual bitumen, lowmaturity kerogen and residual kerogen) in both China and abroad and maturity by the EasyRo(%) method. Here, the main gas-generation phase was determined as Ro%=1.4%-2.4% for type Ⅰ kerogen, Ro%=1.5-3.0% for low-maturity type Ⅱ kerogen, Ro%=1.4-2.8% for residual kerogen, Ro%=1.5-3.2% for residual bitumen and Ro%=1.6-3.2% for reservoir oil cracking. The influences on the main gas-generation phase from the openness of the simulated system and the "dead line" of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on computing the main gas-generation phase. The main gas-generation phase of type Ⅱ kerogen is Ro%=1.4-3.1% in an open system, which is earlier than that in a closed system. According to our results, the "dead line" of natural gas generation is determined as Ro=3.5 % for type Ⅰ kerogen, Ro=4.4-4.5% for type Ⅱ kerogen and Ro=4.6% for marine oil. Preliminary applications are presented taking the southwestern Tarim Basin as an example. 展开更多
关键词 marine organic matter KEROGEN oil cracking hydrocarbon generating kinetics main gasgeneration phase southwestern Tarim Basin gas source kitchen
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Performance analysis of 20 Pole 1.5 KW Three Phase Permanent Magnet Synchronous Generator for low Speed Vertical Axis Wind Turbine 被引量:2
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作者 Shahrukh Adnan Khan Rajprasad K. Rajkumar +1 位作者 Rajparthiban K. Rajkumar Aravind CV 《Energy and Power Engineering》 2013年第4期423-428,共6页
This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in considerati... This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in consideration and the entire simulation is carried in Matlab/Simulink environment. The rated power for the generator is fixed at 1.5 KW and number of pole at 20. It is observed under low wind speed of6 m/s, a turbine having approximately1 mof radius and2.6 mof height develops 150 Nm mechanical torque that can generate power up to 1.5 KW. The generator is designed using modeling tool and is fabricated. The fabricated generator is tested in the laboratory with the simulation result for the error analysis. The range of error is about 5%-27% for the same output power value. The limitations and possible causes for error are presented and discussed. 展开更多
关键词 Vertical Axis WIND TURBINE Three phase Multi-pole PERMANENT MAGNET SYNCHRONOUS generator Low WIND Speed Modeling Performance Analysis
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Determination of Trace Amounts of Lead by Modified Graphite Furnace Atomic Absorption Spectrometry after Liquid Phase Microextraction with Pyrimidine-2-thiol 被引量:1
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作者 Saeid Nazari 《American Journal of Analytical Chemistry》 2011年第7期757-767,共11页
The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorption spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration step, lea... The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorption spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration step, lead was extracted from a 2 ml of its aqueous sample in the pH = 5 as lead-Pyrimidine-2-thiol cationic complex into a 4 μl drop of 1,2 dichloroethane and ammonium tetraphenylborate as counter ion immersed in the solution. In the drop, the lead-Pyrimidine-2-thiol ammonium tetraphenylborate ion associated complex was formed. After extraction, the microdrop was retracted and directly transferred into a graphite tube modified by [W.Pd.Mg] (c). Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time, stirring rate and effect of salt were optimized. Under the optimum conditions, the enrichment factor and recovery were 525% and 94%, respectively. The calibration graph was linear in the range of 0.01 - 12 μg?L–1 with correlation coefficient of 0.9975 under the optimum conditions of the recommended procedure. The detection limit based on the 3Sb criterion was 0.0072 μg?L–1 and relative standard deviation (RSD) for ten replicate measurement of 0.1 μg?L–1 and 0.4 μg?L–1 lead was 4.5% and 3.8% respectively. The characteristic concentration was 0.0065 μg?L–1 equivalent to a characteristic mass of 26 fg. The results for determination of lead in reference materials, spiked tap water and seawater demonstrated the accuracy, recovery and applicability of the presented method. 展开更多
关键词 lead Liquid phase MICROEXTRACTION PRECONCENTRATION Graphite Furnace Atomic Absorption Spectrometry
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Phase control in an open A-type system with spontaneously generated coherence 被引量:4
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作者 崔妮 樊锡君 +3 位作者 李爱云 刘呈普 龚尚庆 徐至展 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第3期718-724,共7页
This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence (SGC). It shows ... This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence (SGC). It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence. 展开更多
关键词 spontaneously generated coherence phase control electromagnetically induced transparency lasing without inversion
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Microstructure,crystalline phase and electrical properties of Li_(0.06)(Na_(0.5)K_(0.5))_(0.94)Nb_(1-2x/5)Mg_xO_3 lead-free piezoelectric ceramics 被引量:1
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作者 Hai-tao Li Bo-ping Zhang +2 位作者 Qian Zhang Peng-peng Shang Gao-lei Zhao 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2010年第3期340-346,共7页
MgO-modified Li0.06(Na0.5K0.5)0.94NbO3O3 (L6NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a rela- tively low temperature of 1000℃. The crystalline phase, microstructure, and electr... MgO-modified Li0.06(Na0.5K0.5)0.94NbO3O3 (L6NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a rela- tively low temperature of 1000℃. The crystalline phase, microstructure, and electrical properties of the ceramics were investigated with a special emphasis on the influence of MgO content. The addition of MgO effectively improves the sintembility of the L6NKN ceramics. X-my diffr cfion analysis indicates that the morphotropic phase boundary (MPB) separating orthorhombic and tetragonal phases for the ceramics lies in the range of Mg doping content (x) from 0.3at% to 0.7at%. High electrical properties of the piezoelectric constant (d33=238 pC/N), planar electromechanical coupling coefficient (kp=41.5%), relative dielectric constant (εr=905), and remanent polarization (Pr=38.3 μC/cm2) are obtained from the specimen with x=0.5at%, which suggests that the Li0.06(Na0.5K0.5)0.94Nb(1-2x/5)MgxO3 (x=0.5at%) ceramic is a promising lead-free piezoelectric material. 展开更多
关键词 lead-flee piezoelectric ceramics SINTERABILITY SINTERING morphotropic phase boundary
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Modified phase transition and electrical properties of [Li_(0.05)(Na_(0.535)K_(0.48))_(0.95)]- (Nb_(0.94)Sb_(0.06))O_3 lead-free piezoelectric ceramic by sintering temperature 被引量:1
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作者 Zhao Xiaokun Zhang Boping +3 位作者 Zhao Lei Zhu Lifeng Li Yan Cheng Liqian 《Rare Metals》 SCIE EI CAS CSCD 2012年第6期590-594,共5页
Li/Sb-doped (Na,K)NbO3 with a nominal composition of [Li0.05(Na0.535K0.48)0.95](Nb0.94Sb0.06)O3 ceramic was synthesized by normal sintering. The phase structure, microstructure, and electrical properties were investig... Li/Sb-doped (Na,K)NbO3 with a nominal composition of [Li0.05(Na0.535K0.48)0.95](Nb0.94Sb0.06)O3 ceramic was synthesized by normal sintering. The phase structure, microstructure, and electrical properties were investigated with a special emphasis on the influence of the sintering temperature. A polymorphic phase transition (PPT) from orthorhombic to tetragonal symmetry was observed when the sintering temperature was raised from 1040 to 1050 ℃, whereby the piezoelectric coefficient d33 and the electromechanical coupling coefficient kp reached the peak values of 245 pC·N-1 and 41.2%, respectively. The PPT induced by varying the sintering temperature is due to the different volatilization extents of alkali metals and appears to a lower sintering temperature with increasing Li content. The trace modifying of alkali metal content is more effective than doping B site element to enhance the d33 value. 展开更多
关键词 lead-FREE sintering temperature microstructure phase piezoelectric properties piezoelectric ceramic
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Generalized thermoelastic interaction in functional graded material with fractional order three-phase lag heat transfer 被引量:3
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作者 Ibrahim A.Abbas 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第5期1606-1613,共8页
The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governi... The present work is concerned with the solution of a problem on thermoelastic interactions in a functional graded material due to thermal shock in the context of the fractional order three-phase lag model. The governing equations of fractional order generalized thermoelasticity with three-phase lag model for functionally graded materials(FGM)(i.e., material with spatially varying material properties) are established. The analytical solution in the transform domain is obtained by using the eigenvalue approach.The inversion of Laplace transform is done numerically. The graphical results indicate that the fractional parameter has significant effects on all the physical quantities. Thus, we can consider the theory of fractional order generalized thermoelasticity an improvement on studying elastic materials. 展开更多
关键词 three-phase lag model fimctionally graded materials fractional calculus generalized thermoelasticity
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Large phase shift of spatial soliton in lead glass by cross-phase modulation in pump-signal geometry
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作者 寿倩 刘东文 +2 位作者 张翔 胡巍 郭旗 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第8期345-349,共5页
We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton (SNSOS) can be realized via cross-ph... We investigate the co-propagation of a strong pump beam and a weak signal beam in lead glass, and find that the large phase shift of the strongly nonlocal spatial optical soliton (SNSOS) can be realized via cross-phase modulation. The theoretical study suggests a synchronous propagation of the pump SNSOS and the signal SNSOS under the required initial condition. A π-phase shift of the signal SNSOS is experimentally obtained by changing the power of the pump SNSOS by about 13 mW around the soliton critical power, which agrees qualitatively with our theoretical prediction. The ratio of the phase shift rate of the signal SNSOS to that of the pump SNSOS shows a close match to the reciprocal of the ratio between their wavelengths. 展开更多
关键词 strongly nonlocal spatial solitons large phase shift lead glass
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NEW THREE PHASE VFVA SINE WAVE GENERATOR AND PWM HARMONICS ANALYSIS
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作者 林棋 《Journal of Electronics(China)》 1994年第1期79-87,共9页
The new three phase VFVA sine wave generator is presented in this paper. A new sampling holding three phase VFVA sine wave generator’s principle, circuit and experimentation waveform are introduced. The principle of ... The new three phase VFVA sine wave generator is presented in this paper. A new sampling holding three phase VFVA sine wave generator’s principle, circuit and experimentation waveform are introduced. The principle of this sampling holding circuit is simple and the realization of har’dware circuit is easy. Here we describe the three phase reference sine wave which is produced by this generator’s circuit and is required by PWM inverter is described in this paper, and also introduced the speed control and harmonir analysis of PWM inverter variable frequency. 展开更多
关键词 SINE WAVE generATOR HARMONICS analysis THREE phase VFVA
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New approach for analysing master equations of generalized phase diffusion models in the entangled state representation
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作者 徐兴磊 李洪奇 范洪义 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第3期918-921,共4页
By virtue of the well-behaved properties of the bipartite entangled states representation, this paper analyse and solves some master equations for generalized phase diffusion models, which seems concise and effective.... By virtue of the well-behaved properties of the bipartite entangled states representation, this paper analyse and solves some master equations for generalized phase diffusion models, which seems concise and effective. This method can also be applied to solve other master equations. 展开更多
关键词 generalized phase diffusion entangled state representation master equations
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A Relation of the Noncommutative Parameters in Generalized Noncommutative Phase Space
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作者 林冰生 衡太骅 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第11期22-24,共3页
We introduce the deformed boson operators which satisfy a deformed boson algebra in some special types of generalized noncommutative phase space. Based on the deformed boson algebra, we construct coherent state repres... We introduce the deformed boson operators which satisfy a deformed boson algebra in some special types of generalized noncommutative phase space. Based on the deformed boson algebra, we construct coherent state representations. We calculate the variances of the coordinate operators on the coherent states and investigate the corresponding Heisenberg uncertainty relations. It is found that there are some restriction relations of the noncommutative parameters in these special types of noncommutative phase space. 展开更多
关键词 of on is in HAVE A Relation of the Noncommutative Parameters in generalized Noncommutative phase Space
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Preconcentration of Lead in Sugar Samples by Solid Phase Extraction and Its Determination by Flame Atomic Absorption Spectrometry
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作者 Saied Saeed Hosseiny Davarani Neda Sheijooni-Fumani +2 位作者 Amin Morteza Najarian Mohammad-Ali Tabatabaei Siavash Vahidi 《American Journal of Analytical Chemistry》 2011年第5期626-631,共6页
A simple and sensitive solid phase extraction utilizing C18 filled cartridges incorporated with dithizone for preconcentration of lead and its subsequent determination by flame atomic absorption spectrometry (FAAS) wa... A simple and sensitive solid phase extraction utilizing C18 filled cartridges incorporated with dithizone for preconcentration of lead and its subsequent determination by flame atomic absorption spectrometry (FAAS) was developed. Several parameters such as type, concentration and volume of eluent, pH of the sample solution, flow rate of extraction and volume of the sample were evaluated. The effect of a variety of ions on preconcentration and recovery was also investigated. At pH = 7.4 and 1.0 mol?L–1 HCl eluting them, lead ions were recovered quantitatively. The limit of detection (LOD) defined as 3Sbl was determined to be 8.1 μg L–1 for 500 mL of sample solution and eluted with 5 mL of 1.0 mol?L–1 HCl under optimum conditions. The accuracy and precision (RSD %) of the method were >90% and <10%, respectively. In the end, the proposed method was applied to a number of real sugar samples and the amount of lead was determined by spiking a known concentration of lead into the solution. 展开更多
关键词 Solid phase Extraction lead DITHIZONE FLAME Atomic Absorption Spectroscopy (FAAS) C18 Modified Cartridges
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Three-step self-calibrating generalized phase-shifting interferometry
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作者 Yu Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第3期234-240,共7页
An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry(SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normali... An accurate and fast three-step self-calibrating generalized phase-shifting interferomertry(SGPSI) is proposed. In this approach, two new phase-shifting signals are constructed by the difference interferograms normalization and noise suppressing, then the unknown phase shift between the two difference phase-shifting signals is estimated quickly through searching the minimum coefficient of variation of the modulation amplitude, a limited number of pixels are selected to participate in the search process to further save time, and finally the phase is reconstructed through the searched phase shift. Through the reconstruction of phase map by the simulation and experiment, and the comparison with several mature algorithms, the good performance of the proposed algorithm is proved, and it eliminates the limitation of requiring more than three phase-shifting interferograms for high-precision SGPSI. We expect this method to be widely used in the future. 展开更多
关键词 self-calibrating generalized phase-shifting interferomertry phase shift difference interferograms modulation amplitude
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Carrier envelope phase effect on the spatial distribution of high-order harmonic generation in asymmetric molecule 被引量:1
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作者 Jun Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第5期135-139,共5页
The spatial distribution in high-order harmonic generation(HHG) from the asymmetric diatomic molecule He H^(2+) is investigated by numerically solving the non-Born–Oppenheimer time-dependent Schr?dinger equatio... The spatial distribution in high-order harmonic generation(HHG) from the asymmetric diatomic molecule He H^(2+) is investigated by numerically solving the non-Born–Oppenheimer time-dependent Schr?dinger equation(TDSE). The spatial distribution of the HHG spectra shows that there is little contribution in HHG around the geometric center of two nuclei(z = 1.17 a.u.) and the equilibrium internuclear position of the H nucleus(z = 3.11 a.u.). We demonstrate the carrier envelope phase(CEP) effect on the spatial distribution of HHG in a few-cycle laser pulse. The HHG process is investigated by the time evolution of the electronic density distribution. The time–frequency analysis of HHG from two nuclei in HeH^(2+) is presented to further explain the underlying physical mechanism. 展开更多
关键词 high-order harmonic generation spatial distribution asymmetric molecule carrier envelope phase
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Effects of Na/K ratio on the phase structure and electrical properties of Na_xK_(1-x)NbO_3 lead-free piezoelectric ceramics 被引量:1
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作者 ZHANG Qian, ZHANG Boping, Li Haitao, and SHANG Pengpeng School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 《Rare Metals》 SCIE EI CAS CSCD 2010年第2期220-225,共6页
Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special ... Lead-free piezoelectric NaxK1-xNbO3(x = 0.3-0.8)(NKN) ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary(MPB) in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively. 展开更多
关键词 lead-free piezoelectric ceramics NKN sintering morphotropic phase boundary(MPB)
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The Implementation and Lateral Control Optimization of a UAV Based on Phase Lead Compensator and Signal Constraint Controller
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作者 Adil Loya Muhammad Duraid +1 位作者 Kamran Maqsood Rehan Rasheed Khan 《Engineering(科研)》 2018年第10期704-729,共26页
Unmanned Aero Vehicles (UAV) has become a useful entity for quite a good number of industries and facilities. It is an agile, cost effective and reliable solution for communication, defense, security, delivery, survei... Unmanned Aero Vehicles (UAV) has become a useful entity for quite a good number of industries and facilities. It is an agile, cost effective and reliable solution for communication, defense, security, delivery, surveillance and surveying etc. However, their reliability is dependent on the resilient and stabilizes performance based on control systems embedded behind the body. Therefore, the UAV is majorly dependent upon controller design and the requirement of particular performance parameters. Nevertheless, in modern technologies there is always a room for improvement. In the similar manner a UAV lateral control system was implemented and researched in this study, which has been optimized using Proportional, Integral and Derivative (PID) controller, phase lead compensator and signal constraint controller. The significance of this study is the optimization of the existing UAV controller plant for improving lateral performance and stability. With this UAV community will benefit from designing robust controls using the optimized method utilized in this paper and moreover this will provide sophisticated control to operate in unpredictable environments. It is observed that results obtained for optimized lateral control dynamics using phase lead compensator (PLC) are efficacious than the simple PID feedback gains. However, for optimizing unwanted signals of lateral velocity, yaw rate, and yaw angle modes, PLC were integrated with PID to achieve dynamical stability. 展开更多
关键词 Lateral Control Simulink PID SIGNAL Constraining phase lead COMPENSATORS Unmanned Aero Vehicle
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