期刊文献+
共找到73,678篇文章
< 1 2 250 >
每页显示 20 50 100
Mechanisms mediating cholinergic antral circular smooth muscle contraction in rats 被引量:4
1
作者 HelenaFWrzos TarunTandon AnnOuyang 《World Journal of Gastroenterology》 SCIE CAS CSCD 2004年第22期3292-3298,共7页
AIM:To investigate the pathway(s)mediating rat antral circular smooth muscle contractile responses to the cholinomimetic agent,bethanechol and the subtypes of muscarinic receptors mediating the cholinergic contraction... AIM:To investigate the pathway(s)mediating rat antral circular smooth muscle contractile responses to the cholinomimetic agent,bethanechol and the subtypes of muscarinic receptors mediating the cholinergic contraction. METHODS:Circular smooth muscle strips from the antrum of Sprague-Dawley rats were mounted in muscle baths in Krebs buffer.Isometric tension was recorded.Cumulative concentration-response curves were obtained for(+)-cis- dioxolane(cD),a nonspecific muscarinic agonist,at 10^(-8)- 10^(-4)mol/L,in the presence of tetrodotoxin(TTX,10^(-7)mol/L). Results were normalized to cross sectional area.A repeat concentration-response curve was obtained after incubation of the muscle for 90 min with antagonists for M1(pirenzepine), M2(methoctramine)and M3(darifenadn)muscarinic receptor subtypes.The sensitivity to PTX was tested by the ip injection of 100 mg/kg of PTX 5 d before the experiment.The antral circular smooth muscles were removed from PTX-treated and non-treated rats as strips and dispersed smooth muscle cells to identify whether PTX-linked pathway mediated the contractility to bethanechol. RESULTS:A dose-dependent contractile response observed with bethanechol,was not affected by TTx.The pretreatment of rats with pertussis toxin decreased the contraction induced by bethanechol.Lack of calcium as well as the presence of the L-type calcium channel blocker,nifedipine,also inhibited the cholinergic contraction,with a reduction in response from 2.5±0.4 g/mm^2 to 1.2±0.4 g/mm^2(P<0.05).The dose- response curves were shifted to the right by muscarinic antagonists in the following order of affinity:darifenacin (M_3)>methocramine(M_2)>pirenzepine(M_1). CONCLUSION:The muscarinic receptors-dependent contraction of rat antral circular smooth muscles was linked to the signal transduction pathway(s)involving pertussis-toxin sensitive GTP-binding proteins and to extracellular calcium via L-type voltage gated calcium channels.The presence of the residual contractile response after the treatment with nifedipine,suggests that an additional pathway could mediate the cholinergic contraction.The involvement of more than one muscarinic receptor(functionally predominant type 3 over type 2)also suggests more than one pathway mediating the cholinergic contraction in rat antrum. 展开更多
关键词 Anesthetics Local Animals BENZOFURANS BETHANECHOL Calcium Calcium Channel Blockers Cholinergic Agonists Dose-Response Relationship Drug GTP-Binding Proteins In Vitro Male Muscarinic Antagonists Muscle contraction Muscle Smooth Nifedipine Pertussis Toxin Pirenzepine Pyloric Antrum PYRROLIDINES RATS Rats Sprague-Dawley Receptor Muscarinic M1 inhibitors Receptor Muscarinic M2 Receptor Muscarinic M3 Signal Transduction Tetrodotoxin
下载PDF
The Origins of Bosons and Fermions
2
作者 ShaoXu Ren 《Journal of Modern Physics》 2014年第17期1848-1879,共32页
This paper proposes that all Bosons and all Fermions originate from even more elementary constituents, which called Spin Angular Momentum Vacuum (SAMV). SAMV is filled with Primitive Spin Particles (PSP). The total sq... This paper proposes that all Bosons and all Fermions originate from even more elementary constituents, which called Spin Angular Momentum Vacuum (SAMV). SAMV is filled with Primitive Spin Particles (PSP). The total square spin angular momentum of each PSP is negative, less than zero. Those PSP labeled by index ?of Casimir Operator, are called Vacuum Spin Particle (VSP), which could be contracted into so-called Vacuum Bubbles (VB). VB are identical bubbles, are 'sub-observable physical quantities'. VB are paired up into Vacuum Bubble Pair VBP. VSP ωj(or ω+,ω-) results from Self-identical vacuum bubble interaction ?through the zero order Phase Transition PT. When the 1st, 2nd, 3rd,... order PT of VBP occur, ?then VBP turn into Bosons and Fermions, excited out of sea level of SAMV ocean. 展开更多
关键词 SPIN Angular Momentum VACUUM SAMV Primitive SPIN PARTICLES PSP VACUUM SPIN PARTICLES VSP Abnormal Casimir Operator ACO VACUUM contractionS VC VACUUM Bubbles VB VACUUM Bubble Pair VBP Phase Transitions PT BOSONS FERMIONS The Third Kind Of PARTICLES TKP Chaos SPIN Hierarchy CSH The Equivalence of VACUUM Bubbles Locality and Nonlocality of VACUUM contractionS Local and Nonlocal Angular Momentum Commutations
下载PDF
Optimal Threshold Determination for Securities Exchange Volumes Using Improved Maximum Product of Spacing Methodology
3
作者 Peter Murage Joseph Mung’atu Everlyne Odero 《Open Journal of Statistics》 2019年第3期327-346,共20页
To Statisticians, the structure of the extreme levels which exist in the tails of the ordinary distributions is very important in analyzing, predicting and forecasting the likelihood of an occurrence of extreme event.... To Statisticians, the structure of the extreme levels which exist in the tails of the ordinary distributions is very important in analyzing, predicting and forecasting the likelihood of an occurrence of extreme event. Extreme events are defined as values of the event below or above a certain value called threshold. A well chosen threshold helps to identify the extreme levels. Several methods have been used to determine threshold so as to analyze and model extreme events. One of the most successful methods is the maximum product of spacing (MPS). However, there is a problem encountered while modeling data through this method in that the method breaks down when there is a tie in the exceedances. This study offers a solution to model data even when it contains ties. In the study, a method that improved MPS method for determining an optimal threshold for extreme values in a data set containing ties was derived. The Generalized Pareto Distribution (GPD) parameters for the optimal threshold were derived and compared to GPD parameters determined through the standard MPS model. The study improved the standard MPS methodology by introducing the concept of frequency and used Generalized Pareto Distribution (GPD) and Peak over threshold (POT) methods as the basis of identifying extreme values. The improved MPS models and the standard models were applied to Nairobi Securities Exchange (NSE) trading volume data to determine the GPD parameters for different sectors registered in NSE market and their performance compared. It was realized that the improved MPS model performed better than the standard models. This study will help the Statisticians in different sectors of our economy to model extreme events involving ties. 展开更多
关键词 Extreme Value Theory (EVT) maximum PRODUCT of SPACING (MPS) Generalized Pareto Distribution (GPD) Peaks over Threshold (POT) NAIROBI SECURITIES EXCHANGE (NSE)
下载PDF
A New Maximum Test via the Dependent Samples t-Test and the Wilcoxon Signed-Ranks Test 被引量:3
4
作者 Saverpierre Maggio Shlomo S. Sawilowsky 《Applied Mathematics》 2014年第1期110-114,共5页
A maximum test in lieu of forcing a choice between the two dependent samples t-test and Wilcoxon signed-ranks test is proposed. The maximum test, which requires a new table of critical values, maintains nominal α whi... A maximum test in lieu of forcing a choice between the two dependent samples t-test and Wilcoxon signed-ranks test is proposed. The maximum test, which requires a new table of critical values, maintains nominal α while guaranteeing the maximum power of the two constituent tests. Critical values, obtained via Monte Carlo methods, are uniformly smaller than the Bonferroni-Dunn adjustment, giving it power superiority when testing for treatment alternatives of shift in location parameter when data are sampled from non-normal distributions. 展开更多
关键词 maximum TEST DEPENDENT SAMPLES T-TEST Wilcoxon Signed-Ranks TEST Bonferroni-Dunn Adjustment Experiment-Wise Type I Error Inferential Statistics Monte Carlo Method
下载PDF
Parasitic Effects on the Performance of DC-DC SEPIC in Photovoltaic Maximum Power Point Tracking Applications
5
作者 Nur Mohammad Muhammad Quamruzzaman +1 位作者 Mohammad Rubaiyat Tanvir Hossain Mohammad Rafiqul Alam 《Smart Grid and Renewable Energy》 2013年第1期113-121,共9页
This paper presents an analysis of the effect of parasitic resistances on the performance of DC-DC Single Ended Pri- mary Inductor Converter (SEPIC) in photovoltaic maximum power point tracking (MPPT) applications. Th... This paper presents an analysis of the effect of parasitic resistances on the performance of DC-DC Single Ended Pri- mary Inductor Converter (SEPIC) in photovoltaic maximum power point tracking (MPPT) applications. The energy storage elements incorporated in the SEPIC converter possess parasitic resistances. Although ideal components significantly simplifies model development, but neglecting the parasitic effects in models may sometimes lead to failure in predicting first scale stability and actual performance. Therefore, the effects of parasitics have been taken into consideration for improving the model accuracy, stability, robustness and dynamic performance analysis of the converter. Detail mathematical model of SEPIC converter including inductive parasitic has been developed. The performance of the converter in tracking MPP at different irradiance levels has been analyzed for variation in parasitic resistance. The converter efficiency has been found above 83% for insolation level of 600 W/m2 when the parasitic resistance in the energy storage element has been ignored. However, as the parasitic resistance of both of the inductor has increased to 1 ohm, a fraction of the power managed by the converter has dissipated;as a result the efficiency of the converter has reduced to 78% for the same insolation profile. Although the increasing value of the parasitic has assisted the converter to converge quickly to reach the maximum power point. Furthermore it has also been observed that the peak to peak load current ripple is reduced. The obtained simulation results have validated the competent of the MPPT converter model. 展开更多
关键词 PHOTOVOLTAIC (PV) Renewable Energy Systems DC-DC CONVERTER PARASITIC Resistance maximum Power Point Tracking (MPPT) Single Ended Primary INDUCTANCE CONVERTER (SEPIC)
下载PDF
Probabilistic Global Maximum Power Point Tracking Algorithm for Continuously Varying Partial Shading Conditions on Autonomous PV Systems
6
作者 Kha Bao Khanh Cao Vincent Boitier 《Energy and Power Engineering》 2024年第1期21-42,共22页
A photovoltaic (PV) string with multiple modules with bypass diodes frequently deployed on a variety of autonomous PV systems may present multiple power peaks under uneven shading. For optimal solar harvesting, there ... A photovoltaic (PV) string with multiple modules with bypass diodes frequently deployed on a variety of autonomous PV systems may present multiple power peaks under uneven shading. For optimal solar harvesting, there is a need for a control schema to force the PV string to operate at global maximum power point (GMPP). While a lot of tracking methods have been proposed in the literature, they are usually complex and do not fully take advantage of the available characteristics of the PV array. This work highlights how the voltage at operating point and the forward voltage of the bypass diode are considered to design a global maximum power point tracking (GMPPT) algorithm with a very limited global search phase called Fast GMPPT. This algorithm successfully tracks GMPP between 94% and 98% of the time under a theoretical evaluation. It is then compared against Perturb and Observe, Deterministic Particle Swarm Optimization, and Grey Wolf Optimization under a sequence of irradiance steps as well as a power-over-voltage characteristics profile that mimics the electrical characteristics of a PV string under varying partial shading conditions. Overall, the simulation with the sequence of irradiance steps shows that while Fast GMPPT does not have the best convergence time, it has an excellent convergence rate as well as causes the least amount of power loss during the global search phase. Experimental test under varying partial shading conditions shows that while the GMPPT proposal is simple and lightweight, it is very performant under a wide range of dynamically varying partial shading conditions and boasts the best energy efficiency (94.74%) out of the 4 tested algorithms. 展开更多
关键词 PHOTOVOLTAIC PV Global maximum Power Point Tracking GMPPT Fast Varying Partial Shading Conditions Autonomous PV Systems GMPPT Review
下载PDF
航天湍流退化图像的极大似然估计规整化复原算法 被引量:24
7
作者 洪汉玉 张天序 余国亮 《红外与毫米波学报》 SCIE EI CAS CSCD 北大核心 2005年第2期130-134,共5页
为了从有噪的湍流退化图像中有效地恢复出目标图像,提出了一种基于极大似然估计准则的规整化复原算法.根据图像随机场模型建立了有关多帧图像数据的对数似然函数,同时为了平滑噪声和保护图像边缘以及避免无价值的解,将一些合理的惩罚项... 为了从有噪的湍流退化图像中有效地恢复出目标图像,提出了一种基于极大似然估计准则的规整化复原算法.根据图像随机场模型建立了有关多帧图像数据的对数似然函数,同时为了平滑噪声和保护图像边缘以及避免无价值的解,将一些合理的惩罚项和辅助平滑项融合到该对数似然函数中.推导出了湍流点扩展函数和目标图像的交替迭代求解公式,通过迭代方式可将点扩展函数和目标图像同时估计出来,给出了算法的并行处理方案.在微机上对强噪声条件下的湍流退化图像进行了恢复实验,实验结果表明本算法具有较强的抗噪能力和实用价值. 展开更多
关键词 退
下载PDF
Application of maximum rank distance codes in designing of STBC-OFDM system for next-generation wireless communications
8
作者 Arslan Khalid Prapun Suksompong 《Digital Communications and Networks》 SCIE CSCD 2024年第4期1048-1056,共9页
Space-Time Block Coded(STBC)Orthogonal Frequency Division Multiplexing(OFDM)satisfies higher data-rate requirements while maintaining signal quality in a multipath fading channel.However,conventional STBCs,including O... Space-Time Block Coded(STBC)Orthogonal Frequency Division Multiplexing(OFDM)satisfies higher data-rate requirements while maintaining signal quality in a multipath fading channel.However,conventional STBCs,including Orthogonal STBCs(OSTBCs),Non-Orthogonal(NOSTBCs),and Quasi-Orthogonal STBCs(QOSTBCs),do not provide both maximal diversity order and unity code rate simultaneously for more than two transmit antennas.This paper targets this problem and applies Maximum Rank Distance(MRD)codes in designing STBCOFDM systems.By following the direct-matrix construction method,we can construct binary extended finite field MRD-STBCs for any number of transmitting antennas.Work uses MRD-STBCs built over Phase-Shift Keying(PSK)modulation to develop an MRD-based STBC-OFDM system.The MRD-based STBC-OFDM system sacrifices minor error performance compared to traditional OSTBC-OFDM but shows improved results against NOSTBC and QOSTBC-OFDM.It also provides 25%higher data-rates than OSTBC-OFDM in configurations that use more than two transmit antennas.The tradeoffs are minor increases in computational complexity and processing delays. 展开更多
关键词 Bit error rate(BER) Galois field maximum rank distance(MRD)codes Orthogonal frequency division multiplexing (OFDM) Primitive polynomials Space-time block codes(STBC)
下载PDF
Optimal Threshold Determination for the Maximum Product of Spacing Methodology with Ties for Extreme Events 被引量:1
9
作者 Peter Murage Joseph Mung’atu Everlyne Odero 《Open Journal of Modelling and Simulation》 2019年第3期149-168,共20页
Extreme events are defined as values of the event below or above a certain value called threshold. A well chosen threshold helps to identify the extreme levels. Several methods have been used to determine threshold so... Extreme events are defined as values of the event below or above a certain value called threshold. A well chosen threshold helps to identify the extreme levels. Several methods have been used to determine threshold so as to analyze and model extreme events. One of the most successful methods is the maximum product of spacing (MPS). However, there is a problem encountered while modeling data through this method in that the method breaks down when there is a tie in the exceedances. This study offers a solution to model data even if it contains ties. To do so, an optimal threshold that gives more optimal parameters for extreme events, was determined. The study achieved its main objective by deriving a method that improved MPS method for determining an optimal threshold for extreme values in a data set containing ties, estimated the Generalized Pareto Distribution (GPD) parameters for the optimal threshold derived and compared these GPD parameters with GPD parameters determined through the standard MPS model. The study improved maximum product of spacing method and used Generalized Pareto Distribution (GPD) and Peak over threshold (POT) methods as the basis of identifying extreme values. This study will help the statisticians in different sectors of our economy to model extreme events involving ties. To statisticians, the structure of the extreme levels which exist in the tails of the ordinary distributions is very important in analyzing, predicting and forecasting the likelihood of an occurrence of the extreme event. 展开更多
关键词 Extreme Value Theory (EVT) maximum PRODUCT of SPACING MPS Generalized Pareto Distribution (GPD) Peak Over Threshold (POT)
下载PDF
A Maximum Likelihood TOA Based Estimator For Localization in Heterogeneous Networks
10
作者 Mohamed LAARAIEDH Stephane AVRILLON Bernard UGUEN 《International Journal of Communications, Network and System Sciences》 2010年第1期38-42,共5页
In this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by di... In this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by different precisions in order to enhance the positioning accuracy. A new Maximum Likelihood estimator is developed to fuse different measured ranges with different variances. In order to evaluate this estimator, Monte Carlo simulations are carried out in a generic environment and Cramer Rao Lower Bounds (CRLB) are investigated. This algorithm shows enhanced positioning accuracy at reasonable noise levels comparing to the typical Weighted Least Square estimator. The CRLB reveals that the choice of the number, and the configuration of Anchor nodes, and the type of RAT may enhance positioning accuracy. 展开更多
关键词 LOCALIZATION TOA RANGING Weighted least square maximum LIKELIHOOD Hybrid Data Fusion UWB WLAN Cramer RAO Lower BOUND
下载PDF
Revisiting the Electron Radius in Light of Length Contraction
11
作者 Julie Marty 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第4期1743-1748,共6页
In previous work, the electron radius was identified as the “actual electron radius.” However, this is more accurately described as the electron radius at rest. This study reexamines the electron with an emphasis on... In previous work, the electron radius was identified as the “actual electron radius.” However, this is more accurately described as the electron radius at rest. This study reexamines the electron with an emphasis on the electron radius under motion, incorporating the effects of length contraction. The findings suggest that the radius is subject to Lorentz contraction, which has interesting implications for relativistic effects at the subatomic level. 展开更多
关键词 Electron Radius Length contraction Lorentz Factor Relativistic Effects Subatomic Particles Compton Scattering
下载PDF
Maximum Correntropy Criterion-Based UKF for Loosely Coupling INS and UWB in Indoor Localization
12
作者 Yan Wang You Lu +1 位作者 Yuqing Zhou Zhijian Zhao 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第6期2673-2703,共31页
Indoor positioning is a key technology in today’s intelligent environments,and it plays a crucial role in many application areas.This paper proposed an unscented Kalman filter(UKF)based on the maximum correntropy cri... Indoor positioning is a key technology in today’s intelligent environments,and it plays a crucial role in many application areas.This paper proposed an unscented Kalman filter(UKF)based on the maximum correntropy criterion(MCC)instead of the minimummean square error criterion(MMSE).This innovative approach is applied to the loose coupling of the Inertial Navigation System(INS)and Ultra-Wideband(UWB).By introducing the maximum correntropy criterion,the MCCUKF algorithm dynamically adjusts the covariance matrices of the system noise and the measurement noise,thus enhancing its adaptability to diverse environmental localization requirements.Particularly in the presence of non-Gaussian noise,especially heavy-tailed noise,the MCCUKF exhibits superior accuracy and robustness compared to the traditional UKF.The method initially generates an estimate of the predicted state and covariance matrix through the unscented transform(UT)and then recharacterizes the measurement information using a nonlinear regression method at the cost of theMCC.Subsequently,the state and covariance matrices of the filter are updated by employing the unscented transformation on the measurement equations.Moreover,to mitigate the influence of non-line-of-sight(NLOS)errors positioning accuracy,this paper proposes a k-medoid clustering algorithm based on bisection k-means(Bikmeans).This algorithm preprocesses the UWB distance measurements to yield a more precise position estimation.Simulation results demonstrate that MCCUKF is robust to the uncertainty of UWB and realizes stable integration of INS and UWB systems. 展开更多
关键词 maximum correntropy criterion unscented Kalman filter inertial navigation system ULTRA-WIDEBAND bisecting kmeans clustering algorithm
下载PDF
Tree Network Formation in Poisson Equation Models and the Implications for the Maximum Entropy Production Principle
13
作者 Hiroshi Serizawa Takashi Amemiya Kiminori Itoh 《Natural Science》 2014年第7期514-527,共14页
This paper presents not only practical but also instructive mathematical models to simulate tree network formation using the Poisson equation and the Finite Difference Method (FDM). Then, the implications for entropic... This paper presents not only practical but also instructive mathematical models to simulate tree network formation using the Poisson equation and the Finite Difference Method (FDM). Then, the implications for entropic theories are discussed from the viewpoint of Maximum Entropy Production (MEP). According to the MEP principle, open systems existing in the state far from equilibrium are stabilized when entropy production is maximized, creating dissipative structures with low entropy such as the tree-shaped network. We prepare two simulation models: one is the Poisson equation model that simulates the state far from equilibrium, and the other is the Laplace equation model that simulates the isolated state or the state near thermodynamic equilibrium. The output of these equations is considered to be positively correlated to entropy production of the system. Setting the Poisson equation model so that entropy production is maximized, tree network formation is advanced. We suppose that this is due to the invocation of the MEP principle, that is, entropy of the system is lowered by emitting maximal entropy out of the system. On the other hand, tree network formation is not observed in the Laplace equation model. Our simulation results will offer the persuasive evidence that certifies the effect of the MEP principle. 展开更多
关键词 DISSIPATIVE Structure Far from Equilibrium Fractal POISSON Equation maximum ENTROPY PRODUCTION (MEP) PRINCIPLE Minimum ENTROPY PRODUCTION (MinEP) PRINCIPLE Tree Network
下载PDF
Correlation between the rock mass properties and maximum horizontal stress:A case study of overcoring stress measurements
14
作者 Peng Li Meifeng Cai +2 位作者 Shengjun Miao Yuan Li Yu Wang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS 2025年第1期39-48,共10页
Understanding the mechanical properties of the lithologies is crucial to accurately determine the horizontal stress magnitude.To investigate the correlation between the rock mass properties and maximum horizontal stre... Understanding the mechanical properties of the lithologies is crucial to accurately determine the horizontal stress magnitude.To investigate the correlation between the rock mass properties and maximum horizontal stress,the three-dimensional(3D)stress tensors at 89 measuring points determined using an improved overcoring technique in nine mines in China were adopted,a newly defined characteristic parameter C_(ERP)was proposed as an indicator for evaluating the structural properties of rock masses,and a fuzzy relation matrix was established using the information distribution method.The results indicate that both the vertical stress and horizontal stress exhibit a good linear growth relationship with depth.There is no remarkable correlation between the elastic modulus,Poisson's ratio and depth,and the distribution of data points is scattered and messy.Moreover,there is no obvious relationship between the rock quality designation(RQD)and depth.The maximum horizontal stress σ_(H) is a function of rock properties,showing a certain linear relationship with the C_(ERP)at the same depth.In addition,the overall change trend of σ_(H) determined by the established fuzzy identification method is to increase with the increase of C_(ERP).The fuzzy identification method also demonstrates a relatively detailed local relationship betweenσ_H and C_(ERP),and the predicted curve rises in a fluctuating way,which is in accord well with the measured stress data. 展开更多
关键词 overcoring stress measurements elastic modulus Poisson's ratio rock quality designation maximum horizontal stress fuzzy identification
下载PDF
A method for extracting the preseismic gravity anomalies over the Tibetan Plateau based on the maximum shear strain using GRACE data
15
作者 Hui Wang DongMei Song +1 位作者 XinJian Shan Bin Wang 《Earth and Planetary Physics》 EI CAS CSCD 2024年第4期589-608,共20页
The occurrence of earthquakes is closely related to the crustal geotectonic movement and the migration of mass,which consequently cause changes in gravity.The Gravity Recovery And Climate Experiment(GRACE)satellite da... The occurrence of earthquakes is closely related to the crustal geotectonic movement and the migration of mass,which consequently cause changes in gravity.The Gravity Recovery And Climate Experiment(GRACE)satellite data can be used to detect gravity changes associated with large earthquakes.However,previous GRACE satellite-based seismic gravity-change studies have focused more on coseismic gravity changes than on preseismic gravity changes.Moreover,the noise of the north–south stripe in GRACE data is difficult to eliminate,thereby resulting in the loss of some gravity information related to tectonic activities.To explore the preseismic gravity anomalies in a more refined way,we first propose a method of characterizing gravity variation based on the maximum shear strain of gravity,inspired by the concept of crustal strain.The offset index method is then adopted to describe the gravity anomalies,and the spatial and temporal characteristics of gravity anomalies before earthquakes are analyzed at the scales of the fault zone and plate,respectively.In this work,experiments are carried out on the Tibetan Plateau and its surrounding areas,and the following findings are obtained:First,from the observation scale of the fault zone,we detect the occurrence of large-area gravity anomalies near the epicenter,oftentimes about half a year before an earthquake,and these anomalies were distributed along the fault zone.Second,from the observation scale of the plate,we find that when an earthquake occurred on the Tibetan Plateau,a large number of gravity anomalies also occurred at the boundary of the Tibetan Plateau and the Indian Plate.Moreover,the aforementioned experiments confirm that the proposed method can successfully capture the preseismic gravity anomalies of large earthquakes with a magnitude of less than 8,which suggests a new idea for the application of gravity satellite data to earthquake research. 展开更多
关键词 Gravity Recovery And Climate Experiment(GRACE)data maximum shear strain offset index K preseismic gravity anomalies Tibetan Plateau fault zone
下载PDF
Contractions of Certain Lie Algebras in the Context of the DLF-Theory
16
作者 Alexander Levichev Oleg Sviderskiy 《Advances in Pure Mathematics》 2014年第1期1-10,共10页
Contractions of the Lie algebras d = u(2), f = u(1 ,1) to the oscillator Lie algebra l are realized via the adjoint action of SU(2,2) when d, l, f are viewed as subalgebras of su(2,2). Here D, L, F are the correspondi... Contractions of the Lie algebras d = u(2), f = u(1 ,1) to the oscillator Lie algebra l are realized via the adjoint action of SU(2,2) when d, l, f are viewed as subalgebras of su(2,2). Here D, L, F are the corresponding (four-dimensional) real Lie groups endowed with bi-invariant metrics of Lorentzian signature. Similar contractions of (seven-dimensional) isometry Lie algebras iso(D), iso(F) to iso(L) are determined. The group SU(2,2) acts on each of the D, L, F by conformal transformation which is a core feature of the DLF-theory. Also, d and f are contracted to T, S-abelian subalgebras, generating parallel translations, T, and proper conformal transformations, S (from the decomposition of su(2,2) as a graded algebra T + Ω + S, where Ω is the extended Lorentz Lie algebra of dimension 7). 展开更多
关键词 LIE ALGEBRAS with Invariant LORENTZIAN Forms LORENTZIAN Symmetric Spaces contractionS of LIE ALGEBRAS Conformal LIE Algebra Segals Chronometric Theory DLF-Theory
下载PDF
亚甲蓝与硫酸化茯苓多糖相互作用机理的研究 被引量:3
17
作者 高贵珍 焦庆才 +1 位作者 丁一磊 陈雷 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2005年第4期608-612,共5页
为从分子水平认识硫酸化多糖分子与小分子之间相互作用的机理,文章采用氯磺酸吡啶法(Wol from法)对茯苓多糖进行结构修饰,制得硫酸化茯苓多糖(SP)。通过理论模型测得亚甲蓝(MB)与SP最大结合数N =5 4 ,结合常数K =1 .5 6 3×10 6,考... 为从分子水平认识硫酸化多糖分子与小分子之间相互作用的机理,文章采用氯磺酸吡啶法(Wol from法)对茯苓多糖进行结构修饰,制得硫酸化茯苓多糖(SP)。通过理论模型测得亚甲蓝(MB)与SP最大结合数N =5 4 ,结合常数K =1 .5 6 3×10 6,考察了反应体系中MB/SP摩尔比、NaCl、乙醇、羟丙基 β环糊精以及TritonX 10 0对相互作用的影响。探讨了MB与SP相互作用产生变色反应的机理,认为其是在MB与SP大分子间发生静电相互作用的基础上,结合态MB分子之间的疏水相互作用所引起的。 展开更多
关键词 -Β- TRITON X-100 NaCl SP MB
下载PDF
Integrated design optimization of composite frames and materials for maximum fundamental frequency with continuous fiber winding angles 被引量:3
18
作者 Zunyi Duan Jun Yan +2 位作者 Ikjin Lee Jingyuan Wang Tao Yu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2018年第6期1084-1094,共11页
Fiber reinforced composite frame structure is an ideal lightweight and large-span structure in the fields of aerospace,satellite and wind turbine.Natural fundamental frequency is one of key indicators in the design re... Fiber reinforced composite frame structure is an ideal lightweight and large-span structure in the fields of aerospace,satellite and wind turbine.Natural fundamental frequency is one of key indicators in the design requirement of the composite frame since structural resonance can be effectively avoided with the increase of the fundamental frequency.Inspired by the concept of integrated design optmization of composite frame structures and materials,the design optimization for the maximum structural fundamental frequency of fiber reinforced frame structures is proposed.An optimization model oriented at the maximum structural fundamental frequency under a composite material volume constraint is established.Two kinds of independent design variables are optimized,in which one is variables represented structural topology,the other is variables of continuous fiber winding angles.Sensitivity analysis of the frequency with respect to the two kinds of independent design variables is implemented with the semi-analytical sensitivity method.Some representative examples in the manuscript demonstrate that the integrated design optimization of composite structures can effectively explore coupled effects between structural configurations and material properties to increase the structural fundamental frequency.The proposed integrated optimization model has great potential to improve composite frames structural dynamic performance in aerospace industries. 展开更多
关键词 Integrated OPTIMIZATION maximum FUNDAMENTAL frequency Composite FRAME structures Continuous fiber WINDING angle SEMI-ANALYTICAL sensitivity analysis
下载PDF
Effect of areca on contraction of colonic muscle strips in rats 被引量:20
19
作者 Dong-Ping Xie Lian-Bi Chen,Department of Physiology,Medical College,Shandong University,Jinan 250012,Shandong Province,China Wei Li Song-Yi Qu Tian-Zhen Zheng,Department of Physiology,Lanzhou Medical College,Lanzhou 730000,Gansu Province,China Ying-Li Yang,Northwest Normal University,Lanzhou 730070,Gansu Province,China Yong-Hui Ding Yu-Ling Wei,Drug Control Institute of Gansu Province,Lanzhou 730000,Gansu Province,China 《World Journal of Gastroenterology》 SCIE CAS CSCD 2002年第2期350-352,共3页
AIM: To investigate the effects of areca on the contractile activity of isolated colonic muscle strips in rats and mechanism involved. METHODS: Each strip (LMPC, longitudinal muscle of proximal colon; CMPC, circular m... AIM: To investigate the effects of areca on the contractile activity of isolated colonic muscle strips in rats and mechanism involved. METHODS: Each strip (LMPC, longitudinal muscle of proximal colon; CMPC, circular muscle of proximal colon; LMDC, longitudinal muscle of distal colon; CMDC, circular muscle of distal colon.) was suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees C), bubbled continuously with 950 mL.L(-1) O(2) and 50 mL.L(-1) CO(2). The mean contractile amplitude (A), the resting tension (T), and the contractile frequency (F) were simultaneously recorded on recorders. RESULTS: Areca dose dependently increased the mean contractile amplitude, the resting tension of proximal and distal colonic smooth muscle strips in rats (P【0.05). It also partly increased the contractile frequency of colonic smooth muscle strips in rats (P【0.05). The effects were partly inhibited by atropine (the resting tension of LMPC decreased from 0.44 +/- 0.12 to 0.17 +/- 0.03; the resting tension of LMDC decreased from 0.71 +/- 0.14 to 0.03 +/- 0.01; the mean contractile amplitude of LMPC increased from -45.8 +/- 7.2 to -30.5 +/- 2.9; the motility index of CMDC decreased from 86.6 +/- 17.3 to 32.8 +/- 9.3; P【0.05 vs areca), but the effects were not inhibited by hexamethonium (P】0.05). CONCLUSION: Areca stimulated the motility of isolated colonic smooth muscle strips in rats. The stimulation of areca might be relevant with M receptor partly. 展开更多
关键词 ARECA Animals ATROPINE Colon Female Hexamethonium In Vitro Male Muscle contraction Nicotinic Antagonists Parasympatholytics Plant Extracts RATS Rats Wistar Research Support Non-U.S. Gov't
下载PDF
A Model for the Mass-Growth of Wild-Caught Fish 被引量:1
20
作者 Katharina Renner-Martin Norbert Brunner +2 位作者 Manfred Kühleitner Werner-Georg Nowak Klaus Scheicher 《Open Journal of Modelling and Simulation》 2019年第1期19-40,共22页
The paper searched for raw data about wild-caught fish, where a sigmoidal growth function described the mass growth significantly better than non-sigmoidal functions. Specifically, von Bertalanffy’s sigmoidal growth ... The paper searched for raw data about wild-caught fish, where a sigmoidal growth function described the mass growth significantly better than non-sigmoidal functions. Specifically, von Bertalanffy’s sigmoidal growth function (metabolic exponent-pair a = 2/3, b = 1) was compared with unbounded linear growth and with bounded exponential growth using the Akaike information criterion. Thereby the maximum likelihood fits were compared, assuming a lognormal distribution of mass (i.e. a higher variance for heavier animals). Starting from 70+ size-at-age data, the paper focused on 15 data coming from large datasets. Of them, six data with 400 - 20,000 data-points were suitable for sigmoidal growth modeling. For these, a custom-made optimization tool identified the best fitting growth function from the general von Bertalanffy-Pütter class of models. This class generalizes the well-known models of Verhulst (logistic growth), Gompertz and von Bertalanffy. Whereas the best-fitting models varied widely, their exponent-pairs displayed a remarkable pattern, as their difference was close to 1/3 (example: von Bertalanffy exponent-pair). This defined a new class of models, for which the paper provided a biological motivation that relates growth to food consumption. 展开更多
关键词 GROWTH Models Described by the von Bertalanffy-Pütter Differential Equation MODEL Selection USING the Akaike Information Criterion maximum LIKELIHOOD Fit Based on a LOGNORMAL Distribution of Mass Optimization USING Simulated Annealing
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部