Synthesis of RC transfer immittance functions with a minimum number of capacitors     

H.C. Reddy  C.P. Reddy  M.N.S. Swamy  V. Ramachandran 《Journal of The Franklin Institute》1982,313(4):197-206

In this paper a method for the realization of RC transfer immittance functions with an unsymmetrical lattice is presented. The method yields minimal capacitor realizations for Z₁₂(s) with no pole at s = 0 and ?y₁₂(s) having no pole at s = ∞. The number of resistors needed are only two more than the minimum needed.  相似文献   

秦岭自然保护区群成本效益研究(Ⅱ)——成本效益预测     

王昌海  曹世雄  温亚利  李强  司开创  胡崇德 《资源科学》2012,34(7):1362-1368

本研究在秦岭自然保护区群成本效益计量研究成果的基础上,对成本效益进行进一步分析及预测。运用统计软件SPSS17.0结合十余种拟合曲线,根据秦岭自然保护区群中7个国家级自然保护区的成本效益截面数据,尝试性地进行了综合效益及三大成本之间关系曲线拟合。研究结果表明：根据模型拟合优度R2大小及显著水平Sig.判断,最终得出了成本效益之间的关系式。即三个拟合函数分别是：①综合效益（Qt）与直接保护成本（Xa）的函数曲线方程为：Qt=-68.244＋870.688Xa-2493.849Xa2＋2304.879Xa3;②综合效益（Qt）与间接保护成本（Xb）的函数曲线方程为：Qt=17.844e1.986Xb;③综合效益（Qt）与机会保护成本（Xc）的函数曲线方程为：Qt=-78.157＋104.775Xc-32.953Xc2＋3.296Xc3。本研究结果可以为国家有关部门进行保护区投资做有益的帮助,同时为陕西省自然保护区保护政策的完善做理论支撑。  相似文献   

Report on the work of the Bartol Research Foundation, 1933–1934     

W.F.G. Swann 《Journal of The Franklin Institute》1934,218(2):173-241

Using the velocity analyzer of Zartman with improved technique the combined velocity spectrum of Bi atoms and Bi₂ molecules was obtained at 827°, 851°, 875°, 899°, 922°, 947° C. From the spectral distribution curves the relative abundance of Bi atoms and Bi₂ molecules in the beams at the above temperatures could be determined to 1 per cent. The vapor pressure curve of Bi was obtained experimentally by the method of effusion and the values so obtained were combined with the degree of dissociation of the vapor as computed from the beams to give the heat of dissociation. The heat of dissociation was computed from the data, assuming the pressure to be given by the temperature of the crucible T_c. In calculating the heat of dissociation, the equilibrium temperature was taken as that of the slit chamber T_s which was 24° above T_c. The results of these calculations plotted with log₁₀K_p as ordinates against $\text{1}\text{T}{}_{\mathrm{s}}$ give a straight line whose slope yields the value of the heat of dissociation as 77,100±1200 calories. The curves for the distribution of velocities observed and computed on the assumption of a given ratio of Bi atoms to Bi₂ molecules in the beam were compared in an attempt to test the law of distribution of velocities. On the high velocity side agreement in two curves was obtained within the limits of experimental accuracy. On the low velocity side important deviations were noted of such a sort that the observed curves below a velocity $\text{α}\text{2}$, (α is the most probable velocity) gave more molecules than the theory demanded. Other deviations were observed on some of the runs taken with a fourth slit in which a deficiency of molecules was observed between velocities of .75α and $\text{α}\text{2}$. This deviation was probably due to a warping of the fourth slit carriage due to heat. The nature of the variation at velocities less than $\text{α}\text{2}$ indicated the presence of molecules of greater mass than Bi₂ in the beam and at the lower temperatures a distinct peak corresponding to Bi₈ molecules was observed which were present to less than 2 per cent. The vapor pressure curve for Bi was determined by least square reduction of the observed points to be given by $\text{log}{}_{10}\text{P = ? 52.23 ×}\text{195.26}\text{T}\text{+ 8.56}$ between 1100° and 1220° abs. It lies very close to the extrapolated curve given in the International Critical Tables.  相似文献   

Influence of buoyancy-driven flow on mass transfer in a two-stream microfluidic channel: Introduction of cryoprotective agents into cell suspensions     

Rohini Bala Chandran  Jennifer Reinhart  Erin Lemke  Allison Hubel 《Biomicrofluidics》2012,6(4)

A variety of methods have been used to introduce chemicals into a stream or to mix two or more streams of different compositions using microfluidic devices. In the following paper, the introduction of cryoprotective agents (CPAs) used during cryopreservation of cells in order to protect them from freezing injuries and increase viability post thaw is described. Dimethylsulphoxide (DMSO) is the most commonly used CPA. We aim to optimize the operating conditions of a two-stream microfluidic device to introduce a 10% vol/vol solution of DMSO into a cell suspension. Transport behavior of DMSO between two streams in the device has been experimentally characterized for a spectrum of flow conditions (0.7 < Re < 10), varying initial donor stream concentrations, (1% vol/vol < C_o < 15% vol/vol) and different flow rate fractions (0.23 < f_q < 0.77). The outlet cell stream concentration is analyzed for two different flow configurations: one with the cell stream flowing on top of the DMSO-rich donor stream, and the other with the cell stream flowing beneath the heavy DMSO-laden stream. We establish a transition from a diffusive mode of mass transfer to gravity-influenced convective currents for Atwood numbers (A_t) in the range of (1.7 × 10⁻³ < A_t < 3.1 × 10⁻³) for the latter configuration. Flow visualization with cells further our understanding of the effect of A_t on the nature of mass transport. Cell motion studies performed with Jurkat cells confirm a high cell recovery from the device while underscoring the need to collect both the streams at the outlet of the device and suggesting flow conditions that will help us achieve the target DMSO outlet concentration for clinical scale flow rates of the cell suspension.  相似文献   

Growth dynamics of citations of cumulative papers of individual authors according to progressive nucleation mechanism: Concept of citation acceleration     

Keshra Sangwal 《Information processing & management》2013

Using data generated by progressive nucleation mechanism on the cumulative fraction of citations of individual papers published successively by a hypothetical author, an expression for the time dependence of the cumulative number L_sum(t) of citations of progressively published papers is proposed. It was found that, for all nonzero values of constant publication rate ΔN, the cumulative citations L_sum(t) of the cumulative N papers published by an author in his/her entire publication career spanning over T years may be represented in distinct regions: (1) in the region 0 < t < Θ₀ (where Θ₀ ≈ T/3), L_sum(t) slowly increases proportionally to the square of the citation time t, and (2) in the region t > Θ₀, L_sum(t) approaches a constant L_sum(max) at T. In the former region, the time dependence of L_sum(t) of an author is associated with three parameters, viz. the citability parameter λ₀, the publication rate ΔN and his/her publication career t. Based on the predicted dependence of L_sum(t) on t, a useful scientometric age-independent measure, defined as citation acceleration a = L_sum(t)/t², is suggested to analyze and compare the scientific activities of different authors. Confrontation of the time dependence of cumulative number L_sum(t) of citations of papers with the theoretical equation reveals one or more citation periods during the publication careers of different authors.  相似文献   

Parameter identification of a class of time-varying systems via orthogonal shifted legendre polynomials     

Chyi Hwang  Tong-Yi Guo 《Journal of The Franklin Institute》1984,318(1):56-69

A method of using orthogonal shifted Legendre polynomials for identifying the parameters of a process whose behaviour can be modelled by a linear differential equation with time-varying coefficients in the form of finite-order polynomials is presented. It is based on the repeated integration of the differential equation and the representations of $\text{∫}\text{0}\text{t}$s(τ) dτ = Ps(t) and ts(t) = Rs(t), where P and R are constant matrices and s(t) is a shifted Legendre vector whose elements are shifted Legendre polynomials. The differential input-output equation is converted into a set of overdetermined linear algebraic equations for a least squares solution. The results of simulation studies are included to illustrate the applicability of the method.  相似文献   

Theory of nonlinear systems     

Y.H. Ku 《Journal of The Franklin Institute》1983,315(1):1-26

This paper gives a general review of the Theory of Nonlinear Systems. In 1960, the author presented a paper “Theory of Nonlinear Control” at the First IFAC Congress at Moscow. Professor Norbert Wiener, who attended this Congress, drew attention to his work on the synthesis and analysis of nonlinear systems in terms of Hermitian polynomials in the Laguerre coefficients of the past of the input.Wiener's original idea was to use white noise as a probe on any nonlinear system. Applying this input to a Laguerre network gives u₁, u₂,…, u_s, and then to a Hermite polynomial generator gives V(α)'s. Applying the same input to the actual nonlinear system gives output c(t). Putting c(t) and V(α)'s through a product averaging device, we get $\text{c(t)V(α)}\text{=}\text{A}{}_{\mathrm{\alpha }}\text{2л}{}^{\mathrm{<mtext>s</mtext><mtext>2</mtext>}}$, where the upper bar denotes time average and A_α's can be considered as characteristic coefficients of the nonlinear system. A desired output z(itt) may replace c(itt) to get a new set of A_α's.The Volterra functional method suggested by Wiener in 1942 has been greatlydeveloped from 1955 to the present. The method involves a multi-dimensional convolution integral with multi- dimensional kernels. The associated multi-dimensional transforms are given by Y.H. Ku and A.A. Wolf (J. Franklin Inst., Vol. 281, pp. 9–26, 1966). Wiener extended the Volterra functionals by forming an orthogonal set of functionals known as G-functionals, using Gaussian white noise as input. Volterra kernels and Wiener kernels can be correlated and form the characteristic functions of nonlinear systems.From an extension of the linear system to the nonlinear system, the input-output crosscorrelation φ_xy can be shown to be equal to the convolution of system impulse response h₁ with the autocorrelation φ_xx. Using the white noise as input, where its power density spectrum is a constant, say, A, the crosscorrelation is given by φ_xy(σ) = Ah₁(σ), while the autocorrelation is φ_xx(τ) = Au(τ). This extension forms the basis of an optimum method for nonlinear system identification. Measurement of kernels can be made through proper circuitry.Parallel to the Volterra series and the Wiener series, another series based on Taylor-Cauchy transforms developed since 1959 are given for comparison. The Taylor-Cauchy transform method can be applied in the analysis of simultaneous nonlinear systems. It is noted that the Volterra functional method and the Taylor-Cauchy transform method give identical final results.A selected Bibliography is appended not only to include other aspects of nonlinear system theory but also to show the wide application of nonlinear system characterization and identification to problems in biology, ecology, physiology, cybernetics, control theory, socio- economic systems, etc.  相似文献   

High-Chern-number and high-temperature quantum Hall effect without Landau levels     

Jun Ge  Yanzhao Liu  Jiaheng Li  Hao Li  Tianchuang Luo  Yang Wu  Yong Xu  Jian Wang 《国家科学评论(英文版)》2020,7(8):1280

The quantum Hall effect (QHE) with quantized Hall resistance of h/νe² started the research on topological quantum states and laid the foundation of topology in physics. Since then, Haldane proposed the QHE without Landau levels, showing nonzero Chern number |C| = 1, which has been experimentally observed at relatively low temperatures. For emerging physics and low-power-consumption electronics, the key issues are how to increase the working temperature and realize high Chern numbers (C > 1). Here, we report the experimental discovery of high-Chern-number QHE (C = 2) without Landau levels and C = 1 Chern insulator state displaying a nearly quantized Hall resistance plateau above the Néel temperature in MnBi₂Te₄ devices. Our observations provide a new perspective on topological matter and open new avenues for exploration of exotic topological quantum states and topological phase transitions at higher temperatures.  相似文献   

Charmonium and charmoniumlike states at the BESIII experiment     

Chang-Zheng Yuan 《国家科学评论(英文版)》2021,8(11)

Charmonium is a bound state of a charmed quark and a charmed antiquark, and a charmoniumlike state is a resonant structure that contains a charmed quark and antiquark pair but has properties that are incompatible with a conventional charmonium state. While operating at center-of-mass energies from 2 to 5 GeV, the BESIII experiment can access a wide mass range of charmonium and charmoniumlike states, and has contributed significantly in this field. We review BESIII results involving conventional charmonium states, including the first observation of the M1 transition ψ(2S) → γη_c(2S) and the discovery of the ψ₂(3823) state; and report on studies of charmoniumlike states, including the discoveries of the Z_c(3900) and Z_c(4020) tetraquark candidates, the resolution of the fine structure of the Y(4260) state, the discovery of the new production process e⁺e⁻ → γX(3872) and the uncovering of strong evidence for the commonality among the X(3872), Y(4260) and Z_c(3900) states. The prospects for further research at BESIII and proposed future facilities are also presented.  相似文献   

Dielectrophoresis based discrimination of human embryonic stem cells from differentiating derivatives     

Srinivas Velugotla  Steve Pells  Heidi K. Mjoseng  Cairnan R. E. Duffy  Stewart Smith  Paul De Sousa  Ronald Pethig 《Biomicrofluidics》2012,6(4)

Assessment of the dielectrophoresis (DEP) cross-over frequency (f_xo), cell diameter, and derivative membrane capacitance (C_m) values for a group of undifferentiated human embryonic stem cell (hESC) lines (H1, H9, RCM1, RH1), and for a transgenic subclone of H1 (T8) revealed that hESC lines could not be discriminated on their mean f_xo and C_m values, the latter of which ranged from 14 to 20 mF/m². Differentiation of H1 and H9 to a mesenchymal stem cell-like phenotype resulted in similar significant increases in mean C_m values to 41–49 mF/m² in both lines (p < 0.0001). BMP4-induced differentiation of RCM1 to a trophoblast cell-like phenotype also resulted in a distinct and significant increase in mean C_m value to 28 mF/m² (p < 0.0001). The progressive transition to a higher membrane capacitance was also evident after each passage of cell culture as H9 cells transitioned to a mesenchymal stem cell-like state induced by growth on a substrate of hyaluronan. These findings confirm the existence of distinctive parameters between undifferentiated and differentiating cells on which future application of dielectrophoresis in the context of hESC manufacturing can be based.  相似文献   

Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency     

Ran An  Katherine Massa  David O. Wipf  Adrienne R. Minerick 《Biomicrofluidics》2014,8(6)

AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (f_c), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above f_c. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H⁺] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5f_c). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H⁺] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 V_pp potential, and voltage dependency was explored from 3.5 to 7.5 V_pp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial position.  相似文献