Total Decay Rate Research Articles

Design of adaptive load shedding by artificial neural networks

The design of an adaptive load-shedding strategy by executing an artificial neural network (ANN) and transient stability analysis for an electric utility system is presented. To prepare the training data set for an ANN, the transient stability analysis of an actual power system has been performed to solve for minimum load shedding with various operation scenarios without causing the tripping problem of generators. The Levenberg–Marquardt algorithm has been adopted and incorporated into the back-propagation learning algorithm for training feedforward neural networks. By selecting the total power generation, total load demand and frequency decay rate as the input neurons of the ANN, the minimum amount of load shedding is determined to maintain the stability of power systems. To demonstrate the effectiveness of the proposed ANN minimum load-shedding scheme, a utility power system has been selected for computer simulation and the amount of load shedding is verified by stability analysis.

Competition between adiabatic and nonadiabatic fragmentation pathways in the unimolecular decay of the ArI2(B) van der Waals complex

The competition between vibrational and electronic predissociations of the ArI2(B) van der Waals complex has been studied using several dynamical computational methods: exact quantum wave-packet propagation, time-dependent golden rule, and quasiclassical trajectory with quantum jumps model. Five electronic states are considered using recent three-dimensional coupled surfaces obtained with a perturbative diatoms-in-molecules method. Final vibrational and electronic populations, predissociation rates, and absorption spectra have been computed for I2(B,v=18-24)<--I2(X,v=0) excitations within the complex. The contribution of vibrational predissociation into the total decay oscillates as a function of vibrational excitation due to intramolecular vibrational relaxation in a sparse-intermediate regime, which induces irregular variations of the total decay rate. Franck-Condon oscillations control the branching ratios of the individual electronic predissociation channels. However, since these oscillations are out of phase as a function of vibrational excitation, they have limited effect on the oscillatory behavior of the total predissociation rate. Comparison between exact quantum and perturbative golden rule calculations shows that vibrational predissociation has some impact on the electronic predissociation process and affects the final electronic distributions. On the contrary, vibrational product distributions are not significantly affected by the electronic predissociation. A classical description of the ArI2 dynamics provides an averaged picture of the competing predissociation processes, being better adapted for treating intermolecular vibrational relaxation in the statistical limit.

Wess-Zumino current and the structure of the decay tau- -->K- pi- K+ nu tau.

We present the first study of the vector (Wess-Zumino) current in tau(-)-->K-pi-K+nu(tau) decay using data collected with the CLEO III detector at the Cornell Electron Storage Ring. We determine the quantitative contributions to the decay width from the vector and axial vector currents. Within the framework of a model by Kühn and Mirkes, we identify the quantitative contributions to the total decay rate from the intermediate states omegapi, rho(')pi, and K*K.

Decay rate of triaxially deformed proton emitters

The decay rate of a triaxially-deformed proton emitter is calculated in a particle-rotor model, which is based on a deformed Woods-Saxon potential and includes a deformed spin-orbit interaction. The wave function of the $I=7/2^{-}$ ground state of the deformed proton emitter $^{141}$Ho is obtained in the adiabatic limit, and a Green's function technique is used to calculate the decay rate and branching ratio to the first excited 2$^{+}$ state of the daughter nucleus. Only for values of the triaxial angle $\gamma$ $<5^{\circ}$ is good agreement obtained for both the total decay rate and the 2$^{+}$ branching ratio.

Nutrient Pollutant Load Analysis of Xitiaoxi Watershed in Taihu Region

污染负荷研究是实施污染物总量控制、保护水质的基础,由于非点源污染一直是水环境研究的一个难题,致使河流污染负荷估算缺乏合理的估算方法.本项研究针对太湖的富营养化问题,选取太湖上游西苕溪流域,采用GIS的流域分析方法,选取单一土地利用类型的小流域,分析流域土地类型与径流量及流域出口浓度的统计关系,获取不同土地利用类型营养盐污染的产出率,合理估算了西苕溪流域的非点源营养盐污染负荷,并根据西苕溪流域社会经济统计数据及已有的污染产出率研究成果,估算了西苕溪的点源营养盐污染负荷,在此基础上估算了西苕溪流域的营养盐污染总负荷量,分析了不同污染源在总负荷量的比例.最后通过比较估算的总负荷量与实测负荷量,计算了西苕溪流域河网体系对营养盐的降解能力.研究得出, 林地产出径流浓度总氮0.715mg/L、总磷0.039mg/L,耕地产出径流浓度总氮为2.092mg/L, 总磷0.166mg/L,西苕溪流域总氮负荷量为3143.43t/a,非点源污染负荷量为1589.52t/a;总磷负荷量为226.32t/a,非点源为108.36t/a,西苕溪流域河网体系对总氮、总磷的年降解率分别为 35.39%、21.48%.;The total pollutant load assessment is the key of water quality protection and total quantity control policy. Due to complicated mechanism of non-point pollution, there is lack of the effective methods to assess the non-point pollutant load, and the total pollutant load assessment are limited. This paper, aim at the eutrophication problem of Taihu lake, selects the sub-watersheds in Xitiaoxi watershed and nearby region with one landuse type mainly, analyze the relationship between landuse type and runoff concentration, and assess the nutrient pollutant load. Then, the point pollutant load is assess by the social-economic data and pollutant output rate of different industry type and living water. Based on the assessment of point and non-point pollutant load, the total nutrient pollutant and decay rate are calculated. According to the result of this study, the total nitrogen and phosphorus concentration of runoff from forest land are 0.715mg/l and 0.039mg/l, from agriculture land 2.092mg/l and 0.166mg/l, respectively. The total nitrogen load are 3143.43t/a in Xitiaoxi watershed, non-point nitrogen load is 1589.52t/a. The total phosphorus load are 226.32t/a and non-point phosphorus load is 108.36t/a. In Xitiaoxi river system, the annual decay rate of river network to total nitrogen load and phosphorus are 35.39% and 21.48%, respectively.

CharmlessBs→VVdecays in QCD factorization

The two body charmless decays of ${B}_{s}$ mesons to light vector mesons are analyzed within the framework of QCD factorization. This approach implies that the nonfactorizable corrections to different helicity amplitudes are not the same. The effective parameters ${a}_{i}^{h}$ for helicity $h=0,+,\ensuremath{-}$ states receive different nonfactorizable contributions and hence are helicity dependent, contrary to the naive factorization approach where ${a}_{i}^{h}$ are universal and polarization independent. The branching ratios for ${B}_{s}\ensuremath{\rightarrow}\mathrm{VV}$ decays are calculated and we find that the branching ratios of some channels are of the order of ${10}^{\ensuremath{-}5},$ which are measurable at future experiments. The transverse to total decay rate ${\ensuremath{\Gamma}}_{T}/\ensuremath{\Gamma}$ is also evaluated and found to be very small for most decay modes; so, in charmless ${B}_{s}\ensuremath{\rightarrow}\mathrm{VV}$ decays, both light vector mesons tend to have zero helicity.

Vibrational energy transfer involving Renner–Teller levels of the NCO [formula omitted] molecule

Stimulated emission pumping has been employed to prepare specific Renner–Teller levels associated with the (0 1 2) vibrational manifold of the NCO ( X ̃ 2 Π) molecule. Transfer out of these vibronic levels due to collisions with argon collision partner was monitored by laser fluorescence excitation. The total removal bimolecular rate constants were found to be large [(2–5) × 10 −10 cm 3 molecule −1 s −1]. In several cases, it was possible to observe collisional transfer between specified X ̃ (0 1 2) Renner–Teller levels. The collisional transfer of population between the Renner–Teller levels was found to be a small fraction of the total collisional loss but was comparable in magnitude to the total decay rates for the X ̃ (0 1 0) levels.

Instanton contribution to scalar charmonium and glueball decays

We study instanton contributions to hadronic decays of the scalar glueball, the pseudoscalar charmonium state $\eta_c$, and the scalar charmonium state $\chi_c$. Hadronic decays of the $\eta_c$ are of particular interest. The three main decay channels are $K\bar{K}\pi$, $\eta\pi\pi$ and $\eta'\pi\pi$, each with an unusually large branching ratio $\sim 5%$. On the quark level, all three decays correspond to an instanton type vertex $(\bar{c}c)(\bar{s}s)(\bar{d}d)(\bar{u}u)$. We show that the total decay rate into three pseudoscalar mesons can be reproduced using an instanton size distribution consistent with phenomenology and lattice results. Instantons correctly reproduce the ratio $B(\pi\pi\eta)/B(\pi\pi\eta')$ but over-predict the ratio $B(K\bar{K}\pi)/B(\pi\pi\eta(\eta'))$. We consider the role of scalar resonances and suggest that the decay mechanism can be studied by measuring the angular distribution of decay products.

Semileptonic D decay into scalar mesons

Semileptonic decays of D-mesons into scalar hadronic states are investigated. Two extreme cases are considered: a) the meson decays directly into an uncorrelated scalar state of two mesons and b) the decay proceeds via resonance formation. QCD sum rules including instanton contributions are used to calculate total and differential decay rates under the two assumptions.

Effects of light scalar mesons inη→3πdecay

We study the role of a possible nonet of light scalar mesons in the still interesting � ! 3� decay process, with the primary motivation of learning more about the scalars themselves. The framework is a conventional non-linear chiral Lagrangian of pseudoscalars and vectors, extended to include the scalars. The parameters involving the scalars were previously obtained to fit the s-wave �� and �K scatterings in the region up to about 1 GeV as well as the strong decay � ' ! ���. At first, one might expect a large enhancement from diagrams including a light �(560). However there is an amusing cancellation mechanism which prevents this from occurring. In the simplest model there is an enhancement of about 13 per cent in the � ! 3� decay rate due to the scalars. In a more complicated model which includes derivative type symmetry breakers, the cancellation is modified and the scalars contribute about 30 percent of the total decay rate (although the total is not significantly changed). The vectors do not contribute much. Our model produces a reasonable estimate for the related a0(980) f0(980) mixing strength, which has been a topic of current debate. Promising directions for future work along the present line are suggested.

NONMESONIC DECAY OF Λ AND ΛΛ HYPERNUCLEI

Nonmesonic weak decays of single and double hypernuclei are studied on the basis of two-body baryon-baryon interactions, ΛN → NN and ΛΛ → YN transitions. The two-body weak transition is described by the combination of two processes, i.e., meson exchange and direct quark processes. The result indicates the importance of the direct quark(DQ) contribution. It largely enhances both the total decay rate and Γnn/Γpn ratio, and its property is different from the heavy meson exchanges (i.e. η, ρ, ω, and K*). The quark-meson hybrid picture, such as π+K+ DQ , reproduces the current experimental data except for the asymmetry parameter for light hypernuclei. The ΛΛ → YN transition in ΛΛ hypernucleus is complement of the ΛN → NN transition because it occurs only in the J = 0 channel which is hidden by J = 1 transition in the ΛN → NN case.

M1/E2/M2 decay rates in Fe VII, Fe IX, Fe X and Fe XIII measured using aheavy-ion storage ring

Lifetimes (the inverse of the total decay rates) of several 3p and 3d levels in Ca-,Ar-, Cl- and Si-like ions of Fe that decay only by electric-dipole-forbiddentransitions have been measured optically using a heavy-ion storage ring, observingeither near-UV or EUV light. In several cases, more than one decay contributes toa given decay curve, which complicates the analysis. The lifetime results, with aprecision ranging from 0.8 to 10%, compare well with some theoretical predictions.

Semi-inclusive nonleptonic decaysB→Ds(*)X

We calculate the total and differential decay rates for the semi-inclusive nonleptonic decays $B\to D_s^{(*)} X_q$ ($q=c$ or $u$) under the factorization hypothesis. The initial bound state effect is treated using the light-cone expansion and the heavy quark effective theory. We investigate the contribution of the penguin amplitude for the decay mode $B\to D_s^{(*)} X_c$ and find that it is small but non-negligible. The resulting decay rates for $B\to D_s^{(*)} X_c$ agree with the measurements. The use of the decay mode $B\to D_s^{(*)} X_u$ to determine $|V_{ub}|$ is discussed.

SemileptonicDdecay into scalar mesons: A QCD sum rule approach

Semileptonic decays of D mesons into scalar hadronic states are investigated. Two extreme cases are considered: (a) the meson decays directly into an uncorrelated scalar state of two mesons and (b) the decay proceeds via resonance formation. QCD sum rules including instanton contributions are used to calculate total and differential decay rates under the two assumptions.

Quantum tunneling of Bose-Einstein condensates in optical lattices under gravity.

We investigate the quantum tunneling of Bose-Einstein condensates in optical lattices under gravity in the "Wannier-Stark localization" regime and "Landau-Zener tunneling" regime. Our results agree with experimental data [B. P. Anderson et al., Science 282, 1686 (1998); F. S. Cataliotti et al., Science 293, 843 (2001)]. We obtain the total decay rate which is valid over the entire range of temperatures, and show how it reduces to the appropriate results for the classical thermal activation at high temperatures, the thermally assisted tunneling at intermediate temperatures, and the pure quantum tunneling at low temperatures. We design an experimental protocol to observe this new phenomenon in further experiments.

Is Nuclear Structure Relevant to Non-Mesonic Hyper-nuclear Weak Decay?

This work studies the relevance of nuclear structure in the nonmesonic weak decay of Λ-hypernuclei, with the mechanism of ΛN → NN transition being restricted to one pion exchange (OPE) only. As an application, for the hypernucleus Λ12C a comparison between the L-S coupling and the j-j coupling gives an estimate of the range of nuclear structure effects. A considerable dependence is found of the total decay rate and the ratio Гn/qGp on the single particle properties of nuclear models. The possible contribution from the ΔI = 3/2 channel is investigated in a phenomenological manner.

Dissipation, noise, and vacuum decay in quantum field theory.

We study the process of vacuum decay in quantum field theory focusing on the stochastic aspects of the interaction between long- and short-wavelength modes. This interaction results in a diffusive behavior of the reduced Wigner function describing the state of long-wavelength modes, and thereby to a finite activation rate even at zero temperature. This effect can make a substantial contribution to the total decay rate.

Vacuum decay in quantum field theory

We study the contribution to vacuum decay in field theory due to the interaction between the long- and short-wavelength modes of the field. The field model considered consists of a scalar field of mass M with a cubic term in the potential. The dynamics of the long-wavelength modes becomes diffusive in this interaction. The diffusive behavior is described by the reduced Wigner function that characterizes the state of the long-wavelength modes. This function is obtained from the whole Wigner function by integration of the degrees of freedom of the short-wavelength modes. The dynamical equation for the reduced Wigner function becomes a kind of Fokker-Planck equation which is solved with suitable boundary conditions enforcing an initial metastable vacuum state trapped in the potential well. As a result a finite activation rate is found, even at zero temperature, for the formation of true vacuum bubbles of size ${M}^{\ensuremath{-}1}.$ This effect makes a substantial contribution to the total decay rate.

Ratio of hadronic decay rates ofJ/ψandψ(2S)and theρπpuzzle

The so-called $\ensuremath{\rho}\ensuremath{\pi}$ puzzle of $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ decays is examined using the experimental data available to date. Two different approaches were taken to estimate the ratio of $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ hadronic decay rates. While one of the estimates could not yield the exact ratio of $\ensuremath{\psi}(2S)$ to $J/\ensuremath{\psi}$ inclusive hadronic decay rates, the other, based on a computation of the inclusive $\mathrm{ggg}$ decay rate for $\ensuremath{\psi}(2S)(J/\ensuremath{\psi})$ by subtracting other decay rates from the total decay rate, differs by two standard deviations from the naive prediction of perturbative QCD, even though its central value is nearly twice as large as what was naively expected. A comparison between this ratio, upon making corrections for specific exclusive two-body decay modes, and the corresponding experimental data confirms the puzzles in $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ decays. We find from our analysis that the exclusively reconstructed hadronic decays of the $\ensuremath{\psi}(2S)$ account for only a small fraction of its total decays, and a ratio exceeding the above estimate should be expected to occur for a considerable number of the remaining decay channels. We also show that the recent new results from the BES experiment provide crucial tests of various theoretical models proposed to explain the puzzle.

Local-field corrections to the decay rate of excited molecules in absorbing cavities: The Onsager model

The decay rate and the classical radiation power of an excited molecule (atom) in the center of a dispersive and absorbing dielectric sphere, taken as a simple model of a cavity, are calculated adopting the Onsager model for the local field. The local-field correction factor to the external (radiation and absorption) power loss of the molecule is found to be $|3\ensuremath{\varepsilon}(\ensuremath{\omega})/[3\ensuremath{\varepsilon}(\ensuremath{\omega})+1]{|}^{2},$ with $\ensuremath{\varepsilon}(\ensuremath{\omega})$ being the dielectric function of the sphere. However, local-field corrections to the total decay rate (power loss) of the molecule are found to be much more complex including those to the decay rate in the infinite cavity medium, as derived recently by Scheel et al. [Phys. Rev. A $60,$ 4094 (1999)], and similiar corrections to the cavity-induced decay rate. The results obtained can be cast into general forms that do not rely on the specific cavity shape and molecule position considered. This suggests the general results for the local-field corrections to the decay rate and to the external power loss of a molecule in an absorbing cavity that are valid for molecule positions away from the cavity walls.