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1.
We present an alternative scheme for implementing the unconventional geometric two-qubit phase gate and preparing multiqubit entanglement by using a frequency-modulated laser field to simultaneously illuminate all ions. Selecting the index of modulation yields selective mechanisms for coupling and decoupling between the internal and the external states of the ions. By the selective mechanisms, we obtain the unconventional geometric two-qubit phase gate, multiparticle Greenberger--Horne--Zeilinger states and highly entangled cluster states. Our scheme is insensitive to the thermal motion of the ions. 相似文献
2.
This paper realizes a nondestructive and complete Bell-state analysis for atomic qubit systems by a designed nondestructive and complete Bell-state analyser. In the scheme, Bell states are completely discriminated by two bits of classical informations which comes from the locality single atom detection on two auxiliary atoms, during which the Bell states are not affected. The needed devices are well within the bounds of current technology, and then the scheme is experimentally feasible. 相似文献
3.
《Marine Policy》2013
Defining, strengthening and enforcing rights over fisheries resources is frequently identified as central to overcoming ‘the tragedy of the commons’ and associated environmental and economic challenges in fisheries systems. Though economic theory generally suggests that output control (e.g. quotas) creates the strongest incentives for efficiency and conservation, input controls (e.g. on effort) remain common. This paper explores the rationale for, and implications of, employing a transferable effort scheme in one of the largest and most valuable fisheries. In 2007, eight Pacific Island countries implemented the Vessel Day Scheme with the aims of strengthening their rights over tuna resources and control over economic and environmental trends. Four years since implementation, the scheme has significantly increased economic returns for the island states and generated improvements in data reporting. However, it has not generated a firm limit on fishing effort and its structure has made it difficult to directly target the biological concerns of individual species within the multi-species fishery. In the future, outcomes of the Vessel Day Scheme will continue to be tempered by the structural limitations of effort-based regulatory scheme, market conditions in the sector and the willingness of firms and island states to clarify, abide by and enforce the technical components of the scheme. 相似文献
4.
Using a proper approximation scheme to the centrifugal term, we study any l-wave continuum states of the Schrõdinger equation for the modified Morse potential. The normalised analytical radial wave functions are presented, and a corresponding calculation formula of phase shifts is derived. It is shown that the energy levels of the continuum states reduce to those of the bound states at the poles of the scattering amplitude. Some numerical results are calculated to show the accuracy of our results. 相似文献
5.
This paper proposes scalable schemes to generate the Greenberger--Horne--Zeilinger (GHZ) state and the cluster state with atomic ensembles via the dipole blockade mechanism on an atom chip, where the qubit is not carried by a single atom but an atomic ensemble. In the protocols, multiqubit entangled states are determinately prepared. Needlessness for single-photon source further decreases the complexity of the experiment. Based on the present laboratory technique, the schemes may be realized. The achieved results reveal a prospect for large-scale quantum communication and quantum computation. 相似文献
6.
Feedback and Feedforward Optimal Control for Offshore Jacket Platforms 总被引：18，自引：0，他引：18
The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load that offshore structures are subjected to, and it can be taken as harmonic excitation for the system. The iineafized Morison equation is employed to estimate the wave loading. The main result concerns the existence and design of a realizable optimal regulator, which is proposed to damp the forced oscillation in an optimal fashion. For demonstration of the effectiveness of the control scheme, the platform performance is investigated for different wave states. The simulations axe based on the tuned mass damper (TMD) and the active mass damper (AMD) control devices. It is demonstrated that the control scheme is useful in reducing the displacement response of jacket-type offshore platforms. 相似文献
7.
A numerical method is proposed for solving the two layer shallow water equations with variable bathymetry in one dimension based on high-resolution f-wave-propagation finite volume methods. The method splits the jump in the fluxes and source terms into waves propagating away from each grid cell interface. It addresses the required determination of the system’s eigenstructure and a scheme for evaluating the flux and source terms. It also handles dry states in the system where the bottom layer depth becomes zero, utilizing existing methods for the single layer solution and handling single layer dry states that can exist independently. Sample results are shown illustrating the method and its handling of dry states including an idealized ocean setting. 相似文献
8.
9.
We propose a scheme for the deterministic generation of qutrit entanglement for two atoms trapped in an optical cavity. Taking advantage of the adiabatic passage, the operation is immune to atomic spontaneous emission as the atomic excited states are never populated; under certain conditions, the probability that the cavity is excited is negligible. We also study the influences of the dissipation due to the atomic spontaneous emission and cavity decay. 相似文献
10.
The impact of mean dynamic topography on a sea-level anomaly assimilation in the South China Sea based on an eddy-resolving model 总被引：1，自引：0，他引：1
The sea-level anomaly (SLA) from a satellite altimeter has a high accuracy and can be used to improve ocean state estimation by assimilation techniques. However, the lack of an accurate mean dynamic topography (MDT) is still a bothersome issue in an ocean data assimilation. The previous studies showed that the errors in MDT have significant impacts on assimilation results, especially on the time-mean components of ocean states and on the time variant parts of states via nonlinear ocean dynamics. The temporal-spatial differences of three MDTs and their impacts on the SLA analysis are focused on in the South China Sea (SCS). The theoretical analysis shows that even for linear models, the errors in MDT have impacts on the SLA analysis using a sequential data assimilation scheme. Assimilation experiments, based on EnOI scheme and HYCOM, with three MDTs from July 2003 to June 2004 also show that the SLA assimilation is very sensitive to the choice of different MDTs in the SCS with obvious differences between the experimental results and observations in the centre of the SCS and in the vicinity of the Philippine Islands. A new MDT for assimilation of SLA data in the SCS was proposed. The results from the assimilation experiment with this new MDT show a marked reduction (increase) in the RMSEs (correlation coefficient) between the experimental and observed SLA. Furthermore, the subsurface temperature field is also improved with this new MDT in the SCS. 相似文献
11.
In this scheme, two quantum oscillators in a planar radio frequency ion trap are coupled by the trap electrodes. The ions motional states encode the quantum bits (qubits), and a swap gate could be achieved. Under different conditions of the experiments, the intensity of the coupling between two quantum oscillators and the dissipation of the system are calculated. We compute fidelities for a quantum swap gate and discuss experimental issues. 相似文献
12.
During the last decades, marine pollution with anthropogenic litter has become a worldwide major environmental concern. Standardized monitoring of litter since 2001 on 78 beaches selected within the framework of the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) has been used to identify temporal trends of marine litter. Based on statistical analyses of this dataset a two-part multi-criteria evaluation system for beach litter pollution of the North-East Atlantic and the North Sea is proposed. Canonical correlation analyses, linear regression analyses, and non-parametric analyses of variance were used to identify different temporal trends. A classification of beaches was derived from cluster analyses and served to define different states of beach quality according to abundances of 17 input variables. The evaluation system is easily applicable and relies on the above-mentioned classification and on significant temporal trends implied by significant rank correlations. 相似文献
13.
The performance of coastal vertical seawalls in extreme weather events is studied numerically, aiming to provide guidance in designing and reassessing coastal structures with vertical wall. The extreme wave run-up and the pressure on the vertical seawall are investigated extensively. A time-domain higher-order boundary element method (HOBEM) is coupled with a mixed Eulerian-Lagrangian technique as a time marching technique. Focused wave groups are generated by a piston wave-maker in the numerical wave tank using a wave focusing technique for accurately reproducing extreme sea states. An acceleration-potential scheme is used to calculate the transient wave loads. Comparisons with experimental data show that the extended numerical model is able to accurately predict extreme wave run-ups and pressures on a vertical seawall. The effects of the wave spectrum bandwidth, the wall position and the wave nonlinearity on the wave run-up and the maximum wave load on the vertical seawall are investigated by doing parametric studies. 相似文献
14.
Parameter estimation is defined as the process to adjust or optimize the model parameter using observations. A long-term problem in ensemble-based parameter estimation methods is that the parameters are assumed to be constant during model integration. This assumption will cause underestimation of parameter ensemble spread,such that the parameter ensemble tends to collapse before an optimal solution is found. In this work, a two-stage inflation method is developed for parameter estimation, which ... 相似文献
15.
《Ocean Modelling》2010,35(3-4):92-110
A convective adjustment (CA) algorithm is thought to be responsible for grid-scale oceanic-state sustained oscillations seen in oceanic general circulation models (OGCM), an effect that is most evident in simulations with coarse spatio-temporal scales. The CA algorithm is thought to inadvertently create a salt oscillator. Several studies have confirmed that a flip-flop type salt oscillator, which is reminiscent in some respects of simple CA schemes, can develop sustained oscillations. Subsequently, several researchers were able to show how coupled salt oscillators, reacting in a particular temporal sequence, are capable of producing large-scale oscillations not unlike those found in the OGCM simulations. However, the proxy models used to study how CA can create these oscillations in large-scale simulations were never directly related to OGCM results.Here we couple hydrodynamics to the CA and look at zonally-driven flows in the low-frequency, large-scale limit. Adding flow is a step in the direction of developing an analytically tractable model with which to understand the basics of OGCMs. We analytically determine whether, and under what circumstances, the CA scheme is responsible for sustained oscillations.We carry out this program for four basic box-model configurations, each inspired by the general shape of the eigenfunctions and constraints of the large-scale zonally-averaged forced flow over a hemisphere. Furthermore, in order to make our results relevant to the Meridional Ocean Circulation, we also investigate the effect of replacing the usual assumption of a linear relation between thermohaline flow rate and horizontal density gradient with a nonlinear hydraulic relationship.We find that a salt oscillator does not occur in the most common box-model configurations. In one of our models, however, we find wide parameter ranges in which all steady states calculated for the model fail to satisfy the CA scheme, the situation which is expected to result in CA-induced oscillations. The model in question corresponds to a hemispheric shallow thermohaline flow over a deep reservoir. However, we find that oscillations occur in these parameter ranges only if the density threshold for convection is negative, i.e., if the CA scheme turns on convection between vertically adjacent boxes when the density stratification between them is still slightly stable. In this situation, the amplitude and period of the oscillations depend strongly on the size of the density threshold, both vanishing as the threshold is taken toward zero. We also show that the same is true in the Welander flip-flop model of a single salt oscillator. For positive values of the threshold, that is, when the CA scheme is allowed to ignore small unstable stratification changes, oscillations do not occur in the limit of integration time step going to zero, but can still be seen when the time step is finite, even if small. Moreover, the system evolves toward a new steady state, one in which the stratification in one box is exactly the threshold value itself. We show how to calculate these new steady states, and explain why they give way to oscillations when the density threshold is negative. 相似文献
16.
用于数值分类的聚类分析 总被引：24，自引：0，他引：24
这里所谓聚类分析包括传统的聚类分析和作者提出的聚类统计检验分析。传统的聚类分析是常用的重要数值分类方法。但是，这个方法由于缺乏显著性检验，在国际上已长期公认是一个在多元统计中并不完整的方法。本文把聚类统计检验分析在其具有显著性检验的优越性上，和传统聚类分析作了对比分析。聚类统计检验分析区分有均匀聚类与中心聚类。前者用（１６）作为聚类判据，后者则用（２７），并且各用相应的公式（１７）－（２１）与（２ 相似文献
17.
In this paper, we present a mathematical model including seakeeping and maneuvering characteristics to analyze the roll reduction for a ship traveling with the stabilizer fin in random waves. The self-tuning PID controller based on the neural network theory is applied to adjust optimal stabilizer fin angles to reduce the ship roll motion in waves. Two multilayer neural networks, including the system identification neural network (NN1) and the parameter self-tuning neural network (NN2), are adopted in the study. The present control technique can save the time for searching the optimal PID gains in any sea states. The simulation results show that the present developed self-tuning PID control scheme based on the neural network theory is indeed quite practical and sufficient for the ship roll reduction in the realistic sea. 相似文献
18.
The methods of Okuboet al. (1976a) are used to calculate the Lagrangian deformations and diffusivities of a cluster of drifters. A solution of the two-dimensional first-order advection-diffusion equation (Okuboet al., 1983a) is then used to calculate the dimensions and orientation of the cluster from these Lagrangian deformations and diffusivities. The solution is shown to be internally consistent (to give cluster areas that are consistent with the observed cluster areas) to within a 0.5% error. As time progresses a larger portion of the dispersion is caused by the diffusivities rather than the deformations. In the experiments analyzed the Lagrangian deformations and diffusivities are generally observed to increase at a constant rate over time intervals of about one hour. Dimensional arguments suggest that Lagrangian diffusivities increase proportional tot
2 and the deformations proportional tot
1,5 for time intervals large compared to the period required to spread from a point source to the initial cluster dimensions. Small quadratic velocity gradients cause the solution of the first order advection-diffusion equation to overestimate cluster spreading. Most of the displacement (once motion due to the mean velocity and linear deformations is extracted) is caused by scales of motion much smaller than the cluster. This explains the relatively small magnitude of the errors caused by parameterizing quadratic and other statistically significant nonlinear shears as a component of the eddy-diffusivity. 相似文献
19.
张力腿平台(TLP)水下丛式井口布局设计关系到立管服役期间的安全性,是含有丛式井口平台设计过程中考虑的主要因素。根据TLP立管安装、钻井以及防碰等要求,考虑尾流效应对丛式立管的影响,研究水下丛式井口布局设计准则,对丛式井口—立管系统进行碰撞分析以确定水下井口间距阈值,提出水下丛式井口圆形布局方法和相应的布局设计流程。通过算例对计算方法进行了具体运用。研究表明:与目前采用的"等边三角形网格"方法相比,水下丛式井口圆形布局方法可允许水下整体基盘安装位置误差达到水下井口间距阈值的20%,立管的最大倾角可达到0.5°,安装作业窗口增加1倍以上。本方法对水下整体基盘安装位置误差的容错能力强,能有效扩大丛式立管钻井和安装作业窗口,提高丛式立管作业安全性,研究结果可为TLP丛式井口的设计提供参考。 相似文献
20.
采用兔抗5-羟色胺抗体和SABC免疫细胞化学方法,对日本囊对虾视神经节、脑和胸神经节进行定位研究。结果表明,视神经节内的5-羟色胺免疫阳性细胞分布于视外髓、视内髓和视端髓。前脑前中群,前脑中部前端神经髓质、中央体,中脑嗅叶内侧细胞群,后脑后中群、侧位群和后侧群呈5-羟色胺免疫阳性反应。胸神经节5-羟色胺阳性细胞较少,第4对胸神经节检出1对阳性细胞,第5对胸神经节检出2对阳性细胞,神经髓质不呈阳性反应。5-羟色胺的特异性分布,为日本囊对虾体内的生理功能和甲壳动物腹神经索演化提供了形态学依据。 相似文献