振动筛过共振区的控制──微机共振控制器

本文介绍一种采用单片机系统控制振动筛延时反接制动的方法，它可以有效地消除振动筛停机过共振区时产生的巨大振幅。

船用螺旋桨分区域加工共振控制研究

为了解决螺旋桨叶片等薄壁件在加工中因振动而难以达到加工精度要求的问题,给出了一种通过调节主轴转速来实现薄壁件分区域加工共振控制的方法。通过模态锤击实验获取不同切削区域工件与刀具的固有频率,结合工件与刀具的固有频率及其与刀具齿数的关系,确定薄壁类零件不同区域加工的主轴转速,进而减弱和避免加工过程中的振动。通过薄板切削实验,验证了分区域加工共振控制方法对避免铣削加工振动和提高加工质量的有效性。将所提方法应用于螺旋桨叶片加工过程中,有效地解决了螺旋桨叶片等薄壁类零件的弱刚性及其不同区域动态特性分布的差异性而导致精加工过程中极易发生振动的问题。

核磁共振控制台

该发明专利是一种核磁共振控制台。其特征为：射频信号发生单元、信号接收与处理单元和磁场梯度信号产生单元通过背板／扁平电缆进行连接；同时射频信号发生单元、信号接收与处理单元和磁场梯度信号产生单元又通过以太网交换机与主计算机连接。

超导磁共振系统日常的质量控制与质量保证

本研究依据磁共振系统的结构性能、成像原理,结合临床的诊断需求,分别从设备的操作人员、医院的临床医学工程师、厂家的专业工程师三者出发,探索磁共振质量控制的具体内容及可实施操作方案,从而短时间内,使风险和成本降到最低的情况下,保证获得稳定和高质量的诊断图像。

双级驱动隔振系统反共振频率控制器设计与验证

为了解决扫频过程中隔振器不能很好地隔离扫频频率在0Hz和固有频率之间的平台基座惯性力的干扰,提出一种双级驱动主动隔振系统的可调反共振频率控制器。对双级驱动主动隔振系统的运动学模型、可调反共振频率控制器及参数设计等进行了研究。首先,根据设计的双级驱动主动隔振系统建立其运动学模型。接着,基于系统的反共振频率特性提出了可调反共振频率控制器及其参数设计。然后,分析可调反共振频率控制的隔振性能。最后,搭建实验平台进行实验验证。实验结果表明:从0到初始反共振频率,闭环传递率小于-15 dB。此外,通过改变控制器的参数,附加的反共振频率可以在0 Hz和初始反共振频率之间调节。且在附加反共振频率附近,闭环传递率小于-30 dB。利用该控制器,有效载荷的扰动幅度从4 mm·s^(-1)衰减到0.5 mm·s^(-1),平台基座的冲击扰动降低了87.5%。双级驱动主动隔振系统配合可调反共振频率控制器可以通过跟踪扫频干扰实时调整反共振频率点,可应用于半导体制造业超低振动要求的扫频环境,达到良好的隔振效果。

简支铁路桥梁加固前后共振响应分析

研究目的:由于加固前后铁路简支桥梁自振频率发生变化,车桥系统发生共振时对应的列车速度发生改变,因此需要分析加固前后桥梁的共振响应是否满足要求。本文介绍车桥系统发生共振的原理,研究影响车桥系统共振响应的因素,采用ANSYS软件和多体动力学软件UM(Universal Mechanism)分析加固前后桥梁仿真模型的车桥耦合动力性能。研究结论:(1)对于小跨径直线桥梁,加固前后桥梁发生共振时对应的列车速度发生明显改变;(2)通过桥梁加固,其发生竖向共振时列车速度已经超出高速列车的速度范围;(3)列车第二共振速度时桥梁的竖向振幅和加速度远小于列车处于第一共振速度时,故可以不考虑;(4)对桥梁进行加固,能够明显减小共振时桥梁竖向及横向的跨中振幅和跨中加速度;(5)本研究成果可为简支铁路桥梁的共振控制提供借鉴。

基于形状记忆合金的转子系统振动控制

利用反共振控制原理 ,提出了基于形状记忆合金 (Shape Memory Alloy— SMA)的转子系统振动的反共振控制策略 ,其主要思路是将 SMA弹簧并联形成转子轴承的支撑部分 ,并通过 SMA弹簧刚度变化改变转子轴承刚度 ,从而使转子处于反共振状态 ,达到振动控制的目的。

磁共振信噪比与均匀度智能评价系统

本文研究了一种基于SMR170体模的磁共振信噪比与均匀度的智能评价系统。通过分析磁共振质量控制的常规检测方法,基于Matlab设计并优化了质量控制重要参数智能评价的软件实现方法,可以实现信噪比、均匀度的智能检测与评估;自动生成每次评估结果报告,并能对同一设备多次检测结果长期跟踪记录,可用于磁共振质量控制的日常工作。

发动机薄壁盘类零件振动疲劳试验技术研究

以某发动机薄壁盘类零件为例,采用分析与试验相结合的方法进行了薄壁盘类零件振动疲劳试验方案设计与调试,验证了分析与试验方法的可靠性。并在此基础上,采用共振驻留控制方式进行了振动疲劳正式试验,获取了振动疲劳试验过程中的相关物理参数的变化规律,包括共振频率和等效应力与激振加速度量值及循环数之间的关系,并且验证了高温合金材料在高周振动疲劳服役中的材料硬化等性能,最后得到了该薄壁零件的疲劳寿命。所提出的试验设计方法、试验方法及得出的结论可为发动机薄壁盘类零件振动疲劳性能考核验证及强度性能评估提供一定的参考。

直流充电桩前级变换器快时标分岔抑制

为分析直流充电桩前级峰值电流控制Boost功率因数校正变换器在快时标下的非线性分岔现象,加入控制手段对分岔现象进行有效抑制。首先,建立变换器的频闪映射模型,通过模型数值仿真结果再现系统电感电流出现的间歇性分岔和混沌现象;然后,加入自整定PI控制共振微扰法的控制手段对分岔现象进行抑制,让系统始终稳定工作在单周期态。仿真结果表明,与固定斜坡补偿控制法相比,自整定PI控制共振微扰法在对分岔和混沌现象有效抑制的同时,弥补了固定斜坡补偿方法会出现输入电流死区的不足,并使系统具有较高的功率因数和更好的鲁棒性,且该算法在工程应用中易于实现。

ACR体模与Magphan SMR 170体模MRI性能测试对比研究

目的:探究Magphan SMR 170磁共振性能测试专用体模与美国放射学会(ACR)体模在进行磁共振成像(MRI)设备质量控制(QC)时的性能对比情况,分析两种体模测试结果的优劣。方法:采用同一个ACR体模和同一个Magphan SMR170体模对西南地区41家医院的41台MRI设备进行质量检测,并对两种体模的测试结果进行相关性检验和线性回归分析。结果:不分场强时,Magphan SMR 170体模与ACR体模测量的层厚、空间分辨率、伪影和几何畸变率4个指标均具有较好的一致性。场强为1.5 T的所有指标、0.5 T的空间分辨率和0.35 T的层厚和空间分辨率均通过了线性回归检验。Magphan SMR 170体模的信噪比和空间分辨率检测值稳定性良好,ACR体模除0.5 T外其他场强的层厚检测值更稳定。两个体模的其余指标在各场强下,稳定性相同。Magphan SMR 170体模在测量层厚和空间分辨率具有更高的精度但较耗时;ACR体模在测量信噪比和影像均匀性具有更优的QC意义且耗时短。结论:Magphan SMR 170体模和ACR体模均可作为QC的有效手段,根据QC不同的目的选择不同的体模。日常QC时可选择ACR体模作为检测工具,长周期QC时可选用Magphan SMR170体模或者结合ACR体模作为检测工具。

Complete Assignment and Benchmarking of an 8-Qubit System

In this paper, the assignment of acomplex 8-spin-half system （7,7-dichloro-6-oxo-2-tio-bicycle [3.2.0] heptane-4-carboxlic acid） using nuclear magnetic resonance （NMR） techniques is presented and the hamiltonian obtained, was used to demonstrate universal control. The system has 313C and 51H,in our work, we carried out traditional 1-D and 2-D experiments and also made use of coherent control together with simulation to get the full hamiltonian of this weakly coupled system. Spin-echo J-resolved 2-D experiments were used to obtain the heteronuclear and homonuclear coupling values; COSY45 experiments were used to obtain the signs of homonuclear coupling constants. The signs of heteronuclear coupling constants were obtained using the polarization transfer method. All the data obtained in the experiments were used in the simulation of the 1-D spectra and then optimized using the least square fitting method. After obtaining the full hamiltonian of the 8-spin system, we used it in QIP, prepared pseudopure states and implemented 1-qubit and 2-qubit gates on one of its 6-qubit subsystems.

Research on Noise Control for Ventilators with Resonance

A study was carried out to control the noise produced by the ventilators at the Luling coalmine, which had caused serious noise pollution to the residents living around the mine for a long time. The main noise source was found to be the dynamic noise at the outlet of the diffuser. The frequency of its peak value was 250 Hz. A special brick with a resonant frequency of 250 Hz was designed to eliminate this noise. The diffusion of a lower frequency noise has been successfully controlled by the installation of a noise-eliminating tower above the diffuser outlet. The detection results show that the noise in the nearby residential area has been lowered to an average 55.3dB(A) in the daytime from 69.8dB(A) and to 48.4dB(A) at night from 65.8dB(A).

Deterministic and Multi-Controlled Teleportation of an Arbitrary Unknown Two-Ion State in Ion-Trap System

We propose a simple scheme for deterministic and multi-controlled teleportation of an arbitrary unknown two-level two-ion state in ion-trap system. In the scheme, the special entangled W states used as quantum channels and the requisite unitary transformations may be achieved via a single resonant interaction, respectively. The required time to complete the whole procedure does not increase with the number of agents.

Enhanced Deflection of Light Ray by Atomic Ensemble on Coherent Population Oscillation

In recent experiments [e.g., Nature Physics 2 （2006） 332], the enhanced light deflection in an atomic ensemble due to inhomogeneous fields is demonstrated by the electromagneticaJly induced transparency （EIT） based mechanism. In this paper, we explore a different mechanism for the similar phenomenon of the enhanced light deflection. This mechanism is based on the coherent population oscillation, which leads to the hole burning in the absorption spectrum. The medium causing the deflection of probe light is an ensemble of two-level atoms manipulated by a strong controlled field on the two photon resonances. In the large detuning condition, the response of the medium to the pump field and signal field is obtained with steady state approximation. And it is found that after the probe field travels across the medium, the signal ray bends due to the spatial-dependent profile of the control beam.

A Simple Scheme for Realizing a Multiqubit Controlled-Phase Gate Through a Resonant Interaction of Three-Level Atoms with a Single-Mode Cavity

A very simpJe theoretical scheme is proposed to implement two-and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. In the presented protocol, the quantum information is encoded on the stable ground states of the atoms （as the controlling qubits） and the zero- and one-photon Fock states of cavity-field （as the target qubit）. Under the influence of the atomic spontaneous emission, the decay of the cavity-mode, and deviation of the coupling strength, the three-qubit controlled- phase gate may have a comparatively high fidelity. The experimental feasibility of controlled-phase gate and the ease that is extended to realize N-qubit controlled-phase gate are also discussed.

A Connectome Computation System for discovery science of brain

Much like genomics, brain connectomics has rapidly become a core component of most national brain projects around the world. Beyond the ambitious aims of these projects, a fundamental challenge is the need for an efficient, robust, reliable and easy-to-use pipeline to mine such large neuroscience datasets. Here, we introduce a computational pipeline--namely the Connectome Compu- tation System （CCS）-for discovery science of human brain connectomes at the macroscale with multimodal magnetic resonance imaging technologies. The CCS is designed with a three-level hierarchical structure that includes data cleaning and preprocessing, individual connectome mapping andconnectome mining, and knowledge discovery. Several functional modules are embedded into this hierarchy to implement quality control procedures, reliability analysis and connectome visualization. We demonstrate the utility of the CCS based upon a publicly available dataset, the NKI- Rockland Sample, to delineate the normative trajectories of well-known large-scale neural networks across the natural life span （6-85 years of age）. The CCS has been made freely available to the public via GitHub （https：//github.com/ zuoxinian/CCS） and our laboratory＇s Web site （http：//lfcd. psych.ac.cn/ccs.html） to facilitate progress in discovery science in the field of human brain connectomics.

Electronic Structure of Helium Atom in a Quantum Dot

Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method.To be specific,precise energy eigenvalues of bound 1sns(~1S^e)(n=1-6)states and the resonance parameters i.e.positions and widths of^lS^e states due to 2sns(n=2-5)and 2pnp(n=2-5)configurations of confined helium below N=2 ionization threshold of He^+have been estimated.The two-parameter(Depth and Width)finite oscillator potential is used to represent the confining potential due to the quantum dot.It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size.It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters.A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here.