共查询到20条相似文献,搜索用时 15 毫秒
1.
《金属工艺学》是一门理论性、应用性、实践性、综合性都很强的技术基础课和工程训练课,横跨6个专业,内容丰富,知识面广,信息量大,其理论知识广泛而又抽象,专业名词较多,所以“难讲授、难理解、难记忆、难应用”成为教学中的明显特点。“二元相图”是制订热加工工艺和选材的重要依据,也是热处理的理论基础,要求熟练掌握,但内容比较抽象,既是教学重点,又是难点。针对学科特点,突出“抓本质、抓联系、抓重点、抓应用”,在教学时数减少的同时提高教学质量,我们利用VB开发了“二元相图”教学CAI课件,采用计算机多媒体技术和交互技术,集图… 相似文献
2.
Information was stored as quantum phase in an N-state Rydberg atom data register. One or more flipped states stored in an eight-state atomic wave packet could be retrieved in a single operation, in agreement with a recent proposal by Grover. 相似文献
3.
蛋白质折叠机理的研究是基因重组蛋白质高效生产的前提条件,对于工业化生产重组蛋白以及治疗与蛋白集聚密切相关的疾病都有重要意义。为了探索一个统一的蛋白质折叠机理,用荧光相图法分别对脲和盐酸胍诱导的胃蛋白酶的去折叠过程进行了研究。结果表明,无论变性体系中有无还原剂2-巯基乙醇存在,当脲浓度为0~8.0 mol/L时,脲诱导胃蛋白酶的变性过程都符合"二态模型";而无论变性体系中有无还原剂2-巯基乙醇存在,当盐酸胍浓度为0~6.0 mol/L时,该蛋白的变性过程均符合"三态模型"。 相似文献
4.
Fushman I Englund D Faraon A Stoltz N Petroff P Vuckovic J 《Science (New York, N.Y.)》2008,320(5877):769-772
Optical nonlinearities enable photon-photon interaction and lie at the heart of several proposals for quantum information processing, quantum nondemolition measurements of photons, and optical signal processing. To date, the largest nonlinearities have been realized with single atoms and atomic ensembles. We show that a single quantum dot coupled to a photonic crystal nanocavity can facilitate controlled phase and amplitude modulation between two modes of light at the single-photon level. At larger control powers, we observed phase shifts up to pi/4 and amplitude modulation up to 50%. This was accomplished by varying the photon number in the control beam at a wavelength that was the same as that of the signal, or at a wavelength that was detuned by several quantum dot linewidths from the signal. Our results present a step toward quantum logic devices and quantum nondemolition measurements on a chip. 相似文献
5.
Xu G Broholm C Soh YA Aeppli G Ditusa JF Chen Y Kenzelmann M Frost CD Ito T Oka K Takagi H 《Science (New York, N.Y.)》2007,317(5841):1049-1052
Mesoscopic quantum phase coherence is important because it improves the prospects for handling quantum degrees of freedom in technology. Here we show that the development of such coherence can be monitored using magnetic neutron scattering from a one-dimensional spin chain of an oxide of nickel (Y2BaNiO5), a quantum spin fluid in which no classical static magnetic order is present. In the cleanest samples, the quantum coherence length is 20 nanometers, which is almost an order of magnitude larger than the classical antiferromagnetic correlation length of 3 nanometers. We also demonstrate that the coherence length can be modified by static and thermally activated defects in a quantitatively predictable manner. 相似文献
6.
Grigera SA Gegenwart P Borzi RA Weickert F Schofield AJ Perry RS Tayama T Sakakibara T Maeno Y Green AG Mackenzie AP 《Science (New York, N.Y.)》2004,306(5699):1154-1157
Condensed systems of strongly interacting electrons are ideal for the study of quantum complexity. It has become possible to promote the formation of new quantum phases by explicitly tuning systems toward special low-temperature quantum critical points. So far, the clearest examples have been appearances of superconductivity near pressure-tuned antiferromagnetic quantum critical points. We present experimental evidence for the formation of a nonsuperconducting phase in the vicinity of a magnetic field-tuned quantum critical point in ultrapure crystals of the ruthenate metal Sr3Ru2O7, and we discuss the possibility that the observed phase is due to a spin-dependent symmetry-breaking Fermi surface distortion. 相似文献
7.
V Pellegrini A Pinczuk BS Dennis AS Plaut LN Pfeiffer KW West 《Science (New York, N.Y.)》1998,281(5378):799-802
Inelastic light scattering by low-energy spin-excitations reveals three distinct configurations of spin of electron double layers in gallium arsenide quantum wells at even-integer quantum Hall states. The transformations among these spin states appear as quantum phase transitions driven by the interplay between Coulomb interactions and Zeeman splittings. One of the transformations correlates with the emergence of a spin-flip intersubband excitation at vanishingly low energy and provides direct evidence of a link between quantum phase transitions and soft collective excitations in a two-dimensional electron system. 相似文献
8.
We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those of conventional insulators, can be realized in mercury telluride-cadmium telluride semiconductor quantum wells. When the thickness of the quantum well is varied, the electronic state changes from a normal to an "inverted" type at a critical thickness d(c). We show that this transition is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. We also discuss methods for experimental detection of the QSH effect. 相似文献
9.
Chou CW Laurat J Deng H Choi KS de Riedmatten H Felinto D Kimble HJ 《Science (New York, N.Y.)》2007,316(5829):1316-1320
We demonstrated entanglement distribution between two remote quantum nodes located 3 meters apart. This distribution involves the asynchronous preparation of two pairs of atomic memories and the coherent mapping of stored atomic states into light fields in an effective state of near-maximum polarization entanglement. Entanglement is verified by way of the measured violation of a Bell inequality, and it can be used for communication protocols such as quantum cryptography. The demonstrated quantum nodes and channels can be used as segments of a quantum repeater, providing an essential tool for robust long-distance quantum communication. 相似文献
10.
金春花 《延边大学农学学报》2012,34(1):83-86
针对绘制液压系统原理图时重复性工作多的特点,利用AutoCAD的开放体系结构,以AutoCAD2004为开发平台,以AutoLisp语言为开发工具,系统研究液压元件图形符号库和液压元件数据库的开发,并给出部分程序代码和运行结果。该程序可大大提高CAD的使用效率,减轻劳动强度。 相似文献
11.
12.
Degenerate exciton systems have been produced in quasi-two-dimensional confined areas in semiconductor coupled quantum well structures. We observed contractions of clouds containing tens of thousands of excitons within areas as small as (10 micron)2 near 10 kelvin. The spatial and energy distributions of optically active excitons were determined by measuring photoluminescence as a function of temperature and laser excitation and were used as thermodynamic quantities to construct the phase diagram of the exciton system, which demonstrates the existence of distinct phases. Understanding the formation mechanisms of these degenerate exciton systems can open new opportunities for the realization of Bose-Einstein condensation in the solid state. 相似文献
13.
A general photonic channel for quantum communication is defined. By means of local quantum computing with a few auxiliary atoms, this channel can be reduced to one with effectively less noise. A scheme based on quantum interference is proposed that iteratively improves the fidelity of distant entangled particles. 相似文献
14.
15.
[目的]探讨微波技术提取锦鲤鱼鳞总色素的适宜条件,并与振荡浸提法进行比较。[方法]采用单因素试验设计,以石油醚为提取溶剂,在不同辐射功率(160~800W)和辐射时间(60~180s)微波处理下,测定相同质量鱼鳞色素提取液的吸光度。[结果]微波辐射功率为640W、辐射时间为150s的条件下,鱼鳞总色素提取效率最高;微波法(辐射功率为640W,时间为150s)提取鱼鳞总色素的效果比振荡法(提取温度为30℃,时间为3h)差。[结论]建立了微波技术提取鱼鳞色素的适宜条件。 相似文献
16.
17.
Rice SA 《Science (New York, N.Y.)》1992,258(5081):412-413
18.
NH Bonadeo J Erland D Gammon D Park DS Katzer DG Steel 《Science (New York, N.Y.)》1998,282(5393):1473-1476
Picosecond optical excitation was used to coherently control the excitation in a single quantum dot on a time scale that is short compared with the time scale for loss of quantum coherence. The excitonic wave function was manipulated by controlling the optical phase of the two-pulse sequence through timing and polarization. Wave function engineering techniques, developed in atomic and molecular systems, were used to monitor and control a nonstationary quantum mechanical state composed of a superposition of eigenstates. The results extend the concept of coherent control in semiconductors to the limit of a single quantum system in a zero-dimensional quantum dot. 相似文献
19.
20.
武夷山自然保护区景观格局指数的尺度效应分析 总被引:2,自引:0,他引:2
采用变换矢栅转换过程中像元尺度的方法,对福建省武夷山自然保护区景观格局指数的尺度效应进行分析.并利用分维数方法选取最佳的像元尺度值。结果表明:蔓延度指数、邻近相似度指数、破碎度指数和多样性指数都是随着像元尺度的增加而单调递减,递减的速率在10~50m区间上较快,在50~500m区间的减少较慢;连接度、结合度、均匀度和优势度指数随着像元尺度的增加出现了各自不同的变化曲线;对武夷山自然保护区而言,矢栅转换的像元尺度选择30m较为合理。 相似文献