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Distributions of Charged Hadrons Associated with High pT Particles

Distributions of Charged Hadrons Associated with High p T Particles

Fuqiang Wang (for the STAR Collaboration)

Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA

fqwang@https://www.sodocs.net/doc/628647967.html,

Abstract. Recent results from STAR on angular correlations of charged hadrons associated

with high transverse momentum particles are presented. Emphasis is put on the correlations of

soft associated hadrons, which provide rich information on the properties of the bulk medium

created in RHIC collisions. The results are discussed in the context of three pertinent questions

regarding QGP formation: sufficient energy density, parton thermalization, and deconfinement.

Quantum Chromodynamics (QCD) predicts a phase transition between hadronic matter and quark-gluon plasma (QGP), a deconfined and thermalized state of quarks and gluons, at a critical energy density of approximately 1 GeV/fm3 [1]. Such a phase transition is being actively pursued at the Relativistic Heavy Ion Collider (RHIC) at BNL via ultra-relativistic heavy-ion collisions.

The RHIC experiments [2] have critically assessed the three-year wealth of experimental data and concluded that a new form of hot and dense matter has been created in RHIC collisions. Theory and theoretical models, confronting available experimental data, conclude that the matter created in RHIC collisions is a strongly coupled QGP [3]. In this proceedings article we focus on angular correlations with high transverse momentum particles and try to address three pertinent questions regarding QGP formation:

(1)Is the energy density created in RHIC collisions sufficiently high for QGP formation?

(2)Is the created system a thermalized state of quarks and gluons?

(3)Are the quarks and gluons deconfined over a volume of nuclear size?

1. Energy Density

In the Bjorken boost invariant picture [4], initial energy density can be estimated from the produced total transverse energy. Such estimates indicate an energy density of 4-5 GeV/fm3 at proper time of 1 fm/c for central Au+Au collisions at RHIC [5]. Such large energy densities (which are also estimated at the CERN SPS [6]), taken at face values, are well above the predicted critical energy density for phase transition [1].

A perhaps more “direct” way to gauge initial energy density is to “send” a self-generated probe – hard-scattering partons – through the created medium and measure any modifications to the probe by the medium. Due to the large bombarding energies at RHIC, high transverse momentum (p T) particles become statistically abundant for the first time in heavy-ion collisions. High p T particles come predominantly from jets emerging from initial hard-scatterings between partons. They need finite time to escape the collision zone, during which a dense medium is formed. The partons and fragmented hadrons are expected to lose energy via interactions with the medium, resulting in the so-called jet quenching phenomena - suppression of inclusive yield and angular correlation strength at high p T [7].

The larger the medium gluon density is, the stronger the interaction and the larger the suppression magnitude. Thus, high p T particles and jet quenching provide a powerful, direct tool to measure the medium density created in ultra-relativistic heavy-ion collisions.

1.1. High p T Suppression

All four RHIC experiments have observed suppressed yields at high pT in central Au+Au collisions per binary nucleon-nucleon collision [8,9,10,11]. Figure 1 (from [12]) shows the centrality dependence of the single inclusive hadron suppression factor, R AA, for charged hadrons at p T > 6 GeV/c measured by the STAR collaboration [9] and for neutral pions measured by the PHENIX collaboration [8]. The suppression rate increases gradually with centrality, up to about 4 in the most central 5% collisions.

For the observed high p T particles, whose overall yield is strongly suppressed, STAR has measured the correlated hadrons in azimuthal angle in the p T range of 2 < p T < 4 GeV/c [13,14]. While the jet-like angular correlation strengths are similar on the near side between pp and central Au+Au, those on the away side are strongly suppressed at large p T [13,14].

Figure 1. The centrality dependence of

the measured single inclusive hadron

suppression factor at high p T [8,9] as

compared to theoretical calculation with

parton energy loss [12]. The figure is

taken from Ref. [12].

1.2. Inferred Energy Density

The observed high-p T suppressions could in principle come from, not the final state jet quenching effect discussed above, but initial state effects present in the Au nuclei (such as saturation of gluon density [15]). In order to discriminate between initial and final state effects, d+Au collisions were measured by all four RHIC experiments. The measured d+Au results [10,16] are similar to the pp results at high p T, demonstrating that the suppression phenomena in central Au+Au collisions are due to final state interactions. Invoking partonic energy loss due to final state interactions of hard partons with the created medium, and assuming that all high p T hadrons coming from parton fragmentation, perturbative QCD (pQCD) model calculations [17] indicate a gluon density of about 30 times (or energy density of about 100 times) that of normal nuclear matter in order to reproduce the observed magnitudes of high p T suppression. The curves in Fig. 1 show such a calculation. Note that the inferred energy density from pQCD model calculations is in general agreement with the Bjorken energy density estimate that is from a completely different line of argument. The agreement reassures that a high enough energy density may indeed have been achieved in central Au+Au collisions for the predicted phase transition.

2. Thermalization

The QGP is a state of thermalized quarks and gluons. If thermalization is reached at an initial stage, the measured final stage hadrons will possess thermal distributions. Indeed, soft physics results on particle spectra and yields [18] and event-by-event

fluctuations [19] indicate a chemically and (local-)kinetically equilibrated system at the final freeze-out stage. This is of course a necessary, but not sufficient condition for early thermalization. Meanwhile elliptic flow (v2), established early in the collision because of its self-quenching nature, is found to be well described at low p T by ideal hydrodynamic calculations [20]. Since ideal hydrodynamic fluid is a thermalized system with zero mean-free-path, they give the maximum possible v2 value. Thus, the consistency between the measured v2 and hydrodynamics result suggests an early thermalization in heavy-ion collisions at RHIC.

Another, perhaps more “direct” way to investigate thermalization is to study the energy distribution of final hadrons related to initial hard-scattered partons after interactions with the medium by the partons, hadrons, or both. In other words, we have effectively two distinct sources of particles: jet fragments, which are initially hard (or would be in the absence of a medium), and decay products of the bulk medium, which are generally soft. Particles from the two sources are brought together to interact and, as an inevitable consequence, reach equilibration with each other.

2.1. Hard-Soft Angular Correlations

The away side associated hadrons (opposite to a high p T trigger particle) are significantly depleted at large p T [13,14]. The depleted energy must be redistributed to low p T particles. Reconstruction of these low p T particles will serve as an experimental confirmation of jet quenching. But moreover, complete reconstruction of jets and study of their modifications will provide information about the properties of the nuclear medium [12,21]. For example, by studying the amount of energy loss and how the energy is distributed, one may experimentally learn about the medium density, the underlying energy loss mechanism(s), and the degree of equilibration between the energy and the medium.

STAR has performed a nearly complete statistical reconstruction of charged hadron jets by correlating charged hadrons at all p T with a leading particle and subtracting the combinatoric background [14]. The background is obtained from mixed-events, with the elliptic flow modulation added in by hand and normalization fixed to the correlation function in the 0.8 < |?φ| < 1.2 region [14]. Figure 2 shows the background subtracted angular correlation functions in pp and the 5% most central Au+Au collisions with trigger particle transverse momentum of 4 < p T trig < 6 GeV/c and associated particle 0.15 < p T < 4 GeV/c [14]. The systematic uncertainties mainly come from uncertainties in background normalization and in the measured elliptic flow [14]. In contrast to correlations at high p T, it is found that the low p T hadrons are present on the away side of the trigger particle (away side being |?φ| > 1.0 and |η| < 1.0) and there are more of them in central Au+Au collisions than in pp. It is also found that the ?φ correlation becomes broader on the away side in central Au+Au collisions, reaching the limit that can be described [14,22] by the so-called statistical momentum balance [23]. The away-side associated particles, in fact, no longer appear jet-like because large p T particles are essentially depleted. Instead, what are left on the away side, in the picture of initial di-jet production, are the remnants of the away-side jet after intensive interactions with the medium.

On the near side (|?φ| <1 and |?η| < 1.4), correlation in ?φ remains similar, while that in ?η becomes broader in central Au+Au collisions; The ?η correlation in central Au+Au collisions appears to have two components: a Gaussian peak on a more or less flat pedestal. Such a two-component feature is not present in pp and d+Au collisions [24]. One may separate the correlated yield into two parts: one contained in the Gaussian peak and the other in the pedestal. The Gaussian peak yield is found to be rather invariant between pp, d+Au, and Au+Au collisions at all centralities. The Gaussian peak width is broader in central Au+Au than in pp or d+Au for 4 < p T trig < 6 GeV/c [24]. The underlying reason(s) for the broad ?η distribution or the pedestal-Gaussian structure are not yet

identified; there could be a number of reasons, such as longitudinal [25] and transverse [26] flow developed in the medium.

Figure 2. Background subtracted, per trigger particle normalized (a,b) ?φ and (c,d) ?η correlation functions for pp and the 5% most central Au+Au collisions between trigger particles of 4< p T trig <6 GeV/c and associated hadrons of (a,c) 0.15 < p T < 4 GeV/c and (b,d) 2 < p T < 4 GeV/c [14]. The subtracted background level for associated p T=0.15-4 GeV/c is approximately 1.4 in pp and 211 in the 5% most central Au+Au; That for associated p T=2-4 GeV/c is approximately 0.007 in pp and 2.1 in the 5% most central Au+Au.

2.2. Away-Side Associated

Figure 3 shows the p T spectra of the associated hadrons on the near side and away side. While the near-side hadron spectral shapes are similar in pp and Au+Au, the away-side associated hadrons are significantly softened in central Au+Au collisions, becoming similar to those from the bulk [14]. The lost energy at high p T has been moved to low p T. By triggering on a high p T particle in the final state, due to significant energy loss, only those di-jets produced near the surface of the medium are selected. The two jet partners encounter quite different amounts of medium: The near-side jet goes through a thin layer of medium, losing a modest amount of energy, and emerges with a leading particle at high p T accompanied by hadrons with a minimally modified p T distribution; The away-side jet goes deep into the medium, suffering significant energy loss, and emerges with a collective excess of particles with a significantly softened p T distribution and with little jet-like characteristics surviving. Recent calculations of large angle hadron correlations from medium-induced gluon radiation can qualitatively describe our results [27].

Figure 4 shows the

of the away-side associated hadrons and of inclusive hadrons in p+p and as a function of centrality in Au+Au collisions from STAR [14]. The

of associated hadrons decreases with centrality, while that of inclusive hadrons increases with centrality due to collective radial flow. In central collisions the

of associated hadrons is not much larger than that of inclusive hadrons. Particles from the two distinct sources, one from initial hard-scattered partons (or jets) and the other from the bulk medium, appear to have reached partial but significant degree of

thermalization due to intensive interactions on the away side. Hard-soft parton interactions are likely responsible for the observed partial thermalization. Because soft-soft parton interactions within the medium are much stronger than hard-soft parton interactions, the observed softening in Fig. 4 may in turn indicate a high degree of thermalization in the medium itself.

Figure 3. Near-side (a) and away-side (b) p T

distributions of associated charged hadrons with

trigger particle 4 < p T trig < 6 GeV/c in pp,

peripheral and central Au+Au collisions, and

ratios of Au+Au to pp distributions for near-side

(c) and away-side (d) [14]. Errors shown are

statistical. The bands show the systematic errors

for central collisions. The lines are p T

distributions of inclusive hadrons in central

collisions.

Figure 4. Associated charged hadron

within 0.15 < p T < 4 GeV/c on the away side

in pp (the leftmost set of data points) and

Au+Au collisions [14]. The trigger particle

p T ranges are 4 < p T < 6 GeV/c (large

triangles, systematic uncertainties shown by

the shaded area) and 6 < p T < 10 GeV/c

(small triangles, systematic uncertainties

shown by the caps). The line shows

of

inclusive hadrons.

2.3. Away-Side Associated

versus ?φ

Due to the collision geometry, the associated

may depend on the emission direction of particles. Study of such dependence will yield more insight into medium modification of the away-side hadrons. Figure 5 shows the number and p T-weighted correlation functions in central Au+Au collisions. The shaded areas show the correlated systematic uncertainties. The correlation functions are consistent with a flat distribution in ?φ within errors. Also shown are the minimum-bias pp and d+Au correlation functions (the systematic errors are not shown). The pp and d+Au data are similar. Both are peaked at ?φ = π and are significantly narrower than the central Au+Au data.

The

are obtained from the ratio of the background subtracted p T-weighted over number correlation functions. Figure 6 shows the obtained

on the away side as a function of ?φ for 4

, obtained directly from the ratio of the subtracted backgrounds in Fig. 5 is shown as the straight horizontal lines (the small modulation due to p T

-dependent elliptic flow is invisible on this scale). The shaded areas depicted in

both panels show the systematic uncertainties in central Au+Au collisions for 4

is more robust than the correlation functions themselves because the background uncertainties in the number and p T -weighted correlation functions are correlated and largely cancel in their ratio.

Figure 5. Background subtracted number

(upper) and p T -weighted (lower) correlation

functions in min-bias pp, the 20% most

central d+Au, and the 5% most central

Au+Au collisions. The shaded areas are

systematic uncertainties for the central

Au+Au data.

Figure 6. The

of associated hadrons on the away side. Upper panel shows those for min-bias pp, the 20% most central d+Au, and the 5% most central Au+Au collisions with trigger particle 4

In Fig. 6 upper panel one observes that

for pp and d+Au are peaked at ?φ = 180o , and are much larger than that of inclusive hadrons. These features are expected from jet fragmentation: the fragment hadron momentum component perpendicular to the jet axis is independent of the parallel momentum component. Hence, fragments with larger parallel momentum component are more collimated with the jet axis. These hadrons are the relatively large p T particles in our measurements (which are made at mid-rapidity), resulting in a larger

for ?φ closer to 180o from the trigger particle. For central Au+Au collisions, however, the

is the smallest at ?φ = 180o . The change from the peaked structure in pp, d+Au, and peripheral Au+Au (not shown) to the dipped structure in central Au+Au seems gradual with increasing centrality. The

at ?φ = 180o in central Au+Au collisions appears equal to that of inclusive hadrons, while at other angles it is still larger. Figure 6 lower panel shows that the dipped shape of

in central collisions is the same for 3

for 6

Our correlation function data are qualitatively consistent with the recently proposed sonic shock wave picture [28]. Sonic shock waves may result in a larger

> along the conical flow direction,

approximately ?φ = π ± 1 [28]; However, theoretically this aspect is little explored. The seemingly flattening of the

versus ?φ distribution from low to high trigger p T may be understood if one considers two contributions to the away-side associated hadrons: one from jet fragmentation and the other from sonic conical flow of the medium. Their relative contributions change with trigger p T.

3. Deconfinement

The QGP is a state of deconfined quarks and gluons. While experimental search for deconfinement is elusive, recent theoretical and experimental developments in the constituent quark coalescence picture are encouraging [29].

3.1. Baryon/Meson Puzzle, Elliptic Flow Scaling, and Constituent Quark Coalescence

Recent results from PHENIX [30] and STAR [31,32] indicate that the high p T suppression is particle-type dependent. In central Au+Au collisions, charged and neutral pions [30] and K S [31,32] are suppressed by an approximately constant factor at p T > 3 GeV/c while (anti-)protons [30] and (anti-)lambdas [31,32] are little suppressed in the intermediate p T range of 2 < p T < 4 GeV/c. The p/π and K S/Λ ratios in central Au+Au collisions are 3 times that expected from jet fragmentation in the 2 < p T < 4 GeV/c range, start to drop at p T = 4 GeV/c, and approach the corresponding jet fragmentation values at p T > 6 GeV/c. The suppression pattern of K* [33] and φ [34] mesons seem to follow those of pions and kaons, rather than the similar mass protons and lambdas.

Moreover, the measured elliptic flow [35], well described by hydrodynamics at low p T, saturates at p T > 2 GeV. The saturation value depends on particle type: the v2 of mesons is about 2/3 of the v2 of baryons. This separation pattern holds for pions [36], kaons [31,36], K* [33], protons [36], lambdas [31], and cascades [37], and seems to hold for the ? baryons [37].

These results suggest that neither the mass nor the species, but the baryon-meson difference, govern the dynamics of the intermediate p T region. Coalescence of constituent quarks [38] in the thermal bath at hadronization temperature gives an attractive explanation for both results: (1) It is more effective to produce baryons than mesons at the same p T: To become a baryon, three quarks each at p T/3 coalesce where they are much more abundant than at p T/2 where two quarks coalesce into a meson, provided that the quark spatial density is so high that three quarks are equally available at same configuration space point as two quarks are. (2) The coalesced baryon will carry three times the elliptic flow of the constituent quarks while the coalesced meson, twice.

If constituent quark coalescence is indeed the production mechanism giving rise to the baryon-meson difference at intermediate p T, i.e. hadronization of the bulk medium does occur, then it seems natural to conclude that a deconfined phase of quarks and gluons is created, prior to the hadronization. However, coalescence is expected to produce no jet-like angular correlations (in the case of coalescence of pure thermal partons), or weaker correlations than those from jet fragmentation (in the case of recombination of shower and thermal partons [39,40]). Therefore, jet-like angular correlations with a leading baryon and with a leading meson should generally differ in central Au+Au collisions as compared to pp.

3.2. Angular Correlations with Identified Trigger Particles

PHENIX [41] found little difference between angular correlations of hadrons in 1.7 < p T < 2.5 GeV/c with a proton and with a pion of 2.5 < p T trig < 4.0 GeV/c. Figure 7 shows STAR preliminary results of ?φ correlations of charged hadrons in 0.15 < p T < 3 GeV/c with protons and with pions of 3 < p T trig < 4 GeV/c. The protons and pions at high p T are identified by the relativistic rise of the specific ionization energy loss in the STAR TPC and are required to have 75% and 90% purity, respectively. The upper panel of Fig. 7 shows the correlation functions with a constant background subtraction. The lower panel has an additional subtraction of the elliptic flow effect. The v2 values for trigger protons and pions are extracted from the measured charged hadron v2 and the relative abundances of protons and pions, assuming 3/2 for the baryon/meson v2 ratio. Little difference is found in Fig. 7 between the ?φcorrelation functions for trigger protons and trigger pions, and additionally between particles and anti-

particles. STAR has also measured angular correlations with leading (anti-)lambdas and leading K S, and also little difference is found [42].

Figure 7. Azimuthal correlation

functions of charged hadrons in

the range of 0.15 < p T < 3 GeV/c

with identified trigger particles

(proton, anti-proton, π+, and π?)

of 3 < p T < 4 GeV/c. Only a

constant background is

subtracted in the upper panel;

The full background with elliptic

flow modulation is subtracted in

the lower panel.

Clearly, the success of the coalescence/recombination model in describing the single particle yield and elliptic flow measurements, but its apparent difficulty in explaining the observed indifference between jet-like correlations with leading baryons and leading mesons, needs to be reconciled. It will benefit from more detailed measurements, with greater statistics, of angular correlations with identified particles. While it is still tempting to conclude that deconfined quarks and gluons are likely,

a firmer conclusion is premature.

4. Summary

The measured suppression magnitudes of high p T yields and jet-like angular correlations in central

Au+Au collisions at RHIC suggest, within the framework of pQCD models with partonic energy loss,

an initial medium energy density two orders of magnitude larger than normal nuclear density, well above the critical energy density for QGP formation. The reconstructed correlated hadrons over a wide

p T range on the away side of a triggered jet are broadly distributed in azimuthal angle and become partially thermalized with the bulk medium, suggesting a high degree of thermalization in the bulk medium itself. The division between baryon and meson results in the intermediate p T range suggests

the intriguing relevance of the constituent quark degrees of freedom at hadronization, which may be

the first experimental hint for deconfinement.

The experimental evidences for QGP formation seem strong. A firmer conclusion, however, requires further systematic investigations, with high statistics data at several bombarding energies and with several colliding nuclei species, to verify that the existing models and interpretations indeed give

a consistent description of the dynamics in heavy-ion collisions.

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为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格 要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责 的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在 班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并 在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类 团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意 识和良好的心理素质.

英语三大基本句型[1]

I wonder whether he will come or not. 我想知道他来还是不来。 e. 后接动词不定式时。例如: Can you tell me whether to go or to stay? 你能否告诉我是去还是留? 4. 注意宾语从句中的时态呼应,当主句动词是现在时,从句根据自身的句子情 况,而使用不同时态。例如: he studies English every day. (从句用一般现在时) he studied English last term. (从句用一般过去时) I know (that) he will study English next year. (从句用一般将来时) he has studied English since 1998. (从句用现在完成时) 当主句动词是过去时态(could, would除外),从句则要用相应的过去时态,如 一般过去时,过去进行时,过去将来时等;当从句表示的是客观真理,科学原理,自 然现象,则从句仍用现在时态。例如: The teacher told us that Tom had left us for America. 5. think, believe, imagine, suppose等等动词引起的否定性宾语从句中,要把上述主句中的动词变为否定式。即将从句中的否定形式移到主句中。例如: We don’t think you are here. 我们认为你不在这。 I don’t believe he will do so. 我相信他不会这样做。 3)表语从句 在句中作表语的从句叫表语从句。引导表语从句的关联词与引导主语从句的关联 词大致一样,表语从句位于连系动词后,有时用as if引导。其基本结构为:主语 + 系动词 + that从句。例如: The fact is that we have lost the game. 事实是我们已经输了这场比赛。 That’s just what I want. 这正是我想要的。 This is where our problem lies. 这就是我们的问题所在。 That is why he didn’t come to the meeting. 那就是他为什么不到会的原因。 It looks as if it is going to rain. 看上去天要下雨了。 需要注意的,当主语是reason时,表语从句要用that引导而不是because。例如: The reason why he was late was that he missed the train by one minute this morning . 【注意】whether 可引导表语从句,但与之同义的if却通常不用于引导表语从句。 4)同位语从句 同位语从句说明其前面的名词的具体内容。同位语从句通常由that引导,可用于同位语从句的名词有 advice、demand、doubt、fact、hope、idea、information、message、news、order 、problem、promise、question、request、suggestion、truth、wish、word等。例如:

英语翻译常用句型

翻译中常见的句型 1.否定句型 1)部分否定。其否定意义只局限于整体中的一部分。其形式:“概括词all, every等+not+谓语动词”。常用于该句型词:all, both, everybody, everywhere, always, altogether, entirely, wholly等。 All is not gold that glitters. I do not wholly agree. 2) 完全否定。其形式:no, none 等否定词+肯定式谓语。常用于该句型词:no, none, nobody, nothing, nowhere, never, neither, nowhere, nowise, 等。还有一种句型:all等概括词+肯定式谓语+否定意义的词。 No words can describe the scene. 任何言词均不能描绘那景色。 All his plan came to nothing. 3)双重否定 a.主语+cannot+ help/refrain/keep + from + v-ing He could not help showing his pleasure.他不由得喜形于色。 b.主语+cannot+ but/choose but/ help but +do They can not choose but admit that they are wrong. c.(there be) not +主语+but+谓语 (There is )Nobody but has his faults. 人人都有缺点。 2.判断句型 1)强调判断句 a.主语+be+ no/none +other than/but +表语(强调内容) The tall figure that I saw was none other than our commander. b.主语+be+ nothing+(else)but/ else than/ less than+ 表语 Genius is nothing but labor and diligence.天才只不过是劳动加勤奋而已。 c.it is/was +强调部分+that/ who +从句 It is I who am to blame. 2) 正反判断句 a.主语+be +not+表语a, but +表语b What I admire in Columbus is not his discovered a world, but his having gone to search for it on the faith of an opinion. b.(it is) not… that(who) …, but…that (who) Not that we are afraid of them, but that they are afraid of us. 3)比较判断句: a.主语+be less+表语a +than表语b / more+表语b+表语a Experience shows that success is due less to abilities than to zeal. b.主语+be+表语b+ rather than+表语a He is an artist rather than a philosopher. c.主语+be+ not so much +表语a+ as+表语b It is so much advice as approval that he seeks. 他寻求的与其说是忠告,不如说是忠告。3.倍数表示句型: a.主语+be+倍数+that of 被比较对象/ as +形容词+as+被比较对象

设备管理系统毕业设计(设计与代码实现)1

目录 前言――――――――――――――――――――――― 摘要――――――――――――――――――――――― 第一章系统需求分析 第二章系统设计 2.1系统方案确定 2.2系统功能实现 第三章怎样开发一个人事工资管理系统? 3.1 编程环境的选择 3.2 关系型数据库的实现 3.3 二者的结合(DBA) 第四章 Visual basic下的控件所实现的功能 4.1实现菜单选项 4.2 实现工具栏 4.3 帮助 第五章系统总体规划 5.1 系统功能 5.2 流程图 第六章系统具体实现 6.1 用户界面的实现 6.2 数据库的实现 第七章结束语 第八章主要参考文献 第九章程序源代码、各功能模块的程序流程图 --------------前言-------------- 设备管理信息系统是一个企事业单位不可缺少的部分,它的内容对于企事业单位的决策者和管理者

来说都至关重要,所以设备管理信息系统应该能够为用户提供充足的信息和快捷的查询手段。但一直以来人们使用传统人工的方式管理设备的信息,这种管理方式存在着许多缺点,如:效率低、保密性差,另外时间一长,将产生大量的文件和数据,这对于查找、更新和维护都带来了不少的困难。本论文主要介绍的是设备管理信息系统的整个设计过程。 随着计算机技术的不断发展,计算机应用于各大领域,并给人们的生活带来了极大的便利,在固定管理系统亦是如此。以往设备员由于缺乏适当的软件而给其工作带来了很多不便。本论文所介绍的便是一个设备管理信息系统,以方便在设备安排和设备管理信息上的工作任务。 该系统适用于普通设备的管理,在使用上力求操作容易,界面美观,另外,本系统具有较高的扩展性和可维护性,可能在以后需要的时候进行软件升级。 整个系统的开发过程严格遵循软件工程的要求,做到模块化分析、模块化设计和代码编写的模块化。 作为计算机应用的一部分,使用计算机对设备信息进行管理,具有着手工管理所无法比拟的优点.例如:检索迅速、查找方便、可靠性高、存储量大、保密性好、寿命长、成本低等。这些优点能够极大地提高设备管理信息的效率,也是企业的科学化、正规化管理,与世界接轨的重要条件。 --------------摘要-------------- 设备管理信息系统是典型的信息管理系统(MIS),其开发主要包括后台数据库的建立和维护以及前端应用程序的开发两个方面。对于前者要求建立起数据一致性和完整性强、数据安全性好的库。而对于后者则要求应用程序功能完备,易使用等特点。 经过分析,我们使用MICROSOFT公司的VISUAL BASIC开发工具,利用其提供的各种面向对象的开发工具,尤其是数据窗口这一能方便而简洁操纵数据库的智能化对象,首先在短时间内建立系统应用原型,然后,对初始原型系统进行需求迭代,不断修正和改进,直到形成用户满意的可行系统。 整个系统从符合操作简便、界面友好、灵活、实用、安全的要求出发,完成设备管理信息的全过程,包括每一物品,例如办公设备、家具、计算机及其他有价值的设备分配一个唯一的物品编码,并根据此编码在计算机中建立设备信息库,对设备的新增、领用、折旧等进行管理,使管理人员可对设备的流向进行跟踪,随时掌握设备的现状及公司雇员领用设备情况,减少设备丢失现象,解决查找、盘点困难等问题,提高管理人员的工作效率。因此,开发这样一套管理软件成为很有必要的事情,在下面的各章中我们将以开发一套设备管理信息系统为例,谈谈其开发过程和所涉及到的问题及解决方法。 企业要想不断提高设备的使用效率,并且在预期的时间内收回所投资金和实现预期的投资收益,就要加强设备管理信息。设备管理信息的主要内容有: ?设备日常管理 ?设备使用效率管理 ?设备投资规模变动的边际收入与边际成本分析 ?设备折旧管理 论文主要介绍了本课题的开发背景,所要完成的功能和开发的过程。重点的说明了系统设计的重点、设计思想、难点技术和解决方案。 关键字:Visual Basic6.0,控件、窗体、数据库,设备管理信息 第一章. 系统需求分析 1.1现行业务系统描述 设备管理信息对每个企业单位都是十分重要的工作,设备管理信息的好,可以使设备发挥最大效益,杜绝各种不良设备,反之则会造成生产资料利用率低下,甚至造成设备流失。 本管理系统是为适应于的设备管理信息而开发的软件。从设备使用的角度管理设备,协助学校建立一套完善的数据管理模型,提供全面数据的编辑、查询、系统管理等等功能,达到对设备科学管理的目

英语翻译常用句型(加精)

英语翻译常考句型详解 1.It is not that…but that… 这不是说…,而是说… 「例文」It is not that the scales in the one case, and the balance in the other, differ in the principles of their construction or manner of working; but that the latter is much finer apparatus and of couse much more accurate in its measurement than the former. 「译文」这并不是说在一种情况下所使用的磅秤和在另一种情况下所使用的天平在构造原理上或工作方式上存在差别,而是说与前者相比,后者是一种更精密得多的装置,因而在计量上必然更加准确。 2.nothing else than 完全是,实在是 「例文」What the man said was nothing else than nonsense. 「译文」那个人讲的话完全是一派胡言。 3.as引导的特殊状语从句,翻译时做定语从句处理。 「例文」We hope the measures to control prices, as they have been taken by the government, will succeed. 「译文」我们希望,政府已经采取的控制物价的措施将取得成功。 4.名词+or+名词结构中,or后的名词是同位语,应译为即…;或者称…. 「例文」Moreover, technology includes techniques , or ways to do things , as well as the manchines that may or may not be necessary to apply them. 「译文」再者,除机器外技术还包括技艺,即制作方法,而运用这些记忆并不一定都需要机器。 5.more…than…结构有三种译法:than连接肯定形式的从句时,该从句译为否定句;在比较的基础上表示选择关系时,可译为与其说…不如说;进行同类比较时,译成比…更. 「例文」The complexity of the human situation and injustice of the social order demand far more fundamental changes in the basic structure of society itself than some politicians are willing to admit in their speeches. 「译文」人类社会形势的复杂性和社会制度的不公正性要求对社会基本结构进行彻底变革,而一些政客口头上是很不愿意承认这一点的。 「分析」这是一个主从复合句,连词than前为主句,than后为从句。虽然本句是进行程度上的比较,但从句意义是否定的, 故译成否定句。 6.no more …than 与not… any more than no more …than 与not… any more than同义,不可简单地看成是more …than的否定形式。具体地说,这一结构可能是带有一定的感情色彩的否定形式,也可能是一种较特殊的类比形式。其翻译方法有二;表示同类否定比较时,可译为不比…更或都…同样不;表示比喻关系时,可译为正如…不,…也不. 「例文」The food on the ship was no better than on any other ship on which Billy had sailed. 「译文」这条船上(供应的)食品并不如比利工作过的其他船上的(食品)好。(括号里的词是可以省略的。) 「分析」这是一个主从复合句、主句是The food …no better , than on any other ship 是省略了比较对象的比较状语从句,从句on which引导的定语从句修饰先行词ship.本句中no more… than用于同类否定的比较,可译为不如…. 7.not so much as与其说…不如说… 「例文」Science moves forward, they say, not so much through the insights of great men of genius as because of more ordinary things like improved techniques and tools. 「译文」新学派科学家说,科学的发展与其说源于天才伟人的真知灼见,不如说源于改进了的技术和工具等等更为普遍的东西。 「分析」这是一个主从复合句。插入语they say是主句,Science moves forward,……and tools是宾语从句。not so much……as 连接的是状语,as引导的状语从句中,由于上下文清楚,主谓语都省略了,即as(sciencemoves forward.)because of……not so much……as也可译为与其说……不如说……,它所表达的逻辑关系和more than有相似之处,也是在比较的基础上进行判断和选择,被比较的事物也同属一个范畴。所不同的是,more……than表示前重后轻的逻辑关系,而not so much… as和less than表示前轻后重的逻辑关系,这两个结构中信息重心落在句尾,因此不必倒过来译,只须按原文的词序顺译即可。

数据库设备管理系统

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