Pair production of charged Higgs bosons in association with bottom quark pairs at the Large

a r X i v :h e p -p h /0308215v 4 4 D e c 2003

SHEP-03-07

TSL/ISV-2003-0271

August 2003

Pair production of charged Higgs bosons in association with bottom quark pairs at the Large Hadron Collider

S.Moretti 1

School of Physics &Astronomy,University of Southampton,

High?eld,Southampton SO171BJ,UK

J.Rathsman 2

High Energy Physics,Uppsala University,Box 535,75121Uppsala,Sweden

Abstract

We study the process gg →b ˉbH +H ?at large tan β,where it represents the dominant production mode of charged Higgs boson pairs in a Type II 2-Higgs Doublet Model,including the Minimal Supersymmetric Standard Model.The ability to select this signal would in principle enable the measurements of some triple-Higgs couplings,which in turn would help understanding the structure of the extended Higgs sector.We outline a selection procedure that should aid in disentangling the Higgs signal from the main irreducible background.This exploits a signature made up by ‘four b -quark jets,two light-quark jets,a τ-lepton and missing energy’.While,for tan β>～30and over a signi?cant M H ±range above the top mass,a small signal emerges already at the Large Hadron Collider after 100fb ?1,ten times as much luminosity would be needed to perform accurate measurements of Higgs parameters in the above ?nal state,rendering this channel a primary candidate to bene?t from the so-called ‘Super’Large Hadron Collider option,for which a tenfold increase in instantaneous luminosity is currently being considered.Keywords:

Beyond Standard Model,Two Higgs Doublet Models,Supersymmetry,Charged Higgs Bosons.

1Introduction

Charged Higgs bosons appear in the particle spectrum of a general2-Higgs Doublet Model (2HDM).We are concerned here with the case of a Type II2HDM[1],possibly in presence of minimal Supersymmetry(SUSY),the combination of the two yielding the so-called Minimal Supersymmetric Standard Model(MSSM).To stay with the Higgs sector of the extended model,unless two or more neutral Higgs states3are detected at the Large Hadron Collider (LHC),only the discovery of a spinless charged Higgs state would unquestionably con?rm the existence of new physics beyond the Standard Model(SM),since such a?eld has no SM counterpart.In the MSSM,e.g.,if M H±,M A0,M H0?M h0and tanβis below10or so, the only available Higgs state(h0)is indistinguishable from the one of the SM:this is the so-called‘decoupling scenario’4.

Not surprisingly then,a lot of e?ort has been put lately,by theorists and experimen-talists alike,in clarifying the Higgs discovery potential of the LHC in the charged Higgs sector[2].(This is particularly true within the MSSM scenario,where one could also ex-ploit interactions between the Higgs and sparticle sectors[3]in order to extend the reach of charged Higgs bosons at the LHC,beyond the standard channels.)Results are now rather encouraging,as charged Higgs bosons could indeed provide the key to unveil the nature of EWSB over a large area in M H±and tanβ,as they may well be the next available Higgs boson states,other than the h0,provided tanβis rather large(above10or so).Once the H±and h0Higgs bosons will have been detected,the next step would be to determine their interactions with SM particles,among themselves and also with the other two neu-tral Higgs states,H0and A0.While the measurement of the former would have little to teach us as whether one is in presence of a general Type II2HDM or indeed the MSSM, constraints on the latter two would certainly help to clarify the situation in this respect.In fact,triple-Higgs vertices enter directly the functional form of the extended Higgs potential and,once folded within a suitable Higgs production process,may lead to the measurement of fundamental terms of the extended model Lagrangian.As the H±states have a?nite

Electro-Magnetic(EM)charge,the?rst Lagrangian term of relevance would be the one involving two such states and a neutral Higgs boson:chie?y,the vertices H+H?Φ0,where Φ0=h0and H0.5This requires the investigation of hard scattering processes with two charged Higgs bosons in the?nal state,as their direct couplings to valence quarks in the proton would be very small,hence inhibiting processes like:e.g.,qˉq′→H±?→H±Φ0.

2Hadroproduction of charged Higgs boson pairs

A summary of all possible production modes of charged Higgs boson pairs at the LHC in the MSSM can be found in Ref.[4].Three channels dominate H+H?phenomenology at the LHC:(i)qˉq→H+H?(via intermediateγ?/Z0?production but also via Higgs-strahlung o?incoming bˉb pairs)[5];(ii)gg→H+H?(primarily via a loop of top and bottom(s)quarks)[6];(iii)qq→qqH+H?(via vector boson fusion)[4].Corresponding cross sections are found in Fig.2of Ref.[4].For all phenomenologically relevant tanβvalues it is essentially the?rst process which dominates.One important aspect should be noted here though,concerning the simulation of the bˉb component of the qˉq→H+H?process,which can become the dominant contribution to the cross section of process(i)at very large tanβvalues.In fact,the use of a‘phenomenological’b-quark parton density, as available in most Parton Distribution Function(PDF)sets currently on the market, requires crude approximations of the partonic kinematics,which result in a mis-estimation of the corresponding contribution to the total production cross section.(The problem is well known already from the study of the leading production processes of charged Higgs bosons at the LHC,namely,ˉbg→ˉt H+and gg→bˉt H+:see,e.g.,[8,10].)In practice,the b-(anti)quark in the initial state comes from a gluon in the proton beam splitting into a collinear bˉb-pair,resulting in large factors of～αS log(μF/m b),whereμF is the factorisation scale.These terms are then re-summed to all orders, nαn S log n(μF/m b),in evaluating the phenomenological b-quark PDF.In contrast,in using a gluon density while computing

the‘twin’process(iv)gg→bˉbH+H?(see Fig.1for the associated Feynman graphs),one basically only includes the?rst terms(n=1)of the corresponding two series,when the b andˉb in the?nal state are produced collinearly to the incoming gluon directions.It turns out that,forμF?m b,as it is the case here if one uses the standard choice of factorisation scaleμF>～2M H±,the re-summed terms are large and over-compensate the contribution

of the large transverse momentum region available in the gluon-induced case.In the end, di?erences between the two cross sections as large as one order of magnitude are found,well in line with the?ndings of Refs.[8]and[10],if one considers that two g→bˉb splittings are involved here.

One way to reconcile the large di?erences in the cross section for the two processes, gg→bˉbH+H?and bˉb→H+H?,is to use a signi?cantly lower factorisation scale,as argued in[11,12,13,14]for similar processes.Following the suggestion in part A.1.of[15],we look at the transverse momentum distribution of the b-quarks in the process gg→bˉbH+H?,as shown in Fig.2,to get an indication of the most suitable factorisation scale for bˉb→H+H?. From the?gure we see that a proper choice for the latter,when M H±=215GeV,is of the √

orderμF=0.1

?https://www.sodocs.net/doc/149553598.html,ing such a lower scale we do get a much better agreement between the leading order(LO)cross sections for the two processes,as shown in Tab.1in the case of the MSSM speci?ed below(M A0=200GeV and tanβ=30) if the renormalisation scale(μR)is also changed accordingly.However,one should also bear in mind that both processes are subject to possibly large QCD corrections and that the choice of(factorisation and/or renormalisation)scales that minimises the di?erences between the two descriptions in higher orders of H+H?production may alternatively be viewed as the most suitable one.Or else,one may arguably choose a scale that minimises the size of the higher order corrections themselves in either process independently of the other.All such additional values may eventually turn out to be di?erent from the one extracted from Tab.1.Such exercises in higher orders cannot unfortunately be performed in the present context,as next-to-leading order(NLO)corrections to the two processes of interest are unavailable.Yet,some guidance may be a?orded again by the study of the single charged Higgs production modes already referred to.In fact,NLO corrections toˉbg→ˉt H+ were?rst computed in Ref.[7]and then later con?rmed in[11].Following Ref.[11],it is clear that a choice for the renormalisation scaleμR as low as the one recommended for the factorisation oneμF is not sustainable forˉbg→tH+at NLO,no matter the choice for the latter:see Fig.5of[11].Besides,if one?xes,e.g.,μR=(m t+M H±)/2but varies μF,the minimal di?erence between the NLO and the LO results forˉbg→tH+is found at largeμF,at values around or even larger than m t+M H±(again,see Fig.5of Ref.[11]). Be the most suitable combination of scales as it may,we take here a pragmatical attitude

Table1:Cross sections for gg→bˉbH+H?and bˉb→H+H?as functions of the factorisation (μF)and renormalisation(μR)scales(at leading order the bˉb→H+H?cross section does not depend onμR)in the MSSM speci?ed below(M A0=200GeV and tanβ=30).

√

?s

?s 2.3

m T b ? m T b ?8.2

√

?s 4.4

)2)/2.

m2b+((p T b)2+(p Tˉ

b

√

and use the standard setupμF=μR=

reaction is the dominant production mode of neutral Higgs scalars(chie?y,the H0state) at tanβvalues above7or so,for any neutral Higgs mass of phenomenological interest[17], this justifying our choice of privileging here the gg→bˉbH+H?channel.Finally,whereas the already recalled MSSM relation M H±?M A0?M H0?M h0clearly prevents the appearance of a H0→H+H?resonance in the diagrams proceeding via intermediate states

of the form gg→bˉbH0,this is no longer true in a general2HDM,wherein one may well have M H0>2M H±,with the consequent relative enhancement of the mentioned subset of diagrams with respect to all others appearing in Fig.1.

We will attempt the signal selection for the case of rather heavy charged Higgs bosons, with masses above that of the top quark.The case for the existence of such massive Higgs states has in fact become phenomenologically pressing,since rumours of a possible evidence of light charged Higgs bosons being produced at LEP2[18]have faded away.Instead,one is now left from LEP2with a model independent limit on M H±,of order M W±.Within the MSSM,the current lower bound on a light Higgs boson state,of approximately110 GeV[19],can be converted at two-loops into a minimal value for the charged Higgs boson mass,of order130–140GeV,for tanβ?3–47.This bound grows rapidly stronger as tanβis decreased while tapering very gradually as tanβis increased(staying in the110–125GeV interval for tanβ>～7).Besides,in the mass interval M H±

√

well be found at Tevatron(Run2)[21],which has already begun data taking at

=14TeV,

s

pp

at CERN.As hinted at in the beginning,we also make the assumption in our study that the charged Higgs boson mass is already known,e.g.,from studies of the leading production and decay channels,gg→tˉbH?and H?→τ?ˉντor bˉt,during the?rst years of running of the CERN hadron machine.

Under the above parameter assumptions,i.e.,large tanβ(>～10)and large M H±val-ues(>～m t),a sensible choice of decay channels[22]for our pair of charged Higgs bosons would be to require one to decay via the leading mode,i.e.,H+→tˉb(with the t-quark further decaying hadronically,so to allow for the kinematic reconstruction of the charged Higgs boson resonance in a four-jet system)and the other via H?→τ?ˉντ(whose rate increases with tanβand that yields a somewhat cleaner trigger in the LHC environment,

independently of whether theτ-lepton decays leptonically or hadronically,as opposed to the above multi-jet and high hadron-multiplicity signature).As such decays would induce an intermediate signal state made up by bˉbtˉbτ?ˉντand since we will assume tagging all four b’s,it is clear that the dominant irreducible background would be bˉbtˉt production followed by the decayˉt→ˉbW?→ˉbτ?ˉντ.

3Calculation

The hard subprocess describing our signal is then

gg→bˉbH+H?,(1) whereas for the main irreducible background we have to deal with

gg→bˉbtˉt.(2)

(We neglect here the computation of the quark-antiquark initiated components of both signal and background,i.e.,qˉq→bˉbH+H?and qˉq→bˉbtˉt,respectively,as they are negligible at the LHC,in comparison to the gluon-gluon induced modes.)The matrix elements for(1)–(2) have been calculated by using the HELAS[23]subroutines and MadGraph[24].All unstable particles entering the two processes(t,H±and W±)were generated not only o?-shell(i.e., with their natural widths)but also in Narrow Width Approximation(NWA)for comparison. For the MSSM and2HDM Higgs bosons,the program HDECAY[25]has been exploited to generate the decays rates eventually used in the Monte Carlo(MC)simulations.For the MSSM,we have assumed the following set up for the relevant SUSY input parameters:μ=0,A?=A u=A d=0(with?=e,μ,τand u/d referring to u/d-type quarks)and M SUSY=1TeV,the latter implying a su?ciently heavy scale for all sparticle masses,so that no H±→SUSY decay can take place8.

As a2HDM con?guration,we have basically maintained the previous setup in the rele-vant input parameters of HDECAY,with the most important di?erence being the assumption of a di?erent relation between the input M A0value and the derived M H0one,by assuming a linear relation between the H0and H±masses,i.e.,M H0=x H±,with x being a num-ber larger than2,while maintaining the MSSM relations among the H±and A0masses,

thereby allowing for the already intimated onset of H0→H+H?resonant decays in dia-grams4,8,14,19,23,29,34and38of Fig.1.As already remarked upon,this is a crucial phenomenological di?erence with respect to the MSSM,wherein such a decay threshold is never reached over the unexcluded region of parameter space.Another important di?erence, in a more general2HDM,is the value of the triple Higgs coupling g H0H+H?which can be much larger than what is the case in the MSSM.

Before giving the details of the2HDM setup we are using let us recall the most general CP-conserving2HDM scalar potential which is symmetric underΦ1→?Φ1up to softly breaking dimension-2terms(thereby allowing for loop-induced?avour changing neutral currents)[1],

V(Φ1,Φ2)=λ1(Φ?1Φ1?v21)2+λ2(Φ?2Φ2?v22)2

+λ3 (Φ?1Φ1?v21)+(Φ?2Φ2?v22) 2

+λ4 (Φ?1Φ1)(Φ?2Φ2)?(Φ?1Φ2)(Φ?2Φ1)

+λ5 Re(Φ?1Φ2)?v1v2 2+λ6 Im(Φ?1Φ2) 2(3) where v21+v22=v2=2M2W/g2?(174GeV)2.In general,the potential is thus parameterised by seven parameters(theλi and tanβ=v2/v1)whereas in the MSSM only two of them are independent.In the following we will replace?ve of theλi with the masses of the Higgs bosons(M h0,M H0,M A0,M H±)and the mixing angleαof the CP-even Higgs bosons.

From the scalar potential the di?erent three-and four-Higgs couplings can be obtained. (See[26,27]for a complete compilation of couplings in a general CP-conserving2HDM.) Using the Higgs masses andαas parameters together withλ3the g H0H+H?coupling takes a particularly simple form(see for example[28])

g H0H+H?=?i g

2 +sin(α+β)2(M2H0+M2h0)+

+4λ3v2?1

Table2:Examples of values of the parameters in the Higgs potential used for di?erent values of M A0together with the corresponding values ofαand g H0H+H?.

M A0αg H0H+H?[GeV][GeV]?4.81618?4.02795 4.816180.941863 4.131140.745433

?3.90929?2.75838 3.90929 1.521647.16375 1.32521

1.69717 3.17924?1.54105

2.2670710.9783 2.07065

5.165587.63614?3.79044 3.178169.19537 2.98173

9The selection procedure outlined above did not lead to any acceptable solution for M A0>～310GeV.

as input values,as we will do below.In this case we get g2HDM

=?563GeV in the2HDM

H0H+H?

=?1.8GeV.With the value ofα2HDM=0.26859not instead of the MSSM value,g MSSM

H0H+H?

being much larger thanαMSSM=?0.05774the di?erence in e?ective coupling g H0H+H?cosα

is more than a factor hundred and as we will see below it has a large impact on the magnitude of the cross section.(The H0widths will of course be di?erent too in the MSSM and2HDM just described:their e?ects have been included in the numerical analysis.) As intimated already in Sect.2,a non-running b-quark mass was adopted for both the kinematics and the Yukawa couplings:m b=4.25GeV.For the top parameters,we have taken m t=175GeV withΓt computed according to the model used(in the limit M H±?m t,we haveΓt=1.56GeV in both the2HDM and MSSM scenarios considered here).EW parameters were as follows:αEM=1/128,sin2θW=0.232,with M Z0=91.19 GeV(ΓZ0=2.50GeV)and M W±=M Z0cosθW(ΓW±=2.08GeV).For theτ-lepton mass we used mτ=1.78GeV,whereas all the other leptons and quarks were assumed to be massless.

The integrations over the multi-body?nal states have been performed numerically with the aid of VEGAS[30],Metropolis[31]and RAMBO[32],for checking purposes.Finite calorimeter resolution has been emulated through a Gaussian smearing in transverse mo-mentum,p T,with(σ(p T)/p T)2=(0.60/

p T)2+(0.01)2for leptons.The corresponding missing transverse momentum,p T miss, was reconstructed from the vector sum of the visible momenta after resolution smearing. Furthermore,we have identi?ed jets with the partons from which they originate and applied all cuts directly to the latter,since parton shower and hadronisation were not included in our study.The only exception is theτ-lepton decay which has been taken into account

using the Pythia[33]MC event generator.

√As default PDFs we have adopted the set MRS98LO(05A)[34]with Q=μ=

4Selection

The signature that we are then considering is in practice:

4b?jets+2light?jets+τ+p T miss,(5)

wherein the two b-jets from the hard process are actually de?ned as the two most for-ward/backward ones that also display a displaced vertex.

We have assumed a standard detector con?guration by imposing acceptance and sepa-ration cuts on all light-quark(including c’s)and b-jets,labeled as j and b,respectively,as follows:

p T b>20GeV,|ηb|<2.5,p T j>20GeV,|ηj|<5,?R jj,jb>0.4.(6) The two most forward/backward b-jets(with pseudorapidities of opposite sign)are further required to yield

M bb>M H±(7) for their invariant mass.Forτ-jets(we only consider hadronic decay modes)we impose: p Tτ>10GeV,|ητ|<2.5,?R jτ,bτ>0.4.(8)

The setup corresponds to the standard ATLAS/CMS detectors.Presently it is not clear to what extent this setup will also be applicable for the same apparata in the context of the Super LHC(SLHC)option[35].

Having now excluded the two most forward/backward b-jets from the list of jets,we impose hadronic W±-and t-mass reconstruction:

|M jj?M W±|<15GeV,|M bjj?m t|<35GeV,(9) where the two light-quark jets entering the last inequality are of course the same ful?lling the?rst one.Finally,the missing transverse momentum should be10:

p T miss>60GeV.(10)

The combined e?ects of these cuts on the signal(1)in the MSSM and2HDM models is shown in Figs.3and4respectively in the case of retaining the?nite width e?ects using o?-shell masses for the H±and W±.(The di?erence when instead using the NWA is very

small and this option is therefore not shown.)As can be seen from the?gures the e?ects of the cuts on the magnitude of the cross sections is quite severe.On the other hand the cuts are needed(especially in case of the MSSM)in order to beat down the background as is illustrated in Fig.5.From the?gure it is also clear that the signal cross section reaches its maximum around M H±=200GeV and that the magnitude of the signal varies by up to2 orders of magnitude depending on which model we are considering.It should also be noted that in the2HDM setup we are using it was not possible to go above M H±?320GeV (corresponding to M H0=700GeV)due to the unitarity contraints[29].In the following we will be considering the case M H±?215GeV(corresponding to M A0=200GeV)in more detail.

After the above cuts have been implemented and the jet momenta assigned,one can reconstruct the would-be charged Higgs boson mass,by pairing the three jets entering the equation in the right-hand side of(9)with the left-over central jet,a quantity which we denote by M4jets.The corresponding mass spectrum is presented in Fig.6for our two customary setups of MSSM and2HDM,assuming M H±=215GeV and tanβ=30as representative values.The?gure shows clear peaks at the charged Higgs boson mass for the signal on top of a combinatorial background in both models whereas for the background process there is no such peak.Thus,by selecting events with

180GeV

we can get an additional discrimination against the background.

Furthermore,using the visibleτ-jet momentum and the missing transverse one,it is possible to reconstruct the transverse mass,as

M Tτν

=

τ

This gives a very strong suppression of the background whereas the signal is only mildly a?ected.

After having reconstructed the two charged Higgs bosons and applied the respective cuts (11)and(13)we can form the(e?ectively,transverse)mass M T4jets+τνof the combined two charged Higgs boson system,giving the possibility to look for possible resonances.As can be seen from the magnitudes of the cross sections in Fig.8the selection outlined above gives a very clear signal in the2HDM case with essentially no background,whereas in the MSSM case the signal is still clear but very small.Of course,the cuts could be tightend to give a very clear signal also in the MSSM case,but the absolute cross section would then be even smaller.From the?gure it is also clear that there is a signi?cant di?erence in shape between the two models,with the2HDM showing a clear enhancement for M T4jets+τν<～500

GeV due to the resonant contributions.However,given the limited statistics that will be available at the LHC,it is not clear to what extent the di?erence in shape alone can be used to extract any information about possible H0→H+H?resonances and the corresponding coupling.In addition the di?erence in shape will be smaller if the width of the H0Higgs boson is larger and/or the detector resolution is worse than what we have assumed.

5Conclusion

As we have shown,it is possible to outline a selection procedure that enables one to extract a signal of heavy charged Higgs pair production in association with two b-quarks at tanβ>～30 in extensions of the standard model with two Higgs doublets of Type II.In a general case the mass relations in the Higgs sector may be favourable such that a sizeable signal would appear already at the LHC through the resonant channel gg→bˉbH0→bˉbH+H?.However, in the MSSM the resonance is not accessible over the allowed parameter region and the non-resonant contributions turn out to be very small making it di?cult to extract a signal even after upgrading the luminosity at LHC by a factor ten(SLHC).The large di?erence in cross section between the MSSM and a more general2HDM shows that indeed the pair production of charged Higgs production is sensitive to the H0H+H?coupling even though it will probably be di?cult to reconstruct a resonant transverse mass peak mainly due to the limited statistics and possibly also due to the?nite detector resolution.

In our study we have not included e?ects of the b-tagging e?ciency.On the one hand, requiring four b-tags will give a sizeable reduction(of the order of a factor ten)of the signal as well as the backgrounds.On the other hand,the selection procedure outlined above was

designed to get a signal in the case of the MSSM leading to unnecessarily tight cuts for the general2HDM case.Furthermore,being a leading order calculation,the cross section we get for the signal is also sensitive to the choice of factorisation and renormalisation scales. If we,instead of using the standard choice of the invariant mass of the hard subsystem,use the mean transverse mass of the two b-quarks in the gg→bˉbH+H?process as scale,the cross section increases by a factor5.Such a scale choice also gives a better agreement with the cross section for the‘twin’process bˉb→H+H?.In order to get a better handle on the uncertainties due to scale choices a next-to-leading order calculation will eventually be necessary.Nonetheless,we believe that our results already call for the attention of ATLAS and CMS in further exploring the scope of the(S)LHC in reconstructing the form of the Higgs potential in extended models through signals of charged Higgs boson pairs.Besides, in presence of parton shower,hadronisation and detector e?ects,one may also realistically attempt exploitingτ-polarisation techniques in hadronic decays of the heavy lepton[36]in order to increase the signal-to-background rates,an e?ort that was beyond the scope of our parton level analysis.

Acknowledgments

SM is grateful to The Royal Society of London(UK)for partial?nancial support in the form of a Study Visit and thanks the High Energy Theory Group of the Department of Radiation Science of Uppsala University for kind hospitality.

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从后面所接成分看apairof的用法

从后面所接成分看 a p a i r o f的用法 The document was prepared on January 2, 2021

从后面所接成分看a pair of的用法 简单的来理解，a pair of不仅可以表示“一对”，还可以表示“一副”。那么a pair of在这两个不同的含义下，后面可以接怎样的成分呢?下面我们就来详细的看这部分a pair of的用法。 从后面所接成分看a pair of的用法： 1. a pair of后面可以接由两部分构成的单件事物名词，例如trousers，scissors，glasses，spectacles，jeans等等。 例句：My father has small eyes, wear a pair of glasses, looking more gently. 我的父亲有一双小小的眼睛，戴着一副眼镜，看上去很温和。 It was a pair of jeans from a denim shop. 那是一条从牛仔裤店偷来的牛仔裤。 注意事项：对于这样的由两部分构成的单件事物，我们不可以用one或者ones来替代它，而是要用pair或者pairs。 2. a pair of后面可以接包括两件东西且习惯上一起使用的名词，例如shoes，boots，gloves，socks，earrings，chopsticks等等。 例句：It's cold, I need a pair of gloves. 天气冷，我需要一副手套。 I brought my father a pair of socks on the Father's Day. 父亲节那天我为父亲买了一双短袜。 3. a pair of后面可以接表身体中两个相同的部位的名词。

PDI产品使用常见问题解答——PIT篇

PDI产品使用常见问题解答——PIT篇 PIT检测仪时间设置无法保存，什么原因？ PIT的时间是由主板上一个专门的电池负责供电的，电池寿命一般3-5年，当发现设备时间设置无法保存时，往往是这个电池没电了，您可联系相关区域的售后服务人员，更换电池即可解决，更换电池是收费的，具体收费需咨询我公司售后工程师。 PIT双通道采集仪的几种模式分别是什么意思？如何选用？ 目前，EPC在国内销售的PIT检测仪均为双通道，可进行常规单通道检测，也可进行瞬态阻抗法检测及双速度检测。检测时，共有四种模式可供选择，分别是：ACC、VEL、F+V 和V+V。ACC表示加速度模式，我们使用的传感器其实加速度传感器，ACC模式采集的就是原始的加速度信号，但通常我们不采用这种模式，因为不符合我们的分析习惯，如果不小心选了这个模式也没关系，后期在电脑软件中可以转换为速度信号分析；VEL表示速度模式，就是讲采集的加速度信号积分为速度信号显示，是我们最常用的模式；F+V 模式是瞬态阻抗法测试，需要用到内置传感器的力锤进行测试，对分析桩身浅部缺陷很有帮助；V+V模式为双速度模式，需用到两个侧置加速度传感器，主要用于测试既有基础下桩身完整性及确定桩长等。 PIT采集信号时，采样频率如何选择？ PIT-VV的采样频率为50kHz、100kHz、150kHz；PIT-XA及PIT-Q的采样频率范围为32~128kHz。 正常情况下，PIT-VV的采样频率我们选择50kHz，PIT-XA和PIT-Q的采样频率我们选择64kHz，即可满足要求。采样频率的不同，影响的是相邻采样点之间的距离，频率越高，相邻采样点之间的间隔就越小，信号精度就相应越高。但由于PIT的采样点数是固定的（1K），所以采样频率的改变，势必会影响到信号所能覆盖的桩长范围，频率越高，覆盖的桩长越短。因此，一般只有我们需要查看桩身浅部缺陷的时候，才会设置较高的采样频率，不过即使这样，精度的提高其实也是有限的。

Origin 使用问题

Origin 使用问题集锦 1. 请教怎样反读出 origin 曲线上全部数据点？ 如，我用 10个数据点画出了一条 origin 曲线，并存为 project的.OPJ 格式。但，现在我想利用 OPJ 文件从这条曲线上均匀的取出 100个数据点的数值，该如何做？注：要一切都使用 origin 软件完成，不用其他曲线识别软件。 Answer： ORIGIN 中，在分析菜单（或统计菜单）中有插值命令，打开设置对话框，输入数据的起点和终点以及插值点的个数，OK！生成新的插值曲线和对应的数据表格。 2. 如何用origin 做出附件中的图： 其中标注的三角形、方块是怎么整上去的？ Answer: 选中左侧竖工具条中的 draw tool(显示是几个点，第七个工具），移动到你要标注的位置双击，就产生了一个点，依次标注完方块。再标注三角的第一个点，标注完后改成三角，以后标注的就都是三角了。改动点的类型的方法和正常画曲线方式一样。 3. 如何用origin 做出附件图中的坐标轴（带刻度）？

Answer: 你把刻度改成那样不就行了。 8.0 的具体方法是双击坐标轴，title & format --> 选左边那个 bottom，然后在右边把 axis 改为 at position=。同理，然后选左边的 left，把axis也改为 at position=。 4. origin能否读取导入曲线的坐标？ 一张 bmp 格式的图片，图片内容是坐标系和拟合曲线，但是不知道用什么软件绘制的。请问能否将该图片导入 origin，读出曲线上任意一点的数据？ Answer: (1). 1.ORIGIN 有一个图形数字化插件可完成该任务。 2.有许多专门的图形数字化软件也可完成此任务。个人感觉专门的比插件也用、便捷。推荐 WINDIG25 (2). origin下的数字化插件是digitizer,下载地 址：https://www.sodocs.net/doc/149553598.html,/fileexchange/details.aspx?fid=8拖入origin即可，但使用不是很方便。比较方便的是un-scan-it。 5. 如何在origin7.5 中标峰值？ 用origin7.5 作的XRD图，怎样直接在峰上标数据？ Answer: Tools/Pick peaks 设置一下点击 Find Peaks 就 OK了。Positive和Negative 是标正负峰值的意思，其他数值改变一下就知道干吗用的了。 6. 关于origin 拟合曲线延长的问题？ 我想把拟合之后的直线向前或向后延长一段距离与坐标轴相交。但是不知道该怎么弄。是不是要改那个范围的最大值和最小值啊？可是怎么改？

从后面所接成分看irof的用法

从后面所接成分看i r o f 的用法 Newly compiled on November 23, 2020

从后面所接成分看a pair of的用法 简单的来理解，a pair of不仅可以表示“一对”，还可以表示“一副”。那么a pair of在这两个不同的含义下，后面可以接怎 样的成分呢下面我们就来详细的看这部分a pair of的用法。 从后面所接成分看a pair of的用法： 1. a pair of后面可以接由两部分构成的单件事物名词，例如trousers，scissors，glasses，spectacles，jeans等等。 例句：My father has small eyes, wear a pair of glasses, looking more gently. 我的父亲有一双小小的眼睛，戴着一副眼镜，看上去很温和。 It was a pair of jeans from a denim shop. 那是一条从牛仔裤店偷来的牛仔裤。 注意事项：对于这样的由两部分构成的单件事物，我们不可以 用one或者ones来替代它，而是要用pair或者pairs。 2. a pair of后面可以接包括两件东西且习惯上一起使用的名词，例如shoes，boots，gloves，socks，earrings，chopsticks 等等。 例句：It's cold, I need a pair of gloves. 天气冷，我需要一副手套。 I brought my father a pair of socks on the Father's Day. 父亲节那天我为父亲买了一双短袜。 3. a pair of后面可以接表身体中两个相同的部位的名词。

快速英语学习法(7)：“吃”的英文用法大全

快速英语学习法（7）：“吃”的英文用法大全 小伙伴们都纷纷封自己为中国最合格的“小吃货”，当然，要把中国文化发扬光大，就要做最合格的国际吃货。 那么，一看到“吃”，你想到的第一个单词除了eat之外，还有别的？其实，这是应该根据不同的情景和意义给予恰当的表达。常见的表达法如下： 1．译作take或have。 The patient can't take food yet．病人还不能吃饭。 We are having dinner now．我们现在正在吃晚饭。 2．译作dine，feed，taste，touch，graze等词。 She invites me to dine with her tomorrow． 她邀请我明天和她一起吃饭。 Have you fed yet？你吃饭了吗？ He hasn't touched ／tasted food for two days．他两天没吃东西了。 The horses were grazing quietly in the field． 马群正在田野里静静地吃草。 3．译作like，love，prefer，enjoy，care for，be fond of等。 Would you like `ice-cream`？你想吃冰淇淋吗？ She loves bananas．她爱吃香蕉。 Southerners prefer rice while northerners prefer noodles． 南方人喜欢吃米饭而北方人喜欢吃面条。 He is enjoying his dinner．他正津津有味地吃晚饭。 Tom doesn't care for meat．汤姆不怎么喜欢吃肉。 Ants are fond of sweet food．蚂蚁喜欢吃甜食。

Population用法

Population用法 population是一个集合名词（无复数形式)，它的用法有时较为特殊,所以很容易用错。 下面谈一下它的用法: 一、population常与定冠词the连用,作主语用时,谓语动词常用第三人称单数形式。 例如: The world\'s population is increasing faster and faster. 全世界的人口增长得越来越快。 At the beginning of the twentieth century, the world\'s population was about 1,700 million. 在二十世纪初,全世界的人口大约是十七亿。 二、当主语是表示\"人口的百分之几、几分之几\"时,谓语动词用复数形式。 例如: About seventy percent of the population in China are farmers. 中国大约有百分之七十的人口是农民。 三、有时population可用作可数名词,其前可用不定冠词。 例如: China has a population of about 1.3 billion. (=There is a population of about 1.3 billion in China.) 中国大约有十三亿人口。 New York is a big city with a population of over 10 million. 纽约是一个有一千多万人口的大城市。 在表示多个地区的人口时,population要用复数形式populations。 例如: Many parts of the world, which once had large populations and produced plenty of crops, have become deserts. 世界上很多地区一度人口众多,种植大量的农作物;现在,这些地区已经变成了沙漠。 四、表示人口的\"多\"或\"少\",不用\"much\"或\"little\",而要用\"large\"或\"small\"。 例如: India has a large population. 印度人口众多。 Singapore has a small population. 新加坡人口少。 五、询问某国、某地有多少人口时,不用\"How much...?\",而用\"How large...?\";在问具体人口时用\"What...?\" 例如: -How large is the population of your hometown? 你们家乡有多少人口? -The population of our hometown is nearly twice as large as that of yours. 我们家乡的人口是你们家乡人口的将近两倍。 -What is the population of Canada? 加拿大的人口有多少? -The population of Canada is about 29 million. 加拿大的人口大约有二千九百万。 六、population还表示\"某地、某类的动、植物或物品的总数\"。 例如: In India, however, the population of tigers has increased, from 2,000 in 1972 to about 5,000 in 1989. 然而在印度,老虎的总数已从1972年的2,000只增长到了1989年的大约5,000只。

origin8使用小技巧

人人网- 日志分享 1. 请教怎样反读出origin曲线上全部数据点？ 如，我用10个数据点画出了一条origin曲线，并存为project的.OPJ格式。 但，现在我想利用OPJ文件从这条曲线上均匀的取出100个数据点的数值，该如何做？ 注：要一切都使用origin软件完成，不用其他曲线识别软件。 https://www.sodocs.net/doc/149553598.html,/bbs/viewthread.php?tid=1390313 [1] Answer： ORIGIN中，在分析菜单（或统计菜单）中有插值命令，打开设置对话框，输入数据的起点和终点以及插值点的个数，OK！生成新的插值曲线和对应的数据表格。 2. origin中非线性拟合中logistic模型的疑问？ origin 中非线性拟合中的logistic模型为 y = A2 + (A1-A2)/(1 + (x/x0)^p) 其初始参数设置为 sort(x_y_curve); //smooth(x_y_curve, 2); x0 = xaty50( x_y_curve ); p = 3.0;

A1 = max( y_data ); A2 = min( y_data ); A1 = min( y_data ); A2 = max( y_data ); 而据我看到的logistic的模型都是（自己origin中自定义的） y =A1/(1+(A1/A2-1)*exp(-k*x)) 也就是说 origin 中的logistic有4个数值需要确定，而自定义的有3个数值 从结果来看，没有太大区别，但为什么函数不一样呢？ 不是学数学，高人能否详细说明下。 https://www.sodocs.net/doc/149553598.html,/bbs/viewthread.php?tid=1391522 [2] Answer: 你可以看一下这个文档，里面有数种不同形式的 logistic 模型： https://www.sodocs.net/doc/149553598.html,/web/packages/drc/drc.pdf [3] 当然，这是一个 R (https://www.sodocs.net/doc/149553598.html,) 包的文档，但不妨碍你看其中的公式。 R 是开源的啊，以 GPL 发布，可以从 https://www.sodocs.net/doc/149553598.html, [4]上了解更多。I 3. 如何用origin做出附件中的图：其中标注的三角形、方块是怎么整上去的？https://www.sodocs.net/doc/149553598.html,/bbs/viewthread.php?tid=1393739 [5] Answer:

(完整版)主谓一致用法总结

主谓一致用法总结 I.主谓一致定义 II.谓语受主语支配，和主语在人称和数上保持一致，这叫做主谓一致。 III.例: My favorite food is noodles. II. 主谓一致的重要原则 ?语法原则 ?意义原则 ?就近一致 （一）语法一致 IV.顾名思义，即谓语在语法角度上与主语保持一致，不考虑主语的意义。 V.以单数名词或代词，动词不定式短语作主语时，谓语动词要用单数;主语为复数时，谓语用复数。例如： 注意：不定式及动名词作主语时，谓语 动词单数。E.g. 2) 由and或both……and连接的并列成分作主语时，谓语动词用复数。例如： Both you and he are right. Mr. and Mrs. Brown have a son called Tom. 但并列主语如果指的是同一人，同一事物或同一概念，谓语动词用单数。例如：The poet and writer has written lots of books. The poet and the writer have come. 可通过名词前定冠词来判断。 3) 由and连接的并列单数主语之前如果分别由each, every修饰时，其谓语动词要用单数形式。例如： Now every man and every woman has the right to receive education. 4) 主语后面跟有 but ,except, besides, with ，together with 等介词短语时，谓语动词仍用与主语（即前面的词语）保持一致。例如： The teacher with his students is going to have a picnic in the park. The students with the teacher are going to have a picnic in the park. Nobody but two boys was late for class. 5) 集合名词作主语谓语动词要用复数。 如people, police, cattle, clothes等。 集合名词指可用来指称一群对象的词语，这些对象可以是人、动物、或是一群概念等事物。 常见集合名词：people, police, cattle, goods, clothes等。 e.g. The police are looking for him. ?有些集合名词如class, team, group, family 根据其表达意义不同，单复数用法也不同。

blade特殊用法

错误!不能读取或显示文件。特殊用法adjustable blade 可调整叶片 可调整刀片 变距桨叶, 活距桨叶 air cooled cascade blade 气冷叶栅桨 airscrew blade 螺旋桨叶 anchor blade 锚爪 articulated blade 【航空】铰接桨叶 back saw blade 锯条 backward curve blade 后曲叶片 beater blade 轮叶, 逐稿轮叶片, 击轮叶片 bent blade 弯刀, 弯形旋耕刀 blower blade 吹送机轮叶片, 鼓风机轮叶片 calling-on signal blade 引导信号臂板 cambered blade 曲面桨叶, 弯曲叶片 carbide blade (无心磨床的)硬质合金刀片, 硬质合金托板 cascade blade 叶栅的叶片 cast blade 铸造叶片 central blade

(多叶舵的)中间舵叶 centrifuge blade 离心叶片; 离心刀片 ceramic rotor blade 陶瓷动叶片 circular shear blade (圆剪床的)圆形刀片completeblade 整叶片 compressorblade 压缩机叶片 conduction-cooled turbine blade (导热)冷却式涡轮叶片 constant reaction blades 等反应度叶片 constant speed chopper blade 恒速调制盘叶片 counter blade 对刃 covering blade 覆土铲 Cuban blade 无柄刀(生产雪茄烟用) cutter blade (铣)刀片 切割器动刀片 Damascus blade 大马士革钢刀 detachable blade 可折桨叶 可换刀片[刀刃] diamond-impregnated blade 金刚砂刀片 die blade

population 的用法

population 的用法 1.population 常以单数形式出现，意为“人口”“人数”。如果指世界不同地区的人口时，用复数。 （1）The population of this city is growing every year. (2) Many parts of the world, which once had large populations and produced plenty of crops, have become deserts. 2.做主语时，谓语动词的数的选用，population直接做主语，谓语动词一般用单数，前面有some, most 或者百分数时，谓语动词常用复数，前面有分数时，谓语动词单复数即可。 (1).The population is increasing faster and faster. (2).At the beginning of the twentieth century, the world\'s population was about 1,700 million. (3).About seventy percent of the population in China are farmers. (4).Most of the population of the city are workers. (5).One third of the population now smoke/smokes. 3.population 前的冠词的选用，population of 跟地名或者事物时，用定冠词the, population of 跟数词时，用不定冠词a, population 表示抽象意义时，用零冠词。 （1）.China has a population of about 1.3 billion. (2). New Y ork is a big city with a population of over 10 million. (3). The population of Canada is about 29 million. (4). The people’s living standard has risen, causing a rise in population. 4.询问某国、某地有多少人口时,不用\"How much...?\",而用\"How large...?\";在问具体人口时用\"What...?\"。表示人口的\"多\"或\"少\",不用\"much\"或\"little\",而要用\"large\"或\"small\" (1).How large is the population of your hometown? 你们家乡有多少人口? (2).The population of our hometown is nearly twice as large as that of yours. 我们家乡的人口是你们家乡人口的将近两倍。 (3).What is the population of Canada? 加拿大的人口有多少? 5. 在表示多个地区的人口时,population要用复数形式populations。例如: Many parts of the world, which once had large populations and produced plenty of crops, have become deserts. 世界上很多地区一度人口众多,种植大量的农作物;现在,这些地区已经变成了沙漠。

英语量词用法大全

英语量词用法大全 常用语法 场景1：当和外国友人走在公园，突然看到一群鸽子。这时候你是不是就会说:There are many pigeons 或者a lot of呢？想再高大上一点吗？Sam, look! There is a flock of pigeons over there. 场景2:当说三张纸的时候，是不是很习惯说：“three papers”？错了哦。paper 是不可数名词。正确说法是：three pieces of paper。 ◆◆量词用法整理+讲解◆◆ 量词可以用于描述可数名词比如a herd of elephants(一群大象）, 也可以描述不可数名词；比如three pieces of paper（三张纸） 1、描述一群...量词+群+of+名词 一群人a/an crowd／group／army／team／of people； 一群牛、象、马、天鹅a herd of cattle／elephants／horses／swans

一群鸟、鹅、母鸡、羊、燕子a flock of birds／geese／hens／goats／swallows 一群猎狗、狼a pack of hounds／wolves 2、描述一丝／点／层 一丝怀疑a shadow of doubt 一线未来之光a glimpse of future 一缕月光a streak of moonlight 一层霜／雪／糖霜a layer of frost／snow／cream 3. piece块；片；段；项；件；篇；首；幅；张 a piece of bread／paper／wood／furniture／land／advice／news／meat ／cloth／music... 4、英译“一阵” 一阵哭泣／喝彩／炮击／ 雷声

PIT501J 液晶式塑料摆锤冲击试验机使用手册

前 言 感谢您选择了本公司的产品，本公司不仅为您提供质量优良的产品，而且将为您提供可靠的售后服务！ 深圳万测试验设备有限公司是先进计量仪器的制造商，而且是研制塑料塑料塑料摆摆锤冲击试验机 锤冲击试验机的专业厂商。本公司生产的各种计量、测试设备不但具有外观造型美观、结构简单紧凑，而且试验功能完善、测量精度高等特点，在同行业中性能价格比最好。 为了适应试验机市场的发展除塑料摆锤冲击试验机塑料摆锤冲击试验机塑料摆锤冲击试验机外，本公司还研制金属摆锤冲击试验机（PIT 系列）、微机控制管材耐压爆破试验机（PRB 系列）、微机控制热变形维卡软化点试验机（HVT 系列）、全自动落锤冲击试验机（DIT 系列）等多种材料试验机以及缺口型、哑铃型制样机，客户可以根据自身的需要选择机型，也可提出要求向本公司专门订制特殊类型的试验机，本公司将热忱为广大用户服务。 本说明书中带有本说明书中带有“★”“★”“★”的地方的地方的地方，，请您特别注意并仔细阅读请您特别注意并仔细阅读。。 随机文件： 本机装有如下随机文件： 1、 《摆锤冲击试验机使用说明书》 2、 《产品出厂装箱单》 3、 《产品保修卡》 4、 《产品合格证》 在您接收本设备时，请检查上述文件是否齐全，并妥善保管。 ★提示提示提示：：为确保设备的正常使用，本公司要求用户在使用该设备之前，务必认真阅读本《塑料摆锤冲击试验机使用说明书》。 ★提示提示提示：：本公司对出厂的仪表提供一年的保修服务，但违反操作规程而造成的人为因素引起的损坏则不属保修范围。

★提示提示提示：：在您的设备调试合格后，为确保您得到最佳服务,请您签写《产品验收报告》和《现场安装调试/培训记录表》,由我们公司的调试人员带回本公司存档。 本说明书是按照出版当时所生产的产品所编制，随着产品的不断改进，书中内容可能会与出版之后生产的产品有所不同。 不同之处，不再另行通知，敬请谅解！ ★特别声明特别声明特别声明：：本说明书不能作为向本公司提出任何要求的依据。 本说明书的解释权在本公司。 虽竭尽全力，但疏漏与谬误在所难免，竭诚欢迎广大用户批评指正。 2016/05/01版本/版次：B/0

数词用法归纳

▲掌握小数，分数、百分数和时间、日期的表达法。 【复习要点】 （一）基数词num. 基数词用来表示数目，或者说表示数量的词叫基数词。最基本的基数词如下表所示。 1 one 11 eleven 100 a hundred 2 two 12 twelve 20 twenty 1000 a thousand 3 three 13 thirteen 30 thirty 1，000，000 a million 4 four 14 fourteen 40 forty 10，000，000 ten million 5 five 15 fifteen 50 fifty 100，000，000 a hundred million 6 six 16 sixteen 60 sixty 1，000，000，000 a billion 7 seven 17 seventeen 70 seventy 8 eight 18 eighteen 80 eighty 9 nine 19 nineteen 90 ninety 10 ten 说明： 1．13—19是由个位数加后缀-teen构成。注意其中13、15的拼写是thirteen 和fifteen。 2．20—90由个位数加后缀-ty构成，注意其中20—50的拼写分别是twenty, thirty, forty 和fifty;80的拼写是eighty。 3．其它非整十的两位数21—99是由整十位数加连字符“-”，再加个位数构成。如：81 eighty-one。 4．101—999的基数词先写百位数，后加and再写十位数和个位数。如：691 six hundred and ninety-one。5．1000以上的基数词先写千位数，后写百位数，再加and，最后写十位数和个位数。 如：5893 five thousand eight hundred and ninety-three。在基数词中只有表示“百”、“千”的单位词，没有单独表示“万”、“亿”的单位词，而是用thousand（千）和million（百万）来表达，其换算关系为：1万=10 thousand;1亿=100 million; 10亿=a thousand million=a billion。 Hundreds of Thousands of 6．多位数的读法： 1）1000以上的多位数，要使用计数间隔或逗号“，”。即从个位起，每隔三位加一个间隔或逗号。第一个间隔或逗号前是thousand（千），第二个间隔或逗号前是million（百万），第三个间隔或逗号前是a thousand million或a billion(十亿)。 2）每隔三位分段以后就都成了101—999。读的时候十位数（或个位数）的前面一般要加and。如： 888，000，000读作：eight hundred and eighty-eight million。 基数词的用法： 1. 基数词在句中的作用 基数词的作用相当于名词和形容词，在句中可作定语、主语、宾语（介宾）、表语、同位语等。 例如：Three and five is eight. 3+5=8 （作表语）How many oranges do you want?你要多少桔子？ I want eight. 我要八个。（作宾语）There are eight boats in the lake. 湖里有八条小船。（作定语） 2．Hundred, thousand, million, dozen, score这些词前面如有表示具体数字的词，它们不能加“s”,反之则须加“s”, 并要与of短语连用。例如：

the的用法归纳

The的用法归纳 1 表示特指的人或物 例：Please hand me the key on the desk. 请把桌上的钥匙递给我。 The girl in red is his sister. 穿红色衣服的女孩是他妹妹。 The building over there is the tallest in the town. 那边那幢大楼是这个城里最高的。 I like the music of the film. 我喜欢这部电影的音乐。 2 表示双方都知道的或心中明白的人或物 例：Shut the door, please. 请关门。 Has he returned the book? 那本书他还了吗？ Take the blue one, it is cheaper. 拿那个蓝的，它便宜些。 3 第二次提到某人或某物第一次提到时用不定冠词，第二次提到时要用定冠词。 例：He saw a house in the distance. Jim's parents lived in the house. 他看见远处有一所房子，吉姆的父母就住在那所房子里。 There was once an old fisherman. The old fisherman had a cat. The cat was white. 从前有一个老渔夫。这个老渔夫有一只猫。这只猫是只白猫。 4 用在世界上独一无二的名词前 这类词有： the sun太阳, the earth地球, the moon月亮, the sky天空, the world 世界 例：The moon goes round the earth. 月亮绕着地球转。 There is not any cloud in the sky. 天空中没有一丝云彩。 It was a fine day in spring. The sun shone brightly. 这是一个晴朗的春日，阳光灿烂。 He is the richest man in the world. 他是世界上最富的人。 5 用在表示方向、方位的名词前 这类词有： the east东方，the west西方，the south南方，the north北方，the right右边，the left左边 例：The birds are flying to the north. 这些鸟向北方飞去。 The moon rises in the east and sets in the west. 月亮从东方升起，在西方落下。 The wind was blowing from the south. 风从南方吹来。 She lived to the west of the Summer Palace. 她住在颐和园的西边。 Walk along the road and take the first turning on the right. 沿着这条路往前走，在第一个路口往右拐。He stood at the back of the door. 他站在门背后。 提示 方位词成对使用构成平行结构时，不用定冠词。 例：The river is two thousand kilometers long from west to east. 这条河自西向2000公里长。 They traveled through the country from south to north. 他们自南向北在这个国家旅行。 6 用在形容词最高级前 例：Summer is the hottest season of the year. 夏天是一年中最炎热的季节。 She is the best person for the job. 她是最适合这个工作的人。 Hangzhou is one of the most beautiful cities in the world. 杭州是世界上最美的城市之一。 The car is the most expensive of the four. 这部车是四部车中最贵的。 7 用在序数词等前 定冠词用在序数词前，也用在表示序列的next, last等前，还有在表示“同一”或“唯一”等的词前。 例：The first man to land on the moon is an American. 第一个登上月球的人是美国人。 She was the fifth to climb to the top of the mountain. 她是第五个到达山顶的人。 This may be the last chance. 这可能是最后一次机会。 If I miss this train I'll catch the next one. 如果赶不上这趟火车，我就赶下一趟。 He is the only person who knows the secret. 他是唯一一个知道这个秘密的人。 The two coats are of the same colour. 这两件外衣颜色相同。 This is the very book I want. 这正是我要的书。（用very表示强调）

上厕所多种英语口语表达

上厕所多种英语口语表达 和朋友一起吃饭也好，正在开会也好，如果你忽然感觉想去方便一下，又不好意思直接说“我要上厕所”，英语中可以怎么说呢？ 在中文里，我们有不少这方面的委婉说法，比如“出恭”，“方便”，“去洗手间”等等，同样在美语中也有很多表达这一意思的委婉说法。如果不知道的话，很容易在交际过程中闹出笑话。 1. I need to go somewhere. 听到这句话可千万别回答成：You can go anywhere you like.那可是要闹大笑话了。I need to go somewhere. 的意思就是“我要上厕所”。当有老外这么说的时候，指示给他卫生间在哪里就行了。 2. I want to wash my hands. 你在同女生吃饭的时候有没有注意过她们说“我去洗下手”？这句话隐含的意思也是“我要上厕所”。在英语中这句话就是“I want to wash my hands.”女生说得更客气的一句话是“I need to powder my nose.”，是很含蓄的说法。而“I want/need to go (or use) to the bathroom/restroom. ”则是比较普通的委婉了，程度没有上面两个高。 3. I need to answer the call of nature. 一种更为文雅的说法称内急为“the call of nature”，那么上厕所就成了“to answer the call of nature.”。有时个别年纪大的女士在这种情况下还会说“I need to make a pit stop.”其实“pit stop”是指在赛车过程中，赛车在途中紧急停留加油、维修的地方。看来，她们肯定将解决问题看作是一种“紧急维修”了。 4. I need to go pee. 说过了委婉的说法，一些俚语和口语中很直接的说法我们也要了解一下，这些说法经常出现在一些电视剧和电影中，比如“I need to go pee.”或“I need to take a leak (小便)。”或“I need to take a dump.”但这些讲法是非常粗鲁的，通常在小孩子或者受教育程度不高的人中间使用比较普遍。 说到这儿，有人也许要问，那么上课，开会，听报告或者赴宴会时要上厕所，应该如何说呢？其实在任何场合中，你需要使用卫生间，去就是了，不用跟任何人打招呼。正如美国人所说的那样“If you gotta go, you gotta go.”

从后面所接成分看aairof的用法

从后面所接成分看a p a i r o f的用法简单的来理解，apairof不仅可以表示“一对”，还可以表示“一副”。那么apairof在这两个不同的含义下，后面可以接怎样的成分呢下面我们就来详细的看这部分apairof的用法。 从后面所接成分看apairof的用法： 1.apairof后面可以接由两部分构成的单件事物名词，例如trousers，scissors，glasses，spectacles，jeans等等。 例句： Myfatherhassmalleyes,wearapairofglasses,lookingmoregently. 我的父亲有一双小小的眼睛，戴着一副眼镜，看上去很温和。 Itwasapairofjeansfromadenimshop. 那是一条从牛仔裤店偷来的牛仔裤。 注意事项：对于这样的由两部分构成的单件事物，我们不可以用one或者ones来替代它，而是要用pair或者pairs。 2.apairof后面可以接包括两件东西且习惯上一起使用的名词，例如shoes，boots，gloves，socks，earrings，chopsticks等等。 例句：It'scold,Ineedapairofgloves. 天气冷，我需要一副手套。 IbroughtmyfatherapairofsocksontheFather'sDay. 父亲节那天我为父亲买了一双短袜。 3.apairof后面可以接表身体中两个相同的部位的名词。

例句：Mysisterhasahugepairofeyes.我的妹妹长有一双大眼睛。 4.apairof后面可以接表一般意义的“两个”或者“一对”等。 例句：ApairofthievesswipedaChristmastree. 一对小偷盗取一棵圣诞树。 看了上面的内容，是不是觉得apairof的用法简单而明了呢实际上，就是这么简单，只要懂得总结，懂的归纳，一切都不再是难事。

英语俚语解释及用法 英文

●Balancing act (compromise in dilemma /deal successfully with two or more people, groups, or situations that are in opposition to each other ) [The UN must perform a delicate balancing act between the different sides in the conflict. ] ●Hot air (loud and confused empty talks) [No one likes a person who thinks very highly of his own opinions but is really full of hot air.] ●Go belly-up (collapse/to be dead-end) [My brother’s company went belly-up last month when its revenues were far below its monthly debts, so now he’s looking for a job.] ●Keep the head above water [Earning barely enough to support the family, father was quite happy only if he could keep his head above water.] ●XYZ (Check your zipper) ●Rome was not built in a day. ●Penny wise and pound foolish.(小事聪明、大事聪明) ●Variety is the spice of life. ●Honesty is the best policy. ●Bellybutton ●Plain sailing(easy unobstructed progress) ●Flowery language/plain flowery ●Snak e charmer(a performer who uses movements and music to