a r X i v :a s t r o -p h /0408581v 1 31 A u g 2004
Astronomy &Astrophysics manuscript no.February 2,2008
(DOI:will be inserted by hand later)
Absolute kinematics of radio source components in the complete
S5polar cap sample
II.First and second epoch maps at 15GHz
M.A.P′e rez-Torres 1,2,J.M.Marcaide 3,J.C.Guirado 3,and E.Ros 4
1Istituto di Radioastronomia,Via P.Gobetti 101,40129Bologna,Italy
2Instituto de Astrof ′?sica de Andaluc ′?a (CSIC),Apdo.Correos 3004,E-18080Granada,Spain 3Departament d’Astronomia i Astrof ′?sica,Universitat de Val`e ncia,E-46100Burjassot,Val`e ncia,Spain 4
Max-Planck-Institut f¨u r Radioastronomie,Auf dem H¨u gel 69,D–53121Bonn,Germany
Submitted:10March 2004/Accepted:27July 2004
Abstract.We observed the thirteen extragalactic radio sources of the complete S5polar cap sample at 15.4GHz with the Very Long Baseline Array,on 27July 1999(1999.57)and 15June 2000(2000.46).We present the maps from those two epochs,along with maps obtained from observations of the 2cm VLBA survey for some of the sources of the sample,making a total of 40maps.We discuss the apparent morphological changes displayed by the radio sources between the observing epochs.Our VLBA observations correspond to the ?rst two epochs at 15.4GHz of a program to study the absolute kinematics of the radio source components of the members of the sample,by means of phase delay astrometry at 8.4GHz,15.4GHz,and 43GHz.
Our 15.4GHz VLBA imaging allowed us to disentangle the inner milliarcsecond structure of some of the sources,thus resolving components that appeared blended at 8.4GHz.For most of the sources,we identi?ed the brightest feature in each radio source with the core.These identi?cations are supported by the spectral index estimates for those brightest features,which are in general ?at,or even inverted.Most of the sources display core-dominance in the overall emission,as given by the core-to-extended ratio in the 15.4GHz frame,Q .We ?nd that three of the sources have their most inverted spectrum component shifted with respect to the origin in the map,which approximately coincides with the peak-of-brightness at both 15.4GHz and 8.4GHz.
Key words.astrometry –techniques:interferometric –quasars:general –BL Lacertae objects:general
1.Introduction
This paper is the second of a series aimed at conducting absolute kinematics studies of a complete sample of extra-galactic radio sources,using astrometry techniques.The sample consists of the thirteen sources from the S5polar cap sample,selected by Eckart et al.(1986,1987)from the S5survey (K¨u hr et al.1981),that satisfy the following cri-teria:(i)δ≥70?,(ii)|b II |≥10?,(iii)S 5GHz ≥1Jy at the epoch of the survey,and (iv)α2.7,5GHz ≥?0.5(S ～ν+α).Hereafter,we shall refer to those thirteen radio sources as “the complete S5polar cap sample”.
We described the goals of our astrometric program in Ros et al.(2001,hereafter Paper I),and presented 8.4GHz VLBA maps obtained at two di?erent epochs,1997.93and 1999.41.We refer the reader to that paper for further de-
2P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
et al.2002).We discuss in detail the apparent changes in the brightness distribution of some of the radio sources during the time covered by the15.4GHz observations,as well as a comparison with the results presented at8.4GHz (Paper I).Throughout the paper,we use a Hubble con-stant H0=65h km s?1Mpc?1and a deceleration parame-ter q0=0.5.
2.Observations
We observed the complete S5polar cap sample at 15.4GHz on27July1999(epoch1999.57)and on15June 2000(epoch2000.46)with the VLBA,each time for24 hours.For the?rst epoch,we used the standard VLBA recording mode128–8–1(data rate of128Mbps,recording in8IFs of16channels each),in left circular polarization, thus yielding a total bandwidth of64MHz.For scheduling reasons,in our second epoch we used the standard record-ing VLBA mode64–4–1(data rate of64Mbps,recording in4IFs of8channels each),also in left circular polar-ization,yielding a total bandwidth of32MHz.All data were correlated at the VLBA Array Operations Center of the National Radio Astronomy Observatory(NRAO)in Socorro,New Mexico,using a basic integration time of 4s.All radio sources were detected and provided fringes for all baselines.We cycled around in groups of three or four radio sources,with duty cycles of about5min.Every scan was55s long,and antenna slew times were<～20s. We replaced one or two members of the group of observed sources by new ones every two hours approximately,until all thirteen sources of the sample had been observed.We tracked the clock behaviour—of relevance for the astro-metric analysis—by including some scans of BL0454+844 in all groups observed during the?rst(second)half of the experiment on27July1999(15June2000),and of BL2007+777in all groups observed during the second (?rst)half.
After fringe-?tting the correlator output,we obtained correlation amplitudes for each source.We calibrated the visibility amplitudes in a standard manner,using the antenna gain and system temperature information pro-vided by each station.We then used the Caltech VLBI Package(Pearson1991)and the di?erence mapping soft-ware difmap(Shepherd et al.1994)to obtain the radio images shown in this paper.
3.Imaging results
We imaged all thirteen radio sources using standard hy-brid mapping techniques.We found minor amplitude cal-ibration problems for the Saint Croix antenna at epoch 1999.57;the noise level was high for most of the observ-ing run.Nevertheless,we used the data for Saint Croix, since it provides long baselines,and hence high resolution. We show the maps obtained in Figs.2through14.In all ?gures,east is left,and north is up.We list the main pa-rameters of those maps in Tables1and3.
We also present images of several sources of the S5po-lar cap sample obtained from observations of the VLBA 2cm Survey that were relatively close in time to our ob-servations.We used the same data reduction and standard hybrid mapping techniques that were used with our own data.To distinguish the2cm VLBA survey maps from ours,we have labelled the latter“2cm survey”.
We now proceed to discuss the apparent morpholog-ical changes displayed by each of the radio sources of the complete polar cap sample,as seen from15.4GHz VLBA observations made in1999.57and2000.46,com-plemented with maps of some of the sources,which we obtained from observations of the2cm VLBA Survey (Kellermann et al.1998;Zensus et al.2002;see also https://www.doczj.com/doc/1512202929.html,/2cmsurvey).To quantify the mor-phological changes displayed by the radio sources,we used the tasks modfit and erfit of the Caltech pack-age(Pearson1991)to?t the visibility data to a model of elliptical components with Gaussian brightness pro?les. Those models are listed in Tables2and3.
We compare our observations with those taken at 8.4GHz with the VLBA in1997.93,and in particular in1999.41(very close to our?rst epoch,1999.57),and presented in Paper I.These yield the spectral index,α(S～να)for those15.4GHz source components that have clear counterparts at8.4GHz.We refer the reader to Paper I for a comprehensive discussion of historical de-tails for each radio source.
We also show in Fig.3.1the distance to the core for sources of the S5polar cap sample that were observed at least three times,and in Table4we present proper motions obtained from model?tting source component positions at di?erent epochs.We list proper motions only for those components that were identi?ed in at least three epochs,and whose proper motion exceeded1σ.
3.1.QSO0016+731
The source QSO0016+731(Fig.2,z=1.781)shows at 15.4GHz a core-jet structure at an angle of～130?.The modeling of the radio source provides a good?t with three components:a compact,strong one(UA),which likely corresponds to the core,and two extended,weak components(UB and UC),directed to the east-southeast, and which correspond to the jet.The total?ux den-sity increased signi?cantly from647mJy to817mJy(26% change)between our two observing epochs.The corre-sponding monochromatic luminosity is L15GHz≈(1.3to 1.6)×1039W.The increase in the total?ux density of the source was due to a strong increment in the?ux of the westernmost component(UA,the brightest feature in Fig.2).Correspondingly,the observed,uncorrected ratio of the core?ux density to the extended?ux density in
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.3 Table1.Map parameters for sources of the complete S5polar cap sample at15.4GHz.
———–Epoch1999.57———–———–Epoch2000.46———–
Beam FWHM a Beam FWHM a
Source Size P.A.S peak S tot(b)rms level c Size P.A.S peak S tot(b)rms level c [mas][mJy/beam][mJy][mJy/beam][mas][mJy/beam][mJy][mJy/beam] a The restoring beam is an elliptical Gaussian with full-width-half-maximum(FWHM)axes a×b.For each source,the position
angle(P.A.)stands for the direction of the major axis measured north through east.
b Total?ux density recovered in the hybrid mapping process.
c Contours in the maps of the?gures shown in Sects.3.1to3.13are the tabulate
d rms values times(?3,3,3√
1We have kept the name convention used in Paper I.Thus,“UA”represents the?rst component(“A”)at the observing frequency band(“U”,corresponding to15.4GHz).We have also tried to assign to a given feature of a source the same name as used in Paper I.However,this has not always been possible.For example,we have no component labeled UE,nor UF for QSO0212+735(see Sect.3.3).This means we found no counterpart at15.4GHz for components XE and XF.3.2.QSO0153+744
QSO0153+744(Fig.3,z=2.341)is a one-sided radio
source(e.g.,Hummel et al.1988),whose15.4GHz VLBA emission is dominated by two components,UA and UB,
separated by～10mas(～61h?1pc).The main component, UA(likely the core),is composed of three sub-components,
UA1,and UA2and UA3(the innermost regions of the
jet).UA2and UA3trace a smooth change in the di-rection of the jet,changing from65?±3?at a distance r=(0.65±0.05)mas[～(3.6to4.2)h?1pc],to88?±8?at a distance r=(1.35±0.05)mas.No emission is de-tected above3σ(3mJy),up to a distance of～10mas (～61h?1pc),where component UB traces the outermost regions of the jet.At this distance,the jet is at an angle ～150?.
The total?ux density stayed remarkably stable be-
tween1999.57and2000.46,decreasing from(316±3)mJy to(312±2)mJy.It decreased by8%between2000.46and 2000.99,down to(288±2)mJy,implying L15GHz≈(1.0 to1.1)×1039W.At all three epochs,component UA con-tributed≈80%to the total?ux density,while component UB contributed the remaining≈20%.The brightest sub-component of UA,UA1,slightly increased its?ux den-sity in spite of the total?ux decrease.On the contrary, both UA2and UA3continued to fade between1999.57and 2000.99(e.g.,UA2decreased its?ux density by≈50%). The value of Q(taken to be the ratio of emission from UA1to the rest of the emission)increased from1.26in 1999.57to1.94in2000.99,indicating that the compact core marginally dominates the total emission,and tended to increase this dominance.
4P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
Table2.Elliptical Gaussian component model parameters for the radio sources of the complete S5polar cap sample.
———————Epoch1999.57——————————————Epoch2000.46———————
Source Comp.S rθa b/aφS rθa b/aφ
[mJy][mas][mas][mJy][mas][mas]
0153+744UA1176±130–0.12±0.070.15±1.4163±21188±20–0.12±0.010.54±5.9381±12 UA250±170.58±0.0970±20.51±0.220.33±0.21?80±1938±40.65±0.0965±10.48±0.080.32±1.3289±10
UA325±5 1.29±0.0983±10.63±0.080.33±0.11139±922±2 1.38±0.0995±2 1.00±0.130.33±0.07?23±5.4
UB143±410.27±0.09153±1 1.14±0.120.87±0.12?66±2236±510.13±0.09154±1 1.35±0.120.65±0.1234±10
UB220±411.14±0.09151±10.73±0.120.59±0.10?32±930±511.02±.09151±10.90±0.120.66±0.15?73±18
0454+844UA93±50–0.37±0.010.49±0.04?1±2121±10–0.35±0.010.27±0.03?2±1 UB a20±50.49±0.08137±30.65±0.120.73±0.16?31±19
UC a10±1 1.71±0.08172±1 1.01±0.090.58±0.08?48±819±1 1.15±0.08158±1 1.77±0.090.31±0.04?31±4
0716+714UA1058±50–0.17±0.010.21±0.0522±2981±170–0.12±0.010.10±0.8836±8 UB53±50.71±0.0817±1 1.49±0.090.16±0.027±262±170.45±0.1030±40.77±0.100.11±0.114±4
1039+811UA883±20–0.27±0.010.34±0.01100±1785±20–0.32±0.010.43±0.01101±1 UB a29±6 1.12±0.07?68±2 1.13±0.240.26±0.11?80±648±2 1.68±0.06?65±1 2.22±0.150.11±0.04109±1
UC a23±4 2.38±0.11?67±1 1.36±0.180.09±0.12?92±4
1749+701UA198±60–0.26±0.210.22±0.17?17±15218±80–0.42±0.270.19±0.15?36±19 UB78±60.26±0.02?48±30.43±0.230.11±0.10?70±25105±80.39±0.02?48±20.31±0.170.09±0.07?88±23
UC112±1 1.11±0.04?61±30.28±0.200.30±0.16?169±3516±1 1.28±0.05?63±20.45±0.270.56±0.23143±28
UC215±2 1.42±0.04?77±20.42±0.230.63±0.1948±15
UD31±2 2.25±0.02?73±20.74±0.320.47±0.2151±847±2 2.40±0.02?70±10.66±0.300.43±0.1771±14
UE155±3 3.19±0.12?57±1 3.09±0.160.42±0.15?44±7
UE228±2 3.65±0.13?54±2 2.40±0.220.21±0.1487±11
1928+738UA941±250.26±0.11?20±60.20±0.100.26±0.13?6±1774±80.39±0.14?16±10.52±0.010.11±0.03?13±2 UB1656±270–0.23±0.010.16±0.08?19±2602±200–0.52±0.010.11±0.03?14±1
UB2571±300.38±0.11155±10.34±0.020.61±0.03?28±1660±130.32±0.14143±10.38±0.090.27±0.02?13±1
UC390±2 1.15±0.11152±10.34±0.020.61±0.036±2331±1 1.26±0.14152±10.31±0.080.72±0.14?38±3
UD184±3 2.50±0.11162±10.91±0.020.52±0.0219±2184±6 2.55±0.14158±10.57±0.040.44±0.04?165±2
UE157±2 2.96±0.11173±1 1.27±0.020.17±0.05?14±2181±2 3.07±0.14173±1 1.22±0.120.31±0.01?13±1
UF40±2 3.93±0.11162±10.72±0.050.13±0.32?46±963±3 3.82±0.14163±1 1.38±0.100.39±0.05?32±6
UG19±1 5.57±0.11164±10.61±0.050.23±0.23?79±1311±2 5.26±0.14168±2 1.59±0.450.17±0.1621±7
UI76±311.46±0.11167±1 2.60±0.100.65±0.05?15±593±311.58±0.14167±1 2.46±0.160.84±0.086±13
Note:For each source component,we list its?ux density,separation and position angle relative to the component?xed at the origin(r=0,θ=0), major axis,axis ratio,and position angle of the major axis.The uncertainties given here have been estimated from the exploration of the parameter space(S,r,θ,a,b/a,andφ),and from empirical considerations(e.g.,the nominal errors of the component positions are in general smaller than10μas,but to be conservative we increased this?gure up to a tenth of a beam width).
a This component is model?tted as double only in the?rst epoch.In the second epoch the model?t algorithm merged both components into a single one.
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.5
D i s t a n c e t o t h e c o r e (m a s )
Epoch (yr since 1998.00)
Fig.1.Angular distance to the core vs.time elapsed since 1998.0.The plots show the change in angular separation with time
of source features for which we have measured an angular velocity from observations at three or more epochs.The lines are linear ?ts to the data,the slope representing the proper motion,μ,tabulated in Table 4.
Our model ?t indicates a proper motion for UA2of μ=(71±6)μas/yr [βapp =(4.7to 0.4)h ?1].UA3,located at a radial distance of (1.3to 1.4)mas at an angle 90?,does not show evidence for any proper motion.The extended,optically thin emission of the jet is characterized by two components,UB1and UB2,that lie at an angular distance of (10.15±0.15)mas and (11.1±0.1)mas,respectively,and at an angle of ～150?.
Since QSO 0153+744did not show evidence of intra-day variability (IDV)(A.Kraus,private communication),we assumed that the 8.4GHz VLBA ?ux density of the source did not change between 1999.41and 1999.57,and obtained a global spectral index α=?0.79.We also ob-
tain α≈?0.01for component UA/XA (a perfect ?at spectrum for the innermost regions of the core-jet struc-ture).The sub-component XA1/UA1has α=0.52,which supports our suggestion that this sub-component might be the core.We noticed that α≈?2.05for XB/UB,which corresponds to a synchrotron spectrum partially suppressed by an external medium.In this case,this would indicate that at a distance of ～60pc from the putative core the outer regions of the jet of QSO 0153+744interact strongly with their surrounding medium.Finally,we failed to detect the jet components that in Paper I were found to form an arc between XA/UA and XB/UB,which results
in upper limits of αXC/UC <～?2.24,αXD/UD <～?3.09,
6P′e rez-Torres et al.:Absolute kinematics of radio source components.
II.
Fig.2.VLBA images of QSO 0153+744on 27July 1999
(1999.57),15June 2000(2000.46),and 28December 2000(2000.99).See Tables 1–3for contour levels,beam sizes (bot-tom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
Fig.3.VLBA images of QSO 0153+744on 27July 1999(1999.57),15June 2000(2000.46),and 28December 2000(2000.99).See Tables 1–3for contour levels,beam sizes (bot-tom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.7
Table3.Map parameters and elliptical Gaussian component model parameters for selected sources of the complete S5polar cap sample from the2cm Survey
Source Comp.S rθa b/aφ
[mJy][mas][mas]
Epoch2000.99,(0.647×0.452,2.?4)a,731b,811c,0.5d UA742±10–0.09±0.010.30±0.08-81±1
UB35±60.79±0.06140±10.55±0.050.88±0.08178±28
UC36±6 1.41±0.06131±10.76±0.070.84±0.0988±21
Epoch2000.99,(0.833×0.446,8.?9),188,288,0.7 UA1190±10–0.13±0.010.16±15.074±8
UA228±20.68±0.0869±10.31±0.050.20±0.25-96±15
UA317±1 1.27±0.0887±20.63±0.100.11±0.13153±10
UB142±310.24±0.08153±1 1.01±0.100.79±0.11131±15
UB214±311.16±0.08151±10.53±0.090.86±0.2657±125
Epoch1999.55,(0.687×0.492,-14.?8),126,186,0.6 UA144±120–0.34±0.020.58±0.0618±5
UB24±130.49±0.18134±70.78±0.290.20±0.17-22±9
UC18±3 1.52±0.11168±2 1.34±0.240.47±0.1019±7 0716+714
Epoch2001.17,(0.770×0.451,31.?9),572,643,0.3 UA549±330–0.12±0.050.27±0.0628±4
UB71±340.43±0.1022±20.35±0.160.47±0.2616±9
UC15±2 1.94±0.0919±1 1.27±0.160.38±0.058±4
UD8±2 3.95±0.3515±2 3.28±0.650.22±0.0727±5
Epoch1998.22,(0.681×0.442,-12.?5),1378,2298,1.0 UA11672±260–0.38±0.010.69±0.0133±19
UA2228±330.21±0.04-84±20.21±0.030.63±0.26-139±42
UA360±90.47±0.04-114±20.34±0.210.35±1.069±13
UB38±1 1.37±0.04-135±10.39±0.260.84±0.93174±19
UC159±1 2.71±0.04-141±10.69±0.010.81±0.0119±2
UF72±311.61±0.41-147±1 3.17±0.140.41±0.032±5
Epoch1999.39,(0.657×0.419,-12.?6),246,415,0.5 UA196±30–0.15±0.010.22±0.13-17±4
UB95±30.20±0.07-48±10.32±0.010.32±0.10-63±2
UC128±1 1.02±0.07-62±10.43±0.360.61±0.07-84±7
UC222±1 1.49±0.07-75±10.37±0.020.86±0.1465±24
UD30±1 2.25±0.07-73±10.68±0.030.80±0.05-25±6
UE126±2 2.80±0.08-59±1 1.43±0.070.90±0.08-1±10
UE222±3 3.90±0.09-53±1 1.79±0.120.77±0.0784±11
Epoch2000.99,(0.640×0.441,20.?4),271,434,0.5 UA245±10–0.05±0.200.25±0.26-8±17
UB111±40.41±0.06-51±10.43±0.010.31±0.03-52±1
UC112±1 1.06±0.06-69±10.61±0.050.93±0.51-62±84
UC2
UD36±1 2.48±0.06-71±10.78±0.020.93±0.0456±25
UE1
UE234±2 3.56±0.06-53±1 3.03±0.130.74±0.068±9αXE/UE<～?3.09,at the3σlevel.The spectral be-haviour displayed by component XB/UB,as well as the non-detection of any signi?cant motion,is typical of a sta-
Table3.Continued
Source Comp.S rθa b/aφ
[mJy][mas][mas]
Epoch1998.84,(0.731×0.425,-8.?8),1498,2291,0.9 UA1310±460–0.12±0.010.86±0.03-74±36
UB1452±430.23±0.01-88±10.28±0.010.75±0.2976±39
UB2157±40.70±0.01-80±10.81±0.280.46±0.47102±55
UC193±3 1.41±0.01-93±10.33±0.350.79±0.0217±3
UD109±3 1.75±0.01-99±10.59±0.280.70±0.14165±3
UE52±2 3.32±0.05-93±1 2.93±0.110.43±0.03106±25 2007+777
Epoch2001.17,(0.617×0.421,-0.?9),393,948,0.4 UA1330±70.25±0.0187±10.17±0.010.22±0.1585±1
UA2189±40–0.38±0.010.24±0.0390±1
UB1213±30.40±0.01-87±10.22±0.010.37±0.05104±2
UB2115±10.87±0.01-76±10.52±0.010.38±0.03104±1
UC77±1 1.28±0.01-96±10.46±0.010.54±0.03-79±2
UE7±1 5.08±0.03-106±10.82±0.080.31±0.29112±7
UF15±1 6.86±0.06-95±1 2.08±0.150.29±0.0671±3 Note:For each source component,we list its?ux density,separation and position angle relative to the component?xed at the origin
(r=0,θ=0),major axis,axis ratio,and position angle of the major axis.The uncertainties given here have been estimated from the exploration of the parameter space(S,r,θ,a,b/a,andφ),and from empirical considerations(e.g.,the nominal errors of the component positions are in general smaller than10μas,but to be conservative we increased this?gure up to a tenth of a beam width).
a The restoring beam is an elliptical Gaussian with FWHM axes a×
b [mas].For each source,the position angle(P.A.)stands for the direction of the major axis,measured north through east.
b S
peak
:brightness peak[mJy/beam].
c S
tot
:total?ux density recovered in the hybrid mapping process[mJy].
c rms:root-mean-square noise in the image[mJy].Contours in the maps of the?gures shown in Sects.3.1to3.13are the tabulate
d rms values times(?3,3,3
√
8P′e rez-Torres et al.:Absolute kinematics of radio source components.II. Table4.Proper motions?in the S5polar cap sample
0016+731UC32±311.9±1.8
0153+744UA271±64.7±0.4
0454+844UB?100±3?5.1±0.2
UC?217±140?11.0±7.4
0716+714UB?105±100?1.6±1.5
0836+710UA2?13±6?0.8±0.4
UA3118±77.6±0.5
UB110±167.1±1.0
UC101±166.5±1.0
1749+701UB141±255.1±0.9
UC2732±60326.5±21.8
UD161±195.8±0.7
UE2?150±62?5.4±2.2
1803+784UB117±160.6±0.5
UB2133±244.4±0.8
2007+777UA152±481.0±1.0
UB156±111.1±0.2
UC?88±61?1.8±1.2
UF350±2037.0±4.0
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.9
Assuming that the8.4GHz?ux density of the source did not change between1999.41and1999.57,we obtain a global value ofα=?0.07.A detailed comparison of our model?t at15.4GHz for the?rst epoch with the model ?t made at8.4GHz for the second epoch(see Paper I), gives the following results.The position of component XA nicely corresponds to that of UA.The inferred spectral index is thenα=0.78,a rather inverted spectrum,as we would expect if UA/XA were the https://www.doczj.com/doc/1512202929.html,ponent XB is very likely a blend of two components(UB1and UB2), which yieldsαUB/XB=?0.45.The positions at8.4GHz and15.4GHz for the remaining components are the same within the uncertainties.For those components,we?nd a progressive steepening of the spectral index with distance from the https://www.doczj.com/doc/1512202929.html,ly,αUC/XC=?0.49,αUD/XD=?1.00, andαUG/XG=?1.76.The position of component UG/XG has remained remarkably stable,both in the X-and U-band between1997.93and2000.46,at a nominal position of13.8mas at angle93?.Most likely,component UG/XG is a stationary region of the source.We do not see emission from components UE+UF(clearly detected at8.4GHz as XE+XF;see Paper I)above3σ,which implies a very steep spectrum for those components.
3.4.BL0454+844
BL0454+844is,at z>～1.340(Stocke&Rector1997),the most distant BL Lacertae source of our sample with known redshift.Its monochromatic luminosity is L15GHz≈(1.2to 2.6)×1038W(note that the previously accepted redshift for BL0454+844,z=0.112,implying a lower intrinsic lu-minosity by a factor of200,which makes BL0454+844the least powerful radio source of the sample).BL0454+844 shows,together with BL0716+714,the least structure of all the sources of the complete sample,as seen at15.4GHz (Fig.5).Indeed,there is no emission above3σoutside the inner2mas(13.2h?1pc)away from component UA.Our VLBA observations showed a signi?cant variation in the ?ux density of BL0454+844between1999.55and1999.57, decreasing from186mJy down to120mJy(35%change). It then started to slowly increase up to131mJy in2000.46 (9%change),after which the source almost doubled its total?ux density in less than nine months(257mJy in 2001.17).We?tted each observing epoch,except epoch 2000.46,with a three-component model(see Table2), which seems a reasonable model?t of the radio source. We?nd the following values for the ratio Q(value,epoch: 3.43,1999.55;3.44,1999.57;6.37,2000.46;3.59,2000.99). Those values seem to con?rm the dominance of the core emission.Note that Q is signi?cantly larger in2000.46 than at the other epochs,while the map for this epoch does not show signi?cant di?erences with,e.g.,the map in1999.57.This enhanced value of Q in2000.46must be taken with caution,as the somewhat noisier data for this epoch resulted in a poorer model?t of the source struc-ture.
At all epochs,most of the emission comes from compo-
nent UA,likely to be the core,which contributes≈78%of the total emission(except in2000.46,where it amounts
to≈92%;but see the caveat above).The spectral in-dex for UA/XA is,assuming the8.4GHz did not change signi?cantly between1999.41and1999.55,αUA/XA=0.06,
as expected for a core https://www.doczj.com/doc/1512202929.html,ponent UB be-longs to the innermost regions of BL0454+844,lying at a distance of(0.3to0.5)mas from component UA,
at an angle of140?.Component UC traces the jet re-gion of BL0454+844.It probably consists of two or more sub-components,judging by the fact that the ra-
dial distances span a huge range(1.2mas to 1.7mas) in less than20months.Our model?t indicates a back-wards proper motion for both components UB(μ= (?100±3)μas/yr;βapp=(?5.1±0.2)h?1),and UC (μ=(?217±140)μas/yr;(βapp=(?11.0±7.4)h?1). However,the morphological structure of this source is so complex that those results must be taken with caution.
3.5.QSO0615+820
Our VLBA maps of QSO0615+820(Fig.6,z=0.710) show a complex,albeit compact structure at both epochs, with a maximum extension<～2.5mas(=15.4h?1pc). The15.4GHz total?ux density of the source slightly de-creased between1999.57and2000.46,from434mJy down to410mJy(6%change),with a monochromatic luminos-ity of L15GHz=(1.0to1.2)×1038W.Assuming that the 8.4GHz?ux density of the source did not change between 1999.41and1999.57,we obtainα=?0.26,a moderately steep to?at spectrum for the milliarcsecond structure of the source.
We?tted reasonably well the milliarcsecond ra-dio structure of QSO0615+820using three components (Table2)within the inner0.8mas(5h?1pc).It might well be that components UA2and UA3consist,in turn,of two sub-components each,as the maps seem to hint,but this fact is not supported by the model?t at this stage.The co-ordinates of components UA1,UA2,and UA3in1999.57 are so close to those obtained in Paper I at8.4GHz(com-ponents XA1,XA2,and XA3in1999.41),that their phys-ical association is very likely to be real.The ratio,Q,of the core(UA1)to the extended emission increased steadily with time(value,epoch:0.88,1999.55;1.04,1999.57;1.44, 2000.46).
This object is,given the intriguing(and underlying) substructure of its components,worth being studied in detail.In particular,the core position is highly uncertain, and might not correspond to the position of UA1.
10P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
Fig.5.VLBA images of BL 0454+844from observations on 19July 1999(1999.55),27July 1999(1999.57),15June 2000
(2000.46),and 4March 2001(2001.17).See Tables 1–3for contour levels,beam sizes (bottom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
3.6.BL 0716+714
BL 0716+714is the only radio source of the sample whose redshift is unknown,though the absence of any host galaxy seems to rule out distances z <～0.25even for a low lumi-nosity object (Wagner et al.1996).The source displays intra-day variability (Quirrenbach et al.1991;Wagner et al.1996).The total ?ux density of BL 0716+714at 15.4GHz halved its value between 1999.55and 2001.17(19months),decreasing from 1254mJy down to 643mJy,in accordance with the fact that BL 0716+714is also a long-term variable.(At 8.4GHz,the source displayed an op-posite,increasing trend between 1997.93and 1999.41,its ?ux growing by a factor 2.6,from 377mJy up to 990mJy in less than 18months [see Paper I]).At a redshift of 0.25,the monochromatic luminosity of BL 0716+714is L 15GHz ≈(1.8to 3.4)×1037W,a low-to-intermediate value for a BL Lac object.
The 15.4GHz VLBA maps (Fig.7)show a core-jet structure that extends northwards up to 4mas.The ap-pearance of the source at all epochs is very similar,and rather featureless but for the last epoch.Our observations at 8.4GHz made in 1999.41resemble a scaled-up version of the 15.4GHz ones in 1999.57.We modeled the 15.4GHz
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
11
Fig.6.VLBA images of QSO 0615+820from observations on 27July 1999(1999.57)and 15June 2000(2000.46).Axes are relative αand δin mas.See Table 1for contour levels,syn-thesized beam sizes (bottom left in the maps),and peak ?ux densities.See Table 2for component parametrization.
radio structure of BL 0716+714in 1999.57and 2000.46with two components (see Table 2),instead of three,as we did for our 8.4GHz observations (Paper I).Nonetheless,we had to use up to four components to model the source radio emission seen in 1999.55and 2001.17,the two ex-tra components being needed to account for the extended radio emission of the jet.
Component UA,the brightest one,is at the origin and contributes 85%to 96%of the total VLBA emission at all epochs.Its ?ux density evolves in almost exactly the
same way as the total ?ux of the source (the core activity
drives the whole behaviour of the source).The ratios of the core (UA)to the extended emission were the following:(value,epoch:14.7,1999.55;21.6,1999.57;14.0,2000.46;5.8,20001.17).Those values make of BL 0716+714one of the most compact and core dominated sources of the sam-ple.The relatively low value of Q in 2001.17is chie?y due to the decreasing ?ux density of the core (see the model ?ts in Table 3).Component UB probably lies close to the jet base.It contributes 5%to 11%of the total 15.4GHz VLBA ?ux.The model ?t algorithm gave signi?cantly dif-ferent values for the position of this component at each epoch (see Table 2).This could be an indication that mo-tions could be taking place in this engine.Alternatively,it could be that UB is in fact composed of several sub-components.Unfortunately,neither the 8.4GHz nor the 15.4GHz VLBA observations have resolved the innermost structure of BL 0716+714.Our 43GHz observations might yield enough resolution to say whether changes in its ?ux density are due to the emergence of components along the core-jet structure.The remaining 2%to 3%of the 15.4GHz ?ux comes from components UC and UD,which are not well modeled in 1999.57and 2000.46.
Our model ?t for the source shows an inward proper motion for component UB (see Table 4),but only at the 1σlevel.Bach et al.(2003)have reanalysed multi-frequency VLBI data obtained between 1993and 2001,and found that the source components display moderate superlumi-nal motions (0.3mas yr ?1;βapp =4.6h ?1)from the inner 3mas of the jet,up to 0.8mas yr ?1(βapp =12.3h ?1)for the outer regions of the jet.
Since BL 0716+714is an intra-day variable,the as-sumption that the 15.4GHz ?ux density of the source did not change between 1999.41and 1999.55is not well based.Yet,if we assume the ?ux density did not change we ob-tain αUA/XA =0.38,an inverted spectrum for the inner-most structure of the source,in agreement with expecta-tion if component UA/XA is the core.
3.7.QSO 0836+710(4C 71.07)
The 15.4GHz VLBA maps of QSO 0836+710(Fig.8;z =2.218,V′e ron-Cetty &V′e ron [2003])show at all three epochs a rather complex,one-sided core-jet structure at P.A.=-(140?to 150?).We detected emission up to 12mas (74h ?1pc)away from the core.The source radio emis-sion is well represented by six components,?ve of them within the inner 3mas (10h ?1pc)of the core,and one at a distance of 12mas.
The 15.4GHz total ?ux density of QSO 0836+710var-ied signi?cantly between 1998.22and 1999.57,decreasing by 23%,from 2298mJy down to 1766mJy at a monthly rate of 1.4%.It continued to decrease until 2000.46(down to 1728mJy,a further 2%decrease at the much slower rate of 0.2%per month).QSO 0836+710is the fourth bright-
12P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
Fig.7.VLBA images of BL 0716+714from observations on 19July 1999(1999.55),27July 1999(1999.57),15June 2000
(2000.46),and 4March 2001(2001.17).See Tables 1–3for contour levels,beam sizes (bottom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
est object of the complete sample,yet it is the second most powerful emitter with L 15GHz ≈(5.5to 7.3)×1039W.The ?ux density trend of the brightest component,UA1(likely the core),seems to follow that of the overall source.The values of the core-to-extended emission,Q ,were 2.7(1998.22),2.9(1999.57),and 2.5(2000.46),indicative of a relatively compact,core-dominated source.The ?ux den-sity of component UA2remained very stable with time,at the 220mJy level (10%to 13%of the total ?ux den-sity),but its radial distance is https://www.doczj.com/doc/1512202929.html,ponent UA3,at a 30mJy level,contributes about 2%of the
total ?ux density.Provided the 8.4GHz ?ux density of the (XA+XB)region did not change signi?cantly between 1999.41and 1999.57,we obtain αUA /(XA+XB)=0.27.This value indicates an inverted spectrum for the innermost re-gion source,and suggests that UA is likely to be the core (namely,UA1,which dominates the emission of the re-gion).UB,at a distance of (1.5±0.1)mas (≈5h ?1pc)at an angle of 140?sets the transition from the core region to the extended emission of the jet.Its contribution re-mained constant at the 2%level at all epochs.Similarly,
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.13
Fig.8.VLBA images of QSO 0836+710from observations on 20March 1998(1998.22),27July 1999(1999.57),and 15June 2000(2000.46).See Tables 1–3for contour levels,beam sizes (bottom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
the spectral indices of components UC/XC and UF/XF
are αUC /XC =?1.21and αUF /XF =?1.36,respectively.
Compared to our 8.4GHz VLBA maps,we now have a clearer view of the innermost regions of the source.In particular,we are able to disentangle the ?ne structure of XA into three sub-components:UA1,UA2,and https://www.doczj.com/doc/1512202929.html,ponent XB in Paper I is likely the result of a blend-ing of several subcomponents at 15.4GHz,most probably UA3and UB.
Our model ?t suggests the existence of superluminal motions for components UA3,UB,and UC (βapp ≈7h ?1;see Table 4).We identi?ed components UC and UF with XC and XF,respectively (Paper I).The positions of UF are consistent with no superluminal motion,which sug-gests that it is a stationary feature in the jet.UF shows an optically thin spectrum.We detected no emission from components XD or XE above our 3σlevel of 2.4mJy in 1999.57.Our non-detection implies an upper limit for their
synchrotron spectra of α<～?1.34and α<～?2.07.The
disappearance of the jet beyond component UC might well be due to the prominent curvature displayed at 5GHz,as shown in exquisite detail with VSOP (Lobanov et al.1998),and to a lesser extent in our 8.4GHz VLBA images (Paper I).
The ejection of a new component at mas scales re-ported by Otterbein et al.(1998)at epoch 1992.65,with an apparent superluminal motion of μ=(0.26±0.03)mas/yr has been directly related to gamma-,X-ray,and opti-cal activity observed in February 1992by these authors (Otterbein et al.1998).The intense radio activity shown in the inner 1.5mas from our 15.4GHz VLBA observa-tions seems to suggest the ejection of at least one new component.
3.8.QSO 1039+811
Our VLBA maps of QSO 1039+811(Fig.9,z =1.264)show a relatively simple,one-sided core-jet structure at an angle of -70?at pc-scales.The 15.4GHz jet extends up to 3mas (20h ?1pc)from the core,a much less extended jet than seen at 8.4GHz (8mas long;see Paper I).The emission is heavily concentrated within the core region (UA),which contributes more than 94%of the total VLBA ?ux den-sity at 15.4GHz at both epochs.The remaining 6%comes from the weak,relatively extended jet.Correspondingly,the ratio of the core-to-jet emission,Q ,was as large as 21in 1999.57,and 19in 2000.46,making of QSO 1039+811the most compact,core-dominated QSO of the complete sample.The jet shows some substructure,which we are able to model as two components in the ?rst epoch (com-ponents UB1and UB2,50mJy).These components are model ?tted as just one blended component at the second epoch,having almost the same ?ux density of UB1+UB2.Although our maps show that the jet morphology seems to have experienced dramatic changes between 1999.57and
14P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
2000.46,its interpretation should be taken with caution.
In particular,our second epoch is noisier than the ?rst one,thus resulting in a lower con?dence of the position of the features inside the
jet.
Fig.9.VLBA images of QSO 1039+811from observations on 27July 1999(1999.57)and 15June 2000(2000.46).Axes are relative αand δin mas.See Table 1for contour levels,syn-thesized beam sizes (bottom left in the ?gure),and peak ?ux densities.See Table 2for component parametrization.
Our model ?t results do not show any evidence of back-wards motion in the jet,in contrast to what was reported for components XB and XC at 8.4GHz (Paper I;also for XD,XE,and XF,without counterparts at 15.4GHz).As noted in Paper I,such apparently contracting motion
could be related to changes in the core region,e.g.,the emergence of a component can induce,in its early stage of ejection,an apparent backwards motion of the rest of the jet components at cm wavelengths (e.g.,Marcaide et al.1985,Guirado et al.1998,Ros et al.1999).Our model ?t also did not show the counterpart for component XB seen in 1999.41,at r ≈0.4mas of the core.We tried to set an upper limit to the position of such a component in our ?rst epoch,1999.57,by forcing a model ?t of the core with two components.Although we managed to model the core with two components,the model ?t was no better,and therefore we found that a second component is not needed to explain the emission from the core.We suggest that if a second such component does exist,it should have stayed at roughly the same distance (≈0.2mas)at both epochs,and with an estimated uncertainty in its ?ux density of 100%.
The 15.4GHz total ?ux density of QSO 1039+811de-creased by 12%between 1999.57and 2000.46,changing from (926±2)mJy down to (826±3)mJy,which corre-sponds to a monochromatic luminosity of L 15GHz =(7.4to 8.3)×1038W.The ?ux decrease is mainly due to the decrease in ?ux density of UA,from (883±2)mJy to (785±2)mJy (11%change).Assuming that the 8.4GHz ?ux density of the source did not change between 1999.41and 1999.57,we obtain α=0.08,a ?at spectrum for the milliarcsecond structure of QSO 1039+811.The inverted spectrum of component UA (αUA /XA =0.34)supports our suggestion that this component is the core.
3.9.QSO 1150+812
Our 15.4GHz VLBA maps of QSO 1150+812(Fig.10,z =1.250)show a one-sided core-jet structure directed southwards up to 4mas (27h ?1pc)from the core.There is also a hint for very faint emission extending up to about 5mas,as our previous 8.4GHz VLBA observations clearly con?rm (Paper I).The 15.4GHz total ?ux density of QSO 1150+812slightly decreased from 946mJy in 1999.57down to 907mJy in 2000.46(4%change).Its monochro-matic luminosity is L 15GHz ≈(8.0to 8.3)×1038W,almost the same as the luminosity of QSO 1039+811,due to their very close values in redshift and ?ux density.Assuming that the 8.4GHz ?ux density of the source did not change between 1999.41and 1999.57,we obtain α=?0.40,a moderately steep spectrum for the milliarcsecond struc-ture of QSO 1150+812.
From the maps,there is no clear evidence of signi?cant morphological changes in either the core or the jet struc-ture.Nevertheless,our model ?t does show such evidence.We modeled the source (Table 2)with six components at each observing epoch.The ?ux density of the bright-est component,UA,decreased from 405mJy in 1999.57down to 355mJy (～12%)in 2000.46,yielding δmin ≈2.1to 3.8.The ratio Q decreased from 1.46in 1999.57to 1.39
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
15
Fig.10.VLBA images of QSO 1150+812from observations on 27July 1999(1999.57)and 15June 2000(2000.46).Axes are relative αand δin mas.See Table 1for contour levels,synthesized beam sizes (bottom left in the maps),and peak ?ux densities.See Table 2for component parametrization.
in 2000.46.We detected component UB1at a distance of r ≈0.33at an angle of θ=(235?±5)?at both https://www.doczj.com/doc/1512202929.html,ponent UB2is at a distance r ≈0.65mas to 0.74mas at an angle of 220?at both epochs.We suggest that com-ponent XB in Paper I,at distance r ≈0.5mas,is a blend of components UB1and UB2.UB2seems to trace the curv-ing of the jet,changing from an angle of 235?(component UB1)to a value of 170?,as displayed by the southern components of the https://www.doczj.com/doc/1512202929.html,ponent UC seems to corre-spond to XC in Paper I.We obtain αUC /XC =?1.53,if
UC and XC correspond to the same physical feature of
the jet.The increase in ?ux density for this component is 28%between 1999.57and https://www.doczj.com/doc/1512202929.html,ponent UD is at a distance r =(2.25±0.05)mas at an angle θ=175?±5?.Very similar values of r and θare found for XC (Paper I).Its ?ux density remained very stable.
3.10.BL 1749+701
The 15.4GHz VLBA observations of BL 1749+701(Fig.11;z =0.770)show a core-jet structure directed to the west/northwest that extends up to 4mas.We identify in the images up to seven Gaussian components (Table 2).In all images,the central region (UA+UB)contributes 70%to 80%of the total radio ?ux.This region extends up to a distance of 0.4mas (2.5h ?1pc),and we tentatively identify the brightest component,UA,with the core.The rest of the components,UC through UE,correspond to the jet,which extends up to r ≈4mas (25h ?1pc).UC,at a distance of (1.15±0.15)mas,is likely the base of the jet.The jet is oriented to the west/northwest at an angle -69?±9?for the inner 2.5mas (16h ?1pc;components UC and UD),and then changes its direction northwards (θ=-55?±3?)around a distance of (3.0±0.2)mas,keeping this orientation until the radio jet fades away.
The 15.4GHz total ?ux density of BL 1749+701oscil-lated around a mean value of 416mJy between 1999.39and 2000.99(19months),with variations usually not ex-ceeding 7%.The corresponding monochromatic luminos-ity is L 15GHz ≈(1.2to 1.3)×1038W.The ratio of the core (taken as UA+UB)to the extended emission,Q ,increased with time as follows:2.4(1999.39),2.6(1999.57),2.9(1999.85),3.9(2000.46),and 4.6(2000.99),in agreement with the increasing activity of the core region.Assuming that the 8.4GHz total ?ux density of the source did not change between 1999.39and 1999.41(one week),we obtain α=0.0,showing a perfect ?at spectrum for the source.The spectral index of component UA/XA is αUA /XA =0.19,an inverted spectrum,which supports the suggestion that this is the core of the source.
Our previous 8.4GHz VLBA observations of BL 1749+701(Paper I)showed the existence of two components,XB and XC,at distances of (0.45±0.05)mas and (1.2±0.1)mas of the core (at P.A.≈-60?),https://www.doczj.com/doc/1512202929.html,ponent UB,at a distance of (0.3±0.1)mas,likely corresponds to XB.Similarly,component UC1,at (1.15±0.15)mas,is likely the counterpart of XC.In addition,we ?nd another component between XC and XD,which we labeled UC2,at a distance of (1.6±0.2)mas from the core.This component is seen in the ?rst three epochs (1999.39through 1999.85),but was not detected later.This behaviour points towards real morphological changes in the inner 10h ?1pc of BL 1749+701,most likely the ejection and passage of components from the https://www.doczj.com/doc/1512202929.html,ponents UD and UE belong to the weak,ex-
16P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
Fig.11.VLBA images of BL1749+701from observations on21May1999(1999.39),27July1999(1999.57),6November1999 (1999.85),15June2000(2000.46),and28December2000(2000.99).See Tables1–3for contour levels,beam sizes(bottom left in the maps),peak?ux densities,and component parametrization.Axes are relativeαandδin mas.
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.17
tended jet.We identi?ed UD with component XD(Paper I),based on their similar coordinates.Our model?t shows
evidence for signi?cant proper motions of components UB and UD,and of marginal signi?cance for UC2(see Table4).The apparent proper motion of component UD
coincides with the reported separation rate by Gabuzda et al.(1992)for their component K2.We hope to unam-biguously con?rm or rule out the existence of this proper
motion from our astrometric https://www.doczj.com/doc/1512202929.html,ponent XE (Paper I)could be a blend of two components,namely
UE1and UE2.At the position of UE1the jet suddenly changes its direction of propagation,towards the north (r=(3.0±0.2)mas;θ≈?58?).In our15.4GHz observa-tions of1999.57,this component seems to correspond to XE(epoch1997.93;Paper I).We fail,however,to?t this component at epochs later than1999.57.Our model?t
shows a backwards superluminal motion for component UE2(Table4).We are skeptical about this motion,given the strong?ux and morphological variability of the source beyond component UD.We do not detect any emission above3σat angular distances>～4.0mas from the core, implying a spectral indexαUF/XF=-(2.1to3.5).
3.11.QSO1803+784
The15.4GHz VLBA maps of QSO1803+784(Fig.12; z=0.680,V′e ron-Cetty&V′e ron[2003])reveal the same basic emitting structure seen at8.4GHz(Paper I);a one-sided core-jet oriented westward(P.A.≈?90?).(Note that 1803+784has been previously classi?ed as a BL Lac ob-ject,but is now considered to be a QSO[V′e ron-Cetty &V′e ron2003]).There are,however,signi?cantly di?er-ent features that appear in our model?t(Table2),com-pared to our8.4GHz observations.We characterize rea-sonably well the source with six components,instead of the eight needed at8.4GHz,because of signi?cant absorption at15.4GHz of the jet emission at r>～4mas(we barely detect emission above3σ,which cannot be adequately model?tted).From our model?ts,it follows that the inner0.8mas(4.9h?1pc)structure needs at least three components(UA,UB1,and UB2)to describe this region adequately describe this region,in contrast with the two components found at8.4GHz(XA and XB).We iden-tify the brightest component,UA(likely the core),with component https://www.doczj.com/doc/1512202929.html,ponents UB1and UB2indicate the transition of the core to the jet region,and we suggest that component XB could be a blend of the two components seen at15.4GHz.The source structure at r>～1mas is well characterized at15.4GHz by three components,UC,UD, and UE.Whilst the positions of UC and UD agree well with those of XC and XD,respectively(Paper I),we did not?nd clear counterparts for component XE,–at least for the?rst three epochs–nor for XF,XG,and XH.
The15.4GHz total?ux density of QSO1803+784 changed signi?cantly from epoch to epoch(up to26%between1988.84and1999.57).Its monochromatic lumi-nosity is L15GHz≈(5.3to6.6)×1038W.The innermost
regions of QSO1803+784(r<～1mas,equivalent to a lin-ear distance of6.4h?1pc)encompass components UA, UB1,and UB2.The contribution of this innermost re-
gion to the total?ux density amounts to80%to94%,de-pending on the epoch.(If we include component UC/XC, then the above?gures become93%to98%,in agree-ment with the percentages reported in Paper I.)The to-tal?ux density variability of QSO1803+784closely fol-lows that of the brightest component,UA,and is also partially modulated by?uctuations in the?ux density of UB1and UB2.The ratio of the core(taken as UA+UB1) to the extended emission,Q,con?rms that the activity of QSO1803+784is core-dominated:3.3(1998.84),5.2 (1999.57),4.1(1999.85),and3.3(2000.46).
Assuming that the15.4GHz total VLBI?ux density of the source did not vary noticeably between1999.41 and1999.57,we obtainα=0.41,a rather inverted spec-trum for the milliarcsecond structure of QSO1803+784. Similarly,we obtain the following indices for each com-ponent:αUA/XA=0.39,α(UB1+UB2)/XB=1.0,αUC/XC=?0.04,αUD)/XD≈?0.70,andαUE/XE≈0.52.The spec-tral indices of UA and UB correspond with those ex-pected for the innermost regions of the core,and those of UC and UD with what is expected in the inner-to-outer jet region.The value ofαUE/XE is not expected for an optically thin component.While the non-simultaneity of the8.4GHz and15.4GHz could have some e?ect,it could also be that our component UE is indeed the re-sult of the blending of XE and XF,in which case we obtainαUE/(XE+XF)≈?0.63,a more typical value for an extended jet component.Our non-detection of signif-icant emission around the positions of components XG and XH allows us to set upper limits for the spectral in-dices of these components(5σ):αUG)/XG<～?2.6,and αUH/XH<～?2.4.
The study of this source by VLBI is likely to give us
relevant information on the kinematics and morphologi-cal changes of their innermost regions.The dramatic?ux density variations displayed by the innermost regions of QSO1803+784along with the identi?cation of a complex structure close to the core point to a possible ejection of components from the central engine.Another remarkable aspect of QSO1803+784is the stationarity of a compo-nent at(1.3±0.1)mas.Schalinski(1990)suggested the ex-istence of such a(stationary)component at1.2mas from the core.Krichbaum et al.(1993,1994)used43GHz VLBI observations to show the existence of traveling compo-nents between the core and this component,setting it at a distance of1.4mas from the core.Both our15.4GHz and 8.4GHz observations show this component(UC/XC)to be at(1.45±0.05)mas,and no sign of any component at 1.2mas existed between1998.84and2000.46.We therefore
18P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
Fig.12.VLBA Images of QSO 1803+784from observations on 1November 1998(1998.84),27July 1999(1999.57),6November
1999(1999.85),and 15June 2000(2000.46).See Tables 1–3for contour levels,beam sizes (bottom left in the maps),peak ?ux densities,and component parametrization.Axes are relative αand δin mas.
suggest that there does indeed exist a stationary compo-nent at ≈1.4mas (9h ?1pc)from the core.
3.12.QSO 1928+738(4C 73.18)
QSO 1928+738(Fig.13,z =0.3021)is the most extensively studied radio source of the complete S5polar cap sample,and the one that shows the richest structure.Our 15.4GHz VLBA maps display a core-jet structure,with the jet southward-oriented (at an angle of 160?),and extend-ing up to 11.5mas (49h ?1pc).The 15.4GHz total ?ux density of QSO 1928+738decreased from 3006mJy down
to 2889mJy (4%change).Assuming that the 8.4GHz ?ux density of the source did not vary signi?cantly be-tween 1999.41and 1999.57,we obtain α=0.02,a remark-ably ?at spectrum for the milliarcsecond structure of QSO 1928+738.We ?tted reasonably well the brightness radio structure of QSO 1928+738with nine components (Table 2).We model the innermost region (r <～1mas,
corresponding to a linear distance of 4.3h ?1
pc),with three components:UA,UB1,and https://www.doczj.com/doc/1512202929.html,ponent UC (r =1.2mas at P.A.=152?)indicates the transition from the innermost to the outermost structure of the jet.
P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
19
Fig.13.VLBA images of QSO 1928+738(4C 73.18)from observations on 27July 1999(1999.57)and 15June 2000(2000.46).Axes are relative αand δin mas.See Table 1for contour levels,synthesized beam sizes (bottom left in the maps),and peak ?ux densities.See Table 2for component parametrization.
UA,the brightest component of QSO 1928+738at both epochs,is not at the origin of coordinates,but to the north at r =(0.35±0.05)mas from the origin,at an angle of -18?±2?.Component UB1is at the origin,and component UB2is at r =(0.35±0.05)mas at an angle of 145?±5?.The total intensity emission is dominated by this innermost region.Indeed,the combined emission from components UA,UB1,and UB2amounts to 71%(70%)of the total at the ?rst (second)epoch.The inclusion of the closest jet components up to a distance of 3mas increases
those ?gures to 96%and 94%on 1999.57and 2000.46,respectively.The ratio of the emission from the core re-gion (taken here as UA+UB1)to the extended emission was Q =1.1in 1999.57,and Q =0.9in 2000.46.Although the compactness of the source is thus moderate,the over-all source activity seems to be driven by the core,as the total ?ux density closely follows the core behaviour.
The spectral index of the innermost component,UA,is αUA /XA =0.04,as one would expect if UA were the core.Note that though the total intensity of QSO 1928+738only varied by 4%between 1999.57and 2000.46,the ?ux density of each component varied much more strongly.The decrease in ?ux density of UA,together with its change in position (a shift of 0.13mas northward),could indicate that a component was ejected around or before 1999.57.Assuming this is the case,our model ?t for UA at the second epoch suggests that the core is at least 0.4mas to the north of component UB1,in agreement with previous estimates (e.g.,Guirado et al.1998,Ros et al.1999).
Component XC (Paper I)is likely a blend of com-ponents UB2and UC.As mentioned earlier,compo-nent UC is a signpost in the inner-to-intermediate struc-ture of the jet.From this position onwards,the jet dis-plays a noticeable change in its direction,from 150?at r =1.25±0.05mas (UC)to 160?at r =2.55±0.05mas (UD).Component UE at r =3.05±0.05mas at θ=173?,shows a sudden change in the main orientation of the jet,which at the distance of component UF (r =3.95±0.05mas)re-covers its initial orientation (θ=162?±2?).Component UG (r =5.45±0.15mas;θ=166?±2?)signals a ?rst ter-mination of the jet at a linear distance of 25h ?1pc.The 15.4GHz jet reappears at almost twice that distance (r =11.55±0.05mas,corresponding to 50h ?1pc,at an an-gle of 167?).We identify this component,UI,with com-ponent XI (Paper I),which is found at essentially the same distance and angle,and suggests it is a station-ary component of the jet.The extended jet structure of QSO 1928+738at 8.4GHz (Paper I)is richer in compo-nents than the one seen at 15.4GHz.In particular,we fail to detect any signi?cant emission beyond component UI (r =11.6mas),while the 8.4GHz VLBA jet extends at least out to (25±1)mas.
The activity of QSO 1928+738is so intense that the task of identifying components from VLBI obser-vations taken at di?erent epochs and frequencies be-comes challenging.For example,the astrometric stud-ies carried out by Guirado et al.(1998)and Ros et al.(1999)indicated that the core position of QSO 1928+738is to the north of the reference point chosen in earlier works.Ros et al.(1999)estimated the o?set between the true core position and their 8.4GHz observations to be about 1.5mas to 2mas.Our previous 8.4GHz obser-vations (Paper I)showed component XA to be at r =0.65±0.15mas northward.The shift we ?nd for its coun-terpart at 15.4GHz,UA,is,however,signi?cantly smaller
20P′e rez-Torres et al.:Absolute kinematics of radio source components.II.
(r=0.35±0.05mas).If,as Guirado et al.and Ros et al.
suggested,the“true”core is very much self-absorbed,we should expect to see a15.4GHz VLBI component north-
ward of the8.4GHz component detected in Paper I(i.e.,
UA northward of XA).We fail,however,to detect such a component.A likely explanation is the potential confu-
sion in the identi?cation of components at8.4GHz and
15.4GHz,despite our relatively close campaigns in1999.
Another remarkable point is the proper motion of com-
ponents in the jet of QSO1928+738.Ros et al.(1999)re-ported a mean proper motion of(0.32±0.10)mas/yr for
components in the inner2.5mas of the jet.Our model?t
for the innermost regions of QSO1928+738does not,at this stage,show evidence for such large motions.Murphy
et al.(2003)have recently reported a wide range of
proper motions in QSO1928+738,from nearly station-ary(0.02mas/yr or0.5c)to relatively fast(0.82mas/yr or
19c),based on VSOP observations.Unfortunately,there is no reference in their work to make it possible to identify
which regions show superluminal motions.The authors
mention that their model?tting shows that a relativistic, variable speed-ejecta ballistic model is preferred over a rel-
ativistic helical-jet model.If this is the case,then it is no
surprise that component identi?cation is so di?cult for the source,especially if observations are widely spaced in time.
Our quasi-simultaneous VLBA observations at15.4GHz and43GHz will shed light on the above two controver-
sial issues(component identi?cation and proper motion),
and might be very useful in setting stringent limits on the putative core position.
3.13.BL2007+777
Our VLBA maps of BL2007+777(Fig.14,z=0.342)dis-
play a one-sided core-jet structure oriented westward.The
jet extends up to6.9mas(31h?1pc).The15.4GHz total ?ux density of BL2007+777seems to have steadily in-
creased between1999.57and2000.46,from825mJy up to
1258mJy(52%).From then on,the source started to fade down to948mJy in2001.17,corresponding to a decrease of25%in less than nine months.Its monochromatic lumi-nosity is quite modest(L15.4GHz≈(4.3to6.6)×1037W); it is the least powerful source after BL0454+844.
We?tted its brightness radio structure with six com-ponents at all epochs except2000.46,where only?ve com-ponents were model?tted(Table2).We need up to four components(UA1,UA2,UB1,and UB2)to adequately describe the inner1-mas region(4.6h?1pc).In contrast, the modeling of this region at8.4GHz required only two components,one at the origin(XA),and a second one at r=0.55±0.05mas(XB).The brightest15.4GHz compo-nent at all epochs is UA1,which is not at the origin,but shifted0.3±0.1mas eastward.This component went unde-tected at8.4GHz(Paper I).If this?nding is con?rmed by our43GHz observations,we have another case,along with those of QSO0212+735and QSO1928+738,in which the
core position is shifted from the reference point normally used,the https://www.doczj.com/doc/1512202929.html,ponent UA2is at the
origin,component UB1is at r=0.35±0.05mas at angle-
85?,and component UB2is at r=0.85±0.25mas at angle -83?±7?.Our model?t shows a signi?cant proper motion for component UB1,and marginally signi?cant ones for
UA1,UC,and UF(Table4).The model?tting proce-dure merged UB1and UB2into just one component in 2000.46.Note that the?ux density of UB1in2000.46is more than50%greater than at the other three epochs, and close to the common?ux of UB1+UB2in the closest epochs.Hence we suggest that the motion of an unde-tected component,probably traveling from UA2toward UC(and passing through UB1),could be responsible for the blending.This could,in turn,explain the apparent paradox of a forward superluminal motion of UB1,and a backward one for UC.The ratio Q of the emission from the core region(taken as UA1+UA2)to the extended emission shows a moderate dominance of the core which modulates the overall emission:1.59(1999.57),1.63(1999.85),1.71 (2000.46),and1.21(2001.17).The total intensity emis-sion is strongly dominated by that of the innermost region (the inner5h?1pc).Indeed,the combined emission from components UA1,UA2,UB1,and UB2amounts to90% of the total at both https://www.doczj.com/doc/1512202929.html,ponent UC contributes 3%to9%,and component UF2%to5%.Assuming that the8.4GHz?ux density of the milliarcsecond struc-ture of BL2007+777did not change appreciably between 1999.41and1999.57,we obtainα=-0.16,a moderately steep spectrum.Despite the non-varying global contribu-tion to the?ux density from the inner1mas structure of BL2007+777,signi?cant?ux density variations do exist for each component.
Component UC,at a distance of1.28±0.10mas at
P.A.-92?±5?is likely to correspond to component XC in Paper I.We fail,however,to see any clear counterpart to component XD(r=1.65±0.05mas at angle-92?±6?; Paper I).We encounter a similar situation with respect to component XE(r=4.75±0.05mas at-100?),for which we only?nd a clear counterpart in our last epoch (UE,at r≈5.1mas at P.A.≈?106?).This component indicates a curvature in the jet of BL2007+777,as con-?rmed by our previous8.4GHz VLBA observations(pa-per I),and VSOP observations at5GHz(Peng et al. 2000,Jin et al.2001).From the images,there are hints for the existence of component UE at the other epochs, with marginal detections just above3σ,but which our model?t failed to reproduce.If real,the inferred spec-tral index isαUE/XE<～?1.9.The15.4GHz jet reappears at an angular distance of r=6.5±0.4mas,at an angle of≈?95?(component UF).The similar component at 8.4GHz(XF in Paper I),is at r≈6.7mas,which agrees relatively well.In the maps,there seems to be more than just one,albeit weak,component around6mas to7mas
湖北理工学院毕业设计（论文） “慧鱼模型”三自由度机械手 设 计 小 册 学院：机电工程学院 班级：机械设计与制造 指导老师： 姓名：学号：201030120130 湖北理工学院毕业设计（论文） 一、概述 ............................................................ 1 1.1机电一体化技术 ................................................... 1 1.1.1机电一体化技术的定义和内容 (1) 1.1.2机电一体化系统组成 (1) 1.2. 慧鱼机器人 ..................................................... 2 1.2.1慧鱼创意教学组合模型简介 (2) 二、机器人的组成 .....................................................
2.1组成构件 ......................................................... 3 2.2慧鱼机器人分析 ................................................... 6 2.2.1机器人机构组成 (6) 2.2.2主要成分构成及功能 (7) 2.3. 机器人的工作空间形式 ............................................ 9 2.4机器人的机械运动形态和变换控制 .................................. 11 2.5机器人的位移、速度、方向的控制方法 (13) 湖北理工学院毕业设计（论文） 一、概述 1.1机电一体化技术 1.1.1机电一体化技术的定义和内容 机电一体化技术综合应用了机械技术、计算机与信息技术、系统技术、自动控制技术、传感检测技术、伺服传动技术,接口技术及系统总体技术等群体技术,从系统的观点出发,根据系统功能目标和优化组织结构目标,以智能、动力、结构、运动和感知等组成要素为基础,对各组成要素及相互之间的信息处理、接口耦合、运动传递、物质运动、能量变换机理进行研究,使得整个系统有机结合与综合集成,并在系统程序和微电子电路的有序信息流控制下,形成物质和能量的有规则 运动,在高质量、高精度、高可靠性、低能耗意义上实现多种技术功能复合的最佳功能价值的系统工程技术。 1.1.2机电一体化系统组成 1.机械本体机械本体包括机架、机械连接、机械传动等，它是机电一体化的基础，起着支撑系统中其他功能单元、传递运动和动力的作用。 2.检测传感部分检测传感部分包括各种传感器及其信号检测电路，其作用就是检测机电一体化系统工作过程中本身和外界环境有关参量的变化，并将信息传递给电子控制单元，电子控制单元根据检查到的信息向执行器发出相应的控制。 3.电子控制单元电子控制单元是机电一体化系统的核心，负责将来自各传感器的检测信号和外部输入命令进行集中、存储、计算、分析，根据信息处理结果，按照一定的程度和节奏发出相应的指令，控制整个系统有目的地进行。 4.执行器执行器的作用是根据电子控制单元的指令驱动机械部件的运动。执行器是运动部件，通常采用电力驱动、气压驱动和液压驱动等几种方式。 5.动力源动力源是机电一体化产品能量供应部分，是按照系统控制要求向机械系统提供能量和动力使系统正常运行。提供能量的方式包括电能、气能和液压
西方投资组合理论及其新发展综述 投资组合理论有狭义和广义之分。狭义的投资组合理论指的是马柯维茨投资组合理论；而广义的投资组合理论除了经典的投资组理论以及该理论的各种替代投资组合理论外，还包括由资本资产定价模型和证券市场有效理论构成的资本市场理论。同时,由于传统的EMH不能解释市场异常现象，在投资组合理论又受到行为金融理论的挑战。 一、50年代以前的投资组合理论 在马柯维茨投资组合理论提出以前，分散投资的理念已经存在。Hicks(1935)提出了“分离定理”,并解释了由于投资者有获得高收益低风险的期望,因而有对货币的需要；同时他认为和现存的价值理论一样,应构建起“货币理论”,并将风险引入分析中,因为风险将影响投资的绩效,将影响期望净收入。Kenes(1936)和Hicks(1939)提出了风险补偿的概念，认为由于不确定性的存在，应该对不同金融产品在利率之外附加一定的风险补偿，Hicks还提出资产选择问题，认为风险可以分散。Marschak(1938)提出了不确定条件下的序数选择理论,同 时也注意到了人们往往倾向于高收益低风险等现象。Williams(1938)提出了“分散折价模型”(dividend dis-count model),认为通过投资于足够多的证券,就可以消除风险,并假设总存在一个满足收益最大化和风险最小化的组合,同时能通过法律保证使得组合的事实收益和期 望收益一致。Leavens(1945)论证了分散化的好处。随后V on Neumann(1947)应用预期效用的概念提出不确定性条件下的决策选择方法。 二、马柯维茨投资组合理论及其扩展 美国经济学家Markowitz（1952)发表论文《资产组合的选择》，标志着现代投资组合理论的开端。他利用均值--方差模型分析得出通过投资组合可以有效降低风险的结论。 同时，Roy(1952)提出了“安全首要模型”(Safety-First Portfolio Theory)，将投资组合的均值和方差作为一个整体来选择，尤其是他提出以极小化投资组合收益小于给定的“灾险水平”的概率作为模型的决策准则，为后来的VaR(Value at Risk)等方法提供了思路。 Tobin（1958)提出了著名的“二基金分离定理”:在允许卖空的证券组合选择问题中，每一种有效证券组合都是一种无风险资产与一种特殊的风险资产的组合。 在Markowitz等人的基础上，Hicks(1962)的“组合投资的纯理论”指出，在包含现金的资产组合中,组合期望值和标准差之间有线形关系,并且风险资产的比例仍然沿着这条线形的有效边界这部分上,这就解释了Tobin的分离定理的内容。Wiliam.F.Sharpe(1963)提出“单一指数模型”，该模型假定资产收益只与市场总体收益有关，从而大大简化了马柯维茨理论中所用到的复杂计算。 马柯维茨的模型中以方差刻画风险，并且收益分布对称，许多学者对此提出了各自不同的见解。
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九世纪早期英吉利王国形成 843年查里曼帝国分裂，法兰西、德意志、意大利雏形产生九世纪封建制度在西欧确立 962年神圣罗马帝国建立 1054年基督教会分裂 1066年 法国诺曼底公爵征服英国 十一世纪中叶加纳王国全盛时期 1192年日本幕府政治建立 十三世纪 埃塞俄比亚封建国家兴起 十四世纪马里王国全盛时期，意大利出现资本主义萌芽 十四至十六世纪欧洲文艺复兴运动 1337年英法百年战争开始 1358年法国农民起义 1381年英国瓦特。泰勒起义 1453年东罗马帝国灭亡，英法百年战争结束 十五世纪桑海兴起 十五世纪晚期 英法中央集权国家形成，圈地运动开始 1480年俄罗斯摆脱蒙古控制 1487年迪亚士到达好望角 1492年哥伦布初次航行到美洲 1497-1498年达加马开辟西欧到印度的新航路 1517年 马丁。路德发动宗教改革 1519-1522年麦哲伦船队环航地球 十六世纪 葡萄牙和西班牙殖民者在亚、美强占殖民地 1524-1525 德意志农民起义 1588年 英国海军击败西班牙“无敌舰队” 1592-1598年朝鲜军民抗击日本侵略的卫国战争 1600年 英国东印度公司建立 十七世纪初法国殖民者开始在北美拓殖 1607年英国殖民者开始在北美拓殖 1632年沙俄在西伯利亚修建侵略扩张的基地—雅库次克1640年英国资产阶级革命开始 1649年 英国王查理一世被处死 1660年英国斯图亚特王朝复辟 1688年英国政变，资产阶级和新贵族的统治确立 1689年中俄签定“尼布楚条约”
马科维茨投资组合理论 马科维茨(Harry M.Markowitz,）1990年因其在1952年提出的投资组合选择（Portfolio Selection)理论获得诺贝尔经济学奖。 主要贡献：发展了一个在不确定条件下严格陈述的可操作的选择资产组合理论：均值方差方法 Mean-Variance methodology. 主要思想：Markowitz 把投资组合的价格变化视为随机变量，以它的均值来衡量收益，以它的方差来衡量风险（因此Markowitz 理论又称为均值－方差分析）；把投资组合中各种证券之间的比例作为变量，那么求收益一定的风险最小的投资组合问题就被归结为一个线性约束下的二次规划问题。再根据投资者的偏好，由此就可以进行投资决策。 基本假设： H1. 所有投资都是完全可分的。每一个人可以根据自己的意愿（和支出能力）选择尽可能多的或尽可能少的投资。 H2. 一个投资者愿意仅在收益率的期望值和方差（标准差）这两个测度指标的基础上选择投资组合。 p E =对一个投资组合的预期收益率 p σ=对一个投资组合的收益的标准差（不确定性） H3. 投资者事先知道投资收益率的概率分布，并且收益率满足正态分布的条件。 H4. 一个投资者如何在不同的投资组合中选择遵循以下规则： 一,如果两个投资组合有相同的收益的标准差和不同的预期收益，高的预期收益的投资组合会更为可取； 二,如果两个投资组合有相同的收益的预期收益和不同的标准差，小的标准差的组合更为可取； 三,如果一个组合比另外一个有更小的收益标准差和更高的预期收益，它更为可取。 基本概念 1．单一证券的收益和风险： 对于单一证券而言，特定期限内的投资收益等于收到的红利加上相应的价格变化，因此特定期限内的投资收益为： 1 1P P P t t t r --==价格变化＋现金流(如果有）持有期开始时的价格 －＋CF 假定投资者在期初时已经假定或预测了该投资期限内的投资收益的概率分布；将投资收益看成是随机变量。 任何资产的预期收益率都是加权平均的收益率，用各个收益发生的概率p 进行加权。预期收益率等于各个收益率和对应的概率的乘积之和。 11221 ()...n i i n n i E r p r p r p r p r ===+++∑ i p 为第i 个收益率的概率；12,,...,n r r r 为可能的收益率。 资产的风险用资产收益率的方差（variance ）和标准差（standard deviation ）来度量。 风险来源：市场风险（market risk ）,利息率风险（interest-rate risk ）,购买力风险（purchasing-power risk ）,管理风险（management risk ）,信用风险（credit risk ）,流动性风险（liquidity risk ）,保证金风险（margin risk ）,可赎回风险（callability risk ）,可转换风险（convertibility risk ）,国内政治风险（domestic political risk ）,行业风险（industry risk ）。 2．投资组合： 通常说投资组合由证券构成，一种证券是一个影响未来的决策，这类决策的整体构成一个投资组合。 3．投资组合的收益和风险： (1)投资组合的收益率 构成组合的证券收益率的加权平均数。以投资比例作为权数。
慧鱼创意组合设计实验指导书
《慧鱼创意组合设计实验》课程 实验指导书 江西理工大学 机械基础实验室
慧鱼创意组合设计实验指导书 一、实验目的 本实验主要基于慧鱼创意模型系统（fischertechnik）。实验的目的是经过让学生学习动手组装模型机器人和建造自己设计的有一定功能的机器人模型产品，使学生体会创意设计的方法和意义；同时经过创意实验，使学生了解一些计算机控制、软件编程、机电一体化等方面的基础知识，加深对专业课学习的理解，为后续课的学习做一个很好地铺垫。 二、实验设备介绍 1．慧鱼创意模型系统的组成： 慧鱼创意模型系统（fischertechnik）硬件主要包括：1000多种的拼插构件单元、驱动源、传感器、接口板等。 拼插构件单元：系统提供的构件主料均采用优质的尼龙塑胶，辅料采用不锈钢芯铝合金架等，采用燕尾槽插接方式连接，可实现六面拼接，多次拆装。系统提供的技术组合包中机械构件主要包括：齿轮、联杆、链条、齿轮（普通齿轮、锥齿轮、斜齿轮、内啮合齿轮、外啮合齿轮）、齿轴、齿条、涡轮、涡杆、凸轮、弹簧、曲轴、万向节、差速器、齿轮箱、铰链等。 驱动源：①直流电机驱动（9V、最大功率1.1W、转速7000 prn），由于模型系统需求功率比较低（系统载荷小，需求功率只克服传动中的摩擦阻力），因此它兼顾驱动和控制两种功能。②减速直流电机驱动（9V、最大功率1.1瓦，减速比50：1/20:1）。③气动驱动包括：储气罐、气缸、活塞、电磁阀、气管等元件。
传感器：在搭接模型时，你能够把传感器提供的信息（如亮/暗、通/断，温度值等）经过接口板传给计算机。系统提供的传 感器做为控制系统的输入信号包括：①感光传感器 Brightness sensor （光电管）：对亮度有反应，它和 聚焦灯泡配合使用，当有光（或无光）照在上面 时，光电管 产生不同的电阻值，引发不同信号。 ②接触传感器Contact sensor （触动开关）：如图1所示， 当红色按钮按下，接触点1、3接通，同时接触点1、2 断开，因此有两种使用方法：常开：使用接触点1、3，按下按钮＝导通；松开按钮＝断开；常闭：使用接触点1、2，按下按钮＝断开；松开按钮＝导通。③热传感器Thermal sensor （NTC 电阻）：可测量温度。温度20°C 时，电阻值1.5K Ω。NTC 的意思是负温度系数，温度升高电阻值下降。④磁性传感器 Magnetic sensor ：非接触性开关。⑤红外线发射接收装置：新型的运用可控制所有马达电动模型的红外线遥控装置由一个强大的红外线发射器和一个微处理器控制的接收器组成。有效控制范围是10米，分别可控制三个马达。 接口板：自带微处理器，程序可在线和下载操作，用LLWin3.0或高级语言编程，经过RS232串口与电脑连接，四路马达输出，八路数字信号输入，二路模拟信号输入，具有断电保护功能（新版接口），两接口板级联实现输入输出信号加倍。 PLC 接口板：实现电平转换，直接与PLC 相连。智能接口板自带微处理器，经过串口与计算机相连。在计算机上编的程序能够移植到接口板的微处理器上，它能够不用计算机独立处理程序（在激活模式下）。 3 2 图1触动开关原理
投资组合理论简介 投资组合理论有狭义和广义之分。狭义的投资组合理论指的是马柯维茨投资组合理论；而广义的投资组合理论除了经典的投资组合理论以及该理论的各种替代投资组合理论外，还包括由资本资产定价模型和证券市场有效理论构成的资本市场理论。同时,由于传统的EMH 不能解释市场异常现象，在投资组合理论又受到行为金融理论的挑战。 投资组合理论的提出[1] 美国经济学家马考维茨(Markowitz)1952年首次提出投资组合理论（Portfolio Theory)，并进行了系统、深入和卓有成效的研究，他因此获得了诺贝尔经济学奖。 该理论包含两个重要内容：均值－方差分析方法和投资组合有效边界模型。 在发达的证券市场中，马科维茨投资组合理论早已在实践中被证明是行之有效的，并且被广泛应用于组合选择和资产配置。但是，我国的证券理论界和实务界对于该理论是否适合于我国股票市场一直存有较大争议。 从狭义的角度来说，投资组合是规定了投资比例的一揽子有价证券，当然，单只证券也可以当作特殊的投资组合。 人们进行投资，本质上是在不确定性的收益和风险中进行选择。投资组合理论用均值—方差来刻画这两个关键因素。所谓均值，是指投资组合的期望收益率，它是单只证券的期望收益率的加权平均，权重为相应的投资比例。当然，股票的收益包括分红派息和资本增值两部分。所谓方差，是指投资组合的收益率的方差。我们把收益率的标准差称为波动率，它刻画了投资组合的风险。 人们在证券投资决策中应该怎样选择收益和风险的组合呢？这正是投资组合理论研究 的中心问题。投资组合理论研究―理性投资者‖如何选择优化投资组合。所谓理性投资者，是指这样的投资者：他们在给定期望风险水平下对期望收益进行最大化，或者在给定期望收益水平下对期望风险进行最小化。 因此把上述优化投资组合在以波动率为横坐标，收益率为纵坐标的二维平面中描绘出来，形成一条曲线。这条曲线上有一个点，其波动率最低，称之为最小方差点（英文缩写是MVP）。这条曲线在最小方差点以上的部分就是著名的（马考维茨）投资组合有效边界，对应的投资组合称为有效投资组合。投资组合有效边界一条单调递增的凹曲线。 如果投资范围中不包含无风险资产（无风险资产的波动率为零），曲线AMB是一条典型的有效边界。A点对应于投资范围中收益率最高的证券。 如果在投资范围中加入无风险资产，那么投资组合有效边界是曲线AMC。C点表示无风险资产，线段CM是曲线AMB的切线，M是切点。M点对应的投资组合被称为―市场组合‖。 如果市场允许卖空，那么AMB是二次曲线；如果限制卖空，那么AMB是分段二次曲线。在实际应用中，限制卖空的投资组合有效边界要比允许卖空的情形复杂得多，计算量也要大得多。 在波动率－收益率二维平面上，任意一个投资组合要么落在有效边界上，要么处于有效边界之下。因此，有效边界包含了全部（帕雷托）最优投资组合，理性投资者只需在有效边界上选择投资组合。
中国 一、原始社会（约170万年前到约公元前21世纪） 约0.5-0.7万年前河姆渡、半坡母系氏族公社 约0.4-0.5万年前大汶口文化中晚期，父系氏族公社 约4000多年前传说中的炎帝、黄帝、尧、舜、禹时期 二、奴隶社会（公元前2070年到公元前476年） 夏公元前2070年到公元前1600年 商公元前1600 年到公元前1046年 西周公元前1046年到公元前771年 春秋公元前770年到公元前476年 三、封建社会（公元前475年到公元1840年） 战国（公元前475年到公元前221年） 公元前356年商鞅开始变法 秦（公元前221年到公元前206年） 公元前221年秦统一，秦始皇确立郡县制，统一货币、度量衡和文字 公元前209年陈胜、吴广起义爆发 公元前207年巨鹿之战 公元前206年刘邦攻入咸阳，秦亡 公元前206年—公元前202年楚汉之争 西汉（公元前202年到公元8年） 公元前202年西汉建立 公元前138年张骞第一次出使西域 公元8年王莽夺取西汉政权，改国号新东汉（25年到220年） 25年东汉建立 105年蔡伦改进造纸术 132年张衡发明地动仪 184年张角领导黄巾起义 200年官渡之战 208年赤壁之战 三国（220年到280年） 220年魏国建立 221年蜀国建立 222年吴国建立 263年魏灭蜀 265年西晋建立，魏亡 西晋（265年到316年） 280年东晋灭吴 316年匈奴攻占长安，西晋结束东晋（317年到420年） 317年东晋建立 383年淝水之战 南北朝（420年到589年） 420年南朝宋建立 隋（581年到618） 581年隋朝建立 589年隋统一南北方 605年开始开通大运河 611年隋末农民起义开始 唐（618年到907年） 618年唐朝建立，隋朝灭亡627年-649年贞观之治
“慧鱼模型” 三自由度机械手 设 计 小 册 学院：机电工程学院班级：机械设计与制造 指导老师：蔺绍江 姓名：王连海 学号：201030120130
一、概述 (1) 1.1机电一体化技术 (1) 1.1.1机电一体化技术的定义和内容 (1) 1.1.2机电一体化系统组成 (1) 1.2. 慧鱼机器人 (2) 1.2.1慧鱼创意教学组合模型简介 (2) 二、机器人的组成 (3) 2.1组成构件 (3) 2.2慧鱼机器人分析 (6) 2.2.1机器人机构组成 (6) 2.2.2主要成分构成及功能 (7) 2.3. 机器人的工作空间形式 (9) 2.4机器人的机械运动形态和变换控制 (11) 2.5机器人的位移、速度、方向的控制方法 (13)
一、概述 1.1机电一体化技术 1.1.1机电一体化技术的定义和内容 机电一体化技术综合应用了机械技术、计算机与信息技术、系统技术、自动控制技术、传感检测技术、伺服传动技术,接口技术及系统总体技术等群体技术,从系统的观点出发,根据系统功能目标和优化组织结构目标,以智能、动力、结构、运动和感知等组成要素为基础,对各组成要素及相互之间的信息处理、接口耦合、运动传递、物质运动、能量变换机理进行研究,使得整个系统有机结合与综合集成,并在系统程序和微电子电路的有序信息流控制下,形成物质和能量的有规则运动,在高质量、高精度、高可靠性、低能耗意义上实现多种技术功能复合的最佳功能价值的系统工程技术。 1.1.2机电一体化系统组成 1.机械本体机械本体包括机架、机械连接、机械传动等，它是机电一体化的基 础，起着支撑系统中其他功能单元、传递运动和动力的作用。 2.检测传感部分检测传感部分包括各种传感器及其信号检测电路，其作用就是 检测机电一体化系统工作过程中本身和外界环境有关参量的变 化，并将信息传递给电子控制单元，电子控制单元根据检查到 的信息向执行器发出相应的控制。 3.电子控制单元电子控制单元是机电一体化系统的核心，负责将来自各传感器 的检测信号和外部输入命令进行集中、存储、计算、分析，根 据信息处理结果，按照一定的程度和节奏发出相应的指令，控 制整个系统有目的地进行。 4.执行器执行器的作用是根据电子控制单元的指令驱动机械部件的运动。执行 器是运动部件，通常采用电力驱动、气压驱动和液压驱动等几种方式。 5.动力源动力源是机电一体化产品能量供应部分，是按照系统控制要求向机械 系统提供能量和动力使系统正常运行。提供能量的方式包括电能、气 能和液压能。
中国的 一、原始社会（约170万年前到约公元前21世纪）约170万年前元谋人生活在云南元谋一带 约70-20万年前北京人生活在北京周口店一带 约1.8万年前山顶洞人开始氏族公社的生活 约0.5-0.7万年前河姆渡、半坡母系氏族公社 约0.4-0.5万年前大汶口文化中晚期，父系氏族公社 约4000多年前传说中的炎帝、黄帝、尧、舜、禹时期二、奴隶社会（公元前2070年到公元前476年） 夏公元前2070年到公元前1600年 公元前2070年禹传予启，夏朝建立 商公元前1600年到公元前1046年 公元前1600年商汤灭夏，商朝建立 公元前1300年商王盘庚迁都殷 西周公元前1046年到公元前771年 公元前1046年周武王灭商，西周开始 公元前841年国人暴动 公元前771年犬戎攻入镐京，西周结束 春秋公元前770年到公元前476年 公元前770年周平王迁都洛邑，东周开始 三、封建社会（公元前475年到公元1840年）
战国（公元前475年到公元前221年） 公元前356年商鞅开始变法 秦（公元前221年到公元前206年） 公元前221年秦统一，秦始皇确立郡县制，统一货币、度量衡和文字公元前209年陈胜、吴广起义爆发 公元前207年巨鹿之战 公元前206年刘邦攻入咸阳，秦亡 公元前206年—公元前202年楚汉之争 西汉（公元前202年到公元8年） 公元前202年西汉建立 公元前138年张骞第一次出使西域 公元8年王莽夺取西汉政权，改国号新 东汉（25年到220年） 25年东汉建立 73年班超出使西域 105年蔡伦改进造纸术 132年张衡发明地动仪 166年大秦王安敦派使臣到中国 184年张角领导黄巾起义 200年官渡之战 208年赤避之战
读书报告之二现代风险投资组合理论简介 孙贞贞吕世超刘伟峰 一、马科维茨投资组合模型介绍 美国经济学家哈里·马科维茨(Harry Markowitz)1952年首次提出投资组合理论（Portfolio Theory)，并进行了系统、深入和卓有成效的研究，他因此获得了1990年诺贝尔经济学奖, 主要贡献:投资组合优化计算、有效边界。该理论包含两个重要内容：均值－方差分析方法和投资组合有效边界模型。在证券市场中，马科维茨投资组合理论在实践中被证明是行之有效的，并且被广泛应用于组合选择和资产配置。 从狭义的角度来说，投资组合是规定了投资比例的有价证券的投资方案，当然，单只证券也可以当作特殊的投资组合。人们进行投资，本质上是在不确定性的收益和风险中进行选择。投资组合理论用均值—方差来刻画这两个关键因素。所谓均值，是指投资组合的期望收益率，它是单只证券的期望收益率的加权平均，权重为相应的投资比例。当然，股票的收益包括分红派息和资本增值两部分。所谓方差，是指投资组合的收益率的方差。我们把收益率的标准差称为波动率，它刻画了投资组合的风险。 人们在证券投资决策中应该怎样选择收益和风险的组合呢？这正是投资组合理论研究的中心问题。投资组合理论研究“理性投资者”如何选择优化投资组合。所谓理性投资者，是指这样的投资者：他们在给定期望风险水平下对期望收益进行最大化，或者在给定期望
收益水平下对期望风险进行最小化。另外,对于风险的度量也是人们所关注的。 马考维茨经过大量观察和分析，他认为若在具有相同回报率的两个证券之间进行选择的话，任何投资者都会选择风险小的。这同时也表明投资者若要追求高回报必定要承担高风险。同样，出于回避风险的原因，投资者通常持有多样化投资组合。马考维茨从对回报和风险的定量出发，系统地研究了投资组合的特性，从数学上解释了投资者的避险行为，并提出了投资组合的优化方法。 一个投资组合是由组成的各证券及其权重所确定。因此，投资组合的期望回报率是其成分证券期望回报率的加权平均。除了确定期望回报率外，估计出投资组合相应的风险也是很重要的。投资组合的风险是由其回报率的标准方差来定义的。这些统计量是描述回报率围绕其平均值变化的程度，如果变化剧烈则表明回报率有很大的不确定性，即风险较大。 从投资组合方差的数学展开式中可以看到投资组合的方差与各成分证券的方差、权重以及成分证券间的协方差有关，而协方差与任意两证券的相关系数成正比。相关系数越小，其协方差就越小，投资组合的总体风险也就越小。因此，选择不相关的证券应是构建投资组合的目标。另外，由投资组合方差的数学展开式可以得出：增加证券可以降低投资组合的风险。 基于回避风险的假设，马考维茨建立了一个投资组合的分析模型,其要点为：
目录 1.机电一体化技术 (6) 1.1机电一体化技术的定义和内容 (6) 1.2机电一体化系统组成 (6) 2.慧鱼机器人 (7) 2.1慧鱼创意教学组合模型简介 (7) 2.2慧鱼机器人分析 (7) 2.2.1机器人机构组成 (8) 2.2.2机器人工作空间形式 (8) 2.2.3机器人机械传动方式 (10) 2.2.4机器人位移速度控制方式 (13) 2.2.5机器人模型图绘制 (14) 3.总结 (17) 4.参考文献 (18) 1.机电一体化技术 1.1机电一体化技术的定义和内容
机电一体化技术综合应用了机械技术、计算机与信息技术、系统技术、自动控制技术、传感检测技术、伺服传动技术,接口技术及系统总体技术等群体技术,从系统的观点出发,根据系统功能目标和优化组织结构目标,以智能、动力、结构、运动和感知等组成要素为基础,对各组成要素及相互之间的信息处理、接口耦合、运动传递、物质运动、能量变换机理进行研究,使得整个系统有机结合与综合集成,并在系统程序和微电子电路的有序信息流控制下,形成物质和能量的有规则运动,在高质量、高精度、高可靠性、低能耗意义上实现多种技术功能复合的最佳功能价值的系统工程技术。 1.2机电一体化系统组成 1.机械本体机械本体包括机架、机械连接、机械传动等，它是机电一体化的基础，起着支撑系统中其他功能单元、传递运动和动力的作用。 2.检测传感部分检测传感部分包括各种传感器及其信号检测电路，其作用就是检测机电一体化系统工作过程中本身和外界环境有关参量的变化，并将信息传递给电子控制单元，电子控制单元根据检查到的信息向执行器发出相应的控制。 3.电子控制单元电子控制单元是机电一体化系统的核心，负责将来自各传感器的检测信号和外部输入命令进行集中、存储、计算、分析，根据信息处理结果，按照一定的程度和节奏发出相应的指令，控制整个系统有目的地进行。 4.执行器执行器的作用是根据电子控制单元的指令驱动机械部件的运动。执行器是运动部件，通常采用电力驱动、气压驱动和液压驱动等几种方式。 5.动力源动力源是机电一体化产品能量供应部分，是按照系统控制要求向机械系统提供能量和动力使系统正常运行。提供能量的方式包括电能、气能和液压能。 2. 慧鱼机器人 2.1慧鱼创意教学组合模型简介
世界近代史 ●西方资本主义的发展 十四世纪意大利出现资本主义萌芽 十五世纪晚期英法中央集权国家形成，圈地运动开始 14-15世纪欧洲出现资本主义萌芽 1840年前后英国率先完成工业革命 18世纪60年代到19世纪中后期自由资本主义阶段 19世纪中后期垄断资本主义开始出现 1933年罗斯福新政后，国家垄断资本主义开始出现 二战结束到20世纪70年代初期西方资本主义国家普遍奉行国家干预的经济政策，出现了经济发展的“黄金时期” 20世纪70年代后美英等国逐渐发展出一种将政府干预与市场相结合的、国有制与私有制并存的“混合经济” ●西方人文主义的发展 十四至十六世纪欧洲文艺复兴运动在意大得兴起 十六世纪以后，文艺复兴从意大利传播到欧洲其他国家 十六世纪 1517年，马丁·路德拉开宗教改革序幕 十七至十八世纪 17世纪时，英国出现了早期启蒙运动 18世纪中叶，启蒙运动在法国进入高潮。 伏尔泰、孟德斯鸠、卢梭 ●新航路开辟： 1487－1488迪亚士远航到达非洲南部沿海 1492 哥伦布远航到达美洲 1497－1498 达伽马远航到达印度 1519－1522 麦哲伦船队环球航行 ●资产阶级代议制度的确立 1640 英国资产阶级革命开始 1688年英国光荣革命，资产阶级和新贵族的统治确立 1775－1783北美独立战争 1776北美大陆会议发表《独立宣言》，宣布美利坚合众国独立 1787年美国1787年宪法 1870－1871普法战争 1871年德意志统一最终完成德意志帝国宪法 1875年法兰西第三共和国宪法，在法律上正式确立共和政体 ●三次工业革命 18世纪60年代英国工业革命开始 1785瓦特的改良蒸汽机投入使用 19世纪70年代第二次工业革命开始 19世纪70年代，人类进入“电气时代” 19世纪七八十年代，内燃机问世
慧鱼机器人 一、概述 1.1机电一体化技术 1.1.1机电一体化技术的定义和内容 机电一体化技术综合应用了机械技术、计算机与信息技术、系统技术、自动控制技术、传感检测技术、伺服传动技术,接口技术及系统总体技术等群体技术,从系统的观点出发,根据系统功能目标和优化组织结构目标,以智能、动力、结构、运动和感知等组成要素为基础,对各组成要素及相互之间的信息处理、接口耦合、运动传递、物质运动、能量变换机理进行研究,使得整个系统有机结合与综合集成,并在系统程序和微电子电路的有序信息流控制下,形成物质和能量的有规则运动,在高质量、高精度、高可靠性、低能耗意义上实现多种技术功能复合的最佳功能价值的系统工程技术。 1.1.2机电一体化系统组成 1.机械本体机械本体包括机架、机械连接、机械传动等，它是机电一体化的基础，起着 支撑系统中其他功能单元、传递运动和动力的作用。 2.检测传感部分检测传感部分包括各种传感器及其信号检测电路，其作用就是检测机电 一体化系统工作过程中本身和外界环境有关参量的变化，并将信息传递 给电子控制单元，电子控制单元根据检查到的信息向执行器发出相应的 控制。 3.电子控制单元电子控制单元是机电一体化系统的核心，负责将来自各传感器的检测信 号和外部输入命令进行集中、存储、计算、分析，根据信息处理结果， 按照一定的程度和节奏发出相应的指令，控制整个系统有目的地进行。 4.执行器执行器的作用是根据电子控制单元的指令驱动机械部件的运动。执行器是运动 部件，通常采用电力驱动、气压驱动和液压驱动等几种方式。 5.动力源动力源是机电一体化产品能量供应部分，是按照系统控制要求向机械系统提供 能量和动力使系统正常运行。提供能量的方式包括电能、气能和液压能。
一、原始社会（约170万年前到约公元前21世纪）二、奴隶社会（公元前2070年到公元前476年） 约170万年前元谋人生活在云南元谋一带夏公元前2070年到公元前1600年 约70-20万年前北京人生活在北京周口店一带公元前2070年禹传予启，夏朝建立 约1.8万年前山顶洞人开始氏族公社的生活商公元前1600 年到公元前1046年 约0.5-0.7万年前河姆渡、半坡母系氏族公社公元前1600年商汤灭夏，商朝建立 约0.4-0.5万年前大汶口文化中晚期，父系氏族公社公元前1300年商王盘庚迁都殷 约4000多年前传说中的炎帝、黄帝、尧、舜、禹时期西周公元前1046年到公元前771年 公元前1046年周武王灭商，西周开始 公元前841年国人暴动 公元前771年犬戎攻入镐京，西周结束 春秋公元前770年到公元前476年 公元前770年周平王迁都洛邑，东周开始 三、封建社会（公元前475年到公元1840年） 战国（公元前475年到公元前221年）公元前356年商鞅开始变法 秦（公元前221年到公元前206年） 公元前221年秦统一，秦始皇确立郡县制，统一货币、度量衡和文字 公元前209年陈胜、吴广起义爆发公元前207年巨鹿之战 公元前206年刘邦攻入咸阳，秦亡公元前206年—公元前202年楚汉之争 西汉（公元前202年到公元8年）公元前202年西汉建立 公元前138年张骞第一次出使西域公元8年王莽夺取西汉政权，改国号新 东汉（25年到220年）25年东汉建立 73年班超出使西域105年蔡伦改进造纸术 132年张衡发明地动仪166年大秦王安敦派使臣到中国 184年张角领导黄巾起义200年官渡之战 208年赤避之战三国（220年到280年）220年魏国建立 221年蜀国建立222年吴国建立 230年吴派卫温等率军队到台湾263年魏灭蜀 265年西晋建立，魏亡西晋（265年到316年） 280年东晋灭吴316年匈奴攻占长安，西晋结束 东晋（317年到420年）317年东晋建立 383年淝水之战南北朝（420年到589年） 420年南朝宋建立494年年到北魏孝文帝迁都洛阳 隋（581年到618）581年隋朝建立 589年隋统一南北方605年开始开通大运河 611年隋末农民起义开始，山东长白山农民起义爆发唐（618年到907年） 618年唐朝建立，隋朝灭亡627年-649年贞观之治 713年-741年开元盛世755年-763年安史之乱 875年-884年唐末农民战争五代（907年到960年） 907年后梁建立，唐亡，五代开始916年阿保机建立契丹国 北宋（960年到1127年）960年北宋建立 1005年宋、辽澶渊之盟1038年元昊建立西夏 11世纪中期毕升发明活字印刷术1069年王安石开始变法 1115年阿骨打建立金1125年金灭辽
投资组合理论简析：美国经济学家马考维茨(Markowitz)1952年首次提出投资组合理论（Portfolio Theory)，并进行了系统、深入和卓有成效的研究，他因此获得了诺贝尔经济学奖。该理论也称证券投资组合理论或资产组合理论。 马克维茨投资组合理论的基本假设为：(1)投资者是风险规避的，追求期望效用最大化；(2)投资者根据收益率的期望值与方差来选择投资组合；(3)所有投资者处于同一单期投资期。马克维茨提出了以期望收益及其方差(E，δ2)确定有效投资组合。 以期望收益E来衡量证券收益，以收益的方差δ2表示投资风险。资产组合的总收益用各个资产预期收益的加权平均值表示，组合资产的风险用收益的方差或标准差表示，则马克维茨优化模型如下： 式中：rp——组合收益； ri、rj——第i种、第j种资产的收益； wi、wj——资产i和资产j在组合中的权重； δ2(rp)——组合收益的方差即组合的总体风险； cov(r,rj)——两种资产之间的协方差。 马克维茨模型是以资产权重为变量的二次规划问题，采用微分中的拉格朗日方法求解，在限制条件下，使得组合风险铲δ2(rp)最小时的最优的投资比例Wi。从经济学的角度分析， 就是说投资者预先确定一个期望收益率，然后通过确定投资组合中每种资产的权重，使其总体投资风险最小，所以在不同的期望收益水平下，得到相应的使方差最小的资产组合解，这些解构成了最小方差组合，也就是我们通常所说的有效组合。有效组合的收益率期望和相应的最小方差之间所形成的曲线，就是有效组合投资的前沿。投资者根据自身的收益目标和风险偏好，在有效组合前沿上选择最优的投资组合方案。 根据马克维茨模型，构建投资组合的合理目标是在给定的风险水平下，形成具有最高收益率的投资组合，即有效投资组合。此外，马克维茨模型为实现最有效目标投资组合的构建提供了最优化的过程，这种最优化的过程被广泛地应用于保险投资组合管理中。在马可维茨的理论基础上又出现了致力于寻求新的度量标准和新的投资准则的现代投资组合理论：均值-V aR投资组合模型 最早应用V aR风险测量方法的是Jm Morgan公司，1994年10月JP Morgan公司开发 的“风险度量"(Riskmetrics)系统中提出了V aR风险测量方法；1995年4月，巴塞尔银 行监管委员会宣布商业银行的资本充足性要求必须建立在V aR基础上；1995年6月，美联储提出相似的预案；1995年12月，美国证券交易委员会建议上市交易的美国公司将V aR 值作为信息披露的一项指标。1996年8月，美国银行业监督管理委员会采用1988年巴塞 尔协议中提出的市场风险修正案(MAR)，市场风险修正案于1998年1月生效。该修正案 规定商业银行进行大宗交易时，其备用资本要超过其面临的市场风险，而市场风险资本备 用额根据V aR方法予以估计。2001年巴塞尔委员会进一步利用V aR对资本充足性作出了三项规定，此外，在美国，评估机构如穆迪与标准普尔、金融会计标准委员会及证券与交易委员会都采纳V aR方法，可见，迄今为止，V aR风险测量方法己经得到广泛的应用。 V aR英文为V alue-at-Risk，通常称为风险价值，其含义是“处于风险中的价值’’，指 在市场正常波动下，某一金融资产或证券组合的最大可能损失，更为精确的讲就是：在一定的概率水平下(置信度)，某一金融资产或证券组合在未来特定时间内的最大可能损失，
中国重大历史事件时间表 一、原始社会（约170万年前到约公元前21世纪） 约170万年前元谋人生活在云南元谋一带 约70-20万年前北京人生活在北京周口店一带 约1.8万年前山顶洞人开始氏族公社 约0.5-0.7万年前河姆渡、半坡母系氏族公社的生活 约0.4-0.5万年前大汶口文化中晚期，父系氏族公社 约4000多年前传说中的炎帝、黄帝、尧、舜、禹时期 二、奴隶社会（公元前2070年到公元前476年） 夏公元前2070年到公元前1600年 公元前2070年禹传予启，夏朝建立 商公元前1600 年到公元前1046年 公元前1600年商汤灭夏，商朝建立 公元前1300年商王盘庚迁都殷 西周公元前1046年到公元前771年 公元前1046年周武王灭商，西周开始 公元前841年国人暴动 公元前771年犬戎攻入镐京，西周结束 春秋公元前770年到公元前476年 公元前770年周平王迁都洛邑，东周开始 三、封建社会（公元前475年到公元1840年） 战国（公元前475年到公元前221年） 公元前356年商鞅开始变法 秦（公元前221年到公元前206年） 公元前221年秦统一，秦始皇确立郡县制，统一货币、度量衡和文字公元前209年陈胜、吴广起义爆发 公元前207年巨鹿之战 公元前206年刘邦攻入咸阳，秦亡 公元前206年—公元前202年楚汉之争 西汉（公元前202年到公元8年） 公元前202年西汉建立 公元前138年张骞第一次出使西域 公元8年王莽夺取西汉政权，改国号新 东汉（25年到220年） 25年东汉建立 73年班超出使西域 105年蔡伦改进造纸术
132年张衡发明地动仪 166年大秦王安敦派使臣到中国 184年张角领导黄巾起义 200年官渡之战 208年赤避之战 三国（220年到280年） 220年魏国建立 221年蜀国建立 222年吴国建立 230年吴派卫温等率军队到台湾 263年魏灭蜀 265年西晋建立，魏亡 西晋（265年到316年） 280年东晋灭吴 316年匈奴攻占长安，西晋结束 东晋（317年到420年） 317年东晋建立 383年淝水之战 南北朝（420年到589年） 420年南朝宋建立 494年年到北魏孝文帝迁都洛阳 隋（581年到618） 581年隋朝建立 589年隋统一南北方 605年开始开通大运河 611年隋末农民起义开始，山东长白山农民起义爆发唐（618年到907年） 618年唐朝建立，隋朝灭亡 627年-649年贞观之治 713年-741年开元盛世 755年-763年安史之乱 875年-884年唐末农民战争 五代（907年到960年） 907年后梁建立，唐亡，五代开始 916年阿保机建立契丹国 北宋（960年到1127年） 960年北宋建立 1005年宋、辽澶渊之盟 1038年元昊建立西夏 11世纪中期毕升发明活字印刷术 1069年王安石开始变法 1115年阿骨打建立金 1125年金灭辽 南宋（1127年到1276年）