Simplified modelling of joints and beam-like structures for BIW optimization in a

Finite Elements in Analysis and Design45(2009)456--

462

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Simplified modelling of joints and beam-like structures for BIW optimization in a concept phase of the vehicle design process

D.Mundo a,?,R.Hadjit b,S.Donders b,M.Brughmans b,P.Mas b,W.Desmet c

a Department of Mechanical Engineering,University of Calabria,87036Arcavacata di Rende,Italy

b LMS International,Interleuvenlaan68,B-3001Leuven,Belgium

c Department of Mechanical Engineering,Katholieke Universiteit Leuven,Division PMA,B-3001,Leuven,Belgium

A R T I C L E I N F O A

B S T R A

C T

Article history:

Received3March2008

Received in revised form3December2008 Accepted10December2008

Available online7February2009

Keywords:

Beam

Joint

Conceptual design

NVH

Vehicle body The paper proposes an engineering approach for the replacement of beam-like structures and joints in a vehicle model.The final goal is to provide the designer with an effective methodology for creating a concept model of such automotive components,so that an NVH optimization of the body in white(BIW) can be performed at the earliest phases of the vehicle design process.The proposed replacement method-ology is based on the reduced beam and joint modelling approach,which involves a geometric analysis of beam-member cross-sections and a static analysis of joints.The first analysis aims at identifying the beam center nodes and computing the equivalent beam properties.The second analysis produces a simplified model of a joint that connects three or more beam-members through a static reduction of the detailed joint FE model.

In order to validate the proposed approach,an industrial case-study is presented,where beams and joints of the upper region of a vehicle's BIW are replaced by simplified models.Two static load-cases are defined to compare the original and the simplified model by evaluating the stiffness of the full vehicle under torsion and bending in accordance with the standards used by automotive original equipment manufac-turer(OEM)companies.A dynamic comparison between the two models,based on global frequencies and modal shapes of the full vehicle,is presented as well.

?2009Elsevier B.V.All rights reserved.

1.Introduction

In highly competitive markets,design engineers face the chal-lenging problem of developing products,which must fulfil complex and even conflicting design criteria.In the field of automotive indus-try,the task of improving various functional performance attributes, such as safety,noise and vibrations,ecological impact etc.,is made more and more difficult by the necessity of launching new products or renewing existing models in an increasingly short time frame.In order to make the complexity of the design criteria compatible with the necessity of reducing the time-to-market,predictive computer-aided engineering(CAE)methods must be already available in the early phases of the design process.

Traditional computer-aided design(CAD)software packages have a very limited applicability in early design stages,since they require detailed data of the vehicle.Besides,they are based on the traditional definition of geometry via points,lines and surfaces,thus making

?Corresponding author.Fax:+39984494673.

E-mail address:d.mundo@unical.it(D.Mundo).

0168-874X/$-see front matter?2009Elsevier B.V.All rights reserved.

doi:10.1016/j.finel.2008.12.003the parameterization of models difficult and time-consuming[1].As a result,the experience of engineers is a key factor for the selection of proper structural concepts at the beginning of the design process.

Recently,research efforts have been spent to enable designers to use CAE as a support in the conceptual phase of the design process, when functional performance targets are defined,while detailed ge-ometrical data are still unavailable.The objective is to improve the initial CAD design,hence shortening the design cycle[2–5].

In the field of NVH and crashworthiness prediction,several con-cept modelling approaches have been proposed by researchers.They can be classified into three categories:methods based on predecessor FE models,methods from scratch,and methods concurrent with CAD.

Methods belonging to the first category,which includes mesh morphing and concept modification approaches[6–8],are used to de-sign a variant or incremental improvement of an existing vehicle model.By using a predecessor FE model,early CAE predictions can be performed to identify issues and to include possible countermea-sures already in the initial CAD design.

If a new car concept is to be designed and a predecessor FE model is not available,methods“from scratch”can be used to support the design process during the early design phases.Two classes of meth-ods are distinguished.The first class is topology design optimization,

D.Mundo et al./Finite Elements in Analysis and Design45(2009)456--462457

where material is eliminated from an initial admissible design domain in order to make the structure lighter without violating functional requirements[9–11].Performance based on the opti-mized topological information is usually improved by optimizing shape and size.The second class of methods“from scratch”,known as functional layout design,aims at building a simplified concept model,consisting of beams,joints and panels,which represents the functional layout and which is used to predict the performance of the model[12].

Methods concurrent with CAD are CAE tools available in an early phase of the design process.These methods provide simulation re-sults as soon as component-level CAD models are available,while vehicle-level models are still unavailable[13].

Among the methods based on predecessor FE models,the “reduced beam and joint modelling”approach has been recently proposed by Donders et al.[14]to improve the fundamental NVH behavior of a vehicle BIW.The proposed approach creates a reduced modal model at the beam center nodes,to which beam elements and joint superelements can be added,thus enabling a concept modification of the body and an accurate prediction of dynamic NVH performance.The commercial software program LMS Virtual Lab.[15]includes a user-friendly implementation of the reduced beam and joint modelling approach.Design engineers can define a beam and joint layout,calculate the body reduced modal model and perform efficient design modification and optimization of the body beam-like sections and joint connections.

In this paper,the reduced beam and joint modelling approach is employed to replace beams and joints of the predecessor FE model with concept models.After identifying the beam center nodes as the geometric center of the cross-sections,the equivalent beam properties are calculated through a geometric analysis and applied to simplified beam elements that connect the beam center nodes. The stiffness parameters of thin-walled beams,as computed by means of a geometric approach,need a correction that takes into account section variations and discontinuities(holes,spot-welds, stiffeners)[16,17].For this purpose,proper correction factors are defined and estimated for each beam-member by means of an iterative model updating procedure.In a next step,a simplified model of joints,connecting two or more beam-members,is then obtained through a static reduction of the detailed FE model of the joint.

In order to validate the proposed approach,a case-study is pre-sented,in which beams and joints of the upper region of a vehicle BIW are replaced by simplified models.A static comparison between the original and the simplified model is performed by evaluating the static stiffness of the full FE vehicle BIW under torsion and bend-ing.A dynamic comparison between the two models,based on the global frequencies and mode shapes of the full vehicle,is performed as well.

2.The reduced beam and joint modelling approach

The reduced beam and joint modelling approach is proposed by Donders et al.[14]for efficient modification of beams and joints of a vehicle,based on the reduced modal model of the nominal vehicle.The basic idea is to identify the so-called beam center nodes, and to create a reduced modal model at these beam center nodes. Subsequently,the mass and stiffness properties of the structure are modified by connecting the beam center nodes through simple beam elements and joint superelements.In this paper,simplified beam and joint models are created to completely replace the original FE model(without the necessity of the reduced modal model),so that an optimization of the vehicle can be performed in the early phase of conceptual design,when a detailed model of the structure is not yet available.

yi

zi

xi

x

B.C.N.

z

y

Fig.1.Schematic representation of a beam end-section.

In this section,an overview of the procedure that is used to es-timate the mass and stiffness properties of the simplified beam and joint models is provided.

2.1.Beam property estimation

Beam-like members,i.e.structures for which the dimension in the longitudinal direction is much larger than the characteristic di-mension of the cross-sectional area,are the primary structural ele-ments in a BIW.They strongly influence the natural frequencies of the vehicle body.

In the FE model of a vehicle,beam-like members are typically thin-walled structures,formed by shell elements.

In order to replace the detailed mesh of such components by sim-plified beam elements,a number of beam cross-sections are consid-ered and the equivalent beam properties are computed for each of them.For this purpose the following procedure is implemented: (1)a cut node is selected in the region of the beam-member where

an intersection plane is to be applied,

(2)an axis system that defines the approximate beam direction and

intersection plane is defined,

(3)the primary member's shell elements along the intersection

plane are cut and analyzed to locate the beam center node in the geometric center of the original cross-section,

(4)the following equivalent beam properties w.r.t.the beam center

node are computed:

?A:cross-section area;

?Ixx:torsional moment of inertia;

?Iyy,Izz:moments of inertia of area;and

?Iyz:product of inertia of area.

Here,x denotes the beam direction,and the y–z plane is the intersection plane,as shown in Fig.1.For an arbitrary cross-section,the calculation of the properties can be implemented by computing the equivalent beam properties for each shell element that belongs to the cross-section,according to the local principal axes(x i,y i,z i).Then,a transformation from the local axis system to that of the intersection plane(x,y,z) is performed.Finally,a summation over all shell elements is performed to find the global properties for that cross-section.

(5)the beam center node is connected to the surrounding mesh by

means of interpolation relations(Nastran superelements RBE3).

These relations are defined between each beam center node and

a particular node group,formed by all nodes of the shell ele-

ments that are defined at the intersection plane at the consid-ered cross-section.

Typically,along each primary beam-member a number of intersec-tion planes are defined,for which equivalent beam properties are computed.The entire beam member can then be represented as a series of linear beam elements taken from a standard FE library.An example is shown in Fig.2,where both the original detailed and the simplified FE model of B-pillars of a vehicle BIW are represented.

458 D.Mundo et al./Finite Elements in Analysis and Design 45(2009)456--

462

Fig.2.(a)Original and (b)conceptual models of a BIW

B-pillars.

Fig.3.Original FE model of a joint group,extracted from the vehicle model for static reduction.

2.2.Joint property estimation

Complementary to the simplified beam modelling approach de-scribed in Section 2.1,a procedure for simplifying joints connecting beam-like structural members in a vehicle body is proposed.After evaluating the equivalent beam properties of all beam-members con-nected by the joint,a joint group is created that includes the inter-polation elements to the beam center nodes at the joint ends [15].In Fig.3an example is shown,in which the mesh of the joint that con-nects the left B-pillar of the vehicle to the roof-rails is extracted from the rest of the vehicle body.For this isolated joint model,Guyan re-duction is used to calculate a small-sized representation of the joint.Guyan reduction [18],also known as static condensation,is a method to reduce the finite element stiffness and mass matrices of structures.For an arbitrary structure,the basic static FE matrix equation is given by K ·x =F

(1)

where K is the stiffness matrix,F and x are the force and the dis-placement vectors,respectively.By identifying n t boundary degrees of freedom (DOFs),which must be retained in the solution,and n o internal DOFs,which are to be removed by static condensation,the system of Eq.(1)can be partitioned as follows: K oo K ot K to K tt · x o x t = F

o F t (2)

where subscripts t and o are used to designate the boundary and the internal DOFs,respectively.From the first line of Eq.(2),the internal displacement vector can be determined as

x o =K ?1

oo (F o ?K ot ·x t )

(3)

By introducing the static reduction matrix G ot =?K ?1oo K ot and substi-tuting Eq.(3)into the second line of Eq.(2),the following equation is obtained:

K tt ,red ·x t =F t ,red

(4)

where F t ,red =F t +G T ot F o is the reduced loading vector,while K tt ,red =

K to G ot +K tt is the n t x n t reduced stiffness matrix.Physically this matrix represents the stiffness values between each pair of boundary DOFs.This way,the stiffness of the structure has been condensed to the boundary DOFs.

The same transformation can be used to condense the mass ma-trix on the boundary DOFs,to obtain a reduced system also for dy-namic analyses.However,while exact for the stiffness matrix,the Guyan reduction is an approximation for the mass matrix.By re-ducing the mass matrix,it is assumed for the considered structure that inertia forces on internal DOFs are less important than elastic forces transmitted by the boundary DOFs.This is true for very stiff components or in cases where local dynamic effects can be ignored.Therefore,the accuracy of the result is case dependent.

For each isolated joint model,a Guyan reduction is performed,with the DOF of the joint's end nodes (i.e.beam center nodes)as the boundary DOFs to be retained in the solution.The FE model of the joint is thus reduced to a small superelement,consisting of a reduced stiffness and mass matrix.For typical automotive joints,the stiffness relations between the end points of the joint have a much stronger influence on the global body behavior than the exact distribution of mass on the joint.For this reason,Guyan reduction of the joint structure to its joint end-nodes (i.e.beam center nodes)seems an appropriate choice to create a small-sized representation of the actual joint [14].

D.Mundo et al./Finite Elements in Analysis and Design 45(2009)456--462459

3.Case-study 3.1.Model description

Fig.4shows an industrial BIW model,consisting of 123panels that are modelled with linear shell elements.The constituent panels are assembled by means of about 3000spot-weld connections [19],which are represented in the FE model by means of Hexa solid ele-ments [15].In order to validate the reduced beam and joint modelling approach,as described in the previous section,a group of beam-like structures,labelled in Fig.4as B 1...B 5,are selected and replaced by equivalent simple beams.

In total,10beams are selected for the replacement,namely the A and B-pillars and the longitudinal and transversal roof-rails.Four joints,symmetrically arranged w.r.t.the longitudinal plane of the vehicle,connecting these beams are labelled in Fig.4as J 1,J 2,J 3and J 4,are statically reduced.Fig.5shows the simplified BIW model,where the detailed shell models of the beam-like structures have been replaced by simple two-node beam elements.The number and length have been selected based on the geometric characteris-tics (i.e.length and cross-section variations)of the original mesh.The original FE joint models have been removed from the BIW FE model,and the joints have been represented by static superelements (i.e.,the equivalent mass and stiffness matrices of each joint).3.2.Static comparison

To validate the proposed approach,static and dynamic indica-tors of the full vehicle performance are considered.These indicators are evaluated for both the original BIW model and the simplified (or conceptual)model.To assess the static behavior,the torsional and bending stiffness of the BIW are calculated.The body is clamped at the rear suspensions,while static vertical forces are applied at

the

Fig.4.Original FE model of the

BIW.

Fig.5.Conceptual FE model of the BIW.The original meshes of 10beam-members and four joints are replaced by simplified beam elements and joint

superelements.

Fig.6.Static load-cases defined to estimate the BIW stiffness under (a)torsion and (b)bending.

front suspensions (points A and B in Fig.6).Based on the estimation of the vertical displacements v A and v B at the excitation points,the bending and torsion deflection angles b and t are determined as

b =arctan

v A +v B

2L

(5) t =arctan

v A ?v B

W (6)where L and W denote the wheelbase and the width of the car,respectively,measured at the front suspension points.

Based on the torsional deflection t ,the torsional stiffness K t is determined as

K t =

M

t

(7)

where M =F ·W is the moment applied at the front suspension,resulting from two oppositely oriented forces F .

Similarly,the bending stiffness K b is determined from b as K b =

2FL

b

(8)

where F is the vertical force applied at the frontal suspension loca-tion.

The stiffness properties of the BIW are estimated for both the models in Figs.4and 5,by performing a static FE analysis (Nastran-Sol 101)with both models.In Table 1,the torsional and bending stiffness indicators are listed,as well as the approximation involved by the simplified model w.r.t.the original model.The results show that the bending stiffness of the original vehicle model is accurately predicted by the model with the replaced simplified beams and joints,while a significant discrepancy between the original and the

460 D.Mundo et al./Finite Elements in Analysis and Design 45(2009)456--462

simplified models is obtained for torsion.In the latter case,the stiff-ness of the full vehicle body is overestimated by 10.15%,which sug-gests that the definition of correction factors is indeed required.This will be evaluated and assessed in Section 4.3.3.Dynamic comparison

In order to compare the simplified and the original model in terms of dynamic behavior,the frequencies and mode shapes of the BIW are estimated through an FE modal analysis (Nastran-Sol 103)in the low-frequency range of 0–50Hz.When a normal mode analysis in

Table 1

Torsional and bending stiffness of the original and of the conceptual FE model.

Torsion Bending Original model

Concept model

Original model

Concept model

Stiffness (Nm/rad) 1.456E+05

1.603E+05 5.013E+04 5.036E+04 (%)

–10.15–0.45

Table 2

Dynamic comparison between the original and the conceptual FE model in terms of global frequencies and modal shapes.Mode n Modal shape

Frequency (Hz)MACii

Original model

Concept model (%)

11st Torsion 18.2219.28 5.820.9922nd Torsion 26.1327.88 6.700.9683Lateral bending 39.3640.01 1.650.9894Vertical bending

41.7342.120.930.9895

Mixed torsion+bending

47.85

47.92

0.15

0.99

10.80.6

0.40.20

I d 7-47.9

I d 5-42.0

I d 4-40.0

I d 2-27.9

I d 1-19.3

I d 1-18.2

I d 3-26.1

I d 7-39.4

I d 8-41.7

I d 10-47.9

D i s c r e t e

v

a l u e s

M o d e S e t .2 - u n c

o r r e

c t e

d D i s c

r e t e v

a l u e s M

o

d e S e t .1 - O

r i g i n a l m o d e l

> 10.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1< 0

Matrix_Graph1 (Model Assurance Criterion)

Fig.7.MAC matrix between the original and the conceptual model.

free–free conditions is performed,the first six modes are rigid body modes.From mode seven onwards,the natural modes are found.The original model of the vehicle body has 10non-rigid modes in the frequency range of interest.Only five out of them are global modes of the BIW,since the remaining modes involve a local deformation of the structure.The eigenfrequency values of the five global modes are used as dynamic indicators to evaluate the correlation between the original and the conceptual BIW model.In Table 2,the global frequencies of both models are listed.Also the dynamic comparison shows that the conceptual model overestimates the stiffness of the full structure.It can be seen that the natural frequencies are shifted upwards by an amount in the range 0.15–6.70%.

A further comparison between the two models is also performed in terms of modal shapes by using the modal assurance criterion (MAC)[20].Let V 1and V 2be the modal matrices of the original and the modified model,respectively.The correlation index between two generic modes {V 1}i belonging to the first matrix and {V 2}j belonging to the second matrix can be evaluated as [21]MAC i ,j =

({V 1}H i

{V 2}j )2

({V 1}H i {V 1}j )({V 2}H i

{V 2}j )(9)

where the superscript H denotes the conjugate transposed of a vector.

Fig.7shows the resulting MAC matrix,evaluated by using all the nodes that are shared by the original and the simplified model.The diagonal MAC values,which are listed in Table 2,show that the concept model accurately approximates the detailed model in terms of mode shapes.4.Correction factors

Based on the results of the previous static and dynamic analyses,it can be concluded that the stiffness parameters of thin-walled

D.Mundo et al./Finite Elements in Analysis and Design45(2009)456--462

461

Fig.8.Virtual test-case defined to estimate the correction factors.

beams,as computed by means of a geometric approach,involve an overestimation of the global stiffness of the vehicle.Such a conclu-sion is in line with the results reported in other research papers [16,17],which suggest a correction of the beam properties in order to take into account section variations and discontinuities(holes, spot-welds,stiffeners).For this reason,proper correction factors are defined as the ratio between the actual value of each stiffness pa-rameter and the nominal value.For instance,according to such a definition,the equivalent bending stiffness parameters of a beam end-section are given by

I yy=c yy·I yy,nom(10) I zz=c zz·I zz,nom(10 )

where I yy,

nom and I zz,

nom

are the stiffness parameters computed

through the geometric approach described in Section2.1,while c yy and c z z are the corresponding correction factors.

A set of correction factors is then defined for each beam-member and estimated by means of a model updating procedure,which is described in the following sub-section.

4.1.Estimation of correction factors

In order to estimate proper correction factors by means of a model updating procedure,the virtual test-case represented in Fig.8is used. The vehicle body is clamped at the rear suspensions(points C and D)and statically loaded at the front suspensions(points A and B). The displacements of10control points P i,(i=1,...,10)are estimated and used to compare the static stiffness of the original model,used as reference,and the simplified model.The following function is defined as a measure of the difference between the simplified and the original model in terms of static response to the load-case shown in the Fig.8

f(c1,...,c N)=

i

y i,A?y i,R

y i,R

+

z i,A?z i,R

z i,R

(11)

where c1,...,c N are the actual values of the correction factors,while subscripts A and R refer to the actual and the reference model,re-spectively.

An optimization problem can be defined as the search for the vector of correction factors that minimizes the difference between the two models,that is

Minimize f(c1,...,c N)

Subject to I1?I2>I12for all beams

(12)

Fig.9.History of the goal function as defined in Eq.(13).

Table3

Optimal values of the correction factors for bending stiffness parameters.

Correction factors

B1B2B3B4B5

Ixx0.2600.1570.3110.0070.001 Iyy0.9330.3910.7710.0790.011 Izz0.7610.4550.8930.1920.219 Ixy0.8090.3710.8120.1130.001

where the inequality constraint ensures that the actual set of cor-rection factors defines a feasible solution.

An optimal and feasible solution can be searched for by means of a genetic algorithm[22].For this purpose,the constrained problem defined above is transformed into an unconstrained problem by us-ing a penalty formulation:a large cost-value is added to the objec-tive function in case that the constraint is violated.Such a procedure ensures that an unfeasible solution has a larger goal function than any feasible solution.This enables the convergence of the algorithm towards a global optimum,which fulfils all constraints.The original constrained optimization problem is then replaced by the following unconstrained problem:

Minimize f(c1,...,c N)+k(c1,...,c N)·C(13)

where C is a penalty cost-value,while k(c1,...,c N)is a Boolean func-tion defined as

k(c1,...,c N)=

0if I1?I2>I12

1otherwise

(14)

The optimization problem is solved by a genetic algorithm imple-mented in Matlab.In Fig.9the history of the goal function defined by Eq.(13)is shown.

Table3lists the optimal values of the correction factors evalu-ated for both bending stiffness-parameters of all the replaced beam-members.

The geometric approach used to compute the equivalent beam parameters considers each cross-section as closed,even for the roof cross members.This is the main reason why correction factors are quite low(significantly lower than one),especially for these mem-bers.Roof cross members,in fact,are formed by two panels con-nected to each other by glue connections,which are much more

462 D.Mundo et al./Finite Elements in Analysis and Design45(2009)456--462

Table4

Torsional and bending stiffness of the original and the final conceptual FE model.

Torsion Bending

Original model Final concept

model

Original

model

Final concept

model

Stiffness

(Nm/rad) 1.456E+05 1.462E+05 5.013E+04 5.024E+04

(%)–0.46–0.22

Table5

Dynamic comparison between the original and the final conceptual FE model in terms of global frequencies and modal shapes.

Mode n Frequency(Hz)MACii Original model Final concept model (%)

118.2218.220.010.99 226.1326.09?0.150.998 339.3639.31?0.120.998 441.7341.990.620.978 547.8547.52?0.680.984

flexible than spot-weld connections.Therefore,the stiffness overes-timation involved by the geometric approach is much bigger than for the other beam-members.

Finally,Tables4and5provide a comparison between the original model and the simplified model,corrected by the optimal factors, in terms of static stiffness,natural frequencies and modal shapes. The results show that the final conceptual model correlates very well with the detailed model,both in terms of static and dynamic performance.

5.Conclusion

An engineering approach for the replacement of beam-like struc-tures and joints in a vehicle model has been presented in this paper. In order to validate the proposed approach,a case-study has been defined,where A-pillars,B-pillars and roof-rails of a vehicle's BIW have been replaced by equivalent beam models.Four joints,con-necting the above-mentioned beam-like structures to each other, have been replaced as well through a static reduction of the detailed mesh.Two static load-cases have been defined to apply torsion and bending to the full vehicle and compare the original and the simpli-fied models.The stiffness of the full vehicle under the two loading conditions has been evaluated and a difference of+0.46%and+0.22% between the simplified and the original models has been obtained for the torsion and bending load-case,respectively.A dynamic com-parison between the two models,based on the first10frequencies and modal shapes of the full vehicle,has been performed as well. The dynamic behavior of the full vehicle is accurately predicted by the simplified model.More specifically,in the comparison of the two models,a maximum eigenfrequency difference of0.68%and a MAC value difference of2.2%have been obtained.The quantitative results described above are well in line with OEM requirements for concept modification predictions in an early design stage.

In summary,a proof-of-concept of the feasibility of a stand-alone beam and joint replacement layout has been realized,which enables an accurate approximation of the global static and dynamic charac-teristics.The stiffness correction factors can be derived in a single optimization procedure(updating w.r.t.the predecessor model)in a replacement scenario.Naturally,once the replacement model has been established,a fast concept optimization is easily achievable. Individual beam properties can be modified,which is not possible (or easily achievable)on the complex-shaped cross-sections of the actual shell mesh.

Acknowledgment

The work presented in this paper has been performed in the framework of the research project“Analysis Leads Design-Frontloading Digital Functional Performance Engineering”,which is supported by I.W.T.Vlaanderen.

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[15]LMS International,LMS Virtual,Laboratory Review6B,November2006.

[16]S.B.Lee,J.R.Park,H.J.Yim,Numerical approximation of vehicle joint stiffness by

using response surface method,International Journal of Automotive Technology 3(3)(2002)117–122.

[17]P.Vinot,S.Cogan,J.Piranda,Shape optimization of thin-walled beam-like

structures,Thin-Walled Structures39(7)(2001)611–630.

[18]R.Guyan,Reduction of stiffness and mass matrices,AIAA Journal3(2)(1965)

380–387.

[19]S.Donders,M.Brughmans,L.Hermans,C.Liefooghe,W.Desmet,The robustness

of dynamic vehicle performance to spot weld failures,Finite Elements in Analysis and Design42(8–9)(2006)670–682.

[20]R.J.Allemang,D.L.Brown,A correlation coefficient for modal vector analysis,

in:Proceedings of the First International Modal Analysis Conference,Orlando, USA,1982,pp.110–116.

[21]W.Heylen,https://www.wendangku.net/doc/1d12033040.html,mmens,P.Sas,Modal Analysis—Theory and Testing,KU Leuven

Press,Leuven,Belgium,2006.

[22]D.Mundo,J.Y.Liu,H.S.Yan,Optimal synthesis of cam-linkage mechanisms for

precise path generation,Journal of Mechanical Design,ASME Transactions128

(6)(2006)1253–1260.

简易应对方式问卷(Simplified Coping Style Questionnaire)

简易应对方式问卷 (Simplified Coping Style Questionnaire） Joff等人指出，应对是个体对现实环境变化有意识、有目的和灵活的调节行为o Martin 指出，应对的主要功能是调节应激事件作用，包括改变对应激事件的评估，调节与事件有关的躯体或情感反应。个体的应对方式与心身健康之间的关系已成为临床心理学研究的重要内容。 国外发展了不少应对方式的评估方法，如由Folkman和Lararus编制的应对方式问卷(ways of coping questionnaire，WCQ )等应用较广和有代表性的方法。但由于文化背景的差异，国外的量表并不完全适合于我国人群。此外，虽然应对方式多种多样，但不同研究者提出的应对方式都有某些共同特点，即有的应对方式积极的成份较多，如寻求支持，改变价值观念体系，而有的则以消极的成分为主，如回避，发泄。因此，在国外应对方式量表基础上，根据实际应用的需要，结合我国人群的特点编制了简易应对方式问卷。 简易应对方式问卷由积极应对和消极应对两个维度（分量表）组成，包括20个条目。积极应对维度由条目1-12组成，重点反映了积极应对的特点，如“尽量看到事物好的一面”和“找出几种不同的解决问题的方法”等；消极应对维度由条目13-20组成，重点反映了消极应对的特点，如“通过吸烟喝酒来解除烦恼”和“幻想可能会发生某种奇迹改变现状”。 问卷为自评量表，采用多级评分，在每一应对方式项目后，列有不采用、偶尔采用、有时采用和经常采用4种选择（相应的评分为0、1，2、3），由受试者根据自己情况选择好一种作答。结果为积极应对维度平均分和消极应对维度平均分。临床应用时还应进一步分析各条目回答评分情况。 信度：量表的重测相关系数为0.89，α系数为0.90；积极应对分量表的α系数为0.89；消极应对分量表的α系数0.78。 效度：采用主成份分析法提取因子，并对因子模型作方差极大斜交旋转。因素分析结果表明，应对方式项目确实可以分出“积极”和“消极”应对两个因子，与理论构想一致。人群测试表明简易应对问卷反映出人群不同应对方式特征及其与心理健康之间的关系。积极应对评分较高时，心理问题或症状分低；而消极应对评分高时，心理问题或症状评分也高。应对方式评分与心理健康水平显著相关。

centrifugemodelling离心模拟centrifuge离心机

centrifugemodelling离心模拟centrifuge离心机centripetalacceleration向心加速度centripetalforce向心力centripetal向心的centrode瞬心轨迹centroidaxis重心轴线centroidofarea面心centroid质心centroidalprincipalaxesofinertia重心诌性轴centrosymmetric中心对称的ceramicbearing陶瓷轴承ceramicbond陶瓷结合剂ceramiccoating陶瓷涂层ceramicengine陶瓷发动机ceramicfilter陶瓷过滤器ceramicindustry陶瓷工业ceramici ulater陶瓷绝缘子ceramictip陶瓷刀片ceramictool陶瓷车刀ceramic 陶瓷的ceramics陶瓷cermettool金属陶瓷刀具cermet金属陶瓷cesium铯cetanenumber十六烷值CF 吸顶型风机CeilingMountedTypeFancfrp碳纤维增强塑料cg ystemcgs单位制cgsunit厘米克秒单位chai eltconveyor链带输送机chai elt链带chai lock链动滑轮chai rake链闸chai ridge链桥nondime ional无量纲的nondirective非定向的nondi ersivewave非弥散波nonelasticbuckling非弹性屈曲nonelasticscattering非弹性散射nonelastic非弹性的nonequilibriumplasma非平衡等离子体nonequilibriumproce非平衡过程nonequilibriumstate非平衡态nonequilibriumstate非平衡状态nonequilibriumsurfacete ion非平衡表面张力nonequilibriumthermodynamics非平衡态热力学nonequilibrium非平衡nonevanescentwave无阻尼波nonferrousalloy非铁合金nonferrousmetal有色金属nonferrousmetallurgy非铁金属冶炼术nonflatne不平面度nonfreepoint非自由质点nongeostrophicflow非地转怜nonholonomicco traint非完整约束nonholonomicsystem非完整系统nonholonomicvelocitycoordinate非完整速度坐标nonhomogeneou oundary非齐次边界nonidealflow非理想怜noninertia无惯性noninertialsystemofcoordinates非惯性坐标系noninertialsystem非惯性系nonisentropicflow非等熵怜nonisotropicmaterial非蛤同性材料nonisotropy非蛤同性nonius游标nonlinearaerodynamics非线性空气动力学nonlineardistortion非线性失真nonlinearelectrodynamics非线性电动力学collarbearing环状止推轴承collarheadscrew带缘螺钉collarjournal有环轴颈collarnut凸缘螺collarpin凸缘销collarthrustbearing环状止推轴承collarvortex涡环collar凸边collateralmotion次级运动collectivemodeofmotion集体运动模式collectivemotion集体运动collectorefficiency集热僻率collectorring滑环collector集电器colletchuck弹簧夹头collier运煤船collimation视准collimation准直collimator视准仪Collimator准直仪collisionchain碰撞链collisioncro ection碰撞截面collisiondiameter 碰撞直径collisiondiffusion碰撞扩散collisionexcitation碰撞激发collisionfrequency碰撞频率

脐带干细胞综述

脐带间充质干细胞的研究进展 间充质干细胞（mesenchymal stem cells,MSC S ）是来源于发育早期中胚层 的一类多能干细胞[1-5]，MSC S 由于它的自我更新和多项分化潜能，而具有巨大的 治疗价值 ,日益受到关注。MSC S 有以下特点：(1)多向分化潜能，在适当的诱导条件下可分化为肌细胞[2]、成骨细胞[3、4]、脂肪细胞、神经细胞[9]、肝细胞[6]、心肌细胞[10]和表皮细胞[11, 12]；(2)通过分泌可溶性因子和转分化促进创面愈合；(3) 免疫调控功能，骨髓源（bone marrow ）MSC S 表达MHC-I类分子，不表达MHC-II 类分子，不表达CD80、CD86、CD40等协同刺激分子，体外抑制混合淋巴细胞反应，体内诱导免疫耐受[11, 15]，在预防和治疗移植物抗宿主病、诱导器官移植免疫耐受等领域有较好的应用前景；(4)连续传代培养和冷冻保存后仍具有多向分化潜能，可作为理想的种子细胞用于组织工程和细胞替代治疗。1974年Friedenstein [16] 首先证明了骨髓中存在MSC S ，以后的研究证明MSC S 不仅存在于骨髓中，也存在 于其他一些组织与器官的间质中：如外周血[17]，脐血[5]，松质骨[1, 18]，脂肪组织[1]，滑膜[18]和脐带。在所有这些来源中，脐血(umbilical cord blood)和脐带(umbilical cord)是MSC S 最理想的来源，因为它们可以通过非侵入性手段容易获 得，并且病毒污染的风险低，还可冷冻保存后行自体移植。然而，脐血MSC的培养成功率不高[19, 23-24]，Shetty 的研究认为只有6%，而脐带MSC的培养成功率可 达100%[25]。另外从脐血中分离MSC S ，就浪费了其中的造血干/祖细胞(hematopoietic stem cells/hematopoietic progenitor cells,HSCs/HPCs) [26, 27]，因此，脐带MSC S (umbilical cord mesenchymal stem cells, UC-MSC S )就成 为重要来源。 一．概述 人脐带约40 g, 它的长度约60–65 cm, 足月脐带的平均直径约1.5 cm[28, 29]。脐带被覆着鳞状上皮，叫脐带上皮，是单层或复层结构，这层上皮由羊膜延续过来[30, 31]。脐带的内部是两根动脉和一根静脉，血管之间是粘液样的结缔组织，叫做沃顿胶质，充当血管外膜的功能。脐带中无毛细血管和淋巴系统。沃顿胶质的网状系统是糖蛋白微纤维和胶原纤维。沃顿胶质中最多的葡萄糖胺聚糖是透明质酸，它是包绕在成纤维样细胞和胶原纤维周围的并维持脐带形状的水合凝胶，使脐带免受挤压。沃顿胶质的基质细胞是成纤维样细胞[32]，这种中间丝蛋白表达于间充质来源的细胞如成纤维细胞的，而不表达于平滑肌细胞。共表达波形蛋白和索蛋白提示这些细胞本质上肌纤维母细胞。 脐带基质细胞也是一种具有多能干细胞特点的细胞，具有多项分化潜能，其 形态和生物学特点与骨髓源性MSC S 相似[5, 20, 21, 38, 46]，但脐带MSC S 更原始，是介 于成体干细胞和胚胎干细胞之间的一种干细胞，表达Oct-4, Sox-2和Nanog等多

欧洲车联网项目 5GCAR_D3.2-Channel Modelling and Positioning for 5G V2X

Fifth Generation Communication Automotive Research and innovation Deliverable D3.2 Report on Channel Modelling and Positioning for 5G V2X Version: v1.0 2018-11-30 This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 761510. Any 5GCAR results reflects only the authors’ view and the Commission is thereby not responsible for any use that may be made of the information it contains. http://www.5g-ppp.eu

Deliverable D3.2 Report on Channel Modelling and Positioning for 5G V2X

Abstract 5GCAR has identified the most important use cases for future V2X communications together with their key performance indicators and respective requirements. One outcome of this study is that accurate positioning is important for all these use cases, however with different level of accuracy. In this deliverable we summarize existing solutions for positioning of road users and justify that they are not sufficient to achieve the required performance always and everywhere. Therefore, we propose a set of solutions for different scenarios (urban and highway) and different frequency bands (below and above 6 GHz). Furthermore, we link these new technical concepts with the ongoing standardization of 3GPP New Radio Rel-16. An important prerequisite for this work is the availability of appropriate channel models. For that reason, we place in front a discussion of existing channel models for V2X, including the sidelink between two road users, their gaps, as well as our 5GCAR contributions beyond the state of the art. This is complemented with results from related channel measurement campaigns.

脐带血造血干细胞库管理办法(试行)

脐带血造血干细胞库管理办法（试行） 第一章总则 第一条为合理利用我国脐带血造血干细胞资源，促进脐带血造血干细胞移植高新技术的发展，确保脐带血 造血干细胞应用的安全性和有效性，特制定本管理办法。 第二条脐带血造血干细胞库是指以人体造血干细胞移植为目的，具有采集、处理、保存和提供造血干细胞 的能力，并具有相当研究实力的特殊血站。 任何单位和个人不得以营利为目的进行脐带血采供活动。 第三条本办法所指脐带血为与孕妇和新生儿血容量和血循环无关的，由新生儿脐带扎断后的远端所采集的 胎盘血。 第四条对脐带血造血干细胞库实行全国统一规划，统一布局，统一标准，统一规范和统一管理制度。 第二章设置审批 第五条国务院卫生行政部门根据我国人口分布、卫生资源、临床造血干细胞移植需要等实际情况，制订我 国脐带血造血干细胞库设置的总体布局和发展规划。 第六条脐带血造血干细胞库的设置必须经国务院卫生行政部门批准。 第七条国务院卫生行政部门成立由有关方面专家组成的脐带血造血干细胞库专家委员会（以下简称专家委

员会），负责对脐带血造血干细胞库设置的申请、验收和考评提出论证意见。专家委员会负责制订脐带血 造血干细胞库建设、操作、运行等技术标准。 第八条脐带血造血干细胞库设置的申请者除符合国家规划和布局要求，具备设置一般血站基本条件之外， 还需具备下列条件： （一）具有基本的血液学研究基础和造血干细胞研究能力； （二）具有符合储存不低于1 万份脐带血的高清洁度的空间和冷冻设备的设计规划； （三）具有血细胞生物学、HLA 配型、相关病原体检测、遗传学和冷冻生物学、专供脐带血处理等符合GMP、 GLP 标准的实验室、资料保存室； （四）具有流式细胞仪、程控冷冻仪、PCR 仪和细胞冷冻及相关检测及计算机网络管理等仪器设备； （五）具有独立开展实验血液学、免疫学、造血细胞培养、检测、HLA 配型、病原体检测、冷冻生物学、 管理、质量控制和监测、仪器操作、资料保管和共享等方面的技术、管理和服务人员； （六）具有安全可靠的脐带血来源保证； （七）具备多渠道筹集建设资金运转经费的能力。 第九条设置脐带血造血干细胞库应向所在地省级卫生行政部门提交设置可行性研究报告，内容包括：

cultureSimplifiedChinese

2007 a) 复习要点 1.中国是一个统一的多民族国家，共有56个民族。 China is a unitary multi-national country. There are 56 ethnic groups in china. 中国的地势西高东低，呈三级阶梯状分布

2. 汉族不仅是中国人口最多的民族，也是世界上人口最多的民族。壮族、回族、满族、蒙古族、藏族是主要的少数民族。 The Han is the most populous ethnic group not only in China, but also throughout the world. The Zhuang, Hui, Manchu, Mongolian and Tibetan is the major ethnic minorities. 3. 春节是中国传统节日中最重要的一个。家人团聚，就象西方人的圣诞节。 The Spring Festival is the most important festival for the Chinese people and is when all family members get together, just like Christmas in the West. 4．春节的前夜叫除夕。农历正月初一是春节。 The Chinese New Year Eve is called Chuxi, which indicates the end of an old year and a start of a new year. The first day of the first lunar month is the New Year in Chinese Lunar Calendar. 5. 中国人过春节有很多传统习俗。比如：大扫除、买年货、贴窗花、挂年画、写春联、蒸年糕等等。 Chinese have many traditional customs relation to the Spring Festival, every family will undertake thorough cleaning，do their Spring Festival shopping, create paper-cuts for window decoration, put up New Year pictures, write Spring Festival couplests, make New Year cakes and so on. 6. 过年吃年糕，因为“糕”与“高”谐音。年高，就是“一年比一年高”的意思。 Chinese eat niangao (New Year cake made of glutinous rice flour) on this occasion, because as a homophone, niangao means "higher and higher, one year after another." 7．春节期间的重要活动是放爆竹，据说可以驱除妖魔。 Lighting Chinese crackers is one of the highlights during Chinese Spring Festival, which would drive demons away by folks. 8．在门上贴“福”字也是人们喜欢的，因为“福”有“吉祥”“好运”的意思。人们还喜欢把“福”颠倒过来贴，意思是“福到（倒）了”。

卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规范(试行)

卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规 范(试行)》的通知 【法规类别】采供血机构和血液管理 【发文字号】卫办医政发[2009]189号 【失效依据】国家卫生计生委办公厅关于印发造血干细胞移植技术管理规范(2017年版)等15个“限制临床应用”医疗技术管理规范和质量控制指标的通知 【发布部门】卫生部(已撤销) 【发布日期】2009.11.13 【实施日期】2009.11.13 【时效性】失效 【效力级别】部门规范性文件 卫生部办公厅关于印发《脐带血造血干细胞治疗技术管理规范（试行）》的通知 （卫办医政发〔2009〕189号） 各省、自治区、直辖市卫生厅局，新疆生产建设兵团卫生局： 为贯彻落实《医疗技术临床应用管理办法》，做好脐带血造血干细胞治疗技术审核和临床应用管理，保障医疗质量和医疗安全，我部组织制定了《脐带血造血干细胞治疗技术管理规范（试行）》。现印发给你们，请遵照执行。 二〇〇九年十一月十三日

脐带血造血干细胞 治疗技术管理规范（试行） 为规范脐带血造血干细胞治疗技术的临床应用，保证医疗质量和医疗安全，制定本规范。本规范为技术审核机构对医疗机构申请临床应用脐带血造血干细胞治疗技术进行技术审核的依据，是医疗机构及其医师开展脐带血造血干细胞治疗技术的最低要求。 本治疗技术管理规范适用于脐带血造血干细胞移植技术。 一、医疗机构基本要求 （一）开展脐带血造血干细胞治疗技术的医疗机构应当与其功能、任务相适应，有合法脐带血造血干细胞来源。 （二）三级综合医院、血液病医院或儿童医院，具有卫生行政部门核准登记的血液内科或儿科专业诊疗科目。 1.三级综合医院血液内科开展成人脐带血造血干细胞治疗技术的，还应当具备以下条件： （1）近3年内独立开展脐带血造血干细胞和（或）同种异基因造血干细胞移植15例以上。 （2）有4张床位以上的百级层流病房，配备病人呼叫系统、心电监护仪、电动吸引器、供氧设施。 （3）开展儿童脐带血造血干细胞治疗技术的，还应至少有1名具有副主任医师以上专业技术职务任职资格的儿科医师。 2.三级综合医院儿科开展儿童脐带血造血干细胞治疗技术的，还应当具备以下条件：

financial modelling training

财务模型培训

今天的议题
财务预测模型介绍 工具与数据 构建简单的财务预测模型 构建复杂的财务预测模型

财务模型可以用来做什么？ 财务模型可以用来做什么？
预算Budgeting 成本估算Cost Estimating 销售预测Sales Forecasting 销售预测 市场表现预测Market Share Forecasting 市场表现预测 投资项目的选择Project Selection & Management 投资项目的选择 业务/产品组合管理－ 业务 产品组合管理－组合方案与优化 产品组合管理 实时的市场分析Time-to-Market Analysis 战略决策的评估Real Options Valuation 并购M & A

战略规划项目中的财务预测模型是什么？用来干什么？ 战略规划项目中的财务预测模型是什么？用来干什么？
战略规划项目中的财务预测模型是 模拟各业务在不同运营策略/ 各业务在不同运营策略 模拟各业务在不同运营策略/业务模 式下及不同市场环境下各项业务的 式下及不同市场环境下各项业务的 大体财务表现及发展趋势。因此， 大体财务表现及发展趋势。因此，
在模拟业务表现时，先不考虑股权比 例、投资收益、少数股东权益等问 题；在最后并总表时，可以综合考虑 最后计数单位宜采用“千元”、“百 万元”等较大计量单位，切忌采用 元、角、分等极其精准的单位计量
财务预测模型绝对不能直接作为： 财务预测模型绝对不能直接作为： 直接作为
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精准的预算 绩效考核的标准
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但是，可以作为制定预算时的初步参 照，且其中部分有关运营方面的假设 项，例如产能利用率、损耗率等也可在 绩效考核中作为参照
在战略项目中， 财务预测模型将用于 在战略项目中，财务预测模型将用于 在战略项目中， 在战略项目中， 比较不同战略备选方案的经济价值 比较不同战略备选方案的经济价值 促进战略规划、行动方案的细化，并进行验证，反过来指导战略的制定 促进战略规划、行动方案的细化，并进行验证，反过来指导战略的制定 根据财务计划对未来进行资源安排提供依据 根据财务计划对未来进行资源安排提供依据

Simplified Receiver of GMSK(含matlab仿真代码)

Simplified Receiver of GMSK Abstract : This paper mainly describes the theory and process of modulation as well as demodulation of GMSK signal, which also include the theory of Viterbi Algorithm and Laurent Decomposition. Then we will simulate the process and show the results of simulation in Matlab. At last, we will analyze the performance of demodulation of GMSK by Simplified Receiver. Key word : GMSK, Simplified Receiver, V A, Laurent Decomposition Ⅰ. Modulation of GMSK signal Gaussian minimum shift keying (GMSK) is a kind of continuous phase modulation (CPM). CPM schemes are classi?ed as being full r esponse or partial response, depending, respectively, on whether the modulating frequency pulse is of a single bit duration or longer. Within the class of full response CPMs, the subclass of schemes having modulation index 0.5 but arbitrary frequency pulse shape results in a form of generalized MSK. The subclass of full-response schemes with rectangular frequency pulse but arbitrary modulation index is referred to as continuous phase frequency-shift-keying (CPFSK), which, for all practical purposes, served as the precursor to what later became known as CPM itself. Within the class of partial-response CPMs, undoubtedly the most popular scheme is that of Gaussian minimum-shift-keying (GMSK) which, because of its excellent bandwidth efficiency, has been adopted as a European standard for personal communication systems. In simple terms, GMSK is a partial-response CPM scheme ob tained by ?ltering the rectangular frequency pulses characteristic of MSK with a ?lter having a Gaussian impulse response prior to frequency modulation of the carrier. [1] Mathematical Model of CPM: ()(,))c s t f t t π0=+φα+φ, (1)b b nT t n T ≤≤+ (1) ,(,))l CPM s j t 0= φα+φ, (1)b b nT t n T ≤≤+ (2)

卫生部关于印发《脐带血造血干细胞库设置管理规范(试行)》的通知

卫生部关于印发《脐带血造血干细胞库设置管理规范(试行)》的通知 发文机关：卫生部(已撤销) 发布日期： 2001.01.09 生效日期： 2001.02.01 时效性：现行有效 文号：卫医发(2001)10号 各省、自治区、直辖市卫生厅局： 为贯彻实施《脐带血造血干细胞库管理办法（试行）》，保证脐带血临床使用的安全、有效，我部制定了《脐带血造血干细胞库设计管理规范（试行）》。现印发给你们，请遵照执行。 附件：《脐带血造血干细胞库设置管理规范（试行）》 二○○一年一月九日 附件： 脐带血造血干细胞库设置管理规范（试行） 脐带血造血干细胞库的设置管理必须符合本规范的规定。 一、机构设置 （一）脐带血造血干细胞库（以下简称脐带血库）实行主任负责制。 （二）部门设置 脐带血库设置业务科室至少应涵盖以下功能：脐带血采运、处理、细胞培养、组织配型、微生物、深低温冻存及融化、脐带血档案资料及独立的质量管理部分。 二、人员要求

（一）脐带血库主任应具有医学高级职称。脐带血库可设副主任，应具有临床医学或生物学中、高级职称。 （二）各部门负责人员要求 1．负责脐带血采运的人员应具有医学中专以上学历，2年以上医护工作经验，经专业培训并考核合格者。 2．负责细胞培养、组织配型、微生物、深低温冻存及融化、质量保证的人员应具有医学或相关学科本科以上学历，4年以上专业工作经历，并具有丰富的相关专业技术经验和较高的业务指导水平。 3．负责档案资料的人员应具相关专业中专以上学历，具有计算机基础知识和一定的医学知识，熟悉脐带血库的生产全过程。 4．负责其它业务工作的人员应具有相关专业大学以上学历，熟悉相关业务，具有2年以上相关专业工作经验。 （三）各部门工作人员任职条件 1．脐带血采集人员为经过严格专业培训的护士或助产士职称以上卫生专业技术人员并经考核合格者。 2．脐带血处理技术人员为医学、生物学专业大专以上学历，经培训并考核合格者。 3．脐带血冻存技术人员为大专以上学历、经培训并考核合格者。 4．脐带血库实验室技术人员为相关专业大专以上学历，经培训并考核合格者。 三、建筑和设施 （一）脐带血库建筑选址应保证周围无污染源。 （二）脐带血库建筑设施应符合国家有关规定，总体结构与装修要符合抗震、消防、安全、合理、坚固的要求。 （三）脐带血库要布局合理，建筑面积应达到至少能够储存一万份脐带血的空间；并具有脐带血处理洁净室、深低温冻存室、组织配型室、细菌检测室、病毒检测室、造血干/祖细胞检测室、流式细胞仪室、档案资料室、收/发血室、消毒室等专业房。 （四）业务工作区域应与行政区域分开。

脐带血间充质干细胞的分离培养和鉴定

脐带血间充质干细胞的分离培养和鉴定 【摘要】目的分离培养脐带血间充质干细胞并检测其生物学特性。方法在无菌条件下用密度梯度离心的方法获得脐血单个核细胞，接种含10%胎牛血清的DMEM培养基中。单个核细胞行贴壁培养后，进行细胞形态学观察，绘制细胞生长曲线，分析细胞周期，检测细胞表面抗原。结果采用Percoll(1.073 g/mL)分离的脐血间充质干细胞大小较为均匀，梭形或星形的成纤维细胞样细胞。细胞生长曲线测定表明接后第5天细胞进入指数增生期，至第9天后数量减少;流式细胞检测表明50%～70%细胞为CD29和CD45阳性。结论体外分离培养脐血间充质干细胞生长稳定，可作为组织工程的种子细胞。 【关键词】脐血;间充质干细胞;细胞周期;免疫细胞化学 Abstract: Objective Isolation and cultivation of mesenchymal stem cells (MSCs) in human umbilical cord in vitro, and determine their biological properties. Methods The mononuclear cells were isolated by density gradient centrifugation from human umbilical cord blood in sterile condition, and cultured in DMEM medium containing 10% fetal bovine serum. After the adherent mononuclear cells were obtained, the shape of cells were observed by microscope, then the cell growth curve, the cell cycle and the cell surface antigens were obtained by immunocytochemistry and flow cytometry methods. Results MSCs obtained by Percoll (1.073 g/mL) were similar in size, spindle-shaped or star-shaped fibroblasts-liked cells. Cell growth curve analysis indicated that MSCs were in the exponential stage after 5d and in the stationary stages after 9d. Flow cytometry analysis showed that the CD29 and CD44 positive cells were about 50%～70%. Conclusions The human umbilical cord derived mesenchymal stem cells were grown stably in vitro and can be used as the seed-cells in tissue engineering. Key words:human umbilical cord blood; mesenchymal stem cells; cell cycle; immunocytochemistry 间充质干细胞(mesenchymal stem cells，MSCs)在一定条件下具有多向分化的潜能，是组织工程研究中重要的种子细胞来源。寻找来源丰富并不受伦理学制约的间充质干细胞成为近年来的研究热点[1]。脐血(umbilical cord blood, UCB)在胚胎娩出后，与胎盘一起存在的医疗废物。与骨髓相比，UCB来源更丰富，取材方便，具有肿瘤和微生物污染机会少等优点。有人认为脐血中也存在间充质干细胞(Umbilical cord blood-derived mesenchymal stem cells，UCB-MSCs)。如果从脐血中培养出MSCs，与胚胎干细胞相比，应用和研究则不受伦理的制约，蕴藏着巨大的临床应用价值[2,3]。本研究将探讨人UCB-MSCs体外培养的方法、细胞的生长曲线、增殖周期和细胞表面标志等方面，分析UCB-MSCs 作为间充质干细胞来源的可行性。

Simplified Design of Steel Structures结构特性分析

4.1 INVESTIGATION OF STRUCTURAL BEHA VIOR Investigating how structures behave is an important part of structural design: it provides a basis for ensuring the adequacy and safety of a design, In this section I discuss structural investigation in general. As I do throughout this book. I focus on material relevant to structural design tasks. Purpose of Investigation Most structures exist because they are needed. Any evaluation of a structure thus must begin with an analysis of how effectively the structure meets the usage requirements. Designers must consider the following three factors: ●Functionality. or the general physical relationships of the structure's form. detail. durability. fire resistance. deformation resistance. and so on. ●Feasibility. including cost. availability of materials and products. and practicality of construction. ●Safety. or capacity 10 resist anticipated loads. Means An investigation of a fully defined structure involves the following: 1. Determine the structure's physical being-materials, form, scale. orientation. location. support conditions, and internal character and detail. 2. Determine the demands placed on the structure-that is. loads. 3. Determine the structure's deformation limits. 4. Determine the structure's load response-how it handles internal forces and stresses and significant deformations. 5. Evaluate whether the structure can safely handle the required structural tasks. Investigation may take several forms. You can ●Visualize graphically the structure's deformation under load. ●Manipulate mathematical models. ●Test the structure or a scaled model, measuring its responses to loads. When precise quantitative evaluations are required. use mathematical models based on reliable theories or directly measure physical responses. Ordinarily. mathematical modeling precedes any actual construction-even of a test model. Limit direct measurementto experimental studies or to verifying untested

modelling_the_wireless_propagation_channel_a

Brochure More information from https://www.wendangku.net/doc/1d12033040.html,/reports/2171649/ Modelling the Wireless Propagation Channel. A simulation approach with Matlab. Wireless Communications and Mobile Computing Description: A practical tool for propagation channel modeling with MATLAB? simulations. Many books on wireless propagation channel provide a highly theoretical coverage, which for some interested readers, may be difficult to follow. This book takes a very practical approach by introducing the theory in each chapter first, and then carrying out simulations showing how exactly put the theory into practice. The resulting plots are analyzed and commented for clarity, and conclusions are drawn and explained from the obtained results. Key features include: A unique approach to propagation channel modeling with accompanying MATLAB? simulations to demonstrate the theory in practice Contains step by step commentary and analysis of the obtained simulation results in order to provide a comprehensive and structured learning tool Covers a wide range of topics including shadowing effects, coverage and interference, Multipath Narrowband channel, Multipath Wideband channel, propagation in micro and pico–cells, the land mobile satellite (LMS) channel, the directional Multipath channel and MIMO and propagation effects in fixed radio links (terrestrial and satellite) The book comes with an accompanying website that contains the MATLAB? simulations and allows readers to try them out themselves Well suited for lab–use, as reference and as a self–learning tool both for advanced students and professionals Modeling the Wireless Propagation Channel: A simulation approach with MATLAB? will be best suited for postgraduate (Masters and PhD) students and practicing engineers in telecommunications and electrical engineering fields, who are seeking to familiarise themselves with the topic without too many formulas. The book will also be of interest to network engineers, system engineers and researchers. Contents:Contents About the Series Editors Preface Acknowledgments 1 Introduction to Wireless Propagation 1.1 Introduction 1.2 Wireless Propagation Basics 1.3 Link Budgets 1.4 Projects 1.5 Summary References Software Supplied 2 Shadowing Effects 2.1 Introduction 2.2 Projects 2.3 Summary