Describing the position of backhoe dredge buckets

C.F. Hofstra1,A.J.M. van Hemmen2,S.A. Miedema3,J. van Hulsteyn4

Abstract There is growing interest in the automation of the production cycle of backhoe dredges. In order to realise an effective control mechanism for a non-rigid body it is necessary to acquire an adequate insight in not only the dynamic behaviour of the hydraulic system but also of the mechanical systems. This second factor is also influenced by the fact that bigger and bigger machines are being used. As there is no real reference material on this subject the first step has been the description of the kinematics of a backhoe. This was followed by determining of the Denavit-Hartenberg matrix to describe the mechanical motions of the system with respect to the position and orientation of the bucket. Using this method a dynamical model has been developed. The paper will give a description of the dynamical model (using Matlab and Adams) and show some of the simulation results with respect to the influences of the flexibility of the hydraulic fluid and the steel structure on the achievable accuracy. Keywords: Denavit-Hartenberg, trajectory control, flexible bodies, accuracy.

Introduction Over the last decades the backhoe has come to replace the bucket dredge as the primary tool for the excavation of trenches and localised sites. Mainly because of the noise production and the ability to perform environmental dredging operations. This has been accompanied by an increase in the size of these machines in order to work in deeper locations. The increase in size and capacity leads to a reduction in achievable accuracy of the dredging process. In order to improve the accuracy of the dredged level one must first determine the prime factors influencing the accuracy of the process. This is especially true if one wishes to automate the process in the future. This paper describes a dynamical model that was used to determine the effects of the flexibility of the boom and the stick with respect to the position of the tip under various loading conditions during the dredging cycle compared to the rigid body approach. First the conventional approach to bucket position is described which was used to determine the points of interest. The next phase is the description of the degrees of freedom as available independent of the control system. To round off the system the influence of the (non-) rigidity of the steel structure in two digging situations and the responses to external loads are described and analysed. The model used in this paper is based on the Komatsu H245S with a 12 m boom and a 8.5 m stick.

1 C.F.Hofstra, B. Mech. Eng., Graduate student, TU Delft, Gezel 3 3161 LB Rhoon, The Netherlands, ..-31-10-5012254,hofstra@igr.nl 2 A.J.M.van Hemmen, MSc Civil Eng., Project manager, Boskalis, Rosmolenweg 20 3356LK, Papendrecht, The Netherlands, ..-31-78- 6969634, a.j.m.vanhemmen@boskalis.nl. 3 S.A.Miedema, PhD, MSc Mech. Eng., Associate professor, chair of dredging technology, TU Delft, Mekelweg 2 2628 CD Delft, The Netherlands,..-31-15-2788359,s.a.miedema@wbmt.tudelft.nl 4 J.van Hulsteijn, Graduate student, TH Rijswijck, Zalm 9 2986 PC, Ridderkerk, The Netherlands,..-31-180-426061

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Trajectory planning The trajectory described by the bucket tip is determined beforehand. This trajectory is then converted to the machine co-ordinates (angles) after which the necessary sequence of piston positions is determined. The relationship between the orientation of the machine and the position of the piston is determined from figure 1.

Figure 1 Model with angle definitions Boom

ε−ζ−γ=α with: ⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅⋅−+

=γ (1) bdbc

21

2bd

2bc

ll2cilll

cosa

Stick

with: κ+λ−δ−α=β⎥⎥⎦

⎤

⎢⎢⎣

⎡

⋅⋅

−+=λ

fgef

22

2fg

2ef

ll2cilll

cosa (2)

Bucket

⎟⎟⎠

⎞⎜⎜⎝

⎛⋅⋅−+

−⎟⎟⎠

⎞⎜⎜⎝

⎛

⋅⋅

−+−∠−π+β=

∠−∠−∠−π+β=σ

knkm

mnknkm

jmjk

jmkmjk

ll2lllcosa

ll2lll

cosaFKJ

NKMJKMFKJ

(3)

with :

( )μ−ν−∠−∠−π⋅⋅⋅⋅−+= FJHKJF2cosll2lll jmjk2

jm2

jkkm (4)

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⋅⋅

−+=ν

jkhj

23

2jk

2hj

ll2cilll

cosa (5)

The next step is to determine the relation between the machine orientation and the desired trajectory. In order to do this effectively while describing the position and orientation of the bucket the Denavit-Hartenberg (DH) approach based on homogenous co-ordinates is utilised.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Derivation of the position of the bucket (tip) using Denavit-Hartenberg

As stated the position of the bucket, specifically the bucket tip, is derived from the orientation of boom, stick and bucket with respect to each other. This is measured by means of their respective angles. For the DH approach the modelling of figure 1 is modified to give a "chain' as depicted in figure 2.

SIDE VIEW

TOP VIEW

Figure 2 Backhoe “chain” Using homogenous co-ordinates the Denavit-Hartenberg matrices for boom, stick and bucket based on an orthogonal Cartesian system are:

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛φ⋅φ−φφ⋅φφ

=

1000c010

ScC0SCcS0C

bz

bx

bx

machineH

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛Θ⋅ΘΘΘ⋅Θ−Θ

=

10000100Sl0CSCl0SC

1bf11

1bf11

boomH

(6)

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛Θ⋅ΘΘΘ⋅Θ−Θ

=

10000100Sl0CSCl0SC

2fk22

2fk22

stickH

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛Θ⋅ΘΘΘ⋅Θ−Θ

=

10000100Sl0CSCl0SC

3kp33

3kp33

bucketH

In these matrices Cφ=cos(φ) and Sφ=sin(φ). Multiplication of these matrices yields the "hand" matrix for the position and orientation of the bucket tip:

(7) ( )( )

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛

+Θ⋅+χ⋅+ψ⋅ψψ+Θ⋅+χ⋅+ψ⋅⋅φφ−ψ⋅φ−ψ⋅φ+Θ⋅+χ⋅+ψ⋅⋅φφψ⋅φ−ψ⋅φ

=

⋅⋅⋅=

1000cSlSlSl0CS

cClClClSCSSSScClClClCSSCCC

bz1bffkkp

l1bffkkp

bx1bffkkp

bucketstickboommachine HHHHH

With χ 321 Θ+Θ+Θ=ψ , 21 Θ+Θ= This is the forward kinematics of the backhoe. Given a trajectory f(t) in time for the bucket we can determine the accompanying angles by solving the following equation:

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

(8) ( ) ( )tt Hf = Control of the machine is achieved using the hydraulic cylinders. If there is a small change in the orientation of the machine, what is the corresponding change in the piston position? The equations (1 to 5) clearly show the difficulty in extracting the cylinder length, which in turn leads to the piston position. This is certainly true for the bucket cylinder. Modifying the DH matrix to include only boom and stick reduces this problem. Bucket position and orientation are added to the equation as boundary conditions. Because rotation of the machine influences neither the boom angle nor the stick angle it can likewise be added as a boundary condition. The dredge cycle with respect to boom, stick and bucket reduces to in plane motion. The reduced DH matrix now reads:

(9)

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛Θ⋅+ψ⋅ψ−ψΘ⋅+ψ⋅ψ−ψ

=

⋅=

10000100

ClCl0SSClCl0SC

1bffk

1bffk

stickboom HHH

With: 21 Θ+Θ=ψ

Trajectory control To effectively follow a prescribed path we have to know the relationship between small changes in angles and the piston positions. Differentiating the DH matrix yields:

(10) ⎟⎟⎠

⎞⎜⎜⎝

⎛ΘΘ

⋅⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛ψ⋅Θ⋅+ψ⋅ψ⋅−Θ⋅−ψ⋅−

=⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

Θ 2

12112

212

dd

11CLCLCLSL1SLSL

ddbda

The corresponding changes in the cylinder lengths can be determined from equations 1 and 2 in a similar fashion. Adding time to these equations gives us the necessary tools to describe the motion of the bucket tip along a specified trajectory.

The hydraulic system The use of hydraulic cylinders introduces flexible elements into the system enabling it to move independently of the controls. The magnitude of the flexibility is determined by the bulk modulus and the volume of fluid between the control block and the piston and the flexibility of the supply lines. This flexibility is incorporated into the model by modelling the cylinders as springs. The stiffness of the spring is determined by total change in the volume: (11) hosepipecylinderfluidtot VVVVV Δ+Δ+Δ+Δ=Δ From which the displacement of the piston is determined:

piston

tot

AV

yΔ

=Δ (12)

Resulting in a spring stiffness:

tot

2piston

piston

tot

piston

VAp

AV

ApyFK

Δ

⋅Δ=

⎟⎟⎠

⎞⎜⎜⎝

⎛ Δ

⋅Δ=

ΔΔ

= (13)

This formula is used for both piston and rod side incorporating the supply lines and hoses. This is necessary because

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

in contrast to normal practice the effects of both cannot be disregarded due to their length. Damping in the cases studied was assumed to be limited to 1% of the spring stiffness.

Additional degrees of freedom - Flexible bodies This study is intended to determine the effects of flexibility of the steel structure. For this purpose the Adams program was utilised. In the Adams program flexible bodies are described using the eigen-frequencies and eigen-vector approach. These are used to calculate the effective stiffness and damping matrices. Frequencies and vectors are determined using the Ansys finite element program and imported into the program. As these results vary with the orientation of the machine they are reproduced here. From past experience it is known that the effective damping of steel structures can be taken as equal or less than 1% of the effective stiffness matrix.

Forces on the backhoe Forces on the backhoe can be subdivided into external and internal forces. Internal forces are those caused by the friction in the hydraulic cylinders. Due to the mismatch between the moment arms of the forces involved, friction forces in the joints can be disregarded. External forces are digging force and those caused by the movement of the parts through the water, to which are added the wave and current forces.

External forces The digging forces on the bucket are determined using existing models for sand, Miedema (1987), clay, Miedema (1997). In the absence of models for the cutting of loose or sprung rock the following analogy is used: (14) hbEF spcut ⋅⋅= The force exerted by current, waves and moving through the water can be calculated by combining the Morison equation with the formula for flow resistance. This results in:

( ) ulACuulbC21xACC

21xClAFFF MD

2fPawavemass ⋅⋅⋅⋅ρ+⋅⋅⋅⋅⋅ρ⋅+⋅ρ⋅⋅+⋅+⋅⋅⋅⋅ρ=+= (15)

Except for Cf, which is a function of the Reynolds number, the other coefficients Ci have to be determined experimentally for the submerged parts of the structure.

Internal forces Friction in the cylinders cannot be disregarded due to its necessity for determining the equilibrium over the piston and its effects on the system damping. A linear function for the friction is used according to: ( ) ( )ysgnFywF Nscil,fr ⋅⋅μ+⋅= (16)

Analysis of the dredging cycle Based on a rigid body approach these aspects were used to model various dredging cycles with the Matlab program. These show that during operations the largest accelerations and therefore forces on the structure occur during the positioning and the digging part of the cycle. During the other parts of the cycle the available hydraulic power is not sufficient to induce significant accelerations and the structure itself is not subjected to the rapid changes in kinetic energy. As a whole these results were comparable to the results of previous studies, for example Van Velzen (1999), Salcudean et al. (1999). The main points of interest are therefore limited to the positioning of the bucket and the digging part of the cycle.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Apart from production the single most important factor of the dredging cycle is the accuracy achieved during digging. The achievable accuracy decreases with increasing machine size. This is ascribed in part to the flexibility of the hydraulic and mechanical systems, the positioning of the pontoon and the operator. If the backhoe were automated the operator influence would be taken up by the control system. For the design of such a system we need to know in advance whether the basic assumptions for a rigid system are applicable. To this end the effects of the flexibility of the steel structure are studied first followed by flexibility of the hydraulic system.

Example Using prismatic beam theory the deflection of the end of a beam with dimensions according to figure 3 under a load F of 20 tons amounts to 25.2 mm.

Figure 3 Cantilever beam If the same applies for a backhoe structure of comparable length it would lead to a sizeable error in the achievable accuracy. In the case of the studied machine the force reaches approximately 45 tons (deflection≅6cm).

Influence of the mechanical subsystem To study the effect of the flexibility of the steel structure two digging situations are modelled. In the first the bucket digs horizontally starting at an inclined the digging front (figure 4 - left). In the second the bucket scoops up material (figure 4 - right). In these simulations dynamic effects due to motion are not taken into account.

Figure 4 Digging profiles The position of the machine is of course but one of a number of possible ones. However, the resulting deflections will not vary substantially from on situation to another.

Case 1 - Digging horizontally Using the previously described flexibility the bucket is placed at the digging front and commences digging. The digging force is assumed to be zero at the beginning and increases to 40tons after which it is kept constant. Figure 6

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

shows the resulting paths for (continuous) the rigid simulation and (dash) the flexible situation.

Figure 5 Digging along horizontal profile The main difference occurs during the application of the digging force. This results in an error of less than 1.5cm with respect to the rigid model in the vertical direction and a slight lag in the horizontal.

Case 2 Scooping up material

Figure 6 Scooping up a load As can be seen the deviation during the entry part is comparable to the previous case. When the bucket is rotated to the horizontal digging position a vertical difference of about 3 cm appears. The lag in the horizontal direction is about the same.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

The hydraulic subsystem The hydraulic system exerts force by means of pressure in the cylinders, which is then transmitted via the structure to the bucket tip. The build-up of pressure in a cylinder compresses the hydraulic oil and allows the oil to absorb energy due to the compressibility of the hydraulic fluid. In normal situations the volume of oil under compression and therefore the amount of energy absorbed is small and its effects are neglected except for control purposes. However in this application the size of the cylinders and the length of the hoses and pipes result in a large volume of oil. Release of pressure due to the removal of an external load can lead to a change in the volume of the oil and thereby to a significant change in the bucket position. Two instances are described, the effect of the stepped removal of a horizontal ramped load in the plane of the machine and a similar load perpendicular to this plane. The external forces acting on the structure are the first two terms of equation 14 for components below the waterline. The experimental factors in this equation are assumed to be equal to 1 as there is no available data. The structure is assumed to be free of the ground after the release of the load.

Case 3 - Ramped load in the working plane In this example the boom and stick mentioned in the introduction (12 m and 8.5 m respectively) are used.. Boom and stick angles are 30° and -120° respectively, the bucket angle is -15° (following the definitions of figure 2). For the hydraulic stiffness and damping values according to table 1 are used, these are based on a hydraulic bulkmodulus of 15000 kPa.

Table 1: Hydraulic stiffness and damping values

Stiffness Damping Boom cylinder 1x108 N/m 1x106 Ns/m Stick cylinder 5x107 N/m 5x105 Ns/m Bucket cylinder 5x106 N/m 5x105 Ns/m

Figures 7 and 8 show the resulting displacements of the bucket tip. Starting from the original equilibrium position the bucket tip oscillates with amplitude of about 10 cm in horizontal direction and 5 cm in the vertical about the new equilibrium.

Figure 7: Displacement bucket tip in the orizontal direction in the working plane h

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

As can be seen the addition of flexibility for the steel structure leads to a slight increase in the displacements. This is due to the hi

Figure 8: Displacement bucket tip in vertical direction in the working plane

se

e case with the isplacements the cylinder forces show little difference between the rigid and the flexible models.

Case 4 - Ramped load perpendicular to the working plane

icular to the working plane as seen in figure 9. The resulting displacement is much larger than the in previous

Figure 9: Displacement bucket tip perpendicular to the working plane

gher level of potential energy when using flexible bodies.

It is obvious from both figures that the actual amount of damping, both internal as well as external, is small becauthe displacements are accompanied by relatively low velocities. This in turn leads to low values for the dampingforces. The structure will oscillate for a considerable period of time due to the absence of control input. Figures showing the paths of the corresponding forces in the cylinders can be found in the appendix. As is thd

The swing mechanism of the backhoe is modelled also as a hydraulic cylinder (torque). The ramped load leads to a displacement perpend

case.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

This is due to the distance between the tip of the bucket and the turning point of the machine itself (a relatively small force causes a large displacement). What can also be seen is that there is no discernible difference between the rigid and the flexible model. The magnitude of the displacements in the other directions is comparable to those described in the previous case. They and the forces in the cylinders the are depicted in the appendix. The forces in the x- and y-direction are not equal to zero due to the calculation of the equilibrium. The applied force does not follow the rotation of the model, thereby causing a small pre-load on the bucket in the working plane. The resulting motion is not significantly effected by this error.

Discussion and conclusions In the first two cases, modelling the elements of the steel structure as rigid, does not lead to deviations from the specified path of the magnitude that the deflection of the prismatic beam implied. The primary cause of this phenomenon is that although the steel structure does bend, this bending takes place after the bucket tip has been placed in the digging position. When force is applied the structure bends but this leads to a very small alteration of the boom and stick angles. The deflection of the structure is only visible in a slight lag in the horizontal plane. This lag is slightly larger than the error in the vertical direction but does not exceed 2 cm. The resulting differences imply that direct bending of the steel structure can be ignored in the design of control systems for this type of machine. The other cases show that the structure is capable of significant displacements in the absence of control inputs. As can be seen in the appendix this in turn leads to large variations in the cylinder forces. This can lead to the pressures in the cylinders approaching zero in cases where the digging forces approach the maximum. Modern machines are fitted with relief systems that deliver extra fluid to combat the cavitation that could then occur. As a consequence the resulting displacement would be even larger as the equilibrium positions of the cylinder pistons change. As was said the motion in cases 3 and 4 is assumed to be free of the ground. Digging in a continuous soil will of course limit the possible motions, but in for example loose rock there can be quite large spaces along the digging profile. The digging forces can also vary considerably. It will be necessary in future to determine what the effects of these situations are. As a result we can state that accurate control of a backhoe's motion can be achieved using a rigid body approach as the flexibility of the steel structure can be disregarded. This is certainly true when the effects of pontoon motion on the achievable accuracy are taken into account.

Abbreviations A = Area, plate cross section [m2] b = Width of the plate [m] Ca = Experimentally deter. mass coefficient [-] Cf = Flow coefficient [-] CD = Experimentally deter. drag coefficient [-] CM = Experimentally deter. inertia coefficient [-] E = Specific energy [kPa] F = Force [N] h = Height [m] K = Stiffness coefficient [N/m] l = (plate) length [m] p = Pressure [kPa] u = Flow speed [m/s] V = Volume [m3] w = Viscous friction term [Ns/m] x = Relative speed of with respect to the water [m/s] y’ = Piston speed [m/s] ρ = Density [kg/m3] μS = Static coefficient of friction [-] sgn() = Sign function [-]

Bibliography Stadler, W. (1995). Analytical robotics and mechatronics, McGraw-Hill. Miedema, S.A. (1987). Calculation of cutting forces when cutting sand fully saturated with water, Doctoral thesis, Delft University Press. Miedema, S.A. (1992). "New developments of cutting theories with respect to dredging. The cutting of clay", Proceedings XIIIth World Dredging Congress 1992, EADA, Bombay. Velzen, R.J.M. van (1999). "Automatisering van de positie en stand van de bucket van een backhoedredger", Afstudeerverslag A-863 vakgroep Meet- en regeltechniek, Faculteit Werktuigbouw en Maritieme Techniek, Delft, 1999. "Automation of the position and orientation of a backhoe bucket"

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Salcudean, S.E., Hashtrudi-Zaad, K., Tafoli, S., Dimaio, S.P. and Reboulet, C. (1999). "Bilateral matched impedance teleoperation with application to excavator control." IEEE control systems mag., december 1999,29-36.

Appendix

Case 3

Boom cylinder force

Stick cylinder force

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Bucket cylinder force

Case 4

Displacement bucket tip x-direction

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Displacement bucket tip y-direction

Boom cylinder force

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Stick cylinder force

Bucket cylinder force

14

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Bibliography Dr.ir. S.A. Miedema 1980-2010

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4. Miedema, S.A., "Computer program for the determination of the reaction forces on a cutterhead, resulting from the motions of the cutterhead" (PDF in Dutch 11 MB). Delft Hydraulics, 1981, 82 pages.

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6. Miedema, S.A.,"The Interaction between Cutterhead and Soil at Sea" (In Dutch). Proc. Dredging Day November 19th, Delft University of Technology 1982.

7. Miedema, S.A., "A comparison of an underwater centrifugal pump and an ejector pump" (PDF in Dutch 3.2 MB). Delft University of Technology, 1982, 18 pages.

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13. Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.

14. Miedema, S.A., "Longitudinal and Transverse Swell Compensation of a Cutter Suction Dredge" (In Dutch). Proc. Dredging Day November 9th 1984, Delft University of Technology 1984.

15. Miedema, S.A., "Compensation of Velocity Variations". Patent application no. 8403418, Hydromeer B.V. Oosterhout, 1984.

16. Miedema, S.A., "Mathematical Modeling of the Cutting of Densely Compacted Sand Under Water". Dredging & Port Construction, July 1985, pp. 22-26.

17. Miedema, S.A., "Derivation of the Differential Equation for Sand Pore Pressures". Dredging & Port Construction, September 1985, pp. 35.

18. Miedema, S.A., "The Application of a Cutting Theory on a Dredging Wheel (Adobe Acrobat 4.0 PDF-File 745 kB)". Proc. WODCON XI, Brighton 1986.

19. Miedema, S.A., "Underwater Soil Cutting: a Study in Continuity". Dredging & Port Construction, June 1986, pp. 47-53.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

20. Miedema, S.A., "The cutting of water saturated sand, laboratory research" (In Dutch). Delft University of Technology, 1986, 17 pages.

21. Miedema, S.A., "The forces on a trenching wheel, a feasibility study" (In Dutch). Delft, 1986, 57 pages + software.

22. Miedema, S.A., "The translation and restructuring of the computer program DREDMO from ALGOL to FORTRAN" (In Dutch). Delft Hydraulics, 1986, 150 pages + software.

23. Miedema, S.A., "Calculation of the Cutting Forces when Cutting Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 16 MB)". Basic Theory and Applications for 3-D Blade Movements and Periodically Varying Velocities for, in Dredging Commonly used Excavating Means. Ph.D. Thesis, Delft University of Technology, September 15th 1987.

24. Bakker, A. & Miedema, S.A., "The Specific Energy of the Dredging Process of a Grab Dredge". Delft University of Technology, 1988, 30 pages.

25. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Proc. WODCON XII, Orlando, Florida, USA, April 1989. This paper was given the IADC Award for the best technical paper on the subject of dredging in 1989.

26. Miedema, S.A., "The development of equipment for the determination of the wear on pick-points" (In Dutch). Delft University of Technology, 1990, 30 pages (90.3.GV.2749, BAGT 462).

27. Miedema, S.A., "Excavating Bulk Materials" (In Dutch). Syllabus PATO course, 1989 & 1991, PATO The Hague, The Netherlands.

28. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Terra et Aqua No. 41, December 1989, Elseviers Scientific Publishers.

29. Miedema, S.A., "New Developments of Cutting Theories with respect to Dredging, the Cutting of Clay (Adobe Acrobat 4.0 PDF-File 640 kB)". Proc. WODCON XIII, Bombay, India, 1992.

30. Davids, S.W. & Koning, J. de & Miedema, S.A. & Rosenbrand, W.F., "Encapsulation: A New Method for the Disposal of Contaminated Sediment, a Feasibility Study (Adobe Acrobat 4.0 PDF-File 3MB)". Proc. WODCON XIII, Bombay, India, 1992.

31. Miedema, S.A. & Journee, J.M.J. & Schuurmans, S., "On the Motions of a Seagoing Cutter Dredge, a Study in Continuity (Adobe Acrobat 4.0 PDF-File 396 kB)". Proc. WODCON XIII, Bombay, India, 1992.

32. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "On the Closing Process of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 1 MB)". Proc. WODCON XIII, Bombay, India, 1992. This paper was given the IADC Award for the best technical paper on the subject of dredging in 1992.

33. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "The Closing Process of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 1 MB)". Terra et Aqua No. 49, September 1992, IADC, The Hague.

34. Miedema, S.A., "Modeling and Simulation of Dredging Processes and Systems". Symposium "Zicht op Baggerprocessen", Delft University of Technology, Delft, The Netherlands, 29 October 1992.

35. Miedema, S.A., "Dredmo User Interface, Operators Manual". Report: 92.3.GV.2995. Delft University of Technology, 1992, 77 pages.

36. Miedema, S.A., "Inleiding Mechatronica, college WBM202" Delft University of Technology, 1992.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

37. Miedema, S.A. & Becker, S., "The Use of Modeling and Simulation in the Dredging Industry, in Particular the Closing Process of Clamshell Dredges", CEDA Dredging Days 1993, Amsterdam, Holland, 1993.

38. Miedema, S.A., "On the Snow-Plough Effect when Cutting Water Saturated Sand with Inclined Straight Blades (Adobe Acrobat 4.0 PDF-File 503 kB)". ASCE Proc. Dredging 94, Orlando, Florida, USA, November 1994. Additional Measurement Graphs. (Adobe Acrobat 4.0 PDF-File 209 kB).

39. Riet, E. van, Matousek, V. & Miedema, S.A., "A Reconstruction of and Sensitivity Analysis on the Wilson Model for Hydraulic Particle Transport (Adobe Acrobat 4.0 PDF-File 50 kB)". Proc. 8th Int. Conf. on Transport and Sedimentation of Solid Particles, 24-26 January 1995, Prague, Czech Republic.

40. Vlasblom, W.J. & Miedema, S.A., "A Theory for Determining Sedimentation and Overflow Losses in Hoppers (Adobe Acrobat 4.0 PDF-File 304 kB)". Proc. WODCON IV, November 1995, Amsterdam, The Netherlands 1995.

41. Miedema, S.A., "Production Estimation Based on Cutting Theories for Cutting Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 423 kB)". Proc. WODCON IV, November 1995, Amsterdam, The Netherlands 1995. Additional Specific Energy and Production Graphs. (Adobe Acrobat 4.0 PDF-File 145 kB).

42. Riet, E.J. van, Matousek, V. & Miedema, S.A., "A Theoretical Description and Numerical Sensitivity Analysis on Wilson's Model for Hydraulic Transport in Pipelines (Adobe Acrobat 4.0 PDF-File 50 kB)". Journal of Hydrology & Hydromechanics, Slovak Ac. of Science, Bratislava, June 1996.

43. Miedema, S.A. & Vlasblom, W.J., "Theory for Hopper Sedimentation (Adobe Acrobat 4.0 PDF-File 304 kB)". 29th Annual Texas A&M Dredging Seminar. New Orleans, June 1996.

44. Miedema, S.A., "Modeling and Simulation of the Dynamic Behavior of a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 318 kB)". 17th Annual Meeting & Technical Conference of the Western Dredging Association. New Orleans, June 1996.

45. Miedema, S.A., "Education of Mechanical Engineering, an Integral Vision". Faculty O.C.P., Delft University of Technology, 1997 (in Dutch).

46. Miedema, S.A., "Educational Policy and Implementation 1998-2003 (versions 1998, 1999 and 2000) (Adobe Acrobat 4.0 PDF_File 195 kB)". Faculty O.C.P., Delft University of Technology, 1998, 1999 and 2000 (in Dutch).

47. Keulen, H. van & Miedema, S.A. & Werff, K. van der, "Redesigning the curriculum of the first three years of the mechanical engineering curriculum". Proceedings of the International Seminar on Design in Engineering Education, SEFI-Document no.21, page 122, ISBN 2-87352-024-8, Editors: V. John & K. Lassithiotakis, Odense, 22-24 October 1998.

48. Miedema, S.A. & Klein Woud, H.K.W. & van Bemmel, N.J. & Nijveld, D., "Self Assesment Educational Programme Mechanical Engineering (Adobe Acrobat 4.0 PDF-File 400 kB)". Faculty O.C.P., Delft University of Technology, 1999.

49. Van Dijk, J.A. & Miedema, S.A. & Bout, G., "Curriculum Development Mechanical Engineering". MHO 5/CTU/DUT/Civil Engineering. Cantho University Vietnam, CICAT Delft, April 1999.

50. Miedema, S.A., "Considerations in building and using dredge simulators (Adobe Acrobat 4.0 PDF-File 296 kB)". Texas A&M 31st Annual Dredging Seminar. Louisville Kentucky, May 16-18, 1999.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

51. Miedema, S.A., "Considerations on limits of dredging processes (Adobe Acrobat 4.0 PDF-File 523 kB)". 19th Annual Meeting & Technical Conference of the Western Dredging Association. Louisville Kentucky, May 16-18, 1999.

52. Miedema, S.A. & Ruijtenbeek, M.G. v.d., "Quality management in reality", "Kwaliteitszorg in de praktijk". AKO conference on quality management in education. Delft University of Technology, November 3rd 1999.

53. Miedema, S.A., "Curriculum Development Mechanical Engineering (Adobe Acrobat 4.0 PDF-File 4 MB)". MHO 5-6/CTU/DUT. Cantho University Vietnam, CICAT Delft, Mission October 1999.

54. Vlasblom, W.J., Miedema, S.A., Ni, F., "Course Development on Topic 5: Dredging Technology, Dredging Equipment and Dredging Processes". Delft University of Technology and CICAT, Delft July 2000.

55. Miedema, S.A., Vlasblom, W.J., Bian, X., "Course Development on Topic 5: Dredging Technology, Power Drives, Instrumentation and Automation". Delft University of Technology and CICAT, Delft July 2000.

56. Randall, R. & Jong, P. de & Miedema, S.A., "Experience with cutter suction dredge simulator training (Adobe Acrobat 4.0 PDF-File 1.1 MB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

57. Miedema, S.A., "The modelling of the swing winches of a cutter dredge in relation with simulators (Adobe Acrobat 4.0 PDF-File 814 kB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

58. Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges (Adobe Acrobat 4.0 PDF-File 257 kB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

59. Miedema, S.A., "Automation of a Cutter Dredge, Applied to the Dynamic Behaviour of a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 254 kB)". Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.

60. Heggeler, O.W.J. ten, Vercruysse, P.M., Miedema, S.A., "On the Motions of Suction Pipe Constructions a Dynamic Analysis (Adobe Acrobat 4.0 PDF-File 110 kB)". Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.

61. Miedema, S.A. & Zhao Yi, "An Analytical Method of Pore Pressure Calculations when Cutting Water Saturated Sand (Adobe Acrobat PDF-File 2.2 MB)". Texas A&M 33nd Annual Dredging Seminar, June 2001, Houston, USA 2001.

62. Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport (Adobe Acrobat PDF-File 246 kB)". 21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.

63. Zhao Yi, & Miedema, S.A., "Finite Element Calculations To Determine The Pore Pressures When Cutting Water Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB)". CEDA Dredging Day 2001, November 2001, Amsterdam, The Netherlands.

64. Miedema, S.A., "Mission Report Cantho University". MHO5/6, Phase Two, Mission to Vietnam by Dr.ir. S.A. Miedema DUT/OCP Project Supervisor, 27 September-8 October 2001, Delft University/CICAT.

65. (Zhao Yi), & (Miedema, S.A.), "

" (Finite Element Calculations To Determine The Pore Pressures When Cutting Water

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB))". To be published in 2002.

66. Miedema, S.A., & Riet, E.J. van, & Matousek, V., "Theoretical Description And Numerical Sensitivity Analysis On Wilson Model For Hydraulic Transport Of Solids In Pipelines (Adobe Acrobat PDF-File 147 kB)". WEDA Journal of Dredging Engineering, March 2002.

67. Miedema, S.A., & Ma, Y., "The Cutting of Water Saturated Sand at Large Cutting Angles (Adobe Acrobat PDF-File 3.6 MB)". Proc. Dredging02, May 5-8, Orlando, Florida, USA.

68. Miedema, S.A., & Lu, Z., "The Dynamic Behavior of a Diesel Engine (Adobe Acrobat PDF-File 363 kB)". Proc. WEDA XXII Technical Conference & 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.

69. Miedema, S.A., & He, Y., "The Existance of Kinematic Wedges at Large Cutting Angles (Adobe Acrobat PDF-File 4 MB)". Proc. WEDA XXII Technical Conference & 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.

70. Ma, Y., Vlasblom, W.J., Miedema, S.A., Matousek, V., "Measurement of Density and Velocity in Hydraulic Transport using Tomography". Dredging Days 2002, Dredging without boundaries, Casablanca, Morocco, V64-V73, 22-24 October 2002.

71. Ma, Y., Miedema, S.A., Vlasblom, W.J., "Theoretical Simulation of the Measurements Process of Electrical Impedance Tomography". Asian Simulation Conference/5th International Conference on System Simulation and Scientific Computing, Shanghai, 3-6 November 2002, p. 261-265, ISBN 7-5062-5571-5/TP.75.

72. Thanh, N.Q., & Miedema, S.A., "Automotive Electricity and Electronics". Delft University of Technology and CICAT, Delft December 2002.

73. Miedema, S.A., Willemse, H.R., "Report on MHO5/6 Mission to Vietnam". Delft University of Technology and CICAT, Delft Januari 2003.

74. Ma, Y., Miedema, S.A., Matousek, V., Vlasblom, W.J., "Tomography as a Measurement Method for Density and Velocity Distributions". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

75. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of a Development of a Density Wave in a Long Slurry Pipeline". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

76. Miedema, S.A., Lu, Z., Matousek, V., "Numerical simulation of the development of density waves in a long pipeline and the dynamic system behavior". Terra et Aqua, No. 93, p. 11-23.

77. Miedema, S.A., Frijters, D., "The Mechanism of Kinematic Wedges at Large Cutting Angles - Velocity and Friction Measurements". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

78. Tri, Nguyen Van, Miedema, S.A., Heijer, J. den, "Machine Manufacturing Technology". Lecture notes, Delft University of Technology, Cicat and Cantho University Vietnam, August 2003.

79. Miedema, S.A., "MHO5/6 Phase Two Mission Report". Report on a mission to Cantho University Vietnam October 2003. Delft University of Technology and CICAT, November 2003.

80. Zwanenburg, M., Holstein, J.D., Miedema, S.A., Vlasblom, W.J., "The Exploitation of Cockle Shells". CEDA Dredging Days 2003, Amsterdam, The Netherlands, November 2003.

81. Zhi, L., Miedema, S.A., Vlasblom, W.J., Verheul, C.H., "Modeling and Simulation of the Dynamic Behaviour of TSHD's Suction Pipe System by using Adams". CHIDA Dredging Days, Shanghai, China, november 2003.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

82. Miedema, S.A., "The Existence of Kinematic Wedges at Large Cutting Angles". CHIDA Dredging Days, Shanghai, China, november 2003.

83. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of the Development of Density Waves in a Long Pipeline and the Dynamic System Behaviour". Terra et Aqua 93, December 2003.

84. Miedema, S.A. & Frijters, D.D.J., "The wedge mechanism for cutting of water saturated sand at large cutting angles". WODCON XVII, September 2004, Hamburg Germany.

85. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "The development of a concept for accurate and efficient dredging at great water depths". WODCON XVII, September 2004, Hamburg Germany.

86. Miedema, S.A., "THE CUTTING MECHANISMS OF WATER SATURATED SAND AT SMALL AND LARGE CUTTING ANGLES". International Conference on Coastal Infrastructure Development - Challenges in the 21st Century. HongKong, november 2004.

87. Ir. M. Zwanenburg , Dr. Ir. S.A. Miedema , Ir J.D. Holstein , Prof.ir. W.J.Vlasblom, "REDUCING THE DAMAGE TO THE SEA FLOOR WHEN DREDGING COCKLE SHELLS". WEDAXXIV & TAMU36, Orlando, Florida, USA, July 2004.

88. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "A new concept for accurate and efficient dredging in deep water". Ports & Dredging, IHC, 2005, E163.

89. Miedema, S.A., "Scrapped?". Dredging & Port Construction, September 2005. 90. Miedema, S.A. & Vlasblom, W.J., " Bureaustudie Overvloeiverliezen". In opdracht

van Havenbedrijf Rotterdam, September 2005, Confidential. 91. He, J., Miedema, S.A. & Vlasblom, W.J., "FEM Analyses Of Cutting Of Anisotropic

Densely Compacted and Saturated Sand", WEDAXXV & TAMU37, New Orleans, USA, June 2005.

92. Miedema, S.A., "The Cutting of Water Saturated Sand, the FINAL Solution". WEDAXXV & TAMU37, New Orleans, USA, June 2005.

93. Miedema, S.A. & Massie, W., "Selfassesment MSc Offshore Engineering", Delft University of Technology, October 2005.

94. Miedema, S.A., "THE CUTTING OF WATER SATURATED SAND, THE SOLUTION". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

95. Miedema, S.A., "La solution de prélèvement par désagrégation du sable saturé en eau". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

96. Miedema, S.A. & Vlasblom, W.J., "THE CLOSING PROCESS OF CLAMSHELL DREDGES IN WATER-SATURATED SAND". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

97. Miedema, S.A. & Vlasblom, W.J., "Le processus de fermeture des dragues à benne preneuse en sable saturé". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

98. Miedema, S.A. "THE CUTTING OF WATER SATURATED SAND, THE SOLUTION". The 2nd China Dredging Association International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

99. Ma, Y, Ni, F. & Miedema, S.A., "Calculation of the Blade Cutting Force for small Cutting Angles based on MATLAB". The 2nd China Dredging Association

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

100. ,"" (download). The 2nd China Dredging

Association International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

101. Miedema, S.A. , Kerkvliet, J., Strijbis, D., Jonkman, B., Hatert, M. v/d, "THE DIGGING AND HOLDING CAPACITY OF ANCHORS". WEDA XXVI AND TAMU 38, San Diego, California, June 25-28, 2006.

102. Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

103. Miedema, S.A., "Polytechnisch Zakboek 51ste druk, Hoofdstuk G: Werktuigbouwkunde", pG1-G88, Reed Business Information, ISBN-10: 90.6228.613.5, ISBN-13: 978.90.6228.613.3. Redactie: Fortuin, J.B., van Herwijnen, F., Leijendeckers, P.H.H., de Roeck, G. & Schwippert, G.A.

104. MA Ya-sheng, NI Fu-sheng, S.A. Miedema, "Mechanical Model of Water Saturated Sand Cutting at Blade Large Cutting Angles", Journal of Hohai University Changzhou, ISSN 1009-1130, CN 32-1591, 2006. 绞刀片大角度切削水饱和沙的力学模型, 马亚生[1] 倪福生[1] S.A.Miedema[2], 《河海大学常州分校学报》-2006年20卷3期 -59-61页

105. Miedema, S.A., Lager, G.H.G., Kerkvliet, J., “An Overview of Drag Embedded Anchor Holding Capacity for Dredging and Offshore Applications”. WODCON, Orlando, USA, 2007.

106. Miedema, S.A., Rhee, C. van, “A SENSITIVITY ANALYSIS ON THE EFFECTS OF DIMENSIONS AND GEOMETRY OF TRAILING SUCTION HOPPER DREDGES”. WODCON ORLANDO, USA, 2007.

107. Miedema, S.A., Bookreview: Useless arithmetic, why environmental scientists can't predict the future, by Orrin H. Pilkey & Linda Pilkey-Jarvis. Terra et Aqua 108, September 2007, IADC, The Hague, Netherlands.

108. Miedema, S.A., Bookreview: The rock manual: The use of rock in hydraulic engineering, by CIRIA, CUR, CETMEF. Terra et Aqua 110, March 2008, IADC, The Hague, Netherlands.

109. Miedema, S.A., "An Analytical Method To Determine Scour". WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.

110. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells". WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.

111. Miedema, S.A., "An Analytical Approach To The Sedimentation Process In Trailing Suction Hopper Dredgers". Terra et Aqua 112, September 2008, IADC, The Hague, Netherlands.

112. Hofstra, C.F., & Rhee, C. van, & Miedema, S.A. & Talmon, A.M., "On The Particle Trajectories In Dredge Pump Impellers". 14th International Conference Transport & Sedimentation Of Solid Particles. June 23-27 2008, St. Petersburg, Russia.

113. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells". WEDA Journal of Dredging Engineering, December 2008.

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema

114. Miedema, S.A., "New Developments Of Cutting Theories With Respect To Dredging, The Cutting Of Clay And Rock". WEDA XXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.

115. Miedema, S.A., "A Sensitivity Analysis Of The Scaling Of TSHD's". WEDA XXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.

116. Liu, Z., Ni, F., Miedema, S.A., “Optimized design method for TSHD’s swell compensator, basing on modelling and simulation”. International Conference on Industrial Mechatronics and Automation, pp. 48-52. Chengdu, China, May 15-16, 2009.

117. Miedema, S.A., "The effect of the bed rise velocity on the sedimentation process in hopper dredges". Journal of Dredging Engineering, Vol. 10, No. 1 , 10-31, 2009.

118. Miedema, S.A., “New developments of cutting theories with respect to offshore applications, the cutting of sand, clay and rock”. ISOPE 2010, Beijing China, June 2010.

119. Miedema, S.A., “The influence of the strain rate on cutting processes”. ISOPE 2010, Beijing China, June 2010.

120. Ramsdell, R.C., Miedema, S.A., “Hydraulic transport of sand/shell mixtures”. WODCON XIX, Beijing China, September 2010.

121. Abdeli, M., Miedema, S.A., Schott, D., Alvarez Grima, M., “The application of discrete element modeling in dredging”. WODCON XIX, Beijing China, September 2010.

122. Hofstra, C.F., Miedema, S.A., Rhee, C. van, “Particle trajectories near impeller blades in centrifugal pumps. WODCON XIX, Beijing China, September 2010.

123. Miedema, S.A., “Constructing the Shields curve, a new theoretical approach and its applications”. WODCON XIX, Beijing China, September 2010.

124. Miedema, S.A., “The effect of the bed rise velocity on the sedimentation process in hopper dredges”. WODCON XIX, Beijing China, September 2010.

 

Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

Copyright: Dr.ir. S.A. Miedema