bluuebunny/crossref_metadata_2025 huggingface dataset:
A variable gain amplifier using a very‐high speed OTA
Authors: Zheng You , Saavedra Carlos E.
Published: March 2010

A variable gain amplifier is demonstrated using only one fully‐differential operational transconductance amplifier (OTA) as the core circuit element.Gain control is achieved by varying the transconductance of the OTA and by using an output buffer circuit to sum the output signals of the OTA in the correct phase relationship. The circuit was designed and fabricated using 0.18 μm CMOS technology. Measured results show a gain control range of 15 dB between 1 GHz and 3 GHz and the input and output reflection coefficients are below −10 dB and −20 dB, respectively. The output power of the amplifier is +2.3 dBm at its 1‐dB compression point. The chip has a maximum DC power consumption 12.6 mW and it measures 0.25 mm2 including bonding pads. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1112–1116, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25114
An integrated compact coplanar waveguide high‐pass filter implemented on high resistivity silicon substrate
Authors: Hung Cheng‐Yuan , Weng Min‐Hang , Yang Ru‐Yuan , Wu Hung‐Wei
Published: March 2010

In this article, the fabrication of a compact and high performance semi‐lumped coplanar waveguide high‐pass filter (CPW‐HPF) implemented on high resistivity silicon (HRS) substrate is proposed.The design procedure and the equivalent circuit of the proposed semi‐lumped CPW‐HPF is discussed. The filter structure is simple, and the performances are fairly good. This designed filter at cutoff frequency fc of 21.6 GHz has very good measured characteristics including a balance passband of S21 of −0.5 ± 0.3 dB and a sharp band edge rejection. Experimental results of the fabricated filter show a good agreement with the predicted results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1150–1153, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25116
Design of compact and wideband metamaterial balun based on closed‐form solutions
Authors: Jung Youn‐Kwon , Lee Bomson
Published: March 2010

This letter presents a very compact (17.5 mm × 24.2 mm or 0.18 λ0 × 0.24 λ0) and wideband balun at 3 GHz designed using the derived closed‐form solutions. The EM‐simulated difference of the transmitted signals at two ports is less than 0.6 dB from 2.45 to 6 GHz (118% at 3 GHz). Based on 180° ± 10° phase difference, the measured bandwidth of the proposed balun is 3.84 GHz from 2.16 to 6 GHz (or 128% at 3 GHz). © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1153–1156, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25117
Design of planar bandpass filters from tapered slot resonators
Authors: Abbosh Amin , Bialkowski Marek , Thiel David
Published: March 2010

A compact planar bandpass filter is designed using a tapered slot resonator, which is formed using two tapered slot antennas connected in a face‐to‐face configuration. The tapering profile and dimensions of the resonator control the characteristics of the filter. The success of the method is demonstrated via full wave electromagnetic simulations and measurements. Passbands of 30–50% centred at about 6 GHz with an insertion loss of less than 1 dB and a peak‐to‐peak group delay of less than 0.5 ns are achieved in two filters having different tapering profiles and fabricated on RT6010 substrate with an overall dimension of 25 mm × 30 mm. The use of an open‐ended series stub within the coplanar waveguide feeder of the filters extends their high stopband beyond 15 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1190–1194, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25118
Dual‐band unequal Wilkinson power divider with reduced length
Authors: Kim TaeGyu , Lee Byungje , Park Myun‐Joo
Published: March 2010

A new dual‐band Wilkinson divider structure is proposed for the arbitrary power division ratio and matched output ports.The compact dual‐band stubbed Π sections are employed in both the Wilkinson divider and the output matching section. It has simple structure based on the compact open stub topology and the overall divider length can be reduced in half as compared with similar works based on the two cascaded section transformers. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1187–1190, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25119
Coplanar stripline ultra‐wideband compact uniplanar bandpass filter with a notched band
Authors: Mandal Mrinal Kanti , Chen Zhi Ning
Published: March 2010

In this article, a coplanar stripline (CPS) coupling configuration is presented for a compact, ultra‐wideband (UWB), uniplanar bandpass filter with a notched band.The passband width of the filter is greatly increased by adding two parallel strips with a coupled‐CPS section. Furthermore, spur line is used to create a notched band in the UWB passband to reject the undesired wireless local‐area network radio signals in 5 GHz bands. The notched band can be tuned by varying the spur line length. One prototype bandpass filter is fabricated with overall size of 17 × 7.2 mm2on a 0.813‐mm thick substrate with dielectric constant of εr= 3.38. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1201–1203, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25124
The hybrid higher order MoM‐UTD formulation for electromagnetic radiation problems
Authors: Liu Zi‐Liang , Yang Juan , Liang Chang‐Hong
Published: March 2010

This article presents a new efficient hybrid higher order MoM‐UTD method. It overcomes the limitation of traditional MoM‐UTD method, which is difficult to be applied to the arbitrary structures because of complex ray tracing. Using the large quadrilateral patches and higher order basis functions, the hybrid method in this article can save much more computer memory than the traditional low‐order MoM with RWG basis functions. So, it is feasible for complex and electrically large structures. Good accuracy is achieved as the numerical results illustrated. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1087–1091, 2010; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.25125
Develop compact dual‐band bandpass filters on the aluminum oxide
Authors: Yang Hung‐Chi , Yang Cheng‐Fu , Cheng Chien‐Ming
Published: March 2010

For the purpose of minimizing the dual‐band bandpass filters (2.4 and 5.7 GHz), two stepped impedance resonator structures are modified and involved in a pair of distorted coupled lines to form a compact structure.And because the designed filter is printed on the high quality factor and dielectric constant aluminum oxide ceramic substrate by the screen‐printing technique, the characteristics of the filters could be improved and the size of the filters could be minimized to only 22.2 × 12 mm2. Furthermore, the modified SIR structure can be used to tune the second resonant frequency (harmonic) for the applications of dual bands, and the modified coupled line structures can be used to excite additional transmission zeros and adjust its locations, which can improve the characteristics of the filters effectively. In this article, the optimum measured insertion loss and bandwidth for 2.4 GHz are −0.98 dB and 11.1%, respectively, and for 5.7 GHz are −1.05 dB and 10.1%, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1091–1094, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25126
Design of a new type of metamaterial radome for low frequencies
Authors: Latrach M. , Rmili H. , Sabatier C. , Seguenot E. , Toutain S.
Published: March 2010

A new type of radome was designed around 2 GHz, comprising alternately layers with negative permeability and positive index of refraction materials.The negative permeability, obtained by the square ring resonators (SRRs) network and the thickness of the radome are optimized so that the radiated electromagnetic waves generated by the antenna are passing through with minimum reflection. The compact electrical size of the SRR structure (∼λ/20) was obtained by optimizing the geometrical and electrical parameters as increasing the coupling between the resonators. The effect of the radome on the antenna characteristics is evaluated by simulation and measurements with good agreement. Enhancements of the gain, directivity, and impedance bandwidth are also observed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1119–1123, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25127
The compact 3‐stage 2.4/5.2 GHz bandpass filter with modified winding hairpin structure and insert coupling
Authors: Kung Cheng‐Yuan , Chen Yin‐Chung , Yang Cheng‐Fu , Huang Chih‐Yu
Published: March 2010

Two hairpin resonators, one “Z‐type” modified stepped‐impedance resonator, and two transmission lines are composed to design the compact and miniature dual‐band bandpass filters (BPFs).The designed BPFs are presented to operate at 2.4/5.2 GHz for industrial, scientific, and medical (ISM, 2.4 GHz) and WLAN applications (2.4/5.2 GHz) without additional impedance matching network. The 2.4 GHz and 5.2 GHz dual‐band can be simultaneously excited and tuned by adjusting the electric length ratio (θ) and characteristic impedance ratio (K) of resonators. Cascaded arrangement is designed for wide bandwidth and high out‐of‐band rejection, and the “Z‐type” resonator and insert coupled modification are used to increase the utility rate of space and reduce the size of designed filter. Al2O3 ceramic with thickness of 0.635 mm and dielectric constant of 9.4 used as the substrate, and the designed filters are fabricated by printing method. Because of higher dielectric constant substrate and modified structure, the proposed filters show the advantages of wide bandwidth, low insertion loss, high out‐of‐band rejection, simple circuit, and tiny size. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1156–1159, 2010; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.25128
Wideband dual‐polarized stacked‐patch antenna array for base stations
Authors: Serra A.A. , Nepa P. , Manara G. , Cioci S. , Tribellini G.
Published: March 2010

In this article, a 16‐element antenna array for wireless communication services is presented. The antenna operates in the universal mobile telecommunications system (UMTS), ISM, 2.4 GHz worldwide interoperability for microwave access, and in the new UMTS 3G expansion band from 2500 to 2690 MHz. A prototype of the antenna has been realized and measured. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1048–1052, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25131
Design of experiments as a microwave CAD tool
Authors: Naishadham Krishna
Published: March 2010

With the increase in geometrical and physical complexity of microwave circuits, statistical techniques to reduce the design cycles continue to grow in importance.The objective of this article is to review the theory of a statistical design tool called the design of experiments (DOE) and discuss its utility in developing Computer‐aided design models for microwave circuits. A circuit example of DOE application, pertaining to identification of dominant sources of variation in the return loss of a coplanar waveguide flip‐chip interconnect package, is reviewed. An empirical design formula is developed for the return loss based on regression analysis, which demonstrates that interaction between factors cannot be neglected, as is the norm in trialanderror analysis using one factor at a time. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1020–1024, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25133
TEM horn antenna for near‐field microwave imaging
Authors: Campbell Mark A. , Okoniewski Michal , Fear Elise C.
Published: March 2010

Antennas capable of sending and receiving ultra‐wideband pulses are required for radar‐based microwave breast imaging.This article describes a TEM horn antenna designed to operate over a 2–12 GHz band with specific radiated near‐field characteristics. Simulations and experimental measurements are presented, including detection of objects representing tumors. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1164–1170, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25136
Planar ultrawideband antenna array for short‐range wireless communications
Authors: Ahmed Osama M. H. , Sebak Abdel‐Razik
Published: March 2010

In this article, novel 2‐element and 4‐element planar ultrawideband (UWB) antenna arrays with bidirectional radiation patterns based on identical UWB antenna elements for UWB communications applications have been proposed, simulated and experimentally investigated. Each array is constructed by means of feeding omni‐directional printed UWB monopole antennas with a UWB power divider. The proposed 2‐element antenna array yields an impedance bandwidth of 110% (3.1–10.6 GHz) covering the whole UWB frequency bandwidth while the impedance bandwidth is multi‐band in case of the 4‐element antenna array because of the increasing effect of mutual coupling among antenna elements. The calculated gain of the 2‐element and 4‐element array is quite stable with about 3 and 6 dB higher than that of the single element, respectively. Both measured and calculated E‐plane radiation patterns of the array and the single element are almost the same while the H‐plane radiation patterns of the array are distinctively bidirectional compared to the omni‐directional pattern of the single element. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1061–1066, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25140
Dual‐band antenna design using genetic algorithm‐generated topology
Authors: Kim Jae Hee , Park Wee Sang
Published: March 2010

This article represents an antenna topology selection for dual‐band mobile phone using an optimization technique that applies a genetic algorithm (GA) in the early stage of the design. Commercial software (CST MWS) is used to predict the performance of the antenna. Then, the fitness function is evaluated by integrating the CST with the GA using visual basic language. After the antenna topology was selected, a dual‐band antenna for GSM and DCS applications was designed by adding a parasitic line. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1170–1174, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25141
CPW‐based composite right/left‐handed transmission line and UWB‐filter application
Authors: Liu Chuan‐Yun , Chu Qing‐Xin
Published: March 2010

A coplanar‐waveguide‐based (CPW‐based) composite right/left‐handed (CRLH) transmission line (TL) is proposed. By introducing parallel‐plate capacitors to enlarge the distributed series capacitance, it can be exploited in diverse miniaturized components. In addition, planar structure is easier to implement. Using such a structure, an ultra‐wideband (UWB) filter is proposed. Two transmission zeros are located close to the passband edges, which makes a good selectivity and stopband rejection of the filter. The fractional 3‐dB bandwidth is larger than 71%. Agreements between simulated and measured responses of the filter are demonstrated. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1024–1027, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25143
Concepts for millimeter‐wave waveguide‐MEMS phase shifters
Authors: Hesselbarth Jan , Vahldieck Ruediger
Published: March 2010

This article presents concepts for MEMS‐enabled low‐loss millimeter‐wave metal ridge waveguide phase shifters. Design examples for 80 GHz show 2.6 dB insertion loss for 90° continuously variable phase shift and 1.6 dB insertion loss for 140° phase shift, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1028–1030, 2010; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.25144
A novel chirp‐coded en/decoder for coherent 2D time‐wavelength OCDMA systems
Authors: Zheng Jilin , Wang Rong , Pu Tao , Lu Lin , Fang Tao , Cheng Yun , Chen Xiangfei
Published: March 2010

A novel fiber Bragg grating (FBG)‐based chirp‐coded en/decoder is proposed for a coherent two‐dimensional (2D) time‐spreading wavelength‐hopping optical code‐division multiple‐access system. Combined with reconstruction‐equivalent‐chirp technology, the proposed coder can be easily realized in a single FBG with a conventional fabrication setup. Compared with other 2D encoders, the chirp‐coded encoders are expected to provide enhanced security, increased power efficiency, expanded code cardinality, and reduced coherent beat noise. Experimental results of such en/decoders and the corresponding system test‐bed at a data rate of 5 Gb/s verify the feasibility. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1104–1106, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25147
Bandwidth enhancement of small‐size internal WWAN laptop computer antenna using a resonant open slot embedded in the ground plane
Authors: Wong Kin‐Lu , Lee Li‐Chun
Published: March 2010

A new bandwidth‐enhancement method of using a resonant open slot embedded in the ground plane or supporting metal frame of the display panel for a small‐size internal wireless wide area network (WWAN) laptop computer antenna is presented.To demonstrate the results, a small‐size printed monopole slot antenna with a length of 50 mm only, which is about the smallest among the internal WWAN laptop computer antenna that have been reported, is applied in this study. For such a small‐size WWAN antenna, the impedance matching in the 900‐MHz band is usually very poor and hence the obtained antenna's lower band cannot cover the desired GSM850/900 operation. By embedding a resonant open slot in the ground plane, which does not increase the size of the internal WWAN antenna, a wideband resonant mode with good impedance matching at about 900 MHz contributed by the resonant open slot can be generated to cover the GSM850/900 operation. Further, a wide upper band for the antenna to cover the GSM1800/1900/UMTS operation can also be obtained. Details of the proposed bandwidth‐enhancement method are studied in this article. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1137–1142, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25148
Harmonic pass‐band suppression in coupled‐serial‐shunted lines Elliptic band‐pass filters
Authors: Tsai Lin‐Chuan
Published: March 2010

A synthesizing method is presented to design Elliptic band‐pass filters in the microwave frequency range. The Elliptic band‐pass filter is implemented by using a coupled‐serial‐shunted line structure. Using a continuous perturbation of wiggly‐groove and ring resonator of the couple line the harmonic pass‐band of the filter is rejected. An Elliptic band‐pass filter is implemented to validate this method correct by measuring. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1177–1179, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25151
Low mutual coupling 2 × 2 microstrip patch array antenna by using novel shapes of defect ground structure
Authors: Elsheakh Dalia N. , Elsadek Hala A. , Abdallah Esmat A. , Iskander Magdy F. , Elhenawy Hadia
Published: March 2010

In this article, to reduce the mutual coupling between the arrays patch antennas, electromagnetic band‐gap structure has been used as defected ground structure (DGS).Novel shapes of DGS are investigated to provide good band‐gap features and decrease the surface wave propagation. The mutual coupling of microstrip patch array antenna (MPAA) is parametrically studied, including both E‐ and H‐coupling directions, with different substrate thickness and various dielectric constants. The new DGS shapes applied on both 2 × 2 MPAA with line feed and coaxial feed array then applied on 2 × 2 planar‐inverted F antenna array antenna for improved performance and reduced overall size. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1208–1215, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25152
C‐shaped ultra‐wideband bandpass filter with WLAN notch band
Authors: Hsiao Pai‐Yi , Weng Ro‐Min
Published: March 2010

A compact bandpass filter (BPF) embedded with 5.8 GHz wireless‐LAN notch is presented for 3.1–10.6 GHz ultra‐wideband (UWB) systems. The proposed UWB‐BPF based on a defect‐grounded structure is implemented with an FR4 board. Two open‐loop resonators on the top layer provide a narrow notch band whose center frequency can be easily adjusted by varying the sizes of the open‐loop. A simple C‐shaped slot on the bottom ground layer is adopted to improve the bandwidth performance. The characteristics of UWB‐BPF are analyzed and simulated using a circuit model of LC lump elements. The size of the filter is at least 34% less than those filters with the same specification. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1215–1218, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25153
Structure elucidation of new oleanane‐type glycosides from three species of Acanthophyllum
Authors: Timité Gaoussou , Mitaine‐Offer Anne‐Claire , Miyamoto Tomofumi , Ramezani Mohammad , Rustaiyan Abdolhossein , Mirjolet Jean‐François , Duchamp Olivier , Lacaille‐Dubois Marie‐Aleth
Published: March 2010

From the roots of three species of Acanthophyllum (Caryophyllaceae), two new gypsogenic acid glycosides, 1 and 2, were isolated, 1 from A. sordidum and A. lilacinum, 2 from A. elatius and A. lilacinum, together with three known saponins, glandulosides B and C, and SAPO50. The structures of 1 and 2 were established mainly by 2D NMR techniques as 23‐O‐β‐D‐galactopyranosylgypsogenic acid‐28‐O‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→6)]‐β‐D‐galactopyranoside (1) and gypsogenic acid‐28‐O‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→6)]‐β‐D‐galactopyranoside (2). The cytotoxicity of several of these saponins was evaluated against two human colon cancer cell lines (HT‐29 and HCT 116). Copyright © 2010 John Wiley & Sons, Ltd.
Numerical optimization for constrained image registration
Authors: Haber Eldad , Horesh Raya , Modersitzki Jan
Published: March 2010

Image registration or image matching is a technique to establish meaningful correspondences between points in different scenes. It is a mandatory tool for various applications in medicine, geoscience, and other disciplines. However, obtaining plausible deformations is a complex task. For example, many applications require the transformations to be locally invertible, or even harder, keep volume changes within a reasonable bandwidth.

In this work, solutions to the registration problem are obtained by direct imposition of a volume constraint on each voxel in a discretized domain. In contrast to previous work, the focus here is on development of an efficient and robust numerical algorithm and in particular, the study of an augmented Lagrangian method with a multigrid solver. The paper demonstrates that this combination yields an almost optimal solver (i.e. linear time) for the problem. Copyright © 2010 John Wiley & Sons, Ltd.
Time‐continuous modeling of microstructures in single‐slip finite elasto‐plasticity based on energy relaxation
Authors: Kochmann Dennis M. , Hackl Klaus
Published: March 2010

The non‐(quasi)convexity of the free energy of single crystals in finite elasto‐plasticity gives rise to the formation of fine‐scale fluctuations of the displacement field, which can be interpreted as material microstructures. We outline a numerical procedure to model the origin and subsequent evolution of laminate microstructures. This approach incrementally solves the evolution equations by employing relaxed energy potentials. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FE2‐Simulations in Elasto‐Plasticity using Statistically Similar Representative Volume Elements
Authors: Balzani Daniel , Schröder Jörg , Brands Dominik , Carstensen Carsten
Published: March 2010

In the field of direct homogenization methods large representative volume elements (RVE's) cause a high computational cost, which is indicated by a large number of history variables allocating a large amount of memory. Additionally, a high computation time is necessary to solve the systems of equations on the micro‐scale as well as on the macro‐scale. In this contribution we focus on random microstructures consisting of a continuous matrix phase with a high number of embedded inclusions with arbitrary morphology. We present a method for the construction of statistically similar representative volume elements (SSRVE's) which are characterized by a much less complexity than usual RVE's in order to obtain an efficient simulation tool. The basic goal of the underlying procedure is to find a SSRVE, where some selected statistical measures describing the inclusion morphology are as close as possible to the ones of the original arbitrary microstructure. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Model for the Evolution of Laminates
Authors: Hackl Klaus , Heinz Sebastian , Mielke Alexander
Published: March 2010

We study the time evolution of a generalized standard material in elastoplasticity. Of our particular interest are the formation and the evolution of microstructure. Our aim is to prove the existence of solutions. This is a challenging task, since the presence of microstructure comes along with a lack of convexity and, hence, compactness arguments cannot be applied to prove the existence of solutions. In order to overcome this problem, we will incorporate information on the microstructure into the internal variable, which is still compatible with the notion of generalized standard materials. More precisely, we shall allow such forms of microstructure that are given by simple laminates. We will consider a model for the evolution of these laminates and we will state a result on the existence of solutions to the time‐incremental minimization problem. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigations on autogenous shrinkage of cement paste and mortar
Authors: Leusmann Thorsten , Nothnagel Reinhard
Published: March 2010

Autogenous shrinkage of cement paste and concrete is defined as the macroscopic length change occurring with no moisture transferred to the exterior surrounding environment. It is a result of chemical shrinkage affiliated with the hydration of cement particles and the ongoing process of self‐desiccation. The process of self‐desiccation can be modeled starting from the formation of the capillary pore space during hydration in the cement paste. In this proposal a working model will be introduced explaining the difficulties to obtain the autogenous shrinkage strains directly from a simulated or measured microstructure of cement paste. In a second step the autogenous shrinkage of a hardening cement mortar was described on a mesoscopic level. It based on measurements on cement paste. The mortar simply consists of cement paste and a defined fraction of spherical aggregates with a known modulus of elasticity. Furthermore the influence of the interfacial transition zone (ITZ) is studied in numerical simulations. The results of these finite‐element‐calculations are introduced and compared with testing results of the autogenous shrinkage of hardening mortar samples. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
3D modelling of arterial growth for adaptation to hypertension — the influence of transmural changes in the mechanical environment
Authors: Schmid Holger , Watton Paul , Röhrle Oliver , Wang Yikun , Itskov Mikhail
Published: March 2010

Many phenomenological models of cerebral aneurysm formation have been proposed. Such studies have focused on modeling the structural adaption of the arterial wall. However, further development is required to accurately represent the underlying mechanobiology during growth and remodeling processes. Here, we present a 3D computational model that incorporates transmurally heterogeneous material concentrations. This is a critical step toward more realistic models for growth and adaptation. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Simulations of Arterial Walls Based on IVUS‐Data
Authors: Brands Dominik , Schröder Jörg , Klawonn Axel , Rheinbach Oliver , Böse Dirk , Erbel Raimund
Published: March 2010

Atherosclerosis has become one of the most frequent causes of death in the last decades. So the analysis and improvement of corresponding medical treatments, e.g., balloon‐angioplasty or stenting, are significant tasks in the fields of biomechanics and biomedical engineering. One important component of the simulation of arterial walls, especially of atherosclerotically degenerated ones, is the knowledge of their anatomical and physiological composition. The intravascular ultrasound and the interpretation by the Virtual Histology provide cross‐sectional images of the diseased arterial walls where the different components are characterized by color‐coding. The topic of this contribution is the 3D reconstruction and discretization of the artery using these color‐coded images and the biplane angiography. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐domain analysis of wave propagation in unbounded domains based on the scaled boundary finite element method
Authors: Birk Carolin
Published: March 2010

Transient wave propagation in unbounded domains is considered in this paper. The scaled boundary finite element method is used to model the far field. This technique is originally formulated in the frequency‐domain. Two extensions of the method which lead to a direct description of the unbounded medium in the time‐domain are described, that is the rational approximation and the continued‐fraction expansion of the dynamic stiffness. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large Scale Simulation with Scaled Boundary Finite Element Method
Authors: Schauer Marco , Lehmann Lutz
Published: March 2010

Nowadays scientific and engineering applications often require wave propagation in infinite or unbounded domains. In order to model such applications we separate our model into near‐field and far‐field. The near‐field is represented by the well‐known finite element method (FEM), whereas the far‐field is mapped by a scaled boundary finite element (SBFE) approach. This latter approach allows wave propagation in infinite domains and suppresses the reflection of waves at the boundary, thus being a suitable method to model wave propagation to infinity. It is non‐local in time and space. From a computational point of view, those characteristics are a drawback because they lead to storage consuming calculations with high computational time‐effort. The non‐locality in space causes fully populated unit‐impulse acceleration influence matrices for each time step, leading to immense storage consumption for problems with a large number of degrees of freedom. Additionally, a different influence matrix has to be assembled for each time step which yields unacceptable storage requirements for long simulation times. For long slender domains, where many nodes are rather far from each other and where the influence of the degrees of freedom of those distant nodes is neglectable, substructuring represents an efficient method to reduce storage requirements and computational effort. The presented simulation with substructuring still yields satisfactory results. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics and control of underactuated mechanical systems: analysis and simple experimental verification
Authors: Blajer Wojciech , Dziewiecki Krzysztof , Kołodziejczyk Krzysztof , Mazur Zenon
Published: March 2010

Underactuated mechanical systems are systems with fewer control inputs than the degrees of freedom, m < n, the relevant technical examples being e.g. cranes, aircrafts and flexible manipulators. The determination of an input control strategy that forces an underactuated system to complete a set of m specified motion tasks (servo‐constraints) is a demanding problem. The solution is conditioned to differential flatness of the problem, denoted that all 2n state variables and m control inputs can algebraically be expressed, at least theoretically, in terms of the desired m outputs and their time derivatives up to a certain order. A more practical formulation, motivated hereafter, is to pose the problem as a set of differential‐algebraic equations, and then obtain the solution numerically. The theoretical considerations are illustrated by a simple two‐degree‐of‐freedom underactuated system composed of two rotating discs connected by a flexible rod (torsional spring), in which the pre‐specified motion of the first disc is actuated by the torque applied to the second disc, n = 2 and m = 1. The determined control strategy is then verified experimentally on a laboratory stand representing the two‐disc system. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical behavior of washing machines
Authors: Gödecker Holger , von Wagner Utz , Heubner Axel
Published: March 2010

Due to the maximum rotational speed of modern washing machines (1600 rpm) and the resulting high excitation forces, an appropriate modeling of the dynamical behavior is of interest. As an example, different models of a front‐end loader fabricated by Bosch Siemens Hausgeräte GmbH (BSH) are discussed. Using AUTOLEV, a symbol manipulation tool, the nonlinear and linearized differential equations are derived. Based on those, the dynamical behavior is examined with particular interest in the stability of the solutions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of model reduction techniques on the impact force calculation of two flexible bodies
Authors: Eberhard Peter , Fehr Jörg , Mathuni Stefan
Published: March 2010

One important issue for the simulation of flexible multibody systems is the reduction of the flexible body's degrees of freedom. For the reduction process finite element data and user inputs are necessary. The model reduction program for elastic multibody systems MOREMBS, which is developed at the ITM, has an easy‐to‐use interface and the data can be gained from the programs ABAQUS or ANSYS. In this work, the simulation of a fuel injection process is investigated with MOREMBS. We focus on the interaction between valve and armature. These two bodies impact in every injection circle. The impacting bodies are modeled as flexible and the contact force is calculated by a penalty approach. One essential part of this work is the investigation of the influence of different model reduction techniques on the impact force calculation of the flexible multibody system. The main reduction techniques modal reduction, Krylov‐subspace based and Gramian matrix based techniques are compared. The results achieved with modal reduction, the state of the art reduction method, are not acceptable here. Krylov‐subspace based techniques are especially well‐suited for large sparse systems but are not error controlled. However, by choosing appropriate moment‐matching properties the impact force calculation is nearly as good as with a full finite element model. The Gramian matrix based reduction techniques can be fully automated and are error controlled but require high computational effort. Hence, appropriate approximation schemes have to be used for them. With Gramian matrix based methods we can even further reduce the size of the subsystems compared to Krylov‐subspace based methods and still have an impact force calculation nearly as good as with finite element results, but we gain a simulation speedup by the factor 4000. In addition, a parameter study of the parameters involved in the model reduction process is presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
3D domain decomposition problems, consistent in time and space
Authors: Hesch Christian , Betsch Peter
Published: March 2010

During the past years tremendous developments have been achieved in the field of domain decomposition problems as well as in the field of time integration schemes. In the present work actual developments in both fields are merged; the result of this is an extremely stable numerical method in space and in time. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An energy‐momentum conserving method for the optimal control of multibody dynamics
Authors: Siebert Ralf , Betsch Peter
Published: March 2010

The present work deals with inverse multibody dynamics problems, more precisely with optimal control problems for dynamical systems governed by differential‐algebraic equations. The used numerical integration method relies on the Hamilton formulation of the equations of motion. We will apply an energy and momentum conserving time discretization which typically exhibits superior numerical stability properties. The rigid body equations of motion are basically formulated using the director formulation, which requires the implementation of internal constraints. To eliminate the constraints the system will be reduced to its minimal dimension by applying the discrete nullspace method [3]. For the derivation of the necessary conditions of optimality the calculus of variation is used [4]. This approach leads to an indirect transcription method. The arising algorithm yields a sequence of discrete configurations together with a sequence of actuating forces. We test the formulation with the help of representative numerical example problems. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of Different Methods to Compute Excitation Signals Based on Measured Targets in Agricultural Machines
Authors: Reichl Stefan , Steiner Wolfgang , Steinbatz Michael , Hofer Manfred
Published: March 2010

Basis for a strength calculation of a mechanical system is the knowledge of the outer excitation. In the case of agricultural machines it is either not possible or financially not affordable to measure such variables directly at the wheels. Therefore, measureable output parameters are defined as targets and they are used to calculate the input variables in an inverse process. Trailed agricultural machines are characterized by nonlinearities like complex tires, bearing slackness or elasticity of hydraulic components. All these phenomena have to be included in a MBS (multi‐body simulation) in order to describe the behaviour of the real system. As shown in this paper, the results of a test track can be reproduced with a model consisting of rigid and flexible bodies. The excitation signals can be calculated in different ways. A well known method and a new approach are evaluated. By using mathematical methods in combination with a virtual test rig, time and costs can be reduced compared to a real test rig. Another advantage is that inner variables can be calculated, which cannot be taken out from the physical system. Key words: virtual test rig, virtual iteration, multi‐body simulation, inverse problem (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling Elasto‐plastic Material Behaviour within the Multi‐Body Frame
Authors: Fischer Katrin , Ostermeyer Georg‐Peter
Published: March 2010

Highly dynamic problems can be well described using multi‐body systems. Nevertheless this method is limited to systems whithout large elasto‐plastic deformations that can e.g. be found during an extrusion process. To model such a system, multi‐body systems can be adequately combined with special particle approaches like the mesoscopic particle method [1], [2]. These mesoscopic particles have internal variables describing hidden degrees of freedom. Interaction forces between particles similar to those on the atomic scale have to be taken into account to describe phase transitions. So materials' properties concerning temperature and pressure can successfully be reproduced. This paper therefore deals with the description of an extrusion process in the multi‐body frame using mesoscopic particles. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Contribution to Jerk Detection
Authors: Schiefer Frank , Ostermeyer Georg‐Peter
Published: March 2010

In technical applications the jerk information will be used for i.a. motion control, comfort evaluation or prediction of acceleration. In the majority of cases the jerk will be determined indirectly by differentiation of measured acceleration signals and depends consequently on the acceleration signals' quality and the differentiation's algorithms. An accurate jerk determination can only be realized by using an appropriate filter with respect to the relevant frequency range. In order to avoid such limitation a method of direct jerk detection will be required. Based on a 2 DOF mass system with viscous coupling a possible method was presented in [1] to detect directly the jerk. Thereby, in certain conditions the jerk is proportional to the displacement of one mass. Another method of direct jerk detection is given implicitly in [2]. With this method the jerk information will be generated by an additional inner variable of a damped single mass system based on the fundamental idea of the Mesoscopic Particle Method [3]. Both presented methods will be investigated and evaluated regarding its limits of applicability as a result of arbitrary periodical and impact‐like excitations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of wing deformation on highlift systems of transport aircraft
Authors: Winter Evelyn , Woernle Christoph , Heyden Thomas
Published: March 2010

An elastic multibody model is developed that combines highlift system models consisting of flap and slat mechanisms with an elastic wing model. It describes the motions and deformations of the highlift systems with airloads applied and, in particular, the effect of wing deformations on the highlift systems. In addition the model contains a flexible wing with the engine and the middle section of the fuselage that is fixed at the symmetry plane of the aircraft. While previously wing deformation was taken into account in static FE simulations only the developed multibody model provides the investigation of the motions and inner loads of the highlift mechanisms with consideration of the wing deformations with dynamical effects. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A fast method for computing time‐dependent normal pressure distributions with cellular automaton
Authors: Graf Matthias , Ostermeyer G.‐P.
Published: March 2010

When two bodies slide against each other, one part of the dissipated energy causes a topography change. Tribological research on brake bads shows a rich dynamic of the boundary layer: plateau‐like structures of a typical length scale grow with time due to agglomerating wear particles and collapse spontaneously at a stability limit [4], [1]. This time‐dependent behaviour can be modeled with cellular automata, which consider local resolution of temperature, wear particle density and frictional power [4]. Beside this the instationary normal pressure distribution and the distinction between areas with and without contact is expected to have a significant influence [3]. This paper derives a fast scheme to estimate the time‐variant pressure distribution of a deterministic and dynamic topography by a cellular automaton. The approach is discussed in the light of computational performance and the solution's characteristics. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Co‐Simulation Approach for the 3D Dynamic Simulation of Vehicles Considering Sloshing in Cargo and Fuel Tanks
Authors: Fleissner Florian , Eberhard Peter
Published: March 2010

The sloshing of liquids in cargo and fuel tanks mounted on vehicles can have a significant influence on the vehicle's driving dynamics and stability. To evaluate and optimize the quality of tank designs, we propose a co‐simulation approach that consists of a coupled multibody system simulation for the vehicle and a Discrete Element Method and Smoothed Particle Hydrodynamics simulation for the sloshing cargo. This approach is beneficial especially for the simulation of fluid cargos, as Smoothed Particle Hydrodynamics does not require additional models to track and reconstruct free fluid surfaces. By means of dynamic 3D simulations of a double lane change maneuvers we compare the two different cargo models and demonstrate the viability of the co‐simulation approach. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kinematics of Drawbar Combinations with Many Trailers
Authors: Beitelschmidt M.
Published: March 2010

Modern articulated busses as well as road trains can be modeled as a chain of simple drawbar trailers. If the cross slip of the wheels is neglected, the system can be simplified to a planar single track model. The motion of the chain is governed by the geometrical constraints of the pivot joint in each coupling point and the nonholonomic kinematical constraints at each wheel contact point. With these simplifications a system of first order non‐linear differential equations for the angular velocities of all trailers is obtained that can be calculated recursively along the chain beginning at the forced movement of the first drawbar. The geometry and the kinematics of the trailer chain depend on two parameter sets: The drawbars' lengths of each trailer and the distances between the successors' coupling points and the axles on the predecessor's trailers. Especially the trailers' path‐following depends strongly on the ratio of these lengths. Systems of up to 50 identical trailers are examined. If special values for the ratio of the lengths are chosen, very strange behavior of the trailer chain can be observed. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New cases of integrability in dynamics of a rigid body with the cone form of its shape interacting with a medium
Authors: Shamolin Maxim V.
Published: March 2010

The purpose of the activity is to elaborate the qualitative methods for studying the dynamics of rigid bodies interacting with a resisting medium under quasistationarity conditions. This material refers equally to the qualitative theory of ordinary differential equations and the dynamics of rigid bodies. We use the properties of body's motion in a medium under conditions of the jet flow past this body. We study the plane model problems of the motion of a body with the cone form of its shape in a resisting medium. The new families of phase portraits of variable dissipation systems are obtained, their absolute or relative roughness is demonstrated. The integrable cases of equations of motion of rigid bodies are found. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A viscoelastic‐diffusion model for cartilage replacement material
Authors: Stoffel Marcus , Weichert Dieter , Müller‐Rath Ralf
Published: March 2010

In order to predict deformations and internal stresses of articular cartilage replacement material, two viscoelastic diffusion models are proposed in the present study. Also, the remodeling effect of the material seeded with human cells is verified experimentally. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Absorbed power as a method to evaluate the health risk of seated occupants exposed to vertical vibration
Authors: Rodean S. , Arghir M.
Published: March 2010

The biodynamic responses of seated occupants exposed to whole‐body vibration have been mostly investigated in terms of apparent mass characteristics, which show negligible contributions due to exposure level. Considering that the severity of vibration exposure is related to the level and duration of exposure, the apparent mass responses cannot be used for assessment of the associated risks. Alternatively, the absorbed power characteristics of the seated vibration exposed occupants show strong dependence on the level of exposure. The measured data, expressed in terms of the vertical absorbed power, are analyzed to study the effects of sitting posture on the biodynamic response under whole‐body vertical vibration. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)