bluuebunny/crossref_metadata_2025 huggingface dataset:
Biopolymer Networks for the Solid‐State Production of Porous Magnetic Beads and Wires
Authors: Bakandritsos A. , Bourlinos A. B. , Tzitzios V. , Boukos N. , Devlin E. , Steriotis T. , Kouvelos V. , Petridis D.
Published: April 2007

Aqueous solutions of sodium carboxymethyl cellulose are used for the morphosynthesis of spherical and wire‐shaped biopolymer networks, in which Fe3+ cations serve as a crosslinking and hardening agent. Their morphology remains intact upon drying, resulting in monolithic beads (1 mm) and wires (ca. 80 μm), which are exploited as reaction vessels to pre‐encapsulate poly(ethylene glycol) 400 (PEG 400) and cobalt cations. A solid‐state reaction in an inert atmosphere at 600 °C affords porous carbonaceous xerogels, macroscopically shaped as beads or wires and decorated with nanocrystalline magnetic iron oxide, metallic iron, or iron–cobalt alloy particles, thus imparting magnetic properties to the products. As such the reduction of Fe3+ species to α‐Fe nanoparticles can be achieved without H2 treatment, since poly(ethylene glycol) serves as a reducing agent and the encapsulated Co2+ aids in the subsequent growth of the metallic iron particles. Particularly interesting are the magnetic properties of the carbon–α‐Fe composite, in which the size of the magnetic particles, estimated near the boundaries of the single magnetic domain, gives rise to increased coercivity compared with that of bulk iron.
Surface‐Transfer Doping of Organic Semiconductors Using Functionalized Self‐Assembled Monolayers
Authors: Chen W. , Gao X. Y. , Qi D. C. , Chen S. , Chen Z. K. , Wee A. T. S.
Published: April 2007

Controlling charge doping in organic semiconductors represents one of the key challenges in organic electronics that needs to be solved in order to optimize charge transport in organic devices. Charge transfer or charge separation at the molecule/substrate interface can be used to dope the semiconductor (substrate) surface or the active molecular layers close to the interface, and this process is referred to as surface‐transfer doping. By modifying the Au(111) substrate with self‐assembled monolayers (SAMs) of aromatic thiols with strong electron‐withdrawing trifluoromethyl (CF3) functional groups, significant electron transfer from the active organic layers (copper(II) phthalocyanine; CuPc) to the underlying CF3‐SAM near the interface is clearly observed by synchrotron photoemission spectroscopy. The electron transfer at the CuPc/CF3‐SAM interface leads to an electron accumulation layer in CF3‐SAM and a depletion layer in CuPc, thereby achieving p‐type doping of the CuPc layers close to the interface. In contrast, methyl (CH3)‐terminated SAMs do not display significant electron transfer behavior at the CuPc/CH3‐SAM interface, suggesting that these effects can be generalized to other organic‐SAM interfaces. Angular‐dependent near‐edge X‐ray absorption fine structure (NEXAFS) measurements reveal that CuPc molecules adopt a standing‐up configuration on both SAMs, suggesting that interface charge transfer has a negligible effect on the molecular orientation of CuPc on various SAMs.
Magnetic and Temperature‐Sensitive Release Gels from Supramolecular Polymers
Authors: Binder W. H. , Petraru L. , Roth T. , Groh P. W. , Pálfi V. , Keki S. , Ivan B.
Published: April 2007

Supramolecular gels consisting of trivalent polyisobutylene and bivalent poly(ethylene oxide) are generated. Strong hydrogen bonding interactions, affixed to the end‐group moieties of the respective polymers (binding constant Kassn = 105 M–1), serve as molecular glue, leading to the formation of weak gels. Two different gels were prepared: one, with a short telechelic poly(ethylene glycol) (PEG) segment (gel A), and one with a longer PEG segment (number‐average molecular weight Mn = 2000 g mol–1) (gel B). Both gels show a significant increase in viscosity upon mixing of the two polymeric components, with a lag time of several minutes, indicative of nucleation mechanisms as the formation principle. However, only gel A displays classical gel‐like behavior, with a loss modulus G′ larger than the storage modulus G″ after formation. Both gels display microphase‐separated behavior with a spacing between 4–5 nm as probed via small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) measurements. The incorporation of magnetic nanoparticles (Fe2O3; radius r = 3.5 nm) is successfully achieved, generating new magnetic gels with strongly thermoresponsive properties, displaying a strong temperature‐dependent release profile of included dye molecules. Magnetic measurements indicate a superparamagnetic behavior of the incorporated nanoparticles, prospecting the application as magneto‐sensitive delivery gels for pharmaceutical purposes.
Hand preferences on unimanual and bimanual tasks in white‐faced capuchins (Cebus capucinus)
Authors: Meunier Hélène , Vauclair Jacques
Published: April 2007

This study examined hand preference in white‐faced capuchins on a unimanual task and on a coordinated bimanual task. For the unimanual task, handedness was assessed by observing simple reaching for small grains. For the bimanual task, tubes lined with chocolate paste inside were presented to the capuchins. The hand and the finger(s) used to remove chocolate paste were recorded. Seven individuals out of eight in the reaching task and 12 out of 13 in the tube task exhibited a hand preference. Moreover, test–retest correlations showed stability in hand use across time for the coordinated bimanual task. We found no significant differences in strength of hand preference between sexes. Finally, as noted in other primate species, the capuchins were more lateralized in the bimanual task compared to the unimanual task. Am. J. Primatol. 69:1064–1069, 2007. © 2007 Wiley‐Liss, Inc.
Kinetics of microbial bromate reduction in a hydrogen‐oxidizing, denitrifying biofilm reactor
Authors: Downing Leon S. , Nerenberg Robert
Published: April 2007

Bromate (BrO) is an oxidized contaminant produced from bromide (Br−) during ozonation and advanced oxidation of drinking water. Previous research shows that denitrifying bioreactors can reduce bromate to innocuous bromide. We studied a hydrogen‐based, denitrifying membrane‐biofilm reactor (MBfR) for bromate reduction, and report the first kinetics for a hydrogen‐based bromate reduction process. A mixed‐culture MBfR reduced up to 1,500 µg/L bromate to below 10 µg/L with a 50‐min hydraulic residence time. Kinetics were determined using short‐term tests on a completely mixed MBfR at steady state with an influent of 5 mg N/L nitrate plus 100 µg/L bromate. Short‐term tests examined the impact of pH, nitrite, nitrate, and bromate on bromate reduction rates in the MBfR. Kinetic parameters for the process were estimated based on the short‐term bromate tests. The qmax for bromate reduction was 0.12 mg BrO·mg·day−1, and the K was 1.2 mg BrO/L. This qmax is 2–3 times higher than reported for heterotrophic enrichments, and the K is the first reported in the literature. Nitrite and nitrate partially inhibited bromate reduction, with nitrite exerting a stronger inhibitory effect. Bromate was self‐inhibitory at concentrations above 15 mg/L, but up to 50 mg/L of bromate had no inhibitory effect on denitrification. The optimum pH was approximately 7. We also examined the performance of an MBfR containing pure culture of the denitrifying bacterium Ralstonia eutropha. Under conditions similar to the mixed‐culture tests, no bromate reduction was detected, showing that not all denitrifying bacteria are active in bromate reduction. Our results suggest the presence of specialized, dissimilatory bromate‐reducing bacteria in the mixed‐culture MBfR. Biotechnol. Bioeng. 2007;98: 543–550. © 2007 Wiley Periodicals, Inc.
Multi‐objective optimization of an industrial penicillin V bioreactor train using non‐dominated sorting genetic algorithm
Authors: Lee Fook Choon , Rangaiah Gade Pandu , Ray Ajay Kumar
Published: April 2007

Bulk of the penicillin produced is used as raw material for semi‐synthetic penicillin (such as amoxicillin and ampicillin) and semi‐synthetic cephalosporins (such as cephalexin and cefadroxil). In the present paper, an industrial penicillin V bioreactor train is optimized for multiple objectives simultaneously. An industrial train, comprising a bank of identical bioreactors, is run semi‐continuously in a synchronous fashion. The fermentation taking place in a bioreactor is modeled using a morphologically structured mechanism. For multi‐objective optimization for two and three objectives, the elitist non‐dominated sorting genetic algorithm (NSGA‐II) is chosen. Instead of a single optimum as in the traditional optimization, a wide range of optimal design and operating conditions depicting trade‐offs of key performance indicators such as batch cycle time, yield, profit and penicillin concentration, is successfully obtained. The effects of design and operating variables on the optimal solutions are discussed in detail. Biotechnol. Bioeng. 2007;98: 586–598. © 2007 Wiley Periodicals, Inc.
Highly Interpenetrated Supramolecular Networks Supported by N⋅⋅⋅I Halogen Bonding
Authors: Metrangolo Pierangelo , Meyer Franck , Pilati Tullio , Proserpio Davide M. , Resnati Giuseppe
Published: April 2007

Halogen bonding (XB) has been used to assemble tetrakis(4‐pyridyl)pentaerythritol (tetradentate XB acceptor) with different α,ω‐diiodoperfluoroalkanes (bidentate XB donors) or tetrakis(4‐iodotetrafluorophenyl)pentaerythritol (tetradentate XB donor). The remarkable linearity of the XB formed, the rodlike character of α,ω‐diiodoperfluoroalkanes and the mutual complementarities of pentaerythritol partners, translate the three‐dimensional character of the XB acceptor into open primary networks, which interpenetrate to avoid the presence of voids and to ensure segregation of the modules. Two‐dimensional (2D) square 44 layers (sql) with fourfold and fivefold interpenetration, as well as an eightfold diamondoid network (dia) of class Ia and a remarkable tenfold dia network of class IIIa, have been obtained.
Intracystic bleomycin therapy for craniopharyngioma in children
Authors: Hukin Juliette , Steinbok Paul , Lafay‐Cousin Lucie , Hendson Glenda , Strother Douglas , Mercier Claude , Samson Yvan , Howes William , Bouffet Eric
Published: April 2007

BACKGROUND.

Surgical removal and radiation therapy are associated with significant risk for morbidity in the pediatric population with craniopharyngioma. Intracystic therapies have been utilized in some centers to potentially decrease morbidity associated with cystic craniopharyngioma. The aim of the study was to review the Canadian experience with intracystic bleomycin therapy (ICB).

METHODS.

All centers in the Canadian Pediatric Brain Tumor Consortium (CPBTC) were invited to participate in a retrospective review of this treatment. A questionnaire was sent to each center. The data were analyzed at British Columbia's Children's Hospital.

RESULTS.

In all, 6 of 17 centers utilized ICB and submitted data. A total of 17 of 19 patients with the intention to treat received bleomycin. Twelve were treated at the time of diagnosis, and 5 at the time of recurrence. Five patients achieved a complete response, 6 achieved a partial response, and 5 achieved a minor response to bleomycin. One patient was stable for 2.8 years. At the time of last follow‐up, 8 patients have not required further intervention. Complications included transient symptomatic peritumoral edema (2 patients), precocious puberty (1 patient) and panhypopituitarism (2 patients). The median follow‐up was 4 years (range, 0.5–10.2 years). The median progression‐free survival was 1.8 years (range, 0.3–6.1 years). One patient died of a massive infarct secondary to radiation‐induced moyamoya syndrome.

CONCLUSIONS.

ICB was found to be well tolerated in this group of children. ICB may be a feasible and effective therapy for certain children with craniopharyngioma. Bleomycin may delay the need for aggressive surgery or radiation therapy for several years. Prospective multiinstitutional clinical trials are required to further evaluate the feasibility, effectiveness, and dose schedules of this treatment. Cancer 2007. © 2007 American Cancer Society.
Elevated plasma tissue inhibitor of metalloproteinase‐1 level predicts decreased response and survival in metastatic breast cancer
Authors: Lipton Allan , Ali Suhail M. , Leitzel Kim , Demers Laurence , Evans Dean B. , Hamer Peter , Brown‐Shimer Sheryl , Pierce Karen , Carney Walter
Published: April 2007

BACKGROUND.

Tissue inhibitors of metalloproteinase (TIMPs) have at least 2 different functions. They inhibit the catalytic activity of matrix metalloproteinases, and they act as growth factors.

METHODS.

Pretreatment ethylenediamine tetracetic acid plasma TIMP‐1 was assayed from 251 patients who were enrolled in a Phase III, second‐line, hormone therapy trial, and from a control group of 50 healthy, postmenopausal women by using the TIMP‐1 enzyme‐linked immunosorbent assay.

RESULTS.

The plasma TIMP‐1 levels from the postmenopausal control group (n = 50 women) were 201 ± 86 ng/mL mean ± standard deviation (range, 49–455 ng/mL). The upper limit of normal was defined as the mean ± 2 standard deviations of the control group (373 ng/mL). Patient pretreatment plasma TIMP‐1 levels ranged from 70 ng/mL to 982 ng/mL. Plasma TIMP‐1 was elevated above the mean + 2 standard deviations of the control group (373 ng/mL) in 19 patients (7.6%). In univariate analysis, patients who had elevated versus normal plasma TIMP‐1 levels had a reduced clinical benefit rate (CBR) (16% vs 42%; P = .03). The time to progression (TTP) (84 days vs 174 days; P < .0001) and overall survival (141 days vs 860 days; P = .0001) also were significantly shorter in patients who had elevated TIMP‐1 levels. TTP and overall survival also were significantly shorter in patients who had higher TIMP‐1 plasma levels when it was analyzed as a continuous variable. In multivariate analysis, elevated plasma TIMP‐1 level remained a prognostic factor for reduced overall survival (P < .0001) along with elevated serum HER‐2/neu (P < .0001) and the presence of visceral metastases (P = .008).

CONCLUSIONS.

Elevated pretreatment plasma levels of TIMP‐1 predicted a decreased response to second‐line hormone therapy and reduced survival in women with metastatic breast cancer. Cancer 2007. © 2007 American Cancer Society.
Distributed communication model in hierarchical Infostation systems
Authors: Tlais M. , Weis F.
Published: April 2007

The Infostations system, small and separated islands of coverage, provides intermittent but very high speed data rates. A new communication model is needed to carry this kind of architecture. Mainly, the discontinuous coverage affects the way data are exchanged between mobile terminals and the network. Moreover, the short time the mobile terminal spends in the coverage area has a direct impact on the network performance. Thus, it is essential to avoid bandwidth wasting due to the overall delay by performing mobility prediction. A new mobility prediction protocol called the Distributed Neighbor Discovery Protocol (DNDP) is proposed. DNDP handles a neighbor graph table that dynamically configures itself according to the terminals' mobility. The simulation shows that the terminals service continuity is significantly improved thanks to DNDP. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of redundancy on the mean time to failure of wireless sensor networks
Authors: Speer Anh Phan , Chen Ing‐Ray
Published: April 2007

In data‐driven wireless sensor networks (WSNs), the system must perform data sensing and retrieval and possibly aggregate data as a response at runtime. As a WSN is often deployed unattended in areas where replacements of failed sensors are difficult, energy conservation is of primary concern. While the use of redundancy is desirable in terms of satisfying user queries to cope with sensor and transmission faults, it may adversely shorten the lifetime of the WSN, as more sensor nodes will have to be used to answer queries, causing the energy of the system to drain quickly. In this paper, we analyze the effect of redundancy on the mean time to failure (MTTF) of a WSN in terms of the number of queries the system is able to answer correctly before it fails due to either sensor/transmission faults or energy depletion. In particular, we analyze the effect of redundancy on the MTTF of cluster‐structured WSNs for energy conservations. We show that a tradeoff exists between redundancy and MTTF. Furthermore, an optimal redundancy level exists such that the MTTF of the system is maximized. Copyright © 2007 John Wiley & Sons, Ltd.
OpenUH: an optimizing, portable OpenMP compiler
Authors: Liao Chunhua , Hernandez Oscar , Chapman Barbara , Chen Wenguang , Zheng Weimin
Published: April 2007

OpenMP has gained wide popularity as an API for parallel programming on shared memory and distributed shared memory platforms. Despite its broad availability, there remains a need for a portable, robust, open source, optimizing OpenMP compiler for C/C++/Fortran 90, especially for teaching and research, for example into its use on new target architectures, such as SMPs with chip multi‐threading, as well as learning how to translate for clusters of SMPs. In this paper, we present our efforts to design and implement such an OpenMP compiler on top of Open64, an open source compiler framework, by extending its existing analysis and optimization and adopting a source‐to‐source translator approach where a native back end is not available. The compilation strategy we have adopted and the corresponding runtime support are described. The OpenMP validation suite is used to determine the correctness of the translation. The compiler's behavior is evaluated using benchmark tests from the EPCC microbenchmarks and the NAS parallel benchmark. Copyright © 2007 John Wiley & Sons, Ltd.
PALF: compiler supports for irregular register files in clustered VLIW DSP processors
Authors: Lin Yung‐Chia , You Yi‐Ping , Lee Jenq‐Kuen
Published: April 2007

A wide variety of register file architectures—developed for embedded processors—have recently been used with the aim of reducing power dissipation and die size, in contrast with the traditional unified register file structures. This article presents a novel register allocation scheme for a clustered VLIW DSP, which is designed with distinctively banked register files in which port access is highly restricted. Whilst the organization of the register files is designed to decrease power consumption by using fewer port connections, the cluster‐based design makes register access across clusters an additional issue, and the switched‐access nature of the register file demands further investigation into the use of optimizing register assignment as a means of increasing instruction‐level parallelism. We propose a heuristic algorithm, namedping‐pong aware local favorable(PALF) register allocation, to obtain a register allocation that is expected to better utilize irregular register file architectures. The results of experiments performed using a compiler based on the Open Research Compiler (ORC) showed significant performance improvement over the original ORC's approach, which is considered to be an optimized approach for common register file architectures. Copyright © 2007 John Wiley & Sons, Ltd.
A role for plasmacytoid dendritic cells in the rapid IL‐18‐dependent activation of NK cells following HSV‐1 infection
Authors: Barr Daniel P. , Belz Gabrielle T. , Reading Patrick C. , Wojtasiak Magdalena , Whitney Paul G. , Heath William R. , Carbone Francis R. , Brooks Andrew G.
Published: April 2007

Natural killer (NK) cells play a crucial role in the initial response to viral infections but the mechanisms controlling their activation are unclear. We show a rapid and transient activation of NK cells that results in the production of IFN‐γ immediately following infection with herpes simplex virus type 1 (HSV‐1). Activation of NK cells leading to synthesis of IFN‐γ was not mediated by a direct interaction with virus but required the presence of additional cell types and was largely dependent on the cytokine IL‐18, but not IL‐12. HSV‐1‐induced IFN‐γ expression by NK cells in vitro was impaired in spleen cultures depleted of CD11c+ cells. Conversely, coculture of NK cells with virus‐exposed conventional DC or plasmacytoid (p)DC restored the production of IFN‐γ, indicating that multiple DC subsets could mediate NK cell activation. While conventional DC populations stimulated NK cells independently of IL‐18, they were less effective than pDC in promoting NK cell IFN‐γ expression. In contrast, the potent stimulation of NK cells by pDC was dependent on IL‐18 as pDC from IL‐18‐deficient mice only activated a similar proportion of NK cells as conventional DC. These data identify IL‐18 as a crucial factor for pDC‐mediated NK cell regulation.
Development of real‐time pseudo dynamic testing
Authors: Nakashima Masayoshi , Kato Hiroto , Takaoka Eiji
Published: April 2007

This paper presents a study for the development of a system capable of performing real‐time pseudo dynamic testing. The system combines the basics of the pseudo dynamic test with a dynamic actuator, a digital displacement transducer and a digital servo‐mechanism. The digital servo‐mechanism has been introduced to ensure accurate displacement and velocity control, in which digital feedback control with a time interval of 2 msec has been performed continuously during actuator motion. Using the system, pseudo dynamic tests under sinusoidal and earthquake ground motion are carried out for a structure having a viscous damper, demonstrating that a perfectly real‐time pseudo dynamic test can be achieved by incorporating the modified central difference method into an extra buffer operation of the digital servo‐mechanism. The responses solved by the pseudo dynamic tests are compared with the responses of the test structure as well as those obtained from post‐numerical analysis, and it is found that the real‐time pseudo dynamic test conducted in this study is accurate.
Soil amplification based on seismometer array and microtremor observations in Chiba, Japan
Authors: Lu Lin , Yamazaki Fumio , Katayama Tsuneo
Published: April 2007

Soil amplification characteristics of earthquake ground motion were investigated in terms of peak ground acceleration and transfer function based on the Chiba array observation records. The amplification of peak ground acceleration occurred mostly at the top soft layer and was similar for the three components. The effects of non‐linear response of soil deposits on the transfer function were examined. Transfer functions calculated by ensemble average were close for the two horizontal components while those obtained from a smoothing operation were generally different. Both the transfer functions from the ensemble average and the smoothing operation underestimated the gain factor around the natural frequencies. A two‐step smoothing procedure was proposed and a rotary spectrum was used to improve the estimation of the transfer function. Microtremors were observed at the locations of the boreholes where seismometers are buried. The power spectrum and spatial coherency of the microtremors were compared with those of the earthquake ground motion. Emphasis was placed on the wavetypes which dominated the peaks in the power spectra.
Non‐linear seismic response analysis using vector superposition methods
Authors: Léger P. , Dussault S.
Published: April 2007

Computational algorithms based on the pseudo‐force method (PFM) and the tangent spectrum method (TSM) for the seismic analysis of elasto‐plastic MDOF structures by mode superposition are presented. The emphasis is put on the effect of the truncation of higher modes on the convergence of the ductility demand and energy dissipated during the earthquake. Eigenvectors and load‐dependent vectors have been used in comparative analyses. Applications on a flexible 25‐storey building and a stiff, 5‐storey shear building indicate that, for a flexible structure, the ductility demand computed from the PFM is more sensitive to basis truncation than that computed from the TSM. However, for the stiff structure, the opposite behaviour is observed. The results indicate that the use of load‐dependent vectors in inelastic analyses maintains the computational advantages found for elastic analyses in previous investigations. Although the PFM is more stable and computationally more effective than the TSM, it does not provide any information on the evolution of tangent modal properties in time that reflects dynamic response modification as the structure becomes inelastic.
Generation of critical stochastic earthquakes
Authors: Srinivasan Mukund , Corotis Ross , Ellingwood Bruce
Published: April 2007

A stochastic critical excitation is defined as that excitation with a given variance that maximizes the variance in the dynamic response of a system. A non‐stationary filtered shot noise is used to develop a stochastic critical excitation model of an earthquake ground motion process, and the response statistics for a linear system are determined in both time and frequency domains. The sensitivity of response to several assumed earthquake pulse arrival rate functions is examined. Responses to recorded strong ground motion and to stochastic critical excitations with the same total energy are compared to assess the degree of conservatism in the procedure. An application of the procedure to seismic qualification of equipment is presented.
Response of pile foundations to rayleigh waves and obliquely incident body waves
Authors: Kaynia Amir M. , Novak Milos
Published: April 2007

The paper presents results of a study on the harmonic response of piles and pile groups embedded in a halfspace to various forms of seismic waves. These include the Rayleigh wave as well as obliquely incident P, SV and SH waves. The pertinent mixed boundary value problems of pile‐soil‐pile interaction are solved by a numerical model of the boundary integral nature. All modes of foundation vibrations, i.e. translational, rocking and torsional, are included in the model. The results presented are used to highlight the salient features of the seismic response of piles. In addition, the influence of certain pile‐soil parameters, such as pile rigidity and pile spacing, on the seismic behaviour of pile foundations is investigated.
Torsion in two buildings—1987 whittier narrows earthquake
Authors: Lu Shi , Hall William J.
Published: April 2007

Study of the data from the extensively instrumented buildings in the 1987 Whittier Narrows earthquake suggests that torsional modes probably were excited in buildings that outwardly appear quite symmetric. Accordingly this study involves: (i) investigation of the observed response of two low‐rise buildings in both the elastic and moderately inelastic domains, (ii) comparison of such behaviour with the results obtained from modelling studies, and (iii) examination of the possible effects arising from stronger shaking. The study was directed towards attempting to provide a partial answer to the critical question of whether or not the torsional response was important in the gross total response of these low‐rise buildings, and to what extent torsional concepts should be considered in design. Also the numerical results were extrapolated to examine the survivability of the same buildings if subjected to a somewhat stronger earthquake. The ultimate goal was to contribute insight to the practical guidelines for design and analysis of low‐rise buildings subjected to strong ground motion.
Dynamic interaction analysis of a circular cylindrical shell of finite length in a half‐space
Authors: Cheung Y. K. , Zhu J. X.
Published: April 2007

A study on the transient response of a circular cylindrical shell of finite length embedded in a homogeneous, isotropic and linear elastic half‐space is presented. The soil‐structure system is subjected to suddenly applied explosion waves. The numerical method employed is a combination of the time domain semi‐analytical boundary element method used for the semi‐infinite soil medium and the finite strip method used for the circular cylindrical shell. The two methods are combined through equilibrium and compatibility conditions at the soil‐structure interface. The dynamic responses at the interface between the soil medium and the structure for every time step are obtained. Numerical examples are presented in detail to demonstrate the use and versatility of the proposed method. The following parameters are found to affect the response: (1) the slenderness ratio of the length over the diameter of the shell, L/D; (2) the relative wall thickness, h/a; (3) the relative stiffness ratio between the shell and the medium, Es/Em; and (4) the incidence angle of the explosion wave, α.
Lumped‐parameter model and recursive evaluation of interaction forces of semi‐infinite uniform fluid channel for time‐domain dam‐reservoir analysis
Authors: Wolf John P. , Paronesso Antonio
Published: April 2007

To calculate the hydrodynamic interaction forces of the reservoir directly in the time‐domain, the dynamic stiffness of each mode of the semi‐infinite uniform fluid channel is either represented by a lumped‐parameter model with frequency‐independent real coefficients of the springs, dashpots and masses and with only a few additional internal degrees of freedom, or the interaction forces are calculated recursively. For each mode characterized by its eigenvalue, the coefficients of the lumped‐parameter model and the recursive coefficients are specified, which can be used directly in a practical application. The procedures exhibit many advantages: the only approximation (replacing the rigorous dynamic stiffness by a ratio of two polynomials) can be evaluated visibly. No unfamiliar discrete‐time manipulations such as the z‐transformation are used. The stiffness, damping and mass matrices corresponding to the lumped‐parameter model are automatically symmetrical. Stability of the procedures is also guaranteed. Combining the lumped‐parameter model of the semi‐infinite uniform channel with the finite‐element discretization of the irregular fluid region or calculating the interaction forces recursively allows a reservoir of arbitrary shape to be analysed directly in the time domain. Non‐linearities in the dam can, thus, be taken into consideration in a seismic analysis.
Efficient mode superposition algorithm for seismic analysis of non‐linear structures
Authors: Villaverde Roberto , Hanna Melad M.
Published: April 2007

A step‐by‐step integration method is proposed to compute within the framework of the conventional mode superposition technique the response of bilinear hysteretic structures subjected to earthquake ground motions. The method is computationally efficient because only a few modes are needed to obtain an accurate estimate of such a response, and because it does not require the use of excessively small time steps to avoid problems of accuracy or stability. It is developed on the basis that the non‐linear terms in the equations of motion for non‐linear systems may be considered as additional external forces, and the fact that by doing so such equations of motion can be interpreted as the equations of motion of an equivalent linear system, excited by a modified ground motion. These linear equations are then subjected to a conventional modal decomposition and transformed, as with linear systems, into a set of independent differential equations, each representing the system's response in one of its modes of vibration. To increase the efficiency of the method and account properly for the participation of higher modes, these independent equations are solved using the Nigam‐Jennings technique in conjunction with the so‐called mode acceleration method. The accuracy and efficiency of the method is verified by means of a comparative study with solutions obtained with a conventional direct integration method. In this comparative study, including only a few modes, the proposed method accurately predicts the seismic response of three two‐dimensional frame structures, but requiring only, on an average, about 47 per cent less computer time than when the direct integration method is used.
Hybrid isolation systems for equipment protection
Authors: Inaudi José A. , Kelly James M.
Published: April 2007

This paper presents a formulation for earthquake resistant design of optimum hybrid isolation systems for sensitive equipment protection. The hybrid system under consideration consists of laminated rubber bearings, viscodampers and a set of actuators which, grounded on the main structural system, deliver forces on the basement of the isolated substructure mounted on the main structural system. An integrated design procedure for the passive and active components of the isolation system is developed aiming at acceleration reduction under random excitation. Linear models are used for the isolated structure, the main structural system and the isolation system. Fractional derivative Maxwell elements are used to model the mechanical behaviour of the viscodampers. The active component of the isolation system applies forces proportional to the absolute velocity of the isolated piece of equipment. Constraints in the deformation capacity of the isolators as well as constraints in the capacity of the actuators are considered for the design of an optimal hybrid isolation system. Simple numerical examples are developed herein to illustrate the design procedure. The superiority of hybrid systems over passive systems in reducing acceleration response is demonstrated.
Inelastic seismic response of code‐designed multistorey frame buildings with regular asymmetry
Authors: Duan X. N. , Chandler A. M.
Published: April 2007

Based on an asymmetric multistorey frame building model, this paper investigates the influence of a building's higher vibration modes on its inelastic torsional response and evaluates the adequacy of the provisions of current seismic building codes and the modal analysis procedure in accounting for increased ductility demand in frames situated at or near the stiff edge of such buildings. It is concluded that the influence of higher vibration modes on the response of the upper‐storey columns of stiff‐edge frames increases significantly with the building's fundamental uncoupled lateral period and the magnitude of the stiffness eccentricity. The application of the equivalent static torsional provisions of certain building codes may lead to non‐conservative estimates of the peak ductility demand, particularly for structures with large stiffness eccentricity. In these cases, the critical elements are vulnerable to excessive additional ductility demand and, hence, may be subject to significantly more severe structural damage than in corresponding symmetric buildings. It is found that regularly asymmetric buildings excited well into the inelastic range may not be conservatively designed using linear elastic modal analysis theory. Particular caution is required when applying this method to the design of stiff‐edge frame elements in highly asymmetric structures.
Seismic energy demands on reinforced concrete moment‐resisting frames
Authors: Tso W. K. , Zhu T. J. , Heidebrecht A. C.
Published: April 2007

This paper examines the seismic energy demands on reinforced concrete ductile moment‐resisting frames. Three frames having 4, 10 and 18 storeys, representing low, medium and tall frames, were designed to the current Canadian seismic provisions and structural design requirements. Three groups of earthquake records having different frequency contents were selected as input ground motions. The input, hysteretic and damping energies were evaluated for these three frames and correlation was established with other response parameters. The use of equivalent single‐degree‐of‐freedom systems to estimate the energy demands on these frames was examined in order to simplify the computational effort. It is shown that the energy demand concept together with the equivalent single‐degree‐of‐freedom system is a viable design approach for low‐rise frames. Additional research to allow for the higher modal effect is required before the same concept can be extended to medium and tall frames.
Optimum damping in linear isolation systems
Authors: Inaudi Jose A. , Kelly James M.
Published: April 2007

Optimum isolation damping for minimum acceleration response of base‐isolated structures subjected to stationary random excitation is investigated. Three linear models are considered to account for the energy dissipation mechanism of the isolation system: a Kelvin element, a linear hysteretic element and a standard solid linear element, commonly used viscoelastic models for isolation systems comprising natural rubber bearings and viscous dampers. The criterion selected for optimality is the minimization of the mean‐square floor acceleration response. The effects of the frequency content of the excitation and superstructure properties on the optimum damping and on the mean‐square acceleration response are addressed. The study basically shows that the attainable reduction in the floor acceleration largely depends on the energy dissipation mechanism assumed for the isolation system as well as on the frequency content of the ground acceleration process. Special care should be taken in accurately modelling the mechanical behaviour of the energy dissipation devices.
A design study of an energy‐dissipating cladding system
Authors: Cohen Julie Mark , Powell Graham H.
Published: April 2007

A design study has been conducted to explore the use of structural cladding panels with energy‐dissipating cladding‐to‐frame connections for seismic‐resistant design. The study identifies several issues involved in the modelling and analysis of frames with energy‐dissipating cladding‐to‐frame connections, establishes concepts for design, and provides a preliminary assessment of the force and deformation demands that are likely to be placed on panels and connections. Non‐linear dynamic analyses indicate that the clad frames perform well, based on observations about maximum interstorey drifts, maximum plastic hinge rotations in the frames, and maximum ductility demands on the cladding‐to‐frame connections.
Spectral analysis of systems with non‐classical damping using classical mode superposition technique
Authors: Jangid R. S. , Datta T. K.
Published: April 2007

A spectral method for random vibration analysis of a structural system with non‐proportional damping is presented using classical (undamped) mode superposition technique. The method obtains the frequency response function of the system by solving the dynamic equilibrium equations in generalized co‐ordinates through an iterative process. The iterative solution is written in closed form and the proof for convergence of the iterative process is given. Numerical examples show the convergence characteristics of the process and an excellent accuracy of the obtained results. The method turns out to be computationally more efficient than the conventional methods of spectral analysis using damped mode shapes and frequencies.
Optimum tuned‐mass dampers for minimizing steady‐state response of support‐excited and damped systems
Authors: Tsai Hsiang‐Chuan , Lin Guan‐Cheng
Published: April 2007

A numerical searching procedure to find the optimum tuning frequency and damping ratio of the tuned‐mass damper which can reduce the steady‐state response of damped main systems to a minimum level is developed and applied to the two different harmonic excitation sources, support motion of fixed‐displacement amplitude and support motion of fixed‐acceleration amplitude. The explicit formulae for these optimum parameters are then derived through a sequence of curve‐fitting schemes. It has been found that, as the error of the explicit formulae is negligible, they provide a convenient tool to compute the optimum parameters in engineering applications.

The numerical results show that the tuned‐mass damper is less effective in reducing the system's response when there is a high level of damping incorporated into the system. It is also found that the optimum tuning frequency is strongly influenced by the damping level of a system, especially in regard to the fixed‐acceleration support motion, but the optimum damping ratio of the tuned‐mass damper is not sensitive to the damping level of a system. The response of the damped system using the undamped optimum value as the damping of the tuned‐mass damper is not much different from the response using the damped optimum value.
Instrumental seismological data since 1900 for northeastern Italy
Authors: Margottini Claudio , Martini Guido , Slejko Dario
Published: April 2007

Statistical analyses on a catalogue of instrumental data for earthquakes in northeastern Italy since 1900 are presented. The different types of magnitude, which are the main parameters under study, have been evaluated so as to be as homogeneous as possible. Comparisons of the different magnitude values show linear dependence, at least in the medium magnitude range represented by the available data set. Correlations between the magnitude most significant for this region and chosen macroseismic data indicate a methodology for assessing the macroseismic magnitude of historical earthquakes which seems to be stable.
Modal analysis of a DAM–Foundation system based on an FE–BE method in the time domain
Authors: Touhei Terumi , Ohmachi Tatsuo
Published: April 2007

A modal analysis procedure based on an FE–BE method in the time domain is first formulated and then applied to a dam–foundation system. In the application, horizontal and vertical impulsive responses are calculated for the system having six different impedance ratios. Modal characteristics such as natural frequencies, damping ratios and mode shapes are evaluated from the Fourier spectra of the responses. The proposed procedure allows analysis of not only the underdamped but also the overdamped modes. According to the analysis, the radiation damping pertinent to the vertical vibration is half of that pertinent to the horizontal vibration and the interaction effect on the modes is not negligibly small when the impedance ratio exceeds 0·3.
Dynamic behaviour of pile foundations in homogeneous and non‐homogeneous media
Authors: Miura Kenji , Kaynia Amir M. , Masuda Kiyoshi , Kitamura Eiji , Seto Yutaka
Published: April 2007

A three‐dimensional formulation based on Green's functions of cylindrical loads in layered semi‐infinite media is employed to investigate the dynamic behaviour of piles in homogeneous and non‐homogeneous half spaces. The pile‐soil‐pile interaction taking place in pile groups is incorporated in the model. The results presented in this paper include the dynamic stiffnesses and dampings of single piles as well as those of representative 2 × 2 and 4 × 4 square pile groups in the soil media considered in this study. In addition, the distribution of forces applied on the pile cap among the individual piles in a group is investigated.
Dynamic soil pressures on rigid vertical walls
Authors: Veletsos A. S. , Younan A. H.
Published: April 2007

A critical evaluation is made of dynamic pressures and the associated forces induced by ground shaking on a rigid, straight, vertical wall retaining a semi‐infinite, uniform viscoelastic layer of constant thickness. The effects of both harmonic and earthquake‐induced excitations are examined. Simple approximate expressions for the responses of the system are developed, and comprehensive numerical data are presented which elucidate the effects and relative importance of the various parameters involved. These solutions are then compared with those obtained by the use of a simple model previously proposed by Scott, and the accuracy of this model is assessed. Finally, two versions of an alternative model are proposed which approximate better the action of the system. In the first, the properties of the model are defined by frequency‐dependent parameters, whereas in the second, which is particularly helpful in analyses of transient response, they are represented by frequency‐independent, constant parameters.
Consistent inelastic design spectra: Hysteretic and input energy
Authors: Fajfar Peter , Vidic Tomaž
Published: April 2007

This is the second of two companion papers on inelastic design spectra (for strength, displacement, hysteretic and input energy) for systems with a prescribed ductility factor. All the spectra are consistent (interrelated and based on the same assumptions). This paper deals with two quantities related to cumulative damage: hysteretic and input energy. The input data for the procedure are the characteristics of the expected ground motion in terms of a smooth elastic pseudo‐acceleration spectrum and the time integral of the square of the ground acceleration ∫a2 dt. Simple, approximate expressions for two dimensionless parameters (the parameter γ and the hysteretic to input energy ratio EHEI) have been proposed. The parameter 7, which controls the reduction of the deformation capacity of structures due to low‐cycle fatigue, depends on the natural period of the system, the prescribed ductility factor, the hysteretic behaviour and the ground motion characteristics. The ratio EH/EI is influenced by damping, the ductility factor and the hysteretic behaviour. Very good approximations to the inelastic spectra for hysteretic and input energy can be derived from the elastic spectrum using the spectra for the reduction factor R, proposed in the companion paper, and the proposed values for γ and EH/EI
Non‐linear soil response in ground motions
Authors: Wen Kuo‐Liang
Published: April 2007

From both theoretical and empirical studies, we know that a soft soil layer will amplify seismic waves of certain frequencies and cause damage to structures, depending on the physical properties and the thickness of the layer. Most developed cities are situated on a plane or a basin with soft geological strata. Thus, understanding the characteristics of soft soil response to seismic loading is important. Seismologists and engineers are interested in questions of linear versus non‐linear soil response and isotropy versus anisotropy as a soil property. The records of the downhole accelerographs of an array in Lotung provide an opportunity to study these problems. The results show that the soil response in Lotung does not have an anisotropy effect, and significant non‐linear soil response occurred during the strong ground motions in which peak ground acceleration values at ground surface are larger than 150 gal.
Structural control considering soil–structure interaction effects
Authors: Smith H. Allison , Wu Wen‐Hwa , Borja Ronaldo I.
Published: April 2007

A discussion of the effects of Soil‐Structure Interaction (SSI) on the formulation of active structural control algorithms is presented. Two approaches for incorporating SSI effects in linear optimal control theory are developed: one which performs the control analysis on a structure with a fixed base and then considers the effects of SSI on the controlled structural response; and another which performs the control analysis using a structural equation of motion reformulated to include SSI effects. The two control formulations are studied and compared using a single‐degree‐of‐freedom structure supported through a rigid foundation resting on a linear, elastic half‐space. Results show that control effectiveness is affected by the approach used in formulating the equations of motion of the interacting system.
A measure of the capacity of earthquake ground motions to damage structures
Authors: Rodriguez Mario
Published: April 2007

Even though a number of parameters have been proposed in the literature for measuring the capacity of earthquake ground motions to damage structures, most of them are not consistent with building damage observed during earthquakes. In this study, a parameter for measuring seismic damage capacity is proposed. It uses the energy dissipated by a structure in inelastic deformations and a structural overall drift, and it is evaluated for three typical ground motions recorded in severe earthquakes. By using this parameter, consistent results with building damage observed in these earthquakes are obtained, which indicate the importance of displacement control for minimizing seismic damage.