Challenge Future – Technical Progress and Globalization

Central elements of the challenges of the future are the population, supply and disposal trap, the question of how the increasing world population will be supplied with long‐lasting and effective sources of energy, raw materials and food? How do we deal with the problems of greenhouse effect, ozone hole, forest dieback, ground erosion, desertification and other environmental threats? Driven by the dynamics of the technical progress the world is in the midst of experiencing the transition from an industrial to an information society. The process of globalization is intrinsically tied to the information society and plays a vital role in the path to a new, digital development of the world. Therefore, new challenges have been added to the traditional ecological challenges at the beginning of the 21^st century, which the world community must react swiftly to.     

A probabilistic performance‐based approach for mitigating the seismic pounding risk between adjacent buildings

Existing design procedures for determining the separation distance between adjacent buildings subjected to seismic pounding risk are based on approximations of the buildings' peak relative displacement. These procedures are characterized by unknown safety levels and thus are not suitable for use within a performance‐based earthquake engineering framework. This paper introduces an innovative reliability‐based methodology for the design of the separation distance between adjacent buildings. The proposed methodology, which is naturally integrated into modern performance‐based design procedures, provides the value of the separation distance corresponding to a target probability of pounding during the design life of the buildings. It recasts the inverse reliability problem of the determination of the design separation distance as a zero‐finding problem and involves the use of analytical techniques in order to evaluate the statistics of the dynamic response of the buildings. Both uncertainty in the seismic intensity and record‐to‐record variability are taken into account. The proposed methodology is applied to several different buildings modeled as linear elastic single‐degree‐of‐freedom (SDOF) and multi‐degree‐of‐freedom (MDOF) systems, as well as SDOF nonlinear hysteretic systems. The design separation distances obtained are compared with the corresponding estimates that are based on several response combination rules suggested in the seismic design codes and in the literature. In contrast to current seismic code design procedures, the newly proposed methodology provides consistent safety levels for different building properties and different seismic hazard conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Geological interpretation of a deep seismic‐reflection transect across the boundary between the Delamerian and Lachlan Orogens,in the vicinity of the Grampians,western Victoria

A deep seismic‐reflection transect in western Victoria was designed to provide insights into the structural relationship between the Lachlan and the Delamerian Orogens. Three seismic lines were acquired to provide images of the subsurface from west of the Grampians Range to east of the Stawell‐Ararat Fault Zone. The boundary between the Delamerian and Lachlan Orogens is now generally considered to be the Moyston Fault. In the vicinity of the seismic survey, this fault is intruded by a near‐surface granite, but at depth the fault dips to the east, confirming recent field mapping. East of the Moyston Fault, the uppermost crust is very weakly reflective, consisting of short, non‐continuous, west‐dipping reflections. These weak reflections represent rocks of the Lachlan Orogen and are typical of the reflective character seen on other seismic images from elsewhere in the Lachlan Orogen. Within the Lachlan Orogen, the Pleasant Creek Fault is also east dipping and approximately parallel to the Moyston Fault in the plane of the seismic section. Rocks of the Delamerian Orogen in the vicinity of the seismic line occur below surficial cover to the west of the Moyston Fault. Generally, the upper crust is only weakly reflective, but subhorizontal reflections at shallow depths (up to 3 km) represent the Grampians Group. The Escondida Fault appears to stop below the Grampians Group, and has an apparent gentle dip to the east. Farther east, the Golton and Mehuse Faults are also east dipping. The middle to lower crust below the Delamerian Orogen is strongly reflective, with several major antiformal structures in the middle crust. The Moho is a slightly undulating horizon at the base of the highly reflective middle to lower crust at 11–12 s TWT (approximately 35 km depth). Tectonically, the western margin of the Lachlan Orogen has been thrust over the Delamerian Orogen for a distance of at least 25 km, and possibly over 40 km.     

Effects of the oophagous bivalve Acesta oophaga on the morphology and fecundity of its deep‐sea tubeworm host,Lamellibrachia luymesi

The deep‐sea bivalve Acesta oophaga lives attached to the anterior end of the vestimentiferan tubeworm, Lamellibrachia luymesi, at cold methane seeps. The bivalve is found almost exclusively on female tubeworms, where it consumes the lipid‐rich eggs of L. luymesi that are spawned year round (Biological Bulletin, 209, 2005, 87). It is apparent that A. oophaga benefits directly from this close association, but the consequences for the tubeworm host may be more complicated than just a simple predator–prey interaction. Since A. oophaga completely surrounds the tube opening and plume of the worm, it is likely that its presence would limit oxygen uptake by L. luymesi, thereby inhibiting worm growth and reproduction. We hypothesized that occupied tubeworms would compensate for this by growing larger plumes for oxygen uptake. To explore the effects of bivalve presence/absence on female tubeworms, several morphological features, including body size, plume length, tube diameter, and tube segment length, as well as instantaneous fecundity, were compared. Results suggest that the mere presence of A. oophaga has a significant impact on the morphology of its host worm, as all measures of worm size, except for tube segment length, were significantly greater with clams present. Additionally, instantaneous fecundity was 3.5 times higher in occupied worms, implying that tubeworms are not oxygen‐deprived or energy limited as a result of bivalve presence. Our findings suggest that the association between these two deep‐sea organisms may be a more complex form of symbiosis than the simple predator–prey relationship, as previously thought.     

SHORT COMMUNICATION­­A field experiment of cusp formation on a coarse clastic beach using a suspended video‐camera system

Cusp formation was continuously monitored on a manually flattened, plane section of a coarse clastic, microtidal, pocket beach on the Pacific coast of Japan using a CCD camera suspended in the air. Vertical video pictures enabled the examination of the temporal change in foreshore morphologies and swash pattern. Boulders on the beach face appeared to have triggered the formation of beach cusps, which gradually and successively grew up alongshore. In 2·5 h, two well defined beach cusps had developed with a spacing of 2·2 and 2·5 m, respectively. Copyright © 2000 John Wiley & Sons, Ltd.     

Frequency domain modal analysis of earthquake input energy to highly damped passive control structures

A new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.     

A Comparison of Sediment Varves (1950–2003 AD) in Two Adjacent Lakes in Northern Sweden

Koltjärnen and Nylandssjön are two closely situated lakes (<2 km apart) in northern Sweden. During the past century, distinct varved sediments have formed in these lakes. Nylandssjön has two varved, deep basins. Since lake and catchment characteristics superficially appear very similar for the two lakes and they are exposed to the same climate, one would expect the sediment varves to be similar. This investigation compares the varves in the two deep basins of Nylandssjön, and in the two lakes. The comparison of basins of Nylandssjön shows that varve thickness, water content and annual accumulation rates of organic matter and nitrogen are correlated for the period (1970–2003). The grey-scale curves are only clearly similar in about 50% of the varves. In the between-lake comparison varve thickness, water content and annual accumulation rates of organic matter and nitrogen are correlated for the period (1950–1996). However, the annual accumulation rates of dry mass, minerogenic matter and biogenic silica differ between the lakes, as well as within-varve successions in grey-scale. A general explanation to the differences is that the prerequisites for varve formation are not totally similar because of differences in catchment size, catchment- to-lake material fluxes, lake productivity and land-use influence. This study illustrates the complex relationships that exist between a lake, its catchment, in-lake productivity and formation of sediment varves. As a consequence, we must not apply a too simplistic view of the potential of varves as past climatic indicators, especially if the lakes are affected by land-use.     

乌干达Albert湖凹陷北部沉积特征及油气成藏模式

乌干达Albert湖凹陷是世界上最年轻的生烃凹陷,受构造和沉积控制,油气多分布于北部构造调节带。为分析Albert湖北部构造调节带内部油气成藏特征,笔者利用地震、钻井、测井和孢粉等资料,开展北部构造调节带沉积特征研究,进而分析北部构造调节带的油气成藏模式。研究表明,由于边界正断层持续活动,北部构造调节带两侧沉积特征存在差异,研究区西部发育曲流河-三角洲沉积体系;东部发育冲积扇-扇三角洲沉积体系。由于北部构造调节带西部三角洲砂体向南推进至湖盆中心,与深湖相烃源岩直接沟通,成为Albert湖盆最有利的油气汇聚区。     

Micro‐geomorphology determines community structure of biological soil crusts at small scales

Biological soil crusts (BSCs) are ubiquitous communities of diminutive organisms such as cyanobacteria, green algae, lichens, mosses and others associated closely with particles of surface soil, forming a cohesive thin horizontal layer. The ecological roles of BSCs affecting soil nutrient cycling, stability and hydrological processes, influencing the germination and establishment of vascular plants, and serving as habitats for numerous arthropods and microorganism have been well documented. We tested the hypothesis that micro‐geomorphological features determine the spatial distribution of BSCs by reallocating related abiotic resources at small‐ and medium‐scales in the Tengger Desert. Our results showed that higher soil pH and higher total potassium content in topsoil positively correlated with the colonization of cyanobacteria and algae in the earliest successional stages of BSCs, while increasing dust deposition onto the topsoil enhanced the development of lichen and mosses in the later stages of BSCs. Increasing soil moisture raised the proportion of mosses and lichen in BSCs, this will possibly change the ecological functions of BSCs, such as nitrogen‐fixation by cyanobacteria, due to the conversion from a complex to relative simple type of BSC. Micro‐geomorphology has created various habitats at a small‐scale affecting colonization and development of cryptogams. This paper considers the contribution of micro‐geomorphology to biodiversity in the extreme arid desert systems. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of an interface boundary layer on the resonance properties of a buried structure

This paper presents a model for the analysis of the diffraction of plane waves at a cavity in an infinite homogeneous linear elastic medium supported by a segmented lining. An elastic boundary layer is introduced between the cavity lining and the infinite medium. The boundary layer is simulated by ‘elastic boundary conditions’ in which the stress is proportional to the relative displacement of the lining and of the surrounding medium boundary. A closed‐form analytical solution of the problem was obtained using the Fourier–Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance. Using amplitude–frequency response analysis it was shown that the boundary layer produces additional ‘pseudo‐resonance’ frequencies that depend on the layer properties. These frequencies are almost identical to the eigenvalues obtained from the simple analysis of a segmented elastically supported lining. Copyright © 2003 John Wiley & Sons, Ltd.