Response of pendulums to complex input ground motion

Dynamic response of most seismological instruments and many engineering structures to ground shaking can be represented via response of a pendulum (single-degree-of-freedom oscillator). In most studies, pendulum response is simplified by considering the input from uni-axial translational motion alone. Complete ground motion however, includes not only translational components but also rotations (tilt and torsion). In this paper, complete equations of motion for three following types of pendulum are described: (i) conventional (mass-on-rod), (ii) mass-on-spring type, and (iii) inverted (astatic), then their response sensitivities to each component of complex ground motion are examined. The results of this study show that a horizontal pendulum similar to an accelerometer used in strong motion measurements is practically sensitive to translational motion and tilt only, while inverted pendulum commonly utilized to idealize multi-degree-of-freedom systems is sensitive not only to translational components, but also to angular accelerations and tilt. For better understanding of the inverted pendulum's dynamic behavior under complex ground excitation, relative contribution of each component of motion on response variants is carefully isolated. The systematically applied loading protocols indicate that vertical component of motion may create time-dependent variations on pendulum's oscillation period; yet most dramatic impact on response is produced by the tilting (rocking) component.     

Estimating daily pan evaporation using adaptive neural-based fuzzy inference system

Estimation of evaporation is important for water planning, management, and hydrological practices. There are many available methods to estimate evaporation from a water surface, comprising both direct and indirect methods. All the evaporation models are based on crisp conceptions with no uncertainty element coupled into the model structure although in daily evaporation variations there are uncontrollable effects to a certain extent. The probabilistic, statistical, and stochastic approaches require large amounts of data for the modeling purposes and therefore are not practical in local evaporation studies. It is therefore necessary to adopt a better approach for evaporation modeling, which is the fuzzy sets and adaptive neural-based fuzzy inference system (ANFIS) as used in this paper. ANFIS and fuzzy sets have been evaluated for its applicability to estimate evaporation from meteorological data which is including air and water temperatures, solar radiation, and air pressure obtained from Automated GroWheather meteorological station located near Lake E?irdir and daily pan evaporation values measured by XVIII. District Directorate of State Hydraulic Works. Results of ANFIS and fuzzy logic approaches were analyzed and compared with measured daily pan evaporation values. ANFIS approach could be employed more successfully in modeling the evaporation process than fuzzy sets.     

A short note on the geo-archeological significance of the ancient Theodosius harbour (İstanbul, Turkey)

The sedimentary sequence discovered at archaeological excavations in ancient Theodosius Harbour at İstanbul contains the records of sea level, environmental changes and the cultural history of the region. The cobbles at the base of the sequence include archaeological remnants of Neolithic culture that settled in the area between 8.4 and 7.3 ¹⁴C ka BP, and are located at 6 m below the present sea level. The sediments representing a coastal environment indicate that the area was used as a harbour from AD 4th to at least the 11th century and were filled by the sediments derived from Lykos Stream after 11th century.     

Stratigraphic organisation,spatial distribution,palaeoenvironmental reconstruction,and demise of Lower Cretaceous (Barremian-lower Aptian) carbonate platforms of the Western Pontides (Black Sea region,Turkey)

Barremian-Lower Aptian platform carbonates (“Urgonian limestones”) of the northern margin of the Istanbul zone extend from Zonguldak to the Kurucasile area along the Black Sea coast. New stratigraphic data on the “Inpiri” Formation of the Inpiri-Kurucasile area are based on the identification of calcareous algae, foraminifera, and rudists. They show that this lithostratigraphic unit is stratigraphically and lithologically equivalent to the Ökü?medere Formation from Zonguldak. Some of the biostratigraphic markers are reported for the first time in Anatolia. Foraminifera are represented by several forms with a significant biostratigraphic potential used to distinguish the Barremian from the lower Aptian. Lower Aptian beds also yield relatively advanced caprinid rudists.The Ökü?medere Formation is relatively thin, terrigeneous-rich, and rudist-free or rudist-poor in the Kurucasile sector, and thick, terrigeneous-poor, and rudist-rich from Amasra to Zonguldak, with a set of marker beds including either charophytes or Palorbitolina and capped by a coral unit underlying ammonite bearing marls. Terrigeneous-rich carbonates from the eastern sector are interpreted as marginal marine coastal, infralittoral environments and grade distally, northward, to marly basinal sediments. By contrast “Urgonian type” limestones from the Zonguldak-Amasra region possess a wide extent and no transition to coastal or basinal sediments has been observed. A transition from a typical platform westward to a mixed siliciclastic-carbonate ramp eastward was controlled by both the nature of the adjacent exposed area and tectonic factors affecting the overall continental margin that is a northward downwarping. The exposed area was flanked southward by a belt of coastal siliciclastics grading southward and eastward to deep water sediments of the Ulus basin. In mid-Bedoulian time, carbonate platform demise from the western region was drowned below deeper marly sediments whereas the eastern siliscilastic-carbonate ramp was buried below coastal clastics.     

Spatial distribution and assemblage structure of macrobenthos in a tidal creek in relation to industrial activities

The impact of petrochemical special economic zone activities on the health status of Jafari Creek was studied by assessing the changes in macroinvertebrate assemblages in nine sites during September 2006–January 2008. The relationship between spatial pattern of macroinvertebrate assemblages and ambient factors (i.e. water temperature, salinity, pH, dissolved oxygen, sediment grain size distribution, sediment organic content, heavy metals contents) was measured. Background enrichment indices, contamination factor and contamination degree, were used to assess the health status in the study area based on nickel, lead, cadmium and mercury contents of the sediments. The macrobenthic communities had a low diversity and were dominated by opportunistic taxa. The BIO-ENV analysis identified salinity, dissolved oxygen, pH and silt/clay content of sediments as the major environmental variables influencing the infaunal pattern. This suggests that management should attempt to ensure minimal disturbance to environmental variables underlying the spatial variation in macroinvertebrate assemblages. Background enrichment indices showed that the health of Jafari Creek has declined over time due to the constant discharge of heavy metals to the Creek system. These indices also identified a significant degree of pollution in the study area. The decrease in the ecological potential of Jafari Creek was best highlighted by the alteration in macrobenthic assemblages.     

Reinterpretation of an archaeological pebble culture from the Middle Mekong River valley,Cambodia

In 1963, E. Saurin and J.‐P. Carbonnel discovered the Sre Sbov site on an alluvial terrace of the Mekong River in central Cambodia. Saurin described a lithic typology dating to the Lower/Middle Pleistocene from this site. Although the original lithic assemblage has been lost, this typology has been used continuously as a reference by Southeast Asian prehistorians. In 2007, a Khmer–French team conducted excavations at Sre Sbov that yielded numerous pebbles and cobbles showing apparently convincing handmade removals, as Saurin had previously described. However, an in‐depth study of this assemblage, combined with a geological survey of the area, led to the conclusion that the stones were, in fact, of natural origin, and that for this reason their typology should be disregarded. Using satellite imagery and geological surveys, we explain how such a misinterpretation may have occurred and define a “buffer zone,” corresponding to the maximal extent of the proto‐Mekong River, where fluvially reworked pebbles and cobbles resembling artifacts may be recovered. © 2009 Wiley Periodicals, Inc.     

Thermal stresses in borehole heat exchangers

The backfilling materials of borehole heat exchangers (BHE), particularly the grout material, must provide a suitable thermal contact and ensure durability to the induced thermal stresses because of the heat loading. In this paper, the thermal stresses that occurred in BHEs because of heat injection or extraction is investigated with an analytical solution of a hollow cylinder model that is adapted for time‐dependent heat loading, the geometry of a BHE, and the thermo‐mechanical properties of surrounding ground conditions. Firstly, the hollow cylinder model is solved with the considered boundary conditions in 2D plane stress. Secondly, the temperature differences at the inner and outer circles of the cylinder are evaluated with the heat line source models for continuous and discontinuous loading to observe the impact of the heat loading schedule. The developed analytical solution for thermal stress investigation is validated with numerical models. It is demonstrated that the analytical solutions agree well with numerical results for two types of BHE configurations (co‐axial and single U‐shaped pipes). Furthermore, the calculated maximum stresses are compared with the tensile strength of grout materials obtained from Brazilian tests. It is predicted that the thermal contraction of the grout, partially constrained by the surrounding rock, generates tensile stresses that may lead to cracking in the BHE. According to the results, the stiffness of rock has a primary role on the developed tensile stresses, and the relationship between the thermal conductivity of the ground and of the grout induces a proportional impact on the magnitude of thermal stresses. Copyright © 2015 John Wiley & Sons, Ltd.     

Stochastic Modeling Approach for the Evaluation of Backbreak due to Blasting Operations in Open Pit Mines

Backbreak is an undesirable side effect of bench blasting operations in open pit mines. A large number of parameters affect backbreak, including controllable parameters (such as blast design parameters and explosive characteristics) and uncontrollable parameters (such as rock and discontinuities properties). The complexity of the backbreak phenomenon and the uncertainty in terms of the impact of various parameters makes its prediction very difficult. The aim of this paper is to determine the suitability of the stochastic modeling approach for the prediction of backbreak and to assess the influence of controllable parameters on the phenomenon. To achieve this, a database containing actual measured backbreak occurrences and the major effective controllable parameters on backbreak (i.e., burden, spacing, stemming length, powder factor, and geometric stiffness ratio) was created from 175 blasting events in the Sungun copper mine, Iran. From this database, first, a new site-specific empirical equation for predicting backbreak was developed using multiple regression analysis. Then, the backbreak phenomenon was simulated by the Monte Carlo (MC) method. The results reveal that stochastic modeling is a good means of modeling and evaluating the effects of the variability of blasting parameters on backbreak. Thus, the developed model is suitable for practical use in the Sungun copper mine. Finally, a sensitivity analysis showed that stemming length is the most important parameter in controlling backbreak.     

Shaping the Kuiper belt size distribution by shattering large but strengthless bodies

The observed size distribution of Kuiper belt objects (KBOs)—small icy and rocky Solar System bodies orbiting beyond Neptune—is well described by a power law at large KBO sizes. However, recent work by Bernstein et al. (2004, Astron. J. 128, 1364-1390) indicates that the size distribution breaks and becomes shallower for KBOs smaller than about 70 km in size. Here we show that we expect such a break at KBO radius ∼40 km since destructive collisions are frequent for smaller KBOs. Specifically, we assume that KBOs are gravity-dominated bodies with negligible material strength. This gives a power-law slope q?3 where the number N>r of KBOs larger than a size r is given by N>r∝r1−q; the break location follows from this slope through a self-consistent calculation. The existence of this break, the break's location, and the power-law slope we expect below the break are consistent with the findings of Bernstein et al. (2004, Astron. J. 128, 1364-1390). The agreement with observations indicates that KBOs as small as ∼40 km are effectively strengthless.