Control strategies and experimental verifications of the electromagnetic mass damper system for structural vibration control

The electromagnetic mass damper （EMD） control system, as an innovative active control system to reduce structural vibration, offers many advantages over traditional active mass driver/damper （AMD） control systems. In this paper, studies of several EMD control strategies and bench-scale shaking table tests of a two-story model structure are described. First, two structural models corresponding to uncontrolled and Zeroed cases are developed, and parameters of these models are validated through sinusoidal sweep tests to provide a basis for establishing an accurate mathematical model for further studies. Then, a simplified control strategy for the EMD system based on the pole assignment control algorithm is proposed. Moreover, ideal pole locations are derived and validated through a series of shaking table tests. Finally, three benchmark earthquake ground motions and sinusoidal sweep waves are imposed onto the structure to investigate the effectiveness and feasibility of using this type of innovative active control system for structural vibration control. In addition, the robustness of the EMD system is examined. The test results show that the EMD system is an effective and robust system for the control of structural vibrations.     

Co–rich Mn crusts from the Magellan Seamount cluster: the long journey through time

The Magellan seamounts began forming as large submarine shield volcanoes south of the equator during the Cretaceous. These volcanoes formed as a cluster on the small Pacific plate in a period when tectonic stress was absent. Thermal subsidence of the seafloor led to sinking of these volcanoes and the formation of guyots as the seamounts crossed the equatorial South Pacific (10–0°S) sequentially and ocean surface temperatures became too high for calcareous organisms to survive. Guyot formation was completed between about 59 and 45 Ma and the guyots became phosphatized at about 39–34 and 27–21 Ma. Ferromanganese crusts began formation as proto-crusts on the seamounts and guyots of the Magellan Seamount cluster towards the end of the Cretaceous up to 55 Ma after the formation of the seamounts themselves. The chemical composition of these crusts evolved over time in a series of steps in response to changes in global climate and ocean circulation. The great thickness of these crusts (up to 15–20 cm) reflects their very long period of growth. The high Co contents of the outer parts of the crusts are a consequence of the increasing deep circulation of the ocean and the resulting deepening of the oxygen minimum zone with time. Growth of the Co-rich Mn crusts in the Magellan Seamount cluster can be considered to be the culmination of a long journey through time.     

Estimating the geostrophic velocity obtained by HF radar observations in the upstream area of the Kuroshio

A method to extract geostrophic current in the daily mean HF radar data in the Kuroshio upstream region is established by comparison with geostrophic velocity determined from the along-track altimetry data. The estimated Ekman current in the HF velocity is 1.2% (1.5%) and 48° (38°)-clockwise rotated with respect to the daily mean wind in (outside) the Kuroshio. Furthermore, additional temporal smoothing is found necessary to remove residual ageostrophic currents such as the inertial oscillation. After removal of the ageostrophic components, the HF geostrophic velocity agrees well with that from the altimetry data with rms difference 0.14 (0.12) m/s in (outside) the Kuroshio.     

Effects of an Artificial Breakwater on the Distributions of Planktonic Microbial Communities

The summer distributions of planktonic microbial communities (heterotrophic and phtosynthetic bacteria, phtosynthetic and heterotrophic nanoflagellates, ciliate plankton, and microphytoplankton) were compared between inner and outer areas of Lake Sihwa, divided by an artificial breakwater, located on the western coast of Korea, in September 2003. The semienclosed, inner area was characterized by hyposaline surface water (<17 psu), and by low concentrations of dissolved oxygen (avg. 0.4 mg L¹) and high concentrations of inorganic nutrients (nitrogenous nutrients >36 μM, phosphate <4 μM) in the bottom layer. Higher densities of heterotrophic bacteria and nanoflagellates also occurred in the inner area than did in the outer area, while microphytoplankton (mainly diatoms) occurred abundantly in the outer area. A tiny tintinnid ciliate, Tintinnopsis nana, bloomed into more than 10⁶ cells L¹ at the surface layer of the inner area, while its abundance was much lower (10³-10⁴ cells L¹) in the outer area of the breakwater. Ciliate abundance was highly correlated with heterotrophic bacteria (r = 0.886, p < 0.001) and heterotrophic flagellates (r = 0.962, p < 0.001), indicating that rich food availability may have led to theT. nana bloom. These results suggest that the breakwater causes the eutrophic environment in artificial lakes with limited flushing of enriched water and develops into abundant bacteria, nanoflagellates, and ciliates.     

Use of laser range and height texture cues for building identification

Airborne LiDAR has found application in an increasing number of mapping and Geo-data acquisition tasks. Apart from terrain information generation, applications such as automatic detection and modeling of objects like buildings or vegetation for the generation of 3-D city models have been explored. Besides the height itself, height texture defined by local variations of the height is a significant parameter for object recognition. The paper explores the potential of the analysis of height texture as a cue for the automatic detection of objects in LiDAR datasets. A number of texture measures were computed. Based on their definition and computation these measures were used as bands in a classification algorithm, and objects like buildings, single trees, and roads could be recognized.     

Origin of dyke swarms in Wadi El Redi-Wadi Lahami area,southern Eastern Desert of Egypt

Dykes predominate within the Neoproterozoic rocks, especially granites, of Wadi El Redi-Wadi Lahami area in the southern Eastern Desert of Egypt. The dyke swarms form three major suites: from the oldest to the youngest, they are basaltic andesite—Suite 1 (E-W and ENE-WSW), rhyolite—Suite 2 (NE-SW), and andesite—Suite 3 (NNE-SSW, NNW-SSE, and NW-SE). Despite the wide ranges of the dyke compositions, the feldspar and amphibole are usually the essential forming minerals. The plagioclase arrays between Ab_0.9An_99.10 in the basaltic andesite and Ab_98.80An_0.70 in the rhyolite, while sanidine ranges from Or_44.60Ab_49.70 to Or_98.40Ab_1.60. Amphibole in Suite 1 and 3 (Al₂O₃, TiO₂, Na₂O, and K₂O are the lowest and those of SiO₂ and CaO are the highest) samples are usually magnesio-hornblende, whereas it is edenite and tschermakite in Suite 2 dykes. Despite all parent magmas have calc-alkaline affinity, some elements such as Ni show an erratic behavior against the progressing differentiation from one magma chamber and implying for an assimilation of the country rocks. The high contents of amphibole, the depletion in Ti, and the enrichment in large-ion lithophile elements (such as K, Rb, Ba, Sr, and Ba) compared to the primitive mantle composition are consistent with parent hydrous melts generated due to extension above the subduction zone. The estimated compositions of liquids in equilibrium with amphiboles and the pressures at which they crystallized (4.61–7.8 kbar for the Suite 2 and 1.5–2 kbar for the Suites 1 and 3) are greatly varied. These are indications for a difference in the source regions of the parent magmas of the studied dykes. It is supposed that the Suite 1 and 2 dykes are a conjugate set emplaced due to the NW-SE crustal extension in the Arabian-Nubian shield, whereas the Suite 3 dykes generated due to the rifting along the Red Sea.     

Recession of Milam Glacier,Kumaun Himalaya,Observed via Lichenometric Dating of Moraines

Glaciers being very sensitive to climate change have been identified as one of the best indicators of climate change and evidences have proved that most of the Himalayan glaciers have receded with an increased rate during the recent past under the influence of global warming. Lichenometric study was carried out on the moraines of Milam glacier (located in Pithoragarh district of Uttarakhand) with the help of lichen species Dimelaena oreina having an average annual growth rate of 1.31 mm. The study revealed that Milam glacier has receded 1450 m in last 69.37 years with an average recession rate of 20.90 m/year. Since lichenometric studies are cost effective and ecofriendly in comparison to carbon dating, satellite and remote sensing based studies and also reliable, hence, it should be promoted in Himalaya which is an abode of glaciers.     

Mineralogical,geochemical and microfabric evidences of gypsum crusts: a case study from Budapest

High levels of SO₂ and particulate pollution enable the rapid development of gypsum-rich weathering crusts in Budapest. Two types of white crusts, thin and thick ones, and two forms of black crusts, laminar and framboidal ones, were studied in limestone buildings of the parliament and Citadella. The percentage of crust cover and damage categories were documented on selected walls. Petrographic, XRD, XRF and sulphur isotope analyses were performed under laboratory conditions to understand the mechanism of crust formation. White crusts found both on exposed and sheltered walls display a calcite-rich layer with gypsum, while black crusts are enriched with gypsum. The sulphur isotopic composition of white and black crusts overlaps, but the crusts are slightly enriched in heavy isotopes compared to rainwater. S content, Si/Al ratios and particulates in black crusts suggest that air pollution (SO₂, dust) contributes to black crust formation. The accumulation of sulphur and Zn enrichment of white crusts were also documented indicating that under high pollution levels, even these compound can accumulate on exposed facades.     

Observing changes in groundwater resource using hydro-chemical and isotopic parameters: a case study from Bist Doab,Punjab

The continuous and large-scale abstraction of groundwater has created a groundwater depletion problem in several parts of the Punjab state including Bist Doab, the interfluve region of Beas and Satluj rivers. In the present study, a few important parameters, viz. water level, stable isotope, EC, temperature, groundwater age, that can be used to fingerprint the over-exploitation of groundwater have been examined. It has been observed that with the increase in over-exploitation, the yield of shallow aquifer is progressively getting reduced and as a result forcing the farmers to sink their wells to deeper depths. With abstraction of deeper aquifer, the storage of old groundwater at the deeper aquifer is declining and getting replaced by induced accelerated inflow of young water from the recharge zone and the overlying shallow aquifer. The signatures of the modern water have been observed in the data analyzed for isotopic, hydro-chemical facies, electrical conductivity and temperature of water from deeper aquifer. The study has identified the usefulness of these parameters for identifying groundwater over-exploitation in the region. Depleting water resource may stagnate the economic progress of the region. The paper provides suitable water resource management strategies to be adopted to improve the sustainability of water resources and economic growth in the region.     

DISASTER ANALYSIS AND COUNTERMEASURES OF LAND SUBSIDENCE CAUSED BY COAL CUTTING IN CHINA

In recent years, many coal-producing countries have paid great attention to the land subsidence causedby coal cutting. In China, because of the dense population in coalfield areas, the land subsidence hazard is more seri-ous. After a brief analysis on the mechanism of land subsidence, this paper gives a comprehensive and systematical ac-count on all kinds of hazards caused by the land subsidence in China. The study shows that land subsidence has endan-gered land, buildings, traffic and communication lines, dykes and dams. It also causes damage to ecological and socialenvironment. In order to lessen the hazard of land subsidence, preventive measures should be taken to reduce the col-lapse amount, such as extraction with stowing, banded mining system, succession and coordination mining system, orhigh-pressure mudflow between rock strata. Measures of reinforcing or moving certain buildings should also be taken toreduce the destructive degree. In order to harness the subsidence land and bring them under control for fanning, mea-sures should be taken such as filling with spoil or fine breeze, excavating the deeper and covering the shallower land.