293 research outputs found
Data for: Coral reef carbonate δ13C records from the northern South China Sea: A useful proxy for seawater δ13C and the carbon cycle over the past 1.8 Ma
No full textCarbon and Strontium isotopes dat
Data for: 3500-year western Pacific storm record warns of additional storm activity in a warming warm pool
No full textIn this study, a regional storm reconstruction is performed based on a grain-size analysis (1450 samples) and stratigraphic modelling of the accelerator mass spectrometry radiocarbon dates of benthic foraminifera (19 samples) from two neighbouring lagoon cores from Lingyang Reef in the Xisha Islands located in the northern South China Sea of the western Pacific
High-precision TIMS U-series and AMS 14C dating of a coral reef lagoon sediment core from southern South China Sea and its environmental significance
No full textAccurate dating of lagoon sediments has been a haunting problem, although lagoon profiles, usually with high deposition rates, have a great potential for high-resolution climate reconstruction. We report 26 high-precision TIMS U-series dates (for coral branches) and 5 AMS 14C dates (for foraminifera) for a 15.4-m-long lagoon core from Yongshu reef, Nansha area, southern South China Sea (SCS). All the dates are in the correct depositional sequence, revealing a ~4000-yr continuous depositional history. The results indicate the deposition rate varied in the range of 0.8 and 24.6 mm/yr, with an average of 3.85mm/yr, corresponding to an average net carbonate accumulation rate of 4,197 g CaCO3 m-2yr-1. Two fast deposition periods, one from 103 to 305 AD and the other for the last 1000 years, are identified. Episodes of elevated depositions within the last 1000 years correlated well in timing with strong storm events identified from storm-relocated coral blocks in the area (Yu et al., 2004, Palaeo3). The highest deposition rates in the 1800s may be related to the tsunamis generated by the 1833 Sumatran earthquake and the 1883 Krakatau eruption. The combination of coral TIMS U-series ages and foraminifera AMS 14C ages reveals that the radiocarbon reservoir ages (R) varied between 557 and 1042 years during the last 4000 years, which are 150 to 650 years greater than the estimated global mean of 400 yr. The reservoir ages show a decreasing trend since mid-Holocene, consistent with those in the Pacific
Piezoelectric Energy Harvesting with a Nonlinear Energy Sink
No full textEnergy transfer from one system to another system, or vice versa, is happening constantly in many
processes with various forms. Vibration in machines or structures can be considered as a form of
energy transfer from a source to a receiver. In general, such vibration is unwanted. Vibration
suppression is of importance in order to protect machines or structures. To monitor vibration of a
large system such as building or bridge, a network of sensors is used. Supply of power to these
sensors is challenging due to various difficulties such as accessibility or cost. Energy harvesting
using ambient vibration is motivated to make sensors autonomous. Vibration energy can be
converted into electric energy through electromagnetic transduction or piezoelectric effect. This
research proposes a method to achieve simultaneous vibration suppression and energy harvesting
in the broadband manner.
A nonlinear energy sink (NES) is a special vibration absorber that is capable of sinking or
localizing vibration energy from a primary system. Unlike a linear or nonlinear vibration absorber,
the NES’s spring is essentially nonlinear. In this research, a variant NES is developed to achieve
vibration suppression and energy harvesting in a broad frequency band. The developed apparatus
consists of a fixed-fixed composite beam acting as the NES spring and two magnets attached at
the middle of the beam acting as the NES mass. The composite beam is formed by a thin steel
beam and two piezoelectric bimorphs attached at the ends of the steel beam. The piezoelectric
bimorphs convert the NES vibration energy into electric one. The system modeling is presented.
System identification is conducted to determine the parameter values. The transient behaviours of
the system are investigated numerically and experimentally. It has shown that the developed
apparatus demonstrates the characteristics similar to those of the NES. The harmonically forced
responses of the system are examined. The approximate analytical solutions of the steady-state
responses are derived. The Matcont is used to obtain the frequency responses plots for various
cases. An experimental study has been conducted. Both the numerical solutions and experimental
results show that the developed apparatus is capable of harvesting energy while suppressing
vibration in a wide frequency band
3D Fiber Reinforced Concrete Printing of Houses in Wujiazhuang, China
No full textNowadays, with the rapid development of 3D printing technology, more and more applications of this technology can be seen in daily life, and architecture is one of the important directions. There are already a lot of creative buildings completed by 3D printing in the world, and many of them have already been put into use. One of the big challenges of this technology is that since the properties of freshly extruded concrete are not high enough, it becomes necessary to use reinforcement strategies to make the concrete meet the requirements of 3D printing. One of the common reinforcement strategies is achieved by adding fibers to the concrete.In this study, through finite element modeling and analysis of a 3D concrete printed farmhouse located in Wujiazhuang, China, the whole process of 3D printing of the farmhouse, as well as the internal forces of the structure when it enters into use after the printing is completed was analyzed, and the effect of the application of fiber reinforced concrete in the whole process of 3D printing, as well as the optimization strategy was shown in detail.The literature study summarizes the current state of development of additive manufacturing and 3D printing, as well as the different types classified through the process; introduces FEM and describes its application in 3D printing; describes the process of making fiber reinforced concrete and its advantages over the material properties of normal concrete; reveals the changes in material properties of materials used for 3D printing in the early stages; and describes the field situation of the Wujiazhuang farmhouse and the printing process.The deformation and stress distribution of the whole structure under the use state had been analyzed by linear static analysis in finite element software, and the material distribution of the structure had been preliminarily determined. After that, the whole printing process of the structure was analyzed by stage and structural nonlinear analysis, and the key issues such as how to simulate the truss structure wall and what parameters will affect the number of printable layers of the structure were analyzed by building multiple models. Finally, the material distribution and printing solution of the structure were given.The results given were further modified by continuing to reduce the deformation of the structure to meet the code requirements for the displacement of the formwork structure. Several methods were given to minimize the deformation to meet the code requirements from two different perspectives: the geometry of the structure and the material properties.The reliability of the modeling in this study and the accuracy of the results were verified by using finite element software modeling to analyze a 3D printing model from a paper and comparing the results. The conclusions of this study and the possible applications of the conclusions in 3D printing were finally given, as well as possible directions for future follow-up research.Civil Engineering | Building Engineerin
Three windows to Mid-Holocene seasonal SST changes from 18O and Sr/Ca records of a Porites lutea coral of Leizhou Peninsula and their comparison with the warmest decade of the 20th century (1990-2000)
No full text
Strontium/Calcium ratio measurements and sea surface temperatures from corals of Hainan Island, South China Sea
No full textStrontium/Calcium ratio measurements and sea surface temperatures from corals of Hainan Island, South China Se
(Table 1) Isotopic ratios of corals from the South China Sea
No full text(Table 1) Isotopic ratios of corals from the South China Se
(Table 1) Uranium-Thorium datings from corals of Hainan Island, South China Sea
No full textAll isotopic ratios are activity ratios. Errors are quoted as 2 sigma. Half lives used in the calculation are as follows: 230Th, 77381 ± 590 (2s); 234U, 244600 ± 490 (2s); Ludwig et al. [1992]. Corrected 230Th ages assume an 232Th/238U atomic ratio of 3.83 ± 1.9 for the detrital materials, which is at secular equilibrium. Delta 234U initial is calculated on the basis of 230Th age
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