Surface Sediments of the Pearl River Estuary (South China Sea) - Spatial Distribution of Sedimentological/Geochemical Properties and Environmental Interpretation

The Pearl River Delta (South China) is one of the densest populated regions of the world. This study aims at the investigation and interpretation of the spatial distribution of grain size parameters and geochemical parameters obtained from surface sediment samples. These samples have been taken during cruises in 2003, 2004 and 2005. Investigations of the spatial correlations of the parameters obtained reveal an approximately north-south directed trend for the majority of the parameters. The trend was removed before applying Ordinary Kriging for interpolation. The maps obtained show non-uniform distribution patterns of the sedimentological and geochemical parameters. Here e.g. the concentrations of the As, Co, Cu, Hg and Ni decrease to the more marine influenced southeastern parts and show a higher concentration in the central part and at the western shoals of the estuary.The Pearl River Delta (South China) is one of the densest populated regions of the world. This study aims at the investigation and interpretation of the spatial distribution of grain size parameters and geochemical parameters obtained from surface sediment samples. These samples have been taken during cruises in 2003, 2004 and 2005. Investigations of the spatial correlations of the parameters obtained reveal an approximately north-south directed trend for the majority of the parameters. The trend was removed before applying Ordinary Kriging for interpolation. The maps obtained show non-uniform distribution patterns of the sedimentological and geochemical parameters. Here e.g. the concentrations of the As, Co, Cu, Hg and Ni decrease to the more marine influenced southeastern parts and show a higher concentration in the central part and at the western shoals of the estuary

Low-density star cluster formation: Discovery of a young faint fuzzy on the outskirts of the low-mass spiral galaxy NGC 247

The classical globular clusters found in all galaxy types have half-light radii of rh ~2-4 pc, which have been tied to formation in the dense cores of giant molecular clouds. Some old star clusters have larger sizes, and it is unclear if these represent a fundamentally different mode of low-density star cluster formation. We report the discovery of a rare, young \u27faint fuzzy\u27 star cluster, NGC 247-SC1, on the outskirts of the low-mass spiral galaxy NGC 247 in the nearby Sculptor group, and measure its radial velocity using Keck spectroscopy. We use Hubble Space Telescope imaging to measure the cluster half-light radius of rh ≃ 12 pc and a luminosity of LV ≃ 4 × 105Lθ. We produce a colour-magnitude diagram of cluster stars and compare to theoretical isochrones, finding an age of ≃300 Myr, a metallicity of [Z/H] ~-0.6 and an inferred mass of M∗ ≃ 9 × 104Mθ. The narrow width of blue-loop star magnitudes implies an age spread of ≲50 Myr, while no old red-giant branch stars are found, so SC1 is consistent with hosting a single stellar population, modulo several unexplained bright \u27red straggler\u27 stars. SC1 appears to be surrounded by tidal debris, at the end of an ∼2 kpc long stellar filament that also hosts two low-mass, low-density clusters of a similar age. We explore a link between the formation of these unusual clusters and an external perturbation of their host galaxy, illuminating a possible channel by which some clusters are born with large sizes

Overview of the MOSAiC expedition: Snow and sea ice

Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice–ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice

No Excuses Charter Schools: A Meta-Analysis of the Experimental Evidence on Student Achievement

While charter schools differ widely in philosophy and pedagogical views, the United States’s most famous urban charter schools typically use the No Excuses approach. Enrolling mainly poor and minority students, these schools feature high academic standards, strict disciplinary codes, extended instructional time, and targeted supports for low-performing students. The strenuous and regimented style is controversial amongst some scholars, but others contend that the No Excuses approach is needed to rapidly close the achievement gap. We conduct the first meta-analysis of the achievement impacts of No Excuses charter schools. Focusing on experimental studies, we find that No Excuses charter schools significantly improve math scores and reading scores. We estimate gains of 0.25 and 0.16 standard deviations on math and literacy achievement, respectively, as the effect of attending a No Excuses charter school for one year. Though the effect is large and meaningful, we offer some caveats to this finding and discuss policy implications for the United States as well as other countries

Design of a Readout Scheme for a MEMS Microphone

This design mainly proposes a readout scheme for MEMS microphone with positive feedback to decrease the parasitic capacitance. It is designed in CMOS014 technology with a supply voltage of 3.3 V. The proposed architecture can increase the microphone’s sensitivity with a comparatively low bias voltage. It enables the microphone to achieve high sensitivity even if it is loaded by an amplifier with large input capacitance. In the mean time, the SNR and THD are not affected much. The Spectre simulation shows that the system can achieve 61 dB SNR (A-weighted), 0.5% THD (1Pa sound pressure) and 1 mW power consumption. Several traditional readout schemes for MEMS microphone are also discussed and compared. The scheme which is based on amplitude modulation is tested and measured on PCB level.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Acoustic Emission-Based Detection in Restricted-Access Areas Using Multiple PZT Disc Sensors

The performance of the Acoustic Emission (AE) technique is significantly dependent on the sensors attached to the structural surface. Although conventional commercially AE sensors, like R15a and WSa sensors, have been extensively employed in monitoring many different structures, they are unavailable in restricted-assess areas. In contrast, thin PZT sensors are small, inexpensive and lightweight. These thin PZT sensors have a great potential for passive sensing to detect AE signals. However, their utility in AE monitoring is limited due to their low signal-to-noise ratio and information incompleteness because of their simple construction. This work discusses the issues and possible solutions with regards to the specific selection and application of thin PZT sensors for passive sensing. The compatibility of different thin PZT sensors and conventional bulky sensors is investigated using pencil break lead (PBL) tests. The comparison between the recorded signals is carried out in both the time domain and frequency domain for these sensors. To improve the reliability and performance of the thin PZT sensors, a methodology employing multiple thin PZT sensors of different sizes is proposed based on machine learning techniques and sensor data fusion.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite StructuresStructural Integrity & Composite

The impact of social media on software engineering practices and tools

Software Engineerin

Long-range correlations of microseism-band pressure fluctuations in the ocean

We investigate the spatial coherence of underwater ambient noise using a yearlong time-series measured off Ascension Island. Qualitative agreement with observed cross-correlations is achieved using a simple range-dependent model, constrained by earlier, active tomographic studies in the area. In particular, the model correctly predicts the existence of two weakly dispersive normal modes in the microseism frequency range, with the group speed of one of the normal modes being smaller than the sound speed in water. The agreement justifies our interpretation of the peaks of the measured cross-correlation function of ambient noise as modal arrivals, with dispersion that is sensitive to crustal velocity structure. Our observations are consistent with Scholte to Moho head wave coupled propagation, with double mode conversion occurring due to the bathymetric variations between receivers. We thus demonstrate the feasibility of interrogating crustal properties using noise interferometry of moored hydrophone data at ranges in excess of 120 km.Applied Geophysics and Petrophysic

Screening the stones of Venice: Mapping social perceptions of cultural significance through graph-based semi-supervised classification

Mapping cultural significance of heritage properties in urban environment from the perspective of the public has become an increasingly relevant process, as highlighted by the 2011 UNESCO Recommendation on the Historic Urban Landscape (HUL). With the ubiquitous use of social media and the prosperous developments in machine and deep learning, it has become feasible to collect and process massive amounts of information produced by online communities about their perceptions of heritage as social constructs. Moreover, such information is usually inter-connected and embedded within specific socioeconomic and spatiotemporal contexts. This paper presents a methodological workflow for using semi-supervised learning with graph neural networks (GNN) to classify, summarize, and map cultural significance categories based on user-generated content on social media. Several GNN models were trained as an ensemble to incorporate the multi-modal (visual and textual) features and the contextual (temporal, spatial, and social) connections of social media data in an attributed multi-graph structure. The classification results with different models were aligned and evaluated with the prediction confidence and agreement. Furthermore, message diffusion methods on graphs were proposed to aggregate the post labels onto their adjacent spatial nodes, which helps to map the cultural significance categories in their geographical contexts. The workflow is tested on data gathered from Venice as a case study, demonstrating the generation of social perception maps for this UNESCO World Heritage property. This research framework could also be applied in other cities worldwide, contributing to more socially inclusive heritage management processes. Furthermore, the proposed methodology holds the potential of diffusing any human-generated location-based information onto spatial networks and temporal timelines, which could be beneficial for measuring the safety, vitality, and/or popularity of urban spaces.Heritage & Architectur

Controlling the Lithium-Metal Growth to Enable Low-Lithium-Metal-Excess All-Solid-State Lithium-Metal Batteries

Solid-state lithium-metal batteries are considered to be promising candidates for next-generation high-energy density storage devices to power electrical vehicles. Critical challenges for solid-state lithium-metal batteries include the large morphological changes associated with the plating and stripping of lithium metal and decomposition of the solid electrolyte, because of the reductive nature of the lithium metal, both increasing the lithium metal-solid electrolyte interface resistance. This is especially challenging when starting in the discharged state with a bare anode or "anode-less"current collector facing the solid electrolyte. To overcome this, a 100-nm thin layer of ZnO is deposited on the copper current collector with atomic layer deposition (ALD). During the first charge, this results in more homogeneous lithium-metal growth, rationalized by the formation of a Zn-Li alloy that acts as seed crystals for the lithium metal. The resulting more homogeneous lithium-metal growth maintains better contact with the solid electrolyte, leading to more reversible cycling of lithium metal. Minor prelithiating of the ZnO/Cu anode with 1 mAh/cm2 further improves the cycling performance, as demonstrated in a full all-solid-state cell using LiFePO4 as a cathode, resulting in an average Coulombic efficiency of >95%. These findings mark the first steps in an interface strategy to overcome the challenges at the solid electrolyte/lithium-metal interface in solid-state lithium-metal batteries.RST/Storage of Electrochemical EnergyInstrumenten groe