519 research outputs found
Ma.
No full text馬 /鍾景輝譯[鍾景輝譯]原書名: Equus.二幕劇.[Zhong Jinghui yi]Detailed notes in vernacular field onlyDetailed notes in vernacular field only
Chronology and geochemistry of Neoarchean BIF-type iron deposits in the Yinshan Block, North China Craton: implications for oceanic ridge subduction
No full textAbstract not available.Xudong Ma, Hong-Rui Fan, M. Santosh, Jinghui Gu
An analysis and experimental validation of natural frequencies of elastic ellipsoids with the Rayleigh–Ritz method
Get PDFThe Rayleigh–Ritz method is widely employed to analyze free vibrations of elastic solids and structures. For a simple formulation and efficient evaluation of vibrations of elastic ellipsoids, which also include spheres, the Cartesian coordinate system is utilized. It is hoped that the formulation with lengthy expressions can be solved with fewer terms of displacement functions in Chebyshev polynomials for simple evaluations of stiffness and mass matrices of the elastic ellipsoids with the procedure. The vibrations of elastic ellipsoids are calculated with geometric parameters for the validation of the procedure and formulation with known results and the analysis from this study
Short, Multineedle Frequency Domain Reflectometry Sensor Suitable for Measuring Soil Water Content
Get PDFTime domain reflectometry (TDR) is a well-established electromagnetic technique used to measure soil water content. Time domain reflectometry sensors have been combined with heat pulse sensors to produce thermo-TDR sensors. Thermo-TDR sensors are restricted to having relatively short needles to accurately measure soil thermal properties. Short needle lengths, however, can limit the accuracy of the TDR measurement of soil water content. Frequency domain reflectometry (FDR) sensors are an alternative to TDR sensors that can provide an inexpensive measurement of soil water content. The objective of this study was to determine whether short FDR sensors can accurately measure soil water content. We designed and constructed a short FDR sensor. For four soil types across a range of water contents, temperatures, and salt contents, we measured soil dielectric spectra with the short FDR sensor. A vector network analyzer was used to obtain soil dielectric spectra in the 1-MHz to 3-GHz frequency range. The ideal frequency of a short FDR sensor is the frequency at which the permittivity is not altered by changing temperature or salt content. The 47- to 200-MHz range was an ideal frequency range for measuring soil water content, and 70 MHz was the frequency least influenced by temperature and salt content. The short FDR sensor provided quick, continuous, stable, and cheap measurements of soil water content. Because of the promising performance of the short thermo-FDR sensor in laboratory studies, sensors should be evaluated in future field studies.This article is published as Xu, Jinghui, Xiaoyi Ma, Sally D. Logsdon, and Robert Horton. "Short, multineedle frequency domain reflectometry sensor suitable for measuring soil water content." Soil Science Society of America Journal 76, no. 6 (2012): 1929-1937. doi: 10.2136/sssaj2011.0361. Posted with permission.</p
Measurement of Soil Water Content with Dielectric Dispersion Frequency
Get PDFFrequency domain reflectometry (FDR) is an inexpensive and attractive methodology for repeated measurements of soil water content (θ). Although there are some known measurement limitations for dry soil and sand, a fixed-frequency method is commonly used with commercially available FDR probes. The purpose of our study was to determine if the soil dielectric spectrum could be used to measure changes in θ. A multifrequency FDR probe was constructed with a 6-mm diameter, and a soil dielectric spectrum was obtained. Using the dielectric spectrum, the dielectric dispersion frequency (fd) was determined. It was discovered that changes in fd were highly correlated with changes in θ, and a third-order polynomial equation (R2 = 0.96) was developed describing the relationship. The effectiveness of fd for θ measurement was evaluated for three soils and a sand across a range of θ. The effects of soil temperature and soil salinity were also evaluated. Accurate measurements of θ were obtained even in dry soil and sand. The root mean square error of the θ estimated by the fdmeasurement was 0.021. The soil temperature and soil salinity had no measureable effects on θ determination. The use of fd for θ determination should be an effective and accurate methodology, especially when dry soils, soil temperature, and/or soil salinity could potentially cause problems with the θ measurements.This article is published as Xu, Jinghui, Sally D. Logsdon, Xiaoyi Ma, Robert Horton, Wenting Han, and Ying Zhao. "Measurement of Soil Water Content with Dielectric Dispersion Frequency." Soil Science Society of America Journal 78, no. 5 (2014): 1500-1506. doi: 10.2136/sssaj2013.10.0429. Posted with permission.</p
Geochemistry and zircon U-Pb chronology of charnockites in the Yinshan Block, North China Craton: tectonic evolution involving Neoarchaean ridge subduction
No full textThe Yinshan Block, part of the Neoarchaean basement of the Western Block of the North China Craton, is composed of granite–greenstone and granulite–charnockite complexes. We report research on a suite of charnockites from the granulite– charnockite complex and characterize their geochemistry, zircon U–Pb geochronology, and Hf isotopic composition. The charnockites can be divided into intermediate (SiO₂ = 59–63 wt.%) and silicic (SiO₂ = 69–71 wt.%) groups. U–Pb zircon data yield protolith formation ages of 2524 ± 4 Ma, 2533 ± 15 Ma, followed by metamorphism at 2498 ± 3 Ma, 2490 ± 11 Ma, respectively, for these groups. Although the intermediate charnockites are characterized by higher Al₂O₃, TiO₂, Fe₂O₃Τ, MnO, MgO, CaO, P₂O₅, K₂O, Sr, and ∑REE content than the silicic charnockites, the ages and Hf isotopic composition of zircons and REE patterns of both intermediate and silicic charnockites are remarkably consistent, which indicates that they are genetically related. These charnockites are predominantly metaluminous to slightly peraluminous, calc-alkalic to calcic, and magnesian – characteristics generally related to a subduction setting. High-Sr + Ba granites with low K₂O/Na₂O characteristics, shown by these charnockites, imply a mixture of mafic and felsic magmas generated from an enriched mantle + lower crust. High MgO, Ni, Cr and Mg#, low K₂O/Na₂O, and metaluminous to slightly peraluminous natures imply that the source rocks most likely were amphibolites. Coeval calc-alkaline magmatism and high-T granulite– facies metamorphism under low-H₂O activity in the area lead us to propose a model involving mid-ocean ridge subduction within a Neoarchaean convergent margin. The arc-related rocks accreted along the continent margin, and became a barrier when the lithospheric mantle ascended through the slab window. Melt derived from the decompressing mantle mixed with melt derived from the overlying, juvenile lower crust melt, which was warmed and metamorphosed by the ascending lithospheric mantle.Xudong Ma, Hong-Rui Fan, M. Santosh and Jinghui Gu
Abstract 2587: VCF2CNA: a tool for efficiently detecting copy number alteration using VCF genotype data
No full textAbstract
Whole genome sequencing (WGS) is increasingly used in both research and clinical settings. The Variant Call Format (VCF) specification is a widely adopted file format for genetic variation data exchange partially due to its smaller file size compared to raw WGS BAMs. Each variant in a typical VCF file contains its chromosome position, reference/alternative alleles and corresponding allele counts. This makes it possible to identify copy number alterations (CNAs). To this end, we developed VCF2CNA (http://vcf2cna.stjude.org), a web interface tool for CNA analysis from VCF files.
A user of VCF2CNA, uploads a VCF file via the provided web interface. The entire analysis runs remotely with an average run time of 23 minutes. Results are emailed to the user as either a downloadable link or file attachments. VCF2CNA also accepts input in the Mutation Annotation Format (MAF) and the variant file format produced by the Bambino program.
We analyzed 22 TCGA glioblastoma tumor/normal pairs by Illumina technology to evaluate VCF2CNA’s performance. It achieved high consistency (average F1-score: 0.952 ± 0.082) with CONSERTING, a tool that incorporated read-depth and SV data from raw BAMs for CNA detection. A segment-by-segment comparison between results from CONSERTING and VCF2CNA indicated that the latter was less sensitive to focal CNAs. This is expected because there is less information in the VCF input than in raw BAMs. Further analysis using samples with a “fractured genome” pattern revealed that VCF2CNA was more robust to library artifacts and produced relatively clean CNA profiles (on average 76.2-fold reduction compared to the number of segments reported by CONSERTING).
Finally, we analyzed 137 pediatric neuroblastoma samples from the TARGET project, sequenced by Complete Genomics, Inc. (CGI) technology. MYCN amplification has been clinically validated in 33 samples. VCF2CNA identified high amplitude MYCN gains in 32 samples and the remaining sample carried a low-level broad gain covering MYCN. For comparison, CGI’s HMM-based method reported MYCN gains in only 15 out of the 33 samples. VCF2CNA further identified two additional MYCN amplifications among the remaining samples. Collectively, our analysis suggests that VCF2CNA is a platform-independent, efficient, robust and accurate tool for general WGS-based CNA analysis. It further complements CONSERTING, which produces more accurate result in focal CNAs at the cost of significantly higher computational burden.
Citation Format: Daniel K. Putnam, Xiaotu Ma, Stephen V. Rice, Yu Liu, Jinghui Zhang, Xiang Chen. VCF2CNA: a tool for efficiently detecting copy number alteration using VCF genotype data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2587. doi:10.1158/1538-7445.AM2017-2587</jats:p
Optimizing Edge Computing in 5G Networks
No full textMulti-access Edge Computing (MEC) is a concept brought up by ETSI and it places computing, storage, processing and network resources into MEC hosts and places these MEC hosts as close as needed to the telecom network edge in order to reduce service latency and bandwidth usage. For self-driving vehicles, streaming video and real-time gaming, the devices involved (e.g. vehicles, cellphones, etc.) might not have enough capabilities to perform all the computations and might not have sufficient storage capacity; MEC can be used here for offloading data computations and content caching. To enhance service quality and user experience, MEC hosts and MEC applications should be located close(r) to the end-users, which increases the number of handovers between MEC hosts to maintain MEC service continuity for mobile end-users as well as the costs for the telecom operators. Therefore, a balance needs to be found. Consider the fact that mobile UEs need MEC service handovers to maintain service continuity and handovers may cause service interruptions which can cause severe degradation to MEC service qualities and user experience, hence the number of handovers between MEC hosts experienced by end-users should be minimized. To find a suitable deployment of MEC hosts and MEC applications in order to minimize the number of handovers, three greedy algorithms and two heuristic algorithms are introduced, implemented, tested, compared and analyzed in this thesis to see which identifies the deployment mechanism that has the smallest number of handovers. When it is time for a mobile UE to connect to a new MEC host and there are multiple potential choices of the new MEC host, the most suitable one for the UE needs to be determined dynamically according to the real-time condition of each possible MEC host. To achieve this, reinforcement learning is considered. Three different reinforcement learning algorithms based on SARSA learning and Deep Q Network are introduced, implemented, tested, compared and analyzed in this thesis. Furthermore, a decision-making mechanism is designed to cope with exceptional situations where the required service quality cannot be guaranteed
Lithiation-induced phase transitions in alloying anodes for thin film lithium-ion batteries
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2020Cataloged from PDF version of thesis. "Due to the condition of the original material, there are unavoidable flaws in this reproduction. We have made every effort possible to provide you with the best copy available. Thank you. The images contained in this document are of the best quality available"--Disclaimer page.Includes bibliographical references (pages 114-129).As a result of the ever-increasing demands for miniaturized autonomous devices, high-performance batteries compatible with micro-systems have been attracting researchers' attention. Amorphous silicon (a-Si) and germanium (a-Ge), which store lithium through alloying processes rather than through intercalation, are among the top candidates as anodes for thin film Li-ion batteries. This thesis explores different types of lithiation-induced phase transitions and develops corresponding kinetic models in amorphous Si and Ge films using a framework consisting of electrochemical, structural and analytic approaches. The first section of this thesis covers the initial lithiation process of a-Si. Potentiostatic techniques reveal a kink feature in the temporal evolution of current, indicating an interface propagation mechanism for the irreversible phase transition. The rate-limiting step for propagation of the interface between unlithiated Si and the lithiated alloy is further determined to be the diffusion of Li through the lithiated phase, based on quantitative analyses of film-thickness dependence in potentiostatic tests. The second section deals with the reversible lithiation of a-Si beyond the first cycle, often assumed to be governed by simple diffusion into single-phase a-Si. We show that reversible lithiation proceeds through phase transitions between amorphous phases with different stoichiometries. Using a two-step potentiostatic technique and the Johnson-Mehl-Avrami-Kolmogorov model, it is shown that these amorphous-to-amorphous transitions occur through three-dimensional nucleation and growth processes. This conclusion is supported by TEM observations for which phase contrast is achieved through preferential high-energy electron-beam induced sputtering of Li. Instead of a complete transition at fixed voltage, reversible phase transitions in a-Si occur in a step-by-step nucleation fashion. The last section focuses on phase transitions during reversible lithiation of a-Ge using similar techniques to those used for the studies of a-Si. The only crystalline phase, Li₁₅Ge₄, is found to coexist with two amorphous alloy phases over a wide voltage range during lithiation. The formation of this crystalline phase turns is found to be highly constrained by kinetic barriers, and is very sensitive to structural evolutions such as cracking in the early cycles.Jinghui Miao.Ph. D.Ph. D. Massachusetts Institute of Technology, Department of Materials Science and Engineerin
Functional dissociation of the left ventral occipito-temporal cortex in the direct and indirect retrieval of color features
No full textPrevious studies suggest that the storage/retrieval of object features is related to brain regions that are involved in the processing of these features. However, it remains unclear whether, and under what conditions, retrieving information about a feature reactivates the same region that specifically supports that feature's perception. In this functional magnetic resonance imaging ( fMRI) study, we compared brain activation in the left ventral occipito-temporal cortex during subjects performing a color perception task, and direct and indirect color retrieval tasks. After performing the color perception task to localize the regions responsible for color perception, subjects were intensively trained ( outside of the scanner) to remember associations between colors and motion directions, and associations between colors and letters. Then, they were asked to perform two color retrieval tasks in the scanner, with stationary and gray scaled images as control stimuli. The results showed that the bilateral posterior occipito-temporal cortex was activated during the color perception task. When color information was retrieved by direct cues ( motion direction), the same bilateral occipito-temporal region was activated. When color information was retrieved indirectly ( judging whether a motion direction matched a letter by their associated colors), a region anterior to the color perception region in the left ventral occipito-temporal cortex was additionally activated. Our results provided evidence for the functional dissociation in the two subregions of the ventral occipito-temporal cortex during retrieval of color features: the posterior area might relate to perceptual features of color, while the anterior region might relate to the knowledge of associations with color.Previous studies suggest that the storage/retrieval of object features is related to brain regions that are involved in the processing of these features. However, it remains unclear whether, and under what conditions, retrieving information about a feature reactivates the same region that specifically supports that feature's perception. In this functional magnetic resonance imaging ( fMRI) study, we compared brain activation in the left ventral occipito-temporal cortex during subjects performing a color perception task, and direct and indirect color retrieval tasks. After performing the color perception task to localize the regions responsible for color perception, subjects were intensively trained ( outside of the scanner) to remember associations between colors and motion directions, and associations between colors and letters. Then, they were asked to perform two color retrieval tasks in the scanner, with stationary and gray scaled images as control stimuli. The results showed that the bilateral posterior occipito-temporal cortex was activated during the color perception task. When color information was retrieved by direct cues ( motion direction), the same bilateral occipito-temporal region was activated. When color information was retrieved indirectly ( judging whether a motion direction matched a letter by their associated colors), a region anterior to the color perception region in the left ventral occipito-temporal cortex was additionally activated. Our results provided evidence for the functional dissociation in the two subregions of the ventral occipito-temporal cortex during retrieval of color features: the posterior area might relate to perceptual features of color, while the anterior region might relate to the knowledge of associations with color. (C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved
- …
