Monitoring the Characteristics of the Bohai Sea Ice Using High-Resolution Geostationary Ocean Color Imager (GOCI) Data

Satellite remote sensing data, such as moderate resolution imaging spectroradiometers (MODIS) and advanced very high-resolution radiometers (AVHRR), are being widely used to monitor sea ice conditions and their variability in the Bohai Sea, the southernmost frozen sea in the Northern Hemisphere. Monitoring the characteristics of the Bohai Sea ice can provide crucial information for ice disaster prevention for marine transportation, oil field operation, and regional climate change studies. Although these satellite data cover the study area with fairly high spatial resolution, their typically limited cloudless images pose serious restrictions for continuous observation of short-term dynamics, such as sub-seasonal changes. In this study, high spatiotemporal resolution (500 m and eight images per day) geostationary ocean color imager (GOCI) data with a high proportion of cloud-free images were used to monitor the characteristics of the Bohai Sea ice, including area and thickness. An object-based feature extraction method and an albedo-based thickness inversion model were used for estimating sea ice area and thickness, respectively. To demonstrate the efficacy of the new dataset, a total of 68 GOCI images were selected to analyze the evolution of sea ice area and thickness during the winter of 2012–2013 with severe sea ice conditions. The extracted sea ice area was validated using Landsat Thematic Mapper (TM) data with higher spatial resolution, and the estimated sea ice thickness was found to be consistent with in situ observation results. The entire sea ice freezing–melting processes, including the key events such as the day with the maximum ice area and the first and last days of the frozen season, were better resolved by the high temporal-resolution GOCI data compared with MODIS or AVHRR data. Both characteristics were found to be closely correlated with cumulative freezing/melting degree days. Our study demonstrates the applicability of the GOCI data as an improved dataset for studying the Bohai Sea ice, particularly for purposes that require high temporal resolution data, such as sea ice disaster monitoring

Состав углеводородов в продуктах синтеза из окиси углерода и водяного пара

Исследован состав продукта синтеза из окиси углерода и водяного пара методами газожидкостной хроматографии. Показано, что продукт представлен смесью углеводородов C5-C20, спиртами и кислотами состава C1-C12; наряду с н-парафинами и а-олефинами присутствуют соединения изостроения. Определен индивидуальный состав фракции С5-С8, где обнаружено 83 компонента

Macro and nanoscale wear behaviour of Al-Al 2 O 3 nanocomposites fabricated by selective laser melting

Aluminium-based composites are increasingly applied within the aerospace and automotive industries. Tribological phenomena such as friction and wear, however, negatively affect the reliability of devices that include moving parts; the mechanisms of friction and wear are particularly unclear at the nanoscale. In the present work, pin-on-disc wear testing and atomic force microscopy nanoscratching were performed to investigate the macro and nanoscale wear behaviour of an Al-Al2O3 nanocomposite fabricated using selective laser melting. The experimental results indicate that the Al2O3 reinforcement contributed to the macroscale wear-behaviour enhancement for composites with smaller wear rates compared to pure Al. Irregular pore surfaces were found to result in dramatic fluctuations in the frictional coefficient at the pore position within the nanoscratching. Both the size effect and the working-principle difference contributed to the difference in frictional coefficients at both the macroscale and the nanoscale

Исследование прочности концевых фрез методом конечных элементов

В процессе исследования проводились: обзор и анализ научно-технической литературы по теме магистерской работы, формулирование цели и задач исследования прочности режущих пластин концевой фрезы, проведение экспериментов для измерений технологических и физических составляющих силы резании, исследование распределения контактных напряжений на передней и задней поверхностях острозаточенного и изношенного инструмента, анализ полученных эпюр, вывод эмпирических формул для расчёта эпюр контактных напряжений, исследование НДС режущей пластины фрезы, определение оптимальной геометрии режущей пластины при обработке разных материалов.In the course of probe were spent: the review and the assaying of the scientific and technical literature on a theme of master Diploma Thesis, a formulation of the purpose and research problems of strength of cutting inserts of an end mill, carry out experiments for measurements of technological and physical components of force cutting, research of distribution of contact stresses on a rake both flank surfaces of new and the worn out cutting tool, the assaying received epures, an output empirical formulas for calculation of contact stresses, probe of the SDC of a cutting plate of a mill, definition of optimum geometry of a cutting plate in machining of different materials

Al-Cu-Mg alloy powder reinforced with graphene nanoplatelets: morphology, flowability and discrete element simulation

Research in metal matrix composites (MMCs) indicates that superior mechanical properties may be achieved by embedding reinforcement materials. However, the development of new composite powder for additive manufacturing requires an in-depth understanding of its key characteristics prior to its use in the fabrication process. This paper focuses on the low-energy ball milling (LEBM) of aluminium 2024 alloy (AA2024) reinforced with graphene nanoplatelets (GNPs). The main aim is to investigate the effect of the milling time (from 0.5 to 16 h) on the morphology and flowability of the powder. The study shows that, while short milling times (under 2 h) could not break the Van der WaRals forces between nanoparticles, GNPs were well separated and sufficiently covered the powder surface after 4 h of milling, thanks to the continuously applied impact energy. Longer milling time provides increasingly similar flowability results, confirmed by both the experimental work and discrete element model (DEM) simulations. Moreover, the ball milling process decreases the crystallite size of the milled powder by 24%, leading to a 3% higher microhardness. Lastly, the surface energy of the powder was determined as 1.4 mJ/m2 by DEM, using the angle of repose of the as-received powder from experimental work

Pretrained Language Model based Web Search Ranking: From Relevance to Satisfaction

Search engine plays a crucial role in satisfying users' diverse information needs. Recently, Pretrained Language Models (PLMs) based text ranking models have achieved huge success in web search. However, many state-of-the-art text ranking approaches only focus on core relevance while ignoring other dimensions that contribute to user satisfaction, e.g., document quality, recency, authority, etc. In this work, we focus on ranking user satisfaction rather than relevance in web search, and propose a PLM-based framework, namely SAT-Ranker, which comprehensively models different dimensions of user satisfaction in a unified manner. In particular, we leverage the capacities of PLMs on both textual and numerical inputs, and apply a multi-field input that modularizes each dimension of user satisfaction as an input field. Overall, SAT-Ranker is an effective, extensible, and data-centric framework that has huge potential for industrial applications. On rigorous offline and online experiments, SAT-Ranker obtains remarkable gains on various evaluation sets targeting different dimensions of user satisfaction. It is now fully deployed online to improve the usability of our search engine