6,340 research outputs found

    Performance evaluation of channel estimation techniques for MIMO-OFDM systems with adaptive sub-carrier allocation

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    Cross-institution online problem based learning in Chinese Medicine Education

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    New education technology drives the pedagogical changes nowadays. Teaching and learning collaborations can now be extended beyond institutional boundaries. This study reports a new attempt of cross-institution collaboration in co-teaching a Chinese Medicine course. A Cross-institution Online Problem-based Learning (COPBL) is designed and implemented by the University of Hong Kong (HKU) and Chengdu University of Traditional Chinese Medicine (CDUTCM). There are 25 students from HKU and 24 students from CDUTCM who have participated in the COPBL. It is a supplementary component to courses and a seven-step approach has been adopted. Students work individually and collaboratively with floating-facilitators. The classes are blended with face-to-face and online components. As an initial step to understand the effectiveness of COPBL, this study specifically focuses on students’ use of the discussion forum, which is a key online component in COPBL. There are 91.8% of students who have viewed the discussion forum in total, 839 of view counts in all discussion forums. There are 63 replies recorded in all of the discussion forums. The replies could be identified into following categories, comments (33%), comments and questions (27%), responses (37%), and others (3%).This study has demonstrated that problem-based learning can be conducted in a blended form with traditional classroom teaching methods and well-designed online components. The COPBL offers new possibilities in redesigning pedagogy with new education technology. It could bring our education into a new era surrounded with new learning experiences.postprin

    Kinetics of carbonate mineral dissolution in CO2-acidified brines at storage reservoir conditions.

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    We report experimental measurements of the dissolution rate of several carbonate minerals in CO2-saturated water or brine at temperatures between 323 K and 373 K and at pressures up to 15 MPa. The dissolution kinetics of pure calcite were studied in CO2-saturated NaCl brines with molalities of up to 5 mol kg(-1). The results of these experiments were found to depend only weakly on the brine molality and to conform reasonably well with a kinetic model involving two parallel first-order reactions: one involving reactions with protons and the other involving reaction with carbonic acid. The dissolution rates of dolomite and magnesite were studied in both aqueous HCl solution and in CO2-saturated water. For these minerals, the dissolution rates could be explained by a simpler kinetic model involving only direct reaction between protons and the mineral surface. Finally, the rates of dissolution of two carbonate-reservoir analogue minerals (Ketton limestone and North-Sea chalk) in CO2-saturated water were found to follow the same kinetics as found for pure calcite. Vertical scanning interferometry was used to study the surface morphology of unreacted and reacted samples. The results of the present study may find application in reactive-flow simulations of CO2-injection into carbonate-mineral saline aquifers

    An investigation of dynamic subcarrier allocation in MIMO–OFDMA systems

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    An investigation of dynamic sub-carrier allocation in OFDMA systems

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    Diminished temperature and vegetation seasonality over northern high latitudes

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    Global temperature is increasing, especially over northern lands (>50° N), owing to positive feedbacks1. As this increase is most pronounced in winter, temperature seasonality (ST)—conventionally defined as the difference between summer and winter temperatures—is diminishing over time2, a phenomenon that is analogous to its equatorward decline at an annual scale. The initiation, termination and performance of vegetation photosynthetic activity are tied to threshold temperatures3. Trends in the timing of these thresholds and cumulative temperatures above them may alter vegetation productivity, or modify vegetation seasonality (SV), over time. The relationship between ST and SV is critically examined here with newly improved ground and satellite data sets. The observed diminishment of ST and SV is equivalent to 4° and 7° (5° and 6°) latitudinal shift equatorward during the past 30 years in the Arctic (boreal) region. Analysis of simulations from 17 state-of-the-art climate models4 indicates an additional STdiminishment equivalent to a 20° equatorward shift could occur this century. How SV will change in response to such large projected ST declines and the impact this will have on ecosystem services5 are not well understood. Hence the need for continued monitoring6 of northern lands as their seasonal temperature profiles evolve to resemble thosefurther south.Lopullinen vertaisarvioitu käsikirjoitu

    Automated NMR relaxation dispersion data analysis using NESSY

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    <p>Abstract</p> <p>Background</p> <p>Proteins are dynamic molecules with motions ranging from picoseconds to longer than seconds. Many protein functions, however, appear to occur on the micro to millisecond timescale and therefore there has been intense research of the importance of these motions in catalysis and molecular interactions. Nuclear Magnetic Resonance (NMR) relaxation dispersion experiments are used to measure motion of discrete nuclei within the micro to millisecond timescale. Information about conformational/chemical exchange, populations of exchanging states and chemical shift differences are extracted from these experiments. To ensure these parameters are correctly extracted, accurate and careful analysis of these experiments is necessary.</p> <p>Results</p> <p>The software introduced in this article is designed for the automatic analysis of relaxation dispersion data and the extraction of the parameters mentioned above. It is written in Python for multi platform use and highest performance. Experimental data can be fitted to different models using the Levenberg-Marquardt minimization algorithm and different statistical tests can be used to select the best model. To demonstrate the functionality of this program, synthetic data as well as NMR data were analyzed. Analysis of these data including the generation of plots and color coded structures can be performed with minimal user intervention and using standard procedures that are included in the program.</p> <p>Conclusions</p> <p>NESSY is easy to use open source software to analyze NMR relaxation data. The robustness and standard procedures are demonstrated in this article.</p
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