Channel estimation techniques for WCDMA communication systems

This thesis focuses on the study of efficient channel estimation techniques for WCDMA communication systems. Some background material pertaining to wireless multipath propagation and WCDMA systems is first presented. The maximum-likelihood principle based data-aided channel estimation techniques are then investigated, resulting in two new estimation methods using pilot and information symbols. The first method combines the pilot-assisted and the decision-directed estimation schemes, yielding a much better estimation result compared to each of the two schemes alone. The second technique corresponds to an adaptive channel estimation scheme in which a new update mechanism using a variable step-size is proposed. A theoretical analysis of the mean square error of the least mean square (LMS) algorithm is conducted, showing the superiority of a variable step-size update scheme in convergence speed over the conventional constant step-size algorithm. The proposed scheme is not only able to increase the convergence speed but also can decrease the steady-state error of the adaptive estimation filter to a certain degree. The bit-error rate (BER) performance of both downlink and uplink of the WCDMA systems using the proposed channel estimation techniques is evaluated through extensive computer simulations for different mobile velocities, confirming the improved estimation accuracy of the proposed methods for both slow to fast fading channels in comparison with some of the existing techniques (Abstract shortened by UMI.

Effects of Chinese University Students’ Academic Achievement and Course Satisfaction on Their Ratings of Teachers’ Instruction

The purpose of this study was to investigate the relationships between students’ perception of teachers’ instruction, course satisfaction, and student academic achievement. The data were extracted from TsingHua Education Online (THEOL) Management Information System (MIS) and analyzed via structuring equation modeling. The researchers hypothesized student ratings of instruction were affected by their achievement and course satisfaction. The results confirmed a positive relationship between course satisfaction and student ratings of instruction, but did not find direct effect of student academic achievement on their ratings of teachers’ instruction. This suggests that course satisfaction is a more important factor than academic achievement when students rate their teachers’ instruction. The finding also suggests that the student ratings of instruction may be an objective and acceptable performance indicator for teachers’ instruction in a course

On the Design of an Advanced Web-Based System for Supporting Thesis Research Process and Knowledge Sharing

Recently many universities have adopted web-based systems to manage the supervision and administration of postgraduate programs. The existing web-based systems mainly focus on monitoring the thesis management process rather than on supporting thesis research itself. This study aims on designing an advanced web-based system to support the Master’s degree thesis research process and the knowledge sharing. Master’s degree. This study firstly identifies the main steps of the thesis research process. It then presents an instructional model based on the analysis of practical thesis research workflow and relevant instructional approaches, such as problem-based learning, cognitive apprenticeship learning and collaborative learning. Based on this instructional model and the relevant literature, six principles were adopted to develop an advanced web-based system for the supporting thesis research process. This system includes three key modules: research process, research group and knowledge sharing. A preliminary evaluation of the system was conducted and the results showed that the system is effective to support the thesis research by providing multi-supervision in the research process. Moreover, a literature resources database plays an important role in knowledge sharing

Online Learning in Vocational Education of China during COVID-19: Achievements, Challenges, and Future Developments

COVID-19 has challenged education systems globally. Traditional teaching and learning activities of more than 1,300 vocational colleges and nearly 11,000 vocational high schools in China have had to be paused and transformed into an online mode. A study had been conducted to trace the unprecedented change which would provide reflections on policies and practical experience worthy of reference for the follow-up development of online vocational education in China and other countries in the world. The study used two methods to collect data: (1) delivering questionnaires to 767 schools, 17009 teachers, 270,732 students, and (2) gathering 110 institute cases from 21 provinces and 170 curriculum cases from 14 provinces. The result showed that vocational institutions coped with the pandemic’s outbreak through online learning and achieved the overall goal of “Not Going to School but Classes still Ongoing.” Further, vocational institutions have faced problems and challenges of online learning in practice training and internship, organization, and technical environment. The development of vocational education in the information era requires thinking about the system-driven reform path and online learning strategy and putting it into action

Development of a protocol to obtain the composition of terrigenous detritus in marine sediments -a pilot study from International Ocean Discovery Program Expedition 361

The geochemical and isotopic composition of terrigenous clays from marine sediments can provide important information on the sources and pathways of sediments. International Ocean Discovery Program Expedition 361 drilled sites along the eastern margin of southern Africa that potentially provide archives of rainfall on the continent as well as dispersal in the Agulhas Current. We used standard methods to remove carbonate and ferromanganese oxides and Stokes settling to isolate the clay fractions. In comparison to most previous studies that aimed to extract the detrital signal from marine sediments, we additionally applied a cation exchange wash using CsCl as a final step in the sample preparation. The motivation behind the extra step, not frequently applied, is to remove ions that are gained on the clay surface due to adsorption of authigenic trace metals in the ocean or during the leaching procedure. Either would alter the composition of the detrital fraction if no cation exchange was applied. Moreover, using CsCl will provide an additional measure of the cation exchange capacity (CEC) of the samples. However, no study so far has evaluated the potential and the limitations of such a targeted protocol for marine sediments. Here, we explore the effects of removing and replacing adsorbed cations on the clay surfaces with Cs+, conducting measurements of the chemical compositions, and radiogenic isotopes on a set of eight clay sample pairs. Both sets of samples underwent the same full leaching procedure except that one batch was treated with a final CsCl wash step. In this study, organic matter was not leached because sediments at IODP Site U1478 have relatively low organic content. However, in general, we recommend including that step in the leaching procedure. As expected, significant portions of elements with high concentrations in seawater were replaced by Cs+ (2SD 2.8%.) from the wash, including 75% of the sodium and approximately 25% of the calcium, 10% of the magnesium, and 8% of the potassium. Trace metals such as Sr and Nd, whose isotopes are used for provenance studies, are also found to be in lower concentrations in the samples after the exchange wash. The exchange wash affected the radiogenic isotope compositions of the samples. Neodymium isotope ratios are slightly less radiogenic in all the washed samples. Strontium and Pb isotopes showed significant deviations to either more or less radiogenic values in different samples. The radiogenic isotopes from the CsCl-treated fractions gave more consistent correlations with each other, and we suggest this treatment offers a superior measure of provenance. Although we observed changes in the isotope ratios, the general trend in the data and hence the overall provenance interpretations remained the same. However, the chemical compositions are significantly different. We conclude that a leaching protocol including a cation exchange wash (e.g. CsCl) is useful for revealing the terrestrial fingerprint. CEC could, with further calibration efforts, be useful as a terrestrial chemical weathering proxy

Biomarker records of D5-6 columns in the eastern Antarctic Peninsula waters: responses of planktonic communities and bio-pump structures to sea ice global warming in the past centenary

Molecular biomarkers (e.g., isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) and proxies, such as di-unsaturated to tri-unsaturated highly branched isoprenoids (D/T) ratio, total organic carbon, δ13C and ice-rafted debris (IRD)) were used to reconstruct the dominant phytoplankton (diatoms, dinoflagellates and coccolithophores), phytoplankton and zooplankton productivity, biological pump structure, and archaea assemblage (Euryarchaeota and Crenarchaeota) from a marine sediment core (D5-6) dated with 210Pb (1922–2012). We characterized the environmental response to sea ice variations/global warming off the eastern Antarctic Peninsula. The results showed that (1) the biomarkers brassicasterol (average = 519.79 ng·g−1), dinosterol (average = 129.68 ng·g−1) and C37 alkenones (average = 40.53 ng·g−1) reconstructed phytoplankton (average = 690.00 ng·g−1) and zooplankton (cholesterol average = 669.25 ng·g−1) productivity. The relative contribution to productivity by different phytoplankton groups was diatoms > dinoflagellates > coccolithophores. This is consistent with field surveys showing that diatoms dominate the phytoplankton in waters adjacent to the Antarctic Peninsula. (2) The relative abundances of different highly branched isoprenoids reflected the contributions of sea ice algae and open water phytoplankton (D/T = 1.2–30.15). Phytoplankton productivity and sea ice showed a good linear relationship with a negative correlation, indicating that more open water during periods of warming and reduced sea ice cover led to an enhanced biological pump. (3) Over the past 100 years, phytoplankton productivity and zooplankton biomass increased. This trend was particularly evident in the last 50 years, corresponding to increased global warming, and showed a negative correlation with IRD and D/T. This suggests that with decreasing sea ice coverage in a warming climate, diatom biomass greatly increased. Coccolithophore/diatom values and the ratio of C37 alkenones to total phytoplankton productivity decreased, indicating the proportion of coccolithophores in the phytoplankton community decreased. The reduction in coccolithophores changes the phytoplankton assemblage and affects the overall efficiency of the biological pump and carbon storage. (4) The results also showed that the abundance of iGDGTs and archaea phyla (Euryarchaeota and Crenarchaeota) showed consistent changes over the past 100 years in response to global warming. Since 1972, trends in archaea, phytoplankton and zooplankton showed variations but a consistent decline. Whether their response to the changing climate off the Antarctic Peninsula involves interactions and influence among different marine biological groups remains an open question. As a result of global warming and reductions in Antarctic sea ice, the relative effectiveness of the Antarctic biological pump can significantly affect global ocean carbon storage

Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475

The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted

Gpr124 is essential for blood-brain barrier integrity in central nervous system disease

Although blood-brain barrier (BBB) compromise is central to the etiology of diverse central nervous system (CNS) disorders, endothelial receptor proteins that control BBB function are poorly defined. The endothelial G-protein-coupled receptor (GPCR) Gpr124 has been reported to be required for normal forebrain angiogenesis and BBB function in mouse embryos, but the role of this receptor in adult animals is unknown. Here Gpr124 conditional knockout (CKO) in the endothelia of adult mice did not affect homeostatic BBB integrity, but resulted in BBB disruption and microvascular hemorrhage in mouse models of both ischemic stroke and glioblastoma, accompanied by reduced cerebrovascular canonical Wnt-β-catenin signaling. Constitutive activation of Wnt-β-catenin signaling fully corrected the BBB disruption and hemorrhage defects of Gpr124-CKO mice, with rescue of the endothelial gene tight junction, pericyte coverage and extracellular-matrix deficits. We thus identify Gpr124 as an endothelial GPCR specifically required for endothelial Wnt signaling and BBB integrity under pathological conditions in adult mice. This finding implicates Gpr124 as a potential therapeutic target for human CNS disorders characterized by BBB disruption

Prediction of Learning Outcomes With a Machine Learning Algorithm Based On Online Learning Behavior Data In Blended Courses

Learning outcomes can be predicted with machine learning algorithms that assess students’ online behavior data. However, there have been few generalized predictive models for a large number of blended courses in different disciplines and in different cohorts. In this study, we examined learning outcomes in terms of learning data in all of the blended courses offered at a Chinese university and proposed a new classification method of blended courses, in which students were primarily clustered on the basis of their online learning behaviors in blended courses using the expectation–maximization algorithm. Then, the blended courses were classified on the basis of the cluster of students who were present in the course and had the highest proportion. The advantage of this method is that the criteria used for classification of the blended courses are clearly defined on the basis of students\u27 online behavior data, so it can easily be used by machine learning systems to algorithmically classify blended courses based on log data collected from a learning management system. Drawing on the classification of the blended courses, we also proposed and validated a general model using the random forest algorithm to predict learning outcomes based on students’ online behaviors in blended courses with different disciplines and different cohorts. The findings of this study indicated that after blended courses were classified on the basis of students’ online behavior, prediction accuracy in each category increased. The overall accuracies for Course I (380 courses out of 661 after screening), L (14 courses out of 661 after screening), A (237 courses out of 661 after screening), V (8 courses out of 661 after screening), and H (22 courses out of 661 after screening) were 38.2%, 48.4%, 42.3%, 42.4%, and 74.7%, respectively. According to these results, it was found that a prerequisite for the accurate prediction of students\u27 learning outcomes in a blended course was that most students should be highly engaged in a variety of online learning activities rather than being focused on only one type of activity, such as only watching online videos or submitting online assignments. The prediction model achieved accuracies of 80.6%, 85.3%, 63%, 54.8%, and 14.3% for grades A, B, C, D, and F in Course H, respectively. The results demonstrated the potential of the proposed model for accurately predicting learning outcomes in blended courses. Finally, we found that there was no single online learning behavior that had a dominant effect on the prediction of students\u27 final grades