Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density

A comparative study of combined spinal epidural anaesthesia and general anaesthesia in patients undergoing percutaneous nephrolithotomy

Background: Our primary aim was to study the efficacy, safety, hemodynamic stability, postoperative pain relief, and complication with combined spinal epidural anaesthesia (CSE) and to compare it with general anaesthesia (GA) for percutaneous nephrolithotomy (PCNL).  Methods: The present study was a prospective, randomized, open, controlled trial to compare the effects of CSE and GA in patients undergoing PCNL. Study was carried out in 100 adult patients, who were randomly divided into two groups of 50 each, Group GA and Group CSE. Post-operative pain relief and amount rescue analgesia required were noted. Postoperatively samples were collected for haemoglobin and arterial blood gases. Incidence of complications were noted and compared among both the groups.Results: Mean arterial pressure in CSE group was less compared to GA group during the procedure. 30 % patients in group GA required first rescue analgesia within first hour of completion of surgery whereas no patient in group CSE required analgesia within first hour indicating better pain relief in CSE group. Mean haemoglobin and the fall in haemoglobin between the groups were comparable. 48.0% of the cases among GA group and 14.0% of the cases among CSE group had postoperative nausea and vomiting. Mean pH in GA group was 7.33±0.05 and in CSE group was 7.36±0.04. There was one case of hydrothorax post operatively.Conclusions: We conclude that CSE is a safe alternative to GA for PCNL with better pain relief, less PONV. Hypotension due to sympathetic blockade is always a possibility

Degradation Issues in Solid Oxide Cells During High Temperature Electrolysis

Idaho National Laboratory (INL) is performing high-temperature electrolysis (HTE) research to generate hydrogen using solid oxide electrolysis cells (SOECs). The project goals are to address the technical and degradation issues associated with the SOECs. This paper provides a summary of ongoing INL and INL-sponsored activities aimed at addressing SOEC degradation. These activities include stack testing, post-test examination, degradation modeling, and issues that need to be addressed in the future. Major degradation issues relating to solid oxide fuel cells (SOFC) are relatively better understood than those for SOECs. Some of the degradation mechanisms in SOFCs include contact problems between adjacent cell components, microstructural deterioration (coarsening) of the porous electrodes, and blocking of the reaction sites within the electrodes. Contact problems include delamination of an electrode from the electrolyte, growth of a poorly (electronically) conducting oxide layer between the metallic interconnect plates and the electrodes, and lack of contact between the interconnect and the electrode. INL's test results on HTE using solid oxide cells do not provide clear evidence as to whether different events lead to similar or drastically different electrochemical degradation mechanisms. Post-test examination of the SOECs showed that the hydrogen electrode and interconnect get partially oxidized and become nonconductive. This is most likely caused by the hydrogen stream composition and flow rate during cooldown. The oxygen electrode side of the stacks seemed to be responsible for the observed degradation because of large areas of electrode delamination. Based on the oxygen electrode appearance, the degradation of these stacks was largely controlled by the oxygen electrode delamination rate. Virkar et al. [19-22] have developed a SOEC model based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic nonequilibrium. This model is under continued development. It shows that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential within the electrolyte. The chemical potential within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just under the oxygen electrode (anode)/electrolyte interface, leading to electrode delamination. This theory is being further refined and tested by introducing some electronic conduction in the electrolyte.United States. Department of Energy. Office of Energy Efficiency and Renewable EnergyUnited States. Office of the Assistant Secretary for Nuclear Energ

Transformation Textures in Zirconia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65433/1/j.1151-2916.1993.tb03696.x.pd

Seminar Users in the Arabic Twitter Sphere

We introduce the notion of "seminar users", who are social media users engaged in propaganda in support of a political entity. We develop a framework that can identify such users with 84.4% precision and 76.1% recall. While our dataset is from the Arab region, omitting language-specific features has only a minor impact on classification performance, and thus, our approach could work for detecting seminar users in other parts of the world and in other languages. We further explored a controversial political topic to observe the prevalence and potential potency of such users. In our case study, we found that 25% of the users engaged in the topic are in fact seminar users and their tweets make nearly a third of the on-topic tweets. Moreover, they are often successful in affecting mainstream discourse with coordinated hashtag campaigns.Comment: to appear in SocInfo 201

Image Analysis Enhanced Event Detection from Geo-tagged Tweet Streams

Events detected from social media streams often include early signs of accidents, crimes or disasters. Therefore, they can be used by related parties for timely and efficient response. Although significant progress has been made on event detection from tweet streams, most existing methods have not considered the posted images in tweets, which provide richer information than the text, and potentially can be a reliable indicator of whether an event occurs or not. In this paper, we design an event detection algorithm that combines textual, statistical and image information, following an unsupervised machine learning approach. Specifically, the algorithm starts with semantic and statistical analyses to obtain a list of tweet clusters, each of which corresponds to an event candidate, and then performs image analysis to separate events from non-events---a convolutional autoencoder is trained for each cluster as an anomaly detector, where a part of the images are used as the training data and the remaining images are used as the test instances. Our experiments on multiple datasets verify that when an event occurs, the mean reconstruction errors of the training and test images are much closer, compared with the case where the candidate is a non-event cluster. Based on this finding, the algorithm rejects a candidate if the difference is larger than a threshold. Experimental results over millions of tweets demonstrate that this image analysis enhanced approach can significantly increase the precision with minimum impact on the recall.Comment: 12 pages, 4 figure