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  • 1
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    5 G WiFi Signal-Based Indoor Localization System Using Cluster -Nearest Neighbor Algorithm (2014)
    Hindawi
    Details
    Publication Date: 2014-12-18
    Description: Indoor localization based on existent WiFi signal strength is becoming more and more prevalent and ubiquitous. Unfortunately, the WiFi received signal strength (RSS) is susceptible by multipath, signal attenuation, and environmental changes, which is the major challenge for accurate indoor localization. To overcome these limitations, we propose the cluster -nearest neighbor (KNN) algorithm with 5 G WiFi signal to reduce the environmental interference and improve the localization performance without additional equipment. In this paper, we propose three approaches to improve the performance of localization algorithm. For one thing, we reduce the computation effort based on the coarse localization algorithm. For another, according to the detailed analysis of the 2.4 G and 5 G signal fluctuation, we expand the real-time measurement RSS before matching the fingerprint map. More importantly, we select the optimal nearest neighbor points based on the proposed cluster KNN algorithm. We have implemented the proposed algorithm and evaluated the performance with existent popular algorithms. Experimental results demonstrate that the proposed algorithm can effectively improve localization accuracy and exhibit superior performance in terms of localization stabilization and computation effort.
    Print ISSN: 1550-1329
    Electronic ISSN: 1550-1477
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Hindawi
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  • 2
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    Seroprevalence and Risk Factors of Chlamydia abortus Infection in Tibetan Sheep in Gansu Province, Northwest China (2014)
    Hindawi
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    Publication Date: 2014-10-24
    Description: Chlamydia abortus, an important pathogen in a variety of animals, is associated with abortion in sheep. In the present study, 1732 blood samples, collected from Tibetan sheep between June 2013 and April 2014, were examined by the indirect hemagglutination (IHA) test, aiming to evaluate the seroprevalence and risk factors of C. abortus infection in Tibetan sheep. 323 of 1732 (18.65%) samples were seropositive for C. abortus antibodies at the cut-off of 1 : 16. A multivariate logistic regression analysis was used to evaluate the risk factors associated with seroprevalence, which could provide foundation to prevent and control C. abortus infection in Tibetan sheep. Gender of Tibetan sheep was left out of the final model because it is not significant in the logistic regression analysis (). Region, season, and age were considered as major risk factors associated with C. abortus infection in Tibetan sheep. Our study revealed a widespread and high prevalence of C. abortus infection in Tibetan sheep in Gansu province, northwest China, with higher exposure risk in different seasons and ages and distinct geographical distribution.
    Electronic ISSN: 1537-744X
    Topics: Natural Sciences in General
    Published by Hindawi
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  • 3
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    Time-tracking tests and interpretation for a horizontal well at different wellbore positions (2018)
    Society of Exploration Geophysicists
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    Publication Date: 2018-08-01
    Description: We have developed a time-tracking test method for pressure buildup tests of horizontal wells to reduce the costs associated with testing wells. The time-tracking test method requires several tests that are performed chronologically from the midsection of the horizontal wellbore to the kickoff point. The purpose of time-tracking tests is to determine the production conditions of horizontal wells that allow the tests to be conducted at the kickoff point. Two horizontal wells associated within a sandstone oil reservoir were specifically chosen to determine how our time-tracking test method is to be implemented. The two wells had completely different production conditions. One had a small gas rate and a large water cut, whereas the other had a large gas rate and a small water cut. We recorded and analyzed the tested pressure data at numerous wellbore positions along the same horizontal well. Then, we interpreted the tested pressure data and compared the test results at different points along each well using the test curve shape and the interpretation parameter values. Through comparisons of the two wells, we found that the well-test curve shape and the interpretation results of tests performed above the kickoff point were completely different from those of the tests at the midsection of the horizontal wellbore under the conditions of a large gas rate and a small water cut. If a horizontal well has a small gas rate and a large water cut, the well can be tested at the kickoff point in the well using the wireline. We recommend that field petroleum engineers adopt the time-tracking test method to judge whether their horizontal wells should be tested at the kickoff point.
    Print ISSN: 2324-8858
    Electronic ISSN: 2324-8866
    Topics: Geosciences
    Published by Society of Exploration Geophysicists
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  • 4
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    Baseline Serum Cystatin C Is a Potential Predictor for Acute Kidney Injury in Patients with Acute Pancreatitis (2018)
    Hindawi
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    Publication Date: 2018-11-19
    Description: Aims. The study is aimed at studying the incidence of acute kidney injury (AKI) and exploring the potential predictor for AKI in patients with acute pancreatitis. Methods. A retrospective study adopting a stratified cohort sampling design was performed in a cohort of patients (n=237) diagnosed with acute pancreatitis without any renal injury. The following information including age, gender, serum creatinine, serum urea nitrogen, serum uric acid, serum cystatin C, fasting serum glucose, serum amylase, serum lipase, serum choline esterase, total protein, albumin, globulin, total bilirubin, direct bilirubin, total bile acids, glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, gamma glutamyl transpeptidase, and alkaline phosphatase were collected from each patient when they were diagnosed with acute pancreatitis. Student t-test was conducted to figure out the difference between patients with and without AKI. Univariate and multivariate logistic regression analyses were used for investigating the predictors for AKI in patients with acute pancreatitis. Results. 18 (7.6%) patients in total had developed AKI among the study group. Compared with patients without AKI (1.01 ± 0.26 mg/L), the level of baseline serum cystatin C (CYS-C) was significantly higher in patients with AKI (3.64 ± 2.17 mg/L, P
    Print ISSN: 0278-0240
    Electronic ISSN: 1875-8630
    Topics: Biology , Chemistry and Pharmacology
    Published by Hindawi
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