Browsing by Author "Xu, Hong"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Determination of Reservoir Characteristics Using Geostatistical Analysis
    (2017) Xu, Hong; Innanen, Kristopher; Russell, Brian; Lines, Laurence; Trad, Daniel
    Geostatistics offers a robust way to estimate the spatial distribution of reservoir properties. Geostatistical methods, such as kriging, cokriging, and sequential simulation have been applied to integrate well-log data and seismic attributes. However, conventional deterministic methods of geostatistics, kriging and cokriging often have difficulty identifying the characteristics of lithologic reservoirs because only one secondary attribute is incorporated. To decrease the uncertainty and improve the definition of the final estimate, two modified techniques, cokriging with multiple secondary attributes and block cokriging with multiple secondary attributes, are implemented. However, these deterministic methods can only provide one predicted result, which has trouble capturing the natural heterogeneity of reservoirs and assessing the uncertainty of the predicted map. To solve this issue, an improved stochastic technique, sequential simulation using multi-variable cokriging, is presented. All these presented techniques are applied to real datasets. Case studies are presented to predict the thickness of the reservoir, total organic carbon, and porosity. The final predicted maps demonstrate that these methods can enhance the lateral resolution. Leave-one-out cross-validation is used to evaluate the construction models, and shows that the uncertainty of the estimate can be reduced due to the use of more seismic attributes than traditionally implemented, while still optimizing cross-validation.
  • Thumbnail Image
    ItemOpen Access
    Factors influencing survival in sphingosine phosphate lyase insufficiency syndrome: a retrospective cross-sectional natural history study of 76 patients
    (2024-09-27) Keller, Nancy; Midgley, Julian; Khalid, Ehtesham; Lesmana, Harry; Mathew, Georgie; Mincham, Christine; Teig, Norbert; Khan, Zubair; Khosla, Indu; Mehr, Sam; Guran, Tulay; Buder, Kathrin; Xu, Hong; Alhasan, Khalid; Buyukyilmaz, Gonul; Weaver, Nicole; Saba, Julie D.
    Abstract Background Sphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is a recently recognized inborn error of metabolism associated with steroid-resistant nephrotic syndrome as well as adrenal insufficiency and immunological, neurological, and skin manifestations. SPLIS is caused by inactivating mutations in SGPL1, encoding the pyridoxal 5’phosphate-dependent enzyme sphingosine-1-phosphate lyase, which catalyzes the final step of sphingolipid metabolism. Some SPLIS patients have undergone kidney transplantation, and others have been treated with vitamin B6 supplementation. In addition, targeted therapies including gene therapy are in preclinical development. In anticipation of clinical trials, it will be essential to characterize the full spectrum and natural history of SPLIS. We performed a retrospective analysis of 76 patients in whom the diagnosis of SPLIS was established in a proband with at least one suggestive finding and biallelic SGPL1 variants identified by molecular genetic testing. The main objective of the study was to identify factors influencing survival in SPLIS subjects. Results Overall survival at last report was 50%. Major influences on survival included: (1) age and organ involvement at first presentation; (2) receiving a kidney transplant, and (3) SGPL1 genotype. Among 48 SPLIS patients with nephropathy who had not received a kidney transplant, two clinical subgroups were distinguished. Of children diagnosed with SPLIS nephropathy before age one (n = 30), less than 30% were alive 2 years after diagnosis, and 17% were living at last report. Among those diagnosed at or after age one (n = 18), ~ 70% were alive 2 years after diagnosis, and 72% were living at time of last report. SPLIS patients homozygous for the SPL R222Q variant survived longer compared to patients with other genotypes. Kidney transplantation significantly extended survival outcomes. Conclusion Our results demonstrate that SPLIS is a phenotypically heterogeneous condition. We find that patients diagnosed with SPLIS nephropathy in the first year of life and patients presenting with prenatal findings represent two high-risk subgroups, whereas patients harboring the R222Q SGPL1 variant fare better than the rest. Time to progression from onset of proteinuria to end stage kidney disease varies from less than one month to five years, and kidney transplantation may be lifesaving.
  • Thumbnail Image
    ItemOpen Access
    MOP: mining opinion from customer reviews
    (2009) Xu, Hong; Barker, Kenneth E.
  • Thumbnail Image
    ItemOpen Access
    Teaching Machine Learning: Student Project Reports for CPSC 599.66 and 601.66 Winter 2007
    (2007-04-25) Richter, Michael; Bilawshuk, Tyler; Leclerc, Eric; McClocklin, Landon; Lyons, Allan; Kendon, Tyler; Kidney, Jordan; Xu, Hong; MacKas, Brenan; Obied, Ahmed; Olsen, Luke; Park, Justin; Walker, Scott; Olsen, Luke; Park, Justin; Tkachyk, Stephanie; Ma, Lizhe; Kianmehr, Kevin
    Teaching machine learning has two parts. One part is the lectures. These can be found under www.cpsc.ucalgary.ca/~mrichtet/ml. But lecturing is only half of the story. That is, because passive learning by listening does not provide the same expertise compared to active learning by doing. For this purpose a project work was required. Students had the choice to work on their own or to form a group of two. At the beginning of the course, after some introduction and overview, the projects started. The start had the following steps: 1) Selecting a domain of application as, e.g. spam filters, playing games, cooperative multiagents etc. 2) Formulating a learning goal in that domain, as improving cooperation. The choice was completely free. 3) Selecting one or more candidates for learning techniques presented in the course that were focused in the sequel. These topics were presented first very early and then in some more detail at midterm. In this volume the final reports are listed. Particular emphasis was put on the aspects of the difficulties that occurred during the project and how to overcome them. The difficulties had different sources. The major ones are problems with the tools and getting enough data, or underestimating the complexity. The free choice of the application domain had the consequence that the authors were quite familiar with it, could use existing environments and use the results for further activities like masters or PhD theses. Formal projects implementation details are available, write to mrichter@cpsc.ucalgary.ca