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Journal of Data Analysis and Information Processing 2024年第2期12卷 151-162页

作者： Christopher Watitwa Makokha Ananda Kube oscar ngesa Department of Mathematics Pan African University Institute of Basic Sciences Technology and Innovation Nairobi Kenya Department of Mathematics and Actuarial Sciences Kenyatta University Nairobi Kenya Department of Mathematics Statistics and Physical Sciences Taita Taveta University Voi Kenya

Peer-to-peer (P2P) lending offers an alternative way to access credit. Unlike established lending institutions with proven credit risk management practices, P2P platforms rely on numerous independent variables to evaluate loan applicants’ creditworthiness. This study aims to estimate default probabilities using a mixture-of-experts neural network in P2P lending. The approach involves coupling unsupervised clustering to capture essential data properties with a classification algorithm based on the mixture-of-experts structure. This classic design enhances model capacity without significant computational overhead. The model was tested using P2P data from Lending Club, comparing it to other methods like Logistic Regression, AdaBoost, Gradient Boosting, Decision Tree, Support Vector Machine, and Random Forest. The hybrid model demonstrated superior performance, with a Mean Squared Error reduction of at least 25%.

关键词： Credit-Scoring Clustering Classification Neural Networks

Spatio-Temporal Agricultural Drought Quantification in a Rainfed Agriculture, Athi-Galana-Sabaki River Basin

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Journal of Geographic Information System 2024年第4期16卷 201-226页

作者： Joe Ndundi Tete Godfrey Ouma Makokha oscar Owino ngesa John Ngugi Muthami Bonface Wabwire Odhiambo Department of Informatics and Computing Taita Taveta University Voi Kenya Department of Finance and Economic Planning County Government of Kilifi Kilifi Kenya

This study employs a quantitative approach to comprehensively investigate the full propagation process of agricultural drought, focusing on pigeon peas (the most grown crop in the AGS Basin) planting seasonal variations. The study modelled seasonal variabilities in the seasonal Standardized Precipitation Index (SPI) and Standardized Agricultural Drought Index (SADI). To necessitate comparison, SADI and SPI were Normalized (from −1 to 1) as they had different ranges and hence could not be compared. From the seasonal indices, the pigeon peas planting season (July to September) was singled out as the most important season to study agricultural droughts. The planting season analysis selected all years with severe conditions (2008, 2009, 2010, 2011, 2017 and 2022) for spatial analysis. Spatial analysis revealed that most areas in the upstream part of the Basin and Coastal region in the lowlands experienced severe to extreme agricultural droughts in highlighted drought years. The modelled agricultural drought results were validated using yield data from two stations in the Basin. The results show that the model performed well with a Pearson Coefficient of 0.87 and a Root Mean Square Error of 0.29. This proactive approach aims to ensure food security, especially in scenarios where the Basin anticipates significantly reduced precipitation affecting water available for agriculture, enabling policymakers, water resource managers and agricultural sector stakeholders to equitably allocate resources and mitigate the effects of droughts in the most affected areas to significantly reduce the socioeconomic drought that is amplified by agricultural drought in rainfed agriculture river basins.

关键词： Agricultural Drought Food Security Standardized Precipitation Index Standardized Agricultural

A Comparative Analysis of Generalized Estimating Equations Methods for Incomplete Longitudinal Ordinal Data with Ignorable Dropouts

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Open Journal of Statistics 2018年第5期8卷 770-792页

作者： Kago Edwin Ditlhong oscar Owino ngesa Abdalla Yusuf Kombo Pan African University Institute of Basic Sciences Technology and Innovation Nairobi Kenya Department of Mathematics and Informatics Taita Taveta University Nairobi Kenya

In longitudinal studies, measurements are taken repeatedly over time on the same experimental unit. These measurements are thus correlated. Missing data are very common in longitudinal studies. A lot of research has been going on ways to appropriately analyze such data set. Generalized Estimating Equations (GEE) is a popular method for the analysis of non-Gaussian longitudinal data. In the presence of missing data, GEE requires the strong assumption of missing completely at random (MCAR). Multiple Imputation Generalized Estimating Equations (MIGEE), Inverse Probability Weighted Generalized Estimating Equations (IPWGEE) and Double Robust Generalized Estimating Equations (DRGEE) have been proposed as elegant ways to ensure validity of the inference under missing at random (MAR). In this study, the three extensions of GEE are compared under various dropout rates and sample sizes through simulation studies. Under MAR and MCAR mechanism, the simulation results revealed better performance of DRGEE compared to IPWGEE and MIGEE. The optimum method was applied to real data set.

关键词： Longitudinal Ordinal Data MAR MCAR Multiple Imputation GEE Inverse Probability Weighted GEE Double Robust GEE

Multivariate Ratio Estimator of the Population Total under Stratified Random Sampling

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Open Journal of Statistics 2012年第3期2卷 300-304页

作者： oscar O. ngesa G. O. Orwa R. O. Otieno H. M. Murray Department of Statistics Jomo Kenyatta University of Agriculture and Technology Nairobi Ministry of State for Planning National Development and V2030 Kenya

Olkin [1] proposed a ratio estimator considering p auxiliary variables under simple random sampling. As is expected, Simple Random Sampling comes with relatively low levels of precision especially with regard to the fact that its variance is greatest amongst all the sampling schemes. We extend this to stratified random sampling and we consider a case where the strata have varying weights. We have proposed a Multivariate Ratio Estimator for the population mean in the presence of two auxiliary variables under Stratified Random Sampling with L strata. Based on an empirical study with simulations in R statistical software, the proposed estimator was found to have a smaller bias as compared to Olkin’s estimator.

关键词： Ratio Estimator Stratification Auxiliary Variables Lagrange’s Multiplier

A Survey on Type-3 Fuzzy Logic Systems and Their Control Applications

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IEEE/CAA Journal of Automatica Sinica 2024年第8期11卷 1744-1756页

作者： oscar Castillo Fevrier Valdez Patricia Melin Weiping Ding Tijuana Institute of Technology/Tecnologico Nacional de Mexico Division of Graduate StudiesCalzada Tecnologico S/NTijuana 22414Mexico School of Information Science and Technology Nantong UniversityJiangsu 226019China

In this paper,we offer a review of type-3 fuzzy logic systems and their applications in *** main objective of this work is to observe and analyze in detail the applications in the control area using type-3 fuzzy logic *** this case,we review their most important applications in control and other related topics with type-3 fuzzy *** algorithms have been receiving increasing attention in control and for this reason a review in this area is *** paper reviews the main applications that make use of Intelligent Computing ***,type-3 fuzzy logic *** aim of this research is to be able to appreciate,in detail,the applications in control systems and to point out the scientific trends in the use of Intelligent Computing *** is done with the construction and visualization of bibliometric networks,developed with VosViewer Software,which it is a free Java-based program,mainly intended to be used for analyzing and visualizing bibliometric *** this tool,we can create maps of publications,authors,or journals based on a co-citation network or construct maps of keywords,countries based on a co-occurrence networks,research groups,etc.

关键词： Applications control systems optimization review type-3 fuzzy logic.

Improving colorectal cancer screening programs

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World Journal of Gastroenterology 2024年第22期30卷 2849-2851页

作者： oscar J Cordero Lucia Mosquera-Ferreiro Iria Gomez-Tourino Department of Biochemistry and Molecular Biology University of Santiago de CompostelaSantiago de Compostela 15782Spain Centre for Research in Molecular Medicine and Chronic Diseases(CiMUS) University of Santiago de CompostelaSantiago de Compostela 15782GaliciaSpain

In this editorial we comment on the article by Agatsuma et al published in the World Journal of *** suggest policies for more effective colorectal *** is the main policy that has led to lower mortality rates in later years among the population that was eligible for *** is the gold standard tool for screening and has preventive effects by removing precancerous or early malignant ***,colonoscopy is an invasive process,and fecal tests such as the current hemoglobin immunodetection were developed,followed by endoscopy,as the general tool for population screening,avoiding logistical and economic *** so,participation and adherence rates are *** screening options are being developed with the idea that if people could choose between the ones that best suit them,participation in population-based screening programs would *** tests,such as a recent one that detects cell-free DNA shed by tumors called circulating tumor DNA,showed a similar accuracy rate to stool tests for cancer,but were less sensitive for advanced precancerous *** the time when the crosstalk between the immune system and cancer was being established as a new hallmark of cancer,novel immune system-related biomarkers and information on patients’immune parameters,such as cell counts of different immune populations,were studied for the early detection of colorectal cancer,since they could be effective in asymptomatic people,appearing earlier in the adenoma-carcinoma development compared to the presence of fecal ***26,for example,detected 80.37%of advanced *** reach as many eligible people as possible,starting at an earlier age than current programs,the direction could be to apply tests based on blood,urine or salivary fluid to samples taken during routine visits to the primary health system.

关键词： Mortality rates Colorectal cancer Screening Biomarker Fecal hemoglobin immunodetection Soluble sCD26 Colonoscopy Immunoscores

Effect of reaction and post-treatment conditions on physico-chemical properties of magnetic iron oxide nano-particles Author links open overlay panel

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Particuology 2024年第8期91卷 155-167页

作者： Masome Moeni Mohamed Edokali Matthew Rogers oscar Cespedes Louey Tliba Tamseela Habib Robert Menzel Ali Hassanpour School of Chemical and Process Engineering Faculty of Engineering and Physical ScienceUniversity of LeedsLeedsLS29JTUK School of Physics and Astronomy Faculty of Engineering and Physical ScienceUniversity of LeedsLeedsLS29JTUK Mechanical Engineering Department University of Engineering&TechnologyLahorePakistan School of Chemistry Faculty of Engineering and Physical ScienceUniversity of LeedsLeedsLS29JTUK

Poor stability and dispersibility,as well as aggregation are considered as major challenges in clinical application of iron oxide nanoparticles(IONPs).Several studies have shown that the synthesis parameters and post-synthesis treatments e.g.,drying methods,have the capability to improve the particles'***,we investigate the combined effect of synthesis and post-treatment parameters on the particle size,stability and magnetism of ***(Fe_(3)O_(4))NPs were prepared via co-precipitation and post-treated using different methods,i.e.(i)freeze dried at-53℃,0.133 mbar for 48 h(liquid nitrogen frozen(LFD)and freezer frozen(FFD)),(ii)vacuum oven dried(VOD)at 60℃for 24 h,and(iii)kept wet colloidal(WET),dispersed in deionized *** Fe_(3)O_(4)NPs’chemical functional groups,size,shape,crystallinity,stability,aggregation,porosity,and magnetic properties were further analysed using different characterisation *** results showed that,while the WET sample had the best stability and significantly less aggregation at different temperatures,amongst post-treated Fe_(3)O_(4)NPs,LFD sample exhibited the best stability(up to 37℃),dispersion and smallest polydispersity ***,all dried NPs had superparamagnetic characteristics,while,LFD Fe_(3)O_(4)NPs had better magnetic properties and stability than other drying methods.

关键词： Iron oxide nanoparticles Co-precipitation Stability Aggregation Magnetic properties

Output feedback adaptive super twisting sliding mode control for quadrotor UAVs

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Control Theory and Technology 2024年第1期22卷 92-105页

作者： oscar Salas-Peña Jesus DeLeón-Morales Susana V.Gutiérrez-Martínez École Centrale de Nantes-LS2N UMR 6004 CNRS44300NantesFrance Facultad de Ingeniería Mecánica y Eléctrica Universidad Autónoma de Nuevo León66451San Nicolás de Los GarzaMexico

In this paper, a sliding mode control with adaptive gain combined with a high-order sliding mode observer to solve the tracking problem for a quadrotor UAV is addressed, in presence of bounded external disturbances and parametric uncertainties. The high order sliding mode observer is designed for estimating the linear and angular speed in order to implement the proposed scheme. Furthermore, a Lyapunov function is introduced to design the controller with the adaptation law, whereas an analysis of finite time convergence towards to zero is provided, where sufficient conditions are obtained. Regarding previous works from literature, one important advantage of proposed strategy is that the gains of control are parameterized in terms of only one adaptive parameter, which reduces the control effort by avoiding gain overestimation. Numerical simulations for tracking control of the quadrotor are given to show the performance of proposed adaptive control–observer scheme.

关键词： Adaptive super twisting controller High-order sliding modes observer UAV

Effect of autologous serum after amniotic membrane transplantation for persistent corneal ulcers

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International Journal of Ophthalmology(English edition) 2024年第9期17卷 1639-1644页

作者： Rozaliya Hristova Petya Yankova Georgi Markov Alexander oscar Yani Zdravkov Department of Ophthalmology Medical University SofiaUniversity Hospital AlexandrovskaSofia 1431Bulgaria Department of Clinical Immunology Medical University SofiaUniversity Hospital AlexandrovskaSofia 1431Bulgaria

AIM:To investigate the effect of adding autologous serum eye drops to the postoperative regime after amniotic membrane transplantation for severe persistent corneal ***:Forty eyes of 40 patients with persistent corneal ulcers were randomly assigned to artificial tears(sodium hyaluronate 0.2%,ATs group,n=20)or autologous serum eye drops(ASEDs,n=20)following treatment with amniotic membrane *** slit lamp images were acquired from all patients before and 30d post *** area with fibrovascular tissue was calculated using Image *** corneal sensitivity was assessed by Cochet-Bonnet aesthesiometry before and one month after *** tissue transparency was assessed with a novel optical ***:Mean age of patients was 61.65±16.47y and 57.3±19.11y in the ATs group and ASEDs group,***-two male and 18 female patients were included in the *** improvement in visual acuity was significantly greater in the ASEDs group(0.14±0.04)than the ATs(0.08±0.04;P=0.00046).Cochet-Bonnet aesthesiometry improved significantly after treatment with a similar rate between *** were no statistically significant differences in the area of postoperative fibrovascular tissue between the two groups(P=0.082).The success rate in the two groups was *** difference in densitometry between the ATs and ASEDs group was statistically significant(P=0.042)with greater reduction from baseline in the ASEDS ***:Autologous serum eye drops can lead to better visual acuity,more stable results and improved densitometry and should be considered in the postoperative care following amniotic membrane transplantation.

关键词： autologous serum amniotic membrane ocular surface persistent corneal ulcer

Outcomes and variables that impact pneumatic retinopexies

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International Journal of Ophthalmology(English edition) 2024年第3期17卷 564-569页

作者： Maria V.Castanos Daniel Vail oscar Otero-Marquez Yash Shah Avnish Deobhakta New York Eye and Ear Infirmary of Mount Sinai New York 10003New YorkUSA

●AIM:To evaluate the efficacy of pneumatic retinopexy(PR)in patients undergoing PR as primary treatment for rhegmatogenous retinal detachment(RRD)and analyze the factors associated with success and failure in the studied population.●METHODS:A retrospective chart review was done of patients with RRD treated with PR as primary management method treated at New York Eye and Ear Infirmary of Mount Sinai between January 2017 and December *** outcome measured success or failure of *** outcome measured best corrected visual acuity(BCVA)after PR.A separate risk analysis was done to identify and stratify risks associated with success and failure of PR.●RESULTS:A total of 179 eyes from 179 patients were included for final *** 83 patients(46.37%)achieved anatomical reattachment of the retina after primary PR with no need for additional *** 96 patients(53.63%)had a failed primary PR and required a PPV and 6 of them required pars plana vitrectomy(PPV)with scleral buckle(SB).In total,19 cases(10.61%)were done as temporizing pneumatics,18(94.74%)underwent PPV,and 1(5.26%)did not require further *** visual acuities at postoperative month 1(POM1)for patients who underwent primary PR successfully and for those that underwent PPV after,were 0.58(20/80)and 1.03(20/200)*** who met Pneumatic Retinopexy Versus Vitrectomy for the Management of Primary Rhegmatogenous Retinal Detachment Outcomes Randomized Trial(PIVOT)criteria had a statistically significant decreased risk of primary PR failing(hazard ratio 0.29,P=0.00).Majority of missed or new breaks were found superotemporally.●CONCLUSION:PR is a good treatment option for treating RRDs in patients that meet PIVOT criteria and can be conducted as a temporizing *** criteria and fovea on status decrease the risk of PR failure.

关键词： retina pneumatic retinopexy rhegmatogenous retinal detachment