regression methods
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2022 ◽  
Author(s):  
Mathieu M. Molenaar ◽  
Ali Al-Ghaithi ◽  
Said Kindi ◽  
Fahad Alawi

Abstract The first application of Hydraulic Fracturing in the South Oman started in 2000 to enhance water disposal wells. In 2004 the first oil wells were frac'ed. Although the technology was deployed many times, it never grew into a conventional practice. From 2004 to 2017 on average 5 Oil Wells were hydraulically fractured on yearly basis. In November 2017, a Hydraulic Fracturing Maturation & Expansion Workshop was conducted with the vision of growing the application by applying new frac concepts. A focused effort was initiated to drastically reduce cost, and simultaneously increase the scope by executing larger frac campaigns. The first hydraulic fracturing campaign introducing the frac new concepts, started end 2018 and a rapid growth from 5 wells per year to 45 wells per year was anticipated in the next three years. This large growth of scope relied on a steady supply of frac candidates and needed to be supported by screening and selecting processes that are fit for purpose in finding candidates. Although more than a hundred wells had already been frac'ed wells, selection of the most appropriate wells for stimulation was and remains one of the greatest challenges. A frac performance database was created for over 100 wells that had been hydraulically fracture stimulated to date. Recognizing that the frac performance depends on many variables ranging from subsurface properties to surface execution of the frac job, the size of the dataset proved to be too small to find correlations using sophisticated multivariable regression methods. Instead, the dataset was analyzed through careful investigation and evaluation of each frac job. In this paper the net oil gain will be used as the key success criteria i.e., value driver to demonstrates how effective the frac is achieving its business objective. Some 40% of the producers had been producing from the same zone before the hydraulic fracture stimulation. This provided the opportunity to understand the efficiency of the stimulation in terms of the "stimulation ratio" i.e., measuring the net oil gain. This paper will focus on investigating the suitability of frac'ing the reservoir based on the initial production variables; Gross Rate and BS&W. Also, this paper will discuss benefits and impacts of Hoist versus Coiled-Tubing clean-out on the frac delivery process and compare the frac performance. To date, the project demonstrated that hydraulic fracturing at low cost, can be applied as a viable development concept for producing oil wells, with the potential unlock additional and new reserves. Significant folds in production increase are possible from 2x to 7x.


2022 ◽  
pp. 0739456X2110654
Author(s):  
Brian Y. An

Can self-organizing special districts created from the bottom up be a tool for community change and development? Focusing on community services districts in California, this study introduces the context in which communities opt out of a county service system to reshape their governing structure for better representation. The empirical part measures their effectiveness, using single-family home sale prices as an impact metric. Leveraging multi-level difference-in-difference hedonic regression methods, the analysis shows that district formation increases the prices annually up to 16 percent, compared to both the surrounding and distant county service areas, indicating their efficacy as a tool for community change and development.


2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Johannes Müller ◽  
Walter Plöchl ◽  
Paul Mühlbacher ◽  
Alexandra Graf ◽  
Anne-Margarethe Kramer ◽  
...  

AbstractA high number of trauma patients are under the influence of alcohol. Since many of them need immediate surgical procedures, it is imperative to be aware of the interaction of alcohol with general anesthesia. To counter challenges that arise from clinical studies, we designed an animal experiment in which 48 adult Wistar rats either received 1 g · kg−1 ethanol, 2 g · kg−1 ethanol or placebo via intraperitoneal application. Subsequently, they were anesthetized with an individual concentration of sevoflurane. The minimum alveolar concentration (MAC) of the different groups was assessed using Dixon’s up-and-down design and isotonic regression methods. The bootstrap estimate of the MAC of sevoflurane in the placebo group was 2.24 vol% (95% CI 1.97–2.94 vol%). In the low dose ethanol group, the bootstrap estimate was 1.65 vol% (95% CI 1.40–1.98 vol%), and in the high dose ethanol group, it was 1.08 vol% (95% CI 0.73–1.42 vol%). We therefore report that intraperitoneal application of 1 g · kg−1 or 2 g · kg−1 ethanol both resulted in a significant reduction of the MAC of sevoflurane in adult Wistar rats: by 26.3% and 51.8% respectively as compared to placebo.


2022 ◽  
Vol 11 (2) ◽  
pp. 285
Author(s):  
Leszek Tylicki ◽  
Ewelina Puchalska-Reglińska ◽  
Piotr Tylicki ◽  
Aleksander Och ◽  
Karolina Polewska ◽  
...  

Introduction: The determinants of COVID-19 mortality are well-characterized in the general population. Less numerous and inconsistent data are among the maintenance hemodialysis (HD) patients, who are the population most at risk of an unfavorable prognosis. Methods: In this retrospective cohort study we included all adult HD patients from the Pomeranian Voivodeship, Poland, with laboratory-confirmed SARS-CoV-2 infection hospitalized between 6 October 2020 and 28 February 2021, both those who survived, and also those who died. Demographic, clinical, treatment, and laboratory data on admission, were extracted from the electronic medical records of the dedicated hospital and patients’ dialysis unit, and compared between survivors and non-survivors. We used univariable and multivariable logistic regression methods to explore the risk factors associated with 3-month all-cause mortality. Results: The 133 patients (53.38% males) aged 73.0 (67–79) years, with a median duration of hemodialysis of 42.0 (17–86) months, were included in this study. At diagnosis, the majority were considered to have a mild course (34 of 133 patients were asymptomatic, another 63 subjects presented mild symptoms), while 36 (27.07%) patients had low blood oxygen saturation and required oxygen supplementation. Three-month mortality was 39.08% including an in-hospital case fatality rate of 33.08%. Multivariable logistic regression showed that the frailty clinical index of 4 or greater (OR 8.36, 95%CI 1.81–38.6; p < 0.01), D-Dimer of 1500 ng/mL or greater (6.00, 1.94–18.53; p < 0.01), and CRP of >118 mg/L at admission (3.77 1.09–13.01; p = 0.04) were found to be predictive of mortality. Conclusion: Very high 3-month all-cause mortality in hospitalized HD patients was determined mainly by frailty. High CRP and D-dimer levels upon admission further confer mortality risk.


Author(s):  
Jiamin Zhao ◽  
Yang Yu ◽  
Xu Wang ◽  
Shihan Ma ◽  
Xinjun Sheng ◽  
...  

Abstract Objective. Musculoskeletal model (MM) driven by electromyography (EMG) signals has been identified as a promising approach to predicting human motions in the control of prostheses and robots. However, muscle excitations in MMs are generally derived from the EMG signals of the targeted sensor covering the muscle, inconsistent with the fact that signals of a sensor are from multiple muscles considering signal crosstalk in actual situation. To identify more accurate muscle excitations for MM in the presence of crosstalk, we proposed a novel excitation-extracting method inspired by muscle synergy for simultaneously estimating hand and wrist movements. Approach. Muscle excitations were firstly extracted using a two-step muscle synergy-derived method. Specifically, we calculated subject-specific muscle weighting matrix and corresponding profiles according to contributions of different muscles for movements derived from synergistic motion relation. Then, the improved excitations were used to simultaneously estimate hand and wrist movements through musculoskeletal modeling. Moreover, the offline comparison among the proposed method, traditional MM and regression methods, and an online test of the proposed method were conducted. Main results. The offline experiments demonstrated that the proposed approach outperformed the EMG envelope-driven MM and three regression models with higher R and lower NRMSE. Furthermore, the comparison of excitations of two MMs validated the effectiveness of the proposed approach in extracting muscle excitations in the presence of crosstalk. The online test further indicated the superior performance of the proposed method than the MM driven by EMG envelopes. Significance. The proposed excitation-extracting method identified more accurate neural commands for MMs, providing a promising approach in rehabilitation and robot control to model the transformation from surface EMG to joint kinematics.


2022 ◽  
Vol 75 (2) ◽  
Author(s):  
Caroline Ribeiro de Sousa ◽  
Janaína Fonseca Victor Coutinho ◽  
João Bastos Freire Neto ◽  
Rachel Gabriel Bastos Barbosa ◽  
Marília Braga Marques ◽  
...  

ABSTRACT Objectives: to assess factors associated with vulnerability and fragility in the elderly. Methods: crosssectional study with 384 elderly people in Fortaleza, Ceará. The Vulnerable Elders Survey and Clinical-Functional Vulnerability Index - 20 were used. Chi-square and Fisher’s exact tests were used for associations. In the analysis of the combined influence of risk factors, the stepwise logistic regression and multinomial regression methods were adopted. Results: 251 (65.4%) non-vulnerable and 133 (34.6%) vulnerable elders. From the vulnerable elders analyzed, 42 (30.9%) are at high risk for frailty. Factors associated with vulnerability: age, gender, presence of comorbidities, hypertension, diabetes, osteoporosis and use of polypharmacy. There is a 30% increase in the chance of vulnerability for each additional drug. Physical activity reduces the chance of vulnerability by 60%. Factors associated with frailty: educational level; self-perception of health; comorbidities; polypharmacy. Conclusions: it is important to pay attention to the presence of arterial hypertension, osteoporosis, polypharmacy, and encourage the practice of physical activity.


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