15 research outputs found

    A Least Squares Ensemble Model Based on Regularization and Augmentation Strategy

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    Surrogate models are often used as alternatives to considerably reduce the computational burden of the expensive computer simulations that are required for engineering designs. The development of surrogate models for complex relationships between the parameters often requires the modeling of high-dimensional functions with limited information, and it is challenging to choose an effective surrogate model over the unknown design space. To this end, the ensemble models—combined with different surrogate models—offer effective solutions. This paper presents a new ensemble model based on the least squares method, which is a regularization strategy and an augmentation strategy; we call the model the regularized least squares ensemble model (RLS-EM). Three individual surrogate models—Kriging, radial basis function, and support vector regression—are used to compose the RLS-EM. Further, the weight factors are estimated by the least squares method without using the global or local error metrics, which are used in most existing methods. To solve the collinearity in the least squares calculation process, a regularization strategy and an augmentation strategy are developed. The two strategies help explore the unknown regions and improve the accuracy on one hand; on the other hand, the collinearity can be reduced, and the overfitting phenomenon that may occur can be avoided. Six numerical functions, from two-dimensional to 12-dimensional, and a computer numerical control (CNC) milling machine bed design problem are used to verify the proposed method. The results of the numerical examples show that RLS-EM saves a considerable amount of computation time while ensuring the same level of robustness and accuracy compared with other ensemble models. The RLS-EM used for the CNC milling machine bed design problem also shows good accuracy characteristics compared with other ensemble methods

    Estimating the influencing factors for T1b/T2 gallbladder cancer on survival and surgical approaches selection

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    Abstract Background The influencing factors, especially time to treatment (TTT), for T1b/T2 gallbladder cancer (GBC) patients remain unknown. We aimed to identify the influencing factors on survival and surgical approaches selection for T1b/T2 GBC. Methods We retrospectively screened GBC patients between January 2011 and August 2018 from our hospital. Clinical variables, including patient characteristics, TTT, overall survival (OS), disease‐free survival (DFS), surgery‐related outcomes, and surgical approaches were collected. Results A total of 114 T1b/T2 GBC patients who underwent radical resection were included. Based on the median TTT of 7.5 days, the study cohort was divided into short TTT group (TTT ≤7 days, n = 57) and long TTT group (TTT >7 days, n = 57). Referrals were identified as the primary factor prolonging TTT (p  0.05) between both groups. Decreased referrals (p = 0.005), fewer positive lymph nodes (LNs; p = 0.004), and well tumor differentiation (p = 0.004) were all associated with better OS, while fewer positive LNs (p = 0.049) were associated with better DFS. Subgroup analyses revealed no significant difference in survival between patients undergoing laparoscopic or open approach in different TTT groups (all p > 0.05). And secondary subgroup analyses found no significance in survival and surgery‐related outcomes between different TTT groups of incidental GBC patients (all p > 0.05). Conclusions Positive LNs and tumor differentiation were prognostic factors for T1b/T2 GBC survival. Referrals associating with poor OS would delay TTT, while the prolonged TTT would not impact survival, surgery‐related outcomes, and surgical approaches decisions in T1b/T2 GBC patients

    Hepatopancreatoduodenectomy for advanced biliary malignancies

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    Abstract. Background:. Hepatopancreatoduodenectomy (HPD) has been considered the only curative treatment for metastatic cholangiocarcinoma and some locally advanced gallbladder cancers (GBCs). However, HPD has not yet been included in treatment guidelines as a standard surgical procedure in consideration of its morbidity and mortality rates. The aim of this study was to evaluate the safety and effectiveness of HPD in treating biliary malignancies. Methods:. The medical records of 57 patients with advanced biliary cancer undergoing HPD from January 2009 to December 2019 were retrospectively retrieved. A case-control analysis was conducted at our department. Patients with advanced GBC who underwent HPD (HPD-GBC group) were compared with a control group (None-HPD-GBC group). Baseline characteristics, preoperative treatments, tumor pathologic features, operative results, and prognosis were assessed. Results:. Thirteen patients with cholangiocarcinoma and 44 patients with GBC underwent HPD at our department. Significant postoperative complications (grade III or greater) and postoperative pancreatic fistula were observed in 24 (42.1%) and 15 (26.3%) patients, respectively. One postoperative death occurred in the present study. Overall survival (OS) was longer in patients with advanced cholangiocarcinoma than in those with GBC (median survival time [MST], 31 months vs. 11 months; P < 0.001). In the subgroup analysis of patients with advanced GBC, multivariate analysis demonstrated that T4 stage tumors (P = 0.012), N2 tumors (P = 0.001), and positive margin status (P = 0.004) were independently associated with poorer OS. Patients with either one or more prognostic factors exhibited a shorter MST than patients without those prognostic factors (P < 0.001). Conclusion:. HPD could be performed with a relatively low mortality rate and an acceptable morbidity rate in an experienced high- volume center. For patients with advanced GBC without an N2 or T4 tumor, HPD can be a preferable treatment option

    Hotspots and difficulties of biliary surgery in older patients

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    Abstract. With the accelerated aging society in China, the incidence of biliary surgical diseases in the elderly has increased significantly. The clinical characteristics of these patients indicate that improving treatment outcomes and realizing healthy aging are worthy of attention. How to effectively improve the treatment effect of geriatric biliary surgical diseases has attracted widespread attention. This paper reviews and comments on the hotspots and difficulties of biliary surgery in older patients from six aspects: (1) higher morbidity associated with an aging society, (2) prevention and control of pre-operative risks, (3) extending the indications of laparoscopic surgery, (4) urgent standardization of minimally invasive surgery, (5) precise technological progress in hepatobiliary surgery, and (6) guarantee of peri-operative safety. It is of great significance to fully understand the focus of controversy, actively make use of its favorable factors, and effectively avoid its unfavorable factors, for further improving the therapeutic effects of geriatric biliary surgical diseases, and thus benefits the vast older patients with biliary surgical diseases. Accordingly, a historical record with the highest age of 93 years for laparoscopic transcystic common bile duct exploration has been created by us recently
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