利用刀切法和Bayes估计方法,在加权平方损失函数下,得到Rayleigh分布在选取先验分布为Jefferys无信息分布和Gamma分布的情况下参数的Bayes估计的精确形式,在此基础上进一步研究了参数的刀切Bayes估计.最后在R软件中运用MCMC(Markov Chai...利用刀切法和Bayes估计方法,在加权平方损失函数下,得到Rayleigh分布在选取先验分布为Jefferys无信息分布和Gamma分布的情况下参数的Bayes估计的精确形式,在此基础上进一步研究了参数的刀切Bayes估计.最后在R软件中运用MCMC(Markov Chain Monte Carlo)算法对Rayleigh分布参数的Bayes估计和刀切Bayes估计进行数值模拟.模拟结果显示:当样本容量较大时,相同先验分布下刀切Bayes估计模拟效果更好.展开更多
针对混频数据的建模问题,提出自回归U-MIDAS(unrestricted mixed data sampling)分位回归模型.首先,结合嵌套Lasso惩罚方法及spike-and-slab先验进行Bayes参数估计和变量选择;其次,通过数值模拟证明该方法的优越性;最后,将该方法用于美...针对混频数据的建模问题,提出自回归U-MIDAS(unrestricted mixed data sampling)分位回归模型.首先,结合嵌套Lasso惩罚方法及spike-and-slab先验进行Bayes参数估计和变量选择;其次,通过数值模拟证明该方法的优越性;最后,将该方法用于美国名义国内生产总值(GDP)年化季度增长率的预测,结果表明,该方法预测精度较好.展开更多
When assessing seismic liquefaction potential with data-driven models,addressing the uncertainties of establishing models,interpreting cone penetration tests(CPT)data and decision threshold is crucial for avoiding bia...When assessing seismic liquefaction potential with data-driven models,addressing the uncertainties of establishing models,interpreting cone penetration tests(CPT)data and decision threshold is crucial for avoiding biased data selection,ameliorating overconfident models,and being flexible to varying practical objectives,especially when the training and testing data are not identically distributed.A workflow characterized by leveraging Bayesian methodology was proposed to address these issues.Employing a Multi-Layer Perceptron(MLP)as the foundational model,this approach was benchmarked against empirical methods and advanced algorithms for its efficacy in simplicity,accuracy,and resistance to overfitting.The analysis revealed that,while MLP models optimized via maximum a posteriori algorithm suffices for straightforward scenarios,Bayesian neural networks showed great potential for preventing overfitting.Additionally,integrating decision thresholds through various evaluative principles offers insights for challenging decisions.Two case studies demonstrate the framework's capacity for nuanced interpretation of in situ data,employing a model committee for a detailed evaluation of liquefaction potential via Monte Carlo simulations and basic statistics.Overall,the proposed step-by-step workflow for analyzing seismic liquefaction incorporates multifold testing and real-world data validation,showing improved robustness against overfitting and greater versatility in addressing practical challenges.This research contributes to the seismic liquefaction assessment field by providing a structured,adaptable methodology for accurate and reliable analysis.展开更多
We present the diagnostic performance of[18F]Fluorodeoxyglucose positron emission tomography(FDG PET)for adrenal incidentalomas based on lesion size and unenhanced computed tomography(CT)density in Hounsfield units(HU...We present the diagnostic performance of[18F]Fluorodeoxyglucose positron emission tomography(FDG PET)for adrenal incidentalomas based on lesion size and unenhanced computed tomography(CT)density in Hounsfield units(HU),following current literature and guidelines.A 20 HU cutoff can be applied to differentiate potentially benign from malignant lesions,particularly in ruling in or out adrenocortical carcinoma.While FDG PET provides valuable metabolic information,its likelihood ratios for a positive(LR+)or negative(LR-)result do not exceed the robust diagnostic thresholds of>10.0 or<0.1,respectively.This suggests that positron emission tomography alone is insufficient for definitive characterization and should be integrated with CT or magnetic resonance imaging to leverage their complementary anatomical and functional imaging strengths for optimal diagnostic accuracy.展开更多
文摘利用刀切法和Bayes估计方法,在加权平方损失函数下,得到Rayleigh分布在选取先验分布为Jefferys无信息分布和Gamma分布的情况下参数的Bayes估计的精确形式,在此基础上进一步研究了参数的刀切Bayes估计.最后在R软件中运用MCMC(Markov Chain Monte Carlo)算法对Rayleigh分布参数的Bayes估计和刀切Bayes估计进行数值模拟.模拟结果显示:当样本容量较大时,相同先验分布下刀切Bayes估计模拟效果更好.
文摘针对混频数据的建模问题,提出自回归U-MIDAS(unrestricted mixed data sampling)分位回归模型.首先,结合嵌套Lasso惩罚方法及spike-and-slab先验进行Bayes参数估计和变量选择;其次,通过数值模拟证明该方法的优越性;最后,将该方法用于美国名义国内生产总值(GDP)年化季度增长率的预测,结果表明,该方法预测精度较好.
文摘When assessing seismic liquefaction potential with data-driven models,addressing the uncertainties of establishing models,interpreting cone penetration tests(CPT)data and decision threshold is crucial for avoiding biased data selection,ameliorating overconfident models,and being flexible to varying practical objectives,especially when the training and testing data are not identically distributed.A workflow characterized by leveraging Bayesian methodology was proposed to address these issues.Employing a Multi-Layer Perceptron(MLP)as the foundational model,this approach was benchmarked against empirical methods and advanced algorithms for its efficacy in simplicity,accuracy,and resistance to overfitting.The analysis revealed that,while MLP models optimized via maximum a posteriori algorithm suffices for straightforward scenarios,Bayesian neural networks showed great potential for preventing overfitting.Additionally,integrating decision thresholds through various evaluative principles offers insights for challenging decisions.Two case studies demonstrate the framework's capacity for nuanced interpretation of in situ data,employing a model committee for a detailed evaluation of liquefaction potential via Monte Carlo simulations and basic statistics.Overall,the proposed step-by-step workflow for analyzing seismic liquefaction incorporates multifold testing and real-world data validation,showing improved robustness against overfitting and greater versatility in addressing practical challenges.This research contributes to the seismic liquefaction assessment field by providing a structured,adaptable methodology for accurate and reliable analysis.
文摘We present the diagnostic performance of[18F]Fluorodeoxyglucose positron emission tomography(FDG PET)for adrenal incidentalomas based on lesion size and unenhanced computed tomography(CT)density in Hounsfield units(HU),following current literature and guidelines.A 20 HU cutoff can be applied to differentiate potentially benign from malignant lesions,particularly in ruling in or out adrenocortical carcinoma.While FDG PET provides valuable metabolic information,its likelihood ratios for a positive(LR+)or negative(LR-)result do not exceed the robust diagnostic thresholds of>10.0 or<0.1,respectively.This suggests that positron emission tomography alone is insufficient for definitive characterization and should be integrated with CT or magnetic resonance imaging to leverage their complementary anatomical and functional imaging strengths for optimal diagnostic accuracy.
