2,859 research outputs found
Flexible combination of multiple diagnostic biomarkers to improve diagnostic accuracy
In medical research, it is common to collect information of multiple
continuous biomarkers to improve the accuracy of diagnostic tests. Combining
the measurements of these biomarkers into one single score is a popular
practice to integrate the collected information, where the accuracy of the
resultant diagnostic test is usually improved. To measure the accuracy of a
diagnostic test, the Youden index has been widely used in literature. Various
parametric and nonparametric methods have been proposed to linearly combine
biomarkers so that the corresponding Youden index can be optimized. Yet there
seems to be little justification of enforcing such a linear combination. This
paper proposes a flexible approach that allows both linear and nonlinear
combinations of biomarkers. The proposed approach formulates the problem in a
large margin classification framework, where the combination function is
embedded in a flexible reproducing kernel Hilbert space. Advantages of the
proposed approach are demonstrated in a variety of simulated experiments as
well as a real application to a liver disorder study
Experimental Study on Match for Indoor and Outdoor Heat Exchanger of Residential Air-conditioner
In this study, the effects of indoor unit heat transfer area and air flow rate and outdoor unit air flow rate on the system performance of residential air-conditioner were experimentally investigated under rated cooling and heating conditions. The experimental results showed that the system cooling capacity, EER, heating capacity and COP all had evident variation with indoor unit heat transfer area and air flow rate and out unit air flow rate, which predicated that there was a proper match range for indoor unit and outdoor unit to make the system overall performance best. The increase of indoor unit heat transfer area and air flow rate significantly improved system cooling and heating performances especially for the smaller heat transfer area indoor unit, and the improvement was more obvious for heating performance. The heat transfer area ratio of indoor unit and outdoor unit was smaller, the indoor unit air flow rate should be designed as higher air velocity, but that should not be higher than 1.2m/s. In addition, with the specified outdoor unit in this study, the matched heat transfer area of indoor unit should not be too high or too low, and the optimal heat transfer area ratio of indoor and outdoor unit was between 0.33 and 0.37, which was better to choose the smaller value for higher indoor unit air flow rate. The increase of outdoor unit air flow rate also was advantageous for improving system cooling and heating performances especially for system EER and COP, but excessive higher air flow rate can cause the degradation of the system performance. The proposed outdoor unit designed air velocity should not be higher than 1.6m/s
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