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Search Results: 1 - 10 of 104325 matches for " Chunming Zhang "
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Composition of substituents on pyrrole ring of high-carbon-number geoporphyrins and its dealkylation
Chunming Zhang,Renzi Lin
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02896290
Abstract: Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry (EIMS) and Tandem mass spectrometry (MS/MS). The spectrum of EIMS shows that the geoporphyrins are mainly composed of two types: DPEP and eito. Most of the porphyrin carbon numbers are greater than C32. The daughter spectra of the molecular ions (C34-36DPEPs) display the loss of methyl and ethyl groups, which indicate there are ethyl and propyl groups in the mother ions. The average condensed structural formulae, derived from the data of the spectra on MS/MS, have clearly shown the composition of the substituents on the porphyrin pyrrole ring, and the regular changes of the substituents reveal the characteristics of the dealkylation of the porphyrins in the geosphere.
Assessing prediction error of nonparametric regression and classification under Bregman divergence
Jianqing Fan,Chunming Zhang
Mathematics , 2005,
Abstract: Prediction error is critical to assessing the performance of statistical methods and selecting statistical models. We propose the cross-validation and approximated cross-validation methods for estimating prediction error under a broad q-class of Bregman divergence for error measures which embeds nearly all of the commonly used loss functions in regression, classification procedures and machine learning literature. The approximated cross-validation formulas are analytically derived, which facilitate fast estimation of prediction error under the Bregman divergence. We then study a data-driven optimal bandwidth selector for the local-likelihood estimation that minimizes the overall prediction error or equivalently the covariance penalty. It is shown that the covariance penalty and cross-validation methods converge to the same mean-prediction-error-criterion. We also propose a lower-bound scheme for computing the local logistic regression estimates and demonstrate that it is as simple and stable as the local least-squares regression estimation. The algorithm monotonically enhances the target local-likelihood and converges. The idea and methods are extended to the generalized varying-coefficient models and semiparametric models.
Semiparametric detection of significant activation for brain fMRI
Chunming Zhang,Tao Yu
Mathematics , 2008, DOI: 10.1214/07-AOS519
Abstract: Functional magnetic resonance imaging (fMRI) aims to locate activated regions in human brains when specific tasks are performed. The conventional tool for analyzing fMRI data applies some variant of the linear model, which is restrictive in modeling assumptions. To yield more accurate prediction of the time-course behavior of neuronal responses, the semiparametric inference for the underlying hemodynamic response function is developed to identify significantly activated voxels. Under mild regularity conditions, we demonstrate that a class of the proposed semiparametric test statistics, based on the local linear estimation technique, follow $\chi^2$ distributions under null hypotheses for a number of useful hypotheses. Furthermore, the asymptotic power functions of the constructed tests are derived under the fixed and contiguous alternatives. Simulation evaluations and real fMRI data application suggest that the semiparametric inference procedure provides more efficient detection of activated brain areas than the popular imaging analysis tools AFNI and FSL.
Single-index modulated multiple testing
Lilun Du,Chunming Zhang
Statistics , 2014, DOI: 10.1214/14-AOS1222
Abstract: In the context of large-scale multiple testing, hypotheses are often accompanied with certain prior information. In this paper, we present a single-index modulated (SIM) multiple testing procedure, which maintains control of the false discovery rate while incorporating prior information, by assuming the availability of a bivariate $p$-value, $(p_1,p_2)$, for each hypothesis, where $p_1$ is a preliminary $p$-value from prior information and $p_2$ is the primary $p$-value for the ultimate analysis. To find the optimal rejection region for the bivariate $p$-value, we propose a criteria based on the ratio of probability density functions of $(p_1,p_2)$ under the true null and nonnull. This criteria in the bivariate normal setting further motivates us to project the bivariate $p$-value to a single-index, $p(\theta)$, for a wide range of directions $\theta$. The true null distribution of $p(\theta)$ is estimated via parametric and nonparametric approaches, leading to two procedures for estimating and controlling the false discovery rate. To derive the optimal projection direction $\theta$, we propose a new approach based on power comparison, which is further shown to be consistent under some mild conditions. Simulation evaluations indicate that the SIM multiple testing procedure improves the detection power significantly while controlling the false discovery rate. Analysis of a real dataset will be illustrated.
Numerical Simulation of PRHR System Based on CFD  [PDF]
Bin Jia, Jianping Jing, Xuedong Qiao, Chunming Zhang
Journal of Applied Mathematics and Physics (JAMP) , 2013, DOI: 10.4236/jamp.2013.16015
Abstract: In this paper numerical simulation of PRHR HX and IRWST is demonstrated using FLUENT, and different numbers of C-type heat transfer tubes and coolant inlet temperature’s effects for the residual heat removal capacity of PRHR HX, IRWST thermal stratification and natural circulation have been researched. It’s found that at a constant flow area when heat transfer tubes’ number increased outlet temperature of PRHR HX is lower, the whole water temperature of IRWST is higher, thermal stratification and natural circulation are more oblivious. At a constant mass flow when inlet temperature of PRHR HX increased, inlet flow velocity increases and outlet temperature is higher. But on the other hand the cooling rate increases at the same time, the average temperature of IRWST is higher, the range of thermal stratification expands and the velocity of natural circulation increases.
Stress Analysis for Reactor Coolant Pump Nozzle of Nuclear Reactor Pressure Vessel  [PDF]
Lijing Wen, Chao Guo, Tieping Li, Chunming Zhang
Journal of Applied Mathematics and Physics (JAMP) , 2013, DOI: 10.4236/jamp.2013.16013
Abstract: Integrated reactor structural design makes the pressure vessel itself and loads more complicated, so stress concentration makes strength failure easier at reactor coolant pump nozzle. The general purpose finite element program ANSYS/ WORKBENCH was used for 3D stress and fatigue analysis and the results of the evaluation are based on RCC-M criteria. The integrated reactor structural design is evaluated to demonstrate with applicable criteria and ANSYS/WORK- BENCH has better operability than ANSYS APDL on stress analysis of reactor pressure vessel.
Repealing the LIFO Inventory Accounting Choice? A Review of LIFO and Inventory Management  [PDF]
Yibin Zhang, Chunming Shi, Patrick Gao, Feng Wang
American Journal of Operations Research (AJOR) , 2014, DOI: 10.4236/ajor.2014.46034
Abstract: Researchers in the disciplines of both Operations and Accounting have studied Inventory Management, though in relative isolation. In this paper, one of our goals is to help inform researchers in Operations Management about an extensively debated question in inventory accounting: whether to repeal the LIFO (Last-In-First-Out) inventory accounting choice? This question has received extensive scrutiny from various stakeholders including academics, businesses, and different levels of governmental agencies such as US Congress. Specifically, we provide a literature review on how LIFO affects and is affected by inventory management. This is done by first reviewing the potential determinants of LIFO inventory accounting choice and then reviewing potential interactions between LIFO and inventory management. It is our hope that this review will help stakeholders have a more comprehensive understanding of LIFO before making their decisions.
Composition of substituents on pyrrole ring of high-carbon-number geoporphyrins and its dealkylation

Chunming Zhang,Renzi Lin,

科学通报(英文版) , 1999,
Abstract: Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry (EIMS) and Tandem mass spectrometry (MS/MS). The spectrum of EIMS shows that the geoporphyrins are mainly composed of two types: DPEP and eito. Most of the porphyrin carbon numbers are greater than C32. The daughter spectra of the molecular ions (C34-36DPEPs) display the loss of methyl and ethyl groups, which indicate there are ethyl and propyl groups in the mother ions. The average condensed structural formulae, derived from the data of the spectra on MS/MS, have clearly shown the composition of the substituents on the porphyrin pyrrole ring, and the regular changes of the substituents reveal the characteristics of the dealkylation of the porphyrins in the geosphere.
Analysis of Changing Factors on Airborne Allergenic Pollens Distribution in Taiyuan Downtown, North China  [PDF]
Kejun Zhang, Binquan Wang, Yanli Zhang, Yanli Zhang, Nasha Cheng, Changsheng Wang, Chunming Zhang, Wei Gao, Ganggang Chen
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2015, DOI: 10.4236/ijohns.2015.42026
Abstract: To study and analyse 2 surveys on airborne allergenic pollens distribution in Taiyuan Downtown, North China 30 years apart, the surveys focused on the phenomenon and the influence factors on types, counts, drift patterns, growth and decline rhythm and distribution features of airborne pollen with the same methods in the region in March 1977 to February 1978 and July 2008 to June 2009, respectively. The data of two airborne pollens surveys were treated with statistics, comparation and analysis, and the influence factors of pollen distribution in Taiyuan Downtown were explored. In the 2 surveys, 24 species and 35 species of pollen were collected in the region, respectively. Two pollen drift peaks were formed in spring and autumn in the two surveys. Artemisia L. is still the absolute dominant allergy airborne pollen. The types, counts, drift patterns and composition of pollen in air could be changed by the plants variation. Climate warming might affect pollen peak appearing time and lasting time, climate warming and Poplar & Willow contents changes in spring and autumn reversed the airborne pollen peak. It was found that Humulus L. had become the region’s main allergic pollen. Invasive strong allergen ragweed was spread to the inland city Taiyuan. Allergists should focus on exotic invasive harmful plants in the region.
A Deflection-Based Bridge Diagnosis Method
Xiaofan Yang,Chunming Zhang,Weimin Chen
Mathematical Problems in Engineering , 2009, DOI: 10.1155/2009/284368
Abstract: By exploiting the “correlation of deflections” phenomena, we propose a new bridge diagnosis method. First, we introduce the notion of deflection correlation (DC) graphs and propose a method for building a DC graph. Second, we present a new algorithm for locating the abnormal cliques. Finally, we demonstrate the potential utility of the new method by applying it to the simulated diagnosis of a real-life bridge.
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