Application of covariance adjustment to seemingly unrelated multivariate regressions

Wang, Lichun,Pettit, Lawrence The Korean Statistical Society 2018 Communications for statistical applications and me Vol.25 No.6

Employing the covariance adjustment technique, we show that in the system of two seemingly unrelated multivariate regressions the estimator of regression coefficients can be expressed as a matrix power series, and conclude that the matrix series only has a unique simpler form. In the case that the covariance matrix of the system is unknown, we define a two-stage estimator for the regression coefficients which is shown to be unique and unbiased. Numerical simulations are also presented to illustrate its superiority over the ordinary least square estimator. Also, as an example we apply our results to the seemingly unrelated growth curve models.

How to Improve Classical Estimators via Linear Bayes Method?

Wang, Lichun The Korean Statistical Society 2015 Communications for statistical applications and me Vol.22 No.6

In this survey, we use the normal linear model to demonstrate the use of the linear Bayes method. The superiorities of linear Bayes estimator (LBE) over the classical UMVUE and MLE are established in terms of the mean squared error matrix (MSEM) criterion. Compared with the usual Bayes estimator (obtained by the MCMC method) the proposed LBE is simple and easy to use with numerical results presented to illustrate its performance. We also examine the applications of linear Bayes method to some other distributions including two-parameter exponential family, uniform distribution and inverse Gaussian distribution, and finally make some remarks.

Empirical Bayes Test for the Exponential Parameter with Censored Data

Wang, Lichun The Korean Statistical Society 2008 Communications for statistical applications and me Vol.15 No.2

Using a linear loss function, this paper considers the one-sided testing problem for the exponential distribution via the empirical Bayes(EB) approach. Based on right censored data, we propose an EB test for the exponential parameter and obtain its convergence rate and asymptotic optimality, firstly, under the condition that the censoring distribution is known and secondly, that it is unknown.

Room Temperature Electroluminescence from n-ZnO:Ga/i-ZnO/p-GaN:Mg Heterojunction Device Grown by PLD

Lichun Zhang,Qingshan Li,Feifei Wang,Chong Qu,Fengzhou Zhao 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.3

The n-ZnO:Ga/p-GaN:Mg and n-ZnO:Ga/i-ZnO/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated by the pulsed laser deposition (PLD) technique. The blue electroluminescence (EL) of the n-ZnO:Ga/ p-GaN:Mg heterojunction LEDs is emitted mainly from the p-GaN layer instead of the n-ZnO:Ga layer, for the reason that the electron injection from n-ZnO:Ga prevailed over the hole injection from p-GaN:Mg due to the higher carrier concentration and carrier mobility in n-ZnO:Ga. On the other hand, the n-ZnO:Ga/i-ZnO/p- GaN:Mg heterojunction LEDs exhibited dominant ultraviolet-blue emission. The reason for this difference is attributed to the inserted undoped i-ZnO layer between n-ZnO:Ga and p-GaN:Mg, in which the holes from p- GaN:Mg and the electrons from n-ZnO:Ga are recombined.

Postthrombolytic Antiplatelet Use for Patients with Intercerebral Hemorrhage without Extensive Parenchymal Involvement Does Not Worsen Outcome

Weihua Jia,Lichun Zhou,Xiaoling Liao,Yuesong Pan,Yongjun Wang 대한신경과학회 2015 Journal of Clinical Neurology Vol.11 No.4

Background and Purpose It is unclear whether postthrombolytic antiplatelet (AP) therapy after thrombolytic-related hemorrhage without extensive parenchymal involvement (THEPI) afects the clinical outcome. Tis study explored whether AP administration in patients with THEPI afects short- and long-term outcomes. Methods All of the data for this study were collected from the Trombolysis Implementation and Monitor of Acute Ischemic Stroke in China (TIMS-China) registry. Patients with THEPI were assigned to either the AP (AP therapy should be commenced 24 h afer intravenous thrombolysis) or AP-naïve groups. THEPI was defned according to European-Australasian Acute Stroke Study II criteria. Te 90-day functional outcome, 7-day National Institutes of Health Stroke Scale (NIHSS) score, and 7-day and 90-day mortalities were compared between the AP and AP-naïve groups. Logistic regression analysis was used to evaluate the effects of AP therapy on the short- and long-term clinical outcomes. Results Of the 928 patients enrolled from those in the TIMS-China registry (n=1,440), 89 (9.6%) had nonsymptomatic intracerebral hemorrhage (ICH) within 24–36 h afer thrombolysis; 33 (37%) of these patients were given AP therapy (AP group) and 56 (63%) were not (APnaïve group). No significant differences were found for the risk of 7-day aggravated ICH (p=0.998), 7-day NIHSS score (p=0.5491), 7-day mortality [odds ratio (OR)=3.427; 95% confdence interval (95% CI)=0.344–34.160; p=0.294], 90-day mortality (OR=0.788, 95% CI=0.154– 4.040, p=0.775), or modifed Rankin score 5 or 6 at 90-days (OR=1.108, 95% CI=0.249–4.928, p=0.893) between the AP and AP-naïve groups afer THEPI. Conclusions Early administration of postthrombolytic AP therapy afer THEPI does not worsen either the short- or long-term outcome. AP therapy may be a reasonable treatment option for patients with THEPI to reduce the risk of ischemic stroke recurrence.

Optoelectronic Characteristics of UV Photodetector Based on GaN/ZnO Nanorods p-i-n Heterostructures

Qingshan Li,Lichun Zhang,Fengzhou Zhao,Caifeng Wang,Feifei Wang,Ruizhi Huang 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4

We demonstrate an efficient ultraviolet (UV) photodetector operating at room temperature based on n-ZnO nanorods/i-ZnO/p-GaN heterojunctions. We employ x-ray diffraction and field-emission scanning electron microscopy to confirm the high quality of the ZnO nanorods using an undoped ZnO film as the interlayer. Then, we investigate the photoelectric properties of the fabricated photodetector with UV light illumination under a different reverse bias. Based on the current-voltage curve, the photocurrent to dark current ratio is approximately 73.3 at −4 V. At zerobias voltage, the peak responsivity was 138.9 mA/W at 362 nm under front-illumination conditions. Time-varying measurements indicate the reproducibility and stability of the heterojunction photodetector.

Computerized bone age estimation system based on China-05 standard

Yin, Chuangao,Zhang, Miao,Wang, Chang,Lin, Huihui,Li, Gengwu,Zhu, Lichun,Fei, Weimin,Wang, Xiaoyu Techno-Press 2022 Advances in nano research Vol.12 No.2

The purpose of this study is to develop an automatic software system for bone age evaluation and to evaluate its accuracy in testing and feasibility in clinical practice. 20394 left-hand radiographs of healthy children (2-18 years old) were collected from China Skeletal Development Survey data of 1998 and China Skeletal Development Survey data of 2005. Three experienced radiologists and China-05 standard maker jointly evaluate the stages of bone development and the reference bone age was determined by consensus. 1020 from 20394 radiographs were picked randomly as test set and the remaining 19374 radiographs as training set and validation set. Accuracy of the automatic software system for bone age assessment is evaluated in test set and two clinical test sets. Compared with the reference standard, the automatic software system based on RUS-CHN for bone age assessment has a 0.04 years old mean difference, ±0.40 years old in 95% confidence interval by single reading, a 85.6% percentage agreement of ratings, a 93.7% bone age accuracy rate, 0.17 years old of MAD, 0.29 years old of RMS; Compared with the reference standard, the automatic software system based on TW3-C RUS has a 0.04 years old mean difference, a ±0.38 years old in 95% confidence interval by single reading, a 90.9% percentage agreement of ratings, a 93.2% bone age accuracy rate, a 0.16 years of MAD, and a 0.28 years of RMS. Automatic software system, AI-China-05 showed reliably accuracy in bone age estimation and steady determination in different clinical test sets.

Appraisal of Guidelines for the Management of Blood Pressure in Patients with Diabetes Mellitus: The Consensuses, Controversies and Gaps

Menghui Liu,Shaozhao Zhang,Xiaohong Chen,Yue Guo,Xiangbin Zhong,Zhenyu Xiong,Yifen Lin,Huimin Zhou,Yiquan Huang,Zhengzhipeng Zhang,Lichun Wang,Xiaodong Zhuang,Xinxue Liao 대한당뇨병학회 2021 Diabetes and Metabolism Journal Vol.45 No.5

Background: Currently available guidelines contain conflicting recommendations on the management of blood pressure (BP) in patients with diabetes mellitus (DM). Therefore, it is necessary to appraise the guidelines and summarize the agreements and differences among recommendations.Methods: Four databases and the websites of guideline organizations were searched for guidelines regarding BP targets and thresholds for pharmacologic therapy in DM patients, and the included guidelines were appraised with the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument.Results: In 6,498 records identified, 20 guidelines met our inclusion criteria with 64.0% AGREE II scores (interquartile range, 48.5% to 72.0%). The scores of the European and American guidelines were superior to those of the Asian guidelines (both adjusted P<0.001). Most of the guidelines advocated systolic BP targets <130 mm Hg (12 guidelines, 60%) and diastolic BP targets <80 mm Hg (14 guidelines, 70%) in DM patients. Approximately half of the guidelines supported systolic BP thresholds >140 mm Hg (10 guidelines, 50%) and diastolic BP thresholds >90 mm Hg (nine guidelines, 45%). The tiny minority of the guidelines provided the relevant recommendations regarding the lower limit of official BP targets and the ambulatory BP monitoring (ABPM)/home BP monitoring (HBPM) targets and thresholds in DM patients.Conclusion: The lower official BP targets (<130/80 mm Hg) in patients with DM are advocated by most of the guidelines, but they contain conflicting recommendations on the official BP thresholds. Moreover, the gaps regarding the lower limit of official BP targets and the ABPM/HBPM targets and thresholds need to be considered by future study.