Comparison of Different LGM-Based Methods with MAR and MNAR Dropout Data

The missing not at random (MNAR) mechanism may bias parameter estimates and even distort study results. This study compared the maximum likelihood (ML) selection model based on missing at random (MAR) mechanism and the Diggle–Kenward selection model based on MNAR mechanism for handling missing data through a Monte Carlo simulation study. Four factors were considered, including the missingness mechanism, the dropout rate, the distribution shape (i.e., skewness and kurtosis), and the sample size. The results indicated that: (1) Under the MAR mechanism, the Diggle–Kenward selection model yielded similar estimation results with the ML approach; Under the MNAR mechanism, the results of ML approach were underestimated, especially for the intercept mean and intercept slope (μi and μs). (2) Under the MAR mechanism, the 95% CP of the Diggle–Kenward selection model was lower than that of the ML method; Under the MNAR mechanism, the 95% CP for the two methods were both under the desired level of 95%, but the Diggle–Kenward selection model yielded much higher coverage probabilities than the ML method. (3) The Diggle–Kenward selection model was easier to be influenced by the non-normal degree of target variable's distribution than the ML approach. The level of dropout rate was the major factor affecting the parameter estimation precision, and the dropout rate-induced difference of two methods can be ignored only when the dropout rate falls below 10%

Influence of Alternation of Sulfate Attack and Freeze-Thaw on Microstructure of Concrete

The effects of sulfate attack and freeze-thaw alternation on the concrete microstructure were systemically investigated by advanced test methods such as water absorption method, air void analysis, XRD, and SEM. The experimental results indicated that freeze-thaw damage is the major effective factor in the sulfate attack and freeze-thaw alternation test. In the alternation test, average aperture of capillary pores of specimens was smaller, pores uniformity was better, and water absorption rate was lower than those specimens used in the single freeze-thaw damage test. The average aperture and uniformity of pores could be improved by adding fly ash and slag. Damage was accumulated in many cycles of freeze-thaw and microcracks increased during the test. At the same time, the hydration products of the concrete developed into expansive gypsum, AFt, and TSA without any strength during sulfate attack. The results of the microstructure analysis form XRD and SEM are in accordance with that of AFt, about 3 μm length, around which other hydration products decomposed by C-S-H after sulfate attack resulted in loss of concrete strength

Subgroup selection in adaptive signature designs of confirmatory clinical trials

The increasing awareness of treatment effect heterogeneity has motivated flexible designs of confirmatory clinical trials that prospectively allow investigators to test for treatment efficacy for a subpopulation of patients in addition to the entire population. If a target subpopulation is not well characterized in the design stage, it can be developed at the end of a broad eligibility trial under an adaptive signature design. The paper proposes new procedures for subgroup selection and treatment effect estimation (for the selected subgroup) under an adaptive signature design. We first provide a simple and general characterization of the optimal subgroup that maximizes the power for demonstrating treatment efficacy or the expected gain based on a specified utility function. This characterization motivates a procedure for subgroup selection that involves prediction modelling, augmented inverse probability weighting and low dimensional maximization. A cross-validation procedure can be used to remove or reduce any resubstitution bias that may result from subgroup selection, and a bootstrap procedure can be used to make inference about the treatment effect in the subgroup selected. The approach proposed is evaluated in simulation studies and illustrated with real examples

Exploring the Relationships Between Yield and Yield-Related Traits for Rice Varieties Released in China From 1978 to 2017

Despite evidence from previous case studies showing that agronomic traits partially determine the resulting yield of different rice (Oryza sativa L.) varieties, it remains unclear whether this is true at the ecotype level. Here, an extensive dataset of the traits of 7686 rice varieties, released in China from 1978 to 2017, was used to study the relationship between yield and other agronomic traits. We assessed the association between yield and other agronomic traits for four different rice ecotypes, i.e., indica inbred, indica hybrid, japonica inbred, and japonica hybrid. We found that associations between agronomic traits and yield were ecotype-dependent. For both the indica inbred and indica hybrid ecotypes, we found that greater values of certain traits, including the filled grain number per panicle, 1000-grain-weight, plant height, panicle length, grains per panicle, seed setting rate, long growth period, low panicle number per unit area, and low seed length/width ratio, have accounted for high grain yield. In the japonica inbred and japonica hybrid ecotypes, we found that only high panicle number per unit area and long growth period led to high grain yield. Indirectly, growth period consistently had a positive effect on yield in all ecotypes, and plant height had a positive effect on yield for the indicas and japonica inbred only. Plant height had a negative effect for the japonica hybrid. Altogether, our findings potentially have valuable implications for improving the breeds of rice ecotypes

Properties and Microstructure of Roller Compacted Concrete With High Volume Low Quality Fly Ash

The properties of roller compacted concrete (RCC) with high dosage low quality fly ash are investigated, including strength, elastic modulus, ultimate tensile strain, drying shrinkage, autogenous deformation and durability, meanwhile the microstructure of the same paste containing low quality fly ash and ground low quality fly ash are studied, too. The properties of RCC containing 60% or more ground fly ash meet the design requirement. The microstructure is also tested by using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA) and Mercury Intrusion Porosimetry (MIP). The results indicate that ground fly ash plays the role of active component besides the physical filling effect at early age, while after 90 days, the surface of the glass beads is erroded and a lot of calcium silicate hydrate and calcium hydroxide staggered as storied dense structure. Low quality fly ash can accelerate the formation of hydration products, resulting in higher degree of cement hydration and denser microstructure, while the hydration heat in total is reduced. At the age of 90 days, fly ash has significant chemical activity and the properties of RCC will be improved at the later stage.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16318</p

Seasonal Characteristics of Black Carbon Aerosol and its Potential Source Regions in Baoji, China

Continuous measurements of black carbon (BC) aerosol were made at a midsized urban site in Baoji, China, in 2015. The daily average mass concentrations varied from 0.6 to 11.5 mu g m(-3), with an annual mean value of 2.9 +/- 1.7 mu g m(-3). The monthly variation indicated that the largest loading of BC occurred in January and the smallest in June. The mass concentrations exhibited strong seasonality, with the highest occurring in winter and the lowest in summer. The large BC loadings in winter were attributed to the increased use of fuel for domestic heating and to stagnant meteorological conditions, whereas the low levels in summer were related to the increase in precipitation. BC values exhibited similar bimodal diurnal patterns during the four seasons, with peaks occurring in the morning and evening rush hours and an afternoon trough, which was associated with local anthropogenic activities and meteorological conditions. A potential source contribution function model indicated that the effects of regional transport mostly occurred in spring and winter. The most likely regional sources of BC in Baoji were southern Shaanxi province, northwestern Hubei province, and northern Chongqing during spring, whereas the northeastern Sichuan Basin was the most important source region during winter

Thermoluminescence (TL) analysis for otoliths of the wild carps (cyprinoid) from Baiyangdian Lake and Miyun Reservoir: Some implications for monitoring water environment

Otolith is a typical biomineral carrier growing on insides of fish skull with prominent zoning structure formed by alternating layers of protein and calcium carbonate growing around the nucleus. Even though thermoluminescence (TL) analysis on biomineral has been widely used to measure the radiation exposure in the recent twenty years, the TL characteristics of the fish otolith have not yet been reported in literature. TL characteristics of otoliths from the wild carps (cyprinoid) living in the Baiyangdian Lake, Hebei Province and Miyun Reservoir, Beijing City was first studied, and the differences of energy gap (E) between the fish otoliths in the two waters have also been discussed in this paper. The experimental results indicated that TL curve parameters: peak temperature (Tp), luminous intensity (I), integrated intensity (S) and middle width (Wm) for the glow curves of the cyprinoid otoliths from Baiyangdian Lake are greater than those from Miyun reservoir, and the stability of the formers’ TL curve parameters value and energy gap (E) was weaker than the latter. In comparison to the Miyun Reservoir, the analysis manifested that the electrons and vacancies trapped in the otoliths from Baiyangdian Lake are more likely to escape. According to the investigation, the contaminative degree and eutrophication in the water of Baiyangdian Lake was heavier than that of Miyun Reservoir. Therefore, the characteristics of TL growth curves of the cyprinoid otoliths is quite sensitive to heavier contaminated and less contaminated water, and this could be regarded as an important typomorphic biomineral for monitoring the contaminative degree and environment change of the water.Keywords: Cyprinoid otoliths, thermoluminescence, water environment, typomorphic minera

A 5.8 GHz DSRC Digitally Controlled CMOS RF-SoC Transceiver for China ETC

This paper presents a 5.8 GHz dedicated short range communication (DSRC) CMOS RF-SoC transceiver with digitally controlled RF architecture for China electronic toll collection (ETC) system. The operation of key RF blocks, such as ASK modulator, power amplifier, LNA, and mixer, are directly controlled by digital baseband. Compared with state-of-the-art designs in literature, this work demonstrates remarkable advantages in design simplicity, Tx output peak power, adjacent channel power ratio (ACPR), dynamic range, occupied bandwidth (OBW), bit error rate (BER), and so on