The association of ambient air pollution with airway inflammation in schoolchildren.

Chen, Bing-Yu,Chan, Chang-Chuan,Lee, Chung-Te,Cheng, Tsun-Jen,Huang, Wen-Chuan,Jhou, Ji-Ci,Han, Yueh-Ying,Chen, Chu-Chih,Guo, Yue Leon School of Hygiene and Public Health of the Johns H 2012 American Journal of Epidemiology Vol.175 No.8

<P>The biologic mechanisms involved in airway inflammatory response to air pollution are not clearly understood. The authors conducted a longitudinal study to investigate whether exposure to ambient air pollutants affected inflammatory cells and mediators from nasal lavage in schoolchildren. Study participants were 100 elementary and middle-school students in New Taipei City, Taiwan. A structured respiratory health questionnaire was administered in September 2007, followed by monthly measurement of nasal inflammation from October 2007 to November 2009. During the study period, daily concentrations of air pollutants were obtained from the Environmental Protection Administration monitoring station and the Aerosol Supersite. Mixed-effects models were applied to examine the association between air pollution and nasal inflammatory cells and mediators, including percentages of neutrophils, eosinophils, and monocytes in lavaged cells and interleukin-8. A total of 824 measurements were obtained from 100 participants over a period of 10 months. The level of particulate matter with an aerodynamic diameter of 2.5 μm or less (PM(2.5)) was found to be associated with percentage of neutrophils (β = 3.45%, 95% confidence interval: 0.89, 6.01) and interleukin-8 level (β = 29.98 pg/mL, 95% confidence interval: 3.26, 56.69) in the nasal lavage on the day of exposure. In this longitudinal cohort study of schoolchildren, results indicated that exposure to PM(2.5) might induce nasal inflammation.</P>

Ozone and Daily Mortality Rate in 21 Cities of East Asia: How Does Season Modify the Association?

Chen, Renjie,Cai, Jing,Meng, Xia,Kim, Ho,Honda, Yasushi,Guo, Yue Leon,Samoli, Evangelia,Yang, Xin,Kan, Haidong Oxford University Press 2014 American Journal of Epidemiology Vol.180 No.7

<P>Previous studies in East Asia have revealed that the short-term associations between tropospheric ozone and daily mortality rate were strongest in winter, which is opposite to the findings in North America and Western Europe. Therefore, we investigated the season-varying association between ozone and daily mortality rate in 21 cities of East Asia from 1979 to 2010. Time-series Poisson regression models were used to analyze the association between ozone and daily nonaccidental mortality rate in each city, testing for different temperature lags. The best-fitting model was obtained after adjustment for temperature in the previous 2 weeks. Bayesian hierarchical models were applied to pool the city-specific estimates. An interquartile-range increase of the moving average concentrations of same-day and previous-day ozone was associated with an increase of 1.44% (95% posterior interval (PI): 1.08%, 1.80%) in daily total mortality rate after adjustment for temperature in the previous 2 weeks. The corresponding increases were 0.62% (95% PI: 0.08%, 1.16%) in winter, 1.46% (95% PI: 0.89%, 2.03%) in spring, 1.60% (95% PI: 1.03%, 2.17%) in summer, and 1.12% (95% PI: 0.73%, 1.51%) in fall. We found significant associations between short-term exposure to ozone and higher mortality rate in East Asia that varied considerably from season to season with a significant trough in winter.</P>

Applying a Forced Censoring Technique with Accelerated Modeling for Improving Estimation of Extremely Small Percentiles of Strengths

Chen Weiwei,Leon Ramon V.,Young Timothy M.,Guess Frank M. The Korean Reliability Society 2006 International Journal of Reliability and Applicati Vol.7 No.1

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

Simulation of Rayleigh wave’s acoustoelastic effect in concrete, aluminum and steel

Guadalupe Leon,Hung-Liang (Roger) Chen 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.91 No.4

In this study, a finite-element surface wave simulation using an effective elastic constant (EEC) was developed to calculate the Rayleigh wave velocity change and polarization change in aluminum, steel, and concrete under uniaxial stress. Under stress, an isotropic medium behaves like an anisotropic material during the wave propagation. The EEC is an equivalent anisotropic stiffness matrix which was derived to simulate the acoustoelastic effect using classical finite-element software. The vertical and horizontal surface displacements located 8-mm from a 1-μs excitation load were used to find the acoustoelastic coefficients and and compared to an analytical scheme. It was found that for aluminum and concrete matched within 4% of the analytical solution. The finite-element simulation showed that the Rayleigh wave arrival time for concrete and aluminum was greatly influenced by the stress level. Thus, predicting the stress level using concrete and aluminum’s acoustoelastic effect is applicable.

Investigation on the seismic performance of T-shaped column joints

Changhong Chen,He Gong,Yao Yao,Ying Huang,Leon M. Keer 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.3

More and more special-shaped structural systems have been widely used in various industrial and civil buildings in order to satisfy the new structural system and the increasing demand for architectural beauty. With the popularity of the specialshaped structure system, its seismic performance and damage form have also attracted extensive attention. In the current research, an experimental analysis of six groups of (2/3 scale) T-shaped column joints was conducted to investigate the seismic performance of T-shaped column joints. Effects of the beam cross section, transverse stirrup ratio and axial compression ratio on bearing capacity and energy dissipation capacity of column joints were obtained. The crack pattern of T-shaped column joints under low cyclic load was presented and showed a reversed “K” mode. According to the crack configurations, a tensile-shear failure model to determine the shear bearing capacity and crack propagation mechanisms is developed.

Applying a Forced Censoring Technique with Accelerated Modeling for Improving Estimation of Extremely Small Percentiles of Strengths

Weiwei Chen,Ramon V. Leon,Timothy M. Young,Frank M. Guess 한국신뢰성학회 2006 International Journal of Reliability and Applicati Vol.7 No.1

Significant effects of exposure to relatively low level ozone on daily mortality in 17 cities from three Eastern Asian Countries

Huang, Wei-Heng,Chen, Bing-Yu,Kim, Ho,Honda, Yasushi,Guo, Yue Leon Elsevier 2019 Environmental research Vol.168 No.-

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>Studies have examined the variation in mortality risk associated with ambient ozone. We conducted an international cooperation study for investigating the non-linear ozone–mortality association accounting for lag effect and for examining the ozone level with significant health effect.</P> <P><B>Methods</B></P> <P>Daily counts of total non-accidental death and ambient air pollutant concentration were obtained in 17 cities from 3 Eastern Asian countries or regions (Taiwan, Korea, and Japan). The total study period was from 1979 to 2010 and differed by city based on data availability. The ozone–mortality association in each city was estimated by running a time-series quasi-Poisson regression model, allowing for overdispersion. The city-specific estimates were then pooled by country by using multivariate random effects meta-analysis.</P> <P><B>Results</B></P> <P>The non-linear ozone exposure–mortality response curves were generated in 17 cities from Taiwan, Korea, and Japan. The association curves in the three countries all showed increased mortality with elevated ozone, and the significant mortality effects of ozone exposure were observed at level higher than 40, 50, and 40 ppb for Taiwan, Korea, and Japan, respectively. These associations are unaffected by co-pollutant of particulate matter in Taiwan and Japan. But the potential confounding effect of co-pollutant could not be ignorable in Korea.</P> <P><B>Conclusions</B></P> <P>Our study provides evidence that exposure to a relative low level of ambient ozone is associated with an increased risk of mortality. Our results emphasize the continual need to examine the existing standard by documenting potential human adverse effects.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Non-linear ozone-mortality associations were observed in three East Asian countries (Taiwan, Korea, and Japan). </LI> <LI> A low level of observable effect (40–50 ppb) existed for ozone. </LI> <LI> Our result emphasizes the continual need to examine the existing standard. </LI> </UL> </P>

Forcing a Closer Fit in the Lower Tails of a Distribution for Better Estimating Extremely Small Percentiles of Strengths

Guess, Frank-M.,Leon, Ramon-V.,Chen, Weiwei,Young, Timothy-M. The Korean Reliability Society 2004 International Journal of Reliability and Applicati Vol.5 No.4

We use a novel, forced censoring technique that closer fits the lower tails of strenth distributions to better estimate extremly smaller percentiles for measuring progress in continuous improvement initiatives. These percentiles are of greater interest for companies, government oversight organizations, and consumers concerned with safely and preventing accidents for many products in general, but specifically for medium density fiberboard (MDF). The international industrial standard for MDF for measuring highest quality is internal bond (IB, also called tensile strengh) and its smaller percentiles are crucial, especially the first percentile and lower ones. We induce censoring at a value just above the median to weight lower observations more. Using this approach, we have better fits in the lower tails of the distribution, where these samller percentiles are impacted most. Finally, bootstrap estimates of the small percentiles are used to demonstrate improved intervals by our forced censoring approach and the fitted model. There was evidence from the study to suggest that MDF has potentially different failure modes for early failures. Overall, our approach is parsimonious and is suitable for real time manufacturing settings. The approach works for either strengths distributions or lifetime distributions.

A general solution to structural performance of pre-twisted Euler beam subject to static load

Ying Huang,Chang Hong Chen,Leon M. Keer,Yao Yao 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.2

Based on the coupled elastic bending deformation features and relationships between the internal force and deformation of pre-twisted Euler beam, the generalized strain, the equivalent constitutive equation and the equilibrium equation of pre-twisted Euler beam are developed. Based on the properties of the dual-antisymmetric matrix, the general solution of pretwisted Euler beam is obtained. By comparison with ANSYS solution by using straight Beam-188 element based on infinite approach strategy, the results show that the developed method is available for pre-twisted Euler beam and also provide an accuracy displacement interpolation function for the subsequent finite element analysis. The effect of pre-twisted angle on the mechanical property has been investigated.

Prediction of elastic constants of Timoshenko rectangular beams using the first two bending modes

Hung-Liang (Roger) Chen,Guadalupe Leon 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.6

In this study, a relationship between the resonance frequency ratio and Poisson’s ratio was proposed that can be used to directly determine the elastic constants. Using this relationship, the frequency ratio between the 1st bending mode and 2nd bending mode for any rectangular Timoshenko beam can be directly estimated and used to determine the elastic constants efficiently. The exact solution of the Timoshenko beam vibration frequency equation under free-free boundary conditions was determined with an accurate shear shape factor. The highest percent difference for the frequency ratio between the theoretical values and the estimated values for all the beam dimensions studied was less than 0.02%. The proposed equations were used to obtain the elastic constants of beams with different material properties and dimensions using the first two measured transverse bending frequencies. Results show that using the equations proposed in this study, the Young’s modulus and Poisson’s ratio of rectangular Timoshenko beams can be determined more efficiently and accurately than those obtained from industry standards such as ASTM E1876-15 without the need to test the torsional vibration.