Effect of Biaxial Stretching on Thermal Properties, Shrinkage and Mechanical Properties of Poly (Lactic Acid) Films

This study produced poly (lactic acid) sheets using a biaxial stretching process, to investigate the effects of biaxial stretching on thermal properties, crystallinity, shrinkage and mechanical properties of PLA films. The results of differential scanning calorimetry show that the glass temperature peak of PLA films, which weakened after stretching. The cold crystallization peak of PLA films nearly disappeared at stretch ratios of 4 × 4 with a stretching rate above 50 %/s. The orientation and strain crystallization of PLA films were suppressed at stretching temperatures of approximately 100–110 °C. The shrinkage of PLA decreased proportionally to the stretch rate and inversely proportional to the stretching temperature, suggesting that the internal stresses frozen in the amorphous phase were an indication of a decrease in the crystallinity of the films, implying that PLA films would be best suited to low-shrinkage applications. The stress–strain of the PLA films increased considerably following the biaxial stretching process. In addition, PLA films exposed to hot water treatment show a slight decrease in stress values, probably attributable to a relaxation of the molecules, which have undergone orientation but failed to crystallize.     

Removal of pesticides from rinsate by adsorption using agricultural residuals as medium

Abstract

The feasibility of using agricultural residual with highly organic matter content ‐ spent mushroom compost (SMC) as adsorption medium for removal of pesticides including carbaryl, carbofuran, and aldicarb with a concentration range of 0–30 mg/L from rinsate was investigated. Bottle‐point method was used to determine adsorption isotherms for single‐pesticide and multi‐pesticides. It was found that SMC might potentially be used for on‐farm treatment of pesticide rinsate. The adsorption capacity of SMC was increased compared to most soils, possibly related to the increased organic matter content. The rapid equilibrium of pesticide solution and SMC was consistent with a physical type of adsorption mechanism. The adsorption of carbamate pesticides on SMC was found to exhibit nonlinear “favorable”; adsorption behavior that could be characterized well by the Freundlich isotherm model. In addition, the multi‐pesticide adsorption tests displayed the characteristics of competitive behavior. The competitive ability of these three pesticides in multi‐components adsorption was in the order carbaryl > carbofuran > aldicarb, which was consistent with the adsorbability of pesticides.     

Photocatalytic oxidation of xenobiotics in water with immobilized TIO2 on agitator

Abstract

A novel photocatalytic oxidation reactor, using Degussa P‐25 T_iO₂ as a stationary phase with a thickness of 1.5–2.0 um on the blades of agitator, was developed to study the photocatalytic oxidation of xenobiotics. Particularly in this device, separation of photocatalyst from the purified water after oxidation reaction was not necessary, and no other aeration equipment was required to supply oxygen. To examine the efficiency of this device, photocatalytic degradation of xenobiotic organics such as carbofuran was studied as an example. Results indicated that carbofuran could be degraded completely with mineralization efficiency of 20 % after 6 hours of oxidation under the imposed conditions. The mineralization rate of carbofuran was found to follow the pseudo‐first order reaction kinetics. Moreover, the rate constant of mineralization was found to be proportional to T_iO₂ film area and the square root of UV light intensity. These results implied the mineralization efficiency of carbofuran could be improved through increasing T_iO₂ film area and UV light intensity. Accordingly, this novel device showed potential application for degrading xenobiotics in water.     

Concentration and composition variations of metals in the outdoor PM10 of elementary schools during river dust episodes

Aeolian river dust can seriously affect the air quality in central Taiwan. The main purpose of this study was to assess the concentration variations of PM₁₀ and metals at different elementary schools during river dust episodes. River dust samples were taken from eight sites in the main bare soil areas of the Choshui River. PM₁₀ aerosols from four elementary schools in Yulin County were collected by means of high-volume samplers. Fifteen elements (Fe, Al, Ca, Mg, Mn, Zn, Ti, Ni, V, Cr, As, Pb, Cu, Co, and Cd) in the river dust and PM₁₀ were analyzed in this study. The coefficients of divergence (CDs) were obtained by comparing the metal compositions in PM₁₀ aerosols at the four schools on the sampling days with the mean metal contents in the river soil samples as reference. The CD values showed that metal compositions in the aerosols at high-exposure sites during river dust episodes were similar to those compositions in the river dust. The concentrations of PM₁₀ at the high-exposure schools during river dust episodes were much higher than those during non-river-dust episodes. This study also indicated that at the high-exposure sites, both the PM₁₀ and metal concentrations were higher than at the low-exposure and control sites, not only during the river dust episodes, but also after the river dust episodes. The concentrations of toxic metals (Ni, Cr, As, and Cd) at the high-exposure sites were about 11.3 times higher during the river dust episodes (189 ng/m³) than during non-river-dust episodes (16.7 ng/m³) and about 8.9 times higher during the same periods at the control site (21.3 ng/m³).     

Lake eutrophication management modeling using dynamic programming

Lake eutrophication problems have received considerable attention in Taiwan, especially because they relate to the quality of drinking water. In this study, steady-state river water quality and lake eutrophication models are solved using dynamic programming algorithms to find the nutrient removal rates for eutrophication control during dry season. The kinetic cycle of chlorophyll-a, phosphorus and nitrogen for a complete-mixed lake is considered in the optimization framework. The Newton-iterative technique is adopted to solve the nonlinear equations for the steady-state lake eutrophication model. The optimization framework is applied to Cheng-Ching Lake in southern Taiwan. Several nutrient loading scenarios for eutrophication control are studied. Optimization results for nutrient removal rates and corresponding wastewater treatment capacities of each reach of the Kao-Ping River define the least cost approach to lake eutrophication control. A natural purification method, structural free water surface wetland, is also suggested to save more investment and improve river water quality at the same time.     

Factors affecting the concentrations of PM10 in central Taiwan

In this study, the synoptic weather types that have high probability and low probability of producing PM10 episode are referred to as HPE and LPE, respectively. Multiple linear regressions analysis showed that NO2 was the most important contributor (35.61%) to the concentrations of PM10 for HPE weather. For LPE weather, the season factor had the greatest contribution (48.11%) to the concentrations of PM10. Using the correlation coefficients between the concentrations of PM10 and SO2 or NO2 on HPE and LPE to calculate the increase of PM10 from LPE to HPE, we found that the increase of PM10 owing to the increase of SO2 and NO2 from LPE to HPE was 12.93microg/m3 which was about 51% of the total amount of PM10 increased from LPE to HPE. Results of factor analysis showed that the first component could be attributed to the result of local pollution especially for the weather patterns of types P3 and P6, while the secondary component for the weather patterns of types P1 and P4 can be attributed to the long-range transport of SO2 pollutants from China.     

Modified grey model for estimating traffic tunnel air quality

This study compared three forecasting models based on the mean absolute percentage errors (MAPE) of their accuracy in forecasting air pollution in a traffic tunnel: the Grey model (GM), the combination model used four sample point and five sample point prediction with GM (1,1)(GM(1,1)^4 + 5), and the modified grey model (MGM). An MGM was combined using the four points of the original sequence using the original grey prediction GM (1,1) for short-term forecasting. The proposed method cannot only enhance the prediction accuracy of the original grey model, but can also solve the jump data forecasting problem something for which the original grey model is inappropriate. The MAPE was applied to the models, and the MGM found the proposed method to be simple and efficient. The MAPE of MGM, calculated over 3 h of forecasts, were as follows: 10.12 (Upwind), 10.07 (Middle) and 7.68 (Downwind) for CO; 10.79 (Upwind), 6.05 (Middle) and 5.98 (Downwind) for NO _x , and 11.67 (Upwind), 7.32 (Middle) and 4.56 (Downwind) for NMHC. The MGM model results reveal that the combined forecasts can significantly decrease the overall forecasting error. Results of this demonstrate that MGM can accurately forecast air pollution in the Kaohsiung Chung–Cheng Tunnel.     

Modeling of organic pollutant destruction in a stirred-tank reactor by ozonation

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Prenatal ultrasonographic diagnosis of congenital megalourethra

Congenital megalourethra is a rare genital anomaly characterized by dilatation of the penile urethra without evidence of distal obstruction. Reports of the prenatal diagnosis of this condition in the literature are limited. We present a case of congenital megalourethra with obstructive uropathy from the posterior urethra diagnosed prenatally at 18 weeks of gestation. ‘Prune-belly’-like features, colonic malrotation, and imperforate anus were also found on autopsy.     

Analysis of herbicide Krovar I by liquid chromatography with atmospheric pressure chemical ionization mass spectrometry

A simple, very efficient method is presented for routine analysis of herbicide Krovar I (active components bromacil and diuron) in water and soil samples. Water samples were extracted by liquid-liquid extraction with dichloromethane (DCM) as extraction solvent. For soil samples two different extraction techniques were compared: microwave-assisted solvent extraction and a shaking technique using a platform shaker. Extracts were analyzed by high performance liquid chromatography using a water:methanol gradient. Liquid chromatography was coupled with atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) for quantification of bromacil and diuron. Optimization of the APCI-MS was done by using standards in the flow injection analysis mode (FIA). Method detection limit for liquid samples for bromacil is 0.04 microg L(-1) and for diuron 0.03 microg L(-1). Method detection limit for soil samples is 0.01 microg g(-1) dry weight for both compounds. Results of analysis of field samples of water and soil are also presented.