Nowadays, the heating, ventilation, and air conditioning (HVAC) system has been an important facility for maintaining indoor air quality. However, the primary function of typical HVAC systems is to control the temperature and humidity of the supply air. Most indoor air pollutants, such as volatile organic compounds (VOCs), cannot be removed by typical HVAC systems. Thus, some air handling units for removing VOCs should be added in typical HVAC systems. Among all of the air cleaning techniques used to remove indoor VOCs, photocatalytic oxidation is an attractive alternative technique for indoor air purification and deodorization. The objective of this research is to investigate the VOC removal efficiency of the photocatalytic filter in a HVAC system. Toluene and formaldehyde were chosen as the target pollutants. The experiments were conducted in a stainless steel chamber equipped with a simplified HVAC system. A mechanical filter coated with Degussa P25 titania photocatalyst and two commercial photocatalytic filters were used as the photocatalytic filters in this simplified HVAC system. The total air change rates were controlled at 0.5, 0.75, 1, 1.25, and 1.5 hr(-1), and the relative humidity (RH) was controlled at 30%, 50%, and 70%. The ultraviolet lamp used was a 4-W, ultraviolet-C (central wavelength at 254 nm) strip light bulb. The first-order decay constant of toluene and formaldehyde found in this study ranged from 0.381 to 1.01 hr(-1) under different total air change rates, from 0.34 to 0.433 hr(-1) under different RH, and from 0.381 to 0.433 hr(-1) for different photocatalytic filters. 相似文献
Environmental Science and Pollution Research - To mitigate the negative environmental and public health concerns associated with increased industrial discharges amid the rapid industrial growth,... 相似文献
Indicator or ”good genes” models of sexual selection predict that mating preferences allow females to choose mates that are
genetically superior. Female gray tree frogs (Hyla versicolor) prefer male advertisement calls of long call duration, which can be indicators of enhanced offspring growth performance.
We tested the effects of father’s call duration and the presence of a caged predator (dragonfly naiad) on tadpole activity
and growth in a factorial experiment, controlling for maternal and environmental effects. The effect of food availability
(a repeated measure) on tadpole activity was also examined. Tadpoles responded to predator presence and to high food availability
by decreasing activity and feeding. Tadpoles exposed to a caged predator were smaller after 14 days than those exposed to
an empty cage, suggesting that spending less time feeding carries the cost of reduced growth. Offspring of males with long
versus short calls responded similarly to the presence of a predator. Nonetheless, offspring of long-calling males spent more
time feeding than did offspring of short-calling males, except when a predator was present but no food was available. Increased
time spent feeding may contribute to enhanced offspring growth and, therefore, to the indirect benefit that a female may realize
by selecting a mate with long calls. However, because the behavioral differences depended on the environment, and because
the fitness consequences of such behavioral differences should also vary with the environment, the benefit of mating with
a long-calling male may depend on the conditions encountered by the offspring.
Received: 15 February 2000 / Revised: 24 September 2000 / Accepted: 16 October 2000 相似文献
Sediments and/or fish were collected from Sardis, Enid and Grenada Lakes, which are located in three different watersheds in North Mississippi, in order to assess mercury contamination. The mean total mercury concentration in sediments from Enid Lake in 1997 was 0.154 mg Hg/kg, while 1998 sediment concentrations in Sardis, Enid and Grenada Lakes were 0.112, 0.088 and 0.133 mg Hg/kg, respectively. Sediment mercury concentrations in 1999 were similar in all three lakes but, generally lower than 1998. Mean total mercury concentrations in edible fillets of fish collected from Enid Lake in 1998 were above the human health FDA action level (>1.0 mg Hg/kg) for bass (1.40), crappie (1.69) and gar (1.89); however, tissue concentrations were less than 1.0 mg Hg/kg in carp (0.63) and catfish (0.82). Human hazard indexes for each species was 1 for both adults and children, indicating that there is a potential for toxic effects to occur. In addition, calculated consumption limits indicate that adults may consume 4–12 oz. of fish per month, depending on the species consumed. For children, 2 oz. per month may be consumed. Further studies are needed to determine the exact environmental consequences and human health impacts associated with mercury contamination in North Mississippi and the Southeastern United States. 相似文献
Objective: Since 2005, National Association for Stock Car Auto Racing, Incorporated (NASCAR) drivers have been required to use a head and neck restraint system (HNR) that complies with SFI Foundation, Inc. (SFI) 38.1. The primary purpose of the HNR is to control and limit injurious neck loads and head kinematics during frontal and frontal oblique impacts. The SFI 38.1 performance specification was implemented to establish a uniform test procedure and minimum standard for the evaluation of HNRs using dynamic sled testing. The purpose of this study was to evaluate the repeatability of the current SFI 38.1 test setup and explore the effects of a polyester seat belt restraint system.
Method: Eight sled tests were conducted using the SFI 38.1 sled test protocol with additional test setup constraints. Four 0° frontal tests and 4 30° right frontal (RF) oblique tests were conducted. The first 3 tests of each principal direction of force (PDOF) used nylon SFI 16.1 seat belt restraint assemblies. The fourth test of each PDOF used polyester SFI 16.6 seat belt restraint assemblies. A secondary data set (Lab B Data) was also supplied by the HNR manufacturer for further comparisons. The International Organization for Standardization (ISO) 18571 objective comparison method was used to quantify the repeatability of the anthropomorphic test device (ATD) resultant head, chest, and pelvis acceleration and upper neck axial force and flexion extension bending moment time histories across multiple tests.
Results: Two data sets generated using the SFI 38.1 test protocol exhibited large variations in mean ISO scores of ATD channels. The 8 tests conducted with additional setup constraints had significantly lower mean ISO score coefficients of variation (CVs). The Lab B tests conducted within the current specification but without the additional test setup constraints had larger mean ISO score standard deviation and CV for all comparisons. Specifically, tests with the additional setup constraints had average CVs of 3.3 and 2.9% for the 0° and 30° RF orientations, respectively. Lab B tests had average CVs of 22.9 and 24.5%, respectively. Polyester seat belt comparisons had CVs of 5.3 and 6.2% for the 0° and 30° RF orientations, respectively.
Conclusion: With the addition of common test setup constraints, which do not violate the specification, the SFI 38.1 test protocol produced a repeatable test process for determining performance capabilities of HNRs within a single sled lab. A limited study using polyester webbing seat belt assemblies versus the nylon material called for in SFI 38.1 indicates that the material likely has less effects on ATD upper neck axial force and flexion extension bending moment time histories than the test setup freedom currently available within the specification. The additional test setup constraints are discussed and were shown to improve ATD response repeatability for a given HNR. 相似文献
A modified time series approach, a Box-Jenkins regression with time series errors (RTSE) model plus a principal component (PC) trigger, has been developed to forecast peak daily 1-hr ozone (O3) in real time at the University of Wisconsin-Milwaukee North (UWM-N) during 1999 and 2002. The PC trigger acts as a predictor variable in the RTSE model. It tries to answer the question: will the next day be a possible high O3 day? To answer this question, three PC trigger rules were developed: (1) Hi-Low Checklist, (2) Discriminant Function Approach I, and (3) Discriminant Function Approach II. Also, a pure RTSE model without including the PC trigger and a persistence approach were tested for comparison. The RTSE model with DFA I successfully forecast the only two 1-hr federal exceedances (124 ppb), one in 1999 and one in 2002. In terms of the O3 100-ppb exceedances, 60-80% of the incorrect forecasts occurred with incorrect PC decisions. A few others may have been caused by unexpected O3-weather relations. When the three approaches used UWM-N data to forecast a 100-ppb exceedance somewhere in the Milwaukee, WI, metropolitan area, their performance was dramatically improved: the false alarm rate was reduced from 0.89 to 0.44, and the probability of detection was increased from 0.71 to 0.88. 相似文献
Environmental Science and Pollution Research - Good brain health refers to a condition in which a person may fully realize their talents and improve their psychological, emotional, cognitive, and... 相似文献