Functional classification of swine manure management systems based on effluent and gas emission characteristics.

Gaseous emissions from swine (Sus scrofa) manure storage systems represent a concern to air quality due to the potential effects of hydrogen sulfide, ammonia, methane, and volatile organic compounds on environmental quality and human health. The lack of knowledge concerning functional aspects of swine manure management systems has been a major obstacle in the development and optimization of emission abatement technologies for these point sources. In this study, a classification system based on gas emission characteristics and effluent concentrations of total phosphorus (P) and total sulfur (S) was devised and tested on 29 swine manure management systems in Iowa, Oklahoma, and North Carolina in an effort to elucidate functional characteristics of these systems. Four swine manure management system classes were identified that differed in effluent concentrations of P and S, methane (CH4) emission rate, odor intensity, and air concentration of volatile organic compounds (VOCs). Odor intensity and the concentration of VOCs in air emitted from swine manure management systems were strongly correlated (r2 = 0.88). The concentration of VOC in air samples was highest with outdoor swine manure management systems that received a high input of volatile solids (Type 2). These systems were also shown to have the highest odor intensity levels. The emission rate for VOCs and the odor intensity associated with swine manure management systems were inversely correlated with CH4 and ammonia (NH3) emission rates. The emission rates of CH4, NH3, and VOCs were found to be dependent upon manure loading rate and were indirectly influenced by animal numbers.

Scandium oxide coatings for high-power UV laser applications.

Scandium oxide has proved to be a damage-resistant high-index material in laser coatings for use at 248 nm. The results of damage threshold measurements on laser reflectors and antireflection coatings of various designs, material combinations, and deposition temperatures are presented. The most significant effects are observed for overcoat layers on high reflectors and undercoat layers on antireflection coatings. Thresholds >6 J/cm(2) for 20 nsec pulses were observed in both cases.

Influence of deposition parameters on laser-damage threshold of silica-tantala AR coatings.

A series of 4-layer silica-tantala antireflection coatings was deposited under 18 different combinations of substrate temperature (175, 250, and 325 degrees C), oxygen pressure (0.5,1.0, and 2.0 x 10(-4) Torr), and rate of deposition (1.5 and 5 A/sec). Measurements of laser-damage threshold for 1064-nm, 1-nsec pulses, average absorption, net stress, and reflectivity were then made on these coatings. Coatings deposited at the lowest temperature had the highest damage thresholds. Damage thresholds were found not to be directly related to average absorption or net stress. Coatings deposited on fused silica substrates which had been polished by a bowl-feed process had generally higher damage thresholds than coatings deposited on conventionally polished fused silica or on BK-7 glass polished by either conventional or bowl-feed processes. Baking coatings in air for 4 h at 400 degrees C generally reduced average absorption and net stress, changed the net stress from compression to tension and, in some cases, increased the damage threshold.