ABSTRACT: A number of aspects of the discharging of non-oily wastewaters by transiting ships are treated in this overview paper. In the introduction, options to discharging (the use of holding tank, on board treatment) and the impact of changing regulations are discussed. Assessment of the effects of sewage discharges on coastal waters required that data, at first not available, be generated. An account is given of the characterization of Navy shipboard wastewaters and of experiments involving sewage discharges at sea, measurements of water quality before, during and after an amphibious operation, and fore and aft of transitting Navy ships. A better understanding of sewage dilution after discharge led to the verification of a method for controlled discharging of sewage (and other wastewaters). This method permits limiting the coliform bacteria count in the ship's wake to values below acceptable limits. The final sections contain information on long range effects of ships’sewage discharges, obtained in studies by the U.S. Navy and others, as well as public health considerations. 相似文献
Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of
a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D
radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power
absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber
using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained
in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm
away from the head. 相似文献
Objective: Soldiers in military vehicles subjected to underbelly blasts can sustain traumatic head and neck injuries due to a head impact with the roof. The severity of head and neck trauma can be influenced by the amount of head clearance available to the occupant as well as factors such as wearing a military helmet or the presence of padding on the interior roof. The aim of the current study was to examine the interaction between a Hybrid III headform, the helmet system, and the interior roof of the vehicle under vertical loading.
Methods: Using a head impact machine and a Hybrid III headform, tests were conducted on a rigid steel plate in a number of different configurations and velocities to assess helmet shell and padding performance, to evaluate different vehicle roof padding materials, and to determine the relative injury mitigating contributions of both the helmet and the roof padding. The resultant translational head acceleration was measured and the head injury criterion (HIC) was calculated for each impact.
Results: For impacts with a helmeted headform hitting the steel plate only, which represented a common scenario in an underbelly blast event, velocities of ≤6 m/s resulted in HIC values below the FMVSS 201U threshold of 1,000, and a velocity of 7 m/s resulted in HIC values well over the threshold. Roof padding was found to reduce the peak translational head acceleration and the HIC, with rigid IMPAXX foams performing better than semirigid ethylene vinyl acetate (EVA) foam. However, the head injury potential was reduced considerably more by wearing a helmet than by the addition of roof padding.
Conclusions: The results of this study provide initial quantitative findings that provide a better understanding of helmet–roof interactions in vertical impacts and the contributions of the military helmet and roof padding to mitigating head injury potential. Findings from this study will be used to inform further testing with the future aim of developing a new minimum head clearance standard for occupants of light armored vehicles. 相似文献
This work describes how a general, process-based mass-balance model (CoastMab) for phosphorus for coastal areas may be used as a tool to estimate realistic values of “natural” or preindustrial reference levels of key bioindicators in coastal science, including the Secchi depth, a standard measure of water clarity, the chlorophyll-a concentration, an operational measure of phytoplankton biomass and the concentration of cyanobacteria, a measure of the concentration of harmful algae. The CoastMab-model is an ecosystem model giving monthly predictions to achieve seasonal variations of basin-wide properties. The selected case-study area, the Gulf of Riga, is sensitive to nutrient loading because of its shallowness and low openness towards the Baltic Proper. The morphometry of any coastal area, as given by the size and form parameters, influences all internal processes, such as sedimentation, resuspension, diffusion in water and from sediments to water, biouptake and retention in biota, stratification, mixing and outflow. There has been no mass-balance modeling for nitrogen (N) in this work because empirical data (from the HELCOM database) clearly indicate that the monthly primary production in the Gulf of Riga is regulated by phosphorus (P) – the mean monthly total-N to total-P ratios are well over 7.2 (the Redfield-ratio) and generally higher than 15 for the data used in this study (from 1992 to 2005). At present anthropogenic loads, the average modeled monthly values for Secchi depth, chlorophyll (Chl), cyanobacteria (CB) and total-P (TP) are 3.2 m, 3.8 μg/l, 78 μg/l and 31.3 μg/l, respectively. If 50% of all anthropogenic sources to the Gulf of Riga via rivers, point sources and diffuse sources were to be removed, these values would be 3.6 m, 3.4 μg Chl/l, 63 μg CB/l and 29.1 μg TP/l. If 60% of the anthropogenic phosphorus fluxes to the Baltic Proper were to be omitted and as well as 75% of all direct anthropogenic sources to the Gulf of Riga, the values would be 4.6 m, 2.7 μg Chl/l, 45 μg CB/l and 25.4 μg TP/l. These values represent the “natural” reference levels and it is not realistic to expect that remedial measures would improve the conditions more than that. Using the CoastWeb-model, similar calculations can be made for any given coastal area and the data necessary for such calculations are discussed in this work. 相似文献