Assessing the Reliability of the B-1B Lancer Using Survival Analysis

During the 2017 posture statement to the US Senate Armed Services Committee, the Secretary of the Air Force and Chief of Staff of the Air Force stated the Air Force suffers from shrinking aircraft inventory, aging aircraft fleets, and flying beyond the expected service life. These trends are not an exception to the B-1B Lancer, which has been in service since 1986. Recently, the B-1B Lancer has maintained the lowest mission capable (MC) rates of 47.7 percent. The purpose of this research is to explore the failure rates of the B-1B Lancer using survival analysis that investigates the failure behavior of the B-1B Lancer. A Cox proportional hazards regression model with frailty confirms the existence of unobserved heterogeneity or frailty in our analysis. When the frailty is controlled, combat missions increase in failure rates. Other variables, mainly flight hour or sortie duration related variables, are inconclusive and require further analysis. This study proposes insights based on findings and suggests future research directions

Evaluation of 1,4-Dioxane Biodegradation Under Aerobic and Anaerobic Conditions

Used mainly as a solvent stabilizer, 1,4-dioxane is present at many sites contaminated along with chlorinated solvents and other chemical compounds. Considered a probable human carcinogen by the U.S. Environmental Protection Agency, this contaminant has raised considerable concerns because of its potential adverse effects on health. Therefore, remediation of 1,4-dioxane has gained importance, and although there are several approaches for its treatment, such as ex situ physicochemical processes, bioremediation is a key alternative because it is a low energy demanding process. Anaerobic conditions are present at most contaminated sites, however, there is insufficient scientific evidence for anaerobic biodegradation of 1,4-dioxane. On the other hand, aerobic biodegradation of 1,4-dioxane has been widely studied under metabolic and cometabolic conditions. Nevertheless, limited information is known about the rate of 1,4-dioxane cometabolism with substrates, such as propane, that can be used for in situ bioremediation. Bacteria that grow on 1,4-dioxane have a low affinity for the contaminant since their half saturation coefficient (Ks) values are often high, but the contaminant half saturation coefficients (Kc) associated with cometabolism are usually lower. However, kinetic parameters for cometabolic biodegradation of 1,4-dioxane with a non-toxic and convenient substrate such as propane have not been evaluated. Based on the gaps in the scientific literature, and in order to expand the understanding of 1,4-dioxane biodegradation and its potential in situ bioremediation applications, the objectives of this study included: 1) Estimate the kinetic parameters for 1,4-dioxane metabolism and for cometabolism by propane-oxidizing bacteria that are relevant to field applications in bioremediation; and 2) Evaluate the potential for in situ bioremediation of a 1,4-dioxane plume using metabolic and cometabolic biosparging and bioaugmentation, based on simulations using a subsurface transport model; and 3) Evaluate the potential for anaerobic biodegradation of 1,4-dioxane. To achieve the first objective, kinetic parameters for aerobic cometabolic biodegradation of 1,4-dioxane by propane-oxidizing bacteria were evaluated for a pure culture, Rhodococcus ruber ENV425, and a mixed culture, ENV487. The 1,4-dioxane metabolizer Pseudonocardia dioxanivorans CB1190 was also tested for its kinetic parameters. Kinetics for metabolic and cometabolic biodegradation of 1,4-dioxane were successfully modeled using modified Monod equations. Results indicate that the propanotrophic bacteria have lower half saturation constants (KC = 6.05 ± 0.26 and 3.25 ± 0.05 mg COD L-1) for 1,4-dioxane than CB1190 (KS = 11.5 ± 0.4 mg COD L-1). Other parameters measured included the biomass yield (Y) for propane and 1,4-dioxane, transformation capacity (TC), half saturation coefficients for oxygen (KSO and KCO), biomass decay coefficient (b), and substrate utilization rates (kS and kC). Coinhibition parameters (KiS and KiC) between propane and 1,4-dioxane were also estimated. Batch simulations showed that cometabolism is more advantageous than metabolism when the initial concentration of 1,4-dioxane is low (~1 mg L-1) and that both processes are heavily impacted by dissolved oxygen concentrations less than 2 mg L-1. The second objective was achieved by simulating the effect of biodegradation reactions on a 1,4-dioxane subsurface plume treated with biosparging and bioaugmentation. The effect of the injection rates of propane, biomass and oxygen as well as the initial 1,4-dioxane concentrations were evaluated in terms of the time to reach an average 1,4-dioxane level of 1 µg L-1, as well as the percentage of 1,4-dioxane that underwent biodegradation. Data from a biosparging pilot study at Vandenburg Air Force base was used to calibrate the model as it applied to propanotrophic cometabolism. The simulation results indicated that propanotrophic cometabolism achieves remediation at a faster rate when the initial 1,4-dioxane concentration is less than 7.5 mg L-1; lower concentrations do not support enough growth of microbes that grow of 1,4-dioxane to adequately offset the effect of cell decay. A continuous supply of propane to support cometabolism negates the effect of cell decay. The model provides a framework for comparing metabolic and cometabolic approaches to in situ bioremediation at other sites. To achieve the third objective, microcosms were prepared with groundwater and sediment from two contaminated sites at which the field data suggest that 1,4-dioxane is undergoing anaerobic biodegradation. The groundwater contains high levels of acetone and isopropanol, which ensure anaerobic conditions. High levels of halogenated solvents are also present. The microcosms were amended with uniformly labeled [14C]-1,4-dioxane to characterize degradation products. Amendments included Fe(III) oxide, Fe(III)-ethylene-diaminetetraacetic acid (Fe(III)-EDTA), anthraquinone disulfonate (AQDS), sulfate and oxygen. Following four years of incubation, biodegradation of many of the halogenated solvents was observed, as was iron reduction, sulfate reduction, and methanogenesis. However, there was no significant evidence to support biodegradation of 1,4-dioxane under anaerobic conditions, although partial mineralization in aerobic microcosms was observed. Further laboratory studies are needed to determine the feasibility of anaerobic biodegradation of 1,4-dioxane. Until then, aerobic treatment remains the only viable bioremediation alternative

Concrete Swelling in Existing Dams

Several chemical reactions are able to produce swelling of concrete for decades after its initial curing, a problem that affects a considerable number of concrete dams around the world. Principia has had several contracts to study this problem in recent years, which have required reviewing the state-of-the-art, adopting appropriate mathematical descriptions, programming them into user routines in Abaqus, determining model parameters on the basis of some parts of the dams’ monitored histories, ensuring reliability using some other parts, and finally predicting the future evolution of the dams and their safety margins. The paper describes some of the above experience, including the programming of sophisticated non-isotropic swelling models, that must be compatible with cracking and other nonlinearities involved in concrete behaviour. The applications concentrate on two specific cases, an archgravity dam and a double-curvature arch dam, both with a long history of concrete swelling and which, interestingly, entailed different degrees of success in the modelling effort

Adoption of GMHT Crops: Coexistence Policy Consequences in the European Union

Agricultural and Food Policy, Crop Production/Industries,

Spatial and temporal variation in the diet of the California sea lion (Zalophus californianus) in the Gulf of California, Mexico

Between June 1995 and May 1996 seven rookeries in the Gulf of California were visited four times in order to collect scat samples for studying spatial and seasonal variability California sea lion prey. The rookeries studied were San Pedro Mártir, San Esteban, El Rasito, Los Machos, Los Cantiles, Isla Granito, and Isla Lobos. The 1273 scat samples collected yielded 4995 otoliths (95.3%) and 247 (4.7%) cephalopod beaks. Fish were found in 97.4% of scat samples collected, cephalopods in 11.2%, and crustaceans in 12.7%. We identified 92 prey taxa to the species level, 11 to genus level, and 10 to family level, of which the most important were Pacific cutlassfish (Trichiurus lepturus), Pacific sardine (Sardinops caeruleus), plainfin midshipman (Porichthys spp.), myctophid no. 1, northern anchovy (Engraulis mordax), Pacific mackerel (Scomber japonicus), anchoveta (Cetengraulis mysticetus), and jack mackerel (Trachurus symmetricus). Significant differences were found among rookeries in the occurrence of all main prey (P≤0.04), except for myctophid no. 1 (P>0.05). Temporally, significant differences were found in the occurrence of Pacific cutlassfish, Pacific sardine, plainfin midshipman, northern anchovy, and Pacific mackerel (P<0.05), but not in jack mackerel (χ 2=2.94, df=3, P=0.40), myctophid no. 1 (χ 2=1.67, df= 3, P=0.64), or lanternfishes (χ 2=2.08, df=3, P=0.56). Differences were observed in the diet and in trophic diversity among seasons and rookeries. More evident was the variation in diet in relation to availability of Pacific sardine

Innovative concepts of Integrated Solar Combined Cycles (ISCC) using a Solid Oxide Fuel Cell (SOFC)

Concentrating Solar Power (CSP) is one of the most promising ways for electricity production of the upcoming years with high penetration of intermittent renewable energy sources such as wind and solar-photovoltaics. This is due to the fact that CSP when coupled to Thermal Energy Storage (TES) system enables large, inexpensive and flexible energy dispatch, which contributes to energy grid stabilization. At the same time, TES allows for steady operation of the power block by reducing undesirable fluctuations due to weather transient conditions and increasing the number of hours that the power block operates at design conditions 1. Despite the abovementioned advantages of CSP systems, a step further is needed for increase overall system efficiency and decrease CO2 emissions. Several studies have been performed considering high efficiency plant layouts such as combined cycle. For the latter, several works have been investigated about solar integration of combined cycle using parabolic trough and solar tower technologies. In both cases, solar energy was used for water/steam preheating and evaporation steps of the Rankine cycle in combination with the exhaust gases of fossil-fuel gas turbine engine. However, no research has been performed considering ISCC coupled with a Solid Oxide Fuel Cell (SOFC). In this research, two innovative layouts of ISCC power plants will be analyzed. First considers a ISCC based on solar tower and second a ISCC with a parabolic trough collector field coupled to the Heat Recovery Steam Generator (HRSG). The objective of this research is analyze the energy behavior of both layouts, selecting the best ISCC scheme to be coupled with a SOFC. The simulations will be performed using Thermoflex software. In both layouts, a SOFC is introduced before the combustion chamber at the topping cycle, and a Rankine cycle (bottoming cycle) with 2 pressures is considered.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

CLIL Implementation applied to Mathematics for Engineering

CLIL methodology aims to facilitate the learning of contents in a second language. Authors have tested an experience of implementation in English of these methods in subjects of Mathematics for Engineering at the University of Malaga.CLIL methodology aims to facilitate the learning of contents in a second language. Authors have tested an experience of implementation in English of these methods in subjects of Mathematics for Engineering at the University of Malaga. - Objectives: To create groups which will be taught in English. To try to integrate concepts and maths terminology in the target language, in this case English, maintaining the lessons in Spanish. To improve the integration of foreign students and our student’s knowledge in the target language in order to gain mobility to other universities where English is offered. To elaborate teaching materials and assessment tests in English. - Method: Experience has been developed for two academic years in Engineering degrees at Malaga University in the frame of the Educational Innovative Project PIE17-181. Many students hold an adequate level of English, but some others do not know it enough to follow full teaching in English without difficulties. By keeping lessons and assessments in Spanish, we integrated, in a gradual way, materials such as notes, summaries, exercises and powerpoint documents , all written in English. The use of ICTs has been important for the development of this implementation. - Results: This methodology improves the student's English, mainly in the field of scientific/technical terminology, without loss of content in mathematics. - Conclusions: Among others, we believe that the results are positive and we will continue with this experience.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech