Ocean thermal energy: Potentials and pitfalls
Abstract Thermal energy in vast reaches of the world's oceans lies waiting to be tapped by a fuel‐hungry world. The United States— the one heavily industrialized nation with “OTEC”; waters lapping its shores—is actively developing the technology; Japan and a European consortium are also pressing forward. The resource may be of practical value soon to favorably situated islands (e.g., Hawaii, Puerto Rico, Cuba) and Third World countries. Meaningful contributions to mainland U.S. electricity needs are almost certainly a decade or more in the future, and conjectural. Environmental dangers loom if OTEC is too extensively and hurriedly deployed, and for the United States it is not a substitute for nuclear fission and fossil fuel in meeting immediate energy needs.
Modeling and Optimization of a Friction Stir Extrusion Process Using Finite Element Methods
by Tyler R. Jaramillo Friction stir extrusion (FSE) is a relatively new manufacturing process that allows for reduced cost production of metallic piping with a fine, equiaxed grain structure. While some research has been conducted into computational modeling of varying FSE techniques, little has been done in terms of creating models to predict process parameter requirements, such as extrusion force or mandrel torque. To that end, models of a sample FSE process for the extrusion of 6061 aluminum were created in the commercial finite element analysis software DEFORM. The models were validated by two means. First, simple die geometries were analyzed using upper and lower bound methods. The same geometry was simulated in DEFORM and the results compared. Second, the sample FSE process was modeled and compared to physical trials. Once the computational model was validated, various process variants were modeled to optimize the technique subject to machine constraints. In gratitude to my parents, Patricia E. Jaramillo and Lewis E. Fick III, without whose support for Catholic education this work would not have been possible.
An Ultrasensitive Analytical Method Based on Chemiluminescence Sensing Electrochemical Parallel Catalytic Reaction Event
An ultrasensitive electrochemiluminescence (ECL) method on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed for improving ECL analytical characteristics using vanadate(V) as a representative. Vanadate(V) could be electrochemically reduced to generate vanadate(II) which could be chemically oxidized by potassium periodate to regenerate vanadate(V) and give parallel catalytic wave effect. Then, the reduced product of potassium periodate could react with butyl-rhodamine B to emit a sensitive chemiluminescence signal. The chemiluminescence intensity was correlative with vanadate(V) concentration. The investigation on the electrochemical reaction rate constant (k0) confirmed that the speed of electrochemical reaction was faster than that of the subsequent chemiluminescence reaction. The possibility of the combination of electrochemical parallel catalytic reaction with chemiluminescence signal sensing was proved. The similar ECL behaviors could be observed at zirconia nanowires-Nafion modified electrode. Because of the separation and enrichment effect of the modified electrode on vanadate(V), the selectivity and sensitivity was further improved greatly. Based on these findings, a new concept on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed and an ultrasensitive ECL method for the determination of vanadate(V) was developed at zirconia nanowires-Nafion modified electrode. Under the optimum experimental conditions, the ECL intensity was linear with the concentration of vanadate(V) in the range of 2.0×10−12 mol/L–2.0×10−10 mol/L. The detection limit was 8.0×10−13 mol/L, which was more than 6 orders of magnitude lower than that observed by electrochemical current transduction for electrochemical parallel catalytic reaction at zirconia nanowires-Nafion modified electrode.