MAXIMUM ECONOMIC YIELD AND RESOURCE ALLOCATION IN THE SPINY LOBSTER INDUSTRY

Resource /Energy Economics and Policy,

Low temperature transient liquid phase bonding of copper

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005."June 2005."Includes bibliographical references (leaf 34).This thesis describes a Pb-free solder alternative that is capable of fluxless bonding. The main advantage of this process is that it offers the benefits of low fabrication temperature (125⁰C) while producing a joint capable of withstanding low stresses at very high service temperatures (300⁰C+). The ternary alloy system of Bi-In-Sn was investigated in the bonding of copper substrates. All bonds were made at 125⁰C with 25psi of fixturing pressure. Primary solidification was observed in as little as 15 minutes. The mechanical properties of the joints were shear tested both at room temperature and at 1000C to simulate a conventional service environment. With sufficient dwell time ([approx.] 250h), joints would not fail in shear even at stresses that caused significant substrate deformation. Scanning electron microscopy was used to examine the joints and the evolution of the diffusion process.by Joel C. Williams.S.M

A Performance Analysis of a Rocket Based Combined Cycle (RBCC) Propulsion System for Single-Stage-To-Orbit Vehicle Applications

Rocket-Based Combined Cycle (RBCC) engines combine the best performance characteristics of air-breathing systems such as ramjets and scramjets with rockets with the goal of increasing payload/structure and propellant performance and thus making LEO more readily accessible. The idea of using RBCC engines for Single-Stage-To-Orbit (SSTO) trans-atmospheric acceleration is not new, but has been known for decades. Unfortunately, the availability of detailed models of RBCC engines is scarce. This thesis addresses the issue through the construction of an analytical performance model of an ejector rocket in a dual combustion propulsion system (ERIDANUS) RBCC engine. This performance model along with an atmospheric model, created using MATLAB was designed to be a preliminary `proof-of-concept\u27 which provides details on the performance and behavior of an RBCC engine in the context of use during trans-atmospheric acceleration, and also to investigate the possibility of improving propellant performance above that of conventional rocket powered systems. ERIDANUS behaves as a thrust augmented rocket in low speed flight, as a ramjet in supersonic flight, a scramjet in hypersonic flight, and as a pure rocket near orbital speeds and altitudes. A simulation of the ERIDANUS RBCC engine\u27s flight through the atmosphere in the presence of changing atmospheric conditions was performed. The performance code solves one-dimensional compressible flow equations while using the stream thrust control volume method at each station component (e.g. diffuser, burner, and nozzle) in all modes of operation to analyze the performance of the ERIDANUS RBCC engine. Plots of the performance metrics of interest including specific impulse, specific thrust, thrust specific fuel consumption, and overall efficiency were produced. These plots are used as a gage to measure the behavior of the ERIDANUS propulsion system as it accelerates towards LEO. A mission averaged specific impulse of 1080 seconds was calculated from the ERIDANUS code, reducing the required propellant mass to 65% of the gross lift off weight (GLOW), thus increasing the mass available for the payload and structure to 35% of the GLOW. Validation of the ERIDANUS RBCC concept was performed by comparing it with other known RBCC propulsion models. Good correlation exists between the ERIDANUS model and the other models. This indicates that the ERIDANUS RBCC is a viable candidate propulsion system for a one-stage trans-atmospheric accelerator

Inerrancy, Inspiration, and Dictation

Williams, Joel S. (1995) Inerrancy, Inspiration, and Dictation, Restoration Quarterly: Vol. 37 : No. 3. This repository hosts selected Restoration Quarterly articles in downloadable PDF format. For the benefit of users who would like to browse the contents of RQ, we have included all issue covers even when full-text articles from that issue are unavailable. All Restoration Quarterly articles are available in full text in the ATLA Religion Database, available through most university and theological libraries or through your local library’s inter-library loan service

Numerical Investigations of a High Frequency Pulsed Gaseous Fuel Jet Injection into a Supersonic Crossflow

The investigation of fuel delivery mechanisms is a critical design point in the development of supersonic combustion ramjet (scramjet) technology. Primary challenges include proper penetration of the jet in the supersonic cross-flow while keeping total pressure losses and wall drag to a minimum. To reduce drag and heat loads especially at high burner entry Mach numbers it is desirable to use a minimally intrusive means of fuel delivery. Pulsation of gaseous jets has been shown to increase penetration and mixing in subsonic flows. A limited number of experimental studies and even fewer numerical studies have suggested that when applied to supersonic crossflows, gaseous jets pulsed in the kilohertz range of frequencies improve jet penetration and mixing. To improve on the limited number of numerical studies of pulsed jets in supersonic crossflows (PJISF), 2D and 3D computational fluid dynamics (CFD) simulation models of non-excited (steady) and sinusoidally excited (pulsed) jets were constructed using ANSYS FLUENT 15.0. The 2D results included pulsation at 8, 16, 32 and 48 kHz. These simulation results showed that pulsation at 16 kHz provided the best penetration improvement in the jet near field and far field among all frequencies sampled. A 3D wall-modeled Large Eddy Simulation (WMLES) was constructed with the goals resolving large scale turbulent flow structure and time evolution of a jet pulsed in a supersonic crossflow, as well as to compare the effects of sinusoidal pulsation at 16 kHz with steady injection for the same flow conditions as the 2D case. A comparison of the jet trajectories between the steady and pulsed injection cases demonstrated that for sinusoidal pulsation of a jet at 16 kHz over the equivalent cycle averaged injection total pressure and momentum flux ratio, pressure, jet penetration is improved over the steady jet, up to 50% in the near field of the jet. Furthermore, improved mass concentration decay associated with jet-crossflow mixing and far field total pressure recovery has been demonstrated as a result of pulsation of the jet