Multiple Raters in Survey-Based Operations Management Research: A Review and Tutorial

Research in the area of operations strategy has made significant progress during the past decade in terms of quantity of articles published, as well as the quality of these articles. Recent studies have examined the published literature base and determined that, in general, the field has progressed beyond an exploratory stage to a point where there is a core set of basic terminology and models. Concurrent with the formation and solidification of a core terminology, there is an increasing emphasis on developing and employing a set of reliable, valid, and reproducible methods for conducting research on operations strategy. We provide a review of common methods for assessing the degree of reliability and agreement of the responses provided by multiple raters within a given organization to a set of qualitative questions. In particular, we examine four methods of determining whether there is evidence of disagreement or bias between multiple raters within a single organization in a mail survey

Stuck in the slow lane: traffic composition and the measurement of labor productivity in the US trucking industry

Mirroring the railroad industry of the 1940's and 1950's, the trucking industry today appears to be achieving impressive productivity gains. But it is easy to confuse true productivity advances in transportation industries with changes in ton-miles per unit of input that are due simply to changes in the composition of traffic, as initially happened with the mid-20th century U.S. railroads. This is due to the fact that transportation has vastly different productivities in different settings - for example, when moving long haul versus short haul traffic - and the measurement of changes in physical productivity can be overwhelmed by even subtle changes in the traffic mix. After controlling for endogenous changes in the composition of truck traffic, we find that trucking has in fact been a lagging sector of the U.S. economy over the period of our data, 1982-1997, with observed productivity changes much more likely due to changes in speed limits and the dimensions of vehicles than adoption of information technology. Our finding of a slow improvement in the physical productivity of trucking inputs does not deny the real improvements in the quality of trucking services (reliability, predictability, speed, order tracking, etc.) that have taken place in the last quarter century. But as in other service industries, true physical productivity improvements in trucking are hard to fin

NASA Space Flight Human System Standard, Volume 2, and HIDH (Human Integration Design Handbook)

This viewgraph presentation reports on the review and re-issuance of the NASA Space Flight Human System Standard, Volume 2, and the Human Integration Design Handbook. These standards were last updated in 1995. The target date for the release is September 2009

Formulation and Testing of Paraffin-Based Solid Fuels Containing Energetic Additives for Hybrid Rockets

Many approaches have been considered in an effort to improve the regression rate of solid fuels for hybrid rocket applications. One promising method is to use a fuel with a fast burning rate such as paraffin wax; however, additional performance increases to the fuel regression rate are necessary to make the fuel a viable candidate to replace current launch propulsion systems. The addition of energetic and/or nano-sized particles is one way to increase mass-burning rates of the solid fuels and increase the overall performance of the hybrid rocket motor.1,2 Several paraffin-based fuel grains with various energetic additives (e.g., lithium aluminum hydride (LiAlH4) have been cast in an attempt to improve regression rates. There are two major advantages to introducing LiAlH4 additive into the solid fuel matrix: 1) the increased characteristic velocity, 2) decreased dependency of Isp on oxidizer-to-fuel ratio. The testing and characterization of these solid-fuel grains have shown that continued work is necessary to eliminate unburned/unreacted fuel in downstream sections of the test apparatus.3 Changes to the fuel matrix include higher melting point wax and smaller energetic additive particles. The reduction in particle size through various methods can result in more homogeneous grain structure. The higher melting point wax can serve to reduce the melt-layer thickness, allowing the LiAlH4 particles to react closer to the burning surface, thus increasing the heat feedback rate and fuel regression rate. In addition to the formulation of LiAlH4 and paraffin wax solid-fuel grains, liquid additives of triethylaluminum and diisobutylaluminum hydride will be included in this study. Another promising fuel formulation consideration is to incorporate a small percentage of RDX as an additive to paraffin. A novel casting technique will be used by dissolving RDX in a solvent to crystallize the energetic additive. After dissolving the RDX in a solvent chosen for its compatibility with both paraffin and RDX, the mixture will be combined with the melted paraffin. With the melting point of the paraffin far below the decomposition temperature of the RDX, the solvent will be boiled off, leaving the crystallized RDX embedded in the paraffin. At low percentages of RDX additive and with crystallized RDX surrounded by paraffin, the fuel grains will remain inert, maintaining a key benefit of hybrids in the safety of the solid fuel

Mechanical and Combustion Performance of Multi-Walled Carbon Nanotubes as an Additive to Paraffin-Based Solid Fuels for Hybrid Rockets

Paraffin-based solid fuels for hybrid rocket motor applications are recognized as a fastburning alternative to other fuel binders such as HTPB, but efforts to further improve the burning rate and mechanical properties of paraffin are still necessary. One approach that is considered in this study is to use multi-walled carbon nanotubes (MWNT) as an additive to paraffin wax. Carbon nanotubes provide increased electrical and thermal conductivity to the solid-fuel grains to which they are added, which can improve the mass burning rate. Furthermore, the addition of ultra-fine aluminum particles to the paraffin/MWNT fuel grains can enhance regression rate of the solid fuel and the density impulse of the hybrid rocket. The multi-walled carbon nanotubes also present the possibility of greatly improving the mechanical properties (e.g., tensile strength) of the paraffin-based solid-fuel grains. For casting these solid-fuel grains, various percentages of MWNT and aluminum particles will be added to the paraffin wax. Previous work has been published about the dispersion and mixing of carbon nanotubes.1 Another manufacturing method has been used for mixing the MWNT with a phenolic resin for ablative applications, and the manufacturing and mixing processes are well-documented in the literature.2 The cost of MWNT is a small fraction of single-walled nanotubes. This is a scale-up advantage as future applications and projects will require low cost additives to maintain cost effectiveness. Testing of the solid-fuel grains will be conducted in several steps. Dog bone samples will be cast and prepared for tensile testing. The fuel samples will also be analyzed using thermogravimetric analysis and a high-resolution scanning electron microscope (SEM). The SEM will allow for examination of the solid fuel grain for uniformity and consistency. The paraffin-based fuel grains will also be tested using two hybrid rocket test motors located at the Pennsylvania State University s High Pressure Combustion Lab

Effects of Noisy Oracle on Search Algorithm Complexity

Grover's algorithm provides a quadratic speed-up over classical algorithms for unstructured database or library searches. This paper examines the robustness of Grover's search algorithm to a random phase error in the oracle and analyzes the complexity of the search process as a function of the scaling of the oracle error with database or library size. Both the discrete- and continuous-time implementations of the search algorithm are investigated. It is shown that unless the oracle phase error scales as O(N^(-1/4)), neither the discrete- nor the continuous-time implementation of Grover's algorithm is scalably robust to this error in the absence of error correction.Comment: 16 pages, 4 figures, submitted to Phys. Rev.

Bred Heifer Price Determinants in the Southeast

Price determinants for bulls, cows, and feeder cattle are well established in the literature but there has been little research on bred heifer price determinants and specifically the impact of feeder cattle prices on the purchase price of bred heifers. We estimated the impact of reproductive characteristics and feeder cattle prices on bred heifer prices for beef production. Data were obtained from a May and November bred heifer sale located in Kentucky and hedonic pricing models were estimated for bred heifers for each sale month. Prices for fall- calving heifers were influenced by number of months bred or expected calving date with longer bred heifers priced the highest. Purchase price of spring- calving heifers did not vary from five to seven months bred, but heifers four months bred were priced lower. Pregnancies resulting from artificial insemination did increase the value of fall-calving heifers but did not impact spring-calving heifer prices. Heifer feeder cattle prices the day of the sale positively influenced the price of spring- and fall-calving bred heifers. This extends previous research by considering the impact of feeder cattle prices on the price of bred heifers. The results can help cow-calf producers in making a more informed purchasing decision of replacement breeding animals