Phased Approach to the Space Operations Center

The Space Operations Center and the Space Manufacturing and Processes Systems have major characteristics of compatibility and can be mutually influential in formulating the next major space initiative. The Phase Program Plan of the SOC provides for increasing capabilities and can be integrated with a Space Manufacturing System\u27s concept in which both the development and operational phases can be implemented. The requirements for the Space Manufacturing System appear to be suitable for SOC on-board development and then operationally as a tender of a free-flying satellite in a station-keeping orbit. The free-flying satellite can be placed in an orbit which hovers about the SOC and never exceeds line of sight communications limits. The services and reboost requirements can likewise be accommodated. The concepts of phased programs, development and operations, station-keeping orbit envelopes, propulsive Harbor Tugs and aspects of servicing will be an issue and presented

Estimating preferences for a dermatology consultation using Best-Worst Scaling: Comparison of various methods of analysis

Background: Additional insights into patient preferences can be gained by supplementing discrete choice experiments with best-worst choice tasks. However, there are no empirical studies illustrating the relative advantages of the various methods of analysis within a random utility framework. Methods: Multinomial and weighted least squares regression models were estimated for a discrete choice experiment. The discrete choice experiment incorporated a best-worst study and was conducted in a UK NHS dermatology context. Waiting time, expertise of doctor, convenience of attending and perceived thoroughness of care were varied across 16 hypothetical appointments. Sample level preferences were estimated for all models and differences between patient subgroups were investigated using ovariateadjusted multinomial logistic regression. Results: A high level of agreement was observed between results from the paired model (which is theoretically consistent with the 'maxdiff' choice model) and the marginal model (which is only an approximation to it). Adjusting for covariates showed that patients who felt particularly affected by their skin condition during the previous week displayed extreme preference for short/no waiting time and were less concerned about other aspects of the appointment. Higher levels of educational attainment were associated with larger differences in utility between the levels of all attributes, although the attributes per use had the same impact upon choices as those with lower levels of attainment. The study also demonstrated the high levels of agreement between summary analyses using weighted least squares and estimates from multinomial models. Conclusion: Robust policy-relevant information on preferences can be obtained from discrete choice experiments incorporating best-worst questions with relatively small sample sizes. The separation of the effects due to attribute impact from the position of levels on the latent utility scale is not possible using traditional discrete choice experiments. This separation is important because health policies to change the levels of attributes in health care may be very different from those aiming to change the attribute impact per se. The good approximation of summary analyses to the multinomial model is a useful finding, because weighted least squares choice totals give better insights into the choice model and promote greater familiarity with the preference data

Consumer Choice of Modularized Products: A Conjoint Choice Experiment Approach

Recent increases in flexibility and automation in the production of goods and services allow a growing number of suppliers to offer their products in flexible sets of modules from which consumers can create their own individualized packages. This paper addresses the question how consumer choices of such modularized products can be modeled and measured by applying conjoint choice experiments. We analyze conceptually the structure of individual consumers’ choices of modularized products and the role of the error component in random utility models of these choices. We propose a simple experimental conjoint choice design strategy that can support estimation of this type of models. An empirical illustration in the area of travel package choice is discussed.Marketing;Consumer choice models;Conjoint experiments;Heteroscedastic logit;Mass-customization

Plain Packaging, Pictorial Warnings and Tobacco Products: An Empirical Assessment

Although tobacco marketing is restricted, tobacco product packaging continues to communicate brand imagery, thereby maintaining brand salience and potentially reducing the impact of health warnings. This study used respondent conditioning theory to predict how disruption of brand imagery would affect the attractiveness of known, unknown and generic tobacco packages. A best-worst study found that familiar branding offset the negative connotations created by a pictorial warning label (PWL). These are the first findings to document the combined effect of PWLs and plain packaging; they suggest generic packs will stimulate cessation attempts and deter smoking initiation

Risks, Benefits and DTC - An Analysis of Information Formats

Critics of direct to consumer prescription medicine advertising (DTC) claim it is unbalanced because benefit information features more prominently than risk information, and that it thus fails to meet the high standards of social responsibility called for in regulatory codes. We used respondent conditioning theory to examine whether variations in risk information format could improve recall of benefits, side effects and contra-indications in print DTC advertisements. A best-worst study confirmed striking differences in preference for varied information formats, while a second study found that visual heuristics increased recall of both risk and benefit information. The findings question marketers reluctance to provide easily accessible risk information and suggest prominent drug information panels may discharge manufacturers social responsibilities while simultaneously improving the effectiveness of their promotions

A Comparison of Elasticities Derived from Multinomial Logit, Nested Logit and Heteroscedastic Extreme Value SP-RP Discrete Choice Models

Developments in the estimation of discrete choice models which relax elements of the independence of irrelevant alternatives (IIA) property of the multinomial logit model (MNL) provide opportunities to explore the richer behavioural sensitivity of a choice model to changes in the levels of attributes influencing choice. Surprisingly, the literature offers limited evidence on the variations in sensitivity (ie elasticity) as we move from an MNL model based on revealed preference (RP) data, to MNL based on stated preference (SP) data, to combined RP-SP data estimated sequentially and jointly with partial relaxation of the differential variance in the unobserved effects by the ‘nested logit’ method, and then as free variance across all RP and SP alternatives by heteroscedastic extreme value (HEV) estimation. This paper draws on a data set collected in 6 Australian capital cities in 1994 to estimate a series of commuter mode choice models in the presence and absence of two ‘new’ alternatives (light rail and busway systems), to derive matrices of direct and cross point elasticities for travel cost and travel time. The evidence suggests that constraining the variance of the unobserved effects to varying degrees tends to over-estimate the elasticities sufficiently to distort the real behavioural sensitivity of specific attributes influencing choice. Furthermore, we seriously question the usefulness of studies which rely solely on SP data

Water-propellant resistojets for man-tended platforms

The selection of a propulsion system for a man-tended platform has been influenced by the planned use of resistojets for drag make-up on the manned space station. For that application a resistojet has been designed that is capable of operation with a wide variety of propellants, including water. The reasons for the selection of water as the propellant and the performance of water as a propellant are discussed. The man-tended platform and its mission requirements are described

Design of discrete choice experiments: A discussion of issues that matter in future applied research

Disagreement among researchers regarding types of optimal choice experiments is often best seen as resulting from differences in the set of assumptions researchers are willing to make about the underlying data generating process. Much of the current debate may have confused, rather than enlightened applied researchers because the underlying source of the debate lacks transparency. We argue that this debate would be better served if it were much more closely tied to the large existing literature on optimal design of experiments, where many of the issues currently being discussed have long been examined. We further argue that the current debate misses several key issues that are likely to be important to making progress in understanding the role played by experimental designs in applied settings of interest in economics, marketing and transportation research