The Impact of E-Commerce Strategies on Firm Value: Lessons from Amazon.com

Managers would like to understand which strategies generate value in e-commerce environments, and researchers are just beginning to explore this issue. Which strategies are useful and which are not? In a step towards answering this question, we estimate the impacts of several competitive strategies on the value of Amazon.com, the well-known Internet retailer, during its first 1000 days as a publicly traded firm. The strategies analyzed include pricing, offline expansion, alliance formation, product line expansion, and service improvement. The results provide insight into the usefulness of various ways of competing online and could be useful for strategic planning in new Internet ventures.alliance; competitive advantage; competitive strategy; event studies; internet; valuation

Active vibration control of a flexible robot link using piezoelectric actuators

Nuisance vibrations are a concern throughout the engineering realm, and many re-searchers are dedicated to finding a solution to attenuate them. This research primarily focusses upon the suppression of vibrations in a robot system, with the control system being designed so that it is both affordable and lightweight. Such constraints aim to provide a solution that may be utilised in a variety of applications. The utilisation of piezoelectric elements as both actuators and sensors provides several advantages in that they are lightweight, easily integrated into an existing system and have a good force to weight ratio when used as actuators. To read and control these elements a single board computer was employed, in acknowledgement of the constraining parameters of the design. The amalgamation of vibration control and robotics has lent to the re-search being conducted with separate objectives set, isolating certain elements of the overall system design for validation. Ultimately, these separate investigations progress to the integration of the robot and control systems prior to further research concerning nonlinear vibrations, dynamic control and the discrete-time domain modelling of the system.This research first investigates the viability of the chosen components as a vibration attenuation solution. In addition, analytical models of the system have been created, for two types of sensors to determine the most effective; an inertial measurement unit and a collocated pair of piezoelectric sensors. These models are based on Euler-Bernoulli beam theory and aim to validate the control theory through a comparison of the experimental data. These experiments isolate the vibration problem from a robot system through the investigation of the control of a long slender beam envisioned as a robot manipulator link, but excited using a shaker platform in a sinusoidal manner. An observation of the theory related to the voltage produced by the piezoelectric elements, suggests that even with the application of only proportional control by the system, the controlled output would have components indicative of both proportional and derivative control. This observation and the underlying theory are further analysed within this research.The next objectives are to compare the performance of the control system developed in this research which utilises a Raspberry Pi 3B+ [1] with one that employs a dSPACE MicroLabBox [2], and to determine the suitability of the former for use with robot sys-tems. With the former ensuring that the constraints placed on the design, those which influenced the selection of the components, does not conclude to the dSPACE Micro-LabBox system being overtly preferable. The latter investigates both the impact of the system’s inclusion on the functionality of the system and the system’s perform-ance with respect to the intended application. The KUKA LBR iiwa 7 R800 [3] robot manipulator is utilised to satisfy this objective, wherein the link is mounted on the end effector of the manipulator acting as an eighth link. The final investigation in this research pertains to the attenuation of nonlinear vibrations experienced by a robot manipulator link. Additional components were added to the link to induce a geometric nonlinearity in the system. An analytical model of the amended system was created to validate the theory through comparison with experimental results. The control system was employed for multiple cases to ascertain the level of its performance with regards to the suppression of nonlinear vibrations

Telemedicine and the digital door doctor

Telemedicine is changing the way medicine can be practiced, and how medical knowledge is communicated, learnt and researched in today\u27s technologically oriented society. The adoption of internet based communication has significantly expanded the patients\u27 ability to access a multitude of world class medical information. Research has shown that patients would welcome the ability to consult a doctor using the same computing tools they use to communicate with family, friends and work colleagues. This paper discusses the use of telemedicine today and how it could be used to access medical services from home. Further, it investigates the incentives and barriers to widespread adoption of such services in Australia with particular reference to the issues of information security. The technology to make home telemedicine a reality is already available and all that remains for this to come to fruition is a shift in culture to accept it as a suitable alternative to current medical consultation practice

Direct processing of structural thermoplastic composites using rapid isothermal stamp forming

A novel rapid isothermal stamp forming process is proposed which enables the rapid manufacture of structural thermoplastic composite laminate parts directly from multilayer hybrid fabrics comprising stitched unidirectional carbon fibre-thermoplastic polymer veil. The process employs rapid-response variothermal tooling, allowing macro-scale (fabric forming/draping) and micro-scale (fibre wetting/laminate consolidation) composite material transformation processes to occur isothermally above the constituent polymer matrix melt temperature (Tm), thus manufacturing a composite component directly from a hybrid dry fabric in a single press cycle in a relatively short overall cycle time. The proposed rapid isothermal stamp forming (RISF) concept is presented, and details of the process are given along with some considerations made throughout the formulation of the process. As a result of the RISF process development work, candidate manufacturing parameters were derived, delivering parts that exhibit acceptable composite laminate microstructure and mechanical performance within a press station cycle time of 330 s

Reverse osmosis brine concentration using falling film freeze crystallisation technology: a pilot-scale study

The reverse osmosis (RO) desalination process has increasingly been utilized with aim of producing drinking water from different marginal sources of water such as seawater, and brackish ground and surface water, due to water scarcity. Unfortunately, desalination applications are limited by the brine disposal challenges including the adverse impact of brine on the surrounding environment. Therefore, this paper is focused on the technical evaluation of falling film freeze crystallization (FFFC) technology for treating and concentrating RO brine. An industrial pilot plant using the FFFC process was tested and assessed for concentrating RO brine in this study. The experimental results showed that the crystallization experiments using a feed stage (without the sweating process) and at the operating end-point heat transfer medium (HTM) temperature of –6°C, achieved a salt rejection ratio and water recovery ratio of 56.6% and 49.8% respectively. Whereas at the endpoint HTM temperature of –24°C, the salt rejection ratio and water recovery ratios were 24.5% and 84.6% respectively. The multi-stage process experiments using feed and rectification stages (without the sweating process) achieved a salt rejection and product water recovery ratio of 46.89% and 64.24% respectively. By using a multi-stage process including feed, rectification, and stripping stages (with the sweating process), the salt rejection and product water recovery ratio reached 70.68% and 50.15% respectively. In general, the results showed that the FFFC technology, using a single freezing stage and without the sweating process, would be an ideal treatment system for concentrating RO brine and to produce saline water to near seawater quality that can be used directly as feed water for a RO plant. The research proved that the investigated FFFC process can be considered as a great solution available for brine concentration and as an alternative for reducing the environmental impact of the large volume of waste streams from coastal and inland desalination plants

Experimental determination of the hydrodynamic forces within nanofiltration membranes and evaluation of the current theoretical descriptions

In this study a series of different molecular weight PEG solutions have been characterised for particle sizeand the results have been used, in conjunction with several other techniques, to determine the pore sizeof the Nadir UH004 membrane. The resulting information, in conjunction with experimentally determinedrejection profiles for the PEG solutions, has then been used to back calculate the hindrance factorsfor nanofiltration rejection theory. These experimentally derived values obtained for the hindrance factorswere found to be in close agreement with the widely accepted theoretical predictions derived fromhydrodynamic theory for micro and ultrafiltration. To our knowledge, this is the first experimental validationof these hindrance factors for nanofiltration and suggests that the correlations found throughoutthe literature are accurate enough for the calculation of hindrance factors describing the hydrodynamicdrag forces experienced by a solute inside a nanopore

The Effect of Lunar-like Satellites on the Orbital Infrared Light Curves of Earth-analog Planets

We investigate the influence of lunar-like satellites on the infrared orbital light curves of Earth-analog extra-solar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet. We use an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites are assumed to lack an atmosphere, have a low thermal inertia like that of the Moon and span a range of plausible radii. The planets are assumed to have thermal and orbital properties that mimic those of the Earth while their obliquities and orbital longitudes of inferior conjunction remain free parameters. Even if the gross thermal properties of the planet can be independently constrained (e.g. via spectroscopy or visible-wavelength detection of specular glint from a surface ocean) only the largest (approximately Mars-size) lunar-like satellites can be detected by light curve data from a TPF-like instrument (i.e. one that achieves a photometric signal-to-noise of 10-20 at infrared wavelengths). Non-detection of a lunar-like satellite can obfuscate the interpretation of a given system's infrared light curve so that it may resemble a single planet with high obliquity, different orbital longitude of vernal equinox relative to inferior conjunction and in some cases drastically different thermal characteristics. If the thermal properties of the planet are not independently established then the presence of a lunar-like satellite cannot be inferred from infrared data, thus demonstrating that photometric light curves alone can only be used for preliminary study of extra-solar Earth-like planets.Comment: 34 pages, 7 figures, accepted to Astrobiolog

Terrestrial Exoplanet Light Curves

The phase or orbital light curves of extrasolar terrestrial planets in reflected or emitted light will contain information about their atmospheres and surfaces complementary to data obtained by other techniques such as spectrosopy. We show calculated light curves at optical and thermal infrared wavelengths for a variety of Earth-like and Earth-unlike planets. We also show that large satellites of Earth-sized planets are detectable, but may cause aliasing effects if the lightcurve is insufficiently sampled.Comment: To appear in Proceedings of the IAU Colloquium 200, Direct Imaging of Exoplanets; Science & Technology, Villefranche-sur-mer, France, October 2-7, 200