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Explains the necessity for measurement of Internet growth so that capacity, commercial potential, etc. may be planned and assessed. Argues that this cannot be measured merely by packet counts and user registrations. Presents detailed analysis of over 13,000 sites, worldwide. Develops a mathematical model which can be used to predict growth, by individual countries and globally. Offers further topics for future research.

The purpose of this paper is to obtain the reachable domain (RD) for spacecraft with a single normal impulse while considering both time and impulse constraints.

The problem of RD is addressed in an analytical approach by analyzing for either the initial maneuver point or the impulse magnitude being arbitrary. The trajectories are considered lying in the intersection of a plane and an ellipsoid of revolution, whose family can be determined analytically. Moreover, the impulse and time constraints are considered while formulating the problem. The upper bound of impulse magnitude, “high consumption areas” and the change of semi-major axis and eccentricity are discussed.

The equations of RD with a single normal impulse are analytically obtained. The equations of three scenarios are obtained. If normal impulse is too large, the RD cannot be obtained. The change of the semi-major axis and eccentricity with large normal impulse is more obvious. For long-term missions, the change of semi-major axis and eccentricity leaded by multiple normal impulses should be considered.

The RD gives the pre-defined region (all positions accessible) for a spacecraft under a given initial orbit and a normal impulse with certain magnitude.

The RD for spacecraft with normal impulse can be used for non-coplanar orbital transfers, emergency evacuation after failure of rendezvous and docking and collision avoidance.

Despite the significance of online communication and interactions, previous research has not systematically compared all features on a single platform from the users' perspective. This study aims to fill this gap by extensively reviewing the current literature on social media affordances and proposes and tests a feature-centric and affordance-based conceptualization of social media platforms (SMPs) between users, features, the audience and content.

This research surveys users on Facebook, one of the largest SMPs, and asks them to assess 20 features of Facebook on six relational affordances between users, features, audience and content. The data in this study were collected on Amazon Mechanical Turk (MTurk) with participants from the US Correspondence analysis was employed to examine the relationship between affordances and the ties among affordances, features and outcomes.

Results of the study indicate that users perceive features differently, and employing features as the unit of analysis captures users' interactions effectively. The findings support the presence of user-oriented affordances, such as presentation flexibility, association and content association. These three affordances can be summarized in two higher-level ones: self-expression and connection (SEC) and persona-linked content (PLC). Our findings of the two dimensions, SEC and PLC, highlight the importance of targets and their connections in understanding social media interactions' dynamic nature.

By proposing to shift the focus from platforms to features, this study suggests that companies should focus on understanding the features they use for their users to interact with their brand, rather than merely ensuring that their company is omnipresent on all platforms. This study underlines the need to focus on features that will help managers influence interpersonal and user-brand communications and interactions on social media.

This research is the first to put features at the center of its investigation and quantitatively examine the relationship between social media features and affordances in a social media context. In all, this research provides a new unit of analysis that is more suitable for researchers to build a robust conceptual foundation for affordances. We believe that conceptualizing audience and content as outcomes, distinguishing it from features and creating connections between them as affordances is the unique aspect of our conceptualization.

To gain the highest performance in technological efforts, firms have to balance their technology sourcing portfolio, i.e. they have to decide how to source the required technology and whom to source from. This paper aims to tackle the issue by investigating the factors affecting the technology sourcing portfolio composition and the effect of the portfolio diversity on the performance outcome.

An inductive multiple case study was performed. Data of four biopharmaceutical producer firms in the period of 1998-2017 were collected. To expand the under study time span, the under study firms were all chosen from the first-comer ones. They entered the NBP arena in the 1998-2008 period, i.e. the period in which Iranian NBP industry was in its formation stage.

This paper detects the affecting technology-, firm-, industry- and national level factors in Iran biopharmaceutical industry and analyses their influencing mechanism. It is demonstrated that there are factors in a developing country, specifically Iran, which do not matter in developed countries. In addition, the synergistic effect of using various technology sources vehicles is confirmed.

Inaccessibility to infrastructures and global communication barrier problems are features of Iran innovation system. Such features discourage the foreign firms to make long-term investments in Iran which consequently deprives Iranian firms of their knowledge and technology. The modification of these problems is suggested.

Factors such as access to infrastructures and global communication barrier are not prevalent in developed countries; therefore, less attention has been paid to them in the literature.

The purpose of this paper is to establish an orbital launch window for manned Moon‐to‐Earth trajectories to support China's manned lunar landing mission requirements of high‐latitude landing and anytime return, i.e. the capability of safely returning the crew exploration vehicle at any time from any lunar parking orbit. The launch window is a certain time interval during which the transearth injection may occur and result in a safe lunar return to the specified landing site on the surface of the Earth.

Using the patched conic technique, an analytical design method for determining the transearth trajectories is developed with a finite sphere of influence model. An orbital launch window has been established to study the mission sensitivities to transearth trip time and energy requirements. The results presented here are limited to a single impulsive maneuver.

The difference between the results of the analytical model and high‐fidelity model is compared. This difference is relatively small and can be easily eliminated by a simple differential correction procedure. The launch window duration varies with launch date, from less than one hour to greater than 20 h, and the launch window occurs every day in the sidereal month.

The solution can be used to serve as an initial estimate for future optimization procedures.

The orbital launch window can be used to provide the basis for the preparation of an orbital launch timetable compatible with lunar missions and re‐entry conditions requirements.

Previous studies were mainly concentrated on the launch windows for the departure from the Earth. This paper investigates and establishes the orbital launch window for Moon‐to‐Earth trajectories.

The purpose of the paper is to study the variation of optimal burnout angle at the end of the ascent phase and the optimal control deflection during the glide phase, that would maximize the downrange performance of a hypersonic boost-glide waverider, with variation in heat rate and integrated heat load limit.

The approach used is to model the boost phase so as to optimize the burnout conditions. The nonlinear, multiphase, constraint optimal control problem is solved using an hp-adaptive pseudospectral method.

The constraint heat load results for the waverider configuration reveal that the integrated heat load can be reduced by more than half with only 10 per cent penalty in the overall downrange of the hypersonic boost-glide vehicle, within a burnout speed range of 3.7 to 4.3 km/s. The angle-of-attack trim control requirements increase with stringent heat rate and integrated heat load bounds. The normal acceleration remains within limits.

The trajectory results imply lower thermal protection system weight because of reduced heat load trajectory profile and therefore lower thermal protection system cost.

The research provides further study on the trajectory design to the hypersonic boost-glide vehicles for medium range application.

Attitude determination and control subsystem (ADCS) is a vital part of earth observation satellites (EO-Satellites) that governs the satellite’s rotational motion and pointing. In designing such a complicated sub-system, many parameters including mission, system and performance requirements (PRs), as well as system design parameters (DPs), should be considered. Design cycles which prolong the time-duration and consequently increase the cost of the design process are due to the dependence of these parameters to each other. This paper aims to describe a rapid-sizing method based on the design for performance strategy, which could minimize the design cycles imposed by conventional methods.

The proposed technique is an adaptation from that used in the aircraft industries for aircraft design and provides a ball-park figure with little engineering man-hours. The authors have shown how such a design technique could be generalized to cover the EO-satellites platform ADCS. The authors divided the system requirements into five categories, including maneuverability, agility, accuracy, stability and durability. These requirements have been formulated as functions of spatial resolution that is the highest level of EO-missions PRs. To size, the ADCS main components, parametric characteristics of the matching diagram were determined by means of the design drivers.

Integrating the design boundaries based on the PRs in critical phases of the mission allowed selecting the best point in the design space as the baseline design with only two iterations. The ADCS of an operational agile EO-satellite is sized using the proposed method. The results show that the proposed method can significantly reduce the complexity and time duration of the performance sizing process of ADCS in EO-satellites with an acceptable level of accuracy.

Rapid performance sizing of EO-satellites ADCS using matching diagram technique and consequently, a drastic reduction in design time via minimization of design cycles makes this study novel and represents a valuable contribution in this field.

The purpose of this paper is to recognize and label the faults in wind turbines with a new density-based clustering algorithm, named contour density scanning clustering (CDSC) algorithm.

The algorithm includes four components: (1) computation of neighborhood density, (2) selection of core and noise data, (3) scanning core data and (4) updating clusters. The proposed algorithm considers the relationship between neighborhood data points according to a contour density scanning strategy.

The first experiment is conducted with artificial data to validate that the proposed CDSC algorithm is suitable for handling data points with arbitrary shapes. The second experiment with industrial gearbox vibration data is carried out to demonstrate that the time complexity and accuracy of the proposed CDSC algorithm in comparison with other conventional clustering algorithms, including k-means, density-based spatial clustering of applications with noise, density peaking clustering, neighborhood grid clustering, support vector clustering, random forest, core fusion-based density peak clustering, AdaBoost and extreme gradient boosting. The third experiment is conducted with an industrial bearing vibration data set to highlight that the CDSC algorithm can automatically track the emerging fault patterns of bearing in wind turbines over time.

Data points with different densities are clustered using three strategies: direct density reachability, density reachability and density connectivity. A contours density scanning strategy is proposed to determine whether the data points with the same density belong to one cluster. The proposed CDSC algorithm achieves automatically clustering, which means that the trends of the fault pattern could be tracked.

The purpose of this paper is to help industrial managers monitor and analyze critical performance indicators in real time during the execution of business processes by proposing a visualization technique using an extended formal concept analysis (FCA). The proposed approach monitors the current progress of ongoing processes and periodically predicts their probable routes and performances.

FCA is utilized to analyze relations among patterns of events in historical process logs, and this method of data analysis visualizes the relations in a concept lattice. To apply FCA to real‐time business process monitoring, the authors extended the conventional concept lattice into a reachability lattice, which enables managers to recognize reachable patterns of events in specific instances of business processes.

By using a reachability lattice, expected values of a target key performance indicator are predicted and traced along with probable outcomes. Analysis is conducted periodically as the monitoring time elapses over the course of business processes.

The proposed approach focuses on the visualization of probable event occurrences on the basis of historical data. Such visualization can be utilized by industrial managers to evaluate the status of any given instance during business processes and to easily predict possible subsequent states for purposes of effective and efficient decision making. The proposed method was developed in a prototype system for proof of concept and has been illustrated using a simplified real‐world example of a business process in a telecommunications company.

The main contribution of this paper lies in the development of a real‐time monitoring approach of ongoing processes. The authors have provided a new data structure, namely a reachability lattice, which visualizes real‐time progress of ongoing business processes. As a result, current and probable next states can be predicted graphically using periodically conducted analysis during the processes.

The purpose of this paper is to study the moving consensus of multi‐agent dynamical systems with time delays and directed weighted networks.

The approach used in the study, the topologies of multi‐agent dynamical systems with directed weighted networks is graph theories. The frequency domain is applied to research the movement characteristics of multi‐agent systems with time delays. The generalized Nyquist criterion and curvature theorem are utilized to analyze the consensus algorithm with heterogeneous input delays and heterogeneous communication delays.

It was discovered that the consensus for the delayed multi‐agent systems with asymmetric coupling weights can be achieved with the hypothesis of directed weighted network composed of n agents with a globally reachable node. The convergence condition is a decentralized consensus condition which uses only local information of each agent.

The novelty associated with this work is to present a new approach to study the consensus of delayed multi‐agent dynamical systems with directed weighted networks. The consensus condition obtained in the paper is less conservative than the consensus condition given in references.