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Article

Michael F. Schwartz and John S. Quarterman

Explains the necessity for measurement of Internet growth so thatcapacity, commercial potential, etc. may be planned and assessed. Arguesthat this cannot be measured…

Abstract

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.

Details

Internet Research, vol. 3 no. 3
Type: Research Article
ISSN: 1066-2243

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Article

Junhua Zhang, Jianping Yuan, Wei Wang and Jiao Wang

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.

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Practical implications

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.

Originality/value

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 7
Type: Research Article
ISSN: 1748-8842

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Article

Sajjad Shekarchian and Amir Albadvi

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Social implications

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.

Originality/value

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.

Details

Journal of Science and Technology Policy Management, vol. 11 no. 1
Type: Research Article
ISSN: 2053-4620

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Article

Jingyang Li, Shengping Gong, Xiang Wang and Jingxia Li

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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

Practical implications

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.

Originality/value

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.

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Article

S. Tauqeer ul Islam Rizvi, He Linshu and Xu Dajun

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Practical implications

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

Originality/value

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

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 87 no. 1
Type: Research Article
ISSN: 0002-2667

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Article

Amirreza Kosari, Alireza Sharifi, Alireza Ahmadi and Masoud Khoshsima

Attitude determination and control subsystem (ADCS) is a vital part of earth observation satellites (EO-Satellites) that governs the satellite’s rotational motion and…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

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Article

Bokyoung Kang, Jae‐Yoon Jung, Nam Wook Cho and Suk‐Ho Kang

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Practical implications

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.

Originality/value

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.

Details

Industrial Management & Data Systems, vol. 111 no. 5
Type: Research Article
ISSN: 0263-5577

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Article

Hong‐yong Yang, Guang‐deng Zong and Si‐ying Zhang

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

Abstract

Purpose

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

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 4 no. 2
Type: Research Article
ISSN: 1756-378X

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Article

Soha Maad and Brian Coghlan

The purpose of this paper is to overview key features of grid portals and e‐government portals and assess the potential for using features of the former in the latter. In…

Abstract

Purpose

The purpose of this paper is to overview key features of grid portals and e‐government portals and assess the potential for using features of the former in the latter. In the context of this paper, grid portals are defined as graphical user interfaces that a user employs to interact with one or more grid infrastructural resources.

Design/methodology/approach

The paper classifies grid portals in five categories and two development frameworks and based on this classification overviews ten existing grid portals. The overview covers, where possible, the developers, the objective, the implementation, and the features of the considered grid portals. For e‐government, the paper focuses on the overview of a typical e‐government portal and best design practices. Based on the overview of grid portals and the typical e‐government portal, the paper assesses the potential benefit of grid portals in meeting the critical success factors for e‐government identified as: integration, knowledge management, personalization, and customer engagement. The results are tabulated, analysed, and discussed.

Findings

Many of the features of existing grid portals have the potential to be used within an e‐government portal, but the lack of any in‐depth study of the nature of the e‐government application domain (from a technical and social perspective) in‐line with grid development makes this potential far from reachable at this stage. This is disappointing but does highlight opportunities.

Practical implications

This paper motivates a greater in‐depth analysis and study of the potential use of the grid for e‐government. The grid infrastructure promises solutions to various applications domains including e‐government.

Originality/value

This paper explored the potential of a technology infrastructure for e‐government. This exploration is based on a novel dual overview and evaluation of the technology and the application domain. The paper can be a basis and a reference for further research in different areas including, among others: technology infrastructures for e‐government, grid development for various application domains, benchmarking of grid utility and usability for various application domains, grid gateways, and emerging technologies to meet the critical success factors for e‐government.

Details

Transforming Government: People, Process and Policy, vol. 2 no. 2
Type: Research Article
ISSN: 1750-6166

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Article

B. McCarthy, C. Edwards and M. Dunmore

This paper aims to discuss network transparency in a mountain rescue domain and aims to introduce the relatively new research concept of MANEMO (MANET + NEMO) and the…

Abstract

Purpose

This paper aims to discuss network transparency in a mountain rescue domain and aims to introduce the relatively new research concept of MANEMO (MANET + NEMO) and the mountain rescue IP network model developed at Lancaster University.

Design/methodology/approach

An analysis of IP mobility techniques that have been designed for use in the Internet today is provided as background, as well as an overview of the whole MANEMO domain. Highlights the importance of the MANEMO concept by working with real scenarios and developing practical implementations (as opposed to simulation).

Findings

During the research it was found that combining the localised multi‐hop behaviour of MANET techniques and the global reachability of NEMO can be a mutually beneficial process. The benefits afforded by using MANET techniques can bring advantages to NEMO scenarios and vice‐versa. Identifying this fact has given rise to the development of two distinct MANEMO scenarios, MANET‐Centric and NEMO‐Centric MANEMO. Finally, the Unified MANEMO Architecture (UMA) implementation, which attempts to support both of these scenarios in an efficient and feasible manner.

Research limitations/implications

Regarding UMA, research continues into addressing the security implications of this approach and the benefits that multi‐homing can provide.

Originality/value

The paper illustrates how MANEMO can conceivably provide powerful solutions to many important scenarios.

Details

Internet Research, vol. 17 no. 5
Type: Research Article
ISSN: 1066-2243

Keywords

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