Directed Explicit Model Checking with HSF-SPIN

We present the explicit state model checker HSF-SPIN which is based on the model checker SPIN and its Promela modeling language. HSF-SPIN incorporates directed search algorithms for checking safety and a large class of LTL-specified liveness properties. We start off from the A* algorithm and define heuristics to accelerate the search into the direction of a specified failure situation. Next we propose an improved nested depth-first search algorithm that exploits the structure of Promela Never-Claims. As a result of both improvements, counterexamples will be shorter and the explored part of the state space will be smaller than with classical approaches, allowing to analyze larger state spaces. We evaluate the impact of the new heuristics and algorithms on a set of protocol models, some of which are real-world industrial protocols

Pre- and post-processing for Cosmic/NASTRAN on personal computers and mainframes

An interface between Cosmic/NASTRAN and GIFTS has recently been released, combining the powerful pre- and post-processing capabilities of GIFTS with Cosmic/NASTRAN's analysis capabilities. The interface operates on a wide range of computers, even linking Cosmic/NASTRAN and GIFTS when the two are on different computers. GIFTS offers a wide range of elements for use in model construction, each translated by the interface into the nearest Cosmic/NASTRAN equivalent; and the options of automatic or interactive modelling and loading in GIFTS make pre-processing easy and effective. The interface itself includes the programs GFTCOS, which creates the Cosmic/NASTRAN input deck (and, if desired, control deck) from the GIFTS Unified Data Base, COSGFT, which translates the displacements from the Cosmic/NASTRAN analysis back into GIFTS; and HOSTR, which handles stress computations for a few higher-order elements available in the interface, but not supported by the GIFTS processor STRESS. Finally, the versatile display options in GIFTS post-processing allow the user to examine the analysis results through an especially wide range of capabilities, including such possibilities as creating composite loading cases, plotting in color and animating the analysis

A Review of patents in tyre cooling

A number of patents on tyre cooling have been reviewed with a focus on those which can be applied to earthmoving tyres for the mining industry. The mechanisms of heat transfer within the tyre carcass are introduced as well as the basic tyre structure and effects of overheating on tyre operation. The tyre cooling patents are separated into five functional groups and reviews are made based on practicality and potential for significant heat transfer. This analysis has made it evident that potential cooling effectiveness is often compromised by practicality of an invention. The patents deemed to have the most potential for cooling are those which incorporate a working fluid which undergoes a phase change to transfer heat between different regions of the wheel assembly. Finally, these inventions are also related to current research projects which aim to develop a new cooling technique and extend the working life of earthmoving tyres

Satellite camera image navigation

Pixels within a satellite camera (1, 2) image are precisely located in terms of latitude and longitude on a celestial body, such as the earth, being imaged. A computer (60) on the earth generates models (40, 50) of the satellite's orbit and attitude, respectively. The orbit model (40) is generated from measurements of stars and landmarks taken by the camera (1, 2), and by range data. The orbit model (40) is an expression of the satellite's latitude and longitude at the subsatellite point, and of the altitude of the satellite, as a function of time, using as coefficients (K) the six Keplerian elements at epoch. The attitude model (50) is based upon star measurements taken by each camera (1, 2). The attitude model (50) is a set of expressions for the deviations in a set of mutually orthogonal reference optical axes (x, y, z) as a function of time, for each camera (1, 2). Measured data is fit into the models (40, 50) using a walking least squares fit algorithm. A transformation computer (66 ) transforms pixel coordinates as telemetered by the camera (1, 2) into earth latitude and longitude coordinates, using the orbit and attitude models (40, 50)

Why wait? Organizational learning, institutional quality and the speed of foreign market re-entry after initial entry and exit

Using a unique dataset of over 1000 foreign marketre-entries by multinational enterprises, we draw on organizational learning and institutional theory perspectives to examine the antecedents of speed of foreign market re-entry into previously exited markets. Contrary to expectations, we find that the length of experience accumulated between initial entry and exit does not lead to earlier re-entries. In turn, the depth of experience accumulated through operating via joint ventures and the nature of the experience determined by the exit process have a significant impact for early re-entrants. Host country institutional quality leads to early re-entry and, under certain circumstances, moderates the relationship between learning from past experiences and re-entry speed. Our findings reveal experience-based learning to be a complex and dynamic process, one highly dependent on the quality of the institutional setting of the firm. Theoretical and practical implications of the paper are discussed, along with directions for future research on international business strategies

Developing potential and realized ACAP: The role of market sensing and responsiveness

This study explores how firms develop potential and realized absorptive capacity. In doing so, we extend the associations between organizational antecedents (coordination, system, and socialization capabilities) and potential and realized absorptive capacity by integrating market sensing and responsiveness as prerequisite contextual variables. The analysis is conducted using multilevel data obtained from 205 managers of 24 banks. Our findings show that coordination capabilities are positively associated with potential absorptive capacity while system and socialization capabilities are positively associated with realized absorptive capacity. Market responsiveness significantly moderates the relationship between socialization capabilities and realized absorptive capacity, such that the positive effect becomes weaker as market responsiveness increases. Also, market responsiveness significantly moderates the relationship between system capabilities and realized absorptive capacity, such that the positive effect becomes weaker when market responsiveness both increases and to a less extent decreases. The findings provide implications for research and practice on developing potential and realized absorptive capacity

Spacecraft camera image registration

A system for achieving spacecraft camera (1, 2) image registration comprises a portion external to the spacecraft and an image motion compensation system (IMCS) portion onboard the spacecraft. Within the IMCS, a computer (38) calculates an image registration compensation signal (60) which is sent to the scan control loops (84, 88, 94, 98) of the onboard cameras (1, 2). At the location external to the spacecraft, the long-term orbital and attitude perturbations on the spacecraft are modeled. Coefficients (K, A) from this model are periodically sent to the onboard computer (38) by means of a command unit (39). The coefficients (K, A) take into account observations of stars and landmarks made by the spacecraft cameras (1, 2) themselves. The computer (38) takes as inputs the updated coefficients (K, A) plus synchronization information indicating the mirror position (AZ, EL) of each of the spacecraft cameras (1, 2), operating mode, and starting and stopping status of the scan lines generated by these cameras (1, 2), and generates in response thereto the image registration compensation signal (60). The sources of periodic thermal errors on the spacecraft are discussed. The system is checked by calculating measurement residuals, the difference between the landmark and star locations predicted at the external location and the landmark and star locations as measured by the spacecraft cameras (1, 2)