Software-Engineering Process Simulation (SEPS) model

The Software Engineering Process Simulation (SEPS) model is described which was developed at JPL. SEPS is a dynamic simulation model of the software project development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life cycle development activities and management decision making processes. The model is designed to be a planning tool to examine tradeoffs of cost, schedule, and functionality, and to test the implications of different managerial policies on a project's outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmodern assessments

Nonlinear rotordynamics analysis

Effective analysis tools were developed for predicting the nonlinear rotordynamic behavior of the Space Shuttle Main Engine (SSME) turbopumps under steady and transient operating conditions. Using these methods, preliminary parametric studies were conducted on both generic and actual HPOTP (high pressure oxygen turbopump) models. In particular, a novel modified harmonic balance/alternating Fourier transform (HB/AFT) method was developed and used to conduct a preliminary study of the effects of fluid, bearing and seal forces on the unbalanced response of a multi-disk rotor in the presence of bearing clearances. The method makes it possible to determine periodic, sub-, super-synchronous and chaotic responses of a rotor system. The method also yields information about the stability of the obtained response, thus allowing bifurcation analyses. This provides a more effective capability for predicting the response under transient conditions by searching in proximity of resonance peaks. Preliminary results were also obtained for the nonlinear transient response of an actual HPOTP model using an efficient, newly developed numerical method based on convolution integration. Currently, the HB/AFT is being extended for determining the aperiodic response of nonlinear systems. Initial results show the method to be promising

Dynamic analysis of nonlinear rotor-housing systems

Nonlinear analysis methods are developed which will enable the reliable prediction of the dynamic behavior of the space shuttle main engine (SSME) turbopumps in the presence of bearing clearances and other local nonlinearities. A computationally efficient convolution method, based on discretized Duhamel and transition matrix integral formulations, is developed for the transient analysis. In the formulation, the coupling forces due to the nonlinearities are treated as external forces acting on the coupled subsystems. Iteration is utilized to determine their magnitudes at each time increment. The method is applied to a nonlinear generic model of the high pressure oxygen turbopump (HPOTP). As compared to the fourth order Runge-Kutta numerical integration methods, the convolution approach proved to be more accurate and more highly efficient. For determining the nonlinear, steady-state periodic responses, an incremental harmonic balance method was also developed. The method was successfully used to determine dominantly harmonic and subharmonic responses fo the HPOTP generic model with bearing clearances. A reduction method similar to the impedance formulation utilized with linear systems is used to reduce the housing-rotor models to their coordinates at the bearing clearances. Recommendations are included for further development of the method, for extending the analysis to aperiodic and chaotic regimes and for conducting critical parameteric studies of the nonlinear response of the current SSME turbopumps

The Effect of Integrating Travel Time

This contribution demonstrates the potential gain for the quality of results in a simulation of pedestrians when estimated remaining travel time is considered as a determining factor for the movement of simulated pedestrians. This is done twice: once for a force-based model and once for a cellular automata-based model. The results show that for the (degree of realism of) simulation results it is more relevant if estimated remaining travel time is considered or not than which modeling technique is chosen -- here force-based vs. cellular automata -- which normally is considered to be the most basic choice of modeling approach.Comment: preprint of Pedestrian and Evacuation 2012 conference (PED2012) contributio

The Network Operations Control Center upgrade task: Lessons learned

This article synthesizes and describes the lessons learned from the Network Operations Control Center (NOCC) upgrade project, from the requirements phase through development and test and transfer. At the outset, the NOCC upgrade was being performed simultaneously with two other interfacing and dependent upgrades at the Signal Processing Center (SPC) and Ground Communications Facility (GCF), thereby adding a significant measure of complexity to the management and overall coordination of the development and transfer-to-operations (DTO) effort. Like other success stories, this project carried with it the traditional elements of top management support and exceptional dedication of cognizant personnel. Additionally, there were several NOCC-specific reasons for success, such as end-to-end system engineering, adoption of open-system architecture, thorough requirements management, and use of appropriate off-the-shelf technologies. On the other hand, there were several difficulties, such as ill-defined external interfaces, transition issues caused by new communications protocols, ambivalent use of two sets of policies and standards, and mistailoring of the new JPL management standard (due to the lack of practical guidelines). This article highlights the key lessons learned, as a means of constructive suggestions for the benefit of future projects

Pile Setup in Cohesive Soil. I: Experimental Investigation

Pile setup in cohesive soils has been a known phenomenon for several decades. However, a systematic field investigation to provide the needed data to develop analytical procedures and integrate pile setup into the design method rarely exists. This paper summarizes a recently completed field investigation on five fully instrumented steel H-piles embedded in cohesive soils, while a companion paper discusses the development of the pile setup method. During the field investigation, detailed soil characterization, monitoring of soil total lateral stress and pore-water pressure, collection of pile dynamic restrike data as a function of time, and vertical static load tests were completed. Restrike measurements confirm that pile setup occurs at a logarithmic rate following the end of driving, and its development correlates well with the rate of dissipation of the measured porewater pressure. Based on the field data collected, it was concluded that the skin friction component, not the end bearing, contributes predominantly to the setup, which can be accurately estimated for practical purposes using soil properties, such as coefficient of consolidation, undrained shear strength, and the standard penetration testN-value

Regeneration of plantlets from nodal and shoot tip explants of Anoectochilus elatus Lindley, an endangered terrestrial orchid

Anoectochilus elatus Lindley is an endangered terrestrial orchid. A procedure for the regeneration of complete plantlets of A. elatus Lindley through node and shoot tip explants resulted directly in shoots when cultured on a full strength Murashige and Skoog (1962) medium supplemented with cytokinins at different concentrations. An average number of shoots per explant is 3 in shoot tip and 4 in node, respectively. The best shoot proliferation was observed in 3.0 mg/l 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ) and the mean shoot length in 3.5 mg/l 6-furfurylaminopurine (KIN) (node) and 0.01 mg/l (shoot tip). Hundred percent rooting was achieved with the regenerated shoots in the same medium with the addition of 0.3 g/l activated charcoal (AC). Plantlets with well developed leaves and roots were transplanted to pots filled with a mixture of coconut coir, activated charcoal, commercial fertilizers (3:1:1) and acclimatized before been transferred to the greenhouse.Keywords: : Anoectochilus elatus, activated charcoal, regeneration, rootingAfrican Journal of Biotechnology Vol. 11(29), pp. 7549-7553, 10 April, 201