How good are your testers? An assessment of testing ability

During our previous research conducted in the Sheffield Software Engineering Observatory [11], we found that test first programmers spent a higher percentage of their time testing than those testing after coding. However as the team allocation was based on subjects' academic records and their preference, it was unclear if they were simply better testers. Thus this paper proposes two questionnaires to assess the testing ability of subjects, in order to reveal the factors that contribute to the previous findings. Preliminary results show that the testing ability of subjects, as measured by the survey, varies based on their professional skill level

Low Complexity Model Predictive Control of a Diesel Engine Airpath.

The diesel air path (DAP) system has been traditionally challenging to control due to its highly coupled nonlinear behavior and the need for constraints to be considered for driveability and emissions. An advanced control technology, model predictive control (MPC), has been viewed as a way to handle these challenges, however, current MPC strategies for the DAP are still limited due to the very limited computational resources in engine control units (ECU). A low complexity MPC controller for the DAP system is developed in this dissertation where, by "low complexity," it is meant that the MPC controller achieves tracking and constraint enforcement objectives and can be executed on a modern ECU within 200 microseconds, a computation budget set by Toyota Motor Corporation. First, an explicit MPC design is developed for the DAP. Compared to previous explicit MPC examples for the DAP, a significant reduction in computational complexity is achieved. This complexity reduction is accomplished through, first, a novel strategy of intermittent constraint enforcement. Then, through a novel strategy of gain scheduling explicit MPC, the memory usage of the controller is further reduced and closed-loop tracking performance is improved. Finally, a robust version of the MPC design is developed which is able to enforce constraints in the presence of disturbances without a significant increase in computational complexity compared to non-robust MPC. The ability of the controller to track set-points and enforce constraints is demonstrated in both simulations and experiments. A number of theoretical results pertaining to the gain scheduling strategy is also developed. Second, a nonlinear MPC (NMPC) strategy for the DAP is developed. Through various innovations, a NMPC controller for the DAP is constructed that is not necessarily any more computationally complex than linear explicit MPC and is characterized by a very streamlined process for implementation and calibration. A significant reduction in computational complexity is achieved through the novel combination of Kantorovich's method and constrained NMPC. Zero-offset steady state tracking is achieved through a novel NMPC problem formulation, rate-based NMPC. A comparison of various NMPC strategies and developments is presented illustrating how a low complexity NMPC strategy can be achieved.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120832/1/huxuli_1.pd

Replication or exploration? Sequential design for stochastic simulation experiments

We investigate the merits of replication, and provide methods for optimal design (including replicates), with the goal of obtaining globally accurate emulation of noisy computer simulation experiments. We first show that replication can be beneficial from both design and computational perspectives, in the context of Gaussian process surrogate modeling. We then develop a lookahead based sequential design scheme that can determine if a new run should be at an existing input location (i.e., replicate) or at a new one (explore). When paired with a newly developed heteroskedastic Gaussian process model, our dynamic design scheme facilitates learning of signal and noise relationships which can vary throughout the input space. We show that it does so efficiently, on both computational and statistical grounds. In addition to illustrative synthetic examples, we demonstrate performance on two challenging real-data simulation experiments, from inventory management and epidemiology.Comment: 34 pages, 9 figure

IS Leadership and Strategy Realization

With alignment of Information Systems (IS) strategy with business strategy, organizations can fully realize full potential of information technology (IT) resources. We view IS leadership as a core enabler to lead IS unit to contribute to organizational performance. Using upper echelons theory, we look at the effects of two characteristics of an IS leader, transformational leadership and gender, on IS unit’s teamwork capability and how this capability, in turn, affects the realization of IS unit’s strategy. We also investigate how the effect of teamwork capability on IS strategy realization is contingent on IS strategy. Consistent with prior studies, the results show that transformational IS leadership is effective in enhancing an IS unit’s teamwork capability, which in turn significantly influences the realization of IS strategy to the extent the IS unit seeks to create systems that enable the organization to be flexible

Target bankruptcy risk and its impact on going-private buyout performance and exit

Research Question/Issue: What is the impact of bankruptcy risk on whether listed corporations are likely to be bought out by private equity firms and on the subsequent exit, including bankruptcy, of private equity backed public to private buy-outs? Research Findings/Insights: Using a sample of 246 UK companies that went from public to private (P2P) company status from 1997 to 2005, we find that going private companies have significantly higher default probability. Private equity firms sponsoring P2P deals acquire firms with higher risk of bankruptcy than non-acquired firms that remain public. We find evidence that high receivership risk at going private increases the chance that the target will end up in receivership, but post-P2P bankruptcy likelihood is less when the P2P is a management buyout rather than any other form of buyout. Independent boards of pre-P2P targets promote P2P deals and reduce the chances of bankruptcy after the buyout, suggesting a good corporate governance structure makes a positive contribution to bankruptcy avoidance after going private transactions. Theoretical/Academic Implications: Our finding that P2P deals involve targets with a higher risk of bankruptcy adds to theoretical insights about private equity as, in contrast to previous research, it suggests that PE firms are not deterred by the risk of financial distress but consider it a value creating opportunity. Our use of the option pricing framework represents a first and novel attempt at measuring bankruptcy risk and its impact on the ability of private equity firms to achieve effective turnaround. We find a link between better governance of the target pre-P2P and lower bankruptcy risk since where the PE investor inherits a strong governance structure, manifested in independent boards, chances of subsequent bankruptcy are reduced. Similarly, where the P2P acquisition is a management buyout, the probability of bankruptcy, post-P2P, is reduced, suggesting lower informational asymmetries and better alignment of interests between managerial and private equity investors. Although, due to the small number of receivership exits in our sample of P2P firms, the results are not as strong as we would like, a more extended analysis involving a larger sample over a longer period, in particular of firms exiting through bankruptcy is expected to produce stronger results. Our results provide a sufficient basis to warrant such further analysis

Time-lapse walkaway vertical seismic profile monitoring for CO2 injection at the SACROC enhanced oil recovery field: A case study

Geologic carbon storage involves large-scale injections of carbon dioxide into underground geologic formations. Changes in reservoir properties resulting from CO2CO2 injection and migration can be characterized using monitoring methods with time-lapse seismic data. To achieve economical monitoring, vertical seismic profile (VSP) data are often acquired to survey the local injection area. We investigated the capability of walkaway VSP monitoring for CO2CO2 injection into an enhanced oil recovery field at SACROC, West Texas. VSP data sets were acquired in 2008 and 2009, and CO2CO2 injection took place after the first data acquisition. Because the receivers were located above the injection zone, only reflection data contain the information from the reservoir. Qualitative comparison between reverse-time migration images at different times revealed vertical shifts of the reflectors’ center, indicating the presence of velocity changes. We examined two methods to quantify the changes in velocity: standard full-waveform inversion (FWI) and image-domain wavefield tomography (IDWT). FWI directly inverts seismic waveforms for velocity models. IDWT inverts for the time-lapse velocity changes by matching the baseline and time-lapse migration images. We found that, for the constrained geometry of VSP surveys, the IDWT result was significantly more consistent with a localized change in velocity as expected from a few months of CO2CO2 injection. A synthetic example was used to verify the result from the field data. By contrast, FWI failed to provide quantitative information about the volumetric velocity changes because of the survey geometry and data frequency content