Structured Linearization of Discrete Mechanical Systems for Analysis and Optimal Control

Variational integrators are well-suited for simulation of mechanical systems because they preserve mechanical quantities about a system such as momentum, or its change if external forcing is involved, and holonomic constraints. While they are not energy-preserving they do exhibit long-time stable energy behavior. However, variational integrators often simulate mechanical system dynamics by solving an implicit difference equation at each time step, one that is moreover expressed purely in terms of configurations at different time steps. This paper formulates the first- and second-order linearizations of a variational integrator in a manner that is amenable to control analysis and synthesis, creating a bridge between existing analysis and optimal control tools for discrete dynamic systems and variational integrators for mechanical systems in generalized coordinates with forcing and holonomic constraints. The forced pendulum is used to illustrate the technique. A second example solves the discrete LQR problem to find a locally stabilizing controller for a 40 DOF system with 6 constraints.Comment: 13 page

Automated Classification of Transient Contamination in Stationary Acoustic Data

An automated procedure for the classification of transient contamination of stationary acoustic data is proposed and analyzed. The procedure requires the assumption that the stationary acoustic data of interest can be modeled as a band-limited, Gaussian random process. It also requires that the transient contamination be of higher variance than the acoustic data of interest. When these assumptions are satisfied, it is a blind separation procedure, aside from the initial input specifying how to subdivide the time series of interest. No a priori threshold criterion is required. Simulation results show that for a sufficient number of blocks, the method performs well, as long as the occasional false positive or false negative is acceptable. The effectiveness of the procedure is demonstrated with an application to experimental wind tunnel acoustic test data which are contaminated by hydrodynamic gusts

Influential Article Review - Connectivity as Trade Determinant For Shipping Lines

This paper examines transportation. We present insights from a highly influential paper. Here are the highlights from this paper: Transport connectivity is a crucial determinant of bilateral exports. This paper presents an empirical assessment of the relationship between bilateral maritime liner shipping connectivity and exports in containerized goods during the period 2006–2013. Making use of probed “gravity” type trade models, the paper incorporates new data on different measurements of maritime distance, as well as a unique new dataset and new bilateral connectivity indices developed by UNCTAD. The empirical investigations unequivocally show that lacking a direct maritime connection with a trade partner is associated with lower values of exports; any additional transshipment is associated with a 40% lower value of bilateral exports. Other indicators of liner shipping connectivity incorporated in the research take into consideration levels of competition and container vessel sizes. Results also indicate that the quality of bilateral connectivity as measured by several composite indices is a crucial determinant of bilateral exports. All empirical results suggest that in the absence of a bilateral connectivity indicator the impact of distance on bilateral exports in classical gravity models is likely to be overestimated. For our overseas readers, we then present the insights from this paper in Spanish, French, Portuguese, and German

Social Skills Preferences Among Internal Auditors An Explanatory Study Using The FIRO-B

This study applies the FIRO-B technique to analyze the social interaction preferences of certified internal auditors working in U.S. corporations. Surveys were developed using the FIRO-B technique and obtained information on internal auditors from corporations located in the Western and Southeastern sections of the United States. This study will determine the social interaction scores of certified internal auditors, and compare them to the scores of other accounting professionals. This study indicates that social interaction skills are of increasing importance to the working success of internal auditors. The SII number is higher than prior research of CPAs employed in large international CPA firms but similar to those results found among accountants at regional CPA firms and national business professionals. This study did not segment the sample by industry to determine if there are any effects due to industry or company size. Future research might compare the internal auditors might make these comparisons. Also, the study did not include samples from outside of the United States. Understanding the social interaction of certified internal auditors is important since such information sheds light on the types of professionals who are most likely to succeed in the diverse work environment that internal auditors face. This is the first exploratory study using the FIRO-B on internal auditors

Dissociating the Role of the Orbitofrontal Cortex and the Striatum in the Computation of Goal Values and Prediction Errors

To make sound economic decisions, the brain needs to compute several different value-related signals. These include goal values that measure the predicted reward that results from the outcome generated by each of the actions under consideration, decision values that measure the net value of taking the different actions, and prediction errors that measure deviations from individuals' previous reward expectations. We used functional magnetic resonance imaging and a novel decision-making paradigm to dissociate the neural basis of these three computations. Our results show that they are supported by different neural substrates: goal values are correlated with activity in the medial orbitofrontal cortex, decision values are correlated with activity in the central orbitofrontal cortex, and prediction errors are correlated with activity in the ventral striatum

Formal Versus Informal Mentoring Of MAS Professionals

CPA firms have consistently experienced high turnover and poor performance amongst their management advisory and information systems professionals. As Keller (2008) suggests, mentoring programs are a mechanism to help attract and maintain good employees. The extant accounting literature well documents the benefits of mentoring such as enhanced communication, greater organizational commitment, higher professional performance and reduced personnel turnover (Scandura & Viator, 1994; Siegel & Reintein, 2001; Siegel et al., 1997). In light of their potential benefits, CPA firms have begun to develop formal mentoring programs for accounting specialists to ensure that the advantages of mentoring are maintained rather than relying on happenstance (Siegel et al., 1997). The extant literature also addresses the benefits and shortcomings of formal mentoring programs for both auditing and tax professionals. (Viator, 2001; Siegel, et al., 1997; Herbohn, 2004). However, to date, no research addresses formal mentoring relative to management advisory services (MAS) professionals employed by CPA firms. MAS professionals work milieu is generally less structured than other professionals employed by CPA firms. In addition, they have greater operating autonomy than is usually the case in public accounting. Thus the purpose of this study is to compare the effects of formal and informal mentoring program effects on MAS professionals working at international public accounting firms. To evaluate the different mentoring programs, the study examines the mentoring processes within the tax departments of two international CPA firms that employ both formal and informal mentoring programs. The results indicate no significant differences between formal and informal programs on MAS professionals career development. However, the statistical analysis did show a significant difference in the perceived influence of the programs at two professional levels on personal development that appears at the middle range of the programs. The results suggest that the informal mentoring approach leads to stronger personal relationships but does not extend to higher professional firm levels. Neither formal nor informal programs appear to have a significant influence to staff level professionals