Neural network modeling of nonlinear systems based on Volterra series extension of a linear model

A Volterra series approach was applied to the identification of nonlinear systems which are described by a neural network model. A procedure is outlined by which a mathematical model can be developed from experimental data obtained from the network structure. Applications of the results to the control of robotic systems are discussed

Comparison of joint space versus task force load distribution optimization for a multiarm manipulator system

It is often proposed that the redundancy in choosing a force distribution for multiple arms grasping a single object should be handled by minimizing a quadratic performance index. The performance index may be formulated in terms of joint torques or in terms of the Cartesian space force/torque applied to the body by the grippers. The former seeks to minimize power consumption while the latter minimizes body stresses. Because the cost functions are related to each other by a joint angle dependent transformation on the weight matrix, it might be argued that either method tends to reduce power consumption, but clearly the joint space minimization is optimal. A comparison of these two options is presented with consideration given to computational cost and power consumption. Simulation results using a two arm robot system are presented to show the savings realized by employing the joint space optimization. These savings are offset by additional complexity, computation time and in some cases processor power consumption

Electromagnetic Monitoring and Control of a Plurality of Nanosatellites

A method for monitoring position of and controlling a second nanosatellite (NS) relative to a position of a first NS. Each of the first and second NSs has a rectangular or cubical configuration of independently activatable, current-carrying solenoids, each solenoid having an independent magnetic dipole moment vector, .mu.1 and .mu.2. A vector force F and a vector torque are expressed as linear or bilinear combinations of the first set and second set of magnetic moments, and a distance vector extending between the first and second NSs is estimated. Control equations are applied to estimate vectors, .mu.1 and .mu.2, required to move the NSs toward a desired NS configuration. This extends to control of N nanosatellites

Automation and robotics considerations for a lunar base

An envisioned lunar outpost shares with other NASA missions many of the same criteria that have prompted the development of intelligent automation techniques with NASA. Because of increased radiation hazards, crew surface activities will probably be even more restricted than current extravehicular activity in low Earth orbit. Crew availability for routine and repetitive tasks will be at least as limited as that envisioned for the space station, particularly in the early phases of lunar development. Certain tasks are better suited to the untiring watchfulness of computers, such as the monitoring and diagnosis of multiple complex systems, and the perception and analysis of slowly developing faults in such systems. In addition, mounting costs and constrained budgets require that human resource requirements for ground control be minimized. This paper provides a glimpse of certain lunar base tasks as seen through the lens of automation and robotic (A&R) considerations. This can allow a more efficient focusing of research and development not only in A&R, but also in those technologies that will depend on A&R in the lunar environment

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN

The Relationship Of Constrained Free‐Response To Multiple‐Choice And Open‐Ended Items

This study examined the relationship of a machine‐scorable, constrained free‐response computer science item that required the student to debug a faulty program to two other types of items: (1) multiple‐choice and (2) free response requiring production of a computer program. Confirmatory factor analysis was used to test the fit of a three‐factor model to these data and to compare the fit of this model to three alternatives. These models were fit using two random‐half samples, one given a faulty program containing one bug and the other a program with three bugs. A single‐factor model best fit the data for the sample taking the 1‐bug constrained free response and a two‐factor model fit the data for the second sample. In addition, the factor intercorrelations showed this item type to be significantly related to both the free‐response items and the multiple‐choice measures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108688/1/ets200147.pd

Shared Control of Multiple-Manipulator, Sensor-Based Telerobotic Systems

A control architecture is presented for real-time, sensor-based, shared control of remote, multiplemanipulator telerobotic systems. The system allows teleoperation, autonomy, or a combination (shared, telerobotic control). The rate-based system accepts control inputs from a variety of sources (joystick position or velocity, automated path planner position or velocity, machine vision, force/moment) simultaneously for all Cartesian axes. The system has been experimentally implemented and has proven effective in laboratory simulations of remote space tasks. 1

Epidemiological evidence for a hereditary contribution to myasthenia gravis: a retrospective cohort study of patients from North America.

ObjectivesTo approximate the rate of familial myasthenia gravis and the coexistence of other autoimmune disorders in the patients and their families.DesignRetrospective cohort study.SettingClinics across North America.ParticipantsThe study included 1032 patients diagnosed with acetylcholine receptor antibody (AChR)-positive myasthenia gravis.MethodsPhenotype information of 1032 patients diagnosed with AChR-positive myasthenia gravis was obtained from clinics at 14 centres across North America between January 2010 and January 2011. A critical review of the epidemiological literature on the familial rate of myasthenia gravis was also performed.ResultsAmong 1032 patients, 58 (5.6%) reported a family history of myasthenia gravis. A history of autoimmune diseases was present in 26.6% of patients and in 28.4% of their family members.DiscussionThe familial rate of myasthenia gravis was higher than would be expected for a sporadic disease. Furthermore, a high proportion of patients had a personal or family history of autoimmune disease. Taken together, these findings suggest a genetic contribution to the pathogenesis of myasthenia gravis