A Kinematically Intelligent Blackboard for Computer Aided Instruction

A CAI (computer-aided instruction) package is being developed to be used as a classroom tool for the instruction of undergraduate mechanical engineering students in an introductory kinematics of mechanisms course. This graphical environment allows the instructor to emulate on the projected graphics screen everything that is currently done on the blackboard for planar mechansims. Unlike the blackboard, the software will have the intelligence to interpret the drawings in a kinematic sense so that the drawing of the linkage will behave as a linkage. The software environment involves three principal components: (1) a sketching method for defining the linkage, (2) the kinematic intelligence to interpret the sketch and animate the linkage, and (3) the ability to develop and demonstrate kinematic concept

Pragmatic versus syntactic approaches to training deductive reasoning

Two views have dominated theories of deductive reasoning. One is the view that people reason using syntactic, domain-independent rules of logic, and the other is the view that people use domain-specific knowledge. In contrast with both of these views, we present evidence that people often reason using a type of knowledge structure termed pragmatic reasoning schemas. In two experiments, syntactically equivalent forms of conditional rules produced different patterns of performance in Wason's selection task, depending on the type of pragmatic schema evoked. The differences could not be explained by either dominant view. We further tested the syntactic view by manipulating the type of logic training subjects received. If people typically do not use abstract rules analogous to those of standard logic, then training on abstract principles of standard logic alone would have little effect on selection performance, because the subjects would not know how to map such rules onto concrete instances. Training results obtained in both a laboratory and a classroom setting confirmed our hypothesis: Training was effective only when abstract principles were coupled with examples of selection problems, which served to elucidate the mapping between abstract principles and concrete instances. In contrast, a third experiment demonstrated that brief abstract training on a pragmatic reasoning schema had a substantial impact on subjects' reasoning about problems that were interpretable in terms of the schema. The dominance of pragmatic schemas over purely syntactic rules was discussed with respect to the relative utility of both types of rules for solving real-world problems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26121/1/0000197.pd

Prehospital transdermal glyceryl trinitrate in patients with ultra-acute presumed stroke (RIGHT-2): an ambulance-based, randomised, sham-controlled, blinded, phase 3 trial

Background High blood pressure is common in acute stroke and is a predictor of poor outcome; however, large trials of lowering blood pressure have given variable results, and the management of high blood pressure in ultra-acute stroke remains unclear. We investigated whether transdermal glyceryl trinitrate (GTN; also known as nitroglycerin), a nitric oxide donor, might improve outcome when administered very early after stroke onset. Methods We did a multicentre, paramedic-delivered, ambulance-based, prospective, randomised, sham-controlled, blinded-endpoint, phase 3 trial in adults with presumed stroke within 4 h of onset, face-arm-speech-time score of 2 or 3, and systolic blood pressure 120 mm Hg or higher. Participants were randomly assigned (1:1) to receive transdermal GTN (5 mg once daily for 4 days; the GTN group) or a similar sham dressing (the sham group) in UK based ambulances by paramedics, with treatment continued in hospital. Paramedics were unmasked to treatment, whereas participants were masked. The primary outcome was the 7-level modified Rankin Scale (mRS; a measure of functional outcome) at 90 days, assessed by central telephone follow-up with masking to treatment. Analysis was hierarchical, first in participants with a confirmed stroke or transient ischaemic attack (cohort 1), and then in all participants who were randomly assigned (intention to treat, cohort 2) according to the statistical analysis plan. This trial is registered with ISRCTN, number ISRCTN26986053. Findings Between Oct 22, 2015, and May 23, 2018, 516 paramedics from eight UK ambulance services recruited 1149 participants (n=568 in the GTN group, n=581 in the sham group). The median time to randomisation was 71 min (IQR 45–116). 597 (52%) patients had ischaemic stroke, 145 (13%) had intracerebral haemorrhage, 109 (9%) had transient ischaemic attack, and 297 (26%) had a non-stroke mimic at the final diagnosis of the index event. In the GTN group, participants’ systolic blood pressure was lowered by 5·8 mm Hg compared with the sham group (p<0·0001), and diastolic blood pressure was lowered by 2·6 mm Hg (p=0·0026) at hospital admission. We found no difference in mRS between the groups in participants with a final diagnosis of stroke or transient ischaemic stroke (cohort 1): 3 (IQR 2–5; n=420) in the GTN group versus 3 (2–5; n=408) in the sham group, adjusted common odds ratio for poor outcome 1·25 (95% CI 0·97–1·60; p=0·083); we also found no difference in mRS between all patients (cohort 2: 3 [2–5]; n=544, in the GTN group vs 3 [2–5]; n=558, in the sham group; 1·04 [0·84–1·29]; p=0·69). We found no difference in secondary outcomes, death (treatment-related deaths: 36 in the GTN group vs 23 in the sham group [p=0·091]), or serious adverse events (188 in the GTN group vs 170 in the sham group [p=0·16]) between treatment groups. Interpretation Prehospital treatment with transdermal GTN does not seem to improve functional outcome in patients with presumed stroke. It is feasible for UK paramedics to obtain consent and treat patients with stroke in the ultraacute prehospital setting. Funding British Heart Foundation

A Geometric Approach to the Spatial Equivalent of Burmester Curves

The geometric aspects of Burmester Theory, as used in planar four-bar linkage synthesis, are examined to define a general procedure which is applied to the generation of the joint loci of spatial dyads. For a given dyad type a figure is drawn showing the joints of the dyad in their assumed positions, subject to the motion constraints of the dyad. A standard approach is used to geometrically relate the joints to the screw axes of the prescribed motion, by means of a screw triangle. The screw triangle relates the geometry between any three related screws. The geometric relationships are typically separated into several geometric constraints. Each geometric constraint is considered separately to generate a loci of lines or points representing joints which satisfy the constraint. The intersection of all of the loci produces a single loci of all the possible fixed or moving joints. The geometric approach is shown to have several advantages over numerical and pure analytical techniques, especially in relating the characteristics of the loci to the physical linkage and its required motion. The cylindrical-cylindrical dyad is considered in detail as a general case for dyads involving joints with axes. The angular and positional constraints are considered separately as independent constraints. Families of quadric cones are generated which correspond to the families of circles for three precision positions in the planar case. The intersection of the families of quadric cones produces the cubic screw cone which degenerates to Burmester\u27s curve in the planar case

A Closed Form Method for Backtracking from a Modified Burmester Curve to a Set of Precision Positions

A method is presented, in the context of Burmester theory, which backtracks from a modified set of poles to a set of precision positions which is likely to satisfy the original precision position tolerances. The motivation is to provide a means of manipulating the Burmester curves into desired regions by moving the poles rather than the precision positions directly. The procedure correlates a movement of a pole to a new set of precision positions which are determined to be more than likely nearest to the original set of precision positions. By checking the most likely precision positions, it is not necessary to check the remaining infinite possible sets of precision positions. Thus, even though it is theoretically impossible to backtrack from four poles to a unique set of precision positions, with this method it is practically possible to do so

Geometric Generation of the Joint Loci of Spatial Dyads with Axis Joints

The geometric aspects of Burmester theory, as used in planar four-bar linkage synthesis, are examined to define a general procedure which is applied to the generation of the joint loci of spatial dyads with axis joints. The joints are geometrically related to the screw axes of the prescribed motion, by means of a screw triangle. The geometric relationships are typically separated into several geometric constraints. Each geometric constraint is considered separately to generate the loci of lines representing joint axes which satisfy, the constraint. Combining the loci from each constraint produces a single loci of all the possible fixed or moving joints. The geometric approach is shown to have several benefits not obtained in numerical and pure analytical techniques, especially in relating the characteristics of the loci to the physical linkage and its required motion

Shigley’s Mechanical Engineering Design, 11th edition

Shigley\u27s Mechanical Engineering Design is intended for students beginning the study of mechanical engineering design. Students will find that the text directs them into familiarity with both the basics of design decisions and the standards of industrial components. It combines a straightforward focus on fundamentals with a modern emphasis on design and new applications