MeshPerturb: MATLAB codes for mesh perturbation and automated pre and post processing of post-bifurcation analyses via COMSOL

Recently, there has been an interest in designing systems that employ buckling bifurcation as a desired mechanism to generate motion and/or form. As buckling has traditionally been considered a failure mode to be avoided, computational tools for predicting the state of the system after buckling are not well developed. For example, modules for post-bifurcation studies are not available in most of the commercial finite element software packages. Herein, we provide MATLAB codes that add the ability to perform post-bifurcation studies to the commercially available COMSOL finite element package. This is achieved by implementing mesh perturbations as a scheme to introduce geometric imperfections to the system. Additionally, we provide codes to automate pre/post processing the studies. These codes enable performing (i) post-bifurcation analysis, (ii) studies on sensitivity to mesh imperfections, and (iii) unattended parametric studies that require re-meshing the geometry

Ethical Attitudes and Education of a Group of California Dietitians

A questionnaire was developed to determine the ethical attitudes and education of a group of California dietitians. A group of 198 randomly selected individuals from the California Dietetic Association membership of 2,180 participated in the study. Great diversity was exhibited in age, type of position held and total years of work experience in the sample group. Eighty-one per cent of the respondents were less than forty-nine years of age. The positions most frequently held by the participants were in hospital therapeutics and administration, teaching and schools, and consultant work. Sixty-three per cent were employed on either a full-time or part-time basis at the time of the study. Ninety per cent were aware that The American Dietetic Association has a code of ethics. Approximately sixty-seven per cent had received some type of ethical education during internship or college in their major field of study or in philosophy, psychology or religion. No correlation was found to exist between the age of the respondent and her ethical education or her ethical attitude toward the questions submitted. A majority opinion was found to exist for most of the questions; and this majority opinion seemed to parallel the ethical principles outlined in the official code of ethics of The American Dietetic Association. Controversial questions were concerned with the political activities of the association(s), the dietitian\u27s obligations (1) to render service for the common good without regard for personal gain, and (2) to accept opportunities for greater responsibility. There was no majority opinion on the degree of frankness required in the dietitian-patient relationship, the conduct of the dietitian in her private life and whether or not the dietitian was justified in using the offer of another position as a lever in gaining a salary increase. Judging from the high percentage of returned questionnaires and from the expressed interest of the participants in the subject, it would seem reasonable to expect that similar studies could be made with probable success. Use of a similar questionnaire could be made in determining the ethical education needs of dietetic interns. Preparation of some type of textbook on ethical considerations specific to the dietetic profession seems justified

Statistical comparisons of non-deterministic IR systems using two dimensional variance

Retrieval systems with non-deterministic output are widely used in information retrieval. Common examples include sampling, approximation algorithms, or interactive user input. The effectiveness of such systems differs not just for different topics, but also for different instances of the system. The inherent variance presents a dilemma - What is the best way to measure the effectiveness of a non-deterministic IR system? Existing approaches to IR evaluation do not consider this problem, or the potential impact on statistical significance. In this paper, we explore how such variance can affect system comparisons, and propose an evaluation framework and methodologies capable of doing this comparison. Using the context of distributed information retrieval as a case study for our investigation, we show that the approaches provide a consistent and reliable methodology to compare the effectiveness of a non-deterministic system with a deterministic or another non-deterministic system. In addition, we present a statistical best-practice that can be used to safely show how a non-deterministic IR system has equivalent effectiveness to another IR system, and how to avoid the common pitfall of misusing a lack of significance as a proof that two systems have equivalent effectiveness

Compliant quasi-kinematic couplings

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (p. 113-116).Better precision at lower costs is a major force in design and manufacturing. However, this is becoming increasingly difficult to achieve as the demands of many location applications are surpassing the practical performance limit (~ five microns) of low-cost couplings. The absence of a means to meet these requirement has motivated the development of the Quasi-Kinematic Coupling (QKC). This thesis covers the theoretical and practical considerations needed to model and design QKCs. In a QKC, one component is equipped with three spherical protrusions while the other contains three corresponding conical grooves. Whereas Kinematic Couplings rely on six points of contact, the six arcs of contact between the mated protrusions and grooves of QKCs result in a weakly over-constrained coupling, thus the name Quasi-Kinematic. QKCs are capable of sub-micron repeatability, permit sealing contact as needed in casting, and can be economically mass produced. The design and application of a QKC is demonstrated via a case study on the location of two engine components. Integration of the QKC has improved coupling precision from 5 to 0.7 microns. In addition, this QKC uses 60% fewer precision features, 60% fewer pieces, costs 40% less per engine, and allows feature placement tolerances which are twice as wide as those of the previous dowel-pin-type coupling.by Martin L. Culpepper.S.M

Design of debris cleaner with compound auger and vacuum pick up

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.by Martin L. Culpepper.M.S

DETC2004-57606 A FRAMEWORK AND DESIGN SYNTHESIS TOOL USED TO GENERATE, EVALUATE AND OPTIMIZE COMPLIANT MECHANISM CONCEPTS FOR RESEARCH AND EDUCATION ACTIVITES

ABSTRACT In 2002, a Microsoft-MIT iCampus effort was initiated to generate methods and tools which accelerate the process by which students and researchers acquire perspective and skill in compliant mechanism design: (1) Experience and skill: A synthesis tool, CoMeT, was developed as a means for researchers and students to gain experience and skill in working with old (education) and new (research) compliant mechanisms. The simulator is based on compliance theory and screw theory. (2) Perspective: A framework, the 5 Fs, was developed to help designers form a holistic perspective on compliant mechanisms. A "big picture" view helps them systematically identify and link the important elements of a compliant mechanism problem. This opens to door for them to properly conceptualize, model and fabricate these mechanisms. In this paper we discuss the work of early compliant mechanism/instrument designers to gain insight into how they thought about, designed and taught others about compliant mechanisms. We explain how their work has influenced the development of our framework and simulator. We then show results obtained by using the framework and simulator at MIT in: (1) Compliant mechanism research: Generation of a compliant mechanism for an R&D 100 award winning, six-axis Nanomanipulator. (2) Compliant mechanism education: Use within student projects to design two devices: A compliant x-y Nanomanipulator with 30x30 µm range and a MEMS accelerometer. Both devices are designed, fabricated and tested in a semester-long class

Understanding the drivers for the development of design rules for the synthesis of cylindrical flexures

Cylindrical flexures (CFs), defined as flexures with only one finite radius of curvature loaded normal to the plane of curvature, present an interesting research direction in compliant mechanisms. CFs are constructed out of a cylindrical stock which leads to geometry, manufacturability, and compatibility advantages. Synthesis rules must be developed to design these new systems effectively. Current knowledge in flexure design pertains to straight-beam flexures or curved flexures loaded along the plane of curvature. CFs present a challenge because their mechanics differ from those of straight beams, and although their modelling has been researched thoroughly it has yet to be distilled into element and system creation rules. This paper uses models and finite element analysis to demonstrate that current design rules for straight-beam flexures are insufficient and inadequate for the design of CF systems. The presented discussion will show that CFs differ both at the element and systems levels, and therefore future research will focus on developing the three components of the building block approach: (i) reworking of element mechanics models to reveal the parameters which cause the kinematics of the curved beam to differ from those of the straight beam, (ii) development of a visual stiffness representation, and (iii) formation of system creation rules

Wildlife Damage to Seedlings in Reforested in Hardwood Sites in Mississippi

Herbivory assessments were conducted on seven reforested sites that were less than one year old in the following Mississippi counties: Bolivar, Leflore, and Attala. At each site, 100ft. x 100 ft. plots were established and randomly selected seedlings were marked and measured to determine seedling species, height, condition, survival, and type and extent of animal feeding sign. Surveys were conducted in March/April, May, and August 2004. Herbivory rates were highest during May with approximately 47% of seedlings showing signs of herbivory. In March/ April and August, the percentage of seedlings exhibiting signs of herbivory was 37% and 30%, respectively. Foraging by white-tailed deer (Odocoileus virginianus) was recorded on \u3e 90% of the damaged seedlings during each survey. Tree mortality for all study sites and tree species was negligible, with the highest amount (7%) recorded during August, despite the recorded rates of herbivory by white-tailed deer. Herbivory by rabbits (Sylvilagus spp.) and rodents occurred on approximately 6% of the seedlings throughout the 2004 growing season