6,820 research outputs found
Cutting ice on Seeley Lake
No full textFive men and two horses work to mark and cut ice from Seeley Lake. Two men lead horses harnessed to horse-drawn ice markers held by a second man. The fifth man uses a hand ice saw to cut the marked ice. Imprinted on the paperboard matte under the photograph, 'F.E. BAKER, ---GREELEY, COLO.'; Verso In pencil, 'Cutting ice on Seeley Lake near Greeley, Colo.
Imaging the SAW Field on Suspended 2D Membrane
No full textSurface acoustic wave (SAW) is widely used in biological research and sensor applications, acomprehensive understanding of SAW propagation and visualization on suspended 2D membranes is crucial for the manipulation of nanoparticles in biological research and sensitivity improvement of SAW sensors based on 2D material. The initial step of this project involved exciting a standing SAW field on the SAW device and attempting to use Digital Holography Microscopy (DHM) for imaging the standing SAW field on the substrate. This attempt was very challenging and unfortunately was not successful. We used an Atomic Force Microscope (AFM) as an alternative solution for SAW field imaging. Initially, AFM was used to image the SAW field on the SAW device substrate, and the impacts of input frequency and power on the amplitude of the SAW field were investigated. Subsequently, microcavities were fabricated on the SAW device to record images of the SAW field within the microcavities and their surrounding areas, aiming to investigate the impact of microcavities on the SAW field. Finally, the prepared graphene membrane was transferred to the microcavities, the SAW propagation was recorded on the suspended membrane and the influence of the suspended membrane on SAW propagation was analyzed.Mechanical Engineering | Precision and Microsystems Engineerin
State-of-the-art instruments based upon SAW wireless tags, SAW match filters, and SAW resonators
No full textA theoretical analysis for the SAW wireless tag for wireless instrumentation was proposed. Employing the developed wireless tag, a telemetry instrument was also developed. Other SAW device based systems such as SAW match filter based optical time-domain reflectometer and high Q-value SAW resonator based analytical instruments are also reported. These state-of-the-art instruments can enlarge the application scope of SAW technology.AcousticsInstruments & InstrumentationPhysics, AppliedCPCI-S(ISTP)
A study on vibration disorder among chain saw operators -Effect of leaving off chain saw operation on recovery of disorder-
No full textRecently a study on vibration disorder among chain saw operators has been developed rapidly, while the number of workers suffering from vibration disorder has been increasing. It is one of the most important disposal as health care among chain saw operators to leave a worker with disorders off using a chain saw. The author discussed on results of health examination for chain saw operators performed before and after the disposal introduced in 1973. Two hundred and six examinees were divided into five groups classified by clinical findings of Raynaud's phenomenon, types of work after leaving off a chain saw work and medical care. The results were as follows: 1) It was not effective for a worker with Raynaud's phenomenon to leave off a chain saw operation. 2) It was also not effective for an elder worker with long term experience of a chain saw operation to leave off the work. 3) It was effective for a worker without abnormal findings on X-ray film of the elbow to stop using a chain saw. The author concluded that the disposal of leaving off a chain saw operation should be provided before appearance of Raynaud's phenomenon and a change from operating a chain saw to using a hand saw and an axe was not effective for the worker with abnormality on X-ray film of the elbow
Rapid growth of Coalescing Droplets and Observation of Fine Structures in Turbulent Flow
No full textI will present our results on size-growth dynamics of coalescing droplets in simulation of isotropic turbulent flow. In the short time limit, we observe very fast growth due to correlations of these droplets which can be related to the interaction between their inertia to turbulent advection (this work is done with colleagues at affiliations 1 \& 2). In a later part, I will describe our attempt to experimentally observe the intermittent fine structures of turbulence flow using high resolution Particle Image Velocimetry (PIV) technique (this work is done with colleagues at affiliation 3)
Design and evaluation of an abrasive saw kickback machine
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020Supervised by Alexander H. Slocum. Cataloged from the PDF version of thesis.Includes bibliographical references (page 65).Injuries from power saw kickback are often fatal. However, only woodcutting saws have regulations and assessment methodologies for kickback. These regulations do not apply to metal and masonry saws, as the cutting mechanism and dominant kick-back mode are different from those of woodcutting saws. In this work, the kickback of abrasive saws is investigated by combining theoretical and experimental tools. A theoretical model developed based on frictional engagement during a pinch-based kickback event is shown to predict the resultant kickback energy for various saws in good agreement with experimental measurements. These measurements were obtained using a specialized machine that was designed to generate pinch-based kickback and to measure the resultant kickback energy for both chainsaws and cutoff saws. While the model can predict the resultant kickback energy for a saw given known cutting conditions (i.e. cutting angle and pinch force), it does not predict the maximum possible kickback energy given any cutting angle of a saw because it does not account for the change in speed of the cutting blade. Upon validation of the physics model, two commonly used representative saws, a Stihl TS420 and an ICS 695XL, were tested using this kickback machine to evaluate their comparative kickback risk. This work demonstrates that pinch-based kickback can be a major safety risk for abrasive saw operators, and it provides a machine and analytical framework for evaluating this risk.by Steven Burcat.S.M.S.M. Massachusetts Institute of Technology, Department of Mechanical Engineerin
They Saw the Sun First: Spelman SIS Young Scholar Writings
No full text"Old people's speech is not to be dishonored, after all, they saw the sun first". -Namibian Prover
Corporate responsibility and the media
No full textThis paper discusses how CR is covered in the media and the media’s own corporate responsibilities, covering both traditional and new media.Co published with Centrum fur Corporate Citizenship Deutschlan
Utilisation of Single Tooth Procedures to Establish the Cutting Mechanics of Woodworking Hand-saw Teeth
No full textThe work reported in this thesis details the original research undertaken by the author into the cutting mechanics of wood-working handsaw tooth geometries. The research can be separated into three distinctive sections. The first section is a review of both fundamental and recent literature regarding wood characteristics and machining processes. The second section documents the findings of a cutting process in which a variety of work-piece parameters were evaluated whilst limiting the parameters associated with tooth geometry. The third and final section documents the findings of a cutting process in which a variety of tooth geometry parameters were evaluated whilst limiting work-piece variation.
Two separate experimental procedures were developed to carry out the work for sections two and three respectively: The first of these procedures utilised a CNC router machine to perform the controlled cutting action. A single “rip” tooth was attached to the tool holder. The workpiece was constrained to a tri-axis dynamometer which was used to measure the resultant tool forces in the relative X, Y and Z axes. At the same time a universal testing machine was employed to perform mechanical test procedures on a variety of wood species. A predictive cutting force model was developed using the obtained mechanical properties as categorical predictors.
The second procedure utilised a shaper machine to perform the controlled cutting action. Three different saw tooth geometries were evaluated for only one variety of wood species. A tri-axis dynamometer was again used to measure the resultant tool forces. The geometric parameters of each tooth were carefully evaluated at using SEM micrographs. A predictive cutting force model using the geometric parameters as categorical predictors was developed.
Chip and surface formation was carefully evaluated. For procedure one this involved observation of the chip/surfaces under an optical microscope. For procedure two this involved capturing footage of the cutting process using a high speed camera.
The findings of the research show that un-bevelled teeth with orthogonal edges generally yield high cutting forces. However, these teeth are very effective at removing material along the wood grain in a “chisel like” cutting action. Bevelled teeth with sharp lateral edges generally yield low cutting forces. These teeth are well suited to severing the wood fibres perpendicular to the grain in a “knife like” cutting action
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