Allowable silicon wafer thickness versus diameter for ingot rotation ID wafering

Inner diameter (ID) wafering of ingot rotation reduce the ID saw blade diameter was investigated. The blade thickness can be reduced, resulting in minimal kerf loss. However, significant breakage of wafers occurs during the rotation wafering as the wafer thickness decreases. Fracture mechanics was used to develop an equation relating wafer thickness, diameter and fracture behavior at the point of fracture by using a model of a wafer, supported by a center column and subjected to a cantilever force. It is indicated that the minimum allowable wafer thickness does not increase appreciably with increasing wafer diameter and that fracture through the thickness rather than through the center supporting column limits the minimum allowable wafer thickness. It is suggested that the minimum allowable wafer thickness can be reduced by using a vacuum chuck on the wafer surface to enhance cleavage fracture of the center core and by using 111 ingots

Direct measurement of the electron density of extended femtosecond laser pulse-induced filaments

We present direct time- and space- resolved measurements of the electron density of femtosecond laser pulse-induced plasma filaments. The dominant nonlinearity responsible for extended atmospheric filaments is shown to be field-induced rotation of air molecules.Comment: 12 pages, 5 figure

L&D in the ED: A Game-Based Approach to Learning High-Risk Obstetric Emergencies.

IntroductionTeaching emergency medicine residents the principles of obstetric emergencies is a challenging task, as these emergencies are uncommon in general practice and include specific maneuvers for difficult and precipitous deliveries. These requirements are not easy to satisfy in a standard lecture and are labor intensive for small groups. This resource is a board game that leverages near-peer teaching, engages student collaboration, and supports friendly competition.MethodsThe game was designed to be used by emergency medicine residents and emphasized the evaluation and management of acute issues related to labor and delivery (L&D). To play the game, three to four learners took turns answering questions. Each correct answer was awarded points for forward movement on the game board. The first person to reach the end of the game won. A faculty moderator circulated among the players to clarify questions or answers as needed.ResultsOur residents loved this resource. They were able to teach each other throughout the game while using reference materials. Participants rated the educational value of the L&D board game as 4.81 (out of 5), as compared to 4.37 for prior lectures covering the same topics. The game was rated similarly to delivery procedural skills workshops implemented in prior years (4.62-4.82).DiscussionGame-based exercises are low-tech, highly interactive teaching tools enabling students to learn from each other in a fun and engaging way. Although we did not assess knowledge retention, this activity's educational value was rated similarly to delivery procedural skills sessions

Interpretation of the silver L X-ray spectrum

Silver L X-ray energies were calculated using theoretical binding energies from relaxed orbital relativistic Hartree-Fock-Slater calculations. Theoretical X-ray energies are compared with experimental results

Exchange and relaxation effects in low-energy radiationless transitions

The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements

Systematic study of the symmetry energy coefficient in finite nuclei

The symmetry energy coefficients in finite nuclei have been studied systematically with a covariant density functional theory (DFT) and compared with the values calculated using several available mass tables. Due to the contamination of shell effect, the nuclear symmetry energy coefficients extracted from the binding energies have large fluctuations around the nuclei with double magic numbers. The size of this contamination is shown to be smaller for the nuclei with larger isospin value. After subtracting the shell effect with the Strutinsky method, the obtained nuclear symmetry energy coefficients with different isospin values are shown to decrease smoothly with the mass number $A$ and are subsequently fitted to the relation $\dfrac{4a_{\rm sym}}{A}=\dfrac{b_v}{A}-\dfrac{b_s}{A^{4/3}}$. The resultant volume $b_v$ and surface $b_s$ coefficients from axially deformed covariant DFT calculations are $121.73$ and $197.98$ MeV respectively. The ratio $b_s/b_v=1.63$ is in good agreement with the value derived from the previous calculations with the non-relativistic Skyrme energy functionals. The coefficients $b_v$ and $b_s$ corresponding to several available mass tables are also extracted. It is shown that there is a strong linear correlation between the volume $b_v$ and surface $b_s$ coefficients and the ratios $b_s/b_v$ are in between $1.6-2.0$ for all the cases.Comment: 16 pages, 6 figure

Design and fabrication of prototype system for early warning of impending bearing failure

A test program was conducted with the objective of developing a method and equipment for on-line monitoring of installed ball bearings to detect deterioration or impending failure of the bearings. The program was directed at the spin-axis bearings of a control moment gyro. The bearings were tested at speeds of 6000 and 8000 rpm, thrust loads from 50 to 1000 pounds, with a wide range of lubrication conditions, with and without a simulated fatigue spall implanted in the inner race ball track. It was concluded that a bearing monitor system based on detection and analysis of modulations of a fault indicating bearing resonance frequency can provide a low threshold of sensitivity