Matlab as a Tool to Increase the Math Self-Confidence and the Math Ability of First-Year Engineering Technology Students

Mary Brake\u27s chapter details her efforts to introduce a computational software package (Mathlab) in her Introduction to Engineering Technology course. Mary started off her scholarship of teaching and learning project interested in why women and minorities tend to drop out of engineering programs nationwide; she anticipated it is caused by lack of confidence these students have that they can make it in such a program. Along the way, Mary\u27s focus widened as she discovered that the problem may not exactly be lack of confidence; her students continued to feel their ability to solve complex problems even in the face of clear evidence that they could not. Mary\u27s big goal has become to help students learn to think like experts. She wants her students to excel at using information they have previously learned in solving complex problems. This investigation speaks to how Mathlab can help students learn to do this; ultimately, the goal is to help student feel (deservedly) more self-confident in their ability to do the math necessary for an engineering technology program. From a practical standpoint, this study suggests that Mathlab would be most valuable to students if it were introduced early in the program. Mary also suggests it might prove more valuable when not crammed into an already full class such as hers

A combined continuous‐wave and pulsed microwave copper chloride discharge

Pulsed and continuous‐wave microwaves at 2.45 GHz combined in an Asmussen resonant cavity are used to vaporize, dissociate, and excite copper chloride discharges. Steady state microwaves from 50 to 150 W sustain a microwave discharge which heats and dissociates the copper chloride to a sufficient vapor pressure. A variable frequency (2.45 to 2.60 GHz) pulsed microwave source with pulse widths ranging from 0.5 to 2 ms, repetition rates of 500 to 5000 Hz and a peak output power of 4,500 W then excites the copper atomic states. The two microwave signals are superimposed using a hybrid junction before input into the resonant cavity. Microwave frequencies of the pulsed portion of the signal around 2.50 GHz provided maximum absorption by the discharge. This device is being examined as a potential pump source for a copper vapor laser.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70269/2/RSINAK-63-2-1792-1.pd

Electron density and collision frequency of microwave‐resonant‐cavity‐produced discharges

A review of perturbation diagnostics applied to microwave resonant cavity discharges is presented. The classical microwave perturbation technique examines the shift in the resonant frequency and cavity quality factor of the resonant cavity caused by low‐electron density discharges. However, the modifications presented allow the analysis to be applied to discharges with electron densities beyond the limit predicted by perturbation theory. An ‘‘exact’’ perturbation analysis is presented which models the discharge as a separate dielectric, thereby removing the restrictions on electron density imposed by the classical technique. The ‘‘exact’’ method also uses measurements of the shifts in the resonant conditions of the cavity. Third, an electromagnetic analysis is presented which uses a characteristic equation, based upon Maxwell’s laws, and predicts the discharge conductivity based upon measurements of a complex axial wave number. By allowing the axial wave number of the electromagnetic fields to be complex, the fields are experimentally and theoretically shown to be spatially attenuated. The diagnostics are applied to continuous‐wave microwave (2.45 GHz) discharges produced in an Asmussen resonant cavity. Double Langmuir probes, placed directly in the discharge at the point where the radial electric field is zero, act as a comparison with the analytic diagnostics. Microwave powers ranging from 30 to 100 W produce helium and nitrogen discharges with pressures ranging from 0.5 to 6 Torr. Analysis of the data predicts electron temperatures from 5 to 20 eV, electron densities from 1011 to 3×1012 cm−3, and collision frequencies from 109 to 1011 s−1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69731/2/JAPIAU-74-6-3724-1.pd

A spatially resolved optical emission sensor for plasma etch monitoring

A spatially resolved optical emission spectroscopy sensor has been developed, and the resulting reconstructed radial emission profiles from an ArI and ArII line compare well with Ar sputter etch uniformity profiles. The new sensor collects light from a wedge shaped field of view, and is rotated around a single collection point in order to observe the entire plasma through a relatively small viewpoint. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71036/2/APPLAB-71-11-1467-1.pd

Chamber material effects on actinometric measurements in rf glow discharges

The relative concentration of atomic fluroine was measured in a CF4 rf glow discharge using the actinometric technique. The dependence of fluorine concentration on power, pressure and flow are presented and shown to be dependent upon reactor wall material and electrode material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70093/2/JAPIAU-69-5-2885-1.pd

Radial optical emission profiles of radio frequency glow discharges

Radial optical emission profiles are determined from Abel inverted emission spectroscopy of a parallel plate radio frequency system known as a GEC Reference Cell. These profiles in general show a nonuniform plasma, annular in shape. Etching results of silicon wafers also follow this annular pattern. This effect is explained by numerically computed large radial and axial electric fields near the edge of the electrodes, produced by the presence of the grounded dark shields.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71294/2/JAPIAU-74-5-3590-1.pd

Multipactor experiment on a dielectric surface

A novel experiment to investigate single-surface multipactor on a dielectric surface was developed and tested. The compact apparatus consists of a small brass microwave cavity in a high vacuum system. The cavity is ∼15 cm in length with an outer diameter of ∼10 cm. A pulsed variable frequency microwave source at ∼2.4 GHz, 2 kW peak excites the TE111TE111 mode with a strong electric field parallel to a dielectric plate (∼0.2 cm thickness) that is inserted at midlength of the cavity. The microwave pulses are monitored by calibrated microwave diodes. An electron probe measures electron current and provides temporal measurements of the multipactor electron current with respect to the microwave pulses. Phosphor on the dielectric surface is used to detect multipactor electrons by photoemission. The motivation of this experiment is to test recent theoretical calculations of single-surface multipactor on a dielectric. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71183/2/RSINAK-72-7-3095-1.pd

Energy deposition in metals by laser-guided discharges

Experimental and theoretical results are reported concerning energy deposition on metal surfaces by laser-guided discharges (LGD) in argon and nitrogen at atmospheric pressure. These experiments have demonstrated effective guidance of 30-kV discharges for lengths up to 6 cm. The electron temperature and density have been measured spectroscopically for LGD plasmas. Scaling of the melted metallic mass has been studied as a function of discharge circuit parameters for both argon and nitrogen. Results show that laser-guided discharges in nitrogen couple energy to metal samples more efficiently than argon discharges with identical electrical parameters. This experimentally observed difference in energy deposition has been shown to be in good agreement with a theoretical model which accounts for the recombination energy of nitrogen on the metallic surface. Melting has been accomplished by LGDs in copper, iron, aluminum, and titanium foils. Laser-guided discharges have also bored holes and deposited surface layers of aluminum and titanium onto stainless steel.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45475/1/11090_2004_Article_BF00564625.pd

Relative fluorine concentrations in radio frequency/electron cyclotron resonance hybrid glow discharges

The relative concentration of atomic fluorine was measured in a radio frequency (rf) glow discharge and a modified electron cyclotron resonance microwave/rf hybrid discharge in CF4 using an actinometric technique. The dependence of fluorine concentration on rf and microwave power, pressure, flow, and excitation source are presented. Anomalous behavior with rf power at constant microwave power was observed when using the Ar 750‐nm line as the actinometric species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70900/2/APPLAB-60-7-818-1.pd

Radio-frequency plasma cleaning for mitigation of high-power microwave-pulse shortening in a coaxial gyrotron

Results are reported demonstrating that radio-frequency (rf) plasma cleaning is an effective technique for mitigating microwave-pulse shortening (i.e., lengthening the pulse) in a multimegawatt, large-orbit, coaxial gyrotron. Cleaning plasmas were generated by 50 W of rf power at 13.56 MHz in nitrogen fill gas in the pressure range 15–25 mTorr. Improvements in the averaged microwave energy output of this high-power-microwave device ranged from 15% to 245% for different initial conditions and cleaning protocols. The mechanism for this improvement is believed to be rf plasma sputtering of excess water vapor from the cavity/waveguide and subsequent removal of the contaminant by cryogenic vacuum pumps. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71003/2/APPLAB-77-23-3725-1.pd