Efficient second harmonic conversion of broad-band high-peak-powerNd:glass laser radiation using large-aperture KDP crystals in quadrature

The authors have investigated the second-harmonic conversion efficiency of broadband Nd:glass laser light (Δν/c<30 cm^-1 FWHM). Using two KDP crystals in a quadrature arrangement, they obtain energy conversion efficiencies of ≈55% with an initial bandwidth for the fundamental of Δν/c≈17 cm^-1 FWHM. For these conditions, a modest increase (≈70%) was observed in the harmonic bandwidth (FWHM) relative to the fundamental. The usual theory of three-wave mixing in dispersive birefringent nonlinear crystals is extended to describe the broadband harmonic conversion process; the generalized theory includes the statistical properties of the light and phase mismatch effects on the spectral components in the complex field amplitudes. Good agreement is found between the code calculations and the measurements     

Ethical Validation: Reframing Research Ethics in Engineering Education Research To Improve Research Quality

Background

Prior to undertaking studies involving human subjects, engineering education researchers are required to consider the ethical implications of their work by obtaining approval from an ethical review board.

Purpose/Hypothesis

Recent research suggests that some unintended consequences of this procedure are that it externalizes and inflexibly formalizes ethical considerations, and limits researchers’ readiness to systematically identify and consider ethical questions that arise while conducting research.

Design/Method

We used a collaborative inquiry approach to examine such ethically important moments that emerged in two of our interpretive research projects. We drew on Walther, Sochacka, and Kellam's framework for interpretive research quality as the departure point for our shared sense‐making process.

Results

Our explorations revealed two insights that connect research ethics to research quality in novel ways. First, we found that the quality of our work improved when we critically explored the intersections between our motivations and intentions for investigating particular research topics and broader cultural agendas and assumptions. Second, we found that when we actively sought to do justice to the participants, co‐investigators, and readers of our research, we were afforded with opportunities to increase the quality of our work, in sometimes quite unexpected ways.

Conclusions

We synthesized the findings from our collaborative inquiry into a process‐oriented model for ethical validation, which we propose as a sixth construct to our prior five‐construct framework for interpretive research quality.     

Enhancing the performance of the EWMA control chart for monitoring the process mean using auxiliary information

When using control charts to monitor manufacturing processes, the exponentially weighted moving average (EWMA) control chart is useful for detecting persistent shifts in the process parameter. This paper proposes enhancements to the applications of the EWMA control chart for those scenarios where the exact measurement of process units is difficult and expensive, but the visual ordering of the units can be done easily. The proposed charts use an auxiliary variable that is correlated with the process variable to provide efficient monitoring of shifts in the process mean and are formulated based on ranked set sampling (RSS) and median RSS schemes (MRSS). Simulation results showed that the proposed charting schemes are more efficient in detecting a shift in the process mean than the classical EWMA control chart and its modification. An example is provided to show the application of the proposed charts using a simulated benchmark process: the continuous stirred tank reactor (CSTR).     

Early results using high-resolution,low-voltage,low-temperature SEM

Recent advances in the design of the scanning electron microscope (SEM) column, such as the coupling of a field-emission gun to a low-aberration immersion lens and the availability of a high-stability cryo-transfer stage, make low-temperature, low-voltage SEM (LTLVSEM) possible at very high resolution. We have used this combination to obtain results with uncoated biological specimens. The trichocyst from a Paramecium was used as a test specimen to observe the shrinkage of this structure as the temperature is raised from 170 K to room temperature following freeze-drying. High-magnification stereo images were obtained of trichocysts that had been prepared by freezing, freeze-substitution and critical-point drying and which were subsequently viewed by LTLVSEM to reduce beam damage and contamination.     

A robust micromanipulator for the scanning electron microscope.

A simple device for holding and moving mechanical tools in the region of a sample being viewed in the scanning electron microscope is described. The unit has a 20:1 mechanical reduction and when fitted with a tungsten carbide dental chisel, it is sufficiently rigid to cut biological hard tissues. Alternately, when fitted with an electro-etched tungsten needle, it can be used, in conjunction with specimen stage controls, to remove individual cells from the surface of soft tissues. Examples of these applications are illustrated.