Elementary Teacher Candidates’ Flexibility with Comparing Fractions

The teaching and learning of fractions have been persistent challenges, and data on national assessments continue to show students’ difficulties with fractions. The Common Core State Standards have provided a new lens for the study of fractions, and with it a need to update teacher candidates’ mathematical knowledge for teaching. Fractions are a challenge for mathematics teacher educators working with teacher candidates. Exploring instructional approaches to building teacher candidate understanding is important. Technology could play an important role in building robust teacher candidates’ conceptual understanding of fractions. Whitacre & Nickerson’s (2016) framework provides background knowledge for exploring whether technology can promote flexible strategies for comparing fractions. In this study, we examine the impact on teacher candidates’ flexibility with solving fraction comparison problems through the use of a sequenced set of interactive dynamic technology-based learning experiences modeling the approach advocated in the Common Core Standards. Keywords: fractions, technology, elementary teacher DOI: 10.7176/JEP/11-9-01 Publication date:March 31st 2020

Commissioning results of the HZB Quadrupole Resonator

Recent cavity results with niobium have demonstrated the necessity of a good understanding of both the BCS and residual resistance. For a complete picture and comparison with theory, it is essential that one can measure the RF properties as a function of field, temperature, frequency and ambient magnetic field. Standard cavity measurements are limited in their ability to change all parameters freely and in a controlled manner. On the other hand, most sample measurement setups operate at fairly high frequency, where the surface resistance is always BCS dominated. The quadrupole resonator, originally developed at CERN, is ideally suited for characterization of samples at typical cavity RF frequencies. We report on a modified version of the QPR with improved RF figures of merit for high field operation. Experimental challenges in the commissioning run and alternate designs for simpler sample changes are shown alongside measurement results of a large grain niobium sampl

R&D ERL: Photocathode Deposition and Transport System

The purpose of the photocathode deposition and transport system is to (1) produce a robust, high yield multialkali photocathode and (2) have a method of transporting the multialkali photocathode for insertion into a super conducting RF electron gun. This process is only successful if a sufficient quantum efficiency lifetime of the cathode, which is inserted in the SRF electron gun, is maintained. One important element in producing a multialkali photocathode is the strict vacuum requirements of 10{sup -11} torr to assure success in the production of longlived photocathodes that will not have their QE or lifetime depleted due to residual gas poisoning in a poor vacuum. A cutaway view of our third generation deposition system is shown in figure 1. There are certain design criteria and principles required. One must be able to install, remove, rejuvenate and replace a cathode without exposing the source or cathode to atmosphere. The system must allow one to deposit Cs, K, and Sb on a cathode tip surface at pressures in the 10{sup -10} to 10{sup -9} torr range. The cathode needs to be heated to as high as 850 C for cleaning and maintained at 130 C to 150 C during deposition. There should also be the capability for in-situ QE measurements. In addition the preparation of dispenser photocathodes must be accounted for, thus requiring an ion source for cathode cleaning. Finally the transport cart must be mobile and be able to negotiate the ERL facility labyrinth

A Preliminary List of the Ants of Wisconsin

Author Institution: Entomologist of The University of Idaho, Moscow, Idaho ; Of The Truck Crop Insect Investigations, U. S. Department of Agriculture, Baton Rouge, La

RF Measurements of the 1.6 cell Lead Niobium Photoinjector in HoBiCat

The development of a simple and robust SRF photoinjector capable of delivering 1 mA average current in c.w. operation continues to advance with the horizontal RF testing of the 1.6 cell Pb Nb hybrid photoinjector. This injector utilizes a sputtered lead coating on a removable Nb cathode plug as the photoelectron source and has recently been tested in the horizontal test cryostat facility, HoBiCaT, at Helmholtz Zentrum Berlin. In this paper we will report on the status of these RF measurements and compare the performance to previous vertical RF tests performed at Jefferson Laboratory. We will also provide a summary of the cavity tuning range and microphonics measurements now that it has been installed into a helium vessel equipped with a Saclay style tuner

Pasture management for reduced weed problems

Last page of this document published June 1992. Written by Stanley W. Fultz, John Williams and Larry C. Burrill

R&D ERL: Photocathode Deposition and Transport System

The purpose of the photocathode deposition and transport system is to (1) produce a robust, high yield multialkali photocathode and (2) have a method of transporting the multialkali photocathode for insertion into a super conducting RF electron gun. This process is only successful if a sufficient quantum efficiency lifetime of the cathode, which is inserted in the SRF electron gun, is maintained. One important element in producing a multialkali photocathode is the strict vacuum requirements of 10{sup -11} torr to assure success in the production of longlived photocathodes that will not have their QE or lifetime depleted due to residual gas poisoning in a poor vacuum. A cutaway view of our third generation deposition system is shown in figure 1. There are certain design criteria and principles required. One must be able to install, remove, rejuvenate and replace a cathode without exposing the source or cathode to atmosphere. The system must allow one to deposit Cs, K, and Sb on a cathode tip surface at pressures in the 10{sup -10} to 10{sup -9} torr range. The cathode needs to be heated to as high as 850 C for cleaning and maintained at 130 C to 150 C during deposition. There should also be the capability for in-situ QE measurements. In addition the preparation of dispenser photocathodes must be accounted for, thus requiring an ion source for cathode cleaning. Finally the transport cart must be mobile and be able to negotiate the ERL facility labyrinth