Proto-Model of an Infrared Wide-Field Off-Axis Telescope

We develop a proto-model of an off-axis reflective telescope for infrared wide-field observations based on the design of Schwarzschild-Chang type telescope. With only two mirrors, this design achieves an entrance pupil diameter of 50 mm and an effective focal length of 100 mm. We can apply this design to a mid-infrared telescope with a field of view of 8 deg X 8 deg. In spite of the substantial advantages of off-axis telescopes in the infrared compared to refractive or on-axis reflective telescopes, it is known to be difficult to align the mirrors in off-axis systems because of their asymmetric structures. Off-axis mirrors of our telescope are manufactured at the Korea Basic Science Institute (KBSI). We analyze the fabricated mirror surfaces by fitting polynomial functions to the measured data. We accomplish alignment of this two-mirror off-axis system using a ray tracing method. A simple imaging test is performed to compare a pinhole image with a simulated prediction.Comment: 14 pages, 16 figure

Teachers’ Monitoring and Schools’ Performance: Evidence from Public Schools in Pakistan

This paper evaluates the impact of an innovative monitoring system on teacher attendance and school performance in Pakistan. In 2014, the government in Khyber Pakhtunkhwa province introduced the Independent Monitoring Project aiming at increasing teacher attendance in primary and secondary public schools by distributing to the government-hired monitors smart phones with a special data collection software installed. Our analysis is based on a difference-in-differences approach using the country wide Annual Status of Education Report from 2012 to 2016. Our findings suggest that monitoring of government schools has increased teacher attendance by 7.5 percentage points in the first year of intervention. But the positive effect wears off to 2.7 percentage points in the second year. Child attendance and test scores also increased in the first year, but in the second year they disappeared. Especially, in the first year, the monitoring system improved students’ math, reading, and English test scores by 0.13, 0.14, and 0.15 standard deviation, respectively, if they are grades 1-5. This result suggests that teacher attendance has an important role in delivering better student outcomes, but that monitoring should be coupled with appropriate incentive mechanism in order to have a lasting impact

Spatially resolved penetration depth measurements and vortex manipulation in the ferromagnetic superconductor ErNi2B2C

We present a local probe study of the magnetic superconductor, ErNi$_2$B$_2$C, using magnetic force microscopy at sub-Kelvin temperatures. ErNi$_2$B$_2$C is an ideal system to explore the effects of concomitant superconductivity and ferromagnetism. At 500 mK, far below the transition to a weakly ferromagnetic state, we directly observe a structured magnetic background on the micrometer scale. We determine spatially resolved absolute values of the magnetic penetration depth $\lambda$ and study its temperature dependence as the system undergoes magnetic phase transitions from paramagnetic to antiferromagnetic, and to weak ferromagnetic, all within the superconducting regime. In addition, we estimate the absolute pinning force of Abrikosov vortices, which shows a position- and temperature dependence as well, and discuss the possibility of the purported spontaneous vortex formation