Two-Mirror Apodization for High-Contrast Imaging

Direct detection of extrasolar planets will require imaging systems capable of unprecedented contrast. Apodized pupils provide an attractive way to achieve such contrast but they are difficult, perhaps impossible, to manufacture to the required tolerance and they absorb about 90% of the light in order to create the apodization, which of course lengthens the exposure times needed for planet detection. A recently proposed alternative is to use two mirrors to accomplish the apodization. With such a system, no light is lost. In this paper, we provide a careful mathematical analysis, using one dimensional mirrors, of the on-axis and off-axis performance of such a two-mirror apodization system. There appear to be advantages and disadvantages to this approach. In addition to not losing any light, we show that the nonuniformity of the apodization implies an extra magnification of off-axis sources and thereby makes it possible to build a real system with about half the aperture that one would otherwise require or, equivalently, resolve planets at about half the angular separation as one can achieve with standard apodization. More specifically, ignoring pointing error and stellar disk size, a planet at $1.7 \lambda/D$ ought to be at the edge of detectability. However, we show that the non-zero size of a stellar disk pushes the threshold for high-contrast so that a planet must be at least $2.5 \lambda/D$ from its star to be detectable. The off-axis analysis of two-dimensional mirrors is left for future study.Comment: 21 pages, 7 figures. For author's webpage version see http://www.orfe.princeton.edu/~rvdb/tex/piaa/ms.pdf This version has improved figures and addresses comments of a refere

Tariff-jumping FDI and Domestic Firms' Profits

Studies of the welfare implications of trade policy often do not take account of the potential for tariff-jumping FDI to mitigate positive gains to domestic producers. We use event study methodology to examine the market effects for U.S. domestic firms that petitioned for antidumping (AD) relief, as well as the effect of announcements of FDI by their foreign rivals in the U.S. market on these U.S. petitioning firms. On average, affirmative U.S. AD decisions are associated with 3% abnormal gains to a petitioning firm when there is no tariff-jumping FDI, but no abnormal gains if there is tariff-jumping FDI. The evidence for this mitigating effect is strongest when announcements of the intended tariff-jumping FDI have already occurred before an AD decision takes place, which happened in a fair number of cases. We also find evidence that the announcements of plant expansions (and, to some extent, new plants) have significantly larger negative effects on U.S. domestic firms' profits than other types of FDI, including acquisitions and joint ventures.

Study of shuttle imaging microwave system antenna. Volume 1: Conceptual design

A detailed preliminary design and complete performance evaluation are presented of an 11-channel large aperture scanning radiometer antenna for the shuttle imaging microwave system (SIMS) program. Provisions for interfacing the antenna with the space shuttle orbiter are presented and discussed. A program plan for hardware development and a rough order of magnitude (ROM) cost are also included. The conceptual design of the antenna is presented. It consists of a four-meter diameter parabolic torus main reflector, which is a graphite/epoxy shell supported by a graphite/epoxy truss. A rotating feed wheel assembly supports six Gregorian subreflectors covering the upper eight frequency channels from 6.6 GHz through 118.7 GHz, and two three-channel prime forms feed assemblies for 0.6, 1.4, and 2.7 GHz. The feed wheel assembly also holds the radiometers and power supplies, and a drive system using a 400 Hz synchronous motor is described. The RF analysis of the antenna is performed using physical optics procedures for both the dual reflector Gregorian concept and the single reflector prime focus concept. A unique aberration correcting feed for 2.7 GHz is analyzed. A structural analysis is also included. The analyses indicate that the antenna will meet system requirements

Spectral Evolution of an Earth-Like Planet

We have developed a characterization of the geological evolution of the Earths atmosphere and surface in order to model the observable spectra of an Earth-like planet through its geological history. These calculations are designed to guide the interpretation of an observed spectrum of such a planet by future instruments that will characterize exoplanets. Our models focus on spectral features that either imply habitability or are required for habitability. These features are generated by H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface albedos. We chose six geological epochs to characterize. These epochs exhibit a wide range in abundance for these molecules, ranging from a CO2 rich early atmosphere, to a CO2/CH4-rich atmosphere around 2 billion years ago to a present-day atmosphere. We analyzed the spectra to quantify the strength of each important spectral feature in both the visible and thermal infrared spectral regions, and the resolutions required to unambiguously observe the features for each epoch. We find a wide range of spectral resolutions required for observing the different features. For example, H2O and O3 can be observed with relatively low resolution, while O2 and N2O require higher resolution. We also find that the inclusion of clouds in our models significantly affects both the strengths and resolutions required to observe all spectral features.Comment: 34 pages, 24 fig, pdf, ApJ, TB

Some Confusing Matters Relating to Arbitration in Washington

A review of the case law and statutes of the state of Washington relating to arbitration points up several issues which are of importance to those who may become concerned with arbitrations in the state of either commercial or labor controversies. Some of these issues result from the views which were advanced by the supreme court relating to the arbitration statute of 1881. These issues are still open, although that statute was repealed by the present act, which was originally enacted in 1943. Other uncertainties inhere in the views which have been advanced by the court since the enactment of the present arbitration statute, and still others relate to the intent of the statute after the 1947 amendment of the first section. These matters of uncertainty are bound to plague any lawyer who is called upon to advise any client whether or not to enter upon any arbitration agreement or upon any arbitration. And in the case of employees (or their union) and employers who would agree upon grievance machinery and arbitration provisions in their collective agreements, there is question whether or not their agreement or any arbitrations or awards thereunder will be honored by the courts. These questions may be summarized as follows: 1. Does the present arbitration statute operate to exclude common law arbitration, or may the parties elect to arbitrate under the statute or at common law? 2. May employers and their employees (or their unions) qualify their agreements for grievance procedures and arbitration under the present statute? What are the consequences of their arbitration agreements and any arbitrations and awards thereunder

Freeze Thaw Durability of Internally Cured Concrete Made Using Superabsorbent Polymers

The use of superabsorbent polymers (SAPs) to produce internally cured concrete has been shown to be effective in reducing the potential for restrained shrinkage cracking of high performance concrete mixtures. However, not much is known regarding the freeze–thaw durability of concrete mixtures that incorporate SAPs for internal curing (IC). When SAP particles desorb (or partially desorb) the “water” (pore fluid) they contain for the purposes of IC, some believe that the void space created by these particles can provide enough empty voids to accommodate the additional volume caused by water expansion upon freezing. This paper investigates the freeze–thaw durability of internally cured concrete by the use of SAPs. It has been shown that internally cured concretes made using SAP demonstrate good freeze–thaw performance when the concrete is air entrained. When the SAP was used in concrete without air entrainment it did not provide sufficient freeze–thaw durability

Leading Transportation Indicators: Forecasting Waterborne Commerce Statistics Using Lock Performance Data

This paper develops and applies a forecasting model for transportation data based on the leading economic indicators literature. The specific application is to forecast river tonnages. Waterborne commerce data reflect tonnages of commodities moved on various rivers and in various directions. They are released after the Lock Performance Monitoring System data which reflect tonnages moving through specific locks. The model presented here forecasts waterborne commerce data from lock performance data. The results suggest that even a very simple model can provide precise forecasts