Determinants of Railroad Capital Structure, 1830-1885

U.S. Railroads suffered repeated financial crises in the 19th and 20th Centuries. These crises were caused by a combination of high debt levels and strongly procyclical revenues and profits. Given the inherent instability of profits, why did railroads depend primarily on debt to finance their initial growth? I find that, over 1830-1885, railroads faced significant agency and control problems, which were partially mitigated by the use of debt. Around 1885, new developments reinforced the initial tendency towards debt-heavy capital structures.

Direct emissivity measurements on liquids and corrections to multi-color pyrometers

Optical pyrometry provides a means for non-contact temperature measurements whose accuracy depends on the accuracy with which specimen emittance is known. Two methods for obtaining the required emittance data are discussed in which the emittance is determined from measurements of the wavelength or polarization dependence of light emitted by the specimen. The spectral technique, multi-color pyrometry, yields apparent values for specimen emittance and temperature from emitted intensity measurements at two or more wavelengths. Emittance corrections cannot be eliminated by increasing the number of spectral intensity measurements required by an n-color pyrometer. Even if this were possible, the accuracy of temperature measurements by n-color pyrometry decreases with n such that pyrometers that require four intensity measurements would be impractical. In contrast, emittance values and corrections for one-color pyrometers can be accurately measured by the polarized light technique. The polarized light technique involves measurement of the degree of polarization for light emitted at an angle of 45 deg to the specimen normal. The reflectivities (r) for light polarized parallel (p) and normal (n) to the plane of emission are related by r(p) = r(n) squared. This leads to a simple relation between the intensity ratio for light emitted in the two polarized states and the emittance, i.e., e(n) = 2 - I(p)/I(n). The true specimen temperature is also obtained if absolute intensities are measured. Delvelopment of the polarized light technique in combination with one-color optical pyrometry is recommended to achieve accurate non-contact temperature measurements on liquids

Containerless high temperature property measurements by atomic fluorescence

Laser induced fluorescence (LIF) techniques for containerless study of high temperature processes and material properties was studied. Gas jet and electromagnetic levitation and electromagnetic and laser heating techniques are used with LIF in earth-based containerless high temperature experiments. Included are the development of an apparatus and its use in the studies of (1) chemical reactions on Al2O3, molybdenum, tungsten and LaB6 specimens, (2) methods for noncontact specimen temperature measurement, (3) levitation jet properties and (4) radiative lifetime and collisional energy transfer rates for electronically excited atoms

A New Framework for Unsupervised Semantic Discovery

This paper presents a new framework for the unsupervised discovery of semantic information, using a divide-and-conquer approach to take advantage of contextual regularities and to avoid problems of polysemy and sublanguages. Multiple sets of documents are formed and analyzed to create multiple sets of frames. The overall procedure is wholly unsupervised and domain independent. The end result will be a collection of sets of semantic frames that will be useful in a wide range of applications, including question-answering, information extraction, summarization and text generation

Early Design Challenges in Developing a Reacting to the Past Game

This paper discusses challenges the author encountered in the early stages of designing a Reacting to the Past role-playing game for the college classroom, including how to balance precise historical accuracy with counterfactual elements that add excitement to game play. Reacting to the Past is a high impact pedagogy that is attracting a growing following, and this paper fills a void in academic scholarship on the challenges and pitfalls encountered in early game desig