Correlation of gas-side heat transfer for axisymmetric rocket engine nozzles

Correlation equations for predicting gas-side heat transfer of axisymmetric rocket engine nozzle

Effect of Ice Formations on Section Drag of Swept NACA 63A-009 Airfoil with Partical-span Leading-edge Slat for Various Modes of Thermal Ice Protection

Studies were made to determine the effect of ice formations on the section drag of a 6.9-foot-chord 36 degree swept NACA 63A-009 airfoil with partial-span leading-edge slat. In general, the icing of a thin swept airfoil will result in greater aerodynamic penalties than for a thick unswept airfoil. Glaze-ice formations at the leading edge of the airfoil caused large increases in section drag even at liquid-water content of 0.39 gram per cubic meter. The use of an ice-free parting strip in the stagnation region caused a negligible change in drag compared with a completely unheated airfoil. Cyclic de-icing when properly applied caused the drag to decrease almost to the bare-airfoil drag value

NACA Research Memorandums

From Summary: "In an effort to increase the operational range of existing small icing tunnels, the use of truncated airfoil sections has been suggested. With truncated airfoils, large-scale or even full-scale wing-icing-protection systems could be evaluated. Therefore, experimental studies were conducted in the NACA Lewis laboratory icing tunnel with an NACA 651-212 airfoil section to determine the effect of truncating the airfoil chord on velocity distribution and impingement characteristics. A 6-foot-chord airfoil was cut successively at the 50- and 30-percent-chord stations to produce the truncated airfoil sections, which were equipped with trailing-edge flaps that were used to alter the flow field about the truncated sections. The study was conducted at geometric angles of attack of 00 and 40, an airspeed of about 156 knots, and volume-median droplet sizes of 11.5 and 18.6 microns. A dye-tracer technique was used in the impingement studies.

NACA Research Memorandums

From Summary: "The effects of primary and runback ice formations on the section drag of a 36 deg swept NACA 63A-009 airfoil section with a partial-span leading-edge slat were studied over a range of angles of attack from 2 to 8 deg and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.39 to 1.23 grams per cubic meter and datum air temperatures from 10 to 25 F. The results with slat retracted showed that glaze-ice formations caused large and rapid increases in section drag coefficient and that the rate of change in section drag coefficient for the swept 63A-009 airfoil was about 2-1 times that for an unswept 651-212 airfoil. Removal of the primary ice formations by cyclic de-icing caused the drag to return almost to the bare-airfoil drag value. A comprehensive study of the slat icing and de-icing characteristics was prevented by limitations of the heating system and wake interference caused by the slat tracks and hot-gas supply duct to the slat. In general, the studies showed that icing on a thin swept airfoil will result in more detrimental aerodynamic characteristics than on a thick unswept airfoil.

NACA Research Memorandums

"Investigations have been made in flight and in wind tunnels to determine which components of turbojet installations are most critical in icing conditions, and to evaluate several methods of icing protection. From these studies, the requirements necessary for adequate icing protection and the consequent penalties on engine performance can be estimated. Because investigations have indicated that the compressor-inlet screen constitutes the greatest icing hazard and is difficult to protect, complete removal or retraction of the screen upon encountering an icing condition is recommended" (p. 1)

Challenging National Narratives: On the Origins of Sweet Potato in China as Global Commodity During the Early Modern Period

The introduction of American cereal crops is probably one of the most important events in China¿s agricultural history, having a great effect on the agriculture production, national life, the transformation of consumer behaviour and, to some extent, the nationalization of consumption. The sweet potato (Ipomoea Batatas L.), in Chinese g¿nsh¿ ¿¿, is a staple food crop for ancient Chinese society. Today it still plays an important role in Chinese daily life, as well as guaranteeing national food security.GECEM Project, Global Encounters between China and Europe: Trade Networks, Consumption and Cultural Exchanges in Macau and Marseille (1680-1840), ERC (European Research Council)- Starting Grant, programa Horizon 2020, número de ref. 679371, www.gecem.eu.Versión del edito

Rise and demise of the global silver standard

In the early modern period, the world economy gravitated around the expansion of long-distance commerce. Together with navigation improvements, silver was the prime commodity which moved the sails of such trade. The disparate availability and the particular demand for silver across the globe determined the participation of producers, consumers, and intermediaries in a growing global economy. American endowments of silver are a known feature of this process; however, the fact that the supply of silver was in the form of specie is a less known aspect of the integration of the global economy. This chapter surveys the production and export of silver specie out of Spanish America, its intermediation by Europeans, and the reexport to Asia. It describes how the sheer volume produced and the quality and consistency of the coin provided familiarity with, and reliability to, the Spanish American peso which made it current in most world markets. By the eighteenth century, it has become a currency standard for the international economy which grew together with the production and coinage of silver. Implications varied according to the institutional settings to deal with specie and foreign exchange in each intervening economy of that trade. Generalized warfare in late eighteenth-century Europe brought down governance in Spanish America and coinage fragmented along with the political fragmentation of the empire. The emergence of new sovereign republics and the end of minting as known meant the cessation of the silver standard that had contributed to the early modern globalization

Can teaching agenda-setting skills to physicians improve clinical interaction quality? A controlled intervention

<p>Abstract</p> <p>Background</p> <p>Physicians and medical educators have repeatedly acknowledged the inadequacy of communication skills training in the medical school curriculum and opportunities to improve these skills in practice. This study of a controlled intervention evaluates the effect of teaching practicing physicians the skill of "agenda-setting" on patients' experiences with care. The agenda-setting intervention aimed to engage clinicians in the practice of initiating patient encounters by eliciting the full set of concerns from the patient's perspective and using that information to prioritize and negotiate which clinical issues should most appropriately be dealt with and which (if any) should be deferred to a subsequent visit.</p> <p>Methods</p> <p>Ten physicians from a large physician organization in California with baseline patient survey scores below the statewide 25th percentile participated in the agenda-setting intervention. Eleven physicians matched on baseline scores, geography, specialty, and practice size were selected as controls. Changes in survey summary scores from pre- and post-intervention surveys were compared between the two groups. Multilevel regression models that accounted for the clustering of patients within physicians and controlled for respondent characteristics were used to examine the effect of the intervention on survey scale scores.</p> <p>Results</p> <p>There was statistically significant improvement in intervention physicians' ability to "explain things in a way that was easy to understand" (p = 0.02) and marginally significant improvement in the overall quality of physician-patient interactions (p = 0.08) compared to control group physicians. Changes in patients' experiences with organizational access, care coordination, and office staff interactions did not differ by experimental group.</p> <p>Conclusion</p> <p>A simple and modest behavioral training for practicing physicians has potential to positively affect physician-patient relationship interaction quality. It will be important to evaluate the effect of more extensive trainings, including those that work with physicians on a broader set of communication techniques.</p