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This article considers logistics and supply in the China Relief Expedition. In the China campaign, as in all armed conflicts, the availability of matériel and subsistence determined what military options were available to commanders. In 1900, because of a strong industrial base and a burgeoning logistical network, the US Army, Marine Corps, and Navy demonstrated an increased capacity and capability to project power on hemispheric scales. Throughout the entirety of their intervention in China, Americans moved animals, artillery, medical supplies, men, ordnance, and subsistence across great distances – over sea and land, to and within the theatre of operations – with remarkable efficiency under difficult conditions. Thus, the China Relief Expedition was instructive for the US profession of arms, and pointed to a future in which large-scale combat operations on land and at sea would require careful integration and more extensive logistical support than military operations of nineteenth-century conflicts.

Mathematical education is currently undergoing significant changes that are driven by technology and digital-based learning. Students with visual impairments (VI) may face different challenges in mathematical education due to a lack of accessible materials designed to support the development of conceptual understanding in mathematics. The aim of the study was to summarize current evidence-based knowledge about e-learning in mathematics among students with severe VI. A systematic review was conducted of articles published from January 2000 to November 2017. A total of 13 publications met the inclusion criteria, of which 12 reported studies with an intervention or an experimental design and one had a cross-sectional design. The number of students with VI varied from three to 16 (Mage = 19 years). Four publications reported either ophthalmic diagnoses or World Health Organization’s (WHO) definition of vision loss. The mathematical training was reported as lasting from one session to 18 weeks of training. Eight papers reported the use of audio-based applications as learning aids. The authors conclude that interactive e-learning with audio and tactile learning programmes may be a useful resource for students with VI to enhance their mathematical skills. However, there is lack of evidence for how digital technologies improve inclusion potentials and learning in mathematics for students with VI, and hence, there is a need for additional research and more reflection on the subject. © 2019. This is the authors' accepted and refereed manuscript to the article. The final authenticated version is available online at: https://doi.org/10.1177%2F0264619619876975

At the time of his death at the Battle of Gettysburg, General Reynolds was the highest-ranking Union officer killed in the American Civil War. The return of the General’s body from the batt...

The aim of the study was to conduct a systematic review in order to synthesize the evidence-based literature on mathematics education among students with visual impairment (VI). Studies were identified through searches of electronic databases (SCOPUS, PubMed, ERIC, and Web of Science). The authors included articles published between 1 January 2000 and 31 October 2017. Eleven publications met the inclusion criteria, and seven studies had observational designs. The studies focused on teachers’ attitudes and experiences, the use of abacus, tactile graphics, and the development of mathematical concepts. The results showed that the studies had different aims and methods, and only four studies reported eye disorder diagnoses. The ability to choose suitable teaching strategies that involve individual instructions requires qualified and enthusiastic teachers who allow students to experience a sense of accomplishment and success. Additionally, it is important to gain information on eye disorder diagnoses and possible learning disabilities. The authors conclude that it is to be expected that students with VI but without cognitive disabilities will follow their grade level in mathematics. The findings highlight the need for more randomly controlled, high quality trials in order to obtain more evidence and knowledge of mathematics education among students with VI. © 2019 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license.

Summary Background Treatment guidelines for aphasia recommend intensive speech and language therapy for chronic (≥6 months) aphasia after stroke, but large-scale, class 1 randomised controlled trials on treatment effectiveness are scarce. We aimed to examine whether 3 weeks of intensive speech and language therapy under routine clinical conditions improved verbal communication in daily-life situations in people with chronic aphasia after stroke. Methods In this multicentre, parallel group, superiority, open-label, blinded-endpoint, randomised controlled trial, patients aged 70 years or younger with aphasia after stroke lasting for 6 months or more were recruited from 19 inpatient or outpatient rehabilitation centres in Germany. An external biostatistician used a computer-generated permuted block randomisation method, stratified by treatment centre, to randomly assign participants to either 3 weeks or more of intensive speech and language therapy (≥10 h per week) or 3 weeks deferral of intensive speech and language therapy. The primary endpoint was between-group difference in the change in verbal communication effectiveness in everyday life scenarios (Amsterdam–Nijmegen Everyday Language Test A-scale) from baseline to immediately after 3 weeks of treatment or treatment deferral. All analyses were done using the modified intention-to-treat population (those who received 1 day or more of intensive treatment or treatment deferral). This study is registered with ClinicalTrials.gov, number NCT01540383. Findings We randomly assigned 158 patients between April 1, 2012, and May 31, 2014. The modified intention-to-treat population comprised 156 patients (78 per group). Verbal communication was significantly improved from baseline to after intensive speech and language treatment (mean difference 2·61 points [SD 4·94]; 95% CI 1·49 to 3·72), but not from baseline to after treatment deferral (−0·03 points [4·04]; −0·94 to 0·88; between-group difference Cohen's d 0·58; p=0·0004). Eight patients had adverse events during therapy or treatment deferral (one car accident [in the control group], two common cold [one patient per group], three gastrointestinal or cardiac symptoms [all intervention group], two recurrent stroke [one in intervention group before initiation of treatment, and one before group assignment had occurred]); all were unrelated to study participation. Interpretation 3 weeks of intensive speech and language therapy significantly enhanced verbal communication in people aged 70 years or younger with chronic aphasia after stroke, providing an effective evidence-based treatment approach in this population. Future studies should examine the minimum treatment intensity required for meaningful treatment effects, and determine whether treatment effects cumulate over repeated intervention periods. Funding German Federal Ministry of Education and Research and the German Society for Aphasia Research and Treatment.

This PhD project focuses on mathematics education and braille-reading students in primary school, and thus the thesis is centered at the intersection between mathematics education research and the field of visual impairment studies.The thesis builds on the perspective that mathematics is a language that (sighted) people have developed and continue to develop in order to understand and solve problems in the physical and mental world. On this basis it is argued that mathematics is important for both social participation and independence.The aims of the project are a) to elucidate the heterogeneity among students with visual impairment, and to investigate if a pattern exists in relation to student characteristics and whether student have followed the normal age progression in mathematics education, and b) to provide knowledge about the learning of basic geometry concepts.The PhD project has a research design with mixed methods and both quantitative and qualitative data. The project is based on two studies that are discussed in a comprehensive approach at the end of the thesis. Central in both studies is the dichotomy between attaining and not attaining an educational grade level in school mathematics.The first study (a) has a retrospective population-based study design, with the goal to include all students that have received education in braille from 1967 to 2007.We identified 287 students that had received braille education over forty years. During the above mentioned four decades, there was some variation in the distribution of different diagnoses. The examination of mathematics education is based on data from 248 students, and of these, 57% (141 students) followed standardized educational level. The material shows no significant differences between girls and boys. Students with diagnoses related to the central nervous system had a comparatively higher risk of not attaining their normal grade level in mathematics.A principal finding of the study is that vision is not a prerequisite for following grade-level education in mathematics. Rather than focus on blindness itself as the main causal factor related to the ability to engage in mathematics thinking, it is more appropriate to look for other factors. These findings intensify the need to receive comprehensive and appropriate services from specialists. The challenge is to improve teaching methods and materials that draw on research on how braille students learn.The second study (b) is an educational experiment conducted as a geometry course for students in the fourth and fifth grades. This study indicates that skilled students complement their multiple manual explorations with body movements and postures that correspond to characteristic features of the shape of objects. The students typically rotate small, three-dimensional objects and experiment with the objects’ point of balance. Video recordings show that they continually measure geometric properties, such as length and size related to the units in their own body. Thus the study makes a powerful claim for the idea of embodied mathematics. However, the educational experiment also shows that even if a student can recognize shapes of small prototypes, this is not fully reliable for assessing geometric understanding.The project provides the basis to go thoroughly into theories of geometry learning for sighted students, with hypotheses about how students with visual impairments learn to think geometrically. A central hypothesis is that the theory must be extended with a “pre-geometric level” of geometric understanding. At this level a child/student learns to recognize tactile qualities of objects and also experience through the body that physical objects have surfaces, curves, edges and areas. Students who are visually impaired should be challenged to use geometric concepts in different contexts and in activities with both small and large objects to enable them to build up a repertoire of situations in which the concepts are used.

Introduction The study presented here estimated the occurrence of braille-reading students in Norway who were educated according to their grade-level progression in mathematics from 1967 to 2007. It also analyzed the association among these students’ progression in mathematics and the causes of visual impairment, the age at which the diagnosis was established, the students’ gender, and the students’ use of reading media (braille as the sole, primary, or secondary literacy medium). Methods A retrospective, population-based study design was used. All the students who had received braille education in the past four decades prior to the study were included. The following data were abstracted from each student's records: birth year, country of birth, gender, year diagnosed, diagnosis, type of reading media, and whether the student's education had followed their grade-level progression. Results In total, 248 braille-reading students were identified. Of these students, 141 (57%) had been taught mathematics at grade level. In 19 of the 45 principal eye diagnoses that were registered, all the students were educated according to the normative grade progress in mathematics. There were no statistically significant associations between gender and the abstracted variables or between mathematics education and reading media. Discussion During the four decades under study, there was some variation in the distribution of different diagnoses. Students with diagnoses related to the central nervous system had a comparatively higher risk of not attaining their normal grade level in mathematics. Implication for practitioners Teachers may expect that a braille-reading student will follow his or her grade level in mathematics. It is essential, however, to gain information on the causes of visual impairment, in general, and in cases of the co-occurrence of visual impairment and learning disabilities, in particular. It is essential to document typical learning patterns among braille-reading students and intervention strategies for students with visual impairments and learning disabilities.

It has become fashionable for scholars of Anglo-American religious history to emphasize English anti-Catholic sentiment in the new world. Recent studies from such scholars as Thomas Kidd, Owen Stan...

This PhD project focuses on mathematics education and braille-reading students in primary school, and thus the thesis is centered at the intersection between mathematics education research and the field of visual impairment studies.The thesis builds on the perspective that mathematics is a language that (sighted) people have developed and continue to develop in order to understand and solve problems in the physical and mental world. On this basis it is argued that mathematics is important for both social participation and independence.The aims of the project are a) to elucidate the heterogeneity among students with visual impairment, and to investigate if a pattern exists in relation to student characteristics and whether student have followed the normal age progression in mathematics education, and b) to provide knowledge about the learning of basic geometry concepts.The PhD project has a research design with mixed methods and both quantitative and qualitative data. The project is based on two studies that are discussed in a comprehensive approach at the end of the thesis. Central in both studies is the dichotomy between attaining and not attaining an educational grade level in school mathematics.The first study (a) has a retrospective population-based study design, with the goal to include all students that have received education in braille from 1967 to 2007.We identified 287 students that had received braille education over forty years. During the above mentioned four decades, there was some variation in the distribution of different diagnoses. The examination of mathematics education is based on data from 248 students, and of these, 57% (141 students) followed standardized educational level. The material shows no significant differences between girls and boys. Students with diagnoses related to the central nervous system had a comparatively higher risk of not attaining their normal grade level in mathematics.A principal finding of the study is that vision is not a prerequisite for following grade-level education in mathematics. Rather than focus on blindness itself as the main causal factor related to the ability to engage in mathematics thinking, it is more appropriate to look for other factors. These findings intensify the need to receive comprehensive and appropriate services from specialists. The challenge is to improve teaching methods and materials that draw on research on how braille students learn.The second study (b) is an educational experiment conducted as a geometry course for students in the fourth and fifth grades. This study indicates that skilled students complement their multiple manual explorations with body movements and postures that correspond to characteristic features of the shape of objects. The students typically rotate small, three-dimensional objects and experiment with the objects’ point of balance. Video recordings show that they continually measure geometric properties, such as length and size related to the units in their own body. Thus the study makes a powerful claim for the idea of embodied mathematics. However, the educational experiment also shows that even if a student can recognize shapes of small prototypes, this is not fully reliable for assessing geometric understanding.The project provides the basis to go thoroughly into theories of geometry learning for sighted students, with hypotheses about how students with visual impairments learn to think geometrically. A central hypothesis is that the theory must be extended with a “pre-geometric level” of geometric understanding. At this level a child/student learns to recognize tactile qualities of objects and also experience through the body that physical objects have surfaces, curves, edges and areas. Students who are visually impaired should be challenged to use geometric concepts in different contexts and in activities with both small and large objects to enable them to build up a repertoire of situations in which the concepts are used.

FS CMa type stars are a group of Galactic objects with the B[e] phenomenon. They exhibit strong emission-line spectra and infrared excesses, which are most likely due to recently formed circumstellar dust. The group content and identification criteria were described in the first two papers of the series. In this paper we report our spectroscopic and photometric observations of the optical counterpart of IRAS 00470+6429 obtained in 2003--2008. The optical spectrum is dominated by emission lines, most of which have P Cyg type profiles. We detected significant brightness variations, which may include a regular component, and variable spectral line profiles in both shape and position. The presence of a weak Li {\sc I} 6708 \AA line in the spectrum suggests that the object is most likely a binary system with a B2--B3 spectral type primary companion of a luminosity $\log$ L/L$\odot$ = 3.9$\pm$0.3 and a late-type secondary companion. We estimate a distance toward the object to be 2.0$\pm$0.3 kpc from the Sun., Comment: 37 pages, 13 figures

An isochoric apparatus and a densimeter with a magnetic suspension coupling were used to measure the density of dry air at (10, 30, 75, and 120) kg·m -3 . The results are compared with the Zittau database (Kretzschmar, H.-J., et al. Property Data Base for Humid Air, version 2.0; 2004) and the work of Lemmon et al. (Lemmon, E. W., et al. J. Chem. Ref. Data 2000, 29, 331-384) (NIST standard reference database REFPROP 7.0) as well. The humid air was obtained by adding the synthetic air to a gravitationally determined amount of water. It is important to avoid condensation in the part of the apparatus permanently connected to the measuring cell. For that reason, measurements on humid air were carried out using the isochoric apparatus only. Four isochores were measured in the gaseous region at (30, 60, 86, and 107) kg·m -3 with a mole fraction of water in humid air of (4.45, 4.46, 4.20, and 1.26) %. The results are compared with the Zittau database.

PurposeThe use of alternative oils for the lubrication of automobile engines has a potential of ecological and technical advantages. It requires the detailed knowledge of several thermophysical and viscosimetric properties in a large temperature range.Design/methodology/approachFor 11 different oils, the density, the heat capacity, the thermal conductivity, the viscosity at ambient pressure and the pressure‐viscosity at maximal 1,000 bar have been measured. The latter has been measured with a newly developed apparatus which is described in detail. Two hydrocarbon‐based factory‐fill oils and nine alternative oils have been tested. Five of the alternative oils are based partly or completely on esters, the other four on polyglycols, one of them additionally on water.FindingsData for thermophysical and viscosimetric properties are given in form of diagrams and tables. The consequences for the cooling capacity and the film forming behavior are discussed. The latter is only slightly better for the factory‐fill oils, compared to the alternative oils.Research limitations/implicationsThe pressure‐viscosity is measured at up to 1,000 bar, which is lower than the maximum pressure in the tribological contacts of an engine.Practical implicationsThe published data can be used to calculate tribological contacts which are lubricated with alternative engine oils or with actually used factory‐fill oils. This might help to decide if esters or polyglycols are superior as engine oils.Originality/valueThe results of this test program might be helpful for engineers who are interested in using alternative lubricants in tribosystems.

The present paper describes experiments carried out with a 40-mm regenerative liquid-propellant gun at the Ernst-Mach-Institut and lumped parameter representations of the gun performance developed at WDT 91. The test fixture is equipped with a 2.53 m smooth-bore gun tube and fires conventional 40-mm projectiles of 0.936 kg mass. It has an initial gun chamber volume of 219 cm3 and a reservoir of 575 cm3. A two-piston system, an in-line annular injector with a fixed center piston, are used for liquid propellant injection. The differential area ratio is 2 : 1. The pyrotechnic igniter (DM 1101 primer) supported by a priming charge of 6 g black powder combined with 30 cm3 liquid-propellant containing 80 weight% nitromethane and 20 weight% methanol (type NM/M 80/20) starts piston motion and ignites the injected liquid-propellant jet. Experimental analysis of gun performance is based on pressure measurements in the reservoir and combustion chamber as well as at the muzzle, inductive recordings of injection piston travel, microwave interferometer (5 GHz) measurements of in-bore projectile motion, and inductive measurements of projectile launch velocity. When firing the gun with a charge of 550 cm3 of the liquid propellant type NM/M 70/30, which has a relatively low energy content, then maximum pressures are of the order of 480 MPa in the reservoir, 400 MPa in the combustion chamber, and 50 MPa at the muzzle. Pressure oscillations are superimposed to the pressure recordings which, in the combustion chamber, go up to 250 MPa with a leading frequency of 28 kHz. The projectile launch velocity is 950 m/s. The lumped parameter modeling represents quite well the measured gun performance. It supports gun design and can be used for parameter studies, if properly adjusted to droplet burning. For example, effects caused by variations in the vent area have been simulated. Die vorliegende Veroffentlichung beschreibt Experimente des Ernst-Mach-Institutes mit einer regenerativen Flussigtreibstoffwaffe vom Kaliber 40 mm sowie die Ergebnisse von Rechnungen mit einem einfachen Modell (Lumped-Parameter Modell), die bei der WTD 91 durchgefuhrt worden sind. Die Regenerativwaffe enthalt ein Glattrohr von 2,53 m Lange und feuert ein konventionelles 40-mm Projektil von 0,936 kg Gewicht. Der Verbrennungsraum hat ein Anfangsvolumen von 219 cm3und ein Reservoir von 575 cm3. Ein System mit zwei Kolben, ein feststehender Mittelkolben und ein beweglicher Injektionskolben wird fur die Einspritzung des Flussigtreibstoffes verwendet. Das differentielle Flachenverhaltnis betragt 2 : 1. Der pyrotechnische Anzunder DM 1101 mit einer Beiladung von 6 g Schwarzpulver und 30 cm3Flussigtreibstoff bestehend aus 80 Gew.% Nitromethan und 20 Gew.% Methanol (NM/M 80/20) setzt den Kolben in Bewegung und sorgt fur die Anzundung des injizierten Flussigtreibstoffstrahles. Die experimentelle Analyse des Schusverhaltens basiert auf Ergebnissen von Druckmessungen im Reservoir, im Verbrennungsraum und an der Mundung, auf der induktiven Aufzeichnung der Kolbenbewegung, auf der Mikrowelleninterferometrie (5 GHz) der Geschosbewegung im Rohr und aufder induktiven Messung der Abgangsgeschwindigkeit des Projektiles. Wenn man die Waffe mit einer Ladung von 550 cm3der relativ ernergieschwachen Flussigtreibstoffmischung NM/M 70/30 betreibt, so erhalt man Maximaldrucke von 480 MPa im Reservoir, 400 MPa im Verbrennungsraum und 50 MPa an der Rohrmundung. Druckoszillationen mit Amplituden bis zu 250 MPa mit einer Hauptfrequenz von 28 kHz sind den Kurven uberlagert. Die Abgangsgeschwindigkeit betragt 950 m/s. Das Energiemodell reprasentiert recht gut die gemessene Leistung der Waffe. Die Rechnungen lassen bei entsprechender Anpassung an die reale Tropfchenverbrennung Parameterstudien zu. So lassen sich zum Beispiel Effekte studieren, die auf Anderungen der Dusenoffnung zuruckgehen. La presente publication decrit des experiences realisees a l’Institut Ernst-Mach avec une arme regenerative a propergol liquide de calibre 40 mm ainsi que les resultats de calculs avec un modele simple (modele a parametres concentres) effectues au WTD 91. L’arme regenerative comporte un tube lisse long de 2,53 m et tire un projectile conventionnel de 40 mm et 0,936 kg. La chambre de combustion possede un volume initial de 219 cm3 et un reservoir de 575 cm3. Un systeme compose de deux pistons, un piston central fixe et un piston d’injection mobile, est utilise pour l’injection du propergol liquide. Le rapport de surface differentiel est de 2:1. L’allumeur pyrotechnique DM 1101 comportant une charge additionnelle de 6 g de poudre noire et de 30 cm3 de propergol liquide compose de 80% en poids de nitromethane et 20% en poids de methanol (NM/M 80/20) met le piston en mouvement et assure l’allumage du jet de propergol liquide injecte. L’analyse experimentale du comportement lors du tir repose sur les resultats de mesures de pression dans le reservoir, dans la chambre de combustion et a la bouche, sur l’enregistrement inductif du mouvement du piston, sur l’interferometrie hyperfrequence (5 GHz) du mouvement du projectile dans le tube et sur la mesure inductive de la vitesse initiale du projectile. Si l’on fait fonctioner l’arme avec une charge de 550 cm3 de melange de propergol liquide NM/M 70/30d’energie relativement faible, on obtient des pressions maximales de 480 MPa dans le reservoir, de 400 MPa dans la chambre de combustion et de 50 MPa a la bouche du tube. Des oscillations de pression d’amplitudes allant jusqu’a(c) 250 MPa et de frequence principale 28 kHz se superposent aux courbes. La vitesse initiale est de 950 m/s. Le modele energetique represente assez bien la puissance mesuree de l’arme. Les calculs peuvent etre utilises pour les etudes parametriques lorsqu’ils sont correctement adaptes a la combustion de gouttelettes. Ainsi, on peut par exemple etudier des effets dus a des modifications de l’ouverture de tuyere.

The present paper deals with both the conventional solid propellant and modern liquid propellant gun concepts. Solid propellant guns, known since the 14th century, are still being investigated, although this concept represents a relative mature technology. Thus any progress is predominantly a refinement of existing techniques. Comparatively, liquid propellant gun research and development address a rather new technique and invoke some improvements over conventional solid propellant systems. Especially, automatic system are easier to design, artillery zoning is more easily achieved, cartridge disposal is avoided, and high-energetic liquid propellants or special system designs offer higher performance. Therefore, the liquid propellant gun technology seems to be a near-term technology that, complementary to solid propellant gun concepts, might play a role in future armament.

Actuellement, on developpe de nouvelles propulsions pour armes a tube afin d'obtenir des energies de bouche plus elevees et d'ameliorer ainsi l'effet a l'impact, de reduire les frais, d'augmenter la fiabilite et de diminuer la vulnerabilite. Ces demieres annees, on a surtout etudie des concepts d'arme progressistes promettant une augmentation des performances. Ces etudes ont ete menees parallelement a celles sur les propulsions classiques a poudre ou modemes a propergol liquide. On peut augmenter les performances soit par propulsion electrique (canon a bobines ou a rails), ou par combinaison d'une propulsion chimique et de principes de dynamique des gaz (canon a gaz leger ou lanceur a effet stato) ou de propulsions electrothermiques (canon hybride). Dans la 1ere partie, on decrira les bases techniques qui peuvent etre utilisees pour l'accereration des projectiles. On eveille ainsi la comprehension pour ce type de technologie des armes et on etablit des hypotheses pour l'evaluation des systemes de propulsion modernes.

The present paper deals with pressure oscillations in regenerative liquid propellant guns (RLPG) presenting the state-of-the-art research into sources and control of these combustion instabilities. Pressure oscillations with amplitudes up to 50 % of mean pressure and frequencies up to 60 kHz or more are present in experimental data of RLPGs, especially at medium and large calibers. Amplitudes increase with the volumetric energy density of the liquid propellant and the mass flow rate during injection. Frequency analyses reveal that both acoustic modes and combustion noise are components of the recorded oscillations. Acoustic modes, in particular, have the potential to couple to resonant modes in near-field mechanical structures. A multi-phase, multi-dimensional model investigation at ARL indicates that pressure waves reflected from internal boundaries are amplified as they pass the combustion zone of the highly pressure-sensitive liquid propellant in a localized region near the injector. Experimental data lead to a similar understanding of the amplification of pressure oscillations in RLPGs. Experiments in the United States and in Germany confirm that the pressure oscillations can be mitigated by altering the combustion characteristics of the liquid propellant. Also, techniques that more effectively disperse the liquid propellant jet and thereby decrease the local accumulation of liquid propellant, may reduce pressure oscillations as shown in 30-mm RLPG experiments. Further, energy-absorb-ing chamber walls or liners can serve as broad-band filters and have been shown experimentally to be effective in reducing the amplitude of all frequencies. In addition, physical methods such as cavities and baffles reduce significantly specific acoustic frequencies of the oscillations.

For the investigations of the gas-liquid phase equilibria, a new apparatus has been developed capable of simultaneously determining the pressure and the liquid and vapor densities using Archimedes' principle. The relative measurement uncertainties of the liquid and vapor densities of R134a (purity, 99.999%) at 313 K are 2×10−4 and 7×10−4, respectively (95% confidence level). For the measurements in the liquid region along nine quasi-isochores at pressures up to 5 MPa, an isochoric apparatus was used. The relative measurement uncertainty ofpv/(RT) is less than 1×10−3. In addition to the investigation of the (p, v, T) properties, the temperature and pressure at the triple point and the vapor pressure between the triple point and 265 K were measured. On the basis of these data, a vapor pressure correlation has been developed that reproduces the measured vapor pressures within the uncertainty of measurement. The results of our measurements are compared with a fundamental equation for R134a, which is based on the measurements of other research groups.

The effective areas of two transfer standards were determined from cross-floating experiments. It was possible to reproduce the ratio of the effective areas of the primary standards using data obtained for the transfer standards within 1,6 ? 10-6, but for the absolute effective area values of the transfer standards, relative differences up to 11,6 ? 10-6 were measured. Additional dimensional measurements were performed to discover the reason for the disagreement. It seems likely that this is due to problems in performing sufficiently accurate dimensional measurements.

Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M$_{\sun}$) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M$_{\sun}$), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary., Comment: 7 pages, 5 figures, accepted for publication in A&A

Context. BL Cam is an extreme field multiperiodic short-period low-metallicity high-amplitude SX Phe-type variable where its probably complex pulsational content is subject of controversies. Aims. A comprehensive study has been carried out to investigate the nature and pulsational properties of this object. Methods. The analysis is based on new photometric data collected during the last few years at different sites, as well as on all available previously published data. Frequency analyses have been performed on a number of reliable data sets to analyse the pulsational content. In addition, the classical O−C method was used to study the behaviour of the main period. Results. Our frequency analysis confirms some aspects on the multiperiodicity of BL Cam, previously found by other authors, showing a number of secondary modes close to the main frequency f0 = 25.5769 cd −1 . The secondary modes present eventual amplitude variations. However, the main frequency exhibits no significant changes in its amplitude and seems to correspond to the fundamental mode of radial pulsation. Abrupt changes sometimes observed in the light curves could be due to spurious activity on or close to the star’s photosphere. We confirm the existence of a secondary frequency at 31.6 or 32.6 cd −1 , with variable amplitude, and with the possibility of both frequencies being intrinsic to the star. More than one hundred of new times of light maxima have been determined in the present work. These together with those available in the literature allow us a more discriminating analysis of the O–C diagram. This shows that the observed variations of the main period can be described by two terms: (i) a secular increase of the main period at a rate of dP/Pdt = 117(±3) × 10 −9 yr −1 ; and (ii) a perturbation from a companion star in a rather eccentric orbit with a period of 10.5(±0.2) yr causing a light time semi-amplitude of 148(±12) s.

A single-stage gas gun is used for simulating gun tube flows. The gas gun is driven by the combustion of gas mixtures consisting of Hsub2/0sub2/He, Hsub2/He/CO/Osub2, and CO/Osub2. Thus, the two main combustion reactions occurring in chemical gun propulsion are simulated. Experiments had the goal to improve the knowledge of reacting two-phase (gas/solid) gun tube flows providing a data bank applicable for interior ballistic model validation. Parameters measured include pressure and temperature as well as velocity gradient at various positions along the gun tube. Multi-channel nearinfrared spectroscopy measurements for recording the transient gas phase species were also performed.

The purpose of this paper and work reported herein is to contribute to the understanding of the fundamental physical parameters govering arcless electrical ignition of hydroxylammoniumnitrate (HAN) based liquid monopropellants (LP), especially LGP 1846 in conjunction with its use as propellant charge in the regenerative liquid propellant gun (RLPG). Further, to optimize igniter configurations with the goal of successfully igniting the LP charge of an actual 30-mm RLPG. The feasibility of arcless ignition in a 2 qcm igniter element was demonstrated in a 30-mm RLPG simulator. The igniter consists of a center rodlike electrode separated from a more or less conical vented outer electrode by a hollow cylindrical insulator. Simple steadystate potential field calculations were used. The energy uptake of the igniter is determined mainly by polarity, electrode surface area, and charge voltage. A stronger confinement of the liquid propellant igniter charge will speed up the ignition process. Sca nning electron microscopy (SEM) and x-ray microanalysis definitely show that ignition is affected by the chemical and physical characteristics of the electrode surface. Preliminary tests with a multi-channel IR-spectrometer monitoring the transient ignition reactions yielded encouraging results.

The spatial and temporal temperature distribution in the muzzle blast field of a rifle of caliber 7.62 mm was determined by evaluation of the radiation emitted by the muzzle flash. In the primary flash directly adjacent to the muzzle a maximum gas temperature of 1645 K was observed by means of emission- absorption measurements of both continuum and discrete radiation. The influence of the surrounding cool layers was taken into account by applying Abel-inversion techniques. In the intermediate flash about 100 to 300 mm downstream line-reversal-techniques using K- and Na-resonance lines gave temperatures of about 1600 K increasing with time and with muzzle distance to a maximum temperature of 1940 K. This rise of temperature is due to the onset of combustion processes. Further downstream at a distance of 300 to 500 mm in the secondary flash a fast intense combustion of the propellant gases mixed with air leads to gas temperatures of about 2500 K. By firing into inert gases this flash could be suppressed whereas the primary and intermediate flash remained unchanged. When firing into oxygen a maximum gas temperature of 3000 K was observed in the secondary flash.

Calculation of the pressure dependence of the effective area of pressure balances normally assumes the pressure gradient in the clearance between the piston and cylinder to be constant along the engagement length of the piston which yields a linearly varying clearance between the piston and cylinder. The assumption is not strictly valid. In this work, the assumption is avoided by applying the theory of flow in a converging channel to the pressure balance to calculate: (i) The upward force on the flanks of the piston due to fluid friction; (ii) The flow passing through the clearance and (iii) The pressure coefficient for a pressure balance.

Druckbombenversuche an fluessigen Rohrwaffentreibmitteln (Monopropellants) auf der Basis von Hydroxylammoniumnitrat (HAN) bei Ladedichten von etwa 0,2 g/cbcm wurden sowohl beim Fraunhofer-Institut fuer Kurzzeitdynamik (EMI-AFB), als auch beim Ballistic Research Laboratory (BRL) durchgefuehrt. Untersucht wurde die Dekomposition der Monopropellants auf HAN-Basis bei Variation der Versuchsbedingungen. Druck- und Temperaturmessungen sind an "reinen" und absichtlich durch Zugabe von Eisen-, Kupfer-, Aluminium- und Nickel-Zusaetzen verunreinigten Monopropellants durchgefuehrt worden. Fuer die Temperaturmessungen wurden Thermoelemente und speziell fuer Emissionsmessungen entwickelte Temperaturmessgeber eingesetzt. Die Ergebnisse dieser Versuche charakterisieren das Dekompositionsverhalten der fluessigen Rohrwaffentreibmittel. (EMI)

The local and temporal distribution of gas velocity along the axis of the propellant gas flow ahead of the muzzle of a caliber 7.62 mm rifle is determined by using luminous tracers produced by a laser pulse. Within the main expansion zone of the flow field, maximum gas velocities of 2400 m/s are observed. After passing through the shock front which terminates this expansion zone, the flow is decelerated to ν

Zusammenfassung In the present paper we report a calculation of scattering spectra from weakly ionized plasmas, using two-time probability densities. Williams and Chappell, and Klingenberg and Richter assumed identical BGK collision integrals for the self-and distinct parts of the electron density correlation function. There, BGK terms with different “collision frequencies” are used. Finally, the spectral density is given for modified initial correlations.

The radial and axial distortions of a piston and a cylinder are calculated from exact solutions of the elastic differential equations in the case of a pressure distribution p(z) = α + βz + γz2 in the clearance between the piston and cylinder. The outer curved surface of the cylinder is assumed to be exposed to a constant pressure pj. The end faces of the piston are subjected to the gauge pressure po and to the gravitational force exerted by the load that creates the pressure po. A pressure pce is assumed to act on the end faces of the cylinder. From the results, the distortion coefficient of the pistoncylinder system is calculated using the formula given by Dadson, Greig and Horner.

This investigation is concerned with the combustion of solid propellants and the gas dynamic processes occurring within the flow inside and at the exit plane of the muzzle of 20 mm caliber guns. Two propellants (nitrocellulose-powder) and two types of guns were used. The load density was 0.39 to 0.9. The measurement is highly influenced by the deposition of absorbing particulates in the boundary layers near the tube wall. The main objective of this paper is to verify the validity of recently developed interior ballistic models. In-bore temperature distributions derived from emission-absorption measurements by means of quartz windows mounted into bores along the barrel are compared to theoretical predictions. An in-bore temperature gradient is found near the base of the moving projectile as predicted by one of the models. Neither of the interior ballistic models describes the phenomena in detail. Better agreement was achieved using a high load density. Temperatures measured within in the “primary flash” at the exit plane of the muzzle can only be compared to in-bore values immediately after projectile, emergence; 20 to 30 μsec after projectile emergence, secondary combustion processes lead to an increase of the temperature.

The development of the flow fields generated by firing a 7.62-mm caliber rifle is measured using a time-resolved spark shadograph technique. Two precursor flow fields are forced out ahead of the projectile. The propellant gas flow field forms upon separation of the projectile from the muzzle. While the first precursor develops in a nearly spherical manner, the development of the second precursor and the propellant gas blast field occur anisotropically. In the axial downstream direction the propagation velocity is higher than along the lateral direction. Motion of observable discontinuities is shown to follow time-displacement laws. In addition, the local and temporal pressure distribution in the muzzle blast field of the rifle was determined by immersing quartz probes in the flow. Within the main expansion zone of the flow, subatmospheric pressures of p > 0.2 × 105N/m2 are observed. After passing through the shock fronts which terminate this expansion zone, the pressure increases to p > 1.5 × 105N/m2. Expansion starts anew at some distance from the shock front, and the pressure decreases. This decrease is rapidly disturbed by the onset of combustion, and the buildup of reverse pressure gradients between the shock front and the reaction zone is observed. Further downstream, expansion commences anew until the gas-air interface is reached. At this interface the pressure increases indicating the deceleration of flow within the “contact surface.” The overpressure of the blast was shown to decrease both in-axis and lateral from p > 3.5 × 105N/m2 near the muzzle to about p = 1.1 × 105N/m2 at distance 2 m. The noted features of the flow and the interaction with the combustion processes are discussed in detail.