Construction and analysis of causally dynamic hybrid bond graphs

Engineering systems are frequently abstracted to models with discontinuous behaviour (such as a switch or contact), and a hybrid model is one which contains continuous and discontinuous behaviours. Bond graphs are an established physical modelling method, but there are several methods for constructing switched or ‘hybrid’ bond graphs, developed for either qualitative ‘structural’ analysis or efficient numerical simulation of engineering systems. This article proposes a general hybrid bond graph suitable for both. The controlled junction is adopted as an intuitive way of modelling a discontinuity in the model structure. This element gives rise to ‘dynamic causality’ that is facilitated by a new bond graph notation. From this model, the junction structure and state equations are derived and compared to those obtained by existing methods. The proposed model includes all possible modes of operation and can be represented by a single set of equations. The controlled junctions manifest as Boolean variables in the matrices of coefficients. The method is more compact and intuitive than existing methods and dispenses with the need to derive various modes of operation from a given reference representation. Hence, a method has been developed, which can reach common usage and form a platform for further study

Effects of surface vibrations on interlayer mass-transport: ab initio molecular dynamics investigation of Ti adatom descent pathways and rates from TiN/TiN(001) islands

We carry out density-functional ab initio molecular dynamics (AIMD) simulations of Ti adatom (Tiad) migration on, and descent from, TiN -faceted epitaxial islands on TiN(001) at temperatures T ranging from 1200 to 2400 K. Adatom-descent energy-barriers determined via ab initio nudged-elastic-band calculations at 0 Kelvin suggest that Ti interlayer transport on TiN(001) occurs essentially exclusively via direct hopping onto a lower layer. However, AIMD simulations reveal comparable rates for Tiad descent via direct-hopping vs. push-out/exchange with a Ti island edge atom for T >= 1500 K. We demonstrate that the effect is due to surface vibrations, which yield considerably lower activation energies at finite temperatures by significantly modifying the adatom push/out-exchange reaction pathway.Comment: 13 Figure

Indicators for Women's Health in Developing Countries: What They Reveal and Conceal

Summary The health of women has recently resurfaced in the health policy debate and has tended to become viewed as important primarily because of its contribution to infant health. Maternal deaths are characterised by a range of fairly typical causes, all of which can normally be prevented with good obstetric medical services and antenatal care. The most widely used indicator, the maternal mortality rare, is closely associated with a range of socioeconomic determinants; most notably poverty and access to obstetric services, which suggests that medicine alone cannot solve the whole problem. Factors such as urbanization, female secondary education, contraceptive prevalence and fertility all appear to be important intermediate determinants, which highlight the fact that the problem is really rooted in a much wider one of the status and role of women in development. The indicator of the maternal mortality rate itself actually underestimates the true impact of fertility on women's health. The indicator of lifetime risk (of dying in childbirth) is much more relevant and it provides an even starker picture of differentials in health risks, and the role fertility plays in these risks. It puts fertility back into women's health and the object of measurement is women's lives rather than the disembodied event of birth. Resumé Indicateurs de la santé des femmes dans les pays en voie de développement: ce qu'ils révèlent et ce qu'ils cachent Le sujet de la santé des femmes remonte à la surface dans le débat concernant les politiques de santé; ce sujet a été censé important, du moins récemment, en raison principalement de sa contribution à la santé infantile. Les décès maternels sont caractérisés par une gamme de causes relativement typiques et qu'il est normalement possible d'éviter moyennant une bonne obstétrique médicale et des soins adéquats en période prénatale. L'indicateur le plus fréquemment employé, le taux de mortalité maternel, est étroitement lié à une gamme de déterminants socio?économiques, notamment la pauvreté et l'accès aux services obstétriques, qui suggèrent que l'accès à la médecine seule ne peut entièrement résoudre le problème. Les facteurs tels que l'urbanisation, l'enseignement secondaire des femmes, la disponibilité de la contraception et la fécondité sembleraient tous être des indicateurs d'ordre intermédiaire, et ceci aurait tendance à souligner le fait que le problème véritable est effectivement encastré dans un problème encore plus grave, à savoir celui du rôle et de la situation des femmes dans le développement. L'indicateur de mortalité maternelle sous?estime en fait l'impact véritable de la fertilité sur la santé des femmes. L'indicateur de risque à longueur de vie (de mourir durant un accouchement) est beaucoup plus approprié et offre une image encore plus déprimante des différentiels dans les risques à la santé, et du rôle que la fertilité joue dans ces risques. Cet indicateur remet en cause la fertilité au sein de la santé des femmes et en fait une mesure de la vie des femmes, à la place du simple événement qu'est tel ou tel accouchement. Resumen Indicadores de salud femenina en los países en desarrollo: lo que revelan y lo que ocultan El tema de la salud de la mujer ha resurgido recientemente en el debate sobre directivas de salud, y la tendencia ha sido considerarlo importante primordialmente por su contribución a la salud infantil. Las muertes maternales tienen una serie de causas bastante típicas, todas las cuales pueden normalmente ser evitadas con buenos servicios obstétricos y cuidados prenatales. El indicator más usado, la tasa de mortalidad maternal, está asociado a los determinantes socioeconómicos, notablemente la pobreza y la falta de acceso a los servicios ginecológicos, lo que sugiere que la medicina no puede resolver todo el problema por sí sola. Factores como la urbanización, la educación secundaria femenina, la prevalencia anticonceptiva y la fertilidad parecen ser importantes determinantes intermedios, y eso destaca el hecho de que el problema está realmente enraizado en otro mucho mas amplio: la condición y el papel de la mujer en el desarrollo. El indicador de la tasa de mortalidad maternal en realidad subestima el verdadero impacto de la fertilidad en la salud femenina. El indicador de riesgo vital: muerte de parto es mucho más significativo y da una imagen aún más severa de los diferenciales en riesgos de salud y el papel jugado por la fertilidad en esos riesgos. Pone a la fertilidad dentro de la salud femenina nuevamente, y lo que se mide es la vida de la mujer en vez del evento aislado del parto

Reframing Gender Justice in an Unequal, Volatile World: IDS’ Directions for Future Research on Gender and Sexuality in Development

At a time of major changes in global politics and trends, and major shifts in international development following the establishment of the global Sustainable Development Goals in Agenda 2030, the Gender and Sexuality cluster at the Institute of Development Studies engaged in collaborative discussions and consultations over nine months with partner organisations, networks, external experts and policymakers. Following this process through most of 2016, this brief outlines our priority directions for future research on gender and sexuality in development in an increasingly unequal, polarised and volatile world.UK Department for International Developmen