Background: Pregnancy Nutrition (PN) guidance is an issue of great concern worldwide because of its direct relevance to the maternal healthcare and the healthy prenatal development (Li et al., 2004, p. 11). Providing an effective guidance on PN is an onerous and time-consuming task. Extensive experience, knowledge, and continuous and actual calculations are required for the obstetricians. Consequently, the PN guidance is often faced with difficulties and hurdles. It is, however, dramatically changed with the emergence of a Decision Support System (DSS) for PN guidance based on the computer information management technique. This DSS has been applied for the clinic guidance of PN in obstetrics departments or hospitals in China. Its impacts on obstetricians are investigated in this thesis. Objectives: This thesis investigates the consequences and intrinsic correlations of relevant factors during the application of the DSS, so that its effects on obstetricians can be clearly identified and the usefulness of this system for pregnancy nutrition guidance can be effectively established. It also lays a foundation for an effective communication between system developers and the end users of this system. At the meantime, this work proposes the concepts and methods that allow proper utility of such an information management system. Methods: A number of research methods have been applied for data acquisitions and analyses, including direct observations of the obstetrics department in the hospital in study, conversational interviews with the participating obstetricians, and distance communications. These approaches enable us to prepare the resources to construct the model based on these case studies. As a parallel approach, quantitative methods based on questionnaires have been conducted which reach out a large number of obstetricians in different locations. This allows a statistical analysis that permits the impact analysis and correlation of the intrinsic factors, so that the conclusions of this study can be consolidated. Results: Positive impacts will be measured by five factors including convenience, acceptability, generality, concreteness, and effectiveness, while negative impacts by three factors including verbosity, rigidity, and expensiveness. Conclusions: The DSS has successfully enhanced the application of correct PN guidance. Both positive and negative impacts have been generated on obstetricians by the DSS. These impacts are mainly related to the seniority of obstetricians and their familiarity with the PN guidance and the DSS. The development, utilization, and operation management of the DSS in PN guidance has generated impacts and functions. This study might provide resources and foundation of the systematic management of the DSS together with its development. The DSS and the related Chief Information Officers and Specialists will benefit from this study and therefore provide improved support and assistance for the end users to complete information system management successfully. / PN DSS configuration of Obstetrician Department in Tianjin First Central Hospital, Tianjin, China

Guidance is defined as the determination of a strategy for following a nominal path in the presence of o-nominal conditions, disturbances and uncertainties, and the strategy employed is called a guidance law. Variants of Proportional Navigation (PN), such as True Proportional Navigation (TPN) and Pure Proportional Navigation (PPN), have been studied extensively in the literature on tactical missile guidance. In the absence of target maneuvers, in a linear interceptor guidance problem, TPN was shown to be optimal. However, the standard PN class of guidance laws per se does not show good performance against maneuvering targets, and was found to be eective in intercepting a maneuvering target only from a restrictive set of initial geometries. Also, since these guidance laws were eectively designed for lower speed targets, they show a degraded performance when applied against higher speed targets. However, in the current defense scenario, two classes of agile targets, which are capable of continuous maneuver, and/or of much higher speed than the interceptor, are a reality. This thesis presents analysis of several variants of PN class of guidance laws against these two classes of agile targets. In the literature, an augmentation of the TPN guidance law, termed as Augmented Proportional Navigation (APN), was shown to be optimal in linearized engagement framework. The present work proposes an augmentation of the PPN guidance law, which is more realistic than TPN for an aerodynamically controlled interceptor, and an-alyzes its capturability in fully nonlinear framework, and develops sauciest conditions on speed ratio, navigation gain and augmentation parameter to ensure that all possible initial engagement geometries are included in the capture zone when applied against a target executing piecewise continuous maneuver. The thesis also obtains the capture zone in the relative velocity space for augmented PPN guidance law. In the literature, a novel guidance law was proposed for the interception of higher speed targets in planar engagement by using a negative navigation gain instead of the standard positive one, and was termed as Retro-PN. It was shown that even though the Retro-PN guided interceptor takes more time than PN guided one in achieving successful interception, Retro-PN performs significantly better than the classical PN law, in terms of capturability, lateral acceleration demand, and closing velocity, when used against higher speed targets. The thesis analyzes Retro-PN guidance law in 3-D engagement geometries to yield the complete capture zone of interceptors guided by Retro-PN guidance philosophy, and derives necessary and sucient conditions for the capture of higher speed non-maneuvering targets with and without a constraint on finiteness of lateral acceleration. Terminal impact angle control is crucial for enhancement of warhead eectiveness. In the literature, this problem has been addressed mostly in the context of targets with lower speeds than the interceptor. The thesis analyzes the performance of a composite PN guidance law, that uses standard PPN and the Retro-PN guidance laws based on initial engagement geometry and requirement of impact angle, against higher speed non-maneuvering targets. Then, to expand the set of achievable impact angles, it proposes a modified composite PN guidance scheme, and analyzes the same. For implementation of many modern guidance laws, a good estimate of time-to-go is essential. This requirement is especially severe in case of impact time constrained en-gagement scenarios. To this end, an ecient and fast time-to-go estimation algorithm for generic 3-D engagement is required. Two time-to-go estimation algorithms are presented and analyzed in this work for the engagement of a PPN or Retro-PN guided interceptor and a higher speed target. The first one is a closed form approximation of time-to-go in terms of range, nominal closing speed and an indicator of heading error, and the second one is a numerical recursive time-to-go estimation algorithm. To improve the odds of intercepting an intelligent target and destroying it, a salvo attack of two or more interceptors could be considered as a viable option. Moreover, this simultaneous salvo attack can also be further improved in eciency by incorporating the shoot-look-shoot approach in making a decision about launching interceptors. This can be considered as the first step towards a layered defense system, which has been described in the literature as a potentially eective strategy against short range or long range ballistic threat. To this end, the present work proposes two PPN and Retro-PN based guidance strategies for achieving simultaneous salvo attack on a higher speed non-maneuvering target. For the implementation of the same the numerical recursive time-to-go estimation technique proposed in this work is utilized