Towed-Diver Surveys,a Method for Mesoscale Spatial Assessment of Benthic Reef Habitat: A Case Study at Midway Atoll in the Hawaiian Archipelago

An integrated method for benthic habitat assessment is described, in which divers maneuver boards equipped with digital video, temperature, and depth recorders while being towed behind a small boat. The tow path is concurrently recorded by a GPS receiver, and a layback model is applied to more accurately map the data. Percent cover of salient benthic categories is quantified by whole-image analysis of still frames sampled at 30-s intervals. The results of 15 towed-diver surveys at Midway Atoll in the Hawaiian Archipelago during a mass coral bleaching event are presented to exemplify the method and are compared to results derived from conventional methods. Towed-diver surveys bridge a gap between large-scale mapping efforts using satellite data and small-scale, roving diver assessments, providing a mesoscale spatial assessment of reef habitats. The spatial coverage of towed-diver surveys provides comprehensive data to managers concerning the extent, intensity, differential taxonomic response, and bathymetric correlates of bleaching.     

Minimum order bang-bang guidance for feedforward obstacle avoidance steering maneuvers of vehicles

In this paper, a new methodology is presented for computing time-optimal obstacle avoidance maneuvers for ground vehicles. Usually, the problem of obstacle avoidance is addressed in two parts. In the first part a path is planned. In the second an appropriately designed vehicle controller tracks the desired path. In view of the fact that the main problem concerning emergency maneuvers remains the development of an optimal control for minimum time and maximum maneuverability — with respect to the slip risk due to saturation of the tire forces — the authors propose an alternative approach. Considering that the time optimal control according to Pontryagin’s Maximum Principle (PMP) is of bang-bang type the investigations concern the minimum order and magnitude bang-bang control for “feedforward” steering maneuvers with the target of minimizing the computation time and simplifying the algorithm. This is accomplished by keeping the basic PMP logic but transforming the computational algorithm from an exact to a least squares control problem. Furthermore, the paper addresses how to solve the problem of guiding the vehicle from a non rest to a rest position. Simulations of obstacle avoidance maneuvers illustrate the performance of the controller.     

Weaving marine food webs from end to end under global change

Marine food web dynamics are determined by interactions within and between species and between species and their environment. Global change directly affects abiotic conditions and living organisms, impinging on all trophic levels in food webs. Different groups of marine researchers traditionally study different aspects of these changes. However, over medium to long time scales perturbations affecting food webs need to be considered across the full range from nutrients to top predators. Studies of end-to-end marine food webs not only span organism sizes and trophic levels, but should also help align multidisciplinary research to common goals and perspectives. Topics are described that bridge disciplinary gaps and are needed to develop new understanding of the reciprocal impacts of global change on marine food webs and ocean biogeochemistry. These include (1) the effects of nutrients on biomass and production, (2) the effects of varying element ratios on food web structure and food quality, (3) bulk flows of energy and material in food webs and their efficiencies of transfer, (4) the ecological effects of species richness and the roles of microbial organisms, (5) the role of feeding behaviour in food web dynamics and trophic controls, (6) the spatial dynamics of communities and links between different food webs, (7) the combined effects of body size and behaviour in determining dynamics of food webs, and (8) the extent to which the ability of marine organisms (and communities) to adapt will influence food web dynamics. An overriding issue that influences all topics concerns the time and space scales of ecosystem variability. Threads link different nodes of information among various topics, emphasizing the importance of tackling food web studies with a variety of modelling approaches and through a combination of field and experimental studies with a strong comparative approach.     

Effect of drowsiness on driving performance variables of commercial vehicle drivers

Driver drowsiness is a major safety concern, especially among commercial vehicle drivers, and is responsible for thousands of accidents and numerous fatalities every year. The design of a drowsiness detection system is based on identifying suitable driver-related and/or vehicle-related variables that are correlated to the driver’s level of drowsiness. Among different candidates, vehicle control variables seem to be more promising since they are unobtrusive, easy to implement, and cost effective. This paper focuses on in-depth analysis of different driver-vehicle control variables, e.g., steering angle, lane keeping, etc. that are correlated with the level of drowsiness. The goal is to find relationships and to characterize the effect of a driver’s drowsiness on measurable vehicle or driving variables and set up a framework for developing a drowsiness detection system. Several commercial drivers were tested in a simulated environment and different variables were recorded. This study shows that drowsiness has a major impact on lane keeping and steering control behavior. The correlation of the number and type of accidents with the level of drowsiness was also examined. Significant patterns in lateral position variations and steering corrections were observed, and two phases of drowsiness-related degradation in steering control were identified. The two steering degradation phases examined are suitable features for use in drowsiness detection systems.     

新的美国公路桥抗震设计指导规范

本文简要地讨论了美国国家公路与运输协会新的桥梁抗震指导规范的主要变化.该修订规范是由国家公路合作研究规划项目于2006年5月完成的.拟被美国国家公路与运输协会采用,国家公路合作研究规划项目20-07/专题193于2007年被正式采用.     

自发高血压大鼠心脏功能及血压的增龄性变化

４～１８周之雄性自发高血压大鼠（ＳＨＲ）与正常血压（ＷＫＹ）鼠各分为５个年龄组。乙醚麻醉下测取有关心功能指标，并以短暂的主动脉阻闭所得到的左室发展压峰值（ｐＤｅｖＰ，由左室收缩压减去左室舒张末压获得）作为左室最大压力产生能力的指标。实验结果显示：①各年龄组ＳＨＲ之动脉收缩压、舒张压、平均动脉压、左室收缩压均高于同龄组ＷＫＹ鼠（Ｐ＜０．０５）。ＳＨＲ之上述指标随年龄增长而增高。②各年龄组ＳＨＲ之ｐＤｅｖＰ均高于同龄组ＷＫＹ鼠（Ｐ＜０．０５）。ＳＨＲ之ｐＤｅｖＰ随年龄增长而增大。     

INTERFERON γ－INDEPENDENT EFFECTS OF INTERLEUKIN 12 ADMINISTERED DURING ACUTE OR ESTABLISHED INFECTION DUE TO LEISHMANIAMAJOR

ＩＮＴＥＲＦＥＲＯＮγ－ＩＮＤＥＰＥＮＤＥＮＴＥＦＦＥＣＴＳＯＦＩＮＴＥＲＬＥＵＫＩＮ１２ＡＤＭＩＮＩＳＴＥＲＥＤＤＵＲＩＮＧＡＣＵＴＥＯＲ　ＥＳＴＡＢＬＩＳＨＥＤＩＮＦＥＣＴＩＯＮＤＵＥＴＯＬＥＩＳＨＭＡＮＩＡＭＡＪＯＲＺｈｅｎｇＳｈｉｃｈｕｎ；Ｗ...     

大型基础设施系统设计中的风险及概率

在大型基础设施系统中,不可避免地会出现重大的不确定性,因而,无法确保已建系统的安全性和可靠性.有功能失效甚至破坏的可能,同时也有相应的规避风险的措施.从实用角度出发,不确定性可以分为两大类:数据型(又称偶然型)不确定性和知识型(又称认知型)不确定性.前者可以通过对数据的观察来评估,而后者则需要主观判断.系统地分析了这两...