基于BP神经网络的大跨高空连廊应变监测数据恢复

为了解决大跨高空连廊吊装阶段性态监测中应变监测数据存在缺失的问题,利用BP神经网络进行数据恢复。首先基于相关性分析,选择与数据缺失监测点应变值相关性最强的5个监测点作为参考点;然后利用未缺失时间段内待恢复监测点和参考点的应变数据进行建模和检验,一半数据用来建立BP神经网络模型,一半数据用来进行模型的检验;最后利用建立的模型对缺失的数据进行恢复,得到了完整的应变监测数据。利用得到的恢复数据与参考点数据在缺失段内的相关系数对数据恢复的效果进行了评价。结果表明:该方法可有效地恢复缺失的应变监测数据。

某工程粘土心墙坝高水位运行三年坝体工程性态评价

在此详细介绍某工程粘土心墙坝的监测设计,根据该工程粘土心墙坝具有防渗土料粘粒含量低、抗冲蚀能力差及工程抗震设防烈度高的特点,确定了监测设计的思路和原则以及对特殊部位坝体变形的监测项目,通过对大坝运行三年来粘土心墙内部沉降资料分析、坝体表面沉降和水平位移资料分析,以及大坝渗流资料的分析,对坝体运行性态进行评价。

Climate Variability in Niger： Potential Impacts on Vegetation Distribution and Productivity

Since 2003, the sites of the national environmental monitoring system （DNSE） of Niger, set up by the long term ecological monitoring observatories network （ROSELT） with the support of the Sahel and Sahara Observatory （OSS）, were used to collect ecological data with harmonized methods for spatio-temporal comparisons purpose. Floristic and phytoecological data were collected using the phytosociological methodology of Braun-Blanquet （1932）. Ecosystem vital attributes used included the specific diversity, alpha diversity, equidistribution, biological types and herbaceous phytomass. At the whole system scale, the analysis revealed that the specific diversity, the alpha diversity and the phytomass values were higher in less disturbed biotopes of the north soudanian and south sahelian bioclimates where the rainfall rate is relatively high. Regarding the north sahelian and saharian bioclimates, the topography may play a critical role in the redistribution of this phytodiversity. Besides, the distribution of the biological types showed the prevalence of therophytes （56.8 ± 11%） regardless of the bioclimate and, to a lesser extent, the perennial species （26.5 ± 7.3%）, the later group showing higher values for the north soudanian bioclimate.

Remaining useful life estimation based on Wiener degradation processes with random failure threshold

Remaining useful life(RUL) estimation based on condition monitoring data is central to condition based maintenance(CBM). In the current methods about the Wiener process based RUL estimation, the randomness of the failure threshold has not been studied thoroughly. In this work, by using the truncated normal distribution to model random failure threshold(RFT), an analytical and closed-form RUL distribution based on the current observed data was derived considering the posterior distribution of the drift parameter. Then, the Bayesian method was used to update the prior estimation of failure threshold. To solve the uncertainty of the censored in situ data of failure threshold, the expectation maximization(EM) algorithm is used to calculate the posteriori estimation of failure threshold. Numerical examples show that considering the randomness of the failure threshold and updating the prior information of RFT could improve the accuracy of real time RUL estimation.

Influence of ＂Covercrete＂ Morphology on Durability Properties

Many leading experts agree on the importance of monitoring the ＂concrete skin＂ as the most loaded area affected by the external environment. Surfacing, concrete mixture composition and curing are of great importance for the concrete surface resistance. The paper introduces an experimental program focused on the monitoring of de-icing salts resistance, depending on surface roughness. Quantitative evaluation of the concrete surface was performed by using confocal laser scanning microscopy, which is the new generation of optical systems that are able to make all measurements in 3D resolution. These measurements are supplemented by results of mechanical and absorption tests.

Software Package Evaluation for Lyapunov Exponent and Others Features of Signals Evaluating Condition Monitoring Performance of Nonlinear Dynamic Systems

Efficient use of industrial equipment, increase its availability, safety and economic issues spur strong research on maintenance programs based on their operating conditions. Machines normally operate in a linear range, but when malfunctions occur, nonlinear behavior might set in. By studying and comparing five nonlinear features, which listed in decreasing order by their damage detection capability are： LLE （largest Lyapunov exponent）, embedded dimension, Kappa determinism, time delay and cross error values; i.e., LLE performs best. Using somewhat similar ideas from Chaos control, i.e., vary the ＂mass imbalance＂ forcing parameters, we aim to stabilize the Lorenz equation. Quite interestingly, for certain imbalance excitation values, the system is stabilized. The previous even when paradigmatically chaotic parameters for Lorenz system are used （plus our forcing terms）. This quasi-control approach is validated studying signals obtained from the previously mentioned lab test. Finally, it is concluded that analyzing and comparing nonlinear features extracted from baseline vs. malfunction condition （test acquired）, one might increase the efficiency and the performance of machine condition monitoring.

Damage Detection of Offshore Jacket Structures Using Frequency Domain Selective Measurements

The development of damage detection techniques for offshore jacket structures is vital to prevent catastrophic events. This paper applies a frequency response based method for the purpose of structural health monitoring. In efforts to fulfill this task, concept of the minimum rank perturbation theory has been utilized. The present article introduces a promising methodology to select frequency points effectively. To achieve this goal, modal strain energy ratio of each member was evaluated at different natural frequencies of structure in order to identify the sensitive frequency domain for damage detection. The proposed methodology opens up the possibility of much greater detection efficiency. In addition, the performance of the proposed method was evaluated in relation to multiple damages. The aforementioned points are illustrated using the numerical study of a two dimensional jacket platform, and the results proved to be satisfactory utilizing the proposed methodology.

Effect of direct moxibustion on blood pressure and clinical symptoms in elderly patients with essential hypertension

Objective： To assess the effects of direct moxibustion on 24-hour ambulatory blood pressure （ABP） and clinical symptoms of traditional Chinese medicine （TCM） in elderly patients with essential hypertension, and to explore the antihypertensive effect and influencing factors of moxibustion. Methods： A total of 101 elderly hypertension patients who met the inclusion criteria were randomly assigned to a direct moxibustion I group （n=33）, a direct moxibustion II group （n=34）, and a control group （n----34）. The treatment of calcium antagonist （CCB） or angiotensin II receptor antagonist （ARB） was adopted in the control group. The treatment of direct moxibustion I plus the same medicine as the control group were adopted in the direct moxibustion I group, five cones per acupoint and three times per week, for 5 weeks in total. The treatment of direct moxibustion II plus the same medicine as the control group were adopted in the direct moxibustion II group, five cones per acupoint and three times per week, for 5 weeks in total. The changes of 24-hour ABP and clinical symptoms of TCM after treatment were compared in the three groups. Results： The mean 24-hour ambulatory systolic blood pressure （mean 24 h ASBP）, night ASBP, percentage of mean 24-hour ambulatory diastolic blood pressure （mean 24 h ADBP）~90 mmHg, and percentage of day ADBP^90 mmHg in the control group were elevated after treatment （P^0.05）. The percentage of night ADBP^80 mmHg in the direct moxibustion I group was reduced by treatment （P〈0.01）. There were no significant differences in the other outcome measures of 24 h ABP, such as day ASBP, percentage of mean 24 h ASBP^140 mmHg, percentage of day ASBP^140 mmHg, percentage of night ASBP 〉120 mmHg, mean 24 h ADBP, day ADBP, night ADBP, 24 h ambulatory pulse pressure （APP）, after treatment in all groups （P^0.05）. The degree of improvement of the clinical symptoms of TCM showed significant differences among the three groups of patients （P^0.01）. The total effective rate in the direct moxibustion I group was 73.3%, which was superior to those in the direct moxibustion II group and control group （13.3% and 10.0%, respectively）. Conclusion： The direct moxibustion has benign regulative effect on blood pressure of elderly patients with essential hypertension, and improves their clinical symptoms. The direct moxibustion method I （burning the next moxa cone after the previous one had totally burnt out） was superior to method II （burning the next moxa cone when the previous one had not totally burnt out ） in lowering blood pressure and improving symptoms of elderly patients with essential hypertension.

A National Key R&D Program: Technologies and Guidelines for Monitoring Ecological Quality of Terrestrial Ecosystems in China

Ecological quality is defined as the stability, adaptability and resilience of an ecosystem. Monitoring and assessing ecological quality are important bases for China’s ecological civilization construction. The national key research and development program "Technologies and guidelines for monitoring ecological quality of terrestrial ecosystems in China", launched in July 2017, includes plans to study the observation technologies and provide guidelines on the ecological in-situ observation, the regional biodiversity and ecosystem function monitoring and its applications, all of which contribute to national ecological quality assessment. A year after its implementation,some important progress has been achieved, such as building the indicator system for comprehensive monitoring of ecological quality and improvement of the methods, mass data transmission, infrared camera-based monitoring of biodiversity, multi-angle automatic spectral observation systems, and unmanned aerial vehicle(UAV) based desert monitoring. We have organized this special issue and attempted to introduce the monitoring techniques and assessment methods on ecological quality from different perspectives in order to further promote the development of ecology and its observation methods.

OBSERVATION OF NONLINEAR VERTICUM-TYPE SYSTEMS APPLIED TO ECOLOGICAL MONITORING

In this paper the concept of a nonlinear verticumtype observation system is introduced. These systems are composed from several ＂subsystems＂ connected sequentially in a particular way： a part of the state variables of each ＂subsystem＂ also appears in the next ＂subsystem＂ as an ＂exogenous variable＂ which can also be interpreted as a con trol generated by an ＂exosystem＂. Therefore these ＂subsystems＂ are not observation systems, but formally can be considered as controlobservation systems. The problem of observability of such systems can be reduced to rank conditions on the ＂subsystems＂. Indeed, under the condition of Lyapunov stability of an equilibrium of the ＂large＂, verticumtype system, it is shown that the Kalman rank condition on the linearization of the ＂subsystems＂ implies the observability of the original, nonlinear verticumtype system. For an illustration of the above linearization result, a stagestructured fishery model with reserve area is considered. Observability for this system is obtained by applying the above linearization and decomposition approach. Furthermore, it is also shown that, applying an appropriate observer design method to each subsystem, from the observa tion of the biomass densities of the adult （harvested） stage, in both areas, the biomass densities of the prerecruit stage can be efficiently estimated.

CForBio： a network monitoring Chinese forest biodiversity

China harbors a rich variety of forest types and forest-associated biodiversity, linked to both historical and contemporary environmental factors. However, being a country with a large population and rapid economic development, its diverse forest is facing unprecedent challenges. The Chinese Forest Biodiversity Network （CForBio） was initiated 12 years ago to study the mainte- nance of biodiversity in China＇s forest ecosystems. In this review, we first summarize research progress in CForBio, and then give suggestions for future research. In the past 12 years, the research based on CForBio mainly focused on local ecological factors, such as environment filtering, biotic interactions and small-scale dispersal limitation. We suggest that future studies in CForBio should （1） continue research on trees, but expand more on insects, birds, mammals, microbes and other organism groups; （2） investigate the effects of widespread defaunation on forest biodiversity, structure and functioning; （3） evaluate the diverse effects of climate change on forest composition,structure and functioning; （4） include new technologies, such as remote sensing, to better monitor and study forest biodiversity change and maintenance.