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This paper summarizes the experimental and numerical investigations on an innovative hybrid joint for timber structures. A total of 12 hybrid dowel and bonding steel plate joints divided in four subgroups were investigated. Different parameters such as the presence of self-tapping screws and the surface treatment of the bonding steel plate, were studied. For two subgroups, a vulcanized rubber layer was applied to the bonding steel plate, before gluing it onto the timber surface. Monotonic tensile tests were carried out on the proposed joints and three replicates for each subgroup were constructed. The focus of this research has been on the load-carrying capacity, shear stress and slip stiffness of the proposed joints. Test results showed that the load-carrying capacity of the hybrid joints was much higher than that of similar screw joints. The introduction of the vulcanized rubber layer in the specimens leaded to the slight improvement of load-carrying capacity and the remarkable improvement of maximum slip. The comparisons between numerical and experimental results indicated that the proposed numerical model had a satisfactory agreement with experimental results and could be used to simulate this hybrid joints. The numerical analysis showed that the shear stress was concentrated in edge regions of the bond line for specimens without rubber layer. While the shear stress distribution became much more uniform for specimens with rubber layer. The research results showed that the bonding steel plate joints with 3.0 mm rubber layer were characterized by both high deformability and high load-carrying capacity.

In recent years, a series of studies have highlighted the positive effects of urban green on individual activity behaviour and health. In this paper, we examine salutogenic environment effects of urban green upon walking behaviour and how such effects are mediated by built environment configuration and street-level physical accessibility. The dwelling locations of N = 15,354 respondents of the London Travel Demand Survey were geocoded and individual walking behaviour was extracted from the travel diary. A 0.5-m resolution normalized difference vegetation (NDVI) index derived from spectral reflectance measurements in remotely sensed colour infrared data was employed as an objective measure of greenness , while density of street trees acted as proxy of perceived environmental quality in street corridors. A network model of street-level physical accessibility was developed using spatial Design Network Analysis (sDNA). Logistic regression models reported a significant association of odds of walking with density of street trees and street-level betweenness (a measure of street network connectivity), while sensitivity analyses with continuous regression models for participants doing some walking indicated beneficial associations of distance walked with NDVI greenness and street trees. The results illustrate the necessity for targeted intervention strategies in activity-friendly planning via greening and optimized physical design of urban built environments.

The long-term performance of bonding steel-plate joints in controlled environmental conditions in this work. The bonding steel-plate joint consists of a steel plate with a vulcanized rubber layer and six wood screws. The vulcanized rubber layer is intended to improve the ductility of bonding steel-plate joints. Six pull-pull specimens were tested in order to determine the short-term load bearing capacity of bonding steel-plate joints, and the dimension of the shear plane of each bond line was 80 mm × 80 mm. A total of 12 specimens were employed in long-term tests. Two stress levels, including the 30% and 60% of ultimate bearing capacity, were adopted. All specimens were monitored over 800 days except that one series of specimens with 0.6 stress level which failed during the long-term tests. At the end of 858-day loading, the average slip at the connection for the specimens with 30% and 60% stress level were 0.623 mm and 0.939 mm, respectively. The creep coefficients were calculated according to the measured experimental data. The Burger’s model, two term and six term Kelvin’s model were adopted to fit the curves of creep coefficients, and then predict the creep slip of joints in the duration of service. The long-term slip stiffness and the ratio of stiffness loss are calculated according to experimental curves, and are predicted on the basis of the prediction results of creep coefficients through by six term Kelvin’s model.

The demand for coal resources is increasing with economic development in China.But,the rich mineral resources along with the intensive mining activities,which have led to a lot of ecological and environmental problems,such as environmental pollution,ecological destruction and geological disasters.Eco-risk assessment is an important tool for effective ecological environment management with evaluations of the likelihood and degree of harm. Thus,this paper applied landscape eco-risk assessment methods to estimate the level of the opencast mine area eco-risk.But also the ESDA(Exploratory spatial data analysis) methods were used to analyze the spatial association characteristic of landscape eco-risk in mining area.It turned out that those high-risk areas is the core of the spatial distribution of Landscape eco-risk and from high-risk to low-risk present ring features.In addition,high-risk is mainly distributed in the mining industry and city life areas,sources of which are the mining,coal gangue tie up land and city construction activities.Medium-risk are mainly distributed in nature,half natural functional areas,the main sources of which are the city life and the agricultural production activities.Low-risk areas are covered by sparse vegetation,such as shrub and grassland.However,in research areas,vegetation degradation,soil and water loss leads to the regional ecological base quality was poor.So the ecosystems and environmental factors are fragile here.Moreover,the frequent production activities in mining areas cause more serious ecological and environment problems.The risk degree of the artificial area is higher than the half natural area,and the half natural area is higher than the natural area.It is conform to the conventional law of ecological risk level difference.At the same time,based on the ESDA of the landscape eco-risk in opencast mine area,the space correlation of the risk is up to 0.7521,which indicate that the agglomeration features of the risk obviously.Different characteristics of agglomeration provide the basis for the ecological and environment management.Space differentiation study of Landscape eco-risk in this opencast mine area shows that interference are the main driving factors in the high-risk and low-risk areas.But in the medium-risk area,fragile degree is the main driving factors.With the increase of human interference,landscape lost diversity and tend to simplification.The results of the study on the mining area provide certain data support and theoretical basis to environment management.

Leakage current (LC) passing through the contaminated insulator surface under wet conditions was frequently analyzed by FFT, STFT, spectrogram and wavelet transform, in order to reflect the surface condition of insulators, while more or less, these methods have some limitations on nonstationary and nonlinear signals. A recently reported technique, termed HHT, was applied to provide time-frequency information about typical LC waveforms. Comparative study found HHT is more adaptive and has higher frequency resolution than other time-frequency methods, hence more suitable to study the discharge property of LC waveforms. It was shown that the decrease in the ratio between RMS and absolute maximum value of LC indicates the presence of partial arcs. According to this, this paper first separated the nonlinear LC into transient impulses and noisy signal, then employed HHT and wavelet transform to analyze each parts separately. Present study showed that wavelet transform is sensitive to high frequency impulses, and the discontinuity of fundamental harmonic together with the dramatically enlarged high frequency harmonics indicate LC gets into danger region.

Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.