Holocene climate change and anthropogenic activity records in Svalbard: a unique perspective based on Chinese research from Ny-Ålesund

Climate change in the Arctic region is more rapid than that in other areas owing to Arctic amplification. To better understand climate change and the driving mechanisms, long-term historical reconstructions throughout the Holocene and high-resolution records of the past few hundred years are required. Intense anthropogenic activities in the Arctic have had a great impact on the local environment. Here, we review the Holocene climate change record, responses of the ecosystems to climate change, and the anthropogenic impacts on the environment based mainly on Chinese research from Ny-Ålesund. Climate reconstruction studies from Svalbard have revealed several cold episodes during the Holocene, which are consistent with ice rafting events in the North Atlantic region and glacier activity from Greenland, Iceland, and Svalbard. The ecosystem also showed corresponding responses to climate change, especially during the late Holocene. Over recent decades, anthropogenic activities have caused serious pollution and deterioration to the local environment in Svalbard in areas frequented by people. Greater environmental protection is therefore needed to reduce the anthropogenic impacts on the local environment

Mid-frequency sound propagation through internal waves at short range with synoptic oceanographic observations

Preliminary results are presented from an analysis of mid-frequency acoustic transmission data collected at range 550m during the Shallow Water 2006 Experiment. The acoustic data were collected on a vertical array immediately before, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave’s position as a function of time is developed. Experimental results show a new acoustic path is generated as the internal wave passes above the acoustic source

Preparation and characterization of branched energetic polymers

The energetic binders are important constituents of energetic material composites such as propellants. The most widely used energetic binders such as GAP are the polyurethane based, produced by curing reaction of the energetic prepolymers with isocyanates. Energetic plasticizers are key ingredients which help to improve the processability and flexibility of the energetic binders. The effects of plasticizers on energetic binders are required to be investigated to develop the further applications of plasticized binders. This research aims to investigate the efficiency of GAPA and BuNENA plasticizers to lower the viscosity and glass transition temperature and improve the flexibility of GAP based energetic binder systems with different degree of branching. The viscosities, glass transition temperature and storage modulus of binder/plasticizer mixtures were measured as a function of plasticizer loading. The activation energy for flow and plasticizer efficiencies were calculated respectively for the two plasticizers. The results indicate that the BuNENA plasticizer provides a lower activation energy to flow of the energetic binders as compared to GAPA. The BuNENA plasticizer had a higher plasticizing efficiency in lowering the glass transition temperature of the binders. The BuNENA plasticizer could improve the flexibility and provide the larger elastic region for the cured binders.Bachelor of Engineering (Materials Engineering

An Underwater Acoustic Network Positioning Method Based on Spatial-Temporal Self-Calibration

The emergence of underwater acoustic networks has greatly improved the potential capabilities of marine environment detection. In underwater acoustic network applications, node location is a basic and important task, and node location information is the guarantee for the completion of various underwater tasks. Most of the current underwater positioning models do not consider the influence of the uneven underwater medium or the uncertainty of the position of the network beacon modem, which will reduce the accuracy of the positioning results. This paper proposes an underwater acoustic network positioning method based on spatial-temporal self-calibration. This method can automatically calibrate the space position of the beacon modem using only the GPS position and depth sensor information obtained in real-time. Under the asynchronous system, the influence of the inhomogeneity of the underwater medium is analyzed, and the unscented Kalman algorithm is used to estimate the position of underwater mobile nodes. Finally, the effectiveness of this method is verified by simulation and sea trials

Surface Detection of Solid Wood Defects Based on SSD Improved with ResNet

Due to the lack of forest resources in China and the low detection efficiency of wood surface defects, the output of solid wood panels is not high. Therefore, this paper proposes a method for detecting surface defects of solid wood panels based on a Single Shot MultiBox Detector algorithm (SSD) to detect typical wood surface defects. The wood panel images are acquired by an independently designed image acquisition system. The SSD model included the first five layers of the VGG16 network, the SSD feature mapping layer, the feature detection layer, and the Non-Maximum Suppression (NMS) module. We used TensorFlow to train the network and further improved it on the basis of the SSD network structure. As the basic network part of the improved SSD model, the deep residual network (ResNet) replaced the VGG network part of the original SSD network to optimize the input features of the regression and classification tasks of the predicted bounding box. The solid wood panels selected in this paper are Chinese fir and pine. The defects include live knots, dead knots, decay, mildew, cracks, and pinholes. A total of more than 5000 samples were collected, and the data set was expanded to 100,000 through data enhancement methods. After using the improved SSD model, the average detection accuracy of the defects we obtained was 89.7%, and the average detection time was 90 ms. Both the detection accuracy and the detection speed were improved

Statistical optimisation of process variables and large-scale production of Metarhizium rileyi (Ascomycetes: Hypocreales) microsclerotia in submerged fermentation

Microsclerotia (MS) formation was successfully induced in Metarhizium rileyi (Ascomycetes: Hypocreales) in liquid culture. To optimise the process variables of liquid fermentation, we first used a two-level fraction design to confirm the variables, including inoculum density, initial pH, shaker speed, and temperature, affecting M. rileyi MS production. Three variables were found to be important. Subsequently, a 23 full factorial central composite design (CCD) and response surface methodology were applied to ascertain the optimal level of each variable. A second-order polynomial was determined and shaker speed and inoculum density were found to be the primary variables affecting MS yields. Finally, we realised and optimised M. rileyi MS submerged fermentation based on previous findings. A maximum MS yields (3.84 × 104 MS/mL) were recorded in submerged fermentation at an initial pH of 5.5, growth temperature of 26°C, inoculum density of 10%, higher aeration rate (150 rpm in the initial 3 days and 200 rpm in the subsequent 3 days), and higher agitation rate of 800 L/h sterile air

Analysis of the Cavity Formation Mechanism of Wedge Cut Blasting in Hard Rock

The basic process of cut blasting is to break rock, throw fragments, and form a cavity. Based on the characteristics of cut blasting and the combined effect of stress waves and detonation gas, the evolution process of wedge cut blasting is divided into two stages, and a theoretical model is proposed to investigate the cavity formation mechanism by theoretical analysis and field tests. In phase one, rock breaking is caused by stress waves. By considering the dynamic strength of the rock, a computational model is built for the rock failure zone derived from the coupled cylindrical charge explosion. In phase two, the driving force of the detonation gas overcomes the total resistance of the surrounding rock mass, accelerates fragments, and then throws fragments to form a cavity. The criterion of cavity formation is established on the basis of the quasi-static loading of the detonation gas. The theoretical model provides an overall interpretation of the cavity formation mechanism, in which stress waves break rock and detonation gas throws fragments. A specific case indicates that the range of the failure zone is approximately 18 times the borehole radius in granite and that the hole-bottom spacing of the wedge cut can be designed as 50 cm; in addition, detonation gas is sufficient to overcome the total resistance, accelerate rock fragments, throw fragments, and form a cavity. Field tests present favourable blasting results, with a high utilization rate of boreholes and uniform fragment sizes. Therefore, the model could provide theoretical support and technical guidance for wedge cut blasting in hard rock