Demonstration of laser-produced neutron diagnostic by radiative capture gamma-rays

We report a new scenario of time-of-flight (TOF) technique in which fast neutrons and delayed gamma-ray signals were both recorded in a millisecond time window in harsh environments induced by high-intensity lasers. The delayed gamma signals, arriving far later than the original fast neutron and often being ignored previously, were identified to be the results of radiative captures of thermalized neutrons. The linear correlation between gamma photon number and the fast neutron yield shows that these delayed gamma events can be employed for neutron diagnosis. This method can reduce the detecting efficiency dropping problem caused by prompt high-flux gamma radiation, and provides a new way for neutron diagnosing in high-intensity laser-target interaction experiments

Identification of the karst water flow system and its application in the tunnel line selection of water diversion projects

A critical water diversion project may face serious water inrush problems during tunnel construction when it crosses the carbonate rock formations of Julongshan syncline.Characteristics of karst water flow system in Julongshan syncline were identified by multi-methods such as karst hydrogeological field survey, hydrochemistry and isotope analysis, to find out the hydrogeological conditions of water inrush into the tunnel and select one water diversion scheme with lower risk of karst water disaster.The results show that the aquifer system in Julongshan syncline has a multi-layer structure with an impermeable layer between two aquifers.The Lower Permian is mainly buried underground with weak karst development, while the Upper Triassic bare karst area forms a giant karst basin with multi-stage water flow system.Three tunnel plans were demonstrated in Julongshan syncline area.Plan A passes through the recharge area of the karst water system in the western syncline, in which the length of soluble rock the tunnel passes through is the lowest and all belong to buried karst.It avoids to cross the Triassic karst water basin in the profile, therefore the risk of water-gushing for Plan A is relatively low.However, Plan B and Plan C will cross the Triassic karst water basin with longer soluble rock section and the risk of suffering karst water-gushing is much higher.So, Plan A is recommended.This study can provide a scientific basis for comparison and selection of diversion tunnel line, and also has reference value for similar deep-buried long tunnel construction

Processes and sources identification of intermittent karst water inrush in Xiakou Tunnel

The investigation and prevention of karst water inrush is a difficult problem in tunnel construction. The Xiakou Tunnel has a long history of karst water inrush.To identify the source of intermittent water inrush and explore the controlling effect of karst water system to the process of water inrush, the hydrogeological survey, hydrological and hydrogeochemical methods were used to identify the sources and processes of water inrush. The results show that, there is a groundwater divide at the area of Mengjialing, and the groundwater in the northern and southern area discharge into Xianglongdong and Xiakoudong, respectively. In the events of concentrated water inrush, the total amount of event water inrush has a significant linear positive correlation with the rainfall event, and the hydrogeochemical composition of the water inrush is very similar to that of the four blind drainage ditches, which indicates that all these water inrushes and blind drainage ditches come from the karst water in the northern part of the tunnel. During the stable drainage period, the karst water in the northern part of the tunnel is mainly discharged through the blind drainage ditch on the north of the right tunnel, while the groundwater of other three blind drainage ditches come from the fissure water in clastic rock.The concentrated water inrush point is located on the surface of saturated zone in the karst water system of Xiakou. The heavy rainfall events made the upper part of tunnel to be filled with karst water.The water inrush was caused by intercepting the fast flow in karst channel, and small part of base flow was mixed into the water inrush. In the study of karst water inrush, the comprehensive utilization of multi-technical methods and multi-information verifications can improve the accuracy in the source identification of water inrush

Design and Experiment of Uniform Seed Device for Wide-Width Seeder of Wheat after Rice Stubble

When wide-width sowing wheat after rice stubble (WRS) in a rice-wheat rotation area, there is a problem of poor uniform of seed distribution. To solve the problem, this study designed the seed distribution plate (SDP) structure and optimized its critical structure parameters. Firstly, combined with the operating principles of the wide-width seeder and the agricultural standards for WRS, the main structural parameters affecting seed movement were determined by a theoretical analysis of seed grain dynamics and SDP structure. Secondly, the operational performance of six different structures of SDP under different structural parameters was compared using discrete element simulation technology. The structure of SDP most suitable for WRS wide-width seeding and the value ranges of key structural parameters that have a significant impact on the coefficient of the variation of seed lateral uniformity (CVLU) were determined. Finally, the pattern and mechanism of the influence of key structural parameters of SDP on the CVLU were analyzed. The optimum parameter combination was obtained and a field validation test was conducted on this. The results showed that the anti-arc ridge and arc bottom structure (S6) is more suitable for the agronomy standards of WRS wide-width seeding. The chord length of ridge, installation inclination, angle between the chord and tangent of the end of ridge line (ACT), span, and bottom curve radius are determined as the key structural parameters affecting the CVLU, and there is a lower CVLU (42.8%) when the ACT is 13°. The primary and secondary order of the influence of each factor on CVLU is the chord length of the ridge, span, installation inclination, and bottom curve radius. The corresponding parameter values after optimization are 140 mm, 40°, 75 mm and 50 mm, respectively. A field test was conducted on the SDP after optimizing parameters, and the CVLU was 30.27%, which was significantly lower than the CVLU before optimization

Characteristics of the karst water system on the northeast wing of the Huangling anticline and its impact on water diversion tunnel engineering

The strata in the northeast wing of the Huangling anticline consist of interbedded carbonate rocks and clastic rocks. As the carbonate rocks underwent strong karstification, karst water inrush would be a significant factor impacting the construction of underground engineering in this area. Taking the Huangling anticline section of a critical national water diversion project as the research object, the characteristics of the karst groundwater system and the water inrush conditions in tunnels were identified by various methods, such as karst hydrogeological surveys, tracer tests and hydrogeochemistry analysis. These results show that the aquifer system contains four sub-aqueous systems with a structure of strong and weak permeable interlayers in the vertical direction, in which a multi-stage karst groundwater system has developed with shallow rapid circulation, intermediate rapid circulation and a deep slow circulation subflow systems. The faults constitute the vertical channels for hydraulic exchange between sub-aquifer systems. The water diversion tunnel primarily crosses the deep Dengying Formation (Z2dn) and Tianheban-Shilongdong Formation(∈1t+sl) aquifer systems with weak karst development. However, a large-scale high-pressure water inrush accident may occur when passing through the Dianya fault, which may transfer groundwater from the upper karst sub-aquifer system of the Loushanguan Formation-Nanjinguan Formation (∈3l-O1n) into the tunnel. The risk of encountering conduit water inrush accidents is high during construction when the construction branch tunnel passes through the discharge area of the Bailongdong groundwater flow system in the ∈3l-O1n sub-aquifer systems. The accuracy of identifying of karst groundwater flow system features and inrush conditions can be improved by joint interpretation of multiple hydrogeological methods

Characteristics and genesis of karst water flow system around Huangling anticline

The study of the karst water flow system is helpful for the reasonable evaluation and utilization of groundwater resources.In this paper, the spatial characteristics, hydrological dynamic response, temperature field, and conductivity characteristics of the typical karst water flow system were calculated and quantified by referring to the methods of hydrology research.Four groundwater systems, i.e., fan-shaped, branch-shaped, flat-shaped, and comb-shaped, were divided to comprehensively reflect the surface-underground karst characteristics of the karst flow system.The main pipelines of the first two are perpendicular to the stratigraphic trend, and the structural fractures play a role in catching water.The main pipelines of the latter two are parallel to the stratigraphic trend, and the horizontal fractures play a role in collecting water.The northwest, west, and south wings of the Huangling anticline are branch-shaped and flat-shaped, while the east and north wings are fan-shaped and flat-shaped water systems.The formation and regional differences of different groundwater systems are closely related to the spatial relationship and hierarchy of aquifer systems and water systems which show different dynamic characteristics.The fan-shaped and flat-shaped karst flow system are the most sensitive to rainfall response, while the comb-shaped karst flow system has the slowest response and attenuation process.Based on the obvious correlation between karst groundwater temperature and exposed elevation and circulation depth, the groundwater temperature line in the mountainous area of western Hubei province is established.This study could provide certain theoretical support for karst groundwater flow system research and local engineering practice

Phylogenetic analysis and the tertiary structure of <i>AccDpp</i>.

<p>A, phylogenetic analysis of AccDpp from different species. The species source of the above analysis is listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0149117#pone.0149117.s005" target="_blank">S4 Table</a>. B, the tertiary structure of AccDpp. Helices, sheets, and coils are presented in different colours.</p

The cDNA sequence of <i>AccDpp</i> and its amino acid sequence.

<p>The top line shows the nucleotide sequence of <i>AccDpp</i>, and the second line shows the deduced amino acid sequence. The start codon (ATG) and stop codon (TAG) are boxed. The polyadenylation signal (AATAA) sequence is marked by an oval. The underlined region indicates the signal peptide, and the shaded amino acid sequence denotes the predicted antimicrobial peptide. The sequence was deposited in GenBank, and the GenBank accession no. is KT750952.</p

Influence of Soft Phase and Carbon Nanotube Content on the Properties of Hierarchical AZ61 Matrix Composite with Isolated Soft Phase

Carbon nanotube-reinforced magnesium matrix (CNTs/Mg) composite has great application potential in the transportation industry, but the trade-off between strength and ductility inhibits its widespread application. In order to balance the strength and plasticity of the composite, in this work, on the basis of the AZ61 matrix composite homogeneously reinforced by Ni-coated CNTs (hard phase), 30 vol.% large-size AZ61 particles are introduced as an isolated soft phase to fabricate hierarchical CNTs/AZ61 composites. The compression tests show the fracture strain and compressive strength of this composite increases by 54% and 8%, respectively, compared with homogeneous CNTs/AZ61 composite. During deformation, the hard phase is mainly responsible for bearing the load and bringing high strength, due to the precipitation of the Mg17Al12 phase, uniformly dispersed CNT and strong interfacial bonding of the CNTs/Mg interface through nickel plating and interfacial chemical reaction. Furthermore, the toughening of the soft phase results in high ductility. With the increase in CNT content, the compressive strength of composites is nearly unchanged but the fracture strain gradually decreases due to the stress concentration of CNT and its agglomeration