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BACKGROUND The geochemical exploration for gold deposits is based on the accurate determination of gold. The content of gold in geochemical samples is usually at the level of ng/g, which needs to be preconcentrated before determination by inductively coupled plasma-mass spectrometry (ICP-MS) or graphite furnace absorption spectroscopy (GFAAS). At present, the exploration of buried deposits is the frontier of geochemical exploration technology and the extraction of gold mobile fraction is one of the most effective approaches to find concealed gold deposits. Compared with whole rock gold analysis, the gold mobile fraction content is much lower, which requires specific leaching, efficient preconcentration and accurate determination. OBJECTIVES To selectively extract gold mobile fraction and find surface secondary anomaly information for exploring concealed ore bodies. METHODS Experiments were carried out on the extraction agent and determination of gold mobile fraction by ICP-MS. Ammonium citrate was used to promote the disassociation of the adsorption of exchangeable form gold from the surface of clay minerals and secondary minerals in the soil. The complexation of thiourea and sodium thiosulfate was applied to diffuse the extracted gold into the solution to achieve the purpose of selective extraction. The procedure for gold preconcentration from extraction solution and the ICP-MS determination method were established. RESULTS The experiments determined that the extractant was composed of 5g/L ammonium citrate, 2g/L thiourea, and 5g/L sodium thiosulfate. The extraction time was 24h, and the active carbon was used to preconcentrate gold in the acidic thiourea medium. The gold adsorption rates were 89.6%-109.2%, and the ashing temperature of the concentration materials were 650-700℃. The detection limit of the method was 0.05ng/g, the relative standard deviations (RSDs) ranged from 9.4% to 10.2%, and the recoveries were from 91.2% to 93.4%. CONCLUSIONS Compared with the published method, extraction with ferric sulfate-thiourea-sodium thiosulfate solution and determination by GFAAS, this method has the advantages of low detection limit, wide linear range and fast analysis. This method has been successfully applied in the geochemical exploration of gold deposits in the forest swamp landscape area of Dongan, Heilongjiang Province. Gold anomaly delineated is consistent with the location of the concealed gold deposit.

In this paper, the urban signal propagation characteristics based on the location of blind sources are investigated. To address the issue of blind electromagnetic radiation sources in complex urban environments, intelligent methods for propagation channel path classification, and model determination are brought forth based on field test data. The intelligent classification method distinguishes between the Line-of-Sight (LoS) path channel and a direct path, the LoS multipath channel with a direct path and other multiple paths, and the Non-Line-of-Sight (NLoS) multipath channel without a direct path from the source to the test point. The modeling aspect determines the model type to which the received signal belongs based on the statistical model derived from the tested data of a specific source. A validation measurement system was constructed for the FM broadcasting band, and validation campaigns were conducted in the city of Wuhan. The process and analysis of the data using this method demonstrate the accurate distinction of the different propagation path channels and models and involve the construction of a statistical model for the FM band in Wuhan's urban area. [ABSTRACT FROM AUTHOR]

Parabolic equations (PE) are commonly employed for calculating the spatial propagation loss of wireless signals. The initial field is a crucial factor. To investigate the impact of construction accuracy on the calculation of radio wave propagation loss, we selected the half-wave dipole antenna and its Gaussian approximation to examine the influence of wide-angle PE modeling. We analyzed the disparities between the actual antenna pattern and the Gaussian beam approximation, as well as the discrepancies in the corresponding initial field and the calculation of radio wave propagation loss in PE modeling. The simulation results indicate that the error of the Gaussian approximation increases as the angle of departure from the antenna main beam increases, with a relative error of approximately 30% in the initial field. A comparison between the experimental test of the broadcast signal and the simulation calculation reveals that the model based on the actual antenna aligns more closely with the measured value on a flat underlying surface. However, in mountainous areas with significant fluctuations, the simulation results are consistent with each other and higher than the measured value. The inversion results obtained through the particle swarm optimization algorithm demonstrate that the model based on the actual antenna exhibits superior inversion accuracy for the tropospheric atmospheric duct structure. [ABSTRACT FROM AUTHOR]

Extraction of elements of mobile forms is one of the important techniques in deep-penetrating geochemistry for finding concealed orebodies. However, the single extraction agent cannot be applied to all elements and all coverage areas. Moreover, the effective information of mobile forms is easily obscured because the extraction time, pH and extraction temperature have important effects on the extraction results. Determination of the mobile forms of multi-metal elements (W, Mo, Cu, Pb, Zn) in extractant using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) has been established. The optimum conditions include solid-liquid mixing ratio of 1:10, extraction time of 24 h, pH of 7.0, and an extraction temperature of 25℃. The determination limit of the proposed method is 0.006-0.021 μg/g and the relative standard deviation (RSD) is 1.91%-6.56%. This method has been applied to Xiyuku concealed porphyry Mo-W ore deposit in the Luanchuan ore concentrated district. The prospecting anomaly in mobile forms of W and Mo is consistent with the projection position of concealed orebodies in the ground surface.

This paper analyzed the existing anonymous authentication schemes which have the weakness of high calculation and communication cost and weak security. So we designed a secure and efficient anonymous authentication scheme to meet the need of the space network, which has the characteristic of resource limited, high exposure and intermittent connectivity. At first we proposed a signature algorithm based on certificateless public key cryptosystem and one-off public key, and then presented an anonymous authentication scheme according to the proposed signature algorithm, it needs two message interaction to complete the mutual authentication and key agreement. When the user has the illegal behavior, the service provider can reveal the illegal user’s real identity through cooperation with the trusted center. Compared with the similar literature, the proposed scheme achieves high security with low computation and communication cost. (Abstract)

This paper proposed a labeling to data stream binding method independent of the contents of the packet, which based on packet delay modulation, and introducing the packet inter-arrival delay as the new labeling vector. The method used Himming code to achieve the label error control, designing the data packet randomized blocks, and modulated the packet delay time according to the label binding rules, then realized the implicit binding of security label to data stream. Based on this method, it solved the targeted attack problems caused by explicit binding method and its inflexibility. Theoretical analysis and experimental results demonstrate that the proposed method is robust against the network random timing perturbation and safety the binding security label when is transmitted in the network. [ABSTRACT FROM AUTHOR]

This paper proposed a secure communication model for space delay-tolerant network. This model applied predicate logic, and built SDTN directed multi-path graph, security protocol service set, reliable path selection service set, and forwarding capacity set. It also gave out the model's security constraint rule and secure communication algorithm. It defined the state machine of space delay-tolerant network secure communication, and proved the model's security, reliability and delay-tolerant ability, which laid the foundation for space delay-tolerant network secure communication. [ABSTRACT FROM AUTHOR]

LuPO4:Yb crystals of 6 x 2 x 0.5 mm maximum size are grown from Yb2O3 and Lu2O3 in a Pb2P2O7 flux as high-temperature solvent. [ABSTRACT FROM AUTHOR]

Large single crystals of the title compound are prepared from mixtures of Lu2O3, Yb2O3, and PbHPO4 (Pt crucible, 1350 °C, 16 h). [ABSTRACT FROM AUTHOR]