Risk assessment of marine oil spills using dynamic Bayesian network analyses.

Oil spills are serious threats to the marine ecosystem. Especially when an oil spill is faced with extreme weather, the consequences might be more severe. Until now, no such researches focus on the risk of these extreme scenarios. This paper proposes a novel dynamic assessment method to quantify the risk of oil spills in extreme winds based on dynamic Bayesian networks (DBNs). The physical models of advection, spreading, evaporation, and dispersion are transformed into DBNs, and the vulnerability model is established according to coastline types and socio-economic resources. By integrating all the sub-models, the overall DBN to quantify the dynamic risk of oil spills occurring in extreme winds is obtained. The proposed method is demonstrated by the Laizhou Bay. The developed model is validated by a three-axiom-based approach. Temporal and spatial dynamics of risk caused by oil spills in potential locations could be calculated. Based on the developed DBN, the risk of the Laizhou Bay coast caused by oil spills in annual extreme wind speeds corresponding to different mean recurrence intervals is studied. In addition, the effects of the occurrence time of annual extreme winds are also researched.

Study of the Fischer-Tropsch synthesis on nano-precipitated iron-based catalysts with different particle sizes.

Nano iron-based catalysts with different particle sizes were prepared by a co-precipitated method and characterized by XRD, N2 adsorption, SEM, Mössbauer spectroscopy, XPS, H2-TPR, CO-TPD, H2-TPD and TGA. The CO-TPD results revealed that large particle sizes of catalysts were not conducive to the adsorption of CO, and exhibited low activity of FTS. The decrease of catalyst particle size enhanced the interaction between Fe and Mn, and promoted the CO chemical adsorption and the formation of Fe5C2, but the hydrogenation reaction was inhibited as confirmed by H2-TPD. When the particle size continued to decrease, Mössbauer spectroscopy showed that MnFe2O4 appeared in the catalyst phase, which hindered the reduction of catalysts and the adsorption of feed gas. Overall, the sample FeMnSm-600 showed the highest C[double bond, length as m-dash] 2-4 selectivity of 33% at the highest CO conversion of 79% during the reaction conditions of 300 °C, 1.0 MPa, 12 000 mL (g h)-1, and H2/CO = 2.

A targeting method for robot-assisted percutaneous needle placement under fluoroscopy guidance.

Minimally invasive procedures are rapidly growing in popularity thanks to advancements in medical robots, visual navigation and space registration techniques. This paper presents a precise and efficient targeting method for robot-assisted percutaneous needle placement under C-arm fluoroscopy. In this method, a special end-effector was constructed to perform fluoroscopy calibration and robot to image-space registration simultaneously. In addition, formulations were given to compute the movement of robot targeting and evaluate targeting accuracy using only one X-ray image. With these techniques, radiation exposure and operation time were reduced significantly compared to other commonly used methods. A pre-clinical experiment showed that the maximum angle error was 0.94° and the maximum position error of a target located 80mm below the end-effector was 1.31mm. And evaluation of the system in a robot-assisted pedicle screws placement surgery has justified the accuracy and reliability of proposed method in clinical applications.

Effects of Sm on Fe-Mn catalysts for Fischer-Tropsch synthesis.

Sm-promoted FeMn catalysts were prepared by the co-precipitation method and characterized by N2 adsorption, XRD, CO-TPD, H2-TPD, CO2-TPD, H2-TPR, XPS and MES. It was found that compared with the un-promoted catalyst, when Sm was added at a proper content, the catalyst showed a larger BET surface area and promoted the formation of iron particles with a smaller size. The presence of Sm could increase the surface charge density of iron, which enhanced the Fe-C bond and promoted the stability and amount of CO dissociated adsorption, as confirmed by XPS and CO-TPD. Furthermore, according to MES, Sm could promote the formation of Fe5C2, which was the active phase of FTS. In addition, Sm could also enhance the basicity of the catalysts and suppress the H2 adsorption capacity, which inhibited the hydrogenation reaction and the conversion of olefins to paraffins, as verified by the results of CO2-TPD and H2-TPD. According to the FTS performance results, compared with the observations for the un-promoted catalysts, when the molar ratio of Sm to Fe was 1%, the CO conversion increased from 63.4% to 70.4%, the sum of light olefins in the product distribution increased from 26.6% to 32.6, and the ratio of olefins to paraffins increased to 4.18 from 4.09.

A new hand-eye calibration approach for fracture reduction robot.

OBJECTIVE: The hand-eye calibration is used to determine the transformation between the end-effector and the camera marker of the robot. But the robot movement in traditional method would be time-consuming, inaccurate and even unavailable in some conditions. The method presented in this article can complete the calibration without any movement and is more suitable in clinical applications. METHODS: Instead of solving the classic non-linear equation AX = XB, we collected the points on X and Y axes of the tool coordinate system (TCS) with the visual probe and fitted them using the singular value decomposition algorithm (SVD). Then, the transformation was obtained with the data of the tool center point (TCP). A comparison test was conducted to verify the performance of the method. RESULTS: The average translation error and orientation error of the new method are 0.12 ± 0.122 mm and 0.18 ± 0.112° respectively, while they are 0.357 ± 0.347 mm and 0.416 ± 0.234° correspondingly in the traditional method. CONCLUSIONS: The high accuracy of the method indicates that it is a good candidate for medical robots, which usually need to work in a sterile environment.

[Distribution of organochlorine pesticides in surface sediments from Huangpu River and its risk evaluation].

This paper reports 20 organochlorine pesticides (OCPs) in surface sediments of Huangpu River in Shanghai, China. Pesticides were analyzed by GC/ECD with dual column. The concentration range of sigmaOCPs in sediments was 2.65-19.54 ng/g. DDTs, BHCs, methoxychlor and dieldrin had higher concentration than others. The concentration range of DDTs and BHCs was 0.68-4.43 ng/g and 0.14-0.77 ng/g, respectively, which shows concentration of DDTs was higher than BHCs. OCPs content increasing from upper to downstream Huangpu River implicats that discharging of industrial effluents and inflow of Suzhou River offered lots of OCPs to middle-lower Huangpu River. Distribution of OCPs components indicate that OCPs in sediments may be derived from the aged and weathered agricultural soils. According to correlation analysis between OCPs and TOC of sediments, TOC content influences the distribution of OCPs in sediment strongly. Contamination level of OCPs in sediment of Huangpu River is relatively lower than other areas. Comparing with ERL and ERM value of risk evaluation, sediments in middle-lower Huangpu River pose a bit high risk to consumers of bottom feeders.