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Because of errors in the kinematic parameters of parallel robots, it is necessary to identify them to improve the pose accuracy for accurate task performance of semi-physical simulation platform. In this paper, a methodical way of kinematic parameter identification is introduced. It requires measurements of all legs and the pose information provided by a coordinate measuring machine. Nonlinear least squares algorithm is employed to determine the kinematic parameters. The measurement errors in the leg sensors are considered during kinematic modeling and kinematic parameter identification. Simulations and experimental studies on a Stewart parallel robot built in the Institute of Electro-hydraulic Servo Simulation & Test System of Harbin Institute of Technology reveal the convenience and effectiveness of the proposed robot parameter identification algorithm and calibration method for parallel robots. [ABSTRACT FROM AUTHOR]

Workpiece deformation must be controlled in the numerical control machining process. Fixture layout and clamping force are two main aspects that influence the degree and distribution of machining deformation. In this paper, a multi-objective model was established to reduce the degree of deformation and to increase the distributing uniformity of deformation. The finite element method was employed to analyze the deformation. A genetic algorithm was developed to solve the optimization model. Finally, an example illustrated that a satisfactory result was obtained, which is far superior to the experiential one. The multi-objective model can reduce the machining deformation effectively and improve the distribution condition. [ABSTRACT FROM AUTHOR]

This research focused on removing arsenic (As) from groundwater by coupling iron-tailored activated carbon with iron solubilization. This was achieved by solubilizing iron grains that were interspersed within the tailored activated carbon. A commercially available bituminous coal carbon was preloaded with iron by an evaporation method. With natural groundwater as the source, the media processed 25,000 bed volumes (BV) of water before >10 µg/L As breakthrough occurred. In comparison, when 30% zero-valent iron (NI) grains were interspersed with iron-preloaded bituminous coal carbon, As breakthrough > 10 µg/L occurred at 45,000 BV. The As breakthrough corresponded to when most of the NI source had become visibly corroded. Although some solubilized iron escaped through the granular activated carbon media, this iron could be captured in a subsequent sand or activated carbon filter in order to yield water that would meet both primary and secondary drinking water standards. Field-scale tests are required to determine whether results at large scale corroborate the laboratory findings. [ABSTRACT FROM AUTHOR]

Abstract  We utilized 234Th, a naturally occurring radionuclide, to quantify the particulate organic carbon (POC) export rates in the northern South China Sea (SCS) based on data collected in July 2000 (summer), May 2001 (spring) and November 2002 (autumn). Th-234 deficit was enhanced with depth in the euphotic zone, reaching a subsurface maximum at the Chl-a maximum in most cases, as commonly observed in many oceanic regimes. Th-234 was in general in equilibrium with 238U at a depth of ∼100 m, the bottom of the euphotic zone. In this study the 234Th deficit appeared to be less significant in November than in July and May. A surface excess of 234Th relative to 238U was found in the summer over the shelf of the northern SCS, most likely due to the accumulation of suspended particles entrapped by a salinity front. Comparison of the 234Th fluxes from the upper 10 m water column between 2-D and traditional 1-D models revealed agreement within the errors of estimation, suggesting the applicability of the 1-D model to this particular shelf region. 1-D model-based 234Th fluxes were converted to POC export rates using the ratios of bottle POC to 234Th. The values ranged from 5.3 to 26.6 mmol C m−2d−1 and were slightly higher than those in the southern SCS and other oligotrophic areas. POC export overall showed larger values in spring and summer than in autumn, the seasonality of which was, however, not significant. The highest POC export rate (26.6 mmol C m−2d−1) appeared at the shelf break in spring (May), when Chl-a increased and the community structure changed from pico-phytoplankton (µm) dominated to nano-phytoplankton (2–20 µm) and micro-phytoplankton (20–200 µm) dominated. [ABSTRACT FROM AUTHOR]

Arsenic is of concern in water treatment because of its health effects. This research focused on incorporating hydrous ferric oxide (HFO) into granular activated carbon (GAC) for the purpose of arsenic removal. Iron was incorporated into GAC via incipient wetness impregnation and cured at temperatures ranging from 60 to 90 °C. X-ray diffractions and arsenic sorption as a function of pH were conducted to investigate the effect of temperature on final iron oxide (hydroxide) and their arsenic removal capabilities. Results revealed that when curing at 60 °C, the procedure successfully created HFO in the pores of GAC, whereas at temperatures of 80 and 90 °C, the impregnated iron oxide manifested a more crystalline form. In the column tests using synthetic water, the HFO-loaded GAC prepared at 60 °C also showed higher sorption capacities than media cured at higher temperatures. These results indicated that the adsorption capacity for arsenic was closely related to the form of iron (hydr)oxide for a given iron content. For the column test using a natural groundwater, HFO-loaded GAC (Fe, 11.7%) showed an arsenic sorption capacity of 26mg As/g when the influent contained 300 μg/L As. Thus, the preloading of HFO into a stable GAC media offered the opportunity to employ fixed carbon bed reactors in water treatment plants or point-of-use filters for arsenic removal. [ABSTRACT FROM AUTHOR]

Abstract Background There are few data available on the prevalence, incidence, and residual risk of transfusion-transmitted HBV (TT-HBV) infections among Chinese blood donors. This study investigated the demographic characteristics of blood donors, as well as the prevalence, incidence, and residual risk (RR) of TT-HBV infections in six large blood centers in different regions of China. Methods The demographic characteristics and HBV screening test results of blood donors from six blood centers in different regions in China were collected and analyzed. The hepatitis B surface antigen (HBsAg) yield approach was used to estimate the incidence of HBV. Then, the RR of TT-HBV infections was evaluated using the incidence-window period model. Results The majority of donors were between 18 and 35 years old (including 35), with the exception of the Changzhi Blood Center where a majority of donors were between 35 and 55 years old (including 55). The prevalences of HBV were 0.13%, 0.078%, 0.16%, 0.07%, 0.20%, 0.25% in Hefei, Dalian, Changzhi, Kaifeng, Mianyang and Fujian, respectively. The estimated corresponding incidences were 213.44, 161.59, 989.80, 278.05, 125.31 and 352.19 per 105 person-years. Using an infectious window period of 59 days, the RR for HBV was estimated to be 34.14, 25.85, 158.35, 44.48, 20.04 and 56.35 per 105 person-years in Hefei, Dalian, Changzhi, Kaifeng, Mianyang and Fujian, respectively. Conclusion Despite the introduction of more sensitive assays in blood screening, our data revealed that the current residual risk of TT-HBV infection was still high (overall 56.53 per 105 py). A continuous monitoring of the residual risk of transfusion-transmitted infections is crucial for safe blood management.

Due to the various requirements of users and large volume of machine tools, most machine tool manufacturers are adopting the small-lot production mode, which largely prolongs the product development cycle. To raise the design efficiency and reduce the complexity, modular design is becoming widely used in serial production of machine tools, especially large gantry machining centers. In this paper, we introduced a function and structure decomposition method to construct the function and structure correlations between components and employed a clustering method based on atomic theory to solve the module clustering problems. The clustering algorithm is modified by integrating the function and structure matrices in order that it applies to modularization of large machine tools. Furthermore, an evaluation method based on the concept of entropy is proposed here to evaluate and optimal select module partition schemes. Finally, we took the large gantry machining center QLMT6300 as an example and compiled the program with Microsoft Visual C++ 6.0 to illustrate the validity of the methods proposed. The presented clustering and evaluation method can be easily applied to different machine tools for modular design, reducing the work amount of designers. [ABSTRACT FROM AUTHOR]

Past studies of plasma sheaths enveloping vehicles have shown that the distribution of plasma is time-varying and results in communication and navigation problems. This paper aims to investigate the dynamic characteristics of the plasma sheath through the simulations of the Radio Attenuation Measurements-C II vehicle and the Apollo command module flowfields. The numerical methodology is based on the unsteady Reynolds-averaged Navier-Stokes model and the detached-eddy simulation model, and the thermochemical nonequilibrium effect is considered. The stable flows of both vehicles with a steady plasma sheath widely distributed in the shock-wave layer are first obtained. For the Radio Attenuation Measurements-C II vehicle, the dynamic plasma arising from the vehicle pitching oscillation has the same frequency as the vehicle oscillation, and the magnitude of the disturbance to plasma is related to the oscillation velocity. For the Apollo command module, the oscillation period of the electron density is the same as the evolution period of the vortex structures in the leeward regions. The time-varying surface electron density and pressure reveal a similar variation trend with the phase difference. In addition, the periodicity of the dynamic plasma disappears as the flow instability intensifies in the Apollo command module flowfields, whereas periodic plasma exists for a long time in the Radio Attenuation Measurements-C II vehicle oscillation flowfields. [ABSTRACT FROM AUTHOR]