Tsmghua University

Beijing, China

Tsmghua University

Beijing, China
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Xu L.,Peking University | Xu L.,Shenzhen University | Sun J.,Peking University | Sun J.,Shenzhen University | And 5 more authors.
Chinese Journal of Applied and Environmental Biology | Year: 2012

For understanding the effect of environment factors on the removal of chromate by bacterial strains and to provide chromate-removing strains for the bioremediation of environments contaminated by chromáte, two Gram-positive bacterial strains designated as Chr-9 and Chr-43 respectively, capable of removing Cr (VI) in LB medium, were isolated from sludge collected from one tannery plant in Binzhou, Shandong, China. Based on 16S rRNA genes and phenotype characteristics, strain Chr-9 and Chr-43 were identified as Rhodococcus and Exiguobacterium strains, respectively. The optimal temperature and pH for Cr (Vl)-removal by the two strains were 35 °C and pH 7.0, respectively. The removal of Cr (VI) was enhanced by supplementation of 0.1∼0.5 mol/L NO3 -, SO4 2-, and Cl- for strain Chr-9 and by supplementation of 0.1∼0.2 mol/L NO3 -, SO4 2, and Cl- for strain Chr-43. The growth and Cr (Vl)-removal rate of strain Chr-43 were both enhanced by co-cultivation with strain Chr-9. These results indicated that the removal of chromate by bacterial strains could be affected by temperature, pH, negative ions, and other co-cultured microbes.

Wei Q.,Tsmghua University | Wang S.,Tsmghua University | Dai T.,China Japan Friendship Hospital | Li D.,China Institute of Metrology | And 5 more authors.
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2014 | Year: 2014

Stticon Photomultiplier (SiPM) is a promising sensor for PET with a number of advantages. A traditional design for PET detector module is using a pixelated scintillator array coupled to a SiPM array, and it is critical to design reflectors between crystals to decode photon event location. Unlike PMT based detectors, the pixelated scintillator array may not necessarily require complex reflector schemes for optimal light sharing. An intuitive design method is to fill the gaps between adjacent crystals with reflective materials such as ESR or BaSO4. However, the manufacture of the array with reflectors is still time-consuming and costly. In this paper, we evaluate the performances of pixelated LYSO arrays separated by only air-gap. A mathematical calculation shows that there is not much difference between reflector based and air-gap based detector module design. Three groups of experiments were conducted based on a home-made 8×8 SiPM array, including a single LYSO crystal with three types of reflector process, three 8×8 LYSO arrays and two 15×15 LYSO arrays with different crystal surface treatments and with air or reflective-material gaps. The results show that the air-gap design for polished LYSO has similar event decoding capability and energy resolution compared with the reflector-filled design. In conclusion, the scintillator arrays with air-gap are simple and feasible for SiPM based detector, which would greatly reduce the cost and manufacture time of detector modules without performance deterioration. © 2014 IEEE.

Chen Z.,University of Florida | Yin Y.,University of Florida | He F.,Tsmghua University | Lin J.L.,University of Illinois at Chicago
Transportation Research Record | Year: 2015

This paper discusses a smartphone-based parking reservation system that manages a finite number of curbside parking spaces located at various places in a downtown area. Parking reservation schemes are designed to minimize the total social cost of parking, which is assumed to be a weighted sum of the cruising times for drivers to travel from their current locations to allocated parking spaces and the walking times from parking places to final destinations. With the assumption of perfect information on cruising and walking times, a simple reservation scheme to achieve an optimum allocation of parking spaces is presented. However, although the locations of drivers can be retrieved from their smart-phones, it is shown that drivers have an incentive to misreport their final destinations for their own benefit, which compromises the system benefit. Thus, the Vickrey-Clark-Groves mechanism is applied to determine the allocation of parking spaces and parking fees to minimize the total social cost while ensuring that all drivers report their final destinations truthfully. Last, a revenue redistribution scheme to reduce drivers' financial burden further and increase public acceptance of the reservation system is discussed.

Cai Z.,Tsmghua University | Kang Y.,Tsmghua University | Wang Y.,Tsmghua University | Yuan J.,Tsmghua University
Acta Polymerica Sinica | Year: 2011

A novel and well-defined comb-copolymer, ethyl cellulose-gro/t-poly (ε-caprolactone) (EC-g- PCL) was synthesized via ring-opening polymerization (ROP) of ε-caprolactone (CL) with ethyl cellulose as the macroimtiator. The following coupling reaction of 1-pyrenebutyric acid with hydroxyl-terminated poly (ε- caprolactone) (PCL) was carried out in the presence of dicyclohexylcarbodiimide (DCC) and 4- dimethylaminopyridine (DMAP) . Pyrene-containing comb-copolymers (EC-g-PCL-Pyr) with different graft ratios of pyrene groups were obtained by adjusting the molar ratio of EC-g-PCL and pyrene. The structure of the resultant products was characterized by H-NMR and FTIR spectroscopy. Thermal properties and crystalline morphologies were established by differential scanning calorimetric analysis (DSC) and atomic force microscopy (AFM), respectively. Thermal analysis showed the melting temperature of EC-g-PCL-Pyr was lower than that of EC-g-PCL, because of the change of crystalline form which was demonstrated by AFM photos. Optical feature was determined by UV-Vis and fluorescence spectrometer. Fluorescence analysis indicated that the fluorescence intensity of EC-g-PCL-Pyr comb-copolymers changed with the increasing of the graft ratio of pyrene when the pyrene concentration of their CHCl 3 solution was the same. This comb-copolymer could be used in biomedical applications such as fluorescent drug delivery and fluorescent probe.

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