Search

The exo-hydroxyl group (exo-OH) on isosorbide (ISB) has long been asserted as a highly reactive moiety compared with the endo-hydroxyl group (endo-OH). In this study, calculations based on density functional theory and experiments without adding catalysts reveal that endo-OH has strong nucleophilic ability, and in the case of transesterification with diphenyl carbonate, the nucleophilic attack surmounts steric hindrance in rendering endo-OH more reactive than exo-OH. The kinetics of transesterification with different catalysts is investigated to determine the catalytic reactivity and molecular structure evolution. The results show that preferential activation of exo-OH moieties can be achieved either by reducing the coordination ability of catalytic cations (lg β1) or by enhancing the alkalinity of catalytic anions. Despite the low reactivity of exo-OH on ISB monomers, terminal exo-OH on carbonate oligomers exhibits higher reactivity than terminal endo-OH, justifying the experimental fact that ISB-based polycarbonates (ISB-PCs) are mostly terminated by endo-OH. Balancing the reactivity between endo-OH and exo-OH can be promoted by increasing the reaction temperature, thus accelerating transesterification to a high equilibrium constant. These findings help to clarify the mechanism of ISB transesterification and provide new strategies for the synthesis of high-molecular-weight ISB-PCs.

This paper mainly studies the growth, diffusion and prevention of water hyacinth. First, the Logistic growth model was established. Nitrogen and phosphorus concentration, temperature and light were selected as the influencing factors to simulate the density growth curve of water hyacinth. It was found that the density of water hyacinth reached the environmental bearing capacity and became stable after 90 days. After that, we took a region as an example, regarded the water hyacinth as a cell, and established a logistic-ca model to simulate the diffusion process of water hyacinth. Finally, the spatial and temporal diffusion model of water hyacinth is established by using the differential equation to study the change of the concentration of water hyacinth under the rain with the spatial position.

Experimental advanced superconducting tokamak (EAST) device is a D-shaped full superconducting tokamak with actively water cooled plasma-facing components. Before this upgrade, three generations divertors, which are steel divertor, carbon divertor, and international thermonuclear experimental reactor-like upper divertor, have been applied, respectively. To achieve long-pulse and high- $\beta $ H-mode plasma, new plasma configurations and shapes have been modeled and optimized in 2016 on EAST. The new geometry of lower divertor heavily relies on numerical simulations of the plasma in EAST. The new divertor is designed to fit the high- $\beta $ H-mode plasma and endure the heat flux up to 10 MW/m2. To achieve this goal, the lower carbon divertor will be replaced in EAST, which is now in conceptual design phase. Compared to the outer target side, the inner target side is prone to plasma detachment. First, the geometry and physics of the divertor should be better designed with the advanced physical operation mode. Second, the divertor should be in advanced geometry and high efficient cooling structure. Third, considering balance the detachment between inner target side and outer target side. This paper mainly introduces the research progress of the fourth-generation tungsten divertor in EAST.

This study aimed to improve polydimethylsiloxane (PDMS) conversion in the preparation of polycarbonate (PC)–polydimethylsiloxane (PDMS) copolymer through melt polycondensation. We examined the transesterification process of PDMS with diphenyl carbonate (DPC) and its copolymerization products with bisphenol-A (BPA) for different chain lengths of PDMS. The key factors affecting PDMS conversion were investigated. Results showed that long-chain PDMS required a higher critical transesterification level (38.6%) to improve miscibility with DPC. During polycondensation, side reactions were more prone to occur when the equilibrium transesterification level of long-chain PDMS was lower. PDMS conversion was also lower when more short-chain PDMS was fed. Increasing the chain length of PDMS also reduced PDMS conversion. Notably, increasing the amount of KOH can significantly improve PDMS conversion throughout the polycondensation stage by increasing the equilibrium transesterification level of long-chain PDMS, thereby inhibiting the occurrence of side reactions.

In this work, trimesic acid was introduced in the preparation of cerium-manganese oxide, and its effect on thermal aging resistibility for catalytic diesel soot elimination was investigated systematically. The prepared catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR). The experimental results show that trimesic acid addition has no significant effect on the morphologies of cerium-manganese oxide catalyst, and also contribute litter to the suppression of catalyst particles sintering and textual features destroying. In addition, the crystal structure and high-temperature (800 °C) phase separation of CeO2-MnOx solid solution are not improved by the trimesic acid modification. But, noteworthily, trimesic acid assisted synthesis can obviously promote Mn4+ generation and keep up oxygen vacancy concentration and hence improve the product of highly active oxygen species (especially O 2 - ) of CeO2-MnOx catalyst during the thermal aging process. Furthermore, trimesic acid assistance can significantly alleviate the loss of CeO2-MnOx metal-support interaction caused by thermal aging, and maintain the ability to supply active oxygen at low-temperature (approximately 200–400 °C). Finally, after thermal aging at 800 °C for 12 h, the trimesic acid assisted synthesized CeO2-MnOx catalyst shows significantly better catalytic soot oxidation activity. Thus this work reveals that besides stabilizing textual and structural properties, stabilizing and optimizing electronic structure is another feasible pathway to enhance the thermal aging resistibility of CeO2-based soot oxidation catalysts.

In-vessel components of the EAST superconducting tokamak upgraded from full carbon plasma facing material (PFM) to carbon PFM for upper and lower divertor, and molybdenum PFM for other surface in 2011. Carbon tiles were mechanical connected to CuCrZr heat sink can handle heat flux ∼3 MW/m2. EAST was planned to update plasma heating power to 36 MW. After that heat flux to divertor will be up to 10 MW/m2 for steady state operation and 15 MW/m2 for transient. Upgrading divertor accommodate high performance plasma operation requirement is necessary. Tungsten PFM with ITER-like monoblock and flat tungsten technology was developed for EAST upper divertor to handle the high heat flux. To meet tungsten divertor pumping requirement an in-vessel cryo-pump was designed to install in upper divertor area. Type-I edge localized mode (ELM) was observed during EAST plasma operation in 2012. Resonant Magnetic Perturbation (RMP) coils with ITER in vessel coils like insulation technology were developed for the ELM mitigation. Vertical Stability (VS) control coils are also upgrade to ITER-like insulation technology, and coils locations were optimized to obtain more effective instability control.

Chinese Academy of Sciences Institute of Plasma Physics (ASIPP) Experimental Advanced Superconducting Tokamak (EAST) has designed and built a new outer divertor with an ITER-like cooling system. As...

One of the most important research goals of EAST concerns long steady-state high-performance plasma pulse. It is a fusion engineering challenge for divertor to handle steady-state high heat flux form plasma. To accomplish this aim, full tungsten divertor has been designed for EAST to withstand high heat flux which is increasing rapidly. Full tungsten divertor is an ITER-like design which consists of monoblock units, end boxes and cassette body. The newest divertor of EAST will withstand more than 10 MW/m2 heat flux in target zone. The full tungsten divertor should be reliable during plasma discharge campaign to reduce the failure risk of plasma components under critical thermal power from plasma. Analysis and experiment results proved full tungsten divertor of EAST will be very reliable for future long steady-state high-performance plasma pulse. The design and application of full tungsten divertor of EAST can also bring experiences and answers for ITER or any next divertor fusion device on nuclear phase.

The scientific and the engineering missions of EAST are to explore the reactor related regimes with long pulse lengths and high plasma core confinement and solutions for power exhaust and particle control under steady state operation and to establish technology basis of full superconducting tokamaks. EAST can operate with double null or single null divertor mode. The goals of the divertor are to get high parameters plasma, long pulse operation and single or double null plasma shape. So the divertor is designed as up-down symmetry structure to provide large experimental flexibility. The divertor should have the capacity to endure higher heat flux and provide recycling and impurity control. Up to now, three generations divertors which are steel, carbon and tungsten divertor respectively have been developed and installed on EAST. The steel divertor is just used in the commissioning test of the host machine in 2006. The carbon divertor which is composed of graphite tiles, CuCrZr heat sink and stainless steel supports is commissioned to endure thermal load of no more than 4 MW/m2 in 2008. Thus the tungsten divertor which is based upon cassette and mono-block technology like ITER is expected to endure the heat flux up to 10 MW/m2 in 2014.

A temperature control mechanism is presented for the nuclear material design of a breeding blanket module. It aims at exploring the acceptable material fractions maintaining the thermal balance inside a blanket module, which support the temperature requirement for tritium release and inventory. One-dimensional neutronics model is utilized to discuss the calculations. It is found that there is a mutual influence in the blanket interior by using the multi-layers structure. Firstly, the pure Li4SiO4 zones in the front area are the relative independent zones and have little thermal influence to other zones. The Beryllium zones only affect the adjacent zones, but the effect can be ignored. The second beryllium zone and the first mixed pebble zones are mainly limited to the reduced activation ferritic/martensitic material due to the lower temperature limitation. It indicates that the structural casing for nuclear materials should be reckoned in detail because of no cooling with it. It is confirmed that there is a temperature control methodology for the design of blanket nuclear materials using the linear variation of the temperature profile.

Experimental advanced superconducting tokamak device is a D-shaped full superconducting tokamak with actively water cooled plasma facing components. To achieve long pulse and high βH-mode plasma, new plasma position and shape are calculated and optimized during the campaign of 2013-2014. New divertors are designed and developed to fit the plasma and endure the heat flux up to 10 MW/m2. The divertor is International Thermonuclear Experimental Reactor-like. It bases on monoblock and cassette technology and is composed of plasma facing component (PFC) units, cassettes, and support systems. Monoblock structures are just employed on the PFC units of target plates of the divertors, thus W flat tiles are used on the baffles and dome. At the end of monoblocks, end boxes are applied. Cassettes act not only as the supports of the PFC units, but also as manifolds for the cooling channels of the units. The support systems consist of inner support rails, outer support rails, and auxiliary braces. The support systems are installed on the vacuum vessel before cassettes are put on. To dock the cassette with the support system, it is just lifted and pushed forward. To verify and optimize the structure, Research and Development work has carried out for the divertor. The prototypes of PFC units and cassettes are fabricated with different manufacture processes. The total assembly process is also simulated with these prototypes on mockup facility and the vacuum vessel. The results show that the divertor system can be manufactured successfully according to the requirements of drawings and installed conveniently and precisely on the tokamak. All these works certify that the design of the divertor is all right. The batch production of the divertors can be started.

We have developed an all-laser processing technique by means of two industrially-relevant continuous-wave fiber lasers operating at 1070 nm. This approach is capable of both substrate heating with a large defocused beam and material processing with a second scanned beam, and is suitable for a variety of photovoltaic applications. We have demonstrated this technique for rapid crystallization of thin film (~10 μm) silicon on glass, which is a low cost alternative to wafer-based solar cells. We have also applied this technique to wafer silicon to control dopant diffusion at the surface region where the focused line beam rapidly melts the substrate that then regrows epitaxially. Finite element simulations have been used to model the melt depth as a function of preheat temperature and line beam power. This process is carried out in tens of seconds for an area approximately 10 cm 2 using only about 1 kW of total optical power and is readily scalable. In this paper, we will discuss our results with both c-Si wafers and thin-film silicon.

In this work, we demonstrated a simple method to test the point contact design and determine the Surface Recombination Velocity (SRV) of the point contact solar cells from a single PL image. The thermally grown silicon dioxide is patterned by using lithographic means. The size, pitch and pattern of the point contact opening holes are varied in order to find the relationship between opening density and the effective carrier lifetime of the entire cell region. The advantages of this new characterization method compare with other SRV test methods are first, it is simple, reliable and fast, requires no other equipment but only a single PL image; second, a large quantity of design can be tested on a same wafer simultaneously.

Introduction: Mycoplasma pneumoniae ( M. pneumoniae ) is the most common atypical pathogen that causes respiratory infections in humans. Laboratory tests are important in the diagnosis of M. pneumoniae because of the atypical features in clinical signs and symptoms. Nowadays, both the P1 adhesin gene and 16S ribosomal (r) RNA (rRNA) gene of M. pneumoniae have been widely detected by polymerase chain reaction (PCR). The purpose of the present study was to evaluate the most suitable target in the detection of M. pneumonia via nested PCR . Methodology: Both the P1 adhesin gene and 16S rRNA gene for nested PCR reaction conditions were optimized through an orthogonal test and single-factor experiment. Then, the sensitivity of the two sets of targets was evaluated. Finally, based on the optimal conditions, 55 clinical samples of throat swabs collected from adult patients in 2013 were examined by established nested PCR. Result: The results revealed that PCR detection of the 16S rRNA gene was more sensitive than the P1 adhesin gene because the detection limits for both the P1 gene and 16S rRNA gene were at least 100 fg and 10 fg of M. pneumoniae DNA, respectively. Furthermore, the positive rate for detection of the 16S rRNA gene (30/55; 54.5%) was higher than that of the P1 adhesin gene (25/55; 45.5%). Conclusion: Our results indicate that the 16S rRNA gene is more suitable for diagnosis of M. pneumoniae infection than the P1 adhesin gene due to its higher sensitivity and positive rate in clinical samples.

EAST tokamak is one of the advanced full superconducting tokamaks in the world. To achieve better plasma parameters, new plasma position and shape are calculated and optimized in the 2013's update. New divertors should be deigned and developed to endure higher heat flux less than 10MW/m2. The divertor is ITER-like structure. It bases on mono-block and cassette technology. The divertor is composed of PFC units, cassettes and support systems. Mono-block structures are just employed on the PFC units of target plates of the divertors, thus W flat tiles are used on the baffles and dome. Cassettes act as not only the supports of the PFC units, but also the cooling channels of the units. The support systems consist of inner support rails, outer support rails and auxiliary braces. The systems are installed on vacuum vessel before cassettes putting on. When cassette assembly with support system, it is just lifted and pushed forward. To optimize and verify the structure, R&D work has done on the divertor. The prototypes of PFC units in different positions and cassettes with different manufacture processes are fabricated. The assembly process is also simulated with these prototypes on mimic facility and vacuum vessel. The results show that the divertor system can be manufactured successfully according to the drawing requirements. And they can also be installed conveniently and precisely on the tokamak. All R&D work and tests will certify that the design of divertor is all right.

After commissioning in 2005, the EAST superconducting tokamak had been operated with its water cooled divertors for eight campaigns up to 2012, employing graphite as plasma facing material. With increase in heating power over 20 MW in recent years, the heat flux going to the divertors rises rapidly over 10 MW m−2 for steady state operation. To accommodate the rapid increasing heat load in EAST, the bolting graphite tile divertor must be upgraded. An ITER-like tungsten (W) divertor has been designed and developed; and firstly used for the upper divertor of EAST. The EAST upper W divertor is modular structure with 80 modules in total. Eighty sets of W/Cu plasma-facing components (PFC) with each set consisting of an outer vertical target (OVT), an inner vertical target (IVT) and a DOME, are attached to 80 stainless steel cassette bodies (CB) by pins. The monoblock W/Cu-PFCs have been developed for the strike points of both OVT and IVT, and the flat type W/Cu-PFCs for the DOME and the baffle parts of both OVT and IVT, employing so-called hot isostatic pressing (HIP) technology for tungsten to CuCrZr heat sink bonding, and electron beam welding for CuCrZr to CuCrZr and CuCrZr to other material bonding. Both monoblock and flat type PFC mockups passed high heat flux (HHF) testing by means of electron beam facilities. The 80 divertor modules were installed in EAST in 2014 and results of the first commissioning are presented in this paper.