Migration behavior of solidification nuclei in pure Al melt under effect of electric current pulse

A mathematical model considering free nuclei was developed to reveal the migration behavior of the free nuclei. Numerical simulation results show that most of the nuclei on the top surface of the melt move downwards and distribute randomly inside the Al melt, which induces more nucleation sites resulting in grain refinement. At the same time, the effect of nuclei size on the nuclei distribution and refinement employing electric current pulse （ECP） was also investigated. The smaller nuclei migrate a short distance with the Al melt at lower speed. But for the larger nuclei, the migration downwards with higher speed benefits the refinement of interior grains of the melt. The research results help to better understand the refinement process and provide a more reasonable explanation of the grain refinement mechanism using ECP.

电化学法处理DDNP工业污水

DDNP工业污水既含有爆炸性物质，又含有毒性物质，既有碱性又有强力的染色性，而且数量相当大，每生产1kg产品，就会排出150-250kg的此类污水，这类污水处理不当，不仅在污水所到之处留下爆炸或燃烧的潜在的危险，而且流散出去还会污染农田，时间一长，污染源上千米的深井水也会受到污染。目前国内外还没有一个比较理想的处理此工业污水的方法，不是效果不佳（去除不彻底产生二次污染）就是处理费用太高。以下研究的这套电化学法，可以根本解决这一问题。

Effects of Slow-Mixing on the Coagulation Performance of Polyaluminum Chloride （PACI）

Conventional jar tests and on-line size monitoring were used to investigate the effects of slow-mixing intensity and duration on residual turbidity and floc size during charge neutralization coagulation and sweep floc- culation with polyaluminum chloride. The compensatory effect of slow-mixing on coagulation performance fol- low!ng inadequate_or excessive rapid-mi_xing was also examined. It is found that slowTmixing intensity has a more marked positive ettect on charge neutralization coas;ulatlon tlaan on sweep tlocculatlon. llle optimal root-mean- square velocity gradient, G, for slow-mixing is 15 s-＇ for both coagulation mechanisms, and charge neutralization coagulation requires a longer slow-mixing duration. The optimal slow-mixing duration, based on residual turbidity,is longer than the time to tbrm the largest mean Ilocs. The optimal product of G and mixing duration, GT, lbr slow-mixing during charge neutralization coagulation （13500） are higher than that during sweep flocculation （4500） and both are less than the range of values recommended by the American Water Works Association （24000-84000）.The optimal GT value under various slow-mixing conditions increases with G. Appropriate extension＇of slow-mixing duration during charge neutralization coagulation can improve coagulation performance after an inadequate or excessive rapid-mixing duration, but during sweep flocculation, appropriate shortening of slow-mixing duration after an excessive rapid-mixing or appropriate extension of slow-mixing duration after an inadequate rapid-mixing is favorable.

Electrical resistance stability of high content carbon fiber reinforced cement composite

The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

Fast-ionic conductor Li_(2.64)(Sc_(0.9)Ti_(0.1))_(2)(PO_(4))_(3) doped PVDF-HFP hybrid gel-electrolyte for lithium ion batteries

With increasing demand on energy density of lithium-ion battery,wide electrochemical window and safety performance are the crucial request for next generation electrolyte.Gel-electrolyte as a pioneer for electrolyte solidization development aims to solve the safety and electrochemical window problems.However,low ionic conductivity and poor physical performance prohibit its further application.Herein,a fast-ionic conductor(Li_(2.64)(Sc_(0.9)Ti_(0.1))_(2)(PO_(4))_(3))(LSTP)was added into poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)base gel-electrolyte to enhance mechanical properties and ionic conductivity.Evidences reveal that LSTP was able to weaken interforce between polymer chains,which increased the ionic conductibility and decreased interface resistance during the cycling significantly.The obtained LiFePO_(4)/hybrid gel-electrolyte/Li-metal coin cell exhibited excellent rate capacity(145 mA·h/g at 1C,95 mA·h/g at 3C,28℃)which presented a potential that can be comparable with commercialized liquid electrolyte system.

Research and Development of Condensate Water Fined Processing Control System Based on FCS

This paper briefly states the features and advantages of FCS （fieldbus control system）. In view of condensate water fined processing system of domestic 600 MW supercritical coal-fired generating units, it designed and developed a FCS for entirely process control, designed computer monitoring software and organized network monitor the change of data. At the same time, making the simulation device of the system, the FCS control system scheme is implemented on this device. It is verified by practice that the system control technology is advanced, safe, reliable and operation well. It provides a complete project for automation technology upgrade program in power plant. In addition, this device can be used in the power industry technical personnel training and teaching of colleges and universities. It is worth promotion and reference.

Study on heat transfer enhancement of discontinuous short wave finned flat tube

The typical configuration adopted by air-cooled condenser(ACC) in coal-fired power generating unit is the wave finned flat tube. The development of boundary layer between wave fins along long axis of flat tube can suppress the air-side heat transfer enhancement to a great extent. It has been proved that the serrated fins can enhance heat transfer obviously by breaking the development of boundary layer periodically. In the present study,the discontinuous short wave fin was introduced to the flat tube to enhance the air-side heat transfer of ACC. Two different types of arrangements,i.e. staggered and in-line for discontinuous short wave fins on the flat tube,were designed. By numerical simulation,the heat transfer and flow performances of short wave fins were studied under different arrangements(in-line,staggered) ,and the influences on heat transfer and flow characteristics of rows of short wave fin and interrupted distance between discontinuous short wave fins were revealed numerically. The results indicated that,compared with the original continuous wave fin,the discontinuous short wave fin effectively improved the air-side heat transfer of flat tube under the air flow velocities in the practical application of engineering. Moreover,the increment of pressure loss of air-side flow was restricted for the discontinuous short wave fins because of the reduction of contact areas between the air flow and fin surface.

In situ deposited multilayer integrated hydrogels for deformable and stretchable supercapacitors

Hydrogel systems promote the development of flexible energy storage devices because of their inherent mechanical elasticity and ionic conductivity.However,achieving stable energy storage capacity under violent mechanical deformation is still a challenge for hydrogel devices.In this work,an all-in-one integrated supercapacitor(AISC)was assembled using in situ deposited polyaniline/graphene oxide nanocomposites for both sides of the incorporated ionic hydrogel electrolyte.The assembly process of the AISC was greatly simplified,and the displacement and separation of the multilayer structured hydrogel complex were avoided during mechanical deformation.The hydrogel electrolyte with ionic additives exhibited strong adhesion and flexibility,and high ionic conductivity,thereby ensuring the excellent specific capacitance and rate performance of the AISC.The specific capacitances of the AISC were 222.8 mF cm^(−2) at the current density of 0.2 mA cm^(−2) and 151.7 mF cm^(−2) at 3.2 mA cm^(−2).The capacitance retention rate was 68.1%.The energy density of a piece of the device reached 44.6μW h cm^(−2) at a power density of 120.0μW cm^(−2).Moreover,reliable and reproducible energy storage was acquired under bending,compression,and stretching deformations.The AISC was also easily assembled in series to power a light-emitting diode(LED)light.This work provides a facile approach to the construction of flexible supercapacitors for the development of energy storage devices in flexible electronics.

Exploration of structure and mechanism of insoluble gels formed in microwave-assisted Suzuki coupling for poly(9,9-dihexylfluorene)s

A series of poly(9,9-dihexylfluorene)s (PDHFs) have been synthesized via microwave-assisted Suzuki and Yamamoto coupling reactions. Compared with the conventional oil-bath heating (48 h, Mw 20100 g/mol by Suzuki reaction and Mw 24000 g/mol by Yamamoto reaction), microwave-assisted polymerization can yield PDHFs with higher molecular weights (Mw 37200 g/mol by Suzuki reaction and Mw 43400 g/mol by Yamamoto reaction) in shorter time (14 and 60 min). However, sometimes formation of insoluble gels was observed together with PDHF in Suzuki coupling reaction. PDHF and insoluble gels were analyzed by XPS, elemental analysis, FTIR, TGA and DSC. Experimental results demonstrated that H2O might take part in the Suzuki coupling reaction under microwave condition, which could make the cross-linking reaction occur and form gels.

Energy-dissipative dual-crosslinked hydrogels for dynamically super-tough sensors

In the fields of electronic skin and soft wearable sensors,intrinsically stretchable conductors undergo rapid development;however,practical applications of artificial skinlike materials/devices have not been realized because of the difficulty in combining the electromechanical properties and sensing performance.Contrarily,insoluble inorganic conductive domains in the hydrogel matrix are generally incompatible with surrounding elastic networks,decreasing the mechanical strength.Usually,the hydrogels are vulnerable either to severe mechanical stimuli or large deformation,especially when notches are induced.In this study,based on an energy-dissipative dual-crosslinked conductive hydrogel,a mechanically durable and super-tough strain sensor was developed.The highly soft yet dynamically tough hydrogel demonstrated high ionic conductivity(30.2 mS cm^(-1)),ultrastretchability(>600%strain),and superior linear dependence of strain sensitivity with a maximum gauge factor of 1.2 at 500%strain.Because of these advantageous synergistic effects,the resultant hydrogel strain sensor demonstrated reliable and stable detection of a large range of human motion and subtle vibrations.Moreover,it impressively exhibited super toughness that could endure consecutive treading pressure and even retain normal operation after 20 times of car run-over on the road.These demonstrations highly confirm the sensor’s superior mechanical durability and reliability,displaying great potential in developing next-generation mechanically adaptable sensors.