High efficiency synthesis of HKUST-1 under mild conditions with high BET surface area and CO2 uptake capacity

This study focuses on the development of a hydrothermal method for the rapid synthesis of good quality copper benzene-1,3,5-tricarboxylate(referred to as HKUST-1)with high yield under mild preparation conditions to address the issues associated with reported methods.Different synthesis conditions and activation methods were studied to understand their influence on the properties of HKUST-1.It was found that mixing the precursors at50°C for 3 h followed by activation via methanol refluxing led to the formation of a product with the highest BET specific surface area of 1615 m~2/g and a high yield of 84.1%.The XRD and SEM data illustrated that the product was highly crystalline.The sample was also tested on its capacity in CO_2 adsorption.The results showed strong correlation between surface area of the sample and its CO_2 uptake at 1 bar and 27°C.The HKUST-1 prepared in this study demonstrated a high CO_2 uptake capacity of 4.2 mmol/g.It is therefore concluded that this novel and efficient method can be used in the rapid preparation of HKUST-1 with high surface area and CO_2 uptake capacity.     

Research on the control technology of medium-length hole blasting fragmentation in underground mine

The scalloped medium-length hole blasting mining method used in Dahongshan Copper Mine accounted for more than 61% of the total amount of mining, but the large boulder yield restricted the intensity of ore supply for mines, and the average boulder yield was as high as 22.7 %. In order to develop the mine produc- tion efficiency, the circular medium-length hole blasting technology was proposed and field tests were carried out. The test results showed that circular medium-length hole blasting mining can reduce the average boulder yield to 10.3 %. Compared with the traditional scalloped medium-length hole blasting mining, the average boul- der yield was decreased by 12.4 %. The daily yield of ore for the panel on duty was increased by 152.29 t, and the growth rate was 51.1%. The new technology can reduce the time for the handling of boulder and the con- sumption of explosives and detonators for recrushing, and increase the efficiency of mining while reduce the mining cost, which has received good blasting effects.     

Shape control technology during electrochemical synthesis of gold nanoparticles

Gold nanoparticles with different shapes and sizes were prepared by adding gold precursor (HAuCl₄) to an electrolyzed aqueous solution of poly(N-vinylpyrrolidone) (PVP) and KNO₃, which indicates the good reducing capacity of the PVP-containing solution after being treated by electrolysis. Using a catholyte and an anolyte as the reducing agents for HAuCl₄, respectively, most gold nanoparticles were spherical particles in the former case but plate-like particles in the latter case. The change in the pH value of electrolytes caused by the electrolysis of water would be the origin of the differences in shape and morphology of gold nanoparticles. A hypothesis of the H+ or OH? catalyzed PVP degradation mechanism was proposed to interpret why the pH value played a key role in determining the shape or morphology of gold nanoparticles. These experiments open up a new method for effectively controlling the shape and morphology of metal nanoparticles by using electrochemical methods.     

Meshless Least-Squares Method for Solving the Steady-State Heat Conduction Equation

The meshless weighted least-squares (MWLS) method is a pure meshless method that combines the moving least-squares approximation scheme and least-square discretization. Previous studies of the MWLS method for elastostatics and wave propagation problems have shown that the MWLS method possesses several advantages, such as high accuracy, high convergence rate, good stability, and high computational efficiency. In this paper, the MWLS method is extended to heat conduction problems. The MWLS computational parameters are chosen based on a thorough numerical study of 1-dimensional problems.Several 2-dimensional examples show that the MWLS method is much faster than the element free Galerkin method (EFGM), while the accuracy of the MWLS method is close to, or even better than the EFGM These numerical results demonstrate that the MWLS method has good potential for numerical analyses of heat transfer problems.     

MICROPROCESSOR BASED PHASELOCKED LOOP SPEED CONTROL SYSTEM FOR AC MOTOR

In this paper the authors present an analysis and the implementation of microprocessor-baseddigital phase-locked loop speed control system for an induction motor which is actuated by aSPWM-GTR inverter.The system is controlled by a 16-bit single chip microprocessor.A new type of frequency and phase detector is presented in detail,An adaptive method isadopted in speed controller.A three mode control scheme is used.These techniques are very use-ful to the improvement of the dynamic behavior of digital AC motor drive system.Experimental results show that the system is of good stability,high precision and good dynam-ic performance.     

PVP-assisted laser ablation growth of Ag nanocubes anchored on reduced graphene oxide(rGO) for efficient photocatalytic CO_2 reduction

Metallic nanoparticles loaded graphene nanocomposites have been widely studied for various scientific and technological applications. In this study, a facile method was reported to realize a straightforward growth of shape and size-controllable of metallic nanoparticles, and the subsequent hybridization with graphene in solution by strategically coupling wet-chemical route and laser ablation. By mixing graphene oxide(GO) with a tunable concentration level of polyvinylpyrrolidone(PVP) in aqueous solution, Ag nanocubes with a face-centered cubic crystal structure were generated by pulsed laser ablation and then mounted on GO nanosheets with the assistance of PVP. The preferential adsorption of PVP to Ag(100) crystal face led to the production of Ag nanocubes with exposed(100) facet. The result showed that the morphological yield of spherical particles decreased with the increase in PVP concentration. X-ray diffraction(XRD) and UV–visible spectroscopy analyses confirmed that GO was partially reduced. In the reduction of CO_2 gas, the photocatalytic conversion rate could achieve 133.1 μmol g~(-1) h~(-1) in 6 hrs for cubic Ag-loaded reduced GO composites.     

Measurement of contact angle between stainless steel surface and carbon dioxide by pendant drop method

To measure contact angle between CO2 and solid surface, in this study a visual high-pressure vessel has been developed, with a corresponding well-controlled constant temperature system. Pendant drop method is applied to the investigation of the contact angles of CO2 on a stainless steel surface in its own vapor. The image of the pendant drop is recorded by a camera, and a B-Snake method is used to analyze the contour and the contact angle of the droplet. The experimental results have provided a set of well tested data, which show that C02 has good infiltration into stainless steel surface and the developed method can be used as a standard testing one for measuring the contact angle between high-pressure liquid and solid surface.     

Application of Reaction-Bonded Silicon Carbide in Manufacturing of Spacecraft Combustion Chamber

Silicon carbide (SiC) ceramics is a good structural ceramics material, which have a lot of excellent properties such as superior high-temperature strength up to a temperature of 1 350 ℃, chemical stability, good resistance to thermal shock and high abrasion resistance. The silicon carbide ceramics material has so far been used widely for manufacturing various components such as heat exchangers, rolls, rockets combustion chamber. Sintering of ceramics structural parts have many technological method, the reac...     

Detecting the micro-defects in the GaAs materials by time resolved emissions

The GaAs material is a major semiconductor material, and it has high electron transfer rate and direct transition energy band structure. The devices and inte-grated circuits fabricated on the GaAs substrates have a lot of advantages such as high speed information processing. Small perturbations in the manufacturing of GaAs materi-als can lead to defects. The defects in the GaAs materials can degrade the performance of materials. A new method is presented in this paper for detecting the micro-defects in GaAs materials by using time resolved emissions. In this method, the micro-defects in GaAs materials are detected by making use of the photon emission features of micro- defects. The strength of the emitted photons from the micro-defects is increased by applying the electric current or the periodic pulse signals to GaAs materials. The single-photon detector is used to detect the photon emissions of the micro-defects. The time resolved photon emissions and single-photon detection are used to record and compare the amounts of the emitted photons that come from the given regions of the normal GaAs materials and the defective GaAs materials. A lot of experimental results show that the micro-defects in the GaAs materials can be detected by using the method proposed in this paper.     

Hydrothermal synthesis and photoluminescence behavior of CeO_2 nanowires with the aid of surfactant PVP

<正>Well-crystalline CeO_2 nanowires were prepared via a surfactant-assisted hydrothermal process.Reaction temperature and reaction time were changed for the determination of optimal synthesis parameters.The as-obtained products were characterized by X-ray diffraction (XRD),high-resolution transmission electron microscopy(HRTEM),and field emission scanning electron microscopy(FESEM).The results show that single crystal CeO_2 nanowires with high yield and good uniformity can be obtained hydrothermally at 180℃for 12 h with the aid of 2.0 g surfactant(polyvinyl pyrrolidone,PVP).The role of PVP was then discussed and a possible growth mechanism was proposed. Moreover,room temperature photoluminescence(PL) spectra were obtained for these CeO_2 nanowires,which are believed to be related to the abundant defects in these nanostructures.     

Extraction of gold,palladium, and platinum from acidic media with cyclic sulfoxide derivative

The extraction of gold (Ⅲ), palladium (Ⅱ), and platinum (Ⅳ) from the acidic media with the cyclic sulfoxide derivative of α-dodecyl-tetrahydrothiophene 1-oxide (dtmso) was investigated. Gold (Ⅲ), palladium (Ⅱ), and platinum (Ⅳ) could be separated from the acidic media with suitable sulfoxide concentration and acidity. The extraction reaction of gold (Ⅲ), palladium (Ⅱ) or platinum (Ⅳ) is exothermic when dtmso is used as an extracting reagent. The coordination number was studied by the slope method. The results indicate that, in high acidity, the dtmso coordination number for extracting gold (Ⅲ) or palladium (Ⅱ) is 3, and that for platinum (Ⅳ) is 2. UV and FT-IR spectra were used to analyze the structure of the complex. Gold (Ⅲ) is coordinated with the oxygen atom in S=O group in dtmso, and palladium (Ⅱ) or platinum (Ⅳ) is coordinated with the sulfur atom in S=O group in dtmso.     

Retrievals of atmospheric boundary layer temperature and moisture profiles by using Atmospheric Emitted Radiance Interferometer （AERI） measurements in Shouxian

The ground-based Atmospheric Emitted Radi- ance Interferometer （AERI） was deployed in Shouxian, China in 2008 to measure down-welling infrared radiances with high resolution. Based on AERI observations, we propose a new method for retrieving vertical temperature and water vapor profiles in the planetary boundary layer （PBL）. The method exclusively uses NCEP-2, a global reanalysis data as a first-guess profile in an iterative recursive algorithm. The PBL profiles of temperature and moisture under clear sky conditions in Shouxian have been retrieved using this new method. Compared with coinci- dent radiosonde measurements, we find that AERI is able to obtain more accurate temperature and water vapor pro- files in the PBL. The retrieval results with high temporal resolution can be used to monitor the PBL stability and evolution.     

Numerical Simulation and Experimental Studies of Air Treatment Process with Water Spray of One Row Counter Flow

The present work is focused on heat and mass transfer in a direct evaporative air cooler of one row counter flow spray. Models of the two-phase flow in such a air treatment system have been developed. The fields of temperature and relative humidity in spray chamber, as well as the trajectories of sprayed drops have been obtained by numerical method. Experiments aiming at quantifying the system performance and its influence factors have been conducted. It indicates that the increase of air velocity and water/air ratio while thedecrease of nozzle density are favorable. The performance of the system of parallel flow spray and counter flow spray have been compared by means of humidifying efficiency. Comparison between numerical simulation and experimental results demonstrate good agreement for outlet air temperature with a maximum error of 8% observed for air relative humidity.     

Supercondcuting properties in MgB2／Fe wires prepared by PIT method

The discovery of superconductivity at 39 K in MgB2has attracted a lot of interest in the world[15]. Recently, many results on the magnetic and transport properties of bulks have been reported. And high critical currentdensities (Jc) in polycrystalline MgB2 materials indicate that Jc is not limited by the weak link of grain boundaries as high temperature superconductor (HTS), suggestingthat MgB2 has a good potential for electrical engineering applications[2,48]. The fabrication of high qua…     

Improvement in the piezoelectric temperature stability of （K0.5Na0.5）NbO3 ceramics

Through an analysis of the temperature stability of(K0.5Na0.5)NbO3(KNN)based ceramics and KNN solid solutions,we propose a method to enhance the temperature stability of KNN materials.These materials are valuable for their piezoelectric properties.To verify the feasibility of this method,0.9(K1-xNax)NbO3-0.06LiNbO3-0.04CaTiO3(KNLN-CaTiO3)ceramics were designed,and their structure and properties were studied.The results show that KNLN-CaTiO3(x=0.54)ceramics have a good temperature stability over a wide temperature range(25-320°C).Also,they have good piezoelectric properties(d33=152 pC/N in x=0.54).This result confirms the feasibility of our proposed solution for improving the piezoelectric properties of KNN-based ceramics that have poor temperature stability.     

Preparation and Application of Water Dispersible Graphene as Antistatic Agent for SMS Nonwovens

In this paper, glucose was used as a green reducing agent and a capping reagent in the synthesis of water dispersible graphene, while using exfoliated graphite oxide （GO） as the precursor with the modified Hummers method. Characterizations of the graphene were conducted by UV-visihle absorption spectroscopy and X-ray diffraction （XRD）. Then the spunlaid-melthlowing-spuulaid （SMS） nonwovens were treated with the graphene solution via pad-dry-cure process. The surface and the antistatic property of the obtained nonwovens were tested. The results showed that O. 1 mg/mL graphene solution exhibited good stability in water. When treated with this solution, the graphene could be evenly dispersed on SMS nonwovens and the nonwovens had an excellent antistatic performance and a high relatively antistatic durability.     

Large-Scale Self-Assembled Ag Nanotubes

A high yield of silver nanotubes with large aspect ratio were conveniently synthesized via an organic-assist solvothermal preparation technique using polyvinyl pyrrolidone （PVP） as a capping reagent and architecture soft-template. The molecular ratio between the repeating unit of PVP and AgNO3 plays a crucial role in determining the geometric shape of the product. Such novel-type Ag nanotubes were self-assembled by Ag nanoparticles, which had largely similar crystallographic orientation, forming a texture. The fact that nanoparticles without anisotropic crystal structures can form such superstructures by self-assembly may open a window for understanding a range of nanotube formation processes.     

Analyzing global trends of different cloud types and their potential impacts on climate by using the ISCCP D2 dataset

The International Satellite Cloud Climatology roject (ISCCP) D2 dataset is used to study the global distribution of low, middle and high cloud amounts and their rends of 1983-2001. Evidences have shown that global arming has accelerated over the past 20 a and the 1990s as the warmest decade in the instrumental records since 861. Trends of various clouds amounts over this period are nalyzed by employing the linear regression method. The esults show that global mean total cloud amounts, in general,have tended to reduce over the past 20 a. But there are lightly increasing by about 2% before 1987 and decreasing y about 4% since then. Cloudiness trends of both low and igh clouds decrease while increase for the middle cloud.And there exist remarkable discrepancies in different regions.The preliminary analyses suggest that it is likely that the loud change occurring over the past 20 a is a positive feedback to global warming.     

Optimization model of a structural simulation design for a CICC

The engineering design of a Cable-In-Conduit Conductor (CICC) is complicated. A model for the optimal design of a CICC based on conductor stability, AC loss and strain is proposed. The model considers the critical current density as a function of applied strain. A mathematical programming method that minimizes the AC loss of the CICC is established to yield an optimal design for the CICC structure. The optimized structure and related performance agree well with the engineering design values used for the KSTAR project.     

Nanometer TiO2 Modified Polyacrylic Copolymer Sizing Agent

A series of new-type nanometer TiO2 modified polyacrylic copolymer sizing agent were synthesized from acrylic acid, ethyl acrylate, nanometer TiO2, oleic acid etc. by orthogonal design method. Results of the studies show that the synthetic method used in this paper was a new way and had never been found in the synthesis of acrylate sizing agent, and that the properties of those new-type size-agent were be improved, which had potential for substituting PVA （polyvinyl alcohol） sizing agent. The technology for solving the problem of nano-scale powder agglomeration and dispersion were also studied. The transmission electron microscope （TEM） observation showed that nano-TiO2 had good dispersion and stability in aqueous solution and in sizing agent solution.