新型打结装置打结过程的关键参数研究

针对包装袋手绳手工打结劳动成本高、效率低的问题,设计了一种新型手绳打结装置,并对打结过程的关键参数进行了研究。利用建立的打结装置三维模型对关键参数绕绳圈数和成结移动距离的取值范围进行了计算,利用工程分析软件Adams建立了打结装置虚拟样机模型,并对打结过程进行了运动学仿真,得到了转动角度及成结移动距离的值,利用Matlab构建的"绕绳圈数-移动距离"关系图进一步确定了关键参数值,最后制作了样机并进行试验验证。研究结果表明:试验结果与理论计算及仿真结果相符,对提高包装袋手绳打结成功率及打结装置结构进一步改进可提供一定的参考。

Structural,magnetic and electronic properties of FeF_2 by first-principle calculation

First-principle calculation was used to investigate the magnetic properties, electronic structure and bonding mechanism of FeF2. By calculating the lattice parameters and magnetic moment as a function of effective interaction parameter （Ueff）, it is found that the optimum value of Uefr is equal to 4 eV, the magnetic moment is 3.752 μB and the value of c/a is 0.704, which are in good agreement with the experiment results. Simultaneously, on the basis of GGA＋U method, the electronic structure and bonding mechanism of FeF2 were investigated by the analysis of electron localization function, Bader charge and total charge density. The results show that the bonding behavior between Fe and F atoms is a combination of ionic and covalent bond.

Microstructures and formation mechanism of headstand pyrocarbon cones developed by electromagnetic-field-assisted CVD

Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chemical vapor deposition in the absence of catalysts. The fine microstructures of the HPCs were characterized by high-resolution transmission electron microscopy. The results show that the textural features of the HPCs directly transfer from turbostratic structure in roots to a well-ordered high texture in stems. And the degree of high texture ordering decreases gradually from the stem to the tail of the HPCs. The formation mechanism of the HPCs was inferred as the comprehensive effect of polarization induction on electromagnetic fields and particle-filler property under disruptive discharge.

Hydrothermal synthesis, characterization and optical properties of La_2Sn_2O_7:Eu^(3+) micro-octahedra

Pyrochlore structure La2Sn2O7：Eu3＋ microcrystals with uniform octahedron shape were successfully synthesized via a hydrothermal route at 180 °C for 36 h. The crystal structure, particle size, morphologies, and optical properties of the as-synthesized products were investigated by XRD, TEM, SEM, EDS, FT-IR, Raman spectroscopy and PL. The effects of pH of precursor solution, precursor concentration, reaction temperature, and time were investigated. The results reveal that pH of the precursor solution not only plays an important role in determining the phase of the as-synthesized products, but also has a significant influence on the morphologies of the samples. High-quality and uniform octahedrons with an average size of about 700 nm could be easily obtained at the pH value of 12. The possible formation mechanism of octahedral-like La2Sn2O7：Eu3＋ microcrystals was briefly proposed. The photoluminescence spectra show that La2Sn2O7：Eu3＋ micro-octahedra display stronger emission in the range of 582-592 nm compared with the samples with other shapes.

Effect of cooling rate on morphology of primary particles in Al-Sc-Zr master alloy

Al-1.0%Sc-1.0%Zr （mass fraction） master alloy was prepared at different cooling rates. The morphology and thermodynamics data of the primary particles of the master alloy were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）. It shows that the primary particles are dendrite-shaped particles comprised of several attached small cubic, cusped-cubic or crucifer shape particles at slow cooling rate. However, the primary particles are separated with crucifer shape at intermediate cooling rate, and they are cubic with cusped-cubic shape at high cooling rate. Meanwhile, the separated and attached particles present AlaSc/AlaZr1-xScx core-shell structure. The formation mechanism of the structure was systematically investigated by a mathematical model.

Formation mechanism and crystal simulation of Na_2O-doped calcium aluminate compounds

Calcium aluminate clinkers doped with Na2O were synthesized using analytically pure reagents CaCO3, Al2O3, SiO2 and Na2CO3. The effects of Na2O-doping on the formation mechanism of calcium aluminate compounds and the crystal property of 12CaO·7Al2O3 (C12A7) cell were studied. The results show that the minerals containing Na2O mainly include 2Na2O·3CaO·5Al2O3 and Na2O·Al2O3, when the Na2O content in clinkers is less than 4.26% (mass fraction). The rest of Na2O is mainly doped in 12CaO·7Al2O3, which results in the decrease of the crystallinity of 12CaO·7Al2O3. The crystallinity of 2Na2O·3CaO·5Al2O3 is also inversely proportional to the Na2O content in clinkers. The formation processes of 2Na2O·3CaO·5Al2O3 and 12CaO·7Al2O3 can be divided into two ways, which are the direct reactions of raw materials and the transformation of CaO·Al2O3, respectively. The simulation shows that the covalency of O-Na bond in Na2O-doped 12CaO·7Al2O3 cell is weaker than those of O-Ca and O-Al bonds. The free energy of the unit cell increases because of Na2O doping, which results in the improvement of chemical activity of 12CaO·7Al2O3. The leaching efficiency of Al2O3 in clinker is improved from 34.81% to 88.17% when the Na2O content in clinkers increases from 0 to 4.26%.

Microstructural Features and Mechanical Properties Induced by the Spray Forming and Cold Rolling of the Cu-13.5 wt pct Sn Alloy

Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content （Cu-13.5 wt pct Sn） was prepared successfully by spray forming, the feasibility of cold roiling this alloy was investigated, and the cold roiling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-roiled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties. Particularly, it shows a low elastic modulus （-88 GPa） and a high flow stress （over 800 MPa） after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.

Formation mechanism and wear behavior of gradient nanostructured Inconel 625 alloy

The formation mechanism and wear behavior of a gradient nanostructured(GNS) Inconel 625 alloy were investigated using SEM, TEM and ball-on-disc sliding wear tester. The results show that surface mechanical grinding treatment(SMGT) induced an approximately 800 μm-deep gradient microstructure, consisting of surface nano-grained,nano-laminated, nano-twined, and severely deformed layers, which resulted in a reduced gradient in micro-hardness from 6.95 GPa(topmost surface) to 2.77 GPa(coarse-grained matrix). The nano-grained layer resulted from the formation of high-density nano-twins and subsequent interaction between nano-twins and dislocations. The width and depth of the wear scar, wear loss volume, and wear rate of the SMGT-treated sample were smaller than those of untreated coarse-grained sample. Moreover, the wear mechanisms for both samples were mainly abrasive wear and adhesive wear, accompanied with mild oxidation wear. The notable wear resistance enhancement of the GNS Inconel 625 alloy was attributed to the high micro-hardness, high residual compressive stress, and high strain capacity of the GNS surface layer.

Preparation of tricalcium silicate and investigation of hydrated cement

Tricalcium silicate cement(TSC)has been widely used in dental materials because of its self-setting behavior,good bioactivity,biocompatibility,osteoinductivity,and antibacterial effect.Tricalcium silicate(C3S)powder was prepared by Pechini technique with a calcining temperature of 1300℃ for 3 h.The influence of liquid/powder(L/P)rate on the setting time and the mechanical property of TSC was studied.Characterization methods including XRD,FTIR,SEM-EDS,TEM,and ICP-AES were utilized to study the properties of C3S powder and its hydrated cement.The bioactivity and biocompatibility of the cement were investigated by soaking test and cell culture,respectively.The results show that the L/P rate plays an important role in the setting time and the compressive strength of TSC.The surface of TSC was covered by hydroxyapatite deposition during the immersion experiment and the cells attachment on the surface of TSC was well,which indicated that TSC has good bioactivity and biocompatibility.In addition,TSC has excellent antibacterial properties against Staphylococcus aureus.In conclusion,TSC is a promising candidate for root canal filling materials.

Synthesis and Crystal Structure of O,O-Dimethyl-N-(β-triphenylgermanyl)propionyl-α- aminobenzylphosphonates

The title compound (C30H32NO4PGe), O,O-dimethyl-N-(β-triphenylgermanyl) propionyl-α-aminobenzylphosphonates was synthesized by a convenient method, and its crystal structure was determined by single-crystal X-ray diffraction. The crystal is triclinic, space group P-1 with parameters: a=9.7753(5), b=11.5773(5), c=13.5059(6) ?, α=104.185(1),β= 95.971(1), γ =96.727(1)°, V=1457.63(12) ?3, Z=2, Mr=574.13, Dc=1.308 g/cm3, λ=0.71073 ?, μ = 1.139mm-1, and F(000)=596. The structure was solved by direct methods. The structure was refined to R=0.0257, wR=0.0705 for 5080 observed reflections with I >2σ(I).The result of structure analysis indicates that atom Ge is sp3 hydridized because the arrangement of the four carbon atoms bonded to it is a distorted tetrahedron. The geometry of the three phenyl groups linking with the Ge atom looks like a propeller form.

Formation Mechanism and Binding Energy for Body-Centred Regular Octahedral Structure of Li7 Cluster

The formation mechanism for the body-centred regular octahedral structure of Li7 cluster is proposed. The curve of the total energy versus the separation R between the nucleus at the centre and nuclei at the apexes for this structure of Li7 has been calculated by using the method of Gou＇s modified arrangement channel quantum mechanics （MACQM）. The result shows that the curve has a minimal energy of-52.169 73 a.u. at R = 5.06ao. When R approaches infinity, the total energy of seven lithium atoms has the value of-51.996 21 a.u. So the binding energy of Li7 with respect to seven lithium atoms is 0.173 52 a.u. Therefore the binding energy per atom for Li7 is 0.024 79 a.u. or 0.674 eV, which is greater than the binding energy per atom of 0.453 eV for Li2, the binding energy per atom of 0.494 eV for Li3 and the binding energy per atom of 0.632 eV for Li5 calculated previously by us. This means that the Li7 cluster may be formed stably in a body-centred regular octahedral structure with a greater binding energy.

Impacts of the Rising Opportunity Cost of Farm Labor on Agricultural Land Use Structure: Theory and Empirical Evidences

Nowadays the rising of opportunity cost of farm labor comes to the forefront of attention in China. In order to understand its impact on agricultural land-use structure, a theoretical framework of household economics is formulated drawn on Low's model. Under the theoretical framework, the impact of the rising opportunity cost of on-farm on cropping structure is deduced in theory. And then, using statistic and survey data, taking mountain area of southern Ningxia as an example, the theoretical assumes are verified. The results show that the rise of opportunity cost of farm labor leads to less diversified cropping structure.

Atrial fibrosis： an obligatory component of arrhythmia mechanisms in atrial fibrillation？

Advances in clinical and fimdamental research, which have been promoted over last decades have led to a well- established understanding of atrial fibrillation （AF） as an epiphenomenon that despite similar manifestations may have different underlying mechanisms and thus require in- dividualized treatments. With rare exceptions of AF caused by mutations in genes coding ion channels in pa- tients with structurally normal atria, fibrotic replacement of atrial myocardium remains the comer stone of atrial pa- thology in patients with AF.

Synthesis and Structure of a New Dinuclear Molybdenum (I) Compound with Cyclohexanthiolate Ligand, [Mo_2(SC_6H_(11))_2(CO)_8]

Molybdenum(I) -compound [Mo2(SC6H11)2(CO)8]1,crystallizes in monoclinic,space group P21/c with a=9.5863(9),b=9.4469(9),c=13.869(1)A,β=99.697(2)°,V=1238.1(2)A^3,Z=2,Dc=1.734g/cm^3 ,μ=12.23cm^-1 and F(000)=644.The final R=0.0455 and wR=0.1159 for 1590 observed reflections with I>2ó(I).1 possesses a rhombic bimetallic core MoS2Mo with the Mo-Mo bond length of 2.975(1) and Mo-S of 2.485(2)A。

A Three-dimensional Organic-inorganic Hybrid Material Supported by Decavanadate Clusters and Na-O Chains: Synthesis and Crystal Structure of [Na_6(H_2O)_(16)(dod)_4V_(10)O_(28)]

A new organic-inorganic hybrid material [Na6(H2O)16(dod)2V10O28] (dod = 1,4- diazoniabicyclo[2,2,2]octane-1,4-diacetate) has been synthesized and X-ray single-crystal structural analysis reveals it crystallizes in triclinic, space group P with a = 11.533(7), b = 12.031(7), c = 12.187(4) ? a = 72.47(1), b = 73.16(1), g = 68.21(1)o, C20H64N4Na6O52V10, V = 1467(1) ?, Z = 1, Mr = 1840.1, Dc = 2.083 g/cm3, MoKa, l = 0.71073 ? m = 1.686, F(000) = 924, S = 1.027, the final R = 0.0538 and wR = 0.1272 for 4398 observed reflections. The compound has a three-dimensional frame- work constructed from decavanadate clusters, NaO chains and dod ligands. A variety of OH…O and CH…O hydrogen bonds play an important role in stabilizing the framework.

Microstructure and synthesis mechanism of Al-Ti-C-Sr master alloy

Al-5Ti-0.5C-8Sr (mass fraction,%) master alloy was prepared using a melt reaction method.The microstructure and synthetic process of the master alloy were investigated by optical microscopy,X-ray diffraction,scanning electron microscopy and X-ray energy-dispersive spectrum.The results show that the master alloy is composed of α(Al),TiAl3,TiC,Al4Sr and Al-Ti-Sr phases.The synthesis mechanisms of the master alloy are as follows:TiAl3 is formed through the reaction between K2TiF6 and Al melt at 850 ℃;when the melt was heated up to 1 200?1 300 ℃,TiC was formed through the reaction:Ti+C(s)=TiC(s);Al4Sr was formed through the binary uniform reaction when Sr was added into the melt;after the following solidification process in the peritectic reaction:L(Al,Sr)+α(TiAl3)→β(Al-Ti-Sr),the enwrapped structure was formed with the outer layer of Al-Ti-Sr phase and the internal layer of TiAl3 phase.

THREE DIMENSIONAL DIGITIZATION OF HUMAN HEAD BY FUSING STRUCTURED LIGHT AND CONTOURS

Three dimensional digitization of human head is desired in many applications. In this paper, an information fusion based scheme is presented to obtain 3-D information of human head. Structured light technology is employed to measure depth. For the special reflection areas,in which the structured light stripe can not be detected directly, the shape of the structured light stripe can be calculated from the corresponding contour. By fusing the information of structured light and the contours, the problem of reflectance influence is solved, and the whole shape of head,including hair area, can be obtained. Some good results are obtained.

Synthesis and Crystal Structure of (CH_2)_3(3,5-Me_2Pz)_2. [PhBr_2Sn(CH_2)SnBr_2Ph].2HBr.H_2O (Pz=pyrazole)

The reaction of bis(dibromophenylstannyl)methane with 1, 3-bis(3, 5-dimethyl- pyrazol-1-yl)propane in a 1:1 or 1:2 ratio yields only 1:1 adduct which partly hydrolyzes to the title complex (C26H38Br6N4O2Sn2, Mr = 1155.42) during crystal growing. The title complex is of triclinic, space group P with a = 10.886(1), b = 12.508(1), c = 13.879(1) ? = 85.762(2), = 85.159(2), = 84.020(2)? V = 1868.8(4) ?, Z = 2, Dc = 2.046 g/cm3, (MoK) = 0.71073 ? = 7.778 mm-1, F(000) = 1088, R = 0.0488 and wR = 0.1157 for 7560 observed reflections with I ≥ 2(I). The crystal structure analysis indicates that there is no direct interaction between the ligand and bis(dibromophenylstannyl)methane, and two tin atoms are bridged by two bromide atoms from the partial hydrolysis of this adduct.

Synthesis and Crystal Structure of 2-(Diphenylphosphine oxide)-3-(diphenylphosphine oxide ethynyl) spiro [bicyclo[2.2.1]hepta-2,5-diene-7,1'-cyclopropane]

The Diels-Alder reaction of bis(diphenylphosphine oxide)butadiyne (BDPPOB) with spiro[2.4]hepta-4,6-diene affords the title compound, 2-(diphenylphosphine oxide)-3-(diphen- ylphosphine oxide ethynyl)spiro[bicyclo[2.2.1] hepta-2,5-diene-7,1-cyclopropane] (DDSHC, C35H28O2P2, Mr = 542). Its crystal structure belongs to monoclinic system, space group P21/n with a =12.708(3), b = 14.666(4), c = 15.048(4) ? = 93.903(5) ? V = 2798.1(13) ?, Z = 4, Dc = 1.288g/cm3, F(000)=1136, (MoK? = 0.187mm-1, final R = 0.0626 and wR= 0.1422 for 4685 independent reflections with I > 2(I). Structural analyses reveal that the title compound is nonplanar and the dihedral angles between two phenyl rings around each phosphorus atom are 71.7(2) and 70.7(3)? respectively.

Crystal Structure of A Novel Ionic Organotin Complex:{[Ph_(2)Sn]_(2)[2,6-(O_(2)C)_(2)C_(5)H_(3)N]_(3)H_(2)O}^(2-)[HNEt_(3)]_(2)^(+)

A novel ionic organotin complex{[Ph_(2)Sn]_(2)[2,6-(O_(2)C)_(2)]C_(5)H_(3)N}_(3)H_(2)O}^(2-)[HNEt_(3)]^(2+)has been unexpectedly obtained by the reaction of Ph_(3)SnCl and 2,6-pyridine dicarboxylic acid in 1:1 molar ratio in the presence of organic base Et_(3)N.Possible dephenylation mechanism was illustrated.The X-ray diffraction study has shown that the title complex consists of cation moiety[HNEt_(3)]^(+)and anion moiety{[Ph_(2)Sn]_(2)[2,6-(O_(2)C_(2))C_(5)H_(3)N]_(3)H_(2)O}^(2-)with tin(IV)in a pengonal bipyramidal coordination geometry.