27 research outputs found
An exploration of key information models and their relationships in global manufacturing decision support
Global manufacturing businesses are beginning to benefit from the information and knowledge support provided by modern IT tools such as Product Lifecycle Management (PLM), Enterprise Resource Planning (ERP), and Customer Relations Management (CRM). Many types of information and knowledge, from customer requirements through product information to global enterprise manufacturing capability are involved in global manufacturing decisions. Understanding the appropriate structures and relationships for this information and knowledge is a significant issue if effective wide-ranging support is to be provided.
This paper focuses on global manufacturing decision support and explores three key types of information and knowledge relationship: (a) relationships between information and knowledge elements within a single information and knowledge model; (b) relationships between different information and knowledge models at one organizational level; (c) relationships between different information and knowledge models at different organizational levels. The corresponding information and knowledge structures have been presented with Unified Modelling Language (UML) to show the multiplicity of relationship required, and these are explored with an experimental system based on Rational Unified Process, Visual C++, and object-oriented DBMS ObjectStore. A case study has been pursued to explore the application of the information and knowledge models to a real industry environment
Hafnium and Zirconium Complexes Bearing ONN-Tridentate Ligands and Their Catalytic Properties toward Olefin Polymerization
The
development of high-performance catalysts is a goal
that is
constantly being pursued in the field of polyolefins. In this study,
a class of Hf (Hf1 and Hf2) and Zr (Zr1 and Zr2) dimethyl complexes were prepared
by one-pot reactions of phenoxy-imino-quinoline compounds with MMe4 (M = Hf and Zr). Both NMR spectroscopy and X-ray studies
suggested the formation of phenoxy-amido-quinoline metal complexes
because of methyl migration from the metal center to the carbon atom
of imine. These Hf and Zr complexes exhibited moderate to high activity
(up to 9060 kg (PE)·molâ1(M)·hâ1) toward ethylene homopolymerization and copolymerization with 1-octene
in the presence of 1 equiv of [Ph3C][B(C6F5)4] as a cocatalyst. It was significant that Zr
complexes were far more active than Hf complexes bearing the same
ligand under otherwise identical conditions, revealing a tremendous
metal center effect on catalysis. On the other hand, the nature of
the ligand also strongly influenced the catalytic properties, including
the activity and properties, of resultant polymers. Thus, Zr complex Zr1 with a sterically demanding and electron-donating Me group
on the 2-position of quinoline showed the highest activity and good
thermal stability
Dinuclear Group 4 Metal Complexes Bearing Anthracene-Bridged Bifunctional Amido-Ether Ligands: Remarkable Metal Effect and Cooperativity toward Ethylene/1-Octene Copolymerization
Two types of bifunctional amido-ether ligands (syn-L and anti-L) with the rigid
anthracene skeleton were designed to support dinuclear group 4 metal
complexes. All organic ligands and organometallic complexes (syn-M2 and anti-M2; M = Hf,
Zr, and Ti) were fully characterized by 1H and 13C NMR spectroscopies and elemental analyses. The anti-Hf2 complex showed two confirmations
at room temperature with C2-symmetry or S2-symmetry that can inter-exchange, as indicated
by VT NMR, while only a C2-symmetric isomer
was observed for syn-Hf2 complex at room temperature. However, for Zr and Ti analogues,
both syn and anti complexes exhibited
only one conformation at room temperature. The molecular structures
of complexes syn-Hf2, anti-Hf2, and syn-Ti2 in the solid state were further determined by single-crystal X-ray
diffraction, revealing the distances between two metal centers in syn-M2 from 7.138
Ă
(syn-Ti2) to 7.321 Ă
(syn-Hf2) but a much farther separation in anti-M2 (8.807 Ă
in C2-symmetric anti-Hf2). The mononuclear complex (2-CH3OâC6H4âNâC14H9)Zr(NMe2)3 (mono-Zr1) was also prepared for control experiments. In the
presence of alkyl aluminum (AlEt3) as the alkylating agent
and trityl borate ([Ph3C][B(C6F5)4]) as the co-catalyst, all metal complexes were tested for
copolymerization of ethylene with 1-octene at high temperature (130
°C). The preliminary polymerization results revealed that the
activity was highly dependent upon the nature of metal centers, and syn-Zr2 showed the
highest activity of 9600 kg(PE)·molâ1 (Zr)·hâ1, which was about 17- and 2.2-fold higher than those
of syn-Hf2 and syn-Ti2, respectively.
Benefitting from both steric proximity and electronical interaction
of two metal centers, syn-Zr2 exhibited significant cooperativity in comparison
to anti-Zr2 and mono-Zr1, with regard
to activity and molecular weight and 1-octene incorporation of resultant
copolymers
A 1D Helical Ni(II) Coordination Polymer Based on Butylphenyl Imidazole Dicarboxylate
<div><p>Solvothermal reaction of nitrate salt with a multifunctional organic ligand, 2-(<i>p-tert-</i>butylphenyl)-1<i>H</i>-imidazole-4,5-dicarboxylic acid (<i>p</i>-H<sub>3</sub>BuPhIDC), leads to a novel 1-D helical chain coordination polymer, {[Ni<sub>4</sub>(Ό<i><sub>2</sub></i>-<i>p</i>-HBuPhIDC)<sub>4</sub>(H<sub>2</sub>O)<sub>4</sub>]·H<sub>2</sub>O}<sub>n</sub> (1), which has been characterized by single-crystal X-ray diffraction, spectroscopy, and elemental analysis. The thermal and photoluminescent properties of polymer 1 have been investigated as well.</p></div
Dinuclear Group 4 Metal Complexes Bearing Anthracene-Bridged Bifunctional Amido-Ether Ligands: Remarkable Metal Effect and Cooperativity toward Ethylene/1-Octene Copolymerization
Two types of bifunctional amido-ether ligands (syn-L and anti-L) with the rigid
anthracene skeleton were designed to support dinuclear group 4 metal
complexes. All organic ligands and organometallic complexes (syn-M2 and anti-M2; M = Hf,
Zr, and Ti) were fully characterized by 1H and 13C NMR spectroscopies and elemental analyses. The anti-Hf2 complex showed two confirmations
at room temperature with C2-symmetry or S2-symmetry that can inter-exchange, as indicated
by VT NMR, while only a C2-symmetric isomer
was observed for syn-Hf2 complex at room temperature. However, for Zr and Ti analogues,
both syn and anti complexes exhibited
only one conformation at room temperature. The molecular structures
of complexes syn-Hf2, anti-Hf2, and syn-Ti2 in the solid state were further determined by single-crystal X-ray
diffraction, revealing the distances between two metal centers in syn-M2 from 7.138
Ă
(syn-Ti2) to 7.321 Ă
(syn-Hf2) but a much farther separation in anti-M2 (8.807 Ă
in C2-symmetric anti-Hf2). The mononuclear complex (2-CH3OâC6H4âNâC14H9)Zr(NMe2)3 (mono-Zr1) was also prepared for control experiments. In the
presence of alkyl aluminum (AlEt3) as the alkylating agent
and trityl borate ([Ph3C][B(C6F5)4]) as the co-catalyst, all metal complexes were tested for
copolymerization of ethylene with 1-octene at high temperature (130
°C). The preliminary polymerization results revealed that the
activity was highly dependent upon the nature of metal centers, and syn-Zr2 showed the
highest activity of 9600 kg(PE)·molâ1 (Zr)·hâ1, which was about 17- and 2.2-fold higher than those
of syn-Hf2 and syn-Ti2, respectively.
Benefitting from both steric proximity and electronical interaction
of two metal centers, syn-Zr2 exhibited significant cooperativity in comparison
to anti-Zr2 and mono-Zr1, with regard
to activity and molecular weight and 1-octene incorporation of resultant
copolymers
Stereoselective Ring-Opening Polymerization of <i>rac</i>-Lactide Using Organocatalytic Cyclic Trimeric Phosphazene Base
Phosphazene base
is an important organocatalyst in polymer chemistry
owing to its high activity and versatility. In this contribution,
we demonstrate that cyclic trimeric phosphazene base (<b>CTPB</b>) can catalyze stereoselective ring-opening polymerization (ROP)
of <i>rac</i>-lactide (<i>rac</i>-LA) to produce
isotactic stereoblock PLA (<i>P</i><sub>i</sub> up to 0.93).
The polymerizations are highly controlled, as evidenced by linear
relationship between molecular weights (MW) and monomer conversions
and the narrow dispersity (<i>Ä</i> = <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub>) of the resulted polymers
with high fidelity of end groups. The investigations on polymerization
parameters show that the tacticity of produced PLA depends on the
polymerization temperatures and solvents, while the kinetic studies
reveal a faster rate for ROP of l-LA as compared to <i>rac</i>-LA under same conditions. Based on these results, the
chain end control mechanism is proposed to explain the production
of isotactic stereoblock PLA from <i>rac</i>-LA by an achiral
catalyst
Stratigraphic records of the dynamic uplift of the Emeishan large igneous province
<div><p></p><p>Fluid dynamical and numerical modelling predicts a large-scale regional domal uplift prior to basalt eruptions in large igneous provinces, which can be readily measured when a plume head rises below a shallow marine sedimentary basin. Research on the sedimentology, biostratigraphy, and isotopic chronology of the Emeishan large igneous province demonstrates that the sedimentary environment in the Maokou stage is not uniform carbonate platform facies, but rather sedimentary facies with a northâsouth linear alignment and westâeast different distribution controlled by the syn-depositional normal faulting of the Changhai and Xiaojiang faults, which are the result of underwater dynamic uplift induced by deep mantle activity. The dynamic uplift started in the Maokou stage. Thus, thinning of the Maokou limestone was the product of the difference in the initial depositional thickness caused by the underwater uplift and post-depositional surface uplift and erosion, but post-depositional uplift was much less than kilometre scale. Sedimentary facies differentiation and tectonicâsedimentary evolution in the Maokou stage provide a constraint for the time of the initial eruption and eruption environment before and during the Emeishan basalt eruption. Small-scale magmatic activity might have already begun in the middle of the Maokou stage, whereas submarine and terrestrial sedimentary environments coexisted before and during Emeishan basalt eruption.</p></div
Synthesis, Characterization, and Heterobimetallic Cooperation in a TitaniumâChromium Catalyst for Highly Branched Polyethylenes
A heterobimetallic
catalyst, <b>{Ti--Cr}</b>, consisting
of a constrained-geometry titanium olefin polymerization center (<b>CGC<sup>Et</sup>Ti</b>) covalently linked to a chromium bisÂ(thioether)Âamine
ethylene trimerization center (<b>SNSCr</b>) was synthesized
and fully characterized. In ethylene homopolymerizations it affords
linear low-density polyethylene with molecular weights as high as
460 kg·mol<sup>â1</sup> and exclusively <i>n</i>-butyl branches in conversion-insensitive densities of âŒ18
branches/1000 carbon atoms, which are âŒ17 and âŒ3 times
(conversion-dependent), respectively, those achieved by tandem mononuclear <b>CGC<sup>Et</sup>Ti</b> and <b>SNSCr</b> catalysts under
identical reaction conditions
Editorial: fake news, misinformation, and supply chain disruptions: the role of emerging technologies
Editorial: fake news, misinformation, and supply chain disruptions: the role of emerging technologies.</p
Synthesis, Characterization, and Heterobimetallic Cooperation in a TitaniumâChromium Catalyst for Highly Branched Polyethylenes
A heterobimetallic
catalyst, <b>{Ti--Cr}</b>, consisting
of a constrained-geometry titanium olefin polymerization center (<b>CGC<sup>Et</sup>Ti</b>) covalently linked to a chromium bisÂ(thioether)Âamine
ethylene trimerization center (<b>SNSCr</b>) was synthesized
and fully characterized. In ethylene homopolymerizations it affords
linear low-density polyethylene with molecular weights as high as
460 kg·mol<sup>â1</sup> and exclusively <i>n</i>-butyl branches in conversion-insensitive densities of âŒ18
branches/1000 carbon atoms, which are âŒ17 and âŒ3 times
(conversion-dependent), respectively, those achieved by tandem mononuclear <b>CGC<sup>Et</sup>Ti</b> and <b>SNSCr</b> catalysts under
identical reaction conditions