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The evaluation of rock mechanic characteristics of shale reservoir is the key for the success of fracturing. Several limitations such as complex lithology can affect the accuracy of the rock mechanic property computation. In this research, the mechanical rock properties of shale reservoirs were analyzed based on experimental tests including shale-reservoir mineral composition, uniaxial compressive strength, and triaxial compression tests. The results showed that (1) the difference in mineral composition leads to easier fracturing of sand shale reservoirs compared with pure shale reservoir. (2) Under uniaxial conditions, the rock mechanical parameters along the vertical bedding direction of sand shale reservoirs are better than pure shale reservoir parameters. The mechanical properties of shale reservoirs in parallel bedding direction are less affected by lithology. Under triaxial conditions, the confining pressure increases more than 4.0 times with the compressive strength of rocks, and the rock Young's modulus in the parallel bedding direction is higher compared with the vertical bedding direction. (3) Rock failure mode is mainly subdivided into cutting and splitting modes, and the bedding features of rock mechanic properties highly influence the drilling and fracturing operations. This study offers guidelines for the optimization of the drilling and fracturing process based on accurate evaluation of the rock mechanical properties. [ABSTRACT FROM AUTHOR]

Cocrystallizationof a versatile organic tecton, 3,3′,5,5′-tetramethyl-4,4′-bipyrazole(tmbpz), with aliphatic dicarboxylic acid suberic acid (H2sub) and sebacic acid (H2seb) generates two supramolecularsolids [(tmbpz)2·(H2sub)] (1) and [(tmbpz)2·(H2seb)] (2). In the present case, both cocrystals could be obtained from eithersolution evaporation or mechanochemical solid-state reaction. Single-crystalstructural analyses reveal that the 1and 2are 4-fold and 5-fold 2D → 2D parallel interpenetrated 63-hcb networks, respectively. The substantial dissimilaritiesin the degree of interpenetration are modulated by the different lengthsof dicarboxylic acids. The thermal stabilities and photoluminescencebehaviors of them were also discussed. [ABSTRACT FROM AUTHOR]

In order to study the surface electric potential signals during the coal adsorbing gas, designed the experiment system of the coal adsorbing gas and tested the electric potential signal generated during the coal adsorbing gas under different gas pressure. Experiment results show that surface potential signals can be generated in the process of adsorbing gas, and they increases gradually along with the growth of adsorption time. For the same coal samples, different gas pressure from the coal surface potential signal to the first adsorption gas pressure of coal potential signal has a memory effect in the process of absorption. When the adsorption gas pressure is higher than the first adsorption gas pressure, the coal induces stronger surface potential signals. And when the adsorption gas pressure is lower than the first adsorption gas pressure, the coal induce weaker surface potential signals. The main reasons why surface potential signals can be generated from coal adsorbing gas are that the gas seepage in coal pores produces flow potential and free charge is generated when the gas damages micro cracks and crack of coal. [ABSTRACT FROM AUTHOR]

An investigation was conducted on the characteristics of surface current induced by coal under uniaxial compression. An interpretation of the mechanisms governing the electrical behavior of the coal structures under uniaxial stress tests was presented in this paper. The experimental results show that the current signal is generated during the deformation and fracture process of coal samples. When the load is applied, the electric current makes its initial appearance and increases rapidly after a considerable time lag at 8C, until after the stress reaches a value δc ≈0.75δmax where δmax is the maximum applied stress before sample fracture. There is a good correlativity between the current and the load, and the correlation coefficient between them can reach up to 0.8 to 0.9. The current peaks occur under sudden loading and unloading. It suggests that the current is closely related to the loading. The status of coal loading level may be determined by the current signal. The intensive study on coal surface current can provide a way for monitoring the stability of coal and rock. [ABSTRACT FROM AUTHOR]

The experiment was made on the rules of surface potential of coal or rock during friction process. The mechanism producing surface potential of coal or rock friction was discussed initially. The results show that surface potential can be produced during coal or rock friction process, and it has a better corresponding relationship with load. The coal or rock friction process can be divided into two stages: static friction stage and kinetic friction stage. The surface potential signal in kinetic friction stage was stronger than that in static friction stage. During rock friction process, the polarity of surface potential signal was basically bidirectional mutation, and the polarity of surface potential on both sides of friction surface had obvious symmetry. While the polarity of surface potential signal was basically unidirectional mutation in coal friction process, and the polarity of surface potential on both sides of friction surface was not in significant symmetry. The changes of surface potential during coal or rock friction process can be explained by mechanism of electricity produced by friction, thermionic emission and field electron emission. [ABSTRACT FROM AUTHOR]

In order to study the relationship between surface potential distribution and destruction localization of the coal sample, the distribution law of strain field and surface potential of coal samples were tested under load. The relationship between surface potential field and strain localization & fracture of coal samples was studied and analyzed. Results show that the coal samples show obvious strain localization characteristics in deformation and failure process, the strain localization concentrated area is the severe damage and fracture part of coal samples, and the strain localization zones is usually the fracture location of coal samples. The distribution character of surface potential field of coal samples during deformation and fracture is similar to the strain field, the potential field will be centralized in the damage localization area, the connection between the points of high potential and low potential reflects the rupture section of coal samples. [ABSTRACT FROM AUTHOR]

Abstract: A novel series of two-dimensional π-conjugated oligoarylenes has been synthesized by a divergent approach using Pd-catalysed Suzuki cross-coupling of tetraiodophenylbenzene and arylboronic acid as a key step. It has been shown that the ‘X-branched’ structure can provide a useful platform to construct amorphous molecular materials as it can enhance the morphological and thermal stability as well as to facilitate solubility and processibility of a material when compared to those of the corresponding linear oligomers. The diphenylamino end-capped two-dimensional oligoarylenes were found useful as a hole transporting/emitting layer for light emitting applications. [Copyright &y& Elsevier]

The non-coplanar substituted phenyl rings at the 9-position of a fluorenyl unit can be involved in π-electron delocalization in which the resulting oligofluorenes exhibit a very large enhancement of two-photon absorption cross sections up to 2559 GM at 710 nm. [ABSTRACT FROM AUTHOR]

A one-pot, three-component difunctionalization of quinones with indoles and arylamines has been developed to synthesize indole functionalized p -iminoquinones derivatives. The approach employed AgOAc as the catalyst in the presence of 3-chlorophenylboronic acid, giving a series of indole functionalized p -iminoquinones derivatives in moderate to good yields. This catalytic approach represents a step-economic and convenient strategy for the difunctionalization of quinones. A plausible reaction pathway has been proposed based on a series of control experiments. [ABSTRACT FROM AUTHOR]

Concise one-pot biarylamination of quinones with arylamines was developed to synthesize N -arylamine-functionalized p -iminoquinones derivatives. The approach employed AgOAc as the catalyst and (NH4)2 S2 O8 as the oxidant in the presence of 3-chlorophenylboronic acid, giving a series of N -arylamine-functionalized p -iminoquinone derivatives in moderate to good yields whereas reaction in the absence of the 3-chlorophenylboronic acid, gave a series of N -arylamine-functionalized 1,4-naphthoquinone derivatives. This catalytic approach represents a step-economic and convenient strategy for the difunctionalization of quinones. [ABSTRACT FROM AUTHOR]

In order to analyze the failure mechanism of coal under the load, multi-fractal characteristics of surface potential of coal sample under uniaxial compression was studied. The surface potential was analyzed using multi-fractal theory to calculate the multi-fractal spectrum. The change rules of characteristic parameters of multi-fractal spectrum with the loading process were studied. The results show that the surface potential represents multi-fractal feature, and keeps scale invariance in the wide range. The shape of the multi-fractal spectrum of different size specimens shows right hook. The characteristic parameters of multi-fractal spectrum, Δα and Δf, vary with the process of deformation and fracture of coal sample with load. The changes of trend that Δα and Δf increase in a long time, then decrease rapidly can be used as a precursory factor of coal-rock failure to forecast the instability of the samples. The results are helpful to understand the inherent law in the coal specimen failure process and forecast the dynamic disaster using the potential. [ABSTRACT FROM AUTHOR]

Acoustic emission signals generated in process of methane sorption and seepage in coal were observed, and the dynamic characteristic of damage evolution and the seepage process were analyzed based on the characteristic of acoustic emission. The experiments indicated that the strength of acoustic emission decreased with the adsorbed methane increase. And the acoustic emission showed paroxysmal in time domain. The results give implication that the methane seepage in coal layer by layer. In its seepage process, methane shows destructive seepage while the gas pressure gradient was bigger than the threshold value. Then, pressure of the seepage face decreased and the methane shows undestructive seepage. Sorption process tends to equilibrium with the gas pressure increase. [ABSTRACT FROM AUTHOR]

A sequential one-pot approach towards 2-(N- substituted amino)-1,4-quinones or 3-indolyl-quinones from naphthol/hydroquinone with amines or indoles, such as various (hetero)aromatic amine and aliphatic amine, has been developed. The reaction proceeds through oxidation of naphthol/hydroquinone with the CuBr 2 or (NH 4) 2 S 2 O 8 oxidant. This reaction provides efficient access to the biologically important and synthetically useful 2-amino-quinones and 3-indolyl-quinones with good yields under mild conditions. The present protocol is simple, practical and shows good functional group tolerance. To create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered. [Display omitted]. [ABSTRACT FROM AUTHOR]

A homologous series of 9,9-diphenyl substituted oligofluorenes end-capped by diphenylamino groups, (Ph) -OF( n )-NPhs, n = 1–5, has been synthesized using Suzuki cross coupling reaction as a key step and were fully characterized by 1 H NMR, 13 C NMR, MS, and elemental analyses. The functional properties, including thermal stabilities, linear optical properties, fluorescence and electro-chemical properties, were investigated. The TPA cross sections of these newly synthesized oligofluorenes were measured by the TPF method. Compounds (Ph) -OF(4)-NPh and (Ph) -OF(5)-NPh exhibited larger two-photon absorption cross-sections, about 550 GM and 1390 GM at 800 nm, respectively. [ABSTRACT FROM AUTHOR]

Seven new copper(ii) coordination networks combining flexible 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (bpz) and diverse dicarboxylates, [Cu(bpz)0.5(adip)]n (1), [Cu2(bpz)4(sub)2]n (2), [Cu4(bpz)1.5(aze)·H2O]n (3), [Cu2(bpz)(pta)2(H2O)·H2O]n (4), [Cu2(bpz)(ipa)]n (5), [Cu2(bpz)(o-pda)2·H2O]n (6), and [Cu2(μ3-OH)(bpz)(p-pda)1.5·H2O]n (7) (H2adip = adipic acid, H2sub = suberic acid, H2aze = azelaic acid, H2pta = phthalic acid, H2ipa = isophthalic acid, H2o-pda = o-phenylenediacetic acid, H2p-pda = p-phenylenediacetic acid), have been obtained under solvothermal conditions and structurally verified by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), UV-vis spectroscopy and thermogravimetric analyses (TGA). Single crystal X-ray diffraction analysis revealed that both 1 and 6 are 6-connected pcu networks (point symbol: {412·63}) based on paddle-wheel [Cu2(COO)4] secondary building units (SBU). Complexes 2 and 4 are 2D 44-sql networks based on a single metal ion node and a binuclear [Cu2(COO)4(H2O)] SBU, respectively, while complex 3 features an extremely rare 3D 5-connected hxg-d-5-C2/c (point symbol: {42·67·8}) network. Complex 5 shows a 1D tape structure built from bpz sealed 1D helical Cu2(ipa) chains along the b axis, and 7 is a 3D 8-connected hex (point symbol: {36·418·53·6}) network based on a centrosymmetric [Cu4(μ3-OH)2(COO)4] SBU. A thorough structural comparison of these coordination networks suggests that the coordination fashions, conformations of dicarboxylates along with the different inorganic Cu(ii) SBUs simultaneously play a significant role in constructing the diverse networks. Variable-temperature magnetic susceptibility data denote that 4 and 7 display antiferromagnetic interactions in binuclear [Cu2(COO)4(H2O)] and [Cu4(μ3-OH)2(COO)4] SBUs. Moreover, the thermal stability and UV-vis spectra of 1–7 are discussed in detail. [ABSTRACT FROM AUTHOR]

Sevennovel silver(I) coordination networks with mixed flexible3,3′,5,5′-tetramethyl-4,4′-bipyrazole (bpz) andC3–C9 aliphatic dicarboxylic acids, [Ag2(bpz)4(mal)·7H2O]n(1Land 1R), [Ag2(bpz)3(suc)]n(2), [Ag4(bpz)5(glu)2]n(3), [Ag4(bpz)5(adip)2]n(4), [Ag4(bpz)7(pim)2·12H2O]n(5), [Ag2(bpz)4(sub)·7H2O]n(6), and [Ag2(bpz)3(aze)·3.5H2O]n(7) (H2mal = malonic acid,H2suc = succinic acid, H2glu = glutaric acid,H2adip = adipic acid, H2pim = pimelic acid,H2sub = suberic acid, H2aze = azelaic acid),have been synthesized and structurally characterized by single-crystalX-ray diffraction analyses and further characterized by infrared spectra(IR), elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetricanalyses (TGA). Single crystal X-ray diffraction analysis revealsthat 1crystallized into a pair of enantiomerically pure3D 3-fold interpenetrated chiral SrSi2networks (pointsymbol {103}) through spontaneous resolution in the absenceof any chiral source. Complex 2is a 3D 2-fold interpenetrated3-connected uninodal dia-fnetwork (point symbol {4·142}) without consideration of Ag···Ag interaction.Complexes 3and 4are similar 2D + 2D →2D 63-hcblayer featuring 3-fold parallelinterpenetration. Complex 5is a 3D 3-fold interpenetrated3,4-connected 3,4T1network (point symbol {4·6·8}{4·62·83}). Complexes 6and 7are similar 2D + 2D → 2D feslayers(point symbol {4·82}) featuring 3-fold parallel interpenetration.In 1–7, structural diversity rangingfrom 2D hcband feslayers to 3D chiralSrSi2, achiral dia-f, and 3,4T1networks is modulated by dicarboxylates with alkyl chains of differentlengths. Interestingly, a well-resolved octanuclear water clusterbuilt from a chairlike (H2O)6cluster and twowater molecules dangling on two corners of it and a unusual seesaw-likepentanuclear water cluster is observed in the voids of 5and 7, respectively. Furthermore, the solid-state photoluminescenceproperties of the 1–7were investigatedat 298 and 77 K. [ABSTRACT FROM AUTHOR]

Abstract: Four monodisperse symmetric bis-dendronized arylenes, DPh-EG, Ph-EG, FPh-EG and DTh-EG have been successfully synthesized by a convergent approach using copper-catalyzed Buchwald''s amination as a key step and characterized by a combination of 1H NMR, 13C NMR, MS, and HRMS. All these bis-dendronized arylenes exhibit high thermal stabilities, good amorphous morphological stabilities and high energy-transfer efficiencies (76%, 73%, 78% and 68%, respectively for DPh-EG, DTh-EG, FPh-EG and Ph-EG). [Copyright &y& Elsevier]

Abstract: A facile approach for synthesis of the triarylamine-endcapped X-branched oligofluorene, X-OF(2)Ph-NPh and its corresponding linear oligofluorene, OF(2)Ph-NPh by Suzuki cross-coupling as a key reaction has been developed. This novel X-branched oligofluorene exhibits much higher thermal and electrochemical stabilities and enhanced electroluminescent properties as comparison to its corresponding linear counterpart. Using a simple two-layer OLED structure of ITO/oligofluorene (40nm)/PBD (40nm)/LiF (1nm)/Al (150nm), the luminance efficiency of X-OF(2)Ph-NPh-based OLED can also reach up to 2.8cd/A with a maximum brightness of 1700cd/m2 and remarkably better than 1.2cd/A with a maximum brightness of 700cd/m2 for its corresponding linear oligofluorene OF(2)Ph-NPh-based OLEDs. [Copyright &y& Elsevier]

Abstract: 2,7- and 3,6-Bis [7-diphenylamino-9,9-di(n-butyl) fluorene-2-yl]dibenzo-thiophene S,S′-dioxides, 2,7-OF(2)BTO-NPh and 3,6-OF(2)BTO-NPh have been synthesized by a convergent approach using palladium-catalyzed Suzuki cross-coupling or copper-catalyzed Buchwald''s amination as the key reactions. The functional properties including thermal stabilities, optical properties, electrochemical properties of these two oligomers, as well as the performance of 2,7-OF(2)BTO-NPh-based OLEDs have been investigated and discussed. With a simple three-layer structure of ITO/3,6-OF(2)BTO-NPh (40nm)/F-TBB (15nm)/Alq3 (20nm)/LiF (1nm)/Al (75nm), the luminance efficiency of 3,6-OF(2)BTO-NPh-based OLEDs can also reach up to 0.42cd/A with a maximum brightness of 1620cd/m2. [Copyright &y& Elsevier]

Abstract: A new compound 4-(diphenylamino) biphenyl-4′-boronic acid (DBBA) was synthesized. The optical properties including fluorescence quantum yields and change in the dipole moment in various solvents at room temperature were characterized by the absorption and steady-state fluorescence technique. The emission wavelength of DBBA was very sensitive to the polarity of solvents. The magnitude of change in the dipole moment was calculated based on the Lippert–Mataga equation. DBBA has an increase of dipole moment of 4.9 D units on excitation to the lowest singlet state. A high fluorescence quantum yields (φf) and short fluorescence decay times (τf) were determined in all solvents tested. The bathochromic shift of the emission spectra and the increase in the excited state dipole moment occurred. These gave the evidence about the intramolecular charge transfer (ICT) character in the emitting singlet state of DBBA. [Copyright &y& Elsevier]

GaN films with an AlxGa1−xN/AlyGa1−yN superlattice (SL) buffer layer are grown on Si(111) substrates by metal-organic chemical vapor deposition (MOCVD). The structure and strain properties of the samples are studied by optical microscopy, Raman spectroscopy, x-ray diffractometry and atomic force microscopy. The results show that the strain status and crystalline quality of the GaN layers are strongly dependent on the difference of the Al composition between AlxGa1−xN barriers and AlyGa1−yN wells in the SLs. With a large Al composition difference, the GaN film tends to generate cracks on the surface due to the severe relaxation of the SLs. Otherwise, when using a small Al composition difference, the crystalline quality of the GaN layer degrades due to the poor function of the SLs in filtering dislocations. Under an optimized condition that the Al composition difference equals 0.1, the crack-free and compressive strained GaN film with an improved crystalline quality is achieved. Therefore, the AlxGa1−xN/AlyGa1−yN SL buffer layer is a promising buffer structure for growing thick GaN films on Si substrates without crack generation. [ABSTRACT FROM AUTHOR]