Denny Ivanal Hakim  Shohei Nakamura  Yoshihiro Sawano  Takuya Sobukawa 《复变函数与椭圆型方程》2018,63(4):569-590

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Projective and injective dimensions in the category σ[M]     

Seyed Shahin Mousavi  Mina Abbaszade 《代数通讯》2018,46(4):1560-1575

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K. Yu. Fedorovskiy 《复变函数与椭圆型方程》2018,63(7-8):961-975

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Yusuf Zuntu Abdullahi  Tiem Leong Yoon  Mohd Mahadi Halim  Md. Roslan Hashim  Thong Leng Lim 《哲学杂志》2018,98(12):1114-1129

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Mehmet Gumus  Jianhong Xu 《Linear and Multilinear Algebra》2017,65(2):325-340

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《Electroanalysis》2017,29(3):814-820

The blending ratio of biodiesel in petroleum diesel has become one of the most important parameters to ensure the quality of diesel/biodiesel blend. This paper presents a fast and simple method based on electrochemical impedance spectroscopy to determine the biodiesel content in diesel fuel. Different from the method reported in the literature, using a pair of two identical screen printed carbon paste electrodes, in the present work we used two electrodes made from 304 stainless steel with dimensions of 0.8×0.3 cm for the EIS measurements. Improved results were obtained in terms of sensitivity, stability of measurements, electrode reuse, and cost. In this procedure the charge transfer resistance is proportionally related to the biodiesel content, which is used to construct a calibration curve for the analysis of biodiesel content. The procedure was validated by an official method, using two samples, being one of them, certified through an official interlaboratory program of the Brazilian government (Interlaboratory Program for Biodiesel of National Agency of Petroleum, Natural Gas and Biofuels (PIB)/ANP). Good results were obtained in terms of recovery (102.6 %‐102.8 %), precision (coefficient of variation lower than 2.3 %), limit of detection (0.24 %) and limit of quantification (0.80 %). These results indicate that this method is sufficiently suitable as an alternative method to the official method for determining biodiesel content in commercial diesel fuel.  相似文献   

    

Andrea Causero  Holger Elsen  Jürgen Pahl  Prof. Dr. Sjoerd Harder 《Angewandte Chemie (International ed. in English)》2017,56(24):6906-6910

An anionic N-heterocyclic olefin ligand was serendipitously obtained by reaction of an amidinate calcium hydride complex with 1,3-dimethyl-2-methyleneimidazole (NHO). Instead of anticipated addition to the polarized C=CH₂ bond to form an unstabilized alkylcalcium complex, deprotonation of the NHO ligand in the backbone was observed. Preference for deprotonation versus addition is explained by loss of aromaticity in the latter conversion. Theoretical calculations demonstrate the substantially increased ylidic character of this anionic NHO ligand which, like N-heterocyclic dicarbenes, shows strong bifunctional coordination.  相似文献   

    

《化学:亚洲杂志》2017,12(2):239-247

Five bis(quinolylmethyl)‐(1H ‐indolylmethyl)amine (BQIA) compounds, that is, {(quinol‐8‐yl‐CH₂)₂NCH₂(3‐Br‐1H ‐indol‐2‐yl)} ( L¹H ) and {[(8‐R³‐quinol‐2‐yl)CH₂]₂NCH(R²)[3‐R¹‐1H ‐indol‐2‐yl]} ( L^2–5H ) ( L²H : R¹=Br, R²=H, R³=H; L³H : R¹=Br, R²=H, R³=i Pr; L⁴H : R¹=H, R²=CH₃, R³=i Pr; L⁵H : R¹=H, R²=n Bu, R³=i Pr) were synthesized and used to prepare calcium complexes. The reactions of L^1–5H with silylamido calcium precursors (Ca[N(SiMe₂R)₂]₂(THF)₂, R=Me or H) at room temperature gave heteroleptic products ( L^{1, 2} )CaN(SiMe₃)₂ ( 1 , 2 ), ( L^{3, 4} )CaN(SiHMe₂)₂ ( 3 a , 4 a ) and homoleptic complexes ( L^{3, 5} )₂Ca ( D3 , D5 ). NMR and X‐ray analyses proved that these calcium complexes were stabilized through Ca⋅⋅⋅C−Si, Ca⋅⋅⋅H−Si or Ca⋅⋅⋅H−C agostic interactions. Unexpectedly, calcium complexes (( L^3–5 )CaN(SiMe₃)₂) bearing more sterically encumbered ligands of the same type were extremely unstable and underwent C−N bond cleavage processes as a consequence of intramolecular C−H bond activation, leading to the exclusive formation of (E )‐1,2‐bis(8‐isopropylquinol‐2‐yl)ethane.  相似文献   

    

《Crystal Research and Technology》2017,52(2)

The precipitation of calcium carbonate in heat exchanger is a serious problem in seawater desalination which results in significant decrease of heat exchange efficiency and tedious cleaning. Decalcification pretreatment by acidic flue gas provides an efficient and economical solution to this problem, but few literature has been reported about the crystallization mechanism of CaCO₃, including the supersaturation ratio, the relationship between the supersaturation ratio of the reaction solution and the crystallization growth rate of CaCO₃ in the CO₂‐CaCl₂‐H₂O system. In this study, the crystallization of CaCO₃ was studied by combing the dynamic method and the static method to ensure the accuracy in measuring the carbonate ion concentration by chemical titration at pH = 8.0 in the CO₂‐CaCl₂‐H₂O system. It was found that there existed an ion competition between HCO₃⁻ and CO₂ (aq) in the CO₂‐CaCl₂‐H₂O system, which led to fluctuations of CO₂ absorption rate. The supersaturation ratio of the reaction solution still increased when the reaction crystallization rate was reduced. The variations of the concentration of HCO₃⁻, CO₃²⁻ and Ca²⁺ ions with time were investigated. The growth process of the vaterite was monitored and described on mesoscale.  相似文献   

    

《中国化学会会志》2017,64(1):55-60

Imidacloprid (IMI ) was reduced by zero‐valent aluminum (ZVAl ) in sodium carbonate solution and tested by high‐performance liquid chromatography (HPLC ). The IMI degradation rate was heavily dependent on Na₂CO₃ concentration and reaction time but only slightly on temperature, reaching 99.4% in 0.5 mol/L Na₂CO₃ solution with 5 g/L ZVAl in 60 min. The degradation of IMI follows first‐order kinetics. We used high‐performance liquid chromatography‐mass spectrometry (HPLC‐MS ) for analyzing the transformation products, and found that IMI disintegrated into IMI urea, IMI guanidine, IMI nitrosamine, and 1‐choloro‐5‐methcyclohea‐1,4‐diene.  相似文献