内埋炸药下超高韧性水泥基复合材料的抗爆性能

为研究超高韧性水泥基复合材料(ultra-high toughness cementitious composites, UHTCC)在内埋炸药爆炸下的抗爆性能和损伤破坏规律,对不同炸药埋深下的UHTCC和高强混凝土(high-strength concrete, HSC)进行了内埋炸药抗爆实验。得到了两种材料靶体的破坏状态,并利用接触爆炸的实验结果计算出了两种材料的抗爆性能参数。结果表明,在相同条件下,UHTCC抗爆性能优于高强混凝土。为了进一步探究UHTCC的抗压强度、抗拉强度以及拉伸韧性对靶体在内埋炸药下抗爆性能的影响,首先,采用改进的K&C模型对炸药埋深为40 mm的超高韧性水泥基复合材料靶体进行数值模拟,模拟结果与实验结果基本吻合,并根据数值模拟的结果得到了爆炸冲击波沿靶体径向衰减速度大于轴向衰减速度这一规律,验证了数值模型的有效性;然后,通过调整改进K&C模型中与抗压强度、抗拉强度以及拉伸韧性相关的参数,数值预测了不同抗压强度、抗拉强度以及拉伸韧性下UHTCC靶体的破坏状态,发现增强UHTCC的韧性可以有效防止靶体发生整体性破坏,增大UHTCC的抗拉强度可以减小靶体迎爆面的开坑直径,增大UHTCC的抗压强度对减小开坑直径效果不明显。     

Controlled Radical Polymerization of Furfuryl Methacrylate

Atom transfer radical polymerization provides a new method of controlled radical polymerization. The most important advantage of ATRP is that it is tolerant to the different functional groups present in the initiator as well as in the monomer. Furfuryl Methacrylate (FMA) is a specialty monomer, which has applications in coatings, adhesives and in biomedicals. Conventional radical polymerization of FMA leads to excessive gel formation, which limits its applications. In this investigation homo and co-polymerization of FMA has been carried out via ATRP. ATRP of FMA was carried out using CuBr as catalyst and 1, 1, 4, 7, 10, 10 hexamethyltriethylenetetramine (HMTETA) as ligand. There was no gel formation during the polymerization. ATRP of FMA was well controlled with a linear increase of molecular weight (Mn) with monomer conversion. The polymers were characterized by using ¹HNMR, FT-IR and GPC analysis. Interestingly, it was observed that the furfuryl ring was not affected during polymerization.     

Padé approximants and their application to scattering from fluid media

In this work, a numerical method for modeling the scattered acoustic pressure from fluid occlusions is described. The method is based on the asymptotic series expansion of the pressure expressed in terms of sound speed contrast between the host medium and entrained fluid occlusions. Pade? approximants are used to extend the applicability of the result for larger values of sound speed contrast. For scattering from a circular cylinder, an improvement in convergence between the exact and numerical solutions is demonstrated. In the case of scattering from an inhomogeneous medium, a numerical solution with reduced order of Pade? approximants is presented.     

Photoinduced signal amplification through controlled externally sensitized fragmentation in masked sensitizers

Addition of lithiated dithianes to diaryl ketones, potential electron-transfer sensitizers, disrupts conjugation between the two aromatic moieties, effectively masking the sensitizer. A novel photoamplification strategy is developed based on photosensitized cleavage in such adducts, where each fragmentation event releases more diaryl ketone, capable of sensitization. As a result, mass release of dithianes, triggered with a very small amount of the initiator, is observed. Such amplified release can be made contingent on a molecular recognition event, offering a promising methodology for high throughput bioanalytical applications. The concept is proved with the use of micro- and nanosized polymeric supports, including dendrimers.     

Green Sources Derived Carbon Dots for Multifaceted Applications

For the past decade, the Carbon dots (CDs) a tiny sized carbon nanomaterial are typically much attentive due to their outstanding properties. Nature is a fortune of exciting starting materials that provides many inexpensive and renewable resources which have received the topmost attention of researchers because of non-hazardous and eco-friendly nature that can be used to prepare green CDs by top-down and bottom-up synthesis including hydrothermal carbonization, microwave synthesis, and pyrolysis due to its simple synthetic process, speedy reactions and clear-cut end steps. Compared to chemically derived CDs, green CDs are varied by their properties such as less toxicity, high water dispersibility, superior biocompatibility, good photostability, bright fluorescence, and ease of modification. These nanomaterials are a promising material for sensor and biological fields, especially in electrochemical sensing of toxic and trace elements in ecosystems, metal sensing, diagnosis of diseases through bio-sensing, and detection of cancerous cells by in-vitro and in-vivo bio-imaging applications. In this review, the various synthetic routes, fluorescent mechanisms, and applications of CDs from discovery to the present are briefly discussed. Herein, the latest developments on the synthesis of CDs derived from green carbon materials and their promising applications in sensing, catalysis and bio-imaging were summarized. Moreover, some challenging problems, as well as upcoming perspectives of this powerful and tremendous material, are also discussed.

     

Design,synthesis and characterization of a linear hydrogen bonded homologous series exhibiting reentrant smectic C ordering

Design, synthesis and characterization of seven linear hydrogen bonded liquid crystal complexes derived from mesogenic p–n-decyloxy benzoic acid and p–n-alkyl benzoic acids designated as 10OØn (where n varied from ethyl to octyl) are reported. FTIR studies confirm the hydrogen bond formation in all these complexes. The phase transition temperatures and their corresponding enthalpy values are experimentally deduced from Differential Scanning Calorimetry (DSC) studies. POM and DSC data are further utilized for the construction of 10OØn phase diagram. Two Odd–even effects have been evinced, one in enthalpy values and the other in corresponding transition temperatures across the isotropic to nematic phase transition. An interesting result is the observation of re-entrant smectic ordering, designated as smectic C_R in three higher ordered mesogens. A new smectic ordering, smectic X, has been observed which is sandwiched between traditional smectic C and re-entrant smectic C_R. Magnitudes of optical tilt angle in smectic C, smectic X and smectic C_R are experimentally found to attain saturation with decrement of temperature in the corresponding phase. The occurrence of smectic X and smectic C_R are discussed with relation to the molecular chemical structure. The optical filtering action in smectic C and re-entrant smectic C_R phases have been analyzed.     

Growth and characterization studies of 2-bromo-4′-chloroacetophenone (BCAP) crystals

Sintering of barium titanate by microwave heating with barium borate as a liquid-phase forming material was examined as a means of saving energy. A liquid phase was generated faster and over a wider temperature range by intermittent heating at constant power than by constant heating with variable power. When sufficient amount of the liquid-phase forming material were present, the samples were densified at temperatures below those at which the liquid-phase is normally formed. A sample containing 10 mol% of the liquid-phase forming material was densified efficiently. When too much liquid-phase forming material was present, densification of the sample was obstructed.     

Birefringence Study in Hydrogen Bonded Complexes

A novel series of linear complementary hydrogen bonded complexes fashioned between p-n-alkylbenzoic acids (nBA) and m-fluorobenzoic acid (FBA) are isolated. The obtained homologous series comprising of seven mesogens are analyzed by polarizing optical microscope (POM), differential scanning calorimetry (DSC) and Fourier Transform Infra-Red (FTIR) spectroscopy. It is interesting to note the correlation between the alkyl chain length and the mesogenic phases. The order of the transitions is examined through Cox parameter, experimentally derived by thermal analysis (DSC). Optical tilt angle studies in smectic C and thermal stability factors for various phases are discussed. Birefringence study by various techniques enabled to measure the refractive index at various phase transitions. These results are compared and conferred with those obtained from conventional refractometer. Further orientational order parameter for various phases has been discussed.     

Preferable solar cell absorber – Near stoichiometric or stoichiometric CBD CIAS thin films?

Near stoichiometric and stoichiometric [CuIn_(1 − x)Al_(x)Se₂] (CIAS) thin films are prepared by chemical bath deposition (CBD) technique. X-ray diffraction (XRD) analysis have been employed to estimate the structural properties of CBD CIAS thin films and also to identify the near stoichiometric in particular defect free Cu-poor CBD CIAS thin films as preferable solar cell absorber material.