COMPARISON AND OSCILLATION THEOREMS FOR AN ADVANCED TYPE DIFFERENCE EQUATION

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浅谈高等数学教学中的概念引入模式

本文介绍了几何图示等五种概念引入模式．提出高等数学教学中应高度重视概念引入模式的观点,试图以此作为提高教学水平与学生数学素质的一个新的突破口.     

高考改革背景下CAP课程的建设与实践

介绍了中国大学先修课程(CAP)的概念、缘由和价值。以简明有机化学为例,阐述了一门CAP课程具体的建设过程与运行情况。CAP课程改善了高中和大学部分课程的衔接,CAP制度的建设与有效实施有助于传播先进的教学理念和优质教学资源的共享,同时多角度的学习能力考评便于新高考模式下辅助高校进行人才选拔。CAP课程体系建设是新时期教学改革发展的必然趋势,但目前还存在CAP课程成绩的权威性、成绩和学分互认困难、高中师资不足、学生学业负担增加等问题。教育部门进行顶层设计,由专业领域具有权威的第三方机构来提供课程运行管理、考试评价服务和师资培训服务是可行做法。     

Hidden correlation between absorption peaks in achiral carbon nanotubes and nanoribbons

In this paper we study the effect of absorption peak correlation in finite length carbon nanotubes and graphene nanoribbons. It is shown, in the orthogonal π-orbital tight-binding model with the nearest neighbor approximation, that if the ribbon width is a half of the tube circumference the effect takes place for all achiral ribbons (zigzag, armchair and bearded), and corresponding tubes, starting from lengths of about 30?nm. This correlation should be useful in designing nanoribbon-based optoelectronics devices fully integrated into a single layer of graphene.     

Fluorescence Reduction by a Triplet-State Population

The range of applications for fluorescent dyes in medicine and biology is increasing greatly. At the same time, the demands on the dyes are getting bigger. The dye molecules are often expected to emit maximum-intensity fluorescence. The primary requirement for this is naturally a high fluorescence quantum yield. Beyond this, it must be considered that fluorescent molecules located in a meta-stable triplet state are not able to emit fluorescent radiation. This represents a reduction of the intensity of the fluorescence, which is generally underestimated in its importance. The size of this perturbation can be grasped by knowledge of the quantum yield for occupation of the triplet state and its lifetime. Unfortunately these parameters are completely unknown, even for frequently used dyes. On investigating some medically and biologically relevant dyes, it is shown that the attainable fluorescence intensity could be reduced strongly by occupation of the triplet state.     

Reprint of: Decomposition of PPCPs by ultrasound-assisted advanced Fenton reaction: A case study with salicylic acid

The study is about the degradation of a widely used pharmaceutical and personal care product-salicylic acid by sonocatalysis, and the experimental design of the reaction system. The first part of the study consists of sonication (572 kHz) in the presence of zero-valent iron (ZVI) with or without H₂O₂ to select and optimize the operational parameters as frequency, time, initial solute concentration, dose of reagents and pH. The second part consists of the use of response surface methodology and multiple regression to develop an experimental design modeland to assess the individual and interactive effects of pH, power (P_o), ZVI dose and H₂O₂. The results showed that the optimal conditions predicted by the model without defining any restrictions are: pH = 2.0, P_o = 120 W, ZVI = 24 mg L⁻¹, which provide total salicyclic acid and 48% TOC decay. However, the prediction implies intensive consumption of energy and reagents, and must therefore be modified by restricting the value of TOC decay to a lower value and that of pH to a higher one. Cross-validation tests showed that the prediction accuracy of the model was considerably high with 5.0–9.4% deviation from the experimental data.     

The relationship between mathematicians’ pedagogical goals,orientations, and common teaching practices in advanced mathematics

Despite mathematics educators’ research into more effective modes of teaching, lecture is still the dominant mode of instruction in undergraduate mathematics courses. Surveys suggest this is because most mathematicians believe this is the best way to teach. This paper answers a call by mathematics education researchers to explore mathematicians’ needs and goals concerning teaching. We interviewed eight mathematicians about findings in the mathematics education research literature concerning common pedagogical practices of instructors of advanced mathematics classes: “chalk talk,” the presentation of formal and informal content, and teacher questioning. We then analyzed the responses for resources, orientations, and goals that might influence the participants to engage in these practices. We describe how participants believed common lecturing practices allowed them to achieve their goals and aligned with their orientations. We discuss these findings in depth and consider what implications they may have for researchers that aim to change mathematicians’ teaching practices.     

Smart sensors in environmental/water quality monitoring using IoT and cloud services

The growing social awareness and consequent concern for the environment has driven environmental analytical chemistry to a position of great prominence. In recent times, this position has translated into taking advantage of the great benefits provided by cloud computing and the Internet of Things (IoT), which are especially appropriate when devices such as chemical sensors are used. The use of such sensors is very common when in situ monitoring of environmental parameters is performed, but until recently, it was limited to the deployment of a small number of sensors. Currently, this approach has given way to genuine smart sensing systems (for instance, fully consolidated wireless sensor networks) that are able to provide a substantial amount of information. This type of sensor (the so-called smart sensor) is fundamentally characterized by (a) low consumption, versatility, and autonomy, (b) ease of integration with cloud solutions, (c) durability and reliability of IoT platforms and sensors, and (d) easy installation and deployment of sensor nodes. For all these reasons, and given the increasing importance and use of this type of device, a revision of the recent literature relating the development of smart sensors with environmental issues has been conducted, with major contributions being discussed, most notably those addressing the continuous in-line monitoring of water quality.     

Physicochemical and antioxidative properties of ultrasound-assisted extraction of mahua (Madhuca longifolia) seed oil in comparison with conventional Soxhlet and mechanical extractions

Ultrasound-assisted solvent extraction (UAE) was applied to extract underutilized Madhuca longifolia seed oil. The effect of extraction time, temperature, solvent type, solvent/sample ratio, and amplitude on the oil yield and recovery were investigated. Approximately 56.97% of oil yield and 99.54% of oil recovery were attained using mild conditions of 35 min, 35 °C, 40% amplitude, isopropanol to acetone (1:1), and solvent to sample (20 mL/g). UAE oil yield and recovery were comparable with Soxhlet extraction (SXE) whilst mechanical pressing (ME) yielded < 50% of UAE recovery. UAE does not affect the fatty acids composition (46% C18:1; 22% C16:0; 21% C18:0, 10% C18:2), and triacylglycerol profile (23% POO, 17% POS, 16% SOO, and 14% POP). Interestingly, UAE extracted oil conferred remarkably (P < 0.05) higher antioxidant capacity (IC₅₀ of DPPH 106.60 mg/mL and ABTS 39.80 mg/mL) than SXE (IC₅₀ of DPPH 810.40 mg/mL and ABTS 757.43 mg/mL) or ME (IC₅₀ of DPPH 622.38 mg/mL and ABTS 392.87 mg/mL).     

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以平衡程序Jsolver 为基础开展了紧凑型聚变裂变混合堆先进等离子体平衡位形设计,重点研究了反剪切运行模式,并在此位形下研究了自举电流的计算、分布及份额。