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排序方式: 共有322条查询结果,搜索用时 15 毫秒
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《Arabian Journal of Chemistry》2020,13(11):7875-7885
This research focuses on implementing the low cost and rapid front face synchronous fluorescence (SyFS) in order to ensure the quality assurance of Greek milk. Specifically, samples originated from the Greek domestic production of goat, sheep, cow, as well as foreign cow milk samples and adulterated cow milk samples. SyFS spectra were acquired in the excitation area of 250–500 nm with (Δλ)= 100 nm. Greek and foreign cow milk samples were differentiated based on intensity variations at wavelengths 350–515 nm, 540–579 nm, and 580–600 nm. The emissions at these wavelength positions correspond to tryptophan, vitamin A, and riboflavin. The supervised model with 94 samples exhibited p-value = 7,98E-11, RMSEE= 0,29171, RMSEcv= 0,29284 and RMSEP= 0,98013, AUROC for Greek samples= 0,61 and AUROC for foreign= 0,85. We differentiated milk samples according to the animal type with PCA and OPLS-DA models of 107 samples exhibiting RMSEE= 0,225842, RMSEcv= 0,228054 and RMSEP= 0,518635, AUROC for sheep samples= 0,99, AUROC for goat samples= 0,98 and AUROC for cow samples= 0,96. In fact, the emission band 350–591 nm characterized sheep milk and corresponds to aminoacids and fatty acids, cow milk was related to the 350–600 nm emission band related to the b-carotene and to the goat milk the emission bands 350–505 nm and 520–600 nm were attributed to tryptophan, NADH and Rivoflabin. Finally, we investigated whether SyFS coupled with chemometrics may provide preliminary evidence on adulterated cow milk samples. All models were validated with permutation testing, p-values and ROC curves. 相似文献
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电容式编码器是一种新型、耐用、可靠和准确的编码器。由于电容式编码器编码的原理不同于传统的光学式和电磁式编码器,其输出的位置信息是经过两路激励信号调制后的正弦波形,与传统的正余弦(和)和方波(PWM)输出方式差异较大,因此其信号检测技术也和传统的编码器有很大的差别。为了精确地获取电容式编码器输出信号中所携带的位置信息,本文设计了一套基于现场可编程门阵列(FPGA)的电容式编码器数据采集系统。文中介绍了带通滤波器、同步正交解调、低通滤波器和Cordic等算法,并详细分析了系统的稳定性和误差。实验结果表明,系统能够实时的获取转子的位置信息,同时具有较好的分辨率和精度。 相似文献
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工业以太网协议Ethernet POWERLINK(EPL)分布式站点的时钟同步方法并不能在实时运行过程中保持很高的同步精度,无法满足特定环境下的控制要求。研究了工业以太网协议EPL的两种时钟同步机制,通过数理计算分析了时钟同步误差产生的原因,针对误差较大的缺点,提出了减小误差的方法。通过迭代计算消除了主从站同步报文往返的路径延迟,并设计基于现场可编程门阵列(FPGA)的集线器(Hub)用于EPL菊花链网络拓扑结构,有效地克服了时钟同步报文往返传输延时不一致的缺点,测试结果表明新方法明显优于协议自身的时钟同步方法,对于实现基于EPL的高精度分布式时钟同步网络具有重要意义。 相似文献
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Spectrofluorimetric study on the interaction between antimicrobial drug sulfamethazine and bovine serum albumin 总被引:1,自引:0,他引:1
Abdulilah Dawoud Bani-Yaseen 《Journal of luminescence》2011,131(5):1042-1047
The interaction between the antimicrobial drug sulfamethazine (STM) and bovine serum albumin (BSA) has been studied using steady state and synchronous fluorescence spectroscopy. Fluorescence emission data revealed that BSA (2×10−6 M) fluorescence was statically quenched by STM at various concentrations, which implies that STM-BSA complex has been formed. The fluorescence emission data was analyzed via applying the Stern-Volmer analysis in combination with thermodynamic investigation, where obtained results revealed that quenching is static with quenching constants of 2.371, 1.658, and 0.916×105 M−1 at 298, 304, and 310 K, respectively. Binding constants and number of binding sites at different temperatures were also determined by applying the Scatchard method, which in turn were used to construct the van't Hoff plot in order to estimate the enthalpy (ΔH) and entropy changes (ΔS) for the complexation process. An average of 1.00±0.17 was estimated for the number of sites of BSA, which indicated that STM binds to BSA with stoichiometric ratio of 1:1. The values that were estimated from the van't Hoff plot for ΔH and (ΔS) were −36.8 kJ mol−1 and −14.9 J mol−1 K−1, respectively, which indicate that the STM-BSA complex is stabilized with hydrogen bonds and van der Waals interactions. Synchronous fluorescence data was obtained at Δλ of 15 and 60 nm, where obtained results confirmed that STM binds to BSA at the tryptophan residue (Trp. 213). In addition, the distance between STM and the Trp. 213 was estimated via employing the Förster's non-radiative energy-transfer theory, and was found to be 2.73 nm, which in turn indicated that STM can bind to BSA with high probability. 相似文献
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In this paper we investigate the properties of a decentralized consensus algorithm for a network of continuous-time integrators subject to unknown-but-bounded time-varying disturbances. The proposed consensus algorithm is based on a discontinuous local interaction rule. Under certain restrictions on the switching topology, it is proven that after a finite transient time the agents achieve an approximated consensus condition by attenuating the destabilizing effect of the disturbances. This main result is complemented by an additional result establishing the achievement of consensus under different requirements on the switching communication topology. In particular, we provide a convergence result that encompasses situations in which the time varying graph is always disconnected. Lyapunov analyses are carried out to support the suggested algorithms and results. Simulative tests considering, as case study, the synchronization problem for a network of clocks are illustrated and commented on to validate the developed analysis. 相似文献