Methacrylic acid–acrylamide-g-poly(ethyleneterephthalate) fibres for urea hydrolysis

This paper presents the results of urease immobilization onto methacrylic acid–acrylamide grafted poly(ethyleneterephthalate) fibres. The graft yield strongly affected the maximum activity of the immobilized enzyme up to a value of 70·2%. Higher grafting caused a decline in urease activity and led to the degradation of the fibres. The minor changes observed in K_m and V_max demonstrated that the conformational changes existed during immobilization were not extensive. However, 70·2% methacrylic acid–acrylamide-g-fibres containing urease were more stable towards acidic and alkaline pH, high temperature and storage conditions compared with free enzyme. Apart from the increase in stability to heat inactivation, the initial enzymatic activity of the urease–fibre system remained almost unchanged even after 40 repeated assays corresponding to 10 h of operation in 4 months, indicating the excellent durability of the system.     

Recovery of sensor embedded washing machines using a multi-kanban controlled disassembly line

Product recovery involves the recovery of materials and components from returned or end-of-life products. Disassembly, an element of product recovery, is the systematic separation of an assembly into its components, subassemblies or other groupings. Stricter environmental regulations together with dramatic decrease in natural resources and landfills have increased the importance of disassembly as all product recovery options require some level of disassembly. Due to changes made during the lifetime of a product by customers or service personnel, the number and the version of components prior to disassembly is unknown. Customers may also discriminate between and demand different versions of components. The existence of non-functional components further adds to the uncertainty associated with disassembly yield. Sensors implanted into products during their production can address this uncertainty by providing information on the number, condition and version of components prior to disassembly. In this study, we evaluate the impact of sensor embedded products (SEPs) on the various performance measures of a washing machine (WM) disassembly line controlled by a multi-kanban system, which takes into consideration the highly stochastic behavior of the line while managing material and kanban flows. First, separate design of experiments studies based on orthogonal arrays are performed for conventional products and SEPs. In order to observe the response of each experiment, detailed discrete event simulation (DES) models for both types of products are developed considering the precedence relationships among the components of a WM. Then, pair-wise t-tests are conducted to compare the two cases based on different performance measures. According to the results, SEPs provide significant reductions in all costs (viz., backorder, holding, disassembly, disposal, testing and transportation) while increasing revenue and profit.     

Towards quality requirements via animated formal specifications

Assuring a high quality requirements specification document involves both an early validation process and an increased level of participation. An approach and its supporting environment which combines the benefits of a formal system specification and its subsequent execution via a rapid prototype is reported. The environment assists in the construction, clarification, validation and visualisation of a formal specification. An illustrative case study demonstrates the consequences of assertions about system properties at this early stage of software development. Our approach involves the pragmatic combination of technical benefits of formal systems engineering based techniques with the context‐sensitive notions of increased participation of both developer and user stakeholders to move us closer towards a quality requirements specification document.     

Realization of reconfigurable filtering horn antennas using active frequency selective surfaces for GSM and LTE signal filtering

Herein, it is aimed to design an Active Frequency Selective Surface (AFSS) based high performance reconfigurable filtering antenna (Filtenna). The proposed AFSS unit element is consist of a single PIN diode with a simple microstrip patch design which performance characteristics are varies with the state of the diodes. The proposed unit elements have been used to form an array that is placed at the aperture of a double ridge horn antenna. With the variation in state of diodes, the antenna acts as a Filtenna module to filtering the incoming electromagnetic waves in frequency band of 1.8 to 2.8 GHz. From the experimental results, it is shown that the proposed Filtenna achieves a signal attenuation of 7.3 dBi at 2.1 GHz.     

高亮度LED的高效率电流驱动电路

本文介绍调整高亮度LED电流的简单电路.它包括一个流行的高集成降压开关稳压器,此开关稳压器能精确地控制LED电流.MAX5035是工作在125KHz固定频率的DC/DC转换器,其宽范围的输入电压(7.5V～76V)特别适合于汽车应用.对于亮度控制,它能实现模拟(线性调光)或低频占空比调制(PWM调光).     

A versatile signal flow graph realization of a general transfer function by using CDBA

A general synthesis procedure is given for a versatile signal flow graph realization of a general transfer function by using current differencing buffered amplifier (CDBA). The proposed configuration uses n+1 CDBAs, n capacitors and at most 2n+4 resistors. This number of resistors can be reduced to n+1 for special cases. The circuit is eligible to obtain a variety of transfer characteristics with the same common denominator polynomial, and it is easily converted to different modes of operations. It is straightforward to find the values of the passive elements from the coefficients of the transfer function to be realized. Simulations results are obtained by using commercially available active component AD844 and CMOS technology as well. All of these make the proposed circuit attractive.     

Terahertz Absorption of Nematic Liquid Crystals

We present the first systematic study of cyanobiphenyls (CBs) and the phenylcyclohexanes in the range between 50 cm^-1 (1.5 THz) and 500 cm^-1 (15 THz). The impact of the alkyl chain length and of variations in the core structure on the spectrum is investigated using liquid crystals from the cyanobiphenyl and phenylcyclohexane families. Our measurements are supported by calculations based on density functional theory. This enables us to shine light on the vibrational dynamics of liquid crystal molecules in the terahertz frequency range.     

Electronically tunable floating inductance simulator

In this letter, a new floating inductance simulator circuit is presented. The proposed structure consists of only one grounded capacitor without any external resistors and two different active elements. The active elements are dual-output current-controlled current conveyor (DO-CCCII) and operational transconductance amplifier (OTA). The proposed inductance simulator can be tuned electronically by changing the biasing current of the DO-CCCIIs or by changing the current of the OTA. Moreover, the circuit does not require any conditions of component matching. It has a good sensitivity performance with respect to tracking errors. As an application, the proposed inductance simulator is used to construct a fourth-order resistively terminated LC band-pass filter. The theoretical analysis is verified by the SPICE simulation results.     

低噪声APD偏置电路

１ＡＰＤ的特性雪崩光电检测器 (ＡＰＤ)和ＰＩＮ二极管通常被作为接收器用于光通信中。其中ＡＰＤ适合于高灵敏度和高带宽的光接收电路。但这种器件在工作时需要施加一个反向结压 ,这样 ,当接收到射线时产生的电子空穴对会被外加电场收集并转换为电流 ,其电流强度正比于射线强度。另外 ,工作时施加在器件上的反向偏置电压会引发雪崩效应 ,其雪崩增益可通过改变偏压来进行调节。这就有可能对光纤接收器的增益进行优化。然而 ,要得到满意的雪崩增益 ,就必须给ＡＰＤ提供一个比较高的反向偏压。很多ＡＰＤ需要４０Ｖ～６０Ｖ的偏压 ,有些器件…     

A quasi-static analysis for a class of induced-current EIT systems using discrete coils

A discrete coil EIT system is investigated for the general case of an eccentric circular inhomogeneity. The solution methodology of the forward problem of this system is explained. An optimization procedure using this forward problem solution is developed to find optimum currents that maximize the distinguishability. For an eccentric inhomogeneity problem, it is shown that the coil currents can be optimized to focus the current density in a region of interest. Optimum coil currents under limited peak coil currents constraint and limited total power constraint are obtained. Representative examples that demonstrate the performance of the system are presented.