Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses

This paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples of approximately 220 ?m thick. The space charge measurement technique used in this study is the PEA method. There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kVdc/mm and ac (sinusoidal) electric stress level of 30 kVpk/mm at frequencies of 1 Hz, 10 Hz and 50 Hz ac. In addition, ac space charge under 30 kVrms/mm and 60 kVpk/mm electric stress at 50 Hz was also investigated. The volts off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher. The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge. This paper also gave a brief overview of the data processing methods used to analyse space charge under ac electric stress

Si/Ge hole-tunneling double-barrier resonant tunneling diodes formed on sputtered flat Ge layers

We have demonstrated Si/Ge hole-tunneling double-barrier resonant tunneling diodes (RTDs) formed on flat Ge layers with a relaxation rate of 89% by our proposed method; in this method, the flat Ge layers can be directly formed on highly B-doped Si(001) substrates using our proposed sputter epitaxy method. The RTDs exhibit clear negative differential resistance effects in the static current–voltage (I–V) curves at room temperature. The quantized energy level estimation suggests that resonance peaks that appeared in the I–V curves are attributed to hole tunneling through the first heavy- and light-hole energy levels

Disposable Integrated Microfluidic Biochip for Blood Typing by Plastic Microinjection Moulding

Blood typing is the most important test for both transfusion recipients and blood donors. In this paper, a low cost disposable blood typing integrated microfluidic biochip has been designed, fabricated and characterized. In the biochip, flow splitting microchannels, chaotic micromixers, reaction microchambers and detection microfilters are fully integrated. The loaded sample blood can be divided by 2 or 4 equal volumes through the flow splitting microchannel so that one can perform 2 or 4 blood agglutination tests in parallel. For the purpose of obtaining efficient reaction of agglutinogens on red blood cells (RBCs) and agglutinins in serum, we incorporated a serpentine laminating micromixer into the biochip, which combines two chaotic mixing mechanisms of splitting/recombination and chaotic advection. Relatively large area reaction microchambers were also introduced for the sake of keeping the mixture of the sample blood and serum during the reaction time before filtering. The gradually decreasing multi-step detection microfilters were designed in order to effectively filter the reacted agglutinated RBCs, which show the corresponding blood group. To achieve the cost-effectiveness of the microfluidic biochip for disposability, the biochip was realized by the microinjection moulding of COC (cyclic olefin copolymer) and thermal bonding of two injection moulded COC substrates in mass production with a total fabrication time of less than 20 min. Mould inserts of the biochip for the microinjection moulding were fabricated by SU-8 photolithography and the subsequent nickel electroplating process. Human blood groups of A, B and AB have been successfully determined with the naked eye, with 3 mu l of the whole sample bloods, by means of the fabricated biochip within 3 min.X11100104sciescopu

Steady-state Ab Initio Laser Theory: Generalizations and Analytic Results

We improve the steady-state ab initio laser theory (SALT) of Tureci et al. by expressing its fundamental self-consistent equation in a basis set of threshold constant flux states that contains the exact threshold lasing mode. For cavities with non-uniform index and/or non-uniform gain, the new basis set allows the steady-state lasing properties to be computed with much greater efficiency. This formulation of the SALT can be solved in the single-pole approximation, which gives the intensities and thresholds, including the effects of nonlinear hole-burning interactions to all orders, with negligible computational effort. The approximation yields a number of analytic predictions, including a "gain-clamping" transition at which strong modal interactions suppress all higher modes. We show that the single-pole approximation agrees well with exact SALT calculations, particularly for high-Q cavities. Within this range of validity, it provides an extraordinarily efficient technique for modeling realistic and complex lasers.Comment: 17 pages, 11 figure

Tagless indoor positioning and object tracking using a wireless sensor network

This project seeks to implement a passive indoor positioning and tracking platform using Wi-Fi signals. It is well known that RF wave can be blocked by an object which results in signal attenuation [1 - 2]. The principle of this proposal is based on this phenomenon when the line-of-sight (LOS) link is blocked by an object. Hence, when a grid of such LOS links is tresspassed, it can be detected and tracked within the region

A new design of nanocrystalline silicon optical devices based on 3-dimensional photonic crystal structures

We propose a new design of nanocrystalline silicon optical devices which are based on control of electromagnetic fields, electronic states, as well as the phonon dispersion of size-controlled silicon quantum dots

Tagless indoor positioning and object tracking using a wireless sensor network

This project seeks to implement a passive indoor positioning and tracking platform using Wi-Fi signals. It is well known that RF wave can be blocked by an object which results in signal attenuation [1 - 2]. The principle of this proposal is based on this phenomenon when the line-of-sight (LOS) link is blocked by an object. Hence, when a grid of such LOS links is tresspassed, it can be detected and tracked within the region

Mesenchymal stem cells differentiate into hepatocyte-like cells under different induction systems in hepatitis B patients with liver failure

This study aimed to investigate and compare induced differentiation of mesenchymal stem cells from hepatitis B (HB) patients with liver failure into hepatocytes-like cells with different induction systems in vitro. The differentiation of MSCs from HB patients with liver failure was induced in vitro into hepatocytes-like cells by three cell culture media (serum-free medium (group 1), auto serum-containing medium (group 2) and medium supplemented with fetal bovine serum (FBS) (group 3)). Cell morphology,cell growth curve, amount of urea and glycogen and mRNA expressions of ALB, CK18 and AFP were detected and compared. Morphological changes in group 1 and 2 were more evident than that in group 3 and cell growth in group 3 was faster than the other two groups. The amount of urea and glycogen in group 1 and 2 was significantly elevated when compared with that in group 3 after 6 days of culture. RT-PCR analysis indicated the mRNA expressions of ALB, CK18 and AFP in group 1 and 2 were markedly increased as compared to that in group 3. The differentiation of MSCs from HB patients with liver failure into hepatocytes-like cells can be induced by three different cell culture media and the inductive effects were more profound in cells grown in the serum-free medium and auto serum-containing medium.Key words: Liver failure, mesenchymal stem cells, hepatogenic differentiation, in vitro

CAutoCSD-evolutionary search and optimisation enabled computer automated control system design

This paper attempts to set a unified scene for various linear time-invariant (LTI) control system design schemes, by transforming the existing concept of 'Computer-Aided Control System Design' (CACSD) to the novel 'Computer-Automated Control System Design' (CAutoCSD). The first step towards this goal is to accommodate, under practical constraints, various design objectives that are desirable in both time and frequency-domains. Such performance-prioritised unification is aimed to relieve practising engineers from having to select a particular control scheme and from sacrificing certain performance goals resulting from pre-committing to the adopted scheme. With the recent progress in evolutionary computing based extra-numeric, multi-criterion search and optimisation techniques, such unification of LTI control schemes becomes feasible, analytically and practically, and the resultant designs can be creative. The techniques developed are applied to, and illustrated by, three design problems. The unified approach automatically provides an integrator for zero-steady state error in velocity control of a DC motor, meets multiple objectives in designing an LTI controller for a non-minimum phase plant and offers a high-performing LTI controller network for a nonlinear chemical process