降低手持无线产品噪声干扰的新方法

今年全球预计将销售超过4.5亿部手机、3500万台笔记本电脑和1200万部个人数字助理(PDA)。这些产品有两点是相同的:第一,它们都采用电池供电;第二,它们都有某种形式的噪声敏感射频电路(或附加电路)。很明显,手机始终都采用敏感的射频收发器电路,但在PDA和手持计算机中增加此类电路还是最近的事情,这部分是蓝牙技术发展推动的结果。同时在此类产品中,开关电源正在逐步取代线性稳压器以延长电池使用寿命。在产品中同时存在噪声源(开关电源)和噪声敏感的电路可能会带来干扰隐患。传统解决方案是尽量使噪声源电路远离噪声敏感电路。然而,现在…     

大功率LED驱动器找到了利基市场

背景 大功率LED的光输出已经达到了100流明/W这一关键和具有里程碑意义的数值,而且有些制造商声称,在实验室中已经达到了120流明/W。这意味着,就能量效率而言,LED现在已经超过了CFL（SO流明／w）。不过,据进一步预测,到2012年,LED将达到150流明／W的光输出。     

Rapid CO2 capture from ambient air by sorbent-containing porous electrospun fibers made with the solvothermal polymer additive removal technique

Direct air capture (DAC) of CO₂ is an emerging technology in the battle against climate change. Many sorbent materials and different technologies such as moisture swing sorption have been explored for this application. However, developing efficient scaffolds to adopt promising sorbents with fast kinetics is challenging, and very limited effort has been reported to address this critical issue. In this work, the availability and kinetic uptake of CO₂ in sorbents embedded in various matrices are studied. Three scaffolds including a commercially available industrial film containing ion-exchange resin (IER), IER particles embedded in dense electrospun fibers, and IER particles embedded in porous electrospun fibers are compared, in which a solvothermal polymer additive removal technique is used to create porosity in porous fibers. A frequency response technique is developed to measure the uptake capacity, sorbent availability, and kinetic uptake rate. The porous fiber has 90% IER availability, while the dense fibers have 50% particle accessibility. The sorption half time for both electrospun fiber samples is 10 ± 3 min. Our experimental results demonstrate that electrospinning polymer/sorbent composites is a promising technology to facilitate the handleability of sorbent particles and to improve the sorption kinetics, in which the IER embedded in porous electrospun fibers shows the highest cycle capacity with an uptake rate of 1.4 mol CO₂ per gram-hour. © 2018 American Institute of Chemical Engineers AIChE J, 65: 214–220, 2019     

Study of wall-to-bed heat transfer in a bubbling fluidised bed using the kinetic theory of granular flow

Research into heat transfer modelling in fluidised beds is very limited due to its complexity. The kinetic theory of granular flow (KTGF) has been applied successfully to hydrodynamic modelling in the past but its application in heat transfer modelling has not been tested extensively. A two-fluid Eulerian–Eulerian model has been carried out applying the KTGF to a wall-to-bed reactor. The local heat transfer coefficients are compared against experimental data for two drag models, namely the Gidaspow and the Syamlal–O’Brien drag models. Furthermore, a parametric study is carried out for a variety of coefficients of restitution, particle diameter sizes and inlet velocities. Near wall analysis is carried out in both dense and dilute regions. Both drag models detect the passage of the bubble reasonably well but they predict the complete transition of the bubble past the sensors occurs at slightly different times. The heat transfer coefficients obtained with the Syamlal–O’Brien model showed more local fluctuations than the Gidaspow model because the Syamlal–O’Brien models was developed based on the particle terminal velocities which would indicate a slight sensitivity to a microscopic scale. Extension of the simulation for a longer period makes it possible to reveal that a periodic distribution occurred after 1.5 s and the local heat transfer coefficients gradually reduced to agree better with the experimental results which were previously over estimated. The study shows that a regular dynamic pattern is established in the bubbling fluidised bed only after 1.5–2 s.     

Nutrition, metabolism, and fertility in dairy cows: 3. Amino acids and ovarian function

Plasma insulin concentrations influence resumption of ovarian activity in postpartum dairy cows, and plasma insulin can be manipulated by changing dietary starch and fat supply. The objective of this experiment was to investigate the role of dietary amino acids in altering peripheral metabolic hormones and ovarian function. Thirty-two cows were fed a standard diet from calving until 40 d in milk (DIM), and then 8 cows were transferred to each of 4 dietary treatments until 70 DIM. The 4 diets were designed to supply either low (diets 1 and 2) or high (diets 3 and 4) levels of metabolizable protein (MP), containing either low (diet 1 and 3) or high (diets 2 and 4) proportions of Leu. Leucine was manipulated with heat-treated lupins and corn gluten meal. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake and energy balance were similar among diet groups, although cows receiving high MP containing high Leu had a greater milk yield than other groups (means: 37.8, 37.1, 37.4, 39.4 ± standard error 0.85 kg/d for diets 1 to 4, respectively). Interactions between MP and Leu were found for insulin, glucagon, and the ratio between them. Insulin was not affected by Leu in diets with low MP but was decreased by greater Leu in diets with high MP (means: 0.37, 0.32, 0.46, 0.39 ± SE 0.031 ng/mL for diets 1 to 4, respectively). Glucagon was not affected by MP in diets with low Leu but was increased by greater MP in diets with high Leu (means: 92, 81, 88, 95 ± SE 6.0 pg/mL for diets 1 to 4, respectively). For the low-MP treatments, the insulin-to-glucagon ratio was greater with high Leu; for the high-MP treatments, the insulin-to-glucagon ratio was greater with low Leu (means: 4.28, 5.42, 5.16, 4.22 ± SE 0.456 for diets 1 to 4, respectively). There was no effect of MP or Leu on ovarian follicle numbers or reproductive hormones. Based on hormonal and ovarian responses, we conclude that altering metabolic hormones through manipulation of amino acid supply and balance is unlikely to have a significant effect on ovarian function in dairy cows.     

Programmable unitary spatial mode manipulation

Free space propagation and conventional optical systems such as lenses and mirrors all perform spatial unitary transforms. However, the subset of transforms available through these conventional systems is limited in scope. We present here a unitary programmable mode converter (UPMC) capable of performing any spatial unitary transform of the light field. It is based on a succession of reflections on programmable deformable mirrors and free space propagation. We first show theoretically that a UPMC without limitations on resources can perform perfectly any transform. We then build an experimental implementation of the UPMC and show that, even when limited to three reflections on an array of 12 pixels, the UPMC is capable of performing single mode tranforms with an efficiency greater than 80% for the first four modes of the transverse electromagnetic basis.     

今天的绿色POL DC/DC转换器设菅需要高效率和低IQ

大多数嵌入式系统都是由48V背板供电的。这个电压通常要降至较低的24V、12V或5V的中间总线电压,以向系统内的电路板支架供电。然而,这些电路板上的大多数分支电路或集成电路要求在低于1～3．3V的电压范围内工作,电流范围为数十mA至数十A。因此,需要负载点（POL）DC／DC转换器将24V、12V或5V电压轨降至这些分支电路或集成电路所需的电压和电流值。     

Germanium on sapphire substrates for system on a chip

Germanium on sapphire (GeOS) is proposed for system on a chip applications. Sapphire substrates are demonstrated to exhibit lower rf losses and superior crosstalk suppression compared with oxidised silicon handle wafers. Inductors on sapphire also show higher quality factor and better frequency response than those manufactured on an SOI platform. GeOS substrates have been manufactured by wafer bonding. Bond strengths of greater than 2900 mJ m⁻² have been obtained. Thin GeOS has been achieved by He/H₂ ion cut processes. A self-aligned W gate process on Ge has been established with processing temperature limited to 400 °C. P channel MOSTs exhibit low threshold voltage and a carrier mobility of about 400 cm² V⁻¹ s⁻¹.     

Germanium on sapphire by wafer bonding

This paper describes the creation of a germanium on sapphire platform, via wafer bonding technology, for system-on-a-chip applications. Similar thermal coefficients of expansion between germanium (5.8 × 10^?6 K^?1) and sapphire (5 × 10^?6 K^?1) make the bonding of germanium to sapphire a reality. Germanium directly bonded to sapphire results in microvoid generation during post bond annealing. Inclusion of an interface layer such as silicon dioxide layer by plasma enhanced chemical vapour deposition, prior to bonding, results in a microvoid free bond interface after annealing. Grinding and polishing of the subsequent germanium layer has been achieved leaving a thick germanium on sapphire (GeOS) substrate. Submicron GeOS layers have also been achieved with hydrogen/helium co-implantation and layer transfer. Circular geometry transistors exhibiting a field effect mobility of 890 cm²/V s have been fabricated onto the thick germanium on sapphire layer.