Biomimetic approaches to create anti-reflection glass surfaces for solar cells using self-organizing techniques

Aiming to diminish the reflection losses of glass covered light harvesting devices, the optical reflectivity of nanostructured glass surfaces is studied theoretically and experimentally. The work is inspired by the nanoscale roughness of insect eyes, which is tried to be replicated on a technical glass surface. To this end, the reflectivity of glass surfaces with topographies represented by linear, parabolic and Fermi-shaped glass/air fill factor profiles is calculated for normal incidence. It is shown that using the latter ones, an almost complete suppression of reflections can be achieved. A simple, self-organization technique to create such Fermi-shaped filling factor profiles in glass experimentally is also presented.     

Novel techniques in high speed modem implementation using programmable DSPs

We present the design and performance of a high speed MSK modem that incorporates digital heterodyne processing. A novel table look-up procedure for direct IF/RF modulation, based on a suitable maximal-length shift register sequence, is described. High performance, linear phase, low-complexity mixing and filtering in the receiver is achieved using multirate IFIR filters, where the shaping filter may possibly beM-th-band. The configuration of the IFIR filters is chosen based on the carrier frequency and the filtering requirements.     

Commercial applications of overlay coating techniques

As part of a panel discussion this paper was presented to review the wide variety of coating technologies available and the need for consideration of the number of materials, process and product variables in determining the applicability of a technology. Of particular concern is the lack of utilization of a “coating technologist” in the early stages of decision making. This often leads to expensive mistakes and misapplications.     

两种不同微结构的高硅氧/酚醛树脂基复合材料动态压缩性能研究

为获得高硅氧/酚醛树脂基复合材料动态压缩力学性能以及研究微结构对该种材料力学性能影响,利用分离式霍普金森压杆分别对两种不同微结构的高硅氧/酚醛树脂基复合材料进行动态压缩实验。实验结果发现,在相同应变率下,高硅氧丝/酚醛树脂基复合材料强度高于高硅氧布/酚醛树脂基复合材料。此外,实验结果还显示微结构对材料的失效模式有显著影响,高硅氧丝/酚醛树脂基复合材料显现出一种劈裂的失效模式,而高硅氧布/酚醛树脂基复合材料却发生剪切断裂。进一步通过对其断裂形貌分析指出,高硅氧玻璃纤维的排列方式决定复合材料的断裂模式。     

Improved calibration techniques for high density tape recordingsystems

Improvements to a method of calibrating a high-density tape recording system are suggested. The small gap approximation is not made, and allowances for the effects of demagnetization are included. A better and smaller estimate of the effective head-media spacing is obtained     

EPR/Homotaurine: A possible dosimetry system for high doses

An EPR investigation of radiation induced radicals in Homotaurine revealed that there are two types of radicals produced after exposure to gamma radiation (⁶⁰Co). EPR spectra were recorded and analyzed; also the microwave power saturation curves for both radicals were studied. The effect of change in modulation amplitude on peak-to-peak signal height and line width was investigated; this is in addition to the evaluation of energy dependence parameters compared to soft tissue and alanine dosimeters. Response of Homotaurine to different radiation doses (0.5 kGy-50 kGy) was studied and found to follow a linear relationship. Radiation induced radicals in Homotaurine persisted and showed a noticeable stability over 30 days following irradiation. It was found that Homotaurine possesses good dosimetric properties using EPR spectroscopy in high doses and is characterized by its simple spectrum.     

Superhydrophobic and antireflective nanograss-coated glass for high performance solar cells

We present a facile method for producing superhydrophobic nanograss-coated （SNGC） glass surfaces that possess both reduced reflectivity and self-cleaning properties at the air/glass interface. The refractive index of a CaF2 nanograss （NG） layer on a glass substrate, deposited by glancing angle vapor deposition, is 1.04 at 500 nm, which is the second-lowest value ever reported so far. The fluorinated NG layer gives rise to a high water contact angle （〉150°） and very efficient cleaning out of dust with water drops. Using the dual functionalities of the SNGC glass, we demonstrate superhydrophobic and antireflective organic photovoltaic cells with excellent power conversion efficiency.     

Digital signal processing techniques for high accuracy ultrasonicrange measurements

Several digital signal processing (DSP) methods are analyzed and compared with respect to the expected errors for an ultrasonic range measurement arrangement. These include L1, L2 norms and correlation with different approaches for envelope extraction. The influence of different factors such as signal-to-noise ratio (SNR), sampling frequency, and digitizing resolution on measurement errors is analyzed using a synthetic approach through nearly 40000 simulations. Results show different performance levels involving accuracy, computing time, and cost for the studied methods, although all of them allow reduction of errors by several orders of magnitude     

Flowability measurements of pharmaceutical powder mixtures with poor flow using five different techniques

Four different tablet formulations for direct compression with poor flow properties were tested regarding flowability using five different techniques: Hausner ratio, avalanching behavior, powder rheometer, uniaxial tester, and Jenike tester. In addition, the behavior of three of the formulations during emptying of the mixer and tableting was observed and compared to the results of the flowability measurements. The rank order correlation of the formulations was generally the same with all techniques. The flow properties measured by the different techniques reflected the behavior during processing of the powder mixtures.     

应用多种高精度测量机制的电参量分析仪研制

针对计量测试过程中高精度电参量分析的需求,该文提出多种改善分析测量精度的测量机制,包括高精度交流电压采样分压器、高精度改进型双级交流电流互感器、利用DDS实现准同步采样原理进行信号频率跟踪实现同步采样以及非整周期傅里叶补偿谐波算法。并将这些测量方法应用到分析仪的研制设计中,实现电参数测试准确度优于0.01%、谐波分析准确度优于0.02%的高精度电参量分析仪。     

Organ and effective doses from verification techniques in image-guided radiotherapy

The purpose of this work was an evaluation of organ doses and effective doses from three verification techniques in Image-Guided Radiotherapy: from kilovoltage (kV) cone beam computed tomography (CBCT) scans, from two orthogonal kV images and from two orthogonal megavoltage (MV) images for two different treatment sites: pelvis and head and neck (H&N). For comparison reasons, organ doses and effective doses from prostate and H&N radiotherapy were also evaluated. Measurements of organ doses were performed in a male anthropomorphic Rando phantom by means of thermoluminescent dosemeters. In this investigation, measured organ doses from one CBCT scan, from two MV images and from two kV images of pelvis represent typically 1-6, 1-10 and 0.05-1 %, respectively, of organ doses resulting from one fraction of prostate radiotherapy. The maximum effective doses from CBCT scans, kV images and MV images of pelvis are 5.6, 0.8 and 11.9 mSv, respectively.     

Properties of high volume glass powder concrete

Mechanical and durability properties of concrete with cement replaced by finely grounded glass powder in high volume up to 60% were investigated. XRD and TGA analyses indicated that the fine glass powder reacted with calcium hydroxide to form calcium-silicate-hydrates. As such, the microstructures of concrete were more compact and homogeneous, especially at the interfacial transition zone. Concrete with cement replaced by 15% and 30% glass powder exhibited the highest strength increase and correspondingly the lowest porosity. Beyond a replacement of 30%, calcium hydroxide became insufficient for the pozzolanic reaction of glass powder. However, the high volume glass powder concrete retained distinct resistance against water and chloride ingress, due to the reduction in pore size and connectively. Reductions of 77%, 83%, 96%, 91% and 92% were observed respectively for water penetration depth, sorptivity, conductivity, chloride diffusion and migration coefficients in concrete with cement replaced by glass powder by 60%.     

Preparation and characterization of ketorolac tromethamine-loaded ethyl cellulose micro-/nanospheres using different techniques

Sustained-release micro-/nanospheres of the ketorolac tromethamine (KTC) were prepared using four different techniques viz., single emulsion solvent evaporation, high pressure homogenization, spray drying, and using a microreactor. Ethyl cellulose (EC) was used as an encapsulating agent for the preparation of sustained-release micro-/nanospheres of KTC. The Plackett–Burman design was employed for design of the experiments. The resulting micro-/nanospheres were characterized for their size, morphology, encapsulation efficiency, and in vitro drug release performance. Interactions between the KTC and EC were quantified by Fourier transform infrared (FTIR) spectroscopy and X-ray powder diffractometry (XRPD). Particle morphology characterization was performed using field emission scanning electron microscopy. The micro-/nanospheres showed encapsulation efficiency of 42.34–89.33% by the solvent evaporation technique, 76.36–91.13% by the high-pressure homogenization technique, 70.74–79.68% by spray drying, and 79.00–89.49% by the microreactor technique. The micro-/nanospheres were found to be spherical and oval with smooth surface. The FTIR analysis confirmed no interaction of KTC with EC polymer. The XRPD analysis revealed good dispersion of the drug within the micro-/nanospheres formulation. Sustained KTC release profile over 12?h was achieved successfully by EC polymer. In conclusion, EC sustained-release micro-/nanospheres containing KTC can be prepared successfully using different techniques.     

Assessment of high dimensional model representation techniques for reliability analysis

This paper presents an assessment of efficient response surface techniques based on the High Dimensional Model Representation (HDMR) and the Factorized High Dimensional Model Representation (FHDMR). The HDMR is a general set of quantitative model assessment and analysis tools for capturing the high-dimensional relationships between sets of input and output model variables. It is a very efficient formulation of the system response, if higher order variable correlations are weak and if the response function is dominantly of an additive nature, allowing the physical model to be captured by the first few lower order terms. But, if the multiplicative nature of the response function is dominant, then all the right hand side components of the HDMR must be used to be able to obtain the best result. However, if the HDMR requires all components, which means 2^N$2^N$ of them, to get a desired accuracy, making the method very expensive in practice, then the FHDMR can be used. The component functions of the FHDMR are determined by using the component functions of the HDMR. This paper presents the formulation of the FHDMR based response surface approximation of a limit state/performance function which is dominantly multiplicative in nature. It is a given that conventional methods for reliability analysis are computationally very demanding, when applied in conjunction with complex finite element models. This study aims to assess how accurately and efficiently HDMR/FHDMR based response surface techniques can capture complex model output uncertainty. As a part of this effort, the efficacy of the HDMR, which is recently applied to reliability analysis, is also demonstrated. The response surface is constructed using the moving least squares interpolation formula by including constant, first-order, and second-order terms of the HDMR and the FHDMR. Once the response surface form is defined, the failure probability can be obtained by statistical simulation. Results of seven numerical examples involving structural/solid-mechanics/geo-technical engineering problems indicate that the failure probability obtained using the FHDMR based response surface method for a limit state/performance function that is dominantly multiplicative in nature, provides a significant accuracy when compared with the conventional Monte Carlo method, while requiring fewer original model simulations.     

An accelerator-based epithermal neutron beam design for BNCT and dosimetric evaluation using a voxel head phantom

The beam shaping assembly design has been investigated in order to improve the epithermal neutron beam for accelerator-based boron neutron capture therapy in intensity and quality, and dosimetric evaluation for the beams has been performed using both mathematical and voxel head phantoms with MCNP runs. The neutron source was assumed to be produced from a conventional 2.5 MeV proton accelerator with a thick (7)Li target. The results indicate that it is possible to enhance epithermal neutron flux remarkably as well as to embody a good spectrum shaping to epithermal neutrons only with the proper combination of moderator and reflector. It is also found that a larger number of thermal neutrons can reach deeply into the brain and, therefore, can reduce considerably the treatment time for brain tumours. Consequently, the epithermal neutron beams designed in this study can treat more effectively deep-seated brain tumours.     

Determination of equivalent dose rates and committed effective doses in the respiratory system from the inhalation of radon decay products by using SSNTD and a dosimetric compartmental model

Alpha activities per unit volume, due to radon (222Rn), thoron (220Rn) and their progenies, were evaluated inside different dwelling rooms by using CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) and calculating their mean critical angles of etching. The influence of the ventilation rate and nature of the building material has been investigated. Equivalent dose rates and annual committed effective doses due to the inhalation of radon decay products have been determined in the respiratory system by using a dosimetric compartmental model. The influence of the deposition fraction, residual time and activity absorbed fraction of the respiratory system compartments for the radon daughters has been studied.     

Analysis of different techniques for modelling excitons in carbon nanotubes

It is now widely accepted that exciton effects play an important role in the optical processes of carbon nanotubes. However, previous theoretical work has tended to concentrate on an understanding of exciton binding energies, with little attention paid to calculations of exciton sizes. In this work we employ two approaches: a k·p model and a variational technique, and we examine their ability to make simultaneous predictions of exciton binding energy and size, while comparing our results to previous work taken from the literature.     

Exchange bias using a spin glass

Exchange bias is commonly manifested as the hysteresis-loop shift observed when a ferromagnet is in contact with an antiferromagnet. Here, we report observations of exchange bias with unusual features of a ferromagnet in contact with a spin glass, demonstrating that this is a phenomenon of greater generality. The easily measured properties of the ferromagnet allow access to the internal magnetic degrees of freedom of the glass to which they are coupled. Our results show that a Co/CuMn bilayer system exhibits all the rich phenomena of coercivity enhancement, bias-field shifts and training effects associated with a conventional ferromagnet/antiferromagnet system. Nevertheless, striking differences arise, such as an orientation reversal of the bias field in a small temperature range just below the blocking temperature. We argue that all features can be understood within the context of a random-field model for long-ranged oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) coupled spins.