Matrix Of Dots Research Articles

Amplified spontaneous emission in β-In2S3–Ag based SQD-MNP superstructures with switching photoluminescence and enhanced photocatalytic activity

Optically modified MNPs coupled with SQDs (super structures) demonstrating tunable emission and enhanced photocatalytic activity are synthesized through homogeneous nucleation of indium chloride, thioacetamide and silver nitrate. Ag nanospheres (1–15 nm) are embedded in the matrix of β-In2S3 quantum dots. Modification of the absorption profile and shift in excitonic binding energy from 3.60 eV to 3.25 eV occurs due to plasmon mediated indirect columbic interaction between the SQDs. Raman spectrum of β-In2S3 (1:1)-Ag Nanohybrids (NHs) shows asymmetric line-shape broadening due to the fano-interaction (electron-phonon interaction) of the triply degenerate F2g mode of SQDs with a continuum of plasmon excitations. The emission spectra of the quantum dots, with significant peak shifting and enhanced intensity, indicates stronger coupling between the SQDs and MNPs. In the proximity of Ag NPs, the defect emission due to IIn (∼708 nm) is completely quenched, and an enhanced blue emission occurs at ∼ 496 nm. Further with increase in pump beam energy, there is a gradual peak maxima shift, spectral distortion, narrowing of emission profile and enhancement in emission intensity, which is attributed to amplified spontaneous emission assisted amplification in the gain media (SQDs). Measurement of photocatalytic efficiency for irradiation of 60 min (400 nm–700 nm) with β-In2S3 (1:1) QDs-Ag NHs as photocatalyst, prompted 100 % degradation while pure β-In2S3 (1:1) QDs as photocatalyst material could attain 98.6 % degradation only after 280 min of irradiation.

Introduction of CdSe/ZnS Quantum Dots into Liquid Crystalline Matrix

An important aspect of modern materials science, namely the possibility of combining inorganic nanoparticles and liquid crystals in composite materials is discussed. These systems make it possible to combine liquid crystal properties of matrix and luminescent properties of quantum dots. A five-component mixture consisting mainly of 4-cyanobiphenyl derivatives used as a matrix. The substitution of ligands formed during the synthesis of quantum dots with derivatives of organic acids is shown. Using two new optically active ligands, the chiralization of the nematic matrix was demonstrated by introducing quantum dots into it.

Extracting the homogeneous and inhomogeneous linewidths of colloidal quantum dots from the excitation-emission matrix

The excitation-emission matrix (EEM) of colloidal quantum dots implicitly contains information about the inhomogeneous broadening and the homogeneous linewidths of the emission spectrum and of the excitonic peak in the photoluminescence excitation spectrum. Here, the characteristic features by which this information is manifested in the EEM contour plot are identified. In the Gaussian approximation, the contour lines are ellipses, whose parameters can be used to calculate the homogeneous linewidths and the inhomogeneous broadening. The method is illustrated on the core/shell InP/ZnS nanocrystals.

Open Source LaserGRBL – Arduino Based Laser Engraver

Nowadays technology is increasing rapidly, the usage and the implementation of CNC systems in industries and educational institutions are exponentially increasing but at a greater cost. Our main goal is to design a CNC Laser Engraver that is also a compact, cheap and low power unit that is also easy to operate in order to reduce complexity, cost and manual work. The idea of open source laserGRBL – arduino based laser engraver is to use the Open Source LaserGRBL that loads the G-code coordinates of an image that is given by user and sends those coordinates to the arduino which in turn signals the hardware components i.e. stepper-motor and laser to engrave onto the surfaces for example wood, Acrylic or plastic. The engraver will be able to engrave vector graphics in two (X & Y) axes of motion. Most of the engravers are designed in bi-directional movement and square type models. Whereas in this laser engraver, axes movements are mounted on each other and belt driven mechanism is used for engraving. Laser engraver uses a very fine matrix of dots to form images, such that a line may appear continuous to the naked eye, it in fact is a discrete set of points.

Theory of nonequilibrium noise in general multiterminal superconducting hybrid devices: Application to multiple Cooper pair resonances

We consider the out-of-equilibrium behavior of a general class of mesoscopic devices composed of several superconducting or/and normal metal leads separated by quantum dots. Starting from a microscopic Hamiltonian description, we provide a nonperturbative approach to quantum electronic transport in the tunneling amplitudes between dots and leads: using the equivalent of a path integral formulation, the lead degrees of freedom are integrated out in order to compute both the current and the current correlations (noise) in this class of systems, in terms of the dressed Green's function matrix of the quantum dots. In order to illustrate the efficiency of this formalism, we apply our results to the ``all superconducting Cooper pair beam splitter,'' a device composed of three superconducting leads connected via two quantum dots, where crossed Andreev reflection operates Cooper pair splitting. Commensurate voltage differences between the three leads allow us to obtain expressions for the current and noise as a function of the Keldysh Nambu Floquet dressed Green's function of the dot system. This voltage configuration allows the occurrence of nonlocal processes involving multiple Cooper pairs which ultimately lead to the presence of nonzero DC currents in an out-of-equilibrium situation. We investigate in detail the results for the noise obtained numerically in the specific case of opposite voltages, where the transport properties are dominated by the so called ``quartet processes,'' involving the coherent exchange of two Cooper pairs among all three superconducting terminals. We show that these processes are noiseless in the nonresonant case, and that this property is also observed for other voltage configurations. When the dots are in a resonant regime, the noise characteristics change qualitatively, with the appearance of giant Fano factors.

Studying the size-selective precipitation of colloidal quantum dots by decomposing the excitation-emission matrix.

The exciton peak in the excitation-emission matrix (EEM) of colloidal quantum dots implicitly contains information about inhomogeneous broadening and the photoluminescence (PL) and photoluminescence excitation (PLE) spectra of individual particles in the vicinity of the absorption onset. A numerical procedure for extracting this information has been developed and applied to the EEMs of polydisperse InP/ZnS core/shell colloidal quantum dots and their supernatant solutions obtained by partial precipitation with a non-solvent. The inhomogeneous broadenings obtained in this way have been converted by the sizing curve into particle-size distributions. These distributions have been found to be in agreement with the size-selective precipitation theory proposed recently. The homogeneous PL and PLE line shapes obtained by analyzing the EEMs were found to satisfy the Kennard-Stepanov relation, which is the first more or less direct evidence of its validity for colloidal quantum dots.

Carbon Nanolights in Piezopolymers are Self-Organizing Toward Color Tunable Luminous Hybrids for Kinetic Energy Harvesting.

Herein, an all-solid-state sequential self-organization and self-assembly process is reported for the in situ construction of a color tunable luminous inorganic/polymer hybrid with high direct piezoresponse. The primary inorganic self-organization in solid polymer and the subsequent polymer self-assembly are achieved at high pressure with the first utilization of piezo-copolymer (PVDF-TrFE) as the host matrix of guest carbon quantum dots (CQDs). This process induces the spontaneous formation of a highly ordered, microscale, polygonal, and hierarchically structured CQDs/PVDF-TrFE hybrid with multicolor photoluminescence, consisting of very thermodynamic stable polar crystalline nanowire arrays. The electrical polarization-free CQDs/PVDF-TrFE hybrids can efficiently harvest the environmental available kinetic mechanical energy with a new large-scale group-cooperation mechanism. The open-circuit voltage and short-circuit current outputs reach up to 29.6 V cm-2 and 550 nA cm-2 , respectively. The CQDs/PVDF-TrFE-based hybrid nanogenerator demonstrates drastically improved durable and reliable features during the real-time demonstration of powering commercial light emitting diodes. No attenuation/fluctuation of the electrical signals is observed for ≈10 000 continuous working cycles. This study may offer a new design concept for progressively but spontaneously constructing novel multiple self-adaptive complex inorganic/polymer hybrids that promise applications in the next generation of self-powered autonomous optoelectronic devices.

Quantum interference in transport through almost symmetric double quantum dots

We theoretically investigate transport signatures of quantum interference in highly symmetric double quantum dots in a parallel geometry and demonstrate that extremely weak symmetry-breaking effects can have a dramatic influence on the current. Our calculations are based on a master equation where quantum interference enters as non-diagonal elements of the density matrix of the double quantum dots. We also show that many results have a physically intuitive meaning when recasting our equations as Bloch-like equations for a pseudo spin associated with the dot occupation. In the perfectly symmetric configuration with equal tunnel couplings and orbital energies of both dots, there is no unique stationary state density matrix. Interestingly, however, adding arbitrarily small symmetry-breaking terms to the tunnel couplings or orbital energies stabilizes a stationary state either with or without quantum interference, depending on the competition between these two perturbations. The different solutions can correspond to very different current levels. Therefore, if the orbital energies and/or tunnel couplings are controlled by, e.g., electrostatic gating, the double quantum dot can act as an exceptionally sensitive electric switch.

ドット・マトリックスに基づく文字のデザイン その2(第30回研究発表大会)

ドット・マトリックスに基づく文字のデザイン その2(第30回研究発表大会)

OC-0076: Motion Capture Pillow shows potential to replace thermoplastic masks in H&N radiotherapy

Purpose A key challenge to improve patient comfort is the common use of a thermoplastic mask for patients with head and neck cancers. Patients suffer from discomfort and the claustrophobic effect of the mask, or, as they lose soft tissue due to treatment and gain undesirable movement in the mask. A prototype system using a robotic Motion Capture Pillow (MCP) is investigated for proof-of-concept and is pictorially presented for the potential replacement of thermoplastic masks. Methods A radiographer nurtured a concept with robotics engineers and consulted with physicists regarding materials. A 3D head position tracking device – the MCP (Fig. 1) was designed and tested by robotics engineers in a limited user study. The pillow is a biologically-inspired sensing device based upon the deformation of the epidermal layers of the human skin. Deformation of MCP-head interaction is measured optically by tracking the movement of internal artificial papillae pins on the inside of the pillow skin(Fig.1). These papillae pins create an image with a matrix of dots captured by a single camera inside the pillow. The head position image on the pillow has been matched with an absolute head position captured by an optical infrared system (Polararis NDI) with a tracking tool attached to the person’s mouth. The aim of the study was to validate accuracy of the MCP by measuring its resolution (smallest detectable input) and repeatability (the maximum deviation of output for the same input) (Fig. 2). Results Five basic movements of the head were detected 1. two translations across the MCP – laterally (Tx, x-axis) longitudinally (Ty, y axis) and one translation vertical to the pillow (Tz, z axis) and 2. two rotations of the head: roll (α) and pitch (β). A graphic user interface was created in Matlab to view and analyse the two sets of data – Polaris (Tx, Ty, Tz, α, β) and MCP data. A minimum detectable deformation of the MCP in translation is 1mm, and in rotation is 0.3° (α) and 0.6° (β). The repeatability test showed a maximum of one pixel output deviation for the same position. Conclusion The prototype MCP has been patented and proof of concept has shown potential for consideration in clinical practice. The sensing resolution of the MCP can be improved by a larger number of dots per area or adaptations to the software algorithm. There is a small ambiguity between lateral translation and yaw rotations that can be resolved by an initial MCP calibration. The current challenge and future work is to develop a clinical system that will cause limited radiation attenuation, preserve some skin sparing, and is non-ferrous when considering Magnetic resonance Imaging. The preliminary prototype data calls for further investigations in the laboratory, including how to stabilise jaw movement and cranium, prior to being investigated in clinical practice.

3D precision measurements of meter sized surfaces using low cost illumination and camera techniques

Using dedicated stereo camera systems and structured light is a well-known method for measuring the 3D shape of large surfaces. However the problem is not trivial when high accuracy, in the range of few tens of microns, is needed. Many error sources need to be handled carefully in order to obtain high quality results. In this study, we present a measurement method based on low-cost camera and illumination solutions combined with high-precision image analysis and a new approach in camera calibration and 3D reconstruction. The setup consists of two ordinary digital cameras and a Gobo projector as a structured light source. A matrix of dots is projected onto the target area. The two cameras capture the images of the projected pattern on the object. The images are processed by advanced subpixel resolution algorithms prior to the application of the 3D reconstruction technique. The strength of the method lays in a different approach for calibration, 3D reconstruction, and high-precision image analysis algorithms. Using a 10 mm pitch pattern of the light dots, the method is capable of reconstructing the 3D shape of surfaces. The precision (1σ repeatability) in the measurements is <10 µm over a volume of 60 × 50 × 10 cm3 at a hardware cost of ~2% of available advanced measurement techniques. The expanded uncertainty (95% confidence level) is estimated to be 83 µm, with the largest uncertainty contribution coming from the absolute length of the metal ruler used as reference.

Individual magnetization reversal of a square dot matrix by common current excitation

We have proposed a method for magnetization reversal of individual sites of a 2 by 2 matrix of perpendicularly magnetized dots by common current excitation. The spin-polarized current signal consists of a dc-biased ac part followed by a pure dc one. The amplitude of the dc and ac parts of the current, as well as the phase and duration of the ac current, determine the reversal sites through the magnetostatic interaction among the dots. We show that the individual selectivity in magnetization reversal occurs through two consecutive steps, dephasing of the matrix dyadic pairs dynamics followed by nonlinear dephasing of the individual elements. This method can be utilized to increase the storage density of magnetic random access memory by enabling common access for four or more bits.

Long-term-stable near-infrared polymer dots with ultrasmall size and narrow-band emission for imaging tumor vasculature in vivo.

Fluorescent nanoprobes have become one of the most promising classes of materials for cancer imaging. However, there remain many unresolved issues with respect to the understanding of their long-term colloidal stability and photostability in both biological systems and the environment. In this study, we report long-term-stable near-infrared (NIR) polymer dots for in vivo tumor vasculature imaging. NIR-emitting polymer dots were prepared by encapsulating an NIR dye, silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775), into a matrix of polymer dots, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), using a nanoscale precipitation method. The prepared NIR polymer dots were sub-5 nm in diameter, exhibited narrow-band NIR emission at 778 nm with a full width at half-maximum of 20 nm, and displayed a large Stokes shift (>300 nm) between the excitation and emission maxima. In addition, no significant uptake of the prepared NIR polymer dots by either human glioblastoma U87MG cells or human non-small cell lung carcinoma H1299 cells was detected. Moreover, these NIR polymer dots showed long-term colloidal stability and photostability in water at 4 °C for at least 9 months, and were able to image vasculature of xenografted U87MG tumors in living mice after intravenous injection. These results thus open new opportunities for the development of whole-body imaging of mice based on NIR polymer dots as fluorescent nanoprobes.

Magnetization reversal using excitation of collective modes in nanodot matrices.

The large arrays of magnetic dots are the building blocks of magnonic crystals and the emerging bit patterned media for future recording technology. In order to fully utilize the functionalities of high density magnetic nanodots, a method for the selective reversal of a single nanodot in a matrix of dots is desired. We have proposed a method for magnetization reversal of a single nanodot with microwave excitation in a matrix of magneto-statically interacting dots. The method is based on the excitation of collective modes and the spatial anomaly in the microwave power absorption. We perform numerical simulations to demonstrate the possibility of switching a single dot from any initial state of a 3 by 3 matrix of dots, and develop a theoretical model for the phenomena. We discuss the applicability of the proposed method for introducing defect modes in magnonic crystals as well as for future magnetic recording.

EXPERIMENTÁLNÍ STANOVENÍ PARAMETRŮ VYBRANÝCH PRVKŮ DOKUMENTŮ Z RASTROVÝCH GRAFICKÝCH ZDROJŮ

Visual appearance of documents and their formal quality is considered to be as important as the content quality. Formal and typographical quality of documents can be evaluated by an automated system that processes raster images of documents. A document is described by a formal model that treats a page as an object and also as a set of elements, whereas page elements include text and graphic object. All elements are described by their parameters depending on elements’ type. For future evaluation, mainly text objects are important. This paper describes the experimental determination of chosen document elements parameters from raster images. Techniques for image processing are used, where an image is represented as a matrix of dots and parameter values are extracted. Algorithms for parameter extraction from raster images were designed and were aimed mainly at typographical parameters like indentation, alignment, font size or spacing. Algorithms were tested on a set of 100 images of paragraphs or pages and provide very good results. Extracted parameters can be directly used for typographical quality evaluation.

Dot-matrix marks for dynamic overlay measurements in electron beam lithography

Due to the serial pattern data transfer in electron beam lithography (EBL), there is a larger spectrum of dynamic overlay errors as compared to projection optical or extreme ultraviolet lithography. A good EBL overlay mark needs to be of high resolution, i.e., small enough size to capture the details of temporally and spatially distributed overlay error variations across a semiconductor chip. A small, one critical dimension unit or about 10–50 nm size, dot exposed in successive lithography layers is the smallest size overlay mark. This overlay mark size allows for multiple marks to be placed across the chip to measure and analyze spatial variation of the overlay errors. If the single dot is replicated into a small matrix of dots, additional overlay error information can be obtained from local variations within the matrix. Analysis of the time-dependent variations of the local overlay errors in these dot-matrix marks is useful in determining the frequency of sources of overlay errors affecting the different lithography layers.

An Innovative Tactile Interactive Interface Graphical Display for the Visually Impaired Information Technology Access Applications

This paper presents an innovative tactile interactive interface graphical display for visually impaired people, information technology (IT) access application. The display consists of matrix of dots. Each dot is an electro rheological fluid micro actuator. The micro-actuator designed based on linear vertical movement principles. The actuator design and development process is presented in this paper. An advanced software tools and embedded system based on voltage matrix manipulation are developed to provide the display near real time control. Prototype size 124x4 dots, on a matrix form, of 2.54mm pitch, was manufactured. The experimental tests carried out into the prototype showed that each actuator of the matrix was able to provide a vertical holding force of 100 to 200 mN and vertical movement of 0.7 mm. The stroke and dynamic response tests showed the practicability of the developed micro actuation system, for tactile display IT access applications.

Noise effects and tomography of remote entangled spins in quantum dots

We investigate how decoherence affects the entanglement established between two quantum dots in microcavities, and propose a tomographic scheme able to measure the entangled state. The scheme we consider establishes the entanglement via the exchange and measurement of a photon. Making the realistic assumption of noise dominated by pure-dephasing processes, we find that the photon must be exchanged and measured on time scales shorter than the quantum dots' characteristic dephasing time for appreciable levels of entanglement to be achieved. The tomographic scheme is able to reconstruct the full density matrix of the quantum dots, and requires only single spin rotations and the injection of an additional photon. Remarkably, we find that the additional photon need not be exchanged and measured on a time scale shorter than the dephasing time for accurate tomography, and also allows many to be used in order to increase the measurement signal.

The Oscilloscope as a Digital Display

The goal of this paper is to present a method to transform an ordinary analog oscilloscope into a digital display. This task is accomplished using the MC9S12XDP512 microcontroller from Freescale. The entire application is coded in assembly language. The idea is to generate all the characters in an 8×5 matrix of dots. The dots are generated with 5 ramp signals which fall with 8 steps. Every step corresponds to a dot, if a step is omitted, there will be no dot generated. If the time base is reduced, than the 8 steps will look like they are on a straight line - on an analog oscilloscope, the vertical lines are almost invisible, but the horizontal lines are visible and if they are short enough, then they will look like dots. An external trigger generated by the microcontroller is used the oscilloscope has. A DAC08 linked to the microcontroller is used to control the display.

Entrapment of quantum dots in sol–gel matrices to develop sensing material based on fluorescence resonance energy transfer

A simple and general procedure is described for the development of fluorescence resonance energy transfer (FRET) systems by the co-immobilization in a sol-gel matrix of photoluminescent quantum dots with a given dye "acceptor".