Flat Light Research Articles

C-Factor influencing bonding of composite resins to pulpal floor dentin

Aims & Objectives: The purpose of this study was to evaluate the effect of cavity configuration (C-factor) on microtensile bond strengths (MTBS) of two resin composites for core build-up to pulpal floor dentin. Methods: Access cavity preparation and root canal filling with gutta percha were performed on extracted human molars. Following this, the gutta percha in the pulp chamber was completely removed to expose pulpal floor dentin. The cavity walls remained as a control group (Cavity). For the test group (Flat), the cavity walls were removed to create a flat surface for bonding. The Cavity and Flat groups were further divided into light cure and dual cure groups, where the the light cure composite resin (Filtek Z 250) was placed in increments and filled upto 5mm and the dual cure resin(Hard core) was bulk filled upto 5mm. A self etch adhesive (Adper promt) was used in both the groups. Specimens were stored in water for 1 week and then sectioned vertically into slabs of dimension 2x2x1 mm and trimmed for the MTBS test. The MTBS were measured with a universal testing machine at a crosshead speed of 1.0 mm/minute. The results were statistically analyzed using 2-way ANOVA. Results: The results showed that the MTBS for FLAT LIGHT CURE (26.36MPa) >FLAT DUAL CURE (25.56MPa) > CAVITY LIGHT CURE (19.42MPa) > CAVITY DUAL CURE (11.56MPa). Conclusion: Within the limitations of this study, we conclude that the C-factor and type of resin composite could strongly influence the MTBS to dentin of the pulp chamber floor.

一种具有波形槽微结构的导光板设计

The light guide plate is a key component of backlight units,which determines efficiency and uniformity of light emission.In view of the problem of poor uniformity and low brightness of light guide plate at present,a light guide plate was designed by the optical engineering software.A design method of the microstructure with waveform slot in the edge-lighting flat light guide plate was proposed,and distribution mode and parameters of the microstructure were designed.The results show that high-performance light guide plate could be designed when the microstructure with waveform slot distributed in the light guide plate according to regular pattern,and its uniformity is more than 80%.Compared to light guide plate with dot-matrix rectangular distributed macrostructure,whose uniformity is 60%~70%,this high-performance light guide plate uniformity increased very much.When this high-performance light guide plate size in 40 ~ 60 mm scope changes,its uniformity is more than 80%.

How the Leopard Got Its Spots

Evolution![Figure][1] CREDIT: THINKSTOCK.COM The evolution of color patterns in animal coats has long been of interest to evolutionary biologists. From stripes on tigers to leopard spots and even the lion's plain coat, members of the cat family (Felidae) display some of the most striking patterns and variation in the degree of patterning across species. Camouflaging may be especially important in felids due to their stalking predatory behavior; however, the degree to which this shapes patterning across the family is unresolved. Allen et al. now compare mathematical model–generated categories of pattern complexity and variation to the phylogenetic history of the family and find that coat patterning is a highly changeable trait, which is largely related to felids' ecology. For instance, spots occur in species that live in closed environments, such as forests, and particularly complex patterns are found in arboreal and nocturnal species. In contrast, most species that live in open habitats, such as savannahs and mountains, have plain coats. These findings imply that spots provide camouflage in the spotted light found in forest canopies, whereas nonpatterned animals do better in the flat light of an open habitat. Thus, strong selection for background matching has rapidly generated tremendous diversity in coat patterning among felids. Proc. R. Soc. London Ser. B 10.1098/rspb.2010.1734 (2010). [1]: pending:yes

Ultraviolet excitation of remote phosphor with symmetrical illumination used in dual-sided liquid-crystal display

The UV-excited flat lighting (UFL) technique differs from conventional fluorescent lamp or LED illumination. It involves using a remote phosphor film to convert the wavelength of UV light to visible light, achieving high brightness and planar and uniform illumination. In particular, UFL can accomplish compact size, low power consumption, and symmetrical dual-sided illumination. Additionally, UFL utilizes a thermal radiation mechanism to release the large amount of heat that is generated upon illumination without thermal accumulation. These characteristics of the UFL technique can motivate a wide range of lighting applications in thin-film transistor LCD backlighting or general lighting.

Improvement of delay-bandwidth product in photonic crystal slow-light waveguides

We report new results about the improvement of delay-bandwidth product in photonic crystal slow light waveguides. Previous studies have obtained large delay-bandwidth product at the price of small average group index. It is pointed out here that the radius and the distance between the two boundary rows of holes have a key contribution for delay-bandwidth product. We show the possibility of improving this factor of merit meanwhile maintaining the same group index. We succeed in improving normal delay-bandwidth product from 0.15 to 0.35, keeping at the same time the group index unchanged at high value of 90. This optimization approach may be applicable for previous flat band slow light devices.

Flat band slow light in asymmetric photonic crystal waveguide based on microfluidic infiltration

In this paper, an asymmetric photonic crystal waveguide is proposed for flat band slow light transmission. Two structural parameters of one cladding layer of the waveguide are carefully adjusted. They are the refractive index of the liquid infiltrated in the cladding on one side and the radius of the air holes in the infiltrated cladding. In such an asymmetric waveguide, we can achieve a very flat band corresponding to high group index such as 29.4 and low dispersion (10(4)ps(2)/km) for Deltaomega/omega=1.46%. It is found that the value of n(g)Deltaomega/omega of the proposed waveguide can reach 0.429 and this waveguide can also yield a significant increase in the group index-bandwidth product n(g)Deltaomega/omega and improve the bandwidth.

Diffusion-Controlled Glow Discharge Pressure Extended by the Multi-Dual Microhollow Cathode Configuration for Flat Lighting

We investigated pure Xe discharge primarily as a source of vacuum ultraviolet for discharge lamps, using a multi-dual hollow cathode. One of the problems associated with the discharge properties of Xe gas is its easy constriction. We prevented the problem by using an electrode configured as a multi-dual microhollow cathode. This result originated from auxiliary charge particles generated in a lamp discharge space and less variation of electron generation rate, which reduced thermal instability and as a result sequentially suppressed the constriction of Xe discharge. Furthermore, we observed that a six-channel flat-panel lamp could be driven with a pulse power supply.

A Direct-View Backlight With UV Excited Trichromatic Phosphor Conversion Film

This work presents a novel ultraviolet (UV) excited flat lighting (UFL) system consisting of remote phosphor converter (RPC) for liquid-crystal display (LCD) backlight applications. A trichromatic RPC is excited using 254 nm UV lamps to achieve a slim, high color saturation and high luminance backlight. Experimental results indicate that the module thickness reduces to 14.5 mm, along with a high color saturation (92% of the NTSC standard) as well as a high luminance (573 cd/m2 ) when applied to large sized display (42-inch). Additionally, the proposed UFL backlight configuration has already been certified by a lifetime test to ensure the feasibility of proposed system in mass production.

Wideband slow light and dispersion control in oblique lattice photonic crystal waveguides

We find that the angle between elementary lattice vectors obviously affects the bandwidth and dispersion of slow light in photonic crystal line-defect waveguides. When the fluctuation of group index is strictly limited in a +/-1% range, the oblique lattice structures with the angle between elementary lattice vectors slightly larger than 60 degrees have broader available bandwidth of flat band slow light than triangular lattice structures. For example, for the angle 66 degrees , there are increases of the available bandwidth from 20% to 68% for several different structures. For the same angle and a +/-10% variation in group velocity, when group indices are nearly constants of 30, 48.5, 80 and 130, their corresponding bandwidths of flat band reach 20 nm, 11.8 nm, 7.3 nm and 3.9 nm around 1550 nm, respectively. The increasing of bandwidth is related to the shift of the anticrossing point towards smaller wave numbers.

ディスプレイにおけるフリッカ視認性の視距離および発光デューティ比依存性

New display devices such as liquid-crystal displays, plasma displays, and organic LED displays, and high-definition (HD) TV formats may make a change in flicker visibility on displays. The flicker visibility for various viewing distances and light-emission duty ratios using a 44-inch diagonal flat light source was examined for this paper. As the viewing distance is reduced, the perceptible limit luminance of flicker decreases and the perceptible limit frequency increases. This implies that flicker is more perceptible for HDTV. The results show that a lower light-emission duty ratio, which is used to reduce the motion blur, requires a higher field frequency to prevent flicker. We proposed the empirical equations for the flicker-free field frequency and light-emission duty ratio as functions of the luminance. We found from these equations that more than 75 Hz of field frequency is required to prevent flicker when the duty ratio is 50% and the luminance is 300 cd/m2. In addition, more than an 81% duty ratio is required when the luminance is 300 cd/m2, the viewing distance is 3 H, and the field frequency is 60 Hz.

Slow dynamics in dense oil–water emulsions studied using dynamic light scattering

The 3D-echo-DLS (dynamic light scattering) flat cell light scattering instrument(3D-echo-DLS-FCLSI) presents the possibility of measuring slow dynamics of turbid andconcentrated colloidal systems. It combines a modified 3D-DLS component and anecho-DLS component with the flat cell light scattering instrument. While the3D-DLS suppresses multiple scattering, the echo-DLS allows measurements of slowdynamics or even on non-ergodic systems. The advantage of the thin flat cell isthat it increases the transmission and reduces multiple scattering; i.e., singlyscattered light that is required by the 3D-DLS is still available from dense turbidsystems. In the first part of this contribution the 3D-echo-DLS-FCLSI is introducedand the instrumental performance is presented. The second part of the paper isconcerned with the ageing behavior of dense fluids in a flat cell, and with confinementeffects. Here, we show that ageing is strongly influenced by the process of filling ofthe flat cell. In some cases complementary methods can be utilized to measurespecial properties of the system; e.g., the multispeckle method is most appropriatefor measuring heterogeneity effects. In the last part of the paper we compareglass transition measurements of an index-matched emulsion carried out usingthe 3D-echo-DLS-FCLSI and using the multispeckle instrument. We still find anα-relaxation in the glassy state.

HIGH-ENERGY GAMMA-RAY AFTERGLOWS FROM LOW-LUMINOSITY GAMMA-RAY BURSTS

The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs -- low-luminosity GRBs. The nature of the outflow responsible for them is not clear yet. Two scenarios have been suggested: one is the conventional relativistic outflow with initial Lorentz factor of order of $\Gamma_0\ga 10$ and the other is a trans-relativistic outflow with $\Gamma_0\simeq 1-2$. Here we compare the high energy gamma-ray afterglow emission from these two different models, taking into account both synchrotron self inverse-Compton scattering (SSC) and the external inverse-Compton scattering due to photons from the cooling supernova or hypernova envelope (SNIC). We find that the conventional relativistic outflow model predicts a relatively high gamma-ray flux from SSC at early times ($<10^4 {\rm s}$ for typical parameters) with a rapidly decaying light curve, while in the trans-relativistic outflow model, one would expect a much flatter light curve of high-energy gamma-ray emission at early times, which could be dominated by both the SSC emission and SNIC emission, depending on the properties of the underlying supernova and the shock parameter $\epsilon_e$ and $\epsilon_B$. The Fermi Gamma-ray Space Telescope should be able to distinguish between the two models in the future.

Luminance Uniformity of Large-Area OLEDs With an Auxiliary Metal Electrode

One of the key issues of a large-area organic light-emitting diode (OLED) for flat panel lighting applications is to enhance the uniformity of light emission. In this work, we have investigated the effect of an auxiliary metal (chrome) electrode in association with a device configuration on the luminance uniformity of a large-area (15 times 15 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) white OLED. We demonstrate that the ratio between the effective horizontal resistance of anode (indium-tin-oxide (ITO) with the grid patterned metal electrode) and the vertical resistance of the OLED device is the critical factor to determine the luminance uniformity. Moreover, the luminance uniformity is shown to be a function of the current density and degraded with increasing current density. Namely, the OLED panel with the 200-mu m-wide metal lines exhibits the luminance uniformity as high as 90% at 200 mA and 85% at 500 mA.

68.4: Optical Properties of Visible‐Light Excited Phosphor Sheet (VEPS) System

AbstractThe optical properties in Visible‐light Excited Phosphor Sheet (VEPS) system were discussed and calculated. Different to the conventional LED backlight with white LEDs, VEPS system applies blue LED chips to excite the extrinsic flat YAG‐phosphor layer to perform uniform and flat lighting, that can further reduce the backlight thickness. A theoretical model was developed to optimize the structure of VEPS system. Consequently, the optimized result was demonstrated on the small‐Sized VEPS module.

68.3: Dual‐Sided Slim LCD Display System with UV Excited Flat Backlight

AbstractDual‐Sided LCD displays are ideally suited for the public information display (PID) application. The UV excited flat lighting (UFL) was successfully demonstrated to perform dual‐Sided illumination with the features of flat lighting, uniform luminance and high brightness on a 42” TFT‐LCD display. Compared to conventional CCFL or LED lighting source, UFL is superior for the dual‐Sided display application with its slim backlight module profile and power saving.

Vacuum-ultraviolet light emission from xenon directly excited by ballistic output electrons of nanocrystalline silicon planar cathode

The effect of electron incidence into xenon gas molecules has been investigated by using a nanocrystalline silicon (nc-Si) planar ballistic emitter. Vacuum-ultraviolet light emission is observed without discharging when the nc-Si device is driven in xenon gas. The emission spectrum of xenon at 10kPa shows peaks at 152 and 172nm which originate from Xe2* radiation. These results strongly suggest that energetic electrons directly excite xenon molecules followed by radiative relaxations. The observed effect is potentially applicable to mercury-free, efficient, and stable flat panel light sources.

Highly Efficient Quantum-Dot Light-Emitting Diodes with DNA−CTMA as a Combined Hole-Transporting and Electron-Blocking Layer

Owing to their narrow bright emission band, broad size-tunable emission wavelength, superior photostability, and excellent flexible-substrate compatibility, light-emitting diodes based on quantum dots (QD-LEDs) are currently under intensive research and development for multiple consumer applications including flat-panel displays and flat lighting. However, their commercialization is still precluded by the slow development to date of efficient QD-LEDs as even the highest reported efficiency of 2.0% cannot favorably compete with their organic counterparts. Here, we report QD-LEDs with a record high efficiency (approximately 4%), high brightness (approximately 6580 cd/m(2)), low turn-on voltage (approximately 2.6 V), and significantly improved color purity by simply using deoxyribonucleic acid (DNA) complexed with cetyltrimetylammonium (CTMA) (DNA-CTMA) as a combined hole transporting and electron-blocking layer (HTL/EBL). This, together with controlled thermal decomposition of ligand molecules from the QD shell, represents a novel combined, but simple and very effective, approach toward the development of highly efficient QD-LEDs with a high color purity.

Cubic silsesquioxanes for use in solution processable organic light emitting diodes (OLED)

Commercial products using organic light emitting diode (OLED) display technology have begun to appear in cell phones, mp3 players and even televisions. One key area that has allowed and will allow for this technology to continue its ascension into the flat panel display and lighting markets is materials R&D. From this perspective, recent progress in cubic silsesquioxane (SSQ) based materials may provide some new advantageous properties well suited for OLEDs. In this feature article we provide an overview of recent progress in the synthesis, characterization and implementation of SSQ-based materials with properties well suited for application in solution processable organic/polymer electronics, specifically OLEDs.

Hand-based verification and identification using palm–finger segmentation and fusion

Hand-based verification/identification represent a key biometric technology with a wide range of potential applications both in industry and government. Traditionally, hand-based verification and identification systems exploit information from the whole hand for authentication or recognition purposes. To account for hand and finger motion, guidance pegs are used to fix the position and orientation of the hand. In this paper, we propose a component-based approach to hand-based verification and identification which improves both accuracy and robustness as well as ease of use due to avoiding pegs. Our approach accounts for hand and finger motion by decomposing the hand silhouette in different regions corresponding to the back of the palm and the fingers. To improve accuracy and robustness, verification/recognition is performed by fusing information from different parts of the hand. The proposed approach operates on 2D images acquired by placing the hand on a flat lighting table and does not require using guidance pegs or extracting any landmark points on the hand. To decompose the silhouette of the hand in different regions, we have devised a robust methodology based on an iterative morphological filtering scheme. To capture the geometry of the back of the palm and the fingers, we employ region descriptors based on high-order Zernike moments which are computed using an efficient methodology. The proposed approach has been evaluated both for verification and recognition purposes on a database of 101 subjects with 10 images per subject, illustrating high accuracy and robustness. Comparisons with related approaches involving the use of the whole hand or different parts of the hand illustrate the superiority of the proposed approach. Qualitative and quantitative comparisons with state-of-the-art approaches indicate that the proposed approach has comparable or better accuracy.

Dynamic light scattering in turbid nonergodic media

We here present a new device based on dynamic light scattering (DLS) for measuring kinetics in turbid and nonergodic systems. This flat cell light scattering instrument has been developed in our laboratory and is based on an original flat cell instrument employing cells of varying thickness in order to measure the static structure and dynamics of a system. The smallest cell thickness is 10 microm. To this original instrument, we have integrated the three-dimensional (3D)-DLS technology as well as the echo method, and in comparison with other 3D-DLS instruments, ours show the best performance; the maximum intercept was 0.6 as opposed to 0.15 for regular 3D-DLS devices (recently we reached beta=0.75). This was made possible by using crossed polarization filters for the two laser beams, thereby allowing the scattered light from both laser beams to be decoupled and the intercept to no longer be limited at the theoretical value of 0.25. The maximum weight fraction of the sample that is measurable with such a setup is more than ten times higher than with a standard 3D-DLS setup or with the flat cell instrument without the 3D technology. Consequently, with the 3D-DLS flat cell instrument presented here, it truly becomes possible to investigate turbid systems. Moreover, the echo method was integrated to enable measurements of nonergodic systems. Here, a new mechanical design of the echo-DLS component was necessary due to the different geometries of the flat cell in comparison with that of a standard cylindrical cell. The performance of our echo device was compared to that of our multispeckle instrument, and the results were in good agreement for correlation times up to 30,000 s and more. The main limitation of this instrument in its current version is the maximum scattering angle of about 50 degrees (or 30 degrees if echo is used).