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This paper carried out the study of optical system design which can increase the irradiation volume and uniformity of UV LED lamp used in oil-water sterilization device. Sterilizing devices that use LEDs have lower output than UV lamps, making it difficult to sterilize running water as they require a long time to reach the target amount of irradiation. In addition, Cytop, a material used in optical design, has a high transmittance at 275 nm, but the high price range requires minimum volume in optical design. To solve these problems, the volume of the optical system was minimized. In addition, optical system design of sterilizing device was carried out to satisfy target irradiation quantity and have high illumination intensity uniformity. Finally, the design was verified by applying the optical system designed to the actual sterilization environment to carry out the simulation and analyzing the amount of irradiation and uniformity accordingly.

Magnetic properties can be manipulated to enhance certain functionalities by tuning different material processing parameters. Here, we present the controllable magnetization steps of hysteresis loops in double-perovskite single crystals of Eu2CoMnO6. Ferromagnetic order emerges below TC ≈ 122 K along the crystallographic c axis. The difficulty in altering Co2+ and Mn4+ ions naturally induces additional antiferromagnetic clusters in this system. Annealing the crystals in different gas environments modifies the mixed magnetic state, and results in the retardation (after O2-annealing) and bifurcation (after Ar-annealing) of the magnetization steps of isothermal magnetization. This remarkable variation offers an efficient approach for improving the magnetic properties of double-perovskite oxides.

We investigated Ru-doped single-crystal $5d$ iridates, ${\mathrm{Sr}}_{2}{\mathrm{Ir}}_{1\ensuremath{-}x}{\mathrm{Ru}}_{x}{\mathrm{O}}_{4}$, at three different doping concentrations ($x=0.01$, 0.07, and 0.10) using optical spectroscopy. The undoped pristine compound (${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$) is known as a novel ${J}_{\text{eff}}=1/2$ Mott insulator. Remarkably, the optical conductivity spectra of all three samples exhibited insulating behavior, although we observed weak Drude components in the optical conductivity spectra down to the lowest temperature of 30 K. The charge-carrier densities of the Ru-doped iridates estimated from the Drude components are significantly smaller than the expected values estimated from the nominal Ru-doping concentrations. Herein, we provide the temperature- and doping-dependent electronic structure evolution of Ru-doped iridates. We expect that our results will be useful for understanding the intriguing Ru-doping-dependent properties of $5d$ iridate ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$.

The imprinted light guide plate (LGP) fabricated through a diffractive grating was studied for the edge-lit display. Such kind of backlight unit (BLU) can save prismatic sheets. The grating dimension was determined through preliminary experiments, modeling, and computation. Based on the designed parameters, a submicron period grating was fabricated and was transferred to the LGP. Consequently, the outcoupling luminous flux, on-axis luminance, and homogeneousness and chromatic dispersion were measured through the prototyped samples. Compared to the conventional BLU, the imprinted diffractive grating works well as the light extractor but still needs to be improved to meet the illumination characteristics required for the liquid crystal display (LCD) BLU.

We project changes of the Aleutian Low (AL) under global warming using ensemble simulations with a fully coupled ocean-atmosphere-sea ice model, the Kiel Climate Model (KCM). In the global warming simulations, the carbon dioxide (CO2) concentration increases by 1% per year from the preindustrial level of 286.2 ppm to a quadruple value in 140 years. Results from the 40 members of an ensemble simulation show an intensification of the AL such that ensemble mean North Pacific Index (NPI) is decreased by 2.71 hPa. It is also accompanied with an expansion of the AL to north. While the effect of weakened land-ocean thermal contrast and SST warming in the eastern tropical Pacific on the AL strength are relatively weak and marginally significant, sea ice loss in the marginal seas of the North Pacific, such as the Bering Sea and the Sea of Okhotsk, increases the surface air temperature and makes pressure lower over the Bering Sea and the Aleutian Islands. Especially, sea ice loss in the Okhotsk Sea drives the SLP change around the Aleutian Islands and contributes to the strengthening of the AL.

Robust massless Dirac states with helical spin textures were realized at the boundaries of topological insulators such as van der Waals (vdW) layered Bi2Se3 family compounds. Topological properties of massless Dirac states can be controlled by varying the film thickness, external stimuli, or environmental factors. Here, we report single-crystal-quality growth of ultrathin Bi2Se3 films on flexible polyimide sheets and manipulation of the Dirac states by varying the vdW gap. X-ray diffraction unambiguously demonstrates that under uniaxial bending stress the vdW gap substantially changes with interatomic-layer distances unaltered. Terahertz and photoelectron spectroscopy indicate tuning of the number of quantum conducting channels and of work function, by the stress, respectively. Surprisingly, under compressive strain, transport measurements reveal dimensional crossover and suppressed weak antilocalization. First-principles calculations support the observation. Our findings suggest that variation of vdW gap...

The continuously seeking of approaches for enhancing the output of triboelectric nanogenerators (TENGs) has always been the goal of researchers attempting to harvest mechanical energy efficiently. Here a novel methodology for enhancing the output performance of the TENG by introducing electron traps into the common friction layer has been firstly developed. For this purpose, reduced graphene oxide (rGO) embedded in the friction layer has been used as electron traps. Because the triboelectric electrons generated on the surface of a polyimide layer can be efficiently captured and stored in rGO sheets due to the interaction between the rGO sheets and the polyimide layer, the loss of triboelectric electrons can be suppressed. The maximum output power density of a vertical contact-separation mode TENG containing rGO sheets reached 6.3 W/m2, which was 30 times larger than that of a device without rGO sheets. We also showed that the output performance of the lateral sliding-mode TENG, which is the other fundamental working mode of the TENG, can be enhanced due to the advantage of additional electron trapping in the friction layer, indicating that the concept demonstrated in this work holds potential for providing significant enhancements in next-generation triboelectric devices.

We developed Schottky junction photovoltaic cells based on multilayer Mo1–xWxSe2 with x = 0, 0.5, and 1. To generate built-in potentials, Pd and Al were used as the source and drain electrodes in a lateral structure, and Pd and graphene were used as the bottom and top electrodes in a vertical structure. These devices exhibited gate-tunable diode-like current rectification and photovoltaic responses. Mo0.5W0.5Se2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe2 and WSe2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo0.5W0.5Se2 devices. Furthermore, we showed that Mo0.5W0.5Se2-based vertical Schottky diodes yield a power conversion efficiency of ∼16% under 532 nm light and ∼13% under a standard air mass 1.5 spectrum, demonstrating their remarkable potential for photovoltaic applications.

The novel electronic state of the canted antiferromagnetic (AFM) insulator, strontium iridate (Sr2IrO4) has been well described by the spin-orbit-entangled isospin Jeff = 1/2, but the role of isospin in transport phenomena remains poorly understood. In this study, antiferromagnet-based spintronic functionality is demonstrated by combining unique characteristics of the isospin state in Sr2IrO4. Based on magnetic and transport measurements, large and highly anisotropic magnetoresistance (AMR) is obtained by manipulating the antiferromagnetic isospin domains. First-principles calculations suggest that electrons whose isospin directions are strongly coupled to in-plane net magnetic moment encounter the isospin mismatch when moving across antiferromagnetic domain boundaries, which generates a high resistance state. By rotating a magnetic field that aligns in-plane net moments and removes domain boundaries, the macroscopically-ordered isospins govern dynamic transport through the system, which leads to the extremely angle-sensitive AMR. As with this work that establishes a link between isospins and magnetotransport in strongly spin-orbit-coupled AFM Sr2IrO4, the peculiar AMR effect provides a beneficial foundation for fundamental and applied research on AFM spintronics., Advanced Materials, online published (2018)

We observed a hump-like feature in Hall effects of SrRuO$_3$ ultrathin films, and systematically investigated it with controlling thicknesses, temperatures and magnetic fields. The hump-like feature is extremely stable, even surviving as a magnetic field is tilted by as much as 85$^\circ$. Based on the atomic-level structural analysis of a SrRuO$_3$ ultrathin film with a theoretical calculation, we reveal that atomic rumplings at the thin-film surface enhance Dzyaloshinskii-Moriya interaction, which can generate stable chiral spin textures and a hump-like Hall effect. Moreover, temperature dependent resonant X-ray measurements at Ru L-edge under a magnetic field showed that the intensity modulation of unexpected peaks was correlated with the hump region in the Hall effect. We verify that the two-dimensional property of ultrathin films generates stable non-coplanar spin textures having a magnetic order in a ferromagnetic oxide material.

If a three-dimensional physical electronic system emulating synapse networks could be built, that would be a significant step toward neuromorphic computing. However, the fabrication complexity of complementary metal-oxide-semiconductor architectures impedes the achievement of three-dimensional interconnectivity, high-device density, or flexibility. Here we report flexible three-dimensional artificial chemical synapse networks, in which two-terminal memristive devices, namely, electronic synapses (e-synapses), are connected by vertically stacking crossbar electrodes. The e-synapses resemble the key features of biological synapses: unilateral connection, long-term potentiation/depression, a spike-timing-dependent plasticity learning rule, paired-pulse facilitation, and ultralow-power consumption. The three-dimensional artificial synapse networks enable a direct emulation of correlated learning and trainable memory capability with strong tolerances to input faults and variations, which shows the feasibility of using them in futuristic electronic devices and can provide a physical platform for the realization of smart memories and machine learning and for operation of the complex algorithms involving hierarchical neural networks., High-density information storage calls for the development of modern electronics with multiple stacking architectures that increase the complexity of three-dimensional interconnectivity. Here, Wu et al. build a stacked yet flexible artificial synapse network using layer-by-layer solution processing.

We report on the growth of multiferroic Yb2CoMnO6 and Lu2CoMnO6 single crystals which were synthesized by the flux method with Bi2O3. Yb2CoMnO6 and Lu2CoMnO6 crystallize in a double-perovskite structure with a monoclinic P2(1)/n space group. Bulk magnetization measurements of both specimens revealed strong magnetic anisotropy and metamagnetic transitions. We observed a dielectric anomaly perpendicular to the c axis. The strongly coupled magnetic and dielectric states resulted in the variation of both the dielectric constant and the magnetization by applying magnetic fields, offering an efficient approach to accomplish intrinsically coupled functionality in multiferroics.

We developed Schottky junction photovoltaic cells based on multilayer Mo

Lu${}_{2}$MnCoO${}_{6}$ is a rare example of a double-perovskite material exhibiting multiferroic behavior -- coupling of magnetic and electric order -- and a rare example of hysteretic coupling in a bulk material. Here, the authors lay to rest questions about whether it occurs in single crystals and verify that it is an intrinsic effect. The Mn and Co spins are arranged in a frustrated up-up-down-down ordering along the $c$ axis. Data from single crystals show that exchange striction produces electric polarization, albeit with a twist. Unlike other `up up down down' multiferroics, the ferroelectricity emerges orthogonal to the magnetic ordering easy axis. This may be explained by a model taking into account the oxygen bond distortion in Lu${}_{2}$MnCoO${}_{6}$. Consequently, the system has a rich phase diagram: a dielectric response emerges below the magnetic ordering temperature, whereas a hysteretic polarization emerges in the region of magnetic hysteresis, as shown in this paper.

The magnetocrystalline contribution to magnetic anisotropy was studied in the canted antiferromagnetic state of layered ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ single crystals. We performed torque measurements in magnetic fields up to 9 T under various magnetic field orientations. The strong dependence of torque on the magnetic field revealed that the magnetic easy axis is along the in-plane direction and that the observed field-induced weak ferromagnetic order is attributed only to the in-plane component of the external magnetic field. The dependence of torque on the angle produces a twofold symmetric sawtoothlike shape. A simple model consisting of canted antiferromagnetic and magnetic induction terms showed good agreement with the measured torque. These results show that magnetic anisotropy is closely related to the anisotropy of the exchange between antiferromagnetic moments whose canting is mediated by the Dzyaloshinsky-Moriya interaction. Our study demonstrates that torque magnetometry can be extended to the investigation of the magnetic anisotropy of complex magnetic phases.

We accomplished truly scalable, low cost, arbitrarily large-area block copolymer lithography, synergistically integrating the two principles of graphoepitaxy and epitaxial self-assembly. Graphoepitaxy morphology composed of highly aligned lamellar block copolymer film that self-assembled within a disposable photoresist trench pattern was prepared by conventional I-line lithography and utilized as a chemical nanopatterning mask for the underlying substrate. After the block copolymer film and disposable photoresist layer were removed, the same lamellar block copolymer film was epitaxially assembled on the exposed chemically patterned substrate. Highly oriented lamellar morphology was attained without any trace of structure directing the photoresist pattern over an arbitrarily large area.

A highly simplified backlight unit mainly composed of diffractive grating in sub‐micron order imprinted light‐guide plate (LGP) is proposed for edge‐lit backlight unit. Optical characteristics of the imprinted LGP are examined by RCWA and the performance is verified through Monte Carlo simulation. Results show that the diffraction efficiency, luminous flux and its uniformity over the area are significantly affected by the angle of incident ray. Consequently couples of design considerations are additionally proposed to enhance luminous flux. In terms of peak luminance and out‐coupling luminous flux, the experimental results are agreed well with the performance simulation. Finally, compared with optical characteristics of conventional backlight unit, we could conclude that the proposed simplified backlight unit made of diffractive grating imprinted light‐guide plate is a good substitute for the conventional backlight unit.

Organic electronic synapses (e-synapses) based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/graphene quantum dot (GQD) nanocomposites are fabricated by using a solution method. Current–voltage (I–V) curves for the devices under dual positive bias voltage sweeps show that the conductance with a pinched hysteresis gradually increased with increasing applied voltage, and those for the devices under dual negative bias voltage sweeps gradually decreased with increasing applied voltage, indicative of the fingerprint of e-synapses. The current in the devices decreases with increasing concentration of GQDs in the active layer, and the devices fabricated utilizing the ratio of PEDOT:PSS to GQDs of 1:0.4 shows the best performance among the e-synapses. The carrier transport and operating mechanisms of the e-synapses are described on the basis of both the I–V results and the trapping and escape of electrons from the GQDs. An electronic device made from organic materials that behaves like a synapse in the brain has been created by scientists in Korea. Engineering electronic components that mimic the behavior of synapses could revolutionize the currently silicon-based computing industry. Tae Whan Kim and co-workers from Hanyang University combined graphene quantum dots with an electronic polymer to create what could be the building block of a computer that operates like the brain. They made a type of artificial synapse known as a resistive switch, or memristor, that can be controllably flipped between a high and low electrical resistance states. The researchers' device consisted of graphene quantum dots embedded in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. They showed that its electrical properties can be optimized by changing the concentration of quantum dots. Organic electronic synapses based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/graphene quantum-dot (GQD) nanocomposites were fabricated by using a solution method. Current–voltage (I–V) curves for the devices under dual positive bias voltage sweeps and under dual negative bias voltage sweeps showed that the conductance with a pinched hysteresis gradually increased and gradually decreased, respectively, with increasing applied voltage which is a fingerprint of e-synapses. The current in the devices was found to decrease with increasing concentration of GQDs in the active layer, and the devices fabricated utilizing the ratio of PEDOT:PSS to GQDs of 1:0.4 showed the best performance among the e-synapses. The carrier transport and operating mechanisms of the e-synapses are described in this paper on the basis of both the I–V results and the trapping and escape of electrons from the GQDs. We believe that our letter contains significant results of interest to a broad spectrum of NPG Asia Materials readers.

In this paper, we suggest an elegant and cost-effective Backlight Unit which is slim and has locally confined light needed for 1-dimensional local dimming and scanning. We fabricated LGP with micro-structures patterned by CO2 Laser. Lights from LGP are well distributed and uniform with density control of micro-patterns because they are continuous over the whole region of LGP. With one dimensional local dimming, we obtained 43% power-saving effect and contrast ratio of 11400:1 without any hot spot and the artifact.

We have grown single crystals of multiferroic double-perovskite Lu2CoMnO6 and studied the directional dependence of their magnetic and dielectric properties. The ferromagnetic order emerges below TC ≈ 48 K along the crystallographic c axis. Dielectric anomaly arises along the b axis at TC, contrary to the polycrystalline work suggesting ferroelectricity along the c axis. Through the strongly coupled ferromagnetic and dielectric states, the highly non-linear variation of both dielectric constant and magnetization was achieved in application of magnetic fields. This concurrent tunability provides an efficient route to manipulation of multiple order parameters in multiferroics.

These We accomplished truly scalable, low cost, arbitrarily large-area block copolymer lithography, synergistically integrating the two principles of graphoepitaxy and epitaxial self-assembly. Graphoepitaxy morphology composed of highly aligned lamellar block copolymer film that self-assembled within a disposable photoresist trench pattern was prepared by conventional I-line lithography and utilized as a chemical nanopatterning mask for the underlying substrate. After the block copolymer film and disposable photoresist layer were removed, the same lamellar block copolymer film was epitaxially assembled on the exposed chemically patterned substrate. Highly oriented lamellar morphology was attained without any trace of structure directing the photoresist pattern over an arbitrarily large area.

A novel LED backlight unit implementing a light guide plate (LGP) with a two-dimensional array of grating micro-dots is proposed. By optimizing grating-vector orientations of local gratings and applying suitable grating-depth modulation in the array, taking into consideration of the radiation pattern of the LED source, uniform out-coupled light distribution within a narrow luminance angle was achieved without recognizable hot spots. Such a light guide plate was fabricated using a dot-matrix holographic interferometer setup and a UV embossing replication. Fabricated polycarbonate LGP showed ~62% intensity uniformity within ~8 degrees and ~20 degrees luminance angles in two main directions.

In this paper an optical configuration of a transflective liquid crystal (LC) cell driven by a horizontal electric field is proposed, which shows high contrast, high cellgap tolerance, and single gamma, simultaneously. The dark state of the reflective part is realized by a polarizer (0 degrees), a half-wave plate (15 degrees), LC layer (120 degrees), and a quarter-wave layer (-15 degrees), while a wide-band quarter-wave plate (45 degrees) and a polarizer (90 degrees) are added for the dark state of the transmissive part. Since the optic axis of the homogeneously aligned LC layer is set to be parallel to the polarization direction of the light passed through the half-wave plate, the dark state is rarely affected by the cellgap of the LC layer. Due to the different directions of the electric fields, LCs are rotated to 97.5 degrees for the bright state of the reflective part, but to 75 degrees for that of the transmissive part. With the proposed configuration, a high contrast single-gamma transflective display with high cellgap tolerance can be realized in a single-cellgap structure.

Nano-transfer printing is a soft-lithographic technique which allows the transfer of metal patterns deposited on a polymer stamp to different surfaces. The nano-transfer printing process allows various nanostructures to be formed without using sophisticated methods and expensive equipment. In the present work, we present the formation of gold micro- and nano-structures on a glass surface using a self-assembled monolayer as a transfer agent. A polydimethylsiloxane replica was fabricated from a master chip that has micro- and nano-meter size patterns. A thin gold layer was deposited on the replica stamp and the glass surface was modified with a self-assembled monolayer of 3-mercaptopropyltrimethoxysilane, followed by the transfer of the gold patterns from the polydimethylsiloxane stamp to glass by simple contact printing. The patterns sp obtained were characterized using scanning electron microscopy and optical microscopy.

A simple liquid crystal display (LCD) backlight unit (BLU) comprising only a single-sheet polydimethylsiloxane (PDMS) light-guide plate (LGP) has been developed. The PDMS LGP, having micropatterns with an inverse-trapezoidal cross section, was fabricated by backside 3-D diffuser lithography followed by PDMS-to-PDMS replication. The fabricated BLU showed an average luminance of 2878 cd/m(2) with 73.3% uniformity when mounted in a 5.08 cm backlight module with four side view 0.85cd LEDs. The developed BLU can greatly reduce the cost and thickness of LCDs, and it can be applied to flexible displays as a flexible light source due to the flexible characteristic of the PDMS itself.

In this paper, we present comparison of three subjective testing methods: the double stimulus continuous quality scale (DSCQS) method, the single stimulus continuous quality evaluation (SSCQE) method and the absolute category rating (ACR) method. The DSCQS method was used for validate objective models in the VQEG Phase II FRTV test. The SSCQE method is chosen to be used in the VQEG RRTV test. The ACR method is chosen to be used in the VQEG Multimedia test. Since a different subjective test method is used in each test, analyses of the three methods will provide helpful information in understanding human perception of video quality.

In this paper, we propose compression algorithms for hyperspectral images based on the wavelet transform using adjacent band information. In the proposed algorithm, we divide the spectral bands into a number of groups. Then, within each group, we select a representative spectral band which has highest correlations with the remaining spectral bands within the group. The representative image is compressed using the 2-dimensional SPIHT algorithm. A characteristic of the SPIHT algorithm is that it provides information on significant coefficients of transformed images, which have large energies. We explore this characteristic and use the information to encode adjacent band images of the representative image.

In this paper, we investigate video quality on various LCD monitors. There exists a large variance in video quality among various LCD monitors. Due to this unavoidable variance in LCD monitors, there has been a concern about the stability and repeatability of subjective and objective testing for LCD monitors. We performed subjective testing the DSCQS method and compare subjective quality ratings on the 5 LCD monitors. The experimental results show that the correlation coefficients among DMOS’s with respect to each monitor are acceptably high. Thus, it may be possible to develop models for objective measurement of video quality on LCD monitors. In the paper, physical parameters such as color temperature, contrast, brightness, response time, etc will be presented and thorough analyses will be provided.

A single-sheet backlight unit (BLU) for a liquid crystal display (LCD) with improved light extraction efficiency was developed. A new microstructure on the light-guide plate (LGP), namely a merged-dot pattern, is proposed. The effective emission area was significantly increased by using the proposed light-extracting structure, resulting in high light extraction efficiency. Through optical simulation, we investigated the effect of the enlarged emission area on the luminance and vertical light emitting performance of the single-sheet LGP. Then, in order to verify the simulation result, we fabricated a polydimethylsiloxane (PDMS) LGP containing the proposed light-extracting microstructure by using backside 3D diffuser lithography and the PDMS replication processes. The fabricated single-sheet BLU showed an average luminance of 4197 cd m−2 with four 0.97 cd LEDs, corresponding to 27.8% enhancement over the LGP without the merged-dot patterns.

We propose liquid-crystal (LC) devices capable of switching between reflective and transmissive modes using the scattering and transparent states of long-pitch cholesteric LCs (CLCs). Two different device configurations can be realized by changing the location of a CLC layer. Low-power operation without the parallax problem can be achieved using the bistable switching of CLCs. We believe that the proposed devices are potential candidates for highly efficient transflective displays.

We propose an optical configuration for a nematic liquid crystal (LC) device that is switchable between the reflective and the transmissive modes. By placing a reflective polarizer between the two LC layers, we obtain higher reflectance and reduce the parallax effect in the reflective mode. We can eliminate the parallax effect by using a wire-grid polarizer or other in-cell reflective polarizers. We expect that the proposed device can be used in various outdoor applications.

We propose a method to control the pretilt angle of liquid crystals by employing a mixture of the vertical alignment polyimide and the liquid crystalline prepolymer (LCP). The pretilt angle between 10° and 90° can be controlled continuously by changing the mixing ratio of the LCP. Multidomains with different pretilt angles can be formed because the pretilt angle between 50° and 90° can be obtained by varying the UV exposure time region by region under a fixed mixing ratio. We confirmed experimentally that proposed alignment layers are thermally stable.

We developed a novel twisted nematic (TN) liquid crystal display (LCD) having wide viewing angle characteristics through the reduction of the residual liquid crystal phase retardation at oblique angles using an embedded diffusing unit. Compared to a conventional TN panel, this embedded approach provides extended isocontrast contours by more than ±10 deg at a contrast ratio of 100:1 along the horizontal direction and a wide region free of grayscale inversion by a factor of 2 along the vertical direction. Moreover, the off-axis image distortions in our novel LCD are improved by 50% compared to those in a film-compensated TN LCD.

Reflective color filters using two-dimensional photonic crystals based on sub-wavelength gratings were proposed and constructed. Using low-cost nanoimprint lithography, an amorphous silicon layer was deposited through the low-temperature PECVD process and patterned into two-dimensional structures. The isolated amorphous silicon patterns were readily crystallized using a multi-shot excimer laser annealing at low energy. A study of the close relationship between color filter reflectance and silicon pattern crystallinity is introduced. Theoretical and experimental results show that the proposed color filters have high reflectance and, moreover, decrease the dependence on incident angle compared to one-dimensional photonic crystal color filters.

In this paper, we propose a method of suppressing the increase in operating voltage caused by the in-cell retarder in transflective liquid crystal displays (LCDs), by doping nanoparticles with a high dielectric constant in the in-cell material. Doping with nano-particles increases the dielectric constant of the in-cell material by more than 5 times that of a pure in-cell material. The in-cell material with a high dielectric constant reduces the magnitude of the electric field, within the volume of the in-cell retarder, to decrease the operating voltages of a transflective LCD with an in-cell retarder. It is confirmed that the increase in operating voltage, in a transflective vertical alignment (VA) cell with an in-cell retarder, can be suppressed, from 3.8 to 0.7 V, by doping an in-cell material with 5 wt % TiO2.

Sub-wavelength grating color filters are proposed for use with reflective displays. The color filters are composed of two-dimensional silicon gratings on a quartz substrate. Red, green, and blue color filters of 20mm × 20mm size have been fabricated using electron beam lithography method, and have high angular tolerance of up to ±45 degrees for incident angle of light. Numerical simulations reveal that the high angular tolerance is achieved due to the high contrast of the grating's refractive index.

— A polydimethylsiloxane (PDMS) light-guide plate (LGP) having micropatterns with an inverse-trapezoidal cross section was developed for a sheet-less LCD backlight unit (BLU). The micropatterned PDMS LGP was fabricated by backside 3-D diffuser lithography followed by two consecutive PDMS replication processes: photoresist-to-PDMS and PDMS-to-PDMS replications. The fabricated LGP showed an average luminance of 2878 nits and a uniformity of 73.3% in a 2-in. backlight module with four side-view 0.85-cd LEDs. It also could feasibly be applied to a light source for flexible displays owing to the flexible characteristic of the PDMS itself.

A new collimating lighting system based on light-emitting diode (LED) technology is presented. Using an array of LEDs as light source, by means of a tapered waveguides with reflectors, this device makes it possible to obtain an integrated light beam with a high intensity level and the desired divergence, in a compact geometry with large output area. An optical model allowing control of the beam parameters is presented. These characteristics make it applicable in a variety of fields where high luminous intensity, intensity uniformity, high width to length ratio and narrow angular distribution are needed. To improve the color rendering it would be necessary to use a white LED or three different LEDs in an array.

Myocardial ischemia occurs when myocardial oxygen availability is inadequate to meet metabolic requirements. The common cause of myocardial ischemia is atherosclerotic epicardial coronary arteries. Isoflurane is a potent small vessel-type coronary vasodilator and has the potential for causing regional myocardial ischemia in patients with coronary disease, but it's still controversial. We experienced a case of transient myocardial ischemia during general anesthesia with isoflurane. The patient was a 51 year- old male who underwent a direct clipping of an anterior communicating artery aneurysm. There was no specific abnormality on preoperative laboratory tests except for mild mitral valve regurgitation on the cardiac echocardiogram. He had once experienced several minutes of sudden severe chest tightness just 3 months before admission, but it had subsided without any specific treatment. One hour after beginning of operation, abnormal EKG changes such as ST-T elevation, QRS widening, VPC, ventricular tachytcardia and ST-T depression appeared and then normalized within 2 minutes with stopping isoflurane and using isosorbide dinitrate. He discharged 12 days later without complications. After discharge, Tread-mill test, SPECT and 2D echocardiogram were performed but there was no any evidence of coronary artery disease. (Korean J Anesthesiol 1997; 33: 974∼978)