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Thermal circuit modeling is successfully established and utilized for analyzing the temperature distribution within each epitaxial film of InGaN/GaN multiple-quantum-well blue light-emitting diodes (LEDs). The temperature distribution based on the infrared (IR) intensity from the LED surface is also calculated by applying the known emissivity and transmittance values for each epitaxial material to the simulated results. We measure the temperature distribution by using an IR camera on the LED surface and demonstrate that the simulated and measured temperature distributions have very similar distribution tendencies.

We analyzed the changes in electrical and optical characteristics of 1 multiple-quantum-well (MQW) blue LEDs grown on a c-plane sapphire substrate after a stress test. Experiments were performed by injecting 50 mA current for 200 hours to TO-CAN packaged sample chips. We selected the value of injection current for stress through the junction-temperature measurement by using the forward-voltage characteristics of a diode to maintain a sufficiently low junction temperature during the test. The junction temperature at the selected injection current of 50 mA was 308 K. Experiments were performed under the assumption that the average junction temperature of 308 K did not affect the characteristics of the ohmic contact and the GaN-based materials. Before and after the stress test, we measured and analyzed current-voltage, light-current, light distribution on the LED surface, wavelength spectrum and relative external quantum efficiency (EQE). After the stress test, it was observed experimentally that the optical power and the relative EQE decreased. We theoretically investigated and experimentally proved that these phenomena are due to the increased nonradiative recombination rate caused by the increased defect density.

The internal electric field due to the piezoelectric effect in an InGaN/GaN multiple quantum-well structure is measured via photoluminescence (PL), electroreflectance (ER), and photocurrent (PC) spectroscopies, and the measurement results are compared with each other and with theoretically calculated values. The flat-band voltage is estimated by measuring the applied bias voltage that induces the maximum in PL peak energy by the quantum-confined Stark effect, 180° phase shift in the ER spectrum, and the smallest band tail state in the PC spectrum. The internal electric fields estimated by the PL, PC, and ER spectra are -1.81, -2.12±0.14, and -2.04 MV/cm, respectively. The measured piezoelectric fields are in good agreement with theoretically calculated values. Possible factors affecting piezoelectric field measurements are discussed from various perspectives.

YVO 4:Eu 3+ nanocomposites have been synthesized by means of a modified co-precipitation method (CP-CNT). Multi walled carbon nanotubes (MWCNT's) have been employed in the synthesis of the YVO 4:Eu 3+ nanocomposites to enhance its photoluminescence efficiency. The prepared nanocomposites were thoroughly characterized using the characterization techniques namely XRD, SEM, FTIR and Raman scattering. To evaluate the potentiality of the prepared nanocomposites, the same phosphor has also been prepared by using co-precipitation (CP) method without employing multi walled carbon nanotubes and also by means of conventional solid state reaction method (SSR). The photoluminescence spectra of YVO 4:Eu 3+ nanocomposites have shown stronger red emission at 619 nm ( 5D 0 ? 7F 2) for both the excitation wavelengths (254 and 393 nm) than the other two prepared samples. The effect of MWCNT's on photoluminescent properties of the YVO 4:Eu 3+ nanocomposites is also explained. � 2011 Elsevier Ltd. All rights reserved.

We have studied the structural and the electrical properties of BiFeO3 (BFO) and (Bi0.9 Eu0.1)(Fe0.9Mn0.1)O3−δ (BEFMO) thin films prepared by using a chemical solution deposition method. X-ray diffraction studies revealed that the BFO and the BEFMO thin films were composed of a rhombohedrally distorted perovskite structure without secondary phases. For the BEFMO thin film, changes in the peak positions and the intensities of some Raman modes were observed. Improved ferroelectric properties were observed in the BEFMO thin film capacitor. The values of remnant polarization (2P r ) and coercive field (2E c ) of the BEFMO thin film were 95 µC/cm2 and 787 kV/cm at a maximum applied field of 1060 kV/cm, respectively. The leakage current density was 7.6 × 10−5 A/cm2 at an electric field of 100 kV/cm, which is about two orders of magnitude lower than that of the BFO thin film.

A novel class of orange–red phosphors namely CaLa2ZnO5 (CLZ) doped with Eu3+ ions were prepared by adopting citrate based sol–gel method. Those were thoroughly characterized by means of XRD, SEM, Tg-DTA, photoluminescent (PL) spectral profiles. PL studies reveal that its emission intensity strongly depends on sintering temperature as well as the dopant ion (Eu3+) concentration. Eu3+ ion doped CaLa2ZnO5 phosphor has a strong excitation at 468 nm, which correspond to the popular emission line from a GaN based blue light-emitting diode (LED) chip. The influence of the preparation method on the luminescence property was studied by comparing the emission performance of phosphors prepared by sol–gel and solid-state reaction methods along with a commercial red phosphor Y2O2S:Eu3+. Thus, the intense red emission (5D0 → 7F2) of the Eu3+ doped CLZ phosphors under blue excitation suggests them to be a potential candidate for the production of white light by blue LEDs.

High-power and high-linearity photodiodes (PDs) are of critical importance to achieve high-efficiency analogue fibre links. A small-signal analysis is utilised on the nonlinear responsivity of the modified uni-travelling-carrier PDs to understand the theoretical limitation on the third-order output intercept point (OIP3) of the link. It is theoretically shown that a nonlinear responsivity depending on both the voltage and the current can give rise to an enhanced OIP3 at certain bias and current values.

CaZrSi 2 O 7 (CZS), a modification of the thortveitite family, was prepared as a polycrystalline powder material by the conventional solid-state reaction method. Structural, thermal and photoluminescence (PL) properties of the prepared material were investigated in order to evaluate its potentiality. XRD patterns confirm the monoclinic phase of CaZrSi 2 O 7 : Eu 2+ phosphors.. Emissions arising from transitions between the 5d and 4f orbital gaps of Eu 2+ are manifested in the broadband excitation and emission spectra with major peaks at 363 and 512 nm, respectively. The excitation wavelength matches well with that of the emission of the ultraviolet-light emitting diode (UV-LED). Concentration quenching occurs when the Eu 2+ concentration is beyond 0.05 and the dipole–dipole interaction was the reason for the corresponding quenching mechanism. The temperature dependence of emission intensity of CZS: Eu 2+ phosphor was investigated and it showed better thermal stability than the standard YAG: Ce 3+ phosphor.

The reduction of Eu 3+ to Eu 2+ in a non-reducing atmosphere of pure argon gas has been reported for the first time in NaCaPO 4 host matrix prepared by using a solid-state reaction. Photoluminescence spectral profiles confirmed the presence of Eu 2+ ions in the prepared compound and this reduction has been explained by means of a charge compensation model. The effect of lithium incorporation on the photoluminescence efficiency of the NaCaPO 4 :Eu 2+ phosphors were also studied and explained appropriately for various doping concentrations of lithium ions. The CIE coordinates and temperature dependant luminescence profiles of these phosphors were also discussed in order to investigate their potential applications. Besides analyzing its photoluminescence properties, other significant characterizations like XRD, SEM, TG–DTA, FTIR, Raman spectral profiles have also been studied and these interpretations were documented more clearly.

P NMR). IR spectra were obtained on a Mattson Genesis Series FT-IR spectrophotometer. Mass spectra were obtained on a GC Mate 2, JEOL. X-ray di-ffraction data were obtained with a Bruker SMART diffracto-meter equipped with a graphite monochromated Mo Kα (λ = 0.71073 A) radiation source and a CCD detector. The open-bed chromatography was carried out on silica gel (70 ~ 230 mesh, Merck) using gravity flow. The column was packed with slurries made from the elution solvent.

The benzo[b][1,4]oxazin-3(4H)-one derivatives, 1a–p, carrying F, Br, and Cl on the benzene ring, or benzyl, cyclohexyl, n-hexyl, and tetrafuryl methylene groups attached to nitrogen atom were synthesized via Smiles rearrangement and assayed in vitro for their antimicrobial activity against Gram-positive, Gram-negative bacteria, and fungi. The antimicrobial activity of the benzo[b][1,4]oxazin-3(4H)-ones showed, on the whole, potency toward all the tested Gram-positive and Gram-negative microorganism (MIC ranging from 16 to 64 μg/ml), whereas weak effectiveness was exhibited against fungi. Data obtained suggest that fluorine atom in the compounds, 1c, 1f, 1i plays an important role in enhancing the antimicrobial properties of this class of compounds. These observations provide some predictions to design further antimicrobial active compounds prior to their synthesis according to molecular modeling studies.

Diarylamines and arylalkylamines were synthesized in high yields from 2-chlorophenols and amines, activated by chloroacetyl chloride under microwave irradiation (20―60 min) or conventional thermal conditions (3―6 h). The key transformation is believed to proceed via Smiles rearrangement by initial O-alkylation and subsequent cyclization.

A series of novel ferrocenyl pyrazolo[1,5-a]pyrazin-4(5H)-one derivatives was synthesized and characterized by 1H NMR, 13C NMR, IR, HRMS and X-ray diffraction analysis. Preliminary evaluation of biological applications showed that the compounds 6c and 6f inhibit the growth of A549 cells in dosage-dependent manners through cell cycle arrest.

CNT/Fe/Al 2 O 3 mixed powders were synthesized from Fe/Al 2 O 3 nanopowders using thermal CVD for the homogeneous dispersion of carbon nanotubes CNTs. CNTs consisted of MWNT, and the diameter was approximately 20-30 nm. After sintering, CNTs were homogenously located throughout Al 2 O 3 grain boundary and were buckled. A femto-second laser installed with special optical systems was used for micromachining of the nanocomposites. The relationship between material ablation rate and energy fluence was theoretically investigated and compared with experimental results from cross-sectional SEM analysis. The nanocomposites which have higher content of CNT show a fairly good machining result due to its higher thermal conductivity and smaller grain size as well as lower light transmittance.

A series of novel 2-ferrocenyl-6-substituted-4 H -pyrazolo[5,1-c][1,4]oxazin-4-one derivatives were synthesized by the intra-esterification reaction of ethyl 1-(2-aryl-2-oxoethyl)-3-ferrocenyl-1 H -pyrazole-5-carboxylate in the presence of magnesium bromide and diisopropylethylamine in one-pot procedure. The structures of compounds were characterized by 1 H NMR, 13 C NMR, IR, HRMS and X-ray diffraction analysis.

A general method has been developed for the solid phase synthesis of drug-like 7-aryl-benzo[b][1,4]oxazin-3(4H)-one derivatives 6. The method relies on a novel, microwave irradiation promoted cyclization reaction of the BOMBA resin bound, N-substituted-α-(2-chloro-4-bromophenoxy)acetamide 3 that takes place via a Smiles rearrangement. The 7-bromobenzo[ 1,4]oxazine 4, produced in this process is converted to 7-aryloxazin analogs 5 by utilizing Suzuki coupling with various substituted arylboronic acids. Finally, the target 7-aryl-benzo[b][1,4]oxazin-3(4H)-ones 6 are liberated from the resin by treatment with 5% TFA. The progress of the reactions involved in this preparative route can be monitored by using ATR-FTIR spectroscopy on a single bead. The target compounds, obtained by using this five-step sequence, are produced in high yields and purities.

A series of novel 1,3-diallyltrisulfane analogues were synthesized and assayed in vitro for antimicrobial activity against Gram positive, Gram negative bacteria and fungi. The antimicrobial activity of the 1,3-diallyltrisulfane derivatives showed, on the whole, very potent towards all the tested Gram positive, Gram negative and fungi (MIC ranging from 4 to 256 µg/mL). 1,3-Di(pent-4-enyl)trisulfane 3b and 1,3-bis(3-methylbut-2-enyl)trisulfane 3e exhibited the strongest antibacterial activity among all the compounds, and both of them were more active than 1,3-diallyltrisulfane (DATS). Results indicated the relationship of either carbon number or lipophilicity with antimicrobial activity presented “V” shape. These observations provided some predictions in order to further design 1,3-diallyltrisulfane derivatives with antimicrobial activity.

An efficient and operationally simple method for C3-alkylation of 4-hydroxycoumarins has been developed under acidic medium giving good yields of the products. In the present method, a reusable Amberlite ® IR-120 (H + form) was used as an acid catalyst and secondary benzyl alcohols were used as alkylating agents. The obtained 3-alkylated-4-hydroxycoumarins offered an easy access for the synthesis of 3,4-disubstituted coumarins by way of Pd-catalyzed coupling reactions.

An efficient method for the synthesis of benzo[b][1,4]oxazin-3(4H)-ones via Smiles rearrangement using a microwave-assisted one-pot, three-step reaction has been developed. Various benzo[b][1,4]oxazin-3(4H)-ones are obtained in good yields (55–86%) from the corresponding substituted 2-chlorophenols and primary amines in short reaction time (18–40 min).

An efficient method of adjusting the RF parameters of directly modulated laser diodes (LDs) is presented. By using the light-current parameters estimated from initial RF measurements, the new bias and modulation currents are obtained self-consistently for the target extinction ratio and average optical power. Experiments performed using distributed feedback lasers show that this adjustment method works efficiently, bringing the initial RF parameters very close to the target values within a couple of iterations. This method can be useful in manufacturing where there is a need to adjust the RF performance of the direct-modulated LDs to a desired specification.

Resolution enhancement technology (RET) refers to a technique that extends the usable resolution of an imaging system without decreasing the wavelength of light or increasing the numerical aperture (NA) of the imaging tool. Off-axis illumination (OAI) and a phase shift mask (PSM) are essentially accompanied by optical proximity correction (OPC) for semiconductor device manufacturing nowadays. A chromeless PSM is compared with an attenuated PSM (att.PSM) to generate a 45 nm dense line and space pattern. To obtain the best possible resolution, a suitable OPC is required with PSM and the most common application of OPC is the use of bias. An optical system with a high NA, a strong OAI, and a proper polarization can decrease k1 to a value well below 0.3. A chromeless PSM has various advantages over alternating PSM such as the lack of necessity for double exposure, small pattern displacement, and the lack of critical dimension (CD) error caused by intensity imbalance. However, a chromeless PSM has some disadvantages. In the case of a 100% transmittance pure chromeless PSM, there is no shading material that is usually deposited on the line pattern for both att.PSM and alternating PSM to control linewidth. Because there is no shading material for such a chromeless PSM, the required resist CD has to be obtained using phase only and it is difficult to control the resist CD through pitch. As expected, a chromeless PSM needs a smaller dose than an att.PSM to generate a desired 45 nm CD with a 1.0 NA. Our simulation results show that a 10 nm bias is optimum for chromeless PSMs. We demonstrate that chromeless PSM and att.PSM technology can be used to achieve a 45 nm node with optimum biased OPC.

The photomask (PM) surface is covered with a pellicle to protect from dust and other airborne particles. However, a defect known as haze appears on the surface of the PM during exposure even with a pellicle cover. As lithography goes into the deeper UV, the photochemical reactions of contaminants become enhanced to form haze on the PM surface. This affects the lithography as haze absorbs or scatters UV. Ellipsometry may be an ideal technique for the early detection of a haze layer. However, when the PM is covered with a pellicle, the ellipsometric data collected from the surface become extremely distorted owing to the non-normal transmission through the pellicle. In this article, we introduce a novel technique so that the conventional ellipsometric data can be obtained without removing the pellicle. If ellipsometry can be used for the inspection of the PM with a pellicle in place, the cleaning frequency of the PM will be reduced significantly.

The nonthermal effects on the entanglement fidelity for the elastic electron–ion scattering are investigated in generalized Lorentzian plasmas. The dynamically screened effective potential and partial wave analysis are employed to obtain the entanglement fidelity in Lorentzian plasmas as a function of the spectral index, collision energy, and plasma parameters. It is shown that the entanglement fidelity increases with decreasing the collision energy, especially, for small Debye radii. It is also shown that the nonthermal effect enhances the entanglement fidelity in Lorentzian plasmas. In addition, it is found that the entanglement fidelity increases with an increase of the plasma temperature.

Highly efficient synthesis of substituted benzo[1,4]oxazin-3-ones and pyrido[1,4]oxazin-2-ones under microwave irradiation via Smiles rearrangement is reported. Substituted benzo[1,4]oxazin-3-ones and pyrido[1,4]oxazin-2-ones were obtained by treatment of substituted 2-chlorophenols or 2-chloropyridols with N-substituted 2-chloroacetamide in the presence of potassium carbonate in MeCN and subsequent exposure to cesium carbonate in DMF. All the reactions which take 2-10 hours under conventional condition were completed successfully within a few minutes under microwave irradiation giving moderate to excellent yields.

A series of novel 5-alkyl-2-ferrocenyl-6,7-dihydropyrazolo[1,5-a]pyrazin-4(5H)-one derivatives were synthesized by the reaction of ethyl 1-(2-bromoethyl)-3-ferrocenyl-1H-pyrazole-5-carboxylate with non-aromatic primary amines in one-pot procedure and characterized by 1H NMR, 13C NMR, IR, HRMS and X-ray diffraction analysis. The effects of all the compounds on A549 cell growth were investigated. The results showed that all compounds had almost inhibitory effects on the growth of A549 cells.

When we attempted to synthesize (E)‐3‐(benzo[d][1,3]dioxol‐5‐ylmethylene)‐4‐(propan‐2‐ylidene)‐dihydrofuran‐2,5‐dione, we found a novel rearrangement and obtained the unexpected compound that is assigned as benzo‐medium‐ring anhydride instead of the expected compound. We described the novel rearrangement and a potential method for the synthesis of benzo‐medium‐ring anhydride derivatives.

An efficient microwave-assisted protocol for the synthesis of fluorinated coumarino sulfonamides 3 was achieved. First the fluoro arylamines were reacted with methyl 2- chlorosulfonyl acetate to afford compounds 2 followed by Knoevenagel condensation with substituted salicylaldehydes to give fluorinated coumarino sulfonamides 3. Comparison of conventional and microwave irradiation showed the later procedure required shorter reaction times, generally gave higher yields and was applicable to a larger set of substrates.

A method involving iron catalyzed acylative cleavage of cyclic and acyclic ethers with acyl/aroyl chlorides has been studied to produce chloroesters and esters respectively. Examination of the scope revealed that less electron rich alkyl group in unsymmetric, acyclic ether was acylated while the chloride derived from the counterpart moiety was volatile and difficult to isolate. In contrast, α-branched cyclic ethers were converted to the corresponding primary ester and secondary chloride. Steric hindrance of ether also plays an important role in acylative C–O bond cleavage. The mechanism of ether cleavage is proposed to involve a single electron initiated S N 1 dissociative pathway.

The reaction mechanisms for the cyclizations of N-methyl-2-(2-chloropyridin-3-yloxy)acetamide to 1-methylpyrido[3,2-b][1,4]oxazin-2-one and 1 -methyl-pyrido[2,3-b][1,4]oxazin-2-one were investigated using ab initio Hartree-Fock, second-order Moller-Plesset perturbation, single point coupled cluster with both single and double substitution, and density functional theory methods. The 5-membered spiro intermediate (2) is optimized from the cyclization of the acyclic reactants through the proton-transfer reaction, and this intermediate proceeds continuously to the 6-membered intermediate through either a stepwise or a concerted reaction. In the stepwise reaction, an N-bridge-type intermediate as a stable structure is optimized, whereas, in the concerted reaction, the O-bridge-type intermediate is not optimized.

The photon-mode multi-level optical storage properties using a photochromic indolylfulgide compound named 2-(1-benzyl-3-methyl-2-indolylmethylene)-3-isoproplidene succinic anhaydride have been investigated. It has been found that this compound possesses an absorption maximum at 400 nm and undergoes a photocyclization upon irradiation with UV light at 365 nm, leading to the formation of a pinkish product with absorption maximum at 505 nm. By irradiation with visible light at 514.5 nm, the original absorption spectrum was recovered completely. The transmittance of this photochromic material was found to change nonlinearly along with the exposure energy, indicating the potential of this compound as multi-level optical storage material. Eight-level optical storage of amplitude modulation is experimentally realized using the indolylfulgide dispersed PMMA film for the first time. By employing the laser beam at 514.5 nm with power of 3 mW for recording and readout, multi-level signals with high signal-to-noise ratio (SNR) have been detected.

A novel helix-monopole antenna is proposed which combines the helix and monopole together to form improved current distribution. The current magnitudes are computed with Moment Method (MM) and results show the current difference between helix-monopole and helix antenna. Two antennas are fabricated for comparison and measured on the same two-way portable radio with frequency band from 400-420 MHz. Measurements prove that the proposed antenna offers a significant improvement in gain.

Colloidal silica/silane sol solutions were prepared in variation with the amount of silane and reaction time. Such sol solutions were synthesized from colloidal silica/tetramethoxysilane(TMOS)/methyltrimethoxysilane(MTMS). Sol solutions were prepared by sol-gel method through two step reactions. In order to understand their physical and chemical properties, dip coating of sol solutions was performed on the glass substrates. The effects of amount of MTMS and reaction time on the formation of coating films were studied. Coating films became transparent as the reaction time increased. Contact angle of coating films increased with increasing the amount of MTMS. Contact angle of coating films decreased with increasing reaction time. Surface free energy of coating films decreased with increasing the amount of MTMS. Surface roughness of coating films decreased with increasing the amount of MTMS when the reaction time was 6 h. When the reaction time was 24, 48 and 72 h, surface roughness of coating films decreased with increasing the amount of MTMS in the beginning, and then increased when further amount of MTMS was added. Plastic hardness increased with increasing the amount of MTMS. Elastic portion inversely decreased with increasing the amount of MTMS. Coating films were stable until 550°C. Thermal degradation temperature of coating films decreased with increasing the amount of MTMS.

A series of novel 6‐(aroxymethyl)‐2‐aryl‐6,7‐dihydropyrazolo[5,1‐c][1,4] oxazin‐4‐one derivatives was synthesized from ethyl 3‐aryl‐1H‐pyrazole‐5‐carboxylate and 2‐aryloxymethylepoxide by a microwave‐assisted, one‐step method in good yields. The microwave‐assisted reaction of ethyl 3‐aryl‐1H‐pyrazole‐5‐carboxylate and 2‐aryloxymethylepoxide proceeds with higher regioselectivity and is more economical and environmentally friendly in contrast to the normal intramolecular esterification route. A tandem mechanism of the reaction was proposed.

This study investigated three aspects of health status (physical, psychological, social), fall experiences, and contributing factors to falls among 226 community-dwelling Korean women older than age 65. Data were analyzed using descriptive statistics, t tests, and logistic regression. Four factors were statistically significant regarding falls: equilibrium impairment, gait disturbance, mobility in chair, and number of chronic diseases. Falls efficacy and equilibrium impairment were predicting factors for falls. Older women in rural areas are undertreated and have a high risk of experiencing falls and fall-related injuries. Nurses are on the front line in that they represent the initial level of care.

We compare electroabsorption modulators (EAMs) with multiple quantum wells (MQWs) based on InGaAs(P)/InP and InGa(Al)As/InAlAs material systems. We carefully choose the quantum-well structures so that the structures based on different material systems have similar band-offset energies and excition-peak wavelengths. Assuming the same light wavelength of $1.55{\mu}m$ , we show the transfer functions of EAMs with each quantum-well structure and calculate the escape times of photogenerated charge carriers. As the heavy-hole escape time of the quantum well based on InGaAs(P)/InP is much longer than those of photogenerated charge carriers of InGa(Al)As/InAlAs, the EAM based on the InGa(Al)As/InAlAs material seems to be more suitable for high-optical-power operation.

To prepare hydroxyapatite (HA)/poly(vinyl alcohol) (PVA) composite fibers with high processibility applicable to various biomedical fields, HA/PVA composite powders were synthesized through a coprecipitation method and then mixed with pure PVA in dimethyl sulfoxide at 90°C for 2 h to prepare wet-spinning dopes. HA/PVA solutions with HA contents of 0, 1, 3, 5, 10, and 15 wt % were analyzed with a rheometer to elucidate the effect of HA particles on the shear viscosities of the spinning dopes. The spinning dopes with pure PVA and an HA/PVA concentration of 12 wt % showed non-Newtonian flow behaviors, and as the HA content increased from 1 to 15 wt %, the shear viscosities increased simultaneously because of the complex formation between PVA chains, citric acid, and HA particles acting as crosslinkers. The increased viscosities of the spinning dopes diminished the breakage of PVA fibers and enhanced the spinnability. Through the addition of citric acid interacting with both PVA and HA particles, the aggregation of HA particles was suppressed, and it was possible to prepare HA/PVA composite fibers with smooth surfaces. An adequate amount of HA in the PVA fibers improved the thermal and mechanical properties of the fibers because uniformly dispersed HA particles interacting with PVA chains through hydrogen bonding in the PVA matrix complemented the structural defects. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The effects of three major molecular parameters of poly(vinyl alcohol)—the number-average degree of polymerization, degree of saponification, and syndiotactic dyad content—on the characteristics of poly(vinyl alcohol) films were investigated. Various poly(vinyl alcohol) films were prepared by a casting method. Then, the films were characterized with atomic force microscopy, differential scanning calorimetry, wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, and Instron instrumentation. On the basis of atomic force microscopy images and calculated average roughness values, it was determined that the surface roughness of poly(vinyl alcohol) films increased with increasing molecular parameters. The crystallinities obtained with differential scanning calorimetry and wide-angle X-ray diffraction analyses were also enhanced with increasing molecular parameters, especially the degree of saponification. The tensile properties were improved with higher molecular parameters. This might be ascribed to the fact that the higher the molecular parameters were, the stronger the hydrogen bonding was. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

We investigate the efficiency of an optical intensity modulator based on an electrically tunable $LiNbO_3$ reflection grating. Assuming a grating coupling coefficient and the waveguide propagation loss, waveguide length is varied to find its effect on the modulator slope efficiency and the device capacitance. With the low propagation loss of the $LiNbO_3$ waveguide, a very efficient optical intensity modulator can be achieved for a low frequency ( ${\sim}1GHz$ ) as long as the requirement for the grating coupling coefficient is satisfied.

A novel and broadband spiral chip antenna is presented in this paper. The size of the proposed antenna is 20 £ 3:2 £ 8mm 3 and is suitable to be embedded in a mobile phone as an internal antenna. Also, this antenna is designed to be installed at the newest mobile handset whose size is 40 £ 93mm 3 . The minimization of this antenna was realized by using spiral line structure on FR-4 of dielectric permittivity "r = 4:4. The proposed antenna is SMD type to be easily installed in the practical mobile handset. We use PCB technology which can allow this antenna to be produced massively with low cost. We can get the wideband operation in the upper band by overlapping high order resonances of branch structure. The measured bandwidth (VSWR< 3) of the designed antenna is 160MHz (980{1140MHz) in the lower band and 1230 MHz (1910{3140MHz) in the higher band. The antenna has been designed by a commercial software HFSS.

The molecular parameters of poly(vinyl alcohol) have enormous effects on its physical and chemical properties. Therefore, the surface characteristics of poly(vinyl alcohol) films are also determined by the molecular parameters. In this study, the dependence of the surface free energy on the molecular weight, degree of saponification, and stereoregularity of poly(vinyl alcohol) films has been evaluated with contact-angle measurements. The surface free energy of poly(vinyl alcohol) films increases with decreases in the syndiotactic dyad content, molecular weight, and degree of saponification. The polar component of the surface energy is not affected by the deviation of the molecular weight and degree of saponification very much. However, it decreases with increases in the syndiotactic dyad content and ranges from 11.64 to 4.35 dyn/cm.

Through the blending of a rigid polymer, sodium alginate (SA), and a flexible polymer, atactic poly(vinyl alcohol) (PVA), with various ratios of SA and PVA and through the electrospinning of SA/PVA solutions, SA/PVA blend nanowebs were successfully prepared. The structure and morphology of the SA/PVA blend nanowebs were investigated through a series of instrumental analyses. Through the examination of the morphological variations of each blend web, it was found that with only PVA, the electrospun nanowebs had very uniform and fine fiber structures, but the SA/PVA blend nanowebs had a mixture of large beads and fibers, which were generated with increasing SA content. A thermal analysis indicated that the endothermic peaks of the SA/PVA blend nanowebs decreased with an increase in the SA content. The SA content was determined by the observation of the changes in the SA peak intensity via Fourier transform infrared spectroscopy. The tensile strength decreased with increasing SA content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

To understand how each experimental parameter influences optoelectronic performances of InGaN-based LEDs, a method of systematic analysis that assesses the interrelations independently and quantitatively is absolutely necessary. Here, we introduce various characterization techniques to clarify the performance of LEDs and hidden severity of the detrimental effects, starting from the simple I-V measurement to more sophisticated temperature-dependent, spectroscopic, and LED efficiency measurements.

This study aimed to examine the effects of an empowerment program for hypertension self-management among rural older adults in South Korea.A pretest-posttest controlled design for a 12-month hypertension self-management program with assessments at commencement, 6 months and 12 months.Two subsistence farming areas.Subsistence farmers aged 65 and over: intervention group (n = 41) and control group (n = 36).Twelve-month empowerment program for hypertension self-management.Self-efficacy, social support, self-care behaviours, blood pressure control and renal function.There were significant interactions of group by time for self-efficacy (P 0.001) and self-care behaviour (P = 0.019). Blood pressure control at 12 months also showed a significant improvement in the empowered group compared with the control group (82.8% versus 56.8%, P 0.014). Other clinical outcomes, including systolic blood pressure (P = 0.006) and renal function (P 0.001), showed significant interactions of group by time.The empowerment program was effective for rural older adults with hypertension in South Korea. Further investigation of the relationships among core components of empowerment would be beneficial.

We investigate the low-frequency noise characteristics of InGaN-based light-emitting diodes with different forward leakage currents. It is found that the low-frequency noise characteristics are closely correlated with the forward leakage current.