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Forty mobile phones using active-matrix organic light-emitting diode (AMOLED) display glasses were tested as emergency dosimeters. The target material was a substrate glass for AMOLED layers located under a cover glass. The measured thermoluminescence (TL) emission spectra and glow curves showed that the glasses are all included in category A and B of a previous study, and the ratio between category A and B was about 8 to 2 for all measured samples. A pre-bleach was applied for 500 s, and TL signals were acquired by measuring the whole wavelength region by removing a UV filter (U-340). This was possible in the same measurement sequence by modifying the Riso TL/OSL DA-20 reader in such a way, that the LED module, used for pre-bleaching, is separated from the detector unit, used for the TL measurement. The signal increase after removing the filter was approximately 50 and 90 times for category A and B, respectively. The zero dose distribution with an average of 34 mGy and a minimal detectable dose (3σ) of 90 mGy was recorded for the forty mobile phones. The position distribution of zero doses across the entire substrate glass of a phone showed a standard deviation of more than 60% for three phone samples. Linear dose response from 30 mGy to 10 Gy was observed, and fading data of the TL signal from glass samples of 22 mobile phones assessed, for up to twenty days after irradiation.

Phototransferred thermoluminescence (PTTL) characteristics of LiF:Mg,Cu,Si, developed by the Korea Atomic Energy Research Institute, are presented as part of a simple and reliable method for dose re-evaluation that is compatible with routine personal dosimetry services. A 4.5 mm diameter 0.8 mm thick pellet-type thermoluminescence dosimeter (TLD) was used after dual-step thermal annealing at 300 °C for 10 min, and then at 260 °C for 10 min, in order to obtain thermal stability. For optimal UV illumination, samples were placed under a 254 nm ultraviolet (UV) lamp for 90 min. The PTTL signal was only lower than 2% that of the TL because of low residual signals in high-temperature deep traps. The difference of the PTTL signals between samples appeared up to two times, indicating high variation in the charge density of the deep traps between samples. Various thermal treatments were performed after each PTTL measurement to remove the residual PTTL signal. UV exposure at 250 °C for 20 min fully reset the residual PTTL signals to the same level as that after dual-step annealing. No degradation of the TL peak from repeated thermal treatments was observed until after the eighth treatment when a decrease was noticeable. The measured dose response of PTTL in the range of 1.14–51.3 mGy showed good linearity. The zero dose and minimal detectable dose of the PTTL were 1.36 ± 0.51 mGy and 1.53 mGy, respectively. The attenuation of the PTTL signal resulting from successive TL measurements was recorded to provide a correction factor for quarterly recorded TL measurements applicable to the dose re-evaluation of TLDs in routine personal dosimetry services.

N-type and p-type silicon were irradiated by neutrons and protons from low to high fluence range (108 − 1011 cm-2 for neutrons and 1010 − 1013 cm-2 for protons). The carrier recombination lifetime of each irradiated silicon was measured using a microwave photoconductance decay method, and the resistivity of the irradiated silicon was also measured. Both neutron and proton irradiation induced a similar lifetime at the same irradiation fluence. The defect formation rates were determined to vary with irradiation fluence from the inverse lifetime dependence on irradiation fluence. The sheet resistance was increased above a threshold fluence. The result shows that at least three different values of defect formation rate are present in the fluence range of 109 − 1015 cm-2, and it may have potential for practical use as low-dose dosimeters.

A thermally assisted optically stimulated luminescence protocol for the use of display glass samples from mobile phones as a fortuitous dosimeter was developed. Glass samples from 16 different mobile phones from the Samsung Galaxy series were used. The protocol consists of a prebleach with LEDs of 470 nm for 500 s and an OSL reading for 500 s at an elevated temperature. The decay curves were measured at different temperatures from 100 to 400 °C in an interval of 50 °C. A significant baseline increase in the decay curves was observed above 350 °C. For the TA-OSL below 300 °C, the dose response from 10 mGy to 10 Gy was linear and the signals were reproducible within 5% for six repeated readings. Compared with the residual thermoluminescence after an isothermal reading, the TA-OSL protocol showed lower zero doses at the given temperature. By increasing the temperature of the TA-OSL protocol from 100 to 300 °C, the minimum detectable dose increased from 17 to 70 mGy, but the fading rate reduced from 64% to 36% after 41 days from irradiation. In the optical stability test, strong reductions in TA-OSL signals were observed after exposures up to 1000 s with several light sources, and it was found that violet LEDs are more effective than blue LEDs for bleaching. As a result, the TA-OSL protocols investigated showed some improvements in terms of the lower minimum detectable doses and reduced fading rates compared with the prebleached thermoluminescence protocol.

A flame deflector is a structure that prevents damage to a launch vehicle and a launch pad due to exhaust plumes of a lifting-off launch vehicle. The shape of a flame deflector should be designed to restrain the discharged gas from backdraft inside the deflector and to reflect the impact to the surrounding environment and the engine characteristics of the vehicle. This study presents the five preliminary flame deflector configurations which are designed for the first-stage rocket engine of the Korea Space Launch Vehicle-II and surroundings of the Naro space center. The gas discharge patterns of the designed flame deflectors are investigated using the 3D flow field analysis by assuming that the air, in place of the exhaust gas, forms the plume. In addition, a multi-species unreacted flow model is investigated through 2D analysis of the first-stage engine of the KSLV-II. The results indicate that the closest Mach number and temperature distributions to the reacted flow model can be achieved from the 4-species unreacted flow model which employs H2O, CO2, and CO and specific heat-corrected plume.

In this work, we evaluate the use of silicon photomultipliers (SiPMs) as a suitable candidate for use as a photodetector for thermoluminescence measurements. The measurements were based on the Hamamatsu S13360-series with a pixel area of 3 × 3 mm2 and microcell pitches of 25 μm, 50 μm, and 75 μm, which were mounted on a Riso TL/OSL reader system with LiF:Mg,Cu,Si chosen as the reference TL material. Through the experiment, we showed that the typical TL glow curves can be obtained with SiPMs, despite their lower geometric efficiencies. We also demonstrated the dose response of SiPMs ranging from 6 to 66 mGy for three different photon threshold levels. The detection limit was approximately equal to 0.2 mSv, 0.08 mSv, and 0.17 mSv for 25 μm, 50 μm, and 75 μm SiPMs, respectively. More importantly, a sensitivity change and sensor temperature depending on a TL reading up to 260 °C was monitored on a sequential readout. Lastly, we discuss some of the possible benefits and limitations of SiPM-based TL measurements in comparison to PMT-based TL measurements.

The thermoluminescence of different chip cards was measured and analyzed for emergency dosimetry. Three SIM cards that are commonly found in mobile communication providers in South Korea and three smart IC cards that can be purchased online were used for the experiment. Chemical element analysis based on EDS mapping images was carried out and different weight percent of silica was found for each chip card. Glow curves of radiation induced signals through different combinations of optical filters showed blue or red emissions depending on chip cards. Sensitivity change resulting from the thermal stimulation was found to be 1.8 ± 0.27 and 0.5 ± 0.06 for the blue and red emission, respectively. In addition, signal fading resulted in more than 20% of the initial signal remaining 20 days after irradiation, when the 100–150 °C signal is used. Furthermore, the dose response was recorded from 50 mGy to 10 Gy for each chip card.

Phototransferred thermoluminescence (PTTL) of mobile phone display glass (category A) is systematically investigated to develop a robust measurement protocol for its emergency dosimeter usage after an incident with ionizing radiation. First, optimal readout parameters were defined by varying preheat temperature and holding time preceding violet exposure (405 nm). Next, the detection window of the PTTL measurement was adjusted to optimize the ratio between radiation-induced (RIS) and non-radiation-induced signals (nRIS) of the PTTL. Finally, the developed protocol determines PTTL after preheating to 400 °C and holding for 10 s was tested using the detection window centered at 340 nm. Dosimetric properties such as the PTTL reproducibility and dose response were investigated. PTTL signal stability tests showed that the violet PTTL signal originates from deeper and consequently more thermally stable traps. A signal loss of less than 10% after 10.6 days (254 h) storage was observed. Additionally, TL and PTTL spectra were recorded to investigate the luminescence emissions after beta and gamma irradiation and different UV exposures. PTTL emissions are similar to TL emission. Varying UV energy a qualitative comparison demonstrate that the RIS and nRIS PTTL signal intensities increase significantly with decreasing UV stimulation wavelength. In general, the developed PTTL protocol indicates better signal stability and thus some advantages over other techniques, however, further research is needed to test the potential of a new method for physical retrospective dosimetry.

Fading test using the single aliquot additive dose method with pulsed optically stimulated luminescence (SAAD-POSL method) was applied to core–disc samples extracted from heated red brick, tile, roof-tile, and toilet porcelain after X-ray and beta irradiation. From thermoluminescence measurements of each material, the optimal preheat condition of the SAAD-POSL method was first determined as 170 °C for 10 s. Fading characteristics of core–disc samples of heated red brick obtained using the SAAD-POSL method were similar to those of quartz grains (90–250 μm) obtained using the SAR-OSL method, regardless of the differences in the sample and radiation type. Fading evaluations of the core–disc samples of these building materials two weeks after irradiation showed that the equivalent dose (ED) decreased between 5% and 42%. The results indicate that the fading characteristics will be able to contribute to a more accurate estimation of the ED value using the SAAD-POSL method.

Radioluminecscence (RL), the light emitted from a material immediately upon ionizing radiation, has been used to detect the dose rate. On the other hand, thermoluminescence (TL) and optically stimulated luminescence (OSL) by the stimulation with the heat and light after irradiation have been used to find out the cumulated radiation dose. Because it was considered as effective to handle these three phenomena in integration to estimate the energy band structure of the material precisely, an algorithm for calculating the glow rapidly and consistently was developed in this study when three types of stimulations including irradiation are applied concurrently or sequentially. The deconvolution using this algorithm can decide the properties contained in the material more precisely because the glows from different stimulations are related frequently to the different aspects of the properties. The computer program to realize the deconvolution by means of these schemes was also developed and it was applied to the glow curves of RL and OSL from Al 2 O 3 :C to evaluate the efficiency of the developed algorithm.

To establish a fast assessment method of accidental dose, core disc samples were extracted from a heated red brick, roof tile, ceramic tile, and toilet porcelain, which are commonly used building materials. We examined the physical characteristics of pulsed optically stimulated luminescence (POSL) signals from these samples, and tested the reliability of the single aliquot additive dose (SAAD)-POSL method over a range of 7 Gy. In addition, when the SAAD-POSL method was applied, the minimum detectable dose (MDD) was as low as 0.01 Gy for the heated red brick, and the calculation time for an equivalent dose was as short as 2 h. This result indicates that the SAAD-POSL method is more effective as a fast assessment method of accidental dose than the SAR-OSL method.

An algorithm was developed to integrally handle excitation by radiation, relaxation and luminescence by thermal or optical stimulation in thermoluminescence (TL) and optically stimulated luminescence (OSL) processes. This algorithm reflects the mutual interaction between traps through a conduction band. Electrons and holes are created by radiation in the beginning, and these electrons move to the trap through the conduction band. These holes move to the recombination center through a valence band. The ratio of the electrons allocated to each trap differs with the recombination probability and these values also relevant to the process of luminescence. Accordingly, the glow curve can be interpreted by taking the rate of electron–hole pairs created by ionizing radiation as a unique initial condition. This method differs from the conventional method of interpreting the measured glow curve with the initial electron concentration allocated to each trap at the end of irradiation. A program using the Visual Studio's C# subsystem was made to realize such a developed algorithm. To verify this algorithm it was applied to LiF:Mg,Cu,Si. The TL glow curve was deconvoluted with a model of five traps, one deep trap and one recombination center (RC).

In case of a radiation emergency, thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements from materials in a mobile phone have been developed to enable classification of exposed individuals within a short period of time. A reconstructed dose from a mobile phone does not, however, correspond directly to a human body dose. Therefore, several studies were tried to convert a phone dose to a human body dose. Because of the difficulty in obtaining conversion factors experimentally, Monte Carlo simulations have been carried out using human phantoms for various accident situations. In recent years phantoms made of mesh have been developed to solve some problems in traditional voxel phantoms such as limited posture. In the present study, simulations using the GEANT4 computer code were performed to obtain conversion factors using mesh phantoms. The geometry of a mobile phone was designed, reflecting latest structures, and a display glass was selected as a dosimetric material due to its wide detection area with a high radiation sensitivity. Four different positions (chest, hip, thigh, and hand) of a mobile phone on the phantom were considered. In addition, six exposure conditions of anterior-posterior (AP), posterior-anterior (PA), left-lateral (LLAT), right-lateral (RLAT), isotropic (ISO), and rotational (ROT) exposure geometries and three different postures of standing, kneeling, and squatting were selected to reflect actual working situations. Three commonly used radiation sources (Iridium-192, Cesium-137, and Cobalt-60) were applied.

Thermoluminescence (TL) glow curves of LiF:Mg,Cu,Si were deconvoluted with the introduction of enhanced physical model which envisages that both electrons and holes, produced by ionization radiation and trapped at the respective traps, can be thermally released into the conduction and the valence band, respectively and the holes may also radiatively recombine with electrons at the electron recombination centers. The model is more generalized than the ordinary trap interaction model which only permits the traffic of electrons through the conduction band. An effective numerical analysis method was developed to calculate the glow curve to be compatible with the measured curves. The validity of the numerical method was verified through artificially generated TL glow curves for a wide range of trap parameters. In order to identify TL kinetics of LiF:Mg,Cu,Si with higher accuracy, its glow curves were deconvoluted for two more generalized models, namely, the Schon–Klasens model and the Chen–Pagonis–Lawless model as well as the ordinary trap interactive model. The parameters in the more generalized multi-trap multi-recombination center (MTMR) model were found to be consistent with the quasi-static approximation(QSA) method.

Environmental gamma-ray dose rates were measured by using ultra-high sensitive LiF:Mg,Cu,Si thermoluminescence dosimeters (TLDs) during short-term burial. The resultant gamma-ray dose rates were compared with those measured by using optically stimulated luminescence (OSL) of Al 2 O 3 :C and assessed by using HPGe spectrometer. Regardless of the short-term burial and the change of environmental conditions as well as the mismatch of the effective atomic number ( Z eff ) with the soil (mainly SiO 2 ), good agreement was observed between the doses measured by TLDs and OSL dosimeters or the assessed doses. LiF:Mg,Cu,Si TLD has been found to be an effective alternative for the measurement of environmental gamma-ray annual dose rates for use in optical dating.

An efficient computer program has been developed to deconvolute thermoluminescence (TL) glow peaks and optically stimulated (OSL) curves by employing a method of the interactive trap model (ITM). The program is designed to be used easily on the MS Windows-based computer with a graphical user interface. This program could be used to analyze the TL glow curves by using the traditional first-order kinetics (1OK), second-order kinetics (2OK), general order kinetics (GOK), mixed order kinetics (MOK) and the general approximation (GA) method as well as ITM. The program was tested with the generated data and the experimental results of deconvoluted TL glow curves of LiF TLD-100 by assigning five interacting traps and one recombination center. A complete version with full functionalities of this program can be downloaded from the web site http://physica.gnu.ac.kr/TLanal .

The most of the algorithms reported on the deconvolution of the OSL/TL glow curve is basically based on the one trap one recombination center (OTOR) model. In the OTOR model, each individual trap is considered to be independent with each other (mutually exclusive with each other), and the total glow curve is produced solely by the summation of the glow peaks generated from the luminescence emitted by the electrons in one individual trap when transferring to other trap(s). Therefore, there could be a major difference between the model and real physical process of the OSL/TL mechanism. Because the electrons being excited to be in the conduction band barely have past recollection of the original traps, it is widely believed that electrons in one trap can be easily transferred to other trap via the conduction band. Particularly in case of the OSL, the effects of mutual interactions among the traps could be more dominant than those in case of the TL. An algorithm, which can be used to numerically analyze the OSL/TL curves with reflecting the mutual interactions among the individual traps via the conduction band, is developed. This algorithm is able to promptly generate the glow curves for a system with numerous electron traps and recombination centers. Thus, the algorithm can be used to effectively deconvolute the glow curve of a given measurement data.

The LiF:Mg,Cu,Si thermoluminescence materials, recently developed at the laboratory, gain uprising popularity because the materials show several outstanding performance results such as high sensitivities for gamma radiation, flat energy responses with little fluctuation for photons, linear responses over the wide ranges of radiation doses and few residual electrons trapped in the holes. In this study, we investigated the impacts of the Mg concentration and the final thermal treatment conditions on the glow curve structure of LiF:Mg,Cu,Si material to enhance the ratio of high-temperature peak to main peak for the extended application of the two peaks in the high LET radiation dosimetry and in the high-temperature environment. Change in Mg concentration did not affect significantly the ratio of TL responses of high and main dosimetric glow peaks. With Mg concentration in the range from 0.35 to 0.45 mol% and a thermal treatment of 10 min in the range from 400 °C to 440 °C followed by the thermal treatment at 260 °C for 10 min (dual-step thermal treatment) resulted in the highest value of the ratio of TL response of high and main dosimetric glow peaks.

We determine the leading-order nonrelativistic quantum chromodynamics (NRQCD) matrix element 〈 O 1 〉 ϒ and the ratio 〈 q 2 〉 ϒ , for ϒ = ϒ ( n S ) with n = 1 , 2, and 3 by comparing the measured values for Γ [ ϒ → e + e − ] with the NRQCD factorization formula in which relativistic corrections are resummed to all orders in the heavy-quark velocity v . The values for 〈 q 2 〉 ϒ , which is the ratio of order- v 2 matrix element to 〈 O 1 〉 ϒ , are new. They can be used for NRQCD predictions involving ϒ ( n S ) and η b ( n S ) with relativistic corrections. As an application, we predict the two-photon decay rates for the spin-singlet states: Γ [ η b ( 1 S ) → γ γ ] = 0.512 − 0.094 + 0.096 keV , Γ [ η b ( 2 S ) → γ γ ] = 0.235 − 0.043 + 0.043 keV , and Γ [ η b ( 3 S ) → γ γ ] = 0.170 − 0.031 + 0.031 keV .

We investigated the thermal degradation of LiF:Mg,Cu,P (NTL-250) and LiF:Mg,Cu,Si (MCS) for the development of TL sheet. By thermogravimetry and differential scanning calorimetry (TG-DSC), the exothermic reaction was observed between 320 °C and 400 °C in MCS as well as NTL-250. The heat value of MCS was twice as large as that of NTL-250. This ratio corresponded with that of Mg amount in these TL materials measured by ICP-OES (inductively-coupled plasma optical emission spectrometry). X-ray diffraction (XRD) measurements were also carried out, and the peaks of MgF 2 phase were also observed in degraded MCS sample as well as NTL-250. Moreover, X-ray absorption near-edge structures (XANES) of Cu in these LiF TLDs were measured. The valences of Cu did not change before and after degradation. It indicates that the thermal degradation is caused by not Cu but Mg ion state change. The exothermic reaction is possible caused by the stabilization reactions, and then it was expected to correspond with MgF 2 precipitation. From these results, we concluded that the thermal degradations of these LiF TLDs are caused by the precipitation of MgF 2 .

A new method to analyze the thermoluminescence (TL) glow curve has been presented. It has been shown that this method is efficient and fast in generating the TL glow curves and can be adopted in a numerical curve fitting for obtaining the relevant TL parameters of a given TL glow curve data. This new method is based on a general approximation (GA) which assumes only that the concentration of the electrons in the conduction band is negligible when compared with the concentration of the electrons in the traps. The GA method has been tested against the reference glow curve data which was generated by the full iteration method without any prior approximation in the one-trap-one-recombination-centre model. By finding the best fit between the reference data and the curves generated by the GA method, the values of the kinetics parameters have been determined. Also, the general order kinetics (GOK) and the peak shape method have been examined. The fitted values of the activation energy and the initial concentration of electron by the GA method match reasonably well with the original value.

We construct a chiral lagrangian for pentaquark baryons assuming that the recently found Theta^+ (1540) state belongs to an antidecuplet of SU(3) flavor symmetry with J^P = (1/2)^(+-). We derive the Gell-Mann-Okubo formulae for the antidecuplet baryon masses, and a possible mixing between the antidecuplet and the pentaquark octet. Then we calculate the cross sections for pi^- p -> K^- Theta^+ and gamma n -> K^- Theta^+ using our chiral lagrangian. The resulting amplitudes respect the underlying chiral symmetry of QCD correctly. We also describe how to include the light vector mesons in the chiral lagrangian., 4 pages

Thermal treatment of In 0.5 Ga 0.5 As/GaAs quantum dot infrared photodetector (QDIP) structure has been carried out at 700 °C for 1 min with SiO 2 capping layer. Thermal treatment of In 0.5 Ga 0.5 As/GaAs QDIP structure induced a blue-shift in its photoluminescence (PL) spectrum by a 50 meV with a reduction of its intensity. The blue-shift in PL spectrum and the reduction in PL intensity is thought to be due to the interdiffusion of In and Ga at the interfaces of quantum dots (QDs) and GaAs barriers. The fabricated QDIP with thermally treated structure showed a red-shift in its photocurrent spectrum by a 22 meV from the photocurrent peak of 200 meV for as-grown QDIP, as a consequence of the blue-shift of QD bandgap.

InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0 x 10 10 cm -2 was observed by atomic force microscopy before the capping process. The influences of GaAs, In 0.53 Ga 0.47 As, and InP capping layers (5-10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.

The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0– 0.25 mol % ), Cu (0– 0.07 mol % ), Na and Si (0– 1.5 mol % ). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol % . The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol % . The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol % , Cu: 0.05 mol % , Na and Si: 0.9 mol % . The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C.

A calculation is presented of the radiative decay of the Upsilon(nS) into a bound state of bottom squarks. Predictions are provided of the branching fraction as a function of the masses of the bottom squark and the gluino. Branching fractions as large as several times 10^{-4} are obtained for supersymmetric particle masses in the range suggested by the analysis of bottom-quark production cross sections. Data are shown that limit the range of allowed masses. Forthcoming high-statistics data from the CLEO Collaboration offer possibilities of discovery or significant new bounds on the existence and masses of supersymmetric particles.

(Ti,Al)N coatings were deposited on M2 high speed steel substrates by inductively coupled plasma (ICP) assisted d.c. magnetron sputtering, and the structure and mechanical properties such as hardness, Young's modulus, wear resistance and adhesion strength were investigated. A TiAl alloy target (Ti/Al — 50:50 at.%) was sputtered in an Ar and N2 atmosphere with 400 W for d.c. magnetron power as well as 400 W for ICP power at 80 mtorr of working pressure. Both the hardness and adhesion strength of the coating were found to increase with increasing substrate bias voltage. The hardness value was higher than 6500 HK0.01 at the bias voltage higher than –50 V. The Young's modulus of the coating had a maximum value of approximately 450 GPa at −50 V. The wear properties of coatings also improved with the application of the substrate bias voltage. It was found that the grain size decreased (

(Ti 1-x Cr x )N coatings were deposited by an ion-plating technique in a reactor with two evaporation sources, Ti and Cr, which were evaporated by electron beam and resistance heating, respectively. The Ti and Cr concentrations in the coating were controlled by the Ti:Cr evaporation ratio. This study evaluated the wear and corrosion properties of the (Ti 1-x Cr x )N coatings. The wear properties were evaluated from the surface morphology, Cr content (x) in the coatings and the effects of the wear debris as well as the transferred layer on the wear behavior were also examined. The wear resistance was found to increase when Cr was added to TiN. It was found from corrosion experiments that, at vs. (SCE) < 0.5 V, all samples showed an electrochemical behavior similar to that of the CrN coating, irrespective of the Cr content (x) of the coatings. The coatings showed good passivity and the corrosion current was very small, regardless of the Cr content. Above 0.5 V, however, like the CrN coatings, the passivity disappeared and corrosion current increased abruptly.

Several neutron measuring devices were tested experimentally under the neutron fields characterized with two distinct kinds of thermal and fast neutron spectra. These neutron fields were constructed by the mixing of both thermal neutron calibration fields and fast neutron fields of AmBe source. Thermal neutron calibration fields were constructed using a graphite pile with the dimensions of 1.5 × 1.5 × 1.5 m 3 and eight AmBe neutron sources. In order to make the fraction of fast neutron fluence vary in each neutron fields, a 111 GBq of AmBe neutron source was placed additionally in thermal neutron fields from 50 to 200 cm at the reference position. These neutron spectra were measured by using a KAERI Bonner Sphere system and dosimetric quantity delivered to neutron dosemeters such as survey meters and a Thermo Luminescence Dosimeter (TLD) was determined from these measurement results.

A new computerized glow curve deconvolution (CGCD) algorithm for thermoluminescence(TL) and optically stimulated luminescence (OSL) is presented. The proposed approach can be adopted in a numerical curve fitting for obtaining the relevant trapping parameters of a set of glow data taken with both thermal and optical stimulation. This method is based on the one trap one recombination center (OTOR) model with minimal simplifying assumptions. To demonstrate the ability of the method, a new computer program has been developed and tested with some synthetic OSL data.

The short-distance coefficients for the color-octet 3S1 term in the fragmentation function for a gluon to split into heavy quarkonium states is calculated to order alpha_s^2. The gauge-invariant definition of the fragmentation function by Collins and Soper is employed. Ultraviolet divergences are removed using the MS-bar renormalization procedure. The longitudinal term in the fragmentation function agrees with a previous calculation by Beneke and Rothstein. The next-to-leading order correction to the transverse term disagrees with a previous calculation.

We report the results of low-frequency noise characterizations of back-gate n-channel ZnO nanorod field-effect transistor (FET) structure at room temperature. The noise in source–drain current was measured at zero gate bias and different source–drain biases. The power spectral density of noise current showed, in general, 1/f behavior with some variations. The power index of current dependence of the noise density at 10 Hz was about 1.5. The Hooge parameter obtained from the noise density at 10 Hz was comparable to or smaller than carbon nanotube transistors and much higher than those of silicon nanowires and conventional silicon transistors, indicating that special attention should be addressed to low-frequency noise in device applications. Possible noise sources are discussed with different models.

Soluble polypyrrole(PPy) was synthesized chemically by using ammonium persulfate and dodecylbenzene sulfonic acid as an oxidant and a dopant, respectively. It was found that the soluble PPy powder as well as the cast film contained a high concentration of free radicals detected by an electron paramagnetic resonance spectrometer. The polymer solution was cast into a film with a very fine reflective surface. A thin film with the light transmittance of 80% showed the surface resistivity of 25 kΩ/square displaying an increase in the resistivity only by 20 kΩ/square compared to the resistivity of a thick film. DC conductivity of the PPy film fitted nicely the quasi-one-dimensional variable range hopping model. The bulk electrical conductivity of the cast film increased by one order during initial heating to 200°C in air and changed little during isothermal heating at 200°C for 120 minutes. The conductivity kept a half of the initial increase after cooling from 200°C to room temperature. The surface resistivity of the film, however, was found to increase dramatically on heating at 200°C in air. Since the surface resistivity showed no change on heating in nitrogen atmosphere at 200°C, oxidation during heating caused the decrease in the conductivity of the polymer.

We present a model-independent measurement of B(D s − → Φπ − ) B(D 0 → K − π + ) by partially reconstructing the decay B 0 → D ∗+ D s ∗− . Using data collected with the CLEO II detector at CESR, we determine B(D s − → Φπ − ) B(D 0 → K − π + ) = 0.92 ± 0.20 (stat.) ± 0.11(syst.) . Our measurement of B ( D 0 → K − π + ) then gives B ( D s − → Φπ − ) = (3.59 ± 0.77 ± 0.48)%.

Using the CLEO II detector operating at the e + e − Cornell Electron Storage Ring (CESR), we present evidence for new decay modes of the Ξ c + into Ξ 0 π + , Ξ 0 π + π 0 , and Ξ 0 π + π − π + . The branching ratios of these decay modes, relative to Ξ c + → Ξ − π + π + , have been measured to be 0.55±0.13±0.09, 2.34±0.57±0.37, and 1.74±0.42±0.27, respectively.

We have studied the Cabibbo suppressed and color suppressed two-body decays B to ψϱ (ψω or ψa 1 ). Using a data sample of 5.12 million B decays collected with the CLEO II detector we find the 90% confidence level upper limits for branching fractions of B 0 → ψϱ 0 and B 0 → ψω to be 2.5 · 10 −4 and 2.7 · 10 −4 , respectively. We also update the branching fraction B − → ψπ − to be (5.6 ± 2.7) · 10 −5 .

It is pointed out that the radiative decays of a $\phi$ meson, $\phirho$ and $\phiom$, receive dominant contributions from the pseudoscalar ($P = \eta, \eta^{'}$) exchanges. Using the vector meson dominance model, we find that $B (\phirho) \approx 1.3 \times 10^{-4}$ and $B (\phiom) \approx 1.5 \times 10^{-5}$, which are mainly from the $\eta^{'}$ pole. Thus, these decays are well within the reach of the $\phi$ factory. Our estimates are a few orders of magnitude larger than the chiral loop contributions in the heavy vector meson chiral lagrangian, which is about ( a few ) $\times 10^{-9}$.

We present measurements of spectral moments extracted from the invariant mass distributions of the final states of hadronic τ decay products recorded in the CLEO detector. From a fit of theoretical predictions to the measurements of spectral moments and the total hadronic decay width of the τ, we determine the strong coupling constant and a set of non-perturbative QCD parameters. The strong coupling constant is measured to be α s ( m τ ) = 0.306 ± 0.024, which when extrapolated to the Z mass, yields α s ( M z ) = 0.114 ± 0.003.

We have found the first evidence for the Cabibbo suppressed, color suppressed decay B − → ψπ − in a data sample of 4 million B decays obtained by the CLEO detector at the Cornell Electron Storage Ring (CESR). The branching ratio is found to be (4.3±2.3)% of the Cabibbo allowed B − → ψK − decay mode, which is consistent with theoretical expectations.

Using the CLEO II detector at CESR, we have observed two charmed states, where the higher mass state decays to D0π+ and to D ∗0 π + , while the lower mass state decays to D ∗0 π + , but not to D0π+. The masses and widths were measured to be 2425±2±2 MeV/c2 and 26−7−4+8+4 MeV/c2 for the lower mass state, and 2463±3±3 MeV/c2 and 27−8−5+11+5 MeV/c2 for the higher mass state. Properties of these states, including their decay angular distributions and spin-parity assignments have been studied. The results of this analysis support the identification of these states as the charged L = 1 D 1 (2420) + and D 2 ∗ (2460) + , respectively. The isospin mass splittings between these states and their neutral partners have also been measured. This is the first full reconstruction of any decay mode of the D1 (2420)+ and the first observation of the decay of D 2 ∗ (2460) + to D ∗0 π + .

The dynamics of the decay D s + → φe + v e are studied using a sample of 474 events recorded by the CLEO II detector. A three dimensional fit to the decay angles and q 2 is performed to extract the ratios of form factors R 2 = A 2 (0)/ A 1 (0) and R v = V (0 )/ A 1 (0), where A 1 (0) and A 2 (0) are the two axial vector form factors and V (0) is the vector form factor evaluated at q 2 =0. By assuming the single pole parameterization for the form factors, we obtain: R 2 =1.4±0.5±0.3 and R v =0.9±0.6±0.3.

We have observed the previously unseen decay modes Λπ+π0, Σ0π+π0 and Σ0π−π+π+ of the charmed baryon Λc+, as well as Λc+→Σ0π+ observed previously by ARGUS. The branching ratios for these four decay modes relative to Λc+→pK−π+ are measured to be 0.73 ±0.09± 0.16, 0.36 ±0.09±0.10, 0.21±0.05±0.05, and 0.21±0.02 ±0.04, respectively. Using the recent CLEO measurement of the branching ratio for Λc+→pK− π+, these modes account for 6% of Λc+ decays.

Using the CLEO II detector at CESR, we have measured the ratio of branching fractions B (D + S → φl + ν) B (D + S → φπ + ) = 0.54 ± 0.05 ± 0.04 . We use this measurement to obtain a model dependent estimate of B (D + S → φπ + ) .

Using the CLEO II detector at CESR we observe 500 Λ l + pairs consistent with the semileptonic decay Λc+ → λ+ν We measure σ(e + e − → Λ + c X) · B(Λ + c → Λ l + ν l ) = 4.77±0.25±0.66 pb . Combining with the charm semileptonic width and the lifetime of the Λc we also obtain B(Λ+c → pK−π+). We find no evidence for Λ l + ν l final states in which there are additional Λ+c decay products. We measure the decay asymmetry parameter of Λ+c → Λe+νe to be αΛc = −0.89+0.17+0.09−0.11−0.05.

Using 1.16 × 106 B B events collected at the γ(4S) resonance by the CLEO Collaboration at the Cornell Electron Storage Ring (CESR), we have searched for decays of B mesons to exclusive two-body hadronic final states including a Ds+ or a D s ∗+ meson. We obtain the 90% confidence level upper limit β (B → D s (∗)+ π − + D s ∗ +p − + D s (∗)+ π 0 + D s (∗)+ η + D s (∗)+ p 0 + D s (∗)+ (ω) × β(D s + → φπ + ) −5 . We have also searched for the W-exchange decays, B 0 → D s (∗)− K (∗)+ .

Using the CLEO-II detector at CESR, we have observed the Ds1(2536)+ in the decay modes D s1 + →D ∗0 K + and D ∗+ K S + , and measured its fragmentation and production ratios. Using the helicity angle distribution of the daugter D ∗0 , we obtain new evidence for the assignment of 1+ for the spin and parity of the Ds1+. We also set upper limits on the decays D s1 + →D s ∗+ λ, D 0 K + and D+Ks0.

Using the CsI calorimeter of the CLEO-II detector, we have studied exclusive radiative decays of the ϒ(3S) to the χ (2P) states where the final state consists of two photons and two leptons (e + e − or μ + μ − , from either the ϒ(1S) or ϒ(2S)). We observe and measure branching ratios for the J =2 and J =1 χ b (2 3 P J ) states, and set upper limits for the J =0 state.