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The control rod neutron absorbers for light water reactors with extended control rod lifetime and enhanced safety are being developed. It is an innovative material concept that can extend the lifetime by reducing irradiation-induced swelling compared to the existing control rod neutron absorber materials by utilizing the oxide-based materials. Furthermore, it can enhance the safety by improving various characteristics such as oxidation, eutectic reaction, volatilization behaviors of neutron absorber material. First, the oxide-based composition composed of a combination of neutron absorbers and structure stabilizers has been designed as material candidates for neutron absorber materials for control rods. The preliminary manufacturability test of the designed neutron absorber material candidates, and it has been confirmed a possibility that the designed material candidates can be fabricated using the conventional ceramic manufacturing process. In addition, the neutronic calculation/analysis and various out-of-pile tests (neutron absorber phase stability, oxidation and corrosion resistance, interaction and eutectic reaction between neutron absorber material and control rod tube material, melting behavior, etc.) are in progress. It has been also preparing the in-reactor swelling test of the selected material candidates at the HANARO research reactor in KAERI.

Recent X-ray free electron lasers based on a high-energy high-current linear accelerator, such as the Pohang Accelerator Laboratory (PAL-XFEL) uses a third harmonic radio-frequency (RF) linearizer system to improve the laser's longitudinal beam quality. Because the X-ray free electron laser at the PAL-Xfel uses 2856 MHz RF accelerators, we realized a RF linearizer of 11.424 GHz which afforded a 50 MW RF power by using a SLAC X-band klystron. Operation of the X-band klystron required an X-band amplifier with a 1 kW level at the specified frequency of 11.424 GHz. We tested two types of X-band amplifier, a traveling wave tube amplifier and a solid state amplifier. In this work, we present the test results and discuss the features, especially focusing on the X-band solid state amplifier.

Thermally conductive microcell UO2 pellets in which metallic networks enclose UO2 granules have been highlighted due to their enhanced thermal performance for a potential candidate of accident-tolerant fuels. However, studies on thermal expansion effects of microcell UO2 pellets are still lacking. Here, stress and strain distributions of the fabricated UO2-5 vol% Mo microcell pellet under thermal expansion were investigated. After we confirmed that the numerical results agreed well with experimental measurement in terms of linear thermal expansion, stress and strain distributions of the microcell pellets were calculated under maximum stress and maximum strain conditions. As a result, formation of Mo network decreases the maximum hoop stress and the maximum radial strain of UO2 pellets by 50.9% and by 29.4%, respectively under a linear heat generation rate of 200 W/cm. Finally, the UO2-5 vol% Mo microcell pellet can decrease the maximum cladding stresses by 36.7%.

Resonant elastic X-ray scattering has been widely employed for exploring complex electronic ordering phenomena, like charge, spin, and orbital order, in particular in strongly correlated electronic systems. In addition, recent developments of pump-probe X-ray scattering allow us to expand the investigation of the temporal dynamics of such orders. Here, we introduce a new time-resolved Resonant Soft X-ray Scattering (tr-RSXS) endstation developed at the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL). This endstation has an optical laser (wavelength of 800 nm plus harmonics) as the pump source. Based on the commissioning results, the tr-RSXS at PAL-XFEL can deliver a soft X-ray probe (400-1300 eV) with a time resolution about ~100 fs without jitter correction. As an example, the temporal dynamics of a charge density wave on a high-temperature cuprate superconductor is demonstrated., 7 figures, 2 tables

In recent years, precision stages, which are widely used in many industrial fields, have been required to have a higher speed, larger size, and higher precision to help realize higher productivity and product quality. High-performance positioning techniques for inspection and production equipment are classified as one of the most challenging technologies. Vibration control is crucial to realize high-precision positioning technologies. In a precision system, various vibrations exist, which act as disturbances and can degrade the system performance. Minimizing the vibrations generated by the system can, thus, help improve the accuracy of system positioning. This paper proposes a hybrid active mount module for a precision stage. The developed module improves stage performance by reducing the base vibration arising from the floor, minimizing the vibration caused by the driving linear motors of the precision stage, and reducing the settling time by compensating the offset displacement due to the nonlinearity of the passive mount during stage driving. The prototype design is presented herein, and the experimental results demonstrate the potential of the developed device. The developed system is expected to effectively improve the stage performance by controlling the various causes of vibration.

We designed a 20-MV S-band traveling-wave deflecting structure to measure the bunch length of the electron beams for the PAL-XFEL. Since the start of commissioning of all RF systems of the PAL-XFEL on 12 April 2016, two out of three fabricated structures are currently being operated; one each in the hard X-ray and the soft X-ray branches. These deflecting structures were carefully tuned by using a 4-m-long nodal phase scanner in a precisely temperature and humidity controlled cleanroom considering the phase predictions calculated using RF field solvers. We carried out RF conditioning and beam commissioning with highly-stable high-power S-band RF systems and an EPICS-based control system. We briefly present our design of S-band deflecting structure and discuss the test results, including the results of the RF and the beam measurements.

To reduce fission gas release under both accident conditions and normal operation, Korea Atomic Energy Research Institute has developed a metallic micro-cell pellet following the 2011 Fukushima accident. One concern, however, about the metallic micro-cell pellet is that due to the presence of metallic wall that reduces both temperature and gas release, its capability of higher gas retention could result in increased gaseous swelling, leading to earlier pellet-to-cladding gap closure than the conventional UO2 pellet. To analyze and compare the gap closure in two fuel rods in which two kinds of pellets, UO2 and metallic micro-cell, are loaded into each of the two identical Zr claddings, we developed a model to estimate gaseous swelling in the two pellets. Then considering mainly different gaseous swelling and thermal expansion by different temperature profiles in the two pellets, we compared the pellet-to-cladding gaps as a function of burnup for the case where they would be irradiated with the same constant linear power of 30 kW/m up to 60 MWd/kgU. Due to both reduced gaseous swelling and lower thermal expansion, gap closure in the fuel rod loaded with the metallic micro-cell pellet is expected to be delayed by 6–16 MWd/kgU compared with the one loaded with the UO2 pellet, implying pellet-cladding mechanical interaction occurrence would also be postponed by the same degree. We note that the result of this approach is preliminary until confirmed by measured data from metallic micro-cell pellets irradiated up to high burnup.

Gallium nitride (GaN) light-emitting diodes (LEDs) on silicon (Si) substrates have been highlighted due to the potentials to achieve significant cost reduction, effective thermal management, and highly directional light emission, by replacing the conventional sapphire substrates with the opportunities to adopt the well-established Si-based semiconducting technologies. However, large mismatch of physical properties between Si and GaN considerably lowers the material quality of GaN and the corresponding device performances. Herein, we employ three-dimensional faceted Si surfaces (3D faceted Si) to effectively release the generated strain energy during the hetero-epitaxial growth of GaN on Si for fabricating high performance GaN-on-Si LEDs. The resulting outcome not only includes the unique morphology of 3D tetrapodal GaN layers on 3D faceted Si to form space-filling arrays for efficient device utilization, but also contains the excellent material quality of the hetero-integrated GaN layers, comparable to that grown on planar sapphire substrates. Consequently, those 3D tetrapodal GaN-on-Si LEDs exhibit the excellent light extraction characteristics due to their shapes to effectively suppress total internal reflection of generated light. In addition, the anisotropic formation of active layers in the 3D tetrapodal GaN-on-Si LEDs performs multi-color emission characteristics with tunable color capabilities.

The thermal performance of composite UO2 fuel pellets, as a potential candidate for accident-tolerant fuels, is being attempted to be actively enhanced by employing high conductivity materials as additives. Herein, we numerically investigated the thermal performance of UO2 – 3 vol% Mo microplate fuel pellets with microsized Mo plates to enhance the corresponding thermal conductivity in the fuel radial direction. UO2 – 3 vol% Mo microplate fuel pellets were successfully fabricated through the conventional sintering process, and the characteristics of the thermal conductivities were investigated in terms of the shape factor of the Mo microplate, amount of Mo content, and arrangement (such as the spacing and angle) of the Mo microplates in the UO2 fuel pellets. The results demonstrated that the arrangement of the Mo microplates parallel to the main heat transfer flow direction could further enhance the thermal conductivity. The numerical results pertaining to the calculation based on the microplate arrangement exhibited a reasonable agreement with the measured values, and the thermal conductivity was noted to be enhanced by 47% at 1000 °C compared to that of UO2. Moreover, the UO2 – 3 vol% Mo microplate fuel pellets with enhanced thermal conductivities could reduce the maximum pellet temperature by 149 °C compared to that of the UO2 pellet under a linear heat generation rate of 200 W/cm.

The hard X-ray free-electron laser at the Pohang Accelerator Laboratory (PAL-XFEL) in the Republic of Korea achieved saturation of a 0.144 nm free-electron laser beam on 27 November 2016, making it the third hard X-ray free-electron laser in the world, following the demonstrations of the Linac Coherent Light Source (LCLS) and the SPring-8 Angstrom Compact Free Electron Laser (SACLA). The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis has allowed reliable operation of PAL-XFEL with unprecedented temporal stability and dispersion-free orbits. In particular, a timing jitter of just 20 fs for the free-electron laser photon beam is consistently achieved due to the use of a state-of-the-art design of the electron linear accelerator and electron-beam-based alignment. The low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL will be an extremely useful tool for hard X-ray time-resolved experiments. The Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) in South Korea has now entered operation with a timing jitter of just 20 fs.

In order to achieve beam acceleration to the beam energy of 10 GeV at the end of its 716 m-long linear accelerator (Linac), the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) is going to operate the Stanford Linear Accelerator Energy Doubler (SLED) at the maximum klystron output peak power of 80 MW, with a pulse length of 4 μs, and at a repetition rate of 60 Hz. The original SLED that had been used in Pohang Light Source-II (PLS-II) can no longer sustain such a high-power operation because excessive radiation caused by RF breakdown has been frequently detected even at the lower klystron peak power during the PLS-II operation. Therefore, a new SLED is designed by modifying both the 3-dB power hybrid and the waveguide-cavity coupling structure of the original SLED where the excessive radiation has been mainly detected. The finite-difference time-domain (FDTD) simulation in the CST Microwave Studio shows that the new SLED has a peak electric field and a surface current lower than those of the original SLED at the same level of the RF input peak power, which would secure stable high-power operation. All of the 42 SLEDs in the PAL-XFEL Linac are newly fabricated and installed. During the RF conditioning of the PAL-XFEL Linac, no significant vacuum and radiation issue was found in the new SLEDs. Finally, the accelerated electron beam energy of 10 GeV obtained at the end of the PAL-XFEL Linac verified that the RF performance of the new SLED is stable.

The hard XFEL operation procedure established at PAL-XFEL using e-BBA and incorporating undulator radiation spectrum analysis proved to be highly reliable and robust, and essential for the variable-gap undulators. The state-of-the-art design of the electron linear accelerator along with the reliable FEL lasing procedure has allowed reliable operation of PAL-XFEL with unprecedented stability in terms of orbit, energy, and timing; FEL position stability: 8 ~ 9% of beam size, FEL power stability: ~ 4.0% rms, FEL timing jitter: < 20 fs, which can obviously make users’ experiments more successful. And the undulator optics matching using the wire-scanner-based emittance measurement is extensively used to maximize the FEL intensity even at higher photon energy up to 14.5 keV, which is the brightest FEL at this photon energy that has ever been achieved in the world.

The PAL-XFEL has a 716m hard X-ray linac and a soft X-ray linac. There are 51 modulators, 178 accelerators structures, and the pulse energy doublers in the linac. The construction was completed at the end of 2015. After RF-conditioned for one year in 2016, The machines provide to the user service in 30Hz, $\pmb{4\mu} \mathbf{s}$ on hard x-ray. The pulse energy doubler is one of the important devices that increases the peak output power of the 2.856 GHz high frequency generated by the Klystron. The device receives a $\pmb{4\mu}\mathbf{s}$ length for high frequency power from the klystron and reduces the length of the pulse output to Iμs, However, the maximum peak output power can be increased four times. The total of 42 pulsed energy doublers are installed in the PAL XFEL RF system. It consists of two resonators and one 3dB coupler. The amount of heat generated depends on the operation repetition frequency. There are two ways to prevent it. Change the water temperature of the cavity cooling system or adjust the volume of each resonator. We installed a system that can remotely adjust the resonator volume by connecting a motor to each resonator. This paper reports the results of tuning at 30Hz. We also experimented a few to prepare for 60Hz operation. It reports the results of adjusting the resonance frequency by changing the volume and the cavity cooling temperature using a remote cavity tuning system.

A thin transparent wearable patch with silicon nanoneedles is developed for efficient interface with biological cells and tissues., Vertically ordered arrays of silicon nanoneedles (Si NNs), due to their nanoscale dimension and low cytotoxicity, could enable minimally invasive nanoinjection of biomolecules into living biological systems such as cells and tissues. Although production of these Si NNs on a bulk Si wafer has been achieved through standard nanofabrication technology, there exists a large mismatch at the interface between the rigid, flat, and opaque Si wafer and soft, curvilinear, and optically transparent biological systems. Here, we report a unique methodology that is capable of constructing vertically ordered Si NNs on a thin layer of elastomer patch to flexibly and transparently interface with biological systems. The resulting outcome provides important capabilities to form a mechanically elastic interface between Si NNs and biological systems, and simultaneously enables direct imaging of their real-time interactions under the transparent condition. We demonstrate its utility in intracellular, intradermal, and intramuscular nanoinjection of biomolecules into various kinds of biological cells and tissues at their length scales.

U3Si2 is being considered as a potential fuel candidate for water cooled power reactors. Herein, we examine the oxidation behavior and phase separation of U3Si2 under flowing steam to understand the fuel degradation mechanism in the event of a steam ingress through cracks in cladding. The weight gain, microstructure evolution, and phase change after isothermal annealing were investigated for spherical U3Si2 particles fabricated by centrifugal atomization. Equilibrium oxide products and their compositional changes with increasing degree of oxidation were predicted using thermodynamic calculations and compared with experimental results. It was seen that the oxidation reaction of U3Si2 in steam begins with dissociation into UO2 and Si, followed by Si being partially oxidized to amorphous SiO2. From these results, an oxidation mechanism of U3Si2 in steam is proposed. The theoretical volume expansion of U3Si2 during the steam oxidation was estimated and its impact on fuel performance is also discussed.

Metallic micro-cell UO 2 pellet with high thermal conductivity has received attention as a promising accident-tolerant fuel. Although experimental demonstrations have been successful, studies on the potency of current metallic micro-cell UO 2 fuels for further enhancement of thermal performance are lacking. Here, we numerically investigated the thermal conductivities of micro-cell UO 2 Mo pellets in terms of the amount of Mo content, the unit cell size, and the aspect ratio of the micro-cells. The results showed good agreement with experimental measurements, and more importantly, indicated the importance of optimizing the unit cell geometries of the micro-cell pellets for greater increases in thermal conductivity. Consequently, the micro-cell UO 2 Mo pellets (5 vol% Mo) with modified geometries increased the thermal conductivity of the current UO 2 pellets by about 2.5 times, and lowered the temperature gradient within the pellets by 62.9% under a linear heat generation rate of 200 W/cm.

Deploying high thermal conductive materials as additives to UO2 has been highlighted due to their enhanced thermal performance as a potential candidate of Accident-Tolerant Fuels (ATFs). Herein, we investigate thermomechanical behaviors of UO2 – 5 vol% Mo fuel pellets with a sandwiched configuration where Mo layers are positioned on the top and bottom of a UO2 part. The successfully fabricated sandwich-type UO2 fuel pellets with an inclusion of 5 vol% Mo by using a conventional sintering method exhibit up to 3.0 and 2.5 times higher effective thermal conductivities at 800 °C than standard UO2 and dispersion-type UO2 – 5 vol% Mo fuel pellets, due to the effective heat transfer characteristics in the Light Water Reactor (LWR) fuel. Accordingly, the sandwich-type fuel pellets not only effectively reduce the thermal stress gradients across the pellets, but also significantly decrease the maximum tensile hoop stresses of fuel pellets. Finally, the radial deformation behaviors of the sandwich-type fuel pellets are also investigated under a simulated irradiation condition, showing that an hourglass-shaped deformation of UO2 pellets are considerably mitigated.

Lithium nitrate has been highlighted as a high temperature phase change material with the melting temperature of ~256 °C for the applications of thermal energy storage. However, low thermal conductivity and corrosive property of lithium nitrate needs to be improved for wide applications. This report experimentally investigates thermal properties of a phase change composite consisting of lithium nitrate and porous copper oxide nanowires integrated on folded meshes. Specifically, porous copper oxide nanowires vertically aligned on the folded copper meshes with desired shapes are synthesized by carrying out chemical solution growth and subsequent heat treatment. Then, lithium nitrate is infiltrated in the network of the thermal conductive fillers under vacuum conditions. Our platform can provide a flexible geometrical configuration to enhance thermal performance by modifying the folded geometries to the target objects. As a result, the fabricated phase change composites with 7 vol% of filling materials exhibit the 6.7 times higher thermal conductivities than pure lithium nitrate, showing the excellent thermal transport by the fillers in the composite. Moreover, the porous copper oxide nanowires exhibit excellent anti-corrosive properties to lithium nitrate for stable operation under repeated phase change processes. Finally, the phase change composite heat storages exhibit the 1.3 times faster thermal charging and discharging characteristics than pure lithium nitrate ones.

This study reports fabrication of layer-by-layer assembled phase change composites by locating phase change material (paraffin) into the network of aluminum meshes after which they are sandwiched by ultra-thin graphite sheets. The fabricated phase change composites with 90 vol% phase change materials exhibit up to 285 times higher thermal conductivities than bare paraffin with directional characteristics of heat flow due to the incorporation of graphite sheets which have anisotropic thermal conductivities. We further examine thermal performance of bare paraffin, aluminum, and phase change composite heat spreaders by monitoring maximum hot-spot temperatures under different cooling conditions. As a result, the phase change composite heat spreaders perform superior cooling capacities to bare paraffin and aluminum heat spreaders in high power intensity conditions with high heating and low cooling rates by lowering their hot-spot temperatures by up to 121 °C and 7 °C, respectively. It is enabled by the effective utilization of thermal capacitive effects of phase change materials with significantly enhanced thermal conductivities. This study represents an effort to develop novel heat spreaders with enhanced cooling capacities for the potential applications of high thermal budgets with limited cooling resources.

PAL-XFEL utilizes a three-chicane bunch compression (3-BC) scheme (the very first of its kind in operation) for free-electron laser (FEL) operation. The addition of a third bunch compressor allows for more effective mitigation of coherent synchrotron radiation during bunch compression and an increased flexibility of system configuration. Start-to-end simulations of the effects of radiofrequency jitter on the electron beam performance show that using the 3-BC scheme leads to better performance compared with the two-chicane bunch compression scheme. Together with the high performance of the linac radiofrequency system, it enables reliable operation of PAL-XFEL with unprecedented stability in terms of arrival timing, pointing and intensity; an arrival timing jitter of better than 15 fs, a transverse position jitter of smaller than 10% of the photon beam size, and an FEL intensity jitter of smaller than 5% are consistently achieved.

We report an overview of soft X-ray scientific instruments and X-ray optics at the free electron laser (FEL) of the Pohang Accelerator Laboratory, with selected first-commissioning results. The FEL exhibited a pulse energy of 200 μJ/pulse, a pulse width of

The purpose of this study was to examine the relationship between the oral health behavior and oral health belief of transportation workers. The subjects in this study were 270 selected taxi drivers who engaged in the taxi transportation industry in Jeollabuk-do. They were selected by convenience sampling. To determine the influence of their general characteristics and oral health belief on scaling experience and oral health education experience, a logistic regression analysis was made. And a multiple regression analysis was made by selecting general characteristics and oral health behavior as independent variables and by selecting oral health belief as a dependent variable. A statistical package SPSS for Windows ver. 12.0 was employed to make all the statistical analysis. As a result of making the logistic regression analysis, benefit that was one of the subfactors of oral health belief had something to do with oral health education experience, and the subfactors that exerted an influence on scaling experience were benefit, susceptibility and barrier. When the multiple regression analysis was carried out to find out influential factors for oral health belief, monthly mean income had an impact on susceptibility and barrier among the subfactors of oral health belief, and self-rated oral health status affected seriousness and barrier. There were differences among the taxi drivers in oral health belief according to their own characteristics, and oral health belief was linked to oral health behavior. Therefore oral health belief and oral health behavior should be taken into account when it's planned to promote the oral health of taxi drivers.

We developed an S-band traveling-wave accelerating structure for the Pohang Accelerator Laboratory’s X-ray free-electron laser (PAL-XFEL), and we fabricated and tested a full-scale prototype. In order to reduce the field asymmetry inside the coupler cavity, we used the SUPERFISH code and the CST MWS electromagnetic field solvers to design the constant-gradient traveling-wave accelerator to use quasi-symmetric single-feed racetrack couplers. The RF measurement results indicate that the accelerating gradient of the prototype structure is as high as 27 MV/m for an input RF power of 65 MW.

One hundred seventy-two accelerating structures are required for the Pohang Accelerator Laboratory X-ray free-electron laser’s (PAL-XFEL’s) 10-GeV main linear accelerator. So far, we have purchased 80 structures from Mitsubishi Heavy Industry (MHI), which have quasi-symmetric couplers in the accelerating structure to reduce the quadruple and the sextuple components of the electric field in the coupling cavity. High-power tests have been conducted for the first structure of the MHI structure, and Research Instruments (RI) has developed a 3-m long accelerating structure that has an operating frequency of 2856 MHz and in/out couplers of quasi-symmetric racetrack shape for the PAL-XFEL linear accelerator. This structure also has been tested by PAL and RI in the Pohang accelerator laboratory (PAL) to check the maximum available electric field gradient. We will describe the test results of these structures and the current status for the fabrication of the other accelerating structures in this paper.

We report a facile method for fabricating polymer hierarchical structures, which are the engineered, ratchet-like microscale structures with nanoscale dimples, for the directional movement of droplets. The fabricated polymer hierarchical structures with no surface modifier show hydrophobic, superhydrophobic, or omniphobic characteristics depending on their intrinsic polymer properties. Further treatment with a surface modifier endows the polymer surfaces with superomniphobicity. The fabricated polymer substrates with no surface modifier enable the movement of the water droplet along the designed track at almost no inclination of the substrate.

Objectives :Thepurposeofthestudyistodevelopaprogramoforalhealtheducationbyinvestigatingtheuseandeducationalneedsonauxiliaryoralcareproduc tsinemployees.Methods :Aself-administeredquestionnairewasfilledoutby321emplo yeesintheheavyindustryinYoungam-gun. CorrespondingAuthor SinYoungParkDepartmentofhealthscienceGraduateschoolofhealthenvironmentWonkwanguniversity,songamronamgu,gwangju,503-742,Korea.Tel:+82-62-360-5967+82-10-3093-3532E-mail:sy0914p@hanmail.netResults:Mostoftheemployeesusedthedentalfloss.Approximately72.6%answere dthattheydidnotreceivetheeducationonauxiliaryoralcareproductsand81.3 %ofsubjectsdidnotparticipateintheeducationfortheauxiliaryoralcareproducts.Iff reeeducationisprovided,66.5%wouldreceivetheauxiliaryoralcareproductsuseeducation.Thebe stwaysofeducationwereexpertlectureandbrochure.Conclusions :Theemployeeswantthecontinuingeducationfortheuseofaux iliaryoralcareproducts.Theoralhealthpromotionprogrammustbefocusedontheact ivepracticeoforalhealthbehavior.KeyWords :auxiliaryoralcareproducts,employees색인:,보조구강관리용품근로자

The 3-dB power splitter to be used in the Pohang Accelerator Laboratory X-ay Free-electron Laser (PAL XFEL), which have been under construction since 2011, must operate at a peak power of 400 MW and a repetition rate of 120 Hz. For these operational conditions of the PAL XFEL, the old 3-dB power splitter that was originally designed to be used in the PLS LINAC will most suffer from RF breakdown. Therefore, for the new 3-dB power splitter, the original design has been modified to reduce the field gradient and the surface current. The new 3-dB power splitter is designed by using a finite-difference time-domain (FDTD) simulation. We have fabricated a prototype, and the result of a high-power test indicates that the RF performance of the new 3-dB power splitter satisfies the specifications of the PAL XFEL S-band LINAC RF system.

The directional coupler to be used in the Pohang Accelerator Laboratory X-ray free electron laser (PAL XFEL) under construction since 2011 must satisfy the conditions for operating at a peak power of 400 MW and a repetition rate of 120 Hz. In these operational conditions of the PAL XFEL, the old Bethe-hole directional coupler that was originally designed to be used in the Pohang Light Source linac is more likely to inflict damages on the ceramic window that cause vacuum leaks. Therefore, for the new Bethe-hole directional coupler, the original design has been modified to use a conventional N-type RF vacuum feedthrough for vacuum sealing instead of the ceramic window. The new Bethe-hole directional coupler is designed by using a finite-difference time-domain simulation. We have fabricated a prototype, and the result of a high-power test indicates that the RF performance of the new DC satisfies the specifications of the PAL XFEL S-band Linac RF system.

The Stanford Linear Accelerator Energy Doubler (SLED) system for the PAL (Pohang Accelerator Laboratory) XFEL (X-ray Free Electron Laser) is required to operate with an RF input power of 80 MW and a pulse width of 4 µs. Due to the high radiation dose from RF breakdown at coupling holes and power dividers in such a high-power operation, a modification of the original SLED system is called for. We designed a new SLED system with a biplanar 3-dB power divider and dual side-wall coupling-irises by using a finite-difference time-domain (FDTD) simulation. The new SLED system proved to be a good solution that reduced the probability of RF breakdown in high-powered operations due to the reduced field gradient and surface current. In addition, a time-domain simulation was carried out to estimate the performance of new SLED system and to study the process for the question of the SLED output waveform.

The fate and transport of contaminants induced into a deep and stratified reservoir after flood events are largely governed by the thermal structure of the reservoir. For last two decades, diverse three-dimensional (3D) hydrodynamic and water quality models have been developed and applied for supporting reservoir water quality management, but validation of the models to simulate stratification processes in deep and dendritic reservoirs in monsoon climate region is rare. The study was aimed to evaluate the performance of a 3D hydrodynamic model, ELCOM, in a deep and dendritic reservoir located in Geum River of Korea for simulating heat fluxes and stratification processes. The model was applied to two different hydrological years; dry (2008) and normal (2009), and validated against extensive field data. The model showed satisfactory performance in simulating the water temperature profiles within the acceptable errors at all monitoring stations. The turbid density flows induced by flood events incurred a significant modification of the structure of thermal stratification, and which was well replicated by the model. In addition, the model reasonably captured the instant surface vertical mixings that observed during flood and strong wind events. The net heat flux across the free surface was positive (gain heat) from April to September, which resulted in the development of thermal stratification in the reservoir.

Objectives : The purpose of this study was to examine the oral health behavior of shipbuilding company workers in some regions in a bid to provide information on the oral health plans for industrial fields. Methods : The subjects in this study were 310 workers in 10 shipbuilding companies and suppliers in Jeolla Namdo Province, on whom a self-administered survey was conducted. Results : 1. Concerning general information about the subjects who participated in the research, gender was possessed 94.8% by men and 5.2% by women. Age was the largest in 31~40 years old with 44.2%. Marital status was the largest in the married with 64.5%. It was the largest in under high school graduate with 71.9% for academic background, in 2,000,000 won~3,000,000 won with 49.0% for monthly family income, and in cooking with 33.9% for work field. 2. Research subjects` toothbrushing time was indicated to be the largest in after having breakfast. It was indicated to be twice a day with 41.3% for toothbrushing frequency. 90.3% of the respondents are not using auxiliary oral hygiene devices. 3. Recognition on periodontal health status was found larger in workers whose response was that their own periodontal health status is `healthy` than workers who responded that their status is `not healthy.` Workers, who don`t have subjective symptom on periodontal status, were indicated to be larger. 4. Ratio of subjects with tooth scaling experience accounted for 59.7%. The ratio of tooth scaling experience was indicated to be different depending on academic background and monthly family income. Conclusions : Academic credential, monthly family income and the line of work were identified as the main factors to affect oral health care of the shipbuilding workers. Oral health education and dynamic implementation of corporate oral health promotion which are designed to meet the needs of workers are required.

This study was survey about the oral health knowledge and behaviors with alternative school students results are as follow. 1. As a result of this study, toothbrushing period was the largest with 29.5% in students of doing `after dinner.`, The appearance of taking food of containing sugar for preventing caries was the largest with 53.3% in students who responded as saying of `tending to be not so.`, A path of acquiring information on oral health knowledge was the highest with 72.0% in neighbor and family. 2. A review of Toothbrushing frequency per day, this was the largest with 45.2% in execution with 3 times, There were difference depending on grade, sex, a path of go to school, come home from school, financial status. 3. A review of the oral hygiene auxiliary supplies, this was the largest with 64.5% in students who used it, There were difference depending on the higher school year in the high school, financial status. 4. as a result of taking snack of students, it was similar to two or three times with 37.7%, one time with 34.6% per day, there was difference depending on financial status. taking drink was similar to non-drink with 38.0%, one time with 37.7%, there were difference depending on grade, financial status in a statistics.

In this study, impact elastic-wave method was performed at the bottom surface of RC slab cut from an existing highway bridges to survey the horizontal cracks. Before measurements by impact elastic-wave method, impact response analysis was applied to determine optimal steel ball diameter, distance between impact point and receiving point of elastic-wave. Efficiency of analysis-aided impact elastic-wave method was confirmed by drilling and observing the interior of the RC slab by stick scanner. Evaluation results by this method agreed well with results of visual inspection. Thus, validity of the analysis-aided impact elastic-wave method on detection of horizontal cracks in RC slabs of highway bridges was demonstrated.

The relationship between discharge (Q) and suspended sediment (SS) concentration often is used for the estimation of inflow SS concentration in reservoir turbidity modeling in the absence of actual measurements. The power function, SS

A series of new anthracene based semiconductors are designed and synthesized. By substituting appropriate acenes at the 2,6-positions of triisopropylsilylethynyl anthracene (NMR, IR, DSC and TGA spectra and crystallographic information of TIPSAntBT and TIPSAntNa), two different derivatives were prepared. Especially, TIPSAntNa (naphthalene as a side group) showed superior performance when it was used as channel material. A hole mobility as high as 3.7 cm2 V−1 s−1 was obtained from single crystal OFETs. To elucidate the origin of this high performance, we carried out comparative studies to investigate the direct relationship between the molecular-packing parameters and the field-effect mobility in single-crystal OFETs because the performance of such single-crystal OFETs is not affected by defects and grain boundaries. Comparing TIPSAN single crystal OFETs having four different acene derivatives, and applying the concept of molecular overlap ratio along the long/short axis, we could show that the effective π-stacking area dominantly determines the field-effect mobility of π-stacked materials. In the case of TIPSAntNa, a large π-stacking area and a small π-stacking distance enabled the highest field-effect mobility.

The Pohang Light Source (PLS) at the Pohang Accelerator Laboratory (PAL) is a third-generation light source, the only synchrotron radiation facility in Korea, and the fifth machine of its kind in the world (see Figure 1). In 1988, PAL was organized for the construction of the PLS. Ground-breaking was celebrated in 1991, and PLS construction was completed in 1994. In 1995, the PLS opened two beamlines to public users. The PLS was initially operated at 2.0 GeV in 1995. Since 2002, the energy of the electron beam has been upgraded to 2.5 GeV (see Table 1 for the principal parameters of PLS). Remarkable increases in the number of beamlines, users, and scientific results have been achieved since the opening of the PLS in 1995. Two or three beamlines have been added each year for the past 15 years, and as of February 2009 we have in total 27 beamlines in operation and 3 beamlines under construction, which will be completed by the end of 2009 (Figures 2 and 3).

Sambucus pendula Nakai, which is an endemic on Ulleung Island of Korea, is characterized by a large pendulous inflorescence and small fruit. A set of 256 individuals were used to investigate the patterns of intraspecific variation of S. racemosa subsp. kamtchatica, S. racemosa subsp. sieboldiana, and S. williamsii including S. pendula using PCA (principal components analysis). This analysis showed that S. pendula was distinct based on its large inflorescence and long peduncle. Our data showed a morphological distinction between subsp. kamtchatica from northeastern areas and subsp. sieboldiana from Jeju Island, but the two taxa overlap in the southern and eastern parts of Korea in terms of chromosome number, color of style, and allozyme data. Our study agrees that S. pendula on Ulleung Island may be the result of genetic drift that occurred during isolation since the Quarternary period. This has been suggested as a reason for the genetic differences observed between two taxa and would explain the unique variation patterns of S. pendula. However, the morphological differentiation between the S. racemosa complex and S. pendula is not considered sufficient to warrant recognition of specific status. Therefore, we recommend that only one polymorphic species of S. racemosa in Eurasia be recognized and that S. pendula be considered a subspecies of S. racemosa.

Store it away: Methane adsorption isotherms of Zn2(bdc)2(dabco) (1) are measured up to a pressure of 35 bar. X-ray structure analysis of methane-adsorbed 1 at 90 K reveals that methane molecules occupy three independent sorption sites A, B, and C while interacting with the framework as well as each other through van der Waals interactions. Sorption isotherms of methane in Zn2(bdc)2(dabco) are measured up to a pressure of 35 bar in the temperature range between 198–296 K. The methane sorption measurements at 296 K showed an uptake of 137 cm3 cm−3 at 35 bar. The enthalpy of methane adsorption for Zn2(bdc)2(dabco) estimated by the virial equation is 13.6 kJ mol−1 at zero coverage. X-ray structure analysis of methane-adsorbed Zn2(bdc)2(dabco) by synchrotron radiation at 90 K revealed that methane molecules occupy three independent sorption sites (A, B, and C) with a stoichiometry of Zn2(bdc)2(dabco)⋅6.69CH4, which is consistent with the results of the gas sorption measurements at 198 K. In a cavity, eight symmetry-related methane sorption sites A are located near the {Zn2(CO2)4} paddle-wheel units, while four symmetry-related methane sorption sites B are near the center of the small windows along the a and b axes. Both A and B sites are half-occupied. Methane molecules occupying sites A are not only in van der Waals contact with the paddle-wheel units, but also interact with the phenyl rings of bdc ligands through partial π-HC interactions. Methane molecules in B sites interact with the side of the phenyl rings through van der Waals interaction. The site C, located at the center of the cavity, is a secondary sorption site; methane molecules occupying sites C are in van der Waals contact with those in sites A and B.

Single crystals of zeolite Y, |Na71|[Si121Al71O384]-FAU, with diameters up to 0.20 mm were grown. They were ion exchanged to generate |(NH4)64Na5K2|[Si121Al71O384]-FAU. Crystals 1 through 6, respectively, were vacuum dehydrated at 323, 373, 423, 473, 523, and 573 K, and without reexposure to the atmosphere, their structures were determined crystallographically at 294 K using synchrotron X-radiation. Their compositions (best integers) are seen to be respectively |(NH4)59H5Na5K2(H2O)3|[Si121Al71O384]-FAU (incomplete dehydration and partial deamination), |(NH4)31H33Na5K2|[Si121Al71O384]-FAU (further deamination), |(NH4)2H62Na5K2|[Si121Al71O384]-FAU (nearly complete deamination), |H61Na5K2(Al2O)0.5|[Si122Al70O384]-FAU (onset of dealumination and framework reconstruction), |H53Na5K2(Al2O)2|[Si124Al68O384]-FAU (further dealumination and reconstruction), and |H51Na5K2(Al2O)2.5|[Si124Al68O384]-FAU. The extent of deamination of NH4+ increases with increasing evacuation temperature until it is complete in crystal 4...

Laboratory tests were conducted to determine the susceptibility of the alfalfa weevil, Hypera postica to Korean entomopathogenic nematodes, Steinernema carpocapsae GSN1 strain (ScG), S. glaseri Dongrae strain (SgD), Heterorhabditis bacteriophora Hamyang strain (HbH), and Heterorhabditis sp. Gyeongsan strain (HeG) at the petri dish assay. The larval mortality of H. postica was significantly different depending on nematode species and treatment concentration. SgD and HeG strain were more effective against H. postica larva than ScG and HbH strain. When SgD and HeG strain were treated with the rate of >20 infective juveniles (ijs) per alfalfa weevil larva, mortality was ca. 77.5-100% at the late instars of H. postica in 3 days. The number of established nematode was significantly different depending on nematode species, whereas number of progeny was not significantly different. The mean number of established us of SgD strain in a host was the highest at 80 ijs by 30.2. The highest progeny number of HeG strain was 2,671.5 with 80 ijs. All nematode strains were not parasitic entirely to H. postica adults. These results show that alfalfa weevil late larva is highly susceptible to Korean entomopathogenic nematodes in the laboratory

Asarum sieboldii has been used in traditional folk medicine to treat dental caries and periodontal disease. In the present study, we investigated the inhibitory effect of the ethanol and aqueous extracts of A. sieboldii on the growth, acid production, adhesion, and water-insoluble glucan synthesis of Streptococcus mutans. The ethanol and aqueous extracts of A. sieboldii inhibited the growth and acid production of S. mutans. In the bacterial adherence assay, the ethanol and aqueous extracts of A. sieboldii significantly lowered the adherence of S. mutans. We also found that the ethanol and aqueous extracts of A. sieboldii significantly inhibited the synthesis of water-insoluble glucan by crude glucosyltransferase. These results suggest that A. sieboldii extracts may inhibit the caries-inducing properties of S. mutans. Further studies are necessary to clarify the active constituents of A. sieboldii extracts responsible for such biomolecular activities.

The emergence and dissemination of extended-spectrum (ES) beta-lactamases induce therapeutic failure and a lack of eradication of clinical isolates even by third-generation beta-lactam antibiotics like ceftazidime. CMY-10 is a plasmid-encoded class C beta-lactamase with a wide spectrum of substrates. Unlike the well-studied class C ES beta-lactamase from Enterobacter cloacae GC1, the Omega-loop does not affect the active site conformation and the catalytic activity of CMY-10. Instead, a three-amino-acid deletion in the R2-loop appears to be responsible for the ES activity of CMY-10. According to the crystal structure solved at 1.55 A resolution, the deletion significantly widens the R2 active site, which accommodates the R2 side-chains of beta-lactam antibiotics. This observation led us to demonstrate the hydrolysing activity of CMY-10 towards imipenem with a long R2 substituent. The forced mutational analyses of P99 beta-lactamase reveal that the introduction of deletion mutations into the R2-loop is able to extend the substrate spectrum of class C non-ES beta-lactamases, which is compatible with the isolation of natural class C ES enzymes harbouring deletion mutations in the R2-loop. Consequently, the opening of the R2 active site by the deletion of some residues in the R2-loop can be considered as an operative molecular strategy of class C beta-lactamases to extend their substrate spectrum.