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In this paper, structural modelling and dynamic analysis methods reflecting the characteristics of a liquid propellant were developed for a pogo analysis. The pogo phenomenon results from the complex interaction between the vehicle structural vibration in the longitudinal direction and the propulsion system. Thus, for an accurate vibration analysis of a liquid propellant launch vehicle, both the consumption of the liquid propellant and the change in the stiffness reflecting the nonlinear hydroelastic effect were simultaneously considered. A complete vehicle structure, including the liquid propellant tanks, was analytically modelled while focusing on pogo. In addition, a feasible liquid propellant tank modelling method was established to obtain an one-dimensional complete vehicle model. With these methods, comparative studies of the hydroelastic effect were conducted. Evaluations of the dynamic analysis of a reference vehicle were also conducted during the first burning stage. The numerical results obtained with the present orthotropic model and the dynamic analysis method were found to be in good agreement with the natural vibration characteristics according to previous analyses and experiments. Additionally, the reference vehicle showed the estimated occurrence of pogo in the first structural mode when compared with the frequencies of the propellant feeding system. In conclusion, the present structural modelling and modal analysis procedures can be effectively used to analyse dynamic characteristics of liquid propellant launch vehicles. These techniques are also capable of identifying the occurrence of pogo and providing design criteria related to pogo instability.
A new approach is proposed to analyze Bremsstrahlung X-rays that are emitted from laser-produced plasmas (LPP) and are measured by a stack type spectrometer. This new method is based on a spectral tomographic reconstruction concept with the variational principle for optimization, without referring to the electron energy distribution of a plasma. This approach is applied to the analysis of some experimental data obtained at a few major laser facilities to demonstrate the applicability of the method. Slope temperatures of X-rays from LPP are determined with a two-temperature model, showing different spectral characteristics of X-rays depending on laser properties used in the experiments.
Reduction of potential environmental pollutants is a major issue for the sustainable development of the poultry industry. Accumulation of excessive manure and nitrogen poses a risk to animal and human health and ground and surface water cleanliness. In conventional poultry, synthetic amino acids and enzyme supplementations are commonly used to balance the diet and improve digestibility of nutritive compounds. However, diet preparation with sufficient nutrients and minimum amount of excessive nitrogen which still provides optimal growth and health performance continues to be a challenge. This review focuses on various approaches leading to improvement of feed formulation in conventional poultry production systems. The use of crystalline amino acids and genetically engineered plant protein sources in the conventional poultry industry with regard to optimisation of nitrogen level in poultry diets are discussed, and the application of the ideal protein ratio concept in poultry feed preparation as a tool for nitrogen level optimisation is outlined.
RZ Cas is an Algol-type eclipsing binary system where the primary component was recently discovered as a δ Set pulsator. A three-continent multisite photometric campaign was carried out during 1999. Preliminary results are reported here indicating a semi-detached system where the secondary fills its Roche lobe. The light curves also suggest a hot spot on the surface of the primary component as a consequence of the impact of the mass stream from the secondary. The pulsational behaviour can be well described with only one frequency.
A total of eighteen times of minimum lights for YY Eri were determined from relatively new or unpublished photoelectric observations collected from Korea and Turkey. All minima available to us were intensively analyzed to deduce the character of period variation of YY Eri. It is either formed by a sinusoidal variation superimposed on an upward parabola, or a set of abrupt changes. The abrupt changes appeared to have alternatively occured in the pattern of two increases following one decrease, which may be an indication of sinusoidal variations rather than real sudden changes of period. Upward parabolic variation can be due to a secular period increase caused by mass transfer from less massive to more massive component. The sinusoidal character can arise from a third body or from a strong magnetic activity cycle. Long term sinusoidal light level variation in the light curves supports the cyclic magnetic activity effect on the orbital period. However, the third body hypothesis can not be ruled out by the present data.
One of the most pleasurable features of the plays of Euripides is his exploration of a wide range of character types, each of whom has the potential to be more exciting than the previous one. The fictional Aeschylus in the underworld of Aristophanes' Frogs (1043) remembers in particular the wicked women (Stheneboea, Phaedra), but Euripides also had his share of pious and self-sacrificing virgins (Macaria, Polyxena, Iphigenia), faithful wives (Helen in her name play, Andromache, Alcestis, Evadne), shrewd matriarchs (Hecuba, Jocasta, Aethra, Alcmene), and priestesses (Cassandra, Iphigenia in I. T., Theonoe, the Pythia).
All of the materials necessary for integrated isolators were grown and the application of 2D photonic crystal structures to isolators has been explored. Magnetooptical garnets were grown monolithically by reactive rf sputtering. MgO was used as a substrate because it will useful for future buffer layers and optical claddings. The chemical, structural, and optical properties of the resulting films were analyzed. In order to incorporate photonic crystal structures into the magneto-optic integration scheme, we have calculated a range of radii and spacings necessary to fabricate YIG/air structures with 2D photonic bandgaps using an advanced plane-wave expansion technique. Selfassembled alumina nanostructures have been grown with similar symmetries as those calculated, namely hexagonal close-packed pores. These nanostructures were grown onto semiconductor and oxide substrates in order to demonstrate their use as RIE masks in fabricating photonic crystals. The nanostructures can also be transferred into YIG using separate alumina masks. However, the actual structures grown in this work were smaller than those required for telecommunications due to power supply limitations. For biasing the magneto-optical elements, sputtering was used to monolithically integrate permanent SmCo magnet films using semiconductor-friendly processing. These magnets were sufficient for biasing our magneto-optical waveguides. The chemical, structural and magnetic properties of these materials, as well as total integration with SiO2 cladding layers were analyzed.
Limited research has been conducted to understand the relationship between heat wave warnings with public awareness and behavioral changes in the Asian population. The Hong Kong Observatory introduced the “very hot weather warning” in 2000 to alert the public of heatstroke and sunburn in Hong Kong. However, the population's behavioral responses to these weather alerts is unclear. Moreover, the relationship between perceived health risks and behavioral changes has not been examined. The goal of this study is to examine the health risk perceptions and behavioral changes following public heat wave warnings in Hong Kong.
A cross-sectional, population-based, telephone survey, using the last-birthday method was conducted within two weeks following a heat wave warning in 2009. A heat warning and a health study instrument, based on Intergovernmental Panel on Climate Change (IPCC) guidelines and related literature was developed and validated. Descriptive and multivariate logistic regression analyses were conducted.
The questionnaire was completed by 1,123 individuals whose socio-demographic characteristics were comparable to 2009 Hong Kong population census data. Of respondents, 83.6% were aware of the heat wave weather warning. Multivariate logistic regression of socio-demographic factors indicated that being female, those in middle age groups, and those with higher educational attainment was significantly associated with heat wave warning awareness. Among those aware of the public warning, the majority were unconcerned about potential adverse health effects, < 40% were aware of the community heat-related preparedness plans, and < 50% changed their behavior to mitigate the potential adverse health impacts of hot weather.
This is the first study to examine climate change and health behavioral responses in an urban Chinese population. Future research direction should further investigate correlations between awareness and health protective actions, as well as the drivers for health behavioral changes that mitigate the impact of climate change.
With advancement of infrared space telescopes during the past decade, infrared wavelength
regime has been a focal point to study various properties of galaxies with respect to
evolution of galaxies. Polycyclic Aromatic Hydrocarbons (PAHs) have emerged as one of the
most important features since these features dominate the mid-infrared spectra of
galaxies. These PAH features provide a great handle to calibrate star formation rates and
diagnose ionized states of grains. However, the PAH 3.3 μm feature has
not been studied as much as other PAH features since it is weaker than others and resides
outside of Spitzer capability, although it will be the only PAH feature accessible by JWST
for high-z galaxies. AKARI mJy Unbiased Survey of Extragalactic Sources in 5MUSES (AMUSES)
intends to take advantage of AKARI capability of spectroscopy in the
2 ~ 5 μm to provide an unbiased library of 44 sample
galaxies selected from a parent sample of 5MUSES, one of Spitzer legacy projects. For
these 3.6 μm flux limited sample galaxies whose redshifts range between
0 < z < 1, AMUSES will calibrate PAH 3.3
μm as a star formation rate (SFR) indicator while measuring ratios
between PAH features. We present preliminary results of AMUSES.
SiB6 has proved to a potentially useful material because of its excellent thermoelectrical properties above 700°C, low specific gravity, high degree of hardness, and moderate melting point. SiB6, which has poor sinterability with a conventional sintering technique due to the covalent characteristic, has been successfully densified fully using a spark plasma sintering(SPS) method. The SPS-processed specimens consisted of SiB6, SiB4 and SixBy phases. Pure SiB6 powder were densified fully at the sintering temperature of 1600°C. In particular, it was found that the rare earth element was very effective in evolving the microstructure of SiB6 phase, resulting in reducing the sintering temperature and controlling grain growth. These effects were discussed in details in terms of microstructure evolution during the SPS process.
For applications at ultrahigh temperatures the multiphase microstructural options that can be developed in the Mo-Si-B system have demonstrated an effective and attractive balance of essential characteristics. The coexistence of the high melting point (>2100°C) ternary intermetallic Mo5SiB2 (T2) phase with Mo provides a useful option for in-situ toughening. A further enhancement is available from a precipitation reaction of Mo within the T2 phase that develops due to the temperature dependence of the solubility behavior of the T2 phase. However, direct access to Mo+T2 microstructures is not possible in ingot castings due to solidification segregation reactions that yield nonequilibrium boride and silicide phases with sluggish dissolution. Alternate routes involving rapid solidification of powders are effective in suppressing the segregation induced phases. The processing and microstructure options can also be augmented by selected refractory metal substitutional alloying, such as the incorporation of Nb, that alters the solubility of the T2 phase and the relative phase stability to yield solidification of two phase refractory solid solution + T2 structures directly. The observed alloying trends highlight the role of atomic size in influencing the relative stability of the T2 phase. A key component of the overall microstructural control and long term microstructural stability is determined by the kinetics of diffusional processes. The analysis of selected diffusion couples involving binary boride and silicide phases has been used to assess the relative diffusivities in the T2 phase and coexisting phases over the range of solubility and to provide a basis for the examination of the kinetics of reactions involved in coatings and oxidation.
The high melting temperature and oxidation resistance of the Mo5SiB2 (T2) phase and multiphase microstructures incorporating the T2 phase in the Mo-Si-B system have motivated further studies for applications in very high temperature environments. Since the long term microstructural stability is determined by diffusional processes, diffusion couples consisting of binary boride and silicide phases have been examined in order to evaluate the kinetics of T2 phase development and the relative diffusivities controlling the kinetics. Long term annealing (500 hrs) of the Mo5Si3/Mo2B diffusion couple yields the phase sequence of Mo5Si3/Mo3Si/T2/Mo2B at 1600°C. This indicates that the T2 phase initiates and grows from the Mo2B side to a thickness of about 32μm and the Mo3Si phase initiates and grows from the Mo5Si3 side to a thickness of about 15μm. Other annealing treatments allow for an analysis of the diffusion kinetics based upon the layer thickening and composition profile measurements. To identify the crystallographic growth direction of T2 on Mo2B, a wedge shaped TEM sample with very thin leading edge was prepared. Microstructure images indicate that the growth mode of the T2 phase is columnar. There is a clear tendency for the growth of T2 to be approximately normal to c-axis.
In this work, was investigated both numerically and experimentally, the excimer laser processing of a-Si films deposited on SiO2-coated glass substrates, using the very large area (∼ 20 cm2) and long pulse duration (200 ns) excimer source from SOPRA Company. Experiments were carried out in air or in neutral atmosphere, using both the single- and multi-shot mode. From the microstructural analysis of the laser irradiated area the formation of a large-grained material through the so-called SLG regime was evidenced. In addition, the application of a multi-shot process was demonstrated to be very efficient to prepare uniform polysilicon layers with enlarged grain sizes (up to 1.5 µm after 20 shots). Finally, poly-Si TFTs prepared in the optimized conditions (multi-shot, neutral ambience) exibited field effect mobilities up to 235 cm2/V.s (for N-type) and 84 cm2/V.s (for P-type), with fairly uniform device characteristics over large area and excellent stability under electrical stress.
A high-quality silicon dioxide (SiO2) suitable for a gate oxide on plastic substrates is successfully deposited by e-gun evaporation at room temperature. The e-gun evaporated oxide film is free from troublesome hydrogen atoms and high-energy ion damage, which ensures good electrical characteristics. N2O/N2 plasma post-treatment was effective to reduce the flat band voltage and leakage current of the evaporated oxides due to the passivation of high-energy nitrogen and oxygen radicals. In the SiO2 film treated by N2O/N2 plasma for 1 minute, the flat band voltage has been reduced from −2.5V to about −0.5V and the leakage current has been decreased by more than one order. Our experimental results show that very low temperature SiO2 film suitable for a gate insulator of TFTs on the plastic substrates has been successfully obtained by the e-gun evaporation and N2O/N2 plasma post-treatment.
A simple process sequence for fabrication of low temperature polysilicon (LTPS) TFTs with self-aligned graded LDD structure was demonstrated. The graded LDD structure was self-aligned by side-etch of Al under the photo-resist followed by excimer laser irradiation for dopant activation and laterally diffusion. The graded LDD polysilicon TFTs were suitable for high-speed operation and active matrix switches applications because they possessed low-leakage-current characteristic without sacrificing driving capability significantly and increasing overlap capacitance. The leakage current of graded LDD polysilicon TFTs at Vd = 5V and Vg = −10V could attain to below 1pA/μm without any hygrogenation process, when proper LDD length and laser activation process were applied. The on/off current ratios of these devices were also above 108. Furthermore, due to graded dopant distribution in LDD regions, the drain electric field could be reduced further, and as a result, graded LDD polysilicon TFTs provided high reliability for high voltage operation.
We suggest to enhance the performance of image acquisition systems based on large area amorphous silicon based sensors by optimizing the readout parameters such as the intensity and cross-section of scanner beam, acquisition time and bias conditions. The main output device characteristics as image responsivity, signal to noise ratio and spatial resolution were analyzed in open circuit, short circuit and photodiode modes. The result show that the highest signal to noise ratio and best dark to bright ratio can be achieved in short circuit mode.
It was shown that the sensor resolution is related to the basic device parameters and, in practice, limited by the acquisition time and scanning beam properties. The scanning beam spot size limits the resolution due to the overlapping of dark and illuminated zones leading to a blurring effect on the final image and a consequent degradation in the resolution.
This contribution investigates the crystallization behavior of amorphous silicon films on glass by using pulsed lasers with very high repetition rates up to 100 kHz. We determine the influence of the laser repetition rate f and of the film thickness d on the grain width g of the resulting polycrystalline silicon films. Our experimental results indicate a strong dependence of the grain width g on film thickness d as well as on the repetition rate f of the laser. The grain width rises from g = 0.27 µm to g = 3.59 µm if the film thickness increases from d = 50 nm to d= 300 nm and the repetition rate f from f = 20 kHz to 100 kHz. We use a purpose developed two- dimensional finite difference numerical model to calculate the evolution of the temperature in the silicon film and in the glass substrate. An increase of both, the film thickness d, and the repetition rate f decrease the solidification velocity v of the film. A comparison of the solidification velocity vs and the measured grain width g shows a linear correlation.