[en] It is generally assumed that the solution of the galactic shock wave is a local one and that no account of gaseous self-gravitation is taken in the theory of stellar density wave. Both assumptions are dropped in this paper, and the unsteady two-dimensional gas dynamic equations with gaseous self-gravitation are solved. The formation process of the galactic shock wave is studied responding to an applied perturbed spiral gravitational field within an initial axisymmetric gaseous disk, and the velocity and gas density distributions with the properties of galactic shock wave are obtained. The features of local shock wave solution without gaseous self-gravitation are qualitatively similar to but quantitatively different from the results of this paper. The calculation shows that the pattern velocity of galactic shock grand design varies both in time and in space. The magnitude of variation in the shock pattern velocity from that of the applied density wave exceeds even the pattern velocity of the applied density wave. Because a typical time for the formation of shock waves is about 5 x 10⁸ yr, it is difficult to maintain the galactic density wave with quasistationary properties, because of the relative winding between the shock pattern and the applied density wave pattern. However, there clearly exists a large-scale galactic shock-wave grand design at all times

[en] The rate of CO₂ assimilation of leaf lettuce changed with its respiration rate and gas constitution in a storage chamber. The optimum irradiance on the surface of leaf lettuce during storage using low light irradiation can be obtained by the prediction of the rate of CO₂ assimilation. For the above mentioned purpose the following equation were derived. -kd[C]/dt=0.5(1-f)I([C]-Γ/4.5[C]+10.5Γ)-ae^-bt where, k: proportional constant (4.87×10^-3mol⋅m^-2) [C]: CO₂ concentration (ppm), t: time (h), f: fraction of light not absorbed by chloroplasts (0.23), I: irradiance (μmol⋅m-2⋅s^-1), Γ: CO₂ compensation point without respiration (21.5ppm), a, b: parameters (0.308μmol⋅m^-2⋅s^-1, 0.010h^-1). Calculated values of rate of CO₂ assimilation by the equation agreed well with experimental ones at 3.4 and 6.5μmol⋅m^-2⋅s^-1 of irradiance, so it appeared that the assimilation rate could be sufficiently predicted

[en] The microstructural changes at the interfaces in a NiAl composite reinforced with BN-coated continuous single crystal Al₂O₃ fibers were studied by analytical electron microscopy and high-resolution electron microscopy (HREM) after annealing at 1000 deg. C for 100 h and 500 h. Both NiAl/BN and BN/Al₂O₃ interfaces exhibited excellent stability during annealing, as did the AlN layer formed at NiAl/BN interface during processing. In the case of contamination which was introduced through the use of a glue during diffusion bonding of the composite, significant changes of the microstructure at both NiAl/BN and BN/Al₂O₃ interfaces were observed. A continuous reaction layer formed at the BN/Al₂O₃ interface during annealing. The reaction product was identified by electron diffraction as Al₁₈B₄O₃₃. We propose to attribute this to the reaction: 9Al₂O₃+2B₂O₃→Al₁₈B₄O₃₃. Many nanoparticles were observed in the BN matrix near the BN(AlN)/NiAl interface in the as-fabricated composite. Neither the AlN layer nor these nanoparticles grew during annealing. HREM images of the precipitates revealed a structure distinctly different from that of the BN matrix. B, C, N and Al were detected in these precipitates by EELS analysis

[en] Unprotected loss of flow accident (ULOF) is the most typical severe accident in sodium cooled fast reactor, which is focused by scholars civil and abroad. Metallic fuel has different safety characteristics with the oxide fuel as the important development direction of future sodium fast reactor, accident analysis of which is also a research focus at home and abroad. This paper bases on one Cooperation Research Project proposed by ANL and organized by IAEA, analyses the Shut-down Removal Test-45R of the metallic fuel sodium cooled fast reactor EBR-II in the US with SAS4A code, to research the transient characteristics of it in ULOF accident. Studies have shown that, metallic fuel sodium cooled fast reactor has very good inherent safety performance, which can reduce the reactor power in ULOF accident through the negative feedback itself. (author)

[en] Purpose: GafChromic RTQA2 film is known as a quality assurance (QA) tool for light field and radiation field verification. This study is attempted to apply the RTQA2 film to the patient specified quality assurance. Methods: Pre-irradiated and post-irradiated RTQA2 films were scanned in a reflection mode using a flatbed scanner. A plan-based dose calibration method utilized the mapping information of calculated dose image and measured film image to create a dose vs. pixel value calibration model. This model was used to calibrate the measured film image from the pixel value (gray value) image to the dose image. The dose agreement between calculated and measured dose images were analyzed using the gamma analysis. To evaluate the feasibility of this method, three clinical approved RapidArc cases (one abdomen cancer and two head-and-neck cancer patients) were tested. The tolerance of 3% dose difference and 3 mm distance to agreement (DTA) and gamma index ≤ 1 were set for the analysis. Results: The calibrated film dose image from measurement was successfully compared to the predicted dose image from the commercial treatment planning. The gamma analysis results showed good consistency. Gamma passing rates were 99.02%, 94.84%, and 98.33% for the three patients, respectively. Conclusion: The plan based calibration method has the feasibility for dose verification without shortages of film batch and development time variation

[en] In this work, we calculate the electron impact ionization cross sections for H-like and He-like isoelectronic-sequence ions by means of a distorted-wave Born exchange approximation method including a relativistic correction. A computer program has been developed and used to calculate these cross sections. Systematic study of the dependence of the cross sections on impact energies and nuclear charges is carried out. The results of calculations are fitted by empirical formulas to meet the requirements of applications. The fitted values are in good agreement with the calculated results. 17 refs., 4 figs., 6 tabs

[en] In order to preserve fresh lettuce, the dim light irradiation storage was investigated. Lettuce (Lactuca sativa L.) stored for about 120 hours at 5 or 20 deg C under continuous illumination at 0 (darkness), 1.6, 3.4, 6.5, 13 or 19.7 micro mol/m**-2/s**-1 photosynthetic photon flux. The light compensation point was about 3.4 micro mol/m**-2/s**-1 at 5 deg C, about 19.7 micro mol/m**-2/s**-1 at 20 deg C. Fresh weight of lettuce decreased by promotion of transpiration caused by the dim light. Accordingly the root of lettuce should not be removed, so as to up-take water. The optimum dim light irradiation preserved the chlorophyll content in lettuce leaf or increased it. Therefore it appeared that the dim light irradiation was effective for the fresh lettuce preservation

[en] We analytically study the effects of periodically alternating magnetic fields on the dynamics of a tight-binding ring. It is shown that an arbitrary quantum state can be frozen coherently at will by the very frequent square-wave field as well as the monochromatic-wave field when the corresponding optimal amplitudes are taken. Numerical simulations show that the average fidelity depends on not only the system parameters, but also the features of the quantum state. Moreover, taking the initial zero-momentum Gaussian wave packets as examples, we show the dependence of the threshold frequency on the width of the packet for the given average fidelities. These observations provide a means to perform the quantum-state engineering.

[en] Purpose: This study was to investigate the dosimetric benefit of a novel intensity modulated radiation therapy (IMRT) technique for irradiating the left breast and regional lymph node (RLN). Methods: The breast and RLN (internal mammary node and periclavicular node) and normal tissue were contoured for 16 consecutive left-sided breast cancer patients previously treated with RT after lumpectomy. Nine equi-spaced fields IMRT (9 -field IMRT), tangential multi-beam IMRT (tangential-IMRT) and IMRT with fixed-jaw technique (FJT-IMRT) were developed and compared with three-dimensional conformal RT (3DCRT). Prescribed dose was 50 Gy in 25 fractions. Dose distributions and dose volume histograms were used to evaluate plans. Results: All IMRTs achieved similar target coverage and substantially reduced heart V30 and V20 compared to the 3DCRT. The average heart mean dose had different changes, which were 9.0Gy for 9-field IMRT, 5.7Gy for tangential-IMRT and 4.2Gy for FJT-IMRT. For the contralateral lung and breast, the 9-field IMRT has the highest mean dose; and the FJT-IMRT and tangential-IMRT had similar lower value. For the thyroid, both 9-field IMRT and FJT-IMRT had similar V30 (20% and 22%) and were significantly lower than that of 3DCRT (34%) and tangential-IMRT (46%). Moreover, the thyroid mean dose of FJT-IMRT is the lowest. For cervical esophagus and humeral head, the FJT-IMRT also had the best sparing. Conclusion: All 9-field IMRT, tangential-IMRT and FJT-IMRT had superiority for targets coverage and substantially reduced the heart volume of high dose irradiation. The FJT-IMRT showed advantages of avoiding the contralateral breast and lung irradiation and decreasing the thyroid, humeral head and cervical esophagus radiation dose at the expense of a slight monitor units (MUs) increasing

[en] The electronic structures of the ground states of chalcogenide defect pairs in Si are investigated using the Green's function method with a tight-binding Hamiltonian. Three different points of view are discussed: (1) Janzen et al [1] used an effective mass approach and obtained an A/sub 1g/ ground state; this approach seems able to describe the optical absorption spectra from the ground state to excited states rather well. But in order to achieve this success, they must assume that the E/sub g/ state of the defect is unoccupied by electrons. (2) Worner et al [2] suggested a defect molecule model with the anti-symmetrical antibonding state higher in energy than the symmetrical bonding state, a point of view that has perhaps been too easily accepted [3]. (3) Green's function calculations [4,5] give the seemingly surprising result that the symmetrical A/sub 1g/ state is higher than the antisymmetrical A/sub 2u/ state. However they show that only this last theory describes both the optical absorption spectra (in a simple and natural way) and the g factor of (Se₂)⁺ obtained by Worner et al