Thermoluminescence characteristics of rare-earth-doped LiCaBO3 phosphor

LiCaBO3 was synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Dy3+, Tb3+. TM3+ and Ce3+, on thermoluminescence (TL) of LiCaBO3 phosphor was discussed. We studied the TL properties and some dosimetric characteristics of Ce3+-activated LiCaBO3 phosphor in detail. The effect of the concentration of Ce3+ on TL was investigated, the result of which showed that the optimum Ce3+ concentration was 1 mol%. The TL kinetic parameters of LiCaBO3:0.01 Ce3+ were studied by computer glow curve deconvolution (CGCD) method.

Thermoluminescence characteristics of NaSr4(BO3)(3):Ce3+ under beta-ray irradiation

The thermoluminescence (TL) properties of Ce3+ doped NaSr4(BO3)(3) phosphor under the beta-ray irradiation were reported. The polycrystalline sample was synthesized by high temperature solid-state reaction. The TL glow curve of NaSr4(BO3)(3):Ce3+ phosphor was composed of only one peak. TL kinetic parameters of NaSr4(BO3)(3):Ce3+ were deduced by the peak shape method, the activation energy (E) was 0.590 eV and the frequency factor was 1.008x10(6) s(-1). TL dose response was linear in the range of measurement. The 3-dimensional (3D) TL emission spectrum was also recorded, the emission spectrum consisted of two bands located at 441 and 479 nm respectively, corresponding to the characteristic 4f(0)5d(1)-> F-2((5/2,7/2)) transitions of the Ce3+ ion. The fading behavior of the NaSr4(BO3)(3):Ce3+ phosphor over a period of 15 d was also studied.

A preliminary study on thermoluminescence characteristics of sediments from the North Pacific

Thirty-eight surficial deposit samples were collected from the equatorial North Pacific, and the natural thermoluminescence (TL) characteristics of both bulk and clay fraction samples ( < 2 mu m fractions) were studied by the FJ427 - Al automatic TL Dosimeter for the first time. With the measurements of clay mineral composition, element composition by XRD and ICP, the correlations between TL intensity and sedimentary environment proxies were analyzed, such as water depth, ratio of FeO to Fe2O3 contents, LOI, and major clay mineral concentration, and it was found the bulk sample's TL signal was stronger than the clay ones. Usually, increase in the clay components may result in the decrease of TL intensity. From the shape of TL curves, the pelagic sediments can be divided into two groups: the majority group has two glow peaks, in general, the first peak is broad and flat, but the second narrow and sharp; the minority group only has a single peak because the first is absent. The peak centers of TL curves are almost fixed, falling in the temperature sections 230 similar to 260 and 390 similar to 405 degrees C respectively. Lorentz model packed in the Origin 7.5 was chosen to deal with the TL curves. From the processing results, three parameters ( H, C and A), corresponding to the height, center, and kurtosis of TL curve, were obtained to describe the curve characteristics. The correlations between TL curve parameters and sedimentary environment proxies were also calculated. On the basis of the above work, the relationship between TL characteristics and sediment type, mineral composition, sedimentary environment of surface sediments was discussed in the study area, and a conclusion is: sediments from the environment of shallower water, higher organic contents and weaker reductivity have stronger TL signals.

Effect of Single- and co-Dopant on TL of Sr2Mg(BO3)(2) Phosphor

Sr2Mg(BO3)(2) thermoluminescence (TL) phosphor was synthesized by a high temperature solid state reaction and the effect of Li+, Bi3+, Gd3+ or Ti4+ as a codopant on TL of Sr2Mg(BO3)(2) : Dy was investigated. The results show that Li+ as a codopant improves the emission intensity of high temperature TL peak of Sr2Mg(BO3)(2) : Dy phosphor whereas the addition of Bi3+, Gd3+ or Ti3+ leads to the decrease of TL intensity. The TL emission bands of Sr2Mg(BO3)(2) : Dy phosphors with Li+, Bi3+, Gd3+ or Ti4+ as a codopant are situated at 480, 579, 662 and 755 nm, which were attributed to the characteristic F-4(9/2)-> H-6(15/2), F-4(9/2)-> H-6(13/2), F-4(9/2)-> H-6(11/2) and F-4(9/2)-> H-6(9/2) transitions of Dy3+ ion, consistent with the emission of Sr2Mg(BO3)(2) : Dy phosphors. The kinetics parameters of 234 degrees C TL peak of Sr2Mg(BO3)(2) Dy-0.04(3+), (Li-0.04(+)) phosphor with the values of trap depth E=1.1 eV, frequency factor s=6.3 x 10(9) s(-1) were estimated by a peak shape method, which obey the second order kinetics.

Effect of Single- and co-Dopant on TL of Sr2Mg(BO3)(2) Phosphor(单掺杂与共掺杂离子对Sr_2Mg(BO_3)_2磷光体热释发光的影响)

Sr2Mg(BO3)(2) thermoluminescence (TL) phosphor was synthesized by a high temperature solid state reaction and the effect of Li+, Bi3+, Gd3+ or Ti4+ as a codopant on TL of Sr2Mg(BO3)(2) : Dy was investigated. The results show that Li+ as a codopant improves the emission intensity of high temperature TL peak of Sr2Mg(BO3)(2) : Dy phosphor whereas the addition of Bi3+, Gd3+ or Ti3+ leads to the decrease of TL intensity. The TL emission bands of Sr2Mg(BO3)(2) : Dy phosphors with Li+, Bi3+, Gd3+ or Ti4+ as a codopant are situated at 480, 579, 662 and 755 nm, which were attributed to the characteristic F-4(9/2)-> H-6(15/2), F-4(9/2)-> H-6(13/2), F-4(9/2)-> H-6(11/2) and F-4(9/2)-> H-6(9/2) transitions of Dy3+ ion, consistent with the emission of Sr2Mg(BO3)(2) : Dy phosphors. The kinetics parameters of 234 degrees C TL peak of Sr2Mg(BO3)(2) Dy-0.04(3+), (Li-0.04(+)) phosphor with the values of trap depth E=1.1 eV, frequency factor s=6.3 x 10(9) s(-1) were estimated by a peak shape method, which obey the second order kinetics.

Edge-defined, film-fed growth (EFG) technique for the preparation of alpha-Al2O3 : C crystal with highly sensitive thermoluminescence response

In this work, alpha-Al2O3:C, a highly sensitive thermoluminescence dosimetry crystal, was grown by the EFG method in which a graphite heating unit and shield acted as the carbon source during the growth process. The optical, luminescent properties and dosimetric characteristics of the crystal were investigated. The as-grown crystal shows a single glow peak at 536 K, which is associated with Cr3+ ions. After annealing in H-2 at 1673 K for 80 h, the crystal shows a single glow peak at 460 K and a blue emission band at 415 nm. The thermoluminescent response of the annealed crystal shows linear-sublinear-saturation characteristics in the dose range from 5 x 10(-6) to 100 Gy.

Thermoluminescence properties of Ce3+-doped LiSr4(BO3)(3) phosphor

Borates LiSr4(BO3)(3) were synthesized by high-temperature solid-state reaction. The thermoluminescence (TL) and some of the dosimetric characteristics of Ce3+-activated LiSr4(BO3)(3) were reported. The TL glow curve is composed of only one peak located at about 209 degrees C between room temperature and 500 degrees C. The Optimum Ce3+ concentration is 1 mol% to obtain the highest TL intensity. The TL kinetic parameters of LiSr4(BO3)(3):0.01Ce(3+) were studied by the peak shape method. The TL dose response is linear in the protection dose ranging from 1 mGy to 1 Gy. The three-dimensional thermoluminescence emission spectra were also studied, peaking at 441 and 474 nm due to the characteristic transition of Ce3+.

圆柱受限空间内喷雾燃烧振荡特性研究=Investigation of the Characteristics of Thermal Instability in A Confined Combustor

本文研究了圆柱受限空间内的喷雾火焰嫩烧压力振荡的特性。为了更清楚地了解火焰的构造, 首先测量了火焰的温度场，在较大的一次风和二次风变化范围内, 测量了压力的振荡特性。结果表明，火焰的稳定是由回流区完成的, 在较小的一次风燃料当量比和中等的二次风量时, 振荡最强, 达到100Pa左右的量级,其频率为200-230Hz左右,分析表明燃烧室中的振荡是轴向驻波振荡。

Characteristics of Argon Laminar DC Plasma Jet at Atmospheric Pressure

利用特殊设计的等离子体发生器,选择等离子体产生的工艺参数,实现工艺过程的精确控制,在大气压环境下获得了性能稳定的氖气直流层流等离子体射流。与湍流等离子体射流长度较短、径向尺寸较大、工作噪音高等特点相比,层流等离于体射流长度可达到550mm,而且沿整个射流长度其径向尺寸维持不变,工作噪音很小。当气流量为120cm~3/s、弧电流在70-200A的范围时,射流长度随弧电流的增加而增加,热效率起初略有降低然后维持平稳。随气流量的增加,层流等离子体射流的热效率也增加,在弧电流为200A时,可以达到40%。实验中测

Dynamic Characteristics of Spherically Converging Detonation Waves

The spherically converging detonation wave was numerically investigated by solving the one-dimensional multi-component Euler equations in spherical coordinates with a dispersion-controlled dissipative scheme. Finite rate and detailed chemical reaction models were used and numerical solutions were obtained for both a spherical by converging detonation in a stoichiometric hydrogen-oxygen mixture and a spherically focusing shock in air. The results showed that the post-shock pressure approximately arises to the same amplitude in vicinity of the focal point for the two cases, but the post-shock temperature level mainly depends on chemical reactions and molecular dissociations of a gas mixture. While the chemical reaction heat plays an important role in the early stage of detonation wave propagation, gas dissociations dramatically affect the post-shock flow states near the focal point. The maximum pressure and temperature, non-dimensionalized by their initial value, are approximately scaled to the propagation radius over the initial detonation diameter. The post-shock pressure is proportional to the initial pressure of the detonable mixture, and the post-shock temperature is also increased with the initial pressure, but in a much lower rate than that of the post-shock pressure.

Characteristics of Micronozzle Gas Flows

The fluid characteristics of gas flows in the micronozzle whose throat height is 20 μm were investigated by the direct simulation Monte Carlo (DSMC) method. In a series of cases, the dependence of mass flux on the pressure difference was gained, and the DSMC's results show good agreement with the experimental data. The comparison of mass flux and the Mach number contours between the DSMC and Navier-Stokes equations adding slip boundary also reveals quantitatively that the continuum model will be invalid gradually even when the average Knudsen number is smaller than 0.01. As one focus of the present paper, the phenomenon of the multiple expansion-compression waves that comes from the nozzle's divergent part was analyzed in detailed.

Investigation of kerosene combustion characteristics with pilot hydrogen in model supersonic combustors

Experimental investigations on the ignition and combustion stabilization of kerosene with pilot hydrogen in Mach 2.5 airflows were conducted using two test combustors, with cross sections of 30.5 x 30 and 51 x 70 mm, respectively. Various integrated modules, including the combinations of different pilot injection schemes and recessed cavity flameholders with different geometries, were designed and tested. The stagnation pressure of vitiated air varied within the range of 1.1-1.8 NiPa, while the stagnation temperature varied from 1500 to 1900 K. Specifically, effects of the pilot hydrogen injection scheme, cavity geometry, and combustor scaling on the minimally required pilot hydrogen equivalence ratio were systematically examined. Results indicated that the cavity depth and length had significant effects on the ignition and flameholding, whereas the slanted angle of the aft wall was relatively less important. Two cavities in tandem were shown to be a more effective flameholding mechanism than that with a single cavity. The minimally required pilot hydrogen equivalence ratio for kerosene ignition and stable combustion was found to be as low as 0.02. Furthermore, combustion efficiency of 80% was demonstrated to be achievable for kerosene with the simultaneous use of pilot hydrogen and a recessed cavity to promote the ignition and global burning.

Modeling Study on the Characteristics of Laminar and Turbulent Argon Plasma Jets Impinging Normally upon a Flat Plate in Ambient Air

Modeling study is performed to compare the flow and heat transfer characteristics of laminar and turbulent argon thermal-plasma jets impinging normally upon a flat plate in ambient air. The combined-diffusion-coefficient method and the turbulence-enhanced combined-diffusion-coefficient method are employed to treat the diffusion of argon in the argon-air mixture for the laminar and the turbulent cases, respectively. Modeling results presented include the flow, temperature and argon concentration fields, the air mass flow-rates entrained into the impinging plasma jets, and the distributions of the heat flux density on the plate surface. It is found that the formation of a radial wall jet on the plate surface appreciably enhances the mass flow rate of the ambient air entrained into the laminar or turbulent plasma impinging-jet. When the plate standoff distance is comparatively small, there exists a significant difference between the laminar and turbulent plasma impinging-jets in their flow fields due to the occurrence of a large closed recirculation vortex in the turbulent plasma impinging-jet, and no appreciable difference is found between the two types of jets in their maximum values and distributions of the heat flux density at the plate surface. At larger plate standoff distances, the effect of the plate on the jet flow fields only appears in the region near the plate, and the axial decaying-rates of the plasma temperature, axial velocity and argon mass fraction along the axis of the laminar plasma impinging-jet become appreciably less than their turbulent counterparts.