On the reassessment of thermal neutron doses in TLD-100 by measuring the residual dose

By employing second readouts and the Phototransferred thermoluminescence (PTTL) method, high doses may be reassessed on the basis of residual dose information. It was shown in the past that for TLD-100, gamma doses can be reassessed by using a simple and efficient method, which consists of expanding the heating time to 30 s. In the present study, the 'extended time' method and the PTTL residual dose evaluations are used for reassessing thermal neutron doses when using TLD-100 crystals. Reassessment characteristics are presented for relatively low thermal neutron doses, in the range between approximately 1 and 18 mSv gamma dose equivalent.     

Relative frequency stability of stable He-Ne gas laser structures

Enhanced He-Ne gas laser stability has been achieved by constructing the mirror and gas discharge tube as an integral unit. The primary components are made from Corning ULE and 99JJW ultralow thermal expansion materials; ultrahigh-vacuum-type materials are used throughout. The ambient pressure sensitivity of these 6328-Å laser structures is 2.5 MHz/torr. Preliminary beat frequency measurements between two lasers, under pressure and temperature-controlled conditions, have yielded a beat frequency spectral width of the order of 2 kHz over an interval of 1 s. This result was achieved without the use of any elaborate sound or vibration isolation. Improved isolation reduced the spectral width to 100 Hz for a measurement duration of 0.02 s. The single-structure mirror-discharge tube has provided relative output power stabilities of better than 3 parts in 1000 over a period of 12 h. The frequency-modulation sensitivity is 1.2 kHz/μA of discharge current, from dc to 100 kHz.     

Measurements of stratospheric aerosols with a combined elastic-Raman-backscatter lidar

Improvements made to the NASA Goddard Space Flight Center Stratospheric Ozone Lidar system have extended its atmospheric-aerosol-measuring capabilities. The methods by which aerosol-scattering ratio, aerosol backscatter, and aerosol extinction are simultaneously derived from lidar data are reported, and results obtained during several intercomparison campaigns at worldwide locations are shown. The results track the evolution of the Mt. Pinatubo aerosol cloud from 1991 to 1994 and report wavelength-dependence information for aerosol backscatter between 308 and 351 nm. Two analysis techniques, a more common inversion method and a combined elastic-Raman-backscatter approach, are also compared.     

Fe3Si基合金的制备及应用研究进展

Ｆｅ３Ｓｉ基合金具有优异的软磁性能,不仅有希望硅钢片（在高频信息领域）,而且还广泛用作音几视频磁头材料和卡片阅读器用磁头材料。本文综述了Ｆｅ３Ｓｉ基合金的制备工艺及应用,并结合我们的研究工作,分析了其研究现状,简要论述了其发展前景。     

Nicrofer 5923 hMo,ein neuer hochkorrosionsbeständiger Werkstoff für die Chemische Industrie,die Umwelttechnik und verwandte Anwendungen

Alloy 59, a new highly corrosion resistant material for the chemical process industry, environmental pollutioncontrol and related applications

1 Vortrag anläßlich der ACHEMA '91, Frankfurt/Main, 09.–15. Juni 1991.

A new nickel-chromium-molybdenum alloy, Alloy 59 has been designed to withstand severest corrosive conditions as encountered in chemical process industry and today's environmental pollution control systems. This alloy, which is composed of about 59% nickel, 23% chromium and 16% molybdenum is compared to the common NiCrMo-alloys Alloy C-276, Allo C-4, Alloy 22 and Alloy 625. Conditions of corrosion testing have been varied between oxidizing and reducing mineral acids combined with differing halide contaminations. Furthermore, corrosion data in hot concentrated sulfuric acid and in technical relevant solutions of flue gas desulfurization plants are given. The general resistance to corrosion in sulfuric acid and in hydrochloric acid is highlighted in isocorrosion diagrams. Alloy 59 has an excellent resistance to uniform and localized corrosion in all these environments. The new Alloy 59 clearly outperforms the other NiCrMo-alloys C-276, C-4 and 22 as well under oxidizing conditions as in the strongly reducing hydrochloric acid environment. The time-temperature-sensitization-diagram demonstrates the alloy's excellent thermal stability and reveals an improvement compared to Alloy 22 or the well-known Alloy C-276. Alloy 59, therefore, can be used in the as-welded condition without any additional solution annealing treatment. The excellent corrosion resistance is not impaired if the alloy is processed or fabricated to equipment even in larger sections. Weldability with a matching filler metal is without problems as demonstrated i.a. in the varestraint test.     

The influence of nickel and copper on the austempering of ductile iron

In the present investigation, the effect of alloying elements on the austempering process, austempered microstructure, and structural parameters of two austempered ductile irons (ADI) containing 0.6% Cu and 0.6% Cu/1.0% Ni as the main alloying elements was investigated. The optical metallography and x-ray diffraction were used to study the changes in the austempered structure. The effect of alloying additions on the austempering kinetics was studied using the Avrami equation. Significantly more upper bainite was observed in the austempered Cu-Ni alloyed ADI than in Cu alloyed ADI. The volume fraction of retained austenite (X _γ), the carbon level in the retained austenite (C _γ), and the product X _γ C _γ in an austempered structure of Cu-alloyed ADI are higher than in Cu-Ni-alloyed ADI. The austempering Kinetics is slowed down by the addition of Ni.     

Improvement of Formability by Oscillation of Internal Pressure in Pulsating Hydroforming of Tube

A new history of internal pressure in the hydroforming processes of tubes is developed to attain high formability. The effect of improvement of formability by the oscillation of internal pressure in a pulsating hydroforming process of tubes is examined using both finite element simulation and experiment. The deformation behaviour during the hydroforming is greatly affected by the oscillation of internal pressure. For a monotonic history of small internal pressure, the wrinkling was caused by insufficient bulging, whereas the necking and bursting occurred for a monotonic history of large internal pressure. The occurrence of these defects can be avoided by oscillating the internal pressure in the pulsating hydroforming. The improvement of formability in the pulsating hydroforming is due to both low pressure and oscillation of pressure. The effects of the amplitude and cycle number of pressure in the pulsating hydroforming on the deformation behaviour are investigated. It is found the oscillation of internal pressure is effective in preventing the occurrence of defects.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Downward movement of nitrate and ammonium nitrogen in a flatland ultisol

Three field trials were conducted in the early and late rainy season on a Piarco Series soil (Aquoxic Tropudults) in Central Trinidad to monitor downward movement of NH ₄ ⁺ -N and NO ₃ ^- -N under flat-tilled and ridge-tilled conditions as affected by mulch application. The first experiment was carried out in the early rainy season under bare-fallowed conditions, while okra (Abelmoschus esculentus) was the test crop used in the two remaining trials, which were conducted during the early and late rainy season periods. The plots were fertilized with urea seven days after crop emergence and 14 days after land preparation for the cropped and bare-fallowed experiments respectively. Soil samples were collected weekly after fertilizer application and analyzed for NH ₄ ⁺ -N, NO ₃ ^- -N and soil water.Urea application increased NH ₄ ⁺ -N levels in the soil and NH ₄ ⁺ -N was the dominant inorganic N form observed for the first four weeks after fertilization. Mulch application decreased NH ₄ ⁺ -N and NO ₃ ^- -N soil levels. Ridging the soil increased downward movement of NH ₄ ⁺ -N and NO ₃ ^- -N. Under bare-fallowed conditions, downward movement of NH ₄ ⁺ -N was noted in the 30 to 45 cm soil layer at seven days after fertilization, while under cropped conditions its movement was restricted to the 15 to 30 cm layer within the same period. In bare-fallowed soil, increased NO ₃ ^- -N and its downward movement was noted after four weeks of fertilization. In the cropped soil, downward movement of NO ₃ ^- -N was observed one week after fertilization in the early rainy season and three weeks after fertilization in the late rainy season.