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301.
The rate of filtration and the water content of cake are influenced by the existence of a dense skin in a highly compressible
cake. The phenomenon of the dense skin has been rarely studied, and its existence has not been verified experimentally. In
this study, the porosity variation in a very compressible cake is measured by using a new experimental apparatus, and with
this the existence of dense skin has been established experimentally. ‘Unified theory on solid-liquid separation’, a recently
developed theory, is utilized for calculating the porosity variation in a very compressible cake. 相似文献
302.
303.
Chih-Chun Hsieh Tao-Chih Chang Dong-Yih Lin Ming-Che Chen Weite Wu 《Metals and Materials International》2007,13(5):411-416
The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel
welds at various welding passes during a tungsten are welding (GTAW) process. The morphology, quantity, and chemical composition
of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD),
scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS),
respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless
steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding.
The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of σ→ϱ+λ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe−Cr−Si intermetallic compound found in
the fusion zone of the third pass welds during multi-pass welding. 相似文献
304.
Marielle Montginoul 《Water Resources Management》2007,21(5):861-871
This paper presents the results of a 2003 national survey of urban water pricing structure implemented by 429 district level
water utilities. After providing some background elements on the diversity of existing water pricing structures, the paper
shows how each structure can be used to achieve different management objectives (water allocation efficiency, costs recovery,
and equity). It then describes the structures adopted by French water utilities, showing that flat rate are rarely adopted;
declining blocks frequently used; and increasing blocks pricing which should be used to promote water use efficiency remain
extremely rare. A statistical clustering is then conducted and a typology of situations elaborated. The paper concludes with
highlighting that current pricing structures are influenced by past practices and that the dominant objective of water utilities
is to cover costs. 相似文献
305.
Ram Devanathan William J. Weber 《JOM Journal of the Minerals, Metals and Materials Society》2007,59(4):32-35
The safe immobilization of nuclear waste in geological repositories is one of the major scientific challenges facing humanity
today. Crystalline ceramics hold the promise of locking up actinides from nuclear fuel and excess weapons plutonium in their
structure thereby isolating them from the environment. This paper presents the atomistic details of radiation damage in a
model ceramic, zircon. 相似文献
306.
Calogero D. Presti Francesco Carrara Giuseppe Palmisano 《Analog Integrated Circuits and Signal Processing》2007,51(1):51-54
A variable-gain up-conversion mixer for 5-GHz WLAN applications is presented, whose input stage is based on a novel variable
gain transconductor. The proposed topology features reduced power consumption by exploiting dc current reuse for mixer biasing.
Moreover, a new low-consumption control circuit is introduced, which achieves a temperature-stable and linear-in-dB characteristic,
providing a 40-dB dynamic range within ±1 dB gain error. 相似文献
307.
308.
309.
310.
Hopkinson bar techniques have played an important role in the study of high-rate deformation and fracture behavior of materials.
In the current work, a split Hopkinson pressure bar was developed for dynamic four-point bend fracture testing, referred to
as a “two-bar (incident and transmitted bars)/four-point” (2-bar/4-pt) bend test. To further understand some fundamental issues
regarding stress wave propagation in this 2-bar/4-pt bend testing system, dynamic fracture tests were performed in pulse-shaped
and unshaped pulse testing conditions. The effect of the pulse shaper on the incident pulse characteristics (rise time and
duration), specimen’s dynamic response (load and loading point displacement), crack initiation time and stress-state equilibrium
were investigated experimentally in the current work. The present results show that stress state equilibrium can be achieved
prior to fracture initiation in notched and precracked specimens. In the pulse-shaped bending test, the specimen is more likely
to attain stress-state equilibrium than in an unshaped incident pulse test. The crack initiation time was extended and the
time required for attaining stress equilibrium was reduced by pulse shaping due to the tailored incident pulse having a longer
rise time, which ensures that stress equilibrium is achieved prior to crack initiation.
This article is based on a presentation made in the symposium entitled “Dynamic Behavior of Materials,” which occurred during
the TMS Annual Meeting and Exhibition, February 25–March 1, 2007 in Orlando, Florida, under the auspices of The Minerals,
Metals and Materials Society, TMS Structural Materials Division, and TMS/ASM Mechanical Behavior of Materials Committee. 相似文献