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51.
The limit of penetration of a given coal-tar pitch into two cokes during mixing of the coke and liquid tar has been studied. It was shown that tar penetration is limited by compression of gas occluded in pores. Mercury porosimetry of cokes and pyrolysed coke-tar mixtures as well as micrographs of cokes impregnated with tar allow one to estimate the limiting pore diameter of tar penetration into coke at ca. 6 μm for the system considered. 相似文献
52.
53.
54.
Jean-Paul Randin 《Journal of Applied Electrochemistry》1985,15(3):365-377
The prediction of the state-of-discharge of numerous types of Zn-Ag2O button cells from six international manufacturers has been investigated using the impedance technique over an extended frequency range. The frequency responses at various states-of-discharge are presented and it is shown that the changes in impedance which result from discharging provide several potential parameters for the state-ofdischarge prediction. The complex impedance plot of the undischarged cells usually shows a fairly welldefined semicircle at high frequencies and a straight line with a slope between 40 and 50° at low frequencies. As discharge proceeds, the diameter of the semicircle increases and the overlap between the semicircle and the low-frequency straight line increases. The most attractive method would be to determine a parameter such as a characteristic relaxation frequency in the complex impedance plot. Unfortunately, no unambiguous characteristic parameter can be extracted due to the non-ideal shape of the impedance response at high frequencies. The determination of the diameter of the high-frequency semicircle has been faced with the same difficulties. The most reliable test was found to be the determination of either the phase of the impedance, or a corrected phase
– taken from the high-frequency intercept. The proposed prediction is a go/no go indication on the basis of one- or two-frequency measurements for or,
– respectively. The selection is made at 20–40% state-of-discharge. The charge withdrawn is negligibly small and the time of the test is between 1 and 100 s depending on the type of cell. A calibration is necessary for each cell dimension and each manufacturer. Some 10–16% of the types of cells investigated could not be selected successfully, mainly because of too large a dispersion of the electrical characteristics of the cells, especially for small newly developed types, and of the similarity of the ( and values in the low and high state-of-discharge in the appropriate frequency range. The latter difficulty arises from the difference of the frequency response between the undischarged and the partly discharged cells occurring at high frequencies.This is the second of a series of papers dedicated to Professor Ernest Yeager on the ocasion of his 60th birthday. 相似文献
55.
56.
Jean-Marc David Jean-Paul Krivine Jean-Pierre Tiarri Benoit Ricard 《Journal of Intelligent and Robotic Systems》1988,1(3):287-298
DIVA is an expert system for turbine generator diagnosis. Its aim is to help a plant operator interpret vibration evolution to diagnose developing faults. Interpretation of vibration evolution is primarily a recognition process which is achieved by a particular model of heuristic classification. DIVA tries to recognize the observed situation among a hierarchy of typical situations.The purpose of this paper is to present the model we used for heuristic classification, based on prototypes. Prototypes represent typical problem situations and may also be seen as experts with special knowledge of what to do in such situations. We argue that this model presents significant advantages to deal with complex problems such as vibration surveillance. 相似文献
57.
Hothaifa Al Dabbagh Nikolaos Perakis Ch-Michel Wolff Jean-Paul Schwing 《Electrochimica acta》1984,29(4):567-573
Studies of air pollution by metals contained in dust particules usually require mineralization of a dust-collecting filter. This treatment introduces impurities into the sample. To avoid such contamination, an anodic stripping cell was constructed requiring no preliminary treatment of the sample filter. The cell uses a three-electrode amperometric system in differential pulse anodic stripping mode (DPAS). Solubilization of the metals from dust by a complexing agent, instead of the strong acid normally encountered in other methods, allows selective determination of metals according to their chemical form. With this cell, minimal handling of the collection filter and a large area mercury-coated vitreous carbon electrode located close to the sample filter (2 mm) lead to limits of detection as low as 0.15 μg of lead and 10 ng of copper. Precision is 2% for lead determination and 4% for copper determination (RSD). 相似文献
58.
Jean-Paul Decruppe Francis Dujardin Marie-France Charlier Alphonse Charlier 《Carbon》1979,17(3):237-241
Electrical resistance measurements were performed on different varieties of carbon blacks (Sterling Fr, MT, S, Black Pearls 2) under compression up to 660 kgf/cm2 to determine the real resistivity of the carbon material. The general shape of the curves log p= - s log P are in good agreement with those reported by Mrozowski. Two theories have been proposed to explain the mechanism of the current flow through the particles. Holm's Contacts and the Tunnel effect between particles. The results for thermal blacks seem to agree with the first interpretation while the behaviour of the Channel blacks rather follows the second. 相似文献
59.
Oryctes monoceros is the most serious pest in coconut plantations, causing up to 40% damage in tropical Africa, especially in Ivory Coast. With a view to reducing pest populations by olfactory trapping, field trials were carried out to assess the efficiency of a synthetic aggregation pheromone: ethyl 4-methyloctanoate (1), 4-methyloctanoic acid (2), a related volatile produced by males, and decaying palm material, either oil palm empty fruit bunches (EFB) or pieces of coconut wood (CW) of various ages. Vertical polyvinyl chloride tube traps (2 × 0.16 m with two openings in the upper half), embedded in the soil, were more efficient than 30-L pail traps 1.5 m above ground. EFB, which were inactive alone, synergized captures with synthetic pheromone. CW was more effective than EFB in comparative trials. Compound 2 did not catch any beetles when assessed with EFB, and reduced catches by 1 + EFB when tested at >10% with the pheromone. Trapping over 6 mo in 2002 and 2003 in a 19-ha coconut plot inside a 4,000-ha oil palm estate reduced damage from 3.8% in 2001 to 0.5% in 2002, then to 0.2% in 2003. Damage was 0.0% in 2004 with routine trapping using 32 traps, which caught 3369 beetles in 9 mo. The results are discussed in relation to other Dynastid palm pests and coconut protection in Ivory Coast. 相似文献
60.
Gwladys Perrais Sophie Derelle Laurent Mollard Jean-Paul Chamonal Gerard Destefanis Gilbert Vincent Sylvie Bernhardt Johan Rothman 《Journal of Electronic Materials》2009,38(8):1790-1799
The impulse response in frontside-illuminated mid-wave infrared HgCdTe electron avalanche photodiodes (APDs) has been measured
with localized photoexcitation at varying positions in the depletion layer. Gain measurements have shown an exponential gain,
with a maximum value of M = 5000 for the diffusion current at a reverse bias of V
b = 12 V. When the light was injected in the depletion layer, the gain was reduced as the injection approached the N+ edge
of the junction. The impulse response was limited by the diode series resistance–capacitance product, RC, due to the large capacitance of the diode metallization. Hence, the fall time is given by the RC constant, estimated as RC = 270 ps, and the rise time is due to the charging of the diode capacitance via the transit and multiplication of carriers
in the depletion layer. The latter varies between t
10–90 = 20 ps (at intermediate gains M < 500) and t
10–90 = 70 ps (at M = 3500). The corresponding RC-limited bandwidth is BW = 600 MHz, which yields a new absolute record in gain–bandwidth product of GBW = 2.1 THz. The increase
in rise time at high gains indicates the existence of a limit in the transit-time-limited gain–bandwidth product, GBW = 19 THz.
The impulse response was modeled using a one-dimensional deterministic model, which allowed a quantitative analysis of the
data in terms of the average velocity of electrons and holes. The fitting of the data yielded a saturation of the electron
and hole velocity of v
e = 2.3 × 107 cm/s and v
h = 1.0 × 107 cm/s at electric fields E > 1.5 kV/cm. The increase in rise time at high bias is consistent with the results of Monte Carlo simulations and can be
partly explained by a reduction of the electron saturation velocity due to frequent impact ionization. Finally, the model
was used to predict the bandwidth in diodes with shorter RC = 5 ps, giving BW = 16 GHz and BW = 21 GHz for x
j = 4 μm and x
j = 2 μm, respectively, for a gain of M = 100. 相似文献