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51.
A continuous precipitation flame atomization atomic absorption spectrometric method for the indirect determination of sulphate is proposed. By using a reversed flow-injection configuration for precipitation as barium sulphate, this anion was determined in the range 10–150 g/ml, with a relative standard deviation of 2.6%. The sensitivity was increased by a factor of seven by using a nitrous oxide-acetylene flame to measure barium. 相似文献
52.
Zhen Jun WANG* Zheng Hua SONG Department of Chemistry Northwest University Xian 《中国化学快报》2003,14(3):283-286
Benzoicacidisacommonadditiveusedwidelyasfoodpreservativeandplasticizer.Itcouldpromoteseverereactiontoallergicpopulationevenatlowconcentrationlevel1.Routinemethodsfortheassayofbenzoicacidincludeschromatographic2-6,spectrophotometry7,8,capillaryelectrophoresis9-13andelectrochemicaltitration14.Stokes15etal.monitoredairbornebenzoicacidbasedonsurface-enhancedRamanscatteringtechniques.Thereisalsoreportonamicrobialsensorusingpseudomonasforbenzoicacidandtheirderivativesinaqua16.Interestofusinglumines… 相似文献
53.
Nidetzky Bernd Griessler Richard Weinhausel Andreas Haltrich Dietmar Kulbe Klaus D. 《Applied biochemistry and biotechnology》1997,(1):159-172
Some important process properties of α-l,4-D-ghican phosphorylases isolated from the bacteriumCorynebacterium callunae and potato tubers (Solatium tuberosum) were compared. Apart from minor differences in their stability and specificity (represented by the maximum degree of maltodextrin
conversion) and a 10-fold higher affinity of the plant phosphorylase for maltodextrin (K
M of 1.3 g/L at 300 mM of orthophosphate), the performances of both enzymes in a continuous ultrafiltration membrane reactor
were almost identical. Product synthesis was carried out over a time course of 300–400 h in the presence or absence of auxiliary
pullulanase (increasing the accessibility of the glucan substrate for phosphorolytic attack up to 15–20%). The effect of varied
dilution rate and reaction temperature on the resulting productivities was quantitated, and a maximum operational temperature
of 40°C was identified. 相似文献
54.
55.
56.
D. A. Carlson 《Journal of Optimization Theory and Applications》1986,51(1):41-62
In this paper, we investigate the existence of finitely optimal solutions for the Lagrange problem of optimal control defined on [0, ) under weaker convexity and seminormality hypotheses than those of previous authors. The notion of finite optimality has been introduced into the literature as the weakest of a hierarchy of types of optimality that have been defined to permit the study of Lagrange problems, arising in mathematical economics, whose cost functions either diverge or are not bounded below. Our method of proof requires us to analyze the continuous dependence of finite-interval Lagrange problems with respect to a prescribed terminal condition. Once this is done, we show that a finitely optimal solution can be obtained as the limit of a sequence of solutions to a sequence of corresponding finite-horizon optimal control problems. Our results utilize the convexity and seminormality hypotheses which are now classical in the existence theory of optimal control.This research forms part of the author's doctoral dissertation written at the University of Delaware, Newark, Delaware under the supervision of Professor Thomas S. Angell. 相似文献
57.
58.
建立了耐硫甲烷化循环式反应器的拟均相一维模型,考察了床层直径,循环比,入口气体温度及压力和温度范围对反应器操作的影响,结果表明:循环比和温度操作范围是反应器操作的决定因素,对日产5万标准立方煤气的反应器进行了优化设计分析。 相似文献
59.
Pulverized coal plasma gasification 总被引:11,自引:0,他引:11
R. A. Kalinenko A. P. Kuznetsov A. A. Levitsky V. E. Messerle Yu. A. Mirokhin L. S. Polak Z. B. Sakipov A. B. Ustimenko 《Plasma Chemistry and Plasma Processing》1993,13(1):141-167
A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (c), the level of sulfur conversion into the gas phase (s), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.Nomenclature
c
i
volume concentration of components (kmol m–3)
-
x
longitudinal coordinate (m)
-
f
i
source members, determined by variation of the ith component due to chemical reactions in unit volume in unit time (kmol m–3s–1)
-
velocity (m s–1)
-
M
s
ash mass in one particle (kg)
-
C
D
particle drag coefficient
-
3.14
-
r
s
particle radius (m)
-
d
particle diameter (m)
-
density (kg m–3)
-
C
p
heat capacity of components (J molt– K–1)
-
Q
j
thermal effect of reaction (J kmol–1)
- Ej
activation energy of reaction
-
N
l
volume concentration of particles of thelth fraction (m–3)
-
T
temperature (K)
-
emissivity factor of coal particles
-
5.67 × 10–8, blackbody emissivity coefficient (W m–2 K–4)
-
P
pressure (Pa)
-
S
reactor cross section (m2)
-
D
reactor diameter (m)
-
V
reactor volume (m3)
-
L
R
reactor length (m)
-
F
W
friction force on the wall (N)
-
f
g
friction coefficient
-
residence time (s)
- Nu
Nusselt number
- Re
Reynolds number
- Pr
Prandtl number
-
thermal conductivity of gas (J m– s–1 K–1)
-
R
8.3 × 103, universal gas constant (J kmol K–1)
- µ
i
molecular mass of component (kg kmol–1)
-
dynamic viscosity coefficient of gas (kg m–1 s–1)
-
thermal efficiency of plasma reactor
- qarc
specific heat flow from arc (W m–3)
-
P
1
heat supplied in vapor at T = 405 K (W)
-
P
2
heat loss to wall (W)
-
P
3
heat loss in the gas and slag separator chamber (W)
-
P
4
heat loss in the synthesis gas oxidation chamber (W)
-
P
5
heat loss in the slag catcher (W)
-
P
6
heat carried away in the off-gas (W)
- P
heat input of arc (W)
-
P
arc
electric power of arc (W)
- Qsp
specific power consumption (kw Hr kg–1)
-
d
w
specific heat flow to wall (W m–2)
-
c
degree of carbon gasification (%)
-
s
level of sulfur conversion into gas phase (%) 相似文献
60.