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61.
The nonlinear Boussinesq equation is used to understand water table fluctuations in various ditch drainage problems. An approximate solution of this equation with a random initial condition and deterministic boundary conditions, recharge rate and aquifer parameters has been developed to predict a transient water table in a ditch-drainage system. The effects of uncertainty in the initial condition on the water table are illustrated with the help of a synthetic example. These results would find applications in ditch-drainage design.Notation
A
/ tanh t
-
a
lower value of the random variable representing the initial water table height at the mid point
-
a+b
Upper value of the random variable representing the initial water table height at the midpoint
-
B
tanh t
-
C
4/
-
h
variable water table height
- h
mean of the variable water table height
-
h
m
variable water table height at the mid point
- h
m
mean of the variable water table height at the mid point
-
K
hydraulic conductivity
-
L
half spacing between the ditches
-
m
0
initial water table height at the mid point
-
N
Uniform rate of recharge
-
S
specific yield
-
t
time of observation
-
x
distance measured from the ditch boundary
-
(4/SL)(NK)1/2
-
(L/4)(N/K)1/2
-
dummy integral variable 相似文献
62.
朱爱华 《山西财政税务专科学校学报》2004,6(5):30-31
“入世”使企业的经营环境由国内的有限市场突变为广阔的全球大市场。环境的巨变必然要改变企业整体的经营方式,理财模式的改变则首当其冲。 相似文献
63.
文章简要介绍了山西天镇晚白垩世恐龙化石的发现、发掘概况及动物群的特征,讨论了含化石地层—灰泉堡组的时代,认为无疑应属晚白垩世。以晚白垩世蜥脚类巨龙科和鸟臀类甲龙科化石为代表,别具特色的新恐龙动物群为一突破性的发现,对它的深入研究,将对蜥脚类、甲龙类及其共生动物群的组成、性质、演化、迁徙和动物地理区的划分及探讨白垩纪末恐龙的绝灭有重要的科学意义。 相似文献
64.
B. L. Myers Ph.D. N. L. Enrick Ph.D. A. J. Melcher Ph.D. 《Journal of the Academy of Marketing Science》1974,2(1):249-261
The efficiency of a research design may be measured in terms of the degree to which knowledge is enhanced within given resource
constraints. Thus, two different types of research design, even though they contain the same number of expected observations,
may differ considerably in the amount of information provided. An example is the number N of 32 observations obtained with
an analysis of variance witheither 2 factors, 2 levels per factor and a replication of 8or 4 factors, 4 levels per factor and a replication of 2. We analyze and compare the relative efficiencies of regression and
variance analysis models and their implications to research strategy development. Three major considerations are evaluated:
(1) short versus long time horizon (interval until effects of a decision are realized), (2) small versus large cost of erroneous
rejection of the Null Hypothesis and (3) gross versus refined stage of development of the research study. A set of general
guidelines towards improved designs is developed. 相似文献
65.
Yu. K. Zaretskii V. N. Vorob'ev 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1991,25(1):30-36
1. | The predicted character of development of landslide movements permits saying that the slope is in a state of long-term creep and is extremely sensitive in the initial operating period to the character of technogenic effects. |
2. | Long-term stability of the slope is provided only in the case of implementing the complete system of landslide-control measures. |
3. | For monitoring the dynamics of the landslide process, it is necessary to continue instrumental observations during the entire operating period. |
66.
N. N. Arshenevskii M. I. Klasson 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1991,25(1):15-20
1. | The obtainment, as a result of numerous calculations on a computer, of generalized relations of the main indices of the load dropping process in the field TW/Tu–TW/TS makes it possible at the initial design stages to rapidly analyze the decisions made about the parameters of pressure conduits and pump-turbines and regulating regimes. |
2. | By virtue of the peculiarities of the universal characteristics of reversible diagonal-flow pump-turbines, the maximum value of the temporal nonuniformity of the operation of the unit during load dropping in real ranges of the constants of inertia of the conduits and unit does not exceed the allowable standard value max=nmax/n0=1.6. |
3. | The search for efficient regulating regimes reducing water hammer facilitates the introduction of the new concepts initial and final water hammer and plotting the corresponding zones on generalizing graphs. |
4. | Rotating the runner blades of the diagonal-flow pump-turbines along with closing the gate apparatus after dropping the load is favorable for reducing water hammer. In this respect they can be more preferable than reversible mixed-flow pump-turbines for the same values of the heads, TW/TS and TW/Tu. |
67.
68.
Runoff simulation is highly significant for hydrological monitoring, flood peak simulation, water resource management, and basin protection. Runoff simulation by distributed hydrological models, such as the soil and water assessment tool (SWAT) model which is the most widely used, is becoming a hotspot for hydrological forecasting research. However, parameter calibration is inefficient and inaccurate for the SWAT model. An automatic parameter calibration (APC) method of the SWAT model was developed by hybrid of the genetic algorithm (GA) and particle swarm optimization (PSO). Multi‐station and multi‐period runoff simulation and accuracy analysis were conducted in the basin of the Zhangjiang River on the basis of this hybrid algorithm. For example, in the Yaoxiaba Station, the calibration results produced an R2 of 0.87 and Nash Sutcliffe efficiency (NSE) index of 0.85, while verification results revealed an R2 of 0.83 and NSE of 0.83. Results of this study show that the proposed method can effectively improve the efficiency and simulation accuracy of the model parameters. It can be concluded that the feasibility and applicability of GA‐PSO as an APC method for the SWAT model were confirmed via case studies. The proposed method can provide theoretical guidance for many hydrological research fields, such as hydrological simulation, flood prevention, and forecasting. 相似文献
69.
Upgrading management opportunities for women 总被引:1,自引:0,他引:1
Powell GN 《HRMagazine : on human resource management》1990,35(11):67-70
70.
Time--there is never enough of it. There are never enough hours in the day to do everything at work and at home. Today's employees, forced to choose between work obligations and family responsibilities, often feel frazzled and guilty. Some employers recognize these conflicts and are finding ways to lighten the work/family load. They are offering a sophisticated combination of dependent-care options, flexible work hours and family-related benefits tailored to meet the needs of the employees within their specific industries. HRMagazine looks at leaders in six major industries--manufacturing, health, communications/technology, financial management, government and retail. No one can give employees that 25-hour day that everyone feels they need to juggle all their work and family obligations. But these industry leaders have provided a nurturing environment where employees can successfully balance those obligations. 相似文献