热交换器中典型水盖密封结构及其成本分析

介绍热交换器中3种典型的水盖密封结构,并通过示例对各种水盖密封结构的制造成本进行对比和分析,得出成本相对较低的水盖密封结构型式,便于在制冷压力容器设计过程中优化结构及降低成本。

Influence of Vegetation Coverage on Surface Runoff and Soil Moisture in Rainy Season in Dry-hot Valley

[Objective]The research aimed to study the effects of vegetation coverage on the changes of soil moisture in rainy season in dry-hot valley.[Method]The surface runoff and soil moisture of slope with vegetation coverage and bare land in rainy reason in Jinsha River at Yuanmou County of Yunnan Province were observed continuously.Moreover,the statistical analysis was made based on the observation data.[Result]The vegetation coverage could decrease surface runoff and the surface runoff on bare land（CK） was 22 times as the plot with vegetation coverage.The soil water content in 0-180 cm layer with vegetation coverage increased by 37.8% than bare land.The stability of soil moisture content in deep layer was enhanced and the physical properties stability of soil was maintained.The soil moisture content in different depth of soil had significant difference and the changes of soil moisture content were obviously different.[Conclusion]The vegetation coverage of slope could change the soil hydrology obviously and keep soil moisture at the higher level,especially at soil layer below 20 cm.

Effects of Ground Mulching Treatments on Soil Moisture Content in Second-generation Seed Garden of Pinus elliottii

Different ground mulching treatments were designed to observe the effects on soil moisture content in a second-generation seed orchard of Pinus elliottii. The results showed that： （1） there were extreme differences in soil moisture content Ⅰ and soil moisture content Ⅲ, but no obvious difference in soil moisture content II was observed; and （2） the high-to-low order of soil moisture content Ⅰ under different ground mulching treatments was white film〉sawdust〉black film〉the control, and the highest value was higher than the lowest one by 26.69%; the high-to-low order of soil moisture content Ⅱ under different ground mulching treatments was white film〉black film〉sawdust〉the control, and the highest value was higher than the lowest one by 20.64%; and the high-to-low order of soil moisture content Ⅲ under different ground mulching treatments was black film〉white film〉sawdust〉the control, and the highest value was higher than the lowest one by 26.61%.

Effects of Different Plastic films Mulching on Soil Temperature and Moisture, the Growth and Yield of Sugarcane

[Objective] The effects of different plastic films mulching on soil temperature and moisture, and growth and yield of sugarcane were discussed in order to provide references for using different plastic film in sugarcane pro-duction. [Method]Four kinds of plastic films viz., normal colorless transparent plastic film, milky photodegradation weeding plastic film, black plastic film and gray-black plastic film were used in sugarcane cultivation by using no film mulching as the control. Soil temperature and moisture were measured during plastic film mulching period, and sugarcane agronomic traits such as emergence rate, tillering rate, plant hight, stalk diameter and effective stalk number were investigated during growth period, the cane yield and economic benefits were calculated during harvest period. [Result] The results showed that plastic film mulching could significantly increase soil temperature and moisture. Com-pared with the control, soil temperature was increased by 0.3-0.8 ℃ in three plastic films mulching treatment except for gray-black plastic film mulching. The soil moisture of all mulching treatments was 10.1%-17.4% higher than the control. Furthermore, the seedling emergence rate, tillering rate, effective stalk number and cane yield also could be improved using plastic film mulching,which were increased by 0.8%-9.9%, 20.6%-34.9%, 5190-10980 stalks/hm^2and6.4%-14.9% as compared to the control,while plant height and stalk diameter were found to be no significant effect by plastic film mulching. The results of benefit analysis indicated that, milky photodegradation weeding film mulching had the highest economic benefit, the second were normal colorless transparent plastic film mulching and black plastic film mulching, which were 5 987.2, 1 876.5 and 1 813.5 Yuan/hm^2 higher than the control. The gray-black film mulching treatment had poor benefit.[Conclusion] The milky photodegradation weeding plastic film could be vigorously extended in sugarcane production. Normal colorless transparent plastic film and black plastic film could be ex-tended gradually as a new kind of plastic film. The grayblack film should not be used for its higher cost and more thickness.

Effects of Tillage and Mulch Methods on Soil Moisture inWheat Fields of Loess Plateau, China

Effects of different methods of tillage and mulch on soil moisture at fallow stage were studied in rainy andrain-deficient years. Soil moisture content per 20 cm was measured vertically within 0-300 cm soil layers in anexperiment with five treatments: deep-loosening tillage (DLT), traditional tillage (TT), plastic mulch (PM),straw mulch (SM) and plastic plus straw mulch (PSM). All mulch treatments were under no tillage conditions.Total storage of precipitation in soil from 0 to 300 cm was determined before sowing. Results showed thatthe new methods of tillage and mulch were the basic ways to improve water condition in dryland wheat fields.In a rainy year, PM with no tillage played a significant role in storing and conserving precipitation, while ina rain-deficient year, the role was not significant. Due to evaporation, DLT did not promote the storage ofsoil moisture. SM was the best way to store and conserve soil moisture. In SM treatment the wheat yieldsincreased by more than 20%.

Experimental Study on the Resistance of a Transport Ship Navigating in Level Ice

This study investigates the resistance of a transport ship navigating in level ice by conducting a series of model tests in an ice tank at Tianjin University. The laboratory-scale model ship was mounted on a rigid carriage using a one-directional load cell and then towed through an ice sheet at different speeds. We observed the ice-breaking process at different parts of the ship and motion of the ice floes and measured the resistances under different speeds to determine the relationship between the ice-breaking process and ice resistance. The bending failure at the shoulder area was found to cause maximum resistance. Furthermore, we introduced the analytical method of Lindqvist （1989） for estimating ice resistance and then compared these calculated results with those from our model tests. The results indicate that the calculated total resistances are higher than those we determined in the model tests.

Influence of groundwater level change on vegetation coverage and their spatial variation in arid regions

Sampling and testing are conducted on groundwater depth and vegetation coverage in the 670 km2 of the Sangong River Basin and semi-variance function analysis is made afterwards on the data obtained by the application of geo-statistics. Results showed that the variance curve of the groundwater depth and vegetation coverage displays an exponential model. Analysis of sampling data in 2003 indicates that the groundwater depth and vegetation coverage change similarly in space in this area. The Sangong River Basin is composed of upper oasis, middle ecotone and lower sand dune. In oasis and ecotone, influenced by irrigation of the adjoining oasis, groundwater level has been raised and soil water content also increased compared with sand dune nearby, vegetation developed well. But in the lower reaches of the Sangong River Basin, because of descending of groundwater level, soil water content decreased and vegetation degenerated. From oasis to abandoned land and desert grassland, vegetation coverage and groundwater level changed greatly with significant difference respectively in spatial variation. Distinct but similar spatial variability exists among the groundwater depth and vegetation coverage in the study area, namely, the vegetation coverage decreasing (increasing) as the groundwater depth increases (decreases). This illustrates the great dependence of vegetation coverage on groundwater depth in arid regions and further implies that among the great number of factors affecting vegetation coverage in arid regions, groundwater depth turns out to be the most determinant one.

Iron Phosphate Coating: A Novel Approach to Controlling Pyrite Oxidation

A novel coating technique was developed for controlling Pyrite oxidation. The technique invo1ved leachingpyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide. Duringthe leaching process, the iron released from pyrite by hydrogen proxide was precipitated by phosphate as aferric phosphate coating. This coating was shown to be able to effectively prevent Pyrite from oxidation and itcould be established at the expense of only surface portions of Pyrite. The emergence of this technique couldprovide a unique potential route for abating acid mine drainage and reclaiming sulfide-containing degradedmining land.

Discretization Approach in Integrated Hydrologic Model for Surface and Groundwater Interaction

The commonly used discretization approaches for distributed hydrological models can be broadly categorized into four types,based on the nature of the discrete components:Regular Mesh,Triangular Irregular Networks(TINs),Representative Elementary Watershed(REWs) and Hydrologic Response Units(HRUs).In this paper,a new discretization approach for landforms that have similar hydrologic properties is developed and discussed here for the Integrated Hydrologic Model(IHM),a combining simulation of surface and groundwater processes,accounting for the interaction between the systems.The approach used in the IHM is to disaggregate basin parameters into discrete landforms that have similar hydrologic properties.These landforms may be impervious areas,related areas,areas with high or low clay or organic fractions,areas with significantly different depths-to-water-table,and areas with different types of land cover or different land uses.Incorporating discrete landforms within basins allows significant distributed parameter analysis,but requires an efficient computational structure.The IHM integration represents a new approach interpreting fluxes across the model interface and storages near the interface for transfer to the appropriate model component,accounting for the disparate discretization while rigidly maintaining mass conservation.The discretization approaches employed in IHM will provide some ideas and insights which are helpful to those researchers who have been working on the integrated models for surface-groundwater interaction.

Ranking Agricultural Sub-basins for Environmental Protection

Reconstructing long-term vegetation buffers along streams in agricultural landscapes has become a common environmental restoration strategy for improving water quality and wildlife habitat connectivity.This article developed a linear weighted model to rank the priority of agricultural sub-basins for the establishment of vegetative buffers.The method was applied to an agricultural watershed of 146 km2 in Ontario,Canada.The watershed was divided into 11 sub-basins as basic decision units.In each subbasin,four stream buffer schemes with widths of 5,10,15 and 20m were generated.For each buffer,three benefit-cost attributes of reconstructing vegetation cover were estimated,which include acreage per dollar,sediment abatement per dollar and habitat benefit per dollar.These attributes were first normalized using a linear normalization approach to eliminate the effects across different units.The normalized attributes were then integrated using a simple additive weighting method to rank the 11 sub-basins for prioritizing spatial restoration action.A sensitivity analysis was also conducted to observe the impact of a change in attribute weights on the management decisions.The results suggest that vegetation buffers reconstructed for achieving the water quality goal are not effective in improving habitat connectivity and vice versa.

Persistence of Snow Cover Anomalies over the Tibetan Plateau and the Implications for Forecasting Summer Precipitation over the Meiyu-Baiu Region

The present reported study investigated the persistence of snow anomalies over the Tibetan Plateau(TP) from the preceding seasons to summer and the relationship between the previous snow cover anomaly and summer precipitation over East Asia. The results showed that, relative to other snow indices, such as the station observational snow depth(SOSD) index and the snow water equivalent(SWE) index, the snow cover area proportion(SCAP) index calculated from the SWE and the percentage of visible snow of the Equal-Area Scalable Earth Grids(EASE-grids) dataset has a higher persistence in interannual anomalies, particularly from May to summer. As such, the May SCAP index is significantly related to summer precipitation over the Meiyu-Baiu region. The persistence of the SCAP index can partly explain the season-delayed effect of snow cover over the TP on summer rainfall over the Meiyu-Baiu region besides the contribution of the soil moisture bridge. The preceding SST anomaly in the tropical Indian Ocean and ENSO can persist through the summer and affect the summer precipitation over the Meiyu-Baiu region. However, the May SCAP index is mostly independent of the simultaneous SSTs in the tropical Indian Ocean and the preceding ENSO and may affect the summer precipitation over the Meiyu-Baiu region independent of the effects of the SST anomalies. Therefore, the May SCAP over the TP could be regarded as an important supplementary factor in the forecasting of summer precipitation over the Meiyu-Baiu region.

Effects of Winter Cover Crop and Straw Returning on the Functional Diversity of Rhizosphere Microflora in Double-crop Rice Paddies

The functional diversity of rhizosphere microflora which is also known as the “microbial community” is a sensitive indicator of soil quality subject to the type of winter cover crop and straw returning.In order to evaluate the effects of different winter cover crops and returning patterns on the functional diversity of rhizosphere microflora in double-crop rice paddies,we designed five winter cover crops and straw returning combinations to analyze their effects on the functional diversity of rhizosphere microflora in rice paddies: ryegrass (Lolium multiflorumL.)–double-crop rice (Ry),milk vetch (Astragalus sinicus L.)–double-crop rice (Mv),Rape (Brassica napus L.)–Double-crop rice (Ra), Potato (Solanum tuberosum L.)–double-crop rice (Po),and winter fallow–doublecrop rice (CK,the control).In this paper,the average well color development (AWCD) in Biolog-GN plates indicated the capacity for carbon utilization by the rhizosphere microbial community.We analyzed the rhizosphere microbial community functional diversity of the paddy soils with the above five treatments by using the Biolog-GN system.The results showed that applications of winter cover crop and straw returning caused high increases in AWCD compared with CK,and the AWCD values for samples with Po treatment was greater than those with Ry and CK treatments at the early and late rice maturity stages. It was concluded that applications of winter cover crop and straw returning can cause changes in the carbon utilization efficiency of rhizosphere microflora.There were differences in the genetic diversity of the rhizosphere microflora among different treatments at the maturity stage of early and late rice.The richness,Shannon,and McIntosh Index under different winter cover crop and straw returning treatments were significantly different.The highest indexes were observed in the Po treatment and the lowest in the CK at the maturity stage of early and late rice.The richness, Shannon,and McIntosh Index under different treatments ranked in descending order is as follows: Po>Ra>Mv>Ry>CK.Principal Component Analysis (PCA) of substrate reactions were conducted in this research.The results indicated that the pattern of carbon source utilization varied with winter cover crop treatments,and that carbohydrates and amino acids were the main carbon sources of rhizosphere microorganisms.To conclude,the application of winter cover crop and straw returning to paddy fields could significantly increase the carbon source utilization, species richness,and species evenness of rhizosphere microflora in double-crop rice paddies.

Regimes of Runoff Components on the Debris-covered Koxkar Glacier in Western China

By using a degree-day based distributed hydrological model, regimes of glacial runoff from the Koxkar glacier during 2007-2011 are simulated, and variations and characteristics of major hydrological components are discussed. The results show that the meltwater runoff contributes 67.4%, of the proglacial discharge, out of which snowmelt, clean ice melting, buried-ice ablation and ice-cliff backwasting account for 22.4%, 21.9%, 17.9% and 5.3% of the total melt runoff, respectively. Rainfall runoff is significant in mid-latitude glacierized mountain areas like Tianshan and Karakorum. In the Koxkar glacier catchment, about 11.5% of stream water is initiated from liquid precipitation. Spatial distributions for each glacial runoff component reveal the importance of climatic gradients, local topography and morphology on glacial runoff generation, and temporal variations of these components is closely related to the annual cycle of catchment meteorology and glacier storage. Four stages are recognized in the seasonal variations of glacier storage, reflecting changes in meltwater yields, meteorological conditions and drainage systems in the annual hydrological cycle.

Degradation of Wetlands on the Qinghai-Tibet Plateau:A Comparison of the Effectiveness of Three Indicators

The Qinghai-Tibet Plateau encompasses a large quantity of wetlands, some of which have been degraded to varying severity levels. In the literature, a number of degradation indicators have been proposed to evaluate ecological health of wetlands, but their effectiveness in the plateau environment remains unknown. In this study, we assessed the effectiveness of three degradation indicators, soil moisture content at lo em deep, vegetative cover, and density of pika burrows. The degradation severity of wetlands in Maduo County on the Qinghai-Tibet Plateau is enumerated at four levels, intact, slight, moderate and severe. Analysis of xo6 samples collected in the field demonstrates that the density of pika burrows is the least reliable indicator. By comparison, vegetative cover and underlying soil moisture content are more reliable, even though neither is a perfect indicator as the difference among adjacent levels of severity as revealed by t-test is not always statistically significant. The imperfection of vegetative cover as an indicator is due to its variation among different types of wetlands. The limitation of moisture content is attributed to its non-linear relationship with wetland degradation. Above the threshold of about 50% in moisture content wetlands are unlikely to be degraded. It is recommended that moisture be measured at the point near the surface and vegetative cover be further differentiated by species in order to improve their effectiveness.

Water Wave Scattering by a Nearly Circular Cylinder Submerged Beneath an Ice-cover

Assuming linear theory, the two-dimensional problem of water wave scattering by a horizontal nearly circular cylinder submerged in infinitely deep water with an ice cover modeled as a thin-elastic plate floating on water, is investigated here. The cross-section of the nearly circular cylinder is taken as r=a（1＋δC（θ））, where a is the radius of the corresponding circular cross-section of the cylinder, δ is a measure of small departure of the cross-section of the cylinder from its circularity and C（θ） is the shape function. Using a simplified perturbation technique the problem is reduced to two independent boundary value problems up to first order in δ. The first one corresponds to water wave scattering by a circular cylinder submerged in water with an ice-cover, while the second problem describes wave radiation by a submerged circular cylinder and involves first order correction to the reflection and transmission coefficients. The corrections are obtained in terms of integrals involving the shape function. Assuming a general Fourier expansion of the shape function, these corrections are evaluated approximately. It is well known that normally incident wave trains experience no reflection by a circular cylinder submerged in infinitely deep water with an ice cover. It is shown here that the reflection coefficient also vanishes up to first order for some particular choice of the shape function representing a nearly circular cylinder. For these cases, full transmission occurs, only change is in its phase which is depicted graphically against the wave number in a number of figures and appropriate conclusions are drawn.

Study on the Injection Molding and Optimization of Radiator Cap based on CAE Technology

In order to improve the radiator cap of the automobile cover forming quality and efficiency, this paper applies the UG software to carry out the design of the injection mold, and use Moldflow software to simulate and analyze the position of gate filling, flow, cooling and other aspects of application, to determine the best inject location and optimize die structure design. The research results show that the combination of CAD and CAE technology can effectively improve the mold design quality, shorten die development cycle, and reduce the cost of development.