Search

Retaining ring which keeps the wafer in place is an essential component in chemical mechanical polishing. Meanwhile, it helps to reduce the edge exclusion region where the material removal rate deviates significantly from that of the central region of the wafer. However, it may increase the slurry flow resistance and hence decrease the slurry flow rate. For properly designing a retaining ring of reasonable structure, the effects of retaining ring on slurry flow and contact pressure distribution in CMP process are analyzed by the mixed elastohydrodynamic lubrication model. It is found that the slurry flow is sensitive to the protrusion height of retaining ring used in the first generation carrier. The same as the first generation carrier, the slurry flow is obviously reduced with increasing pressure acting on the retaining ring in the second generation carrier. In addition, the floating retaining ring used in the second generation CMP carrier has better performance and is more controllable than the fixed retaining ring used in the first generation CMP carrier.

Single crystal diamond is widely used in high-tech fields for its remarkable performance on mechanics, calorifics, optics, acoustics, etc. High-quality diamond surface with small roughness and low scathe are required in these applications. However, the extreme hardness and high chemical inertness of diamond result in severe processing difficulties. Chemical mechanical polishing (CMP) is a promising processing method which can obtain super-smooth and low-damage diamond surface. Oxidant is a key issue for CMP of single crystal diamond. In this study, five different oxidants were used to polish diamond samples. The results indicated that Fenton reagent was an appropriate CMP oxidant and a super-smooth diamond surface of Ra 2.4 nm was achieved by using Fenton reagent in CMP.

Diamond is a kind of ultra-hard and difficult-to-machine material. By means of the graphitization of diamond, dynamic friction polishing (DFP) technology is used to achieve a high-efficiency material removal of diamond. The polishing plate of DFP plays a key role in the process of polishing, and catalytic metal with unpaired d electrons is considered as ideal polishing material. To discuss and verify the feasibility that amorphous alloy can be used to polish CVD diamond film by DFP, Fe based amorphous alloy was prepared by mechanical alloying method and spark plasma sintering technology. The results showed that diamond film got a higher removal and a better polishing effect. This work provided a new selection for the polishing plate used for DFP of diamond.

Diamond is widely used in the fields of precise and ultraprecise machining because of its superlative characters. Due to high hardness and great brittleness of diamond, the grinding of diamond needs a kind of high effective and stable polishing method. Dynamic friction polishing (DFP) is deemed to be an innovative method by means of a synergistic reaction of mechanical effect and chemical change. The condition of high pressure and high temperature puts forward a high requirement for mechanical property of the grinding wheel in DFP, other than that, the graphitization of diamond catalyzed by catalytic metal is also a focus of research. In this paper, the transition metals with unpaired d electrons were selected as polishing materials, and powder metallurgy technique was used to prepare alloy grinding wheel for polishing diamond by dynamic friction polishing.

For costly and dangerous experiments, growing attention has been paid to the study of the performance and reliability of rolling bearings with poor information. The existing reliability theory relying on the classical statistical theory and Bayesian theory will become ineffective if the probability distribution is unknown. In view of this, the developments of studies on forecasting methods for the performance and reliability of rolling bearings with poor information are summarized in this article.

With the help of social-economy statistical data of Dunhuang City during 1987-2012, based on the related data processing technology, this paper measure the coordination between tourism development and urban development in Dunhuang City through TOPSIS evaluation method, and analyses the reasons of the coordinated development. Results show that the tourism development and urban development coordination is continuously increasing during the 1987-2012 of Dunhuang city, illustrate the development maintain a state of positive interaction and coordinated development. Dunhuang tourism development and urban development coordination optimization is closely relate to the development environmental and policy opportunities, and has great role in promoting Dunhuang ecological development and environmental improvement, just like the implement of the western development strategy, the Dunhuang water resources rational utilization and ecological protection planning and so on.

De-watered sludge (DS) and beer lees (BL) are mixed to be co-pyrolyzed into bio-char in this work. Bio-char was produced by heating at carbonization temperatures (550°C) with the ratio of DS to BL (1:1, 1.5:1, 2:1 and 4:1). Yield, ash content, FTIR, zeta potential and SEM of the bio-char were investigated. With temperature increasing, yield (39.4-57.3%, wt.%) decreased, while ash content (33.9-56.4%) increased in a high DS ratio, changing of the functional groups on bio-char (e.g., C=C, aromatic ring) in the co-pyrolysis process improve adsorption capacity for pollutant. Moreover, negative potentials (-10.583~-35.563 mV) of bio-char can provide breeding sites for microorganism and electrostatic attraction for heavy metal ions. The result showed this conversion could become a promising approach to dispose pollution problems, simultaneously, for the environmental remediation.

Praseodymium doped KNbO3 (KNbO3:Pr) phosphors were synthesized by a facile solgel combustion method. Phase evolution, particle size and luminescent properties of the powders synthesized at various temperatures were investigated. Single-phase KNbO3:Pr nanoscale particles were obtained at 600°C by directly crystallizing from amorphous precursors. The particle size of KNbO3:Pr powders can be well controlled by varying the heat treatment temperature. Under the excitation of 450 nm, KNbO3:Pr phosphors showed the well-known Pr3+ emissions associated with the 4f inter-level electronic transitions in Pr3+ ions.

The study takes Shiyang River Basin as a study area, and bases on resource environment-population, social economy-ecological environmental stress and response, and combines the present situation of ecological environment in Shiyang river basin as well as its influencing factors to construct the comprehensive evaluation index.The results show that:(1)The quality of eco-environment in Shiyang River Basin is low, and it shows the descendent trend year by year. The comprehensive evaluation index of ecological environment decreased from 5.05 in 2000 to 3.70 in 2012.(2)Seen from spatial distribution, the order of the descending degrees of the comprehensive evaluation index of ecological environment in Shiyang river basin in recent year is Yongchang County, Su yugur autonomous county, Liangzhou district, Gulang county, Tianzhu Tibetan autonomous country, Minqin county and Jinchuan district.(3) Inside the Shiyang River Basin, because of the dual effects from natural conditions and human activities, the eco-environment in the main ecological barrier regions such as Minqin and Wuwei oasis have changed obviously, especially in MinQin oasis.

Sewage sludge was pyrolyzed in order to assess the effect of pyrolysis temperature on the yield of biochar production and its characteristics. The pyrolysis temperature was a key factor affecting biochar yield, while the highest yield was obtained at a temperature of 400 °C. Biochar surface area increased with increasing pyrolysis temperature and was maximized (8.4 m2/g),which was beneficial for capturing ammonia and phosphate in aqueous solution. Biochar removed 48.3-82.2% of ammonia at equilibrium time, whereas 35.4 to 69.6% was adsorbed onto biochar surface, implying that biochar is more efficient in removing cations than anions from aqueous solutions.

This paper mainly introduces the principle and usage of dynamic probe technology, and makes comparisons between traditional test method and the most popular debugging methodutilizes the embedded tool of debugging on chip to debug. The research depends on self-designed FPGA test service system based on dynamic probe technology. It also explores how to use existent tools and technology for high efficiency test method in FPGA debug and verify process. Through comparisons, it is possible conclude that dynamic probe technology is able to cope with the complex test requirements, and provide more accurate sampling data than the general method in the debugging process. More importantly, the dynamic probe can complete switching a group of the internal signal to be measured within a few seconds, which greatly reducing the waiting time of debugging.

Ultraviolet aging of B.mori silk fabric was carried out under natural and artificial weathering conditions. A series of properties evaluations such as whiteness, mechanical property, ultraviolet protection factor (UPF) and Fourier Transform Infrared (FTIR) Spectroscopy were applied to test on the structure and properties of B.mori silk fabric. The correlation between natural and artificial aging experiments was also investigated. The results showed that the whiteness index of B.mori silk surface declined with increasing aging time. The breaking strength decreased rapidly with the extension of aging time, and adopting the curve regression analysis method to analysis the correlation between two types of aging experiments. The accelerated factor obtained is about 12.33 between natural and artificial aging experiments. In addition, ultraviolet protection factor depicted the anti-ultraviolet performance enhanced. And FTIR spectra confirmed the intensity of characteristic peaks such as amide I and II, etc. decreasing in the aging process.

Ammonia sulfite pulping liquor of wheat straw was treated by ultrafiltration. Experimental results indicated that the membrane with a cut-off of 10kDa was suitable for concentrating wheat straw liquor and had good anti-fouling property against pulping liquor. Permeability of ash turn higher with the increasing of volume reduction at the operating condition of 200 kPa and 25°C, and retentate was concentrated when volume reduced. Influences of ultrafiltration on physical properties of ammonia sulfite pulping liquor and its retentate after ultrafiltration were studied. Results showed that retentate had better performances as surfactant, concrete additive and dispersant. Surface tension of 1% lignin solution of retentate was 54.7 mN/m, which was lower than that of the untreated original lignosulfonate by 2.2 mN/m. Dispersing effect of retentate on cement was also investigated, it was found that flowability of neat cement paste improved from 70mm to 102mm.

Based on Ganzhou land use planning, analysis issues through forecasting and evaluation of Ganzhou, combined with the environmental impact assessment technical guidelines, proposed the DPSIR evaluation system of Ganzhou borough, and use years from 2001 to 2010 and forecast of the year 2020, the base maps and data to evaluation of Ganzhou with the DPSIR model, the corresponding conclusions and countermeasures. Aims to make the appropriate planning guidance, and play a positive promoting role.

The paper selects slope, aspect, Relief Degree of Land Surface, land use, vegetation index, hydrology, transportation density and climate as evaluation indexes and sets up the Human Settlements Environmental Index (HEI) model to evaluate the environmental suitability for Human Settlements in Shiyang river basin. Through using spatial analysis technology of GIS such as spatial overlay analysis, buffer analysis and density analysis to establish the spatial situation of nature suitability and spatial pattern for human settlement. The Results showed that: the index of nature suitability for human settlement in Shiyang river basin was between 17.13 and 84.32. In general, nature suitability for human settlement decreased from southwest to northeast. Saw from area pattern, the suitable region mainly distributed in Minqin oasis, Wuwei oasis and Changning basin, which accounting for about1080.01 km2, 2.59% of the total area. Rather and comparatively suitable region mainly distributed around the county in Gulang, Yongchang and north of Tianzhu, which accounting for about1100.30 km2.The common suitable region mainly distributed outside of the county inYongchang, Jinchuan and most area of Minqin county, which accounting for about 23328.04km2, 56.08% of the total area. The unsuitable region mainly distributed upstream and north of river, which accounting for about 9937.60 km2, 23.89% of the total area. Meanwhile, the least suitable region distributed around the Qilian Mountain which covered by snow and cold desert and the intersecting area between Tenger Desert and Badain Jaran Desert. The total area was about 6154.05 km2, which accounting for 14.79% of the total area. Suitable regions for human inhabitance mainly distributed around rivers in the form of ribbons and batches, while others are scattered. Their distribution pattern was identical with the residential spatial pattern. In addition, the relationships between HEI and some factors were also analyzed. There was a clear logarithm correlation between situation of residential environment and population, that is, the correlation coefficient between evaluation value and population density reached 0.851. There was also positive correlation between situation of residential environment and economics, which reached 0.845 between evaluation value of residential environment and GDP. Results also showed the environment was out of bearing the existing population in Shiyang river basin. Spatial distribution of population was profoundly affected by severe environment such as the expanded deserts, the wavy terrains, and the changeful climate. Surface water shortage and slowly economic growth was the bottleneck of nature suitability for human settlement in Shiyang river basin. So according to these problems and various planning, some of residential parts need to relocate in order to improve situation of residential environment.

Land use structure optimization is the core of land use planning, which has significant influence to the carbon cycle in terrestrial ecosystems. In this paper, we put Lanzhou as case study, to realize the land ecosystem carbon balance is the breakthrough point, using the method of fuzzy linear programming, constructing model from carbon source and carbon sink, trying to put forward a new approach to optimize the land use structure. Contrast with the former planning with the optimization scheme based on carbon balance, carbon stock volume and carbon emissions of the year 2005 and 2020 are evaluated .We got a low carbon optimization scheme of land use planning finally. The results of the study show that the objective to make carbon storage maximization and to make carbon emissions minimization is consistent and the two optimizing schemes have dramatically beneficial effect on increase carbon sink and reduce carbon source, which can slow down carbon emissions in terrestrial ecosystems and realize the rational utilization of land resources and the sustainable development.

Based on the detailed survey of land use change in Shiyang river basin, referencing Costanza, and Xie et al’ research results of the value of ecosystem services, this article probed the variation of land use and value of ecosystem service in Wuwei region. The results are: from 1997 to 2006, the area of woodland, construction land and garden land are increasing, while farmland, grassland, water and unused land are continuing to decrease. Land-use intensity is gradually increasing, the land use pattern towards to a centralized style. The values of ecosystem services are overall upward, and change faster than ever. The main part of the value of ecosystem service is constituted by the value of grassland, woodland and farmland. So it’s important to control the expansion of urban construction, strength the protection of the water, restore and enhance regional ecosystem services in the future.

Qingyang City is located in the central hilly area of Loess Plateau with arid climate and fragile ecological environment. From the ecological point of view, using related theories and methods on the ecological carrying capacity, this paper analyses the situation of the Scale structure of urban system of the study area, using the degree of ecological flexibility, carrying capacity and the degree of load pressure to evaluate the ecological carrying capacity briefly and discuss the relationship between ecological carrying capacity and urban scale structure. On this basis, this paper finally proposes some suggestions to adjust and optimize the Scale structure of urban system under fragile ecological conditions.

With support of GIS software, we use the spatial analysis method of vector data. Calculating the isochronous rings of central cities, and prefecture-level cities’ time accessibility. Then we divide city service scope. Next we using ArcInfo programming in linear programming optimization technology to optimize the city service scope. The results show that, the magnitude has changed dramatically among city service scope after optimization, before optimization, and the city administrative divisions. It provide technical and theoretical support for government departments to make planning of city zone divides.

Cr-substituted mesoporous aluminophosphate molecular sieve (Cr-MAP) was prepared and characterized. Cr-MAP is a typical mesoporous molecular sieve with long-range ordered structure, providing effective molecular sieve for fabricating acetophenone by selectively oxizing ethylbenzene with tertiary butyl hydro peroxide (TBHP). When the reaction is at 100 °C for 8 h, using chlorobenzene as solvent and TBHP as oxidant, ethylbenzene conversion, acetophenone selectivity and acetophenone yield reach 72.8 %, 85.4 %, and 62.2 %, respectively.

Bamboo lignosulfonate was modified under the role of H2O2 and catalyst in order to improve the dispersing property of lignosulfonate. Results show that the amount of H2O2 and pH value have strong influences on characteristics of lignosulfonate. Cement paste fluidity of lignosulfonate modified at pH5 and 11% H2O2 is 178mm, which is 68% higher than that of unmodified lignosulfonate. Both of oxidative degradation and condensation occur during catalytic oxidation reaction, but oxidation is the main reaction when high amount of H2O2 is applied. The structure of lignosulfonate has some relationship to water reducing property. High molecular weight, high carboxylic content and proper sulfonic group content are the main reasons that enhance water reducing property of lignosulfonate.

In order to optimize coefficient of heat pump, the finite time thermodynamic optimization theory is applied in this paper. By introducing area ratio of the condenser and evaporator, the analytical expressions for the optimal allocation of heat exchanger area for the irreversible Carnot heat pump with variable-temperature heat reservoirs are derived. For illustration, a real vapor compression heat pump example is utilized. Empirical results show that the optimal values for real vapor-compression heat pump cycles are obtained when area ratio is equal to 0.916. The results can guide the evaluation of existing heat pump plants or influence design practice for future plants.The results can guide the evaluation of existing heat pump plants or influence design practice for future plants.

Based on Landsat ETM+ data within the metropolitan area of Lanzhou, China, green vegetation(GV) and impervious surface was extracted by a constrained linear spectral mixture analysis (LSMA),together with single window algorithm to invert land surface temperature ,and the correlation analysis was then conducted to examine the relationship between urban heat island (UHI) effect and impervious surface. Four types of end members with high albedo, GV, soil and low albedo are selected to model complicated urban land cover, estimation accuracy is assessed using Root-Mean-Square (RMS)error and color aerial images, with the help of Mantel and Partial Mantel. Spatial relationship of land surface temperatures (LST), impervious surface and GV were analyzed. Results indicate that impervious surface distribution and GV can be derived from Landsat TM/ETM+ images with satisfactory precision. Impervious surface and GV were positively correlated with UHI, while LST has space dependence, it has high space dependence, and was higher correlated with impervious surface than GV.

The main task of this paper was to evaluate the influence of hardfacing technique and service temperature on the fatigue properties of heat-resistant steel X45CrSi9-3 coated with Co-based alloy Stellite 12. The results of rotating bending fatigue tests showed that at room temperature (RT), the fatigue strength of specimens welded by the acetylene gas welding (AGW) was lower than that of specimens welded by the plasma transferred arc welding (PTAW). For PTAW specimens, the fatigue strength at 500oC was much higher than that at RT. Two failure modes were presented, one was termed as the coating failure mode at RT and the other was termed as coating-interface failure mode at 500oC. The fatigue life prediction was conducted by using a modified Murakami’s model.

Damage of metals due to the influence of hydrogen is quite frequent and leads to dangerous failures. The characteristics of the hydrogen embrittlemnt of the 65Mn steel were evaluated with small punch test. With the increment of the amount of the hydrogen absorbed into the alloy at room temperature, the strength and the toughness of the material reduce. From the small punch experimental results, it is found the total impact energy, the fracture strain and the fracture stress decrease with the increment of the cathodic hydrogen charging time. The fracture surfaces change from the typical ductile fracture with big voids to the typical intergranular brittle fracture mode after hydrogen absorbed in the specimens with higher charging current density.

Small fatigue crack behaviors in a nickel-based directionally solidified superalloy DZ4 were studied by in situ scanning electron microscopy. The crack initiation and propagation manners were identified under different temperatures, i.e. 25oC, 350oC, 700oC. Crack growth showed to be associated with the configuration and relative direction of carbide. The anomalous short crack growth was pronounced at 25oC, 350oC and not evident at 700oC, which was analyzed by in situ examining the effect of microstructure.

Specimens of a directionally solidified superalloy with different shot peening pressure were annealed at 1220oC in vacuum condition to get recrystallized surface layers with different micro-structures. Low cycle fatigue tests of these specimens were performed at room temperature and 400oC by using an electrohydraulic load frame in the SEM system for real-time observation. The initiation and propagation of cracks were inspected and the influence of the micro-structure of the recrystallized layer on the material fatigue behavior was analyzed. The low cycle fatigue life of the specimens depends mainly on the characteristics of the recrystallized layer. When the shot peening pressure is lower, the recrystallized layer is thin and not integrated, and the fatigue life decreases obviously in comparison with that of the specimen without recrystallized surface layer. When the shot peening pressure increases, the recrystal grains are more integrated, and the fatigue life rises. A comparison of the recrystallized layers between the blade surface and the specimen surface has been done and it points that the incompact surface recrystal layer is very dangerous to gas turbine blades.

In structural welded joints after long-term service under elevated temperature, fracture occurred mainly in the heat affected zone (HAZ). Recently, the nucleation and growth of creep voids in the fine-grained HAZ of weldments, recognized as Type IV fracture, has become an important problem for ferritic heat resisting steel. In this paper, a new computational model was presented to analyse the void growth induced creep damage development in HAZ. The new constitutive model based on continuum damage mechanics (CDM) equations is combined with a micromechanism-based model in order to account for the void growth process, which is different from the previous studies of creep damage. Material properties used for the creep damage computations are fitted from actual creep test data. Basic benchmark tests were performed to verify the new computational model. Then the model was used to study the creep damage development in the welded joints where four different material properties, base material, coarse-grained HAZ, fine-grained HAZ, and weld material, are taken into account. The numerical simulation results for creep lifetimes agreed well with the experimental results.

The fatigue behaviors of a directionally solidified (DS) nickel base superalloy, coated with a MCrAlY coating (NiCrAlYSi) were studied. Two kinds of tests were performed. One kind of tests are low cycle fatigue (LCF) test under strain control at different temperatures, another kind of tests are stress controlled LCF test with SEM-servo hydraulic testing machine for in situ cracking observation. The results show that the effect of coating on LCF life of coating/substrate system was rather different according to different strain levels and temperatures. The coating has no or less effect on LCF life under high strain range and the LCF life is governed by fatigue behavior of substrate in spite of the difference of temperature. However, when strain range is smaller, crack initiation and propagation are observably affected by temperature, which leads to a shorter LCF life of coating/substrate system at 500°C and a longer LCF life at 760°C or 980°C. This means the failure of coating/substrate system is dominated by the cracking of surface coating under low strain range. The brittleness at 500°C lower than DBTT results in rapid stage II crack propagation. The crack initiation from coating surface was in situ observed at room temperature and 700 °C and it was found that cracks usually initiated from the surface roughness of coating and then propagate to failure. The brittleness and surface roughness are the basic acceptable causes leading to the early damage of a coating/substrate system.

Detailed experiments of fracture toughness in which SENB specimens of five different thicknesses were included were carried out to investigate the size effect in the ductile to brittle transition temperature region. It is found that the fracture toughness of the upper shelf increases with the thickness of the specimens with the similar geometry. While the fracture toughness of the lower shelf decreases with the thickness in the range of 4mm to 12mm and then drops up from 12mm to 16mm with the appearance of shear lips which present the shearing fracture under the plane stress state. The tearing modulus dJ/da which determines the resistance to stable crack growth increases with the increment of thickness and the reduction of the temperature. The results of the stress triaxiality increasing with the reduction of the thickness explain well the experimental results.