Influence of Portland Cement Type on Unconfined Compressive Strength and Linear Expansion of Cement-Stabilized Phosphogypsum

This technical note summarizes the results of a laboratory-testing program aimed at evaluating the engineering properties of cement-stabilized phosphogypsum mixtures for road base and subbase construction. Phosphogypsum is a solid byproduct of the production of phosphoric acid, a major constituent of many fertilizers that has chemical and radioactive properties may cause environmental problems. For every ton of phosphoric acid produced, approximately 5.0 tons of phosphogypsum are generated. This magnifies the problem of dealing with growing phosphogypsum stockpiles. The research program described herein, covered the physical characterization of phosphogypsum, and tests that uncovered the influence of cement type and content, curing time, and compaction energy on its unconfined compressive strength and expansion. The laboratory results indicate that cement-stabilized phosphogypsum mixtures have potential applications as road base and subbase materials.     

Influence Zone for End Bearing of Piles in Sand

An attempt is made to establish an analytically based estimate of the influence zone surrounding the tip of a loaded pile in sand. In the framework of the cavity expansion theory and a confined local failure mechanism, explicit expressions are derived in which the sizes of the upward and downward influence zones are properly linked with the angle of shearing resistance, the stiffness, the volumetric strain, and the mean effective stress of the sand at the pile tip. Based on a series of parametric analyses, the mean range of the influence zone is suggested. For piles in clean sand, the influence zone above the pile tip is between 1.5 and 2.5D and the zone below the tip ranges from 3.5 to 5.5D, where D is pile diameter. For piles in more compressible silty sand, the influence zone extends between 0.5 and 1.5D above the pile tip and between 1.5 and 3D below the tip. Because of its analytical nature, the present study may provide a meaningful insight into the current empirical interpretations.     

Aquifer Parameter Estimation for a Constant-Flux Test Performed in a Radial Two-Zone Aquifer

A patchy aquifer or an aquifer with a finite thickness skin can be considered as a radial two-zone aquifer system, which can be characterized by five parameters, i.e., the thickness of the first zone and four aquifer parameters including the transmissivity and storage coefficient for each of the first and second zones. This paper proposes an approach based on an analytical solution of a constant-flux pumping in a confined two-zone aquifer and the simulated annealing algorithm to determine the five parameters simultaneously. The estimated results for the five parameters are fairly good even assuming the aquifer as a single-zone system at the beginning of the data analysis. The estimated results indicate that the first-zone parameters are much more difficult to accurately identify than the second-zone parameters due to insufficient early-time data and high correlation of the sensitivities among the first-zone parameters. However, the problem of inaccurate results obtained at the first-zone can be significantly improved if more densely temporal drawdown measurements are used.     

温度制度对齿轮钢带状组织的影响

结合20CrMnTiH钢生产过程中实际的温度控制情况,分析了轧制工艺对带状组织的影响。综合考虑组织与性能,不宜采用高的加热温度来控制带状组织;最佳的终轧温度应该在950～1000℃;轧后冷却速度的增加,带状组织级别减小。莱钢通过降低加热温度、控制终轧温度及轧后冷却速度等措施,将20CrMnTiH带状组织控制在2.0级以下。     

Vapor Flow to Trench in Leaky Aquifer

Soil-vapor extraction has become the most common innovative technology for treating subsurface soils contaminated with volatile and semivolatile organic compounds. This popularity is due partly to the low cost of vapor extraction and partly to the fact that mitigation is completed in situ. Previous applications of this technology have generally considered flow to either vertical or horizontal wells. However, vapor flow to a trench offers the advantages of a more uniform velocity field and lower construction costs at sites with shallow water tables. Therefore, an analytical solution is obtained for steady flow to a trench. The trench is assumed to partially penetrate an anisotropic aquifer and to have a finite horizontal length. The bottom aquifer boundary is assumed to be an impermeable water table, and the top boundary is a semipermeable aquitard. A comparison is made with field measurements to illustrate the application of the solution and to give confidence in its use.     

Effect of Wetting on Unconfined Compressive Strength of Cemented Sands

A weakly cemented sand and gravel has been partly or entirely used in the construction of earth structures such as dams and retaining walls. Such cemented soils that are usually highly permeable can undergo repetitive wetting and drying during curing due to temporary rainfall or a change in the groundwater table. In this study, weakly cemented sand specimens with four different cement ratios were compacted at optimum water content and cured for 28 days. When the cemented sand specimens were exposed to repetitive wetting and drying during curing, their 28-day unconfined compressive strength was evaluated. Wetting for one day on the last day was found to decrease the unconfined compressive strength of cemented sand, whereas wetting for one day in the middle of curing resulted in an increase in strength. The strength reduction due to wetting on the last day decreases as the cement ratio increases. For a specimen under repetitive wetting and drying over 28-day curing, the strength increases as the number of wetting increases up to three cycles. After three cycles of wetting and drying, the strength either becomes constant or slightly decreases due to insufficient water for hydration and/or washing cementitious materials.     

Influence of Clay Lens on Migration of Light Nonaqueous Phase Liquid in Unsaturated Zone

This study concerns the control of movement of light nonaqueous phase liquid (LNAPL) in unsaturated zone in the presence of relatively low permeability clay lens. A two-dimensional, finite-difference numerical model for the simultaneous movement of LNAPL and water through the unsaturated zone of the soil has been developed. The system is a three fluid phase system (water, LNAPL, and air) but in the derivation of the model, air was treated as an immobile phase at constant atmospheric pressure. The flow equations for LNAPL and water were cast in terms of the wetting and non-wetting fluid pressure heads, respectively. The finite-difference equations were solved implicitly with explicitly scheme using Newton-Raphson iteration with Taylor series expansion to treat nonlinearity. A physical model to represent the infiltration of kerosene above the clay lens was constructed. The numerical results were compared with those observed experimentally. The results of all tests showed that the presence of clay lens controls the vertical movement of LNAPL in heterogeneous porous medium.     

下部调剂对高炉炉料运动影响的离散模拟

应用三维离散元法对4 000m3高炉内的炉料运动行为进行研究.结果表明:鼓风动能增加,风口回旋区加深并没有改变高炉上部的料层结构与分布状况,而是使得高炉下部死料柱变小、变矮,其对上部炉料的支撑作用减弱,致使上部炉料的下降速度明显增大,冶炼强度得以提高.风口中心线以上2m处炉腹段,炉料的运动速度与应力分布趋于均一化.堵风...     

内部审计在企业管理中的作用

内部审计具有监督、控制和评价三种职能。它不是国家审计在企业的延伸，而是企业不可或缺的管理手段，对企业经营和管理起着保障和促进作用。为了充分发挥内部审计的作用应做到领导重视，为内部审计提供必要的条件；内部审计应以经济效益审计为核心，完善内部控制制度，强化经济责任审计；内部审计方式应转向事前决策审计、事中控制审核等。     

Aerobic Biodegradation of Methyl Tert-Butyl Ether in Gasoline-Contaminated Aquifer Sediments

Intrinsic biodegradation of methyl tert-butyl ether (MTBE) in aquifer sediments under oxic conditions was investigated using laboratory microcosms. Aquifer samples were collected from three different areas (source area, upgradient, and downgradient) of a shallow gasoline-contaminated aquifer within the Atlantic Coastal Plain Province located in Virginia. Biodegradation of MTBE was observed in the source-area microcosms in which MTBE declined from a starting concentration of 2.7 to 0.28 mg/L over a 58-day period, following an initial lag period of 20 days. The same set of microcosms was respiked with MTBE to an initial concentration of 4.8 mg/L and MTBE concentrations declined to 0.20 mg/L over a 52-day period with no lag in biodegradation. First-order MTBE biodegradation rates for the first and second periods were 0.037±0.003 and 0.063±0.003 day?1, respectively. When another set of source-area microcosms was spiked with MTBE (5 mg/L), toluene and ethylbenzene (1 mg/L each), the initial lag period increased to 33 days but there was no significant change in the MTBE biodegradation rate (0.065±0.026 day?1) and MTBE was not detected after 134 days. Biodegradation of MTBE was also observed in the microcosms constructed using aquifer sediment with only limited exposure to MTBE but the degradation rate was lower and statistically different (0.022±0.005 day?1) than the source area microcosms. Biodegradation of MTBE ceased when oxygen was depleted. Methyl tert-butyl ether did not biodegrade in the uncontaminated, upgradient microcosms; however, rapid biodegradation of toluene was observed. Methyl tert-butyl ether biodegradation appears to be limited in the absence of dissolved oxygen and in aquifer sediments where petroleum hydrocarbons including MTBE were not previously observed.     

Influence of Cohesive Zone Shape on Solid Flow in COREX Melter Gasifier by Discrete Element Method

Based on the principle of discrete element method(DEM),a 2Dslot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow,including mass distribution,velocity distribution,normal force distribution and porosity distribution at a microscopic level.The results show that the cohesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape.The particles in the lower central bottom experience large normal force to support the particles above them,while particles around the raceway and in the fast flow zone exhibit weak force network.The porosity distribution was also examined under three kinds of cohesive zones.Like the velocity distribution,the whole packed bed can be divided into four main regions.With the increase of cohesive zone position,the low porosity region located in the root of cohesive zone increases.And the porosity distribution becomes asymmetric in the case of biased cohesive zone.     

Optimizing Aquifer Parameters from Drawdowns in Large Diameter Wells

An optimization method is proposed for estimating the storage coefficient and transmissivity of an aquifer from drawdowns in large diameter wells consequent to an unsteady pumping. The concept of an optimal time step size is propagated in the proposed method. The estimate of the aquifer parameters corresponding to the optimal time step size is termed final estimate. The estimates for any other time step size are not reliable. The proposed method can also take into account the residual drawdowns. The application of the method is illustrated using an example.     

Estimating Aquifer Parameters from Early Drawdowns in Large-Diameter Wells

The existing equation applicable for large diameter wells in confined aquifers is transformed into a convenient form and a set of semilogarithmic diagnostic curves is developed for identifying the aquifer parameters (storage coefficient and transmissivity) from early drawdowns in large diameter wells. A scaled well function is proposed for the diagnostic curves. The aquifer parameters are estimated by matching the diagnostically plotted drawdowns to one of the diagnostic curves by a parallel shift of only one axis. The substantial curvature of the diagnostic curves and shifting of only one axis facilitate matching and reduce subjectivity. The proposed method is an improvement over the existing matching methods. The new method can reliably identify the aquifer parameters from only early drawdowns and would result in a 100-fold saving in time and money. It is hoped that this method would be helpful to field engineers and practitioners.     

Transient Flow into a Partially Penetrating Well during the Constant-Head Test in Unconfined Aquifers

This study derives a semianalytical solution for drawdown distribution during a constant-head test at a partially penetrating well in an unconfined aquifer. The constant-head condition is used to describe the boundary along the screen. In addition, a free-surface condition is used to delineate the upper boundary of the unconfined aquifer. The Laplace-domain solution is then derived using separation of variables and Laplace transform. This solution can be used to identify the aquifer parameters from the data of the constant-head test when integrated with an optimization scheme or to investigate the effects of vertical flow caused by the partially penetrating well and free-surface boundary in an unconfined aquifer.     

工装夹具在洒水车水箱生产中的作用

环卫机械类的洒水车水箱多由4 mm厚的Q235钢板制做而成。由于板材较薄,容易变形,故箱体形位公差难以保证,特别是批量生产,需要借助必备的工装夹具才能完成。为此就制做水箱中常用的工装夹具,介绍其制做方法。     

稀土在金属和材料中的作用

本文根据国内外文献资料和自己的实验研究结果，以几个实例综述了稀土在金属和材料中的作用。     

Actions and occurrences in attribution theory.

Hypothesized that judging behaviors as either voluntary (actions) or nonvoluntary (occurrences) will affect both (a) choosing between consensus and distinctiveness information for the purpose of making an attribution about these behaviors and (b) estimating consensus and distinctiveness drawn from attributions already made. The rationale for these hypotheses was that consensus provides information that may be viewed as the cause of the (nonvoluntary) behavior, whereas distinctiveness provides information that may be viewed as the reason for the (voluntary) behavior. Exp I, with 90 undergraduates, showed that consensus information was seen as more important for interpreting occurrences, whereas distinctiveness information was perceived as more important for interpreting actions. Exp II, with 144 Ss, showed that attributed causes for a given behavior affected inferences about generalizability of the behavior over persons (consensus), objects (distinctiveness), and circumstances (consistency). The effect of attribution on consensus inferences was more emphasized for occurrences than for actions; the effect of attribution on inferences of distinctiveness was somewhat more pronounced for actions, but this effect was not significant; the effect of attribution on inferences of consistency was more pronounced for occurrences than for actions. An unexpected finding was that, in general, Ss viewed actions as more generalizable (behaviors performed by other people, with other objects, and under other circumstances) than occurrences. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Actions and occurrences in Kelley's cube.

Examined the effects of 3 factors on the attribution process: (a) Ss made attributions for behaviors that were either completely voluntary (actions) or not completely voluntary (occurrences). (b) The behaviors were either accompanied (experimental condition) or not (control condition) by consensus, distinctiveness, and consistency information. (c) Consensus, distinctiveness, and consistency were presented in 1 of 3 orders, with each information variable varied over 2 (high/low) conditions. 252 undergraduates served as Ss. In the control condition only, actions were more often attributed to specific factors, whereas occurrences were more often attributed to a combination of factors. Consensus had more impact on attributions for occurrences than on attributions for actions. A recency effect in the use of consensus was found for attributions of occurrences but not for attributions of actions. Finally, highly consistent actions were more likely to be endogenously attributed. The range of behaviors to which different attribution models may be applied is discussed. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confined Aquifer Parameters from Temporal Derivative of Drawdowns

A simple method that uses the time derivative of drawdowns is proposed for the evaluation of confined aquifer parameters. Explicit expressions are proposed for evaluation of the aquifer parameters as well as a graphical procedure. A reliable and accurate scheme to calculate the numerical derivative of drawdowns is developed based upon an analytical approach. The method requires early drawdown data (u > 0.01, where u is the argument of well function), and is shown to converge to the Cooper-Jacob method for late drawdowns (u ≤ 0.01). It does not require curve matching or an initial guess for the parameters. Calculations for the method can be performed on a hand-held calculator. The method has been applied to published data sets and the results have been compared with those obtained using traditional methods. The method accurately estimates the aquifer parameters using only early drawdown data, thereby indicating savings in time and money.     

推板窑升降温段结构设计

推板窑作为热工烧结设备,广泛应用于电子材料高温处理.本文从推板窑的压强分布特点人手,介绍了升降温段的结构特点.