Physico-mechanical behavior of self-cementing class C fly ash-clay mixtures

Self-cementing class C fly ashes are being increasingly used for soil stabilization of road bases and in other civil constructions. Because of their self-cementing capability in the presence of water, they can be used for clay subgrade improvement as cement surrogates, or as road subgrade material. However, for efficient and economic utilization of self-cementing class C fly ash, the physico-mechanical characteristics of these ashes must be determined extensively. This paper focuses upon the laboratory evaluation of the (1) stabilization characteristics of clay soils blended with self-cementing class C fly ash, and (2) residual self-cementation capabilities of ponded class C fly ash. Testing carried out by the authors and other researchers have indicated that curing time, curing condition, clay mineralogy, amount of fly ash and swelling potential in the soil-fly ash mix are the important variables that control stabilization characteristics. In this paper, the stabilization characteristics were evaluated in terms of the gain in the uniaxial compressive strength and stiffness, and swelling potential. To examine these effects, 12 set of mixtures of ideal clay soils with known percentages of kaolinite and montmorillonite, self-cementing class C fly ash and appropriate amount of water were compacted and cured. In the mixed samples, amount of montmorillonite varied from 0, 2, 4 and 6%, and the amount of self-cementing class C fly ash varied from 5, 10 and 20%. To investigate the effect of curing condition, three curing environments were used. For swelling test, the cured samples were inundated and allowed to swell at the seating pressure of about 2 kPa applied by the weight of the top porous stone and load plate using the one dimensional oedometer apparatus. In addition to the stabilization characteristics of clay soils-fly ash blend, the residual self-cementation capabilities of ponded class C fly ash were also investigated in terms of unconfined compression and CBR tests performed at 7 and 14 days of curing. Results obtained from these test were encouraging and compared favorably with the typical subgrade materials.     

Global software development

The last several decades have witnessed a steady, irreversible trend toward the globalization of business, and of software-intensive high-technology businesses in particular. Economic forces are relentlessly turning national markets into global markets and spawning new forms of competition and cooperation that reach across national boundaries. This change is having a profound impact not only on marketing and distribution but also on the way produces are conceived, designed, constructed, tested, and delivered to customers. The author considers how software development is increasingly a multisite, multicultural, globally distributed undertaking     

Genetically evolved radial basis function network based prediction of drill flank wear

The most important factor that governs the performance of a radial basis function network (RBFN) is the optimization of the network architecture, i.e. determining the exact number of radial basis functions (RBFs) in the hidden layer that can best minimize the error between the actual and network outputs. This work presents a genetic algorithm (GA) based evolution of optimal RBFN architecture and compares its performance with the conventional RBFN training procedure employing a two stage methodology, i.e. utilizing the k-means clustering algorithm for the unsupervised training in the first stage, and using linear supervised techniques for subsequent error minimization in the second stage. The validation of the proposed methodology is carried out for the prediction of flank wear in the drilling process following a series of experiments involving high speed steel (HSS) drills for drilling holes on mild-steel workpieces. The genetically grown RBFN not only provides an improved network performance, it is also computationally efficient as it eliminates the need for the error minimization routine in the second stage training of RBFN.     

Base station placement on boundary of a convex polygon

Let P be a polygonal region which is forbidden for placing a base station in the context of mobile communication. Our objective is to place one base station at any point on the boundary of P and assign a range such that every point in the region is covered by that base station and the range assigned to that base station for covering the region is minimum among all such possible choices of base stations. Here we consider the forbidden region P as convex and base station can be placed on the boundary of the region. We present optimum linear time algorithm for that problem. In addition, we propose a linear time algorithm for placing a pair of base stations on a specified side of the boundary such that the range assigned to those base stations in order to cover the region is minimum among all such possible choices of a pair of base stations on that side.     

Performance Evaluation of Recently Developed New Process HAJM during Machining Hardstone Quartz Using Hot Silicon Carbide Abrasives: an Experimental Investigation and Sustainability Assessment

Silicon - The better machining capabilities of abrasive jet machining characterized by the absence of thermal distortion make it highly competitive with other cutting processes employing plasma and...     

Optimized gold nanoshell ensembles for biomedical applications

We theoretically study the properties of the optimal size distribution in the ensemble of hollow gold nanoshells (HGNs) that exhibits the best performance at in vivo biomedical applications. For the first time, to the best of our knowledge, we analyze the dependence of the optimal geometric means of the nanoshells’ thicknesses and core radii on the excitation wavelength and the type of human tissue, while assuming lognormal fit to the size distribution in a real HGN ensemble. Regardless of the tissue type, short-wavelength, near-infrared lasers are found to be the most effective in both absorption- and scattering-based applications. We derive approximate analytical expressions enabling one to readily estimate the parameters of optimal distribution for which an HGN ensemble exhibits the maximum efficiency of absorption or scattering inside a human tissue irradiated by a near-infrared laser.     

Y-junction multibranched carbon nanofibers

Multibranched carbon nanofiber (CNF) is produced by a thermal chemical vapor deposition method using camphor as precursor. Nickel and cobalt catalyst was deposited on silicon substrate by e-beam evaporation and used as substrate for the growth of carbon nanomaterials. Branched carbon nanofibers were grown on the nickel thin film at 900 degrees C, whereas spherical carbon beads formed on the cobalt thin film. These fibers followed base growth mechanism devoid of any catalyst particle at the tip of fibers.     

Distribution of sulphur in coal seams with special reference to the Tertiary coals of North-Eastern India

This investigation makes a systematic study of the distribution of the forms of sulphur in the Tertiary coals of North-Eastern India, i.e. coals of Upper Assam and Arunachal Pradesh, to delineate the areas of low sulphur content and high sulphur content with a low proportion of organic sulphur. These coals have, in general, a high sulphur content. In a particular seam, total-, pyritic- and organic-sulphur contents increase from the floor to the roof of the seam. Upper seams are found to contain, in general, more sulphur than the seams lying below. Certain sections of a seam have low organic sulphur contents which can be mined separately. It is possible to delineate the low sulphur zones in a particular coalfield so assisting the scientific exploration and exploitation.     

Instrumented drop-weight test results for normalised and tempered 9Cr1Mo steel

From instrumented drop-weight tests, the nil ductility transition temperature (T_NDT), and a conservative estimate of dynamic fracture toughness (K_Id), at T_NDT for normalised and tempered 9Cr---1Mo steel, are determined to be −25°C and 70 MPa√m, respectively. The latter value agrees well with that determined from pre-cracked Charpy tests. The K_Id/σ_Yd (σ_Yd is the dynamic yield stress) ratio at T_NDT is estimated to be 0·076 √m, in agreement with previous estimates. The uncertainties in crack profile measurement and effect of microstructural variation in the heat affected zone on fracture loads are also discussed.