Optimization of modern machining processes using advanced optimization techniques: a review

Thorough literature review of various modern machining processes is presented in this paper. The main focus is kept on the optimization aspects of various parameters of the modern machining processes and hence only such research works are included in this work in which the use of advanced optimization techniques were involved. The review period considered is from the year 2006 to 2012. Various modern machining processes considered in this work are electric discharge machining, abrasive jet machining, ultrasonic machining, electrochemical machining, laser beam machining, micro-machining, nano-finishing and various hybrid and modified versions of these processes. The review work on such a large scale was not attempted earlier by considering many processes at a time, and hence, this review work may become the ready information at one place and it may be very useful to the subsequent researchers to decide their direction of research.     

Validation and Examination of Existing Water Distribution Network for Continuous Supply of Water Using EPANET

Dire Dawa, the second largest city of Ethiopia, was facing about the distribution system adopted for supplying clean water. It was being observed that an intermittent type of supply with main and secondary distribution pipes. It was observed that, the current water demand has surpassed the present existing supply about 65%. Hence, in order to provide sufficient quantity and good potable water with continuous (24 X 7) water supply for various sectors of study area: Sabiyan region, Dire Dawa, Ethiopia, was selected. Also, Dire Dawa Water Supply & Sewerage Authority has taken a strong decision in order to validate and examine the existing water distribution network for improved water supply. On the other hand, the main important factor which effects the validation is that the age of pipes and other accessories in present existing network were longstanding. Therefore, to avoid the leakage losses and various problems encountered with the present system, a detailed is study is conducted and the analysis is carried out using EPANET tool to design for continuous water supply. After thorough analysis by considering future concerns, it was suggested that, two GLSRs of each with 2.7 Mm³ capacity may be provided in order to meet the future demands. The tanks are provided at required elevation to ensure that the water flows in all pipes of the network efficiently. Based on the output it was observed that the diameter of pipes from the existing system ought to be revised. Additionally, other parameters which effect the network like frictional losses, velocity of flow in the pipes, residual head and pressure at nodes were also examined thoroughly by the use of different tools like WaterGEMS and Auto CAD in addition to EPANET.     

Valorization of fatty acid waste for bioplastics production using Bacillus tequilensis: Integration with dark-fermentative hydrogen production process

Synthesis of bioplastics (polyhydroxyalkanoates (PHA)) using Bacillus tequilensis, a newly isolated strain was investigated under aerobic condition using designed wastewater with synthetic acids (SA) and acidogenic fermented food waste (AFW) collected from biohydrogen (H₂) producing anaerobic bioreactors as substrates. The isolate showed the ability to grow and accumulate PHA in both the substrates, with simultaneous waste remediation. Higher PHA synthesis was observed with SA (59% dry cell weight) compared to AFW (36% dry cell weight) with good substrate removal (SA, 87%; AFW, 59%). The PHA composition showed presence of co-polymer [P(3HB-co-3HV)] with varying contents of hydroxy butyrate (HB, 80–90%) and hydroxy valerate (HV, 10–15%) in both the substrates. High dehydrogenase activity was observed which leads to the formation of considerable quantity of PHA. AFW from H₂ producing reactor as substrate contributes in reducing the production cost of both H₂ as well as PHA embedded with waste valorization.     

CLAMP: Efficient class-based sampling for flexible flow monitoring

With an increasing requirement to classify traffic and track security threats, newer flexible and efficient ways are needed for collecting traffic statistics and monitoring network flows. However, traditional solutions based on packet sampling do not provide the flexibility required for these applications. For example, operators are often interested in observing as many unique flows as possible; however, random packet sampling is inherently biased towards large flows. Operators may also be interested in increasing the fidelity of flow measurements for a certain class of flows; such flexibility is lacking in today’s packet sampling frameworks. In this paper, we propose a novel architecture called CLAMP that provides an efficient framework to implement class-based sampling. At the heart of CLAMP is a novel data structure we propose called composite Bloom filter (CBF) that consists of a set of Bloom filters working together to encapsulate various class definitions. In particular, we show the flexibility and efficacy of CLAMP by implementing a simple two-class size-based sampling. We also consider different objectives such as maximizing flow coverage and improving the accuracy of certain class of flows. In comparison to previous approaches that implement simple size-based sampling, our architecture requires substantially lower amounts of memory (up to 80×) and achieves higher flow coverage (up to 8× more flows) under specific configurations.     

Oil composition,mineral nutrient and fatty acid distribution in the lipid classes of underutilized oils of Trilepisium madagascariense and Antiaris africana from Nigeria

Trilepisium madagascariense (TM) and Antiaris africana (AA) are two underutilized plants from Nigeria. They have been subjected to standard analytical techniques in order to evaluate the proximate composition, physico-chemical properties, mineral nutrient, fatty acid composition and distribution in the lipid classes of the seeds and seed oils. The carbohydrate composition of these seeds are high; TM is 62.73 ± 0.30% and AA is 53.97 ± 0.50%. Iodine value of TM was found to be 46.10 ± 0.70 mg iodine/g while that of AA was 88.24 ± 0.50 mg iodine/g. The mineral composition of the seeds and the oils varied with K having the highest concentration in the seed and Na the highest concentration in the oils. Linoleic acid is the dominant fatty acid in the oil of AA with the highest composition in the neutral lipids while palmitic acid is the dominant fatty acid in oil of TM. Vitamin E, Gamma-Sitosterol, α and β-Amyrin, Lupeol, Stigmast-4-en-3-one, and hydrocarbons were isolated from these oils. The results of the proximate, mineral nutrient compositions, chemical characterization and fatty acid distribution of these seeds and seed oils shows their possibility as potential resources.     

The Need for Fast Communication in Hardware-Based Speculative Chip Multiprocessors

Chip-multiprocessor (CMP) architectures are a promising design alternative to exploit the ever-increasing number of transistors that can be put on a die. To deliver high performance on applications that cannot be easily parallelized, CMPs can use additional support for speculatively executing the possibly data-dependent threads of an application. For cross-thread dependences that must be handled dynamically, the threads can be made to synchronize and communicate either at the register level or at the memory level. In the past, it has been unclear whether the higher hardware cost of register-level communication is cost-effective. In this paper, we show that the wide-issue dynamic processors that will soon populate CMPs, make fast communication a requirement for high performance. Consequently, we propose an effective hardware mechanism to support communication and synchronization of registers between on-chip processors. Our scheme adds enough support to enable register-level communication without specializing the architecture toward speculation much. Finally, our scheme allows the system to achieve near ideal performance.     

In-situ multi-layer formation in the oxidation of Ti3Al-Nb

The effect of niobium on the oxidation of a Ti₃Al alloy was studied in pure oxygen in the range of 850-1,100°C. The oxidation products for the Ti-30Al-2.7 Nb alloy were mainly TiO₂ (rutile) mixed with A1₂O₃ (alumina) and small amounts of niobium oxide. The oxidation resistance of Ti₃Al was improved by the addition of niobium. An in-situ multiple-layer structure comprising a mixture of rutile and alumina formed on the oxide scale of the alloy at temperatures 1,000°C and above. The number of layers increased as the temperature increased but the individual layer thickness decreased.     

Manufacturing applications of octrees

It is well understood that effective and comprehensive CAD representation methods are necessary for modelling all the design and manufacturing functions in an automated environment. Recent research work has concentrated on using Constructive Solid Geometry (CSG) methods and Boundary Representation (B-Rep) schemes for representing design and manufacturing functions. This paper presents several novel ideas on the application of octree and quadtree based representation schemes in several manufacturing areas such as robotic task planning, tolerance representation and inspection, feature-based design, and assembly modelling and verification. Suggestions on the application of extended octrees for modelling metal forming operations are also presented.     

Processes for production of high-purity metal powders

Production of high-quality metal powders is becoming important to meet the increasing demand for manufacturing advanced materials. A number of standard powder production techniques have been developed to meet the increasing demand for high-purity metal powders. This paper discusses the different techniques of producing metal powder.     

Optimal mixing to improve the performance of batch and continuous fermentations with recombinant Escherichia coli

Fermentations with genetically altered bacteria tend to lose plasmids as the fermentation progresses. Methods such as two‐stage cultivation, cell recycle and the addition of antibiotics are commonly used to enhance plasmid stability. Here we examine a different method, the regulation of mixing in the bioreactor. In particular, large bioreactors are considered where uniform mixing is difficult to achieve and the probability of plasmid loss varies with the specific growth rate. For both batch and continuous cultivations of Escherichia coli C600 gal K containing the plasmid pBR Eco gap, it is seen through a model that both modes of operation exhibit high plasmid stability and cell growth when the broth is incompletely mixed, and mixing near and away from the point of inoculation are unequal. Thus, the natural incomplete mixing in large bioreactors may be utilized to improve plasmid stability. A practical method to implement this idea is suggested. Copyright © 2005 Society of Chemical Industry