Basic Process Flow Research Articles

Fabrication of silicon oxide microneedles from macroporous silicon

This paper presents a novel technique for silicon dioxide (SiO 2) microneedle fabrication. Microneedles are hollow microcapillaries with tip diameters in the range of micrometers. They can be used in the fabrication of microsyringes. These structures can be of high interest in medical and biological applications, such as DNA injection, antibody manipulation and drug delivery, and cell manipulation. Fabrication process is based on electrochemical etching of n-type silicon in hydrofluoric acid (HF) solutions. Basic process flow and etching conditions that ensure a stable pore growth are described. These conditions also determine the geometry of the resulting microneedle structure. Microneedle arrays of different dimensions can be fabricated in a single run on the same wafer. In this work, microneedle arrays with pore diameters ranging from 2 to 5 μm, pore lengths from 30 to 140 μm and wall thicknesses in the range of 70–110 nm are reported.

Desalination of seawater using nuclear heat

The Nuclear Desalination Demonstration Project (NDDP), Kalpakkam, envisages setting up a 6300 m 3/d capacity hybrid MSF-RO plant based on an indigenous design. The plant will meet the process water requirements of MAPS and will augment the drinking water sources of the nearby complex. This paper describes the basic process flow sheet of the SWRO plant, part of the hybrid MSF-RO desalination plant. The SWRO plant consists of a pretreatment system, high-pressure pumping system with energy recovery turbine, RO modules and membrane cleaning system. The product water from the SWRO plant with a TDS of about 400 ppm will be mixed with product water of the MSF plant containing 10 ppm TDS. The projection of the permeate output and TDS for a few SWRO commercial modules at different seawater temperatures were carried out to select the optimum conditions of the SWRO plant. The role of energy recovery from RO reject stream is also investigated. As the seawater TDS at our site is around 35,000 ppm, it was proposed to study the feasibility of using reject stream from the RO plant as feed for the MSF plant in future.

Decomposition in automatic generation of Petri nets for manufacturing system control and scheduling

Despite the efforts in developing Petri net models for manufacturing control and scheduling, the generation of Petri net models cannot be automated for agile manufacturing control and scheduling without difficulties. The problems lie in the complexity of Petri net models. First of all, it is difficult to visualize the basic manufacturing process flow in a complex Petri net model even for a Petri net modelling expert. The second problem is related to the complexity of using Petri net models for manufacturing system scheduling. In this paper, a decomposition methodology in automatic generation of Petri nets for manufacturing system control and scheduling is developed. The decomposition methodology includes representing a manufacturing process with the Integrated Definition 3 (IDEF3) methodology, decomposing the manufacturing process based on the similarity of resources, transforming the IDEF3 model into a Petri net control model, and aggregating sub Petri net models. Specifically, a sequential cluster identification algorithm is developed to decompose a manufacturing system represented as an IDEF3 model. The methodology is illustrated with a flexible disassembly cell example. The computational experience shows that the methodology developed in this paper reduces the computational time complexity of the scheduling problem without significantly affecting the solution quality obtained by a simulated annealing scheduling algorithm. The advantages of the methodology developed in this paper include the combined benefits of simplicity of the IDEF3 representation of manufacturing processes and analytical and control properties of Petri net models. The IDEF3 representation of a manufacturing process enhances the manmachine interface.