Design and engineering of low-cost centimeter-scale repeatable and accurate kinematic fixtures for nanomanufacturing equipment using magnetic preload and potting

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 127-130).This paper introduces a low-cost, centimeter-scale kinematic coupling fixture for use in nanomanufacturing equipment. The fixture uses magnetic circuit design techniques to optimize the magnetic preload required to achieve repeatability on the order of 100 nanometers. The fixture achieves accuracy to within one micrometer via an adjustable interface composed of UV curing adhesive between the mating kinematic coupling components. The fixture is monitored by a micro-vision system and moved by a six-axis nanopositioner until proper alignment is achieved, at which point the fixture position is permanently set by UV light. This thesis presents design rules and insights for design of a general accurate and repeatable kinematic fixture and presents a case study of fixtures used for tool exchange on dip pen nanolithography machines. A prototype fixturing assembly was fabricated and tested for repeatability and stability in six degrees of freedom. The test results concluded that the fixture has a 1-o- 3-D translational repeatability of 87 nanometers and a 3-D stability of 344 nanometers over 48 hours. This is an order of magnitude improvement on past low-cost accurate and repeatable fixture designs. This optimized accurate and repeatable kinematic fixture will enable repeatable, accurate, quick, and elegant tool change, thus advancing the manufacturing capabilities of nanofabrication techniques.by Adrienne Watral.S.M

Communications for smart grid substation monitoring using WIMAX protocol

The SMARTGRID is a general term for a series of infrastructural changes applied to the electric transmission and distribution systems. By using the latest communication and computing technology, additional options such as Condition Monitoring can now be implemented to further improve and optimise complex electricity supply grid operation. Lifecycle optimisation of high voltage assets and other system components in the utility provide a case in point. Today Utility experts agree that application of scheduled maintenance is not the effective use of resources. To reduce maintenance expenses and unnecessary outages and repairs of equipment due to scheduled maintenance, utilities are adopting condition based approaches. Real time online monitoring of substation parameters can be achieved by retrofitting the existing substation with SMARTGRID technology. The IEC 61850 is a common protocol meant for Substation Automation Systems, designed for the purpose of establishing interoperability, one that all manufacturers of all different assets must comply with. This thesis advocates the estimation of bandwidth required for monitoring a substation after retrofitting the existing substation with smart communication technologies. This includes establishing a latest wireless communication infrastructure from the substation to the control centre and evaluating the performance modelling and simulating the physical layer of communication technologies such as WIMAX (IEEE802.16) and MICROWAVE point to point using MATLAB SIMULINK and RADIO mobile online simulation software. Also, link budget of the satellite communication for the same application is calculated. Satellite communication in this case is considered as a redundant or back up technology to ensure that the communication between entities is continuous. On performing the simulation on different environments the results prove that the selected protocols are best suited for condition monitoring. The measured Latency could be the best approximated value which complies with the current objective. However the white noise that exists in the substation has significant hazard with respect to the security of the wireless network. To compensate this constraint whole substation is hard wired by means of plastic fibre optics and the data sent to the base station located near the substation

Characterization and Modeling of Pneumatic Multi-Material Micro-Extrusion

Functionally Graded Materials (FGMs) are characterized by a continuous variation in the composition of parent materials through the work piece volume. This gradual change in material composition is aimed at improving mechanical, thermal and/or electrical properties of the material. FGMs are being increasingly used in a variety of applications including aerospace, biomedical and nuclear. FGMs have been produced using additive manufacturing processes such as laser engineered net shaping (LENS) and 30 printing. A relatively new process category called direct write (OW) printing has evolved over the past decade. OW techniques such as multi-material micro-extrusion are capable of producing FGMs. To fully utilize the capabilities of multi-material micro-extrusion, experimentation and modeling is needed to determine the factors that significantly affect the mass flow rate and proportion of each nanoink being dispensed. The objectives of this study were to develop a parametric model for multi-material pneumatic microextrusion and to develop equations to determine the parameter values to achieve the desired ink proportions during ink deposition. Experiments were conducted using red, blue and yellow acrylic inks that were printed using a commercially available three material pneumatic micro-extruder from nScrypt. Preliminary experiments determined that air pressure and valve needle position were significant parameters affecting the mass flow rate of the inks. A 26 experiment was then designed and carried out. Parametric equations thus developed provided relationships between the parameter values and the proportions of inks dispensed. The equations were validated by solving them using an AMPL linear program. For a given desired proportion of inks to be dispensed, the AMPL program suggests process parameter values needed to produce the desired multi-material output

Three Decades of Deception Techniques in Active Cyber Defense -- Retrospect and Outlook

Deception techniques have been widely seen as a game changer in cyber defense. In this paper, we review representative techniques in honeypots, honeytokens, and moving target defense, spanning from the late 1980s to the year 2021. Techniques from these three domains complement with each other and may be leveraged to build a holistic deception based defense. However, to the best of our knowledge, there has not been a work that provides a systematic retrospect of these three domains all together and investigates their integrated usage for orchestrated deceptions. Our paper aims to fill this gap. By utilizing a tailored cyber kill chain model which can reflect the current threat landscape and a four-layer deception stack, a two-dimensional taxonomy is developed, based on which the deception techniques are classified. The taxonomy literally answers which phases of a cyber attack campaign the techniques can disrupt and which layers of the deception stack they belong to. Cyber defenders may use the taxonomy as a reference to design an organized and comprehensive deception plan, or to prioritize deception efforts for a budget conscious solution. We also discuss two important points for achieving active and resilient cyber defense, namely deception in depth and deception lifecycle, where several notable proposals are illustrated. Finally, some outlooks on future research directions are presented, including dynamic integration of different deception techniques, quantified deception effects and deception operation cost, hardware-supported deception techniques, as well as techniques developed based on better understanding of the human element.Comment: 19 page

Control of Biological Responses by Isolated Synthetic Material Variables

It is well established that cells sense and respond to stimuli at the sub-micron and nanometre scale, a factor that must be considered in future biomaterial design. The understanding of how biological entities interact with material features at this scale is limited due to the limitations of material fabrication techniques that can readily isolate enrichment of a surface with a chemical group, whilst reproducibly controlling nanotopography and stiffness. Polymer pen lithography (PPL), a nanotechnology that has advanced the technique of single probe nanolithography in combination with traditional microcontact printing, has since been introduced due to its capability of fabricating high throughput surface patterns over large surface areas (multiple cm2) in a short period of time. In this work, PPL has been used as a powerful nanotechnique to fabricate reproducible surface nanofeatures with a size of 300 nm with various centre-to-centre distances using a range of chemicals as “inks” with presentation of pre-selected carboxyl and amino groups on appropriate surfaces as “papers”. These fabricated surfaces have been used to evaluate the isolated and combitorial effects of changes in surface chemistry and topography on mesenchymal stem cell and chondrocyte adhesion and phenotype in vitro. Carboxylic acid terminated nanoarrays with various centre-to-centre distance have been proven to induce mesenchymal stem cell towards chondrogenesis and hypertrophic chondrogenesis. In addition, the selected carboxylic acid terminated nanoarrays successfully promoted the maintenance of chondrogenic phenotype of articular chondrocytes over 3 experimental passages. Conversely, amino terminated nanoarrays with various centre-to-centre distance potentially supported mesenchymal stem cell differentiation towards adipogenesis. In addition to understanding the role of surface chemistry on initial cell response, the in situ control of stiffness at a molecular level has been studied. A range of photoresponsive molecules were synthesised and incorporated within the hydrogel network. Preliminary cell-surface interactions were established with these hydrogels. The developed nanofabrication methodology and established parameters exhibited unprecedented control of cell morphology, differentiation and maintenance of phenotypes that has improved the fundamental understanding of mechanical signalling events

Operational support systems for satellite communications

The role of satellite communications is changing from providing bandwidth linking network operators interconnections towards providing IP enabled communications to end users. This migration from few high-value routes towards many low-value routes means that integration and automation of processes with terrestrial networks becomes critical in driving down unit costs. Integration and automation is necessary on all planes: user, control and management. In satellite communications, management aspects, underpinned by Operational Support Systems (OSS) have received the least research attention, making this a valuable topic for study. In most areas, OSS for satellite systems are similar to other domains. However there are some notable areas of difference which have been the focus of this research. The eTOM business framework, developed by the TMF, has been used to highlight aspects of OSS unique to satellite. Since satellite capacity represents the highest operational cost of a satellite route, effective management while minimising the overhead traffic is critical. The transmission of IP packets is assumed and the real-time measurement of QoS parameters such as packet delay and loss emerged as the most important differences. A number of approaches to QoS measurement are feasible, however the use of trace packets is most promising especially for high network loads. An experiment compares the results from simulations, mathematical models and from a test network, using Poisson and self-similar traffic flows. The relationship between measurement accuracy and trace packet intensity is explored and the measurement response time to steps in traffic load is estimated. It is discovered that measurement accuracy improves as the queue load increases, in contrast to alternative approaches such as sampling of user packets. The response time to steps depends upon the degree of self-similarity and is generally longer than the times recommended by standards. A pragmatic approach to management of different modes is proposed where the measurement method is changed depending on the load