Reliability engineering concepts in design for usability

Engineering and managerial response to the increased demand for more usable computer products is hindered by lack of relevant knowledge in the majority of current Research and Development environments. This paper proposes to use reinterpretation of the existing reliability engineering knowledge base into the language of design for usability, as a way to speed up acceptance and adoption of human factors engineering tools, methods and expertise into the computer designers' set of core competencies. Described similarities in concepts, definitions, formal models and practical aspects between reliability and usability, justify this proposal.     

Rational design of fluorescent phosgene sensors

Phosgene is a very toxic gas, which was used as a chemical weapon in World War I, and is currently widely used in industrial processes. So far, no any phosgene fluorescent sensor has been reported. In this study, we report rational design of unimolecular fluorescent phosgene sensors for the first time. Phosgene was used to initiate intramolecular cyclization and convert nonfluorescent molecules to highly fluorescent products. Bright blue fluorescence of phosgene reaction products can be easily visualized by naked eye. The detection limit for phosgene is as low as 1 nM in solutions at room temperature.     

The design of evanescent-field-coupled waveguide-mode sensors

An evanescent-field-coupled waveguide-mode sensor with a multilayer structure consisting of a dielectric waveguide, a thin reflecting layer, and a glass substrate illuminated under the Kretschmann configuration operates as a sensor that is capable of detecting modifications in the dielectric environment near the waveguide surface with superior sensitivity by measuring the change in reflectivity. The sensitivity of the sensor is strongly dependent on the optical constants of the reflecting layer. Numerical simulations show that a sensor having a reflecting layer with a small value of the real part of the complex refractive index shows a good sensitivity for both S-?and P-polarized light. Materials with values of the real and imaginary parts of the complex refractive index of >4 and ～0.5, respectively, are suitable for use as reflecting layers when S-polarized light excites only the lowest order waveguide mode. The simulations were experimentally confirmed using sensors with Au, Cu, Cr, W, a-Si, or Ge reflecting layers deposited by radiofrequency magnetron sputtering by observation of specific adsorption of streptavidin on biotinyl groups using an S-polarized laser beam with a wavelength of 632.8?nm. From the results, guidelines are given for the fabrication of preferred sensor configurations.     

Technical design basis of microelectronic sensors

An analysis is given of the problem of making sensors for quantities in physics and physical chemistry based on the achievements of microelectronics. The modem technical design basis of microelectronic sensors is considered together with the direction of its further development. Data and results are given concerning the development of microelectronic force, pressure, magnetic field, and hydrogen-leakage sensors.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 10–14, November, 1994.     

Optical sensors for detection of bacteria. 1. General concepts and initial development

The concept of using immobilized nucleic acid stains as detection chemistry to fabricate optical bacterial sensors is first demonstrated. SYTO 13 (a green fluorescent cell stain) is used as the molecular recognition element and fluorescent reporter in the sensor. The sensor responds to aqueous and aerosolized bacterial samples in 15 and 30 min, respectively. In addition, the sensor can discriminate a change in Pseudomonas aeruginosa (Pa) cell concentration of 1 order of magnitude or less and can detect down to 2.4 x 10(5) cells/mL of Pa cells. The utility of the sensor is demonstrated by monitoring the growth of a Pa cell culture over a period of 50 h.     

Synthesis study of magnetic torque sensors

There exist numerous solutions to measure the torque applied to a structure or a shaft, and we first present the available devices. They fall into two groups; some measure the torsion angle resulting from the applied torque, others use the shaft material property changes due to the induced stresses, We then present our contribution in this area: a synthesis study of torque sensors with variable-reluctance magnetic circuits excited by permanent magnets or coils. Among these sensors are new structures not only for stationary devices, but also for fully rotating devices. The advantages of structures of these types lie in their great design and implementation simplicity. The structures' study shows how to choose the different parameters of the sensors to meet specifications, It also demonstrates the advantages of some new designs in terms of performance-the ones using “overlapping” teeth for example     

A heuristic design advisor for incorporating pollution prevention concepts in chemical process design

 The application of pollution prevention concepts to chemical process design is often hampered by lack of sufficient information about potential design alternatives. The high cost of collecting this information can thus present act as a constraint on the thoroughness of the final design optimization. One approach to dealing with such data constraints is the application of design heuristics. Particularly when coupled with the use of robust optimization methods, heuristic approaches can provide useful insight and direction at all stages of the design effort. Pacific Northwest National Laboratory has been developing a heuristic-based tool for use in chemical process design. Known as the Process Heuristic Review of Environmental Design (PHRED) this design tool uses conventional backwards chaining expert systems techniques to identify and prioritize applicable design heuristics based on a minimal set of process data. The development philosophy and current status of the PHRED tool are discussed in this paper. Received: 8 September 1998 / Accepted: 6 May 1999     

Simulation design of electrical capacitance tomography sensors

The resolution and sensing field of electrical capacitance tomography sensors depends upon the configuration of their electrodes and guards, so optimum design is essential in order to provide improved response. Simulations in 2D and 3D are performed based on the finite element method to study the influence of the electrode, guard size and screen arrangement on the sensor characteristics and the reconstructed image     

Model-based optimal design of polymer-coated chemical sensors

A model-based methodology for optimal design of polymer-coated chemical sensors is developed and is illustrated for the example of infrared evanescent field chemical sensors. The methodology is based on rigorous and computationally efficient modeling of combined fluid mechanics and mass transfer, including transport of multiple analytes. A simple algebraic equation for the optimal size of the sensor flow cell is developed to guide sensor design and validated by extensive CFD simulations. Based upon these calculations, optimized geometries of the sensor flow cell are proposed to further improve the response time of chemical sensors.     

Synthesis of ZnO tetrapods for flexible and transparent UV sensors

ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 μW cm(-2) at a wavelength of 365 nm and response time of 0.9 s.     

Analysis and design of ferrite cores for eddy-current-killedoscillator inductive proximity sensors

Finite element modeling of ferrite cores used in the design of eddy-current-killed oscillator inductive proximity sensors was performed. Based on contemplation of the practical operation of the sensors, ferrite core geometries were compared with a reference core by the eddy-current power loss in a metal target at a fixed distance from the face of each transducer. Several of these cores were experimentally evaluated for sensing distance to verify the results of the simulation. It was observed that, for fixed coil, fixed target distance, and given target, the low-frequency sensing distance of a particular transducer is approximately proportional to the fourth root of eddy-current power loss in the target     

Antireflection design concepts with equivalent layers

Some novel concepts of designing antireflection (AR) coatings with equivalent layers are presented. As an introduction, essential papers concerning thin-film optics and AR designs are cited, and the AR problem and a previously introduced AR-hard design type are discussed. Based on the known matrix formalism, a potential AR region, an equivalent stack index, and an equivalent substrate index are defined to use the theory of stop-band suppression as a starting point for the design of broadband AR coatings. The known multicycle AR design type is identified as a typical solution to the AR problem if the presented approach is used.     

Instrumentation design for bridge scour monitoring using fiber Bragg grating sensors

Scour is one of the main causes of bridge failures. In order to measure and monitor scour depth variations including deposition (refilling) process, three designs for a scour monitoring system using fiber Bragg grating (FBG) sensors are discussed in the present study. By a comparative study, one of them is recommended in the present study and its instrumentation manufacture process is also introduced in detail. Using this recommended design, the advantages of FBG sensors for monitoring, such as immunity from electromagnetic interference and multiplexing capability, can be fully utilized. Both scour depth variations and entire scour development process including deposition process can be correctly monitored in real-time by continuously identifying the locations of emerging FBG sensors from the riverbed. A reliable sensor protection measure is also designed for FBG sensors in harsh environments, especially in floods. Finally, a verification test using a flume is carried out in the laboratory and three experimental cases are conducted to demonstrate the capability of FBG sensors and applicability of the recommended scour monitoring system. It can be concluded that the recommended scour monitoring system using FBG sensors is capable of measuring the water level, (maximum) scour depth, entire process of scour development, and deposition height due to refilling process. The advantages over other conventional scour monitoring systems are clearly demonstrated.     

Simulation-based comparison of cell design concepts for phase change random access memory

The RESET operation of different design concepts for phase change random access memory (PCRAM) cell is studied and compared using a three dimensional simulation model. This numerical algorithm comprises four interacting sub-models, which describe the electrical, thermal, phase change, and percolation dynamics in the PCRAM devices during the switching operation. The so-called vertical, confined, and lateral cell geometries are evaluated in terms of their current requirements for RESET operations, which is one of the most critical issues for an achievement of high integration densities. The advantages of the confined and lateral cell architecture as compared to the conventional vertical cell concept are explored, demonstrating their benefits of advanced thermal management and minimized current defined area. The simulation results agree well with experimental features of the RESET operation for the PCRAM design concepts studied.     

Composite feature and variational design concepts in a feature-based design system

The feature-based design system has not prevailed due to its lack of flexibility in feature commands creation and variational design capability. In this paper, concepts of incorporating composite features and variational designs are tested in a feature-based design system. Details of the methodology of how this can be incorporated are also presented. A prototype system for a rotational part is built in order to demonstrate the feasibility of the incorporation. Both simple and complex parts are used in the implementation.     

Behavioural representation and simulation of design concepts for systematic conceptual design of mechatronic systems using Petri Nets

The systematic representation of design concepts is an important requirement for computational support during the conceptual design stage within the process of product development. Behavioural simulation of design concepts is used as a systematic representation framework, and behavioural representation is based on modelling and simulating the behaviour of a design artefact at the conceptual level to perform an overall function, leading to behaviour-based conceptual design. The behaviour-based conceptual design approach is critical for mechatronic systems since they require synergistic integration starting from the initial conceptual design phase. The present study is focused on behavioural representation and simulation of design concepts via discrete event system specification formalism and Petri Nets so as to contribute to systematic conceptual design in mechatronic systems. The paper introduces a representation framework for the behaviour-based conceptual design of mechatronic systems and its implementation on five selected case studies, among laboratory-level educational robots. In addition to Petri Net modelling and computer simulations, the implementation also includes physical simulations of the intended operational behaviours for educational robots on a distributed physical structure called the ‘desktop design model’. In this paper, implementation on one of these case studies, namely the ‘frog robot’, is presented in detail.     

Evolutionary engineering design synthesis of on-board traffic monitoring sensors

In this paper, a formal engineering design synthesis methodology based on evolutionary computation is presented, with special emphasis on the design and optimization of distributed independent systems. A case study concerned with design of a sensory system for traffic monitoring purposes is presented, along with simulations of traffic scenarios at several levels of abstraction. It is shown how the methodology introduced is able to deal with the engineering design challenges present in the case study, and effectively synthesize novel design solutions of good quality. Moreover, when the fitness function is formulated as an aggregation of design preferences with different weights and trade-off strategies, the complete Pareto optimal frontier can be determined by the evolutionary synthesis methodology. The results of this study suggest that the approach can be useful for designers to solve challenging engineering design synthesis problems.     

A minimally designed PD-L1-targeted nanocomposite for positive feedback-based multimodal cancer therapy

Combining immune checkpoint blockade therapy (ICBT) with other treatment modalities through nanotechnology offers an opportunity to further boost immunity for effective cancer treatment. Herein three-in-one programmed death-ligand 1 (PD-L1)-targeted nanocomposite (NC) was minimally fabricated through self-assembling photothermal agent black phosphorus nanosheet (BPN), chemotherapeutic agent Polymetformin (PolyMet), and immune checkpoint inhibitor anti-PD-L1 antibody (aPD-L1), avoiding the easy degradability of BPN through bridging the electrostatic interaction between PolyMet and BPN. The prepared aPD-L1-PolyMet/BPN NC could precisely target primary tumor through the interaction between aPD-L1 and PD-L1 based on ICBT, and the targeting efficacy was gradually reinforced due to the PD-L1 upregulation in tumor sites after photothermal therapy (PTT), ensuring positive feedback-mediated multimodal antitumor effect during continuous treatment loops. Moreover, the combinational therapy composed of photothermal immunotherapy (PIT), chemotherapy and ICBT strengthened the antitumor efficacy owing to their synergistic mechanism. Meanwhile, the generated positive feedback property during treatment displayed powerful antitumor effect, which not only inhibited primary and abscopal tumor progression, but also prevented tumor metastasis and promoted long-term tumor immune memory establishment. Therefore, this antitumor NC provided a prospective insight into the field of multimodal cancer therapy through rational and minimal design.     

Some concepts on design of surfactant gels and vesicles

It is conjectured that anionic-cationic surfactant combination can be regarded as equivalent to a double chain surfactant and using molecular packing considerations it is shown that vesicles, viscoelastic solutions and liquid crystals can be designed by the proper choice of chain lengths of the pair. Using these concepts new systems are designed, from mixtures of cetyltrimethyl ammonium bromide and sodium alkyl sulfonates, to produce both viscoelastic gels and vesicles.     

Inter-sheet-effect-inspired graphene sensors: design, fabrication and characterization

With their sub-nanometer inter-sheet spacing, few-layer graphenes (FLGs) are alignment-free building blocks for nanosensors based on the inter-sheet effects. In this paper, we have tackled the challenges towards batch fabrication of inter-sheet graphene sensors through controlled layer engineering, edge tailoring and selective electrode fabrication on different atomic layers. An oxygen plasma etching (OPE) technique is developed to remove graphene layer by layer, enabling the batch fabrication of FLGs in a controllable fashion because of the faster speed and readiness of patterning of this process as compared to the conventional mechanical exfoliation. Vapor sensing experiments have shown that 'inter-sheet' sensors possess a higher sensitivity than conventional 'intra-sheet' ones. Vapor sensitivity is improved more than two times in normalized resistance changes by taking the 'inter-sheet' design upon exposure to 0.5% ethanol-nitrogen mixture and 500 Pa water vapor environments, respectively. These remarkable improvements can mainly be attributed to the inter-sheet effects such as electron tunneling, chemical doping, physical insertion and enhanced edge effects. Such effects may result from molecule adsorption/desorption, force/displacement, pressure, surface tension or thermal energy, and can potentially remarkably enrich the applicable transduction mechanisms.