Semi-global techniques in image matching and change detection with applications to civil and environmental engineering.

This work of thesis wants to present a dissertation of the wide range of modern dense matching algorithms, which are spreading in different application and research fields, with a particular attention to the innovative “Semi-Global” matching techniques. The choice of develop a semi-global numerical code was justified by the need of getting insight on the variables and strategies that affect the algorithm performances with the primary objective of maximizing the method accuracy and efficiency, and the results level of completeness. The dissertation will consist in the metrological characterization of the proprietary implementation of the semi-global matching algorithm, evaluating the influence of several matching variables and functions implemented in the process and comparing the accuracy and completeness of different results (digital surface models, disparity maps and 2D displacement fields) obtained using our code and other commercial and open-source matching programs in a wide variety of application fields.

The application of knowledge based expert systems to mechanical engineering design

Investigation of the different approaches used by Expert Systems researchers to solve problems in the domain of Mechanical Design and Expert Systems was carried out. The techniques used for conventional formal logic programming were compared with those used when applying Expert Systems concepts. A literature survey of design processes was also conducted with a view to adopting a suitable model of the design process. A model, comprising a variation on two established ones, was developed and applied to a problem within what are described as class 3 design tasks. The research explored the application of these concepts to Mechanical Engineering Design problems and their implementation on a microcomputer using an Expert System building tool. It was necessary to explore the use of Expert Systems in this manner so as to bridge the gap between their use as a control structure and for detailed analytical design. The former application is well researched into and this thesis discusses the latter. Some Expert System building tools available to the author at the beginning of his work were evaluated specifically for their suitability for Mechanical Engineering design problems. Microsynics was found to be the most suitable on which to implement a design problem because of its simple but powerful Semantic Net Knowledge Representation structure and the ability to use other types of representation schemes. Two major implementations were carried out. The first involved a design program for a Helical compression spring and the second a gearpair system design. Two concepts were proposed in the thesis for the modelling and implementation of design systems involving many equations. The method proposed enables equation manipulation and analysis using a combination of frames, semantic nets and production rules. The use of semantic nets for purposes other than for psychology and natural language interpretation, is quite new and represents one of the major contributions to knowledge by the author. The development of a purpose built shell program for this type of design problems was recommended as an extension of the research. Microsynics may usefully be used as a platform for this development.

Nitrogen implantation of tool steels and engineering coatings

Ion implantation modifies the surface composition and properties of materials by bombardment with high energy ions. The low temperature of the process ensures the avoidance of distortion and degradation of the surface or bulk mechanical properties of components. In the present work nitrogen ion implantation at 90 keV and doses above 1017 ions/cm2 has been carried out on AISI M2, D2 and 420 steels and engineering coatings such as hard chromium, electroless Ni-P and a brush plated Co-W alloy. Evaluation of wear and frictional properties of these materials was performed with a lubricated Falex wear test at high loads up to 900 N and a dry pin-on-disc apparatus at loads up to 40 N. It was found that nitrogen implantation reduced the wear of AISI 420 stainless steel by a factor of 2.5 under high load lubricated conditions and by a factor of 5.5 in low load dry testing. Lower but significant reductions in wear were achieved for AISI M2 and D2 steels. Wear resistance of coating materials was improved by up to 4 times in lubricated wear of hard Cr coatings implanted at the optimum dose but lower improvements were obtained for the Co-W alloy coating. However, hardened electroless Ni-P coatings showed no enhancement in wear properties. The benefits obtained in wear behaviour for the above materials were generally accompanied by a significant decrease in the running-in friction. Nitrogen implantation hardened the surface of steels and Cr and Co-W coatings. An ultra-microhardness technique showed that the true hardness of implanted layers was greater than the values obtained by conventional micro-hardness methods, which often result in penetration below the implanted depth. Scanning electron microscopy revealed that implantation reduced the ploughing effect during wear and a change in wear mechanism from an abrasive-adhesive type to a mild oxidative mode was evident. Retention of nitrogen after implantation was studied by Nuclear Reaction Analysis and Auger Electron Spectroscopy. It was shown that maximum nitrogen retention occurs in hard Cr coatings and AISI 420 stainless steel, which explains the improvements obtained in wear resistance and hardness. X-ray photoelectron spectroscopy on these materials revealed that nitrogen is almost entirely bound to Cr, forming chromium nitrides. It was concluded that nitrogen implantation at 90 keV and doses above 3x1017 ions/cm2 produced the most significant improvements in mechanical properties in materials containing nitride formers by precipitation strengthening, improving the load bearing capacity of the surface and changing the wear mechanism from adhesive-abrasive to oxidative.

Assessing the effectiveness of five-year mechanical engineering technology programs of junior colleges in Taiwan, R.O.C.: An application of the CIPP evaluation model

The purpose of this study was to evaluate the mechanical engineering technology curriculum effectiveness at the junior college in Taiwan by using the CIPP evaluation model. The study concerned the areas of the curriculum, curriculum materials, individualized instruction, support services, teaching effectiveness, student achievement, and job performance. A descriptive survey method was used with questionnaires for data collection from faculty, students, graduates, and employers.^ All categories of respondents tended to agree that the curriculum provides appropriate occupational knowledge and skills. Students, graduates, and faculty tended to be satisfied with the curriculum; faculty tended to be satisfied with student achievement; graduates tended to be satisfied with their job preparation; and employers were most satisfied with graduates' job performance.^ Conclusions were drawn in the context, input, process, and product of the CIPP model. In Context area: Students were dissatisfied with curriculum flexibility in students characteristics. Graduates were dissatisfied with curriculum design for student's adaptability in new economic and industrial conditions; practicum flexibility in student characteristics; and course overlap. Both students and graduates were dissatisfied with practicum credit hours. Both faculty and students were dissatisfied with the number of required courses.^ In Input area: Students, faculty, and graduates perceived audiovisuals and manipulative aids positively. Faculty and students perceive CAI implementation positively. Students perceived textbooks negatively.^ In Process area: Faculty, students, and graduates perceived all support service negatively. Faculty tended to perceive the ratios of graduates who enter advanced study and related occupation, and who passed the professional skills certification, negatively. Students tended to perceive teaching effectiveness in terms of instructional strategies, the quality of instruction, overall suitability, and receivable, negatively. Graduates also tended to identify the instructional strategies as a negative perception. Faculty and students perceived curriculum objectives and practicum negatively. Both faculty and students felt that instructors should be more interested in making the courses a useful learning experience.^ In Product area: Employers were satisfied with graduates' academic preparation and job performance, adaptability, punctuality, and their ability to communicate, cooperate, and meet organization needs. Graduates were weak in terms of equipment familiarity and supervisory ability.^ In sum, the curriculum of the five-year mechanical engineering technology programs of junior college in Taiwan has served adequately up to this time in preparing a work force to enter industry. It is now time to look toward the future and adapt the curriculum and instruction for the future needs of this high-tech society. ^

A review of Taiwan's technological five-year junior college mechanical engineering curriculum development: 1948 to 1994

Taiwan's technological five-year junior college (TFYJC) was founded in 1948 to train technicians to meet the demand coming from national construction. Site level professionals never were trained in curriculum development as this was under strict national control. The purpose of this study is to present an accurate narrative of Taiwan's TFYJC mechanical engineering curriculum development history in order to display the focus, rationale, and influencing forces of the evolving curriculum. This study employed historical research methodology and used document analysis as the primary approach.^ This analysis revealed that the target FYJC curriculum was manufacturing-oriented. The range of government control shifted from little, to full, then to partial control of the curriculum, from autonomy to uniformity then to partial autonomy. The intention of the target curriculum development was always to advance domestic economic development. Voices from the academia and government also influenced curriculum development decisions. Currently, the government has instituted a shift in focus and content causing individual institutions to develop curriculum responses addressing the challenge of advancing Taiwan's position in a global economy.^ Considering the shift in policy and practice, individual institutions intending to design curriculum are advised to implement empirical needs assessments of students, graduates, and employers and to engage in critical studies of emerging resources in order to provide effective in service training. To accomplish this end, TFYJC faculty and administration need training in curriculum theory and practice and evaluation. ^

An exergy based engineering and economic analysis of sustainable building

To achieve the goal of sustainable development, the building energy system was evaluated from both the first and second law of thermodynamics point of view. The relationship between exergy destruction and sustainable development were discussed at first, followed by the description of the resource abundance model, the life cycle analysis model and the economic investment effectiveness model. By combining the forgoing models, a new sustainable index was proposed. Several green building case studies in U.S. and China were presented. The influences of building function, geographic location, climate pattern, the regional energy structure, and the technology improvement potential of renewable energy in the future were discussed. The building’s envelope, HVAC system, on-site renewable energy system life cycle analysis from energy, exergy, environmental and economic perspective were compared. It was found that climate pattern had a dramatic influence on the life cycle investment effectiveness of the building envelope. The building HVAC system energy performance was much better than its exergy performance. To further increase the exergy efficiency, renewable energy rather than fossil fuel should be used as the primary energy. A building life cycle cost and exergy consumption regression model was set up. The optimal building insulation level could be affected by either cost minimization or exergy consumption minimization approach. The exergy approach would cause better insulation than cost approach. The influence of energy price on the system selection strategy was discussed. Two photovoltaics (PV) systems—stand alone and grid tied system were compared by the life cycle assessment method. The superiority of the latter one was quite obvious. The analysis also showed that during its life span PV technology was less attractive economically because the electricity price in U.S. and China did not fully reflect the environmental burden associated with it. However if future energy price surges and PV system cost reductions were considered, the technology could be very promising for sustainable buildings in the future.

An investigation into the tension arising between natural language and mathematical language experienced by mechanical engineering students

This investigation is grounded within the concept of embodied cognition where the mind is considered to be part of a biological system. A first year undergraduate Mechanical Engineering cohort of students was tasked with explaining the behaviour of three balls of different masses being rolled down a ramp. The explanations given by the students highlighted the cognitive conflict between the everyday interpretation of the word energy and its mathematical use. The results showed that even after many years of schooling, students found it challenging to interpret the mathematics they had learned and relied upon pseudo-scientific notions to account for the behaviour of the balls.

Mechanical properties and cellular response of novel electrospun nanofibers for ligament tissue engineering: Effects of orientation and geometry

Electrospun nanofibers are a promising material for ligamentous tissue engineering, however weak mechanical properties of fibers to date have limited their clinical usage. The goal of this work was to modify electrospun nanofibers to create a robust structure that mimics the complex hierarchy of native tendons and ligaments. The scaffolds that were fabricated in this study consisted of either random or aligned nanofibers in flat sheets or rolled nanofiber bundles that mimic the size scale of fascicle units in primarily tensile load bearing soft musculoskeletal tissues. Altering nanofiber orientation and geometry significantly affected mechanical properties; most notably aligned nanofiber sheets had the greatest modulus; 125% higher than that of random nanofiber sheets; and 45% higher than aligned nanofiber bundles. Modifying aligned nanofiber sheets to form aligned nanofiber bundles also resulted in approximately 107% higher yield stresses and 140% higher yield strains. The mechanical properties of aligned nanofiber bundles were in the range of the mechanical properties of the native ACL: modulus=158±32MPa, yield stress=57±23MPa and yield strain=0.38±0.08. Adipose derived stem cells cultured on all surfaces remained viable and proliferated extensively over a 7 day culture period and cells elongated on nanofiber bundles. The results of the study suggest that aligned nanofiber bundles may be useful for ligament and tendon tissue engineering based on their mechanical properties and ability to support cell adhesion, proliferation, and elongation.

Developing an engineering approach for migrating from prescriptive to performance-based specification for concrete

The integral variability of raw materials, lack of awareness and appreciation of the technologies for achieving quality control and lack of appreciation of the micro and macro environmental conditions that the structures will be subjected, makes modern day concreting a challenge. This also makes Designers and Engineers adhere more closely to prescriptive standards developed for relatively less aggressive environments. The data from exposure sites and real structures prove, categorically, that the prescriptive specifications are inadequate for chloride environments. In light of this shortcoming, a more pragmatic approach would be to adopt performance-based specifications which are familiar to industry in the form of specification for mechanical strength. A recently completed RILEM technical committee made significant advances in making such an approach feasible.
Furthering a performance-based specification requires establishment of reliable laboratory and on-site test methods, as well as easy to perform service-life models. This article highlights both laboratory and on-site test methods for chloride diffusivity/electrical resistivity and the relationship between these tests for a range of concretes. Further, a performance-based approach using an on-site diffusivity test is outlined that can provide an easier to apply/adopt practice for Engineers and asset managers for specifying/testing concrete structures.

Research Trends in Mechanical Engineering 2016: Conference Proceedings

Professor José Joaquim de Almeida Grácio was a man of many talents. His contribution to the development of physical models to predict the mechanical behaviour of materials for long-term applications in the areas of nanotechnology and forming processes was outstanding and of major international significance. He was a leader not only in his research but also at university administration level. Soon after he received his Ph.D. from the University of Coimbra (Portugal) in 1992, he joined the University of Aveiro with the mission of creating the Department of Mechanical Engineering (DEM). (...)

Using the ultrasound and instrumented indentation techniques to measure the elastic modulus of engineering materials

Currently, the acoustic and nanoindentation techniques are two of the most used techniques for material elastic modulus measurement. In this article fundamental principles and limitations of both techniques are shown and discussed. Last advances in nanoindentation technique are also reviewed. An experimental study in ceramic, metallic, composite and single crystals was also done. Results shown that ultrasonic technique is capable to provide results in agreement with those reported in literature. However, ultrasonic technique does not allow measuring the elastic modulus of some small samples and single crystals. On the other hand, the nanoindentation technique estimates the elastic modulus values in reasonable agreement with those measured by acoustic methods, particularly in amorphous materials, while in some policristaline materials some deviation from expected values was obtained.

A new approach to heart valve tissue engineering: mimicking the heart ventricle with a ventricular assist device in a novel bioreactor

The `biomimetic` approach to tissue engineering usually involves the use of a bioreactor mimicking physiological parameters whilst supplying nutrients to the developing tissue. Here we present a new heart valve bioreactor, having as its centrepiece a ventricular assist device (VAD), which exposes the cell-scaffold constructs to a wider array of mechanical forces. The pump of the VAD has two chambers: a blood and a pneumatic chamber, separated by an elastic membrane. Pulsatile air-pressure is generated by a piston-type actuator and delivered to the pneumatic chamber, ejecting the fluid in the blood chamber. Subsequently, applied vacuum to the pneumatic chamber causes the blood chamber to fill. A mechanical heart valve was placed in the VAD`s inflow position. The tissue engineered (TE) valve was placed in the outflow position. The VAD was coupled in series with a Windkessel compliance chamber, variable throttle and reservoir, connected by silicone tubings. The reservoir sat on an elevated platform, allowing adjustment of ventricular preload between 0 and 11 mmHg. To allow for sterile gaseous exchange between the circuit interior and exterior, a 0.2 mu m filter was placed at the reservoir. Pressure and flow were registered downstream of the TE valve. The circuit was filled with culture medium and fitted in a standard 5% CO(2) incubator set at 37 degrees C. Pressure and flow waveforms were similar to those obtained under physiological conditions for the pulmonary circulation. The `cardiomimetic` approach presented here represents a new perspective to conventional biomimetic approaches in TE, with potential advantages. Copyright (C) 2010 John Wiley & Sons, Ltd.

Research Quality, Publications and Impact in Hydraulic Engineering into the 21st Century. Publish or Perish, Commercial versus Open Access, Internet versus Libraries

One of the main objectives of the first International Junior Researcher and Engineer Workshop on Hydraulic Structures is to provide an opportunity for young researchers and engineers to present their research. But a research project is only completed when it has been published and shared with the community. Referees and peer experts play an important role to control the research quality. While some new electronic tools provide further means to disseminate some research information, the quality and impact of the works remain linked with some thorough expert-review process and the publications in international scientific journals and books. Importantly unethical publishing standards are not acceptable and cheating is despicable.

Impact of Commercial Search Engines and International Databases on Engineering Teaching and Research

For the last three decades, the engineering higher education and professional environments have been completely transformed by the "electronic/digital information revolution" that has included the introduction of personal computer, the development of email and world wide web, and broadband Internet connections at home. Herein the writer compares the performances of several digital tools with traditional library resources. While new specialised search engines and open access digital repositories may fill a gap between conventional search engines and traditional references, these should be not be confused with real libraries and international scientific databases that encompass textbooks and peer-reviewed scholarly works. An absence of listing in some Internet search listings, databases and repositories is not an indication of standing. Researchers, engineers and academics should remember these key differences in assessing the quality of bibliographic "research" based solely upon Internet searches.