Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaf 68. / by Clarence Teh-Ching Chang. / M.S.

ABSTRACT This study is aimed to investigate the transport of air pollutants and traffic flow in Chungcheng and Cross-Harbor Tunnels in Kaohsiung City. The work includes road measurements and three-dimensional numerical modeling. This article reports the first part of the work concerning measurement results. The items on road-side investigation include traffic flow rate traffic, speed, travel time and vehicle catergory. The air pollutants being sampled and analyzed in the tunnels are carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOX) and total hydrocarbon (THC). The road-side investigations show that the major vehicles in Chungcheng Tunnel are passenger cars, the next are small trucks, and the minor are large trucks. The peak hours are at 10:30 ¡V 11:30 in the morning and 15:30 ¡V 17:30 at afternoon with average traffic flow rate in 250 ¡V 350 No./hr. The major vehicles in Cross-Harbor Tunnel are motorcycles, the next are passenger cars, large trucks and small trucks. Traffic flow rate at morning peak hours of 7:00 ¡V 8:00 are 1,800 and 1,000 No./hr for motorcycles and passenger cars, respectively, and are below 800 No./hr for the large and small trucks. Results of air pollutants analysis show that CO in Cross-Harbor Tunnel is about as three times as that of Chungcheng Tunnel due to high motorcycle flow rate in Cross-Harbor Tunnel. The maximum concentration of NOX was about 500 ppb for Cross-Harbor Tunnel and was about 1,000 ppb for Chungcheng Tunnel during the study period, suggesting that cars and trucks are the major emission sources of NOX. The transport of air flow and gaseous pollutants downstream (or to the tunnel exit) is mainly done by tunnel fans and piston effect of moving vehicles in order to decrease pollutants concentrations inside the tunnel. The mechanism is affected by fan number and flow rate, traffic flow rate, traffic speed and net tunnel aspect ratio. Results in two tunnels show that CO and NOX both increase with increasing downstream distance, but are not always so for SO2 and THC. Whether other mechanisms such as absorption of SO2 and THC on tunnel walls or sink and absorption on tunnel floor due to being heavier than air affect distributions of SO2 and THC remains further investigations.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The present work proposes a solution for the conditioning of bakery dough with the purpose of reducing costs by replacing manual work with a mechanized system that will be a piston extruder. In the process, the mass will be contained within a 304 stainless steel prismatic matrix with multiple outlet openings for optimization of the production line. The mechanical properties of bread dough were studied for the design of the platform and the estimation of the necessary compression force. A linear actuator was used, which exerts a compression force of 6 kN, which maximum linear speed is 5 mm/s. Validation of results will be carried out through simulated tests with a density mass of 1452.9 kg/m3. The system is composed of a linear actuator that performs the function of an extruder, followed by a pneumatic wire cutter. The process continues with a conveyor belt and ends with the injection of sesame seeds.The fundamental contribution is in the design of the extrusion chamber, since it allows the flow of the mass leaving minimal residue.

Background: Theoretical disadvantages are associated with the use of heat-crimped piston prostheses in stapedotomy. Loose crimping could result in prosthesis displacement or slippage. Alternatively, overly tight crimping may cause trauma to the incus with resultant necrosis. Objectives: 1) Analyze outcomes of patients undergoing stapedotomy with heat-activated piston-style prostheses, and 2) compare outcomes between prostheses made by different manufacturers. Study Design: Retrospective. Setting: Vanderbilt Medical Center. Patients and Methods: Cases undergoing stapedotomy between 2005 and 2016 were reviewed. Audiometric assessments were recorded in accordance with American Academy of Otolaryngology—Head and Neck Surgery (AAO-HNS) guidelines. Patients who lacked audiometric follow-up before 6 months or after 1 year were excluded. Intervention(s): Diagnostic, therapeutic, and rehabilitative. Main Outcome Measure(s): Postoperative air-bone gap (ABG) and achievement of an ABG is less than or equal to 10dB. Results: Three hundred fifty-eight patients met inclusion criteria. At short-term follow-up (<6 mo), the mean ABG was 11 8 dB in the entire cohort; this did not differ based on manufacturer (p ¼ 0.13). The majority of patients (63%) achieved an ABG less than or equal to 10 dB. At longer-term follow-up, the mean ABG was 9 7 dB; again no differences were noted when comparing prosthesis manufacturer (p ¼ 0.20). 70% of patients achieved an ABG less than or equal to 10 dB at longer-term follow-up. When comparing short- to long-term follow-up, ABG did not significantly change over time (p ¼ 0.76). The overall revision rate was 1.9% (n ¼ 7). Conclusion: Favorable hearing outcomes are obtained both short- and long-term following stapedotomy and placement of heat-crimped piston prostheses. Both prosthesis groups appear stable in the middle ear environment long-term, as evidenced by a 1.9% revision rate among them.

No description available.

Yes / A laser induced fluorescence system has been developed to visualise the oil film thickness between the piston ring and cylinder wall of a fired gasoline engine via a small optical window mounted in the cylinder wall. A fluorescent dye was added to the lubricant in the sump to allow the lubricant to fluoresce when absorbing laser radiation. The concentration of the dye did not disturb the lubricant chemistry or its performance. Degraded engine oil samples were used to investigate the influence of lubricant quality on ring pack lubricant film thickness measurements. The results show significant differences in the lubricant film thickness profiles for the ring pack when the lubricant degrades which will affect ring pack friction and ultimately fuel economy.

No / Measuring piston crown temperature and pressure during engine development cycle is paramount. This paper presents a new development in short distance telemetry system which includes an on board power generation device. A mechatronic data acquisition system is developed whereby signal conditioning is performed by a module inside the piston and the signal passed to a Bluetooth transmitter module for wireless telemetry to a Bluetooth receiver located in very close proximity, connected to an external host PC. The Data Acquisition Bluetooth module integrates a microcontroller that reads the conditioned sensor signal and performs any other required functionality. The microcontroller firmware includes a server that collates the data and transmits them via Bluetooth to the host PC to display via a client interface. An independent power supply consisting of a rotor incorporating NdFeB magnets and a wire wound stator. As the crankshaft rotates the rotor induces an AC voltage into the stator. A rectifying circuit converts the AC voltage into a regulated DC output voltage that drives the signal conditioning and embedded Bluetooth circuits.

Axial piston machines of the swashplate type are commonly used in various hydraulic systems and with recent developments in displacement control, it is essential to maximize their efficiency further reducing operation costs as well as improving performance and reliability. This paper reports findings of a research study conducted for the piston-cylinder interface utilizing a novel fluid structure thermal interaction model considering solid body deformation due to thermal and pressure effects in order to accurately predict the transient fluid film within the gap. A large reduction in energy dissipation is possible due to reduced clearances allowable due to the surface shaping of the piston resulting in a reduction in leakage. From this study, it is shown that surface shaping of the piston in combination with a reduced clearance is not only beneficial by improving the efficiency of a machine, but also increases the reliability and the performance of the machine as the load support is enhanced.

Most modern engines utilise pistons with an offset gudgeon pin. In internal combustion engines, the offset is to the major thrust side of the piston. The piston thrust side is the part of the piston perpendicular to the gudgeon pin that carries the majority of side loading during the power stroke. Primary reason for having the gudgeon pin positioned eccentrically is to prevent the piston from slamming into the cylinder bore after the connecting rod journal passes the top dead centre. This phenomenon is referred to as piston slap, and is more pronounced in compression ignition and high performance engines due to higher combustion pressure than that of commercial spark ignition engines. The coming together of the piston and the bore results in scuffing, at best, or, catastrophic failure at worst. Clearance space between bore and piston is filled by a lubricant film. The main role of the lubricant is to separate the piston and bore by reacting to the applied load. Investigating the above problem requires a holistic approach, whereby a dynamic three degree-of-freedom piston model is coupled with a lubrication model to represent the actual system. The dynamic model determines the motion of the piston in combined axial, lateral and rotation about the gudgeon pin. The reactive forces due to lubricant films on the major and minor thrust sides of the piston play significant roles in piston dynamics and are evaluated by either quasi-static or transient solution of the lubricant contact conjunctions. The novel quasi-static analysis is carried out in the sense of its detailed approach, including many key practical features. not incorporated in other analyses, hitherto reported in literature. These features include first and foremost the development of a specific contact mechanics model for evaluation of conforming contacts for piston skirt against liner or bore. The quasi-static analysis includes many practical feature not encountered in other literature on the subject, such as detailed surface irregularities and modification features, and with thermal distortion. The analysis has been extended to thermohydrodynamics, as well as micro-hydrodynamics, all with high computational mesh densities, and robust methods of solution in space and time domains, including effective influence Newton-Raphson method and linear acceleration integration scheme. The transient tribo-elasto-multi-body dynamics problem includes physics of motion study from film thickness prediction and secondary motion evaluation of the order of micrometers and minutes of arc to large rigid body dynamics, including simultaneous solution of the contact problem at both major and minor thrust sides. Such a comprehensive solution has not hitherto been reported in literature. The thesis discusses many aspects of piston dynamics problem, through the broad spectrum of vehicle manufacture, with many pertinent practical engineering issues. In particular, it provides solutions for high performance Formula 1 racing engines. This is the first ever comprehensive analysis of piston tribodynamics for this range of engines at very high combustion pressures. This study has shown the paramount influence of profile of piston in promoting lubrication between the contiguous bodies, as evident from the pattern of lubricant flow through the contact. Deformation of the bodies increases the volume of lubricant in the contact. During the reversal in direction of piston motion, when the entraining velocity momentarily cases and reversal takes place, the load is held by an elastic squeeze.