• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 579
  • 258
  • 122
  • 67
  • 52
  • 50
  • 25
  • 20
  • 11
  • 11
  • 11
  • 11
  • 11
  • 11
  • 7
  • Tagged with
  • 1399
  • 151
  • 127
  • 118
  • 106
  • 105
  • 99
  • 89
  • 79
  • 78
  • 78
  • 75
  • 67
  • 66
  • 66
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

The Study of Microstructure of Pb/Sn and Au/Sn Solder in Optoelectronics Package

Chen, Chia-Cheng 02 July 2000 (has links)
Abstract The effect of joint strength of PbSn and AuSn solder on temperature cycling tests in laser packages has been studied experimentally and numerically. It was found that the solder joint strength increased as temperature cycle number increased, and then became steady after 400 cycles. This is may be due to the redistribution of the residual stresses within the solder during temperature cycling test, and hence reducing the residual stresses and increasing the solder joint as the temperature cycle increased. Numerical calculations were in good agreement with the experimental measurement that the solder joint strength increased as the temperature cycle increased. In this work, we also study the intermetallic compound (IMC) growth of PbSn and AuSn solders under cycling test and aging test. The thickness of IMC growth do not significantly increase under cycling test, because the cycling test temperature was from ¡V40 to 85ºC. However, under the high temperature aging of 200ºC for 25 days, the IMC thickness was increased to 4.71£gm.

Design of a novel conduction heating based stress-thermal cycling apparatus for composite materials and its utilization to characterize composite microcrack damage thresholds

Ju, Jaehyung 30 October 2006 (has links)
The objective of this research was to determine the effect of thermal cycling combined with mechanical loading on the development of microcracks in M40J/PMR-II- 50, the second generation aerospace application material. The objective was pursued by finding the critical controlling parameters for microcrack formation from mechanical stress-thermal cycling test. Three different in-plane strains (0%, 0.175~0.350%, and 0.325~0.650%) were applied to the composites by clamping composite specimens (M40J/PMR-II-50, [0,90]s, a unitape cross-ply) on the radial sides of half cylinders having two different radii (78.74mm and 37.96mm). Three different thermal loading experiments, 1) 23oC to –196oC to 250oC, 2) 23oC to 250oC, and 3) 23oC to -196oC, were performed as a function of mechanical inplane strain levels, heating rates, and number of thermal cycles. The apparatus generated cracks related to the in-plane stresses (or strains) on plies. The design and analysis concept of the synergistic stress-thermal cycling experiment was simplified to obtain main and interaction factors by applying 2k factorial design from the various factors affecting microcrack density of M40J/PMR-II-50. Observations indicate that the higher temperature portion of the cycle under load causes fiber/matrix interface failure. Subsequent exposure to higher stresses in the cryogenic temperature region results in composite matrix microcracking due to the additional stresses associated with the fiber-matrix thermal expansion mismatch.

Utilitarian cycling : investigating latent demand in Christchurch, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Geography in the University of Canterbury /

Taylor, Katherine Jane. January 2009 (has links)
Thesis (M. Sc.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 227-236). Also available via the World Wide Web.

10-speed bicycle training: cardiovascular training effect in "pushers" and "spinners" during continuous bicycling

Whitlatch, Michele Suzanne Smith, 1952- January 1977 (has links)
No description available.

The oxygen cost of cycling : upright versus recumbent position

Albert, Lee. January 1997 (has links)
Objective. This study investigated the effect of cycling position (upright vs. recumbent) and seat position on the oxygen cost of cycling. / Experimental design. A two-factor ANOVA with repeated measures was used to examine the effect of cycling position (Monark 814E, Lifecycle 9100 R, and Lifecycle 9500 RHR ergometers) and seat position (optimum and +/-1 setting) on VO2 and HR. / Participants. Subjects were 10 male physical education students (age = 24 +/- 2.1 years, height = 178.8 +/- 4.8 cm, weight = 76.2 +/- 7.8 kg). / Interventions. Each subject was tested at three 5-minute workloads (55, 137, and 186 Watts) in a random order on the three ergometers. These workloads corresponded with manual settings of 1, 3, and 5 on the Lifecycle ergometers. The cycling protocols for the Lifecycle ergometers were performed with the seat set at 107% of the symphysis pubis measurement and at seat positions of +/-1 setting from the so-called "optimum" setting. / Measures. Physiological response was assessed by continuously monitoring VO2 and HR. / Results. At the optimum seat setting, the VO2 was significantly higher at the three workloads on the Monark compared to both Lifecycle ergometers. Seat positions of +/-1 setting from the recommended setting did not affect VO2. The HR response was non-significant for cycling position and seat position. / Conclusions. The results indicate that the Lifecycle ergometers (9100 R and 9500 RHR) underestimate oxygen consumption and indirectly underestimate energy expenditure. Seat positions of +/-1 setting from the recommended setting on the Lifecycle ergometers did not affect the VO 2.

Kinetic and kinematic effects of altering cleat placement during cycling

Frame, Jeffrey W. January 2005 (has links)
One of the most important aspects of high performance cycling is the best fit between rider and bike. Developing a proper bike fit requires conducting many biomechanical assessments due to the need to match a myriad of bike geometries and human anthropometric variables. One of the primary bike-rider system measurement parameters for power and pedal efficiencies is the cleat placement and alignment. The purpose of this study was to examine the effects of moving the cleats towards the heel on peak power outputs and pedal efficiencies using a Computrainer (CT) and 2D video analysis. Ten competitive male cyclists participated in the study consisting of tests for peak power (PP) outputs and pedaling efficiencies among two positions of cleats; toe (TP) and heel (HP). No significant differences in peak power outputs were reported between TP and HP (p = .827). Significant differences (p = .027) did exist, however between each condition within the SpinScan (SS) pedal efficiency test. Results from the 2-D video analysis indicate that there exists a difference in ankling patterns between the TP and HP during the first 50 percent of the power phase and the last 50 percent of the recovery phase of the pedal stroke (p = .000 and .001 respectively Based on the results of this study, further research into the longitudinal effects of training in this area are warranted. / School of Physical Education, Sport, and Exercise Science

The effects of cross country endurance bicycling on an individual's fitness

Jones, Gary Joe January 1969 (has links)
There is no abstract available for this thesis.

The effects of revolution rate on cycling efficiency

Jack, Martha Louise January 1975 (has links)
The purpose of this study was to examine the effects off revolution rate (i.e. gear ratio) on cycling efficiency and the energy cost of performance. A group of five trained cyclists performed ergometerr rides at either 60, 90, or 120 rpm and a constant absolute workload. Energy expenditure was determined during each minute of rest,-exercise, and recovery. Gross and net work efficiencies were calculated using several computational methods. Results showed that energy input increased as the rate of cycling increased. Gross and net resting baseline efficiencies decreased and net free wheeling baseline efficiency remained constant with increasing rpm. The increased energy demand with increased rpm was attributed to the increased cost of moving the legs and not to overcoming the resistance. It was concluded that the fastest performance ..s achieved when the energy demand is the greatest for the force exerted on the pedals and the oxygen debt could be tolerated for the duration of the race. Within the limitations of the study, at a constant work output the greatest muscular efficiency was achieved at low revolution rates. Although the net free wheeling efficiencies remained unchanged with increasing rpm, in practical terms these values did not reflect the total energy cost to the rider.

Comparing the utility of the Theory of Planned Behaviour and the Health Belief Model in understanding and promoting the use of protective helmets among school-age cyclists

Arnold, Laurence January 1997 (has links)
No description available.

The impact of bicycle lanes on critical gaps at unsignalised T-junctions /

Wilson, Ben. Unknown Date (has links)
There is a significant gap in the current understanding of issues relating to bicycle safety. The provision of cycling facilities has long been based on professional opinion and has rarely been based on academic research. In particular, it is widely considered that the provision of bicycle lanes improves safety for cyclists, however there is little or no research to confirm this belief. / This thesis seeks to improve the current understanding of the impact of bicycle lanes on safety by utilising gap acceptance theory. Unsignalised T-junctions have been surveyed to gather gap data for the estimation and comparison of critical gaps. The findings of this research indicate that bicycle lanes may in fact reduce safety at unsignalised intersections. / Thesis (MEng(TransportSystemsEng))--University of South Australia, 2006.

Page generated in 0.2671 seconds