• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 929
  • 264
  • 14
  • 10
  • 9
  • 4
  • 4
  • 3
  • 3
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 1315
  • 1315
  • 1071
  • 224
  • 219
  • 132
  • 129
  • 94
  • 90
  • 86
  • 82
  • 82
  • 76
  • 70
  • 61
  • 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.
21

Photogrammetry for health monitoring of bridges : Using point clouds for deflection measurements and as-built BIM modelling

Delehag Lundmark, Joel January 2019 (has links)
Road and railway bridges play a crucial role for the infrastructure network in Sweden to work smoothly and keep the traffic flowing. Damage to a bridge can have catastrophic consequences if they are not corrected properly and in due time. Trafikverket in Sweden is responsible for inspection and maintenance of approximately 20 600 bridges throughout the country. This huge number of bridges require large resources in the form of machinery and experienced bridge inspectors who assess the state of the bridges on the spot. At present, the state of a bridge is to a large extent determined by a visual inspection and by manually taking measurements to assess the condition of the bridge. This approach means that the assessment of the condition of the bridge to a large extent is subjective and shifting between different cases depending on the inspector’s experience. New approaches that both could make it easier for inspectors to make more objective decisions and facilitate and reduce the risk concerning the inspection work are therefore under research. In this thesis Close Range Photogrammetry is evaluated as a mean for assessing deflection on concrete bridges and for creating as-built BIM:s for documentation and visualization of the actual condition of a bridge. To evaluate the technique both laboratory experiments and field work are conducted. Laboratory tests are conducted on concrete slabs that are subjected to pressure to inflict deflection on them. The concrete slabs are photographed using close range photogrammetric techniques for different values of deflection. The photographs are later processed into a point cloud in which measurements of deflection are taken and compared to what is measured using displacement transducers during the tests. The field work conducted is in form of photographing a railway bridge using close range photogrammetry and building a point cloud out of the photographs. This point cloud is then used as a basis for evaluating the process on how a point cloud generated through close range photogrammetry can be used to create as-built Building Information Models. Results from the laboratory experiments show that changes in deflection can be visualized by overlapping point clouds generated at different loading stages using the software Cloud Compare. The distance i.e. the deflection can then be measured in the software. The point cloud generated through the field work resulted in a as-built BIM of the railway bridge containing the basic elements. No hard conclusions can be drawn as to how well the method in this thesis can be used to measure deflection on real concrete bridges. The test basis is to small and the human factor can have affected the results. The results though show that millimeter distances can be measured in the point clouds which indicates that with the right approach, Close Range Photogrammetry can be used to measure deflections with good precision. Point clouds generated through Close Range Photogrammetry works good as a basis for creating as-built BIM:s. The colored point cloud is beneficial over other techniques that are generated in gray scale because it makes it easier to distinguish elements from each other and to detect any deficiencies. To create complete as-built BIM:s more than just a point cloud are needed as it only visualizes the shell of the captured object.
22

Successiv projektering : En kartläggning av informationsflödet

Westring, Johan January 2019 (has links)
A construction project is not the other project alike. Despite this, there are a few subprocesses that a construction project cannot do without. However, the order in which these occur and how far in time these sub-processes extend may differ depending on the project's conditions. What is common is that a construction project is initiated by its project design where project planning documents and later on construction documents are produced before the production begins. But as the construction projects shortens in time, higher demands are placed on streamlining the sub-processes. It has therefore become increasingly common for the project planning to take place gradually along the production. This master thesis is mainly based upon those interviews that were conducted during this study. The interviews were held with different peoples of either contractors or constructors. The main aim with this master thesis were to study the flow of information between those who plans the project and those who executes it, within a project were the project is been planned and designed gradually along the production. In order to form an understanding of how the flow of information work, the tools and methods used to manage information are studied in a project were the project is being planned gradually, seen from both contractors and project designers perspective. It turns out that there are relatively small differences in how the information is handled between a project that is planned gradually versus one that has been planned in advance. The tools used to spread (downstream) and report (upstream) information are the same regardless type of contract. However, what a project that is planned gradually benefits from is the choice of working methods used in the project. These working methods can facilitate the handling of the project information and the information flow created up- and downstream. The conclusions that can be drawn from this thesis are that a project with gradual planning combined with its information flow benefits from a project that is being carried out in cooperation. Which is based on the fact that the communication routes have been clearly identified at an early stage. It will both facilitating and reducing the flow of information compared to if the project would not had been carried out in cooperation. The time gains that are considered to be possible when the project is gradually planned ceases to exist if the project is not carried out in cooperation. In addition, a gain can be seen in being able to streamline the current management of how the information is being both managed and spread from the project planners. Regardless if the project has been planned prior to the production or not. However, given that work tasks such as planning/design and production are particularly close together when planning a project gradually. An efficiency in improving the project planners work while distributing the building document can increase the space for mistakes without impacting on the detailed time schedule.
23

The frequency of total use of manual and automatic low-consumption fixtures in the Langford Architecture Building at Texas A&M University

Chung, Woo Sung, January 1900 (has links)
Thesis (M. S.)--Texas A&M University, 2005. / "Major Subject: Construction Management" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.
24

Documenting Postural Changes and Repetition among Violin Players and their Influence in the Development of Musculoskeletal Disorders

Handal, Cristina 15 May 2013 (has links)
The objective of this study was to document the changes in posture and the number of wrist and forearm repetitions among violin/viola players during an experiment session to attempt to understand the development of musculoskeletal disorders. Also, the perception of discomfort and pain felt by the violin/viola players in the past and the number that had been diagnosed with a disorder was documented. Finally, possible correlations were calculated between pain/discomfort with variables like the number of years playing the violin, hours of practice/day, frequency of pain, gender, and dominant hand and among different pain/discomfort variables (pain/discomfort before the experiment, after the experiment and the change in pain/discomfort throughout the experiment) and ultimately possible relationships were determined between posture and repetition with pain/discomfort. Playing a musical instrument places the highest of demands on the musculoskeletal system of musicians and is considered one of the most complex tasks the human body can perform (Steinmetz, Seidel, & Muche, 2010). This places musicians at a high risk for the development of musculoskeletal disorders. Studies have shown how musicians are at high risk for developing PRMDs ranging in prevalence from approximately 30% to almost 90% (Zaza, 1998). These high statistics was the rationale for using musicians as the focus group. This studys population was violin/viola players (students and professionals) above the age of 18. Electrogoniometers were used to measure the postural changes and the software used with the equipment provided a count of the repetitions. The independent variables accounted for pain and discomfort while the dependent variables accounted for the demographics as well as posture and repetition. Descriptive statistics were computed for the postural changes and averages for the number of repetitions. Left Radial, Left Flexion and Left Supination displayed the most extreme postural changes, while the right hand repetitions in the radial/ulnar plane had the highest number of repetitions. Ratings for the level of pain/discomfort were averaged and a paired t-test showed that there was a significant difference between the level of pain before and after the experiment session. Correlation analyses confirmed that extreme postures of the left hand and high number of repetitions on the right hand are associated with a higher change in discomfort. Finally, predictors in the regression models for the number of pain days in a year, the level of discomfort after the experiment and the change in discomfort included repetitions of the right hand in radial/ulnar plane and gender indicating that repetitive motions and being a female could lead to increased discomfort. Future research should focus on other physical risk factors (i.e. force) as well as psychosocial factors. Future studies could also look at the differences in postural changes and repetition between genders as well as differences in how forces are applied. Other studies could focus on the difference in how both genders report pain/discomfort and which are the most affected body parts. Studies can also attempt to document postural changes in different instrument cohorts to determine which instrument could lead to higher displacements, or which postures cause more strain. In summary, this study helped conclude that more extreme postural deviations, higher number of repetitions, more hours of practice per day are and even shorter periods of practice can lead to an increase in discomfort or pain.
25

Effectiveness of Prequalification Practices in Public Procurement

Berjis, Payman 24 July 2012 (has links)
Due to legally restrictive nature of public work, contracts are often awarded solely based on the price of the bid. This has often resulted in contracts being awarded to less qualified contractors. Between the practices developed to deal with this issue, prequalification has proven to be one of the most effective practices in dealing with this problem. As it was investigated in this research, practice of prequalification is widespread amongst the public owners in the region. However, an in-depth look at the practices has revealed that these owners are not currently using this process to its fullest potential and integration of some of the best practices suggested in this paper has the potential to make this process more effective. This research also contains a specially fabricated model which encumbers all of the suggested practices and aims at creating a simple, practical and transparent model for the public owners in the Southern Ontario region.
26

Effectiveness of Prequalification Practices in Public Procurement

Berjis, Payman 24 July 2012 (has links)
Due to legally restrictive nature of public work, contracts are often awarded solely based on the price of the bid. This has often resulted in contracts being awarded to less qualified contractors. Between the practices developed to deal with this issue, prequalification has proven to be one of the most effective practices in dealing with this problem. As it was investigated in this research, practice of prequalification is widespread amongst the public owners in the region. However, an in-depth look at the practices has revealed that these owners are not currently using this process to its fullest potential and integration of some of the best practices suggested in this paper has the potential to make this process more effective. This research also contains a specially fabricated model which encumbers all of the suggested practices and aims at creating a simple, practical and transparent model for the public owners in the Southern Ontario region.
27

The Effects Of Lean Intervention (5S) On Perceived Musculoskeletal Workload And Perceived Hazardous Working Conditions In A Health Center Pharmacy

Dhindsa, Jastinder Singh 04 June 2012 (has links)
The healthcare industry involves a significant level of health and safety risks in various work processes, and healthcare professionals are at risk for work-related musculoskeletal disorders and other health problems. In recent years, Lean has been introduced in healthcare with the goal of eliminating waste and improving efficiency. Lean is also believed to affect the health and safety of workers. The present research studies the effects of Lean (5S) implementation in an acute care pharmacy of a health center. A version of the Dutch Musculoskeletal Questionnaire (DMQ) was used to record the perceived musculoskeletal workload and perceived hazardous working conditions. There were twelve participants from the two participating pharmacies and they were divided into two groups, study and control. The study group underwent Lean transformation in the form of a 5S event. Work sampling was conducted to determine any changes in the existing process in terms of percentage of value added and non-value added activities over the course of the study. Work sampling results did not indicate any significant changes in the percentage of value added and non-value added activities post 5S. The pharmacists and the pharmacy technicians reported a significant reduction in perceived musculoskeletal workload on the wrist after the 5S event. Perceived hazardous working conditions were not reduced after the 5S for either the pharmacists or the pharmacy technicians.
28

Optimal Production and Delivery Scheduling Models for a Supply Chain System of Deteriorating Items

Wu, Bingqing 10 July 2012 (has links)
The market is varying from minute to minute nowadays. Increase cooperation and pursue the optimal interest of the integrated supply chain become a more effective way than act alone in the competition. In this research, an integrated inventory policy between singleproducer and multi-buyer is developed and two inventory models are built. The first model extends the research of Lin and Lin (2007) by changing the single-buyer system to the multibuyers one. Both backorder of buyers and deteriorating items of each party (producers level, buyers level, and during transport) are considered herein. The second model is based on the research of Woo et al.(2001) and Model 1 by takes raw material cost and remanufacturing proceeds into account additional. In both model, the producer and buyers collaboratively work at minimizing their total operation cost and the problems are solved under an assumption of equal replenishments and production cycles. The algorithms to find the optimal solutions are given, and numerical examples are presented. Sensitivity for systems parameters is also analyzed and all calculations are completed by software Matlab and Maple.
29

An Intelligent Computational Approach to the Optimization of Inventory Policies for Single Company

Duan, Qinglin 27 September 2012 (has links)
This study develops and tests a computational approach for determining optimal inventory policies for single company. The computational approach generally comprises of two major components: a meta-heuristic optimizer and an event-driven inventory evaluation module. Meta-heuristic is a powerful search technique, under the intelligent computational paradigm. The approach is capable of determining optimal inventory policy under various demand patterns regardless their distribution for a variety of inventory items. Two prototypes of perishability are considered: (1) sudden deaths due to disasters and (2) outdating due to expirations. Since every theoretical model is specially designed for a certain type of inventory problem while the real world inventory problems are numerous, it is desirable for the newly proposed computational approach to cover as many inventory problems/models as possible. In a way, the proposed meta-heuristic based approach unifies many theoretical models into one and beyond. Experimental results showed that the proposed approach provides comparable results to the theoretical model when demand follows their assumption. For demands not well conformed to the assumption, the proposed approaches are able to handle it but the theoretical approaches do not. This makes the proposed computational approach advantageous in that it can handle various types of real world demand data without the need to derive new models. The main motivation for this work is to bridge the gap between theory and practice so as to deliver a user-friendly and flexible computational approach for rationalizing the inventory control system for single company.
30

Microencapsulation Techniques of Self-Healing Concrete Properties

Gilford III, James 12 July 2012 (has links)
ABSTRACT Recent studies in the literature have demonstrated the ability of self-healing processes to be effective in enhancing the overall life of concrete. The main goal of this project is to evaluate and to control specific parameters for the production of an effective self-healing matrix that can be utilized within the application of self-healing concrete. Therefore, the project objective is to synthesize microcapsules using dicyclopentadine and sodium silicate and to evaluate the effects of pH, temperature, and agitation rate on microcapsule morphology. The microcapsule diameter, yield analysis, and shell thickness were characterized using scanning electron microscopy. During the experimental analysis, it was determined that temperature possesses a direct relationship with the pH for both sodium silicate and DCDP. As the temperature increased during the trials, the pH decreased. Temperature had a direct impact on the forming of the wall and core during the interfacial polymerization phase. Although the ability to maintain this consistency with the pH is important and essential, agitation rate is the key factor that controls the microcapsule capsule diameter size. As the agitation rate is increased, the microcapsule diameter size will decrease. If the agitation rate decreases, the microcapsules will become larger. Sodium silicate, however, was not consistent with the normal parameter matrix, due to its alkaline nature. As the agitation rate increased, the size remained normal and consistent. This was due to the attempt to stabilize the sodium silicate solution for the micro-encapsulation procedure of Urea-Formaldehyde. Nevertheless, both sodium silicate and DCDP trials were successful in meeting the overall objective of this thesis, which was to control the performance parameters of the two self-healing methods.

Page generated in 0.1411 seconds