The purpose of this Master Thesis is to improve the driving performance of mine hoists. The work is divided into two parts. The first and main part deals with simulation of the rope elongation that occurs at load changes in the mine hoist. A mathematical load model of the elongation in the ropes at a mine hoist is made for four types of mine hoists. Mass less springs and dampers are used to get the elastic behaviour of the ropes. The mathematical model is implemented in Matlab and Simulink for all four hoist types to make load simulations possible. The implementation in the laboratory HoistLab is made by modifying an existing program with the line elongation functionality. It is only done for the tower mounted friction hoist. There are several functions that are modified to make the simulations realistic. The task for the second part of this Master Thesis is to do a pilot study to decide if it is worth making further investigations about how the derivative part will improve the drive performances. A PI controller is designed and gives an acceptable rollback as result when the brakes are released. Then the controller model is extended with the derivative part, D-part, which improves the results essentially. It is still too uncertain how sensitive the system will be for noise when using the derivative part, but the performance potential is clear so the recommendation is to make further investigations. / Syftet med detta examensarbete är att förbättra driftegenskaperna för gruvspel. Arbetet är uppdelat i två olika delar. Den första och största delen handlar om simulering av den lintöjning som uppkommer vid lastförändringar i gruvspel. Matematiska modeller för detta är framtagna för fyra olika sorters typer av gruvspel. Elasticiteten i linorna är modellerad genom masslösa fjädrar och dämpare. De matematiska sambanden är implementerade i Matlab och som modeller i Simulink för att utföra simuleringar. I HoistLab är modellen realiserad genom att utöka ett befintligt lastsimuleringsprogram med de nya funktionerna för lintöjning. Detta är utfört enbart för den toppmonterade typen av friktionsspel. Ett flertal funktioner fick ändras för att få realistiska simuleringar. Den andra delen av examensarbetet går ut på att göra en förstudie kring den deriverande delen i PID-regulatorer och hur den påverkar gruvspelets prestanda. För denna del är en PI-regulator som ger ett acceptabelt resultat av backgången när bromsarna släpps designad. Därefter är modellen utökad med den deriverande delen, D-delen, vilket ger väsentligt bättre resultat. Det är dock osäkert hur bruskänsligt systemet blir när den deriverande delen används men eftersom förbättringspotentialen är tydlig är rekommendationen att göra vidare undersökningar kring D-delen.

A steady-state model for the calculation of temperature and pressure distributions, and heat and work balance for the STAR-LM and the STAR-H2 systems was developed. The STAR-LM system is designed for electricity production and consists of the lead cooled reactor on natural circulation and the supercritical carbon dioxide Brayton cycle. The STAR-H2 system uses the same reactor which is coupled to the hydrogen production plant, the Brayton cycle, and the water desalination plant. The Brayton cycle produces electricity for the on-site needs. Realistic modules for each system component were developed. The model also performs design calculations for the turbine and compressors for the CO2 Brayton cycle. The model was used to optimize the performance of the entire system as well as every system component. The size of each component was calculated. For the 400 MWt reactor power the STAR-LM produces 174.4 MWe (44% efficiency) and the STAR-H2 system produces 7450 kg H2/hr. The steady state model was used to conduct quasi-static passive load follow analysis. The control strategy was developed for each system; no control action on the reactor is required. As a main safety criterion, the peak cladding temperature is used. It was demonstrated that this temperature remains below the safety limit during both normal operation and load follow.

Electric power systems are huge real time energy distribution networks where accurate short term load forecasting (STLF) plays an essential role. This thesis is an effort to comprehensively investigate new and advanced neural network (NN) architectures to perform STLF. Two hybrid and two 3-layered NN architectures are introduced. Each network is individually tested to generate weekday and weekend forecasts using data from three jurisdictions of Canada. Overall findings suggest that 3-layered cascaded NN have outperformed almost all others for weekday forecasts. For weekend forecasts 3-layered feed forward NN produced most accurate results. Recurrent and hybrid networks performed well during peak hours but due to occurrence of constant high error spikes were not able to achieve high accuracy.

Efficient control is often the most cost-effective option to improve on the running cost of a Three-Pipe Water Pumping System. However, the effect of changing the control strategy (i.e. on energy consumption) is usually difficult to predict. To obtain this information more easily, a new simulation tool, QUICKcontrol, was developed. This new tool was used to investigate the energy cost savings potential in a Three-Pipe Water Pumping System. The influence of pump scheduling, dam level set points, control parameters and different combinations thereof was investigated. The simulation models were firstly verified with measurements obtained from the existing system to confirm their accuracy for realistic control retrofit simulations. With the aid of the integrated simulation tool it was possible to predict savings of R 195'000 per year with an average 3.8 MW of load shifted. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2005.

The hypothesis. We supposed the fatigue and its residual phenomena generated by eccentric load to have effect on the changes in vegetative indices, the slow component during exercise of high aerobic intensity in particular. The aim of the research was to establish the residual effect of eccentric load on the changes in vegetative indices during exercise of high intensity. The tasks set were as follows: 1. To estimate the residual effect of eccentric load on the fast component of changes in vegetative indices during exercise of high intensity. 2. To estimate the residual effect of eccentric load on the slow component of changes in vegetative indices during exercise of high intensity. The subjects were 8 students of the Lithuanian University of Agriculture, members of the university basketball team, who gave their informed consent to take part in the experiments within the present study. The age of the subjects was 19,5 ± 0,53 years, height – 191,0 ± 5,8 cm and body mass – 86,5 ± 9,78 kg respectively. The methods used were as follows: changes in the values of VO2, VCO2, heart rate (HR) and Ve indices of the subjects were established applying the test of continuously increased load and the test of constant load when pedalling the veloergometer. After testing blood of the subjects to establish lactate concentration in the blood was taken. To evaluate the level of intensity of the exercise performed by the subjects the evaluation scale of perceptible efforts (intensity of... [to full text]

A Residential Energy Management System (REMS) in smart grid provides capability to manage a daily load curve in order to reduce power consumption and energy cost. Consequently, (REMS) offers significant benefits for both the electricity suppliers and consumers in terms of control and schedule time of use of major appliances. In recent years, however, the rate of energy demand has increased rapidly throughout the world while the price of energy has been fluctuating. Numerous methods for (REMS) are used; this thesis analyzes many candidate scenarios during peak load periods comparing to the tariff to reduce the usage and its associated costs. It presents simulated results of proposed (REMS) to provide an automated least cost demand response. The main approach will be to ensure the satisfaction of the requirements with constraints on efficient use of energy. Multiphasic system behaviors of smart appliances in (REMS) with a realistic manner are proposed. / This thesis examines many mathematical models of home appliances in order to calculate the physical quantities that reflect the parameters’ impact and the system behavior. Main contribution determines the optimal solution of (TOU) problem to reduce energy cost and determine the best operation time by using (Linear optimization technique).

Neįmanoma pagerinti mašinų kokybę, padidinti jų patikimumą ir ilgaamžiškumą, jeigu darbo sąlygos ir medžiagų savybės nėra išanalizuotos. Mes privalome žinoti, medžiagos (kietėjimą, minkštėjimą arba ciklinį stabilumą), kas yra parinkta statinio mažaciklio apkrovimo tipuose, nes įtampos ir apkrovos kaita priklausys nuo šio tipo. Jei mes žinome apie medžiagos rūšį, mes galime nustatyti jos taikymo naudojimo sąlygos galimybes. / It is impossible to improve the quality of the machines, to increase their reliability and lifetime if the working conditions and the properties of the material are not analyzed. We must know the type of the material (hardening, softening or cyclically stabile), what is chosen for the constructions in low cycle loading, because strain and stress change during the exploitation and depend on this type. If we know the type of the material, we can determine the possibility of its application in concrete exploitation conditions.

Transverse load distribution behavior amongst bridge girders is influenced by many parameters including girder material properties, spacing, skew, deck design, and stiffening element interactions. In order to simply and conservatively approximate the bridge superstructure load distribution between girders, the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications contain load distribution factor (LDF) equations for many common bridge types. The Texas Department of Transportation (TxDOT) had recently developed a new design for bridge superstructures that utilizes a spread configuration of prestressed concrete slab beams. AASHTO does not contain LDFs for this type of bridge so the load sharing behavior of this superstructure must be investigated further. TxDOT has funded the Texas A&M University Transportation Institute (TTI) to design, model, construct, test, and analyze a full scale spread slab beam bridge. In addition to this testing, an existing slab beam bridge in Denison, Texas will be instrumented and observed for supplementary slab beam behavior data. To predict bridge behavior, computer models of the Riverside experimental bridge and of the Denison field bridge were developed using both the grillage and finite element methods of analysis. The experimental results from the Riverside and Denison bridges will not be collected by the conclusion of this thesis so a third bridge with existing experimental data, the Drehersville, Pennsylvania bridge, was also modeled for calibration purposes. The work presented by this thesis focuses on how to accurately model transverse load distribution relationships and LDFs for use in bridge design. The analysis covered is concentrated primarily on the grillage method, with the finite element analysis as part of the larger project scope. From this analysis it was determined that the grillage method was able to accurately model bridge LDFs as compared to FEM modeling and experimental results, for spread slab beam and spread box beam bridges. The critical loading configurations for all bridges placed two trucks side by side and as far to one edge of the bridge as possible. It was also determined that at an ultimate loading case, the load is distributed much more evenly across the deck than at service loading.

This study examined mathematics anxiety among elementary teacher candidates, and to what extent it interacted with the modality principle under various degrees of learner-control. The experiment involved a sample of 186 elementary teacher candidates learning from eight versions of a computer program on division with fractions. The eight versions varied in modality of presentation (diagrams with narration, or diagrams with written text), control of pacing (pacing was controlled by either the learner or the system), and control of sequence (sequence was controlled by either the learner or the system). A pre-test, post-test, demographic questionnaire, subjective measure of mental effort, and the Abbreviated Math Anxiety Survey were also administered. This study revealed that mathematics anxiety was significantly positively correlated with mental effort, and significantly negatively correlated with engagement, pre-test and post-test scores. Additionally, a modality x pacing interaction was observed for both high prior knowledge and low mathematics-anxious students. Under system-pacing, the modality effect was observed, and these students achieved higher far transfer scores when learning from the diagrams and narration modality condition. However, under learner-pacing, the modality effect reversed, and high prior knowledge and low mathematics-anxious students performed better on far transfer scores when learning from the diagrams and written text modality condition. Low prior knowledge, and highly mathematics-anxious students performed poorly in all treatment conditions. Additional interactions involving sequence-control, and a four-way interaction involving prior knowledge, modality, sequence-control, and pacing were also uncovered. The results from this study demonstrate that prior knowledge and mathematics anxiety have a complex relationship with the effectiveness of the format of instruction, and the design of instructional materials needs to take into account these individual differences. / Thesis (Master, Education) -- Queen's University, 2008-09-25 19:38:33.9

During field observations of professional movers, it was noticed that some experienced movers carried loads posterior to their pelvis. The purpose of this study was two-fold: (1) to assess the biomechanical differences between hand-held load carriage anterior (AC) and posterior (PC) to the pelvis; and, (2) to determine if an assistive load carriage device could reduce muscle effort while carrying loads either anterior or posterior to the pelvis. In the first laboratory study, an electromyographic (EMG) analysis was conducted while participants carried a load on a treadmill using AC and PC techniques. The subjects conducted three trials of AC and PC techniques while EMG data were being collected. All trial data were normalized to their respective iMVE values. An amplitude probability distribution function (APDF) was used to compare EMG amplitudes between carrying techniques. Results indicated that PC reduced EMG activity of the erector spinae (>50% reduction), trapezius, and anterior deltoid (p<0.05) as well as increasing EMG activity in the posterior deltoid (p<0.05). Eighty percent of the subjects reported that the PC method felt awkward. Due to its awkwardness, many individuals may not use the PC technique; thus, the second purpose of the study was to design an assistive movers’ pack to aid in AC and PC techniques and make the PC method easier to perform. In the second study, subjects were asked to walk unloaded while EMG was recorded. The subjects then performed the AC and PC methods with and without the assistive device. All EMG signals were normalized to unloaded gait followed by EMG APDF analyses. Findings from the first study were confirmed, in that PC, compared to AC significantly reduced erector spinae activity (p<0.05) and focused shoulder activity to the posterior deltoid. Secondly, the assistive device effectively reduced flexor digitorum activity (>40% reduction, p<0.03) and anterior deltoid activity (>75% reduction, p=0.5) in both AC and PC. Erector spinae EMG remained similar to their respective unassisted conditions. The assistive load carriage device may be an effective ergonomic tool in both AC and PC techniques. Subjective surveys indicate that the assistive device decreased the awkwardness in performing the PC technique. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2008-09-29 16:58:19.305