No description available.

Cranes are increasingly used in transportation and construction. increasing demand and faster requirements necessitate better and more efficient controllers to guarantee fast turn-around time and to meet safety requirements. Container cranes are used extensively in ship-to-port and port-to-ship transfer operations. In this work, we will extend the recently developed delayed position feedback controller to container cranes. In contrast with traditional work, which models a crane as a simple pendulum consisting of a hoisting cable and a lumped mass at its end, we have modeled the crane as a four-bar mechanism. The actual configuration of the hoisting mechanism is significantly different from a simple pendulum. It consists typically of a set of four hoisting cables attached to four different points on the trolley and to four points on a spreader bar. The spreader bar is used to lift the containers. Therefore, the dynamics of hoisting assemblies of large container cranes are different from that of a simple pendulum. We found that a controller which treats the system as a four-bar mechanism has an improved response. We developed a controller to meet the following requirements: traverse an 80-ton payload 50 m in 21.5 s, including raising the payload 15 m at the beginning and lowering the payload 15 m at the end of motion, while reducing the sway to 50 mm within 5.0 s at the end of the transfer maneuver. The performance of the controller has been demonstrated theoretically using numerical simulation. Moreover, the performance of the controller has been demonstrated experimentally using a 1/10th scale model. For the 1/10th scale model, the requirements translate into: traverse an 80 kg payload 5 m in 6.8 s, including raising 1.5 m at the beginning and lowering 1.5 m at the end of motion, while reducing the sway to 5 mm in under 1.6 s. The experiments validated the controller. / Master of Science

No description available.

Reach truck masts are subjected to oscillations, which have significant impacts on the dynamics of the entire vehicle. Mast oscillations can cause undesirable outcomes in extreme situations and therefore it is desirable to be able to predict these outcomes before they occur. A forklift manufacturer in Mjölby initiated a thesis with the intention to obtain a model that can simulate mast sway for situations where oscillations occur. The objective of the thesis was to create a model of Triplex masts and find dependencies between model parameters and variables such as fork height and load. The thesis was conducted modelling the mast with a rigid multibody approach where torsion springs and dampers were used between mast parts to simulate mast elasticity. Clearance at the connections were considered and included in the model. The obtained model constitutes of 8 parameters that could be tuned to attain different oscillation characteristics. Parametric optimisation was carried out to find optimal sets of parameters for compliance with sway measurement tests with different load and fork height cases.  The thesis has resulted in a model that is able to simulate mast sway with different oscillation characteristics depending on model parameters. Performed parametric optimisation resulted in parameters that reveal useful information about how model parameters depend on load and fork height. The method used for obtaining optimal parameters can likewise be applied to other mast models in order to gain insight into model parameters as functions of load and fork height.

<p>Syfte</p><p>Tidigare forskning har visat att Tai Chi träning förbättrar balansen hos äldre. Syftet med denna studie var att undersöka om barns balans påverkades av träning som utfördes i ett långsamt tempo liknande Tai Chi träning.</p><p>Studien syftade också till att utreda om det förelåg någon skillnad i balans mellan pojkar och flickor och om något av könen tog till sig träningen bättre. Studien syftade även till att undersöka hur balansen påverkades då barnen utförde olika kognitiva uppgifter.</p><p>Metod</p><p>Studien fullföljdes av 41 barn i åldern 9-10 år. En interventionsgrupp, 19 barn tränade Tai Chi liknande rörelser dagligen under åtta veckor och denna jämfördes med en kontrollgrupp, 22 barn som inte fick denna träning.</p><p>Balansövningar utfördes på en kraftplatta samt på en metallprofil. Från övningarna på kraftplattan mättes standardavvikelse och amplitud av tryckcentrums mediolaterala och anterioposteriora förflyttning. Från övningarna på metallprofilen mättes antalet nedtramp.</p><p>Resultat</p><p>Många parametrar mättes men endast en uppvisade en signifikant träningseffekt. Pojkarna minskade standardavvikelsen på tryckcentrums mediolaterala förflyttning vid stående med öppna ögon.</p><p>Studien uppmätte vissa skillnader i balans mellan pojkar och flickor.</p><p>Mätningar av tryckcentrums förflyttning då barnen utförde olika uppgifter uppmätte en signifikant skillnad vid stående med öppna ögon jämfört med stående då ögonen var stängda (med eller utan utförande av en samtida kognitiv uppgift).</p><p>Övningarna på metallskenan förbättrades lika mycket i tränings- som kontrollgrupp.</p><p>Slutsats</p><p>Studien ger indikationer att träningsformen i viss utsträckning var effektiv då daglig träning under åtta veckor gav signifikant förbättring i en av de testade parametrarna.</p><p>Dessa fynd är i linje med de fåtal studier som finns på träning av balans hos barn.</p><p> </p> / <p>Aim.</p><p>Previous studies have shown that Tai Chi exercises improve postural control in elderly people. The primary aim of this study was to investigate if similar Thai Chi like training affects postural control in children. Secondary aims of the study was 1) to investigate if any such effects from training differs between boys and girls and 2) to investigate whether performing a cognitive task during balance testing had any effect on postural control in these children.</p><p>Method.</p><p>In the balance tests, different tasks were performed on a force plate and on a metal profile. From the tasks performed on the force plate, the standard deviations and amplitudes of the mediolateral and anterioposterior displacements of center of pressure were measured. From the tasks performed on the metal profile, the number of clampdowns were counted.</p><p>The study was conducted over an eight week period with 41 children in the ages 9-10 years old. The children were divided into two groups; children in the training group (n=19) who participated in Tai Chi like training every day, and children in the control group (n=22) who did not participate in this training.</p><p>Results.</p><p>The study also showed some differences in postural control between boys and girls.</p><p>When comparing the displacement in center of pressure between different two-legged tasks performed on the force plate, significantly less displacement was found in the task involving standing with open eyes compared to all tasks involving standing with closed eyes (with or without a concurrent cognitive task).</p><p>The number of clampdowns from the metal profile were reduced after the training period, to a similar extent in the control and the training groups.</p><p>Several different aspects of the postural control were measured in the study. Only one of these improved significantly with training. Boys in the intervention group showed a decrease in the standard deviation of the mediolateral displacement of the center of pressure when standing with open eyes.</p><p>Conclusion.</p><p>These results are also consistent with similar studies on postural control among children.</p><p>This study indicates that slow motion training, similar to Tai Chi, has a small but positive effect on postural control, for boys 9-10 year old, when conducted every day over an eight week period, as one of the tested parameters shows an improvement.</p><p> </p>

Syfte Tidigare forskning har visat att Tai Chi träning förbättrar balansen hos äldre. Syftet med denna studie var att undersöka om barns balans påverkades av träning som utfördes i ett långsamt tempo liknande Tai Chi träning. Studien syftade också till att utreda om det förelåg någon skillnad i balans mellan pojkar och flickor och om något av könen tog till sig träningen bättre. Studien syftade även till att undersöka hur balansen påverkades då barnen utförde olika kognitiva uppgifter. Metod Studien fullföljdes av 41 barn i åldern 9-10 år. En interventionsgrupp, 19 barn tränade Tai Chi liknande rörelser dagligen under åtta veckor och denna jämfördes med en kontrollgrupp, 22 barn som inte fick denna träning. Balansövningar utfördes på en kraftplatta samt på en metallprofil. Från övningarna på kraftplattan mättes standardavvikelse och amplitud av tryckcentrums mediolaterala och anterioposteriora förflyttning. Från övningarna på metallprofilen mättes antalet nedtramp. Resultat Många parametrar mättes men endast en uppvisade en signifikant träningseffekt. Pojkarna minskade standardavvikelsen på tryckcentrums mediolaterala förflyttning vid stående med öppna ögon. Studien uppmätte vissa skillnader i balans mellan pojkar och flickor. Mätningar av tryckcentrums förflyttning då barnen utförde olika uppgifter uppmätte en signifikant skillnad vid stående med öppna ögon jämfört med stående då ögonen var stängda (med eller utan utförande av en samtida kognitiv uppgift). Övningarna på metallskenan förbättrades lika mycket i tränings- som kontrollgrupp. Slutsats Studien ger indikationer att träningsformen i viss utsträckning var effektiv då daglig träning under åtta veckor gav signifikant förbättring i en av de testade parametrarna. Dessa fynd är i linje med de fåtal studier som finns på träning av balans hos barn. / Aim. Previous studies have shown that Tai Chi exercises improve postural control in elderly people. The primary aim of this study was to investigate if similar Thai Chi like training affects postural control in children. Secondary aims of the study was 1) to investigate if any such effects from training differs between boys and girls and 2) to investigate whether performing a cognitive task during balance testing had any effect on postural control in these children. Method. In the balance tests, different tasks were performed on a force plate and on a metal profile. From the tasks performed on the force plate, the standard deviations and amplitudes of the mediolateral and anterioposterior displacements of center of pressure were measured. From the tasks performed on the metal profile, the number of clampdowns were counted. The study was conducted over an eight week period with 41 children in the ages 9-10 years old. The children were divided into two groups; children in the training group (n=19) who participated in Tai Chi like training every day, and children in the control group (n=22) who did not participate in this training. Results. The study also showed some differences in postural control between boys and girls. When comparing the displacement in center of pressure between different two-legged tasks performed on the force plate, significantly less displacement was found in the task involving standing with open eyes compared to all tasks involving standing with closed eyes (with or without a concurrent cognitive task). The number of clampdowns from the metal profile were reduced after the training period, to a similar extent in the control and the training groups. Several different aspects of the postural control were measured in the study. Only one of these improved significantly with training. Boys in the intervention group showed a decrease in the standard deviation of the mediolateral displacement of the center of pressure when standing with open eyes. Conclusion. These results are also consistent with similar studies on postural control among children. This study indicates that slow motion training, similar to Tai Chi, has a small but positive effect on postural control, for boys 9-10 year old, when conducted every day over an eight week period, as one of the tested parameters shows an improvement.

国立情報学研究所で電子化したコンテンツを使用している。

Bakgrund: Personer som opererats för godartad lillhjärnstumör när de var barn upplever sig ha balansproblem och förekomst av lätt balansnedsättning har rapporterats. I en pågående uppföljningsstudie vid Akademiska sjukhuset undersöks bl.a. balansen i denna patientgrupp. Syfte: … att i en delstudie med kontrollpersoner beskriva och jämföra balansförmågan vid genomförande av Mini-BESTest med fokus på Timed-Up-and-Go (TUG) och TUG_kognitiv. Metod: Tvärsnittsstudie. Elva personer 19-33 år rekryterades. Deltagarna utförde Mini-BESTest med rörelseanalyssystemet MoLab. Beroende variabler var poäng på MiniBESTest, absolut och relativ tid för TUG-faser samt balansvariabeln trunk sway velocity. Resultat: Medianvärdet för Mini-BESTest var 31 (Q1-Q3=29-31). En skillnad på 17,3%  framkom för den totala tiden mellan TUG och TUG_kognitiv. Signifikanta skillnader mellan balansuppgifterna påvisades för total absolut tid (p = 0,003), fas 2 (p = 0,013) och fas 3 (p = 0,021). För balansvariabeln trunk sway velocity i antero-/posterior riktning framkom signifikanta skillnader för fas 2 (p=0,008), fas 3 (p=0,010) och fas 4 (p = 0,05), medio-/lateralt en signifikant skillnad för fas 2 (p = 0,03). Konklusion: Denna studie visade att friska unga vuxna får en påverkan på balansen när de samtidigt utför en kognitiv uppgift. Resultatet går inte att generalisera till en större population utan gäller för de undersökta deltagarna / Background: People treated for benign cerebellar tumor during childhood experience balance problems and studies report presence of mild balance impairment. In an ongoing follow-up study at the University Hospital in Uppsala balance in this patient group is being investigated. Objective: ... in a sub-study with control persons describe and compare balance performance of Mini-BESTest focusing on Timed-Up-and-Go (TUG) and TUG_cognitive. Methods: Cross-sectional study. Eleven people 19-33 years were recruited. The participants performed the Mini-BESTest with the MoLab motion analysis system. Dependent variables were points on MiniBESTest, absolute and relative time for TUG-phases, and the balance variable trunk sway velocity. Results: Median value for Mini-BESTest was 31 (Q1-Q3 = 29-31). A difference of 17.3% was shown for total time between TUG and TUG_cognitive. Significant differences between the balance tests were shown for total absolute time (p = 0.003), phase 2 (p = 0.013) and phase 3 (p = 0.021). For trunk sway velocity in the antero-/posterior direction, significant differences were shown for phase 2 (p = 0.008), phase 3 (p = 0.010) and phase 4 (p = 0.05), medio-/laterally  significant difference for phase 2 (p = 0.03). Conclusion: This study demonstrated that healthy young adults have an impact on balance when they simultaneously perform a cognitive task. The result cannot be generalized to a larger population, but applies to the participants investigated.

The objective of this study was to numerically investigate the effects of slenderness ratios and end rotational restraints on the post-buckling behavior of non-sway columns. To study the effect of end restraints, numerical solutions were generated for three different support conditions, namely, hinged-hinged, fixed-hinged and fixed-fixed. Furthermore, for each of these support conditions, the effects of slenderness ratios on the post-buckling response were analyzed by considering the slenderness ratios of 50,125 and 200. Based on the numerical data presented in this thesis, the following conclusions can be made.  The unrestrained columns under mechanical loads do not exhibit any significant post-buckling strength.  Restrained Columns subjected to thermal loading undergo significantly smaller deformations in contrast to unrestrained columns, where deformations are relatively larger as the loads are increased only slightly above their critical levels.  The mechanical post-buckling response does not seem to depend on the slenderness ratios of the columns ;whereas the thermal post-buckling response depends on the slenderness ratios of the columns with the relative deformation decreasing with slenderness ratio at a given temperature ratio.  Post buckling behavior of columns subjected to mechanical loadings does not seem to change when the rotational restraints are added whereas in case of columns subjected to thermal loading, the post-buckling response depends on the rotational restraints at the ends of the column. o For a constant slenderness ratio, the deflection ratio was found out to be the smallest for the hinged-hinged column and largest for the fixed-fixed column subjected to thermal loads at a given temperature ratio.

AN ABSTRACT OF THE THESIS OF Sujan Shrestha, for the Master of Science degree in Civil Engineering, presented on March 3, 2015, at Southern Illinois University, Carbondale. TITLE: POST BUCKLING RESPONSE OF SWAY COLUMNS UNDER MECHANICAL AND THERMAL (FIRE) LOADS MAJOR PROFESSOR: Dr. Aslam Kassimali, Ph.D. The post-buckling response of sway columns under mechanical and thermal loadings are presented by using the geometrical nonlinear analysis. For thermal analysis, the columns are assumed to be fully restrained in their axial directions. The method of analysis uses Beam-Column theory which is based on an Eulerian (corotational) formulation. Numerical solutions are shown for the post-buckling response of sway columns. The numerical investigations of the geometrically nonlinear analysis of sway columns were carried out with three different boundary conditions of sway columns as suggested by AISC, under mechanical loading and temperature changes. The sway columns considered are the cases `c', `e' and `f' in Table C-A-7.1 of AISC Manual (2011). These were modeled and analyzed to predict the post-buckling response under the mechanical and thermal loads. Furthermore, for each of these support conditions, the effects of slenderness ratios on the post-buckling response were analyzed by considering the slenderness ratios of 50,125 and 200. Also, the effects on post-buckling strength were observed keeping the same slenderness ratios but varying rotational end conditions of sway columns. Many useful conclusions can be drawn from this study. The more important conclusions are: 1) As all unrestrained sway columns undergo excessive deformation under mechanical loading, they do not possess significant post-buckling strength once the loading reaches the buckling load. 2) All restrained sway columns undergo much smaller deformations under thermal loading as compared to mechanical loading; thus significant post-buckling strength is achieved even after reaching the buckling temperature. This post-buckling strength can be considered during the design of structures which will aid in safe and economical structures. 3) Slenderness ratios play an important role on post-buckling strength only in thermal analysis but not in mechanical analysis. Increase in slenderness ratio tends to decrease the post-buckling relative deformation of the columns under thermal loading but has no such effect under mechanical loading. 4) Rotational end conditions also play significant role on post-buckling strength during thermal analysis but not during mechanical analysis. Keeping the slenderness ratio constant and varying the rotational end conditions, the post-buckling strength of all sway columns remains same under mechanical loading but is different under thermal loading.