Biomimetic design for an under-actuated leg exoskeleton for load-carrying augmentation

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 79-81).Metabolic studies have shown that there is a metabolic cost associated with carrying a load (Griffin et al, 2003). Further studies have shown that by applying forward propulsive forces a person can walk with a reduced metabolic rate (Farley & McMahon, 1992 and Gottschall & Kram, 2003). Previous work on exoskeleton design has not considered the passive dynamics of walking and has focused on fully actuated systems that are inefficient and heavy. In this thesis, an under-actuated exoskeleton is presented that runs parallel to the human leg. The exoskeleton component design is based on the kinematics and kinetics of human walking. The joint components of the exoskeleton in the sagittal plane consist of a force-controllable actuator at the hip, a variable-damper mechanism at the knee and a passive spring at the ankle. A state-machine control strategy is written based on joint angle and ground-exoskeleton force sensing. Positive, non-conservative power is added at the hip during the walking cycle to help propel the mass of the human and payload forward. At the knee, the damper mechanism is turned on at heel strike as the exoskeleton leg is loaded and turned off during terminal stance to allow knee flexion.(cont.) The spring at the ankle engages in controlled dorsiflexion to store energy that is later released to assist in powered plantarflexion. Kinetic and metabolic data are recorded from human subjects wearing the exoskeleton with a 751b payload. These data are compared to data recorded from subjects walking without the exoskeleton. It is demonstrated that the exoskeleton does transfer loads to the ground with a 90% and higher load transfer depending on the phase of gait. Further, exoskeleton wearers report that the exoskeleton greatly reduces the stress on the shoulders and back. However, although a significant fraction of the payload is transferred through the exoskeleton structure, the exoskeleton is found to increase metabolic economy by 74%. By comparing distinct exoskeleton configurations, the relative effect of each exoskeleton component is determined. Metabolic data show that the variable-damper knee and ankle spring mechanisms increase metabolism by only 32%, whereas a non-actuated exoskeleton (no motor, variable-damper, or spring) increases walking metabolism by 62%. These results highlight the benefit of ankle elastic energy storage and knee variable-damping in exoskeleton design, and further the need for a lighter, more efficient hip actuator.by Conor James Walsh.S.M

Image-guided robots for dot-matrix tumor ablation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 203-208).Advances in medical imaging now provides detailed images of solid tumors inside the body and miniaturized energy delivery systems enable tumor destruction through local heating powered by a thin electrode. However, the use of thermal ablation as a first line of treatment is limited due to the difficulty in accurately matching a desired treatment and a limited region of active heating around an electrode. The purpose of this research is to identify and quantify the current limitations of image-guided interventional procedures and subsequently develop a procedure and devices to enable accurate and efficient execution of image-based interventional plans and thus ablation of a tumor of any shape with minimal damage to surrounding tissue. Current limitations of probe placement for ablation therapy were determined by a detailed retrospective study of 50 representative CT-guided procedures. On average, 21 CT scans were performed for a given procedure (range 11-38), with the majority devoted to needle orientation and insertion (mean number of scans was 54%) and trajectory planning (mean number of scans was 19%). A regression analysis yielded that smaller and deeper lesions were associated with a higher number of CT scans for needle orientation and insertion; highlighting the difficulty in targeting. Another challenge identified was repositioning the instrument distal tip within tissue. The first robot is a patient-mounted device that aligns an instrument along a desired trajectory via two motor-actuated concentric, crossed, and partially nested hoops. A carriage rides in the hoops and grips and inserts an instrument via a two degree-of-freedom friction drive. An imagebased point-and-click user interface relates appropriate clicks on the medical images to robot commands. Mounting directly on the patient provides a sufficiently stable and safe platform for actuation and eliminates the need to compensate for chest motion; thereby reducing the cost and complexity compared to other devices. Phantom experiments in a realistic clinical setting demonstrated a mean targeting accuracy of 3.5 mm with an average of five CT scans. The second robot is for repositioning the distal tip of a medical instrument to adjacent points within tissue. The steering mechanism is based on the concept of substantially straightening a pre-curved Nitinol stylet by retracting it into a concentric outer cannula, and re-deploying it at different axial and rotational cannula positions. The proximal end of the cannula is attached to the distal end of a screw-spline that enables it to be translated and rotated with respect to the casing. Translation of the stylet relative to the cannula is achieved with a second concentric, nested smaller diameter screw that is constrained to rotate with the cannula. The robot mechanism is compatible with the CT images, light enough to be supported on a patient's chest or attached to standard stereotactic frames. Targeting experiments in a gelatin phantom demonstrated a mean targeting error of 1.8 mm between the stylet tip and that predicted with a kinematic model. Ultimately, these types of systems are envisioned being used together as part of a highly dexterous patient-mounted positioning platform that can accurately perform ablation of large and irregularly shaped tumors inside medical imaging machines - offering the potential to replace expensive and traumatic surgeries with minimally invasive out-patient procedures.by Conor James Walsh.Ph.D

PROJECTIONS OF DEMAND FOR HEALTHCARE IN IRELAND, 2015-2030: FIRST REPORT FROM THE HIPPOCRATES MODEL. ESRI RESEARCH SERIES NUMBER 67 OCTOBER 2017

This report provides baseline estimates and projections of public and private healthcare demand for Irish health and social care services for the years 2015–2030. This is the first report to be published applying the Hippocrates projection model of Irish healthcare demand and expenditure which has been developed at the ESRI in a programme of research funded by the Department of Health. Development of the model has required a very detailed analysis of the services used in Irish health and social care in 2015. This is the most comprehensive mapping of both public and private activity in the Irish healthcare system to have been published for Ireland

The great convergence? Mortality in Ireland and Europe, 1956–2014. ESRI Research Bulletin 202019 September 2020.

This study examines differences in mortality in Ireland and the EU-15 between 1956 and 2014 and provides insights into the causes of death and age groups responsible for the recent convergence to our EU-15 peers

How many beds? Capacity implications of hospital care demand projections in the Irish hospital system, 2015-2030. ESRI Research Bulletin 2018/11

The Irish hospital system at present does not have enough hospital beds to meet demand for care adequately. When measured against other OECD countries, Ireland has a low supply of hospital beds and records the highest rate of patient bed occupancy at 95 per cent. The expected rapid growth and ageing of the Irish population is projected to increase demand for hospital care further. This means that in the coming years there will be an even greater need to increase the number of available hospital beds. This paper employs the ESRI HIPPOCRATES healthcare projection model to project the number of public and private hospital beds that may be required between 2015 and 2030. Importantly, in developing these projections we take into account the ability to move care to non-hospital settings

Correction to: Mobility related physical and functional losses due to aging and disease - a motivation for lower limb exoskeletons

The original article contains an error in Fig. 3f whereby data is erroneously extrapolated beyond 80 years of age; this also affects statements made elsewhere in the article. Thus, the correct version of Fig. 3f can be viewed ahead and should be considered in place of the original Fig. 3f; furthermore, the following amendments to affected statements should also be considered

Mobility related physical and functional losses due to aging and disease - a motivation for lower limb exoskeletons

Background: Physical and functional losses due to aging and diseases decrease human mobility, independence, and quality of life. This study is aimed at summarizing and quantifying these losses in order to motivate solutions to overcome them with a special focus on the possibilities by using lower limb exoskeletons. Methods: A narrative literature review was performed to determine a broad range of mobility-related physical and functional measures that are affected by aging and selected cardiovascular, respiratory, musculoskeletal, and neurological diseases. Results: The study identified that decreases in limb maximum muscle force and power (33% and 49%, respectively, 25–75 yrs) and in maximum oxygen consumption (40%, 20–80 yrs) occur for older adults compared to young adults. Reaction times more than double (18–90 yrs) and losses in the visual, vestibular, and somatosensory systems were reported. Additionally, we found decreases in steps per day (75%, 60–85 yrs), maximum walking speed (24% 25–75 yrs), and maximum six-minute and self-selected walking speed (38% and 21%, respectively, 20–85 yrs), while we found increases in the number of falls relative to the number of steps per day (800%), injuries due to falls (472%, 30–90 yrs) and deaths caused by fall (4000%, 65–90 yrs). Measures were identified to be worse for individuals with impaired mobility. Additional detrimental effects identified for them were the loss of upright standing and locomotion, freezing in movement, joint stress, pain, and changes in gait patterns. Discussion: This review shows that aging and chronic conditions result in wide-ranging losses in physical and sensory capabilities. While the impact of these losses are relatively modest for level walking, they become limiting during more demanding tasks such as walking on inclined ground, climbing stairs, or walking over longer periods, and especially when coupled with a debilitating disease. As the physical and functional parameters are closely related, we believe that lost functional capabilities can be indirectly improved by training of the physical capabilities. However, assistive devices can supplement the lost functional capabilities directly by compensating for losses with propulsion, weight support, and balance support. Conclusions: Exoskeletons are a new generation of assistive devices that have the potential to provide both, training capabilities and functional compensation, to enhance human mobility

Trade and trade-offs: shipping in changing climates

This paper addresses the evolution of maritime transport demand in response to global climate change mitigation and adaptation efforts. The complexity of the global shipping system makes predicting volumes and patterns of long-term future international maritime trade a challenging task which is best explored by building scenarios rather than ‘precise’ forecasts. We present four contrasting scenarios of international maritime trade out to 2050, available in high resolution in terms of the dimensions studied (regions, countries, commodities, decades), which are consistent with high and low levels of global CO2 mitigation and associated climate impacts. The scenarios project trade increasing to between two and four times the 2010 value by 2050. Scenarios characterised by low temperature increases and material intensity lead to the lower bound trade increase with high trade growth in bioenergy commodities. Unfettered production growth across countries, high temperature increases and material intensity lead to a quadrupling of trade across energy, containerised, dry and wet commodities. The estimated range is lower than those in existing scenarios and forecasts in which globalisation is assumed to continue apace. The scenarios which project the highest growth presupposes both limited decarbonisation (in contrast to the Paris Agreement) and continued growth in expanding markets. The scenarios therefore become a valuable policy and decision-making tool to address technological and operational change required of the shipping sector, if it is to deliver mitigation in line with the Paris Agreement

Large-area growth of MoS2 at temperatures compatible with integrating back-end-of-line functionality

Direct growth of transition metal dichalcogenides over large areas within the back-end-of-line (BEOL) thermal budget limit of silicon integrated circuits is a significant challenge for 3D heterogeneous integration. In this work, we report on the growth of MoS2 films (~1-10 nm) on SiO2, amorphous-Al2O3, c-plane sapphire, and glass substrates achieved at low temperatures (350 C-550 C) by chemical vapor deposition in a manufacturing-compatible 300 mm atomic layer deposition reactor. We investigate the MoS2 films as a potential material solution for BEOL logic, memory and sensing applications. Hall-effect/4-point measurements indicate that the ~10 nm MoS2 films exhibit very low carrier concentrations (1014-1015 cm-3), high resistivity, and Hall mobility values of ~0.5-17 cm2 V-1 s-1, confirmed by transistor and resistor test device results. MoS2 grain boundaries and stoichiometric defects resulting from the low thermal budget growth, while detrimental to lateral transport, can be leveraged for the integration of memory and sensing functions. Vertical transport memristor structures (Au/MoS2/Au) incorporating ~3 nm thick MoS2 films grown at 550 C (~0.75 h) show memristive switching and a stable memory window of 105 with a retention time >104 s, between the high-low resistive states. The switching set and reset voltages in these memristors demonstrate a significant reduction compared to memristors fabricated from pristine, single-crystalline MoS2 at higher temperatures, thereby reducing the energy needed for operation. Furthermore, interdigitated electrode-based gas sensors fabricated on ~5 nm thick 550 C-grown (~1.25 h) MoS2 films show excellent selectivity and sub-ppm sensitivity to NO2 gas, with a notable self-recovery at room temperature. The demonstration of large-area MoS2 direct growth at and below the BEOL thermal budget limit, alongside memristive and gas sensing functionality, advances a key enabling technology objective in emerging materials and devices for 3D heterogeneous integration

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis