The evolution to bipedalism forced humans to develop suitable strategies for dynamically controlling their balance, ensuring stability, and preventing falling. The natural aging process and traumatic ...events such as lower-limb loss can alter the human ability to control stability significantly increasing the risk of fall and reducing the overall autonomy. Accordingly, there is an urgent need, from both end-users and society, for novel solutions that can counteract the lack of balance, thus preventing falls among older and fragile citizens. In this study, we show a novel ecological approach relying on a wearable robotic device (the Active Pelvis Orthosis, APO) aimed at facilitating balance recovery after unexpected slippages. Specifically, if the APO detects signs of balance loss, then it supplies counteracting torques at the hips to assist balance recovery. Experimental tests conducted on eight elderly persons and two transfemoral amputees revealed that stability against falls improved due to the "assisting when needed" behavior of the APO. Interestingly, our approach required a very limited personalization for each subject, and this makes it promising for real-life applications. Our findings demonstrate the potential of closed-loop controlled wearable robots to assist elderly and disabled subjects and to improve their quality of life.
•Preheaters are used to trigger boiling, preventing superheating in cooling pipes.•A semi-empirical model for the preheater design is proposed.•The model validation closely matches the trends from ...experimental results.•The model is, in principle, applicable to any pure refrigerant fluid.
The fluid properties of CO2 make it an ideal medium for the cooling of tracking detectors in experiments at particle accelerators. Detectors such as the Compact Muon Solenoid Outer Tracker at CERN will be cooled to a nominal temperature of -35 °C with CO2 cooling to ensure the longevity of the silicon sensors. In theory, two-phase CO2 cooling results in a very low temperature change along the detector tube, dependent only on pressure drop. Experimentally, however, superheating – the existence of a fluid in the liquid form above its boiling temperature – has been observed to occur frequently. This results in higher fluid temperatures and a poor heat transfer coefficient over the first section of the detector tube, disrupting the cooling performance of the detector and possibly leading to deterioration of the silicon sensors. In order to prevent superheating, a preheater is proposed to trigger nucleate boiling in the Compact Muon Solenoid Outer Tracker detector cooling tube just upstream of the sensors. A theoretical – semi-empirical – model for the preheater design is presented, starting from experimental data points. With this model, the triggering of nucleation can be characterised for tubes made of the same material as that tested and with the same surface cavity size. The model validation is promising, closely matching the trends from experimental results, and giving preheater specific powers significantly lower than those derived from spinodal theory.
This study investigates the effectiveness of a robot-mediated strategy aimed at promoting balance recovery after multidirectional slippages. Six older adults were asked to manage anteroposterior and ...mediolateral slippages while donning an active pelvis orthosis (APO). The APO was set up either to assist volunteers during balance loss or to be transparent. The margin of stability, in sagittal and frontal planes, was the main metric to assess the effectiveness of balance recovery. Results showed that the assistive strategy is effective at promoting balance recovery in the sagittal plane, for both perturbing paradigms; however, it is not effective at controlling stability in the frontal plane.
Following its pioneering application in the present LHCb Velo detector, CO2 evaporative cooling has become the consolidated technology for the thermal management of low-temperature operated silicon ...detectors at LHC. ATLAS Insertable B-Layer and CMS Phase I Pixel are successfully operating with such cooling system since a few years and LHCb has selected the same technology for the new Upstream Tracker and the upgraded Velo, both to be installed during LS2. The design of the ATLAS and CMS upgrade silicon detectors is well advanced, and both experiments heavily rely on CO2 evaporative cooling. In order to cope with the new detector requirements, several studies are on-going, in particular on the scaling of the cooling plants, their integration in the existing space and infrastructure, the low temperature operation. A demonstrator cooling system, the “Demo”, is presently in the design phase at CERN. This paper discusses the challenges of the CO2 systems for the phase 2 upgrade of the LHC experiments, the design of the “Demo” cooling system and the integration and operational issues under study, presenting a time-line for the CO2 system development from now up to operation.
In the last few years, CO2 evaporative cooling has been one of the favourite technologies chosen for the thermal management of tracking detectors at LHC. ATLAS Insertable B-Layer and CMS Pixel phase ...1 upgrade have adopted it and their systems are now operational or under commissioning. The CERN PH-DT team is now merging the lessons learnt on these two systems in order to prepare the design and construction of the cooling systems for the new Upstream Tracker and the Velo upgrade in LHCb, due by 2018. Meanwhile, the preliminary design of the ATLAS and CMS full tracker upgrades is started, and both concepts heavily rely on CO2 evaporative cooling. This paper highlights the performances of the systems now in operation and the challenges to overcome in order to scale them up to the requirements of the future generations of trackers. In particular, it focuses on the conceptual design of a new cooling system suited for the large phase 2 upgrade programmes, which will be validated with the construction of a common prototype in the next years.
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