Thin, soft, skin-like sensors capable of precise, continuous measurements of physiological health have broad potential relevance to clinical health care. Use of sensors distributed over a wide area for full-body, spatiotemporal mapping of physiological processes would be a considerable advance for this field. We introduce materials, device designs, wireless power delivery and communication strategies, and overall system architectures for skin-like, battery-free sensors of temperature and pressure that can be used across the entire body. Combined experimental and theoretical investigations of the sensor operation and the modes for wireless addressing define the key features of these systems. Studies with human subjects in clinical sleep laboratories and in adjustable hospital beds demonstrate functionality of the sensors, with potential implications for monitoring of circadian cycles and mitigating risks for pressure-induced skin ulcers.

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Abstract:The transient thermal performance of phase change and heat and mass transfer in a two-phase closed thermosyphon are studied with computational fluid dynamics (CFD). A CFD model based on the volume of fluid technique is built. Deionized water is specified as the working fluid of this thermosyphon. The CFD model reproduces evaporation and condensation in the thermosyphon at different heating inputs. The average wall temperatures are also analyzed. Variations of average wall temperatures indicate that this thermosyphon reaches a steady state after 19 s, and starts to work in advance when the heating input increases. Moreover, thermal resistance is decreased until a minimum (0.552 K/W) by increasing the heating input, and the effective thermal conductivity is elevated to a maximum (2.07 × 106 W/m·K).

Peripheral nerves are often vulnerable to damage during surgeries, with risks of significant pain, loss of motor function, and reduced quality of life for the patient. Intraoperative methods for monitoring nerve activity are effective, but conventional systems rely on bench-top data acquisition tools with hard–wired connections to electrode leads that must be placed percutaneously inside target muscle tissue. These approaches are time and skill intensive and therefore costly to an extent that precludes their use in many important scenarios. Here we report a soft, skin-mounted monitoring system that measures, stores, and wirelessly transmits electrical signals and physical movement associated with muscle activity, continuously and in real-time during neurosurgical procedures on the peripheral, spinal, and cranial nerves. Surface electromyography and motion measurements can be performed non-invasively in this manner on nearly any muscle location, thereby offering many important advantages in usability and cost, with signal fidelity that matches that of the current clinical standard of care for decision making. These results could significantly improve accessibility of intraoperative monitoring across a broad range of neurosurgical procedures, with associated enhancements in patient outcomes.

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A numerical model, EC2, is developed to simulate the consolidation of a soil layer subjected to combined electroosmosis and surcharge preloading. EC2 includes the capabilities of a previous model, EC1, in accounting for large-strain-induced nonlinear changes of the physical and geoelectrical properties occurring to the layer, with the additions of two-dimensional consolidation, coupled loading and electric fields, time-dependent loading and current density, and an external hydraulic gradient. A highlight of the EC2 model is the superposition of multiple streams between small elements, which improves the prediction accuracy of the rate of flow and the degree of consolidation. The consolidation algorithm of EC2 is one-dimensional and conducted using finite difference and piecewiselinear methods. This paper presents the theoretical and numerical development of the EC2 model. A companion paper presents the validation of the model and the results of simulations that illustrate the optimization of the consolidating processes for some interesting design scenarios.

The heat pump water heater (HPWH), as a portion of the eco-friendly technologies using renewable energy, has been applied for years in developed countries. Air-source heat pump water heaters and solar-assisted heat pump water heaters have been widely applied and have become more and more popular because of their comparatively higher energy efficiency and environmental protection. Besides use of the above resources, the heat pump water heater system can also adequately utilize an available water source. In order to study the thermal performance of the water-source heat pump water heater (WSHPWH) system, an experimental prototype using the cyclic heating mode was established. The heating performance of the water-source heat pump water heater system, which was affected by the difference between evaporator water fluxes, was investigated. The water temperature unfavorably exceeded 55 • C when the experimental prototype was used for heating; otherwise, the compressor discharge pressure was close to the maximum discharge temperature, which resulted in system instability. The evaporator water flux allowed this system to function satisfactorily. It is necessary to reduce the exergy loss of the condenser to improve the energy utilization of the system.

The results of the numerical simulations for electroosmosis-surcharge preloading consolidation, obtained using the EC2 model, are presented. EC2 accounts for hydraulic and electroosmotic flows under the conditions of changing physical and geoelectrical properties of saturated compressible porous media. Verification checks for EC2 show excellent agreement of the pore pressure and degree of consolidation with analytical solutions for oneand two-dimensional small-strain consolidation. Similarly, excellent agreement is attained for two-dimensional large-strain consolidation occurring to a kaolinite layer subjected to an experimental test. The EC2 model is then used to investigate consolidation optimization for soil layers in three example problems. The electroosmosis-surcharge preloading combined method outperformed single process methods, particularly where hydraulic conductivity is on the order of magnitude 10 −8 m/s or lower. Applying voltage in steps optimizes electric power usage, as does ceasing power supply when the degree of consolidation reaches approximately 80%.