Perancangan Kursi Puzzle Untuk Anak-Anak Dengan Sistem Knockdown

In general, children spending their times with plays and trying new things. In this periods child should doing many things so they can grow optimally. However, gadgets make them don't do what they actually need to do for their physical development, they rely on their little 10 fingers and parents miss the chance to look at their child physical development. Based on the problems that had been described, we realized that we need a cooperation between parents and their children, we need something that attracts children to think and move. Through this knockdown system puzzle chair design, we can use it to improve the cooperation between parents and their children, improving their(child) creativity, and stimulates their(child) motoric, Because this chair is designed not only used as usual chair but also used as children toys

HEAT TRANSFER FLUIDS

The choice of heat transfer fluids has significant effects on the performance, cost, and reliability of solar thermal systems. In this chapter, we evaluate existing heat transfer fluids such as oils and molten salts based on a new figure of merit capturing the combined effects of thermal storage capacity, convective heat transfer characteristics, and hydraulic performance of the fluids. Thermal stability, freezing point, and safety issues are also discussed. Through a comparative analysis, we examine alternative options for solar thermal heat transfer fluids including water−steam mixtures (direct steam), ionic liquids/melts, and suspensions of nanoparticles (nanofluids), focusing on the benefits and technical challenges.Center for Clean Water and Clean Energy at MIT and KFUPM (Project 6918351)United States. Dept. of Energy. Office of Science (Solid-State Solar-Thermal Energy Conversion Center Award DE-SC0001299

Wide-field Magnetic Field and Temperature Imaging using Nanoscale Quantum Sensors

The simultaneous imaging of magnetic fields and temperature (MT) is important in a range of applications, including studies of carrier transport, solid-state material dynamics, and semiconductor device characterization. Techniques exist for separately measuring temperature (e.g., infrared (IR) microscopy, micro-Raman spectroscopy, and thermo-reflectance microscopy) and magnetic fields (e.g., scanning probe magnetic force microscopy and superconducting quantum interference devices). However, these techniques cannot measure magnetic fields and temperature simultaneously. Here, we use the exceptional temperature and magnetic field sensitivity of nitrogen vacancy (NV) spins in conformally-coated nanodiamonds to realize simultaneous wide-field MT imaging. Our "quantum conformally-attached thermo-magnetic" (Q-CAT) imaging enables (i) wide-field, high-frame-rate imaging (100 - 1000 Hz); (ii) high sensitivity; and (iii) compatibility with standard microscopes. We apply this technique to study the industrially important problem of characterizing multifinger gallium nitride high-electron-mobility transistors (GaN HEMTs). We spatially and temporally resolve the electric current distribution and resulting temperature rise, elucidating functional device behavior at the microscopic level. The general applicability of Q-CAT imaging serves as an important tool for understanding complex MT phenomena in material science, device physics, and related fields

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

We present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper–water, stainless steel–mercury, and nickel–liquid potassium thermosyphon-working fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300–1200 K, solar concentrations of 1–100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.United States. Dept. of Energy. Office of Basic Energy Sciences (MIT S3TEC Center, an Energy Frontier Research Center)Natural Sciences and Engineering Research Council of Canad

Role of spectral non-idealities in the design of solar thermophotovoltaics

To bridge the gap between theoretically predicted and experimentally demonstrated efficiencies of solar thermophotovoltaics (STPVs), we consider the impact of spectral non-idealities on the efficiency and the optimal design of STPVs over a range of PV bandgaps (0.45-0.80 eV) and optical concentrations (1-3,000x). On the emitter side, we show that suppressing or recycling sub-bandgap radiation is critical. On the absorber side, the relative importance of high solar absorptance versus low thermal emittance depends on the energy balance. Both results are well-described using dimensionless parameters weighting the relative power density above and below the cutoff wavelength. This framework can be used as a guide for materials selection and targeted spectral engineering in STPVs.United States. Dept. of Energy. Office of Basic Energy Sciences (DE-FG02-09ER46577

Turning bubbles on and off during boiling using charged surfactants

Boiling—a process that has powered industries since the steam age—is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles ‘on and off’ independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications.Singapore-MIT Alliance for Research and TechnologyNational Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (Award DMR-0819762

Real-Time Manipulation with Magnetically Tunable Structures

Magnetically tunable micropillar arrays with uniform, continuous and extreme tilt angles for real-time manipulation are reported. We experimentally show uniform tilt angles ranging from 0° to 57°, and develop a model to accurately capture the behavior. Furthermore, we demonstrate that the flexible uniform responsive microstructures (μFUR) can dynamically manipulate liquid spreading directionality, control fluid drag, and tune optical transmittance over a large range.United States. Air Force Office of Scientific Research (AFOSR, Grant FA9550-11-1-0059

Phononic band structure engineering for high-Q gigahertz surface acoustic wave resonators on lithium niobate

Phonons at gigahertz frequencies interact with electrons, photons, and atomic systems in solids, and therefore have extensive applications in signal processing, sensing, and quantum technologies. Surface acoustic wave (SAW) resonators that confine surface phonons can play a crucial role in such integrated phononic systems due to small mode size, low dissipation, and efficient electrical transduction. To date, it has been challenging to achieve high quality (Q) factor and small phonon mode size for SAW resonators at gigahertz frequencies. Here, we present a methodology to design compact high-Q SAW resonators on lithium niobate operating at gigahertz frequencies. We experimentally verify out designs and demonstrate Q factors in excess of $2\times10^4$ at room temperature ($6\times10^4$ at 4 Kelvin) and mode area as low as $1.87 \lambda^2$. This is achieved by phononic band structure engineering, which provides high confinement with low mechanical loss. The frequency-Q products (fQ) of our SAW resonators are greater than $10^{13}$. These high-fQ and small mode size SAW resonators could enable applications in quantum phononics and integrated hybrid systems with phonons, photons, and solid-state qubits

Jumping-Droplet Electrostatic Energy Harvesting

Micro- and nanoscale wetting phenomena has been an active area of research due to its potential for improving engineered system performance involving phase change. With the recent advancements in micro/nanofabrication techniques, structured surfaces can now be designed to allow condensing coalesced droplets to spontaneously jump off the surface due to the conversion of excess surface energy into kinetic energy. In addition to being removed at micrometric length scales (~10 μm), jumping water droplets also attain a positive electrostatic charge (~10-100 fC) from the hydrophobic coating/condensate interaction. In this work, we take advantage of this droplet charging to demonstrate jumping-droplet electrostatic energy harvesting. The charged droplets jump between superhydrophobic copper oxide and hydrophilic copper surfaces to create an electrostatic potential and generate power during formation of atmospheric dew. We demonstrated power densities of ~15 pW/cm[superscript 2], which, in the near term, can be improved to ~1 μW/cm[superscript 2]. This work demonstrates a surface engineered platform that promises to be low cost and scalable for atmospheric energy harvesting and electric power generation.United States. Dept. of Energy. Office of Basic Energy Sciences (Award DE-FG02-09ER46577)United States. Office of Naval ResearchNational Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374