596 research outputs found
Quantum Pin Codes
No full textarXiv: 1906.11394We introduce quantum pin codes: a class of quantum CSS codes. Quantum pin codes are a vast generalization of quantum color codes and Reed-Muller codes. A lot of the structure and properties of color codes carries over to pin codes. Pin codes have gauge operators, an unfolding procedure and their stabilizers form multi-orthogonal spaces. This last feature makes them interesting for devising magic-state distillation protocols. We study examples of these codes and their properties
Numerical investigation of bubble dynamics and flow boiling heat transfer in cylindrical micro-pin-fin heat exchangers
No full textMicro-pin-fin evaporators are a promising alternative to multi-microchannel heat sinks for two-phase cooling of high power-density devices. Within pin-fin evaporators, the refrigerant flows through arrays of obstacles in cross-flow and is not restricted by the walls of a channel. The dynamics of bubbles generated upon flow boiling and the associated heat transfer mechanisms are expected to be substantially different from those pertinent to microchannels; however, the fundamental aspects of two-phase flows evolving through micro-pin-fin arrays are still little understood. This article presents a systematic analysis of flow boiling within a micro-pin-fin evaporator, encompassing bubble, thin-film dynamics and heat transfer. The flow is studied by means of numerical simulations, performed using a customised boiling solver in OpenFOAM v2106, which adopts the built-in geometric Volume of Fluid method to capture the liquid–vapour interface dynamics. The numerical model of the evaporator includes in-line arrays of pin-fins of diameter of 50μm and height of 100μm, streamwise pitch of 91.7μm and cross-stream pitch of 150μm. The fluid utilised is refrigerant R236fa at a saturation temperature of 30 °C. The range of operating conditions simulated includes values of mass flux G=500–2000kg/(m2s), heat flux q=200kW/m2, and inlet subcooling ΔTsub=0–5K. This study shows that bubbles nucleated in a pin-fin evaporator tend to travel along the channels formed in between the pin-fin lines. Bubbles grow due to liquid evaporation and elongate in the direction of the flow, leaving thin liquid films that partially cover the pin-fins surface. The main contributions to heat transfer arise from the evaporation of this thin liquid film and from a cross-stream convective motion induced by the bubbles in the gap between the cylinders, which displace the hot fluid otherwise stagnant in the cylinders wakes. When the mass flow rate is increased, bubbles depart earlier from the nucleation sites and grow more slowly, which results in a reduction of the two-phase heat transfer. Higher inlet subcooling yields lower two-phase heat transfer coefficients because condensation becomes important when bubbles depart from the hot pin-fin surfaces and reach highly subcooled regions, thus reducing the two-phase heat transfer
GaN-based PIN alpha particle detectors
No full textGaN-based PIN alpha particle detectors are studied in this article. The electrical properties of detectors have been investigated, such as current-voltage (I-V) and capacitance-voltage (C-V). The reverse current of all detectors is in nA range applied at 30 V. which is suitable for detector operation. The charge collection efficiency (CCE) is measured to be approximately 80% but the energy resolution is calculated to be about 40% mostly because the intrinsic layer is not sufficiently thick enough. (C) 2011 Elsevier B.V. All rights reserved.Instruments & InstrumentationNuclear Science & TechnologyPhysics, Particles & FieldsSpectroscopySCI(E)EI2ARTICLE110-1366
Influences of wake-effects on bubble dynamics by utilizing micro-pin-finned surfaces under microgravity
No full textThe influences of wake on bubble dynamics under various heat fluxes have been studied in microgravity. Nucleate pool boiling experiments of FC-72 on silicon chips fabricated with micro-pin-fins were conducted in 10(-3) gravitational acceleration for 3.6 s. Experimental results indicated that wake field had little influence on bubble dynamics at low heat flux, q = 12.53 W/cm(2), but its effects on bubble dynamics became very great at moderate heat flux, q = 27.89 W/cm(2), and high heat flux, q = 39.54 W/cm(2). More importantly, wake-effects appeared even more significant in microgravity. In the wake field, the horizontal flow of the liquid on micro-pin-finned silicon chips promoted the collision, coalescence and movement of bubbles, and the vertical flow of liquid phase exerted an upward force on bubbles, which can effectively shorten the growth cycle and decrease the departure radius of bubbles. Furthermore, fresh liquid could easily be inhaled into the micro-pin-finned structure owning to the negative pressure in wake region, which can supply sufficient liquid for the growth of bubble, avoiding film boiling. The interaction between the micro-pin-finned structure and the wake effect promoted the process of bubble coalescence and departure effectively, so the process of heat transfer was significantly improved on micro-pin-finned surface. In addition, the flow field and bubble behavior in wake region were also briefly analyzed based on some reasonable simplifications and hypotheses. The theoretical analyses showed that the durations of wake-effects lasted longer than the time periods of the bubble in next generation, and the bubble diameters were also smaller than the thickness of Wake region. Therefore, the dominant bubble of next generation was influenced by the wake field during its ebullition cycle, which is consistent with the experimental phenomenon. (C) 2016 Elsevier Ltd. All rights reserved
Bubble dynamics in nucleate pool boiling on micro-pin-finned surfaces in microgravity
No full textBubble dynamics is an important phenomenon, which basically affects the nucleate boiling heat transfer coefficient. Nucleate boiling heat transfer of gas-saturated FC-72 on micro-pin-finned surface was experimentally investigated in microgravity environment by utilizing the drop tower facility in Beijing. The dimensions of the silicon chips were 10 mm x 10 mm x 0.5 mm (length x width x thickness) on which two kinds of micro-pin-fins with the dimensions of 30 x 30 x 60 mu m(3), 50 x 50 x 120 mu m(3) (width x thickness x height, named PF30-60, PF50-120) were fabricated by the dry etching technique. The experimental data were presented for the bubble departure radius on micro-pin-finned surface. Experimental results showed that the bubble detachment radius increases with increasing heat flux, but the traditional force balance model failed to predict the bubble detachment radius on micro-pin-finned surfaces especially at high heat fluxes. Therefore, a new modified model for predicting bubble departure radius on micro-pin-finned surface in microgravity was developed. In this model, both bubble force balance and bubble coalescence are considered as two main factors influencing the size of bubble departure radius, and the predictions agree much better with the experimental data at moderate and high heat fluxes than the force balance model. (C) 2014 Elsevier Ltd. All rights reserved
Design and assessments on a hybrid pin fin-metal foam structure towards enhancing melting heat transfer: An experimental study
No full textSolar energy, as a kind of renewable energy, offers a large reserve to be harvested at a reasonably low cost for engineering applications. To decouple the temporal and spatial relevance of the continuous energy supply of solar energy, latent heat thermal energy storage can deal with this problem at different temperatures. Aiming to improve energy efficiency, a novel hybrid metal foam-pin fin structure is designed and assessed. Upon conducting measurements on a well-designed experimental bench, the phase change processes of paraffin that is filled in fins, metal foam, and a combination of both (hybrid structure) are evaluated. During the experiments, the transient melting interface is snapshotted and temperature development is documented under five different heat source temperatures of 61 °C, 63 °C, 65 °C, 68 °C, and 70 °C. In the foreground of the novel hybrid structure, each segment of the hybrid is also justified and discussed. Results indicate that the hybrid structure augments marked heat transfer. Compared to pure PCM, complete melting time decreases by 63.4% and simultaneously the temperature response rate increases by 143.9% as implementing the hybrid. Attempts to design hybrid structure find a solution to assess and operate thermal storage applications for solar engineering.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Process and Energ
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
A Customized Novel Halo with Displacement Based Pin Tightening for Pre-Operative Gravity Traction to Treat Severe Scoliosis
No full textSevere scoliosis is a deformity of the curvature of the spine, mostly occurring in children. It is currently treated by performing Halo Gravity Traction (HGT) to reduce the curvature prior to surgery. In this procedure, a Bremer halo ring is fitted around the child's head and connected to the skull with a numberof pins. During the 3-month treatment period, step-wise increased weight is applied to pull the ring upwards so as to elongate the spine. With the current design of the Bremer halo ring, the pins are tightened while measuring the amount of torque applied, influences each other during tightening, loosenover time and leave visible scars on the forehead. Furthermore, the Bremer halo ring is not customized.In the present project, a novel halo with a different tightening technique was designed, manufactured and evaluated with the aim of solving the above mentioned shortcomings of the Bremer halo.A Surface Tessellation Language (STL) file was generated from Computed Tomography (CT) images of a male cadaver head. Based on the desired ring stiffness and the geometry of a custom-designed halo for the cadaver head, a model was created in Solid Edge ST 10. The model was analyzed and adjustedby using the Finite Element Method (FEM). The customized halo ring was then produced by means of Selective Laser Sintering (SLS) and then equipped with strain gauges in order to derive the forces acting on the skull by the pins during tightening. The customized novel halo and the Bremer halo were compared with respect to moment arm and pin orientation, both influencing the local pin site behavior. The moment arms, pin positions and pin orientations of the 3D model of the novel halo were validated in reality by consecutive application of the halo to the cadaver head. The halo was analyzed by measuring the pin force degradation over a period of 24 h, which was hypothesized to be caused by the visco-elastic behavior of the skull of the cadaver head. The tightening procedure was analyzed on a block of steel to determine the influence on the axial pin reaction forces.The novel halo showed smaller and more consistent lengths of moment arm than the Bremer halo. Furthermore, one pin of the Bremer halo showed a difference of >15° from 90°, which has been regarded as contributor to pin loosening. The novel halo was predicted to be able to keep sufficient axial pin force without pin re-tightening during the traction period. The intended axial pin forces of the novel halo were achieved with an accuracy of 94.5%.With the customized novel halo, pins were tightened based on the displacement of the C-contours, resulting in an increased accuracy of pin force during tightening. The anterior pins were designed to be located in the musculus temporalis region, thereby leaving no visible scars and to be less prone to loosening due to a lower anterior ring stiffness. In conclusion, customizing the halo ring brings opportunities toengineer and control important parameters which contribute to better wearing comfort, higher pin force accuracy and less pin loosening, although it is yet a costly and time-consuming procedure
Thermal experiment of silicon PIN detector
No full textThe experiment of this paper is the thermal test of the leakage current of silicon PIN detector. Raising temperature may cause the detector to increase leakage current, decrease depletion and increase noise. Three samples are used in the experiment. One (called Delta E) is the sample of 100 mu m in thickness. The other two (called E(1) and E(2)) axe stacks of five detectors of 1000 mu m in thickness. All of them are 12 mm in diameter. The experiment has been done for 21 hours and with power on continuously. The samples have undergone more than 60 degrees C for about one hour. They are not degenerated when back to the room temperature. The depletion rate is temperature and bias voltage related. With the circuit of the experiment and temperature at 35 degrees C, Delta E is still depleted while E(1) and E(2) are 94.9% and 99.7% depleted respectively. The noises of the samples can be derived from the values at room temperature and the thermal dependence of the leakage currents. With the addition of the noise of the pre-amplifier, the noises of E(1), E(2) and Delta E at 24 degrees C are 16.4, 16.3, and 10.5 keV (FWHM) respectively while at 35 degrees C are about 33.6, 33.1, and 20.6 keV (FWHM) respectively.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000265989600011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, NuclearPhysics, Particles & FieldsSCI(E)中国科学引文数据库(CSCD)0ARTICLE10820-8243
The measurement of household cost functions: Revealed preference versus subjective measures
No full textHousehold Economics;Costs
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