14,002 research outputs found
혼합 모드 적분기를 사용하는 시그마-델타 아날로그-디지털 변환기
No full textThe present invention relates to a sigma-delta analog-to-digital converter using a mixed mode integrator composed of an analog integrator and a digital integrator, which can prevent the performance degradation due to the saturation of an integrator of the overload of a quantizer. A sigma-delta analog-to-digital converter having an anti-aliasing filter, a sample and hold circuit, a sigma-delta modulator and a decimation filter comprises an overload estimating unit for judging the saturation or overload of an analog integrator; a mixed mode integrator which has the analog integrator and a digital integrator composed of a digital adder and a digital storing unit and integrates the output of the overload estimating unit in analog or digitally; and a quantization unit for converting the output of the mixed mode integrator to a digital signal
Taehoon Kim: Association between quality of recovery and postoperative opioid use following total knee arthroplasty
No full textOpioids are commonly used following Total Knee Arthroplasty (i.e. knee replacement surgery) to manage pain and improve patient recovery. Persistent opioid use following surgery can lead to short- and long-term adverse effects. We aimed to investigate whether Quality of Recovery-15 surveys collected following TKA are associated with postoperative opioid use.This poster was uploaded for the SGS Research Showcase 2021.Choose your favourite poster to win the People's Choice Award at the 2021 SGS Research Showcase: https://auckland.au1.qualtrics.com/jfe/form/SV_9Fw8Omf43pstYU
Experimental investigation on turbulent flow overlying permeable walls
No full textA turbulent flow overlying a permeable wall can be subdivided into two distinct flow regions separated by a permeable interface. The first is the surface (or free) flow region, which overlies the interface. The second is the subsurface (or pore) flow region, which occurs within the permeable wall. While the near-wall surface flow can be turbulent, deep within the bed the subsurface flow is often laminar and can be described by Darcy's law (a balance of viscous and pressure forces). Thus, a region must exist between these two extremes where the flow undergoes a transition from inertia-dominated turbulence to viscous-dominated, laminar flow across the permeable interface. This region, typically termed the 'transitional layer,' develops across the permeable interface where non-linear flow interactions between the free flow and the pore flow take place. Accessing this region either experimentally or computationally is extremely challenging, with the latter limited by direct physical of optical access near and within the bed.
The goal of this study was to explore the role of wall permeability and surface topography in flow interactions across a permeable interface and the corresponding turbulent boundary layer modifications in the surface flow region. The turbulent flow overlying impermeable and permeable walls with identical surface topography was explored experimentally using the particle-image velocimetry technique coupled with a unique refractive-index matching flow environment, whereby the latter provided full optical access to the flow in the vicinity of and within the permeable interface and the former allowed the acquisition of instantaneous velocity fields in this region with this optical access. Utilizing velocity statistics and conditional averaging, quantitative assessments were made for turbulent boundary layer modifications imposed by permeability and topography as well as the role of these effects in the mutual interplay between the surface and subsurface flows. Surface topography is found to intensify these interactions across the transitional layer, meaning that it enhances mass, momentum and energy transport between these two flow regimes. In addition, it was found that the larger scales of the surface-layer flow modulate the smaller scales near the permeable interface and within the bed itself. This effect was previously identified in canonical turbulent boundary layers (both smooth and rough), but the results presented herein highlight the enhancement of modulation effects owing to permeability. This physical linkage between the surface and subsurface flows across the transitional layer could provide a new framework for modeling such effects based on this unique dynamic connection between the two flow regimes.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2019-08-22 without embargo termsThe student, Taehoon Kim, accepted the attached license on 2019-01-14 at 22:54.The student, Taehoon Kim, submitted this Dissertation for approval on 2019-01-15 at 00:10.This Dissertation was approved for publication on 2019-01-16 at 11:05.DSpace SAF Submission Ingestion Package generated from Vireo submission #13356 on 2019-08-22 at 14:39:07Made available in DSpace on 2019-08-23T19:51:24Z (GMT). No. of bitstreams: 3
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Previous issue date: 2019-01-1
Comparative study on the radiation damage of a-Si : H p-i-n diodes made by PECVD and ion shower doping
No full textFlat-panel detectors using amorphous silicon p-i-n diodes have been developed for chest and therapeutic portal imaging. In radiation therapy, an imaging device is exposed to a high radiation dose. The radiation damage affects the leakage current of diode and may decrease the whole system performance. In this research, we have investigated the radiation damage to the leakage current of a-Si : H diode made by plasma-enhanced chemical vapor deposition (PECVD) and ion-shower doping method, and studied the effect of a copper plate generally used in portal imaging to increase the efficiency of detector. We measured the transient current of diodes between radiation exposures, and obtained the leakage current of diodes as a function of absorbed dose. The two diodes show similar behavior when used with a copper plate. Leakage current shows linear dependence on the absorbed dose, and threshold dose was observed when a copper plate was placed on the top. Ion-shower diode shows higher rate of current increase, which is considered to originate from the intrinsic junction properties.This work was
supported by the Korea Ministry of Commerce, Industry and Energy
Nanoporous Capillary Gripper for Ultragentle Micro-Object Manipulation
No full textSurfaces become &quot;sticky&quot; at the micro/nano length scale as the gravitational force is no longer effective. Ultragentle, high-contrast switching of interfacial adhesion is the key to reliable small-scale object manipulation. Here, a novel approach is presented for surface adhesion control utilizing a liquid-permeable nanoporous surface, which can switch from off-state adhesion (< 0.002 kPa) to on-state attraction (0.8 kPa) without preload. The surface of the gripper is composed of vertically aligned composite nanowires with an average diameter of 79 nm. When a liquid is injected into the nanoporous membrane, capillary adhesion occurs, allowing the object to be picked up. As the liquid evaporates, the object can be released by extremely sparse contact. The off-state adhesion of a millimeter-scale gripper is even lower than the gravitational force of thin polymer films (0.18 mN cm(-2)), enabling the solid-contactless release of lightweight materials. We characterize and model the mechanism across length scales and provide pick-and-place demonstrations including LED chips, micro-architected materials, and thin-film electronics.
Author Correction: Evaluation of skin cancer resection guide using hyper‑realistic in‑vitro phantom fabricated by 3D printing
No full textThe original version of this Article contained an error in the spelling of the author Taehun Kim which was incorrectly given as Teahun Kim. The original Article has been corrected
Impact of Uplink Power Control on User Location Tracking Attacks in Cellular Networks
No full textCellular networks have been successfully evolved over the decades. Especially, Long-Term Evolution (LTE) has been exceedingly successful and the security threats against LTE systems have increased rapidly. Particularly, tracking LTE user devices has been shown to be effective as the temporary user identifiers (IDs), which are used in LTE systems to indicate LTE user devices in the system, are easily extracted and used to locate targeted devices by passive eavesdroppers. In this paper, we investigate the impact of uplink power control on the probability of successful user tracking by an adversary whose location is unknown. We devise the notion of average inference error probability in order to measure the level of users' location privacy. Moreover, we derive the closed-form expression of the approximated average inference error probability and formulate an optimization problem for maximizing the average inference error probability under a constraint of an allowable power budget for each user. For defense, we propose a power control scheme able to effectively degrade an adversary's inference ability by 50% when 10 users are scheduled in each transmission time slot, which will result in almost 100% inference error at the adversary over multiple time slots
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