1,721,147 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
Method for the improvement of lateral resolution in stimulated emission depletion microscopy using a pupil filter
No full textWe present a simple method to improve the lateral resolution of stimulated emission depletion microscopy. In stimulated emission depletion microscopy, a saturated zero-centred spot is usually used to achieve a high lateral resolution. Using a half-coated phase plate, a zero-centred spot was made with a narrow and steep gap at the centre. Numerical and experimental results show that by simply inserting a central obstacle as a pupil filter, it is possible to reduce the central gap of the zero-centred spot. Thus we can get a higher lateral resolution, although this sacrifices light efficiency.
Resource-efficient Mobile Multimedia Streaming with Adaptive Network Selection
No full textFrom the advancements of mobile display and network infrastructure, mobile users can enjoy high quality mobile video streaming anywhere anytime. However, most mobile users are still reluctant to use high quality video streaming when they are mobile due to costly cellular data and high energy consumption. In this work, we develop scheduling algorithms for resource-efficient mobile video streaming, which minimize the weighted sum objective of cellular cost and energy consumption. We first model the scheduling problem as a Markov decision process and propose an optimal scheduling algorithm based on dynamic programming. Then, we derive a heuristic algorithm that approximates the optimal algorithm. To evaluate the performance of proposed algorithms, we run simulation over YouTube video traces with audience retention graphs and mobility/connectivity traces in public transportation (e.g., commuting). Through extensive simulations, we show that our proposed scheduling algorithm has negligible performance loss compared to the optimal scheduling algorithm, where it saves 59% of cellular cost and 41% of energy compared to the YouTube default scheduler. We also implement our scheduling algorithm on an Android platform, and experimentally evaluate the performance compared to existing streaming policies.clos
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.
Hardware-hardened Sandbox Enclaves for Trusted Serverless Computing
No full textIn cloud-based serverless computing, an application consists of multiple functions provided by mutually distrusting parties. For secure serverless computing, the hardware-based trusted execution environment (TEE) can provide strong isolation among functions. However, not only protecting each function from the host OS and other functions, but also protecting the host system from the functions, is critical for the security of the cloud servers. Such an emerging trusted serverless computing poses new challenges: Each TEE must be isolated from the host system bi-directionally, and the system calls from it must be validated. In addition, the resource utilization of each TEE must be accountable in a mutually trusted way. However, the current TEE model cannot efficiently represent such trusted serverless applications. To overcome the lack of such hardware support, this article proposes an extended TEE model called Cloister, designed for trusted serverless computing. Cloister proposes four new key techniques. First, it extends the hardware-based memory isolation in SGX to confine a deployed function only within its TEE (enclave). Second, it proposes a trusted monitor enclave that filters and validates system calls from enclaves. Third, it provides a trusted resource accounting mechanism for enclaves that is agreeable to both service developers and cloud providers. Finally, Cloister accelerates enclave loading by redesigning its memory verification for fast function deployment. Using an emulated Intel SGX platform with the proposed extensions, this article shows that trusted serverless applications can be effectively supported with small changes in the SGX hardware.
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
The removal of nanoparticles from sub-micron trenches using megasonics
No full textThe removal of nanoparticles form patterned wafers is one of the main challenges facing the semiconductor industry. In this paper, the removal of 100 and 200 nm polystyrene latex (PSL) particles from silicon trenches was investigated. Red fluorescent PSL particles were utilized in the cleaning experiments and were counted using fluorescent microscopy. All the experiments were conducted in a single wafer megasonic tank using deionized water (DI). Trenches were fabricated with widths varying from 200 nm to 2 pm and with an aspect ratio of one. Results show that removal of particles from larger trenches is faster compared to smaller trenches and that megasonics power is more important in the removal process than cleaning time. (C) 2009 Elsevier B.V. All rights reserved
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