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A Low-Power Edge Detection Image Sensor Based on Parallel Digital Pulse Computation
Changhyuk Lee,Wei Chao,Sunwoo Lee,Hone, James,Molnar, Alyosha,Sang Hoon Hong IEEE 2015 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 2 E Vol.62 No.11
<P>An all-digital low-power CMOS edge detection image sensor array is presented. Each pixel contains a voltage-controlled ring oscillator to achieve low-power and cost-efficient digital-only edge detection. While conventional edge detection methods require high computing power and large chip area to process intensity maps, this work implements an all-digital parallel processing algorithm that detects differences between neighboring pixel pairs on chip, hence reducing the aforementioned power and cost overheads. In particular, a simple column-shared frequency comparator enables low-power operation by eliminating arithmetic computations with large memory requirement. Such a simple edge detection algorithm allows the processor area to be less than 16% of the entire image sensor, therefore maximizing the proportion of active optical area. The prototype image sensor presented in this work is fabricated using a four-metal 180-nm CMOS image sensor process and contains 105 × 92 pixels. An individual pixel size is 8 × 8 μm<SUP>2</SUP> with a fill factor of 11.69%, while the total chip area is 1 × 1.3 mm<SUP>2</SUP>. The image sensor exhibits a frame rate of 30 frames/s and a power consumption of 8 mW, which is 27.7 nW/pixel/frame at VDD of 1.6 V.</P>
Lee, Woomin,Kihm, Kenneth David,Kim, Hong Goo,Shin, Seungha,Lee, Changhyuk,Park, Jae Sung,Cheon, Sosan,Kwon, Oh Myoung,Lim, Gyumin,Lee, Woorim American Chemical Society 2017 Nano letters Vol.17 No.4
<P>Manipulation of the chemical vapor deposition graphene synthesis conditions, such as operating P, T, heating/cooling time intervals, and precursor gas concentration ratios (CH4/H-2), allowed for synthesis of polycrystalline single layered graphene with controlled grain sizes. The graphene samples were then suspended on 8 mu m diameter patterned holes on a silicon-nitride (Si3N4) substrate, and the in-plane thermal conductivities k(T) for 320 K < T < 510 K were measured to be 2660-1230, 1890-1020, and 680-340 W/m center dot K for average grain sizes of 4.1, 2.2, and 0.5 mu m, respectively, using an opto-thermal Raman technique. Fitting of these data by a simple linear chain model of polycrystalline thermal transport determined k = 5500-1980 W/m center dot K for single-crystal graphene for the same temperature range above; thus, significant reduction of k was achieved when the grain size was decreased from infinite down to 0.5 mu m. Furthermore, detailed elaborations were performed to assess the measurement reliability of k by addressing the hole-edge boundary condition, and the airconvection/radiation losses from the graphene surface.</P>
이창혁(Changhyuk Lee),진재식(Jae Sik Jin),이준식(Joon Sik Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The size effects on the figure of merit (FOM) of BiSb alloy film are analyzed using Boltzmann transport equation (BTE). To show seebeck coefficient change, a simple method and boundary conditions are suggested for BTE of number density form. The size effects due to boundary scatterings are treated by using the effective mean free path concepts. The smaller seebeck coefficient of thinner films can be explained by the ballistic transport phenomena. The effective mean free path of electrons in BiSb thin films is suggested which show good agreement between simulation and experimental results of Mallik et al. BTEs of energy density form for both electrons and phonons are solved to calculate the thermal conductivity. For the electron BTE, force term which contains electrical field is described by the velocity reduction caused by thermoelectric voltage, which means reduction in the thermal conductivity of electrons. Finally, the FOMs of BiSb thin films with respect to thickness of the films are predicted.
이지훈(Jihun Lee),김수진(Soojin Kim),이창혁(Changhyuk Lee) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6
Current mode resistive sensing instrumentation with a high channel count, programmable gain, and wide bandwidth is scientifically essential. However, commercial instruments need more channel count and bandwidth at a reasonable cost. Another critical challenge to resistive sensor read-out systems is the need for the accessibility of resistive sensor arrays with low-shunt parasitic impedance and the simplicity of sensor packaging to switch sensors while reusing the instrumentation. This paper proposes a versatile readout circuit and system that provides plug-and-play ready commercially available packaging. The readout circuit has a wide tunability, including an extended range of gain/bandwidth settings. It also has a programmable voltage across individual resistive sensors, enabling channel-wise dynamic range adjustment. The low noise trans-impedance outputs from AFE are fed to an array of AAF and ADC, which then transmits digitally converted data to custom-designed graphic user interface software via an FPGA-based USB 3.0 port.
Long-term dynamic stiffness of resilient materials in floating floor systems
Kim, Changhyuk,Hong, Yoon-Ki,Lee, Jung-Yoon Elsevier BV 2017 Construction and Building Materials Vol.133 No.-
<P><B>Abstract</B></P> <P>The number of high-rise residential buildings being constructed in countries with high population density is increasing in response to the need to utilize small areas. In Seoul, which is the densest of the Organization for Economic Co-operation and Development (OECD) countries, high-rise buildings have become more common in response to the considerable population increase. To diminish floor impact sound, resilient materials are generally applied between the concrete slab and the finishing mortar. Floor impact sound is affected by various characteristics of resilient materials such as dynamic stiffness, thickness, etc. Many experimental studies have been conducted to evaluate the impact sound reducing capacity of the materials, and have indicated that the dynamic stiffness of resilient materials has a close relation with the floor impact sound reduction. In most cases, a resilient material having lower dynamic stiffness has better floor impact sound reduction capacity. However, the dynamic stiffness of soft resilient materials could be changed under long-term loading and this could result in an increase of floor impact sound. The variation of the dynamic stiffness of 8 of the most widely used resilient materials under four different loadings were monitored for more than 500days. The test results indicated that the dynamic stiffness of the resilient materials for floor impact sound increased with time, and that the variation of the dynamic stiffness was affected by loading time, weight of loading, and material properties. In addition, the proposed formula predicted the dynamic stiffness of resilient materials subjected to long-term load with reasonable agreement.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Increased deflection and dynamic stiffness were observed under long-term loading. </LI> <LI> Material properties of the resilient materials were measured for more than 500days and used for the proposed equation. </LI> <LI> The relation between dynamic stiffness and deflection can be easily and reliably predicted using the proposed equation. </LI> <LI> Increases of the floor impact sound level after ten years were observed in most of the loading cases. </LI> <LI> It was able to understand both the serviceability and structural capacity of the resilient materials in this study. </LI> </UL> </P>