122 research outputs found
Integrated Temperature Sensors based on Heat Diffusion
No full textThis thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and the thermal diffusivity of silicon, and since the thermal diffusivity of crystalline silicon is strongly temperature-dependent, the thermal delay is also temperature dependent. The sensor structures that measure such delays are known as Electrothermal Filters (ETFs). The field of temperature sensing using ETFs is still relatively unexplored. This thesis expands upon recent proof-of-concept research by studying the performance of ETF-based temperature sensors in more detail. Its main goal is to analyze whether or not ETFs can be used as competitive temperature sensors in CMOS technology. The thermal delay in an ETF can be very well-defined, since the silicon used in IC fabrication is highly pure, and the lithographic inaccuracy with which planar structures can be made is constantly improving. ETFs thus scale along the trend of Moore’s law, and they can become smaller, faster and more accurate in more advanced CMOS technologies. The main application of ETF-based temperature sensors is the thermal management of microprocessors: modern microprocessors require tens of small, fast and accurate temperature sensors to prevent overheating and to dynamically allocate processing power. Chapter 1 outlines this and other applications in some detail, and shows why existing temperature sensors are not well-suited for these applications. Chapter 2 presents the theoretical background to ETFs, starting with a discussion on the thermal diffusivity of silicon and silicon dioxide, analyzing their nominal values and their (different) temperature dependencies. It then discusses what type of ETFs to use to measure these most accurately. Furthermore, it outlines a family of performance metrics that enable a more formal study of ETFs characteristics. These are divided in two main categories: accuracy (e.g. error due to lithography, doping sensitivity) and resolution (how to optimize signal-to-noise ratio (SNR), advantages of scaling and using thermally isolated technologies such as silicon-on-insulator (SOI) processes). Chapter 3 presents various systems that can be built around ETFs. Using either silicon ETFs, oxide ETFs or a combination of both, several systems can be built, each with different functionality. The two systems described in most detail are the single silicon-ETF temperature-to-digital converter, and the silicon and oxide ETF-based self-referenced temperature-to-digital converter. The former uses an accurate time reference (such as a crystal oscillator) to convert an ETF’s thermal delay to an absolute temperature measurement. The latter performs a ratiometric temperature measurement and does not require an external time reference. This chapter also defines all of the circuit building blocks required to implement these systems, and derives their specifications from ETF theory and first principles. It concludes by showing that phase-domain sigma-delta modulators (PD??Ms) are the most appropriate readout circuits for precision ETF readout. Chapter 4 discusses PD??Ms in more detail and presents their transistor-level implementation. PD??Ms are a class of time-to-digital converters that are well-suited to digitize the thermal delay contained in the small, noisy signal at the ETF’s output. High precision and resolution are achieved by oversampling, noise shaping and the use of dynamic error correction techniques. Several methods of linearizing ETF-based temperature-to-digital converters are also presented. The chapter ends with measurements on a standalone PD??M, in order to show that its measurement error is sufficiently low to be able to characterize ETFs. Chapter 5 presents the measurement results for the ETFs studied in this thesis. There are results on ETF inaccuracy and resolution as a function of geometry and process technology, as well as results on sensitivity to doping fluctuations, mechanical stress, thermal interference and self-heating. The measured differences in ETF performance in bulk CMOS and SOI CMOS technology are also presented and analyzed. The lowest measured untrimmed inaccuracy for a single-ETF sensor in 0.18?m CMOS technology was ±0.2ºC (3?) from -55ºC to 125ºC. A self-referenced sensor, based on measuring the ratio of the thermal delay in silicon over that in oxide, shows a measured inaccuracy of ±0.4ºC (3?) from -70ºC to 200ºC after a one-point trim. Chapter 6 lists the main findings of this thesis and uses the measurement results to draw some conclusions on the competitiveness of ETFs. It shows that ETFs, due to their scalability, are attractive for thermal management of SoCs in deep submicron CMOS technologies. This thesis ends with some recommendations for further research.Electronic InstrumentationElectrical Engineering, Mathematics and Computer Scienc
Never Landing Drone
No full textIncreasing endurance is a major challenge for battery-powered aerial vehicles. A method is presented which makes use of an updraft around obstacles to decrease the power consumption of a fixed-wing, unmanned aerial vehicle. Simulatory results have shown the conditions that the flight controller can fly in.The effect of a change in wind velocity, wind direction and updraft has been analysed. The simulations showed that an increase in either updraft or absolute wind direction decrease the throttle consumption.A change in wind velocity results in a shift of the flight controller’s boundaries. The simulations achieved sustained flight at 0 per cent throttle. The practical, autonomous tests reduced the average throttle down to 4.5 per cent in front of the boat. The unfavourable wind conditions and inaccuracies explain this minorthrottle requirement during the final experiment.Aerospace Engineerin
A Multi-Path Sigma Delta ADC: For use in battery management systems
No full textThis thesis presents the design and testing of a multi-path analog-to-digital converter for current sensing in battery management systems. The specifications of this converter are (1) continuously integrate and convert a signal at 125 Hz with a resolution of 20 bit and (2) perform on demand fast conversions of 20 μs at a resolution of 14 bit. Both conversions should be done with a maximum 1 LSB offset and 0.1 % gain error. The realized system consists of a discrete time 1st order sigma delta converter, followed by a 10 bit charge redistribution extended counting ADC. This design uses the same analog front end for both conversions, thereby saving both power and chip area. To achieve the lowest offset possible, a system level chopping scheme is implemented. A working prototype has been made in TSMC 0.18 BCD technology, using an area of 570 μm × 150 μm with a 5 V supply voltage. The realized chip proves that the concept of combining the analog front end works and achieves a 15 bit linearity. At the 20 bit level, there are still significant issues and despite serious efforts the root cause of those issues has not yet been isolated. Next design and testing steps have however been identified.Electrical Engineering | Electronic Instrumentatio
Dirichlet Process Gaussian-mixture model: An application to localizing coalescing binary neutron stars with gravitational-wave observations
No full textWe reconstruct posterior distributions for the position (sky area and distance) of a simulated set of binary neutron star gravitational-waves signals observed with Advanced LIGO and Advanced Virgo. We use a Dirichlet process Gaussian-mixture model, a fully Bayesian nonparametric method that can be used to estimate probability density functions with a flexible set of assumptions. The ability to reliably reconstruct the source position is important for multimessenger astronomy, as recently demonstrated with GW170817. We show that for detector networks comparable to the early operation of Advanced LIGO and Advanced Virgo, typical localization volumes are ∼104–105˜Mpc3 corresponding to ∼102–103 potential host galaxies. The localization volume is a strong function of the network signal-to-noise ratio, scaling roughly ∝ −6net . Fractional localizations improve with the addition of further detectorsto the network. Our Dirichlet process Gaussian-mixture model can be adopted for localizing events detected during future gravitational-wave observing runs and used to facilitate prompt multimessenger follow-up
A Histological Study on the X-ray Radiosensibility of the Parametrium in Carcinoma of the Cervix
No full textBy conducting a histological study on the parametrial tissues of the cervical carcinoma in 237 patients previously irradiated with a small dose of X-ray, the author investigated the radiosensibility of the parametium with special references to the relationship between the changes in mitotic picture and giant cells on one hand and the C.P.L. and Nagase's classifications on the other. Those receiving 1-12 x 300 r were 215 cases and they were divided into 2 groups of 6 or 12 times; and also the deep dosis of X-ray was estimated. By obtaining the tissues of cervical carcinoma after hysterectomy, tissue specimens were prepared by Hamazaki's sublimate fixation and stained in a 1.0% Bomer's hematoxylin solution. The following are the results of the present study. 1. The cancer infiltration in the parametrial tissues has been found in 27.8 per cent of the cases studied, and this proves on the left side to be one and half times as great as that on the right side tissues. Moreover, this infiltration is contiguous with the regions adjacent to the cervix and is situated mostly near the uterine arteries. And the cancer infiltration in the parametrial tissues in the C.P.L. classification revealed type L twice as many as type C, and the same in Nagase's classification showed more of types Ⅱ and Ⅲ (particularly type Ⅱ) than type Ⅰ. 2. The changes of the cancer tissues in the parametrial tissues after X-ray irradiation as well as of Feulgen reaction are directly proportional to the amount of X-ray irradiated. 3. The changes in mitosis, atypical cell-division and giant cell appearance clearly paralleled with the amount of X-ray employed. Mitoses decrease after 1-4 times of irradiation, and are arrested thereafter. The atypical cell division increases sensitively after 1-3 times of irradiation, while giant cells increase rapidly after 12 times of irradiation. 4. Relative to the C.P.L. classification, in the cases given 6 irradiations giant cells increase in type L, but in the cases with 12 irradiations mitoses decrease, and in the cases showing an increase in atypical cell division changes due to X-ray are strong in type C. 5. With respect to Nagase's classification in the cases given six times of irradiation the changes due to X-ray are marked in type Ⅰ with a decrease in mitoses and type Ⅱ with an increase in giant cells, while in the casese irradiated 12 times the changes are striking in type Ⅰ with an increase in giant cells. In other words, proportionately with the increase in the amount of X-ray, the changes in connective tissues become greater in type C and type Ⅰ. 6. Considering various atypical cell divisions according to the shape of each cell such a cell division increases well proportionately to the amount of X-ray irradiated in respective case, but by 12 irradiations (especially in type C) cells are condensed at first and then the atypical cell division increases at the terminal stage
子宮頸癌旁結合織に於るレ線感受性に関する組織学的研究
No full textBy conducting a histological study on the parametrial tissues of the cervical carcinoma in 237 patients previously irradiated with a small dose of X-ray, the author investigated the radiosensibility of the parametium with special references to the relationship between the changes in mitotic picture and giant cells on one hand and the C.P.L. and Nagase's classifications on the other. Those receiving 1-12 x 300 r were 215 cases and they were divided into 2 groups of 6 or 12 times; and also the deep dosis of X-ray was estimated. By obtaining the tissues of cervical carcinoma after hysterectomy, tissue specimens were prepared by Hamazaki's sublimate fixation and stained in a 1.0% Bomer's hematoxylin solution. The following are the results of the present study. 1. The cancer infiltration in the parametrial tissues has been found in 27.8 per cent of the cases studied, and this proves on the left side to be one and half times as great as that on the right side tissues. Moreover, this infiltration is contiguous with the regions adjacent to the cervix and is situated mostly near the uterine arteries. And the cancer infiltration in the parametrial tissues in the C.P.L. classification revealed type L twice as many as type C, and the same in Nagase's classification showed more of types Ⅱ and Ⅲ (particularly type Ⅱ) than type Ⅰ. 2. The changes of the cancer tissues in the parametrial tissues after X-ray irradiation as well as of Feulgen reaction are directly proportional to the amount of X-ray irradiated. 3. The changes in mitosis, atypical cell-division and giant cell appearance clearly paralleled with the amount of X-ray employed. Mitoses decrease after 1-4 times of irradiation, and are arrested thereafter. The atypical cell division increases sensitively after 1-3 times of irradiation, while giant cells increase rapidly after 12 times of irradiation. 4. Relative to the C.P.L. classification, in the cases given 6 irradiations giant cells increase in type L, but in the cases with 12 irradiations mitoses decrease, and in the cases showing an increase in atypical cell division changes due to X-ray are strong in type C. 5. With respect to Nagase's classification in the cases given six times of irradiation the changes due to X-ray are marked in type Ⅰ with a decrease in mitoses and type Ⅱ with an increase in giant cells, while in the casese irradiated 12 times the changes are striking in type Ⅰ with an increase in giant cells. In other words, proportionately with the increase in the amount of X-ray, the changes in connective tissues become greater in type C and type Ⅰ. 6. Considering various atypical cell divisions according to the shape of each cell such a cell division increases well proportionately to the amount of X-ray irradiated in respective case, but by 12 irradiations (especially in type C) cells are condensed at first and then the atypical cell division increases at the terminal stage
Deep and rapid observations of strong-lensing galaxy clusters within the sky localization of GW170814
No full textInternational audienceWe present observations of two strong-lensing galaxy clusters located within the 90 per cent credible sky localization maps released following LIGO–Virgo’s discovery of the binary black hole (BH–BH) gravitational wave (GW) source GW170814. Our objectives were (1) to search for candidate electromagnetic (EM) counterparts to GW170814 under the hypothesis that it was strongly lensed, and thus more distant and less massive than inferred by LIGO–Virgo, and (2) to demonstrate the feasibility of rapid target of opportunity observations to search for faint lensed transient point sources in crowded cluster cores located within GW sky localizations. Commencing 20 h after discovery, and continuing over 12 nights, we observed Abell 3084 (z = 0.22) and SMACS J0304.3 − 4401 (z = 0.46) with GMOS on the Gemini-South telescope, and Abell 3084 with MUSE on ESO’s Very Large Telescope. We detect no candidate EM counterparts in these data. Calibration of our photometric analysis methods using simulations yields 5σ detection limits for transients in difference images of the cores of these clusters of i = 25. This is the most sensitive photometric search to date for counterparts to GW sources, and rules out the possibility that GW170814 was lensed by these clusters with a kilonova-like EM counterpart. Based on the detector frame masses of the compact objects, and assuming that at least one neutron star (NS) is required in the merging system to produce a kilonova-like counterpart, implies that GW170814 was neither an NS–NS nor NS–BH merger at z > 8 lensed by either of these clusters. Also, in the first ever emission line search for counterparts to GW sources, we detected no lines down to a 5σ detection limit of ||
Understanding the importance of transient resonances in extreme mass ratio inspirals
No full textExtreme mass ratio inspirals (EMRIs) occur when a compact object orbits a much larger one, like a solar-mass black hole around a supermassive black hole. The orbit has 3 frequencies which evolve through the inspiral. If the orbital radial frequency and polar frequency become commensurate, the system passes through a transient resonance. Evolving through resonance causes a jump in the evolution of the orbital parameters. We study these jumps and their impact on EMRI gravitational-wave detection. Jumps are smaller for lower eccentricity orbits; since most EMRIs have small eccentricities when passing through resonances, we expect that the impact on detection will be small. Neglecting the effects of transient resonances leads to a loss of ~4% of detectable signals for an astrophysically motivated population of EMRIs
Fast methods for training Gaussian processes on large data sets
No full textGaussian process regression (GPR) is a non-parametric Bayesian technique for interpolating or fitting data. The main barrier to further uptake of this powerful tool rests in the computational costs associated with the matrices which arise when dealing with large data sets. Here, we derive some simple results which we have found useful for speeding up the learning stage in the GPR algorithm, and especially for performing Bayesian model comparison between different covariance functions. We apply our techniques to both synthetic and real data and quantify the speed-up relative to using nested sampling to numerically evaluate model evidences
The Irradiation Susceptibility of Cervical Carcinoma, with a Special Reference to the Metastasis to Lymph Nodes
No full textPreoperative roentgen-irradiation (unilaterally 1-12 times) treatment was given to 216 cases with cervical carcinoma, and 24 hours after the completion of irradiation Okabayashi's radical extensive hysterectomy was performed. The author studied the irradiation susceptibility of metastased cancer cells by comparing the original site of cancer with metastased lesions and the metastatic irradiated side with non-irradiated side, with a special emphasis on the mitosis of cancer cells. As for the significance between C.P.L. type (Imai) of the primary cancer and the metastatic foci, the change in the mitotic picture due to roentgen irradiation in C-type metastatic foci is significantly greater than that in L-type metastatic foci; and therefore, the irradiation susceptibility in C-type can be said higher. Namely, in this instance the irradaation susceptibility and the prognosis have the same tendency. As for the relationship between Nagase's classification (Types Ⅰ, Ⅱ, Ⅲ) of the primary cancer and its metastatic foci, the change in mitotic picture due to roentgen irradiation in the case of Type Ⅱ metastatic focus is greater than in Type Ⅰ metastatic focus, and the irradiation susceptibility in Type Ⅱ tends to be higher. In other words, in this instance the irradiation susceptibility is in no way associated with the prognosis. Therefore, it is dangerous to deduce the prognosis from the irradiation susceptibility of cancer cells. Numbers of giant cells appearing due to irradiation increase in proportion to the degree of the destruction of the cancer focus irradiated upon. Therefore, in the observation of dividing cells in the irradiated cancer focus, it is essential to pay attention not only to the change in the number of cells but also to the variety of the degeneration picture. The degree of degeneration in dividing cells increases in propoetion to the irradiation amount, and by a irradiation more than 1,300 r (deep dosis) the mitotic picture changes markedly, thus bringing about the cell disintegration. On applying an irradiation tube on the anterior surface, its lower margin is placed just above the pubic symphysis, and its inner margin is about 2 cm. outside the medial line; and on applying it on the posterior or lateral side, its lower margin is placed on both greater trochanters; and from the posterior side it is irradiated at the angle 20℃ to the side of the head. In other words, it is believed that main lymph nodes in the pelvis are almost all equally irradiated by irradiation at the sites mentioned above
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