423 research outputs found
A new species of Hemiphyllodactylus Bleeker, 1860 (Squamata: Gekkonidae) from Guizhou, China
No full textYan, Jie, Lin, Yubo, Guo, Weibo, Li, Peng, Zhou, Kaiya (2016): A new species of Hemiphyllodactylus Bleeker, 1860 (Squamata: Gekkonidae) from Guizhou, China. Zootaxa 4117 (4): 543-554, DOI: 10.11646/zootaxa.4117.4.
Why do woodpeckers resist head impact injury : a biomechanical investigation
No full textAuthor name used in this publication: Yubo Fan2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishedC
Exploring power-performance-quality tradeoffs for exascale combustion simulation
No full textThe computational demand of high-performance computing (HPC) applications has brought major changes to the HPC system architecture. As a result, it is now possible to run simulations faster and get more accurate results. But behind this, power and energy are becoming critical concerns for HPC systems, e.g. Titan’s electric cost is about $9 million per year. Energy efficiency has become a critical challenge for the exascale research challenges, and U.S. Department of Energy’s (DOE) gives the goal to achieve exascale performance with a power budget of 20MW. Current research efforts have studied power and performance tradeoffs, and how to balance these, e.g., using DVFS to meet power constraints, which significantly impacts performance. However, scientific applications may not tolerate degradation in performance and other tradeoffs need to be explored to meet power budgets, e.g., involving the application in making energy-performance tradeoff decisions. In this research, we focus on studying the properties and exploring the performance and power/energy tradeoffs of Low-Mach-Number Combustion (LMC) application which is an Adaptive Mesh Refinement (AMR) algorithm. Our experimental evaluation provides an empirical evaluation of different application configurations that gives insights into the power-performance tradeoffs space for this LMC or AMR-based application workflows. The key contribution of this work is a better understanding of the running behavior of this AMR-based application and proposed a power-performance tradeoff for this application, which can be used to better schedule power budgets across HPC systems.M.S.Includes bibliographical referencesby Yubo Qi
Hemiphyllodactylus huishuiensis Yan, Lin, Guo, Li & Zhou, 2016, sp. nov.
No full textHemiphyllodactylus huishuiensis sp. nov. Huishui Slender Gecko Fig. 2 Holotype. Adult male (NJNUh00851) collected on 9 July, 2015 by Yubo Lin and Hao Li in the vicinity of Huishui County, Guizhou Province, China (26 °08.36’N, 106 ° 39.72 ’E, at an elevation of 990 m). Paratype. Four adult female specimens: NJNUh00852, NJNUh00854, NJNUh00855, and NJNUh00856, collected on 10–11 July, 2015 from almost the same locality as the holotype; and three adult specimens, NJNUh00857 (female), NJNUh00858 (female) and NJNUh00859 (male), collected on 13–14 July, 2015 from Ziyun County, Guizhou Province, China (25 ° 45.17 ’N, 106 °04.85’E, at an elevation of 1260 m). Diagnosis. Hemiphyllodactylus huishuiensis sp. nov. can be distinguished from the remaining congeners of the genus Hemiphyllodactylus by having the unique combination of the following characters: a bisexual taxon; a maximum SVL of 47.4 mm in males and 51.2 mm in females; 8 or 10 chin scales; enlarged postmental scales; 3 circumnasal scales; 2 or 3 scales between supranasals; 9–11 supralabials; 9–11 infralabials; 13–15 dorsal scales; 7– 9 ventral scales; a lamellar hand formula of 3-4 - 4 - 4 or 4 - 4 / 5 - 5 - 4; a lamellar foot formula of 4 - 4 / 5 - 5 - 4 / 5; 3 subdigital lamellae on the first finger; 3 subdigital lamellae on the first toe; a continuous precloacal and femoral pore series of less than 20; one cloacal spur on each side in both males and females; no enlarged subcaudal scales; dark dorsal transverse blotches; dark postorbital stripe; a brown postsacral mark bearing anteriorly projecting arms; and unpigmented caecum and gonads (Table 4). Description of holotype. Body compressed, size small SVL 42.6 mm, tail regenerated (TailL 4.2 + 19.8 mm), trunk length (TrunkL) 20.5 mm; head longer than wide (HeadL 9.5 mm, HeadW 7.8 mm); eye diameter (EyeD) 2.7 mm; snout-eye length (SnEye) 3.9 mm; nare-eye length (NarEye) 2.8 mm; internarial distance (SnW) 1.3 mm; ear opening distance (EarD) 0.5 mm. Proportions: TrunkL/SVL 48.1 %, HeadL/SVL 22.3 %, HeadW/SVL 18.2 %, HeadW/HeadL 81.5 %, SnEye/HeadL 41.4 %, NarEye/HeadL 29.2 %, EyeD/HeadL 28.3 %, SnW/HeadL 12.7 %, EyeD/NarEye 96.8 %, SnW/HeadW 15.6 %. Scalation. Pupil vertical; supralabials 11 / 11, enlarged from rostral to below eye, smaller in subocular rictus; three circumnasal scales and three scales between supranasals; mental triangular; larger than first infralabial; infralabial 11 / 11; two postmentals, distinctly enlarged, in contact with each other medially, with mental and first infralabials anteriorly; 10 chin scales; dorsal scale granular, in 14 rows at midbody on dorsum (contained within one eye diameter), ventral scales larger than dorsal scales, in 9 rows at midbody on venter (contained within one eye diameter); one cloacal spur on each side; precloacal and femoral pore series continuous, 20 in total; all digits except digit I well developed; digit I vestigial, clawless; three transversely expanded lamellae on digit I (of both forefoot and hindfoot); one triangular lamellae on the distal end of each of the digits II–V of forefoot and hindfoot, digital formulae 3-4 - 4 - 4 (forefoot) and 4-5 - 5 - 5 (hindfoot) (Table 6). Species 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Hemiphyllodactylus huishuiensis - sp. nov. (KU 519707 - 11) H. aurantiacus (JN 393933) 30.5-30.9 - H. banaensis (KF 219783) 16.0- 16.4 3 0.2 - H. changningensis (KP 732436) 26.1-26.4 2 7.2 2 6.9 - H. chiangmaiensis (KF 219782) 26.1-26.6 2 8.0 2 5.6 1 9.1 - H. dushanensis (FJ 971016) 6.6-7.1 3 1.6 1 7.4 2 5.1 2 7.2 - H. engganoensis (KF 219776) 29.3 -30.0 32.0 31.3 27.9 28.3 29.5 - H. ganoklonis (JN 393950) 31.0- 31.3 27.2 30.7 28.1 28.8 30.3 22.7 - H. harterti (KF 219760) 31.8-32.2 35.7 32.7 30.8 30.2 31.8 31.8 30.1 - . H. jinpingensis (FJ 971041) 25.4-25.9 25.4 27.5 17.5 14.8 25.9 27.8 27.4 30.5 - . H. kiziriani (KJ 676800) 20.5-21.2 27.6 22.7 25.9 27.5 20.6 29.9 30.8 32.3 28.1 - . H. longlingensis (FJ 971046) 28.6 -29.0 25.0 30.3 18.4 18.7 29.5 28.3 28.8 32.7 18.5 27.7 - . H. titiwangsaensis (KF 219785) 30.3-31.3 29.0 29.3 27.8 30.0 30.0 30.3 29.6 25.4 28.1 32.5 28.6 - . H. typus (GQ 257745) 29.0- 29.8 26.5 31.7 29.3 27.7 30.1 19.5 19.0 31.1 28.3 28.8 27.9 29.8 - . H. yunnanensis (FJ 971021) 20.5 -21.0 27.9 22.0 23.9 25.0 21.0 28.3 27.9 29.8 25.6 20.7 26.4 29.5 27.9 - . H. zugi (KF 575152) 7.3-7.8 30.9 16.2 25.5 26.7 5.9 30.4 31.9 31.4 25.8 20.5 30.4 30.7 31.0 21.2 - . H. sp. nov. 8 (JN 393949) 27.5-27.9 23.7 27.3 20.3 14.4 27.9 28.2 27.0 31.1 13.2 28.2 18.9 28.4 27.2 25.7 28.1 - . H. sp. nov. 9 (JN 393935) 28.3-28.6 21.7 27.3 27.8 26.5 29.3 32.0 30.3 31.0 26.6 27.4 28.6 30.0 30.8 27.1 29.0 26.9 - ……continued on the next page Holotype Paratype NJNUh00851 NJNUh00859 NJNUh00852 NJNUh00854 NJNUh00855 NJNUh00856 NJNUh00857 NJNUh00858 Holotype Paratype Coloration in preservation. Dorsal surface of head and body brown, darker on body; dorsal surface of the tail yellowish grey with several transverse brown bands, while the regenerated tail dark brown; at the base of the tail, white inconsecutive V- or U-shaped arms stretching forward; dorsal surface of limbs brown similar to head with weak, dark mottling; faint, diffuse dark stripe on lateral head, from the posterior corner of the orbit to neck, edged above by a narrow white stripe; ventral surface of the head and limbs cream grey and the body light brown. Variation. Measurements and scalation characters of the paratypes are presented in Table 5 and Table 6. The scale counts vary among the type series: scales between supranasals 2 or 3; supralabials and infralabials 9–11; dorsal scale rows at midbody 13–15, and ventral scale rows at midbody 7–9; precloacal and femoral pores 0–20. Etymology. This specific epithet is derived from the name of Huishui County of China and is in reference to the type locality. Natural history. Huishui County is located in the central and southern part of Guizhou Province, with an average elevation of 1100 m. These specimens were collected in the evening on the walls of the village houses. Three female paratypes (NJNUh00852, NJNUh00854 and NJNUh00855) were gravid with two shelled eggs each. Distribution. The species is currently known only from Huishui County and Ziyun County in southern Guizhou Province, Southwest China (Fig. 3). Morphological comparisons. We compared the undescribed gecko species from southern Guizhou Province with selected members of the genus Hemiphyllodactylus based on examination of specimens and data obtained from the literature (Zhou et al. 1981 with English translation of Ota 1996; Zug 2010; Grismer et al. 2013, 2014; Nguyen et al. 2013, 2014; Ngo et al. 2014; Guo et al. 2015). Diagnostic characters separating this species from other nominal taxa of Hemiphyllodactylus are shown in Table 4. Hemiphyllodactylus huishuiensis sp. nov. differs from H. chiangmaiensis Grismer, Wood & Cota; H. jinpingensis; H. kiziriani Nguyen, Botov, Le, Nophaseud, Bonkowski & Ziegler; H. longlingensis Zhou & Liu; H. yunnanensis; H. zugi and H. changningensis Guo, Zhou, Yan & Li in having a maximum SVL of 51.2 mm vs. a SVL 17 dorsal scales, and from H. kiziriani and H. zugi additionally by having 7–9 vs.> 11 ventral scales. Hemiphyllodactylus huishuiensis sp. nov. has a lamellar hand formula of 3-4 - 4 - 4 or 4 - 4 / 5 - 5 - 4 which separates chiangmaiensis (3 - 3 - 3 - 3 or 3-4 - 3 - 3) and H. changningensis (3 - 3 / 4 - 3 / 4 - 3), and a lamellar foot formula of 4 - 4 / 5 - 5 - 4 / 5 which separates chiangmaiensis (3 - 3 - 3 - 3 or 3-4 - 4 - 4); H. jinpingensis (4 - 4 - 4 - 4) and H. changningensis (3 - 3 - 3 - 3 or 3-4 - 4 - 4). Subdigital lamellae on first finger/toe can further differentiate Hemiphyllodactylus huishuiensis sp. nov. from H. banaensis; H. jinpingensis; H. kiziriani; H. longlingensis; H. yunnanensis and H. zugi, 3 vs. 4–6. Hemiphyllodactylus huishuiensis sp. nov. can also be separated from H. banaensis; H. chiangmaiensis; H. kiziriani; H. longlingensis and H. zugi by having no light postorbital stripe. From H. dushanensis, Hemiphyllodactylus huishuiensis sp. nov. differs by the coloration of the dorsal surface of the body (brown with dark transverse stripes vs. unicolor light brown in H. dushanensis); having less subdigital lamellae on first finger (3 vs. 4–5 in H. dushanensis) and first toe (3 vs. 5–6 in H. dushanensis); less precloacal and femoral pores (usually <20 vs. 24–26 in H. dushanensis), and having dark postorbital stripe (vs. light postorbital stripe in H. dushanensis).Published as part of Yan, Jie, Lin, Yubo, Guo, Weibo, Li, Peng & Zhou, Kaiya, 2016, A new species of Hemiphyllodactylus Bleeker, 1860 (Squamata: Gekkonidae) from Guizhou, China, pp. 543-554 in Zootaxa 4117 (4) on pages 546-553, DOI: 10.11646/zootaxa.4117.4.6, http://zenodo.org/record/26592
Design of all digital phase-locked loop in serial link communication
No full textThe speed of wireline and wireless communication systems has been increasing aggressively over the past decade. Multi-GHz clocks are in demand more than ever. In particular, wireline inter-IC communications systems such as broadband Internet, multi-core CPU and system-on-chip have fueled the research on faster on-chip clock synthesizers. In addition, mobile products such as cell-phones and tablets have permeated the consumer market. Since these devices are battery-powered, it is necessary to minimize the battery consumption of the communication system circuitry inside to extend the battery life. As a result, low-power inter-IC communication design is another topic that is gaining interest.
In high speed links, clocking circuitry is vital, and phase-locked loop (PLL) is at the heart of every on-chip clocking circuit. The clocking circuitry needs to be robust, low-power and fast in order to fulfill the increasing demand for high data rate links. The performance of the input/output (I/O) communication channel needs to scale proportionally with the semiconductor fabrication technology (SFT). However, conventional analog PLLs are often incompatible from one technology node to the next and require entirely new designs. In recent years, with the increased performance of digital circuits, all digital PLL (ADPLL) has achieved speed performance similar to that of analog PLL. Since digital logic is more robust, portable, and power efficient, ADPLL is gaining traction in research.
This thesis presents the fundamentals and an in-depth analysis of the conventional analog PLL in Chapters 2 and 3. Then the discussion dives into ADPLL. Chapter 4 presents the building blocks and loop analysis of the ADPLL. Chapter 5 presents jitter sources and jitter analysis inside the ADPLL. Chapter 6 presents an ADPLL in model and transistor design. It has center frequency of 1.6GHz and operates from 1.2GHz to 2.0GHz. Chapter 7 concludes the thesis and discusses future work.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01The student, Yubo Liu, accepted the attached license on 2015-04-15 at 11:45.The student, Yubo Liu, submitted this Thesis for approval on 2015-04-15 at 11:50.This Thesis was approved for publication on 2015-04-17 at 14:45.DSpace SAF Submission Ingestion Package generated from Vireo submission #7867 on 2015-07-22 at 14:24:42Made available in DSpace on 2015-07-22T22:45:19Z (GMT). No. of bitstreams: 2
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Efficient Numerical Methods for Kinetic Equations with High Dimensions and Uncertainties
No full textIn this thesis, we focus on two challenges arising in kinetic equations, high dimensions and uncertainties. To reduce the dimensions, we proposed efficient methods for linear Boltzmann and full Boltzmann equations based on dynamic low-rank frameworks. For linear Boltzmann equation, we proposed a method that is based on macro-micro decomposition of the equation; the low-rank approximation is only used for the micro part of the solution. The time and spatial discretizations are done properly so that the overall scheme is second-order accurate (in both the fully kinetic and the limit regime) and asymptotic-preserving (AP). That is, in the diffusive regime, the scheme becomes a macroscopic solver for the limiting diffusion equation that automatically captures the low-rank structure of the solution. Moreover, the method can be implemented in a fully explicit way and is thus significantly more efficient compared to the previous state of the art. We demonstrate the accuracy and efficiency of the proposed low-rank method by a number of four-dimensional (two dimensions in physical space and two dimensions in velocity space) simulations. We further study the adaptivity of low-rank methods in full Boltzmann equation. We proposed a highly efficient adaptive lowrank method in Boltzmann equation for computations of steady state solutions. The main novelties of this approach are: On one hand, to the best of our knowledge, the dynamic lowrank integrator hasn’t been applied to full Boltzmann equation till date. The full collision operator is local in spatial variable while the convection part is local in velocity variable. This separated nature is well-suited for low-rank methods. Compared with full grid method (finite difference, finite volume,...), the dynamic low-rank method can avoid the full computations of collision operators in each spatial grid/elements. Resultingly, it can achieve much better efficiency especially for some low rank flows (e.g. normal shock wave). On the other hand, our adaptive low-rank method uses a novel dynamic thresholding strategy to adaptively control the computational rank to achieve better efficiency especially for steady state solutions. We demonstrate the accuracy and efficiency of the proposed adaptive low rank method by a number of 1D/2D Maxwell molecule benchmark tests.On the other hand, for kinetic equations with uncertainties, we focus on non-intrusive sampling methods where we are able to inherit good properties (AP, positivity preserving) from existing deterministic solvers. We propose a control variate multilevel Monte Carlo method for the kinetic BGK model of the Boltzmann equation subject to random inputs. The method combines a multilevel Monte Carlo technique with the computation of the optimal control variate multipliers derived from local or global variance minimization problems. Consistency and convergence analysis for the method equipped with a second-order positivity-preserving and asymptotic-preserving scheme in space and time is also performed. Various numerical examples confirm that the optimized multilevel Monte Carlo method outperforms the classical multilevel Monte Carlo method especially for problems with discontinuities
Evaluation of rheology and strength development of alkali-activated slag with different silicates sources
No full textThis study provides a detailed investigation on the reproducibility of two groups of alkali-activated slag (AAS) mixtures, from both fresh properties and strength development perspectives. Three different commercial sodium silicate solutions and one lab-produced silicate activator (made of silica fume and sodium hydroxide) were used to prepare AAS pastes with the same nominal composition in each group. The reaction process of each AAS mixture was monitored by calorimetry and ultrasonic pulse velocity (UPV) measurements. Meanwhile, mini-slump and flow curve tests measured by rheometer were conducted in the first hour to characterize the evolution of fresh properties. The compressive and flexural strength of hardened AAS mortars were measured at different curing ages. The results revealed that AAS pastes prepared with three different sodium silicate solutions exhibited almost identical reaction kinetics, as well as the evolution of fresh properties and strength development. However, the reaction took place rather fast in AAS pastes made of silica fume. These mixtures showed worse rheology and less strength than the corresponding mixtures prepared with sodium silicate solutions. Furthermore, the present study also showed the feasibility of making the same AAS paste through different class commercial sodium silicate solutions.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.Materials and Environmen
Investigation on the potential application of MSWI bottom ash as substitute material in Portland cement concrete
No full textIt has been reported that due to the rapid urbanization and economic growth the municipal solid waste (MSW) would double in volume from 1.3 billion tons per year (in 2012) annually by the end of 2025, challenging environmental and public health management worldwide. Given that, most of the MSW incineration (MSWI) bottom ash (BA) are disposed in landfill currently, and technically and economically viable techniques for the reuse and recycling of MSWI BA is still at a premium. This issue would seriously challenge the environmental and public health management worldwide. In some European countries and the US, MSWI BA has been utilized as aggregate in pavement construction or as aggregate in concrete. Previous studies also proved the feasibility of using MSWI BA in concrete, either as aggregates or binder substitute materials. However, it is worth noticing that there are several significant drawbacks of using MSWI BA in concrete, including the potential risk of leaching due to the existence of heavy metals and harmful salts, the low reactivity due to high content of quartz and unburned organic matters, and the metallic aluminum-induced expansion. Therefore, in this study, a characterization of as-received MSWI BA was conducted at the beginning to find out the potential problems when used in concrete, namely the metallic aluminum content, low reactivity and unburned organics. A comprehensive pretreatment was performed subsequently to solve the problems. Specifically, both physical and chemical treatments were carried out to get rid of the metallic aluminum in BA. Afterwards, thermal treatment was conducted to enhance the reactivity of BA and remove the unburned organics. Pre-treated BA samples were characterized again to reveal the effectiveness of pretreatment. The results showed that both chemical and physical treatment were highly effective in removing metallic aluminum. Meanwhile, thermal treatment was proved to be a proper activation method which also removed the remaining organic matters through the high-temperature process.Subsequently, the investigations of the effects of pre-treated BA addition on compressive strength, reaction products and hydration heat development were conducted on cement paste level by varying the replacement material (BA with different treatment methods) and ratio. A proper method of pretreatment was proposed as well as an optimization of a maximum replacement level of BA in cement paste without detrimentally influence the performance of concrete paste was studied. Compared with nonreactive micronized sand (only works as filler) and pure cement, the addition of physically treated BA has a certain amount of contribution to the hydration process from the viewpoint of heat release. Results show that BA do have pozzolanic activity but is much lower than cement, and physically treated BA is suitable to be used as filler in concrete. Additionally, physically treated BA was further activated through thermal treatment according to the result of compressive strength test, which delivered the highest strength among all the treated BA under the same replacement ratio.Finally, to extend the application of MSWI BA in concrete, the mix design was made by blending treated BA with the highest compressive strength into concrete and make it suitable for structural application. The effects of treated BA addition on the workability and compressive strength of concrete were investigated. The addition of treated BA brought slight negative impact both in workability and strength due to the existence of nonreactive phases in BA (quartz and organics).Accordingly, this study proved the potential of BA with proper treatment to be used as a cement substitute material in concrete as well as promoted the understanding of the influence of BA on the hydration process, which also brings the possibility that BA could be widely reused in concrete system in future industry.Civil Engineering | Structural Engineering | Concrete Structure
Investigation on the attenuation trend of Acoustic Emission in reinforced concrete structures
No full textConsidered as an effective real-time monitoring tool, Acoustic Emission (AE) measurements is a promising technology for reinforced concrete (RC) structures. However, its application on real RC structures is still limited. Due to the lack of knowledge on the crack induced acoustic emission in large scale structures.The aim of this study is to explore the relationship between the fracture energy and the energy of AE signals at structural level. This serves as a basis for the quantification and localization of cracking activities at structural level.This study is based on the AE and crack propagation measurement of a series of large scale RC specimen tests. To avoid the influence of existing cracks, the first part of study focuses on the development of the first flexural crack. It was assumed that the amount of energy required for unit length of crack opening is linearly proportional to the energy of the AE signals that are generated upon the opening of this segment of the crack. These signals can only be monitored AE sensors at given locations. By then, they have travelled through the bulk concrete and possibly already existing cracks, thus their energy has attenuated due to the geometric spreading and the damping property of the material. When these effects are taken into account, the total energy of the AE signals that were obtained by the AE sensors at given location (defined as cumulative signal strength CSS) has a potential of reflecting the fracture energy of the corresponding crack. In the part of the study, this process is theoretically studied first. The theoretical result was further validated by the AE measurement obtained from experiments. Theoretical investigation is carried out based on a simplified model considering only length of the crack and the horizontal distance between crack and AE sensor. Theoretical result shows that both crack length and horizontal distance would affect CSS. However, when the horizontal distance is big enough, crack length is no longer the dominant factor, and CSS drops significantly with the increase of horizontal distance. The CSS of different sensors in a row in the experiments are used to validate this attenuation phenomenon. Exponential curve fitting is carried out to describe the attenuation of experimental results in different tests. Finally, a comparison of attenuation in percentage terms between curve fitting results and theoretical results is carried out. In the uncracked specimens, the results fit each other well. Furthermore, the effect of the existing cracks to the attenuation of the CSS is studied as well. In that case, a dramatic drop of CSS is observed compared to the uncracked structures.The study shows CSS detected by AE sensors could partly indicate the cracking behavior of RC structures. The attenuation tendency gives a guidance for sensor installation in future tests.Additional thesi
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