417 research outputs found
Tensile behavior and mechanical anisotropy of branched cerebral vasculature within gray matter
No full textWith increasing effort to prevent, diagnose, and treat traumatic brain injury (TBI), a large amount of research has been dedicated to the investigation of axon-containing white matter for the study of TBI onset and progression, as well as the elastographic techniques used for diagnoses. However, the mechanical response of gray matter with embedded vasculature has not been thoroughly studied. The cerebral vessels play a vital role not only in the mechanical stiffening of the structure of the brain but also in supplying it with the oxygen and nutrients. By incorporating a multiscale approach to the finite element (FE) models, it is possible to determine the transfer of loads from macroscale to microscale and study the progression of traumatic injury in the brain. In the present thesis, an FE representative volume element (RVE) model of the gray matter is developed that incorporates a branching tree structure composed of arteries. Both the gray matter and the vasculature are represented with hyperelastic material models aiming at capturing the complex response of the biological materials under large strains. The RVE model of the composite material results in anisotropy stemming from not only the different material properties, but also attributed to the complex microstructure. Tensile stretches are applied to illustrate the stiffening effect of the vasculature as well as to determine the anisotropic material properties. The response of the whole volume is monitored under various external loadings. In this thesis, a general Fung-type constitutive model is adopted, which is one of the most widely used types of anisotropic material to describe the response behavior of the composites. By implementing a scriptable geometry generation routine, different vasculature geometries are investigated to elucidate the effect of the vascular geometry on the response of the gray matter RVE. By integrating an accurate geometry of the underlying vasculature, and the micromechanical response of the composite material consisting of the gray matter and the vasculature, the study of potential mechanisms of injury and the development of a micro architecture based RVE used in TBI multiscale simulations becomes feasible.M.S.Includes bibliographical referencesby Mengdi Xin
Easy ID: A Wireless Sensor Package to Measure Human Interaction Features
No full textThis thesis proposes a low-cost and small size customized data acquisition sensor badge, called Easy ID, which is specially designed for the Vision Lab Group in TU Delft for their on body data capture during social events. Easy ID is designed based on an open source platform, which provides enough space for future upgrade and extension.The innovate infrared communication algorithm and the open source software created to drive the circuits in this thesis can be shared with other similar implementations. Instead of using C/C++ language, this work uses python to enhance the code readability for our clients and realize a high-level programming method to drive hardware. To overcome the delays while modulating the transistors, a 555 oscillator is adapted, for a 38kHz carrier frequency. The performance of Easy ID’s identification is evaluated under both static and dynamic scenarios. With the infrared communication modules, the Easy ID can detect any facing another Easy ID with a range of 120 degree opening angle and 3.5 meters distance. The sampling frequency of motion capture is typically 20Hz with 9 DoFs inertial sensors. A highly accurate global time stamp can be stored combined with the data from sensors as data logs.Biomedical Engineerin
Fei dui cheng Hubbard mo xing zhi liang zi Mengdi Kaluo yu jing zhun dui jiao hua yan jiu
No full textHui Ka Ming = 非對稱Hubbard模型之量子蒙地卡羅與精準對角化研究 / 許嘉明.Thesis (M.Phil.)--Chinese University of Hong Kong, 2006.Includes bibliographical references (leaves 85-88).Text in English; abstracts in English and Chinese.Hui Ka Ming = Fei dui cheng Hubbard mo xing zhi liang zi Mengdi Kaluo yu jing zhun dui jiao hua yan jiu / Xu Jiaming.Chapter 1 --- Introduction --- p.1Chapter 2 --- The Asymmetric Hubbard Model And Its Physical BackgroundChapter 2.1 --- Physical Motivation of the Study --- p.4Chapter 2.2 --- Symmetry Properties --- p.5Chapter 2.2.1 --- Particle-Hole Transformation --- p.5Chapter 2.2.2 --- U(l) Group --- p.5Chapter 2.2.3 --- SU(2) Group --- p.6Chapter 2.3 --- Relations with Other Models --- p.7Chapter 2.3.1 --- Falicov-Kimball Model --- p.7Chapter 2.3.2 --- Asymmetric t-J and Heisenberg Model --- p.7Chapter 2.3.3 --- Anderson and Kondo Model。 --- p.8Chapter 3 --- Exact Diagonalization and Density Matrix Renormalization Group --- p.11Chapter 3.1 --- Exact Diagonalization --- p.12Chapter 3.1.1 --- Second Quantization Representation --- p.13Chapter 3.1.2 --- Binary Representation Of Quantum States --- p.15Chapter 3.1.3 --- Two-Table Method --- p.15Chapter 3.1.4 --- Generation of Matrix Elements --- p.18Chapter 3.1.5 --- Lanczos Method --- p.20Chapter 3.1.6 --- Continued Fraction Dynamics At T=0 --- p.22Chapter 3.2 --- Density Matrix Renormalization Group --- p.23Chapter 3.2.1 --- Infinite system DMRG --- p.24Chapter 3.2.2 --- DMRG and Quantum Entanglement --- p.27Chapter 4 --- Determinant Quantum Monte Carlo And Finite Temperature Green Function --- p.29Chapter 4.1 --- Introduction --- p.29Chapter 4.2 --- General Scenario of Fermionic Monte Carol Method --- p.30Chapter 4.3 --- Review on Monte Carlo Method for Ising Model --- p.31Chapter 4.3.1 --- Ising Model --- p.31Chapter 4.3.2 --- Metropolis Algorithm --- p.31Chapter 4.3.3 --- Measurement --- p.32Chapter 4.3.4 --- Near The Critical Points --- p.33Chapter 4.4 --- Determinant Quantum Monte Carlo --- p.33Chapter 4.4.1 --- Suzuki-Trotter Decomposition --- p.34Chapter 4.4.2 --- Hubbard-St rant onovich Transformation --- p.34Chapter 4.5 --- Green Functions in DQMC And Wick's Theorem --- p.37Chapter 4.5.1 --- Equal-'Time' Green Functions --- p.37Chapter 4.5.2 --- Unequal-'Time' Green Functions --- p.38Chapter 4.5.3 --- Wick's Theorem --- p.38Chapter 4.6 --- Practical Consideration of DQMC --- p.39Chapter 4.6.1 --- Metropolis for DQMC --- p.39Chapter 4.6.2 --- Updating the Equal-time Green function --- p.41Chapter 4.6.3 --- Matrix Multiplication Stabilization --- p.42Chapter 4.6.4 --- A Survey In Negative Sign Problem --- p.43Chapter 4.6.5 --- Insight from Feynman --- p.44Chapter 4.6.6 --- Sign Problem As A NP-hard problem --- p.45Chapter 4.6.7 --- Personal Account on the Problem --- p.46Chapter 5 --- Dynamical Mean Field Theory --- p.47Chapter 5.1 --- Classical Mean Field Theory . --- p.49Chapter 5.2 --- DMFT as an Impurity Problem --- p.52Chapter 5.3 --- Scaling of Hopping Integral and Self-consistent Condition --- p.53Chapter 5.4 --- A QMC Impurity Solver --- p.55Chapter 5.5 --- Further development of DMFT --- p.56Chapter 6 --- Results and Discussion --- p.57Chapter 6.1 --- Physical Observable --- p.57Chapter 6.2 --- Methodology of the Studies --- p.58Chapter 6.3 --- Results --- p.59Chapter 6.4 --- Discussion and Suggestion --- p.83Chapter A --- DMRG of tight-binding model --- p.89Chapter B --- Scaling and Density of State of D-dimensional Hubbard Model --- p.9
The impacts of entrepreneurship education on corporate entrepreneurship
No full textNowadays, to cope with the continuing changes in the market, more and more organizations and companies seek different methods to maintain and gain market share in the industry. Among all the choices that can help with improve the innovation of service/products, corporate entrepreneurship is a good approach to take.
This thesis examined and studied whether entrepreneurship education can foster such entrepreneurial behaviors that are beneficial in corporate entrepreneurship. To support the aim of this study, a theoretical discussion was presented to identify what kind of entrepreneurial characteristics can benefit corporate entrepreneurship. Then empirically analysis how entrepreneurship education can influence corporate entrepreneurship. By the end, some managerial implications for further research and study were given.
In the theoretical study, the author starts with what is corporate entrepreneurship and why it is important for organizations and companies, and then discuss about different approaches of entrepreneurial skills and behaviors, that is Personality and Value Approach, Action Approach. Later on analyze fostering entrepreneurship skills in entrepreneurial education.
In the empirical study, qualitative method was used. The author run two parts research, one is focus groups as a pre-test research and the other is semi-structured interview. Empirical findings show that Personality Traits and Personal Values decides whether or not the person wants to do something entrepreneurial, while entrepreneurship education have impacts on whether or not the person have the abilities and skills to become a corporate entrepreneur. Moreover, all these characteristics and features work together to decides whether or not the person can be a successful corporate entrepreneur in a long run
Wireless, implantable catheter-type oximeter designed for cardiac oxygen saturation
No full textAccurate, real-time monitoring of intravascular oxygen levels is important in tracking the cardiopulmonary health of patients after cardiothoracic surgery. Existing technologies use intravascular placement of glass fiber-optic catheters that pose risks of blood vessel damage, thrombosis, and infection. In addition, physical tethers to power supply systems and data acquisition hardware limit freedom of movement and add clutter to the intensive care unit. This report introduces a wireless, miniaturized, implantable optoelectronic catheter system incorporating optical components on the probe, encapsulated by soft biocompatible materials, as alternative technology that avoids these disadvantages. The absence of physical tethers and the flexible, biocompatible construction of the probe represent key defining features, resulting in a high-performance, patient-friendly implantable oximeter that can monitor localized tissue oxygenation, heart rate, and respiratory activity with wireless, real-time, continuous operation. In vitro and in vivo testing shows that this platform offers measurement accuracy and precision equivalent to those of existing clinical standards.
Embodied Executable Policy Learning with Language-based Scene Summarization
No full textLarge Language models (LLMs) have shown remarkable success in assisting robot
learning tasks, i.e., complex household planning. However, the performance of
pretrained LLMs heavily relies on domain-specific templated text data, which
may be infeasible in real-world robot learning tasks with image-based
observations. Moreover, existing LLMs with text inputs lack the capability to
evolve with non-expert interactions with environments. In this work, we
introduce a novel learning paradigm that generates robots' executable actions
in the form of text, derived solely from visual observations, using
language-based summarization of these observations as the connecting bridge
between both domains. Our proposed paradigm stands apart from previous works,
which utilized either language instructions or a combination of language and
visual data as inputs. Moreover, our method does not require oracle text
summarization of the scene, eliminating the need for human involvement in the
learning loop, which makes it more practical for real-world robot learning
tasks. Our proposed paradigm consists of two modules: the SUM module, which
interprets the environment using visual observations and produces a text
summary of the scene, and the APM module, which generates executable action
policies based on the natural language descriptions provided by the SUM module.
We demonstrate that our proposed method can employ two fine-tuning strategies,
including imitation learning and reinforcement learning approaches, to adapt to
the target test tasks effectively. We conduct extensive experiments involving
various SUM/APM model selections, environments, and tasks across 7 house
layouts in the VirtualHome environment. Our experimental results demonstrate
that our method surpasses existing baselines, confirming the effectiveness of
this novel learning paradigm.Comment: 15 pages. arXiv admin note: text overlap with arXiv:2107.06912 by
other author
An Improved Convolutional Capsule Network for Compound Fault Diagnosis of RV Reducers
No full textIn fault diagnosis research, compound faults are often regarded as an isolated fault mode, while the association between compound faults and single faults is ignored, resulting in the inability to make accurate and effective diagnoses of compound faults in the absence of compound fault training data. In an examination of the rotate vector (RV) reducer, a core component of industrial robots, this paper proposes a compound fault identification method that is based on an improved convolutional capsule network for compound fault diagnosis of RV reducers. First, one-dimensional convolutional neural networks are used as feature learners to deeply mine the feature information of a single fault from a one-dimensional time-domain signal. Then, a capsule network with a two-layer stack structure is designed and a dynamic routing algorithm is used to decouple and identify the single fault characteristics for compound faults to undertake the diagnosis of compound faults of RV reducers. The proposed method is verified on the RV reducer fault simulation experimental bench, the experimental results show that the method can not only diagnose a single fault, but it is also possible to diagnose the compound fault that is composed of two types of single faults through the learning of two types of single faults of the RV reducer when the training data of the compound faults of the RV reducer are missing. At the same time, the proposed method is used for compound fault diagnosis of bearings, and the experimental results confirm its applicability
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