3D Reconstruction & Assessment Framework based on affordable 2D Lidar

Lidar is extensively used in the industry and mass-market. Due to its measurement accuracy and insensitivity to illumination compared to cameras, It is applied onto a broad range of applications, like geodetic engineering, self driving cars or virtual reality. But the 3D Lidar with multi-beam is very expensive, and the massive measurements data can not be fully leveraged on some constrained platforms. The purpose of this paper is to explore the possibility of using cheap 2D Lidar off-the-shelf, to preform complex 3D Reconstruction, moreover, the generated 3D map quality is evaluated by our proposed metrics at the end. The 3D map is constructed in two ways, one way in which the scan is performed at known positions with an external rotary axis at another plane. The other way, in which the 2D Lidar for mapping and another 2D Lidar for localization are placed on a trolley, the trolley is pushed on the ground arbitrarily. The generated maps by different approaches are converted to octomaps uniformly before the evaluation. The similarity and difference between two maps will be evaluated by the proposed metrics thoroughly. The whole mapping system is composed of several modular components. A 3D bracket was made for assembling of the Lidar with a long range, the driver and the motor together. A cover platform made for the IMU and 2D Lidar with a shorter range but high accuracy. The software is stacked up in different ROS packages.Comment: 7 pages, 9 Postscript figures. Accepted by 2018 IEEE International Conference on Advanced Intelligent Mechatronic

Development and Application of Fluxomics Tools for Analyzing Metabolisms in Non-Model Microorganisms

Decoding microbial metabolism is of great importance in revealing the mechanisms governing the physiology of microbes and rewiring the cellular functions in metabolic engineering. Complementing the genomics, transcriptomics, proteinomics and metabolomics analysis of microbial metabolism, fluxomics tools can measure and simulate the in vivo enzymatic reactions as direct readouts of microbial metabolism. This dissertation develops and applies broad-scope tools in metabolic flux analysis to investigate metabolic insights of non-model environmental microorganisms. 13C-based pathway analysis has been applied to analyze specific carbon metabolic routes by tracing and analyzing isotopomer labeling patterns of different metabolites after growing cells with 13C-labeled substrates. Novel pathways, including Re-type citrate synthase in tricarboxylic acid cycle and citramalate pathways as an alternate route for isoleucine biosynthesis, have been identified in Thermoanaerobacter X514 and other environmental microorganisms. Via the same approach, the utilizations of diverse carbon/nitrogen substrates and productions of hydrogen during mixotrophic metabolism in Cyanothece 51142 have been characterized, and the medium for a slow-growing bacterium, Dehalococcoides ethenogenes 195, has been optimized. In addition, 13C-based metabolic flux analysis has been developed to quantitatively profile flux distributions in central metabolisms in a green sulfur bacterium, Chlorobaculum tepidum, and thermophilic ethanol-producing Thermoanaerobacter X514. The impact of isotope discrimination on 13C-based metabolic flux analysis has also been estimated. A constraint-based flux analysis approach was newly developed to integrate the bioprocess model into genome-scale flux balance analysis to decipher the dynamic metabolisms of Shewanella oneidensis MR-1. The sub-optimal metabolism and the time-dependent metabolic fluxes were profiled in a genome-scale metabolic network. A web-based platform was constructed for high-throughput metabolic model drafting to bridge the gap between fast-paced genome-sequencing and slow-paced metabolic model reconstruction. The platform provides over 1,000 sequenced genomes for model drafting and diverse customized tools for model reconstruction. The in silico simulation of flux distributions in both metabolic steady state and dynamic state can be achieved via flux balance analysis and dynamic flux balance analysis embedded in this platform. Cutting-edge fluxomics tools for functional characterization and metabolic prediction continue to be developed in the future. Broad-scope systems biology tools with integration of transcriptomics, proteinomics and fluxomics can reveal cell-wide regulations and speed up the metabolic engineering of non-model microorganisms for diverse bioenergy and environmental applications

Facial Recognition Law: Why Should We Care?

What if you are a lawyer and you would like to spend an evening enjoying your favorite artist’s concert at the Radio City Music Hall? Or a Knicks game at Madison Square Garden? The first thing you should check is not the ticket price, but rather whether you, or your law firm, has made the MSG blacklist. Even though for years, the owner of MSG has been using the blacklist to exclude its enemies (and their associates) from setting foot in any MSG-owned venue, the facial recognition technology (“FRT”) just brought this practice to a new level. This post was originally published on the Cardozo International & Comparative Law Review on March 27, 2023. The original post can be accessed via the Archived Link button above

Fabrication and characterization of advanced materials using laser metal deposition from elemental powder mixture

Over the past decades of years, a great deal of money has been spent to machine large and complex parts from high-performance metals (i.e., titanium components for aerospace applications), so users attempt to circumvent the high cost of materials. Laser metal deposition (LMD) is an additive manufacturing technique capable of fabricating complicated structures with superior properties. This dissertation aims to improve the applications of LMD technique for manufacturing metallic components by using various elemental powder mixture according to the following three categories of research topics. The first research topic is to investigate and develop a cost-effective possibility by using elemental powder mixture for metallic components fabrication. Based on the studies of fabricating thin-wall Ti-6Al-4V using elemental powder mixture, comparative close particle number for Ti, Al and V powder could easily get industry qualified Ti-6Al-4V components. The particle number for each element in powder blends has been proved to be a key factor for composition control in the final deposit part. The second research topic focuses on the application improvements of elemental powder manufacturing. By fabricating AlxCoFeNiCu1-x (x = 0.25, 0.5, 0.75) high entropy alloys from elemental powder based feedstocks, it enhances the usage of elemental powder to fabricate novel materials with complex compositions. The third research topic extends the applications of using elemental powder mixture to the broader area. A functionally gradient material (FGM) path is developed to successfully join titanium alloy with γ-TiAl. This dissertation leads to new knowledge for the effective fabrication of unique and complex metallic components. Moreover, the research results of the dissertation could benefit a wide range of industries --Abstract, page iv

Deer impact and plant resistance traits

White-tail deer (Odocoileus virginianus), a generalist herbivore, are widely considered to influence ecological communities, ecosystems and human wellbeing by foraging preferentially on certain plant species. Previous research has shown that high deer density can change the relative abundance of tree species in forest communities. Furthermore, some evidence shows that resistance traits of plants can influence plant photosynthetic ability which is an important factor in an ecosystem. The purpose of this experiment is to test whether plant resistance traits can change within species when they are exposed to high levels of deer herbivores. The experiment, established in 1979, enclosed deer within forest stands at high and low densities. Resistance traits of five dominant woody plant species were sampled from individuals that established during the deer density treatments and are now adults. Plant resistance traits (Leaf mass per area, Leaf dry matter content, C:N ratio, and Wood density) were tested and compared between low and high deer density area by using mixed effect statistical models. Leaf mass per area (LMA), leaf carbon—nitrogen ratio (C:N), and wood density did not respond significantly to increasing deer density. However, leaf dry matter content (L D MC) showed a slight but significant increase in response to high deer density. These results indicate that this plant trait may respond to increasing deer density, resulting in potential impacts on ecosystem functioning

Genetic population structure and microbiome of german cockroaches in urban environments

Pests of human habitats may harbor and disperse pathogens that cause human disease. One such pest is the German cockroach (Blattella germanica), which is known to harbor numerous pathogens, including Klebsiella and Pseudomonas. The aim of this study is to reveal the importance of the German cockroach as a potential vector of human medically important diseases. To do so, this study investigates German cockroach population structure and their associated bacterial microbiome in urban residential environments. Ninety German cockroaches are collected from three residential apartment buildings in three New Jersey cities. Samples are caught by glue traps and stored at -20°C. DNA and RNA are extracted from cockroach samples and sent for Next Generation Sequencing. Single-Nucleotide Polymorphisms (SNPs) are the genetic markers used for the cockroach population structure analysis. Thirty samples of the same extractions are also used for bacterial genetic analysis. Phylogeny, Principal Component Analysis (PCA), and STRUCTURE analysis are used for characterizing the population structure of cockroaches, which reflects the dispersal ability and colonization history of the cockroach populations. Results show that population structure exists among the three buildings/cities and within each building, and indicates limited gene flow among buildings/cities. Within buildings, genetic population structure indicates both dispersal within buildings and multiple colonization events within each building. 16S rRNA is studied for understanding the bacterial microbiome community on cockroaches, and is used to quantify the abundance of bacterial operational taxonomic units (OTUs) found on the cockroaches. Bacterial microbiome diversity and ordination of OTUs are used to characterize the bacterial microbiome among the 30 samples from the same three buildings/cities. The results show a low but significant differentiation of bacterial community among three buildings and within one building. To test whether the genetic distance of German cockroaches within and among the three buildings is correlated with community distance among bacterial communities on the cockroaches, a Mantel test is implemented. The result of this test is negative, which indicates the lack of correlation between cockroach populations and bacterial communities. A laboratory test of the bacterial dispersal ability of German cockroaches is done by infecting cockroaches with fluorescence-marked E. coli. This test shows the strong bacterial dispersal ability of cockroaches. In conclusion, German cockroach structure is shaped by geographic separation, which doesn’t affect the bacterial community found on the same cockroach populations. These results have several important implications for control of cockroach infestations and for control of the spread of human disease. First, cockroaches are able to spread among within buildings and cockroaches also may colonize a building multiple time. This indicates that control efforts should aim to eliminate cockroaches from all apartments within a building to prevent recolonization from within. Residents should be informed of effective methods to prevent reintroduction from external sources. Second, cockroaches harbor several medically important human bacterial pathogens. Care should be taken not to interact with cockroaches to limit human infection. Third, because bacterial communities do not appear to be strongly shaped by cockroaches, researchers should investigate other mechanisms of bacterial dispersal

Modelling of directed energy deposition processes

The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed. In the heat transfer and fluid flow model, the governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method. Surface tension was modeled by taking the Continuum Surface Force (CSF) model combined with a force-balance flow algorithm. Laser-powder interaction was modeled to account for the effects of laser power attenuation and powder temperature rise during the laser metal deposition process. Temperature-dependent thermal-physical material properties were considered in the numerical implementation. The calculation domain is logically partitioned into smaller cells in 3D space. This makes the numerical implementation consume large amounts of computational resources as each cell is considered at each step of the implementation. This challenge has been addressed through the use of parallel computing by way of message passing interface. Simulations were performed and a comparison between the sequential and parallel implementations was also made --Abstract, page iv

Size dependent electronic properties of silicon quantum dots - an analysis with hybrid, screened hybrid and local density functional theory

We use an efficient projection scheme for the Fock operator to analyze the size dependence of silicon quantum dots (QDs) electronic properties. We compare the behavior of hybrid, screened hybrid and local density functionals as a function of the dot size up to $\sim$800 silicon atoms and volume of up to $\sim$20nm$^3$. This allows comparing the calculations of hybrid and screened hybrid functionals to experimental results over a wide range of QD sizes. We demonstrate the size dependent behavior of the band gap, density of states, ionization potential and HOMO level shift after ionization. Those results are compared to experiment and to other theoretical approaches, such as tight-binding, empirical pseudopotentials, TDDFT and GW

Three-Dimensional Electromagnetic Scattering from Layered Media with Rough Interfaces for Subsurface Radar Remote Sensing

The objective of this dissertation is to develop forward scattering models for active microwave remote sensing of natural features represented by layered media with rough interfaces. In particular, soil profiles are considered, for which a model of electromagnetic scattering from multilayer rough surfaces with/without buried random media is constructed. Starting from a single rough surface, radar scattering is modeled using the stabilized extended boundary condition method (SEBCM). This method solves the long-standing instability issue of the classical EBCM, and gives three-dimensional full wave solutions over large ranges of surface roughnesses with higher computational e±ciency than pure numerical solutions, e.g., method of moments (MoM). Based on this single surface solution, multilayer rough surface scattering is modeled using the scattering matrix approach and the model is used for a comprehensive sensitivity analysis of the total ground scattering as a function of layer separation, subsurface statistics, and sublayer dielectric properties. The buried inhomogeneities such as rocks and vegetation roots are considered for the first time in the forward scattering model. Radar scattering from buried random media is modeled by the aggregate transition matrix using either the recursive transition matrix approach for spherical or short-length cylindrical scatterers, or the generalized iterative extended boundary condition method we developed for long cylinders or root-like cylindrical clusters. These approaches take the field interactions among scatterers into account with high computational efficiency. The aggregate transition matrix is transformed to a scattering matrix for the full solution to the layered-medium problem. This step is based on the near-to-far field transformation of the numerical plane wave expansion of the spherical harmonics and the multipole expansion of plane waves. This transformation consolidates volume scattering from the buried random medium with the scattering from layered structure in general. Combined with scattering from multilayer rough surfaces, scattering contributions from subsurfaces and vegetation roots can be then simulated. Solutions of both the rough surface scattering and random media scattering are validated numerically, experimentally, or both. The experimental validations have been carried out using a laboratory-based transmit-receive system for scattering from random media and a new bistatic tower-mounted radar system for field-based surface scattering measurements.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91459/1/xduan_1.pd