155 research outputs found
Analysis of big data by split-and-conquer and penalized regressions: new methods and theories
No full textThis dissertation develops methodologies for analysis of big data and its related theoretical properties. Recent years, tremendous progress has been made in analysis of big data, especially techniques via penalization and shrinkages. However, there are still many challenging problems to be solved. This dissertation focuses on two settings where (i) the data is too large to fit into a single computer or too expensive to perform a computationally intensive data analysis; or (ii) there are unknown group structures of highly correlated variables. In this dissertation, we first propose a Split-and-Conquer approach to analyze extraordinarily large data. Then, under linear regression settings with highly correlated variables, we investigate model selection properties of OSCAR (octagonal shrinkage and clustering algorithm for regression) estimators (Bondell & Reich, 2008) and propose a more general method Group OSCAR which incorporates both prior knowledge of group structures and correlation patterns among explanatory variables. We first propose a split-and-conquer approach and illustrate it using a computationally intensive penalized regression method. We show that the combined result is asymptotically equivalent to the corresponding analysis result of using the entire data all together. In addition, we demonstrate that the approach has an inherent advantage of being more resistant to false model selections. Furthermore, when a computational intensive algorithm is used, we show that the split-and-conquer approach can substantially reduce computing time and computer memory requirement. Detecting meaningful `groups' of highly correlated variables has been studied a lot. OSCAR estimators provide a feasible way to perform variable selection and clustering simultaneously. However, no theoretical results are provided for OSCAR estimators. In this dissertation, we provide a set of mild conditions under which OSCAR estimators are able to select the true model and keep the order of the coefficients by their magnitudes when the correlations are high. In the last part of this dissertation, we propose a new method. This method not only takes use of known group structures but also incorporates the correlation patterns leading to the underlying unknown group structure. It extends most of the model selections methods in the literature, and has a general grouping effect.Ph. D.Includes bibliographical referencesIncludes vitaby Xueying Che
Active travelling to school is not associated with increased total daily physical activity levels, or reduced obesity and cardiovascular/pulmonary health parameters in 10–12-year olds : a cross-sectional cohort study
No full textFunding This work was supported by a grant from the Scottish Government Chief Scientist’s office grant CZH/4/458 b awarded to FFS and JRS. JRS was supported by a Wolfson merit award. Author information These authors contributed equally: Xueying Zhang, Nathan A. SmithPeer reviewe
Reducing phosphate losses into water by treating farm dairy effluent before application to land : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
No full textIntensive dairy farming has resulted in the production of large amounts of farm dairy effluent (FDE). FDE is a mixture of water, urine, dung, soil, feed, cleaning chemicals, and milk. Land application of FDE has become a primary method of FDE management in many countries due to its high nutrient content. However, this method can result in high concentrations of phosphorus (P) in the soil, which increases the risk of P losses from the agricultural system and eutrophication of waterways. This poses a threat to water quality, especially through subsurface tile-drain systems. Additionally, FDE contains a large number of pathogenic bacteria that can pose a risk to human health. To address these issues, a new FDE treatment method using poly-ferric sulphate (PFS) has been developed. This new method can clarify water for recycling; reduce water wastage, and reduce health risks and environmental contamination from FDE applied to land. However, there is a lack of detailed knowledge on the effect of applying treated FDE (TE) on the P leaching losses through soil with tile drains. This research aims to improve knowledge and understanding of the effects on P and Escherichia coli (E. coli) leaching losses, soil P fractions, pasture yield, and plant P uptake following the application of TE. To achieve this aim, two drainage model studies were conducted at Lincoln University and a soil and pasture study was conducted at Lincoln University Research Dairy Farm (LURDF).
The objective of drainage experiment 1 was to determine the impact of applying fresh TE and pond-stored TE (TE-S) compared to untreated FDE on P and E. coli leaching losses through subsurface drainage model units. The study found that the cumulative dissolved reactive phosphorus (DRP) lost to drainage water from the TE and TE-S treatments was significantly lower by 93.1% and 92.2%, respectively, compared to the untreated FDE treatment. Additionally, the drainage water from the TE and TE-S treatments showed a significant reduction of 98.3% and 99.9% in E. coli concentrations compared to the FDE treatment. The different treatments did not affect plant biomass and P uptake. The reduction in P and E. coli leaching loss was due to the formation of insoluble iron phosphate in TE, resulting in a decrease in DRP concentration and amount in the drainage water. The acidic nature of PFS and the encapsulation of bacteria within the floc also contributed to the reduction of E. coli. These results demonstrate that PFS-treated effluent application on drained pasture soils can significantly reduce P and E. coli concentrations and amounts in drainage water resulting in substantial environmental benefits, without negatively impacting plant growth.
The objective of drainage experiment 2 was to determine the effect of soil compaction by simulated cattle treading on the P leaching losses following repeated TE application to the soil with subsurface drains. Drainage experiment 2 found that repeated application of TE significantly reduced amounts of P leaching losses by 87.1 to 99.6% compared to the repeated application of FDE, both with or without soil compaction by cattle treading. These reductions were attributed to the less soluble P form in TE compared to FDE and that the less soluble P compounds were less prone to being leached. Soil compaction by simulated cattle treading significantly reduced P leaching losses only with the repeated FDE application but did not affect the P loss from TE applied soil. The compaction induced reduction in P leaching loss from the FDE was attributed to a reduction in macroporosity and preferential flow through the soil.
The objective of the soil and pasture study was to determine the soil P fractions, pasture biomass, and plant P uptake with repeated application of TE compared to repeated application of FDE. This study found that the repeated application of TE resulted in no significant differences in most soil properties, soil P fractionations, pasture biomass and plant P uptake, except significantly increasing concentrations of soil labile P compared with repeated application of FDE.
In summary, this research has improved knowledge and understanding of the benefits of applying treated effluent in reducing P and E. coli leaching losses through the subsurface drains, both fresh or stored TE, and with or without soil compaction by animal treading. The application of TE can, therefore, be used as an effective tool to help protect surface water quality without creating adverse impacts on soil P fractionations, pasture productivity or quality and repeat application of TE has the potential to improve soil fertility
The biological effects of Lupinus polyphyllus on soil nitrogen in acid high country soils : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Agricultural Science at Lincoln University
No full textMany high country soils in South Island have low soil pH and possibly high exchangeable aluminium (Al) concentrations, which limit establishment and persistence of pasture legumes for nitrogen (N) contribution. Lupinus polyphyllus (common name ‘Russell lupin’, also known as perennial lupin) is a species of flowering plants in the legume family, Fabaceae. Perennial lupin is able to grow in acidic soil (pH 3ppm, 0.01 CaCl2) toxic to most other legumes, and low soil P (Olsen P <10). The growth ability of perennial lupin indicates that it is better adapted to low fertility environment than other conventional pasture legumes. The high tolerance of lupin to low fertility and acid soil shows that it occupies a unique edaphic niche among forage legumes. As such, this species may be suitable to develop poor quality soils on south island high country farms in South Island, New Zealand.
This study focused on the biological effects of perennial lupin stands of varying ages on soil N and carbon (C) concentrations in acid high country soils. There were two experiments in this study: a field experiment and a glasshouse experiment.
For the field experiment, soils were collected and analysed for total soil N, total soil C, soil mineral N, mineralizable N, soil pH, soil Olsen P and sulphate sulphur (S) from eight lupin stands of different ages and adjacent established pasture sites. There are eight sites across four farms: Sawdon Station, Glenmore Station, Omarama Station, Dasher Station and one from Lincoln University Campus. To quantify soil labile N status more directly, the glasshouse experiment also was conducted in soil from five sites from the field study. Annual ryegrass (Lolium multilforum) was grown in soil collected from established lupin stands and grass-dominant pasture, and exhaustively harvested to extract the labile soil N. Ryegrass dry matter yield and shoot N were analysed for calculating soil N status. Shoot N was analysed as a measure of labile soil N, in an effort to quantify the effects of perennial lupin biological N inputs to this suite of field soils. Adjacent long-term pasture soils were also included as comparative baseline controls.
In the field experiment, perennial lupin significantly increased total soil N and soil mineralizable N in the plant rooting zone of high country soils and lupin stand soils showed higher soil N status than pasture soils, resulting from N fixation. The highest value of soil mineralizable N among eight sites occurred in Glenmore Station and Lake Tekapo (site 2) soils with 213.8 kg/ha. Soil N status also declined with increasing soil depth in both lupin soils and pasture soils caused by plant residue accumulation in the topsoil. Soil N level generally increased with increasing lupin stand age.
The glasshouse experiment showed a similar trend as the field experiment, that lupin soils exhibited higher soil N status than pasture soils at each site. Higher soil mineralizable N lead to higher ryegrass dry matter yield and higher N uptake. Soil N level also decreased with increasing soil profile depth in both lupin stand soils and pasture soils. Ryegrass dry matter yield and N uptake by ryegrass generally increased with lupin stand age. The significant differences between each site in both experiments were caused by annual rainfall and soil conditions.
This study provides strong evidence that lupin substantially increases soil total and labile soil N, which increases with lupin stand age
LoRaWAN: Vulnerability Analysis and Practical Expoitation
No full textInternet of Things (IoT) applications nowadays have a wide impact on people’s daily life while the size of IoT has been increasing rapidly. Millions of devices huge amount of data and different kinds of new protocols can bring many security issues.LoRaWAN is a MAC layer protocol for long-range low-power communication dedicated to the IoT. It can be used to transmit messages between IoT end devices and gateways. However, since the development of LoRaWAN is still at an early stage, the security level of the protocol is not well developed, and the need for analyzing and developing the security level of LoRaWAN is necessary and urgent.This research summarizes the secure features of LoRaWAN in the aspects of activation methods, key management, cryptography, counter management and message acknowledgement. Then, vulnerabilities of LoRaWAN are found and analyzed. 4 Attacksbased on these vulnerabilities are designed and described via an attack tree method. These attacks are (1) replay attack, (2) eavesdropping, (3) bit flipping and (4) ACK spoofing. As a poof-of-concept, the attacks are implemented and executed in a LoRaWAN environment. Afterwards, mitigation and secure solutions against attacks are given to protect the security of LoRaWAN networks.The result of this research can be used in developing the security level of LoRaWAN protocol and setting the standard criteria for evaluating security of LoRaWAN devices
Metamaterial structures for Wakefield acceleration and high power microwave generation
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 209-218).This thesis presents the theoretical and experimental investigation of the interaction of metamaterial structures with electron beams for two applications: wakefield acceleration and high power microwave generation. Under the topic of wakefield acceleration, on the theoretical side, several metamaterial structures have been designed and simulated. The novel phenomenon of reversed Cherenkov radiation has been found to enhance the beam-wave interaction in metamaterials. A metallic wagon wheel metamaterial structure was designed and built for use in an experiment at the Argonne Wakefield Accelerator (AWA) Facility. On the experimental side, this thesis presents the first demonstration of high-power, reversed Cherenkov wakefield radiation by short electron bunches passing through the wagon wheel structure at the AWA. Single 45 nC electron bunches of 65 MeV energy traversing the structure generated up to 25 MW in 2 ns pulses at 11.4 GHz, in excellent agreement with theory.Two bunches of 85 nC with appropriate temporal spacing generated up to 80 MW by coherent wakefield superposition. If this power were applied to a trailing witness bunch in a collinear wakefield accelerator, it would provide an accelerating gradient of 75 MV/m. Under the topic of high power microwave generation, on the theoretical side, an analytical theory has been developed to predict the novel Cherenkov-cyclotron interaction in metamaterial-based microwave devices. An S-band metamaterial-loaded waveguide with reverse symmetry has been designed and built to work with the Cherenkov-cyclotron interaction. On the experimental side, this thesis presents the experimental results of the metamaterial-loaded waveguide built at MIT. Power levels to 2.9 MW at 2.4 GHz in full 1 [mu]s pulses were generated by an electron beam of up to 490 kV of voltage and 84 A of current.Frequency tuning measurements verified that pulses above 1 MW of output power were only seen in the Cherenkov-cyclotron mode. With these results, this thesis demonstrates the unique features of metamaterial structures that are very attractive for high-gradient wakefield accelerators and high power microwave sources. Advantages include the high shunt impedance for intense beam-wave interaction; the simple and rugged structure; and a large parameter space for various optimization goalsby Xueying Lu.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Physic
The C-E Translation of Business Promotional Material Based on Skopostheorie
No full textBased on Translation Skopostheorie, the author briefly expounds the purpose of C-E translation of businesses’ promotional material. Simultaneously, the typical problems appeared in the translation process have been explored and analyzed. With practical examples, the author probes into some rules for solving these problems. The problems in such translation can be often found in the following four categories---straying away from the source text, being constrained to the source text, lacking in cultural elements, having grammatical errors and improper expressions. However, three rules of Skopostheorie---skopos rule, intratextual coherence rule, and inter-textual coherence rule may be used as guidance for solving these problems
Global well-posedness and scattering for the defocusing mass-critical Schr\"odinger equation in the three-dimensional hyperbolic space
No full textIn this paper, we prove that the initial value problem for the mass-critical
defocusing nonlinear Schr\"odinger equation on the three-dimensional hyperbolic
space is globally well-posed and scatters for data with radial
symmetry in the critical space .Comment: arXiv admin note: substantial text overlap with arXiv:1008.1237 by
other author
The future workplace. Sharing office. A changeable workplace for a changing city
No full textLAUREA MAGISTRALEQuesta tesi è costituita da quattro parti principali. Questa prima parte ha brevemente esaminato l'evoluzione degli spazi per uffici. La seconda parte riguarda la ricerca e comprende il contemporaneo dell'ambiente di lavoro e la nuova forma di ufficio. La terza parte comprende: i fattori che influenzano l'ufficio futuro dell'ufficio, la direzione del futuro e la speculazione sulle caratteristiche dello spazio di lavoro futuro; quarta parte è il progetto - Condivisione ufficio.
Lo spazio per uffici futuro ha molti fattori incerti, luogo di lavoro incerto, ore di lavoro incerte e utenti di spazio incerti, le persone possono scegliere di lavorare in un ufficio più vicino, invece di attraversare una città enorme, riducendo così il tempo di commutazione. E tali punti di raccolta di uffici possono essere lo spazio personale di lavoro di riservatezza o il futuro spazio di lavoro dovrebbe creare un'atmosfera vicina tra le persone e i lavoratori di diversi settori possono incontrare i partner qui, mirano a costruire una rete di relazioni intime tra i posti di lavoro, progettare efficaci social e collaborativi gli spazi diventano sempre più importanti per portare le persone sul posto di lavoro. Il futuro posto di lavoro sarà un ambiente di collaborazione diffuso in una città.
Sulla struttura del posto di lavoro, impiego di unità modulari per uffici che forniscono una migliore adattabilità, flessibilità illimitata e un alto grado di condivisione per futuri luoghi di lavoro imprevedibili. Sia lo spazio unitario che lo spazio combinato, può essere messo in qualsiasi angolo della città in una città altamente satura oggi e in futuro. E con l'assistenza della progettazione di APP, è possibile scegliere oggi il posto di lavoro solo prenotando sul terminale mobile.The development of Internet technology and sharing economy not only lead to the innovative thinking and new trends in management, but also boost the growth of new office types.
The meaning of office space is being rewritten From “Office in the city” to “City as a work platform”, From "Eight hours of working system" to "Work-Life Integration". The office is going through profound changes, which makes the office a place for working rather than the place to work.Office space is no longer the private space of workers, It's the important place to communicate with the outside world. It looks more like a mix between virtual and real.
This thesis consists of Four main parts. This first part briefly reviewed the evolution of office spaces. The second part covers the research and comprises the contemporary of working environment and the new form of office, The third part include: the factors that influence the future office office, the direction of the future and the speculation about the characteristics future working space,The fourth part is the project - Sharing office.
The future office space has many uncertain factors, uncertain working place, uncertain working hours and uncertain space users,people can choose to work at a nearest office complex instead of crossing a huge city, thereby reducing commuting time. And such office collection points can be privacy personal work space, or future work space should create a close atmosphere between people, and workers from different fields can meet partners here, aim to build a network of intimate relationships between jobs, Designing effective social and collaborative spaces is becoming ever more important to bringing people together in the workplace. The future workplace will be a co-working environment spread across a city.
On the structure of the workplace, I will employ modular office space units that provide better adaptability, unlimited flexibility and a high degree of sharing for future unpredictable workplaces. Whether it's unit space or combination space, it can be put in any corner of the city in a highly saturated city today and in the future. And with the assistance of the designing APP, you can choose the workplace today just by booking on the mobile terminal
On the high–low method for NLS on the hyperbolic space
No full text© 2020 Author(s). In this paper, we first prove that the cubic, defocusing nonlinear Schrödinger equation on the two dimensional hyperbolic space with radial initial data in Hs(H2) is globally well-posed and scatters when s > 3/4. Then, we extend the result to nonlinearities of order p > 3. The result is proved by extending the high-low method of Bourgain in the hyperbolic setting and by using a Morawetz type estimate proved by Staffilani and Ionescu
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