Search results
(7,961 - 7,980 of 8,972)
Pages
- Title
- Mental Health Stigma and Care-Seeking in First Generation Indian Immigrants
- Creator
- Shah, Binoy
- Date
- 2019
- Description
-
Objective: Immigrants from India face unique obstacles, including migration related factors and cultural pressures, that may contribute to...
Show moreObjective: Immigrants from India face unique obstacles, including migration related factors and cultural pressures, that may contribute to underutilization of mental health treatment services. The present thesis examined paths between mental health stigma and care-seeking in a sample of first-generation Indian immigrants, with a specific emphasis on the influences of acculturation and parental autonomy support. Method: A sample of 201 first-generation immigrants from India was ascertained using MTurk. Path analysis was conducted to examine the relationships between public stigma of mental illness, disclosure, mental health care-seeking, parental autonomy support, and bi-directional acculturation. Results: Final model was supported by good fit indicators. Greater public stigma was associated with reduced care-seeking, but greater disclosure was associated with increased care-seeking. Interestingly, parental autonomy support, mainstream acculturation, and heritage acculturation facilitated disclosure but had no discernible impact on public stigma. Conclusions: In contrast to traditional anti-stigma strategies that focus on reducing public stigma, present results suggest that it may be more beneficial to facilitate care-seeking by targeting disclosure of status. In turn, disclosure may be promoted by facilitating autonomy supportive social networks and bi-directional acculturation.
Show less
- Title
- IN SITU X-RAY ABSORPTION SPECTROSCOPY STUDY OF TIN-BASED GRAPHITE COMPOSITE ANODES FOR LITHIUM-ION BATTERIES
- Creator
- Ding, Yujia
- Date
- 2019
- Description
-
Sn-based anode materials such as Sn, SnO2, Sn4P3, and SnS2 that exhibit large theoretical capacities are promising alternatives to traditional...
Show moreSn-based anode materials such as Sn, SnO2, Sn4P3, and SnS2 that exhibit large theoretical capacities are promising alternatives to traditional graphite anodes for Li-ion batteries. However, their capacities fade drastically in a few cycles due to substantial volume changes during the lithiation/delithiation process resulting in cracking and pulverization of the electrode. A graphite matrix is introduced by high-energy ball milling to obtain a graphite composite and enhance the electrochemical performance. Indeed, Sn4P3/graphite composite exhibits a reversible capacity of 651 mA h g-1 in the 100th cycle, and SnS2/graphite composite shows 591 mA h g-1 in the 50th cycle.To obtain a better understanding of the improved performance of the composite materials and the reason for the more gradual capacity fading, in situ EXAFS is used to investigate these mechanisms using in situ coin cells and in situ vacuum-sealed pouch cells. The collected EXAFS data were analyzed by modeling to extract detailed local environment changes during the lithiation/delithiation process.In the crystalline phases of Sn-based materials, the conversion reaction forming metallic Sn is partially reversible and partially irreversible, and the subsequent alloying/dealloying reaction forming LiSn alloys is reversible. Introducing the graphite matrix increases electrical conductivity and prevents aggregation of intermediate Sn clusters. The graphite matrix also plays a significant role in transforming composites into highly dispersed amorphous phases. These amorphous phases, formed in the first few cycles of Sn4P3/graphite and SnS2/graphite composites, exhibit excellent reversibility in both conversion and alloying/dealloying reactions, which is the main reason for the significant improvements in electrochemical performance. The slow growth of metallic Sn clusters and the slight reduction in amorphous phases result in gradual capacity loss over long-term cycling. Introducing the graphite matrix and creating highly dispersed composite samples are the successful strategies that can be scaled up to develop new battery materials in the future.
Show less
- Title
- L-cumulants, L-cumulant embeddings and algebraic statistics, AS2012 Special Volume, part 1: This issue includes a second series of papers from talks, posters and collaborations resulting from and inspired by the Algebraic Statistics in the Alleghenies Conference at Penn State, which took place in July 2012.
- Creator
- Zwiernik, Piotr, AS2012 Special Volume, part 1: This issue includes a second series of papers from talks, posters and collaborations resulting from and
- Description
-
Focusing on the discrete probabilistic setting we generalize the combinatorial definition of cumulants to L-cumulants. This generalization...
Show moreFocusing on the discrete probabilistic setting we generalize the combinatorial definition of cumulants to L-cumulants. This generalization keeps all the desired properties of the classical cumulants like semi-invariance and vanishing for independent blocks of random variables. These properties make L-cumulants useful for the algebraic analysis of statistical models. We illustrate this for general Markov models and hidden Markov processes in the case when the hidden process is binary. The main motivation of this work is to understand cumulant-like coordinates in alge- braic statistics and to give a more insightful explanation why tree cumulants give such an elegant description of binary hidden tree models. Moreover, we argue that L-cumulants can be used in the analysis of certain classical algebraic varieties.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Multi-function multi-modality sensing and communication system: a designer's perspective
- Creator
- Fepeussi, Tonmo Vanessa Carine
- Date
- 2019
- Description
-
The combination of sensing and communication functionalities on the same electronic device is the key to autonomous sensing applications in...
Show moreThe combination of sensing and communication functionalities on the same electronic device is the key to autonomous sensing applications in the transportation industry, including driverless vehicles and structural health monitoring (SHM) of aero-vehicles. Due to the limited availability of spectral and hardware resources, there is a need for resource sharing between sensing and communication systems. This is achieved by the efficient integration of sensing and communication functions through a unified design of both systems into smart sensors. To that end, a multi-modality approach is employed in this research to design multi-functional systems at two different bands of the frequency spectrum, namely radio and acoustic frequencies.First, a radio-frequency (RF) software-defined system capable to support radar sensing and RF communication is proposed for use in modern interconnected automotive applications such as driverless vehicles. The proposed RF radar is designed on a software-defined homodyne transceiver prototype capable of radio communication. The system is implemented in the S band over a narrow frequency bandwidth of 34 MHz between 3.550 GHz and 3.584 GHz. Experimental measurements show that the designed radar sensor can measure short-range targets with a range accuracy of less than 21 cm.An acoustic sensing and communication system is developed in parallel for use in autonomous SHM monitoring of aero-vehicles. The proposed communication system uses M-ary time-reversal pulse position modulation (M-TRPPM) as the modulation scheme for dispersion compensated wireless communication across the elastic channel. The time reversal based time division multiple access (TR-TDMA) protocol is introduced to regulate channel access by multiple sensors. Simulation and experimental validation demonstrate that the designed system, using an excitation signal generated by a PZT sensor disc at 300 kHz resonant frequency, is capable of reliable data transmission with a bit error rate (BER) approximating zero at low data rates of a few kilobits per seconds.
Show less
- Title
- EVALUATION OF LISTERIA MONOCYTOGENES ENRICHMENT AND COMPOSITING PROTOCOLS FROM ENVIRONMENTAL SAMPLES
- Creator
- Eckert, Christine
- Date
- 2019
- Description
-
Environmental sampling in a food production plant is routinely conducted using devices, such as sponges or swabs, to verify cleaning...
Show moreEnvironmental sampling in a food production plant is routinely conducted using devices, such as sponges or swabs, to verify cleaning procedures and determine if any foodborne pathogens, such as Listeria monocytogenes (L. monocytogenes), are present. The devices used for environmental monitoring are enriched to improve pathogen detection. This study aims to 1) compare the limit of detection (LOD) of L. monocytogenes of two U.S. Food and Drug Administration (FDA) enrichment procedures (i.e., Bacteriological Analytical Manual (BAM) and Compliance Document) with and without food matrix, and to 2) assess the number of samples which can be wet and dry composited without loss of sensitivity from stainless steel. To compare the LOD of L. monocytogenes using UVM and BLEB, three inoculation levels (0.27±0.07, 0.59±0.05, and 1.00±0.15 CFU per 225 mL enrichment) with 30 enrichments each were used. Results showed that there was no significant difference between the number of samples where L. monocytogenes was detected for UVM and BLEB at any of the three inoculation levels. However, the limit of detection (LOD95%) for UVM/Fraser was higher than that of BLEB (2.13 and 1.44 CFU/mL, respectively). For wet compositing, 1.24±0.34 CFU of L. monocytogenes was inoculated into 45 enrichments of UVM or BLEB without food matrix and 7.2±0.18 CFU of L. monocytogenes was inoculated into 30 enrichments of UVM or BLEB with 4.13±0.12 log CFU of native microflora from Romaine lettuce wash (RLW). Secondary composite enrichments in Fraser broth were conducted at each of four different ratios: 1:1 (1 positive:1 negative), 1:2 (1 positive: 2 negative), 1:4 (1 positive: 4 negative), and 1:7 (1 positive:7 negative). There was no significant difference between the number of samples where L. monocytogenes was detected between BLEB and UVM with or without food matrix at any of the composite ratios. When comparing wet and dry compositing enrichments from stainless steel, 10.16 × 10.16 cm areas on stainless steel plates were inoculated with 464±22 CFU (2.67±0.24 log CFU) L. monocytogenes, dried for 24 h, and sponges were used to swab the surface of the plates. The sponges were then composited (into primary enrichments for dry compositing) or the secondary enrichments were composited (for wet compositing). Compositing was conducted with RLW containing 4.13±0.02 log CFU of background microflora. There was no significant difference between the number of samples where L. monocytogenes was detected for BLEB and UVM when comparing dry or wet compositing at any of the composite ratios tested. Results of this thesis will aid in determining if compositing of environmental samples is an option when L. monocytogenes is the target pathogen.
Show less
- Title
- ENHANCING PRIVACY AND SECURITY IN IOT-BASED SMART HOME
- Creator
- Du, Haohua
- Date
- 2019
- Description
-
The IoT-based smart home is envisioned as a system that augments everyone’s daily life. In the past few years, the smart home attracted...
Show moreThe IoT-based smart home is envisioned as a system that augments everyone’s daily life. In the past few years, the smart home attracted immense attention from the industrial organizations and has been considered as one of the principal pillars of the fourth industrial revolution. However, while the rapidly increasing number of Internet-connected smart devices expends the functionalities of smart homes, it also raises substantial security and privacy concerns.Commonly, a smart home system is composed of three major components, smart devices, communication among devices, and smart applications connecting the devices. Thus, this dissertation aims to enhance the security and privacy of the smart home system without weakening its functionalities from the perspectives of these three components. First, I improve the security of smart devices within the smart home by monitoring their behaviors based on the contextual environment. Then, I enhance the security of the communications among the devices through visible light communication, whose receivers have to be physically visible to senders and avoid possible eavesdropping. Finally, I study two popular smart applications – the augmented reality assistant and the cloud-based surveillance system, to discuss how to define privacy, how to reduce the leakage, and how to balance the privacy and security in the smart home. This dissertation proposes the mechanisms for each component, respectively, and it also implements the design in the real-world for evaluating their effectiveness and efficiency.
Show less
- Title
- Kinetic and Structural Characterization of the Vibrio cholerae Flavin Transferase ApbE
- Creator
- Fang, Xuan
- Date
- 2019
- Description
-
Cholera has long been a global concern and in the past decades traditional antibiotic treatments have failed due to the emergence of the...
Show moreCholera has long been a global concern and in the past decades traditional antibiotic treatments have failed due to the emergence of the antibiotic-resistance of its causative agent, V. cholerae. The resistance is mainly supported by a transmembrane electrochemical gradient of Na+ produced by the respiratory complex Na+-NQR coupled with an internal electron transfer pathway. The assembly and function of Na+-NQR is fulfilled by ApbE, the only known flavin transferase which covalently attaches two FMN molecules to the complex as part of its electron transport chain. Hence, ApbE is closely associated with the cause of antibiotic resistance. Because it does not have any human homologues, ApbE becomes an excellent drug target. In this work, we have investigated the physical properties of the enzyme and clarified its substrate specificity and pH dependence. For instance, our experiments indicate that divalent cations are essential for ApbE function, and that the selectivity depends largely on the size and the coordination sphere of the cation. Our data also show that ApbE regulation by pH, ADP and potassium is an important mechanism that enhances the adaptation, survival and colonization of V. cholerae in the small intestine. Moreover, pH dependence, mutagenesis, and steady-state kinetic studies have led us to identify the conserved His257 as a residue with dual roles: substrate binding and catalysis. Furthermore, bi-substrate kinetic studies have also revealed that ApbE follows a random Bi Bi mechanism. Together with structural studies, we propose a reaction mechanism where His257 functions as a base, shedding light into the understanding of the ApbE family.
Show less
- Title
- DIAGNOSING AND TREATING ADHD: CLINICIAN CHARACTERISTICS, METHODS OF DIAGNOSIS, DIAGNOSTIC RATES, AND TREATMENT RECOMMENDATIONS
- Creator
- Haak, Christopher Luke
- Date
- 2019
- Description
-
Attention-deficit/hyperactivity disorder (ADHD) is one of the top five most common referrals among all neuropsychologists (Sweet et al. 2015)...
Show moreAttention-deficit/hyperactivity disorder (ADHD) is one of the top five most common referrals among all neuropsychologists (Sweet et al. 2015) and continues to elicit public and professional concern about over-diagnosis in children (Sciutto & Eisenberg, 2007) and under-diagnosis in adults (Asheron et al., 2012; Kooji et al., 2010). In recent years, the prevalence of ADHD has increased (Polanczyk et al., 2007 & 2014, Thomas et al., 2015). It is unclear what is driving these changes though changes in criteria may be playing a role (van de Voort et al., 2014). Further, there has been little research on whether professional training, beliefs, and practice factors can influence the likelihood to diagnose ADHD. The purpose of this study was to examine the extent to which neuropsychologists’ professional characteristics, training, and beliefs about ADHD diagnosis and treatment influence their likelihood to diagnose ADHD. The study also evaluated whether there are differences in assessing and treating ADHD based upon the client population focus (child, lifespan, or adult) of neuropsychologists. Participants in this study were 106 neuropsychologists from across the United States and Canada who were recruited through neuropsychology listservs to participate in an online survey. Results indicated that population focus was associated with significant differences in approach to diagnosing and treating ADHD, with child- and lifespan-focused neuropsychologists reporting higher rates of ADHD diagnosis. Additionally, having a higher percent of clinical cases in which ADHD is a referral question and greater self-reported adherence to following full diagnostic criteria for making a diagnosis were associated with higher ADHD diagnostic rates, controlling for age, gender, ethnicity, and other professional characteristics. This study is among the first to examine specific clinician factors impacting diagnostic rates and its findings have several implications for practice and research.
Show less
- Title
- WIND MICRO-CLIMATE CONFORMATION IN HOT DRY CITIES; RIYADH
- Creator
- Alhawsah, Saeed Idris
- Date
- 2019
- Description
-
Recently, the transformation in urban development in Saudi Arabia has caused abrupt and sporadic change to its desert climate. Careful...
Show moreRecently, the transformation in urban development in Saudi Arabia has caused abrupt and sporadic change to its desert climate. Careful environmental consideration of vernacular architecture practices is lost by the vast modernization. The significant changes of modernization contain desertification, sand rapping due to massive urban construction, and urban heat islands, all that has created a severe issue with sandstorms. Saudi’s modernization changed sandstorms phenomena from its seasonal occasions to a frequent rapid increase as a result of the urban inability to maintain its naturally mild and soothing condition. All the global incidents from the natural refugees in Gobi Desert, China, to the 1930s U.S. dustbowl are evident to the urban environmental disturbance. This research is an environmental investigation to reduce the sandstorm effects in Saudi Arabia through designing multiple territorial landscape interventions to filter out the sandstorms and trap its sediments to avoid reoccurring sandstorms.
Show less
- Title
- Wireless Body Sensor Network for Tracking Human Mobility using Long Short-Term Memory Neural Network for Classification
- Creator
- Gupta, Saumya
- Date
- 2019
- Description
-
A large number of sensors are used without justification of the number chosen or placement choice. Many papers about body sensor networks...
Show moreA large number of sensors are used without justification of the number chosen or placement choice. Many papers about body sensor networks explore how to capture a type or types of motion, but all their sensors are placed in different locations; making their algorithms very specific to that movement. In this research, we explore the enhancement of human activity classification algorithm using long short-term memory (LSTM) neural network and wearable sensor network. There are five identical nodes used in the body sensor network to collect data. Each node incorporates an ESP8266 Microcontroller with Wi-Fi which is connected to an inertial measurement unit consisting of triple axis accelerometer and gyroscope sensor board. An analysis on the accuracy that each sensor node provides separately and in different combinations has been conducted to allow future research to focus their positioning in optimal positions. A Robot Operating System (ROS) central node is used to illustrate the in-built multi-threading capability. For demonstration, the positions chosen are waist, ankles and wrists. The raw sensor data can be observed on screen while it is being labelled live to create fitting dataset for developing an artificial neural network. Expectation is that increasing the number of sensors should raise the overall accuracy of the output but that isn’t the case observed, positioning of the sensor is pertinent to improvement. These platforms can be further extended to understand different motions and different sensor positions, also expanded to include other sensors.
Show less
- Title
- Generalized Fréchet Bounds for Cell Entries in Multidimensional Contingency Tables, Special Volume in honor of memory of S.E.Fienberg
- Creator
- Richards, Donald, Uhler, Caroline
- Description
-
We consider the lattice, L, of all subsets of a multidimensional contingency table and establish the properties of monotonicity and...
Show moreWe consider the lattice, L, of all subsets of a multidimensional contingency table and establish the properties of monotonicity and supermodularity for the marginalization function, n(·), on L. We derive from the supermodularity of n(·) some generalized Fr ́echet inequalities comple- menting and extending inequalities of Dobra and Fienberg. Further, we construct new monotonic and supermodular functions from n(·), and we remark on the connection between supermodularity and some correlation inequalities for probability distributions on lattices. We also apply an inequal- ity of Ky Fan to derive a new approach to Fr ́echet inequalities for multidimensional contingency tables.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Maximal Length Projections in Group Algebras with Applications to Linear Rank Tests of Uniformity
- Creator
- Bargagliotti, Anna E., Orrison, Michael
- Description
-
Let G be a finite group, let CG be the complex group algebra of G, and let p ∈ CG. In this paper, we show how to construct submodules S of CG...
Show moreLet G be a finite group, let CG be the complex group algebra of G, and let p ∈ CG. In this paper, we show how to construct submodules S of CG of a fixed dimension with the property that the orthogonal projection of p onto S has maximal length. We then provide an example of how such submodules for the symmetric group Sn can be used to create new linear rank tests of uniformity in statistics for survey data that arises when respondents are asked to give a complete ranking of n items.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Institute of Design sculpture class, Illinois Institute of Technology, Chicago, Illinois, ca. 1956-1969
- Date
- 1956-1969
- Description
-
Photograph of an Insitute of Design Sculpture class in S.R. Crown Hall. Possibly pictured at center is Professor Cosmo Campoli. Photographer...
Show morePhotograph of an Insitute of Design Sculpture class in S.R. Crown Hall. Possibly pictured at center is Professor Cosmo Campoli. Photographer unknown, possibly Reginal Heron. Date of photograph is unknown. Date range listed is approximate.
Show less - Collection
- Office of Communications and Marketing photographs, 1905-1999
- Title
- Connectivity for 3 x 3 x K contingency tables
- Creator
- Sumi, Toshio, 2012
- Description
-
We consider an exact sequential conditional test for three-way conditional test of no interaction. At each time τ, the test uses as the...
Show moreWe consider an exact sequential conditional test for three-way conditional test of no interaction. At each time τ, the test uses as the conditional inference frame the set F(Hτ) of all tables with the same three two-way marginal tables as the obtained table Hτ . For 3 × 3 × K tables, we propose a method to construct F(Hτ) from F(Hτ−1). This enables us to perform efficiently the sequential exact conditional test. The subset Sτ of F (Hτ ) consisting of s + Hτ − Hτ −1 for s ∈ F(Hτ−1) contains Hτ , where the operations + and − are defined elementwise. Our argument is based on the minimal Markov basis for 3 × 3 × K contingency tables and we give a minimal subset M of some Markov basis which has the property that F (Hτ ) = {s − m | s ∈ Sτ , m ∈ M}.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Matrix Completion for the Independence Model
- Creator
- Kubjas, Kaie, Rosen, Zvi
- Description
-
We investigate the problem of completing partial matrices to rank-one matrices in the standard simplex ∆mn−1. The motivation for studying this...
Show moreWe investigate the problem of completing partial matrices to rank-one matrices in the standard simplex ∆mn−1. The motivation for studying this problem comes from statistics: A lack of eligible completion can provide a falsification test for partial observations to come from the independence model. For each pattern of specified entries, we give equations and inequalities which are satisfied if and only if an eligible completion exists. We also describe the set of valid completions, and we optimize over this set.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- One example of general unidentifiable tensors
- Creator
- Chiantini, Luca, Mella, Massimiliano, Ottaviani, Giorgio
- Description
-
Abstract. Theidentifiabilityofparametersinaprobabilisticmodelisacrucialnotioninstatistical inference. We prove that a general tensor of rank 8...
Show moreAbstract. Theidentifiabilityofparametersinaprobabilisticmodelisacrucialnotioninstatistical inference. We prove that a general tensor of rank 8 in C3 ⊗ C6 ⊗ C6 has at least 6 decompositions as sum of simple tensors, so it is not 8-identifiable. This is the highest known example of balanced tensors of dimension 3, which are not k-identifiable, when k is smaller than the generic rank.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Hilbert Polynomial of the Kimura 3-Parameter Model, AS2012 Special Volume, part 1: This issue includes a second series of papers from talks, posters and collaborations resulting from and inspired by the Algebraic Statistics in the Alleghenies Conference at Penn State, which took place in July 2012.
- Creator
- Kubjas, Kaie, inspired by the Algebraic Statistics in the Alleghenies Conference at Penn State, which took place in July
- Description
-
In [2] Buczyn ́ska and Wi ́sniewski showed that the Hilbert polynomial of the algebraic variety associated to the Jukes-Cantor binary model on...
Show moreIn [2] Buczyn ́ska and Wi ́sniewski showed that the Hilbert polynomial of the algebraic variety associated to the Jukes-Cantor binary model on a trivalent tree depends only on the number of leaves of the tree and not on its shape. We ask if this can be generalized to other group-based models. The Jukes-Cantor binary model has Z2 as the underlying group. We consider the Kimura 3-parameter model with Z2 × Z2 as the underlying group. We show that the generalization of the statement about the Hilbert polynomials to the Kimura 3-parameter model is not possible as the Hilbert polynomial depends on the shape of a trivalent tree.
Show less - Collection
- Journal of Algebraic Statistics
- Title
- Institute of Design faculty members, Illinois Institute of Technology, Chicago, Illinois, ca. 1976
- Date
- 1976
- Description
-
Photograph of Institute of Design faculty members (left to right) John Grimes, John Askwith, James Montague, Len Singer, Robert Graeff, David...
Show morePhotograph of Institute of Design faculty members (left to right) John Grimes, John Askwith, James Montague, Len Singer, Robert Graeff, David Rathbun, Arthur Siegel, and Ken Biasco. Photographer unknown. Date of photograph is unknown. Date range listed is approximate, based on this photograph's use in the 1976 edition of Integral, the Illinois Tech yearbook.
Show less - Collection
- Office of Communications and Marketing photographs, 1905-1999
- Title
- Mathematics of Civil Infrastructure Network Optimization
- Creator
- Rumpf, Adam Andrew
- Date
- 2020
- Description
-
We consider a selection of problems from civil infrastructure network design that are of great importance in modern urban planning but have,...
Show moreWe consider a selection of problems from civil infrastructure network design that are of great importance in modern urban planning but have, until relatively recently, gone largely ignored in mathematical literature. Each of these problems is approached from the perspective of network optimization-based modeling, with a major focus placed on the development of efficient solution algorithms.We begin with a study of the phenomenon of interdependent civil infrastructure networks, wherein the functionality of one network (such as a telecommunications system) requires the input of resources from another network (such as the electrical power grid). We first consider a linear relaxation of an established binary interdependence minimum-cost network flows model, including its unique modeling applications and its use as part of a randomized rounding approximation algorithm for the mixed integer model. We also develop a generalized network simplex algorithm for the efficient solution of this generalized minimum-cost network flows problem. We then move on to consider a trilevel network interdiction game for use in planning the fortification of interdependent networks subject to targeted attacks. A variety of solution algorithms are developed for both the binary and the linear interdependence models, and the linear interdependence model is used to develop an approximation algorithm for the more computationally expensive binary model.We then develop a public transit network design model which incorporates a social access objective in addition to traditional operator cost and user cost objectives. The model is meant for use in planning minor modifications to a public transit network capable of improving equity of access to important services while guaranteeing that service levels remain within a specified tolerance of their initial values. A hybrid tabu search/simulated annealing algorithm is developed to solve this model, which is then applied to a test case based on the Chicago public transit network with the objective of improving equity of primary health care access across the city.
Show less
- Title
- A Risk-Based Approach in Selecting Design Natural Hazard Loads for Temporary Structures
- Creator
- Saleh, Eman
- Date
- 2020
- Description
-
Temporary structures are systems that are used for short period applications such as in maintenance and retrofit applications or for staged...
Show moreTemporary structures are systems that are used for short period applications such as in maintenance and retrofit applications or for staged performances. Examples of its applications are tents, scaffoldings, and other facilities that have a short service life. Structures under construction and structures under serviceability conditions also fall under this category of structures; because their service time period is only limited to the duration of the construction, which is much shorter than the lifetime of the finished structure. One of the main characteristics of these types of structures is their high vulnerability to stability. Most specifications rarely cover temporary structures. Designing these structures to appropriate levels of the dead and live load does not impose an issue, in which using the same load factors as in permanent structures is considered a reasonable choice. However, an issue is raised when choosing the appropriate wind, seismic and snow load levels, where using the same exposure levels as in permanent structures may not be a desirable economic decision. Thus, for temporary structures, it makes sense to reduce the extreme event design loads proportional to the intended design life. In this manner, it is imperative to have specific rules or guidelines that would address the design aspects and reliability of these structures especially against lateral loads such as wind and earthquakes. This study aims at establishing several decision-making processes that could help contractors, designers, and erectors of temporary works to decide upon safety factors and/or return periods for environmental loads, with emphasis on the wind load. This decision-making process can be used in temporary projects (e.g., bridge erecting) to establish a design criterion based on the nature of the project. The study shows that the optimal decision-making process depends on the willingness to take advantage of wind locality characteristics (e.g., seasonality factor) in certain construction period or region, type of information available for the decision-maker (i.e., precise or imprecise), the risk associated with the constructed facility or the temporary structure itself, a potential for recourse actions, and the decision-maker’s attitude toward the trade-off between losses and gains with respect to uncertainty. The suggested decision-making process proposed is Bayesian decision process, the fuzzy decision process; (3) a two-stage stochastic programming solution; and (4) case-based decision theory. Several practical examples are presented in this thesis to show how different situations may require varying decision-making processes in order to reach the optimal decision. The design of temporary structures can be altered in response to a forecasted hurricane; thus, we propose a three-stage stochastic programming solution to decide upon their optimal wind design load. In addition, we extend the hurricane catastrophe models for application in temporary structures. This enables contractors to forecast the hurricane losses as a basis for estimating the adequate catastrophe cover such as insurance premiums and reinsurance for temporary structures. This scheme is then illustrated in an example for deciding the required temporary bracings for a steel frame under construction during the hurricane season.To prevent temporary structures from collapse, it is important to investigate the performance quality of previous projects and remove any causes for potential mishaps. This can be done by continuous monitoring of different projects and an investigation of accidents, if any, to help prevent future failures. In this study, we use an audit evidence scheme based on commonly available evidence theories used in the construction industry. In one such theory, the evidence is represented via a tree structure, in which the propagation is toward the variables that represent the project as a whole and separate work packages within a project. For simplicity, we only consider the binary case of variables i.e. whether or not a project conforms to the quality standards. The formulation of the auditing tool relates belief functions to the assertion of the quality assurance and quality control (QA/QC) measures and provides formulas for human error risk. These formulas provide plausibilities of human error in a belief-function format. An auditor may use the belief values to assess the degree of quality performance and to identify the sources of the problem in temporary work. We further illustrate the method in a practical application to evaluate the shoring/reshoring operations for estimating the construction risk in a multistory concrete structure. This evaluation may be used to decide on an appropriate time for formwork removal, shoring/reshoring schedule, casting cycles, post-tensioning sequence, and the required number of reshoring levels given the available evidence. To reduce the computational burden, we describe the shoring/reshoring system as a multi-state system (MSS) where the universal generating function (UGF) was used to estimate the reliability of the system.
Show less