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Development of Un-Tensioned Pullout Tests to Determine the Bond Quality of Prestressing Reinforcements Used in Pretensioned Concrete Railroad Ties
Get PDFAn experimental program was conducted at Kansas State University (KSU) to evaluate the bond characteristics of prestressing wires and strands used in the manufacture of pretensioned concrete railroad ties. Un-tensioned pullout tests were conducted using both concrete and mortar mediums. The effect of prestressing steel surface condition on bond was evaluated by testing the bond in both the as-received and cleaned condition. A pullout test was developed (and subsequently adopted as ASTM A1096) that can be used to determine the bond quality of prestressing wires that are are in pretensioned concrete members. The pullout test specimens consist of a 4 in. outer-diameter tube with a total length of 8 in. and a steel plate welded to the tube bottom. An un-tensioned wire is held concentrically in the tube while a sand-cement mortar mixture is placed and allowed to cure. Specimens are tested when compressive strength of the mortar is between 4500 and 5000 psi. Pullout test results had excellent correlation with transfer lengths of similar wires when used to manufacture pretensioned concrete railroad ties
Simple model for sequential multiphoton ionization by ultraintense x rays
Get PDFA simple model for sequential multiphoton ionization by ultraintense x rays is presented. The derived scaling of the ion yield with pulse energy quantitatively reproduces the experimental data, which shows that the ion yield increases according to the “power-law” behavior typical of multiphoton ionization, followed by saturation at high pulse energies. The calculated average time interval between ionizations for producing ions at a certain charge state is found to be proportional to the pulse duration and independent of all other x-ray pulse parameters. This agrees with previous studies where the kinetic energy of fragment ions with a given charge state produced by the intense x-ray ionization of molecules was found to be independent of the pulse energy, but to increase with a smaller pulse duration due to the smaller time interval between ionizations
Precise multispecies agricultural gas flux determined using broadband open-path dual-comb spectroscopy
Get PDFAdvances in spectroscopy have the potential to improve our understanding of agricultural processes and associated trace gas emissions. We implement field-deployed, open-path dual-comb spectroscopy (DCS) for precise multispecies emissions estimation from livestock. With broad atmospheric dual-comb spectra, we interrogate upwind and downwind paths from pens containing approximately 300 head of cattle, providing time-resolved concentration enhancements and fluxes of CH4, NH3, CO2, and H2O. The methane fluxes determined from DCS data and fluxes obtained with a colocated closed-path cavity ring-down spectroscopy gas analyzer agree to within 6%. The NH3 concentration retrievals have sensitivity of 10 parts per billion and yield corresponding NH3 fluxes with a statistical precision of 8% and low systematic uncertainty. Open-path DCS offers accurate multispecies agricultural gas flux quantification without external calibration and is easily extended to larger agricultural systems where point-sampling-based approaches are insufficient, presenting opportunities for field-scale biogeochemical studies and ecological monitoring
The Role of Economics in the Fight Against Climate Change
Get PDFKirmser Undergraduate Research Award - Individual Non-Freshman category, grand prizeDan KuesterOver the past century, humans have drained our planet’s natural resources and altered its climate through increasing carbon emissions. Efforts to protect the environment and mitigate warming have yielded little progress. This project seeks to provide a starting point for policymakers, academics, and voters alike by applying economic research and principles to climate change. An analysis of the issue reveals that markets fail to incentivize businesses to consider the long-term health of the planet when making decisions. If market deficiencies are to blame for the conditions that cause pollution and global warming, then economics has powerful potential to direct firms toward more environmentally responsible behaviors. With this foundation in mind, the paper identifies three criteria that can be used to evaluate policy instruments that seek to address climate change. First, policies must force firms to account for the environmental cost of their emissions. Second, policies must incentivize the innovation of more sustainable business practices. Finally, policies should not be so complex or heavy-handed that it is impossible to raise the political support needed to enact them. These criteria are applied to four major policy tools: command and control approaches, information disclosure programs, emissions trading systems, and pollution taxes. In each case, this paper reviews the economic debate on the policy option and examines the varying degrees of scope and success achieved by these policies when implemented. Carbon taxes are identified as a particularly promising candidate for reducing emissions on a large scale. The project concludes by emphasizing that well-designed policy action by wealthy nations, especially the U.S., is critical to stopping climate change and protecting the planet
In search of new identities: the DOD and CIA from the end of the Cold War through the Global War on Terror
Get PDFDoctor of PhilosophySecurity Studies Interdepartmental ProgramMichael KryskoDavid R. StoneSince September 11, 2001, the CIA and DoD have operated together in Afghanistan, Iraq, and during counterterrorism operations. Although the Global War on Terrorism gave the CIA and DoD a common purpose, it was actions taken in the late eighties and early nineties that set the foundation for their current relationship. Driven by the post-Cold War environment and lessons learned during military operations, policymakers made intelligence support to the military the Intelligence Community’s top priority. In response to this demand, the CIA/DoD instituted policy and organizational changes that altered the CIA/DoD relationship. While debates over the future of the Intelligence Community were occurring on Capitol Hill, the CIA and DoD were expanding their relationship in peacekeeping and nation-building operations in Somalia and the Balkans.
By the late 1990’s, some policymakers and national security professionals became concerned that intelligence support to military operations had gone too far, weakening the long-term analysis required for strategy and policy development. Despite these concerns, no major changes to either national intelligence organizations or its priorities were implemented. These concerns were forgotten after 9/11, as the United States fought two wars and policymakers increasingly focused on tactical and operational actions. As policymakers became fixated with terrorism and the United States fought in Iraq and Afghanistan, the CIA focused a significant amount of its resources towards global counterterrorism efforts and in support of military operations.
The CIA/DoD operational relationship has led to successes such as the raid that killed Osama Bin Laden, but CIA’s counterterrorism and military support requirements have placed a significant burden on the organization. As the United States’ only independent intelligence organization, the CIA was conceived to separate the collection of intelligence from the institutions that develop and execute policy. The CIA’s increased focus on support to military and counterterrorism operations weakens this separation, reduces its focus on strategic issues, and risks subordination to the DoD. The CIA and DoD are the ones immediately affected by this evolving relationship, but it is policymaker preference for military force and the militarization of foreign policy that has led both organizations down this path
Leading By Example: A Three-Wave Sequential Mixed Method Food Safety Study Item
Get PDFFoodservice employees that fail to adhere to food safety practices may directly introduce pathogens that can cause illness and death. Therefore, the purpose of this study was to explore managerial practices that influence employee’s food safety behaviors, using a two-phase sequential mixed-method approach.
A total of 642 foodservice employees currently working in the United States participated in a survey about food safety knowledge and food safety behavioral intentions. Among these, 263 were invited to answer a set of open-ended qualitative questions, 36 participants responded to the questions, and two participants were selected for in-depth interviews.
The majority of the employees are optimistic about their daily food safety practices. However, cross-analyses noted that the majority of employees failed the quiz regarding basic food safety knowledge. Further analyses documented that time-constraint and lack of managerial role modeling in daily food safety practices can post a considerable threat to maintaining food safety behaviors
Robust Bayesian Variable Selection for Gene-Environment Interactions
Get PDFGene-environment (G×E) interactions have important implications to elucidate the etiology of complex diseases beyond the main genetic and environmental effects. Outliers and data contamination in disease phenotypes of G×E studies have been commonly encountered, leading to the development of a broad spectrum of robust penalization methods. Nevertheless, within the Bayesian framework, the issue has not been taken care of in existing studies. We develop a robust Bayesian variable selection method for G×E interaction studies. The proposed Bayesian method can effectively accommodate heavy-tailed errors and outliers in the response variable while conducting variable selection by accounting for structural sparsity. In particular, the spike-and-slab priors have been imposed on both individual and group levels to identify important main and interaction effects. An efficient Gibbs sampler has been developed to facilitate fast computation. The Markov chain Monte Carlo algorithms of the proposed and alternative methods are efficiently implemented in C++
Divergence and Gene Flow Between Fusarium subglutinans and Fusarium temperatum isolated from maize in Argentina
No full textFusarium subglutinans and Fusarium temperatum are two important fungal pathogens of maize whose distinctness as separate species has been difficult to assess. We isolated strains of these species from commercial and native maize varieties in Argentina and sequenced >28,000 GBS loci to estimate genetic variation in the sample. Our objectives were to measure genetic divergence between the species, infer demographic parameters related to their split, and describe the population structure of the sample. When analyzed together, over 30% of each species’ polymorphic sites (>2,500 sites) segregate as polymorphisms in the other. Demographic modeling confirmed the species split predated maize domestication, but subsequent between-species gene flow has occurred, with gene flow from F. subglutinans into F. temperatum greater than gene flow in the reverse direction. In F. subglutinans, little evidence exists for substructure or recent selective sweeps, but there is evidence for limited sexual reproduction. In F. temperatum, there is clear evidence for population substructure and signals of abundant recent selective sweeps, with sexual reproduction probably less common than in F. subglutinans. Both genetic variability and the relative number of polymorphisms shared between species increase near the telomeres of all 12 chromosomes, where genes related to plant-pathogen interactions often are located. Our results suggest that species boundaries between closely related Fusarium species can be porous and merit further study. Such porosity could facilitate unanticipated genetic exchange between species and enable quicker permanent responses to changes in the agro-ecosystem, e.g., pathogen-resistant host varieties, new chemical and biological control agents, and agronomic practices
Control of electron recollision and molecular nonsequential double ionization
Get PDFIntense laser pulses lasting a few optical cycles, are able to ionize molecules via different mechanisms. One such mechanism involves a process whereby within one optical period an electron tunnels away from the molecule, and is then accelerated and driven back as the laser field reverses its direction, colliding with the parent molecule and causing correlated non-sequential double ionization (NSDI). Here we report control over NSDI via spectral-phase pulse shaping of femtosecond laser pulses. The measurements are carried out on ethane molecules using shaped pulses. We find that the shaped pulses can enhance or suppress the yield of dications resulting from electron recollision by factors of 3 to 6. This type of shaped pulses is likely to impact all phenomena stemming from electron recollision processes induced by strong laser fields such as above threshold ionization, high harmonic generation, attosecond pulse generation, and laser-induced electron diffraction
Analysis of THz generation by multicolor laser pulses with various frequency ratios
Get PDFTerahertz (THz) generation in a gas medium is simulated by quantum calculations with multicolor intense laser pulses of various frequency ratios. By correlating THz radiation with the above-threshold-ionization photoelectron spectrum, we confirm that our previously proposed free-free transition model for the generation of THz radiation is also applicable to multicolor pulses. THz photon emissions can proceed through transitions between continuous states with similar energies that have opposite parities. This mechanism predicts that THz waves can be efficiently generated at special two-color laser frequency ratios when the multiphoton mixing condition is satisfied. Applying this model to multicolor fields (sawtooth wave shape), we provide a quantum-mechanical interpretation for the reason for THz radiation enhancement. A scheme combining multiple lasers to raise THz radiation satisfying multiphoton mixing conditions is also proposed