Rate of Reaction and Order of the Esterification of Propylene Glycol With Acetic Acid

This 18 page thesis examines the determination of order and specific reaction rate of esterification of propylene glycol with acetic acid at forty degrees centigrade

Physical Model Assisted Probability of Detection in Nondestructive Evaluation for Detecting of Flaws in Titanium Forgings

Nondestructive evaluation is used widely in many engineering and industrial areas to detect defects or flaws such as cracks inside parts or structures during manufacturing or for products that need to be inspected while in service. The commonly-used standard statistical model for such data is a simple empirical linear regression between the (possibly transformed) signal response variables and the (possibly transformed) explanatory variable(s). For some applications, such a simple empirical approach is inadequate. An important alternative approach is to use knowledge of the physics of the inspection process to provide information about the underlying relationship between the response and the explanatory variable or variables. Use of such knowledge can greatly increase the power and accuracy of the statistical analysis and enable, when needed, proper extrapolation outside the range of the observed explanatory variables. This paper describes a set of physical model-assisted analyses to study the capability of two different ultrasonic testing inspection methods to detect synthetic hard alpha inclusion defects in titanium forging disks

Pine Tip Moth (Lepidoptera: Tortricidae) Infestation Rates as Influenced by Site and Stand Characteristics in Loblolly Pine Plantations in East Texas

Three young loblolly pine plantations grown on contrasting soil types produced quantitatively and qualitatively different host material for pine tip moths during 1985 and 1986. Amounts, periodicity, and availability of soil moisture regulated internal moisture conditions within host trees. Host xylem moisture potential in conjunction with soil nutrient status governed tree growth and influenced pine tip moth infestation rates. Pines on a sandy site exhibited the poorest growth with lowest infestation rates, indicative of low-quality hosts with little if any tolerance to damage. A clayey site produced vigorous plant growth with moderate infestation rates. The less apparent hosts appeared capable of withstanding pine tip moth attack and overcoming damage. Pines on a loamy site grew at moderate rates and received the highest infestation rates. This moderate growth indicated susceptible stand conditions

Father-son and other farm partnerships

Cover title

Probability of Detection Modeling for Ultrasonic Testing

Ultrasonic (UT) inspection can be used to detect a wide variety of subsurface discontinuities, such as inclusions, cracks and voids, as well as associated reactive or diffusion zones. In comparison with Eddy-Current inspection, much less work has been done on the determination of the Probability of Detection POD of UT inspections. This is because, unlike Eddy-Current inspection, it is very difficult to produce synthetic sub-surface flaws that adequately represent the acoustic properties of the naturally-occurring flaws (see Burkel et al., 1996). Here traditional methods for POD determination are difficult to apply

Methodology for Estimating Nondestructive Evaluation Capability

This paper outlines a proposed methodology for using combinations of physical modeling of an inspection process along with laboratory and production data to estimate Nondestructive Evaluation (NDE) capability. The physical/statistical prediction model will be used to predict Probability of Detection (POD), Probability of False Alarm (PFA) and Receiver Operating Characteristic (ROC) function curves. These output functions are used to quantify the NDE capability. The particular focus of this work is on the use of ultrasonic methods for detecting hard-alpha and other subsurface flaws in titanium using gated peak detection. This is a uniquely challenging problem since the inspection must detect very complex subsurface flaws with significant “material” noise. However, the underlying framework of the methodology should be general enough to apply to other NDE methods

Estimation of stratospheric input to the Arctic troposphere: 7Be and 10Be in aerosols at Alert, Canada

Concentrations of 7Be and 210Pb in 2 years of weekly high-volume aerosol samples collected at Alert, Northwest Territories, Canada, showed pronounced seasonal variations. We observed a broad winter peak in 210Pb concentration and a spring peak in 7Be. These peaks were similar in magnitude and duration to previously reported results for a number of stations in the Arctic Basin. Beryllium 10 concentrations (determined only during the first year of this study) were well correlated with those of 7Be; the atom ratio 10Be/7Be was nearly constant at 2.2 throughout the year. This relatively high value of 10Be/7Be indicates that the stratosphere must constitute an important source of both Be isotopes in the Arctic troposphere throughout the year. A simple mixing model based on the small seasonal variations of 10Be/7Be indicates an approximately twofold increase of stratospheric influence in the free troposphere in late summer. The spring maxima in concentrations of both Be isotopes at the surface apparently reflect vertical mixing in rather than stratospheric injections into the troposphere. We have merged the results of the Be-based mixing model with weekly O3 soundings to assess Arctic stratospheric impact on the surface O3 budget at Alert. The resulting estimates indicate that stratospheric inputs can account for a maximum of 10-15% of the 03 at the surface in spring and for less during the rest of the year. These estimates are most uncertain during the winter. The combination of Be isotopic measurements and O3 vertical profiles could allow quantification of the contributions of O3 from the Arctic stratosphere and lower latitude regions to the O3 budget in the Arctic troposphere. Although at present the lack of a quantitative understanding of the temporal variation of O3 lifetime in the Arctic troposphere precludes making definitive calculations, qualitative examples of the power of this approach are given

Constraints on the age and dilution of Pacific Exploratory Mission-Tropics biomass burning plumes from the natural radionuclide tracer 210Pb

During the NASA Global Troposphere Experiment Pacific Exploratory Mission-Tropics (PEM-Tropics) airborne sampling campaign we found unexpectedly high concentrations of aerosol-associated 210Pb throughout the free troposphere over the South Pacific. Because of the remoteness of the study region, we expected specific activities to be generally less than 35 μBq m−3 but found an average in the free troposphere of 107 μBq m−3. This average was elevated by a large number of very active (up to 405 μBq m−3) samples that were associated with biomass burning plumes encountered on nearly every PEM-Tropics flight in the southern hemisphere. We use a simple aging and dilution model, which assumes that 222Rn and primary combustion products are pumped into the free troposphere in wet convective systems over fire regions (most likely in Africa), to explain the elevated 210Pb activities. This model reproduces the observed 210Pb activities very well, and predicts the ratios of four hydrocarbon species (emitted by combustion) to CO to better than 20% in most cases. Plume ages calculated by the model depend strongly on the assumed 222Rn activities in the initial plume, but using values plausible for continental boundary layer air yields ages that are consistent with travel times from Africa to the South Pacific calculated with a back trajectory model. The model also shows that despite being easily recognized through the large enhancements of biomass burning tracers, these plumes must have entrained large fractions of the surrounding ambient air during transport

Stochastic Modeling of System Function in a Network of Biological Oscillators

Many living organisms have evolved to anticipate daily circadian cycles and changing seasons of their environment. In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus, a brain region of about 20,000 neurons, serves as the master circadian clock coordinating timing throughout the body and entraining to daily external light cycles. The remarkable precision of the SCN clock relies on intercellular signaling. In its absence, each SCN neuron and the SCN as a whole have significantly less stable oscillations. Though there are candidate signaling neuropeptides and anatomical surveys of the SCN, it is still unknown how the SCN as a whole responds to changes in the environment and regulates function in the body. We model the unstable oscillations in individual cells by developing a stochastic model based on the cell clock's gene regulatory network, then investigate the intercellular signaling properties of the SCN to understand its behavior as a whole. Though many existing deterministic models contain details of the gene regulation in the cell, their output has been compared to the behavior of the SCN as a whole, rather than to individual cells. Characterizing properties of individual cells such as period, phase, and synchronization is challenging due to their non-linear and unstable oscillations. We developed a wavelet analysis method to characterize cell behavior in biological experiments and compare with stochastic cell models. This analysis led to an examination of how period distributions could be influenced by stochastic fluctuations in a nonlinear cell oscillator model, and a hypothesis that the poor or strong oscillators observed in biological experiments could be a stochastic oscillator operating near a bifurcation point, between non-oscillatory and oscillatory conditions.It was observed in SCN tissue and in the SCN stochastic model that the oscillator is less likely to shift phase in response to a vasoactive intestinal polypeptide (VIP) dose at circadian time (CT4) than at other times. A reexamination of the behavior of the SCN as a whole, when modeled as linked stochastic oscillators, led to the hypothesis that the cells of the SCN synchronize to each other using a ``phase tumbling'' process. Our hypothesis is that the SCN synchronizes by its cells shifting with a wide phase distribution when they are perturbed at phases not near CT4. Rather than shifting in a deterministic manner, where all the cells stay synchronized and shift together to a new light schedule, they instead temporarily desynchronize then reorganize aligned to the new light/dark cycle. Within a few cycles the system can rapidly shift to a new light schedule. This rapid re-entrainment to both new light/dark and temperature schedules was confirmed in mice by first desynchronizing the SCN using a neuropeptide that has been considered a synchronizing agent, vasoactive intestinal polypeptide, or by a brief bright light exposure before exposing the animals to a new shifted schedule.Finally, since the behavior of the SCN as a whole may depend on the network topology of its intercellular connections, we applied an information theoretic measure to infer pairwise functional connections between neurons in the SCN. We first validated the method on several model networks. After inferring connection networks of three SCN's, we modeled those networks in our stochastic SCN model and confirmed that we could re-infer the bio-inspired networks. We found that the SCN, at least for these experimental samples, appears to have a small-world network topology and is scale-free. We hope that our results have helped to illuminate how stochastic fluctuations in the SCN system contribute to its behavior