Searching for buried metallic evidence at crime scenes or at potential disposal sites can be a daunting task for forensic personnel. In particular, it is common to search for a small firearm that was discarded or buried by the perpetrator. When performing forensic searches, it is recommended to first use non-invasive methods such as geophysical instruments to minimize damage to evidence and to the crime scene. Geophysical tools are used to pinpoint small areas of interest across a scene that will be invasively tested later. Prior to this project, there was no published research that tested the utility of the conductivity meter to search for metallic weapons such as firearms and blunt or sharp edged weapons. A sample comprised of 32 metallic weapons was buried in a controlled setting to test the applicability of a conductivity meter for forensic searches. Weapons were tested at multiple depths; once data collection was performed for one depth, the weapons were reburied 5cm deeper until they were no longer detected. Results obtained with conductivity meter were compared to results obtained by the ground-penetrating radar using different depths and transect intervals. The effects of several variables on detection such as weapon size, metallic composition, burial depth, and transect interval were analyzed in order to explore the limitations of each instrument. Results obtained from this controlled research can provide guidelines to help law enforcement in real-world searches.

Characterization and assessment of liquefaction potential of gravelly soil in a reliable cost-effective manner has always been a great challenge for the geotechnical engineers. The typical laboratory investigation techniques have proven to be ineffective for characterizing gravelly soil due to the cost and difficulty of extracting undisturbed sample from gravelly deposits. The traditional in-situ tests like SPT or CPT are not very suitable for gravelly soil because of interference with large size gravel particles which can artificially increase the penetration resistance. The Becker Penetration Test, well known for gravelly soil characterization, is cost-prohibitive for routine projects and is not available in most of the world. The Chinese dynamic cone penetration test (DPT) with a larger diameter probe compared to the SPT or CPT, can be economically performed with conventional drilling equipment. Besides the penetration testing, in-situ measurement of shear wave velocity (Vs) is another alternative of characterizing gravel liquefaction. Probabilistic liquefaction triggering curves were developed by performing both DPT and shear wave velocity test at the Chengdu Plain of China where massive gravel liquefaction took place during 2008 Wenchuan earthquake. These curves have significant uncertainty as they were developed from a single event database. As a part of this study, both DPT and Vs tests have been performed at various sites around the world where gravelly soil did or did not liquefy in various past earthquakes. These newly collected data have been added to the existing Chinese dataset to form a large database on gravel liquefaction case histories for both DPT and Vs. Based on this larger database, new magnitude dependent probabilistic liquefaction triggering procedures have been developed for both DPT and Vs. The larger database has significantly improved the triggering curves by reducing the spread and constraining the curves at both the higher and lower end. New Magnitude Scaling Factor (MSF) curves have been developed for both DPT and Vs which were found to be consistent with existing MSF curves. Further, an instructive comparison has been drawn between the performance of CPT and newly developed DPT triggering procedure the liquefaction potential of gravelly deposits CentrePort in Wellington. Results showed that both DPT and CPT performed reasonably well in liquefaction assessment of the gravelly fill. However, the CPT-based CRR profiles contain intermittent spikes due to the interaction with gravel particles whereas the DPT resistance appear to be relatively smooth. Similar comparison has been presented between the DPT and BPT in performing liquefaction assessment of gravelly soil at the Borah Peak sites in Idaho. It is found that both DPT and BPT successfully evaluate the liquefaction potential of the loose critical layers but the medium dense to dense layers are identified as non-liquefiable by the DPT whereas the same deposits are identified as liquefiable by the BPT. Lastly, an investigation has been carried out to observe the effect of hydraulic conductivity and in-situ drainage on the liquefaction triggering in gravelly soils based on field data along with a group of numerical analyses. It is found that the hydraulic conductivity of gravelly soil reduces with sand content which eventually may cause liquefaction during earthquake shaking. Low permeability cap layer may also impede the drainage path to generate excess pore pressure to trigger liquefaction in the gravelly strata.

A new laboratory permeameter was developed for measuring the hydraulic conductivity of gravels ranging from 0.1 to 2 m/s. The release of pneumatic pressure applied to the test specimen induces an underdamped oscillatory response of the water level above the permeameter, similar to an underdamped in situ slug test response in monitoring wells. A closed form model was derived to calibrate the hydraulic minor losses in the permeameter and the hydraulic conductivity of the specimen by performing tests without and with a specimen. The majority of each test series performed on individual specimens produced hydraulic conductivity values within 10% of the average, which is very small for such a measurement. Tests were performed using the permeameter on a collection of subrounded and angular gravels prepared to measured grain size distributions and porosities. The surface area was determined by evaluating the shape and angularity using a method developed in this research and these parameters were used with the measured tortuosity and hydraulic conductivity, to back calculate the packing factor of the Kozeny-Carman equation. The results show that the packing factor for the gravels and materials tested is proportional to the tortuosity cubed. These results provide a valuable update to the Kozeny-Carman equation for predicting the hydraulic conductivity of gravels. Field slug interference tests were performed in pairs of monitoring wells installed at the same elevation in a floodplain deposit of silty sand in Dedham MA. Slug tests were performed in one of the wells while the response was monitored simultaneously in both wells. The measured responses were both analyzed by modifying the KGS model of Hyder et al. (1994) to consider the wellbore storage and filter packs effects. This modification was found to produce estimates of hydraulic conductivity based on the slugged well response that compared well with that estimated based on the observation well's response. Calibrated hydraulic conductivities for the pairs of wells tested ranged from 4x10-6 to 1.5x10-5 m/s and specific storage ranged from 2x10-5 to 7x10-4 m-1.

Molten salts are high-temperature heat transfer fluids intended for cooling and/or storage purposes in a variety of energy applications. The current work seeks to ultimately study the thermophysical properties of fluoride and chloride salts, which are commonly considered for use in advanced nuclear reactors. Thermophysical properties like thermal conductivity are fundamental to ensuring safe, efficient, and competitive designs for advanced commercial nuclear reactors. Measurement challenges with liquid salts such as electrical conduction, corrosion, convection, and thermal radiation have hindered traditional approaches in their attempts to accurately quantify these properties at high temperatures. Here, a needle probe is developed, which modifies principles from existing instrumental techniques in order to experimentally measure the thermal conductivity of molten salts with reduced error. An analytical heat transfer model is developed to characterize 1D radial heat flow in a multilayered cylindrical system. This includes a thin layer of salt located between the needle probe and a crucible to limit natural convection. After being validated with finite-element methods, the needle probe is used to measure the thermal conductivity of several reference liquids, whose thermophysical properties are well-established at low temperatures. These seven samples are water, sodium nitrate (molten salt), potassium nitrate (molten salt), toluene, ethanol, propylene glycol, and galinstan. The needle probe was able to accurately measure thermal conductivity between 0.40-0.66W/mK for these samples with 3.5-10% uncertainty. Three eutectic halide molten salts (presented by molar composition) were selected for high-temperature testing. These include the ternary fluorides LiF(46.5%)-NaF(11.5%)-KF(42%) and NaF(34.5%)-KF(59%)-MgF2(6.5%), as well as the binary chloride NaCl(58.2%)-KCl(41.8%). Because testing temperatures range between 500-750C, the governing model is adapted to account for radiative heat transfer through the salt sample in parallel with conductive heat transfer. Improvements to the experimental apparatus are also made. For all three salts, the needle probe accurately measured thermal conductivity between 0.490-0.849W/mK with total uncertainty generally being less than 20%. A linear fit to the data demonstrates a clear negative relationship between thermal conductivity and an increase in temperature, which agrees with theoretical and computational predictions. These results indicate that the needle probe successfully handles the assortment of measurement challenges associated with high-temperature molten salts and provides reliable data to create correlations for thermophysical property databases.

Cemented paste backfill (CPB) technology is widely used in the mining industry as an effective means of tailings disposal. CPB is a mixture of tailings, binder, water, and additional admixtures when required. It is prepared in a mixing plant on the ground surface and then transported into the mine cavities through pipelines either by gravity and/or using pumps. To ensure efficiency during transportation and avoid pipe clogging (which can cause unnecessary delays and loss of productivity), fresh CPB must have sufficient flowability. To achieve that, high-range water reducing admixtures, also known as superplasticizers, are usually added to the CPB during mixing. These admixtures are widely used in the construction industry due to their ability to improve flowability without undermining other important engineering properties. However, their influence on the rheology, mechanical strength and environmental performance (reactivity and permeability) of CPB is not fully understood. Thus, experimental studies were conducted to investigate the effects of superplasticizers on the performance properties of cemented paste backfill at different curing temperatures. Yield stress and viscosity of fresh CPB cured for 0, 1, 2, and 4 hours were measured using a vane shear device and a Brookfield Viscometer respectively. Unconfined compressive strength (UCS) of samples cured for 1, 3, 7, and 28 days was determined in accordance with ASTM - C39. Superplasticizer contents were varied as 0%, 0.125%, and 0.25% of the total weight of the CPB. Preparations and curing of the specimens were performed at controlled conditions of 2, 20, and 35 °C to investigate the effect of ambient or curing temperatures. To have a better understanding of the environmental performance of CPB containing superplasticizer, reactivity, and hydraulic conductivity up to 90 days of curing were also investigated. The reactivity was measured using oxygen consumption test while hydraulic conductivity was measured using flexible wall permeability test. Microstructural analyses (thermogravimetric analyses, X-Ray diffraction, and mercury intrusion porosimetry) and monitoring tests (pH, zeta potential, electrical conductivity, and matric suction) were carried out to understand the principles behind the changes of the observed properties. The obtained results show that superplasticizer dosage and temperature variation have significant effects on the rheology, strength development, hydraulic conductivity and reactivity of the CPB. The polycarboxylic ether-based superplasticizer significantly reduces the yield stress and viscosity by creating strong electrostatic repulsion between the solid particles in the CPB and by steric hinderance. The CPB containing the superplasticizer remains fluid for longer period (as compared with the CPB without superplasticizer) due to the retardation of binder hydration. However, high curing temperature induces faster cement hydration, which thickens the fresh CPB. The unconfined compressive strength (UCS) of the CPB containing superplasticizer was observed to be lower in the early age (up to 7 days), which is also attributed to retardation of the binder hydration. At later ages, the superplasticizer improves the mechanical strength as the binder hydration accelerates and the solid particles self-consolidate. Coupled THMC processes in the CPB showed the role played by the changes in electrical conductivity, volumetric water content, matric suction, and temperature on the development of mechanical strength of the CPB containing superplasticizer. Similarly, addition of the superplasticizer in the CPB decreases both the hydraulic conductivity and reactivity of CPB, thus improving its environmental performance. The improvement is largely attributed to enhanced binder hydration and self-consolidation which decrease the porosity of the CPB. Increasing the curing temperature was found to magnify the improvement of the CPB properties by inducing faster binder hydration. The findings from this study will undoubtedly inform the design of CPB structure with better mechanical stability and environmental performance.

High resolution solid state 1H NMR is used to investigate proton mobility of Nafion, Sulfonated Polyether Ether Ketones(S-PEEK) and their composites, which provides better understanding of their proton conductivities. Proton exchange between sulfonic acid groups and water was observed in these materials. The proton mobility is dependent on both the temperature and the water content. Variable temperature experiments were used to determine the activation energy for proton transportation which generally increases with decrease in hydration level. The preparation of Nafion/SiO2 composites can cause large difference in proton diffusion coefficients and proton conductivities in dried states. This indicates that the amount of dopants needs to be optimized to minimize the blocking of proton diffusion pathways by dopant particles. Detailed information on the control of surface hydroxyl groups in Nafion/SiO2 is obtained through the combination of 29Si and 1H NMR. Although hydrated Nafion/ZrP composites show reduced proton activation energy, they present lower proton conductivity at 35°C than unmodified Nafion. For composites dried at 160°C, both the conversion of monohydrogen phosphate into pyrophosphate and the protonation of monohydrogen phosphate have been observed, which could be one of reasons for the decreased proton conductivity after rehydration. Under high humidification, a single or multiple sulfonic acid proton environments was observed in S-PEEKs, which explains the small proton conductivity difference between some of S-PEEKs. However, the observed conductivity difference for S-PEEKs cast from different solvents was attributed to distinct mobilities of polymer chains. In the crosslinked S-PEEK, not all the crosslinkers of ethylene glycol are fully crosslinked. Proton exchange between residual sulfonic acid and hydroxyls of the crosslinker was observed, which is the primary reason that the crosslinked S-PEEK, with very low residual degree of sulfonation (13 %), still shows proton conductivity comparable to those of S-PEEKs. / Thesis / Doctor of Philosophy (PhD)

Quantum conductance is a phenomenon associated with nanowires / quantum point contacts where the current through a wire is quantized. Experiments have shown that this phenomenon can be manifested at room temperature using macroscopic wires. This project is aimed to recreate these experiments with emphasis on simplicity. By briefly contacting gold wires and measuring the current using an oscilloscope, current quantization can occasionally be seen as the contact breaks.

This thesis documents research done for a transient hot wire system that will be used in future thermal conductivity measurements of molten salts. Research done with molten salts have been limited because of erroneous measurement capabilities, but the current research strives to introduce a new technique to accurately record thermal conductivity over a wide range of temperatures. This work follows up on past transient hot wire researchers whose designs and tests produced an instrument that can measure the thermal conductivity of molten metals up to 750 K. The transient hot wire (THW) technique has been selected to be used in molten salt to derive thermal conductivity values. While running a THW test in molten salts is outside the scope of this thesis, a modular system has been created for the use of running transient hot wire test that allows for a robust and repeatable testing. A PEGDA/galinstan sensor is used for the validation of the system. A robust GUI has been created to automate the experimental procedure in a glovebox environment. The inverse finite element method has been paired with a non linear fit script to optimize calculations and reduce run times. Test have been done to determine the thermal conductivity of PEGDA. The overall uncertainty of the thermal conductivity measured with the PEGDA sensor is estimated to be ±5% at a 95% confidence level. With a THW system implemented and validated a sensor has been designed to work in molten salts. A model has been created in two separate FEA programs to validate design changes and material properties. The sensor is made up of a chemical vapor deposition (CVD) diamond substrate and tungsten wires to overcome corrosion and heat challenges introduced when measuring molten salts. New manufacturing processes have been designed to allow the technique to use these materials in the THW sensor design. The selected material properties of the sensor and extensive finite element work have laid down the ground work for future experimentation and understanding of the thermal properties of molten salts. It is predicted that the CVD diamond (carbide) apparatus design will use the THW techniques to operate with an estimated accuracy of ±3% over a wide range of temperatures, from ambient up to 1200 K. Manufacturing of the diamond-tungsten sensor have proven the viability of depositing tungsten wire onto CVD diamond and growing a secondary layer of CVD diamond over the tungsten wire.

Laser powder bed fusion (LPBF), one of the most promising additive manufacturing (AM) techniques, has enabled the production of previously impossible structures. This breakthrough in AM has not only facilitated the creation of new designs, but also the redesign of existing industrial and engineering components to produce lightweight and highly efficient dies and molds, biomaterial scaffolds, aircraft brackets, heat sink and heat exchangers. In many of the mentioned applications in industries such as automotive, aerospace, heat exchanger, and electronics, aluminum (Al), Al alloys, and Al matrix composites (AMCs) are considered potential candidates. In the first phase of this study, the optimum powder particle size and size distribution of an Al alloy powder (i.e., AlSi10Mg) was determined with the aim being to achieve highest densification levels and dimensional accuracies. In the second phase, three materials with high thermal conductivities were selected, namely, pure Al, AlSi12 and AlSi10Mg alloys. Since Al/Al alloys are prone to oxidation, the LPBF process parameters were optimized not only in terms of the densification level but also oxygen content of the fabricated parts. It was found out that the rate of oxide diminishment for Al/Al alloys during the LPBF process is more than in-situ oxidation. Despite the efforts, the optimized LPBF fabricated samples showed lower thermal conductivity than their conventionally manufactured counterparts. To tackle the issue, two different potential solutions were put into test. In the third phase, the influence of preheating on thermal properties of pure Al, AlSi12, and AlSi10Mg was investigated and a huge improvement in the thermal conductivity of the optimized as-built parts was obtained. In the fourth phase, the possibility of enhancing thermal conductivity of the LPBF fabricated Al/Al alloys in as-built condition through the incorporation of a second constituent with a higher thermal conductivity (i.e., graphene) was investigated. / Thesis / Doctor of Philosophy (PhD)

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第24149号 / 人博第1052号 / 新制||人||246(附属図書館) / 2022||人博||1052(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 吉田 鉄平, 准教授 松井 敏明, 教授 林 晃敏 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM