Search

Innovations in engineering education are undergoing a noticeable transformation. Higher education institutions are practicing distance education, remote laboratories, studio pedagogies and several other approaches in order to increase their students’ retention, success, and preparedness for the job market. In engineering education, maker spaces have become popular in the last ten years in universities as well as community colleges, high-schools and community innovation hubs. A large number of engineering colleges have allocated significant spaces, and at some universities entire buildings as maker spaces to be used for curricular and extracurricular activities. Success stories of these types of spaces are well documented. This paper describes the activities and programs held at Tennessee Tech University’s maker space called ‘iMakerSpace.’ These accomplishments include several workforce development activities. The impact and effectiveness of the iMakerSpace is evaluated through analysis of survey data.

Innovations in engineering education are undergoing a noticeable transformation. Higher education institutions are practicing distance education, remote laboratories, studio pedagogies and several other approaches in order to increase their students’ retention, success, and preparedness for the job market. In engineering education, maker spaces have become popular in the last ten years in universities as well as community colleges, high schools and community innovation hubs. A large number of engineering colleges have allocated significant spaces, and at some universities entire buildings, as maker spaces to be used for curricular and extracurricular activities. Success stories of these types of spaces are well documented. This paper describes the core activities and programs held at Tennessee Tech University’s maker space called ‘iMakerSpace.’ Accomplishments include several innovative workforce development activities. The impact and effectiveness of the iMakerSpace, presented through workforce innovations and survey statistics, is a unique contribution to this paper. In addition, the modification of operations under COVID-19 pandemic restrictions has resulted in changes that may be carried out post-pandemic.

This paper presents research conducted in modeling specific exposure metrics of communities in the vicinity of public use, nontowered airports to aviation accidents that result in crash sites outside the immediate confines of a runway (termed external airport risk). Two exposure metrics are explored: a relative exposure (termed crash hazard), defined as the probability that a crash site will be located in a specific area if a crash were to occur at an airport, and an absolute exposure (termed crash risk), defined as the expected number of crashes per year within any defined area. Results of this research are presented as a series of choro-pleth maps that define boundaries as contours, within which these metrics exceed some defined threshold. A specific application of this research is presented within the context of a model airport.

Safety of hybrid-electric and fuel cell vehicles is a critical aspect of these new technologies, since any accident exposing occupants of such vehicles to unconventional hazards may result in significant setbacks to successful market penetration. Fuel cell and hybrid-electric drive systems are complex, and it is essential to perform a thorough analysis to determine critical failure conditions. There are several safety concerns for routine operation of such systems, particularly for hydrogen-fueled vehicles. A modified Failure Modes and Effect Analysis (FMEA) has been developed, along with a Criticality Analysis (CrA), to identify potentially hazardous conditions for crash and non-crash situations. A mathematical model of fuel cell operation has been developed and used here in conjunction with the FMEA. Component failures during the event modes are simulated using vehicle models developed with Matlab Simulink tools. Six simulation models were created using the software. In addition, a preliminary finite element model of a fuel cell vehicle, using a Ford Taurus (91′) model year sedan, has been developed and implemented. This finite element model is used as a demonstration of the crash simulation of the vehicle.

technologic, geographic, or regulatory attributes. This paper also discusses the validity of transferring priorities in aviation safety across industry segments (delineated by these same attributes), each of which may have unique hazard and vulnerability exposures. Collectively, this paper discusses the potential for identified aviation safety priorities (which may be biased toward dominant industry segments) to mask unique hazard and vulnerability exposures inherent in emerging aviation markets. This potential biasing of safety priorities becomes a more critical topic when viewed from the perspective of a future commercial aviation industry with a greater reliance on Part 135 commuter- and air-taxi-type operations using nontowered airports under a high-volume operations paradigm. I. Introduction T HIS paper has two purposes. The first is to demonstrate that priorities in aviation safety can be biased toward specific industry segments that may not be fully representative of other subsets of aviation. The second is to demonstrate that establishing safety priorities based on worldwide operations or specific segments of aviation may not be directly applicable to all subsets that cross regional (national or continental), regulatory (Code of Federal Regulations, or CFR, Title 14 Parts 121 and 135), or technological (jet, turboprop, large aircraft, small aircraft, etc.) boundaries. Specifically, this paper demonstrates that safety priorities in domestic commercial aviation operations have been biased to reflect the accident profile of international commercial operations. A metaanalysis of published safety summaries is used to demonstrate the limitations of any assumption that an accident profile of some subset within a global aviation market is correlated to global aviation in the aggregate. The authors consider this review of real vs perceived domestic commercial aviation safety priorities to be a critical factor in forming the perspective that emerging and nascent aircraft operations and aviation markets, such as high-volume operations (HVO) at nontowered airports and the burgeoning air-taxi industry using light and very light jets (VLJ), may have unique hazard and vulnerability exposures relative to more traditional commercial aviation markets. If these emerging industry sectors are not critically analyzed for sector-specific hazards and vulnerabilities, there is a potentialforincreasednumbersandratesofaccidentsasthesesectors grow. Any such increase could lead to subsequent delays in societal acceptance of HVO in the nontowered “community” airport environments and potential delays in the growth of these emerging aviation markets that would directly affect the capacity of the commercial air transport industry in the aggregate as the hub-andspoke infrastructure nears its maximum capacity. This paper first revisits an earlier work by the authors [1] that critically reviewed aviation accident data summaries compiled and released by various governmental, nongovernmental, and quasigovernmentalorganizations[2–6].Inthispreviouswork,theauthors

Results of a scaled experimental study are compared with the predictions produced by the LAVENT and JET computer fire models. As in most large-scale fire testing, characterization of heat release rate (HRR) and accuracy of its measurement creates a lot of uncertainty for validation of these codes. Sensitivity of LAVENT results to the assumed radiative loss of 35% is examined by varying the total HRR which corresponds to varying the convective HRR. Comparisons show that LAVENT uses the wall-jet theory at its core for prediction of the ceiling jet flow and thus does not capture the ceiling jet profile well and overpredicts the upper layer temperature during the development of the layer. The velocity is generally overpredicted since the retardation of the jet momentum by the upper layer does not seem to be modeled accurately. JET has a better user interface and slightly different parameters, but does not provide ceiling jet profiles. The major difference between JET and LAVENT include the ceiling jet temperature and velocity algorithms, the fusible link algorithms, and the use of a variable radiative fraction as a function of fire size and type.

Smooth horizontal and sloped ceiling jets have been studied extensively. The characteristics of these jets, i.e., temperature and velocity profiles, have been defined previously, particularly for horizontal ceilings. The presence of beams and obstructions pose a real challenge for both modeling and detector placement procedures. The present paper reports temperature profiles of ceiling jets for horizontal beamed ceilings, within beamed spaces that do not contain the plume impingement point. Furthermore, these results apply to an unconfined ceiling corresponding to large spaces or long enclosures where the end walls are far away. The research results can be highly useful for prediction of temperature of ceiling jet flows for spaces with continuous beams or joists, but may also be useful for other types of obstructions such as long light fixtures as well as smoke curtains in high bay areas. The correlation developed for temperature distribution within the bays of the beamed ceiling is based on the beam depth to ceiling height and is referenced to the smooth ceiling correlation developed by Motevalli. All data has been obtained from scaled experiments for non-dimensional fire sizes ranging from 0.0024 to 0.035. This range corresponds to fires from 38 kW to 560 kW for a 3 m ceiling height.

Hybrid powertrains with multiple sources of power have generated new control challenges in the automotive industry. Purdue University's participation in EcoCAR 2, an Advanced Vehicle Technology Competition managed by the Argonne National Laboratories and sponsored by GM and DOE, has provided an exciting opportunity to create a comprehensive test-bench for the development and validation of advanced hybrid powertrain control strategies. As one of 15 competing university teams, the Purdue EcoMakers are re-engineering a donated 2013 Chevrolet Malibu into a plug-in parallel- through-the-road hybrid-electric vehicle, to reduce its environmental impact without compromising performance, safety or consumer acceptability.This paper describes the Purdue team's control development process for the EcoCAR 2 competition. It describes the team's efforts towards developing a complete vehicle model of a Parallel-through-the road PHEV which can leverage SIL and HIL simulation platforms for control development. A HIL test-bench was developed for real-time controller testing. The use of parameterized models, a prototyping controller and a unique interfacing philosophy allows the team to transition quickly between the SIL, HIL and vehicle platforms, thus providinga comprehensive test environment for the design and validation of various hybrid supervisory control strategies. Some preliminary data from the team's SIL and HIL simulations has also been presented.

This is work is motivated by the urgent need to find an alternative to the banned halogen-based fire suppressing agents. Fine water mist is a contending alternative especially in total flooding applications. To obtain an optimum design of a water mist fire suppression system, one needs to understand the mechanisms of fire suspension by water mist. This paper presents a study of the relative contributions of the suppression mechanisms in a gaseous diffusion flame. A modified Wolfhard–Parker burner was used to measure temperature drops in a 2D methane diffusion flame, when various quantities of nitrogen, steam and water mist were added independently in a co-flow arrangement. A simple model of the flame was used to estimate the heat generation and loss processes taking place in the flame when small amounts of various suppressants were added. The results of both experiments and the analysis show that in a co-flow arrangement the addition of small quantities of fine water mist has more gas phase cooling effect on the flame than oxygen dilution effect.

A new methodology has been developed for obtaining properties that characterize creeping flame spread over solid materials and for predicting creeping flame spread using these properties. These properties have been reduced to two quantities that are deduced from present measurements or from other tests: the convective energy per unit length. E', from the flame to material near the pyrolysis front and the gaseous thermal length, δg, generated by the opposed flow. The convective energy determines the flame, energy input modified by gaseous chemical kinetics. For fast kinetics, it is independent of the opposed flow velocity. The gaseous thermal length depends on magnitude and profile of the opposed flow velocity. For creeping flame spread at normal gravity conditions, the derived convective energy flux, E', was determined to be 31 W/m for particle board and 97 W/m for PMMA. The thermal length, δg, is 1.36 mm for PMMA and 1.22 for particle board. An additional important contribution of this work is a careful consideration of the effect of external heat fluxes on flame spread, including reradiation losses, acting on the pyrolyzing side of flame front. Neglect of these effects has led to misleading or incomplete interpretation of previous creeping flame spread experiments or test methods.

This paper considers the potential future wherein the General Aviation (GA) infrastructure of airports and aircraft becomes an integral part of the commercial aviation transportation network. Further, this paper discusses inherent individual and societal risks sourced in the very characteristic that makes the GA infrastructure attractive: accessibility and ubiquity. Air traffic controller furloughs, mergers, surface transportation congestion and infrastructure degradation are a few examples of system discontinuities that have led to increased travel time for short and medium air travel (200–500 miles). These, amongst other constraints, are drivers of various initiatives that seek to mitigate these delays via transfer of travel demand from larger towered airport infrastructure to the General Aviation infrastructure via development of aircraft, business plans, operation oversight processes. An example being the nascent air taxi industry coupled with the development of the Very Light Jet designed to operate on 3,000 ft runways. The development of High Volume Operations (HVO) capability in the GA infrastructure (specifically non-towered airports) will subsequently increase risks to communities situated in the vicinity of GA airports via increased potential for accidents. Modeling and understanding these inherent risks in is important if public safety and negative reaction to operational changes, particularly at community airports, is to be avoided; a negative public opinion that could forestall the development of HVO. Similarly, the potential for security threats (i.e. use of aircraft as a missile) from unsecured community airports are greater, but qualitatively less severe than TSA regulated commercial airports. With the potential of 4,000+ additional airports being added to the national commercial air transportation infrastructure, a risk-based allocation of security resources would need to be implemented for efficient allocation of scarce resources.

The current research efforts in airbag modeling are focused on improving airbag deployment and interaction with an out-of-position occupant. This is especially important when other than direct frontal impact is of concern. Thus, the airbag deployment models must address the gas flow dynamics, airbag unfolding and fabric characteristics. This paper discusses the existing capabilities in this field and compares the effect of including gas dynamic details such as inflator jet and airbag unfolding on the deployment predictions. The airbag deployment is simulated using a dynamic model in LS-DYNA3D interacting with a rigid body for 4 different configurations. The simulations were performed on a Silicon Graphics Power Challenge-XL with 10 parallel processors. The analysis shows that the deploying bag may have a much reduced interaction with an occupant positioned oblique to the axis of bag deployment. The inclusion of the inflator jet momentum reveals that it may increase the forces imparted on the occu...

An analog light-scattering-type smoke detector was tested in a wind tunnel at various low velocities. The air flow in the wind tunnel contained an aerosol concentration that resulted in a high ambient optical density, simulating smoke well above threshold optical detector density. The objective of this research was to determine the lag time to alarm, Δt, associated with difficulty of smoke entry into a detector. A “critical velocity” was identified for the smoke detector, below which the lag time increased exponentially with decreasing velocity. Increased lag time results in the detector responding unacceptably late—or not at all—even when ambient obscuration is well above limits defined in UL standard tests.

A methodology for deriving material pyrolysis properties is proposed and validated by using three charring materials (pure cellulose, and two different particle boards designated as N and F). The methodology uses experimental data obtained in a pyrolysis apparatus together with an accurate integral thermal pyrolysis model for the charring pyrolysis process (see CST, 88, 309-328, 1993). The effects of various parameters on pyrolysis rates and surface temperatures are investigated by applying the integral pyrolysis model. This analysis shows that, in addition to the unpyrolyzed (virgin) material thermal properties, char conductivity (kc) and heat of pyrolysis (L) are adequate to describe the transient pyrolysis process for a charring material. The thermal capacity of char is shown to have negligible effects on the pyrolysis process because surface radiation loss from the hot char surface is the dominant mechanism causing the reduction of pyrolysis rates in charring materials. This result, which is ...

The dual mode air-road vehicle is one of those concepts that have intrigued travelers and inventors for a long time. The quest for a vehicle that can be driven on the roads and flown in the sky started as early as the development of airplane by Wright brothers in 1906. With the ever growing traffic and congestion on the roads, increased security procedures at airports and airline hub-spoke system, the travel times for certain range of distances have increased in recent times creating a need for a dual mode vehicle. In the US, for the mid-range distances (200–500 mile), travel options available are limited for other than large population centers. Transportation by train or bus is often limited and involves multi-stops between desired destinations. Therefore, the mid-range travel is more likely accomplished by a car or an airline or sometimes both. Travel by car or airline for this ranged can consumes considerable time because of road, airport and air traffic congestions, security procedures and wait times. A survey published in 2004 by Bureau of Transportation Statistics [1] reveals that 200–500 mile trips account for about 31.8% of the total trips taken in the US. With the premise that a dual mode vehicle could be a potential solution for mid-range travel, particularly around a 300 mile distance, the present work aims at establishing a frame-work and performance envelope for this type vehicle, In other words, the roadable aircraft or the flying car. These vehicles are neither a high performance car nor a high performance aircraft. They are vehicles that have the capability to be driven on the roads and flown in the sky. The present study focuses on identifying the technical, operational and acceptability challenges that have to be overcome to build a dual mode vehicle. This paper also covers some preliminary design aspects like power-fuel requirements, wing-airfoil parameters and an approach to address the road mode issues arising due to the wing.

Transient development of temperature profiles of an unconfined ceiling jet, induced by a constant fire source, are modeled using the Favre-averaged turbulent continuity and energy equations using Prandtl mixing length along with the equation of state. The primary motivation is to examine if one can use existing empirical velocity profiles to obtain temperature profiles, during the transient heating, as well as the vertical component of velocity of the ceiling jet and thus use these transient ceiling jet temperature profiles in room fire models. The numerical predictions show that the approach is promising, however, the agreement with the experimental data (two different heights of 1·0 and 0·5 m) suffers near the ceiling. The numerical results generally under-predict the 1·0 m case and over-predict the 0·5 m case.

Detailed measurements of velocity and temperature in a primary channel of a beamed ceiling are presented in this paper as well as flow spillage under the beams. The data has been used to validate the empirical relation developed by Delichatsios and modify it for use in a more general situation. The primary focus has been to characterize the flow for beam depths that result in a ceiling jet to be in the transition between smooth ceiling jet flow and a corridor flow. As a result of this study, a modified empirical relation to calculate the ceiling jet temperature in a primary channel based on the ceiling heat transfer and the beam to ceiling height ratio has been presented here. The results tend to show that primary channel flow approaches a corridor flow for beam depth higher than 15 % to 20% of the fire to ceiling height.

A methodology and a model are presented for the calculation of radiation distribution from fires. Extensive application of the model is discussed with regard to turbulent buoyant jet fires wherein radiation is controlled by soot and the flame size is such that it produces optically thin conditions. The local soot concentration is modelled, according to previous results, to be 1) proportional to the inverse smoke-point heat release rate, Y,l / ~ , and 2) a function of the local mixture fraction and temperature. The local volumetric emissive power is averaged over the turbulent fluctuations to obtain the radiation losses for optically thin flame situations. Combustion is modelled, in a standard way, by an ensemble of laminar flamelets whose chemical composition of species is known from state relationships. The combustion model is an integral model that has been validated by extensive data from turbulent buoyant jet flames whereas the radiation model is validated here by comparison with propane turbulent jet flames; this comparison allows the determination of a proportionality coefficient for the soot concentration and radiation term. The generality and soundness of the model has been determined by applying it to predict the jet flame radiation from another fuel, propylene (while maintaining the same proportionality constant for the soot as for the propane). Preliminary results and favorable comparisons with experiments are also shown for pool fires of diameter up to 1 m. The proposed methodology and the model can be applied to an arbitrary burning material whose laminar smoke-point heat release rate has been measured in laboratory experiments.

An experimental study of burning of natural gas puffs generated by a fully modulated jet, has been conducted. The present study concentrated on the effects of duty-cycle and puff volume, or equivalently the injection time, on the flame length. It is observed that when individual puffs are well-separated, considerably shorter flame lengths, by as much as a factor of four, are obtained compared to a steady jet flame. Furthermore, the flame length of individual puffs scales with the initial volume of puff, in agreement with the previous studies of buoyant puffs in aqueous media. For a given puff volume, as the duty-cycle is increased beyond a given value, the flame length tends to rise rapidly due to the interaction among neighboring puffs. A dimensionless parameter is found which indicates the transition of puff characteristics.

Effect of obstructions on an unconfined ceiling jet induced by a fire plume has been investigated using small-scale experimental simulations. Parallel beams placed on a ceiling with the ceiling height varied between 0.76 to 1.28 m resulted in a range of beam depth to ceiling height ratio of 0.048 to 0.19. The non-dimensional fire size ranged from 0.003 to 0.027, corresponding to a fire size range of 450 kW to 1160 kW for a 3.5 m ceiling. The results show that the ceiling jet velocity and temperature beyond the obstruction, when normalized by the smooth ceiling jet correlation, can be characterized as a simple function of the ratio of obstruction depth to the ceiling height. The data shows a nearly 80% reduction in the velocity and temperature of the ceiling jet flowing over an obstruction, when compared with the smooth unconfined case, for a beam depth equal to approximately 15% of the fire to ceiling height. It is also shown that a nearly corridor flow condition is attained when the obstruction approache...

Reactions of positive ions known to be present in hydrocarbon flames have been studied for their reactivity toward the fire suppressant CF3Br (Halon 1301) at 300 and 525 K. Rate constants and product branching percentages were measured at the two temperatures. The ions HCO+, CH+3, and CH+5 reacted rapidly with CF3Br producing CF+3 and CF2Br+ in all three cases. For CH+5, proton transfer was also observed at 300K. The ions H2COH+, H3COH+2, and H3O+ were unreactive with CF3Br at 300 and 525 K, and at ≈0.5 eV of collision energy supplied by a drift tube at 300 K. The product ions CF+3 and CF2Br+ were studied in separate experiments for reactivity toward selected hydrocarbons, and rate constants and branching percentages were determined. The hydrocarbons CH4, C2H6, C3H8, C2 H4, C3 H6, and C2H2 were selected for study (CF2] Br+ was studied with CH4, C2 H6, C2 H4, and C2H2 only). Neither CF+3 nor CF2Br+ reacted with CH4, but both ions reacted with other hydrocarbons. Hydrogen fluoride was among the inferred neutral reaction products in the reactions of CF+3 with C2H4 and C3H6. We found no evidence for any ionic process which could release Br atoms, any other free radicals, or the CF3Br+ molecular ion, and therefore no evidence was found to indicate that ions play a role in flame inhibition by CF3Br.

A technique utilizing thermocouple pairs as sensors to measure velocity and temperature profiles in low-speed, turbulent, nonisothermal flows is described here. In this technique, Cross-Correlation Velocimetry (CCV), the temperature-time records from a pair of thermocouples, one downstream of the other, are cross-correlated to determine the flow’s preferred mean velocity while temperature is measured directly. The velocity measurements have undergone extensive verification using hotwire, pitot tube, and Laser-Doppler Velocimetry to determine the degree of confidence in this technique. This work demonstrates that the CCV technique is quite reliable and can measure the mean preferred component of the convective velocity with better than ±5 percent certainty. Application of this technique to the measurement of velocities in a ceiling jet induced by a fire plume is briefly presented here.

Experiments were performed to characterize smoke produced from smoldering materials using light scattering theory. A prototype Scattered Light Detection Instrument (SLDl) was developed to measure the intensity of light scattered at various angles by smoke parti cles. A Gallium Arsenide solid-state laser was used as the source, with photodiodes used as scattered light receivers. A smoke chamber (8.2 m3) was constructed in which to per form experiments using various fuels. Four different fuels — rubber, cotton, douglas fir (wood), and computer printer paper — were burned in the smoldering mode at various positions with respect to the SLDI within the smoke chamber. Experimental data obtained using a test aerosol of known optical properties indicated general agreement with results calculated using Mie scattering theory. Light scattered by smoke particles indicates that the intensity of scattered light at a given angle changes as the fuel changes, consistent with Mie scattering theory. This suggests that an ev...

Combustion using aluminum particles as fuel is an attractive energy source where high energy densities are desired. Very little experimental literature or computational results are available for metal combustion in high-pressure chambers, as most experimental and computational work has been done on chamber operating at near atmospheric pressures. This paper attempts to improve our understanding of metal-fueled combustion chambers at pressures above atmospheric. A numerical model of solid Aluminum fuel particle combustion is developed to investigate the effects of radiation and fuel particle size on the combustion process. Of specific interest are particle specific burn rate, residence time, combustion efficiency, coupled radiation effects, and flame characteristics. This computational model is applied to a linear-type dump combustor. The effects of a range of particle sizes are investigated using mono-dispersed and poly-dispersed particle distributions. Combustion efficiency and characterization of the combustion process are addressed by studying particle ignition delay, surface combustion time, and particle flame radiation intensity as a function of particle diameter and mass fraction. The computational results of this detailed theoretical combustor reveal fundamental physics relating particle sizes and distributions to the variables commonly used to define the effectiveness and performance of the combustion process. The computational models include nonisotropic turbulence models, empirically derived ignition criteria and reaction rates, as well as convective and radiant heat transfer. The numerical results were compared with test data with reasonable agreement.

Development of an upper layer in enclosure fires has a significant effect on the characteristics of the ceiling jet and a direct influence on the placement and performance of fire detection/suppression devices. Detailed transient measurement of ceiling jet velocity and temperature profiles within an upper layer for small-scale fires (2.0 kW and ceiling height of 1 m) are used to analyze the predictions produced by the LAVENT computer fire model. While the model predictions have been compared with large-scale experimental results with fires as large as 33 MW and ceiling height of up to 22m, the large-scale measurements do not have high special resolution and the present work offers a more thorough analysis of the model prediction. Various radiative losses (10–25%) were used to produce predictions that matched the experimental data. Comparison of the small-scale experimental data with the predictions from LAVENT shows that the model, which uses unconfined ceiling jet correlations, does not capture the ceiling jet profile well and over predicts the upper layer temperature during the development of the layer. The peak temperature prediction requires a different radiative loss factor than that which matches the upper layer temperature. In general, the peak temperature measurements are within 10% of the measured value. The velocity is generally over predicted since the retardation of the jet momentum by the upper layer does not seem to be modeled accurately.Copyright © 2003 by ASME

A variable geometry swirl combustor, consisting of four concentric annuli was used to examine the effect of combustor geometry variation on pollutant emission. All annuli, except the central one, were equipped with vane-type swirl generators. Natural gas was used as the fuel. Air and fuel were introduced alternatively into the combustor annuli with the central annul us carrying the fuel. Species concentration measurements using gas chromatography, temperature measurements and NOx gas analysis were conducted to evaluate the combustor performance. Detailed species and temperature measurements were obtained over a radial distance of 1.5 times the combustor exit radius and up to 2.5 diameters down-stream of the combustor. A total swirl number for the combustor was determined from a theoretical formulation. It is shown here that finer control of the local equivalence ratio and air/fuel mixing may be achieved, yielding optimal combustion efficiencies and low pollutant emission, via variation of the combustor geometry.