Journal articles on the topic 'Eye-safe; lasers; atmospheric measurements'

Abstract. A field-deployable water vapor profiling instrument that builds on the foundation of the preceding generations of diode-laser-based differential absorption lidar (DIAL) laboratory prototypes was constructed and tested. Significant advances are discussed, including a unique shared telescope design that allows expansion of the outgoing beam for eye-safe operation with optomechanical and thermal stability; multistage optical filtering enabling measurement during daytime bright-cloud conditions; rapid spectral switching between the online and offline wavelengths enabling measurements during changing atmospheric conditions; and enhanced performance at lower ranges by the introduction of a new filter design and the addition of a wide field-of-view channel. Performance modeling, testing, and intercomparisons are performed and discussed. In general, the instrument has a 150 m range resolution with a 10 min temporal resolution; 1 min temporal resolution in the lowest 2 km of the atmosphere is demonstrated. The instrument is shown capable of autonomous long-term field operation – 50 days with a > 95% uptime – under a broad set of atmospheric conditions and potentially forms the basis for a ground-based network of eye-safe autonomous instruments needed for the atmospheric sciences research and forecasting communities.

Abstract. A field deployable water vapor profiling instrument that builds on the foundation of the preceding generations of diode-laser-based differential absorption lidar (DIAL) laboratory prototypes has been constructed and tested. Significant advances are discussed, including: a unique shared telescope design that allows expansion of the outgoing beam for eye-safe operation with opto-mechanical and thermal stability, multi-stage optical filtering enabling measurement during daytime bright-cloud conditions, rapid spectral switching between the online and offline wavelengths enabling measurements during changing atmospheric conditions, and enhanced performance at lower ranges by the introduction of a new filter design and the addition of a wide field-of-view channel. Performance modeling, testing and intercomparisons have been performed and are discussed. In general, the instrument has 150 m range resolution with 10 min temporal resolution – 1 min temporal resolution in the lowest 2 km of the atmosphere is demonstrated. The instrument was shown capable of autonomous long term field operation – 50 days with a >95% uptime – under a broad set of atmospheric conditions and potentially forms the basis for a ground-based network of eye-safe autonomous instruments needed for the atmospheric sciences research and forecasting communities.

Abstract. Continuous water vapor and temperature profiles are critically needed for improved understanding of the lower atmosphere and potential advances in weather forecasting skill. Ground-based, national-scale profiling networks are part of a suite of instruments to provide such observations; however, the technological method must be cost-effective and quantitative. We have been developing an active remote sensing technology based on a diode-laser-based lidar technology to address this observational need. Narrowband, high-spectral-fidelity diode lasers enable accurate and calibration-free measurements requiring a minimal set of assumptions based on direct absorption (Beer–Lambert law) and a ratio of two signals. These well-proven quantitative methods are known as differential absorption lidar (DIAL) and high-spectral-resolution lidar (HSRL). This diode-laser-based architecture, characterized by less powerful laser transmitters than those historically used for atmospheric studies, can be made eye-safe and robust. Nevertheless, it also requires solar background suppression techniques such as narrow-field-of-view receivers with an ultra-narrow bandpass to observe individual photons backscattered from the atmosphere. We discuss this diode-laser-based lidar architecture's latest generation and analyze how it addresses a national-scale profiling network's need to provide continuous thermodynamic observations. The work presented focuses on general architecture changes that pertain to both the water vapor and the temperature profiling capabilities of the MicroPulse DIAL (MPD). However, the specific subcomponent testing and instrument validation presented are for the water vapor measurements only. A fiber-coupled seed laser transmitter optimization is performed and shown to meet all of the requirements for the DIAL technique. Further improvements – such as a fiber-coupled near-range receiver, the ability to perform quality control via automatic receiver scanning, advanced multi-channel scalar capabilities, and advanced processing techniques – are discussed. These new developments increase narrowband DIAL technology readiness and are shown to allow higher-quality water vapor measurements closer to the surface via preliminary intercomparisons within the MPD network itself and with radiosondes.

In this paper we present a development of novel algorithms and techniques implemented within the Laser Remote Sensing Laboratory (LRSL) of the National Technical University of Athens (NTUA), in collaboration with Raymetrics S.A., in order to incorporate them into a 3-Dimensional (3D) lidar. The lidar is transmitting at 355 nm in the eye safe region and the measurements then are transposed to the visual range at 550 nm, according to the World Meteorological Organization (WMO) and the International Civil Aviation Organization (ICAO) rules of daytime visibility. These algorithms are able to provide horizontal, slant and vertical visibility for tower aircraft controllers, meteorologists, but also from pilot’s point of view. Other algorithms are also provided for detection of atmospheric layering in any given direction and vertical angle, along with the detection of the Planetary Boundary Layer Height (PBLH).

Abstract The first airborne wind measurements of a pulsed, 2-μm solid-state, high-energy, wind-profiling lidar system for airborne measurements are presented. The laser pulse energy is the highest to date in an eye-safe airborne wind lidar system. This energy, the 10-Hz laser pulse rate, the 15-cm receiver diameter, and dual-balanced coherent detection together have the potential to provide much-improved lidar sensitivity to low aerosol backscatter levels compared to earlier airborne-pulsed coherent lidar wind systems. Problems with a laser-burned telescope secondary mirror prevented a full demonstration of the lidar’s capability, but the hardware, algorithms, and software were nevertheless all validated. A lidar description, relevant theory, and preliminary results of flight measurements are presented.

Abstract A second-generation diode-laser-based master oscillator power amplifier (MOPA) configured micropulse differential absorption lidar (DIAL) instrument for profiling of lower-tropospheric water vapor is presented. The DIAL transmitter is based on a continuous wave (cw) external cavity diode laser (ECDL) master oscillator that is used to injection seed two cascaded tapered semiconductor optical power amplifiers, which deliver up to 2-μJ pulse energies over a 1-μs pulse duration at 830 nm with an average power of ∼40 mW at a pulse repetition frequency of 20 kHz. The DIAL receiver utilizes a commercial 28-cm-diameter Schmidt–Cassegrain telescope, a 250-pm narrowband optical filter, and a fiber-coupled single-photon-counting Avalanche photodiode (APD) detector, yielding a far-field full-angle field of view of 170 μrad. A detailed description of the second-generation Montana State University (MSU) DIAL instrument is presented. Water vapor number density profiles and time–height cross sections collected with the water vapor DIAL instrument are also presented and compared with collocated radiosonde measurements, demonstrating the instruments ability to measure night- and daytime water vapor profiles in the lower troposphere.

AbstractThe performance of a novel water vapor broadband differential absorption lidar (BB-DIAL) is evaluated. This compact, eye-safe, diode-laser-based prototype was developed by Vaisala. It was designed to operate unattended in all weather conditions and to provide height-resolved measurements of water vapor mixing ratio in the lower troposphere. Evaluation of the Vaisala prototype was carried out at the U.S. Department of Energy’s Atmospheric Radiation Measurement site in north-central Oklahoma (i.e., the Southern Great Plains site) from 15 May to 12 June 2017. BB-DIAL measurements were compared with observations from radiosondes that were launched within 200 m of the BB-DIAL’s location. Radiosonde measurements are also compared with observations from a collocated Raman lidar and an Atmospheric Emitted Radiance Interferometer. During the evaluation period, the BB-DIAL operated continuously and did not experience any failures or malfunctions. The data availability was greater than 90% below 900 m but then decreased rapidly with height above this level to less than 10% above 1500 m AGL. From 106 radiosonde profiles, the overall mean difference (averaged temporally and vertically up to 1500 m) between the BB-DIAL and the radiosonde was −0.01 g kg−1, with a standard deviation of 0.65 g kg−1, and a linear correlation coefficient of 0.98. For comparison, the overall mean difference between the Raman lidar and the radiosonde was 0.07 g kg−1, with a standard deviation of 0.74 g kg−1, and a linear correlation coefficient of 0.97.

AbstractA water vapor micropulse differential absorption lidar (DIAL) instrument was developed collaboratively by the National Center for Atmospheric Research (NCAR) and Montana State University (MSU). This innovative, eye-safe, low-power, diode-laser-based system has demonstrated the ability to obtain unattended continuous observations in both day and night. Data comparisons with well-established water vapor observing systems, including radiosondes, Atmospheric Emitted Radiance Interferometers (AERIs), microwave radiometer profilers (MWRPs), and ground-based global positioning system (GPS) receivers, show excellent agreement. The Pearson’s correlation coefficient for the DIAL and radiosondes is consistently greater than 0.6 from 300 m up to 4.5 km AGL at night and up to 3.5 km AGL during the day. The Pearson’s correlation coefficient for the DIAL and AERI is greater than 0.6 from 300 m up to 2.25 km at night and from 300 m up to 2.0 km during the day. Further comparison with the continuously operating GPS instrumentation illustrates consistent temporal trends when integrating the DIAL measurements up to 6 km AGL.

When microscopic-sized liquid droplets travel through a low temperature RF plasma [1] at atmospheric pressure a number of remarkable and unexpected effects have been observed. After a short flight time, ~0.1ms, there is evidence that chemical reactions induced by the plasma and gas flux proceed at a rate that is significantly faster that observed in plasma – bulk liquid studies and many orders of magnitude faster than in standard bulk chemistry.[2] We suspect this is due to the complex interplay between droplet charge, electric fields, both internal and external to the droplet, and high chemical fluxes arriving at the droplet surface. There exists a large potential to develop new plasma-liquid processes for medical, chemical, biological, environmental and materials applications, among others and we can highlight some unique features of the plasma – microdroplet system that may provide opportunities for exploitation, namely: (i) a controlled ambient environment, (ii) a large surface area to volume ratio, (iii) small volume, (iv) low droplet temperature, (v) in-flight chemical synthesis and encapsulation, and (iv) remote delivery. These features offer the possibility of delivering high fluxes of active chemical species and nanoparticles remotely and on demand for applications in, for example, plasma-medicine, agriculture and microreaction while keeping the plasma itself at a safe distance. We have measured reactive oxygen species (ROS) flux variation with distance, up to 150 mm beyond the plasma, along with its effect on bacterial cell viability, DNA and amino acids. We have investigated plasma interactions with single cells, each transported in its own droplet. We have used the individual droplets as chemical microreactors to produce nanoparticles in flight, at rates many orders of magnitude higher that via high energy radiolysis or chemical synthesis. These measurements form the basis for numerical simulation in the gas-plasma and liquid droplet phases. New measurement techniques, based on recently acquired facilities, are being investigated. These include mid-IR absorption studies of droplets and their environment in flight, using tunable supercontinuum and quantum cascade lasers, and freezing plasma-treated droplets in flight for in-situ transfer to XPS surface chemical analysis. Current theories of microparticle charging in a collisional plasma environment are very limited. While in-flight charge measurements represent a significant challenge, the relatively large size of the droplet (10 – 20 μm diameter) and the limited evaporation over the flight time, offer the prospect of using droplets as a spherical probe to develop enhanced collisional probe theories in the regime where the particle size is greater than Debye lengths or mean free paths. In-flight measurements indicate a minimum net charge of 105 electrons, considerably higher than that obtained by other charging methods. Analytical – numerical and finite element simulations, in tandem with charge measurements, are being developed to better understand the droplet electrical environment and ultimately to link chemistry and charge in a consistent framework. References [1] PD Maguire et al., Appl. Phys. Lett. 106, 224101 (2015); http://dx.doi.org/10.1063/1.4922034 [2] PD Maguire et al., Nano Lett., 17, 1336–1343 (2017) http://dx.doi.org/10.1021/acs.nanolett.6b03440 Figure 1

We report an eye-safe aerosol and cloud lidar with an Erbium-doped fiber laser (EDFL) and a free-space intracavity upconversion detector as the transmitter and receiver, respectively. The EDFL was home-made, which could produce linearly-polarized pulses at a repetition rate of 15 kHz with pulse energies of ~70 μJ and pulse durations of ~7 ns centered at 1550 nm. The echo photons were upconverted to ~631 nm via the sum frequency generation process in a bow-tie cavity, where a Nd:YVO4 and a PPLN crystal served as the pump and nonlinear frequency conversion devices, respectively. The upconverted visible photons were recorded by a photomultiplier tube and their timestamps were registered by a customized time-to-digital converter for distance-resolved measurement. Reflected signals peaked at ~6.8 km from a hard target were measured with a distance resolution of 0.6 m for an integral duration of 10 s. Atmospheric backscattered signals, with a range of ~6 km, were also detectable for longer integral durations. The evolution of aerosols and clouds were recorded by this lidar in a preliminary experiment with a continuous measuring time of over 18 h. Clear boundary and fine structures of clouds were identified with a spatial resolution of 9.6 m during the measurement, showing its great potential for practical aerosol and cloud monitoring.

In this paper, a comparison study of a quantum cascade laser used for signal transmission by free-space optics is presented. The main goal is to define the capabilities of medium-wavelength infrared lasers operated in pulsed or continuous wave (cw) mode through testing and analyzing a laboratory setup of a data link operated at wavelengths of 4.5 µm (pulsed, peak power 3 W) and 4.8 µm (cw, average power ~20 mW). In this spectral range, the link budget is also defined by radiation attenuation in the atmosphere (absorption, scattering, and turbulence interaction). The performed measurements define unique operational aspects of the quantum cascade lasers considering on–off keying modulation. The registered light pulse changes for different parameters of driving current signals determine some limitations in both rate and data range. Finally, we present eye diagrams of the signals obtained using two data links.

Traffic visibility is an essential reference for safe driving. Nighttime conditions add to the difficulty of estimating traffic visibility. To estimate the visibility in nighttime traffic images, we propose a Traffic Sensibility Visibility Estimation (TSVE) algorithm that combines laser transmission and image processing and needs no reference to the corresponding fog-free images and camera calibration. The information required is first obtained via the roadside equipment which collects environmental data and captures road images and then analyzed locally or remotely. The proposed analysis includes calculating the current atmospheric transmissivity with the laser atmospheric transmission theory and acquiring image features by using the cameras and the adjustable brightness target. Image analysis is performed using two image processing algorithms, namely, dark channel prior (DCP) and image brightness contrast. Finally, to improve the accuracy of visibility estimation, multiple nonlinear regression (MNLR) is performed on the various visibility indicators obtained by the two methods. Extensive on-site measurements analysis confirms the advantages of TSVE. Compared with other visibility estimation methods, such as the laser atmospheric transmission theory and image analysis method, TSVE significantly decreases the estimation errors.

Abstract. For high-resolution measurements of temperature fields in the atmospheric boundary layer and the lower free troposphere a scanning eye-safe lidar which deploys the rotational Raman technique at 355 nm was developed. To optimize the filters of the receiver for both high nighttime and daytime performance, detailed simulation studies have been performed. The receiver is fiber-coupled to a sequential setup of multicavity interference filters used under small angles of incidence. Examples of nighttime and daytime measurements with the system which has a total power-aperture-efficiency product of 0.006 W m2 are presented. Noontime temperature measurements with a temporal resolution of 60 s result in 1-sigma statistical temperature uncertainty of <1 K up to 1 km height and <2 K up to 2 km height. With an integration time of 60 min and a gliding average of 750 m a 1-sigma statistical temperature uncertainty of <1 K up to 14 km height is achieved during night.

In recent years, optical crystals for 1.3 μm all-solid-state passively Q-switched lasers have been widely studied due to their eye-safe band, atmospheric transmission characteristics, compactness, and low cost. They are widely used in the fields of high-precision laser radar, biomedical applications, and fine processing. In this review, we focus on three types of optical crystals used as the 1.3 μm laser gain media: neodymium-doped vanadate (Nd:YVO4, Nd:GdVO4, Nd:LuVO4, neodymium-doped aluminum-containing garnet (Nd:YAG, Nd:LuAG), and neodymium-doped gallium-containing garnet (Nd:GGG, Nd:GAGG, Nd:LGGG). In addition, other crystals such as Nd:KGW, Nd:YAP, Nd:YLF, and Nd:LLF are also discussed. First, we introduce the properties of the abovementioned 1.3 μm laser crystals. Then, the recent advances in domestic and foreign research on these optical crystals are summarized. Finally, the future challenges and development trend of 1.3 μm laser crystals are proposed. We believe this review will provide a comprehensive understanding of the optical crystals for 1.3 μm all-solid-state passively Q-switched lasers.

Abstract. For high-resolution measurements of temperature fields in the atmospheric boundary layer and the lower free troposphere a scanning eye-safe lidar which deploys the rotational Raman technique at 355 nm was developed. To optimize the filters of the receiver for both high nighttime and daytime performance, detailed simulation studies have been performed. The receiver is fiber-coupled to a sequential setup of multicavity interference filters used under small angles of incidence. Examples of nighttime and daytime measurements with the system which has a total power-aperture-efficiency product of 0.006 W m2 are presented. Noontime temperature measurements with a temporal resolution of 60 s result in 1-sigma statistical temperature uncertainty of <1 K up to 1 km height and <2 K up to 2 km height. With an integration time of 60 min and a gliding average of 750 m a 1-sigma statistical temperature uncertainty of <1 K up to 14 km height is achieved during night.

For today necessity of atmosphere wind remote sensing for wide pool of applications require development of new measurement methods and improvement of already existing.Currently doppler methods for wind speed measuring have largest sensing range. Correlation-based methods are provide lower sensing range for wind speed measurement. However, doppler-based lidar are expensive in opposite to simply designed correlation lidars that additionally allows to measure wind profile along sensing direction.Development of wind correlation lidars required knowledge of atmosphere aerosol inhomogeneities parameters.The most experimental research till now in this area are related to visible spectral range.One of the perspective eye-safety spectral range for wind lidar is UV spectral region. There not so much experimental research works of aerosol inhomogeneities parameters in UV.This paper is related to field experiments of aerosol inhomogeneities parameters in planetary boundary layer on 0.355 um operating wavelength.Block diagram and parameters of lidar with 0.355 operating wavelength is shown. Process of experiments is described. Typical atmosphere backscattering echo-signal for single laser pulse is demonstrated.Procedures if lidar signals processing are described, example of two-dimensional field of relative fluctuations of volume backscattering coefficient for different atmosphere conditions is shown.Results of measurement data processing shown that in planetary boundary layer average contrast of aerosol inhomogeneities in most cases has values in range 0,4% – 10 % (in case of snow up to 25%), and size in range 1,5 – 20 m. Dependency of observation number of aerosol inhomogeneities by range z from lidar to backscattering volume is descending with 1/z manner that the same for dependency for signal-noise ratio SNR(z).

In order to better understand the behavior of particulate pollution and atmospheric dynamics in New York City, it is of great importance to analyze the spatial distribution of aerosols. A scanning lidar system allows for horizontal range-resolved observations of aerosol backscatter with high space and time resolution. A challenge to analyzing the lidar returns is to disentangle extinction over the range of the observations to retrieve the backscatter coefficient with distance. This work presents horizontal measurements taken with a scanning eye-safe Micro Pulse Lidar in New York City. The measurements are analyzed using the Slope Method to get an estimate of the range-resolved aerosol backscatter coefficient. The results are presented as backscatter coefficient maps that display the aerosol spatial distribution within the field of view of the scanning pattern deployed. These observations clearly resolve aerosol dynamics and emission sources within the urban areas.

Abstract. The increasing importance of the coupling of water and aerosol cycles in environmental applications requires observation tools that allow simultaneous measurements of these two fundamental processes for climatological and meteorological studies. For this purpose, a new mobile Raman lidar, WALI (Water vapor and Aerosol LIdar), has been developed and implemented within the framework of the international HyMeX and ChArMEx programs. This paper presents the key properties of this new device and its first applications to scientific studies. The lidar uses an eye-safe emission in the ultraviolet range at 354.7 nm and a set of compact refractive receiving telescopes. Cross-comparisons between rawinsoundings performed from balloon or aircraft and lidar measurements have shown a good agreement in the derived water vapor mixing ratio (WVMR). The discrepancies are generally less than 0.5 g kg−1 and therefore within the error bars of the respective instruments. A detailed study of the uncertainty of the WVMR retrieval was conducted and shows values between 7 and 11%, which is largely constrained by the quality of the lidar calibration. It also proves that the lidar is able to measure the WVMR during daytime over a range of about 1 km. In addition the WALI system provides measurements of aerosol optical properties such as the lidar ratio (LR) or the particulate depolarization ratio (PDR). An important example of scientific application addressing the main objectives of the HyMeX and ChArMEx programs is then presented, following an event of desert dust aerosols over the Balearic Islands in October 2012. This dust intrusion may have had a significant impact on the intense precipitations that occurred over southwestern France and the Spanish Mediterranean coasts. During this event, the LR and PDR values obtained are in the ranges of ~45–63 ± 6 and 0.10–0.19 ± 0.01 sr, respectively, which is representative of dust aerosols. The dust layers are also shown to be associated with significant WVMR, i.e., between 4 and 6.7 g kg−1.

Abstract. The increasing importance of the coupling of water and aerosol cycles in environmental applications requires observation tools which allow simultaneous measurements of these two fundamental processes for climatological and meteorological studies. In this purpose, a new mobile Raman lidar, WALI (Water vapor and Aerosol LIDAR), has been developed and implemented within the framework of the international HyMeX/IODA-MED and ChArMEx programs. This paper presents the key properties of this new device and its first applications to scientific studies. The lidar uses an eye-safe emission in the ultra-violet range at 354.7 nm and a set of compact refractive receptors. Cross-comparisons between rawindsoundings performed from balloon or aircraft and lidar measurements have shown a good agreement in the derived water vapor mixing ratio (WVMR). The discrepancies are generally less than 0.5 g kg−1 and therefore within the error bars of the instruments. A detailed study of the uncertainties was conducted and shows a 7 to 11% accuracy of the WVMR retrieval, which is largely constrained by the quality of the calibration. It also proves that the lidar is able to measure the WVMR during the day over a range of about 1 km. The WALI system otherwise provides measurements of aerosol optical properties such as the lidar ratio (LR) or the particulate depolarization ratio (PDR). An important example of scientific application addressing the main objectives of the HyMeX and ChArMEx programs is then presented, following an event of desert dust aerosols over the Balearic Islands. This dust intrusion may have had a significant impact on the intense precipitations that occurred over southwestern France and the Spanish Mediterranean coasts. During this event, the LR and PDR values obtained are in the ranges of ~ 45–63 ± 6 sr and 0.1–0.19 ± 0.01, respectively, which is representative of dust aerosols. The dust layers are also shown to be associated with significant WVMR, i.e. between 4 and 6.7 g kg−1.

AbstractThe National Aeronautics and Space Administration Micro Pulse Lidar Network, version 3, cloud detection algorithm is described and differences relative to the previous version are highlighted. Clouds are identified from normalized level 1 signal profiles using two complementary methods. The first method considers vertical signal derivatives for detecting low-level clouds. The second method, which detects high-level clouds like cirrus, is based on signal uncertainties necessitated by the relatively low signal-to-noise ratio exhibited in the upper troposphere by eye-safe network instruments, especially during daytime. Furthermore, a multitemporal averaging scheme is used to improve cloud detection under conditions of a weak signal-to-noise ratio. Diurnal and seasonal cycles of cloud occurrence frequency based on one year of measurements at the Goddard Space Flight Center (Greenbelt, Maryland) site are compared for the new and previous versions. The largest differences, and perceived improvement, in detection occurs for high clouds (above 5 km, above MSL), which increase in occurrence by over 5%. There is also an increase in the detection of multilayered cloud profiles from 9% to 19%. Macrophysical properties and estimates of cloud optical depth are presented for a transparent cirrus dataset. However, the limit to which the cirrus cloud optical depth could be reliably estimated occurs between 0.5 and 0.8. A comparison using collocated CALIPSO measurements at the Goddard Space Flight Center and Singapore Micro Pulse Lidar Network (MPLNET) sites indicates improvements in cloud occurrence frequencies and layer heights.

Abstract A series of field campaigns has been made at British airports using a rapid-scanning lidar and other instrumentation in order to measure the dispersion of exhaust plumes from commercial aircraft. The lidar operated at a wavelength of 355 nm and was thus effectively eye safe. Analysis software for the lidar signals has been elaborated to enable the rather weak signals (typically a few tens of percent of ambient backscatter) from aircraft exhaust to be distinguished and to facilitate automatic processing of the measurements obtained. Such processing can deliver images, animations, and numerical parameterizations of the dispersing plumes. Overall, 1353 air traffic movements were monitored over two campaigns at Manchester and 439 in a single campaign at Heathrow. All modes were observed: taxiing, takeoff, rotation, climb-out, approach, and landing. Of these, the most complete dataset was that obtained for the start of the takeoff run: in this mode, the source is on full power but is still moving relatively slowly. Emissions thus remain at their most concentrated. For the same reason, this is the most important mode in respect to local air quality. Tire smoke on landing was likewise easily detected. Conversely, the lidar could only see the engine emissions from about 30% of the aircraft on approach. These data have been archived in an accessible form and are currently being used to develop improved regulatory dispersion models for airports.

As poultry is known to be a perishable food, the use-by date is set in such a way that food safety is guaranteed even with a higher initial bacterial count. This means, however, that some products are wasted, even if they are still safe to eat. Therefore, non-destructive measurement devices might be a good opportunity for individual shelf-life prediction, e.g., in retail. The aim of this study was therefore to use non-destructive measurement devices based on fluorescence quenching (oxygen detection) and mid-infrared laser spectroscopy (carbon dioxide detection) for the monitoring of high-oxygen-packed poultry in different storage conditions. During 15 days of storage, the gas composition of the headspace was assessed (non-destructively and destructively), while total plate count was monitored and a comprehensive sensory evaluation was performed by a trained panel. We were able to demonstrate that in most cases, non-destructive devices have comparable precision to destructive devices. For both storage conditions, the sensory attribute slime was correlated with reaching the critical microbiological value of 107 CFU/g; the attribute buttery was also useful for the prediction of regularly stored poultry. The change in the gas atmosphere as a sign of premature spoilage, however, was only possible for samples stored in irregular conditions.

Huizhou-style ancient architecture was one of the most important genres of architectural heritage in China. The architecture employed bricks, woods, and stones as raw materials, and timber frames were significant structures. Due to the drawback that the timbers were vulnerable to moisture and atmospheric agents, ancient timber buildings needed frequent protective interventions to maintain its good condition. Such interventions unavoidably disrupted the consistency between the original timber components. Besides this, the modifications brought about difficulty in correctly analysing and judging the state of existing ancient buildings, which, in current preservation practices, mainly rely on the expertise of skilled craftsmen to classify wood species and to identify the building-age of the timber components. Therefore, the industry and the research community urgently need a technique to rapidly and accurately classify wood materials and to discriminate building-age. In the paper, we designed an eye-safe 81-channel hyperspectral LiDAR (HSL) to tackle these issues. The HSL used an acousto-optic tunable filter (AOTF) as a spectral bandpass filter, offering the HSL measurements with 5 nm spectral resolution. Based on the HSL measurements, we analysed the relationship between the surface and cross-section spectral profiles of timber components from different ancient architectures built in the early Qing dynasty (~300 years), late Qing dynasty (~100 years), and nowadays, and confirmed the feasibility of using surface spectra of timber components for classification purpose. We classified building-ages and wood species with multiple Naive Bayes (NB) and support vector machine (SVM) classifiers by the surface spectra of timber components; this also unveiled the possibility of classifying gnawed timber components from its spectra for the first time. The encouraging experimental results supported that the AOTF-HSL is feasible for historic timber building preservation.

Purpose: The thermal diffusivity variation of UNS S32304 duplex stainless steel welds was studied after pulsed GTA welding autogenous process without filler addition. This property was measured in the transverse section of thin plates after welding process and post-heat treated at 750°C for 8 h followed by air-cooling. Design/methodology/approach: The present work reports measurements of thermal diffusivity using the laser-flash method. The thermal cycles of welding were acquired during welding by means of k-type thermocouples in regions near the weld joint. The used shielding gas was pure argon and 98% argon plus 2% of nitrogen. The temperature profiles were obtained using a digital data acquisition system. Findings: It was found an increase of thermal diffusivity after welding process and a decrease of these values after the heat treatment regarding the solidified weld pool zone, irrespective of the welding protection atmosphere. The microstructure was characterized and an increase of austenite phase in the solidified and heat-affected zones was observed for post-weld heat-treated samples. Research limitations/implications: It suggests more investigation and new measurements about the influence of the shielding gas variation on thermal diffusivity in the heat-affected zone. Practical implications: The nuclear industry, especially, requests alloys with high thermal stability in pipes for power generation systems and safe transportation equipment’s for radioactive material. Thus, the duplex stainless steel grades have improved this stability over standard grades and potentially increase the upper service temperature reliability of the equipment. Originality/value: After heat treatment, the welded plate with 98%Ar plus 2%N2 as shielding gas presented a thermal diffusivity closer to the as received sample. By means of 2%-nitrogen addition in shielding gas during GTAW welding of duplex stainless steel may facilitate austenite phase reformation, and then promotes stability on the thermal diffusivity of duplex stainless steels alloys.

Abstract. We propose a newly developed modular MObile LIdar SENsor System (MOLISENS) to enable new applications for small industrial lidar (light detection and ranging) sensors. The stand-alone modular setup supports both monitoring of dynamic processes and mobile mapping applications based on SLAM (Simultaneous Localization and Mapping) algorithms. The main objective of MOLISENS is to exploit newly emerging perception sensor technologies developed for the automotive industry for geoscientific applications. However, MOLISENS can also be used for other application areas, such as 3D mapping of buildings or vehicle-independent data collection for sensor performance assessment and sensor modeling. Compared to TLSs, small industrial lidar sensors provide advantages in terms of size (on the order of 10 cm), weight (on the order of 1 kg or less), price (typically between EUR 5000 and 10 000), robustness (typical protection class of IP68), frame rates (typically 10–20 Hz), and eye safety class (typically 1). For these reasons, small industrial lidar systems can provide a very useful complement to currently used TLS (terrestrial laser scanner) systems that have their strengths in range and accuracy performance. The MOLISENS hardware setup consists of a sensor unit, a data logger, and a battery pack to support stand-alone and mobile applications. The sensor unit includes the small industrial lidar Ouster OS1-64 Gen1, a ublox multi-band active GNSS (Global Navigation Satellite System) with the possibility for RTK (real-time kinematic), and a nine-axis Xsens IMU (inertial measurement unit). Special emphasis was put on the robustness of the individual components of MOLISENS to support operations in rough field and adverse weather conditions. The sensor unit has a standard tripod thread for easy mounting on various platforms. The current setup of MOLISENS has a horizontal field of view of 360∘, a vertical field of view with a 45∘ opening angle, a range of 120 m, a spatial resolution of a few centimeters, and a temporal resolution of 10–20 Hz. To evaluate the performance of MOLISENS, we present a comparison between the integrated small industrial lidar Ouster OS1-64 and the state-of-the-art high-accuracy and high-precision TLS Riegl VZ-6000 in a set of controlled experimental setups. We then apply the small industrial lidar Ouster OS1-64 in several real-world settings. The mobile mapping application of MOLISENS has been tested under various conditions, and results are shown from two surveys in the Lurgrotte cave system in Austria and a glacier cave in Longyearbreen on Svalbard.

ABSTRACTRED is a technique we have developed for stand-off detection of trace explosives using infrared (IR) photo-thermal imaging [1,2,3]. RED incorporates compact IR quantum cascade lasers tuned to strong characteristic absorption bands and may be used to illuminate explosives present as particles on a surface. An IR focal plane array is used to image the surface and detect any small increase in the thermal emission upon laser illumination. We have previously demonstrated the technique at several meters to 10’s of meters of stand-off distance indoors and in field tests [4,5], while operating the lasers below the eye-safe intensity limit (100 mWcm2) [6]. Sensitivity to traces of explosives as small as a nanogram has been demonstrated. By varying the incident wavelength slightly, we can readily show selectivity between individual explosives such as TNT and RDX. Using a sequence of lasers at different wavelengths, we increase both sensitivity and selectivity. A complete detection protocol can be performed in a sub-second time domain. More recently, RED has been used to emphasize measurements with cooled detectors in addition to examining the utility of filtering the collected thermal emission signal which is rich in analyte-specific spectroscopic information. A next generation RED system and detection algorithm is being developed to take advantage of these more powerful features. This manuscript will include an overview of the approach and recent experimental results.

Due to the expected increase in available fuel gas variants in the future and the interest in independence from a specific fuel, fuel flexible combustion systems are required for future gas turbine applications. Changing the fuel used for lean premixed combustion can lead to serious reliability problems in gas turbine engines caused by the different physical and chemical properties of these gases. A new innovative approach to reach efficient, safe, and low-emission operation for fuels such as natural gas, syntheses gas, and hydrogen with the same burner is presented in this paper. The basic idea is to use the additionally available fuel momentum of highly reactive gases stemming from their lower Wobbe index (lower volumetric heating value and density) compared with lowly reactive fuels. Using fuel momentum opens the opportunity to influence the vortex dynamics of swirl burners designed for lowly reactive gases in a favorable way for proper flame stabilization of highly reactive fuels without changing the hardware geometry. The investigations presented in this paper cover the development of the optimum basic aerodynamics of the burner and the determination of the potential of the fuel momentum in water channel experiments using particle image velocimetry. The results show that proper usage of the fuel momentum has enough potential to adjust the flow field to different fuels and their corresponding flame behavior. As the main challenge is to reach flashback safe fuel flexible burner operation, the main focus of the study lies on avoiding combustion induced vortex breakdown. The mixing quality of the resulting injection strategy is determined by applying laser induced fluorescence in water channel tests. Additional OH∗ chemiluminescence and flashback measurements in an atmospheric combustion test rig confirm the water channel results for CH4, CH4/H2 mixtures, H2 with N2 dilution, and pure H2 combustion. They also indicate a large operating window between flashback and lean blow out and show expected NOx emission levels. In summary, it is shown for a conical four slot swirl generator geometry that the proposed concept of using the fuel momentum for tuning of the vortex dynamics allows aerodynamic flame stabilization for different fuels in the same burner.

A Site for the Study of Ambience Deep in Melbourne’s subterranean belly lies a long, dark space dedicated to screen-based art. Built along disused train platforms, it’s even possible to hear the ghostly rumblings and clatter of trains passing alongside the length of the gallery on quiet days. Upon descending the single staircase leading into this dimly-lit space, visitors encounter a distinctive sensory immersion. A flicker of screens dapple the windowless vastness ahead, perhaps briefly highlighting entrances into smaller rooms or the faintly-outlined profiles of visitors. This space often houses time-based moving image artworks. The optical flicker and aural stirrings of adjacent works distract, luring visitors’ attention towards an elsewhere. Yet on other occasions, this gallery’s art is bounded by walls, private enclosures which absorb perceptions of time into the surrounding darkness. Some works lie dormant awaiting visitors’ intervention, while others rotate on endless loops, cycling by unheeded, at times creating an environment of visual and aural collision. A weak haze of daylight falls from above mid-way through the space, marking the gallery’s only exit – an escalator fitted with low glowing lights. This is a space of thematic and physical reinvention. Movable walls and a retractable mezzanine enable the 110 metre long, 15 metre wide and almost 10 metre high space to be reformed with each exhibition, as evidenced by the many exhibitions that this Screen Gallery has hosted since opening as a part of the Australian for the Moving Image (ACMI) in 2002. ACMI endured controversial beginnings over the public funds dedicated to its gallery, cinemas, public editing and games labs, TV production studio, and screen education programs. As media interrogation of ACMI’s role and purpose intensified, several pressing critical and public policy questions surfaced as to how visitors were engaging with and valuing this institution and its spaces. In this context, I undertook the first, in depth qualitative study of visitation to ACMI, so as to address these issues and also the dearth of supporting literature into museum visitation (beyond broad, quantitative analyses). Of particular interest was ACMI’s Screen Gallery, for it appeared to represent something experientially unique and historically distinctive as compared to museums and galleries of the past. I therefore undertook an ethnographic study of museum visitation to codify the expression of ACMI’s institutional remit in light of the modalities of its visitors’ experiences in the Gallery. This rich empirical material formed the basis of my study and also this article, an ethnography of the Screen Gallery’s ambience. My study was undertaken across two exhibitions, World without End and White Noise (2005). While WWE was thematically linear in its charting of the dawn of time, globalisation and apocalypse, visitor interaction was highly non-linear. The moving image was presented in a variety of forms and spaces, from the isolation of works in rooms, the cohabitation of the very large to very small in the gallery proper, to enclosures created by multiple screens, laser-triggered interactivity and even plastic bowls with which visitors could ‘capture’ projections of light. Where heterogeneity was embraced in WWE, WN offered a smoother and less rapturous environment. It presented works by artists regarded as leaders of recent practices in the abstraction of the moving image. Rather than recreating the free exploratory movement of WWE, the WN visitor was guided along one main corridor. Each work was situated in a room or space situated to the right-hand side of the passageway. This isolation created a deep sense of immersion and intimacy with each work. Low-level white noise was even played across the Gallery so as to absorb the aural ‘bleed’ from neighbouring works. For my study, I used qualitative ethnographic techniques to gather phenomenological material, namely longitudinal participant observation and interviews. The observations were conducted on a fortnightly basis for seven months. I typically spent two to three hours shadowing visitors as they moved through the Gallery, detailing patterns of interaction; from gross physical movement and speech, to the very subtle modalities of encounter: a faint smile, a hesitation, or lapsing into complete stillness. I specifically recruited visitors for interviews immediately after their visit so as to probe further into these phenomenological moments while their effects were still fresh. I also endeavoured to capture a wide cross-sample of responses by recruiting on the basis of age, gender and reason for visitation. Ten in-depth interviews (between 45 minutes and one hour) were undertaken, enquiring into the factors influencing impressions of the Gallery, such as previous museum and art experiences, and opinions about media art and technology. In this article, I particularly draw upon my interviews with Steven, Fleur, Heidi, Sean, Trevor and Mathew. These visitors’ commentaries were selected as they reflect upon the overall ambience of the Gallery–intimate recollections of moving through darkness and projections of light–rather than engagement with individual works. When referring to ambience, I borrow from Brian Eno’s 1978 manifesto of Ambient Music, as it offers a useful analogy for assessing the complexity within subtle aesthetic experiences, and more specifically, in a spatial environment generated by electronic means. An ambience is defined as an atmosphere, or a surrounding influence: a tint…Whereas the extant canned music companies proceed from the basis of regularizing environments by blanketing their acoustic and atmospheric idiosyncrasies, Ambient Music is intended to enhance these. Whereas conventional background music is produced by stripping away all sense of doubt and uncertainty (and thus all genuine interest) from the music, Ambient Music retains these qualities. And whereas their intention is to ‘brighten’ the environment by adding stimulus to it… Ambient Music is intended to induce calm and a space to think…Ambient Music must be able to accommodate many levels of listening attention without enforcing one in particular; it must be as ignorable as it is interesting. (Eno, "Ambient Music")While Eno’s definition specifically discusses a listening space, it is comparable to the predominantly digital and visual gallery environment as it elicits similar states of attention, such as calm reflection, or even a peaceful emptying of thoughts. I propose that ACMI’s darkened Screen Gallery creates an exploratory space for such intimate, bodily, subjective experiences. I firstly locate this study within the genealogical context of visitor interaction in museum exhibition environments. We then follow the visitors through the Gallery. As the nuances of their journey are presented, I assess the significance of an alternate model for presenting art which encourages ‘active’ aesthetic experience by privileging ambiguity and subtlety–yet heightened interactivity–and is similar to the systemic complexity Eno accords his Ambient Music. Navigating Museums in the Past The first public museums appeared in the context of the emerging liberal democratic state as both a product and articulation of the early stages of modernity in the nineteenth century. Museum practitioners enforced boundaries by prescribing visitors’ routes architecturally, by presenting museum objects within firm knowledge categories, and by separating visitors from objects with glass cabinets. By making their objects publicly accessible and tightly governing visitors’ parameters of spatial interaction, museums could enforce a pedagogical regulation of moral codes, an expression of ‘governmentality’ which constituted the individual as both a subject and object of knowledge (Bennett "Birth", Culture; Hooper-Greenhill). The advent of high modernism in the mid-twentieth century enforced positivist doctrines through a firm direction of visitor movement, exemplified by Le Corbusier’s Musée à Croissance Illimitée (1939) and Frank Lloyd Wright’s Guggenheim Museum in New York (1959) (Davey 36). In more recent stages of modernity, architecture has attempted to reconcile the singular authority imposed by a building’s design. Robert Venturi, a key theorist of post-modern architecture, argued that the museum’s pedagogical failure to achieve social and political reforms was due to the purist and universalist values expressed within modern architecture. He proposed that post-modern architecture could challenge aesthetic modernism with a playful hybridity which emphasises symbolism and sculptural forms in architecture, and expresses a more diverse set of pluralist ideologies. Examples might include Hans Hollein’s Abteiberg Museum (1972-1982), or the National Museum of Australia in Canberra (2001). Contemporary attempts to design museum interactions reflect the aspirations of the ‘new museum.’ They similarly address a pluralist agenda, but mediate increasingly individualised forms of participation though highly interactive technological interfaces (Message). Commenting about art galleries, Lev Manovich greets this shift with some pessimism. He argues that the high art of the ‘white cube’ gallery is now confronting its ‘ideological enemy’, the ‘black box’, a historically ‘lower’ art form of cinema theatre (10). He claims that the history of spatial experimentation in art galleries is being reversed as much moving image art has been exhibited using a video projection in a darkened room, thereby limiting visitor participation to earlier, static forms of engagement. However, he proposes that new technologies could have an important presence and role in cultural institutions as an ‘augmented space’, in which layers of data overlay physical space. He queries whether this could create new possibilities for spatial interaction, such that cultural institutions might play a progressive role in exploring new futures (14). The Screen Gallery at ACMI embodies the characteristics of the ‘new museum’ as far as it demands multiple modalities of participation in a technological environment. It could perhaps also be regarded an experimental ‘black box’ in that it houses multiple screens, yet, as we shall see, elicits participation unbefitting of a cinema. We therefore turn now to examine visitors’ observations of the Gallery’s design, thereby garnering the experiential significance of passage through a moving image art space. Descending into Darkness Descending the staircase into the Gallery is a process of proceeding into shadows. The blackened cavity (fig. 1) therefore looms ahead as a clear visceral departure from the bustle of Federation Square above (fig. 2), and the clean brightness of ACMI’s foyer (fig. 3). Figure 1: Descent into ACMI's Screen Gallery Figure 2: ACMI at Federation Square, Melbourne Figure 3: ACMI’s foyer One visitor, Fleur, described this passage as a sense of going “deep underground,” where the affective power of darkness overwhelmed other sensory details: “I can’t picture it in my mind – sort of where the gallery finishes… And it’s perfect, it’s dark, and it’s… quiet-ish.” Many visitors found that an entrance softened by shadows added a trace of suspense to the beginnings of their journey. Heidi described how, “because it’s dark and you can’t actually see the people walking about… it’s a little bit more mysterious.” Fleur similarly remarked that “you’re not quite sure what you’re going to meet when you go around. And there’s a certain anticipation.” Steven found that the ambiguity surrounding the conventions of procedure through Gallery was “quite interesting, that experience of being a little bit unsure of where you’re going or not being able to see.” He attributed feelings of disorientation to the way the deep shadows of the Gallery routinely obscured measurement of time: “it’s that darkness that makes it a place where it’s like a time sync… You could spend hours in there… You sort of lose track of time… The darkness kind of contributes to that.” Multiple Pathways The ambiguity of the Gallery compelled visitors to actively engage with the space by developing their own rules for procedure. For example, Sean described how darkness and minimal use of signage generated multiple possibilities for passage: “you kind of need to wander through and guide yourself. It’s fairly dark as well and there aren’t any signs saying ‘Come this way,’ and it was only by sort of accident we found some of the spaces down the very back. Because, it’s very dark… We could very well have missed that.” Katrina similarly explained how she developed a participatory journey through movement: “when you first walk in, it just feels like empty space, and not exactly sure what’s going on and what to look at… and you think nothing is going on, so you have to kind of walk around and get a feel for it.” Steven used this participatory movement to navigate. He remarked that “there’s a kind of basic ‘what’s next?’… When you got down you could see maybe about four works immediately... There’s a kind of choice about ‘this is the one I’ll pay attention to first’, or ‘look, there’s this other one over there – that looks interesting, I might go and come back to this’. So, there’s a kind of charting of the trip through the exhibition.” Therefore while ambiguous rules for procedure undermine traditional forms of interaction in the museum, they prompted visitors to draw upon their sensory perception to construct a self-guided and exploratory path of engagement. However, mystery and ambiguity can also complicate visitors’ sense of self determination. Fleur noted how crossing the threshold into a space without clear conventions for procedure could challenge some visitors: “you have to commit yourself to go into a space like that, and I think the first time, when you’re not sure what’s down there… I think people going there for the first time would probably… find it difficult.” Trevor found this to be the case, objecting that “the part that doesn’t work, is that it doesn’t work as a space that’s easy to get around.” These comments suggest that an ‘unintended consequence’ (Beck) of relaxing contemporary museum conventions to encourage greater visitor autonomy, can be the contrary effect of making navigation more difficult. Visitors struggling to negotiate these conditions may find themselves subject to what Daniel Palmer terms the ‘paradox of user control’, in which contemporary forms of choice prove to be illusory, as they inhibit an individual’s freedom through ‘soft’ forms of domination. The ambiguity created by the Gallery’s darkness therefore brings two disparate – if not contradictory – tendencies together, as concluded by Fleur: “The darkness is – it’s both an advantage and a disadvantage… You can’t sort of see each other as well, but there’s also a bit of freedom in that. In that it sort of goes both ways.” A Journey of Subtle Cues Several strategies to ameliorate disorienting navigation experiences were employed in the Screen Gallery, attempting to create new possibilities for meaningful interaction. Some reflect typical curatorial conventions, such as mounting didactic panels along walls and strategically placing staff as guides. However, visitors frequently eschewed these markers and were instead drawn powerfully to affective conventions, including the shadings of light and sound. Sean noted how small beacons of light at foot level were prominent features, as they illuminated the entrances to rooms and corridors: “That’s your over-whelming impression, because it’s dark and there’s just these feature spotlights… and they’re an interesting device, because they sort of lead your eye through the space as well, and say ‘oh that’s where the next event is, there’s a spotlight over there’.” The luminescence of artworks served a similar purpose, for within “the darkness, the boundaries are less visible, and… you’re drawn to the light, you know, you’re drawn to those screens.” He found that directional sound above artworks also created a comparable effect: “I was aware of the fact that things were quiet until you approached the right spot and obviously it’s where the sound was focussed.” These conventions reflect what Trini Castelli calls ‘soft design’, by which space is made cohesively sensual (Glibb in Mitchell 87-88). The Gallery uses light and sound to fashions this visceral ‘feeling’ of spatial continuity, a seamless ambience. Paul described how this had a pleasurable effect, where the “atmosphere of the space” created “a very nice place to be… Lots of low lighting.” Fleur similarly recalled lasting somatic impressions: “It’s a bit like a cave, I suppose… The atmosphere is so different… it’s warm, I find it quite a relaxing place to be, I find it quite calm…Yeah, it has that feeling of private space to it.” Soft design therefore tempers the spatial severity of museums past through this sensuous ‘participatory environment.’ Interaction with art therefore becomes, as Steven enthused, “an exhibition experience” where “it’s as much (for me) the experience of moving between works as attending to the work itself… That seems really prominent in the experience, that it’s not these kind of isolated, individual works, they’re in relation to each other.” Disruptions to this experiential continuity – what Eno had described as a ‘stimulus’ – were subject to harsh judgement. When asked why he preferred to stand against the back wall of a room, rather than take a seat on the chairs provided, Matthew protested that “the spotlight was on those frigging couches, who wants to sit there? That would’ve been horrible.” Visitors clearly expressed a preference towards a form of spatial interaction in which curatorial conventions heighten, rather than detract from, the immersive dynamic of the museum environment. They showed how the feelings of ambiguity and suspense which absorbed them in the Gallery’s entrance gradually began to dissipate. In their place, a preference arose for conventions which maintained the Gallery’s immersive continuity, and where cues such as focused sound and footlights had a calming effect, and created a cohesive sensual journey through the dark. The Ambience of Art Space Visitors’ comments acquire an additional significance when examined in light of Eno’s earlier definition of what he called Ambient Music. He suggested that even in relative stillness, there exists a capacity for active forms of listening which create a “space to think” and generate a “quiet interest.” In addition, and perhaps most importantly, these active forms of listening are augmented by the “atmospheric idiosyncrasies” which are derived from conditions of uncertainty. As I have shown, the darkened Screen Gallery obscures the rules for visitor participation and consequently elicits doubt and hesitation. Visitors must self-navigate and be guided by sensory perception, responding to the kinaesthetic touch of light on skin and the subtle drifts of sound to constructing a journey through the enveloping darkness. This spatial ambience can therefore be understood as the specific condition which make the Gallery a fertile site for new exchanges between visitors, artworks and curation within the museum. Arjun Mulder defines this kind of dynamism in architectural space as a form of systemic interactivity, the “default state of any living system,” in the way that any system can be considered interactive if it links into, and affects change upon another (Mulder 332). Therefore while museums have historically been spaces for interaction, they have not always been interactive spaces in the sense described by Mulder, where visitor participation and processes of exchange are heightened by the conditions of ambience, and can compel self-determined journeys of visitor enquiry and feelings of relaxation and immersion. ACMI’s Screen Gallery has therefore come to define its practices by heightening these forms of encounter, and elevating the affective possibilities for interacting with art. Traditional museum conventions have been challenged by playing with experiential dynamics. These practices create an ambience which is particular to the gallery, and historically unlike the experiential ecologies of preceding forms of museum, gallery or moving space, be it the white cube or a simple ‘black box’ room for video projections. This perhaps signifies a distinctive moment in the genealogy of the museum, indicating how one instance of an art environment’s ambience can become a rubric for new forms of visitor interaction. References Beck, Ulrich. “The Reinvention of Politics: Towards a Theory of Reflexive Modernization.” Reflexive Modernization: Politics, Tradition and Aesthetics in the Modern Social Order. Eds. Ulrich Beck, Anthony Giddens, and Scott Lash. Cambridge: Politics, 1994. 1-55. Bennett, Tony. The Birth of the Museum: History, Theory, Politics. London; New York: Routledge. 1995. ———. “Culture and Governmentality.” Foucault, Cultural Studies and Governmentality. Eds. J.Z. Bratich, J. Packer, and C. McCarthy. 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New York: Van Nostrand Reinhold, 1993. Mulder, Arjun. “The Object of Interactivity.” NOX: Machining Architecture. London: Thames and Hudson, 2004. 332-340. Palmer, Daniel. “The Paradox of User Control.” Melbourne Digital Art and Culture 2003 Conference Proceedings. Melbourne: RMIT, 2003. 167-172. Venturi, Robert. Complexity and Contradiction in Architecture. New York: Museum of Modern Art, 1966.