Department of Environmental Engineering

Visual discomfort has been the subject of considerable research in relation to stereoscopic and autostereoscopic displays. In this paper, the importance of various causes and aspects of visual discomfort is clarified. When disparity values do not surpass a limit of 1°, which still provides sufficient range to allow satisfactory depth perception in stereoscopic television, classical determinants such as excessive binocular parallax and accommodation-vergence conflict appear to be of minor importance. Visual discomfort, however, may still occur within this limit and we believe the following factors to be the most pertinent in contributing to this: (1) temporally changing demand of accommodation-vergence linkage, e.g., by fast motion in depth; (2) three-dimensional artifacts resulting from insufficient depth information in the incoming data signal yielding spatial and temporal inconsistencies; and (3) unnatural blur. In order to adequately characterize and understand visual discomfort, multiple types of measurements, both objective and subjective, are required.

Visual discomfort has been the subject of considerable research in relation to stereoscopic and autostereoscopic displays, but remains an ambiguous concept used to denote a variety of subjective symptoms potentially related to different underlying processes. In this paper we clarify the importance of various causes and aspects of visual comfort. Classical causative factors such as excessive binocular parallax and accommodation-convergence conflict appear to be of minor importance when disparity values do not surpass one degree limit of visual angle, which still provides sufficient range to allow for satisfactory depth perception in consumer applications, such as stereoscopic television. Visual discomfort, however, may still occur within this limit and we believe the following factors to be the most pertinent in contributing to this: (1) excessive demand of accommodation-convergence linkage, e.g., by fast motion in depth, viewed at short distances, (2) 3D artefacts resulting from insufficient depth information in the incoming data signal yielding spatial and temporal inconsistencies, and (3) unnatural amounts of blur. In order to adequately characterize and understand visual discomfort, multiple types of measurements, both objective and subjective, are needed. Downloaded from SPIE Digital Library on 21 May 2010 to 131.180.130.114. Terms of Use: http://spiedl.org/terms SPIE-IS&T/ Vol. 6490 64900I-2 Downloaded from SPIE Digital Library on 21 May 2010 to 131.180.130.114. Terms of Use: http://spiedl.org/terms SPIE-IS&T/ Vol. 6490 64900I-3 SPIE-IS&T/ Vol. 6490 64900I-11 Downloaded from SPIE Digital Library on 21 May 2010 to 131.180.130.114. Terms of Use: http://spiedl.org/terms

This article concerns the benefits of presenting abstract data in 3D. Two experiments show that motion cues combined with stereo viewing can substantially increase the size of tbe graph that can be perceived. The first experiment was designed to provide quantitative measurements of how much more (or less) can be understood in 3D than in 2D. Tbe 3D display used was configured so that the image on the monitor was coupled to the user's actual eye positions (and it was updated in real-time as the user moved) as well as being in stereo. Thus the effect was like a local "virtual reality" display located in the vicinity of the computer monitor. The results from this study show that head-coupled stereo viewing can increase the size of an abstract graph that can be understood by a factor of three; using stereo alone provided an increase by a factor of 1.6 and bead coupling alone produced an increase by a factor of 2.2, Tbe second experiment examined a variety of motion cues provided by head-coupled perspective (as in virtual reality displays), hand-guided motion and automatic rotation, respectively, both with and without stereo in each case. The results show that structured 3D motion and stereo viewing both help in understanding, but that the kind of motion is not particularly important; all improve performance, and all are more significant than stereo cues. These results provide strong reasons for using advanced 3D graphics for interacting with a large variety of information structures.

We examined how depth information from two different cue types (object motion and texture gradient) is integrated into a single estimate in human vision. Two critical assumptions of a recent'model of depth cue combination (termed moa!i@d weak fusion) were tested. The first assumption is that the overall depth estimate is a weighted linear combination of the estimates derived from the individual cues, after initial processing needed to bring them to a common format. The second assumption is that the weight assigned to a cue reflects the apparent reliability of that cue in a particular scene. By this account, the depth combination rule is linear and dynamic, changing in a predictable fashion in response to the particular scene and viewing conditions. A novel procedure was used to measure the weights assigned to the texture and motion cues across experimental conditions. This procedure uses a type of perturbation analysis. The results are consistent with the weighted linear combination rule. In addition, when either cue is corrupted by added noise, the weighted linear combination rule shifts in favor of the uncontaminated cue.

Codes 935 and 588, Greenbelt, MD 20771 ______________________________________________________________________ More powerful contemporary computer hardware has enabled the development and exploration of a wide variety of techniques to depict spatial characteristics of computer-generated objects in three dimensional (3D) space. Particularly, the role of stereoscopic viewing and the use of object motion to reflect the position and size of objects in 3D space have been extensively studied. However, the effective use of computer-rendered object shadows to provide spatial information about the relative position and size of objects in virtual space has not. Subjects perform two tasks with 3D geometric patterns of objects presented on a computer screen: (1) positioning the object to complete a symmetrical geometric and resizing the object to match the size of other objects. Performance accuracy and speed are recorded under the following conditions: (1) objects casting shadows on and off; (2) shadows from one or two light sources (nested within the shadows on condition); (3) stereoscopic and monoscopic viewing; and (4) different scene backgrounds: flat plane (i.e. floor); 'stair-step' floor with no walls; and floor with walls (i.e. room). The use of object shadows as depth cues enhances the accuracy (but not the speed) of object positioning, but does not enhance either the accuracy or the speed of object resizing. Moreover, the object shadows are not as effective as stereoscopic viewing in facilitating both positioning and resizing task performances. Furthermore, task performances degrade with the stair-step scene background, and when the number of shadowing light sources increases from one to two.

In this paper, the new challenges of 3DTV for subjective assessment are discussed. Conventional 2D methods have severe limitations which will be revealed. Based on the understanding of the new characteristics brought by 3DTV, changes and additions in the requirements for subjective assessment are proposed in order to develop a novel subjective video quality assessment methodology for 3DTV. In particular, depth rendering for 3D display is selected to give a further discussion. The depth rendering abilities are defined as a combination of the physical parameters and the perceptual constrains. We analyze different types of stereoscopic and multiview displays. Several problems regarding depth rendering are discussed in order to highlight the diversity and complexity of assessing 3DTV.

At present the foundations are being laid out for the implementation of three-dimensional television. Apart from the engineering problems to be solved there are a number of questions connected with human factors which have to be answered. These questions are related to fundamental requirements with regard to certain system features such as screen size, viewing distance and the spatio-temporal resolution of the image in the three dimensions of space. Since the implementation of data-compressing techniques is essential for the recording and transmission of 3DTV picture signals, it is necessary to show the possibilities of irrelevance reduction as well as to define the demands made on the quality of reconstructed images. The present paper summarizes the latest results of research and shows in which fields work must be carried out on hitherto unanswered questions.

An accurate perception of the distance between an object and a nearby surface can increase a viewer's sense of presence in an immersive environment, particularly when a user is performing actions that affect or are affected by this distance. Two experiments were conducted examining the effectiveness of stereoscopic viewing, shadows, and interreflections at conveying this distance information. Subjects performed simple tasks based on the perception of the distance between a fixed virtual table and an approaching block in a virtual environment. In the first experiment, subjects lowered a virtual block to a virtual table. For this task, both stereoscopic viewing and shadows had statistically significant effects on subject performance. In the second experiment, subjects mechanically reported the perceived distance between a virtual block and virtual table. For this task, viewing condition, shadows, and interreflections were shown to be statistically significant distance cues.

Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, occurs in a wide variety of environments and plays a central role in the global nitrogen cycle. Catalyzed by the enzyme ammonia monooxygenase, the ability to oxidize ammonia was previously thought to be restricted to a few groups within the ␤and ␥-Proteobacteria. However, recent metagenomic studies have revealed the existence of unique ammonia monooxygenase ␣subunit (amoA) genes derived from uncultivated, nonextremophilic Crenarchaeota. Here, we report molecular evidence for the widespread presence of ammonia-oxidizing archaea (AOA) in marine water columns and sediments. Using PCR primers designed to specifically target archaeal amoA, we find AOA to be pervasive in areas of the ocean that are critical for the global nitrogen cycle, including the base of the euphotic zone, suboxic water columns, and estuarine and coastal sediments. Diverse and distinct AOA communities are associated with each of these habitats, with little overlap between water columns and sediments. Within marine sediments, most AOA sequences are unique to individual sampling locations, whereas a small number of sequences are evidently cosmopolitan in distribution. Considering the abundance of nonextremophilic archaea in the ocean, our results suggest that AOA may play a significant, but previously unrecognized, role in the global nitrogen cycle.

Limbah yang digunakan adalah grey water. Jenis reaktor adalah kombinasi Anaerobic Baffled Reactor (ABR) dan Anaerobic Filter (AF). Reaktor I terdiri atas 4 kompartemen ABR dan 1 kompartemen AF, sementara Reaktor II terdiri atas 3 kompartemen ABR dan 1 kompartemen AF. Waktu detensi Reaktor I adalah 25,36 jam, sedangkan Reaktor II adalah 27,02 jam. Variasi konsentrasi zat organik Reaktor I adalah 20, 30, dan 35 mg/L, sedangkan Reaktor II adalah 50, 100, dan 150 mgCOD/L. Reaktor kombinasi ABR-AF menghasilkan penurunan PV tertinggi sebesar 54,54% dan 64,75% pada Reaktor I dan Reaktor II, serta penurunan COD tertinggi sebesar 68,98% pada Reaktor II.

The micropore volumes of 2 montmorillonites (SAz-1 and SWy-1), each exchanged with Ca, Na, K, Cs and tetramethylammonium (TMA) ions, were calculated from the measured vapor adsorption data of N 2 and neo-hexane by use of t-and a~-plots. The corresponding surface areas of the exchanged clays were determined from Brunauer-Emmett-Teller (BET) plots of N 2 adsorption data. Micropore volumes and surface areas of the samples increased with the size of exchanged cation: TMA > Cs > K > Ca > Na. The SAz-1 exchanged clays showed generally greater micropore volumes and surface areas than the corresponding SWy-1 clays. The vapor adsorption data and d(001) measurements for dry clay samples were used together to evaluate the likely locations and accessibility of clay micropores, especially the relative accessibility of their interlayer spacing. For both source clays exchanged with Na, Ca and K ions, the interlayer spacing appeared to be too small to admit nonpolar gases and the accessible micropores appeared to have dimensions greater than 5.0 .~, the limiting molecular dimension of neo-hexane. In these systems, there was a good consistency of micropore volumes detected by N2 and neo-hexane. When the clays were intercalated with relatively large cations (TMA and possibly Cs), the large layer expansion created additional microporosity, which was more readily accessible to small N: than to relatively large neo-hexane. Hence, the micropore volume as detected by N 2 was greater than that detected by neo-hexane. The micropore volumes with pore dimensions greater than 5 A determined for clays exchanged with Na, Ca and K likely resulted from the pores on particle edges and void created by overlap regions of layers. The increase in micropore volumes with pore dimensions less than 5 A determined for clays exchanged with TMA and possibly Cs could be caused by opening of the interlayer region by the intercalation of these large cations.

A high-charge smectite from Arizona [cation-exchange capacity (CEC) = 120 meq/100 g] and a low-charge smectite from Wyoming (CEC = 90 meq/100 g) were used to prepare homoionic tetramethylammonium (TMA)-clay complexes. The adsorption of benzene, toluene, and o-xylene as vapors by the dry TMA-clays and as solutes from water by the wet TMA-clays was studied. The adsorption of the organic vapors by the dry TMA-smectite samples was strong and apparently consisted of interactions with both the aluminosilicate mineral surfaces and the TMA exchange ions in the interlayers. In the adsorption of organic vapors, the closer packing of TMA ions in the dry high-charge TMA-smectite, compared with the dry low-charge TMA-smectite, resulted in a somewhat higher degree of shape-selective adsorption of benzene, toluene, and xylene. In the presence of water, the adsorption capacities of both samples for the aromatic compounds were significantly reduced, although the uptake of benzene from water by the low-charge TMA-smectite was still substantial. This lower sorption capacity was accompanied by increased shape-selectivity for the aromatic compounds. The reduction in uptake and increased selectivity was much more pronounced for the water-saturated, high-charge TMA-smectite than for the low-charge TMA-smectite. Hydration of the TMA exchange ions and/or the mineral surfaces apparently reduced the accessibility of the aromatic molecules to interlamellar regions. The resulting water-induced sieving effect was greater for the high-charge TMA-smectite due to the higher density of exchanged TMAions. The low-charge Wyoming TMA-smectite was a highly effective adsorbent for removing benzene from water and may be useful for purifying benzene-contaminated water.