Visibility Problems Research Articles

Event Tree Analysis of Marine Accidents in Bangladesh

The frequency of marine accidents in Bangladesh is observed to be one of the highest in the world. Maritime disasters in the country took more than 10,000 lives in past three decades. Each time an accident occurs with terrible loss of lives, the issue goes viral through newspapers and social media for several days, and then it is simply consigned to oblivion. Most of the records kept of marine accidents are limited to unsubstantiated news reports with a few exceptions marked in a handful of accidents that were subjected to detailed reporting conducted by maritime authorities. Several research works have been carried out to point out the core reasons behind accidents. But there was a demand of time to find out and represent the sequence of events leading to an accident with the help of a tool more effective than those used in earlier papers. The tool used in this paper is event tree, showing how a single factor, when coupled with other factors or not, is likely to lead to an accident. Despite being a widely-used tool for accident analysis, event tree has been applied for the first time with quantitative study in analyzing maritime accidents in Bangladesh. The research work didn’t end up using event tree as a tool only, but it also conducted a probabilistic analysis. In this research work, the factors, most likely to lead to a disaster, has been identified and then assessed with the data of previous accidents. The probabilistic analysis yielded to the finding that the number of accidents can be reduced considerably if the problem of poor visibility, when the vessel is overloaded, can be solved. The event tree showing the sequence of events will help future researchers and system designers to find out and eliminate the factors contributing to marine accidents and eventually curb the very high frequency of disasters.

블루투스 기반 청각장애인을 위한 의사소통 앱의 효용성 연구

Background and Objectives: For deaf and hard-of-hearing people, the effective communication with hearing people is important for their independent living. As smart mobile devices have become very popular, lots of mobile applications are available for hard-of-hearing people to communicate with hearing people. Currently available such applications are ineffective. Some applications require extra cost for data communication, while others lack text typing aids for convenient and fast input by hard-of-hearing people. The purpose of this study was to develop a bluetooth-based mobile application for hard-of-hearing persons to communicate with hearing ones, and to verify the effectiveness of the application. Method: We identified the requirements of mobile applications for effective communication between hard-of-hearing and hearing people, and then developed a bluetooth-based mobile application. Bluetooth needs no extra cost in data communication. The application supports text typing aids for hard-of-hearing people, such as auto-completion of words, text reuse and built-in dialogs, and supports speech recognition for hearing people. Using speech recognition and synthesis makes hearing people more comfortable than using key pad in communication. In order to verify the effectiveness of our application, we conducted a usability test of the application with 20 hard-of-hearing persons. In the usability test, we measured the overall satisfaction, learnability and effectiveness of the application by using 5-point Likert scale. Results: The mean scores of overall satisfaction, learnability and effectiveness were 4.25, 4.31 and 4.45, respectively. Conclusion: The usability test showed that the application was very effective for hard-of-hearing persons. Some subjects pointed out a visibility problem of the user interface. The developed application focused on face-to-face conversation. Further studies are required to develop one-to-many communication applications that enable hard-of-hearing people to talk with many other persons in meetings and conferences.

Mutual visibility by luminous robots without collisions

We consider the Mutual Visibility problem for anonymous dimensionless robots with obstructed visibility moving in a plane: starting from distinct locations, the robots must reach, without colliding, a configuration where no three of them are collinear. We study this problem in the luminous robots model, in which each robot has a visible light that can assume colors from a fixed set.Among other results, we prove that Mutual Visibility can be solved in SSynch with 2 colors and in ASynch with 3 colors. If an adversary can interrupt and stop a robot moving to its computed destination, Mutual Visibility is still solvable in SSynch with 3 colors and, if the robots agree on the direction of one axis, also in ASynch.As a byproduct, we provide the first obstructed-visibility solutions to two classical problems for oblivious robots: collision-less convergence to a point (also known as near-gathering) and circle formation.

Image Set Creation using different Image Enhancement Technique for Underwater Image Segmentation

Underwater images suffer from less visibility problem due to principal of light refraction under water environment. Therefore, this paper address the problem of enhancing the contrast of the underwater images captured under different lightning conditions and depths. This paper presenting the comparison of the two distinct popular enhancement methods and it concluded that this different method generates two different image sets from original low contrast image. These sets can be further utilized for object segmentation using fuzzy based clustering methods efficiently. Paper presents enhancement using contrast limit adaptive histogram equalization (CLAHE) and, global contrast adjustment method.. The CLAHE method is used to the images so that contrast of output images is improved also gives better information. It is concluded that using the different contrast enhancement method different image data set can be created for same input image which can be utilized for higher level processing task and features extractions. General Terms Image processing, Underwater Images,

Fabrication of Invisible Ag Nanowire Electrode Patterns Based on Laser-Induced Rayleigh Instability

We here present a laser-patterning method that may solve the visibility problem associated with silver nanowire (AgNW) transparent electrodes. In conventional methods, AgNW electrodes are patterned on a transparent substrate by either selective removal or deposition of the material. Therefore, the fabricated pattern becomes visible due to the difference in transmittance/reflectance between the regions with and without AgNWs. Our approach is to disconnect the AgNW networks in selective areas by a laser and thus make the irradiated areas electrically insulating. This method is fundamentally based on Rayleigh instability. Given that the laser-cut nanowires remain on the substrate, the electrode pattern fabricated by the method can be invisible. The feasibility of the presented approach is demonstrated by fabricating organic light-emitting diodes using patterned AgNW electrodes and then characterizing their performance capabilities.

Vision-targeted health related quality of life in older adults: patient-reported visibility problems in low luminance activities are more likely to decline than daytime activities.

BackgroundCommonly used vision-targeted health-related quality of life questionnaires almost exclusively focus items on vision under daytime conditions. Older adults even when in good eye health frequently report experiencing vision problems at night and under low environmental light levels, and psychophysical studies also document these visibility problems. Here we compare the progression of self-reported low luminance visibility problems and self-reported visibility problems under daytime conditions in older adults.MethodsTrained interviewers administered two questionnaires to older adults in normal eye health: the National Eye Institute Visual Function Questionnaire – 25 (NEI VFQ-25) where items are almost entirely focused on difficulties in daytime activities, and the Low Luminance Questionnaire (LLQ) where items are focused on difficulties seeing at night and under low luminance conditions. The following visual functions were also measured: visual acuity, low luminance visual acuity, low luminance deficit, contrast sensitivity, light sensitivity in the macula, and rod-mediated dark adaptation. The protocol was repeated 3 years later.ResultsScores on the NEI VFQ-25 composite and its subscales were unchanged between baseline and 3-year follow-up, whereas scores on the LLQ composite and 5 of 6 subscales significantly decreased (corresponding to less functionality) at the 3-year follow-up. Participants were more likely to display a ≥ 5 point decrease on the LLQ composite than on the NEI VFQ-25 over 3 years. Visual functional tests were largely unrelated to changes in NEI VFQ-25 and LLQ scores from baseline to follow-up.ConclusionsOlder adults’ vision-targeted quality of life as measured by questionnaire is more likely to exhibit a practically significant decrease over 3 years using a questionnaire that focused on low luminance activities (LLQ) than one focused on daytime activities (NEI VFQ-25). That the results of visual functional testing did not correspond to older adults’ decline in self-reported problems in low luminance activities emphasizes the importance of questionnaires in understanding visual difficulties from the patients’ own perspective.

Impacts of meteorological condition and aerosol chemical compositions on visibility impairment in Nanjing, China

With rapid industrialization and urbanization, air pollution and corresponding visibility problems in Nanjing were increasingly severe during the last few years. To better understand the potential causes of impaired visibility, particulate matter (PM) mass and chemical composition were measured from May 2013 to May 2014 in Nanjing. During the period, major water soluble ions and organic carbon exhibited obvious seasonal variations with the highest level in winter. On average, the water-soluble ions ranked in the order of SO42− > NO3− > NH4+ > Cl− > Na+ > Ca2+ > K+ > F− > Mg2+. The NO3−/SO42− average ratios were over 1.0 in the fall and winter due to the low temperature favored a shift from the gas phase as nitric acid to the particle phase as ammonium nitrate. The averaged mass concentrations of organic carbon (OC) and elemental carbon (EC) were 18.96 and 2.60 μg m−3 respectively. The daily average visibility in Nanjing over study period ranged from 1.2 km to 18.4 km. High aerosol concentration and relative humidity were two important factors that cause low visibility events in Nanjing. The correlation between PM2.5 concentration and visibility under different relative humidity values showed that visibility was exponentially decreased with the increased PM2.5 concentrations when relative humidity less than 80%. However, the relationship was no longer to follow the exponentially decreasing trend when relative humidity >80%, and the visibility maintained in very low values, even with low PM2.5 concentrations. This indicated the hygroscopic growth of particles played more important roles for reduction of visibility. The annual average chemical extinction coefficient based on the revised IMPROVE (Interagency Monitoring of Protected Visual Environments) equation was 267.69 ± 139.24 Mm−1 in Nanjing. On average, organic matter was found to be the largest contributor accounting for 35.69% of chemical extinction coefficient. The contributions of ammonium sulfate and ammonium nitrate were also important with the annual average of 28.80% and 24.08%, respectively. For visibility >10 km, organic matter was the largest contributor to extinction coefficient, while organic matter and ammonium sulfate were the main contributors for visibility <5 km. The results showed that the most influential factors affecting visibility in Nanjing were organic matter and sulfate. The reduction of carbonaceous species and sulfate could effectively improve the visibility of Nanjing. The paper aims to help environmental scientists and policy makers understand air pollution in Nanjing and air pollution control strategies taken by government.

An Adaptive and Hybrid Approach for Revisiting the Visibility Pipeline

We revisit the visibility problem, which is traditionally known in Computer Graphics and Vision fields as the process of computing a (potentially) visible set of primitives in the computational model of a scene. We propose a hybrid solution that uses a dry structure (in the sense of data reduction), a triangulation of the type Ja 1 , to accelerate the task of searching for visible primitives. We came up with a solution that is useful for real-time, on-line, interactive applications as 3D visualization. In such applications the main goal is to load the minimum amount of primitives from the scene during the rendering stage, as possible. For this purpose, our algorithm executes the culling by using a hybrid paradigm based on viewing-frustum, back-face culling and occlusion models. Results have shown substantial improvement over these traditional approaches if applied separately. This novel approach can be used in devices with no dedicated processors or with low processing power, as cell phones or embedded displays, or to visualize data through the Internet, as in virtual museums applications.

Unveiling network and service performance degradation in the wild with mplane

Unveiling network and service performance issues in complex and highly decentralized systems such as the Internet is a major challenge. Indeed, the Internet is based on decentralization and diversity. However, its distributed nature leads to operational brittleness and difficulty in identifying the root causes of performance degradation. In such a context, network measurements are a fundamental pillar to shed light on and unveil design and implementation defects. To tackle this fragmentation and visibility problem, we recently conceived mPlane, a distributed measurement platform that runs, collects, and analyzes traffic measurements to study the operation and functioning of the Internet. In this article, we show the potentiality of the mPlane approach to unveil network and service degradation issues in live operational networks, involving both fixed-line and cellular networks. In particular, we combine active and passive measurements to troubleshoot problems in end-customer Internet access connections, or to automatically detect and diagnose anomalies in Internet-scale services (e.g., YouTube) that impact a large number of end users.

Long-Term Results and Refinement of the Turkish Delight Technique for Primary and Secondary Rhinoplasty

All grafts present the potential problem of late visibility, distortion, and (occasionally) absorption. To overcome these problems and obtain a smoother surface, in 1989, the author initiated the use of finely diced cartilage wrapped in Surgicel. It is well known that the resolution of edema at the end of 1 year postoperatively is approximately 90 to 95 percent. Complete resolution continues until the end of 4 years postoperatively. However, it is important to understand what occurs beyond 4 years, and how the nose changes as the face ages. The author presents his experience of the past 25 years on 9398 primary and secondary rhinoplasty patients treated using his personal approach, the Turkish delight. Patients with a postoperative range from 4 to 25 years were selected. The Turkish delight type of cartilage graft (diced cartilage wrapped in Surgicel) has been free of late show complications often experienced with other types of tip grafts. Long-term results from 4 to 25 years are very satisfactory, with an acceptably low complication rate. This technique is safe, reliable, effective, simple, and easily applicable by plastic surgeons at all levels of experience. Early and long-term results from 1 to 25 years are very satisfactory. The overall complication rate is very low compared with other techniques. In addition, there is no late show as is sometimes seen with other types of cartilage grafts such as crushed, oval, or rectangular grafts. Therapeutic, IV.

Rearward Visibility Issues Related to Agricultural Tractors and Self-Propelled Machinery: Contributing Factors, Potential Solutions.

As the size, complexity, and speed of agricultural tractors and self-propelled machinery have increased, so have the visibility-related issues, placing significant importance on the visual skills, alertness, and reactive abilities of the operator. Rearward movement of large agricultural equipment has been identified in the literature as causing both fatalities and injuries to bystanders who were not visible to the operator and damage to both the machine and stationary objects. The addition of monitoring assistance, while not a new concept, has advanced significantly, offering agricultural machinery operators greater options for increasing their awareness of the area surrounding the machine. In this research, we attempt to (1) identify and describe the key contributors to agricultural machinery visibility issues, i.e., operator-related and machine-related factors, and (2) enumerate and evaluate the potential solutions being offered that address these factors. Enhanced operator safety and efficiency should result from a better understanding of the efforts to solve the visibility problems inherent in large tractors and self-propelled agricultural machinery.

Improving Histopathology Laboratory Productivity: Process Consultancy and A3 Problem Solving.

The ISO 17020 quality program has been run in our pathology laboratory for four years to establish an action plan for correction and prevention of identified errors. In this study, we aimed to evaluate the errors that we could not identify through ISO 17020 and/or solve by means of process consulting. Process consulting is carefully intervening in a group or team to help it to accomplish its goals. The A3 problem solving process was run under the leadership of a 'workflow, IT and consultancy manager'. An action team was established consisting of technical staff. A root cause analysis was applied for target conditions, and the 6-S method was implemented for solution proposals. Applicable proposals were activated and the results were rated by six-sigma analysis. Non-applicable proposals were reported to the laboratory administrator. A mislabelling error was the most complained issue triggering all pre-analytical errors. There were 21 non-value added steps grouped in 8 main targets on the fish bone graphic (transporting, recording, moving, individual, waiting, over-processing, over-transaction and errors). Unnecessary redundant requests, missing slides, archiving issues, redundant activities, and mislabelling errors were proposed to be solved by improving visibility and fixing spaghetti problems. Spatial re-organization, organizational marking, re-defining some operations, and labeling activities raised the six sigma score from 24% to 68% for all phases. Operational transactions such as implementation of a pathology laboratory system was suggested for long-term improvement. Laboratory management is a complex process. Quality control is an effective method to improve productivity. Systematic checking in a quality program may not always find and/or solve the problems. External observation may reveal crucial indicators about the system failures providing very simple solutions.

Visibility Problems for Manhattan Towers

Visibility Problems for Manhattan Towers

Accelerating Many-Lights Rendering with Multi-directional Scene Voxelization

Many scenes of interest to computer graphics applications contain a large number of dynamic light sources. Lighting is computationally expensive because it implies solving a visibility problem for every point light source. We present a method for voxel based approximation of the geometry of a scene. The ray is intersected with the approximation to accelerate the visibility determination. The scene geometry is approximated with a 2D array of voxelizations, with one voxelization for each direction from a dense sampling of the 2D space of all possible directions. The ray/scene intersection is approximated using the voxelization whose rows are most closely aligned with the ray. We support dynamic scenes with rigidly moving objects and complex dynamic scenes. The results of our experiments show our method can render scenes containing thousands lights.

An Approach for Shallow Underwater Images Visibility and Color Improvement

It has been observed that characteristics of underwater images are similar to day hazy images under poor lighting situation. So the problem of image visibility and color cast for underwater scenes is still challenging and demands more research attempts in this direction. This paper proposes an approach for shallow underwater visibility improvement which utilizes a combination of histogram equalization, gamma correction, and dark channel prior with morphological operation, in order to achieve effective haze subtraction and avoid halo effects in a single image with a complex structure. Our methodology, also considerthe effect of an adaptive gamma correction technique for further refinement of transmission map. The outcomes shows better peak signal to noise ratio and contrast noise ratio values over existing state-of-the-art methods based ondark channel prior. Results shows that our proposed approachin turn can be utilized in various underwater applications such as forensic image recognition, telecommunication cables recognition etc.

How Far Can You See in a Forest?

We address a visibility problem posed by Solomon & Weiss. More precisely, in any dimension $n := d + 1 \ge 2$, we construct a forest $\F$ with finite density satisfying the following condition : if $\e > 0$ denotes the radius common to all the trees in $\F$, then the visibility $\V$ therein satisfies the estimate $\V(\e) = O(\e^{-2d-\eta})$ for any $\eta > 0$, no matter where we stand and what direction we look in. The proof involves Fourier analysis and sharp estimates of exponential sums.

Computational modeling of wake flow to improve visibility during high speed snow plowing

The snow particles entrained in the wake of the maintenance trucks and the subsequent snow accumulation on the rear warning lights appear as the most pronounced visibility problems during high speed snowplowing (HSSP). Development of reliable and cost-effective methods have been demanded by State Department of Transportations to address the visibility hazards that impair safety of the operator and following traffic. An experimentally validated three dimensional computational fluid dynamics (CFD) model was developed to study the performance of a convex shaped tailgate airfoil to reduce visibility problems during HSSP. Possibility of snow coverage at the rear side of the truck is assessed by evaluating pressure and shear stress distributions. The airfoil selected based on the numerical study is installed to the tailgate of the truck and tested in the field. The full scale field tests validated the accuracy of the CFD model and confirmed the improved rear-side visibility by the tailgate airfoil.

Electrochemical detection of nitrate in PM2.5 with a copper-modified carbon fiber micro-disk electrode

The accurate measurement of nitrate in PM2.5 is essential for a complete understanding of the effects of aerosols on human health, the impact of aerosols on the radiative balance of the earth and the role of aerosols in visibility problems. In this paper, we present a novel, quick, easy, cheap and eco-friendly electroanalytical procedure for the determination of nitrate in PM2.5 samples using a carbon-fiber micro-disk electrode (CFMDE) coupled with square-wave voltammetry (SWV). Under optimal experimental conditions the nitrate SWV response increases linearly with nitrate concentration over a range of 0.003–2.0mmolL−1, and the detection limit is 1.10μmolL−1 (S/N=3). Nitrate contents in daily PM2.5 of Yangzhou in China were detected successfully by employing this novel method, and the results were compared well with those obtained by using ion chromatography. Then, we detected nitrate in two-hour PM2.5 filter samples via the standard addition method, and the concentrations were applied in an analysis of the daily change of nitrate contained in PM2.5 of Yangzhou. The research in this work indicates that the electrochemical method opens a new opportunity for fast, portable, and sensitive analysis of components in PM2.5.

The Earliest Neolithic at Vedbæk Fjord, Denmark

The investigation of a stratigraphically isolated settlement layer from the Earliest Neolithic (3950 – 3640 cal BC) at the Maglemosegård site, Northeast Zealand, reveals the nature of the Earliest Funnel Beaker horizon by the Stone Age Vedbæk Fjord. The settlement layer at Maglemosegård consists of small concentrations of fi nds, where only the presence of Funnel Beaker ceramics is typologically datable to the Neolithic. This is also the case on other Funnel Beaker sites in the area, where the Neolithic element is diffi cult to recognize from the lithic material and among the faunal remains. This problem of visibility is also relevant in a larger geographical perspective, especially where Early Neolithic and Mesolithic material are present at the same site. The lesson from Vedbæk and elsewhere too, suggests that the character and speed of the Mesolithic-Neolithic transition has to be revised.

Computing Shortest Paths among Curved Obstacles in the Plane

A fundamental problem in computational geometry is to compute an obstacle-avoiding Euclidean shortest path between two points in the plane. The case of this problem on polygonal obstacles is well studied. In this article, we consider the problem version on curved obstacles, which are commonly modeled as splinegons . A splinegon can be viewed as replacing each edge of a polygon by a convex curved edge (polygons are special splinegons), and the combinatorial complexity of each curved edge is assumed to be O (1). Given in the plane two points s and t and a set s of h pairwise disjoint splinegons with a total of n vertices, after a bounded degree decomposition of S is obtained, we compute a shortest s -to- t path avoiding the splinegons in O ( n + h log h + k ) time, where k is a parameter sensitive to the geometric structures of the input and is upper bounded by O ( h 2 ). The bounded degree decomposition of S , which is similar to the triangulation of the polygonal domains, can be computed in O ( n log n ) time or O ( n + h log 1 + ϵ h ) time for any ϵ &gt; 0. In particular, when all splinegons are convex, the decomposition can be computed in O ( n + h log h ) time and k is linear to the number of common tangents in the free space (called “free common tangents”) among the splinegons. Our techniques also improve several previous results: (1) For the polygon case (i.e., when all splinegons are polygons), the shortest path problem was previously solved in O ( n log n ) time, or in O ( n + h 2 log n ) time. Thus, our algorithm improves the O ( n + h 2 log n ) time result, and is faster than the O ( n log n ) time solution for sufficiently small h , for example, h = o (√ n ,log n . (2) Our techniques produce an optimal output-sensitive algorithm for a basic visibility problem of computing all free common tangents among h pairwise disjoint convex splinegons with a total of n vertices. Our algorithm runs in O ( n + h log h + k ) time and O ( n ) working space, where k is the number of all free common tangents. Note that k = O ( h 2 ). Even for the special case where all splinegons are convex polygons , the previously best algorithm for this visibility problem takes O ( n + h 2 log n ) time. (3) We improve the previous work for computing the shortest path between two points among convex pseudodisks of O (1) complexity each. In addition, a by-product of our techniques is an optimal O ( n + h log h ) time and O ( n ) space algorithm for computing the Voronoi diagram of a set of h pairwise disjoint convex splinegons with a total of n vertices.