3D CITYGML BUILDING MODELS DEVELOPMENT WITH CROSS-SCALE QUERY DATABASE

CityGML model-based is now a norm for smart city or digital twin city development for better planning, management, risk-related modelling and other applications. CityGML comes with five levels of details (LoD, in version 2.0) of buildings. The LoDs are also known as pre-defined multi-scale models requiring a large storage-memory-graphic consumption than a single scale model. LoD CityGML models are primarily constructed using point cloud measurements and images of multiple systems, resulting in a range of accuracies and detailed model representations. Additionally, it entails several software, procedures, and formats for the construction of the respective LoDs prior to the final result in the CityGML schema. Thus, this paper discusses several issues of accuracy and consistency, proposing several quality controls (QC) for multiple data acquisition systems (e.g. airborne laser systems and mobile laser systems), model construction techniques (e.g. LoD1, LoD2, and LoD3), software (interchange formats), and migration to a PostgreSQL database. Additionally, the paper recommends the importance of minimising implementation errors. A scale-specific unique identifier is introduced to link all associated LoDs, enabling cross-LoD information queries within a database. Proper model construction, accuracy control, and format interchange of LoD models in accordance with national and international standards will undoubtedly encourage and expedite data sharing among data owners, agencies, stakeholders, and public users. A summary of the work and accomplishments is included, as well as a plan for future research on this subject.

Laser beam welding setup for the coaxial combination of two laser beams to vary the intensity distribution

Deep-penetration laser beam welding is highly dynamic and affected by many parameters. Several investigations using differently sized laser spots, spot-in-spot laser systems, and multi-focus optics show that the intensity distribution is one of the most influential parameters; however, the targeted lateral and axial intensity design remains a major challenge. Therefore, a laser processing optic has been developed that coaxially combines two separate laser sources/beams with different beam characteristics and a measuring beam for optical coherence tomography (OCT). In comparison to current commercial spot-in-spot laser systems, this setup not only makes it possible to independently vary the powers of the two laser beams but also their focal planes, thus facilitating the investigation into the influence of specific energy densities along the beam axis. First investigations show that the weld penetration depth increases with increasing intensities in deeper focal positions until the reduced intensity at the sample surface, due to the deep focal position, is no longer sufficient to form a stable keyhole, causing the penetration depth to drop sharply.

Investigation of the ejected mass during high-intensity laser solid interaction for improved plasma mirror generation

The interaction of very intense and ultrashort laser pulses with solid targets is a topic that has attracted a large amount of interest in science and applications. This interest is boosted by the large progress made in the development of high repetition rate, high-power laser systems. With the significant increase in average power, there is concern about how to deal with ablated debris that may lead to contamination and damage during interaction experiments with solid targets. This issue is also highly relevant in experiments that include plasma mirrors. These are often employed to increase the contrast ratio of the intense laser pulse to unwanted laser pre-pulses from the amplifier chain and/or the background of amplified spontaneous emission. For this reason, the present work investigates the mass ejected from the target into vacuum for different conditions, particularly those present when plasma mirrors are introduced. The total amount of ablated mass can be reduced by making use of a temporally controlled plasma expansion that enhances the plasma mirror reflectivity. In this way, high intensity laser interaction experiments can be carried out with efficient and clean plasma mirrors significantly reducing the degradation of the laser optics and plasma diagnostics placed near the interaction.

Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

Understanding the mode components is of great importance to manipulate the optical modes and to improve the optical system performance. However, various forms of aberrations, stemming from misalignment and imperfect optical components and system design, degrade the performance of the modal decomposition (MD) system. Here we analyze the influence of various Zernike aberrations on MD performance in large-mode-area fiber laser systems. Using computer-generated optical correlation filter together with angular multiplexing technique, we can simultaneously measure multi-modal contents. Among the common aberrations, we find that the MD results are least sensitive to vertical astigmatism aberration. However, the vertical coma aberration and horizontal coma aberration have a large impact on MD results under the same aberration strength, which show a rather large change in modal weight and intermodal phase. Our analysis is useful to construct a precise MD system applicable for high-power optical fiber modal analysis and mode control.

Emerging Military Applications of Free Space Optical Communication Technology: A Detailed Review

Free Space Optical Communication (FSOC) technology, designed to operate through free space as medium is rapidly emerging as reliable, fast & secure alternative for broadband communication. It is being researched & investigated for applications and technical utilities in both civil & military domain systems owing to its immense benefits including high security, better data rates & fast installations, no requirement of licensed spectrum, best costs & simplicity of design as compared to contemporary Radio Frequency (RF) systems. FSOC networks once established are difficult to detect & intercept in view of small divergence of the laser beams. This paper reviews the FSOC technology and presents features based merits as well as unmatched advantages & associated major applications in various fields collating them into a single reference point for future research. Efforts have also been invested to present a review of FSOC’s limitations & innovative emerging mitigation techniques which can prove to be a one stop feeder & a launch pad for future research in FSOC domain. A literature survey has been undertaken of available FSOC related military applications to review & gather relevant inputs to throw light on emerging trends in military applications including recent experiments & researched areas pertaining to laser systems & weapons, Unmanned Aerial Vehicles (UAVs), under sea usages, terrestrial applications, aerial, naval ships/shore based applications & RF/hybrid systems. It has been endeavored to shed light on findings & developments in these classified military domains to generate inputs for future work in this domain. Finally, a future technical roadmap and a way ahead & suggestions have been coined up pointing towards required impetus & focus areas in FSOC research domain.

A Case of Huge Vocal Polyp in a Patient With Difficult Laryngeal Exposure Treated by Fiberoptic Laryngeal Laser Surgery Under Local Anesthesia

Indications of fiberoptic laryngeal laser surgery (FLS) procedure have broadened by the development of flexible fiberoptic endoscopes and flexible laser systems. FLS procedure performed under local anesthesia and it is the unique value of FLS. The surgery can be performed on patients who are impossible to undergo general anesthesia and difficult to be exposed by laryngeal microsurgery. Main indication of FLS procedure was small to moderate sized hemorrhagic vocal polyp, but we experienced a case of huge vocal polyp with difficult laryngeal exposure treated by FLS procedure under local anesthesia. The vocal polyp was removed successfully without vocal fold scar through fiberoptic laryngeal laser surgery under local anesthesia.

SIGNAL PROCESSING AND CYBERSECURITY IN SOME CHAOTIC OPTICAL COMMUNICTAION SYSTEMS

A chaos –geometric approach to investigation of complex chaotic dynamical systems is applied to an analysis, modeling and processing the time series of emission intensities of chaotic transmitter/receiver systems (two unidirectionally coupled semiconductor laser systems in the all-optical scheme) suited for encoding at rates of GBit/s. the problem of a signal processing is directly connected with the corresponding cybersecurity in some optical chaos communictaion systems. The estimated values for the dynamic and topologic invariants such as the correlation and Kaplan-York dimensions, Lyapunov indicators, Kolmogorov entropy etc for investigated chaotic signal time series of two unidirectionally coupled semiconductor laser systems in the all-optical scheme.

Enriching Existing 3D Pavement Condition Survey Datasets to Support Paving Project Cost Estimates, Project Planning, Designs, and Automated Machine Guidance

State departments of transportation (DOTs) typically perform annual pavement condition inspections, which serve as an important input into pavement management systems (PMS) software. Road surface defects (cracking, rutting, smoothness, etc.) are analyzed by PMS software to model the deterioration of pavements and to make budget and performance-based recommendations about which roads to maintain and how and when to maintain them. Increasingly at the state DOT level, these data are captured using high-speed 3D lasers (laser triangulation systems) that acquire the 3D shape of the road surface to evaluate its condition. Traditionally the capture of road elevation data relied entirely on the use of survey crews. Although accuracy can be quite high, the process of capturing elevations can require a lot of manpower, is time-consuming, requires lane closures, and results in a relatively small number of points per kilometer of road with which to perform all of the tasks from early project planning through construction. This paper explores an alternate approach that leverages existing 3D laser technology utilized by DOTs to measure the condition of in-service pavements. Typically, these laser systems capture “relatively referenced” 3D profiles of the roadway to evaluate pavement condition based on surface distortion. However, there is often no connection between these “relative” 3D profiles and real-world locations. This new approach involves the addition of high-accuracy blended global navigation satellite system + inertial navigation system positioning systems, as well as specialized software, to map the absolute position of 3D profiles in real-world coordinates.