scholarly journals Laser Scanning Based Surface Flatness Measurement Using Flat Mirrors for Enhancing Scan Coverage Range

2021 ◽  
Vol 13 (4) ◽  
pp. 714
Author(s):  
Fangxin Li ◽  
Heng Li ◽  
Min-Koo Kim ◽  
King-Chi Lo
Keyword(s):  
Construction Industry ◽  
Laser Scanning ◽  
Incident Angle ◽  
Measurement Range ◽  
Concrete Slabs ◽  
Important Indicator ◽  
Surface Flatness ◽  
Physical Barriers ◽  
Interior Walls ◽  
Speed And Accuracy

Surface flatness is an important indicator for the quality assessment of concrete surfaces during and after slab construction in the construction industry. Thanks to its speed and accuracy, terrestrial laser scanning (TLS) has been popularly used for surface flatness inspection of concrete slabs. However, the current TLS based approach for surface flatness inspection has two primary limitations associated with scan range and occluded area. First, the areas far away from the TLS normally suffer from inaccurate measurement caused by low scan density and high incident angle of laser beams. Second, physical barriers such as interior walls cause occluded areas where the TLS is not able to scan for surface flatness inspection. To address these limitations, this study presents a new method that employs flat mirrors to increase the measurement range with acceptable measurement accuracy and make possible the scanning of occluded areas even when the TLS is out of sight. To validate the proposed method, experiments on two laboratory-scale specimens are conducted, and the results show that the proposed approach can enlarge the scan range from 5 m to 10 m. In addition, the proposed method is able to address the occlusion problem of the previous methods by changing the laser beam direction. Based on these results, it is expected that the proposed technique has the potential for accurate and efficient surface flatness inspection in the construction industry.

scholarly journals Application of BIM and 3D Laser Scanning for Quantity Management in Construction Projects

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Thu Anh Nguyen ◽  
Phong Thanh Nguyen ◽  
Sy Tien Do
Keyword(s):  
Construction Industry ◽  
Construction Projects ◽  
Laser Scanning ◽  
Essential Role ◽  
Industrial Revolution ◽  
Management Process ◽  
3D Laser Scanning ◽  
Economic Sectors ◽  
Construction Companies

The construction industry has played an essential role in the process of modernization and industrialization and it has also been a major factor in determining the development of the infrastructure for other economic sectors. Construction companies consider the measurement of work progress, which often wastes time and has a low resolution, to be one of the most challenging problems faced by project management. Therefore, this research aimed to propose practical solutions by applying recent technological achievements of the 4.0 industrial revolution to improve the efficiency of the quantity management process. By utilizing the advantages and features of a BIM model and 3D laser scanning, this paper proposes that adopting a BIM model and 3D laser scanning has the potential to improve the accuracy and efficiency of the quantity management process. The case study demonstrated some typical tasks to evaluate accuracy and efficiency as well as to showcase the research proposal.

scholarly journals Dependence of Microcrack Behavior in Wood on Moisture Content during Drying

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Hiroyuki Yamamoto ◽  
Hiroki Sakagami ◽  
Yoshio Kijidani ◽  
Junji Matsumura
Keyword(s):  
Electrical Resistivity ◽  
Moisture Content ◽  
Wood Surface ◽  
Laser Scanning ◽  
Measurement Range ◽  
Cellular Level ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Sequential Images

A modified confocal laser scanning microscopy (CLSM) system was developed not only to observe the microcracks on the surface ofCryptomeria japonicaD. Donin situat the cellular level but also to obtain information about the moisture content (MC) of the wood surface by measuring the change in its electrical resistivity. The sequential images and changes in the electrical resistivity of the wood surface indicated that microcracks formed between the tracheid and ray parenchyma in the latewood region at >1.0E+ 07 Ω/sq (square). Microcracks formed when the MC of the wood surface was below the fiber saturation point determined through regression analysis of the surface electrical resistivity and MC. Most of the microcracks develop when the surface electrical resistivity ranged from 3.95E+ 10 to 3.60E+ 12 Ω/sq. When the surface MC was~2.5%, microcracks closed and the surface electrical resistivity was either~1.00E+ 15 Ω/sq or outside the measurement range. The modified CLSM and the method to measure the MC of the wood surface can be used to acquire information about the surface MC in specific areas shown in CLSM images. The findings indicated that the MC of the surface of the wood plays an important role in suppressing the emergence of microcracks in drying wood. The modified CLSM system and the method of measuring the MC of the surface of wood can be used to efficiently evaluate methods of drying wood and the quality of dried wood.

scholarly journals Mobile Laser Scanning Data for the Evaluation of Pavement Surface Distress

2020 ◽  
Vol 12 (6) ◽  
pp. 942 ◽  
Author(s):  
Maria Rosaria De Blasiis ◽  
Alessandro Di Benedetto ◽  
Margherita Fiani
Keyword(s):  
Point Cloud ◽  
Laser Scanning ◽  
Road Traffic ◽  
Single Point ◽  
Three Dimensional ◽  
Point Clouds ◽  
Road Surface ◽  
Important Indicator ◽  
The Road ◽  
Laser Systems

The surface conditions of road pavements, including the occurrence and severity of distresses present on the surface, are an important indicator of pavement performance. Periodic monitoring and condition assessment is an essential requirement for the safety of vehicles moving on that road and the wellbeing of people. The traditional characterization of the different types of distress often involves complex activities, sometimes inefficient and risky, as they interfere with road traffic. The mobile laser systems (MLS) are now widely used to acquire detailed information about the road surface in terms of a three-dimensional point cloud. Despite its increasing use, there are still no standards for the acquisition and processing of the data collected. The aim of our work was to develop a procedure for processing the data acquired by MLS, in order to identify the localized degradations that mostly affect safety. We have studied the data flow and implemented several processing algorithms to identify and quantify a few types of distresses, namely potholes and swells/shoves, starting from very dense point clouds. We have implemented data processing in four steps: (i) editing of the point cloud to extract only the points belonging to the road surface, (ii) determination of the road roughness as deviation in height of every single point of the cloud with respect to the modeled road surface, (iii) segmentation of the distress (iv) computation of the main geometric parameters of the distress in order to classify it by severity levels. The results obtained by the proposed methodology are promising. The procedures implemented have made it possible to correctly segmented and identify the types of distress to be analyzed, in accordance with the on-site inspections. The tests carried out have shown that the choice of the values of some parameters to give as input to the software is not trivial: the choice of some of them is based on considerations related to the nature of the data, for others, it derives from the distress to be segmented. Due to the different possible configurations of the various distresses it is better to choose these parameters according to the boundary conditions and not to impose default values. The test involved a 100-m long urban road segment, the surface of which was measured with an MLS installed on a vehicle that traveled the road at 10 km/h.

Design of a New-Type Electro-Optical Sensor Based on the Total-Internal Reflection Theory in Heterodyne Interferometry

2015 ◽  
Vol 1105 ◽  
pp. 136-140
Author(s):  
Shinn Fwu Wang ◽  
Fu Hsi Kao ◽  
An Li Liu
Keyword(s):  
Refractive Index ◽  
Optical Sensor ◽  
Incident Angle ◽  
Optical Fiber Sensor ◽  
High Sensitivity ◽  
Measurement Range ◽  
Heterodyne Interferometry ◽  
Optical Source ◽  
Bk7 Glass ◽  
New Type

In this paper, a new-type electro-optical sensor based on the total-internal reflections theory in heterodyne interferometry is proposed. The sensor is designed as a semi-circle shape. It is made of BK7 glass with the refractive index of 1.51509. And the end surface of the sensor is designed as a micro-mirror. The phase difference between s-and p-polarizations at the output of the optical fiber sensor can be obtained when a heterodyne optical source is launched into the electro-optical sensor at a suitable incident angle. By numerical calculation, the resolution of the system by using the intensity method can reach refractive index unit (RIU) in the measurement range of. The electro-optical sensor could be valuable for chemical, biological and biochemical sensing. It is with some advantages, such as, high resolution and stability, high sensitivity and real-time measurement.

scholarly journals Contribution of open-air concrete slabs to the heat stress on working mano

2018 ◽  
Author(s):  
Alex Augusto Marcelo ◽  
Lucila Chebel Labaki ◽  
Adriana Eloá Bento Amorim
Keyword(s):  
Heat Stress ◽  
Construction Industry ◽  
Sao Paulo ◽  
Concrete Slabs ◽  
São Paulo ◽  
Temperature Index ◽  
Wet Bulb Globe Temperature ◽  
Index Data ◽  
Globe Temperature ◽  
The City

The objective of this work was to evaluate the heat stress on workers of the construction industry on open-air concrete slabs in the city of Campinas, São Paulo, Brazil. Brazilian NR-15 provides a method for evaluating the heat stress to which a person is exposed using the WBGT (wet bulb globe temperature) index, prescribing rest pauses according to the type of activity. The methodology included measurements of environmental thermal variables and atmospheric quantities, followed by the calculation of the WBGT index. Data was collected at 12 different locations from August/2017 to March/2018, covering three diferent seasons. Results show that moderate and heavy activities on concrete slabs require pauses in every month, except in August.

Improving project communication in the architecture, engineering and construction industry: Coupling virtual reality and laser scanning

2020 ◽  
Vol 30 ◽  
pp. 101287
Author(s):  
Fábio Matoseiro Dinis ◽  
Luís Sanhudo ◽  
João Poças Martins ◽  
Nuno M.M. Ramos
Keyword(s):  
Virtual Reality ◽  
Construction Industry ◽  
Laser Scanning

Hybrid assembled MEMS scanner array with large aperture for fast scanning LIDAR systems

2019 ◽  
Vol 86 (3) ◽  
pp. 151-163 ◽  
Author(s):  
Thilo Sandner ◽  
Thomas Grasshoff ◽  
Michael Wildenhain ◽  
Markus Schwarzenberg
Keyword(s):  
System Integration ◽  
Laser Scanning ◽  
Measurement Range ◽  
Frame Rate ◽  
High Yield ◽  
Scanning Rate ◽  
Large Aperture ◽  
Mems Fabrication ◽  
Scanning Lidar ◽  
Tof Camera

AbstractThis article presents a large aperture micro scanning mirror (MSM) array especially developed for the panoramic 3D-ToF camera Fovea-3D. The Fovea-3D system uses a fiber amplified pulsed laser ToF technique at \lambda =1550\hspace{0.1667em}\text{nm} with 1 MVoxel distance measuring rate. It targets for real time 3D imaging with a panoramic optical field of view (FOV) of 360^\circ \times 60^\circ (horizontal × vertical) combined with a large distance measurement range of 100 m and a video-like frame rate of 10 Hz. For fast vertical scan axis a MEMS scanner module with large receiver aperture was especially developed. It increases the scanning rate to 3200 Hz which is four times faster in comparison to state-of-the-art fast macroscopic polygon scanning systems used for LIDAR systems. To guarantee at the same time a large reception aperture of {D_{\mathit{eff}}}=23\hspace{0.1667em}\text{mm}, large FOV of 60^\circ and high vertical scanning rate of 3200 Hz, a hybrid assembled MSM array was developed consisting of 22 reception mirrors and a separate emitting mirror for laser scanning of the target. For Fovea3D hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS scanner array to guaranty a high yield of MEMS fabrication. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezo-resistive position sensors are integrated on each MEMS chip for position feedback of driving control. The paper discusses details of the MEMS system integration including the synchronized operation of multiple MEMS scanning elements.

scholarly journals Detailed Study on Critical Delay Factors Affecting the Construction Industry

2019 ◽  
Vol 1 (1) ◽  
pp. 45-53
Author(s):  
Ravisankar K.L. ◽  
Bragateeswaran T
Keyword(s):  
Literature Review ◽  
Construction Industry ◽  
Questionnaire Survey ◽  
Construction Projects ◽  
Site Investigation ◽  
Site Management ◽  
Negative Effects ◽  
Local Conditions ◽  
Important Indicator ◽  
Factors Affecting

The Construction industry of India is an important indicator of the growth as it generates investment opportunities across various related sectors. Delay in construction projects is considered one of the most common problems causing a multitude of negative effects on the construction projects. Construction delays can be defined as the late completion of work compared to the planned schedule or contract schedule. Construction delays can be minimized only when their cause are identified. The objective of this study was to identify the major causes of construction delays. In this context the management of the delay may influence the financial performance of the project, since the overall value of contractual penalties may exceed ten percentage or more than that of the project budget. This study was carried out based on literature review and a questionnaire survey. The data for this study will be gathering through a detailed questionnaire survey. The questionnaire consists of total factors of seventeen group were contributed to the causes of construction delay based on literature review. In that seventeen groups have been consist of total 50 factors for delay. The questionnaire form is forwarded to various construction industries through email and in personal. The objectives of the study were successfully achieved. The top five most important factors that contributed to the causes of delays were Delay in financial support by owner to the contractor (Stage by stage payment), Design errors made by designers due to unfamiliarity with local conditions & environment, Equipment allocation problem, Poor site management & Inaccurate site investigation, Fluctuation of prices. To minimize delay in construction projects it has been identified that the top three effective methods of minimizing construction delays includes: site management and supervision, effective strategic planning, and clear information and communication channels.

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