Mapping buried utilities in difficult environments

There is a large number of underground utilities buried in urban areas, which is one of the most complex networks in the world. It has been estimated that only 50% of buried utilities are accurately recorded. However, failure to identify accurately the location of existing buried utilities results in numerous practical problems, costs and dangers for utility owners, contractors and road users. The underground utilities positioning accuracy requirement is 100 mm for both the accuracy of positioning system and the accuracy of detection devices. While the accuracy up to 300 mm would be acceptable for many respondents. This aim of this thesis is to research various means of improving the accuracy of positioning systems and the accuracy of detection devices for underground utilities in urban areas. GNSS is mainly used to find and record the position of utilities. However, the performance of GNSS is constrained by an insufficient number of visible satellites, poor satellite geometry and multipath in urban areas. The combination of GNSS systems increases the possible visible satellite number. Moreover, the geometry of satellites will be improved by integrating different GNSS constellations. This thesis evaluates the performance of different GNSS constellations such as GPS, GLONASS, BDS and QZSS and multi-GNSS integration in a controlled environment at UNNC and Ningbo city centre. The results provide evidence that using more than one GNSS constellation will significantly increase the availability of GNSS positions and improve the satellite geometry. There are 75% markers (21 out of 28) on campus of UNNC obtained the positioning error within 10cm either by GPS, BDS or GPS and BDS integration. In Ningbo city centre static test, 47% positions (7 out of 15) obtain ambiguity fixed solutions by GPS and BDS. For the underground utilities detection system, this thesis develops a low-cost IMU and odometer integration system to estimate the position of an approximately 30m long test pipeline. Moreover, a tightly coupled integration between IMU and odometer is developed to decrease error caused by the odometer installation attitude error and scale factor error. Besides this, a novel approach to this application of using a Robust Kalman filter is developed to remove the effect of odometer measurement outliers due to wheel-slip. Compared with the loosely coupled integration method, the use of loosely coupled integration with scale factor correction, tightly coupled integration and tightly coupled with Robust Kalman filter provide a horizontal position improvement of 11%, 41% and 43%, respectively. Similarly, the height accuracy is improved by 14%, 50% and 57% before the wheel-slip. The Wheel-slip leads to wrong odometer measurement that makes the positioning results far away from the truth. After applying Robust Kalman filter, the positioning error is reduced to 0.61 m in the horizontal plane, and 0.11 m in the height. Moreover, if using the forward and backward Kalman filter with known start and end positions, the test pipeline positioning maximum error in height is 4 cm, and the maximum horizontal error is 10 cm

2D-based indoor mobile laser scanning for construction digital mapping application

A common issue which occurs often in construction projects is how to determine the discrepancies between as-built or existing constructions and initial design. Physical manual measurement usually brings many of problems such as long measuring time, high labor consumption, and measurement error accumulation and in some cases lower accuracy. Therefore, more advanced technologies such as laser scanning and total station, which are used in geospatial mapping and surveying have been adopted in order to provide much more reliable and accurate measurements. However, technical and financial issues still constrain the widespread applications of well-known 3-dimensional (3D) terrestrial and aerial laser scanning, such as high equipment cost, complex pre-preparation, inconvenience of use and spatial limitation. This paper aims to introduce an innovative laser scanning method for indoor construction mapping. This method integrates an IMU-GPS positioning approach with a more convenient, more time saving and lower costed 2-dimensional (2D) laser scanner to realize indoor mobile 3D mapping for construction model creation, which can be integrated with Building Information Modelling (BIM) design in order to realize the applications, such as quality control of as-built construction or indoor mapping of existing building. Although compared with traditional 3D laser scanning, its accuracy and reliability cannot reach such a high level currently, experimental results still indicate feasibility, reliability and potential capability of this indoor mobile laser scanning method. It is hoped that this method will be further improved to substitute the stationary 3D laser scanning for narrow and limited construction spatial mapping in the near future

Positioning buried utilities in difficult environments

Recently an increasing number of underground pipes have been established, particularly in city centres, for different applications such as sewage, electricity, gas, water and drainage. How to detect and make a precise 3-dimensional survey of buried pipelines has become a focused issue. This paper first of all reviews four trenchless technologies for locating buried utilities with an emphasis on describing their application and limitations. It is found that there is no single technology, which is able to locate all underground utility service infrastructures, particularly for deep buried plastic pipes. Meanwhile, these trenchless detection technologies need to be integrated with positioning technologies to create maps for buried utilities. One of the most attractive positioning technologies for providing absolute global position is Global Navigation Satellite Systems (GNSS). However a large percentage of buried utilities are in urban areas, where is not ideal for GNSS positioning technology. This paper evaluates the performance of single and multi GNSS constellations by carrying out a test in a controlled environment. The results show that using combined GNSS systems improve availability in urban canyons compared with using GPS alone. In addition, this paper describes an inertial based pipeline positioning technology called ‘Ductrunner’, which can locate and position the buried objects in spite of the material and depth without extra positioning systems. An approximately 30m long test pipeline has been established to evaluate the performance of Ductrunner. The maximum positioning errors are found to be 8cm in plan and 4cm in height. This shows that this technology is very promising for measuring deep pipes over relatively short distances

Satellite mapping in cities and below cities: how good is it now?

Global navigation satellite systems (GNSS) have existed since the launch of the US global positioning system constellation in 1978. There is an increasing need for better maps in the digital age, particularly for buried utilities. One of the most convenient methods for creating accurate maps is the use of navigation satellites for positioning. However, built-up urban areas are not ideal for the use of this positioning technology. This paper provides an update on the situation regarding GNSS and assesses how new satellites and signals are contributing to better positioning availability by carrying out a test in a controlled environment. The results show that using combined satellite systems improves availability in urban canyons in some cases, but not in all scenarios. In addition, pipeline mapping technology has been tested and been shown to be an effective means of mapping pipes deep under the ground over short distances

The Role of Sleep Deprivation in Arrhythmias

Sleep is essential to the normal psychological and physiological activities of the human body. Increasing evidence indicates that sleep deprivation is associated with the occurrence, development, and poor treatment effects of various arrhythmias. Sleep deprivation affects not only the peripheral nervous system but also the central nervous system, which regulates the occurrence of arrhythmias. In addition, sleep deprivation is associated with apoptotic pathways, mitochondrial energy metabolism disorders, and immune system dysfunction. Although studies increasingly suggest that pathological sleep patterns are associated with various atrial and ventricular arrhythmias, further research is needed to identify specific mechanisms and recommend therapeutic interventions. This review summarizes the findings of sleep deprivation in animal experiments and clinical studies, current challenges, and future research directions in the field of arrhythmias

Mapping buried utilities in difficult environments

There is a large number of underground utilities buried in urban areas, which is one of the most complex networks in the world. It has been estimated that only 50% of buried utilities are accurately recorded. However, failure to identify accurately the location of existing buried utilities results in numerous practical problems, costs and dangers for utility owners, contractors and road users. The underground utilities positioning accuracy requirement is 100 mm for both the accuracy of positioning system and the accuracy of detection devices. While the accuracy up to 300 mm would be acceptable for many respondents. This aim of this thesis is to research various means of improving the accuracy of positioning systems and the accuracy of detection devices for underground utilities in urban areas. GNSS is mainly used to find and record the position of utilities. However, the performance of GNSS is constrained by an insufficient number of visible satellites, poor satellite geometry and multipath in urban areas. The combination of GNSS systems increases the possible visible satellite number. Moreover, the geometry of satellites will be improved by integrating different GNSS constellations. This thesis evaluates the performance of different GNSS constellations such as GPS, GLONASS, BDS and QZSS and multi-GNSS integration in a controlled environment at UNNC and Ningbo city centre. The results provide evidence that using more than one GNSS constellation will significantly increase the availability of GNSS positions and improve the satellite geometry. There are 75% markers (21 out of 28) on campus of UNNC obtained the positioning error within 10cm either by GPS, BDS or GPS and BDS integration. In Ningbo city centre static test, 47% positions (7 out of 15) obtain ambiguity fixed solutions by GPS and BDS. For the underground utilities detection system, this thesis develops a low-cost IMU and odometer integration system to estimate the position of an approximately 30m long test pipeline. Moreover, a tightly coupled integration between IMU and odometer is developed to decrease error caused by the odometer installation attitude error and scale factor error. Besides this, a novel approach to this application of using a Robust Kalman filter is developed to remove the effect of odometer measurement outliers due to wheel-slip. Compared with the loosely coupled integration method, the use of loosely coupled integration with scale factor correction, tightly coupled integration and tightly coupled with Robust Kalman filter provide a horizontal position improvement of 11%, 41% and 43%, respectively. Similarly, the height accuracy is improved by 14%, 50% and 57% before the wheel-slip. The Wheel-slip leads to wrong odometer measurement that makes the positioning results far away from the truth. After applying Robust Kalman filter, the positioning error is reduced to 0.61 m in the horizontal plane, and 0.11 m in the height. Moreover, if using the forward and backward Kalman filter with known start and end positions, the test pipeline positioning maximum error in height is 4 cm, and the maximum horizontal error is 10 cm

A Nuclear Reactor Transient Methodology Based on Discrete Ordinates Method

With the rapid development of nuclear power industry, simulating and analyzing the reactor transient are of great significance for the nuclear safety. The traditional diffusion theory is not suitable for small volume or strong absorption problem. In this paper, we have studied the application of discrete ordinates method in the numerical solution of space-time kinetics equation. The fully implicit time integration was applied and the precursor equations were solved by analytical method. In order to improve efficiency of the transport theory, we also adopted some advanced acceleration methods. Numerical results of the TWIGL benchmark problem presented demonstrate the accuracy and efficiency of this methodology

Flux Pinning Properties of Single-Grain Bulk GdBCO Superconductors Processed by Different Thicknesses of Y123 Liquid Source

The performance of critical current density of GdBa2Cu3O7−δ (GdBCO or Gd123) superconductor bulk has an important influence on its practical applications. In this work, four single-domain GdBCO superconductor bulks were successfully processed by the modified top-seeded melt-texture growth method. The addition of a YBa2Cu3O7−δ (Y123) liquid source with different thicknesses, 0 mm (S0), 3 mm (S3), 5 mm (S5), 7 mm (S7), was introduced to study the influence on the superconducting properties. GdBCO bulk with the addition of the Y123 liquid source with a 3-mm thickness shows the best superconducting properties. The addition of the Y123 liquid source results in a decrease in the Gd3+ ion concentration required for Gd123 growth; thus, Gd2BaCuO5 (Gd211) particles in the liquid source need a larger self-decomposition to diffuse Gd3+ ions to Gd123 growth front, which refines the size and leads to a homogenous distribution of the Gd211 particles in the bulks. Thus, the more pinning centers of fined Gd211 particles improve the superconducting properties of GdBCO bulk. With increases in the thickness of Y123 liquid source to 5 mm and 7 mm, high RE3+ (Gd3+ and Y3+) concentration can coarsen Gd211 particles and fuse with Gd211 liquid source. The superconducting properties apparently drop. Therefore, the addition of a Y123 liquid source with a suitable thickness is a positive modification to obtain high-performance GdBCO bulk

recentadvancesonthereductionofco2toimportantc2oxygenatedchemicalsandfuels

The chemical utilization of CO2 is a crucial step for the recycling of carbon resource. In recent years, the study onthe conversion of CO2 into a wide variety of C2+ important chemicals and fuels has received considerable attentionas an emerging technology. Since CO2 is thermodynamically stable and kinetically inert, the effective activationof CO2 molecule for the selective transformation to target products still remains a challenge. The welldesigned CO2 reduction route and efficient catalyst system has imposed the feasibility of CO2 conversion into C2+ chemicals and fuels. In this paper, we have reviewed the recent advances on chemical conversion of CO2 into C2+ chemicals and fuelswith wide practical applications, including important alcohols, acetic acid, dimethylether, olefins and gasoline. In particular, the synthetic routes for C-C coupling and carbon chain growth, multifunctionalcatalyst design and reaction mechanisms are exclusively emphasized

Synthesis and Characterization of Rh/B–TNTs as a Recyclable Catalyst for Hydroformylation of Olefin Containing –CN Functional Group

The TiO2-based nanotubes (TNTs, B–TNTs) of different surface acidities and their supported Rh catalysts were designed and synthesized. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), tempera–ture–programmed desorption of ammonia (NH3–TPD), atomic emission spectrometer (ICP), and Brunauer–Emmett–Tellerv (BET) surface-area analyzers. Images of SEM and TEM showed that the boron-decorated TiO2 nanotubes (B–TNTs) had a perfect multiwalled tubular structure; their length was up to hundreds of nanometers and inner diameter was about 7 nm. The results of NH3-TPD analyses showed that B–TNTs had a stronger acid site compared with TNTs. For Rh/TNTs and Rh/B–TNTs, Rh nanoparticles highly dispersed on B–TNTs were about 2.79 nm in average diameter and much smaller than those on TNTs, which were about 4.94 nm. The catalytic performances of catalysts for the hydroformylation of 2-methyl-3-butennitrile (2M3BN) were also evaluated, and results showed that the existence of B in Rh/B–TNTs had a great influence on the catalytic performance of the catalysts. The Rh/B–TNTs displayed higher catalytic activity, selectivity for aldehydes, and stability than the Rh/TNTs