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The international network of submarine cables plays a crucial role in facilitating global telecommunications connectivity, carrying over 99% of all internet traffic. However, submarine cables challenge digital sovereignty due to their ownership structure, cross-jurisdictional nature, and vulnerabilities to malicious actors. In this article, we assess these challenges, current policy initiatives designed to mitigate them, and the limitations of these initiatives. The nature of submarine cables curtails a state’s ability to regulate the infrastructure on which it relies, reduces its data security, and threatens its ability to provide telecommunication services. States currently address these challenges through regulatory controls over submarine cables and associated companies, investing in the development of additional cable infrastructure, and implementing physical protection measures for the cables themselves. Despite these efforts, the effectiveness of current mechanisms is hindered by significant obstacles arising from technical limitations and a lack of international coordination on regulation. We conclude by noting how these obstacles lead to gaps in states’ policies and point towards how they could be improved to create a proactive approach to submarine cable governance that defends states’ digital sovereignty. [ABSTRACT FROM AUTHOR]

Expanding floating wind into new markets could support emission reduction targets in several national contexts. It furthers the need for adequate assessments to gain a full understanding of the technology's potential in future markets. South Africa is a prime case study as it has seen limited industry and policy developments despite its huge technical potential for floating offshore wind (FOW). This paper assessed the locational potential of floating wind in South Africa through a three-phased approach that evaluated the key technical drivers/barriers of the technology, conducted a Geographic Information System analysis (GIS) using ArcMap 10.8 to exclude unsuitable sites based on a predetermined exclusion criteria (including marine protected zones, underwater cables, major oil and gas deposits, etc.), and estimated the total harvestable capacity in the feasible sites. The study found that 2% (246,105.4 km2) of South Africa's entire Exclusive Economic Zone (EEZ) is suitable for hosting floating wind turbines, with a potential to generate a maximum of 142.61 GW of floating wind power. Although the Western Cape province holds the highest potential (80.52 GW) for floating wind in the country, the Eastern Cape region, with a locational potential of 20.04 GW, is considered most suitable for early-stage developments due to the availability of grid connection points, limited marine traffic, and proximity to appropriate port facilities. Future work can conduct techno-economic assessments to evaluate the technical and economic implications of developing floating wind in distinct sites in the country's EEZ. [ABSTRACT FROM AUTHOR]

The full understanding of the importance of submarine cables as part of the global network infrastructure in the digital economy era, along with decades of knowledge accumulation in this field, has not prevented Hong Kong from facing increasing difficulties in gaining more access to submarine cable systems since 2017. Given that geopolitical differences between China and the U.S. are dividing the international network infrastructure, the business interests of Hong Kong enterprises and the urban development prospects of the Hong Kong government have been forced to defer to Beijing's security concerns. Meanwhile, in recent years China has been acquiring data power by modelling the "data collection – data sharing – data space governance" path that the United States and its allies set previously. During this process, the power shaped by China's unique technological, social and institutional characteristics offers an alternative to American dominance, although it exacerbates the global divergence of internet infrastructure. Many projects along the Belt and Road Initiative and the Digital Silk Road are the examples of China's data power projection, and will bring opportunities for Hong Kong's own submarine cables sector and for the city's role as a super connector in the coming years. [ABSTRACT FROM AUTHOR]

To assess the insulation aging in high-voltage XLPE submarine cables using frequency domain dielectric spectroscopy, this study presents a methodology for separating the polarization and conductance components from the dielectric response data by analyzing the physical significance of the complex dielectric constant. Initially, four sets of samples of high-voltage XLPE submarine cables exhibiting varying degrees of aging were procured, which were generated through accelerated aging tests and measured the mechanical properties and frequency domain dielectric spectra of these samples. Subsequently, the polarization and conductance components were separated from the measured dielectric curves to investigate the impact of aging on polarization and conductivity losses within the low-frequency range. Finally, the precision of the dielectric model in reconstructing the measured dielectric curves was compared, and characteristic parameters for quantifying the aging condition were suggested. The discoveries indicate that the polarization and conductance processes in the dielectric response of high-voltage XLPE submarine cables accelerate with increasing aging, and removing the conductivity loss from the imaginary part of the complex dielectric constant enhances the accuracy of the dielectric model in reconstructing the measured dielectric curves. The model parameters ∆ε, ε∞, and α can effectively characterize the aging state of XLPE insulation in high-voltage submarine cables, enabling the assessment of aging insulation in high-voltage XLPE submarine cables. [ABSTRACT FROM AUTHOR]

In situ observations under typhoon conditions are sparse and limited. Distributed acoustic sensing (DAS) is an emerging technology that uses submarine optical-fiber (OF) cables to monitor the sea state. Here, we present DAS-based ocean current observations when a super typhoon passed overhead. The microseismic noise induced by ocean surface gravity waves (OSGWs) during Typhoon Muifa (2022) is observed in the ~0.08–0.38 Hz frequency band, with high-frequency (>0.3 Hz) component being tidally modulated. The OSGW propagation along the entire cable is successfully revealed via frequency–wavenumber analysis. Further, a method based on the current-induced Doppler shifts of DAS-recorded OSGW dispersions is proposed to calculate both speeds and directions of horizontal ocean currents. The measured current is consistent with the tidally induced sea-level fluctuations and sea-surface winds observed at a nearby ocean buoy. These observations demonstrate the feasibility of monitoring the ocean current under typhoon conditions using DAS-instrumented cables. Using microseismic noise observed by distributed acoustic sensing (DAS) with a submarine cable, this study measures the magnitude and direction of ocean currents during the passage of typhoon Muifa and estimates the ocean wave propagation. [ABSTRACT FROM AUTHOR]

Background: Subsea power cable failures in offshore wind farms result in significant financial losses. One common failure mode is submarine power cable bending. Objective: The primary objective of this study is to validate two analytical models using strain readings obtained from a novel 3-point bending setup designed for power cable specimens. The setup incorporates two types of optical fiber sensors for simultaneous strain measurement. Methods: A 3-point bending setup is constructed, integrating optical fiber sensors installed on the embedded fiber optic cable within the submarine power cable. One set of sensors is fixed to the fiber optic cable sheath, while a second set consists of loose tube fibers that are inside the fiber optic cable. The strain readings of the fixed sensors are compared to two analytical models. The first analytical model assumes a constant power cable curvature, while the second model considers variable curvature. Results: The analytical models both predict nearly flat strain profiles and are in line with each other. The strain data, however, approaches zero strain away from the cable center. Model assumptions such as perfect sensor positioning and zero slip of the fiber optic cable cause this discrepancy. The results of the constant curvature model agree well with strain averages of the fixed sensors around the central region of the power cable, and both scale linearly with amplitude. Finally, the strain readings from the loose tube fibers demonstrate high reproducibility, facilitating the development of a calibration curve for estimating power cable curvature. Conclusions: The analytical models surpass existing models by providing good agreement with the measured strain around the cable center. Moreover, the highly reproducible strain readings from the loose tube fibers allow estimating power cable curvature. [ABSTRACT FROM AUTHOR]

The USA recently announced it is planning on deploying 30 GW of offshore wind by 2030 (national goal for offshore wind). Part of this development will be in the Gulf of Mexico, which has both wind potential and pre-existing oil and gas pipelines, only a portion of which is currently being used. Examining whether these assets can be used to economically transport power back from future Gulf wind farms should be a first step for developers. The question of whether laying new high-voltage direct current submarine cable versus repurposing pipeline to transport wind power will be examined. This paper looks at the hydrogen market and its use to transport wind power, what it would take to retrofit pipeline to carry hydrogen, a cost analysis given available data, and a look at potential policy support. There is a need to assess pipelines individually; however, retrofitting existing infrastructure should be considered an alternative to laying new submarine transmission cables. Additionally, alleviating the issue of oil and gas stranded assets through pipeline reuse may provide political support in hastening the energy transition. [ABSTRACT FROM AUTHOR]

The damage characteristics of coral limestone are of great significance for guiding the design and construction of offshore engineering such as submarine tunnels and pipelines. The mechanical properties and damage behavior of coral limestone collected from the Zhongsha Islands, South China Sea were investigated based on the results of uniaxial compression tests. A theoretical porosity calculation method was put forward and applied to the coral limestone with a large number of closed internal pores. The failure characteristics of the coral limestone are very different from those of terrestrial rocks because the strength decreases gradually after failure. The threshold stresses of coral limestone were calculated based on the uniaxial compression tests and compared with that of terrigenous rocks. The crack initiation stress is 39–56% of peak strength, similar to that of most terrigenous rocks. The crack damage stress is 70–100% of peak strength, differing greatly from most terrigenous rocks. Coral limestone presents a pattern of shreds after failure due to its unique biological pore structure. In this paper, a new damage variable was proposed to quantitatively analyze the damage behavior of coral limestone. Because coral limestone contains numerous original pores, damage occurs to a large extent in the unstable cracking stage. Good linear correlations were identified between each threshold stress and peak stress, and corresponding empirical formulae were put forward. This paper analyzed the damage characteristics of coral limestone from the Zhongsha Islands, which can provide reference for damage analysis of other porous brittle rocks. Highlights: Damage characteristics and the threshold stresses of coral limestone were investigated. A theoretical calculation method of porosity of coral limestone was proposed. A new damage variable was proposed to quantitatively characterize the damage behavior of coral limestone with complex pore structure. Investigate the relationships between the threshold stresses and peak stress of coral limestone, and the corresponding empirical formulas were put forward. [ABSTRACT FROM AUTHOR]

As the main electrical equipment of offshore power grids, optical fiber composite submarine cables undertake the task of power transmission and data communication. In order to ensure the proper functioning of the submarine cable, it is necessary to analyze the working state of it and identify the fault event. This paper proposes a fault detection method for submarine cables, that is, the VMD and self-attention-based Bi-LSTM model. First, we use ANSYS software to generate the vibration waveforms of three main fault events of optical fiber composite submarine cables. Then, by generating the detection matrix of background noise and the vibration waveforms, it can realize the orientation and detection of fault events in single submarine cable. In addition, the vibration signal can be decomposed into IMF components using variational mode decomposition (VMD) for feature extraction. Moreover, the IMF components are input to the self-attention layer for feature fusion and Bi-LSTM module for further feature extraction. Finally, the result of the fault detection is output through the classification layer. According to the comparative experiment and the ablation experiment, the proposed model has proved to outperform the other benchmark models and is robust and stable under the condition of different signal-to-noise ratios. [ABSTRACT FROM AUTHOR]

The Irukandji jellyfish (Carukia barnesi) is a medically important species. While the medusa stage of this species is well known, due to its highly venomous sting, the benthic polyp has core roles in regulating both the timing and abundance of medusa making it a research priority. However, due to their small size, Carukia barnesi polyps have never been found in situ and, basic ecological knowledge surrounding this life stage is limited. In this study we adopt a lab-based approach, utilizing physiological tolerance as a functional tool, to gain new insights into the in situ location for Carukia barnesi polyps. The physiological tolerance of Carukia barnesi polyps was characterized by measuring the oxygen consumption rates of polyps exposed to different salinity/temperature combinations. A total of nine salinities and seven temperatures were investigated, ranging from 11 °C/16‰ to 34 °C/42.5‰, encompassing the spectrum of environments experienced on the Great Barrier Reef. Polyps were also monitored for morphological changes such as asexual reproduction, polyp deterioration, and mortality. Salinity did not have a significant effect on oxygen consumption rates, with Carukia barnesi polyps displaying a significant tolerance to a wide range of salinities. The effect of temperature, however, was statistically significant with oxygen °consumption rates increasing alongside water temperature. There was no statistical evidence to support an interactive effect between salinity and temperature. Based on these results, we conclude that the polyp stage of this species is likely located in an environment with stable temperatures and fluctuating salinities and, consequently, future endeavors aimed at locating this life stage should expand targeted survey areas outside stable oceanic environments, typical of medusa, and encompass dynamic environments such as estuaries and submarine freshwater upwellings. [ABSTRACT FROM AUTHOR]

Many communication and signaling systems still rely on cables routed trackside and are thus exposed to induction. The evaluation of induced voltage as touch voltage and as coupled interference is particularly relevant for safety assessment, in terms of electrical and functional safety, and in general for system availability. Induction may be estimated by simplified and conservative closed-form expressions or with more complex simulation models; available models are in general developed for frequency domain. The proposed method provides accurate induced voltage waveform with moderate complexity, as caused by AC traction supply major transients for both 1 × 25 (no autotransformer) and 2 × 25 (with autotransformer) configurations. The method can use simulated or measured frequency responses followed by fitting of a polynomial transfer function H(s) with good approximation (about 3–6%) over an extended frequency interval (up to 1000 Hz). Input to H(s) are the transient waveforms, namely for short circuit and inrush phenomena. For short circuit the proposed calculation method is that of an equivalent circuit including all relevant elements, confronted to standardized method of EN 60909-0 for what regards peak and steady state value and time constant. The H(s) output is the transient induced voltage waveform: comparing the intensity for 1 × 25 and 2 × 25 cases achieves a first validation by comparing to reduction factors documented in the literature. The method is validated using measured inrush current and resulting cable voltage, showing an average error of 2–3%. [ABSTRACT FROM AUTHOR]

The results of numerical simulation of the characteristics of a superconducting CORC cable under synchronous cyclic loading by electric current and magnetic field under liquid neon cooling are presented. Distributions of the magnetic field and currents in the system, mechanical stresses and deformations, and energy losses occurring during remagnetization by the magnetic field and electric current are calculated. The features of electrodynamic and thermophysical processes occurring in the system under synchronous current and magnetic-field loading at different winding angles of HTS tapes are shown. The simulation was performed by the finite element method in the Comsol Multiphysics software. The model is designed for calculating the magnetic system of a superconducting inductive energy storage system as part of the Nuclotron based Ion Collider fAcility (NICA), which is under construction at the Laboratory of High Energy Physics (HEPL) of the Joint Institute for Nuclear Research (JINR). [ABSTRACT FROM AUTHOR]

The MCRT and its corresponding anchoring method are easy to use, reliable, and can be used to install cable bolts with a resin-surrounding rock bond strong enough to match the supporting force of the high-strength cable in the cable bolt. The breaking force of conventionally anchored cable bolt with a diameter of 17.8 mm was 355 kN. After the resin had hardened, the cable bolts were pre-tightened so that the changes in cable bolt support forces could be monitored as the working face advanced toward test site. Keywords: Multiple Conical Reaming Tool (MCRT); Weak rock; Cable bolt; Anchoring force; Resin; Anchorage quality improvement EN Multiple Conical Reaming Tool (MCRT) Weak rock Cable bolt Anchoring force Resin Anchorage quality improvement 7887 7897 11 11/15/22 20221201 NES 221201 Introduction Cable bolts have several advantages including their strength, large anchoring ranges, and their capability to transmit high pre-tightening forces. [Extracted from the article]

​Oil-filled submarine cables have come to dominate the reliable delivery of electrical power today, but oil leakages still remain a challenge. This work focuses on exploring the detection of dodecylbenzene (DDB) after leakage. DDB can be dispersed as small droplets in seawater, which the diameter of DDB droplets increased from 60 nm to 200 nm with the increase of the concentration from 10 ppm to 1000 ppm. Moreover, excitation-emission matrix (EEM) spectra were employed to investigated the detection of DDB. DDB has characteristic fluorescence peaks located at λEx/λEm = 225/350 and 255/350. The FIo/w value of 50 ppm DDB was 28.869, which was significantly different from simulated seawater low as 1.3926. Contaminants such as metal ions (Cu2+, Cd2+, Zn2+) and organic matter (tetracycline) do not significantly affect the qualitative identification of DDB by EEMs. This study suggests a research basis for exploring the way for detection of DDB. [ABSTRACT FROM AUTHOR]

Cable containing two semiconductor screens has higher influence of the screen on line constants and wave propagation compared to cable with single semiconductor as reported in existing literature. Considering this fact, this work investigates the possible influence of quantitative increase in semiconductor screen on line constants and wave properties of a cable. Here the quantitative increase in semiconductor screen in a cable structure is achieved by considering an additional screen on sheath outer surface along with preexisting screen attached with sheath inner and core outer surface of the cable. For such cable structure, sheath interleaved between double semiconductor screens forms a three layered conductor-semiconductor assembly compared to two layered such assembly in conventional cable. Closed form expressions of surface and mutual impedance of such three layered assembly are derived here using electromagnetic analysis. Then using these expressions, internal impedance matrix of the concerned cable is developed and then validated by reproducing the same matrix using independent circuit approach. Frequency variations of surface impedance of such three layered assembly indicates that both semiconductor screens contribute to the impedance of the assembly compared to single semiconductor in two layered assembly, thus enhancing the influence of screen in concerned cable. Finally a comparative study on the influence of semiconductor properties on line constants and wave properties of cable with sheath containing double, single and no semiconductor screen is performed. Such study indicates that the quantitative increase in semiconductor screen in cable structure considerably improves its attenuation property and wave velocity for a certain ranges of semiconductor properties. [ABSTRACT FROM AUTHOR]

Preheating is a key step for the start-up of new submarine hot oil pipelines, which is characterized by the unsteady hydraulic and thermal coupling, and affected by many factors, including the fluid flow rate and temperature of preheating medium, the properties of subsea soil, the temperature of seawater, etc. To investigate the quantitative effects on the preheating results caused by the above influential factors, simulation research is performed in this paper with a numerical methodology named DMOC-FEM established before by taking a new Chinese submarine crude oil pipeline as example. The factors studied include the flow rate and inlet temperature of preheating medium, riser, physical properties of subsea soil, temperature of seawater, etc. The results show that the preheating medium mainly warms submarine pipe walls rather than the surrounding subsea soil. Among the influencing factors, the fluid flow rate and temperature of preheating medium have the most notable and direct effect on the distribution and change of fluid temperature in the subsea pipe. That caused by other factors happens to be much lighter in comparison. Due to the excellent insulation effect of the pipe-in-pipe structure, the temperature drop happens on the subsea pipe risers can be ignored. Furthermore, among the properties of subsea soil, thermal conductivity has the greatest influence on the outlet temperature during the preheating process.. [ABSTRACT FROM AUTHOR]

The use of fiber infrastructures for environmental sensing is attracting global interest, as optical fibers emerge as low cost and easily accessible platforms exhibiting a large terrestrial deployment. Moreover, optical fiber networks offer the unique advantage of providing observations of submarine areas, where the sparse existence of permanent seismic instrumentation due to cost and difficulties in deployment limits the availability of high-resolution subsea information on natural hazards in both time and space. The use of optical techniques that leverage pre-existing fiber infrastructure can efficiently provide higher resolution coverage and pave the way for the identification of the detailed structure of the Earth especially on seismogenic submarine faults. The prevailing optical technique for use in earthquake detection and structural analysis is distributed acoustic sensing (DAS) which offers high spatial resolution and sensitivity, however is limited in range (< 100 km). In this work, we present a novel technique which relies on the dissemination of a stable microwave frequency along optical fibers in a closed loop configuration, thereby forming an interferometer that is sensitive to deformation. We call the proposed technique Microwave Frequency Fiber Interferometer (MFFI) and demonstrate its sensitivity to deformation induced by moderate-to-large earthquakes from either local or regional epicenters. MFFI signals are compared to signals recorded by accelerometers of the National Observatory of Athens, Institute of Geodynamics National Seismic Network and by a commercially available DAS interrogator operating in parallel at the same location. Remarkable agreement in dynamical behavior and strain rate estimation is achieved and demonstrated. Thus, MFFI emerges as a novel technique in the field of fiber seismometers offering critical advantages with respect to implementation cost, maximum range and simplicity. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental study of shear testing of 15.2 mm, 25 t capacity seven wire cables at zero, 30° and 45° angles using two different shear testing facilities at the University of Wollongong (UOW) and the University of Southern Queensland (USQ) in Toowoomba. A circular double-shear rig MK-IV was used for testing cable perpendicular to the sheared joint faces (zero angle of orientation), while testing the cable at 30° and 45° was carried out using a larger-size rectangular-shaped rig. Testing was carried out based on the double-shear testing methodology wherein cable bolts were fully encapsulated using Stratabinder HS inside of three concrete blocks representing host rocks. This study was part of the tri-universities-funded ACARP project C27040 awarded jointly to the University of New South Wales, University of Wollongong and University of Southern Queensland. The objective of the experimental testing programme was to provide the essential information for the development of numerical models that included not only the technical parameters, but also the behavioural outcomes from various tests with respect to the angles of testing and their effect on the nature of cable failure, be it pure shear, tensile shear or shear tensile, cable pretension and the credibility of the effectiveness of the Barrel and Wedge (B&W) anchorage system were evaluated. Laboratory facilities at both UOW and USQ were used in the study. The prepared double-shear samples were then positioned inside of compression testing machines and were subjected to shear testing. The values of shear load and displacement were recorded for various inclinations angles. It was found that increased angle of shear contributes to increased stiffness of the cable in shear with other parameters being equal. Subroutine codes were developed in UDEC and 3DEC to simulate shear behaviour of cable bolts installed in angles for different pretension loads. The numerical simulations indicated that UDEC and 3DEC can simulate the general shear behaviour of cable bolts reasonably well for various inclination angles and pretension values. Highlights: The historical information that sets the record on the early development and application of cable bolt on ground reinforcement along with the relevant literature review was presented, The results of large-scale experimental study on shear behaviour of cable bolts were presented and discussed, The results of large-scale experimental studies on shear behaviour of cable bolts installed in angles for various pretension values were presented and discussed in detail at a level that has not been investigated in previous geotechnical projects, The capabilities of distinct element code in modelling shear behaviour of cable bolts were studied for different geotechnical conditions by developing original subroutine programs, and Parametric studies were carried out to investigate the effects of relevant parameters on shear behaviour of cable bolts. [ABSTRACT FROM AUTHOR]

Complex geological structures like pores, fractures and faults in submarine hydrothermal reservoirs have significant but unclear effects on internal hydrothermal flow and heat transfer, which hinders reservoir exploitation. This study establishes a heat transfer model of a buried pipe coupled in fracture-porous media based on the reservoir characteristics. The model is verified through experiments using fractured porous media test rigs and computational fluid dynamics simulations. Simulations are performed to investigate the effects of fracture flow velocity, width, cornerstone porosity on the heat transfer efficiency of the buried pipe. Results show that optimizing fracture flow velocity, fracture width and cornerstone porosity can substantially improve the heat transfer performance of the buried pipe. Increasing fracture flow velocity from 10–4 m/s to 10–3 m/s, results in a 161.92% increase of Nusselt number. When the fracture width increases to 5 times the pipe diameter, Nusselt number rises by 35.52%. The heat transfer is optimal at a porosity of 0.3. This study provides theoretical guidance for exploiting submarine hydrothermal resources and designing fracture-porous couplings to enhance buried pipe heat transfer. [ABSTRACT FROM AUTHOR]

In this paper, the optimal fiber length in optical ground wire (OPGW) cable during production process is determined. The results show that in OPGW cable, if the fiber stranding length is less than the maximum lay length, the ultimate tensile stress (UTS) percentage decreases, but if it is higher, it would increase the bending losses and uses more fiber length, which is economically not viable. The calculation results show that by determining the maximum fiber lay length, the UTS percentage of OPGW cable can be controlled for a desired value. [ABSTRACT FROM AUTHOR]

A medium resolution underwater in-situ gamma-ray spectrometer (GeoMAREA) was deployed in the submarine spring (Kiveri) for continuous monitoring of the gross gamma-ray intensity enriched in groundwater. The gross gamma-ray intensity was elaborated for earthquake study using the Rayleigh Probability Distribution Function. Gross γ-ray intensity had increased gradually since 10 days before the earthquake (Itea, 30/3/2019), in which the Rayleigh probability distribution gave weak and strong anomalies 52 h 20 min and 7 h 20 min before the earthquake, respectively. The anomaly of gross gamma-ray intensity was observed for short period of time which was returned to pre-earthquake values after the earthquake. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) is a novel seismic observation system developed in recent years that can realize ultrahigh density observations and has attracted extensive attention in the field of seismology. DAS uses fiber-optic cables as sensing units, which are easy to incorporate with urban telecommunication fiber-optic cables for seismological observations. Compared with seismometers, DAS has the advantages of being rapidly deployed and recyclable, being able to acquire dense observations at low cost, and convenient data collection. In this study, a 5.2 km long telecom fiber-optic internet cable was utilized as a DAS array in an urban area to record ambient noise, and the noise cross-correlation function (NCF) was calculated. There are two different distribution types of ambient noise sources along the cable, regular along-road trucks (Taihe Road) and complex ambient noise, including human activities and traffic sources along and across the Jinniu road. In the first case, we constructed a 2D S-wave velocity model down to 100 m depth and a low-velocity zone was revealed. The S-wave model well explained the traffic signal along the Taihe road and the low-velocity zone is also consistent with the results obtained from co-located geophone arrays. In the second case, due to the complexity of the traffic noise distribution, empirical Green's functions were barely achieved. Therefore, we performed a synthetic test obtaining different NCFs with different source distributions, and two specific cases that dominate the NCF results were matched. Finally, we obtained the traffic noise distribution along the road, which is consistent with the power spectra density of the ambient noise. In conclusion, by combining DAS and urban fiber-optic internet cables with urban traffic noise, we can effectively reveal the traffic activities and image shallow structures with high resolution, which could offer a reference for urban construction and disaster prevention. Article Highlights: DAS turns the urban fiber-optic internet cables into ultra-dense permanent seismic observation arrays We revealed a high-resolution shallow structure using urban fiber-optic internet cables We obtained the distribution of traffic activities along the road [ABSTRACT FROM AUTHOR]

The vertical distribution of temperature (T), salinity (S), dissolved oxygen (O2) concentration, flow velocity (U) in the underwater canyon over the gas seepage site in the Golubaya Bay (the Black Sea) is studied. A significant decrease in the O2 concentration in the bottom water layer over the seep site as compared to the background site is shown, with a minimum of 0.2 mg/L, which was kept during the entire measurement period. The minima at the bottom were also revealed in the distribution of salinity in the first dataset; in the second dataset, desalination lenses were registered at a depth of 4, 10, and 8 m for three consecutive soundings. Such distribution potentially indicates a pulsed freshwater discharge, during which the desalination lenses gradually rise to the surface. The bottom current in the canyon was on average two times weaker than at the background station, where its velocity varied within 0.04–0.09 m/s. The described features of the distribution of hydrological parameters are associated with the gas bubble seepage and geomorphology of the study area. [ABSTRACT FROM AUTHOR]

Submarine cables are a typical weak magnetic target. Studying the magnetic anomaly principle of these cables and establishing their magnetic anomaly model are the bases of realizing magnetic detection, location, and recognition. The magnetic anomaly model of a 2D, infinite-length, horizontal cylinder is traditional and typical. However, when the cable is laid on a polygonal line under the constraints of geographical conditions or it is broken, the traditional model is no longer applicable. In this study, a magnetic anomaly analysis model of a finite-length submarine cable was proposed based on magnetic anomaly theory of finite-length horizontal cylindrical shells. The characteristics, applicability, and magnetic anomaly variation law of the model were analyzed. Exploration of the critical length ratios for the magnetic anomaly of a finite-length submarine cable that cannot be calculated by the traditional model improves the present magnetic anomaly theory of submarine cables. [ABSTRACT FROM AUTHOR]

The alternating current (AC) loss is a key consideration of the operation economy and stability of the high temperature superconducting (HTS) cables. In this paper, the sources of the AC loss in the HTS cable are analyzed firstly. The three-phase HTS cable, adopted in the 35 kV km-level HTS cable demonstrating project in Shanghai, China, is modeled by the finite element method (FEM) to calculate the AC loss by the COMSOL Multiphysics. The AC loss of the designed 35 kV HTS cable is 1.31 W/m. The theoretical calculation method is also implemented to verify the modeling results. Furthermore, considering the on-site conditions of the demonstrating project in Shanghai, China, the calorimetric method is conducted by measuring the temperature difference between the inlet and outlet of liquid nitrogen. The obtained results provide useful indications for the future design and research of HTS AC systems. [ABSTRACT FROM AUTHOR]

The pressure-based acoustic approximation of the elastic wave equations in anisotropic media has advantages corresponding to computational efficiency and numerical stability. However, the numerical scattering potentials from the anisotropic parameter perturbations for the pressure wavefield are not consistent with the elastic scattering theory. In multiparameter full-waveform inversion (FWI), choosing a suitable parameterization, considering the acquisition parameters (e.g., the offset-to-depth ratio and frequency band) and the accuracy of the anisotropy information in the background initial velocity model, is an important component to a successful anisotropic parameter estimation, because the parameterization determines the trade-off between inverted model parameters and their resolution power. However, because it is difficult to perform multiparameter FWI with various types of parameterization using the pressure-based acoustic wave equation, inaccurate scattered wavefields cause the gradient direction to lose its unique properties with respect to each model parameter. To overcome these issues, we adopt the combination of pressure- and vector-based acoustic wave equations converted vector virtual sources, which preserves the computational efficiency and the angular dependency of the partial derivative wavefields in elastic media. With the proposed method, we generate the numerical PP scattering patterns for various parameterizations, which are consistent with the elastic scattering theory. Through the numerical tests using the synthetic anisotropic Marmousi-II models and a real ocean bottom cable dataset from the North Sea, we conduct acoustic FWI with three different parameterizations using the proposed method and verify that the modified scattering patterns accurately reflect the characteristics of the anisotropic parameter perturbations. [ABSTRACT FROM AUTHOR]

Gas hydrates from the continental margin settings are mostly confined to continental slopes. The free gas occurring below the gas hydrate laden sediments play a crucial role in the submarine slope failures and can potentially trigger the submarine landslides. The present study is carried out to investigate such a scenario in the shale dominated Krishna–Godavari (KG) basin having proven gas hydrate deposits. Shale reservoirs are less permeable compared to sandstone reservoirs and as such, the free gas that is locked in the pore spaces of shales would eventually create hydro fractures or faults to escape from the pore spaces. This overpressure from the gas zone will find a pathway to reach the shallower depths. In the present study, two faults are identified of which, one is acting as a potential pathway for overpressures to travel through it, while the other is found to be critically pressurized due to the gas zone below it. The calculated gas column height is ~51 m and any further increase in the gas column height would create a fault slip and cause the mechanical failure of the sediments, creating another potential pathway. We infer that these faults are acting as a migration pathway in our study area and the advection of fluid/gas from the gas zone via the pathway might have played a major role in creating a slope break above the fault. Research highlights: Gas migration and role of free gas on slope stability. Seismic attributes for characterization of free gas zones and migration pathways Gas column height and critical gas pressure necessary to initiate fault activation. Active and passive faults and their role as migration pathways. [ABSTRACT FROM AUTHOR]

By combining the photovoltaic (PV) effect, heat exchanger principle, heat storage capability and phenomena of heat generation in PV cells and power cables, it is possible to increase significantly the transmission performance (i.e. the ampacity) of any 110 kV underground cable line. This can be achieved by installing power cables in a trench which is completely filled with high thermal conductivity bedding and which is covered with a hydronic concrete pavement (HCP) and a layer of PV floor tiles. This HCP, a heat storage system and a circulating pump are the three main parts of a HCP system, which should be used as a cooler for the PV tiles and cables. In particular, the PV cells would generate waste heat and direct current electricity from sunlight (using the PV effect), the cable bedding would conduct waste heat well from the cables to the heat collecting pipes of the HCP system (by improved heat conduction), while the HCP system would collect and store waste heat from the PV cells and cables as well as some heat from the Sun (using the heat exchanger principle and heat storage capability). The main aims of this paper are to show that the proposed method is highly energy-efficient, cost-effective and applicable in practice. The proposed method is regarded as a novelty, while the electricity generation in the PV floor tiles and the storage of heat within the HCP system represent additional advantages of this method. An adequate experimental background, one reference FEM-based model and one necessary base case are provided. For specified environmental conditions, the proposed method is verified numerically by means of COMSOL Multiphysics. Finally, the results of a techno-economic analysis are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper deals with premature failure of two well fluid lines of an offshore asset. The well fluid lines leaked due to internal corrosion. In the internal surface of the failed pipes, longitudinal groove and holes were observed at the 6 o'clock position. The superficial liquid velocity of both the lines was significantly low which resulted in settling, deposition and accumulation of suspended solids, and biomass as a result of proliferation of bacterial colonies. These conditions made the site prone to microbial-induced corrosion and under deposit corrosion. Apart from low velocity, lack of required cleaning pigging, inadequate dosing of corrosion inhibitor and bactericide caused premature failure of the pipes. The details of tests carried out with their results and suitable recommendations have been provided in this paper. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) is a new method that measures the strain change along a fiber-optic cable and has emerged as a promising geophysical application across a wide range of research and monitoring. Here we present the results of DAS observations from a submarine cable offshore Cape Muroto, Nankai subduction zone, western Japan. The observed signal amplitude varies widely among the DAS channels, even over short distances of only ~ 100 m, which is likely attributed to the differences in cable-seafloor coupling due to complex bathymetry along the cable route. Nevertheless, the noise levels at the well-coupled channels of DAS are almost comparable to those observed at nearby permanent ocean-bottom seismometers, suggesting that the cable has the ability to detect nearby micro earthquakes and even tectonic tremors. Many earthquakes were observed during the 5-day observation period, with the minimum and maximum detectable events being a local M1.1 event 30–50 km from the cable and a teleseismic Mw7.7 event that occurred in Cuba, respectively. Temperature appears to exert a greater control on the DAS signal than real strain in the quasi-static, sub-seismic range, where we can regard our DAS record as distributed temperature sensing (DTS) record, and detected many rapid temperature change events migrating along the cable: a small number of large migration events (up to 10 km in 6 h) associated with rapid temperature decreases, and many small-scale events (both rising and falling temperatures). These events may reflect oceanic internal surface waves and deep-ocean water mixing processes that are the result of ocean current–tidal interactions along an irregular seafloor boundary. [ABSTRACT FROM AUTHOR]

Three real-time permanent observatories (EOS02–EOS04) connected by a submarine cable were constructed and deployed to monitor seismicity, tsunamis, and other geophysical phenomena off eastern Taiwan, southwestern Ryukyu subduction zone. In this study, we process the pressure data (January 26, 2017, to December 31, 2019) recorded by three ocean bottom pressure gauges. After removing of tidal and short-period oceanographic effects and the linear trend caused by long-term sensor drift, overall, the variation patterns of the ocean bottom pressure (OBP) records at stations EOS02 and EOS03 are similar, while that at station EOS04 (located on a slope) exhibits different characteristics. The amplitude fluctuations of the OBP records are very large, even reaching approximately 3 × 102 mbar at station EOS02. In addition, we observe a significant permanent change in the OBP data at station EOS04 where the pressure variation reaches approximately 4.2 × 102 mbar (approximately equals a 4.2 m water column variation). Considering the seismicity and background tectonic characteristics of station EOS04, we speculate that this permanent pressure change may have been caused by submarine landslides and/or slumps (triggered by nearby earthquakes). [ABSTRACT FROM AUTHOR]

A ship-based seismic survey was conducted close to a fiber-optic submarine cable, and 50 km-long distributed acoustic sensing (DAS) recordings with air-gun shots were obtained for the first time. We examine the acquired DAS dataset together with the co-located hydrophones to investigate the detection capability of underwater acoustic (hydroacoustic) signals. Here, we show the hydroacoustic signals identified by the DAS measurement characterizing in frequency-time space. The DAS measurement can be sensitive for hydroacoustic signals in a frequency range from 10 - 1 Hz to a few tens of Hz which is similar to the hydrophones. The observed phases of hydroacoustic signals are coherent within a few kilometers along the submarine cable, suggesting the DAS is suitable for applying correlation analysis using hydroacoustic signals. Although our study suggests that virtual sensor's self-noise of the present DAS measurement is relatively high compared to the conventional in-situ hydroacoustic sensors above a few Hz, the DAS identifies the ocean microseismic background noise along the entire submarine cable except for some cable sections de-coupled from the seafloor. [ABSTRACT FROM AUTHOR]

The performance of surface plasmon resonance (SPR) sensors has great dependence on its plasmonic material's frequency response, which is described by the complex dielectric function. Through history, researchers developed and enhanced mathematical models to accurately describe the material dielectric function. Although many papers compared the accuracy of different dielectric function models and stated its limitations, none of it addressed the effect of dielectric function model on the SPR sensor's characteristics. In this paper, we investigated the performance of the three most used dielectric function models (Drude, Lorentz-Drude, and Brendel-Bormann) and their effect on the theoretically obtained sensor parameters when used in a gold SPR sensor's model and validated it with the experimentally measured dielectric function. The result showed that using less accurate dielectric function's model has a drastic effect on the theoretically obtained sensor's parameters. Among the three models, the widely used Drude model was not the most accurate; alternatively, Brendel-Bormann model was the most accurate. [ABSTRACT FROM AUTHOR]

In order to solve the problem of space charge accumulation in high-voltage DC cable accessories, nanometer titanium dioxide (TiO2) doping method is used to improve the space charge performance of liquid silicone rubber (LSR). Conductivity, dielectric spectrum and DC breakdown field strength, space charge distribution, and the trap level distribution of nano-TiO2/LSR composite samples were tested in this paper. With the increase of the doping concentration of nanoparticles, the DC conductivity increased, and the DC breakdown field strength decreased. The εr of the TiO2/LSR composite sample increased with the increase in the doping concentration of nano-TiO2. As the frequency increased, tanδ decreased first in the low-frequency region and then increased in the high frequency. When the electric field strength increases from 10 to 20 kV/mm, the same polarity charges appear near the upper and lower electrodes of the sample, and the space charge accumulation doubled. After the addition of nano-TiO2, under the two electric field strengths, the space charge accumulation of 4 wt%-TiO2/LSR composite materials decreased by 24.55 nc and 81.03 nc, respectively. The trap energy level of the 4 wt% nano-TiO2 composites becomes smaller, and shallow traps are introduced, it was verified that the addition of 4 wt% nano-TiO2 particles reduced the space charge inside the composite sample and achieved the effect of suppressing space charge. [ABSTRACT FROM AUTHOR]

Grouting cable bolt was employed to control the stability of the retaind goaf side gateraod (RGSG) in the Panyidong coalmine by considering severe stress disturbances and soft rock mechanics associated in deep mining environment. To have a deep insight of the effectiveness of the grouting cable bolt supporting on the stability control of the deep RGSG, a FLAC3D numerical model was built according to the geotechnical condition of the Panyidong coalmine, in which strain softening constitutive material was introduced to model the softening behavior of the surrounding rock supported by end-anchored cable bolt or grouting cable bolt. Simulated results demonstrated that: Confining stress release during roadway driving and stress concentration during longwall face retreating are the main driving force to the large deformation of the RGSG supported by end-anchored cable bolt; Grouting cable bolt supporting can improve the stability of the deep RGSG considerably thought providing high bolting strength and grouts injection, and ideally, the RGSG's roof sag and right coal rib convergence making main contributions to the RGSG section shrinkage could be reduced by 22.0% and 23.0%, 26.6% and 29.4%, 30.2% and 34.9% when the RGSG is supported by grouting cable bolt I, II and III, respectively. Field application also verified that the integrity of the surrounding rock of RGSG was improved and the residual section of the RGSG was large enough to reserve for the second longwall panel mining when the grouting cable bolt technology was applied in the Panyidong coalmine with 850 m depth. [ABSTRACT FROM AUTHOR]

Electrical power systems are becoming more susceptible to disturbances in the power grid such as harmonic distortions. The reason for this is the improvement of power in electronics, which allows for more efficient motor control and starting techniques through electronic converters. However, the use of these devices distorts the voltage and current waveform of the power system due to the harmonics injection. In the case of production platforms and drilling rigs, there are several motors that are fed by frequency converters. These facilities have a peculiarity that worsens the harmonics issues, which is the risk of resonance, consequently causing voltage peaks that can lead to equipment damage. The risk of resonance is due to the use of long submarine cables that in turn, because of the long distances, have considerable capacitance values that can resonate with the inductance from the inductive loads such as power transformers. The present work aims to evaluate a platform electrical system in terms of power quality considering the situation of resonance caused by a submarine power cable. Overviews of the electrical system and of the adopted submarine cable model will first be presented, and then, the results of the simulations are discussed. [ABSTRACT FROM AUTHOR]

This paper introduces the basic situation of the 35-kV domestic high temperature superconducting (HTS) power cable project in Shanghai. The target of this project is to construct and put into operation the first 35-kV km level three-phase turn-key HTS power cable project in the world. The cable transmission capacity, cable routing selection, cable structure design, cooling system configuration, etc. of the project are introduced. The project is implemented by the State Grid Corporation Shanghai Electric Power Company. A 35-kV, 1.2-km-long 220-kV inter-substation connecting HTS cable line will be constructed in the core urban area of Shanghai. So far, the type test of the HTS power cable system has been completed, and the construction of the project has begun. The project is expected to be completed and put into operation in the second half of 2020. [ABSTRACT FROM AUTHOR]

There has been prior research exploring the exposure of common electrical cords and cables to fire, but that has traditionally been at the lab scale and under near steady-state exposures. The goal of these experiments was to expose six types of cords and cables in a room-scale compartment with a fuel load sufficient to drive the compartment through flashover. The basic test design was to expose the cords and cables on the floor of a compartment to a growing fire to determine the conditions under which the cord/cable would trip the circuit protection device. All of the cords were energized and installed on a non-combustible surface. The six cables and cords were protected by three different circuit protection devices which were remote from the thermal exposure. This configuration resulted in 18 exposures per experiment. The room fires experiments consisted of three replicate fires with two sofas as the main fuel source, two replicate fires with one sofa as the main fuel source and one fire with two sofas and vinyl-covered MDF paneling on three walls in the room. Each fuel package was sufficient to support flashover conditions in the room. The average peak heat release rate of the sofa fueled compartment fires with gypsum board ceiling and walls prior to suppression was 6.8 MW. The addition of vinyl covered MDF wall paneling on three of the compartment walls increased the pre-suppression peak heat release rate to 12 MW. In each experiment during post flashover exposure, the insulation on the cords and cables ignited and burned through, exposing bare wire. During this period, the circuits faulted. Assessments of both the thermal exposure and physical damage to the cords did not reveal any correlation between the thermal exposure, cord/cable damage, and trip type. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of super-long-span cable-stayed bridges with hybrid cables, including steel and carbon fiber-reinforced polymer (CFRP) cables arranged in the short- and long-cable regions, respectively. Three 1600-m-span cable-stayed bridges with steel, CFRP and hybrid cables are first designed. Their static and dynamic structural performance was subsequently investigated by finite element analysis. Simulation results demonstrate that arranging CFRP cables in the long-cable regions can fully utilize the advantage of CFRP through examining their equivalent elastic modulus, load-carrying efficiency ratio and self-weight/stress ratio. The hybrid cable-stayed bridge exhibits the higher stiffness enhancement in comparison with the CFRP cable-stayed bridge. In comparison with the CFRP cables, the use of hybrid cables is able to increase the frequency for the first-order vertical mode, thus overcoming the weakness of the CFRP cable-stayed bridge in terms of stiffness. In addition, the natural frequencies of CFRP cables are much higher than the low-order vertical vibration frequencies of cable-stayed bridge, which is beneficial to reducing the probability of cable–deck coupling vibrations. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) is considered to be a potential eco-friendly cable insulation material. However, space charge accumulation in PP under high electric stress limits its application for HVDC cable. In this paper, PP was modified with 4-acetoxystyrene (AOS) by melt grafting to improve electric properties. The molecular structure of the polypropylene-graft-4-acetoxystyrene (PP-g-AOS) was characterized by means of Fourier Transform Infrared Spectroscopy (FT-IR). The effects of temperature, screw speed, time, initiator content and monomer content on grafting degree of PP-g-AOS were investigated. Furthermore, the influence of grafting degree of PP-g-AOS on space charge suppression, volume resistivity and dc breakdown field strength was investigated. The FT-IR result showed that AOS was successfully grafted onto PP. It was found that under the proper grafting conditions, the obtained PP-g-AOS exhibited a maximum grafting degree of 1.31%. Moreover, PP-g-AOS with grafting degree of 1.14% can suppress space charge efficiently, and increase both volume resistivity and dc breakdown strength. This provides a new idea for the study of polypropylene HVDC cable insulation. [ABSTRACT FROM AUTHOR]

With the exposure of these problems of low ductility, easy breakage and high cost of grouting anchor cable, the application of "manila + grouting" full length anchorage technology in the prevention and controlling of coal face failure is more and more widely, the key procedure of which is the selection of manila diameter. Aiming at the difficulty of the choice of reasonable manila diameter, the uniaxial compressive and the wedge shear test of grouting coal samples with manila at different manila diameters were performed using the rock mechanics testing machine. The study shows that: The existence of manila extends the deformation of grouting coal samples and improves the tensile strength of coal samples; The manila has good ductility and high shear strength and the damaged coal body of coal face will not fall down immediately due to the function of manila; The uniaxial compressive strength and residual strength value of coal samples with an appropriate diameter of manila in it can reach the maximum, and the effect of the prevention and controlling of coal face failure is better and the cost is lower. It is concluded that the research result can provide the theory foundation for the "manila + grouting" full length anchorage technology. [ABSTRACT FROM AUTHOR]

It is well known that hot spots limit the ampacities of underground power cables. There are many commonly applied methods to control the thermal environment in hot spots of underground power cables. However, applications of cool pavements for this specific purpose would be a novelty in the field of power cable engineering. This paper considers the use of different cool pavements in combination with thermally stable bedding and/or pure quartz sand for mitigating or eliminating the thermal effect of an actual hot spot on the ampacities of a 110 kV cable line and a group of four 35 kV three-core cables installed in Belgrade, the Republic of Serbia. In the hot spot, the 110 kV cable line is installed in parallel with the group of 35 kV cables and crosses a district heating pipeline. All distances between these underground installations are lower than the recommended ones, and the 110 kV and 35 kV cables are laid at depths greater than required. The mutual thermal effects between the underground installations in the hot spot are simulated using FEM-based models for different environmental conditions. An experimental background is also provided. In comparison with the corresponding base cases, it has been found that the ampacities of the 110 kV cable line and group of 35 kV cables can be increased up to 25.1% and 60.9% in summer, and up to 62.8% and 170% in winter, respectively. [ABSTRACT FROM AUTHOR]

Partial discharges (PDs) are one of the main causes of cable fault. Early detection and pre-analysis of PD characteristics are paramount in preventing cable breakdown. This paper analyzed the PD characteristics of 22.9 kilovolts (kV) calculated nerve conduction velocity (CN-CV) cross-linked polyethylene (XLPE) cable subjected to various artificial defects, based on the maintenance method by PD diagnosis. Various artificial defects were created in a 3-m CN-CV test cable to which a power frequency voltage of 60 hertz (Hz), 13.2 kV was applied. To compare the PD characteristics difference by cable length, a 3-m cable specimen was connected to a 70-m three-phase cable system using a high-voltage mating connector. A measurement unit and a high-frequency current transformer were used for PD data acquisition. As a result, different PD characteristics were found in each defect type, which provided better understanding of the PD phenomena. A maintenance method of 22.9 kV XLPE power cable through PD diagnosis was developed from the data obtained, which will help to ensure greater accuracy in the on-site diagnosis of a cable in service. [ABSTRACT FROM AUTHOR]

This article evaluates the performance of titanium tetraisopropoxide (TTIP) and γ-alumina nanofiller (Al2O3) in rejuvenation and restoration of degraded XLPE underground medium voltage–power distribution cables. These two materials will be injected into aged cables in the form of two rejuvenation composition groups based on silane coupling agents. The injected and aged specimens were then compared in terms of dielectric loss factor (tanδ) measurement, scanning electron microscopy (SEM) analysis, Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray (EDX) analysis. After measurement of dielectric loss factor in 7-day intervals, 1 month after the injection of rejuvenation fluids, it was found that the injected cable specimen dielectric loss tangent in the second group, which contained γ-alumina nanofiller, was lower than the specimens injected with TTIP (first group); even their tanδ was lower than the new unused cables. Microstructures of the rejuvenated and aged specimens were compared by means of SEM analysis and the results indicated that titanium and aluminum nanoparticles filled the water-filled microscopic cavities and modified the polymeric insulation surface. FTIR analysis compared the chemical bonds of the insulation layer in injected and aged cables. EDX analysis also detected the element type and value on the treated insulation specimen surface area. Comparing the four afore-mentioned analysis illustrated that both fluids were efficacious in rejuvenation and rehabilitation of degraded XLPE cable insulations. However, γ-alumina nanofiller performs better than TTIP in rejuvenation of degraded XLPE power cables. [ABSTRACT FROM AUTHOR]

Considering the effects of seepage and dynamic pressure, defining a rock mass as a saturated porous media, and using the finite element method, a dynamic fluid–structure interaction model of a subsea tunnel with a viscous spring artificial boundary is established. Adopting rubber and foam concrete as shock absorption layers and inputting both horizontal and vertical earthquake waves, the time history curves of the first principal stress at key points in the secondary lining structure are comparatively analyzed based on the presence and absence of shock absorption layers. The principal stress peaks are also analyzed. The damping effect of the shock absorption layer is studied. The results show that the peak and principal stresses at the main parts of the tunnel lining structure decrease after the shock absorption layer is established. Obvious decreases occur in the vault and inverted arch. A certain degree of peak stress reduction is also observed after the shock absorption layer is established. Establishing the shock absorption layer does not change the spectrum characteristics of the tunnel structure. Foam concrete shock absorption is recommended because the damping effect of foam concrete is more observable than that of rubber. [ABSTRACT FROM AUTHOR]

In marine seismic exploration, ocean bottom cable technology can record multicomponent seismic data for multiparameter inversion and imaging. This study proposes an elastic multiparameter lease-squares reverse time migration based on the ocean bottom cable technology. Herein, the wavefield continuation operators are mixed equations: the acoustic wave equations are used to calculate seismic wave propagation in the seawater medium, whereas in the solid media below the seabed, the wavefields are obtained by P- and S-wave separated vector elastic wave equations. At the seabed interface, acoustic-elastic coupling control equations are used to combine the two types of equations. P- and S-wave separated elastic migration operators, demigration operators, and gradient equations are derived to realize the elastic least-squares reverse time migration based on the P- and S-wave mode separation. The model tests verify that the proposed method can obtain high-quality images in both the P- and S-velocity components. In comparison with the traditional elastic least-squares reverse time migration method, the proposed method can readily suppress imaging crosstalk noise from multiparameter coupling. [ABSTRACT FROM AUTHOR]

A tunable low-pass Gm-C filter with 1 GHz cutoff frequency is presented. The core of this filter is a high frequency low voltage operational transconductance amplifier (OTA) in which CMOS inverters are used. For enhancing the linearity of the filter, a novel common mode feedforward circuit is merged with a common mode feedback circuit. Moreover, in this paper, a new tuning circuit is presented for tuning transconductance in order to compensate effects of elements mismatch and temperature variations on OTA. Accordingly, the cutoff frequency is compensated by the bulk voltage tuning, while this circuit is less complex and consumes low power. The circuit is designed and simulated using TSMC 90 nm CMOS technology and a 1 V power supply. The results of simulation show that the DC differential gain, − 3 dB cutoff frequency and the unity-gain frequency of OTA are 37.7 dB, 325 MHz and 25 GHz, respectively. After applying two-tone input voltages 0.2 Vp-p, the IM3 value of the filter at 1 GHz is − 36 dB. The filter consumes 8 mW of power and occupies an area of 0.113 mm × 0.144 mm. [ABSTRACT FROM AUTHOR]

Although submarine landslides rarely occur in shallow or coastal areas, they are intensely violent and dangerous, causing serious damage to submarine structures and cables and drilling platforms. In this study, simulation experiments in the wave flume reveal that the submarine sand slope will oscillate, disperse, and form sand grains under the action of waves. In addition, the erosion depth of the wave on the seabed gradually deepens over time. Water depth decreases gradually. When the water depth reaches a certain depth, the erosion reaches a critical state. In combination with previous studies, the failure conditions and failure mechanisms of submarine slopes under wave action are analyzed, and a mechanism is proposed for the submarine slope failure induced by liquefied flow slip failure, shear failure, and shallow erosion failure. The risk of shear failure on the seabed is considered greater than that of liquefaction under wave action. Under shear failure, the seabed slope experiences a nearly complete liquefaction damage. By contrast, for shallow erosion damage, the structure of the seabed soil loosens, and the related strength becomes lower than that of the surrounding soil. [ABSTRACT FROM AUTHOR]

We present new trends in the performance evaluation of submarine fiber cable system with different ultrahigh multiplexing and propagation techniques over a wide range of the affecting parameters. Our model takes into account the ultimate optical transmission of huge submarine cables with 14,400 channels under different depth conditions. We employ Raman and erbium-doped fiber amplifiers in our study. We investigate the double impact of both temperature and pressure through the defined depth penalty. We also study the soliton transmission technique using two multiplexing methods considered in the design of ultra-wide wavelength division multiplexing (UW-WDM) with 14,400 optical channels and ultra-wide space division multiplexing (UW-SDM) with 440 fiber links. Based on experimental data, both the deep ocean water temperature and pressure are obtained as functions of the water depth. [ABSTRACT FROM AUTHOR]