Mechanical instability of monocrystalline and polycrystalline methane hydrates

Abstract Considering the fact that its existence is abundant while maintaining the ability to generate freshwater while burning, methane hydrates have been classified as sources of sustainable energy. China currently maintains an international role in developing technology meant to explore offshore methane hydrates buried under the mud of the seabed, their primary laboratory being the South China Sea. However, such a process does not come without its hazards and fatal consequences, ranging from the destruction of the flora and fauna, the general environment, and—the greatest hazard of all—the cost of human life. The United Nations Convention on the Law of the Sea (hereinafter ‘UNCLOS’), being an important international legal regime and instrument, has assigned damage control during the exploration of methane hydrates, as being the responsibilities and liability of individual sovereign states and corporations. China adopted the Deep Seabed Mining Law (hereinafter the DSM Law) on 26 February 2016, which came into force on the 1 of May 2016; a regulation providing the legal framework also for the Chinese government’s role in methane hydrate exploratory activities. This article examines the role of the DSM Law and its provisions, as well as several international documents intended to prevent transboundary environmental harm from arising, as a result of offshore methane hydrate extraction. Despite the obvious risk of harm to the environment, the DSM Law has made great strides in regulating exploratory activities so as to meet the criteria of the UNCLOS. However, this article argues that neither the UNCLOS nor the DSM Law are adequately prepared to address transboundary harm triggered by the exploitation of offshore methane hydrates. In particular, the technology of such extraction is still at an experimental stage, and potential risks remain uncertain—and even untraceable—for cross-jurisdictional claims. The article intends to seek available legal instruments or models, to overhaul the incapacity within the current governing framework, and offers suggestions supporting national and international legislative efforts towards protecting the environment during methane hydrate extraction.

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Mechanical Stability of Hybrid Corrugated Sandwich Plates under Fluid-Structure-Thermal Coupling for Novel Thermal Protection Systems

Applied Sciences ◽

10.3390/app10082790 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2790

Author(s):

Wenzheng Zhuang ◽

Chao Yang ◽

Zhigang Wu

Keyword(s):

Mechanical Stability ◽

Thermal Protection ◽

Element Model ◽

Parameter Study ◽

The Novel ◽

Thermal Coupling ◽

Mechanical Instability ◽

Fluid Structure ◽

Thermal Protection Systems ◽

Protection Systems

Hybrid corrugated sandwich (HCS) plates have become a promising candidate for novel thermal protection systems (TPS) due to their multi-functionality of load bearing and thermal protection. For hypersonic vehicles, the novel TPS that performs some structural functions is a potential method of saving weight, which is significant in reducing expensive design/manufacture cost. Considering the novel TPS exposed to severe thermal and aerodynamic environments, the mechanical stability of the HCS plates under fluid-structure-thermal coupling is crucial for preliminary design of the TPS. In this paper, an innovative layerwise finite element model of the HCS plates is presented, and coupled fluid-structure-thermal analysis is performed with a parameter study. The proposed method is validated to be accurate and efficient against commercial software simulation. Results have shown that the mechanical instability of the HCS plates can be induced by fluid-structure coupling and further accelerated by thermal effect. The influences of geometric parameters on thermal buckling and dynamic stability present opposite tendencies, indicating a tradeoff is required for the TPS design. The present analytical model and numerical results provide design guidance in the practical application of the novel TPS.

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Clinical evaluation of manual stress testing, stress ultrasound and 3D stress MRI in chronic mechanical ankle instability

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-03998-z ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Markus Wenning ◽

Dominic Gehring ◽

Thomas Lange ◽

David Fuerst-Meroth ◽

Paul Streicher ◽

...

Keyword(s):

Stress Testing ◽

Ankle Instability ◽

Tilt Test ◽

Diagnostic Study ◽

Mechanical Instability ◽

Subjective Character ◽

Balance Test ◽

Research And Practice ◽

Cutoff Values ◽

Patient Reported

Abstract Background Chronic ankle instability (CAI) arises from the two etiological factors of functional (FAI) and mechanical ankle instability (MAI). To distinguish the contributions of the two etiologies, it is necessary to quantitively assess functional and mechanical deficits. Validated and reproducible assessment of mechanical instability remains a challenge in current research and practice. Physical examination, stress sonography and a novel 3D stress MRI have been used, while stress radiography has been called into question and arthrometry is limited to research purposes. The interaction of these primarily mechanical measurements with the functional and subjective components of CAI are subject to debate. The aim of this study was the evaluation of the clinical and biomechanical preferences of the three different methods in the diagnosis of MAI. Methods In this cross-sectional diagnostic study, we compared three different diagnostic approaches to mechanical ankle instability: (1) manual stress testing (anterior drawer test [ADT] and talar tilt test [TTT]), (2) stress sonography and (3) 3D stress MRI (3SAM) The latter includes quantification of 3D cartilage contact area (CCA) in plantarflexion-supination compared to neutral-null position. We applied these measurements to a cohort of patients suffering from chronic mechanical ankle instability (n = 25) to a matched cohort of healthy controls (n = 25). Perceived instability was assessed using the Cumberland Ankle Instability Tool (CAIT) and Forgotten Joint Score (FJS). Functional deficits were measured using postural sway and the y-Balance test. Results Significant differences between the two groups (single-factor “group” ANOVA, p < 0.05) were found in all of the mechanical assessments with strong effect sizes. Spearman’s correlations were strong for CAIT and manual stress testing (TTT rho = − 0.83, ADT rho = − 0.81), 3D stress MRI (rho = − 0.53) and stress sonography (TTT rho = − 0.48, ADT rho = − 0.44). Furthermore, the correlation between manual stress testing and CCA in the fibulotalar articulation (CCAFT) was strong (rho = 0.54) and the correlations to stress sonography were moderate (ADT rho = 0.47 and TTT rho = 0.43). The calculation of cutoff values revealed a distance of > 5.4 mm increase in ligament length during stress sonography (sensitivity 0.92, specificity 0.6) and > 43% loss of articulating surface in the fibulotalar joint (CCAFT in supination-plantarflexion using 3SAM, sensitivity 0.71, specificity 0.8) as potential cutoff values for diagnosing MAI. Conclusions Manual stress testing showed to be a valuable method of identifying mechanical ankle instability. However, due to is subjective character it may overvalue patient-reported instability as a factor which explains the high correlation to the CAIT-score, but this may also reduce its value in diagnosing the isolated mechanical quality of the joint. Thus, there is a persisting need for objective and reproducible alternatives focusing on MAI. According to our results, 3D stress MRI and stress sonography represent valuable alternatives and may be used to quantitively assess mechanical ankle instability in research and practice. Trial registration German Registry of Clinical Trials # DRKS00016356, registered on 05/11/2019.

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Management of recurrent or progressive spinal metastases: reirradiation techniques and surgical principles

Neuro-Oncology Practice ◽

10.1093/nop/npaa045 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. i45-i53

Author(s):

Rupesh Kotecha ◽

Nicolas Dea ◽

Jay S Detsky ◽

Arjun Sahgal

Keyword(s):

Progressive Disease ◽

Organs At Risk ◽

Methodological Approach ◽

Spinal Metastases ◽

Multidisciplinary Care ◽

Rehabilitation Medicine ◽

Surgical Approaches ◽

Mechanical Instability ◽

Conventional Radiotherapy ◽

Treated Site

Abstract With the growing incidence of new cases and the increasing prevalence of patients living longer with spine metastasis, a methodological approach to the management of patients with recurrent or progressive disease is increasing in relevance and importance in clinical practice. As a result, disease management has evolved in these patients using advanced surgical and radiotherapy technologies. Five key goals in the management of patients with spine metastases include providing pain relief, controlling metastatic disease at the treated site, improving neurologic deficits, maintaining or improving functional status, and minimizing further mechanical instability. The focus of this review is on advanced reirradiation techniques, given that the majority of patients will be treated with upfront conventional radiotherapy and further treatment on progression is often limited by the cumulative tolerance of nearby organs at risk. This review will also discuss novel surgical approaches such as separation surgery, minimally invasive percutaneous instrumentation, and laser interstitial thermal therapy, which is increasingly being coupled with spine reirradiation to maximize outcomes in this patient population. Lastly, given the complexities of managing recurrent spinal disease, this review emphasizes the importance of multidisciplinary care from neurosurgery, radiation oncology, medical oncology, neuro-oncology, rehabilitation medicine, and palliative care.

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Formation of a Low-Density Liquid Phase during the Dissociation of Gas Hydrates in Confined Environments

Nanomaterials ◽

10.3390/nano11030590 ◽

2021 ◽

Vol 11 (3) ◽

pp. 590

Author(s):

Lihua Wan ◽

Xiaoya Zang ◽

Juan Fu ◽

Xuebing Zhou ◽

Jingsheng Lu ◽

...

Keyword(s):

Natural Gas ◽

Methane Hydrate ◽

Phase State ◽

Solid Phase ◽

Potential Method ◽

Methane Hydrates ◽

Low Density ◽

Hydrate Dissociation ◽

State Of Water ◽

Confined Environment

The large amounts of natural gas in a dense solid phase stored in the confined environment of porous materials have become a new, potential method for storing and transporting natural gas. However, there is no experimental evidence to accurately determine the phase state of water during nanoscale gas hydrate dissociation. The results on the dissociation behavior of methane hydrates confined in a nanosilica gel and the contained water phase state during hydrate dissociation at temperatures below the ice point and under atmospheric pressure are presented. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) were used to trace the dissociation of confined methane hydrate synthesized from pore water confined inside the nanosilica gel. The characterization of the confined methane hydrate was also analyzed by PXRD. It was found that the confined methane hydrates dissociated into ultra viscous low-density liquid water (LDL) and methane gas. The results showed that the mechanism of confined methane hydrate dissociation at temperatures below the ice point depended on the phase state of water during hydrate dissociation.

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Phase Behaviour of Methane Hydrates in Confined Media

Crystals ◽

10.3390/cryst11020201 ◽

2021 ◽

Vol 11 (2) ◽

pp. 201

Author(s):

Hao Bian ◽

Lu Ai ◽

Klaus Hellgardt ◽

Geoffrey C. Maitland ◽

Jerry Y. Y. Heng

Keyword(s):

Phase Behaviour ◽

Methane Hydrates ◽

Scanning Calorimetry ◽

Macroporous Silica ◽

Interfacial Energies ◽

Temperature Method ◽

Hydrate Phase ◽

Dissociation Temperature ◽

Confined Media ◽

Decomposition Behaviour

In a study designed to investigate the melting behaviour of natural gas hydrates which are usually formed in porous mineral sediments rather than in bulk, hydrate phase equilibria for binary methane and water mixtures were studied using high-pressure differential scanning calorimetry in mesoporous and macroporous silica particles having controlled pore sizes ranging from 8.5 nm to 195.7 nm. A dynamic oscillating temperature method was used to form methane hydrates reproducibly and then determine their decomposition behaviour—melting points and enthalpies of melting. Significant decreases in dissociation temperature were observed as the pore size decreased (over 6 K for 8.5 nm pores). This behaviour is consistent with the Gibbs–Thomson equation, which was used to determine hydrate–water interfacial energies. The melting data up to 50 MPa indicated a strong, essentially logarithmic, dependence on pressure, which here has been ascribed to the pressure dependence of the interfacial energy in the confined media. An empirical modification of the Gibbs–Thomson equation is proposed to include this effect.

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Fast formation kinetics of methane hydrates loaded by silver nanoparticle coated activated carbon (Ag-NP@AC)

Chemical Engineering Journal ◽

10.1016/j.cej.2021.129206 ◽

2021 ◽

Vol 417 ◽

pp. 129206

Author(s):

Guodong Zhang ◽

Runcheng Zhang ◽

Fei Wang

Keyword(s):

Activated Carbon ◽

Silver Nanoparticle ◽

Methane Hydrates ◽

Formation Kinetics ◽

Kinetics Of

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The fibula and talus position difference in functional and mechanical ankle instability: MRI findings

Journal of Orthopaedic Surgery ◽

10.1177/2309499020984575 ◽

2021 ◽

Vol 29 (1) ◽

pp. 230949902098457

Author(s):

Chengjie Yuan ◽

Genrui Zhu ◽

Zhifeng Wang ◽

Chen Wang ◽

Xu Wang ◽

...

Keyword(s):

Healthy Volunteers ◽

Ankle Instability ◽

Medial Malleolus ◽

Mechanical Instability ◽

Mri Findings ◽

Functional Instability ◽

Post Hoc Analysis ◽

Ankle Stability ◽

Post Hoc

Purpose: This study aimed to use MRI to evaluate the fibula and talus position difference in functional and mechanical ankle stability patients. Methods: 61 and 68 patients with functional and mechanical instability, and 60 healthy volunteers were involved. Based on the axial MRI images, the rotation of the talus was identified through the Malleolar Talus Index (MTI). The position relative to the talus (Axial Malleolar Index, AMI) and medial malleolus (Intermalleolar Index, IMI) were used to evaluated the displacement of the fibula. Results: Post hoc analysis showed that the values of malleolar talus index was significantly larger among mechanical instability (89.18° ± 2.31°) than that in functional instability patients (86.55° ±61.65°, P < 0.001) and healthy volunteers (85.59° ± 2.42°, P < 0.001). The axial malleolar index of the mechanical instability patients (11.39° ± 1.41°) were significantly larger than healthy volunteers (7.91° ± 0.83°) (P < 0.0001). There were no statistically significant differences in the above three indexes between the functional instability patients and healthy volunteers. Conclusion: The functional instability patients didn’t have a posteriorly positioned fibula and an internally rotated talus. The malleolar talus index was significantly larger among mechanical instability patients than that in functional instability patients. Increased malleolar talus index may become a new indirect MRI sign for identifying functional and mechanical instability patients.

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