A bond contact model for methane hydrate-bearing sediments with interparticle cementation

While methane hydrates (MHs) can be present in various forms in deep seabeds or permafrost regions, this paper deals with MH-bearing sediments (MHBS) where the MH has formed bonds between sand grains. A bond model based on experimentally validated contact laws for cemented granules is introduced to describe the mechanical behavior of the MH bonds. The model parameters were derived from measured values of temperature, water pressure and MH density. Bond width and thickness adopted for each bond of the MHBS were selected based on the degree of MH saturation. The model was implemented into a 2D distinct element method code. A series of numerical biaxial standard compression tests were carried out for various degrees of MH saturation. A comparison with available experimental data shows that the model can effectively capture the essential features of the mechanical behavior of MHBS for a wide range of levels of hydrate saturation under drained and undrained conditions. In addition, the analyses presented here shed light on the following: (1) the relationship between level of cementation and debonding mechanisms taking place at the microscopic level and the observed macro-mechanical behavior of MHBS and (2) the relationship between spatial distribution of bond breakages and contact force chains with the observed strength, dilatancy and deformability of the samples. Copyright © 2014 John Wiley & Sons, Ltd

Dawning public health services dogma:An indigenous Southwest Chinese perspective in managing hypertension-with or without the “BPHS”?

BACKGROUND: To alleviate the rising mortality burden due to hypertension and other non-communicable diseases, a new public health policy initiative in 2009 called the Basic Public Health Services (BPHS). Program was introduced by the Chinese government. The goal of the study is to assess the feasibility and impact of a nationwide health care service—the “BPHS”. METHODS: From January to December 2021, a stratified multistage random sampling method in the survey was conducted to select 6,456 people from 8 cities/districts in Yunnan Province, China, who were above the age of 35 years. 1,521 hypertensive patients were previously aware of their high blood pressure status were matched to the BPHS program database based on ID number and then further divided into BPHS group and non-BPHS (control) group. The results of the current study are based on their responses to a short structured questionnaire, a physical examination, and laboratory tests. The association between BPHS management and its effect on the control of hypertension was estimated using multivariable logistic regression models. We evaluated the accessibility and efficacy of BPHS health care services by analyzing various variables such as blood pressure, BMI, lifestyle modification, anti-hypertensive drugs taken, and cardiovascular risk factors. RESULTS: Among the 1,521 hypertensive patients included in this study, 1,011 (66.5%) were managed by BPHS programme. The multivariable logistic regression model demonstrated that the BPHS facilitated hypertension control (OR = 1.640, 95% CI: 1.237–2.175). A higher proportion of participants receiving lifestyle guidance from the BPHS management showed lowering of total cholesterol. In comparison to the non-BPHS group, those under BPHS management adhered better to antihypertensive medications either single drug (54.3%) or in combination (17.3%) of drugs. Additionally, we also noticed that urban areas with centralized and well-established digital information management system had better hypertension treatment and control. CONCLUSIONS: Nearly two-thirds of the hypertensive patients in Yunnan Province were included in BPHS management. The impact of the national BPHS program was evident in lowering risk factors for cardiovascular diseases, promoting healthy lifestyles, lowering blood pressure, increasing medication adherence, and the better control rate of hypertension

Review of advanced road materials, structures, equipment, and detection technologies

As a vital and integral component of transportation infrastructure, pavement has a direct and tangible impact on socio-economic sustainability. In recent years, an influx of groundbreaking and state-of-the-art materials, structures, equipment, and detection technologies related to road engineering have continually and progressively emerged, reshaping the landscape of pavement systems. There is a pressing and growing need for a timely summarization of the current research status and a clear identification of future research directions in these advanced and evolving technologies. Therefore, Journal of Road Engineering has undertaken the significant initiative of introducing a comprehensive review paper with the overarching theme of “advanced road materials, structures, equipment, and detection technologies”. This extensive and insightful review meticulously gathers and synthesizes research findings from 39 distinguished scholars, all of whom are affiliated with 19 renowned universities or research institutions specializing in the diverse and multidimensional field of highway engineering. It covers the current state and anticipates future development directions in the four major and interconnected domains of road engineering: advanced road materials, advanced road structures and performance evaluation, advanced road construction equipment and technology, and advanced road detection and assessment technologies

Toughness improvement mechanism and evaluation of cement concrete for road pavement: A review

Traditional cement concrete has the disadvantages of low tensile strength, poor toughness, and rapid development of cracks while cracking, which causes a significantly negative influence on the safety and durability of concrete road pavement. This paper presents a state-of-the-art review of toughness improvement mechanisms and evaluation methods of cement concrete for road pavement. The review indicates that (i) The performance of concrete material depends on its material composition and internal structure. Aggregate size, cement properties and admixtures are the main factors of concrete toughness. (ii) The incorporation of rubber or fiber in pavement concrete improves the toughness of concrete materials. However, these additions must be maintained within a reasonable range. The amount of rubber and fiber are encouraged not more than 30% of the volume of fine aggregate and 2% of the volume of concrete, respectively. (iii) The toughness of pavement concrete material includes the toughness regarding bending, impact and fracture. The toughness of cement concrete for highway and municipal pavement is generally evaluated by bending and fracture toughness, while the toughness of airfield pavement concrete is more focused on impact toughness. (iv) The toughening measures of cement concrete for road pavement are mainly mixed with rubber or fiber, while these two materials have their defects, and the application of high-toughness cement concrete in the actual road still faces many challenges. For example, the synergistic effect of rubber and fiber, the development and application of new flexible admixtures, and the formulation of the toughness index of pavement cement concrete materials need further research

Evolution of swelling pressure of cohesive-frictional, rough and elasto-plastic granulates

The subject of this study is the modeling of the evolution of the swell-ing pressure of granulates with cohesive-frictional, rough and elasto-plastic “mi-croscopic” contact properties. The spherical particles are randomly arranged in a periodic cubic space with a fixed volume so that an increase of the particle size – i.e. swelling that can be caused by intake of some fluid – is accompanied by a de-crease of the void space. An analytical function is proposed that properly de-scribes the (macroscopic) void ratio as function of pressure for different micro-scopic contact properties

DEM investigation of weathered rocks using a novel bond contact model

The distinct element method (DEM) incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stress–strain relationship and failure pattern of rocks

Alternating Feature Spaces in Relevance Feedback

Image retrieval using relevance feedback can be considered as a classification process. In practice, the generalization of classifier is often constrained by the insufficiency of training samples. In this paper, we propose a novel relevance feedback approach capable of collecting more representative samples. Image labeling and classifier training are conducted in two complementary image feature spaces. The complementarities between feature spaces are also studied. Our experimental result based on 10,000 images indicates that the proposed approach significantly improves image retrieval performance