High Damage Rate Research Articles

Serologic and urinary characteristics of laboratory-confirmed genitourinary tuberculosis at a tertiary hospital in the Philippines

BackgroundGenitourinary tuberculosis (GUTB) is known to cause high rates of structural organ damage, however, literature on its biochemical manifestations is limited. Additionally, local studies in the Philippine setting, where cases are rampant, are few and dated. This study aimed to determine the serologic and urinary profile of patients with GUTB admitted at a tertiary hospital within January 2009 to March 2020 and their association with short-term outcomes.MethodsThis retrospective study included 112 patients with laboratory-confirmed GUTB (i.e., positivity in acid-fast smear, polymerase chain reaction, culture, or histology). Demographic data, clinical characteristics, laboratory and radiologic findings, histopathology reports, treatment, and short-term outcomes were recorded.ResultsBladder (54.5%) and kidney (36.4%) were the most affected organs. The male:female ratio was 1:1.15, and the mean age was 35.79 ± 18.29 years. Weakness (14.29%) was the most common chief complaint. A majority presented with anemia (83.04%), while several had leukocytosis (41.96%) and thrombocytosis (26.79%). Hypoalbuminemia (58.10%), impairment of renal function (36.94%), and electrolyte abnormalities such as hyponatremia (50.93%), hypercalcemia (20.19%), and hypokalemia (21.82%) were common. Proteinuria (67.96%) and pyuria (67.96%) were the most frequent abnormal findings, followed by hematuria (51.46%), acidic urine (45.63%) and low specific gravity (31.07%). Age, leukocytosis, and the need for pressors were all significantly associated with mortality (p values of <0.001, 0.010, and <0.001, respectively).ConclusionsThe young age at presentation with severe clinical and laboratory manifestations may reflect local epidemiology as TB continues to be widespread in the country. Apart from the more commonly cited abnormalities in literature, multiple electrolyte imbalances and urinary concentration defects were also observed in many cases, possibly indicating tubulointerstitial involvement—a complication increasingly mentioned in case reports. As several patient characteristics were found to be associated with the high mortality rates observed in the study, further research is recommended to explore predictive modeling.

Design and Experimental Study of the General Mechanical Pneumatic Combined Seed Metering Device

To address the problems of high damage rate, low seeding accuracy, and poor seeding generally in the seeding process, a general-purpose seeding device was designed in this study based on the principle of mechanical pneumatic combined seeding. The air-blowing-type cleaning and seed unloading of the device laid the conditions for precise seeding and flexible seeding. In addition, single-factor experiments were performed on seeds (e.g., soybeans, corn, and rape-seeds) with different particle sizes and shapes to verify the general properties of the seed metering device. A multi-factor response surface optimization experiment was performed by applying soybean seeds as the test object to achieve the optimal performance parameters of the seed metering device. At a seed-clearing air velocity of 16.7 m/s, a seed feeding drum speed of 13.7 r/min, and a hole cone angle of 35.6°, corresponding to the optimal performance index, the qualified index, the replay index, and the missed index reached 97.94%, 0.03%, and 2.03%, respectively. The verification test results are consistent with the optimized ones. As indicated from the results, the seed metering device exhibits good general properties, low damage rate, great precision, and high efficiency; it is capable of meeting general seeding operations of different crop seeds and technically supporting for the reliability and versatility of the seeder.

Cost Analysis of Multimodal Transport on Refrigerated Container

Refrigerated container multimodal transport is a long-distance interprovincial transportation, which effectively ensures the quality of agricultural products. The application of refrigerated containers and other means of transportation in the long - distance transportation of perishable agricultural products can reduce the cost of multimodal transport of agricultural products and improve the logistics efficiency. Therefore, it is of practical significance to study the multimodal transport cost analysis of refrigerated containers for perishable agricultural products. The article classifies the applicable goods in refrigerated containers and refrigerated containers; Erishable agricultural products have short shelf life and high damage rate. Refrigerated transportation tools have the particularity; In the cold chain logistics environment, in addition to considering the transportation cost, transit cost and time penalty cost of normal temperature multimodal transport, we should also consider the loss cost of perishable agricultural products in transit and the energy loss cost of refrigerated container refrigeration in transit.

A Slow Positron Beam Study of Helium Clustering in Oxide Dispersion Strengthened Steels

The present work provides an innovative approach to the experimental study of the radiation tolerance of oxide dispersion strengthened (ODS) steel comparing to its non-ODS variant. Inhomogeneous radiation damage, introduced by helium irradiation, was probed in a depth profile manner by a variable energy positron beam. Although numerous studies reporting the use of slow positron beam (SPB) experiments on ion-implanted materials have been published in the literature, only a few of them address the continuous distribution of microstructural damage introduced by ion beam. In this paper, we use SPB to probe a wide range of radiation damage in a single sample of each material. By evaluating positron diffusion in different parts of the Bragg peak, we were able to track the evolution of radiation-induced damage from a high density of small defects such as helium-vacancy clusters to large bubbles grown by coalescence. Combining with the transmission electron microscopy results and slow positron Doppler broadening spectroscopy, we offer new insight into different stages of microstructural bubble evolution in steels exposed to harsh radiation conditions. The obtained results show that the higher density of vacancy-type defects in the oxide dispersion strengthened steel, which act as recombination centres, suppress the formation of large defect agglomerations. While the TEM provides an indication of this effect in high displacement damage and helium production rates, positron annihilation spectroscopy elucidates the origin of this behaviour, improving the understanding of the fundamental mechanism of helium embrittlement.

Design and testing of seed maize ear peeling roller based on Hertz theory

Seed maize Zea mays (corn in the USA) have a very high value and thus it is crucial to avoid problems of high grain damage and low removal rates that can occur during the peeling of ears to remove the bracts. A mechanical model of the dynamic process of seed maize ear peeling was established using a finite element explicit dynamics simulation of the peeling process based on the Hertz theory and a mechanical analysis of the collisions and friction between the ears and the rollers during the peeling process was carried out. The main factors that affect the magnitude of the collision force and friction force were obtained. Based on the results of the modelling, peeling rollers consisting of four rubber-cast iron mixed rollers with different patterns were designed. The rationality of the mechanical model was verified and, based on the designed peeling roller; a test rig was built to carry out high-speed video tests. The whole peeling process of seed maize ear using the rollers was observed, and the test results showed that the redesigned roller had a peeling rate of 93% and a grain damage rate of 1.87%. The performance of the peeling device designed in this study was significantly better than that of the standard peeling device. This research provides a theoretical basis for various types of seed maize peeling operations. • Hertz and film peeling theory calculated frictional force on during maize ear peeling. • Rollers redesigned to facilitate low damage but and high peeling rate. • FEM simulation and high-speed video used to asses force and movement. • Average force of the seed maize ear 17.9N with the peeling rate is 93%. • Grain damage rate was 1.87%.

Assessing the performance of qpAdm: a statistical tool for studying population admixture

qpAdm is a statistical tool for studying the ancestry of populations with histories that involve admixture between two or more source populations. Using qpAdm, it is possible to identify plausible models of admixture that fit the population history of a group of interest and to calculate the relative proportion of ancestry that can be ascribed to each source population in the model. Although qpAdm is widely used in studies of population history of human (and nonhuman) groups, relatively little has been done to assess its performance. We performed a simulation study to assess the behavior of qpAdm under various scenarios in order to identify areas of potential weakness and establish recommended best practices for use. We find that qpAdm is a robust tool that yields accurate results in many cases, including when data coverage is low, there are high rates of missing data or ancient DNA damage, or when diploid calls cannot be made. However, we caution against co-analyzing ancient and present-day data, the inclusion of an extremely large number of reference populations in a single model, and analyzing population histories involving extended periods of gene flow. We provide a user guide suggesting best practices for the use of qpAdm.

Phase-field simulation of dose rate effect on the Cu precipitation with neutron irradiation.

Radiation-enhanced precipitation (REP) of Cu in Fe-Cu alloys results in hardening and degradation of the mechanical properties. By combining the CALPHAD-based free energy for phase-field modeling, and radiation-enhanced diffusion (RED) with neutron irradiating energetic particle, the precipitation of Cu in binary Fe-Cu alloys is studied under different dose rates, concentrations, and temperatures. Rate theory (RT) provides the RED that serves as an input parameter for the phase-field simulation to capture the morphology of the precipitates. The REP results agree with the theoretical predictions: the increase in the dose rates increases the concentration of defects, and accelerates the kinetics of precipitation. The simulation predicts the stability of the precipitates even under high damage rates. The increase in radius is achieved for high damage rates. Precipitate dissolution is observed to be dependent on the combination of dose rate, concentration, and temperature. The work also outlines the limitations of the model and the potential future improvements.

Design and test on double-roller sweet potato vine crushing and returning machine

ABSTRACT At present, all most sweet potato crushing machineries are improved based on potato seedling killer or straw crushing and returning machine, and adopt single-roller mulch type seedling killing structure, and there are problems such as low crushing qualification rate of ridge vines, easy entanglement of stalks and high damage rate. This not only requires manual further removal of the vines, but also the damaged sweet potato cannot be stored, which affects the yield. To solve the problems, a double-roller sweet potato vine crushing and returning machine with the structure of the front roller picking and the back roller crushing was designed. The Box-Behnken test design method was adopted to establish a quadratic regression model that took the picking roller speed, the cutter roller speed and the ground clearance as the test factors, and the vines breaking qualified rate, the stubble height, and the sweet potato damage rate as evaluating indicator.The analysis of the influence of interactive factors showed that the contribution rate of each factor to the vines breaking qualified rate was picking roller speed> cutter roller speed > ground clearance; the contribution rate of each factor to the stubble height was ground clearance> pickling roller speed > cutter roller speed; the contribution rate of various factors to the sweet potato damage rate was ground clearance> cutter roller speed > pickling roller speed. The optimization results showed that when the picking roller speed was 631 r/min, the cutter roller speed was 1906 r/min, and the ground clearance was 21 mm, the vines breaking qualified rate was 96.2%, the stubble height was 28.8 mm, and the sweet potato damage rate was 0.16%. The research results can provide new test schemes and complete design parameters for sweet potato vine crushing operations.

Representatives of Lepidoptera groups occurred in forestry and agricultural crops and their effective entomophage types

This article summarizes the data collected on the basis of several years of scientific and practical research, and identifies the bioecology of the main Lepidoptera family with high rates of economic damage to forest and agricultural crops, developmental stages, and species composition and systematics. Accordingly, several species of parasitic entomophages belonging to the families Trichogrammatidae, Braconidae, Ichneumonidae, Chalcididae, Pteromalidae were studied and systematically analyzed for species composition.

Pyrosilviculture: Combining prescribed fire with gap-based silviculture in mixed-conifer forests of the Sierra Nevada

We used a prescribed fire study to demonstrate the concept of pyrosilviculture, defined here as (i) using prescribed fire to meet management objectives or (ii) altering nonfire silvicultural treatments explicitly in order to optimize the incorporation of prescribed fire in the future. The study included implementation of relatively hot prescribed burns in mixed-conifer forests that have been managed with gap-based silviculture. The fires burned through 12-, 22-, 32-, and 100-year-old cohorts, thus enabling an analysis of stand age influences on fire effects. Mastication and precommercial thinning were assessed as prefire treatments in the 12-year-old stands. Postburn mortality and crown scorch declined with stand age. There was a clear tradeoff between fuel consumption and high rates of tree damage and mortality in the 12-year-old stands. Masticated stands had higher levels of mean crown scorch (78%) compared with precommercially thinned stands (52%). Mortality for all 12-year-old stands was high, as nearly half of the trees were dead 1 year after the fires. Giant sequoia and ponderosa pine had relatively high resistance to fire-related mortality. When applying the concept of pyrosilviculture, there may be opportunities to combine prescribed fire with regeneration harvests that create a variety of gap sizes to sustain both low fire hazard and promote structural heterogeneity and sustainable age structures that may not be achieved with prescribed fire alone.

Ballistic Trajectory Modeling for Missile with Deflectable Nose

With the development of science and technology, significant changes have taken place in the mode of modern wars. Application of military operating concepts such as ‘surgical precision strike' and ‘decapitation strike' make higher demands on precision-strike weapons. Ballistic trajectory correction ammunition is being rapidly developed due to its lucrative combination of low cost, high cost-effectiveness ratio, high damage rate, and applicability of existing inventory ammunition. Ballistic control technology has distinct advantages both in cost saving and improvement of the ammunition operational performance. Nose deflection is a feasible, effective, and fast-response flight control mode. The nose part of a projectile can be deflected at a certain angle relative to the projectile body axis, including a pressure difference between the windward and leeward sides of the warhead and generating the respective aerodynamic control force. In this study, a two-rigid-body trajectory model is established based on the multiple rigid body system theory. The proposed model is used to predict the flight trajectory of a projectile with the deflectable nose. Finally, the nose deflection effect on the ballistic trajectory variation is analyzed. The research results obtained provide the theoretical basis for the development of adaptive control smart ammunition and its engineering applications.

High-density geopolymer concrete for Port Kembla breakwater upgrade

Marine environments can pose continuous threats to coastal infrastructure, especially during episodic storm events. Thus, monitoring and maintenance of rock or concrete units-armoured coastal breakwaters are required, especially under present climate change scenarios, where changes in wave behaviour are anticipated and coastal structures are likely to be exposed to even greater wave energy resulting in higher rates of damage. A possible pathway towards the upgrading of existing breakwaters is to introduce high-density armour units, suggested by theoretical estimates and physical model test findings. In this project, a unique, sustainable high-density geopolymer concrete (GPC) mix was developed and trialled in fabricating armour units for upgrading existing coastal breakwaters. The system developed in laboratories was upscaled for field applications and is being tested at the Northern breakwater of NSW Ports’ Port Kembla Harbour. The concrete uses steel furnace slag (SFS) aggregate in an alkali-activated blended fly ash-blast furnace slag binder proportioned to facilitate the elimination of delayed expansion of the aggregate. The concrete properties were measured and microstructural analyses undertaken. The results show that SFS aggregate offers higher bulk density to the concrete alongside satisfactory strength in on-site curing and can reduce armour mass requirements at the same level of structural stability. Microstructural analyses confirm the elimination of SFS aggregate free-lime expansion. This important result provides a novel approach to both repair of existing structures and construction of new structures with reductions to both cost and carbon footprint.

Epidemiology and risk factors for avascular necrosis in childhood systemic lupus erythematosus in a Taiwanese population

Childhood-onset systemic lupus erythematosus (SLE) is associated with greater disease activity, more aggressive course, and high rates of organ damage. The prolonged use of corticosteroids in childhood SLE contributes to increased morbidity, including avascular necrosis (AVN). We conducted this retrospective study using claims data from the Taiwan National Health Insurance Research Database, enrolling 1,472 children with newly-diagnosed SLE between 2005 and 2013. The mean age at the diagnosis of SLE was 15.5 ± 3.3 years, and the female to male ratio was 6.2:1. Thirty-nine patients (2.6%) developed symptomatic AVN during a mean follow-up of 4.6 ± 2.5 years. In multivariate analysis, the risk of AVN was higher in the patients with a daily prednisolone dose between 7.5 mg and 30 mg (HR 7.435, 95% CI 2.882–19.178, p < 0.001) and over 30 mg (HR 9.366, 95% CI 2.225–39.418, p = 0.002) than in those with a dose ≤ 7.5 mg/day. In addition, AVN was inversely correlated with the use of hydroxychloroquine > 627 days (HR 0.335, 95% CI 0.162–0.694, p = 0.003). In conclusion, high daily doses of prednisolone were associated with a significant risk of AVN, whereas the use of hydroxychloroquine > 627 days conferred an advantage. We suggest that the judicious use of corticosteroids combined with hydroxychloroquine might be a promising preventive strategy for AVN.

Women With Spontaneous Coronary Artery Dissection Are at Increased Risk of Iatrogenic Coronary Artery Dissection

Spontaneous coronary artery dissection (SCAD) is a non-atherosclerotic cause of acute coronary syndrome (ACS) that affects women disproportionately. Previous case series have found that patients with SCAD undergoing cardiac catheterisation have high rates of iatrogenic coronary damage. We formally compared the rate of iatrogenic coronary artery dissection in women with and without SCAD undergoing cardiac catheterisation over a 11-year period. Women with SCAD were identified by a search of the cardiac catheterisation database 2007-2017 for the keywords 'SCAD', 'spontaneous coronary artery dissection', 'spontaneous coronary dissection', and 'spontaneous dissection'. For each identified case, the medical record and the coronary angiogram images were reviewed to confirm spontaneous coronary dissection. For cases of recurrent SCAD, duplicates were removed so that each patient was included only once in this analysis. For each identified case of SCAD, a control case was chosen from women aged <70 years, without SCAD, undergoing cardiac catheterisation for an ACS during the same 10-year period. One control case was chosen to match each SCAD patient as closely as possible for age and year of cardiac catheterisation. Iatrogenic coronary dissection was defined as new, proximal, flow limiting coronary artery dissection in a different coronary segment to the presenting spontaneous coronary dissection. Eighty-five (85) cases of women with SCAD were identified. Mean age was not different between SCAD and non-SCAD women (51±11 and 51±10 years, respectively). The SCAD group had lower rates of ST elevation myocardial infarction, lower rises in serum creatine kinase (CK) and troponin levels, lower rates of diabetes and smoking, and far less placement of stents during the procedure than the control group. The rate of additional iatrogenic dissection relating to the cardiac catheterisation procedure was 4 of 85 (4.7%) versus 0 of 85 (0%), p=0.04 in SCAD and control groups, respectively, despite a much lower rate of percutaneous coronary intervention in the SCAD group. No common factors could be identified regarding particular equipment or procedural factors associated with iatrogenic dissection. The rate of iatrogenic dissection in women with SCAD during cardiac catheterisation is confirmed to be high and significantly higher than a contemporaneous age-matched group of women without SCAD. This observation likely indicates generalised coronary fragility in this disease, and emphasises the importance of the utmost care in the engagement, injection and intervention involving the coronary arteries in this disease. Development of a non-invasive coronary imaging modality or biomarker able to diagnose SCAD non-invasively would be a great advance in the care of patients with this condition, because it would avoid the need for invasive coronary angiography for diagnosis.

Validation of advanced tools to evaluate sperm function in barramundi (Lates calcarifer).

Barramundi (Lates calcarifer) is a tropical finfish species rapidly growing in popularity for aquaculture production. However, sperm quality tests have yet to be adapted to enable selection of highly fertile male broodstock in this species. Accordingly, in this study advanced tools were optimized to evaluate barramundi sperm function to facilitate the future study of male fertility and address some of the reproductive constraints currently observed in captive-bred broodstock. Sperm morphology data were used to calibrate and validate automated sperm counting and motility detection by computer-assisted sperm analysis (CASA; AndroVision, Minitube). Several parameters were examined to determine the optimum settings for accurate CASA sperm counting and were compared to manual haemocytometer methods including: sample dilution (1:1000, r = 0.87), minimum number of fields (n = 4, CV = 7.5%), and the effect of motile vs. immotile spermatozoa on automated counting (no effect, r = 0.99, P < .001). Assays for cell viability and DNA damage were also validated for barramundi spermatozoa using 70 °C heat-treated controls and a 5-point intact:damaged dilution curve (r = 0.98, P < .001), and DNase-treated sperm controls, respectively. Data from these optimized assessments indicated high variation between individuals for each parameter assessed and the presence of high rates of DNA and membrane damage in sperm samples tested. Further research building upon this preliminary sperm quality data, is required to identify the cause of DNA and membrane damage in barramundi spermatozoa and understand any potential relationships with paternal performance in commercial spawns.

Understanding bubble and void nucleation in dual ion irradiated T91 steel using single parameter experiments

Ferritic-martensitic steels are attractive candidates for structural materials in next generation nuclear reactor systems due to their resistance to radiation induced swelling. Cavity and dislocation loop evolution was characterized in dual ion irradiated T91 steel in three separate irradiation campaigns examining single parameter dependencies of temperature, helium co-injection rate, and damage rate. Irradiations resulted in bimodal cavity size distributions across nearly all ranges of experimental parameters. It was determined that irradiation temperature and helium co-injection rate are stronger influences on bubble stability and the transition from bubbles to voids than is the irradiation damage rate. At low helium injection rates all helium is in vacancy clusters that evolve into bubbles or voids. At high helium injection rates, bubbles become saturated with helium resulting in accumulation of helium at other traps such as dislocation loops. At intermediate levels of He that should aid in the nucleation of bubbles and enhance swelling, the high density of sinks in the F-M microstructure suppresses bubble nucleation and therefore, the onset of swelling. At high enough temperatures, helium is only in bubbles as other strong helium traps, such as dislocation loops, did not form. The mechanism of bubble to void transition was found to shift from being driven by the accumulation of helium to the critical bubble at low damage rates to being driven by spontaneous formation by stochastic vacancy fluctuation at high damage rates.

Vegetation survival and condition in public green spaces after their establishment: evidence from a semi-arid metropolis.

Urban vegetation is generally exposed to adverse environmental conditions, such as high temperatures, compacted soils, low fertility, and a high pollutant concentration. The influence of biophysical and social factors on the survival and condition of trees and nontrees was analyzed using a census of plants in 37 green spaces of the Metropolitan Region of Santiago de Chile (MRS) several years after their establishment. The tree survival rate was higher (77%) than that of other species (24%). Survival was primarily explained by municipality management and species selection, but the relevance of these factors differed between trees and nontrees. Species with low water requirements outperformed species that were more sensitive to water stress. A high mechanical damage rate was observed, with 91% of trees showing severe or medium damage. Soil quality was better than expected, with a bulk density less than 1.0 g m-3 and moderate and high levels of P, and only 8% of sites had low K levels. The N content was highly variable, but most of the sites had levels greater than 20 mg kg-1, which indicates a trend of accumulation that is consistent with urban soils. More in-depth studies are required to establish the factors that explain plant survival in public spaces of the AMS, and irrigation monitoring is especially needed.

Optimization and experiment of key components in pneumatic peanut pod conveyor

Research interest in pneumatic conveying technologies in processes such as peanut harvesting and shelling has grown rapidly in recent years. However, the use of pneumatic conveyors in this application suffers from high pod damage rates and duct obstruction. To address these issues, we analyzed the critical speed of pneumatic transport for conveying the peanut pods and measured the angle of friction and coefficient of restitution of peanut pods on a variety of material surfaces. Based on the results of these tests, optimizations and improvements were made to the separator bowl, air supply duct, and conveying duct. A pneumatic conveying experiment was then performed using peanut pods. In the factorial experiment, it was found that increases in fan speed increase the pod damage rate and transport efficiency, while increases in the thickness of the cushioning/anti-obstruction layer decrease the rate of pod damage and transport efficiency. Pod damage rates were significantly affected by fan speed, the thickness of the cushioning/obstruction prevention layer, and interaction between these factors, while transport efficiency was only significantly affected by fan speed. It is proved by the machine verification test, the optimal parameters for the pneumatic transport of Baisha peanut pods with a moisture content of 7.24% was a fan speed of 2700 r/min and a cushioning/anti-obstruction layer thickness of 6 mm. A pod damage rate of 5.19% and transport efficiency of 92.03% were achieved using these parameters, which are sufficient for meeting the requirements of industrial applications. Keywords: pneumatic transport, material properties, peanut pods, damage rate, transport efficiency DOI: 10.25165/j.ijabe.20201303.4609 Citation: Gao X M, Xie H X, Gu F W, Wei H, Liu M J, Yan J C, et al. Optimization and experiment of key components in pneumatic peanut pod conveyor. Int J Agric & Biol Eng, 2020; 13(3): 100–107.

Study on Preparation and Properties of CNTs/Al2009 Composites by Cryogenic Milling

The CNTs/Al2009 composite powders were prepared by cryogenic milling. The CNTs were uniformly dispersed on the surface of Al2009 powders. And then the CNTs/2009Al composites were fabricated by hot extrusion/hot isostatic pressing method. The effects of CNTs content and cryogenic milling process on the dispersion of CNTs in Al2009 matrix, the microstructure of powders and the properties of composites were studied by Scanning electron microscopy, Raman spectroscopy and tensile strength testing at room temperature. The results showed that the dispersion of CNTs was improved with the extension of ball milling time (1h~4h), but the damage degree of CNTs was intensified. In comparison, CNTs had the highest damage rate at the beginning of ball milling. As the milling time increased, the mechanical properties began to increase slightly and then decreased. When the ball milling time was 2h, the mechanical properties reached the highest. Cryogenic milling could achieve good dispersion in the Al2009 matrix for mixed powders with low CNTs content. When the CNTs content increased to 1.0%, a small amount of agglomeration appeared, but for composites, the strengthening effect of CNTs was more dominant. When CNTs were further added, the dispersion was remarkably lowered and the performance was deteriorated. CNTs (1.0wt.%)/Al2009 composites had excellent mechanical properties. The tensile strength reached 560MPa, which was 25% higher than Al2009.

Effects of pore-fracture structure of ductile tectonically deformed coals on their permeability: An experimental study based on raw coal cores

The distribution area of ductile tectonically deformed coals (TDCs) usually coincides with the forbidden zones for coalbed methane (CBM) development. Permeability of coal reservoirs, an important indicator to evaluate the energy potential of CBM, is directly affected by the pore-fracture structures. To study the controlling mechanism of pore-fracture structures on permeability, we investigated the micropore - micro-fracture structures of various ductile TDCs by adopting mercury intrusion porosimetry (MIP) and low-pressure gas adsorption. The permeability and the pressure sensitivity of the standard TDC cores were tested by the pressure pulse decay method. The results showed that the total pore volume of ductile TDCs, especially the mesopores and macropores, significantly increased from that of primary structure coals (PSCs), while the volume of transitional pores only slightly increased in strongly crumpled and mylonitized coals, and thus, the dominant pores in coals gradually changed from micro-fractures to mesopores and macropores. The pore-fracture structure of ductile TDCs showed a poorer connectivity and a higher roughness than PSCs. The permeability of typical ductile TDCs obviously decreased, the permeability heterogeneity significantly increased, and the pressure sensitivity of permeability generally showed a pattern of “weakly crumpled - > PSCs > strongly crumpled - and mylonitized coals”. Correlation analysis showed that the weakly crumpled coals that contain well-developed and well-connected micro-fractures and fewer <10 μm coal particles usually display high permeability. In strongly crumpled – and mylonitized coals, the connected pore-fracture structures were damaged and many pore throats and flask-shaped pores formed, which is the main reason for the reduced permeability and the high permeability damage rate.