Study on the Mechanical Parameters and Permeability of Coal Reservoirs at Different Temperatures.

Deep coal reservoirs, as opposed to their shallower counterparts, exhibit characteristics of higher temperatures and pressures. These conditions affect the fracture structure and mechanical properties of coal, which in turn controls permeability. Substantial studies have been conducted to determine the effects of overburden pressure on permeability, but the correlation between the temperature and mechanical parameters/permeability of coal remains unclear. This study focused on low-rank bituminous coal from the southern edge of the Junggar Basin in Xinjiang. Using experiments conducted on seepage and mechanics at different depths (considering effective stress and temperature), the study investigated how temperature affects the mechanical parameters and permeability of coal column samples. A permeability prediction model was established incorporating temperature, mechanical parameters, and effective stress. The results show that from 20 to 80 °C, the elastic modulus of coal column samples decreases by 31.0%, and the Poisson ratio increases by 72.0%. Permeability decreases between 48.37 and 90.12% under different depths. The stress sensitivity coefficient under various temperature conditions decreased exponentially as the effective stress increased, and the temperature sensitivity coefficient under various effective stress conditions decreased with increasing temperature. The permeability was more sensitive to a temperature below 40 °C. In the permeability prediction model, the fracture compressibility coefficient is bifurcated into two coefficients, each controlled by temperature and effective stress. The permeability prediction error of the model was 12.7% under constant effective stress and 17.2% under varying effective stress and temperature conditions. The study could provide guidance for fracturing and coalbed methane production in deep coal reservoirs.

The Difference between Stress Deformation and Adsorption Deformation of Coal Reservoirs and Its Role in Permeability Prediction.

The key to the variation in permeability within coal reservoirs lies in the stress-induced deformation and desorption-induced deformation during the coalbed methane (CBM) production. The differences in sample scale and measurement methods between stress-induced deformation and desorption-induced deformation significantly affect the accuracy of permeability measurements. Therefore, in order to elucidate the relationship between stress-induced deformation and adsorption-induced deformation, as well as the influencing factors, and to assess the accuracy of permeability evolution prediction, this study conducted a series of parallel experiments, including compression deformation experiments under stress loading (stress-induced deformation), methane adsorption-induced deformation experiments (adsorption-induced deformation), µCT scanning, and overburden permeability measurements.The results of the study indicate that stress-induced deformation and adsorption-induced deformation are negatively correlated but exhibit a relatively weak correlation. Stress-induced deformation encompasses deformation of coal matrix, minerals, and fractures, whereas adsorption-induced deformation primarily reflects coal matrix deformation. While there is some overlap between the two, they are not entirely identical. The main influencing factor of stress-induced deformation is the mechanical strength of coal, with minerals in coal increasing the Young's modulus of coal reservoirs. Among them, minerals that are more dispersed and have smaller particles have a more significant impact on stress-induced deformation. The primary influencing factor of adsorption-induced deformation is the deformation capability of the coal matrix, with minerals and fractures having less significant effects. Permeability changes are controlled by fracture deformation, but stress-induced deformation measurements weakly reflect this aspect, leading to an inability to accurately predict the scale of the impact of effective stress changes on permeability during CBM production and CO2-ECBM processes. In contrast, adsorption-induced deformation relatively accurately reflects the deformation capability of the coal matrix and provides a more accurate prediction of permeability rebound under the condition of almost unchanged effective stress in the late stages of mining. Therefore, deformation parameters under stress loading are challenging to directly apply to the prediction of permeability evolution, while adsorption-induced deformation parameters can be effectively utilized.

High Curvature PEDOT:PSS Transport Layer Toward Enhanced Perovskite Light-Emitting Diodes.

The rapidly developed metal halide perovskite light-emitting diodes (PeLEDs) are considered as a promising candidate for next-generation display and illumination, but the unbalanced charge transport is still a hard-treat case to restrict its efficiency and operational stability. Here, a high curvature PEDOT:PSS transport layer is demonstrated via the self-assembly island-like structures by the incorporation of alkali metal salts. Benefiting from the dielectric confinement effect of the high curvature surface, the modified CsPbBr3 -based PeLEDs present a 2.1 times peak external quantum efficiency (EQE) from 6.75% to 14.23% and a 3.3 times half lifetime (T50 ) from 3.96 to 13.01 h. Besides, the PeLEDs show high luminance up to 44834 cd m-2 . Evidently, this work may provide a deep insight into the structure-activity relationship between the micro-structures at the PEDOT:PSS/perovskite interface and the performance of PeLEDs, and crack the codes for ameliorating the performance of PeLEDs via interfacial micro-structured regulation.

Structurally Tolerance-Factor-Tuned Metal Halide Nanocrystals for Environmentally Stable and Efficient Red Light-Emitting Diodes.

Black phase CsPbI3, naturally possessing the superiority of high radiative recombination efficiency and narrow emission line width, shows promise for commercial applications of red perovskite light-emitting diodes (PeLEDs). However, the metastable black phase CsPbI3 with a marginal tolerance factor (t) of 0.81 would easily convert to the nonoptical yellow phase. Herein, we demonstrate the strategy of partial substitution of larger dimethylammonium cation (DMA+) for Cs+ to achieve the stable tolerance factor of 0.903 for greatly improved Cs0.7DMA0.3PbI3 nanocrystals. These NCs present a superior ultraviolet (UV) irradiation stability by retaining 80% of the initial photoluminescence intensity after 5 h, which is much better than that of its counterparts (retaining 30%). Based on this, the as-developed red PeLEDs demonstrate remarkable luminance of 1258 cd/m2 and external quantum efficiency of 3.39%, which are almost 6 times and 3 times that of its counterparts, respectively (203 cd/m2 and 1.28%). This strategy may pave the way to improving the stability and efficiency of PeLEDs.

Permeability Loss of Bituminous Coal Induced by Water and Salinity Sensitivities: Implications of Minerals' Occurrence and Pore Structure Complexity.

Water sensitivity (WS) and salinity sensitivity (SS) are key issues to be investigated for instructing coalbed methane (CBM) production. This work studied the influences of minerals and pores on WS and SS of medium-volatile bituminous coal (MVBC) and highly volatile bituminous coal (HVBC) deposited in northwestern China by detecting and observing minerals using the TESCAN Integrated Mineral Analyzer, simulating WS and SS, and characterizing pore structural complexities using rate-controlled mercury penetration. The results show that (1) kaolinite is mainly distributed as irregular particles or fragile aggregates attaching on the bedding surface or filling in meso-pores or transition pores, showing a high potential for detachment; (2) MVBC and HVBC in this study are characterized as medium to weak WS and weak SS, respectively; (3) for HVBC during the WS or SS process, kaolinite distributed in meso-pores or transition pores first detaches and then migrates to the narrow throat of macro-pores and super macro-pores, leading to volume decreases of macro-pores and super macro-pores and loss of permeability; and (4) kaolinite filling in macro-pores of MVBC detaches, then migrates, and finally deposits in super macro-pores after WS and SS, leading to losses of super macro-pore volume and permeability. Results of this study can enhance the scientific knowledge on WS and SS of coal during CBM development.

Thermodynamics-Induced Injection Enhanced Deep-Blue Perovskite Quantum Dot LEDs.

Precisely tuning emission spectra through the component control of mixed halides has been proved to be an efficient method for procuring deep-blue perovskite LEDs (PeLEDs). However, the inferior color instability and lifetime attenuation, originated from vacancy- and trap-mediated mechanisms under an external field, remain an uninterruptedly formidable challenge for the commercial development of PeLEDs. Here, an ultrafast thermodynamics-induced injection enhancement strategy was employed to promote efficient carrier recombination within perovskite quantum dots (QDs), accompanied by less inefficient charge accumulation and trap generation, enabling deep-blue PeLEDs with improved thermal and spectral stability. The resultant PeLEDs feature an external quantum efficiency (EQE) of 3.66%, a max luminance of 2100 cd/m2 at the electroluminescence (EL) of 460 nm, and a halftime of 288 s. This work provides a general platform for promoting the EL performances and a deep insight into unraveling the degradation mechanism of blue PeLEDs.

The metal doping strategy in all inorganic lead halide perovskites: synthesis, physicochemical properties, and optoelectronic applications.

All inorganic perovskites CsPbX3 (X = Cl, Br, I), rising stars of optical materials, have shown promising application prospects in optoelectronic and photovoltaic fields. However, some open issues still exist in these perovskites, like poor long-term stability, inevitable intrinsic defects and much nonradiative recombination, which greatly weakens their optical capability and seriously hinders their further development. The metal doping strategy, through the partial substitution of foreign ions for native ions, has gradually become an effective method for significantly enhancing the comprehensive properties of CsPbX3. Whereas some previous studies have reported the impressive properties of metal-doped CsPbX3, there is still a lack of a comprehensive review on the influences of metal doping on CsPbX3. In this review, we aim to provide a systematic review of the latest achievements in metal-doped CsPbX3, which focuses on their synthetic methods and the positive effects of metal doping on structure, optical properties, morphology control, carrier behavior and related optoelectronic and photovoltaic devices. Finally, we put forward a few opportunities and challenges about the further investigation of metal-doped perovskites, which may help researchers explore new research directions.

A Study on Three-Phase Gas Content in Coal Reservoirs and Coalbed Methane-Water Differential Distribution in the Western Fukang Mining Area, Xinjiang, China.

The daily gas production of a single well (coalbed methane (CBM) vertical well) in the western Fukang mining area in the southern margin of the Junggar Basin, Xinjiang, China is relatively high. However, there are significant differences between gas and water production of CBM wells at different locations in the area, and the reason has not been adequately explained. To explore the distribution characteristic of coalbed methane and water in the Fukang mining area, the three-phase CBM gas (adsorption gas, free gas, and water-soluble gas) content was determined based on theoretical analysis and simulation. Combining the calculation results and the basis of geological data, the CBM-water differential distribution in the study area was discussed. The results show that the average daily water production and average daily gas production of CBM wells show a negative correlation in the study area. The CBM wells with high daily gas production are mainly located in the high areas of the structure, and these wells commonly begin to produce gas within a short period. The calculation of three-phase CBM gas content and the test results of gas composition show that the gas content (especially the free gas) is relatively high in the high areas of the structure, while the concentration of C2H6 is relatively low. Meanwhile, the concentration of C2H6 shows a positive correlation with buried depth, which indicates that CBM migrates from the deep areas to the higher areas. The calculation of equivalent water level elevation and hydraulic head shows that the groundwater mainly flows from the central part to the east and the west within the CBM well areas, and the groundwater flows downward along the coal seam controlled by gravity, which results in the CBM-water differential distribution. The CBM-water differential distribution in the western Fukang mining area is the result of coupling control of tectonic and hydrological geology factors. Multistage tectonic movements formed large-scale folds and faults in the area, which controlled the migration direction of CBM and groundwater. The dip angle of the stratum in the study area is commonly greater than 45°, and the gravity effect is greater in the process of groundwater flow, which promotes the CBM-water differential distribution. Free gas migrates to the high area of the structure, and groundwater accumulates in the axial part of the syncline. The results in this study provide a basis for the large-dip angle CBM exploration and development in the Fukang mining area.

Mineral Composition and Its Control on Nanopores of Marine-Continental Transitional Shale from the Ningwu Basin, North China.

There is a large difference between the sedimentary environment and maturity of organic matter between marine shale and marine-continental transitional shale. It is of great significance to discuss the effect of inorganicminerals on the pores for marine-continental transitional shale gas exploration. In this study, scanning electron microscopy (SEM), low temperature liquid nitrogen adsorption and Xray diffraction (XRD) were conducted on eight marine-continental transitional shale samples from the Ningwu Basin, Shanxi Province, China. The pore structure differences in the different minerals were discussed, and the relationship between the mineral content and pore parameters was analysed. The results show that the mineral composition of shale is dominated by clay minerals, quartz, carbonate minerals and a small amount of pyrite. The clay minerals content is between 39.5% and 77.0%, with an average of 59.9%. The quartz content ranges from 21.8% to 47.8%, with an average of 31.9%. The carbonate minerals content in shale is between 0.6% and 23.9%, and the average is 6.3%. The clay minerals are composed of mixed illite-montmorillonite layer, kaolinite and chlorite. The content of mixed illite-montmorillonite layer is between 13.8% and 27.4%, with an average of 20.4%. The kaolinite content ranges from 57.0% to 86.2%, with an average of 76.0%. The content of chlorite is between 0 and 15.6%, with an average of 5.7%. The types of pores are mainly intergranular pores and interlaminar pores, which are mostly presented as slit and parallel plates. The mixed illite-montmorillonite layer contributes more to the specific surface area, which is favourable for shale gas adsorption. The pores in kaolinite are more developed than those of the mixed illite-montmorillonite layer, but the pore diameter is relatively large. The quartz granule has a complete crystal type, and intergranular pores with a large pore size are often developed at the mineral contacts. Compared with clay minerals and quartz, the pore development in the carbonate minerals is relatively poor and develops more micro-fractures. The pyrite contributes a certain number of intergranular pores and mold pores.

Characterization of Pore Structure and Its Relationship with Methane Adsorption on Medium-High Volatile Bituminous Coal: An Experimental Study Using Nuclear Magnetic Resonance.

A number of studies have used the nuclear magnetic resonance (NMR) technique to analyse pore characteristics and to discuss the influencing mechanisms of pore structure on methane adsorption. However, there are few studies on the dynamic characteristics of methane adsorption over time under the same temperature and pressure conditions, especially by using the cylindrical coal samples. In this study, scanning electron microscopy (SEM), mercury injection porosimetry (MIP), isothermal adsorption and NMR techniques were carried out on the four medium-high volatile bituminous coal samples from Shanxi Province, China. The simulation of methane adsorption was carried out with the custom adsorption instruments. Based on the experimental results and the Hodot pore size classification standard, the pore size distribution of the samples was analysed. In addition, the influence of nanopore structure and water content on methane adsorption was discussed. The results show that the T2 relaxation diagram of the four coal samples has a bimodal-triple peak, which reflects the complexity of the pore structure. Due to the clay minerals filling microfractures in the sample HX, the connectivity of the nanopores is reduced, in addition there is an obvious gap between the peaks in the relaxation diagram. After calculation of the T2 relaxation diagrams of the coals, the results can be converted into the pore size distribution map. The pores in the four samples are mainly composed of the macropores, followed by the mesopores, and the ratio of micropores and transition pores is relatively small. At Sw (saturated in 5% brine for 24 h) and Sir (dried at 333 K for 3 h) conditions, the adsorption capacity of the four samples presented a positive correlation with the effective porosity and the ratio of micropores, and presented a negative correlation with the ratio of mesopores, while the macropores contribute less to the adsorption. Compared with samples at Sw conditions, the adsorption capacity of the samples at Sir conditions shows an overall increasing trend, which is approximately 1.6 times that of the samples at Sw conditions on average. When a large amount of liquid water invades the nanopores and fractures, the water occupies the adsorption space of the methane due to the wettability effects and capillary pressure, which reduces the adsorption capacity.

Failure patterns and survival in patients with nasopharyngeal carcinoma treated with intensity modulated radiation in Northwest China: a pilot study.

PURPOSE: To evaluate the clinical outcomes and patterns of failure in patients with nasopharyngeal carcinoma (NPC) treated with intensity modulated radiotherapy (IMRT) in Northwest China. METHODS AND MATERIALS: From January 2006 to December 2009, 138 NPC patients were treated at Xijing Hospital. Of them, 25 cases with stage I-II received IMRT only, 113 cases with stage III-IVb received IMRT plus accomplished platinum-based chemotherapy. The IMRT prescribed dose was PTV 68-74 Gy to gross disease in nasopharynx and 66-72 Gy to positive lymph nodes in 30-33 fractions, and high risk and low risk region PTV was 60-63 Gy and 50.4~56 Gy in 30~33 and 28 fractions respectively. Plasma Epstein Barr virus (EBV) DNA load was measured before treatment. The clinical toxicities, outcomes and patterns of failure were observed. RESULTS: The median follow up time was 23 months (range 2 to 53 months). EBV infection positive was only 15.9%. Overall disease failure developed in 36 patients, 99% belonged to stage III/IV disease. Among these, there were 26 distant metastases, 6 local recurrence, and 4 regional recurrence. The 3-year local control rate(LCR), distant metastasis-free survival (MFS), disease-free survival (DFS) and the overall survival (OS) was 93.9%, 79.5%, 70% and 83.1% respectively. Multivariate analyses revealed that age and anemia pre-radiotherapy were independent predictors for OS. CONCLUSION: IMRT with or without chemotherapy can improve the long term survival of NPC patients in Northwest China. Distant metastasis becomes the main cause of treatment failure. Age and anemia before radiotherapy were the main prognosis factors of NPC patients.

Adjuvant chemotherapy and radiotherapy in triple-negative breast carcinoma: a prospective randomized controlled multi-center trial.

BACKGROUND AND PURPOSE: Triple-negative breast cancer (TNBC) presents a high risk breast cancer that lacks the benefit from hormone treatment, chemotherapy is the main strategy even though it exists in poor prognosis. Use of adjuvant radiation therapy, which significantly decreases breast cancer mortality, has not been well described among poor TNBC women. The aim of this study was to evaluate whether the combination of chemotherapy and radiotherapy could significantly increase survival outcomes in TNBC women after mastectomy. PATIENTS AND METHODS: A prospective randomized controlled multi-center study was performed between February 2001 and February 2006 and comprised 681 women with triple-negative stage I-II breast cancer received mastectomy, of them, 315 cases received systemic chemotherapy alone, 366 patients received radiation after the course of chemotherapy. Recurrence-free survival (RFS) and overall survival (OS) were estimated. Simultaneously local and systemic toxicity were observed. RESULTS: After a median follow-up of 86.5 months, five-year RFS rates were 88.3% and 74.6% for adjuvant chemotherapy plus radiation and adjuvant chemotherapy alone, respectively, with significant difference between the two groups (HR 0.77 [95% CI 0.72, 0.98]; P=0.02). Five-year OS significantly improved in adjuvant chemotherapy plus radiation group compared with chemotherapy alone (90.4% and 78.7%) (HR 0.79 [95% CI 0.74, 0.97]; P=0.03). No severe toxicity was reported. CONCLUSIONS: Patients received standard adjuvant chemotherapy plus radiation therapy was more effective than chemotherapy alone in women with triple-negative early-stage breast cancer after mastectomy.

Three-dimensional conformal radiation therapy for refractory laryngeal granuloma.

AIMS AND BACKGROUND: The etiology of laryngeal granulomas is often multifactorial and the benefit of pharmacological therapy remains unclear. Anti-reflux treatment is only effective in granulomas definitely induced by gastroesophageal reflux. Steroid inhalation has shown favorable results but it is unclear whether it shortens the healing process. Surgical excision is associated with high recurrence rates. The aim of this study was to evaluate the role of 3-dimensional conformal radiation therapy (3DCRT) in the treatment of refractory laryngeal granuloma. METHODS AND STUDY DESIGN: The study was a retrospective review including all patients presenting to the Department of Radiation Oncology at Xijing Hospital from January 2004 to March 2007. We studied a total of 15 cases of refractory laryngeal granuloma that had recurred ≥2 times. Patients had previously been managed with voice rest, corticosteroids, antibiotics, antacids, surgery and botulinum toxin. All patients accepted surgical excision and immediate adjuvant 3DCRT at a total dose of 15 Gy over 5 days. RESULTS: All patients were successfully treated with surgery and 3DCRT. There has been no granuloma recurrence in 3 years of follow-up. CONCLUSIONS: 3DCRT is a safe and effective therapy for refractory laryngeal granulomas, especially when other methods have failed.