Applicability of Constitutive Models to Describing the Compressibility of Mining Backfill: A Comparative Study

The compressibility of mining backfill governs its resistance to the closure of surrounding rock mass, which should be well reflected in numerical modeling. In most numerical simulations of backfill, the Mohr–Coulomb elasto-plastic model is used, but is constantly criticized for its poor representativeness to the mechanical response of geomaterials. Finding an appropriate constitutive model to better represent the compressibility of mining backfill is critical and necessary. In this paper, Mohr–Coulomb elasto-plastic model, double-yield model, and Soft Soil model are briefly recalled. Their applicability to describing the backfill compressibility is then assessed by comparing numerical and experimental results of one-dimensional consolidation and consolidated drained triaxial compression tests made on lowly cemented backfills available in the literature. The comparisons show that the Soft Soil model can be used to properly describe the experimental results while the application of the Mohr–Coulomb model and double-yield model shows poor description on the compressibility of the backfill submitted to large and cycle loading. A further application of the Soft Soil model to the case of a backfilled stope overlying a sill mat shows stress distributions close to those obtained by applying the Mohr–Coulomb model when rock wall closure is absent. After excavating the underlying stope, rock wall closure is generated and exercises compression on the overlying backfill. Compared to the results obtained by applying the Soft Soil model, an application of the Mohr–Coulomb model tends to overestimate the stresses in the backfill when the mine depth is small and underestimate the stresses when the mine depth is large due to the poor description of fill compressibility. The Soft Soil model is recommended to describe the compressibility of uncemented or lightly cemented backfill with small cohesions under external compressions associated with rock wall closure.

Evaluation of Cucumber Hybrids for Yield and Quality Under Plastic House and Open Field Conditions

Low yield of off-season cucumber due to use of open-pollinated varieties with high male to female ration, long gestation period and high incidence of diseases are the major problems of cucumber production in Nepal. The use of imported hybrids varieties during the off-season and plastic film technology has shown to lead to enhanced growth and higher yield in recent years. However, there is a little work on hybrid cucumber research and their testing in Nepal. Therefore, experiments were conducted at the National Horticulture Research Center (NHRC), Directorate of Agricultural Research (DoAR), Tarahara and Farmer's field in Dhankuta district accordingly to select best hybrids. Sixteen genotypes including best Indian hybrid Dynasty and 3 open-pollinated check genotypes were evaluated at NHRC, Khumaltar during the years 2018 and 2019 in Randomized Complete Block Design (RCBD) with three replications under the plastic house. Previously selected seven genotypes were evaluated in DoAR, Tarahara in 3 replications and best hybrid was compared with farmers' varieties in Dhankuta at open field conditions. Tested genotypes showed a significant difference in yield and other parameters like male to female ratio, early flowering, vine length, disease scoring etc. both under the plastic house and open field conditions. The new hybrids HRD CUM 009 x 003 (107.05 mt/ha), HRD CUM 006 x 003 (91.55 mt/ha) and HRD CUM 004 x 001(88. 10 mt/ha) were promising due to higher yield, earlier to 50% female and male flowering, a greater number of female flowers, short vine length, higher number of fruits per plants and earliness harvesting than other cultivated varieties. Most of the tested hybrids produced more than double yield than open-pollinated genotypes.

Synthesis and biological activity of N6-mannopyranosyladenines

In this work, potentially bioactive condensation products of adenine with D-mannose and 6-deoxy-L-mannose (L-rhamnose) were synthesized in water and ethanol solutions. According to FTIR spectroscopy and elemental analysis, mono-N6-glycosylated adenines were isolated from water systems in satisfactory yields, while ethanol solutions contained mixtures of N6 and N9-products, as well as complexes of the latter with copper ions. A detailed analysis of the vibrational spectra of N6-glycosyladenines confirmed the structure of carbohydrate fragments in the form of pyranose rings, while some part of the product was obtained in the form of deoxyaminoketosis. N-rhamnosyladenine was formed with a more than double yield because of a higher stability of rhamnose with regard to side reactions. The reflection spectra of model solutions of glycosyladenines, recorded 4 days after preparation, showed no bands characteristic of free adenine in the range of 1250-1110 cm-1, which indicates a sufficient resistance of the synthesized products towards hydrolytic cleavage under experimental conditions. The conducted biotesting of the isolated products on wheat seeds (Triticum aestivum L.) showed an increase in the content of chlorophylls in seedlings for both mannosilade-nines compared to the control. A decrease in the concentration of synthesized products in germination solutions from 0.1 to 0.001% led to an increase in the accumulation of photosynthetic pigments, while this effect was more pronounced for rhamnosyladenine. The latter can be connected with the structural features of car-bohydrate fragments, in particular, the differences in the hydroxylation degree of glucoside fragments. Future research will investigate the mechanisms of transformation and action of N6-substituted adenines.

Study on Stability Control of Retained Gob-Side Entry by Blasting Fracturing Roof Technology in Thick Immediate Roof

A retained gob-side entry technique is popular in longwall mining coal mines, because the excavation of an entry is reduced for the next panel. However, it is influenced by multiple excavations and mining, so the stability control of the surrounding rock becomes a problem. In view of the above problems, a typical retained gob-side entry with thick immediate roof was carried out, and a blasting fracturing roof technology was used in it to improve the stress environment, reduce the deformation and damage, and ensure stability and safety. To study the fracturing roof parameters, a global model with thick immediate roof considering strain-soft and double-yield constitution was built. It found that the stress, damage range, and deformation of surrounding rock were closely related to the height and angle of fracturing roof, and an optimal case was given out. The simulation result was applied to the field practice, and a good application effect was achieved. The above technique and research method can be used as a reference for the coal mine with similar conditions.

Microstructural Origin of the Double Yield Points of the Metallocene Linear Low-Density Polyethylene (mLLDPE) Precursor Film under Uniaxial Tensile Deformation

The microstructural origin of the double yield points of metallocene linear low-density polyethylene (mLLDPE) precursor films has been studied with the assistance of the synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS). It has been shown that the microstructural origin of the double yield points is highly related to the initial orientation of the original precursor film. For less oriented mLLDPE precursor films, the rearrangement of lamellae and the appearance of the monoclinic phase are the microstructural origins of the first yield point. In comparison, for the highly-oriented mLLDPE precursor film, only the orthorhombic-monoclinic phase transition appears at the first yield point. The melting-recrystallization and the formation of the fibrillary structure happen beyond the second yield point for all studied mLLDPE precursor films. Finally, the detailed microstructural evolution roadmaps of mLLDPE precursor films under uniaxial tensile deformation have been established, which might serve as a guide for processing high-performance polymer films by post-stretching.

A Single Input Dual Output Multiport DC–DC Converter with Minimal Switches

This paper proposes a topology for multiport DCDC converter with double yield for a solitary facts. Essentially the buck converter's yield is lesser than the records. Boost converter's yield is more distinguished than the info. buck-boost converter's yield is each more noteworthy or lesser than the facts. Be that as it is able to, the interest of the proposed converter is, it surrenders the both increase and undertaking down yields all the at the same time as. The contemporary-day topology of the multiport DC-DC Converter applied four switches however the proposed topology uses less number of switches with excessive yield contrasted with existing one. It likewise brings approximately decrease of replacing misfortunes. The skillability of the converter is improved, yield voltages get controlled and the charge of the circuit diminishes because of its minimization. The near circle PI controlling approach is embraced. The results were checked with the resource of making use of MATLAB simulink software program program