Determination of a potential set of factors which influence the situation of methane emission into roadways being driven

The currently applied methodology of absolute gassiness forecasting in roadways being driven in Polish hard coal mines is based on the results of investigations frombefore more than twenty years. At present the roadways are being driven in majority ofcases in quite different conditions than those which had been the subject of the said investigations. The application of 'old' methods of forecasting of methane emission during driving of roadways often brings about great discrepancies between the results of the forecasts and actual situation. It is firstly necessary to determine a potential set of factorswhich exert an influence on situation regarding methane emission into roadways beingdriven in order to prepare a verified mathematical model of absolute gassiness forecastingOn the basis of available literature and the investigations conducted by the Central MiningInstitute an initial list of factors has been prepared which can have an impact upon methane emission into roadways being driven. The assumptions of heuristic method have beentaken advantage of for selection of parameters and indices describing the phenomenon ofmethane emission. It has been dictated by the fact that the available literature is lacking apretty unambiguous viewpoint on the subject under consideration and at the same time itis necessary to perform an a priori assessment of the information contained in a givenfeature (factor). A prepared initial set has been scrutinized to be verified on the basis of aconducted expert survey among seventy specialists in this field. After collecting of the results of the survey their statistical elaboration was prepared. The co-efficient of agreementof multiple ordering, the so called concordance co-efficient has been taken advantage of inorder to check the competency of experts. The investigations prove that the experts are inagreement in their opinions. The estimation of a collective assessment of all participants ofthe survey was conducted with the use of the rank sum's test by J. Gren, The results ofthe conducted analysis allowed determining a potential set of factors which influence thesituation of methane emission into roadways being driven. This set, after conductance offurther detailed investigations, can constitute a base for elaboration of a function describ-ing methane emission into roadways being driven in hard coal mines.

Soil particle size range correction for improved calibration relationship between the laser-diffraction method and sieve-pipette method

Particle size fraction(clay, silt, and sand) is an important characteristic that influences several soil functions. The laser-diffraction method(LDM) provides a fast and cost-effective measurement of particle size distribution, but the results usually differ from those obtained by the traditional sieve-pipette method(SPM). This difference can persist even when calibration is applied between the two methods. This partly relates to the different size ranges of particles measured by the two methods as a result of different operational principles, i.e., particle sedimentation according to Stokes’ Law vs. Mie theory for laser beam scattering. The objective of this study was to identify particle size ranges of LDM equivalent to those measured by SPM and evaluate whether new calibration models based on size range correction can be used to improve LDM-estimated particle size fractions, using 51 soil samples with various texture collected from five soil orders in New Zealand. Particle size distribution was determined using both LDM and SPM. Compared with SPM, original data from LDM underestimated the clay fraction(< 2 μm), overestimated the silt fraction(2–53 μm), but provided a good estimation of the sand fraction(53–2 000 μm).Results from three statistical indices, including Pearson’s correlation coefficient, slope, and Lin’s concordance correlation coefficient, showed that the size ranges of < 2 and 2–53 μm defined by SPM corresponded with the < 5 and 5–53 μm size ranges by LDM, respectively. Compared with the traditional calibration(based on the same particle size ranges), new calibration models(based on the corrected size ranges of these two methods) improved the estimation of clay and silt contents by LDM. Compared with soil-specific models(i.e., different models were developed for different soils), a universal model may be more parsimonious for estimating particle size fractions if the samples to be assessed represent multiple soil orders.

The inter-visit variability of retinal blood flow velocity measurements using retinal function imager (RFI)

Background:To determine the inter-visit variability of retinal blood flow velocities(BFVs)using a retinal function imager(RFI)in healthy young subjects.Methods:Twenty eyes of 20 healthy young subjects were enrolled.RFI imaging was performed to obtain the BFVs in retinal arterioles and venules in a field measuring 7.3×7.3 mm^(2)(setting:35 degrees)centered on the fovea,and repeated measurements were obtained on two separate days.The inter-visit variability of BFVs was assessed by the concordance correlation coefficient(CCC)and coefficient of variance(CV).Results:At the first visit,the mean BFV was 3.6±0.8 mm/s and 3.0±0.7 mm/s in arterioles and venules,respectively,which were not significantly different from those at the second visit(the BFV of arterioles was 3.5±0.8 mm/s,and the BFV of venules was 3.0±0.7 mm/s,P>0.05,respectively).The CCC was 0.72 in the BFVs of arterioles and 0.67 in venules,and the CV was 10.8%in the BFVs of arterioles and 11.0%in venules.Conclusion:The inter-visit variability using the retinal function imager(RFI)with a large field of view appeared to be good and comparable to previously reported intra-visit and inter-eye variability.