Determination of the mass diffusion coefficient of wood by thin-layer drying kinetics

ArticleThe aim of this paper is to present the method of using thin layer drying under controlled conditions, to obtain variable moisture diffusion coefficient expression of wood drying. The obtained relationship parameters can then be used for a larger sample drying process simulation. This paper includes the theoretical study of changes of moisture content determination in wood in response to high temperature of the drying air (105 °C). A 1-D diffusion model with a variable concentration-dependent diffusion coefficient is considered. This problem is solved, using the differential scheme. Paper described theory and experimental results of wood drying by the high temperature at 105 °C. For studies have selected five types of wood: oak (Quercus robur), beech (Fagus silvatica), spruce (Picea abies), scots pine (Pinus silvestris), and larch (Larix decidua). Experimental measurements and modelling results are given

Shrinkage effect on diffusion coefficient during carrot drying

ArticlesMany studies have been previously carried out on the carrot drying and the undergoing processes. The developed mathematical models provide an opportunity to gain an understanding of this complex process and its dynamics. But they are sim plified and based on a number of assumptions, including calculation of diffusion coefficient values. In one of the previous studies, the authors of this study determined that the diffusion coefficient is linearly dependent on the moisture concentration wit h the assumption that the sample's geometric shape does not change. The aim of this study is to determine the dependence of the diffusion coefficient on the moisture concentration taking into account the change in sample thickness during the drying experim ent. The experiments were carried out with carrot slices of three different thicknesses: 5 mm, 10 mm and 15 mm thickness on the film infrared dryer at temperature 40 °C . During the experiments, measurements of the weight and thickness of the slices were pe rformed. Using the experimental data the average thickness and diffusion coefficient of slices was calculated depending on the moisture concentration . Obtained results show that thickness depends linearly on the moisture concentration. Using experimental d ata and obtained average values of samples thickness, the values of diffusion coefficient was calculated. The results indicate that diffusion coefficient value depend linearly on moisture concentration. Their values are close and tend to zero when the conc entration decreases if the thickness changes are taken into account during the experiment

Red clover drying coefficient dependences on air velocity at constant drying temperature

ArticleThe clover is widely used as feed of animals and preservation of fodder is an important problem. This paper informs about the experimental and theoretical investigations of red clover ( Trifolium pratense ) drying by force d convection. This research is focused on verification of influence of different air velocities on the drying process of red clover in thin layer in mild temperatures (22 °C ) and rather high relative humidity of air (70 % ). The initial moisture content of clover was determined by gravimetric method using the hot air drying in the electric oven. Special device for convection drying with air flow passing through material from the bottom through supporting trays with a sieve (dimensions of mesh 3 x 4 mm) by co nstant temperature was used for drying when the air velocity 0.7 m s - 1 , 1.0 m s - 1 , 1.2 m s - 1 and 2.0 m s - 1 . These results was compared with drying by free convection. Changes of clover samples were determined from the measured values of weight using the gr avimetric method. The function of drying coefficient K(t) is determined (using thin layer theory) and theoretical results are compared with experimental results. Using experimental results were determined relationships between air velocity and parameters i ncluded in function of drying coefficient. This allows theoretically to predict the drying process depending on the air velocity

Farm manure amount calculation using statistical data in Latvia

ArticleTo calculate ammonia emissions caused by production, storage and application of farm manure, it is necessary to know the amount of farm manure obtained in the country and also the kinds of manure. For this purpose, methodology and computer software are dev eloped to calculate the amount of farm manure based on the data of the Central Statistical Bureau, the technology of farm animal handling in the country and the respective valid normative documents. Upon calculating the amount of farm manure produced in La tvia in 2016, it was stated that approximately a half of the manure is litter manure, one third – liquid manure, and one fifth – manure left in the pastures. The most of manure in Latvia (69% of the total amount) is obtained from milk cows, their calves an d young stock

Effect of slurry lagoon redesign on reduction of ammonia emission during livestock manure storage

ArticleIn accordance with the international and EU aims to reduce emissions of ammonia and other air pollution substances farm manure management, including its storage, especially for the animal breeding sector, is one of the most essential stages. One of the preventing steps is covering of the slurry lagoons. The most effective – hard covering can be provided only after the lagoon is constructed. The aim of the research: to develop methodology for calculations of emission reducing lagoon design volume and surface area. In the result of the theoretical research the possibilities of reducing the reflection surfaces at the same capacity of the lagoon have been discovered, as well as the changes of the reflection surface area, if instead of one lagoon several lagoons with less volume are installed and sequential filling of these lagoons is ensured. The article presents the calculation algorithms obtained during the research and recommendations for construction of low emission lagoons

Approximate approach of research and assessment of crack resistance of cylindrical housings

In this work, we propose a procedure that allows us to quickly, without involving finite-element packages at the execution stage, evaluate the state of postulated cracks in cylindrical structural elements with internal anticorrosion cladding under pressure and unsteady temperature loading. The procedure contains three components. The first component of the procedure is based on the analytical solution of the unsteady thermal conductivity problem. The second component of the procedure is also analytical relations specifying circumferential and longitudinal stresses in a two-layer cylinder as a function of internal pressure and temperature distribution along the depth of the wall. In the third stage of the procedure, the coefficients of stress intensity along the crack front are determined by the method of influence functions using the known distribution of stresses. To implement this part of the procedure, the influence functions must first be calculated by the finite element method. In this work the example of calculating the functions of influence for longitudinal semi-elliptical cracks of 1/8 wall thickness depth and with the ratio of the principal half-diameters 0.3 and 0.7 is presented. As an example of the implementation of the procedure, comparative calculations were carried out and the elastic-plastic calculation of a cylindrical shell containing longitudinal cracks was given. Stress intensity coefficients along the part of the front located in the base metal were calculated. The results of analytical calculations were conservative until plastic deformations developed in the cladding. At significant plastic strains, the values of the stress intensity coefficients calculated by the proposed procedure, on the contrary, are significantly inferior. This demonstrates once again the fact that calculations in the framework of linear fracture mechanics are not always conservative in relation to calculations in the elastic-plastic formulation. The paper gives an explanation of the reason for the obtained effect

Theoretical research into directional stability of trailed tandem- type disk harrow

Received: August 27th, 2021 ; Accepted: October 6th, 2021 ; Published: October 7th, 2021 ; Correspondence: [email protected] is one of the methods of soil cultivation, provides its effective crumbling, loosening, partial mixing and soil inversion. This ensures that crop residues on the soil surface are shredded and intermixing with loosened soil particles. Since, in addition to crop stubble, weeds are also counted as crop residues, soil disking, along with the use of herbicides, is often regarded as the most effective method of controlling the weediness of the agricultural background. Despite the fact that numerous studies on the disk harrow working process are available, insufficient attention has been paid to the study of the stability of harrow machine-tractor units, especially trailed ones. The purpose of this study is to establish the theoretical patterns that would provide for selecting the trailed disk harrow parameters that ensure the desired directional stability of the implement, which, in its turn, helps to achieve the desired qualitative performance of the disk harrowing machine-tractor unit. The principles of the theory agricultural machine, analytical mechanics, higher mathematics, as well as methods of PC-assisted numerical calculations have been used. According to the results of the study, it has been established that sufficient directional stability of the trailed disk harrow can be ensured if its working width B, the distance from the hitch point to the centre of resistance (parameter d) and the operating speed are properly selected. Determining the above-mentioned parameters of the disk harrow with the use of the obtained new analytical relations ensures achieving just their optimal combination, which provides for the maximum field productivity of the harrow machine-tractor unit with the satisfactory stability of disk harrow movement in the horizontal plane

Clinical characteristics, etiology, and initial management strategy of newly diagnosed periprosthetic joint infection: A multicenter, prospective observational cohort study of 783 patients

Background Periprosthetic joint infection (PJI) is a devastating complication of joint replacement surgery. Most observational studies of PJI are retrospective or single-center, and reported management approaches and outcomes vary widely. We hypothesized that there would be substantial heterogeneity in PJI management and that most PJIs would present as late acute infections occurring as a consequence of bloodstream infections. Methods The Prosthetic joint Infection in Australia and New Zealand, Observational (PIANO) study is a prospective study at 27 hospitals. From July 2014 through December 2017, we enrolled all adults with a newly diagnosed PJI of a large joint. We collected data on demographics, microbiology, and surgical and antibiotic management over the first 3 months postpresentation. Results We enrolled 783 patients (427 knee, 323 hip, 25 shoulder, 6 elbow, and 2 ankle). The mode of presentation was late acute (>30 days postimplantation and 30 days postimplantation with ≥30 days of symptoms; 148, 19%). Debridement, antibiotics, irrigation, and implant retention constituted the commonest initial management approach (565, 72%), but debridement was moderate or less in 142 (25%) and the polyethylene liner was not exchanged in 104 (23%). Conclusions In contrast to most studies, late acute infection was the most common mode of presentation, likely reflecting hematogenous seeding. Management was heterogeneous, reflecting the poor evidence base and the need for randomized controlled trials

One hundred and twelve infected arthroplasties treated with ‘DAIR’ (debridement, antibiotics and implant retention): antibiotic duration and outcome

OBJECTIVES: We describe treatment failure rates by antibiotic duration for prosthetic joint infection (PJI) managed with debridement, antibiotics and implant retention (DAIR). METHODS: We retrospectively collected data from all the cases of PJI that were managed with DAIR over a 5 year period. Surgical debridement, microbiological sampling, early intravenous antibiotics and prolonged oral follow-on antibiotics were used. RESULTS: One hundred and twelve cases of PJI were identified. Twenty infections (18%) recurred during a mean follow-up of 2.3 years. The mean duration of antibiotic use was 1.5 years. Failure was more common after arthroscopic debridement, for previously revised joints and for Staphylococcus aureus infection. There were 12 failures after stopping antibiotics and 8 while on antibiotics [hazard ratio (HR) = 4.3, 95% confidence interval (CI) 1.4-12.8, P = 0.01]. However, during the first 3 months of follow-up, there were eight failures after stopping antibiotics and two while on antibiotics (HR = 7.0, 95% CI 1.5-33, P = 0.015). The duration of antibiotic therapy prior to stopping did not predict outcome. CONCLUSIONS: PJI may be managed by DAIR. The risk of failure with this strategy rises after stopping oral antibiotics, but lengthening antibiotic therapy may simply postpone, rather than prevent, failure