IS THE TWO-STROKE ENGINE HISTORY OR THE FUTURE OF MOTORING?

The paper presents a condensed history of the development of the two-stroke engine. The various stages of implementation of the most significant design solutions are described chronologically to achieve the best technical and economic performance for this type of power unit. The review of selected design solutions is supplemented with illustrations and concise comments. Examples of practical engineering solutions, thanks to which previous techno-economic problems were optimized, such as insufficient lubrication efficiency of individual parts and components, significant lubricating oil consumption, ...) are presented. The work was concluded with an analytical summary and conclusions indicating the need to undertake more intensified research into developing the two-stroke engine (in particular, the possibility of using ecological propellants). Consideration of the presented research directions (suggestions) can help, among other things, to optimize power processes, i.e., to minimize the negative environmental impact of a two-stroke internal combustion engine

WOODEN SLIDING BEARINGS

Wood, acting as a construction material, has been utilized by humans since the beginning of times. The early human-made machines were made entirely from wood. With time, technical progress gradually displaced wood from machine design and construction. However, despite the passage of time, due to the low cost and availability of wood, the elements in the quickly worn out machine parts still were made from wood. Sliding bearing shells or replaceable gear teeth need to be replaced here. These elements can still be found in pre-war mills. This article contains examples overview of wood application in such areas as bearings, and discusses their advantages and disadvantages. It also indicates the desirability of undertaking further research on the use of wood in tribological pairs

A Latent Class Analysis of the Relationship Between Identity Development and Protestant Fundamentalism

Latent Class Analysis was used to explore different subgroups of individuals based on identity processes (using the DIDS) and protestant fundamentalism. Results indicate that a 6-group solution provided the best fit for our data. The six groups differed in terms of identity process variables (especially exploration in breath, exploration in depth, and identification with commitment), but only modestly in terms of fundamentalism

Numerical Modelling of Heat Dissipation for the Pin-On-Disc Type Tribometer

This article presents numerical tests of heat distribution for the Pin-On-Disc type frictional contact. The tests were conducted for the friction pair brass CuZn39Pb2 (pin) - cast iron GJL250 (disc). The heat distribution was tested both experimentally and numerically. Experimental tests were carried out on a conventional CA 6140 lathe properly adapted for these tests. The simulations used the method of elementary balances (MEB) based on an explicit calculation algorithm. The studies were carried out with a normal force of 5N and three cutting speeds of 0.24, 0.35, and 0.48 m/s respectively. The measurements were made after the process had lasted 0, 5, 10, 15, 20, 25, and 30 minutes. As a result of the research, the average and maximum temperature of the measurement point located directly behind the pin-disc contact field was determined. On the basis of the conducted analyses, the imperfection of the applied calculation method was indicated as the probable cause of discrepancies in experimental and simulation results and the acceptance for calculations of constant and time-varying thermo-physical properties of friction pair materials. In addition, the studies proved that a change in the calculation time step has little effect on the average and maximum temperature of the measurement point

Clustering with minimum spanning trees: How good can it be?

Minimum spanning trees (MSTs) provide a convenient representation of datasets in numerous pattern recognition activities. Moreover, they are relatively fast to compute. In this paper, we quantify the extent to which they can be meaningful in data clustering tasks. By identifying the upper bounds for the agreement between the best (oracle) algorithm and the expert labels from a large battery of benchmark data, we discover that MST methods can overall be very competitive. Next, instead of proposing yet another algorithm that performs well on a limited set of examples, we review, study, extend, and generalise existing, the state-of-the-art MST-based partitioning schemes, which leads to a few new and interesting approaches. It turns out that the Genie method and the information-theoretic approaches often outperform the non-MST algorithms such as k-means, Gaussian mixtures, spectral clustering, BIRCH, and classical hierarchical agglomerative procedures

Personality, Identity, and American Protestant Fundamentalism: What are the Connections?

This study examined the associations between personality, identity, and protestant fundamentalism (subscales included inerrancy, evangelism, premillennialism, and separatism). 440 college students between the ages of 18 and 29 participated in the study, and self-identified as protestant. A step-wise regression revealed the following findings. Neuroticism was negatively associated with inerrancy, evangelism, and separatism; extroversion was negatively related to separatism; and agreeableness was positively related to inerrancy, evangelisms, and premillennialism. Exploration in depth was positively associated with evangelism, premillennialism, and separatism; identification with commitment was positively related with separatism; and rumination was positively associated with premillennialism, and separatism

Nontuberculous mycobacterial lung disease in a patient with COPD and bronchiectasis, with radiological signs of lung tumor

Mycobacterial lung disease is caused by nontuberculous mycobacteria (NTM), also known as atypical mycobacteria. NTM arewidely distributed in the environment, particularly in soil and water; they may colonize the airways, gastrointestinal tract andgenitourinary system, without the apparent signs of disease. Nevertheless, in some risk groups such as patients with chronic lungdiseases or with immunodeficiency, mycobacterial lung disease is identified. Recently, increased recognition of mycobacteriallung disease in chronic obstructive pulmonary disease (COPD) patients has been observed, especially in those treated with highdoses of inhaled corticosteroids.In the present paper, we describe the patient treated for many years due to COPD and bronchiectasis, with clinical and radiologicalpicture suggestive of lung tumor, in whom final diagnosis of mycobacterial lung disease caused by Mycobacterium avium wasmade

Formation of residual stresses during discontinuous friction treatment

The tool with grooves on its working surface is used to improve the properties of the strengthened layer. This allows us to reduce the structure's grain size and increase the thickness of the layer and its hardness. Mineral oil and mineral oil with active additives containing polymers are used as a technological medium during friction treatment. It is shown that the technological medium used during the friction treatment affects the nature of the residual stresses’ distribution. Thus, when using mineral oil with active additives containing polymers, residual compressive stresses are more significant in magnitude and depth than when treating mineral oil. The nature of the residual stresses diagram depends on the treated surface’ shape. After friction treatment of cylindrical surfaces, the highest compressive stresses near the treated surface decreases with depth. And after friction treatment of flat surfaces near the treated surface, the compressive stresses are small. They increase with depth, pass through the maximum, and then decrease to the original values. The technological medium used during friction treatment affects residual stresses in the grains and in the crystal lattice

Cats with diabetes mellitus have diastolic dysfunction in the absence of structural heart disease

Diabetes mellitus (DM) can result in cardiovascular dysfunction and heart failure characterized by diastolic dysfunction with or without the presence of systolic dysfunction in people and laboratory animals. The objective of this prospective study was to determine if cats with newly diagnosed DM had myocardial dysfunction and, if present, whether it would progress if appropriate antidiabetic therapy was commenced. Thirty-two diabetic cats were enrolled and received baseline echocardiographic examination; of these, 15 cats were re-examined after 6 months. Ten healthy age- and weight-matched cats served as controls. Diabetic cats at diagnosis showed decreased diastolic, but not systolic function, when compared to healthy controls, with lower mitral inflow E wave (E) and E/E' than controls. After 6 months, E and E/IVRT' decreased further in diabetic cats compared to the baseline evaluation. After excluding cats whose DM was in remission at 6 months, insulin-dependent diabetic cats had lower E, E/A and E' than controls. When classifying diastolic function according to E/A and E'/A', there was shift towards impaired relaxation patterns at 6 months. All insulin-dependent diabetic cats at 6 months had abnormal diastolic function. These results indicate that DM has similar effects on diastolic function in feline and human diabetics. The dysfunction seemed to progress rather than to normalize after 6 months, despite antidiabetic therapy. In cats with pre-existing heart disease, the development of DM could represent an important additional health risk

Hypersensitivity pneumonitis recognised in a single pulmonary unit, between 2005 and 2015 — comparison with recently proposed diagnostic criteria

Introduction: Hypersensitivity pneumonitis (HP) is the third most common interstitial lung disease after idiopathic pulmonaryfibrosis and nonspecific interstitial pneumonia. Pathogenesis of HP is related to repeated exposure to inhaled environmentalantigens that sensitise the susceptible, genetically predisposed persons.The aim of the present retrospective study was to summarise the diagnostic methods used in consecutive patients with HP,recognised in a single pulmonary unit, between 2005 and 2015, and to compare them with current diagnostic criteria. Material and methods: 135 patients, 68 males, 67 females, median age 53 years (18–75 years), entered the study. Chest CTfeatures characteristic of HP were defined as: mosaic attenuation of lung parenchyma, air trapping and/or ill-defined centrilobularnodules. Lymphocytosis in BAL was defined as ≥ 30%. Results: Median time from first symptoms to diagnosis was 12 months. The exposure to one or more allergens was found in 94% ofpatients, chest CT features characteristic of HP have been reported in 87%, BAL lymphocytosis — in 86%.According to recent diagnostic criteria — in 54% of patients, clinical diagnosis of HP was confident, in 16% — probable, in 26% — possibleand in 4% — unlikely. The confirmation of HP with lung biopsy has been obtained in 36% of non-confident cases (16% of the study group). Conclusion: HP diagnosis was confirmed according to current diagnostic criteria in 70% of patients diagnosed between 2005 and2015. Contradictions to lung biopsy have been the main reason for inability to confirm HP in non-confident cases