CFD (Computational Fluid Dynamics) computations are carried out in order to investigate the flow distribution and its influence on the heat transfer processes in the high-performance heat exchanger. The subject of this investigation is the classical model of the high-performance heat exchanger with elliptical tubes and rectangular fins. It is possible to find the flow domains where the heat transfer conditions are impaired due to the fully developed turbulent flow. Therefore, the considerable thermal loads occur that may cause the breakdown of the heat exchanger. The emphasis of this investigation is put on the zones and the locations where the tubes are not properly fed with liquid, that result in occurrence of cavitation.
B a c k g r o u n d: Heart failure (HF) is a life-threatening condition which aff ects up to 2% of contemporary populations. Generally, it is a chronic and progressive disease, however in many cases it can be prevented or treated. Nevertheless, effective control of this disease requires awareness of symptoms in the society.
A i m s: The aim of the study was to assess the level of HF knowledge in the Polish population.
M e t h o d s: The questionnaire concerning knowledge about HF prepared by the Competence Network HF under the patronage of the European Heart Failure Association of the ESC, was used. The survey included 534 contributors who formed three groups: medical students — in vast majority at fi rst half of the study course (MS) — 198 (37.1%), HF Awareness Day participants (HFDP) — 134 (25.1%) and other (OP) — 202 (37.8%).
R e s u l t s: Study groups diff ered in terms of gender, age and level of education. As predicted, MS achieved the highest score (22.5 [20.0–24.0]), compared to HFDP (20.0 [17.0–22.0], P <0.001) and OP (19.0 [16.0– 21.0], P <0.001). Knowledge on typical HF symptoms was alarmingly low in the analyzed groups — dyspnea (MS — 96.0%, HFDP — 78.4%, OP — 74.6%), ankle edema (MS — 79.8%, HFDP — 50.6%, OP — 32.2%), body weight gain (MS — 14.1%, HFDP — 17.2%, OP — 4.5%). By multivariate model medical education (β 3.372, 95% CI 2.738–4.005) and own illness or having relatives or friends with HF (β 0.654, 95% CI 0.066–1.242) independently aff ected the score of awareness questionnaire.
C on c l u s i o n s: The basic knowledge on HF in Poland is not sufficient. It is moderately better among MS. Further campaigns improving HF awareness are necessary.
Congestive heart failure (CHF) is the fi nal stage in several heart diseases. The diagnosis of CHF in older patients is a challenge. Preserved left ventricular systolic function is a characteristic type of CHF in seniors. The purpose of the study was to characterize elderly patients with CHF and to highlight specific features of the conditions in seniors. The most common etiology of HF in this group of patients is hypertension and coronary heart disease. In seniors atypical presentations of chronic heart failure is much more common than in younger patients. Malnutrition, limitations of exercise and sedentary lifestyles or comorbid diseases have an influence on asymptomatic, early stage of HF. Th ere are better outcomes of treatment in obese individuals. It is called the obesity paradox. Open communication with a patient and his/her family may improve their response to therapy. When heart failure becomes an incurable disease and aggressive treatment is ineffective, palliative care should be considered in end-of-life heart failure patients. The goal of treatment in the remaining moments of life last moments of life should be maximizing the patient’s comfort.
Numerical analysis of the tensioning cables anchorage zone of a bridge superstructure is presented in this paper. It aims to identify why severe concrete cracking occurs during the tensioning process in the vicinity of anchor heads. In order to simulate the tensioning, among others, a so-called local numerical model of a section of the bridge superstructure was created in the Abaqus Finite Element Method (FEM) environment. The model contains all the important elements of the analyzed section of the concrete bridge superstructure, namely concrete, reinforcement and the anchoring system. FEM analyses are performed with the inclusion of both material and geometric nonlinearities. Concrete Damage Plasticity (CDP) constitutive relation from Abaqus is used to describe nonlinear concrete behaviour, which enables analysis of concrete damage and crack propagation. These numerical FEM results are then compared with actual crack patterns, which have been spotted and inventoried at the bridge construction site.
Despite the consensus on the role of lung and pleura ultrasound in human medicine, veteri- nary medicine questions credibility of the pulmonary evaluation in ultrasound examination, based on the analysis of artifacts in animals with clinical signs of respiratory failure and possibility of pulmonary edema diagnosis with recognition of the degree of its severity. The study was conduct- ed on 47 animals (29 dogs and 18 cats) of different breeds, age and sex. In all of animals prior to the transthoracic lung and pleura ultrasound examination (TLPUS), all animals were subjected to a clinical examination and hematological blood test as well as chest radiography examination in three projections. Ultrasound imaging of the chest in each animal was performed at designated four defined segments. TLPUS in dogs and cats based on an analysis of artifacts allows recogni- tion of pulmonary edema, to the degree comparable to chest X-ray examination. The number of depicted B-lines artifacts is proportional to the degree of pulmonary edema. These results allow to reduce the number of radiographs and allow the shortening of the diagnostic process for pa- tients in life-threatening condition.
Technical system for condition monitoring and failure diagnostics of gear driver with roller bearings was tested in situ. The experimental measurement data of rotors shaft vibration displacements were introduced into physical model of gear teeth meshing dynamics. The modelling and simulation of teeth failures in gear driver with roller bearings was performed by finite element method. The experimental and simulation results were used in identification and elimination of sources of gear teeth damages and bearings failures.
Marine structures are one of the most important industrial and military equipment in each country that should be protected against external forces. The main aim of this paper is a detailed investigation of the underwater explosion (UNDEX) and its effects on marine structures. For this purpose, the UNDEX structure was studied qualitatively and quantitatively using numerical methods. Then, the effects of blast waves on a marine structure reinforced by perpendicular blades were investigated. Finite element and finite volume schemes were used for discretization of the governing equations in the solid and fluid media, respectively. Also, for fluid-structure interaction (FSI), results of fluid and solid media were mapped to each other using the two-way FSI coupling methods. A comparison of numerical results with the empirical formula revealed that the trend of pressure-time curves was reasonable, approving the validity of the numerical method. Moreover, the numerical results indicated that detonation of 1 kg trinitrotoluene (TNT) creates a pressure wave with maximum amplitude of 24 MPa at a distance of 2 m. Also, it was found that the reinforcement blades can be used to improve the resistance of structures against explosive charges, which also results in the reduction of structures deformation.
Effects of charge composition on microstructure, mechanical and fatigue properties of nodular cast irons have been studied. For experiments, five melts of nodular cast iron were used – three types of unalloyed nodular cast irons (with different ratio of steel and pig iron in a charge and different additives for regulation of the chemical composition) and two types of alloyed nodular cast irons (SiMo- and SiCu- nodular cast iron). The microstructure of the specimens was evaluated according to a norm and by automatic image analysis. The mechanical properties were investigated by the tensile test, impact bending test and Brinell hardness test. The fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The best mechanical properties were reached in the nodular cast iron alloyed by Si and Cu, what is related to its microstructure.
To reliably calibrate suitable partial safety factors, useful for the specification of global condition describing structural safety level in considered design case, usually the evaluation of adequate failure probability is necessary. In accidental fire situation, not only probability of the collapse of load-bearing structure, but also another probability related to the people staying in a building at the moment of fire occurence should be assessed. Those values are different one from another in qualitative sense but they are coupled because they are determined by similar factors. The first one is the conditional probability with the condition that fire has already occured, whereas the second is the probability of failure in case of a potential fire, which can take place in the examined building compartment, but its ignition has not yet appeared. An engineering approach to estimate such both probabilities is presented and widely discussed in the article.
The effects of the miniature channel-shaped scratches not detectable by the present inline electromagnetic defect detection system employed for wires’ surface defect detection on the fracture behaviour of the wires for civil engineering applications were investigated numerically. Finite element analysis revealed that both miniature channel-shaped across-the-thickness and across-the-width scratches change the fracture behaviour of the wires in terms of the fracture initiation locations and fracture process sequence. However, miniature across-the-thickness scratches does not affect the fracture shape of the wire while miniature across-the-width scratches changed the wires’ cup and cone fracture to a fracture shape with a predominantly flat fracture. These results provide an understanding of the fracture behaviour of wires with miniature scratches and serve as an alternative or a complimentary tools to experimental or fractographic failure analysis of wires with miniatures scratches which are difficult to carry out in the laboratory due to the sizes of the scratches.
The protection of Polish architectural heritage in the former eastern borderlands, accomplished through the conservation and technical securing of historical structures, constitutes one of the main programmes that are implemented by the Ministry of Culture and National Heritage. Currently, many Polish historical buildings in the former eastern borderlands are in a very bad technical condition. The load-bearing systems of these elements, as well as elements of their finish, require immediate emergency securing work. The basic steps that precede conservation work are emergency structural works, which guarantee the durability and stability of the entire historical substance. The specifics and complexity of the problem of the failure of historical buildings often demands an in-depth analysis of a series of factors that are difficult to measure and which are responsible for the cause and effect relationship during the early stage of the technical evaluation of a structure. The analyses of failures of numerous historical structures, for instance that were carried out by the authors, have become the inspiration for the search for effective methods of analysis that would allow for an in-depth analysis of the causes and effects of the failures in question. The DEMATEL method (Decision Making Trial and Evaluation Laboratory) that has been presented in this work, and its fuzzy extension, has lately become one of the more popular methods used in the cause-and-effect analysis of various phenomena. The authors demonstrated how this method works on the example of the evaluation and securing of the load-bearing system of the XVII Collegiate church of the Holy Trinity in the town of Olykha in the Volhynskiy Oblast, Ukraine.
Mitral regurgitation is the second most common valvular disease. The etiology is either primary or functional-secondary to the left ventricle dysfunction in the course of coronary artery disease, arterial hypertension and diabetes. Along with the population aging and increasing number of comorbidities the number of patients with mitral regurgitation soars. In patients with heart failure the mitral regurgitation significantly decreases the quality of life and worsens the survival prognosis. Surgical correction is the treatment of choice in patients with mitral regurgitation. However, up to 50% of potential candidates are denied surgery for its prohibitive risk. The minimally invasive, percutaneus procedures are potential solution for those subjects. Currently the „edge to edge” technique with use of the MitraClip system is most commonly performed. This procedure is less efficient in MR reduction than open heart surgery. However, the number of periprocedural complications is smaller. It has been shown the MR correction with the MitraClip device improves the duration and quality of life. There are several ongoing preclinical studies on the percutaneusly implanted mitral valve prosthesis. First in men procedures have been performed. However the mitral valve anatomy is much more complex as compared to aortic. Therefore the breakthrough comparable to TAVI procedure will not occur in the very close future.
Shear cracking behaviour of fibrous self-compacting concrete of normal and high strength grade (M30 and M70) is presented here. Two stirrup diameters (6mm Φ and 8 mm Φ) with a constant steel fiber content of 38 kg/m3 (0.5% by volume of concrete) were selected for the present study. The size of the beam was fixed at 100x200x1200mm. The clear span of the beam 1100 mm, was maintained throughout the study. A total of 16 shear-deficient beams were tested under three point loading. Two stirrup spacing (180 mm and 360 mm) are used for the shear span-to-depth ratio (a/d = 2). Investigation indicates that initial cracking load and ultimate load increased as the area of shear reinforcement increased by increasing the diameter of stirrup. It was also noted that the failure mode was modified from brittle shear failure to flexural-shear failure in the presence of fibers. The mechanical behaviour of SFRSCC was improved due to the combined effect of stirrups and steel fibers. The stiffness, toughness, and deflection of the beams increased when compared to SCC beams without fibers. The experimental results were compared with existing models available in literature, and the correlation is satisfactory.
The paper deals with the problem of the determination of the effects of temperature on the efficiency of the nitrification process of industrial wastewater, as well as its toxicity to the test organisms. The study on nitrification efficiency was performed using wastewater from one of Polish chemical factories. The chemical factory produces nitrogen fertilizers and various chemicals. The investigated wastewater was taken from the influent to the industrial mechanical-biological wastewater treatment plant (WWTP). The WWTP guaranteed high removal efficiency of organic compounds defined as chemical oxygen demand (COD) but periodical failure of nitrification performance was noted in last years of the WWTP operation. The research aim was to establish the cause of recurring failures of nitrification process in the above mentioned WWTP. The tested wastewater was not acutely toxic to activated sludge microorganisms. However, the wastewater was genotoxic to activated sludge microorganisms and the genotoxicity was greater in winter than in spring time. Analysis of almost 3 years’ period of the WWTP operation data and laboratory batch tests showed that activated sludge from the WWTP under study is very sensitive to temperature changes and the nitrification efficiency collapses rapidly under 16°C. Additionally, it was calculated that in order to provide the stable nitrification, in winter period the sludge age (SRT) in the WWTP should be higher than 35 days.
This article investigates and evaluates a handover exchange scheme between two secondary users (SUs) moving in different directions across the handover region of neighboring cell in a cognitive radio network. More specifically, this investigation compares the performance of SUs in a cellular cognitive radio network with and without channel exchange scheme. The investigation shows reduced handover failure, blocking, forced and access probabilities respectively, for handover exchange scheme with buffer as compared to exchange scheme without buffer. It also shows transaction within two cognitive nodes within a network region. The system setup is evaluated through system simulation.
The FMEA (Failure Mode and Effects Analysis) method consists in analysis of failure modes and evaluation of their effects based on
determination of cause-effect relationships for formation of possible product or process defects. Identified irregularities which occur
during the production process of piston castings for internal combustion engines were ordered according to their failure rates, and using
Pareto-Lorenz analysis, their per cent and cumulated shares were determined. The assessments of risk of defects occurrence and their
causes were carried out in ten-point scale of integers, while taking three following criteria into account: significance of effects of the defect
occurrence (LPZ), defect occurrence probability (LPW) and detectability of the defect found (LPO). A product of these quantities
constituted the risk score index connected with a failure occurrence (a so-called “priority number,” LPR). Based on the observations of the
piston casting process and on the knowledge of production supervisors, a set of corrective actions was developed and the FMEA was
carried out again. It was shown that the proposed improvements reduce the risk of occurrence of process failures significantly, translating
into a decrease in defects and irregularities during the production of piston castings for internal combustion engines.
The paper presents the calculations for the failure conditions of the ORC (organic Rankine cycle) cycle in the electrical power system. It analyses the possible reasons of breakdown, such as the electrical power loss or the automatic safety valve failure. The micro-CHP (combined heat and power) system should have maintenance-free configuration, which means that the user does not have to be acquainted with all the details of the ORC system operation. However, the system should always be equipped with the safety control systems allowing for the immediate turn off of the ORC cycle in case of any failure. In case of emergency, the control system should take over the safety tasks and protect the micro-CHP system from damaging. Although, the control systems are able to respond quickly to the CHP system equipped with the inertial systems, the negative effects of failure are unavoidable and always remain for some time. Moreover, the paper presents the results of calculations determining the inertia for the micro-CHP system of the circulating ORC pump, heat removal pump (cooling condenser) and the heat supply pump in failure conditions.