Qualitative analysis of AWJ factors affecting the surface roughness

The paper deals with experimental research and evaluation of abrasive waterjet cutting technology process by evaluation of technological factors, which infl uence the microgeometry (average roughness) of 10 mm thick stainless steel tooled workpiece surface through design of experiments. Signifi cance of six chosen process factors – independent variables (traverse rate, abrasive mass fl ow rate, pressure, J/T abbreviation and feeding direction that infl uence the surface quality has been evaluated by factors experiment type 26. The surface quality has been evaluated by static quality characteristic average roughness Ra. The multiple nonlinear regression equation obtained from ANOVA gives the level quality Ra as a function of the treatment factors. Different factor signifi cance has been found, which generated surface profi le under defined conditions by abrasive waterjet. The regression equations obtained from ANOVA and multiple linear regressions give the level quality Ra as a function of the treatment factors

Kinematic analysis of quick-return mechanism in three various approaches

Članak se bavi kinematičkom analizom Whitwordovog mehanizma koja je izvedena u tri različite metode. Suvremene metode su računalno potpomognute s posebnim softverom za analizu obrade, koji može simulirati ne samo gibanje mehanizma, već može odrediti i položaj, brzinu, ubrzanje, sile, momente te druge parametre u svakom trenutku vremena, ali je potrebna provjera i razumijevanje zakona mehanike. Cilj je kinematičke analize istražiti gibanje pojedinih komponenti mehanizma (ili njegovih važnih točaka) u ovisnosti o gibanju pobuđivača. Ovdje su opisani osnovni principi triju pristupa te prednosti i nedostaci prezentiranih rješenja. Dobiveni se rezultati mogu usporediti, ako su rabljeni isti ulazni parametri.The article deals with kinematic analysis of quick-return mechanism that is executed by three various methods. The modern methods are computer aided with the special software for analysis processing, which can simulate not only the motion of the mechanism, but can define the position, velocity, acceleration, forces, moments and other parameters at every moment of time, but verification and mechanics laws understanding are necessary. The goal of the kinematic analysis is to investigate the motion of individual components of mechanism (or its important points) in dependence on the motion of drivers. The article describes the basic principles of three approaches, as well as the advantages and disadvantages of presented solutions. The obtained results can be compared, if the same input parameters are used

Racionalizacija toka materijala u proizvodnji polu-okvira za automobilsku industriju

The core idea of the paper is a value stream mapping with identification of waste sources, and drawbacks which help to uncover hidden reserves of production. The analysis covers the current state of individual processes within the production line. After determination of the present drawbacks the plan of rationalization was created in which the combination of elements of lean production was used. The proposed solutions could be used when establishing the principles of lean production at particular sections of the assembly line within the whole plant. In case that proposed solution cannot be put into practice it can be used as a blueprint for other types of improvement respectively decreasing of waste and drawbacks.Osnovna ideja rada je prikaz toka vrijednosti uz identifikaciju izvora troškova i nedostataka, koji će pomoći da se razotkriju skrivene pričuve u proizvodnji. Analiza obuhvaća postojeće stanje u pojedinačnim postupcima na proizvodnoj traci. Nakon prepoznavanja postojećih nedostataka napravljen je plan racionalizacije u kojemu je rabljena kombinacija elemenata lean proizvodnje. Predložena bi se rješenja mogla primijeniti kad se primijene principi lean proizvodnje na pojedinim dijelovima montažne trake u cijelom pogonu. U slučaju da se predloženo rješenje ne može primijeniti u praksi može se koristiti kao model za druge vrste poboljšanja kao što su smanjenje otpada i nedostataka.Web of Science2341220121

Automatizovaný systém pro návrh technologických parametrů hydro-abrazivního dělení materiálu

The abrasive waterjet technology is used today mainly for cutting metal materials. However, it is possible to use this technology also for cutting non-metal materials like marble or other materials whose surface must comply with specific parameters. Cutting non-metal materials using the abrasive waterjet technology is quite rare at present and we can find it mainly in laboratories. The main reason can be complicated settings of technological parameters. Technicians working with these mechanisms can predict these parameters based on their previous experience. Without such experience or when using new materials they have to make a lot of experiments to find the right technological parameters. The main task of this paper is to show how to use modern small computers to apply the automated system for the prediction of necessary parameters for the abrasive water jet cutting system which is developed at our university. This automated system can be helpful especially for the technicians who works with the abrasive waterjet technology or it may be part of robotized workplaces in future.V dnešní době je technologie hydro-abrazivního paprsku (AWJ) užívána zejména pro dělení kovových materiálů. Avšak tuto technologii je možné také využít pro dělení nekovových materiálů např. mramor nebo jiných materiálů, u kterých je důležité získat povrch s určitými parametry. Využití této technologie pro dělení nekovových materiálů je v dnešní době zatím ojedinělé, protože nastavení technologických parametrů je velice komplikované. Technici, kteří pracují s tímto zařízením, obvykle nastavují technologické parametry podle předchozích zkušeností. Pokud však nemají předchozí zkušenosti nebo pracují s novým materiálem, musí provést mnoho testů, tak aby byli schopni nalézt odpovídající technologické parametry. Článek je zaměřen na seznámení s automatizovaným systémem pro návrh technologických parametrů technologie AWJ a využití malých počítačových systémů. Tento automatizovaný systém je použitelný zejména pro techniky pracující s technologii AWJ a nebo v budoucnu může být součástí robotizovaných pracovišť v dolech

The effect of brumation on memory retention

Long-term torpor is an adaptive strategy that allows animals to survive harsh winter conditions. However, the impact that prolonged torpor has on cognitive function is poorly understood. Hibernation causes reduced synaptic activity and experiments with mammals reveal that this can have adverse effects on memories formed prior to hibernation. The impact of brumation, the winter dormancy that is observed in ectotherms, on memory remains unknown. The aim of this study was to examine whether an amphibian, the fire salamander (Salamandra salamandra), was able to retain learned spatial information after a period of brumation. Twelve fire salamanders were trained to make a simple spatial discrimination using a T-maze. All subjects learned the initial task. Upon reaching criterion, half of the subjects were placed into brumation for 100 days while the other half served as controls and were maintained under normal conditions. A post-brumation memory retention test revealed that animals from both conditions retained the learned response. Control tests showed that they solved the task using learned information and not olfactory cues. This finding contrasts with much of the mammalian research and suggests that the processes involved in prolonged torpor may have a fundamentally different impact on memory in mammals and amphibians

Klasifikacija tehničkih materijala prema klasama obradivosti kod hidroabrazivnog rezanja

This paper presents the major cutting knowledge, the opinion data and the results of actual theoretic parameters solutions and the current results, estimated by contemporary needs of hydro abrasive cutting technology. Here is a newly opened and discussed question of current data terminology disunity in the area of metrology topography surfaces of cutting walls created by abrasive waterjet.U radu su prezentirana temeljna znanja, razmišljanja i rezultati teorijskih rješenja vezano uz trenutne procijenjene suvremene potrebe za hidroabrazivnom tehnologijom rezanja. Ovdje je i ponovo otvoreno pitanje trenutne terminologije u području mjeriteljstva topografi je površina dobivenih rezanjem abrazivnim vodenim mlazom

Utjecaj poprečne brzine na nepravilnosti površine dobivene abrazivnim rezanjem vodenim mlazom

The paper deals with the calculation of the optimal traverse speed for diff erent types of materials, which is very important for predication, imaginings and dimensioning of technological factors and selection of the materials with the aim to increase of surface quality at abrasive waterjet cutting (AWJ) technology. The surface irregularities of the experimental used materials AISI 304, AISI 309 have been measured by non-contact shadow method. New empirically compiled equations of the infl uence of the traverse speed on tensometrical state of cut, deformation resistance of material and surface roughness Ra are at AWJ cutting available.Rad se bavi proračunom optimalne brzine rezanja za različite vrste materijala, što je vrlo važno za predikaciju, osmišljanje i dimenzioniranje tehnoloških čimbenika i izbor materijala s ciljem da se poveća kvaliteta površine reza tehnologijom abrazivnim vodenim mlazom (AWJ). Površinske nepravilnosti eksperimentalno korištenih materijala AISI 304, AISI 309 su mjerene bezkontaktnom metodom sjene. Dobivena je nova empirijska jednadžbe utjecaja brzine na tenzometrijsko stanje rezne površine, deformacijsku otpornost materijala i površinsku hrapavost Ra kod AWJ rezanja

Antibiotic treatment following a dog bite in an immunocompromized patient in order to prevent Capnocytophaga canimorsus infection: a case report

BACKGROUND: Capnocytophaga canimorsus is a commensal bacterium found in the saliva of dogs and cats. Clinically significant infections in humans after a bite are often associated with the presence of immune deficiency. Early recognition and appropriate treatment are crucial for patient survival. In addition, patients with immune deficiency are susceptible to serious life-threatening nosocomial infections, which may also influence the prognosis of patients with Capnocytophaga canimorsus infection. CASE PRESENTATION: A 62-year-old Caucasian female was admitted with septic shock, acute respiratory distress syndrome, acute renal failure, metabolic acidosis and disseminated intravascular coagulation after suffering two small bites from her dog. She had received a splenectomy during childhood. The patient survived after early empiric treatment with antibiotics and intensive supportive care, including ventilation support, a high dose of noradrenalin, and continuous venovenous hemodialysis applied prior to the definitive diagnosis of Capnocytophaga canimorsus sepsis. She improved within 2 weeks but, despite all efforts to prevent nosocomial infection, her hospital course was complicated by Enterococcus species and Candida albicans pleuropneumonia that prolonged her stay in the intensive care unit, and necessitated ventilation support for 2 months. CONCLUSION: Severe Capnocytophaga canimorsus sepsis may be complicated by life-threatening nosocomial infection in immunocompromized patients. The prophylactic application of antibiotics after a dog bite should be considered in high-risk individuals with immune deficiency in order to prevent both Capnocytophyga canimorsus sepsis and serious nosocomial complications

Water jet technology used in medicine

Tehnologija abrazivnog vodenog mlaza od nedavno se koristi uglavnom u industrijskim područjima. Ova tehnologija pruža nekoliko prednosti u usporedbi s konvencionalnim metodama. Trenutačno, to je uporaba u medicini. U radu se razmatra mogućnost korištenja tehnologije mlaza vode u medicini. U radu su opisane prednosti i uporaba u ortopedskoj kirurgiji, plastičnoj kirurgiji, neurokirurgiji, dermatologiji, urologiji te u oralnoj kirurgiji.Abrasive water jet technology has been recently used mainly in industrial areas. This technology provides several advantages in comparison with conventional methods. At present, it is used in medicine. This paper discusses the possibility of using water jet technology in medicine. The paper describes the benefits and usage in orthopedic surgery, plastic surgery, neurosurgery, dermatology, urology, and in dental surgery

Analiza topografije površina titanove legure nakon rezanja vodenim mlazom pomoću spektralne analize

Experimental study of a titan grade 2 surface topography prepared by abrasive waterjet cutting is performed using methods of the spectral analysis. Topographic data are acquired by means of the optical profilometr MicroProf®FRT. Estimation of the areal power spectral density of the studied surface is carried out using the periodogram method combined with the Welch´s method. Attention is paid to a structure of the areal power spectral density, which is characterized by means of the angular power spectral density. This structure of the areal spectral density is linked to the fi ne texture of the surface studied.Eksperimentalna studija površine titana klase 2 dobivene abrazivnim rezanjem vodenim mlazom je provedena korištenjem metode spektralne analize. Topografski su podaci prikupljeni pomoću optičkog profi lometra MicroProf®FRT. Procjena površinske snage spektralne gustoće je provedena periodogram metodom u kombinaciji sa Welch metodom. Pozornost je posvećena površinskoj snazi spektralne gustoće koja je karakterizirana pomoću kutnih spektara gustoće snage. Struktura površinskog spektra gustoće je povezana sa istraživanom fi nom teksturom površine