Switching converters with wide DC conversion range

In dc-to-dc conversion applications that require a large range of input and/or output voltages, conventional PWM converter topologies must operate at extremely low duty ratios, which limits the operation to lower switching frequencies because of the minimum ON-time of the transistor switch. This is eliminated in a new class of single-transistor PWM converters featuring voltage conversion ratios with quadratic dependence on duty ratio. Practical circuit examples operating at 0.5 MHz are described

A unified analysis of PWM converters in discontinuous modes

Three discontinuous operating modes of PWM (pulsewidth modulated) converters are considered: the discontinuous inductor current mode (DICM), the discontinuous capacitor voltage mode (DCVM), and a previously unidentified mode called the discontinuous quasi-resonant mode (DQRM). DC and small-signal AC analyses are applicable to all basic PWM converter topologies. Any particular topology is taken into account via its DC conversion ratio in the continuous conduction mode. The small-signal model is of the same order as the state-space averaged model for the continuous mode, and it offers improved predictions of the low-frequency dynamics of PWM converters in the discontinuous modes. It is shown that converters in discontinuous modes exhibit lossless damping similar to the effect of the current-mode programming

A general approach to synthesis and analysis of quasi-resonant converters

A method for systematic synthesis of quasi-resonant (QR) topologies by addition of resonant elements to a parent pulse-width modulation (PWM) converter network is proposed. It is found that there are six QR classes with two resonant elements, including two novel classes. More complex QR converters can be generated by a recursive application of the synthesis method. Topological definitions of all known and novel QR classes follow directly from the synthesis method and topological properties of PWM parents. The synthesis of QR converters is augmented by a study of possible switch realizations and operating modes. In particular, it is demonstrated that a controllable rectifier can be used to accomplish the constant-frequency control in all QR classes. Links between the QR converters and the underlying PWM networks are extended to general DC and small-signal AC models in which the model of the PWM parent is explicitly exposed. Results of steady-state analyses of selected QR classes and operating modes include boundaries of operating regions, DC characteristics, a comparison of switching transitions and switch stresses, and a discussion of relevant design trade-offs

Total Fatigue Life Estimation Of Aircraft Structural Components Using Strain Energy Density Method

This paper is aimed at developing a suitable computation method for estimating the fatigue life of structural elements exposed to the load spectrum. The total fatigue life can be divided into two parts, until the appearance of the initial damage and the other part represents the remaining life, i.e. until the effective fracture. The conventional approach to estimating the total life requires that low-cycle fatigue characteristics of the material be used until the initial damage occurs, and dynamic characteristics of the material for the remaining life. In order to obtain a more efficient method, the Strain Energy Density (SED) method was used in this paper. The essence of this approach is to use the same low - cycle fatigue characteristics of the material to estimate the life expectancy and the remaining life. This work is focused to developing efficient computation method and software for total fatigue life of metal aircraft structural components. To obtain efficient computation method, here the same fatigue low cyclic material properties for crack initiation and crack growth are used together with finite element method (FEM) for stress analyzes. To validate quality computation methods and in-house software for fatigue life estimations computation results are compared with experiments. The results show that the predicted results agree well with the test dat

OD "MEŠTRIJE PUPKOREZNE" J. B. LALANGUEA DO "PORODILJSTVA" PROF. DR. A. LOBMAYERA I PROF. DR. F. DURSTA

A short survey of midwifery and obstetrics development in the northwest part of Croatia is presented in this paper, from J.B. Lalangue’s coming to Varaždin, through the founding and work of Midwifery School and National Maternity in Zagreb to the persons without whom this would not be possible or it would be quite different. Lalangue, being an expert on obstetrics, noticed in a very short period of time, all misfortune caused by incompetent work of then’s midwives, so he published the book “Brevis institutio de re obstetritia illiti kratek navuk od mestrie pupkorezne...”, and started first midwifery courses for peasant women. Focus of this paper is on Prof. Dr Antun Lobmayer textbook analyses, and he was the first professor of midwifery, and the director of the “Royal Midwifery School” and the “National Maternity” in Zagreb. Textbooks for midwives named “Midwifery- Learning Book for Midwives’, had six editions over 50 years and they represent the basis of Croatian midwifery textbook literature. Prof. Dr Franjo Durst, the assistant and successor of Prof. Lobmayer completed and partially revised the last two editions.Besides the biographies of the “Midwifery School” professors, an analyssis and critical review on the mentioned textbooks is given from today’ s medicine point of view.U radu je predstavljen kratak pregled primaljstva i razvoj porodiljstva u sjeverozapadnom dijelu Hrvatske od dolaska J. B. Lalangue-a u Varaždin, preko osnivanja i rada Škole za babice i Zemaljskog rodilišta u Zagrebu, do osoba bez kojih taj razvoj ne bi bio moguć ili bi bio sasvim drugačiji. Lalangue, koji je bio vrstan porodničar, primijetio je vrlo brzo sve nesreće izazvane nestručnim radom tadašnjih babica, pa je napisao i objavio knjigu “ Brevis institutio de re obstetritia illiti Kratek navuk od meštrie pupkorezne...” i započeo prve tečajeve za seoske žene. Težište samog rada je na analizi udžbenika Prof. dr. Anatuna Lobmayera, koji je bio prvi profesor porodiljstva i ravnatelj “Kraljevske babičke škole” i “Zemaljskog rodilišta” u Zagrebu. Udžbenici za babice pod nazivom “Porodiljstvo – Učevna knjiga za primalje” doživjeli su šest izdanja, za preko 50 godina i predstavljaju osnovu za primaljsku udžbeničku literaturu u Hrvatksoj. Prof. dr Franjo Durst, asistent i nasljednik Prof. dr A. Lobamyera dovršio je i dijelom revidirao posljednja dva izdanja ovog udžbenika. Pored biografija profesora “Primaljeske škole” u radu je dana analiza i kritički osvrt na spomenute udžbenike s gledišta današnje medicine

Profesori i direktori te udžbenici Primaljske škole u Zadru

Midwifery in Dalmatia was highly undeveloped at the beginning of the XIX century. The health report from 1813 suggested that there were only 48 midwives in the whole province, and none of them with a degree from the midwifery school. After abolishing the Central Schools („Ecoles Centrales“), which were founded at the time of French reign, and which had the university range, the professors who stayed in Zadar continued their work and teaching in the Midwifery School, which was founded in 1820 according to the decision made by Emperor Franz I, and started working in 1821. Since the school was working continuously for the whole century, a lot of professors and principals passed through. Protomedicus of Dalmatia officially performed the duty of principals of the Midwifery School. Their life and work biographies were gathered in this paper. Although the newcomers were mostly illiterate, very contemporary and valuable textbooks were used at that time. The professors of this school wrote some of these textbooks. This paper analyses those textbooks from the current medical science and praxis point of view, which points out to its significance and contribution of its authors to the reputation that the School enjoyed at that time.Primaljstvo je u Dalmaciji početkom XIX. stoljeća bilo veoma nerazvijeno. Prema zdravstvenom izvješću iz 1813., u cijeloj je pokrajini bilo samo 48 primalja, a nijedna nije imala diplomu škole za primalje. Nakon ukidanja centralnih škola, ustanovljenih u vrijeme francuske vladavine, koje su imale rang sveučilišta, profesori koji su boravili u Zadru nastavili su svoj rad i podučavanje u Školi za primalje osnovanoj 1820. u skladu s odlukom cara Franje I., koja je započela raditi 1821. godine. Budući da je škola radila bez prekida čitavo stoljeće, u njoj je predavalo više profesora, a protomedici Dalmacije po službenoj su dužnosti bili i ravnatelji Primaljske škole. U ovom je radu prikazan njihov život, rad i doprinos medicini Dalmacije. Iako nove učenice uglavnom nisu bile pismene, na raspolaganju su imale kvalitetne udžbenike. Neke od njih su napisali profesori Škole za primalje. Ovdje su analizirani udžbenici s aspekta današnje medicinske znanosti i prakse, što upućuje na njihovo značenje i doprinos njihovih autora ugledu koji je škola uživala u to vrijeme

Some aspects of design ventilation system in road tunnels

In the base, working of ventilation system can be analyzed in regular and incidental modes of operation. This paper concerns the specification of the longitudinal ventilation necessary to prevent upstream movement of combustion products in a tunnel fire. In this work the objective of the study is to analyze the road way tunnel ventilation system using CFD software to create comfort ventilation system in the tunnel. The comfort ventilation concept refers to the situation when air quality within the tunnel is reduced due to presence of polluted air in the tunnel. This paper is focused on ventilation system in a road traffic tunnel in moment of accident situation as fire. In this investigation numerical simulation of fire was carried out and determination of a critical air velocity depending on the power of the fire was conducted. The output results of the software developed for this purpose, which is also used in the realization of practical projects, are shown

Residual life estimation of cracked aircraft structural components

Predmet ovog istraživanja je usmeren na uspostavljanje proračunske procedure za analizu čvrstoće elemenata avionskih konstrukcija sa aspekta zamora i mehanike loma. Za tu svrhu ovde će biti uspostavljena proračunska procedura za procenu preostalog veka elemenata avionskih konstrukcija tipa dela oplate krila i uški pod dejstvom cikličnih opterećenja konstantne amplitude i spektra opterećenja. Poseban aspekt istraživanja se odnosi na primenu gustine energije deformacije (GED) za procenu preostalog veka elemenata konstrukcija sa inicijalnim oštećenjima tipa prskotina. Za određivanje analitičkih izraza za faktore intenziteta napona ovde su korišćeni specijalni singularni konačni elementi. Verifikacija proračunskih procedura za procene preostalog veka je podržana sa sa analitičkim i eksperimentalnim rezultatima uključivši i testove na zamor posebno sa aspekta eksperimentalnog određivanja malociklusnih zamornih karakteristika materijala.The subject of this investigation is focused on developing computation procedure for strength analysis of damaged aircraft structural components with respect to fatigue and fracture mechanics. For that purpose, here will be defined computation procedures for residual life estimation of aircraft structural components such as wing skin and attachment lugs under cyclic loads of constant amplitude and load spectrum. A special aspect of this investigation is based on using of the Strain Energy Density (SED) method in residual life estimation of structural elements with initial cracks. To determine analytic formulae for the stress intensity factors here singular finite elements are used. Verification of computation procedures for residual life estimations will be supported with corresponding experimental tests for determination of low cyclic fatigue properties of materials and corresponding parameters of fracture mechanics, including fatigue tests of representative aircraft structural elements

Gluing together proof environments: Canonical extensions of LF type theories featuring locks

© F. Honsell, L. Liquori, P. Maksimovic, I. Scagnetto This work is licensed under the Creative Commons Attribution License.We present two extensions of the LF Constructive Type Theory featuring monadic locks. A lock is a monadic type construct that captures the effect of an external call to an oracle. Such calls are the basic tool for gluing together diverse Type Theories and proof development environments. The oracle can be invoked either to check that a constraint holds or to provide a suitable witness. The systems are presented in the canonical style developed by the CMU School. The first system, CLLF/p,is the canonical version of the system LLF p, presented earlier by the authors. The second system, CLLF p?, features the possibility of invoking the oracle to obtain a witness satisfying a given constraint. We discuss encodings of Fitch-Prawitz Set theory, call-by-value λ-calculi, and systems of Light Linear Logic. Finally, we show how to use Fitch-Prawitz Set Theory to define a type system that types precisely the strongly normalizing terms

Opremanje palube RoRo tankera po modelu "ključ u ruke"

U članku se najprije ukratko daju osnovne odrednice RoRo tankera. Potom se opisuje projektni zadatak koji se odnosi na opremanje glavne palube i način njegovog rješavanja crtanjem trodimenzionalnog modela. U nastavku se razmatra okruženje u kojem rade brodogradilišta, te se prepoznaje važnost lanaca dobave. Na koncu se analizira pristup dobavljaču po modelu „ključ u ruke“ s naglaskom na primjeni paralelnog inženjerstva u malim poduzećima i mogućnosti smanjenja troškova. Zaključak podržava pristup povezivanja između velikih subjekata-brodogradilišta koja mogu pridobiti važne poslove i manjih/malih subjekata koji odabrani segment proizvodnje mogu izraditi jeftinije, dostatno kvalitetno i na vrijeme