Torsional fracture of fatigue pre-cracked ceramic rods

This paper describes the results of an experimental investigation of the room temperature fracture toughness of polycrystalline aluminium oxide (average grain size 3 m) in pure torsion (Mode III). Circumferentially notched cylindrical rods were stressed in uniaxial cyclic compression to introduce à fatigue pre-crack, following a technique proposed earlier; subsequently, the rods were fractured in quasi-static torsion. The critical stress intensity factor for fracture initiation in Mode III is about 2.3 times higher than that measured for Mode I. The mechanisms of quasi-static torsional fracture are contrasted with those observed in the tensile failure of ceramics. The Mode III failure mechanisms in ceramics are also compared with the relatively more familiar cases of torsional fracture in metallic materials. The effects of crack face rubbing and interference between fracture surface asperities on torsional fracture behaviour are highlighted.On leave from Institute of Applied and Technical Physics, Technical University of Vienna, Karlsplatz 13, A-1040, Vienna, Austria.     

Triple contagion: a two-fears epidemic model

We present a differential equations model in which contagious disease transmission is affected by contagious fear of the disease and contagious fear of the control, in this case vaccine. The three contagions are coupled. The two fears evolve and interact in ways that shape distancing behaviour, vaccine uptake, and their relaxation. These behavioural dynamics in turn can amplify or suppress disease transmission, which feeds back to affect behaviour. The model reveals several coupled contagion mechanisms for multiple epidemic waves. Methodologically, the paper advances infectious disease modelling by including human behavioural adaptation, drawing on the neuroscience of fear learning, extinction and transmission.     

Modelling the effects of the Austrian inpatient reimbursement system on length-of-stay distributions

Abstract. This paper analyses the effects of the new Austrian performance-oriented inpatient payment system on discharge strategies of hospitals by investigating length-of-stay (LOS) distributions. Using generalised linear models applied to data from 1998, we calculate the impact of day and month of admission as well as types of admission and discharge on the LOS of inpatients with major diagnoses. Hereby, we prove significant interdependencies among these variables and reveal hospital behaviour such as 1) premature discharges of inpatients or “unbundling” and 2) “patient splitting”. Hence, our findings illustrate that hospitals react to incentives set by the new system in order to maximise their revenues. Hence, the current reimbursement system still has potential for cost reduction while maintaining high quality of health care. Our strategic policy model supports decision makers in disclosing these effects and provides policy implications to close exploitable gaps within the new reimbursement system. RID="We are grateful to experts of the federal funds and the Ministry of Labour, Health and Social Affairs for providing us with detailed information on the Austrian reimbursement system for inpatients and for approving our data request. In addition, we especially thank Dr. Wilhelm Frank of the Austrian Federal Institute for Health Care for making the needed inpatient data available for us. Special thanks are due to Professor Arjan Shahani, Paul Harper and Sally Brailsford (University of Southampton, United Kingdom), Professor Lucas Delesie (Catholic University of Leuven, Belgium), Professor Bernhard Schwarz (University of Vienna, Austria) and Professor Engelbert Dockner (University of Vienna, Austria) for valuable comments on this investigation. Correspondence to:M. Rauner     

A comparison of the factor loading matrices of two driver behavior investigations

The article reports on two analyses of driver behavior conducted separately, one carried out in Vienna (Austria) and the other in Tübingen (Germany). The data on which the analysis was based were in both cases subjective judgements of 40 behavior characteristics of drivers. In each case two observers accompanying the subject in his vehicle noted the degree in which these characteristics were evident on a nine-point rating scale. Differences between the Vienna investigation and the Tübingen study lay in the team of observers, the test route, the type of vehicle and the size of the samples. The programs for measuring similarities between factor matrices have only recently been developed. The comparison deals primarily with interpretation of the contents of the resulting factor loading matrix and additionally with the interpretation of the measures of similarity for each variable. The experiments are described only as far as is desirable for an understanding of the two basic matrices. The aim of the project was to determine components of driver behavior in terms of reliable, meaningful measures which allow generalization.     

Wave propagation,damage evolution,and dynamic fracture extension. Part II. Blasting

Blasting and blast-induced three-dimensional dynamic fracture propagation in prestressed complex rock formations are addressed. Three-dimensional cube-type laboratory models fabricated from PMMA are dynamically loaded with explosives and the resulting contained fracture structures are studied. Highspeed photography is used to record the dynamic evolution of blast-induced fractures and the effect of stemming of the borehole and blasting under uniaxial stresses is investigated. The series of three-dimensional experiments provide not only new information on the physics and mechanics of the development of the fracture network during blasting but also serve as an input and guide for experts in numerical simulation. This contribution is dedicated to Prof. V. Panasyuk on the occasion of his 70th birthday. Part I was published in the foregoing issue. Institute of Mechanics, Technical University, Vienna, Austria., Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 4, pp. 23–30, July–August, 1996.     

Radon risk in Alpine regions in Austria: risk assessment as a settlement planning strategy

Soil gas radon measurements complement indispensable and well-established radon indoor measurements in Austria. Radon in soil gas is a result of geochemical conditions as well as of geology, mineralogy, geophysics and meteorology. Therefore, geological factors can help to predict potential indoor radon concentrations via soil gas. Soil gas radon measurements in well-defined geological units give an estimate of local and regional radon hazards and build the basis for radon risk maps, which could be used for land-use planning and urban development. The creation of maps makes an important contribution to health care. For this purpose, several research projects were carried out in Austria. On the one hand, a study was already conducted in Lower Austria to determine the influence of meteorological and soil physical parameters on radon concentrations in soil gas and to evaluate soil gas radon concentrations with a radon emanation and migration model. On the other hand, radon measurements on different geomorphologic formations in the Austrian Alps, which are potential settlement areas, are of special interest.     

Shear resistance verification of late 19th century masonry according to EC 6 – State of the art

A large part of buildings in Central European cities like Vienna was built in the Gründerzeit period between about 1840 and 1918 [1]. These buildings were constructed according to traditional rules. Current urban development requires historic buildings to be structurally adapted, which requires retroactive analysis of the masonry walls; in Austria according to ÖNORM EN 1998‐3 [2] and ÖNORM EN 1996‐3 (EC 6) [3]. Here, special focus is on the load transfer of horizontal earthquake loads, i. e. the shear strength of masonry walls. This paper describes the verification of historic masonry in detail and discusses individual components. Initial shear strength, load‐influenced friction and the length of the compressed part of the wall are first determined using results from experimental testing and relevant literature and then compared to the approaches in EC 6. Based on this analysis, recommendations are provided to make theoretical approaches more realistic.     

FRACTURE MECHANICS APPLICATIONS TO DRILLING AND BLASTING

Abstract— This paper gives a brief review of research in rock fracture mechanics as conducted at the Fracture and Photo-Mechanics Laboratory (FPML) at Vienna University of Technology. The mechanisms pertaining to percussion drilling and blasting are investigated, with specific reference to the application of fracture mechanics. In order to gain an improved understanding of the mechanisms controlling rock fragmentation, a multidisciplinary approach is followed which includes laboratory experiments conducted in plexiglass and rock, in-situ field experiments and analytical/numerical modelling techniques.
Field experiments revealed that percussively drilled holes exhibit a very shallow region of damaged rock. An analytical model to simulate damage accumulation and crack initiation due to elastic waves generated by impacting drill bits was developed. This model, based on damage and fracture mechanics, was incorporated into a numerical finite difference code. Fracture and damage mechanics parameters are related to the moment tensor which is determined experimentally by means of acoustic emission. Small scale model blasts were used to investigate the blast-induced fractures in the near-borehole zone as well as in the far field. Analytical and numerical investigations give insight into stress wave and gas driven fracturing. The applicability of the dynamic finite difference program SWIFD to the interaction between stress waves and cracks is illustrated.     

Carbon-specific analysis of humic-like substances in atmospheric aerosol and precipitation samples

A new approach for the carbon-specific determination of humic-like substances (HULIS) in atmospheric aerosols is presented. The method is based on a two-step isolation procedure of HULIS and the determination of HULIS carbon with a dissolved organic carbon analyzer. In the first step, a C18 solid-phase extraction is performed to separate HULIS from inorganic and hydrophilic organic sample constituents in aqueous sample solutions. The second isolation step is conducted on a strong anion exchanger to separate HULIS from remaining carbonaceous compounds. This ion chromatographic separation step including the subsequent on-line detection of HULIS carbon was performed fully automated to avoid the risk of sample contamination and to enhance the reproducibility of the method. With a 5-mL sample volume, a limit of detection of 1.0 mg C/L was obtained; this corresponds to an absolute amount of 5 microg of HULIS carbon. The reproducibility of the method given as the relative standard deviation was 4.3% (n = 10). The method was applied for the determination of water-soluble HULIS in airborne particulate matter. PM10 concentrations at an urban site in Vienna, Austria, ranged from around 0.1 to 1.8 microg of C/m(3) (n = 49); the fraction of water-soluble HULIS in OC was 12.1 +/- 7.2% (n = 49).     

Multiples,poisson distributions,and chance: An analysis of the Brannigan-Wanner model

Brannigan andWanner argue that the empirical distribution of multiple grades can be more adequately explained in terms of a negative contagious poisson model. This alternative is based on a Zeitgeist theory which places emphasis on the role of communication in scientific discovery. Nonetheless, a detailed analysis indicates the following: (a) mathematically, the simple Poisson is the limiting case of the contagious Poisson when the contagion parameter approaches zero; (b) empirically, the mean and variance are so nearly equal (i. e., the contagion effect is very small) that predictions from the contagious Poisson are virtually equivalent to those of the simple Poisson; (c) in particular, both distributions predict that multiples are less common than singletons and even nulltons, the latter occurring with a probability of over one third (thereby implying that chance plays a much bigger part than Zeitgeist or maturational theories would suggest); (d) estimates from theSimonton, Merton, andOgburn-Thomas data sets all concur that the contagion effect is not only small, but positive besides, yielding a modest positive contagious Poisson that contradicts the principal tenet of the communication interpretation.     

First application of calorimetric low-temperature detectors in accelerator mass spectrometry

For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of ²³⁶U/²³⁸U for several samples of natural uranium, ²³⁶U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV ²³⁸U is ΔE/E=4–9×10⁻³, depending on the experimental conditions. This performance enabled to substantially reduce background from neighbouring isotopes and to increase the detection efficiency. Due to the high sensitivity achieved, a value of ²³⁶U/²³⁸U=6.5×10⁻¹² could be obtained, representing the smallest ²³⁶U/²³⁸U ratio measured until now.     

State Feedback and Synergetic controllers for tuberculosis in infected population

Tuberculosis (TB) is a contagious disease which can easily be disseminated in a society. A five state Susceptible, exposed, infected, recovered and resistant (SEIRs) epidemiological mathematical model of TB has been considered along with two non‐linear controllers: State Feedback (SFB) and Synergetic controllers have been designed for the control and prevention of the TB in a population. Using the proposed controllers, the infected individuals have been reduced/controlled via treatment, and susceptible individuals have been prevented from the disease via vaccination. A mathematical analysis has been carried out to prove the asymptotic stability of proposed controllers by invoking the Lyapunov control theory. Simulation results using MATLAB/Simulink manifest that the non‐linear controllers show fast convergence of the system states to their respective desired levels. Comparison shows that proposed SFB controller performs better than Synergetic controller in terms of convergence time, steady state error and oscillations.     

Local Crack‐Programmed Gold Nanowire Electronic Skin Tattoos for In‐Plane Multisensor Integration

Sensitive, specific, yet multifunctional tattoo‐like electronics are ideal wearable systems for “any time, any where” health monitoring because they can virtually become parts of the human skin, offering a burdenless “unfeelable” wearing experience. A skin‐like, multifunctional electronic tattoo made entirely from gold using a standing enokitake‐mushroom‐like vertically aligned nanowire membrane in conjunction with a programmable local cracking technology is reported. Unlike previous multifunctional systems, only a single material type is needed for the integrated gold circuits involved in interconnects and multiplexed specific sensors, thereby avoiding the use of complex multimaterials interfaces. This is possiblebecause the programmable local cracking technology allows for the arbitrary fine‐tuning of the properties of elastic gold conductors from strain‐insensitive to highly strain‐sensitive simply by adjusting localized crack size, shape, and orientations—a capability impossible to achieve with previous bulk cracking technology. Furthermore, in‐plane integration of strain/pressure sensors, anisotropic orientation‐specific sensors, strain‐insensitive stretchable interconnects, temperature sensors, glucose sensors, and lactate sensors without the need of soldering or gluing are demonstrated. This strategy opens a new general route for the design of next‐generation wearable electronic tattoos.     

Mechanical behavior of the ITER TF model coil ground insulation system after reactor irradiation

The mechanical properties of glass fiber reinforced plastics (GFRPs) suggested for the turn and ground insulation of the ITER toroidal field (TF) coils are subject to extensive investigations with respect to their design requirements at present. The insulation system used for the ITER TF model coil, manufactured by European industry, consists of a boron-free R-glass fiber reinforced tape, vacuum-pressure impregnated in a DGEBA epoxy system and partly interleaved with polyimide-foils (e.g. Kapton-H-foils). In order to assess the material performance under the actual operating conditions of ITER-FEAT, the system was irradiated in the TRIGA reactor (Vienna, Austria) to neutron fluences of 5×10²¹ and 1×10²² m⁻² (E>0.1 MeV). The composite was screened at 77 K using static tensile, short-beam-shear (SBS) as well as double-lap-shear tests prior to and after irradiation. Furthermore, tension-tension fatigue measurements were done in order to simulate the pulsed ITER-FEAT operation. We observe that the mechanical strength and the fracture behavior of these GFRPs after irradiation are strongly influenced by the three factors: the winding direction of the tape, the quality of fabrication and the delamination process.     

SEA in Austria and the participative SEA Round Table model

This article firstly gives an overview of Austria’s SEA practice. Secondly it explores the effectiveness of a specific SEA approach, the SEA Round Table. The SEA Round Table is a participative SEA model, involving members of public administration, environmental NGOs and external experts throughout the entire SEA process. This SEA team seeks consensus on an environmentally sound plan or programme. The effects of this SEA Round Table approach are presented by a series of four SEAs carried out for the last four Viennese waste management plans from 1999 to 2018. These four case studies are quite specific SEA cases, which do not allow conclusions on overall SEA effectiveness in Austria. However, some of the outcomes give an idea of how SEA can actually contribute to more environmentally sound plans, which are also easier to implement.     

Hepatitis C virus infection in patients with end‐stage renal disease

Chronic hepatitis C virus (HCV) infection is a major global health problem affecting 3–5 million people in the United States and over 100 million worldwide. Chronic HCV infection, which can lead to cirrhosis and hepatocellular carcinoma, also results in numerous other complications, including impairment of renal function. Because HCV is most often transmitted via parenteral exposure to blood or blood products, patients with end‐stage renal disease (ESRD) treated with hemodialysis are at particular risk for infection. Historically, the medications available to treat HCV infection in these patients had significant side effects and were not particularly effective in generating a sustained virologic response. Since 2011, a number of direct‐acting antiviral therapies have emerged that can lead to virological cure in the vast majority of patients, with low pill burden and few side effects. Here, we describe the biology and pathophysiology of HCV infection, and summarize current information on new therapies, with a particular focus on their application in patients with chronic kidney disease including ESRD.     

A Comparison of Time and Frequency Measurements via OTS-2 with Results Obtained by NAVSTAR/GPS and LORAN-C

Time and frequency transfer measurements between Graz, Austria and Turin, Italy via the OTS-2 satellite over a period of about one month are compared with those of a week of NAVSTAR/GPS results and LORAN-C measurements. In addition to the tracking of OTS-2 by Villafranca (Spain) and Redu (Belgium), SHF-range measurements to OTS-2 were carried out by the Graz station. The differences for the time and frequency comparisons obtained via OTS-2 and via GPS were smaller than 200 ns and 3 × 10-14, respectively.     

Atomic Scale Insights into Single-Atom Catalysis

“Single-Atom” Catalysis (SAC) is a rapidly emerging field aimed at minimizing the amount of precious metals required to perform important catalytic reactions. Modern heterogeneous catalysts already utilize nanoparticles containing 100s to 1000s of atoms on an inexpensive support, but the dream of SAC is to do the same chemistry with single atoms. The concept is firmly entrenched, and SAC systems have demonstrated activity for a variety of reaction, metal, and support combinations. Nevertheless, the topic remains controversial because it is extremely difficult to characterize a catalyst based on single atom active sites, and even harder to figure out how they work. In our group in Vienna, we study model SAC systems in a highly controlled ultrahigh vacuum environment using a variety of state-of-the-art surface-science techniques to discover what makes a stable single atom catalyst, the mechanisms underlying their catalytic activity, and the processes leading to their deactivation.