EFFECT OF ION NITRIDING ON FATIGUE BEHAVIOR OF STEEL 35HGS

В тази статия е изследвано поведението на умора на образци от 35HGS ниско легирана стомана. Направен е сравнителен анализ за ефекта от процеса на втвърдяване с последващо смилане и йонно азотиране. За целта са произведени пет групи екземпляри. Първата група екземпляри е била подложена на втвърдяване и смилане. Останалите четири групи образци са подложени на йонно азотиране с различна продължителност на процеса - съответно 4, 8, 12 и 16 часа. Експерименталното проучване е проведено в два етапа - циклични тестове за умора при огъване и оценка на остатъчните напрежения чрез рентгенов дифракционен анализ. Установено е, че процесът на йониране на йони има по-благоприятен ефект върху живота на умората в областта на умората с висок цикъл в сравнение с процеса на гасене, последван от смилане. Положителният ефект от закаляването и смилането се наблюдава в областта на умората при нисък цикъл. Най-високата граница на умора (сигма_-1 = 800MPa) е получена за образците, подложени на йонно азотиране за продължителност от 4 часа. Резултатите от рентгеновата дифракция показват, че процесът на азотно азотиране осигурява по-големи остатъчни напрежения при натиск в абсолютна стойност в сравнение с процеса на закаляване и смилане. Установено е, че разпределението в дълбочина на остатъчните напрежения на оста и обръча, създадени след йонно азотиране, е много подобно. Установена е различна тенденция между получените граници на умора и интензивността на зоната на остатъчни напрежения при натиск.In this article the fatigue behavior of specimens made of 35HGS low-alloyed steel has been investigated. A comparative analysis has been made for the effect of hardening process with subsequent grinding and ion nitriding process. For this purpose, five groups of specimens have been manufactured. The first group of specimens has been subjected to hardening and grinding. The other four groups of specimens have been subjected to ion nitriding with a different process duration - 4, 8, 12 and 16 hours, respectively. The experimental study has been conducted in two stages- cyclic bending fatigue tests and residual stresses assessment trough X-ray diffraction analysis. It has been established that the ion nitriding process has a more favorable effect on fatigue life in the field of high-cycle fatigue compared to the quenching process followed by grinding. The positive effect by the quenching and grinding has been observed in the field of low- cycle fatigue. The highest fatigue limit (sigma_-1 = 800MPa ) has been obtained for the specimens subjected to ion nitriding for a duration of 4 hours. The X-ray diffraction results show that the ion nitriding process provides greater in absolute value compressive residual stresses compared to the quenching and grinding process. It has been established that the distribution in depth of the axial and hoop residual stresses created after ion nitriding is very similar. A different trend has been established between the obtained fatigue limits and the intensity of the compressive residual stress zone

A Stochastic Liouville Equation Approach for the Effect of Noise in Quantum Computations

We propose a model based on a generalized effective Hamiltonian for studying the effect of noise in quantum computations. The system-environment interactions are taken into account by including stochastic fluctuating terms in the system Hamiltonian. Treating these fluctuations as Gaussian Markov processes with zero mean and delta function correlation times, we derive an exact equation of motion describing the dissipative dynamics for a system of n qubits. We then apply this model to study the effect of noise on the quantum teleportation and a generic quantum controlled-NOT (CNOT) gate. For the quantum CNOT gate, we study the effect of noise on a set of one- and two-qubit quantum gates, and show that the results can be assembled together to investigate the quality of a quantum CNOT gate operation. We compute the averaged gate fidelity and gate purity for the quantum CNOT gate, and investigate phase, bit-flip, and flip-flop errors during the CNOT gate operation. The effects of direct inter-qubit coupling and fluctuations on the control fields are also studied. We discuss the limitations and possible extensions of this model. In sum, we demonstrate a simple model that enables us to investigate the effect of noise in arbitrary quantum circuits under realistic device conditions.Comment: 36 pages, 6 figures; to be submitted to Phys. Rev.

Did the Hilda collisional family form during the late heavy bombardment?

We model the long-term evolution of the Hilda collisional family located in the 3/2 mean-motion resonance with Jupiter. Its eccentricity distribution evolves mostly due to the Yarkovsky/YORP effect and assuming that: (i) impact disruption was isotropic, and (ii) albedo distribution of small asteroids is the same as for large ones, we can estimate the age of the Hilda family to be $4_{-1}^{+0}\,{\rm Gyr}$. We also calculate collisional activity in the J3/2 region. Our results indicate that current collisional rates are very low for a 200\,km parent body such that the number of expected events over Gyrs is much smaller than one. The large age and the low probability of the collisional disruption lead us to the conclusion that the Hilda family might have been created during the Late Heavy Bombardment when the collisions were much more frequent. The Hilda family may thus serve as a test of orbital behavior of planets during the LHB. We tested the influence of the giant-planet migration on the distribution of the family members. The scenarios that are consistent with the observed Hilda family are those with fast migration time scales $\simeq 0.3\,{\rm Myr}$ to $3\,{\rm Myr}$, because longer time scales produce a family that is depleted and too much spread in eccentricity. Moreover, there is an indication that Jupiter and Saturn were no longer in a compact configuration (with period ratio $P_{\rm S}/P_{\rm J} > 2.09$) at the time when the Hilda family was created

Can discrete time make continuous space look discrete?

Van Bendegem has recently offered an argument to the effect that, if time is discrete, then there should exist a correspondence between the motions of massive bodies and a discrete geometry. On this basis, he concludes that, even if space is continuous, it should nonetheless appear discrete. This paper examines the two possible ways of making sense of that correspondence, and shows that in neither case van Bendegem's conclusion logically follows

Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution

The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201

Trees as Dialogue: Negotiating Boundaries with the Anne Frank Sapling Project

My qualitative research paper focuses on the Anne Frank sapling installation at the Clinton Presidential Museum and Library in Little Rock, Arkansas. Saplings grafted from the tree that grew outside Anne Frank’s window in Amsterdam while she wrote her famous diary are provided by the Anne Frank Center for Mutual Respect to organizations that will link the tree to dialogues about past and present social justice issues. Building on Thomas Gieryn’s recent work on “truth-spots,” I explore the sapling installation as a possible “truth-spot,” and reflect on what kind of truth is supported there. From a symbolic interactionist perspective, I consider the sapling as a boundary-crossing entity that, together with other elements of the installation, stimulates reflection and inclusive dialogue, and fosters hope without shunning complexity. I discuss the sapling’s ecological needs and material agency, since it is not a passive recipient of human meanings and orchestrations. I also comment on the changing role of museum installations and exhibit space in the context of social justice

Effect of magnetic field configuration on double layer formation and reverse discharge ignition in bipolar HiPIMS

The reverse discharge (RD) phenomenon in bipolar HiPIMS has been observed when a sufficiently long positive pulse is applied to the magnetron. Due to the magnetic field, electrons accumulated behind the magnetic trap are prevented from reaching the positive target. Consequently, a space charge double layer (DL) is formed between the positive target and the plasma behind the magnetic trap, leading to electron acceleration across the DL and RD ignition. This study reveals the significant impact of the magnetic field configuration on RD ignition. Experiments are performed using a Ti target involving magnetic field variation, wire probe measurements of floating potential, and optical emission spectroscopy imaging. It is found that adjusting the magnetic field to a more balanced configuration leads to earlier RD ignition, while a more unbalanced one delays or even prevents it. Specifically, the time of RD ignition decreases with an increase in the magnetic null point distance from the target. Moreover, the size and shape of optical emission in the RD varies with nearby probe placement, suggesting sensitivity to external electrodes

In situ tension-tension strain path changes of cold-rolled Mg AZ31B

The mechanical behavior of cold-rolled Mg AZ31B is studied during in-plane multiaxial loading and tension-tension strain path changes performed on cruciform samples using in situ neutron diffraction and EBSD. The results are compared with uniaxial tension loading of dogbone-shaped samples measured with in situ neutron diffraction and acoustic emission. The activity of slip and twinning mechanisms and the active twin variants are discussed for the different strain paths. It is shown that initial strains of 4–5% cause a strengthened yield stress during reload for strain path change angles of 90 and 135°. The strengthening is primarily due to dislocation accumulation during the initial load impeding dislocation motion during the reload. The twinning observed during the prestrain activates complex multivariant secondary twinning which may also contribute to the strengthening in the reload

Тренінгові технології у підготовці перекладачів-синхроністів з використанням спеціалізованого обладнання

The article deals with the search for ways to improve the training of simultaneous interpreters in accordance with modern requirements for their professional activities. It has been suggested that special training should be incorporated into the training of these professionals to develop and improve a range of specific abilities, skills and attitudes. They are classified into five groups (linguistic, cognitive, psychological, physical, technical). Particular attention is paid to the technological support for the work of the simultaneous interpreters. A training programme for simultaneous interpreters has been developed and its effectiveness has been tested. It is proposed to conduct training sessions under the modelling of real working conditions of simultaneous interpreters.Стаття присвячена пошуку шляхів удосконалення підготовки перекладачів-синхроністів відповідно до сучасних вимог до їх професійної діяльності. Запропоновано включити до програми підготовки цих фахівців спеціальну підготовку, спрямовану на розвиток і вдосконалення низки специфічних здібностей, навичок і установок. Їх класифіковано на п'ять груп (лінгвістичні, когнітивні, психологічні, фізичні, технічні). Особлива увага приділяється технологічному забезпеченню роботи перекладачів-синхроністів. Розроблено програму підготовки перекладачів-синхроністів та перевірено її ефективність. Запропоновано проводити навчальні заняття в умовах моделювання реальних умов роботи перекладачів-синхроністів