Fatigue crack layer propagation in silicon-iron

Fatigue crack propagation in metal is almost always accompanied by plastic deformation unless conditions strongly favor brittle fracture. The analysis of the plastic zone is crucial to the understanding of crack propagation behavior as it governs the crack growth kinetics. This research was undertaken to study the fatigue crack propagation in a silicon iron alloy. Kinetic and plasticity aspects of fatigue crack propagation in the alloy were obtained, including the characterization of damage evolution

Topological transition from nodal to nodeless Zeeman splitting in altermagnets

In an altermagnet, the symmetry that relates configurations with flipped magnetic moments is a rotation. This makes it qualitatively different from a ferromagnet, where no such symmetry exists, or a collinear antiferromagnet, where this symmetry is a lattice translation. In this paper, we investigate the impact of the crystalline environment on the magnetic and electronic properties of an altermagnet. We find that, because each component of the magnetization acquires its own angular dependence, the Zeeman splitting of the bands has symmetry-protected nodal lines residing on mirror planes of the crystal. Upon crossing the Fermi surface, these nodal lines give rise to pinch points that behave as single or double type-II Weyl nodes. We show that an external magnetic field perpendicular to these mirror planes can only move the nodal lines, such that a critical field value is necessary to collapse the nodes and make the Weyl pinch points annihilate. This unveils the topological nature of the transition from a nodal to a nodeless Zeeman splitting of the bands. We also classify the altermagnetic states of common crystallographic point groups in the presence of spin-orbit coupling, revealing that a broad family of magnetic orthorhombic perovskites can realize altermagnetism.Comment: manuscript + supplementary materia

Interface control of emergent ferroic order in Ruddlesden-Popper Srn+1_{n+1}Tin_nO3n+1_{3n+1}

We have discovered from first-principles an unusual polar state in the low n Sr$_{n+1}$Ti$_n$O$_{3n+1}$ Ruddlesden-Popper (RP) layered perovskites in which ferroelectricity is nearly degenerate with antiferroelectricity, a relatively rare form of ferroic order. We show that epitaxial strain plays a key role in tuning the "perpendicular coherence length" of the ferroelectric mode, and does not induce ferroelectricity in these low dimensional RP materials as is well known to occur in SrTiO$_3$. These systems present an opportunity to manipulate the coherence length of a ferroic distortion in a controlled way, without disorder or a free surface

Magnetodielectric coupling and phonon properties of compressively strained EuTiO3 thin films deposited on LSAT

Compressively strained epitaxial (001) EuTiO3 thin films of tetragonal symmetry have been deposited on (001) (LaAlO3)_0.29-(SrAl_{1/2}Ta_{1/2}O3)_0.71 (LSAT) substrates by reactive molecular-beam epitaxy. Enhancement of the Neel temperature by 1 K with 0.9% compressive strain was revealed. The polar phonons ofthe films have been investigated as a function of temperature and magnetic field by means of infrared reflectance spectroscopy. All three infrared active phonons show strongly stiffened frequencies compared to bulk EuTiO3 in accordance with first principles calculations. The phonon frequencies exhibit gradual softening on cooling leading to an increase in static permittivity. A new polar phonon with frequency near the TO1 soft mode was detected below 150 K. The new mode coupled with the TO1 mode was assigned as the optical phonon from the Brillouin zone edge, which is activated in infrared spectra due to an antiferrodistortive phase transition and due to simultaneous presence of polar and/or magnetic nanoclusters. In the antiferromagnetic phase we have observed a remarkable softening of the lowest-frequency polar phonon under an applied magnetic field, which qualitatively agrees with first principles calculations. This demonstrates the strong spin-phonon coupling in EuTiO3, which is responsible for the pronounced dependence of its static permittivity on magnetic field in the antiferromagnetic phase.Comment: Submitted to Phys. Rev.

Peningkatan Nilai Kalori pada Batubara Lignit dengan Metode Aglomerasi Air dan Minyak Sawit pada PT. Indonesia Power Ujp Pltu Barru

Penggunaan batubara di PLTU sangat bergantung kepada kualitas batubara yang digunakan, karena semakin tinggi kualitas batubara maka akan memaksimalkan pembakaran dan secara langsung akan berdampak pada produksi listrik yang dihasilkan. Penelitian ini bertujuan untuk mengetahui peningkatan nilai kalori pada batubara lignit. Pada penelitian ini digunakan metode aglomerasi dengan media air dan minyak sawit yang pada setiap sampel diberi perlakukan yang sama namun mengalami peningkatan yang berbeda. Ada tiga sampel yang digunakan pada penelitian ini dimana pada setiap sampel memiliki komposisi batubara lignit seberat 1 gram, minyak sawit sebanyak 10,20,30 ml dan air sebanyak 100 ml. Hasil penelitian ini menunjukkan bahwa semakin banyak konsentrasi minyak maka semakin tinggi kadar karbon yang diikat, sehingga dapat meningkatkan nilai kalori batubara. Dilihat dari konsentrasi 30% pada setiap sampel batubara mengalami peningkatan nilai kalori yang sebelumnya 3.765,23 cal/gr menjadi 5.279,46 cal/gr pada sampel pertama, 3.567,44 cal/gr menjadi 4.989,07 cal/gr pada sampel kedua dan 4.026,07 cal/gr menjadi 5.166,98 cal/gr pada sampel ketiga. Dari hasil penelitian ini dapat disimpulkan bahwa batubara lignit yang digunakan di PLTU dapat ditingkatkan nilai kalorinya menggunakan metode aglomerasi air dan minyak sawit

Remote sensing of blood oxygenation using red-eye pupil reflection

To access publisher's full text version of this article click on the hyperlink belowObjective: To develop a technique for remote sensing of systemic blood oxygenation using red-eye pupil reflection. Approach: The ratio of the intensities of light from the bright pupil reflections at oxygen sensitive and isosbestic wavelengths is shown to be sensitive to the oxygenation of blood in the eye. A conventional retinal camera, fitted with an image-replicating imaging spectrometer, was used at standoff range to record snapshot spectral images of the face and eyes at eight different wavelengths. In our pilot study we measured optical-density ratios (ODRs) of pupil reflections at wavelengths of 780 nm and 800 nm, simultaneous with pulse oximetry, for ten healthy human subjects under conditions of normoxia and mild hypoxia (15% oxygen). The low absorption at these infrared wavelengths localises the sensing to the choroid. We propose that this can be used for as a proxy for systemic oximetry. Main results: A significant reduction (P < 0.001) in ODR of the pupil images was observed during hypoxia and returned to baseline on resumption of normoxia. We demonstrate that measurement of the choroidal ODR can be used to detect changes in blood oxygenation that correlate positively with pulse oximetry and with a noise-equivalent oximetry precision of 0.5%. Significance: We describe a new method to remotely and non-invasively sense the oxygen saturation of choroidal blood. The methodology provides a proxy for remote sensing of cerebral and systemic blood oxygenation. We demonstrate the technique at short range but it has potential for systemic oximetry at large standoff ranges

Twin roll casting of Al-Mg alloy with high added impurity content

The final publication is available at Springer from the link belowThe microstructural evolution during twin roll casting (TRC) and downstream processing of AA5754 Al alloy with high added impurity content have been investigated. Strip casts with a high impurity content resulted in coarse α-Al grains and complex secondary phases. The grain size and centreline segregation reduced significantly on the addition of Al-Ti-B grain refiner (GR). Coarse-dendrite arm spacing (DAS) “floating” grains are observed in the impure alloy (IA) with higher volume in the GR strips. Two dimensional (2D) metallographic analysis of the as-cast strip suggests secondary phases (Fe bearing intermetallics and Mg2Si) are discrete and located at the α-Al cell/grain boundaries, while three dimensional (3D) analysis of extracted particles revealed that they were intact, well interconnected and located in interdendritic regions. Homogenizing heat treatment of the cast strip breaks the interconnective networks and modifies the secondary phases to more equiaxed morphology. During rolling, the eqiaxed secondary phases align along the rolling direction. X-ray diffraction (XRD) analysis suggests that α-Al(FeMn)Si and Mg2Si are the predominant secondary phases that formed during casting and remain throughout the downstream processing of the GR-IA. The high impurity sheet processed from TRC resulted in superior strength and ductility than the sheet processed from small book mould ingot casting. This study, have shown that the twin roll casting process can tolerate higher impurity levels and produce formable sheets from recycled aluminium for structural applications.UK Engineering Physical and Sciences Research Council (EPSRC) Centre for Innovative Manufacturing in Liquid Metal Engineering and the Technology Strategic Board (TSB), U

Coherent Pair Production by Photons in the 20-170 GeV Energy Range Incident on Crystals and Birefringence

The cross section for coherent pair production by linearly polarised photons in the 20-170 GeV energy range was measured for photon aligned incidence on ultra-high quality diamond and germanium crystals. The theoretical description of coherent bremsstrahlung and coherent pair production phenomena is an area of active theoretical debate and development. However, under our experimental conditions, the theory predicted the combined cross section and polarisation experimental observables very well indeed. In macroscopic terms, our experiment measured a birefringence effect in pair production in a crystal. This study of this effect also constituted a measurement of the energy dependent linear polarisation of photons produced by coherent bremsstrahlung in aligned crystals. New technologies for manipulating high energy photon beams can be realised based on an improved understanding of QED phenomena at these energies. In particular, this experiment demonstrates an efficient new polarimetry technique. The pair production measurements were done using two independent methods simultaneously. The more complex method using a magnet spectrometer showed that the simpler method using a multiplicity detector was also viable.Comment: 10 pages, 13 figures, 1 table, REVTeX4 two column, Version for publicatio

Linear to Circular Polarisation Conversion using Birefringent Properties of Aligned Crystals for Multi-GeV Photons

We present the first experimental results on the use of a thick aligned Si crystal acting as a quarter wave plate to induce a degree of circular polarisation in a high energy linearly polarised photon beam. The linearly polarised photon beam is produced from coherent bremsstrahlung radiation by 178 GeV unpolarised electrons incident on an aligned Si crystal, acting as a radiator. The linear polarisation of the photon beam is characterised by measuring the asymmetry in electron-positron pair production in a Ge crystal, for different crystal orientations. The Ge crystal therefore acts as an analyser. The birefringence phenomenon, which converts the linear polarisation to circular polarisation, is observed by letting the linearly polarised photons beam pass through a thick Si quarter wave plate crystal, and then measuring the asymmetry in electron-positron pair production again for a selection of relative angles between the crystallographic planes of the radiator, analyser and quarter wave plate. The systematics of the difference between the measured asymmetries with and without the quarter wave plate are predicted by theory to reveal an evolution in the Stokes parameters from which the appearance of a circularly polarised component in the photon beam can be demonstrated. The measured magnitude of the circularly polarised component was consistent with the theoretical predictions, and therefore is in indication of the existence of the birefringence effect.Comment: 12 pages, 12 figures, 1 table, REVTeX4 two column, Version for publicatio