Twisting turning and pulsating of the Antarctic ozone hole, as revealed by TOMS data

Using data from TOMS!Nimbus7 and Meteor 3, the evolution of Antarctic ozone holes during the southern springs of 1992, 1993, 1994 was studied. At the South Pole, the evolution was mostly smooth, a steady decrease up to about September end and a steady recovery up to about December end. At latitudes near 65° S, the ozone levels (~220 DU) at different latitudes and longitudes showed fluctuations compatible with passing of a noncircular (oval) ! vortex boundary (two ends of a major axis of an ellipse), with a rotation period of -15 days (full rotation period ~30 days) in 1992 and ~17 days (full rotation period ~34 days) in 1994, different from the 2-3 weeks reported by earlier workers. However, the rotation was not with uniform speeds. During a full rotation, the speeds varied sometimes from almost zero (stalling) for a few days to ~20° per day during other intervals. Outside the oval boundary, often there were, depletions with spacings of a few (5-8) days, extending to lower latitudes up to ~30° S, indicating corrugations in the oval boundary, probably due to the effects of synoptic disturbances on total ozone through tropopause pressure changes and/or I ozone mini- holes caused by anticyclonic tropospheric forcing under the southern polar vortex. The shape of the ozone hole changed from elliptic to almost circular and vice versa within a few days and the area also changed by ~15-20%. Thus, the ozone hole was twisting, turning and pulsating, probably due to a varying strength of the wave number 2 component of the wind system prevailing there.

Reducing dose of Cone-Beam CT used for patient positioning in radiooncology

Cone-Beam computed tomography (CBCT) has become the most important component of modern radiotherapy for positioning tumor patients directly before treatment. In this work we investigate alternations to standard acquisition protocol, called preset, for patients with a tumor in the thoracic region. The effects of the changed acquisition parameters on the image quality are evaluated using the Catphan Phantom and the image analysis software Smári. The weighted CT dose index (CTDIW) is determined in each case and the effects of the different acquisition protocols on the patient dose are classified accordingly. Additionally, the clinical suitability of alternative presets is tested by investigating correctness of image registration using the CIRS thorax phantom. The results show that a significant dose reduction can be achieved. It can be reduced by 51% for a full rotation by adjusting the gantry speed. A more patientspecific uptake protocol for patients with laterally located tumor was created which allows a dose reduction of 54%.

LOOSENING AND LEVELING DEVICE FOR PREPARING SOIL FOR MELON CROPS

The analysis of soil cultivation technologies for sowing melon crops was carried out. The design of a combined soil tillage tool capable of plowing, pre-sowing treatment and formation of irrigation furrows in one pass was substantiated. The main tillage is recommended to be done by front plow tools for smooth plowing. Plow bodies of two bottom plows should be mounted along the symmetry axis of the implement according to the lister scheme, which allows not to carry out a full rotation of soil layers and provides automatic formation of irrigation furrow. A loosening and leveling device for strip pre-sowing soil tillage in the sowing zone has been developed. The use of a combined soil tillage tool can reduce labor costs up to 25%, energy consumption for soil preparation up to 50%, reduce the duration of work, reduce soil compaction and retain moisture in the soil layer.

A novel geometric model of breathing crack and its influence on rotor dynamics

The present research focuses on performing the dynamic study of a cracked, internally damped, composite rotating shaft system with journal bearing end supports. A novel mathematical formulation is proposed to introduce a time-varying stiffness matrix for simulating the breathing behaviour of the crack. The random search algorithm is used as one of the metaheuristic processes to carry out the optimization and generate time-dependent geometric parameters of the cracked surface for one full rotation. The derived stiffness matrix is used in the composite shaft’s higher order motion equation obtained through equivalent modulus theory, whose internal damping properties are incorporated using operator-based viscoelastic model. Eigenanalysis is carried out to perform a thorough study of dynamic characteristics of cracked shaft considering the crack depth and crack position as two important parameters. The effect of crack on stacking sequence as well as mode shapes of the heterogeneous laminated shaft is also studied.

A novel method for dendrochronology of large historical wooden objects using line trajectory X-ray tomography

Dendrochronology is an essential tool to determine the date and provenance of wood from historical art objects. As standard methods to access the tree rings are invasive, X-ray computed tomography (CT) has been proposed for non-invasive dendrochronological investigation. While traditional CT can provide clear images of the inner structure of wooden objects, it requires their full rotation, imposing strong limitations on the size of the object. These limitations have previously encouraged investigations into alternative acquisition trajectories, including trajectories with only linear movement. In this paper, we use such a line-trajectory (LT) X-ray tomography technique to retrieve tree-ring patterns from large wooden objects. We demonstrate that by moving a wooden artifact sideways between the static X-ray source and the detector during acquisition, sharp reconstruction images of the tree rings can be produced. We validate this technique using computer simulations and two wooden test planks, and demonstrate it on a large iconic chest from the Rijksmuseum collection (Amsterdam, The Netherlands). The LT scanning method can be easily implemented in standard X-ray imaging units available at museum research facilities. Therefore, this scanning technique represents a major step towards the standard implementation of non-invasive dendrochronology on large wooden cultural heritage objects.

Angular Momentum and the Quantum Gyroscope: The Emergence of Spin

Continuing with understanding the implications of the postulates in Chapter 7 and following the approach in Chapter 8 to use operators find solutions to the time independent Schrödinger equation, we return to the subject of angular momentum, of importance to many problems including the quantum gyroscope. Aside from playing a central role in any spherically symmetric quantum system, it plays a central role in inertial guidance systems from airplanes and rockets to autonomous vehicles. Working with only the operators of the angular momentum vector, L^=L^xx̌+L^yy̌+L^zž and L^2 and the corresponding commutation relations, a procedure similar to that used in Chapter 8 for the nano-vibrator is used to completely identify the eigenvectors and eigenvalues. However, in Chapter 6, we required that the magnetic quantum number, m where L^z|l.m〉=mℏ|l.m〉, be integer, because the eigenfunction Yl,m(l,m)∝eimϕ, and we required that a full rotation around the z-axis give the same result requiring, eimϕ=eim(ϕ+2π). In the operator approach, there is no such requirement, but there is still a constraint on m, namely that m is either integer or half integer. The requirements in Chapter 6 hold, so what is the meaning of half-integer? This was one of the first results to indicate the existence of intrinsic (not associated with real space rotation) angular moment known as spin.

Quantum-Classical Simulation of Molecular Motors Driven Only by Light

<div><div><div><p>Molecular motors that exhibit controlled unidirectional rotation provide great prospects for many types of applications including nanorobotics. Existing rotational motors have two key components: photoisomerisation around a pi-bond followed by a thermally activated helical inversion; the latter being the rate-determining step. We propose an alternative molecular system, where the rotation is caused by the electronic coupling<br>of chromophores. This is used to engineer the excited state energy surface and achieve unidirectional rotation using light as the only input and avoid the slow thermal step, potentially leading to much faster operational speeds. To test the working principle we employ quantum-classical calculations to study the dynamics of such a system. We estimate that motors build on this principle should be able to work on a sub-nanosecond timescale for such a full rotation. We explore the parameter space of our model to guide the design of a molecule which can act as such motor.</p></div></div></div>

Quantum-Classical Simulation of Molecular Motors Driven Only by Light

<div><div><div><p>Molecular motors that exhibit controlled unidirectional rotation provide great prospects for many types of applications including nanorobotics. Existing rotational motors have two key components: photoisomerisation around a pi-bond followed by a thermally activated helical inversion; the latter being the rate-determining step. We propose an alternative molecular system, where the rotation is caused by the electronic coupling<br>of chromophores. This is used to engineer the excited state energy surface and achieve unidirectional rotation using light as the only input and avoid the slow thermal step, potentially leading to much faster operational speeds. To test the working principle we employ quantum-classical calculations to study the dynamics of such a system. We estimate that motors build on this principle should be able to work on a sub-nanosecond timescale for such a full rotation. We explore the parameter space of our model to guide the design of a molecule which can act as such motor.</p></div></div></div>

The Gantry as a Drive for a Horizontal Bike: Initial Investigation of Rotary Work

The gantry drive (also, “the gantry”) is a mechanism that receives human-generated mechanical energy. The gantry used in a horizontal bike is a type of drive, and it is an alternative to a typical crankset. The purpose of this paper was to compare rotary work generated by the gantry and the crankset. The comparative criterion for the gantry and the crankset was work in rotational motion. The comparison was based on static tests; forces put into both drive systems were measured, and the rotary work was mathematically calculated. The forces put into the drive systems were measured for a man 177 cm tall and of 76 kg mass. To facilitate analysis and tests, the first gear wheel to receive force from the toothed rack (the gantry drive) was assumed to have the same radius as the crank (the crankset drive). Mathematical analysis performed for one full rotation (360°) of the first gear wheel and crankset showed that rotary work for the gantry was 2117.31 J and for the crankset 804.81 J. Ultimately, it was shown that the gantry can better receive mechanical energy from the human than the crankset. This means that a human will be less tired when riding a horizontal bike equipped with the gantry compared to a horizontal bike equipped with the crankset; assuming that in both cases, the bike speed is the same. Additionally, thanks to the use of the gantry drive in a horizontal bike, it is possible to achieve higher speeds compared to a horizontal bike equipped with the crankset.