Implementasi Rancangan Pembelajaran Berbasis Sharing dan Jumping Task pada Konsep Hukum Kekekalan Massa

The law of conservation of mass is a fundamental law and is related to other chemical materials such as chemical reaction equations so that student's learning obstacles of the law of conservation of mass must be overcome. One of the ways to overcome student's learning obstacles of the law of conservation of mass concept is the implementation of sharing and jumping task based lesson design, which is the aim of this research. The research method used is a qualitative descriptive research method. The research subjects were students of X.1 and X.2 SMA in Bandung and chemistry teacher who collaborate with researcher as team teaching. The data on the implementation of sharing and jumping task based lesson design of the law of conservation of mass was obtained from observations, tests, and interviews. Implementation of sharing and jumping task based lesson design of the law of conservation of mass concept was carried out twice. The result of the first implementation is that the previously identified learning obstacles still appear but in a smaller percentage. After the first implementation of the lesson design, it was revised and implemented in other class. The results of the second implementation can overcome student's learning obstacle who think that the mass of solids is heavier than the mass of liquids, but a small number of students still do not take into account the mass of gases in chemical reactions and do not fully understand the meaning of the law of conservation of mass.

Axisymmetric hydrate monolith destruction problem

A mathematical model is proposed for the destruction of a methane hydrate monolith containing gas inclusions. In this formulation of the problem, it is assumed that there is a cylindrical cavity inside the hydrate monolith, initially filled only with methane. Since the conditions on the surface of the particle correspond to the conditions for the free existence of gas and water, the gas hydrate begins to decompose. On the basis of the obtained system, consisting of the equations of conservation of mass and heat, the temperature distributions in the “cavity - gas hydrate” system were obtained, and the influence of the initial temperature of the system and the temperature in the cavity on the dynamics of hydrate decomposition was analyzed.

Two-dimensional model of wave hydrodynamics with high accuracy dispersion relation. II. Fourth, sixth and eighth orders

Построена полностью нелинейная слабо дисперсионная модель волновой гидродинамики четвертого порядка длинноволновой аппроксимации. За скорость в модели взята усредненная по глубине горизонтальная составляющая скорости трехмерного течения. Учтена подвижность дна. Выполненная модификация модели обеспечивает шестой и восьмой порядки точности аппроксимации дисперсионного соотношения трехмерной модели потенциальных течений. In the numerical simulation of medium-length surface waves in the framework of nonlinear dispersive (NLD) models, an increased accuracy of reproducing the characteristics of the simulated processes is required. A number of works (Kirby (2016), e.g.) describe approaches to improve the known NLD-models. In particular, NLD-models of the fourth order of the long-wave approximation have been proposed and, based on a comparison of numerical results with experimental data, their high accuracy has been demonstrated (Ataie-Ashtiani and Najafi-Jilani (2007); Zhou and Teng (2010)). In these new models, the horizontal component of the velocity vector of the threedimensional (FNPF-) model of potential flows at a certain surface located between the bottom and the free boundary was chosen as the velocity vector. The result was a very cumbersome form of equations. In addition, the laws of conservation of mass and momentum do not hold for these models. The main result of this work is the derivation of a two-parameter fully nonlinear weakly dispersive (mSGN4) model of the fourth order of the long-wave approximation, which is a generalization of the well-known Serre-Green-Naghdi (SGN) second order model. In the derivation, the velocity averaged over the thickness of the liquid layer was used. The assumption about the potentiality of the three-dimensional flow was used only at the stage of closing the model. The movement of the bottom is taken into account. For the derived model, the law of conservation of mass is satisfied, and the law of conservation of total momentum is satisfied in the case of a horizontal stationary bottom. The equations of the mSGN4-model are invariant under the Galilean transformation and are presented in a compact form similar to the equations of gas dynamics. The dispersion relation of the mSGN4-model has the fourth order of accuracy in the long wave region and satisfactorily approximates the dispersion relation of the FNPF-model in the short wave region. Moreover, with a special choice of the values of the model parameters, an increased accuracy of approximating the dispersion relation of the FNPF-model at long waves (sixth or eighth order) is achieved. Analysis of the deviations of the values of the phase velocity of the mSGN4 model from the values of the “reference” speed of the FNPF model in the entire wavelength range showed that the most preferable is the mSGN4 model with the parameter values corresponding to the Pad’e approximant (2,4).

Controls on the hydraulic geometry of alluvial channels: bank stability to gravitational failure, the critical-flow hypothesis, and conservation of mass and energy

The bank-full depths, widths, depth-averaged water velocities, and along-channel slopes of alluvial channels are approximately power-law functions of bank-full discharge across many orders of magnitude. What mechanisms give rise to these patterns is one of the central questions of fluvial geomorphology. Here it is proposed that the bank-full depths of alluvial channels are partially controlled by the maximum heights of gravitationally stable channel banks, which depend on bank material cohesion and hence on clay content. The bank-full depths predicted by a bank-stability model correlate with observed bank-full depths estimated from the bends in the stage–discharge rating curves of 387 U.S. Geological Survey gaging stations in the Mississippi River basin. It is further proposed that depth-averaged water velocities scale with bank-full depths as a result of a self-regulatory feedback among water flow, relative roughness, and channel-bed morphology that limits depth-averaged water velocities to within a relatively narrow range associated with Froude numbers that have a weak inverse relationship to bank-full discharge. Given these constraints on channel depths and water velocities, bank-full widths and along-channel slopes consistent with observations follow by conservation of mass and energy of water flow.

Analysing and simulating energy-based models in biology using BondGraphTools

Like all physical systems, biological systems are constrained by the laws of physics. However, mathematical models of biochemistry frequently neglect the conservation of energy, leading to unrealistic behaviour. Energy-based models that are consistent with conservation of mass, charge and energy have the potential to aid the understanding of complex interactions between biological components, and are becoming easier to develop with recent advances in experimental measurements and databases. In this paper, we motivate the use of bond graphs (a modelling tool from engineering) for energy-based modelling and introduce, BondGraphTools, a Python library for constructing and analysing bond graph models. We use examples from biochemistry to illustrate how BondGraphTools can be used to automate model construction in systems biology while maintaining consistency with the laws of physics.