Mechanics of landslides

The purpose of this investigation was to determine whether landslides could be predicted for hill slopes of known inclinations from data secured by laboratory tests performed on samples of the ground under consideration. Specifically, the investigation was to show whether a correlation existed between experimentally determined values for friction and cohesion of ground and calculated values based upon the configuration of earth masses that had slid. The ability to determine the stability of slopes from experimental data is of obvious significance.

On the feeding of the larvae of Chironomidae during the planktonic period of life [Translation from: Nauch.Dokl.vyssh.Shk.Biol.Nauk 1 19-21, 1965]

It is known that the larvae of Chironomidae in the first stages of life after leaving the egg case, swim for a long time in a body of water. Positive reaction in light, the capability of directed swimming and passive floating in suspension allow the larvae to temporarily carry out a planktonic way of life. This study describes the behaviour of Chironomus dorsalis larvae after leaving the egg case. The feeding of chironomid larvae in the first stages of development was also described.

Selective plankton feeding by the coregonid ”bondella” (Coregonus sp.) of Lake Maggiore [Translation from: Translation from: Memorie dell'Istituto Italiano di Idrobiologia Dott.Marco de Marchi 31 181-203, 1974]

In recent times, some specialists have begun to study the subject of food selection of fish in an organized way, thus highlighting its importance. In the present work, the author intends to evaluate the impact of predation on the eupelagic zooplanktonic biocenosis of Lake Maggiore, producing, in this way, as far as possible, a basis for a better understanding of the population dynamics of the species of zooplankton directly involved. Another aspect which has been studied is that related to the mechanism of selective capture set in action by the predator. To this end the study tries to bear in mind that the subject should be interpreted as a function of numerous factors acting contemporaneously, that is as the interaction of characters peculiar to the predator and to the prey. The species studied, locally called ”bondella”, belongs to the family Salmonidae, subfamily Coregoninae and was introduced into Lake Maggiore in 1950.

Feeding of Gammarus lacustris Sars under different conditions of habitation [Translation from: [Trophic relations of freshwater invertebrates.] (ed. G. G. Vinberg) pp.94-98. Leningrad, Zool.Inst.AN SSSR, 1980]

The amphipod Gammarus lacustris, a regular representative of lacustrine communities, often plays a significant role in the transformation of matter and energy. The object of the present work was to clarify the quantitative side of the feeding of the amphipod under different conditions of habitation. Experimental works on determination of the rate of consumption of food and its dependence on body-weight were carried out in the summer periods 1975-1978 on three water-bodies of the Krasnoyarsk region, of different conditions of habitation for the amphipods.

Review of investigation on the feeding of the European grayling [Translation from: Flora Slodkowodna Polski. Tom 2. Cyanophyta, Glaucophyta (ed. K. Starmach) p350-352. Warsaw, Polska Academia Nauk, 1966]

The composition of the food of the European grayling and the character of its feeding has been studied fully enough, but this knowledge is scattered in the literature and often contradictory. rare exceptions, analysis of the results of different investigations. Therefore the proposed short outline of the history of the study of the problem with a description of the basic data on the feeding of the grayling in different geographical areas is presented as expedient and opportune, primarily in relation to the determination of immediate problems and the trend of research.

Changes in feeding biology of Nile tilapia, Oreochromis niloticus (L.), after invasion of water hyacinth, Eichhornia crassipes (Mart.) Solms, in Lake Victoria, Kenya

Oreochrimis niloticus (L.) was introduced to Lake victoria in the 1950s. It remained relatively uncommon in catches until 1965, when the numbers began to increase dramatically. It is now the third most important commercial fish species after the Nile perch, Lates niloticus (L.) and Rastrineobola argentea (Pellegrin). Oreochromis niloticus is considered a herbivore, feeding mostly on algae and plant material. The diet now appears to be more diversified , with insects, fish, algae and plant materials all being important food items. Fish smaller than 5 cm TL have a diverse diet but there is a decline in the importance of zooplankton, the preferred food item of small fish, as fish get larger. The shift in diet could be due to changes which have occurred in the lake. Water hyacinth, Eichhornia crassipes (Mart.) Solms, which harbours numerous insects in its root balls, now has extensively coverage over the lake. The native fish species which preyed on these insects (e.g. haplochromines) have largely been eliminated and O. niloticus could be filling niches previously occupied by these cichlids and non cichlid fishes. The change in diet could also be related to food availability and abundance where the fish is feeding on the most readily available food items.

Feeding of larval Cricotopus silvestris F. in relation to characters of structure of oral apparatus [Translation from: C.R.Acad.Sci.USSR.100, 1191-1193, 1955]

Laboratory research was done in order to study the feeding of larval Cricotopus silvestris F. in relation to characters of structure of oral apparatus. Results of the experiments are summarised and the oral apparatus morhologically described.

Mechanics of sediment transport and bedrock erosion in steep landscapes

Erosion is concentrated in steep landscapes such that, despite accounting for only a small fraction of Earth’s total surface area, these areas regulate the flux of sediment to downstream basins, and their rugged morphology records transient changes (or lack thereof) in geologic and climatic forcing. Steep landscapes are geomorphically active; large sediment fluxes and rapid landscape evolution rates can create or destroy habitat for humans and wildlife alike, and landslides, debris flows, and floods common in mountainous areas represent a persistent natural and structural hazard. Despite the central role that steep landscapes play in the geosciences and in landscape management, the processes controlling their evolution have been poorly studied compared to lower-gradient areas. This thesis focuses on the basic mechanics of sediment transport and bedrock incision in steep landscapes, as these are the fundamental processes which set the pace and style of landscape evolution. Chapter 1 examines the spatial distribution of slow-moving landslides; these landslides can dominate sediment fluxes to river networks, but the controls on their occurrence are poorly understood. Using a case-study along the San Andreas Fault, California, I show that slow-moving landslides preferentially occur near the fault, suggesting a rock-strength control on landslide distribution. Chapter 2 provides the first field-measurements of incipient sediment motion in streams steeper than 14% and shows a large influence of slope-dependent flow hydraulics and grain-scale roughness on particle motion. Chapter 3 presents experimental evidence for bedrock erosion by suspended sediment, suggesting that, in contrast to prevailing theoretical predictions, suspension-regime transport in steep streams can be the dominant erosion agent. Steep streams are often characterized by the presence of waterfalls and bedrock steps which can have locally high rates of erosion; Chapters 4 and 5 present newly developed, experimentally validated theory on sediment transport through and bedrock erosion in waterfall plunge pools. Finally, Chapter 6 explores the formation of a bedrock slot canyon where interactions between sediment transport and bedrock incision lead to the formation of upstream-propagating bedrock step-pools and waterfalls.

Microoptical research in Shanghai Institute of Optics and Fine Mechanics

This paper summarized the recent research results of Changhe Zhou's group of Information Optics Lab in Shanghai Institute of Optics and Fine Mechanics (SIOM). The first is about the Talbot self-imaging research. We have found the symmetry rule, the regular-rearranged neighboring phase difference rule and the prime-number decamping rule, which is briefly summarized in a recent educational publication of Optics and Photonics News, pp.46-50, November 2004. The second is about four novel microoptical gratings designed and fabricated in SIOM. The third is about the design and fabrication of novel supperresolution phase plates for beam shaping and possible use in optical storage. The fourth is to develop novel femtosecond laser information processing techniques by incorporating microoptical elements, for example, use of a pair of reflective Dammann gratings for splitting the femtosecond laser pulses. The most attractive feature of this approach is that the conventional beam splitter is avoided. The conventional beam splitter would introduce the unequal dispersion due to the broadband spectrum of ultrashort laser pulses, which will affect the splitting result. We implemented the Dammann splitting apparatus by using two-layered reflective Dammann gratings, which generates the almost same array without angular dispersion. We believe that our device is highly interesting for splitting femtosecond laser pulses.

Particle fluid mechanics in shear flows, acoustic waves, and shock waves

Three different categories of flow problems of a fluid containing small particles are being considered here. They are: (i) a fluid containing small, non-reacting particles (Parts I and II); (ii) a fluid containing reacting particles (Parts III and IV); and (iii) a fluid containing particles of two distinct sizes with collisions between two groups of particles (Part V).

Part I

A numerical solution is obtained for a fluid containing small particles flowing over an infinite disc rotating at a constant angular velocity. It is a boundary layer type flow, and the boundary layer thickness for the mixture is estimated. For large Reynolds number, the solution suggests the boundary layer approximation of a fluid-particle mixture by assuming W = W_p. The error introduced is consistent with the Prandtl’s boundary layer approximation. Outside the boundary layer, the flow field has to satisfy the “inviscid equation” in which the viscous stress terms are absent while the drag force between the particle cloud and the fluid is still important. Increase of particle concentration reduces the boundary layer thickness and the amount of mixture being transported outwardly is reduced. A new parameter, β = 1/Ω τ_v, is introduced which is also proportional to μ. The secondary flow of the particle cloud depends very much on β. For small values of β, the particle cloud velocity attains its maximum value on the surface of the disc, and for infinitely large values of β, both the radial and axial particle velocity components vanish on the surface of the disc.

Part II

The “inviscid” equation for a gas-particle mixture is linearized to describe the flow over a wavy wall. Corresponding to the Prandtl-Glauert equation for pure gas, a fourth order partial differential equation in terms of the velocity potential ϕ is obtained for the mixture. The solution is obtained for the flow over a periodic wavy wall. For equilibrium flows where λ_v and λ_T approach zero and frozen flows in which λ_v and λ_T become infinitely large, the flow problem is basically similar to that obtained by Ackeret for a pure gas. For finite values of λ_v and λ_T, all quantities except v are not in phase with the wavy wall. Thus the drag coefficient C_D is present even in the subsonic case, and similarly, all quantities decay exponentially for supersonic flows. The phase shift and the attenuation factor increase for increasing particle concentration.

Part III

Using the boundary layer approximation, the initial development of the combustion zone between the laminar mixing of two parallel streams of oxidizing agent and small, solid, combustible particles suspended in an inert gas is investigated. For the special case when the two streams are moving at the same speed, a Green’s function exists for the differential equations describing first order gas temperature and oxidizer concentration. Solutions in terms of error functions and exponential integrals are obtained. Reactions occur within a relatively thin region of the order of λ_D. Thus, it seems advantageous in the general study of two-dimensional laminar flame problems to introduce a chemical boundary layer of thickness λ_D within which reactions take place. Outside this chemical boundary layer, the flow field corresponds to the ordinary fluid dynamics without chemical reaction.

Part IV

The shock wave structure in a condensing medium of small liquid droplets suspended in a homogeneous gas-vapor mixture consists of the conventional compressive wave followed by a relaxation region in which the particle cloud and gas mixture attain momentum and thermal equilibrium. Immediately following the compressive wave, the partial pressure corresponding to the vapor concentration in the gas mixture is higher than the vapor pressure of the liquid droplets and condensation sets in. Farther downstream of the shock, evaporation appears when the particle temperature is raised by the hot surrounding gas mixture. The thickness of the condensation region depends very much on the latent heat. For relatively high latent heat, the condensation zone is small compared with Ʌ_D.

For solid particles suspended initially in an inert gas, the relaxation zone immediately following the compression wave consists of a region where the particle temperature is first being raised to its melting point. When the particles are totally melted as the particle temperature is further increased, evaporation of the particles also plays a role.

The equilibrium condition downstream of the shock can be calculated and is independent of the model of the particle-gas mixture interaction.

Part V

For a gas containing particles of two distinct sizes and satisfying certain conditions, momentum transfer due to collisions between the two groups of particles can be taken into consideration using the classical elastic spherical ball model. Both in the relatively simple problem of normal shock wave and the perturbation solutions for the nozzle flow, the transfer of momentum due to collisions which decreases the velocity difference between the two groups of particles is clearly demonstrated. The difference in temperature as compared with the collisionless case is quite negligible.

Mechanics of deformable glacier beds

My focus in this thesis is to contribute to a more thorough understanding of the mechanics of ice and deformable glacier beds. Glaciers flow under their own weight through a combination of deformation within the ice column and basal slip, which involves both sliding along and deformation within the bed. Deformable beds, which are made up of unfrozen sediment, are prevalent in nature and are often the primary contributors to ice flow wherever they are found. Their granular nature imbues them with unique mechanical properties that depend on the granular structure and hydrological properties of the bed. Despite their importance for understanding glacier flow and the response of glaciers to changing climate, the mechanics of deformable glacier beds are not well understood.

Our general approach to understanding the mechanics of bed deformation and their effect on glacier flow is to acquire synoptic observations of ice surface velocities and their changes over time and to use those observations to infer the mechanical properties of the bed. We focus on areas where changes in ice flow over time are due to known environmental forcings and where the processes of interest are largely isolated from other effects. To make this approach viable, we further develop observational methods that involve the use of mapping radar systems. Chapters 2 and 5 focus largely on the development of these methods and analysis of results from ice caps in central Iceland and an ice stream in West Antarctica. In Chapter 3, we use these observations to constrain numerical ice flow models in order to study the mechanics of the bed and the ice itself. We show that the bed in an Iceland ice cap deforms plastically and we derive an original mechanistic model of ice flow over plastically deforming beds that incorporates changes in bed strength caused by meltwater flux from the surface. Expanding on this work in Chapter 4, we develop a more detailed mechanistic model for till-covered beds that helps explain the mechanisms that cause some glaciers to surge quasi-periodically. In Antarctica, we observe and analyze the mechanisms that allow ocean tidal variations to modulate ice stream flow tens of kilometers inland. We find that the ice stream margins are significantly weakened immediately upstream of the area where ice begins to float and that this weakening likely allows changes in stress over the floating ice to propagate through the ice column.

I. Quantum mechanics of one-dimensional two-particle models. II. A quantum mechanical treatment of inelastic collisions

Part I

Solutions of Schrödinger’s equation for system of two particles bound in various stationary one-dimensional potential wells and repelling each other with a Coulomb force are obtained by the method of finite differences. The general properties of such systems are worked out in detail for the case of two electrons in an infinite square well. For small well widths (1-10 a.u.) the energy levels lie above those of the noninteresting particle model by as much as a factor of 4, although excitation energies are only half again as great. The analytical form of the solutions is obtained and it is shown that every eigenstate is doubly degenerate due to the “pathological” nature of the one-dimensional Coulomb potential. This degeneracy is verified numerically by the finite-difference method. The properties of the square-well system are compared with those of the free-electron and hard-sphere models; perturbation and variational treatments are also carried out using the hard-sphere Hamiltonian as a zeroth-order approximation. The lowest several finite-difference eigenvalues converge from below with decreasing mesh size to energies below those of the “best” linear variational function consisting of hard-sphere eigenfunctions. The finite-difference solutions in general yield expectation values and matrix elements as accurate as those obtained using the “best” variational function.

The system of two electrons in a parabolic well is also treated by finite differences. In this system it is possible to separate the center-of-mass motion and hence to effect a considerable numerical simplification. It is shown that the pathological one-dimensional Coulomb potential gives rise to doubly degenerate eigenstates for the parabolic well in exactly the same manner as for the infinite square well.

Part II

A general method of treating inelastic collisions quantum mechanically is developed and applied to several one-dimensional models. The formalism is first developed for nonreactive “vibrational” excitations of a bound system by an incident free particle. It is then extended to treat simple exchange reactions of the form A + BC →AB + C. The method consists essentially of finding a set of linearly independent solutions of the Schrödinger equation such that each solution of the set satisfies a distinct, yet arbitrary boundary condition specified in the asymptotic region. These linearly independent solutions are then combined to form a total scattering wavefunction having the correct asymptotic form. The method of finite differences is used to determine the linearly independent functions.

The theory is applied to the impulsive collision of a free particle with a particle bound in (1) an infinite square well and (2) a parabolic well. Calculated transition probabilities agree well with previously obtained values.

Several models for the exchange reaction involving three identical particles are also treated: (1) infinite-square-well potential surface, in which all three particles interact as hard spheres and each two-particle subsystem (i.e. BC and AB) is bound by an attractive infinite-square-well potential; (2) truncated parabolic potential surface, in which the two-particle subsystems are bound by a harmonic oscillator potential which becomes infinite for interparticle separations greater than a certain value; (3) parabolic (untruncated) surface. Although there are no published values with which to compare our reaction probabilities, several independent checks on internal consistency indicate that the results are reliable.