Basic equations for ferroelectrics

A set of new formula of energy functions for ferroelectrics was proposed, and then the new basic equations were derived in this paper. The finite element formulation based on the new basic equations was improved to avoid the equivalent nodal load produced by remnant polarization. With regard to the fundamentals of mathematics and physics, the new energy functions and basic equations are reasonable for the material element of ferroelectrics in finite element analysis.

DNS and LES of turbulent channel flow with hydrophobic surface

Hydrophobic surface benefits for drag reduction. Min and Kim[1] do the first Direct Numerical Simulation on drag reduction in turbulent channel flow. And Fukagata and Kasagi[2] make some theoretical analysis based on Dean[3]'s formula and some observations in the DNS results. Using their theory, they conclude that drag reduction is possible in large Reynolds number. Both Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) are performed in our research. How the LES behaving in the turbulent channel flow with hydrophobic surface is examined. Original Smagorinsky model and its Dynamical model are used in LES. The slip velocities predicted by LES using Dynamical model are in good agreement with DNS as shown in the Figure. Although the percentage of drag reduction predicted by LES shows some discrepancies, it is in the error limit for industrial flow. First order and second order moments of LES are also examined and compared with DNS's results. The first-order moments is calculated well by LES. But there are some discrepancies of second-order moments between LES and DNS. [GRAPHICS]

Invariant-free deduction systems for temporal logic

In this thesis we propose a new approach to deduction methods for temporal logic. Our proposal is based on an inductive definition of eventualities that is different from the usual one. On the basis of this non-customary inductive definition for eventualities, we first provide dual systems of tableaux and sequents for Propositional Linear-time Temporal Logic (PLTL). Then, we adapt the deductive approach introduced by means of these dual tableau and sequent systems to the resolution framework and we present a clausal temporal resolution method for PLTL. Finally, we make use of this new clausal temporal resolution method for establishing logical foundations for declarative temporal logic programming languages. The key element in the deduction systems for temporal logic is to deal with eventualities and hidden invariants that may prevent the fulfillment of eventualities. Different ways of addressing this issue can be found in the works on deduction systems for temporal logic. Traditional tableau systems for temporal logic generate an auxiliary graph in a first pass.Then, in a second pass, unsatisfiable nodes are pruned. In particular, the second pass must check whether the eventualities are fulfilled. The one-pass tableau calculus introduced by S. Schwendimann requires an additional handling of information in order to detect cyclic branches that contain unfulfilled eventualities. Regarding traditional sequent calculi for temporal logic, the issue of eventualities and hidden invariants is tackled by making use of a kind of inference rules (mainly, invariant-based rules or infinitary rules) that complicates their automation. A remarkable consequence of using either a two-pass approach based on auxiliary graphs or aone-pass approach that requires an additional handling of information in the tableau framework, and either invariant-based rules or infinitary rules in the sequent framework, is that temporal logic fails to carry out the classical correspondence between tableaux and sequents. In this thesis, we first provide a one-pass tableau method TTM that instead of a graph obtains a cyclic tree to decide whether a set of PLTL-formulas is satisfiable. In TTM tableaux are classical-like. For unsatisfiable sets of formulas, TTM produces tableaux whose leaves contain a formula and its negation. In the case of satisfiable sets of formulas, TTM builds tableaux where each fully expanded open branch characterizes a collection of models for the set of formulas in the root. The tableau method TTM is complete and yields a decision procedure for PLTL. This tableau method is directly associated to a one-sided sequent calculus called TTC. Since TTM is free from all the structural rules that hinder the mechanization of deduction, e.g. weakening and contraction, then the resulting sequent calculus TTC is also free from this kind of structural rules. In particular, TTC is free of any kind of cut, including invariant-based cut. From the deduction system TTC, we obtain a two-sided sequent calculus GTC that preserves all these good freeness properties and is finitary, sound and complete for PLTL. Therefore, we show that the classical correspondence between tableaux and sequent calculi can be extended to temporal logic. The most fruitful approach in the literature on resolution methods for temporal logic, which was started with the seminal paper of M. Fisher, deals with PLTL and requires to generate invariants for performing resolution on eventualities. In this thesis, we present a new approach to resolution for PLTL. The main novelty of our approach is that we do not generate invariants for performing resolution on eventualities. Our method is based on the dual methods of tableaux and sequents for PLTL mentioned above. Our resolution method involves translation into a clausal normal form that is a direct extension of classical CNF. We first show that any PLTL-formula can be transformed into this clausal normal form. Then, we present our temporal resolution method, called TRS-resolution, that extends classical propositional resolution. Finally, we prove that TRS-resolution is sound and complete. In fact, it finishes for any input formula deciding its satisfiability, hence it gives rise to a new decision procedure for PLTL. In the field of temporal logic programming, the declarative proposals that provide a completeness result do not allow eventualities, whereas the proposals that follow the imperative future approach either restrict the use of eventualities or deal with them by calculating an upper bound based on the small model property for PLTL. In the latter, when the length of a derivation reaches the upper bound, the derivation is given up and backtracking is used to try another possible derivation. In this thesis we present a declarative propositional temporal logic programming language, called TeDiLog, that is a combination of the temporal and disjunctive paradigms in Logic Programming. We establish the logical foundations of our proposal by formally defining operational and logical semantics for TeDiLog and by proving their equivalence. Since TeDiLog is, syntactically, a sublanguage of PLTL, the logical semantics of TeDiLog is supported by PLTL logical consequence. The operational semantics of TeDiLog is based on TRS-resolution. TeDiLog allows both eventualities and always-formulas to occur in clause heads and also in clause bodies. To the best of our knowledge, TeDiLog is the first declarative temporal logic programming language that achieves this high degree of expressiveness. Since the tableau method presented in this thesis is able to detect that the fulfillment of an eventuality is prevented by a hidden invariant without checking for it by means of an extra process, since our finitary sequent calculi do not include invariant-based rules and since our resolution method dispenses with invariant generation, we say that our deduction methods are invariant-free.

Mikroblogintza tekniken erabilera programazioan sortzen diren zalantzak ebazteko

Gaur egun Twitter moduko mikroblogintza aplikazioak zalantzak argitzeko gero eta gehiago erabiltzen dira. Erabiltzaileak laguntza eskaera adierazi eta sare sozialaren bidez bere kontaktuei helarazi egiten zaie. Erabiltzaileak galdera eta erantzunen kudeaketa sare sozial nahaste baten barruan egin beharko du. Proiektuaren helburu nagusia mikroblogintza plataformetako kanala programazio lengoaien IDEen barruan bateratzea da, modu honetan laguntza eskatzeko prozesua IDEetan bertan kudeatzeko.

La poesía bucólica en época de Nerón : lectura virgiliana, ideología senequiana y propaganda imperial

[ES] Durante los pocos años del gobierno de Nerón la poesía bucólica latina experimenta un auge anormal y desarrolla una función propagandística particularmente clara. En este artículo se trata de reconstruir, a partir de textos que hasta ahora no se habían implicado debidamente en la cuestión (cuarta égloga de Virgilio, Apocolocyntosis de Séneca, etc.), las motivaciones inmediatas de este resurgir del género: la poesía bucólica de la época responde en parte a una invitación expresa que Séneca formula en un pasaje de su Apocolocyntosis donde, además, se impone como modelo la égloga cuarta de Virgilio, que proporciona símbolos congruentes con la ideología filohelena de la corte de Nerón y conlleva la identificación entre Augusto y Nerón.

Guidelines for reducing porpoise mortality in tuna purse seining

More than a decade has passed since the passage of the Marine Mammal Protection Act of 1972. During that time the U.S. tuna purse seine neet reduced its incidental porpoise mortality rate more than 10-fold. This was made possible through the development of gear and techniques aimed at reducing the frequency of many low probability events that contribute to the kill. Porpoise are killed by becoming entangled or entrapped in folds and canopies of the net and suffocating. The configuration of the net, both before and during the backdown release procedure, is a major determinant of the number of porpoise killed. Speedboats can be used to tow on the corkllne to prevent net collapse and also to adjust the net configuration to reduce net canopies prior to backdown. Deepening a net can reduce the probability of porpoise being killed by prebackdown net collapse. The effects of environmental conditions and mechanical failures on net configuration can result in high porpoise mortality unless mitigated by skilled vessel maneuvers or prevented by the timely use of speedboats to adjust the net. The backdown procedure is the only means to effectively release captured porpoise from a purse seine. It is also the time during the set when most of the mortality occurs. The use of small mesh safety panels and aprons in the backdown areas of nets reduces porpoise entanglement, and Increases the probability of an effective release. The tie-down points on the net for preparing the backdown channel must be properly located in order to optimize porpoise release. A formula uses the stretched depth of the net to calculate one of these points, making it a simple matter to locate the other. Understanding the dynamics of the backdown procedure permits a thorough troubleshooting of performance, thus preventing the repetition of poorly executed backdowns and thereby reducing mortality. Porpoise that cannot be released must be rescued by hand. A rescuer in a rigidly inflated raft can rescue porpoise effectively at any time during a net set. Hand rescue can make the difference between above average kill and zero kill sets. In all circumstances, the skill and motivation of the captain and his crew are the final determinants in the prevention of incidental porpoise mortality in tuna seining. (PDF file contains 22 pages.)

Black Holes, Cosmological Solutions, Future Singularities, and Their Thermodynamical Properties in Modified Gravity Theorie

54 p.

Studies on the nutrition of brackish water catfish - Chrysichthys nigrodigitatus . 1. Preliminary investigations on the probable use of vegetable oil in catfish feeds

Four groups of brackishwater catfish were fed four diets: N.F. (NIOMR formula 1 feed), A. B. and C. for seven weeks. Feeds N.F., A., B and C. contained 1.21% fish oil + 5.59% vegetable oil; 1.21% fish oil + 7.39% vegetable oil; 1.21% fish oil + 9.09% vegetable oil; 1.21% fish oil + 10.89% vegetable oil respectively. Results of feeding trial showed that growth was best in the group fed diets containing 10.89% vegetable oil and least in those containing 9.09% vegetable oil

关于Gurney公式的强度效应修正

为了使Gurney公式能够在考虑材料强度的前提下预测爆轰驱动速度,采用量纲分析的方法,分析了影响柱壳爆轰驱动的主要因素,建立了抛射速度与主要物理量的函教关系.此函数关系经分离变量后,分别通过理论分析和数值仿真予以确定.分析表明,随着屈服应力的提高,壳体的径向极限速度下降,断裂时间提前.柱壳爆轰驱动的强度效应不容忽略.利用炸药爆速、炸药与柱壳的质量比、柱壳材料的屈服强度和密度等参数,通过拟合公式能够预测柱壳爆轰驱动的极限膨胀速度.

Nigerian fisheries development, challenges and opportunities of the 1980's

With the momentum generated in Nigeria under the Green Revolution Programme to make the country self-sufficient in food, the fishing industry is poised for very rapid development. It is however, realized that there is no quick magic formula for this development, which has to be preceded by careful planning, evaluation of resources, development of necessary management and technical personnel, introduction of appropriate technology and identification of priorities and the needs of the industry. This paper attempts to focus attention on the possibilities and priorities for the development of fisheries in Nigeria during this decade and spells out the role of the agencies in the country connected with fisheries to bring about this development

Two-dimensional Vortex-induced Vibrations of Submerged Floating Tunnel Tethers

A vortex-induced vibration (VIV) model is presented for predicting the nonlinear dynamic response of submerged floating tunnel (SFT) tethers which are subjected to wave, current and tunnel oscillatory displacements at their upper end in horizontal and vertical directions. A nonlinear fluid force formula is introduced in this model, and the effect of the nonlinearity of tether is investigated. First, the tunnel is stationary and the tether vibrates due to the vortices shedding. The calculated results show that the cross-flow amplitude of VIV decreases compared with the linear model. However the in-line amplitude of VIV increases. Next, the periodical oscillation of tunnel is considered. The oscillation caused by wave forces plays the roles of parametric exciter and forcing exciter to the VIV of tether. The time history of displacement of the tether mid-span is obtained by the proposed model. It is shown that the in-line amplitude increases obviously and the corresponding frequency is changed. The cross-flow amplitude exhibits a periodic behavior.

Diffraction integral formulas of the pulsed wave field in the temporal domain

To resolve the diffraction problems of the pulsed wave field directly in the temporal domain, we extend the Rayleigh diffraction integrals to the temporal domain and then discuss the approximation condition of this diffraction formula. (C) 1997 Optical Society of America.

Diagonal forms, linear algebraic methods and Ramsey-type problems

This thesis focuses mainly on linear algebraic aspects of combinatorics. Let N_t(H) be an incidence matrix with edges versus all subhypergraphs of a complete hypergraph that are isomorphic to H. Richard M. Wilson and the author find the general formula for the Smith normal form or diagonal form of N_t(H) for all simple graphs H and for a very general class of t-uniform hypergraphs H.

As a continuation, the author determines the formula for diagonal forms of integer matrices obtained from other combinatorial structures, including incidence matrices for subgraphs of a complete bipartite graph and inclusion matrices for multisets.

One major application of diagonal forms is in zero-sum Ramsey theory. For instance, Caro's results in zero-sum Ramsey numbers for graphs and Caro and Yuster's results in zero-sum bipartite Ramsey numbers can be reproduced. These results are further generalized to t-uniform hypergraphs. Other applications include signed bipartite graph designs.

Research results on some other problems are also included in this thesis, such as a Ramsey-type problem on equipartitions, Hartman's conjecture on large sets of designs and a matroid theory problem proposed by Welsh.

估算等离子体效应对类氢离子束缚态能级能量影响的新公式

在均匀电子气模型下，通过求解Dirac方程，计算了类氢离子束缚态能级能量与等离子体密度的关系，得到了能近似估算能级能量随等离子体密度变化的新拟合公式，该公式同样可以用以估算不同束缚态能级发生压致电离时的临界电子密度．通过与自洽场离子球模型计算结果的比较，作为一种简单和快捷的计算方法，均匀电子汽模型在近似计算束缚态能级能量及压致电离临界电子密度方面是自洽场离子球模型得很好近似方法．

The deuteron-deuteron reaction and the stopping cross section of D_2O ice below 600 kev

The energy loss of protons and deuterons in D_2O ice has been measured over the energy range, E_p 18 - 541 kev. The double focusing magnetic spectrometer was used to measure the energy of the particles after they had traversed a known thickness of the ice target. One method of measurement is used to determine relative values of the stopping cross section as a function of energy; another method measures absolute values. The results are in very good agreement with the values calculated from Bethe’s semi-empirical formula. Possible sources of error are considered and the accuracy of the measurements is estimated to be ± 4%.

The D(dp)H^3 cross section has been measured by two methods. For E_D = 200 - 500 kev the spectrometer was used to obtain the momentum spectrum of the protons and tritons. From the yield and stopping cross section the reaction cross section at 90° has been obtained.

For E_D = 35 – 550 kev the proton yield from a thick target was differentiated to obtain the cross section. Both thin and thick target methods were used to measure the yield at each of ten angles. The angular distribution is expressed in terms of a Legendre polynomial expansion. The various sources of experimental error are considered in detail, and the probable error of the cross section measurements is estimated to be ± 5%.