Academic literature on the topic 'Mole Concept'

En 1969, une septieme unite de base est ajoutee au systeme international d'unites de mesure: la mole est l'unite de quantite de matiere. Cette grandeur, introduite sans bruit, n'est pas encore passee dans les habitudes scientifiques. D'ou procede la creation d'une nouvelle grandeur? a quelles exigences repond la definition d'une unite de mesure pour les chimistes? on montre que l'invention de cette notion se situe a la croisee de trois histoires independantes. Elle implique d'abord la notion de poids atomique issue de la chimie du xixe siecle. Ce nombre proportionnel, relatif a une reference conventionnelle, est une carateristique strictement individuelle qui definit l'identite de chaque element. La molecule-gramme ("mole" en abrege), fut introduite dans la chimie physique a la fin du xixe siecle. Elle associe le poids moleculaire a une unite de masse. Elle fonctionne comme une "jauge" chimique et permet d'exprimer des lois generales en nombre de moles. Ainsi pas plus que les chimistes, les physico-chimistes ne definissaient la dimension de la grandeur qu'ils mesuraient. Cependant, grace a la theorie cinetique des gaz, les physiciens referent la molecule-gramme au nombre de molecules contenues dans un volume donne, bref au nombre d'avogadro. La definition de la mole resulte donc avant tout d'une volonte d'harmonisation entre les mesures des physiciens et des chimistes qui s'est concretisee par l'adoption d'une echelle commune de poids atomiques fondee sur l'isotope 12 du carbone. Cette premiere tentative de standardisation ne fut cependant que le prelude a une reflexion metrologique approfondie sur la nature et la dimension de la grandeur mesuree en chimie, menee conjointement par les unions internationales de chimie et de physique. Chimie, physique, metrologie, ces trois disciplines concourent a la definition actuelle de la mole. D'ou la complexite de cette notion de base qui tresse trois logiques distinctes. D'ou l'originalite de son histoire car l'acte fondateurde l'unite de mesure des chimistes ne constitue pas une solution triomphale qui perimerait les concepts anterieurs.

ABSTRACT THE EFFECT OF EXPLICIT METHOD OF PROBLEM SOLVING ACCOMPANIED WITH ANALOGIES ON UNDERSTANDING OF MOLE CONCEPT &Uuml<br>NL&Uuml<br>, Yal&ccedil<br>in M.S., Department of Secondary Science and Mathematics Education Supervisor: Prof. Dr. &Ouml<br>mer GEBAN September 2006, 56 pages The aim of this thesis was to analyse the effectiveness of explicit method of problem solving accompanied with analogy instruction over traditionally designed chemistry introduction on understanding of mole concept and attitude toward chemistry as a school subject. Participants for this research consisted of 53 students at ninth grade level from two classes taught by the same teacher in Atat&uuml<br>rk Anadolu Lycee. The study was carried out during the second semester in the 2004-2005 school year. During the treatment, students in the experimental group were instructed with explicit method of problem solving accompanied with analogies. Students in the control group studied only with traditionally designed chemistry instruction. Both groups were administered Mole Concept Achievement Test and Attitude Scale toward Chemistry as a School Subject as pre-tests and post-tests. To analyse the data, statistical techniques paired samples t-test and independent samples t-test were used in this study. Statistical analyses were carried out by using the SPSS 10.0. Results of the study showed that explicit method of problem solving accompanied with analogy instruction caused a significantly better acquisition of scientific conception related to mole concept but produced no significant positive attitudes toward chemistry as a school subject than the traditionally designed chemistry instruction.

Um fato verificado pelos professores ligados à área de educação química é que o conceito de mol, de fundamental importância para o ensino de química, constitui um obstáculo de aprendizagem, visto que os alunos de ensino médio sentem considerável dificuldade em seu aprendizado, pois o referido conceito requer conhecimentos básicos nem sempre bem definidos na estrutura cognitiva dos estudantes. Para atenuar este problema, foi desenvolvido um software, na forma de jogo didático, baseado nas dificuldades relatadas em entrevistas com professores e alunos e fundamentado na teoria da atividade de Leontiev. O objetivo deste trabalho foi investigar se este recurso auxilia como mediador na aprendizagem do conceito de mol. O jogo é composto de três fases, das quais duas exploram conceitos matemáticos básicos como reconhecimento de fórmulas, cálculos envolvendo potências e relações proporcionais e a terceira fase aborda o conceito de mol propriamente dito. Estudantes do ensino médio utilizaram o software e os dados coletados foram analisados levando-se em conta os testes escritos respondidos pelos alunos e suas ações durante o jogo. Os resultados obtidos, as observações realizadas durante a aplicação do jogo e os comentários dos participantes indicam claramente que o software foi eficaz e motivador, tendo em seu corpo o aspecto lúdico e o educativo, e que contribuiu na aprendizagem do conceito em questão.<br>A fact verified by teachers involved with Chemistry education is that the concept of mol, extremely important to the teaching of chemistry, makes up an obstacle to the learning process since the referred concept requires some basic knowledge which is not always so well defined in the students\' cognitive structure. In order to attenuate this problem, a software was developed based on the difficulties arisen in the interviews with teachers and students and supported by Leontiev\'s theory of activity. The objective of this paper is to investigate whether this resource could help as a mediator in the learning of mol concept. The game comprises three stages, two of which exploit basic math concepts such as recognizing formulas, calculations involving powers and proportional relations whereas the third one really approaches the concept of mol. Secondary school students made use of the software and the data was collected and analyzed from both the students\' written answers to the tests as well as their actions during the game. The results obtained, the observations made during the game and the comments of the participants clearly point out that the software is effective and motivational, showing also its educative and ludic aspects, which contributed to the learning of the said concept.

Switch mode power supplies are widely used in different applications. High efficiency and high power density are two driving forces for power supply systems. However, high dv/dt and di/dt in switch mode power supplies will cause severe EMI noise issue. In a typical front-end converter, the EMI filter usually occupies 1/3 to 1/4 volume of total converter. Hence, reducing the EMI noise of power converter can help reduce the volume of EMI filter and improving the total power density of the converter. For off-line switch mode power supplies, DM noise is dominated by PFC converter. CM noise is a more complicated issue. It is contributed by both PFC converter and DC/DC converter. While many researches have focused on reducing CM noise for PFC converter, the CM noise of DC/DC converter still remains a challenge. The main objective of this thesis is provide a solution to have best CM noise reduction for DC/DC converters. The shielding concept and balance concept are combined to propose a novel balance double shielding technique. This method can have an effective CM noise reduction in the circuit level. In addition it is easy to design and implement in the real production. The balance condition is easily controlled and guarantees effective CM noise reduction in mass production. Then, a novel one-layer shielding method for PCB winding transformer is provided. This shielding technique can block CM noise from primary side and also cancel the CM noise from secondary side. In addition, shielding does not increase the loss of converter too much. Furthermore, this shielding technique can be applied to matrix transformer structure. For matrix transformer LLC converter, the inter-winding capacitor is very large and will cause severe CM noise problem. By adding shielding layer, CM noise has been greatly reduced. In addition, by modifying the secondary winding, the loss on shielding layer is minimized and experiments show that the total efficiency of converter has almost no impact. Furthermore, although this thesis uses flyback and LLC resonant converter as example to demonstrate the concept, the novel shielding technique can also be applied to other topologies that have similar transformer structure.<br>Master of Science

Characteristic modes (CMs) provide deep insight into the electromagnetic behaviour of any arbitrarily shaped conducting structure because the CMs are unique to the geometry of the object. We exploit this very fact by predicting a perhaps surprising number of important antenna metrics such as resonance frequency, radiation efficiency and antenna Q (bandwidth) without needing to specify a feeding location. In doing so, it is possible to define a collection of objective functions that can be used in an optimizer to shape-synthesize antennas without needing to define a feed location a priori. We denote this novel form of optimization “feedless” or “excitation-free” antenna shape synthesis. Fundamentally, we are allowing the electromagnetics to dictate how the antenna synthesis should proceed and are in no way imposing the physical constraints enforced by fixed feeding structures. This optimization technique is broadly applied to three major areas of antenna research: electrically small antennas, multi-band antennas and reflectarrays. Thus, the scope of applicability ranges from small antennas, to intermediate sizes and concludes with electrically large antenna designs, which is a testament to the broad applicability of characteristic mode theory. Another advantage of feedless electromagnetic shape synthesis is the ability to synthesize antennas whose desirable properties approach the fundamental limits imposed by electromagnetics. As an additional benefit, the feedless optimization technique is shown to have greater computational efficiency than traditional antenna optimization techniques.

In this thesis we show how characteristic mode (CM) theory can be used to in the design of the antennas with the low envelope correlation coefficients preferred for MIMO antennas. This is due to the fact that the radiated fields of CMs are orthogonal over the radiation sphere. We show how a handheld device structure can be excited at various points (which form the multi-antenna ports) to ensure that each port excites a set of CMs such that the mode indices in each set are different for each antenna. It is this important result which causes the natural orthogonality properties of the CMs to be transferred to the overall radiation patterns of the multiple antennas. The CM analysis we have performed includes the effects of structure losses; it appears to be the first time that the computation of such modes have been reported. A logical and satisfying methodology for MIMO antenna design is the result. The methodology is extended to include arbitrary MIMO scattering environments using polarization sensitive generalized characteristic modes, which is the first of its kind from both the theory and methodology perspective. This design approach for MIMO antennas is not restricted to handheld devices, and can be used in a variety of applications. Lastly we discuss the various port mode theories that yield far-field orthogonality for perfect scattering environments, the application of which has already been discussed in the literature. We show succinctly that physical port symmetry yields frequency insensitive modes, but very minor symmetry breaking yields very narrow low envelope correlation bandwidth, something that is not discussed in the literature, but discussed in detail in this thesis.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2002.<br>Includes bibliographical references (leaves 185-188).<br>In this thesis, a self-consistent model for analyzing the transport performance of a Reversed Field Pinch (RFP)-type of thermonuclear fusion reactor has been developed. The study has been focused on determining equilibrium configurations which describe a plasma evolution dominated by particular instabilities originated by plasma electrical resistivity (tearing-, or resistive interchange, modes). The ultimate goal is to provide a model of transport scaling in an RFP which can evaluate the global parameters describing the plasma confinement performance. Starting from a magnetic field configuration essentially given by Taylor's relaxation model, the self-consistent pressure profile is determined by assuming that the ohmic heating source raises the plasma pressure until the profile is locally marginally stable to tearing modes. A critical point here is the long held belief that an RFP, because of its bad curvature, would always be unstable to tearing or resistive interchange modes; that is, no marginally stable state exists. This belief turns out to be untrue. The basis for this statement is a careful ordering of the resistive layer dynamics, showing that thermal conductivity dominates over convection and compressibility. Thus, the use of the adiabatic equation of state in earlier work is not accurate for an RFP.<br>(cont.) As a result, tearing and interchange modes can indeed be stabilized in an RFP. In this model, a proper, selfconsistent definition of tearing-mode marginality has been used as a prescription for building the pressure profile. The actual numerical determination of the marginally stable profiles can be solved by using state-of-the-art personal computers. It is worth emphasizing that there are no free parameters in the model. Point checks indicate reasonable agreement with typical experimental data. Parametric numerical studies are also shown, spanning the operational space of RFP experiments, and finally providing the tearing mode transport scaling relations for the global confinement parameters. Comparisons with experiments as well as other transport models are shown.<br>by Antonio Bruno.<br>Ph.D.

Data Visualization (DV) can be seen as an important tool for communication and data analysis. Especially when huge amounts of data are involved, visual representation of data can facilitate observation of trends and patterns as well as understanding. Currently, two dimensional displays are mainly used for Data Visualization, both in two and three dimensions (2D and 3D). However, two dimensional displays are limited in terms of 3D visualization because they do not allow for true sense of depth and do not cover the observer’s full Field Of View (FOV). An alternative approach is to use Virtual Reality (VR), which provides an immersive and interactive 3D environment. VR has been mainly used for gaming and simulated training. However, other areas are now emerging because VR technologies became relatively affordable. For example, one possibility is to explore VR for DV and this was the main goal of this project. To accomplish that, a literature study was performed to identify terminologies and definitions, hardware and software technologies, techniques and examples in the fields of DV and VR. In addition, in order to exemplify DV through VR, a prototype system was implemented using Unity 3D, a leading engine for VR. To visualize the developed VR environment, a HTC Vive Head Mounted Display (HMD) was used. The developed prototype system can display data from a local dataset in a scatter plot with three axis in VR. In the virtual environment created by the system, the user can select the attributes in the dataset to be displayed by the 3D scatter plot. Once the data is plotted, the user can use the handheld joystick to move, rotate, tilt and scale the scatter plot. Achieved results indicate immersion and interaction as the main perceived benefits of DV using VR.<br>Datavisualisering (DV) kan ses som ett viktigt verktyg för kommunikation och dataanalys, speciellt när stora mängder data behandlas. Visuell representation kan främja observationen av trender och mönster samt förståelsen av datan. För närvarande används tvådimensionella displayer huvudsakligen för datavisualisering, både i två och tre dimensioner (2D och 3D). Emellertid är tvådimensionella displayer begränsade i 3D-visualisering eftersom de inte möjliggör äkta djupseende, och täcker inte observatörens fulla synfält (Field Of View (FOV)). Ett alternativ tillvägagångssätt är att använda Virtual Reality (VR), vilket tillhandahåller en omslutande och interaktiv 3D-miljö. VR har huvudsakligen används för spel och simulerad träning. Däremot börjar nya användningsområden uppstå då VR teknologin har blivit mer prisvärd. Ett användningsområde är VR för DV, vilket var det huvudsakliga syftet för det här arbetet. För att uppnå syftet utfördes en litteraturstudie för att identifiera teknologier och definitioner, hårdvaru- och mjukvaruteknologier, tekniker och exempel inom området av DV och VR. Dessutom, för att exemplifiera DV genom VR, utvecklades ett prototypsystem. Vilket implementerades genom  Unity 3D, en av de ledande spelmotorerna. För att visualisera den utvecklade VR-miljön användes ett HTC Vive Head Mounted Display (HMD). Den utvecklade prototypen kan visualisera data från ett lokalt dataset genom ett spridningsdiagram med 3 axlar, i VR. I den virtuella miljön som skapas av systemet tillåts användaren att välja attribut från datasetet för att sedan visualisera dessa genom det tredimensionella spridningsdiagrammet. När datan väl är visualiserad, kan användaren använda de handhållna kontrollerna för att flytta, rotera, luta och skala grafen. Uppnådda resultat indikerar på omslutning och interaktion som de huvudsakliga fördelarna av DV genom VR.

Cette thèse est dédiée à l’étude du multiplexage de mode spatiaux, depuis ses fondements conceptuels jusqu’à ses applications techniques. Le convertisseur optique multi-plan (MPLC ou multiplane light converter) développé par CAILabs est au centre de notre étude. Le travail mené durant cette thèse s’est organisé autour de deux axes de travail. Nous avons d’une part étudié comment la manipulation de modes transverses du champ électromagnétique permet la manipulation ou la mesure de paramètres. Nous démontrons que la limite théorique de sensibilité sur la mesure de petits déplacements d’un faisceau lumineux est atteinte en effectuant une mesure d’intensité sur la base des modes de Hermite-Gauss. Cette démonstration vaut également pour la mesure de distance entre deux sources de lumière incohérentes entre elles. Nous avons confirmé expérimentalement la validité de ce résultat en utilisant un système MPLC adéquat. Un système MPLC peut également être construit afin de transférer le contrôle d’un degré de liberté spatial sur un autre. Nous présentons une expérience dans laquelle nous montrons que l’utilisation d’un tel système permet de contrôler la position du point focal d’un faisceau à l’aide du déplacement ou de l’inclinaison transverse du faisceau d’entrée. D’autre part, nous avons effectué une étude numérique et théorique des propriétés de transport du système MPLC à l’aide d’outils issus de la théorie des matrices aléatoires. Notre but est d’identifier les mécanismes physiques qui rentrent en jeu dans cette technique de mise en forme de la lumière<br>This thesis is dedicated to spatial mode multiplexing, from its fundamental concepts to its applications. The work is associated with the multi-plane light converter (MPLC) technology developed by CAILabs. This study is divided into two main parts. First, we investigate the use of independent spatial mode shaping to measure or modify spatial parameters of the electromagnetic field. We make the theoretical demonstration that the best sensitivity for the measurement of small displacements of a beam – or of the distance between two incoherent beams – is reached when an intensity measurement is made on the Hermite-Gaussian mode basis. By building the adequate MPLC system, we make the experimental validation of this result. We also make the demonstration that a MPLC system can be designed and used to transfer the control of one spatial parameter of a beam onto another. We built an experimental setup which allows to control the position of the focal point of a beam using transverse displacement and tilt. The second project we conducted was a theoretical and numerical study of the statistical transport properties of the MPLC using tools from random matrix theory. We aim at identifying the underlying physical processes which make up for the efficiency of this transformation technique