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Drilling is widely used in manufacturing of products which need holes, for example for fluid channels, screws or pins. Depending on application, workpiece material, cutting parameters and economic considerations, different types of drills are employed. Indexable insert drills are types of drills which facilitate inserts to make holes. These types of drills can make high pitch noises due to vibrations. The focus of this thesis is to investigate the mechanism behind these vibrations in order to help reducing the generated noise in the future designs. Primary investigations show that the main mechanism which results the mentioned noise is regenerative chatter vibrations due to axial and torsional flexibilities. There is a gap in modeling of chatter vibrations in indexable drills where loadings and geometries are asymmetrical and due to torsional vibrations, delay terms are variable. The first step of simulating regenerative chatter vibrations in the drill is to model static cutting forces in a reliable way. In this thesis, a model is proposed which is capable of predicting static cutting forces through segmentation of cutting edges. Since, using this model, forces can be calculated separately on each insert, it is possible to consider differences of inserts in estimationof the cutting loads. The obtained loads are used in the chatter simulation.A model is proposed to simulate chatter vibrations by considering axialand angular deflections and the coupling between them. The resulted model isa system of delay differential equations with variable delays. Variations in timedelays, tool jump-outs and backward motions of inserts have been included inthe proposed time-domain simulation. A set of experiments is conducted toverify the model.

The study analyzed activities of Spanish Level 1 textbooks used in high school to determine the extent to which they incorporate some of the most respected theories of communicative language learning, in particular the theories of Krashen, Swain, Long and Nunan. Five well known Spanish books were chosen: Realidades, Exprésate, Así­ se dice, Avancemos, and Aventura. For each book, Chapter 2 and Chapter 5 were chosen to be evaluated by two raters. The activities in these chapters were analyzed according to four criteria derived from the abovementioned theories. Results suggest that textbooks may not be in alignment with major theories of how language is acquired. The majority of the activities may fall under the category of meaningless drills, which it is claimed do not contribute to acquisition of a second language.

Thesis (M.Sc.(Engineering)--University of the Witwatersrand, 1990.

Typescript (photocopy). / Digitized by Kansas Correctional Industries / Department: Music.

本研究旨在探討英語歌曲練習文法和機械式練習文法對學生文法學習和記憶保留的成效。主要目標欲探究(1)兩種文法練習方法對於文法學習的成效；(2) 兩種文法練習方法對記憶保留的成效；以及(3)兩種文法練習方法對於高、低成就學習者在文法學習和記憶保留的影響。 研究對象為台灣中部一所公立國中兩班七年級的學生。此均質的兩個班被隨機指定為實驗組與控制組。實驗組於教授文法後施予英語歌曲練習文法，而控制組則施予傳統機械式練習文法。歷時十一週的文法教學後，兩組受試者接受文法測驗(EGT)，以得知兩組受試者文法學習情況。一個月後，兩組受試者再次接受相同文法測驗，以進一步得知其文法的記憶保留情形。本研究主要發現如下：(1)在文法學習成效方面，接受英語歌曲練習文法的實驗組學生表現顯著優於接受機械式文法練習的控制組學生。(2)在記憶保留方面，接受英語歌曲練習文法的實驗組學生表現顯著優於接受機械式文法練習的控制組學生。(3)利用英語歌曲練習文法對於高、低英語學習成就者而言，在文法學習和記憶保留上皆有正面影響。 (4)透過機械式文法練習亦有助於提升高、低英語學習成就者，在文法學習和記憶保留的成效。(5)對於高英語學習成就者而言，利用英語歌曲練習文法和透過機械式練習文法兩者對於其文法學習和記憶保留成效相同。(6)對於低英語高學習成就者而言，利用英語歌曲練習文法在文法學習和記憶保留的成效皆優於透過機械式文法練習。 最後，研究者對於英語歌曲在文法教學上之應用提供建議以作為教育學者們的參考。 / The study investigated the effects of “grammar practice through drills plus English songs” versus the effects of “grammar practice through drills” on students’ grammar learning and retention of grammar points. The study aims to (1) investigate the effects of these two kinds of grammar practices on grammar learning; (2) explore the effects of these two kinds of grammar practices on retention of grammar points; and (3) evaluate the effects of these two kinds of grammar practices on grammar learning and retention of grammar points for high and low English achievers. Participants were two intact classes of seventh-grade students in a public junior high school in central Taiwan. With the homogeneity of English proficiency, the two classes were randomly assigned as the experimental and control groups. The former received “grammar practice through drills plus English songs”, while the latter received “grammar practice through drills.” After receiving an eleven-week instruction, both groups received English Grammar Test (EGT), to assess their grammar learning. One month after EGT, the same grammar test—EGT were conducted to both groups to assess their retention of grammar points. The major findings are summarized as follows. (1) In terms of grammar learning, students receiving “grammar practice through drills plus English songs” outperformed those receiving “grammar practice through drills.” (2) In terms of retention of grammar points, “grammar practice through drills plus English songs” had a more positive influence than “grammar practice through drills.” (3) “Grammar practice through drills plus English songs” possessed a facilitative effect for both high and low English achievers with regard to grammar learning and retention of grammar points. (4) “Grammar practice through drills” benefited both high and low English achievers. (5) “Grammar practice through drills plus English songs” and “grammar practice through drills ” could enhance high English achievers’ grammar learning and retention of grammar points. (6) “Grammar practice through drills plus English songs” exerted a superior effectiveness on low English achievers’ grammar learning and retention of grammar points. Pedagogical implications based on the findings were also provided.

This thesis deals with the design and subsequent realization of a bicameral tester for cordless drills. The tester will contain with two chambers in which the device will be tested. Part of the solution is the description of the parameters of the tested devices and the design of the tester concept. In addition, the thesis deals with the design of a mechanical structure that will test the equipment in both chambers and then design and realization of the relevant electrical equipment including the electrical switchboard. The thesis describes the Mosaic development environment for development of the PLC program according to IEC 61131-3. In this environment, control software has been created, which is described in its chapter. At the end of this work are enclosed images confirming the implementation to the real system and its functionality

This thesis is focused on cutting tools made of cemented carbides. It contains analysis of cemented carbides for uncoated and coated cutting tools. It contains examples of modern tools for turning, milling and drilling. Practical part of this thesis evaluates and compares cutting properties of two types of spiral drills.

This master´s thesis is focused on fibre–filled composite materials, their distribution, labeling, usage, development and production. The aim of this work is complex processing of acquired technical knowledge, and evaluation of technological rehearsals of drilling composite materials which are reinforced by glas fiber and prepreg in terms of the impact of the machined material, wor-king conditions and the tool, and its wear to the feed force value and torque.