Yes / An approximation to the Phan-Thien Tanner (PTT) constitutive model is developed with the aim of giving low-cost simulation of Gas Assisted Injection Moulding (GAIM) while incorporating important viscoelastic characteristics. It is shown that the developed model gives a response typical of full viscoelastic models in transient and steady state uniaxial and constant shear rate deformations. The model is incorporated into a 3D finite element GAIM simulation which uses the ‘pseudo-concentration’ method to predict residual polymer, and applied to published experimental results for a Boger fluid and a shear-thinning polystyrene melt. It is shown that the simulation gives a very good match to published results for the Boger fluid which show increasing Residual Wall Thickness (RWT) with increasing Deborah number. Against the shear-thinning polymer, the quality of match depends upon which of two ‘plausible’ relaxation times is chosen; qualitatively different results arise from two different means of estimating a single relaxation time. A ‘multi-mode’ approach is developed to avoid this uncertainty. It is shown that the multi-mode approach gives decreasing RWT with increasing Deborah number in agreement with the published experimental results, and avoids the issues that arise from estimating a single relaxation time for a molten polymer.

O objetivo deste trabalho é desenvolver um método numérico capaz de simular escoamentos viscoelásticos com superfícies livres governados pela equação constitutiva não-linear PTT (Phan-Thien-Tanner). Neste trabalho foram apresentados três métodos numéricos para simular escoamentos viscoelásticos modelados pela equação PTT. Dois desses métodos foram desenvolvidos para simular escoamentos viscoelásticos bidimensionais enquanto o terceiro método foi desenvolvido para simular escoamentos viscoelásticos tridimensionais. Estes métodos numéricos foram incorporados aos ambientes de simulação FreeDow2D e FreeDow3D, extendendo estes ambientes para escoamentos viscoelásticos descritos por uma equação constitutiva não-linear. Inicialmente, uma descrição de FreeDow2D e FreeDow3D é apresentada. As equações governantes para escoamentos descritos pelo modelo PTT são dadas na forma de tensorial e as formulações matemáticas para obtenção dos métodos numéricos são apresentadas. As equações que descrevem os métodos numéricos são resolvidas pela técnica de diferenças finitas numa malha deslocada e o fluido é representado por partículas arcadoras usando o método Marker-and-Cell. As condições de contorno para cada tipo de contorno são descritas em detalhes e o cálculo do tensor extra-tensão no contorno rígido é obtido utilizando as idéias de Tomé et al. [84] para o modelo Oldroyd-B. Seguindo a metodologia de Alves et al. [2], a solução analítica do modelo PTT para escoamentos totalmente desenvolvidos em um canal bidimensional é apresentada em detalhes. Esta solução analítica é então usada para validar o método numérico desenvolvido neste trabalho. Os métodos numéricos desenvolvidos nesse trabalho foram aplicados para simular os seguintes problemas: um jato de fluido viscoelástico incidindo numa placa rígida; o inchamento do extrudado e o problema de uma gota esférica de fluido viscoelástico incidindo perpendicularmente contra uma superfície rígida plana / The aim of this work is to develop a numerical method capable of simulating viscoelastic free surface flows governed by the non-linear constitutive equation PTT (Phan-Thien-Tanner). In this work three numerical methods to simulate vicoelastic Flows of fluids modelled by the PTT equation are presented. Two of these methods were developed to simulate two-dimensional viscoelastic flows while the third method was developed to simulate three-dimensional viscoelastic flows. These numerical methods were incorporated into the codes FreeFlow2D and FreeFlow3D, extending these codes to viscoelastic flows described by the non-linear constitutive equation PTT. Initially, a description of FreeFlow2D and FreeFlow3D is presented. The governing equations for flows described by the PTT model are given in index form and the mathematical formulations for obtaining the numerical methods are presented. The equations describing the numerical methods are solved by the finite difference method on a staggered grid and the fluid is modelled using a Marker-and-Cell type method. The boundary conditions for each type of boundary are described in details and the calculation of the extra-stress tensor on rigid boundaries is performed using the ideas of Tomé et al. [84] for an Oldroyd-B Fluid. Following the methodology presented by Alves et al. [2], the analytic solution of the PTT model for fully developed flows in a two-dimensional channel is presented in details. This analytic solution is then used to validate the numerical method developed in this work. Finally, the numerical methods developed in this work were applied to simulate viscoelastic flows such as a viscoelastic jet flowing onto a rigid plate, the extrudate swell of viscoelastic fluids and the simulation of a viscoelastic drop hitting a rigid plate

No description available.

O objetivo deste trabalho é desenvolver um método numérico capaz de simular escoamentos viscoelásticos com superfícies livres governados pela equação constitutiva não-linear PTT (Phan-Thien-Tanner). Neste trabalho foram apresentados três métodos numéricos para simular escoamentos viscoelásticos modelados pela equação PTT. Dois desses métodos foram desenvolvidos para simular escoamentos viscoelásticos bidimensionais enquanto o terceiro método foi desenvolvido para simular escoamentos viscoelásticos tridimensionais. Estes métodos numéricos foram incorporados aos ambientes de simulação FreeDow2D e FreeDow3D, extendendo estes ambientes para escoamentos viscoelásticos descritos por uma equação constitutiva não-linear. Inicialmente, uma descrição de FreeDow2D e FreeDow3D é apresentada. As equações governantes para escoamentos descritos pelo modelo PTT são dadas na forma de tensorial e as formulações matemáticas para obtenção dos métodos numéricos são apresentadas. As equações que descrevem os métodos numéricos são resolvidas pela técnica de diferenças finitas numa malha deslocada e o fluido é representado por partículas arcadoras usando o método Marker-and-Cell. As condições de contorno para cada tipo de contorno são descritas em detalhes e o cálculo do tensor extra-tensão no contorno rígido é obtido utilizando as idéias de Tomé et al. [84] para o modelo Oldroyd-B. Seguindo a metodologia de Alves et al. [2], a solução analítica do modelo PTT para escoamentos totalmente desenvolvidos em um canal bidimensional é apresentada em detalhes. Esta solução analítica é então usada para validar o método numérico desenvolvido neste trabalho. Os métodos numéricos desenvolvidos nesse trabalho foram aplicados para simular os seguintes problemas: um jato de fluido viscoelástico incidindo numa placa rígida; o inchamento do extrudado e o problema de uma gota esférica de fluido viscoelástico incidindo perpendicularmente contra uma superfície rígida plana / The aim of this work is to develop a numerical method capable of simulating viscoelastic free surface flows governed by the non-linear constitutive equation PTT (Phan-Thien-Tanner). In this work three numerical methods to simulate vicoelastic Flows of fluids modelled by the PTT equation are presented. Two of these methods were developed to simulate two-dimensional viscoelastic flows while the third method was developed to simulate three-dimensional viscoelastic flows. These numerical methods were incorporated into the codes FreeFlow2D and FreeFlow3D, extending these codes to viscoelastic flows described by the non-linear constitutive equation PTT. Initially, a description of FreeFlow2D and FreeFlow3D is presented. The governing equations for flows described by the PTT model are given in index form and the mathematical formulations for obtaining the numerical methods are presented. The equations describing the numerical methods are solved by the finite difference method on a staggered grid and the fluid is modelled using a Marker-and-Cell type method. The boundary conditions for each type of boundary are described in details and the calculation of the extra-stress tensor on rigid boundaries is performed using the ideas of Tomé et al. [84] for an Oldroyd-B Fluid. Following the methodology presented by Alves et al. [2], the analytic solution of the PTT model for fully developed flows in a two-dimensional channel is presented in details. This analytic solution is then used to validate the numerical method developed in this work. Finally, the numerical methods developed in this work were applied to simulate viscoelastic flows such as a viscoelastic jet flowing onto a rigid plate, the extrudate swell of viscoelastic fluids and the simulation of a viscoelastic drop hitting a rigid plate

No description available.

本文將以目前台灣最大的網路新聞時事討論區──PTT Gossiping看板（以下簡稱「八卦板」）為研究對象，分析透過BBS媒介所形成的網路群眾文化，並探究其民主意涵。有別於一般網路公共領域的研究，本文將由「對抗性公共」與「狂歡節」這兩個概念切入，並借鏡俄國文學批評家Bakhtin所提出的「眾聲喧嘩」與「公共廣場」等說法，嘗試論證透過網路媒介所形成、並帶有集體性狂歡節色彩的社會互動空間，如何落實異於Habermas菁英式公共領域的公共生活想像。 就內容而言，本文可粗略區分為兩部分：首先我們將以Gossiping看板為例，從集體性的角度描繪網路群眾文化的樣貌（第二、三章），接著再進一步說明其民主意涵（第四章）。在第二章當中，我們將藉由回顧八卦板的看板歷程，說明本文所討論的八卦板「網路公眾」，在評論新聞、針砭時事的表面下，其實潛藏著某種不同於理性個人交往的社會關係形態；對於這樣的現象，我們可以暫且稱之為「網路起鬨」。在第三章，我們將透過集體亢奮與狂歡節的概念，進一步擴充網路起鬨現象的抽象意義，並嘗試說明：即便到了今天，人們透過網路媒介進行的互動，仍然表現出「非凡、例外」的強烈集體情緒；這樣的集體性，既不同於公共領域理性論辯的互動方式，亦無法簡單斥之為「非理性」的劣質文化。以此種互動關係樣態為背景，在第四章我們將著重討論帶有狂歡節特質的網路群眾文化，如何透過語言的運用，體現Bakhtin強調多元觀點的「眾聲喧嘩」概念；此種狂歡節語言，能夠跳脫代表語言中心化力量的Habermas公共領域設想，從而落實「公共廣場」概念所描繪的、強調對話而不強加共識的公共生活。最後在第五章結論當中，本文除了對全文進行簡要總結之外，並討論了「社會關係／mob-ility」、「遊戲」以及「日常生活」等等概念，嘗試為網路文化的進一步研究，提供可能的參考方向。 / Taking Taiwan’s largest internet news forum “PTT Gossiping” as research object, this thesis analyses the culture of internet crowds formed through the medium of BBS (Bulletin Board System), and explores its democratic implications. Different from existing researches of “internet public sphere”, this thesis set out its arguments by resorting to concepts of “counterpublics” and “carnival”, and concludes with the notions of “heteroglossia” and “public square”, both proposed by Russian literary critic Mikhail Bakhtin, to demonstrate how a collectively carnivalistic social space of interaction, formed by internet, can provide us with an alternative imagination of public life that is different from Habermasian (elite) public sphere. This thesis consists of two parts: firstly, it analyses the culture of internet crowds from the sociological perspective of collectivity, taking PTT Gossiping as example (Ch. 2 & Ch. 3); secondly, it elaborates the democratic implications of this culture (Ch. 4). In Ch. 2, we review the historical development of PTT Gossiping, in order to demonstrate that the “internet public” constituting this news forum shows a non-personal as well as non-rational mode of social interaction, which we can provisionally describe as “internet mobbing”. In Ch. 3, we elaborate the sociological meaning of internet mobbing, by resorting to concepts such as “collective effervescence” and “carnival”, arguing that the “extraordinary, exceptional” feature of strong collective emotions can still be observed nowadays in internet interactions. This collectivity is neither similar to rational, reasoning mode of interaction proposed by the idea of “public sphere”, nor can it be denounced simply as “irrational” or bad culture. Based on this kind of social interaction, in Ch. 4 we explore how the using of carnivalistic language by internet crowds can embody Bakhtinian heteroglossia. By emphasizing the value of multiple perspectives, the carnivalistic language use of internet crowds breaks away from Habermasian public sphere, and helps to bring about a public life depicted by Bakhtinian “public square”, encouraging dialogue rather than forcing consensus. Finally, in Ch. 5 we sum up the thesis, and discuss ideas such as “social relationship / mob-ility”, “game”, and “everyday life”, which can serve as possible directions for further studies on internet culture.

Abstract This thesis correlates rheological data into a non-linear blown film model that describes the stress and cooling-induced morphological transformations in the axial and flow profiles of the blown films. This will help to improve the physical and mechanical properties of the films in a cost effective way, which will in turn be of great benefit to the food and packaging industries. In this research, experimental and numerical studies of a blown film extrusion were carried out using two different low-density polyethylenes (LDPEs). In the experiment, the key parameters measured and analysed were molecular, rheological and crystalline properties of the LDPEs. In the numerical study, blown film simulation was carried out to determine the bubble characteristics and freeze line height (FLH). A new rheological constitutive equation was developed by combining the Hookean model with the well known Phan-Thien and Tanner (PTT) model to permit a more accurate viscoelastic behaviour of the material. For experimental verification of the simulation results, resins were processed in a blown film extrusion pilot plant using identical die temperatures and cooling rates as used in the simulation study. Molecular characteristics of both LDPEs were compared in terms of their processing benefit in the film blowing process. Based on the experimental investigation, it was found that molecular weight and its distribution, degree of long chain branching and cooling rate play an important role on melt rheology, molecular orientation, blown film processability, film crystallinity and film properties. Effect of short chain branching was found insignificant for both LDPEs. Statistical analysis was carried out using MINITAB-14 software with a confidence level of 95% to determine the effect of process variables (such as die temperature and cooling rate) on the film properties. Film properties of the LDPEs were found to vary with their molecular properties and the process variables used. Blown film model performance based on the newly established PTT-Hookean model was compared with that based on the Kelvin model. Justification of the use of PTT-Hookean model is also reported here using two different material properties. From the simulation study, it has been found that predictions of the blown film characteristics conformed very well to the experimental data of this research and previous studies using different materials and different die geometries. Long chain branching has been found as the most prominent molecular parameter for both LDPEs affecting melt rheology and hence the processability. Die temperature and cooling rate have been observed to provide similar effect on the tear strength and shrinkage properties of blown film for both LDPEs. In comparison to the Kelvin model, the PTT-Hookean model is better suited for the modelling of the film blowing process. It has also been demonstrated in this study that the PTT-Hookean model conformed well to the experimental data near the freeze line height and is suitable for materials of lower melt elasticity and relaxation time.

三角關係的三個角色，在PTT的三個板，大老婆、第二者與第三者板，分別以自我為主體抒發心情故事，依據板規陳述自我或評價他人，現實中對三角關係的看法與解讀的權力角力，延伸到網路討論板裡的各自表述，形成若有似無的隔空對話，這種為對話的自我表述型態與權力的運作息息相關，是一種網路與現實交會所形成的特殊溝通型態：三個角色以遵循與抗拒倫理規範看待自我與他人，而宰制與抗拒是權力運作的一部分，倫理價值觀也是權力產物，板上的文章成為乘載訊息的語藝產物。 本研究結合權力語藝分析、對倫理價值觀宰制與抗拒，分析PTT三角關係的三個角色互相指涉的文章，試圖從中找出三個角色呈現的訊息與形象、權力策略，並了解網路中的情境脈絡如何影響三角關係的三個角色，以及如何與現實社會的倫理規範對話。 整個社會對三角關係有一套約定俗成的主流論述：男外向、女順從忍讓，第一者是受害者，不需負任何責任，第二者是背叛者，罔顧信任與責任，第三者是破壞者、壞女人。網路的匿名性使人願意分享更多在現實世界裡礙於社會規範而較少表達的各種自我告白與揭露；三個板因板規而拉起無形的界線，每個角色都是「主流」，不用擔心勢單力薄。傅柯的權力論述指出，倫理規範透過全景敞視主義使所有人同時成為監視者與被監視者。肖小穗的權力語藝分析方法：解讀權力訊息、分析權力語藝策略（選擇、內化與聯合策略）。 從分析中得知PTT大老婆板、第二者板、第三者板的三個角色各自站在不同立場、宣示不同權力，把對倫理規範的宰制與抗拒也做為策略的一部份，運用某些相同與不相同的策略，企圖獲取認同、抒發心情。三個角色以對倫理規範的宰制與抗拒呈現其訊息、營造形象，其中三個角色多以宰制態度描述自己並指責他人，鞏固立場。以選擇策略來看，三個板中的任何角色都以符合他們角色的定位選擇發聲角度，並延伸其觀點：第一者與第三者所選擇的發聲角度大部分都較被動，第二者則有較多自主性；內化策略，第一者強調現今社會的倫理觀點，第二者強調人有權追求自由，第二者與第三者皆試圖合理化三角關係形成原因；聯合策略，三個角色運用各種論述權力的搭配強化選擇與內化策略。三個角色大部分還是選擇以自己角色為主體的板發表文章，仍有少數到不屬於自己角色的板發文，挑戰以該角色為主體的主流氛圍。文章發表者以女性為主，可能因女性易抒發情感及感受到社會對女性的約束。 三個角色在新舊觀念接軌時，意識與潛意識仍無法擺脫傳統倫理價值觀的影響，實踐層次上，則由於外在條件改變而有新的態度與觀點。三個角色試圖與他人對話、取得認同或影響他人的同時，現實與網路世界都籠罩在權力的控制下，網路與現實也始終相連。

在台灣，電子布告欄系統（Bulletin Board System，BBS）並非像美國一樣隨時間被淘汰，人數不減反增地逆勢成長，且具社會影響力。何以一項現今看來技術「落後」的純文字介面系統，仍能在台灣如此風行？何以批踢踢後來人數會成長一百五十倍，成為全國，乃至於全世界最大的BBS？造就這樣一個容納十五萬人同時在線的BBS的技術與社會條件為何？本研究採用科技的社會建構論（The social construction of Technology，SCOT）作為理論架構，透過台灣BBS發展反省既有的STS與資訊研究，並延伸與修正SCOT的理論架構。 BBS在台灣的發展是一條有別於歐美資訊發展的在地技術創新路徑。紮根於校園的BBS是台灣獨有的技術創新成就。校園一方面作為一個重要的招募及再生產機制，促使Internet BBS能在1990年代中後期快速擴張；另方面校園也成為了不同社會團體權力接合的節點（教育部-校方-站方-使用者）。 BBS站台興盛的必要條件在於是否具有較高的自主性。在有較高的自主性的前提下，「使用者─工程師」（User-Programmer）、「使用者─管理者」（User-Manager）才能為BBS帶來技術創新的可能。換言之，在較不受制於校方規制與市場左右的情況下，BBS社群才得以蓬勃發展。批踢踢經營團隊的動力源自他們同時具備重度使用者的身分；在權限上是高人一等的使用者，可依自身需求參與、實驗、改造自身涉入甚深的社群。這些活動不是迫於生計或懾於威勢，而是有別於日常生活的自發性活動，因而產生遊戲（play）的樂趣。對作為重度使用者的經營團隊來說，BBS作為一種集體記憶的載具，它是個人重要的情感連結並建構了自我認同。BBS人數的提升牽涉到的是經濟面、技術面乃至於社會面的整合。 2005年之後的批踢踢，因頻繁的網路起鬨（internet mobbing）與大眾媒體開始緊密連結，吸引更多使用者加入，同時也提升批踢踢的影響力。與新聞媒體形成的正反饋迴圈開啟了多起批踢踢爭議事件，批踢踢的所有權也成為各方社會團體相互協商（negotiation）的對象。最後所有權爭論終結（closure）在2006至2007發生的「批踢踢出走學網」事件；經此事件後，批踢踢就成為一個人數停滯（同時上線人數停在十五萬人），名義上所有權歸給台灣大學資訊系系方，狀態相對穩定的技術物。 / In Taiwan, Bulletin Board System (BBS) hasn’t been eliminated as that in the US. On the contrary, the number of BBS users is increasing aggressively, BBS users in Taiwan are gaining socail influence as well. Why does a text-based interface, a system appearing so “laggard” in today’s technology, still attract considerable Internet users and become popular in Taiwan? How does PTT(the most popular platform in Taiwan) bloom and even multiply 150 times, becoming the largest BBS nationwide or even worldwide? What are the social and technical conditions to create this magnificent BBS station for 150 thousand users on-line at the same time? This study adopts SCOT（The social construction of Technology，SCOT）as its theoretical framework, reflecting STS and iCT-study, through the development of BBS in Taiwan and trying to extend and modify the theoretical framework of SCOT. The development of BBS in Taiwan, with its local innovative technological conditions, is quitely different from that in the Western countries. On the other hand, with its crucial recruiting and reproduction mechanism based on the campus, BBS bloomed in the late 1990s. On the other hand, campus renders a connection between the power of different social groups. Relatively –high autonomy pushes through BBS’s propertiy. Under higher autonomy condition, user-programmer or user-manager model may bring in technology innovation. In other words, BBS community becomes flourishing on account of fewer restrictions from the authorities. And the managing staff in PPT, because of owning top administrative rights, can get deeply involved, experiment, and modify this social group with innovations. They have done this not for living or oppressed by the authorities, but for fun. To these core managing staff, BBS renders a vehicle, of collective emotional memory, and self-indentification. The growing number of BBS users shows the integrity of economy, technology, and society. PPT after the year 2005, because of frequent internet mobbing along with mass media, has attracted more users to join its social website and gave rise to its influence as well. People start to care about its ownership. And the closure of this issue came to an end in the event of PPT pupils exile; after that, the number of PPT users has suspended (15 thousand users at top.) Now, the ownership belongs the the Department of Information Technology and Ptt becomes a relatively stable artifact in the long run.

Blood pressure is one of the basic indicators of the health state of the cardiovascular system. High blood pressure is the main risk factor of ischemic heart disease, atherosclerosis and stroke. Therefore, it is important to monitor long-term changes in blood pressure and respond in time to these changes. Blood pressure meters are not standard household equipment, while a well-equipped smartphone is. Smartphones contain a large number of sensors capable of measuring biomedical signals. This thesis focuses on creating an application capable of determining blood pressure using data obtained from these sensors.