2,470 research outputs found
Position Paper: The Case for JavaScript Transactions
No full textModern Web applications combine and use JavaScript-based content from multiple untrusted sources. Without proper isolation, such content can compromise the security and privacy of these Web applications. Prior techniques for isolating untrusted JavaScript code do so by restricting dangerous constructs and inlining security checks into third-party code. This paper makes the case that JavaScript must be extended to make isolation a language-level primitive. We propose to extend the language using a new transaction construct that allows a Web application to speculatively execute untrusted code and isolate the changes and effects it performs. The Web application can then inspect these speculative actions and commit them only if they comply with the application’s security policies. We discuss use-cases that can benefit from JavaScript support for transactions, present a formalization of JavaScript transactions and conclude with implementation considerations.Technical report DCS-TR-66
Tunable acoustic attenuation in dilute suspensions of non-spherical magnetic particles
No full textThe microstructure of suspensions of ferromagnetic particles with subwavelength size can be controlled by an external field, making it possible to develop novel broadband acoustic materials with anisotropic and tunable acoustic properties. In this study we experimentally show that dilute suspensions of nickel micro-flakes exhibit a greater than 20% change in attenuation coefficient at MHz frequencies upon changing the direction of an external magnetic field, at particle volume fractions of only 0.5%. Optical transmission measurements and analysis of the characteristic timescales of particle alignment and chaining are used to study the mechanisms behind this acoustic anisotropy. By making comparison to suspensions of spherical particles, we show that the shape and orientation of the nickel micro-flakes play important roles in the tunable acoustic attenuation of these suspensions.Peer reviewed
Liquid democracy: a comparative study of digital urban democracy
No full textIn Liquid Democracy, author Yu-Shan Tseng offers a bold new framework for understanding democracy as a dynamic, fluid process. Challenging the idea that AI and digital tools are inherently anti-democratic, this innovative volume bridges theory and practice to investigate various “liquid conditions,” a novel concept capturing how political action flows and transforms like water within the intersections of urban spaces and digital technologies.Through an in-depth comparative study of three groundbreaking digital democracy platforms—Decide Madrid in Madrid, OmaStadi in Helsinki, and vTaiwan in Taipei—Tseng explores how digital platforms can foster participatory governance, pluralism, and alternative democratic futures. In-depth chapters critically examine the interactions between humans, algorithms, and urban systems, revealing how digital tools reconfigure the boundaries of political participation, decision-making, and collective action. Throughout the text, Tseng offers fresh insights into how democracy emerges under contingent conditions shaped by technology and geography.Drawing from years of ethnographic fieldwork, Liquid Democracy is essential reading for master’s and PhD students in geography, political science, and urban studies, as well as scholars, practitioners, and policymakers interested in digital governance, smart cities, civic technology, and algorithmic politics
Surface-charge effects on the electro-orientation of insulating boron-nitride nanotubes in aqueous suspension
No full textThe alignment of hexagonal boron-nitride nanotubes (BNNTs) in aqueous KCl solutions under spatially uniform electric fields was examined experimentally, using direct optical visualization to probe the orientation dynamics of individual BNNTs for different electric-field frequencies. Different from most previously studied nanowires and nanotubes, BNNTs are wide-bandgap materials which are essentially insulating at room temperature. We analyze the electro-orientation of BNNTs in the general context of polarizable cylindrical particles in liquid suspensions, whose behavior can fall into different regimes, including alignment due to Maxwell-Wagner induced dipoles at high frequencies, and alignment due to fluid motion of the electrical double layer around the particles at lower frequencies. For BNNTs, the variation of the crossover frequencies in the electro-orientation spectra was studied in electrolytes of different conductivity. The effect of BNNT surface charge on electro-orientation was further studied by changing the pH of the aqueous solution. We find that the electric-field alignment of the BNNTs in the low-frequency regime is associated with the charging and motion of the electrical double layer around the particle. However, as BNNTs are non-conducting particles, the reasons for the formation of the electrical double layer are likely to be different than that of conducting particles. We discuss two possible mechanisms for the double-layer formation and alignment of 1D dielectric particles, and make comparison to those for the more commonly studied conducting particles.Peer reviewe
Electrokinetics of Scalable, Electric-Field-Assisted Fabrication of Vertically Aligned Carbon-Nanotube/Polymer Composites
No full textComposite thin films incorporating vertically aligned carbon nanotubes (VACNTs) offer promise for a variety applications where the vertical alignment of the CNTs is critical to meet performance requirements, e.g., highly permeable membranes, thermal interfaces, dry adhesives, and films with anisotropic electrical conductivity. However, current VACNT fabrication techniques are complex and difficult to scale up. Here, we describe a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT composites. Multiwall-carbon nanotubes are dispersed in a polymeric matrix, aligned with an alternating-current (AC) electric field, and electrophoretically concentrated to one side of the thin film with a direct-current (DC) component to the electric field. This approach enables the fabrication of highly concentrated, individually aligned nanotube composites from suspensions of very dilute (Φ = 4 X 10-4 volume fraction. We experimentally investigate the basic electrokinetics of nanotube alignment under AC electric fields, and show that simple models can adequately predict the rate and degree of nanotube alignment using classical expressions for the induced dipole moment, hydrodynamic drag, and the effects of Brownian motion. The composite AC + DC field also introduces complex fluid motion associated with AC electro-osmosis and the electrochemistry of the fluid/electrode interface. We experimentally probe the electric-field parameters behind these electrokinetic phenomena, and demonstrate, with suitable choices of processing parameters, the ability to scalably produce large-area composites containing VACNTs at number densities up to 1010 nanotubes/cm2. This VACNT number density exceeds that of previous electric-field-fabricated composites by an order of magnitude, and the surface-area coverage of the 40 nm VACNTs is comparable to that of chemical-vapor-deposition-grown arrays of smaller-diameter nanotubes.Peer reviewe
Polystichum clarinervium (subg. Haplopolystichum; Dryopteridaceae), a new fern from Emei shan, China
No full textA new fern species, Polystichum clarinervium, a member of P. subg. Haplopolystichum (Dryopteridaceae), is described and illustrated from Emei shan, Sichuan Province, Southwest China. The new species is similar to P. deltodon, but the former has pinnae slightly imbricate, pinna apex rounded, and veins clear, while the latter has pinnae not imbricate, pinna apex acute, and veins obscured. Polystichum clarinervium was found on a limestone slope under sparse forest at an elevation of 1300 m and is currently known from two small populations. It is classified as Critically Endangered (CR) following IUCN Red List criteria
Ethno-Knowledge of the Shan and Modernity
No full textThis paper aims to discuss how the Shan view their self-image and history and focuses on their concept of mäng in Shan/Tay or kuni in Japanese by comparing them with concept of 'nation' in a modern historical sense. Shan as an ethnic term was and is used to refer to Tai-language speaking people in Burma/Myanmar. Its origin and fabrication are ethnologically controversial. During the field research in Kachin State, the author came across a Shan intellectual acquaintance who narrated their own history not by referring their 'glory chiefdom' but by comparing it with that of the Bamar (Burmese): "We, the Shan have never founded a nation like the Bamar". According to some legendary stories, Mogaung (Mäng Kawng) located in the present Kachin State was one of the capital sites among the chiefdoms, having been founded by a legendary hero who came from Mäng Maaw. Mäng Maawis thought to be one of the earliest sites of the Shan in Burma/Myanmar. It is certain that the ethno-knowledge of the Shan was given a framework by Westerners including colonial officers (e.g.J.G. Scott), Christian missionaries (e.g.J.N. Cushing, who edited a Shan-English dictionary) and academics (e.g.E.R. Leach). These phases and their significance in social terms will be treated from the following aspects.
1) Shan and Tai/Tay as ethnic terms and their usage
2) Mäng in Shan and Pyi or Naing in Bamar
3) Ethno-knowledge and modernity
The abovementioned narrative seems to be influenced by not only the 'imagined glory chiefdom' but also the modern concept of 'nation'. The ethno-knowledge of the Shan was and is constructed and reconstructed through ethnic identity and discourse by themselves and intellectual influences originating in Western modernity.本論考は、第44回中国・四国地区研究懇談会中四国人類学談話会(2015年11月7日RCC文化センター)での発表内容に加筆修正したものである
Shaanxi (China), view of Hua Shan mountain
No full textView of Hua-shan, one of five sacred mountains of China.Image is included in the research conducted by Bailey Willis for the article: Among the Mountains of Shen-Si
Author(s): Bailey Willis
Source: Bulletin of the American Geographical Society, Vol. 38, No. 7 (1906), pp. 412-424
Published by: American Geographical Society
Stable URL: http://www.jstor.org/stable/198944http://www.jstor.org/stable/198944Grayscal
[[alternative]]The Ninth Grade Students' Concepts of Acids and Bases
No full text[[abstract]]本研究的目的在於探討現行國中課程內有關酸鹼概念的學習，我國國三學
生對於此概念的理解程度及可能存在的迷思概念。研究對象取自台北市立
景興國中的國三學生合計共三百四十一人。研究重點是統整國中理化教材
內的酸鹼概念，建立教學目標，完成概念構圖；然後據此設計晤談、選擇
題紙筆測驗和開放式紙筆問卷等研究工具，針對學生的回答資料，分別作
定性與定量分析。茲將研究的主要結果摘述如下：一．學生對於酸鹼的定
義可分為描述性定義、操作型定義與離子模型等三類，同時對於酸的瞭解
皆甚於鹼。部分學生會以味覺來判別物質的酸鹼性，將具有酸味、鹹味、
甜味的物質分別歸為酸性、鹼性、中性。二．在強酸和弱酸的定義上，大
都認為是腐蝕性的不同，部分學生會直接以pH值的大小來判斷該酸的強弱
。三．學生大都瞭解酸鹼中和的意義，並確定其為放熱反應，但對於鹽類
的生成與種類的判斷、中和反應之方程式與淨離子反應方程式的表達、以
及酸鹼中和的反應量計算上，皆有困難。部分學生對酸鹼中和後溶液的酸
鹼性判斷，會從參與中和反應之各酸鹼的強弱來考慮，以為中和反應在原
先各自酸與鹼所解離出的離子作用完後就停止，由結束時的氫離子與氫氧
根離子多寡決定最後溶液的酸鹼性。
The main purpose of this study was to explore the compre-
hensive level of our junior high school students in the
third grade in regard to the concepts and misconceptions
about acids and bases. The total 341 students for basic
observation and further discussion involved were from Ching–
Hsing Junior High School, Taipei. This study was based on
the present Physics– Chemistry textbooks for junior high
school students. It attempted to reorganize the concepts of
acids and bases mentioned in those textbooks, to re-establish
the main instructional objectives, and to develop a concept
mapping. The three research instruments which were
generated by the concept mapping included interviews, a
multiple-choice test and a open-ended questionnaire. Analyses
of the quantitative and qualitative data were done according
to the students' responses. The following summary was the
main conclusions of this study : 1. The students gave three
kinds of definitions of acids and bases and understood acids
better than bases. Some students classified materials as
either acidic or basic in accordance with the taste ; they
thought sour materials acidic, salty materials basic, and sweet
materials neutral. 2. Most students considered that the
difference between strong acids and weak acids was the nature
of etching. Some students distinguished the strength of
acids by the pH values. 3. Most students understood the
meaning of neutralization, and associated the release of heat
with the reaction between an acid and a base. But they had
difficulties in identifying its product – salt, in
completing a chemical equation and a net ionic equation, and
in calculating stoichiometric amounts about a
neutralization reaction.
The main purpose of this study was to explore the compre-
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