13,575 research outputs found
Randomness Extractors in AC⁰ and NC¹: Optimal up to Constant Factors
Full text linkWe study randomness extractors in AC⁰ and NC¹. For the AC⁰ setting, we give a logspace-uniform construction such that for every k ≥ n/poly log n, ε ≥ 2^{-poly log n}, it can extract from an arbitrary (n, k) source, with a small constant fraction entropy loss, and the seed length is O(log n/(ε)). The seed length and output length are optimal up to constant factors matching the parameters of the best polynomial time construction such as [Guruswami et al., 2009]. The range of k and ε almost meets the lower bound in [Goldreich et al., 2015] and [Cheng and Li, 2018]. We also generalize the main lower bound of [Goldreich et al., 2015] for extractors in AC⁰, showing that when k < n/poly log n, even strong dispersers do not exist in non-uniform AC⁰. For the NC¹ setting, we also give a logspace-uniform extractor construction with seed length O(log n/(ε)) and a small constant fraction entropy loss in the output. It works for every k ≥ O(log² n), ε ≥ 2^{-O(√k)}.
Our main techniques include a new error reduction process and a new output stretch process, based on low-depth circuit implementations for mergers, condensers, and somewhere extractors
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Preparation and photoluminescence of nc-Si/SiO2 MQW
No full textThe deposition rate and refractive index for a-Si(amorphous silicon) and SiO2 grown by PECVD were studied under different pressure, power and proportion of reactant source gases. a-Si/SiO2 MQW(multi-quantum well) with high quality was deposited under suitable conditions, in which the thickness of the a-Si layers is several nanometers. The sample of a-Si/SiO2 MQW was crystallized by laser annealing. Because of the confinement of the SiO2 layers, crystalline grains were formed during the a-Si layers were being crystallized. The size of the crystalline grains were not more than the thickness of the a-Si layers. The a-Si layers were crystallized to be nanometer crystalline silicon(nc-Si), therefore, nc-Si/SiO2 MQW was formed. For the a-Si/SiO2 MQW with 4.0nm a-Si wells separated by 5nm SiO2 barries, most of the a-Si were crystallized to silicon grains after laser annealing,and the size of the grains is 3.8nm. Strong photoluminescence with three peaks from the nc-Si/SiO2 MQW was detected at 10K. The wavelength of the peaks were 810nm, 825nm and 845nm, respectively
Fiber type and myosin heavy chain compositions of adult pretarsal orbicularis oculi muscle.
No full textApplication of High Performance Concrete in Yu-Cheng Bridge
No full textThis paper focus on the application study of HPC, and both of HPC and normal concrete (NC) were adopted for comparison in the Yu-Cheng Bridge Durability tests were carried out on HPC and NC respectively, based on the comparative analysis of the results obtained from these tests, durability evaluation of HPC is made. The results are useful for the evaluation of durability of HPC.</jats:p
Ultra-thin electron collectors based on nc-Si:H for high-efficiency silicon heterojunction solar cells
No full textLow parasitic absorption and high conductivity enable (n)-type hydrogenated nanocrystalline silicon [(n)nc-Si:H], eventually alloyed with oxygen [(n)nc-SiOx:H], to be deployed as window layer in high-efficiency silicon heterojunction (SHJ) solar cells. Besides the appropriate opto-electrical properties of these nanocrystalline films, reduction of their thickness is sought for minimizing parasitic absorption losses. Many strategies proposed so far reveal practical limits of the minimum (n)-layer thickness that we address and overcome in this manuscript. We demonstrated the successful application of an ultra-thin layer of only 3-nm-thick based on (n)nc-Si:H PECVD plasma growth conditions without the use of additional contact or buffer layers. For simplicity, we still name (n)nc-Si:H this ultra-thin layer and the solar cell endowed with it delivers a certified efficiency η of 22.20%. This cell shows a 0.61 mA/cm2 overall JSC gain over the (n)a-Si:H counterpart mainly owing to the higher transparency of (n)nc-Si:H, while maintaining comparable VOC > 714 mV and FF > 80%. Our optimized (n)nc-Si:H layer yields low absorption losses that are commonly measured for (n)nc-SiOx:H films. In this way, we are able to avoid the detrimental effect that oxygen incorporation has on the electrical parameters of these functional layers. Further, by applying a MgF2/ITO double-layer anti-reflection coating, a cell with 3-nm-thick (n)nc-Si:H exhibits a JSC,EQE up to 40.0 mA/cm2. By means of EDX elemental mapping, we additionally identified the (n)nc-Si:H/ITO interface as critical for electron transport due to unexpected oxidation. To avoid this interfacial oxidation, insertion of a 2-nm-thick (n)a-Si:H on the 3-nm-thick (n)nc-Si:H contributes to FF gains of 1.4%abs. (FF increased from 78.6% to 80.0%), and showing further room for improvements.Photovoltaic Materials and DevicesQN/AfdelingsbureauElectrical Sustainable Energ
Fundamental Studies on the PU-NC Semi-IPNs Wooden Coatings
No full text本研究以屬於天然再生資源之吹製型篦麻油(BCO)為基質之二液型聚胺基
甲酸酯(PU)，與由天然纖維素硝化製成且仍能保留木材質感之硝化纖維
素(NC)，兩者合成半互穿聚合體網狀結構物(Semi-IPNs)，期望藉此提升
PU與NC所無法達到的性能，進而探討其應用於木器塗料之可行性，結果發
現以芳香族聚異氰酸鹽(PTDI)為硬化劑之PU與1/2〞NC可以簡易而成功地
製備PU-NC semi-IPNs，在各種NCO/OH莫耳比及不同PU/NC重量比之配方條
件，PU與NC均具相容性，且均可以明顯縮短PU的乾燥時間，而且膠化時間
達30日以上，可以解決PU乾燥速度緩慢及有可使用時間限制的缺點，其中
又?In this study , the semi-interpenetrating polymer networks
(semi-IPNs) which were made from blown castor oil (BCO) based
polyurethane (PU) and nitrocellulose (NC) were prepared for
wooden coatings. The effects of several factors such as the NCO/
OH molar ratios , PU/NC composition , addition sequence of
components , amount of PU catalyst , kinds of NC and
polyisocyanate on properties of coatings and films were
investigated. Some experiments concerning the viscosity , gel
time , drying time of coatings and me
The semi-IPNs were prepared from PU containing aromatic
polyisocyanate (PTDI) and 1/2〞NC under different NCO/OH molar
ratios of PU and PU/NC compositions. It revealed that PU and NC
were compatible on all of conditions and the drying time of PU
could be shortened significantly and had no limitations of pot-
life by interpenetrating with NC. The formulation of semi-IPNs
with NCO/OH=1.2 , PU/NC=70/30 (R1.2-70)had a best compatible
system and was an ideal interpenetration between PU and NC and
excellent p
For the PU-NC semi-IPNs under NCO/OH=1.2 , the degree of
interpenetration between PU and NC , properties of films of
NCaBCOaPTDI addition sequence were better than those of the
BCOaPTDIaNC sequence . Compared R1.2-70 PU-NC semi-IPNs with
four kinds of polyisocyanates (PTDI , PMDI , PIPDI , PHDI)
respectively , which containing PMDI had the highest viscosity
and containing both PTDI and PMDI had the shortest drying time
of coatings. Except the semi-IPNs containing PMDI would gel
within 12 hours , the gel
Compared the R1.2-70 PU-NC semi-IPNs with three kinds of
NC(1/2〞,1/4〞1/16〞) respectively ,which containing 1/2〞NC
had the shortest drying time of coating and had the best
tensile strength , elongation at break , lightfastness and
solvent resistance of films , while , containing 1/16〞NC had
the lowest viscosity of coating , the best thermal stability
and the highest quantity of thermal expansion of film. In
addition , the gel time for all of the semi-IPNs could reach
above 30 days. Dynamic mechanic
By adding the PU catalyst DBTDL to the PU-NC semi-IPNs ,
the pot-life of coatings would be limited but could shorten the
drying time of coatings and enhanced the tensile strength ,
elongation at break , lightfastness and solvent resistance of
films with alphatic polyisocyanates . It would improve the
thermal stability of films with aromatic polyisocyanates but
the lightfastness and gloss retention were inferior to those of
semi-IPNs without DBTDL. It could shorten the drying time of
coatings and enhance封面
目錄
圖目次
表目次
摘要
SUMMARY
一、前言
二、文廚回顧
（一）IPNs之原理
（二）IPNs之製備
（三）IPNs之歷史與應用
三、材料與方法
（一）試驗材料
（二）試驗方法
1.材料性質之測定
(1)篦麻油酸價之測定
(2)篦麻油羥價之測定
(3)聚異氰酸鹽NCO基之定量
2.PU之調配
3.PU-NC semi-IPNs之合成
(1)不同NCO/OH莫耳比與PU/NC組成之Semi-IPNs
(2)組成分添加次序不同之Semi-IPNs
(3)潻加PU催化劑之Semi-IPNs
(4)不同聚異氰酸鹽之Semi-IPNs
(5)不同NC之Semi-IPNs
4.試材之塗裝
5.塗料性質之測定
(1)粘度
(2)乾燥時間
(3)膠化時間
6.塗膜性質之測定
(1)機械性質
附著性
拉伸強度
硬度
(2)耐光性
(3)冷熱循環試驗
(4)熱機械分析
(5)熱重量分析
(6)耐溶劑性
(7)動態機械分析
(8)傅立葉紅外線光譜分析
(9)掃描式電子顯微鏡觀察
四、結果與討論
（一）NCO/OH莫耳比與PU/NC組成對Semi-IPNs性質之影響
（二）組成分添加次序對Semi-IPNs性質之影響
（三）添加PU催化劑對Semi-IPNs性質之影響
1.添加DBTDL對PU性質之影響
2.添加DBTDL對semi-IPNs性質之影響
（四）聚異氰酸鹽種類對Semi-IPNs性質之影響
1.不同聚異氰酸鹽之semi-IPNs
2.不同PU/NC重量比之semi-IPNs
（五）硝化纖維素種類對Semi-IPNs性質之影響
五、結論
六、參考文
Improving the Anaerobic Treatment of Sludges and High-Strength Wastewaters through Addition of Electrically-Conductive Particles
No full textThe growing list of high-strength wastewaters across North Carolina (NC) are well suited for
treatment and energy recovery using anaerobic digestion (AD). These include livestock wastes,
food wastes, and wastewater-derived sludges that if left untreated, pose risks to NC’s water
resources and public health. AD, however, is largely underutilized to treat these wastes. This can
be attributed to both economic and technology performance barriers. With respect to
performance, one limitation is the operational instability that can arise when syntrophic
relationships between key groups of microorganisms in the digester are disrupted; another is the
incomplete conversion of organics to methane gas (CH4). To overcome these limitations, we
proposed augmenting digesters with electrically conductive microscale particles. These particles
have proven effective as conduits for syntrophic microbe-to-microbe direct electron transfer,
resulting in improved CH4 generation and waste degradation rates using pure microbial strains in
the lab. We hypothesized that supplementing digesters with these materials would result in a
similar effect and could provide operators a means to stabilize and improve performance. Our
objectives were to experimentally determine the impact of 1) material properties (type,
conductivity, size) and 2) particle loading on AD performance. We assessed performance as CH4
generation rates, CH4 recoveries, and organic matter destruction [measured as chemical oxygen
demand (COD) removal]. To fulfill our objectives, we supplemented lab-scale, serum bottlebased digesters with different conductive particle types (graphite, biochar, activated carbon) or
non-conductive glass (a surface area control) and compared all particle amended bottles with
controls lacking particles. We used swine wastewater collected from the NC State Swine
Educational Unit as a representative high-strength wastewater.
Our results indicate that across all particle types tested, graphite was the most consistent in
improving digester performance. Both CH4 production rates and recoveries strongly correlated
with the graphite loading rate, reaching a maximum production rate of 30 ± 2.5 mL-CH4/(gVSseed day), which was 34 ± 11% higher than the no-particle control. The other material types
did not show clear trends with loadings, and in most cases led to reduced performance relative to
the no-particle control. Material electrical conductivity was not found to be a decisive factor for
predicting CH4 generation rates. This result was contrary to our expectations. A primary reason
was that biochar, and more significantly, activated carbon, strongly adsorbed organic matter
from the wastewater. Adsorption was found to have a negative impact on performance. Graphite
exhibited little to no adsorptive behavior, resulting in a larger conversion of the initial COD into
CH4 gas. Under our conditions tested (single batch cycle; 19 day retention time), the additional
CH4 generated with graphite would not recuperate the cost of graphite. Our recommendations
moving forward are threefold. First, fundamental investigations of microbial community
structure and mechanisms in the presence of conductive versus non-conductive material are
needed to determine if the improvements are associated with direct interspecies electron transfer
(DIET). Second, alternative means of providing electrically conductive surfaces, such as
graphitic brushes or cloths, should be explored, so as to avoid the costs associated with
continuous particle amendments. Finally, a broader suite of high-strength wastewaters need to
be studied to determine if similar responses as reported here are observed.NC WRR
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