Repositioning the innovation rationale for public service media

The values that gave rise to the ethos of public service broadcasting (PSB) almost a century ago, and which have provided the rationale for PSBs around the world across that time, are under question. This article argues that the process of reinvention of PSBs is enhanced through repositioning the innovation rationale for public service media (PSM). It is organized around a differentiation which is part of the standard repertoire of innovation studies – that between product, process and organizational innovation – as they are being practised by the two Australian PSBs, the Australian Broadcasting Corporation (ABC) and the Special Broadcasting Service (SBS). The article then considers the general problematics of innovation for PSBs through an analysis of the operations of the public value test in the context of European PSM, and its, to this stage, non-application in Australia. The innovation rationale is argued to be a distinctive via media between complementary and comprehensive roles for PSM, which in turn suggests an international, policy-relevant research agenda focusing on international circumstances in which the public broadcaster is not market dominant.

Australia and the Scottish independence referendum

This essay examines how, given the close historical and cul-tural ties which exist between Australia and the United Kingdom (including Scotland), the Scottish independence referendum was reported, analysed and made sense of in the Australian media. The analysis is based on mainstream news coverage (online and print media) produced in Australia and accessed from the internet between January 2012 and the end of September 2014 (two weeks after the referendum on September 18). A total of 95 items were included in the sample, which does not include broadcast news coverage or specialist current affairs periodicals. The online sites of broadcasters such as the ABC and SBS were included in the sam-ple. The great majority of these items were published in the run-up to polling day, in August and September 2014, with spikes in the frequency of item around particular events such as the Commonwealth Games in Glasgow. to the fore will be relevant for years to come.

Precoder optimization in cognitive radio with interference constraints

We consider precoding strategies at the secondary base station (SBS) in a cognitive radio network with interference constraints at the primary users (PUs). Precoding strategies at the SBS which satisfy interference constraints at the PUs in cognitive radio networks have not been adequately addressed in the literature so far. In this paper, we consider two scenarios: i) when the primary base station (PBS) data is not available at SBS, and ii) when the PBS data is made available at the SBS. We derive the optimum MMSE and Tomlinson-Harashima precoding (THP) matrix Alters at the SBS which satisfy the interference constraints at the PUs for the former case. For the latter case, we propose a precoding scheme at the SBS which performs pre-cancellation of the PBS data, followed by THP on the pre-cancelled data. The optimum precoding matrix filters are computed through an iterative search. To illustrate the robustness of the proposed approach against imperfect CSI at the SBS, we then derive robust precoding filters under imperfect CSI for the latter case. Simulation results show that the proposed optimum precoders achieve good bit error performance at the secondary users while meeting the interference constraints at the PUs.

The optoelectronic swept-frequency laser and its applications in ranging, three-dimensional imaging, and coherent beam combining of chirped-seed amplifiers

This thesis explores the design, construction, and applications of the optoelectronic swept-frequency laser (SFL). The optoelectronic SFL is a feedback loop designed around a swept-frequency (chirped) semiconductor laser (SCL) to control its instantaneous optical frequency, such that the chirp characteristics are determined solely by a reference electronic oscillator. The resultant system generates precisely controlled optical frequency sweeps. In particular, we focus on linear chirps because of their numerous applications. We demonstrate optoelectronic SFLs based on vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback lasers (DFBs) at wavelengths of 1550 nm and 1060 nm. We develop an iterative bias current predistortion procedure that enables SFL operation at very high chirp rates, up to 10^16 Hz/sec. We describe commercialization efforts and implementation of the predistortion algorithm in a stand-alone embedded environment, undertaken as part of our collaboration with Telaris, Inc. We demonstrate frequency-modulated continuous-wave (FMCW) ranging and three-dimensional (3-D) imaging using a 1550 nm optoelectronic SFL.

We develop the technique of multiple source FMCW (MS-FMCW) reflectometry, in which the frequency sweeps of multiple SFLs are "stitched" together in order to increase the optical bandwidth, and hence improve the axial resolution, of an FMCW ranging measurement. We demonstrate computer-aided stitching of DFB and VCSEL sweeps at 1550 nm. We also develop and demonstrate hardware stitching, which enables MS-FMCW ranging without additional signal processing. The culmination of this work is the hardware stitching of four VCSELs at 1550 nm for a total optical bandwidth of 2 THz, and a free-space axial resolution of 75 microns.

We describe our work on the tomographic imaging camera (TomICam), a 3-D imaging system based on FMCW ranging that features non-mechanical acquisition of transverse pixels. Our approach uses a combination of electronically tuned optical sources and low-cost full-field detector arrays, completely eliminating the need for moving parts traditionally employed in 3-D imaging. We describe the basic TomICam principle, and demonstrate single-pixel TomICam ranging in a proof-of-concept experiment. We also discuss the application of compressive sensing (CS) to the TomICam platform, and perform a series of numerical simulations. These simulations show that tenfold compression is feasible in CS TomICam, which effectively improves the volume acquisition speed by a factor ten.

We develop chirped-wave phase-locking techniques, and apply them to coherent beam combining (CBC) of chirped-seed amplifiers (CSAs) in a master oscillator power amplifier configuration. The precise chirp linearity of the optoelectronic SFL enables non-mechanical compensation of optical delays using acousto-optic frequency shifters, and its high chirp rate simultaneously increases the stimulated Brillouin scattering (SBS) threshold of the active fiber. We characterize a 1550 nm chirped-seed amplifier coherent-combining system. We use a chirp rate of 5*10^14 Hz/sec to increase the amplifier SBS threshold threefold, when compared to a single-frequency seed. We demonstrate efficient phase-locking and electronic beam steering of two 3 W erbium-doped fiber amplifier channels, achieving temporal phase noise levels corresponding to interferometric fringe visibilities exceeding 98%.

相位锁定双包层光纤激光器阵列获得18．3W的相干输出

光纤激光器以其结构紧凑、转换效率高、易散热和光束质量好等优点正逐渐成为高功率全固态激光器的主要选择。目前，单根光纤激光器的输出功率已经超过千瓦量级，但是由于受受激拉曼散射（SRS）和受激布里渊散射（SBS）等非线性效应的影响，单根光纤激光器的最终输出功率还是受到限制。要在保证光束质量的同时进一步提高输出功率就需要采用相干组束技术。

Measurement of the elastic constants of nanometric films

Carbon coatings of thickness down to 2 nanometers are needed to increase the storage density in magnetic hard disks and reach the 100 Gbit/in2 target. Methods to measure the properties of these ultrathin hard films still have to be developed. We show that combining Surface Brillouin Scattering (SBS) andX-ray reflectivity measurements the elastic constants of such films are accessible. Tetrahedral amorphous carbofilms of thickness down to about 2 nm were deposited on Si by an S bend filtered cathodic vacuum arc, achieving a continuous coverage on large areas free of macroparticles. Film thickness and mass density are measured by X-ray reflectivity: densities above 3 g/cm3 are found, indicating a significant sp3 content. The dispersion relations of surface acoustic waves are measured by SBS. We show that for thicknesses above ∼4 nm these waves can be described by a continuum elastic model based on a single homogeneous equivalent film. The elastic constants can then be obtained by fitting the dispersion relations, computed for given film properties, to the measured dispersion relations. For thicknesses of 3 nm or less qualitative differences among films are well measurable, but quantitative results are less reliable. We have thus shown that we can grow and characterise nanometer size tetrahedral amorphous carbon film, which maintain their high density and peculiar mechanical properties down to around 4 nm thickness, satisfying the requirements set for the hard disk coating material.

Numerical analysis for four-wave mixing based wavelength conversion of differential phase-shift keying signals

We numerically investigate the main constrains for high efficiency wavelength conversion of differential phase-shift keying (DPSK) signals based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF). Using multi-tone pump phase modulation techniques, high efficiency wavelength conversion of DPSK signals is achieved with the stimulated Brillouin scattering (SBS) effects effectively suppressed. Our analysis shows that there is a compromise between conversion efficiency and converted idler degradation. By optimizing the pump phase modulation configuration, the converted DPSK idler's degradation can be dramatically decreased through balancing SBS suppression and pump phase modulation degradation. Our simulation results also show that these multi-tone pump phase modulation techniques are more appropriate for the future high bit rate systems.

Reducing group-velocity-dispersion-dependent broadening of stimulated Brillouin scattering slow light in an optical fiber by use of a single pump laser

We propose a method of effectively extending the stimulated Brillouin scattering (SBS) gain bandwidth in a single-mode optical fiber to reduce group-velocity-dispersion (GVD)-dependent pulse spread of SBS slow light. This can be done by overlapping doublet SBS gain spectra synthesized from a single pump laser. Numerical calculations are performed to verify our proposed method. We find that there exists the optimum spectral separation between two center frequencies of the doublet SBS gain spectrum with respect to the inherent spectral width of the pump laser, which makes it possible to effectively reduce the signal pulse broadening due to GVD. We show that the maximum time delay of the amplified signal pulse can be approximately two times longer than that by a previously reported method using a single broadband pump laser. (c) 2008 Optical Society of America.

扫描探针技术研究单链颗粒及嵌段共聚物薄膜

扫描探针显微技术是一个不断发展的新领域，在高分子物理中有着广泛的应用。本文利用扫描探针显微技术在形貌测量上的高精度和它所提供的力学测量手段对单链聚集态进行了研究。首先研究了单根高分子链在基板上的形状，从实验上指出高分子链在基板上的形状与高分子链和基板之间的相互作用有关，强的高分子链与基板的相互作用使高分子链以线团的形式躺在基板上，只有适中的高分子链与基板的相互作用才能使高分子链在基板上卷曲成颗粒。接着，运用力调制技术和纳米压印模式对聚苯乙烯单链颗粒和聚苯乙烯本体的力学性质进行了比较，结果发现单链PS颗粒的模量比本体小，这说明存在于聚苯乙烯单链颗粒中的分子链内的缠结点密度不如存在于本体中的分子链间的缠结点密度大。对单链PS颗粒在电场下行为的研究发现PS单链颗粒沿电场方向明显被电场拉长，这种效应与电场强度和电场作用时的温度有关。这是由于聚苯乙烯的g构象在电场下有较大的响应，并且单链颗粒中分子链内的缠结比较弱所致。另外，采用共振模式的原子力显微镜对滴膜法制得的嵌段共聚物膜的微观结构进行了研究。通过控制SBS（PS含量30wt％）溶液的溶剂挥发速率的不同，将不同浓度φ下的微观结构保持下来。随着溶液的变浓，实现了溶剂诱发的嵌段共聚物球状相到柱状相的有序一有序转变；我们还观测到了此过程的中间态：拉长的球和波状柱，证实了理论所预测的波状柱的存在。仔细的分析还发现，在溶剂挥发较快时，得到的是反转相结构（含量多的PB为分散相），当溶剂的挥发速率降低时，反转相结构又恢复成正常的相结构（含量少的PS为分散相）。这是由于在稀溶液中，熵变得相对重要，超过了反转相结构中界面能的增加。这一结果表明控制条件可以得到新的自组装结构。

介孔材料的合成、性能以及应用

自从1992年美孚公司成功地研究开发出介孔材料M41S后，由于其具有不同寻常的结构特点-比较均一的孔径（2-50nm）而且连续可调、较高的比表面积、较大的孔体积、孔的长程有序性以及较好的热稳定性等，具有巨大的潜在应用价值，立即引起了全世界的关注。目前，世界各国的研究主要集中在研究介孔材料的特性、形成机理、介孔材料形貌、结构和孔径的控制、新一代介孔材料的研究开发、介孔材料的改性以及介孔材料的应用等方面。本论文主要在介孔材料的合成、性能以及应用方面开展了研究。选用头尾都是憎水的三嵌段共聚物为模板制备出具有三维无序虫状孔道的介孔材料和以有孔氧化铝膜为模板制备了形态可控的介孔材料，即具有介孔结构高有序纳米管。采用一步法合成了介孔Ag／silica和Y2O3：Eu／silica材料，采用基底受限法制备了银和Y2O3：Eu纳米粒子，同时研究了Ag／silic。作为催化剂时催化性能。（1）在酸性条件下，利用头尾都是憎水的三嵌段共聚物SBS为模板、TEOS为硅源，分别选用丁酮和甲苯作选择性溶剂，通过微乳技术制备出具有三维无序虫状孔道的介孔硅材料。我们通过在SBS胶束溶液中加入TEOS／水的油水混合乳液使SBS胶束与TEOS／水混合乳液之间形成一个界面，从而使TEOS这个界面上完全水解而且生成的小分子硅齐聚物包附在SBS胶束的外表面。经过加热则使TEOS凝聚同时形成具有介孔结构的SBS／硅材料。最后，通过锻烧以移除SBS，从而得到介孔硅材料。在选用甲苯作溶剂，研究发现随着SBS用量的增加或形成胶束温度的升高比表面积、孔体积和孔径等都相应减小。因此，这两个参数可以方便地调节介孔材料的孔径、表面积和孔体积等，进而更好地控制介孔材料的性能。所制备介孔材料的壁厚与SBS用量和形成胶束温度无关，且均超过IOnm，因而材料具有较好的热稳定性，这有利于其进一步在催化剂、吸附和分离等领域应用。（2）以有孔的氧化铝膜为模板制备了具有介孔结构高有序纳米管，即在加热条件下将P123一TEOS薄膜通过毛细力引入有孔的氧化铝膜孔内，同时根据优先润湿机理使P123一TEOS组分润湿氧化铝孔的内壁并同时伴随嵌段共聚物胶束的重排、TEOS组分的凝聚收缩，随后通过烧结手段除去嵌段共聚物、通过溶解手段除去氧化铝模板，这样便在硅基底上得到了形态可控的介孔材料即有序排列的具有介孔结构的纳米管。在一定时间范围内，退火时间对纳米管的形成和生长高度有一定的影响。纳米管垂直于硅基底且纳米管套内的介孔以六方形式排列在整个纳米管套同时介孔孔道相互平行，所制备的纳米管能保持受限在氧化铝模板时的尺寸而且稳定地粘附在硅基底上。（3）在酸性条件下，采用一步法即在模板剂（P123）形成胶束之后，加入硝酸银或氧化铺和氧化忆混合物同P123胶束形成新的复合体，随后加入硅源（TEOS）以包附在复合体的外表面，从而形成具有介孔相的复合物，通过热处理我们分别制备了高有序的具有二维六方结构的介孔Ag／silica和Y203：Eu／silica材料，其中金属银或YZO3：Eu纳米粒子分散在有序的介孔孔道内。二者的比表面积、孔体积和孔径分别为786m2／g、1．22cm3／g、6．Znm和791m2／g、0．95cm3／g、3．snm。另外，我们采用基底受限法，利用旋涂法分别使介孔Ag／silica和YZO3：E记silica材料分散在硅基底上，通过溶解法除去硅墙后便得到了没有聚集的且具有狭窄粒径分布的金属银（2．5-5．snm）和姚03：Eu（1．5-3．onm）纳米粒子。原子力显微镜（AFM）证实所得到的纳米粒子呈现良好的分散状态，具有狭窄的粒径分布而且粒子尺寸都小于其介孔材料孔径。（4）分别用一步法制备的介孔Ag／SBA－－15材料和金属银作为甲醇氧化制备甲醛反应的催化剂，利用甲醇转化率表示催化剂活性、甲醛和二氧化碳产率表示催化剂选择性来研究二者催化性能。由于具有高的比表面积（786扩／g）、较大的孔体积（1．22cm3／g）、较大的孔径（6．2nm）、狭窄的孔径分布和有序的介孔孔洞等特性，在反应温度473K-723K范围内，同本体银作催化剂相比尽管银仅占体系总重量的0．94wt％，介孔Ag／silic。材料却显示出极高的催化活性和催化选择性。

嵌段共聚物及其共混物的相结构和相行为

嵌段共聚物及其共混物的相行为是高分子物理中十分重要的基本问题。论文以三嵌段共聚物SBS、SIS及SBS/PVME、SIS/PVME共混为对象，通过小角散射、透射电镜、流变仪、荧光光谱等手段，细致研究了上述体系的相结构和相行为。首次在三嵌段共聚物中发现一种新的微相结构——双链结构，该结构具有类似于石墨晶体的空间结构，属Rs空间群；在三嵌段共聚物和均聚物共混物中发现双金刚石结构；继Thomas在嵌段共聚物中发现LC结构之后，在嵌段共聚物/均聚物共混物中发现LC结构。论文从理论上预言了嵌段共聚物及其共混物在各种条件下的相图，也是首次研究了嵌段共聚物的微相结构对体系相溶性的影响。

CONTROLLING OF SCHOTTKY-BARRIER HEIGHTS FOR AU/N-GAAS AND TI/N-GAAS WITH HYDROGEN INTRODUCED AFTER METAL-DEPOSITION BY BIAS ANNEALING

Up to now, in most of the research work done on the effect of hydrogen on a Schottky barrier, the hydrogen was introduced into the semiconductor before metal deposition. This letter reports that hydrogen can be effectively introduced into the Schottky barriers (SBs) of Au/n-GaAs and Ti/n-GaAs by plasma hydrogen treatment (PHT) after metal deposition on [100] oriented n-GaAs substrates. The Schottky barrier height (SBH) of a SB containing hydrogen shows the zero/reverse bias annealing (ZBA/RBA) effect. ZBA makes the SBH decrease and RBA makes it increase. The variations in the SBHs are reversible. In order to obtain obvious ZBA/RBA effects, selection of the temperature for plasma hydrogen treatment is important, and it is indicated that 100-degrees-C for Au/n-GaAs and 150-degrees-C for Ti/n-GaAs are suitable temperatures. It is concluded from the analysis of experimental results that only the hydrogen located at or near the metal-semiconductor interface, rather than the hydrogen in the bulk of either the semiconductor or the metal, is responsible for the ZBA/RBA effect on SBH.

Numerical analysis of four-wave-mixing based multichannel wavelength conversion techniques in fibers

We numerically investigate four-wave-mixing (FWM) based multichannel wavelength conversion for amplitude-modulated signals, phase-modulated signals, together with mixed amplitude and phase modulated signals. This paper also discusses the influence of stimulated Brillouin scattering (SBS) effects on high-efficiency FWM-based wavelength conversion applications. Our simulation results show that DPSK signals are more suitable for FWM-based multichannel wavelength conversion because the OOK signals will suffer from the inevitable datapattern-dependent pump depletion. In future applications, when the modulation format is partially upgraded from OOK to DPSK, the influence of OOK signals on the updated DPSK signals must be considered when using multichannel wavelength conversion. This influence becomes severe with the increase of OOK channel number. It can be concluded that DPSK signals are more appropriate for both transmission and multichannel wavelength conversion,especially in long haul and high bit-rate system.

Effects of casting solvents on the formation of inverted phase in block copolymer thin films

Previously, an inverted phase (the minority blocks comprising the continuum phase) was found in solution-cast block copolymer thin films. In this study, the effect of casting solvents on the formation of inverted phase has been studied. Two block copolymers, poly(styrene-b-butadiene) (SB) (M-w = 73 930 Da) and poly(styrene-b-butadiene-b-styrene) (SBS) (M-w = 140 000 Da), with comparable block lengths and equal polystyrene (PS) weight fraction (similar to30 wt %) were used. The copolymer thin films were cast from different solvents, toluene, benzene, cyclohexane, and binary mixtures of benzene and cyclohexane. Toluene and benzene are good solvents for both PS and PB, but have a preferential affinity for PS, while cyclohexane is a good solvent for PB but a Theta solvent for PS (T-Theta = 34.5 degreesC). The differential solvent affinity for PS and PB was estimated in terms of a difference between the polymer-solvent interaction parameter, chi, for each block. Under an extremely slow solvent evaporation rate, the time-dependent phase behavior during such a solution-to-film process was examined by freeze-drying the samples at different stages, corresponding to different copolymer concentrations, rho.

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.