Piecewise Phototuning of Self‐Organized Helical Superstructures

Cholesteric liquid crystals (CLCs) exhibit selective reflection that can be tuned owing to the dynamic control of inherent self‐organized helical superstructures. Although phototunable reflection is reported, these systems hitherto suffer from a limitation in that the tuning range is restricted to one narrow period and the optically addressed images have to sacrifice one color in the visible spectrum to serve as the background, resulting from the insufficient variation in helical twisting power of existing photoresponsive chiral switches that are all bistable. Here, delicate patterns of three primary red, green, and blue (RGB) colors with a black background are presented, which is realized based on piecewise reflection tuning of the CLC induced by a newly designed photoresponsive tristable chiral switch. Three stable configurations of the chiral switch endow the CLC with two continuous and adjacent tuning periods of the reflection, covering not only entire visible spectrum, but also one more wide period within near‐infrared region. Therefore, the concept of piecewise tuning in CLC system demonstrates a new strategy for phototunable RGB and black reflective display.     

A Millimeter Wave Complex Reflection Coeficient Scanner

A broadband microwave measurement system has been designed to make complex reflection coefficient measurements on a swept basis at millineter wave frequencies. This instrument covers a frequency range of 50-75 GHz in WR-15 rectangular waveguide. Two appliques are being added in WR-22 and WR-10 waveguide to extend the frequency range of the system to 33-110 GHz. Measurements can be made while sweeping over bands as wide as 10 GHz. An interesting feature of the complex reflection coefficient scanner is that residuals, or baseline, of the system are automatically subtracted. The resultant output display is a real-time polar plot of the actual reflection coefficient of the network under test. Residuals of 0.03 for reflection coefficients around unity, and 0.013 for reflection coefficients around zero can be measured with a resolution of 0.01 while sweeping over a 5 GHz band. A maximum reflection coefficient range of 46 dB has been achieved using straightforward video detection techniques. For measurements of networks with very low reflection coefficients (0.01 and lower) a time averaging feature is available to reduce the effects of random noise. The complex reflection coefficient of the unknown can be displayed on an oscilioscope and photographed, or read out on an X-Y plotter.     

Livelihood strategy approach to community- based planning and assessment: a case study of Molas,Indonesia

A livelihood strategy is an organized set of lifestyle choices, goals and values, and activities influenced by biophysical, political/legal, economic, social, cultural, and psychological components. The evolution of livelihood strategies was examined in Molas, a coastal village in North Sulawesi province, Indonesia, near the famous coral reefs of Bunaken National Park. Molas was selected to assess how these strategies, especially those of farmers and fishers, are affected in the anticipation stage of tourism development. Study results indicate that documenting the historical evolution, and present and emerging patterns, of livelihood strategies is an essential foundation for successful development and implementation of community-based strategies for environmental planning and management.     

Wave Propagation in a Green–Naghdi Thermoelastic Solid with Diffusion

The Green and Naghdi theory of thermoelasticity is applied to study plane-wave propagation in an elastic solid with thermo-diffusion. The governing equations of an elastic solid with generalized thermo-diffusion are solved to show the existence of three coupled longitudinal waves and a shear vertical (SV) wave in a two-dimensional model of the solid with thermo-diffusion. The reflection of plane waves from a thermally insulated stress-free surface of an elastic solid with thermo-diffusion is also studied. A non-homogeneous system of four equations in reflection coefficients is obtained. The speeds of the plane waves are computed numerically and plotted against frequency for a particular range. The complex absolute values of the reflection coefficients of all reflected waves are computed numerically and plotted against the angle of incidence of the striking wave at the free surface. The effects of diffusion parameters are shown graphically for speeds and reflection coefficients of plane waves.     

Reflection of light by composite volume holograms: Fresnel corrections and Fabry-Perot spectral filtering

Effects in composite volume Bragg gratings (VBGs) are studied theoretically and experimentally. The mathematics of reflection is formulated with a unified account of Fresnel reflections by the boundaries and of VBG reflection. We introduce the strength S of reflection by an arbitrary lossless element such that the intensity of reflection is R=tanh(2) S. We show that the ultimate maximum/minimum of reflection by a composite lossless system corresponds to addition/subtraction of relevant strengths of the sequential elements. We present a new physical interpretation of standard Fresnel reflection: strength for TE or for TM reflection is given by addition or by subtraction of two contributions. One of them is an angle-independent contribution of the impedance step, while the other is an angle-dependent contribution of the step of propagation speed. We study an assembly of two VBG mirrors with a thin immersion layer between them that constitutes a Fabry-Perot spectral filter. The transmission wavelength of the assembly depends on the phase shift between the two VBGs. Spectral resolution Deltalambda(FWHM)=25 pm at lambda=1063.4 nm is achieved with the device of small total physical thickness 2L=5.52 mm.     

圆结构光光条中心亚像素级提取方法

从图像中准确提取光条中心对于主动视觉系统十分重要。分析微小物体内表面视觉检测系统中圆形结构光光条图像特征,将干扰光条分为漫反射和镜面反射两类。利用Hessian矩阵确定图像中光条法线方向,在光条法线方向上求解光条中心亚像素位置,用8方向搜索法剔除干扰光条。实验证明,光条提取和剔除干扰光条方法是有效的。     

“Structuration” by intellectual organization: the configuration of knowledge in relations among structural components in networks of science

Using aggregated journal–journal citation networks, the measurement of the knowledge base in empirical systems is factor-analyzed in two cases of interdisciplinary developments during the period 1995–2005: (i) the development of nanotechnology in the natural sciences and (ii) the development of communication studies as an interdiscipline between social psychology and political science. The results are compared with a case of stable development: the citation networks of core journals in chemistry. These citation networks are intellectually organized by networks of expectations in the knowledge base at the specialty (that is, above-journal) level. The “structuration” of structural components (over time) can be measured as configurational information. The latter is compared with the Shannon-type information generated in the interactions among structural components: the difference between these two measures provides us with a measure for the redundancy generated by the specification of a model in the knowledge base of the system. This knowledge base incurs (against the entropy law) to variable extents on the knowledge infrastructures provided by the observable networks of relations.     

Optical analysis of a liquid-crystal switch system based on total internal reflection

A complete methodology using matrix representations for describing light transmission and reflection at an interface between an isotropic medium with high refractive index and a uniaxial birefringent material where total internal reflection (TIR) could happen is described systematically. A new TIR-based liquid-crystal (LC) switch system is proposed and investigated in detail by using this analyzing method. The criteria of selection of critical parameters such as LC mixture, waveguide, and operation mode of the LC layer, etc., are discussed. Dependence of transmission on incident angle and dynamic characteristics under an electric field are given for different cell gaps. The results give detailed and useful guidance in the fabrication of the LC switch system.     

Combined Twyman-Green and Mach-Zehnder interferometer for microlens testing

A new interferometer design for microlens testing is presented. The phase-shifting system combines the advantages of a Twyman-Green and a Mach-Zehnder interferometer and permits full characterization of the aberrations of microlenses as well as radius of curvature and focal length measurements. The Twyman-Green system is applied to surface testing in reflection (single reflection), whereas the Mach-Zehnder system is used for lens testing in transmission (single pass). Both measurements are performed without removal of the test part, allowing for combination of the results without confusion of the actual lens and without an azimuthal orientation error. The interferometer setup is explained, the test procedure is described, and experimental results are given.     

WR-28功率基准系统中等效源反射系数校准研究

在WR-28功率基准系统中,等效源反射系数是确定量热计有效效率、分析不确定度与进行基准功率量值传递的重要参数,其只与接入量热计的定向耦合器有关,而与信号源无关。介绍了传统三端口测试法、直接校准法和最新提出的Shimaoka K法3种三端口器件等效源反射系数的测试方法。在频段26.5~40 GHz,运用Shimaoka K法对三端口器件（定向耦合器）进行等效源反射系数测量,并与其他两种方法实验结果比较,验证了Shimaoka K法的可行性与准确性,同时通过实验比较,由于Shimaoka K法具有的综合优势,使其成为WR-28功率基准中等效源反射系数的最佳测试方法,并以Shimaoka K法为例,对等效源反射系数不确定度进行了评定。     

Measurement and monitoring of microwave reflection and transmission properties of cement-based specimens

The results of measurement and monitoring of reflection and transmission properties of cement-based specimens (blocks of mortar, concrete) obtained by using a simple and an inexpensive measurement system at microwave frequencies (X-band) are presented. Dependencies of the reflection and transmission coefficients on water-to-cement (w/c) ratio, preparing and curing conditions of the specimens are demonstrated. It is shown that the amplitudes of reflection and transmission coefficients, together with thickness of the specimens, determine the complex dielectric permittivity of the hardened cement-based specimens. The expected applications of the results for the determination of physical properties of cement-based materials are discussed. The causes and effects of measurement errors and uncertainties are also discussed.     

Kunststoffoptiken mit Antireflex‐ und Antibeschlageigenschaften durch Plasmaätzen und Beschichtung

Plastic optics exhibiting anti‐reflection and anti‐fogging properties produced by plasma etching and coating Plasma treatments are capable to generate antireflective surface structures on various polymers. On PMMA a self organized surface with nep‐like bumps exhibits excellent optical properties. Many other materials like polycarbonate, zeonex and lacquers can be etched after depositing a very thin initial layer to form a more holey structure. These surfaces attain high transmission values too and can be better stabilized by coatings than the nep‐ structure on PMMA. Interesting for practical applications are hydrophilic top‐layers to provide anti‐fogging properties in combination with improved transmission.     

Facing future climate change: is the past relevant?

From a socio-economic perspective, the 'sharp end' of climate research is very much about looking forward in time. As far as possible, we need to know what to expect and approximately when to expect it. However, it is argued here that our approach to climate change (including its scientific basis and its policy implications) is firmly linked to our understanding of the past. This is mainly due to the role played by palaeoclimate reconstructions in shaping our expectations of the climate system, in particular via their ability to test the accuracy of our climate models. Importantly, this includes the intuitive models that each of us carries around in our mind, as well as the more complex numerical models hiding inside supercomputers. It is through such models that palaeoclimate insights may affect the scientific and political judgements that we must make in the face of persistent and ultimately irreducible predictive uncertainty. Already we can demonstrate a great deal of confidence in our current understanding of the global climate system based specifically on insights from the geological record. If further advances are to be made effectively, climate models should take advantage of both past and present constraints on their behaviour, and should be given added credence to the extent that they are compatible with an increasingly rich tapestry of past climatic phenomena. Furthermore, palaeoclimate data should be accompanied by clearly defined uncertainties, and organized in arrays that are capable of speaking directly to numerical models, and their limitations in particular.     

Design of reflection retarders by use of nonnegative film-substrate systems

A reflection-type film-substrate retarder is an optical device that changes the relative phase but not the relative amplitude of light upon reflection from a film-substrate system. While there are several such device designs based on the common negative film-substrate system, very little has been done with the other two categories of systems, zero and positive. The system category is determine by the relationship between the refractive indices of the ambient N0, film N1 and substrate N2. If N1 < square root of N0N2, the system is negative; if N1 = square root of N0N2, the system is zero; and if N1 > square root of N0N2, the system is positive. The design procedure and characteristics of zero-system reflection retarders are discussed. The polarization and ellipsometric properties of the positive system preclude the existence of a reflection retarder. First, a brief characterization of the zero and positive systems by means of constant-angle-of-incidence contours and constant-thickness contours of the ellipsometric function is presented and discussed. Then an algorithm outlining the design procedures is presented, and the characteristics of the obtained designs are optimized, analyzed, and discussed. The exact retarder is valid for a single wavelength at a set angle of incidence. The design tolerance to changes in the design parameters is analyzed and discussed. In general, N1 < or = square root of N1N2 is the condition to be satisfied to realize reflection-type retarders with film-substrate systems.     

Nondestructive Measurement of Materials Using a Waveguide-Fed Series Slot Array

The reflection from an array of narrow series slots on the broad face of a rectangular waveguide is used to determine the permittivity of lossy materials. The theoretical study of the electromagnetic field in the vicinity of the slots yields a system of integral equations which takes into account the internal and external coupling between slots. The numerical solution is discussed and an optimization procedure for the array is presented, which provides a simple relationship linking the reflection coefficient to the complex permittivity over a specified range. Computed results are compared to experimental values for air and a lossy dielectric at 10 GHz, showing good agreement. Interpolation from computed data is provided by a polynomial expansion: this allows one to determine the complex permittivity once the reflection factor has been measured.     

Wave scattering by a circular cylinder half-immersed in water with an ice-cover

The problem of scattering of water waves obliquely incident on a fixed long circular cylinder half-immersed in deep water with an ice-cover is investigated here. The ice-cover is modelled as an elastic plate of very small thickness. The problem is formulated using the method of multipoles. This leads to an infinite system of linear equations which are solved numerically by truncation. The reflection and transmission coefficients are obtained and depicted graphically against the wave number for various values of the angle of incidence and flexural rigidity of the ice-cover to show the effect of the presence of ice-cover on these quantities. The effect of ice-cover is seen to increase the reflection coefficient and to decrease the transmission coefficient.     

Polarization-based index of refraction and reflection angle estimation for remote sensing applications

A passive-polarization-based imaging system records the polarization state of light reflected by objects that are illuminated with an unpolarized and generally uncontrolled source. Such systems can be useful in many remote sensing applications including target detection, object segmentation, and material classification. We present a method to jointly estimate the complex index of refraction and the reflection angle (reflected zenith angle) of a target from multiple measurements collected by a passive polarimeter. An expression for the degree of polarization is derived from the microfacet polarimetric bidirectional reflectance model for the case of scattering in the plane of incidence. Using this expression, we develop a nonlinear least-squares estimation algorithm for extracting an apparent index of refraction and the reflection angle from a set of polarization measurements collected from multiple source positions. Computer simulation results show that the estimation accuracy generally improves with an increasing number of source position measurements. Laboratory results indicate that the proposed method is effective for recovering the reflection angle and that the estimated index of refraction provides a feature vector that is robust to the reflection angle.     

Measuring Twitter-based political participation and deliberation in the South Korean context by using social network and Triple Helix indicators

This study investigates the role of Twitter in political deliberation and participation by analyzing the ways in which South Korean politicians use Twitter. In addition, the study examines the rise of Twitter as user-generated communication system for political participation and deliberation by using the Triple Helix indicators. For this, we considered five prominent politicians, each belonging to one of four political parties, by using data collected in June 2010. The results suggest that non-mainstream, resource-deficient politicians are more likely to take advantage of Twitter’s potential as an alternative means of political participation and that a small number of Twitter users lead political discourse in the Twittersphere. We also examined the occurrence and co-occurrence of politicians’ names in Twitter posts, and then calculate entropy values for trilateral relationships. The results suggest that the level of political deliberation, expressed in terms of the level of balance in the communication system, is higher when politicians with different political orientations form the trilateral relationships.     

Fractional Fourier transformers through reflection

We show that an arbitrary paraxial optical system, compounded with its reflection in an appropriately warped mirror, is a pure fractional Fourier transformer between coincident input and output planes. The geometric action of reflection on optical systems is introduced axiomatically and is developed in the paraxial regime. The correction of aberrations by warp of the mirror is briefly addressed.     

Planar-optic-disk pickup with diffractive micro-optics

An integrated optical-disk pickup with a diffractive planar micro-optic system is proposed. In this device, the beam follows a zigzag optical path inside a glass substrate that is used as a light guide. To fabricate off-axis diffractive optical elements, we have recently developed an electron-beam writing system with a curve-pattern generator. It is demonstrated that a transmission off-axis objective microlens, a reflection twin-focusing beam splitter, and reflection layers were integrated on a glass substrate, and such a diffractive planar micro-optic system exhibited an excellent focusing performance and operated forfocus-error signal detection, as designed.