Hongik University

We propose a referenceless perceptual fog density prediction model based on natural scene statistics (NSS) and fog aware statistical features. The proposed model, called Fog Aware Density Evaluator (FADE), predicts the visibility of a foggy scene from a single image without reference to a corresponding fog-free image, without dependence on salient objects in a scene, without side geographical camera information, without estimating a depth-dependent transmission map, and without training on human-rated judgments. FADE only makes use of measurable deviations from statistical regularities observed in natural foggy and fog-free images. Fog aware statistical features that define the perceptual fog density index derive from a space domain NSS model and the observed characteristics of foggy images. FADE not only predicts perceptual fog density for the entire image, but also provides a local fog density index for each patch. The predicted fog density using FADE correlates well with human judgments of fog density taken in a subjective study on a large foggy image database. As applications, FADE not only accurately assesses the performance of defogging algorithms designed to enhance the visibility of foggy images, but also is well suited for image defogging. A new FADE-based referenceless perceptual image defogging, dubbed DEnsity of Fog Assessment-based DEfogger (DEFADE) achieves better results for darker, denser foggy images as well as on standard foggy images than the state of the art defogging methods. A software release of FADE and DEFADE is available online for public use: http://live.ece.utexas.edu/research/fog/index.html.

Deals with three issues in the area of perceived service quality. First, it compares the gap model with the performance model. Second, it investigates the direction of causality between service quality and satisfaction. Finally, it examines whether the influences of some dimensions of service quality vary across service industry types. Three service firms were selected and respondents were interviewed in each firm. As hypothesized, the performance model appeared to be superior to the gap model. In addition, the result shows that perceived service quality is an antecedent of satisfaction, rather than vice versa. Finally, tangibles appeared to be a more important factor in the facility/equipment‐based industries, whereas responsiveness is a more important factor in the people‐based industries. Managerial implications and future research directions are discussed.

Flash memory is becoming increasingly important as nonvolatile storage for mobile consumer electronics due to its low power consumption and shock resistance. However, it imposes technical challenges in that a write should be preceded by an erase operation, and that this erase operation can be performed only in a unit much larger than the write unit. To address these technical hurdles, an intermediate software layer called a flash translation layer (FTL) is generally employed to redirect logical addresses from the host system to physical addresses in flash memory. Previous approaches have performed this address translation at the granularity of either a write unit (page) or an erase unit (block). We propose a novel FTL design that combines the two different granularities in address translation. This is motivated by the idea that coarse grain address translation lowers the resources required to maintain translation information, which is crucial in mobile consumer products for cost and power consumption reasons, while fine grain address translation is efficient in handling small size writes. Performance evaluation based on trace-driven simulation shows that the proposed scheme significantly outperforms previously proposed approaches.

Abstract In this study, the properties and application of natural fiber composites in automobile industries are discussed. Natural fibers are replacing the synthetic fibers in the various parts of automobiles due to their lightweight, low‐cost, and environmental aspects. For centuries, natural fibers have been used for making baskets, clothing, and ropes. Now the trend is changing and natural fibers such as: jute, hemp, flax, and sisal fibers are making their ways especially into the components of automobiles. Comparisons of material indices for beam and panel structures were made to investigate the possibility of using natural fiber composites instead of conventional and non‐conventional materials.

Efficient and effective buffering of disk blocks in main memory is critical for better file system performance due to a wide speed gap between main memory and hard disks. In such a buffering system, one of the most important design decisions is the block replacement policy that determines which disk block to replace when the buffer is full, In this paper, we show that there exists a spectrum of block replacement policies that subsumes the two seemingly unrelated and independent Least Recently Used (LRU) and Least Frequently Used (LFU) policies. The spectrum is called the LRFU (Least Recently/Frequently Used) policy and is formed by how much more weight we give to the recent history than to the older history. We also show that there is a spectrum of implementations of the LRFU that again subsumes the LRU and LFU implementations. This spectrum is again dictated by how much weight is given to recent and older histories and the time complexity of the implementations lies between O(1) (the time complexity of LRU) and O(log(2) n) (the time complexity of LFU), where n is the number of blocks in the buffer, Experimental results from trace-driven simulations show that the performance of the LRFU is at least competitive with that of previously known policies for the workloads we considered.

This article discusses the challenges, benefits and approaches associated with realizing largescale antenna arrays at mmWave frequency bands for future 5G cellular devices. Key design considerations are investigated to deduce a novel and practical phased array antenna solution operating at 28 GHz with near spherical coverage. The approach is further evolved into a first-of- a-kind cellular phone prototype equipped with mmWave 5G antenna arrays consisting of a total of 32 low-profile antenna elements. Indoor measurements are carried out using the presented prototype to characterize the proposed mmWave antenna system using 16-QAM modulated signals with 27.925 GHz carrier frequency. The biological implications due to the absorbed electromagnetic waves when using mmWave cellular devices are studied and compared in detail with those of 3/4G cellular devices.

The use of the Internet is growing in this day and age, so another area has developed to use the Internet, called Internet of Things (IoT). It facilitates the machines and objects to communicate, compute and coordinate with each other. It is an enabler for the intelligence affixed to several essential features of the modern world, such as homes, hospitals, buildings, transports and cities. The security and privacy are some of the critical issues related to the wide application of IoT. Therefore, these issues prevent the wide adoption of the IoT. In this paper, we are presenting an overview about different layered architectures of IoT and attacks regarding security from the perspective of layers. In addition, a review of mechanisms that provide solutions to these issues is presented with their limitations. Furthermore, we have suggested a new secure layered architecture of IoT to overcome these issues.

Crystalline–amorphous phase boundary engineering can be an effective strategy to develop cost-effective and high-performance electrocatalysts for water splitting.

A semiempirical polarimetric backscattering model for bare soil surfaces is inverted directly to retrieve both the volumetric soil moisture content M/sub v/ and the rms surface height s from multipolarized radar observations. The rms surface height s and the moisture content M/sub v/ can be read from inversion diagrams using the measurements of the cross-polarized backscattering coefficient /spl sigma//sub vh//sup 0/ and the copolarized ratio p(=/spl sigma//sub hh//sup 0///spl sigma//sub vv//sup 0/). Otherwise, the surface parameters can be estimated simply by solving two equations (/spl sigma//sub vh//sup 0/ and p) in two unknowns (M/sub v/ and s). The inversion technique has been applied to the polarimetric backscattering coefficients measured by ground-based polarimetric scatterometers and the Jet Propulsion Laboratory airborne synthetic aperture radar. A good agreement was observed between the values of surface parameters (the rms height s, roughness parameter ks, and the volumetric soil moisture content M/sub v/) estimated by the inversion technique and those measured in situ.

White LEDs are fabricated through a combination of blue LEDs with Sr3SiO5:Ce3+,Li+ phosphors and organically capped CdSe quantum dots (QDs), which exhibit a 2D superlattice. The combination of blue emission from the LEDs, greenish-yellow emission from the phosphors, and red emission from the QDs generates white light. As-synthesized white LEDs show excellent color rendering properties and stable color coordinates against increasing forward bias currents (see figure). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2008/adma200702846_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Copper indium sulfide (CIS) quantum dots (QDs) with different Cu/In molar ratios of 1/1, 1/2, and 1/4 are synthesized via a hot colloidal route. The band gap energy of CIS QDs is observed to be dependent on Cu/In ratio, exhibiting a higher band gap from more Cu-deficient QDs. The emission wavelengths of all CIS QDs belong to a deep red region (665–717 nm) with relatively low quantum yields (QYs) of 8.6–12.7%. Compared to respective original core QDs, the absorption peaks of all CIS/ZnS QDs are blue-shifted, and their emission wavelengths move to a higher energy accordingly, showing a quite tunable emission from yellow to red. The effective surface passivation by a ZnS overlayer results in a dramatic increase in QY of CIS/ZnS QDs in the range of 68–78%. All CIS/ZnS QDs are tested as wavelength converters for the fabrication of QD-based light-emitting diodes (LEDs). QD-based white LEDs that consist of only a single type of QD are for the first time realized by applying yellow-emitting CIS/ZnS QDs as a result of the appropriate color mixing between blue emission from a LED chip and yellow emission from QDs. Detailed electroluminescent properties including color rendering index, Commission Internationale de l’Eclairage (CIE) color coordinates, and luminous efficiency of QD-based white LEDs are evaluated as a function of forward current.

Green CdSe@ZnS quantum dots (QDs) of 9.5 nm size with a composition gradient shell are first prepared by a single-step synthetic approach, and then 12.7 nm CdSe@ZnS/ZnS QDs, the largest among ZnS-shelled visible-emitting QDs available to date, are obtained through the overcoating of an additional 1.6 nm thick ZnS shell. Two QDs of CdSe@ZnS and CdSe@ZnS/ZnS are incorporated into the solution-processed hybrid QD-based light-emitting diode (QLED) structure, where the QD emissive layer (EML) is sandwiched by poly(9-vinlycarbazole) and ZnO nanoparticles as hole and electron-transport layers, respectively. We find that the presence of an additional ZnS shell makes a profound impact on device performances such as luminance and efficiencies. Compared to CdSe@ZnS QD-based devices the efficiencies of CdSe@ZnS/ZnS QD-based devices are overwhelmingly higher, specifically showing unprecedented values of peak current efficiency of 46.4 cd/A and external quantum efficiency of 12.6%. Such excellent results are likely attributable to a unique structure in CdSe@ZnS/ZnS QDs with a relatively thick ZnS outer shell as well as a well-positioned intermediate alloyed shell, enabling the effective suppression of nonradiative energy transfer between closely packed EML QDs and Auger recombination at charged QDs.

In this article, we develop a command, xthenreg, that implements the first-differenced generalized method of moments estimation of the dynamic panel threshold model that Seo and Shin (2016, Journal of Econometrics 195: 169–186) proposed. Furthermore, we derive the asymptotic variance formula for a kink-constrained generalized method of moments estimator of the dynamic threshold model and provide an estimation algorithm. We also propose a fast bootstrap algorithm to implement the bootstrap for the linearity test. We illustrate the use of xthenreg through a Monte Carlo simulation and an economic application.

For colloidal quantum dot light-emitting diodes (QD-LEDs), blue emissive device has always been inferior to green and red counterparts with respect to device efficiency, primarily because blue QDs possess inherently unfavorable energy levels relative to green and red ones, rendering hole injection to blue QDs from neighboring hole transport layer (HTL) inefficient. Herein, unprecedented synthesis of blue CdZnS/ZnS core/shell QDs that exhibit an exceptional photoluminescence (PL) quantum yield of 98%, extraordinarily large size of 11.5 nm with a shell thickness of 2.6 nm, and high stability against a repeated purification process is reported. All-solution-processed, multilayered blue QD-LEDs, consisting of an HTL of poly(9-vinlycarbazole), emissive layer of CdZnS/ZnS QDs, and electron transport layer of ZnO nanoparticles, are fabricated. Our best device displays not only a maximum luminance of 2624 cd/m(2), luminous efficiency of 2.2 cd/A, and external quantum efficiency of 7.1%, but also no red-shift and broadening in electroluminescence (EL) spectra with increasing voltage as well as a spectral match between PL and EL.

Here we describe a simple and efficient method for fabricating natural and synthetic hydrogels into 3-D geometries with high aspect ratio and curvature. Fabricating soft hydrogels into such shapes using conventional techniques has been extremely difficult. Combination of laser ablation and sacrificial molding technique using calcium alginate minimizes the stress associated with separating the mold from the hydrogel structure, and therefore allows fabrication of complex structures without damaging them. As a demonstration of this technique, we have fabricated a microscale collagen structure mimicking the actual density and size of human intestinal villi. Colon carcinoma cell line, Caco-2 cells, was seeded onto the structure and cultured for 3 weeks until the whole structure was covered, forming finger-like structures mimicking the intestinal villi covered with epithelial cells. This method will enable construction of in vitro tissue models with physiologically realistic geometries at microscale resolutions.

Abstract In the case of a high-valuable asset, the Operation and Maintenance (O&M) phase requires heavy charges and more efforts than the installation (construction) phase, because it has long usage life and any accident of an asset during this period causes catastrophic damage to an industry. Recently, with the advent of emerging Information Communication Technologies (ICTs), we can get the visibility of asset status information during its usage period. It gives us new challenging issues for improving the efficiency of asset operations. One issue is to implement the Condition-Based Maintenance (CBM) approach that makes a diagnosis of the asset status based on wire or wireless monitored data, predicts the assets abnormality, and executes suitable maintenance actions such as repair and replacement before serious problems happen. In this study, we have addressed several aspects of CBM approach: definition, related international standards, procedure, and techniques with the introduction of some relevant case studies that we have carried out.

A semi-empirical model of the ensemble-averaged differential Mueller matrix for microwave backscattering from bare soil surfaces is presented. Based on existing scattering models and data sets measured by polarimetric scatterometers and the JPL AirSAR, the parameters of the co-polarized phase-difference probability density function, namely the degree of correlation /spl alpha/ and the co-polarized phase-difference /spl sigmav/, in addition to the backscattering coefficients /spl sigma//sub /spl nu//spl nu///sup 0/,/spl sigma//sub hh//sup 0/ and /spl sigma//sub /spl nu/h//sup 0/, are modeled empirically in terms of the volumetric soil moisture content m/sub /spl nu// and the surface roughness parameters ks and kl, where k=2/spl pi/f/c, s is the rms height and l is the correlation length. Consequently, the ensemble-averaged differential Mueller matrix (or the differential Stokes scattering operator) is specified completely by /spl sigma//sub /spl nu//spl nu///sup 0/,/spl sigma//sub hh//sup 0/,/spl sigma//sub /spl nu/h//sup 0/,/spl alpha/, and /spl zeta/.

Given the important role of green environments playing in healthy cities, the inequality in urban greenspace exposure has aroused growing attentions. However, few comparative studies are available to quantify this phenomenon for cities with different population sizes across a country, especially for those in the developing world. Besides, commonly used inequality measures are always hindered by the conceptual simplification without accounting for human mobility in greenspace exposure assessments. To fill this knowledge gap, we leverage multi-source geospatial big data and a modified assessment framework to evaluate the inequality in urban greenspace exposure for 303 cities in China. Our findings reveal that the majority of Chinese cities are facing high inequality in greenspace exposure, with 207 cities having a Gini index larger than 0.6. Driven by the spatiotemporal variability of human distribution, the magnitude of inequality varies over different times of the day. We also find that exposure inequality is correlated with low greenspace provision with a statistical significance (p-value < 0.05). The inadequate provision may result from various factors, such as dry cold climate and urbanization patterns. Our study provides evidence and insights for central and local governments in China to implement more effective and sustainable greening programs adjusted to different local circumstances and incorporate the public participatory engagement to achieve a real balance between greenspace supply and demand for developing healthy cities.

This paper proposes a method to predict fluctuations in the prices of cryptocurrencies, which are increasingly used for online transactions worldwide. Little research has been conducted on predicting fluctuations in the price and number of transactions of a variety of cryptocurrencies. Moreover, the few methods proposed to predict fluctuation in currency prices are inefficient because they fail to take into account the differences in attributes between real currencies and cryptocurrencies. This paper analyzes user comments in online cryptocurrency communities to predict fluctuations in the prices of cryptocurrencies and the number of transactions. By focusing on three cryptocurrencies, each with a large market size and user base, this paper attempts to predict such fluctuations by using a simple and efficient method.

The Internet of Things (IoT) has become a reality. As the IoT is now becoming a far more common field, the demand for IoT technologies to manage the communication of devices with the rest of the world has increased. The IoT is connecting various individual devices called things and wireless sensor networks is also playing an important role. A thing can be defined as an embedded device based on a micro controller that can transmit and receive information. These devices are extremely low in power, memory, and resources. Therefore, the research community has recognized the importance of IoT device operating systems (OSs). An adequate OS with a kernel, networking, real-time capability, and more can make these devices flexible. This review provides a detailed comparison of the OSs designed for IoT devices on the basis of their architecture, scheduling methods, networking technologies, programming models, power and memory management methods, together with other features required for IoT applications. In addition, various applications, challenges, and case studies in the field of IoT research is discussed.