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In this work, we report on the design, fabrication and characterization of Metal-Oxide Graphene Field-effect Transistors (MOGFETs) exploiting novel clamped gate geometries aimed at enhancing the device transconductance. The fabricated devices employ clamped metal contacts also for source and drain, as well as an optimized graphene meandered pattern for source contacting, in order to reduce parasitic resistance. Our experimental results demonstrate that MOGFETs with the proposed structure show improved high frequency performance, in terms of maximum available gain and transition frequency values, as a consequence of the higher equivalent transconductance obtained.

In this paper, we propose a method of identifying human motions, such as standing, walking, running, and crawling, using a millimeter wave radar sensor. In our method, two signal processing is performed in parallel to identify the human motions. First, the moment at which a person’s motion changes is determined based on the statistical characteristics of the radar signal. Second, a deep learning-based classification algorithm is applied to determine what actions a person is taking. In each of the two signal processing, radar spectrograms containing the characteristics of the distance change over time are used as input. Finally, we evaluate the performance of the proposed method with radar sensor data acquired in an indoor environment. The proposed method can find the moment when the motion changes with an error rate of 3%, and also can classify the action that a person is taking with more than 95% accuracy.

Osseointegration of titanium implant is important for the success of both dental and medical implants. Previous studies have attempted to improve osseointegration by considering the use of plasma jet technology, where information with animal models and parameters related to osseointegration is still lacking. Therefore, this study investigated the effects of non-thermal atmospheric pressure plasma jet (NTAPPJ) treatment on titanium implants in terms of osseointegration in mongrel dogs. A total of 41 implants, 21 NTAPPJ treated and 20 control, were placed in the maxilla and mandible of six mongrel dogs for either 4 or 8 weeks. The bone volume (BV) and bone-to-implant contact (BIC) ratio were determined by region of interest (ROI). Statistical analysis was performed with the Wilcoxon rank-sum test. The NTAPPJ group at 4 weeks showed higher numbers in both BV and BIC (p &lt, 0.05) compared to the control group. However, at 8 weeks there were less significant differences between the control or experimental group as the control group had caught up with the experimental group. Hence, NTAPPJ may be an effective treatment for the initial healing period which is critical to ensure reliable long-term predictability. The BV and BIC have been clinically proven to accelerate in the initial stages with the use of NTAPPJ to aid in the healing and initial stability of implants.

Since III-nitride semiconductor-based ultraviolet (UV) light-emitting diodes (LEDs) are compact and efficient, they can be suggested as a substitute for conventional arc-lamps. However, reported UV LEDs focused on a narrow range of UV spectrum contrary to conventional arc-lamps. Here, we introduce GaN quantum dots (QDs) grown on different facets of hexagonal truncated pyramid structures on a conventional sapphire substrate. These structures include semipolar facets as well as a polar facet, which obtain intrinsically different piezoelectric fields and growth rates of QDs. Consequently, we demonstrated a plateau-like broadband UV emitter ranging from UV-C to UV-A from the GaN QDs.

Group III-nitride semiconductor-based ultraviolet (UV) light emitting diodes have been suggested as a substitute for conventional arc-lamps such as mercury, xenon and deuterium arc-lamps, since they are compact, efficient and have a long lifetime. However, in previously reported studies, group III-nitride UV light emitting diodes did not show a broad UV spectrum range as conventional arc-lamps, which restricts their application in fields such as medical therapy and UV spectrophotometry. Here, we propose GaN quantum dots (QDs) grown on different facets of hexagonal truncated pyramid structures formed on a conventional (0001) sapphire substrate. A hexagonal truncated GaN pyramid structure includes {101̄1} semipolar facets as well as a (0001) polar facet, which have intrinsically different piezoelectric fields and growth rates of GaN QDs. Consequently, we successfully demonstrated a plateau-like broadband UV spectrum ranging from ∼400 nm (UV-A) to ∼270 nm (UV-C) from the GaN QDs. In addition, at the top-edge of the truncated pyramid structure, a strain was locally suppressed compared to the center of the truncated pyramid structure. As a result, various emission wavelengths in the UV range were achieved from the GaN QDs grown on the sidewall, top-edge and top-center of hexagonal truncated pyramid structures, which ultimately provide a broadband UV spectrum with high efficiency.

Warm and natural white light (i.e., with a correlated colour temperature 75) is in demand as an indoor lighting source of comfortable interior lighting and mood lighting. However, for warm white light, phosphor-converted white light-emitting diodes (WLEDs) require a red phosphor instead of a commercial yellow phosphor (YAG:Ce3+), and suffer from limitations such as unavoidable energy conversion losses, degraded phosphors and high manufacturing costs. Phosphor-free WLEDs based on three-dimensional (3D) indium gallium nitride (InGaN)/gallium nitride (GaN) structures are promising alternatives. Here, we propose a new concept for highly efficient phosphor-free warm WLEDs using 3D core–shell InGaN/GaN dodecagonal ring structures, fabricated by selective area growth and the KOH wet etching method. Electrically driven, phosphor-free warm WLEDs were successfully demonstrated with a low correlated colour temperature (4500 K) and high colour rendering index (Ra = 81). From our findings, we believe that WLEDs based on dodecagonal ring structures become a platform enabling a high-efficiency warm white light-emitting source without the use of phosphors.

Improvements in the overall efficiency and significant reduction in the efficiency droop are observed in three-dimensional (3D) GaN truncated pyramid structures fabricated with air void and a SiO2 layer. This 3D structure was fabricated using a self-aligned twofold epitaxial lateral overgrowth technique, which improved both the internal quantum efficiency and the light extraction efficiency. In addition, a reduced leakage current was observed due to the effective suppression of threading dislocations. While this study focuses primarily on the blue emission wavelength region, this approach can also be applied to overcome the efficiency degradation problem in the ultraviolet, green, and red emission regions.

The photoluminescence of graphene quantum dots (GQDs) is rigorously investigated due to their potential applications. However, GQDs from graphene oxide are inherently embedded with non-negligible defects and oxygen grafted onto the edge and basal plane, which induce a change of innate electronic structure in the GQDs. Thus, graphene oxide based GQDs can misrepresent the characteristic properties of primitive GQDs. Here we report the size and pH dependent photophysical properties of GQDs that minimize the content of oxygen and defects. From auger electron spectroscopy, the oxygen content of the GQDs with two different lateral sizes (∼2 nm and ∼18 nm) was probed and found to be ∼5% and ∼8%, respectively. Two common photoluminescence (PL) peaks were observed at 436 nm (the intrinsic bandgap) and 487 nm (the extrinsic bandgap) for both GQDs. The characteristic PL properties in extrinsic and intrinsic bandgaps examined by optical spectroscopic methods show that the emission peak was red-shifted and that the peak width was widened as the size increased. Moreover, the PL lifetime and intensity were not only reversibly changed by pH but also depended on the excitation wavelength. This is in line with our previous report and is ascribed to the size variation of sp2 subdomains and edge functionalization.

Optical transition between singlet and triplet is observed in phosphorescent platinum octaethylporphyrin (PtOEP), on a graphene substrate. PtOEP on single layer of graphene not only modulates the dominant emission wavelength but also enhances the emission intensity. This result addresses new light-matter interactions of the hybrid structure of graphene and a single molecule.

In this paper, a novel reversible data hiding by using Reed-Solomon (RS) code is proposed for efficient transmission in encryption image. To increase the recovery of data from encrypted image, RS codes are used to encode messages, and then the codewords can be embedded into encrypted image according to encryption key. After receiving encrypted image which embeds the codewords, the receiver firstly decryptes the encrypted image using the encryption key and get metric about codewords containing messages. According to recovery capability of RS codes, better estimation of message is done in data hiding system. Simulation results about two images and two RS codes show that the performances of the proposed schemes are better than ones of the reference

The graphene oxide (GO) and graphene oxide quantum dots (GOQDs), which have gained research interest as new types of light-emitting materials, were synthesized by the modified Hummers method for oxidation of graphite flake and graphite nanoparticle. The optical properties of GO and GOQDs have been compared by mean of photoluminescence (PL), PL excitation (PLE), UV-vis absorbance, and time-resolved PL. The GO have an absorption peak at 229 nm and shoulder part at 310 nm, whereas the GOQDs show broad absorption with a gradual change up without any absorption peaks. The PL emission of GOQDs and GO showed the green color at 520 nm and the red color at 690 nm, respectively. The red emission of GO showed faster PL decay time than the green emission of GOQDs. In particular, the temporal PL profile of the GO showed redshift from 560 nm to 660 nm after the pump event.

DNP3(Distributed Network Protocol) is one of the most representative protocols which is used in SCADA(Supervisory Control and Data Acquisition) system. IEC 62351 is listing the integrity, confidentiality, availability and non-repudiation or accountability as the security requirement. However, IEEE Std. 1815 that is DNP3 standards does not define a mechanism for non-repudiation or accountability. In this paper, we propose a non-repudiation of origin technique about the sender of critical ASDU and implement the proposed scheme using software such as OpenSSL and SCADA source code library.

In-depth study on upconversion photoluminescence (UCPL) of graphene oxide quantum dots (GOQDs) was presented. Uniform GOQDs with a single-layer and a circular shape within 4 nm diameter were fabricated by acidic exfoliation from the graphite nanoparticles. The green UCPL of the GOQDs at ∼563 nm was observed by a femto-second (fs) Ti:sapphire pulsed laser (λex: 800 nm), and the mechanism of the observed UCPL was systemically characterized. We further utilized the UCPL of GOQD as an optical biosensor for detecting aptamer-based metal ions with high sensitivity and selectivity, and verified that the fluorescence quenching of the UCPL GOQDs was mediated by the electron transfer between the GOQD and the captured metal ion rather than fluorescence energy transfer. The understanding of the UCPL of graphene quantum dots would enhance their applicability in the biosensing and bioimaging research fields.

The assessment of the embodied environmental impacts of buildings can help decision-makers plan environment-friendly buildings and reduce environmental impacts. For a more comprehensive assessment of the embodied environmental impacts of buildings, a hybrid life cycle assessment model was developed in this study. The developed model can assess the embodied environmental impacts (global warming, ozone layer depletion, acidification, eutrophication, photochemical ozone creation, abiotic depletion, and human toxicity) generated directly and indirectly in the material manufacturing, transportation, and construction phases. To demonstrate the application and validity of the developed model, the environmental impacts of an elementary school building were assessed using the developed model and compared with the results of a previous model used in a case study. The embodied environmental impacts from the previous model were lower than those from the developed model by 4.6–25.2%. Particularly, human toxicity potential (13 kg C 6 H 6 eq.) calculated by the previous model was much lower (1965 kg C 6 H 6 eq.) than what was calculated by the developed model. The results indicated that the developed model can quantify the embodied environmental impacts of buildings more comprehensively, and can be used by decision-makers as a tool for selecting environment-friendly buildings.

Accounting is often called a language of business and the grammar of the language is now under transition to a new one – the IFRS. Does the IFRS regime help make accounting a better business language than do other accounting regimes? That is our research question, and to answer the question we examine the effect of IFRS adoption on readability of firms’ financial disclosures. As a global accounting regime, the IFRS puts greater emphasis on understandability in financial reporting than do any other existing accounting standards. In many countries, however, adopting the IFRS involves the process of translating the original IFRS into local non-English languages, and apparently, the IFRS Foundation sticks to word-for-word or literal-translation policy to ensure an adopter country’s complying with the original IFRS. Understandability and literal translation, however, might be less than a good match. It is, therefore, timely and relevant to examine whether financial statement understandability has improved unde...

Many studies use life-cycle assessment (LCA) as a tool to quantify the environmental impact of buildings. Most of these studies have focused on the maintenance and operation phases of construction projects, which account for the largest part of energy consumption during the life cycle of buildings. However, the construction phase may cause significant environmental impacts, so a detailed analysis on the construction phase is required to conduct a more accurate assessment of the energy consumption and environmental impact of a building's entire life cycle. To assess energy consumption and greenhouse gas (GHG) emissions, this study developed a model using process-based LCA and input-output (I-O) LCA. This study divided the construction phase into material manufacturing, transportation, and on-site construction, and applied an appropriate methodology for each part. The analysis of an apartment building project using the developed model showed that the material manufacturing stage had the largest amount of energy consumption and GHG emissions. Quantitatively, material manufacturing, transportation, and on-site construction phases were responsible for 94.89, 1.08, and 4.03% of energy consumption, and 95.16, 1.76, and 3.08% of global warming potential, respectively. It is believed that the developed model would allow a more accurate assessment of energy consumption and GHG emissions during a building's construction phase. DOI: 10.1061/(ASCE)ME.1943-5479.0000199. © 2014 American Society of Civil Engineers.

Background/aims The aim of this study was to develop 'Koreans Gut Quotient Measurement Scales (GQ)', in which Koreans respond to questionnaires about the subjective feelings and symptoms of their intestinal health status. Methods Among 66 items pooled from previous studies and 4 items that were added following a focus group interview, 15 items were chosen using the Delphi survey. The content validity was evaluated using the content validity ratio. Data collected from 1,120 people from the general public in Korea were analyzed to verify the reliability and validity of GQ. Results The finalized GQ consisted of 17 items (including two exploratory measurement items) that were classified into three independent factors based on exploratory factor analysis (EFA): 'perceived intestine discomfort', 'bowel movement discomfort', and 'bowel movement control discomfort'. The discriminant and convergent validity of GQ were identified using EFA, reliability test, and confirmatory factor analysis. In addition, the criterion-related validity of GQ was identified using correlation and multiple regression analysis. Conclusions The GQ, which is a simplified intestinal health index developed based on an easy questionnaire for the public to understand, can be used as a tool for the public to evaluate their own intestinal health and determine when to visit clinics.

In this paper, we suggest the method of pilot tone design for a compressed channel sensing in order to decrease the peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems.

Along with the increasing interest in environmental problems such as global warming, the South Korean government has established policies and regulations to reduce the amount of greenhouse gases, targeting a 30% reduction of compared to business-as-usual levels by 2020. Thus, there have been many studies in construction field to control and reduce the amount of emitted from buildings. emission from the building construction could be obtained by using the life cycle assessment(LCA) methodology. In LCA, it is essential to have life cycle inventory(LCI) data of construction materials consisting of emission data that have been defined and examined in a detailed way in order to obtain more accurate and detailed emission of buildings. To date, however, the LCI data have been acquired only for the representative materials. Accordingly this study aimed to propose detailed emission data for steel rebar and H-beam, which are the essential structural steel materials, by strength and type. To accomplish the objective, this study used Input-Output LCA methodology which is based on the Input-Output table. It is believed that the emission data of steel materials acquired from this study would allow a more accurate assessment of emission for diverse structural design alternatives.

Accurate assessment of CO2 emission from buildings requires gathering CO2 emission data of various construction materials. Unfortunately, the amount of available data is limited in most countries. This study was conducted to present the CO2 emission data of concrete, which is the most important construction material in Korea, by conducting a statistical analysis of the concrete mix proportion. Finally, regression models that can be used to estimate the CO2 emission of concrete in all strengths were developed, and the validity of these models was evaluated using 24 and 35MPa concrete data. The validation test showed that the error ratio of the estimated value did not exceed a maximum of 5.33%. This signifies that the models can be used in acquiring the CO2 emission data of concrete in all strengths. The proposed equations can be used in assessing the environmental impact of various construction structural designs by presenting the CO2 emission data of all concrete types.

We investigate the localized surface plasmon (LSP) effect by Al nanorings on the AlGaN/GaN multiple quantum well (MQW) structure emitting at 365 nm. For this experiment, first, the size of Al nanorings is optimized to maximize the energy transfer (or coupling) between the LSP and MQW using the silica nanospheres. Then, the Al nanorings with an outer diameter of 385 nm, which exhibit a strong absorption peak in the near-ultraviolet region, are applied to the top surface of the AlGaN/GaN MQW. The photoluminescence (PL) intensity of the MQW structure with Al nanorings increased by 227% at 365 nm compared to that without Al nanorings. This improvement is mainly attributed to an enhanced radiative recombination rate in the MQWs through the energy-matched LSPs by the temperature-dependent PL and time-resolved PL analyses. The radiative lifetime was about two times shorter than that of the structure without Al nanorings at room temperature. In addition, the measured PL efficiency at room temperature of the structure with Al nanorings was 33%, while that of the structure without Al nanorings was 19%, implying that LSP-QW coupling together with the nanoring array pattern itself played important roles in the enhancement.

Green photoluminescent graphene quantum dots were synthesized by one step microwave assisted method using organic solvent acetylacetone, which have two different light emissions at 460 and 505 nm irradiated by 370 and 470 nm of monochromatic light from Xenon lamp, respectively.

We studied optical properties of thermally annealed Ge-on-Si. From Raman experiments, tensile strain as well as Si-Ge intermixing were investigated. Significant Γ-band transition peak-shift was confirmed by photoluminescence depending on the thermal annealing conditions.

This study aimed to develop a method for converting CO2 emission data from the life cycle inventory (LCI) of foreign countries into the one that is suitable for one’s own country, to obtain CO2 emission data of products or materials. CO2 emission differs in the energy efficiency and the type of energy sources used in each country. The developed conversion method considered the average share of the energy sources that are used to manufacture products or materials, in addition to different energy efficiency. To verify the feasibility of the developed conversion method, the study applied it to steel rebar and the steel section of the European reference life cycle database (ELCD), which was established by the European Commission. The result was compared with the CO2 emission data from the LCI of the Ministry of Knowledge Economy (MKE) in South Korea. The result showed that the percent difference of the steel rebar and that of the steel section dropped from 36.29 to 12.28%, and 162.59 to 60.47%, respec...

The hybrid nature of exciton polaritons opens up possibilities for developing a new concept nonlinear photonic device (e.g., polariton condensation, switching, and transistor) with great potential for controllability. Here, we proposed a novel type of polariton system resulting from strong coupling between a two-dimensional exciton and whispering gallery mode photon using a core–shell GaN/InGaN hexagonal wire. High quality, nonpolar InGaN multiple-quantum wells (MQWs) were conformally formed on a GaN core nanowire, which was spatially well matched with whispering gallery modes inside the wire. Both high longitudinal-transverse splitting of nonpolar MQWs and high spatial overlap with whispering gallery modes lead to unprecedented large Rabi splitting energy of ∼180 meV. This structure provides a robust polariton effect with a small footprint; thus, it could be utilized for a wide range of interesting applications.

The aim of this thesis is to analyze the economic and environmental effects of the application of a photovoltaic system to the exhibition and convention building (EXCO). To determine the economic and environmental effects of the building, energy consumption data should be obtained. Three sides of the EXCO are assumed to be good places of a photovoltaic system. In order to understand the investment cost, the number of years required to recover the cost has to be calculated. In an environmental evaluation, the amount of carbon dioxide is also calculated over a period of time of 5,10,15 years.

The fish population in an isolated stream pool (Chulma Stream, S. Korea) was investigated from July to February 2001–2. Large size (> 100 mm TL) of Zacco temmincki and Z. platypus were abundant (> 50% of total collected individuals). However, unregulated recreational fishing during August and September dramatically changed the size frequency distribution of the population, with large individuals declining to < 10% of total collected individuals. Three months after fishing, the majority of the population still consisted of small individuals (< 100 mm TL).