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In this study, we developed a photocurable hydroxyapatite (HA) slurry with 43 vol% HA content for a digital light processing (DLP) printing system. We assumed that the biomimetic mineralization coated on the surface of the DLP-printed porous HA scaffold could improve the in vitro cell response of the DLP-printed scaffold, such as in regards to cell adhesion or proliferation. Therefore, to verify the influence of biomimetic mineralization coated on the DLP-printed scaffold, the characteristics of the biomimetic mineralized HA scaffold (S-HA scaffold) were compared with those of HA bulk and HA scaffolds. It was found that the influences of the biomimetic mineralization on the structural characteristics of the HA scaffold were negligible, such as those on the apparent pore size, porosity, and compressive strength. However, the biomimetic mineralization coated on the surface of the HA scaffold improved the cell adhesion, proliferation, ALP activity, and gene expressions (runx2 and osteopontin) relative to the HA bulk and HA scaffolds, owing to the interconnected pores and increased nano-topology from the biomimetic mineralization. Therefore, we revealed that the in vitro cell response of a DLP-printed HA scaffold could be enhanced by biomimetic mineralization.

In bone tissue engineering, the endogenous regeneration of bone defects still represents a clinical challenge despite the development of intervention therapy to achieve bone regeneration via autologous grafts, allogeneic grafts, bone morphogenetic protein (BMP)-2, etc. To overcome the limitation of endogenous bone regeneration, we assumed that the 3D-printed collagen pattern with BMP-2 and fibroblast growth factor (FGF)-2 in the 3D-printed polycaprolactone/nano-hydroxyapatite scaffold could guide the endogenous regeneration of bone defects. Therefore, to test our hypothesis, polycaprolactone/nano-hydroxyapatite/collagen scaffolds with dual growth factors (BMP-2 and FGF-2) and various hydrogel patterns (positive, edge, and radial patterns) were fabricated at the same ratio and concentration of dual growth factors. Consequently, we revealed that the in vitro released concentrations of BMP-2 and FGF-2 were not affected by collagen patterns in the PCL/nano-hydroxyapatite scaffold. Furthermore, endogenous bone regeneration and angiogenesis in the polycaprolactone/nano-hydroxyapatite/collagen scaffold with a radial pattern were promoted compared with those in the polycaprolactone/nano-hydroxyapatite/collagen scaffolds with positive and edge patterns. Therefore, we demonstrated that a collagen design loaded with dual growth factors in the 3D-printed scaffold could affect endogenous bone regeneration and angiogenesis.

In the 3D-printed polycaprolactone/hydroxyapatite composite scaffold, hydroxyapatite particles are usually covered by a thin-film of polycaprolactone because of the rheological characteristics of the extrusion process. This phenomenon could disrupt the original bioactive characteristics of hydroxyapatite particles. In this study, to expose the hydroxyapatite particles covered by a thin-film of polycaprolactone, an alkaline erosion method was proposed. Moreover, to investigate the cell activity and biomimetic mineralization influenced by hydroxyapatite exposure, polycaprolactone scaffolds, polycaprolactone scaffolds with alkaline erosion, and polycaprolactone/hydroxyapatite scaffolds were fabricated as control groups and compared with the polycaprolactone/hydroxyapatite scaffolds with alkaline erosion. Furthermore, to characterize the 3D-printed composite scaffold in terms of hydroxyapatite exposure, several assessments were made including morphology, pore size, porosity, mechanical compressive modulus, surface roughness, water absorption. Consequently, the proposed alkaline erosion for hydroxyapatite particle exposure had little effect on the structure of the fabricated scaffolds via the 3D-printing system including the designed pore size, porosity, and mechanical properties. Moreover, mechanical properties of the polycaprolactone/hydroxyapatite scaffolds were increased by the high dispersion of hydroxyapatite in the polycaprolactone matrix. Additionally, we verified that the exposure of hydroxyapatite particles by alkaline erosion improves cell proliferation and biomimetic mineralization, because calcium and phosphate ions were rapidly deposited on the scaffold.

Dissimilar metal welding that is the joining of two different metals which would not be welded together has been used in nuclear power plants so that the probability of occurrence of cracks that can cause serious accidents is high. Therefore, it is necessary to diagnose and investigate structures with dissimilar metal welds through nondestructive testing techniques. Among them, nondestructive evaluation techniques using phased array ultrasonic waves have been widely used and studied. However, transmitted ultrasound into dissimilar metal welds is split, skewed and distorted due to course grained anisotropy and inhomogeneity. Therefore, there are many limitations in tests using the conventional phased array ultrasonic technique. In this study, the phased array ultrasonic focusing methods such as phase matching method, adaptive focusing method and time reversal method were applied to the nondestructive ultrasonic testing of dissimilar metal welds for detecting internal cracks, and the performance and efficiency of each technique were compared through numerical simulations and experiments.

In this study, to compare the relative abilities of dual-pore structure and hydroxyapatite to enhance the proliferation of osteoblastlike cell in well-interconnected scaffolds, several types of scaffolds were fabricated using combined SLUP (Salt-Leaching Using Powder) and WNM (Wire-Network Molding) techniques: well-interconnected dual-pore scaffolds with hydroxyapatite particles, wellinterconnected dual-pore scaffolds without hydroxyapatite particles, and single-pore scaffolds with hydroxyapatite particles. To assess the characteristics of the fabricated scaffolds, their morphology, compressive modulus, water absorption, and in-vitro cell activity were measured. Consequently, it was found that while the hydroxyapatite (which is hydrophilic) provides some advantage for cell attachment, the cell attachment in the dual-pore scaffold with hydroxyapatite particles was similar to that of the dual-pore scaffold without hydroxyapatite particles. Moreover, regarding cell proliferation, we verified that the effect of the dual-pore structure was dominant compared with the existence of hydroxyapatite particles and co-existence of dual-pore structure/hydroxyapatite particles. However, the cell vitality of the dual-pore scaffold with hydroxyapatite particles was higher than that of the dual-pore scaffold without hydroxyapatite particles because of ions released by the hydroxyapatite particles.

Salt-leaching using powder (SLUP) scaffolds are novel salt-leaching scaffolds with well-interconnected pores that do not require an organic solvent or high pressure. In this study, in vitro and in vivo cell behaviors were assessed using a PCL (polycaprolactone) SLUP scaffold. Moreover, using PCL, conventional salt-leaching and 3D-plotted scaffolds were fabricated as control scaffolds. Morphology, mechanical property, water absorption, and in vitro/in vivo cell response assessments were performed to clarify the characteristics of the SLUP scaffold compared with control scaffolds. Consequently, we verified that the interconnectivity between the pores of the SLUP scaffold was enhanced compared with conventional salt-leaching scaffolds. Moreover, in vitro cell attachment and proliferation of the SLUP scaffold were higher than those of the 3D-plotted scaffold because of their morphological characteristic. Furthermore, we revealed that new bone formation and bone ingrowth of the SLUP scaffold was superior to those of the calvarial defect model and 3D-plotted scaffold because of the high porosity and improved interconnectivity of pores by the SLUP technique without high pressure using powders. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3432-3444, 2017.

We consider an uplink power allocation scheme for single-carrier frequency-division multiple access (FDMA) with iterative multiuser detection, called single-carrier grouped FDMA (SC-GFDMA). SC-GFDMA is a non-orthogonal scheme in which several users share a single time-frequency resource. Hence, the uplink signal of a user can be regarded as both a signal and a source of interference. The signal power of each user should be sufficiently high to ensure reliable signal detection and sufficiently low to suppress inter-user interference. That is, the transmit power of each user should be adjusted appropriately to achieve high spectral efficiency. In this context, a power control method for an uplink SC-GFDMA system is proposed by analyzing the signal-to-interference-plus-noise ratios of users sharing each time-frequency resource. In particular, the uplink spectral efficiency is improved by limiting the transmit power of each user according to a criterion derived using a semi-analytic method called signal-to-noise ratio-variance density evolution. Simulation results demonstrate that the proposed method can significantly increase the spectral efficiency of the system, even with a considerably reduced total transmit power.

In this study, we investigated the dual-pore kagome-structure design of a 3D-printed scaffold with enhanced in vitro cell response and compared the mechanical properties with 3D-printed scaffolds with conventional or offset patterns. The compressive modulus of the 3D-printed scaffold with the proposed design was found to resemble that of the 3D-printed scaffold with a conventional pattern at similar pore sizes despite higher porosity. Furthermore, the compressive modulus of the proposed scaffold surpassed that of the 3D-printed scaffold with conventional and offset patterns at similar porosities owing to the structural characteristics of the kagome structure. Regarding the in vitro cell response, cell adhesion, cell growth, and ALP concentration of the proposed scaffold for 14 days was superior to those of the control group scaffolds. Consequently, we found that the mechanical properties and in vitro cell response of the 3D-printed scaffold could be improved by kagome and dual-pore structures through DfAM. Moreover, we revealed that the dual-pore structure is effective for the in vitro cell response compared to the structures possessing conventional and offset patterns.

In this study, the fabrication method was proposed for the well-interconnected polycaprolactone/hydroxyapatite composite scaffold with exposed hydroxyapatite using modified WNM technique. To characterize well-interconnected scaffolds in terms of hydroxyapatite exposure, several assessments were performed as follows: morphology, mechanical property, wettability, calcium ion release, and cell response assessments. The results of these assessments were compared with those of control scaffolds which were fabricated by precision extruding deposition (PED) apparatus. The control PED scaffolds have interconnected pores with nonexposed hydroxyapatite. Consequently, cell attachment of proposed WNM scaffold was improved by increased hydrophilicity and surface roughness of scaffold surface resulting from the exposure of hydroxyapatite particles and fabrication process using powders. Moreover, cell proliferation and differentiation of WNM scaffold were increased, because the exposure of hydroxyapatite particles may enhance cell adhesion and calcium ion release. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2315-2325, 2017.

Purpose - This paper aims to measure the overall satisfaction of online grocery shopping and identify the quality components of online grocery...

Although attempts to improve tissue-engineering scaffolds have been made using composite materials (synthetic polymers, bioceramics, etc.), research on bone tissue engineering has been limited to improving mechanical properties because of the intrinsic drawbacks of the grid-type structures conventionally used as scaffolds. To overcome this limitation, this study proposes a polycaprolactone/nano-hydroxyapatite scaffold with a kagome structure formed via material-extrusion process. The kagome structure is reported to be a mechanically superior open-pore structure. The mechanical properties and in vitro cell activities of 3D scaffolds have been studied with respect to the nano-hydroxyapatite (nHA) content in the scaffold. The compressive modulus of the PCL/nHA scaffold with kagome structure was found to be significantly improved. In addition, nHA particles on the surface of the scaffold were exposed through alkaline erosion, improving bone-regenerating ability. The alkaline erosion did not affect the structural characteristics of the scaffold, including pore size, porosity, hydroxyapatite content, and compressive modulus. Additionally, we observed that the exposure of PCL/nHA particles promoted bone-regeneration activity through enhanced osteoconduction of the scaffold.

In clinical conditions, the reconstructions performed in the complex and three-dimensional bone defects in the craniomaxillofacial (CMF) area are often limited in facial esthetics and jaw function. Furthermore, to regenerate a bone defect in the CMF area, the used scaffold should have unique features such as different mechanical strength or physical property suitable for complex shape and function of the CMF bones. Therefore, a three-dimensional synthetic scaffold with a patient-customized structure and mechanical properties is more suitable for the regeneration. In this study, the customized kagome-structure scaffold with complex morphology was assessed in vivo. The customized 3D kagome-structure model for the defect region was designed according to data using 3D computed tomography. The kagome-structure scaffold and the conventional grid-structure scaffold (as a control group) were fabricated using a 3D printer with a precision extruding deposition head using poly(e-caprolactone) (PCL). The two types of 3D printed scaffolds were implanted in the 8-shaped defect model on the rabbit calvarium. To evaluate the osteoconductivity of the implanted scaffolds, new bone formation, hematoxylin and eosin staining, immunohistochemistry, and Masson's trichrome staining were evaluated for 16 weeks after implantation of the scaffolds. To assess the mechanical robustness and stability of the kagome-structure scaffold, numerical analysis considering the ‘elastic-perfectly plastic’ material properties and deformation under self-contact condition was performed by finite element analysis. As a result, the kagome-structure scaffold fabricated using 3D printing technology showed excellent mechanical robustness and enhanced osteoconductivity than the control group. Therefore, the 3D printed kagome-structure scaffold can be a better option for bone regeneration in complex and large defects than the conventional grid-type 3D printed scaffold.

Massive multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) is a promising technology for next-generation wireless communications. However, when channel state information (CSI) at the transmitter is obtained using channel feedback, the benefits of this system are severely limited by the tradeoff between downlink capacity and feedback overhead. To solve this problem, we propose a time-domain differential feedback scheme for massive multiple-input single-output (MISO) OFDM systems. The proposed scheme exploits channel correlations in time, frequency, and space domains simultaneously by considering differential channel impulse response (CIR). To simplify the codebook design, and to reduce codeword-search complexity, we partition and then quantize the differential CIR using a number of subcodebooks. Because the total feedback bits are shared by the subcodebooks, we further optimize the bit allocation for them to minimize the total quantization error. For this, we analyze the quantization error of the proposed scheme and then use the analysis results for the bit-allocation optimization. In simulations, the proposed scheme efficiently exploits all correlations and achieves significant spectral-efficiency gain compared to conventional feedback schemes.

This letter focuses on the design of a new frequency-reconfigurable antenna for a mobile handset application. The proposed antenna supports the most important long-term evolution bands: band 17 (704–746 MHz), band 13 (746–787 MHz), band 5 (824–894 MHz), and band 8 (880–960 MHz). A digital variable capacitor (DVC) is used via a coupling pattern proximity to the aperture of an inverted F antenna (IFA) to which a single-pole single throw RF switch is connected to take advantages of the two different kinds of tuning elements. We show that the proposed antenna is able to have a quasicontinuous and wide range of frequency tuning capabilities over 700–960 MHz through simulations and experiments. We also show that the coupled aperture used for connection of the DVC to the aperture of IFA is helpful for reducing the ohmic losses in the DVC from the antenna efficiency degradation which is the most important figure of merit for frequency reconfigurable antennas based on the active tuning elements. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2333–2336, 2015

In this letter, we develop a frequency tunable multiple-input multiple-output antenna for handhelds to achieve both the wideband tunability at the frequency ranges of 704–960 MHz and low correlation properties over the tuning frequencies. The proposed antenna covers various long-term evolution (LTE) service bands: Band 17 (704–746 MHz), Band 13 (746–787 MHz), Band 5 (824–894 MHz), and Band 8 (880–960 MHz). The proposed LTE antennas are based on a switch-loaded antenna structure, with a resonance frequency that can be controlled by a logic circuit. The tuning technique for the LTE antenna uses a SP4T RF switch to match the impedances to realize the bands of interest. The proposed main antenna consists of an inverted-F antenna (IFA), the LTE subantenna is loop antenna structure. The use of two different antenna types of IFA and loop antenna achieves high isolation. We show that the proposed antenna has envelop correlation coefficient value as low as 0.5 over the designed frequency tuning ranges. The proposed antenna was fabricated and tested for experimental verification. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1092–1096, 2015

To enhance the mechanical properties of three-dimensional (3D) scaffolds used for bone regeneration in tissue engineering, many researchers have studied their structure and chemistry. In the structural engineering field, the kagome structure has been known to have an excellent relative strength. In this study, to enhance the mechanical properties of a synthetic polymer scaffold used for tissue engineering, we applied the 3D kagome structure to a porous scaffold for bone regeneration. Prior to fabricating the biocompatible-polymer scaffold, the ideal kagome structure, which was manufactured by a 3D printer of the digital light processing type, was compared with a grid-structure, which was used as the control group, using a compressive experiment. A polycaprolactone (PCL) kagome-structure scaffold was successfully fabricated by additive manufacturing using a 3D printer with a precision extruding deposition head. To assess the physical characteristics of the fabricated PCL-kagome-structure scaffold, we analyzed its porosity, pore size, morphological structure, surface roughness, compressive stiffness, and mechanical bending properties. The results showed that, the mechanical properties of proposed kagome-structure scaffold were superior to those of a grid-structure scaffold. Moreover, Sarcoma osteogenic (Saos-2) cells were used to evaluate the characteristics of in vitro cell proliferation. We carried out cell counting kit-8 (CCK-8) and DNA contents assays. Consequently, the cell proliferation of the kagome-structure scaffold was increased; this could be because the surface roughness of the kagome-structure scaffold enhances initial cell attachment.

Magnesium (Mg) ions are the most abundant intracellular divalent cations and play a pivotal role in numerous cellular processes. Biodegradable Mg-containing materials, including scaffolds, are promising candidates for orthopedic applications. Here, we investigated the effect of Mg ions on the cellular properties of osteoblasts. Cytotoxicity tests on osteoblasts confirmed that no cytotoxic effects were found up to a supplementing Mg ion concentration of 10 mM. Mg ions at a concentration of 5 mM increased the migration and invasiveness of osteoblasts. To investigate the stimulatory effect of Mg ions on cell motility in scaffolds, we fabricated 10 wt% Mg ion-containing polycaprolactone (PCL) scaffolds, using the wire-network molding (WNM) technique. Mg ion-containing scaffolds persistently released Mg ions at a concentration of 5 mM in the media after pre-incubation. Furthermore, increased cell motility was confirmed in Mg ion-containing scaffolds by quantification of genomic DNA and protein content. Our results provide an important basis for the function of Mg ions and their effect on cell motility, and propose a novel role for Mg ions in scaffold applications.

This poster will be a chance for a wider LAK audience to engage with the 2nd LAK Failathon workshop. Both of these will build on the successful Failathon event in 2016 and extend beyond discussing individual experiences of failure to exploring how the field can improve, particularly regarding the creation and use of evidence. \ud Failure in research is an increasingly hot topic, with high-profile crises of confidence in the published research literature in medicine and psychology. Among the major factors in this research crisis are the many incentives to report and publish only positive findings. These incentives prevent the field in general from learning from negative findings, and almost entirely preclude the publication of mistakes and errors. Thus providing an alternative forum for practitioners and researchers to learn from each other’s failures can be very productive. The first LAK Failathon, held in 2016, provided just such an opportunity for researchers and practitioners to share their failures and negative findings in a lower-stakes environment, to help participants learn from each other’s mistakes. It was very successful, and there was strong support for running it as an annual event. The 2nd LAK Failathon workshop will build on that success, with twin objectives to provide an environment for individuals to learn from each other’s failures, and also to co-develop plans for how we as a field can better build and deploy our evidence base. This poster is an opportunity for wider feedback on the plans developed in the workshop, with interactive use of sticky notes to add new ideas and coloured dots to illustrate prioritisation. This broadens the participant base in this important work, which should improve the quality of the plans and the commitment of the community to delivering them.

In this study, a novel technique was proposed to fabricate dual-pore scaffolds combining both SLUP (salt leaching using powder) and WNM (wire-network molding) techniques. This technique has several advantages: solvent-free, no limit on the use of thermoplastic polymers as a raw material, and easiness of fabricating scaffolds with dual-scale pores that are interconnected randomized small pores. To fabricate dual-pore scaffolds, PCL and NaCl powders were mixed at a certain ratio. Subsequently, needles were inserted into a designed mold, and the mixture was filled into the mold thereafter. Subsequently, after the mold was pressurized, the mold was heated to melt the PCL powders. The PCL/NaCl structure and needles were separated from the mold. The structure was sonicated to leach-out the NaCl particles and was dried. Consequently, the remaining PCL structure became the dual-pore scaffold. To compare the characteristics of dual-pore scaffolds, control scaffolds, which are 3D plotter and SLUP scaffolds were fabricated.

In this study, we proposed a novel salt-leaching method using PCL and NaCl powders, known as the SLUP (salt leaching using powder) technique, which has several advantages: this technique does not require solvent, pressure, or unnecessary expensive devices. First, PCL powder (100–180 μm size) and NaCl powder (350–400 μm size) were prepared. Second, the PCL and NaCl powders were mixed at a certain ratio, and then the mixed powder was poured into a mold. Afterward, the mold was heated to melt the PCL powder in an oven at 80 °C for 15 min. Subsequently, after the PCL/NaCl mixture was separated from the mold, the PCL/NaCl mixture was soaked in D.I. water for 24 h to leach out the NaCl particles. Consequently, the remaining PCL structure was porous and could be used as a scaffold. To analyze the compressive modulus of the fabricated scaffold, a uniaxial compression test was performed using a UTM (universal testing machine), and the surface characteristics of the scaffold were observed using an SEM (scanning electron microscope). Additionally, cell-culture experiments were performed using hMSCs (human mesenchymal stem cells), and the cell-culture characteristics were assessed and compared with the characteristics from a conventional salt-leaching scaffold.

In the polycaprolactone/hydroxyapatite scaffold fabricated by the melting-extrusion-type 3D-printing system, hydroxyapatite (bioceramic) particles are usually covered by a thin-film polycaprolactone (thermoplastic polymer) layer because of the rheological characteristics of the melting-extrusion process. The original bioactive characteristics of the bioceramic particles can be disrupted by this thin-film thermoplastic polymer. Therefore, in this study, an alkaline erosion process was employed to eliminate the thin-film polycaprolactone layer to expose the hydroxyapatite particles. To investigate the influence of the enhanced exposure of hydroxyapatite on cell response and bone regeneration, the polycaprolactone scaffold, polycaprolactone scaffold with alkaline erosion, and polycaprolactone/hydroxyapatite scaffold were compared with the polycaprolactone/hydroxyapatite scaffold with alkaline erosion. Furthermore, to identify the characterization of the 3D-printed composite scaffold for hydroxyapatite's exposure, the morphology, pore size, porosity, mechanical compressive modulus, in-vitro cell response, and in-vivo bone regeneration were assessed. Consequently, the proposed alkaline erosion for the exposure of hydroxyapatite did not change the structural characteristics of the 3D-printed scaffolds, such as the pore size, porosity, and mechanical property. Additionally, we verified that the exposure of hydroxyapatite particles on the scaffold's surface promoted the bone-regeneration ability of the scaffold because of enhanced osteoconduction by hydroxyapatite's exposure.

BIM(Building Information Modeling) enables 3D model-base management for all information produced by construction project during its life cycle. Also as a national policy, BIM has been institutionalized as design criteria. But, on the matter of 2D drawing using BIM software (Revit Architecture), it has been recognized as difficult to realize the same quality drawing drawn by CAD. The purpose of this study is verifying the possibility of printable design drawing implemented by BIM software at the same quality of 2D shop drawing drawn by 2D CAD. Through the analysis of basic design elements of 3D BIM software and 2D CAD software, with the case of partial cross sectional drawing which is most faithful representation of the basic design elements, this study find out that the 3D BIM software can produce the same quality 2D printable drawing utilizing its implicit function.

In spectrum-sharing-based cognitive radio networks, multiple secondary systems can access a licensed spectrum to better utilize scarce radio resources. When the multiple secondary transmitters are co-located, the weighted sum-rate of the secondary users (SUs) is mainly limited by the inter-cell interference (ICI). With limited cooperation among co-located secondary transmitters, we propose an algorithm for decentralized beamforming with power allocation via dual decomposition. To maximize the weighted sum-rate of the SUs, the proposed decentralized algorithm efficiently mitigates the ICI by the undesired leakage power limitation at each secondary transmitter. Because the channel information is not perfectly known at the transmitter in practical applications, we also develop a decentralized robust beamformer. To efficiently design the robust beamformer, a convex problem is formulated by semi-definite relaxation. Simulation results show that the proposed algorithm with perfect channel state information (P-CSI) efficiently maximizes the weighted sum-rate performance by the undesired leakage power limitation. For an imperfect CSI with a small error bound, the proposed robust beamformer approaches the performance of a P-CSI case, without causing harmful interference to the primary user.

The recent emergence of diverse platform-based media devices such as smart phones and iPads has aroused interest of consumers all across the world. This interest has led to digitalization of paper books and a steep growth in the digital publishing industry at home and abroad. However, advent of various devices and content has caused the issue of compatibility and produced needs and demand for standardization to exchange and share content related to digital publication. Through collection of opinions of 16 stakeholders from the industrial, academic, research, and public sectors, this study aims to examine predictable future changes about content and its distribution, devices, standardization, technical protective measures, and obstacles in future digital publishing and eventually to draw out areas and elements for future standards development.

In this letter, we consider user scheduling for single-carrier frequency division multiple access with iterative multiuser detection. To achieve high spectral efficiency, a scheduler should allocate a common set of subcarriers to as many users as possible, while guaranteeing the quality-of-service (QoS) of each user. To address this problem, we first investigate optimal user selection via an exhaustive search method. Based on this investigation, we then propose a pattern-aware user scheduling algorithm for the optimal user selection. Simulation results show that the proposed algorithm provides higher spectral efficiency than conventional algorithms and achieves the performance of optimal user selection with much reduced computational complexity.

The airpollutant may accelerate degradation of power line facilities, and may reduce the life of the electric facilities. In case of korea, there are a tendency that the density of air pollution may be increased by industrial development. while lack of research activity and establishment of a countermeasure on this issue. Recently the occurrence of electricity failure have been reduced on the power transmission and distribution lines. but the occurrence of electricity failure by insulator itself has been increased. It means that we should have develop more clear technique for detection of the wrong insulator. In this study to provide a method for detection of the insulator failure or effective management of the troubled insulator, we analyze the chemical composition of the insulator which used on power distribution line at the sea side locations. To define the relation between insulation and corona intensity, we design and develop an corona detector. We define the variation of insulation by pollution changes on the insulator and verify quantitative relation between corona and insulations using the corona detector.

본 연구에서는 일반적으로 연약지반 개량 공사에 사용하는 심층혼합처리 공법을 도심지 공사에서 지반개량 공법으로 적용하는 방안을 평가하였다. 심층혼합처리 공법을 협소한 도심지 현장에서도 시공이 가능하도록 소형화시킨 시공 장비를 사용하여 서울 시내 재개발 현장에서 기초 지반개량 목적으로 적용하고 개량한 지반의 강도 특성, 지반교반 시 발생한 진동, 시공위치와 인접한 석축구조물에 발생한 변위를 측정하였다. 강도 시험 및 현장계측 결과 심층혼합처리 공법은 원지반의 강도를 효과적으로 개량시켰으며 시공 시 발생시킨 진동과 인접 구조물에 발생한 변위가 미소하여 도심지 공사에서 요구하는 기준을 만족시키는 것으로 판단되었다. 따라서 심층혼합처리 공법은 소음 및 진동 문제가 중요한 고려사항인 도심지 공사에서 기초공법으로 유용하게 적용할 수 있을 것으로 판단된다. 【The deep mixing method, which is generally considered as a method for improving soft ground, is assessed in terms of its applicability for urban construction. Using small equipment tailored to perform deep mixing in congested urban areas, deep mixing was performed to reinforce the foundation ground of a retaining wall in a redevelopment site in Seoul. Strengths characteristics, construction vibrations and displacements induced to an adjacent old masonry wall were evaluated by laboratory tests and field monitoring. The results indicate that the strength of ground was improved appropriately whilst the vibrations and displacements induced by deep mixing were slight enough to satisfy the general requirements for construction works in urban environments. Therefore, it is concluded that deep mixing method can be a practical option for foundation methods in urban construction works where minimizing noise and vibrations is an important concern.】

Since Power Plant has tens of thousands welded parts in its structures, the quality on the welded parts are always a key factor for ensuring the reliability of the structures. Film based Radiography Test (hereinafter called “FRT”) is a generally accepted solution in inspecting the welded structure. However, the RT demands complex workflow, high cost, hazardous waste disposal, and etc…. In an effort to get over such shortcomings from FRT and present alternative inspection tools, this study was intended to evaluate a Digital Radiography Test (hereinafter called “DRT”). In this study, the evaluation were focused on if a DRT is applicable to the inspection of Welded structure in Power Plants, and what benefits can be generated in a use of DRT.

In this study, various types of poly(e-caprolactone) (PCL) knitting scaffolds were fabricated and analyzed to assess the cell-culturing characteristics of knitting scaffolds with respect to pore-size heterogeneity, surface wettability, and surface roughness. First, control knitting scaffolds were fabricated using 150-µm-diameter PCL monofilaments. Using chloroform and NaOH, PCL knitting scaffolds with varying roughness, pore-size heterogeneity, and surface wettability were fabricated. Cell-culture assessments were performed on these six types of PCL knitting scaffolds. Saos-2 cells were used for cell assessments and cultured for 14 days on each scaffold. Consequently, heterogeneous pore-size distribution and high surface wettability were found to enhance cell proliferation in knitting scaffolds. In addition, for highly hydrophobic knitting scaffolds exhibiting water contact angles greater than 110 degrees, smaller surface roughness was found to enhance cell proliferation. According to this study, in the case of knitting scaffold, NaOH-treated knitting scaffold, without any control for the pore-size homogenization, could be a candidate as the optimal knitting scaffold. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42566.

This paper capitalizes on recent advances in the area of non-contact ultrasonic guided wave techniques. The present technique provides a decent method for nondestructive testing of defect thinning simulating a hidden corrosion or FAC(Flow Accelerated Corrosion) in a thin aluminum plate. The proposed approach is based on using EMAT(Electro-magnetic Acoustic Transducer) to generate guided waves and detect the wall thinning without any coupling. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cut-off measurement allows us to monitor a defect thinning level while a group velocity change can be used to quantify the thinning depth.

Conventional non-destructive techniques for inspection of weld in pipelines require significant test time and high cost. In order to overcome these drawbacks in conventional NDT techniques, various techniques using ultrasonic guided waves have been developed and applied to the pipeline inspection. Recently, a fast calculation technique for guided wave propagation using a semi-analytical finite element method (SAFEM), PIPE WAVE ver.1.0, has been developed by T. Takahiro et al [1]. In this paper, the calculation of torsional mode propagation in a pipe using PIPE WAVE ver. 1.0 is introduced as a preliminary study and the application of the torsional mode of ultrasonic guided waves to long range pipe inspection is presented.. The characteristics and setup of a long range guided wave inspection system and experimental results in pipes of various diameters are introduced. The experimental results in mock-up pipes with cluster type detects show that the limit of detectable wall thickness reduction with this guided wave system is 2~3% in the pipe cross section area and the wall thickness reduction of 5% in cross section area can be detected when actual detection level is used. Therefore, the applicability of the ultrasonic guided wave technique to long range pipeline inspection for wall thickness reduction is verified.

In this paper, study on evaluation of thickness reduction in a thin plate with guided waves is presented. Ultrasonic guided wave techniques have been widely studied and successfully applied to various non-destructive tests with the advantage of long range inspection. In addition to application of guided waves to NDT, non-contact methods for ultrasonic wave generation and detection have become very useful and well combined with guided wave techniques due to their capability of ultrasonic wave generation and reception in surface of high temperature or on rough surface. An advanced non-contact technique for detection of thickness reduction simulating hidden corrosion in thin plates using guided waves is proposed. The proposed approach uses EMAT(Electro-Magnetic Acoustic Transducer) for the non-contact generation and detection of guided waves in aluminum plates. Interesting features of the dispersive behavior in selected wave modes are used to detect plate thinning. The experimental results show that the mode cutoff measurements provide a qualitative measurement of thinning detects and change in the mode group velocity can be used as quantitative parameter of thinning depth measurement.

It's not easy to detect the defects in fillet weldment which is widely used in various building structures and power plants just with nondestructive inspection due to its complex geometrical shape and difficult access. But it's easy to detect the cracks on the surface or just below the surface of fillet weldment heel part if surface SH-wave, among ultrasonic wave modes, is applied. The traditional ultrasound inspection using surface SH-wave is usually a contact method using piezoelectric transducer, so it's not suitable for a field application because the reliability of inspection varies depending on field environments such as couplant, contact pressure and pre-process, etc. Therefore, the necessity for non-contact ultrasound inspection is increasing. This study proposes non-contact ultrasound inspection method using EMAT (electro-magnetic acoustic transducer), and presented non-contact ultrasound inspection method for fillet weldment through experimental verification.