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Single-Walled Carbon Nanotube-Based Chemi-Capacitive Sensor for Hexane and Ammonia
No full textTwo configurations of single-walled carbon nanotube-based chemi-capacitive gas sensors were fabricated, i.e., horizontal and vertical. Further, their sensing properties for hexane and ammonia (NH3) vapor were characterized and compared with chemi-resistive-type sensing properties. Upon exposure to hexane and NH3 vapor, both capacitance and resistance varied as the analyte concentration increased. The sensing sensitivity measured along the horizontal direction increased with the device resistance. However, the capacitive sensing response along the vertical direction was independent of the number and fraction of semi-conductive single-walled carbon nanotubes. Furthermore, the vertical chemi-capacitive sensing response was dependent on the dipole moment of analytes.This work was supported by the Global Frontier Program through the Global Frontier Hybrid Interface Materials (GFHIM) project (Grant 2013M3A6B1078870) of the National Research Foundation of Korea (NRF), which is funded by the Ministry of Science, ICT, and Future Planning and Technology Innovation Program (20002694, Gas sensor) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) and the Fundamental Research Program of the Korea Institute of Materials Science (Grant POC2930, PNK6170)
Lobar evenness of deposition/retention in rat lungs of inhaled silver nanoparticles: an approach for reducing animal use while maximizing endpoints
No full textBackgroundInformation on particle deposition, retention and clearance are important for the evaluation of the risk of inhaled nanomaterials to human health. Recent revised OECD inhalation toxicity test guidelines require to evaluate the lung burden of nanomaterials after rodent subacute and subchronic inhalation exposure (OECD 412, OECD 413). These revised test guidelines require additional post-exposure observation (PEO) periods that include lung burden measurements that can inform on lung clearance behavior and translocation. The latter being particularly relevant when the testing chemical is a solid poorly soluble nanomaterial. Therefore, in the spirit of 3 R's, we investigated whether measurement of retained lung burden of inhaled nanoparticles (NPs) in individual lung lobes is sufficient to determine retained lung burden in the total lung. If it is possible to use only one lobe, it will reduce animal use and maximize the number of endpoints evaluated.ResultsTo achieve these goals, rats were exposed nose-only for 1 or 5days (6h/day) to an aerosol of 20nm well-dispersed silver nanoparticles (AgNPs), which is the desired particle diameter resulting in maximum deposition in the pulmonary region when inhaled as singlets. After exposure, the five lung lobes were separated and silver concentration was measured using inductively coupled plasma-mass spectrophotometer (ICP-MS). The results showed that the retention of deposited silver nanoparticle in the different lung lobes did not show any statistically significant difference among lung lobes in terms of silver mass per gram lung lobe. This novel finding of evenness of retention/deposition of inhaled 20nm NPs in rats for all five lobes in terms of mass per unit tissue weight contrasts with earlier studies reporting greater apical lobe deposition of inhaled micro-particles in rodents. The difference is most likely due to preferred and efficient deposition of inhaled NPs by diffusion vs. additional deposition by sedimentation and impaction for micron-sized particles.ConclusionAgNPs following acute inhalation by rats are evenly retained in each lung lobe in terms of mass per unit lung tissue weight. Accordingly, we suggest sampling any of the rat lung lobes for lung burden analysis can be used to determine deposited or retained total lung burden after short-term inhalation of NPs and using the other lobes for collecting and analyzing bronchoalveolar lavage fluid (BALF) and for histopathological analysis. Therefore, by combining lung burden measurement, histopathological tissue preparation, and BALF assay in the same rat will reduce the number of animals used and maximize the number of endpoints measured.This research was supported by the Industrial Technology Innovation Program (10052901), Development of highly usable nanomaterial inhalation toxicity testing system in commerce through the Korea Evaluation Institute of Industrial Technology by the Korean Ministry of Trade, Industry & Energy and NIH/NIEHS grants U19ES019545, P30ES007033 and EPA grant RD83573801
Freeway Crashes Involving Drowsy Driving: Crash Characteristics and Severity in South Korea
No full textDrowsy driving is a significant crash risk factor. In 2006–2012, 22.5% of all crashes and 33.3% of fatal crashes were caused by drowsy driving in South Korea. This study examined driver, vehicle, road, weather, and temporal characteristics associated with drowsy-driving crashes in South Korea. This study found that drowsy-driving crashes were often caused by drivers in their thirties through fifties unlike the United States and other Western countries. The multinomial logit model on the crash severity of drowsy-driving crashes showed that older drivers age 60+, male drivers, and vans were more likely to be involved in fatal crashes. Also, the fatal crashes were more likely to occur in work zones, freeway segments with concrete barriers or no shoulder, and the month of August. These findings indicate that it is critical to implement road safety measures, such as rumble strips, in work zones and the areas with a high frequency of drowsy-driving crashes as well as safe and accommodating rest areas to prevent drowsy driving
Nanocatalyst-induced hydroxyl radical (·OH) slurry for tungsten CMP for next-generation semiconductor processing
No full textChemical mechanical polishing (CMP) is one of the important steps that involves during fabrication of semiconductor devices. This research highlights the importance of tungsten (W) polishing slurries consisting of a novel nonionic, heat-activated FeSi nanocatalyst on the performance of W chemical mechanical polishing. The results obtained from the polishing data showed a higher W removal rate of 5910 Å/min with a slurry consisting of FeSi nanocatalyst at a polishing temperature of 80 °C. The increase in W polishing rate using FeSi slurry was explained on the basis of formation of a thicker oxide layer (WO3) due to the interaction between the W surface and hydroxyl radicals (·OH) generated via the reaction between FeSi and hydrogen peroxide at 80 °C. Higher ·OH generation and increase in oxygen depth profile of W film were confirmed by UV–Vis spectrometer and AES analysis, respectively. Compared to Fe(NO3)3 catalyst, the slurry with FeSi showed a higher static etch rate at 80 °C. Potentiodynamic polarization results obtained using FeSi slurry showed thicker WO3 passivation layer as compared to the slurry with Fe(NO3)3. The increase in the polishing rate of W CMP using slurry with FeSi nanocatalyst can be essentially attributed to the generation of much stronger oxidant ·OH due to its increased catalytic effect at a high polishing temperature of 80 °C
Design of Compliant Hinge Joints inspired by Ligamentous Structure
No full textThis paper suggests novel types of joint mechanisms composed of elastic strings and rigid bodies. All of the human hinge joints have the articular capsule and a pair of collateral ligaments. These fibrous tissues make the joint compliant and stable. The proposed mechanism closely imitates the human hinge joint structure by using the concept of tensegrity. The resultant mechanism has several characteristics shown commonly from both the tensegrity structure and the human joint such as compliance, stability, lightweight, and non-contact between rigid bodies. In addition, the role and feature of the human hinge joints vary according to the origins of a pair of collateral ligaments. Likewise, the locations of two strings corresponding to a pair of collateral ligaments produce different function and motion of the proposed mechanism. It would be one of the advantages obtained from the proposed mechanism. How to make a joint mechanism with different features is also suggested in this paper
Internal fork-shaped wideband monopole antenna with a parasitic sleeve for ultra-high-definition television applications
No full textA simple and compact internal fork-shaped monopole antenna with a parasitic sleeve is proposed for operation in the ultra-high frequency (UHF: 470-771 MHz) band for ultra-high-definition television (UHD-TV) applications. The internal antenna is directly implemented into a 49-in TV model on which its bezel frame (made of PC-ABS with epsilon(r) = 3.5 and tan delta = 0.005) is used as a substrate for antenna design. The structure and operation bandwidth of the internal antenna are restricted by the limited space and longitudinal bezel frame. Therefore, the fork-shaped monopole structure with meandering and folding strips is applied, forming a capacitive coupling effect to reduce the antenna size and to enhance the impedance matching. A parasitic sleeve is added and encircled around the monopole to generate additional resonances, hence further broadening the operating bandwidth to cover the entire UHF band. The antenna is then bent to form a three-dimensional structure with a compact dimension of 275 x 17 x 5 mm(3), allowing it to be tightly fitted on the bezel frame of the TV model. The final tested antenna achieves a peak gain of 4.7 dBi and an efficiency of more than 60% over a broad -6 dB reflection bandwidth of 60.3% (440-820 MHz).This work was supported by the Research Fund of Hanyang University under Grant HY-2015-G
Spatially Modulated Integer-Forcing Transceivers With Practical Binary Codes
No full textA new practical multiple-input multiple-output (MIMO) transceiver technique called spatially modulated integer-forcing (SM-IF) is proposed for hybrid beamforming array systems, which combines generalized spatial modulation (GSM) with integer-forcing (IF) MIMO multiplexing transmission to achieve improved spectral efficiency with low system complexity. In the proposed scheme, the transmitter first activates a subset of antennas using analog beamforming and delivers an SM information stream via the index of the activated antenna group. Then MIMO digital multiplexing is applied to send multiple MIMO information streams via multilevel coding (MLC) with binary channel codes through the activated antennas. At the receiver side, the receiver first estimates the index of the activated antenna group to recover the SM stream and then recovers the MIMO streams by IF sum decoding in conjunction with multi-stage decoding. The proposed scheme provides a unified coding framework to achieve a synergistic gain by integrating off-the-shelf practical binary codes and low complexity IF decoding into hybrid beamforming array systems. By extensive link-level numerical simulations, the proposed scheme is shown to outperform both the conventional plain IF MIMO and plain SM approaches. The results demonstrate that the proposed SM-IF can be a promising transceiver technique implementable in practical hybrid beamforming array systems
Predictive Caching via Learning Temporal Distribution of Content Requests
No full textIn this letter, dynamic content placement of a local cache server that can store a subset of content objects in its cache memory is studied. Contrary to the conventional model in which content placement is optimized based on the time-invariant popularity distribution of content objects, we consider a general time-varying popularity distribution and such a probabilistic distribution is unknown for content placement. A novel learning method for predicting the temporal distribution of future content requests is presented, which utilizes the request histories of content objects whose lifespans are expired. Then we introduce the so-called predictive caching strategy in which content placement is periodically updated based on the estimated future content requests for each update period. Numerical evaluation is performed using real-world datasets reflecting the inherent nature of temporal dynamics, demonstrating that the proposed predictive caching outperforms the conventional online caching strategies.This work was supported in part by the Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korean Government (18ZF1100, Wireless Transmission Technology in Multi-point to Multi-point Communications) and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF2017R1D1A1A09000835)
Critical junctures and path dependence in urban planning and housing policy: A review of greenbelts and New Towns in Korea's Seoul metropolitan area
No full textThis study reviews greenbelt and New Town policy in Korea's Seoul Metropolitan Area as a case study by developing the step-wise critical juncture and path dependence repetition model originating in the historical institutionalism. The country is considered to be in a developmental state with significant power, and the capital region has been regarded as politically crucial, so the theory is more appropriately applied to the two policies' changes rather than a gradual institutional developmental model. The results found that decisions on the two policies at the presidential level at critical junctures during times of political change were sustained and reinforced until the next juncture, following the path-dependent tendency across regimes and their political orientation. Because the New Town policy has dominated greenbelt policy since the most recent (third) critical juncture in 1997, the latter is vulnerable despite important environmental issues and a reversal is not expected to occur in the near future.This work was supported by the research fund of Hanyang University (HY-2017)
Note on fuzzy soft sets and fuzzy soft lattices
No full textIn this note, we point out that several assertions (Proposition 7, Lemmas 20, 21 and Theorems 7, 15) in [Y. Shao and K. Qin, Fuzzy soft sets and fuzzy soft lattices, Int. J. Comput. Intell. Sys. 5 (2012), 1135-1147] are not true in general. Appropriate counterexamples are given. Further their modified versions are presented.C. Park was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (NRF-2017R1D1A1B04032937)