This paper describes the design of a high-efficiency vehicular roof-mounted antenna for wireless access for vehicular environment (WAVE) communication systems used for ubiquitous intelligent systems. ...The main objective of the ubiquitous intelligent system's automotive IT technology is to enhance the connectivity among vehicles to ensure seamless communication and to reduce the initial access time using high-performance antenna systems. The efficiency of WAVE communication systems used for ubiquitous intelligent systems depends on the antenna efficiency. The proposed vehicular antenna for WAVE communication systems shows an improvement of approximately 4.77 dB in the return loss, as compared with a conventional antenna system.
The western East Sea (Sea of Japan) is a seismically active region. A major earthquake in the western East Sea may cause damage in the eastern Korean Peninsula. The nature of seismicity in the ...western East Sea is important information for mitigation of seismic hazards. The seismicity in the western East Sea occur around the paleo-rifting structures where seismic and geophysical properties apparently change. Both reverse faulting and strike slip earthquakes occur in the region. Earthquake locations and focal depths are refined. The maximum focal depth generally increases from ∼10 km in the coast to ∼32 km in the continental slope of the western East Sea that is located in distance of ∼60 km from the coast. Mid to lower crust earthquakes continue around the paleo-rifting structures that may extend to the lower crust and Moho. Offshore earthquakes rarely occur in oceanic basins of bathymetry with >2 km. Clustered episodic earthquakes occur in four local offshore areas including the stress-induced areas by the 12 September 2016 ML5.8MW5.4 Gyeongju and 15 November 2017 ML5.4MW5.5 Pohang earthquakes. The spatiotemporal clustering of earthquakes suggests stress accumulation at localized paleo-rifting structures and episodic stress release. The mid to lower crustal earthquakes are confirmed from phase arrival time analyses with collocated vertically-separated sensors. The laterally progressive focal depth changes suggest neotectonic evolution of thrust across the crust in the paleo-rifting structure.
•Middle to lower crustal earthquakes occur continuously in the western East Sea (Sea of Japan).•Paleo-rifting structures spawn earthquakes as response to the ambient stress.•Neotectonic evolution of lower crustal thrust happens around the paleo-rifting structures.
SUMMARY
Thunder-induced seismic waves recorded at dense seismic stations in Seoul, South Korea are analysed for inversion of thunder source spectra. Thunder-induced seismic waves from four local ...thunder events are analysed. A theory is introduced for the inversion of acoustic source spectra from thunder-induced seismic waves. In the course of source-spectral inversion, the propagation and acoustic-to-seismic coupling effects are counted. The thunder-induced seismic signals were well identified at distances of <∼20 km. Direct acoustic-to-seismic coupled seismic waves present apparent phase velocities of sound speed in atmosphere (340 m s−1). Thunder-induced seismic waves are dominant at high frequencies (>20 Hz). Vertical peak ground accelerations of thunder-induced seismic waves in local regions (0.024–0.110 m s−2 at distances of 2.4–3.7 km) are equivalent to the ground motion levels induced by a moderate-size (∼M5) earthquake at regional distances. The thunder-induced acoustic waves in the atmosphere are obtained by removing the acoustic-to-seismic coupling effect and site-response effect from the observed thunder-induced seismic waves. The quality factors for acoustic wave attenuation in the atmosphere are determined. Urban landscapes and atmospheric effects cause strong acoustic attenuation over atmospheric absorption. Acoustic thunder source spectra are determined by stacking the inverted acoustic spectra at all stations. The peak frequencies of acoustic thunder source spectra are around 34–36 Hz, suggesting the acoustic energy per unit length in lightning strikes to be ∼4 × 106 J m−1. Local seismic records are applicable for the investigation of thunder and lightning properties.
Abstract
The average shear‐wave velocity within the top 30 m from the surface,
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, represents site characteristics including the soil classification and site amplification that are essential ...information for building codes and seismic design. A novel method to determine a
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model based on a composite analysis of borehole standard penetration test numbers (SPT N) and horizontal‐to‐vertical (H/V) spectral ambient noise ratios is introduced. A national
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model for South Korea is determined using the method. The shear‐wave velocity structures beneath 20 nationwide broadband seismic stations are determined using the H/V analysis. The SPT N data are collected from 175,619 nationwide densely‐distributed boreholes. The shear‐wave velocity models from SPT N values are calibrated for the local reference velocity models from H/V analysis. A representative relationship between the SPT N values and shear‐wave velocities is introduced. A national
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model for South Korea is determined using the calibrated SPT N models at the nationwide boreholes. The
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model is verified by comparisons with local field measurements. The proposed model is consistent with the USGS model based on a surface slope analysis. The
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structure presents high correlation with geological and topographic features. The
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values are low in coastal (low topographic) areas, and high in mountain (high topographic) areas. Apparent linear relationship is observed between
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and topography. The western and southeastern coastal regions may be vulnerable to strong seismic shaking.
Plain Language Summary
Seismic ground motions are an important factor to control the seismic damages. The seismic amplification is highly dependent on the shear‐wave velocities at shallow depths ≤30 m,
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. We introduce a novel method to determine a
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model based on the standard penetration test numbers (SPT N) from nationwide 175,619 boreholes and horizontal‐to‐vertical spectral ambient noise ratios (H/V ratios) from 20 broadband seismic stations. We determine a
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model for South Korea. The shear‐wave velocity structures beneath broadband seismic stations are used for local reference velocity models. The shear‐wave velocity models from SPT N values are calibrated for the local reference velocity models from the seismic stations. We determine a representative relationship between the SPT N values and shear‐wave velocities. We determine a high‐resolution
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model using the calibrated SPT N models at boreholes. The proposed model is verified by comparisons with other results. The
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structure presents high correlation with geological and topographic characteristics. The
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values are low in coastal areas, and high in mountain areas. The western and southeastern coastal regions may be vulnerable to strong ground motions during earthquakes.
Key Points
A novel method based on SPT N values and H/Vratios is proposed for determination of national
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model for South Korea
A high‐resolution national
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model can be calculated using the calibrated SPT N data at densely distributed boreholes
The
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model presents high correlation with geological and topographic features
A series of midcrustal moderate-size earthquakes occurred in the Korean Peninsula recently. A midcrustal ML4.9 strike-slip earthquake with a fault-plane strike in N-S occurred on December 14, 2021 at ...the southwestern offshore region of Jeju Island, South Korea. The fault plane orientation and slip sense (faulting mechanism) hardly conform with the regional stress field. The deep focal depth and N-S directional strike-slip motion require transient changes in the medium properties and stress field. Strong ground motions of the midcrustal earthquake induce preferential dynamic stress changes in NE-SW direction, triggering subsequent aftershocks in NE-SW-directional adjacent faults. Both the static and dynamic stress changes caused by the mainshock contribute to the aftershock sequence. The number and focal depths of aftershocks decrease with distance from the mainshock. The different fault-plane orientations between the mainshock and aftershocks suggest earthquake nucleations in independent fault structures. The mainshock occurred in aseismic midcrustal paleovolcanic structure on the outskirt of a high seismicity region. The ML4.9 earthquake suggests possible nucleation of earthquake in seismically-inactive paleotectonic structures, successively incurring aftershocks conforming to the ambient stress. The mainshock and aftershocks suggest that paleotectonic structures may behave as source structures to spawn earthquakes.
•Moderate-size earthquake occurs in aseismic paleovolcanic structure.•The stress change and yield stress changes with earthquake induction continue for decades.•Midcrustal moderate-size earthquake induces a series of aftershocks in adjacent regions.
SUMMARY
Earthquakes in the Korean Peninsula often occur in subsurface hidden faults that are hardly identified before the seismic activity. We investigate a midcrustal subsurface hidden fault in a ...seismically quiescent region of the central Korean Peninsula that produced the 28 October 2022 ML 4.1 earthquake. A combined analysis of seismicity, geophysical properties and geological features constrain the subsurface fault geometry. The midcrustal fault may extend to the lineament on the surface that presents low gravity anomalies. The focal mechanism solutions and seismicity distribution suggest that the lineament may correspond to the surface trace of the fault. Further, the responsible fault is a left-lateral strike-slip fault with dip of 88° and bilateral rupture at depths of ∼12–14 km. The lateral extent of the fault may reach >25 km. A series of foreshocks formed the source zone to induce the main shock. The main shock nucleated at a location of lateral contrasts of heat fluxes and magnetic anomalies in the fault. The strong ground motions by the main shock are amplified by the sedimentary layers in the event site, inducing aftershocks to spread along the fault with time. The fault orientation is laid to respond to the ambient stress field. The Coulomb stress changes induced by the main shock load stress the fault, increasing the possibility of another earthquake occurrence. The study suggests that a combined analysis of seismicity, geophysical properties and geological features may provide constraints on seismogenic subsurface hidden faults.
Study for feasibility of commercially available action cameras in recording video of spine.
Recent innovation of the wearable action camera with high-definition video recording enables surgeons to ...use camera in the operation at ease without high costs. The purpose of this study is to compare the feasibility, safety, and efficacy of commercially available action cameras in recording video of spine surgery.
There are early reports of medical professionals using Google Glass throughout the hospital, Panasonic HX-A100 action camera, and GoPro. This study is the first report for spine surgery.
Three commercially available cameras were tested: GoPro Hero 4 Silver, Google Glass, and Panasonic HX-A100 action camera. Typical spine surgery was selected for video recording; posterior lumbar laminectomy and fusion. Three cameras were used by one surgeon and video was recorded throughout the operation. The comparison was made on the perspective of human factor, specification, and video quality.
The most convenient and lightweight device for wearing and holding throughout the long operation time was Google Glass. The image quality; all devices except Google Glass supported HD format and GoPro has unique 2.7K or 4K resolution. Quality of video resolution was best in GoPro. Field of view, GoPro can adjust point of interest, field of view according to the surgery. Narrow FOV option was the best for recording in GoPro to share the video clip. Google Glass has potentials by using application programs. Connectivity such as Wi-Fi and Bluetooth enables video streaming for audience, but only Google Glass has two-way communication feature in device.
Action cameras have the potential to improve patient safety, operator comfort, and procedure efficiency in the field of spinal surgery and broadcasting a surgery with development of the device and applied program in the future.
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After the devastating Tohoku-Oki earthquake (Mw 9.0, 2011) in Japan, the Korean Peninsula has experienced a higher number of large, plus Mw 5.0, earthquakes than recorded in the preceding half ...century of modern monitoring. In addition, seismicity has dramatically increased along with seismic waves arriving later than prior to the 2011 Tohoku-Oki earthquake, suggesting that the Korean crust has notably been perturbed. South Korea is densely populated, hence knowledge about active faults and earthquake mechanisms is of great relevance for public safety and risk mitigations. Quaternary faults, including the Chugaryeong crustal-scale fault, run through the Seoul metropolitan area and recent seismicity studies suggest that these faults are active. Based on two reflection seismic profiles, we provide compelling evidence that the depth clustered seismicity along the Chugaryeong fault is associated with the intersections of other fault systems. The two seismicity clusters, observed at two depth intervals of approximately 4.5–5 and 8–9 km, can be linked with two moderately-to-steeply-dipping bands of reflectivity interpreted to be splay faults and terminating at the Chugaryeong sub-vertical fault. We suggest that stress builds up at these fault intersections and is then released via strike-slip ruptures along the Chugaryeong fault. Time-clustered seismic events at the fault intersections support this hypothesis, indicating a start-stop mechanism is controlling the seismicity in the region at least based on nearly one decade of seismicity observations. The start-stop seismicity behaviour can possibly be used for forecasting earthquakes and their switching depth along the Chugaryeong fault.
•Two reflection seismic profiles were acquired in South Korea for imaging fault systems.•Seismicity shows a temporal and spatial correlation with the interpreted fault systems.•Reflection seismic imaging in mega-cities using innovative solutions is possible.
The objective of this study was to evaluate the effects of lysophospholipids (LPL) supplementation on rumen fermentation, degradability, and microbial diversity in forage with high oil diet in an in ...vitro system.
Four experimental treatments were used: (1) annual ryegrass (CON), (2) 93% annual ryegrass + 7% corn oil on a dry matter (DM) basis (OiL), (3) OiL with a low level (0.08% of dietary DM) of LPL (LLPL), and (4) OiL with a high level (0.16% of dietary DM) of LPL (HLPL). An in vitro fermentation experiment was performed using strained rumen fluid for 48 h incubations. In vitro dry matter degradability (IVDMD), in vitro neutral detergent fiber degradability (IVNDFD), pH, ammonia nitrogen (NH3-N), volatile fatty acid (VFA), and microbial diversity were estimated.
There was no significant change in IVDMD, pH, NH3-N, and total VFA production among treatments. The LPL supplementation significantly increased the proportion of butyrate and valerate (Linear effect Lin, p = 0.004 and < 0.001, respectively). The LPL supplementation tended to increase the total bacteria in a linear manner (p = 0.089). There were significant decreases in the relative proportions of cellulolytic (Fibrobacter succinogenes and Ruminococcus albus) and lipolytic (Anaerovibrio lipolytica and Butyrivibrio proteoclasticus) bacteria with increasing levels of LPL supplementation (Lin, p = 0.028, 0.006, 0.003, and 0.003, respectively).
The LPL supplementation had antimicrobial effects on several cellulolytic and lipolytic bacteria, with no significant difference in nutrient degradability (DM and NDF) and general bacterial counts, suggesting that LPL supplementation might increase the enzymatic activity of rumen bacteria. Therefore, LPL supplementation may be more effective as an antimicrobial agent rather than as an emulsifier in the rumen.
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