The aim of this study is to investigate the effect of audio-visual components on environmental quality to improve soundscape. Natural sounds with road traffic noise and visual components in urban ...streets were evaluated through laboratory experiments. Waterfall and stream water sounds, as well as bird sounds, were selected to enhance the soundscape. Sixteen photomontages of a streetscape were constructed in combination with two types of water features and three types of vegetation which were chosen as positive visual components. The experiments consisted of audio-only, visual-only, and audio-visual conditions. The preferences and environmental qualities of the stimuli were evaluated by a numerical scale and 12 pairs of adjectives, respectively. The results showed that bird sounds were the most preferred among the natural sounds, while the sound of falling water was found to degrade the soundscape quality when the road traffic noise level was high. The visual effects of vegetation on aesthetic preference were significant, but those of water features relatively small. It was revealed that the perceptual dimensions of the environment were different from the noise levels. Particularly, the acoustic comfort factor related to soundscape quality considerably influenced preference for the overall environment at a higher level of road traffic noise.
With the development of microelectronic devices having miniaturized and integrated electronic components, an efficient thermal management system with lightweight materials, which have outstanding ...thermal conductivity and processability, is becoming increasingly important. Recently, the use of polymer-based thermal management systems has attracted much interest due to the intrinsic excellent properties of the polymer, such as the high flexibility, low cost, electrical insulation, and excellent processability. However, most polymers possess low thermal conductivity, which limits the thermal management applications of them. To address the low thermal conduction of the polymer materials, many kinds of thermally conductive fillers have been studied, and the carbon-based polymer composite is regarded as one of the most promising materials for the thermal management of the electric and electronic devices. In addition, the next generation electronic devices require composite materials with various additional functions such as flexibility, low density, electrical insulation, and oriented heat conduction, as well as ultrahigh thermal conductivity. In this review, we introduce the latest papers on thermally conductive polymer composites based on carbon fillers with sophisticated structures to meet the above requirements. The topic of this review paper consists of the following four contents. First, we introduce the design of a continuous three-dimensional network structure of carbon fillers to reduce the thermal resistance between the filler-matrix interface and individual filler particles. Second, we discuss various methods of suppressing the electrical conductivity of carbon fillers in order to manufacture the polymer composites that meet both the electrical insulation and thermal conductivity. Third, we describe a strategy for the vertical alignment of carbon fillers to improve the through-plane thermal conductivity of the polymer composite. Finally, we briefly mention the durability of the thermal conductivity performance of the carbon-based composites. This review presents key technologies for a thermal management system of next-generation electronic devices.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This study presents a new perspective on interrelationships among spatiotemporal patterns in soundscape, acoustic and urban morphological indicators. Spatiotemporal characteristics of soundscapes in ...a multifunctional urban area of Seoul, Korea were analyzed. Physical acoustic and perceived soundscape data were collected during three different daytime sampling periods. Urban morphological indicators representing building, road, open public space, and water feature components, were analyzed to quantify urban textures. Spatial and temporal factors were found to play critical roles in urban soundscapes. Regarding spatial patterns in soundscapes, urban soundscapes were characterized based on the main function of spaces. The temporal variability of soundscapes in urban spaces depended on diurnal patterns in perceived sound sources. Particularly, the perception of birdsong and sounds from human activities showed considerable variation across urban spaces. In addition, significant correlations were found among the spatiotemporal patterns in soundscape, acoustic and morphological factors. Based on the acoustic and morphological indicators, pleasantness and eventfulness models were proposed and the results indicated that the pleasantness model explained 50% of the variance, while the eventfulness model only predicted 13% of the variance. The results from the present study showed that urban morphological factors could be useful indicators for better understanding soundscapes in urban environments.
•Spatiotemporal patterns in soundscapes were collected in an urban area.•Intercorrelations were found among soundscape, acoustic and morphological factors.•A combination of acoustic and morphological indices can be applied to describe urban soundscapes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Psychoacoustic experiments were performed to investigate head-related transfer function (HRTF) and head-mounted display (HMD) effects, to develop a new virtual-reality (VR)-based noise assessment ...methodology and classification method for heavy-weight impact sounds in an apartment indoor environment. Sound pressure levels and frequency characteristics before and after HRTF application were examined to reproduce the “upstairs condition” (overhead movement), for a heavy-weight impact source recorded in an apartment living room. Floor impact noise was assessed using the HMD by modeling a typical living room. For four environments (NONE, HRTF, HMD, and HRTF + HMD), subjective responses (annoyance, allowance limit, semantic expression) were examined for 38–62-dB maximum sound pressure levels with an A-weighted frequency response and fast time constant. Directional information through the HRTF significantly increased annoyance and decreased the allowance limit, and HMD visual information partially (1.2 times) affected the allowance limit in a high inter-floor noise environment owing to increased visual involvement (56 dBA). The semantic expression assessment revealed comprehensive inter-floor noise responses of dissatisfaction, irregularity, and discontinuity, and confirmed greater annoyance due to walking vibration noise in an environment with directional information, because of increased perception of heavy-impact sound-induced discomfort. Regarding annoyance- and allowance-limit-based classification, the satisfaction standards for low-noise environments were assessed as 6–7 dB lower than those of previous studies when both HRTF and HMD were applied, confirming that test subjects respond to noise more sensitively in a virtual environment where audiovisual information is provided. Therefore, a new indoor noise assessment methodology for environmental factors is proposed herein.
•A new virtual-reality-based noise assessment methodology is proposed.•The method can classify heavy-weight impact sounds inside an apartment.•Psychoacoustic experiments reveal the effect of head-related transfer function and head-mounted display.•Inter-floor noise in the HRTF environment leads to inconvenience regarding the building indoor sound environment.•Actual environmental characteristics are incorporated to determine grade criteria for inter-floor noise.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Illuminance levels have been standardized and regulated for many purposes. However, the effects of correlated colour temperature of lighting have received little attention in the field. This study ...investigated the effects of correlated colour temperature of lighting on the brightness sensation, lighting perception, and cognitive performance of 60 students under ambient light emitting diodes (LED) lighting conditions (CCT: 3000 K, 4000 K, and 5700 K; illuminance: 650 lx and 1050 lx) in an actual university classroom. An increase in correlated colour temperature (CCT) led to an increase in brightness sensation. However, increased CCT did not linearly increase lighting comfort. A CCT of 4000 K was considered as the optimum for lighting comfort in educational settings. But in comparison to comfort, higher levels of perceptual properties, satisfaction and acceptance were not affected by CCT from 3000 K to 5700 K. Scores on the working memory test were significantly affected by CCT and illuminance level in men only. The effects of gender appeared in glare sensation and the working memory test. Women were sensitive to glare sensation and had a lower mean score in the working memory test than men. Optimal CCT is more beneficial than increased illuminance in moderately ambient indoor lighting, as it provides better lighting comfort. Further research can look at the long-term effects of CCT on lighting perception depending on brain processing levels and more diverse and in-depth cognitive performance.
To enhance the understanding of solute dynamics within the stream‐to‐riparian continuum during flood event‐driven water fluctuation (i.e., flood wave), a variable saturated groundwater flow and ...solute transport model were developed and calibrated against in situ measurements of the Inbuk stream, Korea, where seasonal flooding prevails. The solute dynamics were further investigated for flood waves (varying by amplitude A, duration T, roundness r, and skewness tp) that were parameterised by real‐time stream stage fluctuations. We found that the solute transferred faster and farther in the riparian zone, especially within the phreatic zone, above which in the variable saturated zone the concentration required a significantly longer time, particularly at higher altitudes, to return to the initial state. By comparison, solute transferred shallowly in the streambed where the solute plume exhibited an exponential growth trend from the centre to the bank. The dynamic changes of solute flux and mass along the stream–aquifer interface and stream concentration were linked to the shape of flood wave. As the flood wave became higher (A↗), wider (T↗), rounder (r↘), and less skewed (tp↗), the maximum solute storage in aquifer increased. Maximum stream concentration (Cstrˍmax) not only presented a positive linear relationship with A or tp but also showed a negative logarithmic trend with increasing T or r. The sensitivity of Cstr_max to A was approximately two times that of tp, and between these values, the r was slightly more sensitive than T. Cstrˍmax linearly increased as hydraulic conductivity increased and logarithmically increased as longitudinal dispersivity increased. The former relationship was more sensitive than the latter.
Highlighted the response of solute dynamics to flood wave and the roles of hydraulic conductivity and dispersivity;
Revealed the spatiotemporal distribution of solute dynamics across stream‐to‐riparian‐continuum during a single flood wave;
Obtained insights into the mechanisms that driven the relative importance of each parameter (A, T, r, and tp) to solute dynamics
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and ...functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane and van der Waals heterostructures to build vertical single electron tunnelling transistors. We grow graphene quantum dots inside the matrix of hexagonal boron nitride, which allows a dramatic reduction of the number of localised states along the perimeter of the quantum dots. The use of hexagonal boron nitride tunnel barriers as contacts to the graphene quantum dots make our transistors reproducible and not dependent on the localised states, opening even larger flexibility when designing future devices.
Appropriate storage of fecal samples is a critical step for unbiased analysis in human microbiome studies. The purpose of this study was to evaluate the stability of the fecal microbial community for ...up to 18 months. Ten healthy volunteers provided fecal samples at the Jeonbuk National University Hospital. Stool samples were stored under the following six conditions: four different storage temperatures (- 70 °C, - 20 °C, 4 °C, and room temperature 20-25 °C) and two different collection tubes (OMNIgene-Gut and DNA/RNA shield-fecal collection tubes). The gut microbiome was analyzed with 16S rRNA sequencing. We compared the taxonomic composition, alpha diversity, beta diversity and inferred pathway abundance between the baseline and 18 months after storage. Samples collected in the DNA/RNA Shield-fecal collection tubes showed the best performance in preservation of the taxonomic composition at 18 months. Pairwise differences in alpha diversity metrics showed the least deviation from zero. The PERMANOVA test showed non-significant change of beta diversity metrics (Unweighted Unifrac: q-value 0.268; Weighted Unifrac: q-value 0.848). The functional stability was significantly well preserved in the DNA/RNA Shield-fecal collection tubes (adjusted p value < 0.05). Our results demonstrate the use of the DNA/RNA Shield-fecal collection tube as an alternative storage method for fecal samples to preserve the taxonomic and functional stability of the microbiome over a long term.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this study, a new noise evaluation method is proposed in which virtual reality (VR) technology in the form of a head-related transfer function (HRTF) and a head-mounted display (HMD) is applied to ...assess the noise experienced inside residential buildings. Firstly, the sound pressure level and frequency characteristics of road traffic noise recorded in a living room were identified before and after applying the HRTF. Secondly, the subjective response was evaluated in terms of loudness, annoyance, disturbance, and allowance for road traffic noise levels LAeq of 40–65 dB in four different test environments, namely, without the HRTF or HMD, with the HRTF, with the HMD, and with both the HRTF and HMD. The impacts of the directional information provided by the HRTF and the visual information provided by the HMD were 77% and 23%, respectively. Furthermore, based on an evaluation of the source- and environment-related spatial attributes, the recognition of road traffic noise was the highest with the HRTF, and the recognition of space was the highest with the HMD. When both the HRTF and HMD were applied, the influence of sound externalization in the VR environment increased along with the sense of immersion and realism. Moreover, the recognition of the noise direction and noise width played a significant role in the psycho-acoustic impact, including the annoyance level of the road traffic noise. The findings of this study provide new insights on the influence of external noise on indoor environments.
•A virtual reality-based indoor noise evaluation method was developed and tested.•A head-related transfer function and head-mounted display are used in this method.•Noise direction and noise width strongly influenced the psycho-acoustic impact.•This work provides new insights on the effects of external noise on indoor spaces.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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