It is necessary to devise innovative techniques to design new high-performance tandem solar cells to meet increasing energy needs. In this study, the theoretical efficiency of intermediate band solar ...cells (IBSCs) was increased by integrating them with tandem solar cells to produce intermediate band tandem solar cells (IBTSCs). The spectral splitting analysis indicated that the efficient absorption of sub-photon energies was necessary to ensure optimal performance of the IBSCs at each junction of the IBTSC. For this calculation, we assumed all absorption of sub-photon energies are unity. In addition, we applied the variation of absorptivity to the detailed balance limit of a double-junction (DJ) IBTSC. Furthermore, we included the impact of series and shunt resistances of a typical DJ IBTSC to investigate the variations in electrical parameters (short circuit current, open circuit voltage). The performance efficiency also depended on the illumination concentration due to the charge carrier transitions at each junction. We analyzed this aspect to determine the overall performance of the IBTSCs. We replaced the IBSC in the bottom junction with a single-junction solar cell to explore the potential of diverse tandem configurations. DJ IBTSCs achieved a limiting efficiency comparable to that of six-junction solar cells, despite the lower number of junctions. It was challenging for these cells to exhibit optimal performance because of the inefficient spectrum management in the bottom junction. It was concluded that full illumination concentration was required to achieve optimal performance in both junctions of the IBTSC.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In geography education, geospatial technologies have been actively researched and widely used in combination with classroom inquiry and fieldwork. Recently, emerging data sources and technologies, ...such as open data, big data, and Artificial Intelligence (AI), are now gaining attention for their educational potential. In this study, both existing and emerging data and technologies are combined and grouped into four categories: (1) Geospatial Web service, (2) open data and big data, (3) fieldwork using Geographic Information Systems (GIS), (4) AI and coding. And based on these, geospatial inquiry activities for learning high school Korean Geography were developed. Learning to use these data sources and technologies is expected to equip students with essential 21st century skills.
Intersubband transitions in n-doped multi-quantum-well semiconductor heterostructures make it possible to engineer one of the largest known nonlinear optical responses in condensed matter ...systems--but this nonlinear response is limited to light with electric field polarized normal to the semiconductor layers. In a different context, plasmonic metasurfaces (thin conductor-dielectric composite materials) have been proposed as a way of strongly enhancing light-matter interaction and realizing ultrathin planarized devices with exotic wave properties. Here we propose and experimentally realize metasurfaces with a record-high nonlinear response based on the coupling of electromagnetic modes in plasmonic metasurfaces with quantum-engineered electronic intersubband transitions in semiconductor heterostructures. We show that it is possible to engineer almost any element of the nonlinear susceptibility tensor of these structures, and we experimentally verify this concept by realizing a 400-nm-thick metasurface with nonlinear susceptibility of greater than 5 × 10(4) picometres per volt for second harmonic generation at a wavelength of about 8 micrometres under normal incidence. This susceptibility is many orders of magnitude larger than any second-order nonlinear response in optical metasurfaces measured so far. The proposed structures can act as ultrathin highly nonlinear optical elements that enable efficient frequency mixing with relaxed phase-matching conditions, ideal for realizing broadband frequency up- and down-conversions, phase conjugation and all-optical control and tunability over a surface.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The objectives of this research are, first, to find mobile technology-informed ways of designing inquiry-based fieldwork, in support of students' inquiry processes and, second, to evaluate how a ...technology-integrated fieldwork project can affect students' knowledge and experience. In order to achieve these objectives, the study adopted a set of core design principles and guidelines for the creation of inquiry-based fieldwork projects, detailing tips and an example (i.e., the Yangdong Village Project) of these principles and guidelines' application. In addition, this study used a questionnaire to determine the influence of the project on students' understanding of the investigation area and their inquiry-related behaviors. It also analyzed conversation between students, to examine how students' learning processes are supported in fieldwork through use of mobile technology. A total of 86 high school students (ages 17-18), from four schools located in the Seoul metropolitan area, participated in the project. The results of the analyses showed that participation in the project helped students become better informed about the area they investigated. While they were conducting the field tasks, they showed more inquiry-driven behaviors, such as being more active and adventurous, more talkative, and more responsible (88.7%). Technological support for the process of field inquiry was prominent in three situations: location identification, data capture, and monitoring. The functionalities of mobile technology that students used during the field inquiry would reflect not only the characteristics of the task, but also the types of mobile technology involved in the project.
Multiple exciton generation solar cells exhibit low power conversion efficiency owing to non-radiative recombination, even after the generation of numerous electron and hole pairs per incident ...photon. This paper elucidates the non-idealities of multiple exciton generation solar cells. Accordingly, we present mathematical approaches for determining the quantum yield to discuss the non-idealities of multiple exciton generation solar cells by adjusting the delta function. We present the use of the Gaussian distribution function to present the occupancy status of carriers at each energy state using the Dirac delta function. Further, we obtained ideal and non-ideal quantum yields by modifying the Gaussian distribution function for each energy state. On the basis of this approach, we discuss the material imperfections of multiple exciton generations by analyzing the mathematically obtained quantum yields. Then, we discuss the status of radiative recombination calculated from the ratio of radiative to non-radiative recombination. Finally, we present the application of this approach to the detailed balance limit of the multiple exciton generation solar cell to evaluate the practical limit of multiple exciton generation solar cells.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In general, it is very difficult to visually locate blood vessels for intravenous injection or surgery. In addition, if vein detection fails, physical and mental pain occurs to the patient and leads ...to financial loss in the hospital. In order to prevent this problem, NIR-based vein detection technology is developing. The proposed study combines vein detection and digital hair removal to eliminate body hair, a noise that hinders the accuracy of detection, improving the performance of the entire algorithm by about 10.38% over existing systems. In addition, as a result of performing venous detection of patients without body hair, 5.04% higher performance than the existing system was detected, and the proposed study results were verified. It is expected that the use of devices to which the proposed study is applied will provide more accurate vascular maps in general situations.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Single-cell RNA sequencing (scRNA-seq) has greatly advanced our understanding of cellular heterogeneity by profiling individual cell transcriptomes. However, cell dissociation from the tissue ...structure causes a loss of spatial information, which hinders the identification of intercellular communication networks and global transcriptional patterns present in the tissue architecture. To overcome this limitation, novel transcriptomic platforms that preserve spatial information have been actively developed. Significant achievements in imaging technologies have enabled in situ targeted transcriptomic profiling in single cells at singlemolecule resolution. In addition, technologies based on mRNA capture followed by sequencing have made possible profiling of the genome-wide transcriptome at the 55-100 μm resolution. Unfortunately, neither imaging-based technology nor capturebased method elucidates a complete picture of the spatial transcriptome in a tissue. Therefore, addressing specific biological questions requires balancing experimental throughput and spatial resolution, mandating the efforts to develop computational algorithms that are pivotal to circumvent technology-specific limitations. In this review, we focus on the current state-of-the-art spatially resolved transcriptomic technologies, describe their applications in a variety of biological domains, and explore recent discoveries demonstrating their enormous potential in biomedical research. We further highlight novel integrative computational methodologies with other data modalities that provide a framework to derive biological insight into heterogeneous and complex tissue organization. BMB Reports 2022; 55(3): 113-124.
Standoff chemical detection and identification techniques are necessary for ensuring safe exposure to dangerous substances. Molecular fingerprints of unknown chemicals can be measured using ...wavelength-tunable quantum cascade lasers operating in long-wavelength infrared. In this work, we present a method that can identify liquid chemicals on a reflective substrate via diffuse reflection spectra measurement from 50 cm away and multiple nonlinear regression analysis. Experimental measurements and numerical analyses were conducted for different chemical surface densities and angles of light incidence using diethyl phthalate (DEP) and dimethyl methylphosphonate (DMMP). Candidate substances can be classified using a deep learning model to reduce analysis time.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Prior research has indicated the extent to which living in a culture of honor can elicit aggressive behaviors in response to insult. Recent work has extended this research to the realm of mental ...health, with research demonstrating that honor endorsement is linked with decreased utilization of mental health resources due to social concerns that the stigma of psychological help-seeking will reflect poorly on one’s reputation. However, measurements of both the mechanism proposed by the extant literature (reputation concern) and individual-level psychological help seeking intentions were not addressed by previous researchers. In order to address this gap in the literature, the current study of 156 participants located in a Southern U.S. state utilized measures of both reputation concern and psychological help-seeking intentions to clarify the relationship between honor endorsement and the stigma of mental health care utilization. Results from path analysis provided further support to the propositions formulated by prior researchers, in that honor endorser’s reputation concerns appear to fuel stigmatization, which ultimately leads to lower intention to seek psychological services. These findings, in conjunction with prior work, demonstrate the importance of considering individual differences in honor endorsement as an influential factor in understanding the utilization of psychological health resources.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK, VSZLJ
A significant amount of stone sludge is generated as a by-product during the production of crushed stone aggregate, and most of it is disposed of in landfill as waste. In order to recycle this stone ...sludge, this study evaluated a controlled low-strength material (CLSM) using ultra-rapid-hardening cement and stone sludge for application as backfill and subbase material for road excavation and restoration work. In addition, considering the limited construction time of excavation and restoration work in urban areas, backfill and subbase materials must simultaneously satisfy conditions of fluidity, workability, quick curing time, and certain levels of strength. Therefore, in this study, CLSM was manufactured according to various mixing ratios and flow, slump, and compressive strength tests with age were evaluated. Additionally, the change trend in the microstructure of the CLSM with age was analyzed. Through indoor experiments, the optimal mixing ratios for backfill and subbase CLSM were determined, and field applicability and performance of field samples were evaluated through small-scale field construction. It was concluded that CLSM, which contains a large amount of stone sludge, can be sufficiently applied as a backfill and subbase material for excavation and restoration work if appropriate admixtures are adjusted according to the weather conditions at sites.
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