A Study on Occupational Mismatch of Korean Labor Market: Labor Supply Estimation Model with Qualitative Variables based on Deep Learning

이지인 포항공과대학교 융합대학원 2023 국내석사

This study aims to find the link between people’s perspectives about occupations and labor demand, regarding the labor mismatch situation. Labor mismatch has been one of the prominent issues to be considered in the Korean labor market. The study devised a labor demand estimation model as the solution for the mismatch problem. In the modeling process, people’s perceptions of occupations were regarded as a qualitative factor. Being one of the features used to define labor mismatch, labor demand tends to be affected by the image of occupations, since people tend to consider those images in their future or current job-seeking process. The study first compared the time-variant job image and their matching efficiency scores from 2010 to 2022. Then, it tested the GRU and LSTM-based labor demand prediction model with the qualitative factors and compared the result with the models with just quantitative factors. This study contributes to the field by handling labor mismatch regarding the perceived job image, furthermore, establishing a deep learning-based model that contains those qualitative factors as the solution for the mismatch.

User Characteristics by News platform and Comment generation : Multiple methods approach for Interest and Interpretation of User

이민구 포항공과대학교 융합대학원 2023 국내석사

Depending on the feature of the media, the characteristics of the users are fixed. As a result, the information selection and interpretation may vary. Therefore, media study should focus on the process of user accepting and interpreting messages rather than simply looking at media as a tool for information delivery. In this study, Internet portal news and Online video platform news are compared from the audiences- centered perspective. Through comparison, we would like to explore whether user characteristics according to media platform appear in comments. For analysis, NAVER and YouTube, the representative of internet portal and Online video platform were analyzed. We collected the same news contents uploaded to each platform and built a dataset of 2,145,698 comments. As a result, it was found that comments of NAVER and YouTube not only concentrated on different news contents by reflecting the characteristics of users, but also there are differences in the trend of comments generation. Also, there are difference in the way how they interpreted the message of news contents. Through this, it was revealed that the characteristics of the user by media platform are actually impact on interest and interpretation of users.

Nowcasting Korean GDP growth using Machine Learning with Economic Policy Uncertainty feature

정승민 포항공과대학교 융합대학원 2022 국내석사

GDP growth is an indicator of a country's economic situation and is a crucial factor in financial decisions. Nevertheless, since it has a problem of being announced lately, 'Nowcasting', the prediction of GDP growth at present, is being treated as an essential issue. Due to the recent increase in uncertainty, studies to increase the accuracy of Nowcasting are primarily divided into two directions. One is to reflect uncertainty as a variable, and the other direction is to use ML models as predictive models. However, there has yet to be an attempt to incorporate both approaches. Therefore, this study aims to integrate both approaches to generate a prediction model for the GDP of Korea. The proposed method first extracts common factors through the Dynamic Factor Model to reduce the dimensions of 83 economic indicators affecting GDP growth. Then, the Economic Policy Uncertainty value, an indicator of uncertainty, is combined with the reduced factors, and they are used as input features of prediction models. Finally, several machine learning models are used to predict GDPs. To validate the proposed approach, we conduct experiments with Korean GDP-related data. In the experiment, we construct two data sets with and without the Economic Policy Uncertainty value to explore the impact of the uncertainty. Random Forest, Gradient Boost, and XGBoost are used as ML-based prediction models, while OLS regression is used as a conventional prediction model. The experimental result shows that including the EPU feature provides higher prediction accuracies for all four models. In addition, the performances of the ML models are more elevated than that of OSL regression.

Long-working(0.3m) distance microscope

조재영 포항공과대학교 일반대학원 2022 국내석사

포항공대 아토초 과학 연구실 내 아토초 광 시설의 경우 반경이 25 수준의 진공 챔버 안에 수십 수준의 TMDC 샘플을 활용하는 실험을 진행하고 있다. 진공 밖에서 30~40 수준의 TMDC 샘플에 대한 레이저의 집속위치를 관측하기 위해서 긴 Working distance의 고배율 현미경의 필요성이 대두되었다. 이를 해결하기 위해 Long-working(0.3m) distanace microscope을 제작을 하여 진공 챔버 안의 TMDC샘플을 측정해야 한다. Microscope를 위의 상황을 고려하며, 간단하게 구현하기 위하여 몇 가지 조건과 제약을 두었다. (1) 색수차를 줄이기 위해 532 의 단일 파장에서 작동 (2) 10배 이상의 배율을 구현 (3) 실제 제작을 위해 첫번째 렌즈로부터 detector까지의 거리를 40 이하 제약 (4) 간단한 제작을 위해 최대한의 상용렌즈 사용 (5) 시뮬레이션을 통해 단색수차의 최소화 위의 조건과 제약을 통해 시뮬레이션을 진행하였고, 시뮬레이션 결과를 바탕으로 실험을 진행하였다.시뮬레이션을 기반으로 한 실험 결과 최대 25배의 배율과 8μm 분해능의 이미지를 얻는 데 성공했다. The need for a high magnification microscope with a long-working distance has emerged in order to observe the laser focus position for TMDC sample with a 30~40 μm. To solve this problem, a long-working (0.3m) distance microscope should be manufactured to measure TMDC samples in a vacuum chamber. Some conditions and restrictions were placed for simple implementation. (1) Operates at a single wavelength of 532 to reduce chromatic aberration (2) Realize a magnification of 10 times or more (3) Limit the distance from the first lens to the detector to 40 or less for actual production (4) Use of commercial lenses as much as possible for simple production (5) Minimization of monochromatic aberration through simulation Simulations were conducted through the above conditions and constraints. As a result of the experiment based on the simulation, it succeeded in obtaining an image with a magnification of up to 25 times and a resolution of 8 μm.

실물옵션을 이용한 OLED TV 사업의 투자가치평가 및 최적 투자시기 결정

김지현 포항공과대학원 일반대학원 2013 국내석사

We evaluate the economic value and the optimal investment timing of OLED TV by using the real options analysis. In fact, DCF has been used for valuing investment in the general cases because it is easy to understand and calculate. However, there are two strong assumptions. One is the numbers which is currently speculated will not be changeable. Another one is there is no room for further improvement once investment valuation is finished. These assumptions can’t reflect the future uncertainty, which makes the DCF results unrealistic. In the contrast, the real option method is to evaluate investment including the opportunity to modify the first draft of the investment. Due to its flexibility, it can increase the value of the investment. In this paper, launching the OLED TV itself is equivalent to the American Call Option, which means delaying option is only thing we consider and binomial lattice approach was employed. As a result, the project value with option is greater than the conventional valuation methods as well as delaying the investment is more favorable. Therefore, real option model enable the management to make decision strategically according to the future states.

전산모사 및 I-V 모델링을 이용한 20-nm 노드 Ge2Sb2Te5 상변화 메모리 특성 분석

장현동 포항공과대학교 일반대학원 2020 국내석사

Phase-change memory (PCM) using chalcogenide materials has been spotlighted as non-volatile memory, which can fill the gap of memory hierarchy between DRAM and NAND Flash. However, as research on scaling down PCM devices has been actively conducted, problems such as resistance drift, cell-to-cell disturbance, undesired programming, and high RESET current have emerged. In particular, the chalcogenide material in the amorphous state has caused side effects, thereby raising the need for research for in nm-class PCM devices. Therefore, in this thesis, electrical and thermal performances of the PCM are characterized and discussed using technology computer-aided design (TCAD) and integrated circuit characterization and analysis program (IC-CAP) tools. Electrical and thermal performances of 20-nm node PCM described the bandgap model are extensively analysed according to physical parameters and geometry using fully-calibrated TCAD simulation. Increasing the maximal crystallization rate (r0) and decreasing the activation energy (Eact) reduces SET resistance and SET programming current, thus resistance ratio can be increased and consumes less power. This result suggests that Eact is more sensitive to electrical performance than r0. SET and RESET current decreases as impact ionization factor (II) increases. Also, programming current decreases and heat efficiency increases as thermal boundary resistance (TBR) thermal conductivity decreases and TBR metal resistivity increases. Decreasing the cell height reduces SET resistance, so increases read latency. However, current which produces the same Joule heating effect increases, thus increasing power consumption. Therefore, read latency and programming current are in a trade-off relationship when the cell height varies. Finally, these parameters can vary the threshold voltage, thus when designing the PCM cell, these parameters must be considered to meet the desired specifications. Threshold switching and snap-back mechanism is explained by the non-equilibrium carrier distribution and non-uniformity of electric field along the amorphous layer. Then, the appropriate barrier lowering change model that describe carrier transport in the subthreshold region is selected by comparing two models. Therefore, the subthreshold region, threshold switching, negative differential resistance, and ON region are implemented using analytical model of PCM. As a result, this model can be applied to circuit simulations of PCM devices with current equations based on physical computation.

The design of all-dielectric metasurface for selectively blocking Near-Infrared region of solar spectrum

김은종 포항공과대학교 일반대학원 2020 국내석사

Blocking near-infrared region (NIR) is indispensable for saving energy consumed to maintain an interior temperature in buildings. The methods of blocking NIR are divided into two types. One is blocking NIR without visible light for applying to windows. The other is blocking the overall solar spectrum including visible light because the visible light accounts for 45% in the solar spectrum. Thus, we designed the metasurface of two types, respectively. In the transparent metasurface blocking NIR, simultaneously enhancing transmission in visible light and blocking in NIR remains challenging. Here, we demonstrate the trans-parent all-dielectric metasurface selectively blocking the NIR by using TiO2 nanocylinder and ITO layer. The ITO layer is implemented as a back reflector because the ITO is trans-parent in visible light whereas the ITO becomes reflective materials in the long-wavelength region (λ > 1500 nm). The designed metasurface exhibits a high average transmittance of 70% in visible light and high solar energy rejection (SER) of 90% in NIR. Furthermore, the performance of the designed metasurface is maintained over a wide range of an incident angle of light. Therefore, the metasurface gives an advanced guide-line for design energy-saving applications. In the opaque metasurface blocking NIR, the previous all-dielectric metasurfaces have difficulty in reflecting overall NIR because the reflection region is too narrow. Here, we demonstrate the all-dielectric metasurface blocking almost overall NIR by using amor-phous Si (a-Si) and SiO2. Since amorphous Si has a high refractive index (~3.3) and high extinction coefficient in NIR, the designed metasurface exhibits high reflection (1050 nm ≤ λ ≤ 2320 nm) as well as high absorption (λ < 1040 nm), thereby leading to high solar energy rejection (SER) of 94% in NIR. The performance of the designed metasurface is independent over a wide range of incident light. Furthermore, a-Si substrate constituting the metasurface can be readily deposited on other materials such as glass and plastic film, so the proposed metasurface has high applicability for a large-area fabrication rather than crystalline Si and GaAs.

Investigation on Thermal Stability of Metal-Interlayer-Semiconductor Contacts Using Carbon Implantation

이동훈 포항공과대학교 일반대학원 2022 국내석사

Effects of carbon implantation (C-imp.) on the thermal stability of MIS (Metal-Interlayer-Semiconductor) contact were investigated. The experiment was conducted on both Si and Ge substrates. To improve the thermal stability in MIS contact, C-imp. into MIS structures was applied. The current density (J) - voltage (V) characteristics showed that C-imp. changed the rectifying behavior to the ohmic-like behavior. The Schottky barrier height (SBH) was also reduced by the C-imp. These improvements can be beneficial to reduce the lower contact resistivity (ρc) with the rapid thermal annealing (RTA) temperatures ranging from 450 to 600 ℃. From the transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) mapping, the MIS contact with C-imp. showed the suppression of oxygen diffusion into Ti layer. From the secondary ion mass spectrometry (SIMS) analysis, the segregation of P dopant at the interface was more facilitated with C-imp.. Thus, the C-imp. is promising to improve the thermal stability and to realize low contact resistivity of MIS contact.

Design and Fabrication of Nanoscale Metal Interconnections for Transparent Deformable Electronic Devices

김동욱 포항공과대학교 일반대학원 2021 국내박사

As transparent displays and touch screens begin to be introduced to the public, the technology for transparent deformable electronic devices is attracting enormous attention as a next-generation electronic technology. Deformable optoelectronic devices, such as displays, solar cells, touch screens, and smart windows that maintain their functions under mechanical deformations have been developed, and various approaches to transparent deformable electrodes have been studied intensively. Despite these interests, transparent deformable nano- and micro-scale integrated interconnections that are easy to be patterned and positioned are receiving somewhat less attention. Since the most successful and feasible concept leading to deformable devices is linking rigid islands of active device components (transistor, light-emitting devices, photovoltaics, etc.) with deformable interconnections, developing transparent interconnections that can retain good electrical performance under high mechanical strain is highly required. In this work, I designed and fabricated three different types of transparent deformable nanoscale metal interconnections; (i) One-dimensional (1D) metal nanolines which were deposited on the flexible substrates by simple and reliable nanofiber (NF) photolithography, (ii) 1D wavy stretchable single metal NF which were individually positioned by the electrohydrodynamic (EHD) printing and metallized through room-temperature electroless plating, and (iii) Two-dimensional (2D) foldable and stretchable gold (Au) film hybrid electrodes which were composed of the anisotropic conductive ultrathin films (ACUFs) and the ultrathin Au film electrodes. These fabricated metal interconnections were not only electrically deformable but also optically transparent due to their nanoscale dimensions, and were able to be individually positioned and patterned in desired positions, shapes, and alignments. Also, all three deformable interconnections are fabricated by low-temperature processes and can easily expanded to large-scale production. The fabricated nanoscale metal interconnections were used as the interconnecting electrodes in the transparent and deformable field-effect transistors (FETs) array and the transparent electrodes of the deformable light-emitting devices.

An Analysis on the Consumption Structure of Contemporary Popular Culture with Network Science

이정우 포항공과대학교 융합대학원 2022 국내석사

Globalization and the development of information technology have enabled people in different societies to share their culture and consume cultural products through digital devices. This social change has made contemporary popular culture to transcend the borders between countries and penetrate the daily lives of consumers. Our thesis focused on investigating which social factors affect the consumption structure of contemporary popular culture. We constructed a consumption network of mobile games between countries to reflect the characteristics of contemporary popular culture. Using Hofstede's cultural dimensions theory and Facebook's social connectedness index, we revealed cultural distance and social ties between countries play important roles in shaping the consumption structure.