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Physical Properties and Photodegradation Mechanism of Nickel Sulfide Nanomaterials
No full textIn order to solve the sewage problem in the chemical and textile industries, the sewage is degraded into water and carbon dioxide which are harmless to the environment through photocatalytic degradation.
In this study, nickel chalcogenides were synthesized by chemical vapor deposition. Compared with other methods, the chemical vapor deposition method is simple to operate, can grow in a large area, and uses simple and cheap precursors. There are two parts in this thesis research. The first part is to use CVD to prepare a-NiS on porous Ni foam, in order to increase the surface areas to induce more efficient photocatalytic function. Then, the resulting a-NiS is characterized by X-Ray diffraction XRD, scanning electron microscopy SEM, energy dispersive spectrometry EDS, UV-visible spectrometry UV-Vis, Xenon lamp, and X-ray photoelectron spectroscopy XPS, etc. Finally, the resulting a-NiS is explored for its photocatalytic properties for multiple cycles, followed by examination of its reaction product and reaction mechanisms. The second part is to prepare g-C3N4 by CVD to grow g-C3N4 either on Si wafer or on porous Ni foam, with or without a-NiS.
Based on the results from the first part, it is confirmed that single-phase a-NiS can be successfully synthesized by CVD. The a-NiS is confirmed to possess the P63/mmc space group, with lattice constants a=b=3.42 \uc3 and c=5.3 \uc3. According to SEM/EDS, this single-phase a-NiS does contain 50 at% Ni and 50 at% S. This a-NiS has good photocatalytic properties, with a high efficiency up to 96% photocatalytic degradation. Even after four cycles of the photocatalytic degradation, there is no basic change of the a-NiS structure and photocatalytic function. Furthermore, by using the Langmuir\ue2Hinshelwood equation analysis, the current CVD-grown a-NiS, with light exposure, the K reaction constant can reach 0.32 h-1, much higher than the K values under no a-NiS or no light exposure condition (only 0.005-0.04 h-1). This high K value of 0.32 h-1 is also apparently higher than the K value of 0.17 h-1, obtained by Mr. Tseng in the same laboratory in National Sun Yat-Sen University in 2021. In addition, by using the XPS analysis, the reaction product during light degradation is found to be SOx2-. After the samples are decomposed, the degradation effect would be decreased.
For the second part, to prepare the combined a-NiS and g-C3N4 by CVD, it is not completed and not successful yet, due to the leave of former advisor to other university. Through the limited tries, it is not yet able to synthesize sound g-C3N4 or combined a-NiS and g-C3N4 by CVD. It is needed to wait for future study
Topology-Morphable Converters for Wide Voltage Range
No full textThis dissertation proposes a topology-morphable mechanism, aiming to maintain a sufficiently high conversion efficiency for converters in a wide operation range of input or output voltage variations, such as power supplies, series-connected solar panels, series-connected battery packs, etc. Firstly, the conventional converters are analyzed for discussing the drawbacks and issues under wide voltage range operations. Opportunities for improvement and refinement are identified. Ultimately, based on the topology morphing, the dissertation avoids the converter operate at a low duty-ratio to decrease the conversion loss. Furthermore, three converters are developed to validate the advantages and benefits of topology morphing.
The first converter operates the converter in either a phase-shifted full-bridge or an asymmetric half-bridge topology through topology morphing. A 1.8 kW experimental converter was implemented to verify that efficiency could be improved by topology morphing, with a maximum increase of 6 %. The second converter operates a dual-battery power module in single-stage or two-stages bidirectional buck/boost conversion through topology morphing. A 104 W experimental power module with a rated voltage of 48 V was implemented. Experimental results demonstrate that the circuit topology achieves a maximum efficiency of 94.7% in single-stage conversion. In two-stage conversion, although the efficiency peaks at 88.7%, it provides higher voltage gain. The third converter connects the primary side of two transformers in serial or parallel or even bypass one transformer through topology morphing. A 1.44 kW experimental converter was implemented to verify that the overall efficiency is improved under wide voltage range operation with topology morphing. The highest efficiencies for series, parallel, and single-bridge modes are 95.67%, 94.74%, and 94.49%, respectively.
This dissertation mainly focuses on thoroughly analyzing the issue of increased losses in traditional converters when operating within a wide voltage range. A topology-morphable method is proposed to mitigate the converter losses, maintain conversion efficiency, and is validated through three different converters. This method can be further applied to existing or newly designed converters, offering opportunities for innovation and expanding its applicability to a broader application fields where voltage varies in a wide operation range
A study of Heat Transfer Enhancement in Smooth/Roughened Microchannels with Hybrid Nanofluids
No full textThis study investigates the phenomenon of heat transfer enhancement in microsystems at low Reynolds numbers by employing hybrid nanofluid flowing through microchannels with roughened surface. The microchannel dimensions were set at length 30 mm, height 100 \uce\ubcm, and width 200 \uce\ubcm. The experiments were conducted at specific Reynolds numbers (Re = 10, 20, 40) using hybrid nanofluid (Al2O3 + graphene) at mixing ratios of (1:1), (1:0.5), and (1:0.25), with volume concentrations (\ucf= 0.05 vol%, 0.1 vol%, and 0.3 vol%). The working fluid flowed over smooth/rough surfaces (e = 0, 20, 25, 30 \uce\ubcm). The investigation utilized Micro Particle Image Velocimetry (\uce\ubcPIV) system to measure velocity and temperature fields via thermal couples. Flow visualizations were made on fluid flow and velocity distribution within the microchannels, obtaining pressure drops and friction factors. The Buckingham Pi theorem was employed to derive main functions relating friction factors to volume concentration (\ucf), Reynolds number (Re), and pin fin height (\uf0/\uf0\ub7\ue2). A correlation for friction factors was successfully established with an error range of \uc2\ub17% when predicting similar flow fields. In the thermal field, calculations were made for local convective heat transfer coefficients (hx) and Nusselt numbers (Nux). The most significant convective heat transfer was obtained at Re = 40, nanofluid mixing ratio of (1:1) with a volume concentration (\ucf = 0.3 vol%) and pin fin height (e = 30 \uce\ubcm), the average convective heat transfer (\ue2) was 1149.2 W/m2K with optimal heat transfer enhancement of 33.8%. Using the Buckingham Pi theorem, a correlation for Nusselt numbers (Nu) was established, involving volume concentration (\ucf), Reynolds number (Re), Prandtl number (Pr), and pin fin height (\uf0/\uf0\ub7\ue2) parameters. The error range for predicting similar thermal fields was within \uc2\ub15%. To further analyze the efficiency of heat transfer enhancement while considering the influence of the flow field, the overall performance factor (\uce\ub7) was defined. The study examined the heat transfer efficiency for each case, concluding that the highest overall heat transfer efficiency reached 1.1 occurred at Re=40 ,using nanofluid mixing ratio (1:1) at volume concentration \ucf=0.3 vol%, and a pin fin height of 25 \uce\ubcm
The Impact of Policy Loans on the Abnormal Returns of Financial Institutions: A Case of Covid-19 Relief Loan
No full textAt the onset of 2020, the COVID-19 pandemic broke out globally, prompting governments worldwide to employ various monetary and fiscal policies to mitigate the pandemic's negative impact on financial markets. The government of Taiwan implemented a series of relief loan policies targeted at businesses and individuals. These policies facilitated financial support through financial institutions to sustain business operations and the quality of life for the general public. However, from the perspective of financial institutions and investors, while the implementation of such loan policies was beneficial for business expansion and enhancing the earnings of financial institutions, it also increased the risk of loan defaults due to simplified loan review processes and poorer credit conditions of borrowers, thereby affecting the asset quality and profits of financial institutions.
This study employs the market model within event study methodology for empirical analysis, exploring whether the implementation of relief loan policies resulted in abnormal returns on the stock prices of financial institutions. The findings indicate that, except for the MOEA Relief Loan, the rest of the loan policies yielded positive accumulated average abnormal returns for both the market and financial institutions in the period around the announcement and implementation dates. Regarding the magnitude of abnormal returns, except for the Post Pandemic Relief Loan, the general trend showed that the market exhibited the highest abnormal returns, followed by bank stocks, with state-owned banks performing the least favorably. This suggests that while loan policies did not directly cause financial institutions to diverge significantly from market trends, they still had a certain degree of negative impact
Investigating the changes in cosmetics purchasing behavior after Covid-19 pandemic
No full textThis study examines and compare the changes in customers' online and offline cosmetics purchasing behavior pre- and post-pandemic, focusing on internal shop environment, interaction with staff, website design, and website security as variables. Through data collection from the cosmetics consumers, the empirical findings indicated that while brick-and-mortars factors like internal shop environment and interaction with staff still positively influence customer purchasing behavior, their impact is lower post-pandemic. Conversely, online shopping factors, website design and security, have an even more significant positive influence after Covid-19. The study highlights the heightened importance of website design and security in the e-commerce strategies of cosmetics brands, emphasizing the need for improved product descriptions, simplified website processes, and enhanced personal information protection. The research offers practical implications for cosmetic brands in adapting to changes in customer purchasing behavior post-pandemic and developing effective business strategies
The Impact of Taiwan Carbon Solution Exchange Establishment on Abnormal Returns of High Carbon-Emitting Industries' Stock Prices
No full textThis research uses an event study method to explore whether the stock prices of high-carbon emission industries produce abnormal returns when the establishment of the Taiwan Carbon Solution Exchange is announced. The event date is set on April 19, 2023, the date when President Tsai Ing-wen of the Republic of China announced that the Taiwan Carbon Exchange will be established. The length of the estimation period is 150 days, that is, from 160 days to 11 days before the event date. The event period is set from 10 days before the event date to 10 days after the event date. The research sample refers to the top 20 largest carbon emitters in 2021 announced by the Taiwan Renewable Energy Alliance on August 19, 2022, and the industry categories of the companies obtained after excluding companies that cannot be publicly traded in the secondary market. There is a total of seven categories, including plastic industry, cement industry, steel industry, semiconductor industry, optoelectronics industry, paper industry and oil, gas & electricity industry.
Empirical results show that among the seven industry categories, abnormal returns in four industry categories (plastic industry, steel industry, semiconductor industry, and optoelectronics industry) have a significant negative impact on event announcements, and in two industry categories (cement industry and paper industry) have a positive impact on event announcements, and one industry category (oil, gas & electricity industry) has no significant impact
Using the environmental factors of organizational change to analyze the key influencing factor on the evolution of government agency
No full textAccording to government agencies around the world, they will continue to adjust their functions and agency names with changes in time and space. The purpose of this study stems from the author's own experience in the restructuring and upgrading of the Kaohsiung City Sports Office, and with reference to the Kaohsiung City Government Sports and Culture Administration Director The history of the evolution of agencies, and then explore the evolution process of the central authorities in charge of sports and culture, and by analyzing the opportunities and reasons for the evolution of past agencies, we will summarize how the central government authorities are affected by environmental factors. The establishment and abolition of government agencies, and then be able to analyze the impact An important factor in how government agencies and organizations will evolve and change their names in the future.
This study is based on the research plan of merging sports and cultural businesses during the restructuring of our country's government organizations, and hopes to use the research approach of historical institutionalism to analyze the organizational development history of our country's sports and culture authorities and our country's central government administrative agencies. In the process of change, the possible influencing factors behind it may even be the key factors that can be used to predict the possible development of future organizational restructuring agencies
The Competition and Cooperation of China and the EU in Mobile Communications Technology and its Application
No full textChina and the European Union (EU) play critical role in the evolution of fifth-generation (5G) mobile communication technology. This thesis examines the transition from globalization to semiglobalization in the context of 5G technology development, where global markets are faced with the decision to collaborate with either the United States or China. This study analyze the developmental strategies and challenges faced by China and the EU amidst this global-to-semiglobalization transition, focusing on their competitive and cooperative dynamics in different phases of 5G technology and application development. Based on the shift from globalization to semiglobalization, this research explores the competitive and cooperative relationship between China and the EU in the realm of 5G technologies and applications in various periods. In the part of conclusion some development strategies in the epoch of semiglobalization for the Taiwan\ue2s government and related industries are recommended
The relation between ADR\ue2s Liquidity and ESG Mandatory Disclosure
No full textThis study empirically analyzes 36 liquidity variables to explore the relationship between liquidity and mandatory disclosure. The research finds that mandatory disclosure is significantly positively correlated with the Spread series variables, indicating that mandatory disclosure significantly increases the cost of ADR transactions and reduces liquidity. In the Motivated series, mandatory disclosure significantly reduces the motivated volume but increases the drive value, which may be related to price factors, investor preferences, and time factors. In addition, mandatory disclosure can improve the balance of buying and selling drives, reduce trading costs, and improve liquidity. Finally, in the Depth series, mandatory disclosure is significantly negatively correlated with depth, indicating a decrease in investor preference for ADRs. In summary, mandatory disclosure has multifaceted impacts on liquidity and affects transaction costs and investor preferences
Compact SESAM Mode-Locked Thin-Disk Oscillator
No full textThis thesis presents the construction of a compact thin-disk laser system utilizing ytterbium-doped yttrium aluminum garnet (Yb:YAG) as the laser gain medium. Initially, crystal analysis was conducted employing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, as well as absorption and fluorescence spectroscopy. The investigation utilized 940 and 969nm laser diodes to compare absorption and heat generation for different spot sizes on the crystal, demonstrating that larger spots effectively reduce crystal temperature. Additionally, it showed that at the same intensity, the 969nm wavelength induced less heat. Tests involving varied doping concentrations and thicknesses indicated that concentration had the most significant impact on surface temperature.
Furthermore, a Fabry-Perot resonator was assembled, employing a 940nm laser diode as the pump source. This laser exhibited wavelength dependence on temperature. Consequently, laser output measurements were conducted at different water-cooled settings, revealing optimal output and stability at 26\uc2\ub0C. Evaluating output coupler at 5%, 10%, and 20%, we found the best results at 5%. Subsequently, a tunable spot-size resonator, with a pump spot size of approximately 500\uce\ubcm, was implemented. Testing the resonator on the crystal with spot sizes ranging from 300 to 1000\uce\ubcm, we identified the optimal CW output at 400\uce\ubcm, achieving a maximum output of 21.8W at 82.5W pump power, with an optical-to-optical efficiency of 26.4%. Additionally, SESAM mode-locking tests were performed, resulting in outputs of 1.9W and 5.11W at 150\uce\ubcm and 200\uce\ubcm spot sizes on the SESAM, respectively.
Subsequent experiments utilized a 969nm laser diode as pump source to reduce thermal effects and enhance output efficiency. The Z-shaped resonator on the crystal achieved maximum continuous wave output with a spot size of 360\uce\ubcm, producing 35.9W at 104.8W pump power in multimode, with an optical-to-optical efficiency of 34.2%. And demonstrated a mode-locked output of 17.13W at a spot size of 600 micrometers, and 300 micrometers on the SESAM. Finally, to explore the relationship between crystal doping concentration, thickness, temperature, and laser output, a 969nm stimulated wavelength was used. Measurements indicated that maximum laser absorbed pump power correlated with crystal temperature, confirming the association between crystal temperature and laser output