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Self-assembly of cyclic peptides for controlled ice crystal growth
No full textAntifreeze proteins (AFPs) enable subzero survival through specific ice surface binding. Drawing inspiration from AFPs, we report a biomimetic approach using rationally designed cyclic peptides (CPs) incorporating ice-binding amino acids (threonine, valine, and serine), conjugated with 4-arm polyethylene glycol. Our designed system exhibits concentration- dependent self-assembly, forming either nanotubes or two-dimensional nanosheets depending on peptide concentration. The formation of β-sheet structures was confirmed through spectroscopic analysis, including fluorescence, FTIR, and circular dichroism, and ice-binding effectiveness was evaluated through ice recrystallization inhibition (IRI), thermal hysteresis (TH), and dynamic ice formation (DIS) measurements. This investigation provides crucial insights for developing optimized cryopreservativesfor biological sample preservation
Synthesis and Structure-Activity Relationship Studies of Diphenyl Ether Derivatives as BKCa Channel Openers
No full textThe large-conductance Ca²⁺-activated K⁺ channel (BKCa channel) is highly expressed in the smooth muscle of the urinary bladder and mediates muscle relaxation. Therefore, BKCa channel activators are expected to address pathological symptoms associated with the overactivity of bladder smooth muscle. Our research team screened 8,364 compounds from the Korea Chemical Bank (KCB)’s GPCR-targeted library, leading to the discovery of a novel BKCa channel opener (LDD-4856) with superior activity compared to previously reported BKCa channel activators. Based on this previous research, compound 9c was synthesized; it exhibited better activity than LDD-4856. Additionally, key pharmacophores were validated, and an acid moiety was introduced to propose a new potent interaction. In this paper, the structure-activity relationships (SAR) and synthetic procedures of 19 diphenyl ether derivatives are discussed.MasterABSTRACT i
CONTENTS ii
LIST of SCHEMES, TABLES and FIGURES viii
Ⅰ. INTRODUCTION 1
Ⅱ. MATERIALS and METHODS 3
2.1. Materials 3
2.2. Chemistry 4
2.2.1. General procedures 4
2.2.1.1. General procedure A: Synthesis of 2, 8a-d, 11, 13a-b, 25, 27, 33, 42, and 43 4
2.2.1.2. General procedure B: BBr3 Demethylation for the synthesis of 9a-d, 14a-b, 21a-b, 23,
and 47a-d 4
2.2.1.3. General procedure C: Pd/C Hydrogenation and hydrogenolysis for the synthesis of 3, 12, 26,
35, 37, and 46a-d 4
2.2.2. Synthetic procedures 5
2.2.2.1.1. 1,2,4,5-tetrafluoro-3-(2-methoxy-4-nitrophenoxy)-6-(trifluoromethyl)benzene (2) 5
2.2.2.1.2. 3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)aniline (3) 5
2.2.2.1.3. 4-(2-chloroethyl)morpholine (5a) 5
2.2.2.1.4. 4-(3-bromopropyl)morpholine (7b) 6
2.2.2.1.5. 4-(6-bromohexyl)morpholine (7c) 6
2.2.2.1.6. 4-(7-bromoheptyl)morpholine (7d) 6
2.2.2.1.7. 3-methoxy-N-(2-morpholinoethyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
aniline (8a) 7
2.2.2.1.8. 3-methoxy-N-(3-morpholinopropyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
aniline (8b) 7
2.2.2.1.9. 3-methoxy-N-(6-morpholinohexyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
aniline (8c) 8
2.2.2.1.10. 3-methoxy-N-(7-morpholinoheptyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
aniline (8d) 8
2.2.2.1.11. 5-((2-morpholinoethyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenol (9a) 8
2.2.2.1.12. 5-((3-morpholinopropyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenol (9b) 9
2.2.2.1.13. 5-((6-morpholinohexyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenol (9c) 9
2.2.2.1.14. 5-((7-morpholinoheptyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenol (9d) 9
2.2.2.2.1. 1-(3,5-bis(trifluoromethyl)phenoxy)-2-methoxy-4-nitrobenzene (11) 10
2.2.2.2.2. 4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxyaniline (12) 10
2.2.2.2.3. 4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxy-N-(2-morpholinoethyl)aniline (13a) 10
2.2.2.2.4. 4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxy-N-(3-morpholinopropyl)aniline (13b) . 10
2.2.2.2.5. 2-(3,5-bis(trifluoromethyl)phenoxy)-5-((2-morpholinoethyl)amino)phenol (14a) 11
2.2.2.2.6. 2-(3,5-bis(trifluoromethyl)phenoxy)-5-((3-morpholinopropyl)amino)phenol (14b) 11
2.2.2.3.1. ethyl 4-morpholinobutanoate (16) 11
2.2.2.3.2. 4-(3-carboxypropyl)morpholin-4-ium (17) 12
2.2.2.3.3. 4-(4-carboxybutyl)morpholin-4-ium (18) 12
2.2.2.3.4. N-(4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxyphenyl)-4-morpholinobutanamide
(19a) 12
2.2.2.3.5. N-(4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxyphenyl)-5-morpholinopentanamide
(19b) 13
2.2.2.3.6. 4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxy-N-(4-morpholinobutyl)aniline (20a) 13
2.2.2.3.7. 4-(3,5-bis(trifluoromethyl)phenoxy)-3-methoxy-N-(5-morpholinopentyl)aniline (20b) 14
2.2.2.3.8. 2-(3,5-bis(trifluoromethyl)phenoxy)-5-((4-morpholinobutyl)amino)phenol (21a) 14
2.2.2.3.9. 2-(3,5-bis(trifluoromethyl)phenoxy)-5-((5-morpholinopentyl)amino)phenol (21b) 14
2.2.2.4.1. N-(3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)-5-
morpholinopentanamide (22) 15
2.2.2.4.2. N-(3-hydroxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)-5-
morpholinopentanamide (23) 15
2.2.2.5.1. 1,2,4,5-tetrafluoro-3-(4-nitrophenoxy)-6-(trifluoromethyl)benzene (25) 16
2.2.2.5.2. 4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)aniline (26) 16
2.2.2.5.3. N-(6-morpholinohexyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)aniline
(27) 16
2.2.2.6.1. tert-butyl (3-hydroxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)carbamate
(29) 16
2.2.2.6.2. 5-((tert-butoxycarbonyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl
methanesulfonate (30) 17
2.2.2.6.3. 5-amino-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl methanesulfonate
(31) 17
2.2.2.7.1. 5-nitro-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)aniline (33) 18
2.2.2.7.2. N-(5-nitro-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)methanesulfonamide
(34) 18
2.2.2.7.3. N-(5-amino-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)
methanesulfonamide (35) 18
2.2.2.7.4. N-(methylsulfonyl)-N-(5-nitro-2-(2,3,5,6-tetrafluoro-4-
(trifluoromethyl)phenoxy)phenyl)methanesulfonamide (36) 18
2.2.2.7.5. N-(5-amino-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)-N-
(methylsulfonyl)methanesulfonamide (37) 19
2.2.2.8.1. 6-bromohexan-1-ol (39) 19
2.2.2.8.2. 6-bromohexanal (40) 20
2.2.2.8.3. 6-bromo-1,1-dimethoxyhexane (41) 20
2.2.2.8.4. N-(6,6-dimethoxyhexyl)-3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
aniline (42) 20
2.2.2.8.5. N-benzyl-N-(6,6-dimethoxyhexyl)-3-methoxy-4-(2,3,5,6-tetrafluoro-4-
(trifluoromethyl)phenoxy)aniline (43) 21
2.2.2.8.6. 6-(benzyl(3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)amino)
hexanal (44) 21
2.2.2.8.7. N-benzyl-3-methoxy-N-(6-(4-methylpiperazin-1-yl)hexyl)-4-(2,3,5,6-tetrafluoro-4-
(trifluoromethyl)phenoxy)aniline (45a) 21
2.2.2.8.8. methyl (R)-1-(6-(benzyl(3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenyl)amino)hexyl)piperidine-3-carboxylate (45b) 22
2.2.2.8.9. methyl (S)-1-(6-(benzyl(3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenyl)amino)hexyl)piperidine-3-carboxylate (45c) 22
2.2.2.8.10. methyl 1-(6-(benzyl(3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)
phenyl)amino)hexyl)piperidine-4-carboxylate (45d) 23
2.2.2.8.11. 3-methoxy-N-(6-(4-methylpiperazin-1-yl)hexyl)-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)
phenoxy)aniline (46a) 24
2.2.2.8.12. methyl (R)-1-(6-((3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)
amino)hexyl)piperidine-3-carboxylate (46b) 24
2.2.2.8.13. methyl (S)-1-(6-((3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)
amino)hexyl)piperidine-3-carboxylate (46c) 24
2.2.2.8.14. methyl 1-(6-((3-methoxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)
amino)hexyl)piperidine-4-carboxylate (46d) 25
2.2.2.8.15. 5-((6-(4-methylpiperazin-1-yl)hexyl)amino)-2-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)
phenoxy)phenol (47a) 25
2.2.2.8.16. (R)-1-(6-((3-hydroxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)amino)
hexyl)piperidine-3-carboxylic acid (47b) 25
2.2.2.8.17. (S)-1-(6-((3-hydroxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)amino)
hexyl)piperidine-3-carboxylic acid (47c) 26
2.2.2.8.18. 1-(6-((3-hydroxy-4-(2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy)phenyl)amino)hexyl)
piperidine-4-carboxylic acid (47d) 26
2.2.3. FluxOR screening assay 27
2.2.3.1. Cell culture 27
2.2.3.2. Fluorescence assay and data analysis 27
2.2.4. Molecular docking study 29
Ⅲ. RESULTS AND DISCUSSION 34
3.1. Structure-Activity Relationship (SAR) 34
Ⅳ. CONCLUSION 42
Ⅴ. REFERENCES 43
Ⅵ. KOREAN ABSTRACT (국문 초록) 45
viii
LIST of SCHEMES, TABLES and FIGURES
Scheme 1. Synthesis of diphenyl ether derivatives 1-9d 30
Scheme 2. Synthesis of diphenyl ether derivatives 10-14b 30
Scheme 3. Synthesis of diphenyl ether derivatives 15-21b 31
Scheme 4. Synthesis of diphenyl ether derivatives 3-23 31
Scheme 5. Synthesis of diphenyl ether derivatives 24-27 31
Scheme 6. Synthesis of diphenyl ether derivatives 28-31 32
Scheme 7. Synthesis of diphenyl ether derivatives 32-37 32
Scheme 8. Synthesis of diphenyl ether derivatives 38-47d 33
Table 1. BKCa channel opening activity of compound 9a-9d 37
Table 2. BKCa channel opening activity of compound 14a-b, 21a-b 37
Table 3. BKCa channel opening activity of compound 8c-d, 9c-d, 23, 27 38
Table 4. BKCa channel opening activity of compound 31, 35, 37 38
Table 5. BKCa channel opening activity of compound 47a-d 39
Figure 1. Representative structure of BKCa channel activators 2
Figure 2. Molecular docking analysis of LDD-4856 and 9c 40
Figure 3. Molecular docking analysis of LDD-4856 and 23 40
Figure 4. Molecular docking analysis of compound 47b and 47d 4
뇌졸중 환자의 걷기 훈련 중 지면 감각 햅틱 정보 제공을 위한 모바일 매니퓰레이터 개발
No full textEffective gait training of the stroke can be performed by leveraging grounded haptic information obtain by touching an external immobile object. Robotic systems with various preset curvatures allow users to undergo gait training without spatial restrictions, as well as straight-path gait training. We developed a mobile manipulator platform in which the handle is positioned along the preset gait-training path while the robot guides the user by providing grounded haptic information along the designated path as a rail. To verify the system’s functionality, experiments were conducted for various curvatures. Based on the results, the robot can guide the user along the defined track while providing grounded haptic information. Further investigation is required to verify the system’s effectiveness across a broad patient population. © ICROS 2025.FALSEscopuskc
Impact of wastewater treatment plants on pesticide contamination in the Yeongsan River basin and prioritization of pesticides in wastewater treatment plant effluents
No full textPesticides are widely distributed in the environment, posing significant risks to aquatic organisms, which necessitates effective management. This study aimed to identify priority pesticides originating from wastewater treatment plant (WWTP) effluents that pose risks to aquatic environments. Herein, a year-long monitoring of pesticides was conducted across six sites in the Yeongsan River basin and three WWTP effluents. Hierarchical cluster analysis was used to evaluate WWTP effluents as potential sources of pesticide contamination in the aquatic environments and to identify pesticides likely originated from effluents. Additionally, an optimized risk quotient (RQf)-based risk assessment was performed on WWTP effluents to evaluate the adverse effects of pesticides when discharged into surface water. Of the 87 target pesticides, 55 were detected in surface waters and 59 in WWTP effluents, with concentrations generally higher in WWTP effluents. Pesticides were categorized into six clusters based on their spatiotemporal occurrence patterns. Thus, this study concluded that pesticides potentially derived from WWTP effluents and posing a significant risk to aquatic environments, such as metribuzin, 3-phenoxybenzoic acid, atrazine, and atrazine-2-hydroxy, should be prioritized for regulation in WWTP effluents. This study highlights the importance of prioritizing pesticides to provide effective pollution management strategies and improve water quality. © 2025 Elsevier B.V.FALSEsciescopu
Functional analysis of Gm11545 in lineage specification during preimplantation embryogenesis in mice
No full textAfter fertilization, embryos undergo continuous cleavage, leading to the first cell fate decision, known as the first lineage specification. This process is tightly regulated by various molecular mechanisms, including the Hippo signaling pathway. Despite extensive research, the exact regulatory mechanisms governing the first lineage specification remain unclear. In this study, I investigated the role of an unnamed gene, designated Gm11545, in early embryogenesis, particularly its involvement in the Hippo signaling pathway during the first cell lineage specification in mouse embryos. Knockdown (KD) of Gm11545 led to an increase in cytoplasmic F-actin meshwork in the outer blastomeres of the morula, which caused the cytoplasmic localization of angiomotin (AMOT) and a reduction in nuclear yes-associated protein (YAP) localization. Consequently, caudal type homeobox 2 (CDX2) expression, a critical transcription factor for trophectoderm differentiation, was downregulated, ultimately leading to failure in blastocyst formation. Additionally, in blastocysts developed from chimeric morulae of which each embryo contains both normal and KD blastomeres, Gm11545 KD blastomeres were predominantly localized in the inner cell mass (ICM) region, suggesting that Gm11545 plays a significant role in promoting trophectoderm (TE) specification. These findings highlight Gm11545 as a crucial regulator of asymmetric Hippo signaling between inner and outer blastomeres, influencing cell fate decisions during the first lineage specification in embryogenesis. Keywords Embryo, lineage specification, Gm11545, Hippo pathwayMasterABSTRACT ⅰ
CONTENTS ⅱ
LIST OF FIGURES ⅳ
1. INTRODUCTION 1
2. MATERIALS AND METHODS 3
2. 1. Mouse embryo collection and culture 3
2. 2. Mouse oocyte collection and In vitro maturation 3
2. 3. RNA extraction and RT-PCR 3
2. 4. Real-Time PCR 3
2. 5. Generation of dsRNA 4
2. 6. Generation of mRNA 4
2. 7. Microinjection 4
2. 8. Immunofluorescence staining (IF) 5
2. 9. Imaging and quantification 5
2. 10. Morula aggregation assay 5
2. 11. Statistical analysis 6
3. RESULTS 7
3. 1. Localization of Gm11545 during embryogenesis 7
3. 2. Confirmation of impaired blastocyst formation in Gm11545 KD embryos 7
3. 3. Expression of lineage marker genes in Gm11545 KD embryos 7
3. 4. Gm11545 KD decreases CDX2 expression in outer blastomeres. 8
3. 5. Gm11545 KD disrupts asymmetric Hippo signaling pathway. 9
3. 6. Gm11545 KD did not affect apical F-actin stability. 10
3. 7. Gm11545 KD promotes ICM lineage specification. 11
4. DISCUSSION AND CONCLUSION 31
5. REFERENCES 35
6. ABSTRACT IN KOREAN 39
7. ACKNOWLEDGEMENT 40
LIST OF FIGURES & TABLES
Table 1. List of primers used for qRT-PCR, RT-PCR. 12
Figure 1. Localization of mCherry tagged Gm11545 during embryogenesis 13
Figure 2. Knockdown analysis with microinjection of Gm11545 dsRNA during preimplantation
embryogenesis. 15
Figure 3. Knockdown analysis of Gm11545 with microinjection of Gm11545 dsRNA during oocyte
maturation. 17
Figure 4. Expression of ICM, TE marker, and YAP-TEAD4 target genes in morula stage of Gm 11545
KD embryos. 19
Figure 5. CDX2 and OCT4 expression in morula stage of Gm11545 KD embryos. 21
Figure 6. YAP, AMOT and F-actin expression in the morula stage of Gm11545 KD embryos 23
Figure 7. FRAP analysis of apical F-actin complex 25
Figure 8. Morula aggregation assay 27
Figure 9. Schematic diagram of main results 2
Surface Functionalization of PLGA Nanoparticles with Hyaluronic Acid of Different Molecular Weight for Targeted Drug Delivery to Acute Kidney Injury
No full textAcute kidney injury (AKI) is a severe renal condition characterized by an abrupt decline in kidney function. Poly(Lactide-co-Glycolide) (PLGA) is a well-known biocompatible polymer widely investigated for nanoparticle carrier systems; however, it faces challenges with non-specific distribution and AKI targeting. In this study, a targeted drug delivery system was developed by using functionalized PLGA nanoparticles with HA to enhance therapeutic delivery efficiency to injured kidneys overexpressing CD44. PLGA nanoparticles were synthesized using a double emulsion (W/O/W) method and subsequently functionalized with thiol groups via cysteamine conjugation. Maleimide-functionalized hyaluronic acid (HA-Mal) of varying molecular weights (200 kDa, 500 kDa, and 3 MDa) were synthesized and conjugated to the nanoparticles through a thiol-maleimide click reaction. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) confirmed spherical morphology and increased hydrodynamic size post-functionalization. Angiotensin 1-7, a therapeutic peptide with anti-inflammatory and renoprotective properties, was encapsulated within the nanoparticles, exhibiting sustained release profiles and high encapsulation efficiency. Cellular uptake studies validated the selectivity of HA-coated nanoparticles for CD44-overexpressing cells. These findings demonstrate the potential of HA-functionalized PLGA nanoparticles as a kidney-specific drug delivery platform, providing a promising approach to enhancing AKI treatment with minimized side effects.MasterAbstract i
Contents ii
List of Tables iv
List of Figures iv
Chapter 1. Introduction 1
1.1. Overview of acute kidney injury and therapeutic treatment 1
1.2. Polymeric nanoparticles in drug delivery and their limitations 1
1.3. Surface functionalization of PLGA nanoparticles for targeted delivery 2
1.4. CD44-Hyaluronic acid interactions 3
1.5. Experimental overview 4
Chapter 2. Materials and Methods 6
2.1. Materials 6
2.2. Methods 6
2.2.1. Synthesis of HA-Maleimide 6
2.2.2. Synthesis of PLGA nanoparticles 7
2.2.3. Introduction of thiol function on PLGA nanoparticles 7
2.2.4. HA-Maleimide coating on PLGA nanoparticles 7
2.2.5. Quantitative determination of thiol functions with Ellman's reagent 8
2.2.6. Characterization of HA-Maleimide 8
2.2.7. Physicochemical analysis of HA-PLGA-NPs 9
2.2.9. Drug loading and encapsulation efficiency 9
2.2.10. In vitro release of Ang 1-7 10
2.2.11. In vitro cytocompatibility test 10
2.2.12. Cellular uptake of NPs 11
Chapter 3. Results and Discussion 12
3.1. Synthesis and characterization of HA-Maleimide 12
3.2. Preparation and characterization of HA-PLGA NPs 14
3.3. Drug loading and encapsulation efficiency 19
3.4. In vitro Ang 1-7 release behaviors of NPs 20
3.5. In vitro cytocompatibility test 21
3.6. Cellular uptake of NPs 23
Chapter 4. Conclusion 26
References 2
Molecular Plasmonic Cavities
No full textGraphene-based photonic structures have emerged as fertile ground for the controlled manipulation of surface plasmon polaritons (SPPs), providing a two-dimensional platform with low optoelectronic losses. In principle, nanostructuring graphene can enable further confinement of nanolight-enhancing light-matter interactions in the form of SPP cavity modes. In this study, we engineer nanoscale plasmonic cavities composed of self-assembled C-60 arrays on graphene. Using scattering-type scanning near-field optical microscopy (s-SNOM) in conjunction with first-principles density functional theory (DFT) calculations, we show that C-60 assemblies behave as molecular plasmonic cavities, giving rise to precisely defined hole-doped regions within continuous samples of graphene. By tuning the deposition conditions of C-60, the lateral dimensions of molecular cavities can be tailored to the SPP wavelength. Finite-element simulations verify the existence of SPP cavity modes, revealing a real-space pattern characteristic of confined SPPs. Thus, our study provides a straightforward scheme for tailoring SPP mode volume by leveraging molecular self-assembly.FALSEsciescopu
Design of Resistive Dipoles Using Chip Resistors With Minimum Number of Resistance Values
No full textThis study proposes a systematic resistive dipole design method and a new discretization method to minimize the number of resistance values. Resistive dipoles are characterized by loading the antenna with a resistive profile to significantly reduce internal reflections. These resistive profiles are typically Wu-King profiles, which have the advantage of minimizing the distortion of the radiated signal. Conventional resistive dipole implementations can be categorized into two types: those that implement the continuous profile as it is, and those that discretize it into lumped resistance. However, when implementing a continuous profile, it is not easy to control the thickness of the resistive layer due to process difficulties, resulting in a resistance profile that is completely different from the intended design. On the other hand, discretization into chip resistors requires a wide range of resistor values, and high-frequency resonance issues can cause an upper limit to the operating frequency band. For these reasons, it is difficult to predict the usable frequency band in conventional resistive dipole designs, and most of them have relied on empirical methods.
In order to solve this problem, the relationship between the main design variables of a resistive dipole (antenna length, resistance per unit length at the drive point) and the lowest possible operating frequency was quantitatively analyzed and a relationship was derived. It also analyzed the phenomenon that a certain resonance frequency is formed depending on the chip resistance spacing when discretizing the resistance profile, and proposed a relationship between the chip resistance spacing and the upper limit of the resonance frequency.
The conventional discretization method is to divide the entire resistive dipole into equal lengths and then integrate each section to load the chip resistor with the corresponding resistance value one by one. In this case, there are many types of resistors required, and the calculated resistors may not have commercially available chip resistors. Therefore, a new discretization method is proposed that changes the discretization interval based on the resistor value. By integrating the newly obtained relationship between design variables and the discretization method, a systematic resistive dipole design process based on the operating frequency band was established. To verify the proposed method, resistive dipoles with 4-6 GHz and 4-8 GHz frequency bands were fabricated and measured by the conventional discretization method and the proposed discretization method, respectively. The results show that there is no difference between the resistive dipoles designed by the proposed discretization method and the conventional discretization method.|저항성 다이폴(resistive dipole)의 길이와 저항 프로파일을 체계적으로 결정하는 방법과 이를 이산 저항으로 구현할 때 사용되는 저항값의 종류를 최소화할 수 있는 새로운 이산화 방법(discretization method)을 제안하였다. 저항성 다이폴은 안테나에 저항 프로파일을 장하함으로써 내부 반사를 크게 줄이는 특징을 갖는다. 이러한 저항 프로파일은 주로 Wu-King 프로파일을 사용하며, 이로 인해 방사된 신호의 왜곡이 최소화되는 장점이 있다. 기존 저항성 다이폴 구현 방식은 연속 프로파일을 그대로 구현하는 방법과 이를 일정 구간별로 나누어 이산화하는 방법 두 가지로 나눌 수 있다. 그러나 연속 프로파일 구현 시에는 공정 상의 어려움으로 인해 저항층 두께 제어가 쉽지 않아, 의도한 설계와 전혀 다른 저항 프로파일이 형성될 수 있다. 반면, 이산화하여 칩저항으로 구현할 경우에는 다양한 저항값이 요구되며, 고주파 공진 문제로 인해 동작 주파수 대역의 상한이 형성되는 문제가 있다. 이러한 이유로 기존 저항성 다이폴 설계는 사용 가능 주파수 대역을 예측하기가 어렵고, 대부분 경험적 방법에 의존해왔다.
이러한 문제를 해결하기 위하여, 저항성 다이폴의 주요 설계 변수(안테나 길이, 급전점에서의 단위 길이당 저항)와 동작 가능한 최저 주파수 사이의 상관관계를 정량적으로 분석하고, 이를 바탕으로 관계식을 도출하였다. 또한 저항 프로파일을 이산화할 때, 칩저항 간격에 따라 특정 공진주파수가 형성되는 현상을 분석하고, 이를 통해 칩저항의 간격과 공진주파수 상한 사이의 관계식을 제안하였다.
기존 이산화 방법은 저항성 다이폴 전체를 동일한 길이로 분할한 뒤, 각 구간을 적분하여 해당하는 저항값을 갖는 칩저항을 하나씩 장하하는 방식이다. 이 경우 필요한 저항값의 종류가 많고, 계산된 저항값에 상용 칩저항값이 없는 경우가 발생할 수 있다. 이를 개선하기 위해 저항값을 기준으로 하여 이산화 간격을 달리하는 새로운 이산화 방법을 제안하였다.
새롭게 구한 설계 변수 간의 관계식 및 이산화 방법을 종합하여 동작 주파수 대역을 기반으로 체계적인 저항성 다이폴 설계 프로세스를 수립하였다. 이를 검증하기 위하여 4–6 GHz 및 4–8 GHz 주파수 대역을 가지는 저항성 다이폴을 기존 이산화 방법과 본 연구에서 제안한 이산화 방법으로 각각 제작하여 측정하였다. 새롭게 제안된 이산화 방법과 기존의 이산화 방식으로 설계한 저항성 다이폴의 차이가 없는 것을 확인하였다.MasterAbstract i
국 문 요 약 ⅲ
Contents v
List of Figures vii
List of Tables ix
Chapter I. Introduction 1
1. Research motivation 1
2. Thesis overview 5
Chapter II. Resistive dipole 6
1. Resistive profile 6
2. Characteristic of resistive dipole 8
3. Conventional implementations and limitations 11
Chapter III. Resistive dipole parameter study 20
1. Parameter study for frequency band 20
2. Resistive profile discretization 26
3. Systematic design procedure 35
Chapter IV. Verification of the design procedure 37
1. Design of resistive dipole based on proposed design procedure 37
2. Design of resistive dipole based on conventional discretization method 43
3. Fabrication 46
4. Measurements and results 50
Chapter V. Conclusion 54
Appendix A – Segmented resistive vee dipole 55
Appendix B – Reference plane shifting 61
References 66
Acknowledgements 69
Curriculum Vitae 7
Broadband miniaturized spectrometers with van der Waals junctions
No full textMiniaturized spectrometers are crucial for applications in on-chip and implantable devices, requiring high spectral resolution in limited spaces. Here, we present our van der Waals heterojunction-based spectrometers that achieve tunable spectral responses through band structure engineering, offering sub-nanometer wavelength resolution and a broad operational bandwidth of similar to 500 to 1600 nanometers
