Novel carbon nanotube counter electrodes for dye sensitized solar cells

Ramasamy, Easwaramoorthi Univ. of Science and Technology 2008 국내박사

Resonance Behavior of Magenetostrictive Sensor In Biological Agent Detection

Ramasamy, Madhumidha Auburn University ProQuest Dissertations & Theses 2010 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The growing threat of bio warfare agents and bioterrorism has led to the development of specific field tools that perform rapid analysis and identification of encountered suspect materials. One such technology, recently developed is a micro scale acoustic sensor that uses experimental modal analysis. Ferromagnetic materials with the property to change their physical dimensions in response to changing its magnetization can be built into such sensors and actuators. One such sensor is fashioned from Metglas 2826MB, a Magnetostrictive strip actuated in their longitudinal vibration mode when subjected to external magnetic field. Due to mass addition, these magnetostrictive strips are driven to resonance with a modulated magnetic field resulting in frequency shifts. In Vibration Mechanics the frequency shift for a certain amount of mass will have a tolerance limit based on their distribution and discrete position over the sensor platform. In addition, lateral positioning of same amount of mass does not influence the resonant frequency shift of the sensor. This work concentrates on developing a model correlating theoretical, experimental and numerical simulations to determine the mass of E. Coli O157:H7 cells attached to the sensor platform.

Parsimonious service replication for tolerating malicious attacks in asynchronous environments

Ramasamy, Harigovind Venkatraj University of Illinois at Urbana-Champaign 2006 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

We consider the subject of tolerance of the most severe kind of faults, namely Byzantine faults, through state machine replication in asynchronous environments such as the Internet. In Byzantine-fault-tolerant (BFT) state machine replication, state consistency among the replicas of a service is maintained by first agreeing on the order of requests to be processed (agreement or atomic broadcast phase) and then executing the requests in the agreed-upon order (execution phase). We propose a methodology for constructing asynchronous BFT replication protocols that leverage perceived normal conditions for parsimony and do not compromise correctness even when such perceptions are inaccurate. Parsimony is to be as frugal as possible for a given metric of interest. We apply this methodology to obtain parsimonious protocols that achieve efficiency in three metrics: (1) overall resource use of request execution, (2) message complexity of atomic broadcast, and (3) latency degree of atomic broadcast. We then present a suite of group management protocols that allow for the dynamic change of the composition of the replication group. Our parsimonious protocols are designed to withstand corruptions of at most one-third of the replicas and do not require the removal of suspected faulty replicas in order to provide liveness. Such a design allows for the enforcement of very selective and conservative policies regarding changes to the replication group membership. We describe the implementation of the protocols within a reusable software framework called the Component-Based Framework for Intrusion Tolerance, or CoBFIT. We also present the experimental evaluation of our protocols in the context of a representative application in both LAN and WAN (Planetlab) settings under both fault-free and controlled fault injection scenarios.

Novel Alloy Electrode Materials by Electrodeposition for Application in Lithium-ion Rechargeable Batteries

Ramasamy Gnanamuthu 경희대학교 2014 국내박사

In this Ph.D. work is describes my exploration and introducing a novel alloy thin film materials prepared by various electrodeposition techniques as negative electrodes for lithium-ion rechargeable batteries. These prepared alloy thin film materials are successfully investigated on structure, electrochemical energy storage ability and thermal properties for Li-ion rechargeable batteries. In chapter-I, the detailed information of batteries like its working principle, types, shapes and applications are described in the introduction part. Although, briefly described the D.C electrodeposition, pulse deposition and brush plating techniques that which is preparation method for all alloy thin film materials and their working principle, types of depositions and applications. In chapter-II, briefly describes that the review of literature survey of the anode and cathode materials. The review of trends in development of Li-ion batteries and since who’s firstly announced the commercialization of battery materials. Although, briefly reviewed the carbon based materials, nanomaterials and especially like alloys electrodes, thin film materials that which has developed and published in previously by other research groups. In chapter III, the discharge-charge capacity of ternary Zn-Co-Ni alloy film electrode is for the first time to investigate in lithium-ion batteries. In this study, the ternary Zn-Co-Ni alloy film electrode is prepared by electroplating method. The electrodes were examined using X-ray diffraction (XRD), FE-SEM with EDX, and impedance studies. The electrochemical results demonstrate that the Zn-Co-Ni alloy film electrode delivers an initial discharge capacity of 281 mAh g-1 and improves of 650 mAh g-1 at the end of 30th cycling with no capacity fading at 0.1C rate. The charge-discharge properties of a lithium insertion capacity of 650 mAh g-1 and a reversible charging capacity of 512 mAh g-1 in the 30th cycling and coulombic efficiency is about 80.0% and good cycleability behavior. The results suggest that the ternary Zn-Co-Ni alloy thin film electrode obtained via electroplating shows a good candidate anode material for lithium-ion batteries. In chapter IV, the thin film Sn-Co-Ni alloy electrodes were prepared by electroplating on copper foil as current collector. The structure of the electroplated porous thin film Sn-Co-Ni alloy electrode is investigated by XRD, FE-SEM, and EDAX. The electrochemical performance is analyzed by using a battery cycler at the current rate of 0.1C to cut-off potentials of 0.01 and 1.20 V vs. Li/Li+ and also cyclic voltammeter. Experimental results illustrate that the initial discharge capacity of the Sn-Co-Ni alloy anode is 717 mAh g-1. The discharge capacity has been in increasing order between 2nd and 10th cycling and then maintained the stable capacity. It is found that the charge and discharge capacity of thin film Sn-Co-Ni alloy electrode obtained an average reversibility behavior and the better cycle stability. In chapter V, a nanoscaled Sn-Cu alloy film material is intended to improve charge-discharge capacities with respect to the negative electrode in lithium ion batteries. Sn-Cu alloy film electrodes are prepared using sulfate electrolyte by a pulse current plating method. Pulse duty cycles of 10% at a frequency of 10 Hz with a peak current density 1 A dm-2 are employed. The electrochemical discharge-charge capacities of the lithium insertion process and the reversible charging process are 1058 mAh g-1 and 612 mAh g-1 in the initial cycling, respectively. Also, coulombic efficiency was 87.2% at the end of the 30th cycle. Thus, nanoscaled Sn-Cu alloy film electrodes are good candidates for anode material in lithium-ion rechargeable batteries. In chapter VI, the application of CoSn2 alloy films deposited by brush electrodeposition as negative electrode, for the first time, in lithium-ion batteries. In this study, we prepared CoSn2 alloy film electrodes by brush electrodeposition on copper foil as a current collector. This technique is very convenient, because of its simplicity and short time process. We characterized the dense structure of the brush-plated CoSn2 alloy film electrodes by XRD, FE-SEM with EDX, and AFM studies. The initial discharge capacity of the electrodes was 336 mAh g-1 which have increased to approximately 740 mAh g-1 at the 30th cycle. The charge capacity of 632 mAh g-1 at the 30th cycle corresponds to coulombic efficiency of 85.4%. Thus, brush-plated CoSn2 alloy film is a promising electrode material for application in new generation lithium-ion batteries. In chapter VII, a crystalline Sb-Cu alloy material is investigated for use in Li-ion rechargeable batteries, and its structural, electrochemical and thermal properties are characterized. A pulse electrodeposition method is used to prepare Sb-Cu alloy film on Cu foil as negative electrode. The structure of the alloy film electrode is characterized by XRD, FE-SEM and EDX. The Electrochemical behavior of the Sb-Cu alloy film is investigated at the current rate of 0.1C to the cut-off potential range of 1.8 and 0.01 V vs. Li/Li+. Our experimental results demonstrate that the initial discharge capacity is 850 mAh g-1 and that the discharge capacity increases to 1034 mAh g-1 at the end of 30th cycle with a stable cycle life. The coulombic efficiency is approximately 83.5% with good cycleability behavior. Moreover, the crystalline Sb-Cu alloy film has relatively low exothermic properties, and it may be an interesting candidate for use in the negative electrode of Li-ion batteries.

Efficient storage and query processing of set-valued attributes

Ramasamy, Karthikeyan The University of Wisconsin - Madison 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In order to better support complex applications, object relational systems provide features that are absent in relational systems. The main features a new type by providing collections of existing types. It is well known that sets are useful in modeling a great deal of real world data. However, such powerful modeling comes at a price; without an efficient implementation, using sets can yield a performance much worse than that obtained using only traditional relational constructs. This dissertation explores novel ways of implementing set-valued attributes in an object relational system. Specifically, it considers various options for storing set-valued attributes, and ways of computing the challenging set containment join operation. We first address the problem of storing set-valued attributes. Using the orthogonal attributes of nesting and location we identify four options for representing sets: nested internal and external, and unnested external and internal. These representations can be combined with the creation of various indices to create various classes of indexed representations. We evaluate each of these representations with respect to conjunctive and disjunctive queries. Our results show that overall the nested implementations perform better than the unnested implementations because: (a) they exploit grouping semantics while fetching the members of a set instance and (b) they allow the evaluation of set predicates directly on the set instance. Next we consider the problem of efficiently evaluating set containment joins. For unnested external representation, the set containment join can be expressed directly in SQL. By contrast, the most obvious algorithm for computing set containment joins on nested representations is the signature nested loops algorithm, which computes set signatures and compares each signature in a relation with all the signatures in the other relation. To improve on the performance of this algorithm we propose a new partitioned set join algorithm (PSJ), which uses a multi-level scheme of partitioning by replicating the inner relation. Our performance study shows that for extremely small relation and small set cardinalities, the SQL query approach and signature nested loops perform comparably to PSJ. However, as the size of the data sets increase (in both relation and set cardinality), PSJ clearly dominates.

Comparison of Translucency and Light-curing Attenuation of Various Monolithic CAD/CAM Ceramics

Ramasamy Selvaponpriya Graduate School of Clinical Dentistry, Korea Unive 2021 국내석사

서론 모놀리식CAD / CAM 세라믹은다층수복물보다매우유리하며축성재료의파절에저항할수있습니다. 반투명도는재료의두께, 조성및색상에영향을받으며심미성과접착성합착에중요한역할을합니다. 이러한 물질이 청색광 감쇠를 극복하게 되면 온도가 상승합니다. 본 연구의 목적은 서로 다른 두께, 조성, 색상을 가지는 모놀리식 CAD / CAM 세라믹들의 청색광과 가시광선에 대한 반투명도와 중합 후의 온도 상승에 대해 비교하는 것입니다. 재료 및 방법 세가지색상(1, A2, A3)의 세가지 모놀리식 세라믹 (리튬디실리케이트, 폴리머 침투 세라믹 네트워크, 지르코니아)을 사용하여 각각 0.5mm, 1.0mm, 2.0mm의 두께를 가지며 길이 10mm, 너비 10mm의직육면체 모양의 표본을 준비했으며 표본은 테플론 블록과 결합되었습니다. 반투명도는 분광 광도계(UV-2600; Shimadzu, Japan)로 측정하였으며 감쇠 효과, 온도 상승은 각각 복사계와 디지털 온도계로 측정했습니다. 결론: 반투명도와 감쇠 효과 사이에는 강한 양의 상관 관계가 있었고 감쇠 효과와 온도 상승사이에는 약한 양의 상관관계가 있었습니다. 세라믹의 두께와 종류에 따라 가시 광선 및 청색광 투과율에 유의한 차이를 보였으며 색상은 유의한 차이를 나타내지 않았습니다. 이러한 매개 변수들의 영향은 온도 상승에 큰영향을 미치지 않았습니다. Introduction: Monolithic CAD/CAM ceramics are highly advantageous than multilayered restorations and overcomes the chipping of veneering materials. The translucency plays an important role for both aesthetics and adhesive luting, which is affected by thickness, composition and shade of these materials. On overcoming the blue light attenuation under these materials, results in temperature rise. The aim of this study was to compare and correlate the effect of thickness, composition and shade of different monolithic CAD/CAM ceramics on translucency for visible and blue light and temperature rise after light curing. Methodology: Three kinds of monolithic ceramics (lithium disilicate, polymer-infiltrated ceramic network, and zirconia) with three shades (A1, A2, and A3), were used to prepare cuboid shape of 10 mm in length and 10 mm in width in three different thickness including 0.5 mm, 1.0 mm, and 2.0 mm. Specimens were combined with the teflon block. Translucency was measured with a spectrophotometer (UV-2600; Shimadzu, Japan) and attenuating effect, the temperature rise were measured with a radiometer and a digital thermometer respectively. Conclusion: There was a strong positive correlation between translucency and attenuating effect and a weak positive correlation between attenuating effect and temperature rise. The effect of thickness and type of ceramics on visible and blue light transmission was significant and not the shade. The effect of these parameters was not significant on temperature rise.

FORMATION OF CuInSe2 (CIS), CuIn(1-x)GaxSe2 (CIGS), AND CIGS/CdS SEMICONDUCTOR STRUCTURES ON Mo/Mo OXIDES BY ELECTROCHEMICAL ATOMIC LAYER DEPOSITION (E-ALD)

RAMASAMY MUKUNTHAN 고려대학교 대학원 2020 국내박사

This dissertation presents the formation of thin layers of CuInSe2 (CIS), CuIn(1-x)GaxSe2 (CIGS) and CIGS/CdS semiconductor structures on the surface of Mo/Mo oxides by electrochemical atomic layer deposition (E-ALD). The simplified and electrochemical version of ALD is the E-ALD, in here the surface-limited reactions (SLRs) are referred as underpotential deposition (UPD), a well-known phenomenon where the deposition of one element takes place less than or positive of the bulk deposition (Nernst potential) of the element itself, hence, it forms deposit with atomic control. The main focus of the research is the formation of CIGS-based thin-film solar cell semiconductor compounds by investigating and optimizing the deposition conditions with the atomic scale control over the growth. The depositions were carried out as binary compounds of Cu2Se, GaSe and InSe lead the development of CIS and CIGS compounds. The growth conditions including deposition potentials, deposition time and sequencing order of binary compounds have been optimized and specific synthesis routes have been achieved. The best stoichiometry of Cu1.01In1.00Se2.04 was achieved from the 3InSe/2Cu2Se sequencing order with the growth condition of Se: –0.27 V (10 s); In: –0.73 V (15 s); and Cu: –0.10 V (15 s). The crystallographic and morphological characteristics revealed in favor of CuInSe2 hexagonal crystal structure. The optimum condition for CIGS structure has been achieved with the sequencing order of 2InSe/2GaSe/1CuSe with the deposition conditions of Cu: –0.10 V (25 s), In: –0.70 V (15 s), Ga: –0.75 V (15 s), and Se: –0.27 V (10 s) with a good stoichiometry of Cu1.0In0.69Ga0.31Se2.04. The crystallographic phases of microstructure formations, morphological and compositional analysis are in agreement with a good quality film produced with p-type photoelectrochemical (PEC) activity. The structural, morphological and compositional characteristics of CIGS/Mo and CdS/CIGS/Mo substrate has been compared and analyzed, that showed the CdS ratio as 1:1 irrespective of different period synthesized CIGS film. This ambient, highly efficient, low-cost synthesis method might be properly utilized and further optimized for the synthesis of high-quality thin films. Further making of Zn(O, S) layers and fabrication of a complete thin-film photovoltaic cell exclusively by this technique could be promising and effective. 이 논문은 전기 화학 원자 층 축적 (E-ALD)에 의해 Mo/Mo 산화물의 표면 상에 CuInSe2 (CIS), CuIn(1-x)GaxSe2 (CIGS) 및 CIGS/CdS 반도체 구조의 얇은 층의 형성을 나타낸다. ALD의 전기 화학적 버전은 E-ALD이며, 여기에서 표면 제한 반응 (SLRs)은 언더 포텐셜 축적 (UPD)이라고하며, 한 원소의 축적이 원소 자체의 벌크 축적 (Nernst potential)은 원자 제어로 축적을 형성합니다. 연구의 주요 초점은 성장에 대한 원자 규모 제어로 축적 조건을 조사하고 최적화함으로써 CIGS 기반 박막 태양 전지 반도체 화합물을 연구하고 형성하는 것입니다. Cu2Se, GaSe 및 InSe의 이원 화합물이 CIS 및 CIGS 화합물의 개발을 주도함에 따라 축적이 수행되었다. 이성분 화합물의 침착 전위, 침착 시간 및 시퀀싱 순서를 포함하는 성장 조건이 최적화되었고 특정 합성 경로가 달성되었다. Cu1.01In1.00Se2.04의 최상의 화학량론은 Se: –0.27 V (10 초), In: –0.73 V (15초), Cu: –0.10 V (15초) 의 성장 조건과 함께 3InSe/2Cu2Se 시퀀싱 순서에서 달성되었다. CuInSe2 육각형 결정 구조에 유리한 결정 학적 및 형태학적 특성이 밝혀졌다. CIGS 구조에 대한 최적의 조건은 Cu : –0.10 V (25 초), In : –0.70 V (15 초), Ga : –0.75 V (15 초) -0.27 V (10초) 의 시퀀싱 순서 2InSe/2GaSe/1CuSe로Cu1.0In0.69Ga0.31Se2.04 의 우수한 화학량론이 달성되었습니다. 미세 구조 형성의 결정학적 단계, 형태학적 및 조성 분석은 p 형 광전기 화학 (PEC) 활성으로 생성된 우수한 품질의 필름과 일치한다. CIGS/Mo 및 CdS/CIGS/Mo 기질의 구조적, 형태적 및 조성적 특성을 비교 분석한 결과, 상이한 기간의 합성된 CIGS 필름에 관계없이 CdS 비율이 1 : 1로 나타났다. 이러한 고효율 저비용 합성법은 고품질 박막의 합성에 적합하게 활용되고 더욱 최적화 될 수 있습니다. 이 기술에 의해 독점적으로 Zn(O, S) 층의 제조 및 완전한 박막 광전지의 제조는 유망하고 효과적 일 수 있다.

Exploring the Biodiversity of Arbuscular Mycorrhizal Fungi and Associated Endobacteria to Improve Maize Growth under Salt Stress Condition

RAMASAMY KRISHNAMOORTHY 충북대학교 2015 국내박사

Arbuscular Mycorrhizal Fungi (AMF) play major roles in ecosystem functioning such as carbon sequestration, nutrient cycling and plant growth promotion. AMF has obligatory symbiotic association with more than 80% of the land plants. In addition, AMF act as a specialized niche for bacteria and establishing a tripartite interaction between plant, fungi and bacteria. It is important to know how this ecologically important soil microbial player is affected by soil salinity. This study was aimed to understand the impact of soil salinity on AMF functional traits, community structure changes and assess the inoculation effect of native endosymbionts on salt stress alleviation. Soil samples were collected from salt affected coastal reclaimed land, samples were used to analyze AMF functional traits by measuring root colonization, glomalin related soil protein (GRSP) and spore count. Soil samples were subjected to three complementary methods such as spore morphology, terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Soil salinity significantly reduces AMF functional traits such as root colonization (P < 0.01), spore count (P < 0.01) and GRSP (P < 0.01). Spore morphology and T-RFLP data showed the predominance of Glomeraceae family in salt affected Saemangeum reclaimed land. T-RFLP and DGGE analysis revealed significant changes in diversity indices between non (ECse <2 dS/m) and extremely (ECse >16 dS/m) saline soil. However, ribotypes of Funneliformis mosseae and Rhizophagus proliferus were ubiquitous in all salt classes. Rhizophagus sp. spores isolated from the salt affected Saemangeum reclaimed soil was tested for their ability to colonize and produce spores in different monosporic mass culturing methods. Significantly higher root colonization and spore count was found in soil based monosporic mass culturing method followed by autotrophic and hairy root culture system. Spores mass cultured in soil based method was used for further studies. Rhizophagus sp. spores were surface decontaminated with chloramine T and antibiotic solution for endobacterial isolation and diversity analysis. Polymerase chain reaction (PCR) and confocal microscopy revealed the presences of rod and coccus shaped bacterial cell in the cytoplasm of AMF spores. DGGE results revealed low bacterial diversity in AMF spore cytoplasm. Endobacterial isolate obtained from Rhizophagus sp. spores cytoplasm was identified as Massilia sp. and tested for their carbon utilization, salt tolerance and plant growth promoting characters. Massilia sp. was found to tolerate upto 1% NaCl stress, produce IAA, EPS and solubilize insoluble P. Isolated endobacteria was found to utilize one of the major storage compound of AMF spores (Palmitic acid) as a carbon source. Tripartite interaction between Rhizophagus sp., Massilia sp. and Maize plant was tested in coastal reclaimed soil with two different levels of salt stress (0mM and 40mM NaCl). Salt stress substantially reduced plant growth, root colonization and spore producing ability of the mycorrhizal fungi. However, single inoculation of AMF alleviated the salt induced reduction of plant growth, dry matter accumulation, glomalin protein, root colonization, nutrient accumulation and reduced leaf proline content. AMF and endobacterial co-inoculation significantly improved root colonization irrespective of the salt concentration compared to single inoculation of AMF. However, co-inoculation of endobacteria and AMF did not show any significant impact on plant growth and nutrient accumulation compared to AMF single inoculation treatment. Overall, soil salinity significantly affects AMF functional traits and diversity. Glomeraceae family population was found to be significantly higher in coastal reclaimed soil irrespective of the salt concentration. Use of native Rhizophagus sp. (Glomeraceae family) significantly alleviate salt stress and improves plant growth under stress condition. This study propose to use native Glomeraceae family AMF species as a bio inoculant to improve plant growth in salt affected coastal lands. In addition, the inoculation effect may be enhanced by the dual effect from AMF and endobacteria, if the AMF species harbors endobacteria in their cytoplasm.

SYNTHESIS OF HOLLOW MESOPOROUS RUTHENIUM NANOPARTICLE: EVALUATION OF PHYSICO-CHEMICAL PROPERTIES AND TOXICITY

Ramasamy, Sakthivel Gachon University Graduate School 2015 국내석사

A hybrid nanoparticle (NP) with mesoporous hollow structure has attracted a great interest for biomolecule delivery, due to the easy fabrication process, the multi-functionalization capability for navigating to a target and the high surface area for encapsulating more therapeutic moieties. In the present study, hybrid ruthenium (Ru) NPs were prepared with a dual template method by using colloidal amine functionalized silica particles and poloxamer 407. The results indicate that the size of the NPs can be controlled; a smooth, spherical, monodispersed, high negative surface charge potential, polycrystalline, and hollow interior architecture particle can be prepared. Also, the Brunauer–Emmett–Teller (BET) analysis provides a specific high surface area of 75m2g-1. The hybrid NPs system also exhibit fluorescent properties. Thus this system could be a great advantage for cell tracking. Then cell cytotoxicity was evaluated with two different based on with electric cell-substrate impedance sensing (ECIS) system. The biophysical data of the melanocyte and melanoma cell reveals higher than 100 μg ml-1 concentration shows cytotoxicity. This hybrid NPs system represents a promising alternative nanocarrier for an effective theranostic system such as therapy together imaging or photodynamic therapy.

Development of New Synthesis Methods for Inorganic Nanomaterials with Improved Performance in Dye-sensitized Solar Cells

Ramasamy, Parthiban 공주대학교 대학원 2015 국내박사