• Title/Summary/Keyword: Charge-Transfer

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Corrosion Inhibition of Carbon Steel in Sulfuric Acid Using Cymbopogon citratus as a Green Corrosion Inhibitor

  • Gadang, Priyotomo;Tamara Emylia Suci, Nurarista;Yanyan, Dwiyanti;Bening Nurul Hidayah, Kambuna;Arini, Nikitasari;Siska, Prifiharni;Sundjono, Sundjono
    • Corrosion Science and Technology
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    • v.21 no.6
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    • pp.423-433
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    • 2022
  • The objective of this study was to determine whether Cymbopogon citratus extract as a corrosion inhibitor from natural tropical resources could prevent corrosion of carbon steel in sulfuric acid solution. Inhibitory action of this extract was investigated using electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Those methods revealed corrosion rate, efficiency of inhibition, and adsorptions isotherm values when the extract was added to the sulfuric acid solution at concentration up to 500 ppm with various immersion time at ambient temperature. Results revealed that higher concentration of the extract and longer immersion time decreased the corrosion rate of carbon steel whereas the inhibition efficiency of the extract was increased up to 97.25%. The value of charge transfer resistance was increased significantly by adding the extract at concentration up to 500 ppm with an immersion time of 60 minutes. The type of the extract was a mixed inhibitor. It could inhibit the corrosion process in both anodic and cathodic sides electrochemically. Results of this study suggest that the mechanism of adsorption on the surface of carbon steel is related to Langmuir adsorption isotherm.

Facile Electrodeposition Technique for the Fabrication of MoP Cathode for Supercapacitor Application

  • Samanta, Prakas;Ghosh, Souvik;Murmu, Naresh Chandra;Lee, Joong Hee;Kuila, Tapas
    • Composites Research
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    • v.34 no.6
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    • pp.345-349
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    • 2021
  • The continued environmental pollution caused by fossil fuel consumption has prompted researchers around the world to develop environmentally friendly energy technologies. Electrochemical energy storage is the significant area of research in this development process, and the research significance of supercapacitors in this field is increasing. Herein, a simple electrodeposition synthetic route was explored to develop the MoP layered cathode material. The layered structure provided a highly ion-accessible surface for smooth and faster ion adsorption/desorption. After Fe was doped into MoP, the morphology of MoP changes and the electrochemical performance was significantly improved. Specific capacitance value of the binder-free FeMoP electrode was found to be 269 F g-1 at 2 A g-1 current density in 6 M aqueous KOH electrolyte. After adding Fe to MoP, an additional redox contribution was observed in the redox conversion from Fe3+ to Fe2+ redox pair, and the charge transfer kinetics of MoP was effectively improved. This research can provide guidance for the development of supercapacitor electrode materials through simple electrodeposition technology.

Effect of electropolishing process time on electrochemical characteristics in seawater for austenitic stainless steel (오스테나이트 스테인리스강의 해수에서 전기화학적 특성에 미치는 전해연마시간의 영향)

  • Hwang, Hyun-Kyu;Shin, Dong-Ho;Heo, Ho-Seong;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.55 no.4
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    • pp.236-246
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    • 2022
  • Electropolishing is a surface finishing treatment that compensates for the disadvantages of the mechanical polishing process. It not only has a smooth surface, but also improves corrosion resistance. Therefore, the purpose of this investigation is to examine the corrosion resistance and electrochemical characteristics in seawater of UNS S31603 with electropolishing process time. The roughness improvement rate after electropolishing was improved by about 78% compared to before polishing, indicating that the electropolishing is effective. As a result of potential measuring of mechanical polishing and electropolishing, the potential of electropolishing was nobler than the mechanical polishing condition. As a result of calculating the corrosion current density after potentiodynamic polarization experiment with electropolishing conditions, the corrosion current density of mechanical polishing was about 6.4 times higher than that of electropolishing. After potentiodynamic polarization experiment with electropolishing conditions, the maximum damage depth of mechanical polishing was about 2.2 times higher than that of electropolishing(7 minutes). In addition, the charge transfer resistance of the specimen electropolished for 7 minutes was the highest, indicating improved corrosion resistance.

Design of resource efficient network reprogramming protocol (자원 효율적인 네트워크 리프로그래밍 프로토콜 설계)

  • Choi, Rock-Hyun;Hong, Won-Kee
    • Journal of Korea Society of Industrial Information Systems
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    • v.15 no.3
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    • pp.67-75
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    • 2010
  • Network reprogramming is a technology that allows several sensor nodes deployed in sensor field to be repaired remotely. Unlike general communication in sensor network where small amount of data is transferred, network reprogramming requires reliable transfer of large amount of data. The existing network reprogramming techniques suffers high cost and large energy consumption to recover data loss in node communication. In this paper, a cluster based network reporgramming scheme is proposed for sensor network. It divides sensor field into several clusters and chooses a cluster header in charge of data relay to minimize duplicated transmission and unnecessary competition. It increases reliability by effective error recovery through status table.

MICROSTRUCTURAL STUDY OF $Fe_{1-x}Ti_x$ ALLOYS FORMED BY ION BEAM MIXING

  • Jeon, Y.;Lee, Y.S.;Choi, B.S.;Woo, J.J.;Whang, C.N.
    • Journal of the Korean Vacuum Society
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    • v.6 no.S1
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    • pp.127-132
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    • 1997
  • Microstructure of the Fe-Ti system by ion beam mixing of multilayers at 300 K and 77 K has been studied in a wide composition range. The ion bombardment was carried out using $Ar^+$ ions at 80 keV. Using grazing angle x-ray diffraction we find that the lattice parameters of these bcc solid solutions are very close to that of $\alpha$-Fe. Extended x-ray absorption fine-structure spectroscopy have been performed to investgate the short-range order in the ion-beam-mixed state. The structure parameters, such as the interatomic distance and the coordination number are estmated from the Fe K-edge Fourier filtered EXAFS spectra. The interatomic distance is independent of the alloy concentration and it is almost constant. The study of x-ray absorption near-edge structure gives information on the individual $\rho$components of the partial densityof states of the conduction band of the Fe and Ti We also find that a charge transfer from Ti to Fe atoms takes place.

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SPIN POLARIZED PHOTOEMISSION AND MAGNETIC CIRCULAY DICHROISM STUDY OF FeAl THIN FILMS

  • Kim, K.W.;Kudryavtsev, Y.V.;Chang, G.S.;Whang, C.N.;Lee, Y.P.
    • Journal of the Korean Vacuum Society
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    • v.6 no.S1
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    • pp.53-58
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    • 1997
  • It is well known that the equiatomic FeAl alloy crystallizes in a paramagnetic CsCl structure and is very stable in a wide temperature range owing to a significant charge transfer from Al to Fe. A presence of structural defects normally enhances the magnetic and magneto-optical properties of this alloy. In this study spin-resolved photoemission and magnetic circular dichroism (MCD) were carried out on both ordered and disordered $Fe_{0.52}Al_{0.48}$ alloy films. The disordered state in the alloy films was obtained by a vapor quenching deposition on cooled substrates. It is shown that the order-disorder transition in the Fe0.52Al0.48 alloy films leads to a significant change in the spin polarization. Form the MCD results the orbital and spin magnetic moments of the constituent atoms are obtained. According to the sum rule the spin and orbital magnetic moments of Fe in the disordered FeAl film are $\mu\frac{SR}{spin}=0.8\mu_B$ and $\mu\frac{SR}{orb}=0.14\mu_B$ respectively. The spin magnetic moment is also evaluated to be $\mu\frac{BR}{spin}=0.77\mu_B$ by the branching ration method employing a photon polarization of 90%.

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A Numerical Analysis Study on Charging Conditions of Type IV High Aspect Ratio Modular Hydrogen Storage Vessel (Type IV 고세장비 모듈형 수소저장용기의 충전 조건에서의 수치해석적 연구)

  • JOONGTAK BACK;JIHUN MUN;JIHOON MIN;KYUNBUM PARK;KWANGTAIK KI;SUNGWOOK JOO
    • Transactions of the Korean hydrogen and new energy society
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    • v.34 no.1
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    • pp.26-31
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    • 2023
  • In this study, in order to propose a modular method for type IV high aspect ratio modular hydrogen storage vessel, a numerical analysis was conducted on the heat transfer behavior in series and parallel connection methods, and the differences according to each connection method were reviewed. Computational fluid dynamics software was used to check the internal temperature and pressure values of the hydrogen storage container under charging conditions. In terms of thermal safety when charging hydrogen gas, it was confirmed that the parallel modularization method was superior.

Fault Diagnosis Method of Complex System by Hierarchical Structure Approach (계층구조 접근에 의한 복합시스템 고장진단 기법)

  • Bae, Yong-Hwan;Lee, Seok-Hee
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.11
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    • pp.135-146
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    • 1997
  • This paper describes fault diagnosis method in complex system with hierachical structure similar to human body structure. Complex system is divided into unit, item and component. For diagnosing this hierarchical complex system, it is necessary to implement special neural network. Fault diagnosis system can forecast faults in a system and decide from current machine state signal information. Comparing with other diagnosis system for single fault, the developed system deals with multiple fault diagnosis comprising Hierarchical Neural Network(HNN). HNN consists of four level neural network, first level for item fault symptom classification, second level for item fault diagnosis, third level for component symptom classification, forth level for component fault diagnosis. UNIX IPC(Inter Process Communication) is used for implementing HNN wiht multitasking and message transfer between processes in SUN workstation with X-Windows(Motif). We tested HNN at four units, seven items per unit, seven components per item in a complex system. Each one neural newtork operate as a separate process in HNN. The message queue take charge of information exdhange and cooperation between each neural network.

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Corrosion Behavior of Fe-Ni Bainitic Steel Through an Inverted Austempering Multi-Step Process for Weathering Steel Applications

  • Miftakhur Rohmah;Gusti Umindya Nur Tajalla;Gilang Ramadhan;Yunita Triana;Efendi Mabruri
    • Corrosion Science and Technology
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    • v.23 no.1
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    • pp.11-19
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    • 2024
  • A Fe-Ni Bainitic steel as a weathering steel application was developed by combining its excellent mechanical properties and corrosion resistance in maritime environments. Nickel concentration (0.4-3 wt%) and inverted austempering multi-step (IAM) process were primary determinants of the microstructure of the Fe-Ni Bainitic steel. The initial austempering steel was performed at 300 ℃ for 600 seconds to obtain a partly bainitic transformation. The steel was heated again for 1800 s at 450 ℃. The microstructure was comprised of ferrite, a blocky martensite/austenite island, and a homogeneous lath-shape bainite structure with widths ranging from 4.67 to 6.89 ㎛. The maximum strength, 1480 MPa, was obtained with 3 wt% nickel. In this study, corrosion behavior was investigated utilizing potentiodynamic and electrochemical impedance spectroscopy (EIS) tests. A higher nickel content in Fe-Ni Bainitic steel refined the grain size, improved the bainite fraction, lowered the corrosion rate to 0.0257 mmpy, and increased the charge transfer of film resistance to 1369 Ω.

Factors Affecting International Transfer Pricing of Multinational Enterprises in Korea (외국인투자기업의 국제이전가격 결정에 영향을 미치는 환경 및 기업요인)

  • Jun, Tae-Young;Byun, Yong-Hwan
    • Korean small business review
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    • v.31 no.2
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    • pp.85-102
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    • 2009
  • With the continued globalization of world markets, transfer pricing has become one of the dominant sources of controversy in international taxation. Transfer pricing is the process by which a multinational corporation calculates a price for goods and services that are transferred to affiliated entities. Consider a Korean electronic enterprise that buys supplies from its own subsidiary located in China. How much the Korean parent company pays its subsidiary will determine how much profit the Chinese unit reports in local taxes. If the parent company pays above normal market prices, it may appear to have a poor profit, even if the group as a whole shows a respectable profit margin. In this way, transfer prices impact the taxable income reported in each country in which the multinational enterprise operates. It's importance lies in that around 60% of international trade involves transactions between two related parts of multinationals, according to the OECD. Multinational enterprises (hereafter MEs) exert much effort into utilizing organizational advantages to make global investments. MEs wish to minimize their tax burden. So MEs spend a fortune on economists and accountants to justify transfer prices that suit their tax needs. On the contrary, local governments are not prepared to cope with MEs' powerful financial instruments. Tax authorities in each country wish to ensure that the tax base of any ME is divided fairly. Thus, both tax authorities and MEs have a vested interest in the way in which a transfer price is determined, and this is why MEs' international transfer prices are at the center of disputes concerned with taxation. Transfer pricing issues and practices are sometimes difficult to control for regulators because the tax administration does not have enough staffs with the knowledge and resources necessary to understand them. The authors examine transfer pricing practices to provide relevant resources useful in designing tax incentives and regulation schemes for policy makers. This study focuses on identifying the relevant business and environmental factors that could influence the international transfer pricing of MEs. In this perspective, we empirically investigate how the management perception of related variables influences their choice of international transfer pricing methods. We believe that this research is particularly useful in the design of tax policy. Because it can concentrate on a few selected factors in consideration of the limited budget of the tax administration with assistance of this research. Data is composed of questionnaire responses from foreign firms in Korea with investment balances exceeding one million dollars in the end of 2004. We mailed questionnaires to 861 managers in charge of the accounting departments of each company, resulting in 121 valid responses. Seventy six percent of the sample firms are classified as small and medium sized enterprises with assets below 100 billion Korean won. Reviewing transfer pricing methods, cost-based transfer pricing is most popular showing that 60 firms have adopted it. The market-based method is used by 31 firms, and 13 firms have reported the resale-pricing method. Regarding the nationalities of foreign investors, the Japanese and the Americans constitute most of the sample. Logistic regressions have been performed for statistical analysis. The dependent variable is binary in that whether the method of international transfer pricing is a market-based method or a cost-based method. This type of binary classification is founded on the belief that the market-based method is evaluated as the relatively objective way of pricing compared with the cost-based methods. Cost-based pricing is assumed to give mangers flexibility in transfer pricing decisions. Therefore, local regulatory agencies are thought to prefer market-based pricing over cost-based pricing. Independent variables are composed of eight factors such as corporate tax rate, tariffs, relations with local tax authorities, tax audit, equity ratios of local investors, volume of internal trade, sales volume, and product life cycle. The first four variables are included in the model because taxation lies in the center of transfer pricing disputes. So identifying the impact of these variables in Korean business environments is much needed. Equity ratio is included to represent the interest of local partners. Volume of internal trade was sometimes employed in previous research to check the pricing behavior of managers, so we have followed these footsteps in this paper. Product life cycle is used as a surrogate of competition in local markets. Control variables are firm size and nationality of foreign investors. Firm size is controlled using dummy variables in that whether or not the specific firm is small and medium sized. This is because some researchers report that big firms show different behaviors compared with small and medium sized firms in transfer pricing. The other control variable is also expressed in dummy variable showing if the entrepreneur is the American or not. That's because some prior studies conclude that the American management style is different in that they limit branch manger's freedom of decision. Reviewing the statistical results, we have found that managers prefer the cost-based method over the market-based method as the importance of corporate taxes and tariffs increase. This result means that managers need flexibility to lessen the tax burden when they feel taxes are important. They also prefer the cost-based method as the product life cycle matures, which means that they support subsidiaries in local market competition using cost-based transfer pricing. On the contrary, as the relationship with local tax authorities becomes more important, managers prefer the market-based method. That is because market-based pricing is a better way to maintain good relations with the tax officials. Other variables like tax audit, volume of internal transactions, sales volume, and local equity ratio have shown only insignificant influence. Additionally, we have replaced two tax variables(corporate taxes and tariffs) with the data showing top marginal tax rate and mean tariff rates of each country, and have performed another regression to find if we could get different results compared with the former one. As a consequence, we have found something different on the part of mean tariffs, that shows only an insignificant influence on the dependent variable. We guess that each company in the sample pays tariffs with a specific rate applied only for one's own company, which could be located far from mean tariff rates. Therefore we have concluded we need a more detailed data that shows the tariffs of each company if we want to check the role of this variable. Considering that the present paper has heavily relied on questionnaires, an effort to build a reliable data base is needed for enhancing the research reliability.