NITROGEN REMOVAL BY USING RICE STRAW

Kawanishi,Takuya,Hayashi,Yoshishige 嶺南大學校 環境問題硏究所 1994 環境硏究 Vol.14 No.1

To overcome the problems brought about by excess nitrogen in water environment, various efforts to enhance denitrification will be necessary, not only in wastewater treatment, but also in the use of natural self-purification processes. We intend to use solid organic matter of high C/N ratio as the carbon source for denitrification. The possible application of this will be enhancement of denitrification in wetland, in soil infiltration wastewater treatments, etc. In this study we use rice straw and investigated the relationship between the amount of rice straw and that of denitrification. Rice straw was packed into column, kept at 25℃, and potassium nitrate solution was supplied continuously at the rate of 25ml per day for 200 days. The amount of rice straw was 0.5, 1.0, 2.0 or 5.0g, concentration of supplied nitrate nitrogen was 0(distilled water), 20, 50 or 200mg per litter. The concentration of nitrate, nitrite, ammonium ion and dissolved organic carbon in the effluent was measured, and the amount of denitrification was calculated based on mass balance. After the continuous nitrate supply experiments, the remained rice straw was weighed and its carbon and nitrogen contents were measured. The mass ratio of denitrified nitrogen to the mass of initial rice straw was about 1.9%. About 68% of original rice straw carbon remained, 21% leached and 9% degraded.

Relationship between LED Energy Consumption and Plant Growth in Small Hydroponic Plant Cultivation System

Satoru YAMAGUCHI,Takuya MOTOSUGI,Ryo UCHIYAMA,Yoshihiko TAKAHASHI,Takeharu HAYASHI 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10

Global population growth and the ongoing climate crisis pose immense risk to the stable food supplies in the future. We have developed a small hydroponic plant cultivation system to ensure even in extreme circumstances. To build a sustainable system, we have utilized an LED lighting system together with conserved energy generated by sunlight. Such hydroponic plant cultivation systems have to operate at an affordable yet efficient principle. In this paper, we examine experimental results of the relationship between LED energy consumption and plant growth in a hydroponic plant cultivation system. LED light intensity directly correlates to electrical power consumed. Energy consumption is the result of electrical power consumed over a period of time. Three experiments with varying conditions utilizing constant electrical energy consumption were conducted. Case-1: Electric power is kept low and the lighting duration is long; Case-2: the electric power is set to medium and the lighting duration is medium; Case-3: the electric power is large and the lighting duration is short. As a result of evaluating the weight of grown lettuces, it was found that lettuce growth is excellent in Case-1. It means that the longer the LED irradiation duration, the better the plant growth even under the same energy consumption conditions.

Effect of boron doping on the electrical conductivity of metallicity-separated single walled carbon nanotubes

Fujisawa, Kazunori,Hayashi, Takuya,Endo, Morinobu,Terrones, Mauricio,Kim, Jin Hee,Kim, Yoong Ahm The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.26

<P>We explored the effect of substitutional boron doping on the electrical conductivity of a metallicity-separated single walled carbon nanotube (SWCNT) assembly. Boron atoms were introduced into semiconducting (S)- and metallic (M)-SWCNT assemblies using high temperature thermal diffusion and the concentration of the doped boron atoms was controlled by the thermal treatment temperature. Depending on the conduction mechanism of the SWCNT assembly, both positive and negative effects upon boron incorporation are observed. For the S-SWCNT sheet, the electrical resistivity decreased by about 1 order on introduction of a small amount of boron atoms, due to the localized state for hopping conduction. In contrast, we observed an increase in the electrical resistivity on boron doping for M-SWCNTs. The pristine and boron doped metallic SWCNTs exhibited a tendency of decreasing electrical resistivity in the presence of an external magnetic field perpendicular to the film, which indicated two-dimensional weak localization behavior. A detailed analysis of the resistivity and the magnetoresistance implied that an increase in the inelastic scattering event at the doped boron site reduced the phase coherence length, leading to an increase in the electrical resistivity.</P>

Development of an Advanced Wide-area Special Protection System

Nakajima, Akino,Morita, Makoto,Hayashi, Takuya,Takeyasu, Takatoshi,Kurose, Ken,Aramaki, Takuo,Kadokami, Atsushi 대한전기학회 2013 The Journal of International Council on Electrical Vol.3 No.4

As a countermeasure against the problem of frequency and dynamic stability caused by drops in a large capacity generator, a wide-area special protection system called the Block System Stabilizer (BSS) has been used for the last approx. 40 years by the Kansai Electric Power Company. The conventional BSS has been updated as the Bulk Power System Stabilizer. The new BSS has been developed based on the concept of improving fault detection functions, concomitant with changing the power system configuration from radial to loop, and thereby enhancing human operational functions.

Electronic transport properties of linear carbon chains encapsulated inside single-walled carbon nanotubes

Tomohiro Tojo,Cheon Soo Kang,Takuya Hayashi,Yoong Ahm Kim 한국탄소학회 2018 Carbon Letters Vol.28 No.-

Linear carbon chains (LCCs) encapsulated inside the hollow cores of carbon nanotubes (CNTs) have been experimentally synthesized and structurally characterized by Raman spectroscopy and transmission electron microscopy. However, in terms of electronic conductivity, their transportation mechanism has not been investigated theoretically or experimentally. In this study, the density of states and quantum conductance spectra were simulated through density functional theory combined with the non-equilibrium Green function method. The encapsulated LCCs inside (5,5), (6,4), and (9,0) single-walled carbon nanotubes (SWCNTs) exhibited a drastic change from metallic to semiconducting or from semiconducting to metallic due to the strong charge transfer between them. On the other hand, the electronic change in the conductance value of LCCs encapsulated inside the (7,4) SWCNT were in good agreement with the superposition of the individual SWCNTs and the isolated LCCs owing to the weak charge transfer.

Carbon Nanotubes: State-of-the-art Technology and Safety for Success

Morinobu Endo,Yoong-Ahm Kim,Takuya Hayashi 한국탄소학회 2009 Carbon Letters Vol.10 No.2

Carbon nanotubes, consisting of rolled graphene layer built from sp2 units, have attracted the imagination of scientists as ideal macromolecules and their unusual physical and chemical properties make them useful in the fabrication of nanocomposites, nano-electronic devices and sensors etc. In this account, the current status and prospect of carbon nanotubes is described with a special emphasis on the safety issue of carbon nanotubes. Even though many challenges to be solved remain, extensive and intensive efforts in both academy and industry will clear out those problems soon and finally enable carbon nanotubes to play a key innovative material of 21st century in numerous industrial processes.

Flexible Transparent Conducting Films Composed of Photochemically Oxidized Thin Multi-Walled Carbon Nanotubes

Ko, Yong-Il,Ha, Yu-Mi,Hayashi, Takuya,Kim, Yoong Ahm,Yang, Cheol-Min,Kim, Jaewoo,Endo, Morinobu,Jung, Yong Chae American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.11

<P>Flexible, transparent conductive films (TCFs) were fabricated by dip-coating polyethylene terephthalate (PET) films in suspensions of thin multi-walled carbon nanotubes (t-MWNTs). The surface density of t-MWNTs in the coatings applied to the PET films was controlled through the number of coatings. In this study, the number of interconnected bundles of t-MWNTs at intersection points and the coverage of MWNTs on the surface of the PET substrates were evaluated because the performance of t-MWNT-based TCFs is influenced by both the electrical conductance and optical transmittance. The microscopic properties of the films were in excellent agreement with the macroscopic properties that were determined by measuring the electrical conductance and optical transmittance of the films, especially for the TCFs with a small number of coatings. The most crucial factor that governs the characteristics of t-MWNT-based TCFs is the network structure of the t-MWNTs. The optimum structure should provide the largest number of intersection points with the smallest number of coatings.</P>

Covalent Attachment of Aromatic Diisocyanate to the Sidewalls of Single‐ and Double‐Walled Carbon Nanotubes

Jung, Yong Chae,Muramatsu, Hiroyuki,Hayashi, Takuya,Kim, Jin Hee,Kim, Yoong Ahm,Endo, Morinobu,Dresselhaus, Mildred S. WILEY‐VCH Verlag 2010 European journal of inorganic chemistry Vol.2010 No.27

<P><B>Abstract</B></P><P>We carried out covalent functionalization of single‐ and double‐walled carbon nanotubes (SWNTs and DWNTs) comparatively by using isocyanate chemistry. The introduction of aromatic diisocyanate on the sidewalls of the tubes was verified by the strong IR peak around 2272 cm<SUP>–1</SUP> arising from the NCO asymmetric stretching mode, by the intensified sp<SUP>3</SUP> peak at 285.2 eV in the C1s photoemission spectra, and by a typical TEM image of the amorphous‐like coating. The suppression of the optical properties in a covalently isocyanate‐functionalized SWNT is due to a breakdown of the van Hove singularities, whereas the strong optical activity in a covalently isocyanate‐functionalized DWNT originates from the geometrically shielded inner tubes. The chemically active isocyanate groups at the end of the phenyl diisocyanate that are covalently attached to the sidewalls of the DWNTs will allow us to utilize isocyanate chemistry in synthesizing functional organic–inorganic hybrid materials as well as high‐performance polymer composites.</P>

Annealing effects on mechanical properties and shape memory behaviors of silicone-coated elastomeric polycaprolactone nanofiber filaments

Ko, Yong-Il,Lee, Yujin,Devarayan, Kesavan,Kim, Byoung-Suhk,Hayashi, Takuya,Kim, Ick-Soo Elsevier 2014 Materials letters Vol.131 No.-

<P><B>Abstract</B></P> <P>The annealing effects on thermodynamic properties and shape memory behaviors of the polycaprolactone (PCL) nanofiber filaments coated with silicone elastomer (Sylgard 184) were studied. The PCL nanofiber filaments were prepared from fiber mats having different thickness at different twist numbers via a twisting process. The thermodynamic and mechanical properties were remarkably enhanced by twist number as well as annealing process. Moreover, the Sylgard-coating has played a significant role to maintain the shape of each PCL nanofibers even above the melting point and to improve the toughness of the PCL nanofiber filaments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We examine shape memory behaviors of Sylgard-coated PCL nanofiber filaments. </LI> <LI> Annealing improves thermodynamic properties of PCL nanofiber filaments. </LI> <LI> Sylgard-coating improves the toughness of the PCL nanofiber filaments. </LI> </UL> </P>

Hybridized double-walled carbon nanotubes and activated carbon as free-standing electrode for flexible supercapacitor applications

강천수,고영일,Fujisawa Kazunori,Yokokawa Taiki,김진희,한종훈,위재형,김융암,Muramatsu Hiroyuki,Hayashi Takuya 한국탄소학회 2020 Carbon Letters Vol.30 No.5

Free-standing hybridized electrode consisting of double-walled carbon nanotubes (DWNTs) and activated carbon have been fabricated for fexible supercapacitor applications. The xanthan-gum, used in our methodology, showed high ability in dispersing the strongly bundled DWNTs, and was then efectively converted to activated carbon with large surface area via chemical activation. The homogeneously dispersed DWNTs within xanthan-gum derived activated carbon acted as both electrical path and mechanical support of electrode material. The hybridized flm from highly dispersed DWNTs and activated carbon was mechanically strong, has high electrical conductivity, and exhibited high specifc capacitance of 141.5 F/g at the current density of 100 mV/s. Our hybridized flm is highly promising as electrode material for fexible supercapacitors in wearable device.