• The Korean Journal of Quaternary Research
• /
• v.17 no.2
• /
• pp.25-32
• /
• 2003

Mongolia, a land-locked country in Central Asia, is located in the region of the highest degree of seasonal contrast on Earth. This paper presents sedimentologic and geomorphic data used to infer Holocene climate change in North-Central Mongolia. Correlation of data show that the climate was cold and dry before 10500 years BP. The post glacial warming occurred from 10500 to 8700 yr BP. The climate was characterized by becoming warmer and dry from 7300 to 6090 radiocarbon years. Between 6100 and 5500 years ago, conditions were hyper arid. Increased effective moisture balance but still arid conditions prevailed between 5500 and 3900 years ago. Since 3900 years ago, generally more humid conditions prevailed and originated varved sediment accumulation. Between about 2300 to 1300 years ago, greater than present day effective moisture balance. Since 1200 years ago climate was cooler and since 600 years ago becoming warmer.

• The Korean Journal of Quaternary Research
• /
• v.16 no.1
• /
• pp.29-36
• /
• 2002

May rainfall (317 years: A.D. 1682~A.D. 1998) of western region of Sorak Mt. was reconstructed using a tree-ring chronology of Pinus densiflora 5. et 2. The reconstruction indicated that the 1690~1710년, 1745~1755 and 1847~1853 periods were the least May rainfalls, whereas 1715~1733 and 1835~1845 the greatest ones. The wet period of 1835~1845 was agreed with that found in Songni Mt., central Korea. This wet epoch seems to be widely spreaded in Korea. There were found no significant differences among the means of the 18th, 19th and 20th century's May rainfalls. The major periodicity of May rainfalls was 2~4 years.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.3
• /
• pp.201-210
• /
• 2002

This paper describes a 3.3 (V) low power 4 digit CMOS quaternary to analog converter (QAC) designed with a neuron MOS($\upsilon$MOS) down literal circuit block and cascode current mirror source block. The neuron MOS down literal architecture allows the designed QAC to accept not only 4 level voltage inputs, but also a high speed sampling rate quaternary voltage source LSB. Fast settling time and low power consumption of the QAC are achieved by utilizing the proposed architecture. The simulation results of the designed 4 digit QAC show a sampling rate of 6(MHz) and a power dissipation of 24.5 (mW) with a single power supply of 3.3 (V) for a CMOS 0.35${\mu}{\textrm}{m}$ n-well technology.

• The Korean Journal of Quaternary Research
• /
• v.17 no.1
• /
• pp.1-6
• /
• 2003

One hundred fifty six pieces of woods were excavated at the muddy sand layer (post-glacial age: about 8,800 bp) above the upper peat layer from Sarori, Chungwongun, Korea in the central Korea. Due to the deteriorated structure of peat woods, all samples were embedded in PEG(polyethylene glycol) 2000 and then sectioned using a rotary microtome. Only two species were found; Alnus spp.(95%) and Ulmus spp.(5%). No conifers were found. Species composition indicates that the climate condition of central Korean peninsula around 8,800 bp was little wetter condition. The sampled region at the Sarori appeared to be a swamp or riverside.

• Nuclear Engineering and Technology
• /
• v.54 no.7
• /
• pp.2579-2585
• /
• 2022

Ceramics of quaternary garnets (Gd,Y)₃Al₂Ga₃O₁₂ doped with Ce, Tb have been fabricated and evaluated as prospective materials for indirect energy converters of α-and β-voltaic. Samples were characterized at excitation with an X-ray source and an intense 150 keV electron beam and showed good temperature stability of their emission and tolerance to irradiation. The role of X-rays accompanied the α-particle emitting in the increase of the conversion efficiency is clarified. The garnet-type structure of the matrix in the developed materials allows the production of quality crystalline mass with a light yield exceeding that of the commonly used YAG: Ce scintillator by a factor of two times.

• Macromolecular Research
• /
• v.17 no.4
• /
• pp.245-249
• /
• 2009

A fluorescing, copolymer(Q)-bearing, quaternary ammonium pendant was mixed with excess natural salmon sperm DNA with a molecular weight of $1.3{\times}10^6$(2,000 base pairs) to afford highly fluorescing, complex mixtures. The fluorescence life-time of the polymer Q was greatly increased when mixed with DNA: for the mixture of Q:DNA=1:750 the fast and slow decay lifetimes increased from ca. 10 to 100 ps and from 20 ps to ca. 1 ns, respectively. The enhanced fluorescence of the mixtures was ascribed to efficient compartmentalization and reduced conformational relaxation of the polymer Q by complexation with excess DNA.

• The Korean Journal of Quaternary Research
• /
• v.21 no.1
• /
• pp.15-26
• /
• 2007

A wide tree-ring data network from Western Himalayan region as well as from Central and Peninsular India have been established by the Indian Institute of Tropical Meteorology (IITM), Pune, India. This includes several ring width and density chronologies of Himalayan conifers (Pinus, Picea, Cedrus, Abies)covering entire area of Western Himalaya and teak (Tectona grandis L.F.) from central and peninsular India. Many of these chronologies go back to $15^{th}$ century. Tree-ring based reconstructed pre-monsoon (March-April-May) summer climate of Western Himalaya do not show any significant increasing or decreasing trend since past several centuries. High altitude tree-ring chronologies near tree line-glacier boundary are sensitive to the winter temperature. Unprecedented higher growth in recent decades is closely associated with the warming trend over the Himalayan region. Dendroclimatic analysis of teak (Tectona grandis) from Central and Peninsular India show significant relationship with pre-monsoon and monsoon climate. Moisture index over the region indicates strong association with tree-ring variations rather than the direct influence of rainfall. It is evident that, two to three consecutive good monsoon years are capable of maintaining normal or above normal tree growth, even though the following year is low precipitation year.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2299-2302
• /
• 2007

A series of quaternary ammonium-based ionic liquids (ILs) containing an alkyl carbonate group on the cation was first prepared and their physical and electrochemical properties including density, viscosity, thermal stability, electrochemical stability, and ionic conductivity were reported. These ILs exhibited wide electrochemical windows of at least 5.0 V and relatively high conductivities. In contrast to dialkyl-substituted ionic liquids, the ILs with an alkyl carbonate group on the cation showed much smaller drop in conductivities when mixed with a lithium salt, due to the interaction of lithium ions with carbonate groups. Upon interaction with a Li salt, the carbonyl stretching frequency of the carbonate group shifted to a lower frequency whereas the peak associated with C-O single bond moved to a higher frequency.

• The Korean Journal of Quaternary Research
• /
• v.14 no.1
• /
• pp.1-5
• /
• 2000

During the last three years (1997∼2000), a research project of beach dynamic environmental process and dynamic nature of the Nobong Beach, East Sea of Korea has been carried out for a better understanding of beach cycle (winter and summer). In fact, however, this paper deals with a particular feature of beach dynamics, that is, overwash process of overwash water and its sediments. The overwash mark sediments (OMS) are analyzed to understand various textural characters.

• Journal of Electrochemical Science and Technology
• /
• v.5 no.4
• /
• pp.95-104
• /
• 2014

Electrochemical performance of Li-ion cells with $LiMn_2O_4$ cathodes and graphite anodes with carbonates electrolytes containing quaternary ammonium-based room temperature ionic liquids (ILs) is investigated. Eight different ILs based on tetraalkylammonium, pyrrolidinium or piperidinium cations paired with bis(trifluoromethylsulfonyl)imide or tris(pentafluoroethyl)trifluorophosphate anions are examined in combination with dimethyl carbonate as a main solvent and fluoroethylene carbonate as a solid electrolyte interface forming agent. It is shown that cycling properties of the cells are strongly affected by the content of ILs in the electrolyte mixtures and its increase corresponds to lower discharge capacity retention. Since viscosity and conductivity of ILs are of a great importance for the electrolytes formulation, some kind of combined parameter should be used for the assessment of IL applicability and calculated values of Walden products for neat ILs represent one of the possible options. Besides, positive effect of ILs on reduction of flammability and enhancement of thermal stability of electrolytes in contact with charged electrodes have been demonstrated by means of self-extinguishing time test and differential scanning calorimetry respectively.