The selective hydrogenation of aromatic and aliphatic nitriles into amines and imines is described. Using a ruthenium pincer complex, the selectivity towards amines or imines can be controlled by ...simple parameter changes. The reactions are conducted under very mild conditions between 50–100 °C at 0.4 MPa H2 pressure without any additives at low catalytic loadings of 0.5–1 mol %, which results in quantitative conversions and high selectivity.
Synthetic double punch: The selective hydrogenation of nitriles into amines and imines is described. The selectivity towards amines or imines can be controlled by using a ruthenium pincer complex. The reactions are conducted at low temperature and low pressure without any additives at low catalytic loadings of 0.5–1 mol %, which results in quantitative conversions and high selectivity.
In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation ...catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process.
MgSiO3 ceramics were synthesized and their microwave dielectric properties were investigated. The Mg2SiO4 phase was formed at temperatures lower than 1200°C, while the orthorhombic MgSiO3 phase ...started to form by the reaction of SiO2 and Mg2SiO4 in the specimen fired at 1200°C. The structure of the MgSiO3 ceramics was transformed from orthorhombic to monoclinic when the sintering temperature exceeded 1400°C. A dense microstructure was developed for the specimens sintered at above 1350°C. The excellent microwave dielectric properties of ɛr=6.7, Q×f=121 200 GHz, and τf=−17 ppm/°C were obtained from the MgSiO3 ceramics sintered at 1380°C for 13 h.
The ceramics, (0.65 + y)Pb(Zr0.47Ti0.53)–(0.35 − y)Pb(Ni1−xZnx)1/3Nb2/3O3 have a morphotropic phase boundary (MPB) of pseudo‐cubic and tetragonal structures. Their ε33T/ε0 value considerably ...decreased on the pseudo‐cubic side of the MPB composition, but the d33 and kp slowly decreased on both sides of the MPB. Therefore, the maximum transduction coefficient (d33 * g33) was obtained from the composition on the pseudo‐cubic side of the MPB, because g33 is given by d33/ε33T. This result could be applied to other systems containing an MPB of pseudo‐cubic and tetragonal structures. Furthermore, a d33 * g33 value of 20 056 × 10−15 m2/N, which is the highest value reported so far for polycrystalline ceramics, was obtained from the 0.68Pb(Zr0.47Ti0.53)O3–0.32Pb(Ni0.6Zn0.4)1/3Nb2/3O3 ceramic.
The catalytic activity of a series of Ru-PNP pincer ligand complexes was studied in the direct amination of alcohols with ammonia. It turned out that all complexes of PNP ligands bearing a secondary ...amine showed no activity in this hydrogen-shuttling reaction sequence, while all complexes of homologous ligands bearing a tertiary amine gave active catalysts. Further comparative studies on catalysts bearing an acridine-based PNP pincer ligand and a PNP ligand of the Xantphos family provided valuable mechanistic insight that led to the design of a highly active catalyst. It appears that in the group of ligands studied here only ligands that do not form stable Ru-amido complexes are active alcohol amination catalysts.
A method has been developed for demonstrating a flow nanogenerator by using a mixture of magnetic nanofluid (MNF) and bubbles in a fluid circulating system, and notable phenomena related to the power ...generation properties of the nanogenerator have been explored. MNF is widely used in various areas because of its interesting magnetic properties under an external magnetic field. The objective of the proposed technique is to obtain the induced electromotive force (EMF) based on Faraday's law due to the flow of MNF in a closed-circulating system. To maximize the induced EMF, magnetic nanoparticles (MNPs) should pass through the induction coil with a perpendicular magnetization direction in accordance with Faraday's law. To control the magnetization direction of the MNPs, a permanent magnet was employed to produce an external magnetic field that considers the Brownian and Néel motions. To obtain a continuously induced voltage, a circulation system was implemented ensuring the flow of the MNF in the closed cycle. Further, power generation properties were investigated considering electric, magnetic, and fluidic effects. To analyze this complicated physics, a multiphysics analysis was used to calculate the flow pattern of the MNF according to its magnetic properties, and the acquired results were compared with those obtained from the experiment. From these experiments, we investigated the generation properties of the nanogenerator considering the flowrate of the MNF as well as the presence or absence of bubbles within the MNF. Our experimental tests demonstrated that the continuous power generation mode was successfully achieved with a mixture of MNF and bubbles.
국내 대학에 ‘통계학과’가 최초로 개설된 해는 1962년이니 국내 대학에 통계학이 독자적인 학문 영역으로 자리 잡은지 어언 57년이 지났다. 김준보 선생은 국내 대학 최초 통계학과인 고려대 통계학과에 처음으로 부임한 전임 교원으로 이 땅 통계학 여명기에 통계학 교재 저술에 힘썼으며, 또한 1971년 한국통계학회 창설을 주도하고 초대 회장을 맡아 국내에 ...통계학이 독자적 학문영역으로 자리매김 할 수 있는 초석을 마련하셨다. 본고에서는 두 가지 논의를 중심으로 연구한다. 하나는 한국통계학회 태동과 김준보 선생, 다른 하나는 이 땅 통계학 여명기에 선생이 저술한 통계학 분야 두 권의 책을 개관한다. 『현대통계학 : 통계와 추계의 종합체계』(Kim, 1954), 『추측통계 : 표본조사와 실험계획법 입문』(Kim, 1956)이 그것이다.
The very first statistics department in Korean universities was founded in 1962, meaning it has been 57 years since Korean academia has regarded statistics as a wholly independent field of study. Dr. Junbo Kim was the first faculty member hired by Korea University’s statistics department. He made a seminal contribution to the development and publication of statistics textbooks in those early years, and in 1971, spearheaded the efforts to found the Korean Statistical Society, serving as its first president. Naturally, Dr. Kim’s significant contributions have laid the cornerstones for the advancement of statistics as an independent field of study in Korea. In this paper, I will explore two main subjects: one is the early history of the Korean Statistical Society with a special emphasis on Dr. Kim’s contributions, and the other is an analytical overview his publications. Specifically, I will focus on Modern Statistics: A Synthesis of Statistics and Estimates』(Kim, 1954), and『Inferential Statistics: An Introduction to Sample Survey and Experimental Design』(Kim, 1956).
Abstract
Wearable pressure sensors having versatile device structures have been extensively investigated to achieve high sensitivity under mechanical stimuli. Here, we introduce piezoelectric ...pressure sensors based on fabrics woven using polyvinylidene fluoride (PVDF) weft and polyethylene terephthalate (PET) warp yarns with different weave structures: 1/1 (plain), 2/2, and 3/3 weft rib patterns. The dependence of the pressure-sensing performance on the weave pattern is demonstrated with an actual large-scale fabric up to the ~2 m scale. An optimized pressure sensor with a 2/2 weft rib pattern produced a high sensitivity of 83 mV N
−1
, which was 245% higher than that of the 1/1 pattern. The detection performance of the optimal fabric was extensively evaluated with a variety of ambient input sources, such as pressing, bending, twisting, and crumpling, as well as various human motions. Further, a large all-fabric pressure sensor with arrayed touch pixel units demonstrated highly sensitive and stable sensing performance.
B2O3 (25.0 mol%) was added to Zn(2-x)SiO(4-x) ceramics (x between 0.0 and 0.5) to decrease the sintering temperature. Specimens with x between 0.0 and 0.3 sintered at 900 C were well sintered with ...high density due to the formation of a B2O3 or B2O3-SiO2 liquid phase. The Qxf value of the Zn2SiO4 ceramic was relatively low, 32000 GHz, most likely due to the presence of a ZnO second phase. A maximum Qxf value of 70,000 GHz was obtained for the specimens with x = 0.2-0.3, and their dielectric constant and temperature coefficient of resonant frequency values were approximately 6.0 and -21.9 ppm/C, respectively. Ag metal did not interact with the 25.0 mol% B2O3-added Zn1.8SiO3.8 ceramic, indicating that Zn(2-x)SiO(4-x) ceramics containing B2O3 are good candidate materials for low temperature co-fired ceramic (LTCC) devices.
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