• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.145-152
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• 2002

Four commercial alumina powders having different particle size of $0.5{\mu}m,\;2.8{\mu}m,\;12{\mu}m,\;and\;45{\mu}m$ were presintered at 1120$^{\circ}C$ for 2h and then lanthanum aluminosilicate glass was infiltrated at 1100$^{\circ}C$ for 2h in the interval of 0.1h to investigate the penetration kinetic of the glass into the alumina preforms. The infiltration distance is parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, increases with raising the alumina particle size. The strength of glass-alumina composites increases as the alumina particle size reaches to 2.8${\mu}m$ due to the increase in packing, however, decreases with further increasing the alumina particle size. The fracture toughness of the composites rises with increasing the alumina particle size due to the crack bowing and the interaction between crack and alumina particles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1367-1372
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• 2014

As the awareness of the environmental crisis has recently increased around the world, numerous studies in the transport industry have been conducted to solve this problem through lightweight car bodies. The hot-stamping process has been presented as solution to achieve a light weight. Hot-stamping is a method that is used to obtain ultra-high strength steel (1,500 MPa or greater) by simultaneously forming and cooling boron steel in a press die after heating it to a temperature of $900^{\circ}C$ or above. This study involved a, fundamental examination of laser parameters to investigate the laser weldability of boron steel. As a result, the following optimum parameters for the shielding gas were found: Q = 20 l/min, ${\alpha}=40^{\circ}$, d = 20mm, and l = 0 mm. The hardness of butt weldment increasesed sharply as a result of martensite formation at the fusion zone.

• Journal of the Daesoon Academy of Sciences
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• v.43
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• pp.67-102
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• 2022

The purpose of this study is to analyze the human rights found in the North Korean Constitution and their core problem by focusing on elements of human rights suggested by Daesoon Jinrihoe's doctrine of Haewon-sangsaeng (解冤相生 the Resolution of Grievances for Mutual Beneficence). Haewon-sangsaeng is seemingly the only natural law that could resolve human resentment lingering from the Mutual Contention of the Former World while leading humans work for the betterment of one another. Haewon-sangsaeng, as a natural law, includes the right to life, the right to autonomous decision-making, and duty to act according to human dignity (physical freedom, the freedom of conscience, freedom of religion, freedom of speech, freedom of press, etc.), the right to equal treatment in one's social environment, and the right to ensure the highest level of health through treatment. The North Korean Constitution does not have a character as an institutional device to guarantee natural human rights, the fundamental principle of the Constitution, and stipulates the right of revolutionary warriors to defend dictators and dictatorships. The right to life is specified so that an individual's life belongs to the life of the group according to their socio-political theory of life. Rights to freedom are stipulated to prioritize group interests over individual interests in accordance with the principle of collectivism. The right to equality and the right to health justify discrimination through class discrimination. The right to life provided to North Koreans is not guaranteed due to the death penalty system found within the North Korean Criminal Code and the Criminal Code Supplementary Provisions. The North Korean regime deprives North Koreans of their right to die with dignity through public executions. The North Korean regime places due process under the direction of the Korea Worker's Party, recognizes religion as superstition or opium, and the Korea Worker's Party acknowledge the freedoms of bodily autonomy, religion, media, or press. North Koreans are classified according to their status, and their rights to equality are not guaranteed because they are forced to live a pre-modern lifestyle according to the patriarchal order. In addition, health rights are not guaranteed due biased availability selection and accessibility in the medical field as well as the frequent shortages of free treatments.

• Korean Journal of Plant Tissue Culture
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• v.27 no.6
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• pp.423-428
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• 2000

In 1997 when cloned sheep Dolly and soon after Polly were born, it had become head-line news because in the former the nucleus that gave rise to the lamb came from cells of six-year-old adult sheep and in the latter case a foreign gene was inserted into the donor nucleus to make the cloned sheep produce human protein, factor IX, in e milk. In the last few years, once the realm of science fiction, cloned mammals especially in livestock have become almost commonplace. What the press accounts often fail to convey, however, is that behind every success lie hundreds of failures. Many of the nuclear-transferred egg cells fail to undergo normal cell divisions. Even when an embryo does successfully implant in the womb, pregnancy often ends in miscarriage. A significant fraction of the animals that are born die shortly after birth and some of those that survived have serious developmental abnormalities. Efficiency remains at less than one % out of some hundred attempts to clone an animal. These facts show that something is fundamentally wrong and enormous hurdles must be overcome before cloning becomes practical. Cloning researchers now tent to put aside their effort to create live animals in order to probe the fundamental questions on cell biology including stem cells, the questions of whether the hereditary material in the nucleus of each cell remains intact throughout development, and how transferred nucleus is reprogrammed exactly like the zygotic nucleus. Stem cells are defined as those cells which can divide to produce a daughter cell like themselves (self-renewal) as well as a daughter cell that will give rise to specific differentiated cells (cell-differentiation). Multicellular organisms are formed from a single totipotent stem cell commonly called fertilized egg or zygote. As this cell and its progeny undergo cell divisions the potency of the stem cells in each tissue and organ become gradually restricted in the order of totipotent, pluripotent, and multipotent. The differentiation potential of multipotent stem cells in each tissue has been thought to be limited to cell lineages present in the organ from which they were derived. Recent studies, however, revealed that multipotent stem cells derived from adult tissues have much wider differentiation potential than was previously thought. These cells can differentiate into developmentally unrelated cell types, such as nerve stem cell into blood cells or muscle stem cell into brain cells. Neural stem cells isolated from the adult forebrain were recently shown to be capable of repopulating the hematopoietic system and produce blood cells in irradiated condition. In plants although the term$\boxDr$ stem cell$\boxUl$is not used, some cells in the second layer of tunica at the apical meristem of shoot, some nucellar cells surrounding the embryo sac, and initial cells of adventive buds are considered to be equivalent to the totipotent stem cells of mammals. The telomere ends of linear eukaryotic chromosomes cannot be replicated because the RNA primer at the end of a completed lagging strand cannot be replaced with DNA, causing 5' end gap. A chromosome would be shortened by the length of RNA primer with every cycle of DNA replication and cell division. Essential genes located near the ends of chromosomes would inevitably be deleted by end-shortening, thereby killing the descendants of the original cells. Telomeric DNA has an unusual sequence consisting of up to 1,000 or more tandem repeat of a simple sequence. For example, chromosome of mammal including human has the repeating telomeric sequence of TTAGGG and that of higher plant is TTTAGGG. This non-genic tandem repeat prevents the death of cell despite the continued shortening of chromosome length. In contrast with the somatic cells germ line cells have the mechanism to fill-up the 5' end gap of telomere, thus maintaining the original length of chromosome. Cem line cells exhibit active enzyme telomerase which functions to maintain the stable length of telomere. Some of the cloned animals are reported prematurely getting old. It has to be ascertained whether the multipotent stem cells in the tissues of adult mammals have the original telomeres or shortened telomeres.