• Title/Summary/Keyword: Difference form

Search Result 2,402, Processing Time 0.031 seconds

Growth of the Korean Public Library from the Point View of Acculturation (문화변용이론의 시각에서 본 우리나라 공공도서관의 발전과정)

  • Chun Myung Sook
    • Journal of the Korean Society for Library and Information Science
    • /
    • v.10
    • /
    • pp.39-70
    • /
    • 1983
  • The concept of the public library defined by the Korean Library Association does not describe the current state of the Korean public library but describes the public libraries in the western society. Korean public library was formed after the western public library but it was modified and reconciled with the tradition of Korea. The difference between the concepts occured in the acculturation process of the Korean public library. According to the International Encyclopeadia of the Social Sciences, acculturation comprehends those phenomena which result when groups of individuals having different cultures come into continuous firsthand contact, with subsequent changes in the original cultural patterns of either of both groups. Korea opened its door to western world in 1876, and it began to contact with the western world. As the consequence, the concept of the public library of the West diffused to Lee Dynasty which were characterized by the confucianism and the extended family system. These two characteristics were against the public library concept and it could not function as it was and it had to be modified to fit to Korean society. The American public library was formed by the diffusion of English public library. The concept fitted in the colonial American society which was characterized by the Christianity and nuclear family system. Religion and family life were closely knitted together and they contributed much to the formation of the American public library. Also the society needed various information to form their new nation. The need of the public library grew and the public library repidly developed as the American society was urbanized and industrialized. The changes of Korean public library has passed the following process of acculturation. 1. The Korean culture contacted with Western world. 2. The public library concept diffused to Korea, but the people were illiterate and the need of the public library was for the preservation of the old books. The collection was not for people. 3. The function of the public library in Korea was altered slightly as several intellectuals who formed the first modern public library tried to literate Koreans as a means of liberation :from Japan through the library service. 4. The traditional libraries such as sodandg and hyangyo disorganized and finally disappeared as the traditional elements of the culture disappeared and the new cultural elements prevailed in Korea. 5. When the traditional elements of culture were disorganized, a reinterpretation of the diffused culture appeared. With the appearance of the vouth group which was not existed in the traditional society, cultural facilities for them were needed. They began to use public library as their reading rooms. This pattern has been institutionalized ever since in Korean public library. 6. When the new element of the culture spread, the traditional cultural elements react against this element. As the new public libraries sprung out, there were movements to restore the old Korean tradition of the family libraries and Hyangyo to counteract to the new libraries. This movements were not successful and they all disappeared as they could not keep up the rapid social change occurred in the Korean society. 7. In the process of the cultral change, cultural lag occurred between the public library and the users who could not adopt to the new library. This has been continued to the present time. 8. This diffused concept of the public library was modified and became native to Korean society. However, the acculturation of the public library concept has not changed the traditional ideas of Korean people and their behavior. The Korean society recently has been changing rapidly and the function of the Korean public library is improving accordingly; 1. The extended Korean family system is disorganizing. As the consequence, the public library could substitute the family system offering information and recreation service, etc. 2. The growth of educated population is requiring a variety of library materials. An individual library can not meet the needs of them and cooperative library service will be needed to share resources. The public library will become the center of the cooperative service. 3. The Koreans are watching TV more hours than they read printed materials. For them, the public library needs to collect audiovisual materials. Especially the teaching materials should be all audiovisualized for the effective teaching. 4. Technology is developing rapidly in Korea, especially computer technology is applied in many parts of the society. This will also influence library service. The public library will be developing as the centralized library computer system. When the Korean public library functions as the extended family system and the center of the cooperative library system, the Korean public library will be functioning as the public library defined by the Korean Library Association.

  • PDF

A Study on the Realities of Custom-made Clothing Production in Middle-aged Women's Clothing Firms (중년여성복업체(中年女性服業體)의 맞춤복(服) 생산실태(生産實態) 연구(硏究))

  • Park, Yu-Jeong;Sohn, Hee-Soon
    • Journal of Fashion Business
    • /
    • v.6 no.2
    • /
    • pp.1-16
    • /
    • 2002
  • The need for ready-to-wear clothing increases as the problem comes to arise from the fit of custommade clothing due to the characteristics of middle-aged women's somatotype. At this point of time, a study on the realities of production of custom-made clothing in middle-aged women's clothing business firms is of very greatly significance. Therefore, this study was intended to identify the problem and improvements through the survey research of production of custom-made clothing in middle-aged women's clothing business firms and further present the plan for development of custom-made clothing business. The questionnaire was framed based on the contents extracted from the preliminary questionnaire research for the pattern section chief of each business firm. Collected data were statistically processed using the SPSS 10.0 Windows program. As a result, the following findings were obtained: 1. The target age of the middle-aged women's clothing business firms ranged from more than 45 years to less than 50 years of age. Clothing business firms much made inroads into the ready-to-wear clothing market largely in the 1980s and the 1990s. Their active entry into the custom-made clothing market occurred in the 1970s and the 1980s. 2. In terms of the clothing production method of middle-aged women's clothing firms, some private boutique and designer brand clothing firms entered the clothing market with a focus on custom-made clothing in the beginning of its organization and introduced the production method of ready-to-wear clothing in accordance with changes in production methods and consumers' needs and wants. National brand clothing firms manufactured clothing with a focus on ready-to-wear clothing from the beginning of its organization, but at last they manufactured both partial custom-made and whole custom-made as the problem arose from ready-to-wear clothing. Seeing that their clothing production showed the ratio readyto-wear to custom-made clothing of 2.58:1. And it was found that the manufacture of ready-to-wear and custom-made clothing took into consideration the great difference in the pattern, size and design plan. The research of the clothing production process showed that whole custom-made and partial custommade were distinguished according to whether or not the sample was presented. 3. The ready-to-wear pattern of middle-aged women's clothing firms were used with a focus on the 'patternmaker-developed pattern' and company-developed pattern'. Most clothing businesses produced clothing in 4 to 5 basic sizes, which is found to be insufficient to complement the physical characteristics of middle-aged women with many specific somatotypes. In the pattern of custom-made clothing, the 'pattern of ready-to-wear were applied' or the 'customized pattern was developed'. Actual measurements were most used as the size of custom-made, and accordingly it is predicted that the level of satisfaction is higher with the fit of custom-made clothing than that of ready-to-wear. The selling place and the head office showed the similar percent as the place for measuring the size of custom-made clothing. Size measurers were mostly the shop master. And it was found that most clothing business firms had a problem when the measured size was applied to the pattern. Accordingly, it is necessary to provide education on size measurement for shop masters. 4. It was found that in the middle-aged women's clothing firms, the pattern correction of the length of sleeve, jacket and slacks occupied the highest percent. Accordingly, it is necessary to provide for the size system to complement the accurate somatotype characteristics of middle-aged women. 5. In custom-made clothing customer management, most firms engaged in customer somatotype management through size management. They provided customers with commodity information by informing them of the sales and event period and practiced human management for customers by maintaining the get-together and friendly relationship. 6. Middle-aged women's clothing businesses responded that it would be necessary to improve the fit of custom-made clothing and complement their pursuit for individuality as the plan to improve its quality. In consequence, it suggests that middle-aged women's clothing businesses should provide middle-aged women with the clothing of better-suited size and refined design. Middle-aged women's clothing businesses responded that it was the most urgent task to form the custom-made clothing manufacturing team as the plan to expand the custom-made clothing market, which is identified as their emphasis on the systematized production of custom-made clothing.

A Study on Changes of Physico-Chemical Properties of Plow Layer Soil and its Response of Tobacco Growth under Polyethylene Film Mulching Condition -3. Effect of Poly Ethylene Film Mulch on the Growth and Nutrients Uptake of Tobacco Plant (연초피복재배(煙草被覆栽培)에서 작토시(作土尸)의 이화학성(理化學性) 변화(變化)와 연초생장반응(煙草生長反應)에 관(關)한 연구(硏究) -3. 피복조건(被覆條件)이 연초생장(煙草生長)과 양분흡수(養分吸收)에 미치는 영향(影響))

  • Hong, Soon Dal;Lee, Yun Hwan;Kim, Jai-Joung;Cho, Seong-Jin
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.18 no.3
    • /
    • pp.312-317
    • /
    • 1985
  • Growth response and nutrients uptake of tobacco grown on mulched and non mulched plots were investigated during the growing period. 1. The whole growing time was about 25 days shorter and relative growth rate was faster in the mulched plot than in the non mulched plot. 2. Nitrate content of leaf in the latter stage of tobacco grown on the non mulched plot was more continuously increased compared with mulched plot. As a result in the latter stage of tobacco leaf nitrate form of nitrogen level was much higher on non mulched plot than on mulched plot. 3. Reducing sugar content in cured leaves of tobacco grown on the non mulched plot was lower that of the mulched plot. This difference in reducing sugar content was remarkable in the bottom leaves that nitrate content was highest. 4. Tobacco growing on nonmulched soil may cause to be low quality owing to increasing of nitrogen compound and decreasing of reducing sugar content in cured leaves. 5. As distributions of nitrate and potassium content in leaves at different stalk position was similar each other, nitrate and potassium ion considered to be counter ion in absorption and translocation through the tobacco plant.

  • PDF

Studies on the Processing and Management Forms of Filatures (우리나라 제사공장의 공정 관리실태에 관한 조사연구)

  • 송기언;이인전
    • Journal of Sericultural and Entomological Science
    • /
    • no.12
    • /
    • pp.37-45
    • /
    • 1970
  • The processing management forms of our country's filature factories in 1969 are summarized as follows. (1) About 80% of total cocoon collection is made within 5 days involving peak day, and 10% of cocoon collection is finished until 3 days before and after the peak day, (2) About 92% of alive cocoons transported on unpaved road, and about 40% of the cocoons purchased by all factories are loaded on trucks from common selling station which is far beyond 40km, therefore a new packing system of alive cocoons to drop the damage of cocoon qualities, should be taken. (3) 22% of all factories in our. country have only low-temperature cocoon drying machine. Therefore the installment of hot-air cocoon drying machine is required urgently. (4) In view of cocoon qualities in our country, the grouping method of cocoon for reeling. taken by about 50% of the factories at percent, which classify cocoons for reeling as high group (1,2,3,4 grades) and low group(5,6 grades), will have to be replaced by the method tat classify them high group (1,2 grades) middle group (3,4 grades), low group (5,6 grades). (5) The .ratio of cocoon assorting stood about 10% in multi-ends reeling, about 15% in automatic reeling, conclusively, the ratio of cocoon assorting for automatic reeling was higher tan that for multi-ends reeling. One person's ability for a day in cocoon assorting reaches to about 80-100kg. (6) Cocoon cooking condition requires the increase of the cooking time, the pressure and temperature used to be prolonged as much as the qualities of cocoons are material cocoon ior automatic and double cocoon machines are treated uncompletely. (7) Automatic silk reeling is being performed at 1-2$^{\circ}C$ lower in reeling water temperature and operated at about twice velocity. (8) The temperature and humidity of rereeling room stood at 25$^{\circ}C$, 67.2% R.H and 32.3$^{\circ}C$, 51.9% R.H of rereeling machine are showed, Average rereeling velocity is 233m/min and large reefs charged for one person are 7.5 reels and form of skein used in all factories is double skein. (9) About 73% of water sources for filature used under-earth water. About 48% of all filature factories in our country have not yet water purifying equipments. Installation of the equipment for these factories seems to be urgent, (10) Denier .balance, sizing reel, seriplane, are being used in most factories as self-inspection apparatus. (11) More than 90% of the factories use the vacum tank in rereeling process and about 20% of them use it in cocoon cooing process (12) Only 21% of the factories use chemicals in filature process. About all them use "Seracol 100" in cocoon cooking process and "Seracol 500" in rereeling process, (13) Above survey results explain each all factories show large difference in the processing management. Therefore, it is believed that intercommunication through seminar or technical exchange will contribute to the production evaluation of cocoon in our filature industry.

  • PDF

Chemical Structures and Physiological Activities of Plant Growth Substance, Malformin B's (식물생장조절물질 말포민 B동족체의 화학구조 및 생리활성)

  • Kim, K.W.
    • Korean Journal of Weed Science
    • /
    • v.15 no.1
    • /
    • pp.85-98
    • /
    • 1995
  • Six malformin B's produced by Aspergillus niger van Tiegh. were separated by HPLC. Their structures determined by the methods of amino acid analyses, mass spectrometry, and two-dimensional NMR were revealed as cyclic pentapeptides structurally related to malformin $A_1$. Both the NMR and MS/MS data suggest that the respective structures of separated malformin B's were as follows; cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-allo-Ile for $B_{1a}$, cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-Leu for $B_{1b}$, cyclo-D-Cys-D-Cys-L-Val-D-Val-L-Leu for $B_2$, cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Leu for $B_3$, cyclo-D-Cys-D-Cys-L-Val-D-Ile-L-Ile for $B_4$, and cyclo-D-Cys-D-Cys-L-Val-D-Val-L-Ile for $B_5$. Among the malformin B's, the structure of $B_{1b}$ was the same as that of malformin $A_3$ or C. All the malformin B's showed physiological activities in the two assay systems using corn(Zea mays L.) roots and mung bean(Phaseolus aureus Roxb.) hypercotyl segments. The malformin B's with molecular weight 529 were more effective for inducing corn root curvature than those with molecular weight 515. The difference in molecular weight of malformin B's, i.e., the retention time on HPLC, results in the polarity change of the whole malformin molecule which affects the revealation of the malformin activities. In addition, the disulfide form of the malformin B's gives the rigidity of the molecule, whereas the combination of the fourth and the fifth amino acid residues provides the optimal three-dimensional configuration to the malformin receptor of plants. Presumably, these two factors are appeared to be essential for the greatest physiological activity of malformin B's. malformin $B_{1a}$ caused the corn root curvature by 90% at a concentration of $0.25{\mu}M$. However, such differential activities with molecular weight of 529 or 515 of malformin B's were not found in the mung bean hypercotyl segment test. Maximum stimulation of mung bean hypercotyl growth was observed at $0.1{\mu}M$ concentration of malformin B's. The growth of the segments treated with $B_5$ was 154% greater than that of the control.

  • PDF

Comparison of Uptake of Ionic and Tf-bound Fe-59 and Ga-67 in Transformed and Untransformed Cells (변형세포와 비변형세포에서 이온형과 Transferrin 결합형 Fe-59와 Ga-67 섭취율의 비교)

  • Sohn, Myung-Hee;Lee, Young-Hwan;Lee, Sang-Yong;Chung, Gyung-Ho;Han, Young-Min;Kim, Jong-Soo;Choi, Ki-Chul;Yim, Chang-Yeol
    • The Korean Journal of Nuclear Medicine
    • /
    • v.30 no.1
    • /
    • pp.145-151
    • /
    • 1996
  • Pathways both mediated by and independent of transferrin(Tf) and the TfR have been described for the accumulation of iron. Although it is not clear whether the same systems take up iron and gallium, these pathways may suggest the contention that uptake of Ga-67 can, in fact, occur by both Tf-independent and Tf-dependent systems and may share with Fe-59 in part the same mechanism for uptake. The predominant system by which uptake of both radiometals occurs may be different in the degree of the transformation of tumor. Transformed(MMSV/3T3) and untransformed(BALB/3T3) cells were incubated with luM of Ga-67-citrate of Fe-59-chloride for 15 min. at $37^{\circ}C$ in either the presence or absence of Tf. After then, the monolayers were washed with HBSS or PBS, and the cells were solubilized in 1% SDS for gamma well counting and protein determinations. There were similarities, as well as differences, in the pattern of uptake of Fe-59 and Ga-67 presented both in ionic from and as bound to Tf. Both radiometals appeared gain to cells in either ionic or Tf-bound forms. Transformed cells appeared to accumulate more radiometal, either Ga-67 or Fe-59 in the presence of Tf than do the their untransforemd counterparts. Conversly the presentation of either radiometal in ionic form resulted in significantly greater accumulation of metal by the untransformed cells than those transformed. The efficiency for uptake of Ga-67 or Fe-59 in the absence of Tf was greater than for uptake of the Ga-Tf or Fe-Tf. However, the magnitude of difference in efficiency of uptake was greater for Fe-59(10-fold) than for Ga-67 (3-fold). Our results Supports the theory that both Tf-independent and Tf-dependent systems for the uptake of Ga-67 both systems operate oppositely between transformed cells and those untransformed, with uptake by the predominating in transformed cells by the Tf-mediated system and in untransformed cells by the Tf-independent. The uptake of Ga-67 by tumor may share with Fe-59 in part the same mechanism.

  • PDF

Autoradiographic Studies on the Inhibitory Effect of Dibutyryl Cyclic AMP on Mouse Oocyte Maturation in Vitro (Dibutyryl Cyclic AMP가 생쥐여포난자의 성숙에 미치는 억제효과에 관한 자기방사법적 연구)

  • Choi, Choon-Keun
    • Applied Microscopy
    • /
    • v.7 no.1
    • /
    • pp.21-43
    • /
    • 1977
  • This experiment was undertaken in order to localize the labeled dbcAMP (dibutyryl cyclic AMP) in oocytes whose development has been suppressed by cold dbcAMP for 6 or 19 hours in vitro. Mouse oocytes were obtained from the ovaries of 3-4 week old A strain female mice, by puncturing the Graafian follicles in the modified Krebs-Ringer bicarbonate salt solution under the dissecting microscope. Those oocytes which have intact germinal vesicle were cultured in the basic culture medium supplemented with 0.4% bovine serum albumin (BSA). Cultivation of the oocytes was carried out in a microtube developed by Cho (1974). The cultures were then incubated in a humidified 5% $CO_2$ incubator maintained at $37^{\circ}C$ for 6 or 19 hours (Donahue, 1968). DbcAMP was added to culture medium for a final concentration of 100ug/ml, and $^3H-dbc$ AMP (specific activity 13 Ci/mM) for a final concentration of $40{\mu}Ci/ml$ was also added to the medium. For electron microscopic autoradiography, those oocytes recovered from the culture were washed with phosphate buffer (pH 7.4), and immediately prefixed in a 2.5% glutaraldehyde overnight and postfixed for 2 hours at $4 ^{\circ}C$ in 1% osmium tetroxide in phosphate buffer with pH 7.4 (Palade, 1952). After fixation, the materials were dehydrated in graded alcohol series and embedded in Epon 812 mixture based on the standard procedures (Luft, 1961). The thin sections $600-700{\AA}$ thick were mounted on the grids of 200 meshes. The grids containing sections were coated with a nuclear emulsion Kodak NTB-3 and stored in a cold dark box (at $4^{\circ}C$) for 3 weeks. After exposure, the samples were developed with Kodak D-19 and stained with uranyl acetate and lead citrate. Routine observation was made with Hitachi HU-11E electron microsocope. The results of the observation were as followings: 1. It was found that the labeled dbcAMP penetrated the egg plasma membrane and dispersed at random in the cytoplasm. 2. It was also observed that most of the labeled dbcAMP was attached to microfibrillar lattices portion of the oocyte cytoplasm. There fore, it is presumed that the receptor of the dbcAMP is localized in the microfibrillar lattices of the oocyte. 3. It also seems that some other cell organells such as mitochondria, Golgi complex, cortical granules are not directly related to the action of the dbcAMP. 4. The labeled dbcAMP was neither observed in the membrane nor in the nucleus. Therefore, it seems that there is no relationship between the concentration of dbcAMP and the nuclear membranous permeability. 5. There was no difference in number of dbcAMP particles when oocytes were cultured for 6 hours and 19 hours. 6. However, it was observed that, in same of the oocytes suppressed in germinal vesicle by dbcAMP for 19 hours, cell organells were moved and concentrated to a small portion of the cytoplasm, and that the morphology of the organells greatly changed to an abnormal. form. Therefore, it is supposed that those oocytes were in the process of degeneration. From the above results, it is expected that dbcAMP penetrated the egg membrane and was bound to the receptor which seems to be located in the microfibrillar lattiees portion, and that this dbcAMP-receptor complex inhibited some enzyme system of the oocytes which are essential for the germinal vesicle breakdown.

  • PDF

EFFECT OF HYDROGEN PEROXIDE CONCENTRATION ON THE WHITENING AND PHYSICAL PROPERTIES OF HYDROXYAPATITE DISCS (Hydrogen Peroxide 농도와 적용시간이 Hydroxyapatite Discs의 미백과 물리적 성질에 미치는 영향)

  • Yang, Yeon-Mi;Lee, Doo-Cheol;Baik, Byeong-Ju;Kim, Jae-Gon;Shin, Jeong-Geun
    • Journal of the korean academy of Pediatric Dentistry
    • /
    • v.34 no.1
    • /
    • pp.1-12
    • /
    • 2007
  • The purpose of this study was to evaluate the effect that various concentration and application time of hydrogen peroxide had on tooth whitening and physical properties. The hydroxyapatite (HA) discs of $12mm({\Phi}){\times}1.2mm(t)$ in dimensions were made by compression $(100kg/cm^2)$ and sintering (at $1350^{\circ}C$ for 2 hours) All specimens were polished sequentially with '240 through '2000 emery paper and one side of each specimen was polished finally with $0.3{\mu}m$ alumina paste. The discs were placed in sterile whole stimulated saliva overnight at $37^{\circ}C$ in order to form an in vitro pellicle layer. Then the discs were rinsed with distilled water and soaked into staining broth at $37^{\circ}C$ for 7 days. These stained specimens were bleached with hydrogen peroxide according to the change of concentration $(3{\sim}30%)$ and application time ($3{\sim}10$ days). The specimens were analyzed with a spectrophotometer, X-ray diffractometer (XRD), scanning electron microscope (SEM), surface roughness tester, microhardness tester and biaxial flexural strength. The results of present study can be summarized as follows : 1. The bleaching effect was increased with the increased concentration and the extended application time of hydrogen peroxide. 2. The surface roughness was significantly increased from the specimen bleached with 15% hydrogen peroxide for 10 days and with 30% for 7 and 10 days respectively (p<0.05). 3. The changes of crystal phase observed by XRD between before and after bleaching weren't shown of any difference, but microporous structure of surface observed by SEM was shown of increase with the increased concentration and the extended application. 4. The biaxial flexural strength was significantly decreased from bleaching of specimen with 30% hydrogen peroxide for 7 and 10 days respectively (p<0.05) 5. Microhardness was significantly decreased from bleaching with 15% hydrogen peroxide for 10 days and with 30% for 3, 7 and 10 days respectively (p<0.05). Although the tooth bleaching effect was greater when the high concentration was applied, further in vivo experiment will be needed to prove it's safety.

  • PDF

Change of Particle Size of Magnesium Silicate According to Reaction Conditions and Evaluation of Its Polyol Purification Ability (반응 조건에 따른 규산마그네슘의 입도 변화 및 폴리올 정제 능력평가)

  • Yoo, Jhongryul;Jeong, Hongin;Kang, Donggyun;Park, Sungho
    • Korean Chemical Engineering Research
    • /
    • v.58 no.1
    • /
    • pp.84-91
    • /
    • 2020
  • The efficiency of the synthetic magnesium silicate used in basic polyols and edible oil purification is evaluated by its purification ability and filtration rate and is affected by the particle size and surface area of magnesium silicate. In this study, it was investigated the change on the particle size of magnesium silicate was influenced by the reaction temperature, injection rate, injection order (Si, Mg) and Mg/Si reaction mole ratio. The synthesized magnesium silicate was compared and analyzed for the synthesis, grinding, and refining processes. In the synthesis process, the reaction temperature and feed rate did not affect the average particle size change of magnesium silicate, while the reaction molar ratio of Mg / Si and the order of injection acted as main factors for the change of average particle size. The average particle size of magnesium silicate increased by 8.7 ㎛ from 54.4 ㎛ to 63.1 ㎛ at Mg injection when Mg molar ratio increased from 0.125 to 0.500, and increased by about 4.8 ㎛ from 47.3 ㎛ to 52.1 ㎛ at Si injection. The average particle size according to the order of injection was 59.1 ㎛ for Mg injection and 48.4 ㎛ for Si injection and the difference was shown 10.7 ㎛, therefore the filtration rate was about 2 times faster under the condition of Mg injection. That is, as the particle size increases, the filtration time is shortened and washing filtration rate can be increased to improve the productivity of magnesium silicate. The cake form of separated magnesium silicate after filtration becomes a solid through drying process and is used as powdery adsorbent through the grinding process. As the physical strength of the dried magnesium silicate increased, the average particle size of the powder increased and it was confirmed that this strength was affected by the reaction molar ratio. As the reaction molar ratio of Mg / Si increased, the physical strength of magnesium silicate decreased and the average particle size after grinding decreased by about 40% compared to the average particle size after synthesis. This reduction of strength resulted in an improvement of the refining ability due to the decrease of the average particle size and the increase of the amount of fine particle after the pulverization, but it resulted in the decrease of the purification filtration rate. While the molar ratio of Mg/Si was increased from 0.125 to 0.5 at Mg injection, the refining ability increased about 1.3 times, but the purification filtration rate decreased about 1.5 times. Therefore, in order to improve the productivity of magnesium silicate, the reaction molar ratio of Mg / Si should be increased, but in order to increase the purification filtration rate of the polyol, the reaction molar ratio should be decreased. In the synthesis parameters of magnesium silicate, the order of injection and the reaction molar ratio of Mg / Si are important factors affecting the changes in average particle size after synthesis and the changes of particle size after grinding due to the changes of compressive strength, therefore the synthetic parameter is an important thing that determines productivity and refining capacity.

Effect of Coolant on PEMFC Performance in Low Humidification Condition (저가습 조건에서 냉각 유체의 고분자전해질 연료전지에 대한 영향)

  • Lee, Hung-Joo;Song, Hyun-Do;Kwon, Jun-Taek;Kim, Jun-Bom
    • Journal of the Korean Electrochemical Society
    • /
    • v.10 no.1
    • /
    • pp.25-30
    • /
    • 2007
  • Proton exchange membrane fuel cell(PEMFC) performance could be affected by various factors such as cell temperature, total pressure, partial pressure of reactants and relative humidity. Hydrogen ion is combined with water to form hydronium ion [$H_3O^+$] and pass through membrane resulting electricity generation. Cooling system is needed to remove heat and other uses on large scale fuel cell. In case that collant conductivity is increased, fuel cell performance could be decreased because produced electricity could be leaked through coolant. In this study, triple distilled water(TDW) and antifreeze solution containing ethylene glycol was used to observe resistance change. Resistance of TDW was taken 28 days to reach preset value, and effect on fuel cell operation was not observed. Resistance of antifreeze solution was not reached to preset value up to 48 days, but performance failure occurred presumably caused by bipolar plate junction resulting stoppage resistance experiment. Generally PEMFC humidification is performed near-saturated operating conditions at various temperatures and pressures, but non-humidifying condition could be applied in small scale fuel cell to improve efficiency and reduce system cost. However, it was difficult to operate large scale fuel cell without humidifying, especially higher than $50{\sim}60^{\circ}C$. In case of small flux such as 0.78 L/min, temperature difference between inlet and outlet was occurred larger than other cases resulting performance decrease. Non-humidifying performance experiments were done at various cell temperature. When both of anode and cathode humidification were removed, cell performance was strongly depended on cell operating temperature.