• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2000.04a
• /
• pp.9-10
• /
• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• Nuclear Medicine and Molecular Imaging
• /
• v.40 no.3
• /
• pp.155-162
• /
• 2006

Purpose: Diabetes mellitus (DM) is a critical disease with higher rates of cardiovascular morbidity and mortality due to myocardial ischemia and infarction. There is glowing interest in how to determine high-risk patients who are candidates for screening testing. This study was performed to evaluate the incidence of coronary artery disease (CAD) in diabetic patients detected by Tc-99m MIBI myocardial perfusion SPECT (MPS) and to assess risk factors of CAD and cardiac hard events. Subjects and Methods: 203 diabetic patients (64 male, mean age $64.1{\pm}9.0$ years) who underwent MPS were included between Jan 2000 and July 2004. Cardiac death and nonfatal myocardial infarction (MI) were considered as hard events, and coronary angioplasty and bypass surgery >60 days after testing were considered as soft events. The mean follow-up period was $36{\pm}18$ months. Patients underwent exercise (n=6) or adenosine stress (n=197) myocardial perfusion SPECT. Results: Perfusion defects on MPS were detected in 28.6% (58/203) of the patients. There was no cardiac death but 11 hard events were observed. The annual cardiac hard event rate was 1.1%. In univariate analysis of clinical factors, typical anginal pain, peripheral vascular disease, peripheral polyneuropathy, and resting ECG abnormality were significantly associated with the ocurrence of hard events. Anginal pain, peripheral vascular disease, and resting ECG abnormality remained independent predictors of nonfatal MIs with multivariate analysis. Abnormal SPECT results were significantly associated with high prevalence of hard events but not independent predictors on uni- and multivariate analyses. Conclusion: Patients who were male, had longer diabetes duration (especially over 20 years), peripheral vascular disease, peripheral polyneuropathy, or resting ECG abnormality had higher incidence of CAD. Among clinical factors in diabetic patients, typical angina, peripheral vascular disease, peripheral polyneuropathy, and resting ECG abnormality were strong predictors of hard events.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.27 no.5
• /
• pp.373-384
• /
• 2001

Cellular proliferation is an intricately regulated process mediated by the coordinated interactions of critical growth control genes. Two of these factors in mammalian cells are the p53 and mdm-2 genes. A protein product of the mem-2 oncogene has been recently shown to associate with the protein encoded by the tumor suppressor gene p53. The p53 tumor suppressor protein is stabilized in response to DNA damage and other stress signals and causes the cell to undergo growth arrest or apoptosis, thus preventing the establishment of mutations in future cellular generations. Mutation or loss of p53 is a very common event in tumor progression. It occurs in about 50% of all tumors analysed including of colon, lung, breast and liver. The cellular mdm-2 gene, which has potential transforming activity that can be activated by overexpression, is amplified in a significant percentage of human sarcoma and in other mammalian tumors. Proteins encoded by the mdm-2 gene are able to bind to the p53 protein and, when overexpressed, can inhibit p53's transcriptional activation function, thus mdm-2 can act as a negative regulator of p53 function. Experimental study was performed to observe the relationship between p53 gene mutation and mdm-2 protein expression and apply the results to the clinical activity. 36 golden syrian hamster each weighing $60{\sim}80g$ were used and painted with 0.5% DMBA by 3 times weekly on the right buccal cheek(experimental side) for 6, 8, 10, 12, 14 and 16 weeks. Left buccal cheek(control side) was treated with mineral oil as the same manner to the right side. The hamsters were sacrificed on the 6, 8, 10, 12, 14 & 16 weeks. Normal and tumor tissues from paraffin block were examined for histology and immunohistochemistry observation, and were completely dissected by microdissection and DNA from both tissue were isolated by proteins K/phenol/chloroform extraction. Segments of the hamster p53 exons 5, 6, 7 and 8 were amplified by PCR using the oligonucleotide primers, and then confirmational change was observed by SSCP respectively. The results were as follows : 1. Dysplasia at 6 weeks, carcinoma in situ at 8 weeks and invasive carcinoma from 10 weeks could be observed in experimental groups. 2. p53 mutations were detected in 10 of the 36(28%) and the exons 6(6 of the 10 : 60%) was the most hot spot area among the highy conserved region(exons 5, 6, 7 & 8). 3. Immunohistochemical study confirmed 22 of the 36(61%) of p53 expression involving 10 of p53 mutations. 4. mdm-2 expression of was showed in 3 of the 36(8%) involving 1 of the 22 of p53 expression and 2 of the 14 of p53 non-expression. From the above results, mutation of p53 gene or expression of p53 protein may have the influence of the DMBA induced carcinoma of hamster buccal pouch but the expression of mdm-2 protein may not have relationship with tumorigenesis.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.26 no.1
• /
• pp.52-72
• /
• 1984

This study was performed to obtain the basic data which can be applied to the use of epoxy resin mortars. The data was based on the properties of epoxy resin mortars depending upon various mixing ratios to compare those of cement mortar. The resin which was used at this experiment was Epi-Bis type epoxy resin which is extensively being used as concrete structures. In the case of epoxy resin mortar, mixing ratios of resin to fine aggregate were 1: 2, 1: 4, 1: 6, 1: 8, 1:10, 1 :12 and 1:14, but the ratio of cement to fine aggregate in cement mortar was 1 : 2.5. The results obtained are summarized as follows; 1.When the mixing ratio was 1: 6, the highest density was 2.01 g/cm$^3$, being lower than 2.13 g/cm$^3$ of that of cement mortar. 2.According to the water absorption and water permeability test, the watertightness was shown very high at the mixing ratios of 1: 2, 1: 4 and 1: 6. But then the mixing ratio was less than 1 : 6, the watertightness considerably decreased. By this result, it was regarded that optimum mixing ratio of epoxy resin mortar for watertight structures should be richer mixing ratio than 1: 6. 3.The hardening shrinkage was large as the mixing ratio became leaner, but the values were remarkably small as compared with cement mortar. And the influence of dryness and moisture was exerted little at richer mixing ratio than 1: 6, but its effect was obvious at the lean mixing ratio, 1: 8, 1:10,1:12 and 1:14. It was confirmed that the optimum mixing ratio for concrete structures which would be influenced by the repeated dryness and moisture should be rich mixing ratio higher than 1: 6. 4.The compressive, bending and splitting tensile strenghs were observed very high, even the value at the mixing ratio of 1:14 was higher than that of cement mortar. It showed that epoxy resin mortar especially was to have high strength in bending and splitting tensile strength. Also, the initial strength within 24 hours gave rise to high value. Thus it was clear that epoxy resin was rapid hardening material. The multiple regression equations of strength were computed depending on a function of mixing ratios and curing times. 5.The elastic moduli derived from the compressive stress-strain curve were slightly smaller than the value of cement mortar, and the toughness of epoxy resin mortar was larger than that of cement mortar. 6.The impact resistance was strong compared with cement mortar at all mixing ratios. Especially, bending impact strength by the square pillar specimens was higher than the impact resistance of flat specimens or cylinderic specimens. 7.The Brinell hardness was relatively larger than that of cement mortar, but it gradually decreased with the decline of mixing ratio, and Brinell hardness at mixing ratio of 1 :14 was much the same as cement mortar. 8.The abrasion rate of epoxy resin mortar at all mixing ratio, when Losangeles abation testing machine revolved 500 times, was very low. Even mixing ratio of 1 :14 was no more than 31.41%, which was less than critical abrasion rate 40% of coarse aggregate for cement concrete. Consequently, the abrasion rate of epoxy resin mortar was superior to cement mortar, and the relation between abrasion rate and Brinell hardness was highly significant as exponential curve. 9.The highest bond strength of epoxy resin mortar was 12.9 kg/cm$^2$ at the mixing ratio of 1:2. The failure of bonded flat steel specimens occurred on the part of epoxy resin mortar at the mixing ratio of 1: 2 and 1: 4, and that of bonded cement concrete specimens was fond on the part of combained concrete at the mixing ratio of 1 : 2 ,1: 4 and 1: 6. It was confirmed that the optimum mixing ratio for bonding of steel plate, and of cement concrete should be rich mixing ratio above 1 : 4 and 1 : 6 respectively. 10.The variations of color tone by heating began to take place at about 60˚C, and the ultimate change occurred at 120˚C. The compressive, bending and splitting tensile strengths increased with rising temperature up to 80˚ C, but these rapidly decreased when temperature was above 800 C. Accordingly, it was evident that the resistance temperature of epoxy resin mortar was about 80˚C which was generally considered lower than that of the other concrete materials. But it is likely that there is no problem in epoxy resin mortar when used for unnecessary materials of high temperature resistance. The multiple regression equations of strength were computed depending on a function of mixing ratios and heating temperatures. 11.The susceptibility to chemical attack of cement mortar was easily affected by inorganic and organic acid. and that of epoxy resin mortar with mixing ratio of 1: 4 was of great resistance. On the other hand, when mixing ratio was lower than 1 : 8 epoxy resin mortar had very poor resistance, especially being poor resistant to organicacid. Therefore, for the structures requiring chemical resistance optimum mixing of epoxy resin mortar should be rich mixing ratio higher than 1: 4.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.12 no.3
• /
• pp.3-12
• /
• 1992

Forage grasses and legumes ar$\varepsilon$ the mam component of livestock diets in Canada. There are over 30 million ha of grassland in Canada and there is a large, undeveloped land base in fringe areas suitable for forage production. The short growing s season limits the grassland farming to the southern p parts of Canada. The win!er season is long and in most parts of Canada cold temperatures, fr$\varepsilon$ezmg, and thawing, and diseases exert sever$\varepsilon$ stress on overwintering forage plants. The development of persistent cultivars is essential for sustained production particularly in the fringe areas with short growmg s$\varepsilon$ason. The seasonality of dry matter production is a result of high growth rates in early summ$\varepsilon$r and low dry matter accumulation in late summer and fall. Innovative management practIces a and cultivars with improved regrowth capacity are n necessary to overcome such skewed production pattern and to extend effiectlVe grazmg season l Improved pasture production is an important part of reducing costs in livestock operations and remaining competitive. It is suggested that applying available technology would increase pasture productivity and reduce d$\varepsilon$pendence on stored feeds thus improving profitability of small producers in particeular. Reducing nutrient losses during harv$\varepsilon$stmg, s storage, and feeding is essential for improved production efficiency during confinement. The devclopment of low cost and labor saving methods of ensiling is critical for improved efficiency and profitability of forage based enterprises Livestock industries must respond to consumer preferences for low fat and cholesterol foods. Research and development of entire production systems is emphasized for dev$\varepsilon$loping viabl$\varepsilon$ enterprises. It is increasingly difficult to secure resources for r$\varepsilon$search, education, and extension, and alliane$\varepsilon$s and cooperation must expand among organizations with interests in forage based livestock systems.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.18 no.4
• /
• pp.188-198
• /
• 2016

In soybeans, responses of high temperature according to shift of sowing dates during the growing season was explored using the crop model, CROPGRO-soybean. In addition, it analyzed impact on change of sowing dates affects yield potential of soybean under future climate scenario (2041-2070). In Jeonju and Miryang during 1981-2010, if sowing at 15 or ten days ahead from 10 June, namely in shorten of the sowing day (i.e. when sown on 25 or 30 May), the yield potential reduced. However, the yield potential increased when sown 5 June. In the case of delay of sowing day (i.e. when sown on 15 or 20 June), reduction of yield potential in the average -5% was higher than increase in the average +2%. In particular, the relative changes for shorten of the sowing day or delay of the sowing day do not be shown in normal years which high temperatures did not abnormally occur during the growing season from 2003 to 2010 except when sown on 25 May. In abnormal years which high temperatures occurred during the critical period, especially R5 to R7, shorten of the sowing day affected to the increase of yield potential in Miryang, while the yield potential decreased in Jeonju except when sown on 5 June. However, delay of the sowing day influenced on the reduction of yield potential both in two sites. In future climate scenario of Representative Concentration Pathway (RCP) 8.5 during from 2041 to 2070, the increase and decrease of yield potential for shorten of the sowing day were +10/-9% for RCP 8.5 of Jeonju, and +14/-9% for RCP 8.5 of Miryang, respectively. Additionally, it showed +10/-17% for RCP 8.5 in Jeonju, and +10/-29% for RCP 8.5 in Miryang, respectively in the increase and decrease of yield potential for delay of the sowing day.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.30 no.3
• /
• pp.97-110
• /
• 2012

This study aimed at considering the original shape of Iljiam Tea Garden at Mt. Daedun. In order to accomplish our goal, we tried to strengthen the authenticity of construction of Iljiam by comparing its space structure depicted in the poetry of Choeui(艸衣) the monk with its current restored state. According to the clues and situation in the poetry along with symbolic words like 'Choeui' and 'Ilji(一枝)', Iljiam seemed to be a tea garden with elegant and celestial beauties, and with a nice view where Choeui the famous monk searched for the highest state of enlightenment by enjoying and living in nature. When we compared the plural aspects of Iljiam like Dacheon(茶泉), Dajo, Mulhwak, Darim(茶林), Chaewon(菜園), and Yeonji(蓮池) with those of Dasan Tea Garden[茶山草堂], we could see that the basic components of tea-culture space of both gardens are the same, showing the organizational principle of the top and bottom area to stress reading and studying. When it is restored, the authenticity of Iljiam should be pursued by linking spatial, historical, and landscaping characteristics as the space of which Choeui the monk carried out Zen meditation and mastered tea. However, the recent grand scale Buddhist business like the expansion of access road and construction of Buddhist sanctuary and Seolimdang became the biggest threat to the authenticity. Especially, it was emphasized many times in various poetry that the view from Iljiam and its surroundings is extraordinary, so it is critical to get rid of obstacles to the view from Iljiam and its surroundings in order to restore Iljiam as its genuine form. The current Iljiam should be re-made because it is like a leaf-roofed garden, not like a hermitage. However, the opinion that Jawoohongryeon-sa(紫芋紅蓮社) is somewhat a Taoistic and Taoist hermit space with a special shape adopted the pattern of building of the Joseon period rather than a Buddhist building can be accepted as long as other convincing historical evidences are found out, considering the ideology of uniting Confucianism and Buddhism and the spirit of Taoist hermit found out from poetry of Choeui and his friends. In conclusion, the restoration of Iljiam in 1979 was carried out to restore the place of Iljiam rather than to restore the originality of Iljiam by combining and referring domestic cases of tea gardens. However, there is not much material for restoration even though the main frame of Iljiam was distorted. Nevertheless, the top and bottom ponds should be constructed as a rectangle shape. In addition, it can be improved much in terms of plants and trees. It is necessary to restore bamboo forest, which was razed in order to make a tea plantation around Seolimdang, to set vines of arbors above the upper limbs, to plant pine trees and willow trees inside of the garden, and to put Dajeolgu under the corner of the eaves. Especially, the bamboo forest emphasized in poetry and took care of by Choeui himself should be restored inside of the garden.

• The Journal of the Petrological Society of Korea
• /
• v.28 no.3
• /
• pp.157-169
• /
• 2019

Pseudotachylytes, produced by frictional heating during seismic slip, provide information that is critical to understanding the physics of earthquakes. We report the results of occurrence, structural characteristics, scanning electron microscopic observation and geochemical analysis of pseudotachylytes, which is presumed to have formed after the Late Cretaceous in outcrops of the Paleoproterozoic granitic gneiss on the Bulil waterfall of the Jirisan area, Yeongnam massif, Korea. Fault rocks, which are the products of brittle deformation under the same shear stress regime in the study area, are classified as pseudotachylyte and foliated cataclasite. The occurrences of pseudotachylyte identified on the basis of thickness and morphology are fault vein-type and injection vein-type pseudotachylyte. A number of fault vein-type pseudotachylytes occur as thin (as thick as 2 cm) layers generated on the fault plane, and are cutting general foliation and sheared foliation developed in granitic gneiss. Smaller injection vein-type pseudotachylytes are found along the fault vein-type pseudotachylytes, and appear in a variety of shapes based on field occurrence and vein geometry. At a first glance fault vein-type seudotachylyte looks like a mafic vein, but it has a chemical composition almost identical to the wall rock of granitic gneiss. Also, it has many subrounded clasts which consist predominantly of quartz, feldspar, biotite and secondary minerals including clay minerals, calcite and glassy materials. Embayed clasts, phenocryst with reaction rim, oxide droplets, amygdules, and flow structures are also observed. All of these evidences indicate the pseudotachylyte formed due to frictional melting of the wall rock minerals during fault slip related to strong seismic faulting events in the shallow depth of low temperature-low pressure. Further studies will be conducted to determine the age and mechanical aspect of the pseudotachylyte formation.

• Journal of Life Science
• /
• v.29 no.1
• /
• pp.9-17
• /
• 2019

As tumors develop, they encounter microenvironmental stress, such as hypoxia and glucose depletion, due to poor vascular function, thereby leading to necrosis, which is observed in solid tumors. Necrotic cells are known to release cellular cytoplasmic contents, such as high mobility group box 1 (HMGB1), into the extracellular space. The release of HMGB1, a proinflammatory and tumor-promoting cytokine, plays an important role in promoting inflammation and metabolism during tumor development. Recently, HMGB1 was shown to induce the epithelial-mesenchymal transition (EMT) and metastasis. However, the underlying mechanism of the HMGB1-induced EMT, invasion, and metastasis is unclear. In this study, we showed that noninvasive breast cancer cells MCF-7 formed tightly packed, rounded spheroids and that the cells in the inner regions of a multicellular tumor spheroid (MTS), an in vitro model of a solid tumor, led to necrosis due to an insufficient supply of O2 and glucose. In addition, after 7 d of MTS culture, the EMT was induced via the transcription factor Snail. We also showed that HMGB1 receptors, including RAGE, TLR2, and TLR4, were induced by MTS culture. RAGE, TLR2, and TLR4 shRNA inhibited MTS growth, supporting the idea that RAGE/TLR2/TLR4 play critical roles in MTS growth. They also prevented MTS culture-induced Snail expression, pointing to RAGE/TLR2/TLR4-dependent Snail expression. RAGE, TLR2, and TLR4 shRNA suppressed the MTS-induced EMT. In human cancer tissues, high levels of RAGE, TLR2, and TLR4 were detected. These findings demonstrated that the HMGB-RAGE/TLR2/TLR4-Snail axis played a crucial role in the growth of the MTS and MTS culture-induced EMT.

• (The)Study of the Eastern Classic
• /
• no.55
• /
• pp.223-264
• /
• 2014

Yeoncheon Hong Seok-joo(淵泉 洪奭周: 1774-1842) faithfully followed a policy of restoration of literary style of king Jeongjo. He was an young vassal after 1794 and influenced by Jeongjo because Yeoncheon was around the king. Furthermore, he had comparatively favorable working period as a vassal(仕宦期, 1795-1836) after death of Jeongjo(1800) while establishing his own academic viewpoint. Therefore, a study about art theory of Yeoncheon Hong Seok-joo is one about logical system to accept various desires for change of then while not getting rid of scope of Neo-Confucianism after Jeongjo. It is catched that exchange of Hong Seok-joo and Jeong Yak-yong was made relating to study of Sangseo. Hong Seok-joo and Jeong Yak-yong absorbed in study of Sangseo, which is come from putting importance on 6 scriptures (經) among studies of scriptures by both of them. Through this, they aimed to re-discover ideology of original Confucian studies as one for cultivating oneself and governing people (修己治人之學). Dasan and Yeoncheon have something in common that they were young vassals who were cultivated as a guarding power for Jeongjo centered on Gyujanggak. They were largely fit to view of literature(文體觀) of Jeongjo. Hong Seok-joo distinguished function of prose(文) and poetry(詩) into teaching moral(明敎) and moving people(感人) in the category of Mun-yi-jae-do(文以載道) based on thoughts of 'literature is linguistic device for Taoism '(道本文末)' which is a core concept of literature theory based on Neo-Confucianism. He gave a careful attention on instructional and social function in prose while on emotional understanding that puts importance on temper and the secrets of nature in poetry. Hong Seok-joo regarded moral impression and edification through this as a core of artistic creation based on Segyoseol(世敎說). Furthermore, expressions such as 'Heunggwangunwon(興觀群怨)' or 'Yeohangguyo(閭巷謳謠) which are mentioned as important elements in his artistic works put importance on actual existence of objective things in artistic activity and this is connected to an attitude to require description fit to fact. So, it is assumed that such expression style aimed for features of genre painting in painting arts. Understanding of the study of ancient documents by Yeoncheon developed from critical perspective. He criticized the study of ancient documents, saying it as first, Pasoijisul(破碎之術), second, Dotaekjisul(塗澤之術), third, Hoimojisul(毁侮之術). Jeong Yak-yong criticized ' theory on the Odes' from viewpoint of theory of Mun-yi-jae-do(文以載道) based on Neo-Confucianism. He stressed political and social function of Sipeon and general poetry in "the Odes" and reinterprets discourses about poetry of Zhu Xi based on his own opinion. He says that poems of national fashion do political and social criticism. The theory of national fashion by Jeong Yak-yong clearly discloses his thoughts that stress practical role of noblemen in the social and political context.