• 폴리머
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• 제33권5호
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• pp.420-428
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• 2009

In this study, the composites containing carbon black (CB) or carbon fibers were prepared, and the microwave absorbing properties and the absorption mechanism of them were investigated and discussed in the frequency range of 2-18 GHz, respectively. The optimum mass fraction of CB has been found as 6%, and the carbon fibers were discovered to absorb radar wave either under parallel or vertical polarization, the suitable gap distance between each bundle of which was 5 mm. According to the results of the single constitute absorber samples, the structured composites with the two kinds of absorbers combination were fabricated and studied at 2-18 GHz. The top layer absorbers affect the absorption performance a lot; the maximum reflection loss of composites with CB as top layer absorbers was -31.8 dB with the frequency range of 2.4 GHz below -10 dB, and the other type with CFs as the top layer absorbers obtained the reflection loss peak value of -31.4 dB with 2 GHz below-10 dB.

• 제어로봇시스템학회논문지
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• 제22권8호
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• pp.585-589
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• 2016

Recently, the robotic assist system for cardiovascular intervention gets continuously growing interest. The robotic cardiovascular intervention systems are largely two folds, systems for cardiac ablation procedure assist and systems for vascular intervention assist. For the systems, the clinician controls the catheter inserted through blood vessel to the heart via a master console or master manipulator. Most of the current master manipulators have structure of joystick-like pivoting 2 degree of freedom (DOF) handle in the core, which is used in parallel with other sliding switches and input devices. It however is desirable to have customized and optimized design manipulator that can provide clinician with intuitive control of the catheter motion fully utilizing the advantage of the use of robotic structure. A 6 DOF kinematic mechanism that can capture the motion control intention of the clinician in translational 3 DOF and rotational 3 DOF is proposed in this paper. Also, a master-slave motion relationship specially designed for the cardiac catheter manipulation motion is proposed and implemented in an experimental prototype. Design revision for implementation of more efficient motion and experiment in combination with an experimental slave robot system for catheter manipulation are underway.

• Journal of Power Electronics
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• 제16권6호
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• pp.2119-2128
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• 2016

Due to detection and control errors, some high-frequency harmonics with voltage-source characteristics cause circulating currents in modular inverters. Moreover, the circulating currents are usually affected by the output filters (OF) of each module due to their filter and resonance properties. The interaction among the circulating currents in the modules increase the power loss and reduce system stability and control precision. Therefore, this paper reports the results of a study on the SPWM high-frequency harmonics circulating currents for a double-module VSI. In the paper, an analysis of the circulating-current circuits is briefly described. Next, a mathematic model of the single-module output voltage based on the carrier frequency of SPWM is built. On this basis, through mathematic modeling of high-frequency harmonic circulating currents, the formation mechanism and distribution characteristics of circular currents and their influences are studied in detail. Finally, the influences of the OF on the circulating currents are studied by mainly taking an LC-type filter as an example. A theoretical analysis and experimental results demonstrate some important characteristics. First, the carrier phase shifting of the SPWM for each module is the major cause of the SPWM harmonic circulating currents, and the circulating currents are in an odd distribution around n-times the carrier frequency $n{\omega}_s$, where n = 1, 2, 3, ${\ldots}$. Second, the harmonic circular currents do not flow into the parallel system. Third, the OF can effectively suppress the non-circulating part of the high-frequency harmonic currents but is ineffective for the circulation part, and actually reduces system stability.

• Geomechanics and Engineering
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• 제12권2호
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• pp.295-312
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• 2017

Cast in situ and grouted concrete helical piles with 150-200 mm diameter half cylindrical ribs have become an economical and effective choice in Shanghai, China for uplift piles in deep soft soils. Though this type of pile has been successful used in practice, the reinforcing mechanism and the contribution of the ribs to the total resistance is not clear, and there is no clear guideline for the design of such piles. To study the inclusion of ribs to the contribution of shear resistance, the shear behaviour between silty sand and concrete slabs with parallel ribs at different spacing and angles were tested in a large direct shear box ($600mm{\times}400mm{\times}200mm$). The front panels of the shear box are detachable to observe the soil deformation after the test. The tests were modelled with three-dimensional finite element method in ABAQUS. It was found that, passive zones can be developed ahead of the ribs to form undulated failure surfaces. The shear resistance and failure mode are affected by the ratio of rib spacing to rib diameter. Based on the shape and continuity of the failure zones at the interface, the failure modes at the interface can be classified as "punching", "local" or "general" shear failure respectively. With the inclusion of the ribs, the pull out resistance can increase up to 17%. The optimum rib spacing to rib diameter ratio was found to be around 7 based on the observed experimental results and the numerical modelling.

• 자원환경지질
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• 제15권3호
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• pp.123-154
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• 1982

Petrochemical, K-Ar dating, Sand Rb/Sr isotopes, metallogenic zoning, paleomagnetic and geotectonic studies of the Gyongsang basin were carried out to examine applicability of plate tectonics to the post-late Cretaceous igneous activity and metallogeny in the southeastern part of Korean Peninsula. The results obtained are as follows: 1. Bulgugsa granitic rocks range from granite to adamellite, whose Q-Ab-Or triangular diagram indicates that the depth and pressure at which the magma consolidated increase from coast to inland varying from 6 km, 0.5-3.3 kb in the coastal area to 17 km, 0.5-10 kb in the inland area. 2. The volcanic rocks in Gyongsang basin range from andesitic to basaltic rocks, and the basaltic rocks are generally tholeiitic in the coastal area and alkali basalt in the inland area. 3. The volcanic rocks of the area have the initial ratio of Sr^{87}/Sr^{86} varying from 0.706 to 0.707 which suggests a continental origin; the ratio of Rb/Sr changing from 0.079-0.157 in the coastal area to 0.021-0.034 in the inland area suggests that the volcanism is getting younger toward coastal side, which may indicate a retreat in stage of differentiation if they were derived from a same magma. The K_2O/SiO_2 (60%) increases from about 1.0 in the coastal area to about 3.0 in the inland area, which may suggest an increase indepth of the Benioff zone, if existed, toward inland side. 4. The K-Ar ages of volcanic rocks were measured to be 79.4 m.y. near Daegu, and 61.7 m.y. near Busan indicating a southeastward decrease in age. The ages of plutonic rocks also decrease toward the same direction with 73 m.y. near Daegu, and 58 m.y. near Busan, so that the volcanism predated the plutonism by 6 m.y. in the continental interior and 4 m.y. along the coast. Such igneous activities provide a positive evidence for an applicability of plate tectonics to this area. 5. Sulfur isotope analyses of sulfide minerals from 8 mines revealed that these deposits were genetically connected with the spacially associated ingeous rocks showing relatively narrow range of ${\delta}^{34}S$ values (-0.9‰ to +7.5‰ except for +13.3 from Mulgum Mine). A sequence of metallogenic zones from the coast to the inland is delineated to be in the order of Fe-Cu zone, Cu-Pb-Zn zone, and W-Mo zone. A few porphyry type copper deposits are found in the Fe-Cu zone. These two facts enable the sequence to be comparable with that of Andean type in South America. 6. The VGP's of Cretaceous and post Cretaceous rocks from Korea are located near the ones($71^{\circ}N$, $180^{\circ}E$ and $90^{\circ}N$, $110^{\circ}E$) obtained from continents of northern hemisphere. This suggests that the Korean peninsula has been stable tectonically since Cretaceous, belonging to the Eurasian continent. 7. Different polar wandering path between Korean peninsula and Japanese islands delineates that there has been some relative movement between them. 8. The variational feature of declination of NRM toward northwestern inland side from southeastern extremity of Korean peninsula suggests that the age of rocks becomes older toward inland side. 9. The geological structure(mainly faults) and trends of lineaments interpreted from the Landsat imagery reveal that NNE-, NWW- and NEE-trends are predominant in the decreasing order of intensity. 10. The NNE-trending structures were originated by tensional and/or compressional forces, the directions of which were parallel and perpendicular respectively to the subduction boundary of the Kula plate during about 90 m.y. B.P. The NWW-trending structures were originated as shear fractures by the same compressional forces. The NEE-trending structures are considered to be priginated as tension fractures parallel to the subduction boundary of the Kula plate during about 70 m.y. B.P. when Japanese islands had drifted toward southeast leaving the Sea of Japan behind. It was clearly demonstrated by many authors that the drifting of Japanese islands was accompanied with a rotational movement of a clock-wise direction, so that it is inferred that subduction boundary had changed from NNE- to NEE-direction. A number of facts and features mentioned above provide a suite of positive evidences enabling application of plate tectonics to the late Cretaceous-early Tertiary igneous activity and metallogeny in the area. Synthesizing these facts, an arc-trench system of continental margin-type is adopted by reconstructing paleogeographic models for the evolution of Korean peninsula and Japan islands. The models involve an extention mechanism behind the are(proto-Japan), by which proto-Japan as of northeastern continuation of Gyongsang zone has been drifted rotationally toward southeast. The zone of igneous activity has also been migrated from the inland in late-Cretaceous to the peninsula margin and southwestern Japan in Tertiary.

• 한국위성정보통신학회논문지
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• 제1권2호
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• pp.95-100
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• 2006

통신해양기상위성의 전력계는 향상된 Eurostar 3000 버전에 바탕을 두고 있다. Eurostar 3000 전력계는 정상상태 또는 하나의 결함에서도 자율적으로 동작하며 높은 수준의 재구성 능력 및 유연성을 제공한다. 본 논문에서는 통신해양기상위성 전력계 예비설계 결과를 소개한다. 통신해양기상위성 전력계는 하나의 배터리, 태양전지어레이 윙, 전력공급기, 파이로 유닛 및 태양전지어레이 구동기 그리고 릴레이 및 퓨즈 브래킷 들로 구성된다. 통신해양기상위성 전력계는 3 kW의 버스 전력을 제공할 수 있다. 태양전지어레이는 2개의 태양전지판으로 구성된 전개할 수 있는 윙으로 구성된다. 태양전지는 GaAs/Ge 3중 접합 셀로 선정되었다. Li-ion 배터리는 10개의 직렬 연결된 셀 모듈로 구성되며 각 모듈은 셀 5개가 병렬로 연결된다. 전력공급기는 태양전지어레이 및 배터리와 함께 50 V로 완전 정류된 하나의 전력 버스를 생성한다. 전력 버스는 릴레이 및 퓨즈 브래킷 들에 의해 중앙 집중되어 보호되고 분배된다. 파이로 유닛은 점화 작동기 장치로 전력을 공급한다. 태양전지어레이는 자세제어계의 제어로 태양전지어레이 구동기에 의해 회전된다. 전력계의 제어 및 감시는, 특히 배터리, 전력공급기와 탑재 소프트웨어의 결합으로 수행된다.

• The Korean Journal of Physiology and Pharmacology
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• 제4권1호
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• pp.33-40
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• 2000

This study was designed to clarify the mechanism of the inhibitory action of a nitric oxide (NO) donor, 3-morpholino-sydnonimine (SIN-1), on contraction, cytosolic $Ca^{2+}$ level $([Ca^{2+}]_i)$ and ionic currents in guinea-pig ileum. SIN-1 $(0.01{\sim}100\;{\mu}M)$ inhibited 25 mM KCl- or histamine $(10\;{\mu}M)-induced$ contraction in a concentration-dependent manner. SIN-1 reduced both the 25 mM KCl- and the histamine-stimulated increases in muscle tension in parallel with decreased $[Ca^{2+}]_i.$ Using the patch clamp technique with a holding potential of -60 mV, SIN-1 $(10\;{\mu}M)$ decreased peak Ba currents $(I_{Ba})$ by $30.9{\pm}5.4%$ (n=6) when voltage was stepped from -60 mV to +10 mV and this effect was blocked by ODQ $(1\;{\mu}M),$ a soluble guanylyl cyclase inhibitor. Cu/Zn SOD (100 U/ml), the free radical scavenger, had little effect on basal $I_{Ba},$ and SIN-1 $(10\;{\mu}M)$ inhibited peak $I_{Ba}$ by $32.4{\pm}5.8%$ (n=5) in the presence of Cu/Zn SOD. In a cell clamped at a holding-potential of -40 mV, application of $10\;{\mu}M$ histamine induced an inward current. The histamine-induced inward current was markedly and reversibly inhibited by $10\;{\mu}M$ SIN-1, and this effect was abolished by ODQ $(1\;{\mu}M).$ In addition, SIN-1 markedly increased the depolarization-activated outward $K^+$ currents in the all potential ranges. We concluded that SIN-1 inhibits smooth muscle contraction mainly by decreasing $[Ca^{2+}]_i$ resulted from the inhibition of L-type $Ca^{2+}$ channels and the inhibition of nonselective cation currents and/or by the activation of $K^+$ currents via a cGMP-dependent pathway.

• 한국영양학회:학술대회논문집
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• 한국영양학회 1995년도 추계학술대회 초록
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• pp.11-34
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• 1995

Growth hormone (GH) plays a key role in regulating postnatal growth and can stimulate growth of animals by acting directly on specific receptors on the plasma membrane of tissues or indirectly through stimulating insulin-like growth factor (IGF)-I synthesis and secretion by the liver and other tissues. IGF-I and IGF-Ⅱ are polypeptides with structural similarity with proinsulin that stimulate cell proliferation by endocrine, paracrine and autocrine mechanisms. The initial event in the metabolic action of IGFs on target cells appears to be their binding to specific receptors on the plasma membrane. Current evidence indicates that the mitogenic actions of both IGFs are mediated primarily by binding to the type I IGF receptors, and that IGF action is also mediated by interactions with IGF-binding proteins (IGFBPs). Six distinct IGFBPs have been identified that are characterized by cell-specific interaction, transcriptional and post-translational regulation by many different effectors, and the ability to either potentiate or inhibit IGF actions. Nutritional deficiencies can have their devastating consequence during growth. Although IGF-I is the major mediator of GH's action on somatic growth, nutritional status of an organism is a critical regulator of IGF-I and IGFBPs. Various nutrient deficiencies result in decreased serum IGF-I levels and altered IGFBP levels, but the blood levels of GH are generally unchanged or elevated in malnutrition. Effects of protein, energy, vitamin C and D, and zinc on serum IGF and IGFBP levels and tissue mRNA levels were reviewed in the text. Multiple factors are involved in the regulation of intestinal epithelial cell growth and differentiation. Among these factors the nutritional status of individuals is the most important. The intestinal epithelium is an important site for mitogenic action of the IGFs in vivo, with exogenous IGF-I stimulating mucosal hyperplasia. Therefore, the IGF system appears to provide and important mechanism linking nutrition and the proliferation of intestinal epithelial cells. In order to study the detailed mechanisms by which intestinal mucosa is regulated, we have utilized IEC-6 cells, an intestinal epithelial cell line and Caco-2 cells, a human colon adenocarcinoma cell line. Like intestinal crypt cells analyzed in vivo or freshly isolated intestinal epithelial cells, IEC-6 cells and Caco-2 cells possess abundant quatities of both type Ⅰ and type Ⅱ IGF receptors. Exogenous IGFs stimulate, whereas addition of IGFBP-2 inhibits IEC-6 cell proliferation. To investigate whether endogenously secreted IGFBP-2 inhibit proliferation, IEC-6 cells were transfected with a full-length rat IGFBP-2 cDNA anti-sense expression construct. IEC-6 cells transfected with anti-sense IGFBP-2 protein in medium. These cells grew at a rate faster than the control cells indicating that endogenous IGFBP-2 inhibits proliferation of IEC-6 cells, probably by sequestering IGFs. IEC-6 cells express many characteristics of enterocyte, but do not undergo differentiation. On the other hand, Caco-2 cells undergo a spontaneous enterocyte differentiation. On the other hand, Caco-2 cells undergo a spontaneous enterocyte differentiation after reaching confluency. We have demonstrated that Caco-2 cells produce IGF-Ⅱ, IGFBP-2, IGFBP-3, and an as yet unidentified 31,000 Mr IGFBP, and that both mRNA and peptide secretion of IGFBP-2 and IGFBP-3 increased, but IGFBP-4 mRNA and protein secretion decreased after the cells reached confluency. These changes occurred in parallel to and were coincident with differentiation of the cells, as measured by expression of sucrase-isomaltase. In addition, Caco-2 cell clones forced to overexpress IGFBP-4 by transfection with a rat IGFBP-4 cDNA construct exhibited a significantly slower growth rate under serum-free conditions and had increased expression of sucrase-isomaltase compared with vector control cells. These results indicate that IGFBP-4 inhibits proliferation and stimulates differentiation of Caco-2 cells, probably by inhibiting the mitogenic actions of IGFs.

• 한방재활의학과학회지
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• 제19권2호
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• pp.125-156
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• 2009

Objectives : To research the trend of studies related to rheumatoid arthritis and to indicate the hereafter direction for its study in oriental medicine and its treatment. Methods : I reviewed 75 domestic oriental medical journals, and 50 medical journals about rheumatoid arthritis published after 2004, and comparative analysis was made. And these theses were classified by college, year, field of study, subject. Results : The following are the results of this study. 1. Classified by oriental medical college, Dae-jeon college published the most theses, followed by Dong-guk, Kyung-hee, Se-myung and Dong-shin college. Han-yang college published the most theses among college of medicine. 2. Classified by type of thesis, experimental theses(70 pieces, 94%) showed higher rate than that of clinical theses(4 pieces, 5%) in oriental medical studies. However, in medical studies, clinical theses(34 pieces, 68%) showed higher rate than that of experimental theses(15 pieces, 30%). 3. Analyzed by subject, the most dealt subject in oriental medicine was herb medication, followed by herbal acupuncture, single herb, electroacupuncture, sasang & gene, acupuncture & moxibustion, complex accordingly. The most dealt subject in medical clinical journals was standards of diagnosis & prognosis, followed by medication, gene analysis, pathogenesis, clinical pattern, operative treatment and complication accordingly. 4. In theses related to herb medication, most of the subject was to evaluate anti-inflammatory and immunoregulatory effects of herb medication with geopungseup, jibitong, hwalhyeolgeoer function. The tendency of experimental methods was focusing on understanding anti-inflammatory and immunoregulatory mechanisms through molecular biologic methods by analyzing cytokine and gene. 5. Most of theses related to herbal acupuncture were experimental studies verifying ant-inflammatory and immnoregulatory effects through methods observing change of cytokine and immunoregulatory factors. Regarding remedies for herbal acupuncture, Ulmus davidiana Planch was most preferred, followed by bee venom. 6. In theses related to single herb, Boik-yak was most prefered, followed by Geopungseup-yak and Hwalhyeolgeoer-yak. Regarding methods of research, there were tendency of shifting from methods verifying travail, anti-inflammatory and anti-pyretic effects through a test of behavior, morphometry, serology and temperature measurement of the rectum and the skin into verifying anti-inflammatory and immunoregulatory effects through observing inflammatory cytokine in the joint and cells of spleen. 7. In theses related to electroacupuncture, ST36 and adjuvant were most preferred as acupoints and induced factor. The tendency of experimental methods was turning from verifying mechanism of travail effect to analyzing inflammation and pain inducing factors. 8. Diverse medical clinical studies were published. Subjects such as diagnosis and prognosis, medication, gene analysis, clinical pattern, operational treatment, complication and pathogenesis were published. Especially, studies about standards of early diagnosis, and research on possible parallel medications with methotrexate were actively inquired. 9. Most of theses related to medical experimental studies was about mediators and receptors related to inflammatory induction and osteoclasia mechanism. Also, it was presented blockage of them can be effective on rheumatoid arthritis. Conclusions : The oriental medicine studies have merit in its diversity of treatment, but it clinical studies is lacking compared to experimental studies. Also, more diversity of subjects is necessary. Therefore, complementary measures are needed. Hereafter, oriental medicine research about rheumatoid arthritis needs more clinical research verifying the effectiveness and safety in clinical field. Also, we require oriental medical standard of diagnosis and researches on pathological generation which would make early checkup and prognosis possible.