• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.11
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• pp.1-10
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• 2007

In this paper, we proposed channel estimation scheme for LR-UWB system which has low data rate for WPAN in IEEE 802.15.4a. At the transmitter, we proposed dynamic power level allocation depends on channel condition in specific period when we modulate signal. We use two orthogonal code to estimate channel at once. It can estimate channel more accurately by using two code which shows good correlation characteristic then it can estimate more accurately by spreading gain. Using estimated channel condition, we synchronize symbol timing of transmitted signal. Then determined power allocation scheme and channel information is transmitted to transmiter side. Finally, using these information, transmiter side change the power level of repeated pulse to adopt to channel condition. Simulation is performed under S-V channel for LR-WPAN in IEEE 802.15.4a and we compare the performance with a different type of receiver type. We use coherent and non-coherent method at the receiver. Simulation result shows us at the NLOS channal performance evaluation is greater than that of LOS channel and the result is independent of receiver type. In the NLOS channel, as the signal delay spreading is big, performance evaluation is also increased.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.618-628
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• 1998

Pure CaO, Mn-doped CaO, Mn/CaO, and K/CaO catalysts were prepared and tested as catalysts for the oxidative coupling of methane in the temperature range of 600 to 800$^{\circ}C$ to investigate the effects of Mn- and K-addition on the catalytic activity of calcium oxide. To characterize the catalysts, X-ray powder diffraction(XRD), XPS, SEM, DSC, and TG analyses were performed. The catalytic reaction was carried out in a single-pass flow reactor using on-line gas chromatography system. Normalized reaction conditions were generally $p(CH_4)/p(O_2)=250$ Torr/50 Torr, total feed flow rate=30 mL/min, and 1 atm of total pressure with He being used as diluent gas. Among the catalysts tested, 6.3 mol% Mn-doped CaO catalyst showed the best $C_2$ yield of 8.0% with a selectivity of 43.2% at 775$^{\circ}C$. The $C_2$ selectivity increased on lightly doped CaO catalysts, while decreased on heavily doped CaO([Mn] > 6.3 mol%) catalysts. 6 wt.% Mn/CaO and 6 wt.% K/CaO catalysts showed the $C_2$ selectivities of 13.2% and 30.9%, respectively, for the reaction. Electrical conductivities of CaO and Mn-doped CaO were measured in the temperature range of 500 to 1000$^{\circ}C$ at Po2's of $10^{-3}\; to\;10^{-1}\;atm.$ The electrical conductivity was decreased with Mn-doping and increased with increasing $P0_2$in the range of $10^{-3}\;to\;10^{-1}\;atm,$ indicating the specimens to be p-type semiconductors. It was suggested that the interstitial oxygen ions formed near the surface can activate methane and the formation of interstitial oxygen ions was discussed on the basis of solid-state chemistry.

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.1-6
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• 2002

Al$\^$3+/ substituted garnet Y$_3$Fe$\_$5-x/Al$\_$x/O$\_$12/ (x=0.0, 0.25, 0.5, 0.75, 1.0) was fabricated by sol-gel method. The crystallographic and magnetic properties of Y$_3$Fe$\_$5-x/Al$\_$x/O$\_$12/ have been studied with Mossbauer spectroscopy, x-ray diffraction (XRD), thermogravimetry analysis (TGA), differential thermal analysis (DTA), and vibrating samples magnetometer (VSM). The crystal structure of Y$_3$Fe$\_$5/O$\_$12/ is found to be a cubic with the lattice constant a$\_$0/= 12.381$\pm$0.005 $\AA$. The lattice constants a$\_$0/ decreases linearly from 12.381 to 12.304 A as the Al concentration (x) increases from x=0.0 to 1.0. Mossbauer spectra of measured at Y$_3$Fe$\_$5-x/A1$\_$x/O$\_$12/ various absorber temperatures of 13 to 600 K. Mossbauer spectrum for x = 0.0 is consist of well resolved two sets of six line patterns. While with increasing Al concentration outer sextet patters, which is originating from octahedral sites, broadens widely. These phenomena are interpreted in terms of random probability distributions of Fe$\^$3+/ and Al$\^$3+/ in tetrahedral site.

• Journal of radiological science and technology
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• v.41 no.5
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• pp.493-504
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• 2018

The diagnostic radiation equipment is managed in accordance with the "Rules for Safety Management of Diagnostic Radiation Equipment" enacted in 1995. The equipments should be inspected before use and every three years after use in accordance with the [Appendix 1] of the same rule. The inspection standard has been maintained without particular revision since enacted. But, over the past two decades new types of equipments have been manufactured and used. So, it is necessary to revise [Appendix 1] by making inspection items and inspection standards. In this study, we revised the classification system of equipments and reviewed international standards of IEC 60601 series, IEC 61223 series and AAPM TG 18 On-line Report No.03. And identified the problem of current inspection standards. Through this, we revised, deleted and added the inspection items and inspection standard of each equipment to meet the domestic circumstances. As a result of the study, we reorganized the classification system of equipment which are current classified as 5 classes into 22 classes as X-ray system etc. (7 classes), CT system etc. (5 classes) and Dental X-ray system etc. (10 classes). And then, we developed 70 inspection items for 6 types of equipments according to the reorganized classification system of equipments. The inspection items and inspection standards derived from this study have been proposed to the KCDC and will be applied to the revision of the Rule's [Appendix 1]. Therefore, we expect to be used as reference materials for domestic medical center, inspection institutions, and equipment manufacturing import companies.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.6
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• pp.333-339
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• 2005

B/K protein is a novel protein containing double C2-like domains. We examined the specific signaling pathway that regulates the transcription of B/K in PC12 cells. When the cells were treated with forskolin ($50{\mu}M$), B/K mRNA and protein levels were time-dependently decreased, reaching the lowest level at 3 or 4 hr, and thereafter returning to the control level. Chemicals such as dibutyryl-cAMP, cellpermeable cyclic AMP (cAMP) analogue and CGS21680, adenosine receptor $A_{2A}$ agonist, also repressed the B/K transcription. However, 1,9-dideoxyforskolin did not show inhibitory effect on B/K transcription, suggesting direct involvement of cAMP in the forskolin-induced inhibition of B/K transcription. Effect of forskolin, dibutyryl cAMP and CGS21680 was significantly reduced in PKA-deficient PC12 cell line (PC12-123.7). One cAMP-response element (CRE)-like sequence (B/K CLS) was found in the promoter region of B/K DNA, and electrophoretic mobility shift assay indicated its binding to CREM and CREB. Forskolin significantly suppressed the promoter activity in CHO-K1 cells transfected with the constructs containing B/K CLS, but not with the construct in which B/K CLS was mutated (AC：TG). Taken together, we suggest that the transcription of B/K gene in PC12 cells may be regulated by PKA-dependent mechanism.

• Biomolecules & Therapeutics
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• v.26 no.5
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• pp.512-519
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• 2018

Phthalates widely used in the manufacture of plastics have deeply penetrated into our everyday lives. Recently, a concern over the toxicity of phthalates on thyroid, has been raised but in most of cases, the doses employed were unrealistically high. To investigate the effects of phthalates on thyroid, we investigated the effects of the repeated oral exposure to low to high doses (0.3, 3, 30 and 150 mg/kg) di-2-ethylhexylphthalate (DEHP) from weaning to maturity for 90 days in juvenile rats on the thyroid. The histological examination revealed that DEHP significantly induced hyperplasia in the thyroid from the doses of 30 mg/kg, which was confirmed with Ki67 staining. In line with this finding, increased mRNA expression of thyrotropin releasing hormone (Trh) was observed in the thyroid of female at 0.3 mg/kg and 150 mg/kg as determined by RNAseq analysis. Moreover, significantly increased expression of parathyroid hormone (Pth) in the female at 0.3 mg/kg, and thyroglobulin (Tg) and thyroid hormone responsive (Thrsp) in the male at 0.3 mg/kg were noted in the blood, of which changes were substantially attenuated at 150 m/kg, alluding the meaningful effects of low dose DEHP on the thyroid hormone regulation. Urinary excretion of mono-2-ethylhexyl-phthalate (MEHP), a major metabolite of DEHP was determined to be 4.10 and 12.26 ppb in male, 6.65 and 324 ppb in female at 0.3 and 30 mg/kg DEHP, respectively, which fell within reported human urine levels. Collectively, these results suggest a potential adverse effects of low dose phthalates on the thyroid.

• Journal of Korean Neurosurgical Society
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• v.67 no.5
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• pp.510-520
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• 2024

Objective : Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases, characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. The treatment of PD aims to alleviate motor symptoms by replacing the reduced endogenous dopamine. Currently, there are no disease-modifying agents for the treatment of PD. Zebrafish (Danio rerio) have emerged as an effective tool for new drug discovery and screening in the age of translational research. The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is known to cause a similar loss of dopaminergic neurons in the human midbrain, with corresponding Parkinsonian symptoms. L-type calcium channels (LTCCs) have been implicated in the generation of mitochondrial oxidative stress, which underlies the pathogenesis of PD. Therefore, we investigated the neuro-restorative effect of LTCC inhibition in an MPTP-induced zebrafish PD model and suggested a possible drug candidate that might modify the progression of PD. Methods : All experiments were conducted using a line of transgenic zebrafish, Tg(dat:EGFP), in which green fluorescent protein (GFP) is expressed in dopaminergic neurons. The experimental groups were exposed to 500 μmol MPTP from 1 to 3 days post fertilization (dpf). The drug candidates : levodopa 1 mmol, nifedipine 10 μmol, nimodipine 3.5 μmol, diethylstilbestrol 0.3 μmol, luteolin 100 μmol, and calcitriol 0.25 μmol were exposed from 3 to 5 dpf. Locomotor activity was assessed by automated tracking and dopaminergic neurons were visualized in vivo by confocal microscopy. Results : Levodopa, nimodipine, diethylstilbestrol, and calcitriol had significant positive effects on the restoration of motor behavior, which was damaged by MPTP. Nimodipine and calcitriol have significant positive effects on the restoration of dopaminergic neurons, which were reduced by MPTP. Through locomotor analysis and dopaminergic neuron quantification, we identified the neuro-restorative effects of nimodipine and calcitriol in zebrafish MPTP-induced PD model. Conclusion : The present study identified the neuro-restorative effects of nimodipine and calcitriol in an MPTP-induced zebrafish model of PD. They restored dopaminergic neurons which were damaged due to the effects of MPTP and normalized the locomotor activity. LTCCs have potential pathological roles in neurodevelopmental and neurodegenerative disorders. Zebrafish are highly amenable to high-throughput drug screening and might, therefore, be a useful tool to work towards the identification of disease-modifying treatment for PD. Further studies including zebrafish genetic models to elucidate the mechanism of action of the disease-modifying candidate by investigating Ca2+ influx and mitochondrial function in dopaminergic neurons, are needed to reveal the pathogenesis of PD and develop disease-modifying treatments for PD.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.743-760
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• 1997

This study was done to evaluate the correlations between the size, the form of the cranial base, head posture and the horizontal and vertical position of craniofacial structures. For this purpose, 100 cephalometric radiographs were taken from the sample composed of 51 male and 49 female, 12 measurement criteria and 37 reference points were established and digitized, then calculation was performed for the values of measurement variables and the horizontal and vertical position of reference points. The correlations be4ween them were analyzed statistically and mean facial diagrams were constructed and compared with the selected groups which were composed of 10 Samples each as large and small group from the measurement value. The following results were obtained: 1. The angles n-s-ba and n-s-ar as variables for the ion of cranial base correlated highly to the horizontal and vertical position of reference points in the cervical column with statistical significance($0.1\%$ level). 2. The angles n-s-ba and n-s-ar as variables for the form of cranial base correlated to the horizontal position of the reference points in the facial structure with statistical significance($1\%$ level), but not to the vertical position of them($5\%$ level). 3. The length n-s, s-ba, and n-ar as variables for the size of cranial base were correlated th the position of craniofacial structures in various ways, but in general, highly correlated to the horizontal and vertical position of midfacial structures around the teeth and alveolar area. 4. the angle NSL/CVT and NSL/OPT as postural variables tot the inclination of cranial base and cervical column were correlated to the horizontal position of the craniofacial structures with statistical significance($1\%$ level), but not to the vortical position of them($5\%$ level). 5. The angle OPT/HOR and CVT/HOR as postural variables lot the inclination of cranial base and true horizontal line were not correlated to the horizontal and vertical position of the craniofacial structures with statistical significance($5\%$ level). 6. The correlation between the measurement variables and horizontal and vortical positions of the reference poits in soft tissue were shown as similar to the related hard tissue points.