Model-based Gradient Compensation in Spiral Imaging (나선주사영상에서 모델 기반 경사자계 보상)
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- Investigative Magnetic Resonance Imaging
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- v.13 no.1
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- pp.15-21
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- 2009
Purpose : A method to estimate a real k-space trajectory based on a circuit model of the gradient system is proposed for spiral imaging. The estimated k-space trajectory instead of the ideal trajectory is used in the reconstruction to improve the image quality in the spiral imaging. Materials and Methods : Since the gradient system has self resistance, capacitance, and inductance, as well as the mutual inductance between the magnet and the gradient coils, the generated gradient fields have delays and transient responses compared to the input waveform to the gradient system. The real gradient fields and their trajectory in k-space play an important role in the reconstruction. In this paper, the gradient system is modeled with R-L-C circuits, and real gradient fields are estimated from the input to the model. An experimental method to determine the model parameters (R, L, C values) is also suggested from the quality of the reconstructed image. Results : The gradient fields are estimated from the circuit model of the gradient system at 1.5 Tesla MRI system. The spiral trajectory obtained by the integration of the estimated gradient fields is used for the reconstruction. From experiments, the reconstructed images using the estimated trajectory show improved uniformity, reduced overshoots near the edges, and enhanced resolutions compared to those using the ideal trajectory without model. Conclusion : The gradient system was successfully modeled by the R-L-C circuits. Much improved reconstruction was achieved in the spiral imaging using the trajectory estimated by the proposed model.
The precipitation of calcium phosphate on implant surface has been known to accelerate osseointegration and to enhance osseous adaptation. The present study was performed to examine whether the precipitation of calcium phosphate on Ti-6Al-4V alloy could be affected by the immersion in NaOH solution and heat treatment. Ti-6Al-4V alloy plates of
This paper aims to explain the safety assessment and remediation mechanism of Granulated Coal Ash (GCA) as a material for the remediation of coastal sediments and to evaluate the improvement of the sediment in Kaita Bay, where GCA was applied. The concentrations of heavy metal contained in GCA and the dissolved amounts of heavy metal from GCA satisfied the criteria for soil and water pollution in Japan. The mechanisms on the remediation of coastal sediments using GCA is summarized as follows; (1) removal of phosphate and hydrogen sulfide (2) neutralization of acidic sediment (3) oxidation of reductive sediment (4) increase of water permeability (5) increase of soil strength (6) material for a base of seagrass. From the results obtained from the field experiment carried out in Kaita Bay, it was clarified that GCA is a promizing material for remediation of coastal sediment. This remediation technology can contribute to promote waste reduction in society and to decrease cost of coastal sediment remediation by applying GCA in other polluted coastal areas.
A new Korean standard for the determination of Cr(VI) in soils has been officially published as ES 07408.1 in 2009. This analytical method is based on the hot alkaline digestion and colorimetric detection prescribed by U.S. EPA method 3060A and 7196A. The hot alkaline digestion accomplished using 0.28 M
In this paper, we develop a cost effective and disposable voltammetric sensing platform involving screen-printed carbon electrode (SPCE) modified with the nanocomposites composed of multi-walled carbon nanotubes, polyelectrolyte, and tyrosinase for bisphenol A. This is known as an endocrine disruptor which is also related to chronic diseases such as obesity, diabetes, cardiovascular and female reproductive diseases, precocious puberty, and infertility. A negatively charged oxidized multi-walled carbon nanotubes (MWCNTs) wrapped with a positively charged polyelectrolyte, e.g., polydiallyldimethylammonium, was first wrapped with a negatively charged tyrosinae layer via electrostatic interaction and assembled onto oxygen plasma treated SPCE. The nanocomposite modified SPCE was then immersed into different concentrations of bisphenol A for a given time where the tyrosinase reacted with OH group in the bisphenol A to produce the product, 4,4'-isopropylidenebis(1,2-benzoquinone). Cyclic and differential pulse voltammetries at the potential of -0.08 V vs. Ag/AgCl was employed and peak current changes responsible to the reduction of 4,4'-isopropylidenebis(1,2-benzoquinone) were measured which linearly increased with respect to the bisphenol A concentration. In addition, the SPCE based sensor showed excellent selectivity toward an interferent agent, bisphenol S, which has a very similar structure. Finally, the sensor was applied to the analysis of bisphenol A present in an environmental sample solution prepared in our laboratory.
In this paper, parameter characteristics such as pH effect, isotherm, kinetic and thermodynamic parameters and competitive adsorption of dyes including malachite green (MG), direct red 81 (DR 81) and thioflavin S (TS), which have different functional groups, being adsorbed onto activated carbon were investigated. Langmuir, Freundlich and Temkin isotherm models were employed to find the adsorption mechanism. Effectiveness of adsorption treatment of three dyes by activated carbon were confirmed by the Langmuir dimensionless separation factor. The mechanism was found to be a physical adsorption which can be verified through the adsorption heat calculated by Temkin equation. The adsorption kinetics followed the pseudo second order and the rate limiting step was intra-particle diffusion. The positive enthalpy and entropy changes showed an endothermic reaction and increased disorder via adsorption at the S-L interface, respectively. For each dye molecule, negative Gibbs free energy increased with the temperature, which means that the process is spontaneous. In the binary component system, it was found that the same functional groups of the dye could interfere with the mutual adsorption, and different functional groups did not significantly affect the adsorption. In the ternary component system, the adsorption for MG lowered a bit, likely to be disturbed by the other dyes meanwhile DR 81 and TS were to be positively affected by the presence of MG, thus resulting in much higher adsorption.
Background: This paper deals with the study of natural radioactivity in rocks from Ogun State in Southwestern Nigeria. The aim is to determine radiation emissions from rocks in order to estimate radiation hazard indices. Objectives: The following objectives were targeted: 1. To determine radiation emissions from each type of rocks; 2. To estimate radiation hazard indices based on the rocks; 3. To correlate the activity concentrations of radionuclides with major oxides. Methods: The samples were analyzed using a NaI (Tl) gamma ray spectrometric detector and PerkinElmer AAnalyst 400 AAS spectrometer. Results: The activity of 40K, 226Ra, and 232Th were found in order of decreasing magnitude from pegmatite>granite>migmatite. In contrast, lower concentrations were found in shale, phosphate, clay stone, sandstone and limestone. The mean absorbed doses were 125±23 nGyh-1 (migmatite), 74±13 nGy/h (granite), 72±13 nGyh-1 (pegmatite), 64±09 nGyh-1 (quartzite), 45±16 nGyh-1 (shale), 41±09 nGyh-1 (limestone), 41±11 nGyh-1 (clay stone), 24±03 nGyh-1 (phosphate), and 21±10 nGyh-1 (sandstone). The outdoor effective dose rates in all rock samples were slightly higher than the world average dose value of 0.34 mSvy-1. The percentage composition of SiO2 in the rock samples was above 50 wt% except for in the limestone, shale and phosphate. Al2O3 ranged from 4.10~21.24 wt%, Fe2O3 from 0.39~7.5 wt%, and CaO from 0.09-46.6 wt%. In addition, Na2O and K2O were present in at least 5 wt%. Other major oxides, including TiO2, P2O5, K2O, MnO, MgO and Na2O were depleted. Conclusions: The findings suggest that Ogun State may be described as a region with elevated background radiation. It is recommended that houses should be constructed with good cross ventilation and residences should use home radiation monitoring instruments to monitor radon emanating from walls.
In this paper, twenty-five kinds of food presented in Sooljip(戌集) 5 and 6 of Food collections of 'Kosa-sibi Jip(攷事十二集)' have been classified into four : Staple food, subsidiary food, Tuck(rice cake) and Han-gwa(Korean confectionery), and Tang-jng and tea. Cooking processes have been examined and scientifically analyzed in terms of cooking, Fourteen kinds of Jook (thick gruel with cereal) as well as Urak-Jook were presented among the methods of making Jook, one of staple foods. Milk and ground rice were boiled together into Urak-Jook, which was nutritious because of carbohydrate, added to milk. Hong-sa Myun was mode of ground shrimps, ground bean, ground rice and flour which were kneaded together. It was a nutritiously balanced food. Nineteen kinds of Kimchi presented in this book were classified by the recipes. The five of Jook-soon Ja, U-so Ja, Tam-bok Ja and Jo-gang were made by adding red malt and cereals(boiled rice or candies). Jo-gang, Jo-ga and Jo-gwa-chae were made by adding salt and rice wine. With salt and fermenters added, eight were made. Chim-jup-jeo-ga was made by adding Jang(soy-bean sauce) and the inner chaff of wheat instead of salt. The four of Ka-za-san, Hwang-gwa-san, Tong-gwa-san and Jo-gang were made by adding salt and vinegar. Jo-gang was made by adding salt, rice wine, residue of rice wine and candies. The four of Kae-mal-ga, Ku-cho-chim-chae, Un-gu-hwa and Suk-hwa-chim-chim-chae were made by adding salt and spices. San-got-Kimchi was made without salt. San-got-Kimchi and Suk-hwa-chim-chae were made originally in Korea. Suk-hwa-chim-chae, in particular, was first classified as a kind of Kimchi in this book and oysters were added, which is notable. Pork could be preserved longer when smoked oven the weak fire of thatch ten days and nights. Dog meat was sauced and placed on the bones in a pot. A porcelain was put on the top of the pot. Flour paste sealed the gap between the porcelain and the pot. Some water was poured into the porcelain, and the meat was steamed, with two or three thatched sacks burned, which was a distilled dry steaming. This process has been in use up to now. Various cooking methods of chicken were presented from in Umsik-dimi-bang to in Chosun Musang Sinsik Yori Jebup. These methods were ever present regardless of ages. Such measuring units as Guin(斤) and Nyang(兩) were most frequently used in cooking processes of this book, except in case of Jang(soy bean sauce), vinegar and liquor. Twenty eight kinds of kitchenware and cookers were used, of which porcelains wee most used and pans and sieves followed. The scientific eight cooking methods were as follows. First, salt was refined through saturated solution. Next, it was recommended Hong-sa Myun containing shrimps should not be taken along with pork, which is thought to be a proper diet in terms of cholesterol contained by shrimps and pork. Third, meat was coated with thin gruel and quickly roasted and cleared of the dried gruel membrane, which prevented nutrients from exuding and helped to make the meat well-done. Fourth, The fruit of paper mulberry trees has the protease which can soften meat. Therefore when meat was boiled with th fruit of paper mulberry trees, it can be softened easily. Fifth, pork was smoked over the weak fire of thatch. Sixth, in cooking dog meat, distilled dry steaming raised the boiling point and made it possible to preserve meat longer. Seventh, in boiling the sole of a bear, lime was added, which made meat tender by making the pH lower or higher than that of raw meat. Finally, in boiling down rice gluten, a porcelain in the pot prevented boiling over the brim, which is applied to pots in which to boil medical herbs.
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70