• Title/Summary/Keyword: true density

Search Result 164, Processing Time 0.026 seconds

Evaluation of Corrected Dose with Inhomogeneous Tissue by using CT Image (CT 영상을 이용한 불균질 조직의 선량보정 평가)

  • Kim, Gha-Jung
    • The Journal of Korean Society for Radiation Therapy
    • /
    • v.18 no.2
    • /
    • pp.75-80
    • /
    • 2006
  • Purpose: In radiation therapy, precise calculation of dose toward malignant tumors or normal tissue would be a critical factor in determining whether the treatment would be successful. The Radiation Treatment Planning (RTP) system is one of most effective methods to make it effective to the correction of dose due to CT number through converting linear attenuation coefficient to density of the inhomogeneous tissue by means of CT based reconstruction. Materials and Methods: In this study, we carried out the measurement of CT number and calculation of mass density by using RTP system and the homemade inhomogeneous tissue Phantom and the values were obtained with reference to water. Moreover, we intended to investigate the effectiveness and accuracy for the correction of inhomogeneous tissue by the CT number through comparing the measured dose (nC) and calculated dose (Percentage Depth Dose, PDD) used CT image during radiation exposure with RTP. Results: The difference in mass density between the calculated tissue equivalent material and the true value was ranged from $0.005g/cm^3\;to\;0.069g/cm^3$. A relative error between PDD of RTP and calculated dose obtained by radiation therapy of machine ranged from -2.8 to +1.06%(effective range within 3%). Conclusion: In conclusion, we confirmed the effectiveness of correction for the inhomogeneous tissues through CT images. These results would be one of good information on the basic outline of Quality Assurance (QA) in RTP system.

  • PDF

Cancellation of Motion Artifact in MRI (MRI에 있어서 체동 아티팩트의 제거)

  • Kim, Eung-Kyeu
    • Journal of the Institute of Electronics Engineers of Korea SP
    • /
    • v.37 no.3
    • /
    • pp.70-78
    • /
    • 2000
  • In this study, a new method for canceling MRI artifacts through the motion translation of image plane is presented Breathing often makes problems in a clinical diagnosis. Assuming that the head moves up and down due to breathing, rigid translational motions in only y(phase encoding axis) direction are treated Unlike the conventional Iterative phase retrieval algorithm, this method is based on the MRI imaging process and analyzing of Image property A new constraint condition with which the motion component and the true image component in the MRI signal can be separated by a simple algebraic operation is extracted After the x(read out) directional Fourier transformation of MRI signal is done, the y(phase encoding) directional spectrum phasing value is Just an algebraic sum of the Image component and the motion component Meanwhile, as It is known that the density of subcutaneous fat area is almost uniform in the head tomographs, the density distribution along a y directional line on this fat area is regarded as symmetric shape If the density function is symmetric, then the phase of spectrum changes linearly with the position Hence, the departure component from the linear function can be separated as the motion component Based on this constrant condition, the new method of artifact cancellation is presented Finally, the effectiveness of this algorithm IS shown by using a phantom with simulated motions.

  • PDF

Changes in Protease and Formonitrogen of Salted Fish and Shellfish (1) (젓갈 성숙과정(成熟過程)에 있어 Protease 및 Formonitrogen의 변화(變化)에 관(關)한 연구(硏究)(1))

  • Suh, Myung-Jah
    • Journal of Nutrition and Health
    • /
    • v.6 no.2
    • /
    • pp.45-56
    • /
    • 1973
  • Salted fish and shellfish have been widely used in Korea from olden times as side-dishes, although the processes and methods of pickling have varied depending on localities. The common raw materials for these subsidiary food articles include anchovy, shrimp, yellow corvina, oysters, octopus, top-shell, shellfish, pollack roe and pollack intestines. It must be pointed out here, however, that the salted stuffs now marketed locally are highly unscientific and unsanitary in the way they are processed and sold, and this has prompted this writer to undertake a study on these native food articles. The following findings have been obtained from this study on the changes in Formonitrogen and Protease Activity, effected by the density of salt and the degree of storing temperature, of the pickles of cedfish gills, codfish intestines, pollack intestines, shellfish, oysters, cuttle fish and octopus. 1) Codfish Gills The Protease Activity of the pickled codfish gills was greater in the groups of lesser doses of salt and higher degrees of storing temperature. The same was true in the case of Formonifrogen, too. The Formonitrogen of the pickled codfish gills was larger in the groups of lesser salt and higher teimperature. 2) Codfish Intestines The amount of Formonitrogen of the pickled codfiah intestines became greater, as time went by, in the groups of lesser salt than those of larger doses of salt, with the speed of its formation getting faster as the storing temperature rose from $5^{\circ}C$ to $15^{\circ}C$ and $30^{\circ}C$. The Protease Activity was also greater in the groups of lesser salt and higher temperature. The group, stored at 10% salt and $30^{\circ}C$, rotted in five days. 3) Pollack Intestines The amount of Formonitrogen of the pickled pollack intestines was greater in the groups of lesser amount of salt and higher degrees of storing temperature. The Protease Activity of the pickled pollack intestines began decreasing from the 11th day after the pickling in the groups stored at colmparatively high degrees of temperature$(15^{\circ}C-30^{\circ}C)$, while that of the group stored at $5^{\circ}C$ kept rising. The effects of the amount of salt were little. The group stored at 15% salt and $30^{\circ}C$ started rotting on the 13th day while that stored at $30^{\circ}C$ decayed on the 7th day. The group stored at 20% salt and $30^{\circ}C$ rotted on the 9th day. 4) Oysters The amount of Formonitrogen of the pickled oysters became greater as the storing temperature rose and the doses of salt were lowered. The Protease Activity was not affected at any measurable degree by the density of salt in the group stored at $5^{\circ}C$, but became greater as the storing temperature rose to $15^{\circ}C$ and $30^{\circ}C$. The group stored at 10% salt and $30^{\circ}C$ rotted on the 5th day while that stored at 20% salt and $30^{\circ}C$ on the 13th day. 5) Shellfish The amount of Formonitrogen of the pickled shellfish became greater, as time went by, it the groups of lower consistency of salt than the groups of higher density of salt, although the decay of the former groups was faster than the latter groups. The density of salt best fitted for the pickling appeared to be about 20% with the storing temperature to be $15^{\circ}C$, at which the pickled stuff became most tasty on the 7th day. The oysters stored in three groups at $5^{\circ}C$, $15^{\circ}C$ and $30^{\circ}C$ respectively showed the greatest Protease Activity alike at 0% of salt, but the activity declined as the density of salt increased. The Protease Activity of each group rose for the first 11 days after the pickling, but began declining from the 13th day onward, with the groups of higher temperature retaining higher Protease Activity than the groups of lower temperature. 6) Cuttlefish Both the amount of Formonitrogen and the degree of Protease Activity of the pickled cuttlefish were greater in the groups of lower density of salt and higher degree of storing temperature. The oysters pickled at 10% salt and $15^{\circ}C$ degenerated on the 13th day while that of 10% salt and $30^{\circ}C$ deteriorated on the 7th day. 7) Octopus Both the Formonitrogen and the Protease Activity of the pickled octopus were greater in the groups of lower density of salt, but as time went by, the Protease Activity in all groups dwindled after a climbing. In general, the Formonitrogen and the Protease Activity of the pickled oysters became greater as the storing temperature got higher. One group stored at 10% salt and $15^{\circ}C$ rotted in 13days while another group stored at $30^{\circ}C$ decayed in 7 days.

  • PDF

Improving Generalization Performance of Neural Networks using Natural Pruning and Bayesian Selection (자연 프루닝과 베이시안 선택에 의한 신경회로망 일반화 성능 향상)

  • 이현진;박혜영;이일병
    • Journal of KIISE:Software and Applications
    • /
    • v.30 no.3_4
    • /
    • pp.326-338
    • /
    • 2003
  • The objective of a neural network design and model selection is to construct an optimal network with a good generalization performance. However, training data include noises, and the number of training data is not sufficient, which results in the difference between the true probability distribution and the empirical one. The difference makes the teaming parameters to over-fit only to training data and to deviate from the true distribution of data, which is called the overfitting phenomenon. The overfilled neural network shows good approximations for the training data, but gives bad predictions to untrained new data. As the complexity of the neural network increases, this overfitting phenomenon also becomes more severe. In this paper, by taking statistical viewpoint, we proposed an integrative process for neural network design and model selection method in order to improve generalization performance. At first, by using the natural gradient learning with adaptive regularization, we try to obtain optimal parameters that are not overfilled to training data with fast convergence. By adopting the natural pruning to the obtained optimal parameters, we generate several candidates of network model with different sizes. Finally, we select an optimal model among candidate models based on the Bayesian Information Criteria. Through the computer simulation on benchmark problems, we confirm the generalization and structure optimization performance of the proposed integrative process of teaming and model selection.

Uncertainties of SO2 Vertical Column Density Retrieval from Ground-based Hyper-spectral UV Sensor Based on Direct Sun Measurement Geometry (지상관측 기반 태양 직달광 관측장비의 초분광 자외센서로부터 이산화황 연직칼럼농도의 불확실성 분석 연구)

  • Kang, Hyeongwoo;Park, Junsung;Yang, Jiwon;Choi, Wonei;Kim, Daewon;Lee, Hanlim
    • Korean Journal of Remote Sensing
    • /
    • v.35 no.2
    • /
    • pp.289-298
    • /
    • 2019
  • In this present study, the effects of Signal to Noise Ratio (SNR), Full Width Half Maximum (FWHM), Aerosol Optical Depth (AOD), $O_3$ Vertical Column Density ($O_3$ VCD), and Solar Zenith Angle (SZA) on the accuracy of sulfur dioxide Vertical Column Density ($SO_2$ VCD) retrieval have been quantified using the Differential Optical Absorption Spectroscopy (DOAS) method with the ground-based direct-sun synthetic radiances. The synthetic radiances produced based on the Beer-Lambert-Bouguer law without consideration of the diffuse effect. In the SNR condition of 650 (1300) with FWHM = 0.6 nm, AOD = 0.2, $O_3$ VCD = 300 DU, and $SZA=30^{\circ}$, the Absolute Percentage Difference (APD) between the true $SO_2$ VCD values and those retrieved ranges from 80% (28%) to 16% (5%) for the $SO_2$ VCD of $8.1{\times}10^{15}$ and $2.7{\times}10^{16}molecules\;cm^{-2}$, respectively. For an FWHM of 0.2 nm (1.0 nm) with the $SO_2$ VCD values equal to or greater than $2.7{\times}10^{16}molecules\;cm^{-2}$, the APD ranges from 6.4% (29%) to 6.2% (10%). Additionally, when FWHM, SZA, AOD, and $O_3$ VCD values increase, APDs tend to be large. On the other hand, SNR values increase, APDs are found to decrease. Eventually, it is revealed that the effects of FWHM and SZA on $SO_2$ VCD retrieval accuracy are larger than those of $O_3$ VCD and AOD. The SZA effects on the reduction of $SO_2$ VCD retrieval accuracy is found to be dominant over the that of FWHM for the condition of $SO_2$ VCD larger than $2.7{\times}10^{16}molecules\;cm^{-2}$.

Effect of Molecular Sieve of Carbon Granules by Controlling Micropores (미세공 조절에 의한 탄소제립물의 분자체 효과)

  • Kim, Tae-Hwan;Lee, Jae Hoon;Kim, Kweon-Ill;Kim, Jong Huy;Sung, Jae Suk
    • Applied Chemistry for Engineering
    • /
    • v.9 no.6
    • /
    • pp.798-802
    • /
    • 1998
  • Carbon granules were prepared by granulating a mixture of coconut shell powder and coal tar solution, and then by carbonizing at different temperatures. To control micropores of the carbonized granules, the deposition time of benzene vapor under nitrogen atmosphere was varied. For each prepared sample, SEM morphology and true density were investigated. The adsorption rates on the granules were measured with respect to oxygen and nitrogen by means of the Cahn D-200 system. Diffusivity, selectivity and amount of equilibrium adsorption for the gases were obtained from the measurement of adsorption rate. Based on the analysis of the adsorption characteristics, the optimum temperature and the deposition time for preparation of the molecular sieve carbon granules were found to be $800^{\circ}C$ and 10 minutes, respectively. At these optimal conditions, the selectivity coefficient, 26.4, 0f oxygen and nitrogen was obtained.

  • PDF

HMM Topology Optimization using HBIC and BIC_Anti Criteria (HBIC와 BIC_Anti 기준을 이용한 HMM 구조의 최적화)

  • 박미나;하진영
    • Journal of KIISE:Software and Applications
    • /
    • v.30 no.9
    • /
    • pp.867-875
    • /
    • 2003
  • This paper concerns continuous density HMM topology optimization. There have been several researches for HMM topology optimization. BIC (Bayesian Information Criterion) is one of the well known optimization criteria, which assumes statistically well behaved homogeneous model parameters. HMMs, however, are composed of several different kind of parameters to accommodate complex topology, thus BIC's assumption does not hold true for HMMs. Even though BIC reduced the total number of parameters of HMMs, it could not improve the recognition rates. In this paper, we proposed two new model selection criteria, HBIC (HMM-oriented BIC) and BIC_Anti. The former is proposed to improve BIC by estimating model priors separately. The latter is to combine BIC and anti-likelihood to accelerate discrimination power of HMMs. We performed some comparative research on couple of model selection criteria for online handwriting data recognition. We got better recognition results with fewer number of parameters.

Screening Procedure of Tobacco Cultivars for Resistant to Bacterial Wilt Caused by Ralstonia solanacearum (담배세균성마름병[립고병(立枯病)]에 대한 담배품종의 저항성 검정법)

  • Jeon, Yong-Ho;Kang, Yue-Gyu
    • Journal of the Korean Society of Tobacco Science
    • /
    • v.30 no.1
    • /
    • pp.1-7
    • /
    • 2008
  • Bacterial wilt caused by Ralstonia solanacearum has become a severe problem on tobacco in Korea. No effective single control measure is available at present time. One of the most potential way for controlling the bacterial wilt on tobacco is growing tobacco cultivars resistant to the bacterial wilt. In this study, optimal conditions for screening tobacco cultivars resistant to the bacterial wilt were examined to provide reproducible and efficient methods in growth chamber testing and field experiments for evaluating plant disease resistance. For this, already-known inoculation methods, inoculum densities, and incubation temperature, and plant growth stages at the time of inoculation were compared using tobacco cultivars resistant (Nicotiana tabacum cv, NC95), moderately resistant (N. tabacum cv. SPG70), and susceptible (N. tabacum BY4) to the bacterial disease. It was determined that root-dipping of tobacco seedlings at six true leaf stage into the bacterial suspension with inoculum level of $10^8$ colony-forming units (CFU)/ml for 20 min before transplanting was simple and most efficient in testing for resistance to the bacterial wilt of tobacco caused by R. solanacearum, for which disease incidences and severities were examined at 2 weeks of plant growth after inoculation at $20{\sim}25^{\circ}C$ in a growth chamber. These experimental conditions could discriminate one tobacco cultivar from the others by disease severity better than any other experimental conditions. In field testing, the optimum time for examining the disease occurrence was late June through early July. These results can be applied to establishing a technical manual for the screening of resistant tobacco cultivars against the bacterial wilt caused by R. solanacearum.

PRML detection using the patterns of run-length limited codes (런-길이 제한 코드의 패턴을 이용한 PRML 검출 방법)

  • Lee Joo hyun;Lee Jae jin
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.30 no.3C
    • /
    • pp.77-82
    • /
    • 2005
  • Partial response maximum likelihood (PRML) detection using the Viterbi algorithm involves the calculation of likelihood metrics that determine the most likely sequence of decoded data. In general, it is assumed that branches at each node in the trellis diagram have same probabilities. If modulation code with minimum and maximum run-length constraints is used, the occurrence ratio (Ro) of each particular pattern is different, and therefore the assumption is not true. We present a calculation scheme of the likelihood metrics for the PRML detection using the occurrence ratio. In simulation, we have tested the two (1,7) run-length-limited codes and calculated the occurrence ratios as the orders of PR targets are changed. We can identify that the PRML detections using the occurrence ratio provide more than about 0.5dB gain compared to conventional PRML detections at 10/sup -5/ BER in high-density magnetic recording and optical recording channels.

Comparison of Ensemble Perturbations using Lorenz-95 Model: Bred vectors, Orthogonal Bred vectors and Ensemble Transform Kalman Filter(ETKF) (로렌쯔-95 모델을 이용한 앙상블 섭동 비교: 브레드벡터, 직교 브레드벡터와 앙상블 칼만 필터)

  • Chung, Kwan-Young;Barker, Dale;Moon, Sun-Ok;Jeon, Eun-Hee;Lee, Hee-Sang
    • Atmosphere
    • /
    • v.17 no.3
    • /
    • pp.217-230
    • /
    • 2007
  • Using the Lorenz-95 simple model, which can simulate many atmospheric characteristics, we compare the performance of ensemble strategies such as bred vectors, the bred vectors rotated (to be orthogonal to each bred member), and the Ensemble Transform Kalman Filter (ETKF). The performance metrics used are the RMSE of ensemble means, the ratio of RMS error of ensemble mean to the spread of ensemble, rank histograms to see if the ensemble member can well represent the true probability density function (pdf), and the distribution of eigen-values of the forecast ensemble, which can provide useful information on the independence of each member. In the meantime, the orthogonal bred vectors can achieve the considerable progress comparing the bred vectors in all aspects of RMSE, spread, and independence of members. When we rotate the bred vectors for orthogonalization, the improvement rate for the spread of ensemble is almost as double as that for RMS error of ensemble mean compared to the non-rotated bred vectors on a simple model. It appears that the result is consistent with the tentative test on the operational model in KMA. In conclusion, ETKF is superior to the other two methods in all terms of the assesment ways we used when it comes to ensemble prediction. But we cannot decide which perturbation strategy is better in aspect of the structure of the background error covariance. It appears that further studies on the best perturbation way for hybrid variational data assimilation to consider an error-of-the-day(EOTD) should be needed.