• Journal of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.125-128
• /
• 2005

In this paper, we argue that the gigahertz peaked spectrum (GPS) quasars are special blazars, blazars in dense and dusty gas enviornment. The ROSAT detection rate of GPS quasars is similar to that of flat spectrum radio quasars (FSRQs), suggesting that the relativistic jets in GPS quasars are oriented at small angle to the line of sight. Due to strong inverse Compton scattering off infrared photons from dense and dusty nuclear interstellar media in GPS quasars, most of them may have significant soft gamma-ray and X-ray emission, which is consistent with ASCA X-ray observations. Because Compton cooling in GPS quasars is stronger than that in FSRQs, synchrotron emission in GPS quasars may less dominate over thermal emission of the accretion disk and hot dust, hence most GPS quasars show low optical polarization and small variability, consistent with observations. We suggest that it is the significant radio emission of electron/positron pairs produced by the interaction of gamma-rays with the dense gas and dust grains in GPS quasars that makes GPS quasars show steep radio spectra, low radio polarization, and relatively faint VLBI/VLBA cores. Whether GPS quasars are special blazars can be tested by gamma-ray observations with GLAST in the near future, with the detection rate of GPS quasars being similar to that of FSRQs.

• Korean Journal of Materials Research
• /
• v.16 no.7
• /
• pp.455-459
• /
• 2006

Coincidence Doppler Broadening (CDB) of positron annihilation spectroscopy was applied to analyze defects in the chemical state of Department of Physics, $Gd_2O_2S$:Tb intensifying screens. The screen samples were irradiated by 80 MV X-rays in hospital and were used for 0, 2, 4, and 6 years respectively. There was a positive relationship between the S-parameter values and time of exposure to X-rays. Most of the defects were indicated to have been generated by X-rays. A 1D CDB was developed in order to reduce the background noise, and the S-parameter values of the $Gd_2O_2S$:Tb intensifying screens, using the 1D CDB, varied between 0.4974 and 0.4991.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.1 no.2
• /
• pp.94-111
• /
• 2008

Traditionally the diagnosis and treatment of the diseases of the knee is based on the findings of the x-rays and the MRI. The x-rays provide good information of the changes of the internal structure of the bone. However, there is a limitation in providing information of the soft tissue and the cartilage. The MRI is one of the most expensive diagnostic modalities and it can not give us a dynamic and real time information. The sonography has a role in diagnosis and treatment of the soft tissue disease and surface of the bone. It gives us a real time dynamic information and it is really cheap. In this article the sonographic findings of the normal and pathologic conditions of the knee joint are introduced in relation to the findings of the x-rays and the MRI.

• Journal of Acupuncture Research
• /
• v.27 no.4
• /
• pp.19-28
• /
• 2010

Objectives : To demonstrate the need for differential diagnosis between discogenic pain and lumbar sprain and strain in acute low-back pain patients. Methods : Outpatients who made their first visits during May 1, 2009 to Oct. 30, 2009(n=53) were examined by history taking, physical examination, X-rays, and CT imaging. Disorders found on lumbosacral spine X-ray cuts and those on lumbosacral spine CT images were separately recorded. The relationship between treatment period, disc space narrowing and disc degeneration on X-rays, and HIVD on CT images was examined. Results : 1. Correlation between disc space narrowing on X-rays and HIVD found on CT images was analyzed. 21(72.41%) out of 29 patients having disc space narrowing on X-rays and HIVD on CT at the same level required treatment for over 8 weeks. 2. 2(50%) out of 4 Lawrence classification grade I patients, 8(66.67%) out of 12 grade II patients, and 14(70%) out of 20 grade III patients needed treatment for over 8 weeks. Conclusions : Disc space narrowing on X-ray and HIVD on CT at the same level, or disc space narrowing and disc degeneration on X-ray image alone indicate a tendency for treatment periods over 8 weeks, which is longer than the conventional treatment period for lumbar strain and sprain.

• Progress in Medical Physics
• /
• v.17 no.1
• /
• pp.1-5
• /
• 2006

A parallel plate detector containing PTFE films in FEP film for relative dosimetry was designed to measure the response of detectors to S and 10 MV X-rays from a medical linear accelerator through different thicknesses of lead. The dielectric materials were 100 m thick. The set-up conditions for measurements with this detector were as follows: SSD=100 cm the test detector was at a depth of 5 cm and the reference chamber was at a depth of 10 cm from the phantom surface for 6 and 10 MV X-rays. Lead blocks were designed to cover the irradiated field. They were added to the tray to increase thickness sequentially. We found that the detector response decreased exponentially with the thickness of lead added. The linear attenuation coefficients of the test detector and reference chamber were 0.1414 and 0.541, respectively, for 6 MV X-rays and 0.1358 and 0.5279 for 10 MV X-rays. The test detector response was greater than that of the reference chamber. The response function was calculated from the measured values of the test detector and reference chamber using optimization. These optimized constants for the detector response function were independent of theenergy. As a result of optimizing the response function between detectors, the use of a relative dosimeter was validated, because the response of the test detector was 1% for 6 MV X-rays and 4% for 10 MV X-rays.

• Progress in Medical Physics
• /
• v.2 no.1
• /
• pp.29-35
• /
• 1991

For accureate treatment planning, new models of dose calculations are being developed which require the knowledge of the energy spectra and angular distributions of the X-rays incident on the surface of the material. In this present study, we applied the Monte Carlo methods to the systematic analysis of the spectra distribution of X-ray beams produced by medical linear accelerator. As expected, the spectra become softer as the distance is farther from the central axis. also, its influenced by the geometrical dffect of head system.

• Journal of the Optical Society of Korea
• /
• v.11 no.2
• /
• pp.76-81
• /
• 2007

The compound refractive X-ray lens (CRL) for focusing hard X-rays is investigated to determine the parameters such as the focal length, the focal spot size, and spatial distribution at the focal spot using a simple theoretical calculations and CRLs fabricated by the self-assembly method. The number of individual compound lenses are defined for the given focal length of 1 m. The X-ray energy of 1 to 40 keV is used in the calculations. The CRL for focusing hard X-rays which generated from the X-ray tube is fabricated by nanoparticle-polymer composite in the form of circular concaves. The self-assembly method is applied to form the nanoaluminum-poly (methly meth-acrylate) composite and carbon-polymer composite CRL lenses. Aluminum nanoparticles of 100 nm and carbon microparticles are diffused in the polymer solution then the high gravity up to 6000G is applied in it to form the concave lens shape. X-ray energy at 8 keV is used for characterization of the composite CRLs. The FWHM of intensity for the fabricated nanoaluminium composite CRL system, N=10 is measured as 1.8 mm, which would give about $70{\mu}m$ in FWHM at 1 m of the focal length.

• The Journal of Internal Korean Medicine
• /
• v.42 no.4
• /
• pp.622-627
• /
• 2021

Objective: This study was designed to analyze the utility of routine chest X-ray on Korean medicine hospital admission. Methods: The chest X-ray reports and medical records of 618 patients who were admitted to Daejeon Korean Medicine Hospital from May 1, 2021 to June 30, 2021 were retrospectively reviewed. Results: Of the 618 patients newly hospitalized from May 1, 2021 to June 30, 2021, 560 patients (excluding readmission) were analyzed. The mean age of 560 patients was 53.26±17.20 years. There were 52 patients with abnormal findings, and their mean age was 69.62±15.59 years. Many of these patients had chest symptoms and a history of chest disease. There was no case that showed a significant diagnostic result by chest X-ray examination. Conclusion: The diagnostic usefulness of routine chest X-rays in Korean medicine hospital admission is low. But this does not mean that there is no need to perform routine chest X-rays upon admission.

• Journal of Biosystems Engineering
• /
• v.34 no.3
• /
• pp.175-182
• /
• 2009

This study was conducted to investigate the drying characteristics of tissue cultured mountain ginseng roots. The far infrared rays dryer of a double blast system used for this experiment can control the drying parameters such as far infrared heater temperature and air velocity. The far infrared rays drying tests of tissue cultured mountain ginseng roots were performed at air velocity of 0.4, 0.6, 0.8 m/s, under drying air temperature of 50, 60, and $70^{circ}C$, respectively. The results were compared with one obtained by the heated air drying method. The drying characteristics such as drying rate, color, energy consumption, saponin components and antioxidant activities were analyzed. The results showed that the drying rate of far infrared rays drying was faster than that of heated air drying and due to high temperature of drying air and fast air velocity, the far infrared rays drying of double blast type was superior to the heated air drying. The value of the color difference for heated air drying was 10.11${\sim}$12.99 and that of far infrared rays drying was in the range of 7.05${\sim}$7.54, which was in the same drying condition, also energy consumption of far infrared rays drying was in the range of 3575${\sim}$6898 kJ/kg-water. At the same time, the antioxidant activities using far infrared rays drying were higher than those using heated air drying.

• Journal of The Korean Astronomical Society
• /
• v.37 no.5
• /
• pp.433-438
• /
• 2004

Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. The basic properties of cluster mergers and their effects are discussed. Mergers drive shocks into the intracluster gas, and these shocks heat the intracluster gas. As a result of the impulsive heating and compression associated with mergers, there is a large transient increase in the X-ray luminosities and temperatures of merging clusters. These merger boost can affect X-ray surveys of clusters and their cosmological interpretation. Similar boosts occur in the strong lensing cross-sections and Sunyaev-Zeldovich effect in merging clusters. Merger shock and turbulence associated with mergers should also (re)accelerate nonthermal relativistic particles. As a result of particle acceleration in shocks and turbulent acceleration following mergers, clusters of galaxies should contain very large populations of relativistic electrons and ions. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these shocks will also be described. Gamma-ray observations with GLAST seem particularly promising.