Maximum Difference Value Research Articles

SU‐FF‐T‐126: Clinical Experience Using Dynalog Files for Verification of IMRT Delivery

Purpose: Validation of IMRT field delivery and the dynamic leaf movement during treatment is an important part of the IMRT QA procedure. In the past this was done using film during treatment. In this presentation, we summarize our experience using the dynalog files to validate the delivered fluence pattern of individual IMRT fields for each patient. Method and Materials: The DynaLog files were generated during IMRT delivery on Varian Trilogy and 21EX linear accelerators. They represent the actual leaf movement, as MLC leaf positions were recorded, during delivery, every 50 ms. Argus IMRT QA software was used to interrogate the dynalog files after delivery for evaluation. The delivered and planned fluence pattern can be displayed for comparison as well as fluence difference and Gamma function values. Maximum and average fluence difference and Gamma function values can be employed for quantitative analysis, as well as actual versus planned leaf positions and speeds. The pass/fail status of each IMRT field can be set based on pre‐determined parameters. Results: We have employed the Argus IMRT QA software in analyzing the fluence patterns and leaf motions for all IMRT fields used for patient treatment. Several hundred fluence patterns were analyzed on 100 patients treated so far. The average and maximum gamma function value of each field was analyzed to determine appropriate limits for the pass/fail criteria in accordance with our clinical data. Conclusion: Verification of delivered fluence patterns is an important part of the IMRT QA process. It assures the accuracy of IMRT delivery on a daily basis. With the aid of Argus IMRT QA software, validation of all the fields used for IMRT treatment can be performed within minutes for qualitative and quantitative analysis. With the proper choice of limits for test parameters, this approach further ensures the quality of IMRT delivery.

Surface deformation analysis in the Ischia Island (Italy) based on spaceborne radar interferometry

The island of Ischia, located at the northwestern end of the Gulf of Napoli (Italy), is a volcanic area that is historically active (the Arso eruption, in 1302 and the Casamicciola earthquake, in 1883) and has diffuse hydrothermal phenomena. We present in this work a study of the surface deformation occurring in the island, which is based on applying the Differential Synthetic Aperture Radar Interferometry (DInSAR) algorithm referred to as Small BAseline Subset (SBAS) technique. This study is focused on the 1992–2003 time interval and SAR data acquired by the European Remote Sensing (ERS) satellites from ascending and descending orbits have been used, thus allowing us to discriminate the vertical and east–west components of the displacements. A validation of the DInSAR results has been carried out first by comparing the vertical deformations estimated from the SAR data with those measured from the spirit leveling network that is present in the area. In particular, we computed the difference between the mean vertical deformation velocities estimated from the SAR and the corresponding geodetic measurements along three main leveling lines; the maximum value of the root mean square difference is of about 1 mm/yr. The final discussion is dedicated to the interpretation of the detected displacements, benefiting from the overall information extracted from the ascending and descending DInSAR measurements. In particular, DInSAR data relative to the vertical deformation component show that the present-day subsidence of Ischia mainly develops in areas characterized by active landsliding and along faults; moreover, the deflation of the island, which is recorded by the horizontal displacement component, is probably related to the de-pressurization of the hydrothermal system.

Work-function changes of treated indium-tin-oxide films for organic light-emitting diodes investigated using scanning surface-potential microscopy

Local surface work-function (WF) measurement on indium-tin-oxide (ITO) films prepared by different cleaning methods for use as anode materials in organic light-emitting diodes were studied using scanning surface-potential microscopy. The ITO WF changes with standard wet-cleaning treatment correspond directly to asperities on the film surface. The maximum difference value (MDV) in the local WF reached 0.41eV. However, after wet-cleaning ITO with the ultraviolet ozone or O-plasma treatment, the WF distribution is more uniform than the original distribution. Owing to the sufficient ITO surface oxidization, the mean local WF value increases effectively to more than 5.00eV and the MDV is less than 0.05eV. Furthermore, the changes in roughness and conductivity on the ITO surface at different treatment times are also discussed. The proper exposure time for the O-plasma treatment can thereby be determined.

A Study on Fretting Fatigue Behavior of Degraded 1Cr-0.5Mo Steel

The aged degradation of material is observed when heat-resisting steel is exposed for long periods of time at high temperatures. In the present study, the degraded 1Cr-0.5Mo steel that is used for long periods of time at high temperature(about 515°C) and artificially reheat-treated materials are prepared. These materials were used to study the effect of aged degradation on fretting fatigue behavior. Through this experiment, it is found that the fretting fatigue strength of reheat-treated 1Cr-0.5Mo steel is approximately 46 percent lower than that of the plain fatigue strength of the same material. Furthermore, the fretting fatigue strength of degraded 1Cr-0.5Mo steel was less than 53 percent of the same material™s plain fatigue strength. The maximum value of fatigue strength difference is observed as 57 percent between the fretting fatigue of degraded material and plain fatigue of reheat-treated material. These results can be used as basic data in a structural integrity evaluation of heat-resisting steel considering aged degradation effects.

1Cr-0.5Mo 강의 재질열화가 프레팅 피로거동에 미치는 영향

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. The fretting damage decreases in 50-70% of the plain fatigue strength. This may be observed in the fossil power plant and the nuclear power plant used in special environments and various loading conditions. The thermal degradation of material is observed when the heat resisting steel is exposed for long period time at the high temperature. In the present study, the degraded 1Cr-0.5Mo steel used for long period time at high temperature (about 515) and artificially reheat-treated materials are prepared. These materials are used for evaluating an effect of thermal aging on the fretting fatigue behavior. Through the experiment, it is found that the fretting fatigue endurance limit of the reheat-treated 1Cr-0.5Mo steel decreased about 46% from the non-fretting fatigue endurance limit, while the fretting fatigue endurance limit of the degraded 1Cr-0.5Mo steel decreased about 53% from the non-fretting fatigue endurance limit. The maximum value of fatigue endurance limit difference is observed as 57%(244 MPa) between the fretting fatigue of degraded material and non-fretting fatigue of reheat-treated material. These results can be a basic data to a structural integrity evaluation of heat resisting steel considered to thermal degradation effect.

The automatic calibration system of humidity fixed points at CMS

The automatic hygrostat is designed to calibrate hygrometers by employing several humidity fixed points under thermostat conditions. The set incorporates a blowing fan, a box-like measuring vessel, a control system, and an assembly of five acrylic resin trays which contain stainless steel covers, labyrinth baffle-boards at the bottom and are all set in a reciprocating motion. The trays are successively turned on or off by operating solenoid valves to give a closed circulation with the measuring vessel, establishing the humidity at a specific value selected by the user. The desired relative humidities are attained by adding lithium chloride, potassium carbonate, sodium chloride, potassium chloride, and potassium sulfate to pure water inside the five trays and can generate levels of approximately 12, 43, 75, 86, and 97% RH respectively, which have a maximum difference value, compared to reference values of ±1% RH in the range around room temperature. After switching to another tray for the control setting, the time required to reach a new equilibrium should be no longer than about 20 minutes.

小ロ径非球面レンズ用母型ジグ加工機の試作

The purpose of this paper is to describe an experimented method of fabricating an aspherical surface of a small lens which has 10 mm diameter, 2.2 mm thick and about 200 μm maximum value of difference between aspherical surface and sphere. To get higher figuring efficiency, the profile had to transmit to the tool-base by the two cams and lever-systems with the zero-method mechanism. Accuracy obtained by this adopted apparatus is ± 1 μm in static condition, and that of the stainless steel surface being injected into a type of plastic lens and finished by this apparatus is ± 10 μm.

Thermoelastic stresses and the energy of earthquakes

The nonuniform distribution of temperature and the heterogeneity of physical properties produce thermoelastic stresses in the earth's mantle. The variation of the earth's temperature with time due to radioactive heat generation results in the accumulation of such stresses. A horizontal temperature gradient is shown to exist and to reach a value of the order of 2 deg/km for the transitional zone between the oceanic and continental crust in the subjacent mantle of the Kuril Islands. The distributions of the radial and tangential stresses as well as the variation of stress differences with depth are calculated for a variable thermal expansion coefficient from the equilibrium equation of the thermoelastic displacements for a sphere. The largest stresses in the upper mantle are tangential. They are tensions in the upper 50 km, and are compressions below 50 km. The radial stresses are much weaker; they are compressions in the upper layers and tensions in the lower layers. The stress differences are shown to reach the strength limit for rocks (109 dynes/cm2). The maximum value of stress difference in the earth can amount to 10 to 30×1010 dynes/cm2. Near the surface the accumulation rate of stress difference appears to be 20 dynes/cm2 year. The calculated thermoelastic energy at different depths is comparable to the rate of the seismic energy release determined by Gutenberg within the accuracy of such determinations. At a depth of over 100 km its increase appears to be greater than that of the seismic energy by one to two orders of magnitude. There remains the possibility that an allowance for relaxation processes will reduce the calculated accumulation of thermoelastic energy.