• Radiation Oncology Journal
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• v.27 no.2
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• pp.91-102
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• 2009

Purpose: To compare the accuracy and efficacy of EDR2 film, a 2D ionization chamber array (MatriXX) and an amorphous silicon electronic portal imaging device (EPID) in the pre-treatment QA of IMRT. Materials and Methods: Fluence patterns, shaped as a wedge with 10 steps (segments) by a multi-leaf collimator (MLC), of reference and test IMRT fields were measured using EDR2 film, the MatriXX, and EPID. Test fields were designed to simulate leaf positioning errors. The absolute dose at a point in each step of the reference fields was measured in a water phantom with an ionization chamber and was compared to the dose obtained with the use of EDR2 film, the MatriXX and EPID. For qualitative analysis, all measured fluence patterns of both reference and test fields were compared with calculated dose maps from a radiation treatment planning system (Pinnacle, Philips, USA) using profiles and $\gamma$ evaluation with 3%/3 mm and 2%/2 mm criteria. By measurement of the time to perform QA, we compared the workload of EDR2 film, the MatriXX and EPID. Results: The percent absolute dose difference between the measured and ionization chamber dose was within 1% for the EPID, 2% for the MatriXX and 3% for EDR2 film. The percentage of pixels with $\gamma$%>1 for the 3%/3 mm and 2%/2 mm criteria was within 2% for use of both EDR2 film and the EPID. However, differences for the use of the MatriXX were seen with a maximum difference as great as 5.94% with the 2%/2 mm criteria. For the test fields, EDR2 film and EPID could detect leaf-positioning errors on the order of -3 mm and -2 mm, respectively. However it was difficult to differentiate leaf-positioning errors with the MatriXX due to its poor resolution. The approximate time to perform QA was 110 minutes for the use of EDR2 film, 80 minutes for the use of the MatriXX and approximately 55 minutes for the use of the EPID. Conclusion: This study has evaluated the accuracy and efficacy of EDR2 film, the MatriXX and EPID in the pre-treatment verification of IMRT. EDR2 film and the EPID showed better performance for accuracy, while the use of the MatriXX significantly reduced measurement and analysis times. We propose practical and useful methods to establish an effective QA system in a clinical environment.

• The Korean Journal of Air & Space Law and Policy
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• v.24 no.1
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• pp.153-194
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• 2009

The resources of outer space are for the common exploitation of mankind, and it is a common responsibility of mankind to protect the outer space environment. With the rapid development of space science and technology, and especially with the busy space activities of some major space powers, environmental contamination or space debris is steadily increasing in quantity and has brought grave potential threats and actual damage to the outer space environment and human activities in space. Especially We must mitigate and seek out a solution to remove space debris which poses a threat directly to man's exploitation and use of outer space activities in the Low Earth Orbit (LEO) and in the Geostationary Orbit (GEO), through international cooperation and agreement in the fields of space science, economics, politics and law, in order to safeguard the life and property of mankind and protect the earth's environment. While the issue of space debris has been the subject of scientific study and discussion for some time now, it has yet to be fully addressed within the context of an international legal framework. During the earlier stages of the space age, which began in the late 1950s, the focus of international lawmakers and diplomats was the establishment of basic rules which sought to define the legal nature of outer space and set out the parameters for space activities and the nature and scope of activities carried out in outer space were quite limited. Consequently, environmental issues and the risks that might arise from the generation of space debris did not receive priority attention within the context of the development international space law. In recent years, however, the world has seen dramatic advances in technology and increases in the type and number of space-related activities which are being carried out. In addition, the number of actors in this field has exploded from two highly developed States to a vast array of different States, intergovernmental and nongovernmental organizations, including private industry. Therefore, the number of artificial objects in the near-Earth space is continually increasing. As has been previously mentioned, COPUOS was the entity that created the existing five treaties, and five sets of legal Principles, which form the core of space law, and COPUOS is clearly the most appropriate entity to oversee the creation of this regulatory body for the outer space environmental problem. This idea has been proposed by various States and also at the ILA Conference in Buenos Aires. The ILA Conference in Buenos Aires produced an extensive proposal for such a regulatory regime, dealing with space debris issues in legal terms This article seeks to discuss the status of international law as it relates to outer space environmental problem and space debris and indicate a course of action which might be taken by the international community to develop a legal framework which can adequately cope with the complexity of issues that have recently been recognized. In Section Ⅱ,Ⅲ and IV of this article discuss the current status of international space law, and the extent to which some of the issues raised by earth and space environment are accounted for within the existing United Nations multilateral treaties. Section V and VI discuss the scope and nature of space debris issues as they emerged from the recent multi-year study carried out by the ILA, Scientific and Technical Subcommittee, Legal Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space ("COPUOS") as a prelude to the matters that will require the attention of international lawmakers in the future. Finally, analyzes the difficulties inherent in the future regulation and control of space debris and the activities to protect the earth's environment. and indicates a possible course of action which could well provide, at the least, a partial solution to this complex challenge.

• Korean Journal of Remote Sensing
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• v.14 no.3
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• pp.213-222
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• 1998

Electro-Optical Camera(EOC) is the main payload of the KOrea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including a Digital Terrain Elevation Map(DTEM). This instalment which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510~730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable gain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response, the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the users of EOC data. The modulation transfer function of EOC was measured as greater than 16 % at Nyquist frequency over the entire field of view, which exceeds its requirement of larger than 10 %. The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.

• Asia Marketing Journal
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• v.7 no.3
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• pp.53-76
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• 2005

With rapid technological and market change, new product development (NPD) complexity is a significant issue that organizations continually face in their development projects. There are numerous factors, which cause development projects to become increasingly costly & complex. A product is more likely to be successfully developed and marketed when the complexity inherent in NPD projects is clearly understood and carefully managed. Based upon the previous studies, this study examines the nature and importance of complexity in developing new products and then identifies several issues in managing complexity. Issues considered include: definition of complexity : consequences of complexity; and methods for managing complexity in NPD projects. To achieve high performance in managing complexity in development projects, these issues need to be addressed, for example: A. Complexity inherent in NPD projects is multi-faceted and multidimensional. What factors need to be considered in defining and/or measuring complexity in a development project? For example, is it sufficient if complexity is defined only from a technological perspective, or is it more desirable to consider the entire array of complexity sources which NPD teams with different functions (e.g., marketing, R&D, manufacturing, etc.) face in the development process? Moreover, is it sufficient if complexity is measured only once during a development project, or is it more effective and useful to trace complexity changes over the entire development life cycle? B. Complexity inherent in a project can have negative as well as positive influences on NPD performance. Thus, which complexity impacts are usually considered negative and which are positive? Project complexity also can affect the entire organization. Any complexity could be better assessed in broader and longer perspective. What are some ways in which the long-term impact of complexity on an organization can be assessed and managed? C. Based upon previous studies, several approaches for managing complexity are derived. What are the weaknesses & strengths of each approach? Is there a desirable hierarchy or order among these approaches when more than one approach is used? Are there differences in the outcomes according to industry and product types (incremental or radical)? Answers to these and other questions can help organizations effectively manage the complexity inherent in most development projects. Complexity is worthy of additional attention from researchers and practitioners alike. Large-scale empirical investigations, jointly conducted by researchers and practitioners, will help gain useful insights into understanding and managing complexity. Those organizations that can accurately identify, assess, and manage the complexity inherent in projects are likely to gain important competitive advantages.