• Analytical Science and Technology
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• v.9 no.1
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• pp.20-25
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• 1996

Trace levels of uranium and thorium in geologic samples are determined rapidly by a direct wavelength-dispersive X-ray fluorescence method. Relative intensity of scattered tube radiation was used as an internal standard to compensate for variations in instrumental operating characteristics. U and Th can be determined within a precision of ${\pm}10%$ and accuracy of ${\pm}15%$ or less with measuring times of 50 seconds for Th and 400 seconds for U, respectively. The results of XRF analysis were in good agreement with those of other methods such as nutron activation analysis and inductively coupled plasma atomic emission spectrometry.

• Membrane Journal
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• v.20 no.1
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• pp.76-86
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• 2010

This study investigated the effect of 2-butoxyethanol (BE) as a nonsolvent additive, relative humidity and air contact time on the structure formation of microfiltration membranes, permeation and morphology properties in phase inversion process. The membranes were prepared by using polyethersulfone (PES)/Dimethyl formamide (DMF)/p-toluenesulfonic acid (TSA)/Polyvinylpyrrolidone (PVP)/BE casting solution and water coagulant. Casting solutions containing various concentration of BE were exposed to a water vapor, under 60 and 80% of relative humidity for 40 and 90 sec, which would be absorbed on. The correlations between the membrane permeation properties and surface/inner structures of membrane were investigated. The characterization of membranes was carried out by a capillary flow porometer, a FE-SEM and a water permeation test apparatus. The surface structure of PES membranes was affected by the exposure time as well as the relative humidity strongly. Furthermore, the addition of BE helped control surface and inner structure at certain humidity and exposure time.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.465-472
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• 2015

In order to improve the performance of TCAS it should improve the performance of the sensor, which transmits a variety of information. In this paper, To improve the performance of the existing radar sensors such as being used in behalf of the next generation air traffic control system, ads-b the applied. In addition, ADS-B in a high precision by using information from the correction GPS system, SBAS assume would be able to apply an improved location accuracy for TCAS and analyzed TCAS and ADS-B. Played the simulation results, TCAS equipment receives the help of these ADS-B can calculate a CPA to determine the position of the aircraft in advance, and it was confirmed that it is possible to reduce the unnecessary RA operation, also, the pilot reduction and the workload, it has advantages such as fuel consumption and time associated with the reduced operation unnecessary RA was confirmed.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.3
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• pp.200-205
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• 2015

An ultra-precise infrared microscope consisting of a high-resolution infrared objective lens and infrared sensors is utilized successfully to obtain location information on the plane and depth of local heat sources causing defects in a semiconductor device. In this study, multi-layer semiconductor chips are analyzed for the positional information of heat sources by using a lock-in infrared microscope. Optimal conditions such as focal position, integration time, current and lock-in frequency for measuring the accurate depth of the heat sources are studied by lock-in thermography. The location indicated by the results of the depth estimate, according to the change in distance between the infrared objective lens and the specimen is analyzed under these optimal conditions.

• Explosives and Blasting
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• v.34 no.4
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• pp.10-18
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• 2016

Explosive blasting utilizes the energy produced from the explosion of explosive materials. Since the black powder, the first type of explosive, was invented, various types of explosives have been developed until a recent emulsion explosive which is powerful as well as safe in use. The detonators continue to be developed from safety fuse to the recent electronic detonators which allow extremely accurate and flexible control of delay time. However, the good explosives and detonators do not always lead to the good blast results. It entirely depends on the blast engineer. It is necessary to develop the empirical or theoretical models based on the field experience and sound theoretical algorithm. Such models would be very useful for blast design and, furthermore, provide the idea of further technical development. This paper introduces some models used in explosive blasting and attention to be paid for field application.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.72-77
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• 2017

The Satellite Based Augmentation System (SBAS) broadcasts to users integrity and correction information for Global Navigation Satellite System (GNSS) such as GPS and GLONASS using geostationary orbit (GEO) satellites. In accordance with the recommendation of the International Civilian Aeronautical Organization (ICAO) to introduce SBAS until 2025, a Korean SBAS system development / construction project is underway with the Ministry of Land, Transport and Maritime Affairs. Korea Augmentation Satellite System (KASS) is a high precision GPS correction system which is composed of KASS Reference Station (KRS), KASS Processing Station (KPS), KASS Uplink Station (KUS), KASS Control Station (KCS) and GEO satellites. In this paper, we provided the conceptual design of the KASS uplink station, which is composed of the Signal Generator Section (SGS) and the Radio-Frequency Section (RFS), and interface between the KASS ground sector and the GEO satellite.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.199-206
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• 2015

For real-time precise positioning, IGS provides ephemeris predictions (IGS ultra-rapid, IGU) and real-time ephemeris estimates (real-time service, RTS). Due to the RTS data latency, which ranges from 5 s to 30 s, a short-term prediction process is necessary before applying the RTS corrections. In this paper, the real-time performance of the RTS correction and IGU prediction are compared. The RTS correction availability for the GPS satellites observed in Korea is computed as 99.3%. The RTS correction is applied to broadcast ephemeris to verify the accuracy of the RTS correction. The 3D orbit RMS error of the RTS correction is 0.043 m. Prediction of the RTS correction is modeled as a polynomial, and then the predicted value is compared with the IGU prediction value. The RTS orbit prediction accuracy is nearly equivalent to the IGU prediction, but RTS clock prediction performance is 0.13 m better than the IGU prediction.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.362-366
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• 2007

In this research, the optimal grinding condition has been obtained by design of experiment (DOE) fur the development of aspheric lens for the 3 Mega Pixel, 2.5x optical zoom camera-phone module. Also, the tungsten carbide (WC) mold was processed by the method of ultra precision grinding under this optimal grinding condition. The influence of diamond-liked carbon (DLC) coating on form accuracy (PV) and surface roughness (Ra) of the mold was evaluated through measurements after DCL coating using ion plating on the ground mold. Also, aspheric glass lenses were molded, some before DLC coating of the mold and some after the DLC coating. The optical characteristics of each sample, molded by the different molds, were compared with each other.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.1
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• pp.84-91
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• 2007

As GPS equipments improve, one can acquire GPS data easily in the field. To obtain precise and accurate coordinates, however, post processing is additionally required and the processing needs high degree of skills. Besides, it is very common that we cannot operate processing softwares in the field because the required system environment is usually not prepared. The aim of this study is the development of an internet-based GPS data processing service. For post processing, we used GIPSY developed by JPL. It has many advantages such as obtaining coordinates quickly by using precise or predicted ephemeris. This service proceeds as following orders by interlocking GIPSY software and internet service which is operated on a Linux platform: Users upload the raw data file on the internet, then GIPSY runs automatically and then the user gets the result in the field. We use an Apache web server as the hosting program and PHP scripts are used in coding web pages. The total processing time including data-uploading was around 30 seconds for a 24-hour data with a 30-second sampling rate.

• Design & Manufacturing
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• v.1 no.1
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• pp.7-11
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• 2007

The fabrication of precision optical components by deterministic CNC grinding is an area of great current interest. Replacement of the traditional, craftsman driven, optical fabrication process is essential to reduce costs and increase process flexibility and reliability. Moreover, CNC grinding is well suited to the fabrication of complex shapes such as aspheres, making it possible to design optical systems with fewer components and reduced weight. Current technology is capable of producing surfaces with less than 2 microns peak to valley error, 50 nm rms surface roughness, and less than 1 micron subsurface damage. Bound abrasive tools, in which the abrasive particles are fixed in a second (matrix) material, play an important part in achieving this performance. In this paper, the factors affecting the ultra-fine surface roughness and profile accuracy of machined surfaces of aspheric parts has been analyzed experimentally and theoretically and on ultra-precision aspheric grinding system and precise adjusting mechanism have been designed and manufactured. In the paper we report the results of experiments and modeling performed to examine the effects of machinability, occurring during grinding of optical surfaces, on the tool surface profile. Profiles of machined surface were measured by using SEM. In order to optimize grinding conditions of aspheric lens processing, we performed experiments by design of experiments.