• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.626-637
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• 2014

On ship, especially on large ship, the flexure deformation between Master (M)/Slave (S) Inertial Navigation System (INS) is a key factor which determines the accuracy of the integrated system of M/S INS. In engineering this flexure deformation will be increased with the added ship size. In the M/S INS integrated system, the attitude error between MINS and SINS cannot really reflect the misalignment angle change of SINS due to the flexure deformation. At the same time, the flexure deformation will bring the change of the lever arm size, which further induces the uncertainty of lever arm velocity, resulting in the velocity matching error. To solve this problem, a $H_{\infty}$ algorithm is proposed, in which the attitude and velocity matching error caused by deformation is considered as measurement noise with limited energy, and measurement noise will be restrained by the robustness of $H_{\infty}$ filter. Based on the classical "attitude plus velocity" matching method, the progress of M/S INS information fusion is simulated and compared by using three kinds of schemes, which are known and unknown flexure deformation with standard Kalman filter, and unknown flexure deformation with $H_{\infty}$ filter, respectively. Simulation results indicate that $H_{\infty}$ filter can effectively improve the accuracy of information fusion when flexure deformation is unknown but non-ignorable.

• 전기학회논문지
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• 제60권11호
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• pp.2000-2006
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• 2011

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. Where calculation method of protection settings and Logic for Protection of Generator Asynchronization will be recommended, A distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, Zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection this paper describes an improved backup protection coordination scheme using a new Logic that will be suggested.

• Restorative Dentistry and Endodontics
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• 제40권3호
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• pp.229-235
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• 2015

Objectives: To determine and compare the fracture resistance of endodontically treated maxillary central incisors restored with different posts and cores. Materials and Methods: Forty-eight upper central incisors were randomly divided into four groups: cast post and core (group 1), fiber-reinforced composite (FRC) post and composite core (group 2), composite post and core (group 3), and controls (group 4). Mesio-distal and bucco-lingual dimensions at 7 and 14 mm from the apex were compared to ensure standardization among the groups. Twelve teeth were prepared for crown restoration (group 4). Teeth in other groups were endodontically treated, decoronated at 14 mm from the apex, and prepared for posts and cores. Resin-based materials were used for cementation in groups 1 and 2. In group 3, composite was used directly to fill the post space and for core build-up. All samples were restored by standard metal crowns using glass ionomer cement, mounted at $135^{\circ}$ vertical angle, subjected to thermo-mechanical aging, and then fractured using a universal testing machine. Kruskal-Wallis and Mann-Whitney U tests were used to analyze the data. Results: Fracture resistance of the groups was as follows: Control (group 4) > cast post and core (group 1) > fiber post and composite core (group 2) > composite post and core (group 3). All samples in groups 2 and 3 fractured in restorable patterns, whereas most (58%) in group 1 were non-restorable. Conclusions: Within the limitations of this study, FRC posts showed acceptable fracture resistance with favorable fracture patterns for reconstruction of upper central incisors.

• 한국인쇄학회지
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• 제26권2호
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• pp.65-77
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• 2008

The color reproduction of digital still camera does not, in general, match those of the final prints. Because color gamut of these devices is different, it is therefore necessary to take account of a way to match. The way uses the optimized profile to print an image. This paper proposed a way to create the input profile of digital still camera for standardization printing process. The results of proposed way showed that for input profiles equivalent, good results relatively. In this paper, an experiment was done where the illumination sources used as the standard illumination 5200K and illuminated at a $45^{\circ}$ angle in the best illumination efficiently. The white balance was in mode 'custom': aperture F11, exposure time 1/60s, ISO50, focal length 80mm. The images were exported and saved as 16bit RGB tiff(AdobeRGB, sRGB, ProphotoRGB) images. To do the test, the RGB values of the RGB tiff images are processed through the ICC input profile to arrive at processed $CIEL^*a^*b^*$ values. A profiling tool such as ProfileMaker 5.0 and Monacoprofile 4.8 are used to do this. The processed CIEL*a*b* values are compared to the reference CIEL*a*b* values and these two values are used to calculate a ${\Delta}E$.

• Journal of Astronomy and Space Sciences
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• 제32권1호
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• pp.63-71
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• 2015

During the reign of King Sejong (世宗, 1418-1450) in the Joseon Dynasty, there were lots of astronomical instruments, including miniaturized ones. Those instruments utilized the technical know-how acquired through building contemporary astronomical instruments previously developed in the Song(宋), Jin(金), and Yuan(元) dynasties of China. In those days, many astronomical instruments had circles, rings, and spheres carved with a scale of 365.25, 100, and 24 parts, respectively, on their circumference. These were called the celestial-circumference degree, hundred-interval (Baekgak), and 24 direction, respectively. These scales are marked by the angular distance, not by the angle. Therefore, these circles, rings, and spheres had to be optimized in size to accomodate proper scales. Assuming that the scale system is composed of integer multiples of unit length, we studied the sizes of circles by referring to old articles and investigating existing artifacts. We discovered that the star chart of Cheonsang yeolcha bunyajido was drawn with a royal standard ruler (周尺) based on the unit length of 207 mm. Interestingly, its circumference was marked by the unit scale of 3 puns per 1 du (or degree) like Honsang (a celestial globe). We also found that Hyeonju ilgu (a equatorial sundial) has a Baekgak disk on a scale of 1 pun per 1 gak (that is an interval of time similar to a quarter). This study contributes to the analysis of specifications of numerous circular elements from old Korean astronomical instruments.

• 한국도로학회논문집
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• 제15권1호
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• pp.143-154
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• 2013

PURPOSES: Design of approach roads of rest areas in highway has many drawbacks such as geometric design elements. There has been traffic accidents occured in these approach roads of rest areas. Thus, design criteria is required in order to protect accidents from being occurred. In case of Korea, geometric structure design criteria of entry facilities, such as toll-gate, interchange, junction etc was established. However there are no presence in a detailed standards for geometric structure of the rest area which affiliated road facilities. METHODS: In this study, analytic on accidents was carried out in regards to the entry of geometric structure of resting areas by utilizing a sight survey and an investigation research of traffic accidents. The survey was targeting 135 general service areas. Collisions with physical channelization and safety facilities occurred due to speeding, rapid entry, and etc at the entrance nose section. At the entrance connector roads, accidents caused by speeding, negligence, over-operation of handle of drivers were main reason of accidents. Discriminant analysis were conducted about geometric elements to distinguish influencing factors for traffic accidents. the lengths and access angles of the entrance connector roads were regarded as to have the high relation with traffic accidents. RESULTS: After classifying the design section of resting areas' entry as well as derive design elements on each section, a speed measurement by targeting entry of rest areas and car behavior surveys were performed, then each element's minimum standard was derived through the analyses. According to the speeds at the starting/end point of entrance connector road, the range of the junction setting angle of the entrance connector road is defined as $12^{\circ}{\sim}17^{\circ}$ and the connector length model was suggested. CONCLUSIONS: Suggest improvement plans for existing rest areas that can be applied realistically. This should be corresponded to the standards of entry and exit of developed rest areas.

• 자원환경지질
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• 제11권1호
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• pp.21-37
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• 1978

The depositional environment of the Manhang and the Geumcheon Formation of the Pennsylvanian Gomog Croup is revealed to the shallow neritic marine milieu in this paper also as the results of Park (1963), Cheong(1975) and Kim (1976), through the analyses of stratigraphy, paleocurrent, properties of cross-beddings and sedimentational features. The formations contains some possible terrestrial sediments suggesting the paralic environment, which are however not recognized definitely within them. The paleocurrent analysis is made to the Manhang Formation only. The paleocurrent of the formation is known to belong to the shallow neritic longshore current. The paleocurrent analysis is based chiefly on the cross-bedding analysis, and subordinately on the texture of elastic coarse sediments. The paleocurrent mean is determined to $269^{\circ}$, that is, from east to west, of which direction is interpreted to the right angle to the slope of the basinal depository plane and also the parallel with die depositional strike, according to Klein (1960) and Selley's (1968) criteria. The variance value of paleocurrent directions of the Manhang Formation in the whole area studied is 6,374, and the values range from 3,394 to 6,957 according to the dirstricts. The paleocurreut pattern of the whole area shows polymodel, and the patterns in each district range from trimodel to quadrimodel. Those models approach to the shallow marine or paralic model of Tohill and Picard (1966), Picard and High (1968 a), Pisnak (1957) and Pettijohn (1962). The mean value of maximum inclinations of cross-beddings of the whole area is $19.9^{\circ}$ with the standard deviation of 8.4, and ranges from $15.6^{\circ}$ to $21.7^{\circ}$ in the districts. Comparing the histogram showing the frequency distribution of the maximum inclinations of cross-beddings of the Manhang Formation with the Pettijohn's (1962) histogram, it is found that the model approaches to his marine model. The Pennsylvanian Gomog Group of the coalfield is considered to have had been deposited in the pseudogeosynclinal zone on the plateau by the transgression of the Tethyan sea caused by the epirogenic movements during the Pennsylvanian Period.

• Membrane and Water Treatment
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• 제9권2호
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• pp.69-77
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• 2018

The use of membrane as an innovative technology for water treatment process has now widely been accepted and adopted to replace the conventional water treatment process in increasing fresh water production for various domestic and industrial purposes. In this study, ultrafiltration (UF) membranes with different formulation were fabricated via phase inversion method. The membranes were fabricated by varying the polymer concentration (16 wt%, 18 wt%, 20 wt%, and 21 wt%). A series of tests, such as field emission scanning electron microscope (FESEM), pore size and porosity, contact angle, and zeta potential were performed to characterize the membranes. The membrane performance in terms of permeation flux and rejection were evaluated using a laboratory bench-scale test unit with mine water, lake water and tube well as model feed solution. Long hour filtration study of the membranes provides the information on its fouling property. Few pore blocking mechanism models were proposed to examine the behaviour of flux reduction and to estimate the fouling parameters based on different degree of fouling. 21 wt% PVDF membrane with smaller membrane pore size showed an excellent performance for surface water treatment in which the treated water complied with NWQS class II standard.

• 한국정보통신학회논문지
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• 제12권1호
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• pp.25-32
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• 2008

본 논문에서는 초고속 광대역 서비스를 제공하기에 적합한 주파수 대역인 60GHz 밀리미터파대역의 전파특성을 파악하기 위하여 직접 파를 제외한 반사파 및 투과파에 대한 신호세기를 측정하여 평균 전력 및 표준 편차를 분석하였다. 먼저, 장애물 투과에 의한 수신 신호 세기를 분석 한 결과, 철문, 동판 등은 약 40dB이상의 투과 손실치를 나타내어 투과가 거의 발생하지 않았으며, 고무, 스티로폼 및 유리등이 약 3dB의 투과 손실치로 가장 적게 나타났다. 입사각이 60도 인 경우 장애물에 의한 반사파 수신신호세기는 파티션에서의 손실치가 약 22dB로서 크게 나타났으며, 벽면 반사 손실치가 약 6dB로 가장 적게 나타났다. 이상의 결과는 반사파와 투과파가 서비스 영역 결정에 영향을 미치는 WPAN과 같은 피코셀 이동통신망의 설계에 이용될 수 있을 것으로 판단된다.

• 대한원격탐사학회지
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• 제17권3호
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• pp.211-218
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• 2001

대기복사모델인 MODTRAN을 이용해 다목적실용위성 2호 탑재체인 Multispectral Camera (MSC)의 총복사량에 대한 계산을 수행하고 그 결과를 분석해 보았다. 모델 계산에서 4계절 조건을 모의실험하기 위해 1월 15일, 7월 15일 계산에 대해 중위도 동절기 및 하절기 모델대기를, 4월 15일, 10월 15일에 대해 US 표준대기를 각각 사용했다. 다목적실용위성 2호 궤도 조건과 각 계절에 대한 대표적인 태양천정각 (solar zenith angle)이 고려되었다. 시정거리는 대류권 에어로솔 소광계수 (tropospheric aerosol extinction)에 해당하는 50km가, 지표의 알베도는 맑은 날 지구 연평균 값에 해당하는 0.135가 가정되었다. MSC 계약서 값은 위 일반적 조건을 가정하고 얻은 모델 계산 총복사량보다 MSC 관측 파장대역 대부분에서 상당히 크다는 것을 알게 되었다. 또한 균일한 지표 알베도를 가정하고 얻은 모델 결과의 분광파장 특징이 MSC 계약서 값의 경향과 다름을 보였다. 이들 결과로부터 향후 획득될 MSC영상은 비교적 어두운 영상이 될 것으로 추론된다.