• International Journal of Fluid Machinery and Systems
• /
• 제10권3호
• /
• pp.218-226
• /
• 2017

Severe radial thrust under off-design operating conditions can be a harmful factor for centrifugal pumps. In the present work, effects of geometry of a double volute casing on the hydrodynamic performance of a centrifugal pump have been investigated focusing on off-design conditions. Three-dimensional steady Reynolds-averaged Navier-Stokes analysis was carried out by using shear stress transport turbulence model. Numerical results for the hydrodynamic performance of the centrifugal pump were validated compared with experimental data. The hydraulic efficiency and radial thrust coefficient were used as performance parameters to evaluate the hydrodynamic characteristics of the centrifugal pump. The cross-sectional area ratio of the volute casing, the expansion coefficient of the rib structure, the distance between the rib starting point and volute entrance, and radius and width of the volute entrance, and length of the rib structure, were selected as geometric parameters. Results of the parametric study show that the performance parameters are significantly affected by the geometric variables and operating conditions. Optimal configurations of the double volute casing based on the design of experiments technique show outstanding performance in terms of the efficiency and radial thrust coefficient.

• 응용통계연구
• /
• 제26권1호
• /
• pp.187-200
• /
• 2013

본 논문에서는 기하브라운운동(geometric Brownian motion)을 기반으로 표준옵션의 델타헤지를 수행하는 경우, 헤지변동성의 선택이 헤지손익에 미치는 영향을 재탐색하였다. 이를 위하여, 헤지변동성과 헤지손익과의 관계를 고찰하였으며, 모의실험과 실증분석을 통하여 기초자산의 추세에 따라 헤지변동성을 달리 선택하는 것이 최종 헤지손익에 유리할 수 있음을 살펴보았다. 구체적으로, 등가격 표준옵션의 헤지매매 시 향후 기초자산이 횡보할 것으로 예상될 때에는 헤지변동성을 상대적으로 크게, 추세가 형성될 것으로 예상될 때에는 비교적 작게 사용하는 것이 손익에 유리하였다.

• 패션비즈니스
• /
• 제11권6호
• /
• pp.11-23
• /
• 2007

This study has investigated the stream of consciousness and the actual conditions of tattoo. A survey of 466 people has found that female prefer tattoo, and a group of age between 21 and 41 and professionals are more interested in it. Both past and present of attitude consciousness about tattoo understand it dynamic and severe. However, it is considered as a feminine these days, whereas it had been understood as a masculine image in the past, which means a decrease of symbolism by gender. Also, in comparison with the past, the current thoughts on tattoo are getting hopeful and affirmative that we could know the attitude about tattoo changes. A survey of 106 tattooists shows that most people get a temporary tattoo, and permanent, semi-permanent tattoo came next. The most preferred area were eyebrows, are, shoulder, forearm, back of hand and waist, and a main reason of getting tattoo were for beauty and ostentation. For the level of satisfaction, 70.7% of the people polled said they were satisfied with it, and male preferred a pattern of animal, geometric and plant while female preferred a pattern of plant, animal, and geometric in order. So far, by the lack of basic information and data, efficiency value of tattoo is in negative view. Thus, it would be required to enhance a level of understanding tattoo focusing on the positive side like a new life style, sense of value, sensation and emotion of contemporary people, and generalize it by providing various technical information and knowledge of beauty image effect accompanied with tattoo.

• 한국정밀공학회지
• /
• 제20권12호
• /
• pp.115-125
• /
• 2003

The design methodology of plastic injection molding die has been gradually moved from two-dimensional line drawings to three-dimensional solid models. The 3D design gives many benefits, a few of which are: ease of design change, data associativity from concept design to final assembly. In the paper represented is the implementation of a program which automatically generates 3D mold-bases and cooling-lines, conforming to given geometric constraints. It utilized a commercial CAD software and the related API(application program interface) libraries. We constructed a DB(database) of typical mold-bases assembled from standard parts, from which the geometry (position & dimension) of a mold-base and composed parts can be automatical]y determined by a few key parameters. Also we classified cooling lines into several typical types and constructed a DB, from which the position of cooling lines is automatically determined. The research is expected not only to simplify construction of a 3D mold-base model including cooling lines but also to reduce design efforts, by way of databases and automatized determination of geometric dimensions.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.252-256
• /
• 1998

Accurate mapping of satellite images is one of the most important Parts in many remote sensing applications. Since the position and the attitude of a satellite during image acquisition cannot be determined accurately enough, it is normal to have several hundred meters' ground-mapping errors in the systematically corrected images. The users which require a pixel-level or a sub-pixel level mapping accuracy for high-resolution satellite images must use a number of Ground Control Points (GCPs). In this paper, the performance of two geometric correction algorithms is tested and compared. One is the polynomial warping algorithm which is simple and popular enough to be implemented in most of the commercial satellite image processing software. The other is full camera modelling algorithm using Physical orbit-sensor-Earth geometry which is used in satellite image data receiving, pre-processing and distribution stations. Several criteria were considered for the performance analysis : ultimate correction accuracy, GCP representatibility, number of GCPs required, convergence speed, sensitiveness to inaccurate GCPs, usefulness of the correction results. This paper focuses on the usefulness of the precision correction algorithm for regular image pre-processing operations. This means that not only final correction accuracy but also the number of GCPs and their spatial distribution required for an image correction are important factors. Both correction algorithms were implemented and will be used for the precision correction of KITSAT-3 images.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권10호
• /
• pp.4042-4059
• /
• 2020

The development of new multimedia techniques such as 3D printing is increasingly attracting the public's attention towards 3D objects. An optimized robust and imperceptible watermarking method based on Ant Colony Optimization (ACO) and Weber Law is proposed for 3D polygonal models. The proposed approach partitions the host model into smaller sub meshes and generates a secret watermark from the sub meshes using Weber Law. ACO based optimized strength factor is identified for embedding the watermark. The secret watermark is embedded and extracted on the wavelet domain. The proposed scheme is robust against geometric and photometric attacks that overcomes the synchronization problem and authenticates the secret watermark from the distorted models. The primary characteristic of the proposed system is the flexibility achieved in data embedding capacity due to the optimized strength factor. Extensive simulation results shows enhanced performance of the recommended framework and robustness towards the most common attacks like geometric transformations, noise, cropping, mesh smoothening, and the combination of such attacks.

• 한국측량학회지
• /
• 제21권2호
• /
• pp.165-172
• /
• 2003

IKONOS 위성영상은 지형·지물의 분포 파악 및 추출에 적합하여 많은 분야에서 이를 이용한 연구가 활발히 진행되고 있다. 그러나, IKONOS 위성영상은 3차원 지형정보를 추출할 수 있는 위성센서의 위치와 자세에 대한 정보를 공개하지 않고 있어 영상의 3차원 지형정보 획득을 위해서는 영상에서 제공하는 유일한 자료인 RPC(Rational Polynomial coefficients) 정보를 이용해야만 하는 실정이다. 이에 본 연구에서는 IKONOS 위성영상이 제공하는 RPC 정보를 통해 3차원 지상좌표 추출 알고리즘을 구현하여 프로그램을 개발하였으며, 이를 통한 3차원 지상좌표 추출시 발생하는 오차를 지상기준점 측량성과에 의해 보정하여 지상기준점의 수와 배치에 따른 위성영상의 기하학적 정확도 분석을 수행하므로써 고해상도 위성영상을 이용한 측정정확도 및 효율성을 향상시킬 수 있었다.

• 한국측량학회지
• /
• 제13권1호
• /
• pp.85-94
• /
• 1995

국토개발에 관한 각종정보, 도시환경 및 토지이용정보, 농수산자원 조사, 지질조사, 수종의 분류, 나무의 생육상태등의 많은 정보를 수집하고 추출하는데 원격탐사는 중요한 일익을 담당하고 있다. 본 연구는 원격탐사를 수행하는데 영상처리 자료의 위치 정확도를 향상시키기 위하여 실시하는 기하학적 보정을 하는데 있어 지도를 이용하는 방법과 GPS를 이용하는 방법을 서로 비교하여 보다 정확한 인공위성 영상의 좌표변환을 위한 것이다. 실제 지형지물에서 GCP를 획득할 때의 문제점과 어려운 점에 대하여 개선방안을 찾으려고 하였으며, 향후 전국적인 인공위성영상 접합을 위한 좌표계에 대한 고려를 고찰해 보았다.

• 대한조선학회논문집
• /
• 제53권5호
• /
• pp.428-434
• /
• 2016

A lot of drawings for pipe construction and installation are needed to construct plant process system on the offshore plant structures. Depending on their scale or complexity, the required number of drawings related pipes sometimes amounts to several hundreds of thousands. Most major shipyards, therefore, have their own system which can automatically depict pipes’ geometric, manufacturing, and BOM(Bill of Material) information on the drawings. However, as the complexity and absolute quantity in the isometric region on the drawings is increased, the information extraction from the customized DB and positioning at the typical locations does not get to be enough to avoid the overlap between geometric contours, labels, and symbols. For this reason, the novel methods to arrange additional annotations without overlaps are presented in the paper. This approach is expected to increase the readability and legibility of the drawing and prevent the human error, and finally decrease the time-consuming and tedious jobs which are unnecessarily required to designers.

• 대한공간정보학회지
• /
• 제8권1호
• /
• pp.73-84
• /
• 2000

차량용 자동 항법장치가 실생활에 적용됨에 정확한 자동차의 위치를 표현하기 위해서 맵매칭 기술에 대한 중요성은 더욱 부각되고 있다. 맵매칭 기술은 GPS의 오차, 수치지도의 오차 등으로 발생하는 오류를 극복하기 위한 과정으로서 자동 항법시스템은 물론 기타 관련분야인 GPS영역등에도 반드시 필요한 기술중의 하나이다. 그러나, 지금까지 맵매칭에 대한 기술을 정확하기 구분하여 기술하거나 가장 적합한 알고리즘을 제시하지 못하고 있는 바, 본 논문에서는 그 동안 개발된 많은 맵매칭 기술에 대하여 크게 지형정보와 위상구조를 토대로 2가지 유형으로 구분하여 각 기술별 문제점과 개선 방안을 소개하였다 더 나아가, 최근 미국 전부의 주도로 SA(Selective Availability) 개념이 사라짐에 따라, 쉽게 적용할 수 있는 간단한 형태의 맵매칭 알고리즘을 제시하였고, 향후의 응용방안에 대하여 간단히 언급하였다.