• Geomechanics and Engineering
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• 제6권2호
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• pp.153-172
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• 2014

In order to investigate the effect of different perforation angles (the angle between the perforation direction and the maximum horizontal principal stress) on the fracture initiation and propagation during hydraulic fracturing of highly deviated well in oil & gas saturated formation, laboratory experiments of the hydraulic fracturing had been carried out on the basis of non-dimensional similar criteria by using 400^3 $mm^3$ cement cubes. A plane fracture can be produced when the perforations are placed in the direction of the maximum horizontal principal stress. When the perforation angle is $45^{\circ}$, the fractures firstly initiate from the perforations at the upper side of the wellbore, and then turn to the maximum horizontal principal stress direction. When the well deviation angle and perforation angle are both between $45^{\circ}$ and $90^{\circ}$, the fractures hardly initiate from the perforations at the lower side of the wellbore. Well azimuth (the angle between the wellbore axis and the maximum horizontal principal stress) has a little influence on the fracture geometries; however it mainly increases the fracture roughness, fracture continuity and the number of secondary fractures, and also increases the fracture initiation and propagation pressure. Oriented perforating technology should be applied in highly deviated well to obtain a single plane fracture. If the well deviation angle is smaller, the fractures may link up.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.276-277
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• 2006

Estimation of power system frequency is an important task because frequency deviation is a good indicator of the system abnormal operating conditions. The algorithms, curve fitting, technique using Taylor series, deviation of phasor angle of fundamental waveform using DFT (Discrete Fourier Transform) and Prony method, are tested under operation of the frequency relaying by using EMTP MODELS. The performance of methods is compared with the simulation results.

• 한국군사과학기술학회지
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• 제21권5호
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• pp.563-571
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• 2018

In order to effectively protect a penetrator, the conically shaped protector was proposed and the protection capability was investigated. The collision and penetration of the penetrator with the protector were analyzed using dynamic finite element analysis. The post impact behaviors of the penetrator, i.e., flying velocity and the change of attitude angle, were monitored to investigate the protection capability. The flying velocity and the attitude angle are used to investigate the deviation and the penetration power respectively. The effect of rotation speed of the protector and the collision position on the protection capability is investigated in the viewpoint of deviation and attitude angle when penetrator colliding with our tank.

• Restorative Dentistry and Endodontics
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• 제29권1호
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• pp.44-50
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• 2004

This study compared the shaping ability of nickel-titanium rotary files with different rake angle and radial land. The nickel-titanium files used in this study were Profile(Dentsply, Maillefer, Ballaigues, Switzerland), Hero 642(Micromega, Besancon, France) and K3 (SybronEndo, Glendora, Ca, USA) file. Resin blocks substituted for root canals. 36 resin blocks were divided into 3 groups with 12 canals each The time for canal preparation was recorded. The images of pre- and postoperative resin canal were scanned and those were superimposed Amounts of canal deviation, total canal widths, inner canal widths, and outer canal widths were measured at apical 1, 2 ,3, 4, 5, 6, and 7mm levels. The amount of canal deviation was the smallest in Profile group , and the time far canal preparation was the shortest in Hero 642 group. K3 group resulted in competent characteristics in both measurements. Positive rake angle seemed to result in fast shaping of root canal and radial land guide the instrument in center of the canals and around curvatures. Radial land also tended to reduce the sense of screwing into the root canal. The proper selection of the nickel-titanium fie based on the knowledge about file design is needed for the safer, simpler and faster root canal therapy.

• 터널과지하공간
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• 제12권4호
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• pp.268-276
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• 2002

In this study, a 3D coordinate measurement system equipped with a laser displacement meter for digitizing rock joint surface was established and the digitized data were used to calculate several roughness parameters. The parameters used in this study were micro avenge inclination $angle(i_{ave})$, average slope of joint $asperity(SL_{ ave})$, root mean square of $i-angle(i_{rms})$, standard deviation of height(SDH), standard deviation of $i-angle(SD_i)$, roughness profile $index(R_P)$, and fractal dimension(D). The relationships between the roughness parameters based on the digitzation of the surface profile were analyzed. Since the measured value varied according to the degree of reflection and the variation of colors at the measuring point, rock joint surface was painted in white to minimize the influence of the surface conditions. The comparison of the measured values and roughness parameters before and after painting revealed the better consequence from measurement on the painted surfaces. Also, effect of measuring interval was studied. As measured interval was increased, roughness parameters were exponentially decreased. The incremental sequence of degree of decrease was $SDH\; i_{ave},\; i_{rms},\; SD_i,\;and\; R_ p-1$. As a result of comparison of parameters from pin-type measurement system and laser type measurement system, all value of parameters were higher when laser-type measurement system was used, except SDH.

• 제어로봇시스템학회논문지
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• 제16권10호
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• pp.1006-1012
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• 2010

The hot rolling process ranks the highest position for production in steel making process. The hot strip manufacturing processes consist of the reheating furnace, roughing and finishing mill and coiler. The reheating furnace heats the slab. The roughing and finishing mill produce the hot strip from slab. The hot strip quality mainly depends on finishing mill, which consists of 4-high 7 stands. The looper is installed between stands and is used for controlling the strip tension by the looper angle for better material flow. It is difficult to control the strip tension with the coupled looper system from interaction between the looper angle and strip tension. Too much deviation of strip tension severely affects the poor width quality of the hot strip. It is important to control simultaneously both the looper angle and strip tension with each of their target values. This paper proposes the fuzzy tension control, which is developed to minimize the width deviation of the hot strip by maintaining the proper strip tension between stands and to achieve the stable operation of the coupled looper system. The fuzzy tension control performance is compared with the conventional PID control by experimental results.

• 한국분무공학회지
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• 제23권1호
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• pp.22-29
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• 2018

The purpose of this study is to investigate the macroscopic spray characteristics and spray pattern of a gasoline direct injection (GDI) injector according to the increase of injection pressure. The macroscopic spray characteristics, such as a spray tip penetration and spray angle, were measured and analyzed from the frozen spray images, which are obtained from the spray visualization system including the high-speed camera, light-source, long-distance microscope (LDM). The spray pattern was analyzed through the deviation of the center of the spray plum and images were acquired using Nd: YAG Laser and ICCD(Intensified charge coupled device) camera. From the experiment and analysis, it revealed that the injection pressure have a significant influence on the spray tip penetration and spray pattern. However, the injection pressure have little influence on the spray angle. The increase of injection pressure induced the reduction of a closing delay. In addition, the deviation of spray center increase with the increase of injection pressure and the distance from a nozzle tip.

• 한국전기전자재료학회논문지
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• 제29권3호
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• pp.175-180
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• 2016

In this study, we proposed an optical compensation method to improve the symmetricity of contrast ratio for wide viewing angle IPS (in-plane switching) LCD. First, the phase retardation depending on the thickness of compensation film is calculated, and then the phase change is presented at the $Poincar{\acute{e}}$ sphere. The phase retardation and the polarization state of the light passing through the optical elements are caculated by using the EJMM (extended Jones matrix method). In addition, the transmittance and the contrast countour are also calculated by using the Berremann's $4{\times}4$ matrix method. The simulation is carried out for a IPS LC cell with positive A/C/A compensation film. From the standard deviation of the contrast ratio, we confirmed the symmetricity at each viewing angle is inversely proportional to the standard deviation and calculated the optimum design condition of the uniaxial compensation film for the IPS LCD.

• 한국정보처리학회논문지
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• 제5권3호
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• pp.824-832
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• 1998

본 논문에서는 영상의 코너점을 추출하기 위한 방법을 제안한다. 먼저 윤곽선을 따라 경계화소의 방향각을 lookup table의 참조에 의해 구하고, 기준치 이상의 화소를 후보점으로 선정한 뒤, 면적편차를 이용하여 코너점을 추출한다. 본 방법은 실시간 처리를 위해 처리시간을 줄이는 동시에 디지털 영상을 표현하는데 있어 라운드 오프 오차에 의해 발생되는 한 화소차를 극복하는 장점을 가진다. 제안된 방법의 검증을 위해 각종 실험 패턴을 이용하여 기존의 방법과 비교분석을 하였다.

• 한국수산과학회지
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• 제57권3호
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• pp.302-309
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• 2024

This study estimates the target strength of anchovy Engraulis japonicus required for studying their distribution and density using acoustics and evaluates the acoustic scattering characteristics of anchovies by frequency using the Kirchoff ray mode (KRM) model. The experiment was conducted on 30 anchovies with 4.7-21.5 cm total length. The maximum TS_cm (Simming angle, 9.1°; standard deviation, ± 13.1°) according to total length was -66.9, -65.2, -64.4, and -63.4 dB at 38, 70, 120, and 200 kHz, respectively. The average TS_cm (Simming angle: 9.1°, standard deviation: ± 13.1°) according to total length was -68.9, -68.8, -69.6, and -70.0 dB at 38, 70, 120, and 200 kHz, respectively. The results of this study provide an important basis for future studies that use acoustics to estimate the target strength of anchovies.