• Journal of Hydrogen and New Energy
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• v.29 no.2
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• pp.219-225
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• 2018

This study was carried out to investigate the injection characteristics of 800 kPa compressed natural gas compressed natural gas (CNG) injector developed in Korea. The CNG injector with multi-holes, employed in this experiment, was designed to inject CNG in the manifold at high pressure of 800 kPa. The spray macroscopic visualization test was carried out via Schlieren photography to study fuel-air mixing process. The fundamental spray characteristics, such as spray penetration, spray cone angle and spray velocity, were evaluated in the constant volume combustion chamber (CVCC) with varying the constant back pressure in CVCC from 0 to 1.8 bar. For the safety reason, nitrogen ($N_2$) and an acetone tracer were utilized as a surrogate gas fuel instead of CNG. The surrogate gas fuel pressures were controlled at 3, 5.5, and 8 bar, respectively. Injection durations were set at 5 ms throughout the experiment. The simulating events of the low engine speed were arranged at 1,000 rpm. The spray images were recorded by using a high-speed camera with a frame rate of 10,000 f/s at $512{\times}256pixels$. The spray characteristics were analyzed by using the image processing (Matlab). The results showed the significant difference that higher injection pressure had more effect on the spray shape than the lower injection pressure. When the injection pressure was increased, the longer spray penetration occurred. Moreover, the linear relation between speed and time are dependent on the injection pressure as well.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.361-368
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• 2005

This study proposes an algorithm for detection and analysis of cracks in digital image of concrete surface to automate the measurement process of crack characteristics such as width, length, and orientation based on image processing technique. The special features of algorithm are as follows: (1) application of morphology technique for shading correction, (2) improvement of detection performance based on enhanced binarization and shape analysis, (3) suggestion of calculation algorithms for width, length, and orientation. A MATLAB code was developed for the proposed algorithm, and then test was performed on crack images taken with digital camera to examine validity of the algorithm. Within the limited test in the present study, the proposed algorithm was revealed as accurately detecting and analyzing the cracks when compared to results obtained by a human and classical method.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.217-224
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• 2008

Trusses are found in many common structures such as bridges and buildings. The truss is a fundamental design element in engineering structures and it is important for an engineer to apply the truss design to engineering structures by understanding the mechanics of truss element. In an experimental course, the experiment selves as an example of the usefulness of the Wheatstone bridge in amplifying the output of a transducer. With the apparatus described here, it is possible to obtain experimental measurements of forces in a truss member which agree within errors to predictions from elementary mechanics. The apparatus is inexpensive, easy to operate, and suitable as either a classroom demonstration or student laboratory experiment. This device is a small table-top experiment. The conventional strain measuring device is costly and complicated - it is not simple to understand its structure. Hence, strain gage and the A/D converter are assembled to come up with a load and a strain measuring device. The device was tested for measuring the strain in a loaded specimen and the results were compared to those predicted by theory of mechanics.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.117-124
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• 2014

Cluttered background is a major obstacle in developing salient object detection and tracking system for mobile device captured natural scene video frames. In this paper we propose a context aware feature vector selection model to provide an efficient noise filtering by machine learning based classifiers. Since the context awareness for feature selection is achieved by searching nearest neighborhoods, known as NP hard problem, we apply a fast approximation method with complexity analysis in details. Separability enhancement in feature vector space by adding the context aware feature subsets is studied rigorously using principal component analysis (PCA). Overall performance enhancement is quantified by the statistical measures in terms of the various machine learning models including MLP, SVM, Naïve Bayesian, CART. Summary of computational costs and performance enhancement is also presented.

• Geotechnical Engineering
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• v.10 no.1
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• pp.71-82
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• 1994

According to the field measurement of dredging-reclaimed land, the actual self-weight consolidation settlement has been frequently reported to be less than the predicted values based on the laboratory tests results. The author estimates that one of the reasons is the reduction of the compressibility due to the sedimentation of the dredging material, Furthemore, the aging effect is ignored in the consolidation characteristics of the very low stress range as a pump dredging-reclaimed land. In this paper, a series of seepage consotidation tests has been carried out by applying the seepage force to the specimen prepared by sedimentation in consolidmeter in order to clarflfy the aging-effect on the compressibility of dredging clayey soil, Also, with a view to overcome unstable consolidation solution occurring in the case where the initial water content is higher as pumpdredging reclaimed land, the finite difference analysis technique using predictorforrector method is suggested that it gets good agreement with ezperimental results. Finally, the compressibility of the dredging clayey soil is depended on self-weight consolidation time.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.147-154
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• 2014

In this study, chlorine modeling technique based on fuzzy system is proposed to reduce the carcinogenic substance and decide the optimal chlorine injection rate, which is affected by chlorine evaporation rate in sedimentation basin according to detention time, weather and water quality. The additional chlorine meter is installed in the inlet part of sedimentation to reduce the feedback time and implement cascade control, which leads to maintaining the residual chlorine concentration decided by fuzzy rule. It helps to take a preemptive action about long time delay, the characteristics of the disinfection process, and reduce the variation of residual chlorine rate by 7.3 times and the chlorine consumption by 40,000 dollars. It made a significant contribution to supply hygienically safe drinking water.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.89-107
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• 1992

The purpose of this study was to investigate the difference between normal and malocclusion subjects in Temporomandibular joint. This study was based on the 44 subjects with normal occlusion, 30 subjects with Class II malocclusion, 30 subjects with Class III malocclusion before treatment. After submental vertex view analysis, each subject was given the TMJ Tomogram in centric relation and centric occlusion and the Cephalogram was taken with Quint Sectograph. The TMJ spaces were measured and analyzed statistically. Following results were obtained. 1. When centric relation was compared to centric occlusion, The condyles were positioned more posteriorly and superiorly in centric relation position of the normal occlusion group and the class II malocclusion group. In the Class III malocclusion group. There was no significant difference in the condylar position between centric occlusion and centric relation. 2. The condyles of the Class III malocclusion group were positioned more superiorly than the normal occlusion group and the Class II malocclusion group. 3. In the correlation between articular eminence posterior slope angle and lingual slope angle of the upper anterior central incisor, there was significant correlation in the normal occlusion group. But no significant correlation was found in the malocclusion group. 4. The mean value of the horizontal angulation of condylar head to the transear rod axis plane was $20.32^{\circ}{\pm}8.12^{\circ}$ in the normal occlusion group, $25.08^{\circ}{\pm}4.83^{\circ}$ in the class II malocclusion group, $14.68^{\circ}{\pm}4.08^{\circ}$ in the class III malocclusion group.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1546-1552
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• 2016

In addition, because it uses preheating to dissolve an alloy in general, it is hard to regulate the appropriate melting temperature of the alloy and brewing time and shows the defect of the supplementation thing due to the super-heating. Once the alloy is molten and then most of the casting by attaching a sight glass or non-contact temperature sensor is suitable casting temperature the operator pressing a button to generate a centrifugal force to inject the molten alloy into a crucible in the casting ring. These results, and most of the cast temperature is too high or too low to generate a lot of casting defects do not get into a uniform cast body. In this paper, we developed a dental casting machine for high frequency using a single temperature sensor which can measure the actual temperature of the alloy than the temperature of the external non-contact measurement using a temperature sensor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.469-472
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• 2007

The telemedicine system provide an efficient means to monitor the status of health and measure bio-information even though the limitation of distance and time. The telemedicine system can be divided into two categories. The first one is Remote Support Service which can monitor the patient including home environments and give those diagnosis information to medical office. and the other one is Alarm Service that can be used for tile emergency status. For the convenience of the patient we will design and implement portable healthcare device and the telemedicine system under the wireless ZigBee network environments.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2029-2033
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• 2007

오늘날 특정 유역에서의 수문현상 및 수문순환에 대한 분석을 위한 연구가 활발히 진행되고 있다. 이를 위해서는 수문자료의 관측은 반드시 수반되어야 하며, 관측자료의 품질관리 및 원시자료의 관리 등이 요구되고 있는 실정이다. 관측된 수문자료의 품질관리라 함은 자료의 신뢰도 분석과 자료의 보완의 두 과정을 포함한다. 여기서, 신뢰도 분석이라 함은 자료 속에 포함된 불확실성을 판별하는 작업을 의미하며, 자료의 불확실성은 위에서 언급된 자료의 불충분 및 불안정을 제외한 부정확, 불일관성에서 비롯된다. 자료의 보완이라 함은 자료의 신뢰도 분석을 통하여 자료 속에 포함된 불확실한 성분들을 찾아내고, 이를 제거한 후 완전한 자료로 대체하고, 자료가 결측된 경우 공백을 연결함으로써 자료의 완전성을 유지하거나 또는 불충분한 자료를 확장하는 일련의 보완작업이라고 정의한다. 자료의 품질을 결정하는 주요 인자는 크게 관측소 관리의 하드웨어적인 측면과 자료 분석의 소프트웨어적인 측면이 있다. 하드웨어적인 측면에서의 수문자료 품질관리를 위해서 본 과제에서는 현장에 설치된 수위계, 강우량계의 센서 등에 대한 장비를 점검하고, 현장실측을 통해 지속적으로 측정값을 보정해주는 역할을 수행하고 있으며, 소프트웨어적인 측면에서 수문자료의 품질관리를 위해서는 수문자료의 수집 단계부터 시작하여 데이터베이스 저장, 필터링, 통계분석, 웹 및 C/S(Client Server)를 통한 배포 등의 일련의 자료 처리 과정을 수행할 수 있는 수문자료관리 프로그램을 웹 시스템과 C/S로 분류하여 정의내릴 수 있다. 본 연구에서는 수문자료의 관리자 입장에서의 보다 효율적이고 체계적으로 자료를 관리하고 분석하기 위한 방안으로 수문자료관리시스템(Hydrologic Data Aquisition and Management System, HDAMS)을 개발하였다. 이 시스템은 안양천 유역에서 시범 적용하고 있으며, 범용성을 전제로 개발되었다. 또한 수문자료 관리 프로그램의 DB 구조 및 DB 자료를 활용한 다양한 분석기능은 갖도록 설계하였으며 계획된 데이터베이스 구조를 바탕으로 계측기 인터페이스와 사용자 인터페이스, 데이터베이스 간의 연동이 원활히 이루어지도록 개발하고자 한다.