• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.739-744
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• 2017

Elastic deformation and fatigue damage can cause the permanent deformation of a kart's frame during turning, affecting the kart's driving performance. A kart's frame does not contain any suspension or differential devices and, therefore, the dynamic behavior caused by torsional deformation when driving along a curve can strongly affect these two kinds of deformations. To analyze the dynamic behavior of a kart along a curved section, the GPS trajectory of the kart is obtained and the torsional stress acting on the kart-frame is measured in real time. The mechanical properties of leisure and racing karts are investigated by analyzing their material properties and conducting a tensile test. The torsional stress concentration and frame distortion are investigated through a stress analysis of the frame on the basis of the obtained results. Leisure and racing karts are tested in each driving condition using driving analysis equipment. The behavior of a kart when being driven along a curved section is investigated through this test. Because load movement occurs owing to centrifugal force when driving along a curve, torsional stress acts on the kart's steel frame. In the case of a leisure kart, the maximum torsional stress derived from the torsional fatigue limit was found to be 230 MPa, and the torsional fatigue limit coefficient was 0.65 when driving at a speed of 40 km/h. Furthermore, the driving elements during the cornering of a kart were measured based on an actual auto-test after installing a driving measurement system, and the driving behavior of the kart was analyzed by measuring its vertical displacement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.379-385
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• 2020

This paper presents a design for preventing coolant leaks in the core part of a heater mounted in a combat vehicle. The heater is a device that makes heated coolant flow through the heater core in the crew room. A problem with coolant leaks in the heater core area during the operation of a combat vehicle was identified. This problem is caused mainly by high pressure at the junction of the tank and tube due to the vulnerability of this area. To solve this problem, an improved core was made by improving the welding method and changing the end region of the heater core to a structure that can withstand high pressure. When pressure was applied sequentially to the existing core and improved core, a leak occurred at 7.0 kgf/㎠ in the existing core while the improved core maintained its structure up to 17.0 kgf/㎠, highlighting the improvement. Finally, performance tests and environment tests were conducted to demonstrate the suitability of the improved structure. The improved heater will be applied to combat vehicles. This paper is expected to serve as a reference for improving defense capabilities by securing reliability as well as the design and analysis of failures of similar equipment.nse capabilities through securing reliability as well as the design and analysis of failures of similar equipment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.541-546
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• 2020

The surveillance radar for naval ships is an essential equipment of a battle system that executes the detection and tracking of targets, and the shooting support function; it calculates the three-dimensional track of the target range, azimuth, and altitude to carry out its duty. The surveillance radar consists of an antenna, a transceiver, a processing unit, and an air dryer section. The radar radiates the transmission signal on the antenna section, receives the reflected signal from the target, and amplifies the signals on the transceiver section. The signal received from the antenna is used to provide the operator with target information in various ways. This study identified the display problems when the information about the target is displayed through the radar. The causes of the problems were analyzed and improved. The tracking disappearance phenomenon caused by the altered-course of the ship was improved on the TWS tracking algorithm. The validity of the improved TWS tracking algorithm was confirmed by the normal condition of the target status on the B-scope.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.37-43
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• 2015

At marine construction sites, there are problems with regard to dispute on the responsibility of safety management of chartered barge and its legal issues. In general, demise charter with crew is used for barge charterparty which is committed to the marine construction. Although Chapter 5 of the Korean Commercial Act enact provisions regulating a Time Chargerparty and a Bareboat Charterparty, it is difficult to clarify where the responsibility lies with regard to the safety control of the chartered barge. For this reason, disputes on accountability arise when accident occurs in effect. As a result, parties of the charterparty shift the responsibility on each other and there is increased risk for occurrence of similar accidents. There is no legally required qualification for a head of barge workers who is in charge of barge management. It is not possible to demand the head of barge workers to take charge of tasks which requires professional judgment as a marine technician considering his daily work scope. Furthermore, the barge committed to the marine construction as a form of bareboat charter or equipment charterage is an object which should be managed by safety supervisor of the charterer's marine construction. The charterer bears a duty to manage the safety of the barge. Therefore, the charterer is generally liable for the damage incurred in the course of using the chartered barge.

• Korean Journal of Construction Engineering and Management
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• v.16 no.3
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• pp.68-77
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• 2015

One of recent concerns for super-tall buildings is how to manage hoisting plans and equipment efficiently. Disasters are frequently occurred in relation to electromotive hoists and cranes which are commonly used in construction sites. For construction lifts, particularly, it is highly important to conduct regular inspections or prepare against breakdown in terms of safety. However, unfortunately the reality is that regular inspections are only flatly conducted according to operating hours only. A lift, whose life span is subject to the complicated considerations such as operating hours, loading condition, and the like of each component, is far too invalid as a means of maintenance. As a way to resolve this problem and improve its convenience and safety for users, this study intends to calculate individual inspection interval for the main components of lifts by measuring their actual operating hours with sensing technology and analyzing their historical data. The findings of study include calculation of inspection intervals for the main components of lifts and classification of components to check by the actual operating hours of lift (40, 90, 130, 400 hours), which are drawn up into tables. This will make an opportunity to suggest efficient maintenance measures by enabling prevention of safety accidents and enhancement of safety for workers. Also, it will lead to increasing productivity of works by eliminating sources of delaying the term due to the breakdown of lifts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.303-310
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• 2018

One of most shocking headlines is a serious chain collision accident (CCA). The development of CCA has a temporal and spatial locality, and the information of the CCA is time-critical. Due to these characteristics of CCA, traffic accident information should be rapidly propagated to drivers in order to reduce chain collisions, right after the first accident occurs. Inter-vehicle communication (IVC) based on ad-hoc communication is one of promising alternatives for locally urgent information propagation. Despite this potential of IVC, research for the effects of IVC on the reduction of CCA has not been reported so far. Therefore, this study develops the parallel platform of microscopic vehicle and IVC communication simulators and then analyses the effects of IVC on the reduction of the second collision related to a series of vehicles. To demonstrate the potential of the IVC-based propagation of urgent traffic accident information for the reduction of CCA, the reduction of approaching-vehicle speed, the propagation speed of accident information, and then the reduction of CCA were analysed, respectively, according to scenarios of combination of market rates and traffic volumes. The analysis results showed that CCA can be effectively reduced to 40~60% and 80~82% at the penetration rates of 10% and 50%, respectively.

• International Journal of Highway Engineering
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• v.3 no.2 s.8
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• pp.113-121
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• 2001

Among the currently available binder specifications, Superpave Performance Grade asphalt specification is regarded as a superior specification on its theoretical background as well as pavement performance relationship. Many difficulties are expected; however, for Superpave implementation in Korea because of heavy burden of equipment cost as well as lack of trained personnel in asphalt industry, which may too much barrier to overcome in Korean situation. As an effort to improve qualify of asphalt binder, recently, people discuss about a possibility of constituting a performance-based asphalt specification using rather easy-to-measure asphalt properties. The objective of this paper is to determine the possibility of constituting a performance-based asphalt specification using an empirical asphalt properties, such as penetration ring and ball softening point rather than using fundamental properties of asphalt. Nine straight asphalts, that covers entire straight asphalt from all Korean refineries, and eighteen modified asphalts that were modified from two modifiers were included in the study. An analysis was made through a comparison between empirical properties and Superpave PG criteria. This study concluded that it may possible to constitute a pseudo-Superpave-like specification using an empirical asphalt properties as a specification criteria. Therefore, more systematic research is needed to constitute the asphalt specification.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.41-49
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• 2009

Cement concrete pavement has become more common in Korean highway systems. However, as its service period increases, there are some technical problems occurs and no clear solution is available primarily due to the lack of active researches. This research, hence, aims to develop a new mix proportion that may provide better strength and durability with extended service life. Based on a variety of literature reviews, the experimental variables were determined as unit cement content, S/a ratio and W/C ratio. From the experimental works, it is recommended to increase the unit cement content up to 375kg/$m^3$, 400kg/$m^3$ and 425kg/$m^3$. The target slump and air content were set 40mm and 5%, respectively. The maximum size of coarse aggregate was decided to be 25mm because of the easiness of supply in the field. The reduction of W/C ratio was necessarily required and decreased to 0.4 which was proven not to cause any mixing problem with the increased unit cement contents along with polycarbon-based high range water reducing agent. In addition, it was known that the S/a ratio could be reduced to 0.34. The lowered S/a might be possible because of the increased cement paste and hence increased cohesiveness and workability.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.375-381
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• 2015

Digital Radiography is a big part of diagnostic radiology. Because uncorrected digital radiography image supported false effect of Patient's health care. We must be manage the correct digital radiography image. Thus, the artifact images can have effect to make a wrong diagnosis. We report types of occurrence by analyzing the artifacts that occurs in digital radiography system. We had collected the artifacts occurred in digital radiography system of general hospital from 2007 to 2014. The collected data had analyzed and then had categorize as the occurred causes. The artifacts could be categorized by hardware artifacts, software artifacts, operating errors, system artifacts, and others. Hardware artifact from a Ghost artifact that is caused by lag effect occurred most frequently. The others cases are the artifacts caused by RF noise and foreign body in equipments. Software artifacts are many different types of reasons. The uncorrected processing artifacts and the image processing error artifacts occurred most frequently. Exposure data recognize (EDR) error artifacts, the processing error of commissural line, and etc., the software artifacts were caused by various reasons. Operating artifacts were caused when the user didn't have the full understanding of the digital medical image system. System artifacts had appeared the error due to DICOM header information and the compression algorithm. The obvious artifacts should be re-examined, and it could result in increasing the exposure dose of the patient. The unclear artifact leads to a wrong diagnosis and added examination. The ability to correctly determine artifact are required. We have to reduce the artifact occurrences by understanding its characteristic and providing sustainable education as well as the maintenance of the equipments.

• Journal of radiological science and technology
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• v.30 no.3
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• pp.237-243
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• 2007

Phantoms are very necessary for quality assurance of radio nuclides imaging systems to maintain standards and to ensure reproducibility of test. General quality assurance and instrument quality control are essential in every hospital. The human tissue equivalent materials are aluminum, areryl, water and epoxy..etc. It is very important to select optimum equivalant materials for a phantoms in QC. Especially, paraffin is very similar with human soft tissue in X or Gamma-ray physical characteristics and easy to buy with economically. We made a paraffin thyroid phantom and compare with thyroid areryl phantom, also used commercially in practice. Two small size cold spots(3 and 6 mm diameter) and a hot spot(3 mm diameter) embeded in paraffin phantom. And imaged with $^{99m}TcO_4$ by camera for analysis about spatial resolution and noise at the hot and cold spots. We got some results as below : 1. No difference in counting rate and noise between both arcryl and paraffin thyroid phantoms. 2. The best spatial resolution can be seen 6 cm distance between pinhole collimator and thyroid phantoms(arcryl and paraffin). 3. More optimal spatial resolution could acquired in paraffin thyroid phantom. Paraffin is very similar with human soft tissue in atomic number, density and relative absorbtion function, and can be shaped easily what we wanted. So we can recommendation paraffin as quality assurance phantom because its usefulness, economical benefit and purchasability.