• Journal of the Korean Society for Railway
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• v.18 no.1
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• pp.33-42
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• 2015

The vertical static stiffness of rail pads or baseplate pads, which are important components in rail fastening systems for track safety, is a key factor to determine the total track stiffness and a guideline of quality control in the manufacturing process. The vertical static stiffness can be checked by laboratory testing: test methods are EN 13146-9 and KRS TR 0014, which are widely used in the railway field. In this paper, to correct some problems, namely the preloading step, the unloading level, and the holding time in the loading program in the vertical static stiffness test of EN 13146-9 and KRS TR 0014, domestic and foreign test standards of pads were analyzed and then certain schemes for a vertical static stiffness test were proposed. To assess the reliability of the proposed schemes, the vertical static stiffness tests were performed with 4 pads and the validity of the test results was estimated.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.38-43
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• 2007

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of $0.4{\mu}m$) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated A ground surface roughness Rz of 0.14 um was achieved Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish $5000mm^2$ of die steel surface without any deterioration of the ground surface roughness.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.129-138
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• 2012

In this study, three types of large scale multi-tasking machine tools together with core technologies involved have been developed and introduced; a multi-tasking machine tool for large scale marine engine crankshafts, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type. Several special purpose devices has been necessarily developed for the purpose of handling and machining big and heavy workpieces accurately, such as PTD (Pin Turning Device) with revolving ring spindle for machining eccentric crankshaft pins, hydrostatic rotary table and steady rest for supporting and resting heavy workpieces, and 2-axis automatic swiveling head for high-quality free surface machining. Core technologies have been also developed and adopted on their detail design stage; 1) structural design optimization with FEM structural analysis, 2) theoretical hydrostatic analysis for the PTD and rotary table bearings, 3) box-in-box type cross-rail and octagonal ram design to secure machine rigidity and accuracy, 4) constant spindle rpm control against gravitational torque due to unbalanced workpiece.

• Journal of Environmental Health Sciences
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• v.34 no.4
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• pp.279-284
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• 2008

This paper aims to provide basic data for work environment control, prevention of worker exposure to asbestos and improvement of air quality to protect workers ‘health after measuring the level of airborne asbestos and workers' exposure in a shipbuilding repair businesses. For this study, a total of 27 samples were collected from 27 workers who had been exposed to asbestos during engine, piping, boiler and other manufacturing processes in 'A' Shipbuilding Repair Company in Gyeongnam. This research was conducted from Oct. 1 to 30, 2007 and had the following results: The target group (27 workers) consisted of all men with an average age of 35.9 years and 6.6 years of work on average. Among them, fifteen 15 (55.6%) were smokers. In terms of their duties at work, there were 12 plumbing repair engineers (44.4%), 8 boiler repair engineers (29.6%) and 7 engine engineers (25.9%). The geometric mean concentration of airborne asbestos was 0.004 f/cc. A total of 4 samples exceeded the exposure limit. In particular, three exceeded the legal limit by more than double, which means that some workers have been highly exposed to asbestos. In terms of the concentration of asbestos fibres by work process, plumbing repair was the highest (0.0071 f/cc($0.001{\sim}0.57\;f/cc$)) while boiler was the lowest (0.0015 f/cc($0.001{\sim}0.007\;f/cc$)). Based on this study, proper action needs to be taken as soon as possible to protect workers from the threat of asbestos.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1045-1053
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• 2013

Boat or yacht hull has been built mainly by FRP composite materials. FRP boat hull manufacturing begins to be restricted after the year 2000 under international regulation on ocean environment safety. The alternative of FRP has been proposed by many boat builders and high strength aluminium is considered as its standard material. But high strength aluminium is very expensive as boat hull material. In this study, boat hull is considered to be built by high density polyethylene and its structural strength is estimated by longitudinal strength test method on small craft. Tensile strength of polyethylene boat hull material is higher than that of FRP boat hull material. But safety factor of polyethylene boat hull is more than that of FRP boat hull. These study results indicate structural integrity and quality control of polyethylene boat is better than those of FRP boat.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.48-56
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• 2013

Prestressed concrete (PSC) members are readly available in civil engineering applications due to the convenience of construction and easy of quality control in the manufacturing process of the member. Especially, half-depth precast concrete composite slab, which is one of the PSC flexural members is developed recently using the long-line method. The half-depth precast concrete composite slabs are composed of the precast concrete and the in-situ concrete placed at the site. In this paper, we present the results of experimental investigations pertaining to the pretensioning efficiency and the flexural behavior of half-depth precast concrete composite slab which is made of precast PSC manufactured by the long-line method. In the long-line method, the pretensioned precast member is manufactured simultaneously, by tensioning tendons at once. In addition, we suggest the equation that can estimate the flexural strength of half-depth precast concrete composite slab reasonably by considering the effects of rebar embedded in the precast PSC flexural member.

• Journal of Distribution Research
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• v.1 no.1
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• pp.41-63
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• 1996

In spite of economy has a critical cycle such as, production, distribution and consumption, we hardly concentrated our study to distributional system and behavior. Especially in Korea, Traditional idea had tried to ignore the people who work in this economic value at all. Manufacturers, other than retailers and wholesalers, had a belief that the manufacturing can control distributional channels forever. Unfortunately, technological and educational advances caused the quality equalization among developing and developed countries as well as among big and small manufacturers in their products. By this reason, economists are searching the economists dark continet' mentioned by Peter Drucker as a new source of wealth. According to a report by well-known economic research institute in Switzerland, Korea has classified in the lower level group in terms of international compatitive power. At the same time, business firms complain that they are suffering from lack of SOC and infrastructures. As an important mean to overcome the economic bottleneck, economists suggest in improve our distributional atmosphere. Basically, distributional study has two sub-fields as: commercial and physical distributions, Distributional system mainly concerns about to shorten the distances of time and space between production and consumption. The closer the distances, the higher efficiency can be achieved. Building distributional system will cost, but tile results will save social costs. Based on this idea, economists proposed several ways to cut the distances and to save costs, Naturally, they hope their beliefs can be adapted by business firms and governments. But frequently, their theories doesn't make any fruit. This paper has studied about the composition of joint transportational and distributional systems. And, even though there's no Marshall in tile real world at this point authors are trying to define the transportational and physical distributional costs, the most powerful factor that can impact to economic decision making.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.36-43
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• 2022

Generally, in construction sites, the pipe support installation workers often use support pins of 9~10 mm which are much smaller than the safety standard sizes for work convenience. Although the safety certification standard thickness of the support pins is 11 mm, and the supervisors are often indifferent to this. Hence, products with far lower performance than the pipe support safety certification value of 40,000 N, which is applied in the supporting post-structural review, are used. Accordingly, this acts as a factor causing collapse accidents in the process of pouring concrete at the construction site. Therefore, this study performed compression experiments on new and reused pipe supports to determine how the thickness of the support pins affects the structural compression performance of the pipe support by considering the thickness of the support pins as a critical variable among various factors affecting the pipe support performance. In the course of the study, the compression test of the pipe support (V2, V4) for the new products showed that only 14 (58.3%) of the total 24 samples satisfied the safety certification standard value of 40,000 N, which indicates that more thorough quality control is required in the manufacturing process. Additionally, comparing the thickness of the support pins and their fracture shape shows that the pipes with support length of 4.0 m or longer are much more affected by the buckling of the entire length than the thickness of the support pins. Of the several factors affecting the performance of reused pipe supports, it was found that, similar to the new products, the use of support pins, with thickness of 12 mm rather than 11 mm, can satisfy the safety certification value more appropriately. Therefore, regardless of the state of usage, it could be concluded that it is necessary to use 12 mm products, whose thickness is larger than that of the safety certification standard value of 11 mm, to improve the performance of the pipe supports.

• Design & Manufacturing
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• v.16 no.4
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• pp.52-59
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• 2022

Currently, Korea is an aging society and is expected to become a super-aged society in about four years. X-ray devices are widely used for early diagnosis in hospitals, and many X-ray technologies are being developed. The development of X-ray device technology is important, but it is also important to increase the reliability of the device through accurate data management. Sensor nodes such as temperature, voltage, and current of the diagnosis device may malfunction or transmit inaccurate data due to various causes such as failure or power outage. Therefore, in this study, the temperature, tube voltage, and tube current data related to each sensor and detection circuit of the diagnostic X-ray imaging device were measured and analyzed. Based on QC data, device failure prediction and diagnosis algorithms were designed and performed. The fault diagnosis algorithm can configure a simulator capable of setting user parameter values, displaying sensor output graphs, and displaying signs of sensor abnormalities, and can check the detection results when each sensor is operating normally and when the sensor is abnormal. It is judged that efficient device management and diagnosis is possible because it monitors abnormal data values (temperature, voltage, current) in real time and automatically diagnoses failures by feeding back the abnormal values detected at each stage. Although this algorithm cannot predict all failures related to temperature, voltage, and current of diagnostic X-ray imaging devices, it can detect temperature rise, bouncing values, device physical limits, input/output values, and radiation-related anomalies. exposure. If a value exceeding the maximum variation value of each data occurs, it is judged that it will be possible to check and respond in preparation for device failure. If a device's sensor fails, unexpected accidents may occur, increasing costs and risks, and regular maintenance cannot cope with all errors or failures. Therefore, since real-time maintenance through continuous data monitoring is possible, reliability improvement, maintenance cost reduction, and efficient management of equipment are expected to be possible.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.169-173
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• 2023

With the increasing concern of global warming caused by greenhouse gases owing to the recent industrial development, there is a growing need for advanced technology to control these emissions. Among the various greenhouse gases, nitrogen dioxide (NO₂) is a major contributor to global warming and is mainly released from sources, such as automobile exhaust and factories. Although semiconductor-type NO₂ gas sensors, such as SnO₂, have been extensively studied, they often require high operating temperatures and complicated manufacturing processes, while lacking selectivity, resulting in inaccurate measurements of NO₂ gas levels. To address these limitations, a novel sensor using PbS quantum dots (QDs) was developed, which operates at low temperatures and exhibits high selectivity toward NO₂ gas owing to its strong oxidation reaction. Furthermore, the use of P3HT conductive polymer improved the thin film quality, reactivity, and reaction rate of the sensor. The sensor demonstrated the ability to accurately measure NO₂ gas concentrations ranging from 500 to 100 ppm, with a 5.1 times higher sensitivity, 1.5 times higher response rate, and 1.15 times higher recovery rate compared with sensors without P3HT.