• Journal of Convergence for Information Technology
• /
• v.10 no.2
• /
• pp.82-88
• /
• 2020

The purpose of this study is to obtain basic data on the optimization of firing process conditions for enamel coating in chemical heat exchanger. The method of increasing the firing temperature in order to apply enamel coating to shell & tube type heat exchanger was examined. The temperature distribution of the heat exchanger in the firing kiln was numerically calculated using a commercial CFD program. The structural safety of the heat exchanger was confirmed by thermal stress analysis using the FSI method. Numerical analysis and experimental results show that there is a problem of safety due to temperature difference when the heat exchanger at room temperature is directly put into a firing kiln at 860℃. Therefore, a preheating process is need to reduce the temperature difference. As in Case2 with fewer firing steps, the first stage preheating temperature of 445℃and the second stage firing temperature of 860 ℃are considered to be most suitable.

• Journal of the Semiconductor & Display Technology
• /
• v.13 no.3
• /
• pp.27-33
• /
• 2014

To develop high efficiency crystalline solar cells, the $SiN_x$ film for surface passivation and anti-reflection coating is very important and it is generally deposited by PECVD. In this paper, the $SiN_x$ film deposited by Hot-Wire chemical vapor deposition(HWCVD) that has no plasma damage was studied. First, to optimize the $SiN_x$ film deposition process, $SiH_4$ gas rate and substrate temperature were varied and then refractive index and thickness were measured. When $SiH_4$ gas rate was 22sccm and substrate temperature was $100^{\circ}C$, refractive index was 1.94 and higher than that of other process conditions. Second, the lifetime was measured by varying the annealing temperature and time. The annealing process was made from 5 to 30 minutes at $300{\sim}500^{\circ}C$. When the annealing temperature was $100^{\circ}C$ and time was 10minute, the lifetime was the highest. The lifetime of annealed samples was also measured after the firing process at $975^{\circ}C$. Although the lifetime of all samples was decreased by firing process, the lifetime of annealed samples before the firing process was higher than that of fired samples only. Finally, the characteristics of solar cells with HWCVD $SiN_x$ film were measured.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.648-655
• /
• 2020

The firing pin of modern automatic rifles detonates the primer of loaded ammunition via a hammer. During this process, the firing pin receives an impact load and repetitive force throughout the life of the rifle. An endurance test of a rifle showed that the firing pin breaks prematurely at 96.26% of life. Accordingly, a case study was conducted through cause analysis and a reconstruction test. Optical microscopy and scanning electron microscopy of the broken surface of the firing pin showed that a crack began in the circumferential direction of the surface, resulting in a fatigue crack to the core after repeated impact. Crack growth and fatigue destruction occurred at the end due to the repetitive impact and was estimated using a notch. For verification, a sample that produced a 0.03mm circumferential notch was broken at 64.25% of life in the reconstruction test. A test of breakage according to the notch types showed that a 0.3mm and a 0.5mm one-side notch were broken at 66.53% and 50.76%, respectively, and a 0.03mm six-point notch was broken at 85.65%. The endurance life of a sample firing pin with a rough surface and tool mark was examined, but an approximately 381 ㎛ internal crack formed. Through this study, failure for each notch type was considered. These results show that quality control of the notch and surface roughness is essential for ensuring the reliability of a component subjected to repeated impact.

• Research in Vestibular Science
• /
• v.17 no.4
• /
• pp.142-151
• /
• 2018

Objectives: Excitability o medial vestibular nucleus (MVN) in the brainstem can be affected by changes in the arterial blood pressure. Several animal studies have demonstrated that acute hypotension results in the alteration of multiunit activities and expression of cFos protein in the MVN. In the field of extracellular electrophysiological recording, tetrode technology and spike sorting algorithms can easily identify single unit activity from multiunit activities in the brain. However, detailed properties of electrophysiological changes in single unit of the MVN during acute hypotension have been unknown. Methods: Therefore, we applied tetrode techniques and electrophysiological characterization methods to know the effect of acute hypotension on single unit activities of the MVN of rats. Results: Two or 3 types of unit could be classified according to the morphology of spikes and firing properties of neurons. Acute hypotension elicited 4 types of changes in spontaneous firing of single unit in the MVN. Most of these neurons showed excitatory responses for about within 1 minute after the induction of acute hypotension and then returned to the baseline activity 10 minutes after the injection of sodium nitroprusside. There was also gradual increase in spontaneous firing in some units. In contrast small proportion of units showed rapid reduction of firing rate just after acute hypotension. Conclusions: Therefore, application of tetrode technology and spike sorting algorithms is another method for the monitoring of electrical activity of vestibular nuclear during acute hypotension.

• Korean Journal of Food Science and Technology
• /
• v.40 no.3
• /
• pp.297-302
• /
• 2008

In this study, Chrysanthemum indicum L. flower tea was prepared according to different pan-firing times (5, 7.5, 10, 12.5, and 15 min) and its quality characteristics were investigated. Total nitrogen and tannin contents increased with increasing pan-firing time, whereas chlorophyll and total amino acid (AA) contents decreased. The total AA contents of the samples ranged from 6,399 to 7,068 mg%, and the highest content (7,068 mg%) was found with the 10 min panfiring treatment. The AAs occurring in the C. indicum L. flower tea included glutamic acid and aspartic acid, which are desirable flavor components. As the pan-firing time increased, antioxidant activity as well as total polyphenol and flavonoid contents increased. The highest total polyphenol and flavonoid contents were found in the 15 min treatment at levels of 13.85 mg tannic acid equiv./g and 9.77 mg catechin equiv./g, respectively. The 15 min pan-firing treatment also had the highest total antioxidant activity at 19.33 mg ascorbic acid equiv. eg/100 g. Finally, based on sensory evaluations, the 10 min pan-fired C. indicum L. flower tea had the best overall quality.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.225-228
• /
• 2009

Hot-firing tests were performed on the gas generator which is a technology development/demonstration model for a 75 ton-class liquid rocket engine. A heat-sink type combustion chamber was used for initial performance examination of the injector and mixing head. This paper explains not only preparation works for hot-firing tests but also the acquired results such as pressure, temperature distribution, and pressure fluctuation.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.5
• /
• pp.525-531
• /
• 2015

In this paper, a novel impact sensing device for an ESAF(Electronic Safe and Arming Fuze) is presented. An impact sensing device is mounted in front of a weapon, and it detects an impact when it crashes against a target. There are two main design requirements to enhance the firing functional reliability of the ESAF; an operational reliability and a reduced latency, which is a delay time needed for sensing the impact. The design method of the contact-type impact sensing device, which employs an FPCB(Flexible Printed Circuit Board) so it can be used other weapons, is proposed. The tests demonstrated that the design described in this work show a reduced delay time with ensuring the operational reliability.

• Journal of Applied Reliability
• /
• v.11 no.4
• /
• pp.399-407
• /
• 2011

Reliability evaluation of One-Shot system which flies at speed of Mach must be evaluated as the result of many firing tests. But many firing tests are impossible because of budget deficit. Consequently the reliability prediction which substitutes firing tests is used. The accuracy of reliability prediction is decided according to a quantity of accumulated test data. If the test data is insufficient, the direction of prediction can not be set. So we propose the reliability prediction method which applies MIL-HDBK-217 Plus. MIL-HDBK-217 Plus is described about reliability prediction method without sufficient test data. So we apply MIL-HDBK-217 Plus to the rocket motor system, and we accomplish a modeling and a reliability prediction about the system.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.14 no.2
• /
• pp.167-172
• /
• 2011

In this paper, a study on variation of an accuracy rate as the gradient of a rifle is shown. In the a state of hostilities, a soldier is not easy to take a shot vertically against the ground. If a soldier shoots as the pistol is inclined, how the accuracy rate is changed. While the pistol is shot, the change of ballistic curve is estimated. And we also verify the accuracy rate through the firing test. Then we compare two results and present some ideas which overcome the decrease of an accuracy rate. Hereafter, it is possible to adapt in the future soldier system and expected that the accuracy rate of the conventional gun is maintained.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.10 no.2
• /
• pp.31-37
• /
• 2007

This paper presents a ballistic lead-computation method which utilizes automatic video tracking, tracking assistance and roll uncoupling. The method is able to improve the firing accuracy of army fighting vehicles such as main battle tanks. In the experiment, the efficiency of the proposed method is evaluated by an error analysis in real operating environment. The proposed method has been applied to the fire control system of a military vehicle and proved through the development test of the vehicle.