• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.333-339
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• 2003

Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BCN) has a 1:2 ordered hexagonal structure. Q-value of BCN increased with increasing sintering temperature however, it significantly decreased when the sintering temperature exceeded 140$0^{\circ}C$ Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$(BZN) has the 1:2 ordered hexagonal structure and the degree of the 1 : 2 ordering decreased with the increase of the sintering temperature. The Q value of the BZN increased with increasing the sintering temperature and BZN sintered at 140$0^{\circ}C$ for 6h has a maximum Q-value. For (1-x) Ba (Co$_{1}$ 3/Nb$_{2}$ 3/)O$_3$-zBa(Zn$_{1}$ 3/Nb$_{2}$ 3/)O$_3$[(1-x)BCN-xBZN] ceramics the 1:2 ordered hexagonal structure was observed in the specimens with x$\leq$0.3 and the BaNb$_{6}$ O$^{16}$ second phase was found in the specimens with x$\geq$0.6. Grain Growth, which is rotated to the BaNb$_{6}$ O$^{16}$ second phase occurred in the specimens with x$\geq$ 0.5. In this work, the excellent microwave dielectric properties of $\tau$r=0.0 ppm/$^{\circ}C$$\varepsilon$r=34.5 and Q,$\times$f=97000GHz sere obtained for the 0.7BCV-0.3BZN ceramics sintered at 1400$0^{\circ}C$ for 20h.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.873-885
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• 2014

To identify the characteristics of extreme heat events and tropical nights in major cities, the correlations between automated synoptic observing station (ASOS), automatic weather station (AWS), and temperature in seven metropolitan areas were analyzed. Temperatures at ASOS were found to be useful sources of the reference temperature of each area. To set the standard for identifying dates of extreme heat events in relation to regional topography and the natural environment, the monthly and yearly frequency of extreme heat in each region was examined, based on the standards for extreme heat day (EHD), tropical night day (TND), and extreme heat and tropical night day (ETD). All three cases identified 1994 as the year with the most frequent heat waves. The frequency was low according to all three cases in 1993, 2003 and 2009. Meanwhile, the yearly rate of increase was the highest in 1994, followed by 2010 and 2004, indicating that the frequency of extreme heat changed significantly between 1993 and 1994, 2003 and 2004, and 2009 and 2010. Therefore all three indexes can be used as a standard for high temperature events. According to monthly frequency data for EHD, TND, and ETD, July and August accounted for 80% or more of the extreme heat of the entire year.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.600-605
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• 2014

The interest in development on luminaires which are available up to $-52^{\circ}C$ is surging as demands in vessels navigating a north pole route increase. A conventional incandescent lamp used in vessels is operated stably at $-52^{\circ}C$, but many countries including Korea have eliminated the use of incandescent lamps gradually because of its low luminous efficacy. In this paper, therefore, to develop the LED luminaires with high-efficiency, long lifetime that enables to substitute for incandescent lamp, it has studied about cryogenic characteristics of LED packages, bulbs, driving circuit and power supply. This experiments were carried out according to standards IEC 60945-8.4.1. Temperature range is from $-60^{\circ}C$ to $25^{\circ}C$, and the light output depending on ambient temperature. It showed that, based on $25^{\circ}C$, light output of a CFL decreased by 80% of CFL at $-20^{\circ}C$ while each increased 12% of LED bulbs and 16~19% of LED packages at $-60^{\circ}C$.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.165-176
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• 2005

A variety of research projects have been undertaken due to the recent catastrophic tunnel fires throughout the world, Among them, more emphasis was given to full scale and scale model fire experiments, and recently the area of fire resistance of tunnel structures attract more interests, On the contrary to the cases in most of the advanced countries where design standards as well as recommendations have already been announced, no local criteria for design can be found, This paper aims at deriving the fire characteristics appropriate for the assessment criteria of fire resistance of structures in local tunnels through studying the existing fire temperature curves including ISO 834 standard temperature curve, HC curve, RWS curve, ZTV curve and EBA curve.

• Journal of the Korean Dietetic Association
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• v.13 no.4
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• pp.345-356
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• 2007

The purpose of this study was to investigate utilization and storage management practice of the frozen and refrigerated foods in school foodservice. 222 dietitians employed in school foodservice were surveyed. In school foodservice, the refrigerated stock farm products and seafoods (78.3%) were more used rather than frozen products (47.5%). According to school foodservice characteristics, the refrigerated meats including dairy products were more frequently used in elementary and middle schools than high school foodservice. On the other hand, the foodservice in high school used more frozen seafoods and processed foods than elementary school did. The data also showed a tendency for the contracted foodservice using more frozen meats and seafoods rather than refrigerated products when comparing with the self-operated foodservice. In terms of receiving conditions, storage methods and storage time, the result indicated that frozen or refrigerated products were often delivered at inappropriate temperature. Especially some products which were needed to be shipped and stored at refrigerated temperature such as mollusks, were delivered and kept at room temperature. The most frequently used thawing method were running water (56.9%), however, the frozen products were often sitted at room temperature for the purpose of thawing. According to the results, several inappropriate handling processes for frozen and refrigerated products were found in school foodservice. In order to improve handling process for frozen and refrigerated products, recognition of food handlers' weakness about storage and distribution, development of radical standards for receiving conditions, storage and thawing methods should be debated.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.65-71
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• 2005

At present, Electronic industries push ahead to eliminate the Pb(Lead) -a hazardous material-from all products. Especially, we have performed to select the optimum standard composition of lead free alloy for the application to products for about 3 years from 2000. These days, we have the chance for applying to the mass-production. This project constructed the system for applying the lead free solders on consumer electronic products, which is one of the major products of the LG Electronics. To select the lead free solders with corresponding to the product features, we have passed through the test and applied with Sn-3.0Ag-0.5Cu alloy system to our products, and for the application to the high melting temperature composition, we secured the thermal resistance of the many parts and substrate and optimized the processing conditions. We have operated the temperature cycling test and the high temperature storage test under the standards to confirm the reliability of the products. On these samples, we considered the consequence of our decision by the operating test. For the long life time of the product, we have operated the temperature cycling test at $-45^{\circ}C\;-\;+125^{\circ}C$, 1 cycle/hour, 1000 cycles. Also we have tested the tin whisker growth about lead free plating on lead finish. We have analyzed with the SEM, EDS and any other equipment for confirming the failure mode at the joint and the tin whisker growth on lead free finish.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2819-2832
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and petroleum plants has been recently concerned. The raw materials used in this study are the 1Cr-1Mo-0.25V steel which intensified P and S compositions along with the nominal compositions of ASTM A 470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging heat treatment at 630.deg.C. The mechanical properties and rotated bending fatigue strength of virgin and aged 1Cr-1Mo-0.25V steel have been investigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at 538.deg.C and room temperature, respectively. Thus the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows ; The decrease of the yield and tensile strength due to degradation was distinguished until 50, 000hrs simulated service time. And it was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The rotated bendingd fatigue strength at 538.deg.C of virgin, 25, 000, 50, 000, 75, 000 and 100, 000 hrs aged material was decreased 44.6 %, 49.6 %, 51.5 %, 52.4% and 53.8% than that of virgin material at 10$_{7}$cycles of room temperature, respectively. The major cracks of virgin and aged materials mainly initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.n.

• Land and Housing Review
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• v.2 no.3
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• pp.269-276
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• 2011

Recently, the chance of dew condensation in apartment buildings is increasing because of several reasons. For example, ventilation rate has been decreased because of high-insulations and airtightness for saving energy. Besides, the humidity has been made by drying washes, cooking and bathing inside of apartment buildings. However, there is lack of resonable design criteria for preventing condensation in real life and real surroundings. Therefore, this study is aimed at making a resonable design criteria of preventing condensation by measuring the indoor temperature and humidity in real life. In addition to this, it is aimed at making a resonable outdoor condition and classifying regions by using weather data. The following are the results. The interior criterion for condensation was set up $25^{\circ}C$ and a relative humidity of 55%. The outdoor criterion for condensation was set up $20^{\circ}C$, $-15^{\circ}C$, and $10^{\circ}C$ respectively for the hard frost, middle, and southern areas.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.11-21
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• 1999

This objective of this paper is to investigate the evaluation and indiction of human thermal comfort in building environment. The issue of defining the boundaries of acceptable thermal comfort conditions in buildings and urban may have significant implication for building design and also may have urban design by climate considerations. And then it is to apply the thermal comfort condition to environmental design by using passive methods in Korea. Since 1920. architects have conducted studies to measure thermal comfort in houses under hot and humid conditions, while industrial hygienists have studied the effects of temperature and humidity on the performance of factory workers. Thermal comfort can be influenced by many variables. This paper conducted to review the previous researches and the human heat balance equation, and to analyse in order to reveal the meaning and usage of the thermal comfort index in two traditional essays, Fanger's PMV and Gagge's ET* Their comfort indexes compared with each other. They were based on human heat balance equation and psychological and physiological responses in the laboratory tests. The researchers and the architectural engineers using thermal comfort index shall be careful in decided the use of indexes and be necessary to recognize the value concept of the design criteria for thermal comfort. Therefore, The opinion of the authors is that different comfort standards have to apply for each building and urban with different climatic conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.81-88
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• 2016

There are many types of national and international standards for low temperature tests depending on the products. This study conducted CFD analysis and estimation of the energy efficiency of the chamber both with and without a test object by considering variations of COP and specific volume according to temperature. The supply air was located in the upper area to compare the cooling performance for each location using various outlets in mixed ventilated conditions. For cases without the test object, the air temperature of the upper supply and center extract on the opposite side type chamber cooled faster than other areas by 4.3~29.8%. However, for cases with the test object, the object temperature of the upper supply and lower extract type chamber cooled faster than the other areas by 7.2~31.5%. The cooling efficiency of the air inside the chamber and the test object did not show the same pattern, which indicates the need to consider the cooling performance by not only the air but also the test object in the cryogenic chamber design for testing.