In this study, the time to endure after conducting a test pressure test was analyzed according to the hose development length of the household hose reel indoor fire hydrant according to the apartment area. First, when the household area is 50㎡, a household hose reel indoor fire hydrant is installed inside the bathroom, and the hose is bent in a circular shape to the farthest fire point, and the test pressure is found to be inadequate only when the hose development length is 5m. When the household area of an apartment is 84㎡. It was found that the test pressure was inappropriate only when the hose deployment length was 5m with the hose bent in a circular shape to the farthest point by installing a household hose reel indoor fire hydrant inside the bathroom. When the hose deployment length was 15m, the average experimental value was 3.9 Mpa and the water pressure resistance time was 8 min. It was found that the test pressure and holding time were suitable for all of the working pressure of 0.7 Mpa, the inner diameter of the hose 25mm and 32mm, and the hose deployment length. When the installation of the hose reel indoor fire hydrant hose was 3 Mpa, the internal diameter of the hose was 25mm, 32mm, and the length of the hose deployment were all suitable.

This study compares and analyzes the discharge status of smoke according to the method of installing a mobile blower in the event of a fire in an underground parking lot of an apartment using an evacuation simulation. An evacuation simulation was conducted on the situation in which the discharge of smoke in the event of a fire was discharged using a mobile blower to extinguish the smoke in the event of a fire by focusing on the part without smoke facilities in the underground parking lot. The results derived through experiments on the amount of smoke discharged using the natural exhaust method and the mobile blower in the underground parking lot are as follows. (1) In the event of a fire in an underground parking lot, the PPV (positive pressure ventilation) method, which has been mainly used in the field, should be used in a limited way. It can be an effective method if the exhaust port corresponding to the amount of the blower and the smoke exhaust is located nearby, or if the capacity of the apartment ventilation fan is designed to meet the 18CMH/㎡ of the National Fire Protection Association (NFPA) 88A or the 27CMH/㎡ standard standard for performance-oriented design evaluation and operation such as fire fighting facilities of the National Fire Protection Association (NFPA) 88A. (2) In the case of the additional mixing method (PPV+NPV) performed in the FDS experiment, smoke emissions increased by 5.1% compared to the NPV single method, and increased by 24.4% compared to the PPV single method.

Due to the smoke generated during a fire in an underground parking lot, initial response is difficult, resulting in an increase in life and property damage. In this study, fire cases in underground parking lots were analyzed and the necessity of legal and institutional amendments was suggested to improve the installation of smoke removal facilities, sprinkler facilities, emergency outlet facilities, and connected water pipe facilities. First, it is necessary to improve the smoke removal facilities of apartment underground parking lots. Second, it is necessary to install wet sprinklers in underground parking lots only when it has a structure or device capable of preventing freezing. It is stipulated in a manner other than wet in the fire safety technology (NFTC 103) of sprinkler facilities. However, wet sprinklers may be installed only in places where there is no fear of freezing, or when a structure or device capable of preventing freezing has been used. Third, it is necessary to amend the "Firefighting Facility Installation and Management Act" so that the standards for installing emergency outlet facilities are not regulated according to the number of underground floors, but according to the sum of the floor areas of the underground floors.

For the aerospace structural application of high-strength 2xxx series aluminum alloys, stress corrosion cracking(SCC) behavior in aggressive environments needs to be well understood. In this study, the SCC sensitivities of 2024- T62, 2124-T851 and 2050-T84 alloys in a 3.5% NaCl solution are measured using a constant load testing method without polarization and a slow strain rate test(SSRT) method at a strain rate of 10-6 /sec under a cathodic applied potential. When the specimens are exposed to a 3.5% NaCl solution under a constant load for 10 days, the decrease in tensile ductility is negligible for 2124-T851 and 2050-T84 specimens, proving that T8 heat treatment is beneficial in improving the SCC resistance of 2xxx series aluminum alloys. The specimens are also susceptible to SCC in a hydrogen-generating environment at a slow strain rate of 10−6/sec in a 3.5% NaCl solution under a cathodic applied potential. Regardless of the test method, low impurity 2124-T851 and high Cu/Mg ratio 2050-T84 alloys are found to have relatively lower SCC sensitivity than 2024-T62. The SCC behavior of 2xxx series aluminum alloys in the 3.5% NaCl solution is discussed based on fractographic and micrographic observations.

H13 tool steels are widely used as metallic mold materials due to their high hardness and thermal stability. Recently, many studies are undertaken to satisfy the demands for manufacturing the complex shape of the mold using a 3D printing technique. It is reported that the mechanical properties of 3D printed materials are lower than those of commercial forged alloys owing to micropores. In this study, we investigate the effect of microstructures and defects on mechanical properties in the 3D printed H13 tool steels. H13 tool steel is fabricated using a selective laser melting(SLM) process with a scan speed of 200 mm/ s and a layer thickness of 25 μm. Microstructures are observed and porosities are measured by optical and scanning electron microscopy in the X-, Y-, and Z-directions with various the build heights. Tiny keyhole type pores are observed with a porosity of 0.4%, which shows the lowest porosity in the center region. The measured Vickers hardness is around 550 HV and the yield and tensile strength are 1400 and 1700 MPa, respectively. The tensile properties are predicted using two empirical equations through the measured values of the Vickers hardness. The prediction of tensile strength has high accuracy with the experimental data of the 3D printed H13 tool steel. The effects of porosities and unmelted powders on mechanical properties are also elucidated by the metallic fractography analysis to understand tensile and fracture behavior.

본 연구는 공동주택의 소방감리제도중 일반공사 소방감리의 적요대상물 방법등의 문제점들을 도출하여 공동주택의 감리대상을 층수가 아닌 세대수를 기준으로 감리원배치기준, 일반건축물에 대한 연면적기준, 일반감리원의 업무수행 기술등급 상향 확대 개선, 사전입찰제도 (PQ)도입등 제반관련 사안들의 개선방안을 모색하였다.

Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results.

A bake-out process using auto switchgear was carried out to evaluate the reduction effect of the concentration of volatile organic compounds (VOCs) and formaldehyde in newly-built apartments for seven days. The reduction rate of VOCs was observed as followings: 19%, 38%, 89%, 90%, and 96% for benzene, toluene, ethylbenzene, xylene, and styrene, respectively, which satisfies at the indoor air quality standards of newly-built apartment houses in Korea. The reduction rate of formaldehyde was 75%. Those results proved that the bake-out process using auto switchgear was effective for reducing indoor air pollutants.

Activated carbon (AC) with very large surface area has high capacitance per weight. However, such activation methods tend to suffer from low yields, below 50%, and are low in electrode density and capacitance per volume. Carbon NanoFibers (CNFs) had high surface area polarizability, high electrical conductivity and chemical stability, as well as extremely high mechanical strength and modulus, which make them an important material for electrochemical capacitors. The electrochemical properties of immobilized CNF electrodes were studied for use as in electrical double layer capacitor (EDLC) applications. Immobilized CNFs on Ni foam grown by thermal chemical vapor deposition (CVD) were successfully fabricated. CNFs had a uniform diameter range from 50 to 60 nm. Surface area was 56 m2/g. CNF electrodes were compared with AC and multi wall carbon nanotube (MWNT) electrodes. The electrochemical performance of the various electrodes was examined with aqueous electrolyte of 2M KOH. Equivalent series resistance (ESR) of the CNF electrodes was lower than that of AC and MWNT electrodes. The specific capacitance of 47.5 F/g of the CNF electrodes was achieved with discharge current density of 1 mA/cm2.

Austenite precipitation behavior was studied with solidification rates and alloying contents, N and Cr, in duplex stainless steels by directional solidification. Directional solidification experiments were carried out with solidification rates, 1~100mm/s, and N and Cr contents, 0~0.27wt.%, 25~28wt.% respectively, in a duplex stainless steel, CD4MCU. As the solidification rate increases, the dendrite spacing reduced and the austenite phase in the ferrite matrix became finer. The volume fraction of austenite phase increased and its shape went to be round with increasing nitrogen contents in duplex stainless alloys. The Cr alloying element, even though it is a ferrite former, showed to enhance the nitrogen solubility in the alloy and caused the austenite round and finer. Also, Cr was supposed to decrease the austenite volume fraction, but it increased the austenite slightly due to increasing nitrogen solubility during solidification.

최근에 고온용 항공기 구조 재료로 Ti, Zr, V, Nb 및 Ta 등의 천이금속을 첨가한 Al 합금계 제조와 특성에 관한 연구가 되어져 왔다. 본 연구에서는 Al-Nb합금에 Zr을 첨가하여 상형성거동을 연구하였다. Al-1.3at.%(Nb+Zr) 합금에서 Nb와 Zr의 원자비를 1:3, 1:1 및 3:1로 하여 기계적합금화하였다. 기계적합금화하는 동안 Al-Nb-Zr의 형태변화와 미세구조를 SEM, XRD 및 TEM으로 관찰하였다. X-선 회절 시험에 의하여 Nb2Al 과 Al3Zr4가 생성됨을 확인하였다. 500˚C에서 1시간동안의 진공열처리에 의하여 Al3Zr, Al3Zr4 등의 금속간화합물을 형성하였다. 30시간동안 기계적 합금화한 분말을 열처리하여 TEM으로 관찰한 결과 100nm 이하의 금속간화합물 입자들을 관찰하였다.

반응고 금속의 반응용 성형법은 그 우수한 성형성으로 생산공정에 있어 주조나 단조와 같은 일반 성형법에 비해 많은 장점을 가지고 있는 반면, 정밀한 공정 변수 제어가 요구되므로 실용화에 있어 크게 제한 받고 있다. 본 연구에서는 반응고 금속인 A356합금을 사용하여 밀폐형 가압 성형 전후의 기계적 특성의 변화를 관찰하여, 가압 성형시의 정확한 공정 변수 제어가 이루어지지 않았을 경우에 일어날 수 있는 기계적 특성의 감소 원인이 가압 성형에 의한 미세조직의 응집과 조대화에 있음을 미세조직과 파단면 관찰을 통하여 규명하였다. 또한 가압 성형 후 본 연구에서 '반응고 열처리'라 명명한 후 처리 공정을 적용하여 인장 특성을 향상시킬수 있었다.

분말야금법으로 제조된 Cu-7.5Ni-5Sn 합금의 용체화 및 시효 열처리 조건에 따른 기계적 특성의 변화를 관찰하였다. As-received 상태의 Cu-7.5Ni-5Sn 합금을 시효한 경우에는 시효 20분 후에 γ' 상의 석출에 의한 강도 증가를 나타내는데 반해, 재용체화 처리된 시편에서는 시효 수십초부터 스피노달 분해에 의한 급격한 강도의 증가를 나타내고 있다. 그러나 전체적인 인장강도는 재용체화 처리를 행한 경우에 비해 as-received 상태에서 등온 시효한 경우가 더욱 우수한 것으로 나타났다. 이러한 현상은 재용체화 처리에 의한 결정립 성장에 기인한 것으로 사료된다. As-received 상태의 Cu-7.5Ni-5Sn 합금을 장시간 시효하게 되면 결정립계에 불연속 석출물이 생성되었으며, 이러한 불연속 석출물의 생성과 성장은 열처리 조건에 영향을 받는 것으로 관찰되었으며, 합금의 최종 기계적 성질에 크게 영향을 미치는 것으로 판단된다.