The atomic fuel rods between top and bottom end pieces of reactor need to be extended for high combustion rate of future-type fuel to increase the irradiation in the axial direction. For allowing axial extension of the fuel rods, the space between top and bottom end pieces should be expanded. Thus the thickness reduction of the flow plate is necessary. This study was carried out the mechanical strength test by using strain gages as a function of flow plate thickness, the existence of skirt and loading condition for the Korean Fuel Assembly(KOFA). The experimental apparatus was designed for load conditions, uniformly distributed load and displacement. Test method using whiffle tree of uniformly distributed load has been comparatively conservative. The test results were compared with those of finite element analysis and the test method on bottom end piece was established.

In this study, a drop-weight impact tester was manufactured to assess the strength of CFRP laminate plates. The tests were conducted on several laminates of different ply orientation. A system for the impact strength of CFRP laminates was made considering stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen, haying four interfaces is higher than that of orthotropic laminates with two interfaces. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.

This paper were performed to evaluate the elastic-plastic fracture toughness $J_IC$ by the unloading compliance method for 1/2 CT specimen of A5083-H112 aluminum alloy. A modified offset method for negative crack growth effect is presented and compared with Voss offset method. We found that the modified offset method presented can be used efficiently for a determination of the stable crack onset. The $J_IC$ by Voss offset method can be overestimated, but the suggested offset method showed a high reliability within 5% of tolerence from the results by the multi-specimen method.

This study has been performed to investigate the stress distribution around defects that behave as stress concentrators. Besides, the effect of stress interaction effects on the initiation of primary cracks were also investigated by rotary bending fatigue tests which were performed with specimens drilled micro surface defects and the stress distribution was analyzed using Finite Element Method. In addition, the stress interaction effects around defects and cracks were investigated by comparing the results of experiments and F.E.M. The results obtained are summarized as follows ; 1) Area which slip and micro cracks initiated at micro surface defects is between the maximum shear stress points and this area is over than ${\pm}30^{\circ}$ from the maximum stress point along the defect edge. 2) The stress interaction effect for the small size defect is larger than that of large size defect when the interval between them is near 3) Interval which there is no shear stress interaction effect analyzed by F.E.M. is larger than that of experimental results.

In a compartment fire with openings, convective heat transfer consists of natural convection from the hot bodies and forced convection by airflow through the openings. The same finite volume method that was applied to pure natural convection in part I was utilized without modification to the square cavity with two openings. The objective of this study is to investigate effects of the openings on temperature distribution. Flow patterns, temperature distribution and heat transfer were compared for different Rayleigh numbers and with and without the openings.

A numerical study on gaseous explosion was carried out to predict the transient pressure behavior with the partial rupture in confined vessels. Equations, assumptions and solutions for central ignition of premixed gases in closed spherical vessels are proposed with various equivalence ratios of gas fuel, as $CH_4$ and $C_3H_8$, vent areas and vent opening pressures. Given vent opening pressure in a vessel, the magnitude of second peak pressure results from the vent areas and burning velocity, varied by equivalence ratio of gas fuel. In a living room of an apartment, the higher second peak pressure than the vent pressure is not appeared due to its large window areas. As vent opening pressure is higher, the larger damage by gaseous explosion is expected and the larger vent area is necessary for relieving the damage. In the same concentration, the gaseous explosion by propane rather than methane shows the larger damage due to its higher adiabatic flame temperature and equivalence ratio.

It is widely recognized that Hartmann tube for measuring the minimum ignition energy(MIE) of powder. But It requires long time and operational skills for measuring. As a variety of new fine powders are being produced day by day in industry, Japen has been developing a measurement system which employs a new method to create a dust/air mixture in a miniature combustion box. In this system, by vibration, the powder is successively fed downward through a hopper made up of metal mesh, and then it is formed into a thin, certain-like, dust/air mixture. With this new apparatus, three types of powder-Lycopodium, Anthraquinone, and Polyacry-lonitrile-were tested and the data of MIE were compared with those of a conventional apparatus (the Hartmann tube). Two of them agreed satisfactory, but the other, Anthraquinone, showed quite different values. It is guessed that the agglomerations of the powder particles appear because of particle shapes, static-charge and humidity.

This paper presents a study on the safety assessment of human body for electromagnetic field at unbalanced power system. The 3-phase load flow algorithm uses Newton-Raphson method based on Taylor series expansion of power flow equations in rectangular coordinates. The use of such a method can result in a solution with good convergence characteristics. In the safety assessment of human body, the approach based on fuzzy linguistic variable is employed to overcome the shortcomings resulting from a crisp set concept. The suggested scheme is applied to a 24bus system to validate the usefulness. The results for an unbalanced power system are compared with the results for a balanced power system.

In this paper, characteristics of ozone generation by using coil and SPCP + DC corona reactor was studied. The ceramic-based surface discharge electrode, which was first invented as a high-efficiency ozonizer, has been used as an experimental plasma chemical reactor.(Surface Induced Plasma Chemical Processing, SPCP.) The electrode, however, has a structural disadvantage that a highly energetic plasma region is localized near the electrode surface, which may make it impossible for higher efficiency to realize. In an attempt to overcome this advantage, we have developed a hybrid reactor which employs a corona discharge unit together with the surface discharge unit. Experimental results suggest that the efficiency of the ozone production rate is improved when positive corona discharge is added.

As the use of automatic handling equipment for sensitive semiconductor devices is rapidly increased, manufacturers of electronic components and equipment need to be more alert to the problem of electrostatic discharges(ESD). Semiconductor devices such as IC, LSI, VLSI become a high density pattern of being more fragile by ESD phenomena. One of the most common causes of electrostatic damage is the direct transfer of electrostatic charge from the human body or a charged material to the electrostatic discharge sensitive devices. Accordingly, characteristics of electrostatic attenuation in domestic semiconductor devices is investigated to evaluate the ESD phenomina in the semiconductors in this paper. The required data are obtained by Static Honestmeter. Also The results in this paper can be used for the prevention of semiconductor failure by ESD.

This work is the experimental study for NO and NOx removal by utilizing non-thermal plasma. To apply to moving pollution source such as diesel automobile, we suggested the metal packed-helical wire reactor(MPHW) and measured properties of MPHW by varying the peak voltage, frequency, NOx concentration and flow rate for simulated NOx gas balanced with $N_2$. And then we compared these results with the results of cylinder-wire(CW) which was one of popularly used reactor in nonthermal plasma applications. The results of MPHW show fairly good NO and NOx removal rate compare with CW around above 20%. However. the power consumption of MPHW is larger than that of CW as much as around 2.5Watt in all range.

The effects of air velocity and excess air on combustion characteristics were studied in a fluidized bed combustor. The domestic low-grade anthracite coal with heating value of 2010 kcal/kg and the imported bituminous coal from Australia with heating value of 6520 kcal/kg were used as coal samples. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by pressure fluctuation properties, ash distribution and gas emission. The properties of the pressure fluctuations, such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function, were obtained from the statistical analysis. From this study, the combustion region increased with increasing air velocity but decreased with excess air due to combustion characteristics of anthracite and bituminous coal.

Decomposition efficiency, power consumption, and applied voltage of CFC(Chlorofluorocatbon) were investigated by SPCP(surface induced discharge plasma chemical processing) reactor to obtain optimum process variables and maximum decomposition efficiencies. Decomposition efficiency of CFC-12 with various electric frequencies(5~50kHz). flow rates (100~1,000mL/min), initial concentrations(100~1,000ppm), electrode materials(W, Cu, Al). electrode thickness(1, 2, 3mm) and reference gases($N_2$, $O_2$, air) were measured and the products were analyzed with FT-IR. Experimental results showed that at the frequency of 10kHz, the highest decomposition efficiency of 92.7% for CFC-12 were observed at the power consumptions of 29.6W. respectively, and that decomposition efficiency decreased with increasing frequency above 20kHz and decomposition efficiency per unit power were 3.13%/W for CFC-12. Decomposition efficiency was increased with increasing residence times and with decreasing initial concentration of pollutants. Decomposition efficiency was increased with increasing thickness of discharge electrode and the highest decomposition efficiency was obtained for the electrode diameter of 3m. As the electrode material, decomposition efficiency was in order that tungsten(W), copper(Cu), aluminum (Al). Decomposition of CFC-12 in the reference gas of $N_2$ showed the highest efficiency among three reference gases, and then the effect of reference gas on the decomposition efficiency decreased in order of air and $O_2$. The optimum power for the maximum decomposition efficiency was 25.3W for CFC.

This study attempts to analyse the solid mixing in the feeder and the packing effect for pressure fluctuations in the fluidized bed. To study the mixing characteristics of solid in vibrating feeder for the stable operations of fluidized combustion, the system consisted of two groups of particles such that fine particles were located on the top of the coarse particles before vibratory mixing had started. The effects of packing materials on the pressure fluctuations in a fluidized bed were analysed by using a statistical method to interpret the behavior of fluidized bed. The experiments were carried out in a fluidized bed of 6.7cm-ID, and the experimental variables were particle sizes, of 115 to 1,015$\mu\textrm{m}$ in diameter and the multi-sized particles haying Rosin-Rammler and Gaussian distributions. The settled bed heights of particles to diameter ratios (L/D) were ranged from 0.5 to 2.0. And fluidizing of particles was carried out by air. The packing materials used were screen packing, and the properties of the pressure fluctuations in the fluidized bed were measured by a differential pressure transducer. The properties of the pressure fluctuations calculated were the mean, the standard deviation, and the major frequency of the power spectral density functions. From the characteristics of fluidizing, it was found that the standard deviation of pressure fluctuations could be effectively used to explain the fluidized phenomena, and the packing materials affected severely the properties of the pressure fluctuations. As a result, from the interpretation by spectral analysis, the effects of measuring radius of pressure fluctuations on standard deviation were constant in the case of the fluidized bed with and without packing materials. However, the effects of measuring the height of pressure fluctuations on standard deviations were linear increasing for the fluidized bed with packing materials, but were constant for the fluidized bed without packing materials at 4.5cm above the gas distributor. The major frequency of pressure fluctuations was found to be nearly independent of fluidized system. Also, the major frequency of pressure fluctuations decreased with increasing packing size, and it had maximum value at 10% of the packing amount.

This study was conducted to invent brake of non-steel material without using asbestos and disc pad added $ZrSiO_4$ was made. The physical properties and friction characteristics were investigated by varying methods. The physical properties were inspected of shear strength, hardness, heat expansion, specific gravity, % of gashole, thickness variation, weight variation and pH variation. The friction stability was measured by friction coefficient on variations of speed, temperature and deceleration condition. It was found that the physical properties were in general excellent. According to the friction characteristics tests, $ZrSiO_4$ had an abrasive property. As a results, the friction materials containing $ZrSiO_4$ 3~5vol% showed better resistance to fading and improved friction stability than the materials without ZrSiO$_4$.

This study was accomplished by measuring the lower and upper flash point with air blowing method and grasping the characteristics of flammability for the three component systems, which are made up of the Benzene-Toluene-o-Xylene and Methylethylketone-Toluene-o-Xylene. These three component systems are widely used in the various industrial fields together with the development of industry. The results are as follows ; 1 ) Isothermal line is plotted on the triangular diagram for flash points determined in each solutions. From this line, the mixed compositions which indicated the same lower and upper flash points in each different composition could be read on this diagram, if the composition of mixtures are known. 2) Lower and upper explosion limits obtained from the flash points determined for the three component solution are compared with the value calculated from Le Chatelier's law. Especially the lower explosion limits are in a good agreement with the calculated values.

One of the major malodorous gas at the working place is hydrogen sulfide and impregnated activated carbon fiber(ACF) was used as a adsorbent to remove this gas. ACF is treated and impregnated with chemicals to increase the adsorption capacity. The experiments showed that the adsorption efficiency for hydrogen sulfide was increased in case of impregnation with $Na_2CO_3$ or KI. Also, by the surface treatment with NaOH, the adsorption efficiency was increased however not so much as impregnation. KI was the best impregnant for this purpose and the optimum concentration was 9wt%. The adsorption capacity of hydrogen sulfide was more than 500mg/g ACF.

In this study, PSII(plasma source ion implantation) was used to improve the biocompatibility of bone-anchored Ti implant. According to potentiodynamic anodic polarization test in deaerated Hank's solution, open circuit potential of ion implanted specimens were increased compare to that of unimplanted specimen ; besides, passive current density and critical anodic current density of ion implanted specimens were lower than unimplanted specimen.

In this study, noise analyses were performed toward ten school and one library-building adjacent to road. In particular, noise levels measured in the case-study city were compared to those from environmental noise standard as well as to encouraged noise level. In the analyses, the following conclusions are emphasized in order to make comfortable educational learning environment. 1) When windows were open, the measured noise level of 9 schools exceeded the encouraged noise level. In order to mitigate the exceeded level, it is necessary to plant trees or lawn and install soundproofing wall. 2) When windows were closed, the measured noise level of the most schools showed lower than that of encouraged level. For sound insulation, installing both double window and casement window are required. 3) Schoolhouse's vertical arrangement from the road in order to minimize the expected noise effect, and provision of green space by which visual hiding as well as psychological comfort are presumably achieved.

The feasibility of using AE for monitoring mechanical failure in concrete structures has been tested. Specifically, the relationship between the fracture and the characteristics of AE signal is theoretically and experimentally investigated. The experimental results manifest that the high sensitivity of AE signal to the fracture of concrete structure makes it a good choice as sensor for monitoring concrete structure.

Small and medium-sized construction sites are most serious in Occupational Safety and Health in the construction industry. The safety consulting engineering has been launched, in 1995, to improve the safety environments and prevent serious injuries and fatalities accidents. The purpose of this study is to analyze the effect of the safety consulting engineering for small and medium-sized construction sites. This study conducts a number of interviews with experienced contractors, consulting engineers, etc. And the questionnaire survey was peformed with 111 respondents. This paper presents several improvements to increase the efficiency of the safety consulting system.

Korea is becoming an aged society as well developed country. Accident rates of elderly workers are increased. When elderly workers injured, elderly workers are more likely to die as a result, and they take longer to recover than young workers. Thus the cost to industry per individual accident gets higher for elderly workers. If information on the occupational accidents of elderly workers could be collected and analyzed for the purpose of preventing occupational accidents, we would be able to get rid of accidents of elderly workers. The accidents of elderly workers in small manufacturing factories were considered in this study. 97 accidents, which occurred in 1995-1998, were investigated. These accidents were analyzed in terms of sex, work period, cause of accident and form of accident. The accidents of elderly workers in small manufacturing factories are numerous and are often serious and worthy of greater attention than they have received. Successful strategies for accident prevention depend on effective analysis.

The purpose of this study is to analyze death injuries and operation troubles of urban transit. No difference was shown in death rates between Line 1 of Pusan urban transit and Line 5, 7, And 8 of Seoul metropolitan transit. And relief time by another train did not depend upon the number of crews. We concluded that thorough inspection and preventive maintenance of trains and facilities are necessary for safe and timely service of urban transit.

The objective of this study was to investigate the effects of carrying postures and weight of load carried one time on a worker when carrying heavy loads. Six male students participated in this study to perform a manual materials carrying task as subjects. To make comparison of work loads with physical work capacity, maximal oxygen uptake measurement tests were performed with submaximal test. The average oxygen consumption for the tasks of this study was 27.59~31.93% $VO_2$max. The results showed that the weight of load carried one time affects on working heart rate and oxygen consumption($VO_2$). It was found that the workload was significantly lower when handling a 20kg load at a frequency rate of 3times/min than when handling a 40kg load at a frequency rate of 1.5 times/min. There was no difference between carrying postures. It is concluded from the results of this study that the workload can be reduced by controlling conditions of a manual materials handling task.

Our government has been continuously making an effort to improve safety management and prevent accidents in small-to-medium sized enterprises, but the accidents are still happening. Since there hasn't been a study on the actual state of safety management for the munitions manufacturing industry so far, this paper aims to investigate and analyze the actual state of the munitions manufacturing companies in Kyung-In area and it also shows the countermeasures of improvement.

By the report of KISCO, the 54.20% of total disaster and the 20.87% of death disaster was caused by unsafe position-control. However, it is possible to decrease this kind of disaster rate by designing the control device in the consideration of safety. One of the most popular control device is vehicle instrument panel. Therefore, not only basic function but safe control under the driving environments should be considered when the vehicle instrument panel is designed. For safe control at the driving time, it is especially important to determine the priority of each part using emergency degree and usage frequency, and to set them with this priority for easy control position. In this paper, developing method to determine the priority of each part by pair-wise comparison for emergency degree and usage frequency was suggested and generated the mutual order weights to give them orders. To apply this method to the parts of instrument panel such as function button, audio, air conditioner, and other several detail parts, the direct questionnaire was implemented to drivers about the emergency degree and usage frequency of each part.