• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.298-302
• /
• 2002

Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

• 한국염색가공학회지
• /
• 제9권5호
• /
• pp.10-18
• /
• 1997

In order to study the properties of safflower yellow colors, thermodynamic parameters and dyeing properties on the silk in several dyeing conditions were investigated. The uv-visible spectra of safflower yellow colors in several solvents show hypsochromic shift with the polarity of solvent but bathochromic shift with increasing acidity of solution. The apparent diffusion coefficients and standard affinities of dyeing increased with the increase of dyeing temperature. The standard heat of dyeing(${\Delta}H^0$), entropy change(${\Delta}S^0$) and activation energy($E_{act}$) were calculated to be - 1.144kcal/mol, -7.498(5$0^{\circ}C$)~-3.804(9$0^{\circ}C$)cal/molㆍdeg and 0.123kcal/mol, respectively. The concentration of safflower yellow colors in the silk fiber increased with dyeing temperature, time, concentration of colors and acidity of initial dyebath. Silk fabrics were dyed bright yellow by pre-mordanting with tin chloride. Lightfastness of silk fabrics pre-mordanted by tin chloride was not excellent.

• Smart Structures and Systems
• /
• 제21권2호
• /
• pp.235-248
• /
• 2018

An efficient method utilizing the multi-stage improved differential evolution algorithm (MSIDEA) as an optimization solver is presented here to detect the multiple-damage of structural systems. Natural frequency changes of a structure are considered as a criterion for damage occurrence. The structural damage detection problem is first transmuted into a standard optimization problem dealing with continuous variables, and then the MSIDEA is utilized to solve the optimization problem for finding the site and severity of structural damage. In order to assess the performance of the proposed method for damage identification, an experimental study and two numerical examples with considering measurement noise are considered. All the results demonstrate the effectiveness of the proposed method for accurately determining the site and severity of multiple-damage. Also, the performance of the MSIDEA for damage detection compared to the standard differential evolution algorithm (DEA) is confirmed by test examples.

• Journal of Preventive Medicine and Public Health
• /
• 제33권1호
• /
• pp.51-55
• /
• 2000

Objectives . In large-scale field trials, randomization by cluster is frequently used because of the administrative convenience, a desire to reduce the effect of treatment contamination, and the need to avoid ethical issues that might of otherwise arise. Cluster randomization trials are experiments in which intact social unit, e.g., families, schools, cities, rather than independent individuals are randomly allocated to intervention groups. The positive correlation among responses of subjects from the same cluster is in matter in cluster randomization. This thesis is to compare the results of three randomization methods by standard error of estimator of treatment effect. Methods : We simulated cholesterol data varing the size of the cluster and the level of the correlation in clusters and analyzed the effect of cholesterol-lowering agent. Results : In intra-cluster randomization the standard error of the estimator of treatment effect is smallest relative to that in inter-cluster randomization and that in individual randomization. Conclusions : Infra-cluster randomization is the most efficient in its standard error of estimator of treatment effect but other factor should be considered when selecting a specific randomization method.

• 자연과학논문집
• /
• 제19권1호
• /
• pp.77-94
• /
• 2008

The purpose of this study is to present a design proposal of the senior housing in the city of Kimje and design guidelines for making outdoor spaces for Korean elderly. To do this, this study examined previous research papers and scholastic writings, related to elderly housing, and analyzed study cases of elderly housing. As a result, design guidelines of outdoor spaces for elderly were classified 5 types. Entrance area of housing complex is subdivided into the condition of location, the entrance of housing complex, an access road, and a direction mark. Building entrance area is subdivided into an access and waiting area, a canopy facility, and the pattern and color of boundary. In & outdoor neutral area is subdivided into a spatial standard, a patio, and a terrace. Parking lots is subdivided into a spatial standard and an entrance access. Outdoor living area is subdivided into a spatial and social standard, the usage of movable chairs, a garden, a pocket park, a lawn area, a sports area, an active and passive sports area, a promenade, a lookout area and so on. In these study cases, outdoor living area is commonly located into a community space, a nature friendly space, a health & sports space, and an outlook space and it plays positive role to the elderly. However, versatile outdoor spaces such as horticultural therapy garden is needed, which can be able to stimulate the physical senses of the elderly. This proposal is meant to create new outdoor spaces of a senior housing and to enhance the way of life of elderly.

• Structural Engineering and Mechanics
• /
• 제77권5호
• /
• pp.661-672
• /
• 2021

In this article, the role of spans number and length in fire-resistance ratings (FRRs) of fireproofed steel frames are investigated. First, over a span-lengthening scenario, two one- and three-bay frames under the ISO834 fire are examined. It is shown that the FRRs of the frames rely highly on the changes made on their span length. Second, a building designed for three spans number of three, four, and five under natural fire is investigated. The beams are designed for two load-capacity-ratios (LCRs) of optimum and ultimate. The fire curves are determined through a probabilistic-based approach. It is shown that the structural vulnerability vastly increases while the number of spans decreases. The results show that for an optimum LCR, while the five-span frame can meet the required FRR in 87% of the fire scenarios, the four- and three-span frames can meet the required FRR in only 56%, and 50% of the fire scenarios, respectively. For an ultimate LCR, the five-, four- and three-span frames can meet the required FRR in 81%, 50%, and 37.5% of the fire scenarios, respectively. Functional solutions are then proposed to resolve the insufficiencies in the results and to rectify the application of the standard-based FRRs in the cases studied. The study here highlights how employing current standard-based FRRs can endanger structural safety if they are not connected to structural characteristics; a crucial hint specifically for the structural engineering community who may be not well familiar with the fundamentals of performance-based approaches.

• 한국지형학회지
• /
• 제27권1호
• /
• pp.91-102
• /
• 2020

Earthquakes and volcanic information can vary in type and extent, from raw data to processed data. In order to be able to analyzed and modeled, information needs to be opened in any formats and provided with metadata from the Korea Meteorological Agency and related data production organizations. We propose the metadata and data registry related to volcanic disasters in a form that can be used in conjunction with the Korea Meteorological Administration system that manages earthquake and volcanic data in Korea. The standard registry refers to a virtual system that checks the standards developed for over 20 years in the field of geographic information and receives information registration to grasp the location of geographical features. It is not only data from natural disasters such as earthquakes and volcanoes, but also national environmental survey results, and the cooperation system with other organizations dealing with national land information is also important, so a registry that creates and operates standards is necessary. Therefore, creating and operating the standard registry is necessary and expected to contribute to academic openness and data-driven policy.

• Journal of Biosystems Engineering
• /
• 제26권2호
• /
• pp.105-114
• /
• 2001

Modulus of elasticity, modulus of rigidity, damping ratio, and natural frequency of three varieties of boxthorn (Lycium chinense Mill) (Cheongyang #2, Cheongyang gugija, and Cheongyang native) branches were analyzed. Modulus of elasticity and modulus of elasticity and modulus of rigidity of the boxthorn branch was determined using standard formula after simple beam bending and torsion test, respectively, using an universal testing machine. Damping ratio and natural frequency of branches were determined using a system consisted of an accelerometer, a PC equipped with A/D converter, and a software for data analysis. Relationship between the elastic modulus and branch diameter in overall varieties and branch types showed a good correlation (r -0.81). There was, however, no correlation between torsional rigidity and branch diameter. The internal damping results were highly variable and the overall range of the damping ratio of the boxthorn branch was 0.014-0.087, which indicated that the branch was a lightly damped structure. The natural frequency of the boxthorn branch was in the range of 89-363 rad/s for the overall varieties and branch types. A good correlation (r 0.82) existed between the natural frequency and branch diameter in overall varieties and branch type.

• 한국자동차공학회논문집
• /
• 제3권3호
• /
• pp.9-18
• /
• 1995

The substitution of conventional fuel oil by alternative fuels is of immense interest due to liquid oil shortage and requirements of emission control standard. Among the alternative fuels, natural gas may be the most rational fuel, because of its widespread resource and clean est burning. Meanwhile, engine simulation is of great importance in engine development. Hence a zero-dimensional combustion model was developed for dual-fuel system. Natural gas was injected directly into the cylinder and small amount of distillate was used to provide the ignition kernel for natural gas burning. The intake air and exhaust gas flow was modeled by filling and emptying method. Although the single zone approach has an inherent limitation, the model showed promise as a predictive tool for engine performance. Its simulation was also made to see how the engine performance was influenced by the fuel injection timings and amount of each fuel.

• Natural Product Sciences
• /
• 제12권1호
• /
• pp.44-49
• /
• 2006

The aqueous extract of Hydrilla verticillata (AEHV) was tested for possible pharmacological effects on experimental animals. AEHV significantly potentiated the sleeping time of mice induced by standard hypnotics viz. pentobarbitone sodium, diazepam, and meprobamate in a dose dependent manner. AEHV showed significant analgesic properties as evidenced by the significant reduction in the number of writhes and stretches induced in mice by 1.2% acetic acid solution. It also potentiated analgesia induced by morphine and pethidine in mice. Pretreatment with AEHV caused significant protection against strychnine and leptazol-induced convulsions. The behavioral studies on mice indicate CNS depressant activity of the aqueous extract of H. verticillata.