Loading [MathJax]/jax/output/CommonHTML/jax.js
  • Title/Summary/Keyword: relative density

Search Result 2,087, Processing Time 0.029 seconds

The Analysis of Assessment Factors for Offshore Wind Port Site Evaluation (해상풍력 전용항만 입지선정 평가항목에 관한 연구)

  • Ko, HyunJeung
    • Journal of Korea Port Economic Association
    • /
    • v.28 no.3
    • /
    • pp.27-44
    • /
    • 2012
  • The offshore wind farm is increasingly attractive as one of future energy sources all over the world. In addition, the capacity of an offshore wind turbine gets larger and its physical characteristics are big and heavy. In this regard, a special port is necessary to assemble, store, and transport the offshore wind systems, supporting to form the offshore wind farms. Thus, this study aims to provide a policy maker which evaluation factors can significantly affect to the optimal site selection of a offshore wind port. For this, Fuzzy-AHP method is applied to capture the relative weights. The results of this study can be summarized as follows. Five criteria in level I was defined such as the accumulation factor, the regional factor, the economic factor, the location factor, and the consortium factor. Of these, the accumulation factor(37.4%), the location factor(34.2%), and the economic factor( 24.5%) were analyzed by major factors. In level II, three assessment items of each factor were selected so that total fifteen items were formed. To sum up, the site selection of offshore wind port should consider the density of the wind industry, cargo volume of securing the economic operation of terminals, the development degree of offshore wind related industry, and the proximity to the offshore wind farms. In other words, the construction of offshore wind port should be paid attention to considering not only the proximity to offshore wind farms but also the preference of turbine manufacturing companies.

Distribution Pattern of Ageratina altissima Along Trails at Mt. Umyeon in Seoul, Korea (우면산 등산로 주변 서양등골나물의 분포 경향)

  • Kim, Hyonook;Jang, Yoo Lim;Park, Pil Sun
    • Korean Journal of Agricultural and Forest Meteorology
    • /
    • v.16 no.3
    • /
    • pp.227-232
    • /
    • 2014
  • Ageratina altissima is an invasive plant species known to threaten native plant communities in Korea. A. altissima is thought to invade shady forests from disturbed open areas; however, uncertainty remains as to how shade and litter depth might affect establishment. A study of A. altissima distribution characteristics in areas adjacent to trails was undertaken at Mt. Umyeon in Seoul, Korea. Increasing densities of A. altissima were found to correlate with greater light availability and decreasing litter depth (p < 0.001) within 10 m distance from trail locations and on ridges rather than further within forests and valleys. The effects of soil moisture content, soil gravel content and soil pH on distribution were not found to be significant, suggesting that A. altissima is adaptable to a broad range of soil conditions. Results indicate that forest areas close to trails may be particularly susceptible place to A. altissima invasion, demonstrating the need to carefully consider implications for A. altissima expansion in trail management.

Production and High Temperature Mechanical Properties of Ti-TiC Composite by Reaction Milling (반응밀링법에 의한 Ti-TiC 복합재료의 제조 및 고온 기계적 특성)

  • Jin, Sang-Bok;Choe, Cheol-Jin;Lee, Sang-Yun;Lee, Jun-Hui;Kim, Sun-Guk
    • Korean Journal of Materials Research
    • /
    • v.8 no.10
    • /
    • pp.918-924
    • /
    • 1998
  • This study has been carried out to investigate the effect of reaction milling time on the synthesis of Ti- TiC p powder synthesised from the elemental titanium and activated carbon by reaction milling(RM), and the effect of vacu­u urn hot pressing temperature and TiC volume fraction on microstructural and mechanical properties of Ti- TiC com­p posite ns이idated by vacuum hot pressing(VHP).T The elemental powders of titanium and activated carbon can be converted into Ti- TiC composite powders by reac­t tion milling for about 300hours, and were the average grain size of the as- milled powders has been measured to be a about 5μm. The relative density of Ti- TiC VHPed above 1000C during Ihr is about 98% and the mechanical properties o of In- situ Ti- TiC composites are improved by TiC particle dispersed uniformly on titanium matrix. In order to investi­g gate thermal stability of Ti- TiC composite, after annealing at 600C for 80hrs micro- Vickers hardness have been per­f formed, and the values have been shown little changed as compared with those before annealing. The compact has b been tested on high temperature compressive test at 700C and has showed a high temperature compressive strength of 330MPa in a Ti- 20vol% TiC.

  • PDF

Study on the fabrication of Ceramic Core using a Gel-casting Process in Aqueous Medium(II) : Physical Properties of Sintered Ceramic Core Body (수용액 매체에서 젤-케스팅 공정을 이용한 세라믹 코어 제조에 관한 연구(II) : 세라믹 코어 소결체의 물성)

  • Kim, Jae-Won;Kim, Du-Hyeon;Kim, In-Su;Yu, Yeong-Su;Choe, Baek-Gyu;Kim, Ui-Hwan;Jo, Chang-Yong
    • Korean Journal of Materials Research
    • /
    • v.11 no.6
    • /
    • pp.465-471
    • /
    • 2001
  • The effect of sintering condition on the mechanical properties and leachability of polydispersed ceramic core body made by gel-casting process in aqueous medium have been investigated. The polydispersed ceramic slip that has low viscosity(1000cP, at 1000cP (at 50sec1 ) and high solid loading(50vo1%) was obtained. The green bodies were fabricated through casting and gelation at room temperature followed by drying at 25Cfor 48hrs under relative humidity of 80%. Crack-free green body was successfully fabricated through the above process. The strength at room temperature, apparent bulk density, and shrinkage of the ceramic core body increased propotionally with increasing sintering temperature(1100~1500C). However, porosity of the ceramic core body showed relatively low vague. Leaching rate of sintered core body increased with increasing porosity of the sintered body, and was significantly dependent upon the concentration of alkali caustic solution at the same leaching temperature.

  • PDF

Parametric Study of Dynamic Soil-pile-structure Interaction in Dry Sand by 3D Numerical Model (3차원 수치 모델을 이용한 건조사질토 지반-말뚝-구조물 동적 상호작용의 매개변수 연구)

  • Kwon, Sun-Yong;Yoo, Min-Taek
    • Journal of the Korean Geotechnical Society
    • /
    • v.32 no.9
    • /
    • pp.51-62
    • /
    • 2016
  • Parametric studies for various site conditions by using 3d numerical model were carried out in order to estimate dynamic behavior of soil-pile-structure system in dry soil deposits. Proposed model was analyzed in time domain using FLAC3D which is commercial finite difference code to properly simulate nonlinear response of soil under strong earthquake. Mohr-Coulomb criterion was adopted as soil constitutive model. Soil nonlinearity was considered by adopting the hysteretic damping model, and an interface model which can simulate separation and slip between soil and pile was adopted. Simplified continuum modeling was used as boundary condition to reduce analysis time. Also, initial shear modulus and yield depth were appropriately determined for accurate simulation of system's nonlinear behavior. Parametric study was performed by varying weight of superstructure, pile length, pile head fixity, soil relative density with proposed numerical model. From the results of parametric study, it is identified that inertial force induced by superstructure is dominant on dynamic behavior of soil-pile-structure system and effect of kinematic force induced by soil movement was relatively small. Difference in dynamic behavior according to the pile length and pile head fixity was also numerically investigated.

A Study of Theoretical Methods for Estimating Void Ratio Based on the Elastic Wave Velocities (탄성파 속도를 이용한 간극비 산출 식의 고찰)

  • Lee, Jong-Sub;Park, Chung-Hwa;Yoon, Sung-Min;Yoon, Hyung-Koo
    • Journal of the Korean Geotechnical Society
    • /
    • v.29 no.2
    • /
    • pp.35-45
    • /
    • 2013
  • The void ratio is an important parameter for reflecting the soil behavior including physical property, compressibility, and relative density. The void ratio can be obtained by laboratory test with extracted soil samples. However, the specimen has a possibility to be easily disturbed due to the stress relief when extracting, vibration during transportation, and error in experimental process. Thus, the theoretical equations have been suggested for obtaing the void ratio based on the elastic wave velocities. The objective of this paper is to verify the accuracy of the proposed analytical solution through the error norm. The paper covers the theoretical methods of Wood, Gassmann and Foti. The elastic wave velocity is determined by the Field Velocity Probe in the southern part of Korean Peninsular. And the rest parameters are assumed based on the reference values. The Gassmann method shows the high reliability on determining the void ratio. The error norm is also analyzed as substitution of every parameter. The results show every equation has various characteristics. Thus, this paper may be widely applied for obtaining the void ratio according to the field condition.

Design of a Low Noise 6-Axis Inertial Sensor IC for Mobile Devices (모바일용 저잡음 6축 관성센서 IC의 설계)

  • Kim, Chang Hyun;Chung, Jong-Moon
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.40 no.2
    • /
    • pp.397-407
    • /
    • 2015
  • In this paper, we designed 1 chip IC for 3-axis gyroscope and 3-axis accelerometer used for various IoT/M2M mobile devices such as smartphone, wearable device and etc. We especially focused on analysis of gyroscope noise and proposed new architecture for removing various noise generated by gyroscope MEMS and IC. Gyroscope, accelerometer and geo-magnetic sensors are usually used to detect user motion or to estimate moving distance, direction and relative position. It is very important element to designing a low noise IC because very small amount of noise may be accumulated and affect the estimated position or direction. We made a mathematical model of a gyroscope sensor, analyzed the frequency characteristics of MEMS and circuit, designed a low noise, compact and low power 1 chip 6-axis inertial sensor IC including 3-axis gyroscope and 3-axis accelerometer. As a result, designed IC has 0.01dps/Hz of gyroscope sensor noise density.

Effect of h-BN Content on Microstructure and Mechanical Properties of AIN Ceramics (AIN 세라믹스의 미세조직과 기계적 성질에 미치는 h-BN 첨가의 영향)

  • 이영환;김준규;조원승;조명우;이은상;이재형
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.9
    • /
    • pp.874-880
    • /
    • 2003
  • The effect of h-BN content on microstructure, mechanical properties, and machinability of AlN-BN based machinable ceramics were investigated. The relative density of sintered compact decreased with increasing h-BN content. The four-point flexural strength also decreased from 238 MPa of monolith up to 182 MPa by the addition of 30 vol% h-BN. Both low Young's modulus and residual tensile stress, formed by the thermal expansion coefficient difference between AIN and h-BN, might cause the strength drop in AlN-BN composite. The crack deflection, and pull-out phenomena increased by the plate-like h-BN. However, the fracture toughness decreased with h-BN content. The second phases, consisted of YAG and γ-Al2O3, were formed by the reaction between Al2O3 and Y2O3. During end-milling process, feed and thrust forces measured for AlN-(10~30) vol% BN composites decreased with increasing h-BN particles, showing excellent machinability. Also, irrespective of h-BN content, relatively good surfaces with roughness less than 0.5 m (Ra) could be achieved within short lapping time.

Classification of Ground Subsidence Factors for Prediction of Ground Subsidence Risk (GSR) (굴착공사 중 지반함몰 위험예측을 위한 지반함몰인자 분류)

  • Park, Jin Young;Jang, Eugene;Kim, Hak Joon;Ihm, Myeong Hyeok
    • The Journal of Engineering Geology
    • /
    • v.27 no.2
    • /
    • pp.153-164
    • /
    • 2017
  • The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

Deposition Velocity of Iodine Vapor ((I2)) for Radish Plants and Its Root-Translocation Factor : Results of Experimental Exposures (요오드 증기(I2)의 무 작물체에 대한 침적속도 및 뿌리 전류계수 : 피폭실험 결과)

  • Choi, Yong-Ho;Lim, Kwang-Muk;Jun, In;Park, Doo-Won;Keum, Dong-Kwon
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.8 no.2
    • /
    • pp.151-158
    • /
    • 2010
  • In order to measure the deposition velocity of I2 vapor for radish plants and its translocation factor for their roots, radish plants were exposed to I2 vapor for 80 min. at different growth stages between 29 and 53 d after sowing. The exposure was performed in a transparent chamber during the morning time. Deposition velocities (ms1) were on the whole in the range of 1.0×1042.0×104 showing an increasing tendency with an increase in the biomass density. The results showed some agreement with existing reports that a higher relative humidity would lead to a higher deposition velocity. The acquired deposition velocities were lower than by factors of several tens than some field measurements probably due to a very low wind speed (about 0.2ms1) in the chamber. Translocation factors (ratio of the total iodine in the roots at harvest to the total plant deposition), estimated in a more or less conservative way, were 1.3×103 for an exposure at 29 d after sowing and 5.0×103 for an exposure at 53 d after sowing. In using the present experimental data, meteorological conditions and chemical and physical forms of iodine need to be carefully considered.