Aquatic ecosystems are receiving various harmful effects due to anthropogenic chemical pollutions. To protect wildlife, risk assessments of the chemicals are conducted using reference indexes of toxicity estimated by species-level laboratory tests and/or micro-/mesocosm community-level studies. However, the existing micro-/mesocosm communities are structurally too complicated, and it is also difficult to compare the experimental results directly with those from species-level tests. Here, we developed a procedure of a simple bi-trophic microcosm experiment which contains the common species (a green algae, Pseudokirchneriella subcapitata and a cladoceran, Daphnia magna) for testing chemical toxicities. For the proper operation of bitrophic microcosm experiment, the minimum required concentration of primary producer (P. subcapitata) is 5×105 cells mL-1. The microcosm system showed higher stability when the initially introduced D. magna population was composed of neonates (<24-h old) than adults and those mixture. This simple microcosm system would be an applicable tool to estimate the disturbing impacts of pollutants on plant-herbivore interactions, and linking the species- and population-/community level risk assessments in the future studies.

본 논문에서는 변위응답 및 가속도 응답의 저감 효과에 있어서, 유리한 형상인 180° 나선형(Helical 180°) 초고층건물을 대상으로 풍진동실험을 수행하여 나선형 초고층건물의 공력불안정 진동 특성 및 공력감쇠 특성을 조사하였고, 정방형 초고층 건물의 결과와 비교분석 하였다. 본 연구에서의 공력감쇠율은 RD법(random decrement technique)을 이용하여 평가하였다. RD법에 의해 평가된 공력감쇠율은 기존문헌 및 준정상가정이론 결과와 비교·검증하였다. 실험결과, 공력진동 실험결과 180° 나선형모형의 풍직각방향에 대한 공력불안정 진동은 발생하지 않는 것이 확인되었다. 정방형과 180° 나선형 형상에 대한 공력감쇠율을 살펴보면, X방향에 대한 공력감쇠율은 무차원 풍속이 증가와 비례하여 점진적으로 증가하는 경향이 나타났다. 반면, Y방향에 대한 공력감쇠율은 정방형모형과 매우 다른 양상이 나타나는 것을 알 수 있었다.

본 연구는 고층건축물의 기본설계 단계에서 평면형태를 결정할 때, 응용할 수 있도록 다양한 형상을 가진 고층건축물에 작용하는 풍력 및 풍응답에 대한 데이터베이스를 구축하는데 목적이 있다. 따라서 본 논문에서는 풍력데이터베이스의 초기 단계로, 높이 200m이상의 고층건축물의 변장비(D/B=0.33, 0.50, 0.77, 0.83, 0.91, 1.0, 1.1, 1.2 ,1.3 ,2.0, 3.0) 변화에 따른 풍력의 특성을 조사하고 기존 문헌과의 비교·검토를 통해 실험결과를 검증하였다. 또한 풍하중조합의 관점에서 풍방향-풍직각방향, 풍방향-비틀림방향 및 풍직각방향-비틀림방향 간의 풍력의 상호상관에 대해서 검토하였다. 실험결과, 풍방향 및 풍직각방향에 대한 평균 및 변동 모멘트계수와 풍직각방향 및 비틀림방향 변동모멘트계수의 파워스펙트럼밀도의 결과는 기존 연구결과와 잘 부합되는 것으로 나타났다. 또한, 지표면조도의 변화에 따른 풍방향, 풍직각방향 및 비틀림방향에 대한 풍력의 특성은 큰 변화가 없는 것으로 나타났다. 시간영역과 주파수영역에서의 변동모멘트의 상호상관계수 분석결과, 풍직각방향-비틀림방향 변동모멘트계수의 상호상관계수가 높게 나타나는 경향을 보였다.

A series of wind tunnel tests were conducted on 7 super-tall buildings with various polygon cross-sections, including triangle, square, pentagon, hexagon, octagon, dodecagon, and circular. The primary purpose of the present study is to investigate the effect of increasing number of sides on aerodynamic characteristics for super-tall buildings. Wind tunnel tests were conducted under the turbulent boundary layers whose power-law exponent is 0.27. Fluctuating wind pressures from more than 200 pressure taps were recorded simultaneously, and time series of overturning moments were calculated considering tributary area of each pressure tap. The results show that the overturning moment coefficients and the spectral values decrease with increasing number of sides, and the largest mean and fluctuating overturning moments were found for the triangular super-tall building, and the largest spectral values were found for the square super-tall building. The analysis should be conducted more in detail, but currently it can be roughly said that there seems to be a little differences in the aerodynamic characteristics for the super-tall buildings whose number of sides is larger than 5 or 6.

Recent tall buildings tend to have unconventional shapes as a prevailing, which is effective for suppressing across-wind responses. Suppression of across-wind responses is a major factor in tall building projects, and the so called aerodynamic modification method is comprehensively used. The purpose of the present study is to investigate the pressure fluctuations on tapered and setback tall buildings, including peak pressures, power spectra and coherences through the synchronous multi-pressure sensing system techniques. And flow measurements around the models were conducted to investigate the condition of vortex shedding. The results show that by tapering and setback, different distributions of mean pressure coefficients at leeward surface were found, which is caused by the geometric characteristics of the models. And the power spectra of wind pressures at sideward surface become wideband and the peak frequencies are different depending on heights, which makes the correlation near the Strouhal component low or even negative. The differences in shedding frequencies were also confirmed by the flow fields around the models.

For most of recent tall buildings, one characteristic is that their building shapes vary with height such as taper and setback, and this implies that the distribution of their structural components may also vary with height. Because of these structural variations, although the sectional shapes of these buildings are symmetric, it is difficult to say whether or not they are structurally symmetric. The acceleration responses of structurally asymmetric tall buildings are larger than those of non-eccentric buildings, thus raising the possibility of problems during strong winds and typhoons. This paper describes wind tunnel tests carried out using building models with height variations and acceleration response analyses, and discusses the resulting response characteristics. For tapered and setback buildings, although the across-wind accelerations are larger than those of a square building, the total root-mean-square accelerations remain small because of smaller along-wind and torsional rms accelerations. And it was found that the effects of statistical couplings between along-wind force and other two forces are negligible.

When a new bonding agent using coal ash is utilized as a substitute for cement, it has the advantages of offering a reduction in the generation of carbon dioxide and securing the initial mechanical strength such that the agent has attracted strong interest from recycling and eco-friendly construction industries. This study aims to establish the production conditions of new hardening materials using clean bottom ash and an alkali activation process to evaluate the characteristics of newly manufactured hardening materials. The alkali activator for the compression process uses a NaOH solution. This study concentrated on strength development according to the concentration of the NaOH solution, the curing temperature, and the curing time. The highest compressive strength of a compressed body appeared at 61.24MPa after curing at 60˚C for 28 days. This result indicates that a higher curing temperature is required to obtain a higher strength body. Also, the degree of geopolymerization was examined using a scanning electron microscope, revealing a micro-structure consisting of a glass-like matrix and crystalized grains. The microstructures generated from the activation reaction of sodium hydroxide were widely distributed in terms of the factors that exercise an effect on the compressive strength of the geopolymer hardening bodies. The Si/Al ratio of the geopolymer having the maximum strength was about 2.41.

본 연구에서는 풍동실험을 통해 인접건축물의 다양한 높이비, 위치와 풍향에 따른 고층건축물에 작용하는 피크풍압계수에 대하여 조사하였다. 그리고 피크풍압계수는 Cook and Mayne의 제안식을 이용하여 산출하였다. 실험결과는 우선적으로, 인접건축물의 유무에 따른 최대 및 최소풍압계수의 분포도를 통해 비교 분석하였다. 풍동실험결과 풍향 135도에서 인접건축물의 높이비가 Hr ≥1.5이고, (Sx, Sy)=(1.5B,0)에 위치할 때, 대상건축물의 정면에 작용하는 최소 풍압계가 단독건축물에 작용하는 최소풍압계수(-3.5)에 비해 전반적으로 크게 나타났으며, 최소풍압계수의 최소값은 정면의 최상부 코너 부근에서 -4.7(Hr=1.5), -5.7(Hr=2.0)으로 나타났다. 본 연구의 결과는 CFD 해석 결과의 정당성 입증과 두동 이상으로 이루어진 고층건축물의 초기설계단계에서 상호간섭효과로 인한 외장재용 풍하중을 대략적으로 평가하는데 유용하게 사용할 수 있을 것이다.

Japan is one of the major forest-rich countries in the world with two thirds of its national territory covered with forests. The various functions of forests, including the prevention of global warming, conservation of national land, recharging of water resources, and maintenance of biotic diversity, play an important role in our safe, secure, and comfortable living. With the increasing national expectations on the role of forests tocontribute to the prevention of global warming and “Accelerating forest carbon-sink measures to achieve Kyoto Protocol Commitment”, it is necessary to make efforts toward a large-scale forest regeneration in order to secure an absorption of 13 million carbon tons through forest carbon sink for the achievement of the target of six percent reduction under the Kyoto Protocol. Most importantly, however, is to accelerate the measures for forests as absorption sources, including thinning and other forestry management activities. However, there is a situation, among others, where thinning is not implemented properly due to the decreased willingness of forest owners to manage forests, because of the long-term low demand for domestic lumber and lumber prices.In addition, forestry workers are aging and decreasing in number. Thus, the circumstances surrounding forestry are severe. It is necessary for the protection of our precious forests to make effortsto create and maintain forests with activities that involve citizens such as the “National Movement for Utsukushii Mori Zukur (Fostering Beautiful Forests)”.