Tsuyoshi Honjo

Thermal Comfort and Outdoor Activity in Japanese Urban Public Places

Subjective thermal comfort and outdoor activity in a park and a square in a satellite city northeast of Tokyo were investigated through structured interviews, observations, and comprehensive micrometeorological measurements. Results showed that the park was on an average 1.1°C cooler than the square. The relatively warmer thermal conditions in the square in comparison to the park resulted in a heat load of greater intensity for humans in the square. In general, there was a low relation between the thermal environment and the use of the two places in terms of total attendance. However, the use of the park was influenced more by the thermal conditions than by the use of the square, which can mainly be attributed to the different functions of the two places. Finally, examples of the differences between the use of the sun, the attitudes toward it, and outdoor exposure in Japan and Sweden are highlighted and discussed.

Simulation of thermal effects of urban green areas on their surrounding areas

Abstract Numerical models were used to estimate the cooling effects of green areas on their surrounding areas. The model uses the equations of turbulent energy and dissipation and simulates the flow over the inhomogeneous surface whose surface roughness and temperature change. The intensity of this effect and the range of influence on surrounding urban areas were calculated. From the results, it is suggested that smaller green areas with sufficient intervals are preferable for effective cooling of surrounding areas.

Visualization of landscape by VRML system

Virtual reality modeling language (VRML) is a high performance language for three-dimensional (3-D) visualization on the World Wide Web (WWW). Three-dimensional information can be easily transferred through the Internet by this technology. In this study, we made a landscape visualization system that enables virtual experience in a planned landscape by using VRML and the applicability of the system to the landscape design was shown. To perform real-time rendering of landscape, a tree was expressed by using two textured planes instead of thousands of polygons. Trees were placed automatically on a textured terrain based on the plant database by the system developed in this study. With the system, we made models of real gardens based on measured data and walk-through simulations in the gardens were tested. The system showed good performance and it also indicated the potential of VRML systems. The information on the virtual landscape can be placed on WWW. This method can be utilized both for the design of and for the public discussion on landscape planning.

Three-dimensional visualization forest of landscapes by VRML

Abstract Computer technology has been used to develop three-dimensional (3D) forest landscape visualization systems that include the function of three-dimensional digital plant modeling. While the earlier systems accurately simulated forest landscapes, they lacked sufficient speed and could not adequately perform walk-through simulations. The objective of this study is to describe the forest landscape visualization procedure capable of walk-through simulations and its application. We developed a forest landscape visualization system using virtual reality modeling language (VRML). This visualization system works with data of forest stands rather than individual trees. To confirm the feasibility of the system, we visualized an actual forest landscape with thousands to tens of thousands of trees. We also simulated a variety of forest landscapes and showed how this system can be used to simulate the changes of forest landscapes that occur as a result of natural processes or man-made disturbances such as planting, thinning, and harvesting. This visualization system was capable of walk-through simulation and the three-dimensional images rendered by the system enabled us to effectively visualize the forest landscape resources. The visualization by computer graphics also made it possible to confirm the accuracy of forest data.

A GIS-based simulation program to predict multi-species size-structure dynamics for natural forests in Hokkaido, northern Japan

Abstract A simulation program that runs on a geographic information system (GIS) was developed to predict the multi-species size-structure dynamics of forest stands. Because important characteristics of a forest stand, including woody biomass accumulation, carbon storage, commercial value of timber, and functions for environmental conservation, can be inferred from the size structures of the component populations, management plans can be made from the predictions of the size-structure dynamics. For example, the simulation can incorporate various forms of thinning; forest managers can then try several thinning plans in simulated forest stands and choose the appropriate plan that achieves the best results. Using GIS to predict the size-structure dynamics of forest stands is of practical importance, because GIS has been used widely in forest management and can easily handle spatial distributions of environmental information (e.g., climate, geology, soils) that may influence tree performance. To predict size-structure dynamics, the program numerically solves a continuum equation that describes size-structure dynamics based on growth and mortality rates of individual trees. When predicting size-structure dynamics of a forest stand, the program obtains the environmental information of the stand from a database stored in the GIS and calculates environmental factors such as warmth index and potential evapotranspiration/precipitation ratio that influence growth and mortality rates. The simulation program calculates growth and mortality rates using published growth and mortality models that incorporate the effects of size of the individual, competition between trees, and abiotic environmental factors. To demonstrate the effects of abiotic environmental factors on the multi-species size-structure dynamics, sensitivity analyses were conducted. The size-structure dynamics varied in a way that was predictable from the responses of the growth and mortality rates to variations in the abiotic environmental factors. To demonstrate the size-structure dynamics in different locations, five test runs of the simulation program were also performed using the same initial size-structure and five different sets of abiotic environmental conditions from five locations. At the end of the simulation, the predicted size structures differed because the growth and mortality rates differed among the five locations. Finally, the response of the size structure to thinning was clarified. The result showed how the size structure of a component species in a forest stand is dependent on the presence of other species.

The Study of Landscape Visualization Method by VRML and Plant Model Database

VRML (Virtual Reality Modeling Language) は, インターネット上での景観可視化に大きな可能性を持つ。本研究では小石川後楽園を対象として, 数千本の樹木を有する本格的な景観の可視化にVRMLを実用的に用いることができるかを検討した。そのため, 2次元植物形状データベースを作成・整備した。また, 高性能の景観設計システムであるAMAPで作成した景観画像との比較を行った。その結果, 本格的な景観設計にVRMLが使用可能であること, 高品質の植物を含む景観画像作成が可能であることを明らかにした。

Identification of water and nutrient supply to hydroponic tomato plants by using neural nets

Abstract Water and nutrient supply to hydroponic tomato plants in a greenhouse is identified by using neural nets. Learning procedure of the nets is back-propagation. Inputs are time series data of 5 environmental conditions (solar radiation, inside temperature, inside humidity, nutrient water temperature and CO 2 concentration) and outputs are water and nutrient supply to hydroponic tomato. All data are measured in a commercial greenhouse. The factors of the neural nets structure, such as span of input layer, number of hidden layers and number of units in hidden layer are investigated. As a result, by using simple nets (input data of 8 hours and single hidden layer which consists of 4 units), the amount of water and nutrient supply is calculated well.

Modeling qualitative and quantitative elements of branch growth in saplings of four evergreen broad-leaved tree species growing in a temperate Japanese forest

Key messageFactors influencing branch growth differed between a qualitative element (whether a branch grows) and a quantitative element (the amount of biomass accretion).AbstractWe measured branch growth in saplings of four evergreen broad-leaved tree species growing in a temperate Japanese forest. A hierarchical Bayesian approach was used to model two elements of branch growth: a qualitative component [whether branches produce new annual shoots (ASn)] and a quantitative component (total ASn mass). The two components were influenced by somewhat different factors. The probability that a branch would produce ASn was affected by the total mass of previous-year annual shoots (total ASn–1 mass), branch age, relative branch height, canopy openness measured at the branch tip, maximum canopy openness within a single sapling, and the interaction between canopy openness and maximum canopy openness. The total ASn mass was influenced by the total ASn–1 mass, relative branch height, branch inclination, and maximum canopy openness. These two components of branch growth should be considered separately when tree architecture is modeled. In addition, we detected interactive responses among branches within individual saplings. The relative importance of interactive modular response and branch autonomy may differ depending on the status of plants, such as individual age, environmental conditions, and the timing of the measurements. We found considerable similarities in the responses of branch growth to the internal and environmental factors among the species studied. We also found some among-species differences in branch growth responses to the explanatory variables measured.

Development of models for estimating leaf chlorophyll and nitrogen contents in tree species with respect to seasonal changes

Models were developed to estimate nondestructively chlorophyll (Chl) content per unit of leaf area (Chlarea) and nitrogen content per unit of leaf area (Narea) using readings of two optical meters for five warm-temperate, evergreen, broadleaved tree species (Castanopsis sieboldii, Cinnamomum tenuifolium, Eurya japonica, Machilus thunbergii, and Neolitsea sericea). It was determined whether models should be adjusted seasonally. Readings (were obtained six times during a year period and Chlarea and Narea were determined using destructive methods. Bayesian inference was used to estimate parameters of models that related optical meter readings to Chlarea or Narea for each species. Deviance information criterion values were used to select the best among models, including the models with seasonal adjustment. The selected models were species-specific and predicted Chlarea accurately (R2 = 0.93–0.96). The best model included parameters with seasonal adjustments for one out of five species. Model-based estimates of Narea were not as accurate as those for Chlarea, but they were still adequate (R2 = 0.64–0.82). For all species studied, the best models did not include parameters with seasonal adjustments. The estimation methods used in this study were rapid and nondestructive; thus, they could be used to assess a function of many leaves and/or repeatedly on individual leaves in the field.

Landscape Visualization on Google Earth

Three-dimensional landscape information can be easily transferred through the Internet with Google Earth. In this study, we developed a landscape visualization system that enables simulation of planned landscape on Google Earth and the applicability of the system to the landscape design was shown. The visualization system generates KML (Keyhole Markup Language) and KML file is visualized on Google Earth. To make the data small, a tree was expressed by using textured planes instead of thousands of polygons. Trees were placed automatically on a terrain based on the measured data by the system developed in this study. With the system, we made models of real gardens based on measured data and walk-through simulations were tested. The system showed good performance and it also indicated the potential of the systems.