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In this article, topology optimization was used to design a magnetic core structure on a $\pi$ -type filter circuit. The newly designed magnetic core canceled the noise generated by conducted and induced currents, and as a result, showed dramatically improved electromagnetic interference (EMI) filter performance. Topology optimization was executed using three-dimensional electromagnetic field analysis to capture the magnetic coupling effect. The designed magnetic core was fabricated by machined milling and its performance was evaluated by measuring the noise reduction effect of a simple EMI filter equipped with the core. The EMI filter equipped with our optimized magnetic core showed about 30 dB higher performance than a filter with conventional ring-shaped cores.These results show that the performance of an EMI filter can be improved by optimizing the structure of its magnetic core.

The Sumida River, a typical urban river in Tokyo, has been recognized as a site for fostering Tokyo’s urbanlife that serves as a venue of leisure and relaxation for its residents. As the Teikyo University of Science(TUS) is located near the Sumida River, students spend a lot of time nearby. Clarifying the characteristics ofSumida River, and teaching it to students, are important not only for enhancing environmental awarenessamong students, but also local environment conservation. In this study, chemical oxygen demand (COD)and electric conductivity (EC) data, major sources of contamination, and the characteristics of the river wereanalyzed and interpreted as follows. 1) Although our COD and EC data showed that Sumida River wasaffected by tidal movement, the river water in our research area (from Otakebashi Bridge to Senju-OhashiBridge) might exhibit backward and forward movements, and it was slightly affected by sea water from theTokyo Bay. 2) Major chemical contaminant sources of investigated area were determined to be the Miyagiwastewater purification facility (WPF) and the Mikawajima WPF at the upstream and downstream sides ofthe TUS, respectively. 3) We presume a two-fraction zone in the Sumida River from our analytical resultsand public data, including a "high COD zone" with an upstream stagnant zone upper the Shirahige Bridge,and a "low COD zone" with a downstream flush zone under the Shirahige Bridge. Raising environmentalawareness concerning the urban river among its residents presumably might contribute to maintaining itsclean and safe environment. We came to conclusion that the importance of educating the citizens aboutkeeping urban rivers environmentally clean and safe for the future generations.

This article aims to realize an isolated dc–dc converter with high power density, high power efficiency, and low noise performance. Although a dual-active-half-bridge (DAHB) converter can achieve high efficiency, it requires input and output low-pass filters to suppress the operational ripple current and switching noise. Owing to the volume of the filters, a DAHB converter cannot be implemented with high power density. This article presents a design theory for a novel isolated bidirectional dc–dc converter with built-in filters. The proposed converter is derived from a DAHB converter and can eliminate the input and output filters via split windings and tank capacitors; the principle of elimination is based on $LC$ low-pass filter function and zero-ripple-current operation. As the number of transistors, capacitors, and magnetic cores of the proposed converter are equal to those of the DAHB converter, the application of the proposed converter allows volume reduction by eliminating the filter components at the input and output ports. Theoretical equations are derived to design a power flow control function and a filter function simultaneously. Finally, prototypes of a DAHB converter and the proposed converter are constructed for comparison. The results demonstrate that the input port noise of the proposed prototype is lower than that of the DAHB prototype by 10 dB (peak) over 1 MHz, and the proposed approach can achieve a significant improvement in efficiency.

Southeast Asian tropical rain forests in the Maritime Continent are among the most important biomes in terms of global and regional water cycling. How land use and land cover change (LULCC) relating to deforestation and forest degradation alter the local hydroclimate over the island of Borneo is examined using the Weather Research and Forecasting (WRF) Model with an appropriate land surface model for describing the influence of changes in the vegetation status on the atmosphere. The model was validated against precipitation data from Tropical Rainfall Measuring Mission (TRMM) satellite 3B42 measurements. A main novelty in this analysis is that the diurnal cycle of precipitation over the island, which is a dominant climatic characteristic of the Maritime Continent, was successfully reproduced. To clarify the impact of the LULCC on the precipitation regimes over the island, numerical experiments were performed with the model that demonstrated the following. Deforestation that generates high albedo areas, such as bare lands, would induce a reduction in precipitation because of reductions in evapotranspiration, convection, and horizontal atmospheric moisture inflow. On the other hand, a decrease in evapotranspiration efficiency without changing the surface albedo could increase precipitation due to an increase in convection and horizontal atmospheric moisture inflow in compensation for the decrease in evapotranspiration. In detail, on the Maritime Continent, through changes in the land surface heating process and land–sea breeze circulation, the LULCC would impact the amplitude of the diurnal precipitation cycle in each region as defined according to the distance from the coast, resulting in changes in the precipitation regimes over the island.

The advection-aridity approach to estimate actual evaporation from natural land surfaces is one of the better known implementations of Bouchet's complementary principle. Detailed measurements at 2, 12, and 32 m above the ground surface during the growing seasons of 2004–2007 allowed validation of a generalized nonlinear form of this approach above the highly variable terrain in Changwu County in the southern Loess Plateau of the Yellow River basin in China. The obtained values of the parameters were found to lie well within the ranges to be expected on physical grounds or from previous measurements by different experimental means; calibration on the basis of any one year of data allowed predictions within roughly 5% on average. Relative to the corresponding observed turbulent vapor fluxes, the evaporation rates calculated with measurements at the highest level of 32 m displayed the least scatter but only slightly less than those calculated with measurements at the lower level of 12 m; however, those based on measurements at the lowest level of 2 m displayed considerably more scatter than those derived at the two higher levels. This is consistent with the existence of a blending height at higher elevations above the ground, where the effects of surface variability tend to fade away.

In electromagnetic compatibility (EMC) design, it is important to mitigate the dominant effect among those caused by many unintentional parasitic elements or couplings. However, the dominant effect is usually unclear and hence EMC engineers often resort to trial and error to find an effective counterplan. This paper presents an approach for aiding engineers in finding a better design plan using topology optimization, which is a simulation-based structural optimization method. The proposed approach is applied to the conductor pattern design in simple circuits of electromagnetic interference filters, in which the dominant effect is conduction or induction noise depending on the circuit parameters. It is demonstrated that a structure with a reduced dominant effect is obtained automatically, and the utilization of the optimized result for EMC design is also discussed.

Topology optimization, a simulation-based optimization technique to mathematically derive an optimal structure, is applied to the conductor design of an inductance cancellation structure to reduce common-and differential-mode noise. The design of an appropriate conductor pattern for an inductance cancellation structure is difficult due to the unintentional magnetic couplings between the multiple loops mounted to cancel the parasitic inductances of X and Y capacitors. In topology optimization, this design problem is formulated as an optimization problem and an optimal structure is obtained by repeated modification of the conductor pattern using mathematical programming. The performance of circuit boards before and after optimization is evaluated using mixed-mode s-parameters. Both simulation and experimental measurement verify that the effect of inductance cancellation is improved by this optimization.

A novel filter built-in converter with split windings is presented. Because of its extreme simplicity, flexibility, and efficiency, it has the potential to replace some of the conventional electric power conversion methods used today. The background, design, and operation of the proposed filter built-in converter are discussed in this paper. The proposed converter is derived from a dual active half bridge (DAHB) converter, and it can achieve zero-ripple-current operation and LC low-pass filter function by the split windings and tank capacitors. Due to the zero-ripple-current operation and the LC low-pass filter function, the proposed converter can eliminate or decrease the input and output filters, and with a phase-shift control strategy, all the switches are operated under zero-voltage switching (ZVS) condition. In order to design a power flow control function and a filter function simultaneously, theoretical equations for these functions are derived. Finally, the DAHB and the proposed converter prototypes are constructed for comparison. The results show that the noise in the input port of the proposed prototype is smaller than that of the DAHB prototype by 16 dB (peak), and the proposed approach can achieve a significant improvement in efficiency.

General circulation models (GCMs) forecast higher global vapor pressure deficit (VPD) but unchanged global relative humidity (RH) in future climates. A literature survey revealed that 50% of Earth system models and land surface models embedded within GCMs employ RH as an atmospheric aridity index when describing stomatal conductance (gs), whereas the remaining 50% employ VPD. The consequences of using RH or VPD in gs models for water cycling and vegetation productivity in future climates on large spatial and temporal scales remain to be explored. Process-based global dynamic vegetation model runs, changes in the hydrological cycle, and concomitant vegetation productivity for the 21st century projected climate were conducted by altering only gs responses to VPD or RH and not changing any other formulations. In the simulations of the African continent under a 21st century warming trend, both stomatal functions of VPD and RH resulted in similar geographic patterns in gross primary production (GPP). However, continental total GPP was larger for the VPD response than that for the RH response. Transpiration rates were lower, resulting in a 13% increase in water-use efficiency for the VPD response compared with its RH counterpart.

The aim of this research is to reduce the amount of high frequency noise propagating through space in a low-pass filter. Generally, high frequency noise is generated from power electronics equipment that is responsible for converting direct current and alternating current in hybrid cars. A device consisting of capacitors and inductors called the low-pass filter is used for absorbing the high frequency noise. Ideally, the low-pass filter absorbs more noise as its frequency is higher, but in practice, the noise absorption rate decreases beyond a certain frequency. This is because of the following reasons. The magnetic flux is generated from a current loop in the circuit according to Ampere’s circuital law. Then, this magnetic flux causes high frequency noise at the output terminal according to Faraday’s law of induction. This phenomenon is called magnetic coupling. The amount of noise that appears at the output terminal depends on the layout of the conductor on the circuit board. Conventionally, designers reduced the area of the current loop to avoid the influence of magnetic coupling. However, it was difficult for them to quantitatively predict the influence and design the conductor pattern optimally. In contrast, a topology optimization method is valid for obtaining a mathematically evident optimal structure. Topology optimization method usually allows grayscale area, which holds intermediate density value. For the conductor layout problem, it is difficult to appropriately set the current conductivity to the intermediate material density, and this possibly causes a computational error. For these reasons, we propose a grayscale-free topology optimization method for the conductor layout that minimize the influence of the magnetic coupling. Several numerical examples are provided to confirm that the appropriate optimal structures are obtained.

This paper reveals how the conducted common mode noise of a boost converter can be reduced by the use of leakage inductance of coupled inductor. Specifically, it shows how the common mode impedance due to the leakage inductance of a coupled inductor can be used to reduce common mode current, and this point is experimentally verified using two kinds of inductors: a gapped core inductor with a higher leakage inductance and a gapless core inductor with a lower leakage inductance. Moreover, it is theoretically explained and experimentally verified that the proposed coupled inductor leakage inductance technique does not affect converter operation waveforms. Because the technique can be implemented simply by splitting the windings of a conventional inductor and changing the wire connections, no additional components are required, and the technique has the potential to eliminate common mode filters, as well as reduce converter costs and volume.

Summary The aim of this study is to evaluate rainfall partitioning at the forest canopy and reveal the physical process of canopy interception loss. Observations were conducted for 19 months in neighboring stands of Chamaecyparis obtusa Sieb. et Zucc. (Hinoki) and Cryptomeria japonica D. Don (Sugi). Cumulative amounts for the period showed that portions of throughfall ( TF ), stemflow ( SF ) and interception ( IC ) to rainfall ( RF ) for Hinoki were 65.3%, 9.1%, and 25.5%, respectively. Corresponding values for Sugi were 67.9%, 6.6%, and 25.5%. The smaller TF and larger SF in Hinoki than those in Sugi were induced by greater mean funneling ratio of a tree and greater tree density in Hinoki. Similar IC / RF would result from similar leaf area index. In analyses for rainfall events, rainfall period ( RP ) was defined as the period excluding short no-rainfall periods within an event, and rainfall intensity ( RFI ) was as RF / RP . In events with canopy saturation ( RF ⩾ 10 mm), IC / RF was insensitive to RP and RFI . This was related to an increasing rate of IC with RFI . Evaporation for IC estimated by the model, based on the Penman–Monteith equation, was approximately 40% of cumulative IC observed. Underestimation was great in events with long RP , but not with large RFI . We suggest that large amount of IC occurred during rainfall, which is induced by splash droplets transport (SDT) by canopy ventilation.

In this paper, we propose a circuit model that can predict the common-mode noise current in the AM radio band that will flow to an evaluation circuit consisting of a DC motor, a motor control unit, and a battery. In this model, the common-mode impedance of each unit and the impedance of the cables are expressed by lumped constant circuits. It is found that the common-mode current that flows in the ground plate concentrates just below the cables, so the path of the current is also modeled by a lumped parameter circuit. We demonstrate that this model can predict the common-mode current in this system to within 6 dB. This model is expected to be an effective method for quantitatively predicting the noise suppression effect of a motor control unit for a vehicle.

This paper is a case study on the detection of forest disturbances in airborne synthetic-aperture radar (SAR) data. We investigated changes in the L-band SAR backscattering coefficient (σ0) following thinning and a typhoon in a larch forest in northern Japan. The thinning caused changes of intermediate magnitude in the above-ground biomass (AGB), whereas the typhoon broke or uprooted most of the trees, thereby significantly changing the forest structure without changing the biomass. Thinning led to back-scattering coefficients change of less than about 1 dB; HV polarization was most sensitive to the change in AGB, and HH was insensitive to it. In the case of the typhoon, VV was sensitive to the change in forest structure, whereas HH and HV were insensitive to it, suggesting that the tree trunks, which were felled in one direction by the typhoon, enhanced the backscattering signal of the polarisation that accorded with the trunk direction.

This paper reviews recent research topics and methodologies on terrestrial evapotranspiration and atmospheric boundary layer (ABL) over land surfaces. The methodologies referred in this paper includes eddy correlation method, use of satellite remote sensing data, cloud resolving model, and atmospheric water budget using re-analysis data. Careful applications would be recommended for estimating terrestrial evapotranspiration in different spatial scales.

We investigated the diurnal variation of water vapor mixing between the atmospheric boundary layer (ABL) and the free atmosphere over the Loess Plateau in China. Water vapor and wind velocity in the troposphere were observed using a ground-based microwave radiometer and a wind profiler radar in 2005 and 2006. On sunny days in early summer, a strong vertical wind was generated in the afternoon followed by ABL development. Strong convection was enhanced when active cumulus convection developed in the afternoon. In such cases, water vapor decreased in the lower atmosphere from the early morning until late afternoon, while water vapor increased in the upper atmosphere. This finding suggests that water vapor was exchanged diurnally between the ABL and the free atmosphere. The strong convection in the ABL, which was developed by sensible heat from the land surface, played critical roles with link to cumulus convection in such vertical mixing of water vapor. Influences of other processes such as a local circulation and advection of cloud systems were also discussed.

Recently, hybrid vehicles (HVs) have become widespread. In the current HVs, a high-voltage (200 V) battery supplies power to the Power Control Unit (PCU) for driving a motor, generator and air conditioner compressor. It is expected that such kinds of power electronic devices will increase in number in the future. We previously proposed a power line communication (PLC) that uses a high-voltage power line. In this paper, we present the development of a high-voltage PLC system that can simultaneously control multiple power electronic devices in real time and demonstrate the system operation. First, in a system of a commercially available HV, the results of transmission characteristics and electromagnetic noise characteristics that are superimposed on the high-voltage power line are shown. Then the bit error rate (BER) performance under the above noise environment is clarified by computer simulations. Finally, we construct a prototype of the high-voltage PLC system and demonstrate that the system can simultaneously control the rotational speed of two motors.

We present methods, based on an analytical solution to a diffusion equation, for estimating the vertical distribution of the rate of CO2 production within soil. The first method assumes an a priori equation that represents the profile of CO2 production. The second method divides the soil into four layers, from the ground surface to a depth of 80 cm; within each layer, constant CO2 production is assumed. These methods were applied to a secondary deciduous temperate forest in Japan. Soil respiration and CO2 concentrations within the soil pores were measured in the forest from March to December of 1998. The value of Q10, the factor by which metabolic processes increase for each 10 8C increase in temperature, was estimated to be 2.55, using the soil temperature at a depth of 10 cm. The annual soil respiration was estimated to be 642 � 91 g C m � 2 y � 1 . The CO2 concentration within soil pores increased with soil depth in every season, and showed temperature dependency at all depths, which was similar to the relationship between soil respiration and soil temperature. By applying the proposed methods, the profiles of the actual CO2 concentrations within soil pores were well reproduced. Within soil, the amplitude of the seasonal variation in the CO2 production rate was larger in the shallow soil layers than in the deep layers. The CO2 production rate in the shallow soil layers was highly correlated with soil temperature, and its response to soil temperature was more sensitive than that estimated from the CO2 efflux from the soil surface. It was found that the temperature sensitivity of the CO2 production rate differed between the shallow and deep soil layers; this would affect the estimated value of Q10. Adding to the necessity of distinguishing heterotrophic and autotrophic respiration, it is suggested that the way in which they are distributed vertically within soil is critical for predicting soil respiration, and should be included in the parameterization of soil respiration. # 2004 Elsevier B.V. All rights reserved.

A multilayered turbulent transport model for the surface layer based on collisions between atmospheric layers is developed. The model can represent the average and perturbed components of turbulence relatively well, for both bare-soil and canopy-covered surfaces. The number of collisions increases linearly with height for a bare-soil surface, and decreases as the leaf-area density increases within the canopy layer. The intermittent nature of turbulent motion is reproduced in the model, even though the model is one-dimensional. The number of collisions increasing with height may cause the intermittent nature of the turbulence and may also relate to the gust motions for canopy flow; such gusts transfer large momentum downward intermittently and cause a secondary maximum in wind velocity in the lower layer within the canopy. In other words, the model can include the large-eddy effect by considering the different number of collisions among layers. Turbulence data measured with an ultrasonic anemometer at 10 Hz in the field were used as model input; plausible results were obtained. The model can represent the overall characteristics of turbulence in the surface layer.

Seasonal changes in the water and energy exchanges over a pine forest in eastern Siberia were investigated and compared with published data from a nearby larch forest. Continuous observations (April to August 2000) were made of the eddy-correlation sensible heat flux and latent heat flux above the canopy. The energy balance was almost closed, although the sum of the turbulent fluxes sometimes exceeded the available energy flux (Rn − G) when the latent heat flux was large; this was related to the wind direction. We examined the seasonal variation in energy balance components at this site. The seasonal variation and magnitude of the sensible heat flux (H) was similar to that of the latent heat flux (λE), with maximum values occurring in mid-June. Consequently, the Bowen ratio was around 1·0 on many days during the study period. On some clear days just after rainfall, λE was very large and the sum of H and λE exceeded Rn − G. The evapotranspiration rate above the dry canopy from May to August was 2·2 mm day−1. The contributions of understory evapotranspiration (Eu) and overstory transpiration (Eo) to the evapotranspiration of the entire ecosystem (Et) were both from 25 to 50% throughout the period analysed. These results suggest that Eu plays a very important role in the water cycle at this site. From snowmelt through the tree growth season (23 April to 19 August 2000), the total incoming water, comprised of the sum of precipitation and the water equivalent of the snow at the beginning of the melt season, was 228 mm. Total evapotranspiration from the forest, including interception loss and evaporation from the soil when the canopy was wet, was 208–254 mm. The difference between the incoming and outgoing amounts in the water balance was from +20 to −26 mm. The water and energy exchanges of the pine and larch forest differed in that λE and H increased slowly in the pine forest, whereas λE increased rapidly in the larch forest and H decreased sharply after the melting season. Consequently, the shape of the Bowen ratio curves at the two sites differed over the period analysed, as a result of the differences in the species in each forest and in soil thawing. Copyright © 2003 John Wiley & Sons, Ltd.

上層に落葉広葉樹, 中·下層に常緑広葉樹から構成される二次林の6樹種について, 気孔コンダクタンスの日変化と季節変化を観測した. 観測された気孔コンダクタンスは, Jarvis型の気孔コンダクタンスモデルで表現し, どの環境因子が気孔コンダクタンスに影響を及ぼしているのかについて調べた. 上層木のコナラに関しては, 直達光にさらされる葉 (陽葉) とさらされない葉 (陰葉) とに分けて計測した. 陽樹であるコナラは, 日変化·季節変化を通して, 気孔コンダクタンスの変動量が大きかった一方, 中·下層の常緑広葉樹 (陰樹) は微少な変動に止まった. 気孔コンダクタンスと光合成光量子束密度との関係を光飽和曲線 (light response curve) と定義した場合, 陽樹はその光飽和点 (light saturation point) が高かったのに対して, 陰樹は光合成光量子束密度が小さい領域において, 光飽和曲線の初期勾配 (quantum yield) が大きかった. Jarvis型の気孔コンダクタンスモデルにおいて, 影響度の低い環境因子をＦ検定により抽出した結果, この二次林では土壌水分ポテンシャルが当てはまった. 一方, 光合成光量子束密度, 気温, 飽差は気孔コンダクタンスに与える影響が大きい環境因子として重要であった. 落葉広葉樹のコナラでは, 新葉展開後の気孔コンダクタンスがそれ以外の時期とは異なる傾向にあり, 中·下層木のソヨゴ·ネズミモチ·アオキでは, 3月∼5月にかけて, 異年葉の気孔コンダクタンスの特性が異なる傾向にあった. 葉齢と気孔コンダクタンスとの関係については, 将来の研究課題と考えられた.

Diurnal variations in δ14C, δ13C and the concentration of atmospheric carbon dioxide in an urban forest were measured on 9 February 1999 to discriminate and quantify contributions from different CO2sources. The biogenic CO2concentration remained relatively constant throughout the day. However, anthropogenic CO2concentration fluctuated with the atmospheric CO2concentration, and seemed to be controlled by wind velocity and the amount of exhaust gases from fossil fuel burning. The vertical profiles of anthropogenic, biogenic, and total CO2showed a constant concentration within forest during daytime because of the large vertical CO2influx, strong winds, and neutral atmospheric condition. The biogenic contribution at night decreased from the forest floor upwards with a smooth gradient, while the anthropogenic contribution showed a direct mirror because of the location of respective CO2sources—the vertical gradient of wind velocity and the horizontal CO2supply.