Hasil untuk "Engineering (General). Civil engineering (General)"

Oumaima Mikram, Abdelmajid Abouloifa, Ibtissam Lachkar et al.

The widespread adoption of nonlinear loads in industry has introduced significant power quality issues in electric power distribution grids. The integration of these nonlinear loads has led to the proliferation of serious power quality problems such as the generation of harmonics and reactive power that negatively impact the quality and stability of the electrical grid. In addition to eliminating current harmonics, a shunt active power filter (APF) can also provide reactive power compensation. By dynamically adjusting the reactive power injection, these APFs can improve the power factor of the system and maintain the desired voltage regulation. The proposed control leverages the differential flatness property of the SAPF system, allowing for exact linearization and simplified tracking control without requiring complex modulation techniques. In this paper, a flatness-based control scheme is proposed for a three-phase three-level Neutral Point Clamped (NPC) APF. The main objectives of this work are twofold. The first objective is to mitigate current harmonics and compensate the reactive power drawn by nonlinear loads. The second objective focuses on maintaining a stable DC-link capacitor voltage of the active power filter (APF). To meet these requirements, a cascaded control structure is used, where the external loop regulates the DC-link voltage, while the inner loop is responsible for harmonic current compensation. The effectiveness of the proposed control strategy is validated through simulation results obtained using the MATLAB/Simulink R2024a environment.

Chao Zhang, Ya-Qin Qiu, Zi-Ao Li

Within the field of permanent magnet synchronous motor sensorless speed control systems, we present a novel scheme with a Multi-dimensional Taylor Network (MTN)-based nonlinear observer as the core, supplemented by two auxiliary MTN modules to realize closed-loop control: (1) MTN Model Identifier: Provides real-time PMSM nonlinear dynamic feedback for the observer; (2) MTN Adaptive Inverse Controller: Compensates for load disturbances using the observer’s estimated states. The study focuses on optimizing the MTN observer to address key limitations of existing methods (high computational complexity, lack of stability guarantees, and low estimation accuracy). Compared with the neural network observer, this MTN-based scheme stands out due to its straightforward structure and significantly reduced approximately 40% computational complexity. Specifically, the intricate calculations and high resource consumption typically associated with neural network observers are circumvented. Subsequently, by leveraging Lyapunov theory, an adaptive learning rule for the MTN weights is meticulously devised, which seamlessly bridges the theoretical proof of the nonlinear observer’s stability. Simulation results demonstrate that the proposed MTN observer achieves rapid convergence of speed and position estimation errors (with steady-state errors within ±0.5% of the rated speed and ±0.02 rad for rotor position) after a transient period of less than 0.2 s. Even when stator resistance is increased by tenfold to simulate parameter variations, the observer maintains high estimation accuracy, with speed and position errors increasing by no more than 1.2% and 0.05 rad, respectively, showcasing strong robustness. These results collectively confirm the efficacy and practical value of the proposed scheme in PMSM sensorless speed control.

Kai Wang, Chuyuan Gao, Zhaofeng Zhu et al.

Abstract Skin converts multisensory stimuli into bioelectrical signals through cutaneous receptors and then transmits them to the central nervous system (CNS), implementing an analog-digital response to perceive the environment. However, target engagement components that access multisensory stimuli face significant challenges in multimodal interaction, especially the intrinsic decoupling in stretchable heterogeneous integrating systems and the dimensional broadening in traditional human five sensations. In this work, we propose a passive wireless multimodal self-decoupling methodology paradigm to optimize the signal scheduling of systems and broaden the cognitive dimensions of humans, which engages the strategic configuration of symmetrical inductor-capacitor (LC) resonant circuit combined with LC tank to unlock the single-port output self-decoupling sensing, thereby decoding five sensible stimuli to augment situational awareness of human. Systematic theoretical model is established to verify the self-decoupling methodology and the multimodal sensing scheme based on RLC-modulated mechanism. Multiple prototypes of single-port liquid metal (LM)-based wireless multimodal electronic skin implement targeted responses of skin-like receptors. That incorporating pressure (0 kPa~40 kPa), temperature (25 °C ~ 45 °C), humidity (5%RH ~ 90%RH), ultraviolet (0 lm~20 lm) and inclination (30°, 45°, 60°, 90°) through accessing corresponding sensing components. This technique proposal is designed to render a self-decoupling methodology for stretchable wireless multimodal unperturbed platforms and bridge the spatial sensory dimensions in traditional multisensory mechanisms for human-machine interaction.

Marta J. Kiraga, Anna Markiewicz

Changes in river channel morphological parameters are influenced by anthropogenic factors, such as climatic changes, river catchment management changes, and hydrotechnical development of rivers. To assess the intensity of individual pressures and the resulting changes in abiotic and biotic factors in the riverbed, water quality monitoring is conducted, including the assessment of the hydromorphological status. The assessment can be based on the River Habitat Survey (RHS) which is a synthetic method that includes the evaluation of habitat character and river quality based on their morphological structure. The input data, which characterise any river include physical features of hydrotechnical structures, bed granulation, occurrence of bedforms, visible morphodynamic phenomena, and a sediment transport pattern. The RHS method allows to determine two quantitative indices used to evaluate the hydromorphological status: Habitat Modification Score ( HMS), which determines the extent of transformation in the morphology of a watercourse, and Habitat Quality Assessment ( HQA), which is based on the presence and diversity of natural elements in a watercourse and river valley. The proposed method can be divided into three stages. The first assesses the river section hydromorphological indices, describing the degree of technical modification ( HMS) and the ecological quality of the reach ( HQA), using the RHS method. The second stage describes morphological changes resulting from the technical regulation and estimates indices for the regulated reach. Finally, we compare HQA and HMS indices before and after the regulation. This comparison is described by numerical indicators and related to reference values.

Cláudio Luis de Araújo Neto, Daniel Epifânio Bezerra, Laércio Leal dos Santos et al.

A disposição dos Resíduos Sólidos Urbanos (RSU) constitui uma das principais problemáticas da sociedade moderna, abrangendo aspectos econômicos, sociais e ambientais. Diante desse contexto, este trabalho tem por objetivo avaliar o potencial econômico dos resíduos passivos para a reciclagem na cidade de Campina Grande - PB. A metodologia deste trabalho foi segmentada em três etapas. A primeira etapa compreendeu o levantamento de dados da cidade de Campina Grande - PB. A segunda etapa abrangeu a caracterização gravimétrica dos resíduos sólidos urbanos que são gerados em Campina Grande e depositados no aterro sanitário. E na terceira etapa houve o processamento das informações obtidas nas etapas anteriores para analisar o potencial econômico dos resíduos recicláveis. Os resultados obtidos demonstraram que os resíduos sólidos urbanos gerados em Campina Grande e destinados para o aterro sanitário possuem um potencial econômico considerável, tendo em vista que 86 toneladas de resíduos passíveis de reciclagem são encaminhados ao aterro sanitário e poderiam gerar uma receita de R$ 25.956.000,00 ao ano.

Saad Kelam, Mohamed Chennafa, Mohamed Belkheiri et al.

The main objective of this paper is to solve state observation and external disturbances estimation for a class of second-order nonlinear systems. The proposed method relies mainly on the high gain observer as an estimator that tries to estimate the state vector and at the same time identifies the system’s unknown combined structured and unstructured uncertainties. The efficiency of the proposed method is demonstrated by estimating the flux and the speed of the induction motor by simulation.

Cheng-Jung Yang, Sin-Syuan Wu

The 3D printers integrated with fused filament fabrication (FFF) are highly valued worldwide because of their properties, which include fast proofing, compatibility with various materials, and low printing cost. The competitiveness of FFF can be enhanced by improving printing quality. However, due to the increasing sustainability issues worldwide, there is an urgent need to lower energy consumption. In this study, we focused on fan rate, printing speed, nozzle temperature, build plate temperature, and layer thickness as factors that directly impact the dimensional accuracy, carbon dioxide emissions, and printing cost of FFF printers. Several single-objective and multiobjective optimization tasks were performed using the Taguchi method and desirability approach to implement sustainable manufacturing decisions. In single-objective optimization, the inner width, outer width, material cost, and labor cost were most easily affected by the layer thickness. The outer length, carbon dioxide emissions, and electricity cost were significantly affected by the build plate temperature. In multiobjective optimization, a different set of printing parameters can be used to optimize dimensional accuracy, carbon dioxide emissions, material cost, labor cost, and electricity cost. This study helps users to obtain optimal solutions under different optimization requirements to cope with diverse manufacturing characteristics.

Shobhit K. Patel, Juveriya Parmar, Vijay Katkar et al.

The solar spectrum energy absorption is very important for designing any solar absorber. The need for absorbing visible, infrared, and ultraviolet regions is increasing as most of the absorbers absorb visible regions. We propose a metasurface solar absorber based on Ge2Sb2Te5 (GST) substrate which increases the absorption in visible, infrared and ultraviolet regions. GST is a phase-changing material having two different phases amorphous (aGST) and crystalline (cGST). The absorber is also analyzed using machine learning algorithm to predict the absorption values for different wavelengths. The solar absorber is showing an ultra-broadband response covering a 0.2–1.5 µm wavelength. The absorption analysis for ultra-violet, visible, and near-infrared regions for aGST and cGST is presented. The absorption of aGST design is better compared to cGST design. Furthermore, the design is showing polarization insensitiveness. Experiments are performed to check the K-Nearest Neighbors (KNN)-Regressor model’s prediction efficiency for predicting missing/intermediate wavelengths values of absorption. Different values of K and test scenarios; C-30, C-50 are used to evaluate regressor models using adjusted R2 Score as an evaluation metric. It is detected from the experimental results that, high prediction proficiency (more than 0.9 adjusted R2 score) can be accomplished using a lower value of K in KNN-Regressor model. The design results are optimized for geometrical parameters like substrate thickness, metasurface thickness, and ground plane thickness. The proposed metasurface solar absorber is absorbing ultraviolet, visible, and near-infrared regions which will be used in solar thermal energy applications.

Sumei Gao, Longxiang Xu, Chaowu Jin

In this paper, the structural characteristics of electromagnetic suspension (EMS) inertial stabilizers are analyzed firstly, and then a mechanical analysis of a single mass block and double mass block is carried out. The relationship model between the inertial anti-rolling mass block and inertial force transmitted to the ship is established. The inertial force is determined by the number of coil turns, coil current, mass block, mass of the ship, electromagnet current, rate of change of the electromagnet current, air gap between the electromagnet and inertial mass block, and rotational angular speed. Through theoretical analysis, it is found that the response speed of inertia force is directly related to the electromagnetic coil current, the voltage at both ends of the electromagnetic coil, the coil resistance and the air gap. It is concluded that the response speed of the inertia force can be controlled by controlling the coil current, adjusting the voltage at both ends of the coil and adjusting the air gap. The inductance of the electromagnetic coil will also increase the nonlinearity of the inertial anti-roll system. On the basis of theoretical analysis, a digital simulation of EMS inertial stabilizer is carried out by MATLAB and ANSYS MAXWELL2D. Finally, a single mass block system of EMS inertial stabilizer is designed and tested. During the test, a 1.5 V sinusoidal excitation voltage is added to the electromagnetic coil after the mass block is suspended stably, and the maximum acceleration values of the inertial anti-rolling mass block and hull are 10.29 m/s² and 1.27 m/s². Finally, the theoretical analysis results, digital simulation results and experimental results are analyzed, which verifies the correctness of the acceleration and inertia force performance analysis of the EMS inertial stabilizer.

Jie Zhang, Zipeng Wang, Jinzheng Hu et al.

The data-driven phenomenological models based on deformation measurements have been widely utilized to predict the slope failure time (SFT). The observational and model uncertainties could lead the predicted SFT calculated from the phenomenological models to deviate from the actual SFT. Currently, very limited study has been conducted on how to evaluate the effect of such uncertainties on SFT prediction. In this paper, a comprehensive slope failure database was compiled. A Bayesian machine learning (BML)-based method was developed to learn the model and observational uncertainties involved in SFT prediction, through which the probabilistic distribution of the SFT can be obtained. This method was illustrated in detail with an example. Verification studies show that the BML-based method is superior to the traditional inverse velocity method (INVM) and the maximum likelihood method for predicting SFT. The proposed method in this study provides an effective tool for SFT prediction.

Mojtaba Pakparvar, Gholamali Nekooeian, Gholamreza Ghahari et al.

Introduction Water scarcity due to climate change and growing water demand in different consumption sectors is a major environmental crisis that drives arable lands to a state of degradation, especially in dry regions. Artificial recharge of groundwater (ARG) through floodwater spreading (FWS) which is a potential measure for reversing this emerging trend is investigated in this research. Floodwater harvesting has become an increasingly important technique to improve water security and caused a renewed interest in research and implementation. According to the diverse objectives and methods of implementing artificial recharge of groundwater (ARG) systems, various factors must be considered when choosing a method for quantifying recharge. Therefore, the rate of aquifer recharge is one of the most difficult items to measure in groundwater (GW) resources evaluation. In the soil water balance method (and in the Zero Flux Plane method), soil water movement is inferred by measuring the changes in water content of the soil profile by gravimetric sampling or automatic devices. These methods have not been proven satisfactory in low flow conditions, as there is often insufficient resolution to detect the movement of small quantities of water. Therefore, other methods, based on hydraulic conductivity, potential gradients, and directly calculated water fluxes for unsaturated flow were developed. The Buckingham-Darcy law can be used under the steady flow condition where water contents and fluxes change with depth but do not vary as a function of time. It has been employed in arid and semiarid conditions for recharge estimation. or for assessing the exchange flow between the surface water reservoir and GW. The method requires measurements or estimates of the vertical total head gradient and the unsaturated hydraulic conductivity at the ambient soil water content following the Buckingham-Darcy equation. The overall objective is to evaluate a floodwater spreading system that was installed in 1981 at the Gareh Bygone Plain, southern Iran for recharging the groundwater table.   Materials and Methods To assess the artificial recharge of groundwater through turbid floodwater spreading, three wells, ~30 m deep, were dug in a 37-year-old recharge basin in planted Acacia forest, bare soil, and pasture land uses, respectively. Soil hydraulic parameters of the vadose zone layers (30 m thickness) were measured in the field and laboratory. One well was equipped with pre-calibrated TDR sensors throughout the well profile for measuring the changes in soil water content along the vadose zone. The volumetric soil-water content was measured continuously from Sep. 2010 to Sep. 2020 with closer temporal increments after floodwater spreading events. Rainfall, ponding water depth, and duration were also measured. Recharge through the vadose zone was assessed by the soil-water balance (SWB) method, as measured in the field as well as by calibrating the Hydrus-1D (H1D) model through the inverse solution.   Results and discussion Results showed that the wetting front was interrupted at a layer with fine soil accumulation over a coarse-textured gravely layer at a depth of ~4 m. The large differences in hydraulic conductivity of the two successive layers seemed to cause the transformation of the wetting front water movement into fingering flow. The changes in downward water flux complicated TDR measurement after the depth of 4 m. However, noticeable but temporary changes in the soil water content were detected in some of the layers below the 4 m was evidence for fingering flow after the flood events. Validation of the simulated flow by the H1D model vs. the one observed by SWB (with RMSE 3.45; R2 0.994) showed that the model performed well in flux estimation. The recharge ratio was calculated for the 2010 to 2020 events as 26 to 84 average of 55 % for all events and 63 to 84 average of 75 % for large impounded floodwater in the basin, respectively.   Conclusion Although a reliable set of data is obtained for calculating recharge at the very location of this study, up-scaling of the results for the entire floodwater systems and for the other flooding events with extreme volume and flow rate needs an extended investigation period and thorough identification of the underlying layers. The determined hydraulic properties of the RLs obtained in this study will be utilized in future research works in the FWS systems in our study site. The contributions of this thesis can be summarized as a) development of approaches for application, calibration, and validation of existing models with limited available data, b) the incorporation of new concepts into the models used, c) generating a unique and robust field data set to support the modeling approaches and d) provision of new information in the context of floodwater harvesting and its impact on groundwater recharge. Floodwater harvesting, especially in the form of FWS, is an emerging issue in water management in dry regions, which needs a better understanding and evaluation of its impact on the surrounding environment. Small-scale but nature-friendly water management plans, such as FWS systems, are seriously criticized since there are numerous methods, which are more attractive in terms of investments and money return to investors. However, they are rarely investigated. This study provided quantitative evidence that proves the effectiveness of FWS systems.

Xiongye Zhang, Lixin Zhang, Xue Hu et al.

The rotary tillage knife roller, as one of the typical soil-touching parts of the tillage equipment cutting process, is in direct contact with the soil. During the cutting process, there are problems related to structural bending, deformation, and high power consumption, caused by impact and load, and it is difficult to observe the micro-change law of the rotary tillage tool and soil. In view of the above problems, we took the soil of the cotton experimental field in Shihezi, Xinjiang, and the soil-contacting parts of the rotary tillage equipment, specifically the rotary tiller roller, as the research subject. Using the finite-element method (FEM) to simulate the structure of the rotary tiller with different bending angle parameters, we obtained its average stress and deformation position information, and obtained a range linear relationship between the bending angle and the structural performance of the rotary tiller tool. Using discrete element method (DEM)-based simulation to build the corresponding contact model, soil particle model, and soil–rotary tillage knife roll interaction model to simulate the dynamic process of a rotary tillage knife roll cutting soil, we obtained the change rules of the soil deformation area, cutting process energy, cutting resistance, and soil particle movement. By using the orthogonal simulation test and the response surface method, we optimized the kinematic parameters of the rotary tiller roller and the key design parameters of a single rotary tiller. Taking the reduction of cutting power consumption as the optimization goal and considering the influence of the bending angle on its structural performance, the optimal parameter combination was obtained as follows: the forward speed was 900 m/h, the rotation speed was 100 rad/min, the bending angle was 115°, and the minimum power consumption of the cutter roller was 0.181 kW. The corresponding average stress and deformation were 0.983 mm and 41.826 MPa, which were 15.8%, 13%, and 7.9% lower than the simulation results of power consumption, stress, and deformation under the initial parameter setting, respectively. Finally, the effectiveness of the simulation optimization model in reducing power consumption and the accuracy of the soil-cutting simulation were verified by a rotary tilling inter-field test, which provided theoretical reference and technical support for the design and optimization of other typical soil-touching parts of tillage and related equipment, such as disc harrow, ploughshare, and sub-soiling shovel.

Vagelis Plevris, Nikolaos P. Bakas, German Solorzano

A new, fast, elegant, and simple stochastic optimization search method is proposed, which exhibits surprisingly good performance and robustness considering its simplicity. We name the algorithm pure random orthogonal search (PROS). The method does not use any assumptions, does not have any parameters to adjust, and uses basic calculations to evolve a single candidate solution. The idea is that a single decision variable is randomly changed at every iteration and the candidate solution is updated only when an improvement is observed; therefore, moving orthogonally towards the optimal solution. Due to its simplicity, PROS can be easily implemented with basic programming skills and any non-expert in optimization can use it to solve problems and start exploring the fascinating optimization world. In the present work, PROS is explained in detail and is used to optimize 12 multi-dimensional test functions with various levels of complexity. The performance is compared with the pure random search strategy and other three well-established algorithms: genetic algorithms (GA), particle swarm optimization (PSO), and differential evolution (DE). The results indicate that, despite its simplicity, the proposed PROS method exhibits very good performance with fast convergence rates and quick execution time. The method can serve as a simple alternative to established and more complex optimizers. Additionally, it could also be used as a benchmark for other metaheuristic optimization algorithms as one of the simplest, yet powerful, optimizers. The algorithm is provided with its full source code in MATLAB for anybody interested to use, test or explore.

Li Xiaopeng, Zhang Xianrong

In this paper, we propose a cost-sensitive twin SVM (cs-tsvm) and apply it to imbalanced data. A weight is added to each instance according to its cost of misclassification which is related to its position. In preprocessing part, features are selected by their difference of majority and minority classes. The feature is selected when its difference value is higher than average one. The experiment is conducted on UCI datasets and G-mean, AUC and accuracy are evaluation metrics. The experimental results show that Feature selection with CS-TWSVM is useful for datasets with high dimension.

Kubilay Karacif, Hasan Karabulut, Ramazan Çıtak

   Bu çalışmada, toz metalurjisi yöntemi kullanılarak elde edilen bor karbür (B4C) takviyeli alüminyum esaslı kompozit malzemelerin tuzlu ortamdaki korozyon davranışları incelenmiştir. Üretim esnasında, alüminyum ve bor karbür tozlarının homojen şekilde birbiri içerisinde dağılımını sağlamak için bir saat karıştırma veya farklı sürelerde mekanik alaşımlama işlemleri uygulanmıştır.  Karıştırma veya farklı sürelerde uygulanan mekanik alaşımlama işlemleri sonrasında presleme ve sinterleme yapılarak elde edilen bor karbür takviyeli alüminyum esaslı kompozit malzemelere %3,5’luk tuzlu su (NaCl) ortamında potansiyodinamik korozyon testleri uygulanmıştır. Elektrokimyasal korozyon testleri sonucunda mekanik alaşımlama süresinin artması ile malzemenin korozyon hızının arttığı, korozyon dayanımının azaldığı belirlenmiştir.  

Deepinder Jot Singh Aulakh

Presented work aims to develop Genetic Algorithm (GA) based simulation approach for tuning of Continuously Variable Transmission (CVT). This study uses force balance to model the behaviour of CVT in MATLAB and employs dual level GA to optimize the tuning variables for desired output from CVT i.e. engagement of belt and sheaves at peak of engine torque curve, start of shifting at peak of engine power curve and keeping constant engine RPM (peak of power curve) during shifting. The variables for tuning are flyweight mass, primary and secondary spring stiffness and profile of primary and secondary cam. The results obtained from simulation are validated through experimental testing. The simulation results show good coherence with experiments in terms of engagement and shift starting RPM and also most of the shifting occurs at constant RPM. Also, the behaviour of CVT tuned by simulation is compared with the traditional method of experimental tuning and results obtained show that the simulation method is comparable to the traditional method in terms of accuracy. This study concludes with strong confidence in the potential of GA simulations for tuning.

J. Stutz, B. Werner, M. Spolaor et al.

Observations of atmospheric trace gases in the tropical upper troposphere (UT), tropical tropopause layer (TTL), and lower stratosphere (LS) require dedicated measurement platforms and instrumentation. Here we present a new limb-scanning Differential Optical Absorption Spectroscopy (DOAS) instrument developed for NASA's Global Hawk (GH) unmanned aerial system and deployed during the Airborne Tropical TRopopause EXperiment (ATTREX). The mini-DOAS system is designed for automatic operation under unpressurized and unheated conditions at 14–18 km altitude, collecting scattered sunlight in three wavelength windows: UV (301–387 nm), visible (410–525 nm), and near infrared (900–1700 nm). A telescope scanning unit allows selection of a viewing angle around the limb, as well as real-time correction of the aircraft pitch. Due to the high altitude, solar reference spectra are measured using diffusors and direct sunlight. The DOAS approach allows retrieval of slant column densities (SCDs) of O₃, O₄, NO₂, and BrO with relative errors similar to other aircraft DOAS systems. Radiative transfer considerations show that the retrieval of trace gas mixing ratios from the observed SCD based on O₄ observations, the most common approach for DOAS measurements, is inadequate for high-altitude observations. This is due to the frequent presence of low-altitude clouds, which shift the sensitivity of the O₄ SCD into the lower atmosphere and make it highly dependent on cloud coverage. A newly developed technique that constrains the radiative transfer by comparing in situ and DOAS O₃ observations overcomes this issue. Extensive sensitivity calculations show that the novel O₃-scaling technique allows the retrieval of BrO and NO₂ mixing ratios at high accuracies of 0.5 and 15 ppt, respectively. The BrO and NO₂ mixing ratios and vertical profiles observed during ATTREX thus provide new insights into ozone and halogen chemistry in the UT, TTL, and LS.

Tri Sudibyo, Imam Muthohar

As the main bus station in Bogor, West Java, Baranangsiang bus station is currently located in the crowded city centre, near many offices, campuses and department stores. There is a plan of Bogor’s Dinas Perhubungan Komunikasi dan Informasi (Diskominfo) to relocate the bus station to the new location in the Pangeran Sogiri Street in Tanah Baru area, near the newly built toll road, the Bogor Outer Ring Road (BORR).This research is conducted to analyze the traffic performance impact of the relocation plan of the bus station to the BORR network and the Pangeran Sogiri Street. The traffic data is obtained from the field survey in the Baranangsiang bus station and the BORR network. Some other secondary data are obtained from the Dinas Lalu Lintas and Angkutan Jalan (DLLAJ) Bogor city. Based on the obtained data, a micro simulation model is built by using Aimsun traffic micro simulation program. The analysis is conducted in three traffic performance parameters; the traffic density, speed, and vehicles queue length. With respect to the analysis result, the relocation causes a serious traffic problem to the BORR network and the P. Sogiri Street. To minimize the problem caused by the relocation, three scenarios are proposed and thus simulated based on the findings and observed traffic problems. The first proposed scenario is conducted by widening the P. Sogiri Street and providing a 4-4 toll payment gate system to the BORR. This first scenario is able to reduce traffic problem in some sections, but the average network density, speed and queue length are still high by 132%, -54%, and 200% respectively compared to the existing condition. The second scenario is conducted by widening the P. Sogiri Street and providing a 5-3 toll gate system. This second scenario is also able to reduce traffic problem in most sections, but the average network density, speed and queue length are still high by 248%, -70%, and 95% respectively compared to the main bus station before the relocation. The third scenario is conducted by widening the P. Sogiri into 4 lanes, providing a 4-3 toll gate system, and providing a new access from/to P. Sogiri Street to Bogor city direction. The simulation result shows that the third scenario is considered as the best scenario since in this scenario, the density, speed and queue length are relatively similar compared to the existing condition.

Ana Lúcia Silva, Everton Marquezini, Francisco Novais et al.

A presente nota técnica compara o desempenho de duas tecnologias para medição de oxigênio dissolvido (OD) em uso em estações de tratamento de esgoto (ETE): sensores com membrana (eletroquímicos) e com luminescência (ópticos). A precisão na medição da concentração do OD é essencial para o controle de vazão dos aeradores, o que influencia diretamente na eficiência do processo de tratamento e na qualidade do efluente final. Além disso, os aeradores representam até 50% do consumo total de energia elétrica em uma ETE. Os sensores por luminescência apresentam resultados bastante satisfatórios, melhores do que os sensores com membrana. Entretanto recomenda-se um acompanhamento de médio a longo prazo, devido ao seu uso ser muito recente não só no Brasil como no mundo.

吴德明

<正> 1990年国际光纤通信会议（OFC′90）于1月22～26日在美国旧金山召开。据估计约有4000人出席会议。会议报告和发表文章226篇,其中辅导性报告11篇,书面报告34篇和迟到报告34篇。其余为分组报告。同时还有一个相当规模的展览会。这次会议的主题为“通过光纤传送电视”（Video Over Fiber）。另一个热点是光纤放大器。此外,还有光纤、激光器、检测器、光纤无源器件、光纤网和系统等。下面作一简单介绍。