Two-Layer Model for Open-Channel Flows with Submerged Vegetation

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Unsteady-state exergy analysis on two types of building envelopes under time-varying boundary condition

In the built environment, the thermal exergy behavior is very sensitive to the change of environmental temperature, because the temperature difference between the reservoir and a system of interest is small. Moreover, the transient characteristics become very important for the building envelope, which is primarily affected by the environmental temperature changes and has a relatively large heat capacity. Most of the exergy analyses have been performed under steady-state assumption. However, it may miss some important details of the transient process. Thus, when the transient transfer process becomes important, the unsteady-state exergy analysis should be conducted. In this study, we propose complete energy, entropy, and exergy equations in their partial differential forms. By solving them numerically, we examined the transient exergy process inside the building envelope composed of concrete and insulation layers under time-varying boundary condition. Using this new methodology, we can improve the temporal and spatial resolution of the exergy analysis and thus provide more complete information about exergetic behavior

Ptychographic lensless coherent endomicroscopy through a flexible fiber bundle

Conventional fiber-bundle-based endoscopes allow minimally invasive imaging through flexible multi-core fiber (MCF) bundles by placing a miniature lens at the distal tip and using each core as an imaging pixel. In recent years, lensless imaging through MCFs was made possible by correcting the core-to-core phase distortions pre-measured in a calibration procedure. However, temporally varying wavefront distortions, for instance, due to dynamic fiber bending, pose a challenge for such approaches. Here, we demonstrate a coherent lensless imaging technique based on intensity-only measurements insensitive to core-to-core phase distortions. We leverage a ptychographic reconstruction algorithm to retrieve the phase and amplitude profiles of reflective objects placed at a distance from the fiber tip, using as input a set of diffracted intensity patterns reflected from the object when the illumination is scanned over the MCF cores. Our approach thus utilizes an acquisition process equivalent to confocal microendoscopy, only replacing the single detector with a camera

Development of TPRT (Thermal Performance-Response Test) for borehole heat exchanger design

To obtain the effective thermal conductivity and borehole thermal resistance required to design borehole heat exchangers (BHEs), thermal response tests (TRTs) are usually conducted. Although many advanced TRT methods have been proposed, most TRTs cannot directly provide the actual thermal performance of an installed BHE. Because many uncertainties exist in constructing even conventional BHEs, examining the transient heat exchange rate allows inspection of the construction quality; the rate can also be used as a reference value for design. To determine the actual heat exchange rates of BHEs, it is necessary to conduct thermal performance tests (TPTs) under a constant inlet fluid temperature. However, TPT requires expensive equipment, including a water tank and a complex control system; thus, generally only TRT is conducted. To overcome the existing problems of TPT, in this study, we proposed a thermal performance-response test (TPRT) that combines TRT and TPT. This method involved the construction of a cost-effective TPRT apparatus by adding only a general PID controller and a solid-state relay to an existing TRT apparatus. Using the apparatus constructed by the proposed method, two TPRTs were conducted to confirm the performance of the apparatus and the validity of the TPRT method. Additionally, by defining the new parameter of the unit heat exchange rate, one potential simple and reliable design method for BHEs was explored

垂直密閉型地中熱交換器の設計精度向上のための熱応答試験に関する実験的、数値的研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 大岡 龍三, 東京大学教授 加藤 信介, 東京大学教授 赤司 泰義, 東京大学教授 桑野 玲子, 東京大学准教授 前 真之University of Tokyo(東京大学

BackTrack: Robust template update via Backward Tracking of candidate template

Variations of target appearance such as deformations, illumination variance, occlusion, etc., are the major challenges of visual object tracking that negatively impact the performance of a tracker. An effective method to tackle these challenges is template update, which updates the template to reflect the change of appearance in the target object during tracking. However, with template updates, inadequate quality of new templates or inappropriate timing of updates may induce a model drift problem, which severely degrades the tracking performance. Here, we propose BackTrack, a robust and reliable method to quantify the confidence of the candidate template by backward tracking it on the past frames. Based on the confidence score of candidates from BackTrack, we can update the template with a reliable candidate at the right time while rejecting unreliable candidates. BackTrack is a generic template update scheme and is applicable to any template-based trackers. Extensive experiments on various tracking benchmarks verify the effectiveness of BackTrack over existing template update algorithms, as it achieves SOTA performance on various tracking benchmarks.Comment: 14 pages, 7 figure