Transmission Power Adaptation Using Link Quality Estimation In IEEE802.11

Nowadays, energy saving for wireless communication is more important than before. Lots of wireless devices are battery operated, like devices used in WLAN, ad hoc mode, sensor network, cellular network and so on. For example, Ad hoc networks which are composed of these wireless mobile devices can automatically establish peer to peer communication networks without using fixed infrastructure. Meanwhile, a lot of functions are added to the mobile devices. GPS and camera functions are integrated into the mobile phones. Energy consumed for the communication functions also grows more and more due to rapid improvement of communication technology and the demand for more communication between people, which means that we need larger battery capacity to increase the service time. Unfortunately, the battery technology does not improve much recently. Therefore in this thesis, we propose an energy saving method to extend the service time of wireless device.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc

Fracture evaluation of ultra-high-performance fiber reinforced concrete (UHPFRC)

The development of numerical simulation for Ultra-high-performance concrete (UHPC) and Ultra-high-performance fiber-reinforced concretes (UHPFRC) is fundamental for the design and construction of related structures. The simplified engineering stress-strain relationship and the input values are necessary in the finite element modeling. Four-linear curves and modified Kent–Park model were proposed to describe the engineering tensile and compressive stress-strain relationship, respectively. An attempt was made to simulate the fracture of UHPC and UHPFRC using concrete damaged plasticity model and element deletion strategies. The predicted tensile and compressive behaviors of UHPC and UHPFRC were successfully validated by the test results in the literature. For a better understanding of the mechanical behavior of UHPC and UHPFRC exposed to biaxial loadings, mixed-mode crack propagation simulation on the double-notched specimens exposed to combined shear-tensile and shear-compressive forces was discussed.Concrete Structure

On the Potential of 3D Transdimensional Surface Wave Tomography for Geothermal Prospecting of the Reykjanes Peninsula

Seismic travel time tomography using surface waves is an effective tool for three-dimensional crustal imaging. Historically, these surface waves are the result of active seismic sources or earthquakes. More recently, however, surface waves retrieved through the application of seismic interferometry have also been exploited. Conventionally, two-step inversion algorithms are employed to solve the tomographic inverse problem. That is, a first inversion results in frequency-dependent, two-dimensional maps of phase velocity, which then serve as input for a series of independent, one-dimensional frequency-to-depth inversions. As such, a set of localized depth-dependent velocity profiles are obtained at the surface points. Stitching these separate profiles together subsequently yields a three-dimensional velocity model. Relatively recently, a one-step three-dimensional non-linear tomographic algorithm has been proposed. The algorithm is rooted in a Bayesian framework using Markov chains with reversible jumps, and is referred to as transdimensional tomography. Specifically, the three-dimensional velocity field is parameterized by means of a polyhedral Voronoi tessellation. In this study, we investigate the potential of this algorithm for the purpose of recovering the three-dimensional surface-wave-velocity structure from ambient noise recorded on and around the Reykjanes Peninsula, southwest Iceland. To that end, we design a number of synthetic tests that take into account the station configuration of the Reykjanes seismic network. We find that the algorithm is able to recover the 3D velocity structure at various scales in areas where station density is high. In addition, we find that the standard deviation of the recovered velocities is low in those regions. At the same time, the velocity structure is less well recovered in parts of the peninsula sampled by fewer stations. This implies that the algorithm successfully adapts model resolution to the density of rays. It also adapts model resolution to the amount of noise in the travel times. Because the algorithm is computationally demanding, we modify the algorithm such that computational costs are reduced while sufficiently preserving non-linearity. We conclude that the algorithm can now be applied adequately to travel times extracted from station–station cross correlations by the Reykjanes seismic network.Applied Geophysics and Petrophysic

Numerical parametric study on ultimate load and ductility of concrete encased equal-leg angle steel composite columns

Steel-concrete composite high bridge pier has been applied increasingly in China and around the world. Most applied steel type in the composite piers are H-shaped steel and steel pipe, while seldom research or practice is associated with angle steel. This paper conducted parametric study on the composite column with equal-leg angle steel and aimed to investigate the ultimate load and displacement ductility of the composite columns with different parameters. The parameters include the type of shear connector (stud and perfobond connectors), the type of structural steel (H-shaped steel and angle steel), steel-plate hooping ratio, shear-span ratio, and axial compression ratio. Finite element analysis was conducted for each specimen, which incorporated the concrete confinement effect, as well as the inelastic behavior of concrete, structural steel, and longitudinal and transverse steel bars. The equal-leg angle steel composite column was found to have slightly higher strength and displacement ductility than H-shaped steel composite column. The increase of steel-plate hooping result in larger strength and displacement ductility for the composite column, and the increase of shear-span ratio and axial compression ratio decrease the displacement ductility. Research results suggest stud and perfobond shear connectors should be applied as axial compression ratio being larger than 0.2 and 0.3, respectively. This paper provides reference for research and engineering practice of the concrete encased angle steel composite columns and bridge piers.Accepted Author ManuscriptSteel & Composite Structure

國中學生學習行為--學習方法、學習習慣、學習態度之研究

[[abstract]]正確的學習方法、良好的學習習慣以及積極的學習態度，都是增進學習效率的必要條 件。本研究旨在探討構成學生學習行為差異之因素以及學習行為對學業成積之影響力 ，做為中國學習輔導之參考。 根據研究的結果，本研究獲致下列幾項主要的發現： 一、不同性別的國中學生在學習行為上有顯著之差異，女生均優于男生。 二、不同學業成績的中國學生在學習行為上有顯著之差異，除「學習技巧」一項外， 與性別之間並無交互作用。一般而言，高分組學生表現最佳，中分組學生次之，低分 組學生則最差。 三、不同人格類型的國中學生在學習行為上有顯著之差異。一般而言，以鎮靜型和指 導型學生表現最好，平均型學生略遜，暴力型和怪僻型學生則居末。 四、不同家庭社經地位的國中學生在學習行為三個層面上的表現，除學習方法方面， 以高社經學生顯著優於低社經學生外，其餘並無顯著之差異。 五、九項學習行為與國中學業成績之間呈中度正相關，其中時間支配、學習技巧、考 試技巧、注意集中力、對課業學習的態度、對學校學習環境的態度和主動學習等七項 學習行為對國中學生的學業成績具有決定性的預測作用，能解釋及預測學業成績總變 異的三分之一。 基于上述發現，本研究提出下列四項建議： 一、在觀念上，教師應體認學習輔導乃責無旁貨之事。 二、全體學生無論成績好環，均需要學習輔導。 三、學習輔導措施應兼顧學習態度輔導和學習方法訓練。 四、學輔導技巧宜重視學生個別差異。

Glacier mass balance in the Nyainqentanglha mountains between 2000 and 2017 retrieved from ZiYuan-3 stereo images and the SRTM DEM

Mountain glaciers are excellent indicators of climate change and have an important role in the terrestrial water cycle and food security in many parts of the world. Glaciers are the major water source of rivers and lakes in the Nyainqentanglha Mountains (NM) region, where the glacier area has the second largest extent on the Tibetan Plateau. The potential of the high spatial resolution ZiYuan-3 (ZY-3) Three-Line-Array (TLA) stereo images to retrieve glacier mass balance has not been sufficiently explored. In this study, we optimized the procedure to extract a Digital Elevation Model (DEM) from ZY-3 TLA stereo images and estimated the geodetic mass balance of representative glaciers in the two typical areas of the NM using ZY-3 DEMs and the C-band Shuttle Radar Topography Mission (SRTM) DEM in three periods, i.e., 2000-2013, 2013-2017 and 2000-2017. The results provide detailed information towards better understanding of glacier change and specifically show that: (1) with our new stereo procedure, ZY-3 TLA data can significantly increase point cloud density and decrease invalid data on the glacier surface map to generate a high resolution (5 m) glacier mass balance map; (2) the glacier mass balance in both the Western Nyainqentanglha Mountains (WNM) and Eastern Nyainqentanglha Mountains (ENM) was negative in 2000-2017, and experienced faster mass loss in recent years (2013-2017) in the WNM. Overall, the glaciers in the western and eastern NM show different change patterns since they are influenced by different climate regimes; the glacier mass balances in WNM was-0.22 ± 0.23 m w.e. a-1 and-0.43 ± 0.06 m w.e. a-1 in 2000-2013 and 2013-2017, respectively, while in 2000-2017, it was-0.30 ± 0.19 m w.e. a-1 in the WNM and-0.56 ± 0.20 m w.e. a-1 in the ENM; (3) in the WNM, the glaciers experienced mass loss in 2000-2013 and 2013-2017 in the ablation zone, while in the accumulation zone mass increased in 2000-2013 and a large mass loss occurred in 2013-2017; as regards the ENM, the glacier mass balance was negative in 2000-2017 in both zones; (4) glacier mass balance can be affected by the fractional abundance of debris and glacier slope; (5) the glacier mass balances retrieved by ZY-3 and TanDEM-X data agreed well in the ablation zone, while a large difference occurred in the accumulation zone because of the snow/firn penetration of the X-band SAR signal.Optical and Laser Remote Sensin

我國高級工業學校機工科技能檢定之評估與改進途徑之研究

[[abstract]]本研究的目的在探討機工科技術檢定的理論基礎與有關措施的配合，以建立機工科技 能檢定的統整觀念，並瞭解我國中等學校機工科技能檢定實際存在的問題，並尋求改 進的途徑，提供具體的結論與建議，作為改進中等學校機工科技能檢定改進的參考。 本研究首先採用理論探討法，以瞭解機工科技能檢定有關的理論，其次採用問卷調查 法，調查的工具為自編之「我國高級工業學校機工科技能檢定調查問卷」，調查對象 為參加六十六學年度機工科之學校全部校長、機工科主任、部份機工科專任教師與應 屆畢業生，藉以蒐集客觀的資料，並採用X2統計方法，加以分析，期能瞭解現況，發 現問題，並進而獲致可能的改進途徑。 由理論探討與調查問卷資料的分析後，本研究已獲致多項重要的發現。 (一)歷年來有關機工科技能檢定試題方面，其難易度是否平均，仍是見仁見智的問題 ，無法遽下定論。 (二)機工科技能檢定所實施的職種，祇有車工與鉗工兩職。 (三)機工科技能檢定之評分方式，目前是分區互評方式，根據調查結果顯示，多數人 認為不適當。 (四)機工科學生為了應付車工與鉗工的技能檢定考試，會因此而忽略了檢定職種以外 之實習課程內容。 (五)各校自從實施機工科技能檢定以來，設備增加的情形均極有限。 (六)政府當局，對於擁有證照的技術人員，宜作何等之管制及保障，這是多數人所關 切的問題。 (七)技能檢定執行機構太複雜，難免會造成意見分歧而失統一之效。 根據調查發現，本研究提出下列建議事項： (一)製訂客觀而有效的技能檢定標準與試題。 (二)考慮機工科技能檢定乙、丙級分開舉行，或是高工祇舉辦丙級檢定。 (三)政府應儘速訂定法規，並嚴格執行，以保障擁有技術士證照的技術人員。 (四)政府應設置技能檢定專門機構。 (五)慎重遴選合格的技能檢定工作及評分人員、負責檢定之監試與評分工作。 (六)技能檢定成品的評分，宜採成品全部集中後再評分的方式較好。 (七)技能檢定成績之好壞，應考慮各校的基本差異。 (八)應擴大機工科技能檢定的範圍（職種數）。 (九)技能檢定應繼續不斷實施。 (十)確立技能檢定之正確觀念。 (十一)考慮技能檢定與技能競賽的合併舉行。

精密鑄造陶殼性質之研究

[[abstract]]精密鑄造所用的陶瓷殼模是由多層的泥漿及數貼在泥漿上的耐火砂所組成的，它是由 反覆的沾漿、敷砂及乾燥等製程所構成。而利用陶殼法將可獲得高精密度、形狀複雜 、以及良好機械性質的鑄件，因此若能對陶殼的性質加以研究，則將有助於陶殼鑄造 法更進一步的改進。 本研究係利用各種不同矽膠質含量的泥漿，以及在陶殼層中加入玻璃纖維來做出所需 要的陶殼試片，經破斷強度試驗，熱膨脹試驗與破散性試驗之三種方法，業探究陶殼 的破斷經度，熱膨脹及破散性等三種性質。研究的主要目的在於探討泥漿之調配對陶 殼強度的影響、溫度（室溫，400℃, 800℃）對陶殼強度的影響、在陶殼中加入玻璃 纖維（Enka silica fibres）對陶殼強度的影響、陶殼成份與熱膨脹之關係、以及泥 漿的成份與加玻璃織維對破散性的影響。 研究結果發現：矽膠質在泥漿中的含量會影響鈷粉粉粒彼此間的黏結情形，因而影響 陶殼之破斷強度。陶殼加入玻璃纖維後，並未影響破斷強度與矽膠質含量的關係，而 且添加玻璃纖維可以顯著提升陶殼的破斷強度，尤其是破斷強度高峰的兩側更明顯。 陶殼隨著溫度的升高，不論添加玻璃纖維與否，陶殼的強度都有跟著升高的趨勢，這 有助於高溫下之澆鑄，陶模更能夠忍受金屬傾入模穴中的衝力。各陶殼均在200℃ ∼ 300℃ 之間發生間斷式膨脹現象，且添入玻璃纖維之後，對線性熱膨脹之影響很小。

柯九思墨竹作品之研究

[[abstract]]本論文以「墨竹」作為探討之範疇，重新檢視柯九思之墨竹畫蹟，以之為研究中心。 由「墨竹」主題所象徵「全德君子」之寓喻為起點，企圖去回溯「墨竹」主題長期以 來之演變，藉以採討元朝畫家作墨竹題材之真正核心；並直接從柯九思之題畫詩和當 代文集中之題跋。以期瞭解擁有鑑畫博士頭銜的柯九思如何經由墨竹主題之製作，實 踐書法入畫之理論，完成其結合書畫合一之理想。 因此在第一章中利用資料的確認與再發現，重建柯九思之生平，企圖對他的生平與書 法入畫的理論，置於當時之脈絡下，作一深入討論。 第二章經由摘要式之敘述，分析柯九思以前長期以來墨竹題材之傳統，透過這些早期 墨竹名家之畫史著錄與其墨竹作品之類型分析，提供了研究柯九思書法入畫理論的有 用背景。 第三章旨在尋繹柯九思書法入畫之本質，希圖推溯柯九思所以書法入畫之緣由，以及 追索造成柯九思仿文同墨竹圖之意圖與「竹譜」製作之原因作為討論重點。 很明顯地，經由這些研究之後，可發現柯九思墨竹作品中書法入畫之表現功能，實深 切地傳達出趙孟頫書畫同源，用筆局法理想化之極致。這也是本論文選擇柯九思之墨 竹作品以討論書法與繪書間之關係的主要原因。

Distributed Model Predictive Contouring Control for Real-Time Multi-Robot Motion Planning

Existing motion planning algorithms for multi-robot systems must be improved to address poor coordination and increase low real-time performance. This paper proposes a new distributed real-time motion planning method for a multi-robot system using Model Predictive Contouring Control (MPCC). MPCC allows separating the tracking accuracy and productivity, to improve productivity better than the traditional Model Predictive Control (MPC) which follows a time-dependent reference. In the proposed distributed MPCC, each robot exchanges the predicted paths of the other robots and generates the collision-free motion in a parallel manner. The proposed distributed MPCC method is tested in industrial operation scenarios in the robot simulation platform Gazebo. The simulation results show that the proposed distributed MPCC method realizes real-time multi-robot motion planning and performs better than three commonly-used planning methods (dynamic window approach, MPC, and prioritized planning).Transport Engineering and Logistic