Pointing, Acquisition, and Tracking Systems for Free-Space Optical Communication Links

Pointing, acquisition, and tracking (PAT) systems have been widely applied in many applications, from short-range (e.g. human motion tracking) to long-haul (e.g. missile guidance) systems. This dissertation extends the PAT system into new territory: free space optical (FSO) communication system alignment, the most important missing ingredient for practical deployment. Exploring embedded geometric invariances intrinsic to the rigidity of actuators and sensors is a key design feature. Once the configuration of the actuator and sensor is determined, the geometric invariance is fixed, which can therefore be calibrated in advance. This calibrated invariance further serves as a transformation for converting the sensor measurement to actuator action. The challenge of the FSO alignment problem lies in how to point to a 3D target by only using a 2D sensor. Two solutions are proposed: the first one exploits the invariance, known as the linear homography, embedded in the FSO applications which involve long link length between transceivers or have planar trajectories. The second one employs either an additional 2D or 1D sensor, which results in invariances known as the trifocal tensor and radial trifocal tensor, respectively. Since these invariances have been developed upon an assumption that the measurements from sensors are free from noise, including the uncertainty resulting from aberrations, a robust calibrate algorithm is required to retrieve the optimal invariance from noisy measurements. The first solution is suffcient for most of the PAT systems used for FSO alignment since a long link length constraint is generally the case. Although PAT systems are normally categorized into coarse and fine subsystems to deal with different requirements, they are proven to be governed by a linear homography. Robust calibration algorithms have been developed during this work and further verified by simulations. Two prototype systems have been developed: one serves as a fine pointing subsystem, which consists of a beam steerer and an angular resolver; while the other serves as a coarse pointing subsystem, which consists of a rotary gimbal and a camera. The average pointing errors in both prototypes were less than 170 and 700 micro-rads, respectively. PAT systems based on the second solution are capable of pointing to any target within the intersected field-of-view from both sensors because two sensors provide stereo vision to determine the depth of the target, the missing information that cannot be determined by a 2D sensor. They are only required when short-distance FSO communication links must be established. Two simulations were conducted to show the robustness of the calibration procedures and the pointing accuracy with respect to random noise

Crossing the city: transformation of Peak Tram Station /cHo Tzung Hsien Joey.

published_or_final_versionArchitectureMasterMaster of Architectur

Quantitative Portal Vein Velocity of Liver Cancer Patients with Transcatheter Arterial Chemoembolization on Angiography

Objective. We applied optical flow method (OFM) to quantify relative velocities of blood flow using digital subtraction angiography (DSA) in the vascular analysis of hepatocellular carcinoma (HCC) patients who underwent transarterial chemoembolization (TACE) treatment. Methods. A total of 40 HCC patients treated by TACE were analyzed in this study. DSA imaging with a 12-inch field of view, 1024 × 1024 pixels and 4 frames/second was acquired. OFM developed for motion estimation is applied for blood flow estimation. Two acrylic phantoms were built to validate the method. Results. The relationship between the OFM and Doppler measurements was found linear with R2=0.99 for both straight and curved tube phantoms. Quantitative blood flow distribution images of the portal vein region were presented. After TACE, the minimum, maximum and mean velocities in the portal vein all decreased (P<0.05). Additionally, the velocity in the portal vein is significantly lower with a higher Child-Pugh score (P<0.01). Conclusions. The present technique provides add-on quantitative information of flows to DSA and the hemodynamic analysis in relative quantifications of blood flow in portal vein of hepatocellular carcinoma patients using DSA

馬祖列島的八種捕植蟎

A survey of phytoseiid mites from the Matsu Islands found 8 species, including Amblyseius eharai Amitai and Swirski, A. herbicolus (Chant), A. okinawanus Ehara, A. ovalis (Evans), A. womersleyi Schicha, Okiseius subtropicus Ehara, Phytoseius crinitus Swirski and Shechter, and P. sonunensis Ryu and Ehara. Amblyseius eharai, P. crinitus, and P. sonunensis have not previously been recorded from Taiwan or the Penghu Archipelago, and these mites are illustrated with drawings. In addition, 3 nymphs that were collected without associated adults are suspected of being P. silvaticus Wu and Li. These are all new records for Matsu. 在馬祖列島採得8種捕植蟎，包括Amblyseius eharai Amitai and Swirski, A. herbicolus (Chant), A. okinawanus Ehara, A. ovalis (Evans), A. womersleyi Schicha, Okiseius subtropicus Ehara, Phytoseius crinitus Swirski and Shechter, and P. sonunensis Ryu and Ehara. 其中，A. eharai, P. crinitus, 及 P. sonunensis未曾記錄於台澎地區，均予以繪圖描述，此外，另採得3隻疑為 P. silvaticus Wu and Li 之若蟎(尚未採得成蟎)，對馬祖列島而言，這些種類都是新記

Primary Aortoduodenal Fistula Caused by Tuberculous Aortitis Presenting as Recurrent Massive Gastrointestinal Bleeding

Upper gastrointestinal bleeding from primary aortoduodenal fistula (PADF) is unusual and fatal. The etiology of PADF from tuberculous aortitis is rare. We report a 69-year-old male patient who suffered recurrent hematemesis and hematochezia with hypovolemic shock of unknown origin. Initial endoscopy failed to lead to a diagnosis. A bleeder over the third portion of the duodenum was found after the third endoscopy. Exploratory laparotomy showed a ruptured aortic pseudoaneurysm with an aortoduodenal fistula. Dacron graft repair of the aorta and simple closure of the duodenal fistula were carried out. Pathologic examination revealed tuberculous aortitis. The patient survived and was symptom-free following operation and antituberculous therapy. Review of the literature revealed that the clinical presentations in this disorder are insidious. The endoscopic findings are atypical. We conclude that so-called “herald bleeding”, a history of tuberculous infection or aortic aneurysm and a high degree of suspicion are critical for successful diagnosis. Early diagnosis and surgical exploration are needed for timely and successful management

Application of a Modified Entropy Computational Method in Assessing the Complexity of Pulse Wave Velocity Signals in Healthy and Diabetic Subjects

Using 1000 successive points of a pulse wave velocity (PWV) series, we previously distinguished healthy from diabetic subjects with multi-scale entropy (MSE) using a scale factor of 10. One major limitation is the long time for data acquisition (i.e., 20 min). This study aimed at validating the sensitivity of a novel method, short time MSE (sMSE) that utilized a substantially smaller sample size (i.e., 600 consecutive points), in differentiating the complexity of PWV signals both in simulation and in human subjects that were divided into four groups: healthy young (Group 1; n = 24) and middle-aged (Group 2; n = 30) subjects without known cardiovascular disease and middle-aged individuals with well-controlled (Group 3; n = 18) and poorly-controlled (Group 4; n = 22) diabetes mellitus type 2. The results demonstrated that although conventional MSE could differentiate the subjects using 1000 consecutive PWV series points, sensitivity was lost using only 600 points. Simulation study revealed consistent results. By contrast, the novel sMSE method produced significant differences in entropy in both simulation and testing subjects. In conclusion, this study demonstrated that using a novel sMSE approach for PWV analysis, the time for data acquisition can be substantially reduced to that required for 600 cardiac cycles (~10 min) with remarkable preservation of sensitivity in differentiating among healthy, aged, and diabetic populations