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This article presents the effects of different grounding strategies (ungrounded, direct grounded, and diode grounded), bonding, and insulation on rail potential and stray currents in the Taipei rapid transit systems (TRTSs). The TRTS is a direct current transit railway and its running rails are used as the return conductor for traction currents. The advantage is that no dedicated return conductor is required, whereas the disadvantages are rail potential and stray-current problems. Thus, the analysis of grounding strategies is important and necessary. Moreover, the effects of cross-bonding of the running rails and stray-current collector cables (traction earth conductors) are investigated since bonding is usually used to balance traction negative return currents, to reduce resistances of the negative return circuit, as well as to decrease rail potential. Meanwhile, the effects of insulation on stray currents are also described. Simulation results for the Blue line are presented in TRTS.

This study investigated some factors influencing the abrasion damage to a woven geotextile using a circular turbid flow chamber test system. Two uniformly graded aggregates composed of different minerals and angularities were used in the turbid flow test. Two important factors—particle concentration and flow velocity—were also investigated. It was found that the percentage of ultimate strength loss (PSR) due to abrasion damage was linearly related to these parameters and to the Los Angeles percentage weight loss, regardless of the particle size and angularity examined in this study. It was also found that the Rt method, which uses an average gradient (Rt = 18% per logarithmic cycle of test duration T) for the PSR-log T relationships obtained for T = 8 h, is potentially useful in predicting the values of PSR for relatively long test durations. The above findings are valid only for the limited test conditions investigated, and should be confirmed on the basis of comprehensive test results regarding the effect of size, hardness and shape of aggregate.

As a preliminary study on the durability of geosynthetic tubes used for seashore and streambank protections, a circular flow chamber was established to investigate the abrasion damage of a woven geotextile subjected to various turbid flow conditions, such as test durations, flow velocities and particle concentrations. It was found that the ultimate strength loss of the tested woven geotextile subjected to a specific flow duration can be expressed as a linear function of particle concentration and flow velocity, based on the experimental results obtained from a limited number of the laboratory circular flow chamber tests. It was also shown that the equations obtained using a linear regression technique generated small errors in predicting the ultimate strength losses when compared with those obtained in the laboratory circular flow chamber tests. The equations derived herein facilitate the assessment of abrasion damage of the tested geotextile to be used in shore protection measures. These equations are also potentially useful in linking in-field abrasion damage of the tested geotextile to that obtained in laboratory index tests, such as the sliding block sand paper method.

We experimentally explore the fluorescent spectrum of the Nd:YAP crystal to manifest the feasibility of tunable single- and multi-wavelength operations in the (4)F3/2 → (4)I11/2 transition. An intracavity etalon is subsequently exploited to effectively select spectral lines at 1073, 1080, and 1084 nm with the tunabilities of 0.56, 1.13, and 0.1 nm, respectively. We also experimentally obtain multi-wavelength oscillations among various intermanifold lines in the Nd:YAP crystal with the output powers on the order of several watts for each group. Employing the Cr(4+):YAG crystal to realize the passively Q-switched operation, the maximum average output powers as high as 2.3 and 3.5 W for 1073 and 1080 nm are obtained. The corresponding pulse energies at 1073 and 1080 nm are up to 177 and 159 μJ, respectively.

We explore the feasibility of the generation of pseudonondiffracting optical beams related to crystal and quasicrystal structures. It is experimentally confirmed that optical crystal and quasicrystal beams can be remarkably generated with a collimated light to illuminate a high-precision mask with multiple apertures regularly distributed on a ring. We also found that exotic kaleidoscopic patterns can be exhibited with the high-order quasicrystal beams. More importantly, the structures of phase singularities in optical quasicrystal beams are manifested.

MIT is developing a MEMS-based gas turbine generator. Based on high speed rotating machinery, this 1 cm diameter by 3 mm thick SiC heat engine is designed to produce 10-20 W of electric power while consuming 10 grams/hr of H/sub 2/. Later versions may produce up to 100 W using hydrocarbon fuels. The combustor is now operating and an 80 W micro-turbine has been fabricated and is being tested. This engine can be considered the first of a new class of MEMS device, power MEMS, which are heat engines operating at power densities similar to those of the best large scale devices made today.

The effect of spatial hole burning (SHB) on dual-wavelength self-mode-locked lasers based on physically combined Nd:YVO4/Nd:LuVO4 and Nd:YVO4/Nd:KGW composite active medium is comparatively investigated. The length of the first Nd:YVO4 crystal is optimized to realize a highly compact and efficient TEM00-mode picosecond laser at 1.06 μm with optical conversion efficiency greater than 20%. When the SHB effect is enhanced by decreasing the separation between the input end mirror and the composite gain medium, it is experimentally found that not only the pulse duration monotonically decreases, but also the temporal behavior gradually displays a narrow-peak-on-a-pedestal shape for the Nd:YVO4/Nd:LuVO4 scheme, while the multipulse operation can be obtained for the Nd:YVO4/Nd:KGW configuration. These phenomena are further explored by numerically simulating mode-locked pulses from the experimentally measured optical spectra.

We originally present a novel tactic to accomplish a compact efficient dual-wavelength synchronously mode-locked laser by physically combining the Nd:YVO4 crystal to the Nd:GdVO4 crystal as a composite gain medium. With the developed method, the total output power at 1.06 μm could be effectually produced to reach 1.3 W under the optimally balanced two-color intensities. The corresponding mode-locked pulse width and repetition rate are measured to be 47 ps and 2.86 GHz, respectively. Through the optical beating between two carrier frequencies of dual-color synchronous pulses, a train of 0.32 THz ultrashort pulses is further generated with the effective duration of down to 1.6 ps.

To determine the alterations of the p16/MTS1 gene in oral squamous cell carcinoma (OSCC), we examined in Taiwanese patients the mutation, deletion and methylation of p16/MTS1 in primary OSCCs associated mostly with betel quid (BQ)/tobacco use. Among 110 tumors undergoing mutational analyses, seven (6%) showed mutations in exon 2 or the intron 1/exon 2 splice site. All but one mutation disrupted the encoded proteins. Base transitions represented the vast majority (6/7) of the mutations identified in BQ/tobacco consuming subjects. It was noted that 15/56 (27%) tumors examined by restriction fragment methylation analysis revealed a significant level of methylation in different loci of exon 1 as compared with the respective non-cancerous tissue. Mutation of p16/MTS1 was exclusively identified in carcinomas of buccal mucosa, whereas methylation of the p16/MTS1 promoter region occurred preferentially in carcinomas of the tongue (54%) rather than at other sites (22%). Homozygous deletion was not found in 56 paired samples examined, nor was hemizygous deletion indicated in 12 informative cases. The results indicated aberrant methylation and mutation as the molecular abnormality of p16/MTS1 in the OSCC from Taiwanese.

This is a report on work in progress on microelectrical and mechanical systems (MEMS)-based gas turbine engines, turbogenerators, and rocket engines currently under development at MIT. Fabricated in large numbers in parallel using semiconductor manufacturing techniques, these engines are based on micro-high speed rotating machinery with the same power density as that achieved in their more familiar, full-sized brethren. The micro-gas turbine is a 1 cm diameter by 3 mm thick SiC heat engine designed to produce 10-20 W of electric power or 0.050.1 Nt of thrust while consuming under 10 grams/hr of H 2 . Later versions may produce up to 100 W using hydrocarbon fuels. A liquid fuel, bi-propellant rocket motor of similar size could develop over 3 lb of thrust. The rocket motor would be complete with turbopumps and control valves on the same chip. These devices may enable new concepts in propulsion, fluid control, and por table power generation.

Cryptic t(12;21)(p12-13;q22) leading to TEL-AML1 fusion has recently been recognized as the most frequent genetic rearrangement in childhood acute lymphoblastic leukemia (ALL) in Western countries. More recently, we found a similar frequency of this abnormality in Chinese children with ALL in Taiwan. In this study, we assessed further the frequency of TEL-AML1 fusion as well as that of BCR-ABL in Chinese adults with ALL, using reverse transcriptase-polymerase chain reaction assays. Among the 81 cases with newly diagnosed B lineage ALL studied, none had the TEL-AML1 fusion whereas 30 had the BCR-ABL fusion. The lack of cases with the TEL-AML1 fusion together with the high frequency of BCR-ABL fusion could largely account for the poorer outcome of adult ALL as compared with childhood ALL.

We report on a high-power diode-pumped self-mode-locked Nd:YLF laser with the pulse repetition rate up to several GHz. A novel tactic is developed to efficiently select the output polarization state for achieving the stable TEM(00)-mode self-mode-locked operations at 1053 nm and 1047 nm, respectively. At an incident pump power of 6.93 W and a pulse repetition rate of 2.717 GHz, output powers as high as 2.15 W and 1.35 W are generated for the σ- and π-polarization, respectively. We experimentally find that decreasing the separation between the gain medium and the input mirror not only brings in the pulse shortening thanks to the enhanced effect of the spatial hole burning, but also effectively introduces the effect of the spectral filtering to lead the Nd:YLF laser to be in a second harmonic mode-locked status. Consequently, pulse durations as short as 8 ps and 8.5 ps are obtained at 1053 nm and 1047 nm with a pulse repetition rate of 5.434 GHz.

The author presents a harmonic analysis of a parallel-connected 12-pulse uncontrolled bridge rectifier without an interphase transformer (IPT). Five normal operating modes of the specific rectifier circuit are classified, using an analytical method by deriving instantaneous AC current and DC voltage waveform equations. The discrete Fourier transformation algorithm is then carried out to obtain both current and voltage harmonic contents. Both the AC current and DC voltage harmonics for rectifiers with and without an IPT have been investigated to discuss the influence of the IPT on rectifier harmonics. Simulation results reveal that discrepancies in harmonic contents of both AC current and DC voltage of the two rectifier circuits are marked. It is noted that, for extremely light load up to rated load conditions, the total harmonic distortion (THD) of line-supply current is reduced, while the THD of DC output voltage is increased when the IPT is deleted from rectifier circuit.

The paper presents the improvements of a commercially available train simulator, the Energy Management Model (EMM), to evaluate the power flows in DC electrified transit railways. The sequential Gauss-Seidel power flow program used in EMM has been replaced by a unified Newton-Raphson AC/DC power flow to speed up the calculations. A precise model of the uncontrolled bridge rectifier with commutation impedance has been applied to the power flow formulation. Effects of regenerative braking on rectifier operations are also taken into account. Both the improved and the original train simulators have been tested on the Blue Line of Taipei Rapid Transit System which is under construction. Simulation results show that the proposed power flow program, with excellent convergence characteristics and accuracy, is of great value for train simulation.