Single Line Operation Research Articles

Multi-objective optimization for through train service integrating train operation plan and type selection

ABSTRACT Providing effective Through Train Services (TTSs) faces challenges due to complex infrastructure conditions, train performances and passenger demands. To enhance TTSs between two different classes of urban rail transit lines with variations in train speed and capacity, we propose a multi-objective Integer Non-Linear Programming (INLP) model. This model maximizes passenger travel time savings and average train load utilization, and develops an integrated approach to simultaneously optimize the frequencies of through express trains and local trains, as well as the operation zones, stopping patterns and type selection of through trains. Additionally, a Non-Dominated Sorting Genetic Algorithm II is designed to solve the INLP model based on a simple test network and a real-world case from the Nanjing Subway. The unique benefits of our proposed method are demonstrated by a comprehensive compared with the Single Line Operation Mode and the all-stop plans under Through Operation Mode.

Influence of long-span bridge deformation on driving quality of high-speed trains

ABSTRACT Bridge time-varying deformation is the time-spatial dynamic deformation of a bridge excited by train motion, which serves as the direct alignment affecting a train’s dynamic response and usually moves ahead of the train. In this study, we investigated the influence of the bridge time-varying deformation on the vertical acceleration of a train with 16 cars on a long-span suspension bridge through the train-track-bridge coupled vibration analysis and chord measurements of dynamic spatial alignment. The analysis and measurements reveal the mechanism of the influence of different bridge positions on the car-body acceleration of different cars. Furthermore, we developed a simple method to identify the most unfavourable intersection position of multi-line driving based on the observed mechanism. In single-line operation, the maximum curvature of the main girder caused by bridge deformation with wavelengths above 200 m appears at the bridge tower and mid-span, while the maximum chord-measurement alignment with wavelengths below 200 m appears at the bridge tower, showing that the deformation at the tower area is more significant and that first car or sixteenth car will experience the maximum acceleration. For the multi-line operation, the curvature and chord measurements can be calculated by the superimposition of alignment with the wavelengths above and below 200 m, consecutively; hence, the most unfavourable intersection can be predicted according to the location and intersection of the maximum value. The intersection of two trains can increase the train’s centrifugal and vibration accelerations, causing the maximum acceleration to occur at the tower, where two trains meet at the most unfavourable one-fourth span of the bridge, which is verified by the train-track-bridge system.

Fairness-oriented train service design for urban rail transit cross-line operation

With the network operation in urban rail transit (URT), accessibility to the URT network increases markedly, leading to a growing transfer demand. As the URT system resource is equivalent to a bottleneck resource, it needs to be fairly allocated to transfer passengers (TP) and direct passengers (DP). Most existing studies focus on single line operation optimization but ignore the transfer demands of TPs. Cross-line operation (CO) has been verified as an efficient way to improve TP travel efficiency. This study focuses on the issue of passenger travel fairness with CO in the URT system. The concept of passenger effective travel time (ET) and ineffective travel time (IET) are proposed first. Based on the concept of α-fairness, the fairness of different classes of passengers was calculated through IET and ET. A mathematical model with decision variables of the turn-back station for CO and train frequency was constructed by analyzing the travel characteristics of passengers in two types of intersecting URT lines (“Y/T”-type and “X”-type) to minimize the passenger IET cost, fairness, and operation cost. Finally, the Changping Line and Line 8 in the Beijing URT system were considered as examples to verify the effectiveness of the proposed approach. The results indicate that from an overall perspective, CO can improve passenger travel fairness without increasing the IET cost for all passengers. Furthermore, considering the fairness of passenger travel may increase the operation costs. Study results contribute to a more fair URT system.

A powerful lidar system capable of 1 h measurements of water vapour in the troposphere and the lower stratosphere as well as the temperature in the upper stratosphere and mesosphere

Abstract. A high-power Raman lidar system has been installed at the high-altitude research station Schneefernerhaus (Garmisch-Partenkirchen, Germany) at 2675 ma.s.l., at the side of an existing wide-range differential absorption lidar (DIAL). An industrial XeCl laser was modified for linearly polarized single-line operation at an average power of about 180 W. This high power and a 1.5 m diameter receiver allow us to extend the operating range for water-vapour sounding to 20 km for a measurement time of just 1 h, at an uncertainty level of the mixing ratio of 1 to 2 ppm. This was achieved for a vertical resolution varied between just 0.2 and 0.6 km in the stratosphere. The lidar was successfully validated with a balloon-borne cryogenic frost-point hygrometer (CFH). In addition, temperature measurements up to altitudes of around 87 km were demonstrated for 1 h of signal averaging. The system has been calibrated with the DIAL, the CFH and radiosondes.

Switch and crossing for single line operation at double track section

Switch and crossing for single line operation at double track section

Гибридная трехфазно-однолинейная режимная модель для оценки состояния электроэнергетической системы

The article considers a new formulation of the state estimation problem, i.e., calculating the electric power system operation mode based on remote measurement data. The suggested approach implies the possibility of computing the electric operation mode parameters in a three-phase formulation for the grid parts equipped with three-phase measurement instruments. As regards the grid parts that are not fitted with such instrumentation, but in which single-line measurements are available, or which are characterized by an insignificant imbalance of operation mode parameters, their state is estimated in the single-line formulation. A distinguishing feature of such problem formulation is that the AC power flows in the grid circuit branches are used as the sought variables. The use of this approach essentially simplifies the problem and brings about additional advantages that are especially important for distribution networks. A hybrid three-phase and single-line operation mode analysis model for solving the state estimation problem is proposed and described. Owing to the use of AC power flows in the grid circuit branches as independent variables (a flow model), it becomes possible to use the phase or line form of the described model depending on the available measurement information in the grid part or component and the requirements posed to the problem being solved. The change over from one system of coordinates to another is made without making essential changes in the analysis model itself. The model errors were analyzed on a test network circuit. The analysis results have shown that the proposed model can be used for calculating the electric operation mode if the phase voltages at the interface between the three-phase and single-line grid submodels do not differ from each other by more than 10%.

Tailoring the output laser wavelength of fiber lasers by the intra-cavity inscription of LPFGs

Tailoring of the output laser spectral characteristics of an Erbium-doped fiber laser (EDFL) by the intra-cavity inscription of long-period fiber gratings (LPFGs) is experimentally demonstrated. The intra-cavity fabrication allows the accurate positioning of the LPFG notch bands in order to tailor the laser wavelength and at the same time suppress the side modes on the output laser spectrum. The red tail of the LPFG notch band is used as an edge filter to modify the gain spectrum, since its shape or slope is modified as the LPFG strength grows. As few as three periods are enough to tailor the laser wavelengths to a single laser line operation, with a side mode suppression ratio (SMSR) of 34.2 dB; while at six periods 37.79 dB of SMSR in a dual wavelength operation is demonstrated. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1430–1433, 2016

The Zugspitze Raman Lidar: System Testing

A high-power Raman lidar system has been installed at the high-altitude research station Schneefernerhaus (Garmisch-Partenkirchen, Germany) at 2675 m a.s.l., at the side of the existing wide-range differrential-absorption lidar. An industrial XeCl laser was modified for polarized single-line operation at an average power of about 175 W. This high power and a 1.5-m-diameter receiver are expected to allow us to extend the operating range for water-vapour sounding to more than 25 km, at an accuracy level of the order of 10 %. In addition, temperature measurements in the free troposphere and to altitudes beyond 80 km are planned. The system is currently thoroughly tested and exhibits an excellent performance up to the lowermost stratosphere. We expect that results for higher altitudes can be presented at the meeting.

Self-Q-switched Er–Yb double clad fiber laser with dual wavelength or tunable single wavelength operation by a Sagnac interferometer

We report a self-Q-switched Erbium-Ytterbium-doped double cladding fiber ring laser with dual wavelength or tunable single wavelength operations. A Sagnac interferometer with a high birefringence fiber in the loop was used for the wavelength tuning of the single line operation and cavity loss adjustment for dual wavelength laser operation. Single wavelength laser operation for a pump power of 421 mW tunable in a range of 1561.4 nm to 1569.8 nm and dual wavelength laser operation at 1561.1 nm and 1571.4 nm with equal output powers are presented.

Erbium-ytterbium co-doped multi-wavelength double-clad fiber laser around 1612 nm

We report an erbium-ytterbium (Er/Yb) co-doped multi-wavelength laser operation around 1612 nm. The fiber laser was constructed in a figure-of-eight configuration and using a piece of polarization-maintaining (PM) Er/Yb double clad fiber as the gain medium. The oscillation laser lines around 1612 nm could be controlled by carefully adjusting the polarization controllers in the cavity, which might result in single line, dual line or triple line fiber laser operation. The line space was measured about 3.3 nm (±0.2 nm) which was believed to be strongly dependent on the length of the PM Er/Yb co-doped double-clad fiber.

A comparative study of approaches for spectral control of Ti:sapphire pulsed lasers

The results of a comparative study (theoretical and experimental) of two original approaches for spectral control of two-wavelength pulsed Ti:sapphire (Ti:S) lasers and the most popular conventional methods are presented. Single line operation as a particular case is considered. We compare our own methods: (i) combined dual pulse pumping–passive self-injection locking (DPP–PSIL) and (ii) coupled cavity dye laser injection locking (CCLIL) with the conventional methods: (i) intracavity selection (IS), (ii) PSIL and (iii) traditional injection locking using an external dye laser. The most important criteria—laser efficiency, emission line width, tuning range, spectral purity and buildup time are compared under optimized conditions. The comparison is made using the same pump source with constant output energy in each case. The results serve as a basis for choosing correctly the most suitable spectral control technique for a particular Ti:S laser application. It is shown that the DPP–PSIL method guarantees a remarkable improvement of the Ti:S laser performance (nearly doubling the laser efficiency with the same line width and comparable laser tuning range as IS, combined with a protection of the selectors). The CCLIL approach assures a maximum laser efficiency in narrow line emission in addition to a minimal and reproducible buildup time. The IS method provides a maximal tuning range.

Terahertz spectral analysis by ac Josephson effect in high-T/sub c/ bicrystal junctions

A prototype of a terahertz Hilbert-transform spectrum analyzer based on a high-T/sub c/ Josephson junction integrated into a Stirling cooler has been developed. The detector response of YBa/sub 2/Cu/sub 3/O/sub 7-x/ Josephson grain-boundary junctions to monochromatic radiation with the frequency f in the range from 60 GHz to 5 THz has been studied. Odd-symmetric resonances near the voltages V=hf/2e in the responses /spl Delta/I(V) of these junctions to radiation with different frequencies f have been observed in a decade of spectral range for any operating temperature between 30 to 85 K. Decreasing the junction temperature from 85 to 30 K by a Stirling cooler, the spectral analysis could be made in two decades of spectral range. A resolving power /spl delta/f/f/spl sim/10/sup -3/ has been shown in the terahertz spectral analysis with the low-resistive Josephson junctions. As an example of application of this analyzer, an optimization of the single-line operation of a far-infrared optically-pumped CH/sub 3/OH laser has been demonstrated.

Frequency stable I 2 Raman laser excited by a cw frequency doubled monolithic Nd:YAG laser

Continuous Raman laser operation with 127I 2, 127I 129I and 129I 2 molecules, excited by a frequency doubled diode pumped monolithic Nd:YAG ring laser is reported. Within the tuning range of the pump laser, the molecules possess several absorption transitions, which so far enabled laser operation on more than 50 lines in the spectral range of 544–1330 nm. Multi-line and single-line operation in standing wave and ring resonators have been investigated. With pump powers of up to 500 mW, output powers up to 10 mW on individual lines were possible. Due to the narrow Raman gain profiles (down to 100 kHz) and the narrow pump laser line width of 10 kHz of the Nd:YAG, correspondingly narrow Raman laser line widths are expected. Therefore, with the pump laser stabilized on a specific hyperfine iodine absorption transition and a frequency locking of the Raman laser resonator to the induced Raman gain profile, a system with many reference laser lines and with expected frequency stabilities of δ ν/ ν≈10 −10 can be realized.

LIF measurement of population density in a pulsed rf discharge

A laser-induced fluorescence (LIF) technique has been applied to the measurement of population density in a pulsed parallel-plates rf discharge at 0.1 Torr pressure. The method is based on a single rotational line excitation-detection LIF scheme on the first positive band system of . This approach makes the correct application of a standard model of three-level rate equations to the description of the LIF process for the treatment of experimental results possible. Conditions for true single-line operation using a line-width pulsed tunable laser are discussed and applied to the measurement. The measured density value is then used for the absolute density calibration of a previous relative vibrational distribution of -9) obtained by a non-single-line excitation-detection LIF measurement.

Single line operation and line competition effects in RF discharge excited cw Xe lasers

We describe the first observation of single-line operation of cw atomic xenon lasers at Watt-level output powers. Single frequency output powers of 3.5 W on the 2.03 μm line and 780 mW on the 3.51 μm line have been observed. The single line performance of the laser is compared with observations made during multi-line operation. An explanation for the observed behaviour is proposed involving the suppression of line competition and the selective quenching and pumping of relevant transitions.

CW radio-frequency excited white-light He-Cd/sup +/ laser

We report on the design and performance of a continuous-wave transverse capacitively coupled radio-frequency excited He-Cd/sup +/ laser, which is capable of simultaneously delivering stable, tens-milliwatt power output at the three primary spectral lines blue: (/spl lambda/=441.6 nm), green (/spl lambda/=533.7 nm and /spl lambda/=537.8 nm), and red (/spl lambda/=635.5 nm and /spl lambda/=636.0 nm). Mixing these lines can result in the laser beam featured by a wide band of colors, including white color. The radio-frequency discharge, that excited the He-Cd mixture inside an alumina ceramic tube (400 mm length and 4 mm inner diameter) inserted into the fused silica tubing, operated between 400 mm long and 4 mm wide outer electrodes. Transformation of the radio-frequency discharge impedance to the 50-/spl Omega/ output resistance of the radiofrequency generator and symmetrization of the radio-frequency voltage were performed by a special matching circuit. Under single-line operation the He-Cd/sup +/ laser output powers of 60 mW, 38 mW and 14 mW were obtained for the blue, green and red lines, respectively, at an input radio-frequency power of 400 W. Owing to the power interaction between the laser oscillations at red and green higher laser output powers in red and green are possible under multi-line operation. At optimum conditions the white-light laser output power of about 60 mW is obtainable from the laser tube of 40 cm active length. The rms noise-to-signal ratio (lower than 0.4%) of the laser output power of the radio-frequency excited He-Cd/sup +/ laser was comparable to that of hollow cathode He-Cd/sup +/ lasers and much lower than that of conventional positive column He-Cd/sup +/ lasers. The presented laser has exhibited stable operation for more than 400 hours, showing ability to become a long life laser.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Very high tunability with single line operation of a transverse excitation multi-atmosphere CO 2 laser

A transverse excitation multi-atmosphere CO 2 laser has been modified to enhance its performance and to prevent damage to its optical components. A systematic investigation has been carried out on this source to verify the effects of the solution and to compare them with theory and previous works. In particular, we have obtained larger fluences coupled with full tunability and narrow laser linewidth.

Mode structure of the p-germanium far-infrared laser with and without external mirrors: Single line operation

The mode structure of p-Ge far-infrared lasers with and without mirrors is investigated. Without external mirrors a multimode spectrum is observed and quantitatively explained in terms of waveguidelike modes. An external resonator drastically reduces the number of oscillating modes. For the first time single line operation is demonstrated in this configuration.

Tunable multiline and single-line operations on a pulsed transversely excited atmospheric pressure CO2 laser by means of an intracavity CO2 gas absorber

The operating rotational-vibrational transition lines are observed in a pulsed transversely excited atmospheric pressure CO2 laser with a separated intracavity CO2 gas absorber. The laser operates a dominant 10.6-μm P-20 and P-18 line in a low pressure of CO2 cell and a single-line operation of P-20 line at more high pressure. In a high pressure, the laser does not operate the 10.6-μm P-20 and P-18, but it operates the single-line operation of 10.6-μm R-14, R-18, P-22, and 9.4-μm R-12, and in multiline oscillation, of various combinations of these lines and 10.6-μm R-16, according to the temperature of this gas absorber. The results are attributed to the absorbing mechanism of the CO2 gas.

Short-cavity hydrogen-halide laser

Laser action in HCl and HBr with a short-length-cavity TEA laser has been investigated. Support of the discharge by preionization resulted in reliable operation with pulse-to-pulse stability of better than 5%. Both efficient multiline and single-line operation are described. Maximum output energies of 120 and 35 mJ were measured in multiline operation, and 55 and 6 mJ were obtained from a single line for HCl and HBr, respectively. Energy conversion was 0.89 and 0.26% for the HCl and HBr system.