Uniform Pumping Research Articles

Analysis of Groundwater Time Series With Limited Pumping Information in Unconfined Aquifer: Response Function Based on Lagging Theory

AbstractGroundwater extraction from aquifers is a common practice for human use, and variations in groundwater levels can provide valuable information on the hydrogeological properties of the aquifer. However, reliable data on pumping rates and distribution are often lacking due to unsupervised groundwater pumping activities. This study presents a new mathematical model for transfer function modeling that depicts the drawdown response caused by pumping in an unconfined aquifer system. To account for the dense and unsupervised pumping events, the uniform pumping approach was used to estimate these effects. To more accurately represent unconfined flow, the model first integrates lagging theory into a response function derived from the Boussinesq equation. The lagging theory accounts for the effects of both inertial force and capillary suction. Furthermore, the model has been used to derive both specific yield and transmissivity along with two lagging parameters simultaneously using only groundwater level information from the Choshui River region in Taiwan. The estimated results suggest that this approach provides reliable estimates of hydrogeological parameters, demonstrating its usefulness for water resource management and water budget evaluation.

4.4 kW Nd:YAG slab amplifier with a high repetition frequency and high beam quality

Using the self-developed fused indium wetting technology and planar waveguide, the uniform heat dissipation of the slab crystal and uniform pumping of the pump light were achieved, respectively. Based on the master oscillator power amplification (MOPA) scheme, the power was then amplified when the seed light source passed through the Nd:YAG slab crystal three times. Additionally, the image transfer system that we added to the amplified optical path achieved high beam quality. Finally, we obtained a rectangular pulsed laser with an output average power of 4461 W, a repetition frequency of 20 kHz, a pulse width of 62 ns, an optical-to-optical conversion efficiency of 26.8%, and a beam quality of β x =7.0 and β y =7.7.

Improved phase-locking of laser arrays by pump shaping.

We introduce a method to enhance the phase-locking quality and duration of an end-pumped laser array by precisely shaping its pump beam to overlap with the array. Shaping the pump beam results in a significant improvement in lasing efficiency and reduces the pump power required to reach the lasing threshold compared to a typical uniform pumping configuration. Our approach involves shaping a highly incoherent laser beam by addressing smaller segments of the beam with higher local spatial coherence. We demonstrate a remarkable increase in the laser array output brightness by up to a factor of 10, accompanied by a substantial extension in the phase-locking duration.

Transmission conductance of a cylindrical tube with wall pumping

The concept of transmission conductance is required to describe phenomena occurring in a tube with wall pumping. This is because the gas flow is not constant along the length of the tube but decreases, which implies that the geometric conductance determined by dimensional parameters of the tube cannot be further used. In one of the previous studies, the transmission conductance of a cylindrical tube was analytically derived using the particle balance equation based on the continuity principle. However, the calculated results well agreed with those of the test particle Monte Carlo (TPMC) simulation only when the sticking coefficient was less than 0.1. This is due to the intrinsic limitation of the analytical method, in which the constant conductance of a tube of unit length with uniform wall pumping was used. In this study, we introduced another analytical method based on the cosine law and finite element analysis using the conductance of the tube of unit length as a function of the position in the tube, considering the beaming effect. Using both methods, the relative difference in transmission conductance with TPMC considerably decreased compared to the previous study when the sticking coefficient was greater than 0.1. The results can be used in the design of a non-evaporable getter coated tube or a cryogenic water pump using an adsorbing wall to determine characteristic dimensions. Furthermore, this can be employed in a windowless vacuum coupling or a distributed pumping system for various light source systems.

PT symmetric single-mode line-defect photonic crystal lasers with asymmetric loss design.

The exploration of parity-time (PT) symmetry in micro-/nano-cavity lasers has recently gained immense research interest. The PT symmetric phase transition to single-mode lasing has been achieved by arranging the spatial distribution of optical gain and loss in single or coupled cavity systems. In terms of photonic crystal (PhC) lasers, a non-uniform pumping scheme is usually employed to enter the PT symmetry-breaking phase in a longitudinal PT symmetric system. Instead, we use a uniform pumping scheme to enable the PT symmetric transition to the desired single lasing mode in line-defect PhC cavities based on a simple design with asymmetric optical loss. The flexible control of gain-loss contrast is realized by removing a few rows of air holes in PhCs. We obtain single-mode lasing with a side mode suppression ratio (SMSR) of around 30 dB without affecting the threshold pump power and linewidth. The output power of the desired mode is six times higher than that in multimode lasing. This simple approach enables single-mode PhC lasers without sacrificing the output power, threshold pump power, and linewidth of a multimode cavity design.

Design and Development of a High-Performance LED-Side-Pumped Nd:YAG Rod Laser

We present a design and development of a high-performance light-emitting diode (LED)-side-pumped Nd:YAG rod laser with strong pulse energy, high efficiency, and consistency, very good beam quality, and high uniform pumping intensity in the active area which reduces the effects of thermal gradient significantly. A five-dimensional 810 nm LED array with a full width of 30 nm at half maximum was intended to achieve high coupling efficiency by putting the LED array as close as possible to the side of the Nd:YAG laser rod for overcoming the large pumped divergence. Under 2.25 J pump energy, maximum single pulse energy of 35.86 mJ with duration of 1.24 μs at 1063.68 nm was obtained, equivalent to optical efficiency of 1.59% and a slope efficiency of 2.53%. The laser was set to repeat at a rate of 10 Hz with a beam quality factor of and , as well as with the output power stability of < 4.1% (root mean square) and < 7.3% (peak to peak). To the best of our ability, this is the highest performance for an LED-side-pumped Nd:YAG rod laser oscillator with a 10-mJ-level output ever reported.

A 658-W VCSEL-pumped rod laser module with 52.6% optical efficiency

A high-efficiency and high-power vertical-cavity surface-emitting laser (VCSEL) side-pumped rod Nd:YAG laser with temperature adaptability are demonstrated. The VCSEL side-pumped laser module is designed and optimized. Five VCSEL arrays are symmetrically located around the laser rod and a large size diffused reflection chamber is designed to ensure a uniform pump distribution. Furthermore, the absorbed pump power distribution of the rod is simulated to verify the uniformity of the pump absorption. Finally, a proof-of-principle experiment is performed in short linear cavity laser with single laser module. A continuous-wave output power of 658 W at 1064 nm is obtained, the corresponding optical-to-optical efficiency is 52.6%, and the power variations are ±0.7% over 400 s and ±3.1% over the temperature range from 16 °C to 26 °C. To the best of our knowledge, this is the highest output power and the highest optical-to-optical efficiency ever reported for VCSEL pumped solid-state lasers. By inserting a telescopic module into the cavity and optimizing the TEM00 mode volume, the average beam quality is measured to be M 2 = 1.34 under an output power of 102 W. The experimental results reveal that such a high power rod laser module with temperature stability is appropriate for field applications.

Topological optical parametric oscillation.

Topological insulators possess protected boundary states which are robust against disorders and have immense implications in both fermionic and bosonic systems. Harnessing these topological effects in nonequilibrium scenarios is highly desirable and has led to the development of topological lasers. The topologically protected boundary states usually lie within the bulk bandgap, and selectively exciting them without inducing instability in the bulk modes of bosonic systems is challenging. Here, we consider topological parametrically driven nonlinear resonator arrays that possess complex eigenvalues only in the edge modes in spite of the uniform pumping. We show parametric oscillation occurs in the topological boundary modes of one and two dimensional systems as well as in the corner modes of a higher order topological insulator system. Furthermore, we demonstrate squeezing dynamics below the oscillation threshold, where the quantum properties of the topological edge modes are robust against certain disorders. Our work sheds light on the dynamics of weakly nonlinear topological systems driven out-of-equilibrium and reveals their intriguing behavior in the quantum regime.

Phonon-induced disorder in dynamics of optically pumped metals from nonlinear electron-phonon coupling

The non-equilibrium dynamics of matter excited by light may produce electronic phases, such as laser-induced high-transition-temperature superconductivity, that do not exist in equilibrium. Here we simulate the dynamics of a metal driven at initial time by a spatially uniform pump that excites dipole-active vibrational modes which couple nonlinearly to electrons. We provide evidence for rapid loss of spatial coherence, leading to emergent effective disorder in the dynamics, which arises in a system unitarily evolving under a translation-invariant Hamiltonian, and dominates the electronic behavior as the system evolves towards a correlated electron-phonon long-time state, possibly explaining why transient superconductivity is not observed. Our framework provides a basis within which to understand correlation dynamics in current pump-probe experiments of vibrationally coupled electrons, highlight the importance of the evolution of phase coherence, and demonstrate that pumped electron-phonon systems provide a means of realizing dynamically induced disorder in translation-invariant systems.

Phenobarbital versus valproate for generalized convulsive status epilepticus in adults (2): A multicenter prospective randomized controlled trial in China (China 2-P vs. V)

ObjectiveA multicenter study of phenobarbital versus valproate (i.e., the China 2-P vs. V study) was conducted to compare the efficacy and safety of phenobarbital and valproate for generalized convulsive status epilepticus (SE) in a multicenter trial design. MethodsThree improvements (uniform intravenous pumping, pump speed adjustment according to adverse events and blood drug level monitoring) over a previous study were made regarding an intravenous regimen of phenobarbital and valproate in a multicenter, prospective, randomized, controlled study. Long-term electroencephalography (EEG) monitoring was performed after initial drug treatment. Termination, relapse, adverse event and poor prognosis rates in patients with generalized convulsive status epilepticus (GCSE) were compared. ResultsThe rate of GCSE termination within one hour were significantly higher in the phenobarbital group (33 cases) than in the valproate group (36 cases) (84.8 % vs. 63.9 %, P = 0.048), but the rates of nontermination of EEG epileptic discharge within one hour were similar between the two groups (12.1 % vs. 8.3 %, P = 0.702). The relapse and adverse event rates were not significantly different between groups, but 3 hypoventilation events and 1 hypotension event occurred in the phenobarbital group compared to 0 in the valproate group. There were no cases of epileptiform EEG discharge relapse in the phenobarbital group, compared to 1 case in the valproate group. ConclusionsThe phenobarbital regimen evaluated in this study has a higher GCSE termination rate than the valproate regimen, indicating that the former is suitable for countries, regions and individuals with limited access to new antiepileptic drugs or limited economic means.

Study on the 400 mm 4 × 2 combined slab amplifier system

This paper provides the experiment results of a 400 mm 4 × 2 combined slab amplifier system for high-power laser devices based on a new pumping configuration, which involves 37 nm-diameter pulse xenon lamps, a multilamp arrangement, an operating voltage of 31 kV and a uniform pumping arrangement comprising 12 and 14 xenon lamps in the middle and side flashlamp cassettes, respectively. The experimental results show that the small signal gain coefficient was 5.60% cm−1. The pump-induced wavefront distortion accumulated by six slabs of Nd:glasses is 1.37λ peak-valley (PV) and the pointing offset value of pump beam is about 0.32 μrad/slab/pass. After discharging, the system was purged with clean gas at 0.4 m s−1. The cleanliness in the cavity returned to level 100 within 20 s, and the heat recovery time of the system was about 2 h.

Effect of elastic anisotropy on thermally induced distortions of a laser beam in single cubic syngony crystals with radial cooling. Part III

We report a study of thermally induced depolarisation of a laser beam in single cubic syngony crystals of 23 and m3 symmetry groups with an anisotropic elastic stiffness tensor. For active elements in the form of a long rod and a thin disk with radial cooling under uniform volume pumping, we investigate the effect of anisotropy of elastic properties on the dependence of the degree of depolarisation in the crystal on the orientation of the crystallographic axes, as well as on the position of the critical orientation in the crystallographic coordinate system.

Effect of elastic anisotropy on thermally induced distortions of a laser beam in single cubic syngony crystals with radial cooling. Part II

We report a study of thermally induced depolarisation of a laser beam in single cubic syngony crystals of 432, , and m3m symmetry groups with an anisotropic elastic stiffness tensor. For active elements in the form of a long rod and a thin disk with radial cooling under uniform volume pumping, we investigate the effect of anisotropy of elastic properties on the dependence of the degree of depolarisation in the crystal on the orientation of the crystallographic axes, as well as on the position of the critical orientation in the crystallographic coordinate system.

Recombinant human vascular endostatin injection to synchronize craniospinal radiotherapy for the treatment of recurrent medulloblastoma in children: A retrospective clinical study*

Abstract Objective Medulloblastoma (MB) is the most common primary central nervous system malignancy in children. Nonetheless, there is no standard treatment for recurrent MB. The purpose of this study was to investigate the clinical value and toxicity of recombinant human endostatin injection (Endostar®) combined with craniospinal radiotherapy for the treatment of recurrent MB in children. Methods This study retrospectively analyzed 13 patients with recurrent MB aged 5-18 years. Endostar® 7.5 mg/m2/d was synchronized during craniospinal radiotherapy for 7 children with a portable micro uniform speed infusion pump. Endostar® was applied 3 days prior to the initiation of radiotherapy. The drug was in continuous use for 7 days. Similarly, the withdrawal of the drug took place over 7 days. This represented a cycle. During radiotherapy, the application was repeated until the end of radiotherapy (experimental group). In the other 6 cases, only craniospinal radiotherapy was used (control group). Results The complete remission rate was 71.4% in the experimental group and 16.7% in the control group. The median progression-free survival (PFS) was 14 months (95% CI: 0.0-29.60) and 19 months (95% CI: 0.0-39.53) in the experimental and control groups, respectively. The median overall survival (OS) was 19 months (95% CI: 0.0-38.20) and 23 months (95% CI: 2.47-43.53) in the experimental and control groups, respectively. The most common adverse events included grade 1 thrombocytopenia (7.7%), grade 3 neutropenia (38.5%), and grade 1 anemia (30.8%). Conclusion Endostar® synchronizing craniospinal radiotherapy significantly improved the complete response rate of children with recurrent MB. It did not increase the side effects of radiation therapy. However, it did not improve the PFS or OS.

A Highly Inclusive Theory of Q-Switched Lasers

A highly inclusive theory of Q-switched lasers is presented which applies to both actively and passively Q-switched lasers. The theory expands on the author’s previous publications on energy optimization to include: (1) saturable absorbers exhibiting excited state absorption and therefore a finite Figure of Merit (FOM); (2) unequal beam areas in the gain and absorbing media; and (3) both pulsed and CW pumping. Design curves for optimizing the output energy for pulse pumped lasers and CW pumped lasers at a desired pulse rate are provided. As in the author’s previous work, the optimization equation is obtained utilizing Lagrange Multipliers and yields the value of the parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho = ln(n_{i}/n_{f})$ </tex-math></inline-formula> which maximizes the single pulse energy, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{i}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{f}$ </tex-math></inline-formula> are the laser inversion population densities before and after Q-switching. Using this initial result, the associated optimum absorber transmission and mirror reflectivity, pulse energy, peak power, and pulse width can be computed sequentially via simple formulas. The aforementioned parameters can all be expressed as functions of two variables, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z_{eff}$ </tex-math></inline-formula> , which are slight modifications of the variables <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and z previously introduced by the author for passively Q-switched lasers having infinite FOM and equal beam areas The term “plane wave theory” has sometimes been used by this and other authors in prior publications to describe a uniform pump profile in the laser medium, but we will refer to this special case more accurately as the “uniform pump theory”. The theory is extended here in the final section to include non-uniform pumping. The common case of a Q-switched laser end-pumped by a quasi-Gaussian CW laser is considered in detail and the theoretical results are found to agree well with experimental data.

Lateral carrier injection for the uniform pumping of several quantum wells in InGaN/GaN light-emitting diodes.

Most optoelectronic devices share the same basic epitaxial structure - a stack of quantum wells (QWs) sandwiched between p- and n-doped layers. In nitride semiconductors, where holes have 20-times lower mobility than electrons, the holes are able to populate only the topmost 1-2 QWs. The inability to distribute the holes in a large-enough number of QWs is a cause of high Auger recombination in nitride LEDs. Lateral carrier injection is an alternative design, in which the doped regions are situated at the sides of the QW stack and the carriers diffuse horizontally into the QWs. Given that the carriers are injected into all available QWs, it finally makes sense to grow structures with a large number of QWs. We report the results of our computer simulations, which explore the advantages of LCI-based LEDs in terms of energy efficiency.

Nonreciprocal photonic topological order driven by uniform optical pumping

Photonic topological insulators (PTIs) have raised significant interest in recent years, in part because of their protected edge propagation. Most PTI realizations have been based on reciprocal platforms, with protection only from symmetry-preserving defects. Nonreciprocal PTIs protect against arbitrary disorder, but their implementation requires breaking reciprocity either through a magnetic bias or complex spatiotemporal modulation schemes. Here, we demonstrate that nonreciprocal topological protection can be achieved by optically pumping a nonlinear photonic crystal with a uniform bias field, drastically simplifying the implementation of quantum-Hall-like topological protection in silicon-compatible platforms for classical and quantum optics.

Spin-waves generation at the thickness step of yttrium iron garnet film

We report on the experimental observation of short, exchange-dominated spin waves (EDSW) generation by a thickness step in the ferrite waveguide under microwave pumping. This effect was explored both experimentally (using mirco-Brillouin light scattering technique) and theoretically (by micromagnetic simulation) for the sample magnetized along the step and for two cases of pumping: a uniform microwave pumping of the step and its pumping through a magnetostatic surface wave (MSSW) traveling across the step. It was shown that efficiency of EDSW generation caused by MSSW scattering on the thickness step increases with the frequency (or wave number) while for the case of the uniform pumping, the generation efficiency demonstrates the opposite behavior.

PT-Symmetric Topological Edge-Gain Effect.

We demonstrate a non-Hermitian topological effect that is characterized by having complex eigenvalues only in the edge states of a topological material, despite the fact that the material is completely uniform. Such an effect can be constructed in any topological structure formed by two gapped subsystems, e.g., a quantum spin-Hall system, with a suitable non-Hermitian coupling between the spins. The resulting complex-eigenvalued edge state is robust against defects due to the topological protection. In photonics, such an effect can be used for the implementation of topological lasers, in which a uniform pumping provides gain only in the edge lasing state. Furthermore, such a topological lasing model is reciprocal and is thus compatible with standard photonic platforms.

Effect of elastic anisotropy on thermally induced distortions of a laser beam in single cubic syngony crystals with radial cooling. Part I

We have studied thermally induced distortions of a beam in single cubic syngony crystals of all symmetry groups with an anisotropic elastic stiffness tensor. The arithmetic mean and the difference between the thermally induced phase incursions of eigenpolarisations, as well as the angle of incidence of these polarisations, are calculated for a long rod and a thin disk with radial cooling under uniform volume pumping of the active element. The position of the specific crystal orientations unrelated to its symmetry elements is investigated. The effective values of the thermo-optical constant Q in two specific orientations, as well as the thermo-optical constant P in an arbitrary orientation, are found.