Efficiency and ownership with reference to British ports

PhDThis study seeks to investigate the empirical basis for the hypothesis, arising from the economics literature, that public enterprises are inherently less efficient than private enterprises, with reference to British ports which provide a comprehensive "laboratory" of mixed—ownership enterprises. The relative productive efficiency of public ports vis—a—vis private ports is evaluated in terms of efficiency frontiers of the industry at a fairly high degree of rigour. By applying the techniques of efficiency measurement the various ways that a British port producer might depart from overall productive efficiency were systematically explored. These include: production on the interior of the production possibilities set; production in the congested region of the boundary of the production possibilities set; and deviation from the scale that arises from the long—run competitive equilibrium. As well as static productive performance, productive performance relative to dynamic production frontiers is also the subject of investigation. Both mathematical programming techniques and econometric techniques are employed. To fulfil the tasks in the empirical analysis, the econometric approach has been enhanced in two ways. First, a less restrictive structure of production technology is specified in estimating efficiency frontiers in order to define parametric measures in a more meaningful way. Second, Solow's (1957) measure of productivity growth is reconsidered in a context of stochastic frontier functions, which enables us to translate efficiency gains over time into a movement towards frontiers and a movement of the frontiers. As far as British ports are concerned we found no evidence for believing the inefficiency associated with public ownership to be unavoidable. The results cast serious doubt on the transformation in productive performance brought about by the port privatisation programme

The physio-biochemical characterization reflected different calcium utilization efficiency between the sensitive and tolerant peanut accessions under calcium deficiency

Peanut yield in southern China is usually limited by calcium deficiency in soil. Most previous studies have found that small-seed varieties showed higher tolerance than large-seed varieties (e.g. Virginia type) under calcium deficiency, however, our preliminary research found that sensitive varieties also existed in small-seed counterparts. Few studies have been conducted to characterize low-calcium tolerance among small-seed germplasms with genetic diversity, and the differences in physiological characteristics between sensitive and tolerant varieties has not been reported yet. Thus, in order to better understand such differences, the current study firstly collected and characterized a diversity germplasm panel consisting of 50 small-seed peanut genotypes via a 2-year field trial, followed by the physiological characterization in sensitive (HN032) and tolerant (HN035) peanut genotypes under calcium deficiency. As a result, the adverse effects brought by calcium deficiency on calcium uptake and distribution in HN032 was much larger than HN035. In details, calcium uptake in the aboveground part (leaves and stems) was reduced by 16.17% and 33.66%, while in the underground part (roots and pods), it was reduced by 13.69% and 68.09% under calcium deficiency for HN035 and HN032, respectively; The calcium distribution rate in the pods of HN035 was 2.74 times higher than HN032. The utilization efficiency of calcium in the pods of HN035 was 1.68 and 1.37 times than that of HN032 under calcium deficiency and sufficiency, respectively. In addition, under calcium deficiency conditions, the activities of antioxidant enzymes SOD, POD, and CAT, as well as the MDA content, were significantly increased in the leaves of HN032, peanut yield was significantly reduced by 22.75%. However, there were no significant changes in the activities of antioxidant enzymes, MDA content, and peanut yield in HN035. Therefore, higher calcium absorption and utilization efficiency may be the key factors maintaining peanut yield in calcium-deficient conditions for tolerant genotypes. This study lays a solid foundation for selecting low-calcium tolerant varieties in future peanut breeding

A strategy of using temporary space-holders to increase the capacity for Li-S batteries

The porous structure within the cathode material influences the capacity and operating performance of Li-S batteries. Here, we prepared special carbon material using sodium chloride as template/temporary space-holders to design mixture of micro-/meso-/macroporous structure with large surface area through a facile water bath and freeze-drying process. Such modification led to a high sulfur content of 73.2 with remarkable initial capacity of 1378 mAh g-1 at 0.1 A g‒1, and maintains 48.6 after 100 cycles. Moreover, the Li-S battery displayed superior rate capability of 807 mAh g–1 at 1.0 A g–1. This abundant micro-/meso-/macropores can improve the content of sulfur, relieve the loss of sulfur and exhibit superior cycling performance and rate capability

Local Online Motor Babbling: Learning Motor Abundance of a Musculoskeletal Robot Arm

Motor babbling and goal babbling has been used for sensorimotor learning of highly redundant systems in soft robotics. Recent works in goal babbling have demonstrated successful learning of inverse kinematics (IK) on such systems, and suggest that babbling in the goal space better resolves motor redundancy by learning as few yet efficient sensorimotor mappings as possible. However, for musculoskeletal robot systems, motor redundancy can provide useful information to explain muscle activation patterns, thus the term motor abundance. In this work, we introduce some simple heuristics to empirically define the unknown goal space, and learn the IK of a 10 DoF musculoskeletal robot arm using directed goal babbling. We then further propose local online motor babbling guided by Covariance Matrix Adaptation Evolution Strategy (CMA-ES), which bootstraps on the goal babbling samples for initialization, such that motor abundance can be queried online for any static goal. Our approach leverages the resolving of redundancies and the efficient guided exploration of motor abundance in two stages of learning, allowing both kinematic accuracy and motor variability at the queried goal. The result shows that local online motor babbling guided by CMA-ES can efficiently explore motor abundance at queried goal positions on a musculoskeletal robot system and gives useful insights in terms of muscle stiffness and synergy.IEEE/RSJ International Conference on Intelligent Robots and Systems (iROS2019), November 4 - 8, 2019, Macau, Chin

64-fs L-band pulse generation by an all-fibre Er-doped laser

We demonstrate a L-band all-fibre erbium-doped laser mode-locked by nonlinear polarisation rotation. The use of a single gain segment with appropriate length and dispersion and a L-band optimised Brewster fibre grating as an in-fibre polariser enables the generation of 64-fs pulses at 1.59µm

Generation of 64-fs L-band stretched pulses from an all-fibre Er-doped laser

We demonstrate an L-band all-fibre erbium-doped laser mode locked by nonlinear polarisation rotation and working in the stretched-pulse regime. The use of a single segment of gain fibre with appropriate length and dispersion and a Brewster fibre grating optimised for the L band as an in-fibre polariser enables the generation of pulses at 1.59-μm central wavelength, which can be linearly compressed to 64-fs duration. Numerical simulations of the laser model support our experimental findings. Our laser design gives a route towards low-cost and low-complexity fibre-integrated laser sources for applications requiring L-band ultrashort pulses

Wavelength-tunable L-band mode-locked fiber laser using a long-period fiber grating

We demonstrate an L-band wavelength-tunable passively mode-locked fiber laser using a single long-period fiber grating (LPFG) as a narrow-band optical attenuator (NBOA). Through bending the LPFG, the central wavelength can be continuously tuned from 1582.02 to 1597.29 nm, while the output power only varies from 1.465 to 1.057 mW, approximately a rate of 22 µW/nm variation. This is the first time that LPFG is functioned as a NBOA in mode-locked fiber lasers, showing the great advantage of less impact on output power variation reduction. Besides, the total cavity length is 5.08 m, which is the shortest length yet reported in wavelength-tunable mode-locked fiber lasers. The wavelength tuning could also be realized at harmonic mode locking with tuning range of 14.69 nm under 5th harmonic

Pump-controlled wavelength switchable dissipative soliton mode-locked Yb-doped fiber laser using a 45° tilted fiber grating

We demonstrate a pump-controlled wavelength switchable Yb-doped fiber laser (YDFL) by nonlinear polarization rotation (NPR) for the first time. The polarizer replaced by a 45° tilted fiber grating (45°-TFG) combines with a section of polarization maintaining fiber (PMF) to form a fiber-based birefringent filter. Stable dissipative soliton (DS) with center wavelength of 1068.39 nm is generated under the mode-locked threshold of 277 mW. The operating wavelength switching between 1046.51 nm and 1067.90 nm can be realized via increasing the pump power simply while keeping the polarization controllers (PCs) in a fixed state. The laser maintains stable mode-locking operation at each wavelength, which can be regarded as a type of multi-wavelength ultrafast light source with precise control and integration potential