High precision motion control of parallel robots with imperfections and manufacturing tolerances

This work attempts to achieve precise motion control using parallel robots with manufacturing tolerances and inaccuracies by migrating the measurements from their joint space to task space in order to decrease control system’s sensitivity to any kinematical uncertainty rather than calibrating the parallel plant. The problem of dynamical model uncertainties and its effect on the derivation of the control law is also addressed in this work through disturbance estimation and compensation. Eventually, both task space measurement and disturbance estimation are combined to formulate a control framework that is unsensitive to either kinematical and dynamical system uncertainties

Sensorless torque estimation in multidegree-of-freedom flexible systems

This paper presents a sensorless torque estimation algorithm for multidegree-of-freedom flexible systems. The proposed algorithm makes it possible to estimate externally applied torques due to flexible system s interaction with the environment without taking any measurement from the system. The algorithm is based on modifying the disturbance observer in order to decouple the reflected torque waves out of the total disturbance on the actuator. Then Reflected torque waves are used along with the actuator s current and velocity to estimate flexible system parameters, dynamics and the external torques or disturbances. Several experimental results are included in order to confirm the validity of the proposed torque estimation algorithm

Trade and the Environment

Trade, the exchange of goods and services across countries, is often viewed as an engine of economic growth. Benefits of liberalized trade include access to a larger variety of goods and services to consumers, easier access to foreign technologies, access to larger markets for producers, and increased efficiency in resource allocation. The impact of trade on the environment, however, is a contentious issue; air and water pollution, the degradation of natural habitats and loss of species, and global pollutants, particularly carbon dioxide emissions, are major concerns.Environmental Economics and Policy, International Relations/Trade,

When Government Spending Serves the Elites: Consequences for Economic Growth in a Context of Market Imperfections

Government spending should be regarded as a social and political phenomenon, not merely as a technical choice. We argue that there is an implicit contract between the organized elites and politicians which often leads to a pro-elite allocation of public resources. A natural and simple taxonomy of government spending follows from this view: spending in public goods broadly defined which mitigate market failures versus spending in non-social subsidies, mainly a vehicle to serve the elites. We theoretically and empirically show that pro-elite spending biases are costly in terms of economic growth. The empirical findings are exceptionally robust.government spending, economic growth, market imperfections, investment, subsidies, International Development, Labor and Human Capital, Political Economy, Public Economics,

Pollution and the State: The Role of the Structure of Government

Government spending has significant environmental implications. This paper analyzes the effect of the allocation of government spending between public goods broadly defined and private goods or non-social subsidies on air and water pollution. The theoretical model predicts that a reallocation of expenditures from private subsidies to public goods improves environmental quality by reducing production pollution. We estimate an empirical model that shows that such a reallocation causes a significant reduction in air pollutants namely sulfur dioxide and lead and an improvement in water quality measures including dissolved oxygen and biological oxygen demand.

Optimal motion control and vibration suppression of flexible systems with inaccessible outputs

This work addresses the optimal control problem of dynamical systems with inaccessible outputs. A case in which dynamical system outputs cannot be measured or inaccessible. This contradicts with the nature of the optimal controllers which can be considered without any loss of generality as state feedback control laws for systems with linear dynamics. Therefore, this work attempts to estimate dynamical system states through a novel state observer that does not require injecting the dynamical system outputs onto the observer structure during its design. A linear quadratic optimal control law is then realized based on the estimated states which allows controlling motion along with active vibration suppression of this class of dynamical systems with inaccessible outputs. Validity of the proposed control framework is evaluated experimentally

Frequency of nodal metastasis in differentiated thyroid carcinoma

Background: Thyroid cancer is the most common endocrine malignancy. Moreover, within thyroid cancer, differentiated thyroid carcinoma (DTC) is the most common variety, with the incidence rising over the past decade. Often, most of the cases present with multicentric disease and presenting with lymph node metastases at the time of diagnosis. Nodal metastasis has prognostic importance, and it may guide surgeons regarding further management. Considering this scientific fact, the study was performed to see the frequency of lymph node metastasis in DTC among the patients admitted to a tertiary care hospital. Methods: This cross-sectional study was conducted in the department of otolaryngology and head-neck surgery, Sher-E-Bangla Medical College Hospital, for 9 months after the acceptance of the protocol. A total of 50 patients (in all age groups) who attended the relevant department due to thyroid malignancies were approached and interviewed. Thorough history taking, physical examination, and relevant investigation were done and recorded into separate case record forms. Informed written consent was taken from each subject. Following collection, data were coded and inputted into statistical software. Data analysis was done with SPSS 21 according to the objective of the study. Data were presented in the form of tables, and charts. Results: Among the 50 patients, the mean age of the patients was 47.86±15.69 SD (years) with minimum and maximum ages of 14 and 78 years respectively. The male-female ratio was 1:4 (20% male vs 80% female). Papillary carcinoma was the most frequent (88%) followed by follicular (10%). Nodal metastasis was most common in the papillary variety, about 54.55% of cases, whereas 20% were present in the follicular variety. The majority of the patients underwent total thyroidectomy with neck dissection (90%) and the remaining cases were managed by lobectomy (10%). Conclusions: This study concluded that nodal metastasis was present in 54.55% of cases of papillary carcinoma.

Application of Numerical Method in Assessing the Variations in Pile Group Efficiency under Different Circumstances

Rapid urbanization creates a demand to expand the cities where using pile foundation became a recurrent practice. To ensure sustainability of projects pile load tests are important but may not be always feasible in terms of costing, on-site constrains etc. In this circumstance numerical analysis is a good alternate to estimate precise pile load capacity rather than conventional conservative approaches. This research illustrates the pile group efficiency fluctuation due to pile diameter, spacing, pile number and orientation in prescribed sandy soils. Using the conventional method the individual pile capacities are calculated for a constant depth with variable diameters and soil profiles. For simulating the piles, geometric models of sandy soils with sufficient boundaries are generated in PLAXIS 3D FOUNDATION software where the parameters of pile and soil components are considered as per predetermined values from reliable references. The analysis results have thoroughly been scrutinized by plotting several graphs at different aspects. The outcomes indicate that the conventional pile spacing i.e. 2.5D to 3.5D has an insignificant effect on pile group efficiency, irrespective to pile diameter and soil type. It also exhibits that the increment of pile number significantly decreases pile group efficiency for diameters of 600mm, 800mm, 1000mm and 1200mm in sandy soils. With a few exceptions as the diameter of the pile increases, the group efficiency decreases. The arrangement of piles in group has minor impact on pile group efficiency which enhances onsite flexibility. It is expected that these outcomes will facilitate the practicing engineers for efficient solutions

EFFECT OF SUPPLEMENTAL IRRIGATION ON WHEAT WATER PRODUCTIVITY UNDER RAINFED ECOLOGY OF POTHOHAR, PAKISTAN

For rainfed ecology, water is the most limiting natural resource and its effective utilization is indispensable in order to optimize crop water productivity. A field study on wheat crop was carried out to asses the impact of different irrigation depths through sprinkler irrigation system at three phonological stages viz. tilleing, anthesis and grain filling. Randomized Complete Block Design (RCBD) was used in the trail and had three repeats.  The area under study received 195 mm seasonal rainfall. Supplemental irrigation depths at three phonological stages, using small quantities of water through sprinkler irrigation system, significantly promoted the crop growth. The irrigation depth 25 mm gave the maximum output for biological yield (6504 ), grain yield (2030 ), thousand grain weight (28), plant height (87 ) and spike length (10 ). The highest water productivity of 0.97 kg/m3 was achieved with 25 mm supplemental irrigation depth when applied at tillering and anthesis stages