720 research outputs found
Corrigendum: Planning for livelihoods under hydrosocial uncertainty in periurban Pune(Front. Water, (2022), 4, (831464), 10.3389/frwa.2022.831464)
No full textIn the published article, there was an error in the author list, and authors “Sharlene L. Gomes, Shreya Chakraborty, and Leon M. Hermans” were erroneously excluded. The corrected author list appears below. “Sarah Luft Faculty of Mathematics and Natural Sciences, Institute for Geography, University of Cologne, Cologne, Germany Sharlene L. Gomes Faculty of Governance and Global Affairs, Institute of Public Administration, Leiden University, The Hague, Netherlands Shreya Chakraborty South Asia Consortium for Interdisciplinary Water Resources Studies, Hyderabad, India Leon M. Hermans Faculty of Technology, Policy, and Management, Delft University of Technology, Delft, Netherlands and Land andWaterManagement Department, IHE Delft Institute forWater Education, Delft, Netherlands.Policy Analysi
Observability Driven Path Generation for Delay Test
Get PDFThis research describes an approach for path generation using an observability metric for delay test. K Longest Path Per Gate (KLPG) tests are generated for sequential circuits. A transition launched from a scan flip-flop (SFF) is captured into another SFF during at-speed clock cycles, that is, clock cycles at the rated design speed. The generated path is a ���longest path��� suitable for delay test. The path generation algorithm then utilizes observability of the fan-out gates in the consecutive, lower-speed clock cycles, known as coda cycles, to generate paths ending at a SFF, to capture the transition from the at-speed cycles. For a given clocking scheme defined by the number of coda cycles, if the final flip-flop is not scan-enabled, the path generation algorithm attempts to generate a different path that ends at a SFF, located in a different branch of the circuit fan-out, indicated by lower observability. The paths generated over multiple cycles are sequentially justified using Boolean satisfiability. The observability metric optimizes the path generation in the coda cycles by always attempting to grow the path through the branch with the best observability and never generating a path that ends at a non-scan flip-flop.
The algorithm has been developed in C++. The experiments have been performed on an Intel Core i7 machine with 64GB RAM. Various ISCAS benchmark circuits have been used with various KLPG configurations for code evaluation. Multiple configurations have been used for the experiments. The combinations of the values of K [1, 2, 3, 4, 5] and number of coda cycles [1, 2, 3] have been used to characterize the implementation. A sublinear rise is run time has been observed with increasing K values. The total number of tested paths rise with K and falls with number of coda cycles, due to the increasing number of constraints on the path, particularly due to the fixed inputs
Heuristics Based Test Overhead Reduction Techniques in VLSI Circuits
Get PDFThe electronic industry has evolved at a mindboggling pace over the last five decades. Moore���s Law [1] has enabled the chip makers to push the limits of the physics to shrink the feature sizes on Silicon (Si) wafers over the years. A constant push for power-performance-area (PPA) optimization has driven the higher transistor density trends. The defect density in advanced process nodes has posed a challenge in achieving sustainable yield. Maintaining a low Defect-per-Million (DPM) target for a product to be viable with stringent Time-to-Market (TTM) has become one of the most important aspects of the chip manufacturing process. Design-for-Test (DFT) plays an instrumental role in enabling low DPM. DFT however impacts the PPA of a chip. This research describes an approach of minimizing the scan test overhead in a chip based on circuit topology heuristics. These heuristics are applied on a full-scan design to convert a subset of the scan flip-flops (SFF) into D flip-flops (DFF). The K Longest Path per Gate (KLPG) [2] automatic test pattern generation (ATPG) algorithm is used to generate tests for robust paths in the circuit. Observability driven multi cycle path generation [3][4] and test are used in this work to minimize coverage loss caused by the SFF conversion process. The presence of memory arrays in a design exacerbates the coverage loss due to the shadow cast by the array on its neighboring logic. A specialized behavioral modeling for the memory array is required to enable test coverage of the shadow logic. This work develops a memory model integrated into the ATPG engine for this purpose. Multiple clock domains pose challenges in the path generation process. The inter-domain clocking relationship and corresponding logic sensitization are modeled in our work to generate synchronous inter-domain paths over multiple clock cycles. Results are demonstrated on ISCAS89 and ITC99 benchmark circuits. Power saving benefit is quantified using an open-source standard-cell library
Delay Differentiation By Balancing Weighted Queue Lengths
Get PDFScheduling policies adopted for statistical multiplexing should provide delay differentiation between different traffic classes, where each class represents an aggregate traffic of individual applications having same target-queueing-delay requirements. We propose scheduling to optimally balance weighted mean instanteneous queue lengths and later weighted mean cumulative queue lengths as an approach to delay differentiation, where the class weights are set inversely proportional to the respective products of target delays and packet arrival rates. In particular, we assume a discrete-time, two-class, single-server queueing model with unit service time per packet and provide mathematical frame-work throughout our work.
For iid Bernoulli packet arrivals, using a step-wise cost-dominance analytical approach using instantaneous queue lengths alone, for a class of one-stage cost functions not necessarily convex, we find the structure of the total-cost optimal policies for a part of the state space. We then consider two particular one-stage cost functions for finding two scheduling policies that are total-cost optimal for the whole state-space. The policy for the absolute weighted difference cost function minimizes the stationary mean, and the policy for the weighted sum-of-square cost function minimizes the stationary second-order moment, of the absolute value of the weighted difference of queue lengths. For the case of weighted sum-of-square cost function, the ‘iid Bernoulli arrivals’ assumption can be relaxed to either ‘iid arrivals with general batch sizes’ or to ‘Markovian zero-one arrivals’ for all of the state space, but for the linear switching curve. We then show that the average cost, starting from any initial state, exists, and is finite for every stationary work-conserving policy for our choices of the one-stage cost-function. This is shown for arbitrary number of class queues and for any i.i.d. batch arrival processes with finite appropriate moments.
We then use cumulative queue lengths information in the one-step cost function of the optimization formulation and obtain an optimal myopic policy with 3 stages to go for iid arrivals with general batch sizes. We show analytically that this policy achieves the given target delay ratio in the long run under finite buffer assumption, given that feasibility conditions are satisfied. We take recourse to numerical value iteration to show the existence of average-cost for this policy. Simulations with varied class-weights for Bernoulli arrivals and batch arrivals with Poisson batch sizes show that this policy achieves mean queueing delays closer to the respective target delays than the policy obtained earlier. We also note that the coefficients of variation of the queueing delays of both the classes using cumulative queue lengths are of the same order as those using instantaneous queue lengths. Moreover, the short-term behaviour of the optimal myopic policy using cumulative queue lengths is superior to the existing standard policy reported by Coffman and Mitrani by a factor in the range of 3 to 8. Though our policy performs marginally poorer compared to the value-iterated, sampled, and then stationarily employed policy, the later lacks any closed-form structure.
We then modify the definition of the third state variable and look to directly balance weighted mean delays. We come up with another optimal myopic policy with 3 stages to go, following which the error in the ratio of mean delays decreases as the window-size, as opposed to the policy mentioned in the last paragraph, wherein the error decreases as the square-root of the window-size. We perform numerical value-iteration to show the existence of average-cost and study the performance by simulation. Performance of our policy is comparable with the value-iterated, sampled, and then stationarily employed policy, reported by Mallesh. We have then studied general inter-arrival time processes and obtained the optimal myopic policy for the Pareto inter-arrival process, in particular. We have supported with simulation that our policy fares similarly to the PAD policy, reported by Dovrolis et. al., which is primarily heuristic in nature.
We then model the possible packet errors in the multiplexed channel by either a Bernoulli process, or a Markov modulated Bernoulli process with two possible channel states. We also consider two possible round-trip-time values for control information, namely zero and one-slot. The policies that are next-stage optimal (for zero round-trip-time), and two-stage optimal (for one-slot round-trip-time) are obtained. Simulations with varied class-weights for Bernoulli arrivals and batch arrivals with Poisson batch sizes show that these policies indeed achieve mean queueing delays very close to the respective target delays. We also obtain the structure for optimal policies with N = 2 + ⌈rtt⌉ stages-to-go for generic values of rtt, and which need not be multiple of time-slots
Electronic characterization of mass-selected acyclic, polycyclic and oxygenated hydrocarbons in neon matrices
Get PDFInterstellar chemistry embarked with the discovery of CH, CH+, and CN in extraterrestrial clouds. Presently, a large number of molecules have been identified in different galactic environments mostly by millimeter-wave and infrared spectroscopy. Molecular complexity and the spectral features dramatically depend on the particle density and the temperature of the astronomical region where they reside. Hence, spectroscopic analysis of extraterrestrial molecules has a valid mean to probe the physical and chemical condition and history of galactic media.
Life on Earth is carbon based and surprisingly, similar tendency has been found in interstellar molecules. Almost 80 percent of detected species contain carbon as a major constituent. Hence, a better characterization of the molecular universe may elucidate the origin of terrestrial life.
Two long standing riddles in molecular astrophysics are the diffuse interstellar absorption lines in the visible and the broad emission features in the mid-infrared. Carbonaceous systems ranging from small acyclic to polycyclic aromatics are considered to be the carriers of these absorption and emission bands. To recognize individual molecules responsible for these transitions, spectroscopic analysis of astrophysically relevant species in the laboratory is needed; comparison studies between astronomical measurements and laboratory spectra are the way for identification. These exotic molecules may be stable in galactic clouds under very cold and low density conditions but are extremely short-lived in the laboratory framework. Therefore, noncontemporary synthesizing and sensitive characterizing methods are required.
The matrix isolation spectroscopy is considered as an outdated-technique after the discovery of laser-based experiments but in combination with theory, it still serves a pivotal role in characterization of transient species. Exotic organics are synthesized in electrical discharge for the respective precursors. The ions of interest are co-deposited with neon on a cold surface (6 K) after mass-selection. Neutrals are generated in the matrix by UV irradiation.
The acyclic unsaturated organics possess very unique structural flexibility. By mass selective deposition of a particular m/z ratio in solid neon, several isomers have been detected. An advantage of the matrix isolation technique is that all possible electronic transitions of trapped species in the experimental measurement range can be recorded at once. Rare gases provide an environment in which the guest-host interactions slightly perturb the experimental band positions as compared to the gas-phase. Still matrix isolated spectrum is a good starting point for high resolution study and thence astrophysical findings.
Moderately intense absorptions are observed both in the visible and UV for C7Hn+/0 and C5Hn+/0, and charged oxygen containing polycarbon chains H2C6O+, HC7O+, and C4O2+ in neon matrices. The structural assignments of the electronic systems have been made on the basis of calculated ground-state stabilities with DFT and MP2 level of theory and computed excitation energies with TD DFT, SAC-CI, and CASPT2 methods. However, some of these ions and radicals have strong possibility to be the carriers of diffuse interstellar bands. The neutral oxygenated hydrocarbons are excluded as the carriers because no transition was detected after irradiation of the matrix. Theory explains that they possess strong transition in the deep UV. In addition, protonated PAHs and their oxygen containing analogs, which are credited for unidentified emission features, have been studied. Strong optical transitions suggest that they could be carriers of diffuse interstellar bands as well. A key species in combustion chemistry likely responsible for PAHs formation via mass-growth processes, fulvenallenyl radical, has been electronically characterized.
A part of this dissertation is devoted to physical organic chemistry. Reaction intermediates are too short-lived to probe. Nevertheless, identification of these species helps to infer a probable synthetic mechanism. Vibrationally resolved electronic spectra of fluorenylium, phenalenylium and fluorenyl radical have been measured in a neon matrix.
This electronic transition database of transient molecules created in the thesis can be used for their further gas-phase analysis and in situ detection in reaction or combustion systems
Achieving Delay Differentiation by Scheduling Based on Optimal Balancing of Weighted Instantaneous and Cumulative Queue Lengths
No full textScheduling policies for statistical multiplexing should provide delay differentiation between different trafic classes, where each class represents an aggregate traffic of individual applications having the same target queueing delay requirements. we propose scheduling to optimally balance weighted queue lengths as an approach to delay differentiation, class weights being set inversely proportional to the respective products of target delays and packet arrival rates. We fomulate the problem in the framework of Markov decision theory, assuming a discrete-time, two-class, single server queueing model with unit service time per packet. We first find a scheduling policy based on weighted instantaneous queue lengths, for the case of Bernoulli packet arrivals, that minimizes the stationary mean of the absolute value of the difference of the weighted instantaneous queue lengths. We then find a scheduling policy based on weighted cumulative queue lengths, for the case of i.i.d. packet batch arrivals, that achieves target mean queueing delays in simulation
TWO-PROTON PHOTOTAUTOMERIZATION DYNAMICS OF 7-AZAINDOLE COMPLEXES
No full textAuthor Institution: Department of Physical Chemistry, Indian Association for the cultivation of science, Calcutta 700032, India.E-mail: [email protected] tautomerization of 7-azaindole in doubly hydrogen-bonded dimeric complexes is one of the extensively investigated photoisomerization processes in recent years. The reaction, in the case of homodimer, takes place with equal ease in non-polar liquids at room temperature as well as in a cold supersonic jet expansion. A lot of studies were devoted arguing whether the double proton transfer occurs sequentially or in a concerted manner. Over the past three decades it has been assumed, on the basis of the observations of some low-temperature photophysical measurements, the double proton exchange barrier of the dimer is . However, we notice that such measurements are flawed by artifact; the apparent barrier depends on sample concentration in the solutions. The tautomerization of the isolated dimer is found stopped at 10 K in an argon matrix, and we propose that the double proton exchange is coupled with the large amplitude hydrogen bond vibrations. Furthermore, the process in several complexes of the molecule with pyrazole and amides displays remarkable contrasts with that of the homodimer. While the tautomerization in the former cases occurs extremely efficiently in hydrocarbon solutions, is hindered fully in supersonic jet expansion condition.The observations also imply that the effective barrier of phototautomerization in the complexes is intimately correlated with the details of double proton transfer mechanism. The details of our findings along with the predictions of some electronic structure calculations will be presented in the talk. References: \\begin{enumerate} \item "Ultraviolet and infrared spectroscopy of matrix-isolated 7-azaindole dimer: Matrix effect on excited state tautomerization", M. Mukherjee, B. Bandyopadhyay and T. Chakraborty, Chem. Phys. Lett. 546, 74-79 (2012). \item "Excited State Tautomerization of 7-Azaindole in a 1:1 Complex with -Valerolactam: A Comparative Study with the Homodimer", M. Mukherjee, S. Karmakar and T. Chakraborty, J. Phys. Chem. A, 116, 9888-9896 (2012). \item "Excited state tautomerization of 7-azaindole catalyzed by pyrazole", S. Karmakar, M. Mukherjee and T. Chakraborty, Chem. Phys. Lett. 561-562, 46-51 (2013). \\end{enumerate
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