Heuristics Based Test Overhead Reduction Techniques in VLSI Circuits

The 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

Observability Driven Path Generation for Delay Test

This 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

Behaviour of a High Frequency Parallel Quasi Resonant Inverter Fitted Induction Heater with Different Switching Frequencies

This paper investigates the behavior of a high frequency parallel quasiresonantinverter fitted domestic induction heater with different switching frequencies. The power semiconductor switch Insulated Gate Bipolar Junction Transistor (IGBT) is incorporated in this high frequency inverter that can operate under ZVS and ZCS conditions during the switching operations at certain switching frequency to reduce switching losses. The proposed induction heating system responds to three different switching frequencies with providing different results. An Insulated Gate Bipolar Junction Transistor (IGBT) provides better efficiency and faster switching operations. After the complete study of the proposed induction heating system at the selected switching frequencies, the results are compared and it is decided that most reliable, efficient and effective operations from the proposed induction heater can be obtained if the switching frequency is selected slightly above the resonant frequency of the tank circuit of the resonant inverter. The proposed scheme is analyzed using Power SystemSimulator (PSIM) environment

Hairy root culture: a potent method for improved secondary metabolite production of Solanaceous plants

Secondary metabolites synthesized by the Solanaceous plants are of major therapeutic and pharmaceutical importance, many of which are commonly obtained from the roots of these plants. ‘Hairy roots’, mirroring the same phytochemical pattern of the corresponding root of the parent plant with higher growth rate and productivity, are therefore extensively studied as an effective alternative for the in vitro production of these metabolites. Hairy roots are the transformed roots, generated from the infection site of the wounded plants with Agrobacterium rhizogenes. With their fast growth, being free from pathogen and herbicide contamination, genetic stability, and autotrophic nature for plant hormones, hairy roots are considered as useful bioproduction systems for specialized metabolites. Lately, several elicitation methods have been employed to enhance the accumulation of these compounds in the hairy root cultures for both small and large-scale production. Nevertheless, in the latter case, the cultivation of hairy roots in bioreactors should still be optimized. Hairy roots can also be utilized for metabolic engineering of the regulatory genes in the metabolic pathways leading to enhanced production of metabolites. The present study summarizes the updated and modern biotechnological aspects for enhanced production of secondary metabolites in the hairy root cultures of the plants of Solanaceae and their respective importance

Cadmium(II) compounds of the bis-cyanoethyl derivative (LCX) of Me8[14]aneC (LC): characterization and antibacterial studies

The isomeric ligand LC, a saturated analogue of 2,9-C-meso-Me8[14]diene, on reflux with excess acrylonitrile afforded 1,8-N-pendant cyanoethyl derivative LCX. Interaction of LCX with cadmium(II) perchlorate, nitrate, acetate, and chloride salts produced six coordinated octahedral compounds, [Cd(LCX) (ClO4)2]∙2H2O, [Cd(LCX) (NO3)2], [Cd(LCX) (CH3COO)2], and [Cd(LCX)Cl2], respectively. Further, axial substitution reactions between [Cd(LCX) (ClO4)2]∙2H2O and KI, KBr, KCl, KSCN, and NaNO2 in a 1:2 ratio yielded six coordinated octahedral compounds, [Cd(LCX)I2]∙H2O, [Cd(LCX)Br2]∙2H2O, [Cd(LCX)Cl(ClO4)]∙2H2O, [Cd(LCX) (NCS)2]∙H2O, and [Cd(LCX) (NO2) (ClO4)]∙2H2O, respectively. All of the newly prepared compounds have been characterized by analytical, spectroscopic, molar conductivity, and magnetochemical data. The crystal structure of the ligand LCX was determined by x-ray crystallography which showed the 14-membered ring to adopt an extended chair conformation. Antibacterial activities of the newly formed cadmium(II) complexes against selected bacteria showed these to exhibit moderate and selective activity with 1-4 and 8 exhibiting greatest potency against the gram negative bacterium Salmonella typhi, and 5, 6, and 7 against the gram positive bacterium Bacillus wiedmannii

Targeting Mitochondrial Cell Death Pathway to Overcome Drug Resistance with a Newly Developed Iron Chelate

Background: Multi drug resistance (MDR) or cross-resistance to multiple classes of chemotherapeutic agents is a major obstacle to successful application of chemotherapy and a basic problem in cancer biology. The multidrug resistance gene, MDR1, and its gene product P-glycoprotein (P-gp) are an important determinant of MDR. Therefore, there is an urgent need for development of novel compounds that are not substrates of P-glycoprotein and are effective against drug-resistant cancer. Methodology/Principal Findings: In this present study, we have synthesized a novel, redox active Fe (II) complex (chelate), iron N- (2-hydroxy acetophenone) glycinate (FeNG). The structure of the complex has been determined by spectroscopic means. To evaluate the cytotoxic effect of FeNG we used doxorubicin resistant and/or sensitive T lymphoblastic leukemia cells and show that FeNG kills both the cell types irrespective of their MDR phenotype. Moreover, FeNG induces apoptosis in doxorubicin resistance T lymphoblastic leukemia cell through mitochondrial pathway via generation reactive oxygen species (ROS). This is substantiated by the fact that the antioxidant N-acetyle-cysteine (NAC) could completely block ROS generation and, subsequently, abrogated FeNG induced apoptosis. Therefore, FeNG induces the doxorubicin resistant T lymphoblastic leukemia cells to undergo apoptosis and thus overcome MDR. Conclusion/Significance: Our study provides evidence that FeNG, a redox active metal chelate may be a promising ne

Achieving Delay Differentiation by Scheduling Based on Optimal Balancing of Weighted Instantaneous and Cumulative Queue Lengths

Scheduling 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

Modelling of air-lift reactors based on bubble dynamics

187-191<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Predictions of hydrodynamic performance of an air-lift reactor (ALR) have traditionally considered bulk gas and liquid phase characteristics. This study aims to present an alternative approach of modelling an ALR by estimating the energy input to the reactor and gas hold-up in the riser based on dynamics of individual bubbles. The bubbles have been assumed to rise in discrete layers in the riser having a diameter in equilibrium with the surrounding pressure. The model predictions of gas hold-up and liquid velocity in the downcomer for ALRs have been compared with the reported experimental data.</span

Delay Differentiation by Optimal-Balancing-of-Queue-Lengths Scheduling

Scheduling policies adopted for statistical multiplexing should provide delay differentiation between different traffic classes. where each class represents an aggregate traffic of individual applications having the same target queueing delay requirement. We propose scheduling to optimally balance queue lengths as an approach to delay differentiation. In particular. we assume a discrete-time, two-class, single-server queueing model with unit service time per packet. We find 3 scheduling policy that we show to be discounted cost optimal, for Bernoulli packet anivals using dynamic programming analysis and for i.i.d. batch arrivals using a step-wise cost-dominance analyticalapproach. We then use cumulative queue length state variables in the one-step cost function of the optimization formulation and obtain the next-stage optimal policy. Simulations show that this policy achieves long-term mean queueing delays closer to the respective target delays than the first policy, and also achieves smaller errors in short-term mean queueing delays than the Coffman-Mitrani policy