Conditional Block Research Articles

Verification of Scheduling of Conditional Behaviors in High-Level Synthesis

High-level synthesis (HLS) technique translates the behaviors written in high-level languages like C/C++ into register transfer level (RTL) design. Due to its complexity, proving the correctness of an HLS tool is prohibitively expensive. Translation validation is the process of proving that the target code is a correct translation of the source program being compiled. The path-based equivalence checking (PBEC) method is a widely used translation validation method for verification of the scheduling phase of HLS. The existing PBEC methods cannot handle significant control structure modification that occurs in the efficient scheduling of conditional behaviors. Hence, they produce a false-negative result. In this article, we identify some scenarios involving path merge/split where the state-of-the-art PBEC approaches fail to show the equivalence even though behaviors are equivalent. We propose a value propagation-based PBEC method along with a new cutpoint selection scheme to overcome this limitation. Our method can also handle the scenario where adjacent conditional blocks (CBs) having an equivalent conditional expression are combined into one CB. Experimental results demonstrate the usefulness of our method over the existing methods.

Alternative Approach to Wellhead Flowline-Pressure Protection

This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 18613, "An Alternative Approach to Wellhead Flowline-Pressure Protection," by Angela E. Summers and Bryan Zachary, SIS-Tech Solutions, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May. For many years, pipe-specification standards have required that piping downstream of the wellhead be adequate to sustain a full wellhead shut-in. This inherently safe design practice ensured that the flowline pipe was specified with a maximum allowable working pressure (MAWP) equal to or greater than the maximum pressure expected to be produced by the well. This practice has proved to provide adequate protection in thousands of wellhead installations throughout the world. Inherently safe practice has been challenged when retrofitting electrical submersible pumps (ESPs). In such cases, the maximum discharge pressure under block-in conditions is greater than the MAWP of existing flowline pipe. A safe alternative to replacing the pipe is the use of a high-integrity protective system (HIPS) designed and managed as a safety-instrumented system (SIS) with a Safety Integrity Level (SIL) of 3. Introduction When the price of crude oil rose above USD 50/bbl, oil-producing companies pursued efforts to increase or renew production in existing oil wells. One solution, especially in ultradeep (4,000-ft water depth) subsea applications, is to boost well pressure. A major challenge in developing these deepwater solutions is the MAWP limitation of the downstream flowline pipe. An HIPS can close block valves placed in front of the low-specification pipe, protecting the lower-rated downstream piping. The introduction of high-pressure ESPs in many offshore fields has increased the maximum shut-in pressure beyond the MAWP of the downstream flowline pipe. The design of the instrumented-system response is complicated by the need to respond quickly. Upon shut-in, the ESP can produce pressure sufficient to challenge the mechanical integrity of the flowline very quickly. The pressure rise is related to the compressibility of the material, but the pressure rise generally is rapid, resulting in a very-short process safety time (e.g., in liquid service, the time may be less than 5 seconds). In typical onshore process-industry applications, an overpressure hazard such as that encountered by the ESP-well flowline would be addressed by a pressure-relief device (PRD) and a disposal system, such as a flare or scrubber to safely process the material relieved during an overpressure event. When PRDs are installed in conventional flowline designs, they typically are sized to mitigate only thermal expansion of the material when the flowline is blocked-in. For HIPS flowline designs, the PRD sizing also should consider possible block-valve leakage. A safe and reliable alternative to replacing the existing wellhead flowlines relies on the use of an HIPS to detect unacceptable operating pressure and initiate closure of block valves. An HIPS is a special class of SIS.

Conditioned blocking and schizophrenia: a replication and study of the role of symptoms, age, onset-age of psychosis and illness-duration

Measures of selective attention processing like latent inhibition (LI) and conditioned blocking (CB) are disturbed in some patients with schizophrenia. [LI is the delay in learning about the associations of a stimulus that has been associated with no event (versus de novo learning); CB is the delay in learning the associations of a stimulus-component when the other component has already started to acquire these associations.] We proposed: (1) to replicate the reported decreases of CB in patients without paranoid-hallucinatory symptoms; (2) to see if CB depends on the age of illness-onset and its duration, as reported for LI. We studied 101 young and old, acute and chronically ill patients with schizophrenia, of whom 62 learned a modified ‘mouse-in-house’ CB task, and compared them with 62 healthy controls matched for age, education and socio-economic background. CB was more evident in patients with a diagnosis of paranoid schizophrenia than other subtypes. An unusual persistence of high CB scores through testing was associated with productive symptoms (including positive thought disorder). Reduced CB related to the expression of (a) Schneider's first rank symptoms of ideas-of-reference and (b) to negative symptoms like poor rapport and poor attention. CB was less evident in the older patients and those with an earlier illness-onset. In contrast to the similar LI test of selective attention, CB is found in patients with paranoid schizophrenia and its expression is not related closely to illness duration. This implies that the two tests reflect the activity of different underlying processes. We suggest that reduced CB on initial test-trials in nonparanoid schizophrenia reflects the unusual persistence of controlled information processing strategies that would normally become automatic during conditioning. In contrast, continued CB during testing reflects an unusual persistence of automatic processing strategies.

Neuropsychological and conditioned blocking performance in patients with schizophrenia: assessment of the contribution of neuroleptic dose, serum levels and dopamine D2-receptor occupancy.

Patients with schizophrenia show impairments of attention and neuropsychological performance, but the extent to which this is attributable to antipsychotic medication remains largely unexplored. We describe here the putative influence of the dose of antipsychotic medication (chlorpromazine equivalents, CPZ), the antipsychotic serum concentration of dopamine (DA) D2-blocking activity and the approximated central dopamine D2-receptor occupancy (DA D2-occupancy), on conditioned blocking (CB) measures of attention and performance on a neuropsychological battery, in 108 patients with schizophrenia (compared with 62 healthy controls). Antipsychotic serum concentration and D2-occupancy were higher in patients with a paranoid versus non-paranoid diagnosis, and in female versus male patients (independent of symptom severity). Controlling for D2-occupancy removed the difference between high CB in paranoid and impaired low CB in non-paranoid patients. Similar partial correlations for antipsychotic drug dose and serum levels of DA D2-blocking activity with performance of the trail-making and picture completion tests (negative) and the block-design task (positive) showed the functional importance of DA-related activity. High estimates of central DA D2-occupancy were related to impaired verbal fluency but were associated with improved recall of stories, especially in paranoid patients. This, the first study of its kind, tentatively imputes a role for DA D2-related activity in left frontal (e.g. CB, verbal fluency) and temporal lobe functions (verbal recall) as well as in some non-verbal abilities mediated more in the right hemisphere in patients with schizophrenia.

Plasma dopamine (DA) activity, DA-D2 binding, neuropsychological signs and conditioned blocking (CB) in schizophrenia

Plasma dopamine (DA) activity, DA-D2 binding, neuropsychological signs and conditioned blocking (CB) in schizophrenia

The development of conditioned blocking and monoamine metabolism in children with attention-deficit-hyperactivity disorder or complex tics and healthy controls: an exploratory analysis

Conditioned blocking (CB) measures the transient suppression of learning that a new stimulus, added during learning, has the same consequences as the conditioned stimulus already present. Normal CB increases between the age of 8 and 20 years (Oades, R.D., Roepcke, B. and Schepker, R., A test of conditioned blocking and its development in childhood and adolescence: relationship to personality and monoamine metabolism, Dev. Neuropsychol., 12 (1996) 207–230). In the present study CB development is compared between healthy children (CN), children with attention deficit (ADHD) and those with complex tics or Tourette's syndrome (TS) with mean ages of 10–11 years. All children needed fewer learning trials with increasing age: the ADHD group showed a slight impairment. Only controls improved CB with increasing age. A trend for worse CB in the TS than the other groups was significant for those over 11 years. While ADHD children over 11 years showed less CB than controls, younger ADHD children showed more. A correlational analysis of the status of monoamine metabolism in 24 h urine samples showed a positive relationship for CB with dopamine metabolism in controls and TS children, but a negative relationship in ADHD children. In contrast, increases of serotonin metabolism were negatively related to CB in TS but positively in ADHD patients. In conclusion, when selective information processing abilities reflected by CB start to develop at puberty-onset, there is a relative worsening in ADHD patients. But TS patients show an impairment independent of age. Changes in the balance between dopamine and serotonin systems may contribute to normal and abnormal cognitive development.

Stimulus dimension shifts in patients with schizophrenia, with and without paranoid hallucinatory symptoms, or obsessive compulsive disorder: strategies, blocking and monoamine status

Reversal, and intra-dimensional (ID) and extra-dimensional (ED) nonreversal discrimination shifts were studied to see if learned inattention to the irrelevant dimension differentially influenced the efficacy of learning and stimulus choice strategy. Performance was compared with conditioned blocking (CB) and monoamine metabolic status between healthy controls, patients with obsessive compulsive disorder (OCD) or schizophrenia with (PH) or without (NP) active paranoid hallucinatory symptoms. PH and NP patients improved learning with practice, but showed an impaired shift on each task. OCD patients were impaired only on the ED-shift. The NP patients' impairment was nonspecific and, unlike PH and controls, it related to reversal performance. All subjects acquired an attentional set for colour reflected in the length of stimulus-response sequences. Analysis of paired-stimulus choice-strategies showed that while all patients showed fewer correct win-stay choices, only PH patients perseverated with lose-stay choices. Learning about the added stimulus in the CB task related to ID-shift efficiency in NP patients. Increases of dopamine activity related to delayed learning but more switches of stimulus choice in the shift-tasks. Increases of serotonin activity correlated with faster learning in controls, OCD and PH patients. In NP patients the opposite held for dopamine and serotonin activity. Thus the two learned inattention tasks have different if related requirements and correlates: the data are consistent with the use of automatic exogenous attention strategies by NP patients, of inefficient controlled attention by PH patients and the automatization of endogenous processes in controls.

Conditioned Blocking in patients with paranoid, non-paranoid psychosis or obsessive compulsive disorder: Associations with symptoms, personality and monoamine metabolism

Conditioned blocking (CB) refers to a delay in learning that a new stimulus, added during learning, has the same consequences as the conditioned stimulus already present. In animals such “learned inattention” depends on monoaminergic and limbic function and, thus, CB performance should be informative on selective information processing impairments found in subgroups of psychotic patients. Attenuated CB in acute schizophrenia has been reported to normalize rapidly. This study examines in young patients the specificity of CB performance to illness, and its associations with symptoms, personality traits and monoaminergic metabolic status. CB was attenuated in psychotic patients with non-paranoid symptoms (NP: n = 12, mean age 17 years) with respect to obsessive-compulsive (OCD: n = 13, mean age 16 years) and healthy subjects (CON, n = 29, mean age 18 years), but only a transient attenuation was observed in paranoid hallucinatory patients (PH: n = 14, mean age 19 years). Outgoing personality traits in CON and OCD subjects correlated with CB. In NP patients attenuated CB was associated with increasing neurotic lability. In PH patients CB correlated positively with “manic” but negatively with psychotic or neurotic scores. The severity of negative symptoms in psychosis and specific negative/positive symptoms in the NP/PH groups was associated with reduced CB. Increased dopamine activity (24-h urine samples) correlated positively with CB, but relative increases of noradrenaline metabolism in NP and serotonin metabolism in OCD patients interfered. In summary, marked psychotic or neurotic traits and some symptom-states were associated with reduced CB. The particular selective processing problems of NP patients may reflect inappropriate NA activity.

A test of conditioned blocking and its development in childhood and adolescence: Relationship to personality and monoamine metabolism

Conditioned blocking (CB) is the undermining of conditioning to a stimulus by conjoint exposure with one already associated with the unconditioned stimulus. CB is one of several tests of “learned inattention” in which performance has been found to depend on personality features of human participants and monoamine activity in animals. In Part 1, the performance of 25 healthy young adults on a new test form for demonstrating CB is described. From personality inventories and 24‐hr urine samples it was proposed that CB may be correlated with extroversion and increased catecholamine utilization. In Part 2, CB was shown to be present in 4 groups of 11 participants with mean ages of 10, 14, 17 and 22 years independent of IQ, but it was least marked in the prepubertal group. No relation of performance with personality features was found. As with the adult group, CB was positively correlated with dopamine activity, but unlike the adults it was negatively correlated with noradrenalin activity. The maturation of att...

Mental Strategies and Materials or Models for Addition and Subtraction up to 100 in Dutch Second Grades

Dutch mathematics programs emphasize mental addition and subtraction in the lower grades. For two-digit numbers up to 100, instruction focuses on “counting by tens from any number” (N10), a strategy that is difficult to learn. Therefore, many children prefer as an easier alternative “decomposition” in tens (1010) and units. Instead of the use of arithmetic blocks (BL), the hundredsquare (HU) was introduced in the 1980s because of a (supposed) better modeling function for teaching N10. In a field study with several schools, (a) we compared the strategies N10 and 1010 on procedural effectiveness and error types, and (b) we assessed the influence of the support conditions BL versus HU on the acquisition of mental strategies (we had also a control condition NO with no extra materials or models). Results confirmed the greater effectiveness of N10 but also the preference of many weaker children for 1010. Support for BL or HU had differential effects on mental strategies. Differences are discussed in terms of cognitive psychology: the role of declarative knowledge and the relation between conceptual and procedural knowledge. New Dutch proposals for the 1990s emphasize teaching both strategies N10 and 1010 to enhance the flexibility of students' mental arithmetic.