Human reliability

Human reliability is related to the field of human factors and ergonomics, refers to the reliability of humans in fields including manufacturing and nuclear power. Human performance can be affected by many factors such as age, state of mind, physical health, emotions, propensity for certain common mistakes and cognitive biases, etc. Human reliability is important due to the contributions of humans to the resilience of systems and to possible adverse consequences of human errors or oversights when the human is a crucial part of the large socio-technical systems as is common today. User-centered design and error-tolerant design are just two of many terms used to describe efforts to make technology better suited to operation by humans. People tend to overestimate their ability to maintain control; the common characteristics of human nature addressed below are accentuated when work is performed in a complex work environment. Stress The problem with stress is that it can accumulate and overpower a person, thus becoming detrimental to performance.

Avoidance of Mental Strain Humans are reluctant to engage in lengthy concentrated thinking, as it requires high levels of attention for extended periods. The mental biases, or shortcuts used to reduce mental effort and expedite decision-making include: Assumptions – A condition taken for granted or accepted as true without verification of the facts. Habit – An unconscious pattern of behavior acquired through frequent repetition. Confirmation bias – The reluctance to abandon a current solution. Similarity bias – The tendency to recall solutions from situations that appear similar Frequency bias – A gamble that a used solution will work. Availability bias – The tendency to settle on solutions or courses of action that come to mind. Limited Working Memory - The mind's short-term memory is the “workbench” for problem solving and decision-making. Limited Attention Resources - The limited ability to concentrate on two or more activities challenges the ability to process information needed to solve problems.

Mind-Set People tend to focus more on what they want to accomplish and less on what needs to be avoided because human beings are goal-oriented by nature. As such, people tend to "see" only what the mind wants, to see. Difficulty Seeing One's Own Error - Individuals when working alone, are susceptible to missing errors. Limited Perspective - Humans cannot see all there is to see; the inability of the human mind to perceive all facts pertinent to a decision challenges problem-solving. Susceptibility To Emotional/Social Factors - Anger and embarrassment adversely influence team and individual performance. Fatigue - People get tired. Physical and mental fatigue can lead to error and poor judgment. Presenteeism - Some employees will be present in the need to belong to the workplace despite a diminished capacity to perform their jobs due to illness or injury. A variety of methods exist for human reliability analysis. Two general classes of methods are those based on probabilistic risk assessment and those based on a cognitive theory of control.

One method for analyzing human reliability is a straightforward extension of probabilistic risk assessment: in the same way that equipment can fail in a power plant, so can a human operator commit errors. In both cases, an analysis would articulate a level of detail for which failure or error probabilities can be assigned; this basic idea is behind the Technique for Human Error Rate Prediction. THERP is intended to generate human error probabilities that would be incorporated into a PRA; the Accident Sequence Evaluation Program human reliability procedure is a simplified form of THERP. More the US Nuclear Regulatory Commission has published the Standardized Plant Analysis Risk - Human Reliability Analysis method to take account of the potential for human error. Erik Hollnagel has developed this line of thought in his work on the Contextual Control Model and the Cognitive Reliability and Error Analysis Method. COCOM models human performance as a set of control modes—strategic, tactical and scrambled - and proposes a model of how transitions between these control modes occur.

This model of control mode transition consists of a number of factors, including the human operator's estimate of the outcome of the action, the time remaining to accomplish the action, the number of simultaneous goals of the human operator at that time. CREAM is a human reliability analysis method, based on COCOM. Related techniques in safety engineering and reliability engineering include failure mode and effects analysis, fault tree, SAPHIRE; the Human Factors Analysis and Classification System was developed as a framework to understand the role of "human error" in aviation accidents. It is based on James Reason's Swiss cheese model of human error in complex systems. HFACS distinguishes between the "active failures" of unsafe acts, "latent failures" of preconditions for unsafe acts, unsafe supervision, organizational influences; these categories were developed empirically on the basis of many aviation accident reports. "Unsafe acts" are performed by the human operator "on the front line"

Lake Zurich

Lake Zürich is a lake in Switzerland, extending southeast of the city of Zürich. Depending on the context, Lake Zürich or Zürichsee can be used to describe the lake as a whole, or just that part of the lake downstream of the Seedamm at Rapperswil, whilst the part upstream of Rapperswil may be called the Obersee or Upper Lake. Lake Zürich is formed by the Linth river, which rises in the glaciers of the Glarus Alps and was diverted by the Escher canal into Lake Walen from where its waters are carried to the east end of Lake Zürich by means of the Linth canal; the waters of the Lake of Zürich flow out of the lake at its north-west end, passing through the city of Zürich. The culminating point of the lake's drainage basin is the Tödi at 3,614 metres above sea level. No streams of importance flow into the lake besides the Linth; the Seedamm, a artificial causeway and bridge, crosses a narrow point of the lake carrying a railway line and road from Rapperswil to Pfäffikon. The eastern section of the lake is known as the Obersee, German for "upper lake".

West of this dam lie the small islands of Lützelau and Ufenau, where in 1523 Ulrich von Hutten took refuge and died. Both shores are well fertile. Another touristic destination is the Au peninsula at the village of Au between Horgen. To the east – separated by Zürichberg-Adlisberg and Pfannenstiel – are two minor lakes: Greifensee and Pfäffikersee. Zimmerberg and the Etzel regions lie to the west. Administratively, Lake Zürich is split between the cantons of St. Gallen and Schwyz; the lower lake, to the west of the Seedamm, is in the canton of Zürich, whilst the upper lake is shared between the cantons of St. Gallen and Schwyz; the lake was frozen in the following years 1223, 1259, 1262 1407, 1491 1514, 1517, 1573 1600, 1660, 1684, 1695 1709, 1716, 1718, 1740, 1755, 1763, 1789 1830, 1880, 1891, 1895 1929, 1963 The three population and transportation centres are Zürich, Pfäffikon SZ and Rapperswil. Besides Bürkliplatz in Zürich and the Seedamm, there are no bridges across the lake; the Zürichsee-Schifffahrtsgesellschaft – the Lake Zürich Navigation Company – provides with its 17-passenger ships touristic services on Lake Zürich.

There are a number of passenger ferry services, noticeably the Horgen–Meilen ferry, an auto ferry between Horgen and Meilen. Zürich, at the north-western end of the lake, is the largest city on Lake Zürich. On the west shore are Rüschlikon, Horgen, Wädenswil, Richterswil, Pfäffikon, Lachen. On the opposite shore are Küsnacht, Meilen, Stäfa, Rapperswil-Jona with the medieval town of Rapperswil, whose castle is home to the Polish museum. Schmerikon is close to the east end of the lake, a little further east is the larger town of Uznach. Lake Zürich's water is clean and reaches, during summer, temperatures well beyond 20 °C. Swimming in the public baths and beaches is popular; the lake's water is fed into Zürich's water system. The Prehistoric pile dwellings around Zürichsee comprises 11 of total 56 Prehistoric pile dwellings around the Alps in Switzerland, that are located around Zürichsee in the cantons of Schwyz, St. Gallen and Zürich. Located on Zürichsee lakeshore, there are Freienbach–Hurden Rosshorn, Freienbach–Hurden Seefeld, Rapperswil-Jona/Hombrechtikon–Feldbach, Rapperswil-Jona–Technikum, Erlenbach–Winkel, Meilen–Rorenhaab, Wädenswil–Vorder Au, Zürich–Enge Alpenquai, Grosser Hafner and Kleiner Hafner.

Because the lake has grown in size over time, the original piles are now around 4 metres to 7 metres under the water level of 406 metres. On the small area of about 40 square kilometres around Zürichsee, there the settlements Greifensee–Storen/Wildsberg on Greifensee and Wetzikon–Robenhausen on Pfäffikersee lakeshore; as well as being part of the 56 Swiss sites of the UNESCO World Heritage Site, each of these 11 prehistoric pile dwellings is listed as a Class object in the Swiss inventory of cultural property of national and regional significance. Obersee Prehistoric pile dwellings around Zürichsee Paddle steamer Stadt Rapperswil Paddle steamer Stadt Zürich Radio Zürisee Seedamm Zürichsee-Zeitung Media related to Lake Zurich at Wikimedia Commons Media related to Obersee at Wikimedia Commons Peter Ziegler: Zürichsee in German and Italian in the online Historical Dictionary of Switzerland, 28 February 2014. Zürichsee Schifffahrtsgesellschaft—Boat schedules non-English. Zürichsee-Fähre Horgen-Meilen—Ferry schedules, in German.

Waterlevels Lake Zürich at Zürich