Electrical engineering graduate studies: Program of the California Institute of Technology

The California Institute of Technology has been indicated as a leader in the field of graduate work in electrical engineering, and thus a consideration of its pattern for such studies should be of profit. Some phases of the institute's program are presented, not because they are considered wholly unique, but because they are of considerable merit and did help to pioneer the way to a high standard of graduate work

The influence of towers and conductor sag on transmission-line shielding

This paper is the third of a sequence of papers intended to present data which may be used in determining the degree of protection from lightning obtainable by shielding transmission lines and structures with grounded overhead wires and masts. The first two papers of the sequence are: “Shielding of Transmission Lines,” and “Shielding of Substations.

Vacuum switching experiments at California Institute of Technology

Successful experiments in switching or breaking a circuit in a high vacuum have been made at the California Institute of Technology. This paper is a report on three sets of these experiments which extended over a period of three years. The conclusions drawn from the experiments may be summed up in the statement that vacuum breakers of laboratory type have been successful in breaking circuits and offer a possible solution of the circuit-breaker problem. The results show that switching in vacuum affords the advantages of no pitting of contacts, quick break, the arc always going out on the first half cycle, small voltage rise across the switch, and small distance of travel necessary for the switch blades. Making the vacuum switch practical calls for a solution of the problem of making commercial apparatus with vacuum-tight joints, and the elimination of the use of liquid air with the vacuum pump

The economic status of the engineer

Data gathered by the Bureau of Labor Statistics are used by the author in this article to support his statement that “the economic status of the engineer is largely a matter determined by each individual engineer according to his particular personal qualifications and the relations these bear to the work he does and to the personalities of those persons with whom and by whom he is employed.

Surge-voltage breakdown characteristics for electrical gaps in oil

This paper, emanating from a request for information regarding surge voltages required to break down gaps in oil, gives surge breakdown voltage values with different gap spacings for ¼-inch, ½-inch, and 1-inch round rod electrodes with hemispherical ends immersed in transformer oil. As expected, these values are a function of “time to breakdown” but for each condition curves show constant breakdown values for breakdown times of the order of about 16 microseconds and longer with the 1½ × 40 negative wave, used on all the tests reported. Particular attention is called to the relatively small amount of oil required for tests of this type, made possible by the special type of test barrel used

Vacuum Switching Experiments at California Institute of Technology

Successful experiments in switching or breaking a circuit in a high vacuum have been made at the California Institute of Technology. This paper is a report on three sets of these experiments, which extended over a period of three years. The conclusions drawn from the experiments may be summed up in the statement that vacuum breakers of laboratory type have been successful in breaking circuits and offer a possible solution of the circuit-breaker problem. The results show that switching in vacuum affords the advantages of no pitting of contacts, quick break, the arc always going out on the first half-cycle, small voltage rise across the switch, and small distance of travel necessary for the switch blades. Making the vacuum switch practical calls for a solution of the problem of making commercial apparatus with vacuum-tight joints, and the elimination of the use of liquid air with the vacuum pump

The influence of towers and conductor sag on transmission-line shielding

This paper is the third of a sequence of papers intended to present data which may be used in determining the degree of protection from lightning obtainable by shielding transmission lines and structures with grounded overhead wires and masts. The first two papers of the sequence are: “Shielding of Transmission Lines,” and “Shielding of Substations.

Vacuum switching experiments at California Institute of Technology

Successful experiments in switching or breaking a circuit in a high vacuum have been made at the California Institute of Technology. This paper is a report on three sets of these experiments which extended over a period of three years. The conclusions drawn from the experiments may be summed up in the statement that vacuum breakers of laboratory type have been successful in breaking circuits and offer a possible solution of the circuit-breaker problem. The results show that switching in vacuum affords the advantages of no pitting of contacts, quick break, the arc always going out on the first half cycle, small voltage rise across the switch, and small distance of travel necessary for the switch blades. Making the vacuum switch practical calls for a solution of the problem of making commercial apparatus with vacuum-tight joints, and the elimination of the use of liquid air with the vacuum pump

Comparing exercise interventions to increase persistence with physical exercise and sporting activity among people with hypertension or high normal blood pressure: study protocol for a randomised controlled trial

BACKGROUND: Increasing physical activity is known to have health benefits for people with hypertension and related conditions. Current general practitioner referrals for gym-based exercise increase physical activity but meta-analyses show that while these are effective the absolute health risk reduction is small due to patients failing to maintain activity levels over time. This study assesses the effectiveness of two sports-oriented interventions that are intended to bridge the intention-behaviour gap and thus increase the likelihood of sustained increases in physical activity. METHODS/DESIGN: Four-arm randomised controlled trial. The study tests two types of intervention that are intended to increase physical activity among currently inactive 18- to 74-year-old people with hypertension or high-normal blood pressure. This study will assess the effectiveness of a 12-week sports-oriented exercise programme, the efficacy of a web-delivered self-help tool to promote and support sports participation and healthy behaviour change and the effect of these interventions in combination. The control arm will be a standard care general practitioner referral for gym-based exercise. Participants will be allocated using block randomisation. The first author and primary analyst is blinded to participant allocation. The primary outcome measures will be time spent in physical activity assessed in metabolic equivalent minutes per week using the International Physical Activity Questionnaire 1 year after commencement of the intervention. Secondary outcomes include increased involvement in sporting activity and biomedical health outcomes including change in body mass index, and waist and hip measurement and reductions in blood pressure. DISCUSSION: If proven to be superior to general practitioner referrals for gym-based exercise, these sports-oriented interventions would constitute low-cost alternatives. The next stage would be a full economic evaluation of the interventions. TRIAL REGISTRATION: Current Controlled Trials ISRCTN71952900 (7 June 2013)