The Important Role of Time Limits When Consumers Choose Their Time in Service

A main challenge that service providers face when managing service systems is how to generate value and regulate congestion at the same time. To this end, classical queueing models suggest managers charge per-use fees and invest in capacity to speed up the service. However, in discretionary services, in which consumers value time in service and choose how long to stay, per-use fees result in suboptimal performance and speeding up does not apply. We study a queueing model of a service provider and rational consumers who are heterogenous in their requirements for service duration. Consumers incur disutility from waiting and choose whether to join and how long to spend in service. We consider time limits as a novel mechanism that may help in controlling congestion. Time limits put a cap on the maximum time that customers can spend in service. We analyze their effectiveness when combined with two price schemes: per-use fees and price rates. Time limits are effective because they reduce time in service and impact waiting times and joining behavior. Revenue maximizing firms and social planners who maximize social welfare benefit from implementing time limits in addition to price rates. Social planners who seek to maximize consumer welfare, however, focus on regulating congestion and should, therefore, offer the service for free but implement time limits if congestion levels are high. The attractiveness of time limits goes further. We show that time limits are not only a useful lever that works well when combined with simple price mechanisms, but they are in fact optimal when congestion is high. Service providers can achieve the first-best outcome and extract all customer surplus by coupling a time limit with an optimal price mechanism. The attractiveness of time limits stems from their ability to reduce not only the average time spent in service, but also its variance. This is highly effective in settings in which customers’ service times impose externalities on others’ waiting times. Thus, we conclude that providers of discretionary services should set time limits when congestion is an issue. This paper was accepted by Vishal Gaur, operations management.

Felonious line-of-duty officer deaths (1995–2015): The impact of tenure and age revisited

The purpose of this article was to reassess patterns previously identified in the Federal Bureau of Investigation’s Law Enforcement Officers Killed and Assaulted (LEOKA) data, expanding the time frame from 5 years to 20 years, for application within law enforcement when considering training needs over the life cycle of an officer's career. Consistent with the findings of the earlier analysis, this study identifies two prevalent patterns: the age range with the highest frequency of death was 30–39, and the years of experience with the highest frequency of death was 0–4. In fact, the analysis indicates an even stronger pattern of the deadly combination of age and tenure. Implications of the study include the need for larger scale data collection on the national population of officers, detailed information on transfers and time of service overall (as opposed to time in service at current department), and evaluations of current training programs and practices regarding de-escalation and the use of force as well as self-defense and situational awareness.

A Four-Step Safety Integrity Level Analysis of Numerous Subsea Control System Components

In this paper, a four-step Safety Integrity Level (SIL) analysis is developed to analyze numerous components of the subsea control system based on the OREDA database. For this purpose, initially, a failure mode classification table is provided aiming to identify the number of dangerous as well as the prevalent failure modes. Then, several parameters such as the total time in service of the components are calculated. Also, failure rates are evaluated and the software checking is provided as the final step of the proposed framework. The results show that the number of dangerous failure modes is a noticeable value and the leakage in closed position is the failure mode occurring more than the other ones. Moreover, the quantification of parameters indicates that the process isolation valve of the subsea X-mass tree has the largest values in all the considered parameters. Besides, hydraulic coupling of the choke module and HC leak sensor are the two components with the highest value of failure rates.

Penerapan Model Antrian Multi Channel-Single Phase pada SPBU Sempu Jurong Cikarang Utara

SPBU Sempu Jurong provides 4 service facilities and two of them are service facilities for two-wheeled vehichles which have the most dominant queues compared to the entire queue of the existing system. The queue that occurs is due to the unbalance between the number of service facilities and the number of two-wheeled vehicle customers. This study aims to increase the level of service by knowing the number of service facilities and service time at optimal level at SPBU Sempu Jurong. In this study, the method used is the Multi Channel-Single Phase queuing model. The results of this research indicate that the addition of one facility line causes the service time required for SPBU Sempu Jurong for two-wheeled vehicle refueling services to be faster. Based on calculations using the Multi Channel-Single Phase model, it is obtained that the service time with 2 lines of service facilities is 0.291 minutes, while the optimal service time needed with 3 lines of facilities takes the longest of 0.027 minutes. This shows that it is optimal because the speed of time in service can be improved so that customer satisfaction of two-wheeled vehicles with services at SPBU Sempu Jurong Cikaran Utara can be achieved.

Environmentally Friendly Polymer Compositions with Natural Amber Acid

Few scientific reports have suggested the possibility of using natural phenolic acids as functional substances, such as stabilizers for polymeric materials. The replacement of commercial stabilizers in the polymer industry can be beneficial to human health and the environment. The aim of this study was to obtain biodegradable composition of polylactide (PLA) and polyhydroxyalkanoate (PHA) with natural amber (succinic) acid. The materials were subjected to controlled thermooxidation and solar aging. The research methodology included thermal analysis, examination of surface energy, mechanical properties and spectrophotometric analysis of the color change after aging. The samples of aliphatic polyesters containing from 1 to 2 parts by weight of succinic acid were characterized by increased resistance to oxidation (DSC analysis). Natural acid, preferably at a concentration of 1–1.5 parts by weight, acted as a stabilizer in the polymer compositions. On the other hand, materials that had amber acid above 2 parts by weight added were more susceptible to oxidation (DSC). They also showed the lowest aging coefficients (K). The addition of acid at 2.5–4 parts by weight caused a pro-oxidative effect and accelerated aging. By adding amber acid to PLA and PHA, it is possible to design their time in service and their overall lifetime.

Social climate and hope amongst staff and prisoners in a high security male prison

Purpose There is an increased focus on making prison cultures more rehabilitative, with clear evidence that certain environmental characteristics contribute towards rehabilitation. To date, limited research has explored the rehabilitative culture in a high security prison. This study aims to measure staff and prisoner ratings of social climate and their levels of hope in such an establishment. Design/methodology/approach The research adopted a quantitative approach, using the EssenCES and State Hope Scale. Data was analysed using parametric and non-parametric tests to explore correlations/relationships between variables. Findings Findings indicated that higher ratings of social climate were associated with higher levels of hope. Staff rated the social climate more favourably than prisoners, and Category B prisoners had higher levels of hope than Category A prisoners. No significant correlation was found between length of time in service or custody and ratings of social climate or hope. Practical implications This paper highlights the importance of developing a positive social climate and hope, supporting the rehabilitative culture initiatives. Originality/value This paper contributes to the limited literature on social climate and hope within UK forensic settings. Furthermore, reliability testing indicates the State Hope Scale is appropriate for use with a UK forensic population, extending its application.

Studies on Thermomechanical Cycling Characteristics of an Ni-Ti-Cu Shape Memory Alloy

Shape memory alloys (SMAs) find use in myriad medical and engineering applications. In these applications, the functional characteristics of the materials are capitalized on. SMAs are used repeatedly over a long period of time in service. With continued usage degradation occurs in their functional properties, leading to a change in recovery strain, recovery stress, phase transformation temperatures and hysteresis. The change in the functional characteristics of the alloys is known as functional fatigue. Functional fatigue affects the performance of the alloys with the alloys losing their intended functionality. This problem is to be addressed if the alloys are to be used effectively and efficiently throughout their lifespan. It is especially important when using the alloys within the human body, where such degradation can affect the performance of the biomedical devices and, in turn, human health and life. Till date not too many researchers have explored this area in greater detail. In order thereforeto better understand this behavior, in the present study, an Ni50Ti44.7Cu5.3 alloy wire with a d=1.43 mm and a l=100 mm was cycled (10,000) under constant stress (55 MPa) between its transformation temperatures, which were determined by DSC (without load). The effect of cycling on the shape memory properties (strain recovery, hysteresis, and transformation temperatures) after a specified number of cycles at regular intervals are considered. The results show that there is considerable difference in the properties obtained and are interpreted and discussed in detail in the paper.

Failure Assessment of Spring-Operated Pressure Relief Valve Proof Test Data for Extending Time-in-Service

The proof test results of 1669 Spring-Operated Pressure Relief Valves (SOPRV), which were previously installed in active processes, were analyzed with respect to proof test ratio (R), time-in-service (TIS), set pressure (SP), working fluid (WF), material composition of the SOPRV and, if an SOPRV failed-to-open (FTO), the root cause of failure in the FTO failure mode if available. Many of these SOPRV had accumulated TIS in excess of the normal maximum of five years yet proof testing indicated that most would have functioned properly. This paper examines the results of the analysis and provides guidelines under which it is appropriate to consider extending TIS for individual SOPRV.