Study of Hazard Rate Functions on the Cumulative Damage Phenomenon

2011 ◽  
Vol 27 (1) ◽  
pp. 47-55 ◽  
Author(s):  
K. S. Wang
Keyword(s):  
Hazard Rate ◽  
Failure Mechanisms ◽  
Operation Time ◽  
Cumulative Damage ◽  
Hazard Rates ◽  
Type B ◽  
The Past ◽  
Rate Functions ◽  
The Mean ◽  
Mean Time

ABSTRACTIn this paper different failure mechanisms which yield cumulative damage are investigated through two types of hazard rate functions. They have been studied during the past two decades. Type A was developed early by assuming the hazard rate as a function of reliability. There are two kinds of trend, one follows the negative logistic decay model, the other the negative Gompertz decay. Some modifications are suggested according to the failure tendency and convenience of fittings. Type B is developed recently by assuming the hazard rate as a function of the expected operation time, T, which is defined as the integration of reliability over the time, normalized by the mean-time-between-failure. In both types the proposed hazard rates grow with the time monotonically. Typical examples are taken to examine these models, meanwhile the comparisons with the Weibull-typed distribution are also made. The results show that the most of proposed relations are successful in the expression of cumulative damage phenomenon, especially the Type B is a better choice even compared with the Weibull-typed description in some respects. The advantages of the models are discussed based on the physical meanings involved in the parameters.

Modifield Desarda Repair and Hernioplastia Lichtenstein Repair for Inguinal Hernia

2021 ◽  
Vol 2 (3) ◽  
pp. 01-05
Author(s):  
Pedro Rolando Lòpez Rodrìguez ◽  
Eduardo Garcia Castillo ◽  
Olga Caridad Leòn Gonzàlez ◽  
Jorge Agustin Satorre Rocha ◽  
Luis Marrero Quiala ◽  
...  
Keyword(s):  
Inguinal Hernia ◽  
Operative Time ◽  
Controlled Trial ◽  
Operation Time ◽  
Lichtenstein Repair ◽  
Prospective Randomized Controlled Trial ◽  
The Mean ◽  
Group 2 ◽  
Location Type ◽  
Mean Time

Introduction: The objective of this study is to compare the outcomes of Modified Desarda repair no mesh and Lichtenstein repair for inguinal hernia. Methods: This is a prospective randomized controlled trial study of 1342 patients having 1394 hernias operated from January 2008 to December 2020. 690 patients were operated using Lichtenstein repair and 652 using Desarda repair. The demographie data (Age,Sex) , hernia type and location , anesthetic , operative time , postoperative pain and complications were analysed. Results: There were no significant differences regarding age, sex, location, type of hernia, and pain in both the groups. The operation time was 52 minutes in Modified Desarda group and 42 minutes in the Lichtenstein group that is significant (p<0.05). The recurrence was 0.0 % in Modified Desarda group and 0.28 % in Lichtenstein group. But, there were 9 cases of infection to the polypropylene mesh in the Lichtenstein group, 2 of this required re-exploration. The morbidity was also significantly more in Lichtenstein group (7,6 %) as compared to Modified Desarda group (3.8 %). The mean time to return to work in the Modified Desarda group was 8.26 days while a mean of 12.58 days was in the Lichtenstein group. The mean hospital stay was 29 hrs. in Modified Desarda group while it was 49 hours in the Lichtenstein group in those patients who were hospitalized. Conclusions: The modified Desarda repair scores significantly on Lichtenstein repair in most of all aspects, including reexplorations and morbidity. Modified Desarda repair is a better option compared to Lichtenstein repair.

scholarly journals An Effective and Feasible Method, “Hammering Technique,” for Percutaneous Fixation of Anterior Column Acetabular Fracture

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Lihai Zhang ◽  
Peng Yin ◽  
Wei Zhang ◽  
Tongtong Li ◽  
Jiantao Li ◽  
...  
Keyword(s):  
Acetabular Fracture ◽  
Guide Wire ◽  
Operation Time ◽  
Anterior Column ◽  
Percutaneous Fixation ◽  
Fluoroscopic Time ◽  
The Mean ◽  
Cortical Perforation ◽  
Mean Time ◽  
Time From Injury

Objective. The objective of this study was to evaluate the effectiveness and advantages of percutaneous fixation of anterior column acetabular fracture with “hammering technique.”Materials and Methods. We retrospectively reviewed 16 patients with percutaneous fixation of anterior column acetabular fracture with “hammering technique.” There were 11 males and 5 females with an average age of 38.88 years (range: 24–54 years) in our study. Our study included 7 nondisplaced fractures, 6 mild displaced fractures (<2 mm), and 5 displaced fractures (>2 mm). The mean time from injury to surgery was 4.5 days (range: 2–7 days).Results. The average of operation time was 27.56 minutes (range: 15–45 minutes), and the mean blood loss was 55.28 mL (range: 15–100 mL). The mean fluoroscopic time was 54.78 seconds (range: 40–77 seconds). The first pass of the guide wire was acceptable without cortical perforation or intra-articular perforation in 88.89% (16/18) of the procedures, and the second attempt was in 11.11% (2/18).Conclusion. Our study suggested that percutaneous fixation of anterior column acetabular fracture with “hammering technique” acquired satisfying surgical and clinical outcomes. It may be an alternative satisfying treatment for percutaneous fixation of anterior column acetabular fracture by 2D fluoroscopy using a C-arm with less fluoroscopic time.

scholarly journals Parametric Regression Models Using Reversed Hazard Rates

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Asokan Mulayath Variyath ◽  
P. G. Sankaran
Keyword(s):  
Hazard Rate ◽  
Regression Models ◽  
Hazard Rates ◽  
Proportional Hazard ◽  
Survival Times ◽  
Parametric Regression ◽  
Reversed Hazard Rate ◽  
Rate Functions ◽  
The Relationship ◽  
Parametric Regression Models

Proportional hazard regression models are widely used in survival analysis to understand and exploit the relationship between survival time and covariates. For left censored survival times, reversed hazard rate functions are more appropriate. In this paper, we develop a parametric proportional hazard rates model using an inverted Weibull distribution. The estimation and construction of confidence intervals for the parameters are discussed. We assess the performance of the proposed procedure based on a large number of Monte Carlo simulations. We illustrate the proposed method using a real case example.

scholarly journals Application of cystourethroscopy during tracheobronchial foreign body removal in children

2018 ◽  
Vol 46 (9) ◽  
pp. 3741-3747
Author(s):  
Bifan Deng ◽  
Weiguang Tang ◽  
Feiqun Su ◽  
Hua Li ◽  
Wanqiang Lai ◽  
...  
Keyword(s):  
Medical Records ◽  
Foreign Bodies ◽  
Operation Time ◽  
Foreign Body Removal ◽  
Operational Risks ◽  
Removal Time ◽  
Tracheobronchial Foreign Body ◽  
Successful Removal ◽  
The Mean ◽  
Mean Time

Objective This study aimed to describe preliminary experiences associated with removal of tracheobronchial foreign bodies (TFBs) by cystourethroscopy (CU). Methods We performed a retrospective analysis of 127 paediatric cases of TFB removal by CU at our centre from January 2009 to August 2016. Data that were extracted from the medical records included age, sex, location and nature of the TFBs, operation time, and complications. Results All TFBs were successfully removed by CU. The mean time of the procedure was 3.38 ± 2.86 minutes. A total of 102 (80.31%) patients had successful removal of TFBs by CU during the initial trial, 19 (14.96%) were successfully treated in the second trial, and six (4.72%) required a third trial. Otolaryngologists with 2, 5, and 7 years of professional CU training showed a mean TFB removal time of 3.38 ± 2.13, 3.40 ± 3.60, and 3.37 ± 2.86 minutes, respectively. In the operations, oxygen saturation fell below 90% at an average occurrence of 0.39 times, but no patients showed a decrease below 85%. Only one patient experienced laryngeal oedema after the procedure. Conclusion CU is a useful technique and minimizes complications and operational risks during removal of paediatric TFBs.

scholarly journals On selecting the most reliable components

1998 ◽  
Vol 2 (2) ◽  
pp. 133-145 ◽  
Author(s):  
Dylan Shi
Keyword(s):  
Markov Process ◽  
Death Process ◽  
Series System ◽  
Birth And Death Process ◽  
Retrograde Motion ◽  
The Past ◽  
Optimal Policies ◽  
Average Proportion ◽  
The Mean ◽  
Mean Time

Consider a series system consisting of n components of k types. Whenever a unit fails, it is replaced immediately by a new one to keep the system working. Under the assumption that all the life lengths of the components are independent and exponentially distributed and that the replacement policies depend only on the present state of the system at each failure, the system may be represented by a birth and death process. The existence of the optimum replacement policies are discussed and the ε-optimal policies axe derived. If the past experience of the system can also be utilized, the process is not a Markov process. The optimum Bayesian policies are derived and the properties of the resulting process axe studied. Also, the stochastic processes are simulated and the probability of absorption, the mean time to absorption and the average proportion of the retrograde motion are approximated.

scholarly journals PROPOSALS FOR STRATEGIES IN THE CURRICULA OF TECHNICAL UNIVERSITIES

2017 ◽  
Vol 19 (4) ◽  
Author(s):  
VALENTIN ZICHIL ◽  
VALENTIN NEDEFF ◽  
CAROL SCHNAKOVSZKY ◽  
CĂTĂLIN DROB
Keyword(s):  
Birth Rate ◽  
Educational Activity ◽  
Product Analysis ◽  
New Techniques ◽  
The Past ◽  
The Mean ◽  
Technical High Schools ◽  
The University ◽  
Mean Time ◽  
Virtual Higher Education

<p>Into the past 20 years, in Romania is registered a continuous decrease of the birth rate. At this problem it has to be added the youth wish to work in economics and laws systems, where the length of time study is smaller (only 3 years), gaining the possibility to own rapidly a salary. In those conditions, technical universities have to challenge greater provocations. The paper propose a solution, partially applied in “Vasile Alecsandri” University  of Bacau, to solve some of these new problems using a few solutions such as: “virtual” higher education and distance learning methods in order to achieve as much as is possible from the goals presented in known theories of career development. In the mean time, the strategy of the staff is presented, to make the university attractive for the youth, in order to continue the educational activity and to form better and better qualified specialists, able to face the new techniques technologies in manufacturing and product analysis. A model of curricula for the first two academic years in technical high schools is proposed.</p>

scholarly journals Maintenance Overtime Policy with Cumulative Damage

2018 ◽  
Vol 3 (2) ◽  
pp. 123-135 ◽  
Author(s):  
Satoshi Mizutani ◽  
Toshio Nakagawa
Keyword(s):  
Damage Model ◽  
Optimal Number ◽  
Cumulative Damage ◽  
Damage Level ◽  
Cost Rate ◽  
Cumulative Damage Model ◽  
The Mean ◽  
Scheduled Time ◽  
Mean Time ◽  
Total Damage

We propose an extended maintenance overtime policy for the cumulative damage model where an operating unit suffers some damage due to shocks. It is assumed that the total damage is additive, and the unit fails when the total damage has exceeded a prespecified damage level. It is supposed that we start to observe occurrence of shocks after time T, and the unit is replaced at Nth (N=1,2,…) shock over time T or at failure, whichever occurs first. That is, we propose a new policy by extending maintenance overtime policy. One example is a rental of system such as industrial equipment with some reservations. For such systems, they should be maintained or replaced at a prespecified number of uses over a scheduled time. For such a model, we obtain the mean time to replacement and the expected costs rate. Further, we discuss about optimal number N^* and time T^* which minimizes the expected cost rate when shocks occur in a Poisson process. Finally, numerical examples are given, and suitable discussions are made.

Homeless men with psychosis are spending more time shelterless

2020 ◽  
pp. 103985622092886
Author(s):  
Daniel Burton ◽  
Simon Jones ◽  
Trevor Carlisle ◽  
Alex Holmes
Keyword(s):  
Affordable Housing ◽  
Low Cost ◽  
Housing First ◽  
Mental Health Team ◽  
Health Team ◽  
The Past ◽  
Homeless Men ◽  
The Mean ◽  
Mean Time

Objective: The objective of this study was to determine if homeless men with psychosis in central Melbourne have spent a greater proportion of the past 12 months in homeless settings as compared with the same group 15 years previously. Method: A 12-month accommodation history was collected from all men with psychosis assessed by a homeless outreach mental health team over a 12-month period commencing 2018 and compared with data from 2006. Results: Between 2006 and 2018, the percentage of time spent homeless in the previous 12 months rose from 50% to 80% ( p = 0.0001). The mean time spent shelterless increased from 72 days to 149 days ( p = 0.0001). Conclusions: The amount of time spent homeless has increased in men with psychosis assessed in central Melbourne. This finding suggests that men with psychosis are becoming increasingly entrenched in homeless settings. Addressing this trend requires an increased emphasis on assertive outreach, greater access to acute inpatient and long-term rehabilitation units, and more low cost affordable housing, including housing first facilities.

Chebyshev-like inequalities for dam models

1972 ◽  
Vol 9 (03) ◽  
pp. 617-629 ◽  
Author(s):  
Bruce W. Turnbull
Keyword(s):  
Conditional Distributions ◽  
The Past ◽  
The Mean ◽  
Mean Time ◽  
Quantities Of Interest

A dam model is proposed for which it is assumed that the conditional distributions of the inputs, given the past, are known only to lie in some class M . For selected M , bounds are derived on various quantities of interest such as the mean time to first emptiness. The case of normal inputs is treated in greater detail and a release rule is discussed. The techniques used are similar to those used in the theory of gambling as developed by Dubins and Savage (1965).

Study on Nanomechanical Properties of Dragonfly Wing

2009 ◽  
Vol 79-82 ◽  
pp. 1325-1328 ◽  
Author(s):  
Ching Hsin Chang ◽  
Ku En Ting ◽  
Kuen Tsan Chen
Keyword(s):  
Structural Properties ◽  
Surface Characteristics ◽  
Flight Mechanics ◽  
The Other ◽  
Nanoindentation Test ◽  
Nanomechanical Properties ◽  
Dragonfly Wing ◽  
The Past ◽  
The Mean ◽  
Mean Time

The flight mechanics of dragonflies including hovering and taking off backwards, flight sideways and vertical directions has been attentions in Bionics. The dragonfly wing consists of the networks of various veins and membranes to make the structural properties complicated. In the past investigations, surface characteristics of dragonfly wing were measured by nanoindentation test. Thus the aim of this study will comprehensively concern the nanomechanical properties of veins, membrane and pterostigma of the wing of the dragonfly with nanoindentation. In the mean time, the modulus and hardness of the wing of the dragonfly’s composites including lengthwise vein, transverse vein, membrane and pterostigma are measured. The value of modulus of lengthwise vein is greater than the other structures. The value of modulus of transverse vein is the smallest due to its soft behavior. Its hardness is also smaller than others.

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