A note on "A LP-based heuristic for a time-constrained routing problem"

In their paper, Avella et al. (2006) investigate a time-constrained routing problem. The core of the proposed solution approach is a large-scale linear program that grows both row- and column-wise when new variables are introduced. Thus, a column-and-row generation algorithm is proposed to solve this linear program optimally, and an optimality condition is presented to terminate the column-and-row generation algorithm. We demonstrate by using Lagrangian duality that this optimality condition is incorrect and may lead to a suboptimal solution at termination

A note on "A LP-based heuristic for a time-constrained routing problem"

Avella et al. (2006) [Avella, P., D'Auria, B., Salerno, S. (2006). A LP-based heuristic for a time-constrained routing problem. European Journal of Operational Research 173:120-124] investigate a time-constrained routing (TCR) problem. The core of the proposed solution approach is a large-scale linear program (LP) that grows both row- and column-wise when new variables are introduced. Thus, a column-and-row generation algorithm is proposed to solve this LP optimally, and an optimality condition is presented to terminate the column-and-row generation algorithm. We demonstrate that this optimality condition is incorrect and may lead to a suboptimal solution at termination. We identify the source of this error and discuss how the generic column-and-row generation algorithm proposed by Muter et al. (2010) may be applied to this TCR problem in order to solve the proposed large-scale LP correctly

Meaning and Uniqueness of Ethics and Ethical Teacher Behaviors in the Teaching Profession

This research aimed to determine ethical teacher behaviors according to the opinions of prospective teachers and teachers. In this qualitatively designed study, the phenomenology design was used, and 30 participants were interviewed. Research results showed that the participants understood the responsibilities of teachers, the respect and importance of the teaching profession, effective teaching, developing healthy relationships with school members, and benefiting students and society from teacher\u27s professional ethics. Almost all of the participants stated that the teaching profession should have unique ethical codes for different reasons. Ethical teacher behavior has emerged within the scope of rights and justice, interest and importance to people and the profession, not to harm or benefit, and the boundary of public and private space. Finally, suggestions for improving professional teaching ethics, which can be evaluated in professional, individual, social, organizational, and political contexts, were put forward in the research. It is believed that the research will make a significant contribution to the literature, as it addresses the issue of ethics by taking the views of teachers both prepared for the profession and within the profession, reveals the specific context in Turkey, and reflects descriptions of real-life experiences

Poverty Dynamics in Turkey: A Multinomial Logit Model

The availability of longitudinal data allows researchers to analyse the dynamics of poverty. By using the Turkish Statistical Institute’s (TurkStat) Income and Living Conditions Survey micro dataset, we analyse the households’ long-term monetary poverty conditions. We categorise poverty as transitory and chronic and employ the multinomial logit method to analyse determinants of each types of poverty. Results indicate that education and household size are the most effective factors for reducing transitory poverty, and for chronic poverty, the most effective factors are having a regular job and having a skilled occupation; insurance, home ownership, and number of children are important determinants for both types of poverty

Optimization of Rheology Parameters for Feedstock by Powder Injection Molding (PIM) Via Taguchi Analysis

The most critical process in the powder injection molding method is determining the powder/binder rate and its properties. The most important feature that distinguishes the powder injection molding method from other powder metallurgy production methods is its advantage in producing high raw density and complex shaped parts. However, providing these advantages includes a multi-parameter process that directly affects the injection molding parameters and the final part's mechanical properties. In addition, the difficulty of experimental studies causes energy, time, and cost losses in determining the powder/binder rate and rheological properties of the feedstock so that the advantages of the method turn into a manageable disadvantage. This study performed rheology studies for three different feedstocks (PW/CW/SA, PW/PE/SA, and PEG8000/PP/SA). In this context, this paper determined the rheological properties of different feedstocks to take advantage of the Taguchi analysis. Flow behavior index, viscosity and optimum loading rates were determined separately for all feedstocks. The results exhibited the injection molding can be done with the determined best (58% steatite+PEG8000/PP/SA) F3 feedstock by volume. Based on it was found that viscosity and melt flow index were not a problem for injection molding in three different feedstocks used in the result, advantages and disadvantages were observed

Optimization of Rheology Parameters for Feedstock by Powder Injection Molding (PIM) Via Taguchi Analysis

The most critical process in the powder injection molding method is determining the powder/binder rate and its properties. The most important feature that distinguishes the powder injection molding method from other powder metallurgy production methods is its advantage in producing high raw density and complex shaped parts. However, providing these advantages includes a multi-parameter process that directly affects the injection molding parameters and the final part's mechanical properties. In addition, the difficulty of experimental studies causes energy, time, and cost losses in determining the powder/binder rate and rheological properties of the feedstock so that the advantages of the method turn into a manageable disadvantage. This study performed rheology studies for three different feedstocks (PW/CW/SA, PW/PE/SA, and PEG8000/PP/SA). In this context, this paper determined the rheological properties of different feedstocks to take advantage of the Taguchi analysis. Flow behavior index, viscosity and optimum loading rates were determined separately for all feedstocks. The results exhibited the injection molding can be done with the determined best (58% steatite+PEG8000/PP/SA) F3 feedstock by volume. Based on it was found that viscosity and melt flow index were not a problem for injection molding in three different feedstocks used in the result, advantages and disadvantages were observed

Solving a robust airline crew pairing problem with column generation

In this study, we solve a robust version of the airline crew pairing problem. Our concept of robustness was partially shaped during our discussions with small local airlines in Turkey which may have to add a set of extra flights into their schedule at short notice during operation. Thus, robustness in this case is related to the ability of accommodating these extra flights at the time of operation by disrupting the original plans as minimally as possible. We focus on the crew pairing aspect of robustness and prescribe that the planned crew pairings incorporate a number of predefined recovery solutions for each potential extra flight. These solutions are implemented only if necessary for recovery purposes and involve either inserting an extra flight into an existing pairing or partially swapping the flights in two existing pairings in order to cover an extra flight. The resulting mathematical programming model follows the conventional set covering formulation of the airline crew pairing problem typically solved by column generation with an additional complication. The model includes constraints that depend on the columns due to the robustness consideration and grows not only column-wise but also row-wise as new columns are generated. To solve this dicult model, we propose a row and column generation approach. This approach requires a set of modifications to the multi-label shortest path problem for pricing out new columns (pairings) and various mechanisms to handle the simultaneous increase in the number of rows and columns in the restricted master problem during column generation. We conduct computational experiments on a set of real instances compiled from a local airline in Turkey

Bankacılık Sektöründe Finansal Etkinlik Analizi: Türkiye ve Irak Örneği Karşılaştırması

Günümüzde finansal piyasalarda rekabet yoğun olarak yaşanmaktadır. Finans alanında önemli bir aktör olan bankacılık sektörü de bu rekabetten etkilenmektedir. Bu sebeple bankacılık sektöründe etkinlik ve verimlilik kavramları önem kazanmıştır. Etkin çalışabilmek bankalar için bir zorunluluk haline gelmiştir. Bu durumdan hareketle yapılan bu çalışmanın amacı, Türk Bankacılık sektörü ile Irak Bankacılık sektöründe faaliyet gösteren bankaların etkinliklerinin ölçülmesi, yıllar itibariyle gösterdikleri gelişmelerin tespit edilmesi ve son olarak sonuçların birbirleriyle karşılaştırılmasıdır. Çalışmada ilk olarak Türk ve Irak Bankacılık sisteminde faaliyet gösteren bankalardan seçilmiş gözlem kümelerinin etkinlikleri, Veri Zarflama Analizi VZA yöntemiyle tespit edilmiştir. Tespit edilen bu değerlerin incelendiği ortalama istatistikler her iki ülke bankalarını içeren gözlem kümeleri için de tablolaştırılarak sunulmuştur. Ardından etkinlik gösteremeyen bankaların analizin son yılında tam etkinliğe ulaşabilmeleri için referans kümeleri ve yoğunluk değerleri belirlenmiş ve tablolaştırılmıştır. Ayrıca oluşturulan potansiyel iyileştirme tabloları ile, gözlem kümelerindeki etkin olmayan karar birimlerinin aynı çıktı düzeyini daha az girdiyle yakalayabilmeleri için hangi girdi oranlarını kullanacağını ve girdilerinde ne oranda bir kısıtlamaya gidilmesi gerektiği gösterilmiştir. Analizin devamında gözlem kümesini oluşturan bankaların etkinlik dereceleri açısından yıllar itibariyle gösterdikleri gelişmeler Malmquist Toplam Faktör Verimliliği Endeksi MTFV yardımıyla incelenmiştir. MTFV Endeksi dört ayrı endeksin bileşiminden oluşan ve karar birimlerinin durumlarında bir önceki yıla göre gerçekleştirdikleri olumlu ve olumsuz gelişmeleri göstermektedir. Ardından Malmquist endeks sonuçlarının gözlem kümeleri açısından ortalama değerleri üzerinden dönemsel karşılaştırmaları tablo yardımıyla yapılmıştır. Son olarak gözlem kümelerini oluşturan her iki ülkenin bankalarının tüm analiz sonuçları birbirleri ile karşılaştırılarak sonuçlar üzerine yorum yapılmıştır. Çalışmada, Türk ve Irak bankacılık sektörlerinde faaliyet gösteren 13’er adet bankanın 2013-2017 yılları arasındaki verilerinden yararlanılmıştır. Banka verilerinin analiz dönemi boyunca kesintisiz olmasına özellikle dikkat edilmiştir. Zira VZA’nın yapısı gereği gözlem kümesindeki karar birimlerinin kesintisiz veriye sahip olmaları gerekmektedir. Gözlem kümesini oluşturan bankalar tespit edilirken bu hususa dikkat edilmiştir. Çalışmanın analiz kısmında girdi olarak Toplam Mevduat/Toplam Aktifler, Faiz Giderleri/Toplam Aktifler ve Diğer Faaliyet Giderleri/Toplam Aktifler ve çıktı olarak da Toplam Kredi ve Alacaklar/Toplam Aktifler ve Faiz Gelirleri/Toplam Aktifler değişkenleri kullanılmıştır. Analiz sonuçlarına göre; 2013-2017 yıllarını kapsayan analiz döneminde Türk Bankaları, Irak Bankaları’na göre hem etkinlik hem de toplam faktör verimliliği açısından daha iyi performans göstermişlerdir. Türk Bankalarının etkinlik değerleri, Irak Bankaları’ndan her yıl daha yüksek çıkmıştır. MTFV endeks değerlerinde de Türk Bankaları her yıl değerlerini artırırken, Irak Bankaları açısından inişli çıkışlı, düzensiz bir durum tespit edilmiştir